JP6481455B2 - Toner for electrostatic latent image development - Google Patents

Description

  The present invention relates to an electrostatic latent image developing toner. More specifically, the present invention relates to an electrostatic latent image developing toner that improves document offset resistance while ensuring low-temperature fixability.

Conventionally, there has been a demand for speeding up and energy saving of copying machines, and development of an electrostatic latent image developing toner (hereinafter, also simply referred to as toner) excellent in low-temperature fixability has been advanced. In particular, in recent years, a method using a crystalline resin has been proposed in order to achieve both heat resistance and low-temperature fixability.
The crystalline resin is excellent in thermal response as compared with the amorphous resin, and melts at a specific temperature while maintaining a sufficient strength at a temperature below the melting point, and the viscosity rapidly decreases. When this feature is applied to toner, low-temperature fixing can be achieved without reducing the fluidity and strength of the toner.

  Further, a technique for incorporating a release agent in the toner in order to ensure fixing separation is known. For example, Patent Documents 1 to 3 describe the use of ester wax as a release agent. .

By the way, when a crystalline resin is used in the toner, there is a concern that the high temperature releasability (fixing separation property) is deteriorated or the material is amorphous due to the compatibility with the main binder. On the other hand, there is a method of using styrene / acrylic resin as a main binder as a method for maintaining elasticity at high temperature and maintaining a high crystallinity of the crystalline resin in the main binder.
When a styrene / acrylic resin is used as the main binder, the uptake of the crystalline resin during toner production becomes a problem. However, by optimizing the chain length of the acrylic ester monomer, It has been found that the uptake into can be improved. If an acrylic ester monomer with an optimized chain length is used, the crystalline state of the crystalline resin during the toner can be maintained to obtain heat resistance and fluidity. Thus, low temperature fixability can be obtained.
However, even on paper, the crystalline resin is compatible and plasticized, resulting in a problem that the document offset resistance is lowered.

JP-A-8-50368 JP 2013-160766 A JP 2014-186348 A

  The present invention has been made in view of the above-described problems and circumstances, and a problem to be solved is to provide a toner for developing an electrostatic latent image that improves document offset resistance while ensuring low-temperature fixability. .

  In order to solve the above problems, the present inventor, in the process of examining the cause of the above problems, the styrene acrylic resin obtained by copolymerizing a polymerizable monomer containing at least a compound having a specific structure as a binder resin A resin and a crystalline resin, the release agent contains at least an ester wax, and in the carbon number distribution of the ester wax, the content of the ester having the carbon number corresponding to the highest content is within a specific range. As a result, the inventors have found that it is possible to provide a toner for developing an electrostatic latent image that can improve document offset resistance while ensuring low-temperature fixability.

  That is, the said subject which concerns on this invention is solved by the following means.

1. An electrostatic latent image developing toner containing toner base particles containing at least a binder resin and a release agent,
The binder resin contains at least a styrene / acrylic resin obtained by copolymerizing a polymerizable monomer containing a compound having a structure represented by the following general formula (1) and a crystalline resin,
The release agent contains at least an ester wax;
In the carbon number distribution of the ester wax, the total content of esters having a carbon number within a range of ± 2 of the carbon number corresponding to the highest content is within a range of 85 to 100 % by mass. A toner for developing an electrostatic latent image.

General formula (1)
H ₂ C = CH-COOR
(In the general formula (1), R represents a linear or branched alkyl group having 6 to 12 carbon atoms or a cyclic alkyl group.)

2 . 2. The electrostatic latent image developing toner according to item 1, wherein the total content of the ester having 40 or less carbon atoms contained in the ester wax is 6% by mass or less.

3 . 3. The electrostatic latent image developing toner according to item 1 or 2 , wherein the crystalline resin is a crystalline polyester resin.

  According to the above-described means of the present invention, it is possible to provide a toner for developing an electrostatic latent image that has improved document offset resistance while ensuring low-temperature fixability.

  The expression mechanism / action mechanism of the effect of the present invention is not clear, but is presumed as follows.

  As described above, the use of an acrylic ester monomer with an optimized chain length as an acrylic ester monomer that is a precursor of a styrene / acrylic resin allows the crystalline resin to be incorporated. In addition, although the compatibility at the time of fixing is improved and the fixing property is improved, the glass transition temperature Tg of the image after fixing is low because of the compatibility and plasticization, and the document offset resistance is lowered.

  Therefore, in the present invention, ester wax having a narrow carbon number distribution and high purity is contained as a release agent. Since such ester wax has high crystallinity, a crystalline resin compatible with fixing can become a crystal nucleus for recrystallization on the image, and as a result, document offset resistance of the image can be improved. Inferred.

The electrostatic latent image developing toner of the present invention is an electrostatic latent image developing toner containing toner base particles containing at least a binder resin and a release agent, wherein the binder resin is at least represented by the general formula ( containing a polymerizable monomer copolymerizable obtained by styrene-acrylic resin comprising a compound having a structure represented by 1) a crystalline resin, the releasing agent contains at least an ester wax in the carbon number distribution of the ester wax, the sum of the content of the ester having a number of carbon atoms contained in the range of ± 2 carbon atoms which corresponds to the highest content, in the range of from 85 to 100 wt% It is characterized by that. This feature is a technical feature common to each of the following realities like.

As an embodiment of the present invention, from the viewpoint of further improving document offset resistance, an ester having a carbon number within a range of ± 2 of the carbon number corresponding to the highest content in the carbon number distribution of the ester wax. sum of the content is, Ru der range of 85 to 100 wt%.

  Moreover, it is preferable that the sum total of the content rate of C40 or less ester contained in ester wax is 6 mass% or less. Thereby, melting | fusing point of ester wax becomes high and the heat-resistant storage property of the electrostatic latent image developing toner can be improved.

  Further, from the viewpoint of thermal characteristics (coexistence of low-temperature fixability and heat-resistant storage stability), the crystalline resin is preferably a crystalline polyester resin.

  Hereinafter, the present invention, its components, and modes and modes for carrying out the present invention will be described in detail. In addition, in this application, "-" showing a numerical range is used by the meaning containing the numerical value described before and behind that as a lower limit and an upper limit.

<Electrostatic latent image developing toner>
The electrostatic latent image developing toner of the present invention contains toner base particles containing at least a binder resin and a release agent, and the binder resin has a structure represented by at least the following general formula (1). It contains a styrene / acrylic resin obtained by copolymerizing a polymerizable monomer containing a compound and a crystalline resin, and the release agent contains at least an ester wax. The sum total of the content rate of the ester which has the carbon number contained in the range of +/- 2 of the carbon number corresponding to a high content rate is in the range of 85-100 mass%, It is characterized by the above-mentioned.
Hereinafter, each material constituting the electrostatic latent image developing toner will be described.

<Toner base particles>
The toner base particles according to the present invention include at least a binder resin and a release agent.
In the present invention, toner base particles obtained by adding an external additive are referred to as toner particles, and toner base particles or an aggregate of toner particles are referred to as toner. The toner base particles can be used as toner particles as they are, but in the present invention, toner base particles added with an external additive are used as toner particles.

<Binder resin>
The binder resin according to the present invention contains at least a styrene / acrylic resin and a crystalline resin.

(Styrene / acrylic resin)
The styrene / acrylic resin according to the present invention is synthesized by copolymerizing a polymerizable monomer containing at least a compound having a structure represented by the following general formula (1).

General formula (1)
H ₂ C = CH-COOR
(In the general formula (1), R represents a linear or branched alkyl group having 6 to 12 carbon atoms or a cyclic alkyl group.)

  Examples of the acrylate ester monomer having the structure represented by the general formula (1) include 2-ethylhexyl acrylate, octyl acrylate, cyclohexyl acrylate, dodecyl acrylate, and the like. 2-ethylhexyl acrylate is preferred.

  In the monomer composition of the styrene / acrylic resin, the content of the acrylate monomer is preferably in the range of 2 to 20% by mass, and preferably in the range of 3 to 15% by mass. More preferred. If the content of the acrylate monomer is within the above range, the crystalline resin uptake and document offset resistance are good, and the glass transition temperature (Tg) of the electrostatic latent image developing toner is low. However, the heat resistance does not deteriorate.

