JP2013073054A - Method for manufacturing decolorable electrophotographic toner, and decolorable electrophotographic toner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a decolorable electrophotographic toner which improves the visibility after decolorization and allows print information before decolorization to be hardly identified or restored after decolorization, and the decolorable electrophotographic toner.SOLUTION: A method includes the steps of mixing a binder resin, a near-infrared absorbing dye, and a decolorizer, melt-kneading the mixture obtained by the mixing, and adding a fluorescent whitening agent in an amount of more than 0.2 mass% and less than 10 mass% relative to the toner mass when the binder resin, the near-infrared absorbing dye, and the decolorizer are mixed and/or when the mixture is melt-kneaded.

Description

  The present invention relates to a method for producing a decolorable electrophotographic toner and a decolorable electrophotographic toner, and more particularly to a method for producing a decolorable electrophotographic toner capable of improving the visibility after decoloring and the decolorizable electron. It relates to photographic toner.

  The printed matter imaged by a copier or printer using a decolorizable toner using a decolorizable leuco dye or a decolorizable photosensitive toner that reacts to near infrared rays is erased by heat or light, and is printed on paper. Has been proposed (see, for example, Patent Documents 1 and 2). These image forming apparatuses are provided with a toner erasing unit inside or outside the apparatus. When the contents of printed paper printed with light-sensitive toner are no longer necessary, the paper is first erased at its erasing part, returned to a printable state, and the paper can be used again. To do.

  In order to erase characters or the like printed on the paper, the color of the toner forming the characters may be erased, and the paper is erased by some method. In recent years, it has been required to completely erase the color with energy saving and high speed on demand. In order to achieve these requirements, it is necessary for the toner to have high erasability and high visibility after erasing, that is, how close the image after erasing is to the color of the underlying paper.

  However, with conventional light-sensitive toners, decoloring is not sufficient, and the color may remain or may turn yellow after being decolored, so that print information before decoloring can be recognized. There was a bug. In that case, there are cases where there is an obstacle to the reuse of the paper, or the original information that has been erased can be easily restored, leading to information leakage.

JP 05-61247 A JP 2000-19770 A

  The present invention has been made in view of the above circumstances, and is a method for producing a erasable electrophotographic toner capable of improving visibility after erasing and making it difficult to identify and restore print information before erasing after erasing. An object of the present invention is to provide an erasable electrophotographic toner.

  In order to solve the above problems, the first aspect of the present invention is to mix a binder resin, a near-infrared absorbing dye, and a decoloring agent, melt and knead the mixture obtained by the mixing, When the infrared absorbing dye and the decolorizer are mixed and / or melt kneaded, the fluorescent brightening agent is added in an amount of more than 0.2% by mass and less than 10% by mass of the toner mass. A method for producing an erasable electrophotographic toner is provided.

  In the first aspect of the present invention described above, the fluorescent brightening agent is at least one selected from the group consisting of a stilbene compound, a benzoxazolyl stilbene compound, a coumarin compound, a pyrazole compound, and an oxazole compound. Seeds can be used.

  Further, when the binder resin, the near infrared absorbing dye, and the decolorizer are mixed, a charge control agent can be further mixed.

  Moreover, the kneaded material obtained by the melt kneading can be pulverized.

  Further, the toner mass may be the total mass of the binder resin, the near infrared absorbing dye, the decolorizer, the charge control agent, the fluorescent whitening agent, and wax.

  According to a second aspect of the present invention, there is provided an erasable electrophotographic toner produced by the above-described method for producing an erasable electrophotographic toner.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the decoloring type electrophotographic toner which can improve the visibility after decoloring, and the decoloring type electrophotographic toner are provided.

1 is a diagram showing a printer with a color erasing function for erasing and reproducing a transfer medium printed using a color erasable electrophotographic toner according to an embodiment of the present invention and printing again. FIG. It is a figure which shows the image sample printed 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.

