Display device and transport means

Abstract

The invention relates to a display device (1) and to transport means comprising a display device (1) of this type. The display device (1) comprises a display panel (2), a backlighting means (3) for the display panel (2), and a light-conversion layer (30). The light-conversion layer (30) has a multitude of quantum dots (300) for conversion of a wavelength of light (L) that is emitted by light sources (31) of the backlighting means (3). The light-conversion layer (30) is mounted on a surface of a component (2, 32, 60) of the display device (1) in spaced relation to the light sources (31).

Description

[0001] Description

[0002] Display device and means of transport

[0003] The present invention relates to a display device and a means of transport with such a display device.

[0004] The number and area of ​​display devices in vehicles are constantly increasing. Display devices can be found on the market, for example, as instrument clusters for the driver, as central displays, and even as passenger displays. Non-self-luminous transmissive displays require backlighting to display the image. The purpose of the backlight is to illuminate the display panel as evenly as possible across the entire active area, creating the most homogeneous display possible right up to the edges.

[0005] Backlights, for example, can be based on light guides into which light from multiple light sources is coupled. The light propagates through total internal reflection in the light guide and is then decoupled again using microstructures on the light guide, creating a homogeneous light distribution. This design enables very compact and efficient illumination of display devices with a wide beam pattern.

[0006] Matrix backlights, on the other hand, use a multitude of light sources arranged in a matrix to generate light. A reflector directs the light from the light sources toward the display panel.

[0007] Light-emitting diodes (LEDs) are typically used as backlight sources for liquid crystal displays. They emit light in the blue spectral range. A phosphor layer converts part of this light into light in the yellow spectral range. The result is a broad spectrum that can be perceived as white light.

[0008] However, a significant portion of this spectrum is absorbed in the color filter of the liquid crystal display, which reduces efficiency.

[0009] An alternative approach is to use a quantum dot-based layer to narrow-band convert the light emitted in the blue spectral range into another spectral range that can be precisely tuned to the transmission spectrum of the liquid crystal display's color filter. This leads to a significant increase in efficiency.

[0010] For example, US 10,287,490 B2 describes a lighting device comprising a light source and a wavelength converter for converting the wavelength of the light emitted by the light source. The wavelength converter is configured as a plate or film and comprises a siloxane polymer matrix with nanoparticles embedded therein.

[0011] US 2017 / 0 125650 A1 describes a backlight unit for a liquid crystal display. The backlight unit comprises a source of electromagnetic radiation in the blue part of the spectrum and a polymer film optically coupled to the source of electromagnetic radiation. The polymer film contains a plurality of quantum dots.

[0012] US 9,199,842 B2 describes a backlight unit for a display device. The backlight unit comprises a primary light source that emits primary light, a light guide plate optically coupled to the primary light source, and a phosphor film comprising a first population of light-emitting quantum dots. The quantum dots are configured to emit first secondary light having a longer wavelength than the primary light. It is an object of the invention to provide an improved display device with a light conversion layer.

[0013] This object is achieved by a display device having the features of claim 1 and by a means of transport according to claim 10. Preferred embodiments of the invention are the subject of the dependent claims.

[0014] According to a first aspect of the invention, a display device comprises a display panel, a backlight for the display panel, and a light conversion layer. The light conversion layer comprises a plurality of quantum dots for converting a wavelength of light emitted by light sources of the backlight. The light conversion layer is arranged spaced apart from the light sources on a surface of a component of the display device.

[0015] In the solution according to the invention, the light-conversion layer is arranged or applied directly to a carrier component already present in the display device, i.e., a component is eliminated. Unlike known solutions, there is no separately arranged light-conversion layer whose surfaces reflect light and thus reduce efficiency. The close contact between the light-conversion layer and the carrier component leads to reduced reflection, particularly when the refractive index of the light-conversion layer is matched to the refractive index of the carrier component. The luminous efficacy can be increased by approximately 4% in this way.

