LIGHT EMISSION DEVICE AND METHOD FOR OPERATION THEREOF

Abstract

A light-emitting device comprises: a display including a plurality of pixels in which a plurality of light-emitting elements are arranged in a predetermined pattern, wherein a light-emitting color of each of the plurality of light-emitting elements is variable according to an operating current; and an illumination control section configured to supply an operating current to each of the plurality of light-emitting elements and control a light-emitting period of each of the plurality of light-emitting elements.The illumination control section is configured to: divide a frame in which the illumination control section operates the plurality of light-emitting elements to emit light into a first sub-frame and a second sub-frame, operate the plurality of light-emitting elements to emit light of a first light-emitting color in the first sub-frame, and operate the plurality of light-emitting elements to emit light of a second light-emitting color in the second sub-frame, the second light-emitting color being different from the first light-emitting color.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on and claims priority from Japanese Patent Application No. 2023-218,221, filed on December 25, 2023, the entire contents of which are incorporated herein by reference. BACKGROUND

[0002] The present disclosure relates to a light emitting device and a method for operating the light emitting device.

[0003] Displays and surface-mounted light-emitting devices that use semiconductor light-emitting elements such as LEDs and LDs are used. To create a full-color LED display, it is generally necessary to provide subpixels of at least the three RGB colors for each pixel. However, this configuration is not suitable for high resolution, as it requires at least three times as many subpixels as pixels, and there are problems such as high cost and lower yield due to a larger number of LEDs.

[0004] However, a micro-LED display that causes a single LED element to emit multicolor light is known (see JP 2021-52168 A). However, with regard to a display configuration using such a multicolor light-emitting micro-LED, no actual circuit configurations and operating methods have been reported. For example, with current technology for controlling a multicolor light-emitting micro-LED, it is not easy to emit light in all RGB chromaticity ranges.

[0005] It is an object of one aspect of the present disclosure to provide a light-emitting device and a method for operating the light-emitting device with which suitable light-emitting color control can be implemented when designing a light-emitting device such as a display using multi-color semiconductor light-emitting elements. It is an object of another embodiment to provide a light-emitting device in which the occurrence of color separation is prevented and a method for operating the light-emitting device. It should be noted that the description of these objects does not exclude the existence of other objects. Not all of these objects are necessarily achieved by one aspect of the present disclosure. Other objects may be apparent from the description, specificity, drawings, and claims of the present disclosure. SUMMARY

[0006] A light-emitting device according to one aspect of the present disclosure includes: a display including a plurality of pixels in which a plurality of light-emitting elements are arranged in a predetermined pattern, wherein a light-emitting color of each of the plurality of light-emitting elements is variable according to an operating current; and an illumination control section configured to supply an operating current to each of the plurality of light-emitting elements and control a light-emitting period of each of the plurality of light-emitting elements.The lighting control section divides a frame into a first sub-frame and a second sub-frame and drives the plurality of light-emitting elements, the one frame being a frame for driving the plurality of light-emitting elements to emit light, the first sub-frame being a sub-frame for driving each of the plurality of light-emitting elements to emit light of a first light-emitting color, the second sub-frame being a sub-frame for driving each of the plurality of light-emitting elements to emit light of a second light-emitting color different from the first light-emitting color.

[0007] A method of operating a light-emitting device according to another aspect of the present disclosure is for operating a light-emitting device having a display with a plurality of pixels in which a plurality of light-emitting elements are arranged in a predetermined pattern, wherein a light-emitting color of each of the plurality of light-emitting elements is variable according to a driving current supplied thereto, an information storage configured to store current chromaticity information for determining a driving current value in accordance with a specific light-emitting color of a light-emitting element of the light-emitting elements to drive the light-emitting element to emit light having a first light-emitting color or a second light-emitting color different from the first light-emitting color, and an illumination control section configured tothat it supplies an operating current to each of the plurality of light-emitting elements and controls a light-emitting period of each of the plurality of light-emitting elements. The method includes, by the illumination control section, dividing a frame into a first sub-frame and a second sub-frame and operating the plurality of light-emitting elements, wherein the one frame is a frame for operating the plurality of light-emitting elements to emit light, wherein the first sub-frame is a sub-frame for operating each of the plurality of light-emitting elements to emit light of the first light-emitting color, wherein the second sub-frame is a sub-frame for operating each of the plurality of light-emitting elements to emit light of the second light-emitting color.

[0008] With the configuration described above, multi-color light emission such as full-color light emission can be achieved by using a light-emitting element whose light-emitting color can be controlled according to an operating current and the occurrence of color separation can be suppressed by separately displaying the light-emitting color in the sub-frame. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a block diagram showing a light emitting device according to a first embodiment. Fig. 2 is a timing diagram for illuminating and driving a light emitting element. Fig. 3 is a block diagram showing an example in which a first control circuit and a second control circuit are arranged in a pixel circuit. Fig. 4 is a block diagram with an enlarged view showing a display of the light emitting device according to the first embodiment. Fig. 5 is a schematic cross-sectional view showing an example of an element structure of a light-emitting element. Fig. 6 is a schematic cross-sectional view showing another example of an element structure of a light-emitting element. Fig. 7 is a schematic representation of an illumination image in a first subframe. Fig. Figure 8 is a schematic representation of an illumination image in a second subframe. Fig. 9 is a functional block diagram illustrating a method for determining an operating current value and a PWM light emission period. Fig. 10 is a chromaticity diagram for illustrating a method for determining a light emission chromaticity in Fig. 9. DETAILED DESCRIPTION

[0009] Hereinafter, embodiments of the present disclosure are described in detail with reference to the drawings. In the following description, terms indicating specific directions and positions (for example, "top," "bottom," and other terms containing these terms) are used as necessary. However, the use of these terms is only intended to facilitate understanding of the invention with reference to the drawings, and the technical scope of the present disclosure is not limited by the meaning of these terms. Parts with the same reference numerals that appear in multiple drawings indicate identical or equivalent parts or elements.

[0010] The following embodiments show specific examples of the technical idea of ​​the present disclosure, and the present disclosure is not limited to the following embodiments. Unless otherwise specified, the dimensions, materials, shapes, relative arrangements, and the like of components to be described below are not intended to limit the scope of the present disclosure only to these, but rather to provide examples. The contents to be described in one embodiment and one example may be applied to another embodiment and another example. The size, spatial relationship, and the like of the elements shown in the drawings may be exaggerated for clarity of explanation. First embodiment

[0011] A block diagram of a light emitting device 100 according to a first embodiment is shown in Fig. 1. The light emitting device 100 shown in this drawing includes a display 10, a driver 30, lighting control sections 50, an information storage 70, a scanning circuit 20, and an operation control section 60.

[0012] The display 10 includes a plurality of pixels 12 and a plurality of first light-emitting elements 11 arranged in a predetermined pattern. Each light-emitting element 11 constitutes one pixel. Specifically, the plurality of light-emitting elements 11 are arranged in a matrix. A period during which image data for one frame is displayed on a screen formed by the pixels 12 arranged in a matrix may be referred to as a vertical scanning period, and a period obtained by dividing the vertical scanning period by the number of lines of the screen may be referred to as a horizontal scanning period. For example, in the horizontal scanning period, a voltage value for controlling the current supply to the pixels 12 arranged in a row direction (X-axis direction) and a voltage value for analog image data are set.In the vertical scanning period, the scanning circuit 20, which scans the pixels 12, is sequentially shifted in a column direction (Y-axis direction). The light-emitting device 100 in . Fig. 1 uses an active matrix operating method as the illumination operating method for illuminating the individual pixels 12.

