Classifications

• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
  • G02B6/0001—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems
  • G02B6/0011—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the light guides being planar or of plate-like form
  • G02B6/0033—Means for improving the coupling-out of light from the light guide
  • G02B6/0035—Means for improving the coupling-out of light from the light guide provided on the surface of the light guide or in the bulk of it
  • G02B6/0038—Linear indentations or grooves, e.g. arc-shaped grooves or meandering grooves, extending over the full length or width of the light guide
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
  • G02B6/0001—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
  • G02B6/0001—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems
  • G02B6/0011—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the light guides being planar or of plate-like form
  • G02B6/0013—Means for improving the coupling-in of light from the light source into the light guide
  • G02B6/0023—Means for improving the coupling-in of light from the light source into the light guide provided by one optical element, or plurality thereof, placed between the light guide and the light source, or around the light source
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
  • G02B6/0001—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems
  • G02B6/0011—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the light guides being planar or of plate-like form
  • G02B6/0033—Means for improving the coupling-out of light from the light guide
  • G02B6/0035—Means for improving the coupling-out of light from the light guide provided on the surface of the light guide or in the bulk of it
  • G02B6/0045—Means for improving the coupling-out of light from the light guide provided on the surface of the light guide or in the bulk of it by shaping at least a portion of the light guide
  • G02B6/0046—Tapered light guide, e.g. wedge-shaped light guide
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
  • G02B6/0001—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems
  • G02B6/0011—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the light guides being planar or of plate-like form
  • G02B6/0033—Means for improving the coupling-out of light from the light guide
  • G02B6/005—Means for improving the coupling-out of light from the light guide provided by one optical element, or plurality thereof, placed on the light output side of the light guide
  • G02B6/0053—Prismatic sheet or layer; Brightness enhancement element, sheet or layer

Definitions

• the invention relates to a device for backlighting a flat display according to the preamble of the main claim. It is already known from WO 98/13709 a front lighting for a flat display, in which punctiform structures with a rectangular cross section for the light exit are present on the underside. The light emerging from the underside is directed onto a surface to be illuminated, reflected there and then traverses the light guide again.
• the device according to the invention with the features of the main claim has the advantage that a backlighting of a display takes place, in which the information display is consequently based on a different absorption or transmission of the light in the display.
• a backlighting of a display takes place, in which the information display is consequently based on a different absorption or transmission of the light in the display.
• the advantages do not have to pass through the light guide plate again.
• the efficient decoupling from the light guide plate by trapezoidal or rectangular extensions on the side surface facing the display the light guide plate are used, without the light coming from the display being influenced again by the light guide plate.
• the extensions are linear and parallel to the first narrow side of the light guide plate. Compared to the prior art, such linear structures result in a more efficient coupling out, since the total area available for coupling out the light is enlarged.
• the light source the light of which is coupled into the light guide plate, is rod-shaped, since this enables a homogeneous light distribution over the entire length of the light guide.
• a cold cathode fluorescent lamp is particularly suitable for this because of its efficiency and the emitted color spectrum.
• the light guide plate is wedge-shaped. Because since the light from the
• the angles, which enclose the light beams with the light guide surface increase in a wedge-shaped light guide towards the wedge tip.
• the probability increases in the light guide plate that light irradiated by the light source is coupled out of the light guide plate.
• the efficiency of the decoupling is therefore lower in the areas near the light source, in which a lot of light is available for decoupling from the light guide plate, compared to areas far from the light source, in which little light is available for decoupling. Consequently, the wedge-shaped design of the light guide plate enables better homogeneity of the display brightness.
• top surfaces of the trapezoidal extensions each enclose an angle with the associated side surfaces of the trapezoidal extension, the amount of which lies in a range from 90 degrees to 105 degrees.
• Light guide plate emerges, to be modified and optimized for the intended application, because when exiting from the rectangular or trapezoidal extensions, the light refracts again.
• the angle of the side surfaces of the rectangular or trapezoidal extensions By changing the angle of the side surfaces of the rectangular or trapezoidal extensions, the light exit angle also changes due to the different refraction process. A better alignment of the exit angle with a viewer of the display is therefore possible.
• a reflector on the side of the light guide plate facing away from the display. In this way, light that has been undesirably coupled out from the side of the light guide plate facing away from the display can be reflected back into the light guide, so that it is again available for decoupling in the direction of the display.
• a film between the light guide plate and the display in which a sawtooth structure is arranged on the side facing away from the display.
