Light-emitting device and method for driving light-emitting device

Abstract

When a light-emitting device such as a display is configured from a multicolor light-emitting semiconductor light-emitting element, appropriate light-emitting color control can be achieved. A light-emitting device (100) is provided with: a display unit (10) in which a plurality of pixels are configured by arranging a plurality of light-emitting elements (11), the light-emitting colors of which can be controlled in accordance with a drive current, in a predetermined pattern; and a lighting control unit (50) that supplies a drive current to the light-emitting element (11) and controls the light-emitting period. The lighting control unit (50) divides a frame in which the plurality of light-emitting elements (11) emit light into a first subframe in which the plurality of light-emitting elements (11) emit light in a first light-emitting color and a second subframe in which the plurality of light-emitting elements (11) emit light in a second light-emitting color different from the first light-emitting color, and drives the frame.

Description

Technical Field

[0001] The present disclosure relates to a light-emitting device and a driving method thereof. Background Art

[0002] There are displays or surface light-emitting devices using semiconductor light-emitting elements such as LEDs and LDs. Here, in order to manufacture a full-color LED display, it is generally necessary to arrange at least three-color sub-pixels of RGB for each pixel. However, in such a structure, it is necessary to provide more than three times the number of sub-pixels of the number of pixels, so it is not suitable for high definition, and there are problems of high cost and reduced yield due to the increase in the number of LEDs.

[0003] In response to this, a micro-LED display that enables a single LED element to emit multi-color light has been disclosed (Patent Document 1). However, when a display is configured by such multi-color light-emitting micro-LEDs, an actual circuit structure and driving method have not been disclosed. For example, it is not easy in the prior art to control the multi-color light-emitting micro-LED to emit light in all chromaticity ranges of RGB.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2021-52168

[0007] Patent Document 2: U.S. Patent No. 10885834 Summary of the Invention

[0008] Technical Problem to be Solved by the Invention

[0009] One of the problems of the present disclosure is to provide a light-emitting device and a driving method thereof that can achieve appropriate light emission color control when a display or other light-emitting device is configured by multi-color light-emitting semiconductor light-emitting elements. Another problem is to provide a light-emitting device and a driving method thereof that suppress the occurrence of color separation. In addition, the description of these problems does not prevent the existence of other problems. In addition, one aspect of the present disclosure does not require solving all of these problems. Furthermore, based on the description of the specification, drawings, claims, etc. of the present disclosure, problems other than these can be extracted.

[0010] Technical Solution for Solving the Technical Problem

[0011] A light-emitting device according to one embodiment of the present disclosure includes: a display unit that forms a plurality of pixels by arranging a plurality of light-emitting elements capable of controlling the emission color according to a drive current in a predetermined pattern; and a lighting control unit that supplies a drive current to the light-emitting elements and controls the emission period. The lighting control unit drives the light-emitting elements by dividing one frame in which the plurality of light-emitting elements emit light into a first sub-frame in which the plurality of light-emitting elements emit light of a first emission color and a second sub-frame in which the plurality of light-emitting elements emit light of a second emission color different from the first emission color.

[0012] A driving method of a light-emitting device according to another embodiment of the present disclosure, the light-emitting device including: a display unit that forms a plurality of pixels by arranging a plurality of light-emitting elements capable of controlling the emission color according to a drive current in a predetermined pattern; an information holding unit that holds current-chromaticity information for determining a drive current value for causing the light-emitting elements to emit light of the first emission color or a second emission color different from the first emission color according to a predetermined emission color; and a lighting control unit that supplies a drive current to the light-emitting elements and controls the emission period of the light-emitting elements. The driving method of the light-emitting device includes the following steps: the lighting control unit drives the light-emitting elements by dividing one frame in which the plurality of light-emitting elements emit light into a first sub-frame in which the plurality of light-emitting elements emit light of the first emission color and a second sub-frame in which the plurality of light-emitting elements emit light of the second emission color.

[0013] Advantages of the Invention

[0014] According to the above structure, by using light-emitting elements capable of controlling the emission color according to the drive current, multi-color emission such as full-color emission can be performed, and by dividing the emission color into sub-frames for display, the occurrence of color breakup can be suppressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a block diagram showing a light-emitting device according to Embodiment 1.

[0016] Figure 2 is a timing chart for lighting and driving the light-emitting elements.

[0017] Figure 3 is a block diagram showing an example of setting a first control circuit and a second control circuit in a pixel circuit.

[0018] Figure 4 is a block diagram showing a display unit of the light-emitting device according to Embodiment 1 with an enlarged view.

[0019] Figure 5 is a schematic cross-sectional view showing an example of the element structure of the light-emitting element.

[0020] Figure 6It is a schematic cross-sectional view showing another example of the element structure of a light-emitting element.

[0021] Figure 7 It is a schematic diagram showing the lighting image of the first sub-frame.

[0022] Figure 8 It is a schematic diagram showing the lighting image of the second sub-frame.

[0023] Figure 9 It is a functional block diagram showing the method for determining the drive current value and the PWM light-emitting period.

[0024] Figure 10 It is used to show in Figure 9 The chromaticity diagram of the steps for determining the light-emitting chromaticity.

[0025] Explanation of reference numerals

[0026] 100: Light-emitting device

[0027] 2: n-type semiconductor layer

[0028] 2A: First n-type semiconductor layer

[0029] 2B: Second n-type semiconductor layer

[0030] 3: Active layer

[0031] 3A: First light-emitting layer

[0032] 3B: Second light-emitting layer

[0033] 4: p-type semiconductor layer

[0034] 4A: First p-type semiconductor layer

[0035] 4B: Second p-type semiconductor layer

[0036] 5: n-side electrode

[0037] 6: p-side electrode

[0038] 6A: First p-side electrode

[0039] 6B: Second p-side electrode

[0040] 7: Ohmic contact layer

[0041] 8, 8B: Pixel drive circuit

[0042] 9, 9B: Power supply line

[0043] 10: Display unit

[0044] 11, 11B: Light-emitting element

[0045] 12: Pixel

[0046] 14: Pixel circuit

[0047] 20: Scanning unit

[0048] 30: Driving unit

[0049] 50: Lighting control unit

[0050] 51: First control circuit

[0051] 52: Second control circuit

[0052] 60: Driving control unit

[0053] 70: Information holding unit

[0054] WS: Write scan line

[0055] WS1: Power control signal write scan line

[0056] WS2: Analog image signal write scan line

[0057] SL: Signal line

[0058] SL1: Power control signal line

[0059] SL2: Analog image signal line

[0060] SW1: First switch

[0061] SW2: Second switch Detailed implementation manner

[0062] Hereinafter, the present disclosure will be described in more detail based on the accompanying drawings. In addition, in the following description, terms indicating specific directions and positions (for example, "up", "down", and other terms including these terms) are used as needed, but the use of these terms is for easy understanding of the invention with reference to the drawings, and does not limit the technical scope of the present disclosure according to the meanings of these terms. In addition, parts with the same reference numerals in multiple drawings represent the same or equivalent parts or components.

