JP5729441B2 - Process for producing decolorizable electrophotographic toner and decolorizable electrophotographic toner - Google Patents

Description

  The present invention relates to a method for producing an erasable electrophotographic toner and an erasable electrophotographic toner produced by the method.

  In recent years, in order to save resources, it has been studied to reuse paper that has been copied and printed in the office. However, most of these printed materials are classified as confidential documents. For this reason, most of the printed materials are disposed of and are rarely reused. Thus, toners using near-infrared light decoloring type recording materials that can absorb and decompose and erase near infrared rays have been proposed (Patent Documents 1 and 2).

  Such a toner is generally produced by uniformly mixing and pulverizing toner raw materials, then classifying the toner raw material into a predetermined particle size, and adding an external additive as necessary. It is manufactured by a so-called melt kneading method. More specifically, binder resin, near-infrared absorbing dye as coloring agent, decoloring agent, and other additives as necessary (charge control agent, anti-fading agent, white filler, ultraviolet absorber, lubricant, etc.) The raw materials to be mixed are mixed and then kneaded by a kneader such as a pressure kneader, a twin screw extruder, or an open roll to obtain a kneaded product. After cooling this kneaded product, it is roughly crushed with a hammer mill or the like, pulverized with a pulverizer such as a jet mill, and classified with an air classifier or the like. A so-called toner can be obtained by mixing an external additive such as silica with the obtained classified product and then sieving it.

  In the manufacturing method by this melt-kneading method, heat and shearing force are given to the whole raw material at the time of kneading. Therefore, in order to prevent this, a master batch in which a resin and a colorant or a decolorizer are dispersed in high concentration in advance is used. It has been proposed to use (Patent Documents 3 and 4). However, even if the master batch is used in this way, the toner raw material is heated during the melt-kneading, so that there is a problem that the colorant is decolored.

  In order to prevent discoloration of the dye, the kneading is divided into two stages, the raw material excluding the colorant is melt-kneaded at a high temperature in the first stage, and the colorant is added to the melt-kneaded product in the first stage in the second stage. A method of melt kneading at a low temperature has been proposed (Patent Document 5). However, even in this method, the problem that the coloring agent and the decoloring agent react with heat in the second-stage melt-kneading and the dye is decolored still remains.

JP-A-5-119520 JP-A-5-278338 JP-A-6-332239 JP-A-7-325428 JP-A-7-234541

  The present invention has been made in view of the above circumstances, and suppresses the decoloring of near-infrared absorbing dyes that may occur during the production of a decolorable electrophotographic toner, thereby producing a decolorable electrophotographic toner having a high print density. The purpose is to provide.

In order to solve the above problems, one embodiment of the present invention provides:
(i) binder resin,
(ii) a near infrared absorbing dye capsule or an unencapsulated near infrared absorbing dye, and
a mixture comprising decolorizer which are not (iii) decolorizing agent capsule or encapsulated, at least one of the near infrared absorbing dye and the decolorizer are melting kneaded mixture is encapsulated, the melt-kneading There is provided a method for producing a decolorable electrophotographic toner comprising the steps of thermally melting and breaking capsules at the end, and then cooling and pulverizing the mixture to obtain toner particles.

  Another aspect of the present invention provides a decolorizable electrophotographic toner produced by the above method.

  According to the present invention, it is possible to provide a method for producing a decolorable electrophotographic toner having a high print density by suppressing the decoloration of a near-infrared absorbing dye that may occur during the production of the decolorable electrophotographic toner. .

Hereinafter, embodiments of the present invention will be described.
The present inventors have found that when a near-infrared absorbing dye is dissolved in a hydrophobic solvent and encapsulated and used as a toner colorant, a high print density and a sufficient decoloring density can be obtained. The present invention has been completed (see Examples 1 to 3 below).

That is, the method for producing a decoloring type electrophotographic toner according to the embodiment of the present invention includes:
(i) binder resin,
(ii) a near infrared absorbing dye capsule or an unencapsulated near infrared absorbing dye, and
(iii) A decolorant capsule or a mixture containing a non-encapsulated decolorant, in which at least one of near-infrared absorbing dye and decolorant is encapsulated, melt-kneaded and pulverized A step of obtaining toner particles.

