JP5139344B2 - Erasable toner - Google Patents

Description

  The present invention relates to a decolorable toner.

To suppress the greenhouse effect caused by protection and CO ₂ global environmental protection of forests is an absolute condition. In order to keep new logging to a minimum and maintain a balance with reforestation including afforestation, how to efficiently use the paper resources that we already have is a major issue.

  The current reuse of paper resources is “recycling” where paper fibers that have undergone the deinking process to peel off the image forming material are re-spread on poor quality paper and used differently for different purposes. It has been pointed out that there are problems and the possibility of new environmental pollution due to the treatment of waste liquid.

  On the other hand, in the past, practical use was also made regarding the reuse of hard copy by correcting the image drawn on paper, that is, “reuse”, such as poppy gum for pencils and correction liquid for ballpoint pens. It is coming. Here, “reuse”, which is used multiple times for the same purpose to prevent paper quality deterioration as much as possible, is a different concept from “recycle”, which is used for other purposes while reducing paper quality. From the viewpoint of protecting paper resources, This is a more important concept. If effective “reuse” is performed at the previous stage of each “recycle”, newly required paper resources can be minimized. For example, in recent years, rewritable paper, which is a special paper for the purpose of reusing hard copy paper, has been proposed. If the rewritable paper technology is used, it is possible to “reuse” 100 times or more without worrying about the pain of paper such as wrinkles and bending caused by use, and the utilization efficiency of paper resources will be dramatically improved.

  However, since the above-mentioned rewritable paper uses special paper, it is a technique that can be “reused” but cannot be “recycled”, and has a drawback that it cannot be applied to recording techniques other than thermal recording.

  On the other hand, the present inventors pay attention to the fact that the color developing compound and the developer are in a colored state when the interaction is increased, and are in the decoloring state when the interaction is decreased. By adding a new color erasing agent to the composition containing the colorant, the color development state is stable at temperatures near room temperature, and the color erasure state is fixed for a long time at the practical temperature by treatment with heat or solvent. Image forming materials, image erasing processes, and image erasing devices have been developed and proposed as an effective paper reuse technology to replace the current technology.

  Furthermore, the present inventors have discovered that cellulose, which is a constituent element of “paper”, has a function of a decoloring agent, and in a limited use in which paper is used as a recording medium, an image forming material containing no decoloring agent. However, it is proposed that the color can be erased by the two methods described above.

  Of the decolorizable toners used in electrophotography, the most important characteristic is the color erasing characteristic. This is because the coloring characteristics are directly linked to the readability of a document, and the decoloring characteristics ultimately determine the number of times paper can be reused. The inventors of the present invention are extremely important in selecting a color developer for improving the color development / decoloration characteristics of a decolorable toner. As color developers having excellent color development / decoloration characteristics, ethyl gallate and 2,4,4 are known. -Dihydroxybenzophenone, ethyl gallate and 2,4,4'-trihydroxybenzophenone, ethyl gallate and 2,2 ', 4,4'-tetrahydroxybenzophenone were shown (Patent Documents 1 and 2) ). As a fact to be noted here, even with a color erasing toner composition using a plurality of color developers in combination, for example, a toner composition using a combination of ethyl gallate and propyl gallate shown in the comparative example of Patent Document 1, There is a composition in which a clear improvement effect is not observed in the color characteristics, and there has been a problem in selecting a material for a decolorable toner using a plurality of developers.

Japanese Patent No. 395574 JP 2008-242316 A

 The object of the present invention was made to further improve the color development / decoloration characteristics of conventional erasable image recording materials, and when used in combination with a specific developer, the color development / decoloration characteristics superior to those of conventional compositions. An object of the present invention is to provide a decolorable toner having

 The decolorizable toner according to an embodiment of the present invention contains a leuco dye, two kinds of developer, and a binder resin, and the developer includes 2,4-dihydroxybenzophenone and 2,4,4. It is characterized by containing '-trihydroxybenzophenone.

  According to the present invention, it is possible to provide a erasable toner having excellent color erasing properties.

