JP7621871B2 - Magnetic Toner - Google Patents

Description

The present invention relates to a magnetic toner used in a recording method that utilizes electrophotography, electrostatic recording, or magnetic toner jet recording.

As copying machines and printers become more widespread, the performance required of toners is becoming more advanced. In recent years, a digital printing technology called print on demand (POD), which prints directly without a plate-making process, has been attracting attention. In the POD market, in addition to the demand for higher speed and higher image quality than ever before, there is also a demand for toners that can provide stable images for a longer period of time than ever before even when used under various environments. On the other hand, as a development method in an image forming system, a one-component development method using a developer with a simple structure is preferably used because it has few problems, a long life, and is easy to maintain.
There are several known methods for this one-component development method. One of them is the jumping development method using a magnetic toner containing magnetic iron oxide. The jumping development method is a method in which a magnetic toner charged by frictional charging with a developing sleeve is made to fly and adhere to an electrostatic latent image carrier using a developing bias, and the electrostatic charge image on the electrostatic latent image carrier is visualized as a magnetic toner image. The jumping development method has been put to practical use in many places because it is easy to control the transport of the magnetic toner and there is little internal contamination of copying machines or printers.
In magnetic toners, there are cases where images with high image quality and low gloss are required from the viewpoints of legibility of printed characters, visibility, and ease of viewing. For example, in Patent Document 1, an attempt is made to realize image output with high image quality and low gloss by using a magnetic toner in which the particle size distribution of the magnetic substance is broadened, particularly toward the small particle size side.
In addition, in the printing market, there is an increasing demand for the quality of the printed product. Depending on the media used, when the image surface of the media is rubbed against each other due to vibration during transportation of the printed matter, the toner image may be rubbed off, causing backside staining of the media. Therefore, Patent Document 2 proposes a technology for improving the abrasion resistance of the printed matter by controlling the amount of wax on the surface of the toner.
In addition, in the POD market, in order to pursue further productivity, in addition to low-temperature fixability of toner, it is required to minimize downtime due to replacement of cleaning members, etc. Therefore, Patent Document 3 proposes a technology for reducing member contamination by using a wax having an acid value.

Japanese Unexamined Patent Publication No. 7-168390 JP 2020-8818 A Patent 5815740

When attempting to increase the amount of wax on the surface of a printed material in order to improve the abrasion resistance of the printed material, as in Patent Document 2, the amount of wax adhering to the fixing member also tends to increase, making it necessary to improve the functionality of the cleaning mechanism for the fixing member.
In Patent Document 3, an attempt is made to improve the strength of the toner by interacting with the polar portion of the binder resin and the wax having an acid value, thereby improving the abrasion resistance, and further to retain the wax in the toner. However, during heat fixing, the binder resin has a low viscosity, and the wax is liquefied after melting, so the effect of suppressing bleeding is limited. In addition, in order to form a low-gloss image, the image surface needs to be uneven, but when the image surface is rubbed, stress is concentrated on the protruding parts, causing offset, so further improvement in abrasion resistance is required.
According to the conventional technology, there remains a problem in achieving both improvement in the abrasion resistance of a low-gloss output image and suppression of contamination of members by wax.
The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a toner that can suppress component contamination and provide stable images even when used for a long period of time, and that enables low-gloss image output with excellent abrasion resistance.

The present invention provides a magnetic toner having toner particles containing a binder resin, a hydrocarbon wax, magnetic iron oxide particles, and inorganic fine particles,
The acid value of the binder resin is 5 mgKOH/g or more and 30 mgKOH/g or less,
The acid value of the hydrocarbon wax is 5 mgKOH/g or more and 50 mgKOH/g or less,
the inorganic fine particles are any fine particles selected from the group consisting of magnesium carbonate fine particles, calcium carbonate fine particles, and strontium carbonate fine particles;
The magnetic toner is characterized in that the content of the inorganic fine particles is 5 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the binder resin.

The present invention provides a toner that suppresses contamination of components and provides stable images even when used over a long period of time, and enables low-gloss image output with excellent abrasion resistance.

In the present invention, the descriptions "XX or more and XX or less" and "XX to XX" indicating a numerical range mean a numerical range including the lower and upper limit endpoints, unless otherwise specified.

The inventors of the present invention have conducted extensive research with the aim of providing a toner that suppresses contamination of components, provides stable images even when used over a long period of time, and enables low-gloss image output with excellent abrasion resistance.

The inventors have found that if the toner contains a binder resin having an acid value of 5 mgKOH/g to 30 mgKOH/g and a hydrocarbon wax having an acid value of 5 mgKOH/g to 50 mgKOH/g, and further contains 5 parts by mass to 20 parts by mass of any of fine particles selected from the group consisting of magnesium carbonate fine particles, calcium carbonate fine particles, and strontium carbonate fine particles per 100 parts by mass of the binder resin, then the toner can suppress contamination of components, provide stable images, and enable the output of low-gloss images with excellent abrasion resistance, even when used for a long period of time.

The factors that lead to the effects of this invention are unclear, but are assumed to be as follows.

The toner of the present invention must contain a binder resin having an acid value of 5 mgKOH/g to 30 mgKOH/g and a hydrocarbon wax having an acid value of 5 mgKOH/g to 50 mgKOH/g. The acid groups of the hydrocarbon wax interact with the acid groups of the binder resin. Furthermore, the toner of the present invention must contain magnesium carbonate fine particles, calcium carbonate fine particles, or strontium carbonate fine particles in an amount of 5 parts by mass to 20 parts by mass per 100 parts by mass of the binder resin. Although the fine particles are salts that are poorly soluble in water, they exhibit slight deliquescence and are highly reactive with acids, so they are considered to have a high interactive property with carboxyl groups. When the inorganic fine particles are present in the toner, they interact with acid groups such as carboxyl groups of the resin or hydrocarbon wax near the surface of the fine particles.

At room temperature, the crystallized hydrocarbon wax, the fine particles, and the magnetic material are dispersed in the binder resin, and interactions occur between the binder resin and wax, between the wax and inorganic fine particles, and between the inorganic fine particles and the binder resin. This increases the internal cohesive force of the toner or the image after image formation, making it more resistant to external forces and improving wear resistance.

When the toner is heated and fixed, the hydrocarbon wax, which increases the internal cohesion through interaction, dissolves, causing the interaction site to suddenly become less viscous. For this reason, it is believed that even when the internal cohesion of the toner is increased, images can be formed without deteriorating low-temperature fixability. When inorganic fine particles are present in the toner, the proportion of the binder resin that deforms during fixing is relatively reduced, making it easier to obtain low-gloss images.

In addition, the solid components of the magnetic material and inorganic fine particles dispersed inside the toner are not exposed to the surface before and after heat fixing, and the dispersed state in the toner is generally maintained even after image formation. Therefore, it is believed that the inorganic fine particles present inside the toner or image act as anchors that prevent the wax from eluting to the outside by interacting with the wax via acid groups, thereby preventing contamination of components.

However, if the acid value of the binder resin is less than 5 mgKOH/g, the interactions between the binder resin and wax, and between the inorganic fine particles and the binder resin are insufficient, and it is not possible to improve abrasion resistance. If the acid value of the binder resin exceeds 30 mgKOH/g, the interaction between the binder resin and wax becomes dominant over the interaction between the wax and the inorganic fine particles, weakening the anchoring role of the inorganic fine particles, and the polarity difference between the wax and the binder resin becomes large, promoting the elution of the wax, making it impossible to suppress contamination of components.

In addition, if the acid value of the hydrocarbon wax is less than 5 mgKOH/g, the interaction between the binder resin and the wax and the wax and the inorganic fine particles is insufficient, and the abrasion resistance cannot be improved. If the acid value of the hydrocarbon wax exceeds 50 mgKOH/g, the internal cohesive force of the toner cannot be increased due to too many polar group sites that have a high affinity with the resin and too few crystalline sites derived from the wax, and therefore the abrasion resistance cannot be improved.

If the content of the inorganic fine particles is less than 5 parts by mass per 100 parts by mass of the binder resin, the interaction between the wax and the inorganic fine particles and between the inorganic fine particles and the binder resin is not sufficient, and furthermore, the effect of suppressing the elution of the wax cannot be sufficiently obtained. Also, if the content of the inorganic fine particles exceeds 20 parts by mass per 100 parts by mass of the binder resin, the interaction between the inorganic fine particles and the binder resin becomes too excessive, making it impossible to maintain low-temperature fixability, and also, since the amount of deformation of the toner during fixing becomes small, the unevenness of the image surface becomes too large, making it impossible to improve abrasion resistance.

