JP2008058395A - Positively chargeable toner for non-magnetic one-component development - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a positively charged toner for nonmagnetic one-component development which suppresses filming and fogging on an organic photoreceptor. <P>SOLUTION: The positively charged toner for nonmagnetic one-component development comprises toner base particles containing a colorant and a polyester as a binder resin and an external additive, wherein positively charged silica having an average particle diameter of 5-30 nm and negatively charged silica having an average particle diameter of 0.2-0.6 μm are contained as the external additive. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a positively chargeable toner for non-magnetic one-component development used for developing a latent image formed in an electrophotographic method, an electrostatic recording method, an electrostatic printing method, and the like, and a method for producing the same.

  In recent years, with the miniaturization, high speed, and high image quality of printers, high performance is required for toner. In particular, these demands for full-color printers are remarkable, and improvement of toner durability is particularly demanded for speeding up printers. As a technique for improving the durability of the toner, studies are mainly made on a binder resin, a charge control agent, an external additive, and the like, and in particular, many studies on an external additive have been conducted.

Patent Document 1 discloses a toner in which small particle size silica having the same polarity as the toner and resin fine particles are added as external additives. Patent Document 2 discloses a toner in which resin fine particles having a polarity opposite to that of the toner are added as an external additive.
JP 2004-109201 A Japanese Patent Laid-Open No. 9-127727

  However, when adding a small particle size silica with the same polarity as the toner, or when adding resin fine particles with the opposite polarity to the toner, the effect on the organic photoreceptor (OPC), etc., is large if the amount added is large. Become.

  An object of the present invention is to provide a positively chargeable toner for non-magnetic one-component development in which the occurrence of filming and fogging on an organic photoreceptor is reduced.

The present invention
[1] A positively chargeable toner for non-magnetic one-component development comprising toner base particles containing polyester as a colorant and a binder resin and an external additive, and having an average particle size of 5 to A positively chargeable toner for non-magnetic one-component development comprising 30 nm positively chargeable silica and negatively chargeable silica having an average particle size of 0.2 to 0.6 μm; and [2] a polyester as a colorant and a binder resin. A positively chargeable silica having an average particle size of 5 to 30 nm as an external additive is added to the toner base particles and stirred, and after the step, negative chargeability having an average particle size of 0.2 to 0.6 μm as an external additive The present invention relates to a method for producing a positively chargeable toner for non-magnetic one-component development, which includes a step of adding silica and stirring.

  The positively chargeable toner for non-magnetic one-component development of the present invention has an excellent effect that filming and fogging on an organic photoreceptor are reduced even after continuous printing, and that they can be maintained well over a long period of time. It is.

  The positively chargeable toner for non-magnetic one-component development of the present invention comprises toner base particles containing a colorant and polyester as a binder resin and an external additive, and the positive additive has an average particle diameter of 5 to 30 nm as an external additive. One characteristic is that it contains a chargeable silica and a negatively chargeable silica having an average particle size of 0.2 to 0.6 μm. By adding positively-charged silica having an average particle diameter of 5 to 30 nm as an external additive having a small particle size that easily adheres to the surface of the toner base particles, a uniform positive charge can be given to the toner surface. By adding negatively-charged silica having an average particle size of 0.2 to 0.6 μm as an external additive having a large particle size that is easily released from the toner mother particles, the toner particles pass between the toner mother particles and the large particle size silica when passing through a charging blade. In addition, since frictional charging occurs before passing through the charging blade, it is presumed that the chargeability of the toner base particles may be improved.

Although what was manufactured by the well-known method can be used as a silica, From the viewpoint of the dispersibility of a silica, what was manufactured by the dry process and the high temperature hydrolysis method is preferable. In addition to anhydrous silica, it may contain aluminum silicate, sodium silicate, potassium silicate, magnesium silicate, zinc silicate, etc., but preferably contains SiO ₂ at 80% by weight or more, Those containing 85% by weight or more are more preferable.

Silica is preferably hydrophobic silica surface-treated with a hydrophobizing agent from the viewpoint of environmental stability. The surface treatment method is not particularly limited, and examples of the hydrophobizing agent include aminosilane, octylsilane, fluorine silane, isobutylsilane, hexamethyldisilazane, dimethyldichlorosilane, silicone oil, and methyltriethoxysilane. The treatment amount with the hydrophobizing agent is preferably 1 to 7 mg / m ² per surface area of silica. In the present invention, the above silica may be used alone or in combination of two or more. Silica itself exhibits negative chargeability. Positively charged silica is positively charged by surface-treating negatively chargeable silica with a positively chargeable hydrophobizing agent such as amino-modified silicone oil. This is adjusted to chargeability.

