JPH10246988A - Negatively chargeable toner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a negatively chargeable toner superior in chargeability characteristics, by using a specified charge controller. SOLUTION: The negatively chargeable toner contains a polyester resin having an acid value of 5-50mgKOH/g as a binder, and a charge controller is a boron-containing compound represented by the formula, in which each of R1 and R3 is an optionally substituted aryl group; each of R2 and R4 is H atom or an alkyl or optionally substituted aryl group; X is a cation; and (n) is 1 or 2. The toner contains, further, fine external additive particles comprising a hydrophobic silica and a hydrophobic titanium dioxide in a weight proportion of 10:1-1:10 and they have a specific surface area S of 40-130 and S is represented by the formula: S=SS×VS+St ×Vt , in which SS is the specific surface area (m<2> /g) of the hydrophobic silica, VS is an addition amount (weight%) of the hydrophobic silica to the toner particles, St is the specific surface area (m<2> /g) of the hydrophobic titanium dioxide, and Vt is an addition amount (weight%) for the hydrophobic silica to the toner particles.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toner for developing an electrostatic latent image, and more particularly to a negatively charged toner used in a digital image forming apparatus.

[0002]

2. Description of the Related Art Conventionally, as an image forming apparatus, an analog system such as a copying machine which forms an electrostatic latent image on a photosensitive member by irradiating a document with light from a light source and irradiating a reflected light thereof to a photosensitive member. Image forming apparatus is generally used. In addition, as a digital image forming apparatus for developing by supplying a developer containing toner to an electrostatic latent image obtained by digital writing, image information read by a printer or an image reader used for output of a computer terminal is used. Digital copiers, electrophotographic facsimile machines, and the like, which form images based on image data, have been put to practical use.

In a digital image forming apparatus,
An electrostatic latent image is formed in units of dots on a negatively chargeable organic photoreceptor by digital writing such as irradiating a light beam, and the latent image is reversely developed with a negatively charged toner. The image is formed by transferring and fixing the image on a recording medium such as. As described above, the toner used in the digital system is required to have excellent dot reproducibility. That is, when developing the electrostatic latent image formed on the photoreceptor, it is necessary to have faithful reproducibility in dot units, and a characteristic that this reproducibility does not decrease even after repeated use is required. In order to satisfy such characteristics, the toner is required to have excellent charge rising characteristics and excellent charge stability. That is, in the two-component developer, the toner is mixed and stirred with the carrier in the developing device and triboelectrically charged, but quickly reaches a desired charge amount in a short stirring time, and thereafter, even if mixed and stirred, the charge amount Is required to have such a characteristic that the charge amount does not increase or the charge amount slightly decreases.

[0004] Further, the above-mentioned toner is required to have not only the charging stability at the time of repeated use but also the charging stability against environmental changes, particularly humidity changes.

Further, in order to improve the reproducibility, it is important that the toner has excellent transferability. That is, if transferability is insufficient, even if the electrostatic latent image is faithfully reproduced and developed, sufficient reproducibility cannot be obtained at the time of transfer.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, and an object of the present invention is to provide a negatively chargeable toner having excellent charge stability when used repeatedly. Things.

Another object of the present invention is to provide a negatively chargeable toner having excellent charge stability against environmental fluctuations.

Another object of the present invention is to provide a negatively chargeable toner having excellent transferability from an electrostatic latent image carrier such as a photoreceptor to a sheet.

Another object of the present invention is to provide a negatively chargeable toner having excellent black reproducibility.

It is a further object of the present invention to provide a negatively chargeable toner in which the collapse of dots hardly occurs at the time of heat fixing and the problem of deterioration in image quality due to heat fixing is eliminated.

[0011]

SUMMARY OF THE INVENTION The present invention provides a negatively charged toner comprising at least a negatively charged toner particle containing at least a binder resin, a colorant and a charge control agent and fine particles of an external additive. Acid value 5-50K
OH mg / g of a polyester resin, wherein the charge control agent has the following general formula (A):

[0012]