  The styrene / acrylic resin according to the present invention is obtained by copolymerizing an acrylate monomer having a structure represented by the general formula (1) and an aromatic vinyl monomer.

  Examples of the aromatic vinyl monomer include styrene, o-methyl styrene, m-methyl styrene, p-methyl styrene, p-methoxy styrene, p-phenyl styrene, p-chloro styrene, p-ethyl styrene, p. -N-butyl styrene, p-tert-butyl styrene, pn-hexyl styrene, pn-octyl styrene, pn-nonyl styrene, pn-decyl styrene, pn-dodecyl styrene, 2, Examples include 4-dimethylstyrene, 3,4-dichlorostyrene, and derivatives thereof.

  As the polymerizable monomer, a third vinyl monomer can also be used. As the third vinyl monomer, acid monomers such as acrylic acid, methacrylic acid, maleic anhydride, vinyl acetic acid, acrylamide, methacrylamide, acrylonitrile, ethylene, propylene, butylene vinyl chloride, N-vinylpyrrolidone, Examples include butadiene.

  The content of the styrene / acrylic resin in the toner for developing an electrostatic latent image is preferably in the range of 50 to 98% by mass, and more preferably in the range of 70 to 95% by mass.

  The glass transition temperature (Tg) of the styrene / acrylic resin is preferably in the range of 20 to 65 ° C, and more preferably in the range of 30 to 63 ° C. When the glass transition temperature (Tg) of the styrene / acrylic resin is within the above range, low temperature fixability is ensured.

In the present invention, the glass transition temperature (Tg) of the styrene / acrylic resin is a value measured using “Diamond DSC” (manufactured by PerkinElmer).
As a measurement procedure, a measurement sample (styrene / acrylic resin) is sealed in an aluminum pan and set in a holder. Use an empty aluminum pan as a reference. The temperature of heating-cooling-heating is controlled, and analysis is performed based on the data of the second heating. From the baseline extension before the rise of the first melting peak and the rising portion of the first peak A tangent line indicating the maximum inclination is drawn up to the peak apex, and the intersection is defined as the glass transition temperature (Tg).

  The softening point of the styrene / acrylic resin is preferably in the range of 80 to 120 ° C., and preferably in the range of 90 to 110 ° C., from the viewpoint of obtaining low temperature fixability for the electrostatic latent image developing toner. More preferred.

In the present invention, the softening point of the styrene / acrylic resin is a value measured by a flow tester.
Specifically, first, in an environment of 20 ° C. and 50% RH, 1.1 g of a measurement sample (styrene / acrylic resin) was placed in a petri dish and left flat for 12 hours or more. -10A "(manufactured by Shimadzu Corporation) with a force of 3820 kg / cm ² for 30 seconds to produce a cylindrical molded sample with a diameter of 1 cm, and then the molded sample is subjected to an environment of 24 ° C and 50% RH. In a cylindrical die (with a load of 196 N (20 kgf), a starting temperature of 60 ° C., a preheating time of 300 seconds, and a heating rate of 6 ° C./min) by a flow tester “CFT-500D” (manufactured by Shimadzu Corporation). 1 mm diameter x 1 mm) from the end of preheating using a 1 cm diameter piston, offset method temperature measured at a melt temperature measurement method of the temperature rising method with an offset value of 5 mm T _offset is the softening point.

The molecular weight measured by gel permeation chromatography (GPC) of a styrene / acrylic resin is preferably in the range of 10,000 to 50,000 in terms of weight average molecular weight (Mw), and preferably in the range of 25,000 to 35,000. More preferred.
Further, the number average molecular weight (Mn) is preferably in the range of 5000 to 20000, and more preferably in the range of 6500 to 12000.
When the molecular weight of the styrene / acrylic resin is within the above range, low-temperature fixability and fixability can be reliably obtained.

In the present invention, the molecular weight of styrene / acrylic resin by gel permeation chromatography (GPC) is a value measured as follows.
Specifically, using an apparatus “HLC-8120GPC” (manufactured by Tosoh Corporation) and a column “TSKguardcolumn + TSKgelSuperHZ-M3 series” (manufactured by Tosoh Corporation), tetrahydrofuran (THF) was allowed to flow as a carrier solvent, and a measurement sample was room temperature (25 ° C.). And dissolved in THF to a concentration of 1 mg / mL using an ultrasonic disperser, and then processed with a membrane filter to obtain a sample solution. This sample solution was injected into the apparatus together with the above carrier solvent, and refracted. Detection is performed using a rate detector (RI detector), and the molecular weight distribution of the measurement sample is calculated using a calibration curve measured using monodisperse polystyrene standard particles. Ten polystyrenes are used for the calibration curve measurement.

The content of styrene / acrylic resin in the binder resin is preferably in the range of 70 to 99% by mass.
When the content of the styrene / acrylic resin is within the above range, when used as a binder resin together with a crystalline resin, sufficient fixability, sufficient heat storage stability of the toner, and heat resistance of the fixed image are obtained. Can be secured.

(Crystalline resin)
The binder resin according to the present invention contains a crystalline resin together with the above-described styrene / acrylic resin.
In the present invention, a crystalline resin is defined as a resin having a clear endothermic peak at the time of temperature rise in an endothermic curve obtained by differential scanning calorimetry (DSC). Here, the “clear endothermic peak” means a peak in which the half-value width of the endothermic peak is within 15 ° C. when measured at a heating rate of 10 ° C./min in differential scanning calorimetry (DSC). To do.

  The crystalline resin according to the present invention includes a crystalline polyester resin, a crystalline polyamide resin, a crystalline polyurethane resin, a crystalline polyacetal resin, a crystalline polyethylene terephthalate resin, a crystalline polybutylene terephthalate resin, a crystalline polyphenylene sulfide resin, Crystalline polyetheretherketone resin, crystalline polytetrafluoroethylene resin, and the like can be mentioned. In particular, from the viewpoint of thermal characteristics (coexistence of low-temperature fixability and heat-resistant storage stability), crystalline polyester resin is preferable, and aliphatic diol is particularly preferable. More preferred is a crystalline aliphatic polyester resin obtained by reacting an aliphatic dicarboxylic acid with an aliphatic dicarboxylic acid.

  The content of the crystalline resin in the binder resin is preferably in the range of 2 to 20% by mass, and more preferably in the range of 5 to 15% by mass. When the content of the crystalline resin is within the above range, sufficient low-temperature fixability and heat-resistant storage properties can be obtained.

  The melting point of the crystalline resin is preferably in the range of 50 to 90 ° C., and more preferably in the range of 60 to 80 ° C., from the viewpoints of low-temperature fixability and heat resistance.

The melting point of the crystalline resin is a value measured as follows.
The melting point of the crystalline resin indicates the temperature at the peak top of the melting peak, and is measured by differential scanning calorimetry using “Diamond DSC” (manufactured by Perkin Elmer).
Specifically, a measurement sample (crystalline resin) is enclosed in an aluminum pan (KITNO.B0143013), this is set in a sample holder of “Diamond DSC”, and temperature control of heating-cooling-heating is performed, The analysis is based on the second heating data.

Examples of the method for preparing the crystalline resin dispersion include a method of emulsifying by mechanical shearing force and a method of phase inversion emulsification, and the method of phase inversion emulsification is preferable.
For example, the phase inversion emulsification includes a dissolution step of dissolving a crystalline resin in an organic solvent to obtain a crystalline resin solution, a neutralization step of adding a neutralizing agent to the crystalline resin solution, and a crystal after neutralization. Emulsifying and dispersing a crystalline resin solution in an aqueous dispersion medium to obtain a crystalline resin emulsion, and a desolvating step of removing the organic solvent from the crystalline resin emulsion to obtain a crystalline resin dispersion. Yes.
The particle size in the crystalline resin dispersion can be controlled by changing the amount of neutralizing agent added.

  Hereinafter, a crystalline polyester resin suitable as the crystalline resin will be described.

(Crystalline polyester resin)
The crystalline polyester resin is defined as described above among polyester resins obtained by a polycondensation reaction between a divalent or higher carboxylic acid (polyvalent carboxylic acid) and a divalent or higher alcohol (polyhydric alcohol). It has a characteristic of crystalline resin.

