Electrostatic latent image developing toner

Abstract

To provide an electrostatic latent image developing toner that exhibits excellent electrostatic properties, low-temperature fixability, and maintains good transferability. [Solution] The toner for electrostatic latent image development consists of toner particles comprising toner core particles and a shell layer. The shell layer is formed of resin fine particles containing a vinyl resin. The resin fine particles include multiple types of first resin fine particles and second resin fine particles. The shell layer has a sea-like region formed using multiple types of first resin fine particles and island-like protrusions scattered within the sea-like region, formed using second resin fine particles having a larger average particle diameter than the first resin fine particles. At least one of the first fine particles contains a quaternary ammonium compound, and the second resin fine particles contain a fluorine-containing vinyl resin. The average particle diameter of the second resin fine particles is 70 nm to 150 nm, and the coverage rate of the protrusions on the surface of the toner core particles is 10% to 50%.

Description

Technical Field

[0001] The present invention relates to a toner for developing an electrostatic latent image.

Background Art

[0002] Generally, in electrophotography, after the surface of an electrostatic latent image carrier is charged by corona discharge or the like, it is exposed by a laser or the like to form an electrostatic latent image. The formed electrostatic latent image is developed with toner to form a toner image. Further, the formed toner image is transferred onto a recording medium to obtain a high-quality image. Usually, for a toner applied to electrophotography, after a colorant, a charge control agent, a release agent, a magnetic material, etc. are mixed with a binder resin such as a thermoplastic resin, kneading, pulverization, and classification are performed to obtain toner particles (toner mother particles) having an average particle size of 5 μm or more and 10 μm or less. And for the purpose of imparting fluidity to the toner, imparting suitable charging performance to the toner, and improving the cleaning property of the toner from the photoreceptor drum, inorganic fine powders such as silica and titanium oxide are externally added to the toner mother particles.

[0003] Regarding such a toner, conventionally, for the purpose of obtaining good fixing property in a low temperature region, improving storage stability at high temperature, and improving blocking resistance, toner core particles using a low melting point binder resin are coated with a shell layer made of a resin having a glass transition point (Tg) higher than that of the binder resin of the toner core particles, and a toner having a core-shell structure is used.

[0004] Patent Document 1 discloses a toner for developing an electrostatic latent image, which includes a core and a shell layer covering the surface of the core, and the surface of the shell layer has a first domain distributed in an island shape and a second domain distributed in a sea shape. The first domain is substantially composed of a first thermoplastic resin, and the second domain is substantially composed of a second thermoplastic resin having stronger hydrophobicity than the first thermoplastic resin.

[0005] Patent Document 2 discloses an electrostatic latent image developing toner comprising a core and a shell layer covering the surface of the core, wherein the surface of the shell layer has a sea-like region and a plurality of island-like regions distributed island-like relative to the sea-like region, each having a stronger positive charge than the sea-like region. At the boundary between the toner core and the shell layer, there are a plurality of boundary particles attached to the toner core. The surface of the shell layer has a plurality of protrusions corresponding to the boundary particles.

[0006] Patent Document 3 discloses a toner comprising core particles, which are resin particles, and shell particles that cover the surface of the core particles. The shell particles include at least one of a styrene-acrylic copolymer resin and a polyester resin. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] International Patent Publication No. 2017 / 057474 [Patent Document 2] Japanese Patent Publication No. 2017-116568 [Patent Document 3] Japanese Patent Publication No. 2009-15175 [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] The toner described in Patent Document 1 is capable of achieving both heat resistance and low-temperature fixation, but the surface of the shell layer does not have any protrusions. Therefore, good transferability could not be expected. In addition, although the use of spacer particles as an external additive could be considered, there was a possibility that the spacer particles would detach, resulting in insufficient effectiveness.

[0009] The toner described in Patent Document 2 improves transferability and cleaning performance by having protrusions formed on the surface of the shell layer act as spacers. However, it has been found that the electrostatic stability deteriorates in high-temperature and high-humidity environments when boundary particles are used to form the protrusions. Furthermore, if the adhesion of the shell layer is high, it is possible that the protrusions may not function as spacers.

[0010] The toner described in Patent Document 3 has shell particles made of a styrene-acrylic acid copolymer resin with a volume-average diameter of 50 to 1000 nm, which are fused to the core particles to form protrusions. This makes it easier for the toner to catch on the cleaning blade, improving cleaning performance. However, the shell layer is thick, and because it lacks a charge control function, it suffers from problems such as poor low-temperature fixation and charge stability.

[0011] In view of the above problems, the present invention aims to provide an electrostatic latent image developing toner that is excellent in chargeability and low-temperature fixability, and that can maintain good transferability. [Means for solving the problem]

[0012] To achieve the above objective, the first configuration of the present invention is an electrostatic latent image developing toner comprising toner particles including toner core particles and a shell layer. The toner core particles include at least a binder resin, a release agent, and a colorant. The shell layer coats the toner core particles. The shell layer is formed of resin fine particles containing a vinyl resin. The resin fine particles include a plurality of first resin fine particles and second resin fine particles having a larger average particle diameter than the first resin fine particles. The shell layer has a sea-like region formed using the plurality of first resin fine particles and island-like protrusions scattered in the sea-like region, formed using the second resin fine particles. At least one of the first fine particles contains a quaternary ammonium compound, and the second resin fine particles contain a fluorine-containing vinyl resin. The average particle diameter of the second resin fine particles is 70 nm to 150 nm. The coverage rate of the protrusions on the surface of the toner core particles is 10% to 50%. [Effects of the Invention]

[0013] According to the first configuration of the present invention, a toner for electrostatic latent image development is obtained that has excellent heat resistance, fixability, charge amount, transfer efficiency, and image density. [Brief explanation of the drawing]

[0014] [Figure 1] This figure shows an example of the cross-sectional structure of the electrostatic electrolysis developing toner 101 of the present invention. [Figure 2] A schematic diagram showing a magnified portion of the cross-section of the electrostatic electrolysis developing toner 101 in Figure 1. [Modes for carrying out the invention]

[0015] Embodiments of the present invention will be described in detail below. Unless otherwise specified, the evaluation results (values ​​indicating shape or physical properties, etc.) for the powder (more specifically, toner core particles, toner mother particles, external additives, or toner, etc.) are the number average values ​​of the values ​​measured for each of the average particles selected from the powder. Unless otherwise specified, the number average particle diameter of the powder is the number average value of the equivalent circle diameter (the diameter of a circle having the same area as the projected area of ​​the particle) of the primary particles measured using a microscope. Unless otherwise specified, the measured value of the median volume diameter (D50) of the powder is the value measured using a laser diffraction / scattering particle size distribution analyzer ("LA-750" manufactured by Horiba, Ltd.). Unless otherwise specified, the measured values ​​of the acid value and hydroxyl value are the values ​​measured according to "JIS (Japanese Industrial Standards) K0070-1992". Furthermore, unless otherwise specified, the measured values ​​for number-average molecular weight (Mn) and mass-average molecular weight (Mw) are those obtained using gel permeation chromatography.

[0016] In the following, the compound name may be followed by "system" to comprehensively refer to the compound and its derivatives. When "system" is followed by a compound name to represent a polymer name, it means that the repeating unit of the polymer originates from the compound or its derivative. Also, acrylic and methacrylic may be comprehensively referred to as "(meth)acrylic". Furthermore, acryloyl (CH)2 =CH-CO-) and methacryloyl (CH 2 =C(CH 3 The terms )-CO-) are sometimes collectively referred to as "(meth)acryloyl".

[0017] The toner according to this embodiment can be suitably used for developing electrostatic latent images, for example, as a positively charged toner. The toner of this embodiment is a powder containing a plurality of toner particles (each particle having a configuration described later). The toner may be used as a one-component developer. Alternatively, a two-component developer may be prepared by mixing the toner and carrier using a mixing device (e.g., a ball mill). To form high-quality images, it is preferable to use a ferrite carrier as the carrier. Furthermore, to form high-quality images over a long period of time, it is preferable to use magnetic carrier particles having a carrier core and a resin layer covering the carrier core. To produce magnetic carrier particles, the carrier core may be formed from a magnetic material (e.g., ferrite), or from a resin in which magnetic particles are dispersed. Alternatively, magnetic particles may be dispersed in a resin layer covering the carrier core. To form high-quality images, the amount of toner in the two-component developer is preferably 5 parts by mass or more and 15 parts by mass or less per 100 parts by mass of carrier. Note that the positively charged toner becomes positively charged due to friction with the carrier.