[0016] According to one aspect of the invention, the light-conversion layer is arranged on an underside of the display panel. In this embodiment, the light-conversion layer is applied to the underside of the display panel facing away from the viewer. This has the advantage that the light-conversion layer is designed over a large area and a very uniform thickness can be achieved. This has a positive effect on color homogeneity.

[0017] According to one aspect of the invention, the light conversion layer is arranged on a surface or a light coupling surface of a light guide of the backlight. This embodiment of the invention can be implemented if the backlight is based on a light guide. Arranging the light conversion layer on the surface of the light guide has the advantage that the light conversion layer is designed over a large area and a very uniform thickness can be achieved. Alternatively, the light conversion layer can also be applied to a light coupling surface of the light guide.

[0018] According to one aspect of the invention, the light-conversion layer is arranged on an optical film of the display device. In this embodiment of the invention, the light-conversion layer is part of a film stack. Such film stacks are regularly installed in display devices and can therefore also include the light-conversion layer without major effort.

[0019] According to one aspect of the invention, a further optical layer is arranged on the light conversion layer. The further optical layer can, for example, be a layer of a film stack that is required anyway. In this way, the efficiency of the display device can be further increased.

[0020] According to one aspect of the invention, the light conversion layer is formed from transparent silicon, polyurethane, or acrylic. These materials have the advantage that extensive data is available on them and they are easy to handle. The specific material used is at the discretion of the person skilled in the art. According to one aspect of the invention, the light conversion layer is designed as an optically clear adhesive film or as a layer of a cured liquid. Implementation as an optically clear adhesive film has the advantage that the light conversion layer can be prefabricated. Alternatively, the material of the light conversion layer with the quantum dots dispersed therein can be applied to the carrier component in liquid form and then cured to form a solid layer. In this case, application can be carried out, for example, using a slot die, and curing can occur by irradiation with ultraviolet light.This alternative has the advantage that a uniform layer thickness and thus the best possible color homogeneity can be achieved in a simple manner.

[0021] According to one aspect of the invention, the light sources are designed to emit light in a blue spectral range. This has the advantage that, through a suitable selection of the quantum dots, the wavelength can be converted to any wavelength range from the entire visible spectral range.

[0022] According to one aspect of the invention, the display panel is a liquid crystal panel. Liquid crystal panels are used in numerous display devices and utilize color filters. The use of the inventive solution is therefore particularly advantageous because the spectrum of the converted light can be precisely matched to the transmission spectrum of the color filter.

[0023] A display device according to the invention is preferably used in a means of transportation. The means of transportation can be, for example, a motor vehicle, but alternatively also an aircraft, a rail vehicle, or a watercraft. Further features of the present invention will become apparent from the following description and the appended claims in conjunction with the figures.

[0024] Figure overview

[0025] Fig. 1 shows schematically a cross section of a first embodiment of a display device according to the invention;

[0026] Fig. 2 shows schematically a cross section of a second embodiment of a display device according to the invention;

[0027] Fig. 3 shows schematically a cross section of a third embodiment of a display device according to the invention;

[0028] Fig. 4 shows schematically a cross section of a fourth embodiment of a display device according to the invention;

[0029] Fig. 5 shows schematically a light conversion layer; and

[0030] Fig. 6 shows schematically a means of transport that uses a display device according to the invention.

[0031] Character description

[0032] To better understand the principles of the present invention, embodiments of the invention are explained in more detail below with reference to the figures. Like reference numerals are used in the figures for like or equivalent elements and are not necessarily described again for each figure. It is understood that the invention is not limited to the illustrated embodiments and that the described features can also be combined or modified without departing from the scope of the invention as defined in the appended claims.

[0033] Fig. 1 schematically shows a cross-section of a first embodiment of a display device 1 according to the invention. The display device 1 has a housing 8, to which a cover glass 4 is attached by means of a connecting element 9. The cover glass 4 seals the housing 8 of the display device 1 from the environment. An externally illuminated display panel 2, for example a liquid crystal panel (LCD panel), is arranged on the inner side of the cover glass 4 facing the housing 8. The display panel 2 is connected to the cover glass 4 by means of an optically clear film 10. This connection, also referred to as "optical bonding," is achieved, for example, by means of a curable, optically clear liquid or by means of an optically clear solid, for example a film provided with an adhesive layer on both sides. Alternatively, an air gap can also be provided at this point. The display panel 2 is illuminated by a backlight 3.

