JP6957988B2 - Toner and image formation method - Google Patents

Description

The present invention relates to a toner for developing an electrostatic charge image and an electrophotographic image forming method using the toner.

In the field of electrophotographic, with the development of electrophotographic systems, the development of toners for electrophotographics corresponding to high image quality and high speed is required. With the diversification of printing media, not only conventional paper but also so-called label printing applications and packaging material applications for printing on the surface of films and the like have begun.

A printed matter of a flexible packaging material, which is one of the uses for packaging materials, is stored in a roll state for a long time after printing, and is stretched to a flat surface and processed in the next step. Further, even after being processed into a packaging form, for example, in the case of bagging packaging, a force is applied to the toner image in all directions as the shape of the package is deformed. When an image is formed on a flexible packaging material by an electrophotographic image forming method, it is required to form an image so that the image does not deteriorate even in the image on the flexible packaging material which is obliged to undergo such radical deformation. Has been done.

On the other hand, the toner used in the image forming method includes a toner having toner matrix particles having voids inside, and a toner in which the toner matrix particles have a core-shell structure and having voids inside the shell layer. It is known (see, for example, Patent Documents 1 and 2).

Japanese Unexamined Patent Publication No. 2011-059372 Japanese Unexamined Patent Publication No. 2013-238748

One of the characteristics required for an image formed on a flexible packaging material is flexibility that can follow the deformation of the packaging material. In addition, one of the characteristics required for an image that is written under pressure, such as a ballpoint pen, is an appropriate flexibility that suppresses image breakage due to pen pressure. However, with conventional toner, the flexibility of the formed image may be insufficient, and the image may be damaged due to deformation of the recording medium or pressurization due to writing.

An object of the present invention is to form an image in which image damage due to deformation of a recording medium or pressure due to writing is suppressed in electrophotographic image formation.

The present invention is a toner matrix having a core particle containing a first binder resin and a shell layer containing a second binder resin that covers the surface of the core particles as one means for solving the above problems. A toner for developing an electrostatic charge image containing particles, wherein the core particles provide a toner having ubiquitous voids.

Further, as another means for solving the above problems, the present invention is an electrophotographic image in which an unfixed toner image on a recording medium formed by the toner is fixed on the recording medium to form an image. A forming method, is provided.

According to the present invention, it is possible to form an image having a high degree of flexibility, and therefore, in electrophotographic image formation, an image is formed in which deformation of a recording medium and image damage due to pressurization due to writing are suppressed. be able to.

It is a figure for demonstrating the measurement of the void which schematically shows the cross-sectional shape of the toner base particle in embodiment of this invention. It is a figure which shows typically the structure of an example of the image forming apparatus used in the image forming method of this embodiment. It is a figure which shows typically the structure of the image forming apparatus used for the image forming method in an Example. It is a figure for demonstrating the content of the bending test of an image in an Example.

The toner of the embodiment of the present invention is a toner for static charge image development used in an electrophotographic image forming method, and contains toner matrix particles having a core-shell structure having core particles and a shell layer.

The toner can be configured in the same manner as a known toner except that the toner matrix particles have a specific structure described later. The toner is a dry toner, and may be a one-component developer composed of toner particles composed of toner matrix particles and an external additive adhering to the surface thereof, or may be composed of the toner particles and carrier particles. It may be a two-component developer to be used. The toner matrix particles can be formed by using a known material of the toner matrix particles such as a binder resin, a colorant, and a wax in a range having a specific core-shell structure described later.

The core particles have ubiquitous voids. The voids are spaces that are not occupied by solids such as binder resin existing in the core particles, and are a large number of cavities (vacancy) that are uniformly dispersed inside the core particles. The fact that the core particles have voids means that, for example, the core particles are a porous body having a large number of fine pores inside. The voids are usually filled with a gas such as air, but may contain other media, such as the solvent used in the production of the toner matrix particles.

The size of the voids is preferably 5 to 180 nm from the viewpoint of increasing the flexibility of the toner image fixed on the recording medium. If the size is too small, the flexibility may be insufficient, and if the size is too large, voids may be crushed when the toner image is fixed and the flexibility may be insufficient. The size of the voids is preferably 5 to 100 nm from the viewpoint of making the voids more uniformly present in the toner matrix particles.

The abundance ratio of the voids in the toner matrix particles is preferably 5 to 50%, preferably 2 to 25%, from the viewpoint of enhancing the flexibility and suppressing damage due to the addition of the toner image. More preferably. If the abundance ratio is too high, the fixed toner image becomes slightly brittle, and writing (pressurizing) on the toner image may cause defects in the toner image. Further, if the abundance ratio is too low, the flexibility of the toner image may be insufficient.

The smaller the variation in the abundance ratio of the voids, the more the voids are ubiquitous, that is, they are uniformly dispersed. The variation in the abundance ratio of the voids is preferably 1% or less from the viewpoint of increasing the flexibility of the toner image fixed on the recording medium. The variation in the abundance ratio of the voids may occur depending on the production conditions of the toner base particles such as stirring strength.

The voids can be confirmed by using an appropriate detection device according to the size of the voids. For example, voids with a pore size of 20 nm or more can be confirmed by observing with a transmission electron microscope, for example, "2000FX" (manufactured by JEOL Ltd.), and voids with a pore diameter of less than 20 nm can be confirmed with a scanning probe microscope. For example, using "AFM5400L" (manufactured by Hitachi High-Technologies Co., Ltd.), for example, the number of pixels at the time of measurement is 512 x 512 pixels, and 200 nm x 200 nm (about 0.4 nm / pixel) is confirmed as the scanning range. be able to.

The size of the void can be obtained as an average value (average pore diameter, Dh) of the pore diameter of the void. The voids may be closed cells or open cells, and thus the individual pore diameters of the voids may be appropriate values representing the size of the voids, for example, minor diameters, major diameters and short diameters. It may be an average value with the diameter. The average pore diameter can be determined by the following method. Toner matrix particles are embedded in a curable resin, and an ultrathin section having a set thickness of 100 nm is prepared by an ultramicrotome, and the section is used.

For voids with a pore size of 20 nm or more, a cross section of 10 toner matrix particles in the above section was photographed with a transmission electron microscope "2000FX (manufactured by JEOL Ltd.)" at a magnification of 50,000 times, and the obtained enlargement was obtained. The image is captured by a scanner, and the pore diameter is determined by the image analysis device "Luzex AP (manufactured by JEOL Ltd.," Luzex "is a registered trademark of the same company)" in a specific measurement area in the enlarged image.

For voids with a pore size of less than 20 nm, the cross section of the 10 toner matrix particles in the above section was photographed in the range of 200 nm × 200 nm with a scanning probe microscope “AFM5400L”, and the obtained enlarged image was captured by a scanner. , The pore diameter is determined by "Luzex AP" in a specific measurement region in the enlarged image. Then, the average pore diameter is calculated from the following formula.
Dh (nm) = (total pore diameter measured) / number of measured voids

Further, the existence ratio of the voids in the toner base particles (Rh), in particular measurement area of the enlarged image, the area of the measurement region and (S _TOTAL), the area of the voids observed in a transmission electron microscope (S _TEM ) And the area of the void ( _SSPM ) observed by the scanning probe microscope, can be obtained from the following formula.
Rh (%) = {(S _TEM + S _SPM ) / (S _TEM + S _SPM + S _TOTAL )} × 100

Further, the variation in the abundance ratio of the voids in the toner matrix particles (Vh) can be obtained by subtracting the abundance ratio in each of the measurement regions from the abundance ratio of the voids in the entire toner matrix particles. The variation in the abundance ratio may be a representative value indicating the tendency of the variation, and may be, for example, the maximum value among the differences in the abundance ratio in each measurement region, or an average value thereof. May be good.

The specific measurement area described above can be determined as follows. First, as shown in FIG. 1, in the cross section of the toner matrix particle 100, the first axis A1 along the direction of the longest diameter in the cross section and the midpoint (intersection) O of the longest diameter in the first axis A1. A second axis A2 orthogonal to each other is set. The toner base particle 100 is composed of core particles 110 and a shell layer 120 that covers the surface of the core particles 110. Then, the distance along the first axis A1 and the second axis A2 from the intersection O to the surface of the shell layer 120 is defined as the radius r. r may have different values on all axes.

The measurement region of the core particle 110 is one region having a predetermined size centered on the intersection O of the first axis A1 and the second axis A2, and the outermost region at a distance of 0.8 r from the intersection O. There are five regions with four regions of predetermined size, one side of which is located so as to intersect the first axis A1 or the second axis A2.

The measurement regions in the shell layer are four regions having a specific predetermined size along the central axes, with the first axis A1 and the second axis A2 as the central axes thereof.

