Display device

Abstract

A display device 10 comprising of a cover panel 3, a light source 11 and an optical structure 12 where the light source 11 emits the light towards the cover panel 3 and may have a first surface 13 tha

Description

The present invention relates to the field of display systems. In particular, the present invention relates to a display device and methods for manufacturing the display device. Background to the Invention A display system may comprise one or more display devices such as liquid crystal displays (LCDs), organic light-emitting diode (OLED) displays and light-emitting diode (LED) displays. These various types of display devices are employed to present visual information to users, enabling the representation of images, videos, and other visual content. The selection of a specific display device depends on the application, where factors such as image quality, energy efficiency, brightness, and the intended environment influence the choice of display device. Each type of display device operates using distinct technologies. For example, non-emissive liquid crystal displays (LCDs) rely on liquid crystals combined with a backlight to create images. Organic light-emitting diode (OLED) displays utilise organic compounds that emit light when an electric current is applied. MicroLED displays use miniature lightemitting diodes as individual display pixels. Additionally, LED display devices are often employed for backlighting, to enhance the overall luminance and visual quality of the display. As display technology continues to advance, there is a growing demand for display devices that not only provide high-quality visual content but also maintain an aesthetically pleasing appearance. Particularly, an important trend is to enhance the perceived size and scale of a display device to create a more immersive and engaging user experience. To achieve this, one or more additional LED display devices are often incorporated into the display system to create the illusion of a larger, more seamless display system surface. However, maintaining a uniform appearance across the entire display system surface, particularly when the display system is inactive, presents a significant challenge. For enhanced display systems that utilise additional LED display devices, a white diffuser is commonly used within the LED display device, to ensure uniform light distribution and homogeneity when the display device is active. While the white diffuser is effective in diffusing light evenly when the display device is turned on, the white appearance of the diffuser becomes problematic when the display device is inactive, as it does not match the desired dark or black panel aesthetic required to blend seamlessly with other display device types, for example those using LCD or OLED devices. A common method to address this issue, and match the appearance of the different display devices, is to apply a specialised ink, namely a dark smoke ink, to the cover panel of the LED display device. The dark smoke ink is designed to create the desired dark or black panel appearance, and to enhance the visual integration of the display device with its surroundings, when the display device is turned off. In particular, the dark smoke ink helps to reduce ambient light being reflected from the white diffuser surface, thus achieving the desired dark or black panel effect. However, this approach is highly inefficient in terms of optical performance. By adding the dark smoke ink above the white diffuser, up to 95% of the generated light can be lost. This inefficiency not only increases energy consumption but also raises production costs. There is generally a need for an apparatus and method to address the problems identified above. Summary of Invention It is an object of an aspect of the present invention to provide a display device that obviates or mitigates one or more drawbacks or disadvantages of the prior art. Further aims and objects of the invention will become apparent from reading the following description. According to a first aspect of the invention there is provided a display device comprising: a cover panel; a light source configured to emit light towards the cover panel; and an optical structure comprising an array of apertures that are transmissive at a wavelength of a light emitted by the light source, the optical structure being located between the light source and the cover panel; wherein the optical structure, except the array of apertures, is opaque at the wavelength of the light emitted by the light source; and wherein two or more of the apertures within the array of apertures comprise a surface area equal to a value A2 for each aperture and have a separation distance between two adjacent apertures in the range of A to A x 103, where 1 micron <A <1000 microns. The display device of the present invention offers several advantages by incorporating an array of apertures within the optical structure of the display device, that are transmissive at the wavelength of light emitted by the light source. The design significantly enhances the optical efficiency of the display device, allowing more light to pass through the optical structure and reach the cover panel. As a result, the display device provides improved brightness when it is turned on, ensuring that visual content is clearly presented. Moreover, the array of transmissive apertures contributes to a sleek and aesthetically pleasing appearance when the display device is turned off or inactive, as the arrangement of the apertures ensures the dark or black panel appearance of the display device is maintained. Optionally, the majority of the apertures within the array of apertures comprise a surface area A2. Alternatively, all of the apertures within the array of apertures comprise a surface area A2. The optical structure has an absorption level greater than about 60% at the wavelength of the light emitted by the light source. Optionally, the optical