JP2005300668A - Liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display capable of maintaining response speed without being affected by temperature and without having a heater and the like. <P>SOLUTION: The liquid crystal display 1 includes an AC generating circuit 6 generating an AC signal and a second driving circuit 7 giving an AC driving signal based on the AC signal to a liquid crystal display part 2. When the AC driving signal is given to the liquid crystal display part 2, liquid crystal molecules contained in the liquid crystal display part 2 are vibrated and the liquid crystal molecules generate heat by the vibration. Thereby, temperature of the liquid crystal display part 2 can be increased even when temperature is low and response speed of the liquid crystal display is reduced. Thus, the response speed of the liquid crystal display can be maintained without being affected by temperature. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a liquid crystal display having display means including liquid crystal molecules.

  A liquid crystal display has a characteristic that the response speed decreases under a relatively low temperature environment of approximately 0 ° C. or less due to an increase in viscosity of liquid crystal molecules contained in the liquid crystal layer. On the other hand, for example, in a liquid crystal display employed as a display device for giving information to a driver of an automobile, it is desirable that the response speed is always maintained without being affected by the environmental temperature.

  Conventionally, in order to cope with such a problem, a liquid crystal display provided with a transparent sheet-like heater so that the liquid crystal layer can be heated has been proposed.

  However, various problems arise in the liquid crystal display provided with a dedicated heater for heating the liquid crystal layer in this way. For example, since the heater is provided in the vicinity of the liquid crystal layer that directly affects the display image quality, the display image quality may be deteriorated due to the light transmission characteristics of the heater. In addition, the installation of the heater increases the size of the liquid crystal display.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a liquid crystal display that can maintain a response speed without being affected by temperature without a heater or the like.

  In order to solve the above-mentioned problem, the invention of claim 1 is a liquid crystal display having display means including liquid crystal molecules, wherein a first drive signal based on a video signal is given to the display means, and an image is displayed on the display means. First driving means for displaying, and second driving means for applying an alternating second driving signal to the display means to vibrate the liquid crystal molecules.

  According to a second aspect of the present invention, in the liquid crystal display according to the first aspect of the present invention, the liquid crystal display further includes switching means for selectively activating either the first or second driving means.

  The invention according to claim 3 is the liquid crystal display according to claim 2, further comprising a temperature sensor for detecting a temperature, wherein the switching means is based on the temperature detected by the temperature sensor. It is determined which of the second driving means is to be activated.

  According to a fourth aspect of the present invention, in the liquid crystal display according to the third aspect, the temperature sensor detects the temperature of the display means.

  According to a fifth aspect of the present invention, in the liquid crystal display according to the third or fourth aspect, the switching unit activates the second driving unit when the detected temperature is equal to or lower than a predetermined first reference value.

  The invention according to claim 6 is the liquid crystal display according to any one of claims 3 to 5, wherein the switching means has a predetermined detection temperature when the second driving means is activated. When the second reference value is exceeded, the first driving means is activated.

  According to a seventh aspect of the present invention, in the liquid crystal display according to any one of the third to sixth aspects, the temperature sensor is a thermistor.

  The invention according to claim 8 is the liquid crystal display according to any one of claims 2 to 7, further comprising time measuring means for measuring a heating time after the second driving means is activated, and wherein the switching is performed. The means activates the first driving means when the heating time exceeds a predetermined reference time.

  According to the first to seventh aspects of the present invention, when the second driving means is activated when the temperature of the display means is low, an alternating second driving signal is given to the display means, whereby the liquid crystal included in the display means. The molecule vibrates. As a result, heat is generated by vibration of the liquid crystal molecules and the temperature of the display means rises, so that the response speed of the liquid crystal display can be maintained. In addition, since a heater or the like for raising the temperature of the display means is not required, the liquid crystal display can be reduced in size and the configuration can be simplified.

  In particular, according to the invention of claim 2, the second driving means can be activated as required.

  In particular, according to the third aspect of the present invention, it is possible to determine which of the first and second driving means is activated according to the actual temperature.

  In particular, according to the invention of claim 4, it is possible to determine which of the first and second driving means is activated according to the actual temperature of the display means.

  In particular, according to the invention of claim 5, the temperature of the display means can be raised only when the response speed of the liquid crystal display cannot be maintained.

  Further, according to the invention of claim 6, it is possible to display an image after ensuring the response speed of the liquid crystal display.

  In particular, according to the invention of claim 7, the thermal response can be accelerated by adopting the thermistor as the temperature sensor.

  In particular, according to the invention of claim 8, the heating time until the video based on the original video signal is displayed is limited to a predetermined reference time. For this reason, it can prevent that the time concerning the process of a heating becomes long term.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<1. Configuration>
FIG. 1 is a block diagram schematically showing a configuration of a liquid crystal display according to an embodiment of the present invention. As shown in the figure, a liquid crystal display 1 includes a liquid crystal display unit 2 that includes liquid crystal molecules and displays various information, a control unit 3, a video signal input unit 4, a first drive circuit 5, an AC generation circuit 6, and a second drive. A circuit 7 is provided.