  The decolorizable electrophotographic toner according to an embodiment of the present invention is obtained by mixing, melt-kneading, and pulverizing a binder resin, a near-infrared absorbing dye, a decolorizer, and a charge control agent. When the binder resin, near-infrared absorbing dye, decolorizer and charge control agent are mixed and / or melt kneaded, the fluorescent whitening agent exceeds 0.2% by mass of the toner mass, and is 10% by mass. Less than the amount is added.

  An optical brightener generally refers to a chemical substance that is added to cloth or paper to increase whiteness, and is a kind of dye. The optical brightener acts to absorb ultraviolet light having a wavelength of 300 to 400 nm, convert it into blue visible light having a wavelength of 400 to 450 nm, and emit it. As a result, the effect of making yellow yellow, which is a complementary color of blue, inconspicuous is exhibited.

  Usually, the binder resin in the toner after erasing becomes a conventional resin color, and the image or printing after erasing is slightly yellowed. Similarly, the dye in the toner is slightly yellowed after decoloring. In contrast, the fluorescent whitening agent has a function of absorbing the ultraviolet region and reflecting blue-violet to blue-green light, so that the fluorescent whitening agent added to the decoloring toner yellows the printed part after decoloring. It was presumed that the effect of making the image inconspicuous was exhibited, and in fact, yellowing of the printed part after decoloring could be suppressed. As a result, it was effective in improving the visibility after decoloring.

  In general, titanium oxide and zinc oxide are known as agents having a whitening effect, but there is no effect of suppressing yellowing of the printed portion after decoloring.

  As a fluorescent brightening agent preferably used in the decolorizing type electrophotographic toner according to this embodiment, stilbene compounds, benzoxazolyl stilbene compounds, coumarin compounds, pyrazole compounds, pyrazoline compounds, pyrene compounds, oxazoles Compounds, thiazole compounds, imidazole compounds, imidazolone compounds, and the like. Of these optical brighteners, stilbene compounds are particularly preferred. Specific examples of stilbene compounds include HAKKOL RF (Biz (2-benzoxazolyl) stilbene) (trade name: manufactured by Showa Chemical Co., Ltd.).

  When a print or image is formed by an electrophotographic process using the decolorizable electrophotographic toner configured as described above, 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 such as paper or OHP paper can be reused.

  In the decolorizing type electrophotographic toner according to the present embodiment, the fluorescent whitening agent is added in an amount of more than 0.2% by mass of the toner mass and less than 10% by mass when the raw materials are mixed and / or melt kneaded. Yes. Therefore, it is possible to improve the visibility after erasing and make it difficult to identify and restore the printing information before erasing after erasing.

  The amount of the optical brightener added is preferably 0.3 to 2.0% by mass of the toner mass, and most preferably about 1% by mass. The toner mass is a so-called internal additive, the total mass of near-infrared absorbing dye, decolorizer (or developer), wax, charge control agent, binder resin, and fluorescent whitening agent. The addition amount (mass%) of the whitening agent is the mass% contained in the toner. The toner mass does not include silica as an external additive.

  On the other hand, when the addition amount of the fluorescent whitening agent is 0.2% by mass or less or 10% by mass or more of the toner mass, the effect of adding the fluorescent whitening agent is not exhibited, and the toner after decoloring The binder resin inside becomes a conventional resin color, and the image or print after decoloring is slightly yellowed. As a result, the print information before erasing is identified and restored after erasing.

  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.

As the near-infrared absorbing dye contained in the decolorable toner according to this embodiment, conventionally known ones can be used. 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.

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 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.

  As the charge control agent, any of those usually used for electrophotographic toners can be used.

  The decoloring toner according to an embodiment of the present invention may include a release material in addition to the binder resin, the near infrared absorbing dye, the decoloring agent, the charge control agent, and the additive resin. As the release agent, any of those usually used for electrophotographic toners can be used.

