JP2009230065A - Electrophotographic toner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophotographic toner capable of obtaining a preferable image, in which a charge control agent is firmly bonded to toner host particle. <P>SOLUTION: The electrophotographic toner is prepared by adding the charge control agent and externally additive silica to the toner host particle containing binder resin and colorant, wherein the charge control agent is ground with grinding silica by a jet mill. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electrophotographic toner, and more particularly to an electrophotographic toner capable of obtaining a good image with a small amount.

  Electrophotographic image formation is generally performed by developing and visualizing an electrostatic charge image with toner and transferring the toner image obtained by development onto a sheet. As a method for producing such a toner used for image formation, there are a pulverization method, a polymerization method, and the like. In general, the pulverization method dominates.

  As a general manufacturing method of the pulverization method, raw materials such as a binder resin, a colorant, a release agent, and a charge control agent are mixed in a dry process, then melt-kneaded with a twin-screw extruder, etc. Crushing is performed to obtain a kneaded crushed material. Thereafter, fine pulverization is performed with a jet mill or the like, and the particle size is adjusted with a classifier so as to obtain an appropriate particle size distribution. Further, the toner is obtained by mixing with an external additive such as silica in a mixer to perform an external addition treatment and passing through a sieve to remove foreign matters and aggregates.

  As described above, the charge control agent is usually kneaded together with the binder resin, but since the charging phenomenon occurs on the surface of the toner particles, the charge control agent inside the toner particles is not involved in the charging phenomenon. For this reason, since non-magnetic one-component toners are particularly required to rise in the charge of the toner, it has been proposed to add a charge control agent to the toner.

In the case of a dry toner, the external addition method of the charge control agent uses a method in which the base toner and the charge control agent are vigorously stirred in a mixer, and in the case of a polymerized toner, most of the methods involve processing the charge control agent on the base in a wet manner. Accounted for.
In dry toners, there are problems such as aggregation and sticking, so the wet method cannot be applied. In addition, when stirring strongly with a mixer, since the particle size of the crystal particles of the charge control agent is as large as 10 μm or more, it is difficult to firmly adhere to the toner base at the end of the external addition. If the charge control agent is not firmly attached to the toner base, the toner will be released from the toner base when the toner receives a shearing force in the developing tank during printing, and normal frictional charging will not be performed. The charging property is lowered, and fogging and the like are remarkably generated in the image.

  The present invention has been made under the circumstances as described above, and an object thereof is to provide an electrophotographic toner capable of obtaining a good image by firmly binding a charge control agent to toner base particles.

  A first aspect of the present invention is an electrophotographic toner obtained by externally adding a charge control agent and silica for external addition to a toner base particle containing a binder resin and a colorant, wherein the charge control agent is pulverized. An electrophotographic toner characterized by being crushed by a jet mill together with silica for use.

In such an electrophotographic toner, the particle size of the charge control agent crushed by the jet mill can be 500 nm or less. Moreover, the quantity of the said silica for crushing can be 0.5-10 mass parts with respect to 100 mass parts of charge control agents.
Moreover, the average particle diameter of the said silica for crushing can be 20 nm or less.

A second aspect of the present invention is an electrophotographic toner obtained by externally adding a charge control agent and silica to a toner base particle containing a binder resin and a colorant, wherein the charge control agent has an average of 500 nm or less. An electrophotographic toner characterized by having a particle size is provided.
In the electrophotographic toner according to the first and second aspects of the present invention, at least one selected from the group consisting of LR-147, E-89, and E-84 is used as the charge control agent. I can do it. Further, it can be an electrophotographic toner used in a non-magnetic one-component developing device.

  The externally added silica is a mixture of two or more types of silica having different average particle diameters, and silica having a large average particle diameter may be treated with silicone oil.

  According to the present invention, there is provided an electrophotographic toner in which a charge control agent is firmly bonded to toner base particles and a good image can be obtained.

Hereinafter, embodiments of the present invention will be described.
The toner for electrophotography according to an embodiment of the present invention is characterized in that the charge control agent as an external additive is pulverized by a jet mill together with pulverizing silica.
The charge control agent usually does not exist as primary particles, and aggregates to a particle size of about 10 μm. Therefore, when the toner base particles are subjected to an external addition treatment, the charge control agent particles are removed from the toner base particles. It is difficult to adhere firmly to the particle surface. Therefore, when the toner receives a shearing force in the developing process, there is a problem that the charge control agent is detached from the toner base particles and the image is fogged due to a decrease in chargeability.

