JP4285183B2 - Liquid crystal display - Google Patents

Description

  The present invention relates to an active matrix liquid crystal display device driving method and a liquid crystal display device, and more particularly, to a liquid crystal display device driving method and a liquid crystal display device using an OCB (Optically Compensated Birefringence) liquid crystal mode having a wide viewing angle and high-speed response. It is about.

The OCB cell used in the OCB liquid crystal display device has characteristics such as a wide viewing angle and a high-speed response compared to the TN type cell, and can be said to be a liquid crystal cell suitable for natural moving image display. The OCB liquid crystal mode has a bend orientation in which video display is possible and a splay orientation in which video display is not possible. In order to shift from the splay alignment to the bend alignment, a unique drive such as applying a high voltage for a certain period of time is used.

  Even if the bend alignment is once caused by the above unique driving, if the voltage of a predetermined level or more is not applied to the liquid crystal layer for a predetermined time or longer, the bend alignment cannot be maintained and the splay alignment is restored (hereinafter, this phenomenon is referred to as this phenomenon). This phenomenon is called reverse transition. Conventionally, as confirmed, as a driving method for preventing the reverse transition phenomenon (hereinafter referred to as reverse transition prevention driving), a high potential is applied to the liquid crystal layer in a period different from the video display period. For details, refer to “Liquid Crystal Society of Japan, Vol. 3, No. 2, 1999”.

Moreover, the voltage value of the input signal is detected in order to provide a liquid crystal display device that uses an OCB cell to suppress the occurrence of reverse transition and display a good image without causing excessive luminance reduction. The reverse transition is determined by determining the likelihood of the reverse transition phenomenon on the liquid crystal display means from the value and controlling the non-video signal holding period and / or the voltage level of the non-video signal based on the determination. The phenomenon was effectively suppressed. (JP 2002-341310)
When the synchronizing signal of the output video signal input to the liquid crystal display means becomes unstable (hereinafter referred to as an illegal signal), a reverse transition occurs because it affects the detected value of the input signal.

For this reason, when there is no signal, a pseudo-synchronization signal is used to display a voltage level that can be recovered from reverse transition for a certain period of time, thereby recovering from reverse transition (hereinafter, this drive is referred to as reverse transition return driving). I was doing it. (Japanese Patent Laid-Open No. 60-194882)
JP-A-60-194882

  The detection result of the first detection means for detecting an irregular signal from the video display means output from the signal processing means may adversely affect the liquid crystal display means under the control of the control means, eliminating erroneous detection. Because it is necessary, the time from the time when the video signal becomes unstable to the detection becomes longer, and it is necessary to set the time to perform the return drive from the reverse transition state that can occur in the liquid crystal display means. There was a problem.

  In view of the above problems, the present invention is characterized in that the period during which an unstable video signal is displayed on the liquid crystal display means can be calculated so that the liquid crystal display means can return from the reverse transition state in a short time. It is what.

  In order to solve the above-mentioned problem, the liquid crystal display device according to the present invention is a second detection in which the detection accuracy for detecting that the output video signal output from the signal processing means has become unstable is inferior but the time until detection is short. A means is added, the period when the video signal displayed using two detection means becomes unstable is calculated, the time required for the reverse transition return drive is calculated, and the reverse transition return drive is displayed on the liquid crystal display from the calculation result. It is characterized by being performed by means.

  According to the present invention, recovery from the reverse transition state can be performed in accordance with the period in which the fraudulent signal is output, and the period until normal liquid crystal display is performed can be shortened.

  Furthermore, reverse transition return driving can be performed without being influenced by the detection signal B when the second detection result is erroneously detected.

  According to the first aspect of the present invention, there is provided a liquid crystal display means for displaying an image, a signal processing means for outputting an output video signal to be displayed on the liquid crystal display means, and a synchronization signal of the output video signal transmitted by the signal processing means. Liquid crystal provided with first detection means for detecting that the normal signal is changed to an abnormal signal and outputting the detection signal A, and control means for controlling the signal processing means with the control signal when the detection signal A is output. In the display device, there is a second detection means for outputting a detection signal B that is shorter than the first detection means until a detection is made that the signal is changed from a normal signal to a non-normal signal. A counter for use, a first calculation for obtaining a transition return drive time required for return from the reverse transition state using the detection signal A, the detection signal B, the control signal, and the counter, and outputting an output signal; And a transition return drive means for performing a transition return drive by outputting a drive signal to the liquid crystal display means during a period in which the output signal is output. Has the effect of performing in a short time.

  The invention according to claim 2 is the liquid crystal display device according to claim 1, which can prevent unnecessary transition recovery drive due to erroneous detection by the second detection means.

  According to a third aspect of the present invention, the first computing means has a function of not outputting the output signal when the detection signal A is not output during a set period after the detection signal B is output. The liquid crystal display device according to claim 2, further comprising a second computing unit added.

(Embodiment 1)
Hereinafter, an embodiment of the present invention will be described with reference to FIGS.

  In FIG. 1, 1 is signal processing means, 2 is liquid crystal display means, 3 is first detection means, 4 is control means, 5 is second detection means, 6 is a counter, 7 is first calculation means, 8 Is transfer return drive means.

  FIG. 3 is a time chart when the input video signal becomes an irregular signal.

  FIG. 4 is a flowchart of the first calculation means.

  3 and 4, the current times Tn and Ta indicated by the counter are the time when the detection signal A becomes H, Tb is the time when the detection signal B becomes H, Twc is the period during which the fraudulent signal is output, and Twc 'Is a period necessary for returning from the reverse transition state, Td is an end time of a period necessary for returning from the reverse transition state, and a flag C is a flag indicating a transition return period calculated by the calculation means.

