Display device and control method for the display device

Abstract

The present invention provides a display device and a method for controlling the display device. [Solution] The display device comprises a display unit for displaying images and a brightness control unit. The brightness control unit, when the brightness of the display unit remains above a first brightness value for a standby period, starts a repeating control that alternately repeats a first control, which maintains the brightness at a second brightness value (lower than the first brightness value) for a first hour, and a second control, which maintains the brightness at the first brightness value for a second hour. If the image is a moving image, the first hour is set to be less than or equal to the second hour. If at least a part of the image is a still image, the first hour is set to be longer than the second hour.

Description

Technical Field

[0001] The present disclosure relates to a display device and a control method for the display device.

Background Art

[0002] In a general display device, a light-emitting element such as a light-emitting diode or an organic electroluminescence element is used as a light source. The luminance of the light-emitting element varies according to the brightness of the video displayed by the display device.

[0003] The greater the luminance of the display device, the greater the current supplied to the light-emitting element. Therefore, in a region where the luminance is high when displaying a video, the amount of heat generated by the light-emitting element in that region increases, and the deterioration of the light-emitting element is accelerated. As a result, for example, when the lifespan of the light-emitting element is shortened or the deterioration of the light-emitting element progresses locally, display defects such as image sticking may occur in the display device. Therefore, in a general display device, in order to suppress the deterioration of the light-emitting element, when the luminance of the display device becomes greater than a predetermined threshold value, control is performed to limit the luminance to below the threshold value to protect the light-emitting element.

[0004] For example, in Patent Document 1, in an image displayed by a display device, the luminance of only a still image portion such as an on-screen display is reduced and combined with a moving image portion having a normal luminance, so that display data with reduced luminance of only the still image portion is displayed to prevent image sticking of the display device. A technique is disclosed.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, the aforementioned technology cannot control the brightness of areas with high brightness when the display device is displaying video. Therefore, when displaying video, if the cumulative time the display device is in a state of high brightness becomes large, there is a problem that the lifespan of the light-emitting element may be shorter than expected, or burn-in may occur on the display device. On the other hand, if control is applied to reduce the brightness of video in the same way as still images, the deterioration of display quality becomes more noticeable than with still images, as video inherently has a tendency for brightness to fluctuate.

[0007] This disclosure was made to resolve the above-mentioned problems, and aims to extend the lifespan of the display device while suppressing the deterioration of display quality when the brightness of video is reduced, by changing the way brightness is controlled depending on whether the image displayed on the display device is a video or at least partially a still image. [Means for solving the problem]

[0008] A display device according to one aspect of the present disclosure comprises a display unit for displaying images and a brightness control unit, wherein if the brightness of the display unit remains greater than a first brightness value for a standby period, the brightness control unit starts a repeating control that alternately repeats a first control, which maintains the brightness at a second brightness value less than the first brightness value for a first hour, and a second control, which maintains the brightness at the first brightness value for a second hour. If the image is a moving image, the first hour is set to two hours or less, and if at least a part of the image is a still image, the first hour is set to be longer than two hours. [Brief explanation of the drawing]

[0009] [Figure 1] This is a block diagram showing the display device according to Embodiment 1. [Figure 2] This is a flowchart illustrating the control method for the display device according to Embodiment 1. [Figure 3] This disclosure is a plan view showing an example of the display unit when the video includes still images. [Figure 4]This disclosure is a plan view showing an example of the display unit when the video includes still images. [Figure 5] This is a graph showing the temporal change in the brightness of the display unit when the image is a video in Embodiment 1. [Figure 6] This is a graph showing the temporal change in the brightness of the display unit when the video includes still images in Embodiment 1. [Figure 7] This is a flowchart illustrating a control method for a display device according to a modified example of Embodiment 1. [Figure 8] This is a graph showing the temporal change in the brightness of the display unit when the image is a video in a modified example of Embodiment 1. [Figure 9] This is a graph showing the temporal change in the brightness of the display unit when the video includes still images, in a modified example of Embodiment 1. [Figure 10] A block diagram showing the display device according to Embodiment 2. [Figure 11] This is a flowchart illustrating the control method for the display device according to Embodiment 2. [Figure 12] This is a graph showing the temporal changes in the brightness of the display unit and the temporal changes in the count value of the counter unit when the image is a video in Embodiment 2. [Figure 13] This is a graph showing the temporal changes in the brightness of the display unit and the temporal changes in the count value of the counter unit when the video includes still images in Embodiment 2. [Figure 14] This is a flowchart illustrating a control method for a display device according to a modified example 1 of Embodiment 2. [Figure 15] This graph shows the temporal changes in the brightness of the display unit and the temporal changes in the count value of the counter unit when the image is a video in a modified example 1 of Embodiment 2. [Figure 16] This is a graph showing the temporal changes in the brightness of the display unit and the temporal changes in the count value of the counter unit when the video includes still images, in a modified example 1 of Embodiment 2. [Figure 17] This is a flowchart illustrating a control method for a display device according to a modified example 2 of Embodiment 2. [Figure 18] It is a block diagram showing a display device according to Embodiment 3. [Figure 19] It is a flowchart showing a control method of the display device according to Embodiment 3. [Figure 20] In Embodiment 3, it is a graph showing the temporal change of the luminance of the display unit when the temperature measured by the temperature sensor is equal to or higher than a predetermined threshold value and the video is a moving image. [Figure 21] In Embodiment 3, it is a graph showing the temporal change of the luminance of the display unit when the temperature measured by the temperature sensor is equal to or higher than a predetermined threshold value and the video includes a still image. [Figure 22] It is a flowchart showing a control method of the display device according to a modified example of Embodiment 3. [Figure 23] In the modified example of Embodiment 3, it is a graph showing the temporal change of the luminance of the display unit when the temperature measured by the temperature sensor is equal to or higher than a predetermined threshold value and the video is a moving image. [Figure 24] In the modified example of Embodiment 3, it is a graph showing the temporal change of the luminance of the display unit when the temperature measured by the temperature sensor is equal to or higher than a predetermined threshold value and the video includes a still image. [Figure 25] It is an exploded view of the display device according to Embodiment 3. [Figure 26] It is a plan view of the display device according to Embodiment 3.

Mode for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the drawings, the same or equivalent elements are denoted by the same reference numerals, and redundant descriptions are omitted. In addition, the embodiments described below do not unduly limit the content of the present disclosure described in the claims, and all the configurations described in the embodiments are not necessarily essential as the solution means of the present disclosure.

[0011] <Embodiment 1> Figure 1 is a block diagram showing a display device 100 according to Embodiment 1 of the present disclosure. The display device 100 includes a video signal processing unit 101, a drive unit 102, a storage unit 103, a display unit 110, and a brightness control unit 120.

[0012] The video signal processing unit 101 processes the video signal received from the outside and transmits it to the drive unit 102 and the brightness control unit 120. For example, the video signal processing unit 101 processes the video signal received from the outside to generate information about the video to be displayed, information about the brightness value specified when displaying the video, information indicating whether the received video signal is a moving image or whether at least a part of the video is a still image, and then appropriately assigns and transmits this information to the drive unit 102 and the brightness control unit 120.

[0013] The drive unit 102 drives the display unit 110 based on the video signal processed by the video signal processing unit 101, and displays the video on the display unit 110.

[0014] The display unit 110 is, for example, a display panel having a display surface for displaying images. The display panel can be any panel capable of displaying images, such as a liquid crystal display panel using liquid crystals, or an organic electroluminescent (hereinafter referred to as organic EL) display panel using organic EL elements. The display panel is equipped with a light source. For example, a typical liquid crystal display panel uses a backlight as a light source, while an organic EL display panel uses organic EL elements that emit light themselves as a light source.

[0015] The brightness control unit 120 controls the brightness of the display unit 110. For example, the brightness control unit 120 controls the brightness of the display unit 110 according to the brightness value specified by the video signal processed by the video signal processing unit 101. Furthermore, as will be described in more detail later, if the brightness value specified by the video signal exceeds a predetermined first brightness value B1, the brightness control unit 120 can control the brightness of the display unit 110 to a brightness value lower than the brightness value specified by the video signal.

[0016] The memory unit 103 stores various parameters and programs used to operate the video signal processing unit 101, the display unit 110, the brightness control unit 120, etc. The memory unit 103 also stores various information acquired by the video signal processing unit 101, the display unit 110, the brightness control unit 120, etc.