Embedded image

(Wherein, R ₁ and R ₃ each represent a substituted or unsubstituted aryl group, R ₂ and R ₄ each represent a hydrogen atom, an alkyl group, a substituted or unsubstituted aryl group, and X represents a cation. N is an integer of 1 or 2.), and the external additive fine particles are composed of hydrophobic silica and hydrophobic titanium dioxide. The addition weight ratio is 10: 1 to 1:10, and the following formula (1): S = Ss × Vs + St × Vt (1) (where Ss is the specific surface area of hydrophobic silica (m ² / g),
Vs is the amount (% by weight) of hydrophobic silica added to the toner particles, and St is the specific surface area of hydrophobic titanium dioxide (m ² /
g) and Vt represent the amount (% by weight) of hydrophobic titanium dioxide added to the toner particles. ) Relates to a negatively chargeable toner having a total specific surface area S of the external additive of 40 to 130.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The negatively chargeable toner of the present invention contains a boron compound represented by the above general formula (A) in order to improve the charge rising characteristics and the stability of the charge amount upon repeated use. The above-described excellent effects can be obtained by incorporating the boron-based compound into a toner using a binder resin having a specific acid value described below. That is, a toner having excellent negative charge property and capable of obtaining a high negative charge amount is used as a toner before containing a boron-based compound. On the other hand, since the toner exhibits a property that the charge amount increases when mixed and stirred excessively, it is considered that the above-described excellent charge stability effect can be obtained by including the above-mentioned boron compound. Further, the boron-based compound represented by the general formula (A) does not contain a heavy metal, and thus has excellent safety.

In the general formula (A), the cation of X is an alkali metal ion such as lithium, sodium and potassium, an alkaline earth metal ion such as magnesium and calcium, a hydrogen ion, an ammonium ion, an iminium ion and a phosphonium ion. And the like. It is preferable that the boron compound is contained in an amount of 0.5 to 5 parts by weight, preferably 1 to 3 parts by weight, based on 100 parts by weight of the binder resin. If the content is less than 0.5 part by weight, the above-mentioned effects will be insufficient, and if it is more than 5 parts by weight, spent on a carrier or the like is likely to occur.

Although the above-mentioned boron compound has excellent properties, since this compound is colorless, when it is used for a black toner, the blackness of the toner tends to decrease. For example, an azo compound containing a heavy metal such as chromium or cobalt which is commonly used as a negative charge control agent has a black color or a dark color close to the black, so that the blackness does not decrease. Therefore, in the present invention, it is preferable to use acidic carbon black having a pH of 1 to 6. Such an acidic carbon black has excellent dispersibility in a polyester resin having a specific acid value described later, and can improve blackness. Also, it works well on the negative charge of the toner. Even if alkaline carbon black is used, such an effect is insufficient. The content of the acidic carbon black with respect to 100 parts by weight of the binder resin is 6 to 12 parts by weight, preferably 7 to 10 parts by weight. If the content is less than 6 parts by weight, the above effect is insufficient. If the content is more than 12 parts by weight, the charge amount of the toner is reduced, and problems such as toner fogging and spillage occur. From the viewpoint of safety, it is desirable to use carbon black having an average primary particle diameter of 40 nm or less, preferably 10 to 40 nm, and more preferably 15 to 35 nm.

The toner of the present invention uses, as a main component of the binder resin, a polyester resin having an acid value of 5 to 50 KOH mg / g, preferably 10 to 40 KOH mg / g. By using a polyester resin having such an acid value, the dispersibility of the carbon black and the boron compound can be improved, and a toner having a sufficient negative charge can be obtained. Acid value is 5KOHmg
/ G is smaller than the above-mentioned effects, and when the acid value is larger than 50 KOHmg / g, environmental fluctuations,
In particular, the stability of the toner charge amount with respect to humidity fluctuation is impaired.

In the present invention, as the polyester resin, a polyester resin obtained by polycondensing a polyhydric alcohol component and a polycarboxylic acid component can be used.

As the dihydric alcohol component of the polyhydric alcohol component, for example, polyoxypropylene (2,
2) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene (3,3) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene (6) -2,2-bis (4-hydroxyphenyl) propanepolyoxyethylene (2,0) -2,2-
Bisphenol A alkylene oxide adducts such as bis (4-hydroxyphenyl) propane, ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, neopentyl glycol 1,4-butenediol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, dipropylene glycol, polyethylene glycol, polytetramethylene glycol, bisphenol A, hydrogenated bisphenol A, etc. Is mentioned.

Examples of the trivalent or higher alcohol component include sorbitol, 1,2,3,6-hexane tetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol,
2,4-butanetriol, 1,2,5-pentanetriol, glycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, 1,3
5-trihydroxymethylbenzene and the like.

The polyvalent carboxylic acid component of the polyvalent carboxylic acid component includes, 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, azelaic acid, malonic acid, n-dodecenyl succinic acid, isododecenyl succinic acid, n-dodecyl succinic acid, isododecyl succinic acid, n-octenyl succinic acid, isooctenyl succinic acid, Examples thereof include n-octylsuccinic acid, isooctylsuccinic acid, anhydrides and lower alkyl esters of these acids.

