JP2011099879A - Liquid crystal display device - Google Patents

Abstract

A liquid crystal display device capable of suppressing the display of an incomplete image immediately after startup regardless of the ambient temperature is provided.
A liquid crystal module including a liquid crystal panel, an LED backlight using an LED as a light source, a temperature sensor for detecting an ambient temperature, and a temperature detected by the temperature sensor after starting the liquid crystal module. And a control unit 2 that activates the LED backlight with a delay corresponding to the time.
[Selection] Figure 1

Description

  The present invention relates to a liquid crystal display device having an LED backlight using a light emitting diode (hereinafter abbreviated as “LED: Light Emitting Diode”) as a light source.

  In recent years, LEDs have come to be used in place of conventional cold cathode fluorescent lamps (CCFLs) as light sources for backlights of liquid crystal display devices. When a liquid crystal display device provided with a CCFL backlight is started at a low temperature, the rise in luminance at a low temperature of the CCFL backlight is slower than the rise of the liquid crystal, so that an image starts to be displayed after the liquid crystal is launched. Therefore, the user did not see an incomplete video immediately after startup.

  However, when a liquid crystal display device having an LED backlight is started at a low temperature, the LED has a characteristic that the brightness immediately rises when it is lit even at a low temperature, whereas the liquid crystal has a slow response speed at a low temperature and rises. Is slow. Therefore, there is a problem that an incomplete video immediately after startup is visible to the user.

  As a technique for suppressing the display of an incomplete image immediately after the start-up, Patent Document 1 can start the discharge lamp with certainty, and can perform the initial operation before the liquid crystal panel is initialized. Disclosed is a liquid crystal display device that can prevent a problem that a pre-image is displayed and can suppress a change in luminance in display when a voltage applied to a discharge lamp is changed.

  In this liquid crystal display device, the liquid crystal panel is driven based on display data. The liquid crystal panel is irradiated with light from the cold cathode lamp of the illumination means from the back side. The lamp control means applies a lighting maintenance voltage lower than the lighting start voltage to the cold cathode lamp after applying the lighting start voltage over the lighting start period. The light transmittance changing means sets the light transmittance of the liquid crystal panel to the first light transmittance in the lighting start period, and the first time when the voltage applied to the cold cathode lamp is changed from the lighting start voltage to the lighting sustain voltage. The second light transmittance is changed to be higher than the light transmittance.

JP 2006-267446 A

  In order to solve the conventional problem that an incomplete video is displayed immediately after the startup described above, it is conceivable to delay the start of lighting the LED backlight, but simply by delaying the start of lighting the LED backlight, There is a problem that it takes a long time until an image becomes visible to the user even at a temperature at which it is not necessary to delay the start of lighting of the LED backlight, for example, at room temperature.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a liquid crystal display device that can prevent an incomplete image from being displayed immediately after startup regardless of the ambient temperature. It is in.

  In order to solve the above problems, a liquid crystal display device according to the present invention activates a liquid crystal module including a liquid crystal panel, an LED backlight using an LED as a light source, a temperature sensor for detecting an ambient temperature, and the liquid crystal module. After that, a control unit that activates the LED backlight with a delay corresponding to the temperature detected by the temperature sensor is provided.

  According to the liquid crystal display device of the present invention, after the liquid crystal module is activated, the LED backlight is activated with a delay corresponding to the ambient temperature, so that the LED backlight is activated immediately after the activation regardless of the ambient temperature. Incomplete video can be prevented from being displayed.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
Embodiment 1 FIG.
1 is a block diagram showing a configuration of a liquid crystal display device according to Embodiment 1 of the present invention. The liquid crystal display device includes a temperature sensor 1, a control unit 2, a liquid crystal control device 3, a liquid crystal module 4, an LED driving device 5, and an LED backlight 6.

  The temperature sensor 1 detects the ambient temperature and outputs it as an analog voltage value. The voltage value output from the temperature sensor 1 is sent to the control unit 2 as a temperature signal S1. The control unit 2 generates a liquid crystal control signal S2 for starting the liquid crystal module 4 and sends it to the liquid crystal control device 3, and also generates an LED control signal S3 based on the temperature signal S1 sent from the temperature sensor 1. Send to LED drive 5. Details of the control unit 2 will be described later.

  The liquid crystal control device 3 generates a liquid crystal activation signal in response to the liquid crystal control signal S2 sent from the control unit 2 and sends it to the liquid crystal module 4. The liquid crystal module 4 is configured by mounting a driver IC for driving on a liquid crystal panel. The activation of the liquid crystal module 4 is started in response to a liquid crystal activation signal sent from the liquid crystal control device 3. By irradiating light generated by the LED backlight 6 from the back surface of the liquid crystal module 4, characters or figures are displayed with a predetermined luminance on the surface of the liquid crystal panel.