The hydrocarbon wax having an acid value used in the present invention will be described in detail below.

The hydrocarbon wax having an acid value according to the present invention has a main skeleton of a hydrocarbon chain consisting of polyolefins such as polyethylene and polypropylene, paraffin, microcrystalline wax, etc., and is generally referred to as a hydrocarbon wax, which has been modified to introduce carboxyl groups. Examples of the modified hydrocarbon waxes are described below, including their manufacturing methods. For example, a manufacturing method can be mentioned in which ethylene is polymerized using a Ziegler catalyst, and after the polymerization is completed, ethylene is oxidized to produce an alkoxide of the catalyst metal and polyethylene, which is then hydrolyzed.

In addition, there is a manufacturing method in which a hydrocarbon wax is oxidized in the liquid phase with a molecular oxygen-containing gas in the presence of boric acid and boric acid anhydride. As a catalyst, a mixture of boric acid and boric acid anhydride, metaboric acid, and pyroboric acid can also be used. In addition, boron oxygen acids, phosphorus oxygen acids, and sulfur oxygen acids can be used. Specifically, boric acid, nitric acid, phosphoric acid, and sulfuric acid can be used. As the molecular oxygen-containing gas to be blown into the reaction system, a wide range of oxygen, air, or a mixture of these diluted with an inert gas can be used. The liquid phase oxidation reaction is usually carried out without using a solvent, while the raw material hydrocarbon wax is in a molten state. The reaction temperature is 120 to 280°C, preferably 150 to 250°C. The reaction time is preferably 1 to 15 hours.

The acid value of the wax having an acid value of the present invention is 5 mgKOH/g or more and 50 mgKOH/g or less, and preferably 20 mgKOH/g or more and 40 mgKOH/g or less. When the acid value is within the above-mentioned range, it is possible to achieve both suppression of component contamination and abrasion resistance of the printed matter.

The hydrocarbon wax having an acid value used in the present invention preferably has a maximum endothermic peak temperature of 80°C or more and 140°C or less when the crystal structure consisting of hydrocarbon chains melts as measured by a differential scanning calorimeter (DSC). More preferably, it is 90°C or more and 130°C or less. If the maximum endothermic peak temperature is within the above-mentioned range, it is preferable from the viewpoint of suppressing contamination of components and abrasion resistance of printed matter.

The content of the hydrocarbon wax having an acid value of the present invention is preferably 2.0 parts by mass or more and 20.0 parts by mass or less per 100 parts by mass of the binder resin. More preferably, it is 5.0 parts by mass or more and 15.0 parts by mass or less. If the content of the wax having an acid value is within the above range, it is preferable because it is possible to achieve a higher level of both suppression of component contamination and abrasion resistance of the printed matter.

The inorganic fine particles used in the present invention are any fine particles selected from the group consisting of magnesium carbonate fine particles, calcium carbonate fine particles, and strontium carbonate fine particles. Among them, calcium carbonate fine particles are preferred from the viewpoint that the hydrophilicity of the particle surface is appropriately low, so that it is more likely to approach the hydrocarbon wax, and that it is more likely to cause an appropriate interaction with the acid group, so that the elution of the hydrocarbon wax is more easily suppressed. Furthermore, calcium carbonate fine particles whose surface has been treated with a fatty acid such as stearic acid are more preferred.

The inorganic fine particles in the present invention are not particularly limited, and commercially available products can be used. In addition, those obtained by any manufacturing method can be used.

As examples of calcium carbonate, both natural calcium carbonate (heavy calcium carbonate) and synthetic calcium carbonate (light calcium carbonate or colloidal calcium carbonate) can be used. The former is produced by mechanically crushing and classifying limestone raw ore to obtain the desired particle size. The latter is produced by first producing calcium oxide (quicklime) by co-firing limestone raw ore with coke or petroleum fuel (heavy oil, light oil), natural gas, LPG, etc., which is then reacted with water to produce calcium hydroxide (slaked lime), and the carbon dioxide gas generated during firing is reacted with the calcium hydroxide to obtain the desired particle size and shape.

The particle size of the inorganic fine particles used in the present invention is preferably 800 nm or less, more preferably 600 nm or less, from the viewpoint of being less likely to be broken when subjected to external force and having good abrasion resistance. In addition, if aggregates are formed inside the toner, the particle interface within the aggregated particles is likely to become an active surface when subjected to external force, so from the viewpoint of being less likely to form aggregates inside the toner, the particle size is preferably 50 nm or more, more preferably 100 nm or more.

The binder resin used in the present invention can be a resin generally used in toners, so long as it has an acid value of 5 mgKOH/g or more and 30 mgKOH/g or less, and among these, polyester resins are preferable from the viewpoint of low-temperature fixability. In addition, hybrid resins in which units derived from polyester are combined with units derived from other resins can also be used, and examples of units derived from other resins include vinyl resins, polyurethane resins, epoxy resins, and phenolic resins.

The components constituting the polyester resin used in the present invention are described in detail below. Note that the following components can be used alone or in combination depending on the type and application.

The divalent acid components constituting the polyester resin include the following dicarboxylic acids or derivatives thereof: benzene dicarboxylic acids such as phthalic acid, terephthalic acid, isophthalic acid, and phthalic anhydride, or their anhydrides or lower alkyl esters; alkyl dicarboxylic acids such as succinic acid, adipic acid, sebacic acid, and azelaic acid, or their anhydrides or lower alkyl esters; alkenyl succinic acids or alkyl succinic acids having 1 to 50 carbon atoms, or their anhydrides or lower alkyl esters; unsaturated dicarboxylic acids such as fumaric acid, maleic acid, citraconic acid, and itaconic acid, or their anhydrides or lower alkyl esters.

On the other hand, examples of the dihydric alcohol components constituting the polyester resin include the following: ethylene glycol, polyethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, diethylene glycol, triethylene glycol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, 2-methyl-1,3-propanediol, 2-ethyl-1,3-hexanediol, 1,4-cyclohexanedimethanol (CHDM), hydrogenated bisphenol A, bisphenol and its derivatives represented by the following general formula (1), and diols represented by the following general formula (2).

（式中、Ｒは、エチレンまたはプロピレン基であり、ｘ、ｙは、それぞれ０以上の整数であり、かつ、ｘ＋ｙの平均値は０乃至１０である。）

(In the formula, R is an ethylene or propylene group, x and y are each an integer of 0 or more, and the average value of x+y is 0 to 10.)

The polyester resin components used in the present invention may contain, in addition to the divalent carboxylic acid compounds and divalent alcohol compounds described above, trivalent or higher carboxylic acid compounds and trivalent or higher alcohol compounds as components.

Examples of trivalent or higher carboxylic acid compounds include, but are not limited to, trimellitic acid, trimellitic anhydride, pyromellitic acid, etc. Examples of trivalent or higher alcohol compounds include trimethylolpropane, pentaerythritol, glycerin, etc.

Furthermore, from the viewpoint of more pronounced interaction with a hydrocarbon wax having an acid value and improved component contamination prevention and abrasion resistance, it is preferable that the polyester resin of the present invention is condensed with at least one aliphatic compound selected from the group consisting of aliphatic monocarboxylic acids and aliphatic monoalcohols having a specific number of carbon atoms.

The aliphatic compound introduced into the polyester resin is preferably at least one aliphatic compound selected from the group consisting of aliphatic monocarboxylic acids and aliphatic monoalcohols having 30 to 102 carbon atoms. Here, the carbon number refers to the average carbon number of the aliphatic compound. The carbon number is more preferably 32 to 80, and particularly preferably 32 to 60. It is preferable that the carbon number of the aliphatic compound is within the above range because the affinity between the binder resin and the wax is appropriately maintained.

The aliphatic compound is preferably monovalent, and by being monovalent, the aliphatic compound is condensed to the end of the polyester unit. The carbon chain derived from the aliphatic compound condensed to the end has affinity with the wax having an acid value, and an interaction is effectively expressed.

The amount of the aliphatic compound added is preferably 0.10% by mass or more and 10% by mass or less, and more preferably 1.0% by mass or more and 5.0% by mass or less, relative to 100% by mass of the total mass of the monomers constituting the polyester resin into which the aliphatic compound is condensed. By adding an amount of the aliphatic compound within the above range, it is possible to effectively express an interaction with a wax having an acid value.

