JP2870194B2 - Pressure-sensitive copy paper - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure-sensitive copying paper excellent in light fastness, surface strength and coloring.

[0002]

2. Description of the Related Art A pressure-sensitive copying paper is provided with a coloring agent capsule composition mainly composed of microcapsules containing an oily substance in which an electron-donating organic coloring agent (hereinafter simply referred to as a coloring agent) is dissolved. An upper paper coated on one side and a colorant composition mainly composed of an electron-accepting colorant (hereinafter simply referred to as a colorant) which forms a color when contacted with the color former on one side of the support. There are various types of sheets, such as a medium sheet having a color former capsule composition applied on the opposite side and a lower sheet having a color former composition applied on one side of a support. Paper is used as a copy set by combining paper and lower paper in this order. In addition, a self-coloring type pressure-sensitive copying paper in which a color former and a color former are coated on the same surface of a support to enable pressure-sensitive recording with one sheet is also known as one form thereof.

However, when a color image obtained from a pressure-sensitive copying paper is directly exposed to sunlight, the density of the color image decreases, and in an extreme case, the color image disappears. Therefore, it is difficult to use it for applications such as delivery slips that are exposed to sunlight, and improvement of this point has been desired. Conventionally, as a method for solving such disadvantages, an organic ultraviolet absorber, an antioxidant and zinc,
Proposals have been made to include oxides, hydroxides, carbonates, sulfates, halides, etc. of aluminum, iron, copper, magnesium, manganese, calcium, titanium, cobalt, nickel in the colorant-containing layer. However, at present, a sufficient improvement effect on the light resistance to sunlight has not been obtained.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a pressure-sensitive copying paper which is excellent in light fastness of a color image without disadvantages such as a decrease in coloration ability and a decrease in surface strength.

[0005]

SUMMARY OF THE INVENTION The present invention relates to an aromatic carboxylic acid colorant which forms a color by reacting with an electron donating organic colorant, and an indirect colorant having a specific surface area (BET method) of 9 to 15 m ² / g. A pressure-sensitive copying paper obtained by applying and drying a colorant coating solution containing zinc oxide produced by a method, wherein the colorant coating solution comprises the aromatic carboxylic acid-based colorant. A pressure-sensitive solution containing an aromatic carboxylic acid colorant dispersion obtained by emulsifying and dispersing a solution in which an agent is dissolved in an organic solvent in an aqueous medium, and subsequently distilling off the organic solvent from the emulsified dispersion. Copy paper.

[0006]

[0007]

According to the present invention, the light resistance of a pressure-sensitive copying paper can be extremely effectively improved without any new defects such as deterioration of a color image due to heat and humidity, deterioration of coloration ability and surface strength.

[0008] Zinc oxide can be produced by a direct method, an indirect method, a wet method, or the like. Zinc oxide obtained by the indirect method has an extremely high light resistance improving effect because it has a very high purity. The indirect method is a method in which zinc oxide is produced by dissolving and evaporating metallic zinc, and collecting by cooling after oxidation. In contrast, the wet method is a method in which a zinc salt solution is reacted with soda ash, washed with water, filtered, dried, and then roasted to obtain zinc oxide, and only low-purity zinc oxide is obtained. According to the wet method, a material having a very high specific surface area can be obtained, but the purity is low and the effect of improving light resistance is poor. In addition, since direct zinc oxide is obtained directly from ore or the like, the zinc oxide is often low in purity, which is also inferior in the effect of improving light resistance.

In the present invention, among various zinc oxides, the BET specific surface area obtained by the indirect method is particularly 9 to 15 m ² /
g of zinc oxide is used. Although the reason for obtaining such an effect is not necessarily clear, zinc oxide has the largest ultraviolet absorbing ability among the white pigments, but the ultraviolet absorbing ability is greatly increased by increasing the specific surface area to 5 m ² / g or more. Therefore, as a result, it is presumed that a pressure-sensitive copying paper having extremely excellent light resistance can be obtained. However, when zinc oxide having an extremely high specific surface area is used, the surface strength tends to be weak. For this reason, it is necessary to use a large amount of the adhesive, and as a result, the color density may be reduced, or the adhesive may reduce the ultraviolet absorbing effect. Therefore, the specific surface area is more preferably about 9 to 15 m ² / g. is there.

It is desirable that the amount of zinc oxide used in combination with the colorant is adjusted in the range of about 10 to 500 parts by weight per 100 parts by weight of the colorant. Examples of the coloring agent that reacts with the electron-donating organic coloring agent include inorganic coloring agents such as acid clay, activated clay, attapulgite, zeolite, bentonite, silica, and aluminum silicate; phenol-aldehyde polymers and phenol-acetylene. Organic colorants such as phenolic polymers such as polymers and polyvalent metal salts of aromatic carboxylic acids or derivatives thereof are known. In the present invention, aromatic carboxylic acid-based colorants are particularly used.

