JP2008242316A - Erasable image recording material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an erasable image recording material having excellent coloring characteristics and presenting a clear blue color. <P>SOLUTION: The image recording material contains a binder resin, a coloring compound dispersed in the binder resin and a color developing agent. The coloring compound contains crystal violet lactone and 2-anilino-6-(N-alkyl-N-alkylamino)-3-methyl-fluoran and the color developing agent contains ethyl gallate and 2, 2', 4, 4'-tetrahydroxy benzophenone or 2, 4, 4'-trihydroxy benzophenone. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an erasable image recording material.

  Color developing compounds known as leuco dyes are known to be erasable. Among them, crystal violet lactone (CVL) has excellent thermal decoloring properties that do not allow other leuco dyes to follow. ing.

  On the other hand, since CVL is easily decomposed by light, a composition has been proposed in which a part of CVL is substituted with a specific leuco dye to improve light resistance without deteriorating decoloring performance (for example, patents). Reference 1). As the second leuco dye to be added in a small amount for substitution, a fluoran type leuco dye is used, among which 2-anilino-6- (N-alkyl-N-alkylamino) -3-methyl- A black leuco dye or its derivative expressed in the form of fluoran is preferred.

However, the composition containing the two kinds of dyes can provide excellent color development and decoloring characteristics, but the hue changes from “blue” to the black direction, so the image is not “brilliant blue” but “dull blue”. Had problems. At present, no erasable image recording material having excellent color development and erasing performance, and a material that develops a bright and dark blue color has not yet been obtained.
JP 2005-205625 A

  An object of the present invention is to provide an erasable image recording material having excellent color development characteristics and exhibiting vivid blue color development.

  An erasable image recording material according to one aspect of the present invention is an image recording material containing a binder resin, a color developing compound and a developer dispersed in the binder resin, wherein the color developing compound is a crystal. Violet lactone and 2-anilino-6- (N-alkyl-N-alkylamino) -3-methyl-fluorane, wherein the developer is ethyl gallate and 2,2 ′, 4,4′-tetrahydroxybenzophenone Or 2,4,4'-trihydroxybenzophenone.

  According to the present invention, there is provided an erasable image recording material having excellent color development characteristics and exhibiting vivid blue color development.

  Embodiments of the present invention will be described below.

  An erasable image recording material according to an embodiment of the present invention comprises three kinds of color developing compound, developer and binder resin as essential components, and the color developing compound dispersed in the binder resin. When the color developer interacts with the developer, the color developing compound enters a colored state. By forming such an image forming material into fine particles, a clear image can be formed on paper by an electrophotographic technique or the like.

  Further, the image forming material according to the present embodiment can be decolored by heating.

  The color erasure of the image forming material is due to the fact that the color developing compound interacting in the binder resin and the developer no longer interact with each other by heating. The developer moves to the paper that is the recording medium when the color is erased by heating. The moved developer forms a hydrogen bond with the hydroxyl group of cellulose constituting the paper, so that the image forming material becomes decolored and the image can be erased.

  As the coloring compound, two specific types of leuco dyes are contained. The first leuco dye is crystal violet lactone (CVL) and the second leuco dye is 2-anilino-6- (N-alkyl-N-alkylamino) -3-methyl-fluorane.

  The blending ratio of these first and second leuco dyes is not particularly limited, but the second leuco dye is about 5 to 30 wt% of the whole dye in consideration of the properties as a painting material exhibiting a vivid blue hue. It is preferable.

  In addition, as long as it is about 10 wt% or less of the whole color developable compound, other compounds may be contained. Examples thereof include a compound represented by the chemical formula 3- (4-diethylamino-2-alkyloxyphenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide.

  As the developer, two specific types of compounds are contained. The first developer is ethyl gallate, and the second developer is a hydroxybenzophenone-based material. As the hydroxybenzophenone-based material, 2,4,4'-trihydroxybenzophenone or 2,2 ', 4,4'-tetrahydroxybenzophenone is used. The inventors have described the following with respect to the developer used in the toner composition comprising CVL and 2-anilino-6- (N-alkyl-N-alkylamino) -3-methyl-fluorane, which is a black leuco dye. The following knowledge was obtained.

