JPS5951960A - Inkjet recording ink - Google Patents

Abstract

PURPOSE:To provide the titled ink which does not cause clogging of nozzle and gives record having good light resistance, consisting of a water-soluble dye, a wetting agent, a specified water-soluble quencher and water. CONSTITUTION:0.1-15wt% water-soluble dye such as C.I. Direct Blue 236, 5- 40wt% wetting agent, 0.1-5wt% at least one water-soluble quencher selected from KI, KBr, KCl, KSCN, CoSO4, CuSO4, FeSO4, NiSO4 and nickel oxalate and, if necessary, surface tension modifier such as sodium alkylsulfate, viscosity modifier such as CMC, preservative such as sodium dehydroacetate, etc. are dissolved in water to obtain ink for ink jet recording, which has a viscosity of 1.2-30cP, a nonvolatile matter content of 50wt% or below and a pH of not higher than 4 or not lower than 10.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to aqueous inkjet recording ink.
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More specifically, the present invention relates to an improved aqueous inkjet recording ink that can be used for a long time without clogging the nozzle of a jet printer, and can provide all recorded materials with good light resistance.

Therefore, the basic printing principles of known inkjet recording methods include electrostatic attraction type, intermittent ejection type using pulse pressure, and application of continuous pressure of several atmospheres in terms of the method of ejecting ink droplets from the nozzle. There are methods such as continuous discharge type. From the viewpoint of how to control ink droplets, there are charge deflection type, electric field deflection type, electroless type (on-demand type), etc.

In practice, it seems that various combinations of the above-mentioned ejection methods and ink droplet control methods are used to present and implement recording methods each having its own characteristics.

However, the physical properties (viscosity, surface tension, etc.) and electrical properties of the ink that are appropriate for these methods, as well as the shape of the nozzles used for them, are different. Therefore, even in the conventional ink jetting method, ink is continuously and stably ejected as uniform ink droplets through fine nozzles.

Therefore, the basic problem to be solved in an ink jet printer is to completely prevent clogging of the nozzle portion and ensure continuous and stable generation of ink particles over a long period of time. Another important point is that it is possible to create stable ink cats even after a temporary hiatus. Naturally, fine nozzles can become clogged even by the adhesion of even a small amount of solid matter insoluble in the solvent. Furthermore, even if a solid object adheres to a part of the nozzle, the ink ejection direction changes.

Therefore, in order to eject continuous and stable ink particles, it is necessary not only to increase the viscosity and surface tension of the ink composition, but also to completely remove the solvent-insoluble solid content in the ink composition. things are necessary. It is also necessary to completely prevent the generation of solvent-insoluble solids over time.

By the way, coloring in water-based inkjet recording inks can be achieved by removing or preventing the generation of solvent-insoluble solids by using a water-soluble dye 1.

However, in systems using water-soluble dyes, it is easier to meet the basic requirements of the inkjet method, such as preventing the generation of solvent-insoluble solids. The disadvantage of sufficiency arises.

To be more specific, recorded characters may disappear or become difficult to read after a certain period of time, and especially in the case of color images, there may be discoloration of the image due to differences in the light-blocking properties of the mixed dyes. occurred often.

In other words, the water-soluble dyes used in conventional water-based jet ink compositions have insufficient four-light properties, clogging of nozzles, and other conditions necessary for jet inks such as continuous jetting and recording. In terms of the types of colors, hues, etc. required when turning them into objects, there were naturally limitations on the types that could be used.

Therefore, one of the inventors of the present invention previously proposed an ink composition completely containing a water-soluble ultraviolet absorber in order to improve the various drawbacks and limiting conditions mentioned above. (%Komei 3 Otsu-/g/3/)
Personally, the requirements for light resistance in this type of market are becoming increasingly strict.

However, the conductive properties of the inkjet recording ink, which is mainly composed of ketone-based organic solvents and solvent-soluble dyes and solvent-soluble synthetic resins such as vinyl chloride copolymers and vinyl acetate copolymers, are used as solvents. Ink compositions containing soluble ionizable salts as imparting agents are known. (Japanese Unexamined Patent Publication No. 5.2-9 Otsu No. 10λ) However, since this ink composition uses an organic ketone solvent with a hydrogen bonding strength of moderate or lower, Therefore, a conductivity imparting agent is essential. In addition, in the ink composition, the solvent-soluble dye is expected to have the effect of improving light resistance due to its compatibility with the synthetic resin;
In particular, when the ionizable component in the composition is a salt of an alkali metal or alkaline earth metal, there is almost no compatibility with the synthetic resin, so that almost no effect of improving the light resistance of the dye can be expected.