structure has an absorption level greater than 70%, greater than 80%, greater than 85%, greater than 90% or greater than 95% at the wavelength of the light emitted by the light source. Most preferably the light source comprises a first surface and a second surface, the first surface located between the optical structure and the second surface. The first surface is preferably configured to reflect incident light at the wavelength of the light emitted by the light source. The first surface of the light source has a reflectivity of greater than about 60% at the wavelength of the light emitted by the light source. Optionally, the first surface of the light source has a reflectivity of greater than 70%, greater than 80%, greater than 85%, greater than 90% or greater than 95% at the wavelength of the light emitted by the light source. Preferably the optical structure comprises a first surface and a second surface the first surface being oriented towards the cover panel and the second surface being oriented towards the light source. Preferably the second surface, excluding the array of apertures, is reflective at the wavelength of light emitted by the light source. This may be achieved through the addition of a reflective layer. Most preferably the second surface comprises a reflectivity of greater than 60% at the wavelength of the light emitted by the light source. Optionally, the second surface comprises a reflectivity of greater than 70%, greater than 80%, greater than 85% or greater than 90% at the wavelength of the light emitted by the light source. Optionally, the second surface comprises a specular reflector or a diffuse reflector. The specular reflector provides direct mirror-like reflections from the second surface. Preferably the second surface comprises a silver reflective coating. Preferably the cover panel comprises an output surface of the display device. Preferably the optical structure is located on the cover panel. The optical structure may comprise a decorative pattern, a black pattern or a dark smoke ink. The pattern and or texture of first layer of the optical structure may comprise a brushed metal, printed wood or black ink. As the optical structure is opaque at the wavelength of light emitted by the light source it provides the display device with the desired dark or black panel appearance when the light source is turned off. However, by additionally providing the reflective second surface an increase in the optical efficiency of the display device is observed. The light that is not transmitted through the array of apertures can be reflected by the second surface preventing that light from being lost or absorbed. This results in greater overall light transmission efficiency to the output surface of the display device. Preferably the two or more apertures within the array of apertures extend completely through the optical structure. Optionally, the two or more apertures within the array of apertures extend partially through the optical structure. Preferably the two or more apertures are greater than 95% transmissive at the wavelength of light emitted by the light source. The two or more apertures may be greater than 60%, greater than 70%, greater than 80%, or greater than 90% transmissive at the wavelength of light emitted by the light source. Optionally, the two or more apertures may be filled with a material transmissive at the wavelength of light emitted by the light source. The two or more apertures may comprise a regular or an irregular shape. Optionally the two or more apertures comprises a circular shape. The two or more apertures may alternatively comprise square, elliptical, triangular, oval, diamond or chevron shapes. Optionally 10 micron <A <500 microns. Alternatively, 100 micron <A <250 microns. The array of apertures may comprise a regular or irregular array. Preferably the array of apertures comprises a rectangular array. The array of apertures may comprise a circular, a square, a triangular, a hexagonal or a Kagome array. Optionally, the array of apertures comprises a random arrangement. A random arrangement of the array of apertures can reduce or avoid Moire Fringing. Preferably the array of apertures are uniformly distributed across the optical structure. Alternatively, the array of apertures may have a non-uniform distribution across the optical structure. The separation distance between the apertures may vary across the optical structure, such that certain regions of the optical structure have higher or lower aperture densities. Preferably the light source comprises a light emitting diode (LED) light source. Preferably, the cover panel comprises a material that is transmissive at the wavelength of light emitted by the light source, such as glass or plastic. In addition, the cover panel may be treated with an anti-reflective or anti-glare coating to improve visibility in various lighting conditions. According to a second aspect of the invention, there is method of manufacturing a display device, the method comprising: providing a cover panel and a light source; configuring the light source to emit light towards the cover panel; providing an optical structure comprising an array of apertures that are transmissive at a wavelength of the light emitted by the light source, locating the optical structure between the light source and the cover panel, configuring the optical structure, except the array of apertures, to be opaque at the wavelength of the light emitted by the light source, and providing two or more apertures within the array of apertures comprising a surface area equal to a value A2 for each aperture and having a separation distance between two adjacent apertures in the range of A to A x 103, where 1 micron <A <1000 microns. Embodiments of the second aspect of the present invention may comprise features to implement the preferred or optional features of the first aspect of the present invention or vice versa. According to a third aspect of the invention, there