  In this embodiment, at least one of the near-infrared absorbing dye and the decoloring agent is encapsulated. By this encapsulation, it is possible to prevent the near-infrared absorbing dye and the color erasing agent from coming into contact with each other at a high temperature during the toner production to cause a color erasing reaction. In addition, when the near-infrared absorbing dye and the color erasing agent are previously dissolved in a hydrophobic solvent and then encapsulated, the capsule can be obtained as a very fine dispersion. As a result, the near-infrared absorbing dye and the decoloring agent can be present in a finely dispersed state after the capsule film is melted, and the decoloring reaction efficiency can be increased.

  On the other hand, the capsule film needs to be destroyed so that the near-infrared absorbing dye and the color erasing agent exhibit their functions in the final product toner. In the present embodiment, the high temperature of the near-infrared absorbing dye and the decoloring agent is obtained by destroying the capsule film by heat melting at the end of the melt-kneading, that is, at the final end of the kneading zone of the melt-kneader. Underneath contact can be minimized.

  The near-infrared absorbing dye and the color erasing agent come into contact with each other due to the destruction of the capsule film, but the toner raw material is not exposed to a high temperature in the manufacturing process after melt-kneading. It is placed in a situation where the decolorization reaction does not occur easily. In order to positively suppress the decoloring reaction, the toner material may be cooled immediately after melt-kneading.

  As described above, the printing density of the obtained toner can be increased by minimizing the contact between the near-infrared absorbing dye and the color erasing agent at a high temperature. For this reason, the toner of the present invention can obtain the same print density as that of the conventional toner with a near-infrared absorbing dye having an addition amount smaller than that of the conventional toner. Further, the toner of the present invention can obtain a higher print density than that of the conventional toner by using the same amount of near-infrared absorbing dye as that of the conventional toner.

  In the present embodiment, the purpose is to prevent the near-infrared absorbing dye and the color erasing agent from contacting each other at a high temperature, so that either the near-infrared absorbing dye or the color erasing agent may be encapsulated. , Both may be encapsulated. However, in the decoloring toner, since the blending amount of the decoloring agent is larger than the blending of the near infrared absorbing dye, it is more economical to encapsulate the near infrared absorbing dye.

  Hereinafter, a method for producing a decoloring toner will be described by taking as an example the case of encapsulating a near-infrared absorbing dye, but the present invention is not limited to the following description.

That is, in one example of the present invention, a method for producing a decolorable toner by encapsulating a near-infrared absorbing dye,
A step of dissolving a near-infrared absorbing dye in a hydrophobic solvent and encapsulating with a heat-meltable capsule material to obtain a near-infrared absorbing dye capsule;
Mixing a binder resin, a near-infrared absorbing dye capsule obtained in the above step, and a mixture containing a decoloring agent, and then melt-kneading and pulverizing to obtain toner particles.

  A conventionally well-known thing can be used as a near-infrared absorption pigment | dye. Examples of such near-infrared absorbing dyes include those described in JP-A-4-362935 and JP-A-5-119520. Specific examples of near-infrared absorbing pigments include IR-T (trade name, manufactured by Showa Denko KK) as shown in the following formula.

In the formula, X and Y both represent N (C ₂ H ₅ ) ₂ , and Z ⁻ is a counter ion represented by the following formula.

As described above, the near-infrared absorbing dye is dissolved in a hydrophobic solvent and then encapsulated with a heat-meltable capsule material to obtain a near-infrared absorbing dye capsule.

  As the hydrophobic solvent, any solvent known in the art as a solvent capable of dissolving the colorant can be used. For example, phenylxylylethane, phenyl-isopropylphenylethane, phenylxylylmethane, etc. Diarylalkane compounds, alkylnaphthalene compounds such as monoisopropylnaphthalene and diisopropylnaphthalene, alkylbiphenyls such as monoisopropylbiphenyl and diisopropylbiphenyl, partially hydrogenated terphenyl compounds, alkylbenzene compounds, paraffins, vegetable oils, fatty acid ester compounds, etc. can do. For example, 1-50 mass parts of near-infrared absorption pigment | dye and 100 mass parts hydrophobic solvent can be mixed with a mixer, and a near-infrared absorption pigment | dye can be dissolved in a hydrophobic solvent.

