阅读说明：本技术 经分段可挠光导中之热点降减技术 (Hotspot reduction in segmented flexible light guides ) 是由 斯特凡·哈尔克马 杰伦·范·登·布兰德 玛格丽塔·玛利亚·德·科 阿德里·范·德·瓦尔 杰伦 于 2019-01-29 设计创作，主要内容包括：以LED照射一光导的段部系导致该光导的其他部份之不想要的光渗。尚且,典型地,由于靠近LED处的一强度尖突,LED系被放置成相距自此LED将光耦出的区域处于一大距离。为了避免在发亮区域中可见到此尖突,该距离系增大,其导致整体系统之不想要的面积增加。本发明系提供一布局来克服这些挑战。(Illuminating a segment of a light guide with LEDs results in unwanted light penetration of other portions of the light guide. Also, typically, due to an intensity spike near the LED, the LED is placed at a large distance from the area from which light will be coupled out of the LED. In order to avoid that such a cusp is visible in the luminous area, the distance is increased, which leads to an unwanted increase in the area of the overall system. The present invention provides a layout to overcome these challenges.)

1. A display having a display area for displaying an illuminated image or picture, the display comprising:

a light guide having an incoupling surface for receiving one or more LED devices, having a principal light emission direction for defining a light path that travels away from the incoupling surface towards an outcoupling surface defining the image or picture;

the light guide having side boundary portions blocking light from the LED in a direction lateral to the primary light emission direction;

the light guide is provided with a transparent portion comprising a light homogenizing zone, wherein a vertex faces the incoupling surface extending along the LED device; the homogenizing zone is beside the face and extends along the light emission direction to about a length of the LED device at a distance from the side face.

2. The display of claim 1, wherein the homogenized region is provided by one or more cavities in the transparent portion.

3. The display according to claim 2, wherein the sides of the cavities are oriented with respect to the primary light emission direction to provide a total internal reflection effect for light emitted from the LED devices.

4. A display according to claim 2 or 3, wherein the one or more cavities have one or more triangular or rounded triangular shapes.

5. A display according to any of the preceding claims, wherein the one or more cavities are provided with a roughening on one side of the triangular or rounded triangular shapes.

6. A display according to any of the preceding claims, wherein the homogenizing zone is formed by a single cavity provided in the transparent portion.

7. A display according to any of the preceding claims, wherein the incoupling surface for receiving one or more LED devices is a side of a planar transparent layer; and wherein the LED devices are upstanding LEDs having a thickness corresponding to the transparent layer.

8. The display of claim 7, wherein the incoupling surface is non-flat to include a cavity between the incoupling surface and the LED device.

9. The display according to any of the preceding claims, wherein a reflective coating is provided between the transparent and border portions.

10. A display according to any of the preceding claims, wherein the side border portion is provided by a non-transparent material formed adjacent to and complementary to the light guide.

11. The display according to any of the preceding claims, wherein the transparent portion and the border portion form a cover layer and a single integrated stack of two or more segmented and complementarily shaped layers.

12. The display of claim 11, wherein the single integrated layer is provided adjacent to an array of LEDs, each facing a respective transparent portion having an outcoupling face.

13. A display according to claim 11 or 12, wherein the cover layer is provided with a light-reflecting coating.

14. The display of claim 13, wherein the light reflective coating has a graded pattern with decreasing reflection away from the incoupling surface disposed on the bottom surface of the stack and away from the outcoupling surface.

15. The display of claim 14, wherein the graded light reflecting pattern extends on the bottom side of the outcoupling surface.

16. A display according to any of the preceding claims, wherein the light guide is formed by a transparent planar layer of 0.1 to 5mm thickness, and wherein the incoupling surface is positioned a distance of about 5 to 8mm away from the outcoupling surface.

17. A display according to any of the preceding claims, wherein the side border portions and transparent portions are made by injection moulding.

Technical Field

The present disclosure relates to segmented flexible light guides with improved homogeneity luminance from embedded LEDs.

Background

Illuminating a segment of a light guide with LEDs results in unwanted light penetration of other portions of the light guide. Also, due to an intensity spike near the LED, the LED is placed at a large distance, in the range of 1 to 10mm, from the area where light is to be coupled out from the LED. In order to avoid that such a cusp is visible in the luminous area, the distance is increased, which leads to an unwanted increase in the area of the overall system.

Most typical methods of achieving homogeneity have a large spacing or have a large amount of light diffusion and/or absorption so that the brightness of the light emitted by the light guide is significantly reduced. For immediately adjacent images, typical light guides do not have a solution to reduce crosstalk between these images to a few% or even 1%. Thus, switching on one image will result in unwanted light emission from the other image. Also, the light guide can be shaped to spread the light more efficiently than just generating an emission area that is at least 5 to 10mm away from the LED where the light is more homogeneous. But in some instances this distance is far too large.

