JP5641032B2 - Decolorizable electrophotographic toner and method for producing the same - Google Patents

Description

  The present invention relates to a color erasable electrophotographic toner and a method for producing the same, and more particularly to a color erasable electrophotographic toner capable of making it difficult to recognize print information before color erasure after color erasure.

  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 (for example, Patent Document 1). 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 a printed character or the like, it is necessary to erase the color of the toner that forms the character, and the color of the toner is erased by performing a decoloring process on the paper. As a recent need, complete decoloring is required at high speed and on demand. In order to achieve this requirement, it is necessary to have high toner erasability and high visibility after erasing (the density of the erased print and the density of the underlying paper are close to each other).

  However, even if the color erasure is sufficient, the toner itself is not removed from the paper surface, so there is a problem that the print information before the color erasure can be recognized from the difference between the gloss of the toner and the paper. . In that case, there is a case where trouble occurs in the next use of the decolored paper, the original information can be easily restored, and the information leaks.

JP 2000-19770 A

  The present invention has been made in view of the above circumstances, and is a decoloring type capable of making it difficult to recognize print information before decoloring after decoloring by matching the gloss and tone of the decolored printing unit and non-printing unit An object is to provide an electrophotographic toner and a method for producing the same.

  In order to solve the above problems, a first aspect of the present invention provides a decolorizable electrophotographic toner comprising a binder resin, a near-infrared absorbing material, a decoloring agent, and a cellulose fiber powder-containing resin. To do.

  In the decolorizable electrophotographic toner configured as described above, paper powder can be used as the cellulose fiber powder.

  The second aspect of the present invention includes a step of melt-kneading a mixture of a binder resin, a near-infrared absorbing material, a decoloring agent, and cellulose fiber powder-containing resin particles, and a step of pulverizing the melt-kneaded product. A method for producing a decolorizable electrophotographic toner is provided.

  In the method for producing a decolorizable electrophotographic toner configured as described above, the cellulose fiber powder-containing resin particles can be formed by pulverizing and granulating the cellulose fiber powder-containing resin.

  Further, paper powder can be used as the cellulose fiber powder.

  According to the present invention, the erasable electrophotographic toner capable of making it difficult to recognize print information before erasing after erasing by matching the gloss and tone of the erased printed part and the non-printed part, and its production A method is provided.

FIG. 2 is a diagram illustrating a printer with a color erasing function for erasing and reproducing paper printed using a color erasable electrophotographic toner according to an embodiment of the present invention and printing again. It is a figure which shows the image sample printed using the toner which concerns on an Example and a comparative example. It is a figure which shows the image sample obtained by erasing the image sample shown in FIG. 2 with the printer with a erasing function shown in FIG. It is a conceptual diagram which shows the surface of the paper which performed the decoloring operation after printing.

  Hereinafter, various embodiments of the present invention will be described.

  The decolorizable electrophotographic toner according to an embodiment of the present invention includes a colorless and transparent binder resin, a near infrared absorbing material such as a near infrared absorbing dye that is a dispersed cyan pigment, and a colorless that promotes a decoloring reaction. It contains a transparent decoloring agent and 3 to 20% by mass of a cellulose fiber powder-containing resin.

  Addition of cellulose fiber powder blended resin to the decolorable electrophotographic toner changes the texture of the toner resin after decolorization, eliminating the difference in gloss and color tone from the non-printed area, thereby eliminating the pre-decoloration It is possible to make the print information difficult to recognize after erasing. Such an effect is presumed to be due to the fact that the unique texture of the cellulose fiber powder reduces the difference between the surface properties of the toner resin after decoloring and the surface properties of the paper.

  The addition amount of the cellulose fiber powder blended resin is, for example, 3 to 20% by mass with respect to the total amount of the toner. If the addition amount of the cellulose fiber powder blended resin is less than 3% by mass, it becomes difficult to make it difficult to recognize the print information before decoloring after decoloring, and if it exceeds 20% by mass, the initial color (before decoloring) Taste may be impaired. This is presumably because the colorant before decoloring was concealed due to the influence of the brightener blended in the toner material. Moreover, when it exceeds 20 mass%, a decoloring value may also deteriorate. This is presumably because the cellulose fiber powder blended resin hindered the entry of light necessary for decoloring.

