JP2009157109A - Electrophotographic toner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophotographic toner equipped with both full durability and high fixability, by increasing the reinforcing effect with respect to binder resin. <P>SOLUTION: The electrophotographic toner contains a binder resin and a colorant and is such that the toner contains rice husk ash as the colorant. In this way, by using a colorant containing at least rice husk ash as the colorant, reinforcing effect with respect to the binder resin can be increased, which improves both the durability and the fixability of the electrophotographic toner, at the same time. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electrophotographic toner, and more particularly to a black electrophotographic toner.

  The black toner for electrophotography is generally obtained by heat-melting and kneading a binder resin, a black colorant, a charge control agent (CCA: Charge Control Agent), a wax and the like, followed by pulverization classification and further external additives. It is manufactured by adding. As the black colorant used in the production of the black toner, black magnetic powder such as magnetite is widely used in the case of magnetic toner, and black pigment or black dye such as carbon black is widely used in the case of non-magnetic toner. Various CCA can be used, and not only white CCA or light color CCA but also black CCA or dark color CCA can be used. By selecting from these, black CCA can be used. Or dark-colored CCA can be used together with the black colorant or instead of the black colorant.

  In general, toner development methods are roughly classified into a two-component development method using a developer in which a magnetic carrier and a toner are mixed, and a one-component development method in which only toner is used as a developer. In the case of the two-component development method, since the stress applied to the toner is small, sufficient durability can be obtained even if a resin having a relatively low melting point is used. However, in the case of the one-component developing method, particularly the non-magnetic one-component developing method, when the toner layer is formed on the developing roller, the toner passes under the toner layer forming blade. At this time, since the toner is subjected to a large pressure as a stress, in order to obtain the durability of the toner, a resin having a high melting point is often used. For this reason, it is difficult to ensure the toner fixing property. In particular, in order to cope with a high-speed machine of 30 ppm or more, the fixing device is increased in size and temperature, and further development for preventing stress from being applied to the toner. Various ingenuity to the vessel was necessary. Even in the case of magnetic toners, it has been impossible to avoid a decrease in toner fixability due to the inclusion of about 50% magnetic powder.

  Therefore, a toner having both sufficient durability and high fixability (wide non-offset region) is required as the toner performance.

  In response to such a demand, for example, Patent Document 1 proposes a toner whose toner performance is improved by using powdered charcoal, particularly wood-based powdered charcoal and coconut-based powdered charcoal. Patent Documents 2 and 3 propose toners using charcoal powder, activated carbon, or a colorant obtained by mixing them with carbon black.

JP 2004-309731 A JP-A-61-203463 Japanese Patent Laid-Open No. 3-164751

  However, the toners described in Patent Documents 1 to 3 have a problem that the reinforcing effect on the binder resin is weak and the durability of the toner is insufficient.

  Further, the toners described in Patent Documents 1 to 3 have a problem that high-temperature offset or wrapping (wrap jam) is likely to occur during fixing because the reinforcing effect on the binder resin is weak.

  Accordingly, the present invention has been made in view of such problems, and an object of the present invention is to provide an electrophotographic toner having both sufficient durability and high fixability by enhancing the reinforcing effect on the binder resin. There is.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have used at least rice bran charcoal as a black colorant to be contained in an electrophotographic toner, thereby reinforcing the binder resin. As a result, it was found that the durability and fixability of the electrophotographic toner can be improved at the same time, and the present invention has been completed based on this finding.

  That is, according to an aspect of the present invention, there is provided an electrophotographic toner containing a binder resin and a colorant, wherein the colorant contains chaff charcoal.

Here, as the chaff charcoal, it may be used those containing SiO ₂ 50 wt% or less than 20 wt%.

  Moreover, it is preferable that the pore diameter of the rice bran charcoal is 1 nm or more and 250 nm or less.

  The content of the rice bran charcoal is preferably 0.2 parts by mass or more and 8 parts by mass or less, more preferably 0.5 parts by mass or more and 6 parts by mass with respect to 100 parts by mass of the binder resin. It is as follows. If the amount of rice husk charcoal added is less than the above range, the effect of adding rice husk charcoal described later is not sufficient, and if the amount of rice husk charcoal added exceeds the above range, the binder resin becomes too hard. preferable.

