JP2014115508A - Decolorable electrophotographic toner, master batch, and manufacturing method of decolorable electrophotographic toner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a decolorable electrophotographic toner that includes a colorant and a UV absorber sufficiently dispersed therein, and has excellent color developability, transparency, and light resistance; a master batch used for the manufacture of the same; and a manufacturing method of a decolorable electrophotographic toner.SOLUTION: A manufacturing method of a decolorable electrophotographic toner according to the present invention includes kneading while heating a UV absorber, a colorant, a master batch including a first resin, and a decoloring agent.

Description

  The present invention relates to a method for producing a decolorable electrophotographic toner and a decolorable electrophotographic toner, and in particular, to a decolorable electrophotographic toner, a masterbatch, and a decolorable electrophotographic toner having excellent light resistance. Regarding the method.

  Prints on which images such as characters are formed by copying machines or printers using decolorable electrophotographic toners such as decolorizable leuco dyes or near-infrared decolorizable toners The image can be erased by light, and the paper can be regenerated. An image forming apparatus used for such an application includes a toner decoloring part inside or outside the apparatus. When the printed material is no longer needed, the image is erased by the erasing unit so that the paper can be used again.

  A printed matter in which an image is formed using the toner described above is required to have high image visibility and be resistant to fading even when exposed to natural light or fluorescent light when used in an office. . In order to satisfy these requirements, for example, a master batch is prepared by kneading a UV absorber and a part of the binder resin, and then the master batch, the remainder of the binder resin and the colorant are kneaded. Thus, it has been proposed to improve light resistance (see Patent Document 1).

  However, this method has a problem that the dispersion of the colorant and the UV absorber in the toner is insufficient, and it is difficult to obtain sufficient light resistance and transparency. Further, the colorant used in the decolorizable electrophotographic toner is vulnerable to heat, light, or mechanical stress. For this reason, if a masterbatch containing both the colorant and the UV absorber is prepared in order to sufficiently disperse the colorant and the UV absorber, the colorant may fade or disappear in the process of preparing the masterbatch. There was a problem that the color performance was affected.

JP 2010-079009 A

  The present invention has been made in view of the above circumstances, and a decoloring type electrophotographic toner excellent in color developability, transparency and light resistance, in which a colorant and an ultraviolet absorber are sufficiently dispersed, and a master used in the production thereof It is an object of the present invention to provide a batch and a method for producing an erasable electrophotographic toner.

  In order to solve the above-described problem, an aspect of the present invention is an erasing method characterized by kneading while heating a masterbatch containing an ultraviolet absorber, a coloring agent, and a first resin, and a decoloring agent. A method for producing a type electrophotographic toner is provided.

  According to the present invention, a color erasable electrophotographic toner in which a colorant and an ultraviolet absorber are sufficiently dispersed and excellent in color developability, transparency, and light resistance, a master batch used in the production thereof, and a color erasable electron A method for producing a photographic toner is provided.

FIG. 2 is a diagram illustrating a printer with a color erasing function for erasing a transferred medium printed using a erasable electrophotographic toner according to an embodiment of the present invention and printing again. It is a figure which shows the image sample printed on the paper using the toner which concerns on an Example and a comparative example. It is a figure which shows the image sample printed on the OHP sheet using the toner which concerns on an Example and a comparative example. FIG. 3 is a diagram illustrating an image sample obtained by erasing the image sample illustrated in FIG. 2 using the printer with the erasing function illustrated in FIG. 1.

Hereinafter, various embodiments of the present invention will be described.
In the method for producing a decolorizable electrophotographic toner according to an embodiment of the present invention, a masterbatch is obtained by kneading a first mixture containing an ultraviolet absorber, a colorant, and a first resin while heating at a first temperature. And kneading the master batch, the decoloring agent, the second resin, and typically the second mixture containing the charge control agent while heating at the second temperature. And after this kneaded material is solidified, it is pulverized.

The first resin is used to uniformly disperse the colorant and the ultraviolet absorber. The first resin has a lower melting point than, for example, a commonly used binder resin for toner.
As the first resin, a resin having a melting point of 60 to 145 ° C. is preferable, and a resin having a melting point of 75 to 130 ° C. is more preferable. The weight average molecular weight of the first resin is, for example, 10,000 or less, and typically 300 to 10,000. The “weight average molecular weight” is obtained by a gel permeation chromatography measurement method.

  Examples of the first resin include novolak resins, modified novolak resins, aliphatic hydrocarbon resins, aromatic hydrocarbon resins, copolymer resins of these resins, terpene resins, C5 petroleum resins, C9 petroleum resins, and coumarone resins. , Modified rosin, and esterified modified rosin. The C5 petroleum resin / C9 petroleum resin is produced by subjecting the C5 fraction / C9 fraction produced from the naphtha cracker to cationic polymerization, and the weight average molecular weight is, for example, 500 to 5,000. . A specific example of the C5 petroleum resin is “Quinton (registered trademark) 1500” (manufactured by Nippon Zeon).

