JPH01198670A - Aqueous ink composition - Google Patents

Abstract

PURPOSE:To obtain a magenta aqueous ink composition useful for printing, writing tools, recorders, stamps, especially ink jet printing, having excellent shelf stability, clarity of image, water resistance, light resistance, etc., free from clogging, containing a specific water-soluble dye. CONSTITUTION:The aimed composition containing a water-soluble dye (e.g. compound shown by formula IV) shown by formula I [R is alkyl; Ar is group shown by formula II or III (R1 is H, alkyl, alkoxy or halogen; M is H, Li, K, Na, quaternary ammonium or organic amine; n is 1 or 2)]. The dye, for example, is produced according to the reaction equation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an aqueous ink composition suitable for printing, writing instruments, recorders, and stamps, and particularly to a magenta aqueous ink composition useful for inkjet printing.

[Prior Art] In inkjet recording, in order to perform good print recording over a long period of time, it is necessary that the ink (aqueous ink composition) used satisfies the following conditions.

1) Excellent ink jetting characteristics. To this end, the viscosity, surface tension, specific conductivity, and density of the ink must be within appropriate ranges as ink physical properties depending on the droplet generation method and droplet flying direction control method.

2) It has excellent storage stability. To achieve this, the ink must not clog the nozzle due to precipitation due to chemical changes during long-term storage, continuous use, or when recording is stopped, and the physical properties of the ink must not change.

3) The printed image has sufficiently high contrast.
The image must be clear and free of blur.

4) The printed image dries quickly.

5) Printed and recorded images should also have good water resistance, light resistance, etc., that is, good storage stability and high abrasion resistance.

6) Inks used in full-color printers, etc. should form images with high purity tones and excellent color reproducibility.

In order to satisfy the above requirements, a number of proposals have been made for inks to be used in inkjet recording, etc., but there is still no ink that fully satisfies all of the above conditions. This is the current situation. This is mainly due to the dyes in the materials that make up the ink.

In other words, a typical water-based ink composition basically consists of a dye, a polyhydric alcohol or its ether known as a wetting agent, and water, and may optionally contain additives such as a fungicide. It is something to do. For example, in the case of magenta ink, the dyes are C, 1, Direct Red -1, -11, -37, -62, -75, -87.
, -89, -95, -227 or C, I.

Acid Red -1, -8, -87, -94, -115
, -131, -144° -152, -154, -186
, -254 and other direct dyes and acid dyes are used.

However, when magenta ink containing such dyes is used for inkjet recording, direct dyes have poor solubility, which can cause nozzle clogging during continuous recording or when recording is resumed, and when a color image is recorded. Images with excellent color reproducibility are not necessarily obtained. Furthermore, although many acidic dyes have good color tone, the water resistance and light resistance of images are poor, and there are problems with image storage stability.

[Objective] An object of the present invention is to provide an aqueous ink composition, particularly an aqueous ink composition for inkjet recording, which solves the above-mentioned conventional problems. More specifically, it is an object of the present invention to provide a magenta water-based ink that has excellent jetting characteristics, is free from clogging, and has excellent image clarity, water resistance, light resistance, and the like.

[Structure] The present inventor has discovered that it is extremely effective to use a dye that has a sufficiently high molecular extinction coefficient and a sufficiently high solubility in a wetting agent as a means to solve the above problems, and has developed the present invention. It has been completed. That is, the aqueous ink composition of the present invention is characterized by containing at least one water-soluble dye represented by the following general formula.

H K (However, in the formula, R and Ar are defined as below.

R: Alkyl group R1: Hydrogen atom, alkyl group, alkoxy group, halogen atom H: Hydrogen atom, lithium, potassium, sodium, quaternary ammonium, organic amine n: 1 or 2) Dye represented by the above general formula of the present invention Specific examples include the following compounds.

H (iso) (iso) 0■ (n) The content of these dyes is 0 based on the total weight of the ink.
．． 5 to 20% by weight, preferably 1.5 to 6% by weight are suitable. If it is less than 0.5% by weight, its effectiveness as a colorant will be reduced and the resulting image will have insufficient color tone, and if it exceeds 20% by weight, precipitation will occur in the ink after a long period of time, making inkjet recording difficult. tend to be insufficiently carried out.

Any of the dyes of the general formula of the present invention as described above can be easily produced, and the production method for the dye of Example (1), for example, is as follows.

The ink of the present invention uses water as a solvent component, and water is used for purposes such as adjusting the physical properties of the ink to desired values, preventing drying of the ink, and improving the solubility of dyes. It is also possible to use a mixture of a water-soluble organic solvent and water.

Water-soluble organic solvents include polyhydric alcohols such as ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, and glycerin: ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, Alkyl ethers of polyhydric alcohols such as diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether; other N-
Examples include methyl-2-pyrrolidone, 2-pyrrolidone, 1,3-dimethylimidazolidinone, dimethylformamide, and triethanolamine.

Among these, particularly preferred are diethylene glycol,
Polyethylene glycol 200-600, triethylene glycol, ethylene glycol, glycerin and N
-Methyl-2-pyrrolidone, and by using these, it is possible to further enhance the solubility of the dye and the effect of preventing clogging by preventing moisture evaporation.

The content of the water-soluble organic solvent in the ink can range from 5 to 80% by weight based on the total weight of the ink, but is preferably from 15 to 60% by weight in view of viscosity, drying properties, etc.

In addition to the above-mentioned dyes and organic solvents, the ink of the present invention may contain additives such as conventionally known antiseptic and fungicides, pH adjusters, chelating reagents, and rust preventives.

For example, as a preservative and fungicide, sodium dehydroacetate,
Sodium sorbate, sodium 2-pyridinethiol-1-oxide, sodium benzoate, sodium pentachlorophenol, etc. can be used.