[0013] Each pixel 12 is formed by a light emitting element 11. In the Fig. In the example shown in FIG. 1, the pixel 12 includes one light-emitting element 11. However, the present disclosure is not limited to this configuration; a pixel may also be formed by multiple light-emitting elements. By using multiple light-emitting elements, the light emission luminance per pixel can be improved.

[0014] The light emission color of the light-emitting element 11 can be controlled according to its operating current. A multi-color wavelength-tunable LED can be suitably used as such a light-emitting element 11. The light emission color of the light-emitting element 11 can be changed, for example, from blue to red. Lighting control section 50

[0015] The illumination control section 50 supplies an operating current to each of the plurality of light-emitting elements 11 to control a light-emitting period. In the enlarged view of Fig. In the example shown in FIG. 1, the illumination control sections 50 are connected to a power supply line 9 and a write scan line WS extending in the horizontal direction. The illumination control section 50 is driven by power supplied via the power supply line 9 and is scanned by the write scan line WS to receive a power supply control signal and an analog image signal. On the other hand, the illumination control section 50 is also connected to a signal line SL extending in a vertical direction and receives the power supply control signal and the analog image signal via the signal line SL.

[0016] The lighting control section 50 divides a frame for driving the plurality of light-emitting elements 11 to emit light into a first sub-frame for driving each of the plurality of light-emitting elements 11 to emit light in the first light-emitting color and a second sub-frame for driving each of the plurality of light-emitting elements 11 to emit light in the second light-emitting color, and drives the plurality of light-emitting elements 11. For example, the first sub-frame is a B sub-frame for emitting blue light, and the second sub-frame is an RG sub-frame for emitting green light to red light.

[0017] In this way, the second light emission color of the second sub-frame has a variable wavelength, while the first light emission color of the first sub-frame has a fixed wavelength, and the illumination of the light emission element 11 is controlled. Thus, the light emission device 100 can be effectively operated with a tunable light emission color. In particular, by limiting the light emission control of the light emission elements 11, which can emit light of different light emission colors according to an operating current, to a light emission control that is variable only in a limited wavelength range, for example, from green light to red light, without controlling the light emission in the entire RGB range, in combination with the first light emission color by a fixed wavelength, full-color light emission can be achieved for each pixel and simpler light emission control can be implemented.Furthermore, pixels can be operated more easily and with lower power consumption because full-color image representation can be implemented without using three sub-fields of RGB as in a commonly known display.

[0018] In a multi-color light-emitting LED with a tunable light-emitting wavelength, a light-emitting color is changed by a driving current. In other words, since the driving current varies greatly depending on the light-emitting color, the light-emitting luminance also varies greatly. For example, when a multi-color light-emitting LED is used to display short-wavelength and long-wavelength light on a display, with the luminance and light-emitting colors appropriately adjusted, a light-emitting period needs to be controlled in a range of approximately 3 to 30 times depending on the light-emitting wavelength. Therefore, to achieve sufficient light-emitting luminance by reducing an unnecessary non-illumination period, field-sequential operation is desirable to perform illumination in different subframes for each light-emitting color.

[0019] However, in field-sequential operation, changing the light emission color for each subframe may result in color separation, especially in a moving image, and the image quality may be significantly deteriorated. That is, in field-sequential operation, since the pixels are of the active matrix type, a certain light emission period must be ensured after display data is written to a selected line by scanning. Thus, a scanning period and the light emission period of each line are defined independently. Thus, in field-sequential operation, light emission occurs not in lines but in subfields, leading to a problem in that color separation occurs as a side effect.

[0020] On the other hand, in the light-emitting device 100 according to the first embodiment, color separation is suppressed by using only blue light with low human visibility in another subframe. A detailed description of this is given below. Light-emitting element 11

[0021] As the light-emitting element 11, a semiconductor light-emitting element such as a light-emitting diode (LED) or a semiconductor laser (LD) can be suitably used. As the LED, an LED comprising one or more semiconductor stacks having light-emitting portions (hereinafter also simply referred to as "semiconductor stacks") can be used. The semiconductor stack is capable of emitting light. Such a semiconductor stack is manufactured by stacking a plurality of semiconductor layers such as ZnS, SiC, GaN, GaP, InN, AlN, ZnSe, GaAsP, GaAlAs, InGaN, GaAlN, AlInGaP, AlInGaN, or the like on a substrate by liquid-phase epitaxy such as HVPE or MOCVD and forming an active layer on one of the semiconductor layers.By selecting the semiconductor layer materials and their mixing ratios, the light emission wavelength of the active layer can be varied from ultraviolet light to infrared light. Particularly in the case of a display device that can be suitably used outdoors, a semiconductor layer body that can emit light with high luminance is advantageous. Therefore, a nitride semiconductor that emits light with high luminance is preferably selected as the material for a light-emitting portion. For example, In. X Al Y Ga 1 - X - Y N (0 ≤ X ≤ 1, 0 ≤ Y ≤ 1, and X + Y ≤ 1) or the like can be used as the material of the light emitting portion.

[0022] In the first embodiment, a semiconductor light-emitting element such as a light-emitting diode or a semiconductor laser is used as each light-emitting element 11. A micro-LED can also be used as the light-emitting diode. The micro-LED has a chip size of 5 µm to 100 µm, or suitably 10 µm to 50 µm, taking luminous efficiency and the like into consideration.

[0023] The light emission color of the light emission element 11 is tunable. The light emission element 11 emits light of a different light emission color according to a driving current. For example, the light emission element 11 emits light of a first light emission wavelength, such as red light, when driven by a first driving current, and emits light of a second light emission wavelength shorter than the first light emission wavelength, such as green light, when driven by a second driving current greater than the first driving current, and emits light of a third light emission wavelength shorter than the second light emission wavelength, such as blue light, when driven by a third driving current greater than the second driving current.

[0024] In this way, the wavelength of each light emission color, such as blue light, can be adjusted when the light emission element 11 is of the wavelength-tunable type. Generally, in a blue light emission element, a variation in light emission wavelength is observed between elements to be manufactured, but the variation in the light emission wavelength of the light emission element, for example, between pixels can be corrected, and the wavelengths of blue light and the like of each pixel can be made the same.

[0025] Each of the light-emitting elements 11 is connected to a plurality of common lines and a plurality of drive lines. The light-emitting elements 11 are connected to one of the plurality of common lines and one of the plurality of drive lines and arranged in a matrix to form the display 10. Scanning circuit 20

[0026] The sampling circuit 20 is arranged in a column that is further to the left than the leftmost column of the pixels 12 arranged in the form of a matrix. The sampling circuit 20 may be arranged in a column that is further to the right than the rightmost column of the pixels 12 arranged in the form of a matrix. As shown in Fig. As shown in Fig. 4, for each row of pixels, a power supply control signal write scan line WS1 and an analog image signal write scan line WS2 are provided as write scan lines WS extending from the scanning circuit 20. The power supply control signal write scan line WS1 and the analog image signal write scan line WS2 extend in the row direction.

