Electrostatic latent image developing toner

Abstract

This invention provides a toner for electrostatic latent image development that offers excellent heat resistance, low-temperature fixing properties, and electrostatic stability. [Solution] The toner for electrostatic latent image development comprises toner particles including toner core particles and a shell layer covering the toner core particles. The toner core particles include at least a binder resin and a colorant. The toner core particles include a specific polyester resin having repeating units derived from 1,2-propanediol as the binder resin. The shell layer includes an alcoholic hydroxyl group-containing resin containing one or more repeating units having alcoholic hydroxyl groups. The proportion of alcoholic hydroxyl group-containing monomers in the alcoholic hydroxyl group-containing resin is 1% by mass or more. The coverage rate of the shell layer on the surface of the toner core particles is 75% or more.

Description

[Technical Field]

[0001] This invention relates to a toner for electrostatic latent image development. [Background technology]

[0002] In general, in electrophotography, the surface of an electrostatic latent image carrier is charged by corona discharge or the like, and then exposed with 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. Furthermore, the formed toner image is transferred to a recording medium to obtain a high-quality image. Typically, the toner used in electrophotography is made by mixing a binder resin such as a thermoplastic resin with a colorant, charge control agent, release agent, magnetic material, etc., and then kneading, grinding, and classifying it to produce toner particles (toner matrix particles) with an average particle size of 5 μm to 10 μm. Inorganic fine powders such as silica or titanium dioxide are added to the toner matrix particles for the purpose of imparting fluidity to the toner, imparting suitable charging performance to the toner, and improving the cleaning performance of the toner from the photoreceptor drum.

[0003] Conventionally, for such toners, core-shell structured toners have been used, in which toner core particles made of a low-melting-point binder resin are coated with a shell layer made of a resin that exhibits a glass transition temperature (Tg) higher than that of the binder resin of the toner core particles, for purposes such as obtaining good fixation in the low-temperature range, improving storage stability at high temperatures, and improving blocking resistance.

[0004] Patent Document 1 discloses a toner comprising toner core particles and a shell layer covering the surface of the toner core particles, wherein the toner core contains a specific polyester resin and a colorant, and the shell layer contains a specific vinyl resin having a specific first repeating unit, and the specific polyester resin has repeating units derived from 1,2-propanediol.

[0005] Patent Document 2 discloses a toner comprising toner core particles and a shell layer covering the surface of the toner core particles, wherein the resin constituting the shell layer contains one or more repeating units having alcoholic hydroxyl groups.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] The toner described in Patent Document 1 is composed of toner core particles made of a resin containing a repeating unit derived from 1,2-propanediol and has low-temperature fixing properties. However, there is little description about the shell layer, and there is room for improvement in heat resistance.

[0008] The toner described in Patent Document 2 has environmental charge stability due to a shell composed of a resin containing one or more repeating units having alcoholic hydroxyl groups. However, there is little description about the toner core particles, and there is room for improvement in heat resistance.

[0009] In view of the above problems, an object of the present invention is to provide an electrostatic latent image developing toner excellent in heat-resistant storage properties, low-temperature fixing properties, and charge stability.

Means for Solving the Problems

[0010] To achieve the above object, a first configuration of the present invention is an electrostatic latent image developing toner composed of toner particles including toner core particles and a shell layer covering the toner core particles. The toner core particles include at least a binder resin and a colorant. The toner core particles include a specific polyester resin having a repeating unit derived from 1,2-propanediol as the binder resin. The shell layer includes an alcohol group-containing resin including one or more repeating units having an alcoholic hydroxyl group. The proportion of the alcohol group-containing monomer in the alcohol group-containing resin is 1% by mass or more. The coverage rate of the shell layer with respect to the surface of the toner core particles is 75% or more.

Effect of the Invention

[0011] According to the first configuration of the present invention, an electrostatic latent image developing toner excellent in heat-resistant storage stability, low-temperature fixing property, and charge stability can be obtained.

Embodiments for Carrying Out the Invention

[0012] Hereinafter, embodiments of the present invention will be described in detail. Note that evaluation results (values indicating shape or physical properties, etc.) regarding powders (more specifically, toner core particles, toner mother particles, external additives, or toner, etc.) are, if not otherwise specified, the number average of values measured for each of a considerable number of average particles selected from the powders. Also, the number average particle diameter of the powder is, if not otherwise specified, the number average value of the equivalent circle diameter of the primary particles (the diameter of a circle having the same area as the projected area of the particles) measured using a microscope. Further, the measured value of the volume median diameter (D50) of the powder is, if not otherwise specified, the value measured using a laser diffraction / scattering type particle size distribution measuring device ("LA-750" manufactured by Horiba, Ltd.). Also, the measured values of the acid value and the hydroxyl value are, if not otherwise specified, the values measured in accordance with "JIS (Japanese Industrial Standard) K0070-1992". Also, the measured values of the number average molecular weight (Mn) and the mass average molecular weight (Mw) are, if not otherwise specified, the values measured using gel permeation chromatography.

[0013] 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".

[0014] 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.

[0015] The toner according to this embodiment can be used, for example, to form images in an electrophotographic apparatus (image forming apparatus). An example of an image forming method using an electrophotographic apparatus will be described below.

