JP4110164B2 - Erasable image forming material - Google Patents

Description

  The present invention relates to an image forming material used for electrophotography, and more particularly to an image forming material capable of erasing an image by heating.

Forest protection is an absolute requirement in order to protect the global environment and to suppress the greenhouse effect caused by CO _2, and in order to keep new logging to a minimum and maintain a balance with reforestation including afforestation A major issue is how to efficiently use the paper resources we already have. The current reuse of paper resources is “recycling” in which paper fibers that have undergone the deinking process to peel off the image forming material are re-spread on poor quality paper and used separately for different purposes. The possibility of new environmental pollution due to the treatment of sewage is pointed out.

  On the other hand, in the past, practical use has been made regarding the reuse of hard copies by correcting images, such as an eraser for pencils and a correction fluid for writing instruments. Recently, special paper rewritable paper has been proposed for the purpose of reusing hard copy paper. Here, “reuse”, which prevents paper quality deterioration as much as possible and uses it multiple times for the same purpose, is more important from the viewpoint of protecting paper resources, unlike “recycle”, which is used for other purposes while reducing paper quality. It can be said that it is a concept. If effective “reuse” is performed at each “recycle” stage, waste of new paper resources can be minimized. For example, since the above-mentioned rewritable paper uses special paper, it can be “reused” but cannot be “recycled” and cannot be applied to recording techniques other than thermal recording.

  The present inventors pay attention to the fact that when the interaction between the color developing compound and the developer increases, the color developing state is obtained, and when the interaction decreases, the color developing compound enters the color erasing state. By adding a new color erasing agent that captures the developer to the contained composition system, the color development state is stable at temperatures near room temperature, and the color erasure state is fixed at a practical temperature for a long time by treatment with heat or solvent. Possible image forming materials, image erasing processes and image erasing apparatuses related to these image forming materials have been proposed as a paper reuse technique. These image forming materials have high stability in the coloring and erasing states of images, high safety as materials, and can be used for all of electrophotographic toner, liquid ink, ink ribbon, and writing instruments. It has advantages over conventional technology that it can be erased in scale and can be recycled after being reused multiple times.

  Further, the present inventors capture a coloring compound by heating or contact with a solvent in which the medium for recording an image is a polar polymer such as paper and the binder contained in the image forming material is a nonpolar material. Even if the image forming material does not contain a color erasing agent having the property of capturing the developer by utilizing the capturing ability of the developer by the image recording medium (paper), the image forming material does not contain an image. Found that can be erased. An image forming material that does not contain a color erasing agent that captures the developer is also proposed (see, for example, Patent Document 1).

Examples of the color former include leucooramines known as leuco dyes, diarylphthalides, polyarylcarbinols, acylauramines, aryloramines, rhodamine B lactams, indolines, spiropyrans, fluorans. And electron donating organic substances such as Among many leuco dyes, blue-colored crystal violet lactone (CVL) and black-colored 2-anilino-6- (N-isopentyl-N-isopentylamino) -3-methylfluorane (manufactured by Yamada Chemical, H10301) 2) are materials excellent in heat erasability compared with other leuco dyes. However, the black image has no residual change before and after erasure, so that an afterimage is conspicuous. Therefore, better thermal erasability is required for black color image forming materials.
JP 2000-284520 A

  An object of the present invention is to provide an erasable image forming material that exhibits black color development and exhibits better thermal erasability than conventional ones.

  An erasable image forming material according to an embodiment of the present invention includes a color developing compound, a color developer, and a binder resin, and the color forming compound includes crystal violet lactone and 2-anilino-6- (N- It contains isopentyl-N-isopentylamino) -3-methylfluorane.

  ADVANTAGE OF THE INVENTION According to this invention, the erasable image forming material which shows black color development and shows the thermal erasability superior to the past can be provided.

  The erasable image forming material according to the embodiment of the present invention is used, for example, in the form of toner. The material used for the erasable image forming material according to the embodiment of the present invention will be described.