• a film makes it possible to redirect the light emerging from the light guide plate, which is generally coupled onto the light guide plate at a very large angle with respect to the solder, in the solder direction. This is advantageous because viewing an advertisement generally takes place largely perpendicular to the display surface.
• the sawtooth structure in such a way that the surfaces facing the light source are in a range from 45 degrees to 60 degrees and the side surfaces facing away from the light source are in an angular range from 65 degrees to 90 degrees to a respective base of the sawtooth .
• a film with the microprisms facing the display on the side of the film with the sawtooth structure facing the display, which are essentially perpendicular to the sawtooth structure. This results in a collimation of the light rays also perpendicular to the alignment of the sawtooth structure, as a result of which the light rays are also aligned in this direction as far as possible in the perpendicular direction to the light guide plate.
• the microprisms can also be integrated into the film with the sawtooth structure by being arranged on the side of the film with the sawtooth structure facing the display. This can save an additional film.
• a prism film between the first narrow side of the light guide plate and the light source.
• This prism film is used to align the light rays that are radiated from the light source into the light guide. It is thus possible to give the light beams an orientation even before they enter the light guide, by means of which a later decoupling from the light guide in a preferred direction is facilitated. Furthermore, this avoids losses that can arise from the fact that the light is coupled into the light guide at an angle that does not allow the light to propagate in the light guide under total reflection, since the light already leaves the light guide close to the light source. The homogeneity of the display brightness can thus be improved by the prism film.
• the second narrow side of the light guide plate has a reflector. This allows light that is not coupled out of the light guide and can be lost through the second narrow side into the Optical fibers are reflected back for the purpose of a later decoupling.
• a diffuser for homogeneous backlighting between the light guide plate and the display, which further increases the homogeneity of the display brightness through light scattering.
• FIG. 1 shows a device according to the invention for flat
• FIG. 1 Figure 2 and Figure 3 other versions of the device for backlighting according to the invention.
• Figure 4 shows a device according to the invention for backlighting in supervision from the direction of the display.
• FIG. 5 shows a microstructure according to the invention.
• FIGS. 6 and 7 show other embodiments of the microstructure according to the invention.
• Figure 8 shows an embodiment of a light guide plate according to the invention with a sawtooth film.
• FIG. 9 shows an embodiment of the
• FIG. 10 shows a liquid crystal display with a planar backlighting according to the invention.
• FIG. 11 shows the coupling of light into a light guide plate according to the invention. Description of the embodiment
• a light guide plate 11 is shown in a cross section.
• the light guide plate 11 has a first side face 14 which faces a display and a second side face 15 which faces away from the display.
• Trapezoidal or rectangular microstructures 12 are arranged on the first side surface 14.
• the trapezoidal or rectangular microstructures 12 are designed as extensions of the light guide plate 11 and have a trapezoidal or rectangular cross section. To simplify the designation, an element is selected from the trapezoidal or rectangular microstructures.
• a reflector 13 is arranged on the second side surface 15.
• a light source 10 is arranged on a first narrow side 16.
• a second narrow side 17 is located opposite the first narrow side 16.
• the light guide plate 11 consists of a material that is as transparent as possible.
• PMMA polymethyl methacrylate
• the light guide plate made of PMMA is preferably produced by injection molding.
• the reflector 13 is preferably a metal foil, a plastic film coated with metal or can also be realized by a reflective housing base which is made of metal or which is coated with metal.
• the light source 10 is preferably a rod-shaped light source that runs along the first narrow side 16. For example, a rod-shaped incandescent lamp or, in a preferred embodiment, a cold cathode fluorescent lamp are suitable for use.
• the electrical ballast device required for their operation is shown in of Figure 1 not shown.
• a display to be backlit which is located in the figure above the first side surface 14, is not shown.
• the light from the light source 10 is through the first
• Narrow side 16 is coupled into the light guide plate 11 and spreads out in the light guide plate.
• a large part of the light rays strikes the first side face 14 and the second side face 15 at such a flat angle that the light rays are reflected with total reflection on the side faces mentioned.
• the reflection process can be repeated several times.
• Light rays that reach the second side surface 15 at a sufficiently steep angle can exit the light guide plate 11 through the second side surface 15. You now meet the reflector 13, through which the light beams are reflected and coupled back into the light guide plate 11.
• the trapezoidal or rectangular extensions 12 of the light guide plate 11 provided on the first side surface 14 serve to decouple the light from the light guide plate 11.
• the reflector 13 can be extended to the second narrow side 17 or so a further reflector (not shown) can also be arranged there.