The figure which shows powder density | concentration about the erasable toner produced in Example 1, 2 and Comparative Example 1,2. FIG. 5 is a graph showing the thermal erasure rate for the decolorizable toners created in Examples 1 and 2 and Comparative Examples 1 and 2. FIG. 6 is a graph showing the powder concentration of decolorizable toners created in Comparative Examples 2 and 3 and Example 3. FIG. 6 is a graph showing the thermal erasure rate for the decolorizable toners created in Comparative Examples 2 and 3 and Example 3.

  Hereinafter, the present invention will be described in detail.

A decolorizable toner according to an embodiment of the present invention includes a leuco dye, two kinds of developer, and a binder resin, and the developer is represented by 2,4-dihydroxybenzophenone (hereinafter referred to as 24DHBP). And 2,4,4′-trihydroxybenzophenone (hereinafter referred to as 244THBP). By using the above two types together as the developer, it is possible to obtain a erasable toner having better color development and decoloring characteristics than using a single developer. Furthermore, this combination has higher erasing performance than the other combinations.
The color developer contained in the erasable toner will be described. 24DHBP and 244THBP are hydroxybenzophenone-based phenols, but 244THBP is more excellent in color development than 24DHBP due to the difference in its molecular structure (position of hydroxyl group). In the erasable toner, the proper blending amount of 244THBP with respect to 4% of leuco dye is about 3%. On the other hand, in order to obtain the same color developability with 24DHBP, it is necessary to increase the addition amount to about 6%. 24DHBP and 244THBP are developers with excellent erasability, but compared with the optimum blend ratio, 24DHBP having a smaller molecular weight is slightly superior in erasability. The reason why the color developability is excellent in the toner using a combination of multiple developers is that the density of the color developer is higher than the composition using a single developer because each developer has an equilibrium reaction that interacts with the dye. Can be estimated. However, the reason why the erasing performance is higher than other combinations depending on the selection type of the developer is difficult to explain at present.

  The leuco dye contained in the decolorable toner will be described. Examples of leuco dyes include leuco auramines, diaryl phthalides, polyaryl carbinols, acyl auramines, aryl auramines, rhodamine B lactams, indolines, spiropyrans, fluorans and the like. Is mentioned. A wide variety of materials can be selected for the leuco dye, such as crystal violet lactone (hereinafter referred to as CVL), malachite green lactone, 2-anilino-6- (N-cyclohexyl-N-methylamino) -3. -Methylfluorane, 2-anilino-3-methyl-6- (N-methyl-N-propylamino) fluorane, 3- [4- (4-phenylaminophenyl) aminophenyl] amino-6-methyl-7- Chlorofluorane, 2-anilino-6- (N-methyl-N-isobutylamino) -3-methylfluorane, 2-anilino-6- (dibutylamino) -3-methylfluorane, 3-chloro-6- (Cyclohexylamino) fluorane, 2-chloro-6- (diethylamino) fluorane, 7- (N, N-dibenzylamino) -3- (N, N-diethylamino) fluorane, 3,6-Bis (diethylamino) fluorane γ- (4'-nitro) anilinolactam, 3-diethylaminobenzo [a ] -Fluorane, 3-diethylamino-6-methyl-7-aminofluorane, 3-diethylamino-7-xylidinofluorane, 3- (4-diethylamino-2-esoxyphenyl) -3- (1-ethyl- 2-Methylindol-3-yl) -4-azaphthalide, 3- (4-diethylaminophenyl) -3- (1-ethyl-2-methylindol-3-yl) phthalide, 3-diethylamino-7-chloroanilino Fluorane, 3-diethylamino-7,8-benzofluorane, 3,3-Bis (1-n-butyl-2-methylindol-3-yl) phthalide, 3,6-dimethylethoxyfluorane, 3- Diethylamino-6-mesoxy-7-aminofluorane, DEPM, ATP, ETAC, 2- (2-chloroanilino) -6-dibutylaminofluorane, crystal violet carbinol, malachite green carbinol, N- (2, 3- (Dichlorophenyl) leucooramine, N-benzoylo Min, Rhodamine B lactam, N-acetyl auramine, N-phenyl auramine, 2- (phenyliminoethanedilidene) -3,3-dimethylindoline, N-3,3-trimethylindolinobenzospiropyran, 8'- Methoxy-N-3,3-trimethylindolinobenzospiropyran, 3-diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-7-methoxyfluorane, 3-diethylamino-6-benzyloxyfluorane, 1, Examples include 2-benz-6-diethylaminofluorane, 3,6-di-p-toluidino-4,5-dimethylfluorane-phenylhydrazide-γ-lactam, 3-amino-5-methylfluorane, and the like.

