JP2019128434A - Toner and method for manufacturing toner - Google Patents

Abstract

To provide a toner excellent in charging maintainability, heat-resistant storage properties, and low-temperature fixability.SOLUTION: A toner contains toner particles 10. The toner particles 10 each contain a toner core 11 and a shell layer 12 covering a surface of the toner core 11. The toner core 11 includes binder resin having a carboxyl group. The shell layer 12 contains resin including a unit having an oxazoline group and a unit having an amide bond. A ratio of absorbancy of a peak of a wave number 1680 cmderived from an oxazoline group to absorbancy of a peak of a wave number 1630 cmderived from the amide bond is larger than 0.00 and 0.25 or less. The content of the shell layer 12 to a mass of the toner particles 10 is 0.15 mass% or more and 0.40 mass% or less.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a toner and a method of manufacturing the toner.

  For example, the toner described in Patent Document 1 contains toner particles including a toner core and a shell layer that covers the surface of the toner core. The shell layer includes a first shell resin and a second shell resin. The first shell resin is a hydrophobic thermoplastic resin. The second shell resin is a hydrophilic thermosetting resin.

JP 2017-9831 A

  The toner described in Patent Document 1 is difficult to attenuate to a certain extent. However, the inventors of the present invention have found that there is room for improvement in terms of improving the charge maintenance property by making it difficult to charge decay the toner further.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a toner that is excellent in heat-resistant storage stability and low-temperature fixability while improving charge maintenance. Another object of the present invention is to provide a method for producing a toner which is excellent in heat-resistant storage stability and low-temperature fixability while improving charge retention.

The toner according to the present invention contains toner particles. The toner particles comprise a toner core and a shell layer covering the surface of the toner core. The toner core contains a binder resin having a carboxyl group. The shell layer contains a resin including a unit having an oxazoline group and a unit having an amide bond. The ratio of the absorbance of the wave number 1680 cm ^-1 peak derived from the oxazoline group to the absorbance of the wave number 1630 cm ^-1 peak derived from the amide bond measured by infrared spectroscopy is greater than 0.00 and 0. 0. 25 or less. The content of the shell layer with respect to the mass of the toner particles is 0.15 mass% or more and 0.40 mass% or less.

The method for producing a toner according to the present invention includes the step of forming a shell layer covering the surface of the toner core by reacting the toner core, the shell material and the ring opening agent in an aqueous medium to obtain toner particles. The shell material has an oxazoline group. The toner core contains a binder resin having a carboxyl group. The ring opening agent has a carboxyl group. The shell layer contains a resin containing a unit having the oxazoline group and a unit having an amide bond. The ratio of the absorbance of the wave number 1680 cm ^-1 peak derived from the oxazoline group to the absorbance of the wave number 1630 cm ^-1 peak derived from the amide bond measured by infrared spectroscopy is greater than 0.00 and 0. 0. 25 or less. The amide bond includes a first amide bond and a second amide bond. The first amide bond is formed by the reaction of the oxazoline group contained in the shell material and the carboxyl group contained in the binder resin contained in the toner core. The second amide bond is formed by the reaction of the oxazoline group of the shell material with the carboxyl group of the ring opening agent. The content of the shell layer with respect to the mass of the toner particles is 0.15 mass% or more and 0.40 mass% or less.

  The toner of the present invention is excellent in charge maintaining property, heat resistant storage property and low temperature fixing property. The toner produced by the production method of the present invention is excellent in charge retention, heat resistant storage stability and low temperature fixability.

FIG. 4 is a diagram illustrating an example of a cross-sectional structure of toner particles contained in a toner according to an exemplary embodiment of the present invention. It is a chromatograph figure of the toner particle measured using the thermal decomposition gas chromatograph mass spectrometer (Py-GC / MS), and this toner particle is contained in the toner concerning an embodiment of the present invention. FIG. 3 is a diagram schematically showing a reaction between a carboxyl group of a binder resin contained in a toner core and an oxazoline group of a shell material. It is a figure which shows typically reaction with the carboxyl group of a ring-opening agent, and the oxazoline group of shell material. It is a graph which shows the calibration curve for calculating shell layer content rate.

The evaluation results (values indicating the shape, physical properties, etc.) of the powder (more specifically, toner core, toner particles, external additive, toner, etc.) were measured for a considerable number of particles unless otherwise specified. It is the number average of the values. Further, the number average particle diameter of the powder is a number average value of equivalent circular diameters of primary particles measured using a microscope, unless specified otherwise. The equivalent circle diameter is the Haywood diameter, and specifically, the diameter of a circle having the same area as the projected area of the particles. In addition, if the measured value of the volume median diameter (D ₅₀ ) of the powder is not specified at all, the Coulter principle (pore electrical resistance method) is performed using “Coulter Counter Multisizer 4” manufactured by Beckman Coulter, Inc. It is the value measured based on The melting point (Mp) is a value measured using a differential scanning calorimeter (“DSC-6220” manufactured by Seiko Instruments Inc.) unless otherwise specified.

  The strength of the charging property is the ease of frictional charging with respect to a standard carrier provided by the Imaging Society of Japan unless otherwise specified. For example, the toner is triboelectrically charged by mixing with a standard carrier (anionic: N-01, cationic: P-01) provided by the Imaging Society of Japan and stirring. Before and after friction charging, the surface potential of the measurement object is measured, for example, with KFM (Kelvin probe force microscope), and the measurement object having a larger potential change before and after friction charging indicates that the charging property is stronger.

  The name of a compound may be followed by “system” to generically generically refer to the compound and its derivative. When a “system” is added after the compound name to represent a polymer name, it means that the repeating unit of the polymer is derived from the compound or its derivative. Acrylic and methacrylic are sometimes collectively referred to as “(meth) acrylic”.

[toner]
Hereinafter, embodiments of the present invention will be described. The present embodiment relates to a toner. The toner comprises toner particles. The toner is an aggregate (powder) of toner particles.

  FIG. 1 shows an example of a cross-sectional structure of toner particles 10 contained in the toner of the present embodiment. A toner particle 10 shown in FIG. 1 includes a toner core 11 and a shell layer 12. The shell layer 12 covers the surface of the toner core 11. The shell layer 12 preferably covers the entire surface of the toner core 11, and more preferably completely covers the entire surface of the toner core 11. The structure of the toner particles contained in the toner has been described above with reference to FIG. Hereinafter, the toner will be further described.

<Absorbance ratio>
In the toner of the present embodiment, the shell layer contains a resin. Hereinafter, “resin contained in the shell layer” may be referred to as “shell resin”. The shell resin includes a unit having an oxazoline group and a unit having an amide bond. The oxazoline group in the unit having an oxazoline group contained in the shell resin has high hydrophilicity. Therefore, if the amount of the oxazoline group in the shell resin is too large, the toner particles are likely to be charge-attenuated, and the charge retention of the toner is lowered. The toner charge maintaining property is a characteristic that the toner particles are difficult to attenuate due to the slow charge decay rate of the toner (the charge decay constant is small), and the charge amount of the toner can be maintained within a desired range. The charge decay of the toner particles due to the hydrophilic oxazoline group is easily caused particularly in a high temperature and high humidity environment. Here, in the toner of the exemplary embodiment, the toner core contains a binder resin having a carboxyl group. The oxazoline group is ring-opened by the reaction of the carboxyl group of the binder resin and the oxazoline group of the shell resin. Moreover, when forming the shell layer of the toner of this embodiment, for example, a ring-opening agent having a carboxyl group is added. The oxazoline group is ring-opened by the reaction of the carboxyl group of the ring-opening agent and the oxazoline group of the shell resin. The ring opening of these oxazoline groups reduces the amount of oxazoline groups in the shell resin. As a result, the amount of the highly hydrophilic oxazoline group can be adjusted within a desired range to make it difficult for the toner particles to be charged and attenuated, and the toner can be improved in charge retention. Further, the carboxyl group of the binder resin and the oxazoline group of the shell resin react to form a chemical bond (specifically, an amide bond) between the toner core and the shell resin. For this reason, it can suppress that a shell layer peels from a toner core. Note that the oxazoline group (unopened oxazoline group) has a cyclic structure and exhibits strong positive chargeability. The positive chargeability of the opened oxazoline group is lower than that of the unopened oxazoline group.

The oxazoline group of the shell resin is reacted with the carboxyl group to open the oxazoline group to form an amide bond. The toner is charged by adjusting the amount of unopened oxazoline group in the shell resin and the amount of oxazoline group opened by reaction with the carboxyl group (corresponding to the amount of amide bond) within a desired range. Maintainability can be improved. The ratio (A / B) of the absorbance (A) of the peak at wave number 1680 cm ^-1 derived from the oxazoline group to the absorbance (B) of the peak at wave number 1630 cm ^-1 derived from the amide bond measured by infrared spectroscopy is , More than 0.00 and not more than 0.25. Hereinafter, “the ratio of the absorbance (A) of the peak at wave number 1680 cm ⁻¹ derived from the oxazoline group to the absorbance (B) of the peak at wave number 1630 cm ⁻¹ derived from the amide bond measured by infrared spectroscopy (A / B) ”may be described as“ IR ratio (A / B) ”.

The absorbance (A) of the peak derived from the oxazoline group indicates the amount of unopened oxazoline group in the shell resin. The peak derived from the oxazoline group is a peak appearing at a wave number of 1680 cm ⁻¹ in the infrared spectrum. The absorbance (B) of the peak derived from the amide bond indicates the amount of the oxazoline group that is ring-opened by reacting with the carboxyl group (corresponding to the amount of the amide bond). The peak derived from the amide bond is a peak appearing at a wave number of 1630 cm ⁻¹ in the infrared spectrum. The IR ratio (A / B) represents the ratio “amount of unopened oxazoline group / amount of open ring oxazoline group”.