  A printer with an erasing function for erasing and reproducing a transfer medium printed using the erasing type electrophotographic toner described above and printing again 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 photosensitive toner developer 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 the transfer medium P printed using photosensitive toner is disposed, and at the top, the transfer medium reprinted using the photosensitive toner is discharged. A paper discharge unit 8 is disposed. Note that the photosensitive toner developing unit 2 is provided with a photosensitive toner cartridge 9 for storing photosensitive toner.

  The printer shown in FIG. 1 operates as follows.

  First, the transfer medium P printed using the photosensitive toner is taken out from the cassette 7 and passes through each part along the transfer medium path 10. The transfer medium P includes paper such as paper and OHP paper. That is, the transfer medium P is heated by the decoloring heater 3 and the decoloring LED head 4 and irradiated with near infrared rays, and the printing is decolored. Next, the developed photosensitive image is transferred to the transfer medium 5 on which the printing has been erased. The developed image of the photosensitive toner is an image developed by the photosensitive toner developer 2 using the photosensitive toner supplied from the photosensitive toner cartridge 9, and is transferred to the transfer portion by the print belt 1. Sent to 5.

  The photosensitive toner image transferred by the transfer unit 5 is further sent along the transfer medium path 10 to the fixing unit, where the fixing process is performed, and then the paper is discharged to the paper discharge unit 8 for operation. Complete.

In the operation of the printer described above, the output of the halogen lamp head 3 was 50 mW / cm ² , and the temperature setting of the decoloring heater 2 was 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
The photosensitive toner to be used was manufactured as follows.

  Infrared photosensitive dye having a sensitivity at a wavelength of 817 nm "IRT" (manufactured by Showa Denko KK) 1.5 parts by mass, organoboron compound decoloring agent "P3B" (manufactured by Showa Denko KK) 7.5 parts by mass, toner Polyester binder resin (manufactured by Kao Corporation) 86.7 parts by mass, negative charge regulator “LR-147” (manufactured by Nippon Carlit Co., Ltd.) 1.5 parts by mass, Carnauba WAX No. 1 powder (Yoyuki Kato Co., Ltd.) ) Imported product) Raw material consisting of 2.5 parts by weight and 0.3 parts by weight of brightening agent “Shigenox 101” (Haccor Chemicals Co., Ltd.) was put into a Henschel mixer (Mitsui Mine Co., Ltd.). , Mixed.

  Subsequently, this mixture was melt-kneaded with a twin-screw kneader. Subsequently, the obtained kneaded material was roughly crushed with a Rotoplex (manufactured by Hosokawa Micron Corporation) to obtain a roughly crushed material. The obtained coarsely pulverized product was pulverized with an impact pulverizer so that the average particle size became 9 μm. One part by mass of silica “R972” (manufactured by Nippon Aerosil Co., Ltd.) as an external additive was added to 100 parts by mass of the obtained pulverized product and mixed with a Henschel mixer to obtain a photosensitive toner.

Example 2
A photosensitive toner was prepared in the same manner as in Example 1 except that the polyester binder resin for toner was 86.0 parts by mass and the fluorescent brightening agent “Shigenox 101” was 1.0 part by mass.

Example 3
A photosensitive toner was prepared in the same manner as in Example 1 except that the polyester binder resin for toner was 85.0 parts by mass and the fluorescent whitening agent “Shigenox 101” was 2.0 parts by mass.

Example 4
A photosensitive toner was prepared in the same manner as in Example 1 except that 0.3 parts by weight of “Shigenox107” (Hackol Chemical) was used instead of “Shigenox 101” as a fluorescent brightening agent.

Example 5
Example 1 with the exception that 86.0 parts by weight of the polyester binder resin for toner and 1.0 part by weight of “Shigenox107” (Hackol Chemical) were used instead of “Shigenox 101” as the fluorescent brightening agent. A photosensitive toner was prepared in the same manner.