  When the near-infrared absorbing dye is thus encapsulated after being dissolved in a hydrophobic solvent, the near-infrared absorbing dye capsule can be obtained as a very fine dispersion. When the near-infrared absorbing dye capsule is present as a fine dispersion, the near-infrared absorbing dye exists in a finely dispersed state even after the capsule film is melted. In addition, an excellent decoloring density can be achieved.

  As the heat-meltable capsule material, materials known in the technical field of microcapsules can be used. For example, polyurea, polyurethane, polyurethane / urea, or the like can be used. Encapsulation can be performed according to a known technique, for example, a polyurethane capsule film can be formed by reaction of polyisocyanate and polyol, and a polyurea capsule film can be formed by reaction of polyisocyanate and polyamine. A polyurethane / urea capsule membrane can be formed by the reaction of polyisocyanate with polyol and polyamine.

  Since this capsule membrane is made of a heat-meltable capsule material, the temperature and time of the melt-kneading are controlled so that the capsule membrane is broken at the end of the melt-kneading. The infrared absorbing dye and the color erasing agent can be kept from contacting as much as possible.

  In the present embodiment, a decolorable toner is produced according to a known method using the obtained near-infrared absorbing dye capsule.

  The toner raw material contains a binder resin, a near infrared absorbing dye capsule, a decoloring agent, and other additives as required.

  The near-infrared absorbing dye capsule is preferably contained in an amount of 0.1 to 20% by mass of the toner mass, and more preferably 1 to 10% by mass of the toner mass. The content of the near infrared absorbing dye is preferably 0.3 to 5% by mass of the toner mass, and more preferably 1 to 3% by mass of the toner mass.

  In this specification, the “toner mass” is defined as the total mass of the toner raw material including the binder resin, the near-infrared absorbing dye capsule, and the decolorizer, and does not include an external additive such as silica.

  A conventionally known quaternary ammonium boron complex can be used as the decolorizer. Examples of such quaternary ammonium boron complexes include those described in JP-A-4-362935 and JP-A-5-119520. Specific examples of the quaternary ammonium boron complex include P3B (trade name, manufactured by Showa Denko KK) represented by the following formula.

When the decolorizer is not encapsulated, a master batch in which a resin and the decolorizer are dispersed at a high concentration in advance may be prepared and used according to a known method.

  The content of the decolorizer is preferably 1 to 15% by mass of the toner mass, and more preferably 3 to 10% by mass of the toner mass. The decolorization reaction occurs when the dye cation of the near infrared absorbing dye is bonded to the alkyl group of the decolorizer. The ratio of the near-infrared absorbing dye and the decoloring agent in the decoloring toner is appropriately selected so that no unreacted near-infrared absorbing dye remains after the decoloring reaction.

  The binder resin 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.

  The content of the binder resin is preferably 70 to 95% by mass of the toner mass, and more preferably 80 to 90% by mass of the toner mass.

  The toner raw material can contain known additives such as a charge control agent and a release agent in addition to the binder resin, the near-infrared absorbing dye capsule, and the decoloring agent. As the charge control agent and the release agent, any of those usually used for electrophotographic toners can be used.

  The toner raw materials are mixed, melt-kneaded and pulverized according to a known method to obtain toner particles.

  The mixing of the toner raw materials can be performed by a powder mixer such as a Henschel mixer.

  Subsequent melt kneading can be performed by a melt kneader, for example, a twin screw extruder or a single screw extruder. Melting and kneading conditions can be appropriately adjusted according to the thermal melting temperature of the Millo capsule itself, but the set temperature of the barrel heater is preferably between the glass transition point of the microcapsule and the melting point Tm. Below the glass transition point, it is difficult to heat melt in the latter half of the kneading apparatus, and above the melting point, it is easy to heat melt in the first half of the kneading apparatus. By adjusting the barrel heater temperature and the material supply speed of each kneading zone so that the microcapsules are thermally melted in the latter half of the melt kneader, at the end of the melt kneading, that is, at the end of the kneading zone of the melt kneader. The capsule membrane can be broken. Thereby, the near-infrared absorbing dye is coated with the capsule film over almost the entire period of melt-kneading, and is protected from contact with the decoloring agent at high temperature.

