Electrophoretic display device and driving method

Abstract

The invention discloses an electrophoretic display device, and relates to the field of electrophoretic display, the electrophoretic display device comprises an electrophoretic display unit, a refraction layer and an ultraviolet light source layer, an ultraviolet light source device area is arranged in a corner area opposite to the electrophoretic display unit, and an ultraviolet light emitting diode is arranged in the ultraviolet light source device area of the ultraviolet light source layer; wherein fluorescent electrophoresis particles of the electrophoresis display unit are excited to perform fluorescence color development under ultraviolet irradiation; the anode, the UV light-emitting layer and the cathode of the UV light-emitting diode are arranged in an inclined stacking mode, and UV light rays firstly pass through the transparent electrode and then pass through the refraction layer to be subjected to light density to light density refraction, deflected to the electrophoresis display unit, subjected to photoluminescence and emitted out through the display window area. In addition, the invention further discloses an electrophoretic display driving method. The UV diode light source is arranged on the side of the electrophoretic display light emitting side to provide an ultraviolet light source for the electrophoretic particles of the electrophoretic display layer and excite fluorescence, and the brightness of the electrophoretic display layer and the uniformity of light emitting are effectively improved.

Description

Technical Field

[0001] The present invention relates to the field of optoelectronic display, and in particular to an electrophoretic display device and a driving method. Background Art

[0002] With the rapid development of display technology, various types of information display devices have gradually entered the market, including liquid crystal displays, electroluminescent displays and electrophoretic displays. Among them, electrophoretic displays display letters, numbers and images by reflecting ambient light. In addition, the total internal reflection of electrophoretic displays has low energy consumption, is convenient and environmentally friendly, and reduces the damage of blue light to the eyes. In recent years, electrophoretic displays have been increasingly used.

[0003] At present, the electronic ink screens on the market usually use an edge-entry backlight as the light source. The light emitted by the edge-entry backlight enters the human eye after being reflected by the electronic ink screen, allowing the human eye to observe the display content on the screen. However, due to the structure of the edge-entry backlight, the light source must be installed on one side of the edge-entry backlight. The light propagation process from the light source to the electrophoretic display unit is always disordered, resulting in the end of the edge-entry backlight close to the light being bright and the end away from the light source being dark. The brightness uniformity is poor, which affects the display effect of the electrophoretic display. In addition, the commonly used edge-entry backlight often uses white light as a supplementary light source, which increases the amount of incident light on the electrophoretic display unit, and then increases the amount of light incident on the human eye. There has not been a significant improvement in the brightness of the electrophoretic display, which is not conducive to people using the electrophoretic display screen in an environment without sunlight or artificial light sources.

[0004] In addition, as shown in Chinese patent CN202411328802.5, a color fluorescent particle for electrophoretic display and a preparation method thereof are provided. The color fluorescent particles provided by this patent also require a UV light source for fluorescence excitation. However, when the traditional edge-entry backlight panel reaches the corresponding pixel point, the brightness and light uniformity are poor. Summary of the invention

[0005] In view of the shortcomings of the prior art, the primary purpose of the present invention is to remedy the shortcomings of the prior art and provide an electrophoretic display device, which aims to provide an ultraviolet light source for the electrophoretic particles of the electrophoretic display layer and excite fluorescence by arranging a UV diode light source on the side of the electrophoretic display light-emitting layer, thereby effectively improving the brightness of the electrophoretic display layer and the uniformity of the light output.

[0006] To achieve the above-mentioned object, in a first aspect of the present invention, an electrophoretic display device is provided, the device comprising: an electrophoretic display layer including an electrophoretic display unit, an ultraviolet light source layer, and a refractive layer arranged between the electrophoretic display unit and the ultraviolet light source layer, the ultraviolet light source layer comprising a display window area and an ultraviolet light source device area, the ultraviolet light source device area being arranged at a corner area opposite to the electrophoretic display unit, the ultraviolet light source device area being provided with an ultraviolet light emitting diode; wherein the electrophoretic display unit comprises fluorescent electrophoretic particles, the fluorescent electrophoretic particles being stimulated to fluoresce and display color under ultraviolet irradiation;

