JP2023056099A - Toner for electrostatic latent image development - Google Patents

Abstract

To provide a toner that can further improve low temperature fixability.SOLUTION: A toner for electrostatic latent image development has a toner base particle and silica particles externally added to the toner base particle. The toner base particle includes at least a binder resin and a colorant. The silica particles are subjected to hydrophobic treatment with an alkyl-silane coupling agent. The substantial throughput of the alkyl-silane coupling agent calculated from the following formulas is 0.01 mass% or more and less than 30 mass%. The substantial throughput (mass%) of the alkyl-silane coupling agent=ignition loss-loss on drying. The ignition loss (mass%): the mass reduction ratio when the silica particles are held at a temperature of 500°C for two hours. The loss on drying (mass%): the mass reduction ratio when the silica particles are held at a temperature of 105°C for two hours.SELECTED DRAWING: None

Description

The present invention relates to an electrostatic latent image developing toner, and more specifically, an electrostatic latent image developing toner (hereinafter simply referred to as "toner for developing an electrostatic latent image" used in image forming apparatuses using so-called electrophotography, such as facsimiles, printers, and copiers). toner), etc.

For example, in image forming apparatuses such as facsimiles, printers, and copiers using an electrophotographic method, generally, a toner image transferred to a transfer material such as paper is heated and melted to be fixed on the transfer material. In recent years, with the growing awareness of energy saving, there is a demand for a toner that can be fixed at a lower temperature than in the past.

Conventional methods for fixing toner at low temperature include a method of adjusting the molecular weight and molecular weight distribution of a binder resin constituting the toner (Patent Document 1), and a method of using both an amorphous resin and a crystalline resin as the binder resin. Various methods such as a method (Patent Document 2) have been proposed.

JP-A-2002-82484 JP 2013-160886 A

According to the proposed method, although the low-temperature fixability of the toner can be achieved to some extent, it cannot be said to be sufficiently compatible with the recent high-speed image forming apparatus, and further improvement of the low-temperature fixability of the toner is desired. It is rare.

SUMMARY OF THE INVENTION An object of the present invention is to provide a toner capable of further improving low-temperature fixability.

A toner according to the present invention for achieving the above object is an electrostatic latent image developing toner comprising toner base particles and silica particles externally added to the toner base particles, wherein the toner base particles at least The silica particles contain a resin-adhering agent and a coloring agent, and the silica particles are hydrophobized with an alkylsilane coupling agent, and the effective processing amount of the alkylsilane coupling agent calculated from the following formula is 0.01 mass. % or more and less than 30% by mass.
Substantial treatment amount by alkylsilane coupling agent (% by mass) = Loss on ignition - Loss on drying Ignition loss (% by mass): Mass reduction rate when silica particles are held at a temperature of 500 ° C. for 2 hours Loss on drying (% by mass) : Mass reduction rate when silica particles are held at a temperature of 105 ° C. for 2 hours

In the toner having the above constitution, the silica particles are preferably fumed silica having an average primary particle size of 5 nm or more and 70 nm or less or colloidal silica having an average primary particle size of 50 nm or more and 200 nm or less.

In the toner having the above constitution, the alkylsilane coupling agent preferably has a linear alkyl group having 3 or more carbon atoms and having no substituent.

Further, in the toner having the above constitution, it is preferable that the amount of the silica particles externally added is in the range of 0.5% by mass or more and 10% by mass or less with respect to the toner base particles.

Further, in the toner having the above constitution, the volume average particle diameter of the toner base particles is preferably in the range of 4 μm or more and 15 μm or less.

Further, according to the present invention, there is provided a developer for developing an electrostatic latent image, comprising any one of the toner described above and a carrier.

According to the toner of the present invention, it is possible to further improve low-temperature fixability. Further, the developer of the present invention can be adapted to high-speed image forming apparatuses.