Example 6
Example 1 except that 85.0 parts by mass of the polyester binder resin for toner and 2.0 parts by mass of “Shigenox 107” (Hackol Chemical) were used instead of “Shigenox 101” as the fluorescent brightening agent. A photosensitive toner was prepared in the same manner.

Example 7
The photosensitive toner was prepared in the same manner as in Example 1 except that 0.3 parts by weight of “TINOPAL OB CO” (BASF Corp.) was used instead of “Shigenox 101” as the optical brightener. Created.

Example 8
Except for using 86.0 parts by weight of the polyester binder resin for toner and using 1.0 parts by weight of “TINOPAL OB CO” (BASF Co., Ltd.) instead of “Shigenox 101” as the fluorescent brightening agent. A photosensitive toner was prepared in the same manner as in Example 1.

Example 9
Except for using 85.0 parts by mass of the polyester binder resin for toner and using 2.0 parts by mass of “TINOPAL OB CO” (BASF Corporation) instead of “Shigenox 101” as the fluorescent brightening agent. A photosensitive toner was prepared in the same manner as in Example 1.

Example 10
The photosensitive toner was prepared in the same manner as in Example 1 except that 0.3 parts by mass of “Uvitex-WG” (BASF Corp.) was used instead of “Shigenox 101” as the optical brightener. Created.

Example 11
Except that 86.0 parts by weight of polyester binder resin for toner and 1.0 part by weight of “Uvitex-WG” (manufactured by BASF Corp.) instead of “Shigenox 101” as a fluorescent brightening agent were used. A photosensitive toner was prepared in the same manner as in Example 1.

Example 12
Except for using 85.0 parts by mass of polyester binder resin for toner and using 2.0 parts by mass of “Uvitex-WG” (manufactured by BASF Corp.) instead of “Shigenox 101” as a fluorescent brightening agent, A photosensitive toner was prepared in the same manner as in Example 1.

Example 13
The photosensitive toner was prepared in the same manner as in Example 1 except that 0.3 parts by weight of “Uvitex-AT” (BASF Corp.) was used instead of “Shigenox 101” as the optical brightener. Created.

Example 14
Except for using 86.0 parts by weight of polyester binder resin for toner and using 1.0 part by weight of “Uvitex-AT” (BASF Corporation) instead of “Shigenox 101” as a fluorescent brightening agent, A photosensitive toner was prepared in the same manner as in Example 1.

Example 15
Except for using 85.0 parts by mass of polyester binder resin for toner and using 2.0 parts by mass of “Uvitex-AT” (BASF Corporation) instead of “Shigenox 101” as a fluorescent brightening agent, A photosensitive toner was prepared in the same manner as in Example 1.

Example 16
The photosensitive toner was prepared in the same manner as in Example 1 except that 0.3 parts by mass of “HAKKOL RF” (manufactured by Showa Chemical Co., Ltd.) was used instead of “Shigenox 101” as the optical brightener. Created.

Example 17
Except for using 86.0 parts by weight of the polyester binder resin for toner and 1.0 part by weight of “HAKKOL RF” (manufactured by Showa Chemical Co., Ltd.) instead of “Shigenox 101” as the fluorescent brightening agent. A photosensitive toner was prepared in the same manner as in Example 1.

Example 18
Except for using 85.0 parts by mass of the polyester binder resin for toner and using 2.0 parts by mass of “HAKKOL RF” (manufactured by Showa Chemical Co., Ltd.) instead of “Shigenox 101” as the fluorescent brightening agent. A photosensitive toner was prepared in the same manner as in Example 1.

Example 19
Except for using 82.0 parts by mass of the polyester binder resin for toner and using 5.0 parts by mass of “HAKKOL RF” (manufactured by Showa Chemical Co., Ltd.) instead of “Shigenox 101” as the fluorescent brightening agent. A photosensitive toner was prepared in the same manner as in Example 1.