  The average particle diameter of the positively chargeable silica is 5 to 30 nm, preferably 5 to 25 nm, more preferably 5 to 20 nm from the viewpoint of adhesion to the toner surface (hereinafter sometimes referred to as positively charged small silica). . In the present specification, the average particle diameter of silica is measured by the method described in Examples described later.

  The average particle diameter of the negatively chargeable silica is 0.2 to 0.6 μm, preferably 0.2 to 0.5 μm, more preferably 0.2 to 0.4 μm, from the viewpoint of releasing from the toner surface.

  Further, from the viewpoint of optimizing the chargeability, the toner base particles further contain positively charged silica having an average particle size larger than that of the positively charged small silica (hereinafter sometimes referred to as positively charged large silica). Preferably it is. When the positively charged large silica is adhered to the surface of the toner base particles as a fluidity adjusting agent, the toner base particles can be more suitably frictionally charged when passing through the charging blade. The average particle diameter of the positively charged large silica is preferably more than 30 nm and 100 nm or less, more preferably 40 to 100 nm, and further preferably 50 to 100 nm for the purpose of reducing the toner fluidity to an appropriate region.

  The ratio of the average particle diameter of the positively chargeable silica and the negatively chargeable silica (positively chargeable silica / negatively chargeable silica) is preferably 0.02 or more, more preferably 0.02 to 0.4, and further preferably 0.02 to 0.2. When the particle size ratio is 0.02 or more, the fluidity of the toner does not become too high, and appropriate frictional charging can be obtained with the blade, and the occurrence of initial fog is easily reduced. In addition, when the particle size ratio is 0.4 or less, the release of the positively chargeable silica and the negatively chargeable silica is easily suppressed, so that the occurrence of initial fogging due to the reduction of the frictional chargeability can be effectively reduced. Note that when two or more types of chargeable silica having the same sign are used, the average particle size of the positively chargeable silica is the weighted average particle size of the positively chargeable silica and the average particle size of the negatively chargeable silica is negative. Represents the weighted average particle size of the chargeable silica. For example, when positively charged large silica and positively charged small silica are used, the average particle size of the positively charged silica is calculated from the average particle size and the amount added. Calculate the diameter.

  The addition amount of the positively charged small silica is preferably 0.1 to 2 parts by weight and more preferably 0.2 to 1 part by weight with respect to 100 parts by weight of the toner base particles.

  The amount of positively charged large silica added is preferably 0.1 to 3 parts by weight, more preferably 0.4 to 2 parts by weight with respect to 100 parts by weight of toner base particles.

  The weight ratio of the positively charged large silica to the positively charged small silica (large silica / small silica) is preferably 0.5 to 10, more preferably 0.7 to 5, and further preferably 1 to 3 from the viewpoint of optimizing the fluidity of the toner. preferable.

  The total amount of positively charged small silica and large silica is preferably 0.2 to 3 parts by weight, more preferably 0.3 to 2 parts by weight, based on 100 parts by weight of toner base particles.

  The addition amount of the negatively chargeable silica is preferably 0.1 to 3 parts by weight and more preferably 0.3 to 2 parts by weight with respect to 100 parts by weight of the toner base particles.

  The weight ratio of positively chargeable silica to negatively chargeable silica (positively chargeable silica / negatively chargeable silica) is preferably 0.4 to 2.8, more preferably 1.0 to 2.5, and more preferably 1.3 to 2.5 from the viewpoint of the chargeability of the toner base particles. 2.3 is more preferred. When the addition ratio is 0.4 or more, it is easy to reduce the occurrence of initial fogging due to the generation of negatively chargeable toner particles. On the other hand, when the addition amount ratio is 2.8 or less, the triboelectric charging effect by the negatively chargeable silica is increased, and the charge amount of the toner tends to be easily maintained. Here, the weight of the positively chargeable silica refers to the total amount of positively charged silica, and the weight of the negatively chargeable silica refers to the total amount of negatively charged silica.

  The toner base particles preferably further contain polymer fine particles as an external additive from the viewpoint of improving the chargeability. Since the fine polymer particles have the same effect as the negatively chargeable silica, the toner base particles can be further improved in chargeability by generating frictional charging when passing through the charging blade or before passing through the charging blade. it can.

  The polymer fine particles are preferably negatively chargeable resin fine particles that are oppositely charged to the positively chargeable silica from the viewpoint of improving the adhesion of the positively chargeable silica to the toner surface by electrostatic force, and have high negative chargeability. As the molecular fine particles, polytetrafluoroethylene fine particles and the like are preferable.