[0027] The power supply control signal write scan line WS1 supplies a first scan signal which is a digital signal for selecting a pixel circuit 14 in the row direction (the illumination control section 50 and the light emitting element 11 in Fig. 1) when desired voltage values ​​are written by the power supply control signal. The analog image signal write scanning line WS2 supplies a second scanning signal, which is a digital signal for selecting the pixel circuit 14 in the row direction, when a light emission period determined by a light emission tone is written as a voltage value by an analog image signal. Driver 30

[0028] As it is in Fig. As shown in Figure 4, the driver 30 includes a power supply control signal line SL1 and an analog image signal line SL2 extending as the signal lines SL in the vertical direction for each column of pixels. The driver 30 supplies a power supply control signal to each pixel circuit 14 via the power supply control signal line SL1. The power supply control signal is an analog signal capable of assuming multiple voltage values. The driver 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 assuming multiple voltage values. Each pixel circuit 14, to which the power supply control signal is supplied and the voltage value is written, sets an operating current based on the written voltage value.Each pixel circuit 14, to which the analog image signal is supplied and the voltage value is written, sets a threshold voltage to be compared with the reference triangular wave signal and a time interval during which the pixel circuit 14 emits light based on the voltage value of the analog image signal. A reference triangular wave signal (not shown) is supplied to the pixel circuit 14 during a light emission period, and the light-emitting element 11 of each pixel circuit 14 emits light during an ON period based on a written analog image signal voltage (for details, see US Pat. No. 1,0885,834).

[0029] Driver 30 can generate the reference triangular wave signal that is supplied to each pixel circuit 14 for each column. Alternatively, the reference triangular wave signal can also be provided separately as a reference triangular wave circuit in a row below the bottom row of the matrix of pixel circuits 14. Driver 30 or the reference triangular wave circuit distributes, for example, a reference triangular wave supplied from outside these circuits to the columns of pixel circuits 14.

[0030] The driver 30 may include a memory unit. The memory unit can store luminance settings for a plurality of voltage values ​​acquired from the power supply control signal and luminance settings for a plurality of voltage values ​​acquired from the analog image signal. The relationship between the voltage values ​​and the luminance settings can be adjusted and determined by visually inspecting the luminance of the light-emitting element 11 constituting the pixel circuit 14. γ-correction can be performed by appropriately adjusting the relationship between the voltage values ​​and the luminance settings. While the gradation characteristics become linear in a digital PWM system, the fact that γ-correction can be applied to a signal is one of the advantages of this system. The memory unit is formed, for example, by an electrically rewritable memory circuit or the like. Information storage 70

[0031] As described above, the light-emitting element 11 is a multi-color wavelength tunable light-emitting type LED and changes the light-emitting color depending on the driving current. Therefore, an driving current value for driving the light-emitting element 11 must be determined in accordance with the second light-emitting color to be emitted by the light-emitting element 11. Therefore, the information storage 70 stores current-chromaticity information indicating the light-emitting color to be emitted by the light-emitting element 11 and a correspondence relationship determining a current value for emitting that color. The driving control section 60 determines the driving current of the light-emitting element 11 according to the light-emitting color by accessing the information storage 70.The information storage 70 may, for example, include a storage element such as a current chromaticity data storage for storing current chromaticity data of the second light emitting element 11.

[0032] The information storage 70 may also store current chromaticity information based on an actual measurement value of each light-emitting element arranged in the display, and current chromaticity information generated by measuring an operating current and a light-emitting color of a light-emitting element corresponding to each light-emitting element arranged in the display. Alternatively, the information storage 70 may store current chromaticity information acquired by statistically determining the relationship between the operating current and the light-emitting color of the light-emitting element. In the example of Fig. 1, the information storage 70 has a light emission-chromaticity-operating current-luminance characteristic table (GR). Where (GR) represents a wavelength range from green light to red light. Driver control 60

[0033] The operation control section 60 further controls the operations of the scanning circuit 20 and the driver 30. The scanning circuit 20 and the driver 30 control the illumination control section 50 of each pixel. As shown in Fig. 3, each illumination control section 50 may include a first control circuit 51 and a second control circuit 52. The first control circuit 51 supplies an operating current to each of the light-emitting elements 11. The second control circuit 52 controls the light-emitting period of each of the light-emitting elements 11. A configuration in which the light-emitting element 11 is connected to the illumination control section 50 may be 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.

[0034] The operation control section 60 controls the driver 30 to supply the operating current to each of the light-emitting elements 11 so that each of the light-emitting elements 11 emits light of a specific light-emitting color and light-emitting luminance. Specifically, the operation control section 60 determines the operating current value for operating each of the light-emitting elements 11 and an ON period for illuminating each of the light-emitting elements 11 by using the current chromaticity information stored in the information storage 70 in accordance with a specific light-emitting color and gradation information for each of the light-emitting elements 11, and performs the illumination operation of each of the light-emitting elements 11 using the operating current from the illumination control section 50.

[0035] The operation control section 60 also performs gradation control of the light emission luminance. For example, the operating current value of each of the light emission elements 11 is determined by referring to the current chromaticity information in accordance with the determined light emission color of each of the light emission elements 11, and the ON period of each of the light emission elements 11 is determined according to the determined operating current value and the determined gradation information for each of the light emission elements 11.

[0036] The operation control section 60 may include a memory unit. The memory unit may store luminance settings for a plurality of voltage values ​​acquired from the power supply control signal, as well as luminance settings for a plurality of voltage values ​​acquired from the analog image signal. The relationship between the voltage values ​​and the luminance settings can be adjusted and determined by visually inspecting the luminance of the light-emitting element constituting the pixel circuit 14. The γ-correction can be performed by appropriately adjusting the relationship between the voltage values ​​and the luminance settings. While the gradation characteristics become linear in a digital PWM system, the fact that the γ-correction can be applied to a signal is one of the advantages of this system. The memory unit is used, for example,formed by an electrically rewritable memory circuit or the like.

[0037] The operation control section 60 may further cause the driver 30 to simultaneously perform the illumination control of each of the light-emitting elements 11 in a state in which ON-period information corresponding to the one screen of each of the light-emitting elements 11 constituting the display 10 is written into the storage unit.

[0038] The operation control section 60 determines an operating current value for driving each of the light-emitting elements 11 and a light-emitting period for emitting light by accessing the current chromaticity information stored in the information storage 70 in accordance with the light-emitting color and gradation information for each of the light-emitting elements 11 transmitted from the outside. Subsequently, the operation control section 60 drives each of the light-emitting elements 11 using the illumination control section 50 via the driver 30. With such a configuration, illumination control of the display 10 constituted by the multi-color light-emitting type light-emitting elements 11 can be realized.

[0039] Regarding the light emission color of the light-emitting element 11, when the operating current values ​​for emitting the respective light emission colors of, for example, red (R), green (G), and blue (B) are IR, IG, and IB, respectively, the magnitudes of the operating current values ​​satisfy the condition of IR < IG < IB. Therefore, the relationship between the lengths of the maximum light emission periods of the respective colors in white display corresponding to full irradiation satisfies the condition of TR > TG > TB when the light emission periods of the maximum gradation of the respective colors are TR, TG, and TB.

