ADDITIVE FOR TONER PARTICLE CONTAINING SILICA PARTICLES SURFACE-TREATED WITH SILANE-COUPLING AGENT AND TONER

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

[0001] This application claims priority to Japanese Patent Application No. 2022- 169333, filed on October 21, 2022, the entirety of which is incorporated by reference herein.

BACKGROUND

[0002] Methods for visualizing image information through electrostatically charged images, such as electrophotography, have been utilized in a variety of fields. In electrophotography, a surface of a photoreceptor is uniformly charged, an electrostatically charged image is formed on the surface of the photoreceptor, an electrostatic latent image is developed with a developer including toner particles, and thereby the electrostatic latent image is visualized as a toner image. The toner image is transferred and fixed onto the surface of a recording medium, and thereby an image is formed.

DETAILED DESCRIPTION

[0003] Hereinafter, examples of an additive for a toner particle are described. The additive for a toner particle according to some examples contains silica particles surface- treated with a silane coupling agent, the agent containing at least one element selected from a group comprising fluorine and sulfur.

[0004] In some examples, the surface treatment of the silica particles is a hydrophobic treatment to make the surface of the silica particles hydrophobic. That is, the silane coupling agent containing at least one element selected from a group comprising fluorine and sulfur is to make the surface of the silica particle hydrophobic. In some examples, the surface treatment of the silica particles is a hydrophobic treatment to make the surface of the silica particles hydrophobic, and may be a treatment to impart a charge (for example, a negative charge) to the silica particles. That is, the silane coupling agent containing at least one element selected from a group comprising fluorine and sulfur is to make the surface of the silica particle hydrophobic and to impart a charge (for example, a negative charge).

[0005] The surface treatment of silica particles as described above is, in some examples, may be without using a silazane compound (for example, hexamethyldisilazane). Thus, for example, when use of a silazane compound is legally regulated, the additive for a toner particle that can be used without the regulation can be provided.

[0006] Examples of a silane coupling agent containing fluorine include a silane coupling agent containing a perfluoroether group. The silane coupling agent containing a perfluoroether group may be, for example, a silane coupling agent represented by the following formula (1):

OR ¹

F— (C _m F _2m O) _n — Si— OR ² (1 )

OR ³ wherein each of R ¹ , R ² and R ³ represents an alkyl group, m represents an integer of 2 or larger, and n represents an integer of 1 or larger.

[0007] The alkyl groups represented by R ¹ , R ² and R ³ may be linear or branched. The number of carbon atoms of the alkyl groups represented by R ¹ , R ² and R ³ may be 1 or more and 3 or less, m may be an integer of 4 or less, n may be an integer of 5 or less, 4 or less, 3 or less, or 2 or less.

[0008] Examples of a silane coupling agent containing sulfur include a silane coupling agent containing a mercapto group. The silane coupling agent containing a mercapto group may be, for example, a silane coupling agent represented by the following formula (2): wherein each of R ⁴ and R ⁵ represents an alkyl group, R ⁶ represents an alkylene group, and each of p and q represents an integer ranging from 0 to 3 satisfying p + q = 3.

[0009] The alkyl groups represented by R ⁴ and R ⁵ may be linear or branched. The number of carbon atoms of the alkyl groups represented by R ⁴ and R ⁵ may be 1 or more and 3 or less. The alkylene group represented by R ⁶ may be linear or branched. The number of carbon atoms of the alkylene group represented by R ⁶ may be 1 or more and 4 or less, p may be 2 or 3. q may be 0 or 1.

[0010] The average particle diameter of the silica particles may be 250 nm or less, 200 nm or less, 150 nm or less, 100 nm or less, 70 nm or less, or 50 nm or less, and may be 5 nm or larger, 10 nm or larger, or 20 nm or larger. The average particle diameter of the silica particles is measured by the method described below.

[0011 ] Next, examples of a method for producing the additive for a toner particle described above are described. A method for producing an additive for a toner particle according to some examples may utilize surface-treating silica particles with a silane coupling agent containing at least one element selected from a group comprising fluorine and sulfur.

