JP2010079008A - Method for manufacturing electrophotographic toner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method capable of manufacturing an electrophotographic toner, which is excellent in color developing property and also has a stable light resistance over a long period of time, and to provide an electrophotographic toner obtained by the method. <P>SOLUTION: The method for manufacturing a toner includes: a step of kneading a mixture, containing a binder resin, a colorant, and an UV absorbent containing titanium oxide fine particles, having a particle diameter of ≤100 nm by 5 to 30 wt.% with respect to the total amount of the binder resin, the colorant and the UV absorbent, in an open roll type kneading machine; and a step of pulverizing and classifying the kneaded material. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing an electrophotographic toner, and more particularly, to a method for producing an electrophotographic toner excellent in light resistance and an electrophotographic toner produced by the method.

  The properties required for the pigment used in the electrophotographic toner are color development, transparency and light resistance. The color developability is caused by the chemical structure peculiar to the pigment, the transparency is largely caused by the pigment dispersion diameter, and the light resistance is caused by the particle diameter and the chemical structure. Among these, the light resistance is generally low because pigments are damaged by ultraviolet rays, and improvement thereof is desired. In particular, in recent diversification of output images of printers, there is an increasing demand for light resistance of toner for electrophotography.

  As techniques for improving the light resistance of toner, there are those described in Patent Documents 1 to 5. In any of these techniques, an ultraviolet absorber is added to the toner in order to prevent damage to the pigment due to ultraviolet rays. However, since these ultraviolet absorbers are all organic compounds, they are expensive and themselves are damaged by ultraviolet rays, so that the ultraviolet absorption effect is not permanent.

Conventionally, an inorganic compound such as titanium oxide or zinc oxide is added to cosmetics or the like in order to reflect and scatter ultraviolet rays. A toner is also known in which titanium oxide particles surface-treated with silicone oil are added as a grinding aid (see, for example, Patent Document 6). However, none of these add titanium oxide particles as an ultraviolet absorber in order to improve the light resistance of the toner.
JP 60-93453 A JP-A-1-172773 JP-A-2-264264 Japanese Patent Laid-Open No. 9-80797 JP 2008-52086 A JP 2007-93681 A

  The present invention has been made under the circumstances as described above, and is a method for producing an electrophotographic toner capable of producing an electrophotographic toner having excellent color development and transparency and having stable light resistance over a long period of time. Another object is to provide an electrophotographic toner obtained thereby.

  In order to solve the above-mentioned problem, a first aspect of the present invention is a UV absorber composed of a binder resin, a colorant, and titanium oxide fine particles having a particle size of 100 nm or less, the binder resin, the colorant, and the UV absorber. A method for producing an electrophotographic toner comprising: a step of kneading a mixture containing 5 to 30% by mass with respect to the total amount by an open roll type kneader; and a step of pulverizing and classifying the kneaded product. I will provide a.

  According to a second aspect of the present invention, there is provided an electron produced by the above method, comprising 5 to 30% by mass of a binder resin, a colorant, and an ultraviolet absorber composed of titanium oxide fine particles having a particle size of 100 nm or less. Provide photographic toner.

  According to the present invention, there is provided a method capable of producing an electrophotographic toner having stable light resistance over a long period of time, and an electrophotographic toner obtained thereby.

  The best mode for carrying out the invention will be described below.

  An electrophotographic toner manufacturing method according to an embodiment of the present invention includes a binder resin, a colorant, and an ultraviolet absorber composed of titanium oxide fine particles having a particle size of 100 nm or less, the binder resin, the colorant, and the ultraviolet absorber. Characterized in that it comprises a step of kneading a mixture containing 5 to 30% by mass with respect to the total amount by an open roll type kneader and a step of pulverizing and classifying the kneaded product. The electrophotographic toner produced by such a method exhibits excellent color developability, transparency, and light resistance.