  In order to further shorten the time during which the near-infrared absorbing dye is brought into contact with the color erasing agent at a high temperature, it is preferable to cool the toner raw material immediately below the glass transition point of the main binder resin after melt kneading.

  Thereafter, the toner can be obtained by pulverizing with a pulverizer such as a jet mill and classifying with an air classifier or the like.

  Here, the particle size of the toner is not particularly limited, but is usually adjusted to be 5 to 10 μm. An external additive can be added to the toner thus obtained in order to improve fluidity, adjust chargeability, and improve durability. As the external additive, inorganic fine particles are generally used, and examples thereof include silica, titania, alumina, and the like. Of these, hydrophobized silica is preferable, and commercially available from Nippon Aerosil, CABOT, and the like.

  When a print or image is formed by an electrophotographic process using the decolorizable electrophotographic toner configured according to the present embodiment, the print or image has a high image density under visible light, but when irradiated with near infrared rays, The print or image disappears. This is based on the following phenomenon.

  That is, when a near infrared ray is irradiated on a print or an image, the near infrared ray absorbing dye in the toner is excited and reacts with the decoloring agent to cause a decoloring phenomenon. As a result, the print or image is erased, and the transfer medium can be reused.

  Examples of the present invention and comparative examples are shown below, and the effects of the present invention will be specifically described.

Example 1
(Preparation of near-infrared absorbing dye capsule)
50 parts by mass of a near-infrared absorbing dye “IR-T” (manufactured by Showa Denko KK) and 50 parts by mass of phenylxylylethane (boiling point 295 to 305 ° C., SAS-296 manufactured by JX Nippon Oil & Energy Co., Ltd.) A near-infrared absorbing pigment oil was prepared by mixing with a mixer.

  The produced near-infrared absorbing dye oil 15 g and Takenate D-103 (tolylene diisocyanate / trimethylolpropane, adduct: 75% ethyl acetate, manufactured by Mitsui Chemicals, Inc.) 14 g were mixed to obtain an oil phase (dye Solution) was formed.

  Next, 1.5 g of PVA-205 (polyvinyl alcohol, saponification degree 88%, polymerization degree 500, manufactured by Kuraray Co., Ltd.) was dissolved in 150 g of water to form an aqueous phase.

  The oil phase was gradually mixed with the aqueous phase thus obtained, and dispersed at high speed with an Ultra Turrax T25 Basic (IKA homogenizer) to obtain a dispersed phase. This dispersed phase was transferred to a 300 ml three-necked round bottom flask, and a reflux tube, a thermometer and a stirring device were attached thereto, and the mixture was kept constant at 70 ° C. with a water bath and reacted for 3 hours.

  The particle size of the microcapsules obtained by the reaction was measured with a particle size distribution type LA-920 (laser explanation / scattering type particle size distribution type; manufactured by Horiba, Ltd.) and found to be 4.2 μm.

  The washing process of separating the obtained microcapsule slurry into water and microcapsules with a centrifuge and discarding the water was repeated several times. After the washing step, it was dried with a freeze vacuum dryer to produce a near-infrared absorbing dye capsule (1).

(Production of toner)
5.8 parts by mass of the obtained near infrared absorbing dye capsule (1) (1.5 parts by mass as a near infrared absorbing dye component)
Glass transition point: 63 ° C., melting point Tm: 126 ° C.
Decolorant (P-3B: Showa Denko KK) 7.5 parts by weight Charge control agent (LR-147: Nippon Carlit Co., Ltd.) 1.5 parts by weight Carnauba wax No. 1 powder (Kato Co., Ltd.) Yoko Co., Ltd.) 2.5 parts by mass Binder resin (polyester resin: Tg: 63 ° C., softening point 135 ° C.) 82.7 parts by mass of a total composition of 3 kg was put into a 20 L Henschel mixer and mixed at 2000 rpm for 3 minutes. did. Thereafter, the mixture was melt-kneaded at a barrel heater temperature of 110 ° C. and a material supply speed of 36 kg / hr by a twin screw extruder Ikegai PCM43 L / D = 34, and cooled by passing 10 ° C. cooling water. Apparatus It was cooled to below Tg of polyester resin with a drum flaker manufactured by Mitsui Mining Co., Ltd. Thereafter, the mixture was roughly crushed with a rotoplex (2 mm pass), pulverized with a collision plate jet pulverizer, and classified with an air classifier to obtain fine particles (1) having a mass average of 9 μm.