  The electrophotographic toner may be for a one-component developing system.

  According to the electrophotographic toner according to the present invention as described above, the reinforcing effect on the binder resin can be enhanced by containing at least rice bran charcoal as the colorant. Durability and fixability can be improved at the same time.

  According to the present invention, an electrophotographic toner having both sufficient durability and high fixability can be provided by enhancing the reinforcing effect on the binder resin.

  Hereinafter, preferred embodiments of the present invention will be described in detail.

(About the components of the electrophotographic toner according to the present invention)
The toner for electrophotography according to the present invention is obtained by dispersing a colorant containing at least rice bran charcoal in a binder resin.

  The binder resin used in the electrophotographic toner of the present invention is not particularly limited as long as it is a conventionally used binder resin for toner. For example, styrene-acrylic copolymers and various toners are used. Polyester resins, toner epoxy resins, and the like can be used alone or in a blend of a plurality of types. When blending multiple types, use the same type of resin with different characteristics such as molecular weight distribution and thermal properties (for example, styrene-acrylic resins for styrene-acrylic resins, polyester resins for polyester resins, etc.) 2 It can be used by blending according to the required characteristics of seeds or three or more kinds. In addition, different types of resins (for example, a styrene-acrylic resin and a polyester resin) can be mixed by selecting an optimum kneading method and additive type.

  Momigara, which is a raw material of rice husk charcoal contained in the colorant of the present invention, is an agricultural waste produced in large quantities when separating rice from rice and is generated in Japan about 2 million tons per year. These rice husks are not easily rotted in normal soil and are difficult to handle as waste, so after carbonization, they are used as husk charcoal as a moisture control agent for barns and fertilizers. . That is, according to the electrophotographic toner according to the present invention, it is possible to obtain a high-performance and low-environmental toner by reusing industrial waste.

In the present invention, chaff charcoal is used as a black colorant for toner. About this rice bran charcoal, unlike charcoal and coconut charcoal as described in Patent Documents 1 to 3 above, since the raw rice cake contains a large amount of Si component, the carbonized rice bran coal contains SiO. ₂ is included. Considering that the content of SiO ₂ in the rice husk charcoal is approximately 20% by mass or more and 50% by mass or less, and the content of SiO _{2 in} normal charcoal is about 2% by mass at the maximum, It can be said that there are many.

Here, SiO ₂ acts as a grinding aid in the grinding step after toner melt-kneading (pulverizing the toner composition so as to have a particle size of about 5 to 10 μm), and prevents aggregation and destruction of the ground particles. Since it has an effect, it is possible to obtain an effect of stabilizing the average particle diameter of the toner after pulverization and classification, an effect that the generation amount of excessively pulverized fine powder is small, and the removal efficiency of the fine powder is high.

  The average particle diameter of the toner after pulverization and classification can be measured by, for example, Coulter Multisizer 3 type manufactured by Coulter, and is expressed by the median value D50 (vol) of the volume average particle diameter. In addition, the amount of excessively pulverized powder is expressed by number% of 5 μm or less measured with the same measuring machine. As D50 (vol) decreases, the number% of 5 μm or less tends to increase. However, according to experiments conducted by the present inventors, the toner to which the present invention is applied has, for example, D50 (vol) of 8.0 μm. In this case, it was found that the number of 5 μm or less was 8% by number or less, and the ratio of the pulverization input amount to the recovered amount after classification, the so-called yield was as high as 88%.

In addition, the rice bran charcoal containing a lot of SiO ₂ improves the durability of the toner because the reinforcing effect on the binder resin (the effect of hardening the resin) is higher than other charcoal materials and carbon black. There is an effect to make. Thus, since chaff charcoal is a colorant having a reinforcing effect on the binder resin, the storage elastic modulus G ′ of the binder resin at room temperature is increased and the storage elastic modulus of the binder resin when the toner is melted. G ′ can be raised. Therefore, by using rice bran charcoal as a colorant, it is possible to suppress high temperature offset and wrapping (wrap jam) during toner fixing.