The measurement region for measuring a void having a pore size of 20 nm or more is a square region having a side of 1 μm, which is a region R11 to R15 for the core particle 110 and a region R16 to 19 for the shell layer 120. If the thickness of the shell layer 120 is less than 1 μm, it may be a region having a width of 1 μm centered on the first shaft or the second shaft.

The measurement region for measuring a void having a pore diameter of less than 20 nm is a square region having a side of 200 nm, which is a region R21 to R25 for the core particle 110 and a region R26 to R29 for the shell layer 120. The regions R26 to R29 may be set at any position within the shell layer 120 with the first axis A1 or the second axis A2 as the central axis, and may be set, for example, the first axis A1 or the second axis. Axis A2 is set around the midpoint of the portion that crosses the shell layer 120.

The particle size of the core particles can be appropriately determined, for example, according to the desired size of the toner matrix particles and the desired thickness of the shell layer. The average particle size of the core particles is preferably 4.0 to 10.0 μm in terms of volume-based median diameter, and more preferably 4.0 to 8.0 μm.

The shell layer covers the surface of the core particles. It is preferable that the shell layer has ubiquitous voids from the viewpoint of increasing the degree of dispersion of the voids in the toner matrix particles. The presence of voids in the shell layer also maintains the voids so that they are more evenly present in the fixed toner image. In particular, voids are sufficiently and uniformly present at the interface between the toner particles in the toner image. As described above, it is considered that the toner image becomes more flexible due to the presence of the voids more uniformly in the entire toner image.

The thickness of the shell layer is preferably 100 nm to 1 μm, more preferably 100 to 300 nm, and more preferably 200 to 300 nm from the viewpoint of enhancing both the low temperature fixability and the heat resistance stability of the toner. More preferred.

The core particles contain a first binder resin. The shell layer contains a second binder resin. The first binder resin constitutes a continuous phase of the core particles, and the second binder resin constitutes a continuous phase of the shell layer. The first binder resin and the second binder resin may be one kind or more, respectively. Further, both may be the same or different.

The first and second binder resins can be appropriately selected from resins that can be used as materials for the toner matrix particles. A typical example thereof is a polymer formed by polymerizing a polymerizable monomer called a vinyl-based monomer. The vinyl-based monomer may be one kind or more.

Examples of the vinyl-based monomers include styrene-based monomers, (meth) acrylic acid-based monomers, olefins, halogenated olefin-based monomers, diolefin-based monomers, vinyl esters, vinyl ethers, and vinyl ketones. , N-vinyl compounds and other vinyl compounds are included.

Examples of the styrene-based monomer include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-phenylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, Includes p-tert-butyl styrene, pn-hexyl styrene, pn-octyl styrene, pn-nonyl styrene, pn-decyl styrene and pn-dodecyl styrene.

Examples of the above (meth) acrylic acid-based monomer include methacrylic acid, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, n-butyl methacrylate. Octyl, 2-ethylhexyl methacrylate, stearyl methacrylate, lauryl methacrylate, phenyl methacrylate, diethylaminoethyl methacrylate, dimethylaminoethyl methacrylate, acrylic acid, methyl acrylate, ethyl acrylate, isopropyl acrylate, n-acrylate Includes butyl, t-butyl acrylate, isobutyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, lauryl acrylate, phenyl acrylate, acrylonitrile, methacrylonitrile and acrylamide.

Examples of the above olefins include ethylene, propylene, butene-1, penten-1 and 4-methylpentene-1. Examples of the halogenated olefin-based monomer include vinyl chloride and vinylidene chloride. Examples of the diolefin-based monomers include butadiene, isoprene and chloroprene.

Examples of the vinyl esters include vinyl propionate, vinyl acetate, vinyl benzoate and vinyl formate. Examples of the vinyl ethers include vinyl methyl ether, vinyl ethyl ether, vinyl n-butyl ether, vinyl phenyl ether and vinyl cyclohexyl ether. Examples of the vinyl ketones include vinyl methyl ketone, vinyl ethyl ketone and vinyl hexyl ketone. Examples of the N-vinyl compounds include N-vinylcarbazole, N-vinylindole and N-vinylpyrrolidone. Examples of the other vinyl compounds mentioned above include vinylnaphthalene and vinylpyridine.

The vinyl-based monomer preferably has an ionic dissociation group. Examples of ionic dissociating groups include carboxyl groups, sulfonic acid groups and phosphate groups. Of these, a vinyl-based monomer having a carboxyl group is preferable.

Examples of vinyl-based monomers having a carboxyl group include acrylic acid, methacrylic acid, maleic acid, itaconic acid, silicic acid, fumaric acid, maleic acid monoalkyl ester and itaconic acid monoalkyl ester. Examples of vinyl-based monomers having a sulfonic acid group include styrene sulphonic acid, allyl sulphosuccinic acid and 2-acrylamide-2-methylpropan sulphonic acid. Examples of vinyl-based monomers having a phosphoric acid group include acid phosphooxyethyl methacrylate.

The fact that one or both of the first binder resin and the second binder resin has a crosslinked structure enhances the viewpoint of suppressing the collapse of voids, and the flexibility and retouching durability of the fixing toner image. From the viewpoint, it is preferable. The crosslinked structure can be constructed, for example, by using a crosslinkable monomer such as a polyfunctional vinyl monomer as the vinyl monomer.

Examples of polyfunctional vinyl-based monomers include compounds having two or more (particularly 2 to 4) polymerizable unsaturated bonds, and specifically, ethylene glycol dimethacrylate and ethylene glycol dimethacrylate. Acrylate, Diethylene glycol dimethacrylate, Diethylene glycol diacrylate, Triethylene glycol dimethacrylate, Triethylene glycol diacrylate, Neopentyl glycol dimethacrylate, Neopentyl glycol diacrylate, Divinylbenzene, Divinylbiphenyl, Divinylnaphthalene, Dialylphthalate, Triallyl cyanurate And tetraethylene glycol dimethacrylate.

Examples of preferable combinations of polyfunctional vinyl-based monomers and other vinyl-based monomers include styrene alone, acrylic acid ester alone, methacrylic acid ester alone, and styrene and acrylic acid as monofunctional monomers. It includes a combination of an ester, a styrene and a methacrylic acid ester, an acrylic acid ester and a methacrylic acid ester, or a styrene and an acrylic acid ester and a methacrylic acid ester, and divinylbenzene as a crosslinkable monomer.

The proportion of the crosslinkable monomer in the polymerizable monomer is preferably 10% by mass or more, and more preferably 30% by mass or more. For example, the second binder resin contains 10 to 100% by mass (particularly 30 to 100% by mass) of the crosslinkable monomer and 90 to 0% by mass (particularly 70 to 0% by mass) of the other polymerizable monomer. ) Is preferably a polymer or a copolymer.

As a method for introducing the voids into one or both of the core particles and the shell layer, a known method for forming voids in the core particles or the shell layer can be adopted. For example, the voids can be introduced into the core particles or shell layer by adding a solution of a polymerizable monomer, a polymerization initiator and an organic solvent to an aqueous solvent to carry out the polymerization.

When the vinyl-based monomer having a carboxyl group described above is used as both the monomers of the first and second binder resins, a vinyl-based single amount having a carboxyl group in the monomer of the second binder resin. The content of the body should be 1.5 to 3.0 times the content of the vinyl-based monomer having a carboxyl group in the monomer of the first binder resin, which is the adhesion between the core particles and the shell layer. It is preferable from the viewpoint of enhancing the sex.

Further, the amount of the above-mentioned polymerizable monomer can be appropriately determined according to the desired particle size of the core particles and the desired thickness of the shell layer, and is generally 1 part by mass of the organic solvent. It is preferably 0.1 to 2 parts by mass, and more preferably 0.5 to 1 part by mass.

Both the core particles and the shell layer may further contain components other than the first and second binder resins as long as the effects of the present embodiment can be obtained. Examples of such other ingredients include colorants and waxes. However, one or both of the core particles and the shell layer may not contain a colorant. A known colorant can be used as the colorant.

Examples of colorants for black include carbon black and magnetic powder. Examples of carbon black include furnace black, channel black, acetylene black, thermal black and lamp black. Examples of magnetic powders include magnetite and ferrite.

Examples of colorants for magenta or red include C.I. I. Pigment Red 2, 3, 5, 6, 6, 7, 15, 16, 48: 1, 53: 1, 57: 1, 60, 63, 64, 68, 68 81, 83, 87, 88, 89, 90, 112, 114, 122, 123, 139, 144, 149, 150, 163, 166, 170, 177, 178, 184, 202, 206, 207, 209, 222, 238 and 269 are included.

