JP2015141361A - Capsule toner for electrostatic charge image development - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a capsule toner for electrostatic charge image development that is excellent in storage stability (blocking property) and low-temperature fixability.SOLUTION: There is provided a capsule toner for electrostatic charge image development having a shell layer made of a cationic encapsulated material formed on the surface of an anionic core, where the encapsulated material contains at least one selected from the group consisting of mono-methylol melamine methyl ether, di-methylol melamine dimethyl ether, and tri-methylol melamine trimethyl ether.

Description

  The present invention relates to an electrostatic image developing capsule toner used for developing an electrostatic latent image formed in electrophotography.

  The capsule toner includes a core and a shell layer (capsule layer) formed on the surface of the core. Patent Documents 1 and 2 disclose a toner manufacturing method in which a core layer is coated with a shell layer in a state where the core is dispersed in an aqueous medium in which a dispersant is dissolved.

  In the production method described in Patent Document 1 or 2, since an anionic dispersant is used, if the anionic dispersant can be attached to the surface of the core, it is considered that aggregation of the core can be suppressed. It is done. However, a dispersant having a low molecular weight is easy to dissolve in an aqueous medium, and thus hardly adheres to the surface of the core. On the other hand, if the molecular weight of the dispersant is increased, the dispersant tends to function as a polymer flocculant, and the core aggregates. Is likely to occur.

  Therefore, by giving the core particles anionic properties, the cationic film-forming material is attracted to the surface without using anionic materials such as anionic dispersants that have been used in the past. It is considered that it is preferable to obtain a dense capsule material by polymerizing and fixing by the above. By attracting and encapsulating the encapsulating material directly to the toner surface without using an anionic additive, the toner particles do not aggregate at the time of capsule formation even when the glass transition point Tg of the toner is lower than the curing temperature of the encapsulating material. A dense capsule toner can be obtained. However, even if such a technique is used, a sufficient capsule film is not formed on the core surface, and the cores aggregate together, resulting in non-uniform capsule film thickness, and the core bleeds from where the capsule film thickness is thin. In addition, the storage stability (blocking property) is inferior and there is a problem that the low-temperature fixability is also inferior because there are places where the film thickness is large.

JP 2004-294468 A JP 2004-294469 A

  An object of the present invention is to provide an electrostatic charge image developing capsule toner excellent in storage stability (blocking property) and low-temperature fixability.

  In view of the above problems, the present inventor has intensively studied to use monomethylol melamine methyl ether, dimethylol melamine dimethyl ether, trimethylol melamine trimethyl ether, which has a particularly small amount of methylol groups among melamine formaldehyde initial condensates. The present inventors have found that an electrostatic charge image developing capsule toner can be obtained which is capable of stable condensation polymerization and is excellent in storage stability (blocking property) and low-temperature fixability.

  That is, the present invention relates to an electrostatic charge image developing capsule toner in which a shell layer made of a cationic encapsulating material is formed on the surface of an anionic core, wherein the encapsulating material is monomethylol melamine methyl The gist is to contain at least one selected from the group consisting of ether, dimethylol melamine dimethyl ether and trimethylol melamine trimethyl ether.

  As described above, according to the present invention, it is possible to provide a capsule toner for developing an electrostatic image having excellent low-temperature fixability while improving storage stability (blocking property).

  Hereinafter, although the embodiment concerning the present invention is described, the present invention is not limited to these.

  The electrostatic charge image developing capsule toner according to this embodiment (hereinafter also simply referred to as “capsule toner”) is composed of a large number of toner particles.

  The toner particles are composed of an anionic core and a cationic shell layer formed on the surface of the core. In the present embodiment, the shell layer is not limited to a single layer, and may be a multilayer. In the case of a multilayer, at least the outermost layer preferably has a cationic property.

  When the core has an anionic property, the material of the cationic shell layer can be attracted to the core surface when the shell layer is formed. Specifically, for example, a negatively charged core in an aqueous medium and a shell layer material positively charged in the aqueous medium are electrically attracted to each other, and a shell layer is formed on the surface of the core. This makes it easy to form a uniform shell layer on the surface of the core without highly dispersing the core in the aqueous medium using a dispersant.

  The core is composed of a binder (binder) and an internal additive (coloring agent, release agent, charge control agent, magnetic powder, etc.).

  In the core, the binder occupies most of the core component (for example, 85% or more). For this reason, the polarity of the binder greatly affects the polarity of the entire core. When the binder has an ester group, a hydroxyl group, an ether group, an acid group, a methyl group, etc., the core has a strong tendency to become anionic, and the binder has an amino group, an amine, an amide group, etc. If so, the core tends to become cationic.

  In this embodiment, an indicator that the core is anionic is that the zeta potential of the core measured in an aqueous medium adjusted to pH 4 exhibits negative polarity, and in order to obtain good anionicity, The zeta potential at pH 4 preferably shows a value of -5 mV or less, more preferably -10 mV or less.

  Examples of the zeta potential measuring method include electrophoresis, ultrasonic method, ESA method and the like.

  In the electrophoresis method, an electric field is applied to the particle dispersion to cause electrophoresis of charged particles in the dispersion, and the zeta potential is calculated based on the electrophoresis speed. Examples of the electrophoresis method include a laser Doppler method (a method in which an electrophoretic velocity is obtained from the amount of Doppler shift of the obtained scattered light by irradiating the electrophoretic particles with laser light). The laser Doppler method has the advantage that the particle concentration in the dispersion does not need to be high, the number of parameters necessary for calculating the zeta potential is small, and the electrophoresis speed can be detected with high sensitivity.

