| EPSRC Reference: |
GR/J45404/01 |
| Title: |
SMALL AREA, HIGH DEFINITION, ELECTROLUMINESCENT DISPLAYS |
| Principal Investigator: |
Thomas, Professor C |
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| Department: |
Electronic & Electrical Engineering |
| Organisation: |
University of Bradford |
| Scheme: |
Standard Research (Pre-FEC) |
| Starts: |
01 October 1993 |
Ends: |
30 September 1995 |
Value (£): |
110,429
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Summary on Grant Application Form |
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A.C. operated thin film electroluminescent (TFEL) devices utilising, manganese doped, zinc sulphide (ZNS:Mn) provide the only flat-screen, light-emitting, displays with life-times in excess of ten thousand hours(1). Observed previously was that lateral emission is stronger than surface emission(2). Thus an objective of this programme is definition of a device structure to maximise lateral emission. A second objective is maximising the performance of the ZnS:Mn phosphor to minimise power consumption, hence facilitating mobile small area, high definition, electroluminescent displays.Progress:Use of lateral emission for displays is effected by reflection from micro-mirrors fabricated around each pixel(3). Theoretical analysis and experiments in progress indicate pixel sizes of approximately 32 -m square maximise the lateral emission. Such geometries correspond to resolutions just in excess of 600 pixels per inch, and therefore are ideally suited to high resolution head-mounted displays (H.M.Ds). For such pixel sizes measurement demonstrates that lateral emission makes a 75 % contribution to the total brightness, compared with only 25 % contribution from conventional surface emission. Improvement has been made also to the conventional ZnS:Mn layer by incorporating 'barrier-layers' of Y2O3 within the phosphor(4). Life-times of these 'barrier-layer' phosphors are identical with those of conventional ZnS:Mn(1), but with a 250% increase of brightness and concomitant reduction of charge flow. Both innovations have been combined to provide 'fixed-legend' demonstrators, corresponding to 600 d.p.i. resolution, with brightnesses of approximately 3000 F-L. Power consumption for 2 mm square H.M.Ds is <0.4W, facilitating mobile operation. Further innovation supported by EPSRC grantGR/KO4330 has seen a 25% improvement in brightness. Sufficient confidence exists in achieving 5000 FL - necessary for bright sunlight operation, that DTI-EPSRC Link funding is being sought to transfer the technology to U.K. Industry. Looking beyond the present programme, EPSRC grant GR/H80309 concluded by demonstrating integration of a TFEL device with a MOSFET driver(5). Hence an opto-electronic integrated display is feasible for H.M.D. applications. References1) L.E. Tannas: Flat-panel Displays & CRTs (Van Nostrand Reinhold N.Y. 1985).2) D.H. Smith, J. Lum. 23 (1981) 209. 3) L. Stevens, C.B. Thomas & W.M. Cranton, IEEE Electron Device Letters 15 (1994) 97.4) C.B. Thomas & W.M. Cranton, Appl. Phys. Letters 63 (1993) 3119. 5) C.B. Thomas, I.P. McClean, R. Stevens and W.M. Cranton, IEEE Electron Device Letters 15 (1994) 97.
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Key Findings |
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Potential use in non-academic contexts |
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Impacts |
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| Description |
This information can now be found on Gateway to Research (GtR) http://gtr.rcuk.ac.uk |
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Sectors submitted by the Researcher |
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This information can now be found on Gateway to Research (GtR) http://gtr.rcuk.ac.uk
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| Project URL: |
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| Further Information: |
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| Organisation Website: |
http://www.brad.ac.uk |