Examples of the polyvalent carboxylic acid include saturated aliphatic dicarboxylic acids such as succinic acid, alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid, aromatic dicarboxylic acids such as phthalic acid, isophthalic acid and terephthalic acid, trimellitic acid, pyro Examples thereof include trivalent or higher polyvalent carboxylic acids such as merit acid, anhydrides of these carboxylic acid compounds, and alkyl esters having 1 to 3 carbon atoms.
These may be used individually by 1 type and may be used in combination of 2 or more type.

Examples of the polyhydric alcohol include 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, and 1,7-heptane. Examples thereof include aliphatic diols such as diol, 1,8-octanediol, neopentyl glycol, and 1,4-butenediol, and trihydric or higher polyhydric alcohols such as glycerin, pentaerythritol, trimethylolpropane, and sorbitol.
These may be used individually by 1 type and may be used in combination of 2 or more type.
In the present invention, a crystalline aliphatic polyester resin obtained by reacting an aliphatic diol with an aliphatic dicarboxylic acid is more preferable.

<Release agent>
The toner for developing an electrostatic latent image of the present invention contains a release agent in order to ensure fixing separation, and the release agent contains at least an ester wax.
The ester wax according to the present invention is composed of a monoester having a structure represented by the following general formula (2) (hereinafter also simply referred to as an ester).

General formula (2)
R ₁ —COO—R ₂
(In General Formula (2), R ₁ and R ₂ each independently represents a linear alkyl group having 15 to 29 carbon atoms.)

In the present invention, the carbon number of the ester is the total number of carbon atoms in the structure represented by the general formula (2). For example, behenyl behenate CH ₃ (CH ₂ ) ₂₀ COO (CH ₂ ) ₂₁ CH ₃ has the molecular formula C ₄₄ H ₈₈ O ₂ , and therefore has 44 carbon atoms.

The ester wax according to the present invention comprises a plurality of ester species having different carbon numbers as defined above, and within the carbon number distribution of the ester wax, within a range of ± 2 of the carbon number corresponding to the highest content rate. The sum total of the content rate of the ester which has the carbon number contained is in the range of 85-100 mass%. In addition, in carbon number distribution, the ester which has arbitrary carbon numbers is not restricted to 1 type, All the esters which have the same molecular formula are included only in the position of an ester bond differing.
The content of the ester having the carbon number corresponding to the highest content can be controlled by using a material whose carbon number distribution shows monodisperse as a raw material, or by refining the ester wax.

Further, in the carbon number distribution of the ester wax, the total content of esters having a carbon number within a range of ± 2 of the carbon number corresponding to the highest content is within a range of 85 to 100% by mass. but if example embodiment, if the number of carbon atoms which corresponds to the highest content of 44, the sum of the content of the ester of 42-46 carbon atoms, and satisfies the above content.

  Moreover, it is preferable that the sum total of the content rate of C40 or less ester contained in ester wax is 6 mass% or less.

In the present invention, the carbon number corresponding to the highest content in the carbon number distribution of the ester wax is preferably in the range of 42 to 46.
If the number of carbons corresponding to the highest content is within the above range, the heat resistance and chargeability are not adversely affected, internal contamination is suppressed, and good low-temperature fixability can be obtained.

As the ester wax, a synthesized one may be used, or a commercially available one may be purified.
Examples of the synthesized products include synthetic reaction products of higher fatty acids such as behenyl behenate, stearyl stearyl, and behenyl stearate with higher alcohols.
Examples of the purification method include a method of recrystallization by dissolving in n-hexane or heptane.

  As ester wax, carnauba wax, montan wax, behenate behenate, trimethylolpropane tribehenate, pentaerythritol tetrabehenate, pentaerythritol diacetate dibehenate, glycerin tribehenate, 1,18-octadecanediol Distearate, trimellitic trimellitic acid, distearyl maleate and the like can be mentioned.

In the present invention, the carbon number distribution of the ester wax is measured using FD / MS “JMS-T100GC (manufactured by JEOL Ltd.)”.
Specifically, the sample was subjected to 1 mg (dissolved in 1 mL of chloroform), cathode voltage: −10 kV, spectral recording interval: 0.4 s, measurement mass range: m / z 10-2000, and the strength of each carbon number of the ester. The relative strength of each carbon number was calculated, and this was defined as the ester content (mass%) corresponding to each carbon number.

The melting point of the release agent is preferably in the range of 65 to 90 ° C, and more preferably in the range of 65 to 85 ° C.
If the melting point of the release agent is within the above range, it is possible to prevent image defects and to secure fixing separation.
In this invention, melting | fusing point of a mold release agent is the temperature of the main maximum peak (mainpeak) value in the endothermic curve measured according to ASTM D3418-8.

  The content of the release agent in the toner is preferably in the range of 3 to 30% by mass, more preferably in the range of 6 to 20% by mass, from the viewpoints of high temperature releasability and low temperature fixability.

<Colorant>
In the case where the toner base particles are configured to contain a colorant, various known colorants such as carbon black, black iron oxide, dyes, and pigments can be used as the colorant.
Examples of the carbon black include channel black, furnace black, acetylene black, thermal black, and lamp black. Examples of the black iron oxide include magnetite, hematite, and iron iron trioxide.
Examples of the dye include C.I. I. Solvent Red 1, 49, 52, 58, 63, 111, 122, C.I. I. Solvent Yellow 19, 44, 77, 79, 81, 82, 93, 98, 103, 104, 112, 162, C.I. I. Solvent Blue 25, 36, 60, 70, 93, 95 and the like.
Examples of the pigment include C.I. I. Pigment Red 5, 48: 1, 48: 3, 53: 1, 57: 1, 81: 4, 122, 139, 144, 149, 150, 166, 177, 178, 222, 238, 269, C.I. I. Pigment Orange 31 and 43, C.I. I. Pigment yellow 14, 17, 74, 93, 94, 138, 155, 156, 158, 180, 185, C.I. I. Pigment green 7, C.I. I. Pigment Blue 15: 3, 60, and the like.
As the colorant for obtaining the toner of each color, one kind may be used alone for each color, or two or more kinds may be used in combination.

The content of the colorant is preferably contained in the toner base particles within a range of 1 to 10% by mass, and more preferably within a range of 2 to 8% by mass.
If the content of the colorant is within the above range, a desired color strength can be obtained in the obtained toner, the colorant is prevented from being liberated or adhering to a carrier, and the chargeability is not affected. .

<Charge control agent>
In the electrostatic latent image developing toner of the present invention, when the toner base particles are configured to contain a charge control agent, various known compounds can be used as the charge control agent.
The content of the charge control agent is preferably in the range of 0.1 to 10% by mass in the toner base particles, and more preferably 1 to 5% by mass.

<External additive>
In the toner for developing an electrostatic latent image of the present invention, the toner base particles can be used as the toner as they are, but in order to improve fluidity, chargeability, cleaning properties, etc., the toner base particles are provided with a so-called fluidizing agent. An external additive such as a cleaning aid may be added.
Various external additives may be used in combination.
The total amount of these external additives added is preferably in the range of 0.05 to 5 parts by mass, more preferably in the range of 0.1 to 3 parts by mass with respect to 100 parts by mass of the toner base particles. It is assumed to be inside.

<Toner particle size>
The average particle diameter of the toner particles is preferably in the range of 3 to 10 μm, more preferably in the range of ₅ to 8 μm, for example, in terms of volume-based median diameter (d ₅₀ ).
The average particle diameter of the toner particles can be controlled by the concentration of the aggregating agent used in the production, the addition amount of the organic solvent, the fusing time, the composition of the binder resin, and the like.
When the volume-based median diameter (d ₅₀ ) is within the above range, it is possible to faithfully reproduce a very small dot image having a 1200 dpi level.

