JP2571240B2 - Water-based ink - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a water-based ink suitable for ink-jet recording, and can also be used as a water-based ink for recorders, pen plotters, writing instruments, and the like.

[Prior Art] Conventionally, many inventions relating to magenta and red aqueous inks have been made. For example, JP-A-57-35728 and JP-A-57-35729 using xanthene dyes and JP-A-58-176275 using monoazo dyes are disclosed.

However, at present, satisfactory magenta and red aqueous inks having a clear color tone, excellent water fastness and light fastness, and excellent storage stability cannot be obtained. In particular, when used as an aqueous ink for inkjet, there are problems in terms of changes in the jetting direction and clogging, and the ink cannot be used unless its solubility in a polyhydric alcohol or the like serving as a solvent is insufficient.

[Purpose] An object of the present invention is to provide a magenta ink for inkjet recording and a red aqueous ink that have solved the conventional disadvantages. More specifically, the present invention has improved image clarity, water resistance, and light resistance. It is an object of the present invention to provide a magenta ink for inkjet recording and a red aqueous ink which are excellent, in particular, have excellent ejection direction stability and are hardly clogged.

[Constitution] The present invention is an aqueous ink comprising at least one water-soluble dye represented by the following general formula.

General formula (A) R ₁ : hydrogen, alkyl group, alkoxy group, hydroxyalkyl group, halogen, acetyl group R ₂ : morpholyl group, l: 0 or 1 X: alkali metal, hydrogen The present invention improves the drawbacks of conventional magenta dyes. As a result of intensive studies, the dye of the general formula (A) has excellent image characteristics,
In particular, when lithium is used as a counter ion, an inkjet ink having particularly excellent solubility and satisfying water resistance and light resistance of an image can be obtained.

The dye of the general formula (A) has better water resistance than a conventional aqueous ink using an acidic dye, and has sufficient dissolution stability as an aqueous ink for inkjet. Particularly, when lithium salt is used as a counter ion, it shows excellent solubility.

When the counter ion is other than an alkali metal, for example, a quaternary ammonium, the light resistance is inferior to that of an alkali metal, and in particular, it is inferior to that of an acidic paper.

Specific examples of the general formula (A) of the present invention and the Ar portion of the comparative example are shown below.

The dye is easily synthesized by a known method.

In addition, the compound of the general formula (A) of the present invention is similarly synthesized by a conventional method. However, it is difficult to completely form the free acid form, and Na ions may remain. In order to convert from the Na salt form to the free acid form, an ion exchange resin can be used. In addition, the aqueous ink of the present invention can also be prepared without using a free acid by using Li ₂ CO ₃ for the pH adjustment of the reaction by using Li salt as a raw material from the synthesis stage.

In the present invention, the sulfonic acid in the dye does not need to be all lithium salt and quaternary phosphonium, and at least
At least 30%, more preferably at least 50%, should be substituted. As another counter ion, a Na ion is preferable. The presence of ions such as polyvalent metals such as Ca ²⁺ , Al ³⁺ , and Mn ²⁺ lowers the solubility of the dye, and is not preferable.

The ink of the present invention uses water as a solvent component, but in order to adjust the physical properties of the ink to a desired value, to prevent drying of the ink, to improve the solubility of the dye, and the like, The following water-soluble organic solvents and water may be mixed for use.

Polyhydric alcohols such as ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, glycerin,
Alkyl ethers of polyhydric alcohols such as ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, and other N-methyl -2-pyrrolidone, 2-pyrrolidone, 1,3-dimethylimidazolidinone, dimethylformamide, triethanolamine and the like.

Among them, particularly preferred are diethylene glycol, polyethylene glycol 200 to 600, triethylene glycol, ethylene glycol, glycerin, and N-methyl-2-pyrrolidone, and the use of these makes it possible to achieve high solubility of the dye and prevention of water evaporation. The effect of preventing clogging can be obtained.

The content of the water-soluble organic solvent in the ink can be used in the range of 5 to 80% with respect to the total weight of the ink, but is preferably used in the range of 15 to 60% from the viewpoint of viscosity and drying property.

Conventionally known additives can be added to the ink of the present invention in addition to the dye and the solvent.

For example, preservatives and fungicides include sodium dehydroacetate, sodium sorbate, 2-pyridinethiol-1-
Sodium oxide, sodium benzoate, sodium pentachlorophenol and the like can be used in the present invention.

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

Examples include amines such as diethanolamine and triethanolamine, hydroxides of alkali metal elements such as lithium hydroxide, sodium hydroxide and potassium hydroxide, ammonium hydroxide, quaternary ammonium hydroxide, and quaternary phosphonium. Examples include hydroxides, carbonates of alkali metals 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 uramildiacetate.

Examples of the rust preventive include acid sulfite, sodium thiosulfate, ammonium thioglycolate, diisopropylammonium nitrite, pentaerythritol tetranitrate, dicyclohexylammonium nitrite, and the like.

In addition, a water-soluble ultraviolet absorber, a water-soluble infrared absorber, a water-soluble polymer compound, a dye dissolving agent, a surfactant and the like can be added according to the purpose.

Hereinafter, examples and comparative examples of the present invention will be described. All percentages are by weight.

Example 1 The following composition was dissolved by stirring and filtered through a filter having a diameter of 0.22 μm to obtain Ink 1.

