Ink for multicolor printing

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Industrial application field]

The present invention relates to printing in which liquid ink is applied to paper in which one or more colors are arranged adjacent to each other. Typically, the ink is applied as droplets from an inkjet printer. To obtain good color quality, the inks do not bleed side-by-side with each other on the paper.

【0002】

[Conventional technology]

In the present invention, in order to eliminate ink bleeding between different colors, 1,2-alkyldiols of C4 to C10 (that is, alkyls are formed of 4 to 10 carbon atoms; hereinafter, simply "C4". ~ C10 ") is mixed and used in general water-soluble ink. The use of alcohol in inks in this way is common practice, for example, U.S. Pat. No. 5,207,824 by Moffatt et al, No. 5,196,056 by Prasad, and Esano et al. It is described in et al), No. 5,196,057. However, they do not use C4-C10 1,2-alkyldiols. U.S. Pat. No. 5,165,968 by Johnson et al states that 1,2-pentanediol is unacceptable as an ink in the patent.

【0003】

U.S. Pat. No. 5,141,558 of Shirota et al. Teach the use of various thiols in such inks to improve bleeding resistance, dryness and permeability. U.S. Pat. No. 4,732,613 by Shiotani et al. Also teaches multicolor printing with inks as intended in the present invention, with some di- or tripropyl or higher alcohols. Are listed. However, although 1,2,6-hexanetriol is described, butane and higher alkanes 1,2-diol are not described.

【0004】

Moffat's US Pat. No. 5,116,409 teaches a mechanism for reducing bleeding by forming micelles with a surfactant. In the present invention, at least with respect to the diols C4 to C6, the formation of micelles is not utilized, as can be seen from the lack of sharp peaks in the surface tension with respect to the density plot of the ink of the present invention.

【0005】

[Problems to be Solved by the Invention]

The mechanism used in the present invention is permeation improvement. Primary alcohols such as n-propanol, n-butanol and n-pentanol increase permeability and thus eliminate bleeding. However, for example, when lower alcohols are used, these primary alcohols should not be used or should be used because the ink becomes flammable (flammable), has a foul odor, and becomes highly volatile. Not desirable. C4 to C10 1,2-diols have similar effects on permeability and thus bleeding, but are not flammable and can be used in inks without special precautions.

【0006】

[Means for solving problems]

The present invention uses at least two colors of water-soluble inks and applies them side by side on paper at the same time so that they are very close to each other. The ink contains at least about 0.1 to 12.5% by weight of 1,2-alkyldiol of C4 to C10, preferably about 2.5% by weight of 1,2-hexanediol. In general, in order to eliminate bleeding, the shorter the carbon chain of the diol, the higher the content ratio is required. As a result, the colors do not bleed and good multicolor image sharpness can be obtained.

【0007】

The use of any diol other than 1,2,6-hexanetriol or 1,2-diol does not provide as much effect as the bleed-reducing effect achieved with 1,2-diol. Moreover, even if the thiol of US Pat. No. 5,141,558 mentioned above is used, it is considered that the bleed reduction effect when 1,2-diol is used is not achieved.

【0008】

Furthermore, this 1,2-diol also has the feature of increasing the permeability of the ink and eliminating bleeding at a relatively low concentration, particularly less than 6% by weight. Common diols having an alcohol substituent at the carbon end, such as 1,4-butanediol and 1,5-pentanediol, do not effectively affect bleed control at a concentration of 10% by weight or less. 1,2,6-hexanetriol is also ineffective at 20% by weight, as discussed in detail below.

【0009】

[Example]

The liquid ink composition according to a preferred specific example of the present invention is as follows. ink Material Weight% Dye 2.5 EDTA (ethylenediaminetetraacetic acid, tetrasodium salt) 0.1 (Chelating agent) 1,2-Hexanediol 5.0 Triethylene glycol (wetting agent) 5.0 Proxel GXL (trade name, fungicide) 0.2 Sodium phosphate (buffer) 0.75 Water balance [0010]

This ink has the following characteristics. Surface tension: 36dyn / cm PH: 7.5 ~ 8.8 (varies depending on the dye) -Viscosity: 1.3cSt (25 ° C) (According to the present invention, high-viscosity inks also show sufficient action.

【0011】

Preferred dyes are:

[Chemical 1]

<img file="JPH07157698A_D0001.tif" />Magenta: (In the formula, M is H, Li, Na, K, -NH₄Is.

【0012】

Blue: Direct Blue 199: Direct Blue 199 is a sulfonized phthalocyanine copper dye sold by companies such as Zeneca Colors Inc.

【0013】

Yellow: Direct Yellow 132: Direct Yellow 132 is a sulfonized azo dye and is sold by companies such as Zeneca Colors Inc.

【0014】

However, the present invention is applicable to inks containing substantially any water-soluble dye.

【0015】

As a typical application example, four inks, that is, one containing a magenta dye, one containing a cyan dye, one containing a yellow dye, and one containing a black dye are used. Magenta, cyan, and yellow dyes are the primary colors of the subtractive color method and are applied on top of each other to create the colors contained in the entire visible spectrum. Black is used as an outrun or symbol. This ink can be applied to any standard inkjet printing. Preferred inks are prepared for thermal inkjet printing, the ink is heated to evaporate water and the water vapor is used as an accelerator (propellant). A preferred ink is a solution that does not contain particulate components. The paper used for the test is ordinary neutral cellulose paper, but the same effect can be obtained by using ordinary acidic or basic paper. These inks are printed adjacently and substantially simultaneously, but no bleeding occurs across the boundary between the two inks.

【0016】

A very similar substitution of this 1,2-hexanediol is 1,2-pentanediol. However, large amounts of 1,2-pentanediol are required to eliminate bleeding. The table below shows pentanediol and other substituents, and their usage levels (amounts).

【0017】

table Minimum level used 1,2-alkyldiol weight% 1,2-Butanediol 12.5 1,2-Pentanediol 7.5 1,2-Hexanediol 2.5 1,2-octanediol 1.0 1,2-decanediol 0.1 [0018]

The above levels are just indicators for reducing bleeding. It is also possible to use a combination of one or more diols to achieve even lower levels. The exact level required for bleed reduction depends on the printhead design, printer driver, and optimized media and environmental conditions. For example, reducing the volume of ink droplets on the printhead improves bleeding. In addition, the output color quality is also improved by such overlaying (singling; repeated overlay printing) and ink depletion (dots are scattered during printing) in the printer drive. In these cases, the diol may be at low levels.

【0019】

1,2-diols are not common. 1,2-diols are not included when higher alkanediols are described in the chemical literature without particular limitation. However, in fact, 1,2-diols are available in limited quantities in the United States.

【0020】

On the other hand, inks were prepared and tested in exactly the same manner as in the preferred specific examples described above, except that 1,2,6-hexanetriol was used instead of 1,2-hexanediol. The test was performed on 1,2,6-hexanetriol from 5% to 20% by weight and no significant reduction in bleeding was observed. On the other hand, as a matter of course, the same ink containing 1,2-hexanediol was substantially free of bleed at 5% by weight.

【0021】

Any modified composition can be adopted as long as 1,2-diol is used in this ink composition.

【0022】

[Effect of the invention]

As described above, according to the multicolor printing ink according to the present invention, it is not flammable, has no foul odor, is not highly volatile, and has excellent image sharpness.