Control device, display device, and control method

Abstract

A display panel according to the present invention has sub-pixels which each include: a first light-emitting element that emits first light having a first color; and a second light-emitting element that emits second light having a color of the same type as a second color. A control device according to the present invention controls the first light-emitting elements and the second light-emitting elements in accordance with the gradation ratio corresponding to the sub-pixels in input image data. The second color is the same type of color as the first color. The luminance characteristics of a first dominant wavelength, which is the dominant wavelength of the first light, are different from the luminance characteristics of a second dominant wavelength, which is the dominant wavelength of the second light. As a result of the control device controlling the first light-emitting elements and the second light-emitting elements, the combined dominant wavelength change amount, which is the amount of change in the dominant wavelength of the combined light of the first light and the second light in a prescribed gradation ratio change range, becomes smaller than at least one of the first dominant wavelength change amount when the first light is emitted only by the first light-emitting elements and the second dominant wavelength change amount when the second light is emitted only by the second light-emitting elements.

Description

Control device, display device, and control method

[0001] The following disclosure relates to a control device for controlling a display panel.

[0002] For example, as shown in Non-Patent Documents 1 and 2 below, various techniques have been proposed for controlling a display device (for example, a display panel) that includes a plurality of light-emitting elements.

[0003] Gu, Y., N. Narendran, T. Dong, and H. Wu. 2006. "Spectral and luminous efficacy change of high-power LEDs under different dimming methods." Sixth International Conference on Solid State Lighting, Proceedings of SPIE 6337, 63370J. Dongdong Teng, Mingyang Wu, Lilin Liu, Gang Wang. "Size- and current-density-controlled tunable wavelength in gan-based leds for potential dense wavelength-division multiplexing applications." IEEE Wirel. Commun. 22(2): 74-79 (2015).

[0004] It is desirable to improve the display quality of display panels.

[0005] A control device according to one aspect of the present disclosure is a control device for controlling a display panel, the display panel having sub-pixels including a first light-emitting element that emits first light having a first color and a second light-emitting element that emits second light having a second color, the control device controls the first light-emitting element and the second light-emitting element according to a gradation ratio corresponding to the sub-pixel in input image data, the second color being the same type of color as the first color, a dominant wavelength of the first light being referred to as a first dominant wavelength, a dominant wavelength of the second light being referred to as a second dominant wavelength, a characteristic of the first dominant wavelength with respect to luminance of the first light being different from a characteristic of the second dominant wavelength with respect to luminance of the second light, and the control device controls only the first light-emitting element to emit the first light. The difference between the maximum and minimum values ​​of the first dominant wavelength in a predetermined gradation ratio change range when the second light is emitted from only the second light-emitting element is referred to as the first dominant wavelength change amount, the difference between the maximum and minimum values ​​of the second dominant wavelength in the gradation ratio change range when the second light is emitted from only the second light-emitting element is referred to as the second dominant wavelength change amount, the dominant wavelength of the combined light of the first light and the second light is referred to as the synthetic dominant wavelength, and the difference between the maximum and minimum values ​​of the synthetic dominant wavelength in the gradation ratio change range is referred to as the synthetic dominant wavelength change amount, and by the control device controlling the first light-emitting element and the second light-emitting element, the synthetic dominant wavelength change amount becomes smaller than at least one of the first dominant wavelength change amount and the second dominant wavelength change amount.

[0006] A control method according to one aspect of the present disclosure is a control method for controlling a display panel, the display panel having sub-pixels including a first light-emitting element that emits first light having a first color and a second light-emitting element that emits second light having a second color, the control method including a step of controlling the first light-emitting element and the second light-emitting element according to a gradation ratio corresponding to the sub-pixel in input image data, the second color being the same type of color as the first color, a dominant wavelength of the first light being referred to as a first dominant wavelength, a dominant wavelength of the second light being referred to as a second dominant wavelength, a characteristic of the first dominant wavelength with respect to luminance of the first light being different from a characteristic of the second dominant wavelength with respect to luminance of the second light, and a difference between the maximum value and the minimum value of the first dominant wavelength in a predetermined gradation ratio change range is referred to as a first dominant wavelength change amount; a difference between the maximum value and the minimum value of the second dominant wavelength in the gradation ratio change range when only the second light-emitting element is caused to emit the second light is referred to as a second dominant wavelength change amount; a dominant wavelength of light synthesized from the first light and the second light is referred to as a synthetic dominant wavelength; and a difference between the maximum value and the minimum value of the synthetic dominant wavelength in the gradation ratio change range is referred to as a synthetic dominant wavelength change amount, and the step of controlling the first light-emitting element and the second light-emitting element includes a step of controlling the first light-emitting element and the second light-emitting element so that the synthetic dominant wavelength change amount is smaller than at least one of the first dominant wavelength change amount and the second dominant wavelength change amount.

[0007] According to one aspect of the present disclosure, the display quality of a display panel can be improved.

[0008] It illustrates the change trend of the main wavelength in the light-emitting element of Embodiment 1. It schematically shows the relationship between the gradation ratio and the main wavelength in the display aimed to be realized in Embodiment 1. It shows some graphs disclosed in Non-Patent Document 2. It illustrates the change of the main wavelength with respect to the change of the Duty ratio before and after the adjustment of the PWM light-emitting element. It illustrates the change of the main wavelength with respect to the change of the current ratio or the Duty ratio in the light-emitting element used in Embodiment 1. It illustrates the change of the main wavelength in the display combining the CC light-emitting element and the PWM light-emitting element after the main wavelength adjustment. It is a block diagram showing a configuration example of the display device in Embodiment 1. It shows a configuration example of one pixel in the display panel. It shows a configuration example of the first drive circuit for driving the first light-emitting element. It shows a configuration example of the second drive circuit for driving the second light-emitting element. It is an example of the timing chart of each signal related to the second drive circuit. It is a flowchart illustrating the process flow in which the first control data generation unit generates the control data of the first light-emitting element. It illustrates the relationship between the gradation ratio of the G component of the gradation data of the input pixel and the control data of the first light-emitting element set by the process of FIG. 12. It is a flowchart illustrating the process flow in which the second control data generation unit generates the control data of the second light-emitting element. It illustrates the relationship between the gradation ratio of the G component of the gradation data of the input pixel and the control data of the second light-emitting element set by the process of FIG. 14. It illustrates the relationship between the gradation ratio of the G component of the gradation data of the input pixel and the luminance ratio corresponding to each control data set based on the gradation ratio of the G component. It illustrates the contribution rate of each light-emitting element in Embodiment 1. It illustrates the change of the main wavelength with respect to the gradation ratio of the first light-emitting element driven by the current ratio shown in FIG. 13 and the second light-emitting element driven by the Duty ratio shown in FIG. 15. It illustrates the characteristics of a virtual green light-emitting element. It shows an example when the first gradation ratio is set to 50%. It illustrates the characteristics of two virtual light-emitting elements. It illustrates the characteristics of each light-emitting element in Embodiment 2. It shows an example of the control of each light-emitting element in Embodiment 2. It illustrates the relationship between the gradation ratio and the luminance ratio of the combined light of the first light and the second light in Embodiment 2. It illustrates the contribution rate in Embodiment 2.23 illustrates a change in dominant wavelength of each light-emitting element with respect to a change in gradation ratio when each light-emitting element having the characteristics shown in FIG. 22 is driven by the control data shown in FIG. 23 in embodiment 2. The characteristics of combined light in embodiment 2 are illustrated. The characteristics of each light-emitting element in embodiment 3 are illustrated. An example of control of each light-emitting element in embodiment 3 is shown. The contribution rate in embodiment 3 is illustrated. The changes in dominant wavelength of each light-emitting element with respect to a change in gradation ratio when each light-emitting element having the characteristics shown in FIG. 28 is driven by the control data shown in FIG. 29 in embodiment 4. The characteristics of combined light in embodiment 3 are illustrated. The characteristics of each light-emitting element in embodiment 4 are illustrated. An example of control of each light-emitting element in embodiment 4 is shown. The contribution rate in embodiment 4 is illustrated. The changes in dominant wavelength of each light-emitting element with respect to a change in gradation ratio when each light-emitting element having the characteristics shown in FIG. 33 is driven by the control data shown in FIG. 34 in embodiment 4. The characteristics of combined light in embodiment 4 are illustrated. The characteristics of each light-emitting element in embodiment 5 are illustrated. An example of control of each light-emitting element in embodiment 5 is shown. 43 is driven by the control data shown in FIG. 44 . The contribution rate is an example of the embodiment 7. In the embodiment 7, the change in the dominant wavelength of each light-emitting element with respect to the change in the gradation ratio is illustrated when each light-emitting element having the characteristic shown in FIG. 38 is driven by the control data shown in FIG. 39 . The characteristics of the combined light are illustrated in the embodiment 5. The characteristics of each light-emitting element are illustrated in the embodiment 6. The control data of each light-emitting element is shown in the embodiment 6. The contribution rate is an example of the embodiment 7. The change in the dominant wavelength of each light-emitting element with respect to the change in the gradation ratio is illustrated when each light-emitting element having the characteristic shown in FIG. 48 is driven by the control data shown in FIG. 49 . The characteristics of the combined light are illustrated in the embodiment 7.5A illustrates the characteristics of each light-emitting element in embodiment 8. An example of control of each light-emitting element in embodiment 8 is shown. An example of contribution rate in embodiment 8 is shown. In embodiment 8, changes in dominant wavelength with respect to changes in gradation ratio of each light-emitting element are illustrated when each light-emitting element having the characteristics shown in FIG. 53 is driven by the control data shown in FIG. 54. An example of characteristics of combined light in embodiment 8. An example of control of each light-emitting element in embodiment 9 is shown. An example of contribution rate in embodiment 9. In embodiment 9, changes in dominant wavelength with respect to changes in gradation ratio of each light-emitting element are illustrated when each light-emitting element having the characteristics shown in FIG. 58 is driven by the control data shown in FIG. 59. An example of characteristics of combined light in embodiment 9 is shown.

[0009] [Embodiment 1] Embodiment 1 will be described below. For convenience of explanation, components having the same functions as those described in embodiment 1 will be denoted by the same reference numerals in the following embodiments, and their description will not be repeated. For simplicity, descriptions of well-known technical matters will be omitted as appropriate. Unless otherwise specified, the components, materials, and numerical values ​​described in this disclosure are merely examples. Therefore, for example, unless otherwise specified, the positional and connection relationships of the components are not limited to the examples in the figures. Furthermore, the figures are not necessarily drawn to scale.

[0010] In this disclosure, unless otherwise contradictory, the notation "A to B" for two numbers A and B means "greater than or equal to A and less than or equal to B." Furthermore, the term "connected" in this disclosure means "electrically connected" in the context of an electric circuit.

[0011] (Premise) Display devices including pixels having light-emitting elements such as LEDs (Light Emitting Diodes) are known. In recent years, self-luminous elements such as μLEDs, OLEDs (Organic LEDs), and QD-LEDs (Quantum Dot LEDs) have been used as light-emitting elements.

[0012] Various methods for changing the luminance of a light-emitting element are known. As one example, current driving can change the luminance of a light-emitting element by changing the amount of current flowing through the light-emitting element. As another example, PWM (Pulse Width Modulation) driving can change the luminance of light emitted by the light-emitting element by changing the time the light-emitting element is made to emit light. In the following description of this disclosure, "the luminance of light emitted by the light-emitting element" will be abbreviated as "the luminance of the light-emitting element" as appropriate.

[0013] When the luminance of a light-emitting element is changed by each of the above-mentioned methods, the emission wavelength of the light-emitting element may shift. First, an example of this phenomenon will be described with reference to FIG. 63. FIG. 63 shows some graphs disclosed in Non-Patent Document 1. Non-Patent Document 1 shows the measurement results of the emission wavelength when the luminance of four types of LEDs is changed by current driving and PWM driving. In the following description, current driving will also be abbreviated as "CC" and PWM driving will also be abbreviated as "PWM." FIG. 63 shows four graphs, as indicated by reference numerals 6300A to 6300D.

[0014] Fig. 63 shows the change in emission wavelength when the duty ratio is changed in CC and PWM. In each graph in Fig. 63, the horizontal axis represents the ratio of current to the maximum current in CC or the duty ratio in PWM, and the vertical axis represents the peak wavelength of emission.

[0015] As an example, graph 6300A shows the measurement results for a red LED (labeled "R" in this example). In the example of 6300A, the peak wavelength increases with increasing current or duty ratio in both CC and PWM modes.

[0016] As another example, graph 6300B shows the measurement results for a green LED (labeled "G" in this example). In the example of 6300B, the peak wavelength shortens as the CC current increases. On the other hand, the peak wavelength generally lengthens as the PWM duty ratio increases.

[0017] As described above, the wavelength shift characteristics of the light-emitting elements may differ depending on the type of the light-emitting elements. Therefore, for example, in a display panel including multiple light-emitting elements each having a different wavelength shift characteristic, a change in the color of the display panel may occur as the luminance of each light-emitting element changes. As described above, the wavelength shift characteristics of the light-emitting elements may cause a decrease in the display quality of the display panel.

[0018] Therefore, an object of the present disclosure is to improve the display quality of a display panel. For example, as described below, the present disclosure provides a display device in which a change in emission wavelength when the luminance of a light-emitting element is changed is reduced compared to conventional devices. The present disclosure also provides a control device for controlling the display panel of the display device.

[0019] (Regarding Wavelength Expressions in the Present Disclosure) In the present disclosure, the wavelength of light emitted (output) from a light-emitting element is described using the dominant wavelength in the XYZ color system. The dominant wavelength is determined according to steps 1 to 4 below.

[0020] Step 1: In the XYZ color system, the chromaticity point of light output by one light-emitting element is determined as point F. Step 2: Next, a predetermined white point W is determined. The x and y coordinates of white point W are, for example, (x, y) = (1 / 3, 1 / 3). Step 3: Next, point D is determined where the line connecting white point W and point F intersects with the spectrum locus. Step 4: The wavelength corresponding to point D is determined as the dominant wavelength.

[0021] In a light spectrum, the wavelength corresponding to the peak value of the light intensity is called the peak wavelength. For light emitted from a single light-emitting element, the peak wavelength and the dominant wavelength generally coincide. Therefore, when describing light emitted from a single light-emitting element, either the peak wavelength or the dominant wavelength can be used.

[0022] However, in the second and subsequent embodiments described below, mixed light may be used, which is light obtained by mixing light emitted from two light-emitting elements (a first light-emitting element and a second light-emitting element) each having a different peak wavelength. Because the spectrum of the mixed light has two peaks, it may be difficult to explain the wavelength of the mixed light using the concept of peak wavelength.

[0023] On the other hand, it is relatively easy to determine the chromaticity point of the mixed light. In the following description, the light emitted from the first light-emitting element will be referred to as the first light, and the light emitted from the second light-emitting element will be referred to as the second light. First, a line segment is determined connecting the first chromaticity point, which is the chromaticity point of the first light, and the second chromaticity point, which is the chromaticity point of the second light. Next, a point on the line segment that divides the first chromaticity point and the second chromaticity point is determined according to the ratio between the luminance of the first light and the luminance of the second light. Then, the point is determined as the chromaticity point of the mixed light. Therefore, the x and y coordinates of the chromaticity point of the mixed light are given as the x and y coordinates of the point.

[0024] The dominant wavelength of the mixed light can be determined from the x and y coordinates of the chromaticity point of the mixed light derived in this way. For this reason, it is considered preferable to use the concept of dominant wavelength to explain the wavelength of the mixed light in this disclosure. Therefore, in this disclosure, the wavelength of light is explained with a focus on the dominant wavelength.

[0025] (Example of characteristics of light-emitting element used in the description of the present disclosure) FIG. 1 illustrates the change trend of the dominant wavelength in the light-emitting element of embodiment 1. The dominant wavelength in the example of FIG. 1 can be read as the peak wavelength. The example of FIG. 1 corresponds to the example of reference numeral 6300B described above. The light-emitting element in the example of FIG. 1 is an InGaN-based green LED.

[0026] In FIG. 1, graph 101 shows the characteristics of a light-emitting element related to CC. Graph 102 shows the characteristics of a light-emitting element related to PWM. In the following description, a light-emitting element related to CC will also be referred to as a CC light-emitting element, and a light-emitting element related to PWM will also be referred to as a PWM light-emitting element. The horizontal axis of the graph in FIG. 1 represents the current ratio in CC or the duty ratio in PWM. The vertical axis of the graph represents the dominant wavelength. The current ratio is a value indicating the ratio of the current based on the maximum current. In other words, the current ratio indicates a current value normalized by the maximum current.

[0027] In the example indicated by the reference numeral 6300B, there is no data for the portion where the current ratio or duty ratio is 5% or less. Therefore, in the example of Fig. 1, the data for the portion where the current ratio or duty ratio is 5% or less is supplemented by extrapolation. Therefore, it should be noted that Fig. 1 illustrates the characteristics of a hypothetical green LED.

[0028] In this disclosure, each explanation will be made using a light-emitting element having the characteristics shown in FIG. 1 . For simplicity of explanation, in this disclosure, the current ratio and duty ratio of a certain light-emitting element are assumed to be proportional to the luminance of the light-emitting element. Therefore, the horizontal axis in the graph of FIG. 1 also corresponds to the luminance ratio. The luminance ratio is a value indicating the ratio of luminance based on maximum luminance. In other words, the luminance ratio indicates a luminance value normalized by the maximum luminance.

[0029] Furthermore, in this disclosure, for the sake of simplicity, the relationship between a certain gradation value and the luminance of a light-emitting element when the light-emitting element is caused to emit light according to the gradation value is assumed to be linear. That is, the description will be made assuming a gamma characteristic of γ=1. Therefore, the horizontal axis in the graph of FIG. 1 also corresponds to the ratio of the gradation value relative to the maximum gradation value of the light-emitting element (gradation ratio). Therefore, the four parameters listed on the horizontal axis may be interpreted interchangeably as long as there is no contradiction in the context. The gradation ratio is a value indicating the ratio of the gradation value relative to the maximum gradation value of the light-emitting element. In other words, the gradation ratio indicates a gradation value normalized by the maximum gradation value.

[0030] Next, the "gradation ratio" will be described in more detail. As described above, in this disclosure, the ratio of a gradation value based on the maximum gradation value is referred to as the gradation ratio. In this disclosure, the gradation ratio varies within a range of 0% to 100%. In this disclosure, the range of variation of the gradation ratio is referred to as the "gradation ratio variation range." The gradation ratio variation range may be a predetermined range. The following two examples of the gradation ratio variation range can be given.

[0031] Example 1: When the gradation value is expressed in 8 bits and the range of the gradation value is 0 to 255, the gradation value 0 corresponds to a gradation ratio of 0%, and the gradation value 255 corresponds to a gradation ratio of 100%.

[0032] Example 2: When the gradation value is expressed in 8 bits and the range of the gradation value is 16 to 235 (e.g. REC.709), the gradation value 16 corresponds to a gradation ratio of 0%, and the gradation value 235 corresponds to a gradation ratio of 100%.

[0033] Therefore, when the minimum value (minimum gradation value) and maximum value (maximum gradation value) that the gradation value T can take are expressed as Tmin and Tmax, respectively, the gradation ratio TV corresponding to the gradation value T is expressed as TV=(T-Tmin) / (Tmax-Tmin). Therefore, the minimum gradation ratio TVmin corresponding to the minimum gradation value Tmin is equal to 0, and the maximum gradation ratio TVmax corresponding to the maximum gradation value Tmax is equal to 1. As described above, the gradation ratio TV takes on values ​​from 0 to 1 (i.e., values ​​from 0% to 100%).

[0034] 1, the CC light-emitting element is an example of the first light-emitting element, and the PWM light-emitting element is an example of the second light-emitting element. According to FIG. 1, the first light-emitting element and the second light-emitting element have different dominant wavelength characteristics relative to the luminance of the light emitted by each light-emitting element.

[0035] In the present disclosure, "the characteristics of dominant wavelength versus luminance of the light emitted by each light-emitting element are different" simply means that the graph of luminance versus dominant wavelength of the first light-emitting element (e.g., graph 101) does not match the graph of luminance versus dominant wavelength of the second light-emitting element (e.g., graph 102).

[0036] Graphs 5301 and 5302 in FIG. 53 of Embodiment 8, which will be described later, show similar trends in the change in dominant wavelength with a change in luminance. However, the dominant wavelength corresponding to a certain luminance in graph 5301 is different from the dominant wavelength corresponding to the same luminance in graph 5302. Therefore, in the present disclosure, the example in FIG. 53 also falls within the category of "different characteristics of the dominant wavelength value relative to the luminance of light output from each light-emitting element."

[0037] (Explanation of the Basic Concept of Embodiment 1) In a display device, it is preferable to display display data, particularly low gradation data, using CC light-emitting elements. This is because flicker becomes noticeable when low gradation display data is displayed using PWM light-emitting elements. However, in the example of Figure 1, the change in dominant wavelength with respect to a change in gradation value is larger with CC light-emitting elements than with PWM light-emitting elements.

[0038] As mentioned above, the CC light emitting element and the PWM light emitting element have different characteristics of the dominant wavelength value relative to the luminance of the light output from each light source. Specifically, as shown in Figure 1, in the range of luminance ratios of 10% or more, the direction of change in dominant wavelength relative to the luminance ratio for the CC light emitting element is opposite to the direction of change in dominant wavelength relative to the luminance ratio for the PWM light emitting element.