The aliphatic compound used in the present invention is not particularly limited as long as it is an aliphatic monocarboxylic acid or an aliphatic monoalcohol having a specific chain length. For example, any of primary, secondary, and tertiary aliphatic compounds can be used. Specific examples of aliphatic monocarboxylic acids include melissic acid, lactoseric acid, tetracontanoic acid, and pentacontanoic acid.

Examples of aliphatic monoalcohols include melissyl alcohol and tetracontanol.

There is no particular limitation on the method for condensing an aliphatic compound to the terminal of a polyester resin. In a preferred embodiment, when producing a polyester resin, an aliphatic compound is added simultaneously to the monomers that make up the polyester resin, and condensation polymerization is carried out. This allows the aliphatic compound to be condensed more uniformly to the terminal of the polyester resin.

In the present invention, the method for producing the polyester resin is not particularly limited, and known methods can be used. For example, the above-mentioned divalent carboxylic acid compound and divalent alcohol compound are charged simultaneously with an aliphatic monocarboxylic acid or an aliphatic monoalcohol, and polymerized through an esterification reaction or an ester exchange reaction and a condensation reaction to produce a polyester resin. The polymerization temperature when producing the polyester resin is not particularly limited, but is preferably in the range of 180°C to 290°C. For the polymerization of the polyester unit, for example, a polymerization catalyst such as a titanium-based catalyst, a tin-based catalyst, zinc acetate, antimony trioxide, or germanium dioxide can be used. In particular, it is more preferable that the binder resin in the present invention contains a polyester unit polymerized using a titanium-based catalyst. The use of a titanium-based catalyst improves the charging uniformity in the toner.

Specific examples of titanium compounds include titanium diisopropylate bistriethanol aminate [Ti( _C6H14O3N ) ₂ ( _C3H7O ) ₂ ], titanium diisopropylate bisdiethanol aminate [Ti( _{C4H10O2N ) 2} ( _C3H7O ) ₂ ], titanium dipentylate bistriethanol aminate _[ Ti( _C6H14O3N ) ₂ ( _C5H11O ) ₂ ] _, titanium _{diethylate bistriethanol aminate [} Ti( _{C6H14O3N)2 ( C2H5O} ) ₂ ], titanium dihydroxyoctylate bistriethanol aminate [ _Ti ( _C6H14O3N ) _{2 ( C2H5O} ) _{2 ]} , titanium _{diisopropyl ...} ( _OHC8H16O ) ₂ ], titanium distearate bis(triethanol aminate _{) [} Ti _{( C6H14O3N} ) _{2 ( C18H37O} ) ₂ ] _, titanium triisopropylate triethanol aminate _[ Ti(C6H14O3N) ₁ ( _C3H7O ) ₃ ], titanium monopropylate _{tris(triethanol aminate) [Ti(C6H14O3N)3(C3H7O ) 1 ] , etc.} Among these, titanium diisopropylate bis(triethanol aminate ₎ , titanium diisopropylate bis(diethanol aminate) and titanium dipentylate _bis (triethanol aminate) _are preferred.

Specific examples of other titanium catalysts include tetra-n-butyl titanate [Ti(C ₄ H ₉ O) ₄ ], tetrapropyl titanate [Ti(C ₃ H ₇ O) ₄ ], tetrastearyl titanate [Ti(C ₁₈ H ₃₇ O) ₄ ], tetramyristyl titanate [Ti(C ₁₄ H ₂₉ O) ₄ ], tetraoctyl titanate [Ti(C ₈ H ₁₇ O) ₄ ], dioctyl dihydroxyoctyl titanate [Ti(C ₈ H ₁₇ O) ₂ (OHC ₈ H ₁₆ O) ₂ ], dimyristyl dioctyl titanate [Ti(C ₁₄ H ₂₉ O) ₂ (C ₈ H ₁₇ O) ₂ ], and the like. Among these, tetrastearyl titanate, tetramyristyl titanate, tetraoctyl titanate and dioctyldihydroxyoctyl titanate are preferred, which can be obtained, for example, by reacting a titanium halide with the corresponding alcohol.

More preferably, the titanium compound contains an aromatic carboxylic acid titanium compound. The aromatic carboxylic acid titanium compound is preferably obtained by reacting an aromatic carboxylic acid with a titanium alkoxide. The aromatic carboxylic acid is preferably a divalent or higher aromatic carboxylic acid (i.e., an aromatic carboxylic acid having two or more carboxyl groups) and/or an aromatic oxycarboxylic acid. Examples of the divalent or higher aromatic carboxylic acid include dicarboxylic acids such as phthalic acid, isophthalic acid, and terephthalic acid, or their anhydrides, and polyvalent carboxylic acids such as trimellitic acid, benzophenone dicarboxylic acid, benzophenone tetracarboxylic acid, naphthalene dicarboxylic acid, and naphthalene tetracarboxylic acid, or their anhydrides and esters. Examples of the aromatic oxycarboxylic acid include salicylic acid, m-oxybenzoic acid, p-oxycarboxylic acid, gallic acid, mandelic acid, and tropic acid. Among these, it is more preferable to use a divalent or higher carboxylic acid as the aromatic carboxylic acid, and in particular, it is preferable to use isophthalic acid, terephthalic acid, trimellitic acid, or naphthalene dicarboxylic acid.

The magnetic toner of the present invention preferably contains magnetic iron oxide particles in an amount of 70 parts by mass or more and 140 parts by mass or less per 100 parts by mass of binder resin, from the viewpoint of achieving good dot reproducibility by allowing the magnetic brush of the magnetic toner to stand appropriately on the developing sleeve.

The number-average particle diameter of the magnetic iron oxide particles is preferably 0.10 μm or more and 0.30 μm or less, and more preferably 0.10 μm or more and 0.18 μm or less. When the number-average particle diameter of the magnetic iron oxide particles is in the above range, the dispersibility of the magnetic iron oxide particles in the toner is improved.

The core particles of the magnetic iron oxide particles may contain a specific type of metal element, and a coating layer containing the specific type of metal element may be formed on the surface of the core particles. For example, in order to appropriately control the resistance of the magnetic iron oxide particles, the core particles of the magnetic iron oxide particles may contain silicon or zinc, and a coating layer containing silicon, aluminum, or zinc may be formed on the surface of the magnetic iron oxide particles.

The inclusion of silicon in the magnetic iron oxide particles makes it easier to obtain magnetic iron oxide particles with excellent blackness, and also slightly increases the hydrophilicity of the surface layer of the magnetic iron oxide particles, making them more compatible with the hydrophilic parts of the resin, which is thought to suppress breakage at the magnetic iron oxide particle-binder resin interface. In addition, during toner production using the melt-kneading pulverization method, the hydrophilic parts derived from silicon have a high affinity with the inorganic fine particles of the present invention, making it easier for the inorganic fine particles to enter the grain boundaries between the magnetic iron oxide particles, and the wax and binder resin that interact with the inorganic fine particles also easily enter the grain boundaries, improving the dispersibility of the magnetic iron oxide particles and inorganic fine particles and improving abrasion resistance.

The amount of silicon contained in the entire magnetic iron oxide particle is preferably 0.2 atomic % or more and 3.0 atomic % or less as silicon element based on the iron element in the magnetic iron oxide particle, and the amount of silicon contained in the surface or coating layer of the magnetic iron oxide particle is preferably 0.1 atomic % or more and 2.0 atomic % or less as silicon element based on the iron element in the magnetic iron oxide particle. The method for measuring the total silicon amount (total Si amount) and surface silicon amount (surface Si amount) will be described later.

A preferred manufacturing method for obtaining the magnetic iron oxide particles of the present invention is described below, but is not limited thereto.

The magnetic iron oxide particles of the present invention can be obtained by carrying out a first reaction step to form magnetic iron oxide seed particles, a second reaction step to grow the seed particles to almost the end point of the reaction by adjusting the pH after the first reaction step, and a third reaction step to obtain the desired magnetic iron oxide particles by adjusting the pH again after the second reaction step. Next, each reaction step for obtaining magnetic iron oxide particles will be described in detail, but is not limited thereto.

<First reaction step>
The aqueous ferrous salt solution is reacted with an aqueous alkali hydroxide solution in an amount of 0.90 to 1.00 equivalent to the ferrous salt in the aqueous ferrous salt solution. The aqueous ferrous salt solution may contain other elements. A water-soluble silicate is added to the obtained ferrous salt solution containing the ferrous hydroxide colloid in an amount of 0.05 to 1.00 atomic % in terms of Si relative to Fe. Note that 0.05 to 1.00 atomic % in terms of Si relative to Fe means that the amount of Si atoms is 0.05 to 1.00 when the amount of Fe atoms contained in the solution is taken as 100. Next, the pH of the ferrous salt reaction solution containing the ferrous hydroxide colloid is adjusted to 8.0 to 9.0. Next, an oxygen-containing gas is passed through the solution while heating it to a temperature range of 70 to 100°C to carry out an oxidation reaction until the oxidation reaction rate of iron reaches 7 to 12%, thereby producing magnetite nucleus crystal particles.

