JPS5953566A - Jet ink composition - Google Patents

Abstract

PURPOSE:To provide a water-based jet ink composition usable for a long period without causing the clogging of the nozzle, and giving a record having excellent light resistance, by adding a water-soluble ultraviolet absorber and a water- soluble quencher to a jet ink composition. CONSTITUTION:A water-based jet ink composition composed mainly of a water- soluble dye, a wetting agent and water, is further added with preferably 0.1- 10wt% of a water-soluble ultraviolet absorber (preferably the compound of formula I and/or formula II) and preferably 0.1-4wt% of one or more water-soluble quenchers (preferably potassium iodide, potassium bromide, copper sulfate, cobalt sulfate or potassium thiocyanate).

Description

[Detailed description of the invention] The present invention relates to aqueous jet ink compositions.

More specifically, it relates to an improved water-based jet ink composition that can be used for a long time without clogging the nozzle of a sheet printer, and can provide recorded matter with good light resistance. .

By the way, the basic printing principles of known inkjet recording methods include electrostatic attraction type, intermittent ejection type using nozzle pressure, and ink droplet ejection method from the nozzle.
There are methods such as a continuous discharge type that applies continuous pressure of several atmospheres.

In addition, from the viewpoint of how to control ink droplets, charge deflection type,
There are electric field deflection type, chargeless type (on-demand type), etc.

In practice, it seems that various combinations of the above-mentioned ejection methods and ink droplet control methods have been proposed and implemented, each with its own unique characteristics. However, the appropriate physical properties (viscosity, surface tension, etc.) and electrical properties of the ink differ depending on the method and the shape of the nozzle used. Therefore, in any inkjet method, ink must be continuously and stably ejected as uniform ink particles from fine nozzles.

Therefore, the basic problem to be solved in inkjet printers 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 stable ink particles can be created again after a temporary pause. Unfortunately, fine nozzles can become clogged even when a small amount of solvent-insoluble solids adheres to them. Furthermore, even if a solid object adheres to a part of the nozzle, the ink ejection direction changes.

Therefore, in order to eject ink particles continuously and stably, the viscosity and surface tension of the ink composition must be adjusted.

Not only does the force have to be appropriate;
It is necessary to completely remove solvent-insoluble solids from the ink composition. It is also necessary to completely prevent the generation of solvent-insoluble solids over time.

By the way, when coloring a water-based jet ink composition, it is usually possible to remove or prevent the generation of solvent-insoluble solids by using a water-soluble dye.

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, but on the other hand, the light resistance of recorded materials is insufficient. There is a drawback that arises.

To explain this more specifically, after a certain period of time, the recorded characters may disappear or become difficult to read, and especially in the case of color images, the image may change color due to differences in the light fastness of the dyes mixed. occurred often.

In other words, the water-soluble dyes used in conventional water-based jet ink compositions had insufficient light resistance, caused nozzle clogging, and other conditions necessary for jet inks such as continuous jetting. In terms of the types of colors, hues, etc. required for recording materials, 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 containing a water-soluble ultraviolet absorber in order to improve the various drawbacks and limiting conditions mentioned above. (Special Publication No. 56-18151)
However, the requirements for light resistance in this type of market are becoming increasingly strict.

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 various conditions such as the substrate, coexisting substances, and environmental conditions. It is difficult to assemble a unified theoretical system regarding these photobleaching problems because sufficient research results have not yet been obtained. For example, regarding substrates, well-known unique problems in interaction with substrates include the high light fastness of cationic dyed acrylic fibers and the low light fastness of nylon dyed yellow vat dyes. etc. are known. However, there is no knowledge of this kind regarding inkjet recorded matter.

The present inventors tested various water-soluble compounds to improve light resistance through interaction with coexisting substances, and found that water-soluble quenching substances significantly improve light resistance in the coexistence of water-soluble ultraviolet absorbers. He discovered that it is possible to pray with one's face facing the other side.

At the same time, the present inventors have developed an ink composition of the present invention that does not generate solvent-insoluble solids that cause nozzle clogging in an inkjet system and does not impair the recording characteristics of inkjet recording, that is, an aqueous jet recording method. A new ink composition has been achieved, which is a combination of an ink composition, a water-soluble ultraviolet absorber, and a water-soluble quenching substance.

Therefore, it is an object of the present invention to further improve the light resistance of recorded materials, to eliminate clogging of nozzles, which has hitherto been unavoidable in inkjet systems, and to provide a water-soluble jet ink composition that can be used in water-based jet ink compositions. The object of the present invention is to provide a new aqueous jet ink composition that is intended to expand the variety of dyes.