Fine particles (1) 100 parts by mass Silica (RY-50: manufactured by Nippon Aerosil Co., Ltd.) A total of 1.025 kg at a ratio of 2.5 parts by mass was put into a 10 L Henschel mixer and mixed at 2000 rpm for 2 minutes. Separately, a decoloring toner (1) was obtained.

(Measurement and evaluation of printing density and decoloring density)
The obtained decoloring toner (1) was mounted on “SPEDIA N3500” (manufactured by Casio Computer Co., Ltd.), and a square image having a side of 1 cm was printed. X-RITE 938 (manufactured by X-rite) The print density was measured with The print density was relatively high at 1.08.

  The printing paper was heated to 190 ° C. and irradiated with 900 W of halogen light for 2.5 seconds, and the printing density (hereinafter referred to as decoloring density) was measured again. The erasing density was 0.09, and the erasing density was good.

The print density after printing was evaluated according to the following criteria.
1.0 or more: 〇 Good 0.95 or more and less than 1.0: △ Level that is not problematic in practical use Less than 0.95: × Level that cannot withstand use The following standards for printing density after erasing (erasing density) Evaluated according to.
0.1 or less: Yes Good Greater than 0.1: X level that cannot withstand use.

Example 2
A near-infrared absorbing dye capsule (1) was prepared in the same manner as in Example 1, and a decolorable toner (2) was obtained in the same manner as in Example 1 except that the composition of the toner was as follows.
Obtained near infrared absorbing dye capsule (1) 6.76 parts by mass (1.75 parts by mass as a near infrared absorbing dye component)
Decolorant (P-3B: Showa Denko KK) 7.5 parts by weight Charge control agent (LR-147: Nippon Carlit Co., Ltd.) 1.5 parts by weight Carnauba wax No. 1 powder (Kato Co., Ltd.) Yoko Co., Ltd.) 2.5 parts by mass Binder resin (polyester resin: softening point 135 ° C.) 81.75 parts by mass.

  With respect to the obtained decoloring toner (2), the printing density and the decoloring density were measured and evaluated in the same manner as in Example 1. The print density was relatively high at 1.02. Further, the decolorization density was 0.07, and the color was well erased.

Example 3
A near-infrared absorbing dye capsule (1) was produced in the same manner as in Example 1, and a decolored toner (3) was obtained in the same manner as in Example 1 except that the composition of the toner was as follows.
Obtained near-infrared absorbing dye capsule (1) 6.57 parts by mass (1.7 parts by mass as a near-infrared absorbing dye component)
Decolorant (P-3B: Showa Denko KK) 7.5 parts by weight Charge control agent (LR-147: Nippon Carlit Co., Ltd.) 1.5 parts by weight Carnauba wax No. 1 powder (Kato Co., Ltd.) Yoko Co., Ltd.) 2.5 parts by mass Binder resin (polyester resin: softening point 135 ° C.) 81.93 parts by mass.

  With respect to the obtained decoloring toner (3), the printing density and the decoloring density were measured and evaluated in the same manner as in Example 1. The print density was high at 1.20. Further, the color erasing density was 0.09, and the color was well erased.

Comparative Example 1
A toner was prepared by blending a near-infrared absorbing dye into the toner raw material without making a near-infrared absorbing dye capsule as in Example 1. That is, a decolorable toner (4) was obtained in the same manner as in Example 1 using the following composition.
Near-infrared absorbing dye “IR-T” (manufactured by Showa Denko KK) 1.5 parts by mass Decolorizer (P-3B: manufactured by Showa Denko KK) 7.5 parts by mass Charge control agent (LR-147: Nippon Carlit Co., Ltd.) 1.5 parts by weight Carnauba wax No. 1 powder (manufactured by Hiroyuki Kato) 2.5 parts by weight Binder resin (polyester resin: softening point 135 ° C.) 87 parts by weight.

  With respect to the obtained decoloring toner (4), the printing density and the decoloring density were measured and evaluated in the same manner as in Example 1. The print density was as low as 0.93. Further, the decolorization density was 0.07, and the color was well erased.

