JP7199814B2 - External additives for toner, toner and core-shell particles for toner - Google Patents

Description

TECHNICAL FIELD The present invention relates to an external additive for toner, toner, and core-shell fine particles for toner used in image forming methods such as electrophotography and electrostatic printing.

Electrophotographic image forming apparatuses are required to have higher speed, longer life, energy saving, and miniaturization. Further improvement in low-temperature fixability is demanded.
Furthermore, in order to be able to start printing as soon as the power is turned on, toner with a fast charging build-up, and in order to achieve image stability when printing a large number of sheets, a phenomenon in which the amount of charge continues to increase (charge-up) There is a demand for a toner in which the volatility is suppressed and a toner with excellent durability.
Numerous studies have been conducted to achieve these performances.
Japanese Patent Application Laid-Open No. 2002-100003 discloses a toner improved in charging rise by using a resin charge control agent and a hydrophobic titanium oxide together.
Patent Document 2 discloses a toner improved in low-temperature fixability and heat-resistant storage stability by externally adding inorganic particles and a large amount of a crystalline resin, which is a medium resistance external additive.

JP 2006-72199 A JP 2011-17913 A

The toner of Patent Document 1 uses a resin charge control agent in which a sulfonate group-containing monomer, an aromatic monomer having an electron-withdrawing group, and an acrylic acid ester monomer and/or a methacrylic acid ester monomer are used in combination to ensure chargeability. Improves environmental stability. At the same time, charge-up is suppressed by using titanium oxide fine particles subjected to a hydrophobizing treatment.
However, according to the studies of the present inventors, these external additives sometimes deteriorate the fixability under some conditions. The reason for this is thought to be that the hydrophobically treated titanium oxide fine particles are embedded in the toner particle surface layer, increasing the melt viscosity of the toner particle surface due to the filler effect, and inhibiting the fusion of the toner interface. ing. In addition, the charge amount may decrease in a high-humidity environment. It is considered that this is due to the hygroscopic property of the resin charge control agent in addition to the embedding of the titanium oxide fine particles.
The toner of Patent Document 2 has improved low-temperature fixability and heat-resistant storage stability by externally adding a large amount of inorganic particles and crystalline resin fine particles.
However, according to the studies of the present inventors, there are cases where the durability is not sufficient under some conditions of use. This is because under severe operating conditions, the externally added inorganic particles detach from the toner particles, affecting the image, and the crystalline resin fine particles are cracked, chipped, and crushed, resulting in changes in toner performance over time. I think it's because
The present invention has been made in view of these problems, and provides an external additive for toner, a toner, and core-shell fine particles for toner, which do not interfere with fixation and are excellent in charging characteristics and durability. Specifically, the object is to provide an external additive for toner, a toner, and core-shell fine particles for toner, which are excellent in charging rise property, suppression of charge-up, and durability without hindrance of fixation.

The present invention provides a core-shell type external additive for toner, which has an inorganic fine particle as a core and a resin as a shell covering the surface of the inorganic fine particle,
the resin is a crystalline resin,
the resin and the surface of the inorganic fine particles are chemically bonded,
The external additive for toner has a volume resistivity of 1.0×10 ⁸ Ω·cm or more and 1.0×10 ¹⁴ Ω·cm or less.
The present invention also relates to toner particles and a toner having the external additive for toner having the above structure on the surface of the toner particles.
Further, the present invention provides core-shell fine particles for a toner comprising an inorganic fine particle as a core and a surface of the inorganic fine particle coated with a resin as a shell ,
the resin is a crystalline resin,
the resin and the surface of the inorganic fine particles are chemically bonded,
The present invention relates to core-shell fine particles for toner, characterized in that the core-shell fine particles for toner have a volume resistivity of 1.0×10 ⁸ Ω·cm or more and 1.0×10 ¹⁴ Ω·cm or less.

According to the present invention, it is possible to provide an external additive for toner, a toner, and core-shell fine particles for toner, which are excellent in charging rise property, suppression of charge-up, and durability without hindrance to fixation.

1 is a schematic diagram of a charge amount measuring device; FIG.

The present invention provides a core-shell type external additive for toner comprising inorganic fine particles and a resin coating the surfaces of the inorganic fine particles, wherein the external additive for toner has a volume resistivity of 1.0. It is characterized by being more than ×10 ⁸ Ω·cm and less than 1.0×10 ¹⁴ Ω·cm.

The outline of the present invention will be described below.

In order to provide an external toner additive which does not interfere with fixation, has excellent charge build-up property, suppression of charge-up, and durability, the present inventors have investigated various materials and forms of external toner additives. Study was carried out.

Among them, the present inventors have found that a core-shell type external additive for toner, in which the surface of inorganic fine particles is coated with a specific resin and the volume resistivity of the particles is adjusted, is effective in improving the charge rising property and chargeability without hindrance to fixation. The inventors have found that the material is excellent in suppressing the rise and durability, and achieved the above-mentioned purpose.

In the present invention, the inorganic fine particles constitute the core in the core-shell type external additive for toner. By using the inorganic fine particles in the core, cracking, chipping, and crushing can be suppressed, and the external additive for toner can have durability.

In the present invention, the resin constitutes the shell in the core-shell type external additive for toner. By forming the resin as a shell, the affinity with the toner particles can be enhanced, and the function of suppressing detachment of the external additive for toner from the toner particles can be imparted.

Furthermore, the volume resistivity of the core-shell type external additive for toner is set to 1.0×10 ⁸ Ω·cm or more and 1.0×10 ¹⁴ Ω·cm or less (preferably 1.0×10 ¹¹ Ω·cm or more). .0×10 ¹³ Ω·cm or less), it is possible to achieve good charging rise and suppression of charge build-up. This volume resistivity is mainly derived from the properties of the resin, but it also varies depending on how the shell covers the core. By setting the volume resistivity within the above range, it is possible to obtain an external additive for toner having good charging performance. A method for measuring volume resistivity in the present invention will be described later.

In addition, the core-shell type external additive for toner suppresses the influence of toner fixation inhibition. Although the detailed mechanism is not clear, the inventors of the present invention believe that the toner fixation inhibition caused by the external additive is caused by the following mechanism. (1) The external additive is embedded in the toner surface by an external force. (2) The filler effect of the embedded external additive increases the melt viscosity of the toner particle surface. Fusion is inhibited. Since the shell portion of the core-shell type external additive for toner of the present invention is made of a resin, it has a higher elasticity than the inorganic fine particles alone, and is less likely to be embedded in the surface of the toner particles. On the other hand, the core-shell type external additive for toner has a high affinity with the toner particles as described above and is difficult to detach, so that it firmly adheres to the surface of the toner particles. Furthermore, even when a core-shell type external additive for toner is embedded, the existence of the shell can ensure a certain distance between the inorganic fine particles, which is a factor of the filler effect, so that the increase in melt viscosity is suppressed. be.

