JPS6363396B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a desensitizing ink for pressure-sensitive copying paper that has excellent desensitizing effects and improved yellowing. In general, pressure-sensitive copying paper is made of paper coated with fine capsules containing an electron-donating colorless or light-colored leuco dye dissolved in an organic solvent (capsule oil) on the back side, and an electron-accepting color developer on the front side. It consists of a combination of coated base paper, and by stacking these two coated surfaces facing each other and applying pressure with a ballpoint pen or typewriter, the capsule in the pressurized part is destroyed and contains the leuco dye. Capsule oil is transferred to the color developing layer and undergoes a coloring reaction, thereby making it possible to obtain printed records. In addition, if inner sheets coated with a color developer on the front side and capsules containing leuco dye on the back side are used by sandwiching them between the upper and lower sheets, a large number of copies can be obtained. When this pressure-sensitive copying paper is used for forms such as business forms, there are some areas where copying is not necessary due to the layout. In order to eliminate the coloring ability of these unnecessary portions of copying, desensitizing ink is usually printed all over the surface of the inner paper or lower paper, that is, the surface coated with a color developer. With the spread of pressure-sensitive copying paper, the proportion of desensitized inks used has increased significantly, and various inks suitable for printing methods are now commercially available. Currently, the main types commonly used are oil-based desensitizing inks for letterpress printing and solvent-based desensitizing inks for flexographic printing, and special types include ultraviolet-curable desensitizing inks. Conventionally known desensitizers include, for example,
Cationic quaternary ammonium salts (e.g., dodecyltrimethylammonium chloride) described in Japanese Patent Publication No. 3921, tertiary amines having two polyethylene oxide groups (e.g., N, N- (di-polyoxyethylene ethylamine), polyoxyethylene monoalkyl esters (e.g., polyoxyethylene oleyl ester) described in Japanese Patent Publication No. 47-38201, polyethylene glycol alkyl phenyl ethers (e.g., described in Japanese Patent Publication No. 49-8288) , polyethylene glycol nonyl phenyl ether), etc., and are usually printed as desensitizing inks using letterpress (for example, rubber letterpress), flexo or gravure printing machines. However, conventional desensitized inks have drawbacks such as insufficient pressure reduction effect and yellowing of the printed surface when exposed to light, and cannot necessarily be said to be inks of satisfactory quality. On the other hand, desensitized printing is usually performed in combination with lined character printing, but since lined characters are often printed using the wet offset method, desensitized printing using a wet offset two-color printing machine is recommended. An increasing number of customers are requesting ink that can be used. In wet offset printing, dampening water is first supplied to the hydrophilic non-image areas of the plate, and then an inking roller supplies the oleophilic (water-repellent) image lines on the plate without dampening water. Ink is supplied to the printer, and the ink is transferred to paper via a blanket for printing. Therefore, in such a printing method, highly lipophilic ink is required. When hydrophilic ink is used, the supply of ink to the printed area becomes poor, resulting in uneven printing, or the ink gets mixed into the dampening water due to water loss, causing problems with the dampening water system and There is a drawback that unnecessary printing areas are contaminated. An object of the present invention is to provide a desensitizing ink that has excellent desensitizing effects and improved yellowing.Another object of the present invention is to provide a desensitizing ink that has excellent printability in wet offset printing methods. be. As a result of various studies, the present inventors have found that the above object can be completely achieved by using a glycerin-propylene oxide adduct as a desensitizing agent. The desensitizer used in the present invention is a triol (having three hydroxyl groups) compound represented by the following general formula, which is obtained by adding propylene oxide to glycerin. (In the formula, a, b, and c are each an integer of 1 or more, and the total of a+b+c is 119 or less.) This compound is a propylene glycol (diol) and dipropylene glycol described in Japanese Patent Publication No. 45-21448. (diol), ethylenediamine-propylene oxide adduct compound (tetraol) represented by the following general formula described in Japanese Patent Publication No. 50-29365 Also, as described in Special Publication No. 1919-1919