In the present invention, before the external addition treatment, the charge control agent is crushed by a jet mill, and the external addition treatment is performed using it. As a result, the charge control agent has a particle size that is sufficiently small to firmly adhere to the surface of the toner base particles, and adheres firmly to the surface of the toner base particles by the external addition treatment. Therefore, when the toner receives a shearing force in the developing process, the charge control agent is not detached from the toner base particles, and there is no problem that the image is fogged due to a decrease in chargeability.
In this case, it is necessary to crush the charge control agent by a jet mill together with a small amount of crushing silica. If the charge control agent is crushed alone, it is difficult to make the particle size small enough to firmly adhere to the surface of the toner base particles, and the charge control agent particles uniformly adhere to the surface of the toner base particles. It becomes difficult.

  The amount of silica for crushing is preferably 0.5 to 10 parts by mass with respect to 100 parts by mass of the charge control agent. If the amount of silica for crushing is less than 0.5 parts by mass, it is difficult to make the charge control agent small enough to adhere firmly to the surface of the toner base particles, and if it exceeds 10 parts by mass, the fluidity Becomes excessive and the shearing force for atomization is insufficient, and it is difficult to obtain a sufficiently small particle size.

The average particle size of the pulverizing silica is preferably 20 nm or less. When the average particle size of the pulverizing silica exceeds 20 nm, a spacer effect other than the fluidity of silica is imparted, and therefore the image characteristics (developability) of the toner are affected.
Note that the particle size of the charge control agent is small enough to firmly adhere to the surface of the toner base particles, for example, when the particle size is 500 nm or less. When the particle size of the charge control agent exceeds 500 nm, the charge control agent is easily detached from the toner base particles when the toner receives a shearing force in the development process.

In addition, as a charge control agent, the arbitrary thing normally used for the toner for electrophotography can be used, For example, alumina, such as LR-147, E-89, and E-84 (all are brand names), is used. It can be preferably used.
Hereinafter, a method for producing an electrophotographic toner according to an embodiment of the present invention will be specifically described.

First, a raw material mixture containing a binder resin, a colorant, a release agent, and the like is mixed using a mixer. As a mixing machine, arbitrary things, such as a Henschel mixer, a super mixer, a V-type blender, and a Nauta mixer, can be used.
Usable binder resins can be selected from a wide range including known ones. Specific examples include styrene resins such as polystyrene, styrene-acrylic acid ester copolymers, styrene-methacrylic acid copolymers, and styrene-butadiene copolymers, saturated polyester resins, unsaturated polyester resins, and epoxy resins. Phenolic resin, coumarone resin, xylene resin, vinyl chloride resin, polyolefin resin and the like can be exemplified, and two or more of these resins may be used in combination. Of these resins, polyester resins are preferred.

As the release agent, any of those usually used for electrophotographic toners can be used.
The raw material mixture is then fed to a kneader where it is melt kneaded. As the kneading machine, any type of extrusion kneading machine such as a twin-screw extrusion kneading machine and a single-screw extrusion kneading machine, an open roll type kneading machine such as a continuous two-roll mill, a continuous three-roll mill, and a batch roll mill can be used. Things can be used.

  The melt-kneaded product discharged from the kneader is usually cooled, pulverized, and classified according to a method used for toner production to obtain a toner particle matrix having a predetermined average particle diameter. The cooling means, the pulverizing means, and the classification means are not particularly limited, and those usually used for toner production can be employed. For example, a cooling means by rolling or blowing an air flow can be used for cooling, and an airflow pulverizer such as a collision plate pulverizer can be used for pulverization, and various airflow classifiers can be used for classification. Can be used.

  A charge control agent and silica are externally added to the toner particle matrix thus obtained. The charge control agent is crushed as follows. That is, a mixture obtained by adding 0.5 to 10 parts by mass of silica (average particle size of 20 nm or less) to the charge control agent is crushed by a jet mill to obtain a charge control agent having an average particle size of 500 nm or less.

A jet mill is a pulverizing apparatus that pulverizes a workpiece with a high-pressure, high-speed gas ejected from a nozzle. In this embodiment, the jet mill is used for pulverizing a charge control agent. The charge control agent applied to the jet mill together with the silica is accelerated by a high-pressure and high-speed gas, for example, air, and is crushed by the collision of the particles, or by the collision with the collision plate.
The toner for electrophotography is obtained by adding the charge control agent thus pulverized together with the other external additive silica (silica for external addition) to the toner particle base, and mixing and stirring. . The externally added silica can be a mixture of two or more types of silica having different average particle diameters, and silica having a large average particle diameter is preferably treated with silicone oil. By doing so, it is possible to obtain an effect that an image excellent in transferability can be obtained due to a spacer effect and a reduction in surface energy.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.
FIG. 1 is a diagram illustrating a non-magnetic one-component image forming apparatus used in Examples and Comparative Examples. The toner for electrophotography of the present invention can be suitably used for a non-magnetic one-component image forming apparatus.
The image forming apparatus shown in FIG. 1 includes a developing device 1 and a photosensitive drum 2. The developing device 1 applies a toner hopper 3 that contains toner therein, a supply roll 4 that supplies toner, and toner supplied from the supply roll 4 to the photosensitive drum 2, so that the electrostatic latent image on the surface of the photosensitive drum 2 is discharged. A developing roll 5 made of an elastic body for developing an image, and a doctor blade 6 that is in sliding contact with the developing roll 5 and regulates the thickness of the toner layer on the surface of the developing roll 5 are provided. Around the photosensitive drum 2, there are a charging roll 7 for uniformly charging the surface of the photosensitive drum 2, and an LED 8 for exposing a document image to the surface of the charged photosensitive drum 2 to form an electrostatic latent image. Has been placed.