  The LED drive device 5 generates an LED drive signal according to the LED control signal S3 sent from the control unit 2 and sends it to the LED backlight 6. The lighting of the LED backlight 6 is started in response to the LED driving signal sent from the LED driving device 5.

  Next, details of the control unit 2 will be described. The control unit 2 includes a temperature detection unit 11, a memory unit 12, a calculation unit 13, a liquid crystal control signal generation unit 14, a delay generation unit 15, and an LED control signal generation unit 16. The temperature detection unit 11 performs A / D conversion on the analog voltage value sent as the temperature signal S1 from the temperature sensor 1 and sends the analog voltage value to the calculation unit 13 as a digital voltage value.

  The memory unit 12 has a temperature-time characteristic of the liquid crystal module 4 used in the liquid crystal display device as shown in FIG. 2, specifically, a relationship between the rise time td of the liquid crystal module 4 and the temperature (° C.). Stored in advance. In this temperature-time characteristic, the rising time td increases as the temperature decreases, and the rising time td decreases as the temperature increases. The contents of the memory unit 12 are read by the calculation unit 13.

  The calculation unit 13 instructs the liquid crystal control signal generation unit 14 to generate the liquid crystal control signal S2 when a power switch (not shown) of the liquid crystal display device is turned on. This instruction is also sent to the delay generation unit 15. Further, the calculation unit 13 calculates a temperature corresponding to the digital voltage value sent from the temperature detection unit 11, and acquires the rise time td corresponding to the calculated temperature from the memory unit 12. The acquired rise time td is sent to the delay generation unit 15.

  The liquid crystal control signal generation unit 14 generates a liquid crystal control signal S2 in response to an instruction from the calculation unit 13. The generated liquid crystal control signal S2 is sent to the liquid crystal control device 3.

  The delay generation unit 15 starts counting the rise time td sent from the calculation unit 13 from the time when the calculation unit 13 instructs the liquid crystal control signal generation unit 14 to generate the liquid crystal control signal S2. After the time td has elapsed, an activation command is sent to the LED control signal generator 16. The LED control signal generation unit 16 generates the LED control signal S3 in response to the start command from the delay generation unit 15. The generated LED control signal S3 is sent to the LED driving device 5.

  Next, the operation of the liquid crystal display device configured as described above is an initial process executed when the power is turned on (a process for controlling the LED driving device 5 and the liquid crystal control device 3 based on the temperature signal S1 from the temperature sensor 1). A description will be given with reference to the flowchart shown in FIG.

  When the power source of the liquid crystal display device is turned on, first, the temperature signal from the temperature sensor is A / D converted (step ST11). That is, the temperature detection unit 11 performs A / D conversion on the analog voltage value sent as the temperature signal S1 from the temperature sensor 1 and sends the analog voltage value to the calculation unit 13 as a digital voltage value. Next, a temperature Temp0 corresponding to the A / D value is calculated (step ST12). That is, the calculation unit 13 calculates the temperature Temp0 corresponding to the digital voltage value sent from the temperature detection unit 11.

  Next, a time Td0 corresponding to the temperature Temp0 is acquired (step ST13). That is, the calculation unit 13 acquires the rise time Td0 corresponding to the temperature Temp0 calculated in step ST12 from the memory unit 12. For example, when the temperature-time characteristic shown in FIG. 5 is stored in the memory unit 12, if the temperature Temp0 is −20 ° C., 3 seconds is acquired as the rise time Td0. The acquired time Td0 is sent to the delay generation unit 15.

  Next, the liquid crystal module is activated (step ST14). That is, the calculation unit 13 instructs the liquid crystal control signal generation unit 14 to generate the liquid crystal control signal S2. At this time, the delay generation unit 15 starts counting the rise time td sent from the calculation unit 13. The liquid crystal control signal generator 14 generates a liquid crystal control signal S2 in response to this instruction and sends it to the liquid crystal control device 3. The liquid crystal control device 3 generates a liquid crystal activation signal for activating the liquid crystal module 4 in accordance with the liquid crystal control signal S <b> 2 received from the liquid crystal control signal generation unit 14, and sends the liquid crystal activation signal to the liquid crystal module 4. Thereby, starting of the liquid crystal module 4 is started.

  Next, it is checked whether or not the rise time td has elapsed (step ST15). That is, the delay generation unit 15 counts the rising time td sent from the calculation unit 13 and checks whether the rising time td has elapsed. If it is determined in step ST15 that the rise time td has not elapsed, the process waits while repeatedly executing step ST15.