  The ultrasonic method is a method of irradiating a particle dispersion with ultrasonic waves to vibrate charged particles in the dispersion and calculating a zeta potential based on a potential difference caused by the vibration.

  The ESA method is a method in which a high frequency voltage is applied to a particle dispersion to vibrate charged particles in the dispersion to generate ultrasonic waves, and a zeta potential is calculated from the magnitude (intensity) of the ultrasonic waves.

  The ultrasonic method and the ESA method have an advantage that the zeta potential can be measured with high sensitivity even in a particle dispersion having a high particle concentration (for example, exceeding 20% by mass).

  Another indicator that the core is anionic is that the triboelectric charge with a standard carrier shows a value of −10 μC / g or less. The triboelectric charge amount is an indicator of whether the core is charged in positive or negative polarity and the ease with which the core is charged. The triboelectric charge amount of the core when rubbed with a standard carrier can be measured by, for example, a QM meter (for example, MODEL 210HS-2A manufactured by TREK).

  Hereinafter, the overall configuration of the core constituting the toner particles, the binder, the internal additives (colorant, release agent, charge control agent, magnetic powder), the overall configuration of the shell layer, the components of the shell layer (charge control agent), and The external additives will be described in order.

〔core〕
The core constituting the toner particles of this embodiment includes a binder and an internal additive (colorant, release agent, charge control agent, and magnetic powder). However, it is not essential that the core has all of the above components, and components that are not necessary (colorants, release agents, charge control agents, magnetic powder, etc.) are omitted depending on the intended use of the toner. Also good.

[Binder (core)]
The binder is preferably composed of a resin having, for example, an ester group, a hydroxyl group, an ether group, an acid group, a methyl group, a carboxyl group, or an amino group as a functional group. The resin constituting the binder is preferably a resin having a functional group such as a hydroxyl group, a carboxyl group, or an amino group in the molecule, and more preferably a resin having a hydroxyl group and / or a carboxyl group in the molecule. The core (binder) having such a functional group easily reacts with the shell layer material (for example, methylol melamine) to be chemically bonded. When such a chemical bond occurs, the bond between the core and the shell layer becomes strong.

  As the resin constituting the binder, a thermoplastic resin is preferable. Preferred examples of the thermoplastic resin include styrene resin, acrylic resin, styrene acrylic resin, polyethylene resin, polypropylene resin, vinyl chloride resin, polyester resin, polyamide resin, polyurethane resin, and polyvinyl alcohol. Examples thereof include resins, vinyl ether resins, N-vinyl resins, and styrene-butadiene resins. Among them, the styrene acrylic resin and the polyester resin are excellent in the dispersibility of the colorant in the toner, the charging property of the toner, and the fixing property to the recording medium, respectively.

(Binder composed of styrene acrylic resin)
The styrene acrylic resin constituting the binder is, for example, a copolymer of a styrene monomer and an acrylic monomer.

  Preferable examples of the styrenic monomer include styrene, α-methylstyrene, p-hydroxystyrene, m-hydroxystyrene, vinyltoluene, α-chlorostyrene, o-chlorostyrene, m-chlorostyrene, p-chloro. Examples include styrene and p-ethylstyrene.

  Preferable examples of the acrylic monomer include (meth) acrylic acid, particularly (meth) acrylic acid alkyl ester or (meth) acrylic acid hydroxyalkyl ester.

  Examples of the (meth) acrylic acid alkyl ester include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, iso-propyl (meth) acrylate, and (meth) acrylic acid n-. Butyl, iso-butyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate are preferred.

  Examples of the (meth) acrylic acid hydroxyalkyl ester include 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, and 4-hydroxy (meth) acrylate. Propyl is preferred.

  When preparing a styrene acrylic resin, a hydroxyl group can be introduced into the styrene acrylic resin by using a monomer having a hydroxyl group (p-hydroxystyrene, m-hydroxystyrene, hydroxyalkyl (meth) acrylate, etc.). . For example, the hydroxyl value of the resulting styrene acrylic resin can be adjusted by appropriately adjusting the amount of the monomer having a hydroxyl group.

  When preparing the styrene acrylic resin, a carboxyl group can be introduced into the styrene acrylic resin by using (meth) acrylic acid as a monomer. For example, the acid value of the resulting styrene acrylic resin can be adjusted by appropriately adjusting the amount of (meth) acrylic acid used.

  In order to improve the strength and fixability of the core, the number average molecular weight (Mn) of the styrene acrylic resin constituting the binder is preferably 2000 or more and 3000 or less. The molecular weight distribution (ratio Mw / Mn of number average molecular weight (Mn) and mass average molecular weight (Mw)) of the styrene acrylic resin is preferably 10 or more and 20 or less. Gel permeation chromatography can be used for the measurement of Mn and Mw of the binder.

(Binder composed of polyester resin)
The polyester resin constituting the binder can be obtained, for example, by polycondensation or copolycondensation of a divalent or trivalent or higher alcohol component and a divalent or trivalent or higher carboxylic acid component.

  Preferable examples of the divalent or trivalent or higher alcohol component include diols, bisphenols, and trivalent or higher alcohols.

  Examples of diols include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, neopentyl glycol, 1,4-butenediol, 1,5 -Pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, dipropylene glycol, polyethylene glycol, polypropylene glycol and polytetramethylene glycol are preferred.

  As bisphenols, for example, bisphenol A, hydrogenated bisphenol A, polyoxyethylenated bisphenol A, and polyoxypropylenated bisphenol A are preferable.