  Among the above leuco dyes, CVL is a material that is excellent in thermal decoloring so as not to allow other leuco dyes to follow. However, CVL has a weak point that it is easily decomposed by light. On the other hand, even though the other leuco dyes were excellent in light resistance, there was no material exhibiting thermal decoloring properties close to CVL.

However, the combined use of CVL and the specific second leuco dye can improve the light fastness without degrading the decoloring performance. As the second leuco dye to be added in a small amount, a fluorane type leuco dye is suitable, and in particular, in the form of 2-anilino-6- (N-alkyl-N-alkylamino) -3-methyl-fluorane. The black leuco dyes or derivatives thereof described are preferred. Specifically, 2-anilino-6- (N, N-diethylamino) -3-methylfluorane, 2-anilino-6- (N, N-dipropylamino) -3-methylfluorane, 2-anilino -6- (N, N-dibutylamino) -3-methylfluorane, 2-anilino-6- (N, N-dipentylamino) -3-methylfluorane, 2-anilino-6- (N, N- Dihexylamino) -3-methylfluorane, 2-anilino-6- (N, N-dioctylamino) -3-methylfluorane, 2-anilino-6- (N, N-diisopropylamino) -3-methylfluor Oran, 2-anilino-6- (N, N-diisobutylamino) -3-methylfluorane, 2-anilino-6- (N, N-diisopentylamino) -3-methylfluorane, 2-anilino- 6- (N-methyl-N-ethylamino) -3-methyl-fluorane, 2-anilino-6- (N-methyl-N-isopropylamino) -3-methyl-fluorane, 2-anilino-6- (N -Methyl-N--isobutylamino) -3-methylfluorane, 2-anily -6- (N-methyl-N-isopentylamino) -3-methylfluorane, 2-anilino-6- (N-methyl-N-propylamino) -3-methyl-fluorane, 2-anilino-6- (N-methyl-N--butylamino) -3-methylfluorane, 2-anilino-6- (N-methyl-N-pentylamino) -3-methylfluorane, 2-anilino-6- (N- Methyl-N-hexylamino) -3-methylfluorane, 2-anilino-6- (N-methyl-N-octylamino) -3-methylfluorane, 2-anilino-6- (N-ethyl-N- Propylamino) -3-methyl-fluorane, 2-anilino-6- (N-ethyl-N-isobutylamino) -3-methylfluorane, 2-anilino-6- (N-ethyl-N-pentylamino)- 3-Methylfluorane, 2-anilino-6- (N-ethyl-N-2
-Methylbutyl) amino) -3-methylfluorane, 2-anilino-6- (N-ethyl-N-2-ethylpropyl) amino) -3-methylfluorane, 2-anilino-6- (N-ethyl- N-hexylamino) -3-methylfluorane and the like, leuco dyes that develop black color.