Examples of colorants for orange or yellow include C.I. I. Pigment Orange 31, 43, C.I. I. Pigment Yellow 12, 14, 15, 15, 17, 74, 83, 93, 94, 138, 155, 162, 180 and 185 are included.

Examples of colorants for green or cyan include C.I. I. Pigment Blue 2, 3, 15, 15, 15: 2, 15: 3, 15: 4, 16, 17, 60, 62, 66 and C.I. I. Pigment Green 7 is included.

Examples of dyes include C.I. I. Solvent Red 1, 49, 52, 58, 63, 111, 122, C.I. I. Solvent Yellow 2, 6, 14, 14, 15, 16, 19, 21, 21, 33, 44, 56, 61, 77, 79, 80, 81, 82, 82, 93, 98, 103, 104, 112, 162, C.I. I. Includes Solvent Blue 25, 36, 60, 70, 93 and 95.

The content of the colorant in the toner matrix particles is preferably 1 to 30% by mass, more preferably 2 to 20% by mass. The number average primary particle size of the colorant varies depending on the type, but is preferably about 10 to 200 nm. The colorant can be introduced into the core particles or the shell layer by adding the resin fine particles to the agglutinating system at the stage of agglutinating the resin fine particles by adding the agglutinating agent. Further, the colorant may be used by treating its surface with a surface treatment agent such as a coupling agent.

The wax can be appropriately selected from known compounds that can be used as a material for the toner matrix particles, and may be one kind or more. Examples of such waxes include polyolefin waxes, long chain hydrocarbon waxes, dialkylketone waxes, ester waxes and amide waxes.

Examples of the polyolefin wax include polyethylene wax and polypropylene wax. Examples of long-chain hydrocarbon waxes include paraffin waxes and sasol waxes. Examples of dialkyl ketone waxes include distearyl ketones. Examples of ester waxes include carnauba wax, montan wax, trimethylolpropan tribehenate, pentaerythritol tetramillistate, pentaerythritol tetrastearate, pentaerythritol tetrabehenate, pentaerythritol diacetate dibehenate, Includes glycerin tribehenate, 1,18-octadecanediol distearate, tristealythritolate and distealyl maleate. Examples of amide waxes include ethylenediamine dibehenyl amide and trimellitic acid tristearyl amide.

The melting point of the wax is usually 40 to 125 ° C, preferably 50 to 120 ° C, and more preferably 60 to 90 ° C. It is preferable that the melting point of the wax is within the above range from the viewpoint of enhancing both the low temperature fixability and the heat resistance stability of the toner. The wax content in the toner matrix particles is preferably 1 to 30% by mass, and more preferably 5 to 20% by mass.

The particle size of the toner matrix particles (or toner particles) is a volume from the viewpoint of faithfully reproducing a very fine dot image (for example, 1200 dpi (dpi; number of dots per inch (2.54 cm)) level). The standard median diameter (D50v) is preferably 3 to 8 μm.

Generally, a toner is required to be able to faithfully reproduce the color of a photographic image, but according to a toner having toner matrix particles having the above particle size, the dot image constituting the photographic image is miniaturized. It is possible to obtain a high-definition photographic image equal to or higher than a printed image. In particular, in the printing field called on-demand printing, in which print orders are received at the level of hundreds to thousands of copies, it is possible to quickly deliver high-quality prints containing high-definition photographic images to users.

The volume-based median diameter (D50v) of the toner matrix particles can be measured and calculated using a device in which a computer system for data processing is connected to "Multisizer 3" (manufactured by Beckman Coulter).

As a measurement procedure, 0.02 g of toner particles or toner base particles is 20 mL of a surfactant solution (for the purpose of dispersing toner, for example, a neutral detergent containing a surfactant component is diluted 10-fold with pure water to form a surfactant. After blending with the solution), 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," ISOTON "is a registered trademark of the same company)" in a sample stand with a pipette until the measured concentration reaches 5 to 10%. Set the measuring machine count to 2500 and measure. The aperture diameter of "Multisizer 3" is 50 μm.

The coefficient of variation (CV value) in the volume-based particle size distribution of the toner matrix particles (or toner particles) is preferably 2 to 21%, more preferably 5 to 15%. The smaller the CV value, the sharper the particle size distribution, which means that the sizes of the toner matrix particles are uniform. That is, since toner matrix particles having the same size can be obtained, it is possible to reproduce fine dot images and fine lines required for digital image formation with higher accuracy. Further, when printing a photographic image, by using a small-diameter toner having a uniform size, it is possible to create a high-quality photographic image at or higher than the image level produced by the printing ink.

The coefficient of variation (CV value) in the volume-based particle size distribution represents the degree of dispersion in the particle size distribution of the toner matrix particles on a volume basis, and is defined by the following formula. In the following formula, "σv" represents the standard deviation in the volume-based particle size distribution, and "D50v" represents the median diameter in the volume-based particle size distribution. The CV value can be adjusted, for example, by classifying the toner particles.
CV value (%) = (σv / D50v) × 100

The softening point (Tsp) of the toner matrix particles is preferably 70 to 110 ° C, more preferably 70 to 100 ° C. Generally, the colorant has a stable property that the spectrum does not change even if it is affected by heat. However, by setting the softening point in the above range, the colorant with respect to the heat colorant applied to the toner matrix particles at the time of fixing. The impact can be further reduced. Therefore, since image formation can be performed without imposing a burden on the colorant, it is expected that a wider and more stable color reproducibility can be exhibited. Further, by setting the softening point of the toner matrix particles in the above range, it is possible to fix the toner image at a low temperature, and it is possible to form an environment-friendly image in which power consumption is reduced.

The softening point of the toner matrix particles can be controlled, for example, by the following methods alone or in combination.
(1) Adjust the type and composition ratio of the monomer used for resin formation.
(2) The molecular weight of the resin is adjusted according to the type and amount of the chain transfer agent added.
(3) Adjust the type and amount of wax added.

As the softening point of the toner matrix particles, for example, "Flow Tester CFT-500 (manufactured by Shimadzu Corporation)" is used to form the toner matrix particles or the toner particles into a cylindrical shape having a height of 10 mm, and the temperature rise rate 6 ° C. / heating min pressure of 1.96 × 10 6 ^Pa from the plunger added with, as extruded from a nozzle having a diameter of 1 mm, length 1 mm, thereby a plunger descent amount of the flow tester - curve between temperature It can be obtained by drawing a (softening flow curve) and setting the temperature when the amount of descent is 5 mm as the softening point.

The toner matrix particles can be produced by using a method for producing toner matrix particles having a normal core-shell structure in which core particles are produced and a shell layer covering the core particles is produced. For example, for the toner base particles, a material solution for a shell layer containing a polymerizable monomer, a polymerization initiator and a solvent is added to the aqueous medium in which the core particles are dispersed while stirring the aqueous medium. It can be produced by forming a shell layer, or the toner matrix particles are obtained by adding fine particles for a shell layer having voids into an aqueous medium in which core particles are dispersed and agglomerating around the core particles. It can be produced by coalescing to form a shell layer.

In addition to this, the toner matrix particles can be produced, for example, by using a phase emulsification method. That is, it can also be produced by gradually adding an aqueous solvent or an aqueous medium in which core particles are dispersed while applying a mechanical shearing force to the mixture for core particles or the mixture for shell layers.

The above-mentioned "aqueous medium" refers to a medium composed of 50 to 100% by mass of water and 0 to 50% by mass of a water-soluble organic solvent. Examples of water-soluble organic solvents include methanol, ethanol, isopropanol, butanol, acetone, methyl ethyl ketone and tetrahydrofuran. The organic solvent is preferably an alcohol-based organic solvent that does not dissolve the obtained resin.

Further, the method of introducing the voids into the core particles or, if necessary, also into the shell layer can be performed by utilizing the method of producing a shell layer having such a porous structure. For example, the voids can be introduced into the material liquid in the form of droplets by sufficiently dispersing the hydrophobic material liquid of the core particles or the shell layer in an aqueous medium by a mechanical shearing force. be. In this state, the toner base particles having the voids can be produced by directly synthesizing the resin fine particles, the core particles, or the shell layer from the material liquid containing the monomer.

As a method for dispersing the material liquid for the core layer or the material liquid for the shell layer in the aqueous medium, a known dispersion method such as a dispersion method by a mechanical shearing force can be adopted. Examples of the disperser used in such a dispersal method include a commercially available disperser "Clearmix" (manufactured by M-Technique Co., Ltd., a registered trademark of the same company) equipped with a rotor that rotates at high speed, an ultrasonic disperser, and a machine. Includes formula homogenizers, manton gorins, and pressure homogenizers.