[0012] The silica particles (i.e., prior to the surface treatment) may be a commercial product according to a desired average particle diameter or the like. To perform the surface treating, in some examples, alcohol (for example, methanol), the silica particles, and a basic aqueous solution (for example, ammonia aqueous solution) may be mixed. A silane coupling agent containing at least one element selected from a group comprising fluorine and sulfur may be gradually added. The mixing may continue after the addition to perform the surface treatment of the silica particles. [0013] The silane coupling agent containing at least one element selected from a group comprising fluorine and sulfur are as described above. The amount of the silane coupling agent added may be 1 part by mass or more or 2 parts by mass or more, and may be 5 parts by mass or less or 4 parts by mass or less, with respect to 100 parts by mass of the silica particles (i.e., the silica particles prior to the surface treatment).

[0014] According to such a method for producing the additive for a toner particle, the surface of the silica particles may be hydrophobized with the silane coupling agent without using a silazane compound (for example, hexamethyldisilazane) used during the surface treatment of the silica particle. That is, the surface treatment of the silica particles is a surface treatment (hydrophobic treatment) in which a silazane compound (for example, hexamethyldisilazane) is not used. Thus, for example, even when use of the silazane compound is legally regulated, the additive for a toner particle that can be used without the regulation can be provided.

[0015] Next, example toner particles are described. The toner particle according to some examples contains a core particle and an additive externally added to the core particle. The additive is an additive for a toner particle as described above.

[0016] The core particle contains a binder resin. The binder resin may contain a polyester resin. The binder resin may contain a first polyester resin having a softening point of 120 °C or higher (a polyester resin having a higher softening point) and a second polyester resin having a softening point of lower than 120 °C (a polyester resin having a lower softening point).

[0017] The softening point in the present specification is defined as Tl/2 based on the flow curve of the resin measured using a flow tester (for example, "Flow Tester Model CFT-500" manufactured by Shimadzu Corporation). The softening point (Tl/2) is measured by the method described in Examples.

[0018] The softening point of the first polyester resin may be 123 °C or higher, 125 °C or higher, or 130 °C or higher, and may be 160 °C or lower, 155 °C or lower, 150 °C or lower, or 145 °C or lower. For low-temperature fixability, offset resistance, and heat-resistant storability, the softening point may be 140 °C or lower, or 135 °C or lower.

[0019] The softening point of the second polyester resin may be 118 °C or lower, 115 °C or lower, or 110 °C or lower, or may be 80 °C or higher, and may be 85 °C or higher or 90 °C or higher for low-temperature fixability and heat-resistant storability.

|0020| The first polyester resin may be a polycondensate of a polyethylene terephthalate, a carboxylic acid, and a diol. In this case, the first polyester resin is obtained by subjecting a polyethylene terephthalate, a carboxylic acid, and a diol (hereinafter collectively referred to as a "first polycondensation component") to an esterification reaction. More specifically, for example, the first polyester resin can be obtained by causing an ester exchange reaction between ethylene glycol contained as a monomer unit in the polyethylene terephthalate and the diol, and causing polycondensation of the carboxylic acid.

[0021 ] Properties of the polyethylene terephthalate are not particularly limited. For example, the number average molecular weight (Mn) of the polyethylene terephthalate may be 5,000 or higher, 10,000 or higher, or 15,000 or higher, and may be 60,000 or less, 55,000 or less, 50,000 or less, or 45,000 or less. The polyethylene terephthalate may be a recycled polyethylene terephthalate. In this case, environmentally-friendly toner particles may be provided.

[0022] The amount (charge amount) of the polyethylene terephthalate may be 5% by mass or more, 10% by mass or more, or 20% by mass or more, and may be 85% by mass or less, 80% by mass or less, or 70% by mass or less, based on the total amount of the first polycondensation component.

