Polarizing plate and liquid crystal display apparatus

Abstract

An object of the present invention is to provide a thin polarizing plate exhibiting a high contrast ratio. A polarizing plate of the present invention includes: a polarizer; a first protective layer provided on one side of the polarizer; and a second protective layer provided on the other side of the polarizer, wherein the first protective layer has a function of separating incident light into two polarized light components perpendicular to each other, transmitting one polarized light component, and reflecting the other polarized light component. Such a polarizing plate can exhibit a high contrast ratio, for example, in the case of being used in a liquid crystal display apparatus.

1 . A polarizing plate, comprising: a polarizer; a first protective layer provided on one side of the polarizer; and a second protective layer provided on the other side of the polarizer,
 wherein the first protective layer has a function of separating incident light into two polarized light components perpendicular to each other, transmitting one polarized light component, and reflecting the other polarized light component.   
     
     
         2 . A polarizing plate according to  claim 1 , wherein a transmission axis direction of the polarizer and a transmission axis direction of the first protective layer are substantially parallel to each other. 
     
     
         3 . A polarizing plate according to  claim 1 , wherein the polarizer comprises a stretched film of a polyvinyl alcohol-based resin containing a dichroic pigment. 
     
     
         4 . A polarizing plate according to  claim 1 , wherein the polarizer comprises a solidified layer or a cured layer of an aligned lyotropic liquid crystal. 
     
     
         5 . A polarizing plate according to  claim 4 , wherein the lyotropic liquid crystal contains an azo-based pigment, an anthraquinone-based pigment, a perylene-based pigment, an indanthrone-based pigment, an imidazole-based pigment, or a mixture thereof. 
     
     
         6 . A polarizing plate according to  claim 1 , wherein the first protective layer comprises a laminate containing a thermoplastic resin layer (A) and a thermoplastic resin layer (B). 
     
     
         7 . A polarizing plate according to  claim 1 , wherein the first protective layer comprises the thermoplastic resin layer (A) and the thermoplastic resin layer (B) provided alternately. 
     
     
         8 . A polarizing plate according to  claim 6 , wherein the thermoplastic resin layer (A) substantially exhibits anisotropy, and the thermoplastic resin layer (B) substantially exhibits isotropy. 
     
     
         9 . A polarizing plate according to  claim 6 , wherein an in-plane birefringent index (Δn xy [590]) at a wavelength of 590 nm of the thermoplastic resin layer (A) is 0.05 or more. 
     
     
         10 . A polarizing plate according to  claim 6 , wherein a refractive index (ny A ) in a fast axis direction of the thermoplastic resin layer (A) and a refractive index (ny B ) in a fast axis direction of the thermoplastic resin layer (B) are substantially the same. 
     
     
         11 . A polarizing plate according to  claim 6 , wherein the thermoplastic resin layer (A) contains a polyethylene terephthalate-based resin, a polytrimethylene terephthalate-based resin, a polybutylene terephthalate-based resin, a polyethylene-naphthalate-based resin, a polybutylene naphthalate-based resin, or a mixture thereof. 
     
     
         12 . A polarizing plate according to  claim 6 , wherein the thermoplastic resin layer (B) contains a polystyrene-based resin, a polymethyl methacrylate-based resin, a polystyrene glycidyl methacrylate-based resin, or a mixture thereof. 
     
     
         13 . A polarizing plate according to  claim 1 , wherein an in-plane retardation value (Re[590]) at a wavelength of 590 nm of the second protective layer is 10 nm to 400 nm. 
     
     
         14 . A polarizing plate according to  claim 1 , wherein a thickness direction retardation value (Rth[590]) at a wavelength of 590 nm of the second protective layer is 10 nm to 800 nm. 
     
     
         15 . A polarizing plate according to  claim 1 , wherein the second protective layer contains at least one kind of resin selected from the group consisting of a cellulose-based resin, a norbornene-based resin, a polyimide-based resin, a polyester-based resin, and an acrylic resin. 
     
     
         16 . A polarizing plate according to  claim 1 , further comprising an adhesion layer on a side of the second protective layer opposite to a side having the polarizer. 
     
     
         17 . A polarizing plate according to  claim 16 , further comprising a retardation layer on a side of the second protective layer opposite to a side having the polarizer. 
     
     
         18 . A polarizing plate according to  claim 17 , wherein the retardation layer has a function of compensating a liquid crystal cell optically. 
     
     
         19 . A liquid crystal display apparatus comprising the polarizing plate according to  claim 1 .