The temperature condition at the time of dispersion may be a temperature or less that affects the decomposition of the polymerization initiator usually blended in the above material liquid, and is usually around room temperature or less, especially about 0 to 30 ° C. It is preferable to have.

The abundance ratio of voids in the core particles or the shell layer can be adjusted by, for example, the content of the organic solvent in the material liquid. For example, if the amount of the organic solvent with respect to the polymerizable monomer in the material liquid is small, the abundance ratio of the voids can be reduced, and the amount of the organic solvent with respect to the polymerizable monomer in the material liquid is large. And the abundance ratio of the voids can be increased.

Further, the size of the voids can be reduced, for example, by strongly applying a mechanical shearing force in the above dispersion, or by selecting a polymerizable monomer and an organic solvent having high affinity with each other. It will be possible. The voids can be increased by weakening the mechanical shearing force or by selecting a polymerizable monomer and an organic solvent having a slightly lower affinity for each other.

The material solution usually contains a polymerization initiator and an organic solvent. In addition, the material liquid may further contain additional components suitable for producing core particles or shell layers. Examples of such additional ingredients include chain transfer agents, dispersion stabilizers and surfactants.

A known oil-soluble or water-soluble polymerization initiator can be used as the polymerization initiator. Examples of oil-soluble polymerization initiators include azo-based or diazo-based polymerization initiators and peroxide-based polymerization initiators.

Examples of azo or diazo polymerization initiators include 2,2'-azobis- (2,4-dimethylvaleronitrile), 2,2'-azobisisobutyronitrile, and 1,1'-azobis (cyclohexane). -1-Carbonitrile), 2,2'-azobis-4-methoxy-2,4-dimethylvaleronitrile and azobisisobutyronitrile.

Examples of the peroxide-based polymerization initiator include benzoyl peroxide, methyl ethyl ketone peroxide, diisopropyl peroxy carbonate, cumene hydroperoxide, t-butyl hydroperoxide, di-t-butyl peroxide, dicumyl peroxide, and the like. Includes 2,4-dichlorobenzoyl peroxide, lauroyl peroxide, 2,2-bis- (4,5-t-butylperoxycyclohexyl) propane and tris- (t-butylperoxy) triazine.

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

The amount of the polymerization initiator in the material liquid is preferably 0.005 to 0.1 parts by mass, preferably 0.01 to 0.05 parts by mass with respect to 1 part by mass of the polymerizable monomer. More preferably.

The organic solvent dissolves the polymerizable monomer and the polymerization initiator, but has low compatibility with the polymerization product, promotes phase separation of the polymerization product, and is produced by polymerization of the polymerizable monomer. It is preferable that the component does not interfere with the formation of the film. Examples of the organic solvent include saturated hydrocarbons having 8 to 18 carbon atoms, particularly 12 to 18 carbon atoms, aromatic hydrocarbons, and fatty acid esters. Particularly preferred are toluene, ethyl acetate and hexadecane.

The chain transfer agent is used for adjusting the molecular weight of resin particles, and examples thereof include octyl mercaptan, dodecyl mercaptan, tert-dodecyl mercaptan, n-octyl-3-mercaptopropionic acid ester, turpinolene, and carbon tetrabromide. And α-methylstyrene dimers are included.

The dispersion stabilizer is used when polymerizing a polymerizable monomer dispersed in an aqueous medium or aggregating and fusing resin particles dispersed in an aqueous medium to prepare toner base particles. It is preferable from the viewpoint of stably dispersing the material of the parent particles in the aqueous medium. Examples of the dispersion stabilizer 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, etc. It also includes polyvinyl alcohol, gelatin, methyl cellulose, sodium dodecylbenzene sulfonate, ethylene oxide adducts and higher alcohol sodium sulfate. It should be noted that the dispersion stabilizer can be used even if it is a component generally regarded as a surfactant.

When the above-mentioned surfactant is polymerized using a polymerizable monomer in an aqueous medium, it is preferable from the viewpoint of uniformly dispersing oil droplets of the material liquid containing the polymerizable monomer in the aqueous medium. .. Examples of such surfactants include ionic surfactants and nonionic surfactants.

Examples of ionic surfactants include sulfonates, sulfates and fatty acid salts. Examples of such sulfonates include sodium dodecylbenzene sulfonate, sodium arylalkylpolyether sulfonate, sodium 3,3-disulfonediphenylurea-4,4-diazo-bis-amino-8-naphthol-6-sulfonate. , Ortho-carboxybenzene-azo-dimethylaniline, and 2,2,5,5-tetramethyl-triphenylmethane-4,4-diazo-bis-β-naphthol-6-sodium sulfonate.

Examples of the sulfate ester salts include sodium dodecyl sulfate, sodium tetradecyl sulfate, sodium pentadecyl sulfate, and sodium octyl sulfate. Examples of the above fatty acid salts include sodium oleate, sodium laurate, sodium caprate, sodium caprylate, sodium caproate, potassium stearate, calcium oleate, and polyoxyethylene (2) dodecyl ether sulfate sodium salt. , Is included.

Examples of the nonionic surfactant include polyethylene oxide, polypropylene oxide, a combination of polypropylene oxide and polyethylene oxide, an ester of polyethylene glycol and a higher fatty acid, an alkylphenol polyethylene oxide, an ester of a higher fatty acid and a polyethylene glycol, and a higher fatty acid. Esters with polypropylene oxide and sorbitan esters are included.

The toner particles can be prepared by adding an external additive to the toner matrix particles. A known external additive can be used as the external additive, and a known technique can be adopted for adding the external additive.

The size of the external additive is preferably 4 to 800 nm in terms of number average primary particle size. The external additive may be one kind or more, and examples thereof include inorganic fine particles, organic fine particles, and lubricants. The addition of the external additive improves the fluidity and chargeability of the toner particles, and also improves the cleanability.

Examples of the inorganic fine particles include fine particles of silica, titania, alumina and strontium titanate. The surface of the inorganic fine particles may be hydrophobized.

Examples of 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., and commercially available products TS-720 manufactured by Cabot Corporation. , TS-530, TS-610, H-5, MS-5.

Examples of titania fine particles include commercially available products T-805 and T-604 manufactured by Nippon Aerodrome Co., Ltd., and commercially available products MT-100S, MT-100B, MT-500BS, MT-600, MT-600SS, manufactured by TAYCA Corporation. JA-1, commercial products TA-300SI, TA-500, TAF-130, TAF-510, TAF-510T manufactured by Fuji Titanium Industry Co., Ltd., and commercial products IT-S, IT-OA manufactured by Idemitsu Kosan Co., Ltd. , IT-OB, IT-OC.

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

Examples of the organic fine particles include spherical organic fine particles having a number average primary particle diameter of about 10 to 2000 nm, and specifically, homopolymers such as styrene and methyl methacrylate and fine particles of these copolymers. Is included.

Examples of the lubricants include metal salts of higher fatty acids such as stearic acid, oleic acid, palmitic acid, linoleic acid and ricinoleic acid. Examples of metal salts of stearic acid include zinc salts, aluminum salts, copper salts, magnesium salts and calcium salts of stearic acid. Examples of metal salts of oleic acid include zinc salts, manganese salts, iron salts, copper salts and magnesium salts of oleic acid. Examples of metal salts of palmitic acid include zinc salts, copper salts, magnesium salts and calcium salts of palmitic acid. Examples of metal salts of linoleic acid include zinc and calcium salts of linoleic acid. Examples of metal salts of ricinoleic acid include zinc and calcium salts of ricinoleic acid.

The content of the external additive in the toner particles is preferably 0.1 to 10.0% by mass. Examples of the method of adding the external additive include a method of adding the external additive using a known mixing device such as a Turbuler mixer, a Henschel mixer, a Nauter mixer, or a V-type mixer.

The toner particles can be used as they are as a one-component developer, and can be used, for example, as a non-magnetic one-component developer. Image formation by the non-magnetic one-component development method has an advantage that the entire image forming apparatus can be made compact because the structure of the developing apparatus can be simplified. Therefore, by using the above-mentioned toner as a non-magnetic one-component developer, a full-color print can be produced by a compact color printer, and a full-color print having excellent color reproducibility can be produced in a work environment where space is limited. It becomes possible to manufacture.

When used as a two-component developer, the toner of the present embodiment contains carrier particles in addition to the toner particles. As the carrier particles, known particles that can be used as carrier particles for the two-component developer can be used. Examples of carrier particles include magnetic particles, resin-coated magnetic particles whose surface is coated with a resin, and magnetic particle-dispersed resin particles in which magnetic particles are dispersed in the resin particles.

Examples of the material of the magnetic particles include metals such as iron, ferrite and magnetite, and alloys of these metals with metals such as aluminum and lead. Above all, the magnetic particles are preferably ferrite particles.