  When the IR ratio (A / B) is 0.25 or less, the amount of unopened oxazoline groups relative to the amount of ring-opened oxazoline groups is appropriately reduced, and the toner particles are less likely to be charged and attenuated. Thereby, the charge maintenance property of the toner can be improved. Further, when the IR ratio (A / B) is 0.25 or less, the toner cleaning property is also improved. The amount of the hydrophilic unopened oxazoline group is moderately reduced, so that the toner particles hardly absorb moisture, and the toner particles adhere to the members of the image forming apparatus (for example, the photosensitive drum or the cleaning unit). It is because it can suppress. Although the lower limit value of IR ratio (A / B) is not specifically limited, For example, it can be 0.15 or more. The IR ratio (A / B) is two selected from 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24, and 0.25. It is also preferable to be within the range of values. In addition, the IR ratio (A / B) is 0.17 or more and less than 0.18, 0.18 or more and less than 0.20, 0.20 or more and less than 0.21, 0.21 or more and less than 0.22, 0.22 It may be less than 0.24 or 0.24 or more and 0.25 or less. The IR ratio (A / B) may be 0.17, 0.19, 0.20, 0.21, 0.23, or 0.24.

The IR ratio (A / B) is obtained by measuring toner by the attenuated total reflection (ATR) method using a Fourier Transform Infrared Spectrophotometer (FT-IR). , IR spectrum can be calculated. From the obtained IR spectrum, the absorbance (A) of the peak at 1680 cm ⁻¹ derived from the oxazoline group and the absorbance (B) of the peak at 1630 cm ⁻¹ derived from the amide bond are obtained. Then, the IR ratio (A / B) is calculated according to the equation “IR ratio (A / B) = A / B”. Details of the measurement method of the IR ratio (A / B) will be described in detail in Examples.

  Examples of a method for adjusting the IR ratio (A / B) to a desired value include the following first method, second method, and third method. The first method for adjusting the IR ratio (A / B) is a method of changing the amount of carboxyl groups of the binder resin contained in the toner core. The greater the amount of carboxyl groups in the binder resin contained in the toner core, the greater the amount of oxazoline groups that react to open the ring, so the IR ratio (A / B) decreases. The amount of the carboxyl group of the binder resin contained in the toner core can be adjusted by changing the acid value of the binder resin. The higher the acid value of the binder resin, the greater the amount of carboxyl groups in the binder resin contained in the toner core.

  A second method for adjusting the IR ratio (A / B) is a method of changing the amount of the material for forming the shell layer (shell material) with respect to the amount of the toner core. As the amount of the shell material added relative to the amount of the toner core increases, the amount of oxazoline groups contained in the shell material also increases, and the IR ratio (A / B) increases.

  The third method for adjusting the IR ratio (A / B) is a method of changing the amount of the ring-opening agent added when forming the shell layer. As the addition amount of the ring opening agent to the amount of shell material (or the amount of toner core) increases, the amount of the oxazoline group which is reacted to open the ring increases, so the IR ratio (A / B) decreases.

  The shell resin contains units having an oxazoline group. Preferable examples of the unit having an oxazoline group include units represented by the following formula (A). Hereinafter, the “unit represented by the formula (A)” may be referred to as “unit (A)”.

In formula (A), R ¹ represents a hydrogen atom or an alkyl group which may have a substituent. Examples of the alkyl group represented by R ¹ include a methyl group, an ethyl group, and an isopropyl group. When R ¹ represents an alkyl group having a substituent, examples of such a substituent include a phenyl group. Preferred examples of R ¹ include a hydrogen atom, a methyl group, an ethyl group and an isopropyl group.

  The shell resin further includes a unit having an amide bond in addition to the unit having an oxazoline group. The unit having an amide bond preferably contains a unit having a first amide bond and a unit having a second amide bond.

  The unit having the first amide bond includes a unit represented by the formula (B1). Hereinafter, the “unit represented by the formula (B1)” may be referred to as “unit (B1)”. Among the plurality of units (A) contained in the shell resin, the oxazoline group of some of the units (A) is reacted with the carboxyl group of the binder resin in the toner core to thereby contain the shell resin containing the unit (A). The unit (B1) can be further contained therein.

Wherein (B1), R ¹ represents the same group as R ¹ in formula (A), R ^B represents the atoms constituting the binder resin containing the toner core. R ^B is a constituent atom of the binder resin, the constituent atoms is bonded to a carboxyl group. The unit (A) in the shell layer reacts with the carboxyl group of the binder resin (represented by R ^B in the formula (B1) in the toner core) to ring-open the oxazoline group to give the formula A first amide bond is formed as shown in B1).

  The unit having a second amide bond includes a unit represented by the formula (B2). Hereinafter, the “unit represented by the formula (B2)” may be referred to as “unit (B2)”. For example, in the shell resin containing the unit (A), the oxazoline group of a part of the units (A) among the plurality of units (A) contained in the shell resin is reacted with the carboxyl group of the ring opening agent. Can further include the unit (B2).

In formula (B2), R ¹ represents the same group as R ¹ in formula (A), and R ² represents an alkyl group having 1 to 3 carbon atoms. As R ² , a methyl group or an ethyl group is particularly preferable. When acetic acid is used as the ring-opening agent for the oxazoline group, R ² becomes a methyl group.

As a ring-opening agent, a short chain fatty acid is preferred, an acid represented by the formula “R ² —COOH” is more preferred, and acetic acid or propionic acid is more preferred. Incidentally, R ² in the formula "R ² -COOH" represents the same group as R ² in the formula (B2). By using such a ring-opening agent, a unit represented by the following formula (B2) can be further included in the shell layer containing the unit (A) and the unit (B1).

The ring opening agent is preferably water soluble. When the ring opening agent is water soluble, the ring opening agent can be suitably dissolved in an aqueous medium in the shell layer forming step described later, and the oxazoline group of the shell resin can be suitably ring-opened. If R ² in the formula "R ² -COOH" represents 1 to 3 of alkyl group carbon atoms, water-soluble ring-opening agent is increased.

In an example of a method for confirming that units (A) in the shell layer are opened to form units (B1) and (B2), toner particles are measured by infrared spectroscopy and derived from an amide bond to verify the peak of wavenumber 1630 cm ^-1, and a peak at a wavenumber of 1680 cm ^-1 derived from an oxazoline group. A peak at a wave number of 1630 cm ^-1 derived from an amide bond indicates that units (B1) and (B2) are present in the toner particle. The peak of wave number 1680 cm ^-1 derived from the oxazoline group indicates that the unit (A) is present in the toner particles. The measurement method by infrared spectroscopy is the same method as the measurement of the IR ratio (A / B) in the example or an alternative method thereof.

In another example of the method for confirming that units (A) in the shell layer are opened to form units (B1) and (B2), ¹ H-NMR spectrum of toner particles is measured. ^{In the 1} H-NMR spectrum, a signal of a triplet (triplet) derived from a secondary amide appears in the vicinity of the chemical shift δ 6.5. Therefore, if a triplet signal is confirmed in the vicinity of the chemical shift δ 6.5 in the obtained ¹ H-NMR spectrum, the unit (A) in the shell layer is opened to form the units (B1) and (B2). Is presumed to have formed.

  In order to ensure sufficient low-temperature fixability of the toner, it is preferable that the toner core does not contain an oxazoline group.

<Shell layer content rate>
The content of the shell layer to the mass of the toner particles is 0.15% by mass or more and 0.40% by mass or less. Hereinafter, “the content of the shell layer with respect to the mass of toner particles” may be described as “the content of the shell layer”. When the shell layer content is 0.15% by mass or more, the heat resistant storage stability of the toner is improved. When the shell layer content is 0.40% by mass or less, the low-temperature fixability of the toner is improved. In order to achieve both the heat-resistant storage stability and the low-temperature fixability of the toner, the shell layer content is preferably 0.20% by mass or more and 0.35% by mass or less. The shell layer content is 0.15% by mass, 0.16% by mass, 0.18% by mass, 0.20% by mass, 0.23% by mass, 0.29% by mass, 0.34% by mass, 0.04% by mass. It is also preferable that it is in the range of two values chosen from 35 mass%, 0.36 mass%, 0.39 mass%, and 0.40 mass%. The shell layer content is 0.15% by mass or more and less than 0.18% by mass, 0.18% by mass or more and less than 0.20% by mass, 0.20% by mass or more and less than 0.29% by mass, 0.29% by mass, % By mass to less than 0.35% by mass, 0.35% by mass to less than 0.36% by mass, 0.36% by mass to less than 0.39% by mass, or 0.39% by mass to less than 0.40% by mass There may be. The shell layer content was 0.16% by mass, 0.18% by mass, 0.23% by mass, 0.29% by mass, 0.34% by mass, 0.36% by mass, or 0.39% by mass. May be

  The shell content is measured using a pyrolysis gas chromatography mass spectrometer (Py-GC / MS). First, prepare a calibration curve. The method of preparing a calibration curve is the method described in the examples. Next, toner particles are measured using Py-GC / MS to obtain a chromatograph. FIG. 2 shows an example of a chromatograph of toner particles (each of six types of toner particles) measured using Py-GC / MS. The vertical axis in FIG. 2 indicates signal intensity, and the horizontal axis indicates time (unit: minute). In the obtained chromatograph, the peak area of the peak of the m / z value (m / z 100 in FIG. 2) common to the shell material and the shell resin is calculated. The shell layer content of the toner is calculated from the peak area of the peak of this m / z value using a calibration curve. In addition, the toner particle showing a peak with a large signal intensity has a higher shell layer content. The method of measuring the shell layer content will be described in detail in the examples.

  As a method of adjusting a shell layer content rate to a desired value, the 1st method shown below and the 2nd method are mentioned, for example.

  The first method for adjusting the shell layer content is to change the amount of shell material added to the amount of toner core. As the amount of the shell material added to the amount of the toner core increases, the shell layer content increases.

  The second method for adjusting the shell layer content is a method of changing the acid value of the toner core. The higher the acid value of the toner core, the more carboxyl groups contained in the toner core. The more carboxyl groups, the more reactive sites in the toner core that react with the oxazoline groups of the shell material. When the reaction site of the toner core increases, the amount of shell material attached to the toner core increases, and the shell layer content increases. As already described, the acid value of the toner core can be adjusted, for example, by changing the acid value of the binder resin.

  Next, the toner core and the shell layer will be further described. Note that unnecessary components may be omitted depending on the use of the toner.

<Toner core>
In order to adjust the IR ratio (A / B) and the shell layer content to a desired range, the acid value of the toner core is preferably 5.0 mg KOH / g or more and 30.0 mg KOH / g or less, 10.0 mg KOH / G or more and 20.0 mgKOH / g or less is more preferable. The acid value of the toner core is, for example, 5.0 mg KOH / g or more and 9.0 mg KOH / g or less, 10.0 mg KOH / g or more and 15.0 mg KOH / g or less, or 25.0 mg KOH / g or more and 30.0 mg KOH It may be / g or less. Also, the acid value of the toner core may be, for example, 5.5 mg KOH / g, 13.4 mg KOH / g, or 29.6 mg KOH / g.