[0063] Furthermore, the following-described embodiments represent specific examples of the technical idea of the present disclosure, and the present disclosure is not limited to the following. In addition, the dimensions, materials, shapes, relative configurations, etc. of the components described below are not intended to limit the scope of the present disclosure only thereto, but are intended to be illustrative as long as there is no specific description. In addition, the content described in one embodiment or example can also be applied to other embodiments or examples. In addition, the sizes or positional relationships of the components shown in the drawings are sometimes exaggerated for clarity of explanation.

[0064] [Embodiment 1]

[0065] Figure 1 A block diagram showing the light-emitting device 100 of Embodiment 1. The light-emitting device 100 shown in this figure includes a display unit 10, a driving unit 30, a lighting control unit 50, an information holding unit 70, a scanning unit 20, and a driving control unit 60.

[0066] The display unit 10 arranges a plurality of light-emitting elements 11 in a prescribed pattern. Each light-emitting element 11 constitutes a pixel 12. Specifically, the plurality of light-emitting elements 11 are arranged in a row-column shape or a matrix shape. Sometimes, the period during which one frame amount of image data is displayed on a screen formed by pixels 12 arranged in a matrix shape is called a vertical scanning period, and the period obtained by dividing the vertical scanning period by the number of rows of the screen is called a horizontal scanning period. For example, during the horizontal scanning period, a voltage value for power control of the pixels 12 arranged in the row direction (X-axis direction) is set, and a voltage value for simulating image data is set. In addition, during the vertical scanning period, the scanning unit 20 that scans the pixels 12 is sequentially shifted in the column direction (Y-axis direction). Figure 1 The light-emitting device 100 adopts an active matrix driving method as the lighting driving method for lighting each pixel 12.

[0067] In addition, each pixel 12 is constituted by one light-emitting element 11. In Figure 1 the example shown, the pixel 12 is constituted by one light-emitting element 11. However, the present disclosure is not limited to this structure, and one pixel may also be constituted by a plurality of light-emitting elements. By using a plurality of light-emitting elements, the light emission luminance per pixel can be increased.

[0068] The light-emitting element 11 can control the emission color according to its driving current. Such a light-emitting element 11 can suitably utilize a multi-color light-emitting type light-emission wavelength variable LED. The emission color of the light-emitting element 11 is, for example, variable from green light to red light.

[0069] (Lighting control unit 50)

[0070] The lighting control unit 50 supplies driving currents to the plurality of light-emitting elements 11 respectively and controls the lighting period. In Figure 1 the example shown in the enlarged view, the lighting control unit 50 is connected to a power supply line 9 extending in the horizontal direction and a write scanning line WS. The lighting control unit 50 is driven by receiving power supply from the power supply line 9, and is scanned by the write scanning line WS and receives a power control signal or an analog image signal. On the other hand, the lighting control unit 50 is also connected to a signal line SL extending in the vertical direction, and receives a power control signal or an analog image signal via the signal line SL.

[0071] The lighting control unit 50 drives by dividing one frame for causing a plurality of light emitting elements 11 to emit light into a first sub-frame in which the plurality of light emitting elements 11 emit light in a first emission color respectively and a second sub-frame in which the plurality of light emitting elements 11 emit light in a second emission color respectively. For example, the first sub-frame is set as a B sub-frame that emits blue light, and the second sub-frame is set as an RG sub-frame that emits light from green light to red light.

[0072] In this way, the second emission color of the second sub-frame is set to light emission at a variable wavelength, while the first emission color of the first sub-frame is set to light emission at a fixed wavelength, and lighting control is performed on the light emitting element 11. Thereby, the light emitting device 100 capable of varying the emission color can be efficiently driven. In particular, even if the light emitting element 11 capable of emitting different emission colors according to the drive current is not subjected to emission control over the entire range of RGB, by limiting the emission control to be variable only in a limited wavelength region such as from green light to red light, full-color emission for each pixel can be performed in combination with the first emission color based on the fixed wavelength, and simpler emission control can be achieved. In addition, even if three sub-fields of RGB are not used as in a generally known display, full-color image display can be achieved, so that pixels can be driven more simply with lower power consumption.

[0073] In a multi-color light emitting type LED in which the emission wavelength is variable, the emission color changes according to the drive current. In other words, the amount of drive current at this time varies greatly depending on the emission color, and the emission luminance also varies greatly. For example, when it is desired to appropriately adjust the luminance and emission color using a multi-color light emitting type LED element to display short wavelength light and long wavelength light on one display, it is necessary to control the emission period in a range of about 3 to 30 times according to the emission wavelength. Therefore, in order to reduce the useless non-emission period and obtain sufficient emission luminance, it is preferable to adopt field sequential drive in which each emission color is lit in a different sub-frame.

[0074] However, if field sequential drive in which the emission color is changed for each sub-frame is performed, color breakup occurs particularly in animations, and there is a problem that the image quality deteriorates significantly. That is, in the case of field sequential drive, since the pixels are active matrix, after writing display data to the row selected by scanning, it is necessary to ensure a certain emission time. Therefore, the scanning period and the emission period of each row are defined independently. Therefore, in the field sequence, emission is not in units of rows but in units of sub-fields, but as a side effect, there is a problem of color breakup.

[0075] On the other hand, in the light emitting device 100 of Embodiment 1, color breakup is suppressed by using only blue light with low human visual sensitivity as the other sub-frame. Details will be described below.

