JP7553294B2 - Toner and its manufacturing method - Google Patents

Description

The present invention relates to a toner and its manufacturing method.

Toner (toner for developing electrostatic images) used in electrophotographic image forming devices such as copying machines, multifunction machines, printers, and facsimile machines usually contains binder resins, release agents, colorants, charge control agents, etc. in the toner particles, and these components are collectively called internal additives.

In small particle size toner, if the internal additive is poorly dispersed, compositional deviations are likely to occur between individual toner particles. Among internal additives, if the charge control agent is poorly dispersed, the toner charge distribution becomes broad, causing problems such as scattering of toner particles and image defects such as fogging. On the other hand, if the charge control agent becomes over-dispersed, it is no longer exposed on the surface of the toner particles, significantly reducing its function as a charge control agent, and the leak effect cannot be expected.

Patent document 1 discloses that in a toner for a non-magnetic one-component development method, in order to stabilize the charging and transport of the toner over a long period of time, a specific charge control agent is used in the toner, and the dispersion state of the charge control agent is such that the toner has a specific relationship between the volume average particle size of the toner particles and the average dispersion diameter of the charge control agent used.

Japanese Patent Application Publication No. 10-20560

The present invention was made based on the above circumstances, and its purpose is to provide a toner and a manufacturing method thereof that can suppress the occurrence of image defects such as toner particle scattering and fogging.

As a result of intensive research into solving the above problems, the inventors discovered that in a toner having toner particles containing a binder resin, a colorant, and a charge control agent, the above problems can be solved by controlling the volume average particle size of the toner particles, the number average dispersed particle size of the charge control agent, and the particle size distribution of the charge control agent as follows, and thus completed the present invention.

That is, the toner according to the present invention is a toner having toner particles containing a binder resin, a colorant, and a charge control agent, and is characterized in that, when the volume average particle diameter of the toner particles is Dt and the number average dispersed particle diameter of the charge control agent is Dc, Dc/Dt is 0.1 to 0.2, and when the particle diameter of the particles whose cumulative number percentage from the small particle diameter side is 90% in the particle size distribution of the charge control agent is Dc90, and the particle diameter of the particles whose cumulative number percentage from the small particle diameter side is 10% is Dc10, Dc90/Dc10 is 3.0 or less.

The toner manufacturing method according to the present invention is a toner manufacturing method, which includes a mixing step of mixing raw materials including a binder resin, a colorant, and a charge control agent, a melting and kneading step of melting and kneading the mixture obtained in the mixing step, a cooling and grinding step of cooling and solidifying the kneaded product obtained in the melting and kneading step and then grinding it, and a classification step of classifying the grinded product into first grinded particles, second grinded particles having a volume average particle size smaller than the first grinded particles, and third grinded particles having a volume average particle size larger than the first grinded particles, and recovering the first grinded particles as toner particles, and is characterized in that the segregation rate of the charge control agent, defined as A/B×100, is 102% or more and 130% or less, where A is the amount of the charge control agent contained in the second grinded particles, and B is the amount of the charge control agent contained in the first grinded particles.

This invention makes it possible to prevent toner particle scattering and image defects such as fogging.

1A to 1C are process diagrams illustrating a first embodiment of a toner production method of the present invention. 3A to 3C are process diagrams illustrating a second embodiment of the toner production method of the present invention.

The toner and its manufacturing method according to the embodiment of the present invention will be described in detail below.

<Toner/toner particles>
The toner of the present invention has toner particles containing at least a binder resin, a colorant, and a charge control agent, and may further contain optional components as necessary within the range not impairing the effects of the present invention.

In the toner of the present invention, when the volume average particle diameter of the toner particles is Dt and the number average dispersed particle diameter of the charge control agent is Dc, Dc/Dt is 0.1 or more and 0.2 or less, and when the particle diameter of the particles whose cumulative number percentage from the small particle diameter side is 90% in the particle size distribution of the charge control agent is Dc90, and the particle diameter of the particles whose cumulative number percentage from the small particle diameter side is 10% is Dc10, Dc90/Dc10 is 3.0 or less.

If Dc/Dt is less than 0.1, the toner may be charged up. If Dc/Dt is more than 0.2, the effect of the charge control agent may be reduced, resulting in fogging.

If Dc90/Dc10 exceeds 3.0, the effect of the charge control agent will be reduced and fogging may occur. It is also preferable that Dc90/Dc10 is 1.0 or more. If Dc90/Dc10 is less than 1.0, the proportion of fine powder and coarse powder will be high in production, and productivity may deteriorate.

When Dc/Dt and Dc90/Dc10 satisfy the above conditions, the toner has the number average dispersed particle size of the charge control agent and the particle size distribution of the charge control agent controlled to match the volume average particle size of the toner particles. This makes it possible to suppress the scattering of toner particles and the occurrence of image defects such as fogging.

The volume average particle size of the toner particles is not particularly limited, but is preferably 3 μm or more and 15 μm or less, more preferably 4 μm or more and 9 μm or less, and even more preferably 5 μm or more and 8 μm or less. Toner particles with such small particle sizes have an appropriate charge amount and can ensure sufficient fluidity. Therefore, the toner particles can be stably supplied to the photoreceptor, making it possible to form clear, high-definition images and preventing the occurrence of contamination inside the machine due to scattering of toner particles.

<Binder resin>
Examples of the binder resin include polyester-based resins, polystyrene-based resins such as styrene-acrylic-based resins, (meth)acrylic acid ester-based resins, polyolefin-based resins, polyurethane-based resins, and epoxy-based resins. Among these, one type may be used alone, or two or more types may be used in combination.

The polyester resin used in the binder resin is usually obtained by polycondensation reaction of one or more selected from dihydric alcohol components and polyhydric alcohol components having 3 or more valences with one or more selected from divalent carboxylic acids and polyvalent carboxylic acids having 3 or more valences, via an esterification reaction or an ester exchange reaction, by a known method.

The conditions for the condensation polymerization reaction can be set appropriately depending on the reactivity of the monomer components, and the reaction can be terminated when the polymer has suitable physical properties. For example, the reaction temperature is about 170 to 250°C, and the reaction pressure is about 5 mmHg to normal pressure.