  The control unit 3 controls each unit of the liquid crystal display 1 and includes a CPU, a RAM, a ROM, a timing circuit, and the like. Each unit of the liquid crystal display 1 is electrically connected to the control unit 3 and operates under the control of the control unit 3.

  The video signal input unit 4 is an interface for inputting a video signal to be displayed on the liquid crystal display unit 2. The input video signal is output to the first drive circuit 5 for driving the liquid crystal display unit 2. The first drive circuit 5 generates a drive signal (hereinafter referred to as “first drive signal”) based on the input video signal, and sends the generated first drive signal to the liquid crystal display unit 2. In this way, an image based on the image signal is displayed on the liquid crystal display unit 2 by the first drive signal supplied from the first drive circuit 5.

  The AC generation circuit 6 is a circuit that generates an AC signal having a predetermined frequency. The AC signal generated by the AC generation circuit 6 is output to the second drive circuit 7 for driving the liquid crystal display unit 2. The second drive circuit 7 generates an AC drive signal having the same frequency as the AC signal (hereinafter referred to as “second drive signal”) based on the input AC signal, and the generated second drive signal is displayed on the liquid crystal display unit. Send to 2. The AC second drive signal generated by the second drive circuit 5 in this way is used not to display an image on the liquid crystal display unit 2 but to heat the liquid crystal display unit 2.

  That is, the liquid crystal display 1 includes a drive system (hereinafter referred to as “first drive system”) that supplies the first drive signal to the liquid crystal display unit 2 and a drive system (hereinafter referred to as “first drive system”) that supplies the second drive signal to the liquid crystal display unit 2. Two drive systems, "second drive system"). In the present embodiment, the first drive system includes the video signal input unit 4 and the first drive circuit 5, and the second drive system includes the AC generation circuit 6 and the second drive circuit 7.

  Only one of the first drive signal and the second drive signal is supplied to the liquid crystal display unit 2. Which of the first drive signal and the second drive signal is given to the liquid crystal display unit 2 is determined by the control unit 3. That is, the control unit 3 selectively activates only one of the first drive system and the second drive system.

  FIG. 2 is a diagram showing a configuration of the liquid crystal display unit 2, and shows each part in an exploded manner in order to facilitate the visual recognition of the structure.

  As shown in the figure, the liquid crystal display unit 2 has a side on which the user visually recognizes the first polarizing plate 21, the first glass substrate 22, the liquid crystal layer 23, the second glass substrate 24, the second polarizing plate 25, and the backlight 26. From this order. The liquid crystal layer 23 containing liquid crystal molecules is formed by enclosing a liquid crystal material between two glass substrates 22 and 24.

  In addition, transistors (TFTs) and electrodes are formed on the second glass substrate 24 at positions corresponding to the plurality of pixels arranged in a two-dimensional matrix. On the other hand, electrodes are formed on the first glass substrate 22 so as to face the electrodes of the respective pixels of the second glass substrate 24.

  Both the first drive signal and the second drive signal described above are supplied to the transistors of the respective pixels of the second glass substrate 24. When the first drive signal is given, a voltage corresponding to the first drive signal is applied to the liquid crystal layer 23 between the opposing electrodes of the two glass substrates 22 and 24. As a result, an image based on the image signal is displayed on the entire pixels included in the liquid crystal display unit 2.

  On the other hand, when an AC second drive signal is given, a voltage whose voltage value changes at a predetermined frequency is applied to the liquid crystal layer 23 between the electrodes facing each other on the two glass substrates 22 and 24. Thereby, the liquid crystal molecules contained in the liquid crystal layer 23 vibrate at a predetermined frequency, and as a result, heat is generated by the vibration. That is, the temperature of the liquid crystal display unit 2 rises.

  The frequency of vibration of the liquid crystal molecules during heat generation coincides with the frequency of the second drive signal. The frequency of the second drive signal is set to a predetermined frequency (for example, about 1 MHz or more) that is significantly higher than the vertical synchronization frequency (generally about 60 Hz) of the liquid crystal display unit 2 in order to improve the heat generation efficiency.

  Returning to FIG. 1, the liquid crystal display unit 2 further includes a temperature sensor 29 that detects the temperature of the liquid crystal layer 23. The temperature sensor 29 is formed of, for example, a thermistor having a quick thermal response and a small error due to lead wire resistance, and is formed on the second glass substrate 24 or the like. The temperature detected by the temperature sensor 29 (hereinafter referred to as “detected temperature”) is input to the control unit 3. Which of the first drive system and the second drive system is activated is determined according to the detected temperature.