  As the coloring compound, crystal violet lactone and 2-anilino-6- (N-isopentyl-N-isopentylamino) -3-methylfluorane are used in combination. The present inventors used a part of 2-anilino-6- (N-isopentyl-N-isopentylamino) -3-methylfluorane, which is a black color developing compound, as a blue color developing compound. It has been discovered that replacement with a crystal violet lactone (CVL) can improve thermal erasure performance over 2-anilino-6- (N-isopentyl-N-isopentylamino) -3-methylfluorane alone or CVL alone. . The content of 2-anilino-6- (N-isopentyl-N-isopentylamino) -3-methylfluorane in the color developing compound is preferably 50 wt% or more and 95.2 wt% or less. In this range, good thermal erasing performance can be obtained.

  Developers include phenols, phenol metal salts, carboxylic acids, carboxylic acid metal salts, benzophenones, sulfonic acids, sulfonates, phosphates, phosphate metal salts, acidic phosphate esters, and acidic phosphate metal salts , Phosphorous acids, metal phosphites and the like. Specific examples of particularly preferred developers include gallic acid; gallic acid esters such as methyl gallate, ethyl gallate, n-propyl gallate, i-propyl gallate, butyl gallate, and the like; dihydroxybenzoic acid esters and Its esters such as 2,3-dihydroxybenzoic acid, methyl 3,5-dihydroxybenzoate and the like; hydroxyacetophenones such as 2,4-dihydroxyacetophenone, 2,5-dihydroxyacetophenone, 2,6-dihydroxyacetophenone, 3,5- Dihydroxyacetophenone, 2,3,4-trihydroxyacetophenone and the like; hydroxybenzophenones such as 2,4-dihydroxybenzophenone, 4,4′-dihydroxybenzophenone, 2,3,4-trihydroxybenzophenone, , 4,4′-trihydroxybenzophenone, 2,2 ′, 4,4′-tetrahydroxybenzophenone, 2,3,4,4′-tetrahydroxybenzophenone, etc .; biphenols such as 2,4′-biphenol, 4, 4'-biphenol and the like; polyhydric phenols such as 4-[(4-hydroxyphenyl) methyl] -1,2,3-benzenetriol, 4-[(3,5-dimethyl-4-hydroxyphenyl) methyl]- 1,2,3-benzenetriol, 4,6-bis [(3,5-dimethyl-4-hydroxyphenyl) methyl] -1,2,3-benzenetriol, 4,4 ′-[1,4-phenylene Bis (1-methylethylidene) bis (benzene-1,2,3-triol)], 4,4 ′-[1,4-phenylenebis (1-methylethyl) Den) bis (1,2-benzenediol)], 4,4 ', 4' '- ethylidene trisphenol, 4,4' - (1-methylethylidene) bisphenol, and the like methylene tris -p- cresol. Particularly suitable developers are gallate esters such as ethyl gallate, n-propyl gallate, i-propyl gallate, butyl gallate; hydroxybenzophenones such as 2,4-dihydroxybenzophenone, 4,4′-dihydroxybenzophenone. 2,3,4-trihydroxybenzophenone, 2,4,4′-trihydroxybenzophenone, 2,2 ′, 4,4′-tetrahydroxybenzophenone, 2,3,4,4′-tetrahydroxybenzophenone . These can be used alone or in admixture of two or more.

  In an image forming material containing a color former, a developer, and a binder resin, generally, the lower the amount of polar groups contained in the binder resin, the higher the color density of the image forming material prepared by kneading, and at the same time, The compatibility with the color compound is also increased. Therefore, it is advantageous to use a nonpolar resin as the binder resin in order to increase the contrast ratio between color development and decoloration of the image forming material. As the binder resin, a styrene copolymer is particularly suitable. Specific examples of the styrene monomer used as a raw material for these binder resins include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, pn. -Butyl styrene, p-tert-butyl styrene, pn-hexyl styrene, pn-octyl styrene, pn-nonyl styrene, pn-decyl styrene, pn-dodecyl styrene, p-methoxy styrene , P-phenylstyrene, p-chlorostyrene, 3,4-dichlorostyrene, and the like. These monomers can be used alone or in combination of two or more. Optimal vinyl monomers copolymerized with styrene monomers include rubber components such as butadiene, propylene and chloroprene. The content of the rubber component in the styrene-based copolymer is preferably 2 to 15 wt%, and more preferably 7 to 13 wt%.

  Other vinyl monomers that can be copolymerized with styrenic monomers include methyl methacrylate, ethyl methacrylate, isobutyl methacrylate, cyclohexyl methacrylate, ethyl hexyl methacrylate, lauryl methacrylate, stearyl methacrylate, vinyl acetate, Examples include 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. These vinyl monomers can be used alone or in combination of two or more. The content of such a vinyl monomer in the styrene copolymer is preferably 10 wt% or less.