[0076] (Light emitting element 11)

[0077] The light-emitting element 11 can preferably use semiconductor light-emitting elements such as light-emitting diodes (LEDs) or semiconductor lasers (LDs). As the LED, an LED configured with one or more semiconductor laminate bodies having a light-emitting portion (hereinafter, also simply referred to as "semiconductor laminate body") can be used. The semiconductor laminate body has light-emitting characteristics. Such a semiconductor laminate body uses a structure in which multiple semiconductor layers such as ZnS, SiC, GaN, GaP, InN, AlN, ZnSe, GaAsP, GaAlAs, InGaN, GaAlN, AlInGaP, and AlInGaN are laminated on a substrate by a liquid-phase growth method, an HVPE method, or an MOCVD method, and an active layer is formed on any one of the semiconductor layers. By selecting the material of the semiconductor layer and its mixed crystal ratio, the emission wavelength from the active layer can be variously selected from ultraviolet light to infrared light. In particular, when a display device that can be appropriately used outdoors is provided, a semiconductor laminate body that can emit light with high brightness is required. Therefore, a nitride semiconductor is preferably selected as the material of the light-emitting portion that emits light with high brightness. For example, as the material of the light-emitting portion, In X Al Y Ga 1-X-Y N (0 ≤ X ≤ 1, 0 ≤ Y ≤ 1, X + Y ≤ 1), etc.

[0078] In Embodiment 1, as each light-emitting element 11, semiconductor light-emitting elements such as light-emitting diodes or semiconductor lasers are used. In addition, a micro LED can also be used as the light-emitting diode. Considering the chip size of 5 μm to 100 μm, luminous efficiency, etc., the micro LED is preferably 10 μm to 50 μm.

[0079] The light-emitting element 11 varies its emission color. The light-emitting element 11 emits different emission colors according to the drive current. For example, if it is driven with a first drive current, it emits light with a first emission wavelength, for example, red. If it is driven with a second drive current larger than the first drive current, it emits light with a second emission wavelength shorter than the first emission wavelength, for example, green. If it is driven with a third drive current larger than the second drive current, it emits light with a third emission wavelength shorter than the second emission wavelength, for example, blue.

[0080] By making the light-emitting element 11 a variable-wavelength type in this way, the wavelengths of each emission color such as blue light can also be adjusted. Generally, a deviation in the emission wavelength is observed among the manufactured blue light-emitting elements. However, for example, the deviation in the emission wavelength of the light-emitting element can be corrected between pixels so that the wavelengths of blue light and the like of each pixel are the same.

[0081] Each light-emitting element 11 is connected to a plurality of common lines and a plurality of drive lines. By connecting each light-emitting element 11 to one of the plurality of common lines and one of the plurality of drive lines and arranging them in a row-and-column configuration, the display unit 10 is constituted.

[0082] (Scanning unit 20)

[0083] The scanning unit 20 is provided in a column further to the left of the leftmost column of the pixels 12 arranged in a matrix. The scanning unit 20 may also be provided in a column further to the right of the rightmost column of the pixels 12 arranged in a matrix. In addition, as Figure 4 shown, the power control signal writing scan line WS1 and the analog image signal writing scan line WS2 are provided from the scanning unit 20 as the writing scan line WS for each row of pixels. The power control signal writing scan line WS1 and the analog image signal writing scan line WS2 extend in the row direction.

[0084] The power control signal writing scan line WS1 supplies a first scan signal according to the power control signal, and this first scan signal is a digital signal that selects the pixel circuit 14 ( Figure 1 the lighting control unit 50 + the light emitting element 11) in the row direction when writing a desired voltage value. The analog image signal writing scan line WS2 supplies a digital signal, that is, a second scan signal, for selecting the pixel circuit 14 in the row direction when writing a voltage value during the light emitting period determined by the light emitting gray scale through the analog image signal.

[0085] (Driver unit 30)

[0086] As Figure 4 shown, for each pixel column, the driver unit 30 extends the power control signal line SL1 and the analog image signal line SL2 vertically as the signal line SL. The driver unit 30 supplies a power control signal to each pixel circuit 14 via the power control signal line SL1. The power control signal is an analog signal capable of obtaining multiple voltage values. The driver unit 30 supplies an analog image signal to each pixel circuit 14 via the analog image signal line SL2. The analog image signal is also an analog signal capable of obtaining multiple voltage values. Each pixel circuit 14 supplied with the power control signal and written with a voltage value sets a drive current based on the written voltage value. Each pixel circuit 14 supplied with the analog image signal and written with a voltage value sets a threshold voltage for comparison with a reference triangular wave signal based on the voltage value of the analog image signal, and sets the time width during which the pixel circuit 14 emits light. During the light emitting period, a reference triangular wave signal (not shown) is supplied to the pixel circuit 14, and the light emitting element 11 of each pixel circuit 14 emits light during the on period based on the voltage of the written analog image signal. In addition, the drive current value when the light emitting element 11 emits light is set according to the power control signal voltage (for details, refer to and cite U.S. Patent No. 10885834).

[0087] In addition, the driving unit 30 can also generate a reference triangular wave signal supplied to each pixel circuit 14 column by column. Alternatively, this reference triangular wave signal can be additionally provided as a reference triangular wave circuit in a row further below the lowermost row of the matrix of the pixel circuits 14. The driving unit 30 or the reference triangular wave circuit distributes, for example, the reference triangular wave supplied from the outside of these circuits to the columns of each pixel circuit 14.

[0088] The driving unit 30 can also include a storage unit. In the storage unit, it is possible to store the luminance settings for multiple voltage values taken for the power control signal and the luminance settings for multiple voltage values taken for the analog image signal. The relationship between these voltage values and the luminance settings can be adjusted and set by visually confirming the luminance of the light-emitting element 11 constituting the pixel circuit 14, etc. By appropriately setting the relationship between the voltage values and the luminance settings, gamma correction can be performed. One of the advantages of this method is that in the digital PWM method, the gray-scale characteristics are linear, whereas gamma correction can be applied to the signal. The storage unit is formed, for example, by an electrically rewritable storage circuit or the like.

[0089] (Information holding unit 70)

[0090] As described above, the light-emitting element 11 is a multi-color light-emitting type light-emitting wavelength variable LED, and its emission color changes according to the drive current. Therefore, it is necessary to determine the drive current value for driving the light-emitting element 11 according to the emission color in which the light-emitting element 11 is desired to emit light. Therefore, the current-chromaticity information indicating the correspondence between the emission color in which the light-emitting element 11 emits light and the current value for emitting the light of that color is held in the information holding unit 70. The drive control unit 60 determines the drive current of the light-emitting element 11 corresponding to the emission color with reference to the information held in the information holding unit 70. The information holding unit 70 can include storage elements such as a current-chromaticity data memory for holding, for example, the current-chromaticity data of the light-emitting element 11.

