JP2021162725A - Liquid crystal display device - Google Patents

Abstract

To provide a liquid crystal display device capable of surely preventing sticking regardless of a form of use and capable of reducing power consumption required for the prevention of the sticking.SOLUTION: A video display device 100 includes a display panel 114, a backlight 116 for illuminating the display panel 114, an end timing detection part 152 for detecting the timing of an operation end, and a display switching part 158 for turning off the backlight 116, when the timing of the operation end is detected by the end timing detection part 152 and sequentially switching the displays of a plurality of screens which are a plurality of screens displayed on the display panel 114 and are different in display content.SELECTED DRAWING: Figure 1

Description

The present invention relates to a liquid crystal display device that displays an image using a liquid crystal panel.

If a screen with the same contents is continuously displayed for a long time on the liquid crystal display device, positive or negative charges are unevenly accumulated in the liquid crystal display, and even after the screen contents are switched, the display of the contents before the switching remains. An event (burn-in) occurs. Once burn-in occurs, problems such as poor visibility and the inability to view a desired image occur. This burn-in may remain for several minutes to several hours after switching, depending on the situation at the time of the burn-in. Further, if the power supply is turned off and the display operation is stopped in the state where the burn-in has occurred, the charge bias is not improved and the burn-in remains even at the next startup. Such burn-in leads to deterioration of display quality, and is not desirable from the viewpoint of improving display quality.

As a method of reducing such burn-in, conventionally, when the user closes the liquid crystal panel toward the camera body, the standby state is set, the backlight is turned off, and the captured image signal and additional information are displayed. After switching to the non-display state, each pixel of the liquid crystal panel within the display range for a predetermined time is driven so that the transmittance corresponds to the gray image of 50% white, and then the driving of the liquid crystal panel is stopped. An image pickup device is known (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2017-1330879

By the way, since the operation of preventing seizure in the image pickup apparatus disclosed in Patent Document 1 described above is performed when the liquid crystal panel is closed and put into a standby state, it is used as an in-vehicle device or indoors. There is a problem that it cannot be applied in a form not provided with a liquid crystal panel that can be opened and closed, as in the case of using it as an installed device. Further, in this imaging device, since the operation of preventing seizure is repeated every time the liquid crystal panel is closed during operation, there is a problem that power consumption increases more than necessary when the liquid crystal panel is closed frequently.

The present invention has been created in view of these points, and an object thereof is a liquid crystal display capable of reliably preventing seizure regardless of the usage mode and reducing power consumption required for that purpose. The purpose is to provide a display device.

In order to solve the above-mentioned problems, the liquid crystal display device of the present invention is operated by a liquid crystal panel, a backlight for illuminating the liquid crystal panel, an end timing detecting means for detecting the end timing of the operation, and an end timing detecting means. When the timing of is detected, the backlight is turned off, and a display switching means for sequentially switching the display of a plurality of screens displayed on the liquid crystal panel having different display contents is provided.

As a result, seizure can be reliably prevented regardless of the usage mode, not only when the liquid crystal panel that can be opened and closed is used, but also when the liquid crystal panel is used as an in-vehicle device or as a device installed indoors or the like. Further, at the end of the operation, the backlight is turned off to prevent seizure, and the power consumption can be reduced by reducing the number of times the backlight is turned off and the seizure prevention operation is performed.

Further, it is desirable that the drive voltage of the display panel is different for each of the plurality of screens described above. Further, it is desirable that the pixel value of each pixel included in the display panel of each of the above-mentioned plurality of screens is different in each of the plurality of screens. Further, it is desirable that the plurality of screens described above are sequentially switched at predetermined time intervals. This makes it possible to gradually eliminate the charge bias caused by applying a constant drive voltage for a long time.

Further, the panel temperature detecting means for detecting the temperature of the liquid crystal panel described above is further provided, and the display switching means sets at least one of the number of times and the time for switching the display screen according to the panel temperature detected by the panel temperature detecting means. It is desirable to do. Since the situation of seizure occurrence differs depending on the panel temperature, appropriate seizure prevention can be achieved by considering the panel temperature.

