JP3493452B2 - Negatively charged toner - Google Patents

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 chargeable 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 photoconductor by irradiating a document with light from a light source and irradiating the photoconductor with the reflected light. Image forming apparatus is generally used. Also, as a digital image forming apparatus that supplies a developer containing toner to the electrostatic latent image obtained by digital writing to perform development, image information read by a printer or image reader used for output from a computer terminal. A digital copying machine for forming an image based on the above, an electrophotographic facsimile, and the like have been put into practical use.

In the digital type image forming apparatus,
An electrostatic latent image is formed in dot units on the negatively chargeable organic photoconductor by digital writing such as irradiation with a light beam, and the latent image is reversely developed with a negatively chargeable toner, and the obtained toner image is recorded paper. A recorded image is formed by transferring the image onto a recording medium such as the above and fixing it. 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 photoconductor, it is necessary to have faithful reproducibility on a dot-by-dot basis, and this reproducibility is required to have a characteristic that does not deteriorate even after repeated use. In order to satisfy such characteristics, it is required that the toner has excellent charging rising characteristics and excellent charging stability. For example, in a two-component developer, the toner is mixed and stirred with the carrier in the developing device and frictionally charged,
It is necessary that the desired charge amount is quickly reached in a short stirring time, and thereafter, the charge amount does not increase or the charge amount slightly decreases even if mixed and stirred. If the toner has such a charging characteristic that the charge amount increases when the toner reaches the desired charge amount and is further mixed and stirred, the toner adhesion amount to the latent image decreases during repeated use, resulting in dot reproducibility. Is reduced. Conventionally, there is known a technique of adding various negative charge control agents to the toner in order to improve the negative chargeability of the toner. However, the negative charge control agents have different charge characteristics depending on their types, and many are known to increase the negative charge amount of the toner. Excellent charging stability cannot be obtained.

[0004]

SUMMARY OF THE INVENTION The present invention is intended to solve the above-mentioned problems, and provides a negatively chargeable toner having excellent charging characteristics and excellent dot reproducibility. That is the purpose.

Another object of the present invention is to provide a negatively chargeable toner having excellent charging characteristics and excellent black reproducibility in which density unevenness does not occur in a solid black image.

A further object of the present invention is to provide a negatively chargeable toner in which dot collapse is less likely to occur during heat fixing and the problem of image quality deterioration due to heat fixing is solved.

According to the present invention, in a negatively chargeable toner containing at least a binder resin, a colorant and a charge control agent, the colorant is based on 100 parts by weight of the binder resin.
The carbon black has an addition amount of 6 to 12 parts by weight and a pH of 1 to 6 , and the charge control agent is represented by the following general formula (A):

[Chemical formula 2] (In the formula, 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.), the volume average particle size of the boron compound is 5 to 25 μm, and the toner surface abundance is 0.05 to toner particles. 0.4% by weight, and the main component of the binder resin is a glass transition point of 50 to 75 ° C.
And a first polyester resin having a softening point of 95 to 120 ° C.,
Glass transition point 50 to 75 ° C and softening point 130 to 160
Weight ratio of the second polyester resin of 7: 3 to 2:
No. 8 and a negatively chargeable toner which is a polyester resin having an acid value of 5 to 50 KOHmg / g.

[0008]

[0009]

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The negatively chargeable toner of the present invention contains a boron-based compound represented by the above general formula (A) in a specific toner surface abundance in order to improve the charge rising characteristics and the stability of the charge amount. Contained in.

The boron-based compound used in the present invention is a material having excellent safety and containing no heavy metal. In the general formula (A), examples of the cation of X include alkali metal ions such as lithium, sodium and potassium, alkaline earth metal ions such as magnesium and calcium, hydrogen ion, ammonium ion, iminium ion and phosphonium ion. To be

