JP7642382B2 - 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, toners that can provide stable images for a longer period of time than ever before even when used under various environments are required. 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 the magnetic toner, which has been charged by frictional charging with the developing sleeve, is caused to fly and adhere to the 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.
It is known that the amount and shape of magnetic iron oxide in a magnetic toner greatly affect image quality. Patent Document 1 discloses a toner containing cubic or octahedral magnetic material and spherical magnetic material in a mass ratio of 9:1 to 1:9 in a toner particle.
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 2 proposes a technology for minimizing contamination of members by using a wax having an acid value.
On the other hand, 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 contamination of the media. Therefore, Patent Document 3 proposes a technology for improving the abrasion resistance of the printed matter by controlling the amount of wax on the surface of the toner.

Patent 5815740 JP 2007-322504 A JP 2020-8818 A

However, when a wax having an acid value is used and the wax is held in the toner as in Patent Document 2, contamination of components can be suppressed, but the improvement in the abrasion resistance of the printed matter is limited. Also, when an attempt is made to increase the amount of wax on the surface of the printed matter to improve the abrasion resistance of the printed matter as in Patent Document 3, the amount of wax adhering to the fixing member also tends to increase, and it is necessary to improve the functionality of the cleaning mechanism for the fixing member. According to the conventional technology, there remains a problem in achieving both suppression of component contamination by wax and improvement of the abrasion resistance of the printed matter.
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, provide stable images, and output printed matter with excellent abrasion resistance, even when used for a long period of time.

The present invention provides a magnetic toner comprising a binder resin, a hydrocarbon wax, and magnetic iron oxide particles,
The content of the magnetic iron oxide particles in the toner is 30% by mass or more and 70% by mass or less,
The magnetic iron oxide particles have a coating layer containing silicon and aluminum,
The magnetic iron oxide particles are
(i) spherical magnetic iron oxide particles;
(ii) containing hexahedral magnetic iron oxide particles or octahedral magnetic iron oxide particles,
The hydrocarbon wax in the magnetic toner is characterized in that it has a carboxyl group and has an acid value of 5 mgKOH/g or more and 50 mgKOH/g or less.

The present invention provides a toner that can suppress component contamination and output printed matter with excellent abrasion resistance even when used over a long period of time.

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 endpoints, that is, the lower limit and the upper limit, unless otherwise specified.

The present inventors conducted extensive research with the aim of providing a toner that can suppress contamination of components and produce printed matter with excellent abrasion resistance even when used for a long period of time. As a result, they arrived at a configuration in which a wax having an acid value is contained in the toner particles, and the amount of magnetic iron oxide in the toner particles and the ratio of spherical magnetic iron oxide particles to hexahedral magnetic iron oxide particles or octahedral magnetic iron oxide particles in the toner particles are controlled within a specific range. They found that by using such a toner, it becomes possible to suppress contamination of components and produce printed matter with excellent abrasion resistance even when used for a long period of time.

The reasons why the effects of this invention are achieved are believed to be as follows:

The wax having an acid value interacts with the binder resin and the magnetic iron oxide particles, so that the wax is controlled so that it does not become excessive on the toner and the surface of the printed image. The magnetic iron oxide particles contained in the toner of the present invention contain spherical magnetic iron oxide particles and hexahedral magnetic iron oxide particles or octahedral magnetic iron oxide particles, and by controlling the amount of magnetic iron oxide in the toner particles and further the ratio of the spherical magnetic iron oxide particles to the hexahedral magnetic iron oxide particles or octahedral magnetic iron oxide particles in the toner particles to a specific range, the interaction between the wax and the binder resin and the magnetic iron oxide particles becomes stronger. The enhanced interaction not only suppresses the contamination of components caused by the release of wax from the toner, but also increases the strength of the printed image. The increased image strength, combined with the lubricating effect of the wax controlled in quantity on the image surface, makes it possible to obtain a printed matter with excellent abrasion resistance.