That is, the present invention provides an aqueous jet ink composition containing a water-soluble dye, a wetting agent, and water as main components, further comprising at least one water-soluble ultraviolet absorber and at least one water-soluble quenching substance. The present invention relates to a jet ink composition characterized by:

The water-soluble ultraviolet absorber used in the present invention includes:
Generally commercially available products can be used. Considering the nozzle clogging or injection characteristics, 2-hydroxy-4-methoxy-benzophenone-5-sulfonic acid (or its Na salt: the following structural formula (I)), or
, 2'-dihydroxy-4,4'-dimethoxy-benzophenone-5-sulfonic acid (or its Na salt) [The following structural formula (ll): 1 is preferably used.

5o6H(' or Na) OH() OH In the ink composition of the present invention, it is necessary that the water-soluble ultraviolet absorber be present in an amount of 3.1% by weight or more from the viewpoint of improving light resistance. In addition, in order to obtain sufficient effect, 0
．． A presence of 5% by weight or more is preferred. On the other hand, in view of the characteristics required for the water-based jet ink composition, such as prevention of nozzle clogging, the amount of the ultraviolet absorber is preferably 10 parts by weight or less, more preferably 5 parts by weight or less.

The aqueous jet ink composition of the present invention to which a predetermined amount of the water-soluble ultraviolet absorber was added did not cause nozzle clogging and could be jetted as stable ink particles for a long period of time. However, in the presence of 5% by weight or more, the solid content will be reduced to air during the temporary rest.
There was a tendency for the ink to precipitate at the interface.

In the present invention, the above-mentioned (I) is used as a water-soluble ultraviolet absorber, particularly from the viewpoint of improving the light resistance of recorded materials, preventing the generation of solvent-insoluble solids, or improving the electrical properties of ink compositions.
and (n) are optimal.

The ultraviolet absorbers shown in (1) and (■) above all have spectral curves that absorb light with a wavelength of 680 millimicrons or less, but hardly absorb visible light beyond that wavelength.

When the light resistance of inkjet recordings becomes a problem, it is thought that the cause of discoloration of these recordings is strongly influenced by ultraviolet rays having a wavelength of 380 millimicrons or less.

Therefore, the present invention particularly focuses on a water-based jet ink that uses ultraviolet absorbers shown in the chemical formulas (■) and (■) and a water-soluble quenching substance described below to reduce discoloration due to ultraviolet rays and further improve light resistance. A composition is obtained.

In the present invention, a water-soluble quenching substance is used together with the water-soluble ultraviolet absorber.

The water-soluble quenching substance, that is, a substance that deactivates the fluorescence of an excited substance through interaction [published by Kyoritsu Shuppan Co., Ltd.,
Chemical Encyclopedia A4, page 769] and I~, particularly preferably water-soluble potassium iodide, potassium bromide, potassium thiocyanate, cobalt sulfate, steel sulfate, ferrous sulfate, nickel sulfate and nickel oxalate. At least one selected compound is used.

Among these, it is particularly preferable to use at least one of potassium iodide, potassium bromide, copper sulfate, cobalt sulfate, and potassium thiocyanate.

The quencher is preferably included in the ink composition in an amount of 0.1 to 5 weight units. If the amount of the water-soluble quenching substance used is too small, the effect of improving light resistance cannot be obtained, which is surprising. 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.

Further, as the water-soluble dye used in the aqueous jet ink composition 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.

Examples of the water-soluble dye include C, l, Di r
ectBlue 236 r C, 1, Direct
Blue 20ro, C, l.

Direct Blue 202, C, 1, Dir
ect Blue 15.

C,1,Ac1d Blue 7, C,1,Ac1
d Blue 9, C, l.

Direct Blue 199, C, 1, Ac1
d Yellow 1, C, l.

Direct Red 227, C, 1, Dire
ct 225 r C0I-Acid Red 87
, C,1,Ac1d Red 92 , C,1,A
c1dRed 52, C,1,Ac1d Red
94, C, l, Ac1d Red289, C
, 1, Direct Black 51, etc.

Further, in the present invention, a wetting agent that is liquid at room temperature is used. Specific examples of the humectant include polyhydric alcohols such as Eva, diethylene glycol, triethylene dalicol, polyethylene glycol Luna 3001 glycerin, propylene glycol, etc. Alkyl ethers of polyhydric alcohols and their acetate esters, such as ethylene glycol Monomethyl ether, diethylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, tripropylene glycol methyl ether, etc.; hydroxyalkylformamides, for example, hydroxyalkylformamides in which the alkyl group has 1 to 4 carbon atoms: or JP-A-Sho N-vinyl-2- synthesized by the method described in No. 50-102407, etc.
Pyrrolidone oligomer etc. are used.