[0034] The backlight 3 has light sources 31 arranged on a 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 sources 31 is coupled into a light guide 32 via a light coupling surface 321 and leaves the light guide 32 through a surface 320 of the light guide 32 in the direction of the display panel 2. A reflective layer 33 is arranged below the light guide 32, for example a reflective film or a reflective coating of the light guide 32 or the inside of the housing 8. The reflective layer 33 serves to guide as much of the light that does not leave the light guide 32 in the direction of the display panel 2 back towards the display panel 2. An optical stack 6 is arranged between the light guide 32 and the display panel 2.The optical films 60 of the film stack 6 are designed to scatter, collect, or direct the light from the light guide 32 in such a way that the requirements for the solid angle of the backlight 3 are met. Typical films for light alignment are brightness enhancement films (BEF) and light control films (LCF). Apertures 11 are arranged in an edge region between the light guide 32 and the display panel 2, which shade stray light.

[0035] The light sources 31 generate light L in a 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 arranged on an 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 can be formed from transparent silicon, polyurethane, or acrylic. On the one hand, it is possible to apply the respective material with the quantum dots dispersed therein in liquid form to the display panel 2 and then cure it. Alternatively, it is possible to apply the light conversion layer 30 to the display panel 2 in the form of an optically clear adhesive film.If necessary, further optical layers can be applied to the light conversion layer 30.

[0036] Fig. 2 shows a schematic cross-section of a second embodiment of a display device 1 according to the invention. The display device 1 has a display panel 2 which is glued to a cover glass 4 by means of an optically clear film 10. The cover glass 4 closes off a housing 8 of the display device 1 from the environment. A backlight 3 for the display panel 2 is arranged in a further housing 7. The backlight 3 has a reflector 34 with a plurality of cavities 35. A light source 31 is arranged in each of the cavities 35. The light sources 31 are arranged on a circuit board 36 which can be glued to the housing 7 of the backlight 3. The reflective walls of the cavities 35 of the reflector 34 are rounded and orient the light L emerging from the light sources 31, which in Fig.2 is indicated by way of example for two light sources 31, in the direction of the display panel 2.

[0037] In the example shown, an optical plate 5 with a film stack 6 arranged thereon is located between the backlight 3 and the display panel 2. The optical films 60 of the film stack 6 have the task of scattering, collecting or directing the light from the reflector 34 in such a way that the requirements for the solid angle of the backlight 3 are met. The optical plate 5 is a transparent plate which ensures the optical distance between the optical film stack 6 and the light sources 31. The cover glass 4, the optical plate 5 and the housing 7 of the backlight 3 are connected to one another by suitable connecting elements 9, e.g. adhesives. Arranged in an edge region between the reflector 34 and the display panel 2 are apertures 11 which shade out stray light.

[0038] The light sources 31 generate light L in a blue spectral range. To obtain a spectrum that can be perceived as white light, the display device 1 again has a light conversion layer 30. In this embodiment, the light conversion layer 30 is arranged on the uppermost optical film 60 of the film stack 6 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.

[0039] Fig. 3 schematically shows a cross-section of a third embodiment of a display device 1 according to the invention. This embodiment largely corresponds to the embodiment shown in Fig. 1, but the light conversion layer 30 is not arranged on the underside of the display panel 2, but on the surface 320 of the light guide 32.

[0040] Fig. 4 schematically shows a cross-section of a fourth embodiment of a display device 1 according to the invention. This embodiment largely corresponds to the embodiment shown in Fig. 2, but the light conversion layer 30 is not arranged on the uppermost optical film 60 of the film stack 6, but below the film stack 6 on the optical plate 5. The optical films 60 of the film stack 6 are arranged on the light conversion layer 30 in this case.