In the toner of the present invention, the amount of the boron-based compound present on the toner surface is 0.05 to 0.
It is 4% by weight, preferably 0.1 to 0.3% by weight. When the amount of the surface present is less than 0.05% by weight, the rise of the charging of the toner cannot be sufficiently improved, and the effect of improving the stability of the charging amount becomes insufficient. If it is more than 0.4% by weight, the negative charge amount of the toner will be low, and fog will easily occur on the non-image area. The amount of the boron-based compound present on the toner surface is determined by dispersing the toner in a solvent that dissolves the boron-based compound to dissolve the boron-based compound present on the toner surface and then separating the solution to obtain atomic absorption and ultraviolet light. It was measured by quantifying the boron compound (or a part of the component) in the solution by absorption or fluorescence X-ray. In the present invention, the toner having the specific toner surface amount uses the boron compound having a volume average particle size adjusted to 5 to 25 μm, preferably 10 to 20 μm, which is added to 100 parts by weight of a binder resin. On the other hand, it can be obtained by containing 0.5 to 5 parts by weight, preferably 1 to 4 parts by weight. When a boron-based compound having a volume average particle size of less than 5 μm is used, the boron-based compound is less likely to be exposed on the toner surface, and the above-described effect of improving charging characteristics becomes insufficient. Desorption becomes easy, the composition variation among the toner particles increases, and the amount of reversely charged toner increases. On the other hand, if the content is less than 0.5 parts by weight, the exposed amount of the boron compound will be insufficient, and if it is more than 5 parts by weight, the exposed amount will increase and the charge amount will decrease.

In the present invention, the toner before the incorporation of the boron compound is excellent in negative chargeability,
It is preferable to use a material capable of obtaining a high negative charge amount. On the other hand, this toner exhibits the property that the charge amount increases when it is mixed and stirred excessively. Therefore, by containing the above-mentioned boron compound in a specific surface amount, the above-mentioned excellent charge stability effect can be obtained. It is considered to be a thing.

The above-mentioned boron compound has excellent characteristics, but since this compound is colorless, the blackness of the toner tends to decrease when it is used for a black toner. For example, an azo compound containing a heavy metal such as chromium or cobalt which is commonly used as a negative charge control agent does not cause a problem of blackness reduction because it is black or a dark color close to this, but such a compound is used instead. When the above boron compound is used, the problem of blackness reduction occurs.

In the present invention, in order to solve this problem, pH 1 to 6, preferably 1 to 5, and more preferably 1 to
It is preferred to use an acidic carbon black of 4. Such acidic carbon black has excellent dispersibility in a polyester resin having a specific acid value described later, and can improve the blackness. Further, it also works well on the negative chargeability of the toner. Even if alkaline carbon black is used, such an effect is insufficient. This acidic carbon black binder resin 10
The content with respect to 0 part by weight is 6 to 12 parts by weight, preferably 7 to 10 parts by weight. When the content is less than 6 parts by weight, the above effect becomes insufficient, and when it is more than 12 parts by weight, the charge amount of the toner is lowered and problems such as toner fog and spilling occur. From the viewpoint of safety, it is desirable to use carbon black having an average primary particle size of 40 nm or less, preferably 10 to 40 nm, and more preferably 15 to 35 nm.

The toner of the present invention preferably uses a polyester resin having an acid value of 5 to 50 KOHmg / g as the main component of the binder resin. By using the polyester resin having such an acid value, it is possible to improve the dispersibility of the carbon black or the boron compound and to provide a toner having a sufficient negative charge amount. When the acid value is less than 5 KOHmg / g, the above-mentioned effects are reduced, and the acid value is 50 KOHmg / g.
If it is larger than g, the stability of the toner charge amount against environmental changes, particularly humidity changes, 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.

Among the polyhydric alcohol components, examples of the dihydric alcohol component include 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) propane polyoxyethylene (2,0) -2,2-
Bisphenol A alkylene oxide adduct 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 trihydric or higher alcohol components include sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, 1,
2,4-butanetriol, 1,2,5-pentanetriol, glycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, 1,3.
5-trihydroxymethylbenzene etc. are mentioned.

