JPH0259780B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) This invention relates to a method for manufacturing pressure-sensitive copying paper. More specifically, the present invention relates to a method for producing pressure-sensitive copying paper that improves the effective utilization rate of color developer. (Prior Art) Generally, pressure-sensitive copying paper consists of a top paper (hereinafter referred to as "top paper") coated with microcapsules of a non-volatile hydrophobic solvent in which a dye precursor such as a phthalide compound or a fluoran compound is dissolved. Solid acids such as acid clay, phenol formaldehyde resin, and polyvalent metal salts of salicylic acid derivatives (hereinafter referred to as "color developers")
After coating and drying a water-based paint composition containing a water-based paint composition (hereinafter referred to as "color developing sheet"), the coated surfaces of each bottom paper (hereinafter referred to as "color developing sheet") are facing each other, and by writing or by applying pressure with a typewriter, printer, etc. The capsules are destroyed, and the dye precursors in the hydrophobic solvent that flow out from the destroyed microcapsules come into contact with the solid acid of the color developer sheet to obtain a colored image through a chemical reaction. Conventionally, acid-treated white earth (activated white earth) is used as a color developer for the color developer sheet of pressure-sensitive copying paper.
Semi-natural inorganic solid acids such as
In addition, the rheological properties of the paint make it unsuitable for high-speed coating, making it difficult to produce. (2) The resulting color-developing sheet easily loses its color-forming ability due to water or gas. (3) The color-forming image is It is extremely sensitive to light, and has drawbacks such as a decrease in color density over time and significant changes in the various phases of color development. On the other hand, synthetic organic solid acids that have been widely used in recent years (1)' The amount of color developer used per unit area is about 1/2 to 1/20 smaller than that of the above-mentioned inorganic solid acids. Water-based paints with various rheological properties can be easily created, allowing efficient production using various coating methods such as air knife coaters, blade coaters, roll coaters, bar coaters, and gravure coaters. It is possible. (2)' The color developing sheet obtained has little change in coloring performance due to water, gas, etc. (3)' The color image obtained is stable and does not tend to decrease in density over time or fade over time under normal storage conditions. Because of these excellent characteristics, it has become the mainstream color developer for pressure-sensitive copying paper, and is playing a major role in the widespread development and reliability of pressure-sensitive recording paper. When manufacturing a color developer sheet using this organic solid acid as a color developer, generally the color developer is used as a dispersant,
An aqueous suspension wet-pulverized in the presence of a surfactant, etc., is mixed with pigments such as kaolin, calcium carbonate, zinc oxide, aluminum hydroxide, etc., and then a dispersant, water-soluble adhesive (starch-based binder,
A water-based paint is prepared by mixing with a water-soluble binder such as PVA), synthetic resin adhesive (synthetic rubber latex emulsion, acrylic polymer emulsion, vinyl acetate polymer emulsion), etc. This water-based paint is usually applied at 3 to 10 g/m ² on a support such as paper using an air knife coater, blade coater, roll coater, bar coater, etc., and then dried with hot air. In addition, the color developer in the above water-based paint is generally 5
It is often ~30% by weight (dry solids percentage). In addition, in order to maintain the stability of the solid content of the paint during continuous processing, starch-based adhesives or adhesives with good water retention are used.
It is common to use a PVA binder and a styrene-butadiene rubber latex emulsion (SBR), which has excellent adhesive strength, in combination. (Problem to be solved by the invention) However, when the water-based paint prepared as described above is coated on a support such as base paper and dried, adhesives may evaporate when the water evaporates, especially during hot air drying. A phenomenon in which the developer is distributed in high concentration at both ends of the paint layer (at the interface between the surface and the support) (generally referred to as binder migration phenomenon) occurs, and the developer concentration on the coated surface tends to decrease. is large. On the other hand, when the upper paper and the color developer sheet are opposed to each other for color development by pressing, the transfer rate of the dye precursor solution inside the microcapsules to the color developer sheet is generally 40 to 60%, or ^about 1.5 to 3 g/m2. This is a very small amount. and,
The color reaction between the dye precursor and the color developer substantially takes place in the surface layer of the paint layer of the color developer sheet.