The reasons why the effects of this invention are achieved are explained in more detail below.

The content of magnetic iron oxide in the magnetic toner of the present invention is 30% by mass or more and 70% by mass or less. It is more preferable that it is 45% by mass or more and 55% by mass or less. If it is 30% by mass or more, the above-mentioned interaction can provide the image strength required for abrasion resistance. If it is 70% by mass or less, the interaction can be prevented from making the toner too hard, and a toner with excellent low-temperature fixing property required for high productivity of printed matter can be obtained.

The magnetic iron oxide in the magnetic toner of the present invention contains (i) spherical magnetic iron oxide particles and (ii) hexahedral magnetic iron oxide particles or octahedral magnetic iron oxide particles, and the ratio of the spherical magnetic iron oxide particles in the magnetic iron oxide particles is preferably 1.0% by number or more and 30.0% by number or less, and more preferably 3.0% by number or more and 15.0% by number or less. As a result of intensive research, the inventors have found that by controlling the ratio of the spherical magnetic iron oxide particles to the hexahedral magnetic iron oxide particles or octahedral magnetic iron oxide particles within the above range, it is possible to achieve both the image strength required for wear resistance and high image quality. The reason for this is unclear, but is speculated as follows.

Hexahedral magnetic iron oxide particles or octahedral magnetic iron oxide particles have a shape with protrusions, which makes it easier for excess charge in the toner to leak out, and the toner is uniformly charged, which is advantageous for the uniform formation of spikes on the developing sleeve.

On the other hand, spherical magnetic iron oxide particles are an aggregate of microcrystals, which tends to have high resistance and is prone to localized concentration of charge. The acid groups of the wax, which has an acid value, are attracted by electrostatic attraction to the area where the charge is locally concentrated, resulting in strong interactions and improved image strength. If the proportion of the spherical magnetic iron oxide particles in the magnetic iron oxide particles is less than 1.0% by number, it becomes difficult to obtain the image strength required for wear resistance, and if it is more than 30.0% by number, the brushes on the developing sleeve will become uneven, making it easy for image quality to deteriorate. This phenomenon becomes more noticeable when the fluidity of the toner deteriorates due to long-term use, especially in high-speed machines such as those used in the POD market.

The magnetic iron oxide particles of the present invention are described in detail below.

The magnetic iron oxide particles of the present invention contain (i) spherical magnetic iron oxide particles and (ii) hexahedral magnetic iron oxide particles or octahedral magnetic iron oxide particles. Here, the shape of the magnetic iron oxide particles can be confirmed from a photograph (magnification 40,000 times) taken with a scanning electron microscope (SEM).

Spherical magnetic iron oxide particles refer to particles that do not have a plate-like surface, and whose entire surface is surrounded by smooth convex lines, for example, elliptical, and even completely spherical.

Hexahedral magnetic iron oxide particles refer to particles that have protrusions and a cubic shape. When observed with a scanning electron microscope (SEM), hexahedral magnetic iron oxide particles have straight lines on the periphery and have faces that appear to be nearly square.

Octahedral magnetic iron oxide particles refer to particles that have convex parts and are in the shape of a convex polyhedron surrounded by eight triangles. When observed with a scanning electron microscope (SEM), octahedral magnetic iron oxide particles are those that have straight lines on the periphery and a diamond shape with faces that appear to be triangles.

In addition, the magnetic toner of the present invention can obtain the effects of the present invention by having the magnetic iron oxide particles of the present invention present inside the toner particles. "Present inside the toner particles" means that the magnetic iron oxide particles are present in a state where they are dispersed in the binder resin. By achieving this state, the strength required for abrasion resistance is imparted and contamination of components by wax is suppressed. Therefore, in order to obtain the effects of the present invention, it is important to control the magnetic iron oxide particles inside the toner particles to within the above-mentioned range.