  The amount of the first resin is preferably 20 to 50% by mass of the toner mass, and more preferably 28.5 to 47.5% by mass. Further, the ratio of the first resin in the total amount of the first resin and the second resin is preferably 40 to 80% by mass, and more preferably 42.5 to 77.5% by mass. When the amount of the first resin is small, it is difficult to uniformly disperse the colorant and the ultraviolet absorber. When the amount of the first resin is large, the fixing temperature is lowered and it is difficult to maintain the fixing characteristics.

  Here, the toner mass is defined as the total mass of the first resin, the ultraviolet absorber, the colorant, the decoloring agent, the second resin, the charge control agent, and the wax. The toner mass does not include external additives such as silica.

  The ultraviolet absorber is added to improve the light resistance of the colorant contained in the toner. The ultraviolet absorber is not particularly limited, and various conventionally known ones such as a benzotriazole ultraviolet absorber, a triazine ultraviolet absorber, a benzophenone ultraviolet absorber, and a benzoate ultraviolet absorber may be used. it can.

  Examples of the benzotriazole ultraviolet absorber include 2- (2H-benzotriazol-2-yl) -p-cresol and 2- (2H-benzotriazol-2-yl) -4-6-bis (1-methyl). -1-phenylethyl) phenol, 2- [5-chloro (2H) -benzotriazol-2-yl] -4-methyl-6- (tert-butyl) phenol, 2- (2H-benzotriazol-2-yl) ) -4,6-di-tert-benzylphenol, 2- (2H-benzotriazol-2-yl) -4- (1,1,3,3-tetramethylbutyl) phenol, methyl-3- [3 -Condensate with t-butyl-5- (2H-benzotriazol-2-yl) -4-hydroxyphenyl] propionate-polyethylene glycol (molecular weight about 300) 2- (2H-benzotriazol-2-yl) -6-dodecyl-4-methylphenol, 2- (2-hydroxy-5-tert-butylphenyl) -2H-benzotriazole, 2-ethylhexyl-3- [3 -Tert-butyl-4-hydroxy-5- (5-chloro-2H-benzotriazol-2-yl) phenyl] propionate, 2- (2H-benzotriazol-2-yl) -4,6-bis (1- Methyl-1-phenylethyl) phenol, 2- (2H-benzotriazol-2-yl) -6- (1-methyl-1-phenylethyl) -4- (1,1,3,3-tetramethylbutyl) Phenol is mentioned.

  Examples of the triazine-based ultraviolet absorber include 2- (4,6-bis (2,4-dimethylphenyl) -1,3,5-triazin-2-yl) -5-hydroxyphenyl, 2- (4, 6-diphenyl-1,3,5-triazin-2-yl) -5-[(hexyl) oxy] phenol, 2- [4-[(2-hydroxy-3-dodecyloxypropyl) oxy] -2-hydroxy Phenyl] -4,6-bis (2,4-dimethylphenyl) -1,3,5-triazine, 2- [4-[(2-hydroxy-3- (2′-ethyl) hexyl) oxy] -2 -Hydroxyphenyl] -4,6-bis (2,4-dimethylphenyl) -1,3,5-triazine, 2,4-bis (2-hydroxy-4-butyloxyphenyl) -6- (2,4 -Bisubutyloxyfe ) -1,3,5-triazine, 2- (2hydroxy-4- [1-octyloxycarbonyloxy] phenyl) -4,6-bis (4-phenylphenyl) -1,3,5-triazine Is mentioned.

Examples of the benzophenone-based ultraviolet absorber include octabenzone, 2,4-hydroxybenzophenone, 2-hydroxy-4-methoxy-benzophenone, and 2-hydroxy-4-n-octyloxy-benzophenone.
Examples of the benzoate ultraviolet absorber include 2,4-di-tert-butylphenyl-3,5-di-tert-butyl-4-hydroxybenzoate.

  These ultraviolet absorbers may be used alone or in combination of two or more.

  The addition amount of the ultraviolet absorber is 1 to 30% by mass of the toner mass, and preferably 1.5 to 27% by mass. When the amount of the ultraviolet absorber is small, it is difficult to impart sufficient light resistance to the toner. Further, when the amount of the ultraviolet absorber is excessively increased, the transparency of the toner is lowered and the decoloring performance tends to be inferior.

  As the colorant, a near infrared absorbing dye may be used, or a decolorizable leuco dye may be used. However, in a decoloring method using a decolorizable leuco dye, a box-type heat erasing device in which a heater is surrounded by a heat insulating structure is usually used to erase a set number of sheets over several hours. It is difficult to erase on demand.

  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 dyes include IRT (trade name, manufactured by Showa Denko KK) as shown in the following formula.

式中、Ｘ及びＹは、いずれもＮ（Ｃ_２Ｈ_５）_２を表し、Ｚ⁻は下記式に示す対イオンである。

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.

  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.

  The second resin is used for the same purpose as a normal toner binder resin. The melting point of the second resin is higher than the melting point of the first resin. The melting point of the second resin is, for example, 70 ° C. or more higher than the melting point of the first resin, typically 20 ° C. or more. Also, typically, the second resin has a higher weight average molecular weight than the first resin.