Here, the storage elastic modulus at normal temperature is usually about 10 ⁸ Pa. However, according to the electrophotographic toner of the present invention, it can be increased to about 5 × 10 ⁸ Pa, and the storage elasticity when the toner is melted. The rate G ′ varies depending on the toner, but can be increased by about 5 times, similar to the storage elastic modulus at room temperature.

  In addition, like other charcoal materials, rice bran charcoal is a porous material having countless pores, so it is effective not only in collecting volatile matter generated during melt kneading of the toner raw material, It is also effective for collecting volatile organic compounds (VOC) that may be generated during fixing. That is, even if a substance for collecting VOC (for example, activated carbon) is not separately added, the generation of VOC at the time of fixing can be suppressed by the toner itself only by adding rice bran charcoal as a black colorant. It becomes possible.

  The pore diameter of the rice husk charcoal used in the present invention is preferably 1 nm or more and 250 nm or less. Since rice husk charcoal has a pore diameter in a wider range than other charcoal-based materials, VOC (carbon number of about 6 to 20) generated from the toner itself and VOC (Si compound) generated from the fixing device Thus, both of them can be efficiently adsorbed. However, if the pore diameter is too small or too large, the kind and amount of the substance adsorbed differs depending on the pore diameter, and VOC generated from the toner itself or the fixing device cannot be efficiently adsorbed. A range is preferred.

  The content of rice husk charcoal contained in the electrophotographic toner of the present invention is preferably 0.2 parts by mass or more and 8 parts by mass or less, more preferably 0 with respect to 100 parts by mass of the binder resin. .5 parts by mass or more and 6 parts by mass or less. If the amount of rice husk charcoal added is less than the above range, the effect of adding rice husk charcoal described later is not sufficient, and if the amount of rice husk charcoal added exceeds the above range, the binder resin becomes too hard. preferable.

  Moreover, well-known colorants other than rice bran charcoal can be used as the colorant in the present invention. For example, carbon black or aniline black can be used as the black colorant. In addition, as the yellow colorant, for example, a condensed nitrogen compound, an isoindolinone compound, an anthraquinone compound, an azo metal complex agent, an allylimide compound, or the like can be used. More specifically, C.I. I. Pigment yellow 12, 13, 14, 17, 62, 74, 83, 93, 94, 95, 109, 110, 111, 128, 129, 147, 168, 180, etc. are used. In addition, as the magenta colorant, for example, a condensed nitrogen compound, anthraquinone, a quinacridone compound, a basic dye rate compound, a naphthol compound, a benzimidazole compound, a thioindigo compound, or a perylene compound can be used. More specifically, C.I. I. Pigment Red 2,3,5,6,7,23,48: 2,48: 3,48: 4,57: 1,81: 1,122,144,146,166,169,177,184,185 202, 206, 220, 221, or 254 are used. Further, as the cyan colorant, for example, a copper phthalocyanine compound and a derivative thereof, an anthraquinone compound, or a basic dye rate compound can be used. More specifically, C.I. I. Pigment blue 1, 7, 15, 15: 1, 15: 2, 15: 3, 15: 4, 60, 62, or 66 is used. Such colorants are used alone or in admixture of two or more, and are selected in consideration of hue, saturation, lightness, weather resistance, dispersibility in the toner, and the like.

Further, the electrophotographic toner of the present invention is not particularly limited depending on whether it is magnetic or non-magnetic, and whether it is a one-component development method or a two-component development method. However, the electrophotographic toner of the present invention is not limited to the above-mentioned one-component development system, particularly a non-magnetic one-component development system, in which the toner receives a large pressure as a stress when a toner layer is formed on the developing roller. As described above, since a large amount of SiO ₂ is contained in the rice bran charcoal, a binder resin having a relatively low melting point can be used due to the reinforcing effect on the binder resin. Therefore, according to the electrophotographic toner of the present invention, even in the case of a one-component development method, particularly a non-magnetic one-component development method, a sufficient durability is maintained while maintaining a low fixing temperature (preventing high temperature offset). A toner having properties can be obtained.

  The electrophotographic toner of the present invention may contain known additives such as a release agent, a charge control agent, and a wax component, if necessary.