The volume reference particle size of the carrier particles is preferably 15 to 100 μm, more preferably 25 to 80 μm. The saturation magnetization value of the carrier particles is preferably 20 to 80 emu / g (2.0 × 10 ^{-2 to} 8.0 × 10 ^-2 A · m ² / g). Carrier particles having such a particle size and a saturation magnetization value are preferable from the viewpoint of forming a soft magnetic brush on the developing sleeve at the time of image formation and forming a toner image having excellent sharpness. The volume average particle size and the saturation magnetization value can be measured by known measuring devices, respectively. Specifically, the volume reference particle size is determined by the laser diffraction type particle size analyzer "HELOS" (manufactured by Sympathec) equipped with a wet disperser, and the saturation magnetization is determined by "DC magnetization characteristic automatic recording device 3257-35" (horizontal). It can be measured by Kawa Denki Co., Ltd.).

The two-component developer is obtained by mixing toner particles and carrier particles by a known method. The content of the toner particles in the two-component developer with respect to the carrier particles is preferably 2 to 10% by mass. Further, the mixing apparatus used for the above mixing is not limited, and examples thereof include a Nauter mixer, a W cone, and a V-type mixer.

The toner can be applied to an electrophotographic image forming method in the same manner as a normal toner. That is, the image forming method is an electrophotographic image forming method in which an unfixed toner image on a recording medium formed by toner is fixed on the recording medium to form an image. This is an image forming method using a form of toner. The image forming method includes, for example, the following steps.
(1) Latent image forming step of forming an electrostatic latent image on the surface of an electrophotographic photosensitive member (2) With a developing agent in which an electrostatic latent image formed on the surface of an electrophotographic photosensitive member is supported on a developing agent carrier. Development step of developing to form a toner image (3) Transfer step of transferring the toner image formed on the surface of the electrophotographic photosensitive member to the surface of the recording medium (4) The toner image supported on the surface of the recording medium Fixing process for heat fixing.

The recording medium is a member for supporting a fixed toner image. A known medium can be used as the recording medium, and examples thereof include plain paper from thin paper to thick paper, coated printing paper such as high-quality paper, art paper, and coated paper, and commercially available Japanese paper and postcard paper. , Plastic films for OHP or packaging, and cloth. Examples of plastic in the above plastic film include polyethylene terephthalate (PET), polypropylene (PP), polystyrene (PS), polyethylene (PE), biaxially stretched polypropylene (OPP), unstretched polypropylene (CPP), and biaxial. Stretched Nylon (ONY), Unstretched Nylon (CNY), Low Density Polyethylene (LDPE), Linear Low Density Polyethylene (LLDPE), High Density Polyethylene (HDPE), Impact Resistant Polyethylene (HIPS), and PLA (Poly) Lactic acid) is included.

The image forming method can be performed by using a known image forming apparatus other than using the toner of the present embodiment described above. Hereinafter, the description will be further described with reference to the drawings.

The image forming apparatus 200 is a so-called tandem type color image forming apparatus, and as shown in FIG. 2, the image forming apparatus 200 includes an original image reading apparatus SC for reading an original image, and four image forming units for forming a toner image. , A transfer device for transferring the toner image formed by the image forming unit to the recording medium P, a paper feed transfer device for transporting the recording medium P, and an unfixed toner image carried by the recording medium P for recording. It has a thermal roll type fixing device 50 as a fixing means for fixing to the medium P.

The four image forming units are devices for forming four-color images of yellow (Y), magenta (M), cyan (C), and black (K), respectively. For example, YMCK from the top of FIG. It is arranged in the order of. Each image forming unit includes a photoconductor 1, a charging device 2, an exposure device 3, a developing device 4, a primary transfer roller 5, and a cleaning device 6.

The photoconductor 1 is, for example, a drum-shaped organic photoconductor, and the charging device 2 is, for example, a non-contact charging device by corona discharge. The exposure apparatus 3 is, for example, a laser oscillator, and the developing apparatus 4 is a developing apparatus for a two-component developer containing a two-component developer of any color of YMCK. The primary transfer roller 5 is, for example, a charging roller that is freely urged toward the photoconductor 1 via an intermediate transfer belt 7, and the cleaning device 6 is, for example, made of rubber that comes into contact with the surface of the photoconductor 1. A blade cleaning device having an elastic blade. The two-component developer is the toner of the present embodiment.

The transfer device includes an endless intermediate transfer belt 7, a plurality of rollers 8 for stretching the intermediate transfer belt 7, a secondary transfer roller 9, and a cleaning device 10. The roller 8 includes one or more driving rollers, and may include a driven roller other than the driving roller. The secondary transfer roller 9 is, for example, a charging roller capable of forming a nip portion between the secondary transfer roller 9 and the intermediate transfer belt 7 via the conveyed recording medium P, and the cleaning device 10 is, for example, the intermediate transfer belt 7. A blade cleaning device having the elastic blade that comes into contact with the surface.

The paper feed transfer device includes a paper cassette 11 that houses the recording medium P, a paper feed roller 12 for taking out the recording medium P from the paper cassette 11, and the recording medium P to the nip portion of the secondary transfer roller 9. A transport roller 13 for transporting, a resist roller 14 for controlling the position of the transporting recording medium P, and a discharge roller 15 for discharging the recording medium P discharged from the fixing device 50 to the outside of the machine. It has a paper ejection tray 16 for accommodating the recording medium P ejected to the outside of the machine.

The document image reading device SC reads the image information of the document, converts it into image data of each color of YMCK, and sends the image data of the corresponding color to the exposure device 3.

In the image forming unit, the surface of the photoconductor 1 that is driven to rotate is charged by applying a voltage from the charging device 2. The exposure apparatus 3 irradiates the surface of the charged photoconductor 1 with a laser beam corresponding to the image data of the corresponding color of YMCK to form an electrostatic latent image. Toner particles are supplied from the developing device 4 to the surface of the photoconductor 1 on which the electrostatic latent image is formed, and the toner particles adhere to the electrostatic latent image portion to develop the electrostatic latent image.

The toner images of each color of YMCK supported on the surface of the photoconductor 1 thus formed in each image forming portion are on the intermediate transfer belt 7 that rotates by applying a voltage from the primary transfer roller 5. A composite color toner image is formed on the intermediate transfer belt 7 by being transferred so as to be sequentially overlapped with each other. The primary transfer roller 5 may come into contact with the photoconductor 1 only during the primary transfer. For example, the primary transfer roller 5 in the image forming portion for a black image is always in contact with the photoconductor 1 and is in contact with the photoconductor 1. The primary transfer roller 5 for color comes into contact with the photoconductor 1 only during the primary transfer.

Adhesions such as transfer residual toner on the surface of the photoconductor 1 after the primary transfer are removed from the surface by the cleaning device 6.

The recording medium P (for example, plain paper) housed in the paper feed cassette 11 is taken out from the paper feed cassette 11 by the paper feed roller 12, and is conveyed to the secondary transfer roll 9 via the transfer roller 13 and the resist roller 14. .. The color toner image on the intermediate transfer belt 7 is transferred onto the recording medium P by applying a voltage from the secondary transfer roller 9. The secondary transfer roller 9 is urged toward the intermediate transfer belt 7 only during the secondary transfer, for example.

Adhesions such as transfer residual toner on the surface of the intermediate transfer belt 7 after the secondary transfer are removed from the surface by the cleaning device 10.

The color toner image on the recording medium P is fixed on the surface of the recording medium P by heating and pressurizing the fixing device 50. In this way, the fixed color toner image is formed on the recording medium P. The recording medium P on which the color toner image is formed is conveyed onto the paper ejection tray 16 via the ejection roller 15. By repeating the above steps, toner images fixed on the recording medium P are formed one after another.

The toner image thus produced has moderate flexibility. The reason is considered as follows.

The toner matrix particles have a core-shell structure and at least have the voids ubiquitous in the core particles. Therefore, even when the toner particles are fixed on the recording medium as an image, the voids are maintained in an ubiquitous state, and the fixed toner image is ubiquitous, so that the flexibility of the toner image is improved. .. Therefore, the followability of the toner image to the bending of the recording medium is improved, and the damage of the toner image during processing of the recording medium after forming the toner image is suppressed.

Further, since the flexibility of the toner image is enhanced, the toner image is less likely to be damaged even if pressure is locally applied to the toner image. Therefore, damage to the toner image due to addition to the toner image is suppressed.

Regarding the above image forming method, a mode using a tandem type image forming apparatus has been described with reference to the drawings, but a drum type image forming portion arranged on the peripheral surface portion of the image forming portion, for example, Japanese Patent Application Laid-Open No. 2010-276754. It can also be performed by using an image forming apparatus as shown in FIG.