[0091] In addition, the information holding unit 70 can hold, in addition to the current-chromaticity information based on the measured values of the respective light-emitting elements 11 arranged in the display unit 10, the current-chromaticity information generated by measuring the drive current and emission color of a light-emitting element equivalent to each light-emitting element arranged in the display unit. Alternatively, the information holding unit 70 can statistically determine the relationship between the drive current and emission color of the light-emitting element and hold the recorded current-chromaticity information. In the Figure 1 example, the information holding unit 70 has a (G-R) emission chromaticity-drive current characteristic table-luminance characteristic table. Here, (G-R) refers to the wavelength region from green light to red light.

[0092] (Drive control unit 60)

[0093] In addition, the drive control unit 60 controls the operations of these scanning units 20 and drive units 30. Further, the scanning unit 20 and the drive unit 30 control the lighting control units 50 of the respective pixels. As Figure 3 shown, each lighting control unit 50 can include a first control circuit 51 and a second control circuit 52. The first control circuit 51 supplies drive current to the light-emitting elements 11 respectively. In addition, the second control circuit 52 controls the light-emitting periods of the light-emitting elements 11 respectively. Sometimes, the structure in which the light-emitting elements 11 are connected to the lighting control unit 50 is referred to as a "pixel circuit 14". The first control circuit 51 is connected between the power supply line 9 and the second control circuit 52.

[0094] The drive control unit 60 controls the drive unit 30 to supply drive current to the respective light-emitting elements 11 so that the light-emitting elements 11 emit light with respective specified light-emitting colors and light-emitting brightnesses. Specifically, the drive control unit 60 determines the drive current value for driving each light-emitting element 11 and the on-period for each light-emitting element 11 to emit light, referring to the current-chromaticity information held in the information holding unit 70, based on the specified light-emitting color and gradation information of each light-emitting element 11, and performs lighting drive on each light-emitting element 11 with the drive current from the lighting control unit 50.

[0095] In addition, the drive control unit 60 performs gradation control of the light-emitting brightness. For example, based on the specified light-emitting color of each of the light-emitting elements 11, referring to the current-chromaticity information, the drive current value of each light-emitting element 11 is determined, and based on the determined drive current value and the specified gradation information of each of the light-emitting elements 11, the on-period of each light-emitting element 11 is determined.

[0096] The drive control unit 60 may include a storage unit. In the storage unit, it is possible to store the brightness settings for a plurality of voltage values taken for the power supply control signal and the brightness settings for a plurality of voltage values taken for the analog image signal. The relationship between these voltage values and the brightness settings can be adjusted and set by visually confirming the brightness of the light-emitting elements constituting the pixel circuit 14, etc. By appropriately setting the relationship between the voltage values and the brightness settings, γ correction can be performed. One of the advantages of this method is that in the digital PWM method, the gradation characteristics are linear, whereas γ correction can be applied to the signal. The storage unit is formed of, for example, an electrically rewritable storage circuit or the like.

[0097] In addition, the drive control unit 60 can also perform lighting control on the light-emitting elements 11 simultaneously by the drive unit 30 in a state where the on-period information of one frame amount of each light-emitting element 11 constituting the display unit 10 is written in the storage unit.

[0098] The drive control unit 60 determines the drive current value for driving each light-emitting element 11 and the light-emitting period for causing each light-emitting element 11 to emit light, based on the light-emitting color and gradation information of each light-emitting element 11 provided from the outside, and also referring to the current-chromaticity information held in the information holding unit 70. Further, the drive control unit 60 drives and controls each light-emitting element 11 to be lit by the lighting control unit 50 via the drive unit 30. With such a configuration, lighting control of the display unit 10 constituted by the multi-color light-emitting type light-emitting elements 11 can be achieved.

[0099] Regarding the light-emitting color of the light-emitting element 11, if the drive current values for emitting the respective light-emitting colors, for example, red (R), green (G), and blue (B) lights, are set as IR, IG, and IB, respectively, the magnitudes of the drive current values are IR < IG < IB. Therefore, if the light-emitting periods of the maximum gradation of each color are set as TR, TG, and TB, the relationship of the lengths of the maximum light-emitting periods of each color during white display corresponding to full lighting is TR > TG > TB.

[0100] In addition, by allocating the light-emitting color for causing the light-emitting element 11 to emit light for each sub-frame, it is also possible to solve the problem of color breakup that occurs during field sequential drive in which the light-emitting color is changed for each sub-frame. That is, by dividing one frame into two sub-frames, the light-emitting color is allocated for each sub-frame such that the light-emitting element 11 emits light of a first light-emitting color in the first sub-frame and emits light of a second light-emitting color in the second sub-frame. Here, consider setting the first light-emitting color as blue light, setting the second light-emitting color as any color from green to red, setting the first sub-frame as the B sub-frame, setting the second sub-frame as the GR sub-frame in which (G - R) is variable, and driving by dividing one frame into two. Since the temporal resolution of the human eye is low for blue light, even if blue light is allocated to other sub-frames and field sequential drive is performed, it is difficult to recognize color breakup. As a result, the occurrence of color breakup can be avoided, and while using multi-color light-emitting type LEDs, useless non-lighting periods can be reduced, and sufficient light-emitting luminance can be obtained.

[0101] Therefore, in the light-emitting device 100 of the first embodiment, the same multi-color light-emitting type light-emitting elements 11 are used, blue light as the first light-emitting color is emitted in the first sub-frame, and any color light from red to green (G - R) as the second light-emitting color is emitted in the second sub-frame. Thereby, color breakup does not occur, and full-color light emission can be achieved. PWM can be used for gradation control of each light-emitting color. Here, the product of the maximum light-emitting period and the drive current value based on PWM drive is R > G > B. This is because the light-emitting luminance efficiency of the light-emitting element 11 increases in the order of R < G < B.

[0102] In this way, by using the same light-emitting element 11 to emit light in the first light-emitting color and the second light-emitting color, full-color light emission can be achieved. According to this structure, compared with the structure in which light-emitting elements of different light-emitting colors are respectively arranged for each pixel, the structure can be simplified and the power consumption can be reduced. This is because, in order to use a single light-emitting element in each pixel, an LED element with a larger chip size can be used. However, when the chip size of the LED element is large, the ratio of the recombination current generated at the end face of the light-emitting layer decreases, so the light-emitting efficiency is improved.

[0103] In addition, in the above description, on the premise of full-color light emission, it is described that the light-emitting color of the light-emitting element 11 can be variable over the entire range of R, G, and B. However, the present disclosure is not limited to a light-emitting device that performs full-color light emission. For example, it can also be applied to a light-emitting device that emits light within a range of two colors, green light and blue light, or two colors, red light and green light. In this case, by manufacturing the light-emitting element according to the required light-emitting color, for example, by manufacturing the light-emitting element in such a way that the light-emitting color of the light-emitting element is only variable in the range from R to G, advantages such as simplification of the manufacturing process and cost reduction can be obtained. For example, the manufacturing process margin of the light-emitting element can be further expanded.

