JP2009204669A - Toner for developing electrostatic image and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide toner for developing electrostatic image having excellent heat resisting storage properties while maintaining excellent low-temperature fixability, and to provide a method of manufacturing the same. <P>SOLUTION: In this toner for developing electrostatic image of a core shell structure having a shell on the surface of a core containing at least resin and a coloring agent, the 8-point average film thickness of the shell is 100 to 300 nm, and when the maximum film thickness of the shell is Hmax and the minimum film thickness is Hmin, the ratio of them: Hmax/Hmin is under 1.50. When the glass transition temperature of the core part is Tg1 and the glass transition temperature of the shell part is Tg2, 30C°≤Tg1≤40°C, and 45C°≤Tg2≤55°C, and the heat resistance index is ≤20%. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a toner for developing an electrostatic image having a core / shell structure (hereinafter also simply referred to as “toner”) and a method for producing the same.

  As energy saving progresses, in the electrophotographic technology, in order to reduce power consumption and to perform high-speed printing, reduction in energy (fixing at a low temperature) of a fixing device has been attempted in recent years.

  However, the thermal stability of the toner has decreased with the low-temperature fixing, and the heat-resistant storage property during storage and transportation has not been sufficient. On the other hand, it has been insufficient to maintain stable chargeability for a long period of time by exposing components such as a colorant and a release agent from the toner surface.

  In order to solve these problems, a technique for improving toner performance by using a so-called core-shell structure having a structure in which the toner surface is coated with a resin has been proposed (for example, Patent Documents 1 and 2). reference).

However, in order to ensure heat-resistant storage by the core-shell structure, it is necessary to increase the thickness of the shell so that the core resin with a low softening point does not flow out due to heat. There was a problem that the low-temperature fixability deteriorated.
JP 2004-191618 A JP 2004-271638 A

  The present invention has been made in view of the above-mentioned problems, and the problem to be solved is a toner for developing an electrostatic charge image having a core / shell structure, which maintains excellent low-temperature fixability and is resistant to heat and storage. An object is to provide an excellent toner for developing an electrostatic image. Moreover, it is providing the manufacturing method.

  The above-mentioned problem according to the present invention is solved by the following means.

  1. An electrostatic charge image developing toner having a core-shell structure having a shell on the surface of a core containing at least a resin and a colorant, wherein the shell has an 8-point average film thickness of 100 to 300 nm, and the maximum of the shell When the film thickness is Hmax and the minimum film thickness is Hmin, the ratio of both: Hmax / Hmin is less than 1.50, the glass transition temperature of the core part is Tg1, and the glass transition temperature of the shell part is Tg2. The toner for developing an electrostatic charge image is characterized in that 30 ° C. ≦ Tg 1 ≦ 40 ° C., 45 ° C. ≦ Tg 2 ≦ 55 ° C., and the heat resistance index is 20% or less.

  2. When the solubility parameter of the resin constituting the core is SP1, and the solubility parameter of the resin constituting the shell is SP2, the difference between SP1 and SP2 is 0.2 to 1.0. The toner for developing an electrostatic charge image according to 1.

  3. 3. The above 1 or 2, characterized in that Tg2−Tg1 ≧ 10 ° C. when the glass transition temperature of the resin constituting the core is Tg1 and the glass transition temperature of the resin constituting the shell is Tg2. Toner for developing electrostatic images.

  4). 4. The core according to any one of 1 to 3, wherein the core is formed by aggregating resin particles and colorant particles, and the shell is formed by coating the surface of the core with resin. Toner for developing electrostatic images.

  5). 4. The method for producing an electrostatic charge image developing toner according to any one of 1 to 3 above, wherein the resin particles and the colorant particles are aggregated to produce a core having a circularity of 0.900 or more. And an electrostatic charge image developing toner having a core / shell structure through a step of forming a shell by adding resin fine particles to the surface of the core, and a method for producing the electrostatic charge image developing toner, .

  By means of the above-mentioned means of the present invention, it is possible to provide an electrostatic image developing toner having excellent heat resistance and storage stability while maintaining excellent low-temperature fixability in the electrostatic image developing toner having a core-shell structure. Moreover, the manufacturing method can be provided.

  That is, in the present invention, by the above-described means, a uniform shell (layer) having a small thickness and no unevenness is formed, so that low temperature fixability can be achieved even for core particles having a low glass transition temperature (Tg). It is possible to ensure heat-resistant storage without lowering.

  The toner for developing an electrostatic charge image of the present invention is a toner for developing an electrostatic charge image having a shell on the surface of a core containing at least a resin and a colorant, and the shell has an eight-point average film thickness. When the maximum film thickness of the shell is Hmax and the minimum film thickness is Hmin, the ratio of both: Hmax / Hmin is less than 1.50, and the core portion (core-shell structure) When the glass transition temperature of the core part) is Tg1 and the glass transition temperature of the shell part (shell part in the core-shell structure) is Tg2, 30 ° C. ≦ Tg 1 ≦ 40 ° C., 45 ° C. ≦ Tg 2 ≦ 55 ° C. The heat resistance index is 20% or less. This feature is a technical feature common to the inventions according to claims 1 to 5.

  As an embodiment of the present invention, when the solubility parameter of the resin constituting the core is SP1, and the solubility parameter of the resin constituting the shell is SP2, the difference between SP1 and SP2 is 0.2 to 1.0. Some embodiments are preferred. Furthermore, it is preferable that Tg2−Tg1 ≧ 10 ° C. when the glass transition temperature of the resin constituting the core is Tg1 and the glass transition temperature of the resin constituting the shell is Tg2.

  In the present invention, the core is preferably formed by aggregating resin particles and colorant particles, and the shell is formed by coating the surface of the core with resin.

  The method for producing a toner for developing an electrostatic charge image of the present invention comprises a step of agglomerating resin particles and colorant particles to produce a core having a circularity of 0.900 or more, and resin fine particles on the surface of the core. It is preferable that the production method is such that the toner for developing an electrostatic charge image having a core / shell structure is produced through a step of adding and forming a shell.

  Hereinafter, the present invention, its components, and the best mode and mode for carrying out the present invention will be described in detail.

(Outline of configuration and structure of toner for developing electrostatic image of the present invention)
The toner for developing an electrostatic charge image of the present invention is a toner for developing an electrostatic charge image having a core-shell structure having a core and a shell satisfying the above specific conditions. The structure and structure containing a component can be taken.

  A preferred embodiment is a constitutional embodiment containing a binder resin, a colorant, a wax and the like. As a structure, the core and the shell must satisfy the above conditions. However, it is not limited to these aspects.

  Hereinafter, each component of the electrostatic image developing toner having a typical core-shell structure will be described in detail.

(Core shell structure)
In the toner for developing an electrostatic charge image of the present invention, a toner having a stable chargeability, which has both low-temperature fixing property and heat-resistant storage property by forming a thin shell with a core-shell structure uniformly. It is necessary to.

  Therefore, the electrostatic image developing toner of the core-shell structure of the present invention has an 8-point average film thickness of the shell of 100 to 300 nm, the maximum film thickness of the shell is Hmax, and the minimum film thickness is Hmin. When the ratio of both: Hmax / Hmin is less than 1.50, the glass transition temperature of the core part is Tg1, and the glass transition temperature of the shell part is Tg2, 30 ° C. ≦ Tg 1 ≦ 40 ° C. 45 ° C. ≦ Tg2 ≦ 55 ° C. and the heat resistance index needs to be adjusted to 20% or less.

  As an embodiment of the present invention, when the solubility parameter of the resin constituting the core is SP1, and the solubility parameter of the resin constituting the shell is SP2, the difference between SP1 and SP2 is 0.2 to 1.0. It is preferable to have a certain aspect.

  Furthermore, it is preferable that Tg2−Tg1 ≧ 10 ° C. when the glass transition temperature of the resin constituting the core is Tg1 and the glass transition temperature of the resin constituting the shell is Tg2.

