In the below, by referring to
By referring to
The liquid crystal display device 10 is provided with an array substrate 12 and an opposing substrate 14, and between the substrates 12 and 14, a liquid crystal material (liquid crystal material of an OCB-mode) is sandwiched.
The array substrate 12 is made of glass, and is formed thereon with a plurality of signal lines 16 being orthogonal to a plurality of scanning lines 18. In the vicinity of intersection portions of the signal lines 16 and the scanning lines 18, a polysilicon-made thin-film transistor (hereinafter, referred to as TFT) 20 is each formed, and pixels are disposed in a matrix. The signal lines 16 are each connected to a source electrode of the TFT 20, and the scanning lines 18 are each connected to a gate electrode of the TFT 20. A drain electrode of the TFT 20 is connected to a pixel electrode.
To the signal lines 16, a liquid crystal drive voltage being a video signal is provided from a signal line driver circuit 22, and to the scanning lines 18, a gate signal is provided from a scanning line driver circuit 24 so that the TFTs 20 are driven.
The pixels in a matrix on the array substrate 12 each have a transition core portion for use to apply a transition voltage, which is a voltage for use for alignment transition of an OCB-mode liquid crystal material from splay to bend. This transition core portion is configured by an ITO (Indium Tin Oxide) configuring a pixel electrode, and has the same electric potential as that of the pixel electrode.
Alternatively, a pixel electrode may include an electrode for forming a storage capacity, and this electrode may be coupled to the scanning line 18 in the stage preceding thereto to derive capacitive coupling.
The signal line driver circuit 22 and the scanning line driver circuit 24 are under the control of a controller 26. This controller 26 is provided with a detection temperature signal related to the detection temperature of a digital temperature sensor 28. This temperature sensor 28 is attached onto a printed wiring board to which the controller 26 is attached.
By referring to
When the liquid crystal display device 10 is turned on, a transition circuit is operated in the signal line driver circuit 22. First of all, the temperature sensor 28 detects an environment temperature, and the resulting detection temperature signal is forwarded to the controller 26. The controller 26 determines a clock count for use for the pulse transition voltage, and based thereon, determines the wavelength length for the transition voltage, i.e., for first and latter pulses respectively (pulse width of each polarity). Based on the determination result, the voltage is changed for application to an opposing electrode of the opposing substrate 14.
The source voltage is driven in a range around 5V from −7V to +7V. The gate voltage is driven in a range from −6V to +12V. After a reset period of 0.4 seconds for setting both the opposing potential and the source potential to +5V to derive the pixel potential of 0V, the voltage of −20V is applied to the opposing electrode for 0.35 seconds as a first pulse of the transition voltage, and then the voltage of +30V is applied thereto for 0.25 seconds as a latter pulse of the transition voltage.
At this time, in this embodiment, the environment temperature is used as a basis to change the ratio of pulse width between the latter pulse and the first pulse, which have different polarities. That is, without changing the potential of the first pulse and that of the latter pulse, examined is the optimum waveform for the respective environment temperatures of causing no flicker after the waveform change due to alignment transition.
With the environment temperature of 0 degree centigrade, for example, no flicker is caused with the width of a first pulse being 0.65 seconds, the width of a latter pulse being 0.6 seconds, and the ratio of pulse width being 0.92. Also with the environment temperature of 30 degrees centigrade, for example, no flicker is caused with the width of a first pulse being 0.35 seconds, the width of a latter pulse being 0.25 seconds, and the ratio of pulse width being 0.71.
As such, through control exercise over the widths of the first and latter pulses based on an environment temperature, no flicker is caused with whichever environment temperature after the waveform change due to alignment transition.
Described next is another OCB-mode liquid crystal display device 10 in a second embodiment by referring to
In the first embodiment, the transition voltage is changed in ratio of pulse width between a first pulse and a latter pulse. In this embodiment, the ratio of pulse width remains the same with whichever environment temperature, and the ratio of pulse potential is changed. This is described by referring to the graph of
As the transition voltage, when the potential of a first pulse is −20V (potential difference of 25V from a reference potential) and a ratio of pulse width is 0.71 between the first pulse and a latter pulse, and when a ratio of potential difference is adjusted as shown in
Described next is the OCB-mode liquid crystal display device 10 in a third embodiment.
In the third embodiment, the occurrence of flicker can be prevented through control exercise, in accordance with an environment temperature, over an integral ratio in the transition voltage, i.e., between an integral value of a first pulse and that of a latter pulse. That is, a ratio is first determined between an area S1 of a first pulse and an area S2 of a latter pulse, and a setting is so made that the ratio is reduced in value with an increase of the environment temperature. For example, if the ratio S2/S1 is changed in a range from 0.5 to 1.5, the occurrence of flicker can be favorably prevented.
The present invention is not restrictive to the embodiments described above, and numerous other modifications and variations can be devised without departing from the scope of the invention.
Number | Date | Country | Kind |
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2006-165271 | Jun 2006 | JP | national |