[0039] More specifically, in the range of luminance ratios of 10% or more, the dominant wavelength of a CC light-emitting element decreases as the luminance ratio increases. On the other hand, in the range of luminance ratios of 10% or more, the dominant wavelength of a PWM light-emitting element increases as the luminance ratio increases. Therefore, as an example, it is possible to use a CC light-emitting element in the range of gradation ratios less than 10% and a PWM light-emitting element in the range of gradation ratios of 10% or more.

[0040] 2 is a diagram showing a relationship between the gray scale ratio and the dominant wavelength in the display that is aimed to be realized in embodiment 1. In FIG. 2, a graph 201 shows the characteristics of a CC light emitting element, and a graph 202 shows the characteristics of a PWM light emitting element.

[0041] Point C in Fig. 2 is an example of a 10% gradation ratio point. As shown in Fig. 2, it is conceivable to make the dominant wavelength of the CC light-emitting element and the dominant wavelength of the PWM light-emitting element approximately coincident with each other at point C and switch the light-emitting element to be used at point C. This makes it possible to reduce the change in dominant wavelength compared to when displaying using only CC light-emitting elements.

[0042] However, the display shown in Figure 2 cannot be achieved by simply combining the CC light-emitting element and the PWM light-emitting element in Figure 1. In Figure 1, point A is the 10% gradation point of the CC light-emitting element, and point B is the 10% gradation point of the PWM light-emitting element. Point A in the example of Figure 1 is significantly separated from point B. Thus, the dominant wavelength of the CC light-emitting element at the 10% gradation point is significantly different from the dominant wavelength of the PWM light-emitting element at the 10% gradation point.

[0043] Therefore, the inventors of the present application performed an adjustment to match (set equal) the dominant wavelength of the CC light-emitting element and the dominant wavelength of the PWM light-emitting element at the 10% gradation ratio point (e.g., point C in Figure 2). The inventors conducted an investigation into the adjustment with reference to Non-Patent Document 2. Figure 3 shows a portion of the graph disclosed in Non-Patent Document 2. Figure 3 shows an example of changes in the dominant wavelength of emitted light when current is passed through four μLEDs made of the same type of material.

[0044] The four μLEDs in the example of FIG. 3 each have a different diameter. Specifically, the diameters of the four μLEDs are 30 μm, 40 μm, 50 μm, and 60 μm. According to FIG. 3, the four graphs showing the characteristics of each of the four μLEDs show approximately the same trend. These four graphs can be nearly superimposed by translating them vertically within the paper.

[0045] As described above, the four μLEDs have different diameters. In other words, the four μLEDs have different areas. When a certain current is passed through a μLED, the current density corresponding to that current increases as the area of ​​the μLED decreases. Therefore, according to FIG. 3 , it can be said that the dominant wavelength decreases as the current density passed through the μLED increases.

[0046] Therefore, to tune a μLED to have a shorter dominant wavelength while maintaining the same luminance, the area of ​​the μLED can be reduced to increase the current density, whereas to tune a μLED to have a longer dominant wavelength while maintaining the same luminance, the area of ​​the μLED can be increased to decrease the current density.

[0047] For simplicity, the present disclosure assumes that the conversion efficiency of a μLED is constant regardless of the area and current density of the μLED. Thus, for example, the present disclosure assumes that when the same current is passed through two μLEDs with different areas, the two LEDs will emit light with the same brightness.

[0048] In the example of Fig. 1, the dominant wavelength at point A is 10.6 nm longer than the dominant wavelength at point B. Therefore, to realize the situation of Fig. 2, for example, the area of ​​the PWM light-emitting element may be increased so that the dominant wavelength of the PWM light-emitting element becomes 10.6 nm longer overall. This moves point B to the position of point A, and the dominant wavelength of the CC light-emitting element at the 10% gradation ratio point can be made to match the dominant wavelength of the PWM light-emitting element.

[0049] FIG. 4 illustrates the change in dominant wavelength with respect to the change in duty ratio before and after adjusting the area of ​​the PWM light-emitting element (in other words, adjusting the dominant wavelength). In FIG. 4, graph 401 shows the characteristics of the PWM light-emitting element before area adjustment, and graph 402 shows the characteristics of the PWM light-emitting element after area adjustment. As shown in FIG. 4, by increasing the area of ​​the PWM light-emitting element, the characteristics of graph 401 were shifted by 10.6 nm in the positive direction of the vertical axis. As a result, point B moved to point D. The dominant wavelength at point D is equal to the dominant wavelength at point A.

[0050] The specific extent to which the area of ​​the light-emitting element needs to be increased to obtain the desired change in dominant wavelength varies depending on the material of the light-emitting layer of the light-emitting element. Therefore, it is desirable to experimentally derive the relationship between the area and the amount of change in dominant wavelength. As an example, suppose that the dominant wavelength can be lengthened by multiplying the area of ​​the PWM light-emitting element by x1, where x1 is a number greater than 1.

[0051] 5 illustrates the change in dominant wavelength with respect to the change in current ratio or duty ratio in the light-emitting element used in embodiment 1. In Fig. 5, graph 501 shows the characteristics of the CC light-emitting element, and graph 502 shows the characteristics of the PWM light-emitting element after area adjustment. Graph 502 in Fig. 5 shows that graph 102 in Fig. 1 has been shifted by 10.6 nm in the positive direction of the vertical axis.

[0052] As another example, to achieve the situation of FIG. 2, the area of ​​the CC light-emitting element may be reduced so that the dominant wavelength of the CC light-emitting element is shortened by 10.6 nm overall.

[0053] As yet another example, the dominant wavelength of a PWM light-emitting element may be increased by increasing its area, and the dominant wavelength of a CC light-emitting element may be decreased by decreasing its area. That is, both the area of ​​the PWM light-emitting element and the area of ​​the CC light-emitting element may be adjusted. That is, both the dominant wavelength of the PWM light-emitting element and the dominant wavelength of the CC light-emitting element may be adjusted.

[0054] This also applies to the embodiments described below. In the embodiments described below, examples are illustrated in which the dominant wavelength of the second light-emitting element G2 is adjusted by adjusting the area of ​​the second light-emitting element G2 (excluding embodiment 7 in which the dominant wavelength is not adjusted). However, in these embodiments, the dominant wavelength of the first light-emitting element G1 may be adjusted by adjusting the area of ​​the first light-emitting element G1. Alternatively, both the dominant wavelength of the first light-emitting element G1 and the dominant wavelength of the second light-emitting element G2 may be adjusted by adjusting both the area of ​​the first light-emitting element G1 and the area of ​​the second light-emitting element G2.

[0055] 6 illustrates the change in dominant wavelength in a display combining a CC light-emitting element and a PWM light-emitting element after adjusting the dominant wavelength, where graph 601 shows the characteristics of the CC light-emitting element and graph 602 shows the characteristics of the PWM light-emitting element after adjusting the dominant wavelength.

[0056] In the example of Figure 6, in the range of gradation ratios less than 10%, display is performed using CC light-emitting elements. On the other hand, in the range of gradation ratios equal to or greater than 10%, display is performed using PWM light-emitting elements. In the example of Figure 6, point A, which is the 10% gradation ratio point of the CC light-emitting elements, is located at the same position as point D, which is the 10% gradation ratio point of the PWM light-emitting elements. Therefore, at the 10% gradation ratio point, the dominant wavelength of the CC light-emitting elements is equal to the dominant wavelength of the PWM light-emitting elements. Therefore, the change in dominant wavelength in the example of Figure 6 is continuous with the change in gradation ratio.

[0057] 6, it is possible to reduce the change in dominant wavelength compared to when only CC light emitting elements are used for display. Furthermore, by using CC light emitting elements for display in a low gray scale ratio range, it is possible to reduce the risk of flicker.

[0058] In the first embodiment, the gradation ratio at which the display by the CC light emitting elements and the display by the PWM light emitting elements are switched is referred to as a “first gradation ratio.” Symbol TV1 in Fig. 6 denotes the first gradation ratio.

[0059] In addition, in the first embodiment, the range of gradation ratio change that is less than the first gradation ratio is referred to as the "first range." On the other hand, the range of gradation ratio change that is equal to or greater than the first gradation ratio is referred to as the "second range." In Figure 6, the symbol RG indicates the gradation ratio change range, the symbol RG1 indicates the first range, and the symbol RG2 indicates the second range.

[0060] That is, both the first range RG1 and the second range RG2 belong to the gradation ratio change range RG. The second range RG2 is adjacent to the first range RG1 on the high gradation ratio side of the first range RG1. The first gradation ratio TV1 can also be expressed as the gradation ratio located on the boundary between the first range RG1 and the second range RG2.

[0061] 7 is a block diagram showing an example of the configuration of the display device 100 according to the first embodiment. The display device 100 receives input image data and displays an image corresponding to the input image data. The display device 100 includes a control device 1 and a display panel 90.

[0062] In the first embodiment, for the sake of simplicity, it is assumed that the resolution of the input image data is the same as the resolution of the pixels PX of the display panel 90. Therefore, the gradation data of each pixel in the input image data corresponds one-to-one to the pixels PX of the display panel 90. In the present disclosure, a "pixel in the input image data" is referred to as an "input pixel." A "sub-pixel in the input image data" is referred to as an "input sub-pixel."

[0063] If the resolution of the input image data is different from the resolution of the pixels PX of the display panel 90, for example, a resolution conversion process may be performed to match the resolution of the input image data with the resolution of the pixels PX of the display panel 90. After the resolution conversion process, the processes described in the first embodiment may be performed.

[0064] The control device 1 comprehensively controls each part of the display device 100. The control device 1 has a control unit 10 that controls the display panel 90. The control device 1 may further have a power supply circuit (not shown) and the like.

[0065] The display panel 90 has a plurality of pixels PX. As shown in FIG. 8 , each of the pixels PX has one or more subpixels SUBPX. At least one subpixel SUBPX has two light-emitting elements.

[0066] In the first embodiment, one of the two light-emitting elements of the subpixel SUBPX is a CC light-emitting element, and the other is a PWM light-emitting element. The display panel 90 may further include a drive circuit (e.g., a driver IC) (not shown) that drives the light-emitting elements.

[0067] As shown in FIG. 7 , the control unit 10 receives input image data. The control unit 10 generates control data for controlling each light-emitting element of the display panel 90 based on the input image data. The control unit 10 supplies the generated control data to the display panel 90. In this disclosure, unless there is a contradiction in the context, "control of light-emitting elements" means "light-emission control of light-emitting elements." In the example of FIG. 7 , the control unit 10 includes a first control data generation unit 11 and a second control data generation unit 12. The input image data is supplied to both the first control data generation unit 11 and the second control data generation unit 12.

[0068] The first control data generation unit 11 generates first control data based on input image data and supplies the first control data to the display panel 90. The first control data is control data for controlling the CC light-emitting element in the subpixel SUBPX of the display panel 90 in accordance with the gradation ratio corresponding to the input subpixel. An example of the processing of the first control data generation unit 11 will be described later.

[0069] The second control data generation unit 12 generates second control data based on the input image data and supplies the second control data to the display panel 90. The second control data is control data for controlling the PWM light-emitting element in the subpixel SUBPX of the display panel 90 in accordance with the gradation ratio corresponding to the input subpixel. An example of the processing by the second control data generation unit 12 will also be described later.

[0070] 8 shows an example of the configuration of one pixel PX in a display panel 90. In the first embodiment, a case where one pixel PX has multiple subpixels SUBPX, each emitting light of a different color, is illustrated. The pixel PX in the example of FIG. 8 includes a red subpixel SUBPX_R, a green subpixel SUBPX_G, and a blue subpixel SUBPX_B. The subpixel SUBPX collectively refers to the red subpixel SUBPX_R, the green subpixel SUBPX_G, and the blue subpixel SUBPX_B.

[0071] In the first embodiment, at least one subpixel SUBPX has two light-emitting elements. In the example of Fig. 8, the green subpixel SUBPX_G has a first light-emitting element G1 and a second light-emitting element G2. The first light-emitting element G1 and the second light-emitting element G2 are green light-emitting elements that emit green light.

[0072] In the example of FIG. 8 , the red sub-pixel SUBPX_R has one light-emitting element R. The light-emitting element R is a red light-emitting element that emits red light. The blue sub-pixel SUBPX_B has one light-emitting element B. The light-emitting element B is a blue light-emitting element that emits blue light. The light-emitting elements R and B in embodiment 1 are CC light-emitting elements.

[0073] 8, the display panel 90 may be a monochrome display panel. When the display panel 90 is a monochrome display panel, one pixel PX may have only one subpixel SUBPX. In this case, it is sufficient for one subpixel SUBPX to have a first light-emitting element (e.g., a CC light-emitting element) and a second light-emitting element (e.g., a PWM light-emitting element).

[0074] The first light-emitting element G1 and the second light-emitting element G2 in the first embodiment correspond to an InGaN-based green LED having the characteristics shown in the graph denoted by reference numeral 6300B. Specifically, the first light-emitting element G1 and the second light-emitting element G2 are miniaturized versions of the InGaN-based green LED so that they can be arranged within a single subpixel. Such miniaturized LEDs are also referred to as μLEDs. The light-emitting element R and the light-emitting element B may also be μLEDs.

[0075] In the present disclosure, the light emitted by the first light-emitting element is referred to as the first light, and the light emitted by the first light-emitting element is referred to as the second light. The dominant wavelength of the first light is referred to as the first dominant wavelength, and the dominant wavelength of the second light is referred to as the second dominant wavelength. The color of the first light is referred to as the first color, and the color of the second light is referred to as the second color. The first color and the second color in the present disclosure may be the same type of color. In the example of the first embodiment, both the first and second colors are green light.

[0076] In the present disclosure, the term "same type of color" does not mean light colors with exactly the same dominant wavelength. For example, in the first embodiment, even if the first dominant wavelength and the second dominant wavelength are different, if the first light and the second light are both green light, the first light and the second light are light of the same type of color.

[0077] 8, the first light-emitting element G1 and the second light-emitting element G2 are arranged on the same plane. However, the first light-emitting element G1 and the second light-emitting element G2 may be arranged on different planes. For example, the first light-emitting element G1 and the second light-emitting element G2 may be arranged so as to form a stacked structure.

[0078] The first light-emitting element G1 is a CC light-emitting element. The first light-emitting element G1 has the characteristics shown in the above-mentioned graph 501. The second light-emitting element G2 is a PWM light-emitting element. The second light-emitting element G2 has the characteristics shown in the above-mentioned graph 502.

[0079] The ratio between the area of ​​the first light-emitting element G1 and the area of ​​the second light-emitting element G2 is 1:x1. As described above, x1 > 1. In this way, the second light-emitting element G2 in the example of FIG. 8 is a PWM light-emitting element after the above-described dominant wavelength adjustment.

[0080] 8, the CC light-emitting elements R, G1, and B have the same area. However, the areas of the light-emitting elements may be different. The area of ​​each light-emitting element may be determined, for example, taking into consideration the brightness required for each color of light.

[0081] (Configuration Example of Drive Circuit) As described above, the display panel 90 may have a drive circuit that drives the light-emitting elements. As an example, the display panel 90 may have a first drive circuit 1gd that drives the first light-emitting element G1 and a second drive circuit 2gd that drives the second light-emitting element G2. FIG. 9 shows a configuration example of the first drive circuit 1gd. FIG. 10 shows a configuration example of the second drive circuit 2gd. FIG. 11 is an example timing chart of signals related to the second drive circuit 2gd. In the following description of FIGS. 9 to 11, items shown in FIGS. 9 to 11 that are not related to the driving method of the present invention will be omitted as appropriate.

[0082] First, let us refer to FIG. 9. The first drive circuit 1gd drives the first light-emitting element G1 by current driving. The first drive circuit 1gd may also be referred to as a CC drive circuit. The first drive circuit 1gd includes a capacitor C and transistors TR1 to TR3. The transistor TR1 is turned on during the high period of the gate scan signal supplied via the scan signal line Gln'. This allows write data supplied via the data signal line Dlm' to be written to the capacitor C.

[0083] During the above period, the transistor TR2 and the transistor TR3, whose gate electrode is supplied with the light-emission control signal EM via the light-emission control line EMI′, are also turned on. Therefore, a current corresponding to the difference between (i) the sum of the first high-potential-side power supply voltage supplied via the first high-potential-side power supply voltage line ELVDD1 and the voltage corresponding to the write data written in the capacitor C, and (ii) the low-potential-side power supply voltage ELVSS flows through the first light-emitting element G1.

[0084] As described above, by changing the voltage of the write data, that is, by changing the value of the current flowing through the first light-emitting element G1 according to the gradation value of the input image data, the brightness of the first light can be controlled by current driving.

[0085] Next, referring to FIG. 10 , the second drive circuit 2gd drives the second light-emitting element G2 by PWM drive. The second drive circuit 2gd may also be referred to as a PWM drive circuit. The second drive circuit 2gd includes a first sub-circuit PAMP, a second sub-circuit PWMP, and a transistor T5. The transistor T5 is a PWM control TFT (Thin Film Transistor) controlled by the voltage at the node Nc.

[0086] The first sub-circuit PAMP has a transistor T1 controlled by a control signal S2, a transistor T2, a transistor T3 controlled by a control signal S1, a transistor T4 controlled by a light emission control signal EM, and a transistor T6 controlled by the control signal S1. The second transistor T2 is a driving TFT controlled by the voltage of the node Na.

[0087] The first sub-circuit PAMP further includes a capacitor Csta, one electrode of which is connected to the source electrode of the transistor T3 and the gate electrode of the transistor T2, and the other electrode of which is connected to the drain electrode of the transistor T6 and the source electrode of the transistor T5.

[0088] The second sub-circuit PWMP includes a transistor T7 controlled by a control signal S3, a transistor T8, a transistor T9 controlled by a control signal S4, and a transistor T10 controlled by a control signal S5 (gate scan signal). The transistor T8 is a switching TFT controlled by the voltage at the node Nb.

[0089] The second sub-circuit PWMP further includes capacitors Cstb and Cstc. One electrode of the capacitor Cstb is connected to the gate electrode of the transistor T8 and the source electrode of the transistor T9. The other electrode of the capacitor Cstb is connected to the source electrode of the transistor T10 and one electrode of the capacitor Cstc. One electrode of the capacitor Cstc is connected to the source electrode of the transistor T10 and the other electrode of the capacitor Cstb. The other electrode of the capacitor Cstc is connected to the sweep signal line SWEEP.

[0090] 11, the period during which the first sub-circuit PAMP is initialized (PAM Initialize) is the period from when the control signal S1 goes high until the control signal S2 goes high, and also the period during which the EMI signal EM is high. During this initialization period, the transistor T6 is turned on, and the initialization voltage VINI is supplied via the transistor T6. As a result, the voltage at the node Na is set to a predetermined value, and the first sub-circuit PAMP is initialized.

[0091] The setup period (PAM Setup) of the first sub-circuit PAMP is the period from when the control signal S2 goes high until the control signal S3 goes high, during which the EMI signal EM is low. During this setup period, PAM DATA is supplied to the transistor T2 via the data signal line DLm and the transistor T1 as write data Data for the first sub-circuit PAMP. Therefore, the voltage of the node Na is set to the sum of PAM DATA and the threshold voltage Vth2 of the transistor T2 (PAM DATA + Vth2). In this way, the first sub-circuit PAMP is in the setup state. Vth2 is the threshold voltage of the transistor T2.

[0092] During the initialization period (PWM Initialize) of the second sub-circuit PWMP, transistors T7, T9, and T10 are turned on. This causes a Reset signal to be written as predetermined write data to nodes Nb, Nc, and capacitor Cstb. This sets the voltages of nodes Nb and Nc to a constant value (ELVSS+Vth8), initializing the second sub-circuit PWMP. Vth8 is the threshold voltage of transistor T8.

[0093] In the PWM setup period (PWM Setup) following the above-mentioned PWM initialization period (PWM Initialize), during the period when the transistor T10 is on, that is, during the period when the control signals S5<1> to S5<n>, which are the Gate Scan signals Gate Scan<1> to Gate Scan<n>, sequentially go High, predetermined write data (PWM DATA) is written to each row of the second drive circuit 2gd.

[0094] During the PWM setup period, the transistor T9 remains turned off, so the gate electrode of the transistor T8 (in other words, the node Nb) maintains a constant voltage (ELVSS+Vth8+VDATA) corresponding to the predetermined write data (PWM DATA).

[0095] Furthermore, during the PWM setup period, the transistor T7 remains turned off, so the gate electrode of the transistor T5 (in other words, the node Nc) maintains the constant voltage (ELVSS+Vth8) after the initialization described above.

[0096] In the period immediately following the PWM setup period, transistor T7 is turned on, and a Reset signal, which is the predetermined write data used in the initialization described above, is supplied to the gate electrode of transistor T5 (i.e., to node Nc). During this period, the constant voltage (ELVSS+Vth8) after the initialization described above rises slightly.

[0097] During the light emission period of the second light-emitting element G2, i.e., the PWM light emission period (Emission), the EMI signal EM is High and the sweep signal SWEEP is supplied with a gradually increasing voltage, so that the voltage of the gate electrode of the eighth transistor T8 (in other words, the voltage of the node Nb) gradually increases due to the influence of the sweep signal SWEEP.

[0098] The voltage of the gate electrode of transistor T5 (i.e., the voltage of node Nc) is maintained until the voltage of the gate electrode of transistor T8 reaches Vth8. Therefore, transistor T5 remains turned on, and a predetermined current flows through second light-emitting element G2, causing second light-emitting element G2 to emit light.