The divalent carboxylic acid component among the polyvalent carboxylic acid components is, 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-dodecenylsuccinic acid, isododecenylsuccinic acid, n-dodecylsuccinic acid, isododecylsuccinic acid, n-octenylsuccinic acid, isooctenylsuccinic acid, Examples thereof include n-octyl succinic acid, isooctyl succinic acid, and anhydrides or 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, 2,
5,7-naphthalene tricarboxylic acid, 1,2,4-naphthalene tricarboxylic acid, 1,2,4-butane tricarboxylic acid, 1,2,5-hexanene tricarboxylic acid, 1,3
-Dicarboxyl-2-methyl-2-methylenecarboxypropane, 1,2,4-cyclohexanetricarboxylic acid, tetra (methylenecarboxyl) methane, 1,2,
7,8-octanetetracarboxylic acid, pyromellitic acid,
Examples thereof include empol trimer acids, anhydrides of these acids, and lower alkyl esters.

In the present invention, as the polyester resin, a mixture of a raw material monomer of the polyester resin, a raw material monomer of the vinyl resin, and a monomer which reacts with the raw material monomers of both resins is used, and the polyester is used in the same container. A resin obtained by carrying out a polycondensation reaction for obtaining a resin and a radical polymerization reaction for obtaining a styrene resin in parallel can also be suitably used. The monomer that reacts with the raw material monomers of both resins is, in other words, a monomer that can be used in both the condensation polymerization reaction and the radical polymerization reaction. That is, a monomer having a condensation polymerization reaction which may be carboxyl group and a vinyl group capable of radical polymerization reaction, such as fumaric acid, maleic acid, acrylic acid, and methacrylic acid.

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

Examples of raw material monomers for vinyl resins include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, and the like.
Styrene or styrene derivatives such as p-tert-butylstyrene and p-chlorostyrene; ethylenically unsaturated monoolefins such as ethylene, propylene, butylene, isobutylene; methyl methacrylate, n-methacrylic acid
Propyl, isopropyl methacrylate, methacrylate n
-Butyl, isobutyl methacrylate, methacrylic acid t-
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 other alkyl methacrylate esters; 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,
Acrylic acid alkyl esters 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. Etc. Examples of the polymerization initiator at the time of polymerizing the raw material monomer of the vinyl resin include, for example,
2,2'-azobis (2,4-dimethylvaleronitrile, 2,2'-azobisisobutyronitrile, 1,1 '
-Azobis (cyclohexane-1-carbonitrile),
Azo or diazo polymerization initiators such as 2,2′-azobis-4-methoxy-2,4-dimethylvaleronitrile,
Examples thereof include peroxide type 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-based resin having a softening point of 95 to 120 ° C. is used to improve the fixability, and the softening point is 13 to improve the offset resistance.
It is preferable to use a second polyester resin having a temperature of 0 to 160 ° C. In this case, when the softening point of the first polyester resin is lower than 95 ° C, the offset resistance is lowered and the dot reproducibility is lowered, and when it is higher than 120 ° C, the effect of improving the fixing property is insufficient. If the softening point of the second polyester resin is lower than 130 ° C, the effect of improving the offset resistance is insufficient, and if it is higher than 160 ° C, the fixability is deteriorated. From this 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 more preferably 135 to 155 ° C. Also the first
And the glass transition point of the second polyester resin is 50 to
It is desirable that the temperature is 75 ° C, preferably 55 to 70 ° C.
This is because if the glass transition point is low, the heat resistance of the toner becomes insufficient, and if it is too high, the pulverizability at the time of production decreases and the production efficiency decreases.