In addition, it is generally known that the light resistance of a dyed product (an inkjet recorded product in the present invention) is closely influenced (interacted) by conditions such as the substrate, coexisting substances, and environmental conditions. As sufficient research results have not yet been obtained regarding these various problems of photobleaching, it is still difficult to construct a unified theoretical system. For example, when talking about substrates, the well-known problems with differences in interaction with substrates include the high light fastness of cationic dye-dyed acrylic fibers and the low light fastness of nylon dyed yellow vat dyes. Gender etc. are known. but,
Regarding inkjet recorded matter, there is no knowledge of this kind.

Therefore, in order to obtain a jet ink composition with excellent light resistance, the present inventors investigated various substances that can completely improve light resistance when coexisting with dyes, and as a result, arrived at the present invention.

Therefore, it is an object of the present invention 1 to further improve the light resistance of recorded materials, to avoid clogging of nozzles, which has conventionally been a common problem in inkjet systems, and to be able to use water-based jet ink compositions that can be used in water-based jet ink compositions. This paper provides a complete set of new water-based inkjet recording inks aimed at expanding the range of water-soluble dyes available.

This objective was unexpectedly solved by the use of certain water-soluble quenchers.

That is, the present invention provides an aqueous inkjet recording ink containing a water-soluble dye, a wetting agent, and water as main components,
In addition, potassium iodide, potassium bromide, potassium chloride,
The present invention relates to an inkjet recording ink characterized in that it contains at least one water-soluble quencher selected from potassium thiocyanate, cobalt sulfate, steel sulfate, ferrous sulfate, nickel sulfate, and nickel oxalate.

In the present invention, the above-mentioned quenching substance, that is, a substance that deactivates the fluorescence of an excited substance by interaction [Kyoritsu Shuppan Co., Ltd., Chemistry Dictionary, page 7]
Potassium iodide, potassium bromide, potassium chloride, potassium thiocyanate, cobalt sulfate, copper sulfate, ferrous sulfate,
At least -m compounds selected from nickel sulphate and nickel oxalate are all used.

Among these, at least one of potassium iodide, potassium bromide, copper sulfate, cobalt sulfate, and potassium thiocyanate is particularly preferably used.

The quenching substance is preferably contained in an ink composition containing a water-soluble dye, a wetting agent, and water as main components in a range of 0 to 1% by weight.

Naturally, if the amount of the quenching substance used is too small, no improvement in light resistance can be obtained. On the other hand, if the amount is too large, the color rendering properties tend to deteriorate and the nozzle gets clogged with precipitates, so it is also not preferable.

On the other hand, as the water-soluble dye used in the aqueous inkjet recording ink of the present invention, any dye having good solubility in water can be used. However, the effect of the present invention is that a stronger addition effect can be achieved in dyes with weak light resistance.

Specific examples of the water-soluble dye include C, 1, D
direct Blue 23 Otsu, C, 1, Dir
ect Blue 203, C, 1, Direc
t Blue 202, C, 1, Direct Blue
e i 31C, 1, Ac1d Blue 7,'
C, 1, Ac1d Blue 9.

C,1, Direct Blue /99, C,1,
Ac1d Yellow / sC, 1, Direct
Red 227, C, 1, DIrect Red 2
23, C, 1, Ac1d Red g7, C, 1, Ac
1d Red 92, C, 1, Ac1d Red! ;
2, C, 1, Ac1d Red 94t.

C, 1, Ac1d Red 2g? ,C,1,D
Direct Black! ;/ , etc.

Further, in the present invention, a liquid wetting agent is used in normal flow. Specific examples of the wetting agent include polyhydric alcohols such as EVA, ethylene glycol, triethylene glycol, polyethylene glycol≠300, glycerin, propylene glycol, alkyl needles of polyhydric 7 alcohols and their acetate esters, etc. , ethylene glycol monomethyl ether, diethylene glycol, monobutyl ether, ethylene glycol monomethyl ether acetate, tripropylene glycol methyl needle, etc.: Hydroxyalkylformamides, for example, hydroxyalkylformamides in which the alkyl group has carbon atoms ranging from 1 to 5: Or 0 Kaisho! ;0-102'10
N-vinyl-2-pyrrolidone oligomer synthesized by the method described in No. 7, etc. is used.