[0016] First, an electrostatic latent image is formed on the photoreceptor (e.g., the surface of the photoreceptor drum) based on the image data. Next, the formed electrostatic latent image is developed using a developer containing toner. In the development process, toner (e.g., toner charged by friction with a carrier or blade) on a developing sleeve (e.g., the surface of the developing roller in the developing unit) placed near the photoreceptor is deposited onto the electrostatic latent image, forming 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, it is first transferred to an intermediate transfer medium (e.g., a transfer belt), and then the toner image on the intermediate transfer medium is secondarily transferred to the recording medium. After that, the toner is heated to fix it 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 superimposing toner images of four colors: black, yellow, magenta, and cyan.

[0017] [1. Basic Toner Configuration] The electrostatic latent image developing toner of the present invention (hereinafter also simply referred to as toner) comprises 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 resin. For example, by covering toner core particles that melt at low temperatures with a shell layer that has excellent heat resistance, it becomes possible to achieve both heat resistance for storage and low-temperature fixation of the toner. Additives may be dispersed in the resin that constitutes the shell layer.

[0018] The shell layer may cover the entire surface of the toner core particles, or it may partially cover the surface of the toner core particles. External additives may be attached to the surface of the shell layer (or to the surface area of ​​the toner core not covered by the shell layer). External additives may be omitted if not necessary. Toner containing mainly toner particles with a shell layer may also contain toner particles without a shell layer. Hereinafter, toner particles before the attachment of external additives will be referred to as toner matrix particles. The material for forming toner core particles will be referred to as toner core material. The material for forming the shell layer will be referred to as shell material.

[0019] (Toner core particles) Toner core particles contain at least a binder resin and a colorant. The toner core particles contain a polyester resin having repeating units derived from 1,2-propanediol (hereinafter referred to as "specific polyester resin") as the binder resin. 1,2-propanediol has a very small molecular weight compared to alcohol components (e.g., bisphenol A) that are raw materials for general toner polyester resins. Therefore, the specific polyester resin has a higher degree of polymerization compared to general toner polyester resins if the molecular weight is similar. In addition, 1,2-propanediol does not have a rigid structure such as a benzene ring structure compared to the aforementioned bisphenol A, etc. Therefore, the specific polyester resin has a more flexible skeleton compared to general toner polyester resins, which tends to reduce the heat resistance and hot offset resistance of the toner.

[0020] (Shell layer) The shell layer is substantially composed of a resin containing one or more repeating units having alcoholic hydroxyl groups (hereinafter referred to as the alcoholic hydroxyl group-containing resin). More specifically, it is preferable that 90% to 100% by mass of the resin constituting the shell layer is the alcoholic hydroxyl group-containing resin, and the ratio of repeating units having alcoholic hydroxyl groups to all repeating units in the alcoholic hydroxyl group-containing resin is 0.1% to 20% by mass. The alcoholic hydroxyl group-containing resin may contain two or more repeating units having alcoholic hydroxyl groups.

[0021] The thickness of the shell layer is not particularly limited as long as it does not hinder the objectives of the present invention. However, if the shell layer is too thick, it is difficult for the shell layer to break due to the pressure applied to the toner when fixing the toner to the recording medium. In this case, the softening or melting of the binder resin and release agent contained in the toner core particles 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 is too thin, the strength of the shell layer becomes low. If the strength of the shell layer is low, it may break due to impacts during transportation, etc., and when storing toner at high temperatures, the toner is more likely to aggregate due to the seepage of the release agent onto the surface of the toner from the area where the shell layer has broken.

[0022] The thickness of the shell layer is preferably 0.03 μm to 1 μm, more preferably 0.04 μm to 0.7 μm, particularly preferably 0.05 μm to 0.5 μm, and most preferably 0.05 μm to 0.3 μm.

[0023] The thickness of the shell layer can be measured by observing a cross-section of the toner 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).

[0024] The toner of the present invention, having the above-described basic configuration, is a capsule toner having toner core particles containing a specific polyester resin and a shell layer containing an alcoholic hydroxyl group-containing resin. This increases the affinity between the toner core particles and the shell layer, resulting in a more uniform shell layer. As a result, the toner of the present invention fully satisfies both low-temperature fixability and heat-resistant storage requirements. Furthermore, it possesses sufficient electrostatic stability regardless of the usage environment, enabling the formation of high-quality images (for example, images with low haze density) both in normal temperature and humidity environments and in high-temperature and high-humidity environments.

[0025] This is because the SP values ​​(solubility parameters) of the 1,2-propanediol constituting the toner core particles and the monomers containing alcoholic hydroxyl groups constituting the shell layer are close together, increasing the affinity between the toner core particles and the shell layer. Furthermore, in certain polyester resins, the hydroxyl groups contained in 1,2-propanediol result in a greater number of hydroxyl groups compared to general polyester resins, leading to better dispersibility of the toner core particles in water.

[0026] Therefore, by combining toner core particles containing a specific polyester resin with a shell layer containing an alcoholic hydroxyl group-containing resin, the functional groups derived from 1,2-propanediol in the toner core particles and the alcoholic hydroxyl groups in the shell layer undergo a chemical reaction and bond. As a result, the shell layer adheres uniformly to the surface of the toner core particles, forming a shell layer with high coverage over the toner core particles.

