JPH0559312A - Fading ink composition - Google Patents

Abstract

PURPOSE:To provide a fading ink composition easily applicable even to a printed matter such as map, fading its color in a parabolic manner after the lapse of a prescribed time and capable of keeping the density over a practically long period. CONSTITUTION:The objective fading ink composition is produced by developing the color of a phthalein-based indicator with a mixed solution of a weakly alkaline salt and a guanidine salt, adding a surfactant to the product and, as necessary, further adding a humectant to the mixture.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a decolorizable ink composition suitable for marking a printed matter such as a road map for an automobile, which is popped by ink and difficult to ride, and the like.

[0002]

2. Description of the Related Art A dye or indicator is colored with an aqueous alkali solution such as sodium carbonate, and an organic amine such as triethanolamine and a humectant such as glycol are added to the ink for marking. The invention of a fluorescent yellow ink that develops hydroxypyrenetrisulfonic acid in the alkaline region of Kaisho 49-127730 is well known. In addition, Japanese Examined Patent Publication No. 55-18758 is also similar in that it uses an alkaline aqueous solution and an organic amine in combination to develop an indicator, but in both cases, water, alkali, amine, moisturizer, etc. are volatilized and lost over time. As a result, the color fades and eventually disappears.

However, the time required for its disappearance depends on the chromophoric compound and can be maintained for a considerably long time by increasing the concentration of the constituents other than water of the composition to a certain degree or more. It is practically used as a fluorescent yellow ink because it can be extended annually if it is not exposed to sunlight, and in the latter case, it can be shortened to a relatively short time of several hours or days. Therefore, it is practically used as a decolorizable ink.

In any of these cases, a combination of a compound corresponding to a pigment that develops color when pH changes, a basic substance, an organic amine, a humectant (generally glycols) and water is used to form each element of the composition. When it volatilizes and loses its influence, the same phenomenon that the color state cannot be maintained and the color disappears eventually occurs.

In the case of the latter phthalein-based indicator, the color change
It has a narrow pH range, is sensitive, and has the property of easily decoloring,
It is used as a marking pen for erasing, but it could not be used for marking road guides on automobile road maps. Because it is necessary to keep the state immediately after marking for a certain period of time in order to use it for such purposes, and there are acidic paper and neutral paper in the map paper, and the properties of the printing ink vary. This is because the erase time often depends on the effect.

Many of the roadmaps for automobiles are offset-printed with oil-based ink, and when marked with conventional decolorizable ink, the ink pops off and is hard to ride, and the straight lines become dotted lines, Due to the paper quality and the pH of the printing ink, there was a defect that the color disappeared and disappeared immediately after marking, making it unusable. If you want to use the decolorizable ink by marking it on the road map for automobiles or the map used for orienteering,
Be kept legible for at least a day or two,
Moreover, it is ideal that it disappears rapidly and not after use. That is, it is desirable that the decoloring does not proceed linearly but disappears in a parabolic shape after a certain period of time.

[0007]

However, according to the latter decolorizable ink, in the case of a printed matter such as a road map for automobiles and the like, not only the ink is hard to ride, but also the color disappears linearly. Rather, there was a problem that it proceeded rapidly in a reverse parabola, and the practical retention time of the concentration was too short.

Therefore, the present invention solves the above-mentioned problems of the prior art, prints such as maps have good ink coverage, and the color disappears in a form of drawing a parabola after a certain period of time. An object of the present invention is to provide a decolorizable ink composition that can keep the holding time practically.

[0009]

Means for Solving the Problems The inventors have developed a phthalein-based indicator with a mixed solution of a weakly alkaline salt and a guanidine salt, and by adding a surfactant to the mixture, ink can be applied to printed matter such as maps. It was confirmed by an experiment that a good decolorizable ink was obtained. Examples of the phthalein-based indicator include orthocresolphthalein, phenolphthalein, thymolphthalein and the like.
The weakly alkaline salts include sodium carbonate, calcium carbonate, trisodium phosphate, potassium phosphate,
Although there are sodium acetate and the like, sodium carbonate gave the best results. Further, the guanidine salt is basic, that is, guanidine carbonate, guanidine phosphate,
Guanidine sulfamate was effective, but guanidine carbonate was the most successful.

Guanidine carbonate is

[Chemical 1] It is a white crystalline powder with the structural formula
/ 100g Water (20 ℃) 42 It is a compound that is easily dissolved in water and has a pH of 4% aqueous solution (25 ℃) of 11.4 ± 0.4. It has been conventionally used as a pH adjuster.