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

As the second polyester resin,
Using a mixture of a polyester resin raw material monomer, a vinyl resin raw material monomer, and a bireactive monomer that reacts with both resin raw material monomers, a polycondensation reaction to obtain a polyester resin and a vinyl resin can be performed in the same container. The polyester resin obtained by carrying out the radical polymerization reaction in parallel is preferable from the viewpoint of improving the dispersibility of the wax, the toughness of the toner, the fixing property, and the offset resistance. The content of the vinyl resin in the second polyester resin is 5 to
It is 40% by weight, preferably 10 to 35% by weight. This is because when the content of the vinyl-based resin is lower than 5% by weight, the fixing strength of the toner is lowered, and when it exceeds 40% by weight, the offset resistance, the toughness of the toner and the negative charge level are easily lowered. Become. When the toner contains wax, the dispersibility of the polyethylene wax tends to decrease when the content of the vinyl resin is lower than 5% by weight, and the dispersibility of the polypropylene wax tends to decrease when the content of the vinyl resin 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 :.
It is preferably set to 4 to 3: 7. By using the first polyester resin and the second polyester resin in such a range, the toner has a small spread due to crushing at the time of fixing and is excellent in dot reproducibility. Excellent fixability can be secured even in a high-speed image forming apparatus. Further, it is possible to maintain excellent dot reproducibility during double-sided image formation (when passing through the fixing device twice). When the proportion of the first polyester resin is less than the above range, the low temperature fixability becomes insufficient and a wide fixability cannot be secured. If the proportion of the second polyester resin is less than the above range, the offset resistance tends to deteriorate and the toner crushing during fixing tends to become large, resulting in deterioration of dot reproducibility. The softening point of the resin is a flow tester (CFT-500:
(Manufactured by Shimadzu Corporation), using a die hole (diameter 1 mm, length 1 mm), pressure 20 kg / cm ² , temperature rising rate 6 ° C./m
The softening point was defined as the temperature corresponding to ½ of the height from the outflow start point to the outflow end point when a 1 cm ² sample was melted out under the in condition. The glass transition point is a differential scanning calorimeter (D
SC-200: manufactured by Seiko Denshi KK, using alumina as a reference, a 10 mg sample was heated at a temperature of 10 ° C.
The temperature was measured at 20 to 120 ° C. under the condition of / min, and the shoulder value of the main endothermic peak was taken as the glass transition point. The acid value was measured by dissolving a 10 mg sample in 50 ml of toluene,
Using a mixed indicator of 1% bromthymol blue and phenol red, titration was performed with a pre-standardized N / 10 potassium hydroxide / alcohol solution, and a value calculated from the consumption amount of the N / 10 potassium hydroxide / alcohol solution was used. is there.

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, sazol wax, montan ester wax, Fischer-Tropsch wax and the like. When the wax is added to the toner as described above, the content of 0.5 to 5 parts by weight relative to 100 parts by weight of the binder resin is effective for addition without causing problems such as filming. Is preferred.

From the viewpoint of improving the offset resistance, it is preferable to contain polypropylene wax, and the smearing property (when the automatic document feeding or the double-sided copying, when the paper having the image already formed on one side is fed, the roller is used) It is preferable to contain polyethylene wax from the viewpoint of improving the phenomenon that the image is rubbed by (1) and the image quality is deteriorated such as bleeding and stains on the image). Particularly preferred polypropylene wax from the above viewpoint is a polypropylene wax 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 KOHmg / g, and a particularly preferred polyethylene wax is 160 Melt viscosity at ℃ 1000-800
It is 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 has excellent dispersibility in the binder resin, and the offset resistance can be improved without causing a problem due to the free wax. Further, polyethylene wax having the above-mentioned melt viscosity and softening point is also excellent in dispersibility in the above-mentioned binder resin, and it is possible to reduce the friction coefficient of the fixed image surface without causing problems due to the free wax to achieve improvement in smearing property. You can The melt viscosity of the wax was measured with a Brookfield viscometer.

If desired, magnetic powder or the like may be added to the toner of the present invention. As the magnetic powder, for example, fine particles of a known magnetic material such as ferrite, magnetite, iron can be used, and may be added from the viewpoint of preventing toner scattering and the like, but the addition amount is 100 parts by weight of the binder resin. On the other hand, 0.5 to 10 parts by weight, preferably 0.5 to
8 parts by weight, more preferably 1 to 5 parts by weight. When the amount added exceeds 10 parts by weight, the magnetic force of the developer bearing member (built-in magnet roller) against the toner becomes strong, and the developability deteriorates.

