JP4980865B2 - Toner manufacturing method for developing electrostatic image - Google Patents

Description

  The present invention relates to a method for producing a toner for developing electrostatic images used in electrophotography, electrostatic recording, and the like.

In recent years, high color developability is desired for toner due to the demand for higher image quality.
This color development is greatly influenced by the dispersion state of the colorant in the toner.
That is, a toner image with good colorant dispersion has a good color developability and a bright color tone, whereas a toner image with poor colorant dispersion has a poor color developability and a dark color tone.
In addition, since the colorant itself has frictional charging properties, in a toner with poor colorant dispersion, the charge amount of individual toner particles becomes non-uniform, and image defects such as a decrease in image density occur. It becomes easy to do.

In order to prevent this poor colorant dispersion, a masterbatch in which the colorant is dispersed in the resin in advance is manufactured, and then mixed with the main resin and various additives, followed by melt-kneading and pulverization classification to form a toner. A method is used (see, for example, Patent Document 1).
A general toner manufacturing method using a master batch is shown in FIG.
First, a master batch is produced by kneading a resin and a colorant.
Next, the resin and the master batch are kneaded, cooled, and pulverized and classified to obtain a classified toner (the coarse powder may be returned to the pulverization and classification process, and the fine powder may be returned to the kneading process and reused).
Then, the toner is manufactured by externally adding the classified toner.
In this method, since the affinity between the colorant surface and the resin is increased during the production of the masterbatch, it has been confirmed that the colorant is well dispersed in the subsequent kneading process.

However, in the toner manufacturing method using the master batch, there is a problem that the process of manufacturing the master batch causes a cost increase.
In addition, there is a combination of a resin and a colorant that cannot be sufficiently dispersed even when a masterbatch is used, and a method of favorably dispersing the colorant by a method other than the masterbatch has been desired.

Japanese Patent Laid-Open No. 10-268573

  The present invention has been made in view of the problems as described above, and the purpose of the process is to disperse the colorant by a method other than the masterbatch, thereby reducing the cost and being excellent in color development. Another object of the present invention is to provide a method for producing a toner for developing an electrostatic image capable of obtaining a sufficient image density.

  The present invention has solved the above problems by the following technical configuration.

(1) A modification step of mixing a colorant and an additive to obtain a modified colorant having the additive attached to the surface; a kneaded product obtained by melt-kneading a binder resin and a raw material containing the modified colorant a kneading step to obtain, cooling the kneaded mixture, possess a pulverizing and classifying to obtain a classified toner by pulverization and classification,
The method for producing a toner for developing an electrostatic image , wherein the additive is either stearic acid or a stearic acid compound .
( 2 ) The method for producing a toner for developing an electrostatic charge image according to (1), wherein the additive is added in an amount of 1 to 15 parts by weight with respect to 100 parts by weight of the colorant.

According to the present invention, it is possible to provide a method for producing a toner for developing an electrostatic charge image, in which a colorant is favorably dispersed by a method other than a masterbatch, thereby reducing costs, excellent color developability, and obtaining a sufficient image density. Can do.
Furthermore, by dispersing the colorant very well, it is possible to provide a toner manufacturing method capable of obtaining a sufficient image density with a small amount of toner and realizing a reduction in toner consumption.

The toner manufacturing method of the present invention will be described with reference to FIG.
The toner production method of the present invention comprises a modification step of mixing a colorant and an additive to obtain a modified colorant having the additive attached to the surface, and melting a raw material containing the binder resin and the modified colorant. It has a kneading step of kneading to obtain a kneaded product, and a pulverizing and classifying step of cooling the kneaded product and pulverizing and classifying to obtain a classified toner.

(Reforming process)
First, a colorant and an additive are mixed to obtain a modified colorant having the additive attached to the surface.
Additives are those that adhere to the surface of the colorant and improve the dispersibility of the binder resin. For example, silica, stearic acid, stearic acid compounds (zinc stearate, calcium stearate, magnesium stearate, aluminum stearate) , Lithium stearate, etc.), titanium oxide, alumina and the like. Of these, silica, stearic acid and stearic acid compounds are preferably used from the viewpoint of colorant dispersibility. The reason is that the flowability of the colorant can be remarkably improved and high dispersion can be obtained.
Mixing is preferably performed by dry blending, and examples of the mixing apparatus include a double cone mixer, a V-type mixer, a drum-type mixer, a super mixer, a Henschel mixer, and a Nauter mixer.
The addition amount of the additive is preferably 1 to 15 parts by weight and more preferably 5 to 10 parts by weight with respect to 100 parts by weight of the colorant.