Therefore, as described above, if the surface color developer concentration of the paint layer decreases significantly, the color density will decrease. As mentioned above, organic solid acid color developers can be used in a smaller amount per unit area of paper than inorganic solid acids, but on the other hand, because they are synthetic products, they are significantly more expensive than inorganic solid acids. Therefore, in order to increase the surface color developer concentration of the paint layer using the method described above, it is necessary to use a considerably large amount of color developer, which increases the price of the pressure-sensitive paper accordingly. However, as pressure-sensitive copying paper has become more widespread, it is no longer treated the same as regular paper, and it is no longer acceptable for pressure-sensitive copying paper to be relatively expensive. In view of the above-mentioned circumstances, it is an object of the present invention to significantly reduce the manufacturing cost of pressure-sensitive copying paper using an organic solid acid color developer. (Means for Solving the Problems) In order to solve the above problems, in the present invention, an undercoat layer containing an inorganic pigment as a main component is provided on a support, and an undercoat layer containing an organic solid acid as a main component is further provided on the support. A color developer sheet for pressure-sensitive copying paper is manufactured by forming a color developer layer. The undercoat layer generally contains inorganic pigments such as calcium carbonate (heavy or light), kaolin, aluminum hydroxide, titanium oxide, zinc oxide, and starch-based, synthetic rubber latex-based, etc.
It is formed by applying a water-based paint mixed with various binders such as PVA and synthetic resin emulsion to the surface of base paper. These undercoat layers are generally preferably manufactured using an on-machine coating method in which they are coated and dried using a bill blade coater, fountain blade coater, gate roll coater, gravure coater, bar coater, etc. in the latter stage of the papermaking process. However, of course, off-machine coated undercoated paper can also be used. The undercoat layer generally has a thickness of about 3 to 10 g/m ² and is composed of a coating layer containing 5 to 30 parts by weight of binder per 100 parts by weight of inorganic pigment. On the other hand, as the organic solid acids used in the color developer layer, for example, one or more of the following organic solid acids can be used. (A) Special phenol formaldehyde resins, such as P-phenylphenol/formaldehyde resin, P-phenylphenol/P-alkylphenol/formaldehyde cocondensation resins, etc. (B) Polyvalent metal salts of phenol formaldehyde condensates, such as P - Zinc salt of tetraoctylphenol formaldehyde condensate, zinc salt of P-cumylphenol/phenol formaldehyde cocondensate (C) Polyvalent metal salt of aromatic carboxylic acid, e.g. 3,
Zinc salt, calcium salt of 5-di-(α-methylbenzyl)salicylic acid, zinc salt of 3-α,α-dimethylbenzyl-5-phenylsalicylic acid (D) Polyvalent metal of 2,2′-biphenolsulfone Oil-soluble organic solid acids such as complexes The color developer layer contains a dispersion of these organic solid acids and an adhesive such as starch, polyvinyl alcohol, and/or synthetic rubber latex as essential components, and further contains appropriate additives as necessary. It is formed by mixing inorganic or organic pigments to prepare a water-based paint, and applying this water-based paint to the above-mentioned undercoat layer. In addition, water-based paint has a color developer concentration (solid content ratio) of 30 to 90%, and the surface of the undercoat layer is coated with an air knife coater, bar coater, gravure coater, blade coater, etc. to control the dry coating amount. It is preferable to apply the coating so that the amount is 0.2 to 3.0 g/m ² . (Effects of the Invention) The thus obtained pressure-sensitive copying paper of the present invention has a significantly higher concentration of organic solid acid type color developer on the surface of the coated paper than conventional color developer sheets, and has less color developer. Sufficient pressure coloring density can be obtained with the appropriate amount of agent, and other physical properties as a pressure-sensitive paper are not impaired in any way. Therefore, according to the present invention, the absolute amount of color developer used can be reduced, thereby making it possible