JPH0415750B2 - - Google Patents

Description

[Detailed description of the invention]

(a) Field of Industrial Application The present invention relates to a self-coloring pressure-sensitive recording paper, and more specifically, to a self-coloring pressure-sensitive recording paper having a cast coating surface. (b) Prior art Self-coloring pressure-sensitive recording paper has unique usefulness, such as printing without a type ribbon or writing or printing on plain paper to obtain a copy record, and the demand for it has increased in recent years. There is. On the other hand, cast coated paper is generally used as high-grade printing paper. Self-coloring pressure-sensitive recording paper is developed from so-called carbonless copying paper, and is also called self-contained paper. Microcapsules containing a coloring agent such as crystal violet lactone or benzoyl leucomethylene blue are coated on a support. A manufacturing method using two-layer coating, which consists of two steps: a step of applying a color developer such as acid clay, phenolic resin, or an organic acidic substance on the coating layer, or a manufacturing method using one or two of the above steps. A method is known (Japanese Patent Publication No. 47-16096) in which the main components of the two steps are mixed uniformly into microcapsules, mixed uniformly, and applied as a single layer. Self-coloring pressure-sensitive recording paper obtained by such a method of adding a smearing step onto a support has a limit in satisfying both high color density and unnecessary color stains. In other words, if you place emphasis on coloring performance, the manufacturing process, printing,
Alternatively, unnecessary colored stains are likely to occur due to handling by the end user, and on the other hand, if emphasis is placed on preventing unnecessary colored stains, the coloring performance itself, which is the most important performance for recording paper, will be impaired. Therefore, this type of self-coloring pressure-sensitive recording paper, which accounts for most of the types currently on the market, is the product of a passive compromise between end users and manufacturers, and both parties naturally desire high coloring performance and unnecessary coloring. What they have in common is that there is little dirt. Other manufacturing methods include self-coloring pressure-sensitive recording paper obtained by paper-making a color former and a color developer together with pulp fibers (Japanese Patent Application Laid-Open Nos. 110008-1982 and 136917-1982). ). This method has the great advantage that self-coloring pressure-sensitive recording paper can be obtained only through the papermaking process. In terms of quality, the color forming agent and color developer are protected by the pulp fibers, so it shows sufficient performance against unnecessary colored stains, but the ratio of the amount of color forming agent and color developer adsorbed to the pulp fibers during the paper making process It has the disadvantage that the color development performance is limited because the color is constant, and it is difficult to obtain a deep color density. On the other hand, the manufacturing method for highly glossy coated paper (hereinafter referred to as cast coated paper), which is usually called cast coated paper, is the wet casting method, in which a wet coating layer is pressed against a heated finished drum surface having a mirror surface to give a highly glossy finish. (For example, Tokuko Shou 28-3407, Tokuko Sho No. 28-3407,
No. 38-25160), the wet coating layer is once dried, then plasticized by re-wetting and pressed against the surface of a heated finished drum having a mirror surface (for example, U.S. Pat. (Japanese Patent Publication No. 102111/1983), gelling cast method in which the wet coating layer is made into a gel state and pressed against the surface of a heated finished drum having a mirror surface (for example, Japanese Patent Publication No. 15751/1989).
Japanese Patent Publication No. 40-7207, U.S. Patent No. 3377192, Japanese Patent Publication No.
51-40410) and other methods are known. All of these methods of producing cast coated paper involve pressing a coating layer containing pigments and adhesives as main components against a heated, mirror-finished surface in a wet state, and copying the mirror surface onto the plastic coating layer. Therefore, it consists of a method of finishing coated paper with a smooth and strong gloss. The present invention is the first to apply such cast coat paper technology to self-coloring pressure-sensitive recording paper. (c) Problems to be Solved by the Invention The purpose of the present invention is to provide a self-coloring pressure-sensitive recording paper having a cast coating surface that has sufficient coloring performance as a recording paper and is significantly less likely to generate unnecessary colored stains. There is a particular thing. (d) Means for Solving the Problems The self-coloring pressure-sensitive recording paper of the present invention is characterized in that it consists of a support and a coating layer containing a color forming agent and a color developer, and that this coating layer has a cast surface. shall be. As for the usage form of the color former used in the present invention, a method in which the color former is dissolved in oil and used as microcapsules is preferred. The properties of the capsule membrane are particularly important when producing self-coloring pressure-sensitive recording paper with a cast surface, and at least one of the microcapsules is a membrane made essentially of polyurethane, polyurea, epoxy resin, urea-formalin resin, or melamine-formalin resin. It must be encapsulated in a material. Microcapsules produced by the gelatin coacervation method and microcapsules produced by the interfacial polymerization method using polyamide, which have been put into practical use or under consideration, are probably due to insufficient properties of the microcapsule membrane, making it difficult to produce good self-coloring pressure-sensitive recording paper. I can't get it. It is not clear why only these polyurethane, polyurea, epoxy resin, urea-formalin resin, and melamine-formalin resin are good, but what they have in common is that they have a dense film, are highly water resistant, and have strong heat resistance. It seems to be for a reason. Microcapsules with a melamine-formalin resin film showed the least amount of microcapsule destruction and good consolidation when brought into close contact under pressure to a mirror-finished surface during the casting process. These encapsulations can be obtained by known interfacial polymerization methods or in-situ methods. The specific interfacial polymerization method is described in Japanese Patent Publication No. 44-27257. Urea resin microcapsules were published in 1977-3495.
Melamine resin microcapsules can be made by the method disclosed in JP-A-54-49984 and JP-A-52-116249. The color forming agent in the present invention is a colorless compound that develops color when it comes into contact with a solid acid, and representative examples include crystal violet lactone and fluoran derivatives, which can also be defined as electron-donating colorless compounds. In the present invention, the type, properties, etc. of the coloring agent have no substantial influence. Therefore, all kinds of coloring agents can be used, and can be appropriately selected and used alone or in combination of two or more kinds. In the case of microcapsules, which are generally used in the form of color formers dissolved in oil, the present invention is not limited in any way to the oil used to dissolve the color formers, and any conventionally known oils or solvents can be used. In the present invention, the color developer means a solid acid, more specifically an electron-accepting solid acid. Specific examples include clays (e.g. acid clay, attapulgiaite, etc.), organic acids (e.g. aromatic carboxy compounds such as salicylic acid or metal salts thereof),
