JP2005279997A - Microcapsule and carbonless copying paper using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a deterioration in post-light-irradiation color development performance of color-undeveloped top paper or intermediate paper by enhancing lightfastness of a microcapsule. <P>SOLUTION: This microcapsule has a wall membrane of an amine-aldehyde condensation-polymerized matter, wherein oil with a blue-based leuco dye dissolved as an electron-donating color development agent is included as a core substance. In the microcapsule, the oil is composed of a diarylethane and a saturated hydrocarbon as a fraction at 200-250°C, and the content of the saturated hydrocarbon as the fraction at 200-250°C is set to be in the range of 1-15 pts.wt. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a microcapsule used in the field of pressure-sensitive copying paper, and relates to a blue-colored pressure-sensitive copying paper having good light resistance.

  Pressure-sensitive copying paper consists of an upper paper coated with an oil containing an electron-donating color former such as a colorless or light leuco dye, coated on one side of the base paper, and a developer layer containing an electron-accepting compound Is applied to one side of the base paper, and, if necessary, a middle sheet having a capsule layer applied to one side and a developer layer applied to the other side. Combining the upper paper capsule layer and the lower paper developer layer in contact with each other, and applying pressure from the non-coated surface of the upper paper with a pen pressure or printer, the capsule breaks and dissolves the color former. Oil moves to the bottom paper. As a result, the electron-donating color former and the electron-accepting compound react with each other, so that color is generated.

Since pressure-sensitive copying paper is used for recording purposes, the storage stability of the paper is very important. One of these is the problem of light resistance, and colored characters and images may fade when exposed to light, particularly ultraviolet rays. Moreover, when the coating layer containing a capsule is exposed to ultraviolet rays, the capsule coating layer may be colored even though the capsule is not broken. Furthermore, when the coating layer containing the capsule is exposed to ultraviolet rays, the dye inside the capsule is decomposed by light, so that the density after color development may decrease.
Several methods have been adopted to increase the stability of the dye contained in the capsule to ultraviolet light. For example, it is known that an ultraviolet absorber is dissolved in oil (Patent Document 1), and the dye stability can be improved by increasing the amount of the ultraviolet absorber added.
JP-A-5-008532

  On the other hand, in recent years, chemical substances have been reviewed to protect the global environment, and the safety of capsule oil has also been reviewed. Since diisopropyl naphthalene is judged to be hardly decomposable and highly accumulative, there is a movement not to use diisopropyl naphthalene in Japan. When diisopropyl naphthalene is not used, when the capsule is exposed to ultraviolet light, the dye in the capsule is likely to be decomposed, or the color development performance after light irradiation is lowered. In particular, in the case of a capsule encapsulating a blue dye, the density is remarkably lowered when color is developed after light irradiation.

  Therefore, the present invention provides the stability of the color former contained in the capsule, that is, the light resistance of the microcapsule, in order to prevent deterioration of the color development performance after the light is applied to the capsule layer of the uncolored upper paper or middle paper. The purpose is to improve the performance.

  The present invention relates to a microcapsule having a wall film of an amine-aldehyde polycondensate containing an oil in which a blue leuco dye is dissolved as an electron donating color former as a core substance, wherein the oil is diarylethane and 200 to 250 ° C. The content of the saturated hydrocarbon which is a fraction of 200 to 250 ° C. is 1 to 15 parts by weight. The above-mentioned problem can be solved by using pressure copy paper.

  According to the present invention, a microcapsule having high safety and excellent light resistance can be efficiently obtained. Further, by using this microcapsule, it is possible to obtain a pressure-sensitive copying paper whose color development performance does not deteriorate even when exposed to light.

  The microcapsules encapsulating the oil in which the color former of the present invention is dissolved should be prepared by a known method such as a coacervation method, an interfacial polymerization method or an in-situ method using an amine-aldehyde condensation polymer as a wall membrane material. Can do. Melamine-formaldehyde, urea formaldehyde, urethane resin, gelatin, etc. are widely used as capsule wall film forming materials. When stored, the capsule wall film breaks down, which may cause scumming in the developer layer. Since gelatin is weak in water resistance, capsules are broken by moisture, which is not preferable for practical use. Capsules that use urethane resin as the membrane material are highly durable against water and heat, but the color after UV irradiation is weak, probably because urethane resin is not very high in the ability to block ultraviolet rays.

  On the other hand, in the case of a capsule using an amine-aldehyde polycondensate, especially a film material composed of melamine-formaldehyde (hereinafter sometimes referred to as melamine resin), heat preservation and water resistance are good, and light resistance The property is also good. The reason for this is not clear, but it is presumed that the melamine resin has a triazine group as a nucleus, which absorbs ultraviolet rays.