[0017] The video signal processing unit 101, the drive unit 102, the memory unit 103, and the brightness control unit 120 are composed of, for example, a microcontroller, an integrated circuit, peripheral circuits, etc. The microcontroller includes a processor and memory, and for example, the processor operates as the brightness control unit 120 and the memory operates as the memory unit 103. The processor operates the microcontroller and peripheral circuits as control units based on the program and various data stored in the memory. At least a part of the processing performed by the microcontroller can also be performed by a dedicated integrated circuit; for example, the video signal processing unit 101 may be an integrated circuit dedicated to communication processing and signal processing, and the drive unit 102 may be a driver integrated circuit. Furthermore, the configuration of the display device 100 is not limited to those described above; for example, the display device 100 may include a clock circuit for measuring time, etc.

[0018] <Control method for the display device 100 of Embodiment 1> Figure 2 is a flowchart showing the control method of the display device 100 according to Embodiment 1. Figures 5 and 6 are graphs showing the temporal change in brightness B of the display unit 110 controlled by the control method shown in the flowchart of Figure 2 in Embodiment 1. As will be described in detail later, Figure 5 is a graph showing the temporal change in brightness B of the display unit 110 when the image is a moving image in Embodiment 1, and Figure 6 is a graph showing the temporal change in brightness B of the display unit 110 when the image includes a still image in Embodiment 1. Note that the brightness value of brightness B of the display unit 110 may be the maximum brightness value measured locally within the display unit 110, or the average brightness value of the entire display unit 110 may be used.

[0019] Step S101 is a step to determine whether the brightness B of the display unit 110 remained greater than the first brightness value B1 for a waiting time T0. For example, the brightness control unit 120 monitors the brightness B of the display unit 110, and if the brightness B remains greater than the first brightness value B1 stored in the storage unit 103 for a waiting time T0 that has been stored in the storage unit 103, the process proceeds to step S102. In Figure 6, for example, when the display unit 110 starts displaying an image after an elapsed time of 3 seconds, the brightness B of the display unit 110 becomes a brightness value B0 that is greater than the first brightness value B1, and step S101 shown in Figure 2 is started. In one example of Embodiment 1, the first brightness value B1 is set to 1500 nits, and the brightness value B0 is the maximum brightness that the display unit 110 can display, for example, 2000 nits. When the brightness B remains at the brightness value B0 for a waiting time T0 that has been set to 3 seconds, the process proceeds to step S102 shown in Figure 2. In step S101, if the brightness B becomes less than or equal to the first brightness value B1 before the waiting time T0 has elapsed, the process does not proceed to step S102, and the control of the display unit 110 shown in Figure 2 is terminated.

[0020] Step S102 is a step in which the display unit 110 determines whether the image it displays is a moving image. For example, when the video signal processing unit 101 displays a video signal received from an external source on the display unit 110, it determines whether the image is a moving image or whether at least a part of the image contains a still image, and transmits the determination information to the brightness control unit 120. Alternatively, the determination information may be stored in the storage unit 103 either directly from the video signal processing unit 101 or via the brightness control unit 120, and the brightness control unit 120 may read the determination information from the storage unit 103 when the process proceeds from step S101 to step S102.

[0021] When the image displayed by the display unit 110 is a video, the entire image displayed by the display unit 110 is a video. In contrast, when at least a part of the image displayed by the display unit 110 includes a still image, in addition to the case where the entire image displayed by the display unit 110 is a still image, as shown in Figure 3, an on-screen display area 201 in which a still image such as text on an on-display screen is displayed is superimposed on a video display area 200 in which a video is displayed, and as shown in Figure 4, a case in which a video display area 200 in which a video is displayed and a fixed display area 202 in which a still image whose position is fixed for a certain period of time, such as a time signal or data display, are displayed together.

[0022] In step S102, the criteria for determining whether the video is a moving image are, for example, if the entire video becomes a moving image when displayed on the display unit 110, then the video is determined to be a moving image. Also, if the entire video is a still image when displayed on the display unit 110, or if a still image such as text information is displayed overlaid on a part of the video in on-screen display, or if the video and still image are displayed simultaneously, then the video is determined to be at least partially a still image and not a moving image. As shown in Figure 2, if it is determined in step S102 that the video is a moving image, the process proceeds to step S103, and if it is determined that at least partially the video is a still image, the process proceeds to step S104.

[0023] Steps S103 and S104 are steps to adjust the relative lengths of the length of the first time T1 for maintaining the first control and the length of the second time T2 for maintaining the second control, in a repeating control that alternately repeats the first control shown in step S105 and the second control shown in step S106, which will be described later. The first time T1 and the second time T2 are set to predetermined initial values ​​in advance and are stored, for example, in the storage unit 103. Embodiment 1 will be explained using the case where the initial values ​​of both the first time T1 and the second time T2 are set to 5 seconds as an example.

[0024] In step S103, the first time T1 is made less than or equal to the second time T2. In Embodiment 1, for example, the brightness control unit 120 changes the first time T1 stored in the storage unit 103 from an initial value of 5 seconds to 3 seconds, while leaving the second time T2 at its initial value of 5 seconds. On the other hand, in step S104, the first time T1 is made longer than the second time T2. In Embodiment 1, for example, the brightness control unit 120 changes the first time T1 stored in the storage unit 103 from an initial value of 5 seconds to 6 seconds, while leaving the second time T2 at its initial value of 5 seconds. Note that in steps S103 and S104, it is sufficient to change at least one of the first time T1 and the second time T2, or both the first time T1 and the second time T2 may be changed. Once step S103 or step S104 is completed, the process proceeds to a repeating control that alternately repeats steps S105 and S106.

[0025] As shown in Figure 2, the repeating control alternately repeats steps S105 and S106 until the condition is met that the brightness B of the display unit 110 is less than the second brightness value B2. For example, if the image is switched and the brightness value specified by the newly received video signal is less than the second brightness value B2, the repeating control is stopped. The second brightness value B2 is preset to a brightness value smaller than the first brightness value B1. For example, if the first brightness value B1 is 1500 nits, the second brightness value B2 is set to 1300 nits.

[0026] Step S105 involves the luminance control unit 120 performing a first control to control the display unit 110 so that the luminance B is maintained at a second luminance value B2, which is smaller than the first luminance value B1, for a first time T1. Step S105 ends when the first time T1 has elapsed since the start of the first control, and the process proceeds to step S106.

[0027] In step S106, the brightness control unit 120 performs a second control, controlling the display unit 110 to maintain the brightness B at a first brightness value B1 for a second time T2. Step S106 ends when the second time T2 has elapsed since the start of the second control, and the process proceeds back to step S105.

[0028] If the brightness B of the display unit 110 is controlled by setting, for example, only one reference value and reducing the brightness B to the reference value when the brightness B is higher than that reference value, then, for example, if the image is a moving image and the brightness B is prone to fluctuations, the brightness B will frequently become higher or lower than the reference value. As a result, the start and stop of the brightness B control will switch frequently, and the brightness B of the image may flicker unnaturally. In Embodiment 1, two reference values, a first brightness value B1 and a second brightness value B2, are used to prevent the start and stop of the brightness B control from switching frequently.

[0029] Furthermore, if the image displayed by the display unit 110 is a video, in step S103 the first time T1 is set to be less than or equal to the second time T2. For example, in Figure 5, the first time T1 is 3 seconds and the second time T2 is 5 seconds. Therefore, as shown in Figure 5, if the image displayed by the display unit 110 is a video, in the repeated control, the cumulative time of the second control controlled by the first brightness value B1 will be greater than or equal to the cumulative time of the first control controlled by the second brightness value B2. For example, in Figure 5, when the first control and the second control are repeated twice each in the repeated control, the cumulative time during which brightness B is maintained at the first brightness value B1 is 10 seconds, and the cumulative time during which brightness B is maintained at the second brightness value B2 is 6 seconds.

[0030] On the other hand, if at least a portion of the video displayed by the display unit 110 includes still images, the first time T1 is made longer than the second time T2 in step S104. For example, in Figure 6, the first time T1 is 6 seconds and the second time T2 is 5 seconds. Therefore, as shown in Figure 6, if at least a portion of the video displayed by the display unit 110 includes still images, in the repeated control, the cumulative time of the second control controlled by the first brightness value B1 is shorter than the cumulative time of the first control controlled by the second brightness value B2. For example, in Figure 6, when the first control and the second control are repeated twice each in the repeated control, the cumulative time during which brightness B is maintained at the first brightness value B1 is 10 seconds, and the cumulative time during which brightness B is maintained at the second brightness value B2 is 12 seconds. Therefore, when the image displayed by the display unit 110 is a video, the time during which the brightness is controlled at a brightness value greater than the second brightness value B2 is longer than when at least a portion of the image displayed by the display unit 110 includes a still image.