As is clear from the above description, the toner of the present embodiment is a toner having a core particle containing a first binder resin and a shell layer containing a second binder resin covering the surface thereof. It is a toner for developing an electrostatic charge image containing base particles, and the core particles have ubiquitous voids. Further, the image forming method of the present embodiment is an electrophotographic image forming method of fixing an unfixed toner image on a recording medium formed by the toner of the present embodiment to the recording medium to form an image. be. Therefore, according to the present embodiment, in the electrophotographic image formation, it is possible to form an image in which deformation of the recording medium and image damage due to pressurization due to writing are suppressed.

Having ubiquitous voids in the shell layer is even more effective from the viewpoint of increasing the flexibility of the formed toner image.

Further, from the viewpoint of increasing the flexibility of the toner image, it is more effective that the size of the void is 5 to 180 nm, and it is even more effective that the size of the void is 5 to 100 nm.

Further, from the viewpoint of increasing the flexibility of the toner image, it is more effective that the abundance ratio of the voids in the toner matrix particles is 5 to 50%, and it is further effective that the abundance ratio is 2 to 25%. It is a target.

Further, the fact that one or both of the first binder resin and the second binder resin has a crosslinked structure is a viewpoint of enhancing the storage stability of the voids, the flexibility of the toner image, and the retouching durability of the toner image. It is even more effective from.

[Preparation of resin particles A1 for core]
(1) First-stage polymerization In a reaction vessel equipped with a stirrer, temperature sensor, cooling tube, and nitrogen introduction device, 4.0 parts by mass of surfactant polyoxyethylene (2) dodecyl ether sulfate sodium salt and ion-exchanged water The surfactant solution 1 was prepared by adding 3000 parts by mass. The temperature of the surfactant solution 1 was raised to 80 ° C. while stirring under a nitrogen stream at a stirring speed of 230 rpm.

Next, after raising the temperature of the monomer mixed solution 1 containing the following components in the following amounts to 80 ° C., the mixture is added to the surfactant solution 1 and the mechanical dispersion device “Clearmix” having a circulation path is provided. (Manufactured by M-Technique Co., Ltd.), a dispersion treatment was carried out at 5000 rpm for 30 minutes to prepare an emulsified particle dispersion. The following "paraffin wax" is "HNP-0190" (manufactured by Nippon Wax Co., Ltd.). Further, toluene is a solvent in the monomer mixed solution 1.
Styrene 650 parts by mass n-butyl acrylate 255 parts by mass Methacrylic acid 45 parts by mass Toluene 620 parts by mass n-octyl mercaptan 18 parts by mass Paraffin wax 140 parts by mass

Next, an initiator aqueous solution 1 obtained by dissolving 15 parts by mass of potassium persulfate (KPS) in 400 parts by mass of ion-exchanged water was added to the emulsion particle dispersion, and the mixture was prepared at 80 ° C. for 1 hour. , The polymerization (first stage polymerization) was carried out by stirring at a stirring speed of 230 rpm. As a result, the resin fine particle dispersion liquid a1 was prepared.

(2) Second Stage Polymerization To the above resin fine particle dispersion liquid a1, an initiator aqueous solution 2 obtained by dissolving 5.45 parts by mass of potassium persulfate (KPS) in 220 parts by mass of ion-exchanged water was added, and the obtained mixture was obtained. The liquid was set to 80 ° C., and dispersion treatment was carried out at 5000 rpm for 30 minutes by "Clearmix". Next, a monomer mixture 2 containing the following components in the following amounts was added dropwise to the obtained dispersion over 1 hour. Toluene is a solvent in the monomer mixed solution 2.
Styrene 310 parts by mass n-butyl acrylate 120 parts by mass Methacrylic acid 20 parts by mass Toluene 290 parts by mass n-octyl mercaptan 7.1 parts by mass

After the dropping of the monomer mixture 2 was completed, the obtained mixture was heated for 2 hours to maintain the temperature at 80 ° C., and the mixture was stirred at a stirring speed of 230 rpm to carry out polymerization (second stage polymerization). .. Then, the obtained reaction solution was cooled to 28 ° C. to prepare a dispersion liquid containing the core resin particles A1.

The particle size of the obtained core resin particles A1 was measured using an electrophoretic light scattering photometer "ELS-800" (manufactured by Otsuka Electronics Co., Ltd.) and found to be 220 nm at a volume-based median diameter D50v.

[Preparation of resin particles A2 for core]
The core resin particles A2 were prepared in the same manner as in the production of the core resin particles A1 except that the amount of the solvent in the first stage polymerization was changed to 515 parts by mass and the amount of the solvent in the second stage polymerization was changed to 240 parts by mass. Made. The D50v of the core resin particles A2 was 220 nm.

[Preparation of resin particles A3 for core]
The amount of the solvent in the first-stage polymerization was 290 parts by mass, the amount of the solvent in the second-stage polymerization was 135 parts by mass, and the rotation speed of "Clearmix" in the first-stage polymerization and the second-stage polymerization was 7,000 rpm. The core resin particles A3 were produced in the same manner as in the core resin particles A1 except for the modification. The D50v of the core resin particles A3 was 210 nm.

[Preparation of resin particles A4 for core]
The amount of the solvent in the first-stage polymerization was 230 parts by mass, the amount of the solvent in the second-stage polymerization was 110 parts by mass, and the rotation speed of "Clearmix" in the first-stage polymerization and the second-stage polymerization was 10000 rpm. The core resin particles A4 were produced in the same manner as in the core resin particles A1 except for the modification. The D50v of the core resin particles A4 was 180 nm.

[Preparation of resin particles A5 for core]
The amount of the solvent in the first-stage polymerization was 195 parts by mass, the amount of the solvent in the second-stage polymerization was 90 parts by mass, and the rotation speed of "Clearmix" in the first-stage polymerization and the second-stage polymerization was 20000 rpm. The core resin particles A5 were produced in the same manner as in the core resin particles A1 except for the modification. The D50v of the core resin particles A5 was 120 nm.

[Preparation of resin particles A6 for core]
The amount of the solvent in the first-stage polymerization was 195 parts by mass, the amount of the solvent in the second-stage polymerization was 90 parts by mass, and the rotation speed of "Clearmix" in the first-stage polymerization and the second-stage polymerization was 21000 rpm. The core resin particles A6 were produced in the same manner as in the core resin particles A1 except for the modification. The D50v of the core resin particles A6 was 120 nm.

[Preparation of resin particles A7 for core]
The amount of the solvent in the first-stage polymerization was 450 parts by mass, the amount of the solvent in the second-stage polymerization was 210 parts by mass, and the rotation speed of "Clearmix" in the first-stage polymerization and the second-stage polymerization was 18,000 rpm. The core resin particles A7 were produced in the same manner as in the core resin particles A1 except for the modification. The D50v of the core resin particles A7 was 150 nm.

[Preparation of resin particles A8 for core]
The amount of the solvent in the first-stage polymerization was 50 parts by mass, the amount of the solvent in the second-stage polymerization was 20 parts by mass, and the rotation speed of "Clearmix" in the first-stage polymerization and the second-stage polymerization was 19000 rpm. The core resin particles A8 were produced in the same manner as in the core resin particles A1 except for the modification. The D50v of the core resin particles A8 was 150 nm.

[Preparation of resin particles A9 for core]
The amount of the solvent in the first-stage polymerization was 245 parts by mass, the amount of the solvent in the second-stage polymerization was 110 parts by mass, and the rotation speed of "Clearmix" in the first-stage polymerization and the second-stage polymerization was 19000 rpm. The core resin particles A9 were produced in the same manner as in the core resin particles A1 except for the modification. The D50v of the core resin particles A9 was 150 nm.

[Preparation of resin particles A10 for core]
The amount of the solvent in the first-stage polymerization was 40 parts by mass, the amount of the solvent in the second-stage polymerization was 20 parts by mass, and the rotation speed of "Clearmix" in the first-stage polymerization and the second-stage polymerization was 16000 rpm. The core resin particles A10 were produced in the same manner as in the core resin particles A1 except for the modification. The D50v of the core resin particles A10 was 150 nm.

[Preparation of resin particles A11 for core]
The amount of the solvent in the first-stage polymerization was 235 parts by mass, the amount of the solvent in the second-stage polymerization was 110 parts by mass, and the rotation speed of "Clearmix" in the first-stage polymerization and the second-stage polymerization was 16000 rpm. The core resin particles A11 were produced in the same manner as in the core resin particles A1 except for the modification. The D50v of the core resin particles A11 was 150 nm.