[0040] Furthermore, by assigning the light emission color to be emitted by the light emission element 11 to each subframe, the color separation problem that occurs in field-sequential operation when a light emission color changes for each subframe can be solved. That is, one frame is divided into two subframes, and light emission colors are assigned to the subframes, so that the light emission element 11 emits light of the first light emission color in the first subframe and light of the second light emission color in the second subframe. Assume that the first light emission color is blue, the second light emission color is any color from green to red, the first subframe is the B subframe, the second subframe is the GR subframe tunable between (GR), and one frame is divided into two subframes that are operated.Since the temporal resolution of the human eye with respect to blue light is low, color separation is hardly recognized even when the blue light is assigned to a different subframe and field-sequential operation is performed. As a result, the occurrence of color separation can be avoided, unnecessary non-illumination periods can be reduced when using a multi-color light-emitting LED, and sufficient light emission luminance can be obtained.

[0041] Accordingly, in the light-emitting device 100 according to the first embodiment, the multi-color light-emitting type light-emitting element 11 is used to emit blue light of the first light-emitting color in the first subframe and light of any color from red to green (GR), which is the second light-emitting color, in the second subframe. Thus, full-color light emission can be implemented without causing color separation. PWM can be used for gradation control of each of the light-emitting colors. Here, the products of the maximum light-emitting periods and the driving current values ​​by the PWM drive satisfy the condition of R > G > B. This is because the light-emitting luminance efficiency of the light-emitting element 11 is higher on the order of R < G < B.

[0042] In this way, full-color light emission can be implemented by using the same light-emitting element 11 to emit light of the first light-emitting color and the second light-emitting color. With this configuration, compared to a configuration in which light-emitting elements emitting light of different colors are arranged in respective pixels, the configuration can be simplified and power consumption can be reduced. Since a single light-emitting element is used for each pixel, an LED element with a larger chip size can be used. However, as the chip size of the LED element is larger, the proportion of a recombination current generated at the end face of a light-emitting layer decreases, so the light-emitting efficiency is improved.

[0043] In the above description, the light emission color of the light emission element 11 is tunable within the entire range of R, G, and B, assuming full-color light emission. However, the present disclosure is not limited to a light emission device that emits full-color light. For example, the present disclosure can also be applied to a light emission device that emits light within a range of two colors of green and blue or two colors of red and green. In this case, by manufacturing the light emission element according to a required light emission color, for example, by manufacturing the light emission element such that the light emission color of the light emission element can be changed only within the range from R to G, advantages such as simplification of a manufacturing process and cost reduction can be achieved.For example, the margin of the manufacturing process of the light emitting element 11 can be made wider. Time diagram

[0044] Fig. 2 is a timing diagram showing illumination times of each of the RGB colors of the Fig. 1. A frame period FT is divided into a first subframe period SF1 in which the light-emitting element 11 emits light of the first light-emitting color, and a second subframe period SF2 in which the light-emitting element 11 emits light of the second light-emitting color. The first subframe period SF1 is the B subframe in which blue light is emitted, and the second subframe period SF2 is the GR subframe in which light of any color from green to red is emitted. In the B subframe, a current having a value for emitting a light-emitting color corresponding to blue light, for example, 470 nm, is supplied to the light-emitting element 11.In the GR subframe, since the light is switched from green to red light, a current having a value in a range from a current value for emitting a light emission color corresponding to green light, for example, 515 nm, to a current value for emitting a light emission color corresponding to red light, for example, 630 nm, is supplied to the light emission element 11. That is, a current having a value that drives the light emission element 11 to emit blue light is supplied in the B subframe, while a drive current corresponding to any color from green to red is supplied in the GR subframe. In this way, in each subframe, the light emission color is represented by the vertical axis (drive current) in . Fig. 2 controlled.

[0045] In each subframe, the light emission luminance is controlled by PWM control. By changing an ON period ONT within a maximum light emission period LTmax, the luminance can be adjusted to a desired value by changing an integrated current value while supplying a current with a maximum value. A maximum light emission period of blue light is denoted by LTmaxB, and the ON period of blue light is denoted by ONTB. On the other hand, in a maximum light emission period from green light to red light, the maximum light emission period of green light is denoted by LTmaxG, and the maximum light emission period of red light is denoted by LTmaxR. The ON period ONT is included in the maximum light emission period.In fact, once the operating current value (vertical axis) is determined in accordance with a desired light emission color, the horizontal axis is determined in accordance with the luminance, as shown by oblique lines in . Fig. 2. In this way, in both the B subframe and the (GR) subframe, the luminance control is performed by the horizontal axis (ON period) in Fig. 2 carried out.

[0046] A pixel signal writing period is provided in each subframe, and PWM control is performed after the pixel signal writing period. During the pixel signal writing period, a pixel signal for one screen of the light-emitting element 11 is written into a pixel memory. The driver 30 controls the illumination of the light-emitting element 11 by accessing the pixel signal written into the pixel memory. The pixel memory is provided in the illumination control section 50 of the pixel circuit 14.

[0047] As it is in Fig. 3, the lighting control section 50 includes the first control circuit 51 and the second control circuit 52. The first control circuit 51 performs current control in accordance with a light emission color. The second control circuit 52 performs PWM control. Specifically, when performing PWM control, the second control circuit 52 sets a time interval for supplying current to the light emission element 11 based on the result of comparison between a first signal including a triangular wave signal and a first DC voltage set at a predetermined period. Based on a second DC voltage set at a period different from the predetermined period, the first control circuit 51 controls a current value to be supplied from the lighting control section 50.

[0048] As it is in Fig. As shown in Figure 4, the power supply control signal write scan line WS1 and the analog image signal write scan line WS2 originate from the scanning circuit 20 and are connected to each pixel 12. The power supply control signal line SL1 and the analog image signal line SL2 originate from the driver 30 and are connected to each pixel 12. The driver 30 is a driver IC that processes a power supply control signal and an analog image signal. The power supply control signal write scan line WS1 and the analog image signal write scan line WS2 are connected to a TFT circuit arranged on a mounting substrate together with the pixel circuit 14. The TFT is made of low-temperature polycrystalline silicon or an oxide semiconductor.

[0049] Each pixel 12 includes the illumination control section 50 and the light emitting element 11, as shown in an enlarged view of the main components of Fig. 4. Each pixel circuit 14 includes the illumination control section 50. The illumination control section 50 includes a first control circuit 51 and a second control circuit 52. The first control circuit 51 supplies an operating 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. The first control circuit 51 is a current supply control circuit, and the second control circuit 52 is an analog image PWM circuit. The first control circuit (current supply control circuit) 51 is connected to the power supply line 9 and the power supply control signal line SL1. 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 to the power supply line 9 via the first control circuit 51.The second control circuit 52 is also connected to the analog image signal line SL2. From the analog image signal line, an analog image signal write timing is input to the scanning line WS2. Thus, each of the light-emitting elements 11 is connected to the power supply line 9 via the power supply control circuit and the analog image PWM circuit. An operating current value is controlled by the power supply control circuit, and an operating time is controlled by the analog image PWM circuit.