  The method for measuring the acid value of the toner core is the method described in the examples or an alternative method thereof. The acid value of the toner core can be adjusted, for example, by changing the acid value of the binder resin contained in the toner core. The higher the acid value of the binder resin, the higher the acid value of the toner core.

  The toner core contains a binder resin. The toner core may optionally contain, for example, at least one of a colorant, a release agent, a charge control agent, and a magnetic powder.

(Binder resin)
The binder resin has a carboxyl group. Examples of the binder resin having a carboxyl group include a polyester resin. The toner core may contain one type of binder resin having a carboxyl group, or may contain two or more types (for example, two types).

  When the toner core contains two or more (for example, two) binder resins having a carboxyl group, the binder resin having a carboxyl group preferably includes a first polyester resin and a second polyester resin. The melting point of the first polyester resin is lower than the melting point of the second polyester resin. The acid value of the first polyester resin is larger than the acid value of the second polyester resin. Alternatively, the acid value of the first polyester resin is equal to the acid value of the second polyester resin. When the toner core contains the first polyester resin and the second polyester resin as the binder resin, the acid value of the toner core can be easily adjusted to a desired value. By adjusting the acid value of the toner core, the IR ratio (A / B) can be adjusted in a desired range.

  The content of the first polyester resin relative to the mass of the toner core is preferably higher than the content of the second polyester resin relative to the mass of the toner core. The ratio of the mass of the first polyester resin to the mass of the second polyester resin is preferably greater than 1.0, more preferably 1.1 or more and 2.0 or less, and 1.1 or more and 1.5 or less. More preferably it is.

  The acid value of the polyester resin is preferably 5 mgKOH / g or more and 50 mgKOH / g or less. When the toner core includes two kinds of the first polyester resin and the second polyester resin, the acid value of the first polyester resin is preferably 5 mgKOH / g or more and 50 mgKOH / g or less, and 7 mgKOH / g or more and 35 mgKOH / g or less. More preferably. The acid value of the second polyester resin is preferably 5 mgKOH / g or more and 50 mgKOH / g or less, and more preferably 5 mgKOH / g or more and 31 mgKOH / g or less. The acid value of the first polyester resin is 15 mg KOH / g and the acid value of the second polyester resin is 15 mg KOH / g; the acid value of the first polyester resin is 35 mg KOH / g and the acid value of the second polyester resin More preferably, the acid value of the first polyester resin is 7 mgKOH / g and the acid value of the second polyester resin is 5 mgKOH / g.

  The acid value of the polyester resin can be measured by a method based on JIS (Japanese Industrial Standard) K0070-1992. The acid value of the polyester resin can be adjusted, for example, by changing the type or amount of the carboxylic acid monomer used to synthesize the polyester resin. The larger the number of carboxylicxyl groups possessed by one carboxylic acid monomer, the higher the acid value of the polyester resin to be synthesized. The greater the amount of carboxylic acid monomer relative to the amount of alcohol monomer, the higher the acid value of the polyester resin.

  The melting point (Mp) of the polyester resin is preferably 80 ° C. or higher and 130 ° C. or lower. When the toner core includes two kinds of the first polyester resin and the second polyester resin, the melting point of the first polyester resin is preferably 80 ° C. or higher and 100 ° C. or lower, and more preferably 92 ° C. The melting point of the second polyester resin is preferably higher than 100 ° C. and 130 ° C. or lower, and more preferably 121 ° C.

  The glass transition point (Tg) of the polyester resin is preferably 80 ° C. or higher and 130 ° C. or lower. When the toner core contains two types of a first polyester resin and a second polyester resin, the glass transition point of the first polyester resin is preferably 40 ° C. or more and 55 ° C. or less, and more preferably 50 ° C. The glass transition point of the second polyester resin is preferably higher than 55 ° C and not higher than 70 ° C, and more preferably 60 ° C. The glass transition point of the polyester resin can be adjusted, for example, by changing the type of alcohol monomer used to synthesize the polyester resin.

  The melting point and glass transition point of the polyester resin can be measured by obtaining an endothermic curve of the sample (polyester resin) using a differential scanning calorimeter (“DSC-6220” manufactured by Seiko Instruments Inc.). Specifically, 15 mg of a sample is placed in an aluminum pan, and the aluminum pan is set in the measurement unit of the measurement apparatus. Use an empty aluminum pan as a reference. In the measurement of the endothermic curve, the temperature of the measurement portion is raised from a measurement start temperature of 10 ° C. to 150 ° C. at a rate of 10 ° C./minute (RUN 1). Thereafter, the temperature of the measurement part is lowered from 150 ° C. to 10 ° C. at a rate of 10 ° C./min. Subsequently, the temperature of the measurement part is increased again from 10 ° C. to 150 ° C. at a rate of 10 ° C./min (RUN2). RUN2 obtains an endothermic curve (vertical axis: heat flow (DSC signal), horizontal axis: temperature) of the sample. The melting point and glass transition point of the sample are read from the obtained endothermic curve. In the endothermic curve, the peak temperature due to the heat of fusion corresponds to the melting point of the sample. In the endothermic curve, the temperature (onset temperature) of the specific heat change point (intersection of the extrapolated line of the base line and the extrapolated line of the falling line) corresponds to the glass transition point of the sample.

  The polyester resin is obtained by condensation polymerization or co-condensation polymerization of an alcohol monomer and a carboxylic acid monomer. The polyester resin is a polymer of an alcohol monomer and a carboxylic acid monomer.

  Examples of alcohol monomers include diol monomers, bisphenol monomers, and trihydric or higher alcohol monomers.

  Examples of diol monomers include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propanediol, 1,3-propanediol, propylene glycol, butanediol (eg, 1,4-butanediol), neopentyl glycol, 2-butene-1,4-diol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, dipropylene glycol, polyethylene glycol, polypropylene glycol, and polytetramethylene glycol .

  Examples of bisphenol monomers include bisphenol A, hydrogenated bisphenol A, and alkylene oxide adducts of bisphenol A. Examples of bisphenol A alkylene oxide adducts include bisphenol A ethylene oxide adducts and bisphenol A propylene oxide adducts.

  Examples of trihydric or higher alcohol monomers include sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, 1,2,4-butanetriol. 1,2,5-pentanetriol, glycerol, diglycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane and 1,3,5-triol. Hydroxymethylbenzene is mentioned.

  Examples of the carboxylic acid monomer include a divalent carboxylic acid monomer and a trivalent or higher carboxylic acid monomer.

  Examples of divalent carboxylic acid monomers include maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, 5-sulfoisophthalic acid, sodium 5-sulfoisophthalate, cyclohexanedicarboxylic acid , Adipic acid, sebacic acid, azelaic acid, malonic acid, succinic acid, alkyl succinic acid, and alkenyl succinic acid. Examples of alkyl succinic acids include n-butyl succinic acid, isobutyl succinic acid, n-octyl succinic acid, n-dodecyl succinic acid, and isododecyl succinic acid. Examples of alkenyl succinic acids include n-butenyl succinic acid, isobutenyl succinic acid, n-octenyl succinic acid, n-dodecenyl succinic acid, and isododecenyl succinic acid.

  Examples of trivalent or higher carboxylic acid monomers include 1,2,4-benzenetricarboxylic acid (trimellitic acid), 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1,2 2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, 1,2,4-cyclohexanetricarboxylic acid, tetra (methylenecarboxyl) methane And 1,2,7,8-octane tetracarboxylic acid, pyromellitic acid, and Empol trimer acid.

  Only one type of alcohol monomer may be used, or two or more types may be used. Only one type of carboxylic acid monomer may be used, or two or more types may be used. Further, the carboxylic acid monomer may be used after being derivatized into an ester-forming derivative. Examples of ester forming derivatives include acid halides, acid anhydrides, and lower alkyl esters. Lower alkyl is, for example, an alkyl group having 1 to 6 carbon atoms.

  The polyester resin is a carboxylic acid containing an alcohol monomer containing at least one of a diol monomer and a bisphenol monomer, and at least one of a divalent carboxylic acid monomer, a trivalent carboxylic acid monomer, and a tetravalent carboxylic acid monomer. It is preferably a polymer with a monomer. The polyester resin is an alcohol monomer containing at least one of bisphenol A alkylene oxide adduct, ethylene glycol, propylene glycol, and butanediol, and at least one of phthalic acid, trimellitic acid, and pyromellitic acid. It is more preferable that it is a polymer with a carboxylic acid monomer containing More preferably, the polyester resin is an alkylene oxide adduct of bisphenol A, ethylene glycol, propylene glycol, butanediol, phthalic acid, trimellitic acid, and a polymer of pyromellitic acid. The polyester resin is particularly preferably a polymer containing only an alkylene oxide adduct of bisphenol A, ethylene glycol, propylene glycol, butanediol, phthalic acid, trimellitic acid, and pyromellitic acid.

  The binder resin may further contain a binder resin other than the polyester resin in addition to the polyester resin. Examples of binder resins other than polyester resins include styrene resins, acrylic acid resins (more specifically, acrylic acid ester polymers or methacrylic acid ester polymers, etc.), olefin resins (more specifically, Polyethylene resin or polypropylene resin, vinyl chloride resin, polyvinyl alcohol, vinyl ether resin, N-vinyl resin, polyamide resin, and urethane resin. Further, a copolymer of each of these resins, that is, a copolymer in which an arbitrary repeating unit is introduced into the resin (specifically, a styrene-acrylic acid resin or a styrene-butadiene resin) is used. May be.

  The content of the binder resin with respect to the mass of the toner core is preferably 30% by mass or more and 95% by mass or less, and more preferably 85% by mass or more and 95% by mass or less. When the toner core contains two or more types of binder resins, the content of the binder resin corresponds to the total content of two or more types of binder resins.

(Colorant)
The toner core may contain a colorant. As the colorant, known pigments or dyes may be used in accordance with the color of the toner. In order to obtain a toner suitable for image formation, the amount of the colorant is preferably 1% by mass or more and 20% by mass or less with respect to the mass of the toner core.