is provided an instrumental panel comprising one or more display devices according to the first aspect of the invention. Brief Description of Drawings There will now be described, by way of example only, various embodiments of the invention with reference to the drawings, of which: Figure 1 presents a cross-sectional view of a display device as is known in the art; Figure 2 presents (a) a cross-sectional view of a display device and (b) a top view of the optical structure of a display device in accordance with an embodiment of the present invention; and Figure 3 presents a cross-sectional view of a section of a display device in accordance with an alternative embodiment of the present invention. In the description which follows, like parts are marked throughout the specification and drawings with the same reference numerals. The drawings are not necessarily to scale, and the proportions of certain parts have been exaggerated to better illustrate details and features of embodiments of the invention. Detailed Description Figure 1 presents a cross-sectional view of a display device, as generally depicted by the reference numeral 1, as is known in the art. The display device 1 comprises a light source 2 and a cover panel 3. The cover panel 3 comprises a first surface 4 and a second surface 5 located opposite to the first surface 4, where the first surface 4 is an output surface for the display device 1. The light source 2 emits light towards the cover panel 3, where a portion of the light is transmitted through the cover panel 3 to the output surface 4, thereby enabling the display device 1 to present visual content to a user. To enhance the aesthetic appeal of the display device 1 when the light source 2 is turned off, a layer of dark smoke ink 6 is typically deposited on the second surface 5 of the cover panel 3. This dark smoke ink 6 acts to enhance the aesthetic appearance of the display device 1 by providing a uniform dark or black appearance when the display device 1 is turned off or inactive. This feature allows the cover panel 3 and hence the display device 1 to blend seamlessly into its surroundings when the light source 2 is turned off, contributing to providing the user with a visually appealing design. However, when the display device 1 is active, the dark smoke ink 6 also absorbs a significant portion of the light emitted by the light source 2. This absorption reduces the amount of light that passes through the cover panel 3, leading to a decrease in the overall brightness. As a result, the visibility and energy efficiency of the display device 1 are adversely affected. Therefore, achieving an appropriate balance between the desired dark or black cover panel appearance when the light source 2 is turned off while maintaining optimal brightness during operation of the display device 1 is a critical consideration in the design and implementation of a display device. A display device 7 in accordance with an embodiment of the present invention, and its method of production, will now be described with reference to Figure 2(a) and (b). Figure 2(a) presents a cross-sectional view of a display device 7 and Figure 2(b) a top view of an optical structure 8 of the display device 7. The display device 7 shown in Figure 2(a) is structurally similar to the prior art display device 1 depicted in Figure 1. In particular, the display device 7 comprises a light source 2 and a cover panel 3. However, as shown in Figure 2(a), the optical structure 8 is deposited on, or applied to, the second surface 5 of the cover panel 3 (rather than the layer of dark smoke ink 6 as shown in Figure 1). As will be appreciated by a person skilled in the art, the display device 7 may further comprise additional panels or layers between the light source 2 and the cover panel 3, on which the optical structure 8 could alternatively be located. The optical structure 8 comprises an array of apertures 9 which extend completely through the optical structure 8 and so are transmissive at the wavelength of the light emitted by the light source 2. As will be appreciated by the skilled person the array of apertures could alternatively extend partially through the optical structure 8, provided they remain partially transmissive at the wavelength of the light emitted by the light source 2. In Figure 2, each aperture 9 extends completely through the optical structure 8. The optical structure 8 is provided as a dark ink that is mostly opaque at the wavelength of the light emitted from the light source 2. However, alternative materials may be used for the optical structure 8 provided that they offer the required colour and or decorative properties to the display device 7. For instance, the optical structure 8 may provide textures or patterns such as brushed metal or printed wood. Furthermore, as will be appreciated by the skilled person, each aperture 9 may alternatively be filled, or partially filled, with any appropriate material transmissive at the wavelength of the light emitted by the light source 2, suitable for the application. The distribution of the array of apertures 9 within the optical structure 8 is more clearly depicted in Figure 2(b). Figure 2(b) shows a top view of the optical structure 8 of the display device 7. As shown in Figure 2(b), each aperture 9 comprises a circular shape and the array of apertures 9 are arranged in a rectangular pattern such that the apertures 9 are uniformly spaced across the optical structure 8. The size of each individual aperture 9 should be small enough they are typically not visible by the naked human eye or are only visible upon close inspection. In Figure 2, the size of each aperture measures 50 microns in diameter and have a spacing of 200 microns between adjacent apertures. With the apertures 9 being transmissive at the wavelength of the light from the light source 2, they act to enhance the optical efficiency of the display device 7 when in operation. The amount of surface area