As the pH adjuster, any substance can be used as long as it can control the pH of the ink within the range of 9.0 to 11.0 without adversely affecting the ink being prepared.

Examples include amines such as jetanolamine and toethanolamine; lithium hydroxide, sodium hydroxide,
Examples include alkali metal hydroxides such as potassium hydroxide: ammonium hydroxide treated with ammonium hydroxide; alkali metal carbonates such as lithium carbonate, sodium carbonate, and potassium carbonate.

Examples of the chelating reagent include sodium ethylenediaminetetraacetate, sodium nitrilotriacetate, sodium hydroxyethylethylenediaminetriacetate, sodium diethylenetriaminepentaacetate, and sodium uracil diacetate.

Examples of rust preventives include acidic sulfites, sodium thiosulfate, ammonium thioglycolate, diisopropylammonium nitrite, pentaerythritol tetranitrate, and dicyclohexylammonium nitrite.

In addition, water-soluble ultraviolet absorbers, water-soluble infrared absorbers, water-soluble polymer compounds, dye solubilizers, surfactants, etc. can be added depending on the purpose.

[Example] Examples and comparative examples of the present invention are shown below. Note that all percentages are percentages by weight.

Example 1 After heating the materials with the following composition to about 50°C and stirring and dissolving them,
An aqueous ink composition was prepared by filtration with a Teflon filter having a pore size of 0.22 μm.

Dye of specific example (1) 3.0% diethylene glycol 20.0% N-methyl-2-pyrrolidone 5.0% sodium dehydroacetate
0.2% water
71.8% Inks of Examples 2 to 5 and Comparative Examples 1 to 3 were produced in the same manner as in Example 1 except that materials having the following compositions were used.

Example 2 Dye of specific example (2) 3.0% polyethylene glycol 200 15.0% triethylene glycol 7 methyl ether io, o% Sodium dehydroacetate 0.2% water
71.8% Example 3 Dye of specific example (5) 3.0% diethylene glycol 20.0% 1,3-dimethylimidazolidinone 5.0% 6-acetoxy-2,4-
Dimethyl-m-dioxane 0.3% Water 71.7
% Example 4 Dye of specific example (7) 3.0% diethylene glycol 20.0% glycerin
5.0% Sodium 2-pyridinethiol-1-oxide 0.3% Water
71.7% Example 5 Dye of specific example (12) 3.0% diethylene glycol 20.0% N-methyl-2
-pyrrolidone 5.0% 6-acetoxy-2
,4-dimethyl-m-dioxane 0.3% water 71.7
% Comparative Example 1 C,1, Acid Red 35 3.0% diethylene glycol 20.0% N-methyl-
2-Pyrrolidone 5.0% Sodium dehydroacetate 0.2% Water
71.8% Comparative Example 2 C,1, Acid Red 92 3.0% Polyethylene Glycol 200 15.0% Triethylene Glycol Monomethyl Ether 10.0% Sodium Dehydroacetate 0.2% Water
71.8% Comparative Example 3 C, 1, Direct Red 227 3.0% diethylene glycol 20.0% Sodium 2-pyridinethiol-1-oxide 0.3% Water
71.7% Next, Example 1
The following tests were conducted on the compositions of Comparative Examples 1 to 5 and Comparative Examples 1 to 3. The results are shown in Table 1.

1) Image clarity An inkjet printer for word processor report 5600J manufactured by Ricoh was filled with the prepared ink and printing was performed.

Ink that produced a clear image is marked ○ in Table 1.
Represented by a mark.

2) Light resistance of the image The image sample obtained in 1) was placed in a fade meter (carbon arc lamp, 63℃) for 3 hours, and the image density before and after light irradiation was measured with a Macbeth densitometer. (rate) was calculated.

3) Water resistance of the image The image sample obtained in 1) was immersed in 30°C water for 1 minute,
The image density before and after dipping was measured using a Macbeth densitometer, and the water resistance (fading rate) was determined using the same formula as in section 2).

4) Place the preservative ink in a polyethylene container and store at -20℃ and 4℃.
, 20°C, 50°C, and 70°C for 3 months, and the changes in viscosity, surface tension, and electrical conductivity before and after storage, and the presence or absence of precipitation were examined.

In Table 1, samples with no change in physical properties or generation of precipitates were marked as ○ no matter what conditions they were stored under.

5) After printing in nozzle clogging test 1), heat the print at 20°C and 65°C with the print stationary.
%RH for 2 months, and it was examined whether normal printing was possible again after being left. One ink sample was tested using three printers.

In Table 1, 0.3 indicates that all three printers were able to print normally. . In addition, the 5600J printer has a system that automatically detects when the nozzle becomes clogged and cannot jet, or when the direction of the jet jet changes significantly compared to before it was left unused, and stops the printer's operation. equipment is installed.

Table 1 [Effects] As is clear from the above explanation, the present invention uses a dye for water-based ink that has a sufficiently high molecular extinction coefficient and has a sufficiently high solubility in a wetting agent, so there is no clogging. It is possible to provide an aqueous ink crude acid with excellent storage stability, image clarity, water resistance, light resistance, etc.

Claims (1)

[Scope of Claims] A water-based ink composition characterized by containing at least one water-soluble dye represented by the following general formula. ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (However, R and Ar in the formula are defined as below. R: Alkyl group Ar: ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ or ▲ Numerical formulas, chemical formulas, tables, etc. ▼ R_1: Hydrogen atom, alkyl group, alkoxy group, halogen atom M: Hydrogen atom, lithium potassium, sodium, quaternary ammonium, organic amine n: 1 or 2)