Display devices and means of transport

Abstract

The present invention relates to a display device (1) and a means of transport comprising this type of display device (1). The display device (1) comprises a display panel (2), a backlight (3) for the display panel (2), and a light conversion layer (30). The light conversion layer (30) has a plurality of quantum dots (300) for converting the wavelength of light (L) emitted by a light source (31) of the backlight (3). The light conversion layer (30) is positioned spaced apart from the light source (31) and is located on the surface of the components (2, 32, 60) of the display device (1).

Description

Technical Field

[0001] The present invention relates to a display device and a means of transportation including this type of display device.

[0002] The number and area of display devices in means of transportation are continuously increasing. Display devices are found in the market, for example, as instrument panels for drivers, as central displays, and also as displays for front-seat passengers. A transmissive display device that does not self-emit light requires a backlight for image representation. The role of the backlight is to illuminate the used display panel as uniformly as possible over the entire active area and generate as homogeneous a display as possible up to the edge region.

[0003] The backlight can be based on, for example, a light guide in which light from a plurality of light sources is combined. The light propagates through the light guide by total reflection and is recombined with the help of a microstructure on the light guide, thereby generating a uniform light distribution. This design enables very compact and efficient illumination of display devices with broad radiation characteristics.

[0004] On the other hand, a matrix backlight generates light using a plurality of light sources arranged in a matrix. The light from the light sources is directed towards the display panel by a reflector.

[0005] Light-emitting diodes (LEDs) that emit light in the blue spectral range are commonly used as light sources for the backlights of liquid crystal displays. A part of this light is converted into light in the yellow spectral range in a phosphor layer. As a result, a broadband spectrum that can be perceived as white light is obtained. However, most of this spectrum is absorbed by the color filters of the liquid crystal display, sacrificing efficiency.

[0006] Another possibility is to use a quantum dot-based layer to convert light emitted in the blue spectral range into a narrow-band spectral range that can be finely tuned to the transmission spectrum of the liquid crystal display's color filter. This would significantly improve efficiency.

[0007] For example, US10,287,490B2 describes a lighting device having a light source and a wavelength transducer that converts the wavelength of light emitted by the light source. The wavelength transducer is configured as a plate or film and includes a siloxane polymer matrix in which nanoparticles are embedded.

[0008] US2017 / 0125650A1 describes a backlight unit for liquid crystal displays. The backlight unit includes a source of electromagnetic radiation in the blue portion of the spectrum and a polymer film optically coupled to the source of electromagnetic radiation. The polymer film contains a plurality of quantum dots.

[0009] US9,199,842B2 describes a backlight unit for a display device. The backlight unit comprises a primary light source emitting primary light, a light guide plate optically coupled to the primary light source, and a phosphor film containing a first collection of light-emitting quantum dots. The quantum dots are configured to emit first secondary light with a wavelength longer than the primary light.

[0010] The object of the present invention is to provide an improved display device having a light conversion layer.

[0011] This objective is achieved by a display device having the features described in claim 1 and by a transport means described in claim 10. Preferred embodiments of the present invention are the subject of the dependent claims.

[0012] According to a first aspect of the present invention, the display device comprises a curved display panel, a backlight for the display panel, and a light conversion layer. The light conversion layer includes a number of quantum dots for converting the wavelength of light emitted by the backlight source. The light conversion layer is mounted on the surface of a component of the display device at a distance from the light source.

[0013] In the solution according to the present invention, the light conversion layer is either directly placed on or coated onto a support component that is present in the display device anyway, i.e., one component is omitted. Therefore, unlike conventional solutions, there is no separately placed light conversion layer whose surface reflects light and reduces efficiency. Close contact between the light conversion layer and the support component leads to a reduction in reflection, especially when the refractive index of the light conversion layer matches the refractive index of the support component. In this way, the luminescence yield can be increased by approximately 4%.

[0014] According to one aspect of the present invention, the light conversion layer is located on the underside of the display panel. In this embodiment, the light conversion layer is added to the underside of the display panel facing away from the observer. This has the advantage that the light conversion layer can be designed over a wide area and achieve a very uniform thickness. This has a favorable effect on color uniformity.