In the magnetic iron oxide of the present invention, (i) spherical magnetic iron oxide particles and (ii) hexahedral magnetic iron oxide particles or octahedral magnetic iron oxide particles may be prepared separately and blended, but it is more preferable that both magnetic iron oxide particles are contained by the same reaction. By using magnetic iron oxide containing both magnetic iron oxide particles by the same reaction, the dispersion of both particles in the magnetic iron oxide is improved. As a result, the chargeability of the entire toner particle and the strength-enhancing effect due to the above-mentioned interaction are uniformed.

The number-average particle size 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 size of the magnetic iron oxide particles is within the above range, the dispersibility of the magnetic iron oxide particles in the toner is improved, and the chargeability between the toner particles and the strength-enhancing effect due to the above-mentioned interaction are uniformed.

The magnetic iron oxide particles preferably have a magnetization strength of 85 ^Am2 /kg or more and 90 ^Am2 /kg or less at 796 kA/m, more preferably 85 ^Am2 /kg or more and 87 ^Am2 /kg or less. When the magnetization strength at 796 kA/m is 85 ^Am2 /kg or more, the stability of the spikes on the developing sleeve is increased. As a result, dot reproducibility is improved, and tailing and scattering can be further suppressed. Furthermore, when the magnetization strength at 796 kA/m is 90 ^Am2 /kg or less, the thickness of the spikes on the developing sleeve becomes thinner and more uniform. As a result, printed matter with good image quality can be obtained even when used for a long period of time.

The maximum relative magnetic permeability of the magnetic iron oxide particles at 0 kA/m to 796 kA/m is preferably 2.70 to 2.80, and more preferably 2.71 to 2.75. By having the maximum relative magnetic permeability at 0 kA/m to 796 kA/m in the above range, the magnetization speed of the toner on the developing sleeve becomes more appropriate. As a result, the toner can be formed in a more dispersed state along the magnetic field lines of the developing sleeve, resulting in prints of good quality even when used for a long period of time.

In order to control the amount of magnetization of the toner on the developing sleeve within an appropriate range, it is preferable that the magnetic iron oxide particles of the present invention contain a specific type of metal element in the core particle of the magnetic iron oxide particle and form a coating layer containing a specific type of metal element on the surface of the core particle. In particular, in terms of being able to balance the amount of magnetization with frictional charging properties and heat resistance, it is more preferable to contain silicon or zinc in the core particle of the magnetic iron oxide particle and form a coating layer containing silicon, aluminum or zinc on the surface of the magnetic iron oxide particle. It is particularly preferable to contain silicon in the core particle and form a coating layer containing silicon and aluminum on the surface.

In addition, the amount of silicon contained in the core particles of the magnetic iron oxide particles is preferably 0.15 atomic % or more and 1.50 atomic % or less, and more preferably 0.20 atomic % or more and 0.80 atomic %, in terms of silicon element, relative to the entire magnetic iron oxide particle.

By controlling the amount of silicon contained in the core particles to within the above range, the uniformity of the magnetization amount in the magnetic iron oxide particles is improved. As a result, the uniformity of the magnetization amount in the toner is increased, resulting in printed matter of good image quality. In addition, the amount of silicon contained in the coating layer is preferably 0.01 atomic % or more and 0.50 atomic % or less, and more preferably 0.05 atomic % or more and 0.30 atomic % or less, in terms of silicon element, relative to the entire magnetic iron oxide particle.

Furthermore, the amount of aluminum contained in the coating layer is preferably 0.01 atomic % or more and 0.50 atomic % or less, and more preferably 0.05 atomic % or more and 0.30 atomic % or less, as Al relative to the entire magnetic iron oxide particle.

By forming a coating layer as described above, the toner charging uniformity is improved, resulting in printed matter with good image quality.