[0031] In order to suppress the degradation of the light-emitting elements included in the display unit 110, it is preferable to increase the time for which the brightness B is controlled to be lower. However, if the brightness B is controlled to be lower and the time for which the image is relatively dark increases, there is a risk that the display quality of the display device 100 may decrease, for example, resulting in a poor visual impression. If at least a part of the image displayed by the display unit 110 includes still images and there are areas where the brightness value does not change, degradation of the light-emitting elements, such as burn-in, is likely to occur in areas with high brightness values. However, if the image is a video, the brightness value tends to change throughout the entire display unit 110, so localized degradation of the light-emitting elements is less likely to progress. Therefore, in Embodiment 1, if the image displayed by the display unit 110 is a video, degradation of the light-emitting elements is less likely to progress. For example, to prioritize maintaining display quality so as to improve the visual impression, the time for control with a first brightness value B1, which is a brightness value greater than the second brightness value B2, is increased. If at least a part of the image displayed by the display unit 110 includes still images and degradation of the light-emitting elements is likely to progress, the control is performed to increase the time for control with a second brightness value B2, which is a brightness value smaller than the first brightness value B1. This makes it possible to suppress the degradation of the light-emitting elements while also suppressing a decrease in the display quality of the display device 100.

[0032] The brightness control unit 120 stops the repetitive control if the brightness B becomes less than the second brightness value B2 while the repetitive control is being executed. For example, if the video is switched and the brightness value specified in the newly received video signal is less than the second brightness value B2, the repetitive control is stopped. Then, as shown in Figure 2, the control of the display unit 110 by the brightness control unit 120 ends. For example, if the scene of the video displayed by the display unit 110 changes or the displayed still image is switched to another still image while the repetitive control is being executed, and the brightness B of the display unit 110 becomes less than the second brightness value B2 even without control by the brightness control unit 120, and control of brightness B becomes unnecessary, the brightness control unit 120 stops the repetitive control. Note that when the control of the display unit 110 by the brightness control unit 120 ends, the first time T1 and the second time T2 may be returned to the initial values ​​stored in the storage unit 103.

[0033] <Modified form of Embodiment 1> Figure 7 is a flowchart showing a control method for the display device 100 according to a modified example of Embodiment 1. Figures 8 and 9 are graphs showing the temporal change in brightness B of the display unit 110 controlled by the control method shown in the flowchart of Figure 7 in the modified example of Embodiment 1. Figure 8 is a graph showing the temporal change in brightness B of the display unit 110 when the image is a moving image in the modified example of Embodiment 1, and Figure 9 is a graph showing the temporal change in brightness B of the display unit 110 when the image includes a still image in the modified example of Embodiment 1. The modified example of Embodiment 1 differs from Embodiment 1 in that the brightness control unit 120 gradually changes the brightness B of the display unit 110 when changing the brightness B, but the other configurations are generally the same as Embodiment 1. In the following description of the modified example of Embodiment 1, the differences from Embodiment 1 will be explained in detail, and the points common to Embodiment 1 will be omitted as appropriate.

[0034] As shown in Figure 7, steps S201, S202, S203, and S204 are the same as steps S101, S102, S103, and S104 of Embodiment 1, so their explanation will be omitted.

[0035] If the image displayed by the display unit 110 is a video, in step S203 the first time T1 is set to be less than or equal to the second time T2. For example, in Figure 8, the first time T1 is 3 seconds and the second time T2 is 5 seconds. On the other hand, if at least a part of the image displayed by the display unit 110 includes a still image, in step S204 the first time T1 is set to be longer than the second time T2. For example, in Figure 9 the first time T1 is 6 seconds and the second time T2 is 5 seconds.

[0036] As shown in Figure 7, in the modified embodiment of Embodiment 1, unlike Embodiment 1, the process proceeds to step S205 after step S203 or step S204 is completed. Step S205 is a step in which the brightness control unit 120 performs initial change control, gradually changing the brightness B of the display unit 110 from a state greater than the first brightness value B1 to the second brightness value B2. In the initial change control of step S205, as shown in Figures 8 and 9, for example, the brightness B is gradually decreased from a brightness value B0 greater than the first brightness value B1 to the second brightness value B2 over a period of 3 seconds. This makes the change in brightness B gradual, making it less likely for the user to feel discomfort while watching the image. When the brightness B reaches the second brightness value B2, step S205 ends, and the process proceeds to a repeat control that repeats steps S206 to S209.

[0037] As shown in Figure 7, the repeating control is a control that repeats steps S206 to S209 until the condition is met that the brightness B of the display unit 110 is less than the second brightness value B2. For example, if the image is switched and the brightness value specified by the newly received video signal is less than the second brightness value B2, the repeating control is stopped. Steps S206 and S208 are the same as steps S105 and S106 of Embodiment 1. Therefore, in step S206, the brightness control unit 120 performs a first control to control the display unit 110 so that the brightness B is maintained at the second brightness value B2, which is less than the first brightness value B1, for a first time T1. In step S208, the brightness control unit 120 performs a second control to control the display unit 110 so that the brightness B is set to the first brightness value B1 and maintained for a second time T2.

[0038] As shown in Figure 7, in the modified embodiment of Embodiment 1, unlike Embodiment 1, step S207 is performed between the first control in step S206 and the second control in step S208. Step S207 is a step in which the brightness control unit 120 performs a first change control in which the brightness B of the display unit 110 is gradually changed from the second brightness value B2 to the first brightness value B1. In other words, in the first change control, the brightness B is gradually changed from the second brightness value B2 to the first brightness value B1 while switching from the first control to the second control. In the first change control in step S207, as shown in Figures 8 and 9, for example, the brightness B is gradually increased from the second brightness value B2 to the first brightness value B1 over a period of 1 second. This makes the change in brightness B gradual, making it less likely for the user to feel discomfort while watching the video.

[0039] Furthermore, as shown in Figure 7, in the modified embodiment of Embodiment 1, unlike Embodiment 1, step S209 is performed in the repeated control before returning from the second control in step S208 to the first control in step S206. Step S209 is a step in which the brightness control unit 120 performs a second change control in which the brightness B of the display unit 110 is gradually changed from a first brightness value B1 to a second brightness value B2. In other words, in the second change control, the brightness B is gradually changed from the first brightness value B1 to the second brightness value B2 while switching from the second control to the first control. In the second change control of step S209, as shown in Figures 8 and 9, for example, the brightness B is gradually decreased from the first brightness value B1 to the second brightness value B2 over a period of 1 second. This makes the change in brightness B gradual, making it less likely for the user to feel discomfort while watching the video.

[0040] As described above, in the modified embodiment of Embodiment 1, similar to Embodiment 1, when the image displayed by the display unit 110 is a moving image, priority is given to maintaining display quality, and the time spent controlling with the first brightness value B1, which is a brightness value greater than the second brightness value B2, is extended. When at least a part of the image displayed by the display unit 110 includes a still image, the time spent controlling with the second brightness value B2, which is a brightness value less than the first brightness value B1, is extended. This suppresses the deterioration of the light-emitting element while also suppressing a decrease in the display quality of the display device 100. Furthermore, in the modified embodiment of Embodiment 1, the brightness control unit 120 gradually changes the brightness B of the display unit 110, so that even when the brightness B is changed as shown in Figures 7 to 9, the user is less likely to feel any discomfort while watching the image.

[0041] <Embodiment 2> Figure 10 is a block diagram showing a display device 100 according to Embodiment 2 of the present disclosure. The display device 100 of Embodiment 2 differs from Embodiment 1 in that it includes a counter unit 130, but the other configurations are generally the same as those of Embodiment 1. In the following description of Embodiment 2, the differences from Embodiment 1 will be explained in detail, and the points common to Embodiment 1 will be omitted as appropriate.

[0042] The counter unit 130 is an electronic circuit that can increase or decrease the count value in accordance with the passage of time. For example, the count value is an integer greater than or equal to zero, and the counter unit 130 can increase or decrease the count value by one per predetermined unit time as time progresses during a period in which a specific control is being performed. As shown in Figure 10, in the display device 100 of Embodiment 2, for example, the counter unit 130 is connected to the brightness control unit 120 and the storage unit 103 by signal lines, so that they can send and receive information from each other. The storage unit 103 stores various parameters and programs used to operate the counter unit 130, and the storage unit 103 also stores various information acquired by the counter unit 130.

[0043] <Control method for the display device 100 of Embodiment 2> Figure 11 is a flowchart showing the control method of the display device 100 according to Embodiment 2. Figures 12 and 13 are graphs showing the temporal changes in the brightness B of the display unit 110 controlled by the control method shown in the flowchart of Figure 11 in Embodiment 2. As will be described in detail later, Figure 12 is a graph showing the temporal changes in the brightness B of the display unit 110 and the temporal changes in the count value C of the counter unit 130 when the image is a moving image in Embodiment 2. Figure 13 is a graph showing the temporal changes in the brightness B of the display unit 110 and the temporal changes in the count value C of the counter unit 130 when the image includes a still image in Embodiment 2. Embodiment 2 differs from Embodiment 1 in that the first time T1 during which the first control is maintained and the second time T2 during which the second control is maintained are controlled using the counter unit 130, but the other configurations are generally the same as Embodiment 1. In the following description of Embodiment 2, the differences from Embodiment 1 will be explained in detail, and the points common to Embodiment 1 will be omitted as appropriate.