  Next, the binder resin contained in the erasable toner will be described. Examples of suitable materials for the binder resin include polystyrene, polystyrene derivatives, and styrenic copolymers. Specific examples of the styrene monomer include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-ethylsterene, 2,4-dimethylstyrene, pn-butylstyrene, p -tert-butylstyrene, pn-hexylstyrene, pn-octylstyrene, pn-nonylstyrene, pn-decylstyrene, pn-dodecylstyrene, p-methoxystyrene, p-phenylstyrene, p-chlorostyrene and 3,4 -Dichlorostyrene. These monomers may be used in combination. Acrylate monomers that can be copolymerized are methyl methacrylate, ethyl methacrylate, isobutyl methacrylate, cyclohexyl methacrylate, ethyl hexyl methacrylate, lauryl methacrylate, stearyl methacrylate, vinyl acetate, vinyl propionate, methacrylonitrile. Dimethyl maleate, diethyl maleate, dimethyl fumarate, dibutyl fumarate, dimethyl itaconate, dibutyl itaconate, methyl vinyl ether, ethyl vinyl ether, n-butyl vinyl ether, isobutyl ether and the like. Examples of suitable resin binders include styrene / n-butyl methacrylate, styrene / isobutyl methacrylate, styrene / ethyl acrylate, styrene / n-butyl acrylate, styrene / methyl methacrylate, styrene / glycidyl methacrylate, and styrene / dimethylamino. Ethyl methacrylate, styrene / diethylaminoethyl methacrylate, styrene / diethylaminopropyl acrylate, styrene / 2-ethylhexyl acrylate, styrene / butyl acrylate-N- (ethoxymethyl) acrylamide, styrene / ethylene glycol methacrylate, styrene / 4-hexafluorobutyl methacrylate, Styrene / butadiene copolymer, styrene / propylene copolymer, acrylonitrile / acrylic rubber / Tylene terpolymer, acrylonitrile / styrene / acrylic ester terpolymer, styrene / acrylonitrile copolymer, acrylonitrile / chlorinated polystyrene / styrene terpolymer, acrylonitrile / ethylene vinyl acetate / styrene terpolymer Polymers, styrene / p-chlorostyrene copolymers, styrene / propylene copolymers, styrene / butadiene rubbers, styrene / maleic acid ester copolymers, styrene / maleic anhydride copolymers and the like are suitable. Thus, only one type of acrylate monomer may be used for copolymerization, or two or more types of monomers may be mixed and copolymerized with styrene. Butadiene, maleic acid ester, chloroprene and the like may be copolymerized, but the weight ratio of these components is more preferably 10% or less. A polymer of the above acrylate monomer can be blended with polystyrene. In this case, the polyacrylate component may be one kind or a mixture of homopolymers, or may be a copolymer.

  In general, in a erasable toner composition, the lower the amount of polar groups contained in the binder resin, the higher the color density of the image material formed by kneading, and the higher the compatibility with the color former. A typical example of a binder resin having a high coloration / decoloration contrast is a nonpolar resin such as polystyrene or polyolefin. If limited to toner applications, the most preferred resins are styrene-butadiene copolymers and their derivatives. To further limit, in the erasable toner of the present embodiment, a composite in which a styrene-butadiene copolymer having a butadiene content of 5 to 15 wt% is mixed with a second styrene resin containing α-methylstyrene. It is recommended to use resin as binder resin. Specific examples of the second styrene resin containing α-methylstyrene include α-methylstyrene resin, α-methylstyrene / styrene copolymer, α-methylstyrene / aliphatic copolymer, and α-methylstyrene. -An alicyclic copolymer, an α-methylstyrene / styrene / aliphatic terpolymer, and an α-methylstyrene / styrene / alicyclic terpolymer. Among these, α-methylstyrene resin and α-methylstyrene / styrene copolymer are preferable. The proper content ratio of the α-methylstyrene derivative in the toner composition is preferably 5 wt% to 50 wt% of the total binder resin, and more preferably 5 wt% to 20 wt% if the range is limited.

  In order to adjust the charging characteristics of the toner, a charge control agent can be blended as necessary. The erasable toner according to the exemplary embodiment is required to leave no color of the charge control agent when the color is erased. Therefore, the charge control agent is preferably colorless or transparent. As the charge control agent for negative charge, Orient Chemical's E-89 (calixarene derivative), Nippon Carlit's N-1, N-2, N-3 (both phenol compounds), LR147 (boron compound), Examples include FCA-1001N (styrene-sulfonic acid resin) manufactured by Fujikura Kasei. Of these, E-89 and LR147 are more preferred. As a charge control agent for positive charging, TP-302 (CAS # 116810-46-9), TP-415 (117342-25-2) of Hodogaya Chemical, P-51 (quaternary amine compound of Orient Chemical) ), AFP-B (polyamine oligomer), Fujikura Kasei's FCA-201PB (styrene-acrylic quaternary ammonium salt resin), and the like.

Waxes may be blended in order to control the fixing property of the toner. The wax used for the toner according to the exemplary embodiment of the present invention is preferably composed of a component that does not cause the leuco dye to develop color. Examples of the waxes include higher alcohols, higher ketones, higher aliphatic esters, and the like, and the acid value thereof is preferably 10 mgKOH / g or less. The waxes preferably have a weight average molecular weight of 10 ² to 10 ⁵ , and more preferably 10 ² to 10 ⁴ . If the weight average molecular weight is in the above range, low molecular weight polypropylene, low molecular weight polyethylene, low molecular weight polybutylene, low molecular weight polyalkane and the like can also be used. The amount of the wax added is preferably 0.1 to 30 parts by weight, and more preferably 0.5 to 15 parts by weight. The heat roll fixing toner is added to give release performance from the heat roll when the addition amount is within 5 parts by weight. The pressure fixing toner is mainly composed of this wax, and is microscopic. It becomes the core part of the capsule structure.