  That is, by using 2,4,4′-trihydroxybenzophenone or 2,2 ′, 4,4′-tetrahydroxybenzophenone as part of the developer, a toner composition exhibiting a vivid blue color is obtained. I found out that

  In addition, 2,4,4′-trihydroxybenzophenone and 2,2 ′, 4,4′-tetrahydroxybenzophenone can be used in combination with ethyl gallate or n-propyl gallate than when used alone. It has been found that the color develops even more vivid colors. In particular, it is preferable to use in combination with ethyl gallate because high erasability is obtained as an erasable image forming material.

  Based on such knowledge, in the image recording material according to the embodiment of the present invention, ethyl gallate as the first developer and 2,4,4′-trihydroxybenzophenone as the second developer. Alternatively, 2,2 ′, 4,4′-tetrahydroxybenzophenone is used in combination.

  The hydroxybenzophenone-based material that is the second developer is preferably contained in a molar ratio of 10 to 80% of the total developer. When the molar ratio of the hydroxybenzophenone-based material is 20 to 30%, various characteristics as an image forming material such as powder concentration, hue, and erasability can be further enhanced.

  Examples of the binder resin include polystyrene, polystyrene derivatives, and styrene copolymers. Specific examples of the styrene monomer include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-ethylsterene, 2,4-dimethylstyrene, and 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, Examples include p-phenylstyrene, p-chlorostyrene, and 3,4-dichlorostyrene. These monomers may be used alone or in combination of two or more.

  A copolymer of styrene can be obtained by copolymerizing with the following acrylate monomer. For example, 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 and isobutyl ether. These vinyl monomers may be used alone or in combination of two or more.

  Suitable binder resins include the following. For example, 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・ Diethylaminopropyl acrylate, Styrene, 2-ethylhexyl acrylate, Styrene, butyl acrylate-N- (Ethoxymethyl) acrylamide, Styrene, ethylene glycol methacrylate, Styrene, 4-hexafluorobutyl methacrylate, Styrene-butadiene copolymer, Acrylonitrile, Acrylic Rubber / styrene terpolymer, acrylonitrile / styrene / Crylic acid ester terpolymer, styrene / acrylonitrile copolymer, acrylonitrile / chlorinated polystyrene / styrene terpolymer, acrylonitrile / ethylene vinyl acetate / styrene terpolymer, styrene / p-chlorostyrene copolymer And a styrene / propylene copolymer, a styrene / butadiene copolymer, a styrene / α-methylstyrene copolymer, a styrene / maleic acid ester copolymer, and a styrene / maleic anhydride copolymer.

  Acrylate monomers can be used alone or in combination. Furthermore, two or more types of monomers may be mixed to form a copolymer with styrene. Butadiene, maleic acid ester, chloroprene or the like can also be copolymerized. In this case, the weight ratio of the copolymer component such as butadiene is desirably 10% or less.

  The polymer of the acrylate monomer mentioned above can also be used as a mixture with polystyrene. In this case, the polyacrylate component may be any of a homopolymer, a copolymer, and a copolymer. Further, styrene or acrylate copolymerized with butadiene, maleic acid ester, chloroprene or the like at a ratio of 10% or less can be used.

  In general, the lower the amount of polar groups contained in the resin, the higher the color density of the image forming material formed by kneading, and at the same time, the compatibility with the color forming compound is enhanced. Typical binder resins that can increase the coloration / decoloration contrast of erasable image forming materials are nonpolar resins such as polystyrene and polyolefin. In the case of toner use, it is preferable to use a styrene / butadiene copolymer and a mixture or derivative thereof.

  In the erasable image recording material according to the embodiment of the present invention, a composite comprising a styrene-butadiene copolymer having a butadiene content of 5 to 15 wt% and a second styrene resin containing α-methylstyrene is compatible. It is desirable to use a resin as a 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-methyl. Examples thereof include styrene / alicyclic copolymers, α-methylstyrene / styrene / aliphatic terpolymers, and α-methylstyrene / styrene / alicyclic terpolymers. Of these, α-methylstyrene resin and α-methylstyrene / styrene copolymer are preferable. The content of these components is preferably 5 wt% or more and 50 wt% or less of the total binder, and more preferably 10 wt% to 20 wt%.

  The color developing compound and the color developer are blended in the binder resin so that the color developer is 0.1 mol to 10 mol with respect to 1 mol of the color developing compound. Further, the amount of the binder resin varies depending on the content of the additive described later, but is preferably 80 wt% or more based on the total amount of toner components.

  In addition to the components described above, various additives can be blended in the image recording material according to the embodiment of the present invention as necessary.