[0099] On the other hand, when the voltage at the gate electrode of transistor T8 exceeds Vth8, transistor T8 is turned on, and the voltage at node Nc drops. Therefore, transistor T5 is turned off, and no current flows through second light-emitting element G2. In this way, second light-emitting element G2 transitions from the light-emitting state to the non-light-emitting state.

[0100] The higher the voltage of the write data, the shorter the time it takes for the voltage of the gate electrode of transistor T8 to reach Vth8. Therefore, the higher the voltage of the write data, the shorter the light-emitting period of the second light-emitting element G2. As described above, the current-carrying time (in other words, the light-emitting period) of the second light-emitting element G2 can be changed while maintaining a constant amount of current flowing through the second light-emitting element G2 in accordance with the voltage of the write data, i.e., the gradation value of the input image data. In this way, the second drive circuit 2gd can control the luminance of the second light by PWM drive.

[0101] 10, the second drive circuit 2gd does not have to include the first sub-circuit PAMP. In this case, the second drive circuit 2gd may be configured to supply ELVSS2 directly to the transistor T5.

[0102] (Example of processing by the first control data generation unit 11) The first control data generation unit 11 generates first control data, which is control data for the CC light-emitting elements (e.g., light-emitting element R, first light-emitting element G1, and light-emitting element B) of the display panel 90, based on input image data.

[0103] For example, the first control data generation unit 11 generates control data for the light-emitting element R in the sub-pixel SUBPX corresponding to the input pixel based on the R component (red component) of the gradation data of the input pixel. Similarly, the first control data generation unit 11 generates control data for the light-emitting element B in the sub-pixel SUBPX corresponding to the input pixel based on the B component (blue component) of the gradation data of the input pixel. These pieces of control data may be generated by known methods.

[0104] Then, the first control data generator 11 generates control data for the first light-emitting element G1 in the sub-pixel SUBPX corresponding to the input pixel, based on the G component (green component) of the gradation data of the input pixel.

[0105] Fig. 12 is a flowchart illustrating a process flow in which the first control data generation unit 11 generates control data for the first light-emitting element G1. The process in Fig. 12 includes steps S1 to S3. The process in Fig. 12 is executed for all input pixels in the input image data. In the example in Fig. 12, a current ratio is illustrated as the control data for the first light-emitting element G1.

[0106] In step S1, the first control data generator 11 determines whether the G component of the gradation data for the input pixel to be processed is less than the first gradation ratio TV1. As described above, the first gradation ratio TV1 is a gradation ratio threshold (boundary point) for switching between using the first light-emitting element G1 and using the second light-emitting element G2. In the example of FIG. 6, the first gradation ratio TV1 is 10%. The first gradation ratio TV1 may be set as appropriate by the designer of the display device 100.

[0107] As will be apparent to those skilled in the art, the gradation ratio can be converted into a gradation value. For example, when the gradation value is expressed in 8 bits (gradation values ​​0 to 255), the gradation value corresponding to a gradation ratio of 10% is 26. Therefore, each process related to the gradation ratio in the present disclosure may be performed using the gradation value instead of the gradation ratio.

[0108] If the result of step S1 is YES, i.e., if the G component of the gradation data is less than the first gradation ratio TV1, the process proceeds to step S2. In step S2, the first control data generation unit 11 sets the control data of the first light-emitting element G1 to a value corresponding to the G component of the gradation data. As described above, in embodiment 1, the conditions related to display control are simplified for ease of explanation. Therefore, in embodiment 1, if the gradation value of the G component is a1, the first control data generation unit 11 sets the control data of the first light-emitting element G1 to a1.

[0109] On the other hand, if the result of step S1 is NO, that is, if the G component of the gradation data is equal to or greater than the first gradation ratio TV1, the process proceeds to step S3, in which the first control data generator 11 sets the control data of the first light-emitting element G1 to 0.

[0110] Fig. 13 illustrates the relationship between the gradation ratio of the G component of the gradation data of the input pixel and the control data of the first light-emitting element G1 set by the process of Fig. 12. The current ratio in Fig. 13 is an example of the control data. As shown in Fig. 13, in the range below the first gradation ratio TV, the current ratio increases as the gradation ratio increases. On the other hand, in the range above the first gradation ratio, the current ratio is 0 at all gradation ratios.

[0111] The first control data generation unit 11 of the present disclosure can generate the control data for the first light-emitting element G1 without necessarily using the process of Fig. 12. As an example, a lookup table showing the relationship between the gradation ratio of the G component of the gradation data of the input pixel and the control data for the first light-emitting element G1 shown in Fig. 13 may be prepared in advance. In this case, the first control data generation unit 11 can use the lookup table to set the control data for the first light-emitting element G1 that corresponds to the gradation ratio of the G component of the gradation data.

[0112] (Example of Processing by Second Control Data Generator 12) Based on input image data, the second control data generator 12 generates second control data, which is control data for a PWM light-emitting element (e.g., second light-emitting element G2) of the display panel 90. For example, based on the G component of the gradation data of an input pixel, the second control data generator 12 generates control data for the second light-emitting element G2 in the sub-pixel SUBPX corresponding to the input pixel.

[0113] Fig. 14 is a flowchart illustrating the flow of processing by the second control data generator 12 to generate control data for the second light-emitting element G2. Fig. 14 is a diagram paired with Fig. 12. The processing in Fig. 14 includes steps S11 to S13. The processing in Fig. 14 is also executed for all input pixels included in the input image data. In the example of Fig. 14, a duty ratio is illustrated as an example of the control data for the second light-emitting element G2.

[0114] In step S11, the second control data generating unit 12 determines whether or not the G component of the gradation data for the input pixel to be processed is less than the first gradation ratio TV1.

[0115] If the result of step S11 is YES, that is, if the G component of the gradation data is less than the first gradation ratio TV1, the process proceeds to step S12. In step S12, the second control data generator 12 sets the control data of the second light-emitting element G2 to 0.

[0116] On the other hand, if the result of step S11 is YES, i.e., if the G component of the gradation data is equal to or greater than the first gradation ratio TV1, the process proceeds to step S13. In step S13, the second control data generation unit 12 sets the control data of the second light-emitting element G2 to a value corresponding to the G component of the gradation data. As described above, in the first embodiment, the conditions related to display control are simplified for the sake of simplicity. Therefore, in the first embodiment, when the gradation value of the G component is a2, the second control data generation unit 12 sets the control data of the second light-emitting element G2 to a2.

[0117] Fig. 15 illustrates an example of the relationship between the gradation ratio of the G component of the gradation data of an input pixel and the control data of the second light-emitting element G2 set by the processing of Fig. 14. Fig. 15 is a diagram paired with Fig. 13. The duty ratios in Fig. 15 are examples of the control data. As shown in Fig. 15, in the range below the first gradation ratio TV, the duty ratio is 0 for all gradation ratios. On the other hand, in the range equal to or greater than the first gradation ratio, the duty ratio increases as the gradation ratio increases.

[0118] As is clear from the above description of the first control data generation unit 11, the second control data generation unit 12 of the present disclosure can also generate control data for the second light-emitting element G2 without necessarily using the process of Fig. 14. As an example, a lookup table showing the relationship between the gradation ratio of the G component of the gradation data of the input pixel and the control data for the second light-emitting element G2 shown in Fig. 15 may be prepared in advance. In this case, the second control data generation unit 12 can use the lookup table to set control data for the second light-emitting element G2 that corresponds to the gradation ratio of the G component of the gradation data.

[0119] 16 illustrates the relationship between the gradation ratio of the G component of the gradation data of an input pixel and the luminance ratio corresponding to each control data set based on the gradation ratio of the G component. Graph 1601 in FIG. 16 shows the luminance ratio of the first light-emitting element G1 set by the first control data. The luminance ratio of the first light is set as the first control data. Graph 1602 shows the luminance ratio of the second light-emitting element G2 set by the second control data.

[0120] 16, in the first range RG1, an input pixel is displayed by a first light emitted from the first light-emitting element G1, which is a CC light-emitting element. Meanwhile, in the second range RG2, an input pixel is displayed by a second light emitted from the second light-emitting element G2, which is a PWM light-emitting element. By providing both the first light-emitting element G1 and the second light-emitting element G2, the luminance ratio increases continuously with increasing gradation ratio throughout the entire gradation ratio change range RG.

[0121] In the present disclosure, the light obtained by the contribution of at least one of the first light-emitting element G1 and the second light-emitting element G2 throughout the entire gradation ratio change range RG is referred to as "composite light." In the example of FIG. 16 , both the first light and the second light are components of the combined light. In the first embodiment, there is no gradation ratio range in which both the first light-emitting element G1 and the second light-emitting element G2 emit light, so the first light and the second light do not mix. It should be noted that even in such a case, the light obtained by combining the first light and the second light is referred to as combined light.

[0122] However, in each embodiment described below, there exists a gradation ratio range in which both the first light-emitting element G1 and the second light-emitting element G2 emit light. In this case, the first light and the second light are mixed. In this disclosure, the light obtained by mixing the first light and the second light is referred to as "mixed light." Therefore, the combined light in this disclosure represents a broader concept that includes mixed light.

[0123] FIG. 17 illustrates the contribution rates of the first light-emitting element G1 and the second light-emitting element G2 to the combined light in the first embodiment. The contribution rates are values ​​indicating the ratios at which the luminance of the first light-emitting element G1 and the luminance of the second light-emitting element G2 contribute to a certain luminance ratio of the combined light. In the present disclosure, the contribution rate of the first light-emitting element G1 is referred to as the first contribution rate, and the contribution rate of the second light-emitting element G2 is referred to as the second contribution rate. In FIG. 17, graph 1701 shows the first contribution rate, and graph 1702 shows the second contribution rate. Graphs 1701 to 1702 in FIG. 17 are obtained based on graphs 1601 to 1602 in FIG. 16. As shown in FIG. 17, at any gradation ratio, the sum of the first contribution rate and the second contribution rate is equal to 100%.

[0124] 17 , in the first range RG1, the first contribution rate is 100% and the second contribution rate is 0%. That is, in the first range RG1, only the first light-emitting element G1 emits the first light, and the second light-emitting element G2 is in a non-light-emitting state. On the other hand, in the second range RG2, the second contribution rate is 100% and the first contribution rate is 0%. That is, in the second range RG2, only the second light-emitting element G2 emits the second light, and the first light-emitting element G1 is in a non-light-emitting state.

[0125] Fig. 18 illustrates the change in dominant wavelength with respect to the gradation ratio of the first light-emitting element G1 driven at the current ratio shown in Fig. 13 and the second light-emitting element G2 driven at the duty ratio shown in Fig. 15. In Fig. 18, graph 1801 shows the characteristics of the first light-emitting element G1, and graph 1802 shows the characteristics of the second light-emitting element G2. The graph in Fig. 18 is equivalent to the graph in Fig. 6.

[0126] Graph 1801 corresponds to the portion of current ratio 0% to 10% in graph 501 of the dominant wavelength of the CC light-emitting element shown in Figure 5. In the second range RG2, the first light-emitting element G1 is in a non-emitting state, so graph 1801 exists only within the first range RG1.

[0127] Graph 1802 corresponds to the portion of graph 502 of the dominant wavelength of the PWM light-emitting element shown in Figure 5 where the duty ratio is 10% to 100%. In graph 1802, this portion of graph 502 is applied to the second range RG2. In the first range RG1, the second light-emitting element G2 is in a non-emitting state, so graph 1802 exists only within the second range RG2.

[0128] As shown in FIG. 18 , in the first range RG1, display is achieved by emitting the first light only from the first light-emitting element G1. On the other hand, in the second range RG2, display is achieved by emitting the second light only from the second light-emitting element G2. Furthermore, at the first gradation ratio TV1, the first dominant wavelength and the second dominant wavelength are substantially the same. Therefore, the dominant wavelength of the combined light of the first light and the second light changes continuously with changes in the gradation ratio. In the present disclosure, the dominant wavelength of the combined light is referred to as the combined dominant wavelength.

[0129] In this disclosure, the difference between the maximum and minimum values ​​of the synthetic dominant wavelength in the gradation ratio change range RG is referred to as the synthetic dominant wavelength change amount. According to Fig. 18, the maximum value of the synthetic dominant wavelength, 536.5 nm, is obtained at the gradation ratio 0% point within the gradation ratio change range RG. Meanwhile, the minimum value of the synthetic dominant wavelength, 532.2 nm, is obtained at the gradation ratio 10% point within the gradation ratio change range RG (i.e., at the second gradation ratio TV2). Therefore, the synthetic dominant wavelength change amount in the example of Fig. 18 is given as 536.5 nm - 532.2 nm = 4.3 nm.

[0130] In the present disclosure, the difference between the maximum and minimum values ​​of the first dominant wavelength within the gradation ratio change range RG when only the first light-emitting element G1 is allowed to emit the first light is referred to as the "first dominant wavelength change amount." According to graph 501 in Figure 5, the maximum value of the first dominant wavelength, 536.5 nm, is obtained at the gradation ratio 0% point within the gradation ratio change range RG. Meanwhile, the minimum value of the first dominant wavelength, 525.4 nm, is obtained at the gradation ratio 100% point within the gradation ratio change range RG. Therefore, the first dominant wavelength change amount in the example of Figure 5 is given as 536.5 nm - 525.4 nm = 11.1 nm.

[0131] In the present disclosure, the difference between the maximum and minimum values ​​of the second dominant wavelength in the gradation ratio change range RG when only the second light-emitting element G2 is caused to emit the second light is referred to as the second dominant wavelength change amount. Examples of the second dominant wavelength change amount will be described in the sixth embodiment below.

[0132] As described above, in the display device 100, the synthetic dominant wavelength change amount can be made smaller than at least one of the first dominant wavelength change amount and the second dominant wavelength change amount by controlling the first light-emitting element G1 and the second light-emitting element G2 by the control unit 10. In the example of the first embodiment, the synthetic dominant wavelength change amount is smaller than the first dominant wavelength change amount.

[0133] Furthermore, according to the display device 100, in the range of low gradation ratios (e.g., in the first range RG1), the risk of flicker can be reduced by displaying using only the first light-emitting element G1, which is a CC light-emitting element.

[0134] However, it is not easy to perfectly match the first dominant wavelength and the second dominant wavelength at the first gradation ratio TV1. For example, manufacturing variations in the light-emitting elements and changes in the light-emitting characteristics of the light-emitting elements due to temperature changes can affect the dominant wavelength. Therefore, in practice, there is often a slight difference between the first dominant wavelength and the second dominant wavelength. However, it is preferable that this difference be as small as possible.

[0135] In this disclosure, the chromaticity point of the first light is referred to as the first chromaticity point, and the chromaticity point of the second light is referred to as the second chromaticity point. The color difference between the first chromaticity point and the second chromaticity point in the CIELAB color space is referred to as ΔE＊ A color difference of 1.0 or less can be barely detected by humans. In addition, a color difference of 0.6 or less can hardly be detected by humans. From this, ΔE ＊ is preferably 1.0 or less, and more preferably 0.6 or less.

[0136] Furthermore, the difference in dominant wavelength corresponding to a color difference of 1.0 or less varies depending on the color of light, but is generally 2 to 4 nm. Therefore, for example, the absolute value of the difference between the first dominant wavelength and the second dominant wavelength is preferably 4 nm or less, and more preferably 2 nm or less. From this, for example, when the absolute value of the difference between the first dominant wavelength and the second dominant wavelength at the first gradation ratio TV1 is 4 nm or less, it can be said that the first dominant wavelength and the second dominant wavelength at the first gradation ratio TV1 are substantially the same.

[0137] (Supplementary Notes on Embodiment 1) (1) In the first embodiment, the area of ​​the second light-emitting element G2, which is a PWM light-emitting element, is increased to adjust the second dominant wavelength to a higher value. However, in some cases, the area of ​​the second light-emitting element G2 may be decreased to adjust the second dominant wavelength to a lower value.

[0138] 19 illustrates the characteristics of a hypothetical green light-emitting element. In FIG. 19, graph 1901 shows the characteristics of a CC light-emitting element, and graph 1902 shows the characteristics of a PWM light-emitting element. The green light-emitting element in FIG. 19 has different characteristics than the green LED shown in FIG.

[0139] 19 has a characteristic that the dominant wavelength becomes longer as the current ratio increases when driven by current, whereas when driven by PWM, the dominant wavelength becomes shorter as the duty ratio increases.

[0140] 19, the area of ​​the PWM light-emitting element can be reduced to adjust the dominant wavelength of the PWM light-emitting element to a lower value. By applying the processes of embodiment 1 using the PWM light-emitting element after adjusting the dominant wavelength, the same effects as those of embodiment 1 can be obtained.

[0141] (2) In the first embodiment, the value of the first gradation ratio TV1 is set to 10%, but the first gradation ratio TV1 is not limited to this example. For example, when using the virtual green light-emitting element shown in Fig. 19, the change in the dominant wavelength can be minimized by setting the first gradation ratio TV1 to 50%.

[0142] Fig. 20 shows an example in which the first gradation ratio TV1 is set to 50%. In Fig. 20, a graph 2001 shows the characteristics of a CC light-emitting element, and a graph 2002 shows the characteristics of a PWM light-emitting element. The CC light-emitting element and the PWM light-emitting element in the example of Fig. 20 have the characteristics shown in Fig. 19.

[0143] In the example of Figure 20, the area of ​​the PWM light-emitting element is reduced, thereby shortening the dominant wavelength of the PWM light-emitting element by 10 nm. In the first range RG1, display is performed using only CC light-emitting elements. Meanwhile, in the second range RG2, display is performed using only PWM light-emitting elements. In this case, the amount of change in the composite dominant wavelength is 5 nm. As described above, the first gradation ratio TV1 may be set appropriately depending on the characteristics of the light-emitting elements used.

[0144] (3) In the first embodiment, an example in which the dominant wavelength is adjusted by adjusting the area of ​​the light-emitting element has been described. However, the method for adjusting the dominant wavelength is not limited to this example. For example, depending on the material used for the light-emitting element and the type of light-emitting element, the dominant wavelength may be shortened by reducing the current density, contrary to the description in the first embodiment. Furthermore, a new method for adjusting the dominant wavelength may be discovered through further investigation. Therefore, the method for adjusting the dominant wavelength is not limited to the area adjustment method described in the first embodiment. Any adjustment method that can be adopted by a person skilled in the art is included in the technical scope of the present disclosure.

[0145] (4) In the first embodiment, the first light-emitting element G1 and the second light-emitting element G2 are green LEDs made of the same material. However, the first light-emitting element G1 and the second light-emitting element G2 may be made of different materials.

[0146] In the first embodiment, the case where both the first light-emitting element G1 and the second light-emitting element G2 are μLEDs is exemplified. However, the first light-emitting element and the second light-emitting element G2 may be different types of light-emitting elements. For example, when the first light-emitting element is a μLED, the second light-emitting element may be a QD-LED.

[0147] In the first embodiment, the case where the first light-emitting element is a CC light-emitting element and the second light-emitting element is a PWM light-emitting element is exemplified. However, the driving method of each light-emitting element is not limited to this example. Therefore, for example, the first light-emitting element may be a PWM light-emitting element and the second light-emitting element may be a CC light-emitting element. As another example, both the first light-emitting element and the second light-emitting element may be CC light-emitting elements (see, for example, the eighth embodiment described below). As yet another example, both the first light-emitting element and the second light-emitting element may be PWM light-emitting elements.

[0148] As is clear from the above, the first light-emitting element and the second light-emitting element in the present disclosure may be realized by any combination of materials, types, and driving methods.

[0149] Fig. 21 illustrates the characteristics of two hypothetical light-emitting elements A and B. Both light-emitting elements A and B are green light-emitting elements and CC light-emitting elements. In Fig. 21, graph 2101 shows the characteristics of light-emitting element A, and graph 2102 shows the characteristics of light-emitting element B. Light-emitting element A has a characteristic in which the dominant wavelength decreases as the luminance ratio increases. On the other hand, light-emitting element B has a characteristic in which the dominant wavelength increases as the luminance ratio increases.

[0150] As an example, when the first light-emitting element and the second light-emitting element are different types of light-emitting elements, the characteristics shown in Fig. 21 may be obtained. Therefore, in the present disclosure, for example, light-emitting elements A and B in Fig. 21 may be used as the first light-emitting element and the second light-emitting element, respectively.

[0151] (5) In the first embodiment, of the three subpixels SUBPX in one pixel PX, only the green subpixel SUBPX_G has the first light-emitting element G1 and the second light-emitting element G2 as green light-emitting elements. However, the other subpixels SUBPX may have the first light-emitting element and the second light-emitting element. Therefore, the same processing as that for the green subpixel SUBPX_G described in the first embodiment may be applied to this subpixel SUBPX.

[0152] For example, by applying the blue LED according to reference numeral 6300C in Fig. 63 to the blue subpixel SUBPX_B, it is possible to realize the blue subpixel SUBPX_B having the first light-emitting element B1 and the second light-emitting element B2 as blue light-emitting elements. In this case, the same processing as described above may be applied to the blue subpixel SUBPX_B.

[0153] As another example, a red subpixel SUBPX_R may be realized that has a first light-emitting element R1 and a second light-emitting element R2 as red light-emitting elements. In this case, the same processing as described above may be applied to the red subpixel SUBPX_R.

