JPH01141966A - Water color ink composition - Google Patents

Abstract

PURPOSE:To obtain a water color ink composition which can give an image having not only high water resistance and sharpness but also high driability and causes no plugging, by using a dye having quat. ammonium or lithium carboxylate groups and quat. ammonium or lithium sulfonate groups at a speci fied ratio. CONSTITUTION:This water color ink composition comprises quat. ammonium or lithium carboxylate groups and quat. ammonium or lithium sulfonate groups in the molecule at a molar ratio of the carboxylate groups to the sulfonate groups of at least 0.3 (e.g., a dye of formula I, II or III). It is possible to provide an ink of high reliability, which can give an image excellent in water resistance and sharpness, does not cause clogging of a nozzle and does not precipitate during storage.

Description

Detailed Description of the Invention [Technical Field] The present invention relates to an inkjet recording ink, for example, an aqueous ink composition used in all types of inkjet recording methods such as charge control type and on-demand type, and relates to an aqueous ink composition used in inkjet recording methods such as charge control type and on-demand type. It is also used as a general recording ink for writing instruments, recorders, plotters, etc.

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

1) Depending on the droplet generation method and droplet flight direction control method, viscosity, surface tension, specific conductivity, i! The ink has appropriate characteristic values such as 7 degrees, 2) Precipitates do not occur or physical properties change due to chemical changes even after long-term storage, 3) The density of the recorded image To meet the above conditions, many proposals have been made with some success.

However, in recent years there has been an increasing demand for inks that can print not only on inkjet paper but also on general paper, but many conventional inks take a long time to dry when printed on paper that has been processed to size like general high-quality paper. This causes problems such as the image being rubbed by the printer's paper ejection system and staining the background.

In order to improve the drying properties of images, a method of adding surfactants etc. to ink to increase the ink's permeability into paper was disclosed in Japanese Patent Application Laid-open No. 5.
No. 5-85262, etc. however,
This method reduces the surface tension of the ink and thus improves the drying performance, but it has the disadvantage that bleeding, called feathering, tends to occur around the image.

[Objective] The present invention solves the above-mentioned problems of the prior art and provides a highly reliable ink that has excellent water resistance and image clarity, and does not cause nozzle clogging or precipitation during storage. The purpose is to

[Configuration] The configuration of the present invention to achieve the above object is as follows: - The carboxylic acid group and the sulfonic acid group name of quaternary ammonium or lithium are present in the molecule; An aqueous dye containing a dye having a molar ratio (carboxylic acid base/sulfonate 2) of 0.3 or more.

It is a liquid ink composition.

The dye used in the present invention will be explained below.

The dye used in the present invention has at least one carboxylic acid group and one sulfonic acid group in its molecule. Water-soluble dyes generally include sulfonate salts. Dyes having sulfonic acid groups generally have good solubility in water and are preferable in terms of clogging resistance and storage stability, but generally do not provide sufficient water resistance to printed images. In order to improve the water resistance of dyes containing sulfonic acid groups, it is generally effective to increase the size of the dye molecule, but increasing the size of the molecule decreases the solubility and further reduces the sharpness of the absorption spectrum, causing the color to change. It tends to become cloudy. One of the reasons why the water resistance of printed images of dyes containing only sulfonate groups is not sufficiently high is that the acid dissociation constant of sulfonate salts is large. Or, it is because it is in a state where it can be dissociated immediately when immersed in water.

On the other hand, since the carboxylic acid group contained in the dye used in the present invention has a small dissociation constant, when it adheres to the recording medium and the pH of the ink decreases, the dye tends to precipitate, especially on high-quality paper used for general recording. is acidic paper sized with rosin, and there is a considerable amount of acidic substances on its surface, so when ink adheres to this recording paper, its pH changes.
decreases to 5 or less. Sulfonic acid is mostly dissociated even at this pH value and does not affect the solubility of the dye, but carboxylic acid is mostly free carboxylic acid at this pH value.

The present invention has been made based on this principle.

In the ink of the present invention, the dye in the ink that adheres to the recording paper precipitates immediately, so the resulting image has excellent water resistance. Even if it penetrates into the recording medium, image bleeding is unlikely to occur.