<Second reaction step>
An aqueous solution of an alkali hydroxide such as sodium hydroxide is added to the ferrous salt reaction solution containing the obtained magnetite nucleus particles and ferrous hydroxide colloid in an amount of 1.01 to 1.50 equivalents, and the pH is readjusted to 8.5 or higher, more preferably 9.5 or higher. Then, an oxygen-containing gas is passed through the reaction solution while heating it to a temperature range of 70 to 100° C. to carry out an oxidation reaction.

<Third reaction step>
After the second reaction step is completed, the temperature of the suspension containing the magnetic iron oxide particles is adjusted to 80° C. or higher, preferably 90° C. or higher, and the pH is adjusted to 6.0 or lower to complete the reaction.

In addition, when forming a compound containing Si on the particle surface of magnetic iron oxide particles, the following operation is carried out.

After the second reaction step is completed, a water-soluble silicate is added to the suspension containing the magnetic iron oxide particles. The temperature of the suspension is then increased to 80°C or higher, preferably 90°C or higher, and the pH is adjusted to a range of 5 to 9 to cause a compound containing Si and/or Al to precipitate and deposit on the surface of the magnetic iron oxide particles, and the pH is then adjusted to 6.0 or lower to terminate the reaction. At this time, when the water-soluble silicate is added, an aqueous solution containing other elements may be added at the same time.

It can also be obtained by subjecting the magnetic iron oxide particles after the third reaction step to mechanochemical treatment or heat treatment to fix a Si-containing compound to the magnetic iron oxide surface.

The magnetic iron oxide particles obtained may be washed with water using a media-less disperser, but it is preferable to use a filter press machine to make it easier to adjust the amount of sulfur and sodium elements present on the surface. By changing the number of washes with the filter press machine and the amount of water used for washing (strength of washing with the filter press machine), the electrical conductivity of the liquid when washed with water changes. By measuring the electrical conductivity at this time, the amount of sulfur and sodium present on the surface can be adjusted.

[Other ingredients]
The toner of the present invention can use a charge control agent to stabilize its charging characteristics. The charge control agent varies depending on the type and the physical properties of other toner particle constituent materials, but in general, it is preferably contained in the toner in an amount of 0.10 parts by mass or more and 10.0 parts by mass or less, and more preferably 0.10 parts by mass or more and 5.0 parts by mass or less, per 100.0 parts by mass of binder resin. As such a charge control agent, one or more of various types can be used depending on the type and application of the toner.

Examples of charge control agents that control the toner to be negatively charged include the following: organic metal complexes (monoazo metal complexes; acetylacetone metal complexes); metal complexes or metal salts of aromatic hydroxycarboxylic acids or aromatic dicarboxylic acids. Other examples of charge control agents that control the toner to be negatively charged include aromatic mono- and polycarboxylic acids and their metal salts or anhydrides; esters, phenol derivatives such as bisphenols, and the like. Among these, monoazo metal complexes or metal salts that provide stable charging characteristics are particularly preferred. Charge control resins can also be used, and can be used in combination with the above-mentioned charge control agents.

Charge control resins include sulfur-containing polymers and sulfur-containing copolymers produced by the methods described below.

Sulfur-containing polymers and copolymers can be produced by various polymerization methods, but the preferred polymerization method is bulk polymerization or solution polymerization, which uses no polymerization solvent or a small amount of polymerization solvent. Solvents such as methanol, ethanol, propanol, 2-propanol, propanone, 2-butanone, and dioxane can be used as reaction solvents. When using a mixture of these solvents, it is preferable to mix methanol, 2-butanone, and 2-propanol in a mass ratio of 2:1:1 to 1:5:5.

Polymerization initiators include t-butylperoxy-2-ethylhexanoate, cumyl perpivalate, t-butylperoxylaurate, benzoyl peroxide, lauroyl peroxide, octanoyl peroxide, di-t-butyl peroxide, t-butylcumyl peroxide, dicumyl peroxide, 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(4-methoxy-2,4-di methylvaleronitrile), 4,4'-azobis-4-cyanovaleric acid, 1,1'-azobis(cyclohexane-1-carbonitrile), 1,1'-di(t-butylperoxy)3-methylcyclohexane, 1,1-bis(t-butylperoxy)3,3,5-trimethylcyclohexane, 1,1'-di(t-butylperoxy)3,3,5-trimethylcyclohexane, 1,1-bis(t-butylperoxy)cyclohexane, 1,4-bis(t-butylperoxycarbonyl)cyclohexane, 2,2-bis(t -butylperoxy)octane, n-butyl-4,4-bis(t-butylperoxy)valerate, 2,2-bis(t-butylperoxy)butane, 1,3-bis(t-butylperoxy-isopropyl)benzene, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, di-t-butyldiperoxyisophthalate, 2,2-bis(4,4-di-t-butylperoxycyclopentane) Examples of suitable tertiary esters include 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, diethylene glycol-bis(t-butylperoxycarbonate), di-t-butylperoxytrimethyladipate, tris(t-butylperoxy)triazine, and vinyltris(t-butylperoxy)silane. These may be used alone or in combination. It is preferable to use 2,2'-azobis(2-methylbutyronitrile), 4,4'-azobis-4-cyanovaleric acid, 1,1'-di(t-butylperoxy)3-methylcyclohexane, and 1,1-bis(t-butylperoxy)3,3,5-trimethylcyclohexane alone or in combination. These polymerization initiators are preferred because they can adjust the molecular weight of the sulfur-containing polymer or copolymer to a range suitable for the toner of the present invention, reduce unreacted monomers, and increase the polymerization addition rate.

On the other hand, examples of charge control agents that control the toner to be positively charged include the following: Nigrosine and modified products of fatty acid metal salts; quaternary ammonium salts such as tributylbenzylammonium-1-hydroxy-4-naphthosulfonate and tetrabutylammonium tetrafluoroborate, and their analogues; onium salts such as phosphonium salts and their lake pigments; triphenylmethane dyes and their lake pigments (lake forming agents include phosphotungstic acid, phosphomolybdic acid, phosphotungstomolybdic acid, tannic acid, lauric acid, gallic acid, ferricyanide compounds, etc.); metal salts of higher fatty acids. In the present invention, these can be used alone or in combination of two or more. Among these, charge control agents such as nigrosine compounds and quaternary ammonium salts are preferred.

In the toner of the present invention, it is preferable to use a flowability improver having a high ability to impart flowability to the toner surface and a smaller number average particle diameter of the primary particles. Any flowability improver can be used as long as it can increase the flowability of the toner by adding it to the outside of the toner. For example, the following can be mentioned. Fluorine-based resin powder such as vinylidene fluoride fine powder and polytetrafluoroethylene fine powder; silica fine powder such as silica fine powder produced by a wet method and silica fine powder produced by a dry method, and treated silica fine powder obtained by surface-treating the silica fine powder with a treating agent such as a silane coupling agent, a titanium coupling agent, or silicone oil; titanium oxide fine powder; alumina fine powder, treated titanium oxide fine powder, and treated alumina oxide fine powder can be mentioned. The flowability improver preferably has a specific surface area of 30 ^m2 /g or more, more preferably 50 ^m2 /g or more and 300 ^m2 /g or less, as measured by the BET method using nitrogen adsorption. The flowability improver is added in an amount of preferably 0.01 parts by mass or more and 8.0 parts by mass or less, and more preferably 0.1 parts by mass or more and 4.0 parts by mass or less, based on 100 parts by mass of the toner.

If necessary, an external additive having electrical conductivity may be added to the toner of the present invention. An example of an external additive having electrical conductivity is carbon black.

Other external additives may be added to the toner of the present invention as necessary. For example, a charge assistant, a conductivity imparting agent, a caking inhibitor, a release agent for use in heat roller fixing, or resin or inorganic fine particles that act as an abrasive.

Examples of abrasives include cerium oxide powder, silicon carbide powder, and strontium titanate powder. These external additives can be thoroughly mixed using a mixer such as a Henschel mixer to obtain the toner of the present invention.

