Stock material or miscellaneous articles – Structurally defined web or sheet – Discontinuous or differential coating – impregnation or bond
Reexamination Certificate
1998-07-21
2002-01-15
Hess, Bruce H. (Department: 1774)
Stock material or miscellaneous articles
Structurally defined web or sheet
Discontinuous or differential coating, impregnation or bond
C427S372200, C428S304400
Reexamination Certificate
active
06338891
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to ink jet recording sheets used for printers or plotters utilizing the ink jet recording system. Particularly, it relates to ink jet recording sheets having a gloss of photographic papers which is highly demanded in color recording or to ink jet recording sheets high in transparency and usable as films for over-head projectors (OHP).
With recent remarkable progress of ink jet printers or plotters, full-color and highly minute images can be easily obtained. Accordingly, development of ink jet recording sheets other than the conventional woodfree papers and coated papers is desired earnestly.
Ink jet recording system performs recording of images or letters by ejecting ink droplets according to various principles and allowing them to adhere to recording sheets such as papers. Ink jet printers or plotters have the features that they are excellent in high-speed print-ability, produce little noise, are great in versatility of recording patterns and require no development-fixation step, and they are noticed in that complicated images can be accurately and rapidly formed. Recently, they have rapidly spread in various uses, especially, as devices for making hard copies of image information such as letters and figures produced by computers. Furthermore, multicolor recording can be easily performed by using a plurality of ink nozzles. The multicolor ink jetting systems are not inferior in the resulting records to the multicolor printing according to reprophotographic systems or printing according to color photographic systems. Moreover, when a small number of prints are to be produced, they can produce the prints more cheaply than the printing techniques or photographic techniques.
Lately, inexpensive ink jet printers are commercially available which can output highly minute images equal to the images obtained by the silver salt photographic system. Ink jet recording sheets can give images of the same quality as those produced by silver salt photographic systems while they are very cheap. Therefore, the ink jet recording sheets provide economically a great merit for users who must change frequently the display images such as advertising products or commercial samples which must have large areas. Moreover, recently, it becomes common to produce images on personal computers and correct color arrangement or layout with observing the printout. Such is utterly impossible according to the conventional silver salt photographic systems while such operation can be readily performed by the ink jet recording, which is one of the merits of the ink jet recording systems.
Thanks to these merits, ink jet printers or plotters have rapidly spread. As a result, demands for recording sheets are diversified, and, there are demanded recording sheets having excellent appearance of high surface gloss equal to silver salt color photographs and recording sheets of high transparency usable as films for OHP.
As for the recording sheets used for ink jet recording systems, efforts have been made from the side of apparatus or ink composition so that the general woodfree papers for printing or writing and coated papers can be used. However, with improvement in performances such as printing speed, minuteness of images, or full-color recording of ink jet recording apparatuses and with expansion of uses, ink jet recording sheets are also required to have the higher characteristics. These characteristics are as follows: ink dots have a high density and a light and clear color tone; ink is quickly absorbed into the recording sheets; even when an ink dot overlaps another ink dot, the ink does not flow or blot; ink dots do not diffuse in lateral direction more than needed; and ink dots have smooth and distinct perimeter lines. Especially, in the case of color recording, not only the single color recording of yellow, magenta, cyan, and black, but also overlaying recording of these colors are carried out, and the amount of ink adhering to the recording sheet is further increased and, hence, very high performances are required for the recording apparatuses.
Ink jet recording sheets using alumina hydrates are proposed as those which are high in ink absorption speed and enhanced in glossiness. That is, JP-A-5-32037, JP-A-6-297831, JP-A-7-76161, JP-A-7-232473, JP-A-7-232474, JP-A-7-232475, JP-A-9-30115, JP-A-9-86035, and JP-A-9-76628 disclose ink jet recording sheets comprise a support on which fine alumina sol is coated together with a water-soluble binder.
These ink jet recording sheets are much superior in ink absorption speed to those which use water-soluble polymer and others as an ink receiving layer and which are described in JP-A-57-38185, JP-A-60-168651 and JP-A-61-181679. However, in the case of these ink jet recording sheets which use alumina hydrates, ink is absorbed through voids between the particles, and, hence, coating amount of the ink receiving layer must be increased so as to ensure ink absorption capacity. However, increase of the coating amount of ink receiving layer makes difficult the production of recording sheets owing to increase of haze and occurrence of cracks in the coat.
Further problem of these ink jet recording sheets using alumina hydrates is that when they are stored for a long period of time in a file made of polyethylene, polypropylene or vinyl chloride resin or are allowed to contact with tapes, pastes, platen rubber rolls and others, the edge portions or the contact portions of the recording sheets yellow to considerably damage the appearance.
The reason for the yellowing is considered that the antioxidant contained in files of polyethylene or polypropylene, tape adhesives, pastes, and rubbers is adsorbed to the alumina hydrates of the ink receiving layer and oxidized on the recording sheet. Polyethylene and polypropylene often contain antioxidants having a phenol group in the molecule, such as butylhydroxytoluene. It is well known that if these phenolic antioxidants are oxidized to have a quinone structure, the yellowing occurs.
In order to overcome these problems, JP-A-6-286297, JP-A-6-316145 and JP-A-7-68920 disclose ink jet recording sheets having a porous ink receiving layer containing a chain polyvalent carboxylic acid, an organic acid having an aromatic nucleus, and a fluorescent brightener. All of them concern with improvement of discoloration due to long-term storing, but definite actions of these additives have not yet been clarified. Furthermore, if amount of these additives is too much, this causes deterioration of ink absorption and change of color tone in the printed portions, and, as a result, satisfactory color images cannot be obtained.
In addition, JP-A-7-314881 discloses an ink jet recording sheet having a porous ink receiving layer that contains at least one of urea derivatives, semicarbazide derivatives, carbohydrazide derivatives and hydrazine derivatives, and JP-A-7-314883 discloses an ink jet recording sheet having a porous ink receiving layer that contains at least one of thiourea derivatives, thiosemicarbazide derivatives and thiocarbohydrazide derivatives. They aim at improvement of discoloration caused by long-term storing, but these additives also result in deterioration of ink absorption and change of color of the printed portions if amount of them is too much, and no satisfactory color images can be obtained.
SUMMARY OF THE INVENTION
The object of the present invention is to provide an ink jet recording sheet which has excellent ink absorption speed and ink absorption capacity (hereinafter called together “ink absorption properties”), is high in surface gloss and transparency of ink receiving layer, shows no change of color tone in the printed portions and no discoloration (yellowing) of unprinted portions (background portions) with lapse of time, and produces clear color tone.
The object has been attained by the following means. That is, in an ink jet recording sheet which comprises a support and, provided thereon, an ink receiving layer containing a pseudo-boehmite alumina hydrate and a binder, high su
Ikeda Mitsuhiro
Kawasaki Katsuhiko
Uto Tetsuya
Grendzynski Michael E.
Hess Bruce H.
Mitsubishi Paper Mills Limited
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