  Examples of the trivalent or higher alcohols include sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, diglycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, 1,3,5-trihydroxymethyl Benzene is preferred.

  Preferable examples of the divalent or trivalent or higher carboxylic acid component include divalent carboxylic acid or trivalent or higher carboxylic acid. Further, these carboxylic acid components may be used as ester-forming derivatives (acid halides, acid anhydrides, lower alkyl esters, etc.). Here, “lower alkyl” means an alkyl group having 1 to 6 carbon atoms.

  Examples of the divalent carboxylic acid include maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, malonic acid. Alkyl or alkenyl succinic acids are preferred. Furthermore, examples of the alkenyl succinic acid include n-butyl succinic acid, n-butenyl succinic acid, isobutyl succinic acid, isobutenyl succinic acid, n-octyl succinic acid, n-octenyl succinic acid, n-dodecyl succinic acid, and n-dodecenyl succinic acid. , Isododecyl succinic acid, and isododecenyl succinic acid are preferable.

  Examples of the trivalent or higher carboxylic acid include 1,2,4-benzenetricarboxylic acid (trimellitic acid), 1,2,5-benzenetricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid, 1,2,4. -Naphthalenetricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, 1,2,4-cyclohexanetricarboxylic acid Acid, tetra (methylenecarboxyl) methane, 1,2,7,8-octanetetracarboxylic acid, pyromellitic acid, and empole trimer acid are preferred.

  When the polyester resin is produced, the acid value of the polyester resin and the amount of the divalent or trivalent or higher alcohol component and the amount of the divalent or trivalent or higher carboxylic acid component are appropriately changed. The hydroxyl value can be adjusted. Moreover, when the molecular weight of the polyester resin is increased, the acid value and hydroxyl value of the polyester resin tend to decrease.

  In order to improve the strength and fixability of the core, the number average molecular weight (Mn) of the polyester resin constituting the binder is preferably 1200 or more and 2000 or less. The molecular weight distribution of the polyester resin (ratio Mw / Mn between the number average molecular weight (Mn) and the mass average molecular weight (Mw)) is preferably 9 or more and 20 or less. Gel permeation chromatography can be used for the measurement of Mn and Mw of the binder.

  In order to obtain a strong anionic property of the binder, the hydroxyl value (OHV value) and acid value (AV value) of the binder are each preferably 10 mgKOH / g or more.

  The solubility index (SP value) of the binder is preferably 10 or more, and more preferably 15 or more. When the SP value is 10 or more, the affinity with water can be improved because it approaches the SP value of water (23), and the wettability of the binder to an aqueous medium is improved. Therefore, the dispersibility of the binder in the aqueous medium is improved without using a dispersant, and the binder fine particle dispersion is easily dispersed uniformly in the aqueous medium.

  The glass transition point (Tg) of the binder is preferably not higher than the curing start temperature of the encapsulating material contained in the shell layer. When such a binder is used, the core is less likely to aggregate during the formation of the shell layer, and sufficient fixability can be obtained even in a high-speed fixing system. The curing start temperature of thermosetting resins such as melamine resins is generally about 55 ° C to 100 ° C. Therefore, the Tg of the binder is preferably 20 ° C. or higher and 55 ° C. or lower, and more preferably 30 ° C. or higher and 50 ° C. or lower. When the Tg of the binder is 20 ° C. or higher, the core is less likely to aggregate when the shell layer is formed.

  The Tg of the binder can be determined from the specific heat change point in the endothermic curve by measuring the endothermic curve of the binder using a differential scanning calorimeter (for example, DSC-6200, manufactured by Seiko Instruments Inc.). Specifically, 10 mg of a measurement sample is put in an aluminum pan, an empty aluminum pan is used as a reference, and an endothermic curve of the binder is obtained under the conditions of a measurement temperature range of 25 to 200 ° C. and a heating rate of 10 ° C./min. The method of calculating | requiring Tg based on the obtained endothermic curve is mentioned.

  The softening point (Tm) of the binder is preferably 100 ° C. or lower, and more preferably 95 ° C. or lower. When the Tm of the binder is 100 ° C. or less, it is possible to obtain a sufficient fixing property even during high-speed fixing. Moreover, Tm of a binder can be adjusted by combining several binder material which has different Tm.

  For the Tm of the binder, for example, a measurement sample is set in a Koka-type flow tester (for example, CFT-500D, manufactured by Shimadzu Corporation), and the sample is melted and flowed out under a predetermined condition to obtain an S-shaped curve (temperature (° C.) / It can be measured by obtaining an S-shaped curve for the stroke (mm) and reading the Tm of the binder from the obtained S-shaped curve.

[Colorant (core)]
As the colorant, for example, a known pigment or dye can be used according to the color of the toner particles. The amount of the colorant to be used is preferably 1 part by mass or more and 20 parts by mass or less, and more preferably 3 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the binder.

(Black colorant)
The core of the toner particles according to the present embodiment may contain a black colorant. The black colorant is composed of, for example, carbon black. In addition, a colorant that is toned in black using a colorant such as a yellow colorant, a magenta colorant, or a cyan colorant can also be used.

(Coloring agent)
The core of the toner particles according to the exemplary embodiment may contain a color colorant such as a yellow colorant, a magenta colorant, and a cyan colorant.