  For example, a charge control agent (CCA). As a charge control agent for an erasable image recording material, it is required that the color of the charge control agent does not remain when an image is erased. For this reason, it is essential to be colorless or transparent.

  Among the charge control agents that are generally used, negatively charged materials include calixarene derivatives (Orient Chemical Co., Ltd .: E-89), phenolic compounds (same: N-1, N-2, N-3), boron. And styrene-sulfonic acid resin (Fujikura Kasei Co., Ltd .: FCA-1001N) and the like. Examples of suitable compounds include E-89 and LR147. On the other hand, as a positively charged material, for example, TP-302 (CAS # 116810-46-9), TP-415 (117342-25-2) manufactured by Hodogaya Chemical Co., Ltd., quaternary amine compound (Orient Chemical Co., Ltd.) Product: P-51), polyamine oligomer (same: AFP-B), and styrene-acrylic quaternary ammonium salt resin (same: FCA-201PB) manufactured by Fujikura Kasei.

Furthermore, waxes for controlling fixing properties may be blended as necessary. Waxes are preferably composed of components that do not develop color developing compounds composed of higher alcohols, higher ketones, and higher aliphatic esters. The acid value is desirably 10 or less. The weight average molecular weight is preferably in the range of 10 ² to 10 ⁵ , and more preferably in the range of 10 ² to 10 ⁴ . Within such a 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 such wax added is preferably 0.1 to 30 parts by weight, and more preferably 0.5 to 15 parts by weight. Note that the wax of the heat fixing toner is 5 parts by weight or less, and is added to impart release performance from the heat roll.

  Furthermore, the erasable image recording material according to the embodiment of the present invention is blended with an external additive for controlling fluidity, storage stability, blocking resistance, photoconductor polishing property, and the like, if necessary. May be. As the external additive, for example, 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, and magnesium silicate. Examples of the metal oxide fine particles include zinc oxide, magnesium oxide, zirconium oxide, strontium titanate, and barium titanate. Examples of cleaning aids include fine resin powders such as polymethyl methacrylate, polyvinylidene fluoride, and polytetrafluoroethylene.

  Such an external additive may be subjected to a surface treatment such as hydrophobization. Most of the hydrophobic treatment is performed when blended with toner. In the case of negative charging, a treatment agent such as a silane coupling agent, a titanium coupling agent, or silicone oil is used. In the case of positive charging, a treatment agent such as an aminosilane type or a silicone oil having an amine in the side chain is used.

  If the external additive is blended in an amount of 0.05 to 5 parts by weight with respect to 100 parts by weight of the toner, the effect can be obtained. The amount is more preferably 0.1 to 3.0 parts by weight with respect to 100 parts by weight of the toner. Further, the number average particle diameter of the primary particles is generally 10 to 20 nm in the case of silica fine particles, and particles of up to 100 nm are also used. For materials other than silica, particles having a large particle size and a number average diameter of 0.05 to 3 μm are generally used.

  The image recording material according to the embodiment of the present invention can be produced by mixing and dispersing a color developing compound and a developer in a binder resin. Examples of the mixing / dispersing method include, for example, a high-speed dissolver, a roll mill, a ball mill, etc., a wet dispersion method using a solvent, a melt kneading method using a roll, a pressure kneader, an internal mixer, a screw type extruder, etc. Can be used. In addition, when a decoloring agent is included, a nonpolar solvent is used. As a mixing means, a ball mill, a V-type mixer, a Forberg, a Henschel mixer, or the like can be used.

  Specific examples of the present invention are shown below.

(Example 1)
First, CVL and 2-anilino-6- (N-ethyl-N-isopentylamino) -3-methylfluorane (Yamada Chemicals leuco dye S-205) were prepared as color developing compounds. The composition ratio of CVL was 3.65 wt%, and the composition ratio of S-205 was fixed to 0.5 wt%.

  As the developer, two kinds of ethyl gallate (EG) and 2,2 ', 4,4'-tetrahydroxybenzophenone (THBP2244) were prepared. Seven types of toners were prepared by changing the mixing ratio of EG and THBP2244 while fixing the molar ratio of the total developer to the color developing compound to 1.4 times.

  The content of THBP2244 in all the developers is 100 wt%, 80 wt%, 50 wt%, 30 wt%, 20 wt%, 10 wt%, and 0 wt% in descending order.