which the apertures 9 occupy is determined by the size of each individual aperture and the spacing between adjacent apertures. By carefully optimising these dimensions, the apertures 9 remain invisible to the human eye, particularly when the light source 2 is inactive, and thus do not compromise the desired dark or black panel appearance of the display device 7 when it is turned off or inactive. However, it will be appreciated by the skilled reader that, in alternative embodiments, each aperture and or the array of apertures 9 may comprise different shapes or configurations. For example, individual apertures within the array of apertures 9 may comprise different regular or irregular shapes (e.g., triangular, oval, diamond, square, or chevron shapes). Similarly, the array of apertures 9 may be arranged in a regular or irregular array (e.g., circular, square, triangular, hexagonal or Kagome). The applicant has found that the above described advantages of the optical structure 8 can be realised for apertures 9 having a surface area equal to a value A2 for each aperture and a separation distance between two adjacent apertures 9 in the range of A to A x 103, where 1 micron <A <1 millimetre. Therefore, for a surface area as small as 1 micron2 the separation of the apertures may be in the range of 1 micron to 1 millimetre. For apertures having a surface area as large as 1 millimetre2 the separation of the apertures may be in the range of 1 millimetre to 1 metre. It will be further appreciated that the surface area of each aperture 9 could comprise a surface area anywhere between the lower range of 1 micron2 and the upper range of 1 millimetre2 dependent on the size and shape of the aperture 9. Furthermore, the surface area of one or more of the apertures may vary across the across the array of apertures 9. As shown in the embodiment of Figure 2(b) the apertures 9 are uniformly spaced across the optical structure 8. However, in order to avoid Moire fringing effects, the apertures may have a random arrangement across the optical structure 8. The amount of light reaching the cover panel 3, and subsequently the output surface 4, can be modified by adjusting the aperture 9 size and distribution density. Note that the apertures 9 could have a non-uniform density distribution across the optical structure 8 if desired for a particular application i.e. the spacing between each aperture need not be uniform across the entire optical structure. The incorporation of an array of apertures 9 within the optical structure 8 of the display device 7 is a crucial design element that influences the overall performance and optical efficiency of the display device 7. The specific configuration of the aperture 9 size, shape, and density distribution are tailored to meet the desired performance criteria for the particular application. An alternative embodiment of a display device 10 is shown in Figure 3. In particular, Figure 3 presents a cross-sectional view of a section of the display device in accordance with an alternative embodiment of the present invention. The display device 10 is similar to the display device 7 illustrated in Figure 2. However, the section of the display device 10 shown in Figure 3 comprises a light source 11 with increased reflectivity towards the cover panel 3 compared to the light source 2 of Figure 2, in combination with an alternative optical structure 12. The light source 11 of Figure 3, comprises a first surface 13, that is adapted to emit light towards the optical structure, and further adapted to reflect light that is incident upon the first surface 13 towards the cover panel 3. In particular, the first surface 13 may comprise a specular reflector (with direct mirror-like reflections) or a diffuse reflector. In general, the first surface 13 of the light source has a reflectivity of greater than 60% at the wavelength of the light emitted from the light source 11. As the first surface 13 of the light source 11 reflects a significant portion of the incident light, it reduces optical loss and significantly enhances the overall efficiency of the display device 10. In particular, light that is reflected within the display device 10 from the optical structure 12 or the cover panel 3 is not lost or absorbed. Instead, the reflected light is redirected or recycled by the light source 11, allowing the light to be reused and increasing the brightness and energy efficiency of the display device 10. The optical structure 12 of Figure 3 comprises an array of apertures 9, similar to the optical structure 8 depicted in Figure 2(a) and (b). However, the optical structure 12 of Figure 3 comprises a first surface 14 and a second surface 15, wherein the second surface 15 is a reflective surface that is designed to reflect incident light at the wavelength of light emitted by the light source 11. This may be achieved through the addition of a reflective layer. The second surface 15 of the optical structure 12 is located closer to the reflective light source 11 than the first surface 14 of the optical structure 12. The second surface 15 therefore ensures that any light not transmitted through the apertures 9 of the optical structure 12 is reflected back towards the light source 11 rather than being absorbed. Therefore, the design of the optical structure 12 in Figure 3 further minimises optical loss, as the light is continually reflected by the second surface 15 and or the light source 11 until it is eventually transmitted through the apertures 9 to reach the output surface 4 of the cover panel 3. This effect is highlighted by the first 16 and second 17 light paths shown in Figure 3. The display device 10 therefore provides greater optical efficiency compared to the display device 7 described with reference to Figure 2. As will be appreciated by the skilled person both the light source 11 and optical structure 12 can be implemented independently or in combination within a display device, depending on the desired