A specific configuration of the present invention will be described below.

(Inorganic fine particles)
The inorganic fine particles used in the present invention may be any inorganic fine particles that can be used as an external additive for toner. Specific examples include the following.

Oxides such as silica, alumina, titanium oxide, strontium titanate, tin oxide, cerium oxide, magnesium oxide, chromium oxide, nitrides such as silicon nitride, carbides such as silicon carbide), calcium sulfate, barium sulfate, carbonate In addition to metal salts such as calcium, carbon black, carbon fluoride, etc.

Among them, silica is preferable from the viewpoints of easy shell formation, size selection, and cost.

The number average particle diameter of the inorganic fine particles used in the present invention is preferably 30 nm or more and 500 nm or less. When the number average particle size of the inorganic fine particles is within the above range, the effect of the present invention can be obtained more easily.

(coating resin)
Any resin may be used as the resin used in the present invention. It is preferable to use a resin having a resistance in the range of 0×10 ⁸ Ω·cm to 1.0×10 ¹⁴ Ω·cm. The volume resistivity of the resin and the volume resistivity of the core-shell type external additive for toner may not match depending on the coating state of the resin (thickness, uniformity, presence or absence of chemical bonding (described later)). A resin having volume resistivity makes it easier to obtain the core-shell type external additive for toner of the present invention.

Specifically, the resin having volume resistivity may have a conductive structure in the molecule, and examples thereof include polyester structure, polyether structure, polyphenylene structure, polypyrrole structure, polythiophene structure, and polyaniline structure. , a polyacetylene structure, and the like. The volume resistivity of the resin can be adjusted by the intramolecular ratio. Also, the volume resistivity can be controlled by the ester concentration in the resin and the crystallinity of the resin.

Moreover, the resin of the present invention is preferably a crystalline resin. Since the shell of the core-shell type external additive for toner is composed of a crystalline resin, the viscosity of the shell part of the core-shell type external additive for toner quickly decreases during fixing, further suppressing fixing inhibition. be done. The melting point of the crystalline resin is preferably 45° C. or higher and 100° C. or lower. When the melting point of the crystalline resin is within this range, the above effect can be obtained more easily.

Furthermore, the resin of the present invention is preferably a crystalline polyester. In addition to the fixation inhibition effect of the crystalline resin, the external additive for toner has a polyester surface, which improves the affinity with paper, so that the fixability of the toner can be further enhanced.

Moreover, the resin is preferably dissolved in an organic solvent from the viewpoint of more uniformly coating the surface of the inorganic fine particles that are the core.

(Shell with coating resin)
The shell thickness of the core-shell type external additive for toner of the present invention is preferably 10.0% or less of the diameter of the inorganic fine particles. With such a structure, the influence of the strength of the surface of the inorganic fine particles can be more strongly imparted to the resin, which is the shell, so that cracking, chipping, and crushing can be further suppressed, and a highly durable external additive for toner can be obtained. can be done.

The shell thickness in the present invention is a converted thickness calculated from the particle size of the inorganic fine particles and the mass of the shell constituting the core-shell type external additive for toner. For example, the number average particle diameter of inorganic fine particles measured by DLS (dynamic light scattering), etc., and the weight of the core-shell type external additive for toner measured by TG-DTA (thermogravimetry/differential thermal analysis), etc. Measure the resin mass, which is the loss. By using these data and the specific gravities of the inorganic fine particles and the resin, it is possible to calculate the shell thickness assuming that the inorganic fine particles are uniformly coated with the resin. The method of measuring DLS and TG-DTA and the method of calculating the shell thickness in the present invention will be described later.

Further, in the core-shell type external additive for toner of the present invention, it is preferable that the shell uniformly covers the core surface of the inorganic fine particles. Uniform coating makes it easier to obtain the effects of the present invention. The state of the coating is examined by cross-sectional TEM (transmission electron microscope) observation of the external additive for core-shell type toner, ESCA (X-ray photoelectron spectroscopy) and TOF-SIMS (Time-of-Flight Secondary Ion Spectroscopy) combined with surface etching. mass spectrometry) and the like.

In the core-shell type external additive for toner of the present invention, it is preferable that the resin and the surface of the inorganic fine particles are chemically bonded. By chemically bonding the resin and the surface of the inorganic fine particles, a more uniform shell can be formed on the surface of the inorganic fine particles. In addition, since the shell is formed more firmly on the surface of the inorganic fine particles by chemically bonding, it is possible to obtain a core-shell type external additive for toner with even higher durability.

A known method can be used to chemically bond the resin to the surface of the inorganic fine particles. For example, a method in which a polymerization reaction initiating group is bound to the surface functional group of the inorganic fine particles and then the polymerization reaction is carried out in the presence of a monomer constituting the resin, or a method in which the surface functional group of the inorganic fine particles and the resin contain reactivity. Examples include a method of reacting a functional group.

As a method for confirming whether the resin is chemically bonded to the surface of the inorganic fine particles, a known method can be used. For example, after dispersing the core-shell type external toner additive in an organic solvent that dissolves the resin, the organic solvent and the external toner additive are separated by centrifugation or the like and dried. By analyzing the surface of the obtained external toner additive after washing with a solvent by ESCA, TOF-SIMS, etc., it is confirmed whether or not the resin of the core-shell type external toner additive is chemically bonded. be able to. If it is not a chemical bond, the resin is dissolved in the organic solvent and removed by centrifugal separation, so the resin is not detected from the surface of the external additive for toner after washing with the solvent. On the other hand, when the resin is chemically bonded, it remains on the surface of the external additive for toner after drying because the resin does not dissolve even when washed with an organic solvent.

(Method for producing external additive for toner)
A method for producing a core-shell type external additive for toner by coating the inorganic fine particles with the resin is not particularly limited, and a known coating method can be used.

As a method for producing a physical coating in which the surfaces of the resin and the inorganic fine particles do not have a chemical bond, for example, a dispersion liquid in which the inorganic fine particles are dispersed is mixed with a solution in which the resin is dissolved, and then the resin is precipitated. There is a method of coating the surface of inorganic fine particles with a resin. Examples of the method for precipitating the resin include a method of adding a solvent that is a poor solvent for the resin, a method of changing the solubility by lowering the temperature, a method of adding an additive to the mixed solution to promote association between the resins, and the like. can be exemplified. In the case of physical coating, the shell thickness can be controlled by changing the ratio of the inorganic fine particles and the resin under the coating conditions. The shell thickness can be increased by increasing the ratio of the resin to the inorganic fine particles.