Examples include mixtures of organic acids and metal compounds, and acidic polymers (eg, phenol formaldehyde resin). The color developer may be used in any form as long as it is uniformly dispersed in the coating layer in the form of fine powder, or an oil-soluble color developer dissolved in oil and microencapsulated may also be used. For the microencapsulation of the color developer, the microencapsulation of the color former described above can be used as is. In the present invention, in addition to the above-mentioned color formers and color developers, the paint liquid includes pigments, dispersants, hardeners, antifoaming agents, mold release agents, adhesives, waterproofing agents, and softeners. , a capsule protectant, etc. can be added as appropriate and used. As pigments, clay, aluminum hydroxide, calcium carbonate, titanium oxide, baium sulfate, zinc oxide, satin white, plastic pigments, etc. can be used. Adhesives include polyvinyl alcohol, carboxymethylcellulose, polyhydroxyethyl methacrylate, methylcellulose, polyacrylic acid, styrene-maleic anhydride copolymer, ethylene-maleic anhydride copolymer, polyvinylpyrrolidone, hydroxyethylcellulose, starch glue, glue. In addition to water-soluble polymer substances such as gelatin, casein, and collagen, styrene-butadiene copolymer, acryl-nitrile copolymer, methyl methacrylate-butadiene copolymer, ethylene-
Latexes such as vinyl acetate copolymers, polyvinyl acetate, vinyl acetate-acrylic acid copolymers, and acrylic acid-based latexes can also be used. In the present invention, it is particularly effective to use at least a protein or latex adhesive. As a mold release agent for smoothing the release from the cast drum, sulfated castor oil, higher fatty acids and salts thereof, wax, emulsion thereof, etc. are used. In the production of self-coloring pressure-sensitive recording paper, cellulose powder, starch particles, talc, calcined kaolin, calcium carbonate, etc. are normally used as capsule protectants. At least starch particles or cellulose powder are not required, but may be used, since the necessary colored stains can be prevented. The coating liquid thus obtained is applied onto the support using an air knife, blade, roll, rubber doctor, etc.
The coating method is applied using a coating method such as a curtain, and the coating liquid layer is applied without solidifying, or after solidifying, it is compressed onto a mirror-finished drum surface. By setting the measurement time to 50 seconds or more, it was possible to provide a self-coloring pressure-sensitive recording paper having a cast surface in which unnecessary colored stains are much less likely to occur. (E) Effects of the Invention The self-coloring pressure-sensitive recording paper having a cast surface of the present invention has high smoothness, has a coating layer with very little unevenness, and microcapsules are protected within the coating layer. Therefore, it exhibits tremendous resistance to friction on the surface of the coating layer, and can prevent colored stains due to unnecessary friction. (f) Examples The present invention will be explained below with reference to Examples, but it is not limited to these Examples. All "parts" in the examples refer to "parts by weight." Example 1 Microcapsules containing a coloring agent were prepared as follows. KMC Crystal Violet Lactone 10 parts
-113 (Aromatic high boiling point oil manufactured by Kureha Chemical Co., Ltd.) 190
The internal phase oil was emulsified in 220 parts of a 5% hydroxyl solution of a styrene-maleic anhydride copolymer with a pH of 5.0. Then 20 parts of melamine, 30 parts of 37% formalin aqueous solution
1 part and 100 parts of water were adjusted to pH 8 with caustic soda, heated to 60°C, and stirred to prepare a melamine-formalin initial condensate. Add this initial condensate to the above emulsion and heat at 70°C.
The mixture was heated and stirred for 2 hours to complete encapsulation. The average particle diameter of this microcapsule was 3.5μ. Microcapsules containing a color developer were prepared as follows. POP resin (PR-26298 manufactured by Sumitomo Duretsu Co., Ltd.)
Microcapsules containing a color developer were obtained in the same manner as the microcapsules containing a color former, except that 100 parts were heated and dissolved in 100 parts of Hysol SAS N-296 (manufactured by Nippon Petrochemicals) to obtain an internal phase oil. Ta. The average particle size of this microcapsule was 2.1μ. A self-coloring pressure-sensitive recording coating liquid for casting was prepared as follows. 0.34 parts of caustic soda, 4 parts of dicyandiamide, and 76 parts of water were added to 20 parts of casein, and the mixture was stirred and dissolved at 70°C. Separately, add 80 parts of an aqueous solution containing 0.3 parts of sodium pyrophosphate to 100 parts of coating clay and stir thoroughly, then add 10 parts of an aqueous solution containing 2.2 parts of bayum chloride (anhydrous) and stir well to mix.
The casein solution described above is added to this solution and mixed by stirring. Finally, 70 parts each of a color former and a color developer-containing microcapsule dispersion were added to complete the liquid preparation. Apply this coating liquid to 60g/m ² of high-quality paper with a solid content of 12g/m2.
Smear it with an air knife so that it is m ² , and this coating layer
When heated to over 50℃, the coating layer solidifies rapidly. This was pressed against the surface of a heat-finished drum having a mirror surface and then peeled off to obtain a self-coloring pressure-sensitive recording paper with high smoothness and mirror gloss. Example 2 [100 parts of casein, 15 parts of ammonium nitrate, and 460 parts of water were dissolved by heating at a temperature of 90°C for 30 minutes, and then cooled to room temperature. ] Completely dissolve 0.5 parts of sodium pyrophosphate, a dispersant, in 117.5 parts of added water, add 100 parts of kaolin, stir and disperse, then add 76.5 parts of the above 20% dissolved acidic casein and 20% styrene-butadiene latex. After stirring, add 60 parts each of the color former and color developer-containing microcapsule dispersion prepared in Example 1 to 80 g/m ² of high-quality paper so that the solid content is 15 g/m ² . Smeared with an air knife. This smeared layer, in a wet state, was pressed against a heated (100° C.) finishing drum having a mirror surface to obtain a self-coloring pressure-sensitive recording paper having a cast surface. Comparative Example 1 A self-coloring pressure-sensitive recording paper without a mirror surface was obtained by applying the coating liquid used in Example 1 in the same manner as in Example 1, except that only the casting process was omitted. Comparative Example 2 A self-coloring pressure-sensitive recording paper without a mirror surface was obtained by coating in the same manner as in Example 2, except that only the casting process was omitted. Test results

