Incremental printing of symbolic information – Ink jet – Fluid or fluid source handling means
Reexamination Certificate
2001-09-27
2003-01-28
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Fluid or fluid source handling means
Reexamination Certificate
active
06511171
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an ink set for an ink-jet recording method and a recording method using the same.
BACKGROUND OF THE INVENTION
Of currently practiced ink-jet recording methods, commonly adopted method is a method employing a pale color ink for printing low density areas and a dark color ink for printing high density areas in order to reproduce smooth gradation of the printed images. When ink-jet ink droplets are ejected onto an image receptive layer, dots are formed. Subsequently, said ink droplets penetrate into the interior of said image receptive layer, and at the same time, said ink droplets spread over the surface of said image receptive layer whereby dots adjacent to each other spread while being partially united.
When the added amount of dyes is markedly different between the pale ink and the dark ink, the surface tension of the pale ink is frequently different from that of the dark ink, even though surface active agents in the same amount are added. The surface tension also varies depending on the type of dyes.
Further, when colorants penetrate deep into portions of said ink receptive layer, the optical density of images often decreases.
Accordingly, the dot diameter of each color ink varies over an elapse of time, and the depth distribution of colorants also varies, whereby color variation occurs.
When the spread of colorants of the pale ink becomes different from that of the dark ink over a long period of time, the gradation of high density areas formed employing the dark ink is not allowed to be continuous with that of low density areas formed employing the pale ink after an elapse of time.
Namely, when density variation between the low density areas and the high density areas is not balanced, the gradation is deteriorated over an elapse of time, whereby problems occur in which smooth gradation is not assured.
When ink comprised of water-soluble dyes is used, said problems are particularly exhibited.
Furthermore, when the density of each color varies at an almost equal rate, color variation is not exhibited. However, when the density of each color is not balanced, color variation is further exhibited.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an ink set capable of maintaining smooth gradation over an elapse of time after printing images, and also capable of maintaining color balance.
Said object can be achieved employing the embodiments described below.
1. An ink set for ink-jet recording, comprising:
a group of inks exhibiting the same hue and having different color densities and containing a colorant, water-soluble organic solvent and water,
wherein among the group of inks, an ink has a largest surface tension &sgr;1 and another ink has a smallest surface tension &sgr;2, and said &sgr;1 and said &sgr;2 satisfy the following conditional formula:
&sgr;2/&sgr;1>0.7, and
wherein at least one of the inks contains iron ions, magnesium ions, calcium ions such that a total amount of the iron ions, the magnesium ions and the calcium ions is not more than 10 ppm by weight.
2. The ink set of item 1, wherein the inks each contain the iron ions of 0.01 to 3 ppm by weight.
3. The ink set of item 1, wherein the inks each contain the magnesium ions of not more than 2 ppm by weight.
4. The ink set of item 1, wherein the inks each contain the magnesium ions of 0.01 to 2 ppm by weight.
5. The ink set of item 1, wherein the inks each contain the calcium ions of not more than 3 ppm by weight.
6. The ink set of item 1, wherein the inks each contain silicon of not more than 10 ppm by weight.
7. The ink set of item 1, wherein the inks each contain nickel of not more than 2.0 ppm by weight.
8. The ink set of item 1, wherein the ink each contain barium of not more than 2.0 ppm by weight.
9. The ink set of item 1, wherein the inks each contain zinc of not more than 2.0 ppm by weight.
10. The ink set of item 1, wherein the inks each contain chromium of not more than 2.0 ppm by weight.
11. The ink set of item 1, wherein the inks each contain strontium of not more than 1.0 ppm by weight.
12. The ink set of item 1, wherein the inks each contain aluminum of not more than 5.0 ppm by weight.
13. The ink set of item 1, wherein the inks each contain zirconium of not more than 10 ppm by weight.
14. The ink set of item 1, wherein the inks each contain zirconium of not more than 2.0 ppm by weight.
15. The ink set of item 1, wherein the inks each contain manganese of not more than 2.0 ppm by weight.
16. The ink set of item 1, wherein an ink of the group of inks contains sodium ions of not more than 500 ppm by weight.
17. The ink set of item 1, wherein the inks each contain potassium ions of not more than 500 ppm by weight.
18. The ink set of item 1, wherein the inks each contain a complexing agent.
19. The ink set of item 1, wherein said &sgr;1 and said &sgr;2 satisfy the following conditional formula:
&sgr;2/&sgr;1>0.85.
20. The ink set of item 1, further comprising:
another group of inks exhibiting the same another hue and having different color densities and containing a colorant, water-soluble organic solvent and water,
wherein among all groups of inks, an ink has a largest surface tension (max and another ink has a smallest surface tension &sgr;min, and said &sgr;max and said &sgr;min satisfy the following conditional formula:
&sgr;min/&sgr;max>0.6.
21. The ink set of item 1, further comprising:
a second group of inks each ink of which has a different color density of the same second hue and contains a colorant, water-soluble organic solvent and water, the same second hue different from the same hue of the group of inks, and a third group of inks each ink of which has a different color density of the same third hue and contains a colorant, water-soluble organic solvent and water, the same third hue different from the same hue of the group of inks and the same second hue of the second group of inks, so that the ink set comprises seven different inks or more,
wherein among each of the second group of inks and the third group of inks, an ink has a largest surface tension &sgr;1 and another ink has a smallest surface tension &sgr;2, and said &sgr;1 and said &sgr;2 satisfy the following conditional formula:
&sgr;2/&sgr;1>0.7.
22. The ink set of item 19, further comprising:
a second group of inks each ink of which has a different color density of the same second hue and contains a colorant, water-soluble organic solvent and water, the same second hue different from the same hue of the group of inks, and a third group of inks each ink of which has a different color density of the same third hue and contains a colorant, water-soluble organic solvent and water, the same third hue different from the same hue of the group of inks and the same second hue of the second group of inks, so that the ink set comprises seven different inks or more,
wherein among each of the second group of inks and the third group of inks, an ink has a largest surface tension &sgr;1 and another ink has a smallest surface tension &sgr;2, and said &sgr;1 and said &sgr;2 satisfy the following conditional formula:
&sgr;2/&sgr;1>0.85.
23. The ink set of item 20, wherein at least two of the inks exhibit black color and have different color densities.
24. The ink set of item 1, wherein the inks each contain a dihydric alcohol of not less than 50% by weight of water-soluble organic solvents contained in said ink.
25. An ink-jet recording method comprising the step of: jetting an ink of the ink set of item 1 from an ink-jet head to an ink-jet recording media;
wherein the recording media comprises a support having thereon a porous ink receptive layer containing inorganic particles and a hydrophilic binder.
26. The ink-jet recording method of item 25, wherein the inorganic particles are made of silica.
27. The ink-jet recording method of item 26, wherein the the porous ink receptive layer contains voids having a diameter of 10 to 100 nm.
28. The ink-jet recording method of item 27, wherein the porous ink receptive layer contains a cationic fixing agent.
Kawashima Yasuhiko
Yoshizawa Tomomi
Barlow John
Brooke Michael S
Konica Corporation
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