Lighting device with a flat light guide plate

Abstract

Lighting device (1) with a flat light guide plate (2) into which at least one electrical luminaire element, preferably designed as a light-emitting diode (3), couples light on at least one side surface (4) and whose limiting side surfaces (5, 6;11) are provided with a reflective layer, and with a limiting structure (8) formed on the light guide plate (2) and provided for light emission adjacent to a receptacle (7) in the light guide plate (2) for integrating a display or actuating element, characterized in that the light guide plate (2) has a light guide platform section which forms a light coupling piece (9) with a light coupling path adjacent to the light coupling side surface (4), which has at least one internal optical defect (10) which widens and scatters the coupling-in light, forming a light curtain overhanging to the limiting structure (8), which forms a circumferential luminous surface on the receptacle (7) for illuminating the display or actuating element, the light curtain being reflectable through the limiting side surfaces (5, 6;11) is coupled out at the boundary structure (8) of the light guide plate (2), and a rear boundary side surface (11) arranged facing away from the light coupling piece (9) follows the boundary contour in a form-fitting manner, wherein a width of the light guide platform section and thus of the light coupling piece (9) corresponds to the width of the rear boundary side surface (11), and the light guide plate (2) delimits the receptacle (7).

Description

[0001] The invention relates to a lighting device with a flat light guide plate according to the preamble of claim 1.

[0002] From US 2004 / 0066659 A1, a lighting device with a ring-shaped circumferential light channel is known, wherein the light channel has an opening area for light illumination from both sides.

[0003] A lighting ring is known from DE 102 08 045 A1. The lighting ring is formed by a light channel into which the light emitted by a light source is directed.

[0004] From EP 0 306 659 B1, an illuminated display unit, in particular a house number, traffic sign, or advertising medium, is known, which has a light guide plate in which at least one electrical luminaire, preferably a light-emitting diode, is embedded at at least one lateral boundary edge. The light guide plate carries the display symbols and has boundary edges provided with a reflective layer. For good luminous efficacy and uniform illumination of even large display areas, the light guide plate contains fluorescent particles. The display symbols can be formed into this light guide plate, in particular milled into it. Light can emerge at the resulting angled edges, causing the corresponding display symbols to stand out brightly.A disadvantage is that commercially available light guide plates cannot be used to ensure reasonably uniform illumination of certain display areas.

[0005] German patent DE 33 22 393 A1 discloses a luminaire in which light-emitting diodes are embedded in a diffuser to obscure the contours of the light source and / or to emit the light over a wider angular range. However, the luminous efficacy is very low.

[0006] From DE 199 54 794 A1, a lighting unit is known that comprises a light guide element with an elongated, curved illuminating surface and at least one light source for illuminating the light guide. Such lighting units are used, for example, to generate a corona around a push button as a searchlight. The light guide element is annular in shape and forms a cyclone-like structure with a light coupling point. The surface of a helically rising underside of the light guide element, for example, has a radially extending corrugation that causes the light coupled in by the light source to be partially reflected to a concentrically arranged ring-shaped illuminating surface above it, while the light passes through the light guide ring. A disadvantage is that the manufacturing process is complex and expensive.

[0007] The invention is therefore based on the objective of creating a lighting device that ensures contour or outline illumination of a display or actuating element with good luminous efficacy and uniform illumination.

[0008] This problem is solved by the features of claim 1.

[0009] This creates a lighting device that allows for contour or outline illumination of test sockets, buttons, switches, lock cylinders, advertising media, etc., with minimal effort. Such contour or outline lighting, also known as searchlight or corona lighting, can provide homogeneous illumination using just one LED.

[0010] The design using a light guide plate can be very flat and is easy to mount on the front panels of electrical devices. Furthermore, the design is easily adaptable to different diameters or shapes of the components to be illuminated.

[0011] For this purpose, only sufficiently dimensioned light guide plates are required, each with a recess for the component to be illuminated. A section of the light guide platform provided on the light guide plate forms a light coupling path, which widens and scatters the coupled light by means of at least one internal optical defect in such a way that a light curtain is formed, which can illuminate the component that can be inserted into the recess. The light curtain is designed to overhang in order to form a continuous illuminated surface on the recess.

