Curved Automatic-Darkening Filter

Abstract

An automatic-darkening filter 10, 10 ′ that comprises a first polarizer 14, a second polarizer 18, a first liquid-crystal cell 16, and a sensor 64. The first polarizer 14 has a first polarization direction, and the second polarizer 18 has a second polarization direction. The liquid crystal cell 16 is disposed between the first and second polarizers 14, 18 and contains first and second optically-transparent, flexible, glass layers 40 and 42 with the liquid crystal layer 48 being located between these layers. The sensor 64 detects incident light and causes a signal to be sent, which causes molecular rotation within the liquid crystal layer. The inventive automatic-darkening filter is beneficial in that overall product weight can be reduced and the view field can be increased.

What is claimed is: 
     
         1 . A switchable filter that comprises:
 (a) a first polarizer having a first polarization direction;   (b) a second polarizer having a second polarization direction, which may be the same or different from the first polarization direction; and   (c) a first liquid-crystal cell disposed between the first and second polarizers, the liquid crystal cell containing first and second optically-transparent flexible glass layers that are curved and that have a first liquid crystal layer located between them.   
     
     
         2 . The switchable filter of  claim 1 , wherein the switchable filter has a viewing area of at least 100 cm 2 . 
     
     
         3 . The switchable filter of  claim 1 , wherein the switchable filter has a viewing area of at least 125 cm 2 . 
     
     
         4 . The switchable filter of  claim 1 , further comprising a band pass filter that attenuates IR and UV wavelength components of incident light. 
     
     
         5 . The switchable filter of  claim 1 , wherein the thickness of the flexible glass layers is 10 to 200 micrometers. 
     
     
         6 . The switchable filter of  claim 1 , wherein the thickness of the flexible glass layers is 30 to 150 micrometers. 
     
     
         7 . The switchable filter of  claim 1 , wherein the thickness of the flexible glass layers is 75 to 125 micrometers. 
     
     
         8 . The switchable filter of  claim 1 , wherein the flexible glass layers have a curvature exhibiting a radius of 5 to 30 centimeters. 
     
     
         9 . The switchable filter of  claim 8 , wherein the flexible glass layers have a non-constant radius. 
     
     
         10 . The switchable filter of  claim 9 , wherein the flexible glass layers are parabolic, catenary, epicycloidal, or free form. 
     
     
         11 . The switchable filter of  claim 1 , wherein the flexible glass layers have inwardly facing surfaces that have transparent conductive electrode layers. 
     
     
         12 . The switchable filter of  claim 1 , wherein the curvature of the first and second flexible glass layers each have a radius of 7 to 20 centimeters. 
     
     
         13 . An automatic darkening filter that comprises the switchable filter of  claim 1  and further comprises:
 (d) a control circuitry; and 
 (e) a sensor that detects incident light and that causes a signal to be sent to the switchable filter via the control circuitry, which signal causes molecular rotation within the liquid crystal layer. 
 
     
     
         14 . The automatic darkening filter of  claim 13 , further comprising: a third polarizer having a third polarization direction, which may be the same or different from the first and second polarization direction; and a second liquid-crystal cell disposed between the second and third polarizers, the second liquid-crystal cell containing third and fourth optically-transparent curved, flexible glass layers and having a second liquid crystal layer being disposed between the third and fourth flexible glass layers. 
     
     
         15 . The automatic darkening filter of  claim 14 , wherein the third polarizer has a polarization direction similar to the first polarizer, and wherein the first liquid-crystal cell is a twisted, nematic, liquid-crystal cell. 
     
     
         16 . The automatic darkening filter of  claim 13 , wherein the first liquid-crystal cell contains nematic molecules and has a twist angle of 1 to 100 degrees. 
     
     
         17 . The automatic darkening filter of  claim 13 , wherein the first and second flexible glass layers of the first liquid-crystal cell have electrodes that provide an electric field between the first and second flexible glass layers in response to an activation signal, each of the first and second flexible glass layers have mutually facing surfaces that have an alignment layer that defines first and second alignment directions, respectively. 
     
     
         18 . The automatic darkening filter of  claim 13 , wherein the automatic darkening filter is configured in concave curved configuration, which is electrically switchable to a dark transmission state over substantially its entire area. 
     
     
         19 . The automatic darkening filter of  claim 13 , wherein the automatic darkening filter has a viewing area between 10 cm 2  and 600 cm 2 . 
     
     
         20 . The automatic darkening filter of  claim 19 , wherein the automatic darkening filter has a viewing area exceeding 125 cm 2 . 
     
     
         21 . The automatic darkening filter of  claim 13 , wherein the curvature of the first and second flexible glass layers has a radius of 5 to 20 centimeters. 
     
     
         22 . The automatic darkening filter of  claim 13 , wherein the automatic darkening filter has a curvature that is not a constant radius and is selected from the group consisting of parabolic, catenary, epicycloidal, and free form. 
     
     
         23 . The automatic darkening filter of  claim 13 , wherein the thickness of the first and second optically-transparent, flexible, glass layers is 10 to 200 μm. 
     
     
         24 . The automatic darkening filter of  claim 13 , wherein the thickness of the first and second optically-transparent, flexible, glass layers is 30 to 150 μm. 
     
     
         25 . The automatic darkening filter of  claim 13 , wherein the thickness of the first and second optically-transparent, flexible, glass layers is 75 to 125 μm. 
     
     
         26 . The automatic darkening filter of  claim 14 , wherein the first, second, third, and fourth optically-transparent, flexible, glass layers are assembled within a frame. 
     
     
         27 . A welding shield that comprises:
 a protective shell that has an opening into which the automatic-darkening filter of  claim 13  is disposed.   
     
     
         28 . The welding shield of  claim 27 , wherein the automatic-darkening filter has a curvature that has a radius of about 5 to 20 centimeters. 
     
     
         29 . Goggles that comprise the automatic darkening filter of  claim 13 .