performance characteristics. For example, the light source 11 could alternatively be employed in combination with the optical structure 8 described with reference to the display device 7 of Figure 2. Similarly, the optical structure 12 of Figure 3 could be employed in combination with the light source 2 of the display device 7 in Figure 2. Examples using Optical Design Software SPEOS, a high-precision simulation tool for optical systems, was employed to simulate an optical structure 8, 12 featuring the fine-pitch apertures 9 of the present invention. The optical structure 8, 12 was designed with 200 micron apertures 9 on a 1 mm pitch, resulting in approximately 4% of the surface area of the optical structure 8, 12 being occupied by apertures 9. This configuration was used for the following simulations. Simulation 1 The first simulation was conducted for an optical structure 8 of the type shown in Figure 2. A simple simulation was set-up with a light source 2 emitting 100 lumens of luminous flux. The light source 11 (of the type in Figure 3) was located behind the optical structure 8, where a white (non-specular) reflector positioned behind the light source 2 acted to recycle forward any reflected light. The optical structure 8 was configured with a black, non-reflective surface of 0 % reflection, allowing only some of the emitted light to pass through the apertures 9 in the optical structure 8 to reach an irradiance sensor. The measured luminous flux after the light passed through the apertures 9 of the optical structure 8 was 2.8 lumens, indicating that roughly 3% of the light was transmitted. This level of transmission is slightly lower than the expected transmission of 4% from the aperture 9 to optical structure 8 ratio. Simulation 2 A similar simulation was conducted for an optical structure 12 of the type shown in Figure 3. In this simulation, the second surface 15 of the optical structure 12 was designed with a white, non-specular reflective surface, providing 95% reflectivity. All the other parameters were maintained as identical to Simulation 1, as described above. For the conditions and optical structure 12 used within this simulation, the measured luminous flux on the sensor was 22 lumens, demonstrating an effective 22% light transmission. The results from the simulations suggest that depending on the particular surface area and distribution of the apertures 9 of the optical structure 8, 12 and the actual reflectivity of the second surface 15 of the optical structure 12, at least a ten times improvement in system efficiency could be achieved for the presently described display devices. In summary, the present invention provides an alternative display device to those know in the art. The display device maintains a dark or black panel appearance when turned off, while providing improved optical efficiency when operated. In particular, an optical structure comprising an array of apertures is provided within the display device between the light source and the cover panel. The optical structure comprises an opaque material to provide the desired dark or black panel appearance when the devices is tuned off, while the array of apertures are transmissive to light emitted by the light source when the device is turned on. Therefore, the array of apertures increases the optical efficiency of the display device by allowing more light to pass through the optical structure and reach the cover panel. The optical efficiency of the display device may be further enhanced by the inclusion of a reflective second surface within the optical structure. The second surface acts to reflect light emitted by the light source that does not pass through the apertures, reducing loss or absorption by the optical structure. Additionally, providing the light source with a reflective surface orientated towards the optical structure can also further increase the optical efficiency, as the light source will then redirect more of the light towards the output surface of the display device. A display device and a method of manufacturing a display device is disclosed. The display device comprises a cover panel, a light source and an optical structure. The optical structure is located between the light source and the cover panel, where the light source emits light towards the cover panel. The optical structure comprises an array of apertures that are transmissive at a wavelength of a light emitted by the light source. Two or more of the apertures within the array of apertures comprise a surface area equal to a value A2 for each aperture and have a separation distance between two adjacent apertures in the range of A to A x 103, where 1 micron <A <1000 microns. The display device of the present invention provides increased optical efficiency, while maintaining the desired black panel appearance for the display device. Throughout the specification, unless the context demands otherwise, the terms “comprise” or “include”, or variations such as “comprises” or “comprising”, “includes” or “including” will be understood to imply the inclusion of a stated integer or group of integers, but not the exclusion of any other integer or group of integers. Furthermore, unless the context clearly demands otherwise, the term “or” will be interpreted as being inclusive not exclusive. The foregoing description of the invention has been presented for purposes of illustration and description and is not intended to be exhaustive or to limit the invention to the precise form disclosed. The described embodiments were chosen and described in order to best explain the principles of the invention and its practical application to thereby enable others skilled in the art to best utilise the invention in various embodiments and with various modifications as are suited to the particular use contemplated. Therefore, further modifications or improvements may be incorporated without departing from the scope of the invention as defined by the appended claims.