  The yellow colorant is preferably composed of, for example, a condensed azo compound, an isoindolinone compound, an anthraquinone compound, an azo metal complex, a methine compound, and an allylamide compound. Examples of yellow colorants include C.I. I. Pigment Yellow (3, 12, 13, 14, 15, 17, 62, 74, 83, 93, 94, 95, 97, 109, 110, 111, 120, 127, 128, 129, 147, 151, 154, 155 168, 174, 175, 176, 180, 181, 191, 194, etc.), Neftol Yellow S, Hansa Yellow G, C.I. I. Butt yellow is preferred.

  The magenta colorant is preferably composed of, for example, a condensed azo compound, diketopyrrolopyrrole compound, anthraquinone compound, quinacridone compound, basic dye lake compound, naphthol compound, benzimidazolone compound, thioindigo compound, and perylene compound. Examples of magenta colorants include C.I. I. Pigment Red (2, 3, 5, 6, 7, 19, 23, 48: 2, 48: 3, 48: 4, 57: 1, 81: 1, 122, 144, 146, 150, 166, 169, 177 , 184, 185, 202, 206, 220, 221, 254, etc.).

  The cyan colorant is preferably composed of, for example, a copper phthalocyanine compound, a copper phthalocyanine derivative, an anthraquinone compound, or a basic dye lake compound. Examples of cyan colorants include C.I. I. Pigment blue (1, 7, 15, 15: 1, 15: 2, 15: 3, 15: 4, 60, 62, 66, etc.), phthalocyanine blue, C.I. I. Bat Blue, C.I. I. Acid blue is preferred.

[Release agent (core)]
The release agent is used for the purpose of improving the fixing property and offset resistance of the toner. In order to improve the fixing property and the offset resistance, the amount of the release agent used is preferably 1 part by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the binder, and 5 parts by mass or more and 20 parts by mass or less. It is more preferable that

  In one example, the release agent is preferably composed of an aliphatic hydrocarbon wax such as low molecular weight polyethylene, low molecular weight polypropylene, polyolefin copolymer, polyolefin wax, microcrystalline wax, paraffin wax, and Fischer-Tropsch wax. In another example, the release agent is preferably composed of an oxide of an aliphatic hydrocarbon wax such as an oxidized polyethylene wax or a block copolymer of oxidized polyethylene wax. In another example, it is preferable that the release agent is composed of a plant-based wax such as candelilla wax, carnauba wax, wood wax, jojoba wax, or rice wax. In another example, it is preferable that the release agent is composed of animal wax such as beeswax, lanolin, spermaceti. In another example, it is preferable that the release agent is composed of a mineral wax such as ozokerite, ceresin, and vetrolactam. In another example, it is preferable that the mold release agent is composed of waxes mainly composed of fatty acid esters such as montanic acid ester wax and caster wax. In another example, it is preferable that the release agent is composed of a wax obtained by deoxidizing a part or all of a fatty acid ester such as deoxidized carnauba wax.

[Charge control agent (core)]
In this embodiment, since the core has an anionic property (negative chargeability), a negatively chargeable charge control agent may be used in the core. The charge control agent is used for the purpose of improving the charge stability and charge rise characteristics and obtaining a toner having excellent durability and stability. The charge rising characteristic is an index as to whether or not charging to a predetermined charge level is possible in a short time.

[Magnetic powder (core)]
When toner is used as a one-component developer, the amount of magnetic powder used is preferably 35 parts by weight or more and 60 parts by weight or less, and 40 parts by weight or more and 60 parts by weight or less with respect to 100 parts by weight of the total amount of toner. It is more preferable.

  Magnetic powder is, for example, iron (ferrite, magnetite, etc.), ferromagnetic metal (cobalt, nickel, etc.), an alloy containing iron and / or ferromagnetic metal, a compound containing iron and / or ferromagnetic metal, and ferromagnetic such as heat treatment. It is preferably made of a ferromagnetic alloy and chromium dioxide that have been subjected to a heat treatment.

  The particle size of the magnetic powder is preferably 0.1 μm or more and 1.0 μm or less, and more preferably 0.1 μm or more and 0.5 μm or less. When the particle size of the magnetic powder is in such a range, the magnetic powder is easily dispersed uniformly in the binder.

[Shell layer (shell film)]
In the present embodiment, monomethylol melamine methyl ether, dimethylol melamine dimethyl ether, and trimethylol melamine trimethyl ether are used as the cationic encapsulating material (shell agent) that forms the shell layer (shell film). These may be used alone or in combination.

A melamine formaldehyde initial condensate such as monomethylol melamine methyl ether can be prepared, for example, by reacting melamine with formaldehyde to methylol, then methylate, and further etherify. Depending on the amount of formaldehyde added to melamine, the amount of methanol reacting with the methylol group, etc., a methylol group (—CH ₂ OH), a methoxy group (—OCH ₃ ), a methylene group (—CH ₂ —) and an imino group (—NH Various compositions having different composition ratios of-) can be produced.

  In the melamine formaldehyde initial condensate, generally, the lower the amount of imino groups, the higher the curing temperature. The amount of methylene groups corresponds to the degree of condensation. The smaller the amount, the higher the concentration of the composition containing the melamine formaldehyde initial condensate and the higher the cross-linking density of the capsule membrane. Further, the larger the amount of the methylol group, the lower the stability because the melamine formaldehyde initial condensate composition has a problem in that the stability of the melamine group condensate is reduced or a large amount of formaldehyde is generated during processing. In addition, the greater the amount of methylol groups, the lower the stability, so there is a production tact problem such as the reaction rate must be slowed.

  In this embodiment, monomethylol melamine methyl ether, dimethylol melamine dimethyl ether, trimethylol melamine trimethyl ether, which has a small amount of methylol groups among melamine formaldehyde initial condensates, can be used for stable condensation polymerization and stable storage. Capsule toner having excellent properties (blocking properties) and low-temperature fixability can be obtained.