  As will be described later, the core particles are preferably prepared so that the circularity of the core particles is 0.900 or more.

  Hereinafter, the method for forming the shell will be described in detail.

[Method for forming uniform shell]
Specific methods for forming a uniform shell, that is, factors that control the formation of the shell include the following. These factors will be described in detail later. That is,
(1) Glass transition temperature and solubility parameter of resin constituting core and shell (2) Circularity of core particle Among these, the glass transition temperature and solubility parameter of resin constituting the core and shell are the same in the toner of the present invention. It is preferable to form a structure in which the core and the shell are hardly compatible with each other. That is, by selecting a resin that forms the core region and a resin that forms the shell region, a toner having a structure in which the core region and the shell region are phase-separated can be obtained. It is possible to produce a toner having excellent heat-resistant storage property that is not exposed on the toner surface.

  As for the circularity of the core particles, for example, if the core particles have a high circularity, the specific surface area is small and the surface properties are uniform. It becomes easy to adhere uniformly, and it becomes easy to produce a toner having a uniform thickness.

  The average film thickness of the shell is required to be 100 to 300 nm from the viewpoints of both the heat dependency of the core particles having the characteristic of low glass transition temperature (Tg) and low temperature fixability. Further, in a toner having a thin shell with an average film thickness of 100 to 300 nm, the ratio (Hmax / Hmin) between the maximum film thickness Hmax and the minimum film thickness Hmin of the shell is less than 1.50. Necessary from a viewpoint.

[Measurement method of 8-point average film thickness of shell]
The film thickness of the shell in the toner having the core-shell structure is measured from a photograph obtained by photographing the cross-sectional layer of the toner with a transmission electron microscope. As a transmission electron microscope, a model well known to those skilled in the art is usually sufficiently observed. For example, LEM-2000 type (Topcon Corporation), JEM-2000FX (JEOL Ltd.) and the like are used.

  Specifically, the toner particles are first sufficiently dispersed in a room temperature curable epoxy resin, then embedded, dispersed in styrene fine powder having a particle size of about 100 nm, and then subjected to pressure molding. After the necessary blocks were dyed with ruthenium tetroxide or osmium tetroxide, a flaky sample was cut out using a microtome with diamond teeth, and a transmission electron microscope (TEM) was used. Then, the photograph is taken at a magnification (about 10,000 times) in which the cross section of one toner enters the field of view.

  Next, in the above photograph, the boundary line that becomes the interface between the core particle and the shell is clarified while visually confirming the existence region of the colorant, wax, and the like.

  Next, as shown in FIG. 1, straight lines are drawn toward the surface at 45 ° intervals from the center of gravity C of the toner particles, A is a point where each straight line intersects the core particle surface, and B is a point where the straight line intersects the shell surface. The distance (that is, the thickness of the shell) is measured at eight points, and the average value of the eight points is defined as the thickness of the shell of one toner particle.

  Further, the maximum shell film thickness (Hmax) and the minimum shell film thickness (Hmin) in one toner particle are extracted, and Hmax / Hmin is calculated.

  In the present application, “Hmax / Hmin” is an average value of Hmax / Hmin in 100 toner particles. The “eight point average film thickness” is an average value of eight point average film thicknesses for 100 toner particles.

  If the minimum thickness of the shell is as close to 0 as possible, the thickness is measured as 10 nm.

  Further, it is necessary that (Hmax / Hmin) of 80% or more of toner particles in 100 toner particles is less than 1.50. Preferably, it is 1.05-1.50, More preferably, it is 1.05-1.40.

[Method of forming a shell having a uniform film thickness]
As described above, in order to form a uniform shell for the low Tg core, the following three means can be mentioned. Hereinafter, the resin constituting the core is simply abbreviated as “resin constituting”.

  (1) Widen Tg difference and SP value difference between core and shell.

  When the glass transition temperature of the core is Tg1 and the glass transition temperature of the shell is Tg2, it is preferable that Tg2-Tg1 ≧ 10 ° C., more preferably Tg2-Tg1 ≧ 20 ° C.

  Further, when the value of the solubility parameter of the core is SP1 and the value of the solubility parameter of the shell is SP2, the difference (ΔSP) between SP1 and SP2 is preferably 0.2 to 1.0, more preferably 0. 25-0.95 is good.

  (2) Shelling after enhancing the circularity of the core particles.

  Shelling is started after increasing the circularity of the core particles to 0.900 or more.

  Hereinafter, the above (1) and (2) will be described in more detail.

[Glass transition temperature Tg]
In the toner of the present invention, when the glass transition temperature of the resin forming the core portion is Tg1 and the glass transition temperature of the resin forming the shell is Tg2, 30 ° C. ≦ Tg 1 ≦ 40 ° C., 45 ° C. ≦ Tg 2 ≦ 55 ° C. It needs to be. More preferably, they are 32 degreeC <= Tg1 <= 37 degreeC and 47 degreeC <= Tg2 <= 52 degreeC.

  Moreover, it is preferable that it is Tg2-Tg1> = 10 degreeC. More preferably, 25 ° C. ≧ Tg 2 −Tg 1 ≧ 10 ° C.

  The glass transition temperature of the resin forming the core and the resin forming the shell can be controlled by appropriately selecting the type, amount and molecular weight of the polymerizable monomer forming the copolymer. The method for adjusting the glass transition temperature is, for example, selecting the type of polymerization monomer of the resin that constitutes the shell and the resin that constitutes the core from the compounds described later, and the glass transition temperature of both falls within the above range. This is possible by adjusting the ratio and molecular weight. However, the exemplified compounds clearly show the means for accomplishment and are not limited to these.

  As a method for calculating the glass transition temperature, the following theoretical glass transition temperature may be calculated in the present invention. Here, the theoretical glass transition temperature is calculated by multiplying the glass transition temperature when each component constituting the copolymer resin forms a homopolymer by each composition mass fraction, that is, by weighted averaging. is there. That is, the theoretical glass transition temperature Tg (referred to as absolute temperature Tg ′) is calculated from the following formula (1) using the glass transition temperature of the homopolymer of the component constituting the copolymer resin.

Formula (1)
1 / Tg ′ = W1 / T1 + W2 / T2 +... + Wn / Tn
(Wherein W1, W2,... Wn is the mass fraction of each polymerizable monomer with respect to the total polymerizable monomer constituting the copolymer resin, and T1, T2,... Tn are each polymerizable. (The glass transition temperature (absolute temperature) of a homopolymer formed using a monomer is shown.)
The glass transition temperature can be measured using a DSC-7 differential scanning calorimeter (Perkin Elmer) and a TAC7 / DX thermal analyzer controller (Perkin Elmer).

  As a measurement procedure, 4.5 to 5.0 mg of toner is precisely weighed to 2 digits after the decimal point, sealed in an aluminum pan (KITNO.0219-0041), and set in a DSC-7 sample holder.

  The reference used an empty aluminum pan. As measurement conditions, the measurement temperature is 0 to 200 ° C., the temperature increase rate is 10 ° C./min, the temperature decrease rate is 10 ° C./min, and the heat-cool-heat control is performed, and the analysis is performed based on the data in the 2nd Heat. went.

  The glass transition temperature draws an extension of the baseline before the rise of the first endothermic peak and a tangent line indicating the maximum slope between the rise of the first peak and the peak apex, and the intersection is taken as the glass transition point. Show.

[Solubility parameter value]
In the present invention, it is preferable that the resin forming the shell in the toner is not compatible with the resin of the core portion, and the resin forming the shell has sufficient adhesiveness with the core portion.

  In order for the resin forming the shell to exhibit incompatibility with the core portion, the solubility parameter value of the resin forming the shell (hereinafter referred to as “SP value”) and the solubility of the resin forming the core portion. This is achieved by setting the difference in parameter values within an appropriate range.