The volume-based median diameter (d ₅₀ ) of the toner particles is obtained by using a measuring apparatus in which a computer system equipped with data processing software “Software V3.51” is connected to “Multisizer 3” (manufactured by Beckman Coulter). Measured and calculated.
Specifically, the measurement sample (toner) is converted into a surfactant solution (for example, a surfactant solution in which a neutral detergent containing a surfactant component is diluted 10-fold with pure water for the purpose of dispersing toner particles). After adding and mixing, ultrasonic dispersion is performed to prepare a toner particle dispersion, and this toner particle dispersion is measured in a beaker containing “ISOTON II” (manufactured by Beckman Coulter) in a sample stand. Pipette until the indicated concentration on the device is 8%. Here, by using this concentration, a reproducible measurement value can be obtained. In the measuring apparatus, the measurement particle count number is 25000, the aperture diameter is 100 μm, and the frequency value is calculated by dividing the range of 2 to 60 μm, which is the measurement range, into 256 parts. % Particle diameter is defined as a volume-based median diameter (d ₅₀ ).

<Average circularity of toner particles>
The toner particles preferably have an average circularity in the range of 0.930 to 1.000, and preferably in the range of 0.950 to 0.995, from the viewpoints of stability of charging characteristics and low-temperature fixability. Is more preferable.
When the average circularity is within the above range, individual toner particles are less likely to be crushed, the contamination of the frictional charge imparting member is suppressed, the chargeability of the toner is stabilized, and the image quality of the formed image is high. It will be a thing.

The average circularity of the toner particles is a value measured using “FPIA-2100” (manufactured by Sysmex).
Specifically, the measurement sample (toner) was blended with an aqueous solution containing a surfactant, dispersed by performing ultrasonic dispersion for 1 minute, and then subjected to measurement conditions HPF by “FPIA-2100” (manufactured by Sysmex). In the (high magnification imaging) mode, photographing is performed at an appropriate density with an HPF detection number of 3000 to 10,000, the circularity is calculated for each toner particle according to the following formula (I), and the circularity of each toner particle is added. , A value calculated by dividing by the total number of toner particles. If the number of HPF detections is within the above range, reproducibility can be obtained.

Formula (I)
Circularity = (perimeter of a circle having the same projection area as the particle image) / (perimeter of the particle projection image)

<Developer>
The toner for developing an electrostatic latent image of the present invention can be used as a magnetic or non-magnetic one-component developer, but may be mixed with a carrier and used as a two-component developer. When the toner is used as a two-component developer, the carrier uses magnetic particles made of a conventionally known material such as a metal such as iron, ferrite, or magnetite, or an alloy of such a metal with a metal such as aluminum or lead. In particular, ferrite particles are preferred.
Further, as the carrier, a coat carrier in which the surface of the magnetic particles is coated with a coating agent such as a resin, a dispersion type carrier in which a magnetic fine powder is dispersed in a binder resin, or the like may be used.
The volume-based median diameter (d ₅₀ ) of the carrier is preferably in the range of 20 to 100 μm, and more preferably in the range of 25 to 80 μm.
The volume-based median diameter (d ₅₀ ) of the carrier can be typically measured by a laser diffraction particle size distribution measuring apparatus “HELOS” (manufactured by SYMPATEC) equipped with a wet disperser. it can.

<Method for producing toner for developing electrostatic latent image>
<Method for producing toner base particles>
Examples of the method for producing toner base particles according to the present invention include a suspension polymerization method, an emulsion aggregation method, and other known methods, among which the emulsion aggregation method is preferably used. According to this emulsion aggregation method, the toner particles can be easily reduced in size from the viewpoint of production cost and production stability.

  The toner base particle manufacturing method by the emulsion aggregation method includes an aqueous dispersion in which styrene / acrylic resin fine particles containing a release agent are dispersed in an aqueous medium, an aqueous dispersion of colorant fine particles, and an aqueous system of a crystalline resin. In this method, toner dispersion particles are mixed to form toner base particles by aggregating styrene / acrylic resin fine particles, colorant fine particles, and crystalline resin, thereby producing a toner for developing an electrostatic latent image.

  Here, the aqueous dispersion is one in which a dispersion (particles) is dispersed in an aqueous medium, and the aqueous medium is one in which a main component (50% by mass or more) is made of water. Examples of components other than water include organic solvents that dissolve in water, and examples include methanol, ethanol, isopropanol, butanol, acetone, methyl ethyl ketone, and tetrahydrofuran. Among these, alcohol-based organic solvents such as methanol, ethanol, isopropanol, and butanol, which are organic solvents that do not dissolve the resin, are particularly preferable.

  The styrene / acrylic resin fine particles may have a multilayer structure of two or more layers made of binder resins having different compositions, and the styrene / acrylic resin fine particles having such a structure have, for example, a two-layer structure. Styrene-acrylic resin fine particles having a resin fine particle dispersion prepared by a conventional polymerization process (first-stage polymerization), a polymerization initiator and a polymerizable monomer are added to the dispersion, This system can be obtained by a polymerization process (second stage polymerization).

  Hereinafter, as an example of a method for producing the toner for developing an electrostatic latent image of the present invention, a production method by an emulsion aggregation method is shown.

(1) Producing fine particles of styrene / acrylic resin containing a release agent, resin fine particle production step (2) Dissolving the crystalline resin in an organic solvent, emulsifying and dispersing in an aqueous dispersion medium, and removing the organic solvent Crystalline resin fine particle preparation step (3) A colorant fine particle is dispersed in an aqueous medium, and an aqueous dispersion preparation step of a colorant fine particle (4) Styrene in the aqueous medium A core particle is formed by agglomerating acrylic resin fine particles, colorant fine particles and crystalline resin fine particles to form core particles. (5) Aging of associated particles with thermal energy to control the shape to obtain toner base particles. An aging step (6) cooling the dispersion of the toner base particles, a cooling step (7) filtering the toner base particles from the aqueous medium, and removing the surfactant and the like from the toner base particles. Dried over and washing step (8) the washed toner base particles, the addition of external additives to a drying step (9) dried toner mother particles, an external additive addition step

(1) Resin Fine Particle Preparation Step In this step, an aqueous dispersion of styrene / acrylic resin fine particles is prepared.
The aqueous dispersion of styrene / acrylic resin fine particles can be prepared by a miniemulsion polymerization method using a vinyl monomer for obtaining a styrene / acrylic resin.
For example, a vinyl monomer is added to an aqueous medium containing a surfactant, mechanical energy is applied to form droplets, and then in the droplets by radicals from a water-soluble radical polymerization initiator. The polymerization reaction is allowed to proceed. An oil-soluble polymerization initiator may be contained in the droplet.

(Surfactant)
As the surfactant used in this step, conventionally known various anionic surfactants, cationic surfactants, nonionic surfactants and the like can be used.

(Polymerization initiator)
As the polymerization initiator used in this step, various conventionally known polymerization initiators can be used. As specific examples of the polymerization initiator, persulfates (potassium persulfate, ammonium persulfate, etc.) are preferably used. In addition, azo compounds (4,4'-azobis-4-cyanovaleric acid and its salts, 2,2'-azobis (2-amidinopropane) salts, etc.), peroxide compounds, azobisisobutyronitrile, etc. are used. Also good.

(Chain transfer agent)
In this step, a commonly used chain transfer agent can be used for the purpose of adjusting the molecular weight of the styrene / acrylic resin. The chain transfer agent is not particularly limited, and examples thereof include mercaptans such as 2-chloroethanol, octyl mercaptan, dodecyl mercaptan, t-dodecyl mercaptan, and styrene dimer.

  The toner base particles according to the present invention contain a release agent. The release agent can be introduced into the toner base particles by, for example, dissolving or dispersing in advance in a monomer solution for forming a styrene / acrylic resin.

Further, the toner base particles according to the present invention may contain other internal additives such as a charge control agent, if necessary. Such an internal additive can be introduced into the toner base particles by, for example, dissolving or dispersing in advance in a monomer solution for forming a styrene / acrylic resin.
Such an internal additive is prepared by separately preparing a dispersion of internal additive fine particles comprising only the internal additive, and in the core particle forming step, the internal additive together with styrene / acrylic resin fine particles, colorant fine particles and crystalline resin fine particles. Although it is possible to introduce the additive fine particles into the toner base particles by aggregating the additive fine particles, it is preferable to adopt a method of introducing them in advance in this step.

