Toner for electrostatic charge image development, image forming apparatus, and image forming method

Abstract

To provide a toner for electrostatic charge image development, an image forming apparatus, and an image forming method that can form an image excellent in varnish application properties, varnish adhesion, and folding resistance.SOLUTION: A toner for electrostatic charge image development includes a toner particle. The toner particle includes at least a toner base particle. The toner base particle is a core-shell type having a core particle and a shell covering the core particle. The toner base particle contains a binder resin, a mold release agent (excluding a saturated hydrocarbon compound having 16 or more and 35 or less carbon atoms), and a saturated hydrocarbon compound having 16 or more and 35 or less carbon atoms. The toner base particle contains, in the core particle, as the binder resin, amorphous polyester and crystalline polyester modified with at least one of styrene and (meth)acrylic ester. The content of the saturated hydrocarbon compound having 16 or more and 35 or less carbon atoms is 1 mass ppm or more and 1000 mass ppm or less based on the total amount of the toner particle.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a toner for developing an electrostatic image, an image forming apparatus, and an image forming method. [Background technology]

[0002] In recent years, in the production printing market, toner images are often subjected to varnishing and folding / bending processes in order to achieve higher quality and accommodate a variety of applications. However, the release agents contained in toner particles are incompatible with varnish. The release agents precipitated on the image surface during fixing repel the varnish during varnishing, making it difficult to obtain the desired varnished image.

[0003] Furthermore, during folding and bending, the fixed toner image has poor adhesion to the paper or the toner image has low toughness, so when the image is folded, the toner cracks and peels off from the paper, causing a problem of loss of image quality.

[0004] To address these issues, Patent Document 1 discloses a technique for improving the affinity between the varnish and the wax (releasing agent) by using a polar wax, thereby improving the varnish application and adhesion. Patent Document 2 discloses a toner with excellent bending resistance, which has a sea-island structure of a binder resin and a releasing agent. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-078565 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-090648 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the technology described in Patent Document 1 is premised on the use of a specific varnish, and if a varnish other than this is used, the varnish application property and varnish adhesion do not improve. The toner described in Patent Document 2 has good resistance to fold cracking, but has poor varnish application property and varnish adhesion.

[0007] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a toner for developing electrostatic images, an image forming apparatus, and an image forming method, which are capable of forming images that are excellent in varnish application property, varnish adhesion property, and bending resistance. [Means for solving the problem]

[0008] The above-mentioned problems of the present invention can be solved by the following means.

[0009] 1. A toner for developing electrostatic images, comprising toner particles, the toner particles include at least toner base particles, the toner base particles are of a core-shell type having a core particle and a shell covering the core particle, the toner base particles contain a binder resin, a release agent (excluding saturated hydrocarbon compounds having 16 to 35 carbon atoms), and a saturated hydrocarbon compound having 16 to 35 carbon atoms, the toner base particles contain, in the core particles, as the binder resin, an amorphous polyester modified with at least one of styrene and a (meth)acrylic acid ester, and a crystalline polyester modified with at least one of styrene and a (meth)acrylic acid ester; the content of the saturated hydrocarbon compound having 16 to 35 carbon atoms is 1 ppm by mass to 1000 ppm by mass with respect to the total amount of the toner particles; Toner for developing electrostatic images.

[0010] 2. The toner base particles further contain a styrene-acrylic resin as the binder resin. 2. The toner for developing electrostatic images according to claim 1.

[0011] 3. The softening point of the amorphous polyester is 70°C or higher and 95°C or lower. 3. The toner for developing electrostatic images according to claim 1 or 2.

[0012] 4. The content of the amorphous polyester is 20% by mass or more and 60% by mass or less with respect to the total amount of the binder resin. 3. The toner for developing electrostatic images according to claim 1 or 2.

[0013] 5. The content of the crystalline polyester is 10% by mass or more and 20% by mass or less with respect to the total amount of the binder resin. 3. The toner for developing electrostatic images according to claim 1 or 2.

[0014] 6. The toner for developing electrostatic images according to item 1 or 2 is used. Image forming device.

[0015] 7. The toner for developing electrostatic images according to item 1 or 2 is used. Image forming method. [Effects of the Invention]

[0016] According to the present invention, an image having excellent varnish coatability, varnish adhesion, and bending resistance can be formed.

[0017] The mechanism by which the effects of the present invention are exhibited or the mechanism of action is presumed to be as follows.

[0018] The electrostatic image developing toner (hereinafter also referred to as "toner") of the present invention contains 1 ppm or more of saturated hydrocarbon compounds having 16 to 35 carbon atoms (hereinafter also referred to as "C16-35 saturated compounds"). Because the C16-35 saturated compounds have 35 or fewer carbon atoms, they have a relatively small molecular weight and a low melting point and viscosity when molten. Therefore, the C16-35 saturated compounds precipitate on the surface of a toner image formed from the toner of the present invention containing 1 ppm or more of the C16-35 saturated compounds. The precipitated C16-35 saturated compounds uniformly coat the surface of the toner image. This uniformizes the distribution of surface energy of the toner image. This allows the varnish to spread uniformly on the surface of the toner image, making it less likely for the varnish to be repelled. Therefore, images formed from the toner of the present invention have good varnish applicability.

[0019] On the other hand, C16-35 saturated compounds do not have a particularly high affinity with varnish. Therefore, if the amount of C16-35 saturated compounds in the toner is excessive and the surface of the toner image becomes densely coated with C16-35 saturated compounds, varnish adhesion will decrease. In contrast, the content of C16-35 saturated compounds in the toner of the present invention is 1000 mass ppm or less. This makes it difficult for the surface of the toner image to become densely coated with C16-35 saturated compounds. Therefore, images formed from the toner of the present invention have good varnish adhesion.

[0020] Furthermore, since the C16-35 saturated compound has a melting point above room temperature due to the carbon number of 16 or more, it exists in a solid state in the toner particles or on the surface of the toner image, and does not impair other qualities.

[0021] The toner base particles contained in the toner of the present invention are of a core-shell type having a core particle and a shell covering the core particle, which makes it easier to control the amount of the release agent and the C16-35 saturated compound that seeps onto the toner image surface.

[0022] Furthermore, the toner base particles contained in the toner of the present invention contain a crystalline polyester as a binder resin in the core particles. This makes the C16-35 saturated compound less compatible with the binder resin, making it more likely to precipitate on the surface of the toner image during image formation. This improves the varnish adhesion of images formed using the toner of the present invention.

[0023] On the other hand, because crystalline polyesters have low toughness, images formed from toners containing crystalline polyesters tend to have poor folding resistance. In contrast, the toner of the present invention also contains an amorphous polyester, thereby suppressing the deterioration of folding resistance. Furthermore, both the crystalline polyester and the amorphous polyester according to the present invention are modified with at least one of styrene and (meth)acrylic acid ester and have similar structures. This improves the compatibility between the crystalline polyester and the amorphous polyester, strengthening the interface between the crystalline polyester domains in the toner image. This makes it less likely for breakage to occur between material domains when folded. As a result, images formed from the toner of the present invention have good folding resistance. Images with good folding resistance do not crack or peel off from paper even when folded. Therefore, images formed from the toner of the present invention have high quality, with the white background of the folded paper being inconspicuous. [Brief explanation of the drawings]

[0024] [Figure 1] Schematic cross-sectional view showing an example of an image forming apparatus DETAILED DESCRIPTION OF THE INVENTION

[0025] The following description describes embodiments of the present invention. The advantages and features of one or more embodiments of the present invention can be understood from the following detailed description and drawings. It should be noted that the following detailed description and drawings are provided for illustrative purposes only and do not limit the scope of the present invention.

[0026] The following description refers to the drawings and describes one or more embodiments of the invention, although the scope of the invention is not limited to the disclosed embodiments.

[0027] In this application, the symbol "to" is used to mean that the numerical values ​​before and after it are included as the lower limit and upper limit.

[0028] [1. Toner for developing electrostatic images] The toner for developing electrostatic images of the present invention contains toner particles. In the present invention, the toner for developing electrostatic images refers to an aggregate of toner particles.

[0029] [1-1. Toner base particles] The toner particles according to the present invention include at least toner base particles, which are of a core-shell type having a core particle and a shell covering the core particle.

[0030] The shell does not have to cover the entire surface of the core particle, and the core particle may be partially exposed to the extent that the electrostatic adhesion between the toner base particle and the external additive is not hindered.

[0031] The core particle and the shell can be made to have different properties such as glass transition point, melting point, and hardness. This allows toner particles to be designed according to the purpose. For example, a shell containing a resin with a relatively high glass transition point can be formed on the surface of a core particle containing a resin or release agent with a relatively low glass transition point.

[0032] The surface, cross section, etc. of the core-shell toner base particles can be confirmed by, for example, the following known observation means. ·Transmission Electron Microscope (TEM) Scanning Probe Microscope (SPM) Scanning Electron Microscope (SEM)

[0033] The toner base particles contain at least a binder resin, a release agent, and a C16-35 saturated compound, and may also contain a colorant, a charge control agent, and the like.

[0034] (binder resin) Examples of binder resins include polyester, styrene-acrylic resin, silicone resin, polyolefin resin, polyamide resin, and epoxy resin.

[0035] Polyesters are, for example, polycondensates of polycarboxylic acids and polyhydric alcohols, and can be synthesized, for example, by esterifying polycarboxylic acids and polyhydric alcohols through polycondensation using a known esterification catalyst.

[0036] The polyester includes amorphous polyester and crystalline polyester. The amorphous polyester includes the "modified amorphous polyester" described below. The crystalline polyester includes the "modified crystalline polyester" described below.

[0037] "Amorphous" means that it does not have a melting point. In other words, "amorphous" means that it does not have a clear endothermic peak when heated in an endothermic curve obtained by differential scanning calorimetry (DSC). "Clear endothermic peak" means a peak with a half-width of 15°C or less in an endothermic curve when heated at a heating rate of 10°C / min.

[0038] "Crystalline" means having a melting point. In other words, "crystalline" means having a clear endothermic peak when heating in an endothermic curve obtained by differential scanning calorimetry (DSC). A "clear endothermic peak" means a peak with a half-width of 15°C or less in an endothermic curve when heating at a rate of 10°C / min.

[0039] Examples of polycarboxylic acids that can be used in the synthesis of amorphous polyesters include phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, naphthalene-2,6-dicarboxylic acid, malonic acid, mesaconic acid, dimethyl isophthalate, fumaric acid, dodecenylsuccinic acid, and 1,10-dodecanedicarboxylic acid.