(Kneading process)
Next, in the kneading step, a raw material containing the binder resin and the modified colorant is melt-kneaded to obtain a kneaded product.
In the kneading process, a batch type (for example, a pressure kneader, a Banbury mixer, etc.) or a continuous hot melt kneader is used, but a monoaxial or biaxial continuous extruder is preferable because of the advantage that it can be continuously produced. . For example, KTK type twin screw extruder manufactured by Kobe Steel, TEM type twin screw extruder manufactured by Toshiba Machine Co., Ltd., twin screw extruder manufactured by Kay CK, PCM type twin screw extruder manufactured by Ikekai Tekko Co., Ltd., Kuriyama Manufacturing Co., Ltd. A twin screw extruder manufactured by Co., Ltd. and a co-kneader manufactured by Buss Co., Ltd. are preferable. An open roll type continuous kneader can also be used.

(Cooling process)
Thereafter, the kneaded product is cooled and solidified by a cooling step.

(Crushing classification process)
In the pulverization and classification step, the cooled and solidified kneaded product is pulverized and classified to obtain a classified toner.
First, it is roughly pulverized with a crusher, hammer mill, feather mill, etc., finely pulverized with a jet mill, a high-speed rotor rotary mill, etc., and pulverized to a predetermined toner particle size step by step.
Then, the toner is classified by an inertia class elbow jet, a centrifugal class microplex, a DS separator, a dry air classifier or the like to obtain a classified toner having a volume average particle diameter of 3 to 15 μm.
The coarse powder obtained at the time of classification may be returned to the pulverization and classification process, and the fine powder may be returned to the kneading process and reused.

Next, an external addition process for attaching an external additive to the classified toner is performed as necessary.
A predetermined amount of the classified toner and various external additives are blended, and the mixture is stirred and mixed with a high-speed stirrer that gives shearing force to the powder such as a Henschel mixer or a super mixer.
At this time, since heat is generated inside the external additive machine and it becomes easy to generate agglomerates, it is preferable to adjust the temperature by means such as cooling the periphery of the container part of the external additive machine with water. The internal material temperature is preferably below the control temperature of about 10 ° C. lower than the glass transition temperature of the resin.

The toner of the present invention is obtained by the above-described method, and the volume average particle diameter is preferably 3 μm to 10 μm, more preferably 5 μm to 8 μm. If the volume average particle size is less than 3 μm, the amount of ultrafine powder less than 2 μm increases, so fogging, image density reduction, occurrence of black spots and filming on the photoconductor, occurrence of fusing on the developing sleeve and layer thickness regulating blade, Cause etc. On the other hand, if it exceeds 10 μm, the resolution is lowered and a high-quality image cannot be obtained.
In the present application, the volume average particle size is determined by measuring the relative weight distribution by particle size using a Coulter Counter TA-II type (manufactured by Coulter Co.) with a 100 μm aperture tube.

The circularity of the toner of the present invention is 0.80 to 0.98, preferably 0.90 to 0.96. If the circularity is less than 0.80, the fluidity is inferior and the charge amount is insufficient, resulting in a decrease in image density. If it exceeds 0.98, the charge amount becomes excessive and the toner consumption increases.
The circularity is
Circularity = π · (diameter of circle equal to particle image area) / (perimeter of particle image)
The flow type particle image analyzer (manufactured by Sysmex, trade name: FPIA-2000).

The obtained toner can be used in a one-component development system, a two-component development system, and other development systems. In the two-component development method, it is used by mixing with a carrier.
As the carrier in the two-component development system, for example, nickel, cobalt, iron oxide, ferrite, iron, glass beads and the like can be used. These carriers may be used alone or in combination of two or more. The average particle size of the carrier is preferably 20 to 150 μm. In addition, the surface of the carrier may be coated with a coating agent such as a fluorine resin, an acrylic resin, or a silicone resin.