[0012] The light coupling path with an internal optical defect, which can simply be a hole, does not reduce the light output, as is often the case with diffusers or scattering particles integrated into the light guide. The at least one internal optical defect essentially forms an internal target for the coupled light beam, fragmenting it so that, in conjunction with the reflective boundary surfaces and the boundary structure adjacent to a sensor, a homogeneous luminous pattern is created that follows the boundary contour of the boundary structure. The shape and width of the boundary contour then determine the luminous pattern of the surrounding illumination.

[0013] Furthermore, the need for a mixing circuit is eliminated when using RGB LEDs as the light source. Uniform illumination for the different light colors is achieved in the same way due to the integrated internal optical interference. This internal optical interference is preferably located locally within the path of light incidence from a lighting element, which is preferably designed as a point light source.

[0014] Further advantages and embodiments of the invention can be found in the following description and the dependent claims.

[0015] The invention is explained in more detail below with reference to the embodiment shown in the accompanying figures. Fig. Figure 1 schematically shows a perspective view of a lighting device. Fig. Figure 2 schematically shows a top view of the lighting device according to Fig. 1.

[0016] How Fig. 1 and Fig. As shown in Figure 2, the invention relates to a lighting device 1 with a flat light guide plate 2. Light is coupled into the light guide plate 2 from at least one electrical lighting element, which is preferably designed as a light-emitting diode 3, at at least one side surface 4 of the light guide plate 2.

[0017] The light guide plate 2, which is flat and has a thickness of, for example, 3 to 8 mm, has boundary surfaces 5, 6 at its edges, which are provided with a reflective layer (not shown). The reflective layer ensures that the coupled light is not coupled out at the outer edge of the light guide plate 2. The light guide plate 2 encloses a recess 7, which is, for example, a cutout. The recess 7 serves to insert a display or actuation element or other object that is to be illuminated.

[0018] To form a designated illuminating surface, a boundary structure 8 is provided on the light guide plate 2 adjacent to the receptacle 7, at which the light coupled into the light guide plate 2 is coupled out. The boundary structure 8, which is designed for light emission and is located adjacent to the display or actuating element that can be integrated into the light guide plate 2, has a boundary contour that can follow the contour of the display or actuating element to be illuminated. The light coupled out by the boundary structure 8 thus forms an illuminating surface that can be elongated and curved to create a corona, for example, around a push button. This is also referred to as a searchlight. Instead of a push button, any type of display or actuating element, such as a switch, a test socket, a lock cylinder, a handle, an advertising symbol, etc., can be illuminated.

[0019] Corona lighting, which replicates and surrounds the contour of a display or operating element (see image 7), improves its location and display in darkness.

[0020] To achieve the most uniform illumination possible of the illuminating area defined by the boundary structure 8, the light guide plate 2 has a light coupling element 9 adjacent to the light-coupling side surface 4. The light coupling element 9 has at least one internal optical defect 10, which widens and scatters the coupled light, forming a light curtain that overhangs the boundary structure 8 and can be coupled out of the light guide plate 2.

[0021] The boundary structure 8 is designed here as a boundary contour surrounding the receptacle 7 for the display or actuation element. Furthermore, a rear boundary surface 11, arranged facing away from the light coupling element 9, follows the boundary contour of the boundary structure 8 and is form-matched to it. The light guide plate 2 then has the shape of a semicircular ring along the boundary surface if the receptacle 7 is round. Even with larger radii, the light guide section can be homogeneously illuminated concentrically to the rear boundary surface 11 with only one light source, here the LED 3.

[0022] The internal optical defect 10 is preferably a mechanically introduced, locally limited defect 10, here for example a simple hole, towards which the light beam of a luminaire element preferably designed as a point light source, here the light-emitting diode 3, is directed.

