JP2005279996A - 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 black-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 15-35 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 more particularly to a pressure-sensitive copying paper coated with a capsule having high environmental safety and 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 them is a problem of light resistance, and colored characters and images may be faded 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 containing a black dye, it is strongly reddish when colored 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 an amine-aldehyde polycondensation wall film encapsulating an oil in which a black 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 15 to 35 parts by weight, and the feeling using this 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 black leuco dye that develops black color. In the case of blue dyes, many of them are generally low in light stability, so that the effect on light resistance is not as remarkable as that of black dyes. Examples of black dyes that can be used include 2-anilino-3-methyl-6-diethylaminofluorane, 2-anilino-3-methyl-6-di-n-butylaminofluorane, and 2-anilino-3-methyl. -6-di-n-amylaminofluorane, 2-anilino-3-methyl-6- (N-methyl-Nn-propylamino) fluorane, 2-anilino-3-methyl-6- (N-ethyl) -N-isobutylamino) fluorane, 2-anilino-3-methyl-6- (N-ethyl-N-isoamylamino) fluorane, 2-anilino-3-methyl-6- (N-cyclohexyl-N-methylamino) Fluorane, 2-anilino-3-methyl-6- [N-ethyl-N- (3-ethoxypropyl) amino] fluorane, 2-anilino-3-methyl-6- (N-ethyl-4-methylanilino) flurane Oran, 2- (3-trifluoromethylanilino) -6-diethylaminofluorane, 3,7-bisdimethylaminobenzoylphenothiazine, 3-N-ethyl-N-isoamylamino) -6-methyl-7-anilinofluorane Etc. can be used.

  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. The mixing ratio of diarylethane and saturated hydrocarbon which is a fraction at 200 to 250 ° C. is preferably 65 parts by weight / 35 parts by weight to 85 parts by weight / 15 parts by weight. When the ratio of the saturated hydrocarbon which is a fraction of 200 to 250 ° C. is less than this, the light resistance tends to deteriorate. Moreover, when the ratio of the saturated hydrocarbon which is a fraction of 200-250 degreeC exceeds 35 weight part, it precipitates at the time of capsule manufacture, and operativity worsens, and it cannot be said that it is preferable.

  Here, the inferior light resistance means that when a color is developed after irradiating light to the capsule, a color that is originally black color becomes a strong reddish color. As the ratio of saturated hydrocarbons increases, light resistance tends to improve. This is considered to be because, in black obtained by mixing various colors, the blue component that is weak to light quickly decomposes or fades, and as a result, redness becomes conspicuous. Even if the light resistance is too strong, variations in the degree of separation / fading of each color increase, and a good black color cannot be obtained. On the other hand, in the present invention, the saturated hydrocarbon has a smaller ultraviolet absorption capacity than the diarylethane, and the light content having a strength suitable for black coloring can be obtained by balancing the content. it is conceivable that.

  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.

  In the following, examples and comparative examples are given 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, 80 parts of a high-boiling solvent mainly composed of phenylxylylethane (manufactured by Nippon Petrochemicals, Hysol SAS-296), 20 parts of normal paraffin which is a fraction at 200 to 250 ° C. 9 parts of -ethyl-N-isoamylamino) -6-methyl-7-anili NO fluorane) were added and dissolved while stirring at 105 ° C. to obtain a core substance. Cool to room temperature, mix with the aqueous solution containing the previously prepared anionic water-soluble polymer, and then use a homomixer M type (manufactured by Tokushu Kika) to stir at 10,000 rpm for 3 minutes, with an average particle size of 4.9 μm A stable emulsion was obtained. Next, 20 parts of melamine and 23.5 parts of 37% formaldehyde were added to 70 parts of water, stirred at 70 ° C. for 20 minutes to prepare a melamine prepolymer, and then added to the emulsion. After raising the temperature to 75 ° C., the capsule film formation reaction was continued for 2 hours to complete the reaction. After cooling to room temperature, a capsule slurry for pressure-sensitive copying paper was obtained.
<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 solution is dry-coated 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 amount was 3 g / m ² , it was dried to obtain an upper sheet.

[Comparative Example 1]
In Example 1, normal paraffin which is a fraction of 200 to 250 ° C. was changed from 20 parts by weight to 5 parts by weight, and phenylxylylethane was changed from 80 parts by weight to 95 parts by weight. I got the top paper.

[Comparative Example 2]
In place of melamine and formaldehyde, 20 g of polymethylene polyphenyl isocyanate as polyisocyanate, 23 parts of hexamethylene diisocyanate, and 8 g of ethylenediamine butylene oxide adduct (molecular weight 1267) as amine alkylene oxide adduct were dissolved. An upper paper was obtained in the same manner as in Example 1 except that the capsule slurry was prepared.

[Comparative Example 3]
An upper sheet was obtained in the same manner as in Example 1 except that the normal paraffin was changed from a fraction of 200 to 250 ° C. to a fraction higher than 250 ° C.

[Reference example]
The upper paper was prepared in the same manner as in Example 1 except that 40.0 parts by weight of phenylxylylethane, 15 parts by weight of normal paraffin which was a fraction at 200 to 250 ° C., and 40.0 parts by weight of diisopropylnaphthalene were used. Obtained.

<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 a * value was measured with a spectrocolorimetric system (manufactured by Murakami Color Research Laboratory) for the degree of redness of the color developed after irradiation and the color developed without irradiation. Since the amber color is reddish, the a * value was used as a scale for measuring redness. It shows that redness is so strong that this value is large. The change rate of the a * value was calculated before and after the light treatment, and the one with a small increase was marked as ◯.
◯: Less than 20% and good light resistance ×: 20% or more and poor light resistance The above test results are shown in the following table.

Claims (2)

In a microcapsule having an amine-aldehyde polycondensation wall film encapsulating an oil in which a black 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 15 to 35 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.