[0050] Fig. 4 shows an example in which each pixel 12 includes an LED. However, the present disclosure is not limited to this configuration; each pixel may include multiple light-emitting elements such as LEDs. For example, two or more light-emitting elements may be connected in series or parallel when multiple light-emitting elements are used for the purpose of increasing luminance or the like. LED

[0051] Fig. 5 shows an example of an element structure when using an LED as the light emitting element 11. The Fig. The light-emitting element 11 shown in FIG. 5 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 may comprise a multiple quantum well (MQW) structure or the like. The light-emitting element 11 is connected to a pixel driving circuit 8 such as a DC power supply and emits light when receiving a driving current supplied from the power supply line 9. The light-emitting color of the light-emitting element 11 is controlled by the driving current, and the light-emitting period of the light-emitting element 11 is controlled by the driving current. The second light-emitting color is tunable to any color from blue to red.

[0052] The light-emitting element may include a first light-emitting section that emits light of a first light-emitting color and a second light-emitting section that emits light of a second light-emitting color. The light emission of the first light-emitting section and the light emission of the second light-emitting section may be selectable by a switch. With such a configuration, by limiting the light emission control of the light-emitting elements that can emit light of different light-emitting colors according to an operating current to a light emission control that is tunable only in a limited wavelength range, for example, from green light to red light, without controlling the light emission in the entire RGB range, a simpler light emission control can be implemented.For example, the first light-emitting portion may be a B light-emitting layer that emits blue light, and the second light-emitting portion may be an RG light-emitting layer that emits any color from red to green. Thus, the RG light-emitting layer is combined with the B light-emitting layer that emits blue light to enable full-color light emission for each pixel.

[0053] An example of such a light emitting element is shown in Fig. 6. A Fig. The light-emitting element 11B shown in Figure 6 comprises a first n-type semiconductor layer 2A, a first light-emitting layer 3A, a first p-type semiconductor layer 4A, an ohmic connection 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. For the first light-emitting layer 3A and the second light-emitting layer 3B, an active layer such as a multiple quantum well (MQW) structure can be used. As the ohmic connection layer 7, an intermediate layer that establishes an ohmic connection between the first p-type semiconductor layer 4A and the second n-type semiconductor layer 2B can be used. Fig. 6 shows an example in which the first p-side electrode 6A is used, the second n-type semiconductor layer 2B can be used as the n-side electrode instead of the first p-type semiconductor layer 4A. Normally, the second n-type semiconductor layer 2B, which has a low resistance value, can be easily formed thicker than the first p-type semiconductor layer 4A, which has a high resistance value. Therefore, this case has the advantage of slightly improving the processing yield in the formation of chip electrodes.

[0054] The light-emitting element 11B is connected to a pixel driving circuit 8B such as the illumination control section 50 and emits light upon receiving a driving current supplied from a power supply line 9B. A light-emitting color of the light-emitting element 11B is controlled by the driving current, and a light-emitting period of the light-emitting element 11 is controlled by the driving current. In the example of Fig. 6, a first light emission color of the first light emitting layer 3A is blue, and a second light emission color of the second light emitting layer 3B is tunable to any color from red to green.

[0055] Such a tandem structure in which the first light-emitting layer 3A and the second light-emitting layer 3B are stacked can be formed by successive epitaxial growth steps on the same growth substrate. For example, a GaN crystal forming a semiconductor layer is formed on a wafer of a sapphire substrate as the growth substrate, and then the first light-emitting layer 3A and then the second light-emitting layer 3B are grown. Here, by forming the first light-emitting layer 3A, which emits blue light, before the second light-emitting layer 3B is formed, an advantage is gained in that defects of the GaN crystal are less likely to occur. Subsequently, the structure is processed into 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 the structure, and the structure is divided into individual elements. Furthermore, by roughening the light-emitting surface side of the first n-type semiconductor layer 2A, the light-emitting efficiency can be improved. Thus, the light-emitting element 11B having the tandem structure in which the first light-emitting layer 3A and the second light-emitting layer 3B are stacked is obtained. Control of a light-emitting color of the light-emitting layer is not limited to the entire RGB range, but limited to a specific wavelength range from green light to red light, thus simplifying emission control.

[0056] The first light-emitting layer 3A and the second light-emitting layer 3B may be connected in series. Furthermore, a first switch SW1 and a second switch SW2 may be arranged at an intermediate point of the series connection between the first light-emitting layer 3A and the second light-emitting layer 3B. The first switch SW1 is connected in parallel to the first light-emitting layer 3A. The second switch SW2 is connected in parallel to the second light-emitting layer 3B.

[0057] The light-emitting element 11B turns the first switch SW1 off and the second switch SW2 on when the first light-emitting layer 3A emits light. Conversely, when the second light-emitting layer 3B emits light, the light-emitting element 11B turns the first switch SW1 on and the second switch SW2 off. Each of the first light-emitting layer 3A and the second light-emitting layer 3B can also be turned on first. That is, blue light from the first light-emitting layer 3A can be turned on first in the first subframe, and red to green light can be emitted from the second light-emitting layer 3B in the subsequent second subframes. However, the image delay with respect to an input signal is advantageously reduced when red-green light is turned on first from the second light-emitting layer 3B because the delay of the blue light is hardly noticeable to the human eye. B subframe

[0058] Fig. Fig. 7 shows an illumination image in the B subframe using such a display 10, and Fig. Figure 8 shows an illumination image in the GR subframe using such a display 10. In these drawings, each pixel 12 is represented in a tiled manner. In the B subframe, the luminance of the pixels 12 is different, but the chromaticity is constant. The luminance gradation is controlled by PWM. The density difference of the individual pixels 12 in Fig. 7 shows the difference in mean luminance in the subframe. GR subframe

[0059] In contrast, in the GR subframe, both the luminance and the chromaticity are tunable between the pixels 12. In the (GR) subframe, the current value supplied to the light-emitting element 11 and the second light-emitting color, i.e., the chromaticity, are controlled within the range of (GR). Specifically, the illumination control section 50 determines the RGB chromaticity in each pixel 12 by accessing the information memory 70. When the chromaticity of B, i.e., the first light-emitting color to be emitted by the light-emitting element 11, is fixed-wavelength light emission, a driving current is uniquely determined. In contrast, the second light-emitting color that causes the light-emitting element 11 to emit a tunable wavelength must be determined.First, a light emission color at the time of (GR) wavelength change and a luminance ratio of B to (GR) are to be displayed from a chromaticity signal to correspond to a color at the time of B emission. Subsequently, a light emission intensity corresponding to a luminance signal to be displayed is determined from the chromaticity of the light emission color and the luminance ratio. Method for operating the light-emitting device

[0060] An example of a method for operating the light-emitting device 100 will be described below. A method in which the illumination control section 50 divides a frame to operate the light-emitting element 11 to emit light into a first sub-frame and a second sub-frame and controls the light-emitting element 11. In the first sub-frame, each of the plurality of light-emitting elements 11 is caused to emit light of the first light-emitting color. Since blue light is emitted as the first light-emitting color in the first sub-frame, it is referred to as a B sub-frame. In the second sub-frame, each of the plurality of light-emitting elements 11 is caused to emit light of the second light-emitting color. Since light in the range from red light to green light is emitted in the second sub-frame, it is referred to as an RG sub-frame.