A transfer belt 9 runs along with the rotation of the photosensitive drum 2 below the photosensitive drum 2. The developed toner image is transferred to the paper 11 by contacting the photosensitive drum 2 with the transfer sheet 10. The Incidentally, the toner that has not been transferred and remains on the surface of the photosensitive drum 2 after the transfer is removed by the cleaning blade 12, and is transferred into the collected toner hopper 15 in the toner hopper 3 by the transfer screw 14 in the transfer tube 13. Collected.
Examples 1-6
92 parts by mass of a polyester resin (softening point 133 ° C.) as a binder resin and C.I. 4 parts by mass of I Pigment Red 57: 1 and “NP056” (manufactured by Mitsui Chemicals, Inc .: polypropylene wax) as a mold release agent were mixed using a Henschel mixer (manufactured by Mitsui Mining Co., Ltd.).

  The mixed powder is melt-kneaded with a twin-screw kneader (screw diameter: 43 mm, L / D = 34), stretched, cooled, and coarsely crushed with a Rotoplex (manufactured by Hosokawa Micron Corporation, 2 mm screen). The mixture was pulverized by a pulverizer and classified by an air classifier so that the average particle diameter of the toner became 8.0 μm, whereby colored fine particles were obtained.

  2.0 parts by mass of “NY50” (manufactured by Nippon Aerosil Co., Ltd .: silicone oil-treated silica, 30 nm) and “RX200” (manufactured by Nippon Aerosil Co., Ltd .: Hexamethyl ヅ) 0.5 parts by mass of silazane-treated silica (12 nm) and a charge control agent (CCA) shown in Table 1 below were added and mixed with a Henschel mixer.

  CCA was blended with pulverizing silica for 1 minute in a mini blender, and then used as a pulverizer using IDS-2 type manufactured by Nippon Pneumatic Industry Co., Ltd., with a pressure of 0.6 MPa, 3 kg / hr. What was crushed with the feed amount was used. In the examples, five types of CCA1 to 5 having different addition amounts of silica for crushing and two types of CCA6 and CCA7 having different types of CCA were used.

After adding externally added silica and CCA to the colored fine particles, the mixture was sieved with an ultrasonic vibration sieve having an opening of 90 μm (mesh name: 166 mesh) to obtain a toner. As the ultrasonic vibration sieve, TMR-50 (sieve diameter: 500 mm) manufactured by Tokuju Kakujo Co., Ltd. was used.
Comparative Examples 1-3
Except for using CCA6 crushed without using crushing silica (Comparative Example 1), using CCA7 not crushed (Comparative Example 2), and not externally adding CCA (Comparative Example 3) Toners were produced in the same manner as in Examples 1-6.

以上のようにして製造した実施例１〜６及び比較例１〜３のトナーについて、篩工程における目詰まり状態を評価し、これらのトナーを用いて形成した画像を評価した。
試験−１
（篩工程での目詰まり）
トナー製造時、飾工程での目詰まり状態を評価する。外添後のトナー３ｋｇを超音波振動篩に投入し、篩が終了するまでの時間と篩後の目詰まり状態を評価した。
◎：篩時間が５分以内であり、篩目詰まりがない。
○：篩時間が５〜１０分で、軽度の詰まりはあるが問題のないレベル。
×：篩時間が１０分以上で、篩の目詰まりが多い。
試験−２
（画像評価）
図１に示すような非磁性一成分現像装置「カシオページプレストＮ−５」（カシオ計算機（株）製：カラープリンタ毎分２９枚（Ａ４横換算）機、プロセススピード１２９ｍｍ／ｓｅｃ）にトナーを実装し、通常環境（２５℃、５０％ＲＨ）において、普通紙（ＸＥＲＯＸ−Ｐ紙Ａ４サイズ）を用いて５％画像を１２，０００枚連続印字した後、Ａ４サイズにて、ベタ画像、ハーフトーン画像、白紙画像を採取し、画像評価を行った。評価項目として、ベタ均一性（印字範囲内の濃度ムラを評価）、スジの発生、かぶり評価を行った。