  The average particle size of primary particles of the polytetrafluoroethylene fine particles is preferably 0.05 μm or more and less than 1 μm, more preferably 0.1 to 0.8 μm, and further preferably 0.15 to 0.6 μm. When the average particle size is 0.05 μm or more, it is considered that the fine particles externally added to the toner base particles during continuous printing are difficult to be embedded in the toner, and the effect is easily maintained, and when the average particle size is less than 1 μm It is difficult to release from the above, and the effect of the present invention is easily exhibited. In the present specification, the average particle diameter of the polymer fine particles is measured by the method described in Examples described later.

  More specific examples of such polytetrafluoroethylene fine particles include those having a shape close to a sphere produced by emulsion polymerization. These are commercially available, for example “KTL-500F” (manufactured by Kitamura Co., Ltd., primary particle average particle size 0.5 μm), “Lublon L2” (manufactured by Daikin Industries, Ltd., primary particle average particle size 0.3 μm) "Lublon L5" (manufactured by Daikin Industries, Ltd., average particle size of primary particles 0.2 μm), "Fluon Lubricant L170J" (manufactured by Asahi IC Fluoropolymers Co., Ltd., average particle size of primary particles 0.1 µm) “Fluon Lubricant L172J” (manufactured by Asahi IC Fluoropolymers Co., Ltd., primary particle average particle size 0.1 μm), “MP-1100” (Mitsui / DuPont Fluoro Chemical Co., Ltd.) primary particle average particle size 0.2 μm diameter), “MP-1200” (Mitsui / DuPont Fluoro Chemical Co., Ltd., primary particle average particle size 0.3 μm), “TLP-10F-1” (Mitsui / DuPont Fluoro Chemical Co., Ltd.) And an average particle diameter of primary particles of 0.2 μm).

  The addition amount of the polytetrafluoroethylene fine particles is preferably 0.01 to 1.5 parts by weight, more preferably 0.05 to 1.0 parts by weight with respect to 100 parts by weight of the toner base particles.

  Further, since the polymer fine particles have the same effect as the negatively chargeable silica, the total amount of addition of the negatively chargeable silica and the polymer fine particles is preferably 0.5 to 3 parts by weight with respect to 100 parts by weight of the toner base particles. 0.5 to 2 parts by weight is more preferable.

Polyester is obtained by polycondensation of a polyhydric alcohol and a polycarboxylic acid component, that is, a polycarboxylic acid or polycarboxylic acid ester, a polycarboxylic acid anhydride.
(A) General formula (I)

(Wherein R is an ethylene or propylene group, x and y are each an integer of 1 or more, and the average value of x + y is 2 to 7)
It is preferable to use the compound represented by these. Specifically, for example, polyoxypropylene (2.2) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene (3.3) -2,2-bis (4-hydroxyphenyl) propane, polyoxyethylene (2.0) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene (2.0) -polyoxyethylene (2.0) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene (6) Examples include -2,2-bis (4-hydroxyphenyl) propane.

  In some cases, other diols such as ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, neopentyl glycol, 1,4-butenediol, Diols such as 1,5-pentanediol and 1,6-hexanediol, and other dihydric alcohols such as bisphenol A and hydrogenated bisphenol A can also be added.

  On the other hand, examples of (b) polycarboxylic acid or polycarboxylic acid ester and polycarboxylic acid anhydride include the following.

  First, as the divalent carboxylic acid component, for example, maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, succinic acid, adipic acid, sebacic acid, azelain Acid, malonic acid and the like, and n-butyl succinic acid, n-butenyl succinic acid, isobutyl succinic acid, isobutenyl succinic acid, n-octyl succinic acid, n-octenyl succinic acid, n-dodecyl succinic acid, n-dodecenyl succinic acid Examples include alkyl or alkenyl succinic acid such as acid, isododecyl succinic acid and isododecenyl succinic acid. In addition, anhydrides of these acids, lower alkyl esters, and other divalent carboxylic acids can be mentioned.

  Next, for trivalent or higher monomers, among the trifunctional or higher polyfunctional monomers, alcohol components include sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, penta Erythritol, dipentaerythritol, tripentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, tri Mention may be made of methylolethane, trimethylolpropane, 1,3,5-trihydroxybenzene and other trivalent or higher alcohols.