Further, the toner of the present invention may be treated by externally adding inorganic fine particles to the surface thereof. The inorganic fine particles may be added by mechanically mixing the toner and the inorganic fine particles. Examples of the inorganic particles include silica particles, titanium dioxide particles, alumina particles, magnesium fluoride particles, silicon carbide particles, boron carbide particles, titanium carbide particles, zirconium carbide particles, boron nitride particles, titanium nitride particles, zirconium nitride particles, magnetite particles. The fine particles of molybdenum disulfide, the fine particles of barium titanate, the fine particles of strontium titanate, the fine particles of aluminum stearate, the fine particles of magnesium stearate, the fine particles of zinc stearate and the like can be used alone or in combination of two or more kinds. Preferably, silica fine particles and titanium dioxide fine particles are used in combination and externally added. The amount of the inorganic fine particles added is 0.05 to 2% by weight, preferably 0.1 to 1% by weight, based on the toner. By using such an added amount,
The fluidity can be improved without impairing the environmental stability of the developer. In addition, as the inorganic fine particles, it is preferable to use those that have been subjected to a hydrophobic treatment from the viewpoint of improving environmental stability, and as the hydrophobic treatment agent, silane coupling agents, titanium coupling agents, higher fatty acids, silicone oils, etc. Can be used. BE as the above-mentioned inorganic fine particles
It is preferable to use a T specific surface area of 80 to 180 m ² / g. By using the inorganic fine particles having such a BET specific surface area, it is possible to reduce the fluidity to 200 with respect to a small particle diameter toner having an average particle diameter of 5 to 9 μm.
Compared with the case of using inorganic fine particles of m ² / g or less, the addition amount can be increased and the fluidity can be improved without impairing the environmental stability. Further, not only the fluidity can be improved, but also the transferability when transferring the toner image formed on the surface of the photoconductor onto a recording medium such as recording paper can be improved, and the dot reproducibility can be improved. You can

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

[0034]

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

(Production Example of Polyester Resins L1 to L3) Polyoxypropylene (2,2) -2,2 was placed in a glass four-necked flask equipped with a thermometer, a stirrer, a flow-down condenser and a nitrogen inlet tube. -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. 2 in a mantle heater under a nitrogen atmosphere
The reaction was carried out with stirring at 20 ° C. to obtain polyester resins L1 to L3 shown in Table 1.

(Production Example of Polyester Resins H1 to H3) Styrene and 2-ethylhexyl acrylate were adjusted to a weight ratio of 17: 3.2, and put in a dropping funnel together with digyl peroxide as a polymerization initiator. on the other hand,
A glass four-necked flask equipped with a thermometer, a stirrer, a flow-down condenser and a nitrogen inlet tube was charged with polyoxypropylene (2,2) -2,2-bis (4-hydroxyphenyl) propane, polyoxyethylene (2 , 2)-
2,2-bis (4-hydroxyphenyl) propane, isododecenyl succinic anhydride, terephthalic acid, anhydrous 1,
2,4-Benzenetricarboxylic acid and acrylic acid were adjusted to a weight ratio of 42: 11: 11: 11: 8: 1 and added together with dibutyltin oxide as a polymerization initiator. After stirring this in a nitrogen atmosphere in a mantle heater at 135 ° C while adding styrene etc. from a dropping funnel,
The temperature was raised and the reaction was carried out at 230 ° C. to obtain polyester resins H1 to H3 shown in Table 1.

[0037]

[Table 1]

Example 1 Polyester resin L1 was added to 4
0 parts by weight, 60 parts by weight of polyester resin H1, polyethylene wax (800P; manufactured by Mitsui Petrochemical Industry Co., Ltd .;
Melt viscosity at 160 ° C. 5400 cps; softening point 13
6 ° C) 1 part by weight, polypropylene wax (100T
S; manufactured by Sanyo Chemical Industries; melt viscosity at 160 ° C. 12
0 cps; softening point 144 ° C.) 2 parts by weight, carbon black (BLACK PEARLS-L; Cabot Co .; pH 2.5; average primary particle size 24 nm) 8 parts by weight and volume average particle size 15
2 parts by weight of a boron-based compound represented by the following formula pulverized and adjusted to have a particle diameter of μm;

[0039]

[Chemical 3]

Was thoroughly mixed with a Henschel mixer, melt-kneaded with a twin-screw extrusion kneader, cooled, then coarsely pulverized with a hammer mill and finely pulverized with a jet pulverizer, and then classified to have a volume average particle diameter of 7.5 μm. Toner particles were obtained.