[0040] Examples of polyhydric alcohols that can be used in the synthesis of amorphous polyesters include ethylene glycol, propylene glycol, 1,4-butanediol, 2,3-butanediol, diethylene glycol, triethylene glycol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, dipropylene glycol, polyethylene glycol, polypropylene glycol, glycerin, sorbitol, 1,4-sorbitan, trimethylolpropane, and bisphenol A derivatives. Bisphenol A derivatives include bisphenol A and its derivatives. Examples of bisphenol A derivatives include bisphenol A, ethylene oxide adducts of bisphenol A, and propylene oxide adducts of bisphenol A. In the present invention, phenols such as bisphenol A derivatives are also considered to be included in alcohols. This definition is based on the fact that phenols such as bisphenol A derivatives can be esterified in the same way as alcohols.

[0041] Examples of polycarboxylic acids that can be used in the synthesis of crystalline polyesters include saturated aliphatic dicarboxylic acids, unsaturated aliphatic dicarboxylic acids, unsaturated aromatic dicarboxylic acids, trimellitic acid, pyromellitic acid, etc. Examples of saturated aliphatic dicarboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, 1,9-nonanedicarboxylic acid, 1,10-decanedicarboxylic acid (dodecanedioic acid), 1,11-undecanedicarboxylic acid, 1,12-dodecanedicarboxylic acid, 1,13-tridecanedicarboxylic acid, 1,14-tetradecanedicarboxylic acid, 1,16-hexadecanedicarboxylic acid, and 1,18-octadecanedicarboxylic acid. Examples of unsaturated aliphatic dicarboxylic acids include methylenesuccinic acid, fumaric acid, maleic acid, 3-hexenedioic acid, 3-octenedioic acid, and dodecenylsuccinic acid. Examples of unsaturated aromatic dicarboxylic acids include phthalic acid, terephthalic acid, isophthalic acid, t-butylisophthalic acid, tetrachlorophthalic acid, chlorophthalic acid, nitrophthalic acid, p-phenylenediacetic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-biphenyldicarboxylic acid, and anthracenedicarboxylic acid. Lower alkyl esters and acid anhydrides of these dicarboxylic acids can also be used as polycarboxylic acids.

[0042] Examples of polyhydric alcohols that can be used in the synthesis of crystalline polyesters include saturated aliphatic diols, unsaturated aliphatic diols, aromatic diols, etc. Examples of saturated aliphatic diols include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, 1,13-tridecanediol, 1,14-tetradecanediol, 1,18-octadecanediol, 1,20-eicosanediol, and neopentyl glycol. Examples of unsaturated aliphatic diols include 2-butene-1,4-diol, 3-butene-1,4-diol, 2-butyne-1,4-diol, 3-butyne-1,4-diol, and 9-octadecene-7,12-diol. Examples of aromatic diols include bisphenols and alkylene oxide adducts of bisphenols. Examples of bisphenols include bisphenol A and bisphenol F. Examples of alkylene oxide adducts of bisphenols include ethylene oxide adducts of bisphenols and propylene oxide adducts of bisphenols. Derivatives of these diols can also be used as polyhydric alcohols.

[0043] Examples of catalysts that can be used in polyester synthesis include metal-containing compounds, phosphorous compounds, phosphoric acid compounds, amine compounds, etc. Examples of metals contained in metal-containing compounds include sodium, lithium, magnesium, calcium, aluminum, zinc, manganese, antimony, titanium, tin, zirconium, germanium, etc. These may be used alone or in combination of two or more.

[0044] In the present invention, an amorphous polyester modified with at least one of styrene and a (meth)acrylic acid ester is referred to as a “modified amorphous polyester.” In the present invention, a crystalline polyester modified with at least one of styrene and a (meth)acrylic acid ester is referred to as a “modified crystalline polyester.”

[0045] Modification of polyester with at least one of styrene and (meth)acrylic acid ester is carried out, for example, via a bireactive compound. The term "bireactive compound" refers to a compound having a substituent reactive with a polyester segment, a substituent reactive with a vinyl-based segment, and a polymerizable unsaturated group. Examples of bireactive compounds include (meth)acrylic acid, fumaric acid, maleic acid, maleic anhydride, etc. The term "vinyl-based segment" refers to a resin containing at least one of styrene and (meth)acrylic acid ester as a constituent monomer.

[0046] (Meth)acrylic acid ester is a general term for acrylic acid ester and methacrylic acid ester. Examples of (meth)acrylic acid ester include (meth)acrylic acid alkyl ester, di(meth)acrylic acid ester, (meth)acrylic acid carboxy-substituted alkyl ester, (meth)acrylic acid hydroxy-substituted alkyl ester, and (meth)acrylic acid alkoxy-substituted alkyl ester.

[0047] Examples of (meth)acrylic acid alkyl esters include (meth)acrylic acid, n-methyl (meth)acrylate, n-ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, n-heptyl (meth)acrylate, n-octyl (meth)acrylate, n-decyl (meth)acrylate, n-dodecyl (meth)acrylate, n-lauryl (meth)acrylate, n-tetradecyl (meth)acrylate, n-hexadecyl (meth)acrylate, n-octadecyl (meth)acrylate, Examples of the acrylates include isopropyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, isopentyl (meth)acrylate, amyl (meth)acrylate, neopentyl (meth)acrylate, isohexyl (meth)acrylate, isoheptyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, decyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, cyclohexyl (meth)acrylate, dicyclopentanyl (meth)acrylate, and isobornyl (meth)acrylate.

[0048] Examples of di(meth)acrylic acid esters include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, butanediol di(meth)acrylate, pentanediol di(meth)acrylate, hexanediol di(meth)acrylate, nonanediol di(meth)acrylate, and decanediol di(meth)acrylate.

[0049] Examples of the carboxy-substituted alkyl (meth)acrylate include β-carboxyethyl (meth)acrylate.

[0050] Examples of hydroxy-substituted alkyl (meth)acrylates include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate.

[0051] Examples of the alkoxy-substituted alkyl (meth)acrylate include 2-methoxyethyl (meth)acrylate.

[0052] The styrene-acrylic resin is formed by addition polymerization of at least a styrene-based monomer and a (meth)acrylic acid ester.

[0053] The styrene-based monomer may be styrene or a styrene derivative having a known side chain or functional group in the styrene structure. Examples of the styrene-based monomer include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-phenylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, p-tert-butylstyrene, pn-hexylstyrene, pn-octylstyrene, pn-nonylstyrene, pn-decylstyrene, and pn-dodecylstyrene.

[0054] The (meth)acrylic acid ester that can be a constituent monomer of the styrene-acrylic resin is the same as the (meth)acrylic acid ester used to modify the polyester described above.

[0055] The (meth)acrylic acid ester monomer used to form the styrene-acrylic resin may be one type or two or more types.

[0056] The content of structural units derived from styrene-based monomers in the styrene-acrylic resin is preferably 40 to 90 mass %, and the content of structural units derived from (meth)acrylic acid esters in the styrene-acrylic resin is preferably 10 to 60 mass %.

[0057] The styrene-acrylic resin may further contain structural units derived from other monomers other than the styrene-based monomer and the (meth)acrylic acid ester.

[0058] The styrene-acrylic resin can be synthesized, for example, by polymerizing monomers using a known oil-soluble or water-soluble polymerization initiator.

[0059] Examples of the oil-soluble polymerization initiator include azo-based polymerization initiators, diazo-based polymerization initiators, and peroxide-based polymerization initiators.

[0060] Examples of the azo-based or diazo-based polymerization initiator include the following: 2,2'-Azobis-(2,4-dimethylvaleronitrile) 2,2'-Azobisisobutyronitrile 1,1′-Azobis(cyclohexane-1-carbonitrile) 2,2′-Azobis-4-methoxy-2,4-dimethylvaleronitrile Azobisisobutyronitrile

[0061] Examples of peroxide-based polymerization initiators include the following: Benzoyl peroxide Methyl ethyl ketone peroxide Diisopropyl peroxycarbonate Cumene hydroperoxide t-Butyl hydroperoxide Di-t-butyl peroxide Dicumyl peroxide 2,4-Dichlorobenzoyl peroxide Lauroyl peroxide 2,2-bis-(4,4-t-butylperoxycyclohexyl)propane Tris-(t-butylperoxy)triazine

[0062] When synthesizing resin particles of a styrene-acrylic resin by emulsion polymerization, a water-soluble radical polymerization initiator can be used as the polymerization initiator.

[0063] Examples of the water-soluble radical polymerization initiator include persulfates, azobisaminodipropane acetate, azobiscyanovaleric acid, azobiscyanovalerate, hydrogen peroxide, etc. Examples of the persulfates include potassium persulfate, ammonium persulfate, etc.

[0064] The toner base particles according to the present invention contain at least a modified amorphous polyester and a modified crystalline polyester as binder resins in the core particles. The modified amorphous polyester and the modified crystalline polyester have similar structures and are therefore highly compatible. Therefore, when the core particles contain the modified amorphous polyester and the modified crystalline polyester, the interface between the crystalline polyester domains in the toner image is strengthened as described above. This makes it less likely for breakage to occur between the material domains when the image is bent. As a result, images formed using the toner of the present invention have good bending resistance.

[0065] The softening point of the modified amorphous polyester is preferably 70° C. or higher and 95° C. or lower. When the softening point is 95° C. or lower, the viscosity of the toner when melted is low, the toner easily penetrates between paper fibers during fixing, and adhesion to the paper is improved, resulting in further improved resistance to fold cracking. When the softening point is 70° C. or higher, the heat resistance of the toner during storage is good.

[0066] The content of the modified amorphous polyester is preferably 20% by mass or more and 60% by mass or less based on the total amount of the binder resin. Because amorphous polyester has flexible resin properties, a content of 20% by mass or more further improves resistance to fold cracking. A content of 60% by mass or less can achieve both the functions of the amorphous polyester and the functions of other materials.

[0067] The content of the modified crystalline polyester is preferably 10% by mass or more and 20% by mass or less based on the total amount of the binder resin. When the content is 10% by mass or more, the C16-35 saturated compound is more likely to precipitate on the surface, further improving the varnish coatability. When the content is 20% by mass or less, deterioration of fold crack resistance can be suppressed.