• the trapezoidal or rectangular extensions 12 are shown greatly enlarged in FIG. 1 in order to maintain the clarity of the drawing.
• the trapezoidal or rectangular extensions 12 are much smaller in design than the size of the light guide plate 11 than shown in the drawing. Furthermore, their number is larger than that shown in FIG. 1.
• FIG. 1 Another embodiment of the backlighting device according to the invention is shown in FIG.
• the same reference numerals designate the same components of a device here and below.
• Figure 2 is shown as a cross section of the device.
• a light guide plate 20 has a first side surface 14 facing the display with trapezoidal or rectangular extensions 12.
• the light guide plate 20 is wedge-shaped and differs from the light guide plate 11 in FIG. 1 only by its shape, not by the material. Furthermore, the light guide plate has a second side surface 21 facing away from the display. Light rays which are coupled into the light guide plate 20 from the light source 10 via the first narrow side 16 are reflected at a sufficiently flat angle with respect to the first side surface 14 and the second side surface 21 with total reflection . Due to the wedge shape of the light guide plate 20, however, the angle of incidence of the light beams is greater in the case of multiple total reflection with respect to the two side surfaces, until total reflection is no longer possible. However, with a steeper angle relative to the two side surfaces, the number of reflections per unit length of the first side surface 14 also increases with increasing distance from the light source.
• Light rays that leave the light guide plate 20 through the second side surface 21 are transmitted through the Reflector 13 reflected and coupled back into the light guide plate 20.
• the light guide plate 20 from FIG. 2 is provided with a reflector 30.
• the reflector 30 in FIG. 3 runs parallel to the second side surface 21.
• the reflector 30 serves to reflect light rays that leave the light guide plate 20 through the second side surface 21 back into the light guide plate 20.
• FIG. 4 shows a light guide plate 50 in a top view from the direction of a display.
• the light guide plate 50 can have a cuboid shape, like the light guide plate 11 in FIG. 1, or a wedge shape, like the light guide plate 20 in FIG. 2.
• the trapezoidal or rectangular microstructures 12, which extend parallel to the first narrow side 16, are arranged on the light guide plate 50.
• the light source 10 is arranged, which has a first electrical connection 41 and a second electrical connection 42.
• a display the display surface of which at least partially extends over the side surface of the light guide plate 50 that is visible in the top view in FIG.
• FIG. 5 shows a section of the light guide plate 50, a piece of the first side surface 14.
• a first rectangular extension 51 and a second rectangular extension 58 are shown in a cross section. The viewing direction corresponds to the view in FIGS. 1-3.
• the first and second extensions 51 and 58 are special designs of the trapezoidal and rectangular microstructures in FIGS. 1-4. The extensions rise above the first side surface 14 of the light guide plate 50. Between the first rectangular extension 51 and the second rectangular extension 58, a distance 57 is shown in dashed lines.
• the first rectangular extension 51 has a top surface 54 and a first side surface 55 facing the light source 10 and a second side surface 56 facing away from the light source 10
• the top surface 54 includes a first angle 52 with the first side surface 55 and a second angle 53 with the second side surface. In this exemplary embodiment, both the first angle 52 and the second angle 53 have the value 90 degrees, so that the first extension 51 is rectangular.
• the design of the second extension 58 corresponds to the first extension 51.
• the distance 57 between the first extension 51 and the second extension 58 is selected such that the distance 57 is at least three times greater than the first extension 51 over the first side surface 14 of the light guide plate 50 rises.
• the second extension 58 has a first side surface 59 which faces the light source 10.
• Light rays coupled into the light guide plate 50 strike either directly or after a reflection at the second side surface 15 or 21 now either on the first side surface 14 or enter into a rectangular extension, for example into the first rectangular extension 51. If light rays strike the first side surface 14, the light rays will generally strike at such a flat angle that they are reflected under total reflection on the first side surface. However, if a light beam enters the first rectangular extension 51, it generally strikes the second side surface 56 of the rectangular extension 51. However, the light beam strikes this second side surface 56 at an angle that is close to a perpendicular impact. A total reflection on the second side surface 56 is therefore not possible. Rather, the light beam is refracted on the second side surface and leaves the light guide plate 50. The height of the rectangular extension 51 is therefore at least three times greater than the distance from the second rectangular extension 58, so that light beams leaving the first rectangular extension 51 do not again can be coupled into the light guide plate through the first side surface 59 of the second rectangular extension 58.
