Polysilicon Heater Circuit for Rapid LCD Warm-Up
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Solution Overview
Problem
Existing LCD technologies face inefficiencies in rapidly warming liquid crystal displays at low temperatures, with external heaters being inefficient and internal row-line heaters limiting usage during cold start conditions as they cannot display images during the heating phase.
Innovation Solution
An integrated polysilicon heater circuit is fabricated within the display active matrix using common voltage conductive lines to supply heat, allowing for rapid heating without interfering with display operations, eliminating the need for external heaters and enabling simultaneous temperature maintenance and video imagery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If an external heater is attached to the LCD cover glass, then heating is provided, but the heating efficiency is low and warm-up time is long
Solution Approach 1:
The patent extracts the heating function from the external heater and relocates it to the internal row-line heater integrated into the active matrix architecture. This internal placement eliminates the thermal resistance barrier of the cover glass, allowing direct heating of the liquid crystal material with significantly improved efficiency and faster warm-up time.
Solution Approach 2:
The patent transitions from a planar external heating approach (heating the cover glass surface) to a three-dimensional internal heating approach (heating the liquid crystal material directly within the pixel array). This dimensional change in heating location dramatically improves thermal coupling efficiency.
2Loss of energy
If a row-line heater is integrated into the active matrix, then heating efficiency is improved, but the display cannot show images during the heating phase
Solution Approach 1:
The patent segments the row-line heater into two distinct functional modes: a heating mode where current flows through the row lines to warm the liquid crystal, and a display mode where the same row lines are used for normal display operation. This segmentation allows the system to switch between heating and display functions without interference, resolving the contradiction between heating efficiency and display continuity.
Solution Approach 2:
The patent implements dynamic control of the row-line heater, allowing the system to transition from a static heating state to a dynamic display state. The heater can be activated or deactivated based on operational requirements, enabling the display to show images during normal operation while providing heating only when needed for cold start conditions.
3Temperature
If the row transistors saturate the row lines to heat them, then heating is achieved, but the warm-up time is extended
Solution Approach 1:
The patent applies preliminary action by pre-heating the liquid crystal material using the row-line heater before the display needs to operate. The heater can be activated in advance during cold start conditions to bring the liquid crystal to operating temperature, reducing the overall warm-up time. The system can also maintain temperature during normal operation to prevent cooling, ensuring rapid response when needed.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach provides efficient and independent heating, reducing costs and power consumption while allowing the LCD to operate and display images during the warming process, overcoming the limitations of previous technologies.
Implementation Method 1
Current can flow through the polysilicon row lines 10 to produce heat close to the pixel elements 20, and hence close to the LC material
Implementation Method 2
an external heater which is attached to the Thin Film Transistor/Indium Tin Oxide TFT/ITO cover glass following display fabrication. This approach provides maintenance heating by conducting current through the LCD cover glass
Data Source
AI summary
A heater, used in a Liquid Crystal Display (LCD) pixel array that uses a common voltage polysilicon line to supply heat to the pixel elements, instead of using active control transistor input lines, such as gate input lines. The approach permits the display to be activated during the warm-up process.