[0027] In the toner of the present invention, it is not necessary for the entire surface of the toner core particles to be covered by the shell layer. However, the heat resistance of the toner tends to worsen as the coverage rate of the shell layer on the toner core particles decreases (the ratio of the area covered by the shell layer to the surface area of ​​the toner core particles). To achieve both heat resistance and low-temperature fixation of the toner, the shell layer must cover 75% or more of the surface area of ​​the toner core particles (the coverage rate must be 75% or more). The state of shell layer coverage on the surface of the toner core particles can be confirmed using a scanning electron microscope (SEM).

[0028] [2. Toner Materials] Next, the essential or optional components constituting the toner of the present invention will be described. The toner core particles contain a colorant in at least the binder resin. They may also contain a release agent, a charge control agent, magnetic powder, etc., as needed. The shell layer contains an alcoholic hydroxyl group-containing resin. Furthermore, the surface of the toner of the present invention may be treated with an external additive as desired.

[0029] The binder resin, colorant, release agent, charge control agent, magnetic powder, alcoholic hydroxyl group-containing resin that forms the toner core particles, and external additives, along with the method for producing the toner of the present invention, will be described in order below.

[0030] (Binding resin) The toner core particles constituting the toner of the present invention use a specific polyester resin as the binder resin. It contains [a specific polyester resin]. The specific polyester resin is preferably amorphous. Amorphous specific polyester resins have less influence on the electrostatic properties of toner particles compared to crystalline specific polyester resins. Therefore, by including amorphous specific polyester resin in the toner core, the electrostatic stability of the toner of the present invention can be further improved. The polyester resin will be described below.

[0031] The specific polyester resin has repeating units derived from 1,2-propanediol. That is, the specific polyester resin uses 1,2-propanediol as a raw material. The specific polyester resin can be obtained, for example, by condensation polymerization of 1,2-propanediol with one or more polycarboxylic acids. Examples of carboxylic acids used to synthesize the specific polyester resin include dicarboxylic acids and trivalent or higher carboxylic acids, as shown below. Alternatively, polycarboxylic acid derivatives that can form ester bonds by condensation polymerization (e.g., anhydrides of polycarboxylic acids, polycarboxylic acid halides, etc.) may be used instead of polycarboxylic acids.

[0032] Furthermore, chemical products that use a large amount of plant-derived industrial resources (biomass), even when burned, do not significantly increase the concentration of carbon dioxide in the atmosphere from a carbon neutrality perspective. Therefore, chemical products that use a large amount of biomass are effective in reducing the burden on the environment. For this reason, it is preferable to use plant-derived 1,2-propanediol as a raw material for specific polyester resins.

[0033] Radiocarbon isotopes are used as an indicator of biomass content. 14 C concentration (radiocarbon isotopes relative to total carbon elements)14 The proportion of C, hereinafter simply referred to as " 14 the concentration of C") is used. Biomass is utilized in a relatively short period after plants stop their life activities. Therefore, the 14 concentration of C in biomass is approximately the same as that in the atmosphere, which is 107.5 pMC (percent Modern Carbon). In contrast, fossil resources such as petroleum are utilized after tens of thousands to hundreds of millions of years have passed since the originative animals and plants stopped their life activities. Therefore, 14 C is hardly detected from fossil resources. From the above, the 14 concentration of C in chemical products using only fossil resources such as petroleum as raw materials is almost 0 pMC. On the other hand, for chemical products using biomass as raw materials, the 14 concentration of C increases in proportion to the amount of biomass used. When the concentration of the radioactive carbon isotope 14 C contained in the toner is X [pMC], the ratio of carbon derived from biomass in the carbon in the toner can be obtained by the following formula. 14 Ratio of carbon derived from biomass [%] = (X / 107.5) × 100

[0034] In the toner of the present invention, it is preferable that the concentration of 14 C in the toner particles is 26.9 pMC or more, and more preferably 53.8 pMC or more. When the concentration of 14 C in the toner particles is 26.9 pMC or more, the biomass-derived (bio-based) carbon content rate is generally 25.0 mass% or more. Toners with such a biomass-derived carbon content rate of 25.0 mass% or more are products that use a relatively large amount of biomass as a raw material, so they have a small environmental load. Therefore, for example, it is possible to obtain a Biomass Plamarck (certified by the Japan Bioplastics Association).

[0035] ​The raw materials for the specified polyester resin may include 1,2-propanediol and polycarboxylic acid, as well as other polyhydric alcohol compounds other than 1,2-propanediol. Examples of other polyhydric alcohols include dihydric alcohol compounds (more specifically, diol compounds, bisphenol compounds, etc.) and trihydric or higher alcohol compounds. However, the raw materials for the specified polyester resin may include toner particles. 14 From the viewpoint of increasing the concentration of C, it is preferable that other polyhydric alcohol compounds are not included. Specifically, in the raw material of a particular polyester resin, the content of other polyhydric alcohol compounds is preferably 10% by mass or less, and more preferably 0% by mass.

[0036] 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.

[0037] As the specific polyester resin, a condensation polymer of 1,2-propanediol, terephthalic acid, and trimellitic anhydride is preferred. The content of the specific polyester resin in the toner core particles is preferably 60% to 95% by mass, and more preferably 75% to 85% by mass.