Examples of the trivalent or higher carboxylic acid component include 1,2,4-benzenetricarboxylic acid (trimellitic acid), 1,2,5-benzenetricarboxylic acid,
5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,5-hexanenetricarboxylic acid, 1,3
-Dicarboxyl-2-methyl-2-methylenecarboxypropane, 1,2,4-cyclohexanetricarboxylic acid, tetra (methylenecarboxyl) methane, 1,2,2
7,8-octanetetracarboxylic acid, pyromellitic acid,
Empol trimer acids, anhydrides of these acids, lower alkyl esters and the like.

In the present invention, a mixture of a raw material monomer for the polyester resin, a raw material monomer for the vinyl resin, and a monomer that reacts with the raw material monomers for both resins is used as the polyester resin in the same container. A resin obtained by performing a polycondensation reaction for obtaining a resin and a radical polymerization reaction for obtaining a styrene-based resin in parallel can also be suitably used. The monomers that react with the raw material monomers of both resins are, in other words, monomers that can be used for both the condensation polymerization reaction and the radical polymerization reaction. That is, it is a monomer having a carboxy group capable of undergoing a polycondensation reaction and a vinyl group capable of undergoing a radical polymerization reaction, and examples thereof include fumaric acid, maleic acid, acrylic acid, and methacrylic acid.

The raw material monomers for the polyester resin include the above-mentioned polyhydric alcohol component and polyvalent carboxylic acid component.

Examples of the raw material monomer for the vinyl resin include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-ethylstyrene, 2,4-dimethylstyrene,
Styrene or styrene derivatives such as p-tert-butylstyrene and p-chlorostyrene; ethylenically unsaturated monoolefins such as ethylene, propylene, butylene and isobutylene; methyl methacrylate and n-methacrylic acid
Propyl, isopropyl methacrylate, n-methacrylate
-Butyl, isobutyl methacrylate, t-methacrylate
Butyl, n-pentyl methacrylate, isopentyl methacrylate, neopentyl methacrylate, methacrylic acid 3
-(Methyl) butyl, hexyl methacrylate, octyl methacrylate, nonyl methacrylate, decyl methacrylate, undecyl methacrylate, dodecyl methacrylate and the like; alkyl methacrylates; methyl acrylate, n-propyl acrylate, isopropyl acrylate , N-butyl acrylate, isobutyl acrylate, t-butyl acrylate, n-pentyl acrylate, isopentyl acrylate, neopentyl acrylate, 3- (methyl) butyl acrylate, hexyl acrylate, octyl acrylate, acrylic acid Nonyl, decyl acrylate,
Alkyl acrylates such as undecyl acrylate and dodecyl acrylate; acrylic acid, methacrylic acid,
Unsaturated carboxylic acids such as itaconic acid and maleic acid; acrylonitrile, maleic acid ester, itaconic acid ester, vinyl chloride, vinyl acetate, vinyl benzoate, vinyl methyl ethyl ketone, vinyl hexyl ketone, vinyl methyl ether, vinyl ethyl ether and vinyl isobutyl ether And the like. As a polymerization initiator when polymerizing the raw material monomer of the vinyl resin, for example,
2,2′-azobis (2,4-dimethylvaleronitrile, 2,2′-azobisisobutyronitrile, 1,1 ′
-Azobis (cyclohexane-1-carbonitrile),
An azo or diazo polymerization initiator such as 2,2'-azobis-4-methoxy-2,4-dimethylvaleronitrile;
Examples thereof include peroxide-based polymerization initiators such as benzoyl peroxide, methyl ethyl ketone peroxide, isopropyl peroxycarbonate, and lauroyl peroxide.

In the present invention, it is preferable to use two kinds of polyester resins having different softening points as the polyester resin in order to improve the fixing property and the offset resistance. That is, the first polyester resin having a softening point of 95 to 120 ° C. is used to improve the fixing property, and the softening point is 13 to improve the offset resistance.
It is preferable to use a second polyester resin at 0 to 160 ° C. In this case, if the softening point of the first polyester resin is lower than 95 ° C., the offset resistance is lowered and the reproducibility of dots is lowered. If the softening point is higher than 120 ° C., the effect of improving the fixability is insufficient. If the softening point of the second polyester resin is lower than 130 ° C, the effect of improving the offset resistance becomes insufficient, and if it is higher than 160 ° C, the fixability decreases. From such a viewpoint, the softening point of the first polyester resin is more preferably 100 to 115 ° C, and the softening point of the second polyester resin is 135 to 155 ° C. Also the first
And the glass transition point of the second polyester resin is 50 to
It is desirably 75 ° C, preferably 55-70 ° C.
This is because if the glass transition point is low, the heat resistance of the toner becomes insufficient, and if the glass transition point is too high, the pulverizability at the time of production is lowered and the production efficiency is lowered.