[0007] The ultraviolet light emitting diode comprises an anode, a UV light emitting layer and a cathode, wherein the anode is located near the electrophoretic display unit, the UV light emitting layer is located between the anode and the cathode, and the cathode is located on the light emitting side of the device; wherein the anode is a transparent electrode and the cathode is an opaque electrode;

[0008] The anode, the UV light-emitting layer and the cathode are arranged in an oblique stack, and the electrophoretic display unit is located directly downstream of the first pointing direction from the cathode through the UV light-emitting layer and the anode. The light-emitting direction of the ultraviolet light-emitting diode is inclined toward the electrophoretic display unit. The refractive index of the refractive layer is smaller than the refractive index of the transparent electrode. The UV light emitted by the ultraviolet light-emitting diode first passes through the transparent electrode and then through the refractive layer to undergo light-dense to light-sparse refraction and is deflected to the electrophoretic display unit to generate photoluminescence and is emitted through the display window area.

[0009] In a specific embodiment, the thickness of the refractive layer is greater than or equal to the thickness of the anode; the thickness of the anode is 10 nm-50 nm, and the thickness of the refractive layer is 50 nm-200 μm.

[0010] In a specific embodiment, one ultraviolet light source device area corresponds to two electrophoretic display units, and the ultraviolet light source device area is located between the two electrophoretic display units; the ultraviolet light-emitting diode in the ultraviolet light source device area includes a common cathode, a first UV light-emitting layer, a second UV light-emitting layer, a first anode, and a second anode; the common cathode, the first UV light-emitting layer, and the first anode are arranged in an oblique stack, and the first electrophoretic display unit is directly downstream in a second direction from the common cathode through the first UV light-emitting layer and the first anode; the common cathode, the second UV light-emitting layer, and the second anode are arranged in an oblique stack, and the second electrophoretic display unit is directly downstream in a third direction from the common cathode through the second UV light-emitting layer and the second anode.

[0011] In a specific embodiment, the device includes a plurality of ultraviolet light emitting diodes, the electrophoretic display unit includes a plurality of electrophoretic pixels, the types of the electrophoretic pixels include red pixel units, green pixel units and / or blue pixel units, and the ultraviolet light emitting diodes are arranged diagonally to each of the electrophoretic pixels.

[0012] In a specific embodiment, the first anode and the second anode are connected to independent positive power supply potential signal lines.

[0013] In a specific embodiment, the material of the anode includes one or a combination of two or more of indium tin oxide film, aluminum-doped zinc oxide film, fluorine-doped tin oxide film, graphene film, carbon nanotube film, metal grid film, and conductive polymer film.

[0014] In a second aspect of the present invention, a driving method for an electrophoretic display is provided. The method is applied to an electrophoretic display device provided in the first aspect of the present invention. The method comprises:

[0015] In response to a first driving signal, driving the electrophoretic display unit to present letters, images, and numbers;

[0016] In response to a second driving signal, a plurality of ultraviolet light emitting diodes in the ultraviolet light source layer are driven to emit light; wherein the UV light emitted by the ultraviolet light emitting diodes first passes through a transparent electrode and then through a refractive layer to undergo light-dense to light-sparse refraction and is deflected to the electrophoretic display unit to generate photoluminescence and is emitted through the display window area.

[0017] In a specific embodiment, the process of driving multiple ultraviolet light emitting diodes in the ultraviolet light source layer to emit light includes: monitoring the light intensity of the external ambient light, and when the monitored light intensity is greater than or equal to the light intensity threshold, not driving the ultraviolet light emitting diodes to emit light; when the monitored light intensity is less than the light intensity threshold, driving the ultraviolet light emitting diodes to emit light.