  The release agent is used to protect the photoreceptor and prevent deterioration of development characteristics to obtain a high quality image. Examples of such release agents include low molecular weight polyolefins such as low molecular weight polyethylene, low molecular weight polypropylene, and low molecular weight polybutylene, and high purity solid fatty acid ester materials such as paraffin wax and polyfunctional ester compounds. .

  Examples of the charge control agent include metal-containing salicylic acid compounds such as zinc or aluminum, boron complexes of bisdiphenylglycolic acid, silicates, and the like.

  The wax component is used to lower the toner fixing temperature and improve the durability and abrasion resistance of the toner. Examples of such waxes include polyethylene wax, polypropylene wax, silicon wax, paraffin wax, ester wax, carnauba wax, metallocene wax, and the like.

According to the present invention as described above, an electron that has a reinforcing effect on the binder resin and a VOC collecting effect that may occur at the time of fixing of the toner by containing rice bran charcoal as the colorant. Photographic toner can be provided. In other words, rice husk charcoal contains more SiO ₂ than other plant charcoal substances as its components, so that the binder resin can be hardened and the durability and fixability of the toner can be improved. As a result, it is possible to suppress image density reduction, high temperature offset, and occurrence of wrap jam. Furthermore, rice bran charcoal, like activated carbon, is a porous material with countless pores, so it may not only occur at the time of fixing, but also at the time of fixing, not only the volatile matter that occurs during the melt kneading of the toner material. A certain VOC can also be collected effectively. As a result, without adding a substance for collecting volatile components and VOC (such as activated carbon) during melting and kneading separately, just adding rice bran charcoal as a black colorant, The occurrence of VOC can be suppressed by the toner itself.

(Regarding the production method of the toner for electrophotography according to the present invention)
The components of the electrophotographic toner according to the present invention have been described in detail above. Subsequently, a method for producing such an electrophotographic toner will be described.

  In the production of the electrophotographic toner of the present invention, first, a predetermined amount of raw materials are weighed and mixed. Care must be taken when mixing the raw materials of the toner because the properties of the toner change depending on the method. For a charge control agent (CCA) that has poor particle dispersion in the toner and adversely affects durability, first, a predetermined amount is mixed with a binder resin. For mixing, a powder mixer such as a Henschel mixer is usually used and mixed for a predetermined time at a predetermined rotation speed. As a mixer used for mass production, for example, a small one having a capacity of about 75 L to a capacity of 300 to 500 L or more can be applied. The input amount (kg) of the raw material with respect to the capacity (L) of the mixer is suitably 20 to 40% (kg) of the capacity (L). That is, the raw material which can be charged into a 100 L mixer is calculated as 20 kg to 40 kg. Generally, the rotation speed and mixing time of the mixer are set by the rotation distance of the outermost circumference of the mixing blade (blade) in the mixer (calculated by the product of the outermost circumference length, the rotation speed, and the rotation time). In the case of the toner raw material, it is about 3000 to 6000 m.

  Next, rice bran charcoal, other black colorant, wax, and CCA, which are raw materials other than CCA, are additionally added, and the raw materials are mixed at a predetermined rotation speed and mixing time (for example, about 3000 to 6000 m).

  Further, the raw material mixture thus produced is melt-kneaded. For melt-kneading, for example, any kneading machine used for normal toner kneading, such as a twin-screw extruder for toner kneading, an open type continuous kneader, a batch kneader, or a batch banbury mixer, can be used. Also good. However, in view of mass productivity, dispersibility, and efficient cooling of the melt after kneading, a twin screw extruder, an open type continuous kneader, or the like is suitable for the toner kneading in the present invention. Since the melt-kneaded toner is discharged from the kneader in a molten state, it is preferable to cool it quickly. For cooling, a drum cooler or the like is used, and the kneaded product is cooled while continuously forming a plate having a thickness of about 0.5 mm to 3 mm. The plate-like material thus cooled is roughly pulverized. Several methods are known as coarse pulverization methods, but the pulverization is usually performed to about 0.2 mm to 1 mm in about one or two stages. Further, as a pre-stage of fine pulverization, it may be pulverized to about 20 μm to 50 μm in the intermediate pulverization step.

