Low-birefringence substrate for touch sensor
View Patent ↗In one embodiment, an apparatus includes a substrate including material having a low birefringence. One or more electrodes of a touch sensor are disposed on the substrate.
1. An apparatus comprising:
a substrate comprising a material having a birefringence B that is less than approximately 1.5×10 −4 , wherein:
the birefringence of the material of the substrate is expressed as B=n 1 −n 2 ;
n 1 is a maximum refractive index of the material of the substrate, the maximum refractive index associated with a refractive index of the material of the substrate along a first axis; and
n 2 is a minimum refractive index of the material of the substrate, the minimum refractive index associated with a refractive index of the material of the substrate along a second axis; and
one or more electrodes of a touch sensor disposed on the substrate.
2. The apparatus of claim 1 , wherein the substrate is located above a display.
3. The apparatus of claim 1 , wherein the substrate material is cyclic olefin polymer, cyclic olefin copolymer, cyclic block copolymer, tri-acetate cellulose, or polyethersulfone.
4. The apparatus of claim 1 , wherein the substrate has a substantially uniform thickness that is between approximately 10 micrometers and approximately 200 micrometers.
5. The apparatus of claim 1 , wherein the substrate has a single-pass optical retardation of less than approximately 30 nanometers.
6. The apparatus of claim 1 , wherein the electrodes are made of a conductive mesh of conductive material.
7. The apparatus of claim 1 , wherein the substrate is located below a polarization layer.
8. The apparatus of claim 7 , wherein the polarization layer comprises a linear polarizer or a combination of the linear polarizer and a quarter-wave plate.
9. The apparatus of claim 1 , wherein:
the substrate comprises an upper surface and a lower surface;
one or more first ones of the electrodes are disposed on the upper surface of the substrate; and
one or more second ones of the electrodes are disposed on the lower surface of the substrate.
10. The apparatus of claim 1 , wherein:
the substrate comprises an upper surface and a lower surface; and
all the electrodes are disposed on the upper surface or the lower surface of the substrate.
11. The apparatus of claim 1 , wherein:
the apparatus comprises two substrates comprising the material having the birefringence B that is less than approximately 1.5×10 −4 ;
one or more of the electrodes are disposed on a surface of a first one of the substrates; and
one or more of the electrodes are disposed on a surface of a second one of the substrates.
12. The apparatus of claim 1 , further comprising an additional layer, other than the substrate on which the one or more electrodes of the touch sensor are disposed, that comprises a material having a birefringence B that is less than approximately 1.5×10 −4 , wherein:
the birefringence of the material of the additional layer is expressed as B=n 1 −n 2 ;
n 1 is a maximum refractive index of the material of the additional layer; and
n 2 is a minimum refractive index of the material of the additional layer.
13. A device comprising:
a substrate comprising a material having a birefringence B that is less than approximately 1.5×10 −4 , wherein:
the birefringence of the material of the substrate is expressed as B=n 1 −n 2 ;
n 1 is a maximum refractive index of the material of the substrate, the maximum refractive index associated with a refractive index of the material of the substrate along a first axis; and
n 2 is a minimum refractive index of the material of the substrate, the minimum refractive index associated with a refractive index of the material of the substrate along a second axis;
one or more electrodes of a touch sensor disposed on the substrate; and
one or more computer-readable non-transitory storage media embodying logic that is configured when executed to control the touch sensor.
14. The device of claim 13 , further comprising a display located below the substrate.
15. The device of claim 13 , wherein the substrate material is cyclic olefin polymer, cyclic olefin copolymer, cyclic block copolymer, tri-acetate cellulose, or polyethersulfone.
16. The device of claim 13 , wherein the substrate has a substantially uniform thickness that is between approximately 10 micrometers and approximately 200 micrometers.
17. The device of claim 13 , wherein the substrate has a single-pass optical retardation of less than approximately 30 nanometers.
18. The device of claim 13 , wherein the substrate is located below a polarization layer.
19. The device of claim 18 , wherein the polarization layer comprises a linear polarizer or a combination of the linear polarizer and a quarter-wave plate.
20. The device of claim 13 , further comprising an additional layer, other than the substrate on which the one or more electrodes of the touch sensor are disposed, that comprises a material having a birefringence B that is less than approximately 1.5×10 −4 , wherein:
the birefringence of the material of the additional layer is expressed as B=n 1 −n 2 ;
n 1 is a maximum refractive index of the material of the additional layer; and
n 2 is a minimum refractive index of the material of the additional layer.