[0044] Step S301 is a step in which it is determined whether the brightness B of the display unit 110 is greater than the first brightness value B1. For example, the brightness control unit 120 monitors the brightness B of the display unit 110, and if the brightness B is greater than the first brightness value B1 stored in the storage unit 103, the process proceeds to step S302. If the brightness B is less than or equal to the first brightness value B1, the process does not proceed to step S302, and the control of the display unit 110 shown in Figure 11 ends.

[0045] Step S302 is a step in which the counter unit 130 increases the count value C as time progresses. For example, a second count value C2 is set as the initial value of the count value C, and as shown in Figures 12 and 13, the counter unit 130 increases the count value C from the second count value C2 as time progresses. After a certain amount of time has elapsed, the process proceeds from step S302 to step S303.

[0046] Step S303 is a step in which the counter unit 130 determines whether the count value C is the first count value C1. The first count value C1 is set in advance as a count value greater than the second count value C2, for example, the first count value C1 is pre-stored in the storage unit 103. In step S303, the counter unit 130 compares the count value C with the first count value C1 stored in the storage unit 103. If the count value C has not reached the first count value C1, steps S301 and S302 are repeated to further increase the count value C. If the count value C has reached the first count value C1, the process proceeds to step S304. Figures 12 and 13 illustrate a case where the first count value C1 is 3 counts and the second count value C2 is zero counts, and the counter unit 130 increases the count value at a rate of 1 count per second. Three seconds elapse for the count value C to increase from the second count value C2 to reach the first count value C1. As shown in Figures 11 to 13, in Embodiment 2, the three seconds elapsed during steps S301 to S303 corresponds to the waiting time T0 in step S101 of Embodiment 1. In other words, steps S301 to S303 of Embodiment 2 correspond to step S101 of Embodiment 1.

[0047] Step S304 is the same as step S102 in Embodiment 1, and is a step to determine whether the image displayed by the display unit 110 is a video. If it is determined that the image is a video, the process proceeds to step S305; if it is determined that at least a part of the image is a still image, the process proceeds to step S306.

[0048] Steps S305 and S306 are steps in which the counter unit 130 adjusts the rate at which the count value C decreases over time while the first control, shown in steps S307 to S309 described later, and the rate at which the count value C increases over time while the second control is being executed, in a repetitive control that alternately repeats the first control, shown in steps S307 to S309, and the second control, shown in steps S310 to S312. More specifically, the counter unit 130 decreases the count value C in a first time interval I1 while the first control is being executed, and increases the count value C in a second time interval I2 while the second control is being executed. The first time interval I1 and the second time interval I2 are set to predetermined initial values ​​in advance and are stored, for example, in the storage unit 103. Embodiment 2 will be explained using the example where the initial values ​​of both the first time interval I1 and the second time interval I2 are set to 1.67 seconds per count (1 count change every 1.67 seconds).

[0049] In step S305, the first time interval I1 is made less than or equal to the second time interval I2. In Embodiment 2, for example, the brightness control unit 120 changes the first time interval I1 stored in the memory unit 103 from an initial value of 1.67 seconds per count (1 count change every 1.67 seconds) to 1 second per count (1 count change every 1 second), while the second time interval I2 remains at its initial value of 1.67 seconds per count (1 count change every 1.67 seconds). On the other hand, in step S306, the first time interval I1 is made longer than the second time interval I2. In Embodiment 2, for example, the brightness control unit 120 changes the first time interval I1 stored in the memory unit 103 from an initial value of 1.67 seconds per count (1 count change every 1.67 seconds) to 2 seconds per count (1 count change every 2 seconds), while leaving the second time interval I2 at 1.67 seconds per count (1 count change every 1.67 seconds). In steps S305 and S306, it is sufficient to change at least one of the first time interval I1 and the second time interval I2, or both the first time interval I1 and the second time interval I2 may be changed. Once step S305 or step S306 is completed, the process proceeds to repeating steps S307 to S309 and steps S310 to S312 alternately. The values ​​for the first time interval I1 and the second time interval I2 described above are examples, and other values ​​may be used.

[0050] In steps S307 to S309, the brightness control unit 120 performs a first control to control the display unit 110 so that the brightness B is maintained at a second brightness value B2 which is smaller than the first brightness value B1. More specifically, in step S307, the brightness control unit 120 maintains the brightness B at a second brightness value B2 which is smaller than the first brightness value B1.

[0051] Step S308 is a step in which the counter unit 130 decreases the count value C at a first time interval I1 as time progresses. As described above, at step S303, the count value C has reached the first count value C1, and in step S308, the counter unit 130 decreases the count value C from the first count value C1 at a rate of the first time interval I1. After a certain amount of time has elapsed, the process proceeds from step S308 to step S309.

[0052] Step S309 is a step in which it is determined whether the count value C of the counter unit 130 is the second count value C2. In step S309, the counter unit 130 compares the count value C with the second count value C2 stored in the storage unit 103. If the count value C has not reached the second count value C2, steps S307 and S308 are repeated to further decrease the count value C. If the count value C has reached the second count value C2, the process proceeds to step S310, where the control of the brightness control unit 120 is switched from first control to second control. In other words, in Embodiment 2, the time calculated by multiplying the count value, which is the difference between the first count value C1 and the second count value C2, by the first time interval I1 is the execution time of the first control, and corresponds to the first time T1 in Embodiment 1.

[0053] In steps S310 to S312, the brightness control unit 120 performs a second control to control the display unit 110 so that brightness B is maintained at a first brightness value B1. More specifically, in step S310, the brightness control unit 120 maintains brightness B at a first brightness value B1.

[0054] Step S311 is a step in which the counter unit 130 increases the count value C at a second time interval I2 as time progresses. As described above, at step S309, the count value C has reached the second count value C2, and in step S311, the counter unit 130 increases the count value C from the second count value C2 at a rate of the second time interval I2. After a certain amount of time has elapsed, the process proceeds from step S311 to step S312.

[0055] Step S312 is a step in which it is determined whether the count value C of the counter unit 130 is the first count value C1. In step S312, the counter unit 130 compares the count value C with the first count value C1 stored in the storage unit 103. If the count value C has not reached the first count value C1, steps S310 and S311 are repeated to further increase the count value C. If the count value C has reached the first count value C1, the process returns to step S307, and the control of the brightness control unit 120 is switched from second control to first control. In other words, in Embodiment 2, the time calculated by multiplying the count value of the difference between the first count value C1 and the second count value C2 by the second time interval I2 is the execution time of the second control, and corresponds to the second time T2 in Embodiment 1.

[0056] If the image displayed by the display unit 110 is a video, in step S305 the first time interval I1 is set to be less than or equal to the second time interval I2. For example, in Embodiment 2, when the first count value C1 is set to 3 counts and the second count value C2 is set to zero counts, in Figure 12, the first time interval I1 is set to 1 second per count (1 count change every 1 second), and the second time interval I2 is set to 1.67 seconds per count (1 count change every 1.67 seconds). Therefore, the first time T1 for performing the first control is 3 seconds, and the second time T2 for performing the second control is 5 seconds. Consequently, as shown in Figure 12, if the image displayed by the display unit 110 is a video, in the repeated control, the cumulative time of the second control controlled by the first brightness value B1 is greater than or equal to the cumulative time of the first control controlled by the second brightness value B2. For example, in Figure 12, when the first control and the second control are repeated twice each in the repeated control, the cumulative time during which brightness B is maintained at the first brightness value B1 is 10 seconds, and the cumulative time during which brightness B is maintained at the second brightness value B2 is 6 seconds.

[0057] On the other hand, if at least a portion of the video displayed by the display unit 110 includes still images, the first time interval I1 is made longer than the second time interval I2 in step S306. For example, in Embodiment 2, when the first count value C1 is set to 3 counts and the second count value C2 is set to zero counts, in Figure 13, the first time interval I1 is set to 2 seconds per count (1 count change every 2 seconds), and the second time interval I2 is set to 1.67 seconds per count (1 count change every 1.67 seconds). Therefore, the first time T1 in which the first control is performed is 6 seconds, and the second time T2 in which the second control is performed is 5 seconds. Consequently, as shown in Figure 13, if at least a portion of the video displayed by the display unit 110 includes still images, in the repeated control, the cumulative time of the second control controlled by the first brightness value B1 is shorter than the cumulative time of the first control controlled by the second brightness value B2. For example, in Figure 13, when the first control and the second control are repeated twice each in the repeated control, the cumulative time during which brightness B is maintained at the first brightness value B1 is 10 seconds, and the cumulative time during which brightness B is maintained at the second brightness value B2 is 12 seconds. Therefore, when the image displayed by the display unit 110 is a moving image, the time during which the brightness is controlled at a higher brightness value is longer than when at least a part of the image displayed by the display unit 110 includes a still image.