  Melamine resin can be obtained by reaction of melamine and formaldehyde. Usually, 1 to 6 parts by weight of formaldehyde can be combined with 4 parts by weight of melamine. In general, formaldehyde is used in an amount of 2.5 to 5 parts by weight with respect to 4 parts by weight of melamine, and if the formaldehyde is less than 2.5 parts by weight, the crosslinking of melamine and formaldehyde is not sufficient. Is not enough. When the amount of formaldehyde is more than 5 parts by weight with respect to 4 parts by weight of melamine, the light resistance decreases, which is not preferable.

  The electron donating color former used in the present invention is a blue leuco dye that develops a blue color. In the case of blue dyes, in general, many of them have low light stability, and it is necessary to improve light resistance. Examples of blue dyes that can be used include 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide, 3- (4-diethylaminophenyl) -3- (1-ethyl-2-methyl- 3-indolyl) phthalide, 3- (4-diethylamino-2-ethoxyphenyl) -3- (1-ethyl-2-methyl-3-indolyl) phthalide, 3- (4-diethylamino-2-ethoxyphenyl) -3 -(1-Ethyl-2-methyl-3-indolyl) -4-azaphthalide, 3- (4-diethylamino-2-ethoxyphenyl) -3- (1-n-octyl-2-methyl-3-indolyl)- 4-Azaphthalide, Nn-butyl-3- [4,4′-bis (N-methylanilino) benzhydryl] carbazole, and the like.

  As the dye in the capsule core material increases, the color density increases, so a higher dye concentration in the oil is better. More preferably, the added amount of the dye is 2 to 10% by weight. However, if the dye concentration is 2% by weight or less, the color density is low, and if the dye concentration is 10% by weight or more, it becomes difficult to encapsulate the dye in the capsule.

  Diarylethane, diisopropylnaphthalene, monoisopropylbiphenyl, isobutylbiphenyl, partially hydrogenated terphenyl, chlorinated paraffin, saturated hydrocarbon, phthalate, etc. are usually used as the oil used for the capsule core material. Among them, diisopropylnaphthalene has an ultraviolet absorbing ability, and there is no big problem in light resistance when using it. However, as a result of reviewing the safety of existing chemical substances and obtaining conventional qualities without using diisopropylnaphthalene for oils used in capsules, in the present invention, diarylethane and 200 to 250 ° C. By using together a saturated hydrocarbon (hereinafter sometimes referred to simply as a saturated hydrocarbon) that is a fraction, a good quality was obtained at a low cost. Examples of diarylethane include phenylxylylethane and phenylisopropyl ethane. As the saturated hydrocarbon, normal paraffin is preferable because it is effective for coloring performance and storage stability.

  Saturated hydrocarbons are obtained by distillation to remove impurities. Among these, those having a fraction of 200 to 250 ° C. are preferable. When the fraction of 250 ° C. or higher is increased, the color development performance is inferior. Further, the content of saturated hydrocarbons is effective for improving the light resistance of the capsule. In the present invention, the mixing ratio of diarylethane and saturated hydrocarbon which is a fraction of 200 to 250 ° C. is preferably 85 parts by weight / 15 parts by weight to 99 parts by weight / 1 part by weight. When the ratio of the saturated hydrocarbon which is a fraction of 200 to 250 ° C. exceeds 15 parts by weight, the light resistance tends to deteriorate. When the ratio of the saturated hydrocarbon which is a fraction of 200 to 250 ° C. is 1 part by weight or less, the initial color development before irradiation with light is poor, which is not preferable.

  Here, the inferior light resistance means that a color density that should originally be obtained cannot be obtained if the capsule is colored after being irradiated with ultraviolet rays. As the ratio of saturated hydrocarbons increases, light resistance tends to deteriorate. This is considered to be because saturated hydrocarbons have a smaller ultraviolet absorbing ability than diarylethane, and the blue dye is easily decomposed and discolored by increasing the content thereof.

  The capsules obtained above are mixed together with the stay material and a binder, applied to high-quality paper, recycled paper, coated paper, or synthetic paper, plastic film, and other sheet-like materials, and dried. The top sheet of copy paper can be obtained. The stay material is added to protect the capsule, and preferably 1.5 to 4 times the capsule particle diameter. As the stay material, starch granules, cellulose fibers, natural polymer fine particles and the like are effective. The binder is not particularly limited as long as it is water-based, but known binders such as PVA, starch and latex can be used. In addition, the pressure-sensitive copying paper of the present invention can be produced according to a conventionally known production method.

  Hereinafter, examples and comparative examples will be given in order to further clarify the effects of the present invention, but the present invention is not limited to these examples. In addition, the part and% of an Example represent a weight part and weight%.