  The toner core may contain a black colorant. An example of a black colorant is carbon black. The black colorant may be a colorant toned to black using a yellow colorant, a magenta colorant, and a cyan colorant.

  The toner core may contain a color colorant. Examples of color colorants include yellow colorants, magenta colorants, and cyan colorants.

  As the yellow colorant, for example, one or more compounds selected from the group consisting of condensed azo compounds, isoindolinone compounds, anthraquinone compounds, azo metal complexes, methine compounds, and arylamide compounds can be used. Examples of yellow colorants include C.I. I. Pigment Yellow (3, 12, 13, 14, 15, 17, 62, 74, 83, 93, 94, 95, 97, 109, 110, 111, 120, 127, 128, 129, 147, 151, 154, 155 168, 174, 175, 176, 180, 181, 191, or 194), naphthol yellow S, Hansa yellow G, and C.I. I. Bat yellow is mentioned.

  Examples of magenta colorants are selected from the group consisting of condensed azo compounds, diketopyrrolopyrrole compounds, anthraquinone compounds, quinacridone compounds, basic dye lake compounds, naphthol compounds, benzimidazolone compounds, thioindigo compounds, and perylene compounds. One or more compounds may be mentioned. Examples of magenta colorants include C.I. I. Pigment red (2, 3, 5, 6, 7, 19, 19, 23, 48: 2, 48: 3, 48: 4, 57: 1, 81: 1, 122, 144, 146, 150, 166, 169, 177 , 184, 185, 202, 206, 220, 221 and 254).

  Examples of cyan colorants include one or more compounds selected from the group consisting of copper phthalocyanine compounds, anthraquinone compounds, and basic dye lake compounds. Examples of cyan colorants include C.I. I. Pigment blue (1, 7, 15, 15: 1, 15: 2, 15: 3, 15: 4, 60, 62 and 66), phthalocyanine blue, C.I. I. Bat Blue, and C.I. I. Acid Blue is mentioned.

(Release agent)
The toner core may contain a release agent. In order to obtain a toner suitable for image formation, the amount of the release agent is preferably 3% by mass or more and 15% by mass or less with respect to the mass of the toner core.

  Examples of the release agent include aliphatic hydrocarbon wax (specifically, low molecular weight polyethylene, low molecular weight polypropylene, polyolefin copolymer, polyolefin wax, microcrystalline wax, paraffin wax, Fischer-Tropsch wax, etc.), fat Group hydrocarbon wax oxides (specifically, oxidized polyethylene wax and block copolymers thereof), vegetable waxes (specifically, candelilla wax, carnauba wax, wood wax, jojoba wax, and rice) Waxes, etc.), animal waxes (specifically, beeswax, lanolin, and whale wax), mineral waxes (specifically, ozokerite, ceresin, and petrolatum), and waxes based on fatty acid esters. (Specifically, montanic acid ester Box, and castor wax, etc.), some or all of the fatty acid ester is de-oxidized waxes (specifically, deoxidized carnauba wax, etc.). As a mold release agent, ester wax is preferable. The toner core may contain only one type of release agent or may contain two or more types of release agents.

(Charge control agent)
The toner core may contain a charge control agent. The charge control agent is used, for example, for the purpose of improving the charging stability and charge rising characteristics of the toner. The charge rising characteristic of the toner is an index as to whether or not the toner can be charged to a predetermined charge level in a short time.

  By adding a negatively chargeable charge control agent (specifically, an organometallic complex, a chelate compound, or the like) to the toner core, the anionicity of the toner core can be enhanced. Further, by adding a positively chargeable charge control agent (specifically, pyridine, nigrosine, quaternary ammonium salt, etc.) to the toner core, the toner core can be made more cationic. However, if sufficient chargeability is ensured in the toner, it is not necessary to include a charge control agent in the toner core.

(Magnetic powder)
The toner core may contain magnetic powder. The material of the magnetic powder includes, for example, ferromagnetic metals (specifically, iron, cobalt, nickel, and alloys thereof), ferromagnetic metal oxides (specifically, ferrite, magnetite, chromium dioxide, etc.) And a material subjected to a ferromagnetic treatment (specifically, a carbon material or the like to which ferromagnetism is imparted by heat treatment). The toner core may contain only one type of magnetic powder, or may contain two or more types of magnetic powder. In order to suppress elution of metal ions (for example, iron ions) from the magnetic powder, it is preferable to surface-treat the magnetic powder.

<Shell layer>
The shell layer contains a shell resin. The shell layer is preferably a layer substantially composed of a shell resin. More preferably, the shell layer contains only a shell resin. In the toner according to the exemplary embodiment, the shell resin includes a unit having an oxazoline group. A suitable example of the unit having an oxazoline group is, for example, the unit (A). Unit (A) can be introduced into the shell resin by polymerizing the compound represented by formula (1). Hereinafter, "the compound represented by Formula (1)" may be described as "the compound (1)." In formula (1), R ¹ represents the same group as R ¹ in formula (A). Preferred examples of R ¹ in formula (1) are the same as the preferred examples of R ¹ in formula (A). When compound (1) is 2-vinyl-2-oxazoline, R ¹ in formula (1) is a hydrogen atom.

The unit (A) corresponds to a repeating unit, and the unit (A) forms the main chain of the shell layer. A polymer (for example, a vinyl resin) is formed by polymerization (addition polymerization) of “C═C” of the compound (1) which is a vinyl compound into “—C—C—”. The vinyl compound is a compound having a vinyl group (CH ₂ CHCH—) or a compound having a group in which a hydrogen atom in the vinyl group is substituted. In addition to the compound (1), a vinyl compound other than the compound (1) may be polymerized to obtain a polymer (for example, a vinyl resin). Examples of vinyl compounds other than the compound (1) include ethylene, propylene, butadiene, vinyl chloride, (meth) acrylic acid, (meth) acrylic acid esters (preferably, (meth) acrylic acid alkyl esters), acrylonitrile, and Styrene is mentioned.

  The shell layer preferably contains a polymer of a monomer containing the compound (1) and the (meth) acrylic acid alkyl ester, and contains a polymer of only the compound (1) and the (meth) acrylic acid alkyl ester Is more preferable. More preferably, the shell layer contains only a polymer of monomers including the compound (1) and the (meth) acrylic acid alkyl ester. A polymer of a monomer containing the compound (1) and a (meth) acrylic acid alkyl ester is a preferred example of a vinyl resin. A monomer is a raw material of shell resin. The monomer which is a raw material of shell resin may be only compound (1) and (meth) acrylic acid alkyl ester. Alternatively, in addition to the compound (1) and the (meth) acrylic acid alkyl ester, the monomer that is a raw material of the shell resin may further include a compound other than the compound (1) and the (meth) acrylic acid alkyl ester.

  A suitable example of compound (1) is 2-vinyl-2-oxazoline. As the (meth) acrylic acid alkyl ester, methyl (meth) acrylate or ethyl (meth) acrylate is preferable, and methyl methacrylate is more preferable. (Meth) acrylic acid alkyl ester is a suitable example of a vinyl compound other than compound (1). By adding the (meth) acrylic acid alkyl ester, the covering property of the shell layer tends to be improved.

  The shell layer may contain a basic substance, but preferably does not contain a basic substance. A basic substance is used as a pH adjuster in the shell layer formation process mentioned later, for example. Examples of the basic substance include ammonia and sodium hydroxide. By not adding the basic substance to the aqueous medium in the shell layer forming step, it is possible to suppress the neutralization (trap) of the carboxylic acid of the binder resin. Thereby, it becomes easy to adjust the IR ratio (A / B) to a desired range. Moreover, it is preferable that a shell layer does not contain a dispersing agent. In order to obtain a toner suitable for image formation, the thickness of the shell layer is preferably 10 nm or more and 100 nm or less.

<External additive>
An external additive (specifically, a powder that is an aggregate of external additive particles) may be adhered to the surface of the toner particles. Unlike the internal additive, the external additive is not present inside the toner particle, and is selectively present only on the surface of the toner particle (the surface layer of the toner particle). For example, the external additive particles can be attached to the surface of the toner particles by stirring the toner particles (powder) and the external additive (powder) together. The toner particles and the external additive particles do not chemically react with each other and physically but not chemically. The strength of bonding between toner particles and external additive particles is determined by stirring conditions (more specifically, stirring time, rotational speed of stirring, etc.), particle diameter of external additive particles, shape of external additive particles, And it can adjust with the surface state of external additive particle etc.

  In order to sufficiently exhibit the function of the external additive while suppressing the detachment of the external additive particle from the toner particles, the amount of the external additive (when using two or more types of external additive particles, The total amount of these external additive particles) is preferably 0.5 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the toner particles. The number average primary particle diameter of the external additive particles is preferably 5 nm or more and 50 nm or less, and more preferably 10 nm or more and 35 nm or less.

  As the external additive particles, inorganic particles are preferable, and particles of silica particles or metal oxides (specifically, alumina, titanium oxide, magnesium oxide, zinc oxide, strontium titanate, barium titanate, etc.) are particularly preferable. preferable. However, as external additive particles, organic acid compound particles such as fatty acid metal salts (specifically, zinc stearate, etc.) or resin particles may be used. The external additive particles may be surface-treated external additive particles, more specifically, external additive particles (positively-charged silica particles) imparted with positive charge by the surface treatment. Only one external additive particle may be provided on the surface of the toner particle, or two or more external additive particles may be provided.

The toner core is roughly classified into a pulverized core and a polymerized core. The toner core obtained by the pulverization method belongs to the pulverization core, and the toner core obtained by the aggregation method belongs to the polymerization core. In the toner of this embodiment, the toner core is preferably a pulverized core. The volume median diameter (D ₅₀ ) of the toner core is preferably 4 μm or more and 9 μm or less. The volume median diameter (D ₅₀ ) of the toner particles is preferably 4 μm or more and 9 μm or less.

  The toner of the present exemplary embodiment can be used for developing an electrostatic latent image, for example, as a positively chargeable toner. The toner may be used as a one-component developer. Further, the toner and the carrier may be mixed to use the toner as a two-component developer. In order to form a high quality image, the amount of toner in the two-component developer is preferably 5 parts by mass or more and 15 parts by mass or less with respect to 100 parts by mass of the carrier. The number average primary particle diameter of the carrier is preferably 20 μm or more and 120 μm or less. When the toner is a one-component developer, the toner is positively charged by friction with the developing sleeve or the toner charging member in the developing device. The toner charging member is, for example, a doctor blade. In the case of a two-component developer containing toner and carrier, the toner is positively charged by being rubbed with the carrier in the developing device.