This toner particle has a BET specific surface area of 140 m.
0.4% by weight of ² / g of hydrophobic silica fine particles (H2000: manufactured by Hoechst) and BET specific surface area of 110 m ² / g
0.2 wt% of the hydrophobic titanium dioxide fine particles (STT30A: manufactured by Titanium Industry Co., Ltd.) was added and mixed to obtain a toner.

Example 2 In Example 1, the boron compound was changed to a volume average particle size of 8 μm, and the carbon black was MONARCH 1300 (manufactured by Cabot Co .; pH 2.
5: Average primary particle diameter 13 nm) A toner was obtained in the same manner except that the amount was changed to 6 parts by weight.

Example 3 In Example 1, the boron compound was changed to a volume average particle size of 22 μm, and carbon black was changed to REGAL 400 (manufactured by Cabot Co .; pH 4.
0: average primary particle size 25 nm) A toner was obtained in the same manner except that the amount was changed to 8 parts by weight.

(Example 4) In Example 1, 50% of polyester resin L2 was used in place of polyester resin L1.
Except that 50 parts by weight of polyester resin H2 is used in place of polyester resin H1 and carbon black is changed to MOGUL-L (manufactured by Cabot; pH 2.5; average primary particle size 24 nm). Was obtained in the same manner as above.

(Embodiment 5) In Embodiment 1, polyester resin L3 is used in place of polyester resin L1.
A toner was obtained in the same manner except that 70 parts by weight of the polyester resin H3 was used instead of the polyester resin H1 and the carbon black was changed to 12 parts by weight of MOGUL-L.

Comparative Example 1 A toner was obtained in the same manner as in Example 1, except that the boron compound was changed to 2 parts by weight having a volume average particle diameter of 3 μm.

Comparative Example 2 A toner was obtained in the same manner as in Example 1 except that the boron compound was changed to 2 parts by weight having a volume average particle size of 28 μm.

Comparative Example 3 A toner was obtained in the same manner as in Example 1, except that the carbon black was changed to 8 parts by weight of REGAL330 (manufactured by Cabot; pH 9.0; average primary particle size 25 nm).

Comparative Example 4 A toner was obtained in the same manner as in Example 1, except that the addition amount of the boron compound was changed to 0.3 part by weight. (Comparative Example 5) A toner was obtained in the same manner as in Example 1, except that the addition amount of the boron compound was changed to 5.5 parts by weight.

The amount of boron compounds present on the surface of each of the above toners was measured as follows, and the results are shown in Table 2.

First, a solvent in which a surfactant (sodium n-dodecylbenzenesulfonate) is dissolved in pure water is quantitatively put in a screw tube, and a weighed sample (toner) is put in the screw tube and stirred. Then, the solution in which the boron compound is dissolved is filtered to separate the residual toner.
The concentration of potassium in the obtained solution was quantified by the atomic absorption method, and the concentration of the boron compound in the solution was calculated from the calibration curve obtained in advance. Then, the amount of boron compound present on the surface (% by weight) was calculated from (concentration of boron compound in solution / concentration of toner in solvent) × 100.

Each of the obtained toners and a digital copying machine (Di
30; manufactured by Minolta Co., Ltd.) was mixed in a weight ratio of toner: carrier = 5: 95 to prepare a developer, and the following evaluations were performed. The results are shown in Table 2.

(Charging Rising Property) Each of the developers described above was put in a polybin, and this was put on a ball mill stand at 120 rpm.
The mixture was rotated by and mixed for 3 minutes and 60 minutes, and each charge amount was measured (25 ° C., 45% RH environment).

(Fog after printing) Digital copying machine Di30
(Minolta Co., Ltd.) was used to print 20,000 sheets of each developer, and the image was visually confirmed after the printing was completed. If there was no fog in the image, it was ○, and there was some fog. Those having no practical problem were evaluated as Δ, and those having a practical problem due to fog were evaluated as ×.