[0018] Beneficial effects of the present invention: 1) The present invention provides an ultraviolet light source and excites fluorescence for the electrophoretic particles of the electrophoretic display layer by arranging a UV diode light source on the side of the electrophoretic display light-emitting side, thereby effectively improving the brightness of the electrophoretic display layer and the uniformity of light emission. 2) In the present invention, the anode of the ultraviolet light-emitting diode is located on the side close to the electrophoretic display unit, the anode is a transparent electrode, and the corresponding cathode is an opaque electrode; on the one hand, the cathode can effectively block ultraviolet rays from irradiating to the light-emitting side, and on the other hand, the amount of irradiation to the electrophoretic display layer is increased. In addition, considering that the light-emitting direction of the LED is biased towards the anode of the PN junction, the anode of the ultraviolet light-emitting diode is also close to the side of the electrophoretic display unit. 3) In the present invention, the anode, UV light-emitting layer and cathode are arranged in an oblique stack, and the electrophoretic display unit is directly downstream of the first pointing direction from the cathode through the UV light-emitting layer and the anode. The light-emitting direction of the ultraviolet light-emitting diode is inclined toward the electrophoretic display unit. The refractive index of the refractive layer is less than the refractive index of the transparent electrode. The UV light emitted by the ultraviolet light-emitting diode first passes through the transparent electrode and then through the refractive layer to undergo light-dense to light-sparse refraction and deflects to the electrophoretic display unit and generates photoluminescence, and is emitted through the display window area. In the UV-LED, controlled by the anode and cathode voltages, electrons and holes recombine in an oblique stacking motion direction, and mainly emit light along the direction of electron motion, and emit light obliquely; then, light-dense to light-sparse deflection occurs at the anode / refractive layer interface to irradiate the electrophoretic display unit, thereby realizing UV-LED light source regulation, effectively ensuring UV irradiation, and increasing the light output window opening rate of the electrophoretic display window to reduce UV-LED shading. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A schematic diagram of the structure of an electrophoretic display device provided in another specific embodiment of the present invention;

[0020] Figure 2 It is a schematic structural diagram of an electrophoretic display device with a single ultraviolet light source device area and dual ultraviolet LEDs provided in another specific embodiment of the present invention;

[0021] Figure 3 It is a schematic structural diagram of a red, green and blue three-primary color electrophoretic display device provided in another specific embodiment of the present invention. DETAILED DESCRIPTION

[0022] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0023] like Figure 1-Figure 3As shown, in a first embodiment of the present invention, an electrophoretic display device is provided, the device comprising: an electrophoretic display layer 100 including an electrophoretic display unit 101, an ultraviolet light source layer 200, and a refractive layer 300 arranged between the electrophoretic display unit 101 and the ultraviolet light source layer 200, the ultraviolet light source layer 200 comprising a display window area 201 and an ultraviolet light source device area 202, the ultraviolet light source device area 202 being arranged at a corner area opposite to the electrophoretic display unit 101, the ultraviolet light source device area 202 being provided with an ultraviolet light emitting diode 203; wherein the electrophoretic display unit 101 comprises fluorescent electrophoretic particles 102, the fluorescent electrophoretic particles 102 being stimulated to fluoresce under ultraviolet irradiation;

[0024] The ultraviolet light emitting diode 203 includes an anode 204, a UV light emitting layer 205 and a cathode 206, wherein the anode 204 is located near the electrophoretic display unit 101, the UV light emitting layer 205 is located between the anode 204 and the cathode 206, and the cathode 206 is located on the light emitting side of the device; wherein the anode 204 is a transparent electrode, and the cathode 206 is an opaque electrode;

[0025] The anode 204, the UV light emitting layer 205 and the cathode 206 are arranged in an oblique stack, and the electrophoretic display unit 101 is directly downstream of the first pointing direction from the cathode 206 through the UV light emitting layer 205 and the anode 204. The light emitting direction of the ultraviolet light emitting diode 203 is inclined toward the electrophoretic display unit 101. The refractive index of the refractive layer 300 is smaller than the refractive index of the transparent electrode. The UV light emitted by the ultraviolet light emitting diode 203 first passes through the transparent electrode and then through the refractive layer 300 to undergo light-dense to light-sparse refraction and is deflected to the electrophoretic display unit 101 and generates photoluminescence, and is emitted through the display window area 201.

[0026] Furthermore, the thickness of the refractive layer 300 is greater than or equal to the thickness of the anode 204 ; the thickness of the anode 204 is 10 nm-50 nm, and the thickness of the refractive layer 300 is 50 nm-200 μm.

[0027] Preferably, the anode 204 is an ITO film with a thickness of 20nm-30nm.