Disclosure of Invention

The present invention provides an optical design profile that improves the homogeneity of the illumination section and reduces the distance from the LED to this section. Accordingly, there is provided a display for displaying an illuminated image or picture, comprising a light guide having an incoupling surface for receiving one or more LED devices, having a main light emission direction for defining a light path which travels away from the incoupling surface towards an outcoupling surface defining the image or picture. The light guide has side boundary portions that block light from the LED in a direction lateral to the primary light emission direction. The light guide is arranged in a transparent portion comprising a light homogenizing zone, wherein a vertex faces the incoupling surface extending along the LED device; the homogenizing zone extends alongside the face and along the light emission direction to about a length of the LED device and is spaced from the side face by less than a length of the LED device. In one example, an air pocket is disposed at the LED that provides light refraction at the interface with the light guide.

The proposed design provides significant improvement in homogeneity. Instead of using a 5 to 10mm separation between the LED and the light emitting section, the distance can be reduced to less than 5, possibly even-3 mm. The light guide may contain a slight air pocket at the LED to provide refraction.

In this way, the light radiated by the LED display is already homogeneous close to the LEDs; where it is typically extremely heterogeneous.

Fused sections of different optical densities, together of the same material type, have also been proposed to form appropriate light guide shapes. In this way, the display has a transparent portion and a border portion that form a single integrated stack of two or more segmented and complementarily shaped layers.

Light leakage reduction (light shielding) may be achieved by creating the light guide from opaque and transparent sections formed, for example, by a high temperature process, such as a high pressure lamination of Thermoplastic Polyurethane (TPU) materials that are fused into a single layer, and/or providing a cover layer. The light guide is arranged as a closed section in which the light is trapped until coupling out. In the present invention, the body can be completely flexible, containing all the components and openings for an efficient light guide to create any desired appearance. The assembly can be easily integrated into or onto a 3D pre-formed rigid or semi-rigid assembly either before or after forming.

The use of multiple high temperature TPUs to form a single layer of light is completely blocked between adjacent sections even though the transparent sections have less than 1mm spacing between them.

Drawings

These and other aspects, and advantages of the disclosed apparatus, systems, and methods will become apparent from the following description, the appended claims, and the accompanying drawings in which:

FIG. 1A is a product portion using opaque and transparent substrates to create segments of light guides and reduce light penetration to adjacent lighted segments;

FIG. 1B is an exemplary structure at an LED or opposing interface. Although one structure is shown, it may be an array of structures. At the LED, an air bag can be maintained by optimizing its shape, size and separately by a lamination process (T and pressure);

FIG. 1C shows different shapes of light guides;

FIGS. 2A-2C illustrate a homogenizing structure and its optical response;

FIG. 3 is a top view of an exemplary image display showing a top and bottom surface containing a pattern for stepped light diffusion;

fig. 4A-4B are an exemplary stacked stack of layers of an assembly in which the light guide and reflective side and back side layers are added by injection molding.

Detailed Description

The terminology used to describe particular embodiments is not intended to be limiting of the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. The term "and/or" includes any and all combinations of one or more of the associated listed items. It will be understood that the terms "comprises" and/or "comprising" are used in an inclusive sense to specify the presence of the stated features but not to preclude the presence or addition of one or more other features. Please understand further that: when a particular step of a method is referred to as being after another step, it can be directly after the other step, or one or more intervening steps can be performed before the particular step, unless otherwise indicated. The same will be understood: when a connection between structures or components is described, unless otherwise indicated, such connection may be made directly or through intervening structures or components.

The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown. The absolute and relative sizes of systems, components, layers and regions may be exaggerated in the figures for clarity. Embodiments may be described with reference to schematic and/or cross-sectional illustrations of potentially idealized embodiments and intermediate structures of the invention. In the description and drawings, like numbers refer to like elements throughout. Relative terms and derivatives thereof should be construed to refer to the orientation as then described or as shown in the drawing under discussion. These relative terms are for convenience of description and do not require that the system be constructed or operated in a particular orientation unless otherwise indicated.

An embodiment is shown in FIG. 1A, in which a display 100 is formed from a light guide 10 and LED devices 20. In more detail, a light guide 10 is shown, the light guide 10 having an incoupling surface 110 for receiving one or more LED devices 20 having a main light emission direction for defining a light path which travels away from the incoupling surface 110 to an outcoupling surface 120 defining an image, slit or picture.

