Liquid Crystal Display Pixel Inspection via Shared Switching Transistors
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Solution Overview
Problem
Conventional liquid crystal display devices using two static random access memories (SRAMs) face challenges in downsizing pixels and accurately inspecting them due to issues with data rewriting on column data lines caused by accumulated electric charges, leading to incomplete charging and inaccurate data output.
Innovation Solution
A liquid crystal display device configuration where two adjacent pixels share a row scanning line, each equipped with a display element, a first switching unit, a signal holding unit, and a second switching unit, allowing for separate data storage and inspection through alternating signal paths between column data lines, enabling accurate pixel inspection and downsizing by reducing the number of transistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If two SRAMs are used in each pixel for subframe driving, then gray scale display capability is improved, but pixel area increases and downsizing becomes difficult
Solution Approach 1:
Two adjacent pixels share a common second switching transistor that controls the connection between their respective first SRAMs and pixel electrodes. This shared switching element reduces the total transistor count per pixel from 4 to 3, enabling pixel downsizing while maintaining dual-SRAM gray scale display capability
Solution Approach 2:
The common second switching transistor serves multiple functions: it controls data output from both pixels during normal operation and enables inspection mode by connecting one pixel's SRAM to the other pixel's column data line for charge verification
2Productivity
If pixel inspection is performed using conventional methods, then manufacturing process continues, but data rewriting occurs due to accumulated electric charges on column data lines leading to inspection errors
Solution Approach 1:
Before inspection, the second switching transistor is turned on to precharge the inspection pixel's SRAM through the common switching element. This preliminary charging action ensures that accumulated charges on the column data line do not cause data rewriting during the actual inspection, maintaining measurement precision
Solution Approach 2:
One pixel acts as an intermediary inspection target for the other pixel. By inspecting pixel B through pixel A's column data line (or vice versa), the system verifies that no charge accumulation has occurred on the shared column data line, ensuring inspection accuracy
Data Source
AI summary
A liquid crystal display device includes an inspection control unit configured to alternately perform a first inspection operation in which an inspection signal is input from a first column data line connected to one pixel of the two pixels in each of the pairs into the one pixel and is read out to a second column data line connected to another pixel through the other pixel of the two pixels in each of the pairs and a second inspection operation in which an inspection signal is input from the second column data line into the other pixel and is read out to the first column data line through the one pixel, on all of the plurality of pixels in a unit of pixels in each row when the pixels being inspected.