[0154] (Example of a Case Where Each Subpixel Has a First Light-Emitting Element and a Second Light-Emitting Element) As an example, consider a case where the red subpixel SUBPX_R has a first light-emitting element R1 and a second light-emitting element R2, the green subpixel SUBPX_G has a first light-emitting element G1 and a second light-emitting element G2, and the blue subpixel SUBPX_B has a first light-emitting element B1 and a second light-emitting element B2. The processing of the first control data generator 11 and the second control data generator 12 in this case is illustrated as follows.

[0155] The first control data generation unit 11 generates control data for the first light-emitting element R1 in the pixel PX corresponding to the input pixel based on the R component of the gradation data of the input pixel. The first control data generation unit 11 generates control data for the first light-emitting element G1 in the pixel PX corresponding to the input pixel based on the G component of the gradation data. The first control data generation unit 11 generates control data for the first light-emitting element B1 in the pixel corresponding to the input pixel based on the B component of the gradation data. As described above, the first control data generation unit 11 generates first control data corresponding to each of the first light-emitting element R1, first light-emitting element G1, and first light-emitting element B1.

[0156] The second control data generation unit 12 generates control data for the second light-emitting element R2 in the pixel PX corresponding to the input pixel based on the R component of the gradation data of the input pixel. The second control data generation unit 12 generates control data for the second light-emitting element G2 in the pixel PX corresponding to the input pixel based on the G component of the gradation data. The second control data generation unit 12 generates control data for the second light-emitting element B2 in the pixel PX corresponding to the input pixel based on the B component of the gradation data. As described above, the second control data generation unit 12 generates second control data corresponding to each of the second light-emitting element R2, the second light-emitting element G2, and the second light-emitting element B2.

[0157] (6) In the first embodiment, only the second light-emitting element G2 in the green subpixel SUBPX_G emits light at a gradation ratio of 100%. However, in the present disclosure, both the first light-emitting element G1 and the second light-emitting element G2 in the green subpixel SUBPX_G may emit light.

[0158] For example, at a gradation ratio of 100%, both the first light-emitting element G1 and the second light-emitting element G2 may be caused to emit light at maximum brightness, which provides twice the brightness compared to when only the second light-emitting element G2 is caused to emit light.

[0159] Therefore, for example, two different modes, a first mode and a second mode, may be set in the display device 100. In this case, the display device 100 may be configured to be switchable between the first mode and the second mode. For example, the display device 100 may switch between the first mode and the second mode in response to a user operation.

[0160] As an example, the first mode may be a mode operating under the control described in the first embodiment. The first mode may also be referred to as a color shift reduction mode. On the other hand, the second mode may be a mode in which, in each subpixel SUBPX, both the first and second light-emitting elements in the subpixel SUBPX are caused to emit light at maximum luminance. The second mode may also be referred to as a high luminance mode.

[0161] (7) The configurations (1) to (6) have been explained above as supplementary information for embodiment 1. These configurations can also be applied to the following embodiments as long as there is no contradiction in content.

[0162] [Embodiment 2] In the above-described embodiment 1, a case where only the first light-emitting element G1 is caused to emit light in the first range RG1 and only the second light-emitting element G2 is caused to emit light in the second range RG2 is illustrated (see, for example, FIG. 16). In embodiment 2, an example of light emission control different from embodiment 1 will be described.

[0163] In the second embodiment, a case where both the first light-emitting element G1 and the second light-emitting element G2 are caused to emit light in a part of the gradation ratio change range RG (a third range RG3 described later) that is different from the first range RG1 and the second range RG2 is illustrated. Also, in the second embodiment, a case where either the first light-emitting element G1 or the second light-emitting element G2 is caused to emit light in a part of the gradation ratio change range RG that is different from the third range RG3 (a fourth range RG4 described later) is illustrated.

[0164] (Example of characteristics of first light-emitting element G1 and second light-emitting element G2 in embodiment 2) Fig. 22 illustrates the characteristics of the first light-emitting element G1 and the second light-emitting element G2 in embodiment 2. In Fig. 22, a graph 2201 shows the characteristics of the first light-emitting element G1, and a graph 2202 shows the characteristics of the second light-emitting element G2.

[0165] In the second embodiment, the area of ​​the second light-emitting element G2 is adjusted so that the second dominant wavelength is longer by 11.0 nm. Thus, in the second embodiment, the ratio between the area of ​​the first light-emitting element G1 and the area of ​​the second light-emitting element G2 is different from that in the first embodiment. Therefore, the graph 2202 in Fig. 22 is a graph in which the graph 102 in Fig. 1 is shifted by 11.0 nm upward in the plane of the paper. As shown in Fig. 22, the first light-emitting element G1 and the second light-emitting element G2 have different dominant wavelength characteristics.

[0166] (Example of control of first light-emitting element G1 and second light-emitting element G2 in embodiment 2) Figure 23 shows an example of control of the first light-emitting element G1 and the second light-emitting element G2 in embodiment 2. In the example of Figure 23, the first light-emitting element G1 is a CC light-emitting element, and the second light-emitting element G2 is a PWM light-emitting element. In Figure 23, graph 2301 shows control data for the first light-emitting element G1, and graph 2302 shows control data for the second light-emitting element G2. Graphs 2301 and 2302 are examples of first control data and second control data, respectively, in embodiment 2.

[0167] 23 , in the second embodiment, the range of the gradation ratio change range RG in which both the first light-emitting element G1 and the second light-emitting element G2 should emit light is referred to as the third range RG3. Furthermore, the range of the gradation ratio change range RG that is adjacent to the third range RG3 on the low gradation ratio side of the third range RG3 and in which only the first light-emitting element G1 should emit light is referred to as the fourth range RG4. The gradation ratio located on the boundary between the third range RG3 and the fourth range RG4 is referred to as the second gradation ratio TV2. In the example of FIG. 23 , the second gradation ratio TV2 is set to 10%.

[0168] As shown in graph 2301, the current ratio of the first light-emitting element G1 increases as the gradation ratio increases in the fourth range RG4. In addition, the current ratio of the first light-emitting element G1 is equal to the current ratio at the second gradation ratio TV2 in the third range RG3. Thus, the current ratio of the first light-emitting element G1 is maintained at a constant value in the third range RG3.

[0169] On the other hand, as shown in graph 2302, the duty ratio of the second light-emitting element G2 is set to 0% in the fourth range RG4. Therefore, in the fourth range RG4, the second light-emitting element G2 is in a non-light-emitting state. The duty ratio of the second light-emitting element G2 continuously changes from 0% as the gradation ratio increases in the third range RG3. In the example of FIG. 23 , the duty ratio of the second light-emitting element G2 continuously increases from 0% as the gradation ratio increases in the third range RG3. Specifically, in the example of FIG. 23 , the duty ratio of the second light-emitting element G2 continuously increases from 0% to 90% as the gradation ratio increases from 10% to 100%.

[0170] As described above, in this disclosure, for the sake of simplicity, it is assumed that the current ratio and duty ratio of a light-emitting element are proportional to the luminance of the light-emitting element. Therefore, the vertical axis in the graph of FIG. 23 also corresponds to the luminance ratio.

[0171] 23 , the control unit 10 in the second embodiment continuously controls the luminance of the first light-emitting element G1 and the luminance of the second light-emitting element G2 in response to changes in the gradation ratio within the gradation ratio change range RG (more specifically, within the fourth range RG4 and the third range RG3). In particular, the control unit 10 continuously controls the luminance of the first light-emitting element G1 and the luminance of the second light-emitting element G2 around the second gradation ratio TV2, which is the gradation ratio at the boundary between the third range RG3 and the fourth range RG4.

[0172] In this disclosure, the control unit 10 "continuously controls" the luminance of the light-emitting element means changing the luminance value so that the luminance value is continuous with respect to the gradation ratio. In actual luminance control, luminance is generally controlled using data with a predetermined number of bits, so strictly speaking, a luminance gap of at least the LSB (Least Significant Bit) occurs. However, in this disclosure, this luminance gap is considered to be within the range of continuous values. Therefore, in this disclosure, it is described as if the luminance gap does not disrupt the luminance continuity.

[0173] 16 in the first embodiment is an example of a discontinuous change in luminance. In the example of graph 1601, the luminance ratio of the first light-emitting element G1 decreases discretely (i.e., discontinuously) from 10% to 0% at the first gradation ratio TV1. In the example of graph 1602, the luminance ratio of the second light-emitting element G2 increases discretely from 0% to 10% at the first gradation ratio TV1.

[0174] 23 in the second embodiment illustrates a continuous change in luminance. In the example of graph 2301, as the gradation ratio increases from the second gradation ratio TV2, the luminance of the second light-emitting element G2 changes continuously from 0%. Also, as shown in graph 2301, the luminance of the first light-emitting element G1 is constant in the third range RG3. On the other hand, as shown in graph 2302, in the third range RG3, the luminance of the second light-emitting element G2 increases continuously as the gradation ratio increases.

[0175] Fig. 24 illustrates the relationship between the gradation ratio and the luminance ratio of the combined light of embodiment 2. The luminance ratio of the combined light in Fig. 24 is determined by the sum of the luminance ratio of the first light and the luminance ratio of the second light in the example of Fig. 23. As shown in Fig. 24 , in embodiment 2, by using both the first light-emitting element G1 and the second light-emitting element G2, it is possible to continuously increase the luminance ratio of the combined light as the gradation ratio increases over the entire gradation ratio change range RG.

[0176] Fig. 25 illustrates the contribution rate in embodiment 2. In Fig. 25, a graph 2501 shows the first contribution rate, and a graph 2502 shows the second contribution rate. The graphs 2501 to 2502 in Fig. 25 are obtained based on the graphs 2301 to 2302 in Fig. 23.

[0177] 25, in the fourth range RG4, the first contribution rate is 100% and the second contribution rate is 0%. That is, in the fourth range RG4, only the first light-emitting element G1 emits light, and the second light-emitting element G2 is in a non-light-emitting state.

[0178] In the third range RG3, the first contribution rate continuously decreases from 100% as the gradation ratio increases. At a gradation ratio of 100%, the first contribution rate reaches a minimum of 10%. On the other hand, in the third range RG3, the second contribution rate continuously increases from 0% as the gradation ratio increases. At a gradation ratio of 100%, the second contribution rate reaches a maximum of 90%. In this way, in the third range RG3, both the first light-emitting element G1 and the second light-emitting element G2 are made to emit light.

[0179] Fig. 26 illustrates the change in dominant wavelength of the first light-emitting element G1 and the second light-emitting element G2 with respect to the change in gradation ratio when the first light-emitting element G1 and the second light-emitting element G2 having the characteristics shown in Fig. 22 are driven by the control data (i.e., the current ratio and duty ratio) shown in Fig. 23. In other words, Fig. 26 illustrates the change in dominant wavelength of the first light-emitting element G1 and the second light-emitting element G2 with respect to the change in gradation ratio when the first light-emitting element G1 and the second light-emitting element G2 are driven according to the contribution ratios shown in Fig. 25. Graph 2601 in Fig. 26 shows the change in the first dominant wavelength of the first light-emitting element G1, and graphs 2602 and 2603 show the change in the second dominant wavelength of the second light-emitting element G2.

[0180] The portion of graph 2601 belonging to the fourth range RG4 corresponds to the portion of graph 2201 in FIG. 22 where the current ratio is 0% to 10%. According to graph 2601, as the gradation ratio increases from 0% to the second gradation ratio TV2 (10%) in the fourth range RG4, the first dominant wavelength decreases from 536.5 nm to 532.2 nm. As shown in FIG. 23 above, the current ratio of the first light-emitting element G1 is constant in the third range RG3. Therefore, as shown in graph 2601, the first dominant wavelength is a constant value of 532.2 nm in the third range RG3.

[0181] Graph 2602 shows the change in the second dominant wavelength of the second light-emitting element G2 before the dominant wavelength is adjusted. Graph 2602 corresponds to the portion of graph 102 for the PWM light-emitting element shown in FIG. 1 where the duty ratio is 0% to 90%. In graph 2602, this portion of graph 102 is applied to the third range RG3. In the fourth range RG4, the second light-emitting element G2 is in a non-emitting state, and therefore graph 2602 exists only within the third range RG3.

[0182] According to the graph 2602, the second dominant wavelength of the second light-emitting element G2 before the dominant wavelength adjustment is shorter than the first dominant wavelength by approximately 10 nm. Therefore, if the second light-emitting element G2 before the dominant wavelength adjustment is used as is, the change in the synthetic dominant wavelength will be large.

[0183] Therefore, as described above, in the second embodiment, the area of ​​the second light-emitting element G2 is adjusted so as to lengthen the second dominant wavelength by 11.0 nm. Specifically, in the second embodiment, the ratio between the area of ​​the first light-emitting element G1 and the area of ​​the second light-emitting element G2 is adjusted to 1:x2, where x2 is a number greater than 1.

[0184] The adjustment amount of the second dominant wavelength, 11.0 nm, is a value appropriately determined by the inventors of the present application in consideration of the change amount of the synthetic dominant wavelength. The adjustment amount of the second dominant wavelength in the second embodiment is not limited to this value. This also applies to the following embodiments.

[0185] In the above-described first embodiment, x1 is set so as to make the second dominant wavelength longer by 10.6 nm. On the other hand, in the second embodiment, x2 is set so as to make the second dominant wavelength longer by 11.0 nm. As is clear from this, x2 is greater than x1. That is, x2 > x1 > 1. As with x1, it is desirable to experimentally determine the value of x2. This also applies to x3 and the like described in each of the following embodiments.

[0186] Graph 2603 shows the change in the second dominant wavelength of the second light-emitting element G2 after the dominant wavelength adjustment. Graph 2603 corresponds to the portion of graph 2202 for the second light-emitting element G2 shown in FIG. 22 where the duty ratio is 0% to 90%. In graph 2603, this portion of graph 2202 is applied to the third range RG3. Because the second light-emitting element G2 is in a non-emitting state in the fourth range RG4, graph 2603 exists only within the third range RG3. Graph 2603 is a graph obtained by shifting graph 2602, which shows the characteristics of the second light-emitting element G2 before the dominant wavelength adjustment, by 11.0 nm upward in the plane of the drawing. In the following description, the second dominant wavelength of the second light-emitting element G2 after the dominant wavelength adjustment is also referred to as the "adjusted second dominant wavelength."

[0187] 26, at the second gradation ratio TV2, the adjusted second dominant wavelength does not match the first dominant wavelength. However, as will be described below, in the second embodiment, the misalignment between the first dominant wavelength and the second dominant wavelength at the second gradation ratio TV2 does not pose a problem.

[0188] 27 illustrates the characteristics of the combined light of the first light and the second light (specifically, the second light after the dominant wavelength has been adjusted) in embodiment 2. As described above, at the second grayscale ratio TV2, the first dominant wavelength and the second dominant wavelength do not match. However, according to FIG. 27, at the second grayscale ratio TV2, the combined dominant wavelength is continuous with respect to changes in the grayscale ratio.

[0189] 23 , the luminance of the second light continuously increases from 0 in the third range RG3. Because the luminance of the second light at the second gradation ratio TV2 is 0, the influence of the second light on the dominant wavelength of the combined light at the second gradation ratio TV2 is also 0. The influence of the second light on the dominant wavelength of the combined light gradually increases as the gradation ratio increases in the third range RG3.

[0190] In this way, by controlling the light-emitting element according to the second embodiment, even if there is a deviation between the first dominant wavelength and the adjusted second dominant wavelength at the second gradation ratio TV2, the synthetic dominant wavelength can be smoothly changed. Therefore, a continuous synthetic dominant wavelength can be obtained without the need for adjustment to precisely match the adjusted second dominant wavelength with the first dominant wavelength.

[0191] Rather, in the second embodiment, in order to reduce the amount of change in the synthetic dominant wavelength, the adjusted second dominant wavelength at the second gradation ratio TV2 may be intentionally shifted from the first dominant wavelength.

[0192] In the example of Fig. 27, as in the example of Fig. 18, the maximum value of the synthetic dominant wavelength is 536.5 nm at the 0% gradation ratio point, and the minimum value of the synthetic dominant wavelength is 532.2 nm at the second gradation ratio TV2. Therefore, the amount of change in the synthetic dominant wavelength in the example of Fig. 27 is also given as 536.5 nm - 532.2 nm = 4.3 nm.

[0193] Also, graph 2201 in Fig. 22 is equivalent to graph 501 in Fig. 5. Therefore, the first dominant wavelength change amount in the example of Fig. 22 is given as 536.5 nm - 525.4 nm = 11.1 nm.

[0194] Therefore, also in the second embodiment, the amount of change in the synthetic dominant wavelength is smaller than at least one of the first amount of change in the dominant wavelength and the second amount of change in the dominant wavelength. Also in the example of the second embodiment, the amount of change in the synthetic dominant wavelength is smaller than the first amount of change in the dominant wavelength.

[0195] Additionally, in the second embodiment, the synthetic dominant wavelength can be continuously changed without strictly adjusting the first dominant wavelength and the second dominant wavelength at the second gradation ratio TV. This allows for more tolerance for variations among light-emitting elements than in the first embodiment, thereby making it possible to relax the manufacturing conditions for the light-emitting elements. This reduces the manufacturing cost of the light-emitting elements. Furthermore, for example, since the process of generating control data in the control unit 10 does not require detailed tuning of the conditions for each light-emitting element, the process in the control unit 10 can be simplified.

[0196] In the example of Fig. 27, when the gradation ratio is between 10% and 15%, the synthetic dominant wavelength increases as the gradation ratio increases. On the other hand, when the gradation ratio is between 15% and 20%, the synthetic dominant wavelength decreases as the gradation ratio increases. Next, when the gradation ratio is 20% or more, the synthetic dominant wavelength increases again as the gradation ratio increases.

[0197] As described above, in the example of Fig. 27, at a gradation ratio of 10% to 20%, both an increase and a decrease in the synthetic dominant wavelength occur as the gradation ratio increases. This is because, as shown in graph 2603 of Fig. 26, at a gradation ratio of 10% to 20%, the adjusted second dominant wavelength decreases as the gradation ratio increases. This characteristic of the adjusted second dominant wavelength affects the synthetic dominant wavelength, resulting in the characteristics of the synthetic dominant wavelength at a gradation ratio of 10% to 20% in Fig. 27.

[0198] (Supplementary Note Regarding the Control Unit 10 in the Second Embodiment) In the second embodiment, a lookup table may be prepared in advance, which represents the relationship between the gradation ratio of the G component of the gradation data of the input pixel and the control data (e.g., current ratio) of the first light-emitting element G1, as shown in the graph 2301 of Fig. 23. In this case, the first control data generation unit 11 can use the lookup table to set the control data of the first light-emitting element G1 that corresponds to the gradation ratio of the G component of the gradation data.

[0199] In the second embodiment, a lookup table may be prepared in advance, which represents the relationship between the gradation ratio of the G component of the gradation data of the input pixel and the control data (e.g., duty ratio) of the second light-emitting element G2, as shown in the graph 2302 of Fig. 23. In this case, the second control data generator 12 can use the lookup table to set the control data of the second light-emitting element G2 that corresponds to the gradation ratio of the G component of the gradation data.

[0200] [Embodiment 3] As shown in Fig. 23, in the above-described embodiment 2, a case was exemplified in which the luminance ratio of the first light is maintained constant and only the luminance ratio of the second light is increased as the gradation ratio increases in the third range RG3. In embodiment 3, an example of light emission control is shown in which the luminance ratios of both the first light and the second light are increased as the gradation ratio increases in the third range RG3.

[0201] (Example of characteristics of first light-emitting element G1 and second light-emitting element G2 in embodiment 3) Fig. 28 illustrates the characteristics of the first light-emitting element G1 and the second light-emitting element G2 in embodiment 3. In Fig. 28, a graph 2801 shows the characteristics of the first light-emitting element G1, and a graph 2802 shows the characteristics of the second light-emitting element G2.

[0202] In the third embodiment, the area of ​​the second light-emitting element G2 is adjusted so that the second dominant wavelength is longer by 14.0 nm. Therefore, the graph 2802 in Fig. 28 is a graph obtained by shifting the graph 102 in Fig. 1 upward by 14.0 nm. As shown in Fig. 28, the first light-emitting element G1 and the second light-emitting element G2 have different dominant wavelength characteristics.

[0203] (Example of control of first light-emitting element G1 and second light-emitting element G2 in embodiment 3) Figure 29 shows an example of control of the first light-emitting element G1 and the second light-emitting element G2 in embodiment 3. In the example of Figure 29, the first light-emitting element G1 is a CC light-emitting element, and the second light-emitting element G2 is a PWM light-emitting element. In Figure 29, graph 2901 shows control data for the first light-emitting element G1, and graph 2902 shows control data for the second light-emitting element G2. Graphs 2901 and 2902 are examples of first control data and second control data, respectively, in embodiment 3. In embodiment 3 as well, an example is shown in which the second gradation ratio TV2 is set to 10%.

[0204] As shown in graph 2901, in the fourth range RG4, the current ratio of the first light-emitting element G1 increases as the gradation ratio increases. In the third range RG3, the current ratio of the first light-emitting element G1 increases to a current ratio of 51% at a gradation ratio of 100%. Thus, the increasing trend of the current ratio of the first light-emitting element G1 in the third range RG3 differs from the increasing trend of the current ratio of the first light-emitting element G1 in the fourth range RG4. The current ratio of 51% in FIG. 29 is an example, and the current ratio at a gradation ratio of 100% is not limited to this value.