  Titanium oxide fine particles used as an ultraviolet absorber are cheaper and more durable than conventional ultraviolet absorbers made of organic compounds. Further, since fine particles having a particle size of 100 nm or less are used, the obtained toner is excellent in transparency. When the particle diameter of the titanium oxide fine particles exceeds 100 nm, the obtained toner is excellent in light resistance but is inferior in transparency and slightly inferior in color development. The preferable particle diameter range of the titanium oxide fine particles is 15 to 100 nm.

  Moreover, since it is a fine particle with a particle size of 100 nm or less, the addition amount of the titanium oxide fine particle can be made larger than that of a conventional ultraviolet absorber, thereby improving the light resistance. Therefore, when the addition amount of the titanium oxide fine particles is less than 5% by mass with respect to the total amount of the binder resin, the colorant and the ultraviolet absorber, the light resistance is poor. However, when it exceeds 30% by mass, the color developability and transparency are slightly inferior. The range of preferable addition amount of the titanium oxide fine particles is 5 to 15% by mass.

  Hereinafter, the method for producing an electrophotographic toner according to an embodiment of the present invention will be described more specifically.

  First, a toner raw material containing a binder resin, a colorant, and titanium oxide fine particles is mixed by 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.

  The raw material mixture is then fed to a kneader where it is melt kneaded. As the kneader, it is necessary to use an open roll type kneader such as a continuous two-roll mill, a continuous three-roll mill, and a batch-type roll mill. By kneading using an open roll type kneader, it is usually possible to highly disperse titanium oxide fine particles that are difficult to disperse in the binder resin.

  Using an extrusion kneader such as a biaxial extrusion kneader or a single screw extrusion kneader makes it difficult to highly disperse titanium oxide fine particles that are difficult to disperse in the binder resin, and the resulting toner has a color developing property. As a result, the transparency is poor.

  FIG. 1 is a front view showing an open type continuous two-roll mill. The open-type continuous two-roll mill includes two open-type rolls 12 and 13 arranged in parallel and a discharge unit 14 through which the kneaded material is discharged. Helical grooves for transporting the kneaded material are formed on the surfaces of the rolls 12 and 13.

  The raw material mixture supplied between the rolls 12 and 13 from the hopper 11 is repeatedly compressed and kneaded by the rotation of the rolls 12 and 13 while being wound around the surfaces of the rolls 12 and 13. It moves to the discharge part 14 side by the groove, and the kneaded material is discharged from there.

  FIG. 2 is a side view showing an example of a twin screw extrusion kneader. This twin-screw extrusion kneader includes a hopper 21 to which a raw material mixture is supplied, a cylinder 22 divided into a plurality of zones C1 to C8, and a die nozzle 23 from which a molten mixture is discharged. Each of the zones C1 to C8 of the cylinder 22 is heated to a predetermined temperature by a heater (not shown), and two cylinders are arranged in the cylinder 22 so that their axes are parallel or have a predetermined angle. A cylindrical screw (not shown) is arranged. The screw rotates in the same direction or in the opposite direction.

  The raw material mixture supplied from the hopper 21 is introduced into the cylinder 22 and is melted by the heat from the heated cylinder 22 in the gap between the screws, and is mixed by the compression force and shearing force due to the rotation of the screw. Then, it moves to the die nozzle 23 side along the spiral blade of the screw and is discharged from the die nozzle 23.

  The melt-kneaded product from the kneader is usually cooled, pulverized, and classified to a predetermined particle size according to the method used for producing the toner to obtain an electrophotographic toner. 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 airflow can be used for cooling, an airflow pulverizer such as a collision plate pulverizer can be used for pulverization, and various airflow classifiers can be used for classification. it can.

  The titanium oxide fine particles to be added may be of a rutile type or anatase type crystal type.

  The binder resin that can be used in the method for producing an electrophotographic toner according to the embodiment of the present invention described above 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.

  Examples of the colorant include the following.