The first polyester resin is a polyester resin obtained by polycondensation of the above-mentioned polyhydric alcohol component and polyhydric carboxylic acid component, particularly, a bisphenol A alkylene oxide adduct as a polyhydric alcohol component. A polyester resin obtained by using at least one selected from the group consisting of only terephthalic acid, fumaric acid, dodecenylsuccinic acid, and benzenetricarboxylic acid as a polycarboxylic acid component as a main component is preferable.

Further, as the second polyester resin,
Using a mixture of a raw material monomer of a polyester resin, a raw material monomer of a vinyl-based resin, and a bi-reactive monomer that reacts with the raw material monomers of both resins, a condensation polymerization reaction to obtain a polyester resin in the same container and a vinyl-based resin are performed. The polyester resin obtained by performing the obtained radical polymerization reaction in parallel is preferable from the viewpoint of improving the dispersibility of the wax, the toughness, the fixability, and the offset resistance of the toner. The content of the vinyl resin in the second polyester resin is 5 to 5.
It is 40% by weight, preferably 10 to 35% by weight. When the content of the vinyl resin is less than 5% by weight, the fixing strength of the toner is reduced. When the content is more than 40% by weight, the offset resistance, the toughness of the toner, the negative charge level and the like are liable to occur. Become. In addition, when the wax is contained in the toner, the dispersibility of the polyethylene wax tends to decrease when the content of the vinyl resin is less than 5% by weight, and the dispersibility of the polypropylene wax tends to decrease when the content exceeds 40% by weight. is there.

The weight ratio of the first polyester resin to the second polyester resin is 7: 3 to 2: 8, preferably 6: 3.
It is preferable to set it to 4: 3: 7. By using the first polyester-based resin and the second polyester-based resin in such a range, as a toner, the spread due to crushing at the time of fixing is small and the dot reproducibility is excellent, and the toner is excellent in low-temperature fixability and low in speed. Excellent fixability can be ensured even in a high-speed image forming apparatus. Also, excellent dot reproducibility can be maintained even when forming a double-sided image (when passing through the fixing device twice). If the proportion of the first polyester resin is smaller than the above range, the low-temperature fixability becomes insufficient and a wide fixability cannot be secured. When the proportion of the second polyester resin is less than the above range, the offset resistance is reduced, and the toner is crushed at the time of fixing, and the dot reproducibility tends to be reduced.

The softening point of the resin is determined by a flow tester (C
Using an FT-500 (manufactured by Shimadzu Corporation), a 1 cm ² sample was melted and flown out under the conditions of pores of a die (diameter 1 mm, length 1 mm), pressurization 20 kg / cm ² , and heating rate 6 ° C./min. 1 / h of the height from the outflow start point to the outflow end point
The temperature corresponding to 2 was taken as the softening point. The glass transition point was measured using a differential scanning calorimeter (DSC-200: manufactured by Seiko Denshi) with alumina as a reference at a temperature rising rate of 10 ° C./min at a temperature of 10 ° C./min. The shoulder value of the main endothermic peak was defined as the glass transition point. Acid value of 10mg sample is 50ml toluene
And a previously standardized N / 1 using a mixed indicator of 0.1% bromthymol blue and phenol red.
Titration with potassium hydroxide / alcohol solution, N / 10
This is a value calculated from the consumption amount of the potassium hydroxide / alcohol solution.

Further, the toner of the present invention may contain a wax in order to improve properties such as offset resistance. Examples of such waxes include polyethylene wax, polypropylene wax, carnauba wax, rice wax, sasol wax, montan ester wax, Fischer-Tropsch wax and the like. In the case where the wax is contained in the toner as described above, the content is preferably 0.5 to 5 parts by weight with respect to 100 parts by weight of the binder resin in order to obtain the effect of the addition without causing a problem such as filming. Is preferred.