Further, it is desirable that the display switching means described above switches the display screen when the panel temperature detected by the panel temperature detecting means is equal to or higher than the first reference value. By stopping the screen switching operation in an environment where burn-in is unlikely to occur, it is possible to further reduce the power consumption required to prevent burn-in.

Further, the ambient temperature detecting means for detecting the ambient temperature of the liquid crystal panel described above is further provided, and the display switching means is at least one of the number of times and the time for switching the display screen according to the ambient temperature detected by the ambient temperature detecting means. It is desirable to set. Since the situation of seizure occurrence differs depending on the ambient temperature, it is possible to appropriately prevent seizure by considering the ambient temperature.

Further, it is desirable that the display switching means described above switches the display screen when the ambient temperature detected by the ambient temperature detecting means is equal to or higher than the second reference value. By stopping the screen switching operation in an environment where burn-in is unlikely to occur, it is possible to further reduce the power consumption required to prevent burn-in.

Further, a screen transition detecting means for detecting the number of transitions of the display screen in a predetermined time immediately before the operation end timing detected by the above-mentioned end timing detecting means is further provided, and the display switching means is detected by the screen transition detecting means. It is desirable to set at least one of the number of times and the time for switching the display screen according to the number of transitions. Since the situation of burn-in occurrence differs depending on the number of transitions of the display screen immediately before the end of the operation, appropriate burn-in prevention can be achieved by considering the number of transitions.

Further, it is desirable that the display switching means described above switches the display screen when the number of transitions detected by the screen transition detecting means is equal to or less than the third reference value. By stopping the screen switching operation in an environment where burn-in is unlikely to occur, it is possible to further reduce the power consumption required to prevent burn-in.

It is a figure which shows the structure of the image display device of one Embodiment. It is a flow chart which shows the operation procedure of the burn-in suppression of a display panel. It is a flow chart which shows the operation procedure of the modification of the burn-in suppression of a display panel.

Hereinafter, an image display device according to an embodiment to which the liquid crystal display device of the present invention is applied will be described with reference to the drawings.

FIG. 1 is a diagram showing a configuration of a video display device according to an embodiment. The video display device 100 shown in FIG. 1 is incorporated in, for example, a head unit mounted on a vehicle, and displays an image based on a video signal output from the head unit main body (not shown). Further, the image display device 100 has a fixed installation position and angle with respect to the main body of the head unit, and cannot be opened / closed according to the operation of the user. It should be noted that such a usage pattern is an example, and the image display device 100 may be used in a form separated from the head unit main body.

The video display device 100 includes a video signal receiving unit 110, a display driver 112, a display panel 114, a backlight 116, a PWM signal generation unit 120, a backlight driver 122, temperature sensors 124 and 126, a power supply circuit 140, and a control unit 150. It is composed of.

The video signal receiving unit 110 receives the LVDS (Low Voltage Differential Signaling) format video signal input from the head unit main body via the video input terminal, performs serial / parallel conversion, and outputs the RGB format video signal. ..

The display driver 112 drives the display panel 114 based on the RGB format video signal output from the video signal receiving unit 110, and displays the image indicated by the video signal. The display panel 114 is, for example, a color liquid crystal display panel, and is assembled in a state of facing the backlight 116 illuminated from the back surface. The backlight 116 is formed of, for example, an LED, but other light sources may be used.

The PWM signal generation unit 120 generates a PWM signal for adjusting the brightness (brightness) of the backlight 116 by controlling the driving voltage of the backlight 116 by PWM (Pulse Width Modulation).

The temperature sensor 124 is installed inside the image display device 100 and detects the temperature of the product (display panel 114).

The temperature sensor 126 is installed around the image display device 100 and detects the ambient temperature of the image display device 100.

The power supply circuit 140 is connected to a battery (not shown) via the battery terminal BATT, and supplies operating power to each part of the image display device 100.