  The toner of the present exemplary embodiment can be used for image formation in, for example, an electrophotographic apparatus (image forming apparatus). An example of an image forming method by the electrophotographic apparatus will be described. First, an electrostatic latent image is formed on the photosensitive layer of the photosensitive drum based on the image data. Next, the formed electrostatic latent image is developed using a positively charged toner (developing step). In the developing process, the developing device supplies the toner on the developing sleeve to the photosensitive layer of the photosensitive drum and causes the toner to adhere to the electrostatic latent image by an electrical force. Thus, the electrostatic latent image is developed, and a toner image is formed on the photosensitive layer of the photosensitive drum. Subsequently, after the toner image is transferred to a recording medium (for example, paper), the unfixed toner image is fixed to the recording medium by heating (fixing step). Thus, an image is formed on the recording medium.

[Toner Production Method]
Next, a method of producing the toner will be described. The toner production method includes a shell layer forming step. The method of producing the toner may further include a toner core forming step and an external addition step, as required.

(Toner core formation process)
Examples of the method for forming the toner core include an aggregation method and a pulverization method.

  An example of the crushing method will be described. In the toner core forming step, the binder resin and an optional internal additive (for example, at least one of a colorant, a release agent, a charge control agent, and magnetic powder) are mixed. The obtained mixture is kneaded while melting to obtain a kneaded product. The kneaded product is pulverized to obtain a pulverized product. The pulverized product is classified to obtain a toner core.

  Hereinafter, an example of the aggregation method will be described. First, the fine particles of the binder resin, the release agent, and the colorant are aggregated in an aqueous medium to obtain aggregated particles containing the binder resin, the release agent, and the colorant. Subsequently, the obtained aggregated particles are heated to unite the components contained in the aggregated particles. As a result, a dispersion of the toner core is obtained. Thereafter, an unnecessary substance (such as a surfactant) is removed from the dispersion liquid of the toner core to obtain the toner core.

(Shell layer formation process)
The shell layer forming step is a step of obtaining toner particles by forming a shell layer covering the surface of the toner core by reacting the toner core, the shell material, and the ring-opening agent in an aqueous medium.

  The shell layer contains a resin including a unit having an oxazoline group and a unit having an amide bond. The amide bond includes a first amide bond and a second amide bond. The shell material has an oxazoline group. As already described, the toner core contains a binder resin having a carboxyl group. A primary amide bond is formed by the reaction of the oxazoline group possessed by the shell material with the carboxyl group possessed by the binder resin contained in the toner core. As already mentioned, the shell material has an oxazoline group. The ring opening agent has a carboxyl group. The second amide bond is formed by the reaction of the oxazoline group of the shell material with the carboxyl group of the ring-opening agent.

  Hereinafter, an example of the shell layer forming step will be specifically described with reference to FIGS. 3 and 4. FIG. 3 schematically shows the reaction between the carboxyl group of the binder resin contained in the toner core 11 and the oxazoline group of the shell material 112. FIG. 4 schematically shows the reaction between the carboxyl group of the ring-opening agent 113 and the oxazoline group of the shell material 112. 3 and 4, the carbon atom (C) of the oxazoline group and the hydrogen atom (H) bonded to the carbon atom are omitted. The curve in the shell material 112 shown in FIGS. 3 and 4 schematically shows the main chain of the shell material 112.

  In an aqueous medium, the toner core 11 (the toner core 11 obtained in the toner core forming step) and the shell material 112 (for example, an oxazoline group-containing water-soluble polymer) are mixed to obtain a dispersion liquid. Next, while stirring the dispersion, the temperature of the dispersion is increased to the first predetermined temperature at a predetermined temperature increase rate. The heating rate is preferably 0.1 ° C./min or more and 1.0 ° C./min or less, and more preferably 0.5 ° C./min. As 1st predetermined temperature, 45 to 80 degreeC is preferable and 65 degreeC is more preferable. Then, the ring opening agent 113 is added to the dispersion. The temperature of the dispersion is then adjusted to a second predetermined temperature. The second predetermined temperature is preferably 45 ° C. to 80 ° C. and the same temperature as the first predetermined temperature or a temperature lower than the first predetermined temperature, and more preferably 60 ° C. While stirring the dispersion, the temperature of the dispersion is maintained at the second predetermined temperature for a predetermined time. The predetermined time is preferably 0.1 hour or more and 3 hours or less, and more preferably 1 hour.

  As shown in FIG. 3, the toner core 11 has a carboxyl group on the surface. The shell material 112 has an oxazoline group. During the temperature rise of the dispersion or while maintaining the dispersion at a predetermined temperature, the carboxyl group of the toner core 11 and the oxazoline group of the shell material 112 react to form the first amide bond 21. Moreover, as shown in FIG. 4, the ring-opening agent 113 has a carboxyl group. While maintaining the dispersion at a predetermined temperature, the carboxyl group of the ring-opening agent 113 and the oxazoline group of the shell material 112 react to form the second amide bond 22. Furthermore, with the formation of the first amide bond 21 and the formation of the second amide bond 22, the reaction between the shell materials 112 proceeds to form the shell resin 114. As a result, the shell layer 12 (see FIG. 1) containing the shell resin 114 is formed on the surface of the toner core 11. Note that the curve in the shell resin 114 shown in FIG. 4 schematically shows the main chain of the shell resin 114.

  The shell resin 114 also has an oxazoline group (unopened oxazoline group 23) that has not reacted with the carboxyl group. Thus, by opening a part of the oxazoline group to form the first amide bond 21 and the second amide bond 22, the IR ratio (A / B) is larger than 0.00 and 0.25. The following can be adjusted. The IR ratio (A / B) indicates the ratio of the amount of the unopened oxazoline group 23 to the total amount of the first amide bond 21 and the second amide bond 22 (corresponding to the amount of the ring-opened oxazoline group).

  Note that the case where the ring-opening agent 113 is added after raising the temperature of the dispersion to a predetermined temperature has been described as an example. However, the timing of adding the ring opening agent 113 is not particularly limited. The ring opening agent 113 may be added before obtaining the dispersion. Specifically, the ring-opening agent 113 may be added simultaneously with the shell material 112. Further, before obtaining the dispersion, adding the ring-opening agent 113 one or more times during at least one of heating the dispersion and maintaining the temperature of the dispersion at a predetermined temperature for a predetermined time. Also good.

  3 and 4, the reaction between the carboxyl group of the binder resin contained in the toner core 11 and the oxazoline group of the shell material 112, and the carboxyl group of the ring-opening agent 113 and the oxazoline group of the shell material 112 are described above. The reaction with was explained.

  The shell material has an oxazoline group. Since the oxazoline group has high hydrophilicity, the shell material having the oxazoline group has high hydrophilicity. For this reason, the shell material is suitably dissolved in the aqueous medium. Thereby, the toner core, the shell material, and the ring opening agent can be suitably reacted in the aqueous medium. The shell material preferably further has a hydrophobic chain in addition to the oxazoline group. Since the oxazoline group has high hydrophilicity, amphiphilicity can be imparted to the shell material by having a hydrophobic chain. Thereby, shell material can be functioned as a dispersing agent, and shell material can be made to react suitably in an aqueous medium, without using a dispersing agent (for example, surfactant). Moreover, a shell material can be made to react suitably in an aqueous medium, without using an organic solvent. The hydrophobic chain is, for example, the main chain of the shell material. The hydrophobic chain is preferably, for example, an alkyl chain, and more preferably an alkyl chain derived from a vinyl group. The hydrophobic chain preferably does not contain a carbonyl group (> C = O) and an ether bond (—O—).

  As the shell material, an oxazoline group-containing water-soluble polymer is preferable, and a polymer containing a unit (A) is more preferable. A commercial item may be used as a shell material. As a commercial item which can be used as shell material, "Epocross (registered trademark) WS-300" and "Epocross (registered trademark) WS-700" manufactured by Nippon Shokubai Co., Ltd. can be mentioned.

  In the toner particles obtained in the shell layer forming step, the shell layer content is 0.15 mass% or more and 0.40 mass% or less. It is preferable to adjust the amount of the toner core and the amount of the solid content of the shell material so that the shell layer content is in such a range. For example, the solid content of the shell material is preferably 0.30% by mass or more and 1.20% by mass or less, and more preferably 0.35% by mass or more and 1.00% by mass or less with respect to the mass of the toner core. It is more preferable. A shell material can be suitably functioned as a dispersing agent as the amount of solid content of shell material to mass of toner core is 0.30 mass% or more, and aggregation of shell material can be controlled. When the amount of the solid content of the shell material with respect to the mass of the toner core is 1.20% by mass or less, the formed shell layer becomes thin, and the low-temperature fixability of the toner can be improved.

  The total content of the solid content of the shell material and the toner core with respect to the mass of the dispersion is preferably 20% by mass or more and 60% by mass or less, and more preferably 45% by mass or more and 55% by mass or less.

  By changing the amount of the ring opening agent, the amount of the oxazoline group can be adjusted, and the IR ratio (A / B) can be adjusted in the desired range. In order to adjust the IR ratio (A / B) to a desired range, the mass of the ring-opening agent with respect to the mass of the toner core is preferably 0.07% by mass or more and 0.28% by mass or less. In order to adjust the IR ratio (A / B) to a desired range, the amount is such that the number of moles of carboxyl groups contained in the ring opening agent is 50 mol% or more of the number of moles of oxazoline groups in the shell It is preferable to add a ring opening agent.

  The aqueous medium is a medium containing water as a main component (specifically, pure water or a mixed liquid of water and a polar medium). As the polar medium in the aqueous medium, for example, alcohol (specifically, methanol or ethanol) can be used. The boiling point of the aqueous medium is about 100.degree. Preferably, no dispersant is added to the aqueous medium. As already described, since the shell material functions as a dispersant, the reaction of the shell material can proceed in an aqueous medium even when no dispersant is added. Moreover, it is preferable not to add a basic substance to the aqueous medium. By not adding a basic substance to the aqueous medium, neutralization (trap) of the carboxylic acid contained in the binder resin can be suppressed. Thereby, IR ratio (A / B) can be adjusted to a desired range.