Examples of dihydric alcohol components include alkylene oxide adducts of bisphenol A such as polyoxypropylene (2.2)-2,2-bis(4-hydroxyphenyl)propane, polyoxypropylene (3.3)-2,2-bis(4-hydroxyphenyl)propane, polyoxypropylene (2.0)-2,2-bis(4-hydroxyphenyl)propane, polyoxypropylene (2.0)-polyoxyethylene (2.0)-2,2-bis(4-hydroxyphenyl)propane, and polyoxypropylene (6)-2,2-bis(4-hydroxyphenyl)propane; ethylene glycol; These include diols such as ethanol, 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, polypropylene glycol, and polytetramethylene glycol; bisphenol A; propylene adducts of bisphenol A; ethylene adducts of bisphenol A; hydrogenated bisphenol A, etc.

Examples of trihydric or higher polyhydric alcohol components include sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, sucrose, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, and 1,3,5-trihydroxymethylbenzene.

In the present invention, one of the dihydric alcohol components and trihydric or higher polyhydric alcohol components may be used alone, or two or more of them may be used in combination.

Examples of divalent carboxylic acids include 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, n-dodecylsuccinic acid, n-octylsuccinic acid, isooctenylsuccinic acid, isooctylsuccinic acid, and their acid anhydrides and lower alkyl esters.

Examples of trivalent or higher polyvalent carboxylic acids include 1,2,4-benzenetricarboxylic acid, 1,2,5-benzenetricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, 1,2,4-cyclohexanetricarboxylic acid, tetra(methylenecarboxyl)methane, 1,2,7,8-octanetetracarboxylic acid, pyromellitic acid, empol trimer acid, and their acid anhydrides and lower alkyl esters.

In the present invention, one of the divalent carboxylic acids and trivalent or higher polyvalent carboxylic acids may be used alone, or two or more of them may be used in combination.

The polyester resin preferably has a weight average molecular weight of 3,000 to 50,000. If the weight average molecular weight of the polyester resin is less than 3,000, there is a risk that the peelability on the high temperature side of the fixable region (non-offset region) will be poor. On the other hand, if the weight average molecular weight of the polyester resin exceeds 50,000, there is a risk that the low temperature fixability will be poor.

The polyester resin preferably has an acid value of 5 to 30 mgKOH/g. If the acid value of the polyester resin is less than 5 mgKOH/g, the charging characteristics of the polyester resin will decrease and the charge control agent will be difficult to disperse in the polyester resin, which may adversely affect the charging start-up and charging stability during continuous use. On the other hand, if the acid value of the polyester resin exceeds 30 mgKOH/g, the hygroscopicity will increase and the charging properties may become unstable.

<Charge Control Agent>
As the charge control agent, a charge control agent for controlling a positive charge or a negative charge can be used.

Examples of charge control agents for controlling positive charges include nigrosine dyes and their derivatives, basic dyes, quaternary ammonium salts, quaternary phosphonium salts, aminopyrine, pyrimidine compounds, polynuclear polyamino compounds, aminosilanes, triphenylmethane derivatives, guanidine salts, and amidine salts.

On the other hand, examples of charge control agents for negative charging include oil-soluble dyes such as oil black and spiron black, metal-containing azo compounds, azo complex dyes, metal naphthenates, metal complexes and metal salts of salicylic acid and its derivatives (metals include chromium, zinc, zirconium, etc.), boron compounds, fatty acid soaps, long-chain alkyl carboxylates, and resin acid soaps.

The content of the charge control agent in the toner of the present invention is not particularly limited, but it is preferably 0.1 to 3 parts by weight, and more preferably 0.2 to 2 parts by weight, per 100 parts by weight of the binder resin.

The adhesion strength of the charge control agent in the toner according to the present invention is preferably 30% or more and 80% or less, more preferably 35% or more and 75% or less, and even more preferably 50% or more and 65% or less. If the adhesion strength of the charge control agent is less than the lower limit, the effect of the charge control agent is reduced, which may cause charging up. On the other hand, if the adhesion strength of the charge control agent exceeds the upper limit, fogging may worsen.

The adhesion strength of the charge control agent in the toner can be measured by determining the remaining rate of the charge control agent when the toner is subjected to vibration. Specifically, it can be measured by a method that executes a step of quantitatively analyzing the elements derived from the charge control agent present on the toner particles by fluorescent X-ray analysis or the like, a step of applying ultrasonic waves to the toner in water, and a step of quantitatively analyzing the elements derived from the charge control agent on the toner particles after the ultrasonic waves are applied and calculating the remaining rate of the charge control agent.

<Release Agent>
Examples of the release agent include petroleum waxes such as paraffin wax and its derivatives, microcrystalline wax and its derivatives; hydrocarbon synthetic waxes such as Fischer-Tropsch wax and its derivatives, polyolefin wax and its derivatives, polypropylene wax and its derivatives, polyolefin polymer wax (low molecular weight polyethylene wax, etc.) and its derivatives; vegetable waxes such as carnauba wax and its derivatives, rice wax and its derivatives, candelilla wax and its derivatives, and Japan wax; animal waxes such as beeswax and spermaceti; oil-based synthetic waxes such as fatty acid amides, phenol fatty acid esters and their derivatives; silicone polymers, higher fatty acids, etc. One of these may be used alone, or two or more may be used in combination. The derivatives include oxides, block copolymers of vinyl monomers and wax, graft modified products of vinyl monomers and wax, etc. The content of the release agent is not particularly limited, but it is more preferable that it is 0.5 to 10 parts by weight per 100 parts by weight of the binder resin.

<Coloring Agent>
Examples of the colorant include black, yellow, magenta, and cyan pigments and dyes. Note that the color of the toner is not limited to these, and the toner may be colored in other colors, and a colorant corresponding to the color may be used.

Black colorants include, for example, inorganic pigments such as carbon black and complex oxide black; and organic pigments such as aniline black.

Carbon black is classified into channel black, roller black, disc black, gas furnace black, oil furnace black, thermal black, acetylene black, etc., depending on the manufacturing method, etc., and an appropriate carbon black can be selected from these according to the design characteristics of the toner to be obtained.