The control unit 150 controls the entire video display device 100. The control unit 150 is connected to the head unit main body via the communication terminal C, and transmits and receives various data to and from the head unit main body by communication according to, for example, a CAN (Controller Area Network) protocol. For example, when a notification indicating that the vehicle accessory switch (not shown) is turned off is output from the head unit main body, this notification is input to the control unit 150 via the communication terminal C.

Further, the control unit 150 operates to suppress the occurrence of the burn-in of the display panel 114, and for that purpose, the end timing detection unit 152, the temperature measurement unit 154, the screen transition detection unit 156, and the display switching unit 158 are used. I have.

The end timing detection unit 152 detects the timing of the end of operation of the video display device 100. For example, the time when the notification indicating that the accessory switch is turned off is input is detected as the timing of the end of operation.

The temperature measuring unit 154 measures the product temperature (the temperature of the display panel 114) based on the detection signal of the temperature sensor 124, and measures the ambient temperature of the image display device 100 based on the detection signal of the temperature sensor 126.

The screen transition detection unit 156 detects the number of transitions of the display screen in a predetermined time immediately before the operation end timing detected by the end timing detection unit 152. For example, the number of transitions is detected based on the video signal input to the video signal receiving unit 110 or the video signal converted into the RGB format.

The display switching unit 158 turns off the backlight 116 when the end timing detection unit 152 detects the end timing of the operation, and displays a plurality of screens on the display panel 114 with different display contents. Performs the operation of switching the screen display in order. In each of these plurality of screens, the pixel value of each pixel included in the display panel 114 is different in the plurality of screens, that is, the drive voltage for driving each pixel of the display panel 114 (each RGB filter corresponding to each pixel). The drive voltage applied to the electrodes of is set to be different.

The end timing detection unit 152 described above is used as the end timing detecting means, the display switching unit 158 is used as the display switching means, the temperature sensor 124 and the temperature measuring unit 154 are used as the panel temperature detecting means, and the temperature sensor 126 and the temperature measuring unit 154 are used as the ambient temperature. The screen transition detection unit 156 corresponds to the detection means, respectively.

The image display device 100 of the present embodiment has such a configuration, and next, an operation of suppressing the occurrence of burn-in of the display panel 114 will be described.

FIG. 2 is a flow chart showing an operation procedure for suppressing the burn-in of the display panel 114. The end timing detection unit 152 determines whether or not the accessory switch has been turned off by monitoring the notification input via the communication terminal C (step 100). If the accessory switch is not turned off, a negative decision is made and this decision is repeated. Further, when the accessory switch is turned off, a positive determination is made in the determination in step 100.

Next, the display switching unit 158 turns off the backlight 116 (step 102). For example, there is a case where an instruction is sent to the PWM signal generation unit 120 to generate a PWM signal having an on-duty of 0%, or a case where an instruction is sent to the backlight driver 122 to stop the application of the drive voltage to the backlight 116. Conceivable.

Next, the display switching unit 158 sets the pixel values of all the pixels constituting the screen of the display panel 114 to the minimum values (step 104), and sets this image for a predetermined time (for example, 0.5 seconds) for the display panel 114. Is displayed in (step 106). In reality, since the video signal receiving unit 110 creates an RGB format video signal, the above-mentioned pixel value setting and 0.5 second image display are transmitted from the display switching unit 158 to the video signal receiving unit 110. It is done against. Further, assuming that each of the three pixel values of RGB corresponds to one display pixel, "0" as the minimum value is initially set as the pixel value of each of RGB.

Next, the display switching unit 158 determines whether or not each pixel value of the image to be displayed is the maximum (step 108). For example, when each RGB pixel value is 8 bits, a value of "0" to "255" can be taken as the pixel value. Therefore, if the maximum value of the pixel value is "255" and not "255" (in the above example, the minimum value is "0"), a negative determination is made. In this case, the display switching unit 158 increments 1 as each pixel value (step 110). Then, the process returns to step 106, and the image display for 0.5 seconds is repeated. In this way, the image in which the pixel value is gradually set to a large value is displayed for 0.5 seconds each. Then, when each pixel value reaches the maximum "255", an affirmative determination is made in the determination in step 108.