Examples of the aromatic carboxylic acid colorants include, for example, JP-B-49-10856 and JP-B-51-2517.
4, benzoic acid, p-tert-butyl-benzoic acid, 4-methyl-3-nitrobenzoic acid, salicylic acid, 3-phenylsalicylic acid, 3-cyclohexyl as described in JP-A-49-55410 and the like. Salicylic acid, 3-tert-
Butyl-5-methylsalicylic acid, 3,5-di-tert-butylsalicylic acid, 3-methyl-5benzylsalicytic acid,
3-phenyl-5, (α, α-dimethylbenzyl) salicylic acid, 3-cyclohexyl-5- (α, α-dimethylbenzyl) salicylic acid, 3- (α, α-dimethylbenzyl) -5-methylsalicylic acid, 3, 5-di-cyclohexylsalicylic acid, 3,5-di- (α-methylbenzyl)
Salicylic acid, 3,5-di- (α, α-dimethylbenzyl) salicylic acid, 3- (α-methylbenzyl-5-
(Α, α-dimethylbenzyl) salicylic acid, 3-methyl-5-isononyl salicylic acid, 3-methyl-5-isododecyl salicylic acid, 3-methyl-5-isopentadecyl salicylic acid, 3-isopropyl-5-isononyl salicylic acid , 3-isopropyl-5-isododecylsalicylic acid, 3-tert-butyl-5-isononylsalicylic acid, 3-isononylsalicylic acid, 3-isononyl-5-
Methylsalicylic acid, 3-isononyl-6-methylsalicylic acid, 3,5-diisononylsalicylic acid, 3-isononyl-5-cyclohexylsalicylic acid, 3-isononyl-
5-phenylsalicylic acid, 3-isononyl-5- (α-
Methylbenzyl) salicylic acid, 3-isononyl-5-
(4, α-dimethylbenzyl) salicylic acid, 3-isononyl-5- (α, α-dimethylbenzyl) salicylic acid,
3-isododecyl salicylic acid, 3-isododecyl-5-
Methylsalicylic acid, 3-isododecyl-6-methylsalicylic acid, 3-isododecyl-5-ethylsalicylic acid, 3
-Isopentadecylsalicylic acid, 3-isopentadecyl-5-methylsalicylic acid, 3-isopentadecyl-6-
Methyl salicylic acid, 3-cyclohexyl-5-isononyl salicylic acid, 3-phenyl-5-isononyl salicylic acid, 3- (α-methylbenzyl) -5-isononyl salicylic acid, 3- (α, α-dimethylbenzyl) -5 -Isononyl salicylic acid, 5-isononyl salicylic acid, 5-isododecyl salicylic acid, 5-isopentadecyl salicylic acid, 4-methyl-5-cyclohexyl salicylic acid, benzylated styrenated salicylic acid, 2-hydroxy-1-benzyl-3-naphthoe Acid, 1-benzoyl-2-hydroxy-3-naphthoic acid, 3-hydroxy-5-cyclohexyl-2-naphthoic acid, 2-hydroxy-4-[(4
-Carboxy-5-hydroxy) phenyl] -1-naphthoic acid and the like;
Salts with polyvalent metals such as aluminum, magnesium, calcium and cobalt; JP-B-48-8215, JP-B-Sho 4
Polymers of aromatic carboxylic acids and aldehydes or acetylenes and polyvalent metal salts thereof as described in JP-A-8-8216 and JP-B-52-1326; And polyvalent metallated carboxy-modified terpephenol resin; pinenated zinc salicylate.

Aromatic carboxylic acids and polyvalent metal salts thereof are excellent in desired effects, do not cause yellowing due to light, have high color-forming ability, and have a color-developed image obtained by adhering moisture, storing files, etc. It has the advantage that the concentration does not decrease.

Usually, a coating solution containing the colorant and the zinc oxide is prepared using water as a medium, and is applied to a support to obtain a pressure-sensitive copying paper. At that time, the method for preparing the colorant dispersion liquid is a method of dissolving in an organic solvent, emulsifying in an aqueous medium with an emulsifying / dispersing agent, and then distilling off the organic solvent by heating or the like.

According to such a preparation method, it is possible to obtain a pressure-sensitive copying paper which is excellent in the above-mentioned effect of improving light fastness and also excellent in initial coloring (a high-density recorded image can be obtained even immediately after printing). In addition, the aromatic carboxylic acid colorant dispersion obtained by such a preparation method has properties as an adhesive, and when used in combination with zinc oxide having a large specific surface area, the surface strength of the coated surface is not reduced at all. On the contrary, excellent surface strength is obtained.