[0104] (Timing diagram)

[0105] Figure 2 Shows a timing diagram Figure 1 indicating the lighting timings of the respective RGB colors of the light-emitting device 100. Here, one frame period FT is divided into a first sub-frame period SF1 in which the light-emitting element 11 emits light in the first light-emitting color and a second sub-frame period SF2 in which the light-emitting element 11 emits light in the second light-emitting color. The first sub-frame period SF1 becomes the B sub-frame that emits blue light, and the second sub-frame period SF2 becomes the GR sub-frame that emits any one color light from green light to red light. In the B sub-frame, a current value corresponding to blue light, for example, a light-emitting color equivalent to 470 nm, is applied to the light-emitting element 11. In addition, in the GR sub-frame, since the light can be changed from green light to red light, the light-emitting element 11 is energized within the range from a current value corresponding to green light, for example, a light-emitting color equivalent to 515 nm, to a current value corresponding to red light, for example, a light-emitting color equivalent to 630 nm. That is, in the B sub-frame, a current value that causes the light-emitting element 11 to emit blue light is applied, and in the GR sub-frame, a drive current corresponding to any one color from green light to red light is applied. In this way, in each sub-frame, Figure 2 the light-emitting color is controlled with the vertical axis (drive current) of

[0106] In addition, in each sub-frame, the emission luminance is controlled by PWM control. By changing the ON time ONT within the maximum emission period LTmax, the current value can be energized at the maximum value, and the cumulative current value can be changed to adjust the luminance to the desired value. Here, the maximum emission period of blue light is set as LTmaxB, and the ON time is set as ONTB. On the other hand, within the maximum emission period of green light to red light, the maximum emission period of green light is set as LTmaxG, and the maximum emission period of red light is set as LTmaxR. In addition, the ON time ONT is included within the maximum emission period. Actually, as shown by the diagonal line in Figure 2 , the drive current value (vertical axis) is determined according to the required emission color, and the horizontal axis is determined according to the luminance. In this way, together with the B sub-frame and the (G-R) sub-frame, luminance control is performed on the Figure 2 horizontal axis (ON time).

[0107] In addition, a pixel signal writing period is set in each sub-frame, and PWM control is performed after the pixel signal writing period. During the pixel signal writing period, the pixel signals of one screen amount of the light-emitting element 11 are written into the pixel memory. The drive unit 30 refers to the pixel signals written into the pixel memory and controls the lighting of the light-emitting element 11. The pixel memory is provided in the lighting control unit 50 of the pixel circuit 14.

[0108] As Figure 3 shown, the lighting control unit 50 includes a first control circuit 51 and a second control circuit 52. The first control circuit 51 drives the current according to the emission color. In addition, the second control circuit 52 performs PWM control. Specifically, when performing PWM control, the second control circuit 52 sets the time width of the current supplied to the light-emitting element 11 based on the result of comparing the first signal including the triangular wave signal and the first DC voltage set during a specified period. In addition, the first control circuit 51 controls the current value supplied to the lighting control unit 50 based on the second DC voltage set during a period different from the specified period.

[0109] In addition, as Figure 4 shown, the power supply control signal writing scan line WS1 and the analog image signal writing scan line WS2 extend from the scan unit 20 and are connected to each pixel 12. In addition, the power supply control signal line SL1 and the analog image signal line SL2 extend from the drive unit 30 and are connected to each pixel 12. The drive unit 30 is a driver IC that processes the power supply control signal and the analog image signal. The power supply control signal writing scan line WS1 and the analog image signal writing scan line WS2 are connected to the TFT circuit provided on the mounting substrate together with the pixel circuit 14. The TFT is composed of low-temperature polycrystalline silicon or oxide semiconductor.

[0110] As Figure 4As shown in the enlarged view of the main part, each pixel 12 includes a lighting control unit 50 and a light-emitting element 11. Each pixel circuit 14 includes a lighting control unit 50. The lighting control unit 50 includes a first control circuit 51 and a second control circuit 52. The first control circuit 51 supplies a drive current to the light-emitting element 11. On the other hand, the second control circuit 52 controls the light-emitting period of the light-emitting element 11. Here, the first control circuit 51 is constituted by a power supply control circuit, and the second control circuit 52 is constituted by an analog image PWM circuit. The first control circuit (power supply control circuit) 51 is connected to the power line 9 and the power supply control signal line SL1. In addition, a power supply control signal write timing is input from the power supply control signal write scan line WS1. On the other hand, the second control circuit (analog image PWM circuit) 52 is connected in series with the power line 9 via the first control circuit 51. In addition, the second control circuit 52 is also connected to the analog image signal line SL2. In addition, an analog image signal write timing is input from the analog image signal write scan line WS2. In this way, the light-emitting element 11 is connected to the power line 9 via the power supply control circuit and the analog image PWM circuit respectively. Moreover, the drive current value is controlled by the power supply control circuit, and the drive time is controlled by the analog image PWM circuit.

[0111] In addition, in Figure 4 the example, an example in which each pixel 12 is constituted by one LED is shown, but the present disclosure is not limited to this structure, and each pixel may be constituted by a plurality of light-emitting elements such as LEDs. For example, in the case of using a plurality of light-emitting elements for the purpose of increasing the brightness or the like, two or more light-emitting elements may be connected in parallel or in series.

[0112] (LED)

[0113] Figure 5 FIG. shows an example of the element structure in the case where an LED is used as the light-emitting element 11. The light-emitting element 11 shown in the figure includes an n-type semiconductor layer 2, an active layer 3, a p-type semiconductor layer 4, an n-side electrode 5, and a p-side electrode 6. The active layer 3 can use a multi-quantum well structure (MQW) or the like. The light-emitting element 11 is connected to a pixel drive circuit 8 such as a DC power supply, and receives the supply of a drive current from the power line 9 to emit light. The light-emitting element 11 controls the emission color by the drive current, and controls the light-emitting period under the obtained current. The emission color can be changed to any color from green light to red light.