[0061] The illumination control section 50 causes the first control circuit 51 to supply an operating current to each of the light-emitting elements 11, and causes the second control circuit 52 to control a light-emitting period of each of the light-emitting elements 11. The step of operating the light-emitting element 11 by the illumination control section 50 includes: a step of determining a chromaticity of the second light-emitting color and a luminance ratio of the luminance of the light-emitting element 11 emitting light of the first light-emitting color to the luminance of the light-emitting element 11 emitting light of the second light-emitting color from a chromaticity signal and a luminance signal displayed by each pixel 12 to correspond to the first light-emitting color; a step of determining a light-emitting intensity corresponding to a luminance signal;to be displayed by the light-emitting element 11 based on the chromaticity of the second light-emitting color and the luminance ratio, a step of supplying, by the first control circuit 51, an operating current having a value corresponding to a light-emitting color of each of the light-emitting elements 11 to the corresponding one of the light-emitting elements 11 by accessing the information memory 70, and a step of controlling, by the second control circuit 52, the light-emitting period of the operating current supplied to each of the light-emitting elements 11 by the first control circuit 51 in accordance with the determined light-emitting intensity.

[0062] In the first subframe, the first control circuit 51 controls the operating current of each of the plurality of light-emitting elements 11 to emit light of the first light-emitting color at a constant value, and the second control circuit 52 controls the light-emitting intensity using PWM control. The operating current of the light-emitting element 11 is set to an operating current value at which blue light emission is highly efficient. For example, this is a rated current value.

[0063] On the other hand, in the second subframe, the first control circuit 51 controls a light emission color by a current value for driving each of the plurality of light emission elements 11. The second control circuit 52 controls the light emission period of the current value of each of the plurality of light emission elements 11 controlled by the first control circuit 51, thereby controlling the luminance. Specifically, the second control circuit 52 determines the chromaticity of the second light emission color and the luminance ratio of the light emission element 11 emitting light of the first light emission color and the light emission element 11 emitting light of the second light emission color from the chromaticity signal and the luminance signal displayed by each pixel 12 to correspond to the first light emission color.Subsequently, the second control circuit 52 determines the light emission intensity corresponding to the luminance signal to be displayed by the light emission element 11 emitting light of the second light emission color based on the chromaticity of the second light emission color and the luminance ratio. In response, the first control circuit 51, by accessing the information memory 70, supplies an operating current having a value corresponding to the light emission color of each of the light emission elements 11 to the corresponding one of the light emission elements 11. The second control circuit 52 further controls the light emission period of each of the light emission elements 11 in accordance with the determined light emission intensity. Method for determining the operating current value and the PWM light emission period

[0064] The following are details of the method for determining the operating current value and the PWM light emission period of each of the light emitting elements 11 with reference to the functional block diagram of Fig. 9 and the chromaticity diagram of Fig. 10 described.

[0065] First, in step S901, the operation control section 60 acquires image data from an external source. The input data includes R luminance, luminance, and B luminance.

[0066] Subsequently, in step S902, a specific light emission chromaticity and a luminance are determined for each pixel. Each light emission chromaticity to be emitted is represented by a point A on the chromaticity diagram of Fig. 10. In this chromaticity diagram, because the light-emitting element 11 emits blue light as the first light-emitting color, it is fixed at a point B near the lower left vertex of the chromaticity diagram. On the other hand, because the same light-emitting element 11 is caused to emit light of any color from green to red as the second light-emitting color in a subframe different from the first light-emitting color, the second light-emitting color is represented on the chromaticity diagram at a point C between green near the upper vertex and red near the right vertex of the chromaticity diagram. Accordingly, the chromaticity at point A expressed by the mixed light of the light-emitting element 11 emitting light of the first light-emitting color and the light-emitting element 11 emitting light of the second light-emitting color can be expressed by points B and C.In other words, the second light emission color of the light emission element 11 is adjusted to the point C to express the chromaticity at the point A. Further, the luminance ratio of B : (GR) with respect to a predetermined point A is determined by considering the luminance balance between the light emission element 11 emitting light of the first light emission color and the light emission element 11 emitting light of the second light emission color. Thus, the operating current value and the light emission period of the light emission element 11 emitting light of the second light emission color are determined at the point C.

[0067] According to the idea described above, considering the light emission chromaticity (B) of B from the light emission chromaticity (A) of A determined in step S902 (step S903), the light emission chromaticity (C) of (GR) and the luminance ratio of B to (GR) are determined (step S904). When the luminance ratio of B to (GR) is determined in step S904, the luminance of (GR) and the luminance of B are necessarily obtained from the luminance at the light emission chromaticity (A) in step S902 (step S908).

[0068] On the other hand, when the light emission chromaticity (C) of (GR) is determined in step S904, the (GR) light emission chromaticity-operation current characteristic table stored in the information memory 70 is accessed (step S905) to determine the operation current value of (GR) (step S906).

[0069] When the operating current value of (GR) is determined in step S906, the (GR) light emission chromaticity operating current luminance characteristic table stored in the information memory 70 (step S907) and the luminance of (GR) (step S908) are accessed to determine the PWM light emission period of (GR) (step S909).

[0070] On the other hand, from the luminance of B obtained in step S908, the PWM light emission period of B is determined (step S911) with reference to the luminance characteristic value (step S910) to the driving current value corresponding to the chromaticity of B. In this way, the driving current value of each of the light-emitting elements 11 emitting light of the second light emission color and the PWM light emission periods of the light-emitting element 11 emitting light of the first light emission color and the light-emitting element 11 emitting light of the second light emission color are determined. The driving current value of the light-emitting element 11 emitting light of the first light emission color is a driving current value at which the blue light emission efficiency is good, for example, a rated current value, or the maximum value of the driving current value that causes the light-emitting element to emit blue light.

[0071] In the light-emitting device 100 according to the first embodiment described above, the light-emitting element 11 is provided for each pixel 12. However, multiple light-emitting elements may be provided for each pixel. This makes it possible to increase the light emission luminance.

[0072] In the first embodiment, the one frame period FT is divided into the first subframe period SF1 in which the light-emitting element 11 emits light of the first light-emitting color, and the second subframe period SF2 in which the light-emitting element 11 emits light of the second light-emitting color, wherein the first subframe period SF1 is the B subframe in which blue light is emitted, and the second subframe period SF2 is the GR subframe in which light of any color from green to red is emitted, wherein Fig.2 shows a state where the first subframe period SF1 precedes the second subframe period SF2. However, the present disclosure is not limited to this configuration. For example, the second subframe, which is the GR subframe for emitting light of any color from green to red, may precede the first subframe, which is the B subframe for emitting blue light. As described above, the human eye is sensitive to brightness in the GR subframe and colors by combining the GR subframe and the B subframe, but it is the timing at which brightness is perceived that determines the time resolution. Accordingly, advancing the GR subframe makes it possible to suppress the human-perceived timing delay with respect to video display data input to a display system.In this case, the preceding GR subframe can be referred to as the first subframe and the B subframe as the second subframe.

[0073] The above examples describe an active matrix operating method. However, the present disclosure may also be applied to a passive matrix operating method.

[0074] A light emitting device of the present disclosure can be suitably used for, for example, a medium-sized or large-sized display, indicator, signage, or the like. Industrial applicability

[0075] The light emitting device and its operating method according to the present invention can be suitably used for, for example, a medium or large-sized display, an indicator, a signage or the like.