[0015] According to one aspect of the present invention, the light conversion layer is disposed on the surface or optical coupling surface of the light guide of the backlight. This embodiment of the present invention is feasible when the backlight is based on a light guide. Disposing of the light conversion layer on the surface of the light guide has the further advantage that the light conversion layer can be designed over a wide area and achieve a very uniform thickness. However, alternatively, the light conversion layer can also be applied to the optical coupling surface of the light guide.

[0016] According to one aspect of the present invention, the light conversion layer is disposed on an optical film of a display device. In this embodiment of the present invention, the light conversion layer is a component of a film stack. Such a film stack is typically installed in a display device and can therefore include the light conversion layer without incurring significant costs.

[0017] According to one aspect of the present invention, a further optical layer is placed on top of the light conversion layer. The further optical layer may be, for example, a layer of the film stack which is required in any case. In this way, the efficiency of the display device can be further improved.

[0018] According to one aspect of the present invention, the photoconversion layer is formed from transparent silicon, polyurethane, or acrylic. These materials have the advantage of having extensive data available and being easy to handle. The choice of which material to use is at the discretion of those skilled in the art.

[0019] According to one aspect of the present invention, the photoconversion layer is configured as an optically transparent adhesive film or as a layer of cured liquid. Realization as an optically transparent adhesive film has the advantage that the photoconversion layer can be pre-formed. Alternatively, the material of the photoconversion layer, in which quantum dots are dispersed, can be applied to a support component in liquid form and then cured to form a solid layer. In this case, application can be performed, for example, using a slit die, and curing can be performed by irradiation with ultraviolet light. This alternative has the advantage that a uniform layer thickness and the associated best possible color uniformity can be achieved in a simple manner.

[0020] According to one aspect of the present invention, the light source is designed to emit light in the blue spectral range. This has the advantage that, with the appropriate selection of quantum dots, wavelength conversion to any desired wavelength range across the entire visible spectral range is possible.

[0021] According to one aspect of the present invention, the display panel is a liquid crystal panel. Liquid crystal panels are used in many display devices and use color filters. Therefore, the use of the solution according to the present invention is particularly advantageous because the spectrum of the converted light can be accurately matched to the transmission spectrum of the color filter.

[0022] The display device according to the present invention is preferably used in a means of transportation. The means of transportation may be, for example, an automobile, but alternatively may be an aircraft, a railway vehicle, or a water vehicle.

[0023] Further features of the present invention will become apparent from the following description and the appended claims in conjunction with the drawings.

Brief Description of the Drawings

[0024] [Figure 1] A cross-section of a first embodiment of a display device according to the present invention is schematically shown. [Figure 2] A cross-section of a second embodiment of a display device according to the present invention is schematically shown. [Figure 3] A cross-section of a third embodiment of a display device according to the present invention is schematically shown. [Figure 4] A cross-section of a fourth embodiment of a display device according to the present invention is schematically shown. [Figure 5] The light conversion layer is schematically shown. [Figure 6] A schematic view of a means of transportation using a display device according to the present invention is shown.

Modes for Carrying Out the Invention

[0025] To better understand the principles of the present invention, embodiments of the present invention will be described in more detail below with reference to the drawings. In the drawings, the same reference numerals are used for the same elements or functionally identical elements, and they will not necessarily be described again for each figure. It should be understood that the present invention is not limited to the illustrated embodiments, and the described features can also be combined or modified without departing from the scope of protection of the present invention defined in the appended claims.

[0026] Figure 1 schematically shows a cross-section of a first embodiment of a display device 1 according to the present invention. The display device 1 has a housing 8, to which a cover glass 4 is fixed by a connecting element 9. The cover glass 4 closes the housing 8 of the display device 1 against the surroundings. An externally illuminated display panel 2, for example a liquid crystal panel (LCD panel), is arranged inside the cover glass 4 facing the housing 8. The display panel 2 is connected to the cover glass 4 by an optically transparent film 10. This connection, also called "optical bonding", is effected, for example, by a curable optically transparent liquid or by an optically transparent solid such as a film provided with adhesive layers on both sides. Alternatively, an air gap may be present at this position. The display panel 2 is illuminated by a backlight 3.