It has a different structure from polypropylene glycol (diol) represented by the formula and is clearly distinguishable. It was found that the desensitizing effect of the glycerin-propylene oxide addition compound according to the present invention is remarkable, and the desensitizing effect is particularly large when the average molecular weight is 7,000 or less. On the other hand, the water solubility and viscosity of glycerin-propylene oxide adducts vary considerably depending on the molecular weight, and the lower the average molecular weight, the higher the water solubility. For example, average molecular weight
Compounds with an average molecular weight of up to 600 are completely soluble in water, but the water solubility is 30 for an average molecular weight of 1000 and less than 0.1 for an average molecular weight of 3000 or more. Further, when the average molecular weight is 7000 or more, the viscosity is high, so there is a drawback that the viscosity as a desensitizing ink becomes too high. Therefore, the glycerin-propylene oxide adduct compound according to the present invention can of course be used as a desensitizing ink for printing with conventional printing presses such as letterpress, flexography, and gravure printing machines. The previous products have extremely excellent printing suitability in wet offset printing methods, and enable continuous printing for long periods of time. The desensitizing ink of the present invention is produced by using the above-mentioned glycerin-propylene oxide adduct compound, pigment, and adhesive as basic components, and adding a set-off inhibitor, wax compound, antioxidant, etc. as necessary. As the pigment, inorganic pigments such as titanium oxide, zinc oxide, barium sulfate, magnesium carbonate, calcium carbonate, barium carbonate, magnesium hydroxide, and talc can be used. As the adhesive, a polymer compound such as a ketone resin, a polyamide resin, a maleic acid resin, a phenol resin, an alkyd resin, a melamine resin, or a urea resin is used. Various methods can be used to produce desensitizing ink, but in general, a varnish is made by heating and dissolving an adhesive in a desensitizing agent, then pigment is added to this, and the varnish is uniformly kneaded using a three-roll mill. Manufactured by In this case, the composition is 20 to 60 parts by weight of desensitizer, 10 to 40 parts by weight of pigment,
A suitable amount of adhesive is 10 to 40 parts by weight. Examples will be described below, but the present invention is not limited thereto. Example 1 Prescription Glycerin-propylene oxide adduct compound (average molecular weight 1000) 50 parts by weight Maleic acid resin 20 Titanium oxide 20 Calcium carbonate 10 A desensitizing ink with the above formulation was prepared as follows. First, 20 parts by weight of maleic acid resin is added to 50 parts by weight of a glycerin-propylene oxide adduct with an average molecular weight of 1000, and the mixture is heated and dissolved at 150°C for 30 minutes to make a varnish. Next, 20 parts by weight of titanium oxide and 10 parts by weight of calcium carbonate are added. was added and thoroughly stirred with a mixer, and then kneaded uniformly with a three-roll mill to obtain a desensitizing ink. Example 2 A desensitizing ink having the following formulation was prepared in the same manner as in Example 1. Glycerin-propylene oxide adduct compound (average molecular weight 3000) 55 parts by weight Rosin-modified maleic acid resin 20 Titanium oxide 25 Example 3 A desensitizing ink having the following formulation was prepared in the same manner as in Example 1. Glycerin-propylene oxide adduct compound (average molecular weight 4000) 45 parts by weight Rosin-modified phenolic resin 25 〃 Titanium oxide 25 〃 Magnesium carbonate 5 〃 Example 4 Instead of the glycerin-propylene oxide adduct compound (average molecular weight 1000) of Example 1, A desensitizing ink was prepared using the same parts by weight of a glycerin-propylene oxide adduct compound (average molecular weight 300). Example 5 A desensitizing ink was prepared by using the same weight of a glycerin-propylene oxide adduct compound (average molecular weight 600) in place of the glycerin-propylene oxide adduct compound (average molecular weight 3000) in Example 2. Comparative Example 1 A desensitizing ink having the following formulation was prepared in the same manner as in Example 1. Propylene glycol 60 parts by weight Rosin-modified maleic acid resin 20 〃 Titanium oxide 15 〃 Calcium carbonate 5 〃 Comparative example 2 In place of the propylene glycol in Comparative example 1, the same weight of polyethylene glycol nonyl phenyl ether (number of moles of ethylene oxide added is 1) A desensitized ink was prepared using Comparative Example 3 A desensitizing ink was prepared by using the same weight part of polyethylene glycol nonyl phenyl ether (number of moles of ethylene oxide added: 12 moles) in place of the glycerin-propylene oxide addition compound (average molecular weight 4000) of Example 3. . Comparative Example 4 A desensitizing ink was prepared by using the same weight part of dodecylmethylammonium chloride in place of propylene glycol in Comparative Example 1. The desensitizing inks obtained in Examples 1 to 5 and Comparative Examples 1 to 4 above were applied to the developer-coated surface of Jujo Paper Co., Ltd. paper (NW40BR), which is a commercially available pressure-sensitive copying paper, using a wet offset printing machine ( Printing was carried out using a letterpress printing machine (manufactured by Miyakoshi) and a letterpress printing machine (manufactured by Miyakoshi) at a coating amount of 2 to 3 g/m ² , and tests for desensitization effect, yellowing, and printability were conducted by the following methods. (1) Desensitization effect: Print with a typewriter by overlapping the desensitization printing section and Jujo paper (KW40T),
The state of color development was evaluated. (2) Yellowing: Using a fading tester (manufactured by Toyo Seiki), the degree of yellowing of the desensitized printed surface was evaluated when treated with a carbon arc lamp for 10 hours. (3) Printing suitability: The suitability for wet offset printing was examined by evaluating the stains on the dampening water device of the printing machine during wet offset printing and the stains on the non-printed areas of the printed base paper. The test results are shown in Table 1.

[Table] (Note) An ○ mark indicates a state in which the product can be put to practical use commercially, a △ mark indicates a state in which it can be used but is difficult to put into practical use commercially, and a × mark indicates a state in which it is not commercially usable.
From Table 1, the superior transparency of the desensitizing ink according to the invention is clear. That is, the desensitizing inks of Comparative Examples 1 to 4 cannot satisfy both the desensitizing effect and yellowing performance at the same time, but the desensitizing inks of Examples 1 to 5 according to the present invention all have sufficient desensitizing effect. It is effective and also shows excellent results against yellowing. Furthermore, it is clear that Examples 1 to 3, in which a glycerin-propylene oxide adduct compound having an average molecular weight of 1000 or more is used as a desensitizer, have excellent properties as a desensitizing ink for wet offset printing.

Claims (1)

[Scope of Claims] 1. In a desensitizing ink for pressure-sensitive copying paper containing a desensitizer, pigment, and adhesive as basic components, a glycerin-propylene oxide adduct compound represented by the following general formula is used as the desensitizer. A desensitizing ink for pressure-sensitive copying paper. (In the formula, a, b, and c are each integers of 1 or more, and the sum of a+b+c is 119 or less.) 2. The average molecular weight of the desensitizer is 1000 (a+b+c=15)
7000 (a+b+c=119). The desensitizing ink for pressure-sensitive copying paper according to claim 1, which is used in a wet offset printing method.