[0023] The carboxylic acid may be a polycarboxylic acid or an anhydride thereof. The polycarboxylic acid may contain a dicarboxylic acid or an anhydride thereof. Examples of the dicarboxylic acid include a dicarboxylic acid having a pendant group and a dicarboxylic acid having no pendant group. [0024] The dicarboxylic acid having a pendant group has a chain (pendant group) which is branched from a main chain having two carboxyl groups. The pendant group may be a chain hydrocarbon group, and may be an alkyl group or an alkenyl group. The carbon number of the pendant group may be 3 or more, 4 or more, 6 or more, 8 or more, 10 or more, or 12 or more, and may be 30 or less, 28 or less, 26 or less, 24 or less, 22 or less, 20 or less, 18 or less, 16 or less, 14 or less, or 12 or less.

[0025] Examples of the dicarboxylic acid having a pendant group include succinic acid having an alkyl group having 3 or more carbon atoms, succinic acid having an alkenyl group having 3 or more carbon atoms, alkylbissuccinic acid having an alkyl group having 3 or more carbon atoms, and alkenylbissuccinic acid having an alkenyl group having 3 or more carbon atoms. Specific examples of the dicarboxylic acid include octylsuccinic acid, decylsuccinic acid, dodecylsuccinic acid, tetradecylsuccinic acid, hexadecylsuccinic acid, octadecylsuccinic acid, isooctadecylsuccinic acid, hexenylsuccinic acid, octenylsuccinic acid, decenylsuccinic acid, dodecenylsuccinic acid, tetrapropenyl succinic acid, tetradecenylsuccinic acid, hexadecenylsuccinic acid, isooctadecenylsuccinic acid, octadecenyl succinic acid, and nonenylsuccinic acid.

[0026] Examples of the dicarboxylic acid having no pendant group include adipic acid, phthalic acid, isophthalic acid, tetrachlorophthalic acid, chlorophthalic acid, nitrophthalic acid, p-carboxyphenylacetic acid, p-phenylene-2-acetic acid, m- phenylenediglycolic acid, p-phenylenediglycolic acid, o-phenylenediglycolic acid, diphenylacetic acid, diphenyl-p,p’-dicarboxylic acid, naphthal ene-l,4-dicarboxylic acid, naphthalene-l,5-dicarboxylic acid, naphthalene-2,6-dicarboxylic acid, anthracenedicarboxylic acid, and cyclohexanedicarboxylic acid.

[0027] The carboxylic acid may contain a tricarboxylic acid or an anhydride thereof. Examples of the tricarboxylic acid include trimellitic acid, naphthalenetricarboxylic acid, and pyrenetricarboxylic acid.

[0028] The carboxylic acid may contain at least one selected from a group comprising a dicarboxylic acid or an anhydride thereof, and a tricarboxylic acid or an anhydride thereof, and contains at least one selected from a group comprising a dicarboxylic acid or an anhydride thereof having a pendant group, and a tricarboxylic acid or an anhydride thereof to obtain toner particles that exhibit no peak of the MDSC described above.

[0029] The amount (charge amount) of the carboxylic acid may be 5% by mass or more, 10% by mass or more, or 15% by mass or more, and may be 65% by mass or less, 60% by mass or less, or 55% by mass or less, based on the total amount of the first polycondensation component.

[0030] Examples of the diol include aliphatic diols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butanediol, hexanediol, neopentyl glycol, and glycerin; alicyclic diols such as cyclohexanediol, cyclohexanedimethanol, and hydrogenated bisphenol A; and aromatic diols such as ethylene oxide adducts of bisphenol A and propylene oxide adducts of bisphenol A. These polyhydric alcohols may be used alone or in combination of two or more. The diol may contain an aromatic diol, and may include an aromatic diol (does not contain any diol other than the aromatic diol) for offset resistance and heat-resistant storability.

[0031] The content of the diol may be 10% by mass or more, 15% by mass or more, or 20% by mass or more, and may be 70% by mass or less, 65% by mass or less, or 60% by mass or less, based on the total amount of the first polycondensation component.