  The toner of the present invention may be a monochrome toner or a color toner, but is preferably used as a color toner, particularly a full color toner, in which the color development is remarkably improved.

  Next, toner raw materials other than the additive will be described.

(Binder resin)
Examples of the binder resin used in the present invention include styrenes such as styrene and chlorostyrene, monoolefins such as ethylene, propylene, butylene, and isobutylene, vinyl esters such as vinyl acetate, vinyl propionate, vinyl benzoate, and vinyl butyrate. Α-methylene aliphatic monocarboxylic acid such as methyl acrylate, ethyl acrylate, butyl acrylate, octyl acrylate, dodecyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, dodecyl methacrylate Acid esters, vinyl ethers such as vinyl methyl ether, vinyl ethyl ether, vinyl butyl ether, vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, vinyl isopropenyl ketone, cyclobutene, Ropenten can cyclohexene, cyclopentadiene, cyclohexadiene, norbornene, cyclic olefins having double bonds, such as dicyclopentadiene, be mentioned homopolymers and copolymers, such as.
Moreover, the polyester resin produced | generated from carboxylic acids, such as maleic acid, fumaric acid, a phthalic acid, and alcohol, such as bisphenol A (EO / PO addition product) and ethylene glycol, can be illustrated.
Among these, styrene- (meth) acrylic acid ester copolymer resins, cyclic olefin copolymer resins such as ethylene-norbornene, and polyester resins are preferably used.
In particular, a polyester resin is preferably used from the viewpoint of durability.
In the case of a nonmagnetic toner, the amount of the binder resin of the present invention is preferably 80 to 95 parts by weight per 100 parts by weight of the toner.

(Coloring agent)
Next, the colorant will be described.
As the pigment system of the yellow colorant, compounds represented by condensed azo compounds, isoindolinone compounds, anthraquinone compounds, azo metal complex methine compounds, and allylamide compounds are used.
Specifically, C.I. I. Pigment Yellow 3, 7, 10, 12, 13, 14, 15, 17, 23, 24, 60, 62, 73, 74, 75, 83, 93, 94, 95, 99, 100, 101, 104, 108, 109, 110, 111, 117, 122, 123, 128, 129, 138, 139, 147, 148, 150, 155, 166, 168, 169, 177, 179, 180, 181, 183, 185, 191: 1, 191, 192, 193, and 199 are preferably used.
Examples of the dye system include C.I. l. solventYellow33, 56, 79, 82, 93, 112, 162, 163, C.I. I. disperse Yellow 42.64.2011.211.

As the magenta colorant, condensed azo compounds, diketopyrrolopyrrole compounds, anthraquinones, quinacridone compounds, basic dye lake compounds, naphthol compounds, benzimidazolone compounds, thioindigo compounds, and perylene compounds are used.
Specifically, C.I. I. Pigment Red 2, 3, 5, 6, 7, 23, 48: 2, 48: 3, 48: 4, 57: 1, 81: 1, 122, 146, 166, 169, 177, 184, 185, 202, 206, 220, 221, 238, 254, 269, C.I. I. Pigment Bio Red 19 is particularly preferable.

As the cyan colorant, copper phthalocyanine compounds and derivatives thereof, anthraquinone compounds, basic dye lake compounds, and the like can be used.
Specifically, C.I. I. Pigment Blue 1, 7, 15, 15: 1, 15: 2, 15: 3, 15: 4, 60, 62, and 66 are particularly preferably used.

  The addition amount of the colorant is 2 to 20 parts by weight, preferably 2 to 15 parts by weight with respect to 100 parts by weight of the binder resin, and less than 12 parts by weight considering the transparency of a suitable OHP film for the toner image. It is preferably used in the range of 3 to 9 parts by weight.

(Charge control agent)
Moreover, a charge control agent can be added to the present invention as necessary.
When added, examples of the positive charge control agent include nigrosine dyes, quaternary ammonium salt compounds, triphenylmethane compounds, imidazole compounds, and polyamine resins.
Examples of negative charge control agents include metal-containing azo dyes such as Cr, Co, Al, and Fe, salicylic acid metal compounds, alkyl salicylic acid metal compounds, curlyx arene compounds, boron complexes, and polymer type charge control agents. .
The addition amount is preferably about 0.05 to 10 parts by weight with respect to 100 parts by weight of the binder resin.

