JP5434129B2 - Negatively chargeable decolorizing toner for electrophotography - Google Patents

Description

The present invention relates to an electrophotographic decolorable toner, and more particularly, to a negatively chargeable electrophotographic decolorable toner capable of forming an image decolored by infrared irradiation.

  Conventionally, a decolorable toner using a near-infrared absorbing dye instead of a pigment is known. This decoloring toner shows a color close to blue under visible light. Further, a quaternary ammonium boron complex is added to the decoloring toner as a decoloring agent (see, for example, Patent Documents 1 and 2).

  When near-infrared rays are irradiated with a halogen lamp, laser, LED, or the like in a state where such a decolored toner printed matter is heated, the infrared absorbing dye in the toner is excited, and a quaternary ammonium boron as a decoloring agent. Reaction with the complex causes a decoloring reaction, and the toner on the printed matter is decolored. Due to such a phenomenon, the printing on the paper once printed is erased and can be used again.

  As described above, a near-infrared absorbing dye and a color erasing agent are added to the color erasing toner, and the color erasing agent has a complex structure of a quaternary ammonium salt and a boron anion. This structure is usually very similar to that of a surfactant and has been used as an antistatic agent for toners. Therefore, the toner added with the decoloring agent has problems such as extremely low chargeability, a lot of fog, and poor image uniformity. In order to prevent this, even if a charge control agent or the like is added, the charge amount is insufficient.

  On the other hand, if no color erasing agent is added to the color erasing toner, the chargeability is very high and a good image can be obtained. However, even if the printed matter is irradiated with infrared rays, the color erasing reaction occurs. This makes it difficult to reduce the original erasing function.

JP-A-4-362935 JP-A-5-119520

The present invention has been made in view of the circumstances as described above, and an object thereof is to provide a negatively chargeable electrophotographic decoloring toner and a decoloring method that exhibit an excellent decoloring function without impairing the chargeability. And

In order to solve the above-mentioned problems, the first aspect of the present invention has a blow-off charge amount larger than the blending amount of a binder resin, a near-infrared absorbing dye, a quaternary ammonium boron complex, and the quaternary ammonium boron complex. A negatively chargeable electrophotographic eraser comprising 10 to 25% by mass of a styrene-acrylic polymer type charge control agent with respect to 100 parts by mass of the binder resin so as to be −54 to −61 μc / g. Provide color toner.

According to a second aspect of the present invention, the image is erased by irradiating a near-infrared ray to a medium on which an image is formed by an electrophotographic process using the negatively chargeable electrochromic toner. A decoloring method is provided.

  According to the present invention, a decoloring toner for electrophotography that exhibits an excellent decoloring function without impairing the chargeability is provided. Also provided is a method for erasing an image formed using this electrophotographic erasing toner.

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

  The decolorable toner according to an embodiment of the present invention includes a binder resin, a near-infrared absorbing dye, a quaternary ammonium boron complex, and a polymer charge of 10 to 25% by mass with respect to 100 parts by mass of the binder resin. It contains a control agent.

  When a print or image is formed by an electrophotographic process using such a decoloring toner, the print or image appears to be a color close to blue under visible light, but when irradiated with near infrared rays in a heated state, the print or image is printed. The image disappears. This is based on the following phenomenon.

  That is, when near infrared rays are irradiated on a print or image at a temperature of, for example, 80 to 160 ° C., the near infrared ray absorbing dye in the toner is excited and reacts with the quaternary ammonium boron complex to cause a decoloring phenomenon. . As a result, the print or image is erased and the paper can be reused.

  The decolorization reaction occurs when the dye cation of the near infrared absorbing dye is bonded to the alkyl group of the quaternary ammonium boron anion.

  In this case, since the quaternary ammonium boron complex has an antistatic action, the presence of the quaternary ammonium boron complex reduces the charge amount and impairs image uniformity. However, the inclusion of a polymer type charge control agent causes such problems. Can be prevented.

  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).

  A conventionally well-known thing can be used as a quaternary ammonium boron complex. Examples of such quaternary ammonium boron complexes include those described in JP-A-4-362935 and JP-A-5-119520. A specific example of the quaternary ammonium boron complex is P3B (trade name, manufactured by Showa Denko KK).