  When the output video signal from the signal processing means 1 becomes an illegal signal, the second detection means 5 outputs a detection signal B. The first calculating means 7 stores the time Tn indicated by the counter 6 when the detection signal B is output as Tb.

  Here, in order to prevent erroneous detection, the first detection means 3 that outputs a longer time until detection than the second detection means 5 outputs the detection signal A.

  When the detection signal A is output, the first calculation means stores the Tn as Ta by the counter, sets the flag C to H, sets the output signal of the calculation means to H, and determines that the time difference between Ta and Tb is incorrect. A period signal output period Twc is obtained, a period Twc ′ necessary for returning from the reverse transition state is obtained from Twc, and an end time of the period necessary for returning from the reverse transition state from the sum of Ta and Twc ′ Td is obtained. When the Tn has passed the Td, the flag C is set to L. When the detection signal A and the flag C are L, the output signal is set to L.

  The transition return driving means performs recovery from the reverse transition state by controlling the liquid crystal display means by the drive signal during the period when the output signal is H.

(Embodiment 2)
Hereinafter, another embodiment of the present invention will be described with reference to FIGS.

  In FIG. 2, 1 is signal processing means, 2 is liquid crystal display means, 3 is first detection means, 4 is control means, 5 is second detection means, 6 is a counter, 7 is second calculation means, 8 Is a transfer return driving means, and 9 is a set time.

  FIG. 5 is a time chart when the second detecting means erroneously detects.

  FIG. 6 is a flowchart of the second calculation means.

  5 and 6, the current times Tn and Ta indicated by the counter are times when the detection signal A becomes H, Tb is the time when the detection signal B becomes H, Twc is a period for outputting the fraudulent signal, Twc 'Is a period necessary for returning from the reverse transition state, Twlim is a set value for limiting the time from the output of the detection signal B until the detection signal A is output, and Td is for returning from the reverse transition state An end time of a necessary period, a flag C is a flag indicating a transition return period calculated by the calculation means, and a flag D is a flag indicating that the detection signal B is H.

  When the output video signal from the signal processing means 1 becomes an illegal signal, the second detection means 5 outputs a detection signal B. The second calculating means 7 stores the current time Tn indicated by the counter 6 when the detection signal B is output as Tb, and sets the flag D to H.

  Here, since the first detection means 3 for preventing erroneous detection does not output the detection signal A, the time from Tb continues to elapse until an irregular signal comes thereafter, so when the detection signal A is output thereafter. There is a possibility that the calculated period may be a long period from the time when the detection signal B is erroneously detected to the time when the detection signal A is output.

  Therefore, the second calculation means 7 obtains the time elapsed from the time when the detection signal B is output from the set Tb + Tn, and limits the time until the detection signal A is output after the detection signal B is output. When the set value Twlim to be used has elapsed, the flag D is set to L to avoid the calculation result by the erroneously detected detection signal B.

  INDUSTRIAL APPLICABILITY The liquid crystal display device according to the present invention is useful as a driving method and a liquid crystal display device for an active matrix type liquid crystal display device, and in particular, a driving method for a liquid crystal display device using an OCB liquid crystal mode having a wide viewing angle and high-speed response. Suitable for liquid crystal display devices.

1 is an overall configuration diagram of a liquid crystal display device according to Embodiment 1 of the present invention. Overall configuration diagram of a liquid crystal display device according to Embodiment 2 of the present invention Time chart when the output video signal in the first embodiment of the present invention becomes an irregular signal The flowchart of the 1st calculating means in Embodiment 1 of this invention Time chart when the second detection means in the second embodiment of the present invention erroneously detects The flowchart of the 2nd calculating means in Embodiment 2 of this invention Overall configuration diagram of a conventional liquid crystal display device

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Signal processing means 2 Liquid crystal display means 3 1st detection means 4 Control means 5 2nd detection means 6 Counter 7 1st calculating means 8 Transition return drive means 9 2nd calculating means

Claims (3)

Liquid crystal display means for displaying an image;
Signal processing means for outputting an output video signal to be displayed on said liquid crystal display means,
A first signal for detecting that the synchronization signal of the output video signal transmitted by the signal processing means has changed from a stable (hereinafter normal signal) state to an unstable (hereinafter irregular signal) state and outputs a detection signal A Detection means;
And control means for controlling a control signal to said signal processing means when the outputted the detection signal A,
A liquid crystal display device using an OCB liquid crystal mode comprising :
Second detecting means for time from the normal signal until detecting that became the irregular signal and outputs a short detection signal B from the first detecting means,
A counter for time measurement,
First computing means for obtaining a transition return driving time required for return from a reverse transition state using the detection signal A, the detection signal B, the control signal, and the counter, and outputting an output signal;
Transition return drive means for performing transition return drive by outputting a drive signal to the liquid crystal display means during a period in which the output signal is output;
A liquid crystal display device using an OCB liquid crystal mode , characterized by comprising: When the case where the second detection means and the detection signal A by a predetermined time has elapsed after detecting that has not been output, the second detecting means is when the erroneously detected, which was erroneously detected as the detection signal A Since there is a possibility that the calculation is performed using the time difference of the detection signal B, unnecessary transfer recovery driving can be prevented by using the second calculation means having means for discarding the detection result at that time. The liquid crystal display device using the OCB liquid crystal mode according to claim 1 . A second calculation in which a function of not outputting the output signal when the detection signal A is not output during a period set by a set value after the detection signal B is output is added to the first calculation means. 3. A liquid crystal display device using an OCB liquid crystal mode according to claim 2, further comprising means.

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