Stock material or miscellaneous articles – Structurally defined web or sheet – Discontinuous or differential coating – impregnation or bond
Reexamination Certificate
1999-05-05
2002-09-24
Schwartz, Pamela R. (Department: 1774)
Stock material or miscellaneous articles
Structurally defined web or sheet
Discontinuous or differential coating, impregnation or bond
C428S500000, C428S910000
Reexamination Certificate
active
06455133
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a tearable ink imaging sheet and a method for producing the same, particularly to an ink imaging sheet which is excellent in ink absorption, ink fixation and print quality, easy tearable or shreddable by a shredder, and transparent enough to be used as a sheet for an overhead projector (OHP), and to a method for producing the same.
BACKGROUND OF THE INVENTION
The ink jet recording system has been popularized in recent years, because the system is well adaptable to full-color image reproduction, less noisy, and superior in print quality. From the standpoints of safety and recordability, water-based inks are mostly employed for ink jet recording in which droplets of an ink are ejected from a nozzle against a recording sheet for image recording. Therefore, the recording sheet is required to absorb the ink quickly. Thus, when a recording sheet of low ink absorption is used, the ink remains or stays long on the surface of the recording sheet even after completion of ink ejection so that the recorded image is easily smeared and stained on contact with the equipment, with the operator, or with recorded sheets piled on one another. Moreover, in the high-density image area, the ink supplied in a large quantity is not well absorbed but flows out to cause a blurred image.
In recent years, overhead projectors (OHP) that use plastic sheets as recording sheets, as their prices go down and they are downsized, have been introduced into various fields for, for instance, presentations, and many recorded images for use with OHPs have been simply formed using inkjet printers and the like. When images are re-corded on plastic sheets, the images suffer from being smeared and blurred on contact, even after the ink have been absorbed. Therefore, the sheets are required to have not only quick ink absorption but also a high ink fixing property.
Moreover, such plastic sheets (especially, sheets for OHPS) are required to have high transparency because of the necessity of light transmission. Besides, they are also required to be good in handling enough not to stick or block to each other even when piled on one after another, regardless of before being recorded or after having been recorded.
On the other hand, as recording methods, recording mediums, or recording materials has largely been improved and, consequently, high quality and low-priced printing devices has become available and easy-affordable, a large amount of recorded sheets are produced, thus raising the problem of disposal. Particularly, when discarding highly confidential recorded sheets, generally, cutting machines such as shredders are used. When using a shredder, good cutting quality can be expected if a recording material is one that is relatively easy to shred, such as paper. On the other hand, recorded matters of plastic sheets are inferior in cuttability to paper, and it is costly to discard them. Particularly, when inserted into a shredder in the form of a sheet, the sheet is jammed and therefore can not be shredded.
Moreover, as OHP sheets, sheets of polyester resin (e.g., polyethylene terephthalate) are usually used. However, since such sheets are tough themselves, it is difficult to cut them by hand or a machine.
Japanese Patent Application Laid-open No. 226233/1997 (JP-A-9-226233) discloses polyesters and polystyrenes as bases or supports and a process for producing an ink jet recording sheet by forming an ink absorbable layer on at least one side of such base.
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to provide tearable ink imaging sheets with high ink absorption and ink fixing property, and a method for producing the same.
It is another object of the present invention to provide ink imaging sheets that are highly transparent and inhibited from being stuck to each other even if they are stacked up one after another, and a method for producing the same.
The inventors of the present invention found that ink absorption, ink fixation and print quality of the ink imaging sheet can be improved by forming an ink imaging layer on at least one surface of a stretched styrenic resin sheet, with high transparency being maintained and largely improved tearability. The present invention was accom-plished based on the above findings.
Thus, the ink imaging sheet of the present invention is a sheet comprising an ink imaging layer formed on at least one surface of a base sheet, and the base sheet is constituted of a stretched styrenic resin sheet. The stretched styrenic resin sheet is tearable in longitudinal, lateral, and diagonal directions. The ink imaging layer may contain a hydrophilic polymer. The ink imaging layer may further comprise a particulate lubricant.
The present invention also includes a method for producing an ink imaging sheet which comprises forming the imaging layer on at least one surface of a stretched styrenic resin sheet.
In this specification, the term “hydrophilic polymer” means various polymers having an affinity for water, and includes absorbable polymers and water-soluble polymers. Moreover, in the specification, acrylic mono-mers and methacrylic monomers are generally referred to as (meth)acrylic monomer.
DETAILED DESCRIPTION OF THE INVENTION
The ink imaging sheet (i.e., a sheet for forming an ink-image) of the present invention comprises a base sheet and an ink imaging layer, and the base sheet is constituted of a stretched (or oriented) styrenic resin sheet. Such ink imaging sheet is useful as an ink jet recording sheet against which droplets of an ink are ejected for forming an ink image.
Base Sheet
Depending on the intended use, a stretched styrenic resin sheet for an ink imaging sheet may be opaque, semitransparent, translucent, or transparent, provided that its tearability is not adversely affected. The sheet is usually transparent when used for an overhead projector (OHP).
A styrenic resin constituting the styrenic resin sheet may be a homopolymer of an aromatic vinyl compound or a copolymer thereof, or a copolymer of an aromatic vinyl compound and a copolymerizable vinyl monomer.
As the aromatic vinyl compound, there may be mentioned, for example, styrene, alkylstyrenes (e.g., vinyltoluenes such as o-, m-, and p-methylstyrenes; p-ethylstyrene, p-isopropylstyrene, butylstyrene, p-t-butylstyrene), &agr;-alkylstyrenes (e.g., &agr;-methylstyrene), and halostyrenes (e.g., o-, m-, and p-chlorostyrene, p-bromostyrene). These aromatic vinyl monomers can be used independently or as a combination of two or more species. Styrene, vinyltoluenes, &agr;-methylstyrene are preferred as the styrenic monomer, and particularly preferred are styrene.
As the copolymerizable vinyl monomers, there may be mentioned, e.g., (meth)acrylonitrile, alkyl (meth)acrylates, vinyl ester-series monomers (e.g., vinyl acetate), hydroxyl group-containing monomers [hy-droxyl-C
1-4
alkyl (meth)acrylate such as hydroxylethyl (meth)acrylate, hydroxypropyl (meth)acrylate], glycidyl group-containing monomers [e.g., glycidyl (meth)acrylate], carboxyl group-containing monomers [e.g., methacrylic acid, maleic anhydride, fumaric acid], and imide-monomers (e.g., maleimide, N-methylmaleimide, N-phenylmaleimide). The alkyl (meth)acrylates include C
1-20
alkyl (meth)acrylates such as methy (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, t-butyl (meth)acrylate, hexyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and lauryl (meth)acrylate. These vinyl monomers can be used independently or as a combination of two or more species.
As a styrenic resin having high transparency, there may be mentioned, e.g., polystyrene, acrylonitrile-styrene copolymer (AS resin), styrene-(meth)acrylic acid copolymer, styrene-maleic anhydride copolymer, sty-rene-(meth)acrylate copolymers (e.g., styrene-methyl methacrylate copoymer), styrene-(meth)acrylate-(meth)acrylic acid copolymers (e.g., styrene-methyl methacrylate-(meth)acrylic acid copolymer), and styrene-(meth)acrylate-maleic anhydride copolymers (e.g., styrene-methyl metha
Furukawa Masayoshi
Notsu Kazuo
Daicel Chemical Industries Ltd.
Schwartz Pamela R.
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