Incremental printing of symbolic information – Ink jet – Medium and processing means
Reexamination Certificate
2000-08-30
2002-07-02
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Medium and processing means
C347S100000, C347S105000
Reexamination Certificate
active
06412940
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ink-jet recording method that ejects ink for recording an image, and an ink-jet printer.
2. Discussion of the Related Art
The so-called ink-jet type printer, which ejects liquid or molten solid ink via a nozzle, slit, porous film or the like onto paper, cloth, film or the like for recording, has various advantages, such as compactness, low price, quietness. These apparatuses falling into this type have been recently used widely, not only for monochromic printers printing high-quality letters or images on common paper, e.g., reporting paper and copy paper, but also for full-color printing, holding an important position in the area of printers. In particular, so-called piezo ink-jet type, which uses piezoelectric device, and thermal ink-jet type, which uses thermal energy to form ink droplets, have various advantages, e.g., high-speed printing and high resolution of the printed letters or the like.
The ink for ink-jet printers is mainly composed of a solvent, colorant, and one or more additives. It is required for such an ink to satisfy the following characteristics:
(1) The letters and images it gives are free of bleeding or fogging, and high in resolution, concentration and uniformity.
(2) It is not dried at the nozzle tip to prevent clogging there, and high in ink discharge response and stability.
(3) It is quickly dried on paper onto which it is ejected.
(4) It gives durable letters and images.
(5) It is stably stored for extended periods.
More recently, another requirement (6) has been added; it can diminish or control curling and cockling of the recording medium, more noted when common paper is printed. Curling means a phenomenon in which paper is rounded during or after printing, and cockling means partial creasing appearing during or after printing.
The curled media are difficult to put one on another, to expand into a sheet, and hence difficult to handle. On the other hand, cockling occurring during printing may cause friction between the ink-jet recording head and medium, possibly deteriorating image quality. Curling and cockling can cause more serious problems, when color graphics images, which are frequently solid-printed, are continuously printed at a high speed, e.g., around 5 ppm and especially 10 ppm or higher. They also prevent smooth printing on both sides. Therefore, diminishing or controlling curling and cockling of recording media is increasingly demanded.
One of the methods for controlling curling is use of a curling inhibitor, e.g., 1,3-diols, 1,3,5-triols and amino-1,3-diols, as disclosed by Japanese Patent Laid-Open No. 6-157955 (1994). This method, although controlling curling, is not highly satisfactory, because of several possible problems resulting from incorporation of a large quantity of the inhibitor in the ink, e.g., deteriorated image quality, nozzle clogging and decreased reliability of the printer.
Another technique proposed to control curling is treating a recording medium. Treating the medium enhances ink reliability and design freedom. For example, Japanese Patent Laid-Open No. 8-310111 (1996) discloses a method for providing a back coat layer on a recording medium opposite to the ink-receiving layer. Japanese Patent Laid-Open No. 9-234946 (1997) discloses a recording medium of common paper type, which limits irreversible shrinkage in the MD and CD directions, when relative humidity is changed. Japanese Patent Laid-Open No. 10-278413 (1998) discloses a method for limiting curl size extent on the coat layer and the opposite side. These conventional techniques do improve resistance of the medium to curling, although still to an insufficient extent, and are more insufficient with respect to improvement of resistance to cockling, image quality and resistance to water.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above circumstances and provides an ink-jet recording method and an ink-jet printer, which can diminish or control curling and cockling of a recording medium.
The present invention also provides an ink-jet recording method and an ink-jet printer, which can form a recorded image of high quality, resistance to water and drying capacity, while diminishing or controlling curling and cockling.
The inventors of the present invention have found, after having extensively studied, that the medium curls, when printed with 1,1,1-tris(hydroxylmethyl)propane, a monosaccharide, oligosaccharide or sugar alcohol alone, in a direction opposite to that observed when it is printed with water alone, and that the above-described objects can be achieved by applying the above effect to an ink-jet recording method and an ink-jet printer, reaching the present invention.
The ink-jet recording method of the present invention forms a recorded image on a recording medium containing at least one organic compound selected from the group consisting of 1,1,1-tris(hydroxylmethyl)propane, monosaccharides, oligosaccharides, and sugar alcohols with an ink composed of at least a colorant, water-soluble organic solvent, and water.
It is accepted that the curling and cockling phenomena are, in general, greatly affected by adsorption and evaporation of water in inter-cellulose void in paper. When printed with an aqueous ink, paper generally curls in the direction toward the printed face. However, paper curls in the opposite direction, when printed with any organic compound selected from 1,1,1-tris(hydroxylmethyl)propane, monosaccharides, oligosaccharides, and sugar alcohols alone (each of these compound is hereinafter referred to as a [specific organic compound]). This phenomenon is hereinafter referred to as [curling in the opposite direction].
It is therefore expected that a recording medium can be prevented from being curled or cockled, when it is incorporated beforehand with a specific organic compound, in accordance with teaching of the present invention, because the ink-caused curling effect and curling effect in the opposite direction by the specific organic compound offset each other. It is also expected, when paper is used as the recording medium, that a specific organic compound works to control curling and cockling of the printed medium by penetrating into the inter-cellulose voids to control adsorption and evaporation of water derived from the ink.
The ink-jet recording method of the present invention can control curling and cockling of the recording medium, particularly efficiently for full-color image recording, where images are printed over a wide area, frequently on almost entire surface, of the medium. It can also control curling and cockling of the medium even for monochromic printing, when solid images are printed over a certain area of the medium.
It is preferable that the above-described recording medium and ink are further incorporated with a cationic substance and an anionic substance, respectively, in order to further diminish or control curling and cockling of the medium. It is considered, although not fully substantiated, that incorporation of cationic and anionic substances promotes interactions between the medium and ink to adequately retard penetration of the ink into the medium and thereby to further diminish or control curling and cockling efficiently and effectively. Moreover, the ionic interactions between the medium and ink promote separation and agglomeration of the dye or pigment, further improving the quality and water resistance of the image.
The above-described cationic substance is preferably at least one selected from the group consisting of cationic surfactants, cationic polymers and multivalent metallic salts. The above-described anionic substance is preferably an aqueous dye having an anionic group, more preferably an anionic compound.
It is preferable that the recording medium for the present invention further contains fine, inorganic particles, preferably of silicon dioxide and/or calcium carbonate. Incorporation of the inorganic particles further improves medium drying capacity and image qua
Doi Takatsugu
Hashimoto Ken
Inoue Hiroshi
Yamashita Yoshiro
Barlow John
Fuji 'Xerox Co., Ltd.
Morgan & Lewis & Bockius, LLP
Shah M
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