toner

Abstract

To provide a toner that, even after a long-term durable use in a low temperature and low humidity environment, exhibits good charge rising properties and electrifying roller stain resistance, and can output images with high density uniformity of a solid image and high uniformity of a half-tone image.SOLUTION: A toner has toner particles containing a binder resin and strontium titanate particles. In TOF-SIMS measurement of the toner particles, a fragment peak derived from boron atoms and a fragment peak derived from a boron-oxygen structure are detected, and a fatty acid is present in the surface of the strontium titanate particle.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a toner used in an electrophotographic image forming apparatus. [Background technology]

[0002] Electrophotographic image forming apparatuses are required to be faster, more compact, and have longer life spans, and toners are also required to have improved performance in various areas to meet these demands. For example, a toner with good charge rise characteristics (the ability to increase the charge amount of the toner in a short time) can contribute to faster speeds, smaller size, and longer life of an electrophotographic image forming apparatus. Specifically, good charge rise characteristics can reduce the number of parts that assist in charging the toner, thereby contributing to smaller size. In addition, increasing charge characteristics in a short time can also contribute to faster speeds. In addition, the charge characteristics of the toner can be easily maintained even after long-term durable use, which can also contribute to longer life. Conventionally, a method for improving the charge rise property of a toner has been proposed in which strontium titanate particles are externally added to toner particles to improve the charge rise property of the toner (Patent Document 1). Although it is true that the charge rise property of a toner can be improved by externally adding strontium titanate particles, conversely, when the toner is used for a long period of time in a low-temperature, low-humidity environment, the strontium titanate particles may contaminate the charging roller (the charging member that charges the photoconductor). On the other hand, a toner has been proposed that uses a resin having a crosslinked structure derived from at least one of boric acid and boric acid derivatives in the toner particles to suppress the decrease in transfer efficiency during long-term use (Patent Document 2). In this proposal, the toner particles contain a boron crosslinked resin, which hardens the toner surface and suppresses the deterioration of the toner particles (external additives being embedded in the toner particle surface, toner particles being deformed, etc.), thereby suppressing the decrease in transfer efficiency, but there is room for improvement in the chargeability. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-45578 A [Patent Document 2] JP 2012-42539 A Summary of the Invention [Problem to be solved by the invention]

[0004] As a result of the inventors' investigation, it was confirmed that the toner described in Patent Document 1 has a certain effect of improving the charge rise property by the externally added strontium titanate particles acting as microcarriers. However, there is a problem with long-term durability, and when used for a long time in a low-temperature, low-humidity environment in particular, the charging roller becomes contaminated with the strontium titanate particles, and when a halftone image is output, a streaky image defect may occur.

[0005] In addition, since the toner described in Patent Document 2 does not contain strontium titanate particles, it has insufficient charge rise characteristics. For example, when a solid image is output in a low-temperature, low-humidity environment where charge rise characteristics are poor, the density at the rear end of the image becomes thin, which is found to be an issue in terms of density uniformity.

[0006] As described above, all of the conventional techniques have problems with performance in low-temperature, low-humidity environments, and the present invention aims to provide a toner that solves the above problems. Specifically, the present invention aims to provide a toner that has good charge build-up properties and good resistance to contamination of a charging roller, and that can output images with high density uniformity for solid images and high uniformity for halftone images even after long-term use in a low-temperature, low-humidity environment. [Means for solving the problem]

[0007] In order to solve the above problems, the present inventors have conducted extensive research into the charge rise property of toner and the contamination resistance of charging rollers. As a result, they have found that by containing a compound derived from a boron-oxygen bond near the surface of toner particles and containing strontium titanate particles surface-treated with a fatty acid, it is possible to achieve both charge rise property (density uniformity of solid images) and anti-contamination of charging members (uniformity of halftone images) even when used for a long time in a low-temperature, low-humidity environment.

[0008] That is, the present invention provides a toner having toner particles containing a binder resin and strontium titanate particles, In a TOF-SIMS measurement of the toner particles, a fragment peak derived from a boron atom and a fragment peak derived from a boron-oxygen structure are detected, The toner is characterized in that a fatty acid is present on the surface of the strontium titanate particles. Effect of the Invention

[0009] According to the present invention, it is possible to provide a toner that has good charge rise properties and good resistance to contamination of the charging roller, and it is possible to provide a toner that can output images with high density uniformity for solid images and high uniformity for halftone images even when used for a long period of time in a low temperature and low humidity environment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] [Features of the present invention] As mentioned above, it is effective to externally add strontium titanate particles to toner particles as a means for improving the charge rise property of the toner. However, when the toner is used for a long period of time in a low temperature and low humidity environment, there is a problem that the strontium titanate particles contaminate the charging members such as the charging roller.

[0011] The inventors conducted a detailed study into why the strontium titanate particles are prone to contaminating charging members, and found that the strontium titanate becomes excessively charged particles, which causes the electrostatic adhesion force with the photosensitive member to become too strong, making it impossible to clean the strontium titanate in the cleaning process and resulting in contamination of the charging member.

[0012] It was also found that this is because, particularly in low-temperature, low-humidity environments, the moisture content in the air is low, so the charge generated in the strontium titanate particles due to "peeling charging with toner particles" is easily retained, and therefore, with long-term durable use, the toner is agitated in the developing device and rubs against the developing blade, developing roller, photoconductor, etc., causing excessive charge to accumulate in the toner particles and the strontium titanate particles.

[0013] We therefore investigated surface treatment agents for strontium titanate particles to prevent the particles from becoming overcharged even when used for long periods of time in low-temperature, low-humidity environments. However, this tends to result in a trade-off with the charge rise properties of the toner, and it was not possible to achieve both charge rise properties (density uniformity of solid images) and resistance to charge-related contamination of components (uniformity of half-tone images) at the same time.

[0014] Furthermore, as a result of extensive investigations into the surface design of toner particles, it was discovered that by having toner particles that contain a compound derived from a boron-oxygen bond (BO bond) near the surface and that contain strontium titanate particles that have been surface-treated with a fatty acid, it is possible to achieve both good charge rise properties (density uniformity of solid images) and anti-charge member contamination (uniformity of half-tone images) even when used for a long time in a low-temperature, low-humidity environment, and this led to the completion of the present invention.

[0015] The reason why the toner of the present invention is able to achieve both charge rise properties (density uniformity of solid images) and anti-electrostatic member contamination (uniformity of half-tone images) in a low temperature and low humidity environment is not entirely clear, but the inventors speculate as follows.

[0016] The toner particles of the present invention have a compound derived from a B-O bond near the surface, and the compound derived from a B-O bond has a biased charge due to the difference in polarity (electronegativity) between the B atom and the O atom. In other words, since the charge of the O atom is negative and the charge of the B atom is positive, it is considered that the toner particles have a hydrogen bond with water molecules, which also have a high polarity, and tend to easily adsorb water molecules near the surface of the toner particles.

[0017] On the other hand, the inventors' research has revealed that by making fatty acids exist on the surface of strontium titanate, the strontium titanate particles are able to hold a small amount of water molecules near the surface, and the positive charge generated by peeling electrification can be gradually released into the air by the water molecules. This is believed to be because the carboxyl terminal of the fatty acid also has hydrogen bonding properties with water molecules.

[0018] In this way, it is presumed that the toner of the present invention does not become excessively charged particles even when used for a long period of time in a low-temperature, low-humidity environment, because the water molecules carried near the surface of the toner particles are transferred to the fatty acids present on the surface of the strontium titanate particles, and the fatty acids steadily carry an appropriate amount of water molecules.

[0019] Furthermore, if the toner particles do not have a compound derived from a B-O bond near the surface, it is difficult for the fatty acids present on the surface of the strontium titanate particles to continue to support water molecules steadily, and the effect of gradually releasing positive charge is insufficient, so that the contamination resistance of the charging member cannot be improved when used for a long period of time in a low-temperature, low-humidity environment.

[0020] Next, the essential components of the present invention will be described.

[0021] <Having a compound derived from a BO bond in the vicinity of the surface of the toner particle> The toner of the present invention has toner particles containing a binder resin, and in a TOF-SIMS measurement of the toner particles, it is necessary that a fragment peak derived from a boron atom and a fragment peak derived from a boron-oxygen structure (BO structure) are detected.

[0022] The TOF-SIMS measurement of the toner particles can identify the composition and structure of the compound present near the surface of the toner particles. The TOF-SIMS measurement detects a fragment peak derived from a boron atom and a fragment peak derived from a BO structure, which indicates that a compound derived from a BO bond is present near the surface of the toner particles.

[0023] The presence of the compound derived from the BO bond near the surface of the toner particles makes it easier for water molecules to be supported near the surface of the toner particles. Therefore, as described above, when the strontium titanate particles are peeled off and charged, water molecules are constantly supplied from the surface of the toner particles to the fatty acid of the strontium titanate particles, which prevents the strontium titanate particles from being overcharged even in a low-temperature, low-humidity environment, and improves the anti-electrostatic member contamination properties.

[0024] TOF-SIMS can qualitatively measure the surface area of ​​the toner below 10 nm. The presence or absence of BO bonds is determined by TOF-SIMS measurement using sodium tetraborate decahydrate (FUJIFILM Wako Pure Chemical Industries, Ltd.) as a standard sample. The peak positions of boron atoms and BO2 (a representative structure with BO bonds) are confirmed for the measurement data. Then, the presence or absence of boron atoms and BO bonds can be determined by performing TOF-SIMS measurement of the target toner.

[0025] The method for measuring the fragment peaks derived from boron atoms and the BO structure will be described later.

[0026] When there are peaks for boron atoms and B-O bonds, the above-mentioned effects are manifested, and even when the strontium titanate particles are used for a long time in a low-temperature, low-humidity environment, overcharging of the particles can be prevented, and anti-electrostatic member contamination properties are improved.

[0027] The means for incorporating BO bonds in the surface layer of toner particles is not particularly limited, but for example, boric acid can be incorporated into the toner particles by adding it internally to the toner particles or using it as an aggregating agent in the aggregation method. By adding boric acid as an aggregating agent, boric acid can be easily introduced near the surface of the toner particles. At the stage of using it as a raw material, it may be used in the form of organic boric acid, boric acid salt, boric acid ester, etc. When the toner particles are produced in an aqueous medium, it is preferable to add it as a boric acid salt from the viewpoint of reactivity and production stability, and specifically, for example, sodium tetraborate, ammonium borate, etc. can be mentioned, and in particular, borax is preferably used.

[0028] Borax is represented by the decahydrate of sodium tetraborate Na2B4O7, and changes to boric acid in an acidic aqueous solution. Therefore, borax is preferably used when used in an aqueous medium under an acidic environment.

[0029] <Having strontium titanate particles with fatty acids on the surface> The toner of the present invention is required to have a compound derived from a BO bond in the vicinity of the surface of the toner particles, and also to have strontium titanate particles having a fatty acid on the surface.

[0030] By containing the strontium titanate particles, even when used for a long period of time in a low temperature and low humidity environment, which is a harsh environment for the toner's charge rise property, good charge rise property is exhibited, and the density uniformity of a solid image is improved. In addition, due to the above-mentioned action and effect, the anti-contamination property of the charge member is also improved.

[0031] The inventors' research has revealed that highly polar water molecules have the effect of increasing the speed at which charges are transferred between objects during frictional charging, and therefore, in a low-temperature, low-humidity environment where the absolute moisture content in the air is low, the charging start-up speed of conventional toners is insufficient, and this can result in poor density uniformity, particularly in solid images. Specifically, this is a phenomenon in which the image density becomes thin at the trailing edge of a solid image.

[0032] It is believed that the toner of the present invention has good charge rise properties in low-temperature, low-humidity environments because of the action of a compound derived from a B-O bond present in the vicinity of the surface of the toner particles and a fatty acid present on the surface of the strontium titanate particles, which results in an appropriate amount of water molecules being present at the interface between the particles.

[0033] <abundance of boron atoms X> In the toner of the present invention, the amount (mass basis) X of boron atoms present in the toner measured by an inductively coupled plasma mass spectrometer (ICP-MS) is preferably 0.1 ppm or more and 100 ppm or less, from the viewpoint of providing a toner with better chargeability and improving fogging suppression in a low-temperature, low-humidity environment and a high-temperature, high-humidity environment. A specific measurement method using the analyzer will be described later.

[0034] By setting the amount X of boron atoms to 0.1 ppm or more, it is possible to hold an appropriate amount of moisture near the surface of the toner particles, and to suppress charge-up of the toner. Therefore, even when low-printing images are continuously output for a long period of time under a low-temperature, low-humidity environment, it is preferable because fogging of the white background can be suppressed. It is more preferable that the amount X of boron atoms is 0.2 ppm or more, and particularly preferably 0.3 ppm or more.

[0035] On the other hand, since the amount of boron atoms present, X, is 100 ppm or less, the amount of moisture carried near the toner particle surface is not too much, so that the charge amount of the toner is easily maintained even in a high-temperature, high-humidity environment. Therefore, even when low-printing images are output for a long period of time in a high-temperature, high-humidity environment, fogging of non-image areas is suppressed, which is preferable, and the amount of boron atoms present, X, is more preferably 70.0 ppm or less, even more preferably 5.0 ppm or less, and particularly preferably 2.0 ppm or less.

[0036] <Strontium titanate particle content Y> In the toner of the present invention, from the viewpoint of achieving both the charge build-up property of the toner and the resistance to contamination of a charging member, the content Y (mass %) of strontium titanate particles is preferably 0.1 or more and 4.0 or less.

[0037] Specifically, the strontium titanate particle content Y of 0.1% by mass or more is preferable because it provides better uniformity of solid density even after long-term use in a low-temperature, low-humidity environment, while the strontium titanate particle content Y of 4.0% by mass or less is preferable because it provides an appropriate amount of the strontium titanate particles transferred to the photoreceptor and prevents excessive supply to the cleaning section, resulting in better anti-electrostatic member contamination properties.

[0038] <Fatty acid> The strontium titanate particles of the present invention must have a fatty acid present on the surface.

[0039] As described above, the presence of fatty acids on the surface allows an appropriate amount of moisture to be steadily supplied from near the toner particle surface to the fatty acids on the surfaces of the strontium titanate particles during peel-off charging, preventing the strontium titanate particles from becoming overcharged and improving the resistance to electrostatic contamination of the charge-generating member.

[0040] The fatty acid of the present invention is not particularly limited as long as it has a structure in which a hydrocarbon group (R-) and a carboxyl group (-COOH) are bonded, and specific examples include caprylic acid, lauric acid, myristic acid, palmitic acid, stearic acid, lignoceric acid, and melissic acid.

[0041] From the viewpoint of controlling the hydrophilicity and hydrophobicity of the fatty acid, the fatty acid is preferably a fatty acid in which an alkyl group having 12 to 30 carbon atoms is bonded to a carboxyl group.