Examples of yellow colorants include organic pigments such as C.I. Pigment Yellow 1, C.I. Pigment Yellow 5, C.I. Pigment Yellow 12, C.I. Pigment Yellow 15, and C.I. Pigment Yellow 17, C.I. Pigment Yellow 74, C.I. Pigment Yellow 93, C.I. Pigment Yellow 180, and C.I. Pigment Yellow 185, which are classified according to the color index; nitro dyes such as C.I. Acid Yellow 1, and oil-soluble dyes such as C.I. Solvent Yellow 2, C.I. Solvent Yellow 6, C.I. Solvent Yellow 14, C.I. Solvent Yellow 15, C.I. Solvent Yellow 19, and C.I. Solvent Yellow 21.

Examples of magenta colorants include organic pigments classified by the Color Index, such as C.I. Pigment Red 49, C.I. Pigment Red 57, C.I. Pigment Red 81, C.I. Pigment Red 122, C.I. Solvent Red 19, C.I. Solvent Red 49, C.I. Solvent Red 52, C.I. Basic Red 10, and C.I. Disperse Red 15.

Examples of cyan colorants include organic pigments such as C.I. Pigment Blue 15, C.I. Pigment Blue 16, C.I. Solvent Blue 55, C.I. Solvent Blue 70, C.I. Direct Blue 25, C.I. Direct Blue 86, and KET. BLUE 111, which are classified by the Color Index.

<Other optional ingredients>
Other optional components include, for example, magnetic materials such as magnetite powder, γ-hematite powder, and various ferrite powders, and among these, one type may be used alone or two or more types may be used in combination.

<Toner Manufacturing Method>
[First embodiment]
Fig. 1 is a process diagram showing a first embodiment of the toner manufacturing method of the present invention. The toner manufacturing method shown in Fig. 1 is a particle manufacturing method by a dry method, and includes a mixing step S1, a melt-kneading step S2, a cooling and pulverizing step S3, a classification step S4, and an external addition step S5.

(Mixing step S1)
In the mixing step S1, a resin material (binder resin), a release agent, a charge control agent, a colorant, and a magnetic material are dry-mixed in a mixer to prepare a mixture. At this time, all of these raw materials may be mixed at once, but it is preferable to mix the raw materials other than the charge control agent and the colorant, mix the charge control agent, and then mix the colorant. By using the latter method, it becomes easier to adjust the particle size of the charge control agent in the kneaded product obtained in the melt-kneading step S2.

In particular, when adding colorants and magnetic materials to the mixture, it is preferable to do the following:

First, a master batch containing a resin material and a colorant is prepared. This allows the colorant to be uniformly dispersed in the resin material (and thus the kneaded product). The master batch can be prepared, for example, by dry mixing the resin material and the colorant in a mixer, melt-kneading them in a kneader to obtain a kneaded product, and then pulverizing (coarsely pulverizing) this kneaded product in a grinder.

The mixing time is preferably about 60 to 180 seconds, and more preferably about 90 to 150 seconds. The kneading temperature depends on the softening temperature of the resin material, but is preferably about 50 to 180°C, and more preferably about 90 to 150°C.

Examples of mixers include Henschel type mixers such as Henschel Mixer (product name, manufactured by Mitsui Mining Co., Ltd.), Super Mixer (product name, manufactured by Kawata Co., Ltd.), and Mechano Mill (product name, manufactured by Okada Seiko Co., Ltd.), Ang Mill (product name, manufactured by Hosokawa Micron Corporation), Hybridization System (product name, manufactured by Nara Machinery Works Co., Ltd.), and Cosmo System (product name, manufactured by Kawasaki Heavy Industries, Ltd.).

Examples of kneading machines include kneaders, twin-screw extruders, two-roll mills, three-roll mills, and lab blast mills. Specific examples of kneading machines include single-screw or twin-screw extruders such as TEM-100B (trade name, manufactured by Toshiba Machine Co., Ltd.), PCM-65/87, and PCM-30 (all trade names, manufactured by Ikegai Corporation), and open-roll type kneading machines such as Kneadex (trade name, manufactured by Mitsui Mining Co., Ltd.).

Examples of the grinding machine include a hammer mill, a cutting mill, and a speed mill. The average particle size (e.g., volume average particle size) of the master batch is usually about 1 to 5 mm.

Next, the master batch, resin material, release agent, and magnetic material are mixed using the same mixer as above to obtain a first mixture. The mixing time is preferably about 60 to 200 seconds, and more preferably about 90 to 180 seconds.

Finally, the first mixture and the charge control agent are mixed using a mixer as described above to obtain a second mixture. The mixing time is preferably about 100 to 700 seconds, and more preferably about 200 to 500 seconds.

By mixing the raw materials in this order to obtain a mixture, i.e., by mixing the raw materials other than the charge control agent and then mixing the charge control agent to obtain a mixture, it is possible to prevent the needle-shaped particles of the charge control agent from being excessively crushed in the mixture. This makes it easier to adjust the particle size of the charge control agent in the kneaded product obtained in the next melt-kneading process S2.

(Melting and kneading step S2)
In the melt-kneading step S2, the second mixture produced in the mixing step S1 is melt-kneaded by a kneader to produce a kneaded product in which the release agent, charge control agent, colorant, and magnetic material are dispersed in the resin material.

In the melt-kneading step S2, a kneader similar to the kneader mentioned in the mixing step S1 can be used. In addition, melt-kneading may be performed using multiple kneaders.

The temperature during melt kneading depends on the type of kneader used, but is preferably about 80 to 200°C, and more preferably about 100 to 150°C. By performing melt kneading at a temperature in this range, the release agent, charge control agent, colorant, and magnetic material can be more uniformly dispersed in the resin material.

By appropriately changing the mixing time in the mixing step S1, the type of kneader used in the melt-kneading step S2, the temperature during melt-kneading, etc., the average particle size of the charge control agent in the kneaded product can be adjusted to the desired value.