  In addition, resin containing cellulose fiber powder refers to a resin containing 2 to 51% by mass of cellulose fiber powder.

  In general, a commercially available paper powder-containing resin contains 51% by mass of paper powder in the resin, so that the net paper powder is contained in an amount of about 1.5 to 10% by mass with respect to the total amount of toner. . By using such a paper powder compounded resin, the difference between the surface property of the toner resin after decoloring and the surface property of the paper is reduced, and good results can be obtained.

  The cellulose fiber blended in the resin may be anything as long as it gives a texture closer to the paper than the toner resin. In addition to paper powder, it is commercially available from Nippon Paper Chemicals, Izumi Senko Co., Ltd., Tosco Corporation, etc. Cellulose powder, chitosan powder, silk powder and the like may be used.

  In this case, the cellulose fiber powder blended resin is added during mixing and / or melt-kneading of the binder resin, the near-infrared absorbing material, and the raw material containing the decolorizer.

  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 image, the near infrared ray absorbing material 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 paper can be reused. Infrared rays generally refer to electromagnetic waves having longer wavelengths than red light and shorter wavelengths than millimeter-wave radio waves, and are distributed in a wavelength range of about 0.7 μm to 1 mm (= 1,000 μm). Among these infrared rays, light having a short wavelength and about 0.7 to 2.5 μm is generally called near infrared ray. The near-infrared absorbing material and derivatives thereof have a maximum absorption wavelength of 817 to 822 nm, and are units used as an index indicating the degree of absorption of light by a substance when light passes through a 1 M solution having a thickness of 1 cm. A dye having a molar extinction coefficient expressed by the reciprocal of the light intensity ratio (transmittance) is about 1 × 10 ⁵ . There are also those having a second absorption band at about 640 nm.

  The decolorization reaction occurs when the dye cation of the near-infrared absorbing material is bonded to the alkyl group of the decolorizer. The ratio between the near-infrared absorbing material and the decoloring agent in the decoloring toner is appropriately selected so that no unreacted near-infrared absorbing material remains after the decoloring reaction.

Conventionally known materials can be used as the near-infrared absorbing material contained in the decolorable toner according to the present embodiment. Examples of such a near infrared ray absorbing material include those described in JP-A-4-362935 and JP-A-5-119520. Specific examples of the near-infrared absorbing material 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.

The decoloring agent is a material that erases the color of the cyan pigment, and after decoloring, it is not completely white but slightly light yellow. 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. By using in combination with a near-infrared absorbing material and a specific organic boron compound, a polymerization function or a decoloring function can be exhibited.

  The binder resin is a resin that is a main component of the toner. 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. Examples thereof include phenol resins, coumarone resins, xylene resins, vinyl chloride resins, polyolefin resins, polycarbonate resins, polyurethane resins, and the like, and these resins may be used in combination of two or more. Of these resins, polyester resins are preferred due to their chargeability, durability, color developability, adhesion to paper, and the like.

  As the charge control agent (charge control agent), any of those usually used for electrophotographic toners can be used, and the effect of the addition can be obtained. Known ones can be used, and particularly those having a high charging speed and capable of stably maintaining a constant charge amount are preferable. Examples of the charge control agent (charge control agent) for controlling the toner to be negatively charged include the following. Polymers or copolymers having sulfonic acid groups, sulfonic acid groups or sulfonic acid ester groups, salicylic acid derivatives and metal complexes thereof, monoazo metal compounds, acetylacetone metal compounds, aromatic oxycarboxylic acids, aromatic mono- and polycarboxylic acids, Metal salts, anhydrides, esters, phenol derivatives such as bisphenol, urea derivatives, metal-containing naphthoic acid compounds, boron compounds, quaternary ammonium salts, calixarene, resin charge control agents, and the like. As specific examples, Spiron Black TRH, T-77, T-95, TN-105 (Hodogaya Chemical Co., Ltd.), BONTRON (registered trademark) S-34, S-44, S-54, E-84, E-88, E-89 (Orient Chemical Co., Ltd.), LR-147 (Nippon Carlit Co., Ltd.), etc. are mentioned.