  After maintaining the dispersion at a predetermined temperature for a predetermined time, the dispersion is cooled. Subsequently, toner particles are obtained by solid-liquid separation (for example, filtration). Thereafter, the toner particles may be washed, and the washed toner particles may be dried.

(External addition process)
The toner particles and the external additive (for example, powder of silica particles) are mixed using a mixer (for example, an FM mixer manufactured by Nippon Coke Co., Ltd.) to adhere the external additive to the surface of the toner particles . When a spray dryer is used in the drying step, the drying of the toner particles and the external addition step can be simultaneously performed by spraying the dispersion of the external additive onto the toner particles.

  The contents and order of the toner manufacturing method can be arbitrarily changed according to the required configuration or characteristics of the toner. For example, the material (for example, shell material, toner core, or ring-opening agent) may be added to the aqueous medium at a time, or may be added to the aqueous medium in a plurality of times. For example, the toner particles may be sieved after the external addition step. Also, unnecessary steps may be omitted. For example, when a commercially available product can be used as a material as it is, the step of preparing the material can be omitted by using a commercially available product. If an external additive is unnecessary, the external addition step may be omitted. Heretofore, the method for producing the toner of the present embodiment has been described.

  The present invention will be more specifically described using examples. In addition, this invention is not limited at all to the range of an Example. Table 1 shows the compositions of toners A-1 to A-7 and B-1 to B-6 according to Examples or Comparative Examples.

  In Table 1, "Polyester 1", "Polyester 2", "AV", "Mp", "Tg", "parts" and "wt%" are respectively the first polyester resin, the second polyester resin, the acid value, The melting point, glass transition point, parts by mass, and% by mass are shown. The “amount of shell material” in Table 1 indicates the addition amount of the shell material (specifically, the aqueous solution of oxazoline group-containing polymer) with respect to 100 parts by mass of the toner core. In Table 1, “Amount of acetic acid” indicates the amount of acetic acid aqueous solution added to 100 parts by mass of the toner core. In Table 1, “shell layer content” indicates the content of the shell layer with respect to the mass of the toner particles. In Table 1, “IR ratio (A / B)” is the ratio of the absorbance (A) of the peak derived from the oxazoline group to the absorbance (B) of the peak derived from the amide bond measured by infrared spectroscopy (A / B).

  Hereinafter, production methods, measurement methods, evaluation methods, and evaluation results of toners A-1 to A-7 and B-1 to B-6 will be described. In addition, in evaluation which an error produces, the measurement value of the considerable number which an error becomes small enough was obtained, and the number average of the obtained measurement value was made into the evaluation value.

[Toner Production Method]
Polyester resins (1-1) to (1-4) having physical properties shown below were used as the first polyester resin to be contained in the toner core.
Polyester resin (1-1): AV 15 mg KOH / g, Mp 92 ° C., Tg 50 ° C.
Polyester resin (1-2): AV 35 mg KOH / g, Mp 92 ° C., Tg 50 ° C.
Polyester resin (1-3): AV 7 mg KOH / g, Mp 92 ° C., Tg 50 ° C.
Polyester resin (1-4): AV 4 mg KOH / g, Mp 92 ° C., Tg 50 ° C.

As the second polyester resin to be contained in the toner core, polyester resins (2-1) to (2-4) having physical properties shown below were used.
Polyester resin (2-1): AV15 mgKOH / g, Mp121 ° C.
Tg 60 ° C
Polyester resin (2-2): AV 31 mg KOH / g, Mp 121 ° C., Tg 60 ° C.
Polyester resin (2-3): AV 5 mg KOH / g, Mp 121 ° C., Tg 60 ° C.
Polyester resin (2-4): AV 35 mg KOH / g, Mp 121 ° C., Tg 60 ° C.

  Each of the polyester resins (1-1) to (1-4) and (2-1) to (2-4) was synthesized by the following method. In the presence of a catalyst, an alcohol monomer and a carboxylic acid monomer were reacted for 2.5 hours under conditions of a pressure of 0.40 MPa and a temperature of 230 ° C. The addition amount of the catalyst was 0.5 mass% with respect to the total mass of the alcohol monomer and the carboxylic acid monomer. Subsequently, the pressure was returned to normal pressure over 1 hour, and the reaction was further continued for 2 hours under the conditions of normal pressure and a temperature of 230 ° C. As a catalyst, tin 2-ethylhexanoate was used. As the carboxylic acid monomer, phthalic acid, trimellitic acid, and pyromellitic acid were used. As alcohol monomers, alkylene oxide adducts of bisphenol A, ethylene glycol, propylene glycol, and butanediol were used. The molar ratio of alcohol monomer to carboxylic acid monomer was 1: 2. The amount of phthalic acid, the amount of trimellitic acid, the amount of pyromellitic acid, the amount of alkylene oxide adduct of bisphenol A, the ethylene glycol added in the synthesis of each polyester resin so that the polyester resin having the above physical properties can be obtained. The amount of propylene glycol, and the amount of butanediol were adjusted.

<Production of Toner A-1>
Toner A-1 was produced by the following method.

(Toner core formation process)
Using an FM mixer ("FM-10B" manufactured by Nippon Coke Industries Co., Ltd.), 50 parts by mass of polyester resin (1-1), 39 parts by mass of polyester resin (2-1), carbon black ("Mitsubishi Chemical Corporation" MA 100 ′ ′) 8 parts by mass, and ester wax (high purity solid ester wax, “Nissan Electol (registered trademark) WEP-5” manufactured by NOF Corporation, component: pentaerythritol behenate ester wax, melting temperature: 84 ° C.) 3 parts by mass were mixed to obtain a mixture. Using a twin-screw extruder (“TEM-26SS” manufactured by Toshiba Machine Co., Ltd.), the mixture was kneaded while melting to obtain a kneaded product. Using a grinder (formerly Rotoplex (registered trademark) 16/8 type manufactured by Toa Kikai Mfg. Co., Ltd.), the kneaded material was subjected to primary grinding until the diameter of the kneaded material became about 2 mm, to obtain a primary ground product. . The primary pulverized product was subjected to secondary pulverization using a pulverizer (“Turbomill RS type” manufactured by Freund Turbo Inc.) to obtain a secondary pulverized product. The secondary pulverized material was classified using a classifier (wind sorter utilizing Coanda effect: “Elbow jet EJ-LABO type” manufactured by Nittetsu Mining Co., Ltd.) to obtain a toner core. The obtained toner core had a volume median diameter of 7.0 μm.

(Shell layer formation process)
As a shell material, oxazoline group-containing polymer aqueous solution ("Epocross (registered trademark) WS-300" manufactured by Nippon Shokubai Co., Ltd., monomer mass ratio: methyl methacrylate / 2-vinyl-2-oxazoline = 1/9, solid content concentration 10 mass%, Tg: 90 ° C., and oxazoline group content: 7.7 mmol / g) were used. 100 parts by mass of a toner core and 6 parts by mass of an aqueous solution containing an oxazoline group-containing polymer were added into a container of a mixer ("uniaxial free mode mixer FM-10" manufactured by Nikkiso Co., Ltd.). Purified water was added to the container so that the solid content concentration of the container contents was 50% by mass. The contents of the container were mixed to obtain a dispersion until the volume median diameter of the solid content of the container contents reached about 7.0 μm. Subsequently, purified water was added to the dispersion to adjust the solid content concentration of the dispersion to 20% by mass. The dispersion was heated to 65 ° C. at a heating rate of 0.5 ° C./min while the dispersion was stirred at a stirring speed of 240 rpm. The temperature rise causes the carboxyl group of the toner core contained in the dispersion to react with the oxazoline group of the shell material. As a result, the oxazoline group was ring-opened, and a shell layer was formed on the surface of the toner core. When the temperature of the dispersion reached 65 ° C., 14 parts by mass of an acetic acid aqueous solution having a concentration of 1% was added to the dispersion. The temperature of the dispersion was then lowered from 65 ° C. to 60 ° C. while stirring the dispersion at a stirring speed of 240 rpm. The dispersion was then held at 60 ° C. for 1 hour while stirring the dispersion at a stirring speed of 240 rpm. By holding at 60 ° C. for 1 hour, the unopened oxazoline group in the shell layer and the carboxyl group of acetic acid reacted to open the oxazoline group. After maintaining at 60 ° C. for 1 hour, the dispersion was filtered to obtain a residue. The residue was washed with purified water, filtered and dried to obtain toner particles. The volume median diameter of the toner particles was 7.0 μm.

(External addition process)
100.0 parts by mass of toner particles obtained in the shell layer forming step using an FM mixer ("FM-10B" manufactured by Japan Coke Industry Co., Ltd.), positively chargeable silica particles ("AEROSIL (registered by Nippon Aerosil Co., Ltd.) Trademark REA 200 ", number average primary particle diameter: 13 nm, 1.5 parts by mass, titanium oxide particles (" MT-500B "manufactured by Tayca Co., Ltd., untreated titanium oxide fine particles, number average primary particle diameter: 35 nm) 1.5 parts by mass were mixed for 5 minutes under the condition of 3500 rpm. As a result, the external additive particles were adhered to the surface of the toner particles to obtain toner A-1 (a powder composed of a large number of toner particles having the external additive adhered thereto).

<Preparation of Toners A-2 to A-7 and B-1 to B-6>
Each of Toners A-2 to A-7 and B-1 to B-6 was produced in the same manner as the production of Toner A-1 except that the following points were changed. The polyester resin (1-1) was used in the toner core forming step of the toner A-1, but in each toner core forming step of the toners A-2 to A-7 and B-1 to B-6, “Polyester 1” is used. The polyester resin (polyester resin (1-1)-(1-4)) shown in the "type" column of "" was used. The polyester resin (2-1) was used in the toner core forming step of the toner A-1, but in each toner core forming step of the toners A-2 to A-7 and B-1 to B-6, “polyester 2” shown in Table 1 was used. The polyester resin (polyester resin (2-1)-(2-4)) shown in the "type" column of "" was used. In the shell layer forming step of Toner A-1, 6 parts by mass of the oxazoline group-containing polymer aqueous solution was added, but in the shell layer forming step of each of Toners A-2 to A-7 and B-1 to B-6. The oxazoline group-containing polymer aqueous solution was added in the amount shown in the column of “shell material” of 1. In the shell layer forming step of the toner A-1, 14 parts by mass of an acetic acid aqueous solution was added. The shells of the toners A-2 to A-7, B-1 to B-3, and B-5 to B-6 were used. In the layer forming step, an acetic acid aqueous solution in an amount shown in the column “Acetic acid” in Table 1 was added. In the preparation of the toner B-4, since aggregation occurred while the dispersion was being heated in the shell layer forming step, acetic acid could not be added in the shell layer forming step.