As mentioned above, dyes containing carboxylic acid groups are excellent in terms of resolution of water-resistant images, but when cations are used in the form of sodium ions or ammonium ions, which have traditionally been used, their solubility decreases. This is insufficient, and clogging is likely to occur when the printer stops printing for a long period of time. Quaternary ammonium ions or lithium ions provide sufficient solubility, and quaternary ammonium having an 01-C4 alkyl group or a 01-C4 alkyl group substituted with a hydroxyl group is particularly preferred. When a quaternary ammonium ion having an alkyl group of 0.05 or more is used, the solubility of the dye decreases.

Even if these quaternary ammonium or lithium ions are used as cations, sufficient solubility may not be provided if the dye has only a carboxylate salt and no sulfonate salt in its molecule.

In particular, when the molecules of the dye are large and the molecular weight becomes large, it becomes difficult to dissolve. In such a case, the solubility can be improved by using a dye having a structure in which the molecule has both a carboxylate and a sulfonate as hydrophilic groups. However, even in such a case, if the number of carboxylic acid bases becomes 0.3 or less in the carboxylic acid base/sulfonate ratio, the above-mentioned dye precipitation effect will be reduced, and the water resistance and image smear prevention effects will almost disappear. . The preferred ratio is 0
．． It is 5 or more.

Specific examples of dyes that can be used in the present invention are listed below.1 These dyes can be used alone, or several types of these compounds can be selected and used in a mixture. Furthermore, dyes that have been conventionally used in inkjet inks, writing inks, dyes, etc. can be mixed and used for the purpose of adjusting color tone, improving solubility, and the like. Conventionally used dyes can be selected from known literature such as Color Index. Preferred examples of these dyes include direct conversion dyes listed in the Color Index, such as C01, Direct Yellow 33, C,1, Direct Yellow 44, and C11, Direct Yellow. 50, C91, Direct Yellow 86, C, 1,
Direct Yellow 144, C, 1, Direct
Orange 26, C91° Direct Orange 102
, C,1, Direct Red 4, C,1, Direct Red 95, C,1, Direct Red 242,
C, 1, Direct Red 9, C81, Direct
Red 17, C, 1, Direct Red 28, C, 1
, Direct Red 81, C,1, Direct Red 83, C,1, Direct Red 89, C,1, Direct Red 225, C,l.

Direct Red 227, C, 1, Direct Blue 15, C01, Direct Blue 76, C11,
Direct Blue 88, C,1, Direct Blue 200, C,1, Direct φ Blue 201, C,
1, Direct Blue 202, C, 1, Direct Black 19, C11, Direct Black 22,
C81, Direct Black 32, C1! , Direct Black 51SC, 1, Direct Black 15
4 etc. can be exemplified.

When these dyes are added to the ink of the present invention, they should be added within a range that does not impede the effects of the present invention. Specifically, the weight ratio is 30 to the dye claimed in the present invention.
% or less.

The amount of the dye used in the present invention added to the ink is the total amount of the ink.
It is 0.5 to 20 wt%, preferably 1.0 to 5 vt%, based on f1Jil.

Furthermore, it is not necessary that all of the cations of the dye used in the present invention be quaternary ammonium ions or lithium ions. In reality, it is difficult to make all of the cations of these dyes specific cations.

For example, even if you attempt to obtain an acid-type dye by precipitating the dye after production with an acid, if other cations are present in the acid precipitation solution, the dye may precipitate while containing those ions. This is because there are many. Furthermore, even if a dye containing no cations other than hydrogen ions is obtained through acid precipitation, even if lithium hydroxide, for example, is added to dissolve the dye to make ink, impurities may be present in the reagent. This is because it often contains sodium, potassium, etc. Furthermore, many additives such as preservatives are generally commercially available as sodium acids, and it is disadvantageous to use these compounds by replacing them with quaternary ammonium or lithium ions because the manufacturing cost increases. The higher the proportion of quaternary ammonium and lithium among all the cations contained in the ink of the present invention, the more preferable it is, but the effect is recognized when the content is 20% or more, and preferably when the content is 50% or more, It is possible to prevent clogging when the printed body stops.

The ink of the present invention uses water as the main solvent component, but in order to adjust the physical properties of the ink to desired values, it prevents the ink from drying and prevents the nozzle from clogging during the printing period. Therefore, a water-soluble organic solvent may be used in combination with water for the purpose of improving the solubility of the dye.