Example 20
Except for using 82.0 parts by mass of polyester binder resin for toner and using 9.0 parts by mass of “HAKKOL RF” (manufactured by Showa Chemical Co., Ltd.) instead of “Shigenox 101” as a fluorescent brightening agent. A photosensitive toner was prepared in the same manner as in Example 1.

Example 21
A photosensitive toner was prepared in the same manner as in Example 1 except that 0.3 part by weight of “Whitex” (manufactured by Sumitomo Chemical Co., Ltd.) was used instead of “Shigenox 101” as a fluorescent brightening agent. did.

Example 22
Except for using 86.0 parts by weight of polyester binder resin for toner and using 1.0 part by weight of “Whitex” (Sumitomo Chemical Co., Ltd.) instead of “Shigenox 101” as a fluorescent brightening agent. A photosensitive toner was prepared in the same manner as in Example 1.

Example 23
Except for using 85.0 parts by weight of polyester binder resin for toner and using 2.0 parts by weight of “Whitex” (Sumitomo Chemical Co., Ltd.) instead of “Shigenox 101” as a fluorescent brightening agent. A photosensitive toner was prepared in the same manner as in Example 1.

Example 24
Leuco dye “CVL” 3.5 parts by mass, “S-205” (manufactured by Yamada Chemical Co., Ltd.) 0.5 parts by mass, developer “24DHBP” (manufactured by Sankyo Kasei Co., Ltd.) 1.5 parts by mass "244THBP" (manufactured by Sankyo Kasei Co., Ltd.) 1.5 parts by mass, binder resin "PTR7734" (manufactured by Eriochem Co., Ltd.) 72 parts by mass, tackifier "FTR-2140" (Mitsui Chemicals, Inc.) 15 parts by mass, negative charge regulator “LR-147” (manufactured by Nippon Carlit Co., Ltd.) 1.0 part by mass, Biscol 660P (manufactured by Sanyo Kasei Co., Ltd.) 4.0 parts by mass, and fluorescent bleaching agent A photosensitive toner was prepared in the same manner as in Example 1 except that a raw material consisting of 1.0 part by mass of “HAKKOL RF” (manufactured by Showa Chemical Co., Ltd.) was used.

Example 25
A photosensitive toner was prepared in the same manner as in Example 24 except that 2.0 parts by weight of “24DHBP” and 1.0 part by weight of “244THBP” were used.

Example 26
A photosensitive toner was prepared in the same manner as in Example 24 except that “24 DHBP” was changed to 6.0 parts by mass, “244THBP” was changed to 1.0 part by mass, and “PTR7734” was changed to 70 parts by mass.

Example 27
2.0 parts by mass of leuco dye “CVL”, 2.0 parts by mass of developer “propyl gallate”, 94 parts by mass of “SB-130” (manufactured by Sanyo Chemical Co., Ltd.) as a binder resin, negative charge regulator Except that 1.0 parts by mass of “LR-147” (manufactured by Nippon Carlit Co., Ltd.) and 1.0 part by mass of “HAKKOL RF” (manufactured by Showa Chemical Co., Ltd.) as a fluorescent bleaching agent were used. Then, a photosensitive toner was prepared in the same manner as in Example 1.

Example 28
Leuco dye “3- (4-dimethylamino-2-ethoxyphenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide” 2.0 parts by mass, developer “gallic acid 2.0 parts by mass of propyl ”, 94 parts by mass of“ styrene / butyl acrylate copolymer (acrylate content 6 parts by mass) ”as a binder resin, negative charge regulator“ LR-147 ”(manufactured by Nippon Carlit Co., Ltd.) Photosensitive in the same manner as in Example 1 except that 1.0 part by mass and a raw material consisting of 1.0 part by mass of “HAKKOL RF” (manufactured by Showa Chemical Co., Ltd.) as a fluorescent bleaching agent was used. Toner was created.