[0205] On the other hand, as shown in graph 2902, in the fourth range RG4, the duty ratio of the second light-emitting element G2 is set to 0%. Therefore, in the fourth range RG4, the second light-emitting element G2 is in a non-light-emitting state. In the third range RG3, the duty ratio of the second light-emitting element G2 continuously increases from 0% as the gradation ratio increases. Specifically, in the example of FIG. 29 , as the gradation ratio increases from 10% to 100%, the duty ratio of the second light-emitting element G2 continuously increases from 0% to 49%. The duty ratio of 49% in FIG. 29 is just an example, and the duty ratio at a gradation ratio of 100% is not limited to this value.

[0206] In this way, in the third embodiment, both the first light-emitting element G1 and the second light-emitting element G2 are caused to emit light in the third range RG3, as in the second embodiment. In the fourth range RG4, only the first light-emitting element G1 is caused to emit light, as in the second embodiment.

[0207] 29 , the control unit 10 in the third embodiment continuously controls the luminance of the first light-emitting element G1 and the luminance of the second light-emitting element G2 in response to changes in the gradation ratio within the gradation ratio change range RG (more specifically, within the fourth range RG4 and the third range RG3). In particular, the control unit 10 continuously controls the luminance of the first light-emitting element G1 and the luminance of the second light-emitting element G2 at the second gradation ratio TV2.

[0208] In the example of graph 2901, as the grayscale ratio increases from the second grayscale ratio TV2, the luminance ratio of the second light-emitting element G2 increases continuously from 0%. As shown in graphs 2901 and 2902, in the third range RG3, the luminance of both the first light-emitting element G1 and the second light-emitting element G2 increases continuously as the grayscale ratio increases.

[0209] The relationship between the gradation ratio and the luminance ratio of the combined light in the third embodiment is similar to the example in Fig. 24 in the second embodiment, and therefore will not be illustrated using a new graph. In the third embodiment as well, by using both the first light-emitting element G1 and the second light-emitting element G2, it is possible to continuously increase the luminance ratio of the combined light as the gradation ratio increases over the entire gradation ratio change range RG.

[0210] Fig. 30 illustrates the contribution rate in embodiment 3. In Fig. 30, a graph 3001 shows the first contribution rate, and a graph 3102 shows the second contribution rate. Graphs 3001 to 3002 in Fig. 30 are obtained based on graphs 2901 to 2902 in Fig. 29.

[0211] 30, in the fourth range RG4, the first contribution rate is 100% and the second contribution rate is 0%. That is, in the fourth range RG4, only the first light-emitting element G1 emits light, and the second light-emitting element G2 is in a non-light-emitting state.

[0212] In the third range RG3, the first contribution rate continuously decreases from 100% as the gradation ratio increases. At a gradation ratio of 100%, the first contribution rate reaches a minimum of 51%. On the other hand, in the third range RG3, the second contribution rate continuously increases from 0% as the gradation ratio increases. At a gradation ratio of 100%, the second contribution rate reaches a maximum of 49%. In this way, in the third range RG3, both the first light-emitting element G1 and the second light-emitting element G2 are made to emit light.

[0213] Fig. 31 illustrates the change in dominant wavelength of the first light-emitting element G1 and the second light-emitting element G2 with respect to the change in gradation ratio when the first light-emitting element G1 and the second light-emitting element G2 having the characteristics shown in Fig. 28 are driven by the control data shown in Fig. 29. In other words, Fig. 31 illustrates the change in dominant wavelength of the first light-emitting element G1 and the second light-emitting element G2 with respect to the change in gradation ratio when the first light-emitting element G1 and the second light-emitting element G2 are driven according to the contribution ratio shown in Fig. 30. Graph 3101 in Fig. 31 illustrates the change in the first dominant wavelength of the first light-emitting element G1, and graph 3102 illustrates the change in the second dominant wavelength of the second light-emitting element G2. Specifically, graph 3102 illustrates the change in the second dominant wavelength of the second light-emitting element G2 after the dominant wavelength has been adjusted.

[0214] The portion of graph 3101 that belongs to the fourth range RG4 corresponds to the portion of graph 2801 in Fig. 28 where the current ratio is 0% to 10%. The portion of graph 3101 that belongs to the third range RG3 corresponds to the portion of graph 2801 in Fig. 28 where the current ratio is 10% to 51%. Specifically, the portion of graph 2801 with a current ratio of 10% to 51% is enlarged horizontally by 2.2 times and applied to the portion of graph 3101 that belongs to the third range RG3. The horizontal enlargement factor of 2.2 times is determined as (100-10) / (51-10) ≈ 2.2.

[0215] Graph 3102 corresponds to the portion of graph 2802 in FIG. 28 where the duty ratio is 0% to 49%. Specifically, the portion of graph 2802 where the duty ratio is 0% to 49% is magnified horizontally by 1.8 times and applied to the portion of graph 3102 that belongs to the third range RG3. The horizontal magnification of 1.8 times is determined as (100-10) / (49-0) ≈ 1.8. In the fourth range RG4, the second light-emitting element G2 is in a non-emitting state, and therefore graph 3102 exists only within the third range RG3.

[0216] As described above, in the third embodiment, the area of ​​the second light-emitting element G2 is adjusted so as to lengthen the second dominant wavelength by 14.0 nm. Specifically, in the third embodiment, the ratio between the area of ​​the first light-emitting element G1 and the area of ​​the second light-emitting element G2 is adjusted to 1:x3.

[0217] In the above-described second embodiment, x2 is set so as to make the second dominant wavelength longer by 11.0 nm. On the other hand, in the third embodiment, x3 is set so as to make the second dominant wavelength longer by 14.0 nm. As is clear from this, x3 is larger than x2. That is, x3 > x2 > x1 > 1.

[0218] In the third embodiment as well, the adjusted second dominant wavelength at the second gradation ratio TV2 does not match the first dominant wavelength at the second gradation ratio TV2. However, in the third embodiment as well, a deviation between the first dominant wavelength and the second dominant wavelength at the second gradation ratio TV2 does not pose a problem.

[0219] 32 illustrates the characteristics of the combined light of the first light and the second light (specifically, the second light after the dominant wavelength has been adjusted) in embodiment 3. According to Fig. 32, at the second gradation ratio TV2, the combined dominant wavelength is continuous with respect to changes in the gradation ratio. This is because, in embodiment 3 as well, the luminance of the second light increases continuously from 0 as the gradation ratio increases in the third range RG3.

[0220] In the example of Fig. 32, similarly to the example of Fig. 18, the maximum value of the synthetic dominant wavelength is 536.5 nm at the 0% gradation ratio point, and the minimum value of the synthetic dominant wavelength is 532.2 nm at the second gradation ratio TV2. Therefore, the amount of change in the synthetic dominant wavelength in the example of Fig. 32 is also given as 536.5 nm - 532.2 nm = 4.3 nm.

[0221] Also, graph 2801 in Fig. 28 is equivalent to graph 501 in Fig. 5. Therefore, the first dominant wavelength change amount in the example of Fig. 28 is also given as 536.5 nm - 525.4 nm = 11.1 nm.

[0222] Therefore, also in the third embodiment, the amount of change in the synthetic dominant wavelength is smaller than at least one of the first amount of change in the dominant wavelength and the second amount of change in the dominant wavelength. Also in the example of the third embodiment, the amount of change in the synthetic dominant wavelength is smaller than the first amount of change in the dominant wavelength.

[0223] 32, in the third range RG3, the maximum value of the synthetic dominant wavelength is 532.7 nm and the minimum value of the synthetic dominant wavelength is 532.2 nm. Therefore, in the third embodiment, the amount of change in the synthetic dominant wavelength in the third range RG3 is given as 532.7 nm - 532.2 nm = 0.5 nm.

[0224] 27, in the second embodiment, the maximum value of the synthetic dominant wavelength in the third range RG3 is 535.6 nm, unlike in the third embodiment. Therefore, in the second embodiment, the amount of change in the synthetic dominant wavelength in the third range RG3 is given as 535.6 nm - 532.2 nm = 3.4 nm.

[0225] Thus, according to the third embodiment, the amount of change in the synthetic dominant wavelength in a part of the gradation ratio change range RG can be made smaller than that in the second embodiment. In the example of the third embodiment, the amount of change in the synthetic dominant wavelength in the third range RG3 is smaller than that in the second embodiment.

[0226] (Supplementary Note Regarding the Control Unit 10 in the Third Embodiment) In the third embodiment, a lookup table may be prepared in advance, which represents the relationship between the gradation ratio of the G component of the gradation data of the input pixel and the control data (e.g., current ratio) of the first light-emitting element G1, as shown in the graph 2901 of Fig. 29. In this case, the first control data generation unit 11 can use the lookup table to set the control data of the first light-emitting element G1 that corresponds to the gradation ratio of the G component of the gradation data.

[0227] In addition, in the third embodiment, a lookup table may be prepared in advance, which represents the relationship between the gradation ratio of the G component of the gradation data of the input pixel and the control data (e.g., duty ratio) of the second light-emitting element G2, as shown in the graph 2902 of Fig. 29. In this case, the second control data generation unit 12 can use the lookup table to set the control data of the second light-emitting element G2 that corresponds to the gradation ratio of the G component of the gradation data.

[0228] [Embodiment 4] In the above-described embodiments 2 and 3, the first light-emitting element G1 and the second light-emitting element G2 are caused to emit light in the third range RG3, and only one of the first light-emitting element G1 or the second light-emitting element G2 is caused to emit light in the fourth range RG4.

[0229] Unlike Embodiments 2 and 3, Embodiment 4 does not have a fourth range RG4. Instead, Embodiment 4 has a fifth range RG5 that is adjacent to the third range RG3 on the high gradation ratio side of the third range RG3. In Embodiment 4, only one of the first light-emitting element G1 or the second light-emitting element G2 emits light in the fifth range RG5.

[0230] (Example of characteristics of first light-emitting element G1 and second light-emitting element G2 in embodiment 4) Fig. 33 illustrates the characteristics of the first light-emitting element G1 and the second light-emitting element G2 in embodiment 4. In Fig. 33, a graph 3301 shows the characteristics of the first light-emitting element G1, and a graph 3302 shows the characteristics of the second light-emitting element G2.

[0231] In the fourth embodiment, the area of ​​the second light-emitting element G2 is adjusted so that the second dominant wavelength is longer by 10.8 nm. Therefore, the graph 3302 in Fig. 33 is a graph obtained by shifting the graph 102 in Fig. 1 upward by 10.8 nm. As shown in Fig. 33, the first light-emitting element G1 and the second light-emitting element G2 have different dominant wavelength characteristics.

[0232] (Example of control of first light-emitting element G1 and second light-emitting element G2 in embodiment 4) Figure 34 shows an example of control of the first light-emitting element G1 and the second light-emitting element G2 in embodiment 4. In the example of Figure 34, the first light-emitting element G1 is a CC light-emitting element, and the second light-emitting element G2 is a PWM light-emitting element. In Figure 34, graph 3401 shows control data for the first light-emitting element G1, and graph 3402 shows control data for the second light-emitting element G2. Graphs 3401 and 3402 are examples of first control data and second control data, respectively, in embodiment 4.

[0233] 34 , in the fourth embodiment, the range of the gradation ratio change range RG that is adjacent to the third range RG3 on the high gradation ratio side of the third range RG3 and in which only the second light-emitting element G2 should emit light is referred to as the fifth range RG5. The gradation ratio at the boundary between the third range RG3 and the fifth range RG5 is referred to as the third gradation ratio TV3. In the fourth embodiment, the third gradation ratio TV3 is set to 90%.

[0234] As shown in graph 3401, in the range of 0% to 45% gradation ratio, the current ratio of the first light-emitting element G1 increases as the gradation ratio increases. At a gradation ratio of 45%, the current ratio of the first light-emitting element G1 reaches a maximum value of 20.25%. On the other hand, in the range of 45% to 90% gradation ratio, the current ratio of the first light-emitting element G1 decreases as the gradation ratio increases. At a gradation ratio of 90% (i.e., at the third gradation ratio TV3), the current ratio of the first light-emitting element G1 reaches a minimum value of 0%. For this reason, graph 3401 depicts an upwardly convex curve in the third range RG3. Furthermore, the current ratio of the first light-emitting element G1 in the fourth range RG4 is set to 0%.

[0235] As shown in graph 3402, the duty ratio of the second light-emitting element G2 in the third range RG3 increases as the gradation ratio increases. Specifically, the duty ratio of the second light-emitting element G2 in the third range RG3 increases so that the rate of change of the duty ratio increases as the gradation ratio increases. Therefore, graph 3402 depicts a downwardly convex curve in the third range RG3. As such, the duty ratio of the second light-emitting element G2 increases nonlinearly in the third range RG3. On the other hand, the duty ratio of the second light-emitting element G2 in the fourth range RG4 increases linearly as the gradation ratio increases. Specifically, the duty ratio of the second light-emitting element G2 in the fourth range RG4 increases linearly from 90% to 100%.

[0236] As described above, in the fourth embodiment, both the first light-emitting element G1 and the second light-emitting element G2 are caused to emit light in the third range RG3, as in the second and third embodiments. However, in the fourth embodiment, only the second light-emitting element G2 is caused to emit light in the fifth range RG5.

[0237] 34 , the control unit 10 in the fourth embodiment continuously controls the luminance of the first light-emitting element G1 and the luminance of the second light-emitting element G2 in response to changes in the gradation ratio within the gradation ratio change range RG (more specifically, within the third range RG3 and the fifth range RG5). In particular, the control unit 10 continuously controls the luminance of the first light-emitting element G1 and the luminance of the second light-emitting element G2 within the third gradation ratio TV3.

[0238] In the example of graph 3401, as the grayscale ratio decreases from the third grayscale ratio TV3, the luminance ratio of the first light-emitting element G1 changes continuously from 0%. On the other hand, in the example of graph 3402, as the grayscale ratio increases from the third grayscale ratio TV3, the luminance ratio of the second light-emitting element G2 changes continuously from 90%.

[0239] The relationship between the gradation ratio and the luminance ratio of the combined light in the fourth embodiment is similar to the example in Fig. 24 in the second embodiment, and therefore will not be illustrated using a new graph. In the fourth embodiment as well, by using both the first light-emitting element G1 and the second light-emitting element G2, it is possible to continuously increase the luminance ratio of the combined light as the gradation ratio increases over the entire gradation ratio change range RG.

[0240] Fig. 35 illustrates the contribution rate in embodiment 4. In Fig. 35, a graph 3501 shows the first contribution rate, and a graph 3502 shows the second contribution rate. Graphs 3501 to 3502 in Fig. 35 are obtained based on graphs 3401 to 3402 in Fig. 34.

[0241] According to graph 3501, the first contribution rate is 90% at a gradation ratio of 0%. In the third range RG3, the first contribution rate decreases as the gradation ratio increases. Then, at a gradation ratio of 90% (i.e., at the third gradation ratio TV3), the first contribution rate reaches its minimum value of 0%. In the fifth range RG5, the first contribution rate is 0%.

[0242] On the other hand, according to graph 3502, the second contribution rate is 10% at a gradation ratio of 0%. In the third range RG3, the second contribution rate increases as the gradation ratio increases. Then, at the third gradation ratio TV3, the second contribution rate reaches a maximum value of 100%. In the fifth range RG5, the second contribution rate is 100%.

[0243] As described above, in the fourth embodiment, both the first light-emitting element G1 and the second light-emitting element G2 are made to emit light in the third range RG3, whereas only the second light-emitting element G2 is made to emit light in the fifth range RG5.

[0244] Fig. 36 illustrates the change in dominant wavelength of the first light-emitting element G1 and the second light-emitting element G2 with respect to the change in gradation ratio when the first light-emitting element G1 and the second light-emitting element G2 having the characteristics shown in Fig. 33 are driven by the control data shown in Fig. 34. In other words, Fig. 36 illustrates the change in dominant wavelength of the first light-emitting element G1 and the second light-emitting element G2 with respect to the change in gradation ratio when the first light-emitting element G1 and the second light-emitting element G2 are driven according to the contribution ratio shown in Fig. 35. Graph 3601 in Fig. 36 shows the change in the first dominant wavelength of the first light-emitting element G1, and graph 3602 shows the change in the second dominant wavelength of the second light-emitting element G2. Specifically, graph 3602 shows the change in the second dominant wavelength of the second light-emitting element G2 after the dominant wavelength has been adjusted.

[0245] The portion of graph 3601 that falls within the third range RG3 corresponds to the portion of graph 3301 in Fig. 33 where the current ratio is between 0% and 20.25%. As described above, the current ratio shown in graph 3401 in Fig. 34 forms an upwardly convex curve within the third range RG3. The first dominant wavelength shown in graph 3601 shows a change trend that corresponds to this curve.

[0246] Specifically, in the third range RG3, the first dominant wavelength gradually decreases from a maximum value of 536.5 nm to a minimum value of 530.0 nm as the gradation ratio increases. Then, in the third range RG3, the first dominant wavelength begins to increase again from the minimum value as the gradation ratio increases. The first dominant wavelength again reaches a maximum value of 536.5 nm at a gradation ratio of 90% (i.e., at the third gradation ratio TV3). In the fifth range RG5, the first light-emitting element G1 is in a non-emitting state, and therefore the graph 3601 exists only within the third range RG3.

[0247] The portion of graph 3602 that falls within the third range RG3 corresponds to the portion of graph 3302 in FIG. 33 where the duty ratio is 0% to 90%. Note that this correspondence is neither a linear relationship nor a relationship resulting from a simple horizontal scale conversion. As described above, the duty ratio shown in graph 3402 in FIG. 34 forms a downwardly convex curve within the third range RG3. The second dominant wavelength shown in graph 3602 shows a change trend that corresponds to this curve.

[0248] The portion of the graph 3602 that belongs to the fifth range RG5 corresponds to the portion of the graph 3302 in Fig. 33 where the duty ratio is 90% to 100%. This correspondence is a linear relationship.

[0249] As described above, in the fourth embodiment, the area of ​​the second light-emitting element G2 is adjusted so as to lengthen the second dominant wavelength by 10.8 nm. Specifically, in the fourth embodiment, the ratio between the area of ​​the first light-emitting element G1 and the area of ​​the second light-emitting element G2 is adjusted to 1:x4, where x4 is a number greater than 1.

[0250] In the fourth embodiment, the adjusted second dominant wavelength at the third gradation ratio TV3 does not match the first dominant wavelength at the third gradation ratio TV3. However, as is clear from the explanations in the second and third embodiments, in the fourth embodiment, a deviation between the first dominant wavelength and the second dominant wavelength at the third gradation ratio TV3 does not pose a problem.

[0251] 36, the first dominant wavelength and the second dominant wavelength coincide with each other at a gradation ratio of 6.3% and a gradation ratio of 88.1. When the first dominant wavelength and the second dominant wavelength coincide with each other at a certain gradation ratio within the third range RG3, the first dominant wavelength and the second dominant wavelength within the third range RG3 are expected to be approximately equal. This provides the advantage of increasing the color purity of the combined light. This also applies to the following embodiments.

[0252] Fig. 37 illustrates the characteristics of the combined light of the first light and the second light (specifically, the second light after the dominant wavelength has been adjusted) in embodiment 4. According to Fig. 37, at the third gradation ratio TV3, the combined dominant wavelength is continuous with respect to changes in the gradation ratio.

[0253] In the example of Fig. 37, the maximum value of the synthetic dominant wavelength is 536.3 nm at the gradation ratio 0% point, and the minimum value of the synthetic dominant wavelength is 531.3 nm at the gradation ratio around 30% point. Therefore, the amount of change in the synthetic dominant wavelength in the example of Fig. 37 is given as 536.3 nm - 531.3 nm = 5.0 nm.

[0254] Also, graph 3301 in Fig. 33 is equivalent to graph 501 in Fig. 5. Therefore, the first dominant wavelength change amount in the example of Fig. 33 is also given as 536.5 nm - 525.4 nm = 11.1 nm.

[0255] Therefore, also in the fourth embodiment, the amount of change in the synthetic dominant wavelength is smaller than at least one of the first amount of change in the dominant wavelength and the second amount of change in the dominant wavelength. Also in the example of the fourth embodiment, the amount of change in the synthetic dominant wavelength is smaller than the first amount of change in the dominant wavelength.

[0256] (Supplementary Note on Processing by the Control Unit 10 in the Fourth Embodiment) In the fourth embodiment, a lookup table may be prepared in advance, which represents the relationship between the gradation ratio of the G component of the gradation data of the input pixel and the control data (e.g., current ratio) of the first light-emitting element G1, as shown in the graph 3401 of Fig. 34. In this case, the first control data generation unit 11 can use the lookup table to set the control data of the first light-emitting element G1 that corresponds to the gradation ratio of the G component of the gradation data.

[0257] In addition, in the fourth embodiment, a lookup table may be prepared in advance, which represents the relationship between the gradation ratio of the G component of the gradation data of the input pixel and the control data (e.g., duty ratio) of the second light-emitting element G2, as shown in graph 3402 of Fig. 34. In this case, the second control data generation unit 12 can use the lookup table to set the control data of the second light-emitting element G2 that corresponds to the gradation ratio of the G component of the gradation data.

[0258] [Embodiment 5] Embodiment 5 is an embodiment that combines embodiment 2 or embodiment 3 with embodiment 4. The gradation ratio change range RG in embodiment 5 includes a third range RG3, a fourth range RG4, and a fifth range RG5.