to significantly reduce the manufacturing cost of pressure-sensitive copying paper. (Example) Example 1 In the paper making process of neutral paper base paper having a dry weight of 40 g/ ^m2 , 70 parts of heavy calcium carbonate, 30 parts of light calcium carbonate, 4 parts of SBR latex, and 3 parts of oxidized starch (as an aqueous solution) A water-based paint having a solid content of 60 wt % and having a weight composition of (1) was coated on-machine using a bill blade coater so that the dry coating amount was 6 g/m ² to obtain pigment precoated paper. Next, a weight composition of 40% P-phenylphenol resin dispersion (RBE-40 manufactured by Mitsui Toatsu Chemical Co., Ltd.), 100 parts of dry solids, 10 parts of light calcium carbonate, and 20 parts of oxidized starch binder was applied to this coated surface. Using an air knife coater, coat the paint (solid content 15wt%) with 0.4
g/m ² and dried to obtain a color developer sheet (A) of pressure-sensitive copying paper. Example 2 100g of P-α,α-dimethylbenzylphenol-phenol formaldehyde co-condensate was
Into a reactor maintained at ℃, a mixture of 20 g of zinc benzoate and 15 g of ammonium bicarbonate was gradually added to add the zinc salt of P-α,α-dimethylbenzylphenol/phenol formaldehyde cocondensate. Using an aqueous suspension with a 40% solids content obtained by wet pulverization in the presence of a polymer anionic surfactant, P-α,α-dimethylbenzylphenol, phenol, and formaldehyde were prepared in a dry solids ratio. A 25% solids water-based paint with a weight composition of 100 parts of zinc salt of the co-condensate, 20 parts of zinc oxide, 7 parts of SBR latex, and 5 parts of polyvinyl alcohol was prepared, and this water-based paint was applied using an air knife coater. Example 1
Pigment is coated on the coated surface of pre-coated paper at a concentration of 0.5 g/m ² and dried to form a developer sheet of pressure-sensitive copying paper (B).
I got it. Comparative example 1 70 parts of heavy calcium carbonate, light calcium carbonate
Solid content with a weight composition of 30 parts, P-phenylphenol resin (RBG-40 manufactured by Mitsui Toatsu Chemical Co., Ltd.) 25 parts, SBR latex 8 parts, and oxidized starch binder 6 parts.
Prepare a 30% water-based paint, apply it to neutral paper base paper with a basis weight of 40 g/m ² using an air knife heater to a dry coating amount of 6 g/m ² , and dry it to form a pressure-sensitive copying paper developer sheet ( C) was obtained. Comparative example 2 40 parts of heavy calcium carbonate, light calcium carbonate
40 parts, zinc oxide 20 parts, same P-α, α as Example 2
- A 30% solids water-based paint with a weight composition of 25 parts of zinc salt of dimethylbenzylphenol-phenol-formaldehyde cocondensate, 8 parts of SBR latex, and 6 parts of polyvinyl alcohol was coated with an air knife coater in a dry coating amount of 7 g/ A pressure-sensitive copying paper developing sheet (D) was obtained by applying and drying the film to a thickness of m ² . The pressure-sensitive copying paper developing sheets of each example and comparative example were used as commercially available top paper for blue coloring (manufactured by Jujo Paper Co., Ltd.).
NW-40T), and apply pressure color using an electric typewriter (HERMES-808).Reflectance for 1 minute and 24 hours after color development (Hunter colorimeter)
was measured.

【table】

[Table] As is clear from the above results, the pressure-sensitive copying paper developer sheet obtained by the method of the present invention uses less expensive developer than the known pressure-sensitive copying paper developer sheet of the comparative example. It was possible to achieve a significant reduction in cost, and the coloring ability was also superior to that of the comparative example.

Claims (1)

[Scope of Claims] 1. A photosensitive material characterized in that an undercoat layer containing an inorganic pigment as a main component is formed on a support, and a color developer layer containing an organic solid acid as a main component is formed thereon. A method for producing a pressure copying paper developer sheet. 2 At the latter stage of the papermaking process, an undercoat layer is formed on the base paper using an on-machine coating method,
A patent claim in which an organic solid acid color developer layer selected from one or more of phenol formaldehyde resin, polyvalent metal salt of phenol formaldehyde resin, and polyvalent metal salt of aromatic carboxylic acid is formed thereon. The method described in Scope 1.