The glass transition temperature (Tg) of the toner of the present invention is preferably 45°C or higher from the viewpoint of storage stability. In addition, from the viewpoint of low-temperature fixability, the Tg is preferably 75°C or lower. More preferably, the Tg is 50°C or higher and 65°C or lower. In addition, the softening point of the toner of the present invention is preferably 95°C or higher and 130°C or lower. More preferably, the softening point is 100°C or higher and 125°C or lower. When the Tg and softening point are within the above-mentioned ranges, it is possible to prevent the wax of the present invention from becoming excessive on the image surface during image formation, and it is possible to achieve both low-temperature fixability and abrasion resistance of the printed matter.

[Toner manufacturing method]
A specific example of the pulverization method for producing the toner of the present invention will be described below, but the present invention is not limited to this.

For example, binder resin, hydrocarbon wax, magnetic iron oxide particles, inorganic fine particles, and other additives, if necessary, are thoroughly mixed using a mixer such as a Henschel mixer or a ball mill, then melted and kneaded using a thermal kneader such as a heated roll, kneader, or extruder, cooled and solidified, and then pulverized and classified to obtain toner (toner particles). Furthermore, if necessary, silica fine particles or the like can be thoroughly mixed with the toner using a mixer such as a Henschel mixer to produce a toner with a flowability improver added.

Examples of mixers include the following: Henschel Mixer (manufactured by Mitsui Mining Co., Ltd.); Super Mixer (manufactured by Kawata Co., Ltd.); Ribocone (manufactured by Okawara Manufacturing Co., Ltd.); Nauta Mixer, Turbulizer, Cyclomix (manufactured by Hosokawa Micron Co., Ltd.); Spiral Pin Mixer (manufactured by Pacific Machinery Co., Ltd.); Loedige Mixer (manufactured by Matsubo Co., Ltd.).

Examples of kneading machines include the following: KRC kneader (manufactured by Kurimoto Iron Works); Buss-Co kneader (manufactured by Buss); TEM type extruder (manufactured by Toshiba Machine); TEX twin-screw kneader (manufactured by Japan Steel Works); PCM kneader (manufactured by Ikegai Iron Works); three-roll mill, mixing roll mill, kneader (manufactured by Inoue Seisakusho); Kneadex (manufactured by Mitsui Mining Co., Ltd.); MS-type pressure kneader, Niderruder (manufactured by Moriyama Seisakusho); Banbury mixer (manufactured by Kobe Steel, Ltd.).

Examples of pulverizers include the following: Counter Jet Mill, Micron Jet, Innomizer (manufactured by Hosokawa Micron Corporation); IDS type mill, PJM jet pulverizer (manufactured by Nippon Pneumatic Mfg. Co., Ltd.); Cross Jet Mill (manufactured by Kurimoto Iron Works); Urmax (manufactured by Nisso Engineering Co., Ltd.); SK Jet-O-Mill (manufactured by Seishin Enterprise Co., Ltd.); Kryptron (manufactured by Kawasaki Heavy Industries, Ltd.); Turbo Mill (manufactured by Turbo Industrial Co., Ltd.); Super Rotor (manufactured by Nisshin Engineering Co., Ltd.).

Classifiers include the following: Classeal, Micron Classifier, and Spedic Classifier (manufactured by Seishin Enterprises); Turbo Classifier (manufactured by Nisshin Engineering); Micron Separator, Turboplex (ATP), TSP Separator, and TTSP Separator (manufactured by Hosokawa Micron); Elbow Jet (manufactured by Nittetsu Mining Co., Ltd.), Dispersion Separator (manufactured by Nippon Pneumatic Industry Co., Ltd.); and YM Microcut (manufactured by Yaskawa Shoji Co., Ltd.).

Examples of sieving devices used to sift coarse particles include the following: Ultrasonic (manufactured by Koei Sangyo Co., Ltd.); Resonaseave, Gyrosifter (Tokuju Kogyo Co., Ltd.); Vibrasonic System (manufactured by Dalton Co., Ltd.); Soniclean (manufactured by Shinto Kogyo Co., Ltd.); Turbo Screener (manufactured by Turbo Industry Co., Ltd.); Microsifter (manufactured by Makino Sangyo Co., Ltd.); and circular vibrating sieve.

[Measurement methods for each physical property]
Next, the methods for measuring the various physical properties according to the present invention will be described.

<1> Quantitative method for total and surface Si content in magnetic iron oxide particles

The amount of Si in the magnetic iron oxide is measured using a fluorescent X-ray analyzer RIX-2100 (manufactured by Rigaku Electric Industry Co., Ltd.) and calculated as an elemental conversion value for the Fe contained in the magnetic iron oxide.

Next, the surface Si amount of the magnetic iron oxide particles is calculated by suspending 3 g of magnetic iron oxide particles in 300 mL of 3 mol/L aqueous sodium hydroxide solution, stirring the suspension at 50°C for at least 30 minutes, filtering and drying the suspension, measuring the amount of Si in the magnetic iron oxide obtained, and taking the difference from the total amount of Si before the suspension treatment with the alkali as the amount of Si on the surface of the magnetic iron oxide, and calculating the value calculated in elemental terms for the Fe contained in the magnetic iron oxide.

<2> Acid value of wax 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 is measured in accordance with JIS K 0070-1992 as follows.

(1) Preparation of Reagents 1.0 g of phenolphthalein was dissolved in 90 mL of ethyl alcohol (95% by volume), and ion-exchanged water was added to make 100 mL to obtain a phenolphthalein solution.

Dissolve 7 g of special grade potassium hydroxide in 5 mL of water and add ethyl alcohol (95% by volume) to make 1 L. Place in an alkali-resistant container to avoid contact with carbon dioxide, etc., leave for 3 days, then filter to obtain potassium hydroxide solution. Store the resulting potassium hydroxide solution in an alkali-resistant container. The factor of the potassium hydroxide solution is determined by placing 25 mL of 0.1 mol/L hydrochloric acid in an Erlenmeyer flask, adding several drops of the phenolphthalein solution, and titrating with the potassium hydroxide solution, from the amount of potassium hydroxide solution required for neutralization. The 0.1 mol/L hydrochloric acid used is prepared in accordance with JIS K 8001-1998.

(2) Procedure (A) Main test 2.0 g of the crushed sample is accurately weighed into a 200 mL Erlenmeyer flask, and 100 mL of a mixed solution of toluene/ethanol (2:1) is added and dissolved over 5 hours. Next, several drops of the above phenolphthalein solution are added as an indicator, and titration is performed using the above potassium hydroxide solution. The end point of the titration is when the light red color of the indicator continues for about 30 seconds.

(B) Blank Test: A titration is carried out in the same manner as above, except that no sample is used (i.e., only a mixed solution of toluene/ethanol (2:1) is used).

(3) The obtained result is substituted into the following formula to calculate the acid value.
A=[(CB)×f×5.61]/S
Here, A is the acid value (mg KOH/g), B is the amount of potassium hydroxide solution added for the blank test (mL), C is the amount of potassium hydroxide solution added for the main test (mL), f is the factor of the potassium hydroxide solution, and S is the mass of the sample (g).

<3> Maximum endothermic peak temperature of wax The maximum endothermic peak temperature is measured using a differential scanning calorimeter “Q2000” (manufactured by TA Instruments) in accordance with ASTM D3418-82.

The temperature of the device's detection section is corrected using the melting points of indium and zinc, and the heat of fusion of indium is used to correct the amount of heat.
Specifically, weigh out approximately 3 mg of sample and place it in an aluminum pan. Using an empty aluminum pan as a reference, measure under the following conditions.
Heating rate: 10° C./min
Measurement start temperature: 30℃
Measurement end temperature: 180°C

Measurements are performed in the measurement range of 30 to 180°C at a heating rate of 10°C/min. The temperature is raised to 180°C once and held for 10 minutes, then cooled to 30°C, and then raised again. During this second heating process, the peak top temperature of the wax is calculated from the temperature-endothermic curve in the range of 30°C to 180°C.

<4> Softening point of toner and resin In the present invention, the "melting temperature in the 1/2 method" described in the manual attached to the "Flow characteristic evaluation device Flow Tester CFT-500D" is used as the softening point. The melting temperature in the 1/2 method is calculated as follows. First, 1/2 of the difference between the piston descent amount Smax at the time when the outflow ends and the piston descent amount Smin at the time when the outflow starts is calculated (this is designated as X; X=(Smax-Smin)/2). Then, the temperature on the flow curve when the piston descent amount on the flow curve is the sum of X and Smin is the softening point Tm in the 1/2 method.