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

  Hereinafter, a printer with a color erasing function for erasing and reproducing paper printed using the color erasable electrophotographic toner described above and printing again will be described 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 arranged around the intermediate transfer belt 1. At the bottom of the printer, a cassette 7 for storing paper P printed using photosensitive toner is disposed, and at the top, a paper discharge unit 8 for discharging paper reprinted using photosensitive toner. Is arranged. 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 paper P printed using the photosensitive toner is taken out from the cassette 7 and passes through each part along the paper path 10 indicated by a broken line. That is, the paper 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. Subsequently, the developed photosensitive toner image is transferred to the paper from which the printing has been erased in the transfer unit 5. The developed photosensitive toner image is an image developed by the photosensitive toner developer 2 using the photosensitive toner supplied from the photosensitive toner cartridge 9, and is transferred by the intermediate transfer belt 1. Sent to part 5.

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

In the operation of the printer described above, the output of the decoloring LED head 4 such as a halogen lamp head was 50 mW / cm ² , and the temperature setting of the decoloring heater 3 was 100 ° C. The paper path 10 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 color erasing toner to be used was produced as follows.

  First, a resin raw material blended with paper powder was crushed with a Rotoplex (manufactured by Hosokawa Micron Corporation) to obtain a crushed material. Mapuka (manufactured by Environmental Management Research Institute Co., Ltd.) was used as a resin raw material blended with paper powder. The obtained coarsely pulverized product was pulverized by a collision pulverizer to obtain a pulverized product. The obtained pulverized product was granulated with a dry roll compactor (manufactured by Freund Sangyo Co., Ltd.) to obtain a granulated product sized by a 2 mm diameter screen.

  Next, 1.5 parts by mass of an infrared photosensitive dye “IRT” (manufactured by Showa Denko KK) having a sensitivity at a wavelength of 817 nm, 7.5 masses of an organic boron compound decolorizer “P3B” (manufactured by Showa Denko KK) Part, 76.7 parts by mass of a polyester binder resin for toner (manufactured by Kao Corporation), 10 parts by mass of the obtained granulated product, negative charge regulator “LR-147” (manufactured by Nippon Carlit Co., Ltd.) 1 .5 parts by mass, Carnauba WAX No. 1 powder (imported by Kato Yoko Co., Ltd.) 2.5 parts by mass, and fluorescent whitening agent “Shigenox 101” (Haccor Chemicals Co., Ltd.) 0.3 parts by mass (Mitsui Mine Co., Ltd.), and then 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 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 decolorized toner.

Example 2
A decolorable toner was prepared in the same manner as in Example 1 except that the polyester binder resin for toner was 83.7 parts by mass and the granulated product was 3 parts by mass.

Example 3
A decolorable toner was prepared in the same manner as in Example 1 except that the polyester binder resin for toner was 66.7 parts by mass and the granulated product was 20 parts by mass.

Comparative Example 1
A decolorable toner was prepared in the same manner as in Example 1 except that the polyester binder resin for toner was 86.7 parts by mass and the granulated product was 0 parts by mass.

Comparative Example 2
A decolorable toner was prepared in the same manner as in Example 1 except that the polyester binder resin for toner was 84.7 parts by mass and the granulated product was 2 parts by mass.

Comparative Example 3
A decolorable toner was prepared in the same manner as in Example 1 except that the polyester binder resin for toner was 65.7 parts by mass and the granulated product was 21 parts by mass.

  The decolorized 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 was transferred to a sheet 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 (manufactured by Fuji Xerox Co., Ltd.) was used as the paper.

  About the obtained image sample, the c (cyan) density of the printing part 11 and the non-printing part 12 shown in FIG. 2 was measured by X-rite 938 (manufactured by X-rite Co., Ltd.). Then, the glossiness of the printing part 11 shown in FIG. 2 was measured by PG1 (Nippon Denshoku Co., Ltd. product). The incident angle and reflection angle were 75 °.