The mixing step S1 and the melt-kneading step S2 may be performed once each, or a set of both steps may be performed multiple times. Alternatively, the mixing step S1 may be performed multiple times in succession, followed by the melt-kneading step S2. The mixing step S1 may also be performed again after the melt-kneading step S2, and finally, the melt-kneading step S2 may be performed before the cooling and grinding step S3 and the classification step S4. Furthermore, the ground material that has been through the cooling and grinding step S3 and the classification step S4 may be used as the material in the mixing step.

In the mixing step S1, the particle size of the charge control agent can be controlled by changing the rotation speed and rotation time of the mixer and the order in which the materials are added. In this case, a charge control agent that has been crushed separately using a mixer or the like may be used.

Similarly, in the grinding and classifying steps (S3 and S4) described below, the toner particle size can be controlled by changing the rotation speed, supply amount, air pressure, etc. of the grinder and classifier. By controlling either or both of the mixing step S1 and the grinding and classifying steps (S3 and S4), the desired toner particle size and charge control agent particle size can be obtained.

(Cooling and grinding step S3)
In the cooling and pulverizing step S3, the kneaded product obtained in the melt-kneading step S2 is cooled and solidified, and then pulverized to obtain a pulverized product.

Specifically, the cooled and solidified kneaded material is coarsely pulverized to obtain a coarsely pulverized product, which is then further pulverized to obtain a pulverized product. The volume average particle size of the coarsely pulverized product is preferably about 100 μm to 5 mm, and the volume average particle size of the pulverized product is preferably 15 μm or less.

The kneaded material can be pulverized using a pulverizer similar to the one mentioned in the mixing step S1. In addition, for finely pulverizing the coarsely pulverized material, for example, a jet pulverizer that uses a supersonic jet stream, or an impact pulverizer that introduces the coarsely pulverized material into the space formed between a rotor and a stator (liner) rotating at high speed and pulverizes it, can be used.

The ground material thus obtained typically contains toner particles (first ground particles), over-ground toner particles (second ground particles) having an average particle size (e.g., volume average particle size) smaller than the average particle size (e.g., volume average particle size) of the toner particles, and coarse toner particles (third ground particles) having an average particle size (e.g., volume average particle size) larger than the average particle size (e.g., volume average particle size) of the toner particles.

(Classification process S4)
In the classification step S4, the pulverized product obtained in the cooling and pulverizing step S3 is classified by a classifier to remove over-pulverized toner particles (second pulverized particles) and coarse toner particles (third pulverized particles) to obtain toner particles (first pulverized particles). The over-pulverized toner particles and coarse toner particles (particularly the over-pulverized toner particles) can be recovered and reused in a different or subsequent toner manufacturing process.

In the following, toner having toner particles before external additives are attached to the surface, such as these toner particles (first pulverized particles), will be referred to as non-additive toner, and toner having toner particles with external additives attached to the surface will be referred to as additive toner.

For classification, a classifier that utilizes centrifugal force and wind force, such as a swirling wind classifier (rotary wind classifier), can be used.

As described above, by adjusting the average particle size of the charge control agent, the dispersion diameter of the charge control agent contained in the kneaded material becomes an appropriate size, which suppresses excessive pulverization of the kneaded material, and as a result, the amount of charge control agent contained in the over-pulverized toner particles (second pulverized particles) (segregation rate of the charge control agent) is reduced. Therefore, even if the over-pulverized toner particles are continuously reused in the toner manufacturing process, the toner particles obtained in the later rounds (recycled toner particles) can fully maintain their excellent charging properties.

The segregation rate of the charge control agent is defined as A/B x 100, where A is the amount of the charge control agent contained in the over-pulverized toner particles (second pulverized particles) and B is the amount of the charge control agent contained in the toner particles (first pulverized particles). For example, A and B can be measured by quantitatively analyzing the elements derived from the charge control agent in both particles using fluorescent X-ray analysis, and calculated using the above formula.

In the present invention, the segregation rate of the charge control agent is preferably 102% or more and 130% or less, more preferably 104% or more and 120% or less, and even more preferably 106% or more and 115% or less. If the segregation rate of the charge control agent is less than the lower limit, the effect of the charge control agent is reduced, which may cause charging up. If the segregation rate of the charge control agent exceeds the upper limit, fogging may worsen.

The volume average particle size of the toner particles (first pulverized particles) to be collected is not particularly limited, but is preferably 3 μm or more and 15 μm or less, more preferably 3 μm or more and 9 μm or less, even more preferably 4 μm or more and 9 μm or less, and particularly preferably 5 μm or more and 8 μm or less. Toner particles with such a small particle size have an appropriate charge amount and can ensure sufficient fluidity. Therefore, the toner particles can be stably supplied to the photoreceptor, making it possible to form clear and high-definition images, and preventing the occurrence of contamination inside the machine due to scattering of toner particles.

The content of toner particles with a number-average particle size of 4 μm or less in the recovered toner (fine powder content) is preferably less than 30%. If the content of toner particles with a number-average particle size of 4 μm or less is equal to or greater than the upper limit, scattering inside the machine and fogging on paper may worsen. The content of toner particles with a number-average particle size of 4 μm or less can be calculated by measuring the particle size distribution using, for example, a flow particle image analyzer (manufactured by Malvern Instruments, model: FPIA-3000).

(External addition step S5)
In the external addition step S5, the toner particles obtained in the classification step S4 are mixed with an external additive to obtain a toner. The addition of the external additive improves the fluidity of the toner and the cleaning property of the toner particles remaining on the photoreceptor surface, and prevents filming on the photoreceptor. Note that the toner particles themselves to which no external additive is added can also be used as the toner (non-additive toner).

Examples of external additives include inorganic compounds such as silica, alumina, titania, zirconia, tin oxide, and zinc oxide, compounds such as acrylic acid esters, methacrylic acid esters, and styrene, copolymer resin particles of these compounds, fluororesin particles, silicone resin particles, higher fatty acids such as stearic acid, metal salts of higher fatty acids, carbon black, graphite fluoride, silicon carbide, and boron nitride. It is preferable that the external additives are surface-treated with, for example, silicone resin, a silane coupling agent, or the like.

The amount of external additive added is not particularly limited and can be selected from a wide range, but is preferably 0.5 parts by weight or more and 5 parts by weight or less per 100 parts by weight of toner particles.