Claims

1. A display device comprising:a cover panel;a light source configured to emit light towards the cover panel; andan optical structure comprising an array of apertures that are transmissive at a wavelength of a light emitted by the light source, the optical structure being located between the light source and the cover panel;wherein the optical structure, except the array of apertures, is opaque at the wavelength of the light emitted by the light source, andwherein two or more of the apertures within the array of apertures comprise a surface area equal to a value A2 for each aperture and have a separation distance between two adjacent apertures in the range of A to A x 103, where 1 micron <A <1000 microns.

2. A display device as claimed in claim 1, wherein the light source comprises a first surface and a second surface, the first surface located between the optical structure and the second surface, wherein the first surface is configured to reflect incident light at the wavelength of the light emitted by the light source.

3. A display device as claimed in claim 2, wherein the first surface of the light source comprises a reflectivity of greater than 60% at the wavelength of the light emitted by the light source.

4. A display device as claimed in any of the preceding claims, wherein the optical structure comprises a first surface oriented towards the cover panel and a second surface oriented towards the light source, wherein the second surface is configured to reflect incident light at the wavelength of the light emitted by the light source.

5. A display device as claimed in claim 4, wherein the second surface of the optical structure comprises a reflectivity of greater than 60% at the wavelength of the light emitted by the light source.

6. A display device as claimed in any of the preceding claims wherein the two or more apertures are greater than 60% transmissive at the wavelength of light emitted by the light source.

7. A display device as claimed in any of the preceding claims wherein the two or more apertures extend completely through the optical structure.

8. A display device as claimed in any of the preceding claims wherein the array of apertures are non-uniformly distributed across the optical structure.

9. A display device as claimed in any of the preceding claims wherein the two or more apertures comprises a circular, square, elliptical, triangular, oval, diamond or chevron shape.

10. An instrumental panel comprising one or more display devices as claimed in claims 1 to 9.s

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