  In the present embodiment, an encapsulating material other than monomethylol melamine methyl ether, dimethylol melamine dimethyl ether, and trimethylol melamine trimethyl ether can be used in combination. Other encapsulating materials include cationic materials that can perform so-called in-situ polymerization, in which a cationic capsule material is ionically attracted to an anionic capsule core (core material) and attached to the surface to perform surface polymerization. There is no particular limitation as long as it is a thermosetting resin such as guanamine resin or its derivative (benzoguanamine etc.), acetoguanamine, spiroguanamine, sulfoamide resin, urea (urea) resin or its derivative, glyoxal resin, aniline resin. Can be mentioned.

  The thickness of the shell layer is preferably 20 nm or less, and more preferably 1 nm or more and 10 nm or less. If the shell layer is too thick, sufficient fixability cannot be obtained. The thickness of the shell layer means the thickness converted in the case of the resin constituting the shell layer (for example, thermosetting resin) alone, and the flexibility is improved by adding a modifier or the like to the melamine resin. When it is given, it is not limited to the above range.

  The thickness of the shell layer can be measured, for example, as follows. That is, the toner particles are sufficiently dispersed in a room temperature curable epoxy resin and cured in an atmosphere of 40 ° C. for 2 days to obtain a cured product. After dyeing this cured product with osmium tetroxide, it is cut out with a microtome (for example, EM UC6, manufactured by Leica Co., Ltd.) with a diamond knife set to obtain a thin piece sample having a thickness of 200 nm. And the cross section of this sample is image | photographed with a transmission electron microscope (TEM) (for example, JEOL Co., Ltd. make, JSM-6700F).

  The thickness of the shell layer is measured by analyzing the TEM image with image analysis software (for example, WinROOF, manufactured by Mitani Corporation). Specifically, two straight lines that are orthogonal to each other at the approximate center of the cross section of the toner particle are drawn, and the lengths of four points on the two straight lines that intersect the shell layer are measured. The average value of the four measured lengths is taken as the thickness of the shell layer of one toner particle that is the measurement target. The thickness of the shell layer is measured for 10 or more toner particles contained in the toner, and the average value of the 10 or more obtained measurement values is used as the evaluation value.

  In addition, when the thickness of the shell layer is small, the interface between the core and the shell layer on the TEM image becomes unclear, which may make it difficult to measure the thickness of the shell layer. In such a case, the thickness of the shell layer is measured by combining TEM imaging and electron energy loss spectroscopy (EELS) to clarify the interface between the core and the shell layer. Specifically, the thickness of the shell layer is specified by mapping an element (nitrogen element) characteristic of the material of the shell layer using EELS in the TEM image.

[Charge control agent (shell layer)]
In this embodiment, since the shell layer has a cationic property (positive chargeability), a positively chargeable charge control agent may be used in the shell layer.

(External additive)
In this embodiment, an external additive may be attached to the surface of the shell layer in order to improve the fluidity and handleability of the toner particles. Hereinafter, the particles before being treated with the external additive are referred to as “toner mother particles”. From the viewpoint of improving fluidity and handling properties, the amount of the external additive used is preferably 0.5 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the toner base particles. It is more preferable that the amount is not more than parts.

  The external additive is preferably composed of a metal oxide such as silica or alumina, titanium oxide, magnesium oxide, zinc oxide, strontium titanate, or barium titanate.

  The particle diameter of the external additive is preferably 0.01 μm or more and 1 μm or less from the viewpoint of improving fluidity and handling properties.

  Next, a case where the toner according to the exemplary embodiment is mixed with a carrier and used as a two-component developer will be described. In order to obtain a desired image density and suppress toner scattering, the toner content is preferably 3% by mass or more and 20% by mass or less with respect to the mass of the two-component developer. It is more preferable that the amount is not more than mass%.

[Carrier]
For example, it is preferable to use a magnetic carrier. A magnetic carrier is comprised from the carrier core material and the resin layer which coat | covers a carrier core material, for example.

  In one example, the carrier core material is composed of particles such as iron, oxidized iron, reduced iron, magnetite, copper, silicon steel, ferrite, nickel, or cobalt, or these materials and metals such as manganese, zinc, and aluminum. It is preferably composed of alloy particles. In another example, the carrier core material is preferably composed of particles of iron-nickel alloy, iron-cobalt alloy, or the like. In another example, the carrier core material is titanium oxide, aluminum oxide, copper oxide, magnesium oxide, lead oxide, zirconium oxide, silicon carbide, magnesium titanate, barium titanate, lithium titanate, lead titanate, lead zirconate It is preferably composed of ceramic particles such as lithium niobate. In another example, the carrier core material is preferably composed of particles of a high dielectric constant material such as ammonium dihydrogen phosphate, potassium dihydrogen phosphate, and Rochelle salt.

  The resin layer covering the carrier core material is, for example, a (meth) acrylic polymer, a styrene polymer, a styrene- (meth) acrylic copolymer, an olefin polymer (polyethylene, chlorinated polyethylene, polypropylene, etc.), Polyvinyl chloride, polyvinyl acetate, polycarbonate, cellulose resin, polyester resin, unsaturated polyester resin, polyamide resin, polyurethane resin, epoxy resin, silicone resin, fluororesin (polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylidene fluoride Etc.), phenol resin, xylene resin, diallyl phthalate resin, polyacetal resin, and amino resin.