This organic solvent must have physical properties to dissolve the dye well, and preferred examples of this solvent include glycerin, ethylene glycol, triethylene glycol, tetraethylene glycol, and those having a molecular weight of 200 to 1500.
Polyhydric alcohols such as polyethylene glycol, propylene glycol, and dipropylene glycol can be mentioned. In addition to these polyhydric alcohols, the ink of the present invention also contains ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol monomethyl ether, and Ethers of polyhydric alcohols such as ethylene glycol monomethyl ether and triethylene glycol monoethyl ether, and other organic solvents such as N-methyl-2-pyrrolidone, 1,3-dimethylimidazolidinone, and 2-pyrrolidone can be added.

Whether the content of these organic solvents in the ink can be used in the range of 5 to 80% based on the total weight of the ink, the physical properties of the ink,
It is particularly preferable to use it within a range of 10 to 60% from the viewpoint of drying properties and the like.

In the present invention, conventionally known compounds can be added in addition to the dyes and solvents mentioned above.

For example, the preservatives and fungicides include dehydroacetate, sorbate, sodium 2-pyridinethiol-■-oxide, benzoate, sodium pentachlorophenol,
．． 4-dimethyl-6-acetoxy-m-dioxane, ■
, 2-benzthiazolin-3-one and the like.

As a pH adjuster, quaternary ammonium hydroxide or lithium hydroxide is preferable, but for fine adjustment of pH or to impart buffering properties to the ink, lithium carbonate, quaternary ammonium carbonate, carbonic acid may be used. Basic compounds such as lithium hydrogen, sodium carbonate, sodium hydroxide, and triethanolamine can be added. The ink of the present invention can provide excellent water resistance and highly clear images by keeping the pH value as low as possible without precipitating the dye. By setting the ink pH value in this manner, the dye containing the carboxylic acid group can be precipitated more quickly after the ink has adhered to the medium. Therefore, the preferred pH value of the ink of the present invention is 0.5 to 6 higher than the pH value at which the dye precipitates, more specifically 4.5 to 10.0, more preferably 5.0 to 6. It is 9.0.

A surfactant or a surface tension reducing agent can be added to the ink of the present invention for purposes such as lowering the surface tension of the ink and improving the drying properties of the ink or improving the solubility of dyes. Specific examples of these compounds include polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, polyoxyethylene alkyl esters, polyoxyethylene alkyl sorbitan esters, polyoxyethylene alkyl amines, glycerin fatty acid esters, and sorbitan fatty acids. esters,
Nonionic surfactants such as propylene glycol fatty acid esters and polyodiethylene glycol fatty acid esters; alkyl sulfates, polyoxyethylene alkyl ether sulfates, polyoxyethylene alkyl ether acetic acid solutions, alkylbenzene sulfonates, N-acylamino acid salts, Anionic surfactants such as alkyl sulfosuccinates and alkyl phosphates; cationic surfactants such as quaternary amines such as benzalkonium salts; perfluoroalkyl phosphates and perfluoroalkyl carboxylic acids Examples include salts, fluorine-based surfactants such as perfluoroalkyl betaines, and the like.

By adding these compounds to lower the surface tension of the ink to 50 dyne/cm or less, the absorbency of the ink to the recording medium increases and drying is performed quickly. Therefore, this makes it possible to further enhance the effects of the present invention.

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, etc. can be added depending on the purpose.

Hereinafter, the present invention will be specifically explained with reference to Examples. Note that the amounts (%) of each component described in the Examples are based on weight.

Example 1 Ink composition compound example No. 1 dye 2.5% glycerin 5% diethylene glycol
8% polyethylene glycol 3005% diethylene glycol monobutyl ether 5% sodium dehydroacetate 0.3% purified water
Mix the remaining amount of ink with the above prescription,
The mixture was stirred and filtered to obtain an ink for testing. The pH value of the ink was adjusted to 7.5. Surface tension is 35.8 dyne/c
It was +*.

This ink is printed on a charge-controlled inkjet printer (Ricoh: Word Processor Report 5800 J).
(inkjet printer) and printed. The ink was evaluated on the following items.