• FIG. 6 shows another embodiment of a trapezoidal or rectangular microstructure 12 according to the invention. The view otherwise corresponds to FIG. 5, which is why FIG. 6 shows only a single embodiment of the microstructure according to the invention, which is likewise in a large number on the
• Light guide plate 50 is arranged.
• a trapezoidal extension 61 points between a top surface 64 and one first side surface 65 facing light source 10 has a first angle 62 which is 90 degrees.
• the trapezoidal extension 61 has a second angle 63 between the top surface 64 and a second side surface 66 applied to the light source. This angle is in a range between 90 degrees and 105 degrees.
• By increasing the angle 63 to a value above 90 degrees the angle of incidence of light rays on the second side surface 66 is changed. This also changes the angle of the light beams emerging from the light guide plate 50 at the trapezoidal extension 61.
• the distance to the next trapezoidal extension corresponds to the distance 57 in FIG. 5, which is therefore not shown in FIG. 6.
• FIG. 7 shows a trapezoidal extension 71 with a first cover surface 74, the first cover surface 74 including a first side surface 75 forming a first angle 72 which is in a range from 90 degrees to 105 degrees.
• the second angle 73 enclosed by the first cover surface 74 and a second side surface 76 is in a range from 90 degrees to 105 degrees. This enables a symmetrical design of the trapezoidal extension 71.
• the view corresponds to FIGS. 5 and 6.
• the light guide plate 50 is made wedge-shaped, the wide side of the wedge, the first narrow side 16, which faces the light source 10, has a thickness of 4 mm.
• the first side surface 14 of the light guide plate 50 has the dimensions 110 mm x 78 mm. The longer edge of the side surface 14 faces the light source 10 and delimits the first narrow side 16.
• On the first side surface 14 of the About 200 trapezoidal extensions corresponding to the trapezoidal extension 71 in FIG. 7 are arranged in the light guide plate 50. Both the first angle 72 and the second angle 73 are each 100 degrees.
• the trapezoidal extensions have a height of 30 ⁇ m above the first side surface 14 and the top surface 74 has a width of 20 ⁇ m. The distance between two trapezoidal extensions is approx. 280 ⁇ m.
• Light guide plate 50 executed in the same area size of the first side surface 14.
• 520 trapezoidal extensions are arranged parallel to each other.
• the top surface 54 has a width of 40 ⁇ m and the trapezoidal extensions have a height of 30 ⁇ m.
• the distance between the trapezoidal extensions and their dimensions over the entire first side surface 14 of the light guide plate 50 is constant.
• the variations are to be adapted to the different light guide plate geometries used.
• a light guide plate 50 according to the invention is shown in cross section in FIG. Rectangular or trapezoidal extensions 12 are arranged on the first side surface 14.
• Rectangular or trapezoidal extensions 12 are arranged on the first side surface 14.
• 10 and 11 the trapezoidal or rectangular extensions 12 are shown larger and simplified.
• they are preferably carried out according to the description of FIGS. 5-7.
• the first part of the first narrow side 16 is shown, which adjoins the first side surface 14.
• a sawtooth foil 80 is arranged on the first side surface 14 and has a structure made of saw teeth 81 on its side facing the light guide plate 50.
• a saw tooth 81 is provided with a reference symbol in FIG.
• the sawtooth film 80 On a side surface 82 facing away from the light guide plate, the sawtooth film 80 has microprisms, the breaking edge of which extends perpendicular to the rectangular or trapezoidal extensions 12 of the light guide plate 50.
• the sawtooth foil 80 serves to deflect the light coupled out of the light guide plate 50 through the rectangular or trapezoidal extensions 12 for display purposes.
• a section of the sawtooth foil 80 is shown enlarged in FIG.
• a sawtooth 81 has a first side surface 92 which faces the light source 10 and a second side surface 93 which faces away from the light source.
• the sawtooth 81 also has a base 96, which is shown in broken lines.
• the first side surface 92 of the sawtooth forms a first angle 94 with the base 96.
• the second side surface 93 forms a second angle 95 with the base 96.
• microprisms 97 are arranged which run perpendicular to the rectangular or trapezoidal extensions on the light guide plate.
• the microprisms are flat prisms executed, ie a breaking angle 98 of the micro prisms 97 is greater than 100 degrees.
• the microprisms 97 lie close together.