[0018] The toner particles included in the toner according to this embodiment include a core (hereinafter referred to as toner core particles) and a shell layer (capsule layer) formed on the surface of the toner core particles. The shell layer is substantially composed of a resin. For example, by covering the toner core particles that melt at a low temperature with a shell layer having excellent heat resistance, it becomes possible to achieve both heat-resistant storage properties and low-temperature fixing properties of the toner. Additives may be dispersed in the resin constituting the shell layer. The shell layer may cover the entire surface of the toner core particles or may partially cover the surface of the toner core particles. An external additive may adhere to the surface of the shell layer (or the surface region of the toner core not covered by the shell layer). If not necessary, the external additive may be omitted. Toner particles not provided with a shell layer may be mixed in the toner mainly containing toner particles provided with a shell layer. Hereinafter, the toner particles before the external additive adheres are referred to as toner mother particles. Also, the material for forming the toner core particles is referred to as toner core material. Also, the material for forming the shell layer is referred to as shell material.

[0019] The toner according to this embodiment can be used for forming an image, for example, in an electrophotographic apparatus (image forming apparatus). Hereinafter, an example of an image forming method by an electrophotographic apparatus will be described.

[0020] First, an electrostatic latent image is formed on a photoreceptor (e.g., the surface layer of a photoreceptor drum) based on image data. Next, the formed electrostatic latent image is developed using a developer containing toner. In the developing process, toner (e.g., toner charged by friction with a carrier or blade) on a developing sleeve (e.g., the surface layer of a developing roller in a developing device) disposed near the photoreceptor is attached to the electrostatic latent image to form a toner image on the photoreceptor. Then, in the subsequent transfer process, the toner image on the photoreceptor is directly transferred to a recording medium (e.g., paper). Alternatively, after primary transfer to an intermediate transfer body (e.g., a transfer belt), the toner image on the intermediate transfer body is further secondarily transferred to the recording medium. Thereafter, the toner is heated to fix the toner to the recording medium. As a result, an image is formed on the recording medium. For example, a full-color image can be formed by overlapping four-color toner images of black, yellow, magenta, and cyan.

[0021] [1. Basic Structure of Toner] FIG. 1 is a diagram showing an example of a cross-sectional structure of a toner for developing an electrostatic latent image of the present invention having the above basic structure. As shown in FIG. 1, a toner 101 for developing an electrostatic latent image of the present invention (hereinafter, also simply referred to as toner) has a shell layer 103 covering the surface of toner core particles 102. The toner core particles 102 contain at least a binder resin, a release agent, and a colorant.

[0022] The thickness of the shell layer 103 is not particularly limited as long as it does not inhibit the object of the present invention, and is preferably 0.03 μm or more and 1 μm or less, more preferably 0.04 μm or more and 0.7 μm or less, particularly preferably 0.05 μm or more and 0.5 μm or less, and most preferably 0.05 μm or more and 0.3 μm or less. In addition, since the toner 101 of the present invention has convex portions 105 (see FIG. 2) on the shell layer 103, the thickness of the shell layer 103 is non-uniform. Therefore, in this specification, the thickness of the thickest portion (convex portion 105) of the shell layer 103 is defined as the "thickness of the shell layer".

[0023] If the shell layer 103 is too thick, the shell layer 103 is less likely to break due to the pressure applied to the toner 101 when fixing the toner 101 to the recording medium. In this case, the softening or melting of the binder resin and release agent contained in the toner core particles 102 does not proceed quickly, making it difficult to fix the toner onto the recording medium at low temperatures. On the other hand, if the shell layer 103 is too thin, the strength of the shell layer 103 will be low. If the strength of the shell layer 103 is low, it may break due to impact during transportation, etc., and when storing the toner 101 at high temperatures, the toner 101 is more likely to aggregate due to the release agent seeping onto the surface of the toner 101 from the area where the shell layer 103 has broken.

[0024] The thickness of the shell layer 103 can be measured by observing a cross-section of the toner 101 using a transmission electron microscope (TEM) and analyzing the TEM image using commercially available image analysis software. Examples of commercially available image analysis software include WinROOF (manufactured by Mitani Corporation).

[0025] In the toner 101 of the present invention, it is not necessary for the entire surface of the toner core particles 102 to be covered by the shell layer 103. In order to achieve both heat resistance for storage and low-temperature fixing properties of the toner 101, it is preferable that the shell layer 103 covers an area of ​​50% to 99% of the surface area of ​​the toner core particles 102. However, the entire surface of the toner core particles 102 may be covered by the shell layer 103.

[0026] The coating state of the shell layer 103 on the surface of the toner 101 can be confirmed using a scanning electron microscope (SEM). In addition, the formation state of the protrusions 105 of the shell layer 103 and the interior of the shell layer 103 of the toner 101 can be confirmed by observing a cross-section of the toner 101 using a transmission electron microscope (TEM).

[0027] Figure 2 is a schematic diagram showing a part of the cross-section of the toner 101 in Figure 1. The toner 101 of the present invention has a shell layer 103 which has a sea-like region 104 and a plurality of island-like protrusions 105. That is, the surface of the toner core particles 102 is covered with the sea-like region 104 and the protrusions 105 of the shell layer 103. This is advantageous for achieving both heat resistance and low-temperature fixation.

[0028] The shell layer 103 is formed of at least two types of vinyl resin microparticles 106 and 107 with different average particle sizes. The sea-like region 104 is formed of vinyl resin microparticles (first resin microparticles) 106 with a relatively small average particle size. The convex portion 105 is formed of vinyl resin microparticles (second resin microparticles) 107 with a relatively large average particle size.

[0029] The ocean-like region 104 is formed from multiple types of first resin fine particles 106. Of the multiple types of first resin fine particles 106, at least one type contains a quaternary ammonium compound. By containing a quaternary ammonium compound in the ocean-like region 104, the toner 101 can obtain stable positive charge at low cost.

[0030] In the toner 101 of the present invention, the surface of the shell layer 103 has a plurality of protrusions 105, which function as spacers. Therefore, the contact area between the toner 101 and the photoreceptor drum and intermediate transfer belt can be reduced compared to a case where the shell layer 103 does not have protrusions 105.

[0031] This reduces the likelihood of toner 101 adhering to the photoreceptor drum, intermediate transfer belt, etc., thereby improving the cleanability (e.g., resistance to adhesion to the photoreceptor drum) and developability (e.g., transfer efficiency) of the toner 101.

[0032] The protrusions 105 contain at least a fluorine-containing vinyl resin. The inclusion of the fluorine-containing vinyl resin in the protrusions 105 reduces their adhesion, improving the release properties of the toner 101 when it comes into contact with the photoreceptor drum and intermediate transfer belt, and maintaining good transferability. The protrusions 105 cover 10 to 50% of the entire surface of the toner core particles 102.

[0033] The toner 101 of the present invention, having the basic configuration described above, is considered to have sufficient positive charge properties both in normal temperature and humidity environments and in high temperature and high humidity environments. Furthermore, the toner 101 is considered to be able to form high-quality images (for example, images with low fogging density) both in normal temperature and humidity environments and in high temperature and high humidity environments.

[0034] It is preferable that the protrusions 105 on the surface of the shell layer 103 are positively charged regions. When toner 101 is mixed with a magnetic carrier to form a two-component developer, the protrusions 105 of the shell layer 103 are more likely to come into contact with the carrier. Therefore, it is thought that if the protrusions 105 are positively charged regions, the toner 101 will be more easily triboelectrically charged.