(0032] The second polyester resin may be a polycondensate of a carboxylic acid and a diol. In this case, the second polyester resin is obtained by subjecting a carboxylic acid and a diol (hereinafter, collectively referred to as "second polycondensation component") to an esterification reaction. The second polycondensation component may further contain a polyethylene terephthalate. Details of the carboxylic acid, the diol, and the polyethylene terephthalate are the same as those described for the first polyester resin.

[0033] The weight average molecular weight of the first polyester resin is larger than the weight average molecular weight of the second polyester resin. The weight average molecular weight of the first polyester resin may be 20,000 or more, 30,000 or more, or 40,000 or more, and may be 80,000 or less, 75,000 or less, or 70,000 or less. The weight average molecular weight of the second polyester resin may be 5,000 or more, 6,000 or more, or 7,000 or more, and may be 30,000 or less, 20,000 or less, or 15,000 or less.

The weight average molecular weights of the first and second polyester resins are measured by the method described in Examples.

[0034] The content of the first polyester resin may be 2% by mass or more, 10% by mass or more, or 20% by mass or more, and may be 50% by mass or less, 45% by mass or less, or 40% by mass or less, based on the total amount of the binder resin. The content of the second polyester resin may be 50% by mass or more, 55% by mass or more, or 60% by mass or more, and or less, 90% by mass or less, or 80% by mass or less, based on the total amount of the binder resin.

[0035] The content of the binder resin in the toner particles may be 40% by mass or more, 45% by mass or more, or 50% by mass or more, and may be 90% by mass or less, 85% by mass or less, or 75% by mass or less, based on the total amount of the toner particles.

10036] The core particle may further contain a colorant. The colorant may contain at least one colorant selected from, for example, a black colorant, a cyan colorant, a magenta colorant, and a yellow colorant. Regarding the colorant, one kind is used alone, or two or more kinds are used as a mixture, in consideration of hue, chroma, brightness, weather-resistance, dispersibility in toner, and the like.

[0037] The black colorant may be carbon black or aniline black. The yellow colorant may be a condensed nitrogen compound, an isoindolinone compound, an anthraquine compound, an azo metal complex, or an allylimide compound. Specific examples of the yellow colorant include C.I. Pigment Yellow 12, 13, 14, 17, 62, 74, 83, 93, 94, 95, 109, 110, 111, 128, 129, 147, 168, and 180.

[0038] The magenta colorant may be a condensed nitrogen compound, anthraquine, a quinacridone compound, a basic dye lake compound, a naphthol compound, a benzimidazole compound, a thioindigo compound, or a perylene compound. Specific examples of the magenta colorant include C.I. Pigment Red 2, 3, 5, 6, 7, 23, 48:2, 48:3, 48:4, 57: 1, 81 : 1, 122, 144, 146, 166, 169, 177, 184, 185, 202, 206, 220, 221, and 254.

[0039] The cyan colorant may be a copper phthalocyanine compound or a derivative thereof, an anthraquine compound, or the like. Specific examples of the cyan colorant include C.I. Pigment Blue 1, 7, 15, 15:1, 15:2, 15:3, 15:4, 60, 62, and 66.

|0040| The content of the colorant may be 1% by mass or more, 2% by mass or more, or 3% by mass or more, and may be 10% by mass or less, 8% by mass or less, or 6% by mass or less, based on the total amount of the toner particle.

[0041 ] The core particle may further contain a release agent. Examples of the release agent include a wax. The wax may be a natural wax or a synthetic wax. Examples of the wax include a polyethylene wax, a polypropylene wax, a silicon wax, a paraffin wax, an ester wax, a carnauba wax, a beeswax, and a metallocene wax. The wax may be an ester wax.

{0042] The ester wax may be, for example, an ester of a fatty acid having 15 to 30 carbon atoms and a monohydric alcohol having 10 to 30 carbon atoms, or may be an ester of a fatty acid having 15 to 30 carbon atoms and a polyhydric alcohol having 3 to 30 carbon atoms. Examples of the ester wax include behenyl behenate, stearyl stearate, stearic acid ester of pentaerythritol, and montanic acid glyceride.