[0259] In embodiment 5, both the first light-emitting element G1 and the second light-emitting element G2 are caused to emit light in the third range RG3. Then, in the fourth range RG4, which is adjacent to the third range RG3 on the low gradation ratio side of the third range RG3, one of the first light-emitting element G1 or the second light-emitting element G2 is caused to emit light. Furthermore, in the fifth range RG5, which is adjacent to the third range RG3 on the high gradation ratio side of the third range RG3, the other of the first light-emitting element G1 or the second light-emitting element G2 is caused to emit light. As an example, in the fourth range RG4, only the first light-emitting element G1 is caused to emit light, and in the fifth range RG5, only the second light-emitting element G2 is caused to emit light.

[0260] (Example of characteristics of first light-emitting element G1 and second light-emitting element G2 in embodiment 5) Fig. 38 illustrates the characteristics of the first light-emitting element G1 and the second light-emitting element G2 in embodiment 5. In Fig. 38, a graph 3801 shows the characteristics of the first light-emitting element G1, and a graph 3802 shows the characteristics of the second light-emitting element G2.

[0261] In the fifth embodiment, the area of ​​the second light-emitting element G2 is adjusted so that the second dominant wavelength is longer by 10.5 nm. Therefore, the graph 3802 in Fig. 38 is a graph obtained by shifting the graph 102 in Fig. 1 upward by 10.5 nm. As shown in Fig. 38, the first light-emitting element G1 and the second light-emitting element G2 have different dominant wavelength characteristics.

[0262] (Example of control of first light-emitting element G1 and second light-emitting element G2 in embodiment 5) Figure 39 shows an example of control of the first light-emitting element G1 and the second light-emitting element G2 in embodiment 5. In the example of Figure 39, the first light-emitting element G1 is a CC light-emitting element, and the second light-emitting element G2 is a PWM light-emitting element. In Figure 39, graph 3901 shows control data for the first light-emitting element G1, and graph 3902 shows control data for the second light-emitting element G2. Graphs 3901 and 3902 are examples of first control data and second control data, respectively, in embodiment 5.

[0263] 39, in the fifth embodiment, both the second gradation ratio TV2 and the third gradation ratio TV3 are set. Therefore, the gradation ratio change range RG is divided into a third range RG3, a fourth range RG4, and a fifth range RG5. In the fifth embodiment, the second gradation ratio TV2 is set to 10%, and the third gradation ratio TV3 is set to 20%.

[0264] As shown in graph 3901, in the fourth range RG4, the current ratio of the first light-emitting element G1 increases from 0% to 10% as the gradation ratio increases. In the third range RG3, the current ratio of the first light-emitting element G1 decreases from 10% to 0% as the gradation ratio increases. In the fifth range RG5, the current ratio of the first light-emitting element G1 is set to 0%. In this way, the current ratio of the first light-emitting element G1 changes continuously with the gradation ratio in the gradation ratio change range RG.

[0265] On the other hand, as shown in graph 3902, in the fourth range RG4, the duty ratio of the first light-emitting element G1 is set to 0%. Then, in the third range RG3, the duty ratio of the second light-emitting element G2 increases from 0% to 20% as the gradation ratio increases. Then, in the fifth range RG5, the duty ratio of the second light-emitting element G2 increases from 20% to 100% as the gradation ratio increases. In this way, the duty ratio of the second light-emitting element G2 also changes continuously with respect to the gradation ratio in the gradation ratio change range RG.

[0266] As described above, in the fifth embodiment, only the first light-emitting element G1 is illuminated in the fourth range RG4, both the first light-emitting element G1 and the second light-emitting element G2 are illuminated in the third range RG3, and only the second light-emitting element G2 is illuminated in the fifth range RG5.

[0267] 39 , the control unit 10 in embodiment 5 continuously controls the luminance of the first light-emitting element G1 and the luminance of the second light-emitting element G2 in response to changes in the gradation ratio within the gradation ratio change range RG (more specifically, within the fourth range RG4, the third range RG3, and the fifth range RG5). In particular, the control unit 10 continuously controls the luminance of the first light-emitting element G1 and the luminance of the second light-emitting element G2 around the second gradation ratio TV2 and around the third gradation ratio TV3.

[0268] In the example of graph 3901, as the grayscale ratio increases from the second grayscale ratio TV2, the luminance ratio of the second light-emitting element G2 changes continuously from 0%. On the other hand, in the example of graph 3901, as the grayscale ratio decreases from the third grayscale ratio TV3, the luminance ratio of the second light-emitting element G2 changes continuously from 0%.

[0269] The relationship between the gradation ratio and the luminance ratio of the combined light in embodiment 5 is similar to the example in Fig. 24 in embodiment 2, and therefore will not be illustrated using a new graph. In embodiment 5 as well, by using both the first light-emitting element G1 and the second light-emitting element G2, it is possible to continuously increase the luminance ratio of the combined light as the gradation ratio increases over the entire gradation ratio change range RG.

[0270] Fig. 40 illustrates the contribution rate in embodiment 5. In Fig. 40, a graph 4001 shows the first contribution rate, and a graph 4002 shows the second contribution rate. Graphs 4001 to 4002 in Fig. 40 are obtained based on graphs 3901 to 3902 in Fig. 39.

[0271] According to the graph 4001, the first contribution rate in the fourth range RG4 is 100%. In the third range RG3, the first contribution rate decreases as the gradation ratio increases. At a gradation ratio of 20% (i.e., at the third gradation ratio TV3), the first contribution rate reaches a minimum of 0%. In the fifth range RG5, the first contribution rate is 0%.

[0272] On the other hand, according to graph 4002, the second contribution rate in the fourth range RG4 is 0%. In the third range RG3, the second contribution rate increases as the gradation ratio increases. At a gradation ratio of 20%, the second contribution rate reaches a maximum value of 100%. In the fifth range RG5, the second contribution rate is 100%.

[0273] As described above, in the fifth embodiment, only the first light-emitting element G1 is lit in the fourth range RG4, both the first light-emitting element G1 and the second light-emitting element G2 are lit in the third range RG3, and only the second light-emitting element G2 is lit in the fifth range RG5.

[0274] Fig. 41 illustrates the change in dominant wavelength of the first light-emitting element G1 and the second light-emitting element G2 with respect to the change in gradation ratio when the first light-emitting element G1 and the second light-emitting element G2 having the characteristics shown in Fig. 38 are driven by the control data shown in Fig. 39. In other words, Fig. 41 illustrates the change in dominant wavelength of the first light-emitting element G1 and the second light-emitting element G2 with respect to the change in gradation ratio when the first light-emitting element G1 and the second light-emitting element G2 are driven according to the contribution ratio shown in Fig. 40. Graph 4101 in Fig. 41 illustrates the change in the first dominant wavelength of the first light-emitting element G1, and graph 4102 illustrates the change in the second dominant wavelength of the second light-emitting element G2. Specifically, graph 4102 illustrates the change in the second dominant wavelength of the second light-emitting element G2 after the dominant wavelength has been adjusted.

[0275] The portion of graph 4101 that belongs to the fourth range RG4 corresponds to the portion of graph 3801 in Fig. 38 where the current ratio is 0% to 10%. The portion of graph 4101 that belongs to the third range RG3 also corresponds to the portion of graph 3801 where the current ratio is 0% to 10%.

[0276] 39 , the portion of graph 4101 belonging to the third range RG3 and the portion belonging to the fourth range RG4 are linearly symmetrical with respect to the second gradation ratio TV2. Therefore, in the fourth range RG4, the first dominant wavelength decreases as the gradation ratio increases, while in the third range RG3, the first dominant wavelength increases as the gradation ratio increases. In the fifth range RG5, the first light-emitting element G1 is in a non-emitting state, and therefore graph 4101 exists only within the fourth range RG4 and the third range RG3.

[0277] The portion of graph 4102 that belongs to the third range RG3 corresponds to the portion of graph 3802 in Fig. 38 where the duty ratio is 0% to 20%. Specifically, the portion of graph 3802 where the duty ratio is 0% to 20% is reduced horizontally by half, and is applied to the portion of graph 4102 that belongs to the third range RG3.

[0278] The portion of the graph 4102 that belongs to the fifth range RG5 corresponds to the portion of the graph 3802 that has a duty ratio of 20% to 100%. In the fourth range RG4, the second light-emitting element G2 is in a non-emitting state, and therefore the graph 4102 exists only within the third range RG3 and the fifth range RG5.

[0279] As described above, in the fifth embodiment, the area of ​​the second light-emitting element G2 is adjusted so as to lengthen the second dominant wavelength by 10.5 nm. Specifically, in the fifth embodiment, the ratio between the area of ​​the first light-emitting element G1 and the area of ​​the second light-emitting element G2 is adjusted to 1:x5, where x5 is a number greater than 1.

[0280] In the fifth embodiment, at the second gradation ratio TV2, the adjusted second dominant wavelength does not match the first dominant wavelength. Similarly, at the third gradation ratio TV3, the adjusted second dominant wavelength does not match the first dominant wavelength. However, even in the fifth embodiment, a discrepancy between the first dominant wavelength and the second dominant wavelength at the second gradation ratio TV2 and the third gradation ratio TV3 does not pose a problem. Meanwhile, according to FIG. 41, the first dominant wavelength and the second dominant wavelength match at a gradation ratio of 12.3%.

[0281] Fig. 42 illustrates the characteristics of the combined light of the first light and the second light (specifically, the second light after the dominant wavelength has been adjusted) in embodiment 5. According to Fig. 42, at the second gradation ratio TV2 and the third gradation ratio TV3, the combined dominant wavelength is continuous with respect to changes in the gradation ratio.

[0282] In the example of Fig. 42, similarly to the example of Fig. 18, the maximum value of the synthetic dominant wavelength is 536.5 nm at the 0% gradation ratio point, and the minimum value of the synthetic dominant wavelength is 532.2 nm at the second gradation ratio TV2. Therefore, the amount of change in the synthetic dominant wavelength in the example of Fig. 42 is also given as 536.5 nm - 532.2 nm = 4.3 nm.

[0283] Also, graph 3801 in Fig. 38 is equivalent to graph 501 in Fig. 5. Therefore, the first dominant wavelength change amount in the example of Fig. 38 is also given as 536.5 nm - 525.4 nm = 11.1 nm.

[0284] Therefore, also in the fifth embodiment, the amount of change in the synthetic dominant wavelength is smaller than at least one of the first amount of change in the dominant wavelength and the second amount of change in the dominant wavelength. Also in the example of the fifth embodiment, the amount of change in the synthetic dominant wavelength is smaller than the first amount of change in the dominant wavelength.

[0285] Here, the fifth embodiment will be compared with the first embodiment. In the first embodiment, the first gradation ratio TV1 is used as a boundary point to switch between display using the first light-emitting element G1 and display using the second light-emitting element G2. Specifically, in the first embodiment, display using only the first light-emitting element G1 is performed in the first range RG1, and display using only the second light-emitting element G2 is performed in the second range RG2.

[0286] In the fifth embodiment, the fourth range RG4 is used for displaying only the first light-emitting element G1, and the fifth range RG5 is used for displaying only the second light-emitting element G2. However, in the fifth embodiment, a third range RG3 is provided as a transition section for gradually switching between the display using the first light-emitting element G1 and the display using the second light-emitting element G2. This allows the fifth embodiment to switch between the first light-emitting element G1 and the second light-emitting element G2 more smoothly than the first embodiment.

[0287] In the first embodiment, display is performed using only one light-emitting element. Therefore, in the first embodiment, it is necessary to match the first dominant wavelength and the second dominant wavelength at the first gradation ratio TV1. On the other hand, in the fifth embodiment, it is not necessary to match the first dominant wavelength and the second dominant wavelength at the second gradation ratio TV2 and the third gradation ratio TV3.

[0288] (Supplementary Note on Processing by the Control Unit 10 in the Fifth Embodiment) In the fifth embodiment, a lookup table may be prepared in advance, which represents the relationship between the gradation ratio of the G component of the gradation data of the input pixel and the control data (e.g., current ratio) of the first light-emitting element G1, as shown in the graph 3901 of Fig. 39. In this case, the first control data generation unit 11 can use the lookup table to set the control data of the first light-emitting element G1 that corresponds to the gradation ratio of the G component of the gradation data.

[0289] In addition, in the fifth embodiment, a lookup table may be prepared in advance, which represents the relationship between the gradation ratio of the G component of the gradation data of the input pixel and the control data (e.g., duty ratio) of the second light-emitting element G2, as shown in the graph 3902 of Fig. 39. In this case, the second control data generation unit 12 can use the lookup table to set the control data of the second light-emitting element G2 that corresponds to the gradation ratio of the G component of the gradation data.

[0290] [Embodiment 6] In the above-described embodiments 1 to 5, the case where either the first light-emitting element G1 or the second light-emitting element G2 is set to a non-light-emitting state in a part of the gradation ratio change range RG has been exemplified. In embodiment 6, unlike embodiments 1 to 5, both the first light-emitting element G1 and the second light-emitting element G2 are made to emit light over the entire gradation ratio change range RG.

[0291] That is, the third range RG3 in the sixth embodiment is the same range as the gradation ratio change range RG. Therefore, in the sixth embodiment, the fourth range RG4 and the fifth range RG5 are not set, and the first range RG1 and the second range RG2 are not set either.

[0292] (Example of characteristics of first light-emitting element G1 and second light-emitting element G2 in embodiment 6) Fig. 43 illustrates the characteristics of the first light-emitting element G1 and the second light-emitting element G2 in embodiment 6. In Fig. 43, a graph 4301 shows the characteristics of the first light-emitting element G1, and a graph 4302 shows the characteristics of the second light-emitting element G2.

[0293] In the sixth embodiment, the area of ​​the second light-emitting element G2 is adjusted so that the second dominant wavelength is longer by 8.5 nm. Therefore, the graph 4302 in Fig. 43 is a graph obtained by shifting the graph 102 in Fig. 1 upward by 8.5 nm. As shown in Fig. 43, the first light-emitting element G1 and the second light-emitting element G2 have different dominant wavelength characteristics.

[0294] (Example of control of first light-emitting element G1 and second light-emitting element G2 in embodiment 6) Figure 44 shows an example of control of the first light-emitting element G1 and the second light-emitting element G2 in embodiment 6. In the example of Figure 44, the first light-emitting element G1 is a CC light-emitting element, and the second light-emitting element G2 is a PWM light-emitting element. In Figure 44, graph 4401 shows control data for the first light-emitting element G1, and graph 4402 shows control data for the second light-emitting element G2. Graphs 4401 and 4402 are examples of first control data and second control data, respectively, in embodiment 6.

[0295] 44, in the sixth embodiment, the third range RG3 is the same as the gradation ratio change range RG. For this reason, the third range RG3 is omitted from the subsequent drawings in the sixth embodiment. This also applies to the seventh and subsequent embodiments described below.

[0296] As shown in the graph 4401, the current ratio of the first light-emitting element G1 increases from 0% to 30% as the gradation ratio increases in the third range RG3. In the example of Fig. 44, the current ratio of the first light-emitting element G1 increases linearly with the increase in the gradation ratio.

[0297] As shown in the graph 4402, the duty ratio of the second light-emitting element G2 increases from 0% to 70% as the gradation ratio increases in the third range RG3. In the example of Fig. 44, the duty ratio of the second light-emitting element G2 increases linearly with the increase in the gradation ratio.

[0298] As described above, in the sixth embodiment, both the first light-emitting element G1 and the second light-emitting element G2 emit light throughout the entire gradation ratio change range RG. As shown in Fig. 44 , the control unit 10 in the sixth embodiment continuously controls the luminance of the first light-emitting element G1 and the luminance of the second light-emitting element G2 in response to changes in the gradation ratio within the gradation ratio change range RG. In the example of Fig. 44 , the control unit 10 linearly changes the luminance of the first light-emitting element G1 and the luminance of the second light-emitting element G2 in response to changes in the gradation ratio within the gradation ratio change range RG.

[0299] The relationship between the gradation ratio and the luminance ratio of the combined light in the sixth embodiment is similar to the example in Fig. 24 in the second embodiment, and therefore will not be illustrated using a new graph. In the sixth embodiment as well, by using both the first light-emitting element G1 and the second light-emitting element G2, it is possible to continuously increase the luminance ratio of the combined light as the gradation ratio increases over the entire gradation ratio change range RG.

[0300] Fig. 45 illustrates the contribution rate in embodiment 6. In Fig. 45, a graph 4501 shows the first contribution rate, and a graph 4502 shows the second contribution rate. Graphs 4501 to 4502 in Fig. 45 are obtained based on graphs 4401 to 4402 in Fig. 44.

[0301] According to graph 4501, the first contribution rate in the third range RG3 is 30%. According to graph 4502, the second contribution rate in the third range RG3 is 70%. In the example of Fig. 44 described above, the luminance of the first light-emitting element G1 and the luminance of the second light-emitting element G2 each change linearly with changes in the gradation ratio. Therefore, as shown in Fig. 45, the first contribution rate and the second contribution rate take constant values ​​throughout the entire third range RG3.

[0302] Fig. 46 illustrates the change in dominant wavelength of the first light-emitting element G1 and the second light-emitting element G2 with respect to the change in gradation ratio when the first light-emitting element G1 and the second light-emitting element G2 having the characteristics shown in Fig. 43 are driven by the control data shown in Fig. 44. In other words, Fig. 46 illustrates the change in dominant wavelength of the first light-emitting element G1 and the second light-emitting element G2 with respect to the change in gradation ratio when the first light-emitting element G1 and the second light-emitting element G2 are driven according to the contribution ratio shown in Fig. 45. Graph 4601 in Fig. 46 shows the change in the first dominant wavelength of the first light-emitting element G1, and graph 4602 shows the change in the second dominant wavelength of the second light-emitting element G2. Specifically, graph 4602 shows the change in the second dominant wavelength of the second light-emitting element G2 after the dominant wavelength has been adjusted.

[0303] Graph 4601 corresponds to the portion of graph 4301 in Fig. 43 where the current ratio is 0% to 30%. Specifically, the portion of graph 4301 where the current ratio is 0% to 30% is enlarged horizontally by 3.3 times and applied to graph 4601. The horizontal enlargement factor of 3.3 times is determined as (100-0) / (30-0) ≈ 3.3.

[0304] Graph 4602 corresponds to the portion of graph 4302 in Fig. 43 where the duty ratio is 0% to 70%. Specifically, the portion of graph 4302 where the duty ratio is 0% to 70% is enlarged horizontally by 1.4 times and applied to graph 4602. The horizontal enlargement factor of 1.4 times is determined as (100-0) / (70-0) ≈ 1.4.

[0305] As described above, in the sixth embodiment, the area of ​​the second light-emitting element G2 is adjusted so as to lengthen the second dominant wavelength by 8.5 nm. Specifically, in the sixth embodiment, the ratio between the area of ​​the first light-emitting element G1 and the area of ​​the second light-emitting element G2 is adjusted to 1:x6, where x6 is a number greater than 1. Furthermore, according to Fig. 46, the first dominant wavelength and the second dominant wavelength coincide at a gradation ratio of 47.9%.

[0306] Fig. 47 illustrates the characteristics of the combined light of the first light and the second light (specifically, the second light after the dominant wavelength has been adjusted) in embodiment 6. According to Fig. 47, the combined dominant wavelength is continuous with respect to changes in the gradation ratio.

[0307] In the example of Fig. 47, the maximum value of the synthetic dominant wavelength is 533.4 nm at the 0% gradation ratio point, and the minimum value of the synthetic dominant wavelength is 531.2 nm at around the 50% gradation ratio point. Therefore, the amount of change in the synthetic dominant wavelength in the example of Fig. 47 is given as 533.4 nm - 531.2 nm = 2.2 nm.

[0308] Also, graph 4301 in Fig. 43 is equivalent to graph 501 in Fig. 5. Therefore, the first dominant wavelength change amount in the example of Fig. 43 is also given as 536.5 nm - 525.4 nm = 11.1 nm.

[0309] According to graph 4302 in Fig. 43, the maximum value of the second dominant wavelength is 533.9 nm at the 100% gradation ratio point, and the minimum value of the second dominant wavelength is 530.1 nm at around the 10% gradation ratio point. Therefore, the amount of change in the second dominant wavelength in the example in Fig. 43 is given as 533.9 nm - 530.1 nm = 3.8 nm.

[0310] Therefore, also in the sixth embodiment, the amount of change in the synthetic dominant wavelength is smaller than at least one of the first amount of change in the dominant wavelength and the second amount of change in the dominant wavelength. In the example of the sixth embodiment, the amount of change in the synthetic dominant wavelength is smaller than the first amount of change in the dominant wavelength and is also smaller than the second amount of change in the dominant wavelength. In this way, the amount of change in the synthetic dominant wavelength can be smaller than both the first amount of change in the dominant wavelength and the second amount of change in the dominant wavelength.

[0311] Of course, in the sixth embodiment as well, the synthetic dominant wavelength change amount only needs to be smaller than either the first dominant wavelength change amount or the second dominant wavelength change amount. This also applies to the seventh and subsequent embodiments described below.

[0312] The synthetic dominant wavelength change amount of 2.22 nm in embodiment 6 is the minimum value of the synthetic dominant wavelength change amount among the embodiments described so far. One of the reasons why such a minimum value is obtained is that in embodiment 6, both the first light-emitting element G1 and the second light-emitting element G2 emit light over the entire gradation ratio change range RG.

[0313] The synthetic dominant wavelength is a value between the first dominant wavelength and the second dominant wavelength. In the sixth embodiment, both the first light-emitting element G1 and the second light-emitting element G2 are caused to emit light over the entire gradation ratio change range RG, so that the change characteristics of the first dominant wavelength and the change characteristics of the second dominant wavelength are generally averaged.