As a result of extensive studies aimed at improving the low-temperature fixability of toner, the inventors of the present invention have found new knowledge that the low-temperature fixability of toner is affected not only by the binder resin but also by the external additives in the toner base particles. Obtained. More specifically, it has been found that hydrophobized silica particles as an external additive increase the viscosity of the molten toner, resulting in a decrease in the fixability of the toner image to the transfer material. Obtained. As a result of further studies, the inventors of the present invention have found that an increase in the viscosity of the fused toner can be suppressed depending on the type and treatment amount of the hydrophobizing agent for the silica particles, and have completed the present invention.

That is, the toner according to the present invention is a toner having toner base particles and silica particles externally added to the toner base particles, and the silica particles are largely hydrophobized with an alkylsilane coupling agent. It is one of the characteristics.

Silica particles have hitherto been widely used as an external additive for toners for the purpose of improving the fluidity and chargeability of toners. In addition, since silica particles themselves are hydrophilic, they are easily affected by temperature and humidity. Therefore, silica particles subjected to hydrophobic treatment have been preferably used. HMDS (hexamethyldisilazane) and PDMS (polydimethylsiloxane) have been mainly used as hydrophobizing agents.

However, according to the results of studies by the present inventors, the toner to which silica particles treated with HMDS or PDMS are externally added has improved toner fluidity and chargeability, but the toner viscosity when the toner is melted is increased, and the fixability of the toner to the transfer material was inhibited. In addition, it was found that if an alkylsilane coupling agent is used as a hydrophobizing agent for silica particles, thickening of the melted toner can be suppressed, and that the treatment amount with the alkylsilane coupling agent should be within a predetermined range. rice field. The alkylsilane coupling agent used in the present invention is explained below.

(Alkylsilane coupling agent)
As the alkylsilane coupling agent used in the present invention, a trialkoxyalkylsilane coupling agent represented by the following formula is preferable.
_{CnH2n +1} -Si( _{OCmH2m +1} ) ₃
(Wherein, n: an integer of 3 or more, m: an integer of 1 to 3)
If n is less than 3, the hydrophobic effect may be reduced. A preferred maximum value for n is eighteen. The thickening effect of the melted toner is suppressed as the value of n increases. A more preferred range for n is an integer of 8-12. Also, if m is more than 3, the reactivity of the hydrophobizing treatment may decrease. A more preferred range for m is an integer of 1-2. Also, the alkyl group preferably has no substituents.

The effective processing amount of the alkylsilane coupling agent relative to the silica particles calculated from the above formula is in the range of 0.01% by mass or more and less than 30% by mass. If the amount of the alkylsilane coupling agent substantially treated is less than 0.01% by mass, the silica particles cannot be made hydrophobic. On the other hand, when the substantial treatment amount of the alkylsilane coupling agent is 30% by mass or more, the viscosity of the melted toner increases. A preferable range of the substantial treatment amount of the alkylsilane coupling agent is 1% by mass or more and 10% by mass or less.

The ignition loss of silica particles is the mass reduction rate when the silica particles are held at 500° C. for 2 hours, and means the mass ratio of organic matter, volatile components, and water present in the silica particles. On the other hand, the weight loss on drying is the mass reduction rate when the silica particles are held at 105° C. for 2 hours, and means the mass ratio of volatile components and water present in the silica particles. Therefore, by subtracting the loss on drying from the loss on ignition, the actual amount of the organic matter present in the silica particles, that is, the alkylsilane coupling agent can be calculated.

The method for hydrophobizing silica particles with an alkylsilane coupling agent is not particularly limited, and conventionally known methods are used. For example, a method of directly mixing silica particles and an alkylsilane coupling agent using a mixer such as a Henschel mixer, a method of spraying an alkylsilane coupling agent onto silica particles, or a method of adding an alkylsilane coupling agent to an appropriate solvent. Examples include a method of adding silica particles to a dissolved or dispersed liquid and then removing the solvent.

(silica particles)
The silica particles used in the present invention may be those produced by conventionally known methods, but those produced by a dry method or a high-temperature hydrolysis method are preferred from the viewpoint of dispersibility of silica particles. . Specifically, fumed silica or colloidal silica is preferably used. When fumed silica is used as the silica particles, the average primary particle size is preferably 5 nm or more and 70 nm or less. When colloidal silica is used as the silica particles, the average primary particle size is preferably 50 nm or more and 200 nm or less.