From the viewpoint of improving the offset resistance, it is preferable to contain a polypropylene wax. Also, it is preferable that the paper has a smear property (for example, when the paper is fed on a sheet on which an image is already formed on one side at the time of automatic document feeding or duplex copying). From the viewpoint of improving the image quality such as bleeding or smearing of the image due to rubbing of the image. Particularly preferred from the above viewpoints are polypropylene waxes having a melt viscosity at 160 ° C. of 50 to 300 cps, a softening point of 130 to 160 ° C. and an acid value of 1 to 20 KOH mg / g. Melt viscosity at 1000C is 1000-800
A polyethylene wax having 0 cps and a softening point of 130 to 150 ° C. That is, the polypropylene wax having the above-mentioned melt viscosity, softening point and acid value is excellent in dispersibility in the above-mentioned binder resin, and can improve the offset resistance without causing a problem due to the free wax. In addition, polyethylene wax having the above-mentioned melt viscosity and softening point is also excellent in dispersibility in the above-mentioned binder resin, and achieves an improvement in smear property by reducing the coefficient of friction of the fixed image surface without causing problems due to free wax. Can be. The melt viscosity of the wax was measured using a Brookfield viscometer.

The toner of the present invention may contain magnetic powder and the like as necessary. As the magnetic powder, for example, fine particles of a known magnetic substance such as ferrite, magnetite, and iron can be used, and may be added from the viewpoint of preventing toner scattering or the like. 0.5 to 10 parts by weight, preferably 0.5 to
8 parts by weight, more preferably 1 to 5 parts by weight. If the amount exceeds 10 parts by weight, the magnetic restraining force of the developer carrying member (with a built-in magnet roller) against the toner becomes strong, and the developing property is reduced.

Further, the toner of the present invention contains hydrophobic silica and hydrophobic titanium dioxide as external additive fine particles. In the present invention, hydrophobic silica and hydrophobic titanium dioxide mean silica and titanium dioxide surface-treated with a hydrophobizing agent such as a silane coupling agent or silicone oil. By using hydrophobic silica and titanium dioxide as described above, it is possible to prevent a decrease in the charge amount in a high-temperature and high-humidity environment, and to improve the charge stability against environmental changes.

The weight ratio of the hydrophobic silica to the hydrophobic titanium dioxide is 10: 1 to 1:10, preferably 8: 1 to 1: 1.
S = Ss × Vs + St × Vt (1) (where Ss is the specific surface area of hydrophobic silica (m ² / g),
Vs is the amount (% by weight) of hydrophobic silica added to the toner particles, and St is the specific surface area of hydrophobic titanium dioxide (m ² /
g) and Vt represent the amount (% by weight) of hydrophobic titanium dioxide added to the toner particles. ) Is added so that the total specific surface area S of the external additive represented by the formula (1) is 40 to 130, preferably 50 to 100. By adding the hydrophobic silica and the hydrophobic titanium dioxide in a specific weight ratio and a specific total specific surface area as described above, the fluidity of the toner, the charge stability against the environmental change of the toner, the transfer of the toner from the photoreceptor to the paper, The transferability and the antifogging property during printing can be sufficiently improved. That is, with respect to the toner particles containing the specific resin and the charge control agent described above, when the addition weight ratio of hydrophobic silica and hydrophobic titanium dioxide and the total specific surface area are out of the above ranges, the fluidity and environmental fluctuation are reduced. This impairs any of the characteristics of charge stability, transferability and antifogging property.

In the present invention, the preferred hydrophobic silica has a BET specific surface area of 100 to 250 (m ² / g), preferably 120 to 200 (m ² / g).

In the present invention, the preferred hydrophobic titanium dioxide has a BET specific surface area of 40 to 150 (m ² / m ² ).
g), preferably of 80~130 (m ² / g). As titanium dioxide, the average primary particle size is 10 to 70.
It is preferable to use amorphous titanium dioxide or anatase titanium dioxide having a thickness of nm. Further, among such titanium dioxides, those having a flaky (disk-like) shape are preferable from the viewpoint of adhesion to toner particles.

It is preferable to use toner particles having a volume average particle diameter of 3 to 9 μm, preferably 6 to 9 μm from the viewpoint of improving the reproducibility of high-definition images.

Further, the toner of the present invention can be used as a two-component developer used with a carrier or a one-component developer not using a carrier. As the carrier used for the two-component developer, a conventionally known carrier can be used.

[0040]

EXAMPLES The present invention will be described below with reference to examples, but is not limited thereto.

