Stock material or miscellaneous articles – Structurally defined web or sheet – Including variation in thickness
Reexamination Certificate
2001-09-14
2004-05-11
Cole, Elizabeth M. (Department: 1771)
Stock material or miscellaneous articles
Structurally defined web or sheet
Including variation in thickness
C428S198000, C442S395000, C442S394000, C442S398000
Reexamination Certificate
active
06733865
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a composite sheet comprising a nonwoven fabric formed from thermoplastic synthetic resin fibers and a plastic film formed from a thermoplastic synthetic resin and joined to one surface of the nonwoven fabric.
Japanese Patent Application Publication No. 1999-349702A discloses a porous sheet comprising a plastic sheet having a number of micro pores and partly embossed such that opaque regions having a total light transmittance of below 50% and transparent regions having a total light transmittance of 50% or above are formed in the sheet. In this porous sheet, the embossed portions define the transparent regions. The transparent regions account for 5-30% of a total area of the sheet. The sheet has a moisture permeability in the range of 0.8-4 g/100 cm
2
·h. This porous sheet, when used as a back sheet of a disposable wearable article such as a disposable diaper or sanitary napkin, is effective to reduce humidity and heat buildup within the wearable article and permits us to see the excrements, e.g., urine and feces, absorbed in the wearable article though the transparent regions from outside of the article.
However, in the porous sheet as disclosed in the above-identified reference, the total light transmittance of the opaque regions, exclusive of the embossed portions, is below 50% and is insufficient for us to see the excrements through the opaque regions. The porous sheet only allows us to see a part of the excrements through the transparent regions. The reference also discloses a composite sheet having a nonwoven fabric laminated to the above porous sheet. However, the presence of the nonwoven fabric reduces a total light transmittance of the composite sheet and accordingly even at the transparent regions of the porous sheet.
SUMMARY OF THE INVENTION
It is an object of this invention to provide a composite sheet which shows high total light transmittance and moisture permeability and which, when used as a back sheet of a disposable wearable article, allows us to see the excrements absorbed in the article through the sheet, without difficulty, from outside of the article.
According to the present invention, there is provided a composite sheet comprises a nonwoven fabric formed from a thermoplastic synthetic resin fibers and a plastic film formed from a thermoplastic synthetic resin and joined to one surface of the nonwoven fabric.
The composite sheet further comprises the film being a moisture permeable film formed from any of urethane-based, ester-based and amide-based thermoplastic elastomer resins, the film and nonwoven fabric each having a total light transmittance of not less than 70% and not greater than 95% when measured according to a Japanese Industrial Standards (hereinafter referred to as JIS) K 7105A method, the film being joined by fusion to synthetic resin fibers constituting the nonwoven fabric, and the composite sheet having a total light transmittance of not less than 60% and not greater than 95% when measured according to a JIS K 7105A method.
This invention encompasses the following embodiments.
(1) The aforementioned film has a number of protuberances arranged in an intermittent manner and protruding toward the nonwoven fabric and flat portions extending in a substantially planar manner between adjacent protuberances, with the protuberances being joined by fusion to synthetic resin fibers constituting the nonwoven fabric.
(2) The composite sheet has a moisture permeability of not less than 1,000 g/m
2
·24 Hr, when measured according to a JIS L 1099A-2 method.
(3) The composite sheet has a hydraulic pressure resistance of not less than 49 hpa, when measured according to a JIS L 1092A method.
(4) In a disposable wearable article which includes a liquid absorbent core interposed between a liquid permeable top sheet and a liquid impermeable back sheets, the composite sheet is used for the back sheet.
REFERENCES:
patent: 3575764 (1971-04-01), McFarren
patent: 08126663 (1996-05-01), None
patent: 11-349702 (1999-12-01), None
Cole Elizabeth M.
Lowe Hauptman & Gilman & Berner LLP
Uni-Charm Corporation
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