In addition, as a method of producing a chemical coating in which a resin and the surface of inorganic fine particles are chemically bonded, for example, a method of arranging an initiating group on the surface of the inorganic fine particle and initiating a polymerization reaction from the initiating group, or a method of A method of bonding a functional group and a functional group contained in a resin can be used. It is generally known that there are many hydroxyl groups on the surface of inorganic fine particles. Coating can be performed. In the case of chemical coating, one way to control the shell thickness is by changing the molecular weight of the resin. The shell thickness can be increased by increasing the molecular weight of the resin.

(Method for producing toner particles)
A method for producing toner particles is not particularly limited, and known suspension polymerization methods, dissolution suspension methods, emulsion aggregation methods, pulverization methods, and the like can be used.

When toner particles are produced in an aqueous medium, they may be used as they are as an aqueous dispersion, or they may be redispersed in an aqueous medium after washing, filtering, and drying.

When toner particles are produced by a dry method, they can be dispersed in an aqueous medium by a known method. In order to disperse the toner particles in the aqueous medium, the aqueous medium preferably contains a dispersion stabilizer.

A method for producing toner particles using the suspension polymerization method will be described below.

First, a polymerizable monomer capable of forming a binder resin and, if necessary, various materials are mixed and dissolved or dispersed using a disperser to prepare a polymerizable monomer composition.

Examples of the various materials include coloring agents, waxes, charge control agents, polymerization initiators, chain transfer agents, and the like.

Dispersers include homogenizers, ball mills, colloid mills, or ultrasonic dispersers.

Next, the polymerizable monomer composition is introduced into an aqueous medium containing poorly water-soluble inorganic fine particles, and a high-speed disperser such as a high-speed stirrer or an ultrasonic disperser is used to disperse the polymerizable monomer composition. to prepare droplets (granulation step).

After that, the polymerizable monomer in the droplets is polymerized to obtain toner particles (polymerization step).

The polymerization initiator may be mixed when preparing the polymerizable monomer composition, or may be mixed into the polymerizable monomer composition immediately before forming droplets in the aqueous medium.

Moreover, it can be added in a state of being dissolved in a polymerizable monomer or another solvent, if necessary, during granulation of droplets or after completion of granulation, that is, immediately before starting the polymerization reaction.

After polymerizing the polymerizable monomer to obtain resin particles, solvent removal treatment may be performed as necessary to obtain a dispersion liquid of toner particles.

(Constituent material of toner particles)
Constituent materials of the toner particles are described below.

The following resins or polymers can be exemplified as the binder resin that constitutes the toner particles. vinyl resin; polyester resin; polyamide resin; furan resin; epoxy resin; xylene resin;

Among these, vinyl-based resins are preferred. In addition, as a vinyl-type resin, the polymer of the following monomers or those copolymers is mentioned. Among them, a copolymer of a styrene-based monomer and an unsaturated carboxylic acid ester is preferred.

Styrenic monomers such as styrene and α-methylstyrene; unsaturated carboxylic acids such as methyl acrylate, butyl acrylate, methyl methacrylate, 2-hydroxyethyl methacrylate, t-butyl methacrylate, and 2-ethylhexyl methacrylate esters; unsaturated carboxylic acids such as acrylic acid and methacrylic acid; unsaturated dicarboxylic acids such as maleic acid; unsaturated dicarboxylic acid anhydrides such as maleic anhydride; nitrile-based vinyl monomers such as acrylonitrile; halogen-containing vinyl monomers; nitro vinyl monomers such as nitrostyrene;

As the colorant, the following black pigment, yellow pigment, magenta pigment, cyan pigment, etc. are used.

Examples of black pigments include carbon black.

Examples of yellow pigments include monoazo compounds; disazo compounds; condensed azo compounds; isoindolinone compounds; isoindoline compounds; benzimidazolone compounds; anthraquinone compounds; Specifically, C.I. I. Pigment Yellow 74, 93, 95, 109, 111, 128, 155, 174, 180, 185 and the like.

Examples of magenta pigments include monoazo compounds; condensed azo compounds; diketopyrrolopyrrole compounds; anthraquinone compounds; quinacridone compounds; basic dye lake compounds; Specifically, C.I. I. Pigment Red 2,3,5,6,7,23,48:2,48:3,48:4,57:1,81:1,122,144,146,150,166,169,177,184, 185, 202, 206, 220, 221, 238, 254, 269, C.I. I. Pigment Violet 19 and the like.

Examples of cyan pigments include copper phthalocyanine compounds and derivatives thereof, anthraquinone compounds, and basic dye lake compounds. Specifically, C.I. I. Pigment Blue 1,7,15,15:1,15:2,15:3,15:4,60,62,66.

Various dyes conventionally known as colorants may be used in combination with the pigment.

The content of the colorant is preferably 1.0 parts by mass or more and 20.0 parts by mass or less with respect to 100.0 parts by mass of the binder resin.

The toner may contain a magnetic material to be a magnetic toner. In this case, the magnetic substance can also serve as a coloring agent. Magnetic substances include iron oxides typified by magnetite, hematite, and ferrite; metals typified by iron, cobalt, and nickel; or these metals and aluminum, cobalt, copper, lead, magnesium, tin, zinc, antimony, Alloys with metals such as beryllium, bismuth, cadmium, calcium, manganese, selenium, titanium, tungsten and vanadium, and mixtures thereof.

Waxes are exemplified below.

Monohydric alcohol and aliphatic monocarboxylic acid esters such as behenyl behenate, stearyl stearate and palmityl palmitate, or esters of monohydric carboxylic acids and aliphatic monoalcohols; A trihydric alcohol such as glycerin tribehenate and an aliphatic monocarboxylic acid ester, or a trihydric carboxylic acid and a fatty acid. esters of group monoalcohols; tetrahydric alcohols and aliphatic monocarboxylic acid esters such as pentaerythritol tetrastearate and pentaerythritol tetrapalmitate, or esters of tetrahydric carboxylic acids and aliphatic monoalcohols; dipentaerythritol hexastearate , dipentaerythritol hexapalmitate and other hexahydric alcohols and aliphatic monocarboxylic acid esters, or esters of hexahydric carboxylic acids and aliphatic monoalcohols; polyhydric alcohols and aliphatic monocarboxylic acids such as polyglycerin behenate Esters or esters of polyhydric carboxylic acids and aliphatic monoalcohols; Natural ester waxes such as carnauba wax and rice wax; Petroleum waxes such as paraffin wax, microcrystalline wax and petrolatum and their derivatives; Hydrocarbons produced by the Fischer-Tropsch process waxes and derivatives thereof; polyolefin waxes such as polyethylene wax and polypropylene wax and derivatives thereof; higher aliphatic alcohols; fatty acids such as stearic acid and palmitic acid;

The wax content is preferably 0.5 parts by mass or more and 20.0 parts by mass or less with respect to 100.0 parts by mass of the binder resin.

