Browse Prior Art Database

Addressing Liquid Crystal Displays

IP.com Disclosure Number: IPCOM000080959D
Original Publication Date: 1974-Mar-01
Included in the Prior Art Database: 2005-Feb-27
Document File: 2 page(s) / 47K

Publishing Venue

IBM

Related People

DasGupta, S: AUTHOR [+3]

Abstract

This method for matrix addressing of liquid crystal displays. eliminates the worst-case conditions inherent in conventional "1/2-select" or "1/3 select" schemes, viz, one or more unwanted cells turning on due to partial select, or selected cells turning off due to partial selection elsewhere.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 53% of the total text.

Page 1 of 2

Addressing Liquid Crystal Displays

This method for matrix addressing of liquid crystal displays. eliminates the worst-case conditions inherent in conventional "1/2-select" or "1/3 select" schemes, viz, one or more unwanted cells turning on due to partial select, or selected cells turning off due to partial selection elsewhere.

The reason behind a cell turning on in partial select mode can best be explained by defining two terms, viz, the AC threshold, V(ac), and the DC threshold, V(dc). H(ac) is the minimum voltage which when applied for a time duration, T, will turn the cell on. Evidently, V(ac) is a function of T, though its variation is not linear with respect to time. V(dc) is the minimum DC voltage that will turn on the cell. So, the reason why a cell in a partially selected column turns on is that the voltage across it, even though it is less than V(ac), is still larger than V(dc) and wide enough to look for all practical purposes like a DC voltage (dc). Hence, in the worst-case conditions in 1/2 or 1/3-select schemes, cells are likely to turn on even when not required or expected. However, in the scheme described here, this difficulty is overcome by using the concepts of V(ac) and V(dc). To address the matrix of Fig. 1, V(1) is applied to select a row and -V(2) or +V(2) on the column to turn the cell on or keep it off, respectively. V(1) and V(2) are defined as Absolute Value Of V(1) = Absolute Value Of V(ac) - Delta (1) Absolute Value Of V(2) Absolute Val...