The average particle diameter of the styrene / acrylic resin fine particles is preferably in the range of 100 to 400 nm in terms of volume-based median diameter (d ₅₀ ).
In the present invention, the volume-based median diameter (d ₅₀ ) of the styrene / acrylic resin fine particles is a value measured using “Microtrac UPA-150” (manufactured by Nikkiso Co., Ltd.).

(2) Crystalline resin fine particle preparation step In this step, an aqueous dispersion of crystalline resin fine particles is prepared.
The aqueous dispersion of crystalline resin fine particles can be prepared by synthesizing a crystalline resin and dispersing the crystalline resin in the form of fine particles in an aqueous medium. Specifically, an oil phase liquid is prepared by dissolving or dispersing a crystalline resin in an organic solvent, and the oil phase liquid is dispersed in an aqueous medium by phase inversion emulsification or the like, so that the desired particle size is controlled. It can be prepared by removing the organic solvent after forming oil droplets in a dry state.

The amount of the aqueous medium used is preferably in the range of 50 to 2000 parts by mass and more preferably in the range of 100 to 1000 parts by mass with respect to 100 parts by mass of the oil phase liquid.
In the aqueous medium, a surfactant or the like may be added for the purpose of improving the dispersion stability of the oil droplets. As surfactant, the thing similar to what was mentioned in said process can be mentioned.

The organic solvent used for the preparation of the oil phase liquid is preferably an organic solvent having a low boiling point and low solubility in water from the viewpoint of easy removal after formation of oil droplets. Specific examples include methyl acetate, ethyl acetate, methyl ethyl ketone, methyl isobutyl ketone, toluene, xylene and the like.
These may be used individually by 1 type and may be used in combination of 2 or more type.
The usage-amount of an organic solvent exists in the range of 1-300 mass parts normally with respect to 100 mass parts of crystalline resins.
The emulsification and dispersion of the oil phase liquid can be performed using mechanical energy.

The average particle diameter of the crystalline resin fine particles is preferably in the range of 100 to 400 nm in terms of volume-based median diameter (d ₅₀ ).
In the present invention, the volume-based median diameter (d ₅₀ ) of the crystalline polyester resin fine particles is a value measured using “Microtrac UPA-150” (manufactured by Nikkiso Co., Ltd.).

(3) Colorant fine particle aqueous dispersion preparation step This step is a step that is performed as necessary when a toner base particle containing a colorant is desired, and the colorant is finely divided in an aqueous medium. This is a step of preparing an aqueous dispersion of colorant fine particles by dispersing in the form of particles.

The aqueous dispersion of colorant fine particles can be obtained by dispersing the colorant in an aqueous medium in which a surfactant is added to a critical micelle concentration (CMC) or higher.
The colorant can be dispersed using mechanical energy, and the disperser to be used is not particularly limited. However, an ultrasonic disperser, a mechanical homogenizer, a manton gourin, a pressure homogenizer, or the like is preferably used. Examples thereof include medium dispersers such as a pressure disperser, a sand grinder, a Getzman mill, and a diamond fine mill.

In the dispersed state, the colorant fine particles preferably have a volume-based median diameter (d ₅₀ ) in the range of 10 to 300 nm, more preferably in the range of 100 to 200 nm, and in the range of 100 to 150 nm. It is particularly preferred that
In the present invention, the volume-based median diameter (d ₅₀ ) of the colorant fine particles is a value measured using an electrophoretic light scattering photometer “ELS-800” (manufactured by Otsuka Electronics Co., Ltd.).

(4) Core particle forming step In this step, styrene / acrylic resin fine particles, colorant fine particles and crystalline resin fine particles, and if necessary, fine particles of other toner constituents are aggregated to form core particles. To do.
Specifically, a flocculant having a critical aggregation concentration or higher is added to an aqueous dispersion in which the above-mentioned fine particles are dispersed in an aqueous medium, so that the temperature is equal to or higher than the glass transition temperature (Tg) of the styrene / acrylic resin fine particles. To agglomerate.

(Flocculant)
The flocculant used in this step is not particularly limited, but those selected from metal salts such as alkali metal salts and alkaline earth metal salts are preferably used. Examples of the metal salt include monovalent metal salts such as sodium, potassium, and lithium, divalent metal salts such as calcium, magnesium, manganese, and copper, and trivalent metal salts such as iron and aluminum. Specific metal salts include sodium chloride, potassium chloride, lithium chloride, calcium chloride, magnesium chloride, zinc chloride, copper sulfate, magnesium sulfate, manganese sulfate, and the like. It is particularly preferable to use a divalent metal salt.
These may be used individually by 1 type and may be used in combination of 2 or more type.

(5) Ripening step This step is performed as necessary, and in the maturing step, the toner base particles obtained in the core particle forming step are aged to a desired shape by heat energy. An aging process for forming toner base particles is performed.
Specifically, the aging treatment is performed by adjusting the heating temperature, the stirring speed, the heating time, and the like until the shape of the associated particles reaches a desired circularity by heating and stirring the system in which the associated particles are dispersed. Done.

(6) Cooling step This step is a step of cooling the dispersion of the toner base particles. As a condition for the cooling treatment, it is preferable to cool at a cooling rate of 1 to 20 ° C./min. The specific method of the cooling treatment is not particularly limited, and examples include a method of cooling by introducing a refrigerant from the outside of the reaction vessel, a method of cooling by directly introducing cold water into the reaction system, and the like. Can do.

(7) Filtration / Washing Step In this step, the toner base particles are solid-liquid separated from the cooled dispersion of toner base particles, and the toner cake obtained by solid-liquid separation (the toner base particles in the wet state are caked). This is a step of removing adhering substances such as a surfactant and an aggregating agent from the aggregate).
The solid-liquid separation is not particularly limited, and a centrifugal separation method, a vacuum filtration method using Nutsche or the like, a filtration method using a filter press or the like can be used. Further, in washing, it is preferable to wash with water until the electric conductivity of the filtrate reaches 10 μS / cm.

(8) Drying Step This step is a step of drying the washed toner cake, and can be carried out according to a drying step in a generally-known method for producing toner base particles.
Specifically, examples of the dryer used for drying the toner cake include a spray dryer, a vacuum freeze dryer, a vacuum dryer, and the like. A stationary shelf dryer, a mobile shelf dryer, a fluidized bed, and the like. It is preferable to use a dryer, a rotary dryer, a stirring dryer, or the like.
The moisture content of the dried toner base particles is preferably 5% by mass or less, and more preferably 2% by mass or less.
In addition, when the dried toner base particles are aggregated with a weak interparticle attractive force, the aggregate may be crushed. Here, as the crushing treatment apparatus, a mechanical crushing apparatus such as a jet mill, a Henschel mixer, a coffee mill, or a food processor can be used.

(9) External additive addition step This step is a step that is performed as necessary when an external additive is added to the toner base particles.
The toner base particles can be used as a toner as they are, but in order to improve fluidity, chargeability, cleaning properties, etc., external additives such as so-called fluidizing agents and cleaning aids are added to the toner base particles. You may use in the state which added.
As an external additive mixing device, a mechanical mixing device such as a Henschel mixer or a coffee mill can be used.

  The method for producing a toner for developing an electrostatic latent image of the present invention is sufficient if it comprises at least the above steps (1), (2) and (4). If necessary, steps (3), (5 ) To (9) may be performed. When step (3) is not performed, in step (4), styrene / acrylic resin fine particles and crystalline resin fine particles are aggregated to form core particles.

The toner base particles according to the present invention do not have a core / shell structure, but may have a core / shell structure from the viewpoint of heat resistance. For example, you may provide a shell layer formation process after the core particle formation process of a process (4). At that time, the shell layer is preferably made of an amorphous resin.
The timing of adding the crystalline resin dispersion is preferably the initial stage (temperature raising process) of the core particle forming process of the process (4).