[0042] The fatty acid having 12 or more carbon atoms has sufficiently high hydrophobicity, and therefore, even in a high-temperature, high-humidity environment with a high absolute moisture content, when high-printing images consuming a large amount of toner are continuously output, the charge amount of the toner can be stabilized, and fogging of non-image areas can be suppressed, which is preferable.

[0043] On the other hand, by having the carbon number of 30 or less, the hydrophilicity of the fatty acid is sufficiently high. Therefore, even when images with a high printing rate that consumes a lot of toner are continuously output in a low-temperature, low-humidity environment with a low absolute moisture content, the charge rise property of the toner is good, and fogging of non-image areas can be suppressed, which is preferable.

[0044] <Combination use of fatty acids> From the viewpoint of obtaining a toner with a sharper charge distribution and better line width stability, it is preferred that two types of fatty acids with different carbon numbers are present on the surface of the strontium titanate particles, both of which have carbon numbers of 12 or more and 30 or less, and the difference in carbon numbers between the two types of fatty acids is 2 or more. For example, a combination of stearic acid, which has 18 carbon atoms, and palmitic acid, which has 16 carbon atoms, and a combination of lignoceric acid, which has 24 carbon atoms, and lauric acid, which has 12 carbon atoms, may be used.

[0045] Although the reason why such an effect is obtained is unclear, it is speculated that the presence of two types of fatty acids with different carbon numbers on the surface of the strontium titanate particles makes it easier for charges to move and be uniformized within the surface of the strontium titanate particles due to the difference in hydrophilicity and hydrophobicity between the fatty acids.

[0046] It is also expected that when the toner particles and the strontium titanate particles are separated from each other, the charge amount between the particles on the toner particle side also becomes more stable, resulting in a sharper charge amount distribution.

[0047] It is believed that this sharp charge distribution leads to uniform development efficiency and transfer efficiency for vertical and horizontal lines, resulting in good line width stability for vertical and horizontal lines.

[0048] <Fatty acid content Z> The content Z (mass %) of fatty acids having 12 to 30 carbon atoms present on the surface of the strontium titanate particles is preferably 0.10 or more and 5.0 or less, from the viewpoints of improving the resistance to electrostatic contamination of components and improving the uniformity of solid image density in high-temperature, high-humidity environments.

[0049] By making the fatty acid content Z 0.10% by mass or more, the strontium titanate particles can easily receive and transfer moisture from the vicinity of the surface of the toner particles, and the strontium titanate particles are not excessively charged, resulting in good resistance to contamination of the charging member. Therefore, even when a high-printing-ratio image is output in a continuous output mode, which is a mode in which the amount of toner consumed is large and the strontium titanate particles are easily supplied to the cleaning unit, and therefore the resistance to contamination of the charging member is severe, the density uniformity of the halftone image is good, which is preferable, and the content Z is more preferably 0.30% by mass or more.

[0050] On the other hand, when the fatty acid content Z is 5.0% by mass or less, the fluidity of the toner containing the strontium titanate is favorable even in a high-temperature and high-humidity environment where the fluidity of the toner is likely to deteriorate due to the influence of moisture. Therefore, even in a severe mode such as continuously outputting high-printing-rate images with a large toner consumption, the charge-up property of the toner is favorable, and the density uniformity between images is favorable, which is preferable.

[0051] A method for quantifying the fatty acid present on the surface of the strontium titanate particles will be described later.

[0052] <Relationship between X and Y> From the viewpoint of better charge member contamination resistance of the toner of the present invention, the abundance (mass basis) X (ppm) of the boron atom in the toner and the content Y (mass%) of the strontium titanate particles in the toner preferably satisfy the following formula. 0.10 ≦ X / Y ≦ 30.0

[0053] X / Y is the ratio of the abundance of boron atoms in the vicinity of the surface of the toner particles to the content of strontium titanate particles in the toner. By controlling the X / Y value within a preferable range, moisture carried in the vicinity of the surface of the toner particles can be stably supplied to the surface of the strontium titanate particles, and the charge member contamination resistance can be further improved, which is preferable.

[0054] When X / Y is 0.10 or more, a sufficient amount of boron atoms X exists in the vicinity of the surface of the toner particles with respect to the content Y of the strontium titanate particles in the toner. Therefore, a sufficient amount of moisture can be supplied to the strontium titanate particles, and overcharging of the strontium titanate particles can be suppressed. Thus, the charge member contamination resistance in a low-temperature and low-humidity environment is further improved. More preferably, X / Y is 0.30 or more.

[0055] On the one hand, when X / Y is 30.0 or less, the amount X of boron atoms in the vicinity of the surface of the toner particles is maintained at an appropriate amount with respect to the content Y of strontium titanate particles in the toner, and is not excessively large. Therefore, the compound having a BO structure in the vicinity of the surface of the toner particles can stably supply moisture to the surface of the strontium titanate particles without excessively attracting moisture.

[0056] Therefore, overcharging of the strontium titanate particles can be suppressed, and the charge member contamination resistance in a low-temperature and low-humidity environment is further improved, which is preferable. More preferably, X / Y is 25.0 or less.

[0057] <Relationship between X and Z> From the viewpoint of better charge rising property, in the toner of the present invention, the amount X (ppm) of the boron atoms in the toner (mass basis) and the content Z (mass%) of the fatty acid having 12 or more and 30 or less carbon atoms present on the surface of the strontium titanate particles preferably satisfy the following formula. 0.020 ≦ X / Z ≦ 15.0

[0058] X / Z is the ratio of the amount of boron atoms in the vicinity of the surface of the toner particles to the content of the fatty acid having 12 or more and 30 or less carbon atoms present on the surface of the strontium titanate particles in the toner. By controlling the X / Z value within a preferable range, the moisture carried in the vicinity of the surface of the toner particles can be kept in an appropriate state without excessively migrating to the surface of the strontium titanate particles. Thereby, the charge rising property of the toner particles can be further improved, which is preferable.

[0059] When X / Z is 0.020 or more, it indicates that the amount of boron atoms present in the vicinity of the surface of the toner particles (X) is sufficient relative to the content Z of fatty acids having 12 to 30 carbon atoms present on the surface of the strontium titanate particles in the toner. Therefore, even if moisture is transferred to the strontium titanate particles, there is a sufficient amount of moisture in the vicinity of the surface of the toner particles, so that even if the toner is left for a long period of time in a low-temperature, low-humidity environment, the charge rise property is good and the density uniformity of a solid image is good, which is preferable. It is more preferable that X / Z is 0.030 or more.

[0060] On the other hand, when X / Z is 15.0 or less, the amount of boron atoms present in the vicinity of the surface of the toner particles is kept at an appropriate amount, not excessively large, relative to the amount of fatty acid Z having 12 to 30 carbon atoms present on the surface of the strontium titanate particles in the toner. Therefore, the compound having a BO structure does not store excessive moisture in the vicinity of the surface of the toner particles, and the toner has a good charge amount even when left for a long period of time in a high-temperature and high-humidity environment, which is a more severe mode. Therefore, the image density uniformity is good, and it is more preferable that X / Z is 12.5 or less.

[0061] <Average circularity of toner> The toner of the present invention preferably has an average circularity of 0.960 or more and 0.990 or less, from the viewpoint of improving the line width stability of a halftone image.

[0062] By having the average circularity of the toner of 0.960 or more, the rolling property of the toner is improved, and the charge rising property is further improved, so that the charge amount distribution in a low temperature and low humidity environment becomes sharp, and the stability of the line width of the vertical line and the horizontal line becomes good, which is preferable.

[0063] On the other hand, by having the average circularity of the toner be 0.990 or less, the rolling property of the toner is not excessively high and the non-electrostatic adhesion can be made moderately high, so that toner dusting during the transfer process is suppressed and line width stability is also favorable.

[0064] The average circularity of the toner is more preferably from 0.965 to 0.985, and particularly preferably from 0.967 to 0.983.

[0065] In order to adjust the circularity of the toner to fall within the preferred range in the present invention, it is preferable to employ a chemical toner production method such as an emulsion aggregation method, a suspension polymerization method, or a suspension granulation method.

[0066] When the emulsion aggregation method is used, it is preferable to adjust the circularity by providing a spheronization step in order to obtain a desired toner surface shape. When the pulverization method is used, the circularity of the toner can also be adjusted by subjecting the toner to a surface treatment using hot air by a thermal spheronization treatment.

[0067] <Titanium oxide particles> The toner of the present invention preferably contains, in addition to the above-mentioned strontium titanate particles, titanium oxide particles which satisfy the following (i) and (ii).

[0068] (i) The major axis is 300 nm or more and 3000 nm or less. (ii) Aspect ratio is 5.0 or more

[0069] Titanium oxide particles that satisfy the above (i) and (ii) are classified as external additives with large particle size and low resistance, and have a needle-like structure. The use of titanium oxide particles suppresses overcharging in a low-temperature, low-humidity environment, and also exhibits a spacer effect on the toner particle surface, thereby reducing changes in flowability during long-term use. In the present invention, the effect of the structure derived from the BO bond existing near the surface of the toner particles, the effect of water molecules forming on the toner particle surface, and the effect of containing titanium oxide particles of the specific shape act synergistically to improve fogging suppression after low-temperature, continuous printing durability evaluation in a low-temperature, low-humidity environment, which is preferable.

[0070] The content of the titanium oxide particles in the toner is preferably 0.1% by mass or more and 10.0% by mass or less. The lower limit is more preferably 0.2% by mass or more. The upper limit is more preferably 1.0% by mass or less.

[0071] The titanium oxide particles are not particularly limited as long as they satisfy the above (i) and (ii). For example, rutile type titanium oxide particles are one of the preferred forms. In addition, from the viewpoint of imparting fluidity to the toner, titanium oxide particles other than the above titanium oxide particles can also be used in combination.

[0072] <Shell layer on the surface of toner particles> The toner of the present invention has a shell layer on the surface of a toner particle, the shell layer contains a polyester resin, and in a cross section of the toner observed with a transmission electron microscope, the shell layer does not contain a crystalline material, and when the thickness of the shell layer is T (nm), it is preferable that the following formula is satisfied: 300≦T≦700

[0073] Toner particles having a shell layer of polyester resin are preferred because they have polarity in areas of the toner particle surface other than the BO structure, making it easier for water molecules to be supported by the BO structure, and making it easier to obtain the effect of suppressing overcharging of the above-mentioned strontium titanate particles. In addition, since the shell layer does not contain a crystalline material and satisfies the above formula, embedding of external additives in the surface of the toner is suppressed even when used for a long period of time in a low-temperature, low-humidity environment, and the microcarrier effect of the strontium titanate particles is stably expressed, which is preferable because it enhances charging stability. This is preferable because it improves fogging in a low-temperature, low-humidity environment, and is particularly preferable because it improves fogging during high-speed printing.

[0074] The process of forming the shell layer on the surface of the toner particles will be described in detail later.

[0075] [Other Configurations of the Present Invention] <Binding resin> The toner particles of the present invention contain a binder resin. The content of the binder resin is preferably 50% by mass or more of the total amount of the resin components in the toner particles.

[0076] The binder resin is not particularly limited, and examples thereof include styrene-acrylic resin, epoxy resin, polyester resin, polyurethane resin, polyamide resin, cellulose resin, polyether resin, mixed resins and composite resins thereof, etc. Among these, from the viewpoints of low-temperature fixability and durability stability, styrene-acrylic resin and polyester resin (details of polyester resin will be described later) are preferred.

[0077] Examples of the styrene-acrylic resin include homopolymers made of the following polymerizable monomers, copolymers obtained by combining two or more of these, and mixtures thereof.

[0078] Styrenic monomers such as styrene, α-methylstyrene, β-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, 2,4-dimethylstyrene, pn-butylstyrene, p-tert-butylstyrene, pn-hexylstyrene, pn-octylstyrene, pn-nonylstyrene, pn-decylstyrene, pn-dodecylstyrene, p-methoxystyrene and p-phenylstyrene; (Meth)acrylic monomers such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, iso-propyl (meth)acrylate, n-butyl (meth)acrylate, iso-butyl (meth)acrylate, tert-butyl (meth)acrylate, n-amyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, n-nonyl (meth)acrylate, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, dimethyl phosphate ethyl (meth)acrylate, diethyl phosphate ethyl (meth)acrylate, dibutyl phosphate ethyl (meth)acrylate and 2-benzoyloxyethyl (meth)acrylate, (meth)acrylonitrile, 2-hydroxyethyl (meth)acrylate, (meth)acrylic acid, maleic acid; Vinyl ether monomers such as vinyl methyl ether and vinyl isobutyl ether; vinyl ketone monomers such as vinyl methyl ketone, vinyl ethyl ketone and vinyl isopropenyl ketone; Polyolefins such as ethylene, propylene, and butadiene.

[0079] The styrene acrylic resin may use a polyfunctional polymerizable monomer as required. Examples of the polyfunctional polymerizable monomer include diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, 2,2'-bis(4-((meth)acryloxydiethoxy)phenyl)propane, trimethylolpropane tri(meth)acrylate, tetramethylolmethane tetra(meth)acrylate, divinylbenzene, divinylnaphthalene, and divinyl ether.

[0080] In order to control the degree of polymerization, it is also possible to further add a known chain transfer agent and a polymerization inhibitor. Examples of the polymerization initiator for obtaining the styrene-acrylic resin include organic peroxide-based initiators and azo-based polymerization initiators.

[0081] Examples of the organic peroxide initiator include benzoyl peroxide, lauroyl peroxide, di-α-cumyl peroxide, 2,5-dimethyl-2,5-bis(benzoylperoxy)hexane, bis(4-t-butylcyclohexyl)peroxydicarbonate, 1,1-bis(t-butylperoxy)cyclododecane, t-butylperoxymaleic acid, bis(t-butylperoxy)isophthalate, methyl ethyl ketone peroxide, tert-butylperoxy-2-ethylhexanoate, diisopropyl peroxycarbonate, cumene hydroperoxide, 2,4-dichlorobenzoyl peroxide, and tert-butylperoxypivalate.

[0082] Examples of the azo polymerization initiator include 2,2'-azobis-(2,4-dimethylvaleronitrile), 2,2'-azobisisobutyronitrile, 1,1'-azobis(cyclohexane-1-carbonitrile), 2,2'-azobis-4-methoxy-2,4-dimethylvaleronitrile, azobismethylbutyronitrile, and 2,2'-azobis-(methyl isobutyrate).

[0083] Furthermore, a redox initiator, which is a combination of an oxidizing substance and a reducing substance, can also be used as the polymerization initiator.

[0084] Oxidizing substances include inorganic peroxides such as hydrogen peroxide, persulfates (sodium, potassium and ammonium salts) and oxidizing metal salts such as tetravalent cerium salts.