In the ink composition of the present invention, the phthalein indicator is 0.1 to 2.0% by weight, sodium carbonate (anhydrous).
Is applied at 1.0-15.0%, and guanidine carbonate at 0.1-3.0% by weight. It is possible to adjust the concentration and sharpness of ink and the time required for decoloring by adjusting the addition amount respectively, but moisturizing The color development time can be adjusted to some extent depending on the amount of the agent added.

The amount of the moisturizing agent added is about 5 to 40%, and the amount is appropriately adjusted before use. As a moisturizer, glycols are often used like general felt-tip pen ink, ethylene glycol,
Diethylene glycol, propylene glycol, glycerin and the like are suitable, but ethylene glycol is the best in the combined use method of sodium carbonate and guanidine carbonate,
Compared with glycerin, diethylene glycol, etc., excellent effects were obtained in terms of concentration and clarity. Other than glycols, urea was also effective.

Since the ink composition of the present invention maintains the coloration state only by being appropriately maintained in the alkaline region, it loses its components by drying or is diluted with water to produce a pH. Below a certain level, it loses color and becomes colorless. Therefore, the ink composition must always be kept in an alkaline state to the extent that the color reaction of the phthalein indicator is maintained. That is, since the pH of the ink has to be set to about 10.5 to 11.5, it is necessary to select and use a surfactant that does not lose its effect even if it is alkaline to this extent and does not cause any adverse effects.

The ink composition of the present invention has a high surface tension without the addition of a surfactant, and the ink does not easily ride on a printed matter such as a map. However, since the pH of the ink composition is fairly alkaline such as about 10.5 to 11.5 as described above, it is easy to lose the effect of the activator and adversely affect the dissolution of the indicator. Therefore, there was a difficult problem in the selection. For example, there is Scoreroll 900 (polyoxyethylene nonylphenol ether) as a nonionic surfactant most commonly used in water-soluble inks for felt-tip pens, but an ink composition containing 0.5% of this is It became cloudy and unusable.

As a result of research on these problems, the following surfactants were found to be particularly effective. That is, funnel oil (fatty acid sulfate ester salt), monopol oil (sulfated oil neutral salt), necal A (alkylnaphthalene sulfonate), Plysurf A215C (phosphate ester of polyoxyethylene alkyl ether)
Was good without losing the effect even on the alkaline side of the above degree.

[0016]

According to the first aspect of the present invention, as described above, the phthalein-based indicator is colored with a mixed solution of a weakly alkaline salt and a guanidine salt, and a surfactant is added to the mixed solution. Ink is very good.
Further, the color disappears in a shape of drawing a parabola after a lapse of a certain time, so that the retention time of the density can be practically maintained in a printed matter such as a map. Since the invention of claim 2 further contains a moisturizing agent, there is an excellent effect that the coloring time can be adjusted also by the addition amount of the moisturizing agent.

[0017]

EXAMPLES Examples of the present invention will be shown below, but the present invention is not limited thereto. Example 1 9.0 g of sodium carbonate (anhydrous) was dissolved in 64.9 g of water, 0.3 g of guanidine carbonate was added and dissolved, 25.0 g of ethylene glycol was added, and 0.1 g of Plysurf A215C was added, followed by ortho 0.7 g of cresolphthalein was added and stirred to make 100 g of a mixed solution. The color of this solution was vivid and exhibited a reddish purple color. When I marked this on a map printed as marking ink, the ink came on well without being interrupted, and the handwriting remained at a practical concentration for about 10 hours to 1 day, then gradually became lighter, and it differed slightly depending on the paper quality. , Disappeared in about 10 days to 2 weeks. Example 2 8.0 g of sodium carbonate (anhydrous) was dissolved in 65.2 g of water, 0.5 g of guanidine carbonate was added and dissolved therein, 28.0 g of ethylene glycol was added, and then 0.1 g of monopol oil was added, followed by phenol. 0.9 g of phthalein was added and stirred to prepare a mixed solution of 100 g. The color of this solution was a bright pink color. When I marked this on a map printed as marking ink, the ink came on well without being interrupted, and the handwriting remained at a practical concentration for about 10 hours to 1 day, then gradually became lighter, and it differed slightly depending on the paper quality. ,about
It disappeared in 10 days to 2 weeks.

Claims (2)

[Claims] 1. A color-erasable ink composition comprising a phthalein-based indicator which is colored with a mixed solution of a weakly alkaline salt and a guanidine salt, and a surfactant is added thereto. 2. The decolorizable ink composition according to claim 1, which contains a humectant.