[0035] Furthermore, in order for the toner 101 to have sufficient positive charge properties both in a normal temperature and humidity environment and in a high temperature and high humidity environment, it is preferable that the protrusions 105 (positive charge regions) are evenly distributed on the surface of the shell layer 103. By having the positive charge regions scattered rather than concentrated in one place, it becomes possible to improve the overall positive charge properties of the surface of the toner 101. In addition, it is possible to ensure stable release of the toner from the photoreceptor drum and intermediate transfer belt.

[0036] [2. Toner Materials] Next, the essential or optional components constituting the toner of the present invention will be described. The toner core particles contain at least a release agent and a colorant in the binder resin. They may also contain a charge control agent, magnetic powder, etc., as needed. Furthermore, the surface of the toner of the present invention may be treated with an external additive if desired.

[0037] The binder resin, release agent, charge control agent, colorant, magnetic powder, resin fine particles that form the toner core particles, and external additives, along with the method for manufacturing the toner of the present invention, will be described below in order.

[0038] (Binding resin) The toner core particles constituting the toner of the present invention contain a binder resin. The binder resin that can be contained in the toner core particles is not particularly limited as long as it is a resin that has been conventionally used as a binder resin for toner. Specific examples of binder resins include thermoplastic resins such as styrene resins, acrylic resins, styrene-acrylic resins, polyethylene resins, polypropylene resins, vinyl chloride resins, polyester resins, polyamide resins, polyurethane resins, polyvinyl alcohol resins, vinyl ether resins, N-vinyl resins, and styrene-butadiene resins. Among these resins, polyester resins are preferred in terms of the dispersibility of the colorant in the binder resin, the electrostatic properties of the toner, and the fixation to paper. Polyester resins will be described below.

[0039] Polyester resins can be obtained by condensation polymerization or copolymerization of a divalent or trivalent or higher alcohol component with a divalent or trivalent or higher carboxylic acid component. The following alcohol and carboxylic acid components are examples of components used in the synthesis of polyester resins.

[0040] Specific examples of divalent or trivalent or higher alcohol components include diols such as 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; bisphenol A, hydrogenated bisphenol A, and polyoxyethylene Examples include bisphenols such as bisphenol A and polyoxypropylene bisphenol A; and trivalent or higher alcohols such as 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, and 1,3,5-trihydroxymethylbenzene.

[0041] Specific examples of divalent or trivalent or higher carboxylic acid components include maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, succinic acid, adipic acid, sebatic acid, azelaic acid, malonic acid, or divalent alkyl or alkenyl succinic acids such as n-butylsuccinic acid, n-butenylsuccinic acid, isobutylsuccinic acid, isobutenylsuccinic acid, n-octylsuccinic acid, n-octenylsuccinic acid, n-dodecylsuccinic acid, n-dodecenylsuccinic acid, isododecylsuccinic acid, and isododecenylsuccinic acid. Carboxylic acids include trivalent or higher carboxylic acids such as 1,2,4-benzenetricarboxylic acid (trimellitic acid), 1,2,5-benzenetricarboxylic acid, 2,5,7-naphthalentricarboxylic acid, 1,2,4-naphthalentricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, 1,2,4-cyclohexanetricarboxylic acid, tetra(methylenecarboxyl)methane, 1,2,7,8-octanetetracarboxylic acid, pyromellitic acid, and empol trimeric acid. These divalent or trivalent or higher carboxylic acid components may be used as ester-forming derivatives such as acid halides, acid anhydrides, and lower alkyl esters. Here, "lower alkyl" means an alkyl group having 1 to 6 carbon atoms.

[0042] When the binder resin is a polyester resin, the softening point of the polyester resin is preferably 70°C to 130°C, and more preferably 80°C to 120°C. To improve the strength of the toner core and the fixation of the toner, the number-average molecular weight (Mn) of the polyester resin is preferably 1000 to 2000. The molecular weight distribution of the polyester resin (ratio of mass-average molecular weight (Mw) to number-average molecular weight (Mn) Mw / Mn) is preferably 9 to 21.

[0043] As the binder resin, a thermoplastic resin is preferable because it has good adhesion to paper. However, thermoplastic resins can be used alone, or crosslinking agents or thermosetting resins can be added to them. By adding crosslinking agents or thermosetting resins and introducing a partially crosslinked structure into the binder resin, the heat resistance, storage properties, and durability of the toner can be improved without reducing the toner's adhesion. When using a thermosetting resin, the amount of crosslinked portion (gel amount) of the binder resin extracted using a Soxhlet extractor is preferably 10% by mass or less, and more preferably 0.1% by mass or more and 10% by mass or less, relative to the mass of the binder resin.

[0044] Epoxy resins and cyanate resins are preferred thermosetting resins that can be used with thermoplastic resins. Specific examples of suitable thermosetting resins include bisphenol A type epoxy resins, hydrogenated bisphenol A type epoxy resins, novolac type epoxy resins, polyalkylene ether type epoxy resins, cyclic aliphatic type epoxy resins, and cyanate resins. Two or more of these thermosetting resins can be used in combination.

[0045] The glass transition temperature (Tg) of the binder resin is preferably between 40°C and 70°C. If the glass transition temperature is too high, the low-temperature fixing performance of the toner tends to decrease. If the glass transition temperature is too low, the heat-resistant storage performance of the toner tends to decrease.

[0046] The glass transition point of a binder resin can be determined from the point of change in the specific heat of the binder resin using a differential scanning calorimeter (DSC). More specifically, the glass transition point of the binder resin can be determined by measuring the endothermic curve of the binder resin using a Seiko Instruments Inc. DSC-6200 differential scanning calorimeter as the measuring device. A 10 mg sample is placed in an aluminum pan, and an empty aluminum pan is used as a reference. The glass transition point of the binder resin can be determined from the endothermic curve obtained by measuring the binder resin at room temperature and humidity with a temperature range of 25°C to 200°C and a heating rate of 10°C / min.

[0047] The mass-average molecular weight (Mw) of the binder resin is not particularly limited as long as it does not hinder the objectives of the present invention. Typically, the mass-average molecular weight (Mw) of the binder resin is preferably 20,000 to 300,000, and more preferably 30,000 to 2,000,000. The mass-average molecular weight of the binder resin can be determined by gel permeation chromatography (GPC) using a calibration curve prepared in advance using standard polystyrene resin.

[0048] (Release agent) The toner core particles contain a release agent to improve adhesion and offset resistance. The type of release agent that can be included in the toner core particles is not particularly limited as long as it does not hinder the objectives of the present invention. Wax is preferred as the release agent, and examples of waxes include carnauba wax, synthetic ester wax, polyethylene wax, polypropylene wax, fluororesin wax, Fischer-Tropsch wax, paraffin wax, montan wax, and rice wax. Two or more of these release agents can be used in combination. By adding such a release agent to the toner core particles 102, the occurrence of offset and image smearing (smudges around the image when the image is rubbed) can be suppressed more efficiently.

[0049] When polyester resin is used as the binder resin, from the viewpoint of compatibility, one or more release agents selected from the group consisting of carnauba wax, synthetic ester wax, and polyethylene wax are preferably used as the release agent. Similarly, when polystyrene resin is used as the binder resin, from the viewpoint of compatibility, Fischer-Tropsch wax and / or paraffin wax are preferably used as the release agent.

[0050] Fischer-Tropsch wax is a straight-chain hydrocarbon compound with few iso-structure molecules or side chains, produced using the Fischer-Tropsch reaction, which is a catalytic hydrogenation reaction of carbon monoxide.

[0051] Among Fischer-Tropsch waxes, those with a mass-average molecular weight of 1,000 or more and whose endothermic peak bottom temperature observed by DSC measurement is in the range of 100°C to 120°C are more preferable. Examples of such Fischer-Tropsch waxes include Sazol wax C1 (endothermic peak bottom temperature: 106.5°C), Sazol wax C105 (endothermic peak bottom temperature: 102.1°C), and Sazol wax SPRAY (endothermic peak bottom temperature: 102.1°C), all available from Sazol.

[0052] The amount of release agent used is not particularly limited as long as it does not hinder the objectives of the present invention. Preferably, the amount of release agent used is 1% by mass or more and 10% by mass or less, relative to the total mass of the toner core particles 102. If the amount of release agent used is too little, the desired effect of suppressing offset and image smearing in the formed image may not be obtained, and if the amount of release agent used is too much, the heat resistance of the toner may decrease due to fusion of toners.