[0085] Examples of reducing substances include reducing metal salts (divalent iron salts, monovalent copper salts, and trivalent chromium salts), ammonia, lower amines (amines having from 1 to 6 carbon atoms, such as methylamine and ethylamine), amino compounds such as hydroxylamine, reducing sulfur compounds such as sodium thiosulfate, sodium hydrosulfite, sodium hydrogensulfite, sodium sulfite, and sodium formaldehyde sulfoxylate, lower alcohols (having from 1 to 6 carbon atoms), ascorbic acid or a salt thereof, and lower aldehydes (having from 1 to 6 carbon atoms).

[0086] The polymerization initiator is selected with reference to its 10-hour half-life temperature and is used alone or in combination. The amount of polymerization initiator added varies depending on the desired degree of polymerization, but is generally 0.5 to 20.0 parts by mass per 100.0 parts by mass of polymerizable monomer.

[0087] In the toner of the present invention, a structure in which the binder resin is a styrene acrylic resin and the shell layer is a polyester resin is preferred because it provides a good balance of chargeability in a low-temperature, low-humidity environment and a high-temperature, high-humidity environment.

[0088] <Polyester resin> The polyester resin used in the toner particles of the present invention will be described below. The polyester resin contained in the shell layer present on the surface of the toner particles of the present invention can also be the polyester resin described below. The polyester resin that can be used in the present invention is not particularly limited, but is preferably an amorphous polyester resin, and examples thereof include the following.

[0089] The polyester resin can be obtained by selecting and combining suitable polycarboxylic acids, polyols, hydroxycarboxylic acids, etc., and synthesizing them using a known method such as an ester exchange method or a polycondensation method. Preferably, the polyester resin contains a condensation polymer of a dicarboxylic acid and a diol.

[0090] Polycarboxylic acids are compounds containing two or more carboxy groups in one molecule. Among them, dicarboxylic acids are compounds containing two carboxy groups in one molecule and are preferably used.

[0091] Examples of the acid include oxalic acid, succinic acid, glutaric acid, maleic acid, adipic acid, β-methyladipic acid, azelaic acid, sebacic acid, nonanedicarboxylic acid, decanedicarboxylic acid, undecanedicarboxylic acid, dodecanedicarboxylic acid, fumaric acid, citraconic acid, diglycolic acid, cyclohexane-3,5-diene-1,2-carboxylic acid, hexahydroterephthalic acid, malonic acid, pimelic acid, suberic acid, phthalic acid, isophthalic acid, terephthalic acid, tetrachlorophthalic acid, chlorophthalic acid, nitrophthalic acid, p-carboxyphenylacetic acid, p-phenylenediacetic acid, m-phenylenediacetic acid, o-phenylenediacetic acid, diphenylacetic acid, diphenyl-p,p'-dicarboxylic acid, naphthalene-1,4-dicarboxylic acid, naphthalene-1,5-dicarboxylic acid, naphthalene-2,6-dicarboxylic acid, anthracenedicarboxylic acid, and cyclohexanedicarboxylic acid.

[0092] Examples of polyvalent carboxylic acids other than the dicarboxylic acids include trimellitic acid, trimesic acid, pyromellitic acid, naphthalene tricarboxylic acid, naphthalene tetracarboxylic acid, pyrene tricarboxylic acid, pyrene tetracarboxylic acid, itaconic acid, glutaconic acid, n-dodecyl succinic acid, n-dodecenyl succinic acid, isododecyl succinic acid, isododecenyl succinic acid, n-octyl succinic acid, n-octenyl succinic acid, etc. These may be used alone or in combination of two or more.

[0093] A polyol is a compound containing two or more hydroxyl groups in one molecule. Among them, a diol is a compound containing two hydroxyl groups in one molecule, and is preferably used.

[0094] Specifically, ethylene glycol, diethylene glycol, triethylene 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, and 1,14-eicosanediol. Examples of bisphenols include dimethyl ether glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene ether glycol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, 1,4-butenediol, neopentyl glycol, polytetramethylene glycol, hydrogenated bisphenol A, bisphenol A, bisphenol F, bisphenol S, and alkylene oxide (ethylene oxide, propylene oxide, butylene oxide, etc.) adducts of the above bisphenols.

[0095] Among these, preferred are alkylene glycols having from 2 to 12 carbon atoms and alkylene oxide adducts of bisphenols, and particularly preferred are alkylene oxide adducts of bisphenols and their combined use with alkylene glycols having from 2 to 12 carbon atoms. Examples of alkylene oxide adducts of bisphenol A include the compounds represented by the following formula (A).

[0096] [ka] (In formula (A), each R is independently an ethylene or propylene group, each of x and y is an integer of 0 or more, and the average value of x+y is 0 or more and 10 or less.)

[0097] The alkylene oxide adduct of bisphenol A is preferably a propylene oxide adduct and / or an ethylene oxide adduct of bisphenol A. More preferably, it is a propylene oxide adduct. The average value of x+y is preferably 1 or more and 5 or less.

[0098] Examples of trihydric or higher alcohols include glycerin, trimethylolethane, trimethylolpropane, pentaerythritol, hexamethylolmelamine, hexaethylolmelamine, tetramethylolbenzoguanamine, tetraethylolbenzoguanamine, sorbitol, trisphenol PA, phenol novolac, cresol novolac, alkylene oxide adducts of the above trihydric or higher polyphenols, etc. These may be used alone or in combination of two or more.

[0099] The polyester resin used in the present invention preferably has a weight average molecular weight of 9,000 or more and 15,000 or less, and an acid value of 4.0 mg / KOH or more and 10.0 mg / KOH or less.

[0100] <Release agent (wax)> In the toner of the present invention, a known wax may be used as a releasing agent.

[0101] Specific examples include petroleum waxes and derivatives thereof, such as paraffin wax, microcrystalline wax, and petrolatum, montan wax and derivatives thereof, hydrocarbon waxes produced by the Fischer-Tropsch process and derivatives thereof, polyolefin waxes and derivatives thereof, such as polyethylene, natural waxes and derivatives thereof, such as carnauba wax and candelilla wax, and derivatives thereof. Derivatives also include oxides, block copolymers with vinyl monomers, and graft modified products.

[0102] Other examples include alcohols such as higher aliphatic alcohols, fatty acids such as stearic acid and palmitic acid or their acid amides, esters and ketones, hydrogenated castor oil and its derivatives, vegetable waxes and animal waxes. These can be used alone or in combination.

[0103] Among these, polyolefin, Fischer-Tropsch hydrocarbon wax, or petroleum wax is preferably used since it tends to improve the developability and transferability. An antioxidant may be added to these waxes within a range that does not affect the effects of the toner. In addition, from the viewpoint of phase separation with respect to the binder resin or crystallization temperature, higher fatty acid esters such as behenyl behenate and dibehenyl sebacate are suitable examples.

[0104] The content of the release agent is preferably 1.0 part by mass or more and 30.0 parts by mass or less with respect to 100.0 parts by mass of the binder resin.

[0105] The melting point of the release agent is preferably from 30° C. to 120° C., and more preferably from 60° C. to 100° C. By using a release agent having the above-mentioned thermal characteristics, the release effect is efficiently exerted and a wider fixing area is secured.

[0106] <Plasticizer> The toner particles may contain a crystalline plasticizer in order to improve sharp melting properties. The plasticizer is not particularly limited, and any of the known plasticizers used in toners such as those described below can be used.

[0107] Specifically, the esters include esters of monohydric alcohols and aliphatic carboxylic acids, such as behenyl behenate, stearyl stearate, and palmityl palmitate, or esters of monohydric carboxylic acids and aliphatic alcohols; esters of dihydric alcohols and aliphatic carboxylic acids, such as ethylene glycol distearate, dibehenyl sebacate, and hexanediol dibehenate, or esters of dihydric carboxylic acids and aliphatic alcohols; esters of trihydric alcohols and aliphatic carboxylic acids, such as glycerin tribehenate, or esters of trihydric carboxylic acids and aliphatic alcohols; and pentaerythritol tetrastearate. esters of tetrahydric alcohols and aliphatic carboxylic acids, such as stearate and pentaerythritol tetrapalmitate, or esters of tetrahydric carboxylic acids and aliphatic alcohols; esters of hexahydric alcohols and aliphatic carboxylic acids, such as dipentaerythritol hexastearate and dipentaerythritol hexapalmitate, or esters of hexahydric carboxylic acids and aliphatic alcohols; esters of polyhydric alcohols and aliphatic carboxylic acids, such as polyglycerin behenate, or esters of polyhydric carboxylic acids and aliphatic alcohols; natural ester waxes, such as carnauba wax and rice wax. These may be used alone or in combination.

[0108] <Coloring agent> The toner particles may contain a colorant. Known pigments and dyes can be used as the colorant. Pigments are preferred as the colorant because they have excellent weather resistance.

[0109] Examples of cyan colorants include copper phthalocyanine compounds and derivatives thereof, anthraquinone compounds, and basic dye lake compounds.

[0110] Specific examples include: CI Pigment Blue 1, 7, 15, 15:1, 15:2, 15:3, 15:4, 60, 62 and 66.

[0111] Examples of magenta colorants include condensed azo compounds, diketopyrrolopyrrole compounds, anthraquinone compounds, quinacridone compounds, basic dye lake compounds, naphthol compounds, benzimidazolone compounds, thioindigo compounds, and perylene compounds.

[0112] Specific examples include: CI Pigment Red 2, 3, 5, 6, 7, 23, 48:2, 48:3, 48:4, 57:1, 81:1, 122, 144, 146, 150, 166, 169, 177, 184, 185, 202, 206, 220, 221 and 254, and CI Pigment Violet 19.

[0113] Examples of yellow colorants include condensed azo compounds, isoindolinone compounds, anthraquinone compounds, azo metal complexes, methine compounds, and allylamide compounds.

[0114] Specific examples include: CI Pigment Yellow 12, 13, 14, 15, 17, 62, 74, 83, 93, 94, 95, 97, 109, 110, 111, 120, 127, 128, 129, 147, 151, 154, 155, 168, 174, 175, 176, 180, 181, 185, 191 and 194.

[0115] Examples of black colorants include those toned to black using the above yellow, magenta and cyan colorants, as well as carbon black and magnetic materials.

[0116] These colorants can be used alone or in mixture, or in the form of a solid solution. The colorant is preferably used in an amount of 1.0 to 20.0 parts by mass per 100.0 parts by mass of the binder resin. When using a magnetic material in a water-based medium, as described below, a hydrophobic treatment can be carried out in order to stably contain the magnetic material in the resin.

[0117] <Charge control agents and charge control resins> The toner particles may contain a charge control agent or a charge control resin. Any known charge control agent can be used as the charge control agent, and a charge control agent that has a high triboelectric charging speed and can stably maintain a constant triboelectric charge amount is particularly preferred. Furthermore, when the toner particles are produced by a suspension polymerization method, a charge control agent that has low polymerization inhibition and is substantially free of solubilized matter in an aqueous medium is particularly preferred.

[0118] Examples of toners that control the toner to be negatively charged include monoazo metal compounds, acetylacetone metal compounds, aromatic oxycarboxylic acids, aromatic dicarboxylic acids, oxycarboxylic and dicarboxylic acid-based metal compounds, aromatic oxycarboxylic acids, aromatic mono- and polycarboxylic acids and their metal salts, anhydrides, esters, phenol derivatives such as bisphenol, urea derivatives, metal-containing salicylic acid-based compounds, metal-containing naphthoic acid-based compounds, boron compounds, quaternary ammonium salts, calixarenes, and charge control resins.

[0119] The charge control resin may be a polymer or copolymer having a sulfonic acid group, a sulfonate group, or a sulfonate ester group. As the polymer having a sulfonic acid group, a sulfonate group, or a sulfonate ester group, a polymer containing a sulfonic acid group-containing acrylamide monomer or a sulfonate group-containing methacrylamide monomer in a copolymerization ratio of 2% by mass or more is preferable, and a polymer containing a sulfonic acid group-containing methacrylamide monomer in a copolymerization ratio of 5% by mass or more is more preferable.

[0120] The charge control resin preferably has a glass transition temperature (Tg) of 35° C. or more and 90° C. or less, a peak molecular weight (Mp) of 10,000 or more and 30,000 or less, and a weight average molecular weight (Mw) of 25,000 or more and 50,000 or less. When used, it is possible to impart preferable triboelectric charging characteristics without affecting the thermal characteristics required for the toner particles. Furthermore, when the charge control resin contains a sulfonic acid group, for example, the dispersibility of the charge control resin itself in the polymerizable monomer composition and the dispersibility of the colorant are improved, and the coloring power, transparency, and triboelectric charging characteristics can be further improved.

[0121] These charge control agents or charge control resins may be added alone or in combination of two or more. The amount of the charge control agent or charge control resin added is preferably 0.01 parts by mass or more and 20.0 parts by mass or less, more preferably 0.5 parts by mass or more and 10.0 parts by mass or less, relative to 100.0 parts by mass of the binder resin.

[0122] [Toner manufacturing method] The method for producing the toner is not particularly limited, and known methods such as a pulverization method, a suspension polymerization method, a dissolution suspension method, an emulsion aggregation method, and a dispersion polymerization method can be used. Here, the toner is preferably produced by the method shown below. That is, the toner is preferably produced by an emulsion aggregation method.

[0123] The toner manufacturing method includes the following steps (1) to (3): (1) a dispersion step of preparing a binder resin microparticle dispersion liquid containing the binder resin; (2) an aggregating step of aggregating the binder resin fine particles contained in the binder resin fine particle dispersion to form aggregates; and (3) a fusion step of heating the aggregates to fuse them together in that order, The method for producing a toner is characterized in that a boric acid source is added in at least one of the aggregation step and the fusion step.

[0124] In addition, during or after the fusion step, the following steps (4) to (6) are carried out: (4) a spheronization step of further heating the agglomerates at an elevated temperature; (5) a cooling step of cooling the aggregate at a cooling rate of 0.1° C. / sec or more; and (6) an annealing step of heating and holding the aggregate at a temperature equal to or higher than the crystallization temperature or glass transition temperature of the binder resin; It is preferable to have them in this order.

[0125] When the toner is produced by the emulsion aggregation method, it is preferable because the toner shape can be controlled and boric acid can be easily dispersed uniformly in the vicinity of the surface of the toner. Details of the emulsion aggregation method will be described below.

[0126] <Emulsification aggregation method> The emulsion aggregation method is a method in which an aqueous dispersion of fine particles made of the constituent materials of toner particles, which are sufficiently small relative to the target particle size, is prepared in advance, and the fine particles are aggregated in an aqueous medium until they reach the particle size of the toner particles, and the resin is fused by heating or the like to produce toner particles.

[0127] That is, in the emulsion aggregation method, toner particles are manufactured through a dispersion process in which a fine particle dispersion liquid made of the constituent materials of the toner particles is prepared, an aggregation process in which fine particles made of the constituent materials of the toner particles are aggregated and the particle size is controlled until it reaches the particle size of the toner particles, a fusion process in which the resin contained in the obtained aggregated particles is fused, a further melting process by heating or the like to control the surface shape of the toner, a subsequent cooling process, a metal removal process in which the obtained toner is filtered and excess polyvalent metal ions are removed, a filtration / washing process in which the toner particles are washed with ion-exchanged water or the like, and a process in which moisture is removed from the washed toner particles and they are dried.