As an example of a styrene copolymer that can be used as a binder resin,
Styrene / n-butyl methacrylate, styrene / isobutyl methacrylate, styrene / ethyl acrylate, styrene / n-butyl acrylate, styrene / methyl methacrylate, styrene / glycidyl methacrylate, styrene / dimethylaminoethyl methacrylate, styrene / diethylaminoethyl methacrylate, styrene / diethylamino Propyl acrylate, Styrene 2-ethylhexyl acrylate, Styrene butyl acrylate-N- (Ethoxymethyl) acrylamide, Styrene ethylene glycol methacrylate, Styrene 4-hexafluorobutyl methacrylate, Styrene butadiene copolymer, Acrylonitrile acryl Rubber / styrene terpolymer, acrylonitrile / styrene / acrylic Ester terpolymer, styrene / acrylonitrile copolymer, acrylonitrile / chlorinated polystyrene / styrene terpolymer, acrylonitrile / ethylene vinyl acetate / styrene terpolymer, styrene / p-chlorostyrene copolymer, Examples thereof include styrene / propylene copolymer, styrene / butadiene rubber, styrene / maleic acid ester copolymer, and styrene / maleic anhydride copolymer. An acrylate monomer polymer may be blended with polystyrene. In this case, the polyacrylate component may be a homopolymer or a copolymer.

  As the charge control agent for the erasable toner, it is necessary that the color of the charge control agent does not remain when erasing, and therefore, a colorless or transparent one is used. Negative charge control agents include Orient Chemical E-89 (calixarene derivatives), Nippon Carlit N-1, N-2, N-3 (all phenolic compounds), LR147 (boron compounds), Examples include FCA-1001N (styrene-sulfonic acid resin) manufactured by Fujikura Kasei. Of these, E-89 and LR147 are preferred. Positive charge control agents include Hodogaya Chemical's TP-302 (CAS # 116810-46-9), TP-415 (117342-25-2), Orient Chemical's P-51 (quaternary amine compound). , AFP-B (polyamine oligomer), Fujikura Kasei's FCA-201PB (styrene-acrylic quaternary ammonium salt resin), and the like.

If necessary, the erasable toner may contain a wax for controlling the fixing property. Examples of waxes include higher alcohols, higher ketones, and higher aliphatic esters. The acid value of the wax is preferably 10 or less so as not to cause the color developing compound to develop color. As the waxes, those having a weight average molecular weight of 10 ² to 10 ⁵ , more preferably 10 ² to 10 ⁴ are preferable. As long as it has a weight average molecular weight within this range, low molecular weight polypropylene, low molecular weight polyethylene, low molecular weight polybutylene, low molecular weight polyalkane and the like can be used as waxes. The amount of the wax added is preferably 0.1 to 30 parts by weight, more preferably 0.5 to 15 parts by weight. In the heat roll fixing toner, the amount of wax added is set within 5 parts by weight in order to ensure the release performance from the heat roll. In the pressure fixing toner, the main component is a wax, which becomes a core part of a microcapsule structure.

  If necessary, the erasable toner may contain an external additive for controlling fluidity, storage stability, blocking resistance, photoconductor polishing properties, and the like. As the external additive, silica fine particles, metal oxide fine particles, cleaning aids and the like are 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. These external additives may be subjected to surface treatment such as hydrophobization. In most cases, the external additive used in the toner is hydrophobized. In the case of a negatively charged toner, a treatment agent such as a silane coupling agent, a titanium coupling agent, or silicone oil is used for the hydrophobic treatment of the external additive. In the case of a positively charged toner, a processing agent such as an aminosilane-based silicone oil having an amine in the side chain is used for the hydrophobic treatment of the external additive. The addition amount of the external additive is preferably 0.05 to 5 parts by weight, more preferably 0.1 to 3.0 parts by weight with respect to 100 parts by weight of the toner. Regarding the number average particle diameter of the primary particles of the external additive, 10 to 20 nm particles are often used as the silica fine particles, and particles of about 100 nm are also used. As fine particles other than silica, particles having a number average particle diameter of 0.05 to 3 μm, which is larger than that of silica fine particles, are often used.