  In order to improve magnetism and fluidity, the particle diameter of the carrier is preferably 20 μm or more and 120 μm or less, and more preferably 25 μm or more and 80 μm or less. The particle diameter can be measured by observing with an electron microscope or the like.

  Next, a toner manufacturing method according to this embodiment will be described.

[Formation of core]
The core is formed by, for example, a pulverization classification method (melt kneading method) or an aggregation method. According to these methods, it is possible to favorably disperse the internal additive in the binder.

(Core formation by pulverization classification)
The binder material and the internal additive material are mixed, and the mixture is melt-kneaded. Next, the melt-kneaded product is pulverized and classified to obtain a core having a desired particle size. According to the pulverization classification method, the core can be formed more easily than the aggregation method.

(Core formation by agglomeration method)
Fine particles containing the core component are aggregated in an aqueous medium. Specifically, the aqueous dispersion liquid (binder fine particle dispersion liquid) containing the binder fine particles is obtained by atomizing the binder material into a desired size in an aqueous medium. Subsequently, the fine particles are aggregated in the binder fine particle dispersion. Thereby, aggregated particles are formed.

[Formation of shell layer]
(Production of encapsulated material)
As described above, a melamine formaldehyde initial condensate such as monomethylol melamine methyl ether can be prepared by, for example, reacting melamine with formaldehyde to methylol, then methylate, and further etherify.

(A) Preparation of trimethylol melamine trimethyl ether To 1 mol of melamine, 3 mol of formaldehyde is added and reacted to prepare trimethylol melamine. Next, 3 mol of methanol is added, heated, and concentrated under reduced pressure to produce trimethylol melamine trimethyl ether as an encapsulating material.

(B) Preparation of dimethylol melamine dimethyl ether To 1 mol of melamine, 2 mol of formaldehyde is added and reacted to prepare dimethylol melamine. Next, 2 mol of methanol is added, heated, and concentrated under reduced pressure to produce dimethylolmelamine dimethyl ether as an encapsulating material.

(C) Preparation of monomethylol melamine methyl ether 1 mol of formaldehyde is added to and reacted with 1 mol of melamine to prepare monomethylol melamine. Next, 1 mol of methanol is added, heated, and concentrated under reduced pressure to produce monomethylol melamine methyl ether as an encapsulating material.

(Preparation of capsule toner particles)
A three-necked flask equipped with a thermometer and a stirring blade is prepared, and the temperature inside the flask is maintained at a predetermined temperature (preferably 30 ° C.) using a water bath. And ion-exchange water is put in a flask, 1N hydrochloric acid is further added, and pH of the aqueous medium in a flask is adjusted to 4. The encapsulating material (such as trimethylol melamine trimethyl ether) is added to the flask, and the contents of the flask are stirred to dissolve the encapsulating material (such as trimethylol melamine trimethyl ether) in an aqueous medium. Next, the core produced above is added into the flask (an acidic aqueous solution in which the encapsulating material is dissolved), and sufficiently stirred. Further, after adding ion-exchanged water and stirring, the temperature is increased at a predetermined rate (preferably 5 ° C./min) and kept at 70 ° C. for 2 hours. Allow to cool. 1N-aqueous sodium hydroxide solution (neutralizing agent) is added to neutralize to pH 7, and the capsule toner particles are recovered by filtration. The collected capsule toner particles are added to water and stirred, and then filtered again to wash the capsule toner particles. When this washing is repeated and the conductivity of the dispersion (filtrate) when the recovered core particles are dispersed in water reaches a predetermined value (preferably 10 μS / cm or less), the recovered core particles are moved to a predetermined temperature (preferably Is allowed to stand in an atmosphere for 40 hours at a predetermined time (preferably 48 hours) and dried to produce a capsule toner in which a shell layer is formed on the surface of the core.

  The conductivity of the dispersion liquid (filtrate) is preferably 10 μS / cm or less in order to suppress the environmental fluctuation of the toner charge amount from increasing. The electrical conductivity of the filtrate can be measured using, for example, Horiba COND METER ES-51 manufactured by Horiba, Ltd.

  Next, examples of the present invention will be described together with comparative examples. However, the present invention is not limited to these examples.

[Example 1]
(Production of core)
A polyester resin having the following characteristics was used as a binder. The OHV value of the polyester resin was 20 mgKOH / g, AV was 40 mgKOH / g, Tm was 100 ° C., and Tg was 48 ° C. For 100 parts by mass of this polyester resin, C.I. I. 5 parts by weight of pigment blue 15: 3 (phthalocyanine pigment) and 5 parts by weight of ester wax (manufactured by NOF Corporation, WEP-3) as a release agent were mixed and mixed using a mixer (Henschel mixer). Chips kneaded with a twin screw extruder (Ikegai, PCM-30) were pulverized to 6 microns with a mechanical pulverizer (Turbo Kogyo, turbo mill). After that, classification was performed with a classifier (manufactured by Nippon Steel Mining Co., Ltd., Elbow Jet) to obtain a core having a volume average diameter of 6.8 microns. This core had a shape index of 0.93, Tm of 90 ° C., and Tg of 49 ° C. When this core was measured for triboelectric charge (anionic property) using a standard carrier N-01, it was −20 μC / g. Furthermore, the measurement of the zeta potential at pH 4 was −15 mV, which showed a clear anionic property. Each measurement of the core was performed as follows.

〔Particle size〕
The volume average particle size (D50) was measured using a Coulter Counter Multisizer 3 manufactured by Beckman Coulter.