Next, the display switching unit 158 sends an instruction to the power supply circuit 140 to stop (power off) the supply of operating power to each unit (step 112).

As described above, the image display device 100 of the present embodiment is not limited to the case of using the display panel that can be opened and closed, but can be used in the case of being used as an in-vehicle device provided with the display panel 114 having a fixed installation position or the like. Regardless of this, seizure of the display panel 114 can be reliably prevented. Further, at the end of the operation in which the accessory switch is turned off, the backlight 116 is turned off to perform the seizure prevention operation, and the power consumption can be reduced by turning off the backlight 116 and reducing the number of seizure prevention operations.

Further, since the display contents (pixel value and drive voltage of each pixel) are different for each of the plurality of screens whose display is switched every 0.5 seconds, a constant drive voltage is long for the same pixel of the display panel 114. It is possible to gradually eliminate the bias of the electric charge caused by the application for a long time.

FIG. 3 is a flow chart showing an operation procedure of a modified example of the burn-in suppression of the display panel 114. The operation procedure shown in FIG. 3 is different from the operation procedure shown in FIG. 2 in that steps 200, 202, 204, and 206 are added between step 100 and step 102. In the following, explanations will be given focusing on these added steps.

When the accessory switch is turned off and a positive judgment is made in the determination in step 100, the display switching unit 158 acquires the product temperature, the ambient temperature, and the number of transitions in a predetermined time (for example, 1 hour) immediately before the accessory switch is turned off. (Step 200). The product temperature needs to be averaged over the immediately preceding hour by the temperature sensor 124, but this averaging process may be performed by the temperature measuring unit 154 or the display switching unit 158. You may do it at. Similarly, this ambient temperature needs to average the ambient temperature detected by the temperature sensor 126 over the immediately preceding hour, but this averaging process may be performed by the temperature measuring unit 154 or the display switching unit. It may be done at 158. Further, for this number of transitions, it is necessary to total the number of transitions of the display screen detected by the screen transition detection unit 156 over the immediately preceding hour, but this totaling process may be performed by the screen transition detection unit 156. It may be performed by the display switching unit 158.

Next, the display switching unit 158 determines whether or not the product temperature acquired in step 200 is equal to or higher than the first reference value (for example, 50 ° C.) (step 202). If it is equal to or higher than the first reference value, an affirmative judgment is made. Further, the display switching unit 158 determines whether or not the ambient temperature acquired in step 200 is equal to or higher than the second reference value (for example, 60 ° C.) (step 204). If it is equal to or higher than the second reference value, an affirmative judgment is made. Further, the display switching unit 158 determines whether or not the number of transitions acquired in step 200 is equal to or less than the third reference value (for example, 10 times) (step 206). If it is less than or equal to the third reference value, an affirmative judgment is made.

When the affirmative determination is made in all of the three steps 202, 204, and 206 in this way, the process proceeds to step 102, and the operation necessary for suppressing the burn-in after the backlight is turned off is performed.

If a negative judgment is made in any of the three steps 202, 204, and 206, the operation immediately proceeds to step 112 without performing the operation necessary for the burn-in suppression, and the operation from the power supply circuit 140 to each part is performed. The power supply is stopped (power off).

As described above, in this modification, it is possible to appropriately prevent seizure when the product temperature (the temperature of the display panel 114) where seizure is likely to occur, the ambient temperature is high, or the number of transitions of the display screen is small. Become.