[0038] The toner core particles preferably contain only a specific polyester resin as the binder resin, but may also contain binder resins other than the specific polyester resin. In the binder resin contained in the toner core particles, the content of other binder resins is preferably 5% by mass or less, and more preferably 0% by mass. Examples of other binder resins include polyester resins other than the specific polyester resin, styrene resins, acrylic ester resins, olefin resins (more specifically, polyethylene resins, polypropylene resins, etc.), vinyl resins (more specifically, vinyl chloride resins, polyvinyl alcohol, vinyl ether resins, N-vinyl resins, etc.), polyamide resins, and urethane resins. In addition, copolymers of each of the above-mentioned resins, i.e., copolymers in which arbitrary repeating units are introduced into the above-mentioned resins (more specifically, styrene-acrylic ester resins, styrene-butadiene resins, etc.) can also be used as other binder resins.

[0039] The acid value of the specific polyester resin is 14 mg KOH / g or more and 32 mg KOH / g or less, preferably 18 mg KOH / g or more and 25 mg KOH / g or less. By setting the acid value of the specific polyester resin to 14 mg KOH / g or more, the shell layer forming resin described later and the specific polyester resin contained in the toner core can be sufficiently crosslinked. As a result, the heat resistance and hot offset resistance of the toner of the present invention can be improved. By setting the acid value of the specific polyester resin to 32 mg KOH / g or less, excessive crosslinking between the shell layer forming resin described later and the specific polyester resin contained in the toner core can be suppressed. As a result, the low-temperature fixing performance of the toner of the present invention can be improved.

[0040] The acid value of a specific polyester resin can be measured using a method compliant with JIS (Japanese Industrial Standards) K0070-1992. The acid value of a specific polyester resin can be adjusted, for example, by changing the type or amount of carboxylic acid used in its synthesis. Specifically, using a carboxylic acid with a large number of carboxyl groups per molecule (e.g., a carboxylic acid with three or more carboxylic acids) can increase the acid value of the synthesized specific polyester resin. Furthermore, increasing the amount of carboxylic acid added relative to the amount of alcohol compound added can also increase the acid value of the specific polyester resin.

[0041] The softening point (Tm) of the specific polyester resin is preferably 108°C to 132°C, and more preferably 115°C to 125°C. By setting the softening point of the specific polyester resin to 108°C or higher, the hot offset resistance of the toner of the present invention can be further improved. By setting the softening point of the specific polyester resin to 132°C or lower, the low-temperature fixability of the toner of the present invention can be further improved.

[0042] The glass transition temperature (Tg) of the specific polyester resin is preferably 40°C to 65°C, and more preferably 50°C to 60°C. By setting the glass transition temperature of the specific polyester resin to 40°C or higher, the heat resistance and storage properties of the toner of the present invention can be further improved. By setting the glass transition temperature of the specific polyester resin to 65°C or lower, the low-temperature fixing properties of the toner of the present invention can be further improved.

[0043] (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.

[0044] 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.

[0045] 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.

[0046] (Release agent) Toner core particles may 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 release agents to toner core particles, the occurrence of offset and image smearing (smudges around the image when the image is rubbed) can be suppressed more efficiently.

[0047] From the viewpoint of compatibility with specific polyester resins used as binders, one or more release agents selected from the group consisting of carnauba wax, synthetic ester wax, and polyethylene wax are preferably used as release agents.

[0048] 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. 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.

[0049] (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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] (magnetic powder) Toner core particles may contain magnetic powder. Suitable materials for the magnetic powder include, for example, ferromagnetic metals (more specifically, iron, cobalt, nickel, or alloys containing one or more of these metals), ferromagnetic metal oxides (more specifically, ferrite, magnetite, or chromium dioxide), or materials that have undergone ferromagnetic treatment (more specifically, carbon materials to which ferromagnetism has been imparted by heat treatment). To suppress the elution of metal ions (e.g., iron ions) from the magnetic powder, it is preferable to use surface-treated magnetic particles as the magnetic powder. One type of magnetic powder may be used alone, or multiple types of magnetic powder may be used in combination.

[0057] (Alcoholic hydroxyl group-containing resin) The shell layer constituting the toner of the present invention is substantially composed of the alcoholic hydroxyl group-containing resin described above. The repeating units having alcoholic hydroxyl groups derived from alcoholic hydroxyl group-containing monomers contained in the alcoholic hydroxyl group-containing resin preferably include, for example, the repeating units represented by the following chemical formula (1).

[0058] [ka]

[0059] In formula (1), R 11 , R 12 Each independently represents a hydrogen atom, a halogen atom, or an alkyl group which may have a substituent. 13 This indicates an alkylene group having a hydroxyl group.

[0060] R 11 , R 12 For each of these, a hydrogen atom or a methyl group is preferred, R 11 is a hydrogen atom, R 12 A combination of hydrogen atoms or methyl groups is particularly preferred. 13 Preferably, an alkylene group having hydroxyl groups with 1 to 6 carbon atoms is preferred, and an alkylene group having hydroxyl groups with 1 to 4 carbon atoms is particularly preferred. In addition, in the repeating unit derived from 2-hydroxyethyl methacrylate, R 11 is a hydrogen atom, R 12 is a methyl group, R 13 These represent (-(CH2)2-OH).