Example 29
4.2 parts by mass of leuco dye “Blue 203”, 6.6 parts by mass of developer “24DHEP” (manufactured by Sankyo Kasei Co., Ltd.), “styrene / butyl acrylate copolymer (acrylate content 6 mass) as binder resin Part) ”82.2 parts by mass, negative charge regulator“ LR-147 ”(manufactured by Nippon Carlit Co., Ltd.) 1.0 part by mass,“ polypropylene wax ”5.0 parts by mass, and“ HAKKOL RF as a fluorescent bleaching agent ” A photosensitive toner was prepared in the same manner as in Example 1 except that 1.0 parts by mass (made by Showa Chemical Co., Ltd.) was used.

Example 30
2.0 parts by mass of a leuco dye “CVL”, 2.0 parts by mass of a developer “gallic propyl”, 16.0 parts by mass of a decoloring agent “cholic acid”, “SB-130” (Sanyo Chemical ( 77.0 parts by mass), negative charge regulator “LR-147” (manufactured by Nippon Carlit Co., Ltd.) 1.0 part by mass, “polypropylene wax” 1.0 part by mass, and “HAKKOL as a fluorescent bleaching agent” A photosensitive toner was prepared in the same manner as in Example 1 except that a raw material consisting of 1.0 part by mass of “RF” (manufactured by Showa Chemical Co., Ltd.) was used.

Example 31
2.0 parts by mass of a leuco dye “CVL”, 2.0 parts by mass of a developer “gallic propyl”, 16.0 parts by mass of a decoloring agent “cholic acid”, “SB-130” (Sanyo Chemical ( 93.0 parts by mass), negative charge regulator “LR-147” (manufactured by Nippon Carlit Co., Ltd.) 1.0 part by mass, “polypropylene wax” 1.0 part by mass, and “HAKKOL as a fluorescent bleaching agent” A photosensitive toner was prepared in the same manner as in Example 1 except that a raw material consisting of 1.0 part by mass of “RF” (manufactured by Showa Chemical Co., Ltd.) was used.

Example 32
Leuco dye “3- (4-dimethylamino-2-ethoxyphenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide” 2.0 parts by mass, developer “gallic acid 2.0 parts by mass of propyl ", 70.0 parts by mass of" styrene / butyl acrylate copolymer (acrylate content 6 parts by mass) "as the binder resin, negative charge regulator" LR-147 "(Nippon Carlit Co., Ltd.) Except that 1.0 parts by mass of “polypropylene wax” and 1.0 part by mass of “HAKKOL RF” (manufactured by Showa Chemical Co., Ltd.) as a fluorescent bleaching agent were used. A photosensitive toner was prepared in the same manner as in Example 1.

Comparative Example 1
Example 1 except that the polyester binder resin for toner (manufactured by Kao) is 87.0 parts by mass and the fluorescent brightening agent “Shigenox 101” (manufactured by Hackol Chemical Co., Ltd.) is 0 parts by mass. A photosensitive toner was prepared in the same manner.

Comparative Example 2
Example 1 except that 86.8 parts by mass of the polyester binder resin for toner (manufactured by Kao) and 0.2 parts by mass of “HAKKOL RF” (manufactured by Showa Chemical Co., Ltd.) as the fluorescent brightening agent were used. A photosensitive toner was prepared in the same manner as described above.

Comparative Example 3
Example 1 except that 77.0 parts by mass of a polyester binder resin for toner (manufactured by Kao) and 10.0 parts by mass of “HAKKOL RF” (manufactured by Showa Chemical Co., Ltd.) as a fluorescent brightening agent were used. A photosensitive toner was prepared in the same manner as described above.