  The solubility parameter value (SP value) is a numerical value representing the magnitude of the cohesive energy of a substance. According to the method proposed by Ferors, “Polym. Eng. Sci., Vol 14, P 147 (1974)”, evaporation of atoms or atomic groups When the energy and the molar volume are Δer and Δvi, respectively, the solubility parameter σ of the binder resin is calculated by the following formula (2).

Formula (2)
σ = (ΣΔer / ΣΔvi) ^1/2
Moreover, the solubility parameter value of each vinyl copolymer is calculated by the product of the solubility parameter value of each component and the molar ratio. For example, assuming that the copolymer resin is composed of two types of monomers, X and Y, the mass composition ratio of each monomer is x, y (mass%), the molecular weight is Mx, My, When the solubility parameter values are SPx and SPy, the monomer ratios are X / Mx (mol%) and y / My (mol%). Here, when the molar ratio of the copolymer resin is C, it is expressed as C = x / Mx + y / My, and the solubility parameter value SP of the copolymer resin is represented by the following formula (3).

Formula (3)
SP = [(x × SPx / Mx) + (y × Spy / My)] × 1 / C
The solubility parameter value can be controlled by changing the composition ratio of the monomers constituting the vinyl copolymer. For example, in the case of a copolymer resin formed using styrene and methyl methacrylate. It has been confirmed that the solubility parameter value tends to decrease by decreasing the composition ratio of styrene and increasing the composition ratio of methyl methacrylate.

  In addition, for an overview of the solubility parameter of the polymer material, the solubility parameter item described in the database PolyInfo (http://polymer.nims.go.jp) provided by the National Institute for Materials Science (http://polymer.nims.go.jp) http://polymer.nims.go.jp/guide/guide/p5110.html).

  In the present invention, the solubility parameter value of the resin contained in the core part and the shell exhibits stable incompatibility when the difference between the shell and the core part is 0.1 or more, preferably 0. It is better to make it in the range of 2 to 0.8.

[Measurement method of circularity of core particles for toner]
The circularity is a value measured using “FPIA-2100” (manufactured by Sysmex Corporation). Specifically, the core particles are blended with an aqueous solution containing a surfactant, and after ultrasonic dispersion for 1 minute, the dispersion is performed. Then, using “FPIA-2100”, in the measurement condition HPF (high magnification imaging) mode, HPF Measurement is performed at an appropriate concentration of 3000 to 10,000 detections. Within this range, reproducible measurement values can be obtained. The circularity is a value defined by the following formula.

Circularity = (perimeter of a circle having the same area as the particle projection image) / (perimeter of the particle projection image)
The average circularity is a value calculated by adding the circularity of each particle and dividing by the total number of particles.

  The higher the degree of circularity after the core particles are formed, the better, and 0.900 or more is preferable. When the circularity is 0.900 or more, it becomes easier to produce a shell having a higher uniformity of the shell film thickness than a lower one. However, if the circularity is extremely increased, industrial productivity and the like are lowered. Therefore, when other conditions are taken into consideration, the circularity after core particle formation is more preferably in the range of 0.900 to 0.930.

  The present invention eliminates the difference in the release property of the release agent caused by the thickness of the shell, but by fixing the circularity in the range of 0.900 to 0.930, the fixing is performed at a temperature lower than that in the past. Even when performing, the offset resistance is good and it is possible to avoid the occurrence of winding. Furthermore, since the release agent in the core can be eluted evenly, a stable fixing process is realized.

[Softening point Tsp]
A method for measuring the softening point of the toner of the present invention will be described.

Temperature: 20 ± 1 ° C., relative humidity: 50 ± 5% In an RH environment, 1.1 g of toner is placed in a petri dish, leveled, and allowed to stand for 12 hours or more, then a molding machine SSP-A (manufactured by Shimadzu Corporation) And pressurizing with a force of 3.75 × 10 ⁸ Pa (3820 kg / cm ² ) for 30 seconds to produce a circular shaped sample with a diameter of 1 cm.

  Temperature: 24 ± 5 ° C., relative humidity: 50 ± 20% RH environment, flow tester CFT-500D (manufactured by Shimadzu Corporation) is used to load the molded sample with a load of 196 N (20 kgf), a starting temperature of 60 ° C., and a preheating time of 300 seconds. Extruding from the end of the preheating using a 1 cm diameter piston through a hole in the cylindrical die (1 mm × 1 mm) under the condition of a heating rate of 6 ° C./min, and an offset value of 5 mm by the melting temperature measuring method of the heating method The offset method temperature Toffset measured with the setting of was used as the softening point of the toner.

[Heat resistance index]
The toner for developing an electrostatic image of the present invention has a heat resistance index of 20% or less.

  In the present application, the “heat resistance index” refers to agglomerates remaining on the sieve after 100 g of toner is left to stand for 24 hours under conditions of a temperature of 55 ° C. and a relative humidity of 90% RH, and sieved with a sieve having an opening of 45 μm. The amount (ratio: mass%). Therefore, the lower the heat resistance index, that is, the fewer the aggregates, the better the heat resistant storage property. The heat resistance index is adjusted by controlling the thickness and uniformity of the shell as described above.

(Binder resin)
In the electrostatic image developing toner of the present invention, the resin forming the core and the resin forming the shell are preferably styrene-acrylic copolymer resins.

  The monomer that forms the resin that forms the core is copolymerized with a polymerizable monomer that lowers the glass transition temperature (Tg) of a copolymer such as propyl acrylate, propyl methacrylate, butyl acrylate, and 2-ethylhexyl acrylate. It is preferable to do.

  It is preferable to copolymerize the monomer which produces resin which forms a shell with the polymerizable monomer which raises the glass transition temperature (Tg) of copolymers, such as styrene, methyl methacrylate, and methacrylic acid.

  As the resin used for each of the core and shell structures of the toner for developing an electrostatic charge image of the present invention, a polymer obtained by polymerizing the following polymerizable monomers can be used.

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

  Further, it is more preferable to use a combination of monomers having an ionic dissociation group as the polymerizable monomer constituting the 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, multifunctional 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.

  In the electrostatic image developing toner of the present invention, a radically polymerizable monomer having a polyvalent carboxylic acid component, which is a polymerizable monomer containing at least two or more carboxylic acid components (carboxyl groups) in the side chain It is also preferable to contain a polymer such as a vinyl polymer formed by polymerizing as a part of the resin forming the core.

  In addition, it is preferable that the content rate of the radically polymerizable monomer which has a polyvalent carboxylic acid component in the polymerizable monomer composition which forms a core is 3-20 mass%, More preferably, it is 5-10 mass. %.

(Coloring agent)
As the colorant used in the toner for developing an electrostatic charge image of the present invention, carbon black, a magnetic material, a dye, a pigment, and the like can be arbitrarily used. As the carbon black, channel black, furnace black, acetylene black, thermal black can be used. Lamp black or the like is used. Magnetic materials include ferromagnetic metals such as iron, nickel and cobalt, alloys containing these metals, compounds of ferromagnetic metals such as ferrite and magnetite, alloys that do not contain ferromagnetic metals but exhibit ferromagnetism by heat treatment, For example, a kind of alloy called Heusler alloy such as manganese-copper-aluminum, manganese-copper-tin, chromium dioxide, or the like can be used.

  As the dye, C.I. I. Solvent Red 1, 49, 52, 58, 63, 111, 122, C.I. I. Solvent Yellow 19, 44, 77, 79, 81, 82, 93, 98, 103, 104, 112, 162, C.I. I. Solvent Blue 25, 36, 60, 70, 93, 95 etc. can be used, and a mixture thereof can also be used. Examples of the pigment include C.I. I. Pigment Red 5, 48: 1, 53: 1, 57: 1, 122, 139, 144, 149, 166, 177, 178, 222, C.I. I. Pigment Orange 31 and 43, C.I. I. Pigment Yellow 14, 17, 93, 94, 138, 156, 158, 180, 185, C.I. I. Pigment green 7, C.I. I. Pigment Blue 15: 3, 60, etc. can be used, and a mixture thereof can also be used. The number average primary particle size varies depending on the type, but is preferably about 10 to 200 nm.