<2. Operation>
Next, the operation of the liquid crystal display 1 will be described. The liquid crystal display 1 heats the liquid crystal display unit 2 when necessary in an initialization operation performed immediately after the power is turned on. FIG. 3 is a diagram showing a flow of initialization operation of the liquid crystal display 1. The initialization operation will be described below with reference to this figure.

  In the initialization operation, first, the temperature of the liquid crystal layer 23 is detected by the temperature sensor 29, and the detected temperature is input to the control unit 3 (step S11).

  Next, the control unit 3 determines whether or not the detected temperature exceeds a predetermined first reference temperature. The first reference temperature is a temperature (for example, 0 ° C.) as a threshold value at which the response speed of the liquid crystal display unit 2 does not decrease (the response speed can be maintained) if the temperature is exceeded. It is determined in advance and stored in the ROM of the control unit 3 (step S12).

  When the detected temperature exceeds the predetermined first reference temperature (Yes in step S12), the response speed of the liquid crystal display unit 2 is maintained, so that no problem occurs even if an image is displayed on the liquid crystal display unit 2. For this reason, the first drive system is activated, and the first drive signal is applied to the liquid crystal display unit 2 (step S16), and the initialization operation is completed.

  On the other hand, when the detected temperature is equal to or lower than the predetermined first reference temperature (No in step S12), the response speed of the liquid crystal display unit 2 may be reduced, so the temperature of the liquid crystal display unit 2 needs to be increased. . For this reason, the second drive system is activated and the second drive signal is given to the liquid crystal display unit 2, thereby starting heating of the liquid crystal display unit 2 (more precisely, heating of the liquid crystal layer 23) (step). S13).

  During heating of the liquid crystal display unit 2, the temperature of the liquid crystal layer 23 is detected by the temperature sensor 29 at a predetermined time period (step S14). This detected temperature is input to the control unit 3, and it is determined whether or not a predetermined second reference temperature has been exceeded (step S15). This second reference temperature is also a temperature that is a threshold value at which the response speed of the liquid crystal display unit 2 is not reduced if the temperature exceeds the second reference temperature, and is preset and stored in the ROM of the control unit 3 or the like. The second reference temperature may be the same value as the first reference temperature described above, or may be a different value.

  If the detected temperature exceeds a predetermined second reference temperature during the heating of the liquid crystal display unit 2, the response speed of the liquid crystal display unit 2 can be maintained, so the heating of the liquid crystal display unit 2 is finished (step) Yes at S15). Then, the first drive system is activated, and the first drive signal is applied to the liquid crystal display unit 2 (step S16), and the initialization operation is completed.

  As described above, the liquid crystal display 1 includes the second drive system that can supply an alternating current second drive signal to the liquid crystal display unit 2 to vibrate liquid crystal molecules. For this reason, even in a state where the environmental temperature is low and the response speed of the liquid crystal display unit 2 is reduced, the temperature of the liquid crystal display unit 2 can be increased by heat generated by vibration of liquid crystal molecules. Therefore, the response speed of the liquid crystal display can be maintained without being affected by the temperature. In addition, since a dedicated heater or the like for raising the temperature of the liquid crystal display unit 2 is not necessary, the liquid crystal display 1 can be reduced in size and the configuration can be simplified. These effects are particularly effective when the liquid crystal display 1 of the present embodiment is employed as a display device for giving information to the driver of the automobile.

  In addition, since the control unit 3 selectively activates one of the first and second drive systems, the second drive system can be activated as necessary. In addition, the control unit 3 determines which of the first and second drive systems is to be activated based on the temperature detected by the temperature sensor 29 that detects the temperature of the liquid crystal layer 23. The temperature of the liquid crystal display unit 2 can be effectively increased based on the temperature.

  Further, in the initialization operation, the control unit 3 activates the second drive system only when the detected temperature is equal to or lower than the predetermined first reference temperature. Therefore, the liquid crystal display unit only when the response speed of the liquid crystal display 1 cannot be maintained. The temperature of 2 can be increased. Further, during the heating of the liquid crystal display unit 2, the control unit 3 switches the drive system to be activated from the second drive system to the first drive system when the detected temperature exceeds a predetermined second reference temperature. The original video can be displayed after sufficiently ensuring the response speed.

<3. Modification>
Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications are possible.

<3-1. Switching by heating time>
In the above embodiment, the condition for switching the drive system to be activated from the second drive system to the first drive system during heating of the liquid crystal display unit 2 is that the detected temperature exceeds the second reference temperature. The time after the second drive system is activated may be a predetermined time. Here, the time after the second drive system is activated corresponds to the heating time after the heating is started.