Toners usually have various organic or inorganic fine particles externally added to the toner particles. In the present invention, the toner having the effects of the present invention can be obtained by adding the external additive for toner of the present invention to toner particles alone or by adding the external additive for toner of the present invention to a conventionally known external additive. can be done.

Conventionally known external additives include organic or inorganic fine particles, and the following are used, for example.
(1) Fluidity imparting agents: silica, alumina, titanium oxide, carbon black and carbon fluoride.
(2) Abrasives: metal oxides (e.g. strontium titanate, cerium oxide, alumina, magnesium oxide, chromium oxide), nitrides (e.g. silicon nitride), carbides (e.g. silicon carbide), metal salts (e.g. calcium sulfate, sulfuric acid) barium, calcium carbonate).
(3) Lubricant: fluororesin powder (eg, vinylidene fluoride, polytetrafluoroethylene), fatty acid metal salt (eg, zinc stearate, calcium stearate).
(4) Charge control particles: metal oxides (eg, tin oxide, titanium oxide, zinc oxide, silica, alumina), carbon black.

Organic or inorganic microparticles can also be hydrophobized. Treatment agents for hydrophobic treatment of organic or inorganic fine particles include unmodified silicone varnishes, various modified silicone varnishes, unmodified silicone oils, various modified silicone oils, silane compounds, silane coupling agents, other organic silicon compounds, organic Titanium compounds are mentioned. These treating agents may be used alone or in combination.

Methods for measuring each physical property defined in the present invention are described below.

<Method for measuring Mn and Mw>
The molecular weights (Mn, Mw) of the resin used in the present invention are measured by gel permeation chromatography (GPC) as follows.

First, the sample is dissolved in tetrahydrofuran (THF) at room temperature for 24 hours. Then, the obtained solution is filtered through a solvent-resistant membrane filter "Myshoridisc" (manufactured by Tosoh Corporation) having a pore diameter of 0.2 μm to obtain a sample solution. The sample solution is adjusted so that the concentration of THF-soluble components is about 0.8% by mass. This sample solution is used for measurement under the following conditions.
Apparatus: HLC8120 GPC (detector: RI) (manufactured by Tosoh Corporation)
Column: 7 columns of Shodex KF-801, 802, 803, 804, 805, 806, 807 (manufactured by Showa Denko)
Eluent: Tetrahydrofuran (THF)
Flow rate: 1.0ml/min
Oven temperature: 40.0°C
Sample injection volume: 0.10 ml
In calculating the molecular weight of the sample, standard polystyrene resin (for example, trade name "TSK Standard Polystyrene F-850, F-450, F-288, F-128, F-80, F-40, F-20, F- 10, F-4, F-2, F-1, A-5000, A-2500, A-1000, A-500", manufactured by Tosoh Corporation).

<Method for measuring number average particle diameter of inorganic fine particles>
In the present invention, the number average particle diameter of inorganic fine particles is measured using Zetasizer Nano-ZS (manufactured by MALVERN). First, a sample was prepared by diluting an organic solvent dispersion of inorganic fine particles to be measured so that the solid-liquid ratio was 0.10% by mass (±0.02% by mass). put in As the measurement conditions, the refractive index of the inorganic fine particles, the refractive index and the viscosity of the dispersion solvent are input and measured.

<Method for Measuring Resin Weight in External Additive for Core-Shell Type Toner>
The weight of the resin in the core-shell external additive for toner of the present invention was measured using a thermogravimetric/differential thermal analyzer (differential thermal balance TG-DTA, ThermoPlus TG8120, manufactured by Rigaku Corporation). Using alumina as a reference substance, the temperature was raised from 25° C. to 150° C. at a rate of 10° C./min, and a TG curve was obtained at a sampling rate of 1 sec. By measuring the weight loss of the core inorganic fine particles in advance and subtracting the weight loss data of the inorganic fine particles from the weight loss data of the core-shell type toner external additive, the resin contained in the core-shell type toner external additive weight.

<Method for Calculating Shell Thickness of External Additive for Core-Shell Type Toner>
The shell thickness of the core-shell type external additive for toner of the present invention is determined by the number average particle size of the inorganic fine particles, the weight of the resin contained in the core-shell type external additive for toner, and the ratio of the inorganic fine particles and the resin. Calculated using specific gravity.

Specifically, first, the resin mass of the core-shell type external additive for toner was measured by the method described above, and then a sample (from which the resin was removed and only the inorganic fine particles remained) was subjected to measurement of the inorganic fine particles. The aqueous dispersion was adjusted so that the solid-liquid ratio was 0.10% by mass (±0.02% by mass). The aqueous dispersion of inorganic fine particles was prepared by using "Contaminon N" (a 10% aqueous solution of a neutral detergent for cleaning precision measuring instruments at pH 7 consisting of a nonionic surfactant, an anionic surfactant, and an organic builder as a dispersing agent, Wako Jun Yakukogyo Co., Ltd.) was used, and the inorganic fine particles were redispersed using an ultrasonic disperser or the like. The number average particle size of this re-dispersed liquid was measured by the method described above.

Based on the data on the number average particle size of the inorganic fine particles obtained by the above method, the weight ratio of the resin contained in the core-shell type external additive for toner, and the specific gravity of the inorganic fine particles and the resin, it was determined that the shells were uniform on the surface of the inorganic fine particles. For example, the converted thickness can be calculated by the following formula.
(Mj×Hj)/((1−Mj)×Hm)×4/3×(Rm/2) ³ ×π=4/3×(r−Rm/2) ³ ×π

In the formula, Mj is the resin mass ratio, Hj is the specific gravity of the resin, Hm is the specific gravity of the inorganic fine particles, and Rm is the number average particle diameter of the inorganic fine particles.

Also, based on the above data, by calculating the resin mass ratio when the thickness of the uniformly coated resin is changed with respect to the mass obtained from the number average particle size and specific gravity of the inorganic fine particles, the converted thickness can be obtained as an approximation of

<Measurement of volume resistivity>
The volume resistivity of the present invention was calculated from the half-life time in charge decay measurement.

The half-life time in the charge decay measurement was measured by a method based on JIS C 61340-2-1 using an electrostatic diffusion rate measuring device ("NS-D100" manufactured by Nanoseeds Co., Ltd.). The method for measuring the half-life time in the charge decay measurement of toner will be described in detail below.