(Production Example of Polyester Resin L) In a glass four-necked flask equipped with a thermometer, a stirrer, a falling condenser and a nitrogen inlet tube, polyoxypropylene (2,2) -2,2-bis ( 4-hydroxyphenyl) propane, polyoxyethylene (2,2) -2,2
-Bis (4-hydroxyphenyl) propane, isododecenyl succinic anhydride, terephthalic acid and fumaric acid were adjusted to a weight ratio of 82: 77: 16: 32: 30 and added together with dibutyltin oxide as a polymerization initiator. This was reacted in a mantle heater under a nitrogen atmosphere at 220 ° C. with stirring. The obtained polyester resin L has a softening point of 110 ° C., a glass transition point of 60 ° C., and an acid value of 1
It was 7.5 KOHmg / g.

(Production Example of Polyester Resin H) Styrene and 2-ethylhexyl acrylate were added in a weight ratio of 1
The mixture was adjusted to 7: 3.2 and placed in a dropping funnel together with a polymerization initiator, digyl peroxide. Meanwhile, a thermometer,
A polyoxypropylene (2,2) -2,2-bis (4-hydroxyphenyl) was placed in a glass four-necked flask equipped with a stirrer, a falling condenser and a nitrogen inlet tube.
Propane, polyoxyethylene (2,2) -2,2-bis (4-hydroxyphenyl) propane, isododecenyl succinic anhydride, terephthalic acid, 1,2,4-benzenetricarboxylic acid and acrylic acid in a weight ratio of 42: 1.
The mixture was adjusted to 1: 11: 11: 8: 1 and added together with the polymerization initiator dibutyltin oxide. This was stirred at 135 ° C. under a nitrogen atmosphere in a mantle heater,
After styrene or the like was dropped from the dropping funnel, the temperature was raised to 23
The reaction was performed at 0 ° C. The obtained polyester resin H has a softening point of 150 ° C, a glass transition point of 62 ° C, and an acid value of 24.
It was 5 KOHmg / g.

Example 1 Polyester resin L was 40
Parts by weight, 60 parts by weight of polyester resin H, polyethylene wax (800P; manufactured by Mitsui Petrochemical Industries, Ltd .; 16 parts by weight)
Melt viscosity at 0 ° C. 5400 cps; softening point 140
° C) 2 parts by weight, polypropylene wax (TS-20
0; manufactured by Sanyo Chemical Industries, Ltd .; melt viscosity at 160 ° C. 12
0 cps; softening point 145 ° C .; acid value 3.5 KOHmg /
g) 2 parts by weight, acidic carbon black (Mogal L; manufactured by Cabot; pH 2.5; average primary particle size 24 nm) 8
Parts by weight and 2 parts by weight of a negative charge control agent represented by the following formula;

[0044]

Embedded image

Was thoroughly mixed in a Henschel mixer, melt-kneaded in a twin-screw extruder, cooled, coarsely ground in a hammer mill, finely ground in a jet mill, and classified to 7.5 μm in volume average particle size. Was obtained.

The toner particles have a BET specific surface area of 140 m.
0.4% by weight of ² / g hydrophobic silica fine particles (H2000; manufactured by Hoechst) and a BET specific surface area of 110 m ² / g
0.1 wt% of hydrophobic titanium dioxide fine particles (STT30A: manufactured by Titanium Industry Co., Ltd.) was added and mixed to obtain a toner. The total specific surface area of the external additive fine particles in this toner is 67 m ^2.
/ G.

Example 2 Same as Example 1, except that the addition amount of the hydrophobic silica fine particles was changed to 0.3% by weight and the addition amount of the hydrophobic titanium dioxide fine particles was changed to 0.05% by weight. To obtain a toner. The total specific surface area of the external additive fine particles in this toner was 47.5 m ² / g.

Example 3 Example 1 was the same as Example 1, except that the addition amount of the hydrophobic silica fine particles was changed to 0.3% by weight, and the addition amount of the hydrophobic titanium dioxide fine particles was changed to 0.4% by weight. To obtain a toner. The total specific surface area of the external additive fine particles in this toner was 86 m ² / g.

Example 4 Same as Example 1, except that the addition amount of the hydrophobic silica fine particles was changed to 0.5% by weight, and the addition amount of the hydrophobic titanium dioxide fine particles was changed to 0.4% by weight. To obtain a toner. The total specific surface area of the external additive fine particles in this toner was 114 m ² / g.

Example 5 A toner was obtained in the same manner as in Example 1, except that the addition amount of the hydrophobic titanium dioxide fine particles was changed to 0.05% by weight. The total specific surface area of the external additive fine particles in this toner was 61.5 m ² / g.