  The trivalent or higher carboxylic acid component includes 1,2,4-benzenetricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1,2,4-butanetricarboxylic acid. Acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, tetra (methylenecarboxyl) methane, 1,2,7,8-octanetetracarboxylic acid, empol Trimeric acids, their anhydrides, lower alkyl esters, and other trivalent or higher carboxylic acids.

  Further, as the polyvalent carboxylic acid, the following general formula (II)

(In the formula, X is an alkylene group or alkenylene group having 5 to 30 carbon atoms having one or more side chains having 3 or more carbon atoms)
The tetracarboxylic acid represented by these is also mentioned. Specific examples include the following (1) to (12).
(1) 4-Neopentylidenyl-1,2,6,7-heptanetetracarboxylic acid
(2) 4-Neopentyl-1,2,6,7-heptene (4) -tetracarboxylic acid
(3) 3-Methyl-4-heptenyl-1,2,5,6-hexanetetracarboxylic acid
(4) 3-Methyl-3-heptyl-5-methyl-1,2,6,7-heptene (4) -tetracarboxylic acid
(5) 3-Nonyl-4-methylidenyl-1,2,5,6-hexanetetracarboxylic acid
(6) 3-decylidenyl-1,2,5,6-hexanetetracarboxylic acid
(7) 3-Nonyl-1,2,6,7-heptene (4) -tetracarboxylic acid
(8) 3-decenyl-1,2,5,6-hexanetetracarboxylic acid
(9) 3-Butyl-3-ethylenyl-1,2,5,6-hexanetetracarboxylic acid
(10) 3-Methyl-4-butylidenyl-1,2,6,7-heptanetetracarboxylic acid
(11) 3-Methyl-4-butyl-1,2,6,7-heptene (4) -tetracarboxylic acid
(12) 3-Methyl-5-octyl-1,2,6,7-heptene (4) -tetracarboxylic acid

  The polyester in the present invention can be obtained by condensation polymerization of the alcohol component and the polycarboxylic acid component. For example, it can be produced by condensation polymerization at a temperature of 180 to 250 ° C. in an inert gas atmosphere.

  In the polymerization reaction, a commonly used esterification catalyst can be used to accelerate the reaction. Examples of the esterification catalyst include dibutyltin oxide, a titanium compound, and tin having no Sn—C bond. (II) compounds and the like, and these may be used alone or in combination.

  As a titanium compound, the titanium compound which has a Ti-O bond is preferable, and the compound which has a C1-28 total carbon number alkoxy group, an alkenyloxy group, or an acyloxy group is more preferable.

Specific examples of titanium compounds include titanium diisopropylate bistriethanolamate [Ti (C ₆ H ₁₄ O ₃ N) ₂ (C ₃ H ₇ O) ₂ ], titanium diisopropylate bisdiethanolamate [Ti (C ₄ H ₁₀ O ₂ N) ₂ (C ₃ H ₇ O) ₂ ], titanium dipentylate bistriethanolamate [Ti (C ₆ H ₁₄ O ₃ N) ₂ (C ₅ H ₁₁ O) ₂ ], titanium diety rate bis triethanolaminate _{[Ti (C 6 H 14 O 3} N) 2 (C 2 H 5 O) 2 ], titanium dihydroxy octylate bis triethanolaminate _{[Ti (C 6 H 14 O 3} N) 2 (OHC 8 H ₁₆ O) ₂ ], titanium distearate bistriethanolamate [Ti (C ₆ H ₁₄ O ₃ N) ₂ (C ₁₈ H ₃₇ O) ₂ ], titanium triisopropylate triethanolamate [Ti (C _{6 H 14 O 3 N) 1 (} C 3 ₇ O) _3], titanium monopropylate tris (triethanolaminate) _{[Ti (C 6 H 14 O 3} N) 3 (C 3 H 7 O) 1 ], and the like, titanium diisopropylate Among these Preferred are rate bistriethanolamate, titanium diisopropylate bisdiethanolamate, and titanium dipentylate bistriethanolamate, which are also commercially available, for example, from Matsumoto Trading Co., Ltd.

Specific examples of other preferable titanium compounds include tetra-n-butyl titanate [Ti (C ₄ H ₉ O) ₄ ], tetrapropyl titanate [Ti (C ₃ H ₇ O) ₄ ], tetrastearyl titanate [Ti ( C ₁₈ H ₃₇ O) ₄ ], tetramyristyl titanate [Ti (C ₁₄ H ₂₉ O) ₄ ], tetraoctyl titanate [Ti (C ₈ H ₁₇ O) ₄ ], dioctyl dihydroxyoctyl titanate [Ti (C ₈ H ₁₇ O) ₂ (OHC ₈ H ₁₆ O) ₂ ], dimyristyl dioctyl titanate [Ti (C ₁₄ H ₂₉ O) ₂ (C ₈ H ₁₇ O) ₂ ] and the like. Among these, tetrastearyl titanate, tetra Preferred are myristyl titanate, tetraoctyl titanate and dioctyl dihydroxy octyl titanate, which react, for example, a titanium halide with the corresponding alcohol. Can also be obtained by a, it is also available as marketed products of Nisso, or the like.

