Substrate with transparent electrodes and devices incorporating it

• US 20040238835A1
• Filed: 03/05/2004
• Published: 12/02/2004
• Est. Priority Date: 03/12/2003
• Status: Active Grant

• Current Assignee: The Swatch Group Research And Development Ltd
• Original Assignee: Asulab S. A.
• Inventors: Grupp, Joachim, Poli, Gian-Carlo, Hoffmann, Patrik, Wagner, Estelle, Baroni, Pierre-Yves
• Granted Patent: US 7,449,732 B2
• Time in Patent Office: Days
• US Class Current: 257/98
• CPC Class Codes: G06F 3/041 Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means

Abstract

The substrate with electrodes is formed of a transparent material onto which is deposited a film (1) of a transparent conductive material of thickness e₁ and of refractive index n₁, said film being structured to form a set of electrodes (1a) whose contours (8) delimit insulating spaces (3), wherein the insulating spaces (3) are filled with a transparent dielectric material of thickness e₂ and of refractive index n₂ so that the respective thicknesses of the conductive material and the dielectric material are inversely proportional to the values of the refractive indices of said materials and said dielectric material forms neither depressions nor beads at the contour (8) of the electrodes. A hardcoating layer (7) may be disposed between the substrate (5) and the electrodes and a protective film (9) added.

The substrate with electrodes is obtained by UV irradiation through a single mask.

Claims

1. A substrate with transparent electrodes and formed of a transparent material onto which is deposited a film of a transparent conductive material of thickness e₁ and of refractive index n₁, said film being structured to form a set of electrodes whose contours delimit insulating spaces, said electrodes having contact areas close to the edge of the substrate that can be connected to an electronic device, which substrate is characterised in that the insulating spaces are filled with a transparent dielectric material of thickness e₂ and of refractive index n₂ so that the respective thicknesses of the conductive material and the dielectric material are inversely proportional to the values of the refractive indices of said materials and said dielectric material forms neither depressions nor beads at the contour of the electrodes.

2. A substrate according to claim 1, wherein a layer of uniform thickness of an additional hard, transparent, non-conductive material is disposed between the substrate and the electrodes.

3. A substrate according to claim 2, wherein the hard intermediate layer consists of a resin incorporating SiO₂ and at least 20 μ

m thick.

4. A substrate according to claim 2, wherein the substrate is made from a plastics material selected from polymethylmethacrylate (PMMA) and polycarbonate (PC).

5. A substrate according to claim 1, wherein the electrodes and the dielectric material filling the insulating spaces are further covered with a protective film that may also have anti-reflection properties.

6. A substrate according to claim 5, wherein the protective film does not cover the contact areas of the electrodes.

7. A substrate according to claim 1, wherein the transparent conductive material forming the electrodes is a transparent conductive oxide (TCO) selected from indium and tin oxide (ITO), In₂O₃ and SnO₂ doped with Sb.

8. A substrate according to claim 1, wherein the dielectric material filling the spaces between the electrodes is a non-conductive transparent oxide (NCTO) selected from TiO₂ and SiO₂.

9. A substrate according to claim 1, wherein the thickness e₁ of the transparent conductive material is from 50 to 100 nm and preferably from 65 to 75 nm.

10. A substrate according to claim 1, wherein it constitutes a capacitive or resistive touch-sensitive screen for controlling the associated electronic device.

11. A substrate according to claim 1, wherein it constitutes at least one closure plate of a liquid crystal display cell or a photovoltaic cell associated with the electronic device.

12. A method of fabricating a substrate with transparent electrodes comprising a transparent substrate on which are structured electrodes of a transparent conductive oxide (TCO) of thickness e₁ and of refractive index n₁, the dielectric spaces between the electrodes being filled with a non-conductive transparent oxide (NCTO) of thickness e₂ and of refractive index n₂, which method is characterised in that it comprises the following steps:

placing the substrate, previously coated with a continuous film of TCO, possibly deposited onto an intermediate layer of a hard transparent material, in a closed enclosure having a window transparent to UV radiation, a gas inlet and an outlet from which said gas is pumped;

effecting a first irradiation by a UV source through the window of the enclosure and through a mask having portions transparent to UV radiation that correspond to the dielectric spaces, the characteristics of the UV radiation being adjusted as a function of the nature and the thickness of the TCO in order to eliminate it in the irradiated areas and form the dielectric spaces;

introducing a precursor gas of the NCTO into the enclosure and, using the same UV source and the same mask, effecting a second irradiation with the characteristics of the UV radiation adapted to the nature of the NCTO to produce a deposit of thickness e₂ in the dielectric spaces; and

pumping out the precursor gas and removing the substrate with transparent electrodes from the enclosure.

13. A method according to claim 12, wherein the fluence and the frequency of the first and second irradiations are adjusted so that the thicknesses of TCO and NCTO are inversely proportional to their refractive indices.

14. A method according to claim 12, wherein the precursor gas is introduced into the enclosure at the same time as a vector gas.

15. A method according to claim 12, wherein it includes an additional step of depositing a protective film, possibly having anti-reflection properties, from another precursor gas, using the same UV source but replacing the mask used to structure the electrodes with a mask corresponding to the required active surface of the substrate with transparent electrodes, leaving exposed the contact areas of the electrodes.

16. A method according to claim 12, wherein the UV source is a 248 nm excimer laser emitting short pulses or a 308 nm excimer laser emitting long pulses.

17. A method according to claim 12, wherein the TCO is selected from indium and tin oxide (ITO), In₂O₃, and SnO₂ doped with Sb.

18. A method according to claim 12, wherein the NCTO is selected from TiO₂ and SiO₂.

19. A method according to claim 18, wherein the TiO₂ is obtained from titanium tetraisopropoxide (TTIP) precursor gas.