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

<Production of ester wax>
Ester waxes (E-2) to (E-7) as release agents were prepared as follows. As the ester wax (E-1) and (E-8), commercially available N252 (manufactured by Chukyo Yushi Co., Ltd.) and LW400 (manufactured by Sanyo Chemical Industries, Ltd.) were used.
In this example, as long-chain alkylcarboxylic acids having 20, 22 and 24 carbon atoms, icosanoic acid (C ₂₀ H ₄₀ O ₂ ), behenic acid (C ₂₂ H ₄₄ O ₂ ), lignoceric acid (C ₂₄ H) ₄₈ O ₂ ), and as long-chain alkyl alcohols having 20, 22 and 24 carbon atoms, arachidyl alcohol (C ₂₀ H ₄₂ O), behenyl alcohol (C ₂₂ H ₄₆ O), lignoceryl alcohol (C ₂₄ H ₅₀ O) ) Was used.

<Preparation of ester wax (E-2)>
In a four-necked flask reactor equipped with a Dimroth reflux apparatus and a Dean-Stark water separator, 1740 parts by mass of benzene, 130 parts by mass of icosanoic acid, 1040 parts by mass of behenic acid, 130 parts by mass of lignoceric acid, 130 parts by mass of arachidyl alcohol, 1170 parts by mass of behenyl alcohol and 120 parts by mass of p-toluenesulfonic acid were added and sufficiently stirred and dissolved. After refluxing for 5 hours, the water separator valve was opened and azeotropic distillation was performed. After azeotropic distillation, the residue was thoroughly washed with sodium hydrogen carbonate and dried to remove benzene. The obtained product was recrystallized, washed and purified to obtain an ester wax (E-2).

<Production of ester wax (E-3) and (E-5) to (E-7)>
In the production of the ester wax (E-2), except that the types and amounts of the long-chain alkyl carboxylic acid and the long-chain alkyl alcohol were changed as shown in Table 1, the ester wax (E-3) and ( E-5) to (E-7) were prepared.

<Preparation of ester wax (E-4)>
70 parts by mass of ester wax (E-3) and 70 parts by mass of ester wax (E-8) (LW400) were mixed to produce ester wax (E-4).

Table 1 shows the carbon number distribution of the ester waxes (E-1) to (E-8).
The carbon number distribution of each ester wax was measured using FD / MS “JMS-T100GC (manufactured by JEOL Ltd.)”.
Specifically, the sample was subjected to 1 mg (dissolved in 1 mL of chloroform), cathode voltage: −10 kV, spectral recording interval: 0.4 s, measurement mass range: m / z 10-2000, and the strength of each carbon number of the ester. The relative strength of each carbon number was calculated, and this was defined as the ester content (mass%) corresponding to each carbon number.

Table 1 shows the melting points of the ester waxes (E-1) to (E-8).
The melting point of the ester wax was defined as the temperature of the main peak value in the endothermic curve measured according to ASTM D3418-8.

<Preparation of resin fine particle dispersion>
<Preparation of resin fine particle dispersion (R-1)>
(1) First-stage polymerization: Preparation of resin fine particle dispersion (r-1a) In a 5 L reaction vessel equipped with a stirrer, a temperature sensor, a cooling tube, and a nitrogen introducing device, 8.00 parts by mass of sodium dodecyl sulfate and ions 3000 parts by mass of exchange water was charged, and the internal temperature was raised to 80 ° C. while stirring at a stirring speed of 230 rpm under a nitrogen stream. After heating, 10.0 parts by mass of potassium persulfate dissolved in 200 parts by mass of ion-exchanged water was added, the temperature was again adjusted to 80 ° C., and a monomer mixture having the following composition was added dropwise over 1 hour. Polymerization was carried out by heating and stirring at 80 ° C. for 2 hours to prepare a resin fine particle dispersion (r-1a).

(Monomer)
Styrene 480 parts by mass n-butyl acrylate 250 parts by mass Methacrylic acid 68.0 parts by mass

(2) Second-stage polymerization: Preparation of resin fine particle dispersion (r-1b) Polyoxyethylene 2-sodium dodecyl ether sulfate 7 in a 5 L reaction vessel equipped with a stirrer, a temperature sensor, a cooling tube, and a nitrogen introducing device 7 A solution in which 0.000 part by mass is dissolved in 3000 parts by mass of ion-exchanged water is charged and heated to 98 ° C., and then 240 parts by mass of the resin fine particle dispersion (r-1a) is mixed with a monomer and a release agent ( Ester wax) is dissolved at 90 ° C., and mixed and dispersed for 1 hour using a mechanical disperser “CLEARMIX” (M Technique Co., Ltd.) having a circulation path, and contains emulsified particles (oil droplets). A dispersion was prepared.

(Monomer and mold release agent)
Styrene 270 parts by mass n-butyl acrylate 47.0 parts by mass 2-ethylhexyl acrylate 47.0 parts by mass Methacrylic acid 27.0 parts by mass n-octyl-3-mercaptopropionate 6.60 parts by mass Ester wax (E -1) 140 parts by mass

  Next, an initiator solution in which 5.60 parts by mass of potassium persulfate was dissolved in 200 parts by mass of ion-exchanged water was added to this dispersion, and polymerization was performed by heating and stirring the system at 84 ° C. for 1 hour. The resin fine particle dispersion (r-1b) was prepared.

(3) Third-stage polymerization: Preparation of resin fine particle dispersion (R-1) After adding 400 parts by mass of ion-exchanged water to the resin fine particle dispersion (r-1b) and mixing well, 6.60 potassium persulfate. A solution in which part by mass was dissolved in 400 parts by mass of ion-exchanged water was added, and a monomer mixture having the following composition was added dropwise over 1 hour under a temperature condition of 82 ° C. After completion of the dropping, the mixture was heated and stirred for 2 hours, and then cooled to 28 ° C. to prepare a resin fine particle dispersion (R-1) that was an aqueous dispersion.

(Monomer)
Styrene 430 parts by mass n-butyl acrylate 155 parts by mass Methacrylic acid 51.0 parts by mass n-octyl-3-mercaptopropionate 10.2 parts by mass

With respect to the obtained resin fine particle dispersion (R-1), the volume-based median diameter (d ₅₀ ) of the resin fine particles was 230 nm, the glass transition temperature (Tg) was 55 ° C., and the weight average molecular weight (Mw) was 33000. .

The volume-based median diameter (d ₅₀ ) of the resin fine particles was measured using “Microtrac UPA-150” (manufactured by Nikkiso Co., Ltd.).

  The glass transition temperature (Tg) of the resin fine particles is “Diamond DSC” (manufactured by Perkin Elmer), 3.0 mg of a measurement sample (resin fine particles) is enclosed in an aluminum pan, set in a holder, and used as a reference. An empty aluminum pan was used. As the measurement conditions, the temperature of heating-cooling-heating is controlled at a measurement temperature of 0 ° C. to 200 ° C., a temperature increase rate of 10 ° C./min, and a temperature decrease rate of 10 ° C./min. The base line before the rise of the first melting peak and the tangent line indicating the maximum slope between the rising portion of the first peak and the peak apex are drawn, and the intersection is expressed as the glass transition temperature ( Tg).

  Moreover, the weight average molecular weight (Mw) of the resin fine particles was measured using the apparatus “HLC-8120GPC” (manufactured by Tosoh Corporation) and the column “TSKguardcolumn + TSKgelSuperHZ-M3 series” (manufactured by Tosoh Corporation) while maintaining the column temperature at 40 ° C. THF (THF) as a carrier solvent is flowed at a flow rate of 0.2 mL / min, and the measurement sample is treated at room temperature (25 ° C.) using an ultrasonic disperser for 5 minutes. Then, a sample solution is obtained by processing with a membrane filter having a pore size of 0.2 μm, 10 μL of this sample solution is injected into the apparatus together with the carrier solvent, and a refractive index detector (RI detector) is used. Detect and measure the molecular weight distribution of the measurement sample using monodisperse polystyrene standard particles Calculation was performed using the measured calibration curve. Ten polystyrene were used for calibration curve measurement.

<Preparation of resin fine particle dispersions (R-2) to (R-13)>
In preparation of resin fine particle dispersion (R-1), the monomer added in the second stage polymerization and its amount, the type of release agent, and the amount of potassium persulfate were changed as shown in Table 2. In the same manner, resin fine particle dispersions (R-2) to (R-13) were prepared.
Table 3 shows the volume-based median diameter (d ₅₀ ), glass transition temperature (Tg), and weight average molecular weight (Mw) of the resin fine particles for the resin fine particle dispersions (R-2) to (R-13). .