(Example 6) In Example 1, the hydrophobic silica fine particles were changed to 0.1 wt% of TS500 (manufactured by Cabosil; BET specific surface area: 225 m ² / g), and the amount of the hydrophobic titanium dioxide fine particles was changed. A toner was obtained in the same manner except that the amount was changed to 0.5% by weight. The total specific surface area of the external additive fine particles in this toner was 77.5 m ² / g.

(Example 7) In Example 1, hydrophobic titanium dioxide fine particles were treated with n-butyltrimethoxysilane to make them hydrophobic, and anatase-type titanium dioxide fine particles having an average primary particle diameter of 50 nm (BET specific surface area: 50 m ^2). / G)
A toner was obtained in the same manner except that the amount was changed to 0.1% by weight. The total specific surface area of the external additive fine particles in this toner is 6
It was 1 m ² / g.

Comparative Example 1 A toner was obtained in the same manner as in Example 1, except that fine hydrophobic titanium dioxide particles were not added. The total specific surface area of the external additive fine particles in this toner was 56 m ² / g.

(Comparative Example 2) A toner was obtained in the same manner as in Example 3, except that fine hydrophobic silica particles were not added. The total specific surface area of the external additive fine particles in this toner was 44 m ² / g.

Comparative Example 3 A toner was obtained in the same manner as in Example 1, except that the hydrophobic silica fine particles were changed to 0.4% by weight of R809 (manufactured by Nippon Aerosil Co., Ltd .; BET specific surface area: 50 m ² / g). . The total specific surface area of the external additive fine particles in this toner was 31 m ² / g. (Comparative Example 4) Toner was prepared in the same manner as in Example 1, except that the addition amount of the hydrophobic silica fine particles was changed to 1.0% by weight, and the addition amount of the hydrophobic titanium dioxide fine particles was changed to 0.1% by weight. I got The total specific surface area of the external additive fine particles in this toner was 151 m ² / g.

Comparative Example 5 In Example 1, the amount of the hydrophobic silica fine particles was changed to 0.2% by weight, and the hydrophobic titanium dioxide fine particles were changed to RX50 (manufactured by Nippon Aerosil Co .; B
A toner was obtained in the same manner except that the ET specific surface area was changed to 30% by weight (0.05 m ² / g). The total specific surface area of the external additive fine particles in this toner was 29.5 m ² / g.

Comparative Example 6 The same procedure as in Example 6 was carried out except that the addition amount of the hydrophobic silica fine particles was changed to 0.2% by weight and the addition amount of the hydrophobic titanium dioxide fine particles was changed to 1.0% by weight. To obtain a toner. The total specific surface area of the external additive fine particles in this toner was 155 m ² / g.

Comparative Example 7 The same procedure as in Example 6 was carried out except that the addition amount of the hydrophobic silica fine particles was changed to 0.4% by weight and the addition amount of the hydrophobic titanium dioxide fine particles was changed to 0.5% by weight. To obtain a toner. The total specific surface area of the external additive fine particles in this toner was 145 m ² / g.

Comparative Example 8 A toner was obtained in the same manner as in Example 5, except that the negative charge control agent was changed to iron-containing azo dye T77 (manufactured by Hodogaya Chemical Industry Co., Ltd.). The total specific surface area of the external additive fine particles in this toner was 67 m ² / g.

Comparative Example 9 A toner was obtained in the same manner as in Example 5, except that the negative charge control agent was changed to calixarene compound E89 (manufactured by Orient Chemical Industries, Ltd.). The total specific surface area of the external additive fine particles in this toner is 6
It was 7 m ² / g.

Comparative Example 10 A toner was obtained in the same manner as in Example 1 except that the negative charge control agent was changed to fluorinated quaternary ammonium salt VP434 (manufactured by Hoechst). The total specific surface area of the external additive fine particles in this toner was 67 m ² / g.

Comparative Example 11 A toner was obtained in the same manner as in Example 1 except that the negative charge control agent was changed to a terpene diphenol compound YP90 (manufactured by Yasuhara Chemical Co., Ltd.). The total specific surface area of the external additive fine particles in this toner was 67 m ² / g.

Each of the toners obtained above was evaluated as follows, and the results are shown in Table 1.

(Toner Fluidity) The apparent specific gravity of each of the toners obtained above was measured using a powder tester (manufactured by Hosokawa Micron Corporation), and those having a loose apparent specific gravity of 0.42 cc / g or more were evaluated as ○, 0. Those having a practicality of not less than .38 cc / g and less than 0.42 cc / g,
Those having a practical problem at less than 0.38 cc / g were evaluated as x.