The average primary particle size of silica particles is the average value of the diameter or the maximum diameter of a plurality of (100) particles randomly extracted by photographing silica particles with a scanning electron microscope (SEM).

The amount of the silica particles externally added to the surface of the toner base particles is preferably in the range of 0.5% by mass or more and 10% by mass or less with respect to the toner base particles. If the amount of the silica particles to be externally added is less than 0.5% by mass, there is a risk that the fluidity and chargeability of the toner cannot be improved. On the other hand, if the amount of the silica particles to be externally added exceeds 10% by mass, the viscosity of the toner when it is melted may increase, and the low-temperature fixability may deteriorate.

(Toner base particles)
The toner base particles used in the present invention contain at least a binder resin and a colorant. The binder resin is not particularly limited, and examples thereof include styrene-acrylic resin and polyester resin. Of course, other resins may be used in combination with these resins if necessary.

Styrene-acrylic resin base monomers include, for example, styrene, α-methylstyrene, p-methylstyrene, pt-butylstyrene, p-chlorostyrene, styrene derivatives such as hydroxystyrene; methacrylic acid, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, glycidyl (meth)acrylate, methoxyethyl (meth)acrylate, propoxyethyl (meth)acrylate, methoxydiethylene glycol (meth)acrylate, Ethoxydiethylene glycol (meth)acrylate, benzyl (meth)acrylate, cyclohexyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, (meth)acrylonitrile, (meth)acrylamide, N-methylol (meth)acrylamide, ethylene glycol di(meth) ) acrylate, 1,3-butylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, and trimethylolethane tri(meth)acrylate.

Polyester resins are obtained mainly by polycondensation of polycarboxylic acids and polyhydric alcohols. ,4-benzenetricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, aromatic polycarboxylic acids such as pyromellitic acid; maleic acid, fumaric acid, succinic acid, adipic acid , sebacic acid, malonic acid, azelaic acid, mesaconic acid, citraconic acid, glutaconic acid and other aliphatic dicarboxylic acids; cyclohexanedicarboxylic acid, methylmedic acid and other alicyclic dicarboxylic acids; anhydrides and lower alkyl esters of these carboxylic acids and one or more of these are used.

Here, the content of trivalent or higher valent components depends on the degree of cross-linking, and the amount thereof to be added may be adjusted to obtain the desired degree of cross-linking. In general, the content of trivalent or higher valent components is preferably 15 mol % or less.

On the other hand, examples of polyhydric alcohols used in polyester resins include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,4-butenediol, and neopentyl glycol. , 1,5-pentane glycol and 1,6-hexane glycol; alkylene ether glycols such as diethylene glycol, triethylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol and polytetramethylene glycol; 1,4 - Alicyclic polyhydric alcohols such as cyclohexanedimethanol and hydrogenated bisphenol A; The above can be used in combination.

For the purpose of adjusting the molecular weight and controlling the reaction, monocarboxylic acids and monoalcohols may be used as necessary. Examples of monocarboxylic acids include benzoic acid, paraoxybenzoic acid, toluenecarboxylic acid, salicylic acid, acetic acid, propionic acid and stearic acid. Monoalcohols include monoalcohols such as benzyl alcohol, toluene-4-methanol, and cyclohexanemethanol.

The binder resin used in the present invention preferably has a glass transition temperature in the range of 45°C to 90°C. If the glass transition temperature is less than 45° C., there is a risk of solidification in the toner cartridge or developing device. On the other hand, if the glass transition temperature is higher than 90° C., the toner may not be sufficiently fixed on the transferred material such as paper.