  As a method for adding the colorant, the resin fine particles are added at the stage of agglomeration by the addition of the flocculant to color the polymer. The colorant can be used by treating the surface with a coupling agent or the like.

(Wax (release agent))
Examples of the wax that can be used in the toner for developing an electrostatic image of the present invention include conventionally known waxes. Specifically, polyolefin waxes such as polyethylene wax and polypropylene wax, long-chain hydrocarbon waxes such as paraffin wax and sazol wax, dialkyl ketone waxes such as distearyl ketone, carnauba wax, montan wax, and trimethylolpropane. Tribehenate, pentaerythritol tetramyristate, pentaerythritol tetrastearate, pentaerythritol tetrabehenate, pentaerythritol diacetate dibehenate, glycerin tribehenate, 1,18-octadecanediol distearate, trimellit Ester waxes such as acid tristearyl and distearyl maleate, ethylenediamine dibehenyl amide, trimellitic acid tristearyl amide, etc. Such as amide waxes.

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

(Charge control agent)
A charge control agent can be added to the electrostatic charge image developing toner of the present invention, if necessary. A known compound can be used as the charge control agent.

(External additive)
In the toner for developing an electrostatic image of the present invention, in order to improve fluidity, chargeability, cleaning properties, etc., external additives such as so-called post-treatment agents such as fluidizing agents and cleaning aids (“external additives” May also be added.

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

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

  Further, as the external additive, spherical organic fine particles having a number average primary particle diameter of about 10 to 2000 nm can be used. As such organic fine particles, polymers such as polystyrene, polymethyl methacrylate, and styrene-methyl methacrylate copolymer can be used.

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

  The polymerization initiator, chain transfer agent, dispersion stabilizer, surfactant, and aggregating agent that can be used in the toner production method will be described.

(Radical polymerization initiator)
The resin constituting the core and the shell constituting the toner for developing an electrostatic charge image of the present invention is produced by polymerizing the aforementioned polymerizable monomer. The radical polymerization initiator usable in the present invention includes the following: There are things. Specifically, as the oil-soluble polymerization initiator, 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 , Diisopropylperoxycarbonate, 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 - like the like (t-butylperoxy) polymeric initiator having a side chain a peroxide-based polymerization initiator or a peroxide, such as triazines.

  Moreover, when forming resin particles by an emulsion polymerization method, a water-soluble radical polymerization initiator can be used. Examples of the water-soluble polymerization initiator include persulfates such as potassium persulfate and ammonium persulfate, azobisaminodipropane acetate, azobiscyanovaleric acid and its salts, hydrogen peroxide and the like.

(Chain transfer agent)
Generally used chain transfer agents can be used for the purpose of adjusting the molecular weight of the resin constituting the composite resin particles.

  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.

(Dispersion stabilizer)
In the present invention, a dispersion stabilizer can be used in order 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.

(Surfactant)
In order to perform polymerization using the above-mentioned radical polymerizable monomer, it is necessary to perform oil droplet dispersion 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 ionic surfactants 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.

(Flocculant)
In the coagulation / fusion process, a coagulant is used, and examples of the coagulant include alkali metal salts and alkaline earth metal salts. Examples of the alkali metal that constitutes the flocculant include lithium, potassium, and sodium, and examples of the alkaline earth metal that constitutes the flocculant include magnesium, calcium, strontium, and barium. Of these, potassium, sodium, magnesium, calcium, and barium are preferable. Examples of the counter ion (anion constituting the salt) of the alkali metal or alkaline earth metal include chloride ion, bromide ion, iodide ion, carbonate ion and sulfate ion.

[Method for producing toner for developing electrostatic image]
As a method for producing the toner for developing an electrostatic charge image of the present invention, various production methods can be employed. A core having a circularity of 0.900 or more is obtained by aggregating resin particles and colorant particles. The method of the aspect which manufactures the toner for electrostatic image development of a core-shell structure through the process of producing and adding the resin fine particle to the surface of the said core, and forming the shell is preferable.

  Next, a method for producing the toner for developing an electrostatic charge image of the present invention will be described.

The electrostatic image developing toner of the present invention is produced through the following steps, for example.
(1) Dissolution / dispersion step for dissolving or dispersing the release agent in the radical polymerizable monomer (2) Polymerization step for preparing a dispersion of resin fine particles (3) Resin fine particles and colorant particles in an aqueous medium Agglomeration and fusion step for agglomerating and fusing the particles to obtain core particles (associate particles) (4) first aging step for adjusting the shape by aging the associated particles with thermal energy (5) in the core particle dispersion Shell forming step of adding shell resin particles to aggregate and fuse the shell particles on the surface of the core particles to form core-shell structured colored particles (6) Thermal energy of the core-shell structured colored particles The second aging step for adjusting the shape of the core-shell structured colored particles (7) The colored particles are solid-liquid separated from the cooled colored particle dispersion, and the surfactant is removed from the colored particles. Cleaning process to remove (8) Cleaning process Dry process also drying the colored particles, after drying if necessary,
(9) There may be a step of adding an external additive to the dried colored particles. The above process will be described in detail later.

  When the toner of the present invention is produced, first, resin particles and colorant particles are associated and fused to produce core particles (hereinafter referred to as “core particles”). Next, resin particles are added to the core particle dispersion, and the resin particles are aggregated and fused on the surface of the core particles to coat the surface of the core particles to produce colored particles having a core / shell structure. As described above, the toner of the present invention is a toner having a core / shell structure in which resin particles are added to a dispersion of core particles prepared by various production methods and fused to the core particles.

  As described above, the toner of the present invention preferably has an extremely thin shell and a uniform film thickness, and after the shell is formed, a toner having a small particle size with a constant particle size and a uniform shape is preferable. In order to produce a toner having such a structure and shape, the core particles are made to have a uniform shape with a uniform particle size, and shell resin particles are added to the core particles to form a shell. Become. In addition, when the shell is formed, the shape of the toner is finally controlled to give an appropriate shape. For that purpose, it is most important to prepare core particles having a uniform shape with uniform particle sizes. is there. With such a core particle, resin fine particles forming a shell uniformly adhere to the surface thereof, and as a result, toner particles having a very uniform film thickness can be produced.

  The core particles constituting the electrostatic charge image developing toner according to the present invention are produced by a production method in which resin fine particles and colorant particles are aggregated and fused. The shape of the core particles is controlled, for example, by controlling the heating temperature in the aggregation / fusion process and the heating temperature and time in the first aging process.

  Of these, the time control in the first aging step is the most effective. Since the ripening step is intended to adjust the circularity of the associated particles, the target circularity is reached by controlling this time.

  The core part constituting the toner of the present invention is prepared by, for example, dissolving or dispersing a release agent component in a polymerizable monomer that forms a resin, and then mechanically dispersing fine particles in an aqueous medium. A method of salting out and fusing the composite resin fine particles and the colorant particles formed through the step of polymerizing the polymerizable monomer by the following method is preferably used. When the release agent component is dissolved in the polymerizable monomer, the release agent component may be dissolved or melted or dissolved.

  Hereinafter, each manufacturing process of the toner according to the present invention will be described.

(1) Dissolution / dispersion step This step is a step of preparing a radical polymerizable monomer solution in which the release agent compound is dissolved in the radical polymerizable monomer and the release agent compound is mixed.

(2) Polymerization step In a preferred example of this polymerization step, a radical polymerizable monomer solution in which a wax is dissolved or dispersed in an aqueous medium containing a surfactant having a critical micelle concentration (CMC) or less is added. Then, mechanical energy is applied to form droplets, and then a water-soluble radical polymerization initiator is added to advance the polymerization reaction in the droplets. An oil-soluble polymerization initiator may be contained in the droplet. 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 strong stirring such as homomixer, ultrasonic wave, and manton gorin or ultrasonic vibration energy applying means.