Second Embodiment
2 is a process diagram showing a second embodiment of the toner manufacturing method of the present invention. In the second embodiment, the over-pulverized toner particles generated in the classification step S4 are returned to the mixing step S1 for reuse. Other than this point, the second embodiment is the same as the first embodiment.

The amount of over-pulverized toner particles contained in the kneaded product is not particularly limited, but is preferably 5 to 40 parts by weight, and more preferably 10 to 35 parts by weight, per 100 parts by weight of the resin material. By adjusting the average particle size of the charge control agent in the mixing step S1 or melt-kneading step S2 as described above, the resulting toner particles can sufficiently and reliably maintain excellent charging characteristics even when a relatively large amount of over-pulverized toner particles is added to the kneaded product.

When the over-pulverized toner particles generated in the classification step S4 are returned to the mixing step S1 for reuse, it is preferable to mix the resin material, release agent, colorant, and magnetic material (raw materials other than the charge control agent and over-pulverized toner particles) and then mix the charge control agent and over-pulverized toner particles in this order to obtain a mixture. This makes it possible to prevent not only the needle-shaped particles of the charge control agent in the mixture, but also the particles of the charge control agent contained in the over-pulverized toner particles from being excessively pulverized. This makes it easier to adjust the particle size of the charge control agent in the kneaded product obtained in the melt-kneading step S2.

In addition, fine toner particles having an average particle size (e.g., volume average particle size) smaller than the average particle size (e.g., volume average particle size) of the toner particles (toner particles to be used as the product) can be provided in the mixing step S1. Therefore, in addition to over-pulverized toner particles generated in the same toner manufacturing process as in this embodiment, the fine toner particles can be finely pulverized material obtained by collecting and separately pulverizing coarse toner particles generated in the same toner manufacturing process, over-pulverized toner particles generated in a different toner manufacturing process, finely pulverized material obtained by collecting and separately pulverizing coarse toner particles generated in a different toner manufacturing process, or a mixture of these. The same effect as above can be obtained by using these fine toner particles.

The present invention will be explained below based on examples and comparative examples, but the present invention is not limited to these examples. First, the measurement methods used in the examples will be explained.

<Method of measuring the volume average particle size (Dt) of toner particles>
20 mg of the sample and 1 ml of sodium alkyl ether sulfate were added to 50 ml of an electrolyte (manufactured by Beckman Coulter, Inc., product name: ISOTON-II), and the mixture was dispersed for 3 minutes at a frequency of 20 kHz using an ultrasonic disperser (manufactured by AS ONE Corporation, tabletop dual-frequency ultrasonic cleaner, model: VS-D100) to obtain a measurement sample. The obtained measurement sample was measured using a particle size distribution measuring device (manufactured by Beckman Coulter, Inc., model: Multisizer3) under the conditions of an aperture diameter of 100 μm and a measurement particle count of 50,000, and the volume average particle size was obtained from the volume particle size distribution of the sample particles.

<Method of measuring number average dispersed particle size (Dc) of charge control agent>
The toner particles were melted at 180°C and cooled to obtain a cooled product. Next, the cooled product was cut using an ultramicrotome (manufactured by Leica Microsystems, product name: EM UC7) equipped with an ultrasonically vibrating knife to prepare a thin slice having a thickness of 100 nm. The cross section of the thin slice was then observed with a scanning transmission electron microscope (STEM, product name: S-4800, manufactured by Hitachi High-Technologies (now Hitachi High-Tech)). The dispersion diameter (circle equivalent diameter) was determined from the obtained STEM image.

To measure the number of particles and the dispersed diameter, the images were binarized using image analysis software (product name: A-zo-kun, manufactured by Asahi Kasei Engineering Co., Ltd.), the number of charge control agents and the dispersed diameter were measured, and the number-average dispersed particle diameter of each sample was calculated.

<Method of measuring Dc10 and Dc90 in particle size distribution of charge control agent>
More than 1000 particles of the charge control agent in the cross-sectional image of the thin section obtained by the above method were measured using a vernier caliper or a scale to obtain the particle size distribution of the charge control agent. Note that image processing software or the like may be used for this measurement. Next, the obtained particle sizes were arranged from the smallest particle size side, and the particle size of the particle with a cumulative number of 10% was defined as Dc10, and the particle size of the particle with a cumulative number of 90% was defined as Dc90, and the values of Dc10 and Dc90 were obtained.

<Method for measuring adhesion strength of charge control agent in toner>
The adhesion strength of the charge control agent in the toner was measured by the following procedure.
(1) 2.0 g of toner (external additive toner) is added to 40 ml of an aqueous solution of Triton (polyoxyethylene octylphenyl ether) with a concentration of 0.2% by weight, and the mixture is stirred for 1 minute.
(2) The aqueous solution is then irradiated with ultrasonic waves (output: 40 μA, for 2 minutes) using a homogenizer: US-300T (manufactured by Nippon Seiki Seisakusho Co., Ltd.).
(3) The aqueous solution after the ultrasonic irradiation is left to stand for 3 hours, and the toner and the liberated charge control agent are separated.
(4) After removing the supernatant, add approximately 50 ml of pure water to the precipitate and stir for 5 minutes.
(5) The mixture is subjected to suction filtration using a membrane filter having a pore size of 1 μm (manufactured by Advantec Co., Ltd.).
(6) The toner remaining on the filter is vacuum dried overnight.
(7) Using a fluorescent X-ray analyzer (manufactured by Rigaku Corporation, model: ZSX Primus II), the intensity of the element (K) in the charge control agent of 1 g of toner before and after the series of ultrasonic treatments (1) to (6) above was analyzed, and the adhesion strength of the charge control agent was calculated using the following formula.

Charge control agent adhesion strength (%) = {(fluorescent X-ray intensity of K element after ultrasonic treatment) / (fluorescent X-ray intensity of K element before ultrasonic treatment)} x 100

<Method for measuring segregation rate of charge control agent>
Using a fluorescent X-ray analyzer (manufactured by Rigaku Corporation, model: ZSX Primus II), elements derived from the charge control agent in the toner particles to which no external additives were added (the first pulverized particles described above) and the over-pulverized toner particles (the second pulverized particles described above) were quantitatively analyzed.

