Low basis weight inkjet printable substrates with lower showthrough and improved waterfastness and print density
An article in the form of a printable substrate having a showthrough value of about 0.14 or less, and an opacity value of at least about 88% which includes a paper substrate with a first and second surfaces formed of paper fibers having a basis weight of from about 12 to about 32 lbs/1300 ft 2 , and a substrate filler in an amount in the range of from 0 to about 30% by weight of the paper substrate; and a surface size layer on at least one of the first and second surfaces, the surface size layer having about 50 lbs or less per ton of the paper substrate of a starch surface sizing agent and a multivalent metal salt drying agent in an amount sufficient to impart to the at least one of the first and second surfaces a black print density value of at least about 0.8 when inkjet printed with pigmented inks and a waterfastness value of at least about 85% when inkjet printed with dye-based inks, the printable substrate having a MD tensile strength of at least about 12 lbs/in. and a CD tensile strength of at least about 6 lbs/in. Also, a method for preparing such a printable substrate.
1. An article comprising a printable substrate, the printable substrate comprising:
a paper substrate having a first surface and a second surface, a basis weight of from about 12 to about 32 lbs/1300 ft 2 , a showthrough value of about 0.14 or less, and an opacity value of at least about 88%, the paper substrate comprising:
paper fibers in an amount of from 60 to 100% by weight of the paper substrate; and
a substrate filler in an amount from 0 to about 30% by weight of the paper substrate; and
a surface size layer on at least one of the first and second surfaces, surface size layer comprising:
about 50 lbs or less per ton of the paper substrate of a starch surface sizing agent; and
a multivalent metal salt drying agent in an amount sufficient to impart to the at least one of the first and second surfaces a black print density value of at least about 0.8 when inkjet printed with pigmented inks and a waterfastness value of at least about 85% when inkjet printed with dye-based inks;
wherein the printable substrate has a MD tensile strength of at least about 12 lbs/in. and a CD tensile strength of at least about 6 lbs/in.
2. The article of claim 1 , wherein the surface size layer is on both the first and second surfaces.
3. The article of claim 1 , wherein the multivalent metal salt drying agent comprises calcium chloride.
4. The article of claim 1 , wherein the paper substrate has a basis weight of from about 15 to about 25 lbs/1300 ft 2 .
5. The article of claim 4 , wherein the paper substrate has a basis weight of from about 18 to about 20 lbs/1300 ft 2 .
6. The article of claim 1 , wherein the substrate filler comprises from about 10 to about 25% by weight of the paper substrate.
7. The article of claim 6 , wherein the substrate filler comprises from about 15 to about 20% by weight of the paper substrate.
8. The article of claim 6 , wherein the substrate filler comprises calcium carbonate.
9. The article of claim 6 , wherein the paper substrate further comprises a cationic starch binder in amount in the range of from about 0.05 to about 3% by weight of the paper substrate.
10. The article of claim 9 , wherein the paper substrate comprises the cationic starch binder in amount in the range of from about 0.1 to about 2% by weight of the paper substrate.
11. The article of claim 1 , wherein the surface size layer comprises about 25 lbs or less per ton of the paper substrate of a starch surface sizing agent.
12. The article of claim 11 , wherein the surface size layer comprises about 10 lbs or less per ton of the paper substrate of a starch surface sizing agent.
13. The article of claim 12 , wherein the surface size layer comprises from about 0.1 to about 10 lbs or less per ton of the paper substrate of a starch surface sizing agent.
14. The article of claim 13 , wherein the starch surface sizing agent comprises ethylated starch.
15. The article of claim 1 , wherein the opacity value of the printable substrate is at least about 90% and wherein the showthrough value is about 0.13 or less.
16. The article of claim 15 , wherein the opacity value of the printable substrate is at least about 92% and wherein the showthrough value is about 0.12 or less.
17. The article of claim 1 , wherein the amount of multivalent metal salt drying agent present in surface size layer is sufficient to impart a black print density value of at least about 1.2, and wherein the waterfastness value is at least about 90%.
18. The article of claim 1 , wherein the paper substrate comprises about 10 to about 40% by weight softwood fibers and from about 60 to about 90% by weight hardwood fibers.
19. The article of claim 1 , wherein the black print density value is at least about 1.0.
20. The article of claim 19 , wherein the black print density value is at least about 1.2.
21. The article of claim 1 , wherein the printable substrate has a MD tensile strength of from about 25 to about 35 lbs/in. and a CD tensile strength of from about 8 to about 12 lbs/in.
22. The article of claim 1 , wherein the paper substrate has an HST value of from about 5 to about 350 seconds.
23. The article of claim 22 , wherein the paper substrate has an HST value of from about 10 to about 100 seconds.
24. A method for preparing a printable substrate, which comprises the following steps:
(a) providing a paper substrate having a first surface and a second surface and having a basis weight of from about 12 to about 32 lbs/1300 ft 2 , the paper substrate comprising:
paper fibers in an amount in the range of from about 60 to 100% by weight of the paper substrate; and
a substrate filler in an amount in the range of from 0 to about 30% by weight of the paper substrate; and
(b) forming on at least one of the first and second surfaces a surface size layer to provide the printable substrate having a showthrough value of about 0.14 or less, and an opacity value of at least about 88%;
(c) wherein the surface size layer of step (b) comprises about 50 lbs or less per ton of the paper substrate of a starch surface sizing agent;
(d) wherein the surface size layer of step (b) comprises a multivalent metal salt drying agent in an amount sufficient to impart to the at least one of the first and second surfaces a black print density value of at least about 0.8 when inkjet printed with pigmented inks and a waterfastness value of at least about 85% when inkjet printed with dye-based inks;
(e) wherein the printable substrate of step (b) has a MD tensile strength of at least about 12 lbs/in. and a CD tensile strength of at least about 6 lbs/in.
25. The method of claim 24 , wherein a surface size layer is formed on both the first and second surfaces during step (b).
26. The method of claim 24 , wherein step (b) is carried out by applying a surface size composition comprising the multivalent metal salt drying agent and the optional starch surface sizing agent to at least one of the first and second surfaces with a size press to form the surface size layer.
27. The method claim 24 , wherein the size press is a rod metering size press.
28. The method of claim 24 , wherein the size press is flooded nip size press.
29. The method of claim 24 , wherein the substrate filler comprises from about 10 to about 25% by weight of the paper substrate of step (a).
30. The method of claim 29 , wherein the substrate filler comprises from about 15 to about 20% by weight of the paper substrate of step (a).
31. The method of claim 24 , wherein the substrate filler of step (a) comprises calcium carbonate.
32. The method of claim 24 , wherein the paper substrate of step (a) comprises cationic starch binder in the range of from about 0.05 to about 3% by weight of the paper substrate.
33. The method of claim 32 , wherein the paper substrate of step (a) comprises cationic starch binder in the range of from about 0.1 to about 2% by weight of the paper substrate.
34. The method of claim 24 , wherein the surface size layer formed during step (b) comprises from about 0.1 to about 10 lbs or less per ton of the paper substrate of a starch surface sizing agent.
35. The method of claim 24 , wherein the starch surface sizing agent comprises ethylated starch.
36. The method of claim 24 , wherein the paper substrate of step (a) comprises about 10 to about 40% by weight softwood fibers and from about 60 to about 90% by weight hardwood fibers.