  Examples of the tin (II) compound having no Sn—C bond include a tin (II) compound having a Sn—O bond, a tin (II) compound having a Sn—X (X represents a halogen atom) bond, and the like. Preferably, a tin (II) compound having a Sn—O bond is more preferable.

Examples of tin (II) compounds having a Sn-O bond include tin (II) oxalate, tin (II) diacetate, tin (II) dioctanoate, tin (II) dilaurate, tin (II) distearate, diolein Carboxylic acid tin (II) having a carboxylic acid group having 2 to 28 carbon atoms such as tin (II) acid; dioctyloxy tin (II), dilauroxy tin (II), distearoxy tin (II), dioleoxy tin (II), etc. Dialkoxytin (II) having an alkoxy group having 2 to 28 carbon atoms; tin oxide (II); tin (II) sulfate and the like having a Sn—X (X represents a halogen atom) bond include chloride. Examples thereof include tin (II) halides such as tin (II) and tin (II) bromide. Among these, (R ¹ COO) ₂ Sn (where R ¹ is a fatty acid tin represented by an alkyl or alkenyl group 5 to 19 carbon ^{atoms) (II), (R 2} O) 2 Sn ( wherein R ² is an alkyl group having 6 to 20 carbon atoms Dialkoxy tin (II) and tin oxide represented by SnO (II) is preferably represented by the alkenyl a group), (R ¹ COO) fatty tin represented by ₂ Sn (II) and tin oxide (II ) Are more preferred, and tin (II) dioctanoate, tin (II) distearate, and tin (II) oxide are more preferred.

  The amount of the esterification catalyst present is preferably 0.01 to 1.0 part by weight, more preferably 0.1 to 0.7 part by weight, based on 100 parts by weight of the total amount of the alcohol component and the carboxylic acid component.

  Specific examples of the polyesters thus produced include Japanese Patent Laid-Open Nos. 62-195676, 62-195677, 62-195678, and 62-195679. Among the polyesters disclosed in JP-A-62-195680, those having an acid value of 10 mgKOH / g or less can be mentioned.

  Of these, the polycarboxylic acid component other than the aromatic polycarboxylic acid component and the polyester obtained by polycondensation of polyhydric alcohol have a lower acid strength than the aromatic carboxylic acid, and the dissociation constant (pKa ) Is small, it is preferably used as the binder resin of the present invention.

  Examples of the polycarboxylic acid component other than the aromatic polycarboxylic acid component include dicarboxylic acids such as maleic acid, fumaric acid, alkyl or alkenyl succinic acid among the polycarboxylic acid components exemplified above, 1,2,4-butane. Examples include tricarboxylic acids, tricarboxylic acids such as 1,2,5-hexanetricarboxylic acid, 1,2,7,8-octanetetracarboxylic acid, tetracarboxylic acids of general formula (II), and the like. Anhydrides, lower alkyl (C1-4) esters and the like can be mentioned.

  The acid value of the polyester is preferably 10 mgKOH / g or less, more preferably 0 to 6 mgKOH / g, from the viewpoint of chargeability of the toner. When the acid value is 10 mg KOH / g or less, the negative chargeability of the resin itself can be relaxed, and therefore, it is preferably used for the positively chargeable toner of the present invention. As a method for controlling the acid value of the polyester to 10 mgKOH / g or less, the alcohol / carboxylic acid ratio at the time of polyester synthesis may be adjusted (alcohol excess) or the reaction may be performed until the carboxylic acid disappears. In this specification, an acid value is measured by the method as described in the below-mentioned Example.

  Further, the glass transition point is preferably 45 to 75 ° C, more preferably 50 to 70 ° C, from the viewpoints of low-temperature fixability and storage stability. In the present specification, the glass transition point is measured by the method described in Examples described later.

  In the present invention, the polyester content is preferably 60 to 100% by weight and more preferably 80 to 100% by weight in the binder resin. Examples of binder resins other than polyester include vinyl resins such as styrene-acrylic resins, epoxy resins, polycarbonates, and polyurethanes.