[Measuring method]
For each sample (Toners A-1 to A-7, B-1 to B-3, and B-5 to B-6), the acid value of the toner core, the shell layer content, and the IR ratio (A / B) and each were measured. The measurement methods of these were as shown below. The measurement results are shown in Table 1. In the toner B-4, aggregation was generated during heating of the dispersion in the shell layer forming step, and toner particles could not be formed. Therefore, Toner B-4 could not be produced, and the shell layer content and IR ratio (A / B) of Toner B-4 could not be measured.

<Method of measuring acid number of toner core>
The acid value of the toner core was measured by a method according to JIS (Japanese Industrial Standard) K 0070-1992.

<Method of measuring shell layer content>
The shell layer content was measured using Py-GC / MS. Py-GC / MS includes a thermal decomposition apparatus, a gas chromatograph apparatus, and a mass spectrometer. The conditions of the thermal decomposition apparatus were a thermal decomposition furnace temperature of 300 ° C. and an interface temperature of 200 ° C. The conditions of the gas chromatograph are a vaporization chamber temperature of 320 ° C., a column oven temperature of 40 ° C. to 320 ° C. at a heating rate of 40 ° C./min, a carrier gas of He, and a purge flow rate Was 3 mL / min, the injection mode was split, the split ratio was 50, and the measurement sample injection amount was 100 μg. The conditions of the mass spectrometer were an ion source temperature of 220 ° C. and an interface temperature of 320 ° C.

  First, a calibration curve was prepared. Specifically, 100 μg of toner core and 10 μg of a shell material (WS-300 aqueous solution) having a predetermined concentration were mixed to prepare a sample for preparation of a calibration curve. The predetermined concentrations of the WS-300 aqueous solution were three concentrations of a first concentration, a second concentration, and a third concentration. The first concentration was such that the content of the mass of the solid content of the shell material was 0.20% by mass with respect to the total of the mass of the toner core and the mass of the solid content of the shell material. The second concentration was a concentration such that the content of the mass of the solid content of the shell material was 0.40% by mass with respect to the total of the mass of the toner core and the mass of the solid content of the shell material. The third concentration was a concentration such that the content of the mass of the solid content of the shell material was 0.80 mass% with respect to the total of the mass of the toner core and the mass of the solid content of the shell material. The total of the mass of the toner core and the mass of the solid content of the shell material corresponds to the mass of the toner particles. The mass of the solid content of the shell material corresponds to the mass of the shell layer. In addition, the toner core used for preparing the concentration calibration curve was a toner core after the toner core forming step and before the shell layer forming step in the preparation of the toner A-1.

  The sample for calibration curve preparation which used shell material of the 1st density | concentration was measured using said Py-GC / MS, and the chromatograph was obtained. The peak area of the peak at m / z 100 in the obtained chromatograph was calculated. The peak of m / z 100 was a peak derived from methyl methacrylate (MMA) which is a main chain of an aqueous oxazoline group-containing polymer solution (Epocross (registered trademark) WS-300). For the calibration curve preparation sample using the second concentration shell material and the calibration curve preparation sample using the third concentration shell material, the measurement of the calibration curve preparation sample using the first concentration shell material In the same manner, the peak area of the m / z 100 peak in the chromatograph was calculated. Content ratio of each calibration curve preparation sample (specifically, the content ratio of the mass of the solid content of the shell material with respect to the sum of the mass of the toner core and the solid content of the shell material contained in the calibration curve preparation sample), A calibration curve was prepared from the and peak areas. The obtained calibration curve is shown in FIG. The vertical axis in FIG. 5 represents the peak area of the m / z 100 peak. The horizontal axis in FIG. 5 represents the content of the solid content of the shell material relative to the sum of the mass of the toner core and the solid content of the shell material (corresponding to the content of the shell layer with respect to the mass of the toner particles, unit: Mass%).

  Next, the shell layer content of each of toners A-1 to A-7, B-1 to B-3, and B-5 to B-6 was measured. The toner particles used for the measurement were after the shell layer formation step and before the external addition step in the preparation of each of the toners A-1 to A-7, B-1 to B-3, and B-5 to B-6. Toner particles. Using the Py-GC / MS, a measurement sample was measured to obtain a chromatograph. The peak area of the peak at m / z 100 in the obtained chromatograph was calculated. Using the calibration curve, the shell layer content of each toner was calculated from the peak area of the m / z 100 peak.

  In addition, a gas chromatograph mass spectrometer ("GCMS-QP2010 Ultra" manufactured by Shimadzu Corporation) was used as a pyrolysis gas chromatograph mass spectrometer. As the column, a GC column (“Agilent (registered trademark) J & W GC column Duraguard 122-5532G” manufactured by Agilent Technologies, inner diameter: 0.25 mm, film thickness: 0.25 μm, length: 30 m) was used.

<Method of measuring IR ratio (A / B)>
The IR ratio (A / B) was measured by ATR method using FT-IR. Specifically, measurement samples (toners A-1 to A-7, B-1) are measured by the ATR method using FT-IR ("FTS-60A / 896" manufactured by Agilent Technologies, Inc.) under the measurement conditions shown below. -B-3 and B-5 to B-6) were measured to obtain IR spectra.

(IR measurement conditions)
Attachment: One-time reflection ATR attachment (Specac "Silver Gate")
Optical crystal: Ge
Incident angle: 45 °
Resolution: 4 cm ^-1
Integration count: 128 times

  When sufficient sensitivity cannot be obtained, instead of the single reflection ATR attachment (“Silver Gate” manufactured by Specac), the variable angle single reflection ATR (“VeeMax III with ATR” manufactured by ST Japan Co., Ltd.) The measurement sample was measured using VeeMax ") and changing the incident angle from 45 ° to 65 °.

From the obtained IR spectrum, the absorbance at a peak of 1680 cm ^-1 and the absorbance at a peak of 1630 cm ^-1 were obtained. The absorbance at the peak at 1680 cm ⁻¹ is the absorbance (A) of the peak derived from the oxazoline group. The absorbance of the peak at 1630 cm ⁻¹ is the absorbance (B) of the peak derived from the amide bond formed by the reaction of the carboxyl group and the oxazoline group. From the obtained absorbance at 1680 cm ^-1 peak (absorbance (A)) and at 1630 cm ^-1 peak absorbance (absorbance (B)), according to the formula “IR ratio (A / B) = A / B”, The IR ratio (A / B) was calculated.

[Evaluation method]
The evaluation method of each sample (Toner A-1 to A-7, each of B-1 to B-3, and B-5 to B-6) was as follows. The toner B-4 could not be evaluated because aggregation occurred during heating of the dispersion in the shell layer forming step and toner particles could not be formed.

<Charge maintenance>
The charge decay constant of the toner was measured by a method in accordance with JIS (Japanese Industrial Standard) C 61340-2-1 using an electrostatic diffusivity measuring device ("NS-D100" manufactured by NANOCASE CORPORATION). Specifically, the samples (toners A-1 to A-7, B-1 to B-3, and B-5 to B-6) were placed in the measurement cell. The measurement cell was placed in a static diffusivity measurement device, and the sample was charged under the conditions shown below. The surface potential of the sample was continuously measured for 300 seconds after charging (the following measurement time). The charge decay constant α (charge decay rate) was calculated from the surface potential measured during the decay time of 0 second or more and 2 seconds or less according to the formula “V = V ₀ exp (−α√t)”. In the formula, V represents a surface potential [unit: V], V ₀ represents an initial surface potential [unit: V], and t represents a decay time [unit: second]. From the charge decay constant α, the toner charge retention was evaluated based on the following criteria. In addition, the smaller the charge decay constant α, the slower the charge decay rate and the higher the charge retention of the toner.

(Measurement conditions of charge decay constant)
Measurement environment: Temperature 32.5 ° C, relative humidity 80% RH
Charging time: 0.5 seconds Charging polarity: Positive frequency: 10 Hz
Measurement time: 300 seconds

(Evaluation criteria for charge retention)
Good: The charge decay constant is 0.020 or less.
Poor: The charge decay constant is greater than 0.020.

<Heat resistant storage stability>
10 g of toner (object of evaluation: each of toner A-1 to A-7, B-1 to B-3, and B-5 to B-6) is put in a 20 mL polyethylene container, and the container is It left still for 1 hour in the thermostat set to (degreeC). Thereafter, the toner taken out from the thermostat was cooled to 25 ° C. to obtain an evaluation toner.

  Subsequently, the obtained evaluation toner was placed on a 200-mesh (75 μm mesh) sieve of known weight. Then, the mass of the sieve containing the evaluation toner was measured, and the mass of the toner on the sieve (the mass of the toner before screening) was determined. Subsequently, the sieve is set in a powder property evaluation apparatus ("powder tester (registered trademark)" manufactured by Hosokawa Micron Corporation), and the sieve is vibrated for 30 seconds under the condition of rheostat graduation 5 according to the powder tester manual. The toner was sieved. Then, the mass of the toner remaining on the sieve (the mass of the toner after sieving) was determined by measuring the mass of the sieve containing the toner after sieving. From the mass of the toner before sieving and the mass of the toner after sieving, the formula “toner passage rate = 100 × (mass of toner before sieving−mass of toner after sieving) / of toner before sieving” Based on the “mass”, the toner passing rate (unit: mass%) was determined. From the toner passing rate, the heat resistant storage stability of the toner was evaluated based on the following criteria.

(Evaluation criteria for heat-resistant storage stability of toner)
Good: Toner passing rate is 80% by mass or more.
Poor: Toner passing rate is less than 80% by mass.

<Preparation of two-component developer>
Carrier (“resin-coated carrier” manufactured by Powdertech Co., Ltd., carrier core: Cu—Zn ferrite core, coating resin: fluororesin, coating resin / carrier core mass ratio: 1/5, particle diameter: 35 μm, volume resistivity) : 10 ⁷ Ω · cm, saturation magnetization: 70 emu / g) 90 parts by mass, toner (evaluation object: toners A-1 to A-7, B-1 to B-3, and B-5 to B-6) 10 parts by mass of each) were mixed for 30 minutes using a ball mill to obtain a two-component developer.