[0114] In addition, the light-emitting element may also have a first light-emitting portion that emits light of a first light-emitting color and a second light-emitting portion that emits light of a second light-emitting color, and the light emission of the first light-emitting portion and the second light-emitting portion can be selected by a switch. By adopting such a structure, even if the light-emitting element that can emit light of different colors according to the drive current is not subjected to light emission control over the entire RGB range region, but is limited to light emission control that is variable only in a limited wavelength region such as from green light to red light, a simpler light emission control can be achieved. For example, the first light-emitting portion can be set as a B light-emitting layer that emits blue light, and the second light-emitting portion can be set as an RG light-emitting layer that emits any one color of light from red light to green light. Thus, by combining the blue light of the B light-emitting layer with the RG light-emitting layer, full-color light emission for each pixel can be achieved.

[0115] Figure 6 An example of such a light-emitting element is shown. The light-emitting element 11B shown in this figure includes a first n-type semiconductor layer 2A, a first light-emitting layer 3A, a first p-type semiconductor layer 4A, an ohmic contact layer 7, a second n-type semiconductor layer 2B, a second light-emitting layer 3B, a second p-type semiconductor layer 4B, an n-side electrode 5, a first p-side electrode 6A, and a second p-side electrode 6B. The first light-emitting layer 3A and the second light-emitting layer 3B can use an active layer such as a multiple quantum well structure (MQW). In the ohmic contact layer 7, an intermediate layer that realizes an ohmic contact between the first p-type semiconductor layer 4A and the second n-type semiconductor layer 2B can be used. In addition, Figure 6 An example of using the first p-side electrode 6A is shown, but the second n-type semiconductor layer 2B can be used as the n-side electrode instead of the first p-type semiconductor layer 4A. Generally, compared with the first p-type semiconductor layer 4A having a high resistance value, the second n-type semiconductor layer 2B having a low resistance value is easier to form thick, so in these cases, it has the advantage of being easy to improve the processing yield when forming the chip electrode.

[0116] The light-emitting element 11B is connected to a pixel driving circuit 8B such as a lighting control unit 50, and receives the supply of a drive current from a power supply line 9B to emit light. The light-emitting element 11B controls the light-emitting color through the drive current, and controls the light-emitting period in this drive current. In Figure 6 this example, the first light-emitting color of the first light-emitting layer 3A is set as blue light, and the second light-emitting color of the second light-emitting layer 3B can be changed to any one color from red light to green light.

[0117] Such a tandem structure formed by stacking the first light-emitting layer 3A and the second light-emitting layer 3B can be formed on the same growth substrate through a continuous epitaxial growth process. For example, as the growth substrate, GaN crystals constituting the semiconductor layer are formed on a wafer of a sapphire substrate. First, the first light-emitting layer 3A is epitaxially grown, and then the second light-emitting layer 3B is grown. Here, by forming the first light-emitting layer 3A that emits blue light before the second light-emitting layer 3B, the advantage of being less likely to generate defects in the GaN crystals can be obtained. Then, it is processed into the shape of an LED element, and the n-side electrode 5, the first p-side electrode 6A, and the second p-side electrode 6B are formed. Furthermore, the sapphire substrate is peeled off and divided into individual elements. In addition, by roughening the light-emitting surface side of the first n-type semiconductor layer 2A, the light extraction efficiency can also be improved. In this way, a light-emitting element 11B having a tandem structure formed by stacking the first light-emitting layer 3A and the second light-emitting layer 3B can be obtained. Without setting the control of the emission color of the light-emitting layer to the entire RGB range, but limiting it to a specific wavelength range from green light to red light, the light emission control can be simplified.

[0118] In addition, the first light-emitting layer 3A and the second light-emitting layer 3B can also be connected in series. In addition, the first switch SW1 and the second switch SW2 can also be provided at the intermediate point where the first light-emitting layer 3A and the second light-emitting layer 3B are connected in series. The first switch SW1 is connected in parallel with the first light-emitting layer 3A. In addition, the second switch SW2 is connected in parallel with the second light-emitting layer 3B.

[0119] When the light-emitting element 11B emits light from the first light-emitting layer 3A, the first switch SW1 is turned off and the second switch SW2 is turned on. On the other hand, when the second light-emitting layer 3B emits light, the first switch SW1 is turned on and the second switch SW2 is turned off. In addition, either the first light-emitting layer 3A or the second light-emitting layer 3B can be lit first. That is, the blue light of the first light-emitting layer 3A can be lit first in the first sub-frame, and the red light to green light of the second light-emitting layer 3B can be emitted in the subsequent second sub-frame. However, if the red light to green light of the second light-emitting layer 3B is lit first, it is difficult for the human eye to recognize the delay of the blue light, so the advantage of reducing the image delay with respect to the input signal is obtained.

[0120] (B sub-frame)

[0121] Figure 7 Shows the lighting image in the B sub-frame of the display unit 10 using such a structure, Figure 8 Shows the lighting image in the GR sub-frame. In these figures, each pixel 12 is represented as a brick shape. In the B sub-frame, the brightness is different between the pixels 12, but the chromaticity is constant. The brightness gray scale is controlled by PWM. Figure 7 The difference in the concentration of each pixel 12 of represents the difference in the average brightness within the sub-frame.

[0122] (GR sub-frame)

[0123] On the other hand, in the GR sub-frame, both the luminance and chrominance are variable between pixels 12. In the (G-R) sub-frame, the range control of (G-R) controls the current value supplied to the light-emitting element 11 and the second emission color, i.e., chrominance. Specifically, in each pixel 12, the lighting control unit 50 acquires the chrominance of RGB with reference to the information holding unit 70. Here, when the first emission color emitted by the light-emitting element 11 is fixed-wavelength emission, the drive current value is uniquely determined. On the other hand, it is necessary to determine the second emission color for the variable-wavelength emission of the light-emitting element 11. Here, first, according to the chrominance signal to be displayed, the emission color when the (G-R) wavelength is variable and the luminance ratio of B:(G-R) are determined in a manner corresponding to the color when B emits light. Then, based on the chrominance and luminance ratio of the emission color, the emission intensity corresponding to the luminance signal to be displayed is determined.

[0124] (Drive method of the light-emitting device)

[0125] Here, an example of the drive method of the light-emitting device will be described. Here, the process of the lighting control unit 50 dividing one frame in which the light-emitting element 11 emits light into a first sub-frame and a second sub-frame and driving them will be described. In the first sub-frame, a plurality of first light-emitting elements 11A emit light in the first emission color respectively. Here, since blue light is emitted as the first emission color in the first sub-frame, it is called the B sub-frame. In addition, in the second sub-frame, a plurality of light-emitting elements 11 emit light in the second emission color respectively. Here, since light is emitted in the range from red light to green light in the second sub-frame, it is called the RG sub-frame.