It is also possible to emulsify and disperse as described above, thereafter distill off the organic solvent, and further treat with an agitator / pulverizer. When the organic colorant is dissolved in an organic solvent and then emulsified in an aqueous medium, the emulsifying and dispersing agents used are usually anionic surfactants and nonionic surfactants, and cationic surfactants are generally good results. Do not give. Examples of the anionic surfactant include an alkali salt of an alkyl sulfate, an alkali salt of an alkylbenzene sulfonic acid, an alkali salt of an alkyl naphthalene sulfonic acid, an alkali salt of a sulfosuccinate, an alkali salt of polystyrene polysulfonic acid, and an alkali salt of lignin sulfonic acid. Examples thereof include alkali salts of alkylphenolsulfonic acid, alkali salts of alkylsalicylic acid, alkali salts of aralkyl salicylic acid, and alkali salts of polyacrylic acid. As the nonionic surfactant, a high molecular weight surfactant having a molecular weight of 400 or more is particularly preferable, and examples thereof include polyvinyl alcohol, modified polyvinyl alcohol, polyacrylamide, and modified polyacrylamide. Here, the term "modification" refers to the incorporation of a foreign structural unit by telomerization or copolymerization at the terminal or intermediate of the basic polymer. Polyvinyl alcohol, modified polyvinyl alcohol, polyacrylamide or modified polyacrylamide is preferred.

When an anionic surfactant and a nonionic surfactant are used together, an aqueous dispersion of a developer having excellent storage stability can be obtained. In addition, the organic solvent used in the present invention has relatively low solubility in water, good solubility of the color developer, low boiling point, or low susceptibility to chemical change during preparation of the dispersion. And other properties are required. Specific examples thereof include benzene, toluene, xylene, chloroform, carbon tetrachloride, trichloroethane, trichloroethylene, chlorobenzene, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, butyl acetate, butanol, amyl alcohol, or methyl tertiary butyl ether And the like. The amount of the dispersant and the amount of the organic solvent used are not constant depending on the size of the target dispersed particles, but the preferred range is 0.1 part to 15 parts of the dispersant per 100 parts of the developer by weight ratio to the developer. Parts, and about 500 parts or less of the organic solvent.

The coating solution for the colorant-containing layer usually contains, as an adhesive, starch, casein, gum arabic, carboxymethylcellulose, polyvinyl alcohol, styrene.
Butadiene copolymer latex, vinyl acetate-based latex, etc. are blended. In addition, inorganic pigments such as magnesium oxide, titanium oxide, aluminum hydroxide, calcium carbonate, magnesium sulfate, calcium sulfate and ordinary zinc oxide, and pressure-sensitive Various auxiliaries known in the field of copy paper production can be added as appropriate. The coloring agent coating solution thus prepared is
It is coated on a support by a usual coating device such as an air knife coater, a blade coater, a roll coater, a size press coater, a curtain coater, a short dwell coater and the like, and is finished as a pressure-sensitive copying paper.

In the present invention, a colorant layer and a colorant-containing capsule layer are provided on the same surface of the support, or a mixed coating layer of a colorant coating solution and a coating solution containing an encapsulated colorant is provided. It can also be applied to self-coloring type pressure-sensitive copying paper (so-called self-contained type). Paper, synthetic paper, film and the like are used as the support.

[0019]

EXAMPLES Examples and comparative examples will be described below to further clarify the effects of the present invention, but the present invention is not limited to these examples. In the examples, “parts” and “%” represent “parts by weight” and “% by weight”, respectively, unless otherwise specified.

Example 1 [Preparation of Coloring Agent Coating Solution] Zinc 3,5-di (α-methylbenzyl) salicylate 10
0 parts were dissolved in 100 parts of toluene and emulsified in 150 parts of a 3% aqueous solution of polyvinyl alcohol using a homomixer, and then toluene was distilled off to obtain an aqueous dispersion of colorant fine particles. To this aqueous dispersion, 700 parts of calcium carbonate, 100 parts of aluminum hydroxide, and BET obtained by an indirect method.
Water is added to a dispersion obtained by mixing 200 parts of zinc oxide having a specific surface area of 9 m ² / g, 200 parts of a 25% aqueous solution of oxidized modified starch, and 208 parts of styrene-butadiene latex (48% dispersion), and solids are added. A colorant coating solution having a concentration of 25% was prepared.

[Production of Colored Paper for Pressure-Sensitive Copying Paper] The above-described colorant coating solution is applied to one side of a 49 g / m ² base paper so that the dry weight is 5 g / m ^2, and dried to form a pressure-sensitive copying paper. A coloring paper was obtained.

Example 2 The BET specific surface area obtained by the indirect method was 10.5 m ² /
Colored paper for pressure-sensitive copying paper was obtained in the same manner as in Example 1 except that g of zinc oxide was used.

Example 3 A color paper for pressure-sensitive copying paper was obtained in the same manner as in Example 1 except that zinc oxide having a BET specific surface area of 13 m ² / g obtained by the indirect method was used.

