JPS645558B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to pressure sensitive recording paper. Pressure-sensitive recording paper is generally made of an electron-donating organic coloring agent (hereinafter referred to as a coloring agent) such as crystal violet lactone or benzoyl leucomethylene blue, and a montmorillonite-type clay mineral (hereinafter referred to as a montmorillonite clay mineral whose activity is increased by acid treatment). It applies the principle of color development through the reaction of electron-accepting color developers (hereinafter referred to as color developers) such as activated clay), phenolic compounds, aromatic carboxylic acids, or metal salts thereof, and contains color formers. Depending on the intended use, the top paper has microcapsules coated on one side of the base paper, the bottom paper has a color developer coated on one side of the base paper, and the inner paper has the microcapsules and color developer coated on different sides of the same base paper. Copies can be made by combining them as appropriate and applying pressure with a ballpoint pen, typewriter, etc. There is also a type of paper called self-contained paper in which the microcapsules and color developer are coated on the same side of a base paper. In the pressure-sensitive recording paper, activated clay is most commonly used as a color developer. This activated clay has the property of reacting well with color formers and producing deep colors. However, the acid strength of activated clay is too strong for crystal violet lactone, which is the most commonly used coloring agent, to react with activated clay to produce the highest concentration of blue-violet color. For this reason, when preparing activated clay paints, alkaline substances (alkali or alkaline earth,
A method has been proposed to adjust the alkalinity to slightly alkaline by adding metal oxides, hydroxides, carbonates, ammonia, amines, etc.). However, when activated clay paint adjusted to slightly alkaline side is also applied to base paper,
There is a problem that the color developing ability decreases over time. The reason for this is that alkali or alkaline earth metal oxides, hydroxides, carbonates, etc. are dissolved in the paint, but when the paint is applied to the base paper and dried, they recrystallize. Furthermore, there is a problem in that the sulfate band in the base paper neutralizes the alkali recrystallized by the influence of the base paper moisture and atmospheric moisture, and also acts on the activated clay, reinforcing the acid strength of the activated clay. Furthermore, when an amine is contained in the coating layer of activated clay, it not only neutralizes the acid points in the strong acid part of the activated clay, but also neutralizes the acid points in the weak acid part that contribute to the color developing reaction. Therefore, there is a problem in that the color developing function of activated clay is significantly reduced. The present inventor has arrived at the present invention as a result of studies to improve the drawbacks of color developing paper using activated clay, which is based on the use of crystal violet lactone as a coloring agent. The structure of the present invention is to completely remove Al ions by acid treatment and make the aromatic adsorption index 40 or more.
Color developer paper coated with activated clay containing Mg ions, crystal violet lactone, and N-n-butyl-3-[bis{4-(N-methylanilino)phenyl}methyl]carbazole as a carbazolylmethane compound are color formers. It is characterized by the combination of colored paper coated with microcapsules containing as the main component. The activated clay used in the present invention can be made by acid-treating a montmorillonite clay mineral, and the montmorillonite clay mineral has the general formula Xm (Y ²⁺ , Y ³⁺ ) _2~3 Z ₄ O ₁₀ (HO) ₂・SH ₂ O where X: K, Na, Ca Y ²⁺ : Mg ²⁺ , Fe ²⁺ , Mn ²⁺ , Ni ²⁺ , Zn ²⁺ , Li ⁺ Y ³⁺ : Al ³⁺ , Fe ³⁺ , Cr ³⁺ , Mn ³⁺ Z: Si, Al The average value of m is 1/3 S is indicated by the number of interlayer water. This is described on page 80 of the Clay Handbook (edited by the Clay Society of Japan, Gihodo).
Among these clay minerals, Al per 100 parts by weight of Si
is preferably 5 to 30 parts by weight. When montmorillonite clay minerals are treated with sulfuric acid or hydrochloric acid, Fe ions, Mg ions, and Ca ions are first eluted. Next, Al ions are eluted, but the activated clay used in the present invention is treated until the Al ions are completely removed. At this time, the aromatic adsorption index of activated clay must exceed 40. Here, the aromatic adsorption index is an index reflecting the degree of adsorption capacity or activity of activated clay, and is also conveniently used as an index indicating the degree of specific surface area of activated clay. An aromatic adsorption index of 40 or more means that the aromatic adsorption index of activated clay used as a color developer other than the present invention is 20 to 20.