[0126] The lighting control unit 50 supplies drive current to each light-emitting element 11 through the first control circuit 51, and controls the light-emitting period of each light-emitting element 11 by the second control circuit 52. The process of the lighting control unit 50 driving the light-emitting element 11 includes the following processes: determining the chrominance of the second emission color, the luminance ratio of the light-emitting element 11 emitting light in the first emission color to the light-emitting element 11 emitting light in the second emission color, in a manner corresponding to the first emission color according to the chrominance signal and luminance signal to be displayed by each pixel 12; determining the emission intensity corresponding to the luminance signal to be displayed by the light-emitting element 11 based on the chrominance and luminance ratio of the second emission color; the first control circuit 51 supplying a drive current value corresponding to each emission color to each light-emitting element 11 with reference to the information holding unit 70; and the second control circuit 52 controlling the light-emitting period of the drive current value supplied to each light-emitting element 11 through the first control circuit 51 according to the determined emission intensity.

[0127] In addition, in the first sub-frame, the first control circuit 51 controls the driving current of the plurality of light-emitting elements 11 that emit the first light-emitting color to be constant, and the second control circuit 52 controls the light-emitting intensity by PWM control. Here, the driving current of the light-emitting element 11 is set to a driving current value with good blue light-emitting efficiency. For example, it is set to the rated current value.

[0128] On the other hand, in the second sub-frame, the first control circuit 51 controls the light-emitting color according to the current value of the current driving the plurality of light-emitting elements 11. In addition, the second control circuit 52 controls the brightness by controlling the light-emitting period of the current value of the plurality of light-emitting elements 11 controlled by the first control circuit 51. Specifically, according to the chrominance signal and the luminance signal to be displayed by each pixel 12, the chrominance of the second light-emitting color is determined in a manner corresponding to the first light-emitting color, and the luminance ratio between the light-emitting element 11 that emits light in the first light-emitting color and the light-emitting element 11 that emits light in the second light-emitting color is determined. Then, based on the chrominance and the luminance ratio of the second light-emitting color, the light-emitting intensity corresponding to the luminance signal to be displayed by the light-emitting element 11 that emits light in the second light-emitting color is determined. Correspondingly, the first control circuit 51 refers to the information holding unit 70 and supplies the driving current value corresponding to each light-emitting color to each light-emitting element 11. In addition, the second control circuit 52 controls the light-emitting period of the light-emitting element 11 according to the determined light-emitting intensity.

[0129] (Method for determining the driving current value and the PWM light-emitting period)

[0130] Here, based on Figure 9 the functional block diagram of Figure 10 and the chromaticity diagram of

[0131] Figure 10 Figure 10The point A on the chromaticity diagram represents an arbitrary emission chromaticity of the desired light emission. In this chromaticity diagram, the light-emitting element 11 emits blue light as the first emission color, so it is fixed at point B near the lower left vertex of the chromaticity diagram. On the other hand, the same light-emitting element 11 emits any color light between green light and red light as the second emission color in other sub-frames different from the first emission color. Therefore, if it is represented on the chromaticity diagram, it becomes any position between green near the upper vertex of the chromaticity diagram and red near the right vertex, point C. Therefore, the chromaticity of point A represented by the mixed color light of the light-emitting element 11 emitting light in the first emission color and the light-emitting element 11 emitting light in the second emission color can be represented by point B and point C. In other words, in order to represent the chromaticity of point A, the second emission color of the light-emitting element 11 is adjusted in such a way as to adjust point C. Furthermore, considering the balance of the brightness of the light-emitting element 11 emitting light in the first emission color and the light-emitting element 11B emitting light in the second emission color, the brightness ratio of B:(G-R) is determined for a specified point A. Thus, the drive current value and the light emission period of the light-emitting element 11 emitting light in the second emission color at point C are determined.

[0132] Based on the above considerations, first, if the emission chromaticity (B) of B is considered according to the emission chromaticity (A) of A determined in step S902 (step S903), then the emission chromaticity (C) of (G-R) and the brightness ratio of B:(G-R) are determined (step S904). When determining the brightness ratio of B:(G-R) in step S904, the brightness of (G-R) and the brightness of B are necessarily obtained according to the brightness of the emission chromaticity (A) in step S902 (step S908).

[0133] On the other hand, when determining the emission chromaticity (C) of (G-R) in step S904, the drive current value of (G-R) is determined by referring to the emission chromaticity-drive current characteristic table of (G-R) held by the information holding unit 70 (step S905) (step S906).

[0134] Furthermore, when the drive current value of (G-R) is determined in step S906, referring to the emission chromaticity-drive current-brightness characteristic table of (G-R) held by the information holding unit 70 (step S907) and the brightness of (G-R) (step S908), the PWM light emission period of (G-R) is determined (step S909).

[0135] On the other hand, based on the luminance of B obtained in step S908, with reference to the luminance characteristic value of the drive current value corresponding to the chromaticity of B (step S910), the PWM emission period of B is determined (step S911). In this way, the drive current values of each of the light-emitting elements 11 that emit light in the second light-emitting color, the PWM emission periods of the light-emitting elements 11 that emit light in the first light-emitting color and the light-emitting elements 11 that emit light in the second light-emitting color are respectively determined. In addition, the drive current value of the light-emitting element 11 that emits light in the first light-emitting color is a drive current value with good blue light emission efficiency, such as a rated current value, or the maximum value of the drive current value that causes the light-emitting element to emit blue light.

[0136] In the light-emitting device 100 of the above-described Embodiment 1, a light-emitting element 11 is provided for each pixel 12. However, a plurality of light-emitting elements may also be provided for each pixel. Thereby, the emission luminance can be increased.

[0137] In addition, in Embodiment 1, one frame period FT is divided into a first sub-frame period SF1 in which the light-emitting element 11 emits light in the first light-emitting color and a second sub-frame period SF2 in which the light-emitting element 11 emits light in the second light-emitting color. The first sub-frame period SF1 is set as a B sub-frame that emits blue light, and the second sub-frame period SF2 is set as a GR sub-frame that emits any one color light from green light to red light. Figure 2 illustrates a case where the first sub-frame period SF1 is before the second sub-frame period SF2. However, the present disclosure is not limited to this structure. For example, it is also possible to make the second sub-frame, which is a GR sub-frame that emits any one color light from green light to red light, precede the first sub-frame, which is a B sub-frame that emits blue light. As described above, the human visual sensitivity perceives luminance in the GR sub-frame, and synthesizes the GR sub-frame and the B sub-frame to perceive color, but has a time resolution that is the timing for perceiving luminance. Therefore, by making the GR sub-frame precede, it is possible to obtain an effect of suppressing the delay of the human perception timing with respect to the video display data input to the display system. In addition, in this case, the preceding GR sub-frame may also be renamed as the first sub-frame, and the B sub-frame may be renamed as the second sub-frame.