[0028] It is worth mentioning that in the present embodiment, in the PN junction region of the ultraviolet light emitting diode 203, the electrons are mainly affected by the PN junction electric field and current, and the direction of their movement is related to the position settings of the cathode 206 and the anode 204 on both sides, that is, since in the present embodiment, the anode 204, the UV light emitting layer 205 and the cathode 206 are arranged in an oblique stack, the direction of electron-hole recombination in the PN junction region also moves in this direction; and the ultraviolet light generated by the electron-hole recombination is emitted from the anode 204 composed of a transparent conductive material. Since the refractive index of the refractive layer 300 is less than the refractive index of the transparent electrode, the UV light emitted by the ultraviolet light emitting diode 203 first passes through the transparent electrode and then through the refractive layer 300, and is refracted from light dense to light sparse, and is deflected to the electrophoretic display unit 101 and generates photoluminescence, and is emitted through the display window area 201. In the anode 204 and outside the anode 204, the direction of the ultraviolet light source is mainly affected by optical refraction and transmission.

[0029] In a typical example, one ultraviolet light emitting diode 203 corresponds to one pixel of the electrophoretic display unit 101; in an optional embodiment, the ultraviolet light source device area 202 can be set between two pixels of the electrophoretic display unit 101, and the two electrophoretic display pixels can be provided with ultraviolet light sources respectively.

[0030] For example Figure 2 As shown, in an optional embodiment, one ultraviolet light source device area 204 corresponds to two electrophoretic display units, and the ultraviolet light source device area 204 is located between the two electrophoretic display units; the ultraviolet light emitting diode of the ultraviolet light source device area 204 includes a common cathode 207, a first UV light emitting layer 208, a second UV light emitting layer 209, a first anode 210, and a second anode 211; the common cathode 207, the first UV light emitting layer 208, and the first anode 210 are arranged in an oblique stack, and the first electrophoretic display unit 103 is directly downstream of the second pointing direction from the common cathode 207, through the first UV light emitting layer 208, and the first anode 210; the common cathode 207, the second UV light emitting layer 209, and the second anode 211 are arranged in an oblique stack, and the second electrophoretic display unit 104 is directly downstream of the third pointing direction from the common cathode 207, through the second UV light emitting layer 209, and the second anode 211.

[0031] like Figure 3 As shown, typically, in this embodiment, the device includes a plurality of ultraviolet light emitting diodes 203, the electrophoretic display unit 101 includes a plurality of electrophoretic pixels, the types of the electrophoretic pixels include red pixel units, green pixel units and / or blue pixel units, and the ultraviolet light emitting diodes 203 are arranged diagonally to each of the electrophoretic pixels.

[0032] In this embodiment, the first anode 204 and the second anode 204 are connected to independent positive power supply potential signal lines, which is conducive to separate control and brightness adjustment.

[0033] Typically, the material of the anode 204 includes one or a combination of two or more of an indium tin oxide film, an aluminum-doped zinc oxide film, a fluorine-doped tin oxide film, a graphene film, a carbon nanotube film, a metal mesh film, and a conductive polymer film.

[0034] An electrophoretic display device provided by the first embodiment of the present invention can be effectively applied to Chinese patent CN202411328802.5. When ultraviolet light or natural light such as sunlight emitted by the UV light source layer is incident on the electrophoretic display layer 100, photoluminescence occurs on the surface of the electrophoretic particles. After being reflected on the surface of the electrophoretic particles, these rays are emitted through the transparent electrode at the top, thereby producing a display effect with high brightness and high uniformity. The electrophoretic display technology of the present invention achieves optimized visual effects by precisely controlling the intensity and color output of various light sources. This technology can not only significantly improve the brightness of the electronic paper, but also ensure the uniformity of the displayed content at different viewing angles. In addition, the design of the system also takes energy efficiency into consideration, and by using ultraviolet light-emitting diodes, energy consumption is effectively reduced. The present invention brings innovative improvements to electrophoretic display technology, making its application in the field of modern display more extensive and efficient.