[Shape index]
Using a flow type particle image analyzer (manufactured by Sysmex Corporation, FPIA 3000), the circularity as a shape index was measured. Specifically, the circularity of 3000 particles was measured for each sample, and the average value was used as the evaluation value.

[Core Tm]
A sample is set in a Koka type flow tester (CFT-500D, manufactured by Shimadzu Corporation), and a 1 cm ³ sample is melted at a die pore diameter of 1 mm, a plunger load of 20 kg / cm ² , and a heating rate of 6 ° C./min. The S-curve was obtained by allowing it to flow out, and the Tm of the core was read from the obtained S-curve.

[Core Tg]
By measuring the endothermic curve using a differential scanning calorimeter (manufactured by Seiko Instruments Inc., DSC-6200), it was determined from the change point of the specific heat in the endothermic curve.

[Triboelectric charge (anionic)]
Using a tumbler mixer (manufactured by Shinmaru Enterprises, model number T2F, setting condition 96 rpm), 10 g of standard carrier N-01 (standard carrier for negatively charged polarity toner provided by the Imaging Society of Japan) On the other hand, 7% by mass of the core was mixed for 30 minutes. Then, the triboelectric charge amount of the core when the obtained mixture was rubbed with a standard carrier as a measurement sample was measured with a QM meter (manufactured by TREK, MODEL 210HS-2A).

[Core zeta potential]
0.2 g of core, 80 g of ion-exchanged water, and 20 g of 1% nonionic surfactant (polyvinylpyrrolidone, “K-85” manufactured by Nippon Shokubai Co., Ltd.) are mixed with a magnetic stirrer, and the core is uniformly dispersed. A liquid was obtained. Dilute hydrochloric acid was added to this dispersion to adjust the pH of the dispersion to 4. Then, using this dispersion as a measurement sample, the zeta potential of the core in the dispersion adjusted to pH 4 was measured with a zeta potential / particle size distribution measuring apparatus (Delsa Nano HC, manufactured by Beckman Coulter, Inc.).

(Production of encapsulated material)
Trimethylolmelamine was prepared by adding 563.1 g of formaldehyde (manufactured by Wako Pure Chemical Industries, Ltd., purity 16%) 563.1 g to 126.1 g of melamine (manufactured by Wako Pure Chemical Industries, Ltd., purity 100%). Next, 96.3 g of methanol (purity 99.8%) was added and heated, followed by concentration under reduced pressure to prepare trimethylol melamine trimethyl ether (active ingredient concentration: 80%) as an encapsulating material.

(Preparation of capsule toner particles)
A three-necked flask with a capacity of 1 liter equipped with a thermometer and a stirring blade was prepared, and the temperature in the flask was maintained at 30 ° C. using a water bath. And 150 g of ion exchange water was put in the flask, and 1N hydrochloric acid was further added to adjust the pH of the aqueous medium in the flask to 4. 1 ml of the trimethylol melamine trimethyl ether (active ingredient concentration: 80%) was added to the flask, and the contents of the flask were stirred to dissolve the trimethylol melamine trimethyl ether in an aqueous medium. Next, 150 g of the core prepared above was added to the flask (an acidic aqueous solution in which the encapsulating material was dissolved), and the mixture was sufficiently stirred. Further, 150 g of ion-exchanged water was added, the temperature was increased at a rate of 5 ° C./min while stirring, the temperature was maintained at 70 ° C. for 2 hours, and then the dispersion was cooled to room temperature at a rate of 5 ° C./min. 1N-aqueous sodium hydroxide solution (neutralizing agent) was added to neutralize the dispersion until pH 7 was reached, and the capsule toner particles were recovered from the dispersion by filtration. The collected capsule toner particles were added to 1 kg of water and stirred, and then filtered again to wash the capsule toner particles. This washing was repeated, and when the conductivity of the dispersion (filtrate) when 2 g of the collected core particles were dispersed in 20 g of water became 10 μS / cm or less, the collected core particles were left in a 40 ° C. atmosphere for 48 hours. Then, capsule toner particles having a shell layer formed on the surface of the core were produced by drying.

[Example 2]
Instead of the trimethylol melamine trimethyl ether of Example 1 (active ingredient concentration: 80%), dimethylol melamine dimethyl ether (active ingredient concentration: 80%) was used. That is, capsule toner particles were prepared in the same manner as in Example 1 except that the amount of formaldehyde added was 375.4 g and the amount of methanol added was 64.2 g to prepare dimethylolmelamine dimethyl ether.

Example 3
Instead of the trimethylol melamine trimethyl ether of Example 1 (active ingredient concentration: 80%), monomethylol melamine methyl ether (active ingredient concentration: 80%) was used. That is, capsule toner particles were prepared in the same manner as in Example 1 except that monomethylol melamine methyl ether was prepared by adding 187.7 g of formaldehyde and 32.1 g of methanol.

Example 4
Except that 0.5 ml of trimethylol melamine trimethyl ether (active ingredient concentration: 80%) of Example 1 and 0.5 ml of monomethylol melamine methyl ether (active ingredient concentration: 80%) of Example 3 were used in combination. In the same manner as in Example 1, capsule toner particles were produced.

[Comparative Example 1]
Instead of the trimethylol melamine trimethyl ether of Example 1 (active ingredient concentration: 80%), hexamethylol melamine hexamethyl ether (active ingredient concentration: 80%) was used. That is, capsule toner particles were prepared in the same manner as in Example 1 except that hexamethylol melamine hexamethyl ether was prepared by adding 1126.1 g of formaldehyde and 192.6 g of methanol.