[0314] However, the amount of change in the synthetic dominant wavelength also depends on the change characteristics of the first dominant wavelength and the second dominant wavelength themselves. Therefore, it should be noted that by using a light-emitting element having characteristics different from those shown in FIG. 1 , which is the premise of this disclosure, the amount of change in the synthetic dominant wavelength may be made even smaller than in the above examples.

[0315] For example, by using a light-emitting element having characteristics different from those in the example of FIG. 1, even when the control method of embodiment 1 is used, it may be possible to make the amount of change in the synthetic dominant wavelength in the tuning ratio change range RG smaller than 4.3 nm (the value exemplified in embodiment 1).

[0316] In any case, when the synthetic dominant wavelength change amount is smaller than both the first dominant wavelength change amount and the second dominant wavelength change amount, the display quality can be further improved, for example, more accurate color display can be achieved.

[0317] (Supplementary Note on Processing by the Control Unit 10 in the Sixth Embodiment) In the sixth embodiment, a lookup table may be prepared in advance, which represents the relationship between the gradation ratio of the G component of the gradation data of the input pixel shown in the graph 4401 of Fig. 44 and the control data (e.g., current ratio) of the first light-emitting element G1. In this case, the first control data generation unit 11 can use the lookup table to set the control data of the first light-emitting element G1 that corresponds to the gradation ratio of the G component of the gradation data.

[0318] In addition, in the sixth embodiment, a lookup table may be prepared in advance, which represents the relationship between the gradation ratio of the G component of the gradation data of the input pixel shown in the graph 4402 of Fig. 44 and the control data (e.g., duty ratio) of the second light-emitting element G2. In this case, the second control data generation unit 12 can use the lookup table to set the control data of the second light-emitting element G2 that corresponds to the gradation ratio of the G component of the gradation data.

[0319] As described above, in the sixth embodiment, the relationship between the gradation ratio and the current ratio of the first light-emitting element G1 is linear. Therefore, for example, in consideration of the linearity of the graph 4401, the first control data generation unit 11 may output, as the control data for the first light-emitting element G1, a value obtained by multiplying the gradation ratio by a coefficient indicating the slope of the graph 4401. In the example of Fig. 44 , the coefficient indicating the slope of the graph 4401 is 0.3.

[0320] In addition, in the sixth embodiment, the relationship between the gradation ratio and the duty ratio of the second light-emitting element G2 is also linear. Therefore, for example, in consideration of the linearity of the graph 4402, the second control data generation unit 12 may output, as the control data for the second light-emitting element G2, a value obtained by multiplying the gradation ratio by a coefficient indicating the slope of the graph 4402. In the example of Fig. 44, the coefficient indicating the slope of the graph 4402 is 0.7.

[0321] [Embodiment 7] In embodiment 7, as in the above-described embodiment 6, both the first light-emitting element G1 and the second light-emitting element G2 are caused to emit light over the entire gradation ratio change range RG. That is, in embodiment 7 as well, the third range RG3 is the same range as the gradation ratio change range RG.

[0322] As shown in Figure 44 above, in the sixth embodiment, a case was exemplified in which the relationship between the gradation ratio of the G component of the gradation data of the input pixel and the control data of each light-emitting element is linear. In this way, the sixth embodiment exemplified a relatively simple light-emitting control. In contrast, in the seventh embodiment, the control data of each light-emitting element corresponding to the gradation ratio is precisely adjusted so that the synthetic dominant wavelength is constant. In other words, the seventh embodiment exemplified a more complex light-emitting control than the sixth embodiment.

[0323] (Example of characteristics of first light-emitting element G1 and second light-emitting element G2 in embodiment 7) Fig. 48 illustrates the characteristics of the first light-emitting element G1 and the second light-emitting element G2 in embodiment 7. In Fig. 48, a graph 4801 shows the characteristics of the first light-emitting element G1, and a graph 4802 shows the characteristics of the second light-emitting element G2.

[0324] In the seventh embodiment, unlike the first to sixth embodiments, the area of ​​the second light-emitting element G2 is not adjusted. Therefore, the graph in Fig. 48 is equivalent to the graph in Fig. 1. As shown in Fig. 48, the first light-emitting element G1 and the second light-emitting element G2 have different dominant wavelength characteristics.

[0325] (Example of control of first light-emitting element G1 and second light-emitting element G2 in embodiment 7) Figure 49 shows an example of control of the first light-emitting element G1 and the second light-emitting element G2 in embodiment 7. In the example of Figure 49, the first light-emitting element G1 is a CC light-emitting element, and the second light-emitting element G2 is a PWM light-emitting element. In Figure 49, graph 4901 shows control data for the first light-emitting element G1, and graph 4902 shows control data for the second light-emitting element G2. Graphs 4901 and 4902 are examples of first control data and second control data, respectively, in embodiment 7.

[0326] As shown in the graph 4901, as the gradation ratio increases in the third range RG3, the current ratio of the first light-emitting element G1 varies from 0% to 25%. In the example of Fig. 49, the current ratio of the first light-emitting element G1 changes nonlinearly with the increase in the gradation ratio.

[0327] As shown in the graph 4902, the duty ratio of the second light-emitting element G2 varies from 0% to 98.5% as the gradation ratio increases in the third range RG3. In the example of Fig. 49, the duty ratio of the second light-emitting element G2 also changes nonlinearly with the increase in the gradation ratio.

[0328] As will be described later, in the seventh embodiment, the current ratio of the first light-emitting element G1 and the duty ratio of the second light-emitting element G2 are adjusted so that the composite dominant wavelength is 525.5 nm for all gradation ratios within the third range RG3. As a result, the first light-emitting element G1 and the second light-emitting element G2 in the seventh embodiment have the nonlinear characteristics shown in FIG.

[0329] As described above, in embodiment 7, both the first light-emitting element G1 and the second light-emitting element G2 emit light over the entire gradation ratio change range RG. As shown in Fig. 49 , the control unit 10 in embodiment 7 continuously controls the luminance of the first light-emitting element G1 and the luminance of the second light-emitting element G2 in response to changes in the gradation ratio within the gradation ratio change range RG. In the example of Fig. 49 , the control unit 10 changes the luminance of the first light-emitting element G1 and the luminance of the second light-emitting element G2 nonlinearly with changes in the gradation ratio within the gradation ratio change range RG.

[0330] The relationship between the gradation ratio and the luminance ratio of the combined light in the seventh embodiment is similar to the example in Fig. 24 in the second embodiment, and therefore will not be illustrated using a new graph. In the seventh embodiment as well, by using both the first light-emitting element G1 and the second light-emitting element G2, it is possible to continuously increase the luminance ratio of the combined light as the gradation ratio increases over the entire gradation ratio change range RG.

[0331] Fig. 50 illustrates the contribution rate in embodiment 7. In Fig. 50, a graph 5001 shows the first contribution rate, and a graph 5002 shows the second contribution rate. The graphs 5001 to 5002 in Fig. 50 are obtained based on the graphs 4901 to 4902 in Fig. 49.

[0332] According to graph 5001, the first contribution rate in the third range RG3 ranges from 1.6% to 38.6%. According to graph 5002, the second contribution rate in the third range RG3 ranges from 61.4% to 98.5%. As shown in Fig. 50 , the first contribution rate and the second contribution rate also change nonlinearly with changes in the tone ratio.

[0333] Fig. 51 illustrates the change in dominant wavelength of the first light-emitting element G1 and the second light-emitting element G2 with respect to the change in gradation ratio when the first light-emitting element G1 and the second light-emitting element G2 having the characteristics shown in Fig. 48 are driven by the control data shown in Fig. 49. In other words, Fig. 51 illustrates the change in dominant wavelength of the first light-emitting element G1 and the second light-emitting element G2 with respect to the change in gradation ratio when the first light-emitting element G1 and the second light-emitting element G2 are driven according to the contribution ratio shown in Fig. 50. Graph 5101 in Fig. 51 shows the change in the first dominant wavelength of the first light-emitting element G1, and graph 5102 shows the change in the second dominant wavelength of the second light-emitting element G2.

[0334] The first dominant wavelength is determined as the value of the dominant wavelength corresponding to the current ratio in the range of 0% to 25% of the current ratio in graph 4801 of Fig. 48. Graph 5101 shows the first dominant wavelength determined in this way.

[0335] The second dominant wavelength is determined as the value of the dominant wavelength corresponding to the duty ratio in the range of 0% to 98.5% of the duty ratio in graph 4802 of Fig. 48. Graph 5102 shows the second dominant wavelength determined in this way.

[0336] As described above, the second dominant wavelength is not adjusted in the seventh embodiment, so that the ratio between the area of ​​the first light-emitting element G1 and the area of ​​the second light-emitting element G2 is maintained at 1:1.

[0337] Fig. 52 illustrates the characteristics of the combined light of the first light and the second light in the seventh embodiment. According to Fig. 52, the combined dominant wavelength is a constant value of 525.5 nm over the entire gradation ratio change range RG. Therefore, the combined dominant wavelength in the seventh embodiment is also continuous with respect to changes in the gradation ratio. The amount of change in combined dominant wavelength in the example of Fig. 52 is given as 525.5 nm - 525.5 nm = 0 nm.

[0338] Also, graph 4801 in Fig. 48 is equivalent to graph 501 in Fig. 5. Therefore, the first dominant wavelength change amount in the example of Fig. 48 is also given as 536.5 nm - 525.4 nm = 11.1 nm.

[0339] Graph 4802 in Fig. 48 is equivalent to graph 502 in Fig. 5. Therefore, graph 4802 is a graph obtained by shifting graph 4302 in Fig. 43 upward in the plane of the paper. From this, the amount of change in the second dominant wavelength in the example of Fig. 48 is given as the same value as in the example of Fig. 43, namely, 3.8 nm.

[0340] Therefore, also in the seventh embodiment, the amount of change in the synthetic dominant wavelength is smaller than at least one of the first amount of change in the dominant wavelength and the second amount of change in the dominant wavelength. Also in the example of the seventh embodiment, the amount of change in the synthetic dominant wavelength can be smaller than both the first amount of change in the dominant wavelength and the second amount of change in the dominant wavelength.

[0341] In addition, according to the seventh embodiment, the amount of change in the synthetic dominant wavelength in the gradation ratio change range RG can be made even smaller than in the sixth embodiment. Specifically, according to the seventh embodiment, the amount of change in the synthetic dominant wavelength can be made zero. Therefore, according to the seventh embodiment, it is possible to further improve the display quality compared to the sixth embodiment.

[0342] (Supplementary Note on Processing by the Control Unit 10 in the Seventh Embodiment) In the seventh embodiment, a lookup table may be prepared in advance, which represents the relationship between the gradation ratio of the G component of the gradation data of the input pixel shown in the graph 4901 of Fig. 49 and the control data (e.g., current ratio) of the first light-emitting element G1. In this case, the first control data generation unit 11 can use the lookup table to set the control data of the first light-emitting element G1 that corresponds to the gradation ratio of the G component of the gradation data.

[0343] In addition, in the seventh embodiment, a lookup table may be prepared in advance, which represents the relationship between the gradation ratio of the G component of the gradation data of the input pixel shown in the graph 4902 of Fig. 49 and the control data (e.g., duty ratio) of the second light-emitting element G2. In this case, the second control data generation unit 12 can use the lookup table to set the control data of the second light-emitting element G2 that corresponds to the gradation ratio of the G component of the gradation data.

[0344] [Embodiment 8] In the above-described embodiments 1 to 7, the first light-emitting element G1 is a CC light-emitting element and the second light-emitting element G2 is a PWM light-emitting element. In embodiment 8, a case where both the first light-emitting element G1 and the second light-emitting element G2 are CC light-emitting elements is illustrated. That is, a case where both the first light-emitting element G1 and the second light-emitting element G2 are current-driven is illustrated. In embodiment 8, the first light-emitting element G1 and the second light-emitting element G2 are made of the same type of material.

[0345] In the eighth embodiment, as in the sixth and seventh embodiments, both the first light-emitting element G1 and the second light-emitting element G2 are caused to emit light over the entire gradation ratio change range RG. That is, in the eighth embodiment, the third range RG3 is the same range as the gradation ratio change range RG.

[0346] (Example of characteristics of first light-emitting element G1 and second light-emitting element G2 in embodiment 8) Figure 53 illustrates the characteristics of the first light-emitting element G1 and the second light-emitting element G2 in embodiment 8. In Figure 53, graph 5301 shows the characteristics of the first light-emitting element G1, and graph 5302 shows the characteristics of the second light-emitting element G2. In embodiment 8, both the first light-emitting element G1 and the second light-emitting element G2 are CC light-emitting elements. Therefore, graph 5301 is equivalent to graph 101 in Figure 1.

[0347] In the eighth embodiment, the area of ​​the second light-emitting element G2 is adjusted so that the second dominant wavelength is longer by 5.0 nm. Specifically, in the eighth embodiment, the ratio between the area of ​​the first light-emitting element G1 and the area of ​​the second light-emitting element G2 is adjusted to 1:x8, where x8 is a number greater than 1. Therefore, the graph 5302 in FIG. 53 is a graph in which the graph 5301 is shifted by 5.0 nm upward in the plane of the paper. As shown in FIG. 53 , the first light-emitting element G1 and the second light-emitting element G2 have different dominant wavelength characteristics.

[0348] Here, we compare and consider the characteristics of the first light-emitting element G1 and the second light-emitting element G2 in embodiments 1 to 7 (e.g., the characteristics shown in graphs 101 to 102) with the characteristics of the first light-emitting element G1 and the second light-emitting element G2 in embodiment 8 (i.e., the characteristics shown in graphs 5301 to 5302).

[0349] 1, the first dominant wavelength generally decreases as the luminance ratio increases. On the other hand, according to graph 102, the second dominant wavelength generally increases as the luminance ratio increases. Thus, in the example of FIG. 1, the direction of change of the first dominant wavelength with an increase in the luminance ratio is generally opposite to the direction of change of the second dominant wavelength with an increase in the luminance ratio.

[0350] Therefore, in the first to seventh embodiments, the first light-emitting element G1 and the second light-emitting element G2 having such complementary characteristics are used in combination to reduce the amount of change in the synthetic dominant wavelength. As described above, in the first to seventh embodiments, the first light-emitting element G1 and the second light-emitting element G2 having complementary characteristics are used in combination to make the amount of change in the synthetic dominant wavelength smaller than at least one of the amount of change in the first dominant wavelength and the amount of change in the second dominant wavelength. This is easy to understand intuitively.

[0351] In contrast, according to graphs 5301 and 5302 in Fig. 53, in the eighth embodiment, both the first dominant wavelength and the second dominant wavelength generally decrease as the luminance ratio increases. Thus, in the example of Fig. 53, the direction of change in the first dominant wavelength with an increase in the luminance ratio is generally the same as the direction of change in the second dominant wavelength with an increase in the luminance ratio. The amount of change in the synthetic dominant wavelength can also be reduced by combining and using the first light-emitting element G1 and the second light-emitting element G2, which have such similar characteristics. This example will be described in the eighth embodiment.

[0352] (Example of control of first light-emitting element G1 and second light-emitting element G2 in embodiment 8) Fig. 54 shows an example of control of the first light-emitting element G1 and the second light-emitting element G2 in embodiment 8. In Fig. 54, graph 5401 shows control data for the first light-emitting element G1, and graph 5402 shows control data for the second light-emitting element G2. Graph 5401 and graph 5402 are examples of first control data and second control data in embodiment 8, respectively.

[0353] As shown in the graph 5401, as the gradation ratio increases in the third range RG3, the current ratio of the first light-emitting element G1 varies from 0% to 25%. In the example of Fig. 54, the current ratio of the first light-emitting element G1 changes nonlinearly with the increase in the gradation ratio.

[0354] As shown in graph 5402, as the gradation ratio increases in the third range RG3, the current ratio of the second light-emitting element G2 varies from 0% to 100%. In the example of Fig. 54, the current ratio of the second light-emitting element G2 changes nonlinearly with the increase in the gradation ratio.

[0355] As described above, in embodiment 8 as well, both the first light-emitting element G1 and the second light-emitting element G2 are caused to emit light over the entire gradation ratio change range RG. As shown in Fig. 54 , the control unit 10 in embodiment 8 continuously controls the luminance of the first light-emitting element G1 and the luminance of the second light-emitting element G2 in response to changes in the gradation ratio within the gradation ratio change range RG. In the example of Fig. 54 , the control unit 10 changes the luminance of the first light-emitting element G1 and the luminance of the second light-emitting element G2 nonlinearly with changes in the gradation ratio within the gradation ratio change range RG.

[0356] The relationship between the gradation ratio and the luminance ratio of the combined light in embodiment 8 is similar to the example in Fig. 24 in embodiment 2, and therefore will not be illustrated using a new graph. In embodiment 8 as well, by using both the first light-emitting element G1 and the second light-emitting element G2, it is possible to continuously increase the luminance ratio of the combined light as the gradation ratio increases over the entire gradation ratio change range RG.

[0357] Fig. 55 illustrates the contribution rate in embodiment 8. In Fig. 55, a graph 5501 shows the first contribution rate, and a graph 5502 shows the second contribution rate. Graphs 5501 to 5502 in Fig. 55 are obtained based on graphs 5401 to 5402 in Fig. 54.

[0358] According to the graph 5501, the first contribution rate in the third range RG3 changes from 100% to 0% as the gradation ratio increases. In the example of Fig. 55, the first contribution rate decreases linearly as the gradation ratio increases.

[0359] According to the graph 5502, the second contribution rate in the third range RG3 varies from 0% to 100% as the gradation ratio increases. In the example of Fig. 55, the second contribution rate increases linearly as the gradation ratio increases.

[0360] Fig. 56 illustrates the change in dominant wavelength of the first light-emitting element G1 and the second light-emitting element G2 with respect to the change in gradation ratio when the first light-emitting element G1 and the second light-emitting element G2 having the characteristics shown in Fig. 53 are driven using the control data (current ratio) shown in Fig. 54. In other words, Fig. 56 illustrates the change in dominant wavelength of the first light-emitting element G1 and the second light-emitting element G2 with respect to the change in gradation ratio when the first light-emitting element G1 and the second light-emitting element G2 are driven according to the contribution ratio shown in Fig. 55. Graph 5601 in Fig. 56 shows the change in the first dominant wavelength of the first light-emitting element G1, and graph 5602 shows the change in the second dominant wavelength of the second light-emitting element G2. Specifically, graph 5602 shows the change in the second dominant wavelength of the second light-emitting element G2 after the dominant wavelength has been adjusted.

[0361] The first dominant wavelength is determined as the value of the dominant wavelength corresponding to the current ratio in the range of 0% to 25% of the current ratio in graph 5301 of Fig. 53. Graph 5601 shows the first dominant wavelength determined in this way.

[0362] More specifically, as shown in graph 5401, the current ratio of the first light-emitting element initially increases as the gradation ratio increases, and then begins to decrease. Corresponding to this change trend, the first dominant wavelength shown in graph 5601 also initially decreases as the gradation ratio increases, and then begins to increase. As such, it should be noted that just because the first light-emitting element G1 itself has the monotonically decreasing first dominant wavelength characteristic shown in graph 5301, the first dominant wavelength characteristic of the first light-emitting element G1 controlled by the control unit 10 does not necessarily become a monotonically decreasing characteristic.

[0363] The second dominant wavelength is determined as the value of the dominant wavelength corresponding to the current ratio in the range of 0% to 100% in graph 5302 of Fig. 53. Graph 5602 shows the second dominant wavelength determined in this manner. Also, according to Fig. 56, the first dominant wavelength and the second dominant wavelength coincide at a gradation ratio of 81.6%.

[0364] Fig. 57 illustrates the characteristics of the combined light of the first light and the second light (specifically, the second light after the dominant wavelength has been adjusted) in embodiment 8. According to Fig. 57, the combined dominant wavelength in embodiment 8 is also continuous with respect to the gradation ratio.

[0365] In the example of Fig. 57, the maximum value of the synthetic dominant wavelength is 536.5 nm at the gradation ratio point of 0%, and the minimum value of the synthetic dominant wavelength is 530.4 nm at the gradation ratio point of 100%. Therefore, the amount of change in the synthetic dominant wavelength in the example of Fig. 57 is given as 536.5 nm - 530.4 nm = 6.1 nm.

[0366] Also, graph 5301 in Fig. 53 is equivalent to graph 501 in Fig. 5. Therefore, the first dominant wavelength change amount in the example of Fig. 53 is also given as 536.5 nm - 525.4 nm = 11.1 nm.

[0367] Graph 5302 in Fig. 53 is a graph obtained by shifting graph 5301 upward in the plane of the paper. From this, the second dominant wavelength change amount in the example of Fig. 53 is also given as 11.1 nm.

[0368] Therefore, also in the eighth embodiment, the amount of change in the synthetic dominant wavelength is smaller than at least one of the first amount of change in the dominant wavelength and the second amount of change in the dominant wavelength. Also in the eighth embodiment, the amount of change in the synthetic dominant wavelength can be smaller than both the first amount of change in the dominant wavelength and the second amount of change in the dominant wavelength.

[0369] As described above, by using a combination of the first light-emitting element G1 and the second light-emitting element G2 having similar characteristics, it is possible to reduce the amount of change in the synthetic dominant wavelength. Since the first light-emitting element G1 and the second light-emitting element G2 in the eighth embodiment are both CC light-emitting elements, the risk of flickering can be reduced compared to the first to seventh embodiments.