The present invention is not limited to the above embodiment, and various modifications can be made within the scope of the gist of the present invention. For example, in the operation procedure of the modified example shown in FIG. 3, when an affirmative judgment is made in all of the three steps 202, 204, and 206, the operation necessary for the burn-in suppression is performed. When an affirmative judgment is made in at least one of 202, 204, and 206, the operation necessary for the burn-in suppression may be performed. In addition, the product temperature, ambient temperature, and display screen are not determined according to the product temperature, ambient temperature, and the number of transitions of the display screen, or in parallel with this determination. The number and time of switching a plurality of screens as an operation required for the burn-in suppression may be variably set according to at least one value of the number of transitions of. For example, as the product temperature or ambient temperature decreases, or as the number of transitions of the display screen increases, the increase in pixel value "1" in step 110 may be changed to "2" or more, or the display time in step 106 may increase. May be shorter than 0.5 seconds.

Further, in the above-described embodiment, the liquid crystal display device 100 mounted on the vehicle has been described, but the present invention may be applied to the liquid crystal display device used in the device installed indoors or the portable device.

Further, in the above-described embodiment, the time when the accessory switch of the vehicle is turned off is detected as the timing of the end of operation, but for example, the power switch of the main body of the device for inputting a video signal to the liquid crystal display device 100 or the liquid crystal display device 100 is used. The time when the operation is turned off by a person may be detected as the timing of the end of the operation.

As described above, according to the present invention, not only when a liquid crystal panel that can be opened and closed is used, but also when it is used as an in-vehicle device or as a device installed indoors or the like, it can be reliably used regardless of the usage mode. It is possible to prevent seizure. Further, at the end of the operation, the backlight is turned off to prevent seizure, and the power consumption can be reduced by reducing the number of times the backlight is turned off and the seizure prevention operation is performed.

100 Video display device 110 Video signal receiver 112 Display driver 114 Display panel 116 Backlight 120 PWM signal generator 122 Backlight driver 124, 126 Temperature sensor 140 Power supply circuit 150 Control unit 152 End timing detection unit 154 Temperature measurement unit 156 Screen transition Detection unit 158 Display switching unit

Claims (10)

LCD panel and
A backlight that illuminates the liquid crystal panel and
End timing detection means to detect the end timing of operation,
When the end timing is detected by the end timing detecting means, the backlight is turned off and a plurality of screens to be displayed on the liquid crystal panel having different display contents are displayed in order. Display switching means to switch and
A liquid crystal display device comprising. The liquid crystal display device according to claim 1, wherein each of the plurality of screens has a different drive voltage of the display panel. The liquid crystal display device according to claim 1 or 2, wherein the pixel value of each pixel included in the display panel is different for each of the plurality of screens. The liquid crystal display device according to any one of claims 1 to 3, wherein the plurality of screens are sequentially switched at predetermined time intervals. Further provided with a panel temperature detecting means for detecting the temperature of the liquid crystal panel,
The display switching means according to any one of claims 1 to 4, wherein at least one of the number of times and the time for switching the display screen is set according to the panel temperature detected by the panel temperature detecting means. The liquid crystal display device described. The liquid crystal display device according to claim 5, wherein the display switching means switches the display screen when the panel temperature detected by the panel temperature detecting means is equal to or higher than the first reference value. An ambient temperature detecting means for detecting the ambient temperature of the liquid crystal panel is further provided.
The display switching means according to any one of claims 1 to 6, wherein at least one of the number of times and the time for switching the display screen is set according to the ambient temperature detected by the ambient temperature detecting means. The liquid crystal display device described. The liquid crystal display device according to claim 7, wherein the display switching means switches the display screen when the ambient temperature detected by the ambient temperature detecting means is equal to or higher than the second reference value. A screen transition detecting means for detecting the number of transitions of the display screen in a predetermined time immediately before the operation end timing detected by the end timing detecting means is further provided.
The display switching means according to any one of claims 1 to 6, wherein at least one of the number of times and the time for switching the display screen is set according to the number of transitions detected by the screen transition detecting means. The liquid crystal display device described. The liquid crystal display device according to claim 9, wherein the display switching means switches the display screen when the number of transitions detected by the screen transition detecting means is equal to or less than a third reference value.

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