[0068] The toner base particles according to the present invention preferably further contain a styrene-acrylic resin as a binder resin in addition to the modified amorphous polyester and modified crystalline polyester. The styrene-acrylic resin has a composition similar to the modified portion of the modified amorphous polyester and modified crystalline polyester. Therefore, when the toner base particles further contain a styrene-acrylic resin, the interface between the binder resins is reduced, further improving the resistance to fold cracking. The toner base particles preferably contain a styrene-acrylic resin in the core particles.

[0069] The resin contained in the shell of the toner base particle according to the present invention is preferably an amorphous resin, more preferably an amorphous polyester, in order to facilitate the exudation of the C16-35 saturated compound.

[0070] In the present invention, the same effect can be obtained whether the resin that accounts for the largest amount of the binder resin is a styrene-acrylic resin or a polyester.

[0071] The content of the binder resin is preferably 20% by mass or more and 99% by mass or less, more preferably 30% by mass or more and 95% by mass or less, and even more preferably 40% by mass or more and 90% by mass or less, based on the total amount of the toner base particles. When the content of the binder resin is 20% by mass or more, the strength of the formed image can be further increased.

[0072] (mold release agent) The release agent can improve the releasability of the toner from the fixing member, etc. In the present invention, a C16-35 saturated compound is not included in the "release agent" even if it has the effect of improving the releasability of the toner from the fixing member, etc. It is preferable that the toner base particle contains a release agent in the core particle.

[0073] The release agent is preferably a wax. Examples of wax release agents include hydrocarbon waxes, dialkyl ketone waxes, ester waxes, and amide waxes. Examples of hydrocarbon waxes include polyethylene waxes, paraffin waxes, microcrystalline waxes, and Fischer-Tropsch waxes. Examples of dialkyl ketone waxes include distearyl ketone. Examples of ester waxes include carnauba wax, montan wax, behenic acid behenate, trimethylolpropane tribehenate, pentaerythritol tetramyristate, pentaerythritol tetrastearate, pentaerythritol tetrabehenate, pentaerythritol diacetate dibehenate, glycerin tribehenate, 1,18-octadecanediol distearate, trimellitate tristearyl, and distearyl maleate. Examples of amide waxes include ethylenediamine dibehenylamide and trimellitate tristearylamide.

[0074] Of these, hydrocarbon waxes are preferred because they have a similar molecular structure to C16-35 saturated compounds and are easy to dissolve in the release agent. When C16-35 saturated compounds are well dissolved, they tend to disperse more finely and uniformly in the toner base particles, and they also tend to precipitate from the toner base particles together with the wax during fixing, which tends to improve the coatability of the varnish.

[0075] In the present invention, the hydrocarbon wax means a linear or branched hydrocarbon compound having 36 to 76 carbon atoms.

[0076] The melting point of the hydrocarbon wax is preferably 80°C or higher and 95°C or lower. When the melting point of the hydrocarbon wax is 80°C or higher, the hydrocarbon wax exuded from the toner particles is more likely to crystallize, thereby more sufficiently suppressing tacking. When the melting point of the hydrocarbon wax is 95°C or lower, the hydrocarbon wax is more likely to exude from the toner base particles during fixing, which tends to improve the release effect and the abrasion resistance of the formed image. Furthermore, when the melting point of the hydrocarbon wax is 95°C or lower, the toner base particles are more likely to melt during fixing, which tends to improve the low-temperature fixability of the toner. From the above viewpoints, the melting point of the hydrocarbon wax is more preferably 80°C or higher and 90°C or lower.

[0077] The content of the release agent is preferably 3% by mass or more and 20% by mass or less, and more preferably 5% by mass or more and 15% by mass or less, based on the total amount of the toner base particles. When the content of the release agent is 3% by mass or more, the releasability of the toner from the fixing member is sufficiently improved and tacking can be more sufficiently suppressed. When the content of the release agent is 20% by mass or less, a sufficient amount of binder resin can be contained in the toner base particles, thereby sufficiently improving the fixability of the image.

[0078] (C16-35 saturated compound) The C16-35 saturated compound has the effect of improving the releasability of the toner from fixing members, etc., and also has the effect of improving the varnish coatability due to the above-mentioned action. It is preferable that the toner base particle contains a C16-35 saturated compound in the core particle. This makes it difficult for the C16-35 saturated compound to exist on the surface of the toner particle, improving the storage stability of the toner.

[0079] The C16-35 saturated compound may be either chain or cyclic, but is preferably chain, which includes linear and branched chains.

[0080] From the viewpoint of achieving both varnish application property and varnish adhesion property, the content of C16-35 saturated compounds is 1 ppm or more and 1000 ppm or less relative to the total amount of the toner (including toner base particles and external additives), preferably 50 ppm or more and 950 ppm or less, and more preferably 100 ppm or more and 900 ppm or less.

[0081] The content of C16-35 saturated compounds can be measured using the following procedure: Separate C16-35 saturated compounds from the toner using a solvent that dissolves them. Qualitatively analyze hydrocarbons with these carbon numbers using gas chromatography-mass spectrometry (GC-MC). Quantify the amount of hydrocarbons using a flame ionization detector (FID) as the gas chromatography detector. Since the extract from the toner may also contain unsaturated hydrocarbons, after extraction, polar groups can be added to the unsaturated bonds, and only the saturated hydrocarbons can be separated using column separation utilizing the polarity difference.

[0082] In this case, multiple internal standards may be added and dissolved in the solvent to determine whether the quantification and pretreatment were performed properly. The concentration of the internal standard to be added may be set according to the amount of C16-35 saturated compound (estimated amount obtained by provisional measurement, etc.).

[0083] The internal standard is preferably a saturated hydrocarbon compound not normally found in toner. For example, using n-undecane or n-tridecane can detect the loss of saturated hydrocarbon compounds due to volatilization during pretreatment, and can serve as a guide for the elution time of the target saturated hydrocarbon compound during solid-phase extraction or GC-FID analysis. Furthermore, bicyclohexyl is less likely to overlap with the elution time of C16-35 saturated compounds, making it easier to improve detection accuracy.

[0084] Extraction from the toner can be performed by a conventionally known method such as solid-liquid extraction, a method in which the toner is dissolved or swollen and then separated by centrifugation, Soxhlet extraction, high-speed solvent extraction, etc. A method can be selected from these methods depending on the expected carbon number of the C16-35 saturated compound and the type of compound that will become a contaminant component such as a binder resin.

[0085] The solvent used for extraction is not particularly limited, but n-hexane, which has high solubility for C16-35 saturated compounds, is preferred. Depending on the type of binder resin, a polar solvent such as dichloromethane or ethanol may be used in combination to swell the binder resin.

[0086] The method for introducing polar groups into unsaturated hydrocarbons contained in the extract is not particularly limited, and can be carried out by methods such as epoxidation using metachloroperbenzoic acid (mCPBA), addition of hydrogen halide, addition of water or alcohol using an acid catalyst, or derivatization into alcohol by oxidation after hydroboration. Among these, epoxidation using mCPBA is preferred because of its high reactivity and reaction selectivity. In this case, for example, 1 The reaction can be confirmed to have progressed sufficiently by confirming the disappearance of the double bond peak by H-NMR measurement. If sufficient detection accuracy can be ensured depending on the type of saturated hydrocarbon or unsaturated hydrocarbon, the addition of a polar group may be omitted.

[0087] Separation utilizing the difference in polarity can be performed by known methods such as solid-phase extraction, online or offline GC, etc. When it is expected that a large amount of impurities will be contained, separation by solid-phase extraction is preferable.

[0088] The solvent used for solid-phase extraction is preferably n-hexane for both conditioning and extraction of saturated hydrocarbons. Depending on the type of contaminants expected, a polar solvent may also be used. After collecting the fraction containing C16-35 saturated compounds, it is preferable to increase the polarity of the solvent and collect the fraction, and then perform qualitative analysis using GC / MS or other methods to confirm that the fraction does not contain saturated hydrocarbon components.

[0089] The solid phase for solid-phase extraction can be a highly polar solid phase used in normal-phase separations using polar interactions. Examples of such solid phases include silica gel, silica gel activated with polar substances such as anhydrous sodium sulfate and silver nitrate, diol, cyanopropyl silica, magnesium silicate, etc. Among these, activated silica activated with silver nitrate is preferred. It is preferable not to use alumina, as it specifically retains long-chain n-alkanes.

[0090] Fractions containing saturated hydrocarbons extracted by solid-phase extraction are preferably concentrated or diluted to a concentration appropriate for qualitative and quantitative analysis by gas chromatography, using methods such as vacuum concentration with an evaporator or nitrogen gas flow concentration. The concentration conditions should be such that the internal standard is not lost due to the concentration of low-boiling components. The fractions after solid-phase extraction can be subjected to GC-FID under the following conditions, for example, to quantify C16-35 saturated compounds.

[0091] (GC conditions) Equipment used: Shimadzu GC-2010 Plus Injection volume: 1μL Saturated hydrocarbon concentration: 500 to 1000 mg / L Guard column: Restek MXT Siltek (10 m x 0.53 mm id) Column: Restek MTX-1 (15 m x 0.25 mm id) x 0.1 μm df) Carrier gas: Helium

[0092] The quantification of C16-35 saturated compounds may be carried out using an instrument with equivalent performance to the above instrument and a column with equivalent performance to the above column, as long as the results are equivalent to those obtained under the above conditions.

[0093] At this time, the elution times of n-alkanes (number of carbon atoms: 10, 16, 24, 35, and 50) measured under the same conditions are measured in advance. In addition, n-hexane alone is injected into the above-mentioned device to prepare a blank chromatogram.

[0094] A blank chromatogram obtained in advance by measurement using only the solvent is subtracted from the chromatogram obtained for the toner to determine the baseline. At this time, it is preferable that a horizontal baseline can be created at the lowest point before and after the peak derived from the saturated hydrocarbon compound. However, if a horizontal baseline cannot be created even after subtracting the blank chromatogram due to column bleeding or the like, the baseline can be set as a horizontal line from the elution time of the C10 compound to the elution time of the C50 compound, whichever has the lower signal intensity, between the C10 compound and the C50 compound.

[0095] Then, vertical lines are drawn on the chromatogram at positions corresponding to the elution times of the 16-carbon atom and 35-carbon atom peaks, and the area of ​​the chromatogram above the baseline enclosed by these vertical lines is calculated. Peaks that are confirmed not to be saturated hydrocarbon compounds are excluded from the calculation. The mass of the C16-35 saturated compound can be calculated from this area. When an internal standard is used, the mass of the C16-35 saturated compound can be calculated from the ratio of the above area to the area of ​​the compound added as the internal standard. The amount of the C16-35 saturated compound in the toner can then be calculated by dividing the obtained mass of the C16-35 saturated compound by the mass of the toner.