  Examples of the color pigment for magenta include C.I. I. Pigment Red 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 21, 22, 23, 30, 31, 32, 37, 38, 39, 40, 41, 48, 49, 50, 51, 52, 53, 54, 55, 57, 58, 60, 63, 64, 68, 81, 83, 87, 88, 89, 90, 112, 114, 122, 123, 163, 202, 206, 207, 209, 238, C.I. I. Pigment violet 19, C.I. I. Bat red 1, 2, 10, 13, 15, 23, 29, 35, etc. are mentioned.

  Examples of the color pigment for cyan include C.I. I. Pigment blue 2, 3, 15, 16, 17; I. Acid Blue 6; I. Acid Blue 45 or a copper phthalocyanine pigment having 1 to 5 phthalimidomethyl groups substituted on the phthalocyanine skeleton.

  Examples of the color pigment for yellow include C.I. I. Pigment Yellow 1, 2, 3, 4, 5, 6, 7, 10, 11, 12, 13, 14, 15, 16, 17, 23, 65, 73, 74, 83, 93, 97, 155, 180, C. I. Vat yellow 1, 3, 20 etc. are mentioned.

  The method for producing an electrophotographic toner according to an embodiment of the present invention can include a charge control agent and a release material in addition to the binder resin, the colorant, and the titanium oxide fine particles. As the charge control agent and the release agent, any of those usually used for electrophotographic toners can be used.

  Examples of the present invention and comparative examples are shown below to describe the present invention more specifically.

Example 1
The following raw materials were mixed with a Henschel mixer (made by Mitsui Mining Co., Ltd.), and melt-kneaded with an open roll type kneader (Needex: made by Mitsui Mining Co., Ltd.).

Cross-linked polyester resin (softening point 141 ° C., glass transition point 62 ° C.) 92 parts by weight Colorant (CI Pigment Red 57: 1) 3 parts by weight Release agent (Bicol 660P, manufactured by Sanyo Chemical Co., Ltd.) 3 parts by weight Charged Control agent (E-84 manufactured by Orient Chemical Co., Ltd.) 1 part by mass Ultraviolet absorber (titanium oxide: particle size 15 nm) 5 parts by mass The kneading conditions by Kneedex are shown in Table 1 below.

  Thereafter, the melt-kneaded product is cooled, pulverized to a particle size of 8.8 μm with a collision plate type pulverizer (“IDS-2” manufactured by Nippon Pneumatic Industry Co., Ltd.), and further classified by a classifier (Nippon Pneumatic Industry Co., Ltd.). ) To obtain colored fine particles having a particle size of 9.0 μm, and then 100 parts by weight of the colored fine particles and 1 part by weight of hydrophobic silica (“R972” manufactured by Nippon Aero Co., Ltd.) Mixing with a Henschel mixer gave a magenta toner.

Examples 2-4, Comparative Example 1
Four types of magenta toners were obtained in the same manner as in Example 1 except that the particle size of titanium oxide was variously changed as shown in Table 3 below.

Examples 5-7, Comparative Examples 2-4
Six types of magenta toners were obtained in the same manner as in Example 1 except that the addition amount of titanium oxide was variously changed as shown in Table 3 below.

Comparative Example 5
A magenta toner was obtained in the same manner as in Example 1 except that the raw material mixture was kneaded by a biaxial extrusion kneader (PCM-43: manufactured by Ikegai Co., Ltd.).

Table 2 below shows the kneading conditions with PCM-43.

  The following characteristics were measured for the toner produced as described above.

1. Particle size measurement device: Multisizer II (manufactured by Coulter Co., Ltd.)
Sample: A small amount of sample, purified water, and a surfactant were placed in a beaker and dispersed with an ultrasonic cleaner.

  Measurement: The aperture was 100 μm, the count was 50,000, and the volume average particle size was obtained.