(Release agent)
Further, a release agent is added to the toner constituting the present invention as necessary.
Specific examples of the release agent dispersed in the toner include paraffin wax, polyolefin wax, Fischer tropish wax, ester wax, modified wax having an aromatic group, hydrocarbon compound having an alicyclic group, and natural wax. Examples thereof include long-chain carboxylic acids having a long-chain hydrocarbon chain having 12 or more carbon atoms, fatty acid metal salts, fatty acid amides, and fatty acid bisamides.
These release agents can be used alone or in combination of plural kinds. The addition amount of the release agent added to the binder resin is less than 30 parts by weight, preferably 100 parts by weight of the binder resin. 2 to 20 parts by weight is preferred.

(External additive)
The toner of the present invention preferably has an external additive attached to the surface from the viewpoint of imparting fluidity.
As the external additive, various inorganic or organic external additives can be used. In particular, inorganic substances such as silica, titanium oxide, alumina, zinc oxide, and magnesium oxide are used for improving the fluidity of the toner and suppressing the aggregation. A fine powder is preferred.
The amount of the external additive to be mixed varies depending on the external additive to be used and the average particle size, particle size distribution, etc. of the toner particles, but an amount for obtaining the desired toner fluidity can be appropriately selected. Generally, 0.05 to 10 parts by weight, and further 0.1 to 8 parts by weight is preferable with respect to 100 parts by weight of toner particles.
If the mixing amount is less than 0.05 parts by weight, the fluidity improving effect is small, the storage stability performance at high temperature is poor, and if the mixing amount is more than 10 parts by weight, filming is caused on the photosensitive member by a partially free external additive. It is not preferable because it occurs or accumulates inside the developing tank and causes troubles such as deterioration of the charging function of the developer.
In addition, the external additive is more preferably hydrophobized with a treatment agent such as silane coupling in the case of an inorganic fine powder from the viewpoint of stability in a high-humidity environment. For example, dimethyldichlorosilane, monooctyltrichlorosilane, hexamethyldisilazane, or silicone oil may be used as a processing agent for imparting negative charge, and aminosilane or the like may be used as a processing agent for imparting positive charge.

  In addition, magnetite, ferrite, conductive titanium, antimony oxide, tin oxide, cerium oxide, hydrotalcite compounds, acrylics other than those for improving fluidity for the purpose of adjusting the electrical resistance of toners and abrasives as external additives An appropriate amount of fine powders such as beads, silicone beads, and polyethylene beads may be mixed, and the mixing amount is preferably 0.005 to 10 parts by weight with respect to 100 parts by weight of the toner.

  Furthermore, resin fine powders such as polytetrafluoroethylene resin powder and polyvinylidene fluoride resin powder may be attached as an external additive. The proportion of the resin fine powder added to the toner can be appropriately selected from the range of 0.01 to 8 parts by weight, preferably 0.1 to 5 parts by weight, and more preferably 0 to 100 parts by weight of the toner. .1 to 4 parts by weight.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example, this invention is not limited by these Examples.

[ Reference Example 1]
First, the following raw materials were mixed uniformly at 2800 rpm for 5 minutes using a Henschel mixer (trade name: “Henschel Mixer 20L”, manufactured by Mitsui Mining Co., Ltd.), and a modified colorant having an additive adhered to the surface was obtained. Obtained.
Cyan pigment 100 parts by weight (manufactured by Dainichi Seika Kogyo Co., Ltd., trade name: “Pigment 15: 4”)
Silica A 10 parts by weight (Aerosil, average primary particle size 16 nm, BET specific surface area 130 m ² / g)

