Method for Determining Internal LCD Temperature

• US 20100061423A1
• Filed: 09/05/2008
• Published: 03/11/2010
• Est. Priority Date: 09/05/2008
• Status: Active Grant

• Current Assignee: Mercury Mission Systems LLC (Mercury Systems, Incorporated)
• Original Assignee: American Panel Corporation (Mercury Systems, Incorporated)
• Inventors: Bartholmae, Jack
• Granted Patent: US 8,702,307 B2
• Time in Patent Office: Days
• US Class Current: 374/185
• CPC Class Codes: G02F 1/133382 Heating or cooling of liquid crystal cells other than for activation, e.g. circuits or arrangements for temperature control, stabilisation or uniform distribution over the cell

Abstract

Embodiments include a system and method for determining the temperature of the liquid crystal layer of a liquid crystal display. Because LCD performance is dependant on the temperature of the liquid crystal layer, performing particularly poorly in colder temperatures many LCD'"'"'s are available with integral heaters. Determining the temperature of the liquid crystal layer of an LCD is imperative for appropriate thermal management, which in turn leads to more-optimal LCD lifetime. Exemplary embodiments relate to accurately determining the temperature of the liquid crystal layer of an LCD by employing the integrated heater layer as a temperature sensor. When the relationship between the temperature of the integral heater is known, and the integral heater is disposed very near the liquid crystal layer, then determining the resistance of the metal heater layer, allows for rapid, accurate determination of the average temperature of the liquid crystal layer, and correspondingly better thermal management.

Claims

1. A method for accurately determining the temperature of liquid crystals in an electronic display comprising:

providing a metal heater layer integral to the TFT array layer of said electronic display;

providing a means for permanently storing a resistance measurement;

determining the relationship between the resistance and the temperature of the metal heater layer; and

measuring the resistance across the metal heater layer and using the known relationship between the temperature and the resistance of said metal heater layer to determine the temperature.

2. The method of claim 1, wherein said metal heater layer is patterned onto said TFT array layer.

3. The method of claim 2, wherein said metal heater layer is comprised of a grid of intersecting horizontal and vertical lines of a conductive material.

4. The method of claim 3, wherein the conductive material is ITO.

5. The method of claim 4, wherein the resistance of the metal heater layer is determined at the time of manufacture.

6. The method of claim 5 wherein the measured resistance value is correlated to the ambient temperature at the time of manufacture.

7. The method of claim 6, wherein the relationship between the measured resistance and the ambient temperature at the time of manufacture is stored in non-volatile memory.

8. The method of claim 7, wherein the relationship between the measured resistance and the ambient temperature at the time of manufacture is used to calibrate the temperature-to-resistance relationship for the electronic display.

9. The method of claim 1, wherein the power flow to the metal heater layer is kept on so long as the measured temperature is below a threshold value.

10. The method of claim 1, wherein when the measured temperature is above a threshold value;

power flow to the metal heater layer is turned off for a predetermined amount of time.

11. The method of claim 1, wherein when the measured temperature is below a threshold value;

power flow to the metal heater layer is increased in proportion to the difference between the actual temperature and the threshold temperature.

12. The method of claim 1, wherein the resistance value of the metal heater layer, determined at the time of manufacture, and the ambient temperature at the time of manufacture are correlated to establish an ordinal intersect for temperature determination.

13. The method of claim 12, wherein the value of the ordinal intersect is stored in non-volatile memory during assembly of the display.

14. The method of claim 13, wherein the resistance of the metal heater layer is determined after manufacture and, using the known relationship between the resistance and the temperature of the metal heater layer, determining the present temperature of the liquid crystal.

15. The method of claim 14, wherein the power flow to the metal heater layer is kept on so long as the measured temperature is below a threshold value.

16. The method of claim 15, wherein when the measured temperature is above a threshold value;

power flow to the metal heater layer is turned off for a predetermined amount of time.

17. The method of claim 14, wherein when the measured temperature is below a threshold value;

power flow to the metal heater layer is increased in proportion to the difference between the actual temperature and the threshold temperature.

18. A method for accurately determining the temperature of liquid crystals in an electronic display comprising:

providing a metal heater layer integral to the TFT array layer of said electronic display;

providing a means for permanently storing a resistance measurement;

determining the relationship between the resistance and the temperature of the metal heater layer;

measuring the resistance across the metal heater layer and using the known relationship between the temperature and the resistance of said metal heater layer to determine the temperature;

allowing the power to the metal heater layer to remain on so long as the temperature of the metal heater layer is below a threshold value; and

turning off the power to the metal heater layer when the temperature rises above a threshold value.