[0027] The backlight 3 has a light source 31 located on a printed circuit board 36 in the lateral region of the housing 8. These are preferably light-emitting diodes or light sources 31 based on LED technology. The light L generated by the light source 31 is coupled to a light guide 32 via an optical input coupling surface 321 and exits the light guide 32 towards the display panel 2 through the surface 320 of the light guide 32. Below the light guide 32, a reflective layer 33 is placed, for example, a reflective film or a reflective coating on the inside of the light guide 32 or the housing 8. The reflective layer 33 serves to guide as much light as possible that did not exit from the light guide 32 towards the display panel 2. A film stack 6 (optical stack) is placed between the light guide 32 and the display panel 2. The optical films 60 of the film stack 6 serve to scatter, focus, or guide the light from the light guide 32 so as to satisfy the spatial angle requirements of the backlight 3. Typical films for photoalignment are brightness-enhancing films (BEF) and light-controlling films (LCF). A diaphragm 11 is positioned in the edge region between the light guide 32 and the display panel 2 to block scattered light.

[0028] The light source 31 generates light L in the blue spectral range. To obtain a spectrum that can be perceived as white light, the display device 1 has a light conversion layer 30. In this embodiment, the light conversion layer 30 is located on the underside 20 of the display panel 2 and has a plurality of quantum dots. The quantum dots convert the light L emitted in the blue spectral range into another spectral range in a narrowband manner. For example, the light conversion layer 30 may be formed from transparent silicone, polyurethane, or acrylic. On the one hand, each material in which the quantum dots are dispersed can be applied to the display panel 2 in liquid form and then cured. Alternatively, the light conversion layer 30 can be applied to the display panel 2 in the form of an optically transparent adhesive film. If necessary, further optical layers can be applied on the light conversion layer 30.

[0029] Figure 2 schematically shows a cross-section of a second embodiment of the display device 1 according to the present invention. The display device 1 has a display panel 2 bonded to a cover glass 4 via an optically transparent film 10. The cover glass 4 isolates the housing 8 of the display device 1 from the environment. A backlight 3 for the display panel 2 is located in a further housing 7. The backlight 3 has a reflector 34 with a plurality of cavities 35. Each cavity 35 contains one light source 31. The light sources 31 are located on a circuit board 36 which can be bonded to the housing 7 of the backlight 3. The walls of the reflectively formed cavities 35 of the reflector 34 are rounded, directing the light L emitted from the light sources 31 (exemplified as two light sources 31 in Figure 2) toward the display panel 2.

[0030] In the illustrated example, an optical plate 5 containing an optical film stack 6 is positioned between the backlight 3 and the display panel 2. The optical films 60 of the film stack 6 scatter, focus, or guide light from the reflector 34 so as to satisfy the spatial angle requirements of the backlight 3. The optical plate 5 is a transparent plate that ensures an optical distance between the optical film stack 6 and the light source 31. The cover glass 4, the optical plate 5, and the housing 7 of the backlight 3 are connected to each other by appropriate connecting elements 9, such as adhesive bonding. A diaphragm 11 is positioned in the edge region between the reflector 34 and the display panel 2 to shield scattered light.

[0031] The light source 31 generates light L in the blue spectral range. To obtain a spectrum that can be perceived as white light, the display device 1 has a light conversion layer 30. In this embodiment, the light conversion layer 30 is located on the optical film 60 at the top of the film stack 6 and has a number of quantum dots. The quantum dots convert the light L emitted in the blue spectral range into another spectral range in a narrowband manner.

[0032] Figure 3 schematically shows a cross-section of a third embodiment of the display device 1 according to the present invention. This embodiment generally corresponds to the embodiment shown in Figure 1, except that the light conversion layer 30 is located on the surface 320 of the light guide 32, rather than on the underside of the display panel 2.