Colorants used in the present invention include, for example, black pigments such as acetylene black, run black, and aniline black; yellow pigments such as yellow lead, zinc yellow, cadmium yellow, yellow iron oxide, mineral fast yellow; Nickel Titanium Yellow, Navels Yellow, Naphthol Yellow S, Hansa Yellow G, Hansa Yellow 10G, Benzidine Yellow G, Benzidine Yellow GR, Quinoline Yellow Lake, Permanent Yellow NCG, Tartrazine Lake; orange, permanent orange GTR, pyrazolone orange, vulcan orange, indanthrene brilliant orange RK, benzidine orange G, indanthrene brilliant orange GK; , Pyrazolone Red, Watching Red Calcium Salt, Lake Red D, Brilliant Carmine 6B, Eosin Lake, Rhodamine Lake B, Alizarin Lake, Brilliant Carmine 3B; As Purple Pigments, Manganese Purple, Fast Violet B, Methyl Violet Lake; As Blue Pigments , Prussian blue, cobalt blue, alkali blue lake, Victoria blue lake, phthalocyanine blue, metal-free phthalocyanine blue, phthalocyanine blue partial chloride, fast sky blue, indanthrene blue BC; as green pigments, chromium green, chromium oxide, pigment green B , malachite green lake, fanal yellow green G; white pigments such as zinc white, titanium oxide, antimony white, zinc sulfide; white pigments such as barite powder, barium carbonate, clay, silica, white carbon, talc, alumina white, etc. mentioned. One or more of these colorants may be used in combination.

The total content of the colorant is preferably in the range of 0.1 to 20 parts by mass, particularly 1 to 15 parts by mass, per 100 parts by mass of the binder resin.

(Preparation of toner base particles)
The toner base particles of the present invention can be produced by a known method such as a pulverization classification method, a melt granulation method, a spray granulation method, a suspension/emulsion polymerization method, and the like. A pulverization classification method can be preferably used. Such pulverization and classification method will be described below.

First, a toner composition such as a binder resin, a colorant and, if necessary, a charge control agent, a release agent, and a magnetic powder are premixed using a Henschel mixer or a V-type mixer, and then a melt-kneading device such as a twin-screw extruder is used. Melt and knead using After the melt-kneaded product is cooled, it is coarsely pulverized and finely pulverized, and if necessary, classified to obtain toner base particles having a predetermined particle size distribution. The volume average particle size of the toner base particles is preferably in the range of 4 μm or more and 15 μm or less. The volume average particle size of the toner base particles is a value measured by Coulter Multisizer II manufactured by Coulter.

Here, as the charge control agent, known charge control agents can be used. , an amine compound, an organometallic compound, and the like, and as the negative charge control agent, a metal complex of oxycarboxylic acid, a metal complex of an azo compound, a metal complex dye, a salicylic acid derivative, and the like can be used. The amount of the charge control agent to be added is preferably in the range of 0.1 to 10 parts by mass with respect to 100 parts by mass of the binder resin.

Various waxes and low-molecular-weight olefin resins can be used as the release agent. Examples of waxes that can be used include polyhydric alcohol esters of fatty acids, higher alcohol esters of fatty acids, alkylenebis fatty acid amide compounds, and natural waxes. As the low molecular weight olefin resin, polypropylene, polyethylene, propylene-ethylene copolymer, etc. having a number average molecular weight in the range of 1,000 to 10,000, particularly 2,000 to 6,000 can be used. Especially polypropylene can be preferably used. The amount of release agent to be added is preferably in the range of 0.1 to 10 parts by mass with respect to 100 parts by mass of the binder resin.

Magnetic powders include, for example, triiron tetroxide (Fe ₃ O ₄ ), ferric oxide (γ-Fe ₂ O ₃ ), zinc iron oxide (ZnFe ₃ O ₄ ), yttrium iron oxide (Y ₃ Fe ₅ O ₁₂ ), cadmium iron oxide ( _CdFe2O4 ) _{, gadolinium iron oxide (Gd3Fe5O12 ) , copper iron} oxide ( _CuFe2O4 ), lead iron oxide ( _PbFe12O19 ), _nickel iron oxide ( _{NiFe2 O4} ), neodymium iron oxide ( _NdFeO3 ) _, barium iron oxide ( _BaFe12O19 ), _magnesium iron oxide ( _{MgFe2O4 )} , manganese iron oxide ( _MnFe2O4 ), lanthanum iron oxide ( _LaFeO3 ), Iron powder (Fe), cobalt powder (Co), nickel powder (Ni) and the like can be mentioned. The amount of magnetic powder to be added is preferably in the range of 0.1 to 5 parts by mass, more preferably in the range of 0.5 to 3.0 parts by mass, per 100 parts by mass of the binder resin.