[0061] To improve the heat resistance, low-temperature fixing properties, and electrostatic stability of the toner, it is preferable that the alcoholic hydroxyl group-containing resin constituting the shell layer further contains one or more repeating units derived from styrene monomers, in addition to repeating units having alcoholic hydroxyl groups derived from alcoholic hydroxyl group-containing monomers. For example, it is preferable that the repeating units derived from styrene monomers include the repeating units shown in the following chemical formula (2).

[0062] [ka]

[0063] In formula (2), R 21 ~R 27Each of these independently represents a hydrogen atom, a halogen atom, a hydroxyl group, an optionally substituted alkyl group, an optionally substituted alkoxy group, an optionally substituted alkoxyalkyl group, or an optionally substituted aryl group.

[0064] R 21 ~R 27 Preferably, each of these is independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or an alkoxyalkyl group having 2 to 6 carbon atoms (more specifically, the total number of carbon atoms of the alkoxy and alkyl groups). 26 , R 27 For each of these, a hydrogen atom or a methyl group is preferred, R 27 is a hydrogen atom, R 26 A combination of hydrogen atoms or methyl groups is particularly preferred. In addition, for repeating units derived from styrene, R 21 ~R 27 Each of these represents a hydrogen atom.

[0065] The proportion of alcoholic hydroxyl group-containing monomers in an alcoholic hydroxyl group-containing resin can be measured by GC / MS. For example, if the alcoholic hydroxyl group-containing resin is a copolymer of a styrene monomer, an acrylic acid monomer, and an alcoholic hydroxyl group-containing monomer, the value obtained by dividing the mass Ma of one or more repeating units derived from the alcoholic hydroxyl group by the mass Mb of one or more repeating units derived from the styrene monomer and one or more repeating units derived from the acrylic acid monomer (Ma / Mb) corresponds to the proportion of repeating units having alcoholic hydroxyl groups in the alcoholic hydroxyl group-containing resin.

[0066] When the proportion of alcoholic hydroxyl group-containing monomers in the alcoholic hydroxyl group-containing resin is low, the affinity of the shell layer to the toner core particles decreases. As a result, the shell layer does not adhere uniformly to the surface of the toner core particles, and the heat-resistant storage properties decrease. By setting the proportion of alcoholic hydroxyl group-containing monomers in the alcoholic hydroxyl group-containing resin to 1% by mass or more, the affinity between the toner core particles and the shell layer is increased, resulting in a toner with a high shell layer coverage and excellent heat-resistant storage properties.

[0067] 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.

[0068] 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.

[0069] The shell layer may contain other thermoplastic resins in addition to the alcoholic hydroxyl group-containing resin. Examples of other thermoplastic resins include styrene resins, acrylic acid resins, styrene-acrylic acid 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.

[0070] (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."

[0071] 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, barium titanate and other metal oxides, and resin particles. Two or more of these external additives can be used in combination.

[0072] 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.

[0073] 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.

[0074] [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.

[0075] (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.

[0076] (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.

[0077] 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.

[0078] 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.

[0079] 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.

[0080] 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 the external additive (for example, silica particles) onto the toner matrix particles. In this way, toner containing a large number of toner particles is produced.

[0081] 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.

[0082] (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.

[0083] 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]

[0084] [Manufacturing Example 1] (Manufacturing of amorphous polyester resin) A 5-liter four-necked flask equipped with a stirrer (SM-104, manufactured by AS ONE), a nitrogen inlet tube, a thermocouple, a dehydration tube, and a rectification column was used as the reaction vessel. 1200 g of 1,2-propanediol (petrochemical) as the alcohol component, 1700 g of terephthalic acid and 300 g of trimetic anhydride were added to this vessel. The reaction was carried out under a nitrogen atmosphere at 220°C and atmospheric pressure for 15 hours, while removing water. Then, the pressure inside the reaction vessel was reduced to 8.3 kPa, and the reaction was continued for 1 hour. Next, after lowering the internal temperature of the reaction vessel to 180°C, 200 g of trimetic anhydride was added. The internal temperature of the reaction vessel was then increased to 210°C at a heating rate of 10°C / hour. The reaction was then carried out at the same temperature under atmospheric pressure for 10 hours. Finally, the pressure inside the reaction vessel was reduced to 20 kPa, and the reaction was continued for approximately 1 hour. After the reaction was complete, the contents of the reaction vessel were removed and cooled to obtain amorphous polyester resin A. The softening point Tm of amorphous polyester resin A was 120°C, and the glass transition point Tg was 53°C.

[0085] Amorphous polyester resin B was obtained by the same method as amorphous polyester A, except that biomass-derived 1,2-propanediol was used.

[0086] Amorphous polyester resin C was obtained using the same method as for amorphous polyester A, except that bisphenol A was used instead of 1,2-propanediol. The raw materials and physical properties of amorphous polyester resins A to C are shown in Table 1.