[0096] (coloring agent) The colorant may be a dye or a pigment. When the toner is a color toner that imparts a predetermined color tone to an image, the toner base particles may contain a colorant such as yellow, magenta, cyan, or black, depending on the color tone to be exhibited by the color toner. The toner base particles may contain only one type of colorant, or a combination of multiple types of colorants.

[0097] Examples of yellow dyes include CI Solvent Yellow 19, 44, 77, 79, 81, 82, 93, 98, 103, 104, 112, 162, etc. Examples of yellow pigments include CI Pigment Yellow 14, 17, 74, 93, 94, 138, 155, 180, 185, etc.

[0098] Examples of magenta dyes include CI Solvent Red 1, 49, 52, 58, 63, 111, 122, etc. Examples of magenta pigments include CI Pigment Red 5, 48:1, 53:1, 57:1, 122, 139, 144, 149, 166, 177, 178, 222, etc.

[0099] Examples of cyan dyes include CI Solvent Blue 25, 36, 60, 70, 93, 95, etc. Examples of cyan pigments include CI Pigment Blue 1, 7, 15, 15:3, 60, 62, 66, 76, etc.

[0100] Examples of black colorants include carbon blacks such as channel black, furnace black, acetylene black, thermal black, and lamp black, magnetic materials such as ferrite and magnetite, and iron-titanium composite oxides.

[0101] The content of the colorant is preferably 0.5% by mass or more and 20% by mass or less, and more preferably 2% by mass or more and 10% by mass or less, based on the total amount of the toner base particles. When the toner is a clear toner, the toner base particles preferably do not substantially contain a colorant, and the content of the colorant relative to the total amount of the toner base particles is preferably 0.1% by mass or less.

[0102] (charge control agent) The charge control agent can adjust the chargeability of the toner base particles.

[0103] Examples of the charge control agent include nigrosine dyes, metal salts of naphthenic acid, metal salts of higher fatty acids, alkoxylated amines, quaternary ammonium salt compounds, azo metal complexes, metal salicylate salts, and metal salicylate complexes.

[0104] The content of the charge control agent is preferably 0.1% by mass to 10% by mass, more preferably 0.5% by mass to 5% by mass, based on the total amount of the binder resin.

[0105] (Average particle size) The volume-based average particle diameter (volume average particle diameter) of the toner base particles is preferably 3.0 μm to 10.0 μm, more preferably 4.0 μm to 8.0 μm, and even more preferably 4.0 μm to 7.0 μm. By setting the volume average particle diameter of the toner base particles to 4.0 μm to 8.0 μm, the migration state of the C16-35 saturated compound to the surface of the toner base particles during fixing can be more appropriately controlled. The larger the particle diameter, the more the toner separability can be improved. On the other hand, the smaller the particle diameter, the more easily the C16-35 compound can bleed out, improving varnish applicability.

[0106] The volume-average particle size of toner base particles can be measured using a particle size distribution analyzer (Beckman Coulter, Coulter Multisizer 3) connected to a computer system equipped with data processing software V3.51. Specifically, 0.02 g of sample (toner base particles) is added to 20 mL of surfactant solution, mixed, and then ultrasonically dispersed for 1 minute to prepare a toner base particle dispersion. The surfactant solution is prepared by diluting a neutral detergent containing surfactant components 10 times with pure water to disperse the toner base particles. This dispersion is pipetted into a beaker containing electrolyte (Beckman Coulter, ISOTON II) in a sample stand until the measurement device displays a concentration of 8%. This concentration ensures reproducible measurements. The measurement device then counts 25,000 particles and sets the aperture diameter to 100 μm. The measurement range of 2 to 60 μm is divided into 256 sections to calculate the frequency value. Based on this, the volume average particle size of the toner base particles can be calculated.

[0107] [1-2. External additives] The toner particles may contain an external additive that is added to the surface of the toner base particles as a post-treatment agent in order to improve the fluidity, chargeability and cleaning properties of the toner particles.

[0108] The external additive is preferably an inorganic particle such as silica particles, alumina particles, zirconia particles, titanium oxide particles, strontium titanate particles, zinc oxide particles, chromium oxide particles, cerium oxide particles, antimony oxide particles, tungsten oxide particles, tin oxide particles, tellurium oxide particles, manganese oxide particles, boron oxide particles, etc. These inorganic particles may be hydrophobized with a surface treatment agent such as a silane coupling agent or silicone oil, as necessary.

[0109] The number-average primary particle diameter of the inorganic particles is preferably 20 nm to 200 nm, more preferably 30 nm to 150 nm. As the number-average primary particle diameter of the external additive, image data captured by a scanning electron microscope (SEM) is binarized using an image processing analyzer (LUZEX AP, manufactured by Nireco Corporation), and the average value of horizontal Feret diameters measured for 100 particles can be used.

[0110] The external additive may be organic particles. Examples of organic particles include particles of a styrene homopolymer, a methyl methacrylate homopolymer, and a styrene-methyl methacrylate copolymer. The peak top particle size of the organic particles measured by the same method as for inorganic particles is preferably 10 nm or more and 1000 nm or less.

[0111] The external additive may be a lubricant such as a metal salt of a higher fatty acid. Examples of the higher fatty acid include stearic acid, oleic acid, palmitic acid, linoleic acid, and ricinoleic acid. Examples of the metal constituting the metal salt include zinc, manganese, aluminum, iron, copper, magnesium, and calcium.

[0112] The content of the external additive is preferably 0.05% by mass or more and 10.00% by mass or less, and more preferably 0.10% by mass or more and 5.00% by mass or less, based on the total amount of the toner particles. The external additive contained in the toner particles may be one kind or two or more kinds.

[0113] [2. Manufacturing method of toner for developing electrostatic images] The method for producing the toner is not particularly limited, and may be any known method such as an emulsion polymerization aggregation method or an emulsion aggregation method in which the above-mentioned components are aggregated.

[0114] An example of a method for producing a toner will be described below.

[0115] First, an aqueous dispersion is prepared by dispersing a modified amorphous polyester particle dispersion, a modified crystalline polyester particle dispersion, a release agent particle dispersion containing a C16-35 saturated compound, and a colorant particle dispersion in an aqueous medium.

[0116] The aqueous dispersion refers to a dispersion in which dispersed bodies (particles) are dispersed in an aqueous medium whose main component (50% by mass or more) is water. The aqueous medium may contain a water-soluble organic medium in addition to water. Examples of the water-soluble organic medium include methanol, ethanol, isopropanol, butanol, acetone, methyl ethyl ketone, and tetrahydrofuran.

[0117] A flocculant such as aluminum sulfate is added to the aqueous dispersion, and the dispersion is agglomerated by heating while warming, thereby forming core particles.

[0118] Separately prepared resin particles for forming the shell are added to the dispersion of core particles. This causes the resin particles for forming the shell to aggregate on the surface of the core particles. This forms toner base particles with a core-shell structure.

[0119] After the toner base particles are formed, the toner base particles are mixed with an external additive to obtain toner particles having the toner base particles and the external additive.

[0120] [3. Developer] The toner of the present invention can be used as a magnetic or non-magnetic one-component developer, or as a two-component developer by mixing it with carrier particles.

[0121] As the carrier particles, for example, magnetic particles made of conventionally known materials can be used. Examples of magnetic particles include metals such as iron, ferrite, and magnetite, and alloys of these metals with metals such as aluminum and lead. Ferrite particles are particularly preferred as the carrier particles.

[0122] Coated carrier particles or dispersed carrier particles may be used as carrier particles. "Coated carrier particles" are magnetic particles whose surfaces are coated with a coating agent such as a resin. "Dispersed carrier particles" are particles in which magnetic fine powder is dispersed in a binder resin. Coated carrier particles are preferred as carrier particles from the viewpoint of suppressing adhesion of the carrier particles to the photoreceptor.

[0123] The average particle size of the carrier particles is preferably 15 to 100 μm, more preferably 25 to 80 μm, in terms of volume-based median diameter, which can be measured, for example, by a laser diffraction particle size distribution analyzer (HELOS, SYMPATEC) equipped with a wet disperser.

[0124] The carrier particles may be mixed in an appropriate amount with the toner particles using a mixing device such as a Nauta mixer, a W-type mixer, or a V-type mixer.

[0125] [4. Image forming device] The image forming apparatus of the present invention forms an image using the toner of the present invention, and includes, for example, a photoreceptor, a first charging unit, an exposure unit, a developing unit, a transfer unit, a second charging unit, and a cleaning unit. The first charging means is a means for charging the surface of the photosensitive member. The exposure means is a means for irradiating the surface of the photoreceptor with light to form an electrostatic image. The developing means is a means for developing the electrostatic image with toner to form a toner image. The transfer means is a means for transferring the toner image onto a transfer material, which is an image support that carries the image, such as plain paper or a transparent sheet. The second charging means is a means for charging the surface of the photosensitive member after the toner image has been transferred onto the transfer material. The cleaning means is a means for removing residual toner from the photoreceptor.

[0126] Fig. 1 is a schematic diagram showing an example of an image forming apparatus. The image forming apparatus 100 shown in Fig. 1 is called a tandem color image forming apparatus, and is equipped with four sets of image forming units 10Y, 10M, 10C, and 10Bk, an intermediate transfer unit 7, a paper feed means 21, a fixing means 24, etc. An original image reading device SC is disposed on top of the apparatus main body A of the image forming apparatus 100.

[0127] The image forming unit 10Y that forms a yellow image has a first charging unit 2Y, an exposure unit 3Y, a developing unit 4Y, a primary transfer roller 5Y, a second charging unit 9Y, and a cleaning unit 6Y, which are arranged in this order along the rotation direction of the photoreceptor 1Y, around the drum-shaped photoreceptor 1Y.

[0128] Image forming unit 10M, which forms a magenta image, has a first charging unit 2M, an exposure unit 3M, a developing unit 4M, a primary transfer roller 5M, a second charging unit 9M, and a cleaning unit 6M, which are arranged in this order along the rotation direction of photoreceptor 1M, around the drum-shaped photoreceptor 1M.

[0129] Image forming unit 10C, which forms a cyan image, has a first charging unit 2C, an exposure unit 3C, a developing unit 4C, a primary transfer roller 5C, a second charging unit 9C, and a cleaning unit 6C, which are arranged in this order along the rotation direction of photoreceptor 1C, around drum-shaped photoreceptor 1C.