  FIG. 4 is a diagram showing the flow of the initialization operation in this case. First, similarly to the operation of FIG. 3 described above, it is determined whether or not the detected temperature exceeds a predetermined first reference temperature (steps S21 and S22), and when the detected temperature is equal to or lower than the predetermined first reference temperature (step S21). In S22, the second drive system is activated (No in S22).

  When the second drive system is activated, the time counting of the heating time is started by the time measuring circuit provided in the control unit 3 (step S24). Thereafter, the liquid crystal display unit 2 is heated until the heating time exceeds a predetermined reference time (step S25). This reference time is predetermined and stored in the ROM of the control unit 3 or the like. The reference time is determined in advance according to the detected temperature, and is set longer as the temperature is lower. When the heating time exceeds a predetermined reference time, the first drive system is activated (step S26), and the initialization operation is terminated.

  In this way, by limiting the heating time to within a predetermined reference time, it is possible to prevent the time required for the heating process from becoming long and the startup time from becoming long.

<3-2. Combined drive circuit>
In the above embodiment, both the first drive system and the second drive system are provided with the drive circuit. However, the first drive system and the second drive system may share one drive circuit.

  FIG. 5 is a block diagram schematically showing the configuration of the liquid crystal display 1 in this case. As shown in the figure, in the liquid crystal display 1 of this example, only one drive circuit 8 is provided as a drive circuit for driving the liquid crystal display unit 2. Other configurations are the same as those shown in FIG.

  Both the video signal from the video signal input unit 4 and the AC signal from the AC generation circuit 6 are input to the drive circuit 8. When the video signal from the video signal input unit 4 is input, the first drive signal is supplied from the drive circuit 8 to the liquid crystal display unit 2, and when the AC signal from the AC generation circuit 6 is input, the drive circuit 8 A second drive signal is supplied from the circuit 8 to the liquid crystal display unit 2. That is, the drive circuit 8 is shared by both the first drive system and the second drive system.

  Whether the video signal or the AC signal is supplied to the drive circuit 8 is controlled by the control unit 3. In the liquid crystal display 1, only one of the first drive system and the second drive system is selectively activated, and thus the drive signal is given to the liquid crystal display unit 2 in the first and second drive systems in this way. Therefore, the configuration of the liquid crystal display 1 can be simplified.

<3-3. Other variations>
The temperature sensor 29 of the above embodiment detects the temperature of the liquid crystal layer 23 of the liquid crystal display unit 2, but is not limited to this, and the temperature sensor may be the temperature of other parts of the liquid crystal display unit 2 or The ambient temperature at which the liquid crystal display 1 is disposed may be detected.

  Further, during the heating of the liquid crystal display unit 2, both conditions of “the detected temperature exceeds the second reference temperature” and “the heating time exceeds the predetermined reference time” are determined. When either one is satisfied, the drive system to be activated may be switched from the second drive system to the first drive system.

  Further, the first and second reference temperatures and the reference time may be settable by the user.

It is a block diagram which shows an example of a structure of a liquid crystal display. It is a figure which shows the structure of a liquid crystal display part. It is a figure which shows an example of the flow of initialization operation | movement of a liquid crystal display. It is a figure which shows an example of the flow of initialization operation | movement of a liquid crystal display. It is a block diagram which shows an example of a structure of a liquid crystal display.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Liquid crystal display 2 Liquid crystal display part 3 Control part 22 1st glass substrate 23 Liquid crystal layer 24 2nd glass substrate 26 Backlight

Claims (8)

A liquid crystal display having display means including liquid crystal molecules,
A first driving means for applying a first driving signal based on a video signal to the display means to cause the display means to display a video;
Second driving means for applying an alternating second driving signal to the display means to vibrate the liquid crystal molecules;
A liquid crystal display comprising: The liquid crystal display according to claim 1.
Switching means for selectively activating either of the first and second driving means;
A liquid crystal display further comprising: The liquid crystal display according to claim 2.
Temperature sensor to detect the temperature,
Further comprising
The liquid crystal display characterized in that the switching means determines which of the first and second driving means is activated based on a temperature detected by the temperature sensor. The liquid crystal display according to claim 3.
The liquid crystal display, wherein the temperature sensor detects a temperature of the display means. The liquid crystal display according to claim 3 or 4,
The liquid crystal display, wherein the switching means activates the second driving means when the detected temperature is equal to or lower than a predetermined first reference value. The liquid crystal display according to any one of claims 3 to 5,
The switching means activates the first driving means when the detected temperature exceeds a predetermined second reference value when the second driving means is activated. . The liquid crystal display according to any one of claims 3 to 6,
The liquid crystal display, wherein the temperature sensor is a thermistor. The liquid crystal display according to any one of claims 2 to 7,
Timing means for timing the heating time after the second driving means is activated;
Further comprising
The liquid crystal display characterized in that the switching means activates the first driving means when the heating time exceeds a predetermined reference time.

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