Water resistance of image The image formed by printing was immersed in water for 1 minute, the image density before and after immersion was measured, and the fading rate (%) was determined by the following formula.

The time it takes for the ink in the dry solid image area to stop transferring to the filter paper is determined by n1.

Image clarity: X with significant feathering, △, with very little feathering, no feathering Storage: 3 months at 20℃, room temperature, and 50℃ If the difference in physical property values (viscosity, surface tension, electrical conductivity) before and after storage was 10% or less and no precipitate was observed, the sample was rated 01, otherwise it was rated X.

Nozzle clogging test After printing was suspended, remove the printer cover and leave it in an environment of 40℃ and 20% for two weeks, then print again. Those that were able to print normally are marked as 0, and those that were not printed are marked as 0. was marked as ×.

The results of each of the above tests are shown in Table-1.

Comparative Example 1.2 In Example 1, the cations were changed from tetramethylammonium ion to sodium ion and ammonium ion (N
An ink was made using a dye different from H4) and a similar test was conducted.

Comparative Example 3 An ink was prepared using a dye having the following structure having a structural formula similar to the dye used in Example 1 in place of the dye in Example 1, and the same test was conducted.

Example 2 Ink composition Compound of Compound Example 5 2.5% glycerin
5% ethylene glycol
10% polyethylene glycol 2005% N-methyl-2-pyrrolidone 3% diethylene glycol monobutyl ether 3% 2-pyridinethiol-1-sodium oxide 0.1% Water
Remaining Amount An ink having the above formulation was prepared in the same manner as in Example 1, and the same test was conducted. The surface tension of ink is 41.5 dyne
/CIB.

Comparative Example 4 A dye having the following structure was used in place of the dye used in Example 2 as a dye similar to the compounds, and a test was conducted in the same manner.

Example 3 Ink composition Dye of Compound Example 11 3% Diethylene glycol 20% 1.3-dimethylimidazolidinone 5% 2.4-dimethyl-6-acetoxy-m-dioxane 0.2% Fluorine surfactant 1% water
Remaining Amount An ink with the above formulation was prepared in the same manner as in Example 1, and the same tests were conducted. The surface tension of the ink was 28.3 dyne/Cm.

Comparative Example 5 An ink using the following dye similar to Compound 11 in place of the dye used in Example 3 was prepared and tested in the same manner.

Example 4 Ink composition Dye of Compound Example 4 2% ethylene glycol 10% diethylene glycol
10% dipropylene glycol 7
% Ethylene glycol monophenyl ether 2% Sodium 2-pyridinethiol-1-oxide 0.2% Water
Remaining Amount An ink with the above formulation was prepared in the same manner as in Example 1, and the same tests were conducted. The surface tension of the ink was 38.5 dyne/aII.

Comparative Example 6, Comparative Example 7 An ink having the same formulation as in Example 4 was prepared using a dye in which the cation of the dye of Compound Example 4 was replaced with trimethylamine and potassium ion, respectively, and the same test was conducted.

Example 5 Dye of Compound Example 13 3% Glycerin
5% diethylene glycol
20% diethylene glycol monobutyl ether 5% 1.2-benzthiazolin-3-one 0.2% water
Surface tension of remaining ink 38.3 dyne
/cm Comparative Example 8 An ink using the following dye as a dye similar to Compound 13 in place of the dye used in Example 5 was prepared and tested in the same manner.

Example 6 An ink was prepared using Compound 8 in place of Compound 13 in Example 5, and a similar test was conducted.

The results are shown in Table-1. Printing was done on commercially available bond paper, electrophotographic paper (PPC paper), and computer paper, and the same trends were found for all papers, Table 1
Regarding water resistance, drying time, and image clarity, the results for PPC paper are shown.

Table 1 [Effects] As described above, the ink of the present invention makes it possible to provide high water resistance and clarity of images while preventing clogging, and at the same time to provide high drying properties. The inks of the present invention also generally provide higher image densities than conventional inks because the dye precipitates on the surface of the paper.

Claims (1)

[Claims] One molecule contains a quaternary ammonium or lithium carboxylate group and a sulfonate group, and the molar ratio of the carboxylate group to the sulfonate group in the molecule (carboxylate base/sulfonate base) is 0.3. An aqueous ink composition characterized by containing the above dye.