JPH0643569B2 - Water-based ink for writing instruments - Google Patents

Description

TECHNICAL FIELD The present invention relates to a water-based ink for a writing instrument used particularly in a felt-tip pen or a ballpoint pen for a plotter.

(Prior Art) A writing instrument used in a plotter does not suffer from deterioration such as blurring of a drawn line even if the user leaves it for a few days to a month without a cap, and of course, it cannot be written, Be able to write in the same state as before leaving,
In other words, it is required that good rewriting performance be obtained, and that the phenomenon that the dyes and additives in the ink solidify or crystallize and deposit at the tip of the pen tip (hereinafter referred to as "Hanasaki phenomenon") does not occur. To be done. For this reason, conventionally, a large amount of a water-soluble organic solvent such as ethylene glycol or propylene glycol (hereinafter referred to as "non-drying solvent") has been added to the ink composition. Further, conventionally, a surfactant such as a fluorine-based or fatty acid-based surfactant has been added to improve the drawing quality.

(Problems to be Solved by the Invention) However, in the ink containing a large amount of the above non-drying solvent, the viscosity of the ink becomes high, the fluidity is impaired, it becomes difficult to follow high-speed writing, and the drawn line is blurred. However, there is a problem that the flower bloom phenomenon cannot be suppressed even if a large amount is added if the type of non-drying solvent is selected incorrectly. In addition, when the above-mentioned surfactant is added, there is a problem that the surface tension of the ink is lowered, the drawn line is easily blurred, and the flower bloom phenomenon occurs.

Therefore, the present invention solves the above problems by suppressing the addition amount of the non-drying solvent used to a small extent, and can also make good the rewriting property of the writing instrument after leaving without a cap for a long time and prevent the flower bloom phenomenon. It is an object of the present invention to provide a water-based ink for a writing instrument, which is capable of further improving the drawing quality.

(Means for Solving the Problems) In order to achieve the above object, the aqueous ink for a writing instrument according to the present invention contains a water-soluble dye and 3-1 in the ink composition.
It contains 0% by weight of glycerin, 5 to 30% by weight of diethylene glycol, and 0.1 to 0.5% by weight of an ethylene oxide / propylene oxide copolymer.

That is, in the present invention, glycerin and diethylene glycol are used in combination as the non-drying solvent. The minimum amount of glycerin added is 3% or more, but 10% or less is desirable. Further, the addition amount of diethylene glycol is required to be 5% or more in order to improve the rewriting property, but is preferably 30% or less. Further, in the present invention, an ethylene oxide / propylene oxide copolymer is used in place of the above-mentioned conventional surfactant in order to improve the drawing quality, which has a molecular weight of about 1000-2.
000 is preferable, and the addition amount is 0.1
0.5% is desirable. Acid dyes are desirable as the water-soluble dyes used in the present invention.

(Operation) Since glycerin used as one of the non-drying solvents in the present invention has a high boiling point, high hygroscopicity, and good dye solubility,
It has the effect of preventing the flower bloom phenomenon. In addition, glycerin has the effect of suppressing the blurring of ink strokes. However, since glycerin has a high viscosity, there is a problem that the ink viscosity increases. Further, the other diethylene glycol used as a non-drying solvent in the present invention has an action of remarkably improving rewriting property after left for a long time without a cap, and has relatively low viscosity among non-drying solvents. Therefore, it has an effect of suppressing an increase in ink viscosity. On the other hand, the ink using diethylene glycol has the drawback that it easily bleeds and the quality of the drawn line tends to deteriorate. Therefore, by using glycerin and diethylene glycol together, the flower bloom phenomenon can be prevented and good rewriting property can be obtained, and the disadvantage of one is offset by the merit of the other, so that the problem of increase in ink viscosity and bleeding is caused. Is eliminated. In addition, ethylene oxide
Propylene oxide copolymer has the effect of improving the quality of the drawn line, but since it has little effect on the ink surface tension, it does not cause the bleeding of the drawn line. Even if it is left for a long time without it, it does not adversely affect the rewriting property.

(Example) Example 1 (wt%) Dye (Edible Blue No. 1) 2.0 Dye (Edible Yellow No. 4) 2.0 Diethylene Glycol 20.0 Glycerin 5.0 Ethylene Oxide / Propylene Oxide Copolymer 0.1 Sodium omadine 10% aqueous solution 0.1 Water 70.8 Example 2 (wt%) Dye (Food yellow No. 5) 1.5 Dye (Food red No. 104) 0.5 Eosin 2.5 Diethylene glycol 22.0 Glycerin 3 0.0 ethylene oxide / propylene oxide copolymer 0.1 sodium omazine 10% aqueous solution 0.1 water 70.3 Comparative Example 1 (wt%) Dye (Edible Blue No. 1) 2.0 Dye (Edible Yellow No. 4) 2.0 Ethylene glycol 30.0 Sodium dodecylbenzene sulfonate 0.1 Sodium omazine 10% aqueous solution 0.1 Water 65.8 Comparative example 2 (% by weight) Food (Edible Yellow No. 5) 1.5 Dye (Edible Red No. 104) 0.5 Eosin 2.5 Ethylene Glycol 30.0 Sodium Dodecylbenzene Sulfonate 0.1 Sodium Omazine 10% Aqueous Solution 0.1 Water 65.3 The compositions of the above Examples and Comparative Examples were stirred at room temperature for 3 hours and then filtered to obtain test inks. still,
The ethylene oxide / propylene oxide copolymer used in each example had a molecular weight of about 2000 and an ethylene oxide ratio in the molecule of 50%. This test ink was filled in a felt-tip pen equipped with a pen tip obtained by extrusion molding polyacetal, and the followability to high-speed writing (60 cm / sec) by a plotter was inspected in the initial state. It was left for 1 month without a cap underneath, and the presence or absence of the flower-blowing phenomenon of the pen tip and the rewriting property were inspected, and also the followability to high-speed writing was examined again. The results are shown in Table 1.

(Effects of the Invention) The writing instrument using the ink of the present invention has good rewriting ability even after being left without a cap for a long time as described above, does not cause a flower bloom phenomenon, and sufficiently follows high-speed writing. In addition, the drawn line does not become blurred and the drawn line quality is improved.

Claims (3)

[Claims] 1. An ink composition comprising a water-soluble dye and 3-1.
An aqueous ink for a writing instrument, which comprises 0% by weight of glycerin, 5 to 30% by weight of diethylene glycol, and 0.1 to 0.5% by weight of an ethylene oxide / propylene oxide copolymer. 2. The water-based ink for a writing instrument according to claim 1, wherein an acid dye is used as the dye. 3. The water-based ink for a writing instrument according to claim 1, wherein the ethylene oxide / propylene oxide copolymer has a molecular weight of about 2000.