[0058] As described above, the display device 100 of Embodiment 2 achieves the same control as in Embodiment 1 by the count value C of the counter unit 130, thereby suppressing the deterioration of the light-emitting element while also suppressing a decrease in the display quality of the display device 100, such as a poor visual impression.

[0059] The brightness control unit 120 stops the repetitive control if the brightness B becomes less than the second brightness value B2 while the repetitive control is being executed. For example, if the video is switched and the brightness value specified in the newly received video signal is less than the second brightness value B2, the repetitive control is stopped. Then, as shown in Figure 11, the control of the display unit 110 by the brightness control unit 120 ends. At the point when the control of the display unit 110 by the brightness control unit 120 ends, the first time interval I1 and the second time interval I2 may be returned to their initial values ​​stored in the storage unit 103. Furthermore, it is preferable to return the count value C to its initial value when the repetitive control ends, and when the brightness B of the display unit 110 becomes less than or equal to the first brightness value B1 in step S301. In Embodiment 2, it is sufficient to return the count value C to the second count value C2 which was set as the initial value of the count value C, for example, the second count value C2 is returned to zero count.

[0060] <Modification 1 of Embodiment 2> Figure 14 is a flowchart showing the control method of the display device according to Modification 1 of Embodiment 2. Figures 15 and 16 are graphs showing the temporal change of brightness B of the display unit 110 controlled by the control method shown in the flowchart of Figure 14 in Modification 1 of Embodiment 2. Figure 15 is a graph showing the temporal change of brightness B of the display unit 110 when the image is a moving image in Modification 1 of Embodiment 2, and Figure 16 is a graph showing the temporal change of brightness B of the display unit 110 when the image includes a still image in Modification 1 of Embodiment 2. Modification 1 of Embodiment 2 differs from Embodiment 2 in that the brightness control unit 120 gradually changes the brightness B of the display unit 110 when changing the brightness B, but the other configurations are generally the same as Embodiment 2. In the following description of Modification 1 of Embodiment 2, the differences from Embodiment 2 will be explained in detail, and the points common to Embodiment 2 will be omitted as appropriate.

[0061] As shown in Figure 14, steps S401 to S406, steps S408 to S410, and steps S412 to S414 are common to steps S301 to S306, steps S307 to S309, and steps S310 to S312 of Embodiment 2, so their explanation will be omitted.

[0062] As shown in Figure 14, in the modified example 1 of Embodiment 2, unlike Embodiment 2, step S407 is performed between steps S406 and S408. Step S407 is a step in which the brightness control unit 120 performs initial change control, gradually changing the brightness B of the display unit 110 from a state greater than the first brightness value B1 to the second brightness value B2. Also, while the initial change control is being performed, the counter unit 130 does not change the count value C. In the initial change control of step S407, as shown in Figures 15 and 16, for example, the brightness B is gradually decreased from a brightness value B0 greater than the first brightness value B1 to the second brightness value B2 over a period of 3 seconds. This makes the change in brightness B gradual, making it less likely for the user to feel discomfort while watching the video.

[0063] Furthermore, in the modified example 1 of Embodiment 2, as shown in Figure 14, unlike Embodiment 2, step S411 is added between the first control in step S410 and the second control in step S412 in the repeated control. Step S407 is a step in which the brightness control unit 120 performs a first change control in which the brightness B of the display unit 110 is gradually changed from the second brightness value B2 to the first brightness value B1. In other words, in the first change control, the brightness B is gradually changed from the second brightness value B2 to the first brightness value B1 while switching from the first control to the second control. Also, while the first change control is being executed, the counter unit 130 does not change the count value C. In the first change control in step S407, as shown in Figures 15 and 16, for example, the brightness B is gradually increased from the second brightness value B2 to the first brightness value B1 over a period of 1 second. As a result, the change in brightness B becomes gradual, making it less likely for the user to feel discomfort while watching the video.

[0064] Furthermore, in the modified example 1 of Embodiment 2, step S415 is added before returning from the second control in step S414 to the first control in step S408. Step S415 is a step in which the brightness control unit 120 performs a second change control in which the brightness B of the display unit 110 is gradually changed from a first brightness value B1 to a second brightness value B2. In other words, in the second change control, the brightness B is gradually changed from the first brightness value B1 to the second brightness value B2 while switching from the second control to the first control. In the second change control in step S415, as shown in Figures 15 and 16, for example, the brightness B is gradually decreased from the first brightness value B1 to the second brightness value B2 over a period of 1 second. This makes the change in brightness B gradual, making it less likely for the user to feel discomfort while watching the video.

[0065] As described above, in Modification 1 of Embodiment 2, similar to Embodiment 1, it is possible to suppress the degradation of the light-emitting element while also suppressing the decline in the display quality of the display device 100. Furthermore, in Modification 1 of Embodiment 2, the brightness control unit 120 gradually changes the brightness B of the display unit 110, so that even when the brightness B is changed as shown in Figures 14 to 16, the user is less likely to feel any discomfort while viewing the image.

[0066] <Modification 2 of Embodiment 2> In the control of the display device 100 described in Embodiment 2 and Modification 1 of Embodiment 2, instead of the first time interval I1 and the second time interval I2, the first change amount A1 and the second change amount A2, which are the amounts by which the counter unit 130 changes the count value C per unit time TU, may be used. Figure 17 is a flowchart showing the control method of the display device according to Modification 2 of Embodiment 2. As shown in Figure 17, steps S505, S506, S509 and S513 of Modification 2 of Embodiment 2 are the same as steps S405, S406, S409 and S413 of Modification 1 of Embodiment 2, but with the first change amount A1 and the second change amount A2, which are the amounts that change per unit time TU. The other steps are the same as Modification 1 of Embodiment 2 and therefore will not be described.

[0067] In step S505, the first change amount A1 is made greater than or equal to the second change amount A2. For example, in modification 2 of Embodiment 2, similar to modification 1 of Embodiment 2, if the first count value C1 is set to 3 counts and the second count value C2 is set to zero counts, the unit time TU stored in the storage unit 103 is 1 second, the initial value of the first change amount A1 is set to approximately 0.6 counts per second, and the initial value of the second change amount A2 is also set to 0.6 counts per second. Then, in step S505, for example, the brightness control unit 120 changes the first change amount A1 from the initial value of 0.6 counts per second to 1 count per second, while the second change amount A2 remains at the initial value of 0.6 counts per second. On the other hand, in step S506, the first change amount A1 is made smaller than the second change amount A2. For example, the brightness control unit 120 changes the first change amount A1 from an initial value of 0.6 counts per second to 0.5 counts per second, while leaving the second change amount A2 at its initial value of 0.6 counts per second. In steps S505 and S506, it is sufficient to change at least one of the first change amount A1 and the second change amount A2, or both the first change amount A1 and the second change amount A2 may be changed.

[0068] As shown in Figure 17, in the first control in step S509, the count value C is decreased by a first change A1 per unit time TU, and in the second control in step S513, the count value C is increased by a second change A2 per unit time TU. For example, if the first count value C1 is 3 counts, the second count value C2 is zero counts, and the unit time TU is 1 second, then if the image displayed by the display unit 110 is a moving image, in step S505, the first change A1 becomes 1 count per second, the second change A2 becomes 0.6 counts per second, the first time T1 for performing the first control becomes 3 seconds, and the second time T2 for performing the second control becomes 5 seconds. Therefore, in the modified example 2 of Embodiment 2, if the image displayed by the display unit 110 is a moving image, the temporal change of the brightness B of the display device 100 is the same as in the modified example 1 of Embodiment 2, as shown in Figure 15.

[0069] On the other hand, if at least a portion of the video displayed by the display unit 110 includes still images, in step S506 the first change amount A1 is set to 0.5 counts per second and the second change amount A2 is set to 0.6 counts per second, so that the first time T1 in which the first control is performed is 6 seconds and the second time T2 in which the second control is performed is 5 seconds. Therefore, in Modification 2 of Embodiment 2, if at least a portion of the video displayed by the display unit 110 includes still images, the luminance B of the display device 100 changes over time as shown in Figure 16, similar to Modification 1 of Embodiment 2. Therefore, Modification 2 of Embodiment 2 also suppresses deterioration of the light-emitting element, suppresses a decline in the display quality of the display device 100, such as a poor visual impression, and has the effect of making it less likely for the user to feel discomfort when viewing the video, even when control is being performed to change the luminance B. In addition, in the modified example 2 of Embodiment 2, similar to Embodiment 2 and Modified Example 1 of Embodiment 2, the first change amount A1 and the second change amount A2 may be returned to their initial values ​​stored in the storage unit 103 when the control of the display unit 110 by the brightness control unit 120 is completed.