[0043] The melting point of the wax may be 60 °C or higher or 70 °C or higher, and may be 100 °C or lower or 90 °C or lower.

[0044] The content of the wax may be 1% by mass or more, 2% by mass or more, or 3% by mass or more, and 15% by mass or less, 10% by mass or less, or 8% by mass or less, based on the total amount of the toner particle.

[0045] The content (addition amount) of the additive (additive for a toner particle) may be 0.2 parts by mass or more, 0.5 parts by mass or more, or 1 part by mass or more, and may be 15 parts by mass or less, 10 parts by mass or less, or 7 parts by mass or less, with respect to 100 parts by mass of the core particle.

[0046] The coverage of the additive for a toner particle (the surface-treated silica particle) on the surface of the toner particle may be 30% or more, 40% or more, or 50% or more, and may be 80% or less, 70% or less, or 60% or less, to obtain a suitable charge amount. The coverage is measured by the method described in Examples.

[0047] The toner particle may further contain inorganic particles externally added to the core particle, in addition to the additive for a toner particle described above.

Examples of the inorganic particles include silica particles other than the surface-treated silica particles described above, alumina particles, zirconia particles, and titania particles.

[0048] The average particle diameter of the toner particles may be 3 pm or larger, 4 pm or larger, or 5 pm or larger, and may be 12 pm or less, 11 pm or less, 10 pm or less, or 9 pm or less.

[0049] In the toner particles described above, since the silica particles surface-treated with the silane coupling agent containing at least one element selected from a group comprising fluorine and sulfur are externally added, the silica particles may function as a negative charge control agent, and thus the reversely charged toner may be reduced and a clear image with less fogging may be produced for a long time. In addition, in some examples, since the surface treatment of the silica particles may be a surface treatment in which a silazane compound (for example, hexamethyldisilazane) is not used, even when use of the silazane compound is legally regulated, toner particles that can be used without the regulation may be provided.

[0050] Next, some examples of a method for producing the toner particle described above are described. A method for producing a toner particle according to some examples includes surface-treating silica particles with a silane coupling agent containing at least one element selected from a group comprising fluorine and sulfur, and externally adding the surface-treated silica particles to core particle. The details of the surface-treating of the silica particles are as described above.

[0051] The method for externally adding the surface-treated silica particles to the core particle may be a known method. For example, the silica particles are externally added to the core particle by mixing the core particle and the silica particles with a powder mixer.

[0052] The toner particles may be used as a one-component developer. The toner particles may be mixed with a magnetic carrier and used as a two-component developer for dot reproducibility and stability of images over a long period of time.

[0053] The toner particles may be contained in a toner cartridge, for example. More specifically, the toner particles may be contained within a container in a toner cartridge. That is, some examples include a toner cartridge containing a container accommodating the above-described toner particles.

EXAMPLES

[0054] Hereinafter, the additive for a toner particle is described in more detail with reference to examples, but the additive for a toner particle is not limited to the examples.

[0055] Surface Treatment of Silica Particles

A 3 -liter glass reaction vessel equipped with a stirrer, a dropping funnel, and a thermometer is charged with 1500 g of methanol, 500 g of silica particles having particle diameters and specific gravities shown in Table 1, and 66.5 g of 28% ammonia aqueous solution, followed by mixing. Subsequently, at 25°C, a silane coupling agent whose type and addition amount are shown in Table 1 is added dropwise over 0.5 hours. After completion of the dropwise addition, stirring is continued for 12 hours to perform surface treatment of the silica particles.