Next, a Henschel mixer (Mitsui Mining Co., Ltd., trade name: “Henschel Mixer 20L”) was mixed uniformly for 5 minutes at 2800 rpm, and then a twin-screw kneading extruder (Ikegai Co., Ltd., product) Name: “PCM-30”) was melt-kneaded under the conditions of a rotational speed of 200 rpm and a discharge rate of 3.0 kg / hr, and the kneaded product was rolled with two rolls and allowed to cool.
・ Binder resin: 100 parts by weight of polyester resin (Mitsubishi Rayon Co., Ltd., Mw25000, Mn5000, Tg (shoulder) 60 ° C.)
-Modified colorant: 4.5 parts by weight-Charge control agent: 2.0 parts by weight of boron complex particles (made by Nippon Carlit Co., Ltd., trade name: "LR-147")
-Mold release agent: 7 parts by weight of wax (manufactured by Kato Yoko Co., Ltd., trade name: “Carnauba No. 2 powder”)

Next, the cooled kneaded product was coarsely pulverized with a hammer mill and finely pulverized with a jet mill (manufactured by Hosokawa Micron Corporation, trade name: “200 APG”).
Then, the toner was classified with a dry air classifier (trade name: “100ATP” manufactured by Hosokawa Micron Corporation) to obtain a classified toner having a volume average particle diameter of 7.1 μm and a circularity of 0.892.

Next, the following external additive consisting of silica and titanium oxide was added to 100 parts by weight of the classified toner and mixed with a 10 L Henschel mixer for 5 minutes at a rotational speed of 2800 rpm to obtain a toner (external addition step).
Silica B 0.2 parts by weight (manufactured by Clariant Japan, average primary particle size 17.5 nm, BET specific surface area 140 m ² / g)
・ 0.5 parts by weight of titanium oxide (manufactured by Aerosil Co., Ltd., primary particle size 10 nm, BET specific surface area 65 ± 10, treatment agent octylsilane)

Thereafter, 5.0 parts by weight of the obtained toner and 95.0 parts by weight of a ferrite carrier (manufactured by Powdertech) having an average particle size of 30 μm were mixed to obtain a cyan developer.
Further, the above cyan pigment is replaced with a magenta pigment (trade name: “Pigment 57-1” manufactured by Dainichi Seika Kogyo Co., Ltd.) and a yellow pigment (trade name: “Fast Yellow 74-16” manufactured by Sanyo Dye Co., Ltd.). Similarly, a magenta developer and a yellow developer were obtained.
The nonmagnetic two-component developer of Reference Example 1 was produced as described above.

[Example 2]
The following zinc stearate was used in place of the silica A of Reference Example 1.
・ 10 parts by weight of zinc stearate (manufactured by Sakai Chemical Industry Co., Ltd., trade name: “SZ-PF”)
Otherwise, the nonmagnetic two-component developer of Example 2 was obtained in the same manner as Example 1.

[Comparative Example 1]
In Comparative Example 1, the modifying step was not performed, and the colorant was melt-kneaded and cooled.
That is, the following composition was mixed uniformly at 2800 rpm for 5 minutes using a Henschel mixer (trade name: “Henschel Mixer 20L”, manufactured by Mitsui Mining Co., Ltd.), and then a twin-screw kneading extruder (trade name, manufactured by Ikegai Co., Ltd.). : "PCM-30") and melt-kneaded under the conditions of a rotation speed of 200 rpm and a discharge rate of 3.0 kg / hr, and the kneaded product was rolled with two rolls and allowed to cool.
-Binder resin: 100 parts by weight of polyester resin (Mitsubishi Rayon, Mw25000, Mn5000, Tg (shoulder) 60 ° C.)
Cyan pigment 4.1 parts by weight (manufactured by Dainichi Seika Kogyo Co., Ltd., trade name: “Pigment 15: 4”)
Charge control agent: 2.0 parts by weight of boron complex particles (Nippon Carlit Co., Ltd., trade name: “LR-147”)
-Mold release agent: 7 parts by weight of wax (manufactured by Kato Yoko Co., Ltd., trade name: “Carnauba No. 2 powder”)
Thereafter, the nonmagnetic two-component developer of Comparative Example 1 was obtained in the same manner as in Reference Example 1.