[0128] [Step of preparing a resin particle dispersion (dispersion step)] The resin microparticle dispersion liquid can be prepared by a known method, but is not limited to these methods.The known methods include, for example, emulsion polymerization method, self-emulsification method, phase inversion emulsification method in which resin is emulsified by adding aqueous medium to the resin solution dissolved in organic solvent, and forced emulsification method in which resin is forcedly emulsified by high temperature treatment in aqueous medium without using organic solvent.

[0129] Specifically, the binder resin is dissolved in an organic solvent capable of dissolving it, and a surfactant or a basic compound is added. In this case, if the binder resin is a crystalline resin having a melting point, it may be dissolved by heating it to above its melting point. Then, while stirring with a homogenizer or the like, an aqueous medium is slowly added to precipitate the resin fine particles. Thereafter, the solvent is removed by heating or reducing pressure to prepare an aqueous dispersion of the resin fine particles. Any organic solvent can be used to dissolve the resin as long as it can dissolve the resin, but it is preferable to use an organic solvent that forms a homogeneous phase with water, such as toluene, from the viewpoint of suppressing the generation of coarse powder.

[0130] The surfactant used in the emulsification is not particularly limited, but examples thereof include anionic surfactants such as sulfate salts, sulfonate salts, carboxylate salts, phosphate esters, and soap salts; cationic surfactants such as amine salts and quaternary ammonium salts; and nonionic surfactants such as polyethylene glycols, alkylphenol ethylene oxide adducts, and polyhydric alcohols. The surfactants may be used alone or in combination of two or more.

[0131] Examples of the basic compound used in the dispersion step include inorganic bases such as sodium hydroxide and potassium hydroxide, and organic bases such as ammonia, triethylamine, trimethylamine, dimethylaminoethanol, and diethylaminoethanol. The basic compound may be used alone or in combination of two or more.

[0132] In addition, the 50% particle size (D50) based on volume distribution of the binder resin particles in the aqueous dispersion of resin particles is preferably 0.05 μm to 1.0 μm, more preferably 0.05 μm to 0.4 μm. By adjusting the 50% particle size (D50) based on volume distribution within the above range, it becomes easy to obtain toner particles with a volume average particle size of 3 μm to 10 μm, which is an appropriate size for toner particles.

[0133] The 50% particle size (D50) based on volume distribution is measured using a dynamic light scattering particle size distribution analyzer Nanotrac UPA-EX150 (manufactured by Nikkiso).

[0134] [Colorant particle dispersion] If necessary, a colorant particle dispersion may be used. The colorant particle dispersion may be prepared by the following known methods, but is not limited to these methods. The colorant particle dispersion may be prepared by mixing a colorant, an aqueous medium, and a dispersant with a known mixer such as a stirrer, an emulsifier, or a disperser. The dispersant used here may be a known one such as a surfactant or a polymer dispersant.

[0135] Both the surfactant and the polymer dispersant can be removed in the washing step described below, but the surfactant is preferred from the viewpoint of washing efficiency.

[0136] Examples of the surfactant include anionic surfactants such as sulfate ester salts, sulfonate salts, phosphate esters, and soaps; cationic surfactants such as amine salts and quaternary ammonium salts; and nonionic surfactants such as polyethylene glycols, alkylphenol ethylene oxide adducts, and polyhydric alcohols. Among these, nonionic surfactants or anionic surfactants are preferred. In addition, nonionic surfactants and anionic surfactants may be used in combination. The surfactants may be used alone or in combination of two or more. The concentration of the surfactant in the aqueous medium is preferably 0.5% by mass or more and 5% by mass or less.

[0137] The content of the colorant particles in the colorant particle dispersion is not particularly limited, but is preferably from 1% by mass to 30% by mass with respect to the total mass of the colorant particle dispersion.

[0138] From the viewpoint of dispersibility of the colorant in the toner finally obtained, the dispersed particle size of the colorant particles in the aqueous dispersion of the colorant is preferably 0.5 μm or less in terms of the 50% particle size (D50) based on volume distribution. For the same reason, it is preferable that the 90% particle size (D90) based on volume distribution is 2 μm or less. The dispersed particle size of the colorant particles dispersed in the aqueous medium is measured using a dynamic light scattering particle size distribution meter (Nanotrac UPA-EX150: manufactured by Nikkiso).

[0139] Known mixers such as stirrers, emulsifiers, and dispersers used when dispersing a colorant in an aqueous medium include ultrasonic homogenizers, jet mills, pressure homogenizers, colloid mills, ball mills, sand mills, and paint shakers. These may be used alone or in combination.

[0140] [Release agent (aliphatic hydrocarbon compound) fine particle dispersion] If necessary, a dispersion of releasing agent particles may be used. The dispersion of releasing agent particles can be prepared by the following known methods, but is not limited to these methods.

[0141] A release agent microparticle dispersion can be produced by adding the release agent to an aqueous medium containing a surfactant, heating the mixture to above the melting point of the release agent, dispersing the mixture into particles using a homogenizer with strong shearing capabilities (e.g., M Technique's "Clearmix W Motion") or a pressure discharge type disperser (e.g., Golin Homogenizer) and then cooling the mixture below the melting point of the release agent.

[0142] The particle size of the release agent microparticle dispersion in the aqueous dispersion of the release agent is preferably 50% particle size (D50) based on volume distribution of 0.03 μm to 1.0 μm, more preferably 0.1 μm to 0.5 μm. It is also preferable that no coarse particles of 1 μm or more exist.

[0143] By setting the particle size of the release agent fine particle dispersion within the above range, the release agent can be finely dispersed in the toner, the exudation effect during fixing can be maximized, and good separation properties can be obtained. The particle size of the release agent fine particle dispersion dispersed in the aqueous medium can be measured using a dynamic light scattering particle size distribution analyzer (Nanotrac UPA-EX150: manufactured by Nikkiso).

[0144] [Mixing process] In the mixing step, a mixture is prepared by mixing the resin fine particle dispersion and, if necessary, at least one of the release agent fine particle dispersion and the colorant fine particle dispersion, using a known mixing device such as a homogenizer or a mixer.

[0145] [Step of forming aggregate particles (aggregation step)] In the aggregating step, the fine particles contained in the mixed liquid prepared in the mixing step are aggregated to form aggregates having a desired particle size. At this time, an aggregating agent is added and mixed, and at least one of heating and mechanical power is appropriately applied as necessary to form aggregates in which the resin fine particles and at least one of the release agent fine particles and the colorant fine particles are aggregated as necessary.

[0146] Examples of the flocculant include organic flocculants such as cationic surfactants of quaternary salts and polyethyleneimine; inorganic metal salts such as sodium sulfate, sodium nitrate, sodium chloride, calcium chloride, calcium nitrate; inorganic ammonium salts such as ammonium sulfate, ammonium chloride, ammonium nitrate; and inorganic flocculants such as divalent or higher metal complexes. It is also possible to add an acid to lower the pH and cause soft flocculation, and for example, sulfuric acid, nitric acid, etc. can be used.

[0147] The aggregating agent may be added in the form of either a dry powder or an aqueous solution dissolved in an aqueous medium, but in order to cause uniform aggregation, it is preferable to add it in the form of an aqueous solution. The addition and mixing of the aggregating agent is preferably performed at a temperature equal to or lower than the glass transition temperature or melting point of the resin contained in the mixed liquid. By performing mixing under this temperature condition, the aggregation proceeds relatively uniformly. The mixing of the aggregating agent into the mixed liquid can be performed using a known mixing device such as a homogenizer or a mixer. The aggregation process is a process of forming aggregates of the toner particle size in an aqueous medium. The volume average particle size of the aggregates produced in the aggregation process is preferably 3 μm to 10 μm. The volume average particle size can be measured using a particle size distribution analyzer (Coulter Multisizer III: manufactured by Coulter) using the Coulter method.

[0148] [Step of obtaining a dispersion liquid containing toner particles (fusion step)] In the fusion step, the dispersion containing the aggregates obtained in the aggregation step is first subjected to termination of aggregation under stirring in the same manner as in the aggregation step by adding an aggregation terminator such as a base capable of adjusting the pH, a chelating compound, or an inorganic salt compound such as sodium chloride.

[0149] After the dispersion state of the aggregated particles in the dispersion liquid becomes stable due to the action of the aggregation terminator, the dispersion liquid is heated to a temperature equal to or higher than the glass transition temperature or melting point of the binder resin to fuse the aggregated particles and adjust the particle size to the desired size. The 50% particle size (D50) based on volume of the toner particles is preferably 3 μm or more and 10 μm or less.

[0150] [Step for obtaining the desired toner surface shape (spheronization step)] During or after the fusion step, it is preferable to further increase the temperature and maintain the temperature until the toner particles reach the desired circularity or surface shape, in a spheronization step.Specific temperatures in the spheronization step are, for example, 90° C. or higher, preferably 92° C. or higher, and preferably 95° C. or lower.The heating time in the spheronization step is, for example, 3 hours or more, 5 hours or more, or 8 hours or more.This step makes it easier to form hydrogen bonds derived from boric acid in the toner particles.

[0151] [Cooling process] After the spheronization step, it is preferable to carry out a cooling step in which the temperature of the dispersion liquid containing the obtained toner particles is cooled to a temperature lower than the crystallization temperature or glass transition temperature of the binder resin by controlling the cooling rate. By carrying out the cooling step, the formation of irregularities on the surface of the toner particles due to volume changes such as expansion or contraction of the materials in the toner particles is suppressed, so that it is easy to control the shape factor SF1 (cross section) to 105 or more and 125 or less, and to control the ground contact area ratio (D / S) of the toner to 14% or less. In addition, by increasing the cooling rate, the volume change can be further suppressed, so that the occurrence of depressions on the surface of the toner particles can be suppressed and the desired circularity or surface shape obtained in the spheronization step can be maintained, and the shape factor SF1 and shape factor SF1 (cross section) of the toner can be 125 or less, and the ground contact area ratio (D / S) of the toner can be 14% or less. The specific cooling rate is 0.1° C. / sec or more, preferably 0.5° C. / sec or more, more preferably 2° C. / sec or more, and even more preferably 4° C. / sec or more.

[0152] [Annealing process] After the cooling step, it is preferable to pass through an annealing step in which the toner particles are heated and held at a temperature equal to or higher than the crystallization temperature or glass transition temperature of the binder resin, and, if a release agent is contained, equal to or lower than the crystallization temperature of the release agent. By passing through the annealing step, the volume change can be further suppressed, so that the occurrence of dents on the surface of the toner particles can be suppressed. Therefore, the desired circularity or surface shape obtained through the cooling step can be maintained, the shape factor SF1 and the shape factor SF1 (cross section) of the toner can be set to 125 or less, and the ground contact area ratio (D / S) of the toner can be controlled to 14% or less. The specific annealing temperature is 45°C or higher and 75°C or lower, preferably 50°C or higher and 70°C or lower, and more preferably 55°C or higher and 65°C or lower. The heat treatment time in the annealing step is, for example, within 5 hours, preferably 2 to 3 hours.

[0153] [Post-processing process] In the toner production method, post-treatment steps such as a washing step, a solid-liquid separation step, and a drying step may be further carried out, and by carrying out the post-treatment steps, toner particles in a dry state are obtained.

[0154] [External addition process] In the external addition step, the strontium titanate particles according to the present invention and further the titanium oxide particles are externally added to the toner particles obtained in the drying step. In addition to these, it is also preferable to add and mix inorganic fine particles such as silica and resin fine particles such as vinyl resin, polyester resin, and silicone resin by applying a shear force in a dry state.

[0155] [Shell layer formation process] On the other hand, in the toner manufacturing method, it is preferable to have a shell layer forming step in which, after forming aggregated particles (core particles) in an aggregation step, resin fine particles containing a shell resin are further added and aggregated to form a shell layer. That is, it is preferable that the toner particles have core particles containing a binder resin and a shell layer on the surface of the core particles. The resin for the shell may be the same as the binder resin, or a different resin may be used. The amount of the resin for the shell added is preferably 1 part by mass or more and 10 parts by mass or less, more preferably 2 parts by mass or more and 7 parts by mass or less, based on 100 parts by mass of the binder resin contained in the core particles.

[0156] In this case, the method for producing the toner preferably includes the following steps.

[0157] (1) a dispersion step for preparing a binder resin fine particle dispersion liquid containing a binder resin; (2-1) an aggregation step of aggregating the binder resin fine particles contained in the binder resin fine particle dispersion to form aggregates; (2-2) a shell formation step of further adding resin fine particles containing a resin for a shell to the dispersion liquid containing the aggregates and aggregating the aggregates to form aggregates having a shell; and (3) a fusion step of heating the aggregates to fuse them together That is, the above-mentioned aggregation step (2) (an aggregation step for aggregating the binder resin fine particles contained in the binder resin fine particle dispersion to form aggregates) preferably includes the following steps (2-1) and (2-2). (2-1) Forming aggregates by aggregating the binder resin fine particles contained in the binder resin fine particle dispersion and (2-2) Add resin particles containing a shell resin to the dispersion containing the aggregates to cause aggregation. A shell formation step in which the agglomerates having a shell are formed by mixing the agglomerates with the In addition, during or after the fusion step, the following steps (4) to (6) are carried out: (4) a spheronization step of further heating the agglomerates at an elevated temperature; (5) a cooling step of cooling the aggregate at a cooling rate of 0.1° C. / sec or more; and (6) An annealing step of heating and holding the aggregate at a temperature equal to or higher than the crystallization temperature or glass transition temperature of the binder resin is more preferable in this order.

[0158] In order to facilitate the incorporation of boric acid in the vicinity of the surface of the toner particles, it is preferred to add a boric acid source to the dispersion liquid containing the aggregates together with the resin particles containing the shell resin in the shell layer formation step.

[0159] Here, the boric acid source may be boric acid or a compound that can be converted to boric acid by pH control during toner production. For example, at least one selected from the group consisting of boric acid, borax, organic boric acid, borate salts, borate esters, etc. may be used. For example, a boric acid source may be added and controlled so that boric acid is contained in the aggregate. Preferably, the pH is controlled to an acidic condition in the aggregation step, and the shell layer formation step is performed.

[0160] The boric acid may be present in the aggregate in an unsubstituted state. The boric acid source is preferably at least one selected from the group consisting of boric acid and borax. When the toner is produced in an aqueous medium, it is preferable to add a borate salt as the boric acid source from the viewpoint of reactivity and production stability. Specifically, the boric acid source more preferably includes at least one selected from the group consisting of sodium tetraborate, borax, ammonium borate, etc., and further preferably is borax.