The light guide 10 has side boundary portions 30 that reflect and/or block light from the LEDs 20 in a direction lateral to the primary light emission direction L.

In more detail, fig. 1B shows: the light guide 10 is provided with a transparent portion 102 comprising a light homogenizing zone 130, wherein a vertex faces the incoupling face 110 extending along the LED device 20. The light homogenizing zone is shaped such that a central apex is formed and the side portions with interfaces are oriented away from the LED device. The homogenizing zone 130 is close to the side face 110, in particular having a distance (measured from the vertex) which is smaller than the length of the LED device 20 measured beside the light emission face. The homogenizing zone 130 extends along the light emission direction L for about a length of the LED arrangement 20. In the example of fig. 1A and 1B, the homogenizing structure 130 is a single triangular cavity; but may be multiple cavities forming a triangular homogenizing structure 130, e.g., having one or more triangular or rounded triangular shapes. The edges of the homogenizing structure 130 can be further roughened to improve light spreading and light mixing in the example using RGB-side LEDs.

FIG. 1B shows: the side boundary portion is provided by a non-transparent material 101 formed adjacent to and complementary to the light guide 10. White TPU may be used as the substrate 102 with an electrical design printed thereon. Alternatively, the TPU may have a white liner or the substrate may be a PEN substrate with a white coating. The ink on the TPU is readily cured due to its high processing temperature of 140 ℃. White is used to allow reflection at the substrate interface of the generated light from the LED bonded to the printed circuit. The side-emitting LED 20 may be bonded to the Ag printed circuit at a height of preferably <2mm, more preferably <1mm, etc. High power LEDs are preferred (output >1000 nits). The substrate 101 may also be formed from a white TPU from which sections are cut by laser or another method. The substrate 101 may also be black, or a combination of black and white, depending on the design. A black TPU will be used to block light when fully absorbent, non-transparent. This will lead to a loss of power efficiency (power efficiency) of the optical system, but on the other hand ensures that unwanted light leakage is avoided and thus sharply defines the bright area.

When combined as shown in fig. 1A, the display 100 has a transparent portion 102, and the boundary portion 101 forms a single integrated stack 50 of two or more segmented and complementarily shaped layers. The assembly can be made by separately cutting out complementary structures and laying the two structures together to form a single layer. After layup, the layup may be provided, for example, by a cover layer (see fig. 4) to preserve an integral structure for the device 100.

FIG. 1C shows that the light guide 10 is not regular or rectangular, but contains a shape that further spreads the light to avoid a reduced intensity on the sides 121 compared to the central portion of the outcoupling surface 120. LEDs are strongly coupled out at close distances, which makes it difficult to achieve homogeneous emission over a large area and at such distances. The light guide may be provided with a patterning at the incoupling region on the incoupling face to spread the light. Thus, the incoupling surface may be non-flat to include a cavity between the incoupling surface and the LED device.

For example, the light guide 10 contains an air pocket 150 at the LED light emission surface 20 that provides refraction of light at the interface with the light guide 10. By means of these air pockets 150, the length D of the LED can be limited with respect to the width of the outcoupling surface 120, but still have its sides homogeneously illuminated. A typical ratio may be about 150 to 300% of the width of the outcoupling face of the LED length D. The air cell is triangular in shape, possibly with rounded curves and a roughening on one base side of the rounded triangular shape, which prevents color splitting. The opposite side of the incoupling surface can be similarly provided with a refractive structure.

Fig. 2A-2C show the optical response of partially homogenized regions of different structures in the light guide 10. In fig. 2A, a substrate optical response is given to the light guide 10, wherein no homogenizing structure is provided. Showing that the coupling plane shows heterogeneity, especially near the center. In FIG. 2B, a homogenizing zone 30 is provided by a single cavity in the transparent portion 102. It is shown that the homogeneity is improved especially towards the sides. In FIG. 2C, a homogenized structure in the form of a perfect lens included in the homogenizing zone shows excellent homogeneity. This embodiment is difficult to manufacture.

FIG. 3 shows an exemplary top view of an image display 121 on a top-coupling surface 120 and a graded bottom surface 140 having a gradient pattern 140. The gradient pattern is formed in a reflective surface, thereby partially reflecting light emitted from the LED 20. The reflective surface is typically provided by a light reflective coating having a graded pattern. The pattern having a reduced reflection away from one of the incoupling surfaces 110. In this example, the graded light reflection pattern extends to the bottom side of the outcoupling surface 120.

