Stock material or miscellaneous articles – Ink jet stock for printing – Plural ink receptive layers
Reexamination Certificate
2002-11-20
2004-08-31
Schwartz, Pamela R. (Department: 1774)
Stock material or miscellaneous articles
Ink jet stock for printing
Plural ink receptive layers
C428S032180, C428S032190, C428S032270, C428S032280, C428S032310, C428S032330, C428S032380
Reexamination Certificate
active
06783817
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ink jet recording sheet. More particularly the present invention relates to an ink jet recording sheet having an ink receiving layer coated on a substrate with high adhesion, having a recording surface with a high gloss and capable of recording thereon ink images having a high clarity with a high ink drying property.
2. Description of the Related Art
In an ink jet recording system, desired ink images are recorded on a recording sheet by jetting imagewise fine drops of an ink from an ink jetting nozzle toward a recording surface of the recording sheet to cause the jetted ink drops to be absorbed imagewise in the recording sheet. Printers using the ink jet recording system are appropriately utilized for color printing and are advantageous in that the sizes of the printers are small and the prices of the printers are lower than that of printers using other recording systems.
Currently, since the performances of personal computers have significantly improved and multimedia functions have become widespread, a demand for printing documents including colored images or colored photographs in office or home has been promoted. For this demand, color printer using the ink jet recording system are considered to be very useful output printers.
As a conventional recording sheet usable for the ink jet recording system, a recording sheet produced by coating a surface of a substrate paper sheet with an ink-absorbing resin, or a mixture of a pigment selected from various types of pigments with a water-soluble resin or latex resin, to form an ink receiving layer, and optionally smoothing the surface of the ink receiving layer by, for example, a supercalender treatment, is employed. The conventional recording sheet is, however, disadvantageous in that since the surface of substrate paper sheet is rough due to the pulp fibers located in the surface portion of the sheet, and has an unsatisfactory smoothness, the resultant recording sheet exhibits an insufficient gloss. Also, when the conventional recording sheet is subjected to an ink jet recording procedure, the ink-absorbed portions of the printed sheet expand and thus the printed sheet is roughened and wavy.
In view of the poor performance of the substrate paper sheet, a polyolefin-coated sheet in which both the surfaces of a base paper sheet are coated with a polyolefin resin, for example, as polyethylene resin, or a plastic resin film, for example, a polyester film is employed in place of the paper sheet, as a substrate sheet for the ink jet recording sheet. As reported in Japanese Unexamined Patent Publications No. 4-216,990 and No. 7-32,723, when this type of the substrate sheet is coated with an ink receiving layer, the resultant ink jet recording sheet is evaluated at a certain high level.
Namely, the polyolefin-laminated substrate sheet or the plastic resin film has a high smoothness and thus the resultant ink jet recording sheet exhibits a high gloss.
However, since the polyolefin-laminating layer or the polyester resin film are hydrophobic, generally, the resultant hydrophobic substrate sheet has a surface having a poor affinity to the ink receiving layer and thus when an aqueous coating liquid for the ink receiving layer is applied onto the hydrophobic surface of the substrate sheet, a repelling phenomenon, for the coating liquid, occurs on the substrate sheet surface to form coating defects in the resultant ink receiving layer, or the resultant ink receiving layer exhibits a poor adhesion to the substrate sheet.
To prevent the above-mentioned disadvantages, before the coating of the substrate sheet with the coating liquid for the ink receiving layer, a surface-activating treatment, for example, a corona discharge treatment, is applied to the substrate sheet surface, and an undercoat layer comprising a water-soluble resin, as a principle component, is formed on the substrate sheet. These pre-treatments are not satisfactory for the ink jet recording sheet for practical use.
Accordingly, there is a strong demand for an ink jet recording sheet in which an ink receiving layer'is firmly bonded to a substrate consisting of a polyolefin-laminated paper sheet with a high adhesion.
When the polyolefin-laminated paper sheet is employed as a substrate sheet for an ink jet recording sheet, there is another disadvantage in that a curling phenomenon occurs.
Generally, the ink jet recording sheet for practical use must have a good appearance and must pass easily through a printer. To satisfy these requirements, the recording sheet preferably has a certain curling property. In the usual use environment, the recording sheet must be flat or be slightly curled in a convex shape. This form is referred to as a back-curling form. After printing, when the printed sheet is observed, if the front surface, namely, the ink receiving layer surface is curled in the form of a concave, which form is referred to as a top-curling form, observation is difficult and the appearance of the curled sheet is bad. Also, when the curled sheet in the top-curling form is attached at the back surface thereof on a wall surface, the edge portions of the sheet are spaced from the wall surface and cannot be stably attached to the wall surface. Also, when the ink jet recording sheets having a top-curling property are subjected to a printing procedure, the sheets cannot travel through the printer and cannot be accurately printed. Thus, the recording sheet must be in a flat form or in a slightly convexed form which form is referred to as a slightly.
The ink receiving layer usually expands or shrinks due to the change in temperature and humidity of the environment. Thus, even when a recording sheet exhibits a desired curling property under a specific environmental conditions, it may exhibit a high top-curling property under a low temperature low humidity condition, or a high back-curling property under a high temperature high humidity condition. These properties may cause the recording sheets to be difficult to use in practice.
The curling property can be reduced to a certain extent by increasing the thickness and the rigidity of the sheet. However, the thick recording sheets have a bad appearance and a high price and thus are not suitable for practical use.
Various attempts were made to obtain a desired curling properties. However, a desired ink jet recording sheet having both the high gloss and the desired curling property has not yet been obtained.
Japanese Unexamined Patent Publication No. 8-269,900 discloses a support for image-carrying material, which comprises a base sheet made from a paper sheet comprising as a principal component, a natural pulp, a film-forming resin layer covering a surface of the base sheet on which surface an image-forming layer is formed, and a polyolefin coating layer covering the opposite surface of the base sheet. The support is wound in the form of a roll. In this roll, the support is wound in such a manner that the image-forming layer becomes outside surface layer and the resultant roll is stored at a temperature of 20° C. or more. However, in this support, only the curling property is fixed by storing the polyolefin resin-coated sheet substrate at a specific temperature. Thus, even if a desired curling property is obtained in specific circumstances, when the circumstances change, it is difficult to restrict the resultant curling phenomenon.
Japanese Unexamined Patent Publication No. 6-171,206 discloses an ink jet recording sheet comprising a support with at least one type of ink receiving layer formed on a front surface of the surface and at least one back-coat layer formed on a back surface of the support. The recording sheet is characterized in that the backcoat layer comprises a pigment and a binder, as principal components, and the pigment has an average equilibrium moisture content of 1.9 to 5.5%. In this recording sheet, the support is formed from a paper sheet made from, as principal component materials, a wood pulp such as a chemical pulp, mechanical
Mukoyoshi Shun-ichiro
Nemoto Hiroyuki
Yasui Koichi
Arent & Fox PLLC
OJI Paper Co. Ltd.
Schwartz Pamela R.
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