STN TYPE LIQUID CRYSTAL DISPLAY DEVICE

• Main Author: SHINDO YOSHIKUNI
• Format: Patent
• Language: English
• Published: 31.03.2000
• Edition: 7
• Subjects: ADVERTISING; ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICESUSING STATIC MEANS TO PRESENT VARIABLE INFORMATION; CRYPTOGRAPHY; DEVICES OR ARRANGEMENTS, THE OPTICAL OPERATION OF WHICH ISMODIFIED BY CHANGING THE OPTICAL PROPERTIES OF THE MEDIUM OF THEDEVICES OR ARRANGEMENTS FOR THE CONTROL OF THE INTENSITY,COLOUR, PHASE, POLARISATION OR DIRECTION OF LIGHT, e.g.SWITCHING, GATING, MODULATING OR DEMODULATING; DISPLAY; EDUCATION; FREQUENCY-CHANGING; NON-LINEAR OPTICS; OPTICAL ANALOGUE/DIGITAL CONVERTERS; OPTICAL LOGIC ELEMENTS; OPTICS; PHYSICS; SEALS; TECHNIQUES OR PROCEDURES FOR THE OPERATION THEREOF

PROBLEM TO BE SOLVED: To provide an STN type liquid crystal display device wherein half-tone reproduction is possible and luminance between different pixels are constant at the time of half-tone reproduction although a PWM light control method is used, by bringing an ON-OFF frequency of each pixel for display and a pulse frequency for PWM into an interleave relation in which both frequencies does not interfere with each other. SOLUTION: A cumulative adder 2 generates a signal P1 of a frequency (n$11)/(2×n) times as many as a frame frequency fV when the number of frames necessary for a half-tone display. A pulse generator 3 outputs 1-bit signal P2. A width (a duty ratio of L-level to H-level) of the signal P2 is set externally. A light quantity of a vacuum fluorescent tube 7 is controlled by varying the pulse width (duty ratio) of this signal P2. And, light emission is controlled so that a half-tone display frequency and an ON-OFF frequency of the vacuum fluorescent tube have an interleave relation in which they do not interfere with each other and each pixel has fixed brightness at the time of half-tone reproduction.