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

The magnetic iron oxide of the present invention can be obtained by carrying out a first reaction step of forming magnetic iron oxide seed particles, a second reaction step of adjusting the pH after the first reaction step to grow the seed particles almost to the end point of the reaction, and a third reaction step of adjusting the pH again after the second reaction step to obtain the desired magnetic iron oxide. In this way, by dividing the reaction step into three stages, it is possible to obtain magnetic iron oxide containing spherical magnetic iron oxide particles and hexahedral magnetic iron oxide particles or octahedral magnetic iron oxide particles. A step of coating the surface of the magnetic iron oxide may be carried out simultaneously with the third reaction step or between the second and third reaction steps.

The particle size and shape of the magnetic iron oxide can be adjusted by adjusting the pH, flow rate of the oxygen-containing gas, reaction temperature, oxidation reaction rate, raw material ratio, etc. in each process.

Next, each reaction step for obtaining magnetic iron oxide will be described in detail, but is not limited to this.

<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. 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 14%, 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 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 and/or Al on the surface of magnetic iron oxide particles, the following operations are carried out.

After the second reaction step is completed, a water-soluble silicate, or a water-soluble silicate and a water-soluble aluminum salt are added to the suspension containing the magnetic iron oxide. 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 precipitate and deposit a compound containing Si and/or Al on the surface of the magnetic iron oxide, and the pH is further 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 after the third reaction step to mechanochemical treatment or heat treatment to fix a compound containing Si and/or Al to the surface of the magnetic iron oxide.

If necessary, in each reaction stage, a salt of one or more elements other than iron selected from Mn, Zn, Ni, Cu, Al, Ti, and Si can be added to incorporate the element. As the salt, a sulfate, nitrate, chloride, etc. can be used. The amount of the salt added is preferably 0 to 10 atomic % relative to Fe, more preferably 0 to 8 atomic %, and even more preferably 0 to 5 atomic % in total.

In the present invention, the binder resin may be any resin generally used in toners. Among them, a resin having a polyester unit is preferred from the viewpoint of interaction with wax having an acid value and magnetic iron oxide. In the present invention, "polyester unit" means a portion derived from polyester, and examples of resins having polyester units include polyester resins and hybrid resins in which polyester units are bonded to other resin units. Examples of the 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.

In order to fully exert the excellent effects of the present invention, it is preferable that the above-mentioned bisphenol derivative and ethylene glycol are contained as alcohol components of the polyester resin. The content ratio of the bisphenol derivative and ethylene glycol, mol% of bisphenol derivative/mol% of ethylene glycol, is preferably 2.0 to 6.0, more preferably 3.0 to 5.0. By setting it in the above range, it is possible to increase the concentration of ester groups in the binder resin, and it is possible to more effectively express the interaction with the acid-modified wax and magnetic iron oxide, thereby improving the component contamination resistance and the abrasion resistance of the printed matter.

Furthermore, in the polyester resin of the present invention, condensation of at least one aliphatic compound selected from the group consisting of aliphatic monocarboxylic acids and aliphatic monoalcohols having a specific number of carbon atoms is effective in fully exerting the effects of the present invention.

It is important that the aliphatic compound introduced into the polyester resin is 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 preferably 32 to 80, more preferably 32 to 60. It is also important that the aliphatic compound is monovalent. By being monovalent, the aliphatic compound is condensed at the end of the polyester unit. The carbon chain derived from the aliphatic compound condensed at the end has affinity with the wax having an acid value, and the interaction is effectively expressed. If the carbon number of the aliphatic compound is 29 or less, the affinity with the wax is insufficient, and if the carbon number of the aliphatic compound is 103 or more, the affinity with the wax becomes large, inhibiting the crystallization of the wax and working against the abrasion resistance of the printed matter.

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 without inhibiting the crystallization of the 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.

Furthermore, examples of aliphatic monoalcohols include melissyl alcohol and tetracontanol.

The method of condensing an aliphatic compound to the terminal of a polyester resin is not particularly limited. 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.

Other specific examples of 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 wax having an acid value used in the present invention will be described in detail below.