  As the second resin, a resin having a melting point of 80 to 165 ° C. is preferable, and a resin having a melting point of 95 to 150 ° C. is more preferable. The weight average molecular weight of the second resin is, for example, 50,000 or more, and typically 100,000 or more.

  The second resin can be selected from a wide range including those known as binder resins for toner. 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, and polyolefin resin can be exemplified, and these resins may be used alone or in combination of two or more. Of these resins, polyester resins are preferred.

  The amount of the second resin is preferably 10 to 50% by mass, and more preferably 13.5 to 38.5% by mass of the toner mass.

  The charge control agent is added to adjust the charge amount and charge speed of the toner. As the charge control agent, any of those usually used for electrophotographic toners can be used.

The decolorizable electrophotographic toner can further contain a release agent.
The release agent is added to prevent an offset phenomenon in which a part of the toner is divided and adheres to the heating surface when the toner is fixed to the transfer medium by contact heating fixing such as heat roller fixing. As the release agent, any of those usually used for electrophotographic toners can be used. The release agent is added, for example, after preparing the master batch.

  As described above, in this method, the first mixture containing the first resin, the ultraviolet absorber, and the colorant is kneaded while being heated to the first temperature to prepare a masterbatch. Next, the second mixture containing the master batch, the color erasing agent, and the second resin is kneaded while being heated to the second temperature.

The first temperature is sufficiently high to melt the first mixture, and is lower than the melting point of a commonly used binder resin for toner. The first temperature is, for example, 60 to 150 ° C., and typically 75 to 135 ° C.
The second temperature is higher than the first temperature. The second temperature is, for example, 70 ° C. or more higher than the first temperature, typically 20 ° C. or more. The second temperature is, for example, 80 to 170 ° C., and typically 95 to 155 ° C.

  According to this method, it is possible to obtain a decolorizable electrophotographic toner in which a colorant and an ultraviolet absorber are sufficiently dispersed, and excellent in color developability, transparency and light resistance. The reason will be described below.

  In order to prevent the colorant in the decolorizable electrophotographic toner from being deteriorated by light, the ultraviolet absorber is present at a sufficiently high density in the vicinity of the colorant, and the area in the vicinity of the colorant. It is necessary that the density of the colorant does not vary. For this purpose, it is necessary to sufficiently knead the colorant. However, when the colorant is subjected to kneading at a high temperature for a long time, the colorant may be faded or its decoloring performance may be hindered. In addition, when the colorant is subjected to kneading at a high temperature for a long time together with the decoloring agent, there is a possibility that decoloring may occur in the toner production process.

  Accordingly, here, first, a colorant and an ultraviolet absorber are uniformly dispersed in the first resin having a low melting point to prepare a master batch, and then the master batch, the color erasing agent, the second resin having a high melting point, Knead the mixture containing Since the first resin has a low melting point, kneading for obtaining a master batch can be performed at a relatively low temperature. Moreover, if the colorant and the ultraviolet absorber are uniformly dispersed in the master batch, the kneading of the mixture containing the master batch, the decoloring agent, and the second resin can be completed in a relatively short time.

  Therefore, according to this method, it is possible to obtain a decolorizable electrophotographic toner in which the colorant and the ultraviolet absorber are sufficiently dispersed, and the color developing property, transparency, and light resistance are excellent.

  In the case where a color erasable electrophotographic toner was produced by the same method as described above except that the colorant was omitted from the first mixture and contained in the second mixture, the color development property of the toner, the OHP transparency, and Light resistance is insufficient. In addition, when an erasable electrophotographic toner is produced by the same method as described above except that the ultraviolet absorber is omitted from the first mixture and is contained in the second mixture, sufficient OHP transparency and light resistance are obtained. I can't get it. And when a decoloring type electrophotographic toner was prepared by the same method as described above except that the master batch was not prepared and the colorant and the ultraviolet absorber were contained in the second mixture, sufficient color developability, OHP transparency and light resistance cannot be obtained.

  First, when a master batch composed of an ultraviolet absorber and a resin and a master batch composed of a colorant, a decoloring agent, a charge control agent, and a resin are prepared and kneaded, sufficient light resistance is obtained. I can't. This is considered to be because the ultraviolet absorber cannot be present at a sufficiently high density in the vicinity of the colorant, or the density of the colorant in the region in the vicinity of the colorant varies.

  When fixing the toner on the OHP sheet, if the surface of the fixed image is rough, incident light is scattered at the time of screen projection, causing a transmission defect, and the image becomes dark. The OHP transparency is obtained by visually evaluating light transmittance by printing on an OHP sheet using a decoloring type electrophotographic toner and projecting the printed image on a screen.

  When a near-infrared absorbing dye is used as a colorant and an image such as characters is printed by an electrophotographic process using the decolorizable electrophotographic toner prepared as described above, the image such as characters is high under visible light. Although it is the printing density, it is decolored when irradiated with near infrared rays. This is based on the following phenomenon.

  That is, when near-infrared rays are irradiated on an image such as a character, the near-infrared absorbing dye in the toner is in an excited state, reacts with the decoloring agent, and a decoloring phenomenon occurs. As a result, images such as characters are erased, and it becomes possible to reuse the transfer medium onto which the erasable electrophotographic toner such as printing paper and OHP sheet is transferred.