  The toner pulverized by coarse pulverization (or until intermediate pulverization) proceeds to a fine pulverization step and a classification step. Examples of the fine pulverization method include impact pulverization such as a method using a collision pulverizer that pulverizes toner powder against a collision plate, a counter jet method that causes toner powder to collide with each other, and a rotor and stator that rotate at high speed. There are known methods such as mechanical pulverization in which the toner powders are opposed to each other through a gap and pulverized when the toner powder passes through the gap, but the method is not particularly limited thereto. The equipment used for classification is, for example, an air classifier that classifies toner particles by applying centrifugal force to the toner particles in a vortex, an elbow jet classifier capable of classifying three products using the Coanda effect, A mechanical classifier using a rotating rotor is known.

  Next, a predetermined amount of silica subjected to hydrophobic surface treatment, titania subjected to hydrophobic surface treatment, metal oxide such as alumina, resin fine particles, and the like are externally added to the classified toner. For example, in addition to a Henschel mixer, a mechano-hybrid (Mitsui Mine) or the like can be used when a high linear velocity is required in addition to a Henschel mixer, but is not limited thereto.

  Finally, the toner after the external addition is passed through a sieve having an opening of about 150 μm to 75 μm to remove the non-external addition of the external additive and foreign matters, thereby obtaining a final toner for electrophotography.

  Next, the present invention will be described more specifically using examples and comparative examples, but the present invention is not limited to the following examples.

  In this example, a toner to which the present invention was applied was manufactured, and the durability and fixability of the toner were evaluated, the presence or absence of wrap jamming, and the amount of VOC adsorption were evaluated. Hereinafter, the toner production methods and the evaluation results of the toner characteristics in each of the examples and comparative examples will be described in detail. The composition of the toner obtained as described below and the evaluation results thereof are shown in Table 1 below.

Example 1
Acid value is 5.0 (mgKOH / gpolymer), number average molecular weight (Mn) is Mn = 4500, ratio of weight average molecular weight (Mw) to number average molecular weight (Mn) is Mw / Mn = 28, glass transition temperature ( 94% by mass of a polyester resin having a Tg) of Tg = 60 ° C. and a melting point (Tm) of Tm = 125 ° C., 1.5% by mass of carbon black, and 1.5% by mass of rice bran charcoal (particle size passes through 300 mesh). And 1.0% by mass of black CCA derived from a complex with iron as a central metal, and 2.0% by mass of ester wax (Tm = 73 ° C.). / D = 40). The kneaded product was cooled and solidified while being stretched to a thickness of 1.5 mm with a cooling drum. This was coarsely pulverized with a coarse pulverizer so that the average particle diameter was about 800 μm, and then pulverized with an intermediate pulverizer so that the average particle diameter was about 30 μm. This is finely pulverized with a mechanical pulverizer so that the volume average particle size (D50) is about 5.5 μm, and the coarse powder and over-pulverized fine powder are cut with a three-product classifier using the Coanda effect. A toner having a volume average particle diameter (D50) of 6.2 μm was obtained. For this toner, 1.0 phr of silica whose surface was hydrophobized with HMDS (hexyldisilazane) having a BET specific surface area of 300 m ² / g, and silica whose surface was hydrophobized with PDMS (polydimethyl siloxane) of 50 m ² / g. 1.5 phr and rutile-type hydrophobized TiO ₂ 0.4 phr were mixed with a Henschel mixer, and further passed through a 200 mesh ultrasonic application type vibration sieve to obtain a final toner.

  The toner thus obtained was evaluated as a black toner for a Samsung CLP600 color printer. As a result, even after printing 6000 sheets or more, the image density was substantially unchanged at 1.39 from the initial 1.40, and the back toner The ground was 0.02 or less on the photosensitive member throughout the evaluation, and the fixing property was neither low temperature offset nor high temperature offset from 130 ° C. to 190 ° C. Further, even when a black image with a margin of 5 mm at the front end of the paper was output, no wrap jam in which the toner was wound around the fixing device was generated. From this, it was suggested that the electrophotographic toner according to the present invention can achieve both excellent durability and fixability.