[0161] Borax is represented by the decahydrate of sodium tetraborate Na2B4O7, and is converted to boric acid in an acidic aqueous solution, so borax is preferably used when used in an aqueous medium under an acidic environment. The addition method may be either in the form of a dry powder or in the form of an aqueous solution dissolved in an aqueous medium, but in order to cause uniform aggregation, it is preferable to add it in the form of an aqueous solution. The concentration of the aqueous solution may be appropriately changed depending on the concentration to be contained in the toner, and is, for example, 1% by mass or more and 20% by mass or less. In order to convert it to boric acid, it is preferable to make the pH an acidic condition before, during, or after the addition. For example, it may be controlled to 1.5 to 5.0, preferably 2.0 to 4.0.

[0162] [Methods for measuring physical properties] Next, the measurement methods for each physical property according to the present disclosure will be described.

[0163] <Measuring method for fragment peaks derived from boron atoms and BO structures> The detection of fragment peaks originating from boron atoms and BO structures in the toner was carried out by using TOF-SIMS.

[0164] To measure the fragment ions on the toner surface using TOF-SIMS, TRIFT-IV manufactured by ULVAC-PHI, Inc. The analysis conditions are as follows: Sample preparation: Depositing toner particles onto an indium sheet Primary ion: Au ion Acceleration voltage: 30 kV Charge neutralization mode: On Measurement mode: Positive Raster: 200μm Measurement time: 60s From the obtained mass profile of secondary ion mass / secondary ion charge number (m / z), it is confirmed whether or not fragment ions derived from boron atoms are observed. In the present invention, the presence or absence of a BO bond is judged based on the presence or absence of a mass profile of BO2, taking into account the balance of peak intensity.

[0165] <Method for measuring maximum Feret diameter and aspect ratio of titanium oxide particles> The number-based primary particle size, maximum Feret's diameter, and aspect ratio of titanium oxide particles are calculated from images of titanium oxide particles on the toner surface taken with a Hitachi ultra-high resolution field emission scanning electron microscope S-4800 (Hitachi High-Technologies Corporation). The image taking conditions for the S-4800 are as follows.

[0166] (1) Sample preparation Apply a thin layer of conductive paste to a sample stage (aluminum sample stage 15 mm x 6 mm) and spray toner onto it. Then use air to remove excess toner from the sample stage and dry thoroughly. Set the sample stage in the sample holder and adjust the sample stage height to 36 mm using the sample height gauge.

[0167] (2) S-4800 observation condition setting The number-based primary particle size, maximum Feret's diameter, and aspect ratio of titanium oxide particles are calculated using images obtained by backscattered electron image observation with the S-4800. Backscattered electron images have less charge-up of titanium oxide particles than secondary electron images, so the particle size of titanium oxide particles can be measured with high accuracy.

[0168] Pour liquid nitrogen into the anti-contamination trap attached to the S-4800 housing until it overflows, and leave it for 30 minutes. Start the S-4800's "PC-SEM" and perform flushing (cleaning the FE chip, which is the electron source). Click the accelerating voltage display area on the control panel on the screen, and press the [Flushing] button to open the flushing execution dialog. Check that the flushing intensity is 2, and execute it. Check that the emission current due to flushing is 20 to 40 μA. Insert the sample holder into the sample chamber of the S-4800 housing. Press [Origin] on the control panel to move the sample holder to the observation position.

[0169] Click the accelerating voltage display to open the HV setting dialog, and set the accelerating voltage to [0.8kV] and the emission current to [20μA]. In the [Basic] tab of the operation panel, set the signal selection to [SE], select the SE detector to [Upper (U)] and [+BSE], and select [LA100] in the selection box to the right of [+BSE] to set the mode to observation with backscattered electron images. In the same [Basic] tab of the operation panel, set the probe current in the electron optical system condition block to [Normal], the focus mode to [UHR], and the WD to [3.0mm]. Press the [ON] button in the accelerating voltage display of the control panel to apply the accelerating voltage.

[0170] (3) Focus adjustment Drag within the magnification display area on the control panel to set the magnification to 100,000 (100k). Rotate the focus knob [COARSE] on the operation panel to adjust the aperture alignment once the image is in focus to a certain extent. Click [Align] on the control panel to display the alignment dialog and select [Beam]. Rotate the STIGMA / ALIGNMENT knobs (X, Y) on the operation panel to move the displayed beam to the center of the concentric circles. Next, select [Aperture] and rotate the STIGMA / ALIGNMENT knobs (X, Y) one by one to stop the image movement or adjust it so that it moves as little as possible. Close the aperture dialog and use autofocus to adjust the focus. Repeat this operation two more times to adjust the focus.

[0171] (4) Image storage Adjust the brightness in ABC mode, take a photo with a size of 640 x 480 pixels, and save it. Use this image file to perform the following analysis. Take one photo for each titanium oxide particle, and obtain images for at least 300 toner particles.

[0172] (5) Calculation of primary particle size based on number of titanium oxide particles The primary particle size of 300 titanium oxide particles is measured to determine the primary particle size based on number. The maximum diameter of those that can be confirmed as primary particles of titanium oxide particles is then determined, and the number-based primary particle size of titanium oxide particles is obtained by arithmetically averaging the maximum diameters obtained.

[0173] (6) Calculation of maximum Feret diameter and aspect ratio of titanium oxide particles The maximum Feret's diameter and aspect ratio of titanium oxide particles are calculated by analyzing the 300 titanium oxide particle images taken in the above (4) Image storage using image analysis software Image-Pro Plus ver.5.0 (Nippon Roper Co., Ltd.). The analysis conditions for the image analysis software Image-Pro Plus ver.5.0 are as follows. Software Image-ProPlus5.1J

[0174] From the "Measurement" menu on the toolbar, select "Count / Size" and then "Options" to set the binarization conditions. In the object extraction options, select 8 connectivity and set smoothing to 0. In addition, do not select pre-sort, fill holes, or encompass lines, and set "Exclude borders" to "None." From the "Measurement" menu on the toolbar, select "Shape descriptors" and "Feret's diameter."

[0175] The maximum Feret diameter and aspect ratio of titanium oxide particles are calculated by automatically binarizing the data using "Processing"-Binarization to determine the maximum Feret diameter and aspect ratio of titanium oxide particles.

[0176] Furthermore, by combining elemental analysis using energy dispersive X-ray analysis (EDS), it is possible to determine whether or not the toner is titanium oxide. Specifically, a scanning electron microscope "S-4800" (product name; manufactured by Hitachi) is used to observe the toner at a field of view magnified up to 100,000 times. The focus is adjusted to the surface of the toner particles, and the external additive to be identified is observed. An EDS analysis is performed on the external additive to be identified, and it is possible to determine whether it is titanium oxide from the elemental peak.

[0177] <Quantitative analysis of fatty acids present on the surface of strontium titanate particles> The amount of fatty acid present on the surface of the strontium titanate particles was determined by GCMS using strontium titanate particles obtained by separating them from the toner surface as described below.

[0178] (1) Method for separating strontium titanate particles from the toner surface Add 1.6 kg of sucrose (Kishida Chemical) to 1 L of ion-exchanged water and dissolve it in a hot water bath to prepare a concentrated sucrose solution. Place 31 g of the concentrated sucrose solution and 6 mL of Contaminon N (a 10% by weight aqueous solution of a neutral detergent for cleaning precision measuring instruments, pH 7, consisting of a nonionic surfactant, an anionic surfactant, and an organic builder, manufactured by Wako Pure Chemical Industries, Ltd.) in a centrifuge tube to prepare a dispersion. Add 10 g of toner to this dispersion, and break up the toner clumps with a spatula or the like.

[0179] The centrifugation tube is placed in an Iwaki Sangyo KM Shaker (model: V.SX) and shaken for 20 minutes at 350 reciprocations per minute. After shaking, the solution is transferred to a glass tube (50 mL) for a swing rotor and centrifuged at 3,500 rpm for 30 minutes.

[0180] After centrifugation, the toner particles are present in the top layer in the glass tube, and the inorganic fine particle mixture containing strontium titanate particles is present in the lower aqueous solution. The lower aqueous solution is separated and then dried to obtain the inorganic fine particle mixture. The above centrifugation process is repeated until the amount of the obtained inorganic fine particle mixture is 10 g or more in total.

[0181] Next, 10 g of the obtained inorganic fine particle mixture is dispersed in a dispersion liquid containing 100 mL of ion-exchanged water and 6 mL of Contaminon N. The obtained dispersion liquid is transferred to a glass tube (50 mL) for a swing rotor, and centrifuged in a centrifuge at 3500 rpm for 30 minutes.

[0182] After the centrifugation, in the glass tube, strontium titanate particles are present in the bottom layer, and other inorganic fine particles are present in the upper layer on the aqueous solution side.

[0183] The mixture of inorganic fine particles containing the strontium titanate particles in the bottom layer is collected, and centrifugal separation is repeated as necessary to separate the strontium titanate particles sufficiently, followed by drying to collect the strontium titanate particles. This process is repeated until the required amount of strontium titanate particles is collected.

[0184] (2) Method for identifying fatty acids present on the surface of strontium titanate particles Add 1 mL of chloroform to 0.05 g of the obtained strontium titanate particles. Treat the obtained sample solution with an ultrasonic disperser for 10 minutes to extract stearic acid into the chloroform solution.

[0185] Furthermore, the solid matter is removed by centrifugation (HITACHI himac CR22G, condition 12000 rpm) and filtration. The obtained solution is analyzed by GC-MS (gas chromatography mass spectrometry).

[0186] Specifically, the measurement conditions are as follows. GCMS equipment: Trace1310 (Thermo Fisher Scientific), ISQ (Thermo Fisher Scientific) Column: HP-5ms 30m Inlet temperature: 250℃ Injection volume: 1μL Column oven temperature: 40℃→300℃ (15℃ / min) MS Ionization mode: EI Ion source temperature: 250℃ Mass range: 35-800m / z The profile obtained by the analysis is analyzed, and the peak positions of the measured sample are compared with the peak positions of the profile obtained from a standard sample of fatty acid such as stearic acid. The fatty acids present on the surface of strontium titanate are then identified by confirming the mass spectrum.

[0187] For example, when the fatty acid is stearic acid, several stearic acid standards (e.g., 200 ng, 300 ng, and 500 ng) are prepared by precisely weighing only the stearic acid standard, and each is measured under the above-mentioned analytical conditions before measuring the external additive sample. Then, a calibration curve is created from the amount of stearic acid charged and the stearic acid peak area value.

[0188] Thereafter, based on the calibration curve, the mass of stearic acid was calculated from the area value of the stearic acid component contained in 0.05 g of strontium titanate particles, and the content (mass %) of fatty acids present on the surface of the strontium titanate particles was determined.

[0189] When multiple fatty acids were contained, each fatty acid was identified and quantified.

[0190] <Measurement of the amount of boron atoms present on the surface of toner particles> The amount of boron atoms present on the surface of the toner particles is measured by the following measurement method using an inductively coupled plasma mass spectrometer (ICP-MS (manufactured by Agilent Technologies)). (a) 20 g of a 50% by weight aqueous solution of methanol is added to 1 g of the toner, and the mixture is shaken for 5 minutes at a shaking speed of 150 revolutions per minute using a shaker, and then the toner is taken out. This operation is repeated 10 times. (b) Prepare a 6.0 mol / L aqueous solution of nitric acid using 60% nitric acid (Kanto Chemical, Ultrapur) and ultrapure water. Add 5.00 g of 6.0 mol / L nitric acid to 50.0 mg of the toner, mix, and stir to prepare a toner-containing solution sample. Leave the sample for 120 minutes to extract boron atoms from the surface of the toner particles. (c) After filtering using filter paper with a pore size of 1 μm to prepare a toner cake, 10.00 g of ultrapure water is added to the toner cake as washing water to separate the toner from the toner-containing solution sample. Ultrapure water is added to the filtrate solution sample so that the total weight becomes 50.00 g to prepare a solution sample for boron atom measurement. (d) Using an inductively coupled plasma mass spectrometer (ICP-MS), a blank solution sample was prepared by adding ultrapure water to 5.00 g of 6.0 mol / L aqueous nitric acid solution to a total of 50.00 g, and a solution sample with a known boron atom content was prepared, and a calibration curve was created. The amount of boron atoms present on the toner surface was measured by quantifying the boron atoms contained in the boron atom measurement sample.

[0191] <Method for measuring thickness T of shell layer present on toner particle surface> The shell layer is a region that does not contain crystalline material and is 25% or less of the distance from the contour of the toner cross section to the center of gravity of the cross section. The cross sections of 100 or more toner particles were observed, and the average value of the distance from the contour to the region that does not contain crystalline material was calculated, and this value was taken as the thickness of the shell layer.

[0192] <Method for measuring molecular weight of polyester resin> The molecular weight of the polyester resin is measured by gel permeation chromatography (GPC) as follows.

[0193] First, polyester resin is dissolved in tetrahydrofuran (THF) at room temperature. The obtained solution is then filtered through a solvent-resistant membrane filter "Maeshori Disk" (manufactured by Tosoh Corporation) with a pore size of 0.2 μm to obtain a sample solution. The sample solution is adjusted so that the concentration of components soluble in THF is 0.8 mass%. This sample solution is used to perform measurements under the following conditions. Equipment: High-speed GPC equipment "HLC-8220GPC" [Tosoh Corporation] Column: LF-604 in two columns Eluent:THF Flow rate: 0.6ml / min Oven temperature: 40℃ Sample injection volume: 0.020 ml In calculating the molecular weight of the sample, a molecular weight calibration curve prepared using standard polystyrene resins (e.g., trade names "TSK Standard Polystyrene F-850, F-450, F-288, F-128, F-80, F-40, F-20, F-10, F-4, F-2, F-1, A-5000, A-2500, A-1000, A-500" manufactured by Tosoh Corporation) is used.

[0194] <Acid value of polyester resin> The acid value is the number of milligrams of potassium hydroxide required to neutralize the acid contained in 1 g of a sample. The acid value in the present invention is measured in accordance with JIS K 0070-1992, and specifically, is measured according to the following procedure.

[0195] Titration is performed using a 0.1 mol / l potassium hydroxide ethyl alcohol solution (Kishida Chemical Co., Ltd.). The factor of the potassium hydroxide ethyl alcohol solution can be determined using a potentiometric titrator (Kyoto Electronics Manufacturing Co., Ltd. Potentiometric titration measuring device AT-510). 100 ml of 0.100 mol / l hydrochloric acid is placed in a 250 ml tall beaker and titrated with the potassium hydroxide ethyl alcohol solution, and the factor is determined from the amount of the potassium hydroxide ethyl alcohol solution required for neutralization. The 0.100 mol / l hydrochloric acid used is prepared in accordance with JIS K 8001-1998.