The silica particles are adhered to the surface of the toner base particles thus produced to obtain the toner of the present invention. As a method for mixing and adding the silica particles to the toner base particles, a conventionally known treatment can be used. A method of throwing in and stirring and mixing can be used.

In addition, a surface treatment agent may be externally added to the toner base particles, if necessary, in order to adjust the chargeability and fluidity of the toner. Examples of surface treatment agents include inorganic fine powders such as alumina, zinc oxide, magnesium oxide, and calcium carbonate; organic fine powders such as polymethyl methacrylate; and fatty acid metal salts such as zinc stearate. mentioned. The amount of the surface treatment agent to be added is preferably in the range of 0.1 to 2.0 parts by mass with respect to 100 parts by mass of the toner base particles.

(Electrostatic latent image developer)
The toner of the present invention can be used as a one-component developer or a two-component developer. There are no restrictions on the carrier used when used as a two-component developer. Examples include magnetic metals such as iron, nickel, and cobalt, alloys thereof, alloys containing rare earth elements, hematite, magnetite, and manganese-zinc. Sintering and atomizing magnetic materials such as ferrite, nickel-zinc ferrite, manganese-magnesium ferrite, soft ferrite such as lithium ferrite, iron oxide such as copper-zinc ferrite, and mixtures thereof. It is possible to use the magnetic particles produced by the method and the magnetic particles whose surfaces are coated with a resin. Further, a magnetic substance-dispersed resin can also be used as the carrier. In this case, the above-described magnetic material can be used as the magnetic material, and the binder resin includes, for example, vinyl resin, polyester resin, epoxy resin, phenol resin, urea resin, polyurethane resin, polyimide resin, cellulose resin, poly Ether resins or mixtures thereof may be mentioned.

The particle size of the carrier is generally 30 μm to 200 μm, preferably 50 μm to 150 μm, as measured by electron microscopy. The apparent density of the carrier, when mainly composed of a magnetic material, varies depending on the composition, surface structure, etc. of the magnetic material, but is generally preferably in the range of 2.4 g/cm ³ to 3.0 g/cm ³ .

The toner concentration in the two-component developer consisting of the toner and carrier is 1% to 10% by mass, preferably 1% to 7% by mass. If the toner concentration is less than 1% by mass, the image density becomes too low. On the other hand, if the toner concentration exceeds 10% by mass, the toner scatters in the developing device and the toner adheres to the inside of the machine and the background of the transfer paper. This is because there is a possibility that a malfunction may occur.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

(Preparation of toner base particles I)
Polyester resin (manufactured by Mitsubishi Chemical Corporation, trade name: ER-508) 100 parts by mass, carbon black (manufactured by Cabot Corporation, trade name: BP-L) 6 parts by mass, zinc salicylate complex 1.0 parts by mass and polypropylene wax (Sanyo 2.0 parts by mass of 660P (trade name, manufactured by Kasei Kogyo Co., Ltd.) were mixed using a Henschel mixer, and then melted and kneaded using a twin-screw extruder. The resulting mixture was rolled using cooled press rollers and coarsely pulverized with a feather mill. Then, the mixture was pulverized using an air jet pulverizer and classified using an air classifier to obtain toner base particles I having a volume average particle size of 7.5 μm.
When the glass transition temperature (Tg) and softening temperature (T1/2) of the toner base particles I were measured by the following methods, the Tg was 63°C and the T1/2 temperature was 128°C.

(Preparation of toner base particles II)
238 parts by mass of adipic acid, 265 parts by mass of 1,6-hexanediol, and 1 part by mass of hydroquinone were subjected to condensation polymerization to prepare a crystalline polyester resin having a melting point of 70° C. and an Mw of 10,000.
Toner base particles II were prepared in the same manner as toner base particles I except that 93 parts by weight of a polyester resin (manufactured by Mitsubishi Chemical Corporation, trade name: ER-508) and 7 parts by weight of the crystalline polyester resin prepared above were used as the polyester resin. was made. When the glass transition temperature (Tg) and softening temperature (T1/2) of toner base particles II were measured in the same manner as for toner base particles I, Tg was 50°C and T1/2 temperature was 104°C.