[0130] Image forming unit 10Bk, which forms black images, has a drum-shaped photoconductor 1Bk and includes a first charging unit 2Bk, an exposure unit 3Bk, a developing unit 4Bk, a primary transfer roller 5Bk, a second charging unit 9Bk, and a cleaning unit 6Bk, which are arranged in this order along the rotation direction of photoconductor 1Bk.

[0131] Image forming units 10Y, 10M, 10C, and 10Bk are configured similarly, except for the colors of the toner images formed on photoreceptors 1Y, 1M, 1C, and 1Bk. Therefore, image forming unit 10Y will be described in detail as an example, and descriptions of image forming units 10M, 10C, and 10Bk will be omitted.

[0132] The image forming unit 10Y has a first charging unit 2Y, an exposure unit 3Y, a developing unit 4Y, a primary transfer roller 5Y, a second charging unit 9Y, and a cleaning unit 6Y arranged around the photoreceptor 1Y, which is an image forming body, and forms a yellow (Y) toner image on the photoreceptor 1Y. In this embodiment, at least the photoreceptor 1Y, the first charging unit 2Y, the developing unit 4Y, the second charging unit 9Y, and the cleaning unit 6Y of the image forming unit 10Y are provided integrally.

[0133] The first charging means 2Y is a means for applying a uniform potential to the photosensitive member 1Y. As the first charging means 2Y, for example, a corona discharge type charger is used.

[0134] The exposure unit 3Y is a unit that exposes the photoreceptor 1Y, which has been given a uniform potential by the first charging unit 2Y, based on an image signal (yellow), to form an electrostatic charge image corresponding to the yellow image. The exposure unit 3Y may be, for example, a unit consisting of an LED in which light-emitting elements are arranged in an array in the axial direction of the photoreceptor 1Y and an imaging element, or a laser optical system.

[0135] The developing means 4Y is composed of, for example, a developing sleeve that incorporates a magnet and rotates while holding a developer, and a voltage application device that applies a DC and / or AC bias voltage between the photoreceptor 1Y and the developing sleeve.

[0136] The primary transfer roller 5Y is a means for transferring the toner image formed on the photosensitive member 1Y onto the endless belt-like intermediate transfer member 70. The primary transfer roller 5Y is disposed in contact with the intermediate transfer member 70.

[0137] The second charging means 9Y is a discharging means that charges (discharges) the surface of the photoreceptor 1Y after the toner image is transferred to the intermediate transfer body 70, and is provided as a pre-cleaning member. As the second charging means 9Y, for example, a corona discharge type charger is used.

[0138] The cleaning means 6Y is composed of a cleaning blade and a brush roller provided upstream of the cleaning blade.

[0139] The intermediate transfer unit 7 has an endless belt-like intermediate transfer member 70 as a second image carrier in the form of a semiconductive endless belt that is wound around and rotatably supported by a plurality of rollers 71, 72, 73, and 74. The intermediate transfer unit 7 is provided with a cleaning means 6b that removes toner from the intermediate transfer member 70.

[0140] The image forming units 10Y, 10M, 10C, and 10Bk and the intermediate transfer unit 7 constitute a housing 8. The housing 8 is configured so as to be able to be pulled out from the apparatus main body A via support rails 82L and 82R.

[0141] The image forming apparatus 100 includes a secondary transfer roller 5b that transfers a color image formed on the intermediate transfer body 70 onto a transfer material P. The paper feed means 21 is a means for supplying the transfer material P to the secondary transfer roller 5b. The paper feed means 21 includes a paper feed cassette 20 that stores the transfer material P, a plurality of intermediate rollers 22A, 22B, 22C, and 22D that transport the transfer material P to the secondary transfer roller 5b, and a registration roller 23.

[0142] The fixing means 24 is a means for fixing the color image transferred onto the transfer material P onto the transfer material P. The fixing means 24 may be, for example, a heat roller fixing type that is composed of a heating roller equipped with a heat source inside and a pressure roller that is placed in pressure contact with the heating roller so as to form a fixing nip portion.

[0143] The image forming apparatus 100 has a paper discharge tray 26 for removing the transfer material P on which an image has been formed. The image forming apparatus 100 also has a paper discharge roller 25 downstream of the fixing means 24 for transporting the transfer material P that has been subjected to the fixing process to the paper discharge tray 26.

[0144] In the above embodiment, the image forming apparatus 100 is a color laser printer. However, the image forming apparatus 100 may be a monochrome laser printer, a copier, a multifunction peripheral, or the like.

[0145] [5. Image forming method] In the image forming method of the present invention, an image is formed using the toner of the present invention, for example, using the image forming apparatus shown in Fig. 1. The steps of the image forming method are not particularly limited, but are, for example, as follows.

[0146] First, first charging devices 2Y, 2M, 2C, and 2Bk discharge the surfaces of photoconductors 1Y, 1M, 1C, and 1Bk to a negative charge. Next, exposure devices 3Y, 3M, 3C, and 3Bk expose the surfaces of photoconductors 1Y, 1M, 1C, and 1Bk based on an image signal to form electrostatic images. Next, developing devices 4Y, 4M, 4C, and 4Bk apply toner to the surfaces of photoconductors 1Y, 1M, 1C, and 1Bk to develop them into toner images.

[0147] Next, the toner images of each color formed on the photoreceptors 1Y, 1M, 1C, and 1Bk are sequentially transferred (primary transfer) by primary transfer rollers 5Y, 5M, 5C, and 5Bk onto the rotating intermediate transfer body 70. This forms a color image on the intermediate transfer body 70.

[0148] Next, the surfaces of photoconductors 1Y, 1M, 1C, and 1Bk are neutralized by second charging devices 9Y, 9M, 9C, and 9Bk. After that, any toner remaining on the surfaces of photoconductors 1Y, 1M, 1C, and 1Bk is removed by cleaning devices 6Y, 6M, 6C, and 6Bk. Finally, in preparation for the next image formation process, photoconductors 1Y, 1M, 1C, and 1Bk are negatively charged by charging devices 2Y, 2M, 2C, and 2Bk.

[0149] Meanwhile, a transfer material P is fed from a paper feed cassette 20 by a paper feed means 21 and transported to a secondary transfer roller 5b via a plurality of intermediate rollers 22A, 22B, 22C, and 22D and a registration roller 23. Then, a color image is transferred (secondary transfer) onto the transfer material P by the secondary transfer roller 5b.

[0150] The transfer material P onto which the color image has been transferred is subjected to a fixing process by fixing means 24. Next, the transfer material P is nipped by paper discharge rollers 25 and discharged to the outside of the apparatus, and placed on a paper discharge tray 26. After the transfer material P is separated from the intermediate transfer body 70, the remaining toner on the intermediate transfer body 70 is removed by cleaning means 6b.

[0151] A toner image can be formed on the transfer material P through the above steps.

[0152] [6. Varnishing] A toner image formed by the above-described image forming method may be varnished.

[0153] Varnishing can be achieved by applying varnish to the toner image formed in the image forming process and curing it to form a varnish layer. The varnish may be applied to cover the entire toner image, or may be applied to cover only a portion of the toner image.

[0154] The method for applying the varnish onto the toner image is not particularly limited as long as it allows for a uniform application of the varnish. Examples of application devices include liquid film coating devices such as varnish coaters, roll coaters, fox coaters, rod coaters, blades, wire bars, air knives, curtain coaters, slide coaters, doctor knives, screen coaters, gravure coaters (e.g., offset gravure coaters), slot coaters, and extrusion coaters. These may be well-known types such as forward or reverse roll coating, offset gravure, curtain coating, lithographic coating, screen coating, and gravure coating.

[0155] The varnish is preferably a photocurable varnish containing, for example, a photopolymerizable compound (polymerizable monomer for varnish) and a polymerization initiator (sensitizer).

[0156] The photopolymerizable compound may be a monomer, an oligomer, or a polymer. The varnish preferably contains a diol di(meth)acrylate having a linear hydrocarbon structure as the photopolymerizable compound. This increases the affinity between the crystalline polyester contained in the toner image and the varnish, improving the wettability of the varnish to the toner image and enhancing the adhesion (varnish adhesion) between the toner image and the varnish layer.

[0157] A diol di(meth)acrylate having a linear hydrocarbon structure is a monomer obtained by dehydration assembly of an aliphatic diol and two (meth)acrylic acids. The hydrocarbon structure of the diol di(meth)acrylate may be partially branched. In this case, the hydrocarbon chain sandwiched between two oxygen atoms derived from the diol is specified as the linear hydrocarbon structure.

[0158] The number of carbon atoms in the linear hydrocarbon structure of the diol di(meth)acrylate is preferably 4 to 12, more preferably 6 to 10, and even more preferably 6 to 9. When the number of carbon atoms in the linear hydrocarbon structure of the diol di(meth)acrylate is within this range, the viscosity of the photocurable varnish falls within an appropriate range, which tends to improve the coatability. Furthermore, the affinity with the crystalline polyester in the toner image also tends to improve.

[0159] Specific examples of diol di(meth)acrylate include hexanediol diacrylate, nonanediol diacrylate, decanediol diacrylate, etc., and among these, hexanediol diacrylate is particularly preferred.

[0160] Examples of photopolymerizable compounds other than diol di(meth)acrylate include the following: Acrylic resin Vinyl and acrylic resins Acrylic esters of polyhydric alcohols Epoxy Acrylate · Urethane · Acrylate Polyester Acrylate Polyether acrylate Acrylates Alkyds Melamine acrylate polymerizable oligomer Melamine acrylate polymer Trimethylolpropane (meth)acrylate Phenoxyethyl (meth)acrylate

[0161] The type and content of the photopolymerizable compound may be appropriately selected according to the curability, viscosity, surface tension, etc. of the photocurable varnish. For example, when the photocurable varnish contains diol di(meth)acrylate, the content of diol di(meth)acrylate is preferably 10% by mass or more and 80% by mass or less, and more preferably 20% by mass or more and 65% by mass or less, based on the total amount of the photopolymerizable compound. When the content of diol di(meth)acrylate is within this range, the varnish adhesion is good.

[0162] Examples of polymerization initiators include anthraquinone initiators, benzophenone initiators, 2-ethylanthraquinone initiators, acylphosphine oxide initiators, and alkylphenone photopolymerization initiators. The content of the polymerization initiator is preferably 5% by mass or more and 25% by mass or less based on the total amount of the photocurable varnish. When the content of the polymerization initiator is within this range, the photocurable varnish has good curability.