The measurement sample is a cylindrical sample of about 8 mm in diameter, compressed at about 10 MPa for about 60 seconds using a tablet compression machine (e.g., NT-100H, manufactured by NPA Systems) at 25°C.

The measurement conditions for CFT-500D are as follows.
Test mode: Heating method Starting temperature: 50°C
Reached temperature: 200°C
Measurement interval: 1.0°C
Heating rate: 4.0° C./min
Piston cross-sectional area: 1.000 ^cm2
Test load (piston load): 10.0 kgf (0.9807 MPa)
Preheat time: 300 seconds Die hole diameter: 1.0 mm
Die length: 1.0 mm

<5> Measurement of Weight Average Particle Size (D4) of Toner The weight average particle size (D4) of the toner is measured with a precision particle size distribution measuring device using a capillary electrical resistance method equipped with a 100 μm aperture tube, “Coulter Counter Multisizer 3” (registered trademark, manufactured by Beckman Coulter, Inc.), and the accompanying dedicated software for setting measurement conditions and analyzing measurement data, “Beckman Coulter Multisizer 3 Version 3.51” (manufactured by Beckman Coulter, Inc.), with an effective measurement channel count of 25,000, and the measurement data is analyzed to calculate the weight average particle size (D4).

The electrolyte solution used for the measurements is one in which special grade sodium chloride is dissolved in ion-exchanged water to give a concentration of approximately 1% by mass, for example "ISOTON II" (manufactured by Beckman Coulter).

Before performing measurements and analysis, configure the dedicated software as follows:

In the "Change Standard Measurement Method (SOM) screen" of the dedicated software, set the total count number in 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" (manufactured by Beckman Coulter). Press the threshold/noise level measurement button to automatically set the threshold and noise level. Also, set the current to 1600 μA, the gain to 2, the electrolyte to ISOTON II, and check the aperture tube flush after measurement.

In the dedicated software's "Pulse to particle size conversion setting screen," set the bin interval to logarithmic particle size, the particle size bin to 256 particle size bins, and the particle size range to 2 μm to 60 μm.

The specific measurement method is as follows.
(1) Pour about 200 ml of the electrolyte solution into a 250 ml round-bottom glass beaker for use with the Multisizer 3, set it on the sample stand, and stir the stirrer rod counterclockwise at 24 revolutions per second. Then, remove dirt and air bubbles from inside the aperture tube using the "aperture flush" function of the analysis software.
(2) Approximately 30 ml of the aqueous electrolyte solution is placed in a 100 ml flat-bottom glass beaker, and 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, having a pH of 7, manufactured by Wako Pure Chemical Industries, Ltd.) three times by weight with ion-exchanged water is added as a dispersant.
(3) A predetermined amount of ion-exchanged water is placed in the water tank of an ultrasonic disperser "Ultrasonic Dispersion System Tetora 150" (manufactured by Nikkaki Bios Co., Ltd.) having two built-in oscillators with an oscillation frequency of 50 kHz and a phase shift of 180 degrees and an electrical output of 120 W, and about 2 ml of the Contaminon N is added to this water tank.
(4) The beaker of (2) is set in the beaker fixing hole of the ultrasonic disperser, and the ultrasonic disperser is operated. Then, the height position of the beaker is adjusted so that the resonance state of the liquid surface of the electrolytic solution in the beaker is maximized.
(5) In a state where the electrolyte solution in the beaker in (4) is 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 so as to be 10°C or higher and 40°C or lower.
(6) The electrolytic solution (5) in which the toner is dispersed is dropped using a pipette into the round-bottom beaker (1) placed in the sample stand, and the measurement concentration is adjusted to about 5%. Then, the measurement is continued until the number of particles measured reaches 50,000.
(7) The measurement data is analyzed using the dedicated software that comes with the device, and the weight-average particle size (D4) is calculated. Note that when the dedicated software is set to Graph/Volume %, the "Average diameter" on the Analysis/Volume Statistics (Arithmetic Mean) screen is the weight-average particle size (D4).

The basic configuration and features of the present invention have been described above. The present invention will now be described in detail with reference to examples. However, the present invention is not limited to these examples.

The magnetic iron oxide used in the magnetic toner of the present invention was produced as follows.

<Production Example of Magnetic Iron Oxide Particles 1>
(First reaction step)
A ferrous salt suspension was prepared by mixing 16 L of an aqueous ferrous sulfate solution containing 1.5 mol/L of Fe2 ⁺ (Fe2 ⁺ 24 mol) with 15.2 L of a 3.0 N sodium hydroxide solution (equivalent to 0.95 equivalent to Fe2 ⁺ , i.e., 2OH/Fe=0.95) and adjusting the pH to 8.0. In this case, 26.6 g of No. 3 water glass ( _SiO2 28.8 mass%) (equivalent to 0.50 atomic % of Si relative to Fe, i.e., Si/Fe (atomic %)=0.50) was diluted with 0.5 L of ion-exchanged water as a silicon component and added to the sodium hydroxide. The above ferrous salt suspension was aerated at a temperature of 90°C with 70 L of air per minute to carry out an oxidation reaction until the oxidation reaction rate of the ferrous salt reached 12%, and a ferrous salt suspension containing magnetite nucleus particles was obtained.

(Second reaction step)
A suitable amount of 3.0 N sodium hydroxide solution was added to the ferrous salt suspension containing the magnetite nucleus particles to adjust the pH to 10.5, and 70 L of air was passed through it at a temperature of 90° C. at a rate of 70 L per minute to obtain magnetic iron oxide core particle precursor 1.

(Third reaction step + coating treatment)
To a suspension containing magnetic iron oxide core particle precursor 1, 26.6 g of No. 3 water glass diluted in 0.2 L of ion-exchanged water was added as a silicon component, and then dilute sulfuric acid was added to adjust the pH to 5.8 and the temperature of the suspension to 90°C to form a coating layer, thereby obtaining magnetic iron oxide 1.

The obtained magnetic iron oxide 1 was washed with water using a filter press, and then filtered, dried, and pulverized in a conventional manner to obtain magnetic iron oxide particles 1. The number-average particle diameter of the obtained magnetic iron oxide particles 1 was 0.15 μm.

<Production Example of Magnetic Iron Oxide Particles 2>
Except for changing the amount of water glass in the first reaction step to 53.2 g, the first reaction step and the second reaction step were carried out in the same manner as for the magnetic iron oxide core particle precursor 1 to obtain magnetic iron oxide core particles 2. The magnetic iron oxide core particles 2 obtained were washed with water using a filter press, filtered, dried and pulverized in a conventional manner to obtain magnetic iron oxide particles 2. The number average particle diameter of the obtained magnetic iron oxide particles 2 was 0.14 μm.

<Production Example of Magnetic Iron Oxide Particles 3>
Magnetic iron oxide particles 3 were obtained in the same manner as magnetic iron oxide particles 2, except that no water glass No. 3 was used in the first reaction step. The number average particle diameter of the obtained magnetic iron oxide particles 3 was 0.15 μm.

Table 1 shows the preparation conditions for magnetic iron oxide particles.

<Production Example of Binder Resin 1>
The constituent monomers of the polyester moiety used in producing the binder resin 1 are listed below.

[Alcohol content]
Polyoxypropylene (2.2)-2,2-bis(4-hydroxyphenyl)propane: 50.0 mol parts Polyoxyethylene (2.2)-2,2-bis(4-hydroxyphenyl)propane: 50.0 mol parts [Carboxylic acid component]
Fumaric acid: 88.0 mol parts Trimellitic acid: 12.0 mol parts First, 100 parts by mass of the total amount of the constituent monomers of the polyester portion, 5 parts by mass of an aliphatic monoalcohol having 50 carbon atoms (a secondary monoalcohol having a hydroxyl group in paraffin wax, an average carbon number of 50), and 0.2 parts by mass of titanium tetrabutoxide were charged into a 5-liter autoclave. A reflux condenser, a water separator, a _N2 gas inlet tube, a thermometer, and a stirrer were attached thereto, and a polycondensation reaction was carried out at 230 ° C. while introducing _N2 gas into the autoclave. In addition, when carrying out the reaction, the reaction time was adjusted so that the desired softening point was obtained. After the reaction was completed, the resin was taken out of the container, cooled, and pulverized to obtain a binder resin 1. The softening point Tm of the obtained binder resin 1 was 118.2 ° C., and the acid value was 20 mg KOH / g.