  The decoloring reaction occurs when the dye cation of the near infrared absorbing dye is bonded to the alkyl group of the decoloring agent. Further, the ratio of the near-infrared absorbing dye and the decoloring agent in the decolorizing type electrophotographic toner is appropriately selected so that no unreacted near-infrared absorbing dye remains after the decoloring reaction.

  A printer with a color erasing function for erasing and reprinting a transfer medium printed using the above-described color erasing type electrophotographic toner will be described below with reference to the drawings.

  The printer shown in FIG. 1 is a modification of a commercially available printer (N3500: manufactured by Casio Computer Co., Ltd.). In this printer, a decoloring type electrophotographic toner developing device 2, a decoloring heater 3, a decoloring LED head 4, a transfer unit 5, and a fixing unit 6 are disposed around the print belt 1. At the bottom of the printer, a cassette 7 for storing a transfer medium P printed using the erasable electrophotographic toner is disposed, and at the top, the reprinted substrate using the erasable electrophotographic toner is disposed. A paper discharge unit 8 for discharging the transfer medium is disposed. The erasing type electrophotographic toner developing device 2 is provided with a erasing type electrophotographic toner cartridge 9 for storing the erasing type electrophotographic toner.

The printer shown in FIG. 1 operates as follows.
First, the transfer medium P printed using the erasable electrophotographic toner is taken out from the cassette 7 and passes through each part along the transfer medium path 10. The transfer medium P includes printing paper such as paper or an OHP sheet. In other words, the transfer medium P is heated by the decoloring heater 3 and the decoloring LED head 4 and irradiated with near infrared rays, and characters and other images are decolored. Next, on the transfer medium on which an image such as a character has been erased, the developed image of the erased electrophotographic toner is transferred in the transfer unit 5. The developed image of the erasable electrophotographic toner is an image developed by the erasable electrophotographic toner developer 2 using the erasable electrophotographic toner supplied from the erasable electrophotographic toner cartridge 9. Yes, and sent to the transfer unit 5 by the print belt 1.

The image of the erasable electrophotographic toner transferred in the transfer unit 5 is further sent to the fixing unit along the transfer medium path 10, where the fixing process is performed, and then discharged to the paper discharge unit 8. The operation is complete.
When the above printer is operated, for example, the output of the halogen lamp head 3 is 50 mW / cm ² and the temperature setting of the decoloring heater 2 is 100 ° C. The transfer medium path 4 can be changed to any set speed.

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

Example 1
A decolorizing type electrophotographic toner was produced as follows.
First, a masterbatch containing an ultraviolet absorber and a colorant was prepared. Specifically, “Sumisorb (registered trademark) 340” (manufactured by Sumika Chemtex) as an ultraviolet absorber is 10 parts by weight, and a near infrared absorbing dye “IRT” (manufactured by Showa Denko KK) 3 having sensitivity at a wavelength of 817 nm. Mass parts and 87 parts by mass of “Tamanol (registered trademark) 521” (manufactured by Arakawa Chemical Co., Ltd.) as the first resin were put into Henschel mixer (registered trademark) (manufactured by Mitsui Mining Co., Ltd.) and mixed. Then, the obtained 1st mixture was kneaded over 10 minutes, heating at 100 degreeC with a biaxial kneader, and the masterbatch was obtained. The melting point of the first resin used here is 110 ° C.

  Furthermore, 50 parts by mass of the masterbatch obtained as described above, 7.5 parts by mass of an organic boron compound decoloring agent “P3B” (manufactured by Showa Denko KK), “a binder resin for toner as a second resin” ”(Made by Kao) 38.5 parts by mass, charge control agent“ LR-147 ”(made by Nippon Carlit Co., Ltd.) 1.5 parts by mass, and“ Carnava WAX No. 1 powder ”(imported product by Hiroyuki Kato) 2 .5 parts by mass was charged into Henschel mixer (registered trademark) (manufactured by Mitsui Mining Co., Ltd.) and mixed. The obtained second mixture was melt-kneaded for 10 minutes while heating to 120 ° C. with a twin-screw kneader, and the cured kneaded material was crushed with Rotoplex (registered trademark) (manufactured by Hosokawa Micron). Crushed material was obtained. The obtained coarsely pulverized product was pulverized by an impact pulverizer so that the average particle size became 9 μm. Here, the average particle diameter is a value obtained by a laser diffraction scattering method.

  1 part by weight of silica “R972” (manufactured by Nippon Aerosil Co., Ltd.) as an external additive is added to 100 parts by weight of the obtained pulverized product and mixed with Henschel mixer (registered trademark) (manufactured by Mitsui Mining Co., Ltd.). A decolorizable electrophotographic toner was prepared.

(Example 2)
Discoloration in the same manner as in Example 1 except that “Tamanol (registered trademark) 510” (produced by Arakawa Chemical) was used as the first resin instead of “Tamanol (registered trademark) 521” (produced by Arakawa Chemical). Type electrophotographic toner was prepared. In addition, melting | fusing point of the 1st resin used here is 85 degreeC.