For the toners of Examples 1 to 6 and Comparative Examples 1 to 3 manufactured as described above, the clogging state in the sieving step was evaluated, and images formed using these toners were evaluated.
Test-1
(Clogging in sieving process)
During toner production, the clogging state in the decoration process is evaluated. 3 kg of the toner after external addition was put into an ultrasonic vibration sieve, and the time until the sieve was finished and the clogged state after the sieve were evaluated.
A: The sieve time is within 5 minutes, and there is no sieve clogging.
◯: Level of sieving time of 5 to 10 minutes, with slight clogging but no problem.
X: The sieve time is 10 minutes or more, and there are many clogged sieves.
Test-2
(Image evaluation)
A toner is applied to a non-magnetic one-component developing device “Casio Page Prest N-5” (manufactured by Casio Computer Co., Ltd .: color printer 29 sheets per minute (A4 horizontal conversion), process speed 129 mm / sec) as shown in FIG. After mounting and printing 12,000 sheets of 5% images continuously using plain paper (XEROX-P paper A4 size) in a normal environment (25 ° C., 50% RH) Tone images and blank paper images were collected and evaluated. As evaluation items, solid uniformity (evaluation of density unevenness in the printing range), generation of streaks, and fogging were evaluated.

  The average particle size of the toner was measured using Multisizer II (manufactured by Coulter Co., Ltd.) as a measuring device, and a small amount of sample, purified water, and surfactant were placed in a beaker as a sample and dispersed with an ultrasonic cleaner. Apertures were performed at 100 μm and counts were performed at 50,000 to obtain a volume average particle size.

The particle size of the external additive is a particle size obtained from an electron microscope for CCA without pulverization, and the particle size after pulverization was measured by a laser diffraction method.
The test results are shown in Table 2 below.

上記表２から、シリカとともにジェットミルにより解砕した帯電制御剤を外添したトナー（実施例１〜６）は、いずれも篩工程での目詰まりがなく、画像評価は良好であることがわかる。
これに対し、解砕用シリカを用いずに解砕したＣＣＡ６を外添したトナー（比較例１）及び解砕しないＣＣＡ７を外添したトナー（比較例２）は、いずれも篩工程において目詰まりが発生し、画像評価において、スジが発生し、かぶりが生じた。また、帯電制御剤を外添しないトナー（比較例３）は、篩工程において目詰まりは発生しなかったが、画像評価は劣っていた。

From Table 2 above, it can be seen that the toners (Examples 1 to 6) externally added with the charge control agent crushed by a jet mill together with silica are not clogged in the sieving step and the image evaluation is good. .
On the other hand, both the toner externally added with CCA6 crushed without using pulverizing silica (Comparative Example 1) and the toner externally added with CCA7 not pulverized (Comparative Example 2) are clogged in the sieving step. Was generated, streaks were generated in image evaluation, and fogging occurred. Further, the toner (Comparative Example 3) to which no charge control agent was externally added did not cause clogging in the sieving step, but the image evaluation was inferior.

1 is a diagram schematically illustrating an image forming apparatus using toner according to an embodiment of the present invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Developing device, 2 ... Photoconductor drum, 3 ... Toner hopper, 4 ... Supply roll, 5 ... Developing roll, 6 ... Doctor blade, 7 ... Charging roll, 8 ... LED, 9 ... Transfer belt, 10 ... Transfer sheet, DESCRIPTION OF SYMBOLS 11 ... Paper, 12 ... Cleaning blade, 13 ... Conveying tube, 14 ... Conveying screw, 15 ... Collected toner hopper.

Claims (8)

  An electrophotographic toner obtained by externally adding a charge control agent and external addition silica to a toner base particle containing a binder resin and a colorant, and the charge control agent is pulverized by a jet mill together with pulverization silica. An electrophotographic toner, characterized by being made.   The toner for electrophotography according to claim 1, wherein the particle size of the charge control agent crushed by the jet mill is 500 nm or less.   3. The electrophotographic toner according to claim 1, wherein the amount of the crushing silica is 0.5 to 10 parts by mass with respect to 100 parts by mass of the charge control agent.   The electrophotographic toner according to claim 1, wherein an average particle size of the crushing silica is 20 nm or less.   An electrophotographic toner obtained by externally adding a charge control agent and silica to a toner base particle containing a binder resin and a colorant, wherein the charge control agent has an average particle size of 500 nm or less. Toner for electrophotography.   The electrophotographic toner according to claim 1, wherein the charge control agent is at least one selected from the group consisting of LR-147, E-89, and E-84.   The toner for electrophotography according to claim 1, wherein the toner is used for a non-magnetic one-component developing device.   The externally added silica is a mixture of two or more types of silica having different average particle diameters, and silica having a large average particle diameter is treated with silicone oil. The toner for electrophotography as described.

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