Comparative Example 4
Leuco dye “CVL” 3.5 parts by mass, “S-205” (manufactured by Yamada Chemical Co., Ltd.) 0.5 parts by mass, developer “24DHBP” (manufactured by Sankyo Kasei Co., Ltd.) 1.5 parts by mass , “244THBP” (manufactured by Sankyo Kasei Co., Ltd.) 1.5 parts by mass, “PTR7734” (manufactured by Eriochem Co., Ltd.) 73.0 parts by mass as the binder resin, tackifier “FTR-2140” (Mitsui Chemicals, Inc.) 15.0 parts by mass, negative charge adjusting agent “LR-147” (manufactured by Nippon Carlit Co., Ltd.), and 4.0 parts by mass of Biscol 660P (manufactured by Sanyo Chemical Co., Ltd.) A photosensitive toner was prepared in the same manner as in Example 1 except that the raw material consisting of

  Table 1 below lists the fluorescent brighteners used in the above examples and comparative examples.

Tables 2 and 3 below show the toner compositions used in the above Examples and Comparative Examples.

  The photosensitive toner obtained in the above examples and comparative examples was packed in a cartridge, and this cartridge was installed in the printer shown in FIG. In response to the print request, the printer performed normal printing in which the image developed with the photosensitive toner in the developing device 2 is transferred to the transfer medium by the transfer unit 5 and fixed by the fixing unit 6. As a result, a printed matter as shown in FIG. 2 was obtained. P paper (Fuji Xerox Co., Ltd.) was used as the transfer medium.

  Next, the samples of Examples 1 to 23 and Comparative Examples 1 to 3 were decolored. 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 obtained decolored image sample is shown in FIG.

  The obtained image sample was measured by X-rite 938 (manufactured by X-rite). The measurement items are L *, a *, and b * of the printing unit 11 and the non-printing unit 12 shown in FIG.

  Next, the samples of Examples 24-32 and Comparative Example 4 are decolored. The temperature of the thermostatic bath was set to 130 ° C. and erased by heating for 120 minutes. The obtained erased image sample is as shown in FIG. For these image samples, L *, a *, and b * of the printing unit 11 and the non-printing unit 12 were measured in the same manner.

  Using the above measurement items, the visibility of each example was evaluated by the following two points.

<Visibility evaluation 1>
The decoloring value ΔE of the printing unit 11 and the non-printing unit 12 shown in FIG. 3 is obtained by the following calculation formula.

ΔE = {(L * of printing unit 11−L * of non-printing unit 12) ² + (a * of printing unit 11−a * of non-printing unit 12) ² + (b * −non-printing unit of printing unit 11) 12 b *) ² } ^1/2
The visibility evaluation 1 indicates that the lower the numerical value of ΔE is, the closer the substrate is to the transferred medium, and the evaluation criteria are as follows.

Less than 5.5: ◎ Very good 5.5 or more and less than 6.0: ○ Good 6.0 or more and less than 6.5: △ Practical problem level 6.5 or more: × Level that cannot withstand use <Visibility evaluation 2>
Expressed by b * value.

  In the visibility evaluation 2, it is considered that as the b * value is lower, the yellowing factor of the printing unit 11 is lower, and the evaluation criteria are as follows.

Less than 5.5: ◎ Very good 5.5 or more and less than 6.0: ○ Good 6.0 or more and less than 6.5: △ Practical problem level 6.5 or more: × Level not tolerate use Above evaluation method The results obtained in Table 4 are shown in Table 4 below.

From Table 4 above, the photosensitive toners according to Examples 1 to 32 to which the fluorescent whitening agent exceeding 0.2% by mass and less than 10% by mass of the toner is added are at least a level at which there is no practical problem. It can be seen that the visibility evaluations 1 and 2 are shown. That is, the visibility evaluation 1 is a level at which there is no practical problem, and is very excellent, and the visibility of the printed part after decoloring and the transferred medium as a base is close,
In addition, the visibility evaluation 2 is a level that is not problematic in practice to be very excellent, and the yellowing of the printed part after erasing has been improved, thereby reliably preventing the identification and restoration of the erased information. Is possible. As a result, it is possible to reuse the transferred medium from which the printing has been erased without a sense of incongruity.