  By this polymerization step, resin fine particles containing a wax and a binder resin are obtained. Such resin fine particles may be colored fine particles or non-colored fine particles. The colored resin fine particles can be obtained by polymerizing a monomer composition containing a colorant. In the case of using uncolored resin fine particles, a dispersion of colorant fine particles is added to the dispersion of resin fine particles in the agglomeration / fusion process described later to melt the resin fine particles and the colorant fine particles. Color particles can be obtained by attaching.

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

  The term “salting out / fusion” as used herein means that aggregation and fusion are performed in parallel, and when the particles have grown to a desired particle size, an aggregation terminator is added to stop the particle growth. The heating for controlling the particle shape according to the above is performed continuously.

  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 fine 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. A medium type disperser is mentioned. 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 dispersion, 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.

  The salting out / fusing method, which is a preferred agglomeration and fusing method, is a salting out method comprising alkali metal salt, alkaline earth metal salt, trivalent salt, etc. 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 the 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 (core particles) formed by salting out / fusing resin fine particles and arbitrary fine particles is obtained.

(4) First aging step And, in the present invention, by controlling the heating temperature of the coagulation / fusion step and particularly the heating temperature and time of the first aging step, the particle size is constant and the distribution is narrow. The core particle surface is controlled so as to have a smooth but uniform shape. Specifically, the heating temperature is lowered in the aggregation / fusion process to suppress the progress of fusion between the resin particles to promote homogenization, the heating temperature is lowered in the first aging process, and the time The surface of the core particles is controlled to have a uniform shape by increasing the length.

(5) Shelling step In the shelling step, the resin particle dispersion for the shell is added to the core particle dispersion to agglomerate and fuse the resin particles for the shell onto the surface of the core particles. The resin particles are coated to form colored particles.

  Specifically, the core particle dispersion is added with a dispersion of resin particles for shells while maintaining the temperature in the above-described aggregation / fusion process and the first aging process, and it takes several hours while continuing heating and stirring. Then, the resin particles for shell are slowly coated on the surface of the core particles to form colored particles. The heating and stirring time is preferably 1 hour to 7 hours, particularly preferably 3 hours to 5 hours.

(6) Second ripening step Resin for shell which is added to a core particle after adding a terminator such as sodium chloride to stop the particle growth at the stage when colored particles become a predetermined particle size by shelling. Heating and stirring are continued for several hours in order to fuse the particles. In the shelling step, a shell having a thickness of 100 to 300 nm is formed on the surface of the core particle. In this way, resin particles are fixed to the surface of the core particles to form a shell, and rounded and colored particles having a uniform shape are formed.

  In the present invention, it is possible to control the shape of the colored particles in the true sphere direction by setting the time of the second aging step longer or by setting the aging temperature higher.

(7) Cooling Step / Solid-Liquid Separation / Washing Step This step is a step of cooling (rapid cooling) the dispersion of the 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.

  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.

(8) Drying step This step is a step of drying the washed cake 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.

(9) External Addition Processing Step This step is a step of preparing a toner by mixing the dried colored particles with an external additive as necessary.

  As an external additive mixing device, a mechanical mixing device such as a Henschel mixer or a coffee mill can be used.

  The mass average particle diameter (dispersed particle diameter) of the composite resin particles is preferably in the range of 10 to 1000 nm, more preferably in the range of 30 to 300 nm.

  The mass average particle diameter is a value measured using an electrophoretic light scattering photometer “ELS-800” (manufactured by Otsuka Electronics Co., Ltd.).

<Developer>
The toner for developing an electrostatic image of the present invention can be used as a one-component developer or a two-component developer.

  When used as a one-component developer, a non-magnetic one-component developer or a magnetic one-component developer containing about 0.1 μm to 0.5 μm of magnetic particles in the toner can be used. be able to.

  Further, it can be mixed with a carrier and used as a two-component developer. As the carrier, conventionally known magnetic particles such as metals such as iron, ferrite, and magnetite, and alloys of these metals with metals such as aluminum and lead can be used. Ferrite particles are particularly preferable. The volume-based average particle diameter of the carrier is preferably 25 to 60 μm, and more preferably 25 to 40 μm.

  The volume-based average particle diameter of the carrier can be typically measured by a laser diffraction particle size distribution measuring apparatus “HELOS” (manufactured by SYMPATEC) equipped with a wet disperser.

  The carrier is preferably a carrier in which magnetic particles are further coated with a resin, or a so-called resin dispersion type carrier in which magnetic particles are dispersed in a resin. The coating resin is not particularly limited, and for example, an olefin resin, a styrene resin, a styrene-acrylic resin, a silicone resin, an ester resin, a fluorine-containing polymer resin, or the like is used. The resin for constituting the resin-dispersed carrier is not particularly limited, and known resins can be used. For example, styrene-acrylic resin, polyester resin, fluorine resin, phenol resin, etc. are used. be able to. Among these, a coat carrier coated with a styrene-acrylic resin is more preferable because it can prevent the external additive from being detached and ensure durability.

[Image Forming Method and Image Forming Apparatus]
The electrostatic image developing toner of the present invention is preferably used in a method of forming an image by loading it in an image forming apparatus equipped with a contact heating fixing device suitable for low-temperature fixing.

  The electrostatic image developing toner of the present invention may be used as a one-component developer or a two-component developer, but is particularly preferably used as a two-component developer.

  The toner of the present invention is used, for example, in a high-speed image forming apparatus having a printing speed of 400 mm / sec (85 sheets / min output performance in terms of A4 paper) level. Specifically, a printer that can create a large amount of documents on demand in a short time can be mentioned. Further, the present invention can be applied to an image forming method in which the temperature of the fixing roller is set to 150 ° C. or lower, preferably 130 ° C. or lower.

  This is mainly because the toner of the present invention has sufficient durability while the shell covering its surface is thin, and the shell can be fixed in a short time. Is called.

  FIG. 2 is an example of an image forming apparatus that can use the toner of the present invention, and shows a cross-sectional view thereof.

  The image forming apparatus shown in FIG. 2 collects toner remaining on the photosensitive member after the transfer step by a cleaning unit, and supplies a recovered toner to the developing device again to recycle and use a collected toner conveyance path corresponding to a toner recycling unit. An image forming apparatus.

  In FIG. 2, reference numeral 10 denotes a photosensitive drum which is an electrostatic latent image carrier, which is, for example, an organic photosensitive member (OPC photosensitive member) applied on a conductive drum and is grounded and rotated clockwise. Reference numeral 11 denotes a scorotron charger for negatively charging the circumferential surface of the photosensitive drum 10 by corona discharge to give a potential of VH. Before charging by the scorotron charger 11, it is necessary to neutralize the photosensitive member surface in order to remove the history of the photosensitive member up to the previous print, and the photosensitive member peripheral surface is exposed by the PCL 11A corresponding to the pre-charging exposure means. Remove the charge.

  After uniform charging of the photosensitive drum 10 by the scorotron charger 11, image exposure based on the image signal is performed by the laser writing device 12 corresponding to the image exposure means. In this image exposure, an image signal input from a computer or an image reading device is processed by an image signal processing unit, and then input to a laser writing device 12 to perform image exposure, and an electrostatic latent image is formed on the photosensitive drum 10. Form.

  The laser writing device 12 uses a laser diode (not shown) as a light source, performs main scanning by a plurality of reflecting mirrors 12d through a rotary polygon mirror 12a, an fθ lens 12b, etc., and performs sub-scanning by rotation of the photosensitive drum 10. As a result, an electrostatic latent image is formed. In this embodiment, the image portion is exposed based on the image signal, and the exposure portion forms a reverse latent image having a low potential absolute value VL.

  On the periphery of the photosensitive drum 10, a developing device 14 corresponding to a developing unit incorporating a two-component developer composed of a negatively charged conductive toner of the present invention and a magnetic carrier is provided. In the developing device 14, the developer is held by a built-in magnet body, and reverse development is performed by a rotating developing sleeve, so that a toner image is formed on the photosensitive drum 10. Further, the toner image formed on the photosensitive drum 10 is transferred onto the transfer material P by a transfer roller 16a corresponding to a transfer unit.