[0163] The varnish may contain a surfactant. When the varnish contains a surfactant, the varnish adhesion is likely to be good. Furthermore, when the varnish contains a surfactant, the wettability of the varnish can be adjusted.

[0164] Examples of surfactants include anionic surfactants, nonionic surfactants, silicone surfactants, and fluorosurfactants. Examples of anionic surfactants include sulfosuccinates, disulfonates, phosphate esters, sulfates, and sulfonates. Examples of nonionic surfactants include polyvinyl alcohol, polyacrylic acid, isopropyl alcohol, acetylenic diols, ethoxylated octylphenol, ethoxylated branched secondary alcohols, perfluorobutane sulfonates, and alkoxylated alcohols. Examples of silicone surfactants include polyether-modified polydimethylsiloxanes. Examples of fluorosurfactants include ethoxylated nonylphenols.

[0165] The surface tension of the varnish at 25°C is preferably 10 mN / m to 50 mN / m, more preferably 15 mN / m to 45 mN / m, and even more preferably 20 mN / m to 40 mN / m. When the surface tension of the varnish is within this range, the varnish easily spreads onto the toner image. The surface tension is measured by the plate method using a KYOWA DY300 (manufactured by Kyowa Interface Science Co., Ltd.).

[0166] The viscosity of the varnish at 25°C is preferably 100 mPa·s or more and 800 mPa·s or less, more preferably 150 mPa·s or more and 700 mPa·s or less, and even more preferably 200 mPa·s or more and 600 mPa·s or less. When the viscosity of the photocurable varnish is within this range, the varnish application is good. This viscosity is measured using a vibration viscometer by immersing the vibrator in the varnish and waiting 30 seconds.

[0167] When the varnish is a light-curable varnish, after application of the light-curable varnish, light energy is irradiated to cure the light-curable varnish. The type of light energy to be irradiated is appropriately selected depending on the type of polymerization initiator, etc., but can typically be ultraviolet light, visible light, etc. Examples of light energy sources include low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, xenon lamps, carbon arc lamps, metal halide lamps, fluorescent lamps, tungsten lamps, LEDs, etc. The light intensity and irradiation time of the light energy are appropriately selected.

[0168] The varnishing may be carried out by applying a solvent-based varnish and then drying the solvent, in addition to the method using the photocurable varnish described above.

[0169] Although embodiments of the present invention have been described and illustrated in detail, the disclosed embodiments are for purposes of illustration and example only and not limitation, and the scope of the present invention should be interpreted by the following claims. [Example]

[0170] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. In the following examples, unless otherwise specified, operations were performed in a standard environment of 25°C and 50% RH. Furthermore, unless otherwise specified, "%", "ppm", and "parts" mean "% by mass", "ppm by mass", and "parts by mass", respectively.

[0171] [Preparation of a mixture of saturated hydrocarbon compounds] Chain saturated hydrocarbons with carbon numbers of 20, 26, 30, and 34 (manufactured by GL Sciences Inc.) were dispensed in a mass ratio of 20:30:30:20 and melt-mixed at 80°C. This was cooled and solidified to obtain a mixture of saturated hydrocarbon compounds with carbon numbers of 16 to 35 (C16-35 saturated compounds).

[0172] [Synthesis of amorphous polyester a1] The following ingredients were placed in a dropping funnel:

[0173] Styrene 80 parts by mass n-Butyl acrylate 20 parts by mass Acrylic acid (bireactive monomer) 10 parts by mass Di-t-butyl peroxide (polymerization initiator) 16 parts by mass

[0174] The following ingredients were placed in a four-neck flask equipped with a nitrogen inlet tube, a dehydration tube, a stirrer, and a thermocouple, and heated to 170°C to dissolve.

[0175] Bisphenol A propylene oxide (polyhydric alcohol) 80 mole parts Bisphenol A ethylene oxide (polyhydric alcohol) 20 mole parts Terephthalic acid (polycarboxylic acid) 60 parts by mole Fumaric acid (polycarboxylic acid) 5 mole parts

[0176] While stirring, the components placed in the dropping funnel were added dropwise to the four-neck flask over 90 minutes, followed by aging for 60 minutes. Subsequently, unreacted monomers were removed under reduced pressure (8 kPa). Then, 0.003 mass% of Ti(OBu)4 was added as an esterification catalyst based on the total amount of polycarboxylic acid monomers. The mixture was heated to 235°C and reacted under normal pressure (101.3 kPa) for 5 hours, and then under reduced pressure (8 kPa) for 1 hour. The mixture was then cooled to 200°C and reacted under reduced pressure (20 kPa) until the desired softening point was reached. The solvent was then removed, yielding amorphous polyester a1.

[0177] [Synthesis of amorphous polyesters a2 to a4] In the synthesis of amorphous polyester a1, the types and amounts of polyhydric alcohol and polycarboxylic acid were changed as shown in Table I, and amorphous polyesters a2 to a4 were synthesized.

[0178] [Synthesis of amorphous polyester a5] The following ingredients were placed in a four-neck flask equipped with a nitrogen inlet tube, a dehydration tube, a stirrer, and a thermocouple, and heated to 170°C to dissolve.

[0179] Bisphenol A propylene oxide (polyhydric alcohol) 100 mole parts Terephthalic acid (polycarboxylic acid) 40 parts by mole Fumaric acid (polycarboxylic acid) 20 mole parts

[0180] While stirring, 0.003% by mass of Ti(OBu)4 was added as an esterification catalyst relative to the total amount of polycarboxylic acid monomers. The temperature was raised to 235°C, and the reaction was carried out under normal pressure (101.3 kPa) for 5 hours and then under reduced pressure (8 kPa) for 1 hour. The mixture was then cooled to 200°C and the reaction was carried out under reduced pressure (20 kPa) until the desired softening point was reached. The solvent was then removed to obtain amorphous polyester a5.

[0181] [Synthesis of amorphous polyester a6] In the synthesis of amorphous polyester a5, the types and amounts of polyhydric alcohol and polycarboxylic acid were changed as shown in Table I to synthesize amorphous polyester a6.

[0182] In Table I, "modified" means modified with at least one of styrene and (meth)acrylic acid ester. "BPA-PO" means bisphenol A propylene oxide. "BPA-EO" means bisphenol A ethylene oxide. The amount of monomer added is the amount added [parts by mole] when the total amount of polyhydric alcohol monomers is 100 parts by mole.

[0183] [Table 1]

[0184] [Preparation of amorphous polyester particle dispersion A1] The resulting amorphous polyester a1 (108 parts by weight) was added to methyl ethyl ketone (64 parts by weight) and stirred at 70°C for 30 minutes to dissolve. Next, an aqueous solution of sodium polyoxyethylene lauryl ether sulfate dissolved in ion-exchanged water (26 parts by weight) to a concentration of 1% by weight was added to the solution. Next, 25% by weight of aqueous sodium hydroxide solution (3.4 parts by weight) was added to the solution. The solution was placed in a reaction vessel equipped with a stirrer, and ion-exchanged water (270 parts by weight) heated to 70°C was added dropwise over 70 minutes while stirring. The liquid in the vessel became cloudy during the dropwise addition, and a uniform emulsion was obtained after the entire amount was added dropwise. Next, while maintaining the emulsion at 70°C, the emulsion was stirred for 1 hour under a reduced pressure of 15 kPa (150 mbar) using a diaphragm vacuum pump "V-700" (Buchi), and the methyl ethyl ketone was distilled off. As a result, an amorphous polyester particle dispersion A1 in which particles of the amorphous polyester a1 were dispersed was obtained.

[0185] The solid concentration of the amorphous polyester particle dispersion A1 was 25% by mass. As a result of measurement with a particle size distribution measuring instrument, the volume average particle size of the particles in the amorphous polyester particle dispersion A1 was 94 nm.

[0186] [Preparation of amorphous polyester particle dispersions A2 to A6] Amorphous polyester particle dispersions A2 to A6 were obtained by changing the amorphous polyester a1 in the preparation of amorphous polyester particle dispersion A1 to a2 to a6, respectively.

[0187] [Synthesis of crystalline polyester c1] The following ingredients were placed in a dropping funnel:

[0188] Styrene 40.0 parts by mass n-Butyl acrylate 16 parts by mass Acrylic acid (bireactive monomer) 3.5 parts by mass Di-t-butyl peroxide (polymerization initiator) 8 parts by mass

[0189] The following ingredients were placed in a four-neck flask equipped with a nitrogen inlet tube, a dehydration tube, a stirrer, and a thermocouple, and heated to 170°C to dissolve.

[0190] Tetradodecanedioic acid (polycarboxylic acid) 400 parts by mass 1,4-butanediol (polyhydric alcohol) 130 parts by mass

[0191] While stirring, the components placed in the dropping funnel were added dropwise to the four-neck flask over 90 minutes, followed by aging for 60 minutes. Subsequently, unreacted monomers were removed under reduced pressure (8 kPa). Then, 0.003 mass% of Ti(OBu)4 was added as an esterification catalyst based on the total amount of polycarboxylic acid monomers. The mixture was heated to 235°C and reacted under normal pressure (101.3 kPa) for 5 hours, and then under reduced pressure (8 kPa) for 1 hour. The mixture was then cooled to 200°C and reacted under reduced pressure (20 kPa) for 1 hour, yielding crystalline polyester c1. The melting point of the resulting crystalline polyester c1 was 77°C.

[0192] [Synthesis of crystalline polyester c2] The following ingredients were placed in a four-neck flask equipped with a nitrogen inlet tube, a dehydration tube, a stirrer, and a thermocouple, and heated to 170°C to dissolve.

[0193] Tetradodecanedioic acid (polycarboxylic acid) 400 parts by mass 1,4-butanediol (polyhydric alcohol) 130 parts by mass

[0194] While stirring, 0.003% by mass of Ti(OBu)4 was added as an esterification catalyst relative to the total amount of polycarboxylic acid monomer. The temperature was raised to 235°C, and the reaction was carried out under normal pressure (101.3 kPa) for 5 hours and then under reduced pressure (8 kPa) for 1 hour. The mixture was then cooled to 200°C and reacted under reduced pressure (20 kPa) for 1 hour to obtain crystalline polyester c2. The melting point of the obtained crystalline polyester c2 was 75°C.

