METHOD OF PRODUCING AN OPTICALLY TRANSPARENT FILM

Abstract

The invention relates to a method of producing an optically transparent film, the method comprising the steps of: providing a ceramic material, wherein the ceramic material is transparent to light having a wavelength of from 380 nm to 1000 nm; and using electromagnetic radiation to adhere together at least some of the components of the ceramic material, wherein the electromagnetic radiation has a wavelength shorter than 450 nm.

Claims

1. A method of producing an optically transparent film, the method comprising the steps of: providing a ceramic material, wherein the ceramic material is transparent to light having a wavelength of from 380 nm to 1000 nm; and using electromagnetic radiation to adhere together at least some of the components of the ceramic material, wherein the electromagnetic radiation has a wavelength shorter than 450 nm.

2. A method as claimed in claim 1, wherein the electromagnetic radiation has a distribution of wavelengths shorter than 450 nm.

3. A method as claimed in claim 1, wherein the ceramic material comprises at least two components, the at least two components are one or more of a different size, a different shape and have a different chemical composition.

4. A method as claimed in claim 3, wherein the at least two components are at least substantially spherical.

5. A method as claimed in claim 4, wherein the at least two components are a different size, the diameter of a first component is 25 to 35% smaller than a second component.

6. A method as claimed in claim 1, wherein the at least some of the components of the ceramic material are oblate in shape.

7. A method as claimed in claim 1, wherein there is only a trace amount of the at least some of the components in the ceramic material.

8. A method as claimed in claim 1, wherein the ceramic material absorbs the electromagnetic radiation having a wavelength of shorter than 450 nm.

9. A method as claimed in claim 1, wherein the electromagnetic radiation used to adhere together at least some of the components of the ceramic material is pulsed electromagnetic radiation.

10. A method as claimed in claim 9, wherein the pulsed electromagnetic radiation is generated by a pulsed light discharge system.

11. A method as claimed in claim 1, wherein the electromagnetic radiation used to adhere together at least some of the components of the ceramic material has a wavelength of from 200 nm to 450 nm.

12. A method as claimed in claim 1, wherein the ceramic material is transparent to light having a wavelength of from 380 nm to 760 nm.

13. A method as claimed in claim 1, wherein the method further comprises providing a substrate, the method including the step of depositing the ceramic material on the substrate.

14. A method as claimed in claim 13, wherein the substrate is electrically non-conductive, the step of depositing the ceramic material on the substrate is done in ambient atmosphere.

15. A method as claimed in claim 1, wherein the method further includes the step of calculating the energy of the electromagnetic radiation needed to adhere together the at least some of the components of the ceramic material.

16. A method as claimed in claim 13, wherein when the at least some of the components of the ceramic material are adjacent to the substrate, the electromagnetic radiation adheres the at least some of the components to the substrate.

17. A method as claimed in claim 1, wherein the optically transparent film is part of an optoelectronic device, the optoelectronic device comprising a series of grooves wherein each groove of the series of grooves has a first and a second face and a cavity therebetween, the cavity is at least partially filled with a first semiconductor material, the first face coated with a conductor material and the second face coated with a second semiconductor material.

18. A method as claimed in claim 17, wherein the optically transparent film is from 100 to 400 nm thick.

19. A method as claimed in claim 14, wherein when the at least some of the components of the ceramic material are adjacent to the substrate, the electromagnetic radiation adheres the at least some of the components to the substrate.

20. A method as claimed in claim 14, wherein when the at least some of the components of the ceramic material are adjacent to the substrate, the electromagnetic radiation adheres the at least some of the components to the substrate.

Description

EXAMPLE 1

[0052] A nanoparticle ceramic material in the form of a paste comprising a mono-dispersion of manganese doped titanium dioxide nanoparticles in ethanol was ultrasonically agitated to obtain good dispersion. This was then applied with a Mayer rod to give a nominal 10-20 microns of coating onto a PET surface (also referred to as a substrate). Little or no reticulation was observed while the solution rapidly dried. The Mayer rod has a grooved surface so that a known volume of liquid coating material is left behind when the rod is drawn across a flat surface. The surface was treated with single pulses of electromagnetic radiation having a 200-1000 nm wavelength and lasting from 100 to 1000 microseconds, to adhere together some of the components of the nanoparticle ceramic paste material. The resultant film showed excellent adhesion and improved the gas barrier properties of the film for oxygen transmission rate (OTR). The control sample had an OTR of 38.8 cc/m.sup.2/day and the coated sample had an OTR of 5.6 cc/m.sup.2/day. The nanoparticle ceramic paste material was transparent to light having a wavelength of 360-760 nm.

EXAMPLE 2

[0053] Two samples were prepared, the first using a single component ceramic material of titanium dioxide stabilised in water and the second ceramic material using that same solution with the addition of 3% of ZnO and diluted with ethanol. The two resultant films would have different thicknesses due to the reduced solids content of the second film. However the second sample used different sizes of particles, the ratio of these particles being 3:1. The packing density of the particles was therefore improved. The resultant barrier properties of these films showed better gas barrier properties for the two component system over the thicker single component film. Barrier performance was therefore different. The first, thicker single component film had an OTR of 10.6 cc/m.sup.2/day and a moisture vapour transmission rate (MVTR) of 23.7 g/m.sup.3/day compared to the thinner two component film with an OTR of 4.66 cc/m.sup.2/day and a MVTR of 5.02 g/m.sup.3/day after similar treatment, as outlined above for example 1. This illustrates that the small addition of the second nanoparticle has had a beneficial effect, unexpectedly exceeding the properties that would be expected based on the thicker film. The otherwise 3-times thicker film due to solids weight was made to the same thickness as the two component film.

EXAMPLE 3

[0054] Samples of ceramic material were prepared using suspensions of manganese doped titanium dioxide nanoparticles of 50 nm size; silicon nanoparticles of 5-15 nm size; hollow silicon nanoparticles of 20 nm size; manganese doped zinc oxide of 50 nm size; zinc oxide of 20 nm size and vanadium doped zinc oxide of 30 nm size. All the materials were volumetrically mixed with 5 ml of ethanol and spray coated onto a carrier PET web. All samples were exposed to electromagnetic radiation to adhere together at least some of their components, wherein the electromagnetic radiation had a wavelength of 200-1000 nm. The silicon dioxide 5-15 nm particle size samples showed no reasonable adhesion when tape tested due to their very low absorption in the 200 to 450 nm wavelength range. Initial voltage pulses of below 500 volts with pulse durations of 1000 microseconds gave samples with little or no reasonable adhesion. Of the remaining samples all showed good results when exposed to pulses of 150% of the initial voltage pulse, that is 700-750 volts for 300 microsecond duration at a wavelength of 200-1000 nm.

[0055] The inventors of the present invention have appreciated that when increasing the voltage discharge in a xenon discharge lamp by 50%, the wavelength intensity below 450 nm is increased some 5 fold over that of the lower voltage pulse. So even with a reduction in pulse width of 70% the total delivered energy below 450 nm for the higher pulse is 150% that of the lower voltage pulse.

[0056] The voltages and pulse durations used are lamp and machine specific so will vary according to the system used.