[0053] (Coloring agent) Toner core particles contain a colorant. The colorant that can be included in the toner core particles can be any known pigment or dye, depending on the color of the toner. Specific examples of suitable colorants that can be added to toner include: black pigments such as carbon black, acetylene black, lamp black, and aniline black; yellow pigments such as lead yellow, zinc yellow, cadmium yellow, yellow iron oxide, mineral fast yellow, nickel titanium yellow, navel yellow, naphthol yellow S, Hansa yellow G, Hansa yellow 10G, benzidine yellow G, benzidine yellow GR, quinoline yellow lake, permanent yellow NCG, tartrazine lake, monoazo yellow, and diazo yellow; orange pigments such as red lead yellow, molybdenum orange, permanent orange GTR, pyrazolone orange, balkan orange, and induthrene brilliant orange GK; red iron oxide, cadmium red, red lead, mercury cadmium sulfide, permanent red 4R, lithol red, and pyrazolone. Examples of colorants include red pigments such as Lon Red, Watching Red Calcium Salt, Lake Red D, Brilliant Carmine 6B, Eosin Lake, Rhodamine Lake B, Alizarin Lake, Brilliant Carmine 3B, and Monoazo Red; purple pigments such as Manganese Violet, Fast Violet B, and Methyl Violet Lake; blue pigments such as Prussian Blue, Cobalt Blue, Alkali Blue Lake, Victoria Blue Partial Chloride, Fast Sky Blue, Induthlene Blue BC, and Phthalocyanine Blue; green pigments such as Chrome Green, Chromium Oxide, Pigment Green B, Malachite Green Lake, and Final Yellow Green G; white pigments such as Zinc Oxide, Titanium Dioxide, Antimony White, and Zinc Sulfide; and extender pigments such as Barite Powder, Barium Carbonate, Clay, Silica, White Carbon, Talc, and Alumina White. Two or more of these colorants can also be used in combination to adjust the toner to a desired hue.

[0054] The amount of colorant used is not particularly limited as long as it does not hinder the objective of the present invention. Specifically, the amount of colorant used is preferably 1% by mass or more and 10% by mass or less, and more preferably 2% by mass or more and 7% by mass or less, relative to the total mass of the toner core particles.

[0055] Furthermore, a colorant can also be used as a masterbatch in which the colorant is pre-dispersed in a resin material such as a thermoplastic resin. When using a colorant as a masterbatch, it is preferable that the resin contained in the masterbatch is the same type of resin as the binder resin.

[0056] (Charge control agent) Toner core particles may contain a charge control agent to improve the charge level of the toner and its charge rise characteristics, which are indicators of whether or not it can be charged to a predetermined charge level in a short time, thereby obtaining a toner with excellent durability and stability. When developing the toner with a positive charge, a positive charge control agent is used, and when developing the toner with a negative charge, a negative charge control agent is used.

[0057] The types of charge control agents that can be contained in toner core particles are not particularly limited as long as they do not hinder the objectives of the present invention, and can be appropriately selected from charge control agents conventionally used in toners. Specific examples of positively charged charge control agents include azine compounds such as pyridazine, pyrimidine, pyrazine, orthoxazine, metaoxazine, paraoxazine, orthothiaidine, metathiaidine, parathiaidine, 1,2,3-triazine, 1,2,4-triazine, 1,3,5-triazine, 1,2,4-oxadiazine, 1,3,4-oxadiazine, 1,2,6-oxadiazine, 1,3,4-thiadiazine, 1,3,5-thiadiazine, 1,2,3,4-tetrazine, 1,2,4,5-tetrazine, 1,2,3,5-tetrazine, 1,2,4,6-oxatriazine, 1,3,4,5-oxatriazine, phthalazine, quinazoline, and quinoxaline; azine compounds Examples include direct dyes consisting of azine compounds such as Stread FC, Azin Fast Red 12BK, Azin Violet BO, Azin Brown 3G, Azin Light Brown GR, Azin Dark Green BH / C, Azin Deep Black EW, and Azin Deep Black 3RL; nigrosine compounds such as nigrosine, nigrosine salts, and nigrosine derivatives; acid dyes consisting of nigrosine compounds such as nigrosine BK, nigrosine NB, and nigrosine Z; metal salts of naphthenic acid or higher fatty acids; alkoxylated amines; alkylamides; and quaternary ammonium salts such as benzylmethylhexyldecylammonium and decyltrimethylammonium chloride. Among these positively charged charge control agents, nigrosine compounds are particularly preferred because they provide a faster charge rise. Two or more of these positively charged charge control agents can be used in combination.

[0058] Resins having quaternary ammonium salts, carboxylates, or carboxyl groups as functional groups can also be used as positively charged charge control agents. More specifically, examples include styrene resins having quaternary ammonium salts, acrylic resins having quaternary ammonium salts, styrene-acrylic resins having quaternary ammonium salts, polyester resins having quaternary ammonium salts, styrene resins having carboxylates, acrylic resins having carboxylates, styrene-acrylic resins having carboxylates, polyester resins having carboxylates, styrene resins having carboxyl groups, acrylic resins having carboxyl groups, styrene-acrylic resins having carboxyl groups, and polyester resins having carboxyl groups. The molecular weight of these resins is not particularly limited as long as it does not hinder the objectives of the present invention, and they may be oligomers or polymers.

[0059] Among resins that can be used as positively charged charge control agents, styrene-acrylic resins having quaternary ammonium salts as functional groups are more preferred because the amount of charge can be easily adjusted to a value within a desired range. Specific examples of preferred acrylic comonomers copolymerized with styrene units in styrene-acrylic resins having quaternary ammonium salts as functional groups include alkyl (meth)acrylates such as methyl acrylate, ethyl acrylate, n-propyl acrylate, iso-propyl acrylate, n-butyl acrylate, iso-butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, and iso-butyl methacrylate.

[0060] Furthermore, as quaternary ammonium salts, dialkylaminoalkyl(meth)acrylates, dialkyl(meth)acrylamides, or units derived from dialkylaminoalkyl(meth)acrylamides through a quaternization process can be used. Specific examples of dialkylaminoalkyl(meth)acrylates include dimethylaminoethyl(meth)acrylate, diethylaminoethyl(meth)acrylate, dipropylaminoethyl(meth)acrylate, and dibutylaminoethyl(meth)acrylate. Specific examples of dialkyl(meth)acrylamides include dimethylmethacrylamide, and specific examples of dialkylaminoalkyl(meth)acrylamides include dimethylaminopropylmethacrylamide. In addition, hydroxyl group-containing polymerizable monomers such as hydroxyethyl(meth)acrylate, hydroxypropyl(meth)acrylate, 2-hydroxybutyl(meth)acrylate, and N-methylol(meth)acrylamide can be used in combination during polymerization.

[0061] Specific examples of negatively charged charge control agents include, for example, organometallic complexes, chelate compounds, monoazometallic complexes, acetylacetone metal complexes, aromatic hydroxycarboxylic acids, aromatic dicarboxylic acid-based metal complexes, aromatic monocarboxylic acids, and aromatic polycarboxylic acids, their metal salts, anhydrides, esters, and phenol derivatives such as bisphenol. Among these, organometallic complexes and chelate compounds are preferred. Among organometallic complexes and chelate compounds, acetylacetone metal complexes such as aluminum acetylacetonate and iron(II) acetylacetonate, and salicylic acid-based metal complexes or salicylic acid-based metal salts such as 3,5-di-tert-butylchromium salicylate are more preferred, and salicylic acid-based metal complexes or salicylic acid-based metal salts are particularly preferred. Two or more of these negatively charged charge control agents can be used in combination.