[0196] The conditions for measuring the acid value are shown below. Titrator: Potentiometric titrator AT-510 (Kyoto Electronics Manufacturing Co., Ltd.) Electrode: Composite glass electrode double junction type (Kyoto Electronics Manufacturing Co., Ltd.) Control software for titrator: AT-WIN Titration analysis software: Tview The titration parameters and control parameters during titration are as follows: Titration parameters Titration mode: Blank titration Titration method: Total volume titration Maximum titration volume: 20ml Waiting time before titration: 30 seconds Titration direction: automatic Control Parameter End point potential: 30dE End point potential: 50 dE / dmL End point detection judgment: Not set Control speed mode: Standard Gain: 1 Data collection potential: 4mV Data collection titration amount: 0.1ml Main test: 0.100 g of the measurement sample is accurately weighed into a 250 ml tall beaker, 150 ml of a mixed solution of toluene / ethanol (3:1) is added, and the mixture is dissolved over 1 hour. Using the above potentiometric titration apparatus, titrate with the above potassium hydroxide ethyl alcohol solution. Blank test: Perform titration in the same manner as above, except that no sample is used (i.e., only a mixed solution of toluene / ethanol (3:1) is used). Substitute the obtained results into the following formula to calculate the acid value. A = [(CB) × f × 5.611] / S (In the formula, A is the acid value (mgKOH / g), B is the amount (ml) of potassium hydroxide ethyl alcohol solution added for the blank test, C is the amount (ml) of potassium hydroxide ethyl alcohol solution added for the main test, f is the factor of the potassium hydroxide solution, and S is the sample (g).)

[0197] <Method for measuring average circularity of toner (particles)> The average circularity of the toner or toner particles is measured using a flow type particle image analyzer "FPIA-3000" (manufactured by Sysmex Corporation) under the measurement and analysis conditions during the calibration work.

[0198] Add an appropriate amount of surfactant and alkylbenzene sulfonate as a dispersant to 20 mL of ion-exchanged water, then add 0.02 g of the measurement sample, and disperse for 2 minutes using a tabletop ultrasonic cleaner disperser (product name: VS-150, manufactured by Vervoclear Co., Ltd.) with an oscillation frequency of 50 kHz and an electrical output of 150 watts to obtain a dispersion for measurement. At this time, cool the dispersion appropriately so that the temperature is between 10°C and 40°C.

[0199] For the measurement, the flow type particle image analyzer equipped with a standard objective lens (10x) is used, and the particle sheath "PSE-900A" (manufactured by Sysmex Corporation) is used as the sheath liquid. The dispersion liquid prepared according to the above procedure is introduced into the flow type particle image analyzer, and 3000 toner particles (particles) are measured in HPF measurement mode and total count mode, the binarization threshold for particle analysis is set to 85%, the analyzed particle diameter is limited to a circle equivalent diameter of 1.98 μm or more and 19.92 μm or less, and the average circularity of the toner particles (particles) is obtained.

[0200] Before starting the measurement, automatic focus adjustment is performed using standard latex particles (e.g., 5100A (trade name) manufactured by Duke Scientific diluted with ion-exchanged water). After that, it is preferable to perform focus adjustment every 2 hours from the start of the measurement.

[0201] <Method of measuring weight average particle size (D4) of toner> The weight-average particle diameter (D4) of the toner was measured with an effective measurement channel count of 25,000 channels using a precision particle size distribution measuring device equipped with a 100 μm aperture tube and a fine hole electrical resistance method, called "Coulter Counter Multisizer 3" (registered trademark, manufactured by Beckman Coulter, Inc.), and the accompanying dedicated software "Beckman Coulter Multisizer 3 Version 3.51" (manufactured by Beckman Coulter, Inc.), for setting measurement conditions and analyzing measurement data. The weight-average particle diameter (D4) of the toner was calculated by analyzing the measurement data.

[0202] The electrolyte solution used for the measurement is prepared by dissolving special grade sodium chloride in ion-exchanged water to a concentration of approximately 1% by mass, for example, "ISOTON II" (manufactured by Beckman Coulter).

[0203] Before carrying out the measurements and analyses, the dedicated software was set up as follows.

[0204] In the "Change Standard Measurement Method (SOM) screen" of the dedicated software, set the total count number in the control mode to 50,000 particles, the number of measurements to 1, and the Kd value to the value obtained using "Standard Particle 10.0 μm" (Beckman Coulter). Press the threshold / noise level measurement button to automatically set the threshold and noise level. In addition, set the current to 1600 μA, the gain to 2, the electrolyte to ISOTON II, and check the aperture tube flush after measurement.

[0205] In the "Pulse to particle size conversion setting screen" of the dedicated software, set the bin interval to logarithmic particle size, the particle size bin to 256 particle size bins, and the particle size range from 2 μm to 60 μm.

[0206] The specific measurement method is as follows. 1. Pour about 200 ml of the electrolyte solution into a 250 ml round-bottom glass beaker made exclusively for the Multisizer 3, set it on the sample stand, and stir the stirrer rod counterclockwise at 24 revolutions per second. Then, use the "aperture flush" function of the analysis software to remove dirt and air bubbles from inside the aperture tube. 2. Place approximately 30 ml of the above electrolyte solution in a 100 ml flat-bottom glass beaker, and add approximately 0.3 ml of a solution prepared by diluting "Contaminon N" (a 10% by weight aqueous solution of a neutral detergent for cleaning precision measuring instruments, consisting of a nonionic surfactant, an anionic surfactant, and an organic builder, with a pH of 7, manufactured by Wako Pure Chemical Industries, Ltd.) three times by weight with ion-exchanged water as a dispersant. 3. A specified amount of ion-exchanged water is placed in the water tank of an ultrasonic disperser "Ultrasonic Dispersion System Tetora150" (manufactured by Nikkaki Bios) that has two oscillators with an oscillation frequency of 50 kHz built in with a phase shift of 180 degrees and an electrical output of 120 W, and approximately 2 ml of the above-mentioned Conaminon N is added to this water tank. 4. Set the beaker from step 2 in the beaker fixing hole of the ultrasonic disperser and operate the ultrasonic disperser. Then, adjust the height of the beaker so that the resonance state of the electrolyte solution level in the beaker is maximized. 5. While the electrolyte solution in the beaker in step 4 is being irradiated with ultrasonic waves, about 10 mg of toner is added little by little to the electrolyte solution and dispersed. Then, ultrasonic dispersion treatment is continued for another 60 seconds. During ultrasonic dispersion, the water temperature in the water tank is appropriately adjusted to be between 10°C and 40°C. 6. Using a pipette, add the electrolyte solution (5) in which the toner has been dispersed, to the round-bottom beaker (1) placed in the sample stand, and adjust the measurement concentration to about 5%. Then, measurements are continued until the number of particles measured reaches 50,000. 7. Analyze the measurement data using the dedicated software that comes with the device and calculate the weight-average particle size (D4). Note that when the dedicated software is set to Graph / Volume%, the "Arithmetic diameter" on the Analysis / Volume Statistics (Arithmetic Mean) screen is the weight-average particle size (D4).

[0207] [Configuration included in the embodiment of the present invention] The disclosure of this embodiment includes the following configuration. (Configuration 1) A toner having toner particles containing a binder resin and strontium titanate particles, In a TOF-SIMS measurement of the toner particles, a fragment peak derived from a boron atom and a fragment peak derived from a BO structure were detected, The toner is characterized in that a fatty acid is present on the surface of the strontium titanate particles. (Configuration 2) The toner according to configuration 1, wherein the amount of boron atoms present (by mass) in the toner measured by inductively coupled plasma mass spectrometry (ICP-MS) is 0.1 ppm or more and 100 ppm or less. (Configuration 3) When the amount of boron atoms present (by mass) in the toner is X (ppm) and the content of the strontium titanate particles in the toner is Y (% by mass), X and Y satisfy the following formula: 0.10≦X / Y≦30.0 3. The toner according to configuration 2. (Configuration 4) When the amount of boron atoms present (by mass) in the toner is X (ppm) and the content of fatty acids having 12 to 30 carbon atoms present on the surfaces of the strontium titanate particles is Z (mass%), X and Z satisfy the following formula: 0.020≦X / Z≦15.0 4. The toner according to configuration 2 or 3. (Configuration 5) The toner according to Configuration 4, wherein Z is 0.10 or more and 5.0 or less. (Configuration 6) The toner according to any one of Configurations 1 to 5, wherein the fatty acid has 12 or more and 30 or less carbon atoms. (Configuration 7) The toner according to any one of Configurations 1 to 6, wherein two types of fatty acids with different carbon numbers are present on the surface of the strontium titanate particles, the carbon numbers of the two types of fatty acids are both 12 or more and 30 or less, and the difference in the carbon numbers of the two types of fatty acids is 2 or more. (Configuration 8) The toner according to any one of Configurations 1 to 7, wherein the toner has an average circularity of 0.960 or more and 0.990 or less. (Configuration 9) The toner according to any one of Configurations 1 to 8, wherein the toner further contains titanium oxide particles that satisfy the following (i) and (ii), in addition to the strontium titanate particles: (i) Maximum Feret diameter is 300 nm or more and 3000 nm or less (ii) Aspect ratio is 5.0 or more EXAMPLES

[0208] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is in no way limited thereto. Parts used in the examples are by weight unless otherwise specified.

[0209] <Production Example 1 of Strontium Titanate Particles> Metatitanic acid obtained by the sulfuric acid method was deironized and bleached, then sodium hydroxide solution was added to adjust the pH to 9.0, desulfurized, neutralized to pH 5.8 with hydrochloric acid, filtered and washed with water. Water was added to the washed cake to make a slurry of 1.85 mol / L in terms of TiO2, and hydrochloric acid was added to adjust the pH to 1.0, followed by peptization.

[0210] After desulfurization and peptization, 1.88 moles of metatitanic acid was collected as TiO2 and placed in a 3L reaction vessel. 2.16 moles of strontium chloride aqueous solution were added to the peptized metatitanic acid slurry so that the Sr / Ti molar ratio was 1.15, and the TiO2 concentration was adjusted to 1.015 moles / L. Next, the mixture was heated to 90°C while stirring, and 440 mL of 10 moles / L sodium hydroxide aqueous solution was added over 45 minutes. After that, the mixture was stirred at 95°C for 1 hour to complete the reaction.

[0211] The reaction slurry was cooled to 50°C, hydrochloric acid was added until the pH reached 5.0, and stirring was continued for 20 minutes. The resulting precipitate was washed by decantation, separated by filtration, and then dried in the air at 120°C for 8 hours.

[0212] Next, 300 g of the dried product was placed in a dry particle composite device (Nobilta NOB-130, manufactured by Hosokawa Micron). The product was crushed for 10 minutes at a processing temperature of 30°C with a rotary processing blade moving at 90 m / sec. The product was then transferred to a separate container, and hydrochloric acid was added until the pH reached 0.1, followed by stirring for 1 hour. The resulting precipitate was washed by decantation.

[0213] The slurry containing the obtained precipitate was adjusted to 40°C, and hydrochloric acid was added to adjust the pH to 2.5. Then, 0.6 parts of stearic acid and 0.6 parts of palmitic acid were added to 100 parts of solids, and stirring was continued for 10 hours. 5 mol / L sodium hydroxide solution was added to adjust the pH to 6.5 and stirring was continued for 1 hour. After that, filtration and washing were performed, and the particles were dried in the air at 120°C for 8 hours to obtain strontium titanate particles 1 (T-1). The hydrophobicity of T-1 was 75 (volume %) and the average primary particle size was 60 nm. Table 1 shows the surface treatment agent of T-1 and the amount of the surface treatment agent added.

[0214] <Production Examples 2 to 25 of Strontium Titanate Particles> Strontium titanate particles 2 to 25 (T-2 to T-25) were produced in the same manner as in Production Example 1 of strontium titanate particles, except that the formulation of the surface treatment agent was changed as shown in Table 1.

[0215] [Table 1]

[0216] <Production Examples of Titanium Oxide Particles 1 to 5> Titanium oxide particles were produced as follows. A 50% NaOH aqueous solution was added to metatitanic acid obtained by the sulfuric acid method in an amount four times the molar amount of NaOH relative to TiO2, and the mixture was heated at 95°C for 2 hours. After thorough washing, 31% HCl was added so that the HCl / TiO2 ratio became 0.26, and the mixture was heated at the boiling point for 1 hour. After cooling, the mixture was neutralized to pH 7 with 1 mol / L NaOH, washed and dried to produce titanium oxide microparticles. The specific surface area of ​​the obtained titanium oxide microparticles was 115 g / m 2 The titanium oxide particles were mixed in a vibration ball mill for 1 hour, and the mixture was fired in an electric furnace at 850°C for 2 hours. The fired product was placed in pure water and heated at 80°C for 6 hours, and then washed to remove soluble salts. All of the particles obtained after drying had a minor axis within the range of 0.03 μm to 0.07 μm and a major axis within the range of 0.4 μm to 0.8 μm, giving titanium oxide particles 1 to 5 (S-1 to S-5). The physical properties of titanium oxide particles 1 to 5 are shown in Table 2.

[0217] [Table 2]

[0218] <Synthesis of polyester resin 1> Bisphenol A ethylene oxide 2 mole adduct 10 mol parts Bisphenol A propylene oxide 2 mole adduct 94 mole parts Terephthalic acid 50 mol parts Fumaric acid 31 mol parts Dodecenylsuccinic acid 24 mol parts The above monomers were charged into a flask equipped with a stirrer, nitrogen inlet tube, temperature sensor, and distillation column, and the temperature was raised to 195°C in 1 hour, and it was confirmed that the reaction system was stirred uniformly. 1.0 part of tin distearate was added to 100 parts of these monomers. The temperature was then raised from 195°C to 250°C over 5 hours while distilling off the water produced, and the dehydration condensation reaction was carried out at 250°C for another 2 hours.

[0219] As a result, polyester resin 1 having a glass transition temperature of 60.5° C., an acid value of 16.7 mgKOH / g, a hydroxyl value of 28.1 mgKOH / g, a weight average molecular weight of 11,300 and a number average molecular weight of 4,200 was obtained.

[0220] <Synthesis of polyester resin 2> Bisphenol A-ethylene oxide 2 mole adduct 48 mol parts Bisphenol A-propylene oxide 2 mole adduct 48 mol parts Terephthalic acid 67 mol parts Dodecenylsuccinic acid 28 mol parts The above monomers were added to a flask equipped with a stirrer, nitrogen inlet tube, temperature sensor, and distillation column, and the temperature was raised to 195°C in one hour, and it was confirmed that the reaction system was uniformly stirred. 0.7 parts of tin distearate were added to 100 parts of these monomers. The temperature was then raised from 195°C to 240°C over five hours while distilling off the water produced, and a dehydration condensation reaction was carried out at 240°C for another two hours. The temperature was then lowered to 190°C, and 5 mol parts of trimellitic anhydride were gradually added, and the reaction was continued at 190°C for one hour.

[0221] As a result, polyester resin 2 having a glass transition temperature of 55.8° C., an acid value of 14.0 mgKOH / g, a hydroxyl value of 24.4 mgKOH / g, a weight average molecular weight of 44,000, and a number average molecular weight of 6,300 was obtained.