[0033] Figure 4 schematically shows a cross-section of a fourth embodiment of the display device 1 according to the present invention. This embodiment generally corresponds to the embodiment shown in Figure 2, except that the light conversion layer 30 is not located on the optical film 60 at the top of the film stack 6, but is located on the optical plate 5 below the film stack 6. In this case, the optical film 60 of the film stack 6 is located on top of the light conversion layer 30.

[0034] Figure 5 schematically shows the photoconversion layer 30. The photoconversion layer 30 is formed from a transparent material 301, for example, transparent silicon, polyurethane, or acrylic. The refractive index of the material 301 is preferably matched to the refractive index of the component to which the photoconversion layer 30 is applied. Numerous quantum dots 300 are dispersed in the photoconversion layer 30, for example, quantum dots 300 based on indium phosphide, cadmium selenide, or carbon. The specific selection of material and quantum dot 300 size is at the discretion of those skilled in the art. The transparent material 301 with dispersed quantum dots 300 can be applied to a support component in liquid form, for example, and then cured to form a solid layer. In this case, application can be performed, for example, using a slit die, and curing can be performed by irradiation with ultraviolet light. Alternatively, the photoconversion layer 30 can be pre-fabricated as a film, for example, in the form of an optically transparent adhesive film, which is then applied to the support component.

[0035] Figure 6 shows a schematic diagram of a transport means 100 utilizing a display device 1 according to the present invention. In this example, the transport means 100 is an automobile. The automobile has a display device 1 according to the present invention located in the dashboard. A sensor system 101 can be used to capture data about the surroundings of the vehicle. The sensor system 101 may include, in particular, ambient awareness sensors, such as ultrasonic sensors, laser scanners, radar sensors, lidar sensors, or cameras. The information captured by the sensor system 101 can be used to generate content to be displayed on the display device 1. Further components of the automobile in this embodiment include a navigation system 102 that can provide location information, and a data transmission unit 103. For example, a connection to a backend can be set up via the data transmission unit 103 to obtain, for example, update software for components of the automobile. A memory 104 is available for storing data. Data is exchanged between various components of the automobile via a network 105. [Explanation of symbols]

[0036] 1 Display device 2 Display Panels 20 lower side 3. Backlight 30 Light conversion layer 300 quantum dots 301 Transparent material 31 Light source 32 Light guide 320 surface 321 Optical input coupling surface 33 Reflective layer 34 Reflector 35 Cavity 36 Circuit boards 4. Cover glass 5 Optical plate 6 Film Stack 60 Optical Film 7. Backlight housing 8 Display device housing 9. Connection elements 10 Optically transparent film 11 Diaphragm 100 Means of transportation 101 Sensor System 102 Navigation System 103 Data transmission unit 104 memory 105 Network L light

Claims

1. Display device (1), Display panel (2), The backlight (3) for the display panel (2), A photoconversion layer (30) comprising a plurality of quantum dots (300) for converting the wavelength of light (L) emitted by the light source (31) of the backlight (3), wherein the photoconversion layer (30) is disposed on the surface of the components (2, 5, 32, 60) of the display device (1) at a distance from the light source (31), The display device (1) includes the above.

2. The display device (1) according to claim 1, wherein the light conversion layer (30) is disposed on the lower side (20) of the display panel (2).

3. The display device (1) according to claim 1, wherein the light conversion layer (30) is disposed on the surface (320) or light input coupling surface (321) of the light guide (32) of the backlight (3).

4. The display device (1) according to claim 1, wherein the light conversion layer (30) is disposed on the optical film (60) of the display device (1).

5. A display device (1) according to any one of the prior claims, wherein a further optical film is disposed on the light conversion layer (30).

6. The display device (1) according to any one of the prior claims, wherein the light conversion layer (30) is formed from transparent silicon, polyurethane, or acrylic.

7. The display device (1) according to any one of the prior claims, wherein the light conversion layer (30) is designed as an optically transparent adhesive film or as a layer of cured liquid.

8. The display device (1) according to any one of the prior claims, wherein the light source (31) is designed to emit light (L) in the blue spectral range.

9. The display device (1) according to any one of the prior claims, wherein the display panel (2) is a liquid crystal panel.

10. A transport means (100) having a display device (1) as described in any one of the prior claims.

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