[Preparation of resin particles A12 for core]
The amount of the solvent in the first-stage polymerization was 195 parts by mass, the amount of the solvent in the second-stage polymerization was 90 parts by mass, and the rotation speed of "Clearmix" in the first-stage polymerization and the second-stage polymerization was 16000 rpm. The core resin particles A12 were produced in the same manner as in the core resin particles A1 except for the modification. The D50v of the core resin particles A12 was 150 nm.

[Preparation of resin particles A13 for core]
The core resin particles A1 except that no solvent was added to either the first-stage polymerization or the second-stage polymerization, and the rotation speed of the "Clearmix" in the first-stage polymerization and the second-stage polymerization was changed to 16000 rpm. The core resin particles A13 were produced in the same manner as in the production. The D50v of the core resin particles A13 was 150 nm.

[Preparation of resin particles 1 for shell]
In a reaction vessel equipped with a stirrer, a temperature sensor, a cooling tube, and a nitrogen introduction device, the above-mentioned surfactant solution 1 is stirred under a nitrogen stream at a stirring rate of 230 rpm to raise the internal temperature to 80 ° C. rice field. Then, an initiator aqueous solution 3 prepared by dissolving 10 parts by mass of potassium persulfate (KPS) in 400 parts by mass of ion-exchanged water was added to the surfactant solution 1, and the temperature of the obtained mixed solution was adjusted to 80 ° C. Then, the monomer mixed solution 3 containing the following components in the following amounts was added dropwise to the mixed solution over 2 hours.
Styrene 340 parts by mass n-Butyl acrylate 113 parts by mass Methacrylic acid 47 parts by mass n-octyl mercaptan 22 parts by mass

After dropping the above-mentioned monomer mixture 3, the polymerization reaction was carried out at 80 ° C. for 1.5 hours while stirring the obtained mixture at a stirring speed of 270 rpm, and then the obtained reaction solution was obtained. Was cooled to room temperature. In this way, the shell resin particles 1 dispersed in the reaction solution were produced. The volume-based D50v of the shell resin particles 1 was 160 nm.

[Preparation of resin particles 2 to 10 and 12 for shell]
The content of toluene in the monomer mixture 3 is 0 to 265 parts by mass, 150 parts by mass, 120 parts by mass, 105 parts by mass, 100 parts by mass, 235 parts by mass, 25 parts by mass, 125 parts by mass, 20 parts. Each of the shell resin particles 2 to 12 was produced in the same manner as in the production of the shell resin particles 1 except that the parts were changed to parts by mass and 233 parts by mass. The D50vs of the shell resin particles 2 to 10 and 12 were 220 nm, 210 nm, 180 nm, 130 nm, 130 nm, 130 nm, 130 nm, 130 nm, 130 nm and 130 nm, respectively.

[Preparation of resin particles 11 for shell]
The content of toluene in the monomer mixed solution 3 is changed from 0 parts by mass to 120 parts by mass, and 5 parts by mass of 1,10-decanediol diacrylate is further added to the monomer mixed solution 3 as a cross-linking agent. The shell resin particles 11 were produced in the same manner as in the production of the shell resin particles 1 except for the above. The D50v of the shell resin particles 11 was 130 nm.

[Preparation of cyan colorant particle dispersion]
11.5 parts by mass of sodium n-dodecyl sulfate was added to 160 parts by mass of ion-exchanged water, and the mixture was dissolved and stirred to prepare an aqueous surfactant solution. 25 parts by mass of "CI Pigment Blue 15: 3" was gradually added to this aqueous surfactant solution, and dispersed using "Clearmix W Motion CLM-0.8" (manufactured by M-Technique Co., Ltd.). The treatment was carried out to prepare a cyan colorant particle dispersion. The average particle size of the cyan colorant particles in the obtained cyan colorant particle dispersion was 98 nm at D50v.

[Preparation of toner particles 1]
The following components were put into a reaction vessel equipped with a stirrer, a temperature sensor, a cooling pipe, and a nitrogen introduction device in the following amounts and stirred. After adjusting the temperature in the reaction vessel to 30 ° C., a 5 mol / liter sodium hydroxide aqueous solution was added to the obtained dispersion to adjust the pH of the dispersion to 10.
1430 parts by mass of dispersion liquid of resin particles A1 for core (in terms of solid content)
Pure water 820 parts by mass Cyan colorant particle dispersion 70 parts by mass (solid content equivalent)

Next, an aqueous solution prepared by dissolving 200 parts by mass of magnesium chloride hexahydrate in 1000 parts by mass of pure water was added dropwise to the dispersion liquid at 30 ° C. for 10 minutes under stirring. After the dropping was completed, the temperature was started while stirring, and the temperature of the dispersion was raised to 75 ° C. to aggregate and fuse the particles in the dispersion.

At this time, the particle size of the agglomerated particles in the dispersion was measured with "Multisizer 3" (manufactured by Beckman Coulter), and "FPIA-2100" (manufactured by Sysmex Co., Ltd., "FPIA" is a registered trademark of the same company) was used. The above aggregation and fusion were performed while measuring the average circularity of the particles in the dispersion liquid. Then, when the volume-based median diameter D50v of the agglomerated particles reaches 6.3 μm, an aqueous solution prepared by dissolving 40 parts by mass of sodium chloride in 500 parts by mass of pure water is added to the dispersion liquid to stop the agglomeration of the particles. Subsequently, the temperature of the dispersion was maintained at 75 ° C., and the agglomerated particles were aged.

When the average circularity of the agglomerated particles reaches 0.87, 180 parts by mass (solid content equivalent) of the dispersion liquid of the above-mentioned "resin resin particles for shell 1" is added to the dispersion liquid to agglutinate and fuse. Was continued.

Subsequently, the temperature of the dispersion liquid was maintained at 75 ° C. to continue the aggregation and fusion of the particles, a small amount of the dispersion liquid was taken out from the reaction vessel, and the dispersion was centrifuged by a centrifuge to obtain a supernatant. After confirming that the particles became transparent, the aging was continued. Then, when the average circularity of the particles in the dispersion liquid reached 0.95, the dispersion liquid was cooled to room temperature. After cooling, the particles in the dispersion were filtered, and the particles were washed by repeating washing with pure water and filtration, and then dried with warm air at 35 ° C. In this way, colored particles 1 having a core-shell structure, which are the base particles of the toner, were produced.

When the particle size D50v of the colored particles 1 was determined using the “multisizer 3” as described above, it was 6.3 μm. Further, the pore diameter Dh of the voids of the colored particles 1 was determined from the above-mentioned image analysis apparatus for 10 colored particles 1 in the magnified image by the transmission electron microscope and the scanning probe microscope in the above-mentioned measurement region. It was 192 nm. Further, when the abundance ratio Rh of the voids of the colored particles 1 was calculated from the above formula, it was 51%.

Toner particles 1 were prepared by adding the following external additives to the colored particles 1 and performing an external additive treatment in which they were mixed with "Henschel Mixer" (manufactured by Nippon Coke Industries, Ltd.). The external additive treatment with the Henschel mixer is a peripheral speed of the stirring blade of 35 m / sec, a treatment temperature of 35 ° C., and a treatment time of 15 minutes. The "surface-treated silica particles" below are hexamethylsilazane-treated silica particles, and the "surface-treated titanium oxide particles" are n-octylsilane-treated titanium dioxide particles.
Surface-treated silica particles (average primary particle size 12 nm) 0.6 parts by mass Surface-treated titanium oxide particles (average primary particle size 24 nm) 0.8 parts by mass

[Preparation of toner particles 2-11]
The dispersions of the core resin particles A2 to A11 are used instead of the dispersions of the core resin particles A1, and the dispersions of the shell resin particles 2 to 11 are used instead of the dispersions of the shell resin particles 1. Each of the colored particles 2 to 11 was prepared and each of the toner particles 2 to 11 was prepared in the same manner as in the production of the toner particles 1 except that they were used.

The D50v of the colored particles 2 was 6.7 μm, the Dh was 190 nm, and the Rh was 53%. The D50v of the colored particles 3 was 6.7 μm, the Dh was 175 nm, and the Rh was 30%. The D50v of the colored particles 4 was 6.7 μm, the Dh was 90 nm, and the Rh was 24%. The D50v of the colored particles 5 was 6.7 μm, the Dh was 5 nm, and the Rh was 20%. The D50v of the colored particles 6 was 6.6 μm, the Dh was 4 nm, and the Rh was 20%. The D50v of the colored particles 7 was 6.9 μm, the Dh was 12 nm, and the Rh was 47%. The D50v of the colored particles 8 was 6.9 μm, the Dh was 10 nm, and the Rh was 5%. The D50v of the colored particles 9 was 6.9 μm, the Dh was 10 nm, and the Rh was 25%. The D50v of the colored particles 10 was 6.9 μm, the Dh was 20 nm, and the Rh was 4%. The D50v of the colored particles 11 was 7.0 μm, the Dh was 20 nm, and the Rh was 24%.