[0195] [Preparation of crystalline polyester particle dispersion C1] The resulting amorphous polyester c1 (174 parts by weight) was added to methyl ethyl ketone (102 parts by weight) and stirred at 75°C for 30 minutes to dissolve. Next, an aqueous solution of sodium polyoxyethylene lauryl ether sulfate dissolved in ion-exchanged water (26 parts by weight) to a concentration of 1% by weight was added to the solution. Next, 25% by weight of aqueous sodium hydroxide solution (4.6 parts by weight) was added to the solution. The solution was placed in a reaction vessel equipped with a stirrer, and ion-exchanged water (375 parts by weight) heated to 70°C was added dropwise over 70 minutes while stirring. The liquid in the vessel became cloudy during the dropwise addition, and a uniform emulsion was obtained after the entire amount was added dropwise. Next, while maintaining the emulsion at 70°C, the emulsion was stirred for 1 hour under a reduced pressure of 15 kPa (150 mbar) using a diaphragm vacuum pump "V-700" (Buchi), and the methyl ethyl ketone was distilled off. As a result, a crystalline polyester particle dispersion C1 in which particles of the amorphous polyester c1 were dispersed was obtained.

[0196] The solid content concentration of the crystalline polyester particle dispersion C1 was 25% by mass. As a result of measurement using a particle size distribution measuring instrument, the volume average particle size of the particles in the crystalline polyester particle dispersion C1 was 202 nm.

[0197] [Preparation of crystalline polyester particle dispersion C2] Crystalline polyester particle dispersion C2 was obtained by changing the crystalline polyester c1 to c2 in the preparation of crystalline polyester particle dispersion C1.

[0198] [Preparation of Colorant Particle Dispersion P1] Sodium dodecyl sulfate (226 parts by mass) was added to ion-exchanged water (1600 parts by mass). While stirring this solution, copper phthalocyanine (CI Pigment Blue 15:3) (420 parts by mass) was gradually added. Dispersion was performed using a stirring device, Clearmix (manufactured by M Technique Co., Ltd., "Clearmix" is a registered trademark of the company), to obtain colorant particle dispersion P1. The volume-based median particle diameter of the colorant particle dispersion P1 was 110 nm.

[0199] [Preparation of release agent particle dispersion W1] The following ingredients were mixed, heated to 110°C, dispersed using a homogenizer (IKA Ultra Turrax T50), and then dispersed using a Manton-Gaulin high-pressure homogenizer (Gaulin).

[0200] Behenyl behenate (mold release agent, melting point 73°C) 50 parts by mass 0.32 parts by mass of the above mixture of saturated hydrocarbon compounds Anionic surfactant (Neogen RK, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) 5 parts by mass Ion-exchanged water 200 parts by mass

[0201] This resulted in a release agent particle dispersion W1 containing a release agent and a saturated hydrocarbon compound. Measurement using a Microtrac UPA-150 (manufactured by Nikkiso Co., Ltd.) revealed that the volume average particle size of the particles in the release agent particle dispersion W1 was 215 nm.

[0202] [Preparation of release agent particle dispersions W2 to W6] In the preparation of release agent particle dispersion W1, the amount of the saturated hydrocarbon compound mixture was changed as shown in Table II to obtain release agent particle dispersions W2 to W6.

[0203] [Table 2]

[0204] [Preparation of styrene-acrylic resin particle dispersion V1] (First stage polymerization) A 5 L reaction vessel equipped with a stirrer, temperature sensor, condenser, and nitrogen inlet was charged with 8 parts by mass of sodium dodecyl sulfate and 3,000 parts by mass of ion-exchanged water. The vessel was stirred at 230 rpm under a nitrogen stream while the internal temperature was raised to 80°C. After the temperature was raised, a solution of 10 parts by mass of potassium persulfate dissolved in 200 parts by mass of ion-exchanged water was added. The liquid temperature was again raised to 80°C, and the following monomer mixture was added dropwise over 1 hour.

[0205] Styrene 480.0 parts by mass n-Butyl acrylate 250.0 parts by mass Methacrylic acid 65.0 parts by mass

[0206] After the dropwise addition of the mixed liquid, the mixture was heated and stirred at 80° C. for 2 hours to polymerize the monomers, thereby preparing a styrene-acrylic resin particle dispersion liquid v1.

[0207] (Second stage polymerization) A 5 L reaction vessel equipped with a stirrer, a temperature sensor, a cooling pipe, and a nitrogen introducing device was charged with ion-exchanged water (1,100 parts by mass) and the above-prepared styrene-acrylic resin particle dispersion v1 (55 parts by mass (solid content equivalent)), and heated to 87°C.

[0208] A dispersion containing emulsified particles (oil droplets) was prepared by dissolving the following monomers and chain transfer agents at 85°C and mixing and dispersing for 10 minutes. A mechanical disperser with a circulation path, Clearmix (registered trademark, manufactured by M Technique Co., Ltd.), was used for the mixing and dispersing process.

[0209] Styrene 256.5 parts by mass 2-Ethylhexyl acrylate 95.3 parts by mass Methacrylic acid 38.2 parts by mass n-Octyl-3-mercaptopropionate (chain transfer agent) 4.0 parts by mass

[0210] This dispersion was added to the 5 L reaction vessel. To this was added a polymerization initiator solution prepared by dissolving 5.4 parts by mass of potassium persulfate in 103 parts by mass of ion-exchanged water. The system was heated and stirred at 87°C for 1 hour to carry out polymerization, thereby preparing styrene-acrylic resin particle dispersion v1'.

[0211] (Third stage polymerization) To the styrene-acrylic resin particle dispersion v1' prepared above, a solution of potassium persulfate (7.3 parts by mass) dissolved in ion-exchanged water (157.9 parts by mass) was added, and a mixture of the following monomers and chain transfer agent was added dropwise over 90 minutes at a temperature of 84°C.

[0212] Styrene 370.0 parts by mass n-Butyl acrylate 165.0 parts by mass Methacrylic acid 40.0 parts by mass Methyl methacrylate 47.2 parts by mass n-Octyl-3-mercaptopropionate (chain transfer agent) 8.6 parts by mass

[0213] After the dropwise addition, polymerization was carried out by heating and stirring for 2 hours. The system was then cooled to 28°C to obtain styrene-acrylic resin particle dispersion V1. The solid content of the obtained styrene-acrylic resin particle dispersion V1 was 30% by mass.

[0214] [Preparation of Toner Base Particles 1] The following materials for forming core particles were placed in a 4-liter reaction vessel equipped with a thermometer, a pH meter, and a stirrer: Dowfax 2A1 (20% aqueous solution, manufactured by Dow Chemical Company) was used as the anionic surfactant.

[0215] Styrene-acrylic resin particle dispersion V1 819 parts by mass (solid content equivalent) Amorphous polyester particle dispersion A1 117 parts by mass (solid content equivalent) Crystalline polyester particle dispersion C1 117 parts by mass (solid content equivalent) Release agent particle dispersion W1 150 parts by mass (solid content) Colorant particle dispersion P1 180 parts by mass (solid content equivalent) Anionic surfactant 40 parts by mass Ion-exchanged water 1500 parts by mass

[0216] This was dispersed at 3000 rpm using a homogenizer (ULTRA-TURRAX T50, manufactured by IKA), while a 2% aluminum sulfate aqueous solution (100 parts by mass) was added as a flocculant over 30 minutes. After the dropwise addition was completed, the mixture was stirred for 10 minutes to thoroughly mix the raw material and flocculant.

[0217] A mantle heater was then installed in the reaction vessel. The temperature was increased at a rate of 0.2°C / min up to 40°C, and then at a rate of 0.05°C / min after the temperature exceeded 40°C, while the agitator speed was adjusted to ensure sufficient stirring of the slurry. Particle size was measured every 10 minutes using a Coulter Multisizer 3 (aperture diameter 100 μm, manufactured by Beckman Coulter).

[0218] The temperature was maintained when the volume average particle size reached 5.5 μm to obtain a dispersion of core particles. A premixed mixture of the following components (shell-forming resin dispersion) was added to the dispersion over a 20-minute period. The anionic surfactant used was Dowfax 2A1 (20% aqueous solution, manufactured by The Dow Chemical Company).

[0219] Amorphous polyester particle dispersion A6 117 parts by mass (solid content equivalent) Anionic surfactant 9 parts by mass

[0220] Next, after maintaining the temperature at 50°C for 30 minutes, 20% EDTA (ethylenediaminetetraacetic acid) solution (8 parts by mass) was added to the reaction vessel. Then, 1 mol / L aqueous sodium hydroxide solution was added to control the pH of the raw material dispersion at 9.0. Thereafter, the temperature was increased to 85°C at a rate of 1°C / min while adjusting the pH to 9.0 every 5°C, and the temperature was maintained at 85°C.

[0221] Thereafter, when the shape factor reached 0.970, the mixture was cooled at a temperature decreasing rate of 10° C. / min using the “FPIA-3000” to obtain a toner base particle dispersion liquid.

[0222] The toner base particle dispersion was then filtered and thoroughly washed with ion-exchanged water. It was then dried at 40°C to obtain core-shell type toner base particles 1. The volume average particle size of toner base particles 1 was 6.0 μm. The average circularity of toner base particles 1 was 0.971.

[0223] [Preparation of toner base particles 2 to 19] In the preparation of toner base particles 1, the types and amounts of various dispersion liquids were changed so that the compositions would be as shown in Table III, and core-shell type toner base particles 2 to 19 were prepared.

[0224] The content of each binder resin in Table III is the content [mass %] relative to the total amount of binder resin.

[0225] [Table 3]

[0226] [Preparation of Silica Particles S1] Methanol (945 parts by mass), 28% aqueous ammonia (45 parts by mass), and water (135 parts by mass) were added to a 3-liter reactor equipped with a stirrer, dropping funnel, and thermometer, and mixed. The temperature of this solution was adjusted to 35°C, and tetramethoxysilane (405 parts by mass) was added dropwise over 6 hours while stirring. After the dropwise addition, stirring was continued for 1 hour to allow hydrolysis, resulting in a suspension of silica particles. This dispersion was distilled under reduced pressure and dried, and the fine particles were then crushed to obtain silica particles S1.

[0227] [Production of toner particles 1] Toner base particles 1 (100 parts by mass) were added silica particles S1 (1.5 parts by mass), and mixed in a Henschel mixer (manufactured by Nippon Coke & Engineering Co., Ltd.) at a rotor peripheral speed of 35 mm / sec and 32°C for 20 minutes. After mixing, coarse particles were removed using a sieve with 45 μm openings, and toner particles 1 were obtained.

