Backlighting device for an information display element of a portable object

• US 7,223,008 B2
• Filed: 06/17/2004
• Issued: 05/29/2007
• Est. Priority Date: 02/20/2004
• Status: Expired due to Term

• Current Assignee: ETA SA Manufacture Horlogere Suisse (The Swatch Group AG)
• Original Assignee: ETA SA Manufacture Horlogere Suisse (The Swatch Group AG)
• Inventors: Henriet, Fabien, Klopfenstein, Franc
• Primary Examiner(s): Luebke; Renee
• Assistant Examiner(s): MAY, ROBERT J
• Application Number:
  US10/869,065
• Publication Number:
  US 20050185389A1
• Time in Patent Office: 1,076 Days
• Field of Search: 362/26, 362606-608, 362/610, 362/612, 362617-619, 362622-624, 362/627, 362/600, 362/602
• US Class Current: 362/617
• CPC Class Codes: G02B 6/0018 Redirecting means on the surface of the light guide
• CPC Class Codes: G02B 6/0051 Diffusing sheet or layer
• CPC Class Codes: G02B 6/0061 to provide homogeneous light output intensity
• CPC Class Codes: G02F 1/133615 Edge-illuminating devices, i.e. illuminating from the side

Abstract

The backlighting device (1) enables an information display element of a portable object such as a wristwatch to be illuminated from the back. This device comprises a light guide plate (7) having a front face and a rear face, a light reflector (6) located on the rear face of the light guide plate, a light diffuser film (9) and a rectifier film (11) located on the front face of the light guide plate and a source of visible light (2). This light source, such as a light emitting diode (2), feeds light beams to the edge of the light guide plate, which spread in the light guide plate between its two faces. A layer, such as a diffuser film, has a zone (10′) with opacity decreasing from a limit (25) located close to the boundary area of the light guide plate, which receives the light beams of the light source, in order to attenuate the intensity of the light crossing said zone. This zone with decreasing opacity is, for example, a shading white or black dye disposed on the diffuser film.

Claims

1. A backlighting device for an information display element of a wristwatch, said device comprising a light guide plate having a front face and a rear face, a light reflector located on the rear face of the light guide plate, and a single source of visible light, which is a light emitting diode for feeding light beams to a boundary or edge of the light guide plate, which spread in the light guide plate and between said rear and front faces,

wherein the device comprises a layer located above the front face of the light guide plate between the front face of said light guide plate and a rear face of the display element of the portable object, said layer having at least one zone with partial opacity decreasing from a limit located close to a boundary area of the light guide plate, which receives the light beams of the light emitting diode located below and close to a visible portion of the display element, in order to attenuate the intensity of a light halo crossing said zone, which is caused by the light source, and

wherein the light guide plate has on a periphery thereof a rounded corner covered by a light-reflecting layer, said light emitting diode being disposed below the rounded corner in order to feed the light beams in a vertical direction in relation to the rear face of the light guide plate so that said beams are reflected by the reflecting layer at the edge of the light guide plate and spread into the light guide plate between the front and rear faces.

2. The backlighting device according to claim 1, wherein said one zone with partial opacity decreasing non-linearly from the limit close to the edge of the light guide plate is obtained by a dye applied to or integrated into the layer, or by a semi-transparent metal covering of variable thickness, or by a metal covering pierced by a plurality of holes of varying diameter and spacing, which are smaller in size than a human eye'"'"'s resolution, or by a metal covering formed from a plurality of metal dots of varying diameter and spacing.

3. The backlighting device according to claim 2, wherein the layer with the partially opaque zone forms an integral part of the front face of the light guide plate or of a polarising film of the display element.

4. The backlighting device according to claim 2, wherein the layer with the partially opaque zone is a light diffuser film or a light rectifier film located on the front face of the light guide plate.

5. The backlighting device according to claim 2, wherein the zone with decreasing partial opacity is obtained by a shading dye of black or white or silver, which extends from the limit, which corresponds to a boundary line of the visible portion of the display element, to a distance determined in relation to the position of the light emitting diode.

6. The backlighting device according to claim 1, wherein it comprises a crosspiece forming a frame, in which the reflector, the light guide plate and a diffuser are held, and wherein a compartment is cut into the periphery of the crosspiece to house the light emitting diode, fixed on a printed circuit board, the crosspiece being detachably mounted and positioned by fitting means on the printed circuit board.

7. The backlighting device according to claim 1, wherein the light guide plate, the reflector and the partially opaque zone form a single element.

8. The backlighting device according to claim 1, wherein said display element is a liquid crystal device.

11. The backlighting device according to claim 1, wherein the light guide plate has, on a periphery thereof, the rounded corner covered by the light reflecting layer and a lens arrangement of nanometre size on a section of the front or the rear face.

12. The backlighting device according to claim 11 wherein a portion of the diffuser film is located on the rounded corner, wherein the portion of the diffuser film is covered with a completely opaque black layer, which extends as far as the limit of the start of the zone with decreasing opacity, and wherein the rounded corner is covered with an opaque white layer or with a metal covering.

9. A backlighting device for an information display element of a potable object, said device comprising a light guide plate having a front face and a rear face, a light reflector located on the rear face of the light guide plate, and a source of visable light feeding light beams to a boundary or edge of the light guide plate, which spread n the light guide plate and between said rear and front faces, wherein the device comprises a layer located above the front face of the light guide plate between the front face of said light guide plate and a rear face of the display element of the portable object, said layer having at least one zone with partial opacity decreasing from a limit located close to a boundary area of the light guide plate, which receives the light beams of the light source located below and close to a visible portion of the display element, in order to attenuate the intensity of a light halo crossing said zone, which is caused by the light source,

wherein the device further comprises a crosspiece forming a frame, in which the reflector, the light guide plate and a diffuser are held, wherein a compartment is cut into the periphery of the crosspiece to house the light source, fixed on a printed circuit board, the crosspiece being detachably mounted and positioned by fitting means on the printed circuit board, and

wherein the crosspiece comprises two flexible fingers disposed on side faces of a first inside shoulder to hold the reflector and the light guide plate inserted between a support face of the first shoulder and each flexible finger.

10. The backlighting device according to claim 9, wherein above the flexible fingers, the crosspiece comprises a second inside shoulder to receive a flexible diffuser film, which is held by means of a tab inserted into a housing cut into a side face of the second shoulder of the crosspiece, and wherein a flexible transparent light rectifying film is located on the diffuser film and held by another tab in the housing of the second shoulder.

13. A backlighting device for an information display element of a portable object, said device comprising a light guide plate having a front face and a rear face, a light reflector located on the rear face of the light guide plate, and a source of visable light feeding light beams to a boundary or edge of the light guide plate, which spread in the light guide plate and between said rear and front faces, wherein the device comprises a layer located above the front face of the light guide plate between the front face of said light guide plate and a rear face of the display element of the portable object, said layer having at least one zone with partial opacity decreasing from a limit located close to a boundary area of the light guide plate, which receives the light beams of the light source located below and close to a visible portion of the display element, in order to attenuate the intensity of a light halo crossing said zone, which is caused by the light source, said light source being a light-emitting diode.

wherein the device further comprises a crosspiece forming a frame, in which the reflector, the light guide plate and a diffuser are held, and wherein a compartment is cut into the periphery of the crosspiece to house the light source, fixed on a printed circuit board, the crosspiece being detachably mounted and positioned by fitting means on the printed circuit board,

wherein the light emitting diode is housed in the compartment of the crosspiece comprising side walls, which partially or completely surround said diode from an upper surface of the printed circuit board, and wherein an edge of the reflector comes to lie flush with an