  Next, the transfer material P to which the toner image has been transferred is neutralized by the pointed electrode 16c arranged with a slight gap, separated from the circumferential surface of the photosensitive drum 10, and conveyed to the fixing device 17 corresponding to the fixing means. The In the fixing device 17, the toner image is melted and fixed on the transfer material P by heating and pressing of the heating roller 17 a and the pressure roller 17 b, and then discharged onto the tray portion 54 by the discharge roller.

  The transfer roller 16a is retracted away from the circumferential surface of the photosensitive drum 10 after the transfer material P passes through until the next toner image is transferred.

  On the other hand, the photosensitive drum 10 on which the toner image is transferred to the transfer material P is subjected to charge removal by the charge eliminator 19 using an AC corona discharger, and then the residual toner is removed by the cleaning device 20 corresponding to the photoreceptor cleaning means. Done. That is, the residual toner on the peripheral surface is scraped into the cleaning device 20 by the cleaning blade 20a made of a rubber material in contact with the photosensitive drum 10, and the recovered toner thus scraped off is transported to the recovered toner containing a screw or the like. It is sent to the developing device 14 through the path 21.

  The photosensitive drum 10 from which the residual toner has been removed by the cleaning device 20 is exposed to light by the PCL 11A and then uniformly charged by the charger 11, and then enters the next image forming cycle.

  FIG. 3 is a cross-sectional view showing an example of the fixing device 17 that can be used in the image forming apparatus shown in FIG. 2, and includes a heating roller 17a and a pressure roller 17b that abuts the heating roller 17a. In FIG. 3, T is a toner image formed on a transfer paper (image forming support) P.

  In the heating roller 17a, a coating layer 171 made of a fluororesin or an elastic body is formed on the surface of the cored bar 172, and includes a heating member 173 made of a linear heater.

  The metal core 172 is made of metal and has an inner diameter of 10 mm to 70 mm. Although it does not specifically limit as a metal which comprises the metal core 172, For example, metals, such as iron, aluminum, copper, or these alloys can be mentioned.

  The wall thickness of the cored bar 172 is 0.1 mm to 15 mm, and is determined in consideration of the balance between energy saving requirements (thinning) and strength (depending on the constituent materials). For example, in order to maintain the same strength as that of a cored bar made of iron of 0.57 mm with a cored bar made of aluminum, the wall thickness needs to be 0.8 mm.

  Examples of the fluororesin constituting the coating layer 171 include PTFE (polytetrafluoroethylene) and PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer).

  The thickness of the coating layer 171 made of a fluororesin is 10 μm to 500 μm, preferably 20 μm to 400 μm. Examples of the elastic body constituting the coating layer 171 include silicone rubber and silicone sponge rubber having good heat resistance such as LTV, RTV, and HTV. The Asker C hardness of the elastic body constituting the coating layer 171 is less than 80 °, preferably less than 60 °. The thickness of the coating layer 171 made of an elastic body is 0.1 mm to 30 mm, and preferably 0.1 mm to 20 mm.

  As the heating member 173, a halogen heater can be preferably used.

  The pressure roller 17 b is formed by forming a coating layer 174 made of an elastic body on the surface of the cored bar 175. The elastic body constituting the covering layer 174 is not particularly limited, and examples thereof include various soft rubbers such as urethane rubber and silicone rubber, and sponge rubber, and the silicone rubber and the silicone sponge rubber exemplified as those constituting the covering layer 174. Is preferably used. The Asker C hardness of the elastic body constituting the coating layer 174 is less than 80 °, preferably less than 70 °, and more preferably less than 60 °. Moreover, the thickness of the coating layer 220 is 0.1 mm to 30 mm, preferably 0.1 to 20 mm.

  Although it does not specifically limit as a material which comprises the metal core 175, Metals, such as aluminum, iron, copper, or those alloys can be mentioned.

  The contact load (total load) between the heating roller 17a and the pressure roller 17b is usually 40N to 350N, preferably 50N to 300N, and more preferably 50N to 250N. This contact load is defined in consideration of the strength of the heating roller 17a (the thickness of the cored bar 110). For example, a heating roller having a cored bar made of iron of 0.3 mm should be 250 N or less. Is preferred.

Further, from the viewpoint of offset resistance and fixing property, it is preferable that as the nip width is 4 mm to 10 mm, the surface pressure of the nip to be ^{0.6 × 10 5 Pa~1.5 × 10 5} Pa preferable.

  The image forming apparatus according to the present invention may use an induction heating type fixing device instead of the heating roll type fixing device.

  The transfer material P used in the present invention is a support for holding a toner image, and is usually called an image support, a recording material, or transfer paper. Specifically, various transfer materials such as plain paper and fine paper from thin paper to thick paper, coated printing paper such as art paper and coated paper, commercially available Japanese paper and postcard paper, plastic film for OHP, cloth, etc. However, it is not limited to these.

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these embodiments. In addition, the following "part" represents a "mass part".
<< Preparation of resin particles for core part >>
(Preparation of resin particle 1 for core part)
As described below, the first-stage polymerization, the second-stage polymerization, and then the third-stage polymerization were performed to prepare “core part resin particles 1” having a multilayer structure.

(1) First-stage polymerization 4 parts of anionic surfactant (Structural Formula 1) shown below in 3040 parts of ion-exchanged water in a 5 L reaction vessel equipped with a stirrer, temperature sensor, cooling pipe, and nitrogen introducing device The dissolved surfactant solution was charged, and the internal temperature was raised to 80 ° C. while stirring at a stirring speed of 230 rpm under a nitrogen stream.

(Structural Formula 1) C ₁₀ H ₂₁ (OCH ₂ CH ₂ ) ₂ SO ₃ Na
To this surfactant solution, an initiator solution in which 10 parts of a polymerization initiator (potassium persulfate: KPS) was dissolved in 400 parts of ion-exchanged water was added, the temperature was adjusted to 75 ° C., 532 parts of styrene, n- A monomer mixture composed of 200 parts of butyl acrylate, 68 parts of methacrylic acid and 16.4 parts of n-octyl mercaptan was added dropwise over 1 hour, and the system was polymerized by heating and stirring at 75 ° C. for 2 hours. (First stage polymerization) was performed to prepare resin particles. This is designated as “resin particle A1”. The “resin particles A1” prepared by the first stage polymerization had a weight average molecular weight (Mw) of 18,000.

(2) Second stage polymerization (formation of intermediate layer)
In a flask equipped with a stirrer, a mold mixture containing 106.2 parts of styrene, 57.2 parts of n-butyl acrylate, 12.3 parts of methacrylic acid, and 1.6 parts of n-octyl mercaptan was released into a mold. As an agent, 94.0 parts of paraffin wax “HNP-57” (manufactured by Nippon Seiki Co., Ltd.) was added, and the mixture was heated to 90 ° C. and dissolved to prepare a monomer solution.

  On the other hand, a surfactant solution in which 3 parts of an anionic surfactant (Structural Formula 1) is dissolved in 1560 parts of ion-exchanged water is heated to 98 ° C., and this surfactant solution is a dispersion of resin particles A1. After adding 32.8 parts of "resin particles A1" in terms of solid content, the monomer solution of the wax was mixed for 8 hours using a mechanical disperser "CLEAMIX" (M Technique Co., Ltd.) having a circulation path. Dispersion liquid was prepared, which contained emulsified particles having a dispersed particle diameter of 340 nm.

  Next, an initiator solution prepared by dissolving 6 parts of potassium persulfate in 200 parts of ion-exchanged water was added to this dispersion, and this system was heated and stirred at 98 ° C. for 12 hours for polymerization (second stage polymerization). ) To obtain resin particles. This resin particle is referred to as “resin particle A2”. Mw of “resin particle A2” prepared by the second stage polymerization was 22,000.