(Example 3)
As Example 1, except that “Marquide (registered trademark) No. 1” (manufactured by Arakawa Chemical) was used instead of “Tamanol (registered trademark) 521” (manufactured by Arakawa Chemical), An erasable electrophotographic toner was produced. The melting point of the first resin used here is 125 ° C.

Example 4
Decolorizable electrophotographic toner in the same manner as in Example 1 except that “YS Resin PX1250” (manufactured by Yasuhara Chemical) was used instead of “Tamanol (registered trademark) 521” (manufactured by Arakawa Chemical) as the first resin. Was made. The melting point of the first resin used here is 125 ° C.

(Example 5)
Except for using “FTR (registered trademark) -6125” (manufactured by Mitsui Chemicals) instead of “Tamanol (registered trademark) 521” (produced by Arakawa Chemical) as the first resin, A color electrophotographic toner was prepared.

(Example 6)
Except for using “FTR (registered trademark) -2140” (manufactured by Mitsui Chemicals) instead of “Tamanol (registered trademark) 521” (manufactured by Arakawa Chemical) as the first resin, A color electrophotographic toner was prepared.

(Example 7)
As the first resin, in the same manner as in Example 1 except that “Imabu (registered trademark) P-140” (manufactured by Idemitsu Kosan) was used instead of “Tamanol (registered trademark) 521” (manufactured by Arakawa Chemical), An erasable electrophotographic toner was produced.

(Example 8)
The decolorizing type was the same as in Example 1 except that “Petocol (registered trademark) 140” (manufactured by Tosoh) was used instead of “Tamanol (registered trademark) 521” (manufactured by Arakawa Chemical) as the first resin. An electrophotographic toner was prepared.

Example 9
As in Example 1, except that “Esclon (registered trademark) V-120” (manufactured by Nippon Steel Chemical Co., Ltd.) was used instead of “Tamanol (registered trademark) 521” (manufactured by Arakawa Chemical) as the first resin. Thus, an erasable electrophotographic toner was produced.

(Example 10)
As the first resin, a decolorizing type was used in the same manner as in Example 1 except that “Carnauba wax No. 1 powder” (manufactured by Hiroyuki Kato) was used instead of “Tamanol (registered trademark) 521” (manufactured by Arakawa Chemical). An electrophotographic toner was prepared.

(Example 11)
Decolorizable electrophotographic toner in the same manner as in Example 1 except that “FT100” (manufactured by Nippon Seiki) was used instead of “Tamanol (registered trademark) 521” (manufactured by Arakawa Chemical) as the first resin. Was made.

(Example 12)
As in Example 1, except that “High Wax (registered trademark) 4202” (manufactured by Mitsui Chemicals) was used instead of “Tamanol (registered trademark) 521” (manufactured by Arakawa Chemical) as the first resin. A color electrophotographic toner was prepared.

(Example 13)
Decolorizable electrophotographic toner in the same manner as in Example 1 except that “Neowax L” (manufactured by Yasuhara Chemical) was used instead of “Tamanol (registered trademark) 521” (manufactured by Arakawa Chemical) as the first resin. Was made.

(Example 14)
Discoloration in the same manner as in Example 1 except that “Quinton (registered trademark) 1500” (manufactured by Zeon Japan) was used as the first resin instead of “Tamanol (registered trademark) 521” (manufactured by Arakawa Chemical). Type electrophotographic toner was prepared.

(Example 15)
As the first resin, “Quinton (registered trademark) 1500” (manufactured by Nippon Zeon) was used instead of “Tamanol (registered trademark) 521” (manufactured by Arakawa Chemical), and the amount of the first resin was changed from 87 parts by mass to 95 masses. The erasable electrophotographic toner was produced in the same manner as in Example 1 except that the amount of the ultraviolet absorber was changed from 10 parts by mass to 2 parts by mass.

(Example 16)
As the first resin, “Quinton (registered trademark) 1500” (manufactured by Nippon Zeon) was used instead of “Tamanol (registered trademark) 521” (manufactured by Arakawa Chemical), and the amount of the first resin was changed from 87 parts by mass to 77 masses. The erasable electrophotographic toner was prepared in the same manner as in Example 1 except that the amount of the ultraviolet absorber was changed from 10 parts by mass to 20 parts by mass.

(Example 17)
As the first resin, “Quinton (registered trademark) 1500” (manufactured by ZEON) was used instead of “TAMANOL (registered trademark) 521” (manufactured by Arakawa Chemical), and the amount of the first resin was changed from 87 parts by mass to 57 masses. The erasable electrophotographic toner was produced in the same manner as in Example 1 except that the amount of the UV absorber was changed from 10 parts by weight to 40 parts by weight.

(Example 18)
As the first resin, “Quinton (registered trademark) 1500” (manufactured by ZEON) was used instead of “TAMANOL (registered trademark) 521” (manufactured by Arakawa Chemical), and the amount of the first resin was changed from 87 parts by mass to 62 masses. Example 1 except that the amount of the ultraviolet absorber was changed from 10 parts by weight to 36 parts by weight, and the amount of the near-infrared absorbing dye was changed from 3 parts by weight to 2 parts by weight. Thus, a master batch was prepared.

