Method for photolithography to manufacture a two-sided touch sensor
A touch sensor having conductive circuits on both surfaces of a substrate is fabricated by including UV-blocking material into the substrate or depositing UV-blocking layer on the substrate. This can be used for fabricating sensors having transparent conductor circuits, or having metallic circuits, which are opaque to visible light. Photoresist is applied to both surfaces of the substrate and patterns are transferred to the photoresist by exposure to UV radiation. The UV-blocking layer prevents UV-radiation applied to one side from exposing the opposite side. If desired, both photoresist layers may be exposed simultaneously by splitting one UV beam.
1. A method of manufacturing a touch sensor with conductive lines, comprising:
applying a UV-blocking layer to a first surface of a transparent substrate, the UV- blocking layer being opaque to UV radiation, the UV-blocking layer is formed by mixing at least one of: 2,2Methylenebis[6-(2 H-benzotriazol-2-yl -4(1,1,3,3-tetramethylbutyl)phenol],2,2′-pphenylenebis-4H-3,1-benzoxazin-4-one, and 2-(4,6-Bis-(2,4-dimethylphenyl)-1,3,5-triazin-2-yl)5-(octyloxy)-phenol, in a polymer binder solvent composition, wherein the polymer binder solvent composition is one of: acrylic, epoxy, urethane, or ester functional material;
applying a first photoresist layer over the UV-blocking layer;
applying a second photoresist layer over a second surface of the transparent substrate;
photo-patterning the first photoresist layer and the second photoresist layer using UV radiation;
developing the first photoresist layer and the second photoresist layer;
forming a first metal circuit over the first surface according to pattern formed by the first photoresist layer; and,
forming a second metal circuit over the second surface according to pattern formed by the second photoresist layer.
2. The method of claim 1 , wherein the UV-blocking layer is formed to be opaque in a region of the electromagnetic spectrum of from 315 to 400 nanometers.
3. The method of claim 1 , wherein the mixing comprises mixing from 0.01 to 4 percent by weight of UV-blocking material.
4. The method of claim 1 , wherein the mixing comprises mixing from 20% to 25% solids polymer and from 3% to 4% UV absorber material.
5. The method of claim 1 , wherein the first metal circuit and the second metal circuit are formed of a transparent conductor material.
6. The method of claim 1 , wherein the first metal circuit and the second metal circuit are formed of metallic conductor material that is opaque in the visible spectrum.
7. The method of claim 6 , wherein the first photoresist layer and the second photoresist layer comprise a catalytic photoresist having catalytic nanoparticles mixed in photoresist material.
8. The method of claim 7 , further comprising forming a standoff photoresist layer on the second surface of the transparent substrate prior to applying the second photoresist layer.
9. The method of claim 7 , further comprising forming a standoff photoresist layer on the UV-blocking layer prior to applying the first photoresist layer.
10. The method of claim 1 , wherein photo-patterning comprises simultaneously exposing the first photoresist layer and the second photoresist layer to UV radiation.
11. The method of claim 1 , wherein the UV-blocking layer is formed to have a thickness of at least 5 microns after draying.
12. A method of manufacturing a touch sensor with conductive lines, comprising:
forming a transparent substrate by mixing a UV-blocking material into a transparent substrate material, the UV-blocking layer being opaque to UV radiation, wherein the UV- blocking layer is formed by mixing at least one of: 2,2Methylenebis[6-(2H-benzotriazol-2-yl-4(1,1,3,3-tetramethylbutyl)phenol],2,2′-pphenylenebis-4H-3,1-benzoxazin-4-one, and 2-(4,6-Bis-(2,4-dimethylphenyl) -1,3,5-triazin-2-yl)5-(octyloxy)-phenol, in a polymer binder solvent composition, wherein the polymer binder solvent composition is one of: acrylic, epoxy, urethane, or ester functional material;
applying a first photoresist layer over a first surface of the transparent substrate;
applying a second photoresist layer over a second surface of the transparent substrate;
photo-patterning the first photoresist layer and the second photoresist layer using UV radiation;
developing the first photoresist layer and the second photoresist layer;
forming a first metal circuit over the first surface according to pattern formed by the first photoresist layer; and,
forming a second metal circuit over the second surface according to pattern formed by the second photoresist layer.
13. The method of claim 12 , wherein the transparent substrate material comprises one of: polyethylene terephthalate (“PET”), polyethylene naphthalate (“PEN”), cellulose acetate (“TAC”), cycloaliphatic hydrocarbons (“COP”), polymethylmethacrylates (“PMMA”), polyimide (“PI”), bi-axially-oriented polypropylene (“BOPP”).
14. A touch sensor for a touch screen, comprising:
a transparent substrate;
a UV-blocking layer on a first surface of the transparent substrate, wherein the UV- blocking layer is formed by mixing at least one of: 2,2Methylenebis[6-(2H-benzotriazol-2-yl-4(1,1,3,3-tetramethylbutyl)phenol],2,2′-pphenylenebis-4H -3,1-benzoxazin-4-one, and 2-(4,6-Bis-(2,4-dimethylphenyl)-1,3,5-triazin-2-yl)5-(octyloxy)-phenol, in a polymer binder solvent composition, wherein the polymer binder solvent composition is one of: acrylic, epoxy, urethane, or ester functional material;
a first conductive circuit over the first surface according to a first pattern; and,
a second conductive circuit over a second surface of the transparent substrate according to a second pattern different from the first pattern.
15. The touch sensor of claim 14 , wherein the first conductive circuit and the second conductive circuit comprise transparent conductor material.
16. The touch sensor of claim 14 , further comprising:
a first catalytic photoresist layer over the UV-blocking layer;
a second catalytic photoresist layer over the second surface of the transparent substrate;
wherein the first conductive circuit comprises metal deposited over the first catalytic photoresist layer, and the second conductive circuit comprises metal deposited over the second catalytic photoresist layer, wherein the metal is opaque to visible light.
17. The touch sensor of claim 14 , wherein the UV-blocking layer has a thickness of from 10 to 15 microns.