[0076] Furthermore, the disclosure includes examples according to the following points: Item 1. A light-emitting device comprising: a display comprising a plurality of pixels in which a plurality of light-emitting elements are arranged in a predetermined pattern, wherein a light-emitting color of each of the plurality of light-emitting elements is variable according to an operating current; and a lighting control section configured to supply an operating current to each of the plurality of light-emitting elements and to control a light-emitting period of each of the plurality of light-emitting elements, wherein the lighting control section is designed to: a frame in which the lighting control section operates the plurality of light-emitting elements to emit light, divided into a first sub-frame and a second sub-frame, operates the plurality of light-emitting elements to emit light of a first light-emitting color in the first sub-frame, and operates the plurality of light-emitting elements to emit light of a second light-emitting color in the second sub-frame, wherein the second light-emitting color is different from the first light-emitting color. Item 2. The light emitting device according to item 1, which further comprises: an information storage configured to store current chromaticity information for determining an operating current value to operate the light-emitting element to emit light of the first light-emitting color or the second light-emitting color in accordance with a specific light-emitting color of a light-emitting element of the light-emitting elements, wherein the illumination control section is configured to control the plurality of light-emitting elements based on the current chromaticity information stored in the information storage so that each of the plurality of light-emitting elements emits light of a specific light-emitting color and light-emitting luminance. Item 3. The light-emitting device according to item 1 or 2, wherein: The lighting control section includes: a first control circuit configured to supply an operating current to each of the plurality of light emitting elements, and a second control circuit configured to control a light emission period of each of the plurality of light emission elements. Item 4. The light emitting device according to item 3, wherein at least one first control circuit and at least one second control circuit are provided for each of the pixels. Item 5. The light-emitting device according to any one of items 1 to 4, wherein either the first light-emitting color or the second light-emitting color is blue. Item 6. The light-emitting device according to any one of items 1 to 5, wherein either the first light-emitting color or the second light-emitting color is tunable between green and red according to an operating current to the first light-emitting element or to the second light-emitting element, respectively. Item 7. The light emitting device according to any one of items 1 to 6, wherein the light-emitting element comprises a first light-emitting section designed to emit light in the first light-emitting color z and a second light-emitting section designed to emit light in the second light-emitting color, and wherein the light emission of the first light emission section and the light emission of the second light emission section are selectable by a switch. Item 8. The light emitting device according to item 7, wherein the first light emitting section and the second light emitting section are connected in series. Item 9. The light emitting device according to item 8, which further comprises: a first switch connected in parallel with the first light emitting section; and a second switch connected in parallel with the second light emitting section, wherein the first switch and the second switch are arranged at an intermediate point of a series circuit between the first light emitting section and the second light emitting section. Item 10. The light-emitting device according to item 2, wherein: the lighting control section further comprises: a first control circuit configured to supply an operating current to each of the plurality of light emitting elements, and a second control circuit configured to control a light emission period of each of the plurality of light emission elements, wherein the first control circuit is configured to supply an operating current having a value corresponding to a light emission color of each of the plurality of light emission elements to the corresponding one of the plurality of light emission elements by accessing the information memory, and wherein the second control circuit is configured to control a light emission period of the operating current supplied to the light emission element emitting light of the first light emission color and the light emission element emitting light of the second light emission color in accordance with a light emission intensity corresponding to a luminance signal to be displayed by each of the plurality of light emission elements, the light emission intensity being determined based on a chromaticity of the second light emission color and a luminance ratio of the luminance of a light emission element of the plurality of light emission elements emitting light of the first light emission color and the luminance of a light emission element of the plurality of light emission elements emitting light of the second light emission color,wherein the chromaticity of the second light emission color and the luminance ratio are determined from a chromaticity signal and a luminance signal, which are the basis of the chromaticity and luminance to be displayed by each pixel, to respectively correspond to the first light emission color in the second subframe. Item 11. The light-emitting device according to any one of items 1 to 10, wherein the first light-emitting color is blue. Item 12. The light-emitting device according to item 11, wherein the first light emission color has a fixed wavelength. Item 13. The light emitting device according to any one of items 1 to 12, wherein: the lighting control section is designed to set a time interval for supplying a current to each of the plurality of light-emitting elements based on a comparison between a first signal comprising a triangular wave signal and a first DC voltage set in a predetermined period, and the lighting control section is configured to control a current value to be supplied based on a second DC voltage set in a period different from the predetermined period. Item 14. A method of operating a light-emitting device comprising: a display having a plurality of pixels in which a plurality of light-emitting elements are arranged in a predetermined pattern, wherein a light-emitting color of each of the plurality of light-emitting elements is variable according to a driving current supplied thereto, an information storage configured to store current chromaticity information for determining a driving current value in accordance with a specific light-emitting color of a light-emitting element of the light-emitting elements to drive the light-emitting element to emit light having a first light-emitting color or a second light-emitting color different from the first light-emitting color, and a lighting control section configured tothat it supplies an operating current to each of the plurality of light-emitting elements and controls a light-emitting period of each of the plurality of light-emitting elements, the method comprising: Operating a frame in which the illumination control section operates the plurality of light emitting elements to emit light into a first sub-frame and a second sub-frame; Operating the plurality of light-emitting elements to emit light of a first light-emitting color into the first sub-frame; and Operating the plurality of light emitting elements to emit light of a second light emission color in the second sub-frame, wherein the second light emission color is different from the first light emission color. Item 15. The method of operating a light emitting device according to item 14, wherein: operating the plurality of light emitting elements with the lighting control section comprises: Determining a chromaticity of the second light emission color and a luminance ratio of the luminance of a light emission element of the plurality of light emission elements emitting light of the first light emission color and the luminance of a light emission element of the light emission elements emitting light of the second light emission color from a chromaticity signal and a luminance signal to be displayed by each pixel so as to correspond to the first light emission color, Determining a light emission intensity corresponding to a luminance signal that forms the basis of the luminescence to be displayed by each of the plurality of light emission elements based on the chromaticity of the second light emission color and the luminance ratio, Supplying an operating current having a value corresponding to a light emission color of each of the plurality of light emission elements to the corresponding one of the plurality of light emission elements with reference to the information storage having a first control circuit of the lighting control section, and Controlling a light emission period of the operating current supplied by the first control circuit in accordance with the determined light emission intensity with a second control circuit of the lighting control section. Item 16. The method of operating a light emitting device according to item 15, wherein: operating the plurality of light emitting elements with the lighting control section comprises: Controlling a light emission intensity by pulse width modulation control in the first subframe with the second control circuit, while the first control circuit keeps an operating current of each of the plurality of light emission elements for emitting light of the first light emission color constant, and Controlling, in the second subframe, by the first control circuit, a light emission color by a current value for driving each of the plurality of light emission elements emitting light of the second light emission color, and controlling, by the second control circuit, a luminance by a light emission period of the current value of each of the plurality of light emission elements controlled by the first control circuit. List of reference symbols