[0041] Fig. 5 schematically shows a light conversion layer 30. The light conversion layer 30 is formed from a transparent material 301, e.g., 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 light conversion layer 30 is to be applied. Numerous quantum dots 300 are dispersed in the light conversion layer 30, e.g., quantum dots 300 based on indium phosphide, cadmium selenide, or carbon. The specific choice of material and size of the quantum dots 300 is at the discretion of the person skilled in the art. The transparent material 301 with the quantum dots 300 dispersed therein can, for example, be applied to the carrier component in liquid form and then cured to form a solid layer. In this case, application can be effected, for example, using a slot nozzle, and curing can occur by irradiation with ultraviolet light.Alternatively, the light conversion layer 30 can also be prefabricated as a film, e.g. in the form of an optically clear adhesive film, which is then applied to the carrier component.

[0042] Fig. 6 schematically shows a means of transport 100 that uses a display device 1 according to the invention. In this example, the means of transport 100 is a motor vehicle. The motor vehicle has a display device 1 according to the invention, which is arranged in a dashboard. Data on the vehicle's surroundings can be acquired using a sensor system 101. The sensor system 101 can in particular comprise sensors for environmental detection, e.g., ultrasonic sensors, laser scanners, radar sensors, lidar sensors, or cameras. The information acquired by the sensor system 101 can be used to generate content to be displayed for the display device 1. Further components of the motor vehicle in this example are a navigation system 102, by means of which position information can be provided, and a data transmission unit 103. By means of the data transmission unit 103, for example,A connection to a backend can be established, for example, to obtain updated software for components of the motor vehicle. A memory 104 is provided for storing data. Data exchange between the various components of the motor vehicle takes place via a network 105.

[0043] List of reference symbols

[0044] 1 display device

[0045] 2 display panel

[0046] 20 subpage

[0047] 3 Backlight

[0048] 30 Light conversion layer

[0049] 300 quantum dots

[0050] 301 Transparent Material

[0051] 31 Light source

[0052] 32 light guides

[0053] 320 surface

[0054] 321 light coupling surface

[0055] 33 Reflective layer

[0056] 34 Reflector

[0057] 35 Cavity

[0058] 36 circuit board

[0059] 4 Cover glass

[0060] 5 Optical disk

[0061] 6 stacks of slides

[0062] 60 Optical Film

[0063] 7 Backlight housing

[0064] 8 Housing of the display device

[0065] 9 Connecting element

[0066] 10 Optically clear film

[0067] 11 aperture

[0068] 100 means of transport

[0069] 101 Sensor Technology

[0070] 102 Navigation system

[0071] 103 Data transmission unit

[0072] 104 Storage 105 Network

[0073] L Light

Claims

Patent claims 1. Display device (1 ) with; - a display panel (2); - a backlight (3) for the display panel (2); and - a light conversion layer (30) having a plurality of quantum dots (300) for converting a wavelength of light (L) emitted by light sources (31) of the backlight (3), wherein the light conversion layer (30) is arranged at a distance from the light sources (31) on a surface of a component (2, 5, 32, 60) of the display device (1).

2. Display device (1) according to claim 1, wherein the light conversion layer (30) is arranged on a bottom side (20) of the display panel (2).

3. Display device (1) according to claim 1, wherein the light conversion layer (30) is arranged on a surface (320) or a light coupling surface (321) of a light guide (32) of the backlight (3).

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

5. Display device (1) according to one of the preceding claims, wherein a further optical film is arranged on the light conversion layer (30).

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

7. Display device (1) according to one of the preceding claims, wherein the light conversion layer (30) is formed as an optically clear adhesive film or as a layer of a cured liquid.

8. Display device (1) according to one of the preceding claims, wherein the light sources (31) are designed to emit light (L) in a blue spectral range.

9. Display device (1) according to one of the preceding claims, wherein the Display panel (2) is a liquid crystal panel.

10. Means of transport (100) with a display device (1) according to one of the preceding claims.

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