[0062] The amount of positively or negatively charged charge control agent used is not particularly limited as long as it does not hinder the objectives of the present invention. Typically, the amount of positively or negatively charged charge control agent used is preferably 0.1% to 10% by mass relative to the total mass of the toner core particles. If the amount of charge control agent used is insufficient, it is difficult to stably charge the toner to a predetermined polarity, which may result in the image density of the formed image falling below the desired value or making it difficult to maintain the image density over a long period of time. In addition, because the charge control agent is difficult to disperse uniformly, the formed image is more prone to blurring, and contamination of the latent image-carrying area by toner components is more likely to occur. If the amount of charge control agent used is excessive, the environmental resistance deteriorates, making it easier for image defects in the formed image due to poor charging under high temperature and high humidity conditions, and contamination of the latent image-carrying area by toner components to occur.

[0063] (Resin fine particles) The shell layer constituting the toner of the present invention is formed from resin microparticles. Furthermore, the resin microparticles consist of a resin containing a charge-controlling resin. For this reason, resin microparticles made of a resin containing a charge-controlling resin are used as the resin microparticles used to form the shell layer. Because the shell layer consists of a resin containing a charge-controlling resin, when forming images over a long period of time in various environments such as high temperature and high humidity environments or low temperature and low humidity environments, the toner can be charged to a desired amount of charge, thereby enabling the formation of images of a desired density.

[0064] The shell layer constituting the toner of the present invention includes vinyl resin fine particles with a relatively small average particle diameter (first resin fine particles) and vinyl resin fine particles with a relatively large average particle diameter (second resin fine particles). The first resin fine particles form the sea-like regions of the shell layer. The second resin fine particles form the convex portions of the shell layer. The average particle diameter of the first resin fine particles is preferably about 10 nm to 40 nm. The average particle diameter of the second resin fine particles is preferably about 70 nm to 150 nm.

[0065] Preferably, the first and second resin microparticles are formed from a styrene-acrylic acid resin containing a styrene monomer and one or more acrylic acid monomers. Styrene-acrylic acid resins have strong hydrophobicity and tend to be positively charged. Furthermore, since both the first and second resin microparticles are made from styrene-acrylic acid resins, the affinity between the first and second resin microparticles is increased, and it is believed that the detachment of the shell layer at the protrusions is suppressed. In addition, by suppressing the detachment of the shell layer at the protrusions, the surface morphology of the shell layer is maintained over a long period of time, and consequently, the function of the protrusions on the surface of the shell layer is maintained over a long period of time. It should be noted that even if the first and second resin microparticles are not made from styrene-acrylic acid resins with exactly the same composition (i.e., even if the types of styrene monomers and / or acrylic acid monomers are different), the above effects can be obtained as long as both the first and second resin microparticles are made from styrene-acrylic acid resins.

[0066] The first resin microparticles include multiple types of resin microparticles. At least one of the first resin microparticles is formed from a resin containing a quaternary ammonium compound. By including a quaternary ammonium compound in at least one of the first resin microparticles, positive charge properties can be imparted to the sea-like regions of the shell layer, thereby improving the charge properties (positive charge properties) of the toner. As the quaternary ammonium compound monomer included in the first resin microparticles, (meth)acryloyl group-containing quaternary ammonium compound monomers are preferred, and (meth)acrylamide alkyltrimethylammonium salts (more specifically, (3-acrylamidepropyl)trimethylammonium chloride, etc.) or (meth)acryloyloxyalkyltrimethylammonium salts (more specifically, 2-(methacryloyloxy)ethyltrimethylammonium chloride, etc.) are particularly preferred.

[0067] The second resin microparticles contain at least a fluorine-containing vinyl resin. The inclusion of the fluorine-containing vinyl resin in the second resin microparticles reduces the adhesion to the protrusions of the shell layer, thereby increasing its effect as a spacer for the protrusions. As a result, toner is more easily transferred from the photoreceptor drum to the intermediate transfer belt and paper, improving transfer efficiency.

[0068] The average particle size of resin microparticles can be adjusted by modifying polymerization conditions, known grinding methods, classification methods, etc. The average particle size of resin microparticles can be determined by measuring the particle size of 50 or more resin microparticles from electron microscope images taken using a field emission scanning electron microscope (JSM-6700F, manufactured by JEOL Ltd.).

[0069] The amount of resin fine particles used is not particularly limited as long as it does not hinder the objective of the present invention. Typically, the amount of resin fine particles used is preferably 1 to 20 parts by mass, and more preferably 3 to 15 parts by mass, per 100 parts by mass of toner core particles. If the amount of resin fine particles used is insufficient, the entire surface of the toner core particles may not be covered with the resin fine particles. If the entire surface of the toner core particles is not covered with the resin fine particles, the toner is prone to agglomeration during storage at high temperatures, and its heat resistance is likely to decrease. If the amount of resin fine particles used is excessive, the shell layer tends to become thick. In this case, it is difficult to obtain toner with excellent fixation properties.

[0070] The mass-average molecular weight (Mw) of the resin constituting the resin nanoparticles is not particularly limited as long as it does not hinder the objectives of the present invention. Typically, the mass-average molecular weight is preferably 20,000 to 1,500,000, and more preferably 200,000 to 400,000. The mass-average molecular weight (Mw) of the resin material for the resin nanoparticles can be measured by gel permeation chromatography according to conventionally known methods.

[0071] The polymerization method of the above-mentioned monomer is not limited to the extent that it does not hinder the objective of the present invention, and any method such as solution polymerization, bulk polymerization, emulsion polymerization, suspension polymerization, etc. can be selected.

[0072] When additive polymerization of monomers having unsaturated bonds is carried out using an aqueous medium, such as emulsion polymerization or suspension polymerization, surfactants can be used. The surfactant is not limited to the extent that it does not hinder the objective of the present invention, and can be appropriately selected from the group consisting of anionic surfactants, cationic surfactants, and nonionic surfactants. Examples of anionic surfactants include sulfate ester salt type surfactants, sulfonate type surfactants, phosphate ester salt type surfactants, and soaps. Examples of cationic surfactants include amine salt type surfactants and quaternary ammonium salt type surfactants. Examples of nonionic surfactants include polyethylene glycol type surfactants, alkylphenol ethylene oxide adduct type surfactants, and polyhydric alcohol type surfactants which are derivatives of polyhydric alcohols such as glycerin, sorbitol, and sorbitan. Among these surfactants, it is preferable to use at least one of anionic surfactants and nonionic surfactants. These surfactants may be used individually or in combination of two or more.

[0073] (External additive) The toner of the present invention can be treated with an external additive after forming a shell layer on the surface of the toner core particles, if desired. Hereinafter, the particles treated with the external additive will also be referred to as "toner mother particles."

[0074] The type of external additive is not particularly limited as long as it does not hinder the objective of the present invention, and can be appropriately selected from external additives conventionally used for toner. Specific examples of suitable external additives include silica, alumina, titanium oxide, magnesium oxide, zinc oxide, strontium titanate, and metal oxides such as barium titanate. Two or more of these external additives can be used in combination.

[0075] The particle size of the external additive is not particularly limited as long as it does not hinder the objective of the present invention, but is typically preferably 0.01 μm or more and 1.0 μm or less.

[0076] The amount of external additive used is not particularly limited as long as it does not hinder the objectives of the present invention. Typically, the amount of external additive used is preferably 0.1% to 10% by mass, and more preferably 0.2% to 5% by mass, relative to the total mass of toner matrix particles manufactured by forming a shell layer on the surface of toner core particles. If the amount of external additive used is insufficient, the hydrophobicity of the toner tends to decrease. As a result, it becomes more susceptible to the influence of water molecules in the air under high temperature and high humidity environments, and problems such as a decrease in image density of the formed image due to an extreme decrease in the charge amount of the toner, and a decrease in toner fluidity are likely to occur. On the other hand, if the amount of external additive used is excessive, there is a risk of a decrease in image density due to excessive toner charge buildup.

[0077] [Toner manufacturing method] Next, the method for manufacturing the toner of the present invention will be described. The method for manufacturing the toner is not particularly limited as long as the toner core particles and the shell layer are formed to have a predetermined structure. In addition, if necessary, toner core particles coated with a shell layer may be used as toner matrix particles, and an external additive treatment may be performed to attach an external additive to the surface of the toner matrix particles. As a preferred method for manufacturing the electrostatic latent image developing toner described above, the method for manufacturing toner core particles, the method for forming the shell layer, and the external additive treatment method will be described in order below.

