Optical film exhibiting excellent blocking properties for ultraviolet light and polarizing plate including the same

Abstract

The invention provides an optical film including an ultraviolet light absorbent having a first peak with a maximum absorption coefficient of 0.07 to 0.10 phr-1 [mu]m-1 in a wavelength band of 290 to 320 nm and a second peak with a maximum absorption coefficient of 0.11 to 0.16 phr-1 [mu]m-1 in a wavelength band of 330 to 400 nm, an acrylic resin, and a hindered amine light stabilizer (HALS), and a polarizing plate including the same.

Description

technical field [0001] The present disclosure relates to an optical film having excellent ultraviolet blocking properties and a polarizing plate including the optical film, and in particular, to an optical film capable of effectively blocking ultraviolet rays in a wide wavelength band even when a small amount of ultraviolet absorbent is contained therein. And an optical film having a stable spectrum even when exposed to ultraviolet rays for a long time, and a polarizing plate using the same Background technique [0002] Polarizing plates currently used in image display units such as liquid crystal displays generally have a triacetyl cellulose film (hereinafter TAC film) contained therein as a protective film to protect the polyvinyl alcohol polarizer. However, the TAC film may not have a sufficient degree of heat resistance and moisture resistance, and thus there may be a problem that properties such as polarization degree or color of the polarizing plate may be deteriorated...

AI Technical Summary

Problems solved by technology

However, the TAC film may not have a sufficient degree of heat resistance and moisture resistance, and thus there may be a problem that properties such as polarization degree or color of the polarizing plate may be deteriorated due to deformation of the film when used under high temperature and high humidity conditions. reduce

However, the protective films containing ultraviolet absorbers proposed so far have a problem that the ultraviolet region that can be blocked is light rays that are limited to the wavelength band of 320 to 400 nm

[0004] In addition, in the acrylic optical films containing ultraviolet absorbers that have been proposed so far, it is necessary to add a large amount of ultraviolet absorbers to achieve an effective ultraviolet blocking effect, but when a large amount of ultraviolet absorbers are added, when the acrylic resin is squeezed Melting under the high temperature and pressure of the exit machine and suddenly cooling through the T die and the subsequent casting roll, the UV absorber decomposes and escapes from the film, so that the UV absorber adheres tightly to the casting roll, this migration phenomenon can become a serious problem in the production process of acrylic films, and as a result, the outer surface of the film may be of poor quality since the thermally decomposed UV absorber also adheres tightly to the film

In addition, ultraviolet absorbers have low molecular weight and low glass transition temperature, and therefore, when the amount of the ultraviolet absorber increases, the molecular weight and glass transition temperature of the acrylic film including this ultraviolet absorber also decrease, resulting in resistance to decrease in heat

[0005] However, when such acrylic optical films are exposed to ultraviolet rays for a long period of time, in the acrylic optical films containing ultraviolet absorbers proposed so far, the part containing the ultraviolet absorbers therein may be damaged by ultraviolet rays, resulting in free base, which results in light absorption in regions other than the region where the UV absorber first begins to absorb

As a result, the light transmission in some wavelength bands can be greatly reduced, causing the film to fade with yellowing with yellow spots

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