[Comparative Example 2]
In Comparative Example 2, a process for producing a master batch was performed instead of the reforming process.
That is, the following raw materials were mixed uniformly at 2800 rpm for 5 minutes using a Henschel mixer (trade name: “Henschel mixer 20L” manufactured by Mitsui Mining Co., Ltd.), melt-kneaded for 20 minutes with a pressure kneader, and then hammered A master batch was obtained by crushing with a crusher.
・ Binder resin: 70 parts by weight of polyester resin (Mitsubishi Rayon Co., Ltd., Mw25000, Mn5000, Tg (shoulder) 60 ° C.)
Cyan pigment 30 parts by weight (manufactured by Dainichi Seika Kogyo Co., Ltd., trade name: “Pigment 15: 4”)

Next, a Henschel mixer (Mitsui Mining Co., Ltd., trade name: “Henschel Mixer 20L”) was mixed uniformly for 5 minutes at 2800 rpm, and then a twin-screw kneading extruder (Ikegai Co., Ltd., product) Name: “PCM-30”) was melt-kneaded under the conditions of a rotational speed of 200 rpm and a discharge rate of 3.0 kg / hr, and the kneaded product was rolled with two rolls and allowed to cool.
・ Binder resin: 90.4 parts by weight of polyester resin (Mitsubishi Rayon Co., Ltd., Mw25000, Mn5000, Tg (shoulder) 60 ° C.)
Master batch: 13.7 parts by weight Charge control agent: 2.0 parts by weight of boron complex particles (manufactured by Nippon Carlit Co., Ltd., trade name: “LR-147”)
-Mold release agent: 7 parts by weight of wax (manufactured by Kato Yoko Co., Ltd., trade name: “Carnauba No. 2 powder”)
Thereafter, the nonmagnetic two-component developer of Comparative Example 2 was obtained in the same manner as in Reference Example 1.
Table 1 shows the main conditions of Examples and Comparative Examples.

  The toners of Examples and Comparative Examples were evaluated as follows.

(Pretreatment cost)
Working time and power consumption were evaluated for pretreatment costs.
◎: No cost, ○: Low cost, ×: High cost

Next, the two-component developers of Examples and Comparative Examples are filled in a cartridge, and the two-component development type copier is used with a printing rate of 20% and a printing speed of 24 pages / min. A printing durability test of up to 50000 sheets was performed at (developing voltage: -250 V, primary transfer voltage: 800 V).
Then, color development, image density and toner consumption were evaluated.

(Color development)
The color development was visually evaluated.
○: Good, ×: Dull

(Image density)
The image density was measured using a spectral densitometer (trade name: X-Rite 939, manufactured by X-Rite).
If the image density is 1.3 or more, there is no practical problem.

(Toner consumption)
The toner consumption was measured by measuring the amount of toner required to print 1000 sheets.
If the toner consumption is less than 50 g, there is no practical problem.
The results are shown in Table 2.

As shown in Table 2, in Reference Example 1 and Example 2, the pretreatment was low in cost, and there were no practical problems in terms of color developability, image density, and toner consumption.
In particular, Example 2 was excellent in toner consumption.
In contrast, Comparative Example 1 had practical problems in terms of color developability, image density, and toner consumption.
Further, in Comparative Example 2, the pretreatment was expensive, and there was a problem in practical use in terms of toner consumption.

As described above, according to the present invention, a toner for electrostatic charge image development that can suppress the cost, has excellent color developability, and obtain a sufficient image density can be obtained by dispersing the colorant by a method other than the master batch. A method can be provided.
Furthermore, by dispersing the colorant very well, it is possible to provide a toner manufacturing method capable of obtaining a sufficient image density with a small amount of toner and realizing a reduction in toner consumption.

The flowchart which shows the toner manufacturing method of the electrostatic charge image development of this invention. A flowchart showing a conventional method for producing a toner for developing an electrostatic charge image

Claims (2)

A modification step of mixing a colorant and an additive to obtain a modified colorant having the additive attached to the surface;
A kneading step of obtaining a kneaded product by melt-kneading a raw material containing a binder resin and the modified colorant;
The kneaded product was cooled, possess a pulverizing and classifying to obtain a classified toner by pulverization and classification,
The method for producing a toner for developing an electrostatic image , wherein the additive is either stearic acid or a stearic acid compound . The method for producing a toner for developing an electrostatic charge image according to claim 1, wherein the additive is added in an amount of 1 to 15 parts by weight with respect to 100 parts by weight of the colorant.

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