  As the binder resin, a nonpolar resin in which a styrene / butadiene copolymer and an α-methylstyrene / styrene copolymer oligomer were blended at a weight ratio of 4: 1 was used.

  As other constituent components, 4 parts by weight of polypropylene wax as a wax component and LR-147 (manufactured by Nippon Carlit Co., Ltd.) as CCA (charge control material) were used.

  The above-mentioned components were mixed with a Henschel mixer to obtain a mixture, which was kneaded with three rolls. Further, it was processed into a fine powder having an average particle diameter of 11 μm by a pulverizer to obtain a blue electrophotographic toner. Thereafter, hydrophobic silica was externally added in an amount of 1 wt% of the whole to prepare a sample.

  The obtained sample was examined for powder concentration, hue, and erasability. The powder density and hue of the toner were measured on the toner powder before external addition. Each toner powder was housed in a powder measurement cell, and the reflectance was measured using a Minolta color difference meter CR300. Based on the measurement data, the powder concentration and hue were calculated.

  FIG. 1 shows the relationship between the EG ratio of the developer and the toner powder concentration. It can be seen that THBP2244 alone has a higher powder concentration than EG alone. Furthermore, it was found that when the EG content is 90 wt% or less, the powder concentration is higher than that of THBP2244 alone.

  FIG. 2 shows the relationship between the EG ratio of the developer and the hue (−a / b) of the toner. In the case of blue, the smaller the (−a / b) value, the brighter the blue. Since THBP2244 alone has a smaller value of (−a / b) than that of EG alone, it indicates that THBP2244 appears more blue than EG. When the EG content is 20 wt% to 80 wt%, the (−a / b) value is smaller than that of THBP2244 alone.

  The same tendency is observed in the powder concentration as described above. If the content of EG in the developer is in the range of 90 wt% or less, both the powder concentration and the hue characteristics can be improved.

  In particular, when the content of EG is within a range of 20 to 80%, a powder concentration of 1.15 or more can be secured, and a bright blue having a (−a / b) value of −0.5 or less. Color development can be obtained.

  For evaluation of toner erasability, an MFP (e-studio 350EB) manufactured by TOSHIBA TEC was used. First, using each toner, a solid pattern having several stages of image IDs was printed on several types of copy paper, and this was used as an evaluation image for erasing performance. Thermal erasure was performed by placing in a thermostatic bath at 130 ° C. for 2 hours.

  For each evaluation paper, [(original image ID) − (paper ID)] before thermal erasure and [(afterimage ID) − (paper ID)] after thermal erasure were obtained. The result of plotting [(original image ID) − (paper ID)] before thermal erasure on the horizontal axis and plotting [(afterimage ID) − (paper ID)] after thermal erasure on the vertical axis is shown in FIG. 3 shows.

  The slope of the regression line of this data was measured, and the arithmetic average value of several types of paper was defined as the erasure rate, which was used as a measure of erasure performance. This numerical value indicates how much the density of the afterimage corresponds to a fraction of the density of the original image, and the smaller the value, the higher the thermal erasing performance. For example, if the thermal erasure rate is 0.05, it means that the residual image density remaining when an image with an image density of 1.0 is thermally erased is 0.05.

  From this erasing performance and the above-mentioned toner powder concentration, the color development / erasing performance of the erasable toner was also evaluated. As a result, the optimum content of the EG ratio in the THBP2244 / EG developer was 20 to 80%. Overall, this range is the most suitable EG content.

  It was confirmed that the THBP2244 / EG color developer vividly developed the CVL / S-205 composite system as compared with the case of EG alone.

(Example 2)
According to the same formulation as in the above (Example 1) except that 2,2 ′, 4,4′-tetrahydroxybenzophenone (THBP2244) was changed to 2,4,4′-trihydroxybenzophenone (THBP244) A toner was prepared.

  For the obtained toner, the powder density and hue were evaluated in the same manner as described above, and the results are shown in FIGS.

  FIG. 4 shows the relationship between the EG ratio of the developer and the toner powder concentration. It can be seen that the THBP244 alone has a higher powder concentration than the EG alone. Further, it has been found that when the EG content is 90 wt% or less, the powder concentration is higher than in the case of THBP244 alone.