These humectants can be used alone or in combination.

The ink jet recording ink of the present invention has the following formulation, for example. Water soluble dye 0. /~75 weight ahead,
Wetting agent 5-IlO゛wt%, water-soluble quenching substance 0.7
~3% by weight, remaining water.

The aqueous inkjet recording ink of the present invention as described above preferably has a viscosity of 2 to 30 centivoise and a nonvolatile content of about 50% by weight or less from the practical standpoint of being used in an inkjet system.

Furthermore, although the pH etc. of the ink can be varied over a wide range, it is preferable to adjust it appropriately before use, since precipitation may occur depending on the type of quenching substance.

For example, it is preferable to use sulfuric acid steel by adjusting the pH to about 5 or less, or to pl+/0, 5 or more with an ammonia solution.

The aqueous inkjet recording ink of the present invention may further contain a water-soluble solvent, for example, dioxane, acetone, noacetone alcohol, alkyl alcohol having up to 3 carbon atoms, dimethylformamide, nomethylsulfocarbonate, etc. Seven or more types such as zide, N-methyl-λ-pyrrolidone, etc. may be used.

If necessary, additional surface tension modifiers include cationic surfactants such as sodium alkyl sulfate; anionic surfactants such as alkyl bilinium sulfates; nonionic surfactants such as polyvinium sulfates; Oxyethylene alkyl ethers, etc.; or zwitterionic activators may also be used.

Furthermore, if necessary, hydroxyprobil cellulose,
Viscosity modifiers such as carboxymethyl cellulose, hydroxyethyl cellulose, and polyvinyl alcohol; preventers such as sodium dehydroacetate, amine salts of 2-penzisothiatholin-3-one, acetic acid λ, and methyl-m-dioxane. Fungicides, preservatives, etc. can also be added to the food.

Further, oxygen absorbers such as thorium sulfite and thorium hydrogen sulfite can also be used together.

The water-based ink jet recording ink of the present invention thus obtained satisfies all the requirements and performance requirements of the ink jet system, such as prevention of nozzle clogging.

Moreover, the light resistance of the recorded material can be significantly improved.

In addition, the so-called range of selection can be expanded, such as being able to be used with various water-readable dyes.

As a result of the above, its industrial effects are immeasurable.

Hereinafter, the present invention will be specifically explained with reference to Examples.

However, there is no intention to limit it to these specific examples.

Examples/~/3 Raw materials for -c and -f in various proportions as shown in Table 1 were stirred and mixed for 0.3 hours or more, and each raw material was dissolved in water.

Next, a 2μ millibore membrane filter.
A water-based jet ink composition is obtained by pressurizing and filtering. These aqueous jet ink compositions were then continuously recorded using an on-demand inkjet printer, and the continuous jetting stability was determined based on the recording state after 100 hours and the print quality of the recorded material.

Regarding 111i'l luminosity, the recorded matter was irradiated for the required time using a xenon fade meter (manufactured by Suga Test Instruments) (irradiation energy:
), using a reflection densitometer (Macbeth Co., Ltd. RD9/left), the degree of discoloration was compared using the ratio of optical density to the initial value (ioo). The results obtained are shown in Table 1.

Comparative Example A water-based jet ink composition was prepared by using the composition shown in Table 1, which appeared to have the best light resistance. Continuous injection stability and light resistance were tested for the Tokumobadam acid product in the same manner as in the Examples.

＼ Judgment criteria: Surface] Optical property ◎a90”3σ or more, ○: gθ~g9%△:
kO ~ 70%, x: 'l Continuous jetting stability below 09 ○: No nozzle clogging As is clear from the results in Table 1 above, the jet ink composition of the present invention does not impair jetting characteristics in the inkjet system at all. It has good continuous jetting stability without any problems, and the light resistance of the recorded matter is also extremely excellent.

Claims (1)

[Claims] (1) In the aqueous ink jet recording ink whose main components are a water-soluble dye, a wetting agent, and water, potassium iodide, potassium bromide, potassium chloride, potassium thiocyanate, cobalt sulfate, steel sulfate, ferrous sulfate, An inkjet recording ink characterized by containing at least one water-soluble quenching substance selected from nickel sulfate and nickel oxalate. (21) The quenching substance is contained in the inkjet recording ink in an amount of 0.7 to 3% by weight.
) The inkjet recording ink described in item ).