[0222] <Preparation of Resin Particle Dispersion 1> 100 parts polyester resin 1 Methyl ethyl ketone 50 parts 20 parts isopropyl alcohol The above methyl ethyl ketone and isopropyl alcohol were added to the container. Then, the above polyester resin 1 was gradually added and stirred to completely dissolve, obtaining a polyester resin 1 solution. The container containing the polyester resin 1 solution was set to 65°C, and a 10% aqueous ammonia solution was gradually dropped to a total of 5 parts while stirring, and 230 parts of ion-exchanged water was gradually dropped at a rate of 10 ml / min to cause phase inversion emulsification. The pressure was then reduced with an evaporator to remove the solvent, obtaining a resin particle dispersion 1 of polyester resin 1. The volume average particle size of the resin particles was 135 nm. The resin particle solid content was adjusted to 20% with ion-exchanged water.

[0223] <Preparation of Resin Particle Dispersion 2> 100 parts polyester resin 2 Methyl ethyl ketone 50 parts 20 parts isopropyl alcohol The above methyl ethyl ketone and isopropyl alcohol were added to the container. Then, the above polyester resin 2 was gradually added, stirred, and completely dissolved to obtain a polyester resin 2 solution. The container containing the polyester resin 2 solution was set to 40°C, and while stirring, 10% aqueous ammonia solution was gradually dropped to a total of 3.5 parts, and 230 parts of ion-exchanged water was gradually dropped at a rate of 10 ml / min to cause phase inversion emulsification. The pressure was further reduced to remove the solvent, and a resin particle dispersion 2 of polyester resin 2 was obtained. The volume average particle size of the resin particles was 155 nm. The resin particle solid content was adjusted to 20% with ion-exchanged water.

[0224] <Preparation of Colorant Particle Dispersion> Copper phthalocyanine (pigment blue 15:3) 45 parts Ionic surfactant Neogen RK (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) 5 parts 190 parts deionized water The above components were mixed and dispersed for 10 minutes using a homogenizer (IKA Ultra Turrax), and then dispersed for 20 minutes at a pressure of 250 MPa using an Ultimizer (opposed collision type wet grinder: Sugino Machine Ltd.) to obtain a colorant particle dispersion having a volume average particle size of 120 nm and a solid content of 20%.

[0225] <Preparation of release agent particle dispersion> Release agent (hydrocarbon wax, melting point: 79°C) 15 parts Ionic surfactant Neogen RK (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) 2 parts 240 parts deionized water The above was heated to 100°C and thoroughly dispersed using an IKA Ultra Turrax T50, and then the mixture was heated to 115°C using a pressure discharge type Gaulin homogenizer and dispersed for 1 hour to obtain a release agent particle dispersion with a volume average particle size of 160 nm and a solid content of 20%.

[0226] <Production of Toner Particle 1> ·Resin particle dispersion 1 500 parts ·Resin particle dispersion 2 400 parts Colorant particle dispersion 50 parts Release agent particle dispersion 80 parts First, in the core formation process, the above materials were put into a round stainless steel flask and mixed. Then, the materials were dispersed for 10 minutes at 5000 r / min using a homogenizer Ultra Turrax T50 (manufactured by IKA). After adding a 1.0% nitric acid aqueous solution to adjust the pH to 3.0, the mixture was heated to 58°C in a heating water bath using a stirring blade while appropriately adjusting the rotation speed so that the mixture was stirred.

[0227] The volume average particle size of the formed agglomerated particles was appropriately confirmed using a Coulter Multisizer III. When agglomerated particles (cores) having a particle size of 5.0 μm were formed, the following materials were added as the shell formation step and stirred for another hour to form a shell. ·Resin particle dispersion 1 40 parts 300 parts deionized water ·10.0% by mass borax aqueous solution 20 parts (Borax; Sodium tetraborate decahydrate, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.)

[0228] Thereafter, in the spheronization step, the pH was adjusted to 9.0 using a 5% aqueous sodium hydroxide solution, and the mixture was heated to 92° C. while continuing to stir.

[0229] When the desired surface shape was obtained, heating was stopped, and as a cooling step, ice was quickly added so that the cooling rate was 10°C / s or more to cool to 40°C. Furthermore, as an annealing step, an annealing treatment was performed at 55°C for 3 hours.

[0230] After that, it was cooled to 25°C, filtered and separated into solid and liquid, and then washed with ion-exchanged water. After washing, it was dried using a vacuum dryer to obtain toner particles 1 (B-1) having a weight average particle size (D4) of 6.7 μm.

[0231] <Production Examples of Toner Particles 2 to 4, 9 to 11, and 15> Toner particles 2 to 4, 9 to 11, and 15 (B-2 to 4, 9 to 11, and 15) were obtained in the same manner as in the production example of toner particle 1, except for changing the formulation and conditions shown in Table 3. The physical properties of the obtained toner particles 2 to 4, 9 to 11, and 15 are shown in Table 4.

[0232] <Toner particles 5 to 8> Toner particles 5 to 8 were obtained in the same manner as in Production Example of Toner Particle 2, except that the conditions in the spheronization step were adjusted so that the circularity of the obtained toner particles would be a desired value. The physical properties of the obtained toner particles 5 to 8 are shown in Table 4.

[0233] <Production Examples of Toner Particles 12 to 14> Toner particles 12 to 14 (B-12 to 14) were obtained in the same manner as toner particle 11, except that the amount of boron in the resulting toner was changed by spraying an aqueous boric acid solution onto toner particle 11 as shown in Table 3. The physical properties of the resulting toner particles 12 to 14 are shown in Table 4.

[0234] <Toner particles 16> Toner particles 16 were obtained in the same manner as in the production example of toner particles 7, except that in the production example of toner particles 7, the recipe for the shell layer formation step was changed as shown in Table 3. The physical properties of the obtained toner particles 16 are shown in Table 4.

[0235] <Toner particles 17> Toner particles 17 were obtained in the same manner as in the production example of toner particles 8, except that in the production example of toner particles 8, the recipe for the shell layer formation step was changed as shown in Table 3. The physical properties of the obtained toner particles 17 are shown in Table 4.

[0236] <Production Example of Toner Particle 18> The following materials were thoroughly mixed in an FM mixer (manufactured by Nippon Coke and Engineering Co., Ltd.), and then melt-kneaded in a twin-screw kneader (manufactured by Ikegai Iron Works Co., Ltd.) set at a temperature of 100°C. Polyester resin 2 95.0 parts Polyester resin 1 5.0 parts HNP9 (melting point: 76°C, manufactured by Nippon Seiro Co., Ltd.) 5.0 parts ·CIPigment Blue15:3 6.0 copies

[0237] The obtained kneaded product was cooled and coarsely crushed to 1 mm or less using a hammer mill to obtain a coarsely crushed product.

[0238] Next, the obtained coarsely crushed material was milled using a turbo mill manufactured by Turbo Kogyo Co., Ltd. to obtain finely ground material of about 5 μm, and then a multi-division classifier utilizing the Coanda effect was used to remove fine and coarse powder. After that, as shown in Table 3, an aqueous boric acid solution was sprayed onto the toner to adjust the amount of boric acid in the toner to the value shown in Table 4, thereby obtaining toner particle 18 (B-18).

[0239] The toner particles 18 had a weight average particle size (D4) of 6.7 μm and a Tg of 58.4° C.

[0240] [Table 3]

[0241] <Toner 1 Manufacturing Example> External addition was carried out on the toner particles 1 (B-1) described above. Using an FM mixer (FM10 manufactured by Nippon Coke & Engineering Co., Ltd.), 2.7 kg of toner particles 1 (B-1) were mixed with silica fine particles 1 (BET150 ml treated with dimethyl silicone oil) to obtain a toner. 2 / g silica particles) was added to 1.0 mass %, strontium titanate particles 1 (T-1) to 0.3 mass %, and titanium oxide particles 1 (S-1) to 0.1 mass %.

[0242] After that, external addition was performed by mixing at 3000 rpm for 5 minutes. At this time, the temperature inside the tank after 5 minutes of mixing was adjusted to 35°C by controlling the flow and temperature of cold water flowing through the cooling jacket.

[0243] Thereafter, the toner was sieved through a mesh having an opening of 75 μm to obtain Toner 1. The physical properties of Toner 1 are shown in Table 4.

[0244] <Toner 2-47 Manufacturing Examples> Toners 2 to 47 were obtained by carrying out the same operations as in the production example of toner 1, except that the type of toner particles, the type and amount of strontium titanate particles, and the type of titanium oxide particles were changed. The physical properties of the obtained toners 2 to 47 are shown in Table 4.

[0245] [Table 4]

[0246] [Examples 1 to 42, Comparative Examples 1 to 5] The following evaluation tests were carried out on the above-mentioned Example toners 1 to 42 and Comparative Example toners 43 to 47. The evaluation results are shown in Table 5.

[0247] Evaluation equipment: A color laser printer, HP LaserJet Enterprise Color M555dn, equipped with a one-component toner contact development blade cleaning system, and its consumable cartridge, a modified HP212X black toner cartridge (W2120X) CRG, were used.

[0248] The main body was modified so that the process speed could be set to 150% and printing tests could be performed only on the black station. The cartridge was also modified so that the toner container volume could be doubled as usual. This enabled a longer life durability evaluation to be performed on a faster main body than before.

[0249] <Evaluation 1. Halftone density difference after durability evaluation in a low temperature and low humidity environment> The printer body and the toner cartridge filled with 400g of evaluation toner were left for 24 hours in an environment of 15°C and 10% RH in order to control the temperature and humidity in the evaluation environment. After leaving it, a LETTER-sized XEROX Vitality (LTR 75g / m 2 ) was used to conduct a durability evaluation in which 30,000 copies of a horizontal line image with a print rate of 1.5% and a margin of 5 mm were printed, with two copies per job.

[0250] Thereafter, as the 30,001st sheet, one halftone image with a print ratio of 23%, a margin of 23%, and a margin of 5 mm was output (halftone image 1).

[0251] Thereafter, the charging roller was replaced with a new one, and then one halftone image with a print rate of 23% was output as the 30,002nd sheet (halftone image 2).

[0252] Using a portable spectrophotometer Exact Advance (manufactured by X-Rite), image density was measured at five points on each of the halftone images 1 and 2, in three rows: the center row, the row 20 mm from the left edge, and the row 20 mm from the right edge, in the vertical direction from the leading edge to the trailing edge of the paper, at 50 mm intervals from the leading edge of the paper, for a total of 15 points on each row.

[0253] The density difference (difference between the maximum and minimum values ​​of 15-point measurements) for halftone images 1 and 2 was obtained, and then the difference between the density difference of halftone image 1 and the density difference of halftone image 2 was calculated to obtain the halftone density difference due to charging roller contamination after the durability evaluation.

[0254] The less the toner that stains the charging roller, the smaller the halftone density difference due to the staining of the charging roller after the durability evaluation becomes, since the toner that stains the charging roller less enables the output of a halftone image with the same density difference as that of a new charging roller. (Half-tone density difference due to charging roller contamination after durability evaluation) A. The halftone density difference is less than 0.05. B. The halftone density difference is equal to or greater than 0.05 and less than 0.10. C. The halftone density difference is equal to or greater than 0.10 and less than 0.15. D. The halftone density difference is 0.15 or more.

[0255] <Evaluation 2. Uniformity of solid density after durability evaluation in a low temperature and low humidity environment> The printer body and the toner cartridge filled with 400g of evaluation toner were left for 24 hours in an environment of 15°C and 10% RH in order to control the temperature and humidity in the evaluation environment. After leaving it, a LETTER-sized XEROX Vitality (LTR 75g / m 2 ) was used to conduct a durability evaluation in which 30,000 copies of a horizontal line image with a print rate of 1.5% and a margin of 5 mm were printed, with two copies per job.

[0256] Using a portable spectrophotometer Exact Advance (manufactured by X-Rite), image density was measured at five points at 50 mm intervals from the leading edge of the paper in the vertical direction from the leading edge to the trailing edge of the paper for three rows of the solid image 1: the center row, the row 20 mm from the left edge, and the row 20 mm from the right edge, for a total of 15 points on each row.

[0257] The density measurements at these 15 points were used to determine the difference between the average density and the minimum density, which was taken as the solid density difference after the durability evaluation.

[0258] The better the charge rising property of the toner in a low temperature and low humidity environment, the smaller the solid density difference is, and the better the toner is. (Difference in solid density after durability evaluation in low temperature and low humidity environment) A. The difference in solid density after durability evaluation is less than 0.05. B. The difference in solid density after durability evaluation is 0.05 or more and less than 0.10. C. The difference in solid density after durability evaluation is 0.10 or more and less than 0.15. D. The solid density difference after durability evaluation is 0.15 or more.

[0259] <Evaluation 3. Fog after durability evaluation under low temperature and low humidity environment> In the same manner as in Evaluation 2, a durability evaluation was carried out in a low temperature and low humidity environment in which a horizontal line image with a print rate of 1.5% and a margin of 5 mm was output on 30,000 sheets.

[0260] After that, a piece of paper with a 5 cm x 5 cm sticky note attached to the center of the printing surface was set in the cassette, and then an all-white image was output as the 30,001st sheet (all-white image 1).

[0261] After removing the sticky note from the all-white image 1, a white light meter TC-6DX (manufactured by Tokyo Denshoku Co., Ltd.) was used to measure the reflectance (%) of the area where the sticky note was attached and the reflectance (%) of the area where the sticky note was not attached. The difference between the two was measured and calculated as fog (%), and evaluation was performed according to the following criteria. (Fogging after durability evaluation in low temperature and low humidity environment) A. The fog after durability evaluation is less than 0.5. B. The fog after the durability evaluation is 0.5 or more and less than 1.0. C. The fog after durability evaluation is 1.0 or more and less than 1.5. D. The fog after durability evaluation is 1.5 or more.

[0262] <Evaluation 4. Fog after durability evaluation under high temperature and high humidity environment> The printer body and the toner cartridge filled with 400g of evaluation toner were left in an environment of 32°C and 80% RH for 24 hours in order to control the temperature and humidity in the evaluation environment. After leaving it, a LETTER-sized XEROX Vitality (LTR 75g / m 2 ) was used to conduct a durability evaluation in which 30,000 copies of a horizontal line image with a print rate of 1.5% and a margin of 5 mm were printed, with two copies per job.

[0263] After that, a paper with a 5cm x 5cm sticky note attached to the center of the printing surface was placed in the cassette, and then an all-white image was output as the 30,001st sheet (all-white image 1). After removing the sticky note from the all-white image 1, a white light meter TC-6DX (manufactured by Tokyo Denshoku Co., Ltd.) was used to measure the reflectance (%) of the area where the sticky note was attached and the reflectance (%) of the area where the sticky note was not attached. The difference between the two was measured and calculated as fog (%), and evaluation was performed according to the following criteria. (Fogging after durability evaluation under high temperature and humidity environment) A. The fog after durability evaluation is less than 0.5. B. The fog after the durability evaluation is 0.5 or more and less than 1.0. C. The fog after durability evaluation is 1.0 or more and less than 1.5. D. The fog after durability evaluation is 1.5 or more.