X = Li ion 2.5% Polyethylene glycol 200 10% N-methyl-2-pyrrolidone 10% 2,4-Dimethyl-6-acetoxy-dioxane 0.2% Ion-exchanged water with the dye of specific example (A-3) The inks of Examples 2 to 4 and Comparative Examples 1 to 6 were produced in the same manner as in Example 1 except that the material having the composition was used.

Example 2 Dye of specific example (A-2) (acid) 2.5% polyethylene glycol 200 10.0% N-methyl-2-pyrrolidone 10.0% lithium hydroxide 0.2% 2,4-dimethyl-6-acetoxy-m-dioxane 0.2 % Ion-exchanged water Remaining Example 3 Ink 3 was produced in the same manner as in Example 1 using the following composition.

Dye (A-11), X = Li ion 3% Diethylene glycol 15% Glycerin 5% Sodium dehydroacetate 0.1% Deionized water Remaining Example 4 Dye (acid type) of specific example (A-9) 2.0% Ethylene glycol 12.0 % Glycerin 5.0% Lithium hydroxide 0.2% 2,4-Dimethyl-6-acetoxy-m-dioxane 0.2% Ion exchange water Remaining Comparative Example 1 CI Direct Red 31 2.0% Diethylene glycol 10.0% Glycerin 5.0% Diethylene glycol monobutyl ether 5.0% Water Sodium oxide 0.1% Sodium dehydroacetate 0.2% Deionized water Remaining comparative example 2 Dye (acid type) of specific example (A-2) 2.5% Polyethylene glycol 200 10.0% N-methyl-2-pyrrolidone 10.0% Tetramethylammonium hydro Oxide 25% Water-soluble 2.0% 2,4-Dimethyl-6-acetoxy-m-di Oxane 0.2% Ion-exchanged water Remaining Comparative Example 3 CI Acid Red 92 2.0% Polyethylene glycol 200 10.0% N-methyl-2-pyrrolidone 10.0% Sodium hydroxide 0.1% 2,4-Dimethyl-6-acetoxy-m-dioxane 0.2 % Ion-exchanged water remaining amount Comparative Example 4 CI Direct Red 83 3.0% triethylene glycol 15.0% 1,3-dimethylimidazolidinone 10.0% sodium hydroxide 0.05% sodium dehydroacetate 0.2% ion-exchanged water remaining amount Comparative Example 5 Ink 2 was prepared in the same manner as in Example 1 except that the dye of Comparative Example 5), X = Na ion, was used.

Comparative Example 6 Ink 4 was produced in the same manner as in Example 3 except that the dye (X = Na ion) of the above (Comparative Example 6) was used.

[Effects] The following tests were performed on Examples (1) to (5) and Comparative Examples (1) to (5).

1) Sharpness of Image An ink-jet printer for Ricoh's Word Processor Report 5600J was filled with the produced ink and printed.

The inks for which clear images were obtained are indicated by a circle in Table 1.

2) Image lightfastness The image sample obtained in 1) was applied to a fade meter (carbon arc lamp, 83 ° C) for 3 hours, and the image density before and after light irradiation was measured with a Macbeth densitometer. (Discoloration rate) was determined.

3) Water resistance of the image The image sample obtained in 1) is immersed in water at 30 ° C. for 1 minute,
The image density before and after immersion was measured with a Macbeth densitometer, and (2)
The water resistance (discoloration rate%) was determined by the same equation as in the section.

4) Storage properties Put the ink in a polyethylene container and store at -20 ℃, 4 ℃, 2
It was stored at 0 ° C, 50 ° C, and 70 ° C for 3 months, and the viscosity, surface tension, change in electrical conductivity before and after storage, and the presence or absence of precipitates were examined. In any of the conditions, no change in physical properties and no generation of a precipitate was observed in Table 1, which was marked with a circle.

5) Nozzle clogging test 1) After printing in 1), with printing paused, 20 ° C, 65% R
It was left for two months in the environment of H, and it was checked whether normal printing was possible again after leaving.

One ink sample was tested using three printers.

Table 1 shows that all three printers were able to print normally, ○ indicates that one or two of the three printers failed to print properly, × indicates that all three printers failed.
Indicated by

In the printer for 5600J, nozzle clogging occurs.
When jetting becomes impossible or when the jetting direction of the jet changes significantly compared to before leaving, it is automatically detected,
A device to stop the operation of the printer is provided.

Regarding the clogging characteristics, the results obtained when the nozzle diameter was 30 μm and when the nozzle was stopped for 6 months were evaluated in addition to the conventional two-month pause.

As is clear from the above results, the aqueous ink of the present invention has excellent water resistance and light resistance of the recorded image, has a good magenta color tone, and does not clog even when used in ink jet recording. In addition, the injection stability is high even if left for a long time.

Continuation of the front page (72) Inventor Hiroyuki Uemura 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (56) References JP-A-61-101574 (JP, A)

Claims (2)

(57) [Claims] An aqueous ink comprising at least one water-soluble dye represented by the following general formula (A): R ₁ : hydrogen, alkyl group, alkoxy group, hydroxyalkyl group, halogen, acetyl group R ₂ : morpholyl group, l: 0 or 1 X: alkali metal, hydrogen 2. The aqueous ink according to claim 1, wherein the counter ion X in the general formula (A) is a lithium ion.