The wax having an acid value according to the present invention is a hydrocarbon chain whose main skeleton is made of olefin, and is generally called a hydrocarbon wax, which has been modified to have hydroxyl or carboxyl groups introduced therein. Examples of the modified hydrocarbon waxes are described below, including their manufacturing methods. For example, a manufacturing method may be used in which ethylene is polymerized using a Ziegler catalyst, and after the polymerization is complete, the 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, there are oxyacids of boron, oxyacids of phosphorus, and oxyacids of sulfur. Specifically, there are boric acid, nitric acid, phosphoric acid, and sulfuric acid. As a 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 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.

The wax having an acid value used in the present invention preferably has a maximum endothermic peak temperature measured by a differential scanning calorimeter (DSC) when the crystalline structure consisting of hydrocarbon chains melts, which is 80°C or more and 150°C or less. More preferably, it is 90°C or more and 140°C or less. If the maximum endothermic peak temperature and acid value are within the above-mentioned ranges, it is possible to achieve both suppression of component contamination and abrasion resistance of the printed matter.

The content of the wax having an acid value of the present invention is preferably 2.0 parts by mass or more and 16.0 parts by mass or less per 100 parts by mass of the binder resin. More preferably, it is 6.0 parts by mass or more and 12.0 parts by mass or less. When the content of the wax having an acid value is within the above range, it is possible to achieve both suppression of component contamination and abrasion resistance of the printed matter.

[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 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 to 10.0 parts by mass, more preferably 0.10 parts by mass to 5.0 parts by mass, 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 and phenol derivatives such as bisphenols. 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 does not use a polymerization solvent or uses a small amount of a 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. Examples of the polymerization initiator 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 agents include phosphotungstic acid, phosphomolybdic acid, phosphotungstomolybdic acid, tannic acid, lauric acid, gallic acid, ferricyanide compounds, etc.); and 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.

The toner of the present invention may also contain other external additives as necessary. For example, resin particles or inorganic particles that act as charge adjuvants, conductivity imparting agents, caking inhibitors, release agents for use in heat roller fixing, and abrasives. 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, it is 100°C or higher and 120°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 method for producing the toner of the present invention (pulverization method) will be described below, but the present invention is not limited thereto.

For example, the binder resin, release agent, and other additives, if necessary, are thoroughly mixed using a mixer such as a Henschel mixer or 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 a toner. 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.); Cryptron (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.

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

<1> Measurement of shape and number average particle size of magnetic iron oxide The particle shape and number average particle size of magnetic iron oxide are observed and measured using a scanning electron microscope S-4800 (manufactured by Hitachi High-Technologies Corporation). Observation is performed according to the following procedure.

First, 0.025 g of sample (magnetic iron oxide particles) is weighed out and 10 g of pure water is added. This solution is dispersed for 5 minutes using an ultrasonic disperser. After that, the dispersion is spread on aluminum foil and the water is thoroughly dried. After drying, the sample is placed on the SEM stage and observed.

The number-average particle size of magnetic iron oxide is determined by measuring the length and width of two sides of the magnetic iron oxide particles in an electron microscope photograph (magnification 40,000 times) and taking the average of the two lengths as the particle size. Several photographs are taken from different fields of view, and the number-average particle size of a total of 500 magnetic iron oxide particles, including spherical magnetic iron oxide particles, hexahedral magnetic iron oxide particles, and octahedral magnetic iron oxide particles, is calculated as the arithmetic mean.

The arithmetic mean of the average particle diameter of the spherical magnetic iron oxide particles contained among these 500 particles is taken as the number-average particle diameter of the spherical magnetic iron oxide particles.

The arithmetic mean of the average particle size of the hexahedral magnetic iron oxide particles or octahedral magnetic iron oxide particles contained among the 500 particles is taken as the number-average particle size of the hexahedral magnetic iron oxide particles or octahedral magnetic iron oxide particles.