[0077] 100 light emitting device 2 n-type semiconductor layer; 2A First n-type semiconductor layer; 2B Second n-type semiconductor layer 3 Active layer; 3A First light-emitting layer; 3B Second light-emitting layer 4 P-type semiconductor layer; 4A First p-type semiconductor layer; 4B Second p-type semiconductor layer 5 n-side electrode 6 p-side electrode; 6A First p-side electrode; 6B Second p-side electrode 7 Ohmic connection layer 8, 8B pixel operating circuit 9, 9B Power supply line 10 Advertisement 11, 11B Light emitting element 12 pixels 14 pixel circuit 20 sampling circuit 30 drivers 50 Lighting control section 51 First control circuit; 52 Second control circuit 60 Operation control section 70 information storage WS write scan line WS1 Power supply control signal write scan line; WS2 Analog image signal write scan line SL Signal line; SL1 Power supply control signal line; SL2 SW1 First switch SW2 Second switch QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP 2023-218,221

[0001] JP 2021-52168 A

[0004] US 10885834

[0028]

Claims

A light emitting device comprising:a display including a plurality of pixels in which a plurality of light emitting elements are arranged in a predetermined pattern, wherein a light emission color of each of the plurality of light emitting elements is variable according to an operating current;and a lighting control section configured to supply an operating current to each of the plurality of light-emitting elements and to control a light-emitting period of each of the plurality of light-emitting elements, wherein the lighting control section is configured to: divide a frame in which the lighting control section operates the plurality of light-emitting elements to emit light into a first sub-frame and a second sub-frame, operate the plurality of light-emitting elements to emit light of a first light-emitting color in the first sub-frame, and operate the plurality of light-emitting elements to emit light of a second light-emitting color in the second sub-frame, the second light-emitting color being different from the first light-emitting color; The light-emitting device according to claim 1, further comprising:an information storage configured to store current chromaticity information for determining an operating current value for operating the light-emitting element to emit light of the first light-emitting color or the second light-emitting color in accordance with a specific light-emitting color of a light-emitting element of the light-emitting elements;wherein the illumination control section is configured to control the plurality of light-emitting elements based on the current chromaticity information stored in the information storage so that each of the plurality of light-emitting elements emits light of a specific light-emitting color and light-emitting luminance. The light emitting device according to claim 1, wherein:the illumination control section comprises:a first control circuit configured to supply an operating current to each of the plurality of light emitting elements, anda second control circuit configured to control a light emitting period of each of the plurality of light emitting elements. A light emitting device according to claim 3, wherein at least one first control circuit and at least one second control circuit are provided for each of the pixels. The light emitting device according to claim 1, wherein either the first light emission color or the second light emission color is blue. The light emitting device according to claim 1, wherein either the first light emission color or the second light emission color is tunable between green and red according to an operating current to the first light emission element or to the second light emission element, respectively. The light emitting device according to claim 1, wherein the light emitting element comprises a first light emitting section configured to emit light in the first light emitting color z and a second light emitting section configured to emit light in the second light emitting color, and wherein the light emission of the first light emitting section and the light emission of the second light emitting section are selectable by a switch. The light emitting device according to claim 7, wherein the first light emitting section and the second light emitting section are connected in series. The light emitting device according to claim 8, further comprising: a first switch connected in parallel to the first light emitting section; and a second switch connected in parallel to the second light emitting section, wherein the first switch and the second switch are arranged at an intermediate point of a series circuit between the first light emitting section and the second light emitting section. The light-emitting device according to claim 2, wherein: the lighting control section further comprises: a first control circuit configured to supply an operating current to each of the plurality of light-emitting elements, and a second control circuit configured to control a light-emitting period of each of the plurality of light-emitting elements, wherein the first control circuit is configured to supply an operating current having a value corresponding to a light-emitting color of each of the plurality of light-emitting elements to the corresponding one of the plurality of light-emitting elements by accessing the information storage, and wherein the second control circuit is configured to control a light-emitting period of the operating current supplied to the light-emitting element emitting light of the first light-emitting color and the light-emitting element emitting light of the second light-emitting color,in accordance with a light emission intensity corresponding to a luminance signal to be displayed by each of the plurality of light emission elements, wherein the light emission intensity is determined based on a chromaticity of the second light emission color and a luminance ratio of the luminance of a light emission element of the plurality of light emission elements that emits light of the first light emission color and the luminance of a light emission element of the plurality of light emission elements that emits light of the second light emission color, wherein the chromaticity of the second light emission color and the luminance ratio are determined from a chromaticity signal and a luminance signal that are the basis of the chromaticity and luminance to be displayed by each pixel to correspond to the first light emission color in the second subframe, respectively. The light emitting device according to claim 1, wherein the first light emission color is blue. The light emitting device according to claim 11, wherein the first light emission color has a fixed wavelength. The light emitting device according to claim 1, wherein: the illumination control section is configured to set a time interval for supplying a current to each of the plurality of light emitting elements based on a comparison between a first signal comprising a triangular wave signal and a first DC voltage set at a predetermined period, and the illumination control section is configured to control a current value to be supplied based on a second DC voltage set at a period different from the predetermined period. A method of operating a light-emitting device comprising: a display having a plurality of pixels in which a plurality of light-emitting elements are arranged in a predetermined pattern, wherein a light-emitting color of each of the plurality of light-emitting elements is variable according to an operating current supplied thereto, an information storage configured to store current chromaticity information for determining an operating current value in accordance with a specific light-emitting color of a light-emitting element of the light-emitting elements in order to operate the light-emitting element to emit light having a first light-emitting color or a second light-emitting color different from the first light-emitting color, and a lighting control section configured tothat it supplies an operating current to each of the plurality of light-emitting elements and controls a light-emitting period of each of the plurality of light-emitting elements, the method comprising: operating a frame in which the illumination control section operates the plurality of light-emitting elements to emit light into a first sub-frame and a second sub-frame; operating the plurality of light-emitting elements to emit light of a first light-emitting color in the first sub-frame; and operating the plurality of light-emitting elements to emit light of a second light-emitting color in the second sub-frame, wherein the second light-emitting color is different from the first light-emitting color. A method for operating a light-emitting device according to claim 14, wherein: operating the plurality of light-emitting elements with the illumination control section comprises: determining a chromaticity of the second light-emitting color and a luminance ratio of the luminance of a light-emitting element of the plurality of light-emitting elements emitting light of the first light-emitting color and the luminance of a light-emitting element of the light-emitting elements emitting light of the second light-emitting color from a chromaticity signal and a luminance signal to be displayed by each pixel so as to correspond to the first light-emitting color; determining a light-emitting intensity corresponding to a luminance signal that forms the basis of the luminescence to be displayed by each of the plurality of light-emitting elements based on the chromaticity of the second light-emitting color and the luminance ratio;Supplying an operating current having a value corresponding to a light emission color of each of the plurality of light emission elements to the corresponding one of the plurality of light emission elements with reference to the information storage with a first control circuit of the lighting control section s, and controlling a light emission period of the operating current supplied by the first control circuit in accordance with the determined light emission intensity with a second control circuit of the lighting control section s. A method of operating a light-emitting device according to claim 15, wherein: operating the plurality of light-emitting elements with the illumination control section comprises: controlling a light emission intensity by pulse width modulation control in the first subframe with the second control circuit while the first control circuit keeps an operating current of each of the plurality of light-emitting elements for emitting light of the first light-emitting color constant, and controlling, in the second subframe, by the first control circuit, a light emission color by a current value for operating each of the plurality of light-emitting elements emitting light of the second light-emitting color, and controlling, by the second control circuit, a luminance by a light emission period of the current value of each of the plurality of light-emitting elements controlled by the first control circuit.

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