[0070] <Embodiment 3> Figure 18 is a block diagram showing a display device 100 according to Embodiment 3 of the present disclosure. The display device 100 of Embodiment 3 differs from Embodiment 1 in that it includes a temperature sensor 150, but is otherwise generally the same as Embodiment 1. In the following description of Embodiment 3, the differences from Embodiment 1 will be explained in detail, and the points common to Embodiment 1 will be omitted as appropriate.

[0071] The temperature sensor 150 is a sensor device for measuring the ambient temperature outside the display device 100. As shown in Figure 18, in the display device 100 of Embodiment 3, for example, the temperature sensor 150 is connected to the brightness control unit 120 by a signal line, enabling them to send and receive information to each other. The storage unit 103 can store the temperature measured by the temperature sensor 150 via the brightness control unit 120, for example.

[0072] <Control method for the display device 100 of Embodiment 3> Figure 19 is a flowchart showing the control method of the display device 100 according to Embodiment 3. Figures 20 and 21 are graphs showing the temporal change in brightness B of the display unit 110 controlled by the control method shown in the flowchart of Figure 19 in Embodiment 3. As will be described in detail later, Figure 20 is a graph showing the temporal change in brightness B of the display unit 110 when the temperature measured by the temperature sensor 150 is above a predetermined threshold and the image is a moving image in Embodiment 3. Figure 21 is a graph showing the temporal change in brightness B of the display unit 110 when the temperature measured by the temperature sensor 150 is above a predetermined threshold and the image includes a still image in Embodiment 3. Embodiment 3 differs from Embodiment 1 in that, if the temperature measured by the temperature sensor 150 is above a predetermined threshold, the first time T1 is changed to an extended time TE and the first control is executed, but the other configurations are generally the same as Embodiment 1. In the following description of Embodiment 3, the differences from Embodiment 1 will be explained in detail, and the points common to Embodiment 1 will be omitted as appropriate.

[0073] As shown in Figure 19, the repeated control of steps S601 to S603, step S606, and steps S611 and S612 is the same as the repeated control of steps S101 to S103, step S104, and steps S105 and S106 in Embodiment 1, so a description will be omitted.

[0074] In Embodiment 3, in step S602, similar to Embodiment 1, it is determined whether the image displayed by the display unit 110 is a video. If it is determined that the image is a video, the process proceeds to step S603; if it is determined that at least a part of the image is a still image, the process proceeds to step S606.

[0075] Step S603 is to set the first time T1 to less than or equal to the second time T2. For example, in Embodiment 3, if the initial value of both the first time T1 and the initial value of the second time T2 are set to 5 seconds, in step S603, the brightness control unit 120 changes the first time T1 stored in the storage unit 103 from the initial value of 5 seconds to 3 seconds, while leaving the second time T2 at its initial value of 5 seconds. Once step S603 is completed, the process proceeds to step S604, which involves making a determination based on the temperature measured by the temperature sensor 150.

[0076] Step S604 is a step in which it is determined whether the temperature measured by the temperature sensor 150 is above a predetermined threshold. Specifically, since the temperature sensor 150 measures the ambient temperature outside the display device 100, step S604 determines whether the ambient temperature of the environment in which the display device 100 is installed is above a predetermined threshold. The predetermined threshold is stored in the storage unit 103 in advance and is set to, for example, 30°C. If the temperature measured by the temperature sensor 150 is below the predetermined threshold, the process proceeds to a repeating control that repeats steps S611 and S612. This repeating control is the same as the repeating control that repeats steps S105 and S106 in Embodiment 1. Therefore, in Embodiment 3, if the video is a moving image and the temperature measured by the temperature sensor 150 is below the predetermined threshold, the same control as the control shown in Figure 5 for the case where the video is a moving image in Embodiment 1 is executed. On the other hand, if the temperature measured by the temperature sensor 150 is above the predetermined threshold, the process proceeds to step S605.

[0077] Step S605 is a step in which the first time T1 is changed to an extension time TE that is longer than the first time T1. For example, the brightness control unit 120 changes the first time T1, which was changed in step S603 and stored in the memory unit, to a longer extension time TE. As described above, in step S603, the brightness control unit 120 changes the first time T1 to 3 seconds, and in step S605, for example, the first time T1 is changed to an even longer extension time TE of 4 seconds (extension time TE when the video is a moving image). After step S605 is completed, the process proceeds to a repeating control, in which the first control in step S609 and the second control in step S610 are repeated alternately until the condition that the brightness B of the display unit 110 is less than the second brightness value B2 is met. For example, if the video is switched and the brightness value specified by the newly received video signal is less than the second brightness value B2, the repeating control is stopped.

[0078] As shown in Figure 19, step S609 is a first control in which the brightness control unit 120 controls the display unit 110 to maintain the brightness B at a second brightness value B2 which is smaller than the first brightness value B1 for an extended time TE. Step S609 ends when the extended time TE has elapsed since the start of the first control, and the process proceeds to step S610.

[0079] In step S610, the brightness control unit 120 performs a second control, controlling the display unit 110 to maintain the brightness B at a first brightness value B1 for a second time T2. Step S610 ends when the second time T2 has elapsed since the start of the second control, and the process proceeds back to step S609.

[0080] As described above, for example, when the image is a video, if the temperature measured by the temperature sensor 150 is above a predetermined threshold, as shown in Figure 20, steps S605, S609, and S610 result in an extended time TE during which the first control is maintained being 4 seconds, and a second time T2 during which the second control is maintained being 5 seconds. In contrast, when the image is a video, if the temperature measured by the temperature sensor 150 is below a predetermined threshold, as shown in Figure 5, steps S611 and S612 result in a first time T1 during which the first control is maintained being 3 seconds, and a second time T2 during which the second control is maintained being 5 seconds. Therefore, when the temperature measured by the temperature sensor 150 is above a predetermined threshold, the brightness B of the display unit 110 is maintained at a second brightness value B2, which is smaller than the first brightness value B1, for a longer period of time compared to when it is not above a predetermined threshold. As a result, when the ambient temperature outside the display device 100 is high and the thermal degradation of the light-emitting elements of the display unit 110 is likely to be accelerated, the degradation of the light-emitting elements can be slowed down by extending the time during which the brightness B of the display unit 110 is maintained at a second brightness value B2 that is lower than the first brightness value B1.

[0081] For example, in repeated control, if the first control and the second control are each repeated twice, in Figure 5, the cumulative time during which luminance B is maintained at the second luminance value B2 is 6 seconds, and the cumulative time during which it is maintained at the first luminance value B1 is 10 seconds, whereas in Figure 20, the cumulative time during which luminance B is maintained at the second luminance value B2 is 8 seconds, and the cumulative time during which it is maintained at the first luminance value B1 is 10 seconds.

[0082] On the other hand, if at least a portion of the video displayed by the display unit 110 includes still images, the process proceeds to step S606, where the first time T1 is made longer than the second time T2. For example, in Embodiment 3, if both the initial value of the first time T1 and the initial value of the second time T2 are set to 5 seconds, in step S606, the brightness control unit 120 changes the first time T1 stored in the storage unit 103 from the initial value of 5 seconds to 6 seconds, while leaving the second time T2 at its initial value of 5 seconds. Once step S606 is completed, the process proceeds to step S607, which involves making a determination based on the temperature measured by the temperature sensor 150.

[0083] Step S607, like step S604, is a step to determine whether the temperature measured by the temperature sensor 150 is above a predetermined threshold. If the temperature measured by the temperature sensor 150 is below the predetermined threshold, the process proceeds to a repeating control that repeats steps S611 and S612. This repeating control is the same as the repeating control that repeats steps S105 and S106 in Embodiment 1. Therefore, in Embodiment 3, if at least a portion of the video contains still images and the temperature measured by the temperature sensor 150 is below the predetermined threshold, the same control as the control shown in Figure 6 for Embodiment 1 when at least a portion of the video contains still images is executed. On the other hand, if the temperature measured by the temperature sensor 150 is above the predetermined threshold, the process proceeds to step S608.

