Incremental printing of symbolic information – Ink jet – Fluid or fluid source handling means
Reexamination Certificate
2000-09-21
2003-07-01
Gordon, Raquel Yvette (Department: 2853)
Incremental printing of symbolic information
Ink jet
Fluid or fluid source handling means
C347S101000, C347S105000
Reexamination Certificate
active
06585365
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to improved coatings for paper for ink jet printing applications and in particular, to coatings which enhance ink drying and produce higher quality printed images.
BACKGROUND OF THE INVENTION
Ink jet printing methods utilize printheads having orifices which eject ink droplets onto a print medium. For higher quality, higher resolution printing applications, the orifices of the printheads have been increased in number and their diameter significantly reduced in size. Accordingly, for full color printed images, inks are formulated to include dyes and/or pigments and various carriers and/or solvents which are resistant to drying or otherwise clogging the nozzle holes of the printhead. Such ink formulations, however often adversely affect the properties of the ink deposited on the print medium resulting in longer drying times and/or color mixing or bleeding of the images resulting in poorer quality images.
Various print media may be used for ink jet printing applications depending on the ink formulations. Such media include cellulosic webs, synthetic papers, polymeric films and the like. As advances in ink jet printing have occurred, specialty papers containing exotic coatings have been developed. Such specialty papers are often more expensive than uncoated papers and may contain coatings which are not compatible with the wide variety of ink formulations being used or developed for ink jet printing applications.
Despite the abundance of specialty webs for ink jet printing, cellulosic webs remain the most widely used print media. Cellulosic webs are made by conventional paper making techniques wherein a fibrous pulp is deposited on a wire screen and dried to form a web. Accordingly, the webs contain minute pores or voids between the cellulosic fibers for absorption of liquids therein. The porosity of the webs may be changed by use of specialty coatings such as clays and the like which may change the hydrophilic properties of the webs so that the webs absorb or repel aqueous and/or organic fluids which may be used as carrier fluids in ink formulations.
Ideally, it is desirable for only the carrier fluid of the ink formulation to penetrate into the web thereby depositing colorant on the outer surface of the web. Balancing the properties of the ink formulations so that the formulations are adaptable for use with a wide variety of print media is extremely difficult. It is even more difficult to provide ink formulations which may be used on uncoated or plain paper webs. Accordingly, a need exists for print medium which is adaptable to accept improved dye and/or pigment based ink formulations.
SUMMARY OF THE INVENTION
With regard to the above and other objects and advantages thereof, the invention provides a system for printing with an ink jet printer. The system includes an ink jet printer containing an ink jet pen and a paper coating device for coating a print media with an effective amount of coating composition prior to printing thereon. The coating composition preferably includes from about 0.25 to about 20% by weight of a first component selected from the group consisting of polyvalent metal salt and organic acid, a second component consisting of from about 1 to about 20% by weight amine polymer, from about 0.25 to about 2.0% by weight surfactant and from about 25 to about 96% by weight glycol-based solvent having a surface tension ranging from about 25 to below about 45 dynes/cm.
In another aspect the invention provides a method for improving print resolution of ink jet printed images. The method includes applying a coating composition to a cellulosic web to provide an ink receptive coating thereon and printing on the coated web prior to drying the coating composition. The preferred coating composition contains from about 0.25 to about 20% by weight of a first component selected from the group consisting of polyvalent metal salt and organic acid, a second component consisting of from about 1 to about 20% by weight amine polymer, from about 0.25 to about 2.0% by weight surfactant and from about 25 to about 96% by weight glycol-based solvent having a surface tension ranging from about 25 to below about 45 dynes/cm.
In yet another aspect the invention provides a cellulosic web containing ink and a penetrant promoter coating the coating being applied to the web prior to printing in an amount sufficient to reduce ink bleeding, promote ink drying and/or penetration of ink into the web. The promoter composition includes from about 0.25 to about 20% by weight of a first component selected from the group consisting of polyvalent metal salt and organic acid, a second component consisting of from about 1 to about 20% by weight amine polymer, from about 0.25 to about 2.0% by weight surfactant and from about 25 to about 96% by weight glycol-based solvent having a surface tension ranging from about 25 to about 45 dynes/cm.
The term “bleeding” as used herein refers to the unintended mixing of colors or wicking of ink colorant into the web rather than remaining on the surface of the web. Webs which are highly absorbent of the colorant tend to produce low resolution images because each ink dot tends to spread due to the affinity of the web fibers for the colorants in the ink. If the ink colorant penetrates too far into the web, too much light may be scattered by the interstices of the upper portion of the web resulting in a lower contrast image. Accordingly, it is desirable that only the ink carrier be absorbed into the web while the colorant remains substantially on the surface of the web.
An important advantage of the invention is that the paper coating composition is more environmentally friendly because of the inclusion of a glycol-based solvent having a surface tension ranging from about 25 to below about 45 dynes/cm. Solvents containing ethylene glycol-based solvents having a surface tension of about 45 dynes/cm or higher are less environmentally friendly than the glycol-based solvents according to the invention. An unexpected benefit of the use of glycol-based solvents having a surface tension ranging from about 25 to below about 45 dynes/cm is that paper coating compositions containing such solvents exhibit increased ink drying rates which enable higher print speeds as compared to other paper coating formulations.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Considering the need to provide enhanced drying of ink formulations in order to reduce or eliminate bleeding and/or ink smearing, the invention provides an improved method and composition for promoting drying of inks on plain paper webs. According to the invention, a formulation is provided for coating cellulosic webs, preferably immediately prior to printing, in order to promote ink drying and color fastness. The formulation is preferably an aqueous-based solution containing a fluid component which promotes increased penetration of the ink carrier into the web without promoting significant penetration of the colorant into the web.
A key component of the formulations according to the invention is a polyhydric alcohol selected from the group consisting of glycol-based solvents having a surface tension ranging from about 25 to below about 45 dynes/cm. Preferred glycol-based solvents of the invention include but are not limited to 1,2-propanediol, dipropylene glycol, tripropylene glycol, and mixtures of two or more of the foregoing provided the glycol-based solvents have a surface tension ranging from about 25 to below about 45 dynes/cm. Glycol-based solvents according to the invention, such as 1,2-Propanediol and di-propylene glycol are widely used in soaps and cosmetics and as such are relatively safer than ethylene glycol-based solvents.
The surface tensions of various glycol-based solvents are contained in the following table:
TABLE 1
Glycol Material
Surface tension in dynes/cm
Tripropylene glycol
34
Dipropylene glycol
37
Tetraethylene glycol
45
Triethylene glycol
47
1,3-propanediol
47
Diethylene glycol
48
Ethylene glycol
48
Polyethylene glycol 400
48
Glycerol
63
1,2-propanediol (propy
Daspit Jacqueline M.
Gordon Raquel Yvette
LaRose David E.
Lexmark International Inc.
Shah Manish
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