[Preparation of toner particles 12]
Colored particles 12 are used in place of the dispersion of the core resin particles A1 and the dispersion of the core resin particles A12 is used in the same manner as in the production of the toner particles 1 except that the dispersion of the “shell resin particles 1” is not added. Toner particles 12 were prepared. The D50v of the colored particles 12 was 6.3 μm, the Dh was 20 nm, and the Rh was 20%.

[Preparation of toner particles 13]
Preparation of toner particles 1 except that the dispersion liquid of the core resin particles A13 is used instead of the dispersion liquid of the core resin particles A1 and the dispersion liquid of the shell resin particles 12 is used instead of the dispersion liquid of the shell resin particles 1. In the same manner as above, the colored particles 13 were produced, and the toner particles 13 were produced. The D50v of the colored particles 13 was 6.8 μm, the Dh was 20 nm, and the Rh was 14%.

When the variation Vh of the abundance ratio of the voids of the colored particles 1 to 13 was determined, it was 1% or less in each case. The above Vh is the maximum value of the difference obtained by subtracting the value of the abundance ratio of the voids in each measurement region from the numerical value of the abundance ratio of the voids for each of the colored particles 1 to 13. However, in the colored particles 13, voids were not substantially observed in the core particles, and Dh, Rh and Vh of the colored particles 13 were determined from the observation results of the shell layer.

The production conditions of the toner particles 1 to 13 are shown in Table 1, and the properties of the toner particles 1 to 13 and the colored particles 1 to 13 are shown in Table 2, respectively.

[Preparation of developing agents 1 to 13]
Carrier particles having an average particle size of 35 μm, which are ferrite particles coated with styrene-acrylic resin, and toner particles 1 to 13 are mixed and treated, and the (two-component) developer 1 to 8% by mass has a toner concentration. 13 were prepared respectively.

[evaluation]
As an image forming apparatus, a modified machine of "bizhub PRO C6500" (manufactured by Konica Minolta Co., Ltd., "bizhub" is a trademark of the company) was prepared. As shown in FIG. 3, the image forming apparatus 300 has a document image reading apparatus SC, an image forming portion, and a fixing apparatus 50 similar to those of the image forming apparatus 200 described above, and conveys a roll-shaped recording medium P. It has a configuration in which the recording medium on which the toner image is formed can be rolled up and accommodated while being able to be supplied to the route.

(1) Image resistance to bending (bending durability)
For each of the developing agents 1 to 13, a transparent polyethylene terephthalate film having a thickness of 40 μm was used as a recording medium using the above-mentioned remodeling machine, and ^{a solid image having an adhesion amount of 8 g / m 2} was formed on the film.

As shown in FIG. 4, the image portion of the film (F) having the fixed image of the toner is bent to 90 ° along the outer peripheral surface of the cylinder 40 having a diameter of 1.5 mm, and then straightened (up to 180 °). Stretching The bending and stretching movement of the image part is repeated 500 times, 1000 times, and 1500 times, and at each of these times, the image of the image part is displayed as "JK Wiper" (Nippon Paper Crecia Co., Ltd., Kimberly-Clark Worldwide Incorporated). The presence or absence of peeling of the image in the above-mentioned image portion, which was rubbed with a load of 3 kgf (29.4 N) and repeatedly subjected to bending and stretching exercises, was confirmed and evaluated according to the following criteria. ◎, ○, and △ are levels that do not cause practical problems, and × indicates that there are problems in practical use.
×: Image peeling occurs at 500 times Δ: Image peeling does not occur at 500 times, image peeling occurs at 1000 times ○: Image does not peel at 1000 times, and image peels at 1500 times Peeling occurs ◎: No image peeling even at 1500 times

(2) Addition resistance test evaluation (addition durability)
For the developing agents 1 to 13, a solid image having ^{a toner adhesion amount of 11 g / m 2} was developed on A4 size high-quality paper in an environment of normal temperature and humidity (temperature 20 ° C., humidity 50% RH) using the above-mentioned remodeling machine. .. Then, the unfixed toner image on the high-quality paper was fixed on the high-quality paper in an environment of 10 ° C./10% RH at a temperature of 170 ° C. of the fixing heat roller to form a toner image.

Next, a sheep pen containing a 0.5 mm shape pen core was attached to the following load-variable friction and wear tester, a load of 200 g was applied to a mechanical pencil, and five 10 cm straight lines were drawn on the solid image under the following conditions. Painted. Then, the state of peeling of the toner image of the added portion (straight portion) and its surroundings was evaluated by the following three-stage evaluation criteria. Ranks 3 and 2 are levels where there is no practical problem, and rank 1 has practical problems.
(conditions)
Equipment: HEIDON Tribo Gear 18L Scratch Strength Tester (manufactured by Shinto Kagaku Co., Ltd.)
Sharp replacement core: "Uni NanoDia" (manufactured by Mitsubishi Pencil Co., Ltd., thickness 0.5 mm, HB, black)
Scratch speed: 200 mm / min (evaluation standard)
Rank 3: No peeling of the toner image Rank 2: Peeling of the toner image occurs, but there is no problem as an image Rank 1: Peeling of the toner image occurs, and the underlying paper is exposed due to the peeling of the toner image in the retouched part. do

As shown in Table 3, the fixing toner images formed by the developing agents 1 to 11 have sufficiently good bending durability and retouching durability.

On the other hand, the fixing toner image formed by the developer 12 has insufficient bending durability and retouching durability. This is because the voids are dispersed in the toner particles, but the toner particles do not have a core-shell structure. Therefore, when the toner image is fixed, the voids are expelled from the toner image or are unevenly distributed and scattered. This is probably because the flexibility of the toner image is not sufficiently expressed.

Further, the fixing toner image formed by the developer 13 has insufficient retouching durability. This is because although the toner particles have a core-shell structure, the voids are scattered only in the shell of the toner particles, so that the above-mentioned voids in a sufficient amount to exhibit the flexibility of the toner image due to the scattered voids are fixed. This is probably because it is not introduced in the toner image.

According to the present invention, a highly flexible toner image can be formed on a recording medium in an electrophotographic full-color image. Therefore, according to the present invention, further widespread use of image formation in the electrophotographic method is expected.

1 Photoreceptor 2 Charging device 3 Exposure device 4 Developing device 5 Primary transfer roller 6, 10 Cleaning device 7 Intermediate transfer belt 8 Roller 9 Secondary transfer roller 11 Paper feed cassette 12 Paper feed roller 13 Transfer roller 14 Resist roller 15 Discharge roller 16 Paper ejection tray 40 Cylindrical 100 Toner matrix particles 110 Core particles 120 Shell layer 200, 300 Image forming device F film P Recording medium SC Original image reading device

Claims (6)

A toner for developing an electrostatic charge image, which contains a toner base particle having a core particle containing a first binder resin and a shell layer containing a second binder resin covering the surface thereof.
The first binder resin contains a styrene-acrylic resin and contains.
The core particles have ubiquitous pores and
The pores include pores containing at least one organic solvent selected from the group consisting of aromatic hydrocarbons and fatty acid esters existing inside the styrene-acrylic resin.
The average pore diameter of the pores is 4 to 192 nm.
The abundance ratio of the pores in the toner matrix particles is 5 to 50%.
The shell layer may be ubiquitous, with a hole for containing the organic solvent, toner. A toner for developing an electrostatic charge image, which contains a toner base particle having a core particle containing a first binder resin and a shell layer containing a second binder resin covering the surface thereof.
The first binder resin contains a styrene-acrylic resin and contains.
The core particles have ubiquitous pores and
The pores include pores containing at least one organic solvent selected from the group consisting of aromatic hydrocarbons and fatty acid esters existing inside the styrene-acrylic resin.
The average pore diameter of the pores is 4 to 192 nm.
The abundance ratio of the pores in the toner matrix particles is 2 to 25%.
The shell layer is a toner having ubiquitous pores containing the organic solvent. The toner according to claim 1 or 2 , wherein the average pore diameter of the pores is 5 to 180 nm. The toner according to claim 3 , wherein the average pore diameter of the pores is 5 to 100 nm. The toner according to any one of claims 1 to 4 , wherein one or both of the first binder resin and the second binder resin has a crosslinked structure. In an electrophotographic image forming method in which an unfixed toner image formed by toner on a recording medium is fixed to the recording medium to form an image.
An image forming method using the toner according to any one of claims 1 to 5 as the toner.

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