A sample (toner) was placed in the measurement cell. An aluminum cell with an inner diameter of 5 mm was used as the measurement cell. The filling amount of the sample was 4 mg or more and 8 mg or less.

The measurement cell filled with the sample was left for 12 hours in an environment with a temperature of 32.5° C. and a humidity of 80% RH. Subsequently, the grounded measuring cell was placed in the static diffusivity measuring device, and ions were supplied to the sample by corona discharge to charge the sample. After 0.5 second from the end of the corona discharge, the surface potential of the sample was continuously measured. The time when the surface potential became 1/2 of the surface potential 0.5 seconds after the end of the corona discharge was defined as the half-life time in the charge decay measurement.

From the equivalent circuit model V = VOexp (-t/RC), the attenuation rate after t seconds is expressed by Δ(t) = (1-exp (-t/ερ) × 100. In the formula, V is the surface potential [ V], V0 is the initial surface potential [V], t is the decay time [second], ε is the dielectric constant [F·m−1], and ρ is the volume resistivity [Ω·cm].

<Method for Measuring Weight Average Particle Diameter (D4) and Number Average Particle Diameter (D1) of Toner Particles>
The weight average particle diameter (D4) and number average particle diameter (D1) of toner particles are calculated as follows.

As a measurement device, a precision particle size distribution measurement device "Coulter Counter Multisizer 3" (registered trademark, manufactured by Beckman Coulter, Inc.) using a pore electrical resistance method equipped with a 100 μm aperture tube is used. The attached dedicated software "Beckman Coulter Multisizer 3 Version 3.51" (manufactured by Beckman Coulter, Inc.) is used for setting the measurement conditions and analyzing the measurement data. The measurement is performed with 25,000 effective measurement channels.

The electrolytic aqueous solution used for the measurement can be prepared by dissolving special grade sodium chloride in deionized water so that the concentration becomes 1.0%, for example, "ISOTON II" (manufactured by Beckman Coulter, Inc.) can be used. .

Before performing measurement and analysis, set the dedicated software as follows.

On the "Change standard measurement method (SOMME)" screen of the dedicated software, set the total number of counts in control mode to 50,000 particles, set the number of measurements to 1, and set the Kd value to "standard particle 10.0 μm" (Beckman Coulter, Inc.) is used to set the value obtained.

By pressing the "threshold/noise level measurement button", the threshold and noise level are automatically set. Also, set the current to 1,600 μA, the gain to 2, the aqueous electrolytic solution to ISOTON II, and put a check in the “Flush aperture tube after measurement” box.

On the "pulse-to-particle size conversion setting" screen of the dedicated software, set the bin interval to logarithmic particle size, the particle size bin to 256 particle size bins, and the particle size range from 2 μm to 60 μm.

A specific measuring method is as follows.
(1) Put 200.0 mL of the electrolytic aqueous solution into a 250 mL round-bottomed glass beaker exclusively for Multisizer 3, set it on a sample stand, and stir the stirrer rod counterclockwise at 24 revolutions/second. Then, remove dirt and air bubbles inside the aperture tube using the dedicated software's "Flush Aperture" function.
(2) Put 30.0 mL of the electrolytic aqueous solution into a 100 mL flat-bottom glass beaker. As a dispersant, "Contaminon N" (a 10% aqueous solution of a neutral detergent for cleaning precision measuring instruments at pH 7 consisting of a nonionic surfactant, an anionic surfactant, and an organic builder, manufactured by Wako Pure Chemical Industries, Ltd.) was used as a dispersant. ) is diluted with ion-exchanged water to 3 times the mass, and 0.3 mL of the diluted solution is added.
(3) Prepare an ultrasonic disperser "Ultrasonic Dispersion System Tetra 150" (manufactured by Nikkaki Bios Co., Ltd.) with an electrical output of 120 W and two oscillators with an oscillation frequency of 50 kHz built in with a phase shift of 180 degrees. do. 3.3 L of deionized water is placed in the water tank of the ultrasonic disperser, and 2.0 mL of Contaminon N is added to this water tank.
(4) Set the beaker of (2) in the beaker fixing hole of the ultrasonic disperser, and operate the ultrasonic disperser. Then, the height position of the beaker is adjusted so that the resonance state of the liquid level of the electrolytic aqueous solution in the beaker is maximized.
(5) 10 mg of toner particles are added little by little to the electrolytic aqueous solution in a state where the electrolytic aqueous solution in the beaker of (4) is irradiated with ultrasonic waves, and dispersed. Then, the ultrasonic dispersion treatment is continued for another 60 seconds. In the ultrasonic dispersion, the temperature of the water in the water tank is appropriately adjusted to 10°C or higher and 40°C or lower.
(6) The electrolytic aqueous solution of (5) above, in which toner particles are dispersed, is dropped into the round-bottomed beaker of (1) above set in the sample stand, and adjusted so that the measured concentration is 5%. . The measurement is continued until the number of measured particles reaches 50,000.
(7) Analyze the measurement data with the dedicated software attached to the apparatus, and calculate the weight average particle size (D4) and the number average particle size (D1). In addition, when the graph / volume% is set with the dedicated software, the "average diameter" on the "analysis / volume statistical value (arithmetic mean)" screen is the weight average particle diameter (D4), and the graph / The "average diameter" on the "analysis/number statistical value (arithmetic mean)" screen when the number % is set is the number average particle diameter (D1).

EXAMPLES The present invention will be specifically described below with reference to Examples and Comparative Examples, but the present invention is not limited to these. All "parts" and "%" of each material in Examples and Comparative Examples are based on mass unless otherwise specified.

<Production Example of Resin 1>
The following raw materials were introduced into a heat-dried two-necked flask while introducing nitrogen.
・Sebacic acid (SA) 130.0 parts by mass ・1,6-Hexanediol (HD) 80.0 parts by mass ・Dibutyltin oxide 0.1 parts by mass Stirring was performed for hours. Thereafter, the temperature was gradually raised to 230° C. under reduced pressure while stirring was continued, and the temperature was maintained for an additional 2 hours. When the mixture became viscous, it was air-cooled to terminate the reaction, thereby synthesizing Resin 1. Table 1 shows the physical properties of Resin 1.

<Production Examples of Resins 2 to 5>
Resins 2 to 5 were synthesized in the same manner as in the synthesis of Resin 1, except that the amounts of raw materials used were changed as shown in Table 1. Table 1 shows the physical properties of resins 2 to 5.