[Table] The color density is the value when the color is developed by passing it between iron rolls with a linear pressure of 21 kg/cm. Unnecessary colored stains represent colored stains that occur when the surface of the coating layer is rubbed, and in both cases, the larger the value, the lower the density. Calculations were done using Nippon Denshoku KK's color difference meter ND-
It was calculated using the following formula using 101D. Density = Reflectance of colored area/Reflectance of blank area x 100 For smoothness, use the Beck smoothness tester specified in JIS P8119, and the higher the value, the greater the smoothness. (G) Effects of the Invention The self-coloring pressure-sensitive recording paper having a cast-coated surface according to the present invention is much less likely to generate unnecessary colored stains, which is the fate of self-coloring pressure-sensitive recording papers. In addition, almost no colored stains occurred due to normal handling, and the paper showed high performance that it could be handled on the same level as common plain paper.

Claims (1)

[Scope of Claims] 1. A self-coloring pressure-sensitive recording paper coated with a coating layer containing a color former and a color developer in which one or both of the color former and the color developer are microencapsulated, A self-coloring pressure-sensitive recording paper having a cast coated surface, which is made to have a mirror gloss by pressing the coated layer against a heated finishing drum when the coated layer is applied to a support in a wet state. 2. A self-coloring property having a cast coating surface according to claim 1, in which the color former and color developer-containing microcapsule wall film is made of a polyurethane resin, a polyurea resin, an epoxy resin, a urea-formalin resin, or a melamine-formalin resin. Pressure recording paper. 3. A self-coloring pressure-sensitive recording paper having a cast-coated surface according to claim 1, wherein the cast-coated surface has a smoothness of 50 seconds or more as measured by a JISP8119 standard Beck smoothness tester. 4. A self-coloring pressure-sensitive recording paper having a cast coating surface according to claim 1, wherein the coating layer provided on the support contains at least a protein or latex adhesive. 5. A self-coloring pressure-sensitive recording paper having a cast coating surface according to claim 1 or 4, wherein the coating layer provided on the support does not contain at least starch particles or cellulose powder.