  Next, the image sample was decolored. First, in the printer shown in FIG. 1, the temperature of the decoloring heater 3 was set to 140 ° C., and the printed paper P was set in the cassette 7. The erasing LED head 4 and the erasing heater 3 of the printer were turned on, and the printed paper P was erased by passing through the path 10. Thereafter, the paper was discharged out of the machine. The obtained decolored image sample is shown in FIG.

  About the obtained image sample, c (cyan) density of the printing part 11 and the non-printing part 12 shown in FIG. 3 was measured by X-rite 938 (made by X-rite Co., Ltd.). Then, the glossiness of the printing part 11 shown in FIG. 3 was measured by PG1 (Nippon Denshoku Co., Ltd. product). The incident angle and reflection angle were 75 °.

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

<Initial visibility evaluation (visual)>
The visibility of the printing unit 11 shown in FIG. 2 was evaluated according to the following criteria.

Visible clearly and clearly: ◎
Visible clearly: ○
Vaguely visible: ×
<C (cyan) density erasing value>
The c (cyan) density decoloration value indicates that the higher the number, the lower the c (cyan) density, and the evaluation was performed according to the following criteria.

7 or more: ◎ Very good 6 or more, but less than 7: ○ Good, less than 6: × Practically problematic level <Gloss evaluation after decoloration>
The gloss evaluation after decoloring was evaluated according to the following criteria.

Less than 10: ◎
10 or more and less than 13: ○
13 or more: ×
<Visibility evaluation after erasing (visual)>
The images shown in FIG. 3 were visually evaluated according to the following criteria.

I do not know the boundary between the print and non-print areas on the paper.
The border between the printed part and the non-printed part is blurred on the paper.
The boundary between the printed and non-printed areas is clearly visible on the paper.
The results obtained by the above evaluation method are shown in Table 1 below.

  From Table 1 above, all the samples obtained with the photosensitive toners according to Examples 1 to 3 blended with 3 to 20% by mass of a paper powder-containing resin granulated product show good visibility evaluation. I understand. That is, the visibility evaluation is good to very excellent, and the visibility of the printed part after erasing and the underlying paper are close to each other, which can surely prevent the erased information from being identified and restored. Is possible. As a result, it was possible to reuse the paper from which the printing was erased without a sense of incongruity.

On the other hand, the sample obtained with the toner according to Comparative Example 1 in which the so-called paper powder-containing resin granulated product containing no paper powder-containing resin granulated product is 0% by mass has an initial visibility and c (cyan). The density erasing value was good, but the gloss after erasing and the visibility after erasing, which are the gloss differences between the surface of the toner binder resin after erasing and the surface of the paper, were not improved.
Further, a sample obtained with the toner according to Comparative Example 2 in which the paper powder-containing resin granulated material is less than 3% by mass includes the surface of the printed portion (toner binder resin) on which the decolored toner is adhered, the paper The gloss after decoloration, which is the difference in glossiness from the surface, was inferior. Furthermore, the sample obtained with the toner according to Comparative Example 3 in which the paper powder-containing resin granulated product exceeds 20% by mass was inferior in initial visibility and c (cyan) density decoloration value.

  FIG. 4 is a conceptual diagram illustrating the surface of a sheet on which a decoloring operation has been performed after printing. FIG. 4 (a) is a diagram showing the surface of a sample obtained with the toner according to Comparative Example 1 in which no paper powder-containing resin granulation is blended, and FIG. 4 (b) is a paper powder-containing resin granulation. It is a figure which shows the surface of the sample obtained with the toner which concerns on Example 1 with which the thing was mix | blended.

The toner is solid, and the paper 21 is in a state where fibers are crossed. After printing, it is melted and embedded in the gap between the surface of the fibrous paper 21. As shown in FIG. 4A, the printed portion 22 where the toner adheres to the surface of the paper 21 has no unevenness on the surface and is glossy, but the non-printed portion 23 of the paper 21 where the toner is not attached. Since there is unevenness, there is no gloss, so that the printed portion 22 can be recognized even after decoloring.
On the other hand, the paper powder 25 has a color similar to that of the paper 21 and includes paper fibers, so that the surface has irregularities. As shown in FIG. 4B, the printed portion 24 where the toner adheres to the surface of the paper 21 is uneven due to the presence of the paper powder 25 and has no gloss. Therefore, the surface state is the same as that of the non-printed portion 23, and the difference in gloss (gloss) between the surface of the printed portion (toner binder resin) 22 to which the decolored toner adheres and the surface of the paper 21 is reduced. Therefore, the printed part 24 cannot be recognized after erasing.