[0087] [Table 1]

[0088] [Manufacturing Example 2] (Manufacturing of toner core particles) As a binder resin, 100 parts by mass of any amorphous polyester resin A to C obtained in Production Example 1, 5 parts by mass of a release agent (WEP-9, manufactured by NOF Corporation), and 6 parts by mass of a coloring agent (MA-100, manufactured by Mitsubishi Chemical Corporation) were mixed in a mixer (FM mixer, manufactured by Nippon Coke Industries Co., Ltd.) at a rotation speed of 2000 rpm for 4 minutes to obtain a mixture. Next, the mixture was melt-kneaded in a twin-screw extruder (PCM-30, manufactured by Ikegai Corporation) under the conditions of a shaft rotation speed of 150 rpm, a set temperature range (cylinder temperature) of 100°C, and a processing speed of 100 g / min to obtain a kneaded product. After the kneaded product was cooled, it was coarsely ground in a pulverizer (Rotoplex, manufactured by Hosokawa Micron Corporation), and then the coarsely ground product was finely ground in a mechanical pulverizer (Turbo Mill RS type, manufactured by Freund Turbo) to obtain a finely ground product. The finely ground material was classified using an elbow jet EJ-LABO type classifier (manufactured by Nippon Steel Mining Co., Ltd.) to obtain toner core particles C-1 to C-3. The volume-average particle size (D50) of the toner core particles was 6.792 μm. The volume-average particle size of the toner core particles was measured using a Coulter Counter Multisizer 3 (manufactured by Beckman Coulter).

[0089] [Manufacturing Example 3] (Manufacturing of resin particle dispersion for shell layer formation) 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 mL of ion-exchanged water at 30°C and 75 mL of anionic surfactant (Latemul WX, manufactured by Kao Corporation, component: sodium polyoxyethylene alkyl ether sulfate, solid content: 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, a mixture of styrene, 2-hydroxyethyl methacrylate (HEMA) as an alcoholic hydroxyl group-containing monomer, and butyl acrylate in the proportions shown in Table 2, and a solution of 0.5 g of potassium persulfate dissolved in 30 mL of ion-exchanged water were added dropwise to the flask contents at 80°C over 5 hours. Furthermore, the temperature inside the flask was maintained at 80°C for another 2 hours to polymerize the flask contents. As a result, resin particle dispersions SA1 to SA3 for shell layer formation were obtained.

[0090] The wt% ratio of alcoholic hydroxyl group-containing monomers (HEMA) in the shell layer, as shown in Table 2, was determined by NMR measurement. Specifically, a 1H NMR spectrometer (JNM-ECX-400, JEOL Resonance) was used, with deuterated chloroform as the solvent. The content of alcoholic hydroxyl group-containing monomers was determined by measuring the proton peak of the hydroxyl group.

[0091] [Table 2]

[0092] [Manufacturing Example 4] [Manufacturing of toners T1-T5] (Shell layer formation process) A 1 L 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. 300 mL of deionized water was added to 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 inside to 4. Subsequently, 150 mL of one of the resin particle dispersions SA1 to SA3 obtained in Production Example 3 was added to the flask to obtain aqueous solutions a to c of the raw materials for the shell layer.

[0093] Next, 300 g of any of the toner core particles C-1 to C-3 obtained in Production Example 2 was added to the flask, and the contents of the flask were stirred at a rotation speed of 200 rpm for 1 hour. Then, 300 mL of deionized water was added to the flask. Next, the temperature inside the flask was raised to 70°C at a rate of 1°C / min while stirring the mixture inside the flask 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. Finally, the contents of the flask were cooled to room temperature (approximately 25°C) to obtain a dispersion containing toner mother particles.

[0094] (Washing process) The resulting dispersion containing toner matrix particles was filtered using a Buchner funnel to remove the wet cake-like toner matrix particles. The wet cake-like toner matrix particles were then dispersed again in deionized water to wash them. This washing operation with deionized water was repeated five times.

[0095] (drying process) A slurry was prepared by dispersing wet cake-like toner matrix particles in a 50% by mass ethanol aqueous solution. The obtained slurry was supplied to a continuous surface modification device (Coatmizer, manufactured by Freund Industrial Co., Ltd.) to dry the toner matrix particles in the slurry and obtain new toner matrix particles. The drying conditions using the Coatmizer were a hot air temperature of 45°C and a blower airflow of 2 m³. 3 It was set to / minutes.

[0096] (External addition process) 100 parts by mass of toner matrix particles obtained in the drying process and 1.0 part by mass of silica (REA90, manufactured by Nippon Aerosil Co., Ltd.) were mixed for 5 minutes using a 10L Henschel mixer (manufactured by Nippon Coke Co., Ltd.) to adhere the external additive. Then, the mixture was sieved using a 200-mesh sieve (mesh opening 75 μm) to obtain toners T-1 to T-5.

[0097] (Measurement of shell layer coverage) 2.0 g of the sample (toner) was dispersed in 100 g of a 2% by mass aqueous solution of a nonionic surfactant (Emulgen 120, manufactured by Kao Corporation, component: polyoxyethylene lauryl ether) to obtain a toner dispersion. Subsequently, the obtained toner dispersion was subjected to ultrasonic treatment using an ultrasonic disperser (Ultrasonic Mini Welder P128, manufactured by Ultrasonic Industries Co., Ltd., output: 100 W, oscillation frequency: 28 kHz) to remove external additives from the toner mother particles. Next, the ultrasonically treated toner dispersion was filtered by suction using qualitative filter paper (FILTER PAPER No. 1, manufactured by Advantec Co., Ltd.). After that, a reslurry was prepared by adding 50 mL of deionized water, and suction filtration was repeated three times to obtain the toner mother particles (toner from which external additives had been removed) of the sample (toner).