(Glass transition temperature (Tg))
Using a differential scanning calorimeter (Shimadzu Corporation, DSC-60), 10 mg ± 0.5 mg of the sample was weighed into an aluminum pan, and the baseline of the chart at a heating rate of 5 ° C./min and the tangent of the endothermic curve. The glass transition temperature Tg was measured from the intersection of

(Softening temperature (T1/2))
Using a capillary rheometer (manufactured by Shimadzu Corporation, flow tester CFT-500D), the temperature rise rate is 6° C./min, the nozzle is 1.0 mmφ×1 mm, the load is 10 kgf, and the sample amount is 1.5 g. The temperature was taken as the temperature at the intermediate point in the process up to.

(Preparation of silica particles A)
100 parts by weight of untreated fumed silica powder (BET specific surface area 130 m ² /g) was mixed with 100 parts by weight of n-propanol with a stirrer. 50 parts by mass of n-propanol and a small amount of diethylamine were added to this mixture and stirred for 1 hour. To this mixture, 100 parts by mass of n-propanol and 4.0 parts by mass of isobutyltriethoxysilane were added, heated under reflux for 5 hours while stirring in an inert atmosphere, and allowed to cool to room temperature. This mixture was heated under reduced pressure to remove the solvent with a rotary evaporator, and then dried in a vacuum oven for 18 hours to prepare silica particles A.

(Preparation of silica particles B)
Silica particles B were produced in the same manner as silica particles A, except that isobutyltriethoxysilane was replaced with 5.0 parts by mass of octyltriethoxysilane.

(Preparation of silica particles C)
Silica particles C were produced in the same manner as silica particles A, except that isobutyltriethoxysilane was replaced with 7.0 parts by mass of decyltriethoxysilane.

(Preparation of silica particles D)
Silica particles were prepared in the same manner as silica particles A, except that the untreated fumed silica powder with a BET specific surface area of 50 m ² /g was changed, and isobutyltriethoxysilane was changed to 2.5 parts by mass of decyltriethoxysilane. D was produced.

(Preparation of silica particles E)
100 parts by mass of untreated fumed silica powder (BET specific surface area: 200 m ² /g) was placed in a reaction vessel, stirred in a nitrogen atmosphere to make the powder fluid, and 3.0 parts by mass of octyltrimethoxysilane was sprayed. With continued stirring, the temperature was raised from room temperature to 340° C. and held there for 30 minutes. By cooling this, silica particles E were obtained.

(Preparation of silica particles F)
A small amount of aqueous ammonia and 2.0 parts by weight of octyltriethoxysilane were added to 100 parts by weight of a commercially available hydrophilic colloidal silica dispersion (BET specific surface area: 30 m ² /g, 40% solid content), and the mixture was stirred at room temperature. Stirred for 24 hours with an overhead stirrer. This mixture was dried in a forced circulation constant temperature dryer at 128° C. to obtain silica particles F.

(Preparation of silica particles G)
As the silica particles G, commercially available hydrophobic silica particles (fumed silica particles surface-treated with HMDS, manufactured by Clariant, trade name: H13TM, average primary particle diameter: 16 nm) were prepared.

(Silica particles H)
As silica particles H, commercially available hydrophobic silica particles (fumed silica particles surface-treated with silicone oil, manufactured by Tayca, trade name: MSN-002, average primary particle size: 16 nm) were prepared.

(Silica particles I)
As silica particles I, commercially available hydrophobic silica particles (fumed silica particles surface-treated with silicone oil, manufactured by Aerosil, trade name: RY-50, average primary particle size: 40 nm) were prepared.

(Silica particles J)
As the silica particles J, commercially available hydrophobic silica particles (fumed silica particles surface-treated with silicone oil, manufactured by Cabot Corporation, trade name: TG-308F, average primary particle diameter: 12 nm) were prepared.