Based on the amount (A) of the charge control agent contained in the over-pulverized toner particles (the above-mentioned second pulverized particles) and the amount (B) of the charge control agent contained in the toner particles (the above-mentioned first pulverized particles) measured by this quantitative analysis, the segregation rate of the charge control agent (A/B x 100) was calculated.

<Method for measuring the content of toner particles with a number-average particle size of 4 μm or less (fine powder ratio)>
The particle size distribution was measured using a flow particle image analyzer (manufactured by Malvern Instruments, model: FPIA-3000) and calculated.

<How to evaluate image quality>
The whiteness of the paper before printing was measured using a colorimeter (manufactured by Nippon Denshoku Industries Co., Ltd., model: ZE 6000), and the whiteness of the same location (unprinted area) was measured again after printing, and the difference was calculated as the fog on the paper.

From the results obtained, the image quality was evaluated according to the following criteria.
◎: Excellent (suitable for use. Difference in whiteness is 0 or more and less than 0.5)
○: Good (can be used. Difference in whiteness is 0.5 or more and less than 1.0)
△: Acceptable (Can be used. Difference in whiteness is 1.0 or more and less than 1.5)
×: Unusable (Cannot be used. Difference in whiteness is 1.5 or more)

[Preparation of master batch]
In this embodiment, first, a master batch containing a part of the binder resin (L body) and a colorant is prepared by dry mixing the part of the binder resin and the colorant, followed by melt kneading.

In this embodiment, 100 parts by weight of L-type resin (glass transition point approximately 60°C, softening temperature approximately 70°C) and 10 parts by weight of carbon black (MA-77, manufactured by Mitsubishi Chemical Corporation) were mixed and dispersed in a Henschel mixer (manufactured by Mitsui Mining Co., Ltd.), and then melt-kneaded using an open-roll type kneader (Kneedex, manufactured by Mitsui Mining Co., Ltd.). The mixing conditions in the Henschel mixer were a rotation speed of 550 rpm and a time of 2 minutes.

[Mixing process, melt-kneading process]
(First manufacturing method)
In the first production method, the toners of Example 4 and Comparative Example 4 were produced.
In the first manufacturing method, the master batch, a part of the binder resin (H body), a release agent, a magnetic material, and a charge control agent are mixed, and then melted and kneaded to produce a kneaded product. After that, the kneaded product is subjected to a pulverization/classification process and an external addition process, and a toner is produced from the kneaded product. That is, in the first manufacturing method, the charge control agent is added at the same time as the binder resin and other materials (mixing 1).

In Example 4, 1 part by weight of a charge control agent (LR-147A, manufactured by Nippon Carlit Co., Ltd.), 3.2 parts by weight of a microcrystalline wax (Hi-Mic-1090, manufactured by Nippon Seiro Co., Ltd.), 1.5 parts by weight of a magnetic material (BL-220, manufactured by Titan Kogyo Co., Ltd.), and 60 parts by weight of an H-body resin were added to the above-mentioned master batch, and the mixture was mixed and dispersed in a Henschel mixer (manufactured by Mitsui Mining Co., Ltd.), and then melt-kneaded using a twin-screw extruder. The mixing conditions for the Henschel mixer were a rotation speed of 1200 rpm and a rotation time of 5 minutes. The operating conditions for the twin-screw extruder were a cylinder setting temperature of 110°C, a barrel rotation speed of 250 rpm, and a raw material supply rate of 10 kg/hour. On the other hand, in Comparative Example 4, the mixing conditions for the above-mentioned Henschel mixer were different, with a rotation speed of 800 rpm and a rotation time of 1 minute, and the timing of material input and kneading were the same as those in Example 4.

(Second manufacturing method)
In the second production method, the toners of Examples 1 and 2, Examples 5 and 6, and Comparative Examples 2 and 3 were produced.
In the second manufacturing method, the procedure for mixing the materials is different from that in the first manufacturing method. After mixing the master batch, a part of the binder resin (H body), the release agent, and the magnetic material, the charge control agent is added to the mixture and mixed again. After all the materials are mixed, the toner is produced through melt-kneading, pulverization, classification, and external addition. In other words, in the second manufacturing method, the other materials are mixed once, and then the charge control agent is added separately.

In Example 1, 3.2 parts by weight of microcrystalline wax (Hi-Mic-1090, manufactured by Nippon Seiro Co., Ltd.), 1.5 parts by weight of magnetic material (BL-220, manufactured by Titan Kogyo Co., Ltd.), and 60 parts by weight of H-body resin were added to the above-mentioned master batch, and mixed and dispersed (first mixing) in a Henschel mixer. The mixing conditions in the Henschel mixer were a rotation speed of 1500 rpm and a rotation time of 2.5 minutes.

1 part by weight of a charge control agent (LR-147A, manufactured by Nippon Carlit Co., Ltd.) was added to the above mixture (first mixing), and the mixture was mixed and dispersed again (second mixing) in the Henschel mixer. The mixing conditions in the Henschel mixer were a rotation speed of 1500 rpm and a rotation time of 2.5 minutes.

The above mixture (second mixing) was melt-kneaded using a twin-screw extruder. The operating conditions of the twin-screw extruder were cylinder set temperature 110°C, barrel rotation speed 250 rpm, and raw material supply rate 10 kg/hour.

In Example 2, the mixing conditions were as follows: the rotation speed of the first mix in the Henschel mixer was 1200 rpm, the rotation time was 2.5 minutes, and the rotation speed of the second mix was 1200 rpm, the rotation time was 2.5 minutes. The timing of adding materials and the kneading were the same as in Example 1.

In Example 5, the mixing conditions were as follows: the rotation speed of the first mix in the Henschel mixer was 1500 rpm, the rotation time was 3 minutes 20 seconds, and the rotation speed of the second mix was 1200 rpm, the rotation time was 1 minute 20 seconds. The timing of adding materials and the kneading were the same as in Example 1.

In Example 6, the mixing conditions were as follows: the rotation speed of the first mix in the Henschel mixer was 1000 rpm, the rotation time was 1 minute 20 seconds, and the rotation speed of the second mix was 1000 rpm, the rotation time was 2.5 minutes. The timing of adding materials and the kneading were the same as in Example 1.