[0035] It is worth mentioning that when the electrophoretic display layer 100 is driven to present an image, based on the electrophoretic display principle, the colored electrophoretic particles in the electrophoretic display layer 100 are driven and controlled to move back and forth. Taking the electrophoretic pixels including red electrophoretic particles and white electrophoretic particles as an example, when the red electrophoretic particles are driven to move to the side close to the light output, the position appears red, and when the white electrophoretic particles are driven to move to the side close to the light output, the position appears white. By driving the movement of electrophoretic particles of different colors at different electrophoretic pixels, the electrophoretic display screen can present different pictures such as letters, numbers, and images. At the same time, under dark conditions or when the light is insufficient, the ultraviolet light source layer 200 can turn on UV light to photoexcite the electrophoretic particles, increase the brightness of the electrophoretic particles, and then increase the diffuse reflected light, so as to realize electrophoretic display in a dark environment or an environment with insufficient light source.

[0036] According to the light-emitting principle of the ultraviolet light source layer 200, a positive driving signal is provided to the anode 204 of the ultraviolet light-emitting diode 203 and a negative driving signal is provided to the cathode 206 to drive the ultraviolet light-emitting diode 203 to emit light. The UV light emitted by the ultraviolet light-emitting diode 203 is incident on the electrophoretic display layer 100 and generates photoluminescence. The diffusely reflected red, green and blue light enters the human eye through the red, green and blue display window areas 201, so that the user can see the letters, numbers, images and other pictures displayed on the electrophoretic display screen.

[0037] Compared with the side-entry light guide plate in the prior art, the ultraviolet light source layer 200 provided in the embodiment of the present invention is used as the light source of the electrophoretic display, which improves the brightness uniformity of the electrophoretic display light source, thereby improving the brightness uniformity of the picture presented by the electrophoretic display screen and improving the user's viewing experience.

[0038] See again Figure 1 , the cathode 206 is an opaque electrode. Such a configuration can, on the one hand, ensure that the ultraviolet light cannot be emitted through the cathode 206, thereby preventing the light emitted by the ultraviolet light emitting diode 203 from directly emitting to the human eye and causing interference, thereby affecting the display effect of the electrophoretic display; on the other hand, a small amount of light emitted by the ultraviolet light emitting diode 203 toward the cathode 206 can be reflected by the cathode 206 to the anode 204, and emitted through the anode 204, thereby improving the light extraction rate of the ultraviolet light emitting diode 203.

[0039] Optionally, the ultraviolet light emitting diode 203 is a passive electro-excited ultraviolet light emitting diode 203. When driving the passive electro-excited ultraviolet light emitting diode 203 to emit light, it is only necessary to directly provide corresponding driving signals to the anode 204 and the cathode 206, without the need to use a driving transistor for driving. Therefore, the ultraviolet light emitting diode 203 in the ultraviolet light source layer 200 is set as a passive electro-excited ultraviolet light emitting diode 203. The ultraviolet light source layer 200 only needs to be provided with the anode 204, the light emitting layer and the cathode 206, and there is no need to set a driving transistor, thereby reducing the thickness of the ultraviolet light source layer 200 and greatly reducing the manufacturing cost.

[0040] In a second embodiment of the present invention, a driving method for an electrophoretic display is provided. The method is applied to an electrophoretic display device provided in the first embodiment. The method includes:

[0041] In response to a first driving signal, driving the electrophoretic display unit to present letters, images, and numbers;

[0042] In response to a second driving signal, a plurality of ultraviolet light emitting diodes in the ultraviolet light source layer are driven to emit light; wherein the UV light emitted by the ultraviolet light emitting diodes first passes through a transparent electrode and then through a refractive layer to undergo light-dense to light-sparse refraction and is deflected to the electrophoretic display unit to generate photoluminescence and is emitted through the display window area.

[0043] In this embodiment, the process of driving multiple ultraviolet light emitting diodes in the ultraviolet light source layer to emit light includes: monitoring the light intensity of the external ambient light, and when the monitored light intensity is greater than or equal to the light intensity threshold, not driving the ultraviolet light emitting diodes to emit light; when the monitored light intensity is less than the light intensity threshold, driving the ultraviolet light emitting diodes to emit light.