  A conventionally well-known thing can be used as a polymer type charge control agent. As such a polymer-type charge control agent, acrylic base FCA (trade name, manufactured by Fujikura Kasei Co., Ltd.) made of a styrene acrylic polymer can be exemplified. This polymer-type charge control agent not only has excellent charging characteristics, but also has characteristics of excellent safety and transparency because it does not contain a metal. There are FCA-N type for negative charging and FCA-P type for positive and negative charging.

  The compounding amount of the polymer charge control agent is 10 to 25% by mass with respect to 100 parts by mass of the binder resin. A sufficient charge amount can be obtained within this blending amount range, and excellent image uniformity can be obtained. When the blending amount of the polymer type charge control agent is less than 10% by mass, a sufficient charge amount cannot be obtained and image uniformity is inferior. On the other hand, if it exceeds 25% by mass, a sufficient charge amount can be obtained, but the durability of the toner is inferior and image defects occur.

  The binder resin can be selected from a wide range including known ones. Specific examples include styrene resins such as polystyrene, styrene-acrylic acid ester copolymers, styrene-methacrylic acid copolymers, and styrene-butadiene copolymers, saturated polyester resins, unsaturated polyester resins, and epoxy resins. Phenolic resin, coumarone resin, xylene resin, vinyl chloride resin, polyolefin resin and the like can be exemplified, and two or more of these resins may be used in combination. Of these resins, polyester resins are preferred.

  The decolorable toner for electrophotography according to an embodiment of the present invention may contain a release material in addition to the binder resin, the near infrared absorbing dye, the quaternary ammonium boron complex, and the polymer charge control agent. As the release agent, any of those usually used for electrophotographic toners can be used.

  EXAMPLES Hereinafter, the Example and comparative example of this invention are shown and this invention is demonstrated more concretely.

Example 1
100 parts by mass of a polyester resin (softening point 147 ° C., glass transition point 75 ° C., manufactured by Kao Corporation) as a binder resin, 3 parts by mass of IRT (manufactured by Showa Denko KK) as a near-infrared absorbing dye, and as a decoloring agent P3B (manufactured by Showa Denko KK) 3 parts by mass, Carnauba wax No. 1 powder (Yoko Kato Co., Ltd. imported) 2.5 parts by weight as a release agent, FCA-1001-NS as a polymer type charge control agent CCR 10 parts by mass (manufactured by Fujikura Kasei Co., Ltd.) was weighed to a total of 10 kg and mixed with a 20 L Henschel mixer at 2800 rpm for 3 minutes.

  Next, the mixture was kneaded with a twin screw extruder (PCM-45: trade name, manufactured by Ikegai Co., Ltd.) to obtain a kneaded product. The obtained kneaded product was cooled and pulverized with a coarse crusher, and then finely pulverized with an impact plate type pulverizer (IDS-2: trade name, manufactured by Nippon Pneumatic Co., Ltd.), and further an air classifier (CSX-2, The product was classified by a trade name, manufactured by Nippon Pneumatic Co., Ltd., and colored fine particles having an average particle size of about 9.0 μm were obtained.

  RY50 (trade name, manufactured by Nippon Aerosil Co., Ltd.) 2.0 parts by mass and RY200 product name, manufactured by Nippon Aerosil Co., Ltd. (0.3 parts by mass) as hydrophobic silica with respect to 100 parts by mass of the obtained colored fine particles. Part, 0.5 parts by mass of alumina (AL45-2: trade name, manufactured by Showa Denko KK) is weighed to a total of 3 kg, introduced into a 20 L Henschel mixer, and 5 minutes at a peripheral speed of 40 m / sec. Then, they were mixed and subjected to external addition treatment to obtain a toner.

Examples 2, 3 and Comparative Examples 1-3
As shown in Table 1 below, a toner was obtained in the same manner as in Example 1 except that the amount of FCA-1001-NS added as the polymer charge control agent CCR was variously changed.

Examples 4-6, Comparative Examples 4-6
As shown in Table 1 below, FCA-2521-NS (manufactured by Fujikura Kasei Co., Ltd.) was used as the polymer charge control agent CCR, and the addition amount was variously changed, as in Example 1. Thus, a toner was obtained.

Comparative Examples 7-12
As shown in Table 1 below, the toner was used in the same manner as in Example 1 except that LR-147 added to normal toner was used as the charge control agent and the amount added was changed variously. Got.

  The following characteristics were evaluated for the 18 toners according to Examples 1 to 6 and Comparative Examples 1 to 12 obtained as described above.