[0138] In addition, in the above examples, the active matrix driving method has been described, but the present disclosure can also be applied to the passive matrix driving method.

[0139] Industrial Applicability

[0140] The light-emitting device of the present disclosure can be suitably used for, for example, medium-sized and large-sized displays, indicators, signs, etc.

Claims

1. A light-emitting device, comprising: a display unit, which arranges a plurality of light-emitting elements whose light-emitting colors can be controlled according to a driving current into a predetermined pattern to form a plurality of pixels; a lighting control unit, which supplies a driving current to the light-emitting elements to control a light-emitting period, wherein: The lighting control unit drives the plurality of light emitting elements so as to divide one frame in which the plurality of light emitting elements emit light into a first subframe in which the plurality of light emitting elements emit light in a first light color and a second subframe in which the plurality of light emitting elements emit light in a second light color different from the first light color.

2. The light emitting device according to claim 1, wherein: The device further comprises an information storage unit, the information storage unit storing current-chromaticity information, the current-chromaticity information being used to determine a driving current value for causing the plurality of light-emitting elements to emit light in the first light-emitting color or the second light-emitting color according to a predetermined light-emitting color, The lighting control unit controls the plurality of light emitting elements so that each of the plurality of light emitting elements emits light at a predetermined light color and light brightness based on the current-chromaticity information held by the information holding unit.

3. The light emitting device according to claim 1 or 2, wherein: The lighting control unit includes a first control circuit that supplies a driving current to the light emitting element, and a second control circuit that controls a light emitting period of the light emitting element.

4. The light emitting device according to claim 3, wherein: At least one of the first control circuit and the second control circuit is provided for each pixel.

5. The light emitting device according to any one of claims 1 to 4, wherein: Either the first luminescent color or the second luminescent color is blue light.

6. The light emitting device according to any one of claims 1 to 4, wherein: Either the first emission color or the second emission color can be changed between green light and red light according to a driving current.

7. The light emitting device according to any one of claims 1 to 6, wherein: The light emitting element includes a first light emitting portion that emits light of the first light emitting color and a second light emitting portion that emits light of the second light emitting color, and light emission of the first light emitting portion and the second light emitting portion can be selected by a switch.

8. The light emitting device according to claim 7, wherein: The first light emitting portion and the second light emitting portion are connected in series.

9. The light emitting device according to claim 8, wherein: A first switch connected in parallel with the first light emitting unit and a second switch connected in parallel with the second light emitting unit are further provided at an intermediate point where the first light emitting unit and the second light emitting unit are connected in series.

10. The light emitting device according to claim 2, wherein: The lighting control unit further includes: a first control circuit that supplies a driving current to the light emitting element; a second control circuit that controls a light emitting period of the light emitting element; In the second subframe, the chromaticity of the second luminous color and the brightness ratio of the brightness of the light-emitting element emitting the first luminous color to the brightness of the light-emitting element emitting the second luminous color are determined in a manner corresponding to the first luminous color based on the chromaticity signal and the brightness signal to be displayed by each pixel. determining the light emission intensity corresponding to the brightness signal to be displayed by the light emitting element based on the chromaticity of the second light emission color and the brightness ratio, The first control circuit refers to the information storage unit to supply a driving current value corresponding to the light emitting color to the light emitting element. The second control circuit controls the light emission period of the driving current value supplied to each of the plurality of light emitting elements emitting light of the first light emission color and the second light emission color, based on the determined light emission intensity.

11. The light emitting device according to any one of claims 1 to 10, wherein: The first luminescent color is blue light.

12. The light emitting device according to claim 11, wherein: The first luminescent color is luminescent with a fixed wavelength.

13. The light emitting device according to any one of claims 1 to 12, wherein: The lighting control unit is configured to set a time width for supplying current to the light emitting element based on a result of comparing a first signal including a triangular wave signal with a first DC voltage set in a predetermined period. A current value supplied to the lighting control unit is controlled based on a second DC voltage set in a period different from the predetermined period.

14. A method for driving a light-emitting device, the light-emitting device comprising: a display unit, wherein a plurality of light-emitting elements whose light-emitting colors can be controlled according to a driving current are arranged in a predetermined pattern to form a plurality of pixels; an information holding unit that holds current-chromaticity information for determining a driving current value for causing the plurality of light-emitting elements to emit light in the first light-emitting color or a second light-emitting color different from the first light-emitting color according to a predetermined light-emitting color; a lighting control unit that supplies a driving current to the light emitting element to control a light emitting period of the light emitting element; The driving method of the light emitting device comprises the following steps: The lighting control unit drives the plurality of light emitting elements so as to divide one frame in which the plurality of light emitting elements emit light into a first subframe in which the plurality of light emitting elements emit light in the first light color and a second subframe in which the plurality of light emitting elements emit light in the second light color.

15. The driving method of the light emitting device according to claim 14, wherein: The step of the lighting control unit driving the plurality of light emitting elements includes the following steps: Determine, based on a chromaticity signal and a brightness signal to be displayed by each pixel, a chromaticity of the second luminescent color and a brightness ratio of the brightness of the light emitting element emitting the first luminescent color to the brightness of the light emitting element emitting the second luminescent color in a manner corresponding to the first luminescent color; determining, based on the chromaticity of the second luminescent color and the luminance ratio, a luminous intensity corresponding to a luminance signal to be displayed by the luminescent element; The first control circuit of the lighting control unit refers to the information holding unit to supply the light emitting elements with driving current values ​​corresponding to the respective light emitting colors; The second control circuit of the lighting control unit controls a light emission period of the driving current value supplied by the first control circuit according to the determined light emission intensity.

16. The driving method of the light emitting device according to claim 15, wherein: The step of the lighting control unit driving the plurality of light emitting elements includes the following steps: In the first subframe, the second control circuit controls the light emission intensity by PWM control in a state where the first control circuit makes the driving current of the plurality of light emitting elements emitting the first light emission color constant; In the second subframe, the first control circuit controls the light emission color according to the current value of driving the plurality of light emitting elements that emit the light of the second light emission color; In the second subframe, the second control circuit controls the brightness according to the light emission period of the current value of the plurality of light emitting elements controlled by the first control circuit.

Images