  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 decolorizing type electrophotographic toner comprising a binder resin, a near infrared ray absorbing material, a decoloring agent, and a resin containing cellulose fiber powder.

[2]
The decolorizable electrophotographic toner according to [1], wherein the cellulose fiber powder-containing resin is contained in an amount of 3 to 20% by mass of the toner mass.

[3]
The decolorizable electrophotographic toner according to [1] or [2], wherein the cellulose fiber powder contains at least one of paper powder, cellulose powder, chitosan powder, and silk powder.

[4]
The decolorizing mold according to [2] or [3], wherein the toner mass is a total mass of the binder resin, the near infrared ray absorbing material, the decoloring agent, a charge control agent, and a wax. Electrophotographic toner.

[5]
A decolorizing type electrophotographic comprising: a step of melt-kneading a mixture of a binder resin, a near-infrared absorbing material, a color erasing agent, and resin particles containing cellulose fiber powder; and a step of pulverizing the melt-kneaded product Toner manufacturing method.

[6]
The method for producing an erasable electrophotographic toner according to [5], wherein the cellulose fiber powder-containing resin is contained in an amount of 3 to 20% by mass of the toner mass.

[7]
The method for producing a decolorizable electrophotographic toner according to [5] or [6], wherein the cellulose fiber powder-containing resin particles are formed by pulverizing and granulating cellulose fiber powder-containing resin. .

[8]
The decolorizable electrophotographic toner according to any one of [5] to [7], wherein the cellulose fiber powder includes at least one of paper powder, cellulose powder, chitosan powder, and silk powder. Manufacturing method.

[9]
The toner mass is a total mass of the binder resin, the near-infrared absorbing material, the decolorizer, the charge control agent, and the wax, according to any one of [6] to [8], A process for producing the erasable electrophotographic toner as described.

  DESCRIPTION OF SYMBOLS 1 ... Intermediate transfer 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, 10: Paper path.

Claims (9)

  A decolorizing type electrophotographic toner comprising a binder resin, a near infrared ray absorbing material, a decoloring agent, and a resin containing cellulose fiber powder.   2. The decolorizable electrophotographic toner according to claim 1, wherein the cellulose fiber powder-containing resin is contained in an amount of 3 to 20% by mass of the toner mass.   3. The decolorizable electrophotographic toner according to claim 1, wherein the cellulose fiber powder contains at least one of paper powder, cellulose powder, chitosan powder, and silk powder.   4. The decolorizable electrophotographic image according to claim 2, wherein the toner mass is a total mass of the binder resin, the near-infrared absorbing material, the decolorizer, the charge control agent, and the wax. toner. A decolorizing type electrophotographic comprising: a step of melt-kneading a mixture of a binder resin, a near-infrared absorbing material, a color erasing agent, and resin particles containing cellulose fiber powder; and a step of pulverizing the melt-kneaded product Toner manufacturing method.   6. The method for producing an erasable electrophotographic toner according to claim 5, wherein the cellulose fiber powder-containing resin is contained in an amount of 3 to 20% by mass of the toner mass.   The method for producing a decolorizable electrophotographic toner according to claim 5 or 6, wherein the cellulose fiber powder blended resin particles are formed by pulverizing and granulating a cellulose fiber powder blended resin.   The production of the decolorizable electrophotographic toner according to any one of claims 5 to 7, wherein the cellulose fiber powder contains at least one of paper powder, cellulose powder, chitosan powder, and silk powder. Method.   9. The toner mass according to claim 6, wherein the toner mass is a total mass of the binder resin, the near-infrared absorbing material, the decoloring agent, a charge control agent, and a wax. A method for producing an erasable electrophotographic toner.

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