[0078] (Method for manufacturing toner core particles) The method for producing toner core particles is not particularly limited as long as any component such as a colorant, release agent, charge control agent, and magnetic powder can be well dispersed in the binder resin. A specific example of a preferred method for producing toner core particles is to mix the binder resin with components such as a colorant, release agent, charge control agent, and magnetic powder using a mixer, then melt-knead the binder resin and the components to be blended into the binder resin using a kneader such as a single-screw or twin-screw extruder, and finally crush and classify the cooled kneaded product. The average particle size of the toner core particles is not particularly limited as long as it does not hinder the objective of the present invention, but is generally preferably 5 μm or more and 10 μm or less.

[0079] (Method for forming the shell layer) The shell layer is formed by attaching resin microparticles to the surface of the toner core particles, creating a shell layer that covers the surface of the toner core particles.

[0080] Let me explain the method in more detail. First, in a mixing device, hydrochloric acid is added to deionized water to prepare a weakly acidic aqueous medium (for example, a pH selected from 3 to 5). Next, a dispersion (suspension) of resin microparticles (first resin microparticles and second resin microparticles) as shell material and toner core particles are added to the pH-adjusted aqueous medium.

[0081] Next, while stirring the mixture containing the shell material and toner core particles, the temperature of the mixture is raised at a predetermined rate (for example, a rate selected from 0.1°C / min to 3°C / min) to a predetermined holding temperature (for example, a temperature selected from 50°C to 90°C). Furthermore, while stirring the mixture, the temperature of the liquid is maintained at the above holding temperature for a predetermined time (for example, a time selected from 30 minutes to 4 hours). It is believed that a reaction (immobilization of the shell layer) proceeds between the toner core particles and the shell material while the temperature of the mixture is maintained at a high temperature. A shell layer is formed when the shell material binds to the toner core particles. A dispersion of toner matrix particles is obtained when a shell layer is formed on the surface of the toner core particles in the mixture.

[0082] As described above, hydrophobic resin microparticles can be attached to the surface of toner core particles in a mixed solution, and the mixed solution can be heated to dissolve the resin microparticles and form a film. However, the film formation of the resin microparticles may also proceed due to heating during the drying process or physical impact force during the external addition process.

[0083] After forming the shell layer as described above, the dispersion of toner matrix particles is neutralized using, for example, sodium hydroxide. Next, the dispersion of toner matrix particles is cooled to, for example, room temperature (approximately 25°C). Subsequently, the dispersion of toner matrix particles is filtered using, for example, a Buchner funnel. This separates the toner matrix particles from the liquid (solid-liquid separation), yielding wet cake-like toner matrix particles. Next, the obtained wet cake-like toner matrix particles are washed. Subsequently, the washed toner matrix particles are dried. After that, if necessary, the toner matrix particles and external additives may be mixed using a mixer (for example, an FM mixer manufactured by Nippon Coke Industries, Ltd.) to adhere the external additives to the surface of the toner matrix particles. When using a spray dryer in the drying process, the drying process and the external additive process can be performed simultaneously by spraying a dispersion of external additives (for example, silica particles) onto the toner matrix particles. In this way, toner containing a large number of toner particles is produced.

[0084] The contents and sequence of the toner manufacturing method described above can be arbitrarily changed according to the required toner composition or characteristics. Furthermore, the toner may be sieved after the external additive step. Unnecessary steps may also be omitted. For example, if a commercially available product can be used as is, the step of preparing that product can be omitted. Also, if the reaction for forming the shell layer proceeds well without adjusting the pH of the mixture, the pH adjustment step may be omitted. If the external additive is not attached to the surface of the toner mother particles (the external additive step is omitted), the toner mother particles correspond to the toner particles. To efficiently manufacture toner, it is preferable to form a large number of toner particles simultaneously. Toner particles manufactured simultaneously are considered to have substantially the same composition.

[0085] (External processing method) The method for treating toner matrix particles with external additives is not particularly limited, and the toner matrix particles can be treated according to conventionally known methods. Specifically, the treatment conditions are adjusted so that the particles of the external additive do not become embedded in the toner matrix particles, and the toner matrix particles are treated with the external additive using a mixer such as a Henschel mixer or a Nauter mixer.

[0086] The toner of the present invention, as described above, has excellent fixability and heat resistance for storage. When forming images over a long period of time in various environments such as high temperature and high humidity environments or low temperature and low humidity environments, the toner can be charged to a desired amount of charge, thereby enabling the formation of images of a desired density. For this reason, the electrostatic latent image developing toner of the present invention can be suitably used in various image forming apparatuses. The effects of the present invention will be further described in detail below with reference to examples. However, the present invention is not limited in any way by these examples. [Examples]

[0087] [Manufacturing Example 1] (Manufacturing of toner core particles) As a binder resin, 750g of low-viscosity polyester resin (Tg=38℃, Tm=65℃), 100g of medium-viscosity polyester resin (Tg=53℃, Tm=84℃), and 150g of high-viscosity polyester resin (Tg=71℃, Tm=120℃) were mixed in a Henschel mixer to obtain a mixture. Next, the mixture was melt-kneaded in a twin-screw extruder to obtain a kneaded product. The kneaded product was coarsely pulverized in a pulverizer (Rotoplex, Toa Machinery Works Co., Ltd.), and then finely pulverized in a mechanical pulverizer (Turbo Mill, Turbo Industries Co., Ltd.) to obtain a finely pulverized product. The finely ground material was classified using an elbow jet classifier (manufactured by Nippon Steel Mining Co., Ltd.) to obtain toner core particles with a volume-average particle size (D50) of 6.8 μm. The volume-average particle size of the toner core particles was measured using a Coulter Counter Multisizer 3 (manufactured by Beckman Coulter).

[0088] [Manufacturing Example 2] (Manufacturing of dispersions SA1 and SA2 of the first resin fine particles) A 1 L three-necked flask equipped with a stirrer, thermometer, condenser, and nitrogen inlet tube was set in a water bath and used as a reaction vessel. 875 g of ion-exchanged water at 30°C and 75 g of an anionic surfactant (Latemul® WX, manufactured by Kao Corporation, component: sodium polyoxyethylene alkyl ether sulfate, solid content concentration: 26% by mass) were added to the flask. The temperature inside the flask was then raised to 80°C using the water bath and maintained at that temperature. Next, the materials shown in Table 1 were added to the flask contents at 80°C, and the flask contents were polymerized by maintaining the temperature at 80°C for a further 2 hours. As a result, dispersions SA1 and SA2 of first resin fine particles with a solid content concentration of 5% by mass were obtained.

[0089] [Table 1] *1; Butyl acrylate *2; Methyl methacrylate

[0090] [Manufacturing Example 3] (Preparation of dispersion SN of first resin fine particles containing a quaternary ammonium compound) A 1L three-necked flask equipped with a stirrer, thermometer, condenser, and nitrogen inlet tube was placed in a water bath and used as the reaction vessel. In a flask, 90 mL of isobutanol, 100 mL of methyl methacrylate, 35 mL of butyl acrylate, 30 mL of 2-(methacryloyloxy)ethyltrimethylammonium chloride (Alfa Aesar), and 6 mL of 2,2'-azobis(2-methyl-N-(2-hydroxyethyl)propionamide (VA-086, Wako Pure Chemical Industries, Ltd.) were added. Subsequently, the contents of the flask were reacted for 3 hours under a nitrogen atmosphere and at a temperature of 80°C with stirring at a stirring speed of 100 rpm. After that, 3 mL of 2,2'-azobis(2-methyl-N-(2-hydroxyethyl))propionamide (VA-086, Wako Pure Chemical Industries, Ltd.) was added to the flask, and the contents of the flask were reacted for another 3 hours under a nitrogen atmosphere and at a temperature of 80°C to obtain a polymer-containing liquid. Subsequently, the obtained polymer-containing liquid was dried under a reduced pressure atmosphere and at a temperature of 150°C. The dried polymer was crushed to obtain a positively charged resin.