2. Evaluation of color development In a normal environment (25 ° C., 50% RH), toner is mounted on a non-magnetic one-component developing device “Casio Page Prest N-5” (manufactured by Casio Computer Co., Ltd .: 29 color printers per minute) The color developability of the solid print image was visually evaluated according to the following criteria.

(Evaluation criteria)
A: Color development is very good.

  ○: Color development is good.

  Δ: Slightly dull.

  X: It is dull.

3. Evaluation of OHP transmittance The toner was mounted on a non-magnetic one-component developing device “Casio Page Presto N-5” (Casio Computer Co., Ltd., color printer, 29 sheets per minute) in a normal environment (25 ° C., 50% RH). After printing a solid print image using OHP paper (dedicated OHP sheet N-OHPS), the obtained image was projected onto a screen with an overhead projector, and color development and transparency were evaluated according to the following criteria.

  A: Very transparent.

  ○: Good.

  Δ: Slightly cloudy.

  X: Dark.

4). Light fastness evaluation An image printed on plain paper “XEROX-L” with magenta toner mounted on “SPEEDIA N5300” (manufactured by Casio Computer Co., Ltd.) with the fixing oil supply device removed, made by Suga Test Instruments: Super A xenon weather meter SX-75 was used, the light source used was 7.5 kW xenon lamp / outer: # 275 / inner: quartz, and the accelerated light resistance test was conducted at a black panel temperature of 63 ° C. The difference in hue change (ΔE) was measured using “SPECTRODENSITOMETER 938” (manufactured by X-rite), and the degree of fading was evaluated according to the following criteria.

  (Double-circle): (DELTA) E is less than 2.0 and is especially favorable on actual use.

  A: ΔE is 2.0 or more and less than 5.0, which is good for practical use.

  (Triangle | delta): (DELTA) E is 5.0 or more and less than 10.0, and it can be actually used.

  X: ΔE is 10.0 or more and cannot be used.

The above measurement results are shown in Table 3 below.

  From Table 3 above, the following can be understood. Titanium oxide fine particles having a particle size of 100 nm or less as an ultraviolet absorber are contained in an amount of 5 to 30% by mass with respect to the total amount of the binder resin, the colorant and the titanium oxide fine particles, and kneaded by Kneedex which is an open roll type kneader. The obtained toners of Examples 1 to 7 show excellent characteristics in all of color development, transparency, and light resistance.

  On the other hand, the toner of Comparative Example 1 using titanium oxide fine particles having a particle diameter exceeding 100 nm is inferior in color developability and transparency. In addition, the toners of Comparative Examples 2 and 3 in which the addition amount of titanium oxide fine particles is less than 5% by mass have poor light resistance, and the toner of Comparative Example 4 in which the addition amount of titanium oxide fine particles exceeds 30% by mass. Has poor color developability and transparency.

  Further, the toner of Comparative Example 5 obtained by kneading with PCM-43, which is a biaxial extrusion kneader, also has poor color development and transparency.

It is a front view which shows an example of the open type continuous 2 roll mill used for one Embodiment of this invention. It is a front view which shows an example of the biaxial extrusion kneader used for the comparative example of this invention.

Explanation of symbols

  11, 21 ... Hopper, 12, 13 ... Roll, 14 ... Discharge part, 22 ... Cylinder, 23 ... Die nozzle.

Claims (2)

Open roll type mixture containing 5-30% by mass of a binder resin, a colorant, and an ultraviolet absorber comprising titanium oxide fine particles having a particle diameter of 100 nm or less, based on the total amount of the binder resin, the colorant and the ultraviolet absorber. A method for producing an electrophotographic toner, comprising: a step of kneading with a kneader; and a step of pulverizing and classifying the kneaded product.   An electrophotographic toner comprising 5 to 30% by mass of an ultraviolet absorber comprising a binder resin, a colorant, and fine titanium oxide particles having a particle size of 100 nm or less, and produced by the method according to claim 1.

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