[0024]

Example 4 Zinc 3,5-di- (α-methylbenzyl) salicylate 1
A color paper for pressure-sensitive copying paper was obtained in the same manner as in Example 1, except that 00 parts was replaced with 100 parts of zinc 3-isododecylsalicylate. Evaluation Effect Excellent light fastness was obtained.

Comparative Example 1 The BET specific surface area obtained by the indirect method was 9.0 m ² / g
A color paper for pressure-sensitive copying paper was obtained in the same manner as in Example 1 except that no zinc oxide was used.

Comparative Example 2 The BET specific surface area obtained by the indirect method was 9.0 m ² / g
Colored paper for pressure-sensitive copying paper was obtained in the same manner as in Example 1 except that zinc oxide having a BET specific surface area of 4.5 m ² / g obtained by an indirect method was used instead of zinc oxide.

Comparative Example 3 The BET specific surface area obtained by the indirect method was 9.0 m ² / g
A color paper for pressure-sensitive copying paper was obtained in the same manner as in Example 1 except that zinc oxide having a BET specific surface area of 60 m ² / g obtained by a wet method was used instead of zinc oxide.

Comparative Example 4 An aqueous emulsion containing 100 parts by weight of a paraphenylphenol resin in solid content was prepared using 3,5-di- (α-methylbenzyl).
Colored paper for pressure-sensitive copying paper was obtained in the same manner as in Example 1 except that the aqueous dispersion of zinc salicylate was used.

COMPARATIVE EXAMPLE 5 100 parts of zinc 3,5-di- (α-methylbenzyl) salicylate having an average particle diameter of 50 μm was dispersed in 150 parts of a 3% aqueous solution of polyvinyl alcohol, and the mixture was sand-milled (each product; sand grinder, Igarashi Kikai) ) To obtain a colorant aqueous dispersion. A color paper for pressure-sensitive copying paper was obtained in the same manner as in Example 1 except that this colorant dispersion liquid was used.

The ten kinds of color paper thus obtained were subjected to the following quality evaluation tests, and the results are shown in Table 1.

[Preparation of Upper Paper] Crystal violet lactone is dissolved in alkylated naphthalene, and a capsule coating liquid prepared by microencapsulating this oily liquid is coated on one side of the base paper with a dry weight of 4 g / m ^2.
And dried to obtain upper paper.

Coloring test The coloring paper and the upper paper are faced with each other with the coated surfaces facing each other, and the color is developed by a drop-type coloring tester (weight: 150 g, height: 20 cm). After 2 hours, the coloring density is measured by a Macbeth reflection densitometer. It was measured.

Light fastness test The color paper and the upper paper are superposed on each other so that the coated surfaces face each other, a color image is formed under a load of 100 kg / cm ² , the color density is measured with a Macbeth reflection densitometer, and the value is measured. It was a D _0. Next, after applied to the sunlight, its value was D ₁ measured color density. The light fastness is represented by [Equation 1]. The closer the value is to 100, the better the light fastness.

[0035]

(Equation 1)

Surface Strength Using an RI printing suitability tester (manufactured by Meiji Seisakusho), the offset ink of tack value 10 made by Toyo Ink was printed three times on the colorant layer coated surface of the lower paper, and the printed surface was printed. The state was visually determined. The evaluation criteria are as follows. ：: There is almost no peeling of the colorant layer applied surface. Δ: Peeling of the colorant layer applied surface is observed. ×: The peeling of the colorant layer applied surface is remarkable.

Initial color development test A color was developed in the same manner as in the color development test, and the color density after 10 seconds was measured with a Macbeth densitometer.

[0038]

[Table 1]

[0039]

As is clear from the results shown in Table 1, the pressure-sensitive copying paper of the present invention was a pressure-sensitive copying paper excellent in light resistance, surface strength, coloring and initial coloring.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-98483 (JP, A) JP-A-53-95704 (JP, A) JP-A-61-173985 (JP, A) ) ”, Sakai Chemical Industry Co., Ltd. (58) Fields surveyed (Int. Cl. ⁶ , DB name) B41M 5/124

Claims (1)

(57) [Claims] 1. An aromatic carboxylic acid colorant which reacts with an electron-donating organic colorant to form a color, and zinc oxide produced by an indirect method having a specific surface area (BET method) of 9 to 15 m ² / g. A pressure-sensitive copying paper obtained by applying and drying a colorant coating solution containing on a support, wherein the colorant coating solution is obtained by dissolving the aromatic carboxylic acid-based colorant in an organic solvent. A pressure-sensitive copying paper containing an aromatic carboxylic acid colorant dispersion obtained by emulsifying and dispersing a solution in an aqueous medium and subsequently distilling off an organic solvent from the emulsified dispersion.