[0228] [Production of Toner Particles 2 to 19] In the production of toner particles 1, toner base particles 1 were changed to toner base particles 2 to 19, respectively, to produce toner particles 2 to 19.

[0229] [Measurement of C16-35 saturated compound content] Hydrocarbon compounds were extracted from each toner particle by solid-liquid extraction using n-hexane. At this time, cyclohexyl was added as an internal standard. Unsaturated hydrocarbons were then epoxidized using metachloroperbenzoic acid (mCPBA) using standard methods. Saturated hydrocarbon compounds were then purified and extracted by solid-phase extraction using silver nitrate silica gel as the solid phase. GC-FID was performed under the following conditions to quantify the C16-35 saturated compounds.

[0230] (GC conditions) Equipment used: Shimadzu GC-2010 Plus Injection volume: 1 μL, saturated hydrocarbon concentration: 500 to 1000 mg / L Guard column: Restek MXT Siltek (10 m x 0.53 mm id) Column: Restek MTX-1 (15 m x 0.25 mm id) x 0.1 μm df) Carrier gas: Helium

[0231] The elution times of n-alkanes (number of carbon atoms: 10, 16, 24, 35, and 50) previously measured under the same conditions were measured. In addition, a blank chromatogram was prepared by injecting only n-hexane into the above-mentioned device.

[0232] A blank chromatogram was subtracted from the chromatogram obtained from each toner particle, creating a stable, horizontal, straight baseline before and after the peaks derived from saturated hydrocarbon compounds. Perpendicular lines were drawn at the carbon atoms 16 and 35, and the area of ​​the chromatogram above the baseline enclosed by these perpendicular lines was calculated. Peaks that were confirmed not to be saturated hydrocarbon compounds were excluded from the calculation. The mass of saturated hydrocarbon compounds with 16 to 35 carbon atoms was calculated from the ratio of this area to the area of ​​bicyclohexyl added as an internal standard. This mass was then divided by the mass of the toner particles to determine the content of C16-35 saturated compounds in the toner particles.

[0233] The content of C16-35 saturated compounds in each toner particle was as shown in Table IV.

[0234] [Production of Developer 1] Toner particles 1 and acrylic resin-coated ferrite carriers with a volume average particle size of 32 μm were mixed so that the toner particle concentration was 6 mass %. In this way, developer 1, a two-component developer containing toner particles 1, was produced.

[0235] [Production of Developers 2 to 19] In the production of developer 1, toner particles 1 were changed to toner particles 2 to 19, respectively, to produce developers 2 to 19.

[0236] [Toner image formation] The multifunction printer used was a "bizhub PRESS (registered trademark) C1070" (manufactured by Konica Minolta). The multifunction printer was modified so that the amount of toner attached could be freely set, and two-component developers were loaded sequentially. The evaluation paper was OK Topcoat+ (157.0 g / m 2 The toner adhesion amount was 8.0 g / m 2 The image was output under normal fixing conditions.

[0237] [Formation of varnished image] UV VECTA Coat Varnish PC-3KW2 (manufactured by T&K Corporation) was applied to the formed toner image using a bar coater to a thickness of 5 μm. Then, a high-pressure mercury lamp was used to apply a cumulative light intensity of 120 to 130 mJ / cm 2 to the image surface. 2 The varnish was then irradiated with ultraviolet light to form a varnish layer. This hardened the varnish and formed a varnish layer. UV VECTA Coat Varnish PC-3KW2 contains a varnish polymerizable monomer and a photopolymerization initiator (radical polymerization initiator). The varnish polymerizable monomer has a polymerizable functional group containing an ethylenic double bond.

[0238] [Evaluation of varnish application] The surface of the varnish layer was visually observed and the applicability of the varnish was evaluated based on the following evaluation criteria, with A, B, and C being considered acceptable levels. The evaluation results are shown in Table IV.

[0239] (Evaluation criteria) A: There are no pinholes within a 10cm x 10cm area, and the toner image does not repel the varnish. B: There are one to two pinholes within a 10cm x 10cm area, and the toner image does not repel the varnish. C: There are 3 to 10 pinholes within a 10 cm x 10 cm area, and the toner image does not repel the varnish. D: There are 11 or more pinholes within a 10cm x 10cm area, or the toner image repels the varnish.

[0240] [Evaluation of varnish adhesion] The adhesion between the toner image and the varnish layer (varnish adhesion) of the image on which the varnish layer was formed as described above (varnish-coated image) was evaluated by the mending tape peeling method according to the following procedures (1) to (7). (1) Images were taken at a magnification of 100x and binarized. A Keyence VHX-6000 digital microscope was used to take the images. A Nireco LUSEX-AP microscope was used for the binarization. (2) "Mending tape" (Sumitomo 3M: No. 810-3-12) was lightly attached to the image. (3) The tape was rubbed back and forth 3.5 times with a pressure of 1 kPa. (4) The tape was peeled off at an angle of 180 degrees with a force of 200 g. (5) After the tape was removed, a photograph was taken at a magnification of 100x using a Keyence VHX-6000 digital microscope. The photographed image was then binarized using a Nireco LUSEX-AP microscope. (6) The area of ​​the varnish layer was determined from the binarized images before and after tape peeling. The varnish layer peeling rate was calculated from the area of ​​the varnish layer before and after tape peeling using the following formula. Varnish layer peeling rate [%] = (AB) / A x 100 A: Area of ​​varnish layer before tape peeling B: Area of ​​varnish layer after tape peeling (7) Adhesion was evaluated based on the following evaluation criteria, with A and B being acceptable levels. The evaluation results are shown in Table IV.

[0241] (Evaluation criteria) A: The varnish layer peeling rate is 0%. B: The varnish layer peeling rate is less than 5%. C: The varnish layer peeling rate is 5% or more and less than 30%. D: The varnish layer peeling rate is 30% or more.

[0242] [Evaluation of resistance to fold cracking] The multifunction printer, "bizhub PRESS (registered trademark) C1070" (manufactured by Konica Minolta), was modified to be able to change the surface temperatures of the upper fixing belt and the lower fixing roller, and two-component developers were sequentially loaded into the device. The device was also modified to be able to freely set the fixing temperature, toner adhesion amount, and system speed.

[0243] Adhesion amount: 11.3g / m 2The fixing experiment to output a solid image was carried out repeatedly by changing the set fixing temperature from 120°C to 180°C, increasing it by 5°C at a time. The fixing experiment was carried out in an environment of normal temperature and humidity (temperature 20°C, humidity 50% RH). A4 size high-quality paper "NPI high-quality (127.9 g / m 2 ) (manufactured by Nippon Paper Industries Co., Ltd.) was used.

[0244] The solid images obtained in the fixing experiments at each fixing temperature were folded in a valley shape so that the solid images would contact each other, using a folding machine with a thickness of 10 g / cm 2 The sheet was folded under a considerable weight load and compressed air of 0.35 MPa was blown onto it. Based on the condition of the folded portion, the solid images obtained in the fixing experiment at each fixing temperature were ranked according to the following criteria.

[0245] (Evaluation criteria) 5: No creases at all 4: Some peeling along the fold 3: Fine linear peeling along the fold 2: Thick linear peeling along the fold 1: Large peeling along the fold

[0246] Among the solid images ranked 2 to 5, the fixing temperature of the solid image fixed at the lowest fixing temperature was designated the "lower limit fixing temperature." Based on this lower limit fixing temperature, the fold crack resistance was evaluated according to the following evaluation criteria. A, B, and C were rated as acceptable levels. The evaluation results are shown in Table IV. (Evaluation criteria) A: The minimum fixing temperature is less than 140°C. B: The minimum fixing temperature is 140°C or higher and lower than 145°C. C: The minimum fixing temperature is 145°C or higher and lower than 150°C. D: The minimum fixing temperature is 150°C or higher.

[0247] [Table 4]

[0248] From the above results, it was confirmed that the toner for developing electrostatic images of the present invention can form images that are excellent in varnish coatability, varnish adhesion, and bending resistance. [Explanation of symbols]

[0249] 100: Image forming device 1Y, 1M, 1C, 1Bk: Photoreceptor 2Y, 2M, 2C, 2Bk: 1st charging means 3Y, 3M, 3C, 3Bk: Exposure means 4Y, 4M, 4C, 4Bk: Developing means 5Y, 5M, 5C, 5Bk: Primary transfer roller 5b: Secondary transfer roller 6Y, 6M, 6C, 6Bk, 6b: cleaning means 7: Intermediate transfer unit 8: Housing 9Y, 9M, 9C, 9Bk: second charging means 10Y, 10M, 10C, 10Bk: Image forming units 21:Paper feeding means 20: Paper cassette 22A, 22B, 22C, 22D: Intermediate rollers 23: Resist roller 24: Fixing means 25: Paper ejection roller 26: Paper output tray 70: Intermediate transfer body 71, 72, 73, 74: Roller 82L, 82R: Support rail P: Transfer material

Claims

1. A toner for developing electrostatic images, comprising toner particles, the toner particles include at least toner base particles, the toner base particles are of a core-shell type having a core particle and a shell covering the core particle, the toner base particles contain a binder resin, a release agent (excluding saturated hydrocarbon compounds having 16 to 35 carbon atoms), and a saturated hydrocarbon compound having 16 to 35 carbon atoms, the toner base particles contain, in the core particles, as the binder resin, an amorphous polyester modified with at least one of styrene and a (meth)acrylic acid ester, and a crystalline polyester modified with at least one of styrene and a (meth)acrylic acid ester; the content of the saturated hydrocarbon compound having 16 to 35 carbon atoms is 1 ppm by mass to 1000 ppm by mass with respect to the total amount of the toner particles; Toner for developing electrostatic images.

2. The toner base particles further contain a styrene-acrylic resin as the binder resin. The toner for developing electrostatic images according to claim 1.

3. The softening point of the amorphous polyester is 70°C or higher and 95°C or lower. The toner for developing electrostatic images according to claim 1 or 2.

4. the content of the amorphous polyester is 20% by mass or more and 60% by mass or less with respect to the total amount of the binder resin; The toner for developing electrostatic images according to claim 1 or 2.

5. the content of the crystalline polyester is 10% by mass or more and 20% by mass or less with respect to the total amount of the binder resin; The toner for developing electrostatic images according to claim 1 or 2.

6. The toner for developing electrostatic images according to claim 1 or 2 is used. Image forming device.

7. The toner for developing electrostatic images according to claim 1 or 2 is used. Image forming method.

Images