(loss on drying)
The loss on drying of silica particles A to J prepared or prepared above was measured by the following method. Table 1 shows the measurement results.
・Precisely weigh 3 g of the sample in a container that has been previously dried, allowed to cool, and accurately weighed.
・Dry at 105°C for 2 hours using a heat drying moisture meter MX-50. After standing to cool in a desiccator for 30 minutes, the mass is accurately weighed and calculated from the following formula.
Weight loss on drying (%) = weight loss due to drying (g) / amount of sample (g) x 100

(Ignition loss)
The ignition loss of the silica particles A to J prepared or prepared above was measured by the following method. Table 1 shows the measurement results.
・Put 0.5 g of a sample into a magnetic crucible that has been previously dried, allowed to cool, and accurately weighed, and accurately weighed.
・Ignite for 2 hours in an electric furnace (small electric furnace black mini-BS1) set at 500°C. After standing to cool in a desiccator for 1 hour, the mass is accurately weighed and calculated from the following formula.
Ignition loss (%) = loss due to ignition (g) / sample amount (g) x 100

(viscoelasticity measurement)
The viscoelasticity of silica particles A to J prepared or prepared above was measured by the following method. Table 1 shows the measurement results.
Polyester resin (manufactured by Mitsubishi Chemical Corporation, trade name: ER-508) 10 parts by mass of each silica particle A to J is mixed with 90 parts by mass using Super Mixer Piccolo SMP-2 manufactured by Kawata Co., Ltd. to obtain a sample. , and 1.0 g of a sample was subjected to viscoelasticity measurement under the following conditions using a viscoelasticity measuring device (ARES-G2 rheometer manufactured by TA Instruments). From the measured data, the ratio (G''/G') between the storage modulus G' and the loss modulus G'' at 110°C was taken as tan δ (110°C).
Dynamic viscoelasticity measurement conditions Parallel plate diameter: 25 mm
Measurement frequency: 1.0Hz
Measurement strain: 0.2%
Measurement temperature: Heated from 70°C to 200°C at a rate of 3.0°C per minute.

Example 1
100 parts by mass of toner base particles I and 2.0 parts by mass of silica particles A are added to a super mixer Piccolo SMP-2 manufactured by Kawata Co., Ltd., mixed at 3000 rotations for 6 minutes, and passed through a sieve with an opening of 74 μm. A toner of Example 1 was prepared by sieving. The minimum fixing temperature, low-temperature fixability and storage stability of the produced toner were measured and evaluated by the following methods. The results are also shown in Table 2.

Examples 2-6 and Comparative Examples 1-5
Toners of Examples 2 to 6 and Comparative Examples 1 to 5 were produced in the same manner as in Example 1, except that the type and amount of silica particles to be added were changed to those shown in Table 2. The minimum fixing temperature, low-temperature fixability and storage stability of the produced toner were measured and evaluated by the following methods in the same manner as in Example 1. The results are also shown in Table 2.

Comparative example 5
A toner of Comparative Example 5 was prepared in the same manner as in Comparative Example 2 except that the toner base particles were changed to toner base particles II. The minimum fixing temperature, low-temperature fixability and storage stability of the produced toner were measured and evaluated by the following methods in the same manner as in Example 1. The results are also shown in Table 2.

The amount of silica particles added in Examples and Comparative Examples is determined by geometric calculation from the particle diameters of the toner base particles and the silica particles so that the surface coverage of the toner base particles with the silica particles is about 100%. rice field.

(Minimum fixing temperature)
The prepared toner was evenly placed on a commercially available 75 g/m ² PPC paper so as to give 0.40 mg/cm ² . This PPC paper was subjected to an external fixation test machine using a commercially available heat roller type toner fixer, fixing speed (peripheral speed of heating roller) 375 mm/sec, heating roller temperature range of 150 to 230 ° C in increments of 10 ° C. After setting and fixing, a fixed image was obtained. After the image density of the obtained fixed image was measured by X-Rite eXact, a peeling test was performed by the following method, and the image density was measured again after peeling. Then, the fixing rate was calculated from the following formula, and the lowest temperature among the heating roller temperatures when the fixing rate was 90% or more was taken as the minimum fixing temperature.
Fixing rate (%)=fixed image density after peeling test/fixed image density before peeling test×100

(Peel test method)
A mending tape is attached to the fixed image, and a weight of 500 g is reciprocated on the tape at 1 cm/sec for 5 times, and then the mending tape is peeled off at 1 cm/sec.