Comparative Example 2
A toner was prepared by blending a near-infrared absorbing dye into the toner raw material without making a near-infrared absorbing dye capsule as in Example 1. That is, a decolorable toner (5) was obtained in the same manner as in Example 1 using the following composition.
Near-infrared absorbing pigment “IR-T” (manufactured by Showa Denko KK) 1.3 parts by mass Decolorizer (P-3B: manufactured by Showa Denko KK) 7.5 parts by mass Charge control agent (LR-147: Nippon Carlit Co., Ltd.) 1.5 parts by weight Carnauba wax No. 1 powder (manufactured by Hiroyuki Kato) 2.5 parts by weight Binder resin (polyester resin: 135 ° C. softening point) 87.2 parts by weight.

  With respect to the obtained decoloring toner (5), the printing density and decoloring density were measured and evaluated in the same manner as in Example 1. The print density was low at 0.89. Further, the decolorization density was 0.06, and the color was well erased.

Comparative Example 3
A toner was prepared by blending a near-infrared absorbing dye into the toner raw material without making a near-infrared absorbing dye capsule as in Example 1. That is, a decolorable toner (6) was obtained in the same manner as in Example 1 using the following composition.
Near-infrared absorbing dye “IR-T” (manufactured by Showa Denko KK) 1.7 parts by mass Decolorizer (P-3B: manufactured by Showa Denko KK) 7.5 parts by mass Charge control agent (LR-147: Nippon Carlit Co., Ltd.) 1.5 parts by weight Carnauba wax No. 1 powder (manufactured by Hiroyuki Kato) 2.5 parts by weight Binder resin (polyester resin: softening point 135 ° C.) 86.8 parts by weight.

  The obtained decoloring toner (6) was measured for printing density and decoloring density in the same manner as in Example 1, and evaluated. The print density was 0.98, which was slightly low. Further, the erasing density was 0.08, and the erasing density was good.

Comparative Example 4
A near-infrared absorbing dye capsule was prepared in the same procedure as in Example 1 except that the near-infrared absorbing dye was encapsulated without being dissolved in phenylxylylethane.

(Preparation of near-infrared absorbing dye capsule)
15 g of near infrared absorbing dye (IR-T: Showa Denko KK) and 14 g Takenate D-103 (tolylene diisocyanate / trimethylolpropane, adduct: 75% ethyl acetate, Mitsui Chemicals) are mixed To form an oil phase.

  Using this oil phase, a near-infrared absorbing dye capsule (2) was produced in the same manner as in Example 1.

(Production of toner)
A decolorable toner (7) was obtained in the same manner as in Example 1 using the following composition containing the obtained near-infrared absorbing dye capsule (2).
Obtained near-infrared absorbing dye capsule (2) 2.9 parts by mass (1.5 parts by mass as a near-infrared absorbing dye component)
Decolorant (P-3B: Showa Denko KK) 7.5 parts by weight Charge control agent (LR-147: Nippon Carlit Co., Ltd.) 1.5 parts by weight Carnauba wax No. 1 powder (Kato Co., Ltd.) Yoko Co., Ltd.) 2.5 parts by mass Binder resin (polyester resin: softening point 135 ° C.) 85.6 parts by mass.

  With respect to the obtained decoloring toner (7), the printing density and the decoloring density were measured and evaluated in the same manner as in Example 1. The print density was good at 1.03. Further, the decolorization density was 0.25 and the decolorization was insufficient.

  Table 1 below summarizes the toner compositions and evaluation results used in Examples 1 to 3 and Comparative Examples 1 to 4.

  In Examples 1 to 3, the near-infrared absorbing dye was dissolved in a hydrophobic solvent, and then encapsulated with a heat-meltable capsule material (polyurethane), which was used as a toner raw material. The toners of Examples 1 to 3 were able to obtain a high printing density and an excellent decoloring density. The reason why the high print density was obtained is thought to be that the near-infrared absorbing dye is encapsulated, so that the decoloring of the dye that can occur during the melt kneading of the toner material is suppressed. In addition, the excellent decoloring density was obtained because the near-infrared absorbing dye was encapsulated after being dissolved in a hydrophobic solvent, so that the capsule became a very fine dispersion, and the near-infrared after the capsule film was melted. It is considered that the absorbing dye was present in a finely dispersed state and was efficiently decolored.