[Example 1]
<Method for preparing capsule slurry>
35 parts of an anionic water-soluble polymer (concentration 20%) were diluted and dissolved in 80 parts of water. Separately, 92 parts of a high-boiling solvent mainly composed of phenylxylylethane (manufactured by Nippon Petrochemical Co., Ltd., Hysol SAS-296), 8 parts of normal paraffin which is a fraction at 200 to 250 ° C. and 4 parts of crystal violet as a dye are added. And it melt | dissolved, stirring at 105 degreeC, and obtained the core substance. Cool to room temperature, mix with the aqueous solution containing the previously prepared anionic water-soluble polymer, and then stir at 10000 rpm for 3 minutes using a homomixer M type (manufactured by Tokushu Kika), with an average particle size of 5.6 μm A stable emulsion was obtained. Next, after adding 20 parts of melamine and 23.5 parts of 37% formaldehyde to 70 parts of water, the mixture was stirred at 70 ° C. for 20 minutes and added to the above emulsion. After the emulsion was heated, the capsule film formation reaction was continued at 75 ° C. for 2 hours to complete the reaction.
<Capsule layer coating solution adjustment and pressure-sensitive copying paper production>
The capsule layer coating solution was adjusted to the following solid ratio to prepare a pressure-sensitive copying paper.
Capsule slurry 100 parts Polyvinyl alcohol (PVA117: manufactured by Kuraray) 10 parts Stay agent (starch particles: average particle size 20 μm) 50 parts The obtained capsule layer coating liquid is dried on one side of a base paper having a basis weight of 40 g / m ^2. After applying using a slide die coater head so that the application amount was 3 g / m ² , it was dried to obtain an upper paper.

[Comparative Example 1]
An upper paper was obtained in the same manner as in Example 1, except that a capsule slurry was prepared using 100 parts of phenylxylylethane as oil.

[Comparative Example 2]
In place of melamine and formaldehyde, 10 parts of polymethylene polyphenyl isocyanate as polyisocyanate, 11.5 parts of hexamethylene diisocyanate, and 8 g of ethylenediamine butylene oxide adduct (molecular weight 1267) as amine alkylene oxide adduct are dissolved. An upper paper was obtained in the same manner as in Example 1 except that the capsule slurry was prepared by liquid.

[Comparative Example 3]
An upper paper was obtained in the same manner as in Example 1 except that the urea formaldehyde capsule slurry prepared by the following procedure was used.
<Method for adjusting urea formaldehyde capsule>
An aqueous solution in which pH was adjusted to 3.5 by adding 5 parts of urea and 0.1 part of resorlucin to a 3.5% PVA aqueous solution was obtained. Separately, 92 parts of a high-boiling solvent mainly composed of phenylxylylethane (manufactured by Nippon Petrochemical Co., Ltd., Hysol SAS-296), 8 parts of a saturated hydrocarbon fraction of 200 to 250 ° C., 4 parts of crystal violet as a dye In addition, it was dissolved at 105 ° C. with heating and stirring. The aqueous solution and the oil in which the dye was dissolved were mixed, and then stirred using a homomixer M type (manufactured by Special Machine) for 3 minutes at 10000 rpm to obtain a stable emulsion having an average particle size of 5.6 μm. Next, after adding 23.5 parts of 37% formaldehyde and 70 parts of water, the mixture was stirred at 70 ° C. for 20 minutes and added to the above emulsion. After the emulsion was heated, the capsule membrane formation reaction was continued at 75 ° C. for 2 hours, and after cooling to 30 ° C., 29% aqueous ammonia was added to PH 7.5, then cooled to room temperature and pressure sensitive. A capsule slurry for copy paper was obtained.

[Comparative Example 4]
Example 1 except that 70 parts of a high-boiling solvent mainly composed of phenylxylylethane (manufactured by Nippon Petrochemicals, Hysol SAS-296) and 30 parts of normal paraffin which is a fraction at 200 to 250 ° C. were used. In the same manner as above, an upper sheet was obtained.

[Comparative Example 5]
In Example 1, the capsule slurry was prepared in the same manner except that 8 parts of normal paraffin having a fraction of 250 ° C. or higher was used.

<Color test>
Using Nippon Paper's CCP Ace for the lower paper, overlaying the upper paper and lower paper obtained above, and printing on the entire surface with a dot impact printer (manufactured by Epson), Macbeth print density after 1 hour Measurement was performed using a densitometer. The color density values were ranked as O to X. ○ and △ are practical levels.
○: Macbeth concentration was 1.2 or more Δ: Macbeth concentration was in the range of 0.8 to 1.2 ×: Macbeth concentration was less than 0.8

<Light resistance test>
After irradiating with a fade meter 67 W / m ² for 15 minutes so that light was applied from the side opposite to the surface coated with the capsule of the upper paper, the upper paper and the lower paper were overlapped and printed by a dot impact printer. The Macbeth concentration was measured before and after the light treatment, and the one with little decrease was marked as ◯.
○: Less than 20% reduction, good light resistance ×: 20% or more reduction, poor light resistance

Claims (2)

In a microcapsule having an amine-aldehyde polycondensation wall film encapsulating an oil in which a blue leuco dye is dissolved as an electron donating color former as a core substance, the oil is a diarylethane and a fraction of 200 to 250 ° C. A microcapsule comprising a saturated hydrocarbon and containing 1 to 15 parts by weight of a saturated hydrocarbon which is a fraction at 200 to 250 ° C. A pressure-sensitive copying paper containing the microcapsules according to claim 1.