  Examples of the colorant used in the toner of the present invention include carbon black; inorganic pigments such as iron black; I. Acetoacetic acid arylamide monoazo yellow pigments such as CI Pigment Yellow 1, 3, 74, 97, 98; I. C.I. Pigment Yellow 12, 13, 13, 17, etc. acetoacetic acid arylamide disazo yellow pigments; I. Solvent Yellow 19, 77, 79, C.I. I. Yellow dyes such as disperse yellow 164; I. Pigment Red 48, 49: 1, 53: 1, 57, 57: 1, 81, 122, 5 and the like; C.I. I. Red dyes such as Solvent Red 49, 52, 58, 8; I. Blue dyes and pigments of copper phthalocyanine and its derivatives such as CI Pigment Blue 15: 3; I. Green pigments such as CI Pigment Green 7 and 36 (phthalocyanine green) can be used. These dyes and pigments may be used alone or in combination of two or more. Usually, about 1 to 15 parts by weight is used for 100 parts by weight of the binder resin.

  In the present invention, in addition to the binder resin and the colorant, a release agent, a charge control agent, a conductivity modifier, an extender pigment, a reinforcing filler such as a fibrous substance, an antioxidant, an anti-aging agent, a magnetic substance, etc. These additives may be blended as a toner raw material.

  As the charge control agent, one or more of all positively chargeable charge control agents conventionally known to be used for electrophotography are used. Specifically, nigrosine dyes such as “Bontron N-07”, “Bontron N-09”, “Bontron N-04” (manufactured by Orient Chemical Co., Ltd.), etc., a triphenylmethane type containing an amine in the side chain Dyes such as `` COPY BLUE PR '' (manufactured by Hoechst), quaternary ammonium salts such as `` TP-415 '' (manufactured by Hodogaya Chemical Co., Ltd.), `` COPY CHARGE PSY '' (manufactured by Hoechst), `` Bontron P-51 '' (Orient Chemical Co., Ltd.), cetyltrimethylammonium bromide and the like, polyamine resins such as “Bontron P-52” (Orient Chemical Co., Ltd.) and the like. The charge control agent is preferably contained in an amount of 0.1 to 8.0 parts by weight, more preferably 0.2 to 5.0 parts by weight with respect to 100 parts by weight of the binder resin.

  As an anti-offset agent to be added if necessary, wax such as polyolefin is used.

  The method for producing the positively chargeable toner of the present invention is not particularly limited, and conventionally known methods are used. For example, kneading, pulverizing and classifying, as well as polymerizable monomer, polymerization initiator, coloring And a method of directly producing toner mother particles by suspending a polymerizable composition containing an agent, a charge control agent and the like in an aqueous dispersion medium and polymerizing. The toner of the present invention can be obtained by adding at least positively-charged silica (positively-charged small silica) and negatively-charged silica having the specific average particle diameter as external additives to the obtained toner base particles.

  In the present invention, from the viewpoint of charging stability of the toner, a toner produced by a method in which positively charged small silica is externally added (first step) and then negatively charged silica is externally added (second step) is preferable. Further, when positively charged large silica is used as an external additive, it may be the same as or different from the addition of positively charged small silica, but it is preferable to add it before the negatively charged silica. In the case of using polymer fine particles, it is preferable to add at the same time as the negatively chargeable silica or after the negatively chargeable silica.

  As the mixer used for mixing the toner base particles and the external additive, a high-speed stirrer such as a Henschel mixer or a super mixer, or a stirrer used for dry mixing such as a V-type blender is preferable. In addition, when using a stirrer, it is preferable to increase the peripheral speed of the stirrer or lengthen the stirring time in order to allow the external additive to sufficiently adhere to the toner base particles.

  In this way, the external additive is added, but if necessary, a fluidity improver, a cleaning property improver, etc. can be added.

  In order to remove free external additives and the like, after the external additives are surface-treated on the toner base particles, a sieving step may be performed.

  Examples of fluidity improvers include alumina, titanium oxide, barium titanate, magnesium titanate, calcium titanate, strontium titanate, zinc oxide, silica sand, clay, mica, wollastonite, diatomaceous earth, chromium oxide, and oxidation. Examples thereof include cerium, bengara, antimony trioxide, magnesium oxide, zirconium oxide, barium sulfate, barium carbonate, calcium carbonate, silicon carbide, and silicon nitride.

  As the cleaning property improver, a metal salt of a higher fatty acid represented by zinc stearate may be used in combination.