[0098] The obtained toner matrix particles (powder) were stained with Ru (ruthenium) by exposing them to a vapor of 2 mL of a 5% by mass RuO4 aqueous solution for 20 minutes under ambient air at room temperature (25°C). The stained toner matrix particles were then imaged using a field emission scanning electron microscope (FE-SEM) (JSM-7600F, JEOL Ltd.) to obtain backscattered electron images of the toner matrix particles. Among the surface areas of the toner matrix particles, the areas stained with Ru (stained areas) appeared brighter than the areas not stained with Ru (unstained areas). The FE-SEM imaging conditions were: acceleration voltage 10.0 kV, irradiation current 95 pA, working distance (WD) 7.8 mm, magnification 5000x, contrast 4800, and brightness 550.

[0099] Next, image analysis of the backscattered electron images was performed using image analysis software (WinROOF, manufactured by Mitani Corporation). Specifically, the backscattered electron images were converted to JPG image data and subjected to a 3x3 Gaussian filter. Subsequently, a luminance value histogram (vertical axis: frequency (number of pixels), horizontal axis: luminance value) was obtained from the filtered image data. The luminance value histogram showed the distribution of luminance values ​​in the surface region of the toner matrix particles (stained region and unstained region). Fitting of the luminance value histogram to a normal distribution and waveform separation were performed using the least squares method to obtain an unstained waveform showing the distribution of luminance values ​​in the unstained region (normal distribution) and a stained waveform showing the distribution of luminance values ​​in the stained region (normal distribution). Subsequently, Ru (staining rate, unit: %) was calculated from the areas of the two obtained waveforms (area RC of the unstained waveform and area RS of the stained waveform) based on the following formula, and the calculated Ru (staining rate) was used as the shell coverage rate. Ru[%] = 100 × RS / (RC + RS)

[0100] (Toner 14 (Measurement of C concentration) The concentration of radiocarbon isotope 14C in toner T-2, which uses toner core particles C-2 derived from biomass-based 1,2-propanediol, was measured using an accelerator mass spectrometer (AMS). Toner T-2 was heat-treated at 500°C for 0.5 hours in the presence of CuO, followed by heating at 850°C for 2 hours, and the generated carbon dioxide gas was collected. This collected carbon dioxide gas was then used in an accelerator mass spectrometer to measure the concentration of the radiocarbon isotope 14C. 14 C, 13 C, 12 The abundance ratio of C was measured. From the obtained carbon content of each isotope, radioactive carbon isotopes were identified. 14 The concentration of C was calculated. The types of toner core particles and shell layer forming resin particle dispersions for toners T-1 to T-5 were determined by the shell layer coverage rate. 14 The concentrations of C are shown in Table 3.

[0101] [Table 3]

[0102] [Evaluation of toner's heat resistance, storage performance, fixation, and electrostatic stability] The heat resistance, fixation properties, and electrostatic stability of the toners of Invention 1 and 2 (T-1, T-2) and the toners of Comparative Examples 1 to 3 (T-3 to T-5) were evaluated according to the method described below. (Heat-resistant storage stability) 10g of toner (T-1 to T-5) was weighed into a glass bottle and left to stand in a constant temperature bath set to 50°C for 100 hours. Then, 10g of the toner stored in the constant temperature bath was placed on a 140-mesh sieve (mesh opening: 106μm), and the toner was sieved using a powder tester (manufactured by Hosokawa Micron Corporation) under conditions of vibration level 2 m / m by vibrating the sieve for 30 seconds. After sieving, the mass T (g) of the toner remaining on the sieve was weighed, and the toner retention rate (degree of toner aggregation) was calculated according to the following formula and used as an indicator of heat resistance storage. Toner remaining percentage [%] = (T / 10) × 100 As the toner retention rate increases, the heat resistance to storage deteriorates; therefore, the heat resistance to storage was evaluated according to the following evaluation criteria. ○ (Good): The toner retention rate on the mesh was 10% or less. × (Defective): The toner residue on the mesh exceeded 10%.

[0103] (Low temperature fixation) First, a developer carrier (a carrier for the "FSC5250DN" manufactured by Kyocera Document Solutions) and toners (T-1 to T-5) were weighed so that the toner-to-carrier ratio (T / C) was 10% by mass, and the mixture was sealed in a plastic bottle. Next, the contents of the plastic bottle were mixed using a ball mill at a rotation speed of 100 rpm for 30 minutes to obtain an evaluation developer (two-component developer). As the evaluation machine, a modified color printer (FSC5250DN, manufactured by Kyocera Document Solutions) with the fuser removed was used. The evaluation developer was put into the black developer unit of the evaluation machine, and the sample (replenishment toner) was put into the black toner container of the evaluation machine.

[0104] 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 recording medium (CC90, manufactured by Mondi), the line speed was 200 mm / second and the toner load was 1.0 mg / cm². 2 Under these conditions, a solid image measuring 25 mm x 25 mm was formed. Subsequently, the obtained unfixed image was fixed to a recording medium at a linear velocity of 105 mm / second. For evaluation, a fixing unit from a modified printer (FS-5200DN, manufactured by Kyocera Document Solutions Corporation) was used, which allowed for adjustment of the fixing temperature and independent operation.