[0264] <Evaluation 5. Density uniformity of solid images after durability evaluation in a low temperature and low humidity environment and then leaving it alone> As in Evaluation 2, a durability evaluation was conducted in which 30,000 sheets of a horizontal line image with a print rate of 1.5% and a margin of 5 mm were printed in a low temperature and low humidity environment, and then one image with a solid black surface was printed as the 30,001st sheet (Solid image 1).

[0265] After that, the plate was left as it was for three days, and then a solid black image was printed out as the 30,002nd print (solid image 2).

[0266] Using a portable spectrophotometer Exact Advance (manufactured by X-Rite), image density was measured at five points at 50 mm intervals from the leading edge of the paper in the vertical direction from the leading edge to the trailing edge of the paper for three rows of the solid image 2: the center row, the row 20 mm from the left edge, and the row 20 mm from the right edge, for a total of 15 points on each row.

[0267] The difference between the average density and the minimum density was calculated using the density measurements at these 15 points, and this was taken as the difference in solid density after standing.

[0268] The toner having a good charge rising property even after being left for a long time in a low temperature and low humidity environment has a smaller solid density difference after the long time, and is therefore good. (Difference in solid density after durability evaluation in a low temperature and low humidity environment) A. The difference in solid concentration after leaving it is less than 0.05. B. The difference in solid concentration after standing is 0.05 or more and less than 0.10. C. The difference in solid concentration after standing is 0.10 or more and less than 0.15. D. The difference in solid concentration after leaving is 0.15 or more.

[0269] <Evaluation 6. Density uniformity of solid images after durability evaluation in a high temperature and high humidity environment and then leaving it> As in Evaluation 4, a durability evaluation was conducted in which 30,000 sheets of a horizontal line image with a print rate of 1.5% and a margin of 5 mm were printed in a high temperature and high humidity environment, and then one image with a solid black surface was printed as the 30,001st sheet (Solid image 1).

[0270] After that, the plate was left as it was for three days, and then a solid black image was printed out as the 30,002nd print (solid image 2).

[0271] Using a portable spectrophotometer Exact Advance (manufactured by X-Rite), image density was measured at five points at 50 mm intervals from the leading edge of the paper in the vertical direction from the leading edge to the trailing edge of the paper for three rows of the solid image 2: the center row, the row 20 mm from the left edge, and the row 20 mm from the right edge, for a total of 15 points on each row.

[0272] The difference between the average density and the minimum density was calculated using the density measurements at these 15 points, and this was taken as the difference in solid density after standing.

[0273] The toner having a good charge rising property even after being left for a long time under a high temperature and high humidity environment has a smaller solid density difference after the long time, and is therefore good. (Difference in solid density after durability evaluation in a high temperature and high humidity environment) A. The difference in solid concentration after leaving it is less than 0.05. B. The difference in solid concentration after standing is 0.05 or more and less than 0.10. C. The difference in solid concentration after standing is 0.10 or more and less than 0.15. D. The difference in solid concentration after leaving is 0.15 or more.

[0274] <Evaluation 7. Halftone density difference after high print durability evaluation in low temperature and low humidity environment> The printer body and the toner cartridge filled with 400g of evaluation toner were left for 24 hours in an environment of 15°C and 10% RH in order to control the temperature and humidity in the evaluation environment. After leaving it, a LETTER-sized XEROX Vitality (LTR 75g / m 2 ) was used to conduct a durability evaluation in which 1,300 halftone images with a print rate of 23% and margins of 5 mm were printed out in a two-sheet job.

[0275] Thereafter, as the 13,01st sheet, one halftone image with a print ratio of 23%, a margin of 23%, and a margin of 5 mm was output (halftone image 1).

[0276] Thereafter, the charging roller was replaced with a new one, and then, as the 13.02nd sheet, one halftone image with a print rate of 23% was output (halftone image 2).

[0277] Using a portable spectrophotometer Exact Advance (manufactured by X-Rite), image density was measured at five points on each of the halftone images 1 and 2, in three rows: the center row, the row 20 mm from the left edge, and the row 20 mm from the right edge, in the vertical direction from the leading edge to the trailing edge of the paper, at 50 mm intervals from the leading edge of the paper, for a total of 15 points on each row.

[0278] The density difference (difference between the maximum and minimum values ​​of 15-point measurements) for halftone images 1 and 2 was obtained, and then the difference between the density difference of halftone image 1 and the density difference of halftone image 2 was calculated to determine the halftone density difference due to charging roller contamination after high-speed printing durability evaluation.

[0279] Based on the halftone density difference due to the charging roller contamination after the high-speed printing durability evaluation, the evaluation was made according to the following criteria.

[0280] In the present invention, in order to improve the half-tone density difference caused by charging roller contamination after high-speed printing durability evaluation, it is preferable to set the amount Z of fatty acid present on the surface of the strontium titanate particles within a preferred range. This is because the charge relaxation speed of the strontium titanate particles can be increased, and charging roller contamination can be suppressed even when a large amount of toner is consumed in a short time, such as in a high-speed printing durability evaluation. (Half-tone density difference due to charging roller contamination after high-speed printing durability evaluation) A. The halftone density difference is less than 0.05. B. The halftone density difference is equal to or greater than 0.05 and less than 0.10. C. The halftone density difference is equal to or greater than 0.10 and less than 0.15. D. The halftone density difference is 0.15 or more.

[0281] <Evaluation 8. Uniformity of solid density after high-print durability evaluation under high temperature and high humidity environment> The printer body and the toner cartridge filled with 400g of evaluation toner were left in an environment of 32°C and 80% RH for 24 hours in order to control the temperature and humidity in the evaluation environment. After leaving it, a LETTER-sized XEROX Vitality (LTR 75g / m2 ) was used to conduct a durability evaluation in which 1,300 halftone images with a print rate of 23% and margins of 5 mm were printed out in a two-sheet job.

[0282] After that, as the 13.01st sheet, one image with a solid black surface was output (Solid Image 1).

[0283] Using a portable spectrophotometer Exact Advance (manufactured by X-Rite), image density was measured at five points at 50 mm intervals from the leading edge of the paper in the vertical direction from the leading edge to the trailing edge of the paper for three rows of the solid image 1: the center row, the row 20 mm from the left edge, and the row 20 mm from the right edge, for a total of 15 points on each row.

[0284] The density measurements at these 15 points were used to determine the difference between the average density and the minimum density, which was taken as the solid density difference after the high-pressure printing durability evaluation.

[0285] The toner having a better charge rise property after the high-speed printing durability evaluation under a high-temperature and high-humidity environment has a smaller solid density difference and is more favorable.

[0286] In the present invention, in order to improve the solid density difference after high-speed printing durability evaluation, it is preferable to set the amount Z of fatty acid present on the surface of the strontium titanate particles within a preferred range. This is because it is possible to improve the fluidity of the toner containing the strontium titanate particles, and to improve the charge rise property of the toner even when a large amount of toner is consumed in a short time, such as in a high-speed printing durability evaluation. (Solid density difference after high print durability evaluation under high temperature and high humidity environment) A. The difference in solid concentration is less than 0.05. B. The difference in solid density is 0.05 or more and less than 0.10. C. The solid density difference is 0.10 or more and less than 0.15. D. The solid density difference is 0.15 or more.

[0287] <Evaluation 9. Fog after high-temperature, high-humidity printing durability evaluation> As in Evaluation 8, a durability evaluation was conducted in a high temperature and high humidity environment, in which 1,300 halftone images with a print rate of 23% and margins of 5 mm were printed, with one job consisting of two sheets.

[0288] After that, a piece of paper with a 5 cm x 5 cm sticky note attached to the center of the printing surface was placed in the cassette, and then an all-white image was printed out as the 1,301st sheet (all-white image 1).

[0289] After removing the sticky note from the all-white image 1, a white light meter TC-6DX (manufactured by Tokyo Denshoku Co., Ltd.) was used to measure the reflectance (%) of the area where the sticky note was attached and the reflectance (%) of the area where the sticky note was not attached. The difference between the two was measured and calculated as fog (%), and evaluation was performed according to the following criteria.

[0290] In the present invention, in order to improve fog after a high-temperature, high-humidity environment high-intensity printing durability test, it is preferable to set the number of carbon atoms of the fatty acid present on the surface of the strontium titanate particles within a preferred range, since strontium titanate has sufficient hydrophobicity even in a high-temperature, high-humidity environment, and therefore the charge rise property of the toner can be improved in a short time. (Fogging after high-temperature, high-humidity printing durability evaluation) A. The fog after high-speed printing durability evaluation is less than 0.5. B. The fog after high-speed printing durability evaluation is 0.5 or more and less than 1.0. C. The fog after high-speed printing durability evaluation is 1.0 or more and less than 1.5. D. The fog after high-speed printing durability evaluation is 1.5 or more.

[0291] <Evaluation 10. Fog after high-speed printing durability evaluation under low temperature and low humidity environment> As in Evaluation 7, a durability evaluation was conducted in a low temperature and low humidity environment, in which 1,300 halftone images with a print rate of 23% and margins of 5 mm were printed, with one job consisting of two sheets.

[0292] After that, a piece of paper with a 5 cm x 5 cm sticky note attached to the center of the printing surface was placed in the cassette, and then an all-white image was printed out as the 1,301st sheet (all-white image 1).

[0293] After removing the sticky note from the all-white image 1, a white light meter TC-6DX (manufactured by Tokyo Denshoku Co., Ltd.) was used to measure the reflectance (%) of the area where the sticky note was attached and the reflectance (%) of the area where the sticky note was not attached. The difference between the two was measured and calculated as fog (%), and evaluation was performed according to the following criteria. (Fogging after high print durability evaluation in low temperature and low humidity environment) A. The fog after high-speed printing durability evaluation is less than 0.5. B. The fog after high-speed printing durability evaluation is 0.5 or more and less than 1.0. C. The fog after high-speed printing durability evaluation is 1.0 or more and less than 1.5. D. The fog after high-speed printing durability evaluation is 1.5 or more.

[0294] <Evaluation 11. Line width stability under low temperature and low humidity conditions> As in Evaluation 1, a durability evaluation was performed in a low temperature and low humidity environment, in which 30,000 sheets of horizontal line images with a print rate of 1.5% and margins of 5 mm were output as one job of two sheets.

[0295] Thereafter, as the 30,001st sheet, a horizontal line image (horizontal line image 1) having a 5 mm margin, a 170 μm wide horizontal line, and a repeated 8.33 mm wide white line was output.

[0296] The line width of the horizontal line image 1 was then measured at 15 points with a magnifying glass, and the line width difference was calculated as the difference between the maximum and minimum line widths, and evaluation was performed according to the following criteria. (Line width stability in low temperature and low humidity environments) A. The line width difference is less than 4 μm. B. The line width difference is 4 μm or more and less than 8 μm. C. The line width difference is equal to or greater than 8 μm and less than 12 μm. D. The line width difference is 12 μm or more.

[0297] <Evaluation 12. Fog after continuous low-printing durability evaluation under low temperature and low humidity environment> As in Evaluation 1, a durability evaluation was performed in a low temperature and low humidity environment, in which a total of 5,000 sheets were output with a horizontal line image having a print rate of 0.5% and a margin of 5 mm, with one job of 500 sheets.

[0298] Then, 100 sheets of paper and one sheet of paper with a 5 cm x 5 cm sticky note attached to the center of the printed surface were placed in the cassette, for a total of 101 sheets.

[0299] The print mode was then set to output 101 sheets continuously in one job, and 100 horizontal line images with a print rate of 0.5% and a margin of 5 mm were output from the 5,001st to the 5,100th sheets, and one all-white image was output on a piece of paper with a 5cm x 5cm sticky note attached to the center of the printed surface of the paper (all-white image 1) as the 5,101st sheet.

[0300] Thereafter, the sticky note from the all-white image 1 was removed, and then a white light photometer TC-6DX (manufactured by Tokyo Denshoku Co., Ltd.) was used to measure the reflectance (%) of the area where the sticky note was attached and the reflectance (%) of the area where the sticky note was not attached. The difference between the two was measured and calculated as the fog (%), and evaluation was performed according to the following criteria.

[0301] When a continuous low-temperature, low-humidity durability test is performed in a low-temperature, low-humidity environment, the toner is likely to be charged up, and the charge tends to broaden, resulting in the generation of strong negative and / or positive components. In the present invention, it is preferable to contain titanium oxide particles having a maximum fillet diameter and an aspect ratio within a preferred range, since this can improve the fogging suppression after the continuous low-temperature, low-humidity durability test. (Fogging after continuous low-printing durability evaluation in a low-temperature, low-humidity environment) A. The fog after durability evaluation is less than 0.5. B. The fog after the durability evaluation is 0.5 or more and less than 1.0. C. The fog after durability evaluation is 1.0 or more and less than 1.5. D. The fog after durability evaluation is 1.5 or more.

[0302] [Table 5-1]

[0303]

Table 5-2

Claims

1. A toner having toner particles containing a binder resin and strontium titanate particles, In a TOF-SIMS measurement of the toner particles, a fragment peak derived from a boron atom and a fragment peak derived from a boron-oxygen structure are detected, The toner is characterized in that a fatty acid is present on the surface of the strontium titanate particles.

2. 2. The toner according to claim 1, wherein the amount (by mass) of boron atoms present in the toner measured by an inductively coupled plasma mass spectrometer (ICP-MS) is 0.1 ppm or more and 100 ppm or less.

3. When the amount of boron atoms present (by mass) in the toner is X (ppm) and the content of the strontium titanate particles in the toner is Y (% by mass), X and Y satisfy the following formula: 0.10≦X / Y≦30.0 The toner according to claim 2.

4. When the amount of boron atoms present (by mass) in the toner is X (ppm) and the content of fatty acids having 12 to 30 carbon atoms present on the surfaces of the strontium titanate particles is Z (mass %), X and Z satisfy the following formula: 0.020≦X / Z≦15.0 The toner according to claim 2 or 3.

5. The toner according to claim 4, wherein Z is 0.10 or more and 5.0 or less.

6. 3. The toner according to claim 1, wherein the fatty acid has 12 or more and 30 or less carbon atoms.

7. 3. The toner according to claim 1, wherein two types of fatty acids having different carbon numbers are present on the surfaces of the strontium titanate particles, the carbon numbers of the two types of fatty acids are both 12 or more and 30 or less, and the difference in the carbon numbers of the two types of fatty acids is 2 or more.

8. 3. The toner according to claim 1, wherein the toner has an average circularity of 0.960 or more and 0.990 or less.

9. 3. The toner according to claim 1, further comprising, in addition to the strontium titanate particles, titanium oxide particles which satisfy the following (i) and (ii): (i) The maximum Feret diameter is 300 nm or more and 3000 nm or less. (ii) Aspect ratio is 5.0 or more.