These humectants can be used alone or in combination.

The aqueous jet ink composition of the present invention has the following formulation, for example. Water-soluble dye 0.1-15 weight, side agent 5-40 weight, hereditary water-soluble ultraviolet absorber 0.1-
10 weight ratio, hereditary water-soluble quenching substance 0.1 to 5 weight ratio hereditary water.

The aqueous jet ink composition of the present invention as described above includes:
From the practical point of view of use in the inkjet system, it is preferable that the viscosity be within the range of 1.2 to 30 centipoise and the nonvolatile property to be less than 50 centipoise.Furthermore, the pH etc. of the ink can be varied over a wide range, but the quenching Since precipitation may occur depending on the type of substance and the pH, it is preferable to adjust the amount appropriately before use. For example, copper sulfate has a pH of about 4 or less, or an ammonia solution has a pH of
It is preferable to use it by adjusting it to 5 or more.

The aqueous jet ink composition of the present invention may further contain a water-soluble solvent, such as dioxane, acetone, diacetone alcohol, alkyl alcohol having 1 to 3 carbon atoms, dimethylformamide, dimethylsulfocarbonate, etc., as necessary. One or more types of zide, N-methyl-2-pyrrolidone, etc. may be used.

If necessary, additional surface tension modifiers include cationic surfactants, such as sodium alkyl sulfates; anionic surfactants, such as alkyl giridine sulfates; and nonionic surfactants, such as polyoxyethylene. Alkyl ethers, etc.; or zwitterionic activators may also be used.

Furthermore, if necessary, hydroxyglobil cellulose,
Viscosity modifiers such as carboxymethyl cellulose, hydroxyethyl cellulose, polyvinyl alcohol; sodium dehydroacetate, 1,2-benzinthiazoline-6-
Amine salt of 6-acetoxy-2,4-dimethyl-
It can also be done by adding a small amount of a fungicide such as m-dioxane or a preservative.

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

The aqueous jet ink composition of the present invention thus obtained completely satisfies the requirements and performance of the inkjet system, such as prevention of nozzle clogging. Moreover, the light resistance of the recorded material can be significantly improved. In addition, it is possible to expand the so-called range of selection by using various water-soluble dyes.

In addition to 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 1 to 11 Ink raw materials' in various proportions as shown in Table 1.
eThe mixture was stirred and mixed for 0.5 hours or more to dissolve each raw material in water.

The mixture was then filtered under pressure using a 1.2μ membrane filter manufactured by Millipore Co., Ltd. to obtain an aqueous jet ink composition.

These aqueous jet ink compositions were then continuously recorded using an on-demand type inkjet printer, and the recording state after 100 hours, the print quality of the recorded matter, and the continuous jetting stability were evaluated. Regarding light resistance, a xenon fade meter [Suga Test Instruments Co., Ltd.]
irradiated the recorded matter for a predetermined time (irradiation energy 46
4 joules/Crn2・hr), use a reflection densitometer (RD91s manufactured by Macbeth) to determine the initial value (100
The degree of fading was compared based on the ratio of optical density to ). The results obtained are shown in Table 1.

Comparative Examples 1 to 2 Water-based jet ink compositions were prepared by using the compositions shown in Table 1, which are conventionally thought to have good light resistance, in the same manner as in the above examples. The resulting composition was tested for continuous jet stability and light resistance in the same manner as in the Examples.

As is clear from the results in Table 1 above, the jet ink composition of the present invention has good continuous jetting stability without any loss of jetting characteristics in the inkjet system, and also has remarkable light resistance of recorded materials. Are better.

544-

Claims (5)

[Claims] (1) A jet ink composition containing a water-soluble dye, a wetting agent, and water as main components, and further comprising at least one water-soluble ultraviolet absorber and at least one water-soluble quencher. . (2) The water-soluble ultraviolet absorber has the following structural formula (I)
The jet ink composition according to claim 1, which is an ultraviolet absorber represented by (■) alone or in a mixture thereof. 5O3H (or Na) (3) The jet ink composition according to claim (1), wherein the water-soluble ultraviolet absorber contains 0.1 to 10% gold by weight in the jet ink composition. (4) A patent claim in which the water-soluble quenching substance is at least one selected from potassium iodide, potassium bromide, potassium thiocyanate, cobalt sulfate, steel sulfate, ferrous sulfate, nickel sulfate, and nickel oxalate. The range of (
The jet ink composition described in item 1). (5) The water-soluble quenching substance is contained in the jet ink composition in an amount of 0.1 to 5% by weight.
The jet ink composition described in item 1).