一种可预测TFT-LCD垂直串扰水平的定量分析方法

电容耦合和TFT漏电引起的垂直串扰问题在高分辨率液晶显示器产品上变得较为突出,大大影响了产品良率。业内通常采用VESA 2.0标准利用窗口画面测试串扰水平,但目前还没有一种预测串扰水平的定量分析方法。本文从垂直串扰形成机理出发,提出了一种可预测垂直串扰水平的定量分析方法,可预测出不同模式产品垂直串扰最严重的画面,有利于我们更好地研究和分析产品的品质。首先,通过分析垂直串扰机理,得到了垂直串扰现象与源电压差之间的定性对应关系。然后,通过分析V-T曲线,得到窗口画面下的亮度变化与源电压差之间的定量关系|ΔL|=kα|ΔV|。通过PCB板上的输出节点可以得到各灰阶对应的正负源电压,依据灰阶画面对应的源电压找到V-T曲线上对应的点可求出对应的斜率k值,依据漏电机理可求出对应的源电压差值|ΔV|,|ΔV|变化不大时可认为漏电电压降系数α为定值,故可计算出不同灰阶背景画面在窗口画面影响下的亮度变化值|ΔL|,将|ΔL|除以V-T曲线上对应灰阶的亮度值即可得到串扰值,通过比较不同窗口画面的串扰计算值即可得出串扰最严重的画面。最后,采用VESA 2.0标准方法测试不同窗口画面下的垂直串扰水平,与此方法的计算结果进行比较,串扰变化趋势吻合较好,TN和ADS模式下的线性相关系数分别达0.98和0.93以上。结果表明,此方法可以用来定量地研究产品垂直串扰的问题。

Aquantitative analysis method for predicting vertical crosstalk level in TFT-LCD

The problem of vertical crosstalk caused by capacitive coupling and TFT leakage becomes particularly prominent in high-resolution TFT-LCD products, which greatly affects the yield of products. The industry usually uses VESA 2.0 standard to test crosstalk level by window patterns, but there is still no quantitative analysis method to predict crosstalk level. Based on the formation mechanism of vertical crosstalk. A quantitative analysis method for predicting the vertical crosstalk level was proposed in this paper, which can predict the most serious vertical crosstalk patterns of products with different display modes, and was conducive to better study and analyze the quality of products. Firstly, by analyzing the mechanism of vertical crosstalk, the qualitative correspondence between vertical crosstalk and source voltage difference was obtained. Secondly, by analyzing the V-T curve, the quantitative relationship between brightness variation|ΔL|under the window pattern and Source voltage difference|ΔV|can be obtained. The positive and negative source voltages corresponding to each gray level can be obtained through the output nodes on the PCB board. The corresponding points on the V-T curve can be found according to the corresponding source voltages of the gray level patterns and the corresponding slope k values can be obtained. According to the leakage mechanism, the corresponding source voltage difference|ΔV|can be calculated. If the leakage voltage drop coefficient is α, there is the formula:|ΔL|=kα|ΔV|. The crosstalk value can be obtained by dividing|ΔL|by the brightness value of corresponding gray scale on V-T curve. The most serious crosstalk pattern can be obtained by comparing the crosstalk calculation values of different window patterns. Finally, compared with the VESA 2.0 standard method to test the vertical crosstalk level under different window patterns, the crosstalk variation trend calculated by this method can be fit well. The linear correlation coefficients in TN and ADS modes are 0.98 and 0.93 respectively. The results show that this method can be used for quantitatively studing the vertical crosstalk of products.