  Subsequently, 75 parts by mass of the masterbatch obtained as described above, 7.5 parts by mass of an organic boron compound decoloring agent “P3B” (manufactured by Showa Denko KK), and “second binder resin” 13.5 parts by weight (manufactured by Kao), 1.5 parts by weight of the charge control agent “LR-147” (manufactured by Nippon Carlit Co., Ltd.), and “Carnava WAX No. 1 powder” (imported by Kato Yoko Co., Ltd.) 2 .5 parts by mass was charged into Henschel mixer (registered trademark) (manufactured by Mitsui Mining Co., Ltd.) and mixed. Thereafter, in the same manner as in Example 1, a decoloring type electrophotographic toner was produced.

(Example 19)
The decolorization-type electron was changed in the same manner as in Example 18 except that the amount of the first resin was changed from 62 parts by weight to 58% by weight and the amount of the ultraviolet absorber was changed from 36 parts by weight to 40% by weight. A photographic toner was prepared.

(Comparative Example 1)
As the first resin, in the same manner as in Example 1 except that “Tamanol (registered trademark) 521” (manufactured by Arakawa Chemical Co., Ltd.) was replaced by “Binder resin for toner” (manufactured by Kao), the decolorizing type electron A photographic toner was prepared.

(Comparative Example 2)
5 parts by mass of “Sumisour (registered trademark)” (manufactured by Sumika Chemtex) as an ultraviolet absorber, 1.5 parts by mass of near-infrared absorbing dye “IRT” (manufactured by Showa Denko KK), “Quinton as a binder resin (Registered trademark) 1500 "(manufactured by ZEON Corporation) 43.5 parts by mass," binder resin for toner "(manufactured by Kao) 38.5 parts by mass, organoboron compound decolorizer" P3B "(manufactured by Showa Denko KK) ) 7.5 parts by mass, 1.5 parts by mass of charge control agent “LR-147” (manufactured by Nippon Carlit Co., Ltd.), and 2.5 parts by mass of “Carnauba WAX No. 1 powder” (imported by Kato Hiroyuki) Was put into Henschel mixer (registered trademark) (manufactured by Mitsui Mining Co., Ltd.) and mixed. Subsequently, the obtained mixture was kneaded with a twin-screw kneader to obtain a kneaded product. The cured kneaded material was crushed with Rotoplex (registered trademark) (manufactured by Hosokawa Micron Corporation) to obtain a crushed material. The obtained coarsely pulverized product was pulverized by an impact pulverizer so that the average particle size became 9 μm.

  To 100 parts by weight of the obtained pulverized product, 1 part by weight of silica “R972” (manufactured by Nippon Aerosil Co., Ltd.) as an external additive is added, mixed with Henschel mixer (registered trademark) (manufactured by Mitsui Mining Co., Ltd.), A color electrophotographic toner was prepared.

(Comparative Example 3)
A masterbatch containing an ultraviolet absorber and no colorant was prepared, and an erasable electrophotographic toner was produced using the masterbatch.
Specifically, the coloring agent was omitted, “Quinton (registered trademark) 1500” (manufactured by ZEON) was used as the first resin, and the amount of the first resin was changed from 87 parts by mass to 90 parts by mass. Except for this, a master batch containing no colorant was obtained in the same manner as in Example 1.

Then, using this master batch, the amount of the second resin was changed from 38.5 parts by mass to 37 parts by mass, except that 1.5 parts by mass of the near-infrared absorbing dye used in Example 1 was further added. A second mixture was prepared as in Example 1.
Further, an erasable electrophotographic toner was produced in the same manner as in Example 1 except that this second mixture was used.

(Comparative Example 4)
A masterbatch containing a colorant and no ultraviolet absorber was prepared, and a decoloring type electrophotographic toner was produced using the masterbatch.
Specifically, the ultraviolet absorber was omitted, “Quinton (registered trademark) 1500” (manufactured by Nippon Zeon Co., Ltd.) was used as the first resin, and the amount of the first resin was changed from 87 parts by mass to 97 parts by mass. Except that, a masterbatch containing no UV absorber was obtained in the same manner as in Example 1.

Thereafter, this master batch was used, except that the amount of the second resin was changed from 38.5 parts by mass to 33.5 parts by mass, and 5 parts by mass of the ultraviolet absorber used in Example 1 was further added. A second mixture was prepared as in Example 1.
Further, an erasable electrophotographic toner was produced in the same manner as in Example 1 except that this second mixture was used.

(Comparative Example 5)
A masterbatch containing an ultraviolet absorber and a masterbatch containing a colorant were prepared, and an erasable electrophotographic toner was produced using these.
Specifically, 80 parts by mass of “Quinton (registered trademark) 1500” (manufactured by Nippon Zeon) and 20 parts by mass of the ultraviolet absorber used in Example 1 were introduced into Henschel mixer (manufactured by Mitsui Mining Co., Ltd.) Mixed. Subsequently, the obtained mixture was kneaded with a twin-screw kneader to obtain a masterbatch kneaded product A of an ultraviolet absorber.