  On the other hand, when it is determined in step ST15 that the rise time td has elapsed, the LED backlight is turned on (step ST16). That is, when the delay generation unit 15 determines that the rise time td has elapsed as a result of counting the rise time td, the delay generation unit 15 sends an activation command to the LED control signal generation unit 16. When the LED control signal generation unit 16 receives the activation command from the delay generation unit 15, the LED control signal generation unit 16 generates the LED control signal S <b> 3 and sends it to the LED drive device 5. The LED drive device 5 that has received this LED control signal S3 generates an LED drive signal and sends it to the LED backlight 6. Thereby, lighting of the LED backlight 6 is started.

  Thereafter, image display is performed (step ST17). That is, by irradiating the light generated by the LED backlight 6 from the back surface of the liquid crystal module 4, characters or figures are displayed with a predetermined luminance on the surface of the liquid crystal panel. Thus, the initial process ends.

  As shown in the timing chart of FIG. 4, the LED backlight 6 is turned on at time t <b> 2 td after the liquid crystal module 4 is activated at time t <b> 1 by the initial processing shown in the flowchart of FIG. 3 described above. Is realized. For example, as described above, when the ambient temperature is −20 ° C., the LED backlight 6 is turned on 3 seconds after the liquid crystal module 4 is activated.

  When a conventional liquid crystal display device equipped with a CCFL backlight is started at a low temperature, the rise in luminance at a low temperature of the CCFL backlight is slower than the rise of the liquid crystal, so that the liquid crystal module is launched as shown in FIG. Later, the brightness of the CCFL backlight rises and the video starts to be displayed, so that the user cannot see the incomplete video immediately after the startup.

  On the other hand, when a liquid crystal display device having a conventional LED backlight is activated at a low temperature, as shown in FIG. Response speed is slow and startup is slow. Therefore, the user can see an incomplete video immediately after startup.

  On the other hand, according to the above-described liquid crystal display device according to the first embodiment, as shown in FIG. 7, the LED backlight 6 is delayed by the time td corresponding to the temperature and turned on after the liquid crystal module 4 is started up. With this configuration, even if the luminance immediately rises after the LED is turned on, an incomplete image is not seen by the user.

  As described above, according to the liquid crystal display device according to the first embodiment of the present invention, when starting a liquid crystal display device equipped with an LED backlight at a low temperature, the user does not show an incomplete image immediately after the start-up. As a result, it is possible to reduce the user's discomfort and improve the satisfaction.

It is a block diagram which shows the structure of the liquid crystal display device which concerns on Embodiment 1 of this invention. It is a figure which shows the temperature-time characteristic of the liquid crystal module used with the liquid crystal display device which concerns on Embodiment 1 of this invention. It is a flowchart which shows operation | movement of the liquid crystal display device which concerns on Embodiment 1 of this invention. It is a timing chart which shows operation | movement of the liquid crystal display device which concerns on Embodiment 1 of this invention. It is a figure which shows the rise characteristic of the liquid crystal module of a liquid crystal display device provided with the conventional CCFL backlight, and CCFL backlight. It is a figure which shows the rise characteristic of the liquid crystal module of a liquid crystal display device provided with the conventional LED backlight, and LED backlight. It is a figure which shows the rise characteristic of the liquid crystal module and LED backlight of the liquid crystal display device which concerns on Embodiment 1 of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Temperature sensor, 2 Control part, 3 Liquid crystal control device, 4 Liquid crystal module, 5 LED drive device, 6 LED backlight, 11 Temperature detection part, 12 Memory part, 13 Calculation part, 14 Liquid crystal control signal generation part, 15 Delay generation Unit, 16 LED control signal generation unit.

Claims (2)

A liquid crystal module including a liquid crystal panel;
An LED backlight using LEDs as a light source;
A temperature sensor that detects the ambient temperature;
A liquid crystal display device comprising: a controller that activates the LED backlight with a delay corresponding to the temperature detected by the temperature sensor after the liquid crystal module is activated. A memory unit storing the relationship between the rise time and temperature of the liquid crystal module;
A liquid crystal control signal generator for generating a liquid crystal control signal for starting the liquid crystal module;
An LED control signal generator for generating an LED control signal for turning on the LED backlight;
Instructing the liquid crystal control signal generation unit to generate a liquid crystal control signal, and obtaining a rise time corresponding to the temperature detected by the temperature sensor from the memory unit,
A delay generation unit that instructs the LED control signal generation unit to generate an LED control signal after a rise time acquired by the calculation unit has elapsed from an instruction to generate the liquid crystal control signal to the liquid crystal control signal generation unit The liquid crystal display device according to claim 1, further comprising:

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