A polyvinyl alcohol-based polarizing film is provided, and the polarizing film has excellent surface smoothness while the light transmittance and the polarization degree are improved due to the high stretch ratio. The polarizing film is obtained from a polyvinyl alcohol film having a thickness ranging from 85 .mu.m to 150 .mu.m by dyeing the film with a dichroic substance and stretching it to 4-7 times its original length. The polarizing film has a light transmittance ranging from 35% to 50% and a polarization degree of at least 80%, and the surface roughness in a direction perpendicular to the stretching axis is at most 0.04 .mu.m based on a centerline average roughness. A transparent protective layer or a transparent protective plate comprising the transparent protective layer is formed on at least one surface of the polarizing film in order to provide a polarizing plate. The transparent protective layer can be subject to a pre-treatment selected from a hard-coat treatment and an anti-glare treatment. Additional optical layers are laminated on the polarizing plate in order to provide an optical element. A polarizing plate or an optical element comprising the above-mentioned polarizing film has an excellent light transmittance and polarization degree, so that stripe-shaped streaks inhibiting visibility will not be observed substantially even in a reflection mode.

A polarizing plate and a liquid crystal display using the same are disclosed. The polarizing plate includes a polarizer made of a synthetic resin and protective films. The same protective films are attached to both sides of the polarizer. When a FTIR-ATR method is carried out with respect to the both sides of the protective film and a peak intensity (A) in the wavelength range around 1488 cm.sup.-1 of one side, a peak intensity (B) in the wavelength range around 1365 cm.sup.-1 of one side, a peak intensity (A') in the wavelength range around 1488 cm.sup.-1 of another side and a peak intensity (B') in the wavelength range around 1365 cm.sup.-1 of another side are measured, and (C) and (C') are represented by the relationships: (A)/(B)=(C) and (A')/(B')=(C'), (C)/(C').gtoreq.1.2 is satisfied. The same sides of the protective films having the (C) and (C') are adhered to both sides of the polarizer. In the polarizing plates, in accordance with the invention, even at the exposure to heat and humidity, advantageously occurrence of curling (warping) is reproduced.

A transparent protective film for polarizing plate being provided via an adhesive layer on at least one surface of a polarizer, wherein a ratio of constituent elements (oxygen ratio/carbon ratio) on the polarizer-adhering surface of the transparent protective film for polarizing plate, which is determined by X-ray photoelectron spectrometry, is larger than 0.75 has facilitate adhesion surface and no deformation without problems attributable to saponification.

The present invention relates to an optical sheet and a method of assembling a liquid crystal display module that is capable of preventing an inflow of impurities on a backlight unit, thereby minimizing screen staining caused by the impurities. An optical sheet installed between a liquid crystal display panel and a light guide member according to the present invention includes a transparent peeling sheet adhered to the front surface of the optical sheet facing the liquid crystal display panel; and a semitransparent peeling sheet stuck to the rear surface of the optical sheet facing the light guide member.

Disclosed is a cellulose ester film comprising a polymer prepared by polymerizing at least one ethylenically unsaturated monomer selected from vinyl esters, vinyl esters having a functional group, acrylic esters, and acrylic esters having a functional group, wherein the polymer has a weight average molecular weight of not more than 5,000.