• the exit angle is essentially influenced by the trapezoidal or rectangular extensions 12, in particular by the angle of the side surface 56, 66 or 76 facing away from the light source 10. Since a display surface advantageously runs parallel to the light guide plate 50, the exit angle with respect to the solder on a display surface thus becomes large. However, since a display is usually viewed in the vertical direction, the light from the backlighting must preferably strike the display in the vertical direction. If the light rays now hit the sawtooth foil 80, the light rays will penetrate through the first side surface 92 of the sawtooth 81 into the sawtooth foil. You will then meet the second side surface
• the light leaves the sawtooth foil 80 through the side surface 82 now almost perpendicular to the first side surface 14 of the light guide plate 50.
• the microprisms 97 arranged on the surface 82 of the sawtooth foil 80 further collimate perpendicular to the alignment of the trapezoidal or rectangular extensions 12, so that the light rays now run perpendicular to the first side surface 14 and also meet a display perpendicularly, since this is aligned parallel to the first side surface 14.
• a suitable deflection of the light results when the first angle 94 of the sawtooth 81 is selected in a range between 65 degrees and 90 degrees and when the second angle 95 is selected in a range between 45 and 60 degrees.
• a choice of the first angle of 80 degrees and the second angle of 50 degrees has proven to be particularly advantageous.
• FIG. 10 shows the device according to the invention when used for backlighting a liquid crystal cell.
• the light from a rod-shaped light source 10 is coupled into a wedge-shaped light guide plate 20.
• the light source 10 is surrounded by a first reflector 100.
• a second reflector 102 is arranged on the light guide plate 20. This covers the second side surface 21 of the light guide plate 20 and a second narrow side 107 of the light guide plate 20, the second narrow side 107 being opposite the first narrow side 16.
• the sawtooth foil 80 likewise shown in simplified form, is arranged on the first side surface 14 of the light guide plate 20.
• a diffuser film 103 is located on the side of the sawtooth film 80 facing away from the light guide plate. Above the diffuser film 103 there is a liquid crystal cell 104 which serves as a display.
• Liquid crystal cell 104 consists of two transparent substrates 105, for example glass plates, between which no drawn liquid crystal molecules are arranged. Polarizer films 106 are laminated onto the transparent substrates 105 on the outside.
• the liquid crystal cell 104 is divided over its surface area into pixels which can be electrically controlled individually.
• the individual pixels, the pixel electrodes required for the control, the control electronics and the liquid crystal molecules are not shown in FIG. 10.
• the electrical control required for the operation of the light source 10 is also not shown.
• the device shown is located in a housing, also not shown, which can accommodate the electrical components required for operation.
• the sawtooth foil 80 and the diffuser foil 103 are preferably made of plastic.
• the remaining inhomogeneities in the display brightness are eliminated by the diffuser film 103.
• the diffuser film has, for example, scattering particles.
• the first reflector 100 is preferably a scattering reflector, which is made, for example, of a white plastic material.
• the second reflector 102 is preferably a non-scattering reflector made of a metal foil or a metal-coated plastic film.
• the second reflector 102 also extends over the second narrow side 107, so that light rays that reach this narrow side are reflected back into the light guide plate 20.
• the light beams generated by the light source 10 are coupled into the light guide plate 20 through the first narrow side 16 and through the trapezoidal or rectangular extensions 12 arranged on the side surface 14 uncoupled.
• the decoupled light beams are deflected and collimated in the direction of the liquid crystal cell 104 by the sawtooth foil 80.
• the first of the two polarizers 106 polarizes the light incident on the liquid crystal cell acting as a display and, depending on the electrical control of the individual pixels by the liquid crystal between the two transparent substrates 105, influences or does not affect its polarization property. Depending on this influence, the light beams are either absorbed by the second of the two polarizers 106 or can leave the liquid crystal cell 104.
• the liquid crystal cell 104 thus creates an image impression for an observer.
• a fixed display e.g. a plastic plate with an unchangeable print
• an image impression is created by varying the light transmission.
• Such use is e.g. at a
• an additional prism film 110 is arranged between the light source 10 and the light guide plate 20, a section of which is shown.
• Microprisms run on a surface of the prism film 110 facing the light guide plate parallel to the light source 10 and point with their refracting edge in the direction of the light guide plate 20.
• the light of the light source 10 is collimated by the prism film 110, so that the

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• General Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Planar Illumination Modules (AREA)

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Citations (5)

• 1999
  • 1999-04-03 DE DE1999115209 patent/DE19915209A1/de not_active Withdrawn
• 2000
  • 2000-03-29 WO PCT/DE2000/000961 patent/WO2000060278A1/de active Application Filing

Patent Citations (5)

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