However, if the total number of particles is less than five for any one particle, observations should be continued until at least five particles are observed. In that case, the total number of particles when five or more particles of the least common shape are counted is used as the total number, and the number-average particle size of the magnetic iron oxide is calculated.

The magnetic iron oxide contained in the magnetic toner can be obtained by dissolving the magnetic toner in a tetrahydrofuran or toluene solution by heating, etc., and then using a magnet to extract only the magnetic iron oxide from the solution.

<2> Oxidation Reaction Rate The oxidation reaction rate of the ferrous salt in the first reaction step can be calculated by measuring the Fe ²⁺ content in the reaction solution and using the following formula.
(A-B)÷A×100=oxidation reaction rate (%)

In the above formula, A is the Fe ²⁺ content in the reaction solution immediately after mixing the ferrous salt aqueous solution and the alkaline aqueous solution, and B is the Fe ²⁺ content in the ferrous salt reaction solution containing a mixture of ferrous hydroxide and magnetite particles.

<3> Method for Quantifying the Internal Si Amount of Magnetic Iron Oxide Particles The internal Si amount of magnetic iron oxide particles is measured as follows. Magnetic iron oxide is mixed with ion-exchanged water, dispersed to form a suspension, which is then mixed with an aqueous alkali hydroxide solution and stirred for 30 minutes or more, after which the suspension is filtered and dried. This sample is measured with a "Fluorescent X-ray Analyzer RIX-2100" (manufactured by Rigaku Electric Industry Co., Ltd.), and the amount of Si in the magnetic iron oxide is calculated as the internal Si amount, calculated as a value calculated in elemental conversion relative to the Fe contained in the magnetic iron oxide.

<4> Surface Si Amount and Surface Al Amount of Magnetic Iron Oxide Particles First, the total Si and Al element amounts in the magnetic iron oxide are determined. The Si amount and Al amount of the magnetic iron oxide are measured using a fluorescent X-ray analyzer RIX-2100 (manufactured by Rigaku Electric Industry Co., Ltd.) and calculated as values calculated in elemental terms relative to the Fe contained in the magnetic iron oxide.

Next, the surface Si amount and surface Al amount of the magnetic iron oxide particles are calculated by mixing the magnetic iron oxide with ion-exchanged water, dispersing the mixture into a suspension, mixing it with an aqueous alkali hydroxide solution and stirring for at least 30 minutes, filtering and drying the suspension, measuring the Si amount and Al amount of the magnetic iron oxide obtained, and calculating the difference between the total Si amount and Al amount before the alkali treatment as the Si amount and Al amount on the magnetic iron oxide surface, and calculating the value calculated in elemental terms with respect to the Fe contained in the magnetic iron oxide.

<5> Method for Measuring Magnetic Properties A vibrating sample magnetometer VSM-P7 manufactured by Toei Industry Co., Ltd. was used to measure the magnetic properties at a sample temperature of 25° C. and an external magnetic field of 795.8 kA/m.

<6> 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 up to 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 blank test 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

Where 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).

<7> Peak Top Temperature of Endothermic Peak of Wax The peak top temperature of endothermic peak of wax is measured in accordance with ASTM D3418-82 using a differential scanning calorimeter “Q2000” (manufactured by TA Instruments).

The melting points of indium and zinc are used to correct the temperature of the device's detection section, and the heat of fusion of indium is used to correct the amount of heat.

Specifically, about 3 mg of a sample is precisely weighed and placed in an aluminum pan, and measurement is performed under the following conditions using an empty aluminum pan as a reference.
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 heated again. During this second heating process, the peak top temperature of the wax is calculated from the temperature-endothermic curve in the temperature range of 30°C to 180°C.