1. Decoloring reaction Toner was mounted on an N3500 printer (manufactured by Casio Computer Co., Ltd.) and printed on paper. In a state where the obtained printed matter was heated to about 70 ° C. on a heater rubber, 50 mW / cm ² of near infrared rays showing a peak of about 830 nm was irradiated from the LED for about 2 seconds, and the decoloring reaction was confirmed.

  The image density before irradiation of the printed matter at this time was measured in advance with X-rite, the image density after irradiation was measured with X-rite, and the density reduction rate was calculated by the following equation.

Density erasing rate (%) = 100− (post-irradiation density / pre-irradiation density) × 100
The larger the value, the better the decoloring reaction.

  The criteria for determining the decoloring reaction are shown below.

95% or more: ○
60% to 95%: △
60% or less: ×
2. Image uniformity Determined visually.

3. Fog was judged visually.

4). durability
Using an N3500 printer (manufactured by Casio Computer Co., Ltd.), printing was performed up to 40000 sheets at a 5% printing rate, and durability evaluation was performed according to the following evaluation criteria.

  ○: No streak or the like was observed and a good image was obtained.

  X: A streak or the like occurred and a fatal image defect was observed.

5. Charge amount The charge amount was measured with a blow-off type powder charge amount measuring device (manufactured by Toshiba Chemical) and evaluated according to the following criteria.

○: −40 μc / g or more Δ: −20 to −40 μc / g
×: -20 μc / g or less Comprehensive evaluation The above decoloring reaction, image uniformity, durability, and charge amount were comprehensively evaluated.

The above evaluation results are shown in Table 2 below.

  The following can be seen from Table 2 above. That is, the decolorizing toners of Examples 1 to 3 containing FCA-1001-NS, which is a polymer type charge control agent, within a range of 10 to 25% by mass show a good charge amount and form a uniform image. Durability is satisfactory, and the color erasing performance is sufficiently satisfied. Similarly, the decolorable toners of Examples 4 to 6 containing FCA-2521-NS, which is a polymer type charge control agent, in the range of 10 to 25% by mass show similarly good results.

  On the other hand, the decoloring toner of Comparative Example 1 containing FCA-1001-NS, which is a polymer type charge control agent, 30% by mass exceeding the upper limit of the range of the present invention is decoloring performance, charge amount, and image uniformity. The durability was good, but streaks occurred in the durability test, resulting in fatal image defects. This is presumably because the charge control agent was added excessively, so that the durability as a toner was weakened and streaks were generated.

  Further, the decoloring toners of Comparative Examples 2 and 3 containing FCA-1001-NS, which is a polymer type charge control agent, 8 mass% and 5 mass% below the lower limit of the range of the present invention, are decoloring performance and durability. Was satisfactory, but a sufficient charge amount could not be obtained, and the image uniformity deteriorated. Although it is a sufficient addition amount as a charge control agent for a normal toner, it is considered that the addition amount of the charge control agent was insufficient because the decoloring agent showed positive chargeability.

  Similar results were obtained with the toners of Comparative Examples 4 to 6 in which the polymer type charge control agent was changed from FCA-1001-NS to FCA-2521-NS.

  Further, the decoloring toners of Comparative Examples 7 to 11 using various addition amounts of the charge control agent LR-147, which is not a polymer type charge control agent, have good decoloring performance and durability, but sufficient charge The amount was not obtained, and the image uniformity deteriorated. This is probably because the charge control ability of the charge control agent LR-147 is inferior, so that the charge amount does not increase no matter how much the addition amount is increased, and as a result, the image uniformity deteriorates.

  Note that the toner of Comparative Example 12 in which the decolorizer was reduced to 1% with respect to the toner of Comparative Example 7 increased the negative charge amount as a whole and obtained a good charge amount. The color erasing performance deteriorated due to the small amount.

Claims (2)

100 masses of the binder resin so that the amount of blow-off charge is −54 to −61 μc / g more than the amount of the binder resin, near-infrared absorbing dye, quaternary ammonium boron complex, and quaternary ammonium boron complex. A negatively chargeable electrophotographic decolorable toner comprising 10 to 25% by mass of a styrene-acrylic polymer type charge control agent with respect to parts.   A medium on which an image is formed by an electrophotographic process using the negatively chargeable decolorizable toner for electrophotography according to claim 1, wherein the image is decolored by irradiating near infrared rays. Decoloring method.