[0091] Next, 200 g of the positively charged resin obtained as described above and 184 mL of ethyl acetate (Wako Pure Chemical Industries, Ltd.) were placed in a mixing apparatus (Hibismix 2P-1 type, manufactured by Primix Corporation). Subsequently, the contents were stirred at a stirring speed of 20 rpm for 1 hour to obtain a high-viscosity solution. Then, an aqueous solution of ethyl acetate, etc. was added to the obtained high-viscosity solution. The aqueous solution of ethyl acetate, etc. was an aqueous solution prepared by dissolving 18 mL of 1N hydrochloric acid, 20 g of anionic surfactant (Emal 0, manufactured by Kao Corporation, ingredient: sodium lauryl sulfate), and 16 g of ethyl acetate (Wako Pure Chemical Industries, Ltd.) in 562 mL of deionized water. When the aqueous solution of ethyl acetate, etc. was added to the high-viscosity solution, a dispersion of first resin fine particles containing a quaternary ammonium compound, SN, was obtained. The solid content concentration in the dispersion was 20% by mass.

[0092] [Manufacturing Example 4] (Manufacturing of dispersions SF1 to SF7 of the second resin fine particles) A 1L three-necked flask equipped with a stirrer, thermometer, condenser, and nitrogen introduction device was set in a water bath and used as a reaction vessel. 875g of ion-exchanged water at 30°C and an anionic surfactant (Latemul WX, manufactured by Kao Corporation, component: sodium polyoxyethylene alkyl ether sulfate, solid content concentration: 26% by mass) were added to the flask. The temperature inside the flask was then raised to 80°C using the water bath and maintained at that temperature. Next, the materials shown in Table 2 were added to the flask contents, and the temperature inside the flask was maintained at 80°C for a further 2 hours to polymerize the contents. The particle size was also varied by changing the amount of sodium dodecyl sulfate. As a result, dispersions SF1 to SF7 of vinyl resin-containing second resin fine particles with a solid content concentration of 5% by mass were obtained. The solid content concentration in the dispersion was adjusted to 10% by mass.

[0093] [Table 2] *3; 2(perfluorodecyl)ethyl methacrylate

[0094] [Measurement of average particle size and Tg of resin microparticles] The dispersions SA1, SA2, and SN of the first resin microparticles obtained in Production Examples 2-4, and the dispersions SF1-SF7 of the second resin microparticles were dried under reduced pressure. The glass transition temperature (Tg) was measured by differential scanning calorimeter (DSC), and the average particle size was measured by field emission scanning electron microscope (FE-SEM). The measurement results are shown in Table 3.

[0095] [Table 3]

[0096] [Manufacturing Example 5] [Manufacturing of toners T1-T17] (Formation of the shell layer) A 1L three-necked flask equipped with a stirrer, thermometer, condenser, and nitrogen introduction device was set in a water bath and used as a reaction vessel. 100g of deionized water was placed in the flask. The temperature inside the flask was then maintained at 30°C using the water bath. Next, dilute hydrochloric acid was added to the flask to adjust the pH of the liquid to 4. Subsequently, either the first resin microparticle dispersion SA1 or SA2 obtained in Production Example 2, the first resin microparticle dispersion SN containing a quaternary ammonium compound obtained in Production Example 3, and either the second resin microparticle dispersion SF1 to SF7 obtained in Production Example 4 were added to the flask. Dispersions SA1 and SA2 were added in amounts corresponding to the toner coverage rates listed in Table 4. Dispersions SF1 to SF7 were added in amounts corresponding to the toner coverage rates listed in Table 4, or not added at all. For dispersion SN, either the amount listed in Table 4 was added, or it was not added at all. The toner coverage ratio was calculated as the ratio of the total projected area, determined from the primary particle size of the resin microparticles, to the specific surface area of ​​the toner.

[0097] Next, 300 g of toner core particles obtained in Production Example 1 were added to the flask, and the contents of the flask were stirred at a rotation speed of 200 rpm for 1 hour. Then, 300 g of deionized water was added to the flask. Next, the temperature of the mixture in the flask was raised to 70°C at a rate of 1°C / min while stirring at a rotation speed of 100 rpm. Then, the mixture was stirred for 2 hours at a temperature of 70°C and a rotation speed of 100 rpm. Next, sodium hydroxide was added to the flask to adjust the pH of the contents of the flask to 7. Next, the contents of the flask were cooled to room temperature (approximately 25°C) to obtain a dispersion containing toner mother particles. The amounts of dispersions SA1, SA2, SN, and SF1-SF7 added per 100 g of toner core particles are shown in Table 4.

[0098] [Table 4]

[0099] (Washing and drying process) The dispersion containing the obtained toner matrix particles was filtered, washed, and dried to obtain toner matrix particles.

[0100] (External processing) To 100 g of the obtained toner matrix particles, 0.6 parts by mass of hydrophobic silica (RA-200H, manufactured by Nippon Aerosil Co., Ltd.) and 0.8 parts by mass of titanium dioxide (EC-100, manufactured by Titanium Industries Co., Ltd.) were added. The mixture was then stirred and mixed for 40 seconds at a rotation speed of 18,000 rpm using a blender mixer (Blender 7011HS, manufactured by Waring Corporation), and aggregates were removed using a 75 μm mesh to obtain toners T1 to T17.

[0101] [Evaluation of toner's heat resistance, fixation performance, charge level, transfer efficiency, and image density] The heat resistance, fixability, charge amount under a predetermined environment, transfer efficiency, and image density of the toners of Invention 1 to 9 (T1 to T9) and Comparative Examples 1 to 8 (T10 to T17) were evaluated according to the following method. (Heat-resistant storage stability) 3g of toner (T1~T17) was placed in a 20cc poly container, and after controlling the temperature and humidity in a normal temperature and humidity environment (23°C, 50%RH) for more than 12 hours, it was left in a drying oven set to 58°C for 3 hours to obtain the toner for measurement. After the toner returned to room temperature, it was sieved for 30 seconds using a powder tester (Hosokawa Micron Corporation) under conditions of vibration memory 5 and mesh opening of 150μm, and the amount remaining on the mesh was expressed as a percentage. A remaining amount of 10% or less was considered acceptable.

[0102] (Persistence) First, 100 parts by mass of a developer carrier (a carrier for the "FSC5250DN" manufactured by Kyocera Document Solutions) and 10 parts by mass of the sample (toners T1 to T17) were mixed using a ball mill for 30 minutes to obtain an evaluation developer (a two-component developer). As the evaluation machine, a modified color printer (FSC5250DN, manufactured by Kyocera Document Solutions) with a roller-roller type heat-pressure type fuser (nip width 8 mm) was used to allow for adjustment of the fixing temperature. The evaluation developer was put into the developer unit of the evaluation machine, and the sample (replenishment toner) was put into the toner container of the evaluation machine.

[0103] Using the evaluation machine described above, under normal temperature and humidity conditions (23°C, 50%RH), a basis weight of 90 g / m² was measured. 2 On a sheet of paper (A4 size plain paper), with a line speed of 200 mm / second and a toner load of 1.0 mg / cm². 2 Under these conditions, a solid image measuring 25mm x 25mm was formed. Subsequently, the paper with the formed image was passed through the fuser of the evaluation machine. The nip passage time was 40ms.

[0104] The lowest temperature at which a solid image (toner image) could be fixed to paper within the fixing temperature range of 120°C to 150°C was measured. Whether or not the toner was fixed was confirmed by a folding and rubbing test. Specifically, the evaluation paper passed through the fuser was folded so that the side with the image formed on it was facing inward, and the image on the fold was rubbed back and forth five times using a 1 kg weight covered with cloth. Next, the paper was unfolded, and the folded part of the paper (the part where the solid image was formed) was observed. The length of the toner peeling off at the folded part (peeling length) was then measured. The lowest fixing temperature among the fixing temperatures at which the peeling length was 1 mm or less was defined as the minimum fixing temperature. A minimum fixing temperature of 140°C or lower was considered acceptable.