In Comparative Example 2, the mixing conditions were as follows: the rotation speed of the first mix in the Henschel mixer was 700 rpm, the rotation time was 1 minute 40 seconds, and the rotation speed of the second mix was 1000 rpm, the rotation time was 1 minute. The timing of adding materials and the kneading were the same as in Example 1.

In Comparative Example 3, the mixing conditions were as follows: the rotation speed of the first mix in the Henschel mixer was 800 rpm, the rotation time was 2.5 minutes, and the rotation speed of the second mix was 800 rpm, the rotation time was 50 seconds. The timing of adding materials and the kneading were the same as in Example 1.

(Third manufacturing method)
In the third production method, the toners of Example 3 and Comparative Example 1 were produced.
In the third manufacturing method, the kneading process and the procedure for mixing materials are different from the first and second manufacturing methods. After mixing the binder resin (L body and H body), the release agent, and the magnetic material, the charge control agent is added to the mixture and mixed again. Then, the colorant and, if necessary, the over-pulverized toner are added and mixed again. After all the materials are mixed, the toner is produced through melt-kneading, pulverization, classification, and external addition. In other words, in the third manufacturing method, the other materials are mixed once without using a master batch, and then the charge control agent is added separately, and then the colorant, etc. are added.

In Example 3, 3.2 parts by weight of microcrystalline wax (Hi-Mic-1090, manufactured by Nippon Seiro Co., Ltd.), 1.5 parts by weight of magnetic material (BL-220, manufactured by Titan Kogyo Co., Ltd.), 60 parts by weight of H-body resin, and 40 parts by weight of L-body resin were added and mixed and dispersed in a Henschel mixer (first mixing). The mixing conditions in the Henschel mixer were a rotation speed of 1200 rpm and a rotation time of 2.5 minutes.

1 part by weight of a charge control agent (LR-147A, manufactured by Nippon Carlit Co., Ltd.) was added to the above mixture (first mixing), and the mixture was mixed and dispersed again (second mixing) in the Henschel mixer. The mixing conditions in the Henschel mixer were a rotation speed of 1200 rpm and a rotation time of 1 minute 15 seconds.

10 parts by weight of a colorant (MA-77, manufactured by Mitsubishi Chemical Corporation) was added to the above mixture (second mixing) and mixed and dispersed again in the Henschel mixer (third mixing). The mixing conditions in the Henschel mixer were a rotation speed of 1200 rpm and a rotation time of 5 minutes.

The above mixture (third mixing) was melt-kneaded using a twin-screw extruder. The operating conditions of the twin-screw extruder were cylinder set temperature 110°C, barrel rotation speed 250 rpm, and raw material supply rate 10 kg/hour.

In Comparative Example 1, the mixing conditions were as follows: the rotation speed of the first mix in the Henschel mixer was 800 rpm, the rotation time was 1 minute, the rotation speed of the second mix was 800 rpm, the rotation time was 1 minute, and the rotation speed of the third mix was 800 rpm, the rotation time was 3 minutes 20 seconds. The timing of adding materials and the kneading were the same as in Example 3.

In this embodiment, the colorant is mixed in the third mixing, but this is not limited to this, and over-pulverized toner, etc. may be mixed in. In this embodiment, the kneading conditions are the same as those in the first and second manufacturing methods, but this is not limited to this, and different kneading conditions may be used.

The mixing conditions for the Henschel mixer in these examples and comparative examples are listed in Table 1 below. In Table 1, the units of rotation speed are rpm, and the units of time are seconds.

[Cooling grinding process, classification process]
The cooling and grinding step and the classification step are common to the first to third production methods.
The resulting kneaded product was cooled with a cooling belt and then coarsely crushed in a speed mill equipped with a φ1 mm screen to obtain a coarsely crushed product having a particle size of 1 mm.

The coarsely crushed material obtained above was finely ground using a counter jet mill (product name: AFG, manufactured by Hosokawa Micron Corporation) to obtain finely ground particles with a volume average particle size of 6.2 μm.

The finely ground particles obtained above were classified using a rotary classifier (product name: TSP Separator, manufactured by Hosokawa Micron Corporation) to obtain non-additive fine particles (non-additive toner) with a volume average particle size of 6.7 μm.

The measurement and evaluation results for the toners obtained in these examples and comparative examples are shown in Table 2 below.

As is clear from Table 2, the toners of Examples 1 to 6, in which Dc/Dt is 0.1 or more and 0.2 or less, and Dc90/Dc10 is 3.0 or less, were excellent in image quality evaluation and suppressed the occurrence of image defects such as fog.

In contrast, comparative examples 1 to 4, which did not meet these requirements, were rated as "× (unacceptable)" for image quality, and were inferior to the examples.

Next, the toners of Examples 1-1 to 1-9 were manufactured according to the following procedure as toners having a Dc/Dt of 0.1 or more and 0.2 or less, and a Dc90/Dc10 of 3.0 or less, and the adhesion strength of the charge control agent, the segregation rate of the charge control agent, and the content rate of toner particles with a number-average particle size of 4 μm or less (fine powder rate) were measured, and image quality was evaluated.

In Examples 1-1 to 1-9, toner was produced in the same manner as in Example 1 above, except that the amount of charge control agent added was changed by the second production method described above. In the second production method, the master batch, part of the binder resin (H body), release agent, and magnetic material were mixed, and then the charge control agent was added to the mixture and mixed again. After all the materials were mixed, the toner was produced through melt-kneading, pulverization, classification, and external addition.

[Example 1-1]
In Example 1-1, 3.2 parts by weight of microcrystalline wax (Hi-Mic-1090, manufactured by Nippon Seiro Co., Ltd.), 1.5 parts by weight of magnetic material (BL-220, manufactured by Titan Kogyo Co., Ltd.), and 60 parts by weight of H-body resin were added to the above-mentioned master batch, and mixed and dispersed (first mixing) in a Henschel mixer. The mixing conditions in the Henschel mixer were a rotation speed of 1500 rpm and a rotation time of 2.5 minutes.