  FIG. 5 shows the relationship between the EG ratio of the developer and the hue (−a / b) of the toner. It can be seen that the value of (−a / b) is smaller for THBP244 alone than for EG alone. This indicates that THBP244 develops more blue than EG. However, when the EG content is 90 wt% or less, the (−a / b) value is higher than that of THBP244 alone. Get smaller.

  The same tendency is observed in the powder concentration as described above. If the content of EG in the developer is in the range of 10 to 90 mol%, both the characteristics of the powder concentration and the hue can be enhanced. In particular, if the content of EG is in the range of 0 to 90%, a powder concentration of 1.15 or more can be secured, and if the content of EG is in the range of 10 to 90%, −0 (-A / b) values of .5 or less can be obtained.

  Further, the toner erasability is examined by the same method as described above, and [(original image ID) − (paper ID)] before thermal erasing and [(afterimage ID) − (paper ID)] after thermal erasing. Asked. The result of plotting [(original image ID) − (paper ID)] before thermal erasure on the horizontal axis and plotting [(afterimage ID) − (paper ID)] after thermal erasure on the vertical axis is shown in FIG. It is shown in FIG.

  From this erasing performance and the above-mentioned toner powder concentration, the color development / erasing performance of the erasable toner was also evaluated. As a result, the optimum content of the EG ratio in the THBP244 / EG developer was 20 to 80%. Overall, this range is the most suitable EG content.

  It was confirmed that the THBP244 / EG developer developed vivid colors on the CVL / S-205 composite system as compared with the case of EG alone.

(Comparative example)
A leuco dye BLUE203 manufactured by Yamada Chemical Co., Ltd. was prepared as a color developing compound, and two kinds of ethyl gallate (EG) and 2,4, -dihydroxybenzophenone (DHBP24) were prepared as color developers.

  Six types of toners were prepared by changing the ratio of EG and DHBP24 by fixing the molar ratio of the total developer to the color developing compound at 1.4 times. The content of DHBP24 in all the developers is 100 wt%, 50 wt%, 20 wt%, 10 wt%, 5 wt%, and 0 wt% in descending order.

  Styrene-butadiene copolymer was used as the binder resin.

  As other constituent components, 5 parts by weight of polypropylene wax as a wax component and LR-147 (manufactured by Nippon Carlit Co., Ltd.) as CCA (charge control material) were used.

  Using these components, a blue electrophotographic toner was obtained in the same manner as in Example 1 above. Thereafter, a sample was prepared by externally adding hydrophobic silica in an amount of 1 wt% of the whole.

  The hue of the obtained sample was evaluated in the same manner as described above. FIG. 7 shows the relationship between the DHBP 24 ratio of the developer and the hue (-a / b) of the toner.

  Since the DHBP 24 alone has a slightly larger value (−a / b) than the case of the EG alone, it can be seen that the EG develops the BLUE 203 more vividly than the DHBP 24. Further, when the developer was constituted by combining EG and DHBP24, no improvement in the blue direction of the hue (a / b value) was observed compared to the case of EG alone.

  As described above, in the embodiment of the present invention, various properties can be enhanced as compared with the case of EG alone by combining EG and THBP2244 or THBP244 to form a developer. The present invention has a great industrial value as a technique for improving the problems of conventional erasable image recording materials, improving the erasure image quality, and facilitating the reuse of paper resources.

The graph which shows the relationship between the developer composition and powder density | concentration in a THBP2244 / EG type developer. The graph which shows the relationship between the developer composition and hue in THBP2244 / EG type developer. The graph which shows the relationship between the developer composition and the erasure rate in the THBP2244 / EG developer. The graph which shows the relationship between the developer composition and powder density | concentration in a THBP244 / EG type developer. The graph which shows the relationship between the developer composition and hue in a THBP244 / EG type developer. The graph which shows the relationship between the developer composition and the erasure rate in the THBP244 / EG developer. FIG. 6 is a graph showing a relationship between a developer composition and hue in a toner of a comparative example.

Claims (2)

An image recording material containing a binder resin, a color developable compound and a developer dispersed in the binder resin,
The color former includes crystal violet lactone and 2-anilino-6- (N-alkyl-N-alkylamino) -3-methyl-fluorane,
An erasable image recording material, wherein the developer comprises ethyl gallate and 2,2 ′, 4,4′-tetrahydroxybenzophenone or 2,4,4′-trihydroxybenzophenone.   The erasable image recording material according to claim 1, wherein the ethyl gallate is contained in the developer in an amount of 20 mol% to 80% mol%.

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