[0084] Step S608, like step S605, is a step in which the first time T1 is changed to an extension time TE that is longer than the first time T1. For example, the brightness control unit 120 changes the first time T1, which was changed in step S606 and stored in the memory unit, to a longer extension time TE. As described above, in step S606, the brightness control unit 120 changes the first time T1 to 6 seconds, and in step S608, for example, the first time T1 is changed to an even longer extension time TE of 7 seconds (extension time TE when at least a part of the video includes a still image). After step S608 is completed, a repeating control is performed, which alternately repeats the first control in step S609 and the second control in step S610, as shown in Figure 21, until the condition that the brightness B of the display unit 110 is less than the second brightness value B2 is met. For example, if the video is switched and the brightness value specified in the newly received video signal is less than the second brightness value B2, the repeating control is stopped.

[0085] As described above, for example, when at least a portion of the video contains still images, if the temperature measured by the temperature sensor 150 is above a predetermined threshold, as shown in Figure 21, steps S608, S609, and S610 result in an extended time TE during which the first control is maintained of 7 seconds and a second time T2 during which the second control is maintained of 5 seconds. In contrast, when at least a portion of the video contains still images, if the temperature measured by the temperature sensor 150 is below a predetermined threshold, as shown in Figure 6, steps S611 and S612 result in a first time T1 during which the first control is maintained of 6 seconds and a second time T2 during which the second control is maintained of 5 seconds. Therefore, even when at least a portion of the video contains still images, if the temperature measured by the temperature sensor 150 is above a predetermined threshold, the brightness B of the display unit 110 is maintained at a second brightness value B2, which is smaller than the first brightness value B1, for a longer period of time compared to the case where it is not. As a result, when the ambient temperature outside the display device 100 is high and the thermal degradation of the light-emitting elements of the display unit 110 is likely to be accelerated, the degradation of the light-emitting elements can be slowed down by extending the time during which the brightness B of the display unit 110 is maintained at a second brightness value B2 that is lower than the first brightness value B1.

[0086] For example, in repeated control, if the first control and the second control are each repeated twice, in Figure 6, the cumulative time during which luminance B is maintained at the second luminance value B2 is 12 seconds, and the cumulative time during which it is maintained at the first luminance value B1 is 10 seconds, whereas in Figure 21, the cumulative time during which luminance B is maintained at the second luminance value B2 is 14 seconds, and the cumulative time during which it is maintained at the first luminance value B1 is 10 seconds.

[0087] As described above, the display device 100 of Embodiment 3, similar to the display device 100 of Embodiment 1, prioritizes maintaining display quality when the image displayed by the display unit 110 is a moving image, as the degradation of the light-emitting element is less likely to progress. To this end, it extends the time during which the display is controlled by the first brightness value B1, which is a brightness value greater than the second brightness value B2. When at least a part of the image displayed by the display unit 110 includes a still image, and the degradation of the light-emitting element is more likely to progress, the display device 3 extends the time during which the display is controlled by the second brightness value B2, which is a brightness value less than the first brightness value B1. This suppresses the degradation of the light-emitting element while also suppressing a decline in the display quality of the display device 100, such as a poor visual impression. Furthermore, in situations where the ambient temperature outside the display device 100 is high and the degradation of the light-emitting element of the display unit 110 due to heat is likely to progress, the display device 100 of Embodiment 3 can further reduce the degradation of the light-emitting element by changing the time during which the display is controlled by the second brightness value B2 to an extended time TE that is longer than the first time T1.

[0088] <Modified form of Embodiment 3> In the control of the display device 100 described in Embodiment 3, instead of changing the first time T1 to an extended time TE and performing the first control, the second control may be performed by changing it to a shortened time TS that is shorter than the second time T2. Figure 22 is a flowchart showing a control method for the display device 100 according to a modified example of Embodiment 3. Figure 23 is a graph showing the temporal change of brightness B of the display unit 110 when the temperature measured by the temperature sensor is above a predetermined threshold and the image is a moving image, in a modified example of Embodiment 3. Figure 24 is a graph showing the temporal change of brightness B of the display unit 110 when the temperature measured by the temperature sensor is above a predetermined threshold and the image includes a still image, in a modified example of Embodiment 3. As shown in Figure 22, the repetitive control that alternately repeats steps S701 to S704, S706, S707, S711, and S712 is the same as the repetitive control that alternately repeats steps S601 to S604, S606, S607, S611, and S612 in Embodiment 3, so its explanation is omitted.

[0089] In a modified version of Embodiment 3, as shown in Figure 22, if the image is a moving image and the temperature measured by the temperature sensor is above a predetermined threshold, in step S705, the second time T2 is changed to a shortened time TS (shortened time TS in the case of a moving image) that is shorter than the second time T2. For example, if in step S703 the brightness control unit 120 changes the first time T1 stored in the memory unit 103 from an initial value of 5 seconds to 3 seconds, and the second time T2 remains at its initial value of 5 seconds, then in step S705, the second time T2 is changed to a shortened time TS of 4 seconds, which is shorter than the second time T2. After step S705 is completed, repeated control is performed, alternating between the first control in step S709 and the second control in step S710, as shown in Figures 22 and 23, until the brightness B of the display unit 110 is less than the second brightness value B2. For example, if the video changes and the brightness value specified in the newly received video signal is less than the second brightness value B2, the repeat control is stopped.

[0090] As shown in Figure 22, step S709 is a first control in which the brightness control unit 120 controls the display unit 110 so that the brightness B is maintained at a second brightness value B2 which is smaller than the first brightness value B1 for a first time T1. Step S709 ends when the first time T1 has elapsed since the start of the first control, and the process proceeds to step S710.

[0091] In step S710, the brightness control unit 120 performs a second control, controlling the display unit 110 to maintain the reduced time TS by setting the brightness B to a first brightness value B1. Step S710 ends when the reduced time TS has elapsed since the start of the second control, and the process proceeds again to step S709.

[0092] As described above, for example, if the image is a video and the temperature measured by the temperature sensor 150 is above a predetermined threshold, as shown in Figure 23, steps S705, S709, and S710 result in a first time T1 during which the first control is maintained being 3 seconds and a shortened time TS during which the second control is maintained being 4 seconds. In contrast, if the image is a video and the temperature measured by the temperature sensor 150 is below a predetermined threshold, as shown in Figure 5, steps S711 and S712 result in a first time T1 during which the first control is maintained being 3 seconds and a second time T2 during which the second control is maintained being 5 seconds. Therefore, in the modified embodiment of Embodiment 3, if the temperature measured by the temperature sensor 150 is above a predetermined threshold, the time during which the brightness B of the display unit 110 is maintained at a first brightness value B1 greater than the second brightness value B2 is shorter compared to the case where it is not. As a result, when the ambient temperature outside the display device 100 is high and the thermal degradation of the light-emitting elements of the display unit 110 is likely to be accelerated, the time during which the brightness B of the display unit 110 is maintained at a first brightness value B1 greater than the second brightness value B2 can be shortened, thereby making the degradation of the light-emitting elements less likely to progress.

[0093] For example, in repeated control, if the first control and the second control are each repeated twice, in Figure 5, the cumulative time during which luminance B is maintained at the second luminance value B2 is 6 seconds, and the cumulative time during which it is maintained at the first luminance value B1 is 10 seconds, whereas in Figure 23, the cumulative time during which luminance B is maintained at the second luminance value B2 is 6 seconds, and the cumulative time during which it is maintained at the first luminance value B1 is 8 seconds.

[0094] On the other hand, if at least a portion of the video displayed by the display unit 110 includes still images, and the temperature measured by the temperature sensor is above a predetermined threshold, in step S708, the second time T2 is changed to a shortened time TS shorter than the second time T2 (shortened time TS when at least a portion of the video includes still images). For example, if in step S706 the brightness control unit 120 changes the first time T1 stored in the storage unit 103 from the initial value of 5 seconds to 6 seconds, and the second time T2 remains at the initial value of 5 seconds, then in step S708, the second time T2 is changed to a shortened time TS shorter than the second time T2, which is 4 seconds. After step S708 is completed, repeated control is performed, alternating between the first control in step S709 and the second control in step S710, as shown in Figures 22 and 24, until the brightness B of the display unit 110 is less than the second brightness value B2. For example, if the video changes and the brightness value specified in the newly received video signal is less than the second brightness value B2, the repeat control is stopped.

[0095] As described above, for example, when at least a portion of the video contains still images, if the temperature measured by the temperature sensor 150 is above a predetermined threshold, as shown in Figure 24, steps S708, S709, and S710 result in a first time T1 during which the first control is maintained being 6 seconds, and a shortened time TS during which the second control is maintained being 4 seconds. In contrast, when at least a portion of the video contains still images, if the temperature measured by the temperature sensor 150 is below a predetermined threshold, as shown in Figure 6, steps S711 and S712 result in a first time T1 during which the first control is maintained being 6 seconds, and a second time T2 during which the second control is maintained being 5 seconds. Therefore, even when at least a portion of the video contains still images, if the temperature measured by the temperature sensor 150 is above a predetermined threshold, the time during which the brightness B of the display unit 110 is maintained at a first brightness value B1 greater than the second brightness value B2 is shorter compared to the case where it is not. As a result, when the ambient temperature outside the display device 100 is high and the thermal degradation of the light-emitting elements of the display unit 110 is likely to be accelerated, the time during which the brightness B of the display unit 110 is maintained at a first brightness value B1 greater than the second brightness value B2 can be shortened, thereby making the degradation of the light-emitting elements less likely to progress.