<Production Example of Binder Resin 2>
The constituent monomers used in producing the binder resin 2 are listed below.

[Alcohol content]
Polyoxypropylene (2.2)-2,2-bis(4-hydroxyphenyl)propane: 50.0 mol parts Polyoxyethylene (2.2)-2,2-bis(4-hydroxyphenyl)propane: 50.0 mol parts [Carboxylic acid component]
Fumaric acid: 90.0 mol parts Trimellitic acid: 10.0 mol parts 100 parts by mass of the above monomer and 0.2 parts by mass of titanium tetrabutoxide were charged into a 5-liter autoclave. A reflux condenser, a water separator, a _N2 gas inlet tube, a thermometer and a stirrer were attached thereto, and a polycondensation reaction was carried out at 230°C while introducing _N2 gas into the autoclave. In addition, when carrying out the reaction, the reaction time was adjusted so as to obtain the desired softening point. After the reaction was completed, the resin was taken out of the container, cooled and pulverized to obtain binder resin 2. The softening point Tm of the obtained binder resin 2 was 118.5°C, and the acid value was 20 mgKOH/g.

<Production Examples of Binder Resins 3 to 6>
Binder resins 3 to 6 were obtained in the same manner as for binder resin 2, except that the constituent monomers were changed as shown in Table 2 and the reaction temperature and reaction time were appropriately changed. The softening points and acid values of binder resins 3 to 6 are summarized in Table 2.

<Production Examples of Waxes 1 to 6 Having Acid Values>
Aliphatic hydrocarbon wax: 100 mol parts Mixture of boric acid and boric anhydride (mol parts of boric acid/mol parts of boric anhydride = 1.5)
: 2 mol parts Aliphatic hydrocarbon wax (maximum endothermic peak temperature 125.1°C) was melted at a container temperature of 200°C, and a mixture of boric acid and boric anhydride was added, and the wax was oxidized in _O2 / _N2 gas with an oxygen concentration of 5% by volume. The oxidation treatment time was adjusted so as to obtain the desired acid value. After the oxidation treatment was completed, water was added and purification was performed to obtain waxes 1 to 6 with different acid values. The acid values and maximum endothermic peak temperatures measured by a differential scanning calorimeter (DSC) are shown in Table 3.

<Production Example of Inorganic Fine Particles>
(Production of calcium carbonate fine particles)
200 ml of 50% ethanol/water solution was cooled to -20 to 10°C, 160 g of Ca(OH) ₂ was added to form a slurry, and carbon dioxide gas/nitrogen gas with a concentration of 30% was introduced from the bottom of the container at a flow rate of 500 to 5000 ml/min while vigorously stirring, and the reaction was allowed to proceed until the pH began to decrease. The reaction temperature and the introduction rate of carbon dioxide gas were adjusted to produce four types of synthetic calcium carbonate slurries with different particle sizes of 70 to 700 nm. Furthermore, this dispersion was filtered while still in a low temperature state, thoroughly washed with pure water, and then dried to obtain calcium carbonate fine particles (inorganic fine particles 1 to 4). The particle sizes of inorganic fine particles 1 to 4 are shown in Table 4.

Furthermore, water adjusted to 70°C was added to inorganic fine particles 1 so that the solid content was 10% by mass, and a slurry was formed using a stirring disperser. 1 kg of this slurry of inorganic fine particles 1 was stirred using a disperser, while 1.0 g of saponified stearic acid was added, and after stirring for 20 minutes, the mixture was pressed and dehydrated. The obtained dehydrated cake was dried and then powdered to obtain approximately 100 g of calcium carbonate (inorganic fine particles 1-1) surface-treated with fatty acid.

(Production of strontium carbonate microparticles)
A strontium hydroxide suspension was prepared by adding 4200 g of ion-exchanged water and 500 g of strontium hydroxide octahydrate to a polytetrafluoroethylene reaction vessel having an internal volume of 5 L. The reaction vessel was placed in a hot bath to adjust the liquid temperature of the suspension to 50° C. Thereafter, while stirring the suspension with a stirrer, carbon dioxide gas was introduced at a flow rate of 5 L/min (about 22 mL/min per 1 g of strontium hydroxide in the suspension) to carbonate the strontium hydroxide and generate strontium carbonate particles. During carbonation, the pH of the suspension was measured, and the introduction of carbon dioxide gas was stopped when the pH of the suspension fell below 7.

The obtained strontium carbonate suspension was concentrated until the solid content concentration reached 10% by mass. It was then placed in a media mill (model: AMC12.5, effective volume: 9.0 L, manufactured by Ashizawa Finetech Co., Ltd.) and pulverized using zirconium oxide beads with an average particle size of 300 μm under conditions of a bead loading amount of 75% by volume, a peripheral speed of 7 m/sec, and a residence time of 30 minutes. The strontium carbonate suspension after pulverization was dried using a spray dryer to obtain strontium carbonate microparticles (inorganic microparticles 5).

(Production of Magnesium Carbonate Fine Particles)
A magnesium hydroxide suspension was prepared by adding 5000 g of ion-exchanged water and 500 g of magnesium hydroxide to a polytetrafluoroethylene reaction vessel having an internal volume of 5 L. The reaction vessel was placed in a hot bath to adjust the liquid temperature of the suspension to 35° C. Thereafter, while stirring the suspension with a stirrer, carbon dioxide gas was introduced at a flow rate of 10 L/min (approximately 20 mL/min per 1 g of magnesium hydroxide in the suspension) to carbonate the magnesium hydroxide and generate magnesium carbonate particles. During carbonation, the pH of the suspension was measured, and the introduction of carbon dioxide gas was stopped when the pH of the suspension fell below 7.5.

The obtained magnesium carbonate suspension was concentrated until the solid content concentration reached 10% by mass. It was then placed in a media mill (model: AMC12.5, effective volume: 9.0 L, manufactured by Ashizawa Finetech Co., Ltd.) and pulverized using zirconium oxide beads with an average particle size of 300 μm under conditions of a bead loading amount of 75% by volume, a peripheral speed of 7 m/sec, and a residence time of 35 minutes. The magnesium carbonate suspension after pulverization was dried using a spray dryer to obtain magnesium carbonate microparticles (inorganic microparticles 6).

Example 1
(Production Example of Toner 1)
Binder resin 1: 100.0 parts by mass Wax 1: 10.0 parts by mass Inorganic fine particles 1-1: 10.0 parts by mass Magnetic iron oxide particles 1: 100.0 parts by mass First, the above materials were premixed in a Henschel mixer, and then melt-kneaded using a twin-screw kneading extruder. At this time, the residence time was controlled so that the temperature of the kneaded resin would be 140° C. The resulting kneaded product was cooled, coarsely pulverized using a hammer mill, and then pulverized using a turbo mill. The resulting finely pulverized powder was classified using a multi-division classifier (Nippon Steel Mining Co., Ltd. Elbow Jet Classifier) utilizing the Coanda effect, and toner particles with a weight average particle size (D4) of 8.0 μm were obtained. 2.0 parts by weight of hydrophobic silica fine powder (specific surface area by nitrogen adsorption measured by the BET method is 140 m ² /g, hydrophobized with hexamethyldisilazane) was externally added to 100 parts by weight of the toner particles and mixed, and sieved through a mesh with 150 μm openings to obtain Example Toner 1.

The materials used in the production of Example Toner 1 are shown below. Table 5 shows the combinations of binder resin and magnetic iron oxide particles used and the parts by weight.

[Examples 2 to 23 and Comparative Examples 1 to 6]
(Production Examples of Working Toners 2 to 23 and Comparative Toners 1 to 6)
Exemplary toners 2 to 23 and comparative toners 1 to 6 were obtained in the same manner as in the production of exemplary toner 1, except that the materials were changed as shown in Table 5. The particle size and softening point Tm of the obtained toners are summarized in Table 5.

<Evaluation>
The experimental toners and comparative toners were evaluated as follows. The evaluation results are shown in Table 6.

[Evaluation of Abrasion Resistance (Scratch Resistance) of Printed Images]
For this evaluation, a commercially available digital copier (Image Press 1135, manufactured by Canon Inc.) was used as an evaluation machine, modified to set the process speed to 800 mm/s and the fixing temperature to 150°C. 80 g/ ^m2 paper (OCE BLACK LABEL, A4) was used as the evaluation paper. A solid black image was output by setting the development bias so that the image density was 1.0. Using a friction and wear tester Tribogear TYPE 40 manufactured by Shinto Scientific Co., Ltd., the output image was rubbed with unused evaluation paper while applying a load, and the amount of toner attached to the rubbed paper was evaluated. The rubbing conditions were as follows.
Weight: 500g
Contact area with the rubbing paper: 2 mm x 20 mm
Sliding speed: 500mm/min Sliding distance: 40mm

The amount of toner adhering to the rubbing paper was evaluated as follows. Using an optical microscope, multiple photographs were taken at 100x magnification to include the entire rubbing area. The photographed images were binarized using image processing to calculate the area ratio of the adhering area. The average value of the area ratio of the adhering area for all photographs was taken as the amount of toner adhering.