[0105] The fixed recording medium was folded so that the side with the image formed on it faced inward, and the image on the fold was rubbed back and forth five times using a 1kg 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 at the folded part (peeling length) was measured, and it was judged as passing if the toner peeling length was 1mm or less, and failing if it exceeded 1mm. The fixing temperature was lowered from 150℃ in 2℃ increments and evaluated, and the lowest fixing temperature at which the toner peeling was judged to be passing was defined as the minimum fixing temperature. Low-temperature fixing performance was evaluated according to the following evaluation criteria. ○ (Good): The minimum fixing temperature was 120°C or lower. × (Defective): The minimum fixing temperature exceeded 120°C.

[0106] (Static stability) The decay of toner charge was measured using an electrostatic diffusion measuring device (NS-D100, manufactured by NanoSeeds Co., Ltd.). This device charges a sample and then monitors the decay using a surface potential meter. The measurement environment was a high-temperature, high-humidity environment (32.5°C / 80%RH), and the sample (toner) was left standing overnight before measurement. Toner (approximately 50 mg) was placed on the sample stand, the surface potential meter was set to zero, and data was sampled at 10kV with a charging time of 0.5 seconds, a sampling frequency of 10Hz, and a maximum measurement time of 300 seconds. The charge decay coefficient α at a decay time of 2 seconds was calculated by applying the measurement results to the following formula. V = V0 exp(-α√t) (In the formula, V represents the surface potential [V], V0 represents the initial surface potential [V], and t represents the decay time [seconds].) Since a larger attenuation coefficient value leads to easier charge loss from the toner and a deterioration in charge stability, charge stability was evaluated according to the following evaluation criteria. ○ (Good): Damping coefficient is -0.0250 or higher × (Defective): Damping coefficient is less than -0.0250

[0107] Table 4 shows the evaluation results for the heat resistance, fixability, and electrostatic stability of the toners of Invention 1, 2, and Comparative Examples 1-3.

[0108] [Table 4]

[0109] As is clear from Table 4, toners T-1 and T-2 of the present invention 1 and 2, which have toner core particles A and B made from 1,2-propanediol as a raw material and a shell layer containing an alcoholic hydroxyl group-containing monomer, and in which the coverage of the shell layer is 75% or more, all exhibited good heat resistance, low-temperature fixing properties, and electrostatic stability. In particular, toner T-2 of the present invention 2, which uses toner core particles B made from biomass-derived 1,2-propanediol as a raw material, showed good heat resistance, low-temperature fixing properties, and electrostatic stability. 14 The concentration of C is 33.2%, which has a low environmental impact.

[0110] In contrast, toner T-3 of Comparative Example 1, in which the proportion of alcoholic hydroxyl group-containing monomers in the shell layer was less than 1% by mass, showed good low-temperature fixing properties and electrostatic stability, but poor heat resistance for storage.

[0111] On the other hand, the toner of Comparative Example 2, which did not contain repeating units having alcoholic hydroxyl groups in the shell layer, and the toner of Comparative Example 3, which used toner core particles C that did not contain 1,2-propanediol, showed deterioration in heat resistance, low-temperature fixing performance, and electrostatic stability.

[0112] Based on the above results, it was confirmed that toner core particles containing a specific polyester resin having repeating units derived from 1,2-propanediol are coated with a shell layer containing an alcoholic hydroxyl group-containing resin to form toner particles, and that the proportion of alcoholic hydroxyl group-containing monomers in the alcoholic hydroxyl group-containing resin constituting the shell layer is 1% by mass or more, and the coverage rate of the shell layer is 75% or more, contributes to improving the chargeability (positive chargeability) of the toner. [Industrial applicability]

[0113] 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 with excellent heat resistance, low-temperature fixing properties, and charge stability.

Claims

1. Toner core particles containing at least a binder resin and a colorant, A shell layer covering the toner core particles, An electrostatic latent image developing toner comprising toner particles containing, The toner core particles include a specific polyester resin having repeating units derived from 1,2-propanediol as the binder resin. The shell layer comprises an alcoholic hydroxyl group-containing resin which includes one or more repeating units having an alcoholic hydroxyl group. The proportion of alcoholic hydroxyl group-containing monomers in the alcoholic hydroxyl group-containing resin is 1% by mass or more. A toner for electrostatic latent image development, characterized in that the coverage rate of the shell layer on the surface of the toner core particles is 75% or more.

2. The toner for electrostatic latent image development according to claim 1, characterized in that the alcoholic hydroxyl group-containing resin includes a repeating unit represented by the following general formula (1) and a repeating unit represented by the following general formula (2). 【Chemistry 1】 【Chemistry 2】 (In formula (1), R 11 , R 12 Each independently represents a hydrogen atom, a halogen atom, or an alkyl group which may have a substituent. 13 R represents an alkylene group having a hydroxyl group. In formula (2), R 21 , R 27 Each of these independently represents a hydrogen atom, a halogen atom, a hydroxyl group, an optionally substituted alkyl group, an optionally substituted alkoxy group, an optionally substituted alkoxyalkyl group, or an optionally substituted aryl group.

3. The electrostatic latent image developing toner according to claim 2, characterized in that the alcoholic hydroxyl group-containing monomer is 2-hydroxyethyl methacrylate.

4. The toner for electrostatic latent image development according to claim 1, characterized in that the toner core particles are formed using 1,2-propanediol derived from biomass as a raw material.

5. Radioactive carbon isotopes in the toner particles 14 The electrostatic latent image developing toner according to claim 4, characterized in that the concentration of C is 26.9 pMC or higher.

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