<Low temperature fixability>
An image was formed using the two-component developer obtained in <Preparation of Two-Component Developer>, and the minimum fixing temperature of the toner was evaluated. As the evaluation machine, a modified machine of a printer (“FS-C5250DN” manufactured by KYOCERA Document Solutions, Inc., configuration of fixing device: Roller-Roller type heat and pressure fixing device, nip width of fixing device: 8 mm) was used. . In the modified machine, the fixing device of the printer (FS-C5250DN) was modified so that the fixing temperature could be changed. The two-component developer was placed in the black developing device of the evaluation machine. Further, a replenishing toner was put in a black toner container of the evaluation machine. As the replenishing toner, the same toner as that contained in the two-component developer was used. The replenishment toners were toners A-1 to A-7, B-1 to B-3, and B-5 to B-6.

Solid, unfixed solid on a paper (A4 size plain paper, 90 g / m ² ) under a toner coverage of 1.0 mg / cm ² in an environment of temperature 23 ° C. and humidity 50% RH using an evaluation machine An image (specifically, an unfixed toner image) was formed. Subsequently, the paper on which the image was formed was passed through the fixing device of the evaluator under the condition that the nip passage time was 40 milliseconds. Then, the fixing temperature of the fixing device was increased from 100 ° C. by 5 ° C., and the lowest temperature (minimum fixing temperature) at which an unfixed solid image can be fixed on paper was measured.

  In the measurement of the lowest fixing temperature, whether or not the toner could be fixed was confirmed by the rubbing test shown below. The evaluation paper passed through the fixing device was folded so that the side on which the image was formed was inside, and was rubbed back and forth 10 times over the crease using a 1 kg weight coated with a fabric. Subsequently, the paper was unfolded, and the folded part of the paper (the part where the solid image was formed) was observed. Then, the peeling length (peeling length) of the toner at the bent portion was measured. The lowest temperature of the fixing temperatures at which the peeling length is 1 mm or less was taken as the lowest fixing temperature (unit: ° C.). From the minimum fixing temperature, the low-temperature fixability of the toner was evaluated based on the following criteria.

(Evaluation criteria for low temperature fixability of toner)
Good: The minimum fixing temperature is 150 ° C. or less.
Poor: The minimum fixing temperature is over 150 ° C.

<Cleanability>
An image was formed using the two-component developer obtained in <Preparation of two-component developer>, and the cleaning property of the toner was evaluated. As an evaluation machine, a color multifunction machine ("TASKalfa 5550ci" manufactured by Kyocera Document Solutions Inc.) was used. A two-component developer was placed in the black developing device of the evaluation machine. Further, a replenishing toner was put in a black toner container of the evaluation machine. As the replenishing toner, the same toner as that contained in the two-component developer was used. The replenishment toners were toners A-1 to A-7, B-1 to B-3, and B-5 to B-6. The developing conditions of the evaluation machine were set such that the amount of toner attached to the photosensitive drum after development was 5 mg / cm ² .

  An image with a printing rate of 5% was continuously formed on 2000 sheets of paper under an environment of temperature 23 ° C. and humidity 50% RH using an evaluation machine. After forming an image on 2,000 sheets of paper, a blank image was formed on one sheet of paper under an environment of a temperature of 23 ° C. and a humidity of 50% RH using an evaluation machine. The obtained blank paper image was visually observed to confirm whether image noise occurred. Image noise is generated when toner drops and adheres to the paper from the cleaning unit of the evaluator. Further, the fog density (FD) of the obtained blank paper image was measured. A fully automatic whiteness meter (“TC-6MC” manufactured by Tokyo Denshoku Co., Ltd.) was used to measure the FD of the blank paper image. The FD of the blank paper image was calculated based on the formula “FD = (reflection density of blank image) − (reflection density of unprinted paper)”. From the FD of the blank paper image, toner cleaning properties were evaluated based on the following criteria.

(Evaluation criteria for toner cleanability)
Good: No image noise due to toner dropping occurs, and FD is 0.01 or less.
Defect: Image noise due to toner dropping occurs, or FD is over 0.01. Alternatively, image noise due to toner drop occurs and the FD exceeds 0.01.

[Evaluation results]
For each of toners A-1 to A-7, B-1 to B-3, and B-5 to B-6, the results of evaluating the charge maintaining property, heat resistant storage property, low temperature fixing property, and cleaning property are It shows in Table 2. In Table 2, “NG” and “wt%” indicate “bad” and “mass%”, respectively.

In the toners A-1 to A-7, the toner particles were provided with a toner core and a shell layer covering the surface of the toner core. The toner core contained a resin having a carboxyl group (specifically, a polyester resin).
The shell layer contained a resin containing a unit having an oxazoline group and a unit having an amide bond. The ratio of the absorbance of the peak derived from the oxazoline group to the absorbance of the peak derived from the amide bond (IR ratio (A / B)) measured by infrared spectroscopy was greater than 0.00 and 0.25 or less. (See Table 1). The content (shell layer content) of the shell layer to the mass of the toner particles was 0.15% by mass or more and 0.40% by mass or less (see Table 1). Therefore, as shown in Table 2, each of the toners A-1 to A-7 was excellent in all of charge retention, heat-resistant storage, and low-temperature fixability. Further, as shown in Table 2, each of the toners A-1 to A-7 was excellent in cleaning properties.

  In Toner B-1, the shell layer content was more than 0.40% by mass (see Table 1). Therefore, as shown in Table 2, the toner B-1 was inferior in low-temperature fixability.

  In Toner B-2, the shell layer content was less than 0.15% by mass (see Table 1). Therefore, as shown in Table 2, the toner B-2 was inferior in heat resistant storage stability.

  In the toner B-3, the shell layer content was more than 0.40% by mass, and the IR ratio (A / B) was more than 0.25 (see Table 1). Therefore, as shown in Table 2, the toner B-3 was inferior in charge maintenance and low-temperature fixability. Further, as shown in Table 2, the toner B-3 was inferior in cleaning properties.

  In the toner B-4, aggregation was generated while the dispersion was heated in the shell layer forming step, and toner particles could not be formed. For this reason, the toner B-4 could not be produced, and it was impossible to evaluate the charge maintaining property, the heat resistant storage property, the low temperature fixing property, and the cleaning property of the toner B-4.

  In each of toners B-5 and B-6, the IR ratio (A / B) was more than 0.25 (see Table 1). Therefore, as shown in Table 2, the toners B-5 and B-6 were inferior in charge maintenance. Further, as shown in Table 2, the toners B-5 and B-6 were inferior in cleaning properties.

  From the above, it has been shown that the toner according to the present invention including the toners A-1 to A-7 is excellent in all of charge maintenance, heat-resistant storage, and low-temperature fixability.

  The toner according to the present invention can be used, for example, to form an image in a copier, a printer, or a multifunction machine.

10: toner particle 11: toner core 12: shell layer 21: primary amide bond 22: secondary amide bond 23: oxazoline group 112: shell material 113: ring opening agent 114: shell resin

Claims (9)

Containing toner particles,
The toner particles include a toner core and a shell layer covering a surface of the toner core,
The toner core contains a binder resin having a carboxyl group,
The shell layer contains a resin containing a unit having an oxazoline group and a unit having an amide bond,
The ratio of the absorbance of the wave number 1680 cm ^-1 peak derived from the oxazoline group to the absorbance of the wave number 1630 cm ^-1 peak derived from the amide bond measured by infrared spectroscopy is greater than 0.00 and 0. 0. 25 or less,
The toner, wherein the content of the shell layer with respect to the mass of the toner particles is 0.15% by mass or more and 0.40% by mass or less. The toner according to claim 1, wherein the unit having an oxazoline group comprises a unit represented by Formula (A).

(In the above formula (A), R ¹ represents a hydrogen atom or an alkyl group which may have a substituent.) The unit having an amide bond includes a unit having a first amide bond and a unit having a second amide bond,
The unit having the first amide bond includes a unit represented by the formula (B1),
The toner according to claim 2, wherein the unit having a second amide bond comprises a unit represented by Formula (B2).

(Wherein (B1), R ¹ represents the same group as R ¹ in the formula (A), R ^B represents the atoms constituting the binder resin the toner core contains.)

(In the formula (B2), R ¹ represents the same group as R ¹ in the formula (A), and R ² represents an alkyl group having 1 or more and 3 or less carbon atoms.) The toner according to claim 2, wherein the shell layer contains a polymer of a monomer including a compound represented by the formula (1) and an alkyl (meth) acrylate.

(In the formula (1), R ¹ represents the same group as R ¹ in the formula (A).)   The toner according to any one of claims 1 to 4, wherein the shell layer contains no basic substance. The binder resin contained in the toner core includes a first polyester resin and a second polyester resin,
The melting point of the first polyester resin is lower than the melting point of the second polyester resin,
The toner according to any one of claims 1 to 5, wherein an acid value of the first polyester resin is larger than an acid value of the second polyester resin or equal to an acid value of the second polyester resin. Forming a shell layer covering the surface of the toner core by reacting the toner core, the shell material, and the ring opening agent in an aqueous medium, to obtain toner particles;
The shell material has an oxazoline group,
The toner core contains a binder resin having a carboxyl group,
The ring opening agent has a carboxyl group,
The shell layer contains a resin containing a unit having the oxazoline group and a unit having an amide bond,
The ratio of the absorbance of the wave number 1680 cm ^-1 peak derived from the oxazoline group to the absorbance of the wave number 1630 cm ^-1 peak derived from the amide bond measured by infrared spectroscopy is greater than 0.00 and 0. 0. 25 or less,
The amide bond includes a first amide bond and a second amide bond,
The first amide bond is formed by reacting the oxazoline group of the shell material with the carboxyl group of the binder resin contained in the toner core.
The second amide bond is formed by reacting the oxazoline group of the shell material with the carboxyl group of the ring opening agent.
The method for producing a toner, wherein the content of the shell layer with respect to the mass of the toner particles is 0.15% by mass or more and 0.40% by mass or less.   The toner manufacturing method according to claim 7, wherein the shell material further has a hydrophobic chain.   The method for producing a toner according to claim 7, wherein the aqueous medium does not contain a dispersant and a basic substance.

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