[0044] The preferred specific embodiments of the present invention are described in detail above. It should be understood that a person skilled in the art can make many modifications and changes based on the concept of the present invention without creative work. Therefore, any technical solution that can be obtained by a person skilled in the art through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. An electrophoretic display device, characterized in that: The device comprises: an electrophoretic display layer including an electrophoretic display unit, an ultraviolet light source layer, and a refractive layer arranged between the electrophoretic display unit and the ultraviolet light source layer, wherein the ultraviolet light source layer comprises a display window area and an ultraviolet light source device area, wherein the ultraviolet light source device area is arranged at a corner area opposite to the electrophoretic display unit, and wherein the ultraviolet light source device area is provided with an ultraviolet light emitting diode; wherein the electrophoretic display unit comprises fluorescent electrophoretic particles, and the fluorescent electrophoretic particles are stimulated to fluoresce and display color under ultraviolet irradiation; The ultraviolet light emitting diode comprises an anode, a UV light emitting layer and a cathode, wherein the anode is located near the electrophoretic display unit, the UV light emitting layer is located between the anode and the cathode, and the cathode is located on the light emitting side of the device; wherein the anode is a transparent electrode and the cathode is an opaque electrode; The anode, the UV light-emitting layer and the cathode are arranged in an oblique stack, and the electrophoretic display unit is located directly downstream of the first pointing direction from the cathode through the UV light-emitting layer and the anode. The light-emitting direction of the ultraviolet light-emitting diode is inclined toward the electrophoretic display unit. The refractive index of the refractive layer is smaller than the refractive index of the transparent electrode. The UV light emitted by the ultraviolet light-emitting diode first passes through the transparent electrode and then through the refractive layer to undergo light-dense to light-sparse refraction and is deflected to the electrophoretic display unit to generate photoluminescence and is emitted through the display window area.

2. An electrophoretic display device according to claim 1, characterized in that: The thickness of the refractive layer is greater than or equal to the thickness of the anode; the thickness of the anode is 10nm-50nm, and the thickness of the refractive layer is 50nm-200μm.

3. An electrophoretic display device according to claim 1, characterized in that: One ultraviolet light source device area corresponds to two electrophoretic display units, and the ultraviolet light source device area is located between the two electrophoretic display units; the ultraviolet light emitting diode in the ultraviolet light source device area includes a common cathode, a first UV light emitting layer, a second UV light emitting layer, a first anode, and a second anode; the common cathode, the first UV light emitting layer, and the first anode are arranged in an oblique stack, and the first electrophoretic display unit is directly downstream in a second direction from the common cathode through the first UV light emitting layer and the first anode; the common cathode, the second UV light emitting layer, and the second anode are arranged in an oblique stack, and the second electrophoretic display unit is directly downstream in a third direction from the common cathode through the second UV light emitting layer and the second anode.

4. An electrophoretic display device according to claim 1, characterized in that: The device includes a plurality of ultraviolet light emitting diodes, the electrophoretic display unit includes a plurality of electrophoretic pixels, the types of the electrophoretic pixels include red pixel units, green pixel units and / or blue pixel units, and the ultraviolet light emitting diodes are arranged diagonally to each of the electrophoretic pixels.

5. The electrophoretic display device according to claim 3, characterized in that: The first anode and the second anode are connected to independent positive power supply potential signal lines.

6. An electrophoretic display device according to claim 1, characterized in that: The material of the anode includes one or a combination of two or more of an indium tin oxide film, an aluminum-doped zinc oxide film, a fluorine-doped tin oxide film, a graphene film, a carbon nanotube film, a metal grid film, and a conductive polymer film.

7. A driving method for an electrophoretic display, characterized in that: The method is applied to an electrophoretic display device as provided in any one of claims 1 to 8, and the method comprises: In response to a first driving signal, driving the electrophoretic display unit to present letters, images, and numbers; In response to a second driving signal, a plurality of ultraviolet light emitting diodes in the ultraviolet light source layer are driven to emit light; wherein the UV light emitted by the ultraviolet light emitting diodes first passes through a transparent electrode and then through a refractive layer to undergo light-dense to light-sparse refraction and is deflected to the electrophoretic display unit to generate photoluminescence and is emitted through the display window area.

8. The driving method according to claim 7, characterized in that: The process of driving multiple ultraviolet light-emitting diodes in the ultraviolet light source layer to emit light includes: monitoring the light intensity of the external ambient light, when the monitored light intensity is greater than or equal to the light intensity threshold, not driving the ultraviolet light-emitting diodes to emit light, and when the monitored light intensity is less than the light intensity threshold, driving the ultraviolet light-emitting diodes to emit light.

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