The volume median particle size (D ₅₀ ) of the toner and toner base particles of the present invention is preferably from 3 to 10 μm, more preferably from 4 to 9 μm, and even more preferably from 5 to 9 μm, from the viewpoint of improving adhesion to the developing roller. . In the present specification, the volume median particle size (D ₅₀ ) means a particle size at which the cumulative volume frequency calculated by the volume fraction is 50% when calculated from the smaller particle size.

  The positively chargeable toner of the present invention is used in a non-magnetic one-component developing system. In particular, when used in a non-magnetic one-component developing system using a positively charged organic photoreceptor, the effects of the present invention are remarkably achieved. Become.

[Glass transition point of resin]
Using a differential scanning calorimeter (Seiko Denshi Kogyo Co., Ltd., DSC210), the temperature was raised to 200 ° C, and the sample was cooled to 0 ° C at a temperature drop rate of 10 ° C / min. The temperature at the intersection of the extended line of the baseline below the maximum peak temperature of endotherm and the tangent line indicating the maximum slope from the peak rising portion to the peak apex.

[Acid value of the resin]
Measured according to the method of JIS K0070. However, only the measurement solvent was changed from the mixed solvent of ethanol and ether specified in JIS K0070 to the mixed solvent of acetone and toluene (acetone: toluene = 1: 1 (volume ratio)).

[Volume Median Particle Size (D ₅₀ ) of Toner and Toner Base Particles]
Measuring machine: Coulter Multisizer II (Beckman Coulter, Inc.)
Aperture diameter: 50μm
Analysis software: Coulter Multisizer AccuComp version 1.19 (Beckman Coulter)
Electrolyte: Isoton II (Beckman Coulter, Inc.)
Dispersion: Emulgen 109P (manufactured by Kao Corporation, polyoxyethylene lauryl ether, HLB: 13.6) is dissolved in the electrolytic solution to a concentration of 5% by weight to obtain a dispersion.
Dispersion conditions: 10 mg of a measurement sample is added to 5 mL of the above dispersion, and dispersed for 1 minute with an ultrasonic disperser, then 25 mL of electrolyte is added, and further dispersed for 1 minute with an ultrasonic disperser. Prepare a dispersion.
Measurement conditions: By adding the sample dispersion to 100 mL of the electrolyte solution, the particle size of 30,000 particles is adjusted to a concentration that can be measured in 20 seconds, and then 30,000 particles are measured. Determine the volume median particle size (D ₅₀ ).

[Average particle diameter of silica]
An average particle diameter is a number average particle diameter, and it calculates | requires from a following formula.
Number average particle diameter (nm) = 6 / (ρ × specific surface area (m ² / g)) × 1000
In the formula, ρ is the specific gravity of silica (2.2), and the specific surface area is the BET specific surface area of silica determined by the nitrogen adsorption method.
Note that the above equation assumes a sphere with a particle size R,
BET specific surface area = S x (1 / m)
m (weight of particle) = 4/3 x π x (R / 2) ³ x specific gravity
S (surface area) = 4π (R / 2) ²
Is an expression obtained from

[Average particle diameter of polymer particles]
The average particle diameter is the number average particle diameter.
The number average particle size is measured with a scanning electron microscope at an appropriate magnification of 5000 to 50000 times and the particle size (average value of major axis and minor axis) is measured for 100 particles, and the average value is increased. The average particle size of the molecular fine particles is used.

Resin production example 1 (Synthesis example of polyester resin)
Polyoxypropylene (2.2) -2,2-bis (4-hydroxyphenyl) propane (3500 g), isododecenyl succinic anhydride (50 g), fumaric acid (1110 g), hydroquinone (2.5 g) and dibutyltin oxide (5 g) were placed in a four-necked flask and a thermometer. A stainless stir bar, a flow-down condenser, and a nitrogen introduction tube were attached, and the mixture was stirred in a mantle heater at a temperature of 210 ° C.
The degree of polymerization was monitored from the softening point according to ASTM E28-67, and the reaction was terminated when the softening point reached 115 ° C.
The glass transition temperature (Tg) of the obtained resin was 60 ° C. with one peak. The acid value of the resin was 6 mg KOH / g.
This is resin a.

Examples 1-11 and Comparative Examples 1-8
Polyester resin a 100 parts by weight Carbon black (REGAL-330R, manufactured by Cabot) 4 parts by weight Nigrosine dye (Bontron N-04, manufactured by Orient Chemical) 4 parts by weight Low molecular weight polypropylene wax 2 parts by weight
(High wax NP-055, manufactured by Mitsui Petrochemical Co., Ltd.)
The above composition is premixed, kneaded with a twin-screw rudder heated to 100 ° C, cooled, and the cooled product is coarsely pulverized with a mechanical pulverizer to pass a 2 mm mesh, and then into a wind-type pulverizer / classifier. The toner base particles were prepared by pulverization and classification so that the volume median particle size (D ₅₀ ) was 8 μm.