  94 parts by mass of “Quinton (registered trademark) 1500” (manufactured by ZEON) and 6 parts by mass of near-infrared absorbing dye “IRT” (manufactured by Showa Denko) are put into Henschel mixer (registered trademark) (manufactured by Mitsui Mining Co., Ltd.) And mixed. Subsequently, the obtained mixture was kneaded with a twin-screw kneader to obtain a master batch kneaded product B of a colorant.

Subsequently, a second mixture was prepared in the same manner as in Example 1 except that 25 parts by mass of master batch kneaded product A and 25 parts by mass of master batch kneaded product B were used instead of 50 parts by mass of master batch. .
Further, an erasable electrophotographic toner was produced in the same manner as in Example 1 except that this second mixture was used.

(Comparative Example 6)
87 parts by mass of “Tamanol (registered trademark) 521” (manufactured by Arakawa Chemical) was changed to 96 parts by mass of “Quinton (registered trademark) 1500” (manufactured by Nippon Zeon), and the amount of the UV absorber was changed from 10 parts by mass to 1 mass. A master batch was obtained in the same manner as in Example 1 except that the part was changed to a part. Thereafter, a decoloring type electrophotographic toner was produced in the same manner as in Example 1.

(Comparative Example 7)
87 parts by mass of “Tamanol (registered trademark) 521” (manufactured by Arakawa Chemical) was changed to 57 parts by mass of “Quinton (registered trademark) 1500” (manufactured by Nippon Zeon), and the amount of the UV absorber was changed from 10 parts by mass to 41 parts by mass. A master batch was prepared in the same manner as in Example 1 except that the amount of the near-infrared absorbing dye “IRT” (manufactured by Showa Denko) was changed from 3 parts by mass to 2 parts by mass. Thereafter, an erasable electrophotographic toner was produced in the same manner as in Example 18.

  Each of the obtained decolorizable electrophotographic toners was placed in the cartridge of the printer shown in FIG. In response to a print request, this printer performs normal printing in which an image developed with a decoloring type electrophotographic toner in the developing device 2 is transferred to a transfer medium by the transfer unit 5 and fixed by the fixing unit 6. went.

  FIG. 2 shows an image printed on P paper (manufactured by Fuji Xerox) using the erasable electrophotographic toner according to Examples and Comparative Examples. FIG. 3 shows an image printed on the OHP sheet using the decoloring type electrophotographic toner according to Examples and Comparative Examples. FIG. 4 shows a state in which the paper shown in FIG. 2 has been decolored. 2 to 4, reference numerals 11 and 12 indicate a printing unit and a non-printing unit, respectively.

  The decoloring was performed as follows. First, the printed transfer medium P was set in the cassette 7 of the printer shown in FIG. The erasing LED head 4 and the erasing heater 3 of the printer were turned on, and the printed transfer medium P was erased by passing through the path 10. Thereafter, the transfer medium was discharged out of the apparatus.

The image samples of FIGS. 2 to 4 were measured with rite (registered trademark) 938 (manufactured by X-rite), and the following four points were evaluated.
Light resistance Color development OHP transparency Decolorization

<Light resistance evaluation>
The paper of FIG. 2 was exposed to 700 lux natural light for 300 hours, the ratio of the c density of the printing unit 11 after irradiation with natural light and the c density of the printing unit 11 before natural light irradiation was determined, and the light resistance was evaluated according to the following criteria. .
0.9 or more: Very good.
0.7 or more and less than 0.9: Good.
0.4 or more and less than 0.7: Δ fading slightly.
Less than 0.4: x fading.

<Color development evaluation>
For the printing section 11 of the paper of FIG. 3, the ratio between the c density and the toner amount per unit area was determined, and the color development was evaluated according to the following criteria.
1.2 or more: Very good.
1.0 or more and less than 1.2: Good.
0.8 or more and less than 1.0: Δ is not slightly colored.
Less than 0.8: No color developed.

<OHP transparency evaluation>
The image shown in FIG. 3 was projected onto a screen with an overhead projector, and the transparency was evaluated visually according to the following criteria.
◎ Very transparent.
○ Good.
ΔSlightly cloudy.
X Dark.

<Decolorization evaluation>
The ratio between the c density of the decolored printing unit 11 shown in FIG. 4 and the c density of the printing unit 11 before decoloring shown in FIG. 2 was determined, and the decoloring property was evaluated according to the following criteria.
Less than 0.15: Very good.
0.15 or more and less than 0.25: Good.
0.25 or more and less than 0.35: Δ There is a slight color residue.
0.35 or more: x There is a color residue.

  The results obtained by the above evaluation method are shown in Table 1 below.

  As can be seen from Table 1, a masterbatch containing an ultraviolet absorber and a colorant is prepared by adding an ultraviolet absorber in the range of 1.0 to 30% by mass with respect to the mass of the decolorizable electrophotographic toner. In Examples 1 to 19, good results were obtained in terms of light resistance, color developability, OHP transparency and decolorization.