(3) Third stage polymerization (formation of outer layer)
An initiator solution in which 5.45 parts of potassium persulfate is dissolved in 220 parts of ion-exchanged water is added to the “resin particles A2” obtained as described above, and styrene 313. A monomer mixed solution composed of 5 parts, n-butyl acrylate 134.4 parts, and n-octyl mercaptan 8 parts was added dropwise over 1 hour. After completion of dropping, the mixture was heated and stirred for 2 hours to perform polymerization (third stage polymerization), and then cooled to 28 ° C. to obtain “resin particle 1 for core part”. Mw of “resin particle A3” prepared by the third stage polymerization was 27,800.

  The mass average particle diameter of the composite resin particles (resin particles) constituting “core part resin particles 1” was 120 nm. The resin particles had a glass transition temperature (Tg) of 35.1 ° C. and a solubility parameter value (SP value) of 10.12.

(Preparation of core part resin particles 2)
In the preparation of “core part resin particles 1”, the styrene used in the second stage polymerization (outer layer formation) was changed to 101.1 parts, n-butyl acrylate 62.2 parts, and methacrylic acid 12.3 parts. “Core part resin particles 2” were prepared in the same manner except that the styrene used in the third stage polymerization (outer layer formation) was changed to 301 parts and n-butyl acrylate 146.9 parts.

(Preparation of core part resin particles 3)
In the preparation of “core part resin particles 1”, the styrene used for the second stage polymerization (outer layer formation) was changed to 111 parts and the n-butyl acrylate was changed to 52.3 parts, and the third stage polymerization (outer layer formation). The “core part resin particles 3” were prepared in the same manner except that the styrene used in was changed to 326.1 parts and 121.8 parts of n-butyl acrylate.

(Preparation of core part resin particles 4)
In the preparation of “core part resin particles 1”, the styrene used in the second stage polymerization (outer layer formation) was changed to 96.6 parts and n-butyl acrylate was changed to 66.7 parts, and the third stage polymerization (outer layer) “Core part resin particles 3” were prepared in the same manner except that the styrene used in the formation was changed to 288.9 parts and 159 parts of n-butyl acrylate.

(Preparation of core part resin particles 5)
In the preparation of “core part resin particles 1”, the styrene used in the second stage polymerization (outer layer formation) was changed to 116 parts and the n-butyl acrylate was changed to 47.4 parts, and the third stage polymerization (outer layer formation). The “core part resin particles 3” were prepared in the same manner except that the styrene used in was changed to 338.2 parts and n-butyl acrylate 109.7 parts.
<< Preparation of resin particles for shell >>
(Preparation of resin particle 1 for shell)
In the first-stage polymerization of the above "core part resin particles 1", styrene was changed to 552 parts, n-butyl acrylate acrylate was changed to 192 parts, methacrylic acid was changed to 56 parts, and n-octyl mercaptan was changed to 16.0 parts. Polymerization reaction and post-reaction treatment were performed in the same manner except that the monomer mixture was used, and “shell resin particles 1” were prepared.

(Preparation of shell resin particles 2)
In the preparation of “Shell Resin Particle 1”, a monomer mixed solution in which styrene is changed to 476 parts, 2-ethylhexyl acrylate is 180 parts, methacrylic acid is 144 parts, and n-octyl mercaptan is changed to 17.0 parts is used. In the same manner as described above, polymerization reaction and post-reaction treatment were performed to prepare “resin particles 2 for shell”.

(Preparation of shell resin particles 3)
In the preparation of “resin particle 1 for shell”, a monomer mixed solution in which styrene is changed to 472 parts, 2-ethylhexyl acrylate is changed to 168 parts, itaconic acid is changed to 160 parts, and n-octyl mercaptan is changed to 16.5 parts is used. In the same manner as described above, the polymerization reaction and the treatment after the reaction were carried out to prepare “shell resin particles 3”.

(Preparation of shell resin particles 4)
In the preparation of “resin particle 1 for shell”, a monomer mixed solution in which styrene is changed to 464 parts, 2-ethylhexyl acrylate is changed to 192 parts, methacrylic acid is changed to 144 parts, and n-octyl mercaptan is changed to 16.5 parts is used. In the same manner as described above, the polymerization reaction and the treatment after the reaction were carried out to prepare “shell resin particles 4”.

(Preparation of resin particles 5 for shell)
In the preparation of “shell resin particles 1”, a monomer mixed solution in which 492 parts of styrene, 164 parts of 2-ethylhexyl acrylate, 144 parts of methacrylic acid, and 16.5 parts of n-octyl mercaptan were used was used. In the same manner as above, the polymerization reaction and the post-reaction treatment were performed to prepare “shell resin particles 5”.

(Preparation of resin particles 6 for shell)
In the preparation of “Shell Resin Particle 1”, a monomer mixed solution in which styrene was changed to 520 parts, n-butyl acrylate acrylate 256 parts, methacrylic acid 24 parts, and n-octyl mercaptan 16.5 parts was used. In the same manner as described above, the polymerization reaction and the treatment after the reaction were carried out to prepare “shell resin particles 6”.

(Preparation of resin particle 7 for shell)
In the preparation of “shell resin particles 1”, a monomer mixed solution in which styrene was changed to 456 parts, 2-ethylhexyl acrylate was changed to 144 parts, itaconic acid was changed to 200 parts, and n-octyl mercaptan was changed to 16.5 parts was used. Except for the above, the polymerization reaction and the post-reaction treatment were performed to prepare “shell resin particles 7”.
<Production of toner>
Toners 1 to 9 were produced as follows.

<Preparation of Toner 1>
(Preparation of dispersion 1 of colorant particles)
90 parts of the anionic surfactant (1) was dissolved in 1600 parts of ion-exchanged water with stirring. While stirring this solution, 400 parts of carbon black “Regal 330” (Cabot Corporation) is gradually added, and then dispersed using a stirring device “Claremix” (Mtechnics Corporation). Agent particle dispersion 1 "was prepared.

  The particle diameter of the colorant particles in this “colorant particle dispersion 1” was 110 nm as measured using an electrophoretic light scatterometer (ELS-800: manufactured by Otsuka Electronics Co., Ltd.).

(Salting out / fusion (association / fusion) process) (core formation)
420.7 parts (in terms of solid content) of “core part resin particles 1”, 900 parts of ion-exchanged water, and 200 parts of “colorant particle dispersion 1” were added to a temperature sensor, a cooling pipe, a nitrogen introducing device, The mixture was stirred in a reaction vessel equipped with a stirrer. After adjusting the temperature in the container to 30 ° C., 5 mol / liter sodium hydroxide aqueous solution was added to this solution to adjust the pH to 8-11. Next, an aqueous solution in which 2 parts of magnesium chloride hexahydrate was dissolved in 1000 parts of ion-exchanged water was added over 10 minutes at 30 ° C. with stirring. After standing for 3 minutes, the temperature was raised and the system was heated to 65 ° C. over 60 minutes. In this state, the particle size of the associated particles was measured with “Coulter Counter TA-II” (manufactured by Coulter Co.). When the particle median system (D ₅₀ ) reached 5.5 μm, 40.2 parts of sodium chloride was used. An aqueous solution in which 1000 parts of ion-exchanged water is dissolved is added to stop the growth of the particle size, and further, the fusion is continued by heating and stirring at a liquid temperature of 70 ° C. for 1 hour as an aging treatment. Formed.

  The circularity of “Core 1” was measured by “FPIA2000” (manufactured by Systex) and found to be 0.900.