(low temperature fixability)
Based on the results of the lowest fixing temperature, the low-temperature fixability was evaluated according to the following criteria.
○: Lower limit fixing temperature is 170°C or less △: Lower limit fixing temperature is higher than 170°C and 180°C or lower ×: Lower limit fixing temperature is higher than 180°C

(storability)
20.0 g of toner was placed in a closed container and allowed to stand at a temperature of 50° C. for 8 hours. After tapping the sealed container after standing still, the entire amount of the toner was transferred to a sieve and sieved under the following conditions using a powder tester. After sieving, the mass of the toner remaining on the sieve was measured, and the storage stability was evaluated according to the following criteria. ○: Less than 0.2 g △: 0.2 g or more and less than 1.0 g ×: 1.0 g or more Sieve processing conditions Device: POWDER TESTER PT-X (manufactured by Hosokawa Micron)
Sieve mesh size: 355 μm
Vibration width: 1mm
Vibration time: 10 seconds Operation method: A sieve is set on the vibration table of the powder tester, toner is placed on the sieve, and the sieve is vibrated for 10 seconds at a vibration width of 1 mm to measure the weight of the toner remaining on the sieve.

As is clear from Table 2, the toners of Examples 1 to 6 all exhibited excellent low-temperature fixing performance, with a minimum fixation temperature of 170° C., and good storage stability.

On the other hand, in the toner of Comparative Example 1 to which silica particles hydrophobized with hexamethylsilazane were externally added and the toners of Comparative Examples 2 to 4 to which silica particles hydrophobized with polydimethylsiloxane were externally added, the fixing lower limit The temperatures were 180° C. and 190° C., which were higher than the toners of Examples 1-6. Further, the toner of Comparative Example 5, in which silica particles hydrophobized with polydimethylsiloxane were externally added to the toner base particles II, had a minimum fixing temperature of 160° C., indicating good low-temperature fixing performance, but poor storage stability.

According to the toner of the present invention, it is possible to further improve the low-temperature fixability.

Claims (6)

An electrostatic latent image developing toner comprising toner base particles and silica particles externally added to the toner base particles,
the toner base particles contain at least a binder resin and a colorant;
The silica particles are hydrophobized with an alkylsilane coupling agent,
A toner for developing an electrostatic latent image, wherein the amount of the alkylsilane coupling agent to be treated, which is calculated from the following formula, is 0.01% by mass or more and less than 30% by mass.
Substantial treatment amount by alkylsilane coupling agent (% by mass) = Loss on ignition - Loss on drying Ignition loss (% by mass): Mass reduction rate when silica particles are held at a temperature of 500 ° C. for 2 hours Loss on drying (% by mass) : Mass reduction rate when silica particles are held at a temperature of 105 ° C. for 2 hours 2. The toner for electrostatic latent image development according to claim 1, wherein the silica particles are fumed silica having an average primary particle size of 5 nm or more and 70 nm or less or colloidal silica having an average primary particle size of 50 nm or more and 200 nm or less. 3. The toner for developing an electrostatic latent image according to claim 1, wherein the alkylsilane coupling agent has a linear alkyl group having 3 or more carbon atoms and having no substituent. 4. The toner for developing an electrostatic latent image according to claim 1, wherein the silica particles are added in an amount of 0.5% by mass or more and 10% by mass or less with respect to the toner base particles. 5. The toner for developing an electrostatic latent image according to claim 1, wherein the toner base particles have a volume average particle size of 4 μm or more and 15 μm or less. A developer for developing an electrostatic latent image, comprising the toner according to any one of claims 1 to 5 and a carrier.