40, which means that it is very active and has a very large specific surface area, and also indicates that there are many acid sites in the weak acid part that contribute to color development with crystal violet lactone. . It also shows that the influence of acid strength exerted by sulfate bands in the base paper over time is less likely to occur. The aromatic adsorption index is determined by the following method. The pulverized sample is dried at 150°C ± 5°C for 3 hours and allowed to cool to room temperature in a desiccator. Take 1.00 g of this dry sample into a container, add 2.00 ml of a mixed solution of 30 volumes of dehydrated toluene and 70 volumes of dehydrated isooctane to disperse the sample, shake at room temperature for 40 minutes, and then use a centrifuge to precipitate the sample and remove the supernatant. Collect the liquid. Measure the refractive index of this supernatant liquid and the original liquid at 20°C, and calculate the aromatic adsorption index (AAI) using the following formula. AAI = [(n ²⁰ _D ) _A − (n ²⁰ _D ) _B ] × 10 ⁴ where (n ²⁰ _D ) _A : Refractive index of a mixture of 30 volumes of toluene and 70 volumes of isooctane (n ²⁰ _D ) _B : Supernatant Refractive index of liquid When the aromatic adsorption index of natural clays is measured using the method described above, most of them are distributed between 4 and 15.
In the case of montmorillonite type clay mineral, which is the source of activated clay, it is distributed between 8 and 15. By acid-treating this montmorillonite clay mineral, it is possible to increase the aromatic adsorption index. Activated clay excluding Al ions consists only of SiO ₂ , and there are almost no acid points in the strong acid part and only acid points in the weak acid part. However, under this condition, it is difficult to develop and maintain the highest concentration of crystal violet lactone. The reason for this is thought to be that although the color-forming reaction is sufficiently carried out at an acid site weaker than the optimum acid strength for coloring crystal violet lactone at its highest concentration, on the other hand, the decomposition of the color-forming body is accelerated by light such as sunlight. Here, the acid strength can be expressed by the acidity of activated clay, that is, the number of acid sites with a certain strength of acid strength.
The acid sites with acid strengths suitable for color development of crystal violet lactone range from acid strength Ho=+0.8 to Ho=+4.8.
It is necessary that the content be 0.4 mmol/g or more within this range. Therefore, the activated clay of the present invention contains Fe, Ca, Mg, Al.
By reintroducing only Mg ions into the SiO ₂ molecular structure of activated clay from which ions have been removed, acid strength can be improved.
0.4 mmol/g in the range of Ho=+0.8 to Ho=+4.8
At that time, from Ho = +0.8, there are no acid sites at all in the strong acid part, and from Ho = +4.8, the acid points in the weak acid part are 0.4 mmol/g or less, and crystal violet. It has been found that activated clay having the optimum acid strength for coloring lactones can be obtained. The Mg introduced into activated clay consisting of SiO ₂ is magnesium nitrate, magnesium chloride, magnesium perchlorate, magnesium formate, magnesium sulfate,
Use magnesium hydroxide etc. The amount of Mg to be added may be 5 to 30 parts by weight, preferably 10 to 20 parts by weight, per 100 parts by weight of Si. Activated clay from which Al ions have been removed is added to a solution containing the above Mg salt and heated. Alkalize and heat at 30-60℃ to fix Mg ions. Then wash with water. At this time, a short acid treatment may be performed using a weak acid such as phosphoric acid. Next, the activated clay is dried at 100 to 350°C to obtain the activated clay of the present invention. The activated clay into which Mg ions have been introduced in the present invention means that it is also possible to use a phenol resin, an aromatic carboxylic acid or a metal salt thereof, or activated clay other than the present invention as a color development aid. In addition, kaolin, clay,