(Environmental resistance) A developer is prepared by mixing each toner obtained and a carrier for a digital copying machine (Di30; manufactured by Minolta) so that toner: carrier = 5: 95 by weight ratio. did.

For these developers, the H / H environment (30 ° C., 85% RH) and the L / L environment (10 ° C.,
The charge amount (μc / g) was measured at 15% RH). If the charge amount difference was less than 10 μc / g,
Those with a value of 15 μc / g or more were evaluated as Δ, and those with a value of 15 μc / g or more were evaluated as x.

(Transferability) Using a digital copying machine Di30 (manufactured by Minolta Co., Ltd.), each developer was subjected to an image output test of 3,000 sheets, and the image was visually confirmed. The sample was evaluated as ○, the one with slight loss but no practical problem was rated as Δ, and the one with image loss and practical problem was rated as ×.

(Charging start-up property) Each of the above-mentioned developers was put into a polybin, and this was supplied to a ball mill stand at 120 rpm.
To mix for 5 minutes, 10 minutes, 30 minutes, 60 minutes,
Each charge amount after 120 minutes and 780 minutes was measured (at 25 ° C.,
45% RH environment).

The charge amount after 5 minutes with respect to the maximum charge amount [(charge amount after 5 minutes / charge amount maximum value) × 100] is 90.
% Or more and excellent in rising property,
Those that were practically usable from 0% to less than 90% were evaluated as Δ, and those that were less than 80% and practically problematic were evaluated as ×.

(Initial and post-print fog) Using a digital copying machine Di30 (manufactured by Minolta), an image output test was performed on 100,000 sheets of each developer.
And the image after printing was visually confirmed, and the image was fog-free and the image was fog-free but not practically problematic, and fog-produced and practically problematic. Was evaluated as x.

[0071]

[Table 1]

[0072]

According to the present invention, it is possible to provide a negatively chargeable toner having excellent charge rising characteristics and charge stability.

Further, according to the present invention, it is possible to provide a negatively chargeable toner having excellent charging stability against environmental fluctuations.

Further, according to the present invention, it is possible to provide a negatively chargeable toner having excellent transferability from an electrostatic latent image carrier such as a photosensitive member to a sheet.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroyuki Fukuda 2-3-113 Azuchicho, Chuo-ku, Osaka-shi Osaka International Building Minolta Co., Ltd.

Claims (6)

[Claims] 1. A negatively charged toner comprising negatively charged toner particles containing at least a binder resin, a colorant and a charge control agent, and external additive fine particles, wherein the binder resin has an acid value of 5 to 50 KOH mg / g. It comprises a polyester resin, and the charge control agent has the following general formula (A): (Wherein, R ₁ and R ₃ each represent a substituted or unsubstituted aryl group, R ₂ and R ₄ each represent a hydrogen atom, an alkyl group, a substituted or unsubstituted aryl group, and X represents a cation. n is an integer of 1 or 2.), and the external additive fine particles are composed of hydrophobic silica and hydrophobic titanium dioxide, and the weight ratio of hydrophobic silica to hydrophobic titanium dioxide added. Is 10: 1 to 1:
10, the following formula (1): S = Ss × Vs + St × Vt (1) (where Ss is a specific surface area of hydrophobic silica (m ² / g),
Vs is the amount (% by weight) of hydrophobic silica added to the toner particles, and St is the specific surface area of hydrophobic titanium dioxide (m ² /
g) and Vt represent the amount (% by weight) of hydrophobic titanium dioxide added to the toner particles. ), Wherein the external additive total specific surface area S is 40 to 130. 2. The binder resin 1 of the boron compound.
2. The negatively chargeable toner according to claim 1, wherein the addition amount is 0.5 to 5 parts by weight based on 00 parts by weight. 3. The hydrophobic silica having a BET specific surface area of 1
00~250 (m ² / g) negatively chargeable toner according to claim 1, wherein a. 4. The negatively chargeable toner according to claim 1, wherein the hydrophobic titanium dioxide has a BET specific surface area of 40 to 150 (m ² / g). 5. The negatively chargeable toner according to claim 1, wherein the colorant is acidic carbon black having a pH of 1 to 6. 6. The negatively chargeable toner according to claim 5, wherein the addition amount of the carbon black to 100 parts by weight of the binder resin is 6 to 12 parts by weight.