<8> Softening Point of Toner 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 taken 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 taken 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 melting temperature 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

<9> 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 pore 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 that it is 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 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 8.3. 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 the suspension containing magnetic iron oxide core particle precursor 1, appropriate amounts of No. 3 water glass as the silicon component and 1.9 mol/L aluminum sulfate solution as the aluminum component were added so that the Si/Fe and Al/Fe ratios were the values shown in Table 1. Dilute sulfuric acid was further 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. After washing, the electrical conductivity was 40 mS. It was then filtered, dried, and pulverized by conventional methods. The obtained magnetic iron oxide 1 contained 8.0% by number of spherical magnetic iron oxide particles and 92.0% by number of octahedral magnetic iron oxide particles, and had a number-average particle diameter of 0.14 μm.

The preparation conditions and composition of magnetic iron oxide 1 are shown in Tables 1 and 2.

<Production Examples of Magnetic Iron Oxide Particles 2 to 6>
In the manufacturing example of magnetic iron oxide 1, magnetic iron oxide particles 2 to 6 were obtained by adjusting the manufacturing conditions as shown in Table 1. The composition values of the obtained magnetic iron oxide particles 2 to 6 are shown in Table 2.

<Production Example of Binder Resin 1>
Monomers constituting the polyester unit used in producing the binder resin 1 are listed below.
Bisphenol A ethylene oxide (2.2 mol adduct): 80.0 mol parts Ethylene glycol: 20.0 mol parts Terephthalic acid: 100.0 mol parts First, 95% by mass of the above monomers with respect to the total amount of monomers constituting the polyester unit, and 100 parts by mass of an aliphatic monoalcohol having 50 carbon atoms (secondary monoalcohol having a hydroxyl group in paraffin wax, average carbon number 50) with respect to the total amount of monomers constituting the polyester unit were charged into a 5-liter autoclave together with 0.2 parts by mass of titanium tetrabutoxide. A reflux condenser, a water separator, an _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 1.

<Production Example of Binder Resin 2>
Monomers constituting the polyester unit used in producing the binder resin 2 are listed below.
Bisphenol A ethylene oxide (2.2 mol adduct): 80.0 mol parts Ethylene glycol: 20.0 mol parts Terephthalic acid: 100.0 mol parts 100 parts by mass of the above monomer was charged into a 5-liter autoclave together with 0.2 parts by mass of titanium tetrabutoxide. 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.

<Production Example of Binder Resin 3>
Monomers constituting the polyester unit used in producing the binder resin 3 are listed below.
Bisphenol A ethylene oxide (2.2 mol adduct): 100 mol parts Terephthalic acid: 100.0 mol parts 100 parts by mass of the above monomer was charged into a 5-liter autoclave together with 0.2 parts by mass of titanium tetrabutoxide. 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 3.

<Production Example of Wax 1 Having Acid Value>
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, 2, and 3 with acid values. The acid values and maximum endothermic peak temperatures measured by differential scanning calorimetry (DSC) were as follows:
Wax 1: 30 mg KOH/g, 123.9° C.
Wax 2: 48 mg KOH/g, 122.3° C.
Wax 3: 6 mg KOH/g, 125.2° C.

Example 1
(Production Example of Toner No. 1)
The materials used in the production of Toner No. 1 are shown below. Table 3 shows the combinations of the binder resin and the magnetic iron oxide particles used, the parts by mass, and the softening points of the toner.
Binder resin 1: 46.0 parts by weight Wax 1: 4.0 parts by weight Magnetic iron oxide particles 1: 50.0 parts by weight 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 was 140° C. The kneaded product obtained 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, to obtain a toner with a weight average particle size (D4) of 7.3 μm. 2.0 parts by weight of hydrophobic silica fine powder (specific surface area measured by nitrogen adsorption using the BET method is 140 m ² /g, hexamethyldisilazane treatment as hydrophobic treatment) was added externally to 100 parts by weight of the toner, and the mixture was sieved through a mesh with an opening of 150 μm to obtain toner No. 1.

The following evaluations were carried out on Toner No. 1. The evaluation results are shown in Table 4.