<Preparation of crystalline resin fine particle dispersion>
<Preparation of crystalline resin fine particle dispersion (C-1)>
315 parts by mass of 1,10-decanedicarboxylic acid (dodecanedioic acid) and 252 parts by mass of 1,9-nonanediol are placed in a reaction vessel equipped with a stirrer, a thermometer, a cooling tube, and a nitrogen gas introduction tube. After replacing the inside with dry nitrogen gas, 0.100 part by mass of titanium tetrabutoxide was added, and a polymerization reaction was carried out for 8 hours while stirring at 180 ° C. under a nitrogen gas stream. Furthermore, 0.200 parts by mass of titanium tetrabutoxide is added, the temperature is raised to 220 ° C., and the polymerization reaction is performed for 6 hours while stirring, and then the reaction vessel is depressurized to 10 mmHg and the reaction is performed under reduced pressure. Thus, a crystalline polyester resin was obtained.
The obtained crystalline polyester resin had a weight average molecular weight (Mw) of 14,000 and a melting point (Tm) of 72 ° C.

  The weight average molecular weight (Mw) of the crystalline resin was measured using the apparatus “HLC-8120GPC” (manufactured by Tosoh Corporation) and the column “TSKguardcolumn + TSKgelSuperHZ-M3 series” (manufactured by Tosoh Corporation) while maintaining the column temperature at 40 ° C. Tetrahydrofuran (THF) as a solvent is flowed at a flow rate of 0.2 mL / min, and the measurement sample is treated with tetrahydrofuran at a room temperature (25 ° C.) for 5 minutes using an ultrasonic disperser so that the concentration is 1 mg / mL. Next, the sample solution is obtained by processing with a membrane filter having a pore size of 0.2 μm, and 10 μL of this sample solution is injected into the apparatus together with the carrier solvent, and detected using a refractive index detector (RI detector). The molecular weight distribution of the sample to be measured using monodisperse polystyrene standard particles It calculated using the calibration curve measured using. Ten polystyrene were used for calibration curve measurement.

  The melting point (Tm) of the crystalline resin is “Diamond DSC” (Perkin Elmer), and 1.0 mg of a measurement sample (crystalline resin) is enclosed in an aluminum pan (KITNO.B0143013). Is set in the sample holder of “Diamond DSC”, and heating-cooling-heating temperature control is performed under the measurement conditions of measurement temperature 0-200 ° C., temperature increase rate 10 ° C./min, temperature decrease rate 10 ° C./min. The endothermic peak temperature in the DSC curve during the second temperature raising process was defined as the melting point of the crystalline resin.

Next, 72.0 parts by mass of the obtained crystalline polyester resin was dissolved in 72.0 parts by mass of methyl ethyl ketone at 70 ° C. for 30 minutes. Next, 2.50 mass parts of 25.0 mass% sodium hydroxide aqueous solution was added to this solution. This solution was put into a reaction vessel having a stirrer, and 252 parts by mass of water warmed to 70 ° C. was dropped and mixed over 70 minutes while stirring. During the dropping, the liquid in the container became turbid, and a uniform emulsified state was obtained after the entire amount was dropped. As a result of measuring the particle size of the oil droplets of this emulsion with a laser diffraction particle size distribution analyzer “LA-750 (manufactured by HORIBA)”, the volume-based median diameter (d ₅₀ ) was 120 nm.

Next, while maintaining the temperature of this emulsion at 70 ° C., a diaphragm type vacuum pump “V-700” (manufactured by BUCHI) was used and stirred at 15 kPa (150 mbar) under reduced pressure for 3 hours to obtain methyl ethyl ketone (MEK). Was removed by distillation to prepare a crystalline resin fine particle dispersion (C-1), which is an aqueous dispersion in which crystalline polyester resin fine particles are dispersed.
As a result of the measurement using the particle size distribution analyzer, the volume-based median diameter (d ₅₀ ) of the crystalline polyester resin fine particles in the dispersion of the crystalline polyester resin fine particles was 75 nm.

<Preparation of crystalline resin fine particle dispersion (C-2)>
A reaction vessel equipped with a stirrer and a thermometer was charged with 45.0 parts by mass of 1,4-butanediol, 60.0 parts by mass of 1,6-hexanediol, and 300 parts by mass of methyl ethyl ketone. To this solution, 250 parts by mass of 4,4′-diphenylmethane diisocyanate was added and reacted at 65 ° C. for 10 hours, and then the solvent was removed to obtain a crystalline polyurethane resin.
The obtained crystalline polyurethane resin had a weight average molecular weight Mw of 37000 and a melting point (Tm) of 70 ° C.

Next, 72.0 parts by mass of the obtained crystalline polyurethane resin was dissolved in 72.0 parts by mass of THF at 75 ° C. for 30 minutes. Next, 1.00 parts by mass of a 25.0% by mass aqueous sodium hydroxide solution was added to the solution. This solution was put into a reaction vessel having a stirrer, and 252 parts by mass of water warmed to 75 ° C. was added dropwise over 70 minutes while stirring. During the dropping, the liquid in the container became turbid, and a uniform emulsified state was obtained after the entire amount was dropped. As a result of measuring the particle size of the oil droplets of this emulsion with a laser diffraction particle size distribution analyzer “LA-750 (manufactured by HORIBA)”, the volume-based median diameter (d ₅₀ ) was 160 nm.

Next, while maintaining the temperature of this emulsion at 75 ° C., a diaphragm vacuum pump “V-700” (manufactured by BUCHI) was used and stirred at 15 kPa (150 mbar) under reduced pressure for 3 hours to distill off THF. Then, a crystalline resin fine particle dispersion (C-2), which is an aqueous dispersion in which the crystalline polyurethane resin fine particles are dispersed, was prepared.
As a result of measurement with the particle size distribution analyzer, the volume-based median diameter (d ₅₀ ) of the crystalline polyurethane resin fine particles in the dispersion of the crystalline polyurethane resin fine particles was 110 nm.

<< Preparation of Colorant Fine Particle Dispersion >>
90.0 parts by mass of sodium dodecyl sulfate was added to 1600 parts by mass of ion-exchanged water. While stirring this solution, 420 parts by mass of copper phthalocyanine (CI Pigment Blue 15: 3) is gradually added, and then dispersed using a stirrer “CLEARMIX” (manufactured by M Technique). Thus, an aqueous dispersion of colorant fine particles was prepared.
With respect to the obtained aqueous dispersion of colorant fine particles, the volume-based median diameter (d ₅₀ ) of the colorant fine particles was 110 nm.

The volume-based median diameter (d ₅₀ ) of the colorant fine particles was measured using an electrophoretic light scattering photometer “ELS-800” (manufactured by Otsuka Electronics Co., Ltd.).

<Production of toner>
<Preparation of Toner (1)>
In a reaction vessel equipped with a stirrer, a temperature sensor, and a cooling pipe, 288 parts by mass of resin fine particle dispersion (R-1) (converted to solid content), 70.0 parts by mass of crystalline resin fine particle dispersion (C-1) ( After the addition of 2000 parts by mass of ion-exchanged water), a 5 mol / L aqueous sodium hydroxide solution was added to adjust the pH to 10.

Thereafter, 30.0 parts by mass of the colorant fine particle dispersion (in terms of solid content) was added, and then an aqueous solution in which 60.0 parts by mass of magnesium chloride was dissolved in 60.0 parts by mass of ion-exchanged water was stirred at 30 ° C. In 10 minutes. Thereafter, the temperature was raised after standing for 3 minutes, and the temperature of the system was raised to 80 ° C. over 60 minutes, and the crystalline resin fine particle dispersion (C-1) was added over 10 minutes. Thereafter, the particle growth reaction was continued while maintaining 80 ° C. In this state, the particle size of the associated particles was measured with “Coulter Multisizer 3” (manufactured by Coulter Beckman). When the volume-based median diameter (d ₅₀ ) reached 6.0 μm, 190 mass of sodium chloride was obtained. Particulate growth was stopped by adding an aqueous solution having a part dissolved in 760 parts by mass of ion-exchanged water. The particles are fused by heating and stirring while maintaining 80 ° C., and using a measuring device “FPIA-3000” (manufactured by Sysmex) for measuring the average circularity of the toner base particles (the number of detected HPF is 4000). ), When the average circularity reached 0.960, it was cooled to 30 ° C. at a cooling rate of 2.5 ° C./min.