[0023] The at least one light-emitting diode 3 is preferably an RGB LED mounted on an integrated circuit board 12. Light of several wavelengths, in particular light of three different wavelengths and / or light of the colors red, green and blue, can thus be coupled in and out.

[0024] The light guide plate 2 is preferably made of a plastic such as PMMA or polycarbonate. The light guide plate 2 is preferably made of a plastic with a refractive index at a wavelength of 589 nm (yellow-orange) in the range of 1.2 to 1.8, particularly 1.5 to 1.6. The transmission is preferably above 70%, particularly 90% to 95%.

[0025] The boundary structure 8 for extracting light can be provided as a band structure with beveled edges and / or roughenings that are milled and / or printed on. The boundary structure 8 can also be covered at its top with a diffuser plate (not shown). The light guide plate 2 is preferably arranged in a housing 13, which carries connecting leads 14 for the at least one lighting element, here the LED 3, to form a pre-assembled component. Preferably, only one LED 3 is provided; alternatively, however, several LEDs 3 and optionally several associated defects 10 can be provided in a light guide plate 2, which can have particularly larger dimensions. The lighting device 1 can also be assembled as a lighting module with other such lighting modules.

Claims

[1] Lighting device (1) with a flat light guide plate (2) into which at least one electrical luminaire element, preferably designed as a light-emitting diode (3), couples light on at least one side surface (4) and whose limiting side surfaces (5, 6; 11) are provided with a reflective layer, and with a limiting structure (8) formed on the light guide plate (2) and provided for light emission adjacent to a receptacle (7) in the light guide plate (2) for integrating a display or actuating element, characterized by, that the light guide plate (2) has a light guide platform section which forms a light coupling piece (9) with a light coupling path adjacent to the light coupling side surface (4), which has at least one internal optical defect (10) which widens and scatters the coupling-in light, forming a light curtain overhanging to the boundary structure (8), which forms a circumferential luminous surface on the receptacle (7) for illuminating the display or actuating element, the light curtain being reflectable through the boundary side surfaces (5, 6;11) is coupled out at the boundary structure (8) of the light guide plate (2), and a rear boundary side surface (11) arranged facing away from the light coupling piece (9) follows the boundary contour in a form-fitting manner, wherein a width of the light guide platform section and thus of the light coupling piece (9) corresponds to the width of the rear boundary side surface (11), and the light guide plate (2) delimits the receptacle (7). [2] Lighting device according to claim 1, characterized by , that the boundary structure (8) is elongated and curved and the rear boundary side surface (11) of the light guide plate (2) is shaped to create a corona luminous surface. [3] Lighting device (1) according to claim 1 and 2, characterized by, that the internal optical defect (10) is a mechanically introduced, locally limited defect (10), for example a hole, towards which the light beam of a luminaire element designed as a point light source is directed. [4] Lighting device (1) according to any one of claims 1 to 3, characterized by , that at least one light-emitting diode (3) is an RGB LED mounted on an integrated circuit board (12). [5] Lighting device (1) according to any one of claims 1 to 4, characterized by , that the light guide plate (2) is made of a plastic such as PMMA or polycarbonate. [6] Lighting device (1) according to any one of claims 1 to 5, characterized by , that the optical fiber plate (2) is made of a plastic with a refractive index at the wavelength 589 nm (yellow-orange) in the range of 1.2 to 1.8, in particular 1.5 to 1.

6. [7] Lighting device (1) according to any one of claims 1 to 6, characterized by , that the boundary structure (8) for coupling out light is designed as a ribbon structure with beveled edges and / or roughenings that are milled and / or printed on. [8] Lighting device (1) according to any one of claims 1 to 7, characterized by , that the boundary structure (8) can be covered at the head end with a diffuser plate. [9] Lighting device (1) according to any one of claims 1 to 8, characterized by that the indicator or actuating element is a switch, a test socket, a lock cylinder, a handle or an advertising symbol. [10] Lighting device (1) according to any one of claims 1 to 9, characterized by , that the light guide plate (2) is arranged in a housing (13) and carries connecting lines (14) for the at least one light element to form a pre-assembled built-in component.

Images