(Image density unevenness after printing) Digital copying machine D
After printing 20,000 sheets of each developer using i30 (Minolta Co., Ltd.), a solid black image of 2 cm × 2 cm was formed on the four corners of the A4 paper and five places in the center after printing. Reflection densities were measured with a Macbeth densitometer, and those in which the difference between the maximum image density and the minimum image density was less than 0.05 were ◯, those in which 0.05 or more and less than 0.1 were Δ, 0.1. The above was evaluated as x.

(Dot reproducibility after printing durability) Digital copying machine D
Printing was performed on 20,000 sheets of each developer using i30 (manufactured by Minolta). After printing, the fixing temperature was set to 180 ° C. to form a halftone image. The obtained halftone dot image was measured for the diameter of each halftone dot image using an image analyzer to measure about 80 to 10
The data of 0 halftone dots were obtained, the maximum diameter value Dmax thereof was obtained, and the ranking was performed as follows. Dmax is 185μ
Less than m is rank 10, 185 μm or more and less than 187.5 μm is rank 9, 187.5 μm or more and less than 190 μm is rank 8, 190 μm or more and less than 192.5 μm is rank 7, 192.5 μm or more and less than 195 μm is rank 6, 1
A rating of 95 μm or more and less than 197.5 μm was evaluated as rank 5, a rating of 9 or 10 was evaluated as ◯, a rating of 7 or 8 was evaluated as Δ, and a rating of 6 or less was evaluated as x.

[0057]

[Table 2]

[0058]

According to the present invention, it is possible to provide a negatively chargeable toner having an excellent charge rising characteristic.

Further, according to the present invention, the charging characteristics are excellent,
Further, it is possible to provide a negatively-charged toner having excellent black reproducibility without causing uneven density in a solid black image.

Further, according to the present invention, it is possible to provide a negatively chargeable toner which does not cause fog in an image even during printing.

Further, according to the present invention, it is possible to provide a negatively chargeable toner in which dot collapse is unlikely to occur even during heat fixing and the problem of image quality deterioration due to heat fixing is solved.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroyuki Fukuda 2-3-13 Azuchi-cho, Chuo-ku, Osaka, Osaka, Osaka International Building Minolta Co., Ltd. (56) Reference JP-A-8-286418 (JP, A) JP-A-8-234492 (JP, A) JP-A-8-220797 (JP, A) JP-A-8-69129 (JP, A) JP-A-8-54754 (JP, A) JP-A-8-44108 (JP, A) JP-A-7-114218 (JP, A) JP-A-6-301240 (JP, A) JP-A-6-250442 (JP, A) (58) Fields investigated (Int.Cl. ⁷⁾ , DB name) G03G 9/08

Claims (5)

(57) [Claims] 1. A negatively chargeable toner containing at least a binder resin, a colorant and a charge control agent,
Addition amount of colorant to 100 parts by weight of binder resin
Is 6 to 12 parts by weight and has a pH of 1 to 6 and the charge control agent is represented by the following general formula (A): (In the formula, 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.), the volume average particle size of the boron compound is 5 to 25 μm, and the toner surface abundance is 0.05 to toner particles. 0.4% by weight, and the main component of the binder resin is a glass transition point of 50 to 75 ° C.
And a first polyester resin having a softening point of 95 to 120 ° C.,
Glass transition point 50 to 75 ° C and softening point 130 to 160
Weight ratio of the second polyester resin of 7: 3 to 2:
8. A negatively chargeable toner which is a polyester resin containing 8 and having an acid value of 5 to 50 KOHmg / g. 2. A binder resin 1 of the boron compound
The negatively chargeable toner according to claim 1, wherein the addition amount is 0.5 to 5 parts by weight relative to 00 parts by weight. 3. The toner according to claim 1, wherein the toner is a toner prepared by a kneading and pulverizing method, and the boron-based compound having a volume average particle diameter of 10 to 20 μm is used in a raw material mixing step.
The negatively charged toner described. 4. The negatively chargeable toner according to claim 1 Symbol placement average primary particle diameter of the carbon black is 10 to 40 nm. 5. The second polyester resin is subjected to a polycondensation reaction and an addition polymerization reaction by using a mixture of a polyester resin monomer, a vinyl resin monomer and a bireactive monomer that reacts with both of these monomers. negatively chargeable toner according to claim 1, wherein the polyester resin obtained by performing.