Talc, calcium carbonate, zinc oxide, aluminum hydroxide, magnesium oxide, magnesium carbonate, silica, etc. can be used in combination for application. When applied to one side of the base paper, as a binder, a latex binder such as styrene-butadiene latex or acrylic latex, oxidized starch, etherified starch, esterified starch, carboxymethyl cellulose, hydroxyethyl cellulose, methyl cellulose, polyvinyl alcohol,
Water-soluble polymer binders such as casein, gelatin, soybean protein, and sodium alginate can be used alone or in combination. The amount of these binders added is 10 to 40 parts by weight, preferably 20 to 30 parts by weight, per 100 parts by weight of activated clay. In contrast to the color developing paper coated with activated clay into which Mg ions of the present invention have been introduced, a color developing paper coated with microcapsules containing crystal violet lactone on one side of the base paper is used. As the color former, crystal violet lactone is most preferred, although the color former loses some concentration upon exposure to sunlight. This is thought to be due to the existence of a small amount of weak acid moieties with Ho=+4.8 or higher in the acid sites of the activated clay into which Mg ions have been introduced, which promotes the decomposition of the colored material by sunlight. For the activated clay used in ordinary pressure-sensitive recording paper, benzoyl leucomethylene blue is used in combination to improve the light resistance to some extent, but in the activated clay of the present invention, the benzoyl leucomethylene blue color is weak and light fastness is improved. There is no improvement effect. Rather, it exhibits the effect of further promoting the decomposition of the chromophore. Therefore, the present inventor investigated various color formers in order to obtain a pressure-sensitive recording paper with better light resistance.As a result, the present inventors developed carbazole as a color former in order to further improve the light resistance of the color former on the activated clay of the present invention. It has been found that a rumethane compound is suitable. This carbazolylmethane compound is produced by the method described in JP-A-53-55223 and JP-A-54-161637. The most suitable carbazolylmethane compound for the present invention is N-n-butyl-3-[bis{4-(N-methylanilino)phenyl}methyl]carbazole. The amount of carbazolylmethane compound added to 100 parts by weight of crystal violet lactone is 0 to 50.
parts by weight, preferably 10 to 30 parts by weight. The coloring agent is dissolved in a solvent, microencapsulated, and applied to the base paper. As a solvent, natural or synthetic oils can be used alone or in combination. Examples of solvents include cottonseed oil, kerosene, paraffin, naphthenic oil, alkylated biphenyl, alkylated terphenyl, triarylmethane, chlorinated paraffin, and the like. A known microcapsule method can be used to microcapsule the oil in which the coloring agent is dissolved. For example, methods for producing microcapsules include a method using core cellvation as seen in U.S. Patent Nos. 2800457 and 2800458;
Examples include methods using polymer precipitation, as disclosed in No. 3418250 and No. 3660304. Microcapsules containing color formers are applied to base paper along with various additives, binders, antioxidants, anti-smudge agents, and surfactants. After completely removing Al ions through acid treatment and making the aromatic adsorption index over 40, color developing paper coated with activated clay into which Mg ions were introduced was used in combination with crystal violet lactone and a carbazolyl methane compound as color formers. It exhibits the highest density blue-purple color when compared with colored paper, and there is almost no decline in color developing ability over time like with conventional products, and it has excellent instantaneous color development and excellent light fastness of the color forming material no matter what time you record it. It is something that can be demonstrated. The present invention will be explained in detail by examples. All "parts" below refer to "parts by weight." Comparative Example 1 Montmorillonite clay mineral (Ignition loss when expressed as weight % based on 110℃ dry matter)
_5.8SiO2 78.0, _{Al2O3 13.0} , _{Fe2O3 1.9} , CaO0.9,
MgO2.6) was treated with sulfuric acid to remove Al, Fe, Ca, and Mg ions to obtain activated clay with an aromatic adsorption index of 56.