  Here, the image density was obtained by printing five 20 mm × 20 mm solid images on A4 paper (Samsung Premium Paper), measuring the density with a Spectroeye type densitometer manufactured by GretagMacbeth, and calculating an average value thereof. In addition, the background is affixed with a Scotch mending tape on a non-image portion on the photosensitive member, and the toner on the non-image portion is collected and pasted on the above-mentioned white paper, and the density is measured at three locations. And the average value was obtained. The image density and background measurement methods are the same in the following examples and comparative examples.

  Further, when the toner of this example was heated to 180 ° C. and the amount of VOC collected by the headspace method was measured by gas chromatography, it was 0.02 ppm. Thus, according to the toner of this example, almost all generated VOCs could be collected. From this, it was suggested that the electrophotographic toner according to the present invention has an excellent collecting effect such as VOC.

(Example 2)
Mn = 4500, Mw / Mn = 28, Tg = 60 ° C., Tm = 125 ° C., 94% by mass of styrene-acrylic copolymer, 1.5% by mass of carbon black, rice husk charcoal (particle size passes 300 mesh) ) 1.5% by mass, 1.0% by mass of black CCA derived from a complex with iron as a central metal, and 2.0% by mass of paraffinic wax (Tm = 73 ° C.) The mixture was heated and melt-kneaded using a machine (double screw, L / D = 40). The kneaded product was cooled and solidified while being stretched to a thickness of 1.5 mm with a cooling drum. This was coarsely pulverized with a coarse pulverizer so that the average particle diameter was about 800 μm, and then pulverized with an intermediate pulverizer so that the average particle diameter was about 30 μm. This is finely pulverized with a mechanical pulverizer so that the volume average particle size (D50) is about 5.5 μm, and the coarse powder and over-pulverized fine powder are cut with a three-product classifier using the Coanda effect. A toner having a volume average particle diameter (D50) of 6.2 μm was obtained. For this toner, 1.0 phr of silica whose surface was hydrophobized with HMDS (hexyldisilazane) having a BET specific surface area of 300 m ² / g, and silica whose surface was hydrophobized with PDMS (polydimethyl siloxane) of 50 m ² / g. 1.5 phr and rutile-type hydrophobized TiO ₂ 0.4 phr were mixed with a Henschel mixer, and further passed through a 200 mesh ultrasonic application type vibration sieve to obtain a final toner.

  The toner thus obtained was evaluated as a black toner for a Samsung CLP600 color printer. As a result, even after printing 6000 sheets or more, the image density was substantially unchanged at 1.39 from the initial 1.40, and the back toner The ground was 0.02 or less on the photosensitive member throughout the evaluation, and the fixing property was neither low temperature offset nor high temperature offset from 130 ° C. to 190 ° C. Further, even when a black image with a margin of 5 mm at the front end of the paper was output, no wrap jam in which the toner was wound around the fixing device was generated. From this, it was suggested that the electrophotographic toner according to the present invention can achieve both excellent durability and fixability.

(Comparative Example 1)
94% by mass of polyester resin having an acid value of 5.0 (mgKOH / gpolymer), Mn = 4500, Mw / Mn = 28, Tg = 60 ° C., Tm = 125 ° C., 3.0% by mass of carbon black, iron A black CCA derived from a complex as a central metal in an amount of 1.0% by mass and an ester wax (Tm = 73 ° C.) in an amount of 2.0% by mass are twin-screw extruders (double screw, L / D = 40). And kneaded with heat. The kneaded product was cooled and solidified while being stretched to a thickness of 1.5 mm with a cooling drum. This was coarsely pulverized with a coarse pulverizer so that the average particle diameter was about 800 μm, and then pulverized with an intermediate pulverizer so that the average particle diameter was about 30 μm. This is finely pulverized with a mechanical pulverizer so that the volume average particle size (D50) is about 5.5 μm, and the coarse powder and over-pulverized fine powder are cut with a three-product classifier using the Coanda effect. A toner having a volume average particle diameter (D50) of 6.2 μm was obtained. For this toner, 1.0 phr of silica whose surface was hydrophobized with HMDS (hexyldisilazane) having a BET specific surface area of 300 m ² / g, and silica whose surface was hydrophobized with PDMS (polydimethyl siloxane) of 50 m ² / g. 1.5 phr and rutile-type hydrophobized TiO ₂ 0.4 phr were mixed with a Henschel mixer, and further passed through a 200 mesh ultrasonic application type vibration sieve to obtain a final toner.