  On the other hand, in Comparative Examples 1 to 3, the near-infrared absorbing dye was blended in the toner raw material without encapsulating. The toners of Comparative Examples 1 to 3 could not obtain a sufficient printing density. This is presumably because the colorant and the color erasing agent contacted at a high temperature during melt-kneading and a color erasing reaction occurred.

  In Comparative Example 4, the near-infrared absorbing dye was encapsulated with a heat-meltable capsule material (polyurethane) without dissolving it in a hydrophobic solvent, and this was used as a toner raw material. With the toner of Comparative Example 4, a sufficient printing density was obtained, but only an insufficient decoloring density was obtained. This is because the contact between the dye and the decoloring agent was suppressed by the encapsulation of the dye, but the dye was not dissolved in advance, so the dye was not finely dispersed during the encapsulation, and the efficiency of the decoloring reaction was poor. Possible cause.

The invention described in the scope of claims at the beginning of the application will be appended.
[1] (i) binder resin,
(ii) a near infrared absorbing dye capsule or an unencapsulated near infrared absorbing dye, and
(iii) A decolorant capsule or a mixture containing a non-encapsulated decolorant, in which at least one of near-infrared absorbing dye and decolorant is encapsulated, melt-kneaded and pulverized And a method for producing a decolorizable electrophotographic toner, comprising a step of obtaining toner particles.
[2] Production of a decolorizable electrophotographic toner comprising a step of melt-kneading and pulverizing a mixture containing a binder resin, a near-infrared absorbing dye capsule, and a decoloring agent to obtain toner particles Method.
[3] The [1] or [2], wherein the near-infrared absorbing dye capsule is obtained by dissolving the near-infrared absorbing dye in a hydrophobic solvent and encapsulating it with a heat-meltable capsule material. A process for producing an erasable electrophotographic toner.
[4] The decoloring type electrophotographic method according to [1], wherein the decoloring agent capsule is obtained by dissolving the decoloring agent in a hydrophobic solvent and encapsulating the decoloring agent with a heat-meltable capsule material. Toner manufacturing method.
[5] The method for producing an erasable electrophotographic toner according to any one of [1] to [4], wherein the mixture is cooled during melt-kneading and pulverization.
[6] The method for producing a decolorizable electrophotographic toner according to [3] or [4], wherein the capsule material is polyurea, polyurethane, or polyurethane / urea.
[7] The method for producing a decolorizable electrophotographic toner according to [3] or [4], wherein the hydrophobic solvent is phenylxylylethane.
[8] A decoloring type electrophotographic toner produced by the method according to any one of [1] to [7].

Claims (7)

(i) binder resin,
(ii) a near infrared absorbing dye capsule or an unencapsulated near infrared absorbing dye, and
a mixture comprising decolorizer which are not (iii) decolorizing agent capsule or encapsulated, at least one of the near infrared absorbing dye and the decolorizer are melting kneaded mixture is encapsulated, the melt-kneading A method for producing an erasable electrophotographic toner, comprising the steps of thermally melting and destroying the capsule at the end, and then cooling and pulverizing the mixture to obtain toner particles. The binder resin, the near infrared absorbing dye capsules, and then melting and kneading a mixture containing a decolorizer, and destroy the capsule was heat melted at the end of melt-kneading, then the mixture cooled, and pulverized, toner A process for producing an erasable electrophotographic toner, comprising a step of obtaining particles.   3. The decolorizable electron according to claim 1, wherein the near-infrared absorbing dye capsule is obtained by dissolving the near-infrared absorbing dye in a hydrophobic solvent and encapsulating it with a heat-meltable capsule material. Method for producing photographic toner.   2. The decolorable electrophotographic toner according to claim 1, wherein the decolorizer capsule is obtained by dissolving the decolorizer in a hydrophobic solvent and encapsulating the decolorizer capsule with a heat-meltable capsule material. Method.   The method for producing a decolorable electrophotographic toner according to claim 3 or 4, wherein the capsule material is polyurea, polyurethane, or polyurethane / urea.   The method for producing a decolorizable electrophotographic toner according to claim 3 or 4, wherein the hydrophobic solvent is phenylxylylethane. Decolorizable electrophotographic toner characterized in that it is produced by a process according to any one of claims 1 to 6.