This activated clay was placed in an aqueous magnesium chloride solution and heat-treated to obtain activated clay consisting of 87.5% SiO ₂ and 12.5% MgO. Acid strength was determined by the Bensei method (J.Am, Chem
Soc, 78, 5490 (1956)), the acid sites were 0.50 mmol/g in the range of acid strength Ho = +0.8 to Ho = +4.8; There were 0.27 mmol/g of acid sites in the range of Ho=+9, and 0 acid sites with acid strength Ho=+0.8 or less. 100 parts of the activated clay thus obtained (moisture 5.6%) was dispersed in 200 parts of water in which 1 part of sodium pyrophosphate was dissolved, and 50 parts of 10% oxidized starch and 50 parts of 48% SBR-latex were added thereto to form a paint. did. 50% of this paint
A dry weight of 7 g/m ² was applied to a base paper of g/m ² to obtain a color developer paper. On the other hand, a coloring agent oil prepared by dissolving 4 parts of crystal violet lactone in 100 parts of diisopropylnaphthalene is microencapsulated by the microcapsule manufacturing method using coacervation described in US Pat. No. 2,800,457. To 200 parts of the obtained microcapsule dispersion (microcapsule solid content 10%), 20 parts of 10% oxidized starch and 4 parts of wheat starch granules were added to form a paint, which was applied to 50 g/ ^m2 base paper at a dry weight of 5 g/ ^m3 . It was colored paper. Table 1 shows the performance when developing color using a combination of color developing paper and color developing paper. Comparative Example 2 A montmorillonite clay mineral was treated with sulfuric acid,
SiO ₂ 80.0 in weight % based on 110°C dry matter,
Activated clay consisting of Al ₂ O ₃ 9.0, Fe ₂ O ₃ 2.0, CaO 1.0, and MgO 2.0 was obtained. The aromatic adsorption index is 24 and the acid strength is
035 mmol/g in the range of Ho=+0.8 to Ho=+4.8
There are 0.2 mmol/g of acid sites at Ho=+0.8 or less, which is a strong acid site. The number of acid sites with Ho=+4.8 or higher was 0.05 mmol/g. 100 parts of this activated clay (6.7% moisture) was dispersed in 200 parts of water in which 1 part of sodium pyrophosphate was dissolved.
Add 50 parts of 10% oxidized starch and 50 parts of 48% SBR-latex, and then add caustic soda to adjust the pH of the paint.
It was set as 9.0. This paint was applied to a base paper of 50 g/m ² at a dry weight of 7.5 g/m ² to obtain a color developing paper. The color developing paper was combined with the color developing paper of Comparative Example 1 to develop color. Example 1 100 parts of diisopropylnaphthalene, 3 parts of crystal violet lactone, 3 parts of N-n-butyl-
-[Bis{4-(N-methylanilino)phenyl}
One part of methyl]carbazole was dissolved to form a color former oil and microencapsulated. A colored paper was obtained in the same manner as in Comparative Example 1. It was combined with the color developing paper obtained in Comparative Example 1 to develop color. Comparative Example 3 3 parts of crystal violet lactone and 1 part of benzoyl leucomethylene blue were dissolved in 100 parts of diisopropylnaphthalene to form a color former oil and microencapsulated. A colored paper was obtained in the same manner as in Example 1, and was combined with the developing paper obtained in Example 1 to develop color.

[Table] Displays the concentration measured using a Macbeth densitometer. ]
As is clear from Table 1, the combination of the specific activated clay color developing paper of the present invention and the color developing paper containing crystallized lactone and a specific carbazolylmethane compound provides excellent color density and color development performance over time. Furthermore, it was found that the highest light resistance was obtained without any decrease in color.

Claims (1)

[Scope of Claims] 1. Color-developing paper coated with activated clay to which magnesium ion is introduced after completely removing aluminum ions and making the aromatic adsorption index 40 or more by acid treatment, and crystal violet lactone containing crystal violet lactone as the main component. 10-30 for Violet Lactone
A pressure-sensitive recording paper comprising a color-forming paper coated with microcapsules containing a color-forming agent containing % by weight of N-n-butyl-3-[bis-(N-methylanilino)phenyl}methyl]carbazole. 2. The pressure-sensitive recording paper according to claim 1, wherein the color former does not contain benzoylleucomethylene blue.