  It should be noted that by adjusting the amount of the fluorescent brightening agent, it is possible to design a photosensitive toner corresponding to various transfer media.

  On the other hand, the toners according to Comparative Examples 1 and 4 to which no fluorescent whitening agent is added are at a level where the visibility evaluations 1 and 2 are both unusable. The visibility of the transfer medium was distant, and yellowing of the printed part after decoloring was observed. In addition, the toner according to Comparative Example 2 in which the amount of the fluorescent brightener added is too small and the toner in which the amount of the fluorescent brightener added is too large, both of the visibility evaluations 1 and 2 are at levels that cannot be used. The visibility of the printed part after decoloring and the transferred medium to be ground was separated, and yellowing of the printed part after decoloring was recognized. That is, in the toners according to Comparative Examples 1 to 4, erased information has been identified and restored.

  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 decoloring type electrophotographic toner obtained by mixing, melting, kneading, and pulverizing a binder resin, a near infrared absorbing dye, a decoloring agent, and a charge control agent, the binder resin, the near infrared absorbing dye, When the decolorizer and the charge control agent are mixed and / or melt kneaded, the fluorescent whitening agent is added in an amount of more than 0.2% by mass and less than 10% by mass of the toner mass. An erasable electrophotographic toner characterized by comprising:

  2. 2. The fluorescent whitening agent comprising at least one selected from the group consisting of a stilbene compound, a benzoxazolyl stilbene compound, a coumarin compound, a pyrazole compound, and an oxazole compound. Decolorizing type electrophotographic toner.

  3. A step of mixing a binder resin, a near-infrared absorbing dye, a decolorizer, and a charge control agent, a step of melt-kneading the mixture obtained by the mixing, and a step of pulverizing the kneaded product obtained by the melt-kneading. And when the binder resin, the near-infrared absorbing dye, the decolorizer, and the charge control agent are mixed and / or melt kneaded, the fluorescent whitening agent is 0.2 mass of the toner mass. %, And less than 10% by mass is added.

  4). 4. The fluorescent whitening agent includes at least one selected from the group consisting of a stilbene compound, a benzoxazolyl stilbene compound, a coumarin compound, a pyrazole compound, and an oxazole compound. A method for producing a decolorizable electrophotographic toner.

  DESCRIPTION OF SYMBOLS 1 ... Printing belt, 2 ... Photosensitive 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.

Claims (6)

Mix binder resin, near-infrared absorbing dye, decolorizer,
Melting and kneading the mixture obtained by the mixing,
When the binder resin, the near-infrared absorbing dye, and the decolorizer are mixed and / or melt kneaded, the fluorescent whitening agent exceeds 0.2% by mass of the toner mass and less than 10% by mass. A method for producing an erasable electrophotographic toner, characterized by adding an amount thereof.   2. The fluorescent brightening agent includes at least one selected from the group consisting of a stilbene compound, a benzoxazolyl stilbene compound, a coumarin compound, a pyrazole compound, and an oxazole compound. A process for producing an erasable electrophotographic toner as described in 1 above.   3. The method for producing a decolorable electrophotographic toner according to claim 1, wherein a charge control agent is further mixed when the binder resin, the near-infrared absorbing dye, and the decolorizer are mixed.   4. The method for producing an erasable electrophotographic toner according to claim 1, wherein the kneaded material obtained by the melt-kneading is pulverized.   5. The toner mass according to claim 3, wherein the toner mass is a total mass of the binder resin, the near-infrared absorbing dye, the decolorizer, the charge control agent, the fluorescent brightener, and wax. A process for producing the erasable electrophotographic toner as described.   An erasable electrophotographic toner produced by the method for producing an erasable electrophotographic toner according to any one of claims 1 to 5.

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