[0056] In Table 1, the types of silica coupling agents are as follows. SCI : silane coupling agent containing a perfluoroether group (in the above formula (1), R ¹ , R ² , and R ³ are -CH3 groups, m is 3, and n is 1)

SC2: silane coupling agent containing a perfluoroether group (in the above formula (1), R ¹ , R ² , and R ³ are -CH3 groups, m is 3, and n is 2)

SC3 : silane coupling agent containing a mercapto group (R ⁴ and R ⁵ are -CH3 groups, R ⁶ is a -C3H6- group, p is 3, and q is 1)

SC4: methyltrimethoxy silane

SC5: phenyltrimethoxysilane

[0057] [Table 1]

[0058] Production of Toner Particles

Polyester resin 1 is produced by a known method using 59.7 parts by mass of polyoxypropylene-2,2-bis (4-hydroxyphenyl) propane (average number of moles added of propylene oxide = 2), 2.6 parts by mass of trimellitic acid, 7.7 parts by mass of dodecenyl succinic anhydride, and 30 parts by mass of polyethylene terephthalate (number average molecular weight Mn: 24000) as raw materials and an esterification catalyst.

Polyester resin 2 is produced by a known method using 25.5 parts by mass of polyoxypropylene-2,2-bis (4-hydroxyphenyl) propane (average number of moles of added propylene oxide = 2.2), 1.3 parts by mass of isophthalic acid, 22.3 parts by mass of dodecenyl succinic anhydride, 50.2 parts by mass of polyethylene terephthalate (number average molecular weight Mn: 24000), and 0.7 parts by mass of trimellitic acid as raw materials and an esterification catalyst.

Subsequently, 30 parts by mass of the polyester resin 1, 70 parts by mass of the polyester resin 2, 10 parts by mass of a colorant "MA-100" (manufactured by Mitsubishi Chemical Corporation), and 7 parts by mass of a release agent "WEP-5" (manufactured by NOF Corporation, melting point: 83°C) are premixed using a Henschel mixer, and then kneaded using a biaxial kneader (PCM-30 manufactured by Ikegai Corporation). Subsequently, the resultant is finely pulverized using a supersonic jet pulverizer Labojet (manufactured by Nippon Pneumatic Mfg. Co., Ltd.), and then classified using an air classifier (MDS-I manufactured by Nippon Pneumatic Mfg. Co., Ltd.) to obtain a powder of core particles having a volume median size (D50) of 6.8 pm. To 100 parts by mass of the obtained core particles, the surface-treated silica particles are added in an amount shown in Table 2, and the mixture is mixed with a sample mill at 10000 rpm for 30 seconds to obtain toner particles. The addition amount of the surface-treated silica particles is adjusted so that the coverage of the surface-treated silica particles is equivalent except for Examples 10 and 15 in order to fairly compare the evaluation results of the charge amount described later.

The coverage of the surface-treated silica particles is determined by the following equation. Coverage (%) = [(particle diameter of toner particle: pm) x (specific gravity of toner particle: g/ml) x (mass ratio of toner particle to silica particle: %)] / [4 x (particle diameter of silica particle: pm) x (specific gravity of silica particle: g/ml)]

[0059] Evaluation of Charge Amount

In a glass bottle with a lid, 30 parts by mass of ferrite particles coated with a styrene / methyl methacrylate resin (volume average particle diameter: 35 pm, measured using a particle size distribution measuring device (Multisizer (registered trademark), manufactured by Beckman Coulter, Inc.) is weighed, and then 1 part by mass of the toner particles is weighed in a state of being placed on the ferrite particles. Thereafter, the resultant is left to stand under normal temperature and normal humidity (25°C / 50% RH) for seasoning for 24 hours, and then stirred and shaken for 3 minutes with a turbula mixer to apply a load for causing triboelectric charging due to collision between the toner particles and the ferrite particles. After 20 seconds and 300 seconds from the application of the load, the charge amount (pC/g) is measured by a flying charge amount measuring device (electric field flying charge amount measuring device II-DC electric field (trade name), manufactured by DIT Corporation). The results are shown in Table 2.

[0060] [Table 2]

[0061 [ Hereinbefore, various examples of the additive for a toner particle, and the toner particles have been described; however, it is obvious to those having ordinary skill in the art that various modifications and alterations may be made within the scope of the disclosure. That is, all alterations are intended to be included within the scope of the spirit described in the claims.