0.05 parts by weight of a charge control agent (LR-147A, manufactured by Nippon Carlit Co., Ltd.) was added to the above mixture (first mixing), and the mixture was mixed and dispersed again (second mixing) in the Henschel mixer. The mixing conditions in the Henschel mixer were a rotation speed of 1500 rpm and a rotation time of 2.5 minutes.

The above mixture (second mixing) was melt-kneaded using a twin-screw extruder. The operating conditions of the twin-screw extruder were cylinder set temperature 110°C, barrel rotation speed 250 rpm, and raw material supply rate 10 kg/hour.

The resulting kneaded material was cooled on a cooling belt and then coarsely crushed in a speed mill with a φ1 mm screen to obtain a coarsely crushed material with a particle size of 1 mm.

The coarsely crushed material obtained above was finely ground using a counter jet mill (product name: AFG, manufactured by Hosokawa Micron Corporation) to obtain finely ground particles with a volume average particle size of 6.2 μm.

The finely ground particles obtained above were classified using a rotary classifier (product name: TSP Separator, manufactured by Hosokawa Micron Corporation) to obtain non-additive fine particles (non-additive toner) with a volume average particle size of 6.7 μm.

[Examples 1-2 to 1-9]
A toner of Example 1-2 was obtained in the same manner as in Example 1-1, except that the amount of the charge control agent (LR-147A, manufactured by Nippon Carlit Co., Ltd.) added was changed to 0.08 parts by weight.
For Examples 1-3 to 1-9, the amount of the charge control agent (LR-147A, manufactured by Nippon Carlit Co., Ltd.) added was changed to 0.1 parts by weight in Example 1-3, 0.15 parts by weight in Example 1-4, 0.5 parts by weight in Example 1-5, 1.0 parts by weight in Example 1-6, 2.0 parts by weight in Example 1-7, 2.5 parts by weight in Example 1-8, and 3.2 parts by weight in Example 1-9. Except for this, each toner was obtained in the same manner as in Example 1-1.

The measurement and evaluation results for the toners obtained in Examples 1-1 to 1-9 are shown in Tables 3 and 4 below.

As is clear from Table 3, the toners of Examples 1-2 to 1-8, in which the adhesion strength of the charge control agent in the toner is 35% or more and 75% or less, had better image quality evaluations and suppressed the occurrence of image defects such as fog than the toners of Examples 1-1 (adhesion strength 33.7%) and 1-9 (adhesion strength 78.1%). The toners of Examples 1-5 to 1-7, in which the adhesion strength of the charge control agent in the toner is 50% or more and 65% or less, had even better image quality evaluations and suppressed the occurrence of image defects such as fog than the toners of the other examples.

The adhesion strength of the charge control agent is thought to correlate with the particle size of the charge control agent; if the particle size of the charge control agent is large, the over-pulverized toner contains a large amount of the charge control agent, and the charge control agent in the toner particles is more likely to be exposed to the toner surface, resulting in low adhesion strength. On the other hand, if the particle size of the charge control agent is small, the charge control agent is not exposed to the toner surface, its effect as a charge control agent is reduced, and its adhesion strength is thought to be high.

As is clear from Table 4, the toners of Examples 1-2 to 1-8, in which the charge control agent segregation rate is 102% or more and 130% or less, had better image quality evaluations and suppressed the occurrence of image defects such as fog than the toners of Examples 1-1 (segregation rate 101%) and 1-9 (segregation rate 142%). The toners of Examples 1-5 to 1-7, in which the charge control agent segregation rate is 106% or more and 115% or less, had even better image quality evaluations and suppressed the occurrence of image defects such as fog than the toners of the other examples.

The toners of Examples 1-3 to 1-8, in which the content of toner particles with a number-average particle size of 4 μm or less (fine powder ratio in the toner after classification) is less than 30%, had better image quality evaluations and suppressed the occurrence of image defects such as fogging than the toners of Examples 1-1 (fine powder ratio: 40%) and 1-9 (fine powder ratio: 38%).

<Other embodiments>
It should be noted that the embodiments disclosed herein are illustrative in all respects and are not intended to be a basis for a restrictive interpretation. Therefore, the technical scope of the present invention is not interpreted solely by the above-described embodiments, but is defined based on the claims. The technical scope of the present invention includes all modifications within the scope and meaning equivalent to the claims.

Claims (4)

A toner having toner particles including a binder resin, a colorant, and a charge control agent,
the toner particles are ground toner particles;
When the volume average particle diameter of the toner particles is Dt and the number average dispersed particle diameter of the charge control agent in the toner particles is Dc, Dc/Dt is 0.13 or more and 0.14 or less ;
In the particle size distribution of the charge control agent in the toner particles, when the dispersed particle size of particles having a cumulative number percentage of 90% from the small particle size side is Dc90 and the dispersed particle size of particles having a cumulative number percentage of 10% from the small particle size side is Dc10, Dc90/Dc10 is 2.3 or more and 2.7 or less ,
The toner is characterized in that the adhesion strength of the charge control agent in the toner is 50% or more and 65% or less . 2. The toner according to claim 1 ,
The toner is characterized in that the volume average particle size of the toner particles is 4 μm or more and 9 μm or less. The toner according to claim 1 or 2 ,
The toner is characterized in that the content of toner particles having a number average particle size of 4 μm or less in the toner is less than 30%. A method for producing the toner according to any one of claims 1 to 3 , comprising the steps of:
a mixing step of mixing raw materials including the binder resin, the colorant, and the charge control agent;
A melt-kneading step of melt-kneading the mixture obtained in the mixing step;
A cooling and grinding step of cooling and solidifying the kneaded product obtained in the melt kneading step and then grinding it;
a classification step of classifying the pulverized product obtained in the cooling and pulverizing step into first pulverized particles, second pulverized particles having a volume average particle size smaller than that of the first pulverized particles, and third pulverized particles having a volume average particle size larger than that of the first pulverized particles, and recovering the first pulverized particles as toner particles;
A method for producing a toner, characterized in that, when the amount of the charge control agent contained in the second pulverized particles is A and the amount of the charge control agent contained in the first pulverized particles is B, a segregation rate of the charge control agent defined as A/B x 100 is 102% or more and 130% or less.

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