It shows the following: the homogenizing zone 130 and/or the sides of the LED incoupling surface 110 have a roughening to prevent color splitting, for example, when using rgb LEDs. In this example, the incoupling surface 110 receives an LED device that is one side of a planar transparent layer. The LED device 20 is a vertical LED having a thickness corresponding to the transparent layer of the light guide 10. The light guide section 10 may be cut from a transparent or foggy TPU and positioned inside the border portion 30 of the white light guide. Separately, a cover foil (PET, PEN, TPU, PVB, PC or other), optionally misted or modified to provide light diffusion, may be printed with a reflective coating, such as a dielectric ink having openings, that allow light to exit the light guide. Alternatively, the cover layer may be a printed coating, such as a coating on a TPU layer. This white dielectric reflective coating may be a cover foil aimed toward the TPU during the lamination assembly step of the transparent portion and the border portion. On top of the cover foil further layers (dielectric, anti-scratch or other) may be printed. Light guiding and outcoupling may be improved by applying an engraved pattern on the inside and/or outside, but may also be incorporated on the inside. This pattern may be random, but may also be periodic in nature. For example, good results can be obtained by engraving of-30 micron lines exhibiting a periodicity of 50 microns, which are laser into PEN and PC with a CO2 laser. In the example shown, the light guide is formed by a transparent planar layer of 2mm thickness, and the incoupling face is positioned at a distance of about 5 to 8mm away from the outcoupling face. The homogenizing zone 130 is disposed in a temperature resistant material so that its shape does not significantly change at higher temperatures.

FIG. 4A shows an exemplary layer stack in which LED 20 is shown as an LED coupled from the side of light guide 10. The stack 100 is not physically sized, but is merely used to illustrate a number of optional layers. The central light guide layer 50 is segmented from a transparent PMMA. Layer 40 is a PMMA interface modified with a gradient engraving for enhanced light guiding. The engraved cover layer 40 is placed in contact with a stone white foil 104, which is laminated to a bottom decorative foil 106. The light guide stack is optically closed by a white coating 104 'and completed by a scattering foil 105 and a top foil 106'.

Fig. 4B shows a variation in which the side border portion and the transparent portion are made by injection molding. In this example, a cover layer 40 is provided, for example by a coated Polycarbonate (PC) transparent front foil 107 of, for example, 250 microns. A reflective white surface 104 is provided by a light reflective coating having a gradient pattern; thus covering the segmented transparent light guide stack G on the top side with a gradient pattern. The side 104a of the reflective white coating 104 may be terminated by a black coating that blocks light from being directed in the cover foil. The PC cover foil 107 is further provided with a top coating 104b, 104w which is a stack of white and black inks-black on the outside. The coating 104 leaves the image picture free so that the transparent polycarbonate layer displays the image when illuminated. On the back side of the cover layer 40, the light-guiding stack G is formed by a segmented light-side boundary portion 30 provided by a non-transparent material formed adjacent and complementary to the transparent portion 10. The light guide 100 thus forms a single integrated stack of two or more segmented and complementary shaped layers 50 and a cover layer 40.

This results in the functional layer being provided as a stack on top of the injection molded portion 50, which is used to provide a suitable thickness. For example, a back side layer atop a back substrate may be provided by a TPU layer, but may also be injection molded. Layer 31 is injection molded simultaneously with the complementary shaped layer 50. By changing the shape from the mold at this side, the shape of the layer 31 can be non-flat, so that a non-flat reflective surface can be created, thereby providing potentially beneficial optical effects. Layer 32 is a single or combined functional and non-functional foil that is flat or contains contacts for lead slits or slots for backside contact that is protected during the molding process. It is also conceivable: functionality in the form of chips, sensors or devices may be added to this portion, thereby enabling the front portion to be contacted or powered. A top emitting LED may also be added to layer 32. The stack of figure 4 would be modified to an injection molded white shape 50 but with a white reflective foil with printed circuitry and components as layer 32.

For clarity and conciseness of description, features are described herein in the same or separate embodiments, but it is understood that the scope of the invention may include embodiments having combinations of all or some of the described features.

In interpreting the appended claims, it should be understood that the term "comprising" does not exclude the presence of other elements or acts than those listed in a given claim; the word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements; any reference signs in the claims do not limit their scope; several "means" may be represented by the same or different items or structures or functions performed; any of the disclosed devices or portions thereof may be combined together or separated into further portions unless otherwise noted. If one request is made to refer to another request, this may indicate that the combination of their respective profiles achieves a comprehensive advantage. The fact that only mutually different request items refer to specific measures does not indicate that a combination of these measures cannot be used as well. The present embodiments may thus include all working combinations of claimed items, wherein each claimed item is referred to in principle as relating to any one of the preceding claimed items, unless the context clearly dictates otherwise.