[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 1000 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 80°C to 120°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 95°C.
B: The fixing start temperature is 95° C. or higher and lower than 100° C.
C: The fixing start temperature is 100° C. or higher and lower than 105° C.
D: The fixing start temperature is 105° C. or higher and lower than 110° C.
E: The fixing start temperature is 110° C. or higher.

[Evaluation of Abrasion 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 with a process speed of 1000 mm/s and a fixing temperature of 120°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: 1000mm/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]
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 1000 mm/s, the fixing temperature to 120° 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 5000 sheets of 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 0.02%.
C: Wp/Bp is 0.02% or more and less than 0.04%.
D: Wp/Bp is 0.04% or more and less than 0.08%.
E: Wp/Bp is 0.08% or more

[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 1,000 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

[Evaluation of Halftone Unevenness]
For this evaluation, an evaluation machine was used in which a commercially available digital copier (image RUNNER ADVANCE 8105 PRO manufactured by Canon Inc.) was modified to have a process speed of 600 mm/s. For the evaluation of halftone unevenness, a halftone image of 2 dots and 3 spaces was output at a resolution of 600 dpi in a low temperature and low humidity (5° C., 5% RH) environment, and the halftone image quality (unevenness in development) of the obtained image was visually evaluated.

The evaluation paper used was CS-520 (basis weight 52.0 g/m ² , A4, sold by Canon Marketing Japan Inc.), which was left in a high-temperature, high-humidity environment for 48 hours or more to fully absorb moisture before use.

(Evaluation Criteria)
A: No unevenness in shade is noticeable.
B: There is slight unevenness in the shade, but it is hardly noticeable.
C: Some unevenness in shading is observed.
D: Unevenness in shading can be observed.
E: Shading unevenness is very noticeable.

[Examples 2 to 10]
Toners Nos. 2 to 10 each having a weight average particle size (D4) of 7.3 μm were produced in the same manner as in Example 1, except for changing the formulation as shown in Table 3. Toners Nos. 2 to 10 were then evaluated in the same manner as in Example 1. The evaluation results are shown in Table 4.

[Comparative Examples 1 to 3]
Toner Nos. 11 to 13 having a weight average particle size (D4) of 7.3 μm were produced in the same manner as in Example 1, except for changing the formulation as shown in Table 5. For wax 4 in toner No. 12, Fischer-Tropsch wax having no acid value (C105 manufactured by Sasol: endothermic peak top temperature 104.8° C.) was used. Toner Nos. 11 to 13 were then evaluated in the same manner as in Example 1. The evaluation results are shown in Table 6.

Claims (4)

A magnetic toner containing a binder resin, a hydrocarbon wax, and magnetic iron oxide particles,
The content of the magnetic iron oxide particles in the toner is 30% by mass or more and 70% by mass or less,
The magnetic iron oxide particles have a coating layer containing silicon and aluminum,
The magnetic iron oxide particles are
(i) spherical magnetic iron oxide particles;
(ii) containing hexahedral magnetic iron oxide particles or octahedral magnetic iron oxide particles,
The magnetic toner is characterized in that the hydrocarbon wax has a carboxyl group and has an acid value of 5 mgKOH/g or more and 50 mgKOH/g or less. The magnetic toner according to claim 1, wherein the ratio of the spherical magnetic iron oxide particles to the magnetic iron oxide particles is 1.0% by number or more and 30.0% by number or less. The magnetic toner according to claim 1 or 2, wherein the number-average particle diameter of the magnetic iron oxide particles is 0.10 μm or more and 0.30 μm or less. The magnetic toner according to any one of claims 1 to 3, wherein the binder resin contains a polyester resin, the polyester resin contains ethylene glycol as an alcohol component, and at least one aliphatic compound selected from aliphatic monocarboxylic acids and aliphatic monoalcohols having 30 to 102 carbon atoms is condensed therein, and the aliphatic compound is contained in an amount of 0.10% by mass to 10% by mass based on the total amount of monomers constituting the polyester resin.