[0096] For example, in repeated control, if the first control and the second control are each repeated twice, in Figure 6, the cumulative time during which luminance B is maintained at the second luminance value B2 is 12 seconds, and the cumulative time during which it is maintained at the first luminance value B1 is 10 seconds, whereas in Figure 21, the cumulative time during which luminance B is maintained at the second luminance value B2 is 12 seconds, and the cumulative time during which it is maintained at the first luminance value B1 is 8 seconds.

[0097] As described above, the modified display device 100 of Embodiment 3, similar to the display devices 100 of Embodiments 1 and 3, prioritizes maintaining display quality when the image displayed by the display unit 110 is a moving image, as the degradation of the light-emitting element is less likely to progress. To this end, it extends the time during which the display is controlled by the first brightness value B1, which is greater than the second brightness value B2. When at least a part of the image displayed by the display unit 110 includes a still image, and the degradation of the light-emitting element is more likely to progress, the display device 100 extends the time during which it is controlled by the second brightness value B2, which is less than the first brightness value B1. This suppresses the degradation of the light-emitting element while also suppressing a decline in the display quality of the display device 100. Furthermore, in the display device 100 of Embodiment 3, when the ambient temperature outside the display device 100 is high and the degradation of the light-emitting element of the display unit 110 due to heat is likely to progress, the time during which the display is controlled by the first brightness value B1 can be changed to a shorter time TS than the second time T2, thereby further reducing the degradation of the light-emitting element.

[0098] <Installation position of the temperature sensor in the display device 100> Figure 25 is an exploded view of the display device 100 according to Embodiment 3, and Figure 26 is a plan view of the display device 100 according to Embodiment 3. As shown in Figures 25 and 26, in the display device 100 of Embodiment 3, it is preferable that the temperature sensor 150 is installed on the back surface 111 of the display unit 110 and positioned to overlap with the central portion 112 of the back surface 111. The central portion 112 is a certain range of area including the center of the back surface 111 of the display unit 110. By using the temperature measured by the temperature sensor 150 at a position overlapping with the central portion 112 as the ambient temperature of the display device 100, the influence of ambient temperature on the entire display unit 110 can be measured more accurately, and by more appropriately controlling the brightness B of the display unit 110 based on temperature in the display device 100 of Embodiment 3 described above, the deterioration of the light-emitting element can be made less likely to progress.

[0099] Furthermore, in the display device 100 of Embodiment 3, the temperature sensor 150 is installed on the back side 111 of the display unit 110, and a cabinet 140 may be provided that covers the back side 111 and the temperature sensor 150 and has a ventilation opening 141 at a position facing the temperature sensor 150. As shown in Figures 25 and 26, the cabinet 140 has, for example, a ventilation opening 141 including a plurality of openings, and the back side 111 and the outside of the display device 100 are connected through the ventilation opening 141. Therefore, by providing the temperature sensor 150 at a position facing the ventilation opening 141, the air outside the display device 100 can more easily come into contact with the temperature sensor 150, making it possible to measure the ambient temperature more accurately. As a result, the influence of ambient temperature on the display unit 110 can be measured more accurately, and by more appropriately controlling the brightness B of the display unit 110 based on temperature in the display device 100 of Embodiment 3 described above, the deterioration of the light-emitting element can be made less likely to progress.

[0100] In Figures 25 and 26, a control board 160 is provided between the rear panel 111 and the cabinet 140. The control board 160 is equipped with a microcontroller, integrated circuit, peripheral circuits, etc., such as a video signal processing unit 101, a brightness control unit 120, and a memory unit 103, as shown in the block diagrams of the display device 100 in Figures 1, 10, and 18. The temperature sensor 150 is provided separately from the control board 160 and is electrically connected to the control board 160 by electrical wiring, etc. The temperature sensor 150 is mounted on top of the control board 160, and for example, the control board 160 may be positioned to overlap the central part 112.

[0101] Furthermore, this disclosure is not limited to the embodiments and modified configurations described above, and may be replaced with configurations that are substantially the same as those shown in the embodiments and modified configurations described above, configurations that produce the same effects, or configurations that can achieve the same purpose. [Explanation of Symbols]

[0102] 100:Display device 101: Video signal processing unit 102: Drive unit 103: Storage section 110: Display section 111: Back 112: Central part 120: Brightness Control Unit 130: Counter section 140: Cabinet 141: Ventilation opening 150: Temperature sensor 160: Control board 200: Video display area 201: On-screen display area 202: Fixed display area

Claims

1. A display unit that displays images, It comprises a brightness control unit, The brightness control unit, If the brightness of the display unit remains higher than a first brightness value for the duration of the standby time, a repeating control is initiated which alternately repeats a first control that maintains the brightness at a second brightness value lower than the first brightness value for a first time, and a second control that maintains the brightness at the first brightness value for a second time. If the aforementioned video is a video, the first time shall be less than or equal to the second time. A display device that, if at least a portion of the video is a still image, makes the first time longer than the second time.

2. The brightness control unit, An initial change control is performed before the start of the repeated control, which gradually changes the brightness from a state greater than the first brightness value to the second brightness value. In the aforementioned repetitive control, A first change control is performed to gradually change the brightness from the second brightness value to the first brightness value during the transition from the first control to the second control, The display device according to claim 1, wherein, during the transition from the second control to the first control, a second change control is performed which gradually changes the brightness from a first brightness value to a second brightness value.

3. The display device according to claim 1 or 2, wherein the brightness control unit stops the repeating control when the brightness becomes less than a second brightness value while the repeating control is being executed.

4. Equipped with a counter section, The aforementioned counter unit, If the brightness is greater than the first brightness value, or if the second control is being executed, the count value is increased over time. While the first control is being executed, the count value is decreased over time. The brightness control unit, When the count value becomes the first count value, the repeating control is started, or the second control that is currently being executed is switched to the first control. The display device according to claim 1, wherein when the count value becomes a second count value that is smaller than the first count value, the currently running first control is switched to the second control.

5. The counter unit decreases the count value at a first time interval while the first control is being executed, and increases the count value at a second time interval while the second control is being executed. If the aforementioned video is a video, the first time interval shall be less than or equal to the second time interval. If at least a portion of the video is a still image, the first time interval is made longer than the second time interval, or The counter unit decreases the count value by a first rate of change per unit time while the first control is being executed, and increases the count value by a second rate of change per unit time while the second control is being executed. If the aforementioned image is a video, the first change amount shall be greater than or equal to the second change amount. The display device according to claim 4, wherein if at least a portion of the video is a still image, the first change amount is made smaller than the second change amount.

6. Equipped with a counter section, The aforementioned counter unit, If the brightness is greater than the first brightness value, or if the second control is being executed, the count value is increased over time. While the first control is being executed, the count value is decreased over time. When any of the initial change control, the first change control, or the second change control is being executed The aforementioned count value will not be changed. The brightness control unit, When the count value becomes the first count value, the repeating control is started, or the second control that is currently being executed is switched to the first control. The display device according to claim 2, wherein when the count value becomes a second count value that is smaller than the first count value, the currently running first control is switched to the second control.

7. Equipped with a temperature sensor, The display device according to claim 1, wherein the brightness control unit performs the first control by changing the first time to an extended time longer than the first time when the temperature measured by the temperature sensor is above a predetermined threshold.

8. Equipped with a temperature sensor, The display device according to claim 1, wherein the brightness control unit performs the second control by changing the second time to a shorter time than the second time when the temperature measured by the temperature sensor is above a predetermined threshold.

9. The temperature sensor is installed on the back side of the display unit and positioned so as to overlap with the center of the back side, or The display device according to claim 7 or 8, wherein the temperature sensor is installed on the rear side of the display unit, and the display device comprises a cabinet installed so as to cover the rear side and the temperature sensor, and having a ventilation opening at a position facing the temperature sensor.

10. If the brightness of the image displayed by the display device remains above a first brightness value for a standby period, a repeating control is initiated which alternately repeats a first control that maintains the brightness at a second brightness value lower than the first brightness value for a first period, and a second control that maintains the brightness at the first brightness value for a second period. If the aforementioned video is a video, the first time shall be less than or equal to the second time. A control method for a display device that makes the first time longer than the second time, in cases where at least a portion of the video is a still image.

Images