To 100 parts by weight of the resulting toner base particles, the amount of positively chargeable silica shown in Table 1 is added and mixed with a Henschel mixer, and then the amount of negatively chargeable silica and / or polymer fine particles shown in Table 1 is further added. The toners of Examples 1 to 11 and Comparative Examples 1 to 8 were obtained by mixing with a Henschel mixer. The volume median particle size (D ₅₀ ) of the toner was 8 μm.

Test Example 1 [Fog]
For the toner of each of the examples and comparative examples obtained, the surface potential was changed by changing the photoconductor of the plain paper facsimile "TF-5500" manufactured by Toshiba Corporation to the following positively charged organic photoconductor (single layer OPC). It was mounted on an apparatus in which +800 V, development bias was +300 V, supply bias was +400 V, and transfer roller was set to −1100 V.

  The positively charged organic photoreceptor is a single-layer OPC in which a bisazo pigment and a tetraphenyldiamine compound (TPD) represented by the following formula are coated on a substrate, and 5 parts by weight of a bisazo pigment and 100 parts by weight of TPD are evenly distributed in 100 parts by weight of a polycarbonate resin. And coated on an aluminum substrate by dip coating so that the film thickness after drying is about 30 μm.

  After mounting the toner as described above, a white solid image was printed, and the power was turned off during the printing. The toner on the surface of the photoreceptor is attached to the mending tape, the color density is measured with an image density measuring device “SPM-50” (manufactured by GURETAG), and the difference from the color density of the tape before the toner is attached is determined. Asked. The smaller the density difference, the smaller the fog and the better. Further, the same evaluation was performed after 7000 sheets were continuously printed. The results are shown in Table 1.

Test Example 2 [Film resistance]
Mount toner on Toshiba's plain paper facsimile “TF-5500” and continuously print up to 7000 charts with a printing rate of 5% up to 7000 sheets. After each 1000 sheets are printed, the residual toner melts onto the surface of the photosensitive drum. The occurrence of wearing was visually observed, and the filming resistance was evaluated according to the following evaluation criteria. The results are shown in Table 1.

[Evaluation criteria for filming resistance]
○: No filming on the photoconductor even after printing 7000 sheets. Δ: Filming on the photoconductor after 5000 prints. ×: Filming on the photoconductor before 5000 prints.

  From the above results, it can be seen that the toner of the example has less fogging and better filming resistance than the toner of the comparative example. The toners of Comparative Examples 1 to 5 that do not contain negatively-charged silica having an average particle size of 0.2 to 0.6 μm and the toners of Comparative Examples 6 to 8 that do not contain positively-charged silica having an average particle size of 5 to 30 nm are all initial. The occurrence of fog was remarkable.

  The positively chargeable toner for nonmagnetic one-component development of the present invention is used for developing a latent image formed in electrophotography, electrostatic recording method, electrostatic printing method and the like.

Claims (6)

  A positively chargeable toner for non-magnetic one-component development comprising toner base particles containing polyester as a colorant and a binder resin and an external additive, wherein the positive additive has an average particle size of 5 to 30 nm as an external additive. A positively chargeable toner for non-magnetic one-component development, comprising a chargeable silica and a negatively chargeable silica having an average particle size of 0.2 to 0.6 μm.   2. The positively chargeable toner according to claim 1, further comprising positively chargeable silica having an average particle size of more than 30 nm and not more than 100 nm as an external additive.   The positively chargeable toner according to claim 1, further comprising polymer fine particles as an external additive.   The positively chargeable toner according to claim 1, wherein a weight ratio of the positively chargeable silica to the negatively chargeable silica (positively chargeable silica / negatively chargeable silica) is 0.4 to 2.8.   The positively chargeable toner according to any one of claims 1 to 4, wherein the ratio of the average particle diameter of the positively chargeable silica and the negatively chargeable silica (positively chargeable silica / negatively chargeable silica) is 0.02 or more. A step of adding positively-charged silica having an average particle diameter of 5 to 30 nm as an external additive to toner base particles containing polyester as a colorant and a binder resin, and stirring the resulting mixture as an external additive. A method for producing a positively chargeable toner for non-magnetic one-component development, comprising a step of adding a negatively chargeable silica having an average particle size of 0.2 to 0.6 μm and stirring.