  On the other hand, as can be seen from the results of Comparative Example 1, when the resin used for preparing the masterbatch containing the colorant and the ultraviolet absorber is a normal binder resin for toner, good image evaluation Cannot be obtained.

  Further, as can be seen from the results of Comparative Examples 2 to 4, the masterbatch was not prepared, the masterbatch containing an ultraviolet absorber and no colorant, or the masterbatch containing a colorant and no ultraviolet absorber. When either one of these is prepared, good image evaluation cannot be obtained.

  Further, as can be seen from the results of Comparative Example 5, when a masterbatch containing an ultraviolet absorber and no colorant and a masterbatch containing a colorant and no ultraviolet absorber were prepared separately, the light resistance of the toner Inferior. Similarly, as the result of Comparative Example 6 shows, when the addition amount of the ultraviolet absorber is less than 1% by mass of the toner mass, even when a masterbatch containing the ultraviolet absorber and the colorant is prepared, the light resistance Problems arise.

  When the addition amount of the ultraviolet absorber is more than 30% by mass of the toner mass, even when a master batch containing the ultraviolet absorber and the colorant is prepared, good image evaluation cannot be obtained.

  As mentioned above, although several embodiment of this invention was described, all of these are contained in the invention described in the claim, and its equality range.

The invention described in the claims is appended below.
1. A method for producing a decolorizable electrophotographic toner, comprising kneading a master batch containing an ultraviolet absorber, a colorant, and a first resin with a decoloring agent while heating.
2. 2. The method of producing an erasable electrophotographic toner according to claim 1, wherein the amount of the ultraviolet absorber is 1 to 30% by mass of the toner mass.
3. The masterbatch is manufactured by kneading a mixture containing the ultraviolet absorber, the colorant, and the first resin while heating at a first temperature higher than the melting point of the first resin. Item 3. The method for producing an erasable electrophotographic toner according to Item 1 or 2.
4). When kneading while heating the masterbatch and the decolorizer, the second resin having a melting point higher than that of the first resin is also mixed together, and the melting point of the first temperature and the second resin is exceeded. Item 4. The method for producing an erasable electrophotographic toner according to Item 3, wherein kneading is performed while heating at a high second temperature.
5. 5. The method of producing an erasable electrophotographic toner according to claim 4, wherein the first temperature is 75 to 135 ° C. and the second temperature is 95 to 155 ° C.
6). 6. The method of producing an erasable electrophotographic toner according to claim 4, wherein the first resin has a melting point of 75 to 130 ° C., and the second resin has a melting point of 95 to 150 ° C.
7). The method for producing a decolorizable electrophotographic toner according to any one of claims 4 to 6, wherein the first resin has a smaller average molecular weight than the second resin.
8). A mixture containing an ultraviolet absorber, a colorant, and a first resin is kneaded while being heated, and in the production of a decolorable electrophotographic toner, the melting point is higher than that of the decolorizer and the first resin. Masterbatch mixed with 2 resins.
9. Item 8. An erasable electrophotographic toner produced by the method for producing an erasable electrophotographic toner according to any one of Items 1 to 7.

  DESCRIPTION OF SYMBOLS 1 ... Printing belt, 2 ... Decoloring type electrophotographic toner developing device, 3 ... Decoloring heater, 4 ... Decoloring LED head, 5 ... Transfer part, 6 ... Fixing part, 7 ... Cassette, 8 ... Paper discharge part , 9... Photosensitive toner cartridge, 10... Printing unit, 11.

Claims (9)

  A method for producing a decolorizable electrophotographic toner, comprising kneading a master batch containing an ultraviolet absorber, a colorant, and a first resin with a decoloring agent while heating.   2. The method of producing an erasable electrophotographic toner according to claim 1, wherein the amount of the ultraviolet absorber is 1 to 30% by mass of the toner mass.   The masterbatch is manufactured by kneading a mixture containing the ultraviolet absorber, the colorant, and the first resin while heating at a first temperature higher than the melting point of the first resin. The method for producing an erasable electrophotographic toner according to claim 1 or 2.   When kneading while heating the masterbatch and the decolorizer, the second resin having a melting point higher than that of the first resin is also mixed together, and the melting point of the first temperature and the second resin is exceeded. 4. The method for producing an erasable electrophotographic toner according to claim 3, wherein the kneading is performed while heating at a high second temperature.   5. The method of producing an erasable electrophotographic toner according to claim 4, wherein the first temperature is 75 to 135 [deg.] C. and the second temperature is 95 to 155 [deg.] C.   6. The method of producing an erasable electrophotographic toner according to claim 4, wherein the first resin has a melting point of 75 to 130.degree. C., and the second resin has a melting point of 95 to 150.degree.   7. The method for producing a decolorable electrophotographic toner according to claim 4, wherein the first resin has an average molecular weight smaller than that of the second resin. 8.   A mixture containing an ultraviolet absorber, a colorant, and a first resin is kneaded while being heated, and in the production of a decolorable electrophotographic toner, the melting point is higher than that of the decolorizer and the first resin. Masterbatch mixed with 2 resins.   An erasable electrophotographic toner produced by the method for producing an erasable electrophotographic toner according to any one of claims 1 to 7.

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