  If necessary, the erasable toner according to the embodiment of the present invention may be blended with an external additive for controlling fluidity, storage stability, blocking resistance, and photoconductor polishing properties. As the external additive, silica fine particles, metal oxide fine particles, cleaning aids and the like can be used. Examples of the silica fine particles include silicon dioxide, sodium silicate, zinc silicate, magnesium silicate and the like. Examples of the metal oxide fine particles include zinc oxide, magnesium oxide, zirconium oxide, strontium titanate, and barium titanate. Examples of the cleaning aid include fine resin powders such as polymethyl methacrylate, polyvinylidene fluoride, and polytetrafluoroethylene, and fine powders of metal fatty acid compounds such as zinc stearate and aluminum stearate. These external additives may be subjected to surface treatment such as hydrophobization. The external additive used for the toner is usually subjected to a hydrophobic treatment. In the case of negative charging, a hydrophobizing agent such as a silane coupling agent, a titanium coupling agent, or silicone oil is used. In the case of positive charging, a hydrophobizing agent such as an aminosilane-based, silicone oil having an amine in the side chain is used. The addition amount of the external additive is preferably 0.05 to 5 parts by weight, and more preferably 0.1 to 3.0 parts by weight with respect to 100 parts by weight of the toner. As the silica used in the toner, particles having an average particle diameter of 10 to 20 nm (primary particles) are generally used, and particles having an average particle diameter of about 100 nm are also used. For materials other than silica, particles having a relatively large particle diameter having an average particle diameter of 0.05 to 3 μm are generally used.

  In the case of producing a decolorizable toner according to the present embodiment, in order to mix and disperse the leuco dye and the developer in the binder resin, a wet dispersion method using a solvent with a high-speed dissolver, a roll mill, a ball mill, etc. A melt kneading method using a roll, a pressure kneader, an internal mixer, a screw type extruder or the like can be used. As a mixing means, a ball mill, a V-type mixer, a Forberg, a Henschel mixer, or the like can be used.

Example 1
As the composition of the toner for electrophotography, CVL and leuco dye S-205 (2-anilino-6- (N-ethyl-N-isopentylamino) -3-methylfluorane; manufactured by Yamada Chemical) are selected as the leuco dye. The composition ratio of CVL was fixed to 3.5 wt%, and the composition ratio of S-205 was fixed to 0.5 wt%. Two types of developer, 24DHBP and 244THBP, were prepared as developer, and the blending amount was 1.5 wt% for 24DHBP and 1.5 wt% for 244THBP. For the other toner components, the wax component is 4% by weight of polypropylene wax, LR-147 (manufactured by Nippon Carlit) is selected as the charge control material, 1% by weight, and the remaining component is 15% by weight of α-methylstyrene / styrene copolymer. Was blended with a styrene-butadiene copolymer having a styrene content ratio of 10% as a binder resin.

  These mixtures were kneaded and then processed into a fine powder having an average particle size of 9.5 μm by a pulverizer to prepare a blue electrophotographic toner. Thereafter, a sample was prepared by adding 1 wt% of hydrophobic silica to the toner using Henschel.

(Example 2)
As a blending amount of the two kinds of developers, 24 DHBP was 2.0 wt%, and 244THBP was 1.0 wt%. Other preparation conditions were the same as those in Example 1.

(Comparative Example 1)
As a developer, only 24 DHBP was added at 3.0 wt%, and 244THBP was not added. Other preparation conditions were the same as those in Example 1.

(Comparative Example 2)
As a developer, 24 DHBP was not added, and only 244THBP was blended at 3.0 wt%. Other preparation conditions were the same as those in Example 1.

  The color erasing characteristics of the decolorable toners prepared in Examples 1 and 2 and Comparative Examples 1 and 2 were evaluated by the following method.

  Using a color difference meter CR300 (manufactured by Minolta) and a dedicated powder measurement cell, the optical reflection density of the toner was measured, and the value was defined as the powder density, which was used as a measure of the color development characteristics of the toner. That is, it can be said that the higher the powder concentration, the higher the color development characteristics of the toner.

  Next, using the created toner, an MFP (e-studio350EB; manufactured by TOSHIBA TEC) uses several stages of image IDs on two types of copy paper having different paper pH (neutral paper and alkaline paper). A solid pattern was printed and used as an evaluation image for erasing characteristics. The thermal erasure was performed under conditions of 130 ° C. and 2 hours using a dedicated jig placed in a thermostatic bath. For each evaluation paper, the erasing characteristics are [(original image ID) − (paper ID)] before thermal erasure on the horizontal axis and [(afterimage ID) − (paper ID)] after thermal erasing on the vertical axis. Plotted. The slope of the regression line of this data was measured, and the arithmetic average value of the two types of paper was defined as the thermal erasure rate, which was used as a measure of the erasing characteristics. The thermal erasure rate indicates how much the density of the afterimage corresponds to the original image, and the smaller the value, the higher the erasing characteristic. For example, a thermal erasure rate of 0.05 means that the residual image density remaining when an image with an image density of 1.0 is thermally erased is 0.05. If the thermal erasure rate is small, it is evaluated that the erasing performance is high.

  Examples 1 and 2 and Comparative Examples 1 and 2 are toner compositions in which the blending amount of the developer is fixed at 3.0 w%. FIG. 1 shows the powder concentration, and FIG. 2 shows the thermal erasure rate. The horizontal axis represents the amount of 24DHBP. In addition, the broken line of each figure is a straight line which shows the characteristic estimated when additivity is materialized in 2 types of developers.

 The powder concentrations in FIG. 1 are compared. It can be seen that Examples 1 and 2 have a color development characteristic equivalent to that of Comparative Example 2 of 244THBP alone, which is significantly higher than Comparative Example 1 of 24DHBP alone.

 Next, the thermal erasure rates in FIG. 2 are compared. It can be seen that Examples 1 and 2 have significantly better erasing characteristics than Comparative Examples 1 and 2. This excellent erasing characteristic is the greatest effect of the present invention.

 When the coloring characteristics and the erasing characteristics are compared together, the toners produced in Examples 1 and 2 satisfy the color erasing characteristics as erasable toners.

(Comparative Example 3)
Here, the blending amount of 24 DHBP, which is one developer, was increased to 6.0 wt%. Other preparation conditions were the same as those in Example 1.

(Example 3)
In addition, as a blending amount of the two developers, 24DHBP was set to 4.0 wt% and 244THBP was set to 1.0 wt%. This is a composition in which the blending amount of 24DHBP employed in Reference Example 1 is reduced by 1/3 and the appropriate amount of 244THBP employed in Comparative Example 2 is increased by 1/3. Other preparation conditions were the same as those in Example 1.

 Comparison between Comparative Examples 2 and 3 and Example 3 shows the powder concentration in FIG. 3 and the thermal erasure rate in FIG.

  FIG. 3 compares the powder concentrations. It can be seen that Example 3 has slightly higher color developability than the composition of 244THBP alone (Comparative Example 2) and the composition of 24DHBP alone (Comparative Example 3).

 Next, the thermal erasure rates are compared in FIG. It can be seen that Example 3 has significantly superior erasing characteristics as compared with Comparative Example 2 and Comparative Example 3.

Here, the compositions of the erasable toners prepared in Examples and Comparative Examples are summarized in Table 1.

Claims (4)

With leuco dyes,
Two developers,
Contains a binder resin,
An erasable toner, wherein the developer contains 2,4-dihydroxybenzophenone and 2,4,4′-trihydroxybenzophenone. The leuco dye contains crystal violet lactone and a fluoran compound;
The erasable toner according to claim 1. The erasable toner according to claim 2, wherein the fluorane compound is represented by 2-anilino-6- (N-alkyl-N-alkylamino) -3-methyl-fluorane. The erasable toner according to claim 1, wherein the binder resin is a styrene / butadiene copolymer or a styrene / butadiene copolymer containing an α-methylstyrene derivative.

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