[0105] (Charge amount, transfer efficiency, and image density under specified environmental conditions) First, 100 parts by mass of a developer carrier (carrier for Kyocera Document Solutions' "TASKalfa5550ci") and 10 parts by mass of the sample (toner T1-T17) were mixed using a ball mill for 30 minutes to obtain an evaluation developer (two-component developer). A color multifunction printer (TASKalfa5550ci, Kyocera Document Solutions) was used as the evaluation machine. The evaluation developer was put into the developer unit of the evaluation machine, and the sample (replenishment toner) was put into the toner container of the evaluation machine.

[0106] (Charge) Using the evaluation machine described above, a print durability test was conducted by continuously printing 100,000 sheets at a print density of 5% under normal temperature and humidity conditions (N / N environment: temperature 23°C, humidity 50%RH). During this test, the charge amount of toner in the developer was measured at the initial stage and after 100,000 sheets had been printed (after durability testing). The charge amount of toner in the developer was measured using a charge amount measuring device (Q / M Meter, Trek "MODEL 210HS-1"). A charge amount of 20-35 μC / g was considered acceptable.

[0107] (Transfer efficiency) Similar to the measurement of charge amount, transfer efficiency was measured at initial printing and after 100,000 prints (after durability testing). Transfer efficiency is calculated using the following formula (1), where Md is the weight of toner on the photoconductor drum and Mp is the weight of toner on the paper when outputting a solid image (evaluation image) with dimensions of 0.5 cm vertically and 20 cm horizontally. The weight of toner on the photoconductor drum (Md) and the weight of toner on the paper (Mp) were measured by stopping the evaluation machine immediately after development and immediately before fixing, respectively, and collecting the toner while the solid image on the photoconductor drum and paper could be visually confirmed, and then weighing it using a precision balance. A transfer efficiency of 88% or higher was considered acceptable. Transfer efficiency (%) = Mp / Md × 100 ... (1)

[0108] (Image density) Similar to the measurements of charge amount and transfer efficiency, image density was measured initially and after 100,000 prints (after durability testing). Image density was calculated by printing five solid images (1 cm vertical x 1 cm horizontal) onto the paper and determining the average image density (ID). Image density was measured using a reflectance densitometer (Gretag Macbeth Spectro-I, manufactured by Gretag Macbeth). A pass was defined as an average image density of 1.4 or higher.

[0109] Next, to evaluate the toner's charge stability, the evaluation machine described above was used to continuously print 10,000 pages at a print density of 2% under normal temperature and humidity conditions (N / N environment: temperature 23°C, humidity 50%RH), then quickly switched to a print density of 30% and printed 1,000 pages continuously. If the toner's charge stability is poor, toner smudges (fog images) gradually appear on the white areas (non-printed areas) of the paper immediately after switching from a print density of 2% to 30%. Therefore, the charge stability can be evaluated by measuring the degree of smudges as image density (FD; fog density). The image density (FD) was calculated as the average of 5 points on the white areas of the paper, and the evaluation was determined based on the highest value among the 1,000 continuously printed documents at a print density of 30%.

[0110] Table 5 shows the evaluation results for the heat resistance, fixability, charge amount, transfer efficiency, and image density of the toners of Inventions 1-9 and Comparative Examples 1-8.

[0111] [Table 5]

[0112] As is clear from Table 5, in Invention 1 to 9, where the average particle size of the second resin fine particles containing fluorine-containing vinyl resin that forms the protrusions of the shell layer is relatively large (70-150 nm) and the coverage rate of the second resin fine particles (coverage rate of the protrusions on the surface of the toner core particles) is relatively high at 10-41%, the transfer efficiency and image density were good.

[0113] In particular, in Inventions 1, 2, 3, 5, and 7-9, where the coverage rate of the second resin fine particles (coverage rate of island-like regions on the surface of toner core particles) is 20% or more, and the proportion of first resin fine particles containing quaternary ammonium compounds to the total first resin fine particles is 3% or more, the image density after durability was extremely good, at 1.5 or higher in all cases.

[0114] In contrast, in Comparative Example 1, where the amount of second resin microparticles was small and the coverage rate was less than 10%, and in Comparative Example 3, where the particle size of the second resin microparticles was less than 70 nm (SF4), the desired transfer efficiency and image density could not be obtained.

[0115] On the other hand, in Comparative Examples 5 and 6, which used second resin microparticles (SF6, SF7) with an average particle size exceeding 100 nm but without silicone resin, the desired transfer efficiency and image density could not be obtained. This is thought to be because, when the second resin microparticles do not contain fluorine-containing vinyl resin, the adhesion to the protrusions of the shell layer is high, reducing its effect as a spacer. As a result, toner is less likely to be transferred from the photoreceptor drum to the intermediate transfer belt and paper.

[0116] Furthermore, in Comparative Example 4, which used second resin microparticles (SF5) with an average particle size of 200 nm, the particle size of the second resin microparticles containing fluorine-containing vinyl resin was too large. As a result, the amount added had to be large to achieve an appropriate coverage rate, leading to poor low-temperature fixation. In addition, in Comparative Example 2, where the coverage rate was excessive even with an appropriate particle size, the toner's chargeability (positive chargeability) deteriorated due to the negative charge properties derived from the fluorine-containing vinyl resin.

[0117] From the above results, it can be seen that when a fluorine-containing vinyl resin is included in the second resin fine particles that form the protrusions of the shell layer, the particle size and coverage of the second resin fine particles must be used at appropriate levels. Specifically, the particle size of the second resin fine particles is preferably 70 nm to 150 nm, and the coverage is preferably 10% to 50%, and more preferably 20% to 50%.

[0118] Furthermore, in Comparative Example 7, where the second resin fine particles (SF1 to SF7) were not incorporated, no protrusions were formed on the shell layer, resulting in increased adhesion to the toner surface, which reduced heat resistance, transfer efficiency, and image density.

[0119] Furthermore, in Comparative Example 8, where the first resin fine particles forming the sea-like region of the shell layer did not contain a quaternary ammonium compound, the toner's chargeability deteriorated, and the desired transfer efficiency and image density could not be obtained. From these results, it was confirmed that the inclusion of a quaternary ammonium compound in the first resin fine particles forming the sea-like region of the shell layer contributes to improving the chargeability (positive chargeability) of the toner. [Industrial applicability]

[0120] This invention is applicable to electrostatic latent image developing toners used in electrophotographic systems. By utilizing this invention, it is possible to provide electrostatic latent image developing toners that exhibit excellent chargeability, low-temperature fixability, and maintain good transferability. [Explanation of symbols]

[0121] 101 Toner 102 Toner core particles 103 Shell Layer 104 Oceanic region 105 Convex part 106 First resin fine particles 107 Second resin fine particles

Claims

1. Toner core particles containing at least a binder resin, a release agent, and a coloring agent, A shell layer covering the toner core particles, An electrostatic latent image developing toner comprising toner particles containing, The aforementioned shell layer is formed of resin fine particles containing a vinyl resin, The resin fine particles include multiple types of first resin fine particles and second resin fine particles having a larger average particle size than the first resin fine particles. The aforementioned shell layer is A sea-like region formed using multiple types of the first resin fine particles, Formed using the second resin fine particles, the island-shaped protrusions are scattered in the sea-like region, It has, At least one of the first fine particles contains a quaternary ammonium compound, and the second resin fine particles contain a fluorine-containing vinyl resin. The average particle size of the second resin fine particles is 70 nm or more and 150 nm or less. A toner for developing electrostatic latent images, characterized in that the coverage rate of the protrusions on the surface of the toner core particles is 10% or more and 50% or less.

2. The electrostatic latent image developing toner according to claim 1, characterized in that the coverage rate of the protrusions on the surface of the toner core particles is 20% or more and 50% or less.

3. The electrostatic latent image developing toner according to claim 1, characterized in that the coverage rate of the sea-like region on the surface of the toner core particles is 80% or more.

4. The electrostatic latent image developing toner according to claim 1, characterized in that the proportion of the first resin fine particles containing the quaternary ammonium compound to the total amount of the first resin fine particles is 3% or more.

5. The toner core particles contain polyester resin as the binder resin, The toner for electrostatic latent image development according to any one of claims 1 to 4, characterized in that the first resin fine particles and the second resin fine particles are formed from a styrene-acrylic acid resin containing a styrene monomer and one or more acrylic acid monomers.

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