  When the toner thus obtained was evaluated as a black toner of a Samsung CLP600 color printer, the image density was greatly reduced to 1.28 from the initial 1.40 within 3000 sheets. Further, the background was 0.02 or less on the photosensitive member throughout the evaluation, but when a black image with a margin of 5 mm at the front end of the paper was output, a wrap jam in which the toner wraps around the fixing device occurred. From this, it was suggested that, as in the electrophotographic toner according to the present invention, unless the charcoal is added as a colorant, the durability and the fixing property are remarkably inferior as compared with the toner of the present invention.

  Further, when the toner of this comparative example was heated to 180 ° C. and the amount of VOC collected by the headspace method was measured by gas chromatography, it was 2.3 ppm. Thus, the toner of this comparative example to which no charcoal was added had a low effect of collecting the generated VOC. From this, it was suggested that rice bran coal has an excellent VOC collection effect.

(Comparative Example 2)
94% by mass of polyester resin having an acid value of 5.0 (mgKOH / gpolymer), Mn = 4500, Mw / Mn = 28, Tg = 60 ° C., Tm = 125 ° C., 1.5% by mass of carbon black, woody system Biaxial extrusion of 1.5% by mass of activated carbon, 1.0% by mass of black CCA derived from a complex with iron as the central metal, and 2.0% by mass of ester wax (Tm = 73 ° C.) The mixture was heated and melt-kneaded using a machine (double screw, L / D = 40). The kneaded product was cooled and solidified while being stretched to a thickness of 1.5 mm with a cooling drum. This was coarsely pulverized with a coarse pulverizer so that the average particle diameter was about 800 μm, and then pulverized with an intermediate pulverizer so that the average particle diameter was about 30 μm. This is finely pulverized with a mechanical pulverizer so that the volume average particle size (D50) is about 6.0 μm, and the coarse powder and over-pulverized fine powder are cut with a three-product classifier using the Coanda effect. A toner having a volume average particle diameter (D50) of 6.8 μm was obtained. For this toner, 1.0 phr of silica whose surface was hydrophobized with HMDS (hexyldisilazane) having a BET specific surface area of 300 m ² / g, and silica whose surface was hydrophobized with PDMS (polydimethyl siloxane) of 50 m ² / g. 1.5 phr and rutile-type hydrophobized TiO ₂ 0.4 phr were mixed with a Henschel mixer, and further passed through a 200 mesh ultrasonic application type vibration sieve to obtain a final toner.

  The toner thus obtained was evaluated as a black toner for a Samsung CLP600 color printer. As a result, a large number of streaks were generated on the developing roller within 2000 prints, and the image density was initially 1.40. Greatly reduced to 1.08. Further, the background was 0.02 or less on the photosensitive member throughout the evaluation, but when a black image with a margin of 5 mm at the front end of the paper was output, a wrap jam in which the toner wraps around the fixing device occurred. From this, instead of using wood-based activated carbon as the colorant as in the conventional toner, when adding rice bran charcoal as the colorant as in the electrophotographic toner according to the present invention, compared to the conventional, It was suggested that the durability and fixability of the toner can be remarkably improved.

  As mentioned above, although preferred embodiment of this invention was described, it cannot be overemphasized that this invention is not limited to this example. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

Claims (5)

In an electrophotographic toner containing a binder resin and a colorant,
The toner for electrophotography, wherein the colorant contains rice bran charcoal. _2. The electrophotographic toner according to claim 1, wherein the rice bran charcoal contains 20 mass% or more and 50 mass% or less of SiO ₂ .   The toner for electrophotography according to claim 1, wherein a pore diameter of the rice bran charcoal is 1 nm or more and 250 nm or less.   4. The electron according to claim 1, wherein a content of the rice bran charcoal is 0.2 parts by mass or more and 8 parts by mass or less with respect to 100 parts by mass of the binder resin. Toner for photography.   The toner for electrophotography according to claim 1, wherein the toner is for a one-component developing system.