[Comparative Example 2]
Instead of the trimethylol melamine trimethyl ether of Example 1 (active ingredient concentration: 80%), pentamethylol melamine pentamethyl ether (active ingredient concentration: 80%) was used. That is, capsule toner particles were prepared in the same manner as in Example 1 except that pentamethylol melamine pentamethyl ether was prepared by adding 938.4 g of formaldehyde and 160.5 g of methanol.

[Comparative Example 3]
Instead of trimethylol melamine trimethyl ether (active ingredient concentration: 80%) in Example 1, tetramethylol melamine tetramethyl ether (active ingredient concentration: 80%) was used. That is, capsule toner particles were prepared in the same manner as in Example 1 except that tetramethylol melamine tetramethyl ether was prepared by adding 750.8 g of formaldehyde and 128.4 g of methanol.

≪Evaluation≫
Using the toners (capsule toner particles) of Examples and Comparative Examples, each characteristic was evaluated according to the following criteria. The results are shown in Table 1 below.

[Toner particle size (polymerization stability)]
As an index of polymerization stability, the particle diameters of the toners (capsule toner particles) of Examples and Comparative Examples were measured. The particle diameter of the toner (capsule toner particles) was measured by using a Coulter Counter Multisizer 3 manufactured by Beckman Coulter, Inc., and a volume average particle diameter (D50) was measured. In the evaluation, a toner (capsule toner particle) having a particle diameter of less than +0.2 μm of the core and “X” of +0.2 μm or more was used.

[Blocking properties]
3 g of toners (capsule toner particles) of Examples and Comparative Examples are weighed into a 30 ml sample bottle, and the sample bottle containing the toner is placed in a 60 ° C. constant temperature bath (Constant Temperature Oven DKN602 (manufactured by Yamato Scientific Co., Ltd.)). It was left for 3 hours. Then, the sample bottle was taken out from the thermostat and allowed to stand at room temperature for 24 hours. Next, a 200-mesh sieve having a known mass was attached to a powder tester (TYPE PT-E 84810 (manufactured by Hosokawa Micron Corporation)), and the toner after standing at room temperature was placed on the sieve. Then, the toner was sieved for 30 seconds under the condition of Rheostat 5.0. Next, the mass of the toner remaining on the sieve was measured. From the mass of the toner on the sieve after sieving, the heat resistant storage stability was evaluated according to the following criteria. In the evaluation, a case where the toner remaining on the mesh was less than 20% by mass was marked as “◯”, and a case where the toner remaining on the mesh was 20% by mass or more was marked as “X”.

[Fixability]
(Mixing of carrier and toner)
A carrier (a carrier for a printer (FS-C5016 (manufactured by Kyocera Document Solutions Co., Ltd.))) and a toner of 10% by mass with respect to the mass of the carrier are mixed with a ball mill for 30 minutes to prepare a two-component developer. did.

As an evaluation machine, a printer (FS-C5350DN (manufactured by Kyocera Document Solutions Inc.)) remodeled so that the fixing temperature can be adjusted was used. The two-component developer prepared as described above was put into a cyan color developing unit of the evaluation machine, and the toner was put into a cyan toner container of the evaluation machine. The amount of applied toner was set to 1.8 mg / cm 2, and an unfixed toner image (2 cm × 3 cm patch sample) was formed on a recording medium (Color Copy 90 (manufactured by Neusidler)). The fixing temperature of the fixing device of the evaluation machine was set to 100 ° C., and an unfixed solid image was fixed at a linear speed of 195 mm / sec. The recording medium on which the solid image was fixed was folded in half so that the surface on which the image was formed was on the inside, and was rubbed 5 times on the crease with a 1 kg weight covered with a fabric. Next, the recording medium was spread, the bent portion of the fixed image was observed, and the toner peeling length (peeling length) of the bent portion was measured. Evaluation was made according to the following criteria. The fixing temperature was increased from 100 ° C. to 200 ° C. in 5 ° C. steps, and the length of peeling at each temperature was measured. The lowest temperature at which the length of peeling became 1 mm or less was defined as the lowest fixing temperature.
(Evaluation)
○: Minimum fixing temperature is 160 ° C. or lower ×: Minimum fixing temperature is 165 ° C. or higher

  From the result of the said Table 1, since Examples 1-4 use monomethylol melamine methyl ether, dimethylol melamine dimethyl ether, trimethylol melamine trimethyl ether with few amounts of methylol groups as an encapsulating material, it is in polymerization stability. Excellent, blocking property and fixing property were all good.

  On the other hand, Comparative Examples 1 to 3 have a large amount of methylol groups in the melamine formaldehyde initial condensate used for the encapsulating material, so the condensation polymerization reaction is slow, and a sufficient capsule film is not formed on the core surface. Aggregation between cores occurred. In addition, the capsule film thickness becomes non-uniform due to aggregation of the cores, and the core bleeds from where the capsule film thickness is thin, so that the blocking property is inferior.

  The present invention can be used as an electrostatic charge image developing capsule toner used for developing an electrostatic latent image formed in electrophotography.

Claims (2)

An electrostatic charge image developing capsule toner in which a shell layer made of a cationic encapsulating material is formed on the surface of an anionic core,
Capsule toner for developing an electrostatic charge image, wherein the encapsulating material contains at least one selected from the group consisting of monomethylol melamine methyl ether, dimethylol melamine dimethyl ether and trimethylol melamine trimethyl ether.   The capsule toner for electrostatic image development according to claim 1, wherein the anionic level exhibits a charging property of −10 μC / g or less as measured by triboelectric charging with a standard carrier N-01 provided by the Imaging Society of Japan.