<Production Example of Resin 6>
The following raw materials were introduced into a heat-dried two-necked flask while introducing nitrogen.
• ε-caprolactone 30.0 parts by mass • Stearyl alcohol 3.3 parts by mass • Dibutyltin oxide 0.20 parts by mass After the system was replaced with nitrogen by pressure reduction, the mixture was stirred at 160°C for 2 hours. Thereafter, the temperature was gradually raised to 230° C. under reduced pressure while stirring was continued, and the temperature was maintained for an additional 2 hours. When the mixture became viscous, it was air-cooled to terminate the reaction, thereby synthesizing a polyester having a hydroxyl group at one end. The molecular weight of Resin 6 was Mn 4,080 and Mw 8,100.

<Production Example of Resin 7>
The following raw materials were introduced into a heat-dried two-necked flask while introducing nitrogen.
• Sebacic acid 125.0 parts by mass • 1,6-Hexanediol 75.0 parts by mass • Dibutyltin oxide 0.1 parts by mass The pressure in the system was replaced with nitrogen, followed by stirring at 180°C for 6 hours. Thereafter, the temperature was gradually raised to 230° C. under reduced pressure while stirring was continued, and the temperature was maintained for an additional 2 hours. When the mixture became viscous, it was air-cooled to stop the reaction, thereby synthesizing Resin 7 prepolymer, which is a crystalline polyester. Resin 7 prepolymer had a molecular weight of Mn 6000, Mw 13000 and a melting point of 69°C.

The following raw materials were introduced into a heat-dried two-necked flask while introducing nitrogen.
· Xylylene diisocyanate (XDI) 55.5 parts by mass · Cyclohexanedimethanol (CHDM) 34.5 parts by mass · Tetrahydrofuran (THF) 80.0 parts by mass This is heated to 50 ° C. and urethanized over 10 hours. was applied. Thereafter, a solution obtained by dissolving 210.0 parts by mass of the resin 7 prepolymer in 220.0 parts by mass of THF was gradually added, and the mixture was further stirred at 50.0° C. for 5 hours. Thereafter, the mixture was cooled to room temperature, and the solvent, THF, was distilled off to synthesize a crystalline polyester-urethane block polymer. The molecular weight of Resin 7 was Mn 12,450 and Mw 29,980.

<Production Example of Resin 8>
50.0 parts by mass of behenyl acrylate, 150.0 parts by mass of toluene, and 50.0 parts by mass of N,N-dimethylformamide were mixed in a heat-dried two-necked flask while introducing nitrogen to obtain a monomer composition. prepared.

After bubbling nitrogen for 30 minutes while stirring the above monomer composition at 250 rpm, 0.3 of 2,2′-azobis[2-methyl-N-(2-hydroxyethyl)propionamide] was added as a polymerization initiator. Parts by mass were mixed. After that, the mixture was heated at 90° C., reacted for 5 hours, further heated to 95° C., and reacted for 1 hour. Next, after air cooling, resin 8 was obtained by reprecipitating with methanol in an amount five times as large as the mixed toluene, and drying the collected precipitate. The molecular weight of the obtained resin 8 was Mn 10,950 and Mw 31,180.

<Production Example of Resin 9>
The following raw materials were introduced into a heat-dried two-necked flask while introducing nitrogen.
・Polyoxypropylene (2.2)-2,2-bis(4-hydroxyphenyl)propane
30.0 parts by mass Polyoxyethylene (2.2)-2,2-bis(4-hydroxyphenyl)propane
32.5 parts by mass, 20.5 parts by mass of terephthalic acid, 14.5 parts by mass of dodecenylsuccinic acid, and 0.1 part by mass of dibutyltin oxide. . Thereafter, the temperature was gradually raised to 230° C. under reduced pressure while stirring was continued, and the temperature was maintained for an additional 2 hours. When the mixture became viscous, it was air-cooled to terminate the reaction, thereby synthesizing Resin 9, which is an amorphous polyester. Resin 9 had an Mn of 4,900 and an Mw of 24,000.

<Production Example of Resin 10>
A reaction vessel equipped with a stirrer, condenser, thermometer and nitrogen inlet tube was charged with 200.0 parts of xylene and refluxed under a nitrogen stream.

next,
· NK Ester M-230G (n = 23: manufactured by Shin-Nakamura Chemical Co., Ltd.) 15.0 parts by mass · Styrene 53.0 parts by mass · 2-ethylhexyl acrylate 14.9 parts by mass · 2,2'-azobis [2- methyl-N-(2-hydroxyethyl)propionamide]
0.6 parts by mass were mixed, dropped into the reaction vessel with stirring, and held at 90° C. for 10 hours. Thereafter, distillation was performed to remove the solvent, and the residue was dried at 40° C. under reduced pressure to obtain Resin 10. Resin 10 had an Mn of 10,900 and an Mw of 22,900.

<Production Example of Resin 11>
100.0 parts by mass of styrene, 150.0 parts by mass of toluene, and 50.0 parts by mass of N,N-dimethylformamide are mixed in a heat-dried two-necked flask while introducing nitrogen to prepare a monomer composition. bottom.

While stirring the above monomer composition at 250 rpm, nitrogen bubbling was performed for 30 minutes. Parts by mass were mixed. After that, the mixture was heated at 90° C., reacted for 5 hours, further heated to 95° C., and reacted for 1 hour. Next, after air cooling, resin 11 was obtained by reprecipitating with methanol in an amount five times as large as the mixed toluene, and drying the collected precipitate. The molecular weights of the obtained resin 11 were Mn 12,120 and Mw 29,660.

<Production Example of Resin 12>
Novaloy E (E81) manufactured by Daicel Polymer Ltd. was used as the resin 12 .

Table 2 shows the volume resistivity of the resins 1 to 12.

<Production Example of External Additive 1 for Toner>
The following raw materials were introduced into a heat-dried two-necked flask while introducing nitrogen.
・Resin 1 10.0 parts by mass ・3-Isocyanatopropyltriethoxysilane 2.5 parts by mass ・Methyl ethyl ketone 87.5 parts by mass This is stirred at room temperature for 1 hour to add the silane coupling agent to Resin 1. rice field. After that, the shell prepolymer 1 was obtained by reprecipitating with methanol 5 times the amount of methyl ethyl ketone and drying the collected precipitate.

The following raw materials were introduced into a heat-dried two-necked flask while introducing nitrogen.
• Shell prepolymer 1 10.0 parts by mass • Methyl ethyl ketone 87.5 parts by mass 1 mol/L of hydrochloric acid was added to the mixed solution to adjust the pH to 3.0, followed by stirring at room temperature for 1 hour. The following raw materials were introduced into a heat-dried two-necked flask while introducing nitrogen.
・ Silica fine particle dispersion (MEK-ST-ZL, methyl ethyl ketone dispersion, solid content 33%, manufactured by Nissan Chemical Industries, Ltd.) 100.0 parts by mass Add tetraethylamine to the silica fine particle dispersion to adjust the pH to 9 to 11.5 , the mixed solution was added dropwise, mixed, and stirred overnight at room temperature. Thereafter, the mixture was mixed with tetrahydrofuran in an amount five times as large as that of methyl ethyl ketone, centrifuged, and dried to obtain a core-shell type external additive 1 for toner. Table 3 shows the physical properties of the core-shell type external additive 1 for toner.