[0370] Furthermore, in the eighth embodiment, both the first light-emitting element G1 and the second light-emitting element G2 can be driven by the same driving method (e.g., current driving), unlike the first to seventh embodiments. Therefore, in the eighth embodiment, each configuration related to driving the light-emitting elements can be simplified compared to the first to seventh embodiments.

[0371] (Supplementary Note on Processing by the Control Unit 10 in the Eighth Embodiment) In the eighth embodiment, a lookup table may be prepared in advance, which represents the relationship between the gradation ratio of the G component of the gradation data of the input pixel shown in the graph 5401 of Fig. 54 and the control data (e.g., current ratio) of the first light-emitting element G1. In this case, the first control data generation unit 11 can use the lookup table to set the control data of the first light-emitting element G1 that corresponds to the gradation ratio of the G component of the gradation data.

[0372] In the eighth embodiment, a lookup table may be prepared in advance, which represents the relationship between the gradation ratio of the G component of the gradation data of the input pixel shown in graph 5402 of Fig. 54 and the control data (e.g., current ratio) of the second light-emitting element G2. In this case, the second control data generation unit 12 can use the lookup table to set the control data of the second light-emitting element G2 that corresponds to the gradation ratio of the G component of the gradation data.

[0373] [Embodiment 9] Embodiment 9 is a combination of the above-described Embodiments 7 and 8. Accordingly, in Embodiment 9 as well, a case where both the first light-emitting element G1 and the second light-emitting element G2 are CC light-emitting elements is illustrated. In Embodiment 9 as well, both the first light-emitting element G1 and the second light-emitting element G2 are caused to emit light over the entire gradation ratio change range RG. That is, in Embodiment 9 as well, the third range RG3 is the same range as the gradation ratio change range RG.

[0374] Additionally, in the ninth embodiment, the control data for each light-emitting element corresponding to the gradation ratio is precisely adjusted so that the synthetic dominant wavelength is constant. That is, the ninth embodiment illustrates a more complex light emission control than the eighth embodiment.

[0375] (Example of characteristics of first light-emitting element G1 and second light-emitting element G2 in embodiment 9) Fig. 58 illustrates the characteristics of the first light-emitting element G1 and the second light-emitting element G2 in embodiment 9. In Fig. 58, graph 5801 shows the characteristics of the first light-emitting element G1, and graph 5802 shows the characteristics of the second light-emitting element G2. Graph 5801 is equivalent to graph 101 in Fig. 1.

[0376] In the ninth embodiment, the area of ​​the second light-emitting element G2 is adjusted so that the second dominant wavelength is longer by 11.2 nm. Specifically, in the ninth embodiment, the ratio between the area of ​​the first light-emitting element G1 and the area of ​​the second light-emitting element G2 is adjusted to 1:x9, where x9 is a number greater than 1. Therefore, the graph 5802 in FIG. 58 is a graph in which the graph 5801 is shifted by 11.2 nm upward in the plane of the paper. As shown in FIG. 58, the first light-emitting element G1 and the second light-emitting element G2 have different dominant wavelength characteristics.

[0377] (Example of control of first light-emitting element G1 and second light-emitting element G2 in embodiment 9) Fig. 59 shows an example of control of the first light-emitting element G1 and the second light-emitting element G2 in embodiment 9. In Fig. 59, graph 5901 shows control data for the first light-emitting element G1, and graph 5902 shows control data for the second light-emitting element G2. Graph 5901 and graph 5902 are examples of first control data and second control data, respectively, in embodiment 9.

[0378] As shown in graph 5901, the current ratio of the first light-emitting element G1 varies from 0% to 18.5% as the gradation ratio increases in the third range RG3. In the example of Fig. 59, the current ratio of the first light-emitting element G1 changes nonlinearly with the increase in the gradation ratio in most of the third range RG3.

[0379] As shown in graph 5402, as the gradation ratio increases in the third range RG3, the current ratio of the second light-emitting element G2 varies from 0% to 95.4%. In the example of Fig. 59, the current ratio of the second light-emitting element G2 changes nonlinearly with the increase in the gradation ratio in most of the third range RG3.

[0380] As will be described later, in the ninth embodiment, the current ratio of the first light-emitting element G1 and the current ratio of the second light-emitting element G2 are adjusted so that the composite dominant wavelength is 536.5 nm at all gradation ratios within the third range RG3. As a result, the first light-emitting element G1 and the second light-emitting element G2 in the ninth embodiment have the nonlinear partial characteristics shown in FIG.

[0381] As described above, in the ninth embodiment as well, both the first light-emitting element G1 and the second light-emitting element G2 emit light over the entire gradation ratio change range RG. As shown in Fig. 59 , the control unit 10 in the ninth embodiment continuously controls the luminance of the first light-emitting element G1 and the luminance of the second light-emitting element G2 in response to changes in the gradation ratio over the gradation ratio change range RG.

[0382] The relationship between the gradation ratio and the luminance ratio of the combined light in the ninth embodiment is similar to the example in Fig. 24 in the second embodiment, and therefore will not be illustrated using a new graph. In the ninth embodiment as well, by using both the first light-emitting element G1 and the second light-emitting element G2, it is possible to continuously increase the luminance ratio of the combined light as the gradation ratio increases over the entire gradation ratio change range RG.

[0383] Fig. 60 illustrates the contribution rate in embodiment 9. In Fig. 60, a graph 6001 shows the first contribution rate, and a graph 6002 shows the second contribution rate. The graphs 6001 to 6002 in Fig. 60 are obtained based on the graphs 5901 to 5902 in Fig. 59.

[0384] According to the graph 6001, the first contribution rate in the third range RG3 ranges from 4.6% to 100%. According to the graph 6002, the second contribution rate in the third range RG3 ranges from 0% to 95.4%.

[0385] Fig. 61 illustrates the change in dominant wavelength of the first light-emitting element G1 and the second light-emitting element G2 with respect to the change in gradation ratio when the first light-emitting element G1 and the second light-emitting element G2 having the characteristics shown in Fig. 58 are driven by the control data shown in Fig. 59. In other words, Fig. 61 illustrates the change in dominant wavelength of the first light-emitting element G1 and the second light-emitting element G2 with respect to the change in gradation ratio when the first light-emitting element G1 and the second light-emitting element G2 are driven according to the contribution ratio shown in Fig. 60. Graph 6101 in Fig. 61 shows the change in the first dominant wavelength of the first light-emitting element G1, and graph 6102 shows the change in the second dominant wavelength of the second light-emitting element G2. Specifically, graph 6102 shows the change in the second dominant wavelength of the second light-emitting element G2 after the dominant wavelength has been adjusted.

[0386] The first dominant wavelength is determined as the value of the dominant wavelength corresponding to the current ratio in the range of 0% to 18.5% of the current ratio in graph 5801 of Fig. 58. Graph 6101 shows the first dominant wavelength determined in this manner.

[0387] The second dominant wavelength is determined as the value of the dominant wavelength corresponding to the current ratio in the range of 0% to 95.4% of the current ratio in graph 5802 of Fig. 58. Graph 6102 shows the second dominant wavelength determined in this manner.

[0388] Fig. 62 illustrates the characteristics of the combined light of the first light and the second light in the ninth embodiment. According to Fig. 62, the combined dominant wavelength is a constant value of 536.5 nm over the entire gradation ratio change range RG. Therefore, the combined dominant wavelength in the ninth embodiment is also continuous with respect to changes in the gradation ratio. The amount of change in combined dominant wavelength in the example of Fig. 62 is given as 536.5 nm - 536.5 nm = 0 nm.

[0389] On the other hand, as is clear from the explanation of the eighth embodiment, the first and second dominant wavelength changes in FIG. 58 are both 11.1 nm.

[0390] Therefore, also in the ninth embodiment, the amount of change in the synthetic dominant wavelength is smaller than at least one of the first amount of change in the dominant wavelength and the second amount of change in the dominant wavelength. Also in the ninth embodiment, the amount of change in the synthetic dominant wavelength can be smaller than both the first amount of change in the dominant wavelength and the second amount of change in the dominant wavelength.

[0391] In addition, according to the ninth embodiment, the amount of change in the synthetic dominant wavelength can be further reduced compared to the eighth embodiment. Specifically, according to the ninth embodiment, the amount of change in the synthetic dominant wavelength can be set to 0, as in the seventh embodiment. Therefore, according to the ninth embodiment, it is possible to further improve the display quality compared to the eighth embodiment.

[0392] In the ninth embodiment, both the first light-emitting element G1 and the second light-emitting element G2 are CC light-emitting elements, unlike the seventh embodiment. Therefore, the risk of flickering can be reduced compared to the seventh embodiment.

[0393] Furthermore, in the 9th embodiment, unlike the 7th embodiment, both the first light-emitting element G1 and the second light-emitting element G2 can be driven by the same driving method (e.g., current driving). Therefore, in the 9th embodiment, each configuration related to driving the light-emitting elements can be simplified compared to the 7th embodiment.

[0394] 58 , the first light-emitting element G1 and the second light-emitting element G2 in the 9th embodiment have a characteristic that the dominant wavelength monotonically decreases with increasing luminance. When light-emitting elements having such a characteristic are used, in order to maintain a constant synthetic dominant wavelength within the gradation ratio change range RG, it is necessary to ensure that the range of change in the first dominant wavelength when the first light-emitting element G1 is caused to emit light alone does not overlap with the range of change in the second dominant wavelength when the second light-emitting element G2 is caused to emit light alone within the gradation ratio change range RG.

[0395] In the ninth embodiment, as shown in graph 5801, the range of change of the first dominant wavelength relative to the gradation ratio change range RG when the first light-emitting element G1 is caused to emit light alone is 525.4 nm to 536.5 nm. On the other hand, as shown in graph 5802, the range of change of the second dominant wavelength relative to the gradation ratio change range RG when the second light-emitting element G2 is caused to emit light alone is 536.6 nm to 547.7 nm. Therefore, in the example of the ninth embodiment, the range of change of the first dominant wavelength does not overlap with the range of change of the second dominant wavelength.

[0396] 58, near the gradation ratio of 0%, the synthetic dominant wavelength can take on approximately values ​​ranging from the maximum first dominant wavelength value of 536.5 nm to the maximum second dominant wavelength value of 547.7 nm in the gradation ratio change range RG. Therefore, the minimum value of the synthetic dominant wavelength near the gradation ratio of 0% is approximately 536.5 nm.

[0397] 58, the synthetic dominant wavelength can take on values ​​ranging from the minimum value of the first dominant wavelength of 525.4 nm to the minimum value of the second dominant wavelength of 536.6 nm in the grayscale ratio change range RG. Therefore, the maximum value of the synthetic dominant wavelength near the grayscale ratio of 100% is approximately 536.6 nm.

[0398] Here, the minimum value of the synthetic dominant wavelength near a gradation ratio of 0% is denoted as Wmin, and the maximum value of the synthetic dominant wavelength near a gradation ratio of 100% is denoted as Wmax. In the ninth embodiment, if Wmin is smaller than Wmax, a constant W can be set that satisfies Wmin≦W≦Wmax. In this case, the current ratio of the first light-emitting element G1 and the current ratio of the second light-emitting element G2 can be set so that the synthetic dominant wavelength is equal to the constant W within the gradation ratio change range RG. The above condition regarding the constant W can be satisfied if, within the gradation ratio change range RG, the range of change of the first dominant wavelength when the first light-emitting element G1 is caused to emit light alone does not overlap with the range of change of the second dominant wavelength when the second light-emitting element G2 is caused to emit light alone.

[0399] Conversely to the example of Fig. 58, it is also conceivable that the first light-emitting element G1 and the second light-emitting element G2 have a characteristic in which the dominant wavelength monotonically decreases with increasing luminance. Even in this case, the current ratio of the first light-emitting element G1 and the current ratio of the second light-emitting element G2 can be set by applying the setting method described above.

[0400] However, it should be noted that the above example does not necessarily apply if a certain light-emitting element does not have the characteristic that the dominant wavelength monotonically decreases or increases with increasing current ratio or duty ratio.

[0401] As an example, according to graph 102 in Figure 1, the second light-emitting element G2 has a characteristic in which the dominant wavelength monotonically decreases in the duty ratio range of 0% to 10%, and monotonically increases in the duty ratio range of 10% to 100%.

[0402] When using the second light-emitting element G2 having such characteristics, even if the above-mentioned condition "within the gradation ratio change range RG, the change range of the first dominant wavelength when the first light-emitting element G1 is caused to emit light alone does not overlap with the change range of the second dominant wavelength when the second light-emitting element G2 is caused to emit light alone" is not satisfied, it may be possible to set the current ratio or duty ratio of each light-emitting element so as to maintain a constant composite dominant wavelength within the gradation ratio change range RG.

[0403] (Supplementary Note on Processing of the Control Unit 10 in the Ninth Embodiment) In the ninth embodiment, a lookup table may be prepared in advance, which represents the relationship between the gradation ratio of the G component of the gradation data of the input pixel shown in the graph 5901 of Fig. 59 and the control data (e.g., current ratio) of the first light-emitting element G1. In this case, the first control data generation unit 11 can use the lookup table to set the control data of the first light-emitting element G1 that corresponds to the gradation ratio of the G component of the gradation data.

[0404] In addition, in the ninth embodiment, a lookup table may be prepared in advance, which represents the relationship between the gradation ratio of the G component of the gradation data of the input pixel shown in graph 5902 of Fig. 59 and the control data (e.g., current ratio) of the second light-emitting element G2. In this case, the second control data generation unit 12 can use the lookup table to set the control data of the second light-emitting element G2 that corresponds to the gradation ratio of the G component of the gradation data.

[0405] [Example of implementation using software] The functions of the display device 100 (hereinafter referred to as the "device") can be realized by a program that causes a computer to function as the device, and a program that causes a computer to function as each control block of the device (particularly each part included in the control device 1).

[0406] In this case, the device includes a computer having at least one control device (e.g., a processor) and at least one storage device (e.g., a memory) as hardware for executing the program. The functions described in each of the above embodiments are realized by executing the program using the control device and storage device.

[0407] The program may be non-transitory and may be recorded on one or more computer-readable recording media. The recording media may or may not be included in the device. In the latter case, the program may be supplied to the device via any wired or wireless transmission medium.

[0408] In addition, some or all of the functions of each of the control blocks can be realized by a logic circuit. For example, an integrated circuit in which a logic circuit that functions as each of the control blocks is formed is also included in the scope of one aspect of the present disclosure. In addition, the functions of each of the control blocks can also be realized by, for example, a quantum computer.

[0409] The processes described in the above embodiments may be executed by AI (Artificial Intelligence). In this case, the AI ​​may run on the control device or on another device (for example, an edge computer or a cloud server).

[0410] [Additional Notes] One aspect of the present disclosure is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of one aspect of the present disclosure. Furthermore, new technical features can be formed by combining the technical means disclosed in each embodiment.

[0411] REFERENCE SIGNS LIST 1 control device 10 control section 11 first control data generation section 12 second control data generation section 90 display panel 100 display device G1 first light-emitting element G2 second light-emitting element SUBPX_G green sub-pixel (sub-pixel including first light-emitting element and second light-emitting element) RG gradation ratio change range RG1 first range RG2 second range RG3 third range RG4 fourth range RG5 fifth range TV1 first gradation ratio TV2 second gradation ratio TV3 third gradation ratio

Claims

1. A control device for controlling a display panel, the display panel having sub-pixels including a first light-emitting element emitting a first light having a first color and a second light-emitting element emitting a second light having a second color, the control device controls the first light-emitting element and the second light-emitting element according to a gradation ratio corresponding to the sub-pixel in input image data, the second color is the same type of color as the first color, a dominant wavelength of the first light is referred to as a first dominant wavelength, and a dominant wavelength of the second light is referred to as a second dominant wavelength, a characteristic of the first dominant wavelength with respect to the luminance of the first light is different from a characteristic of the second dominant wavelength with respect to the luminance of the second light, a difference between a maximum value and a minimum value of the first dominant wavelength in a predetermined gradation ratio change range when only the first light-emitting element is caused to emit the first light is referred to as a first dominant wavelength change amount, and a difference between a maximum value and a minimum value of the second dominant wavelength in the gradation ratio change range when only the second light-emitting element is caused to emit the second light is referred to as a second dominant wavelength change amount, a dominant wavelength of a composite light of the first light and the second light is referred to as a composite dominant wavelength, a difference between a maximum value and a minimum value of the composite dominant wavelength in the gradation ratio change range is referred to as a composite dominant wavelength change amount, and the control device controls the first light-emitting element and the second light-emitting element, so that the composite dominant wavelength change amount becomes smaller than at least one of the first dominant wavelength change amount and the second dominant wavelength change amount.

2. The control device according to claim 1, wherein the control device causes only the first light-emitting element to emit the first light in a first range belonging to the gradation ratio change range, and causes only the second light-emitting element to emit the second light in a second range belonging to the gradation ratio change range and adjacent to the first range on the high gradation ratio side of the first range, and wherein the first dominant wavelength and the second dominant wavelength are approximately identical at a first gradation ratio located on the boundary between the first range and the second range.

3. The control device according to claim 2, wherein the control device controls the first light-emitting element in the first range by current driving.

4. The control device according to claim 1, wherein the control device causes the first light-emitting element to emit the first light and the second light-emitting element to emit the second light in a third range belonging to the gradation ratio change range, and continuously controls each of the luminance of the first light and the luminance of the second light in response to changes in the gradation ratio in the gradation ratio change range.

5. The control device according to claim 4, wherein the control device causes only the first light-emitting element to emit the first light in a fourth range which belongs to the gradation ratio change range and is adjacent to the third range on the low gradation ratio side of the third range.

6. The control device according to claim 5, wherein the control device controls the second light-emitting element so that the luminance of the second light increases continuously from zero as the gradation ratio increases from a second gradation ratio located on the boundary between the fourth range and the third range.

7. A control device as described in claim 5 or 6, wherein the control device controls the first light-emitting element so that the brightness of the first light in the third range is constant, and controls the second light-emitting element so that the brightness of the second light in the third range increases as the gradation ratio increases.

8. The control device described in claim 5 or 6, wherein the control device controls the first light-emitting element so that the brightness of the first light in the third range increases as the gradation ratio increases, and controls the second light-emitting element so that the brightness of the second light in the third range increases as the gradation ratio increases.

9. A control device as described in any one of claims 4 to 6, wherein the control device causes only the second light-emitting element to emit the second light in a fifth range that belongs to the gradation ratio change range and is adjacent to the third range on the high gradation ratio side of the third range.

10. The control device according to claim 9, wherein the control device controls the first light-emitting element so that the luminance of the first light increases continuously from zero as the gradation ratio decreases from a third gradation ratio located on the boundary between the third range and the fifth range.

11. The control device according to claim 4, wherein said third range is the same range as said tone ratio change range.

12. The control device described in claim 11, wherein the control device controls the first light-emitting element and the second light-emitting element so that the contribution rate of the first light and the contribution rate of the second light to the combined light are constant at all gradation ratios within the third range.

13. The control device according to claim 11, wherein the control device controls the first light-emitting element and the second light-emitting element so that the synthetic dominant wavelength is constant for all grayscale ratios within the third range.

14. The control device described in claim 11 or 13, wherein the first light-emitting element and the second light-emitting element are made of the same type of material, and the first dominant wavelength and the second dominant wavelength are different at a certain gradation ratio within the third range.

15. The control device described in claim 13, wherein, in the third range, both the first dominant wavelength and the second dominant wavelength monotonically decrease or increase with increasing luminance, and, in the gradation ratio change range, a change range of the first dominant wavelength when only the first light-emitting element is caused to emit the first light does not overlap with a change range of the second dominant wavelength when only the second light-emitting element is caused to emit the second light.

16. A control device according to any one of claims 4 to 15, wherein in the third range, there exists a gradation ratio at which the first dominant wavelength and the second dominant wavelength are equal.

17. A control device according to any one of claims 1 to 16, wherein the synthetic dominant wavelength change amount is smaller than the first dominant wavelength change amount and smaller than the second dominant wavelength change amount.

18. A display device comprising: a control device according to any one of claims 1 to 17; and the display panel.

19. A control method for controlling a display panel, the display panel having sub-pixels including a first light-emitting element emitting a first light having a first color and a second light-emitting element emitting a second light having a second color, the control method including a step of controlling the first light-emitting element and the second light-emitting element according to a gradation ratio corresponding to the sub-pixel in input image data, the second color being the same type of color as the first color, a dominant wavelength of the first light being referred to as a first dominant wavelength, and a dominant wavelength of the second light being referred to as a second dominant wavelength, a characteristic of the first dominant wavelength with respect to the luminance of the first light being different from a characteristic of the second dominant wavelength with respect to the luminance of the second light, a difference between a maximum value and a minimum value of the first dominant wavelength in a predetermined gradation ratio change range when only the first light-emitting element is caused to emit the first light being referred to as a first dominant wavelength change amount, and a difference between a maximum value and a minimum value of the second dominant wavelength in the gradation ratio change range when only the second light-emitting element is caused to emit the second light being referred to as a second dominant wavelength change amount, a dominant wavelength of a composite light of the first light and the second light is referred to as a composite dominant wavelength, a difference between a maximum value and a minimum value of the composite dominant wavelength in the gradation ratio change range is referred to as a composite dominant wavelength change amount, and the step of controlling the first light-emitting element and the second light-emitting element includes a step of controlling the first light-emitting element and the second light-emitting element such that the composite dominant wavelength change amount is smaller than at least one of the first dominant wavelength change amount and the second dominant wavelength change amount.

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