  Next, the solid-liquid separated and dehydrated toner cake is re-dispersed in ion-exchanged water, and the solid-liquid separation operation is repeated three times, washed, and then dried at 40 ° C. for 24 hours, whereby toner base particles (1) Got.

To 100 parts by mass of the obtained toner base particles (1), 0.600 parts by mass of hydrophobic silica (number average primary particle size = 12 nm, degree of hydrophobicity = 68) and hydrophobic titanium oxide (number average primary particle size = 20 nm). , Hydrophobic degree = 63) 1.00 parts by mass were added, and after mixing for 20 minutes at 32 ° C. with a rotating blade peripheral speed of 35 mm / sec by “Henschel mixer” (manufactured by Mitsui Miike Chemical Co., Ltd.), an opening of 45 μm The toner (1), which is an aggregate of cyan toner particles having a volume-based median diameter (d ₅₀ ) of 6.0 μm, was obtained by performing an external additive treatment that removes coarse particles using a sieve (1).

The volume-based median diameter (d ₅₀ ) of the toner particles is obtained by using a measuring apparatus in which a computer system equipped with data processing software “Software V3.51” is connected to “Multisizer 3” (manufactured by Beckman Coulter). After adding 0.02 g of a measurement sample (toner) to 20 mL of a surfactant solution and acclimatizing, ultrasonic dispersion was performed for 1 minute to prepare a toner particle dispersion, and this toner particle dispersion was used as a sample stand. The solution was poured into a beaker containing “ISOTONII” (manufactured by Beckman Coulter, Inc.) with a pipette until the display concentration of the measuring apparatus reached 8%. In the measuring apparatus, the measurement particle count number is 25000, the aperture diameter is 100 μm, and the frequency value is calculated by dividing the range of 2 to 60 μm, which is the measurement range, into 256 parts. % Particle diameter was defined as a volume-based median diameter (d ₅₀ ).

<Preparation of Toners (2) to (14)>
Toners (2) to (14) were prepared in the same manner except that the resin fine particle dispersion and the crystalline resin dispersion were changed as shown in Table 4 in the production of the toner (1).

<Production of developer>
To each toner obtained, a ferrite carrier having a volume-based median diameter (d ₅₀ ) of 60 μm coated with a silicone resin is added and mixed so that the toner concentration is 6.50% by mass, thereby developing the developer. Was made.

<Evaluation>
As an image forming apparatus for evaluation, a multi-function machine “bizhub PRESS C1070” (manufactured by Konica Minolta Co., Ltd.) was used. The fixing device was modified so that the surface temperature of the heating roller could be changed in increments of 5 ° C. in the range of 120 to 180 ° C.

<Low-temperature fixability (under offset property)>
Under offset refers to an image defect that peels from a transfer material such as recording paper because the toner layer is not sufficiently melted by the heat applied when passing through the fixing device.
Evaluation of low-temperature fixability is carried out by sequentially loading the toner and developer prepared above in an image forming apparatus, and NPI 128 g / m ² (Japan) in an image forming apparatus under a normal temperature and humidity environment (20 ° C., 50% RH). An unfixed solid image (adhesion amount of 11.3 g / m ² ) was formed on paper. Next, the surface temperature of the pressure roller of the fixing device was set to 100 ° C., and the surface temperature of the heating roller was changed in a range of 120 to 180 ° C. in steps of 5 ° C. to perform fixing. At this time, the lower limit fixing temperature of the upper fixing belt where no under-offset occurs was evaluated and used as an index for low-temperature fixability. The lower the fixing lower limit temperature, the better the fixing property, and a temperature lower than 160 ° C. was regarded as acceptable.
The evaluation results are shown in Table 4.

<Document offset resistance>
On the obtained solid image, 5000 sheets (20 kg) of paper were pressed for 24 hours, and then the state when peeled was evaluated according to the following evaluation criteria. An evaluation standard of 4 or higher is regarded as an acceptable level.
The evaluation results are shown in Table 4.

5: Paper does not stick to the solid image.
4: A little paper sticks to the solid image. Fixing strength represented by the following formula (II) is 95% or more.
3: A little paper sticks to the solid image. The fixing strength represented by the following formula (II) is 90% or more and less than 95%.
2: Paper sticks to a solid image. The fixing strength shown in the following formula (II) is 85% or more and less than 90%.
1: Paper sticks to a solid image. Fixing strength represented by the following formula (II) is less than 85%.

Formula (II)
Fixing strength _{(%) = D 1 / D} 0 × 100
Wherein (II), D ₀ denotes the absolute reflection density before peeling. D ₁ represents the absolute reflection density after peeling. ]

  For the measurement of absolute reflection density, a reflection densitometer “RD-918” (manufactured by Macbeth Co.) was used.

<Heat resistant storage>
Take 0.5 g of each prepared toner in a 10 mL glass bottle with an inner diameter of 21 mm, close the lid, and shake it 600 times at room temperature (25 ° C.) using a shaker “Tap Denser KYT-2000” (manufactured by Seishin Enterprise Co., Ltd.). After that, it was left for 2 hours in an environment of a temperature of 55 ° C. and a humidity of 35% RH with the lid removed. Next, the toner is placed on a 48 mesh (aperture 350 μm) sieve, taking care not to break up the toner aggregates, and set in a “powder tester” (manufactured by Hosokawa Micron). After fixing and adjusting the vibration intensity to a feed width of 1 mm and applying vibration for 10 seconds, the ratio (mass%) of the toner amount remaining on the sieve was measured, and the toner aggregation rate was calculated by the following formula. This test was repeated until the toner aggregation rate exceeded 50 mass% while increasing the test temperature by 0.1 ° C. while maintaining the humidity at 35% RH. The maximum test temperature (limit heat resistant storage temperature) at which the toner aggregation rate does not exceed 50% by mass was used as an index of heat resistant storage property. In this invention, the case where a limit heat-resistant storage temperature is 58 degreeC or more is set as a pass.
The evaluation results are shown in Table 4.

  Toner aggregation rate (mass%) = residual toner mass on sieve (g) /0.5 (g) × 100

As is apparent from Table 4, it can be seen that the toner of the present invention is superior in low-temperature fixing property, document offset resistance and heat-resistant storage property as compared with the toner of the comparative example.
From the above, the binder resin contains at least a styrene / acrylic resin obtained by copolymerizing a polymerizable monomer containing a compound having a structure represented by the general formula (1) and a crystalline resin, The release agent contains at least an ester wax, and the ester content having a carbon number corresponding to the highest content in the carbon number distribution of the ester wax is in the range of 70 to 100% by mass. It has been confirmed that it is useful for providing a toner for developing an electrostatic latent image that improves document offset resistance while ensuring low-temperature fixability.

Claims (3)

An electrostatic latent image developing toner containing toner base particles containing at least a binder resin and a release agent,
The binder resin contains at least a styrene / acrylic resin obtained by copolymerizing a polymerizable monomer containing a compound having a structure represented by the following general formula (1) and a crystalline resin,
The release agent contains at least an ester wax;
In the carbon number distribution of the ester wax, the total content of esters having a carbon number within a range of ± 2 of the carbon number corresponding to the highest content is within a range of 85 to 100 % by mass. A toner for developing an electrostatic latent image.
General formula (1)
H ₂ C = CH-COOR
(In the general formula (1), R represents a linear or branched alkyl group having 6 to 12 carbon atoms or a cyclic alkyl group.) 2. The electrostatic latent image developing toner according to claim 1, wherein the total content of the ester having 40 or less carbon atoms contained in the ester wax is 6% by mass or less. The crystalline resin is, an electrostatic latent image developing toner according to claim 1 or claim 2 characterized in that it is a crystalline polyester resin.