<Production Examples of Toner External Additives 2 to 11 and 13>
Core-shell type external additives 2 to 11 and 13 were synthesized in the same manner as in the synthesis of core-shell type toner external additive 1, except that the types of raw materials used were changed as shown in Table 3. Table 3 shows the physical properties of external additives 2 to 11 and 13 for core-shell type toners.

<Production Example of External Additive 12 for Toner>
10.0 parts by mass of hydrophobized strontium titanate was added to 90.0 parts by mass of methyl ethyl ketone and treated for 5 minutes with an ultrasonic homogenizer (UH-300, manufactured by SMT) to prepare a strontium titanate dispersion. 0.6 part by mass of resin 1 was mixed with this dispersion and dissolved completely, and then hexane in an amount 10 times the amount of methyl ethyl ketone was added dropwise to the dispersion at a rate of 10 ml/min while stirring. Thereafter, through centrifugal separation and drying steps, a core-shell type external additive 12 for toner was obtained. Table 4 shows the physical properties of the core-shell type external additive 12 for toner.

<Production Example of External Additive 14 for Toner>
A core-shell type external additive 14 for toner is obtained by performing the same operation except that the resin 1 in the production example of the core-shell type external additive 12 for toner is changed to resin 12 and the amount of resin 12 is changed to 2.5 parts by mass. rice field. Table 4 shows the physical properties of the core-shell type external additive 14 for toner.

<Production Example of Toner 1>
(Production example of aqueous medium 1)
390.0 parts by mass of ion-exchanged water and 14.0 parts by mass of sodium phosphate (dodecahydrate) [manufactured by Rasa Kogyo Co., Ltd.] are added to a reaction vessel and kept at 65°C for 1 hour while purging with nitrogen. bottom.

T. K. Using a homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.), while stirring at 12,000 rpm, 9.2 parts by mass of calcium chloride (dihydrate) dissolved in 10.0 parts by mass of ion-exchanged water. An aqueous calcium solution was added all at once to prepare an aqueous medium containing a dispersion stabilizer.

Furthermore, 10% hydrochloric acid was added to the aqueous medium to adjust the pH to 6.0, and an aqueous medium 1 was obtained.

(Production example of polymerizable monomer composition 1)
Styrene 60.0 parts by mass Colorant (C.I. Pigment Blue 15:3) 6.5 parts by mass The above materials are put into an attritor (manufactured by Nippon Coke Kogyo Co., Ltd.), and zirconia particles with a diameter of 1.7 mm are added. was dispersed at 220 rpm for 5 hours to prepare Dispersion 1 in which the colorant was dispersed.

The following materials were added to Dispersion 1.
Styrene 20.0 parts by mass n-butyl acrylate 20.0 parts by mass Polyester resin 5.0 parts by mass (bisphenol A propylene oxide 2 mol adduct/terephthalic acid/trimellitic acid condensate, glass transition temperature: 75°C)
Fischer-Tropsch wax (melting point: 78°C) 7.0 parts by mass K. A homomixer was used to uniformly dissolve and disperse at 500 rpm to prepare a polymerizable monomer composition 1.

(Granulation process)
While maintaining the temperature of the aqueous medium 1 at 70° C. and the rotation speed of the stirrer at 12,000 rpm, the polymerizable monomer composition 1 was introduced into the aqueous medium 1, and t-butyl peroxypyropyrone as a polymerization initiator was added. 9.0 parts by weight of barate was added. The mixture was granulated for 10 minutes while maintaining 12,000 rpm with the stirring device.

(Polymerization process)
The high-speed stirrer was changed to a stirrer equipped with propeller stirring blades, and the polymerization reaction was carried out by maintaining the temperature at 70°C for 5 hours while stirring at 150 rpm, and then raising the temperature to 85°C for 2 hours to initiate the polymerization reaction. Toner base particle dispersion liquid 1 was obtained.

The weight average particle size (D4) of the toner base particles in the toner base particle dispersion liquid 1 was 6.7 μm, the number average particle size (D1) was 5.3 μm, and the glass transition temperature (Tg) was 56°C. .

After adjusting the pH to 1.5 with 1 mol/L hydrochloric acid and stirring for 1 hour, toner particles 1 were obtained through filtration and drying steps while washing with deionized water.

100.0 parts by mass of toner particles 1 and 1.5 parts by mass of external additive 1 for toner are dry-mixed for 5 minutes using a Henschel mixer (manufactured by Mitsui Mining Co., Ltd.). Toner 1 was obtained by sieving with a mesh having an opening of 150 μm.

Using a color laser printer (LBP-7700C, manufactured by Canon, the fixing unit was modified so that the fixing temperature can be adjusted), the toner in the cyan cartridge was taken out, and 160 g of each toner was filled in this cartridge. Using the filled cartridge, fixing inhibition property, charge amount, member contamination and transfer property were evaluated.

<Manufacturing Examples of Toners 2 to 16>
As shown in Table 5, toners 2 to 16 were produced in the same manner except that toner external additive 1 was changed to toner external additives 2 to 14, TiO ₂ , and crystalline polyester (CPES) fine particles.

[Examples 1 to 12 and Comparative Examples 1 to 4]
Using Toners 1-16, Examples 1-12 and Comparative Examples 1-4 were evaluated.

Using a color laser printer (LBP-7700C, manufactured by Canon Inc.), the toner in the cyan cartridge was taken out, and 160 g of each toner was filled in the cartridge. The setting of the process speed of the printer body and the temperature of the fixing device were changed according to the evaluation conditions, and the fixing inhibition property, charge amount, member contamination after durability, and transferability were evaluated.

