Patent ID: 8383529

Claim:
A cellulose nonwoven fabric having a porosity of not less than 40% and not more than 99% which comprises not less than 50 wt % of cellulose fibers derived from natural cellulose having a maximum fiber diameter of 1,500 nm or less, a number average fiber diameter of 200 nm or less and a crystallinity determined by solid state NMR techniques of 60% or more wherein the nonwoven fabric has an average transmittance Tr,av of 0.70 or more, which is defined by the following formula (1) and determined by scanning a light with a wavelength of 850 nm perpendicularly to the nonwoven fabric immersed in toluene, (wherein Tr,av is defined by the following formula (1) with a ratio between Tr,1, an average value of transmittances obtained by filling toluene in a test tube in a condition that the nonwoven fabric is stuck to an inside wall thereof, irradiating a light with a wavelength of 850 nm to the test tube in a direction perpendicular to the nonwoven fabric, and scanning each 40-μm length along the test tube in a lengthwise direction thereof to the total length of 30,000 μm (number of data: 750), and Tr,2, an average value of transmittances obtained by performing the same measurements except that the nonwoven fabric is removed and only toluene is placed in the test tube) Tr,av=Tr, 1 /Tr, 2 (1), wherein the dried nonwoven fabric has a sheet non-uniformity parameter H′ of 0.20 or less, which is defined by the following formula (3): H′=T′r,sd/T′r,av (3) (wherein T′r,aV and T′r,sd, respectively, mean an average value and a standard deviation of all Tr values obtained by irradiating a light with a wavelength of 850 nm perpendicular to a dried sheet surface, and measuring Tr for each 40-μm length along the sheet surface in a linear direction thereof to the total length of 30,000 μm (number of data: 750)).