(Evaluation Criteria)
A: The adhesion area rate is less than 1.5%.
B: The adhesion area rate is 1.5% or more and less than 2.5%.
C: The adhesion area rate is 2.5% or more and less than 3.5%.
D: The adhesion area rate is 3.5% or more and less than 4.0%.
E: The adhesion area rate is 4.0% or more.

[Evaluation of component contamination suppression]
For this evaluation, a commercially available digital copier (Image Press 1135, manufactured by Canon Inc.) was used as an evaluation machine modified by setting the process speed to 800 mm/s, the fixing temperature to 150° C., and removing the cleaning mechanism of the fixing roller. 80 g/m ² paper (OCE BLACK LABEL, A4) was used as the evaluation paper. The development bias was set so that the image density was 1.0, and a pattern with a width of 45 mm was output in the short axis direction of the A4 paper, and 10,000 images were output under a high temperature and high humidity (30° C., 80% RH) environment. After that, the fixing roller was removed, and the amount of wax attached on the fixing roller corresponding to the image pattern was evaluated using a Fourier transform infrared spectroscopic analyzer. The details of the evaluation method are described below.
Fourier transform infrared spectrometer: Spectrum One (manufactured by PerkinElmer)
Measurement mode: ATR method Incident angle of infrared light (λ = 5 μm): 45°
ATR crystal: Ge (refractive index: 4.0)
Measurement range: 4000 cm ^-1 to 600 cm ^-1
Acquisition wavelength width: 4.00cm ^-1
Number of times accumulated: 16

The infrared absorption spectrum obtained under the above conditions is subjected to baseline correction using Automatic Correction. The maximum peak intensity in the range of 2800 cm ^-1 to 2900 cm ^-1 , which is the absorption peak derived from the methylene of the hydrocarbon wax, is calculated (Wp). The average value of the absorption intensities at 1100 cm ^-1 and 1250 cm ^-1 , which are peaks derived from the surface layer material of the fixing roller, is calculated (Bp). The value of Wp/Bp was taken as the amount of wax attached.

(Evaluation Criteria)
A: Wp/Bp is less than 0.01%.
B: Wp/Bp is 0.01% or more and less than 0.04%.
C: Wp/Bp is 0.04% or more and less than 0.07%.
D: Wp/Bp is 0.07% or more and less than 0.10%.
E: Wp/Bp is 0.10% or more

[Evaluation of Low-Temperature Fixability]
For this evaluation, a commercially available digital copier (image press 1135 manufactured by Canon Inc.) was taken out of the fixing device, and an evaluation machine was used in which the fixing roller temperature could be set arbitrarily and the process speed was modified to 800 mm/s. The evaluation was performed under a normal temperature and humidity (23°C, 50% RH) environment. 80 g/ ^m2 paper (OCE BLACK LABEL, A4) was used as the evaluation paper. The development bias of the image press 1135 was set so that the image density was 1.2, and 9 sheets of solid black unfixed images were output. Next, the temperature control of the fixing device was changed from 120°C to 150°C in 5°C increments, and one sheet was passed at each temperature. The fixed image was cut out to a width of 45 mm x 210 mm, folded in half from the center of the long side so that the image part was on the inside, and a load of 150 g/ _cm2 was applied. The density after rubbing the folded portion with a brush was measured and compared with the density before folding. The image density was measured using an X-Rite color reflection densitometer (X-rite 500 Series, manufactured by X-rite Corporation). The density after folding was divided by the density before folding, and the value was plotted against each fixing temperature to create an approximation curve. The temperature at which the density after folding divided by the density before folding was 0.95 or more was determined as the fixable temperature.

(Evaluation Criteria)
A: The fixable temperature is less than 125°C.
B: The fixing start temperature is 125° C. or higher and lower than 130° C.
C: The fixing start temperature is 130° C. or higher and lower than 135° C.
D: The fixing start temperature is 135° C. or higher and lower than 140° C.
E: The fixing start temperature is 140° C. or higher.

[Evaluation of dot reproducibility]
For this evaluation, a commercially available digital copier (image RUNNER ADVANCE 8105 PRO manufactured by Canon Inc.) was used as an evaluation machine with a process speed modified to 600 mm/s. After 100,000 sheets were printed using each magnetic toner under a high temperature and high humidity (30°C, 80% RH) environment, a halftone (30H) image was formed and the roughness of this image was evaluated based on the following criteria. The paper used was CS-068 A4 paper (basis weight 68.0 g/ ^m2 , sold by Canon Marketing Japan Inc.). The 30H image is a halftone image in which 256 gradations are expressed in hexadecimal, with 00H being solid white (non-image) and FFH being solid black (full image). The images were taken using a digital microscope VHX-500 (lens wide range zoom lens VH-Z100 manufactured by Keyence Corporation), and the area of 1000 dots was measured. The number average (S) of the dot area and the standard deviation (σ) of the dot area were calculated, and the dot reproducibility index was calculated using the following formula.
Dot reproducibility index (I) = σ/S × 100

(Evaluation Criteria)
A: I is less than 2.0 B: I is 2.0 or more and less than 4.0 C: I is 4.0 or more and less than 6.0 D: I is 6.0 or more and less than 8.0 E: I is 8.0 or more

[Gross evaluation]
For this evaluation, a commercially available digital copier (Image Press 1135, manufactured by Canon Inc.) was used as an evaluation machine modified to set the process speed to 800 mm/s and the fixing temperature to 150°C. 80 g/ ^m2 paper (OCE BLACK LABEL, A4) was used as the evaluation paper. A solid black image was output by setting the development bias so that the image density was 1.0. The fixed image was measured using a handy gloss meter PG-3D (manufactured by Nippon Denshoku Industries Co., Ltd.) at an incident angle of light of 75°, and the average value of three arbitrary points on each image was taken as the gloss value.

(Evaluation Criteria)
A: Gloss value is less than 2.0 B: Gloss value is 2.0 or more and less than 3.5 C: Gloss value is 3.5 or more and less than 5.0 D: Gloss value is 5.0 or more and less than 6.5 E: Gloss value is 6.5 or more

Claims (7)

A magnetic toner having toner particles containing a binder resin, a hydrocarbon wax, magnetic iron oxide particles, and inorganic fine particles,
The acid value of the binder resin is 5 mgKOH/g or more and 30 mgKOH/g or less,
The acid value of the hydrocarbon wax is 5 mgKOH/g or more and 50 mgKOH/g or less,
the inorganic fine particles are any fine particles selected from the group consisting of magnesium carbonate fine particles, calcium carbonate fine particles, and strontium carbonate fine particles;
The magnetic toner is characterized in that the content of the inorganic fine particles is 5 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the binder resin. The magnetic toner according to claim 1, wherein the content of the magnetic iron oxide particles is 70 parts by mass or more and 140 parts by mass or less per 100 parts by mass of the binder resin. The magnetic iron oxide particles contain silicon element,
3. The magnetic toner according to claim 1, wherein the content of said silicon element is from 0.2 atom % to 3.0 atom % based on the iron element in the magnetic iron oxide particles. The magnetic toner according to any one of claims 1 to 3, in which 3 g of magnetic iron oxide particles are suspended in 300 mL of a 3 mol/L aqueous sodium hydroxide solution, the suspension is filtered and dried, and the amount of silicon element in the magnetic iron oxide obtained is measured, and the difference from the amount of silicon element before the suspension treatment is 0.1 atomic % or more and 2.0 atomic % or less based on the iron element in the magnetic iron oxide particles. The magnetic toner according to any one of claims 1 to 4, wherein the inorganic fine particles are calcium carbonate fine particles. The magnetic toner according to any one of claims 1 to 5, wherein the calcium carbonate microparticles are fatty acid-treated calcium carbonate microparticles. The magnetic toner according to any one of claims 1 to 6, wherein the binder resin has at least one aliphatic compound selected from the group consisting of aliphatic monocarboxylic acids and aliphatic monoalcohols condensed at its terminal.