<Evaluation of fixation inhibition>
Under normal temperature and normal humidity environment (25° C., 50% RH), the filled cartridge was mounted on the cyan station of the printer. At a process speed of 300 mm/sec, the fixing temperature is changed in increments of 5°C, and an unfixed toner image with a toner load of 0.40 mg/cm ² is heated and pressed onto the receiving paper without oil, and the fixed image is applied to the receiving paper. formed. Fixing inhibition was evaluated by rubbing the fixed image 10 times with Kimwipe [S-200 (Crecia Co., Ltd.)] under a load of 7.35 kPa (75 g/cm ² ) until the density reduction rate before and after rubbing was less than 5%. The lowest temperature was taken as the fixing temperature of the toner. Using Comparative Example 1 having a large fixing inhibition property as a reference for the fixing temperature, the fixing inhibition property was evaluated according to the following criteria to determine how much the fixing temperature decreased compared to Comparative Example 1. Table 6 shows the evaluation results.
A: -10°C or higher B: -5°C or higher and lower than 10°C C: -1°C or higher and lower than 5°C D: 0°C (standard)

<Evaluation of charge rising property>
The following evaluations were performed under a low temperature and low humidity environment (5° C., 15% RH).

19.0 g of magnetic carrier F813-300 (manufactured by Powdertech Co., Ltd.) and 1.0 g of evaluation toner are placed in two 50-mL capped plastic bottles.

A two-component developer was prepared by shaking with a shaker (YS-LD: manufactured by Yayoi Co., Ltd.) at a speed of 4 reciprocations per second for 1.5 minutes and 15 minutes respectively.

0.2 g of a two-component developer whose triboelectrification amount is to be measured is placed in a metal measuring container 2 having a screen 3 of 500 mesh (opening of 25 μm) at the bottom shown in FIG. The mass of the entire measurement container 2 at this time is weighed and defined as W1 (g).

Next, in the aspirator 1 (at least the part in contact with the measurement container 2 is an insulator), the air is sucked from the suction port 7, and the pressure of the vacuum gauge 5 is adjusted to 50 mmAq by adjusting the air volume control valve 6. In this state, the toner is sucked for 1 minute and removed.

The potential of the electrometer 9 at this time is assumed to be V (volt). Here, 8 is a capacitor having a capacity of C (μF). W2 (g) is obtained by weighing the mass of the entire measurement container after suction. The triboelectrification amount of this toner is calculated by the following formula.
Amount of triboelectrification (mC/kg) = (C x V)/(W1-W2)

"Amount of triboelectric charge after shaking for 1.5 minutes"/"Amount of triboelectric charge after shaking for 15 minutes" was calculated. Table 6 shows the evaluation results.
A: Charge rise is 90% or more B: Charge rise is 80% or more and less than 90% C: Charge rise is 70% or more and less than 80% D: Charge rise is less than 70%

<Evaluation of charge amount stability due to environment>
The following evaluations were made under a low temperature and low humidity environment (5° C., 15% RH) and a high temperature and high humidity environment (35° C., 80% RH).

19.0 g of magnetic carrier F813-300 (manufactured by Powdertech) and 1.0 g of evaluation toner are placed in a 50 mL plastic bottle with a lid.

A two-component developer was prepared by shaking with a shaker (YS-LD: manufactured by Yayoi Co., Ltd.) for 1.5 minutes at a speed of 4 reciprocations per second.

The amount of triboelectrification was measured in the same manner as in the evaluation of charging rising properties.

"Triboelectrification amount in high-temperature and high-humidity environment"/"triboelectrification amount in low-temperature and low-humidity environment" was calculated. Table 6 shows the evaluation results.
A: Stability of charge amount is 60% or more B: Stability of charge amount is 40% or more and less than 60% C: Stability of charge amount is 20% or more and less than 40% D: Stability of charge amount is less than 20%

<Evaluation of charging member contamination>
Under a low temperature and low humidity environment (5° C., 15% RH), the filled cartridge was mounted on the cyan station of the printer. Using A4 plain paper Office 70 (Canon Marketing Japan 70 g/m ² ), 5,000 sheets of a 30% coverage chart were continuously printed while replenishing toner, and then a halftone image was printed.

If the charging member is contaminated, uneven charging occurs on the photoreceptor, resulting in uneven density of the halftone image.

Evaluation criteria are as follows. Table 6 shows the evaluation results.
A: Image density is uniform without unevenness B: Image density is slightly uneven C: Image density is slightly uneven D: Image density is uneven

<Evaluation of transferability after durability>
Under a low temperature and low humidity environment (5° C., 15% RH), the filled cartridge was mounted on the cyan station of the printer. Using A4 plain paper Office 70 (Canon Marketing Japan 70 g/m ² ), 5,000 sheets of a 1% coverage chart were continuously printed while replenishing toner, and then a halftone image was printed.

To evaluate the transfer performance, develop 0.35 mg/cm ² of toner on the photosensitive drum, shut down the operation of the main body during the transfer process, tape the transfer residual toner remaining on the photosensitive drum, and measure the density. I went with An optimum transfer current setting was used according to the toner charge amount. An X-Rite color reflection densitometer (500 series: manufactured by X-Rite) was used for density measurement.

The evaluation criteria were as follows (regarding the initial toner, it was ranked A in all the examples and comparative examples). Table 6 shows the evaluation results.
A: less than 0.1 B: 0.1 or more and less than 0.13 C: 0.13 or more and less than 0.16 D: 0.16 or more

1 suction machine, 2 measurement container, 3 screen, 4 lid, 5 vacuum gauge, 6 air volume control valve, 7 suction port, 8 condenser, 9 electrometer

Claims (8)

A core-shell type external additive for toner, comprising an inorganic fine particle as a core and a resin as a shell covering the surface of the inorganic fine particle,
the resin is a crystalline resin,
the resin and the surface of the inorganic fine particles are chemically bonded,
An external additive for toner, which has a volume resistivity of 1.0×10 ⁸ Ω·cm or more and 1.0×10 ¹⁴ Ω·cm or less. 2. The external additive for toner according to claim 1, wherein each particle contained in said external additive for toner comprises one particle of said inorganic fine particles and said resin covering the surface of said particle. 3. The external additive for toner according to claim 1, wherein the shell thickness of the core-shell type external additive for toner is 10.0% or less of the diameter of the inorganic fine particles. 4. The external additive for toner according to claim 1, wherein the crystalline resin is a crystalline polyester. 5. The external additive for toner according to claim 1 , wherein the inorganic fine particles are silica fine particles. 6. The external additive for toner according to claim 1, wherein the bond is a bond formed by a reaction between a surface functional group of the inorganic fine particles and a reactive functional group of the resin. A toner comprising toner particles and the external additive for toner according to any one of claims 1 to 6 on the surfaces of the toner particles. An inorganic fine particle as a core, and a core-shell fine particle for a toner obtained by coating the surface of the inorganic fine particle with a resin as a shell ,
the resin is a crystalline resin,
the resin and the surface of the inorganic fine particles are chemically bonded,
Core-shell fine particles for toner, characterized in that the core-shell fine particles for toner have a volume resistivity of 1.0×10 ⁸ Ω·cm or more and 1.0×10 ¹⁴ Ω·cm or less.

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