(Shell formation (shelling operation))
Next, 96 parts of “shell resin particles 1” were added at 65 ° C., and an aqueous solution in which 2 parts of magnesium chloride hexahydrate was dissolved in 1000 parts of ion-exchanged water was added over 10 minutes. The temperature was raised to (shelling temperature), and stirring was continued for 1 hour. After the particles of “resin particles for shell 1” were fused on the surface of “core part 1”, aging treatment was performed at 75 ° C. for 20 minutes. To form a shell. Here, 40.2 parts of sodium chloride was added, cooled to 30 ° C. under the condition of 8 ° C./min, and the generated fused particles were filtered and repeatedly washed with 45 ° C. ion-exchanged water. By drying with warm air, “toner 1” having a shell on the core surface was obtained. Glass transition temperature (Tg) is measured using a differential scanning calorimeter “DSC-200” (manufactured by Seiko Electronics Co., Ltd.), and 10 mg of a sample to be measured is accurately weighed and placed in an aluminum pan. This was used to raise the temperature from room temperature to 200 ° C. at a rate of temperature increase of 30 ° C./min, then cooled and measured between 10 ° C. and 120 ° C. at a rate of temperature increase of 10 ° C./min. The shoulder value of the main endothermic peak in the range of 20 to 90 ° C. during the temperature raising process was taken as the glass transition point. The weight average molecular weight was measured using gel permeation chromatography “807-1T type” (manufactured by JASCO Corporation). While maintaining the column temperature at 40 ° C., tetrahydrofuran as a carrier solvent was flowed at 1 kg / cm ² , 30 mg of a sample to be measured was dissolved in 20 ml of tetrahydrofuran, 0.5 mg of this solution was introduced into the apparatus together with the carrier solvent, It calculated | required by polystyrene conversion.

<Preparation of Toners 2-9>
The “core resin particles 1” and “shell resin particles 1” used in the production of “toner 1” were changed to the core resin particles, shell resin particles, and core particle circularity shown in the table. Made “Toners 2-9” in the same manner.

A cross-sectional view of the “toners 1 to 9” obtained above was observed with a TEM, one toner was equally divided into eight, and the thickness of the shell at each point was measured and averaged Dave. And the points of the maximum film thickness Dmax and the minimum film thickness Dmin were extracted from the 8 points, and the ratio was calculated. The above operation is performed with 100 toners.
《External treatment process》
1% by weight of hydrophobic silica (number average primary particle size = 12 nm, degree of hydrophobicity = 68) and hydrophobic titanium oxide (number average primary particle size = 20 nm, degree of hydrophobicity) were prepared in the above “Toners 1-9”. = 63) was added in an amount of 1.2% by mass and mixed with a Henschel mixer to prepare "Toners 1 to 9". “Toners 1 to 9” of the obtained toner are referred to as “Examples 1 to 7”, and “Toners 8 and 9” are referred to as “Comparative Examples 1 and 2”.
<Evaluation>
The following evaluation was performed using “Examples 1 to 7” and “Comparative Examples 1 and 2” produced above. In addition, ◎ and ○ of the evaluation criteria are passed and × is rejected.

<Preparation of print image>
The printed image is a commercially available multi-function machine “Sitios 9331” (manufactured by Konica Minolta Business Technologies Co., Ltd.) adopting a print image electrophotographic method, the linear velocity is set to 280 mm (about 50 sheets / min), and the developing roller is set to an outer diameter of 9 mm. Then, the fixing device was changed to a fixing device (type using a belt 180 and a heating roller) having the configuration shown in FIG. 4, and printing was performed to produce a printed image. The following items were evaluated for the state of the multifunction device and the print image.

[Heat resistant storage]
The heat-resistant storage property is that the amount of agglomerates remaining on the sieve after the 100 g of each of the toners prepared above was left for 24 hours under conditions of 55 ° C. and 90% RH and then sieved with a sieve having an opening of 45 μm (ratio: Mass%).

Evaluation criteria:
A: The amount on the sieve is less than 5% and the agglomeration amount is very small, and the heat-resistant storage property is excellent (there is no generation of agglomerates even if transported in summer without any heat insulating packing material).
○: The amount on the sieve is 5 to 30%, and the amount of aggregation is small and the heat-resistant storage property is good (there is no generation of aggregates even if transported in the summer only with cardboard packaging)
×: The amount on the sieve is larger than 30%, and the amount of aggregation is large, which is a practical problem (need to carry out cold transport).

[Minimum fixing temperature]
The heating roller surface temperature of the fixing device of the evaluation machine is changed so that the paper surface temperature changes within a range of 80 to 150 ° C. in increments of 10 ° C., and the toner image is fixed at each changed temperature to produce a fixed image. did. In producing the printed image, high-quality paper of A4 size (80 g / m ² ) was used. The fixing strength of the printed image obtained by fixing is fixed using a method in accordance with the mending tape peeling method described in Chapter 9 Section 1.4 of “Basics and Applications of Electrophotographic Technology: Electrophotographic Society”. The rate was evaluated. Specifically, after a 2.54 cm square solid black print image with a toner adhesion amount of 0.6 mg / cm ² was prepared, images before and after peeling with “Scotch Mending Tape” (manufactured by Sumitomo 3M) The density was measured, and the residual ratio of the image density was determined as the fixing ratio.

  The “transfer material (paper) surface temperature” at which the fixing rate is 95% or more is defined as the minimum fixing temperature. The surface temperature of the transfer material (paper) was measured with a non-contact thermometer. The image density was measured with a reflection densitometer “RD-918” (manufactured by Macbeth).

Evaluation criteria:
A: Fixing is possible at a minimum fixing temperature of less than 100 ° C. ○: Fixing is possible at a minimum fixing temperature of 100 ° C. or more and less than 130 ° C. x: Fixing is possible at a minimum fixing temperature of 130 ° C. or more. It is shown in Table 2.

  As is apparent from the results shown in Tables 1 and 2, it can be seen that the examples according to the present invention are superior in heat-resistant storage property and minimum fixing temperature to the comparative examples. That is, by means of the present invention, it is possible to provide an electrostatic charge image developing toner excellent in heat-resistant storage stability while maintaining excellent low-temperature fixability in the electrostatic charge image developing toner having a core-shell structure. it can. Moreover, the manufacturing method can be provided.

Schematic diagram of toner for developing electrostatic image having core / shell structure Sectional drawing of the image forming apparatus which can use the electrostatic image developing toner of this invention Sectional view showing an example of a heating roll type fixing device Sectional view showing an example of a fixing device of a type using a belt and a heating roller

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Photosensitive drum 11 Scorotron charger 11A Pre-charge exposure means 12 Laser writing apparatus T Toner A Core B Shell C Colorant D Wax

Claims (5)

An electrostatic charge image developing toner having a core-shell structure having a shell on the surface of a core containing at least a resin and a colorant, wherein the shell has an 8-point average film thickness of 100 to 300 nm, and the maximum of the shell When the film thickness is Hmax and the minimum film thickness is Hmin, the ratio of both: Hmax / Hmin is less than 1.50, the glass transition temperature of the core part is Tg1, and the glass transition temperature of the shell part is Tg2. The toner for developing an electrostatic charge image is characterized in that 30 ° C. ≦ Tg 1 ≦ 40 ° C., 45 ° C. ≦ Tg 2 ≦ 55 ° C., and the heat resistance index is 20% or less. The difference between SP1 and SP2 is 0.2 to 1.0 when the solubility parameter of the resin constituting the core is SP1 and the solubility parameter of the resin constituting the shell is SP2. 2. The toner for developing an electrostatic charge image according to 1. The glass transition temperature of the resin that constitutes the core is Tg1, and the glass transition temperature of the resin that constitutes the shell is Tg2, and Tg2−Tg1 ≧ 10 ° C. Toner for developing electrostatic images. The core according to any one of claims 1 to 3, wherein the core is formed by aggregating resin particles and colorant particles, and the shell is formed by coating a resin on a surface of the core. The toner for developing an electrostatic image according to the description. The method for producing an electrostatic charge image developing toner according to claim 1, wherein resin particles and colorant particles are aggregated to produce a core having a circularity of 0.900 or more. A toner for developing an electrostatic charge image, comprising: a step of adding a resin fine particle to the surface of the core to form a shell; and a toner for developing an electrostatic charge image having a core / shell structure. Method.

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