  As a method of mixing and dispersing components such as a color developing compound and a developer in a binder resin, a wet dispersion method using a solvent such as a high-speed dissolver, a roll mill, a ball mill, a roll, a pressure kneader, an internal mixer, A melt kneading method using a screw type extruder or the like can be used. As a mixing means, a ball mill, a V-type mixer, a Forberg mixer, a Henschel mixer, or the like can be used.

  Crystal violet lactone (CVL) and 2-anilino-6- (N-isopentyl-N-isopentylamino) -3-methylfluorane (manufactured by Yamada Chemical Co., Ltd., H10301) were prepared as the color developing compounds. 4.15 parts by weight of a color developing compound, 2 parts by weight of ethyl gallate as a developer, 5 parts by weight of polypropylene wax as a wax component, 88 parts by weight of a styrene / butadiene copolymer having a butadiene content of 10 wt% as a binder resin, charging 0.85 part by weight of a control material (Nippon Carlit, LR-147) was mixed and kneaded with a Banbury kneader. Further, the kneaded product was pulverized by a pulverizer into fine powder having an average particle diameter of 11 μm. Thereafter, 1 part by weight of hydrophobic silica was externally added to 100 parts by weight of the fine powder to prepare an electrophotographic toner.

  According to the above method, five types of toners were prepared by changing the ratio of CVL and H10301 which are color developing compounds. The ratio of H10301 in the color developing compound was 100 wt%, 95.2 wt%, 80.7 wt%, 50 wt%, and 0 wt%.

  Using each prepared toner, an image (solid pattern) with several levels of image density is printed on several types of copy paper with a TOSHIBA TEC multifunction printer (Primage 351), and this is an evaluation image for erasing performance. Used as. The image density is a reciprocal common logarithm obtained by measuring the reflectance of an image printed on paper with a Minolta color difference meter CR300. Thermal erasure was carried out using a thermostat at 130 ° C. for 2 hours.

  For each evaluation paper, the thermal erasing performance is [(image density before thermal erasure) − (paper image density)] on the horizontal axis and [(image density of the afterimage after thermal erasure) − (paper image) on the vertical axis. The slope of the regression line of the data plotted with (concentration)] was measured and evaluated by the arithmetic mean value of several types of paper. This numerical value indicates the ratio of the image density of the afterimage after thermal erasure to the image density before thermal erasure, and the smaller the numerical value, the better the thermal erasing performance. For example, when the above value is 0.05, it means that the image density of an afterimage remaining when an image having an image density of 1.0 is thermally erased is 0.05.

  FIG. 1 shows the relationship between the ratio of H10301 in the color developing compound and the thermal erasing performance. As shown in FIG. 1, when the ratio of H10301 in the color developing compound is in the range of 50 wt% to 95.2 wt%, the thermal erasing performance is better than the case where the color forming compound is CVL alone or H10301 alone. I know that there is.

FIG. 2 shows the hue of each toner prepared above. The color values are represented by a chromaticity diagram of the L ^* a ^* b ^* color system (JIS Z8729) standardized by the International Commission on Illumination (CIE). a ^* represents a hue in the red direction with +, − with a green direction, − ^* with a yellow direction with +, and − with a blue direction. [A ^{* 2} + b ^{* 2} ] An area where ^0.5 is 10 or less and the brightness is low (area shown by a circle in FIG. 2) is a range in which it can be determined as “black”. From FIG. 2, it can be seen that the hue of the toner in which the ratio of H10301 in the color developing compound is 50 wt% or more can be determined as “black”.

The figure which shows the relationship between the ratio of H10301 in a color development compound, and thermal erasing performance about the toner prepared in the Example of this invention. FIG. 3 is a diagram showing the hue of toner prepared in an example of the present invention.

Claims (3)

  A color developing compound, a developer, and a binder resin, wherein the color developing compound includes crystal violet lactone and 2-anilino-6- (N-isopentyl-N-isopentylamino) -3-methylfluorane. An erasable image forming material characterized by containing.   The content of 2-anilino-6- (N-isopentyl-N-isopentylamino) -3-methylfluorane in the color developing compound is 50 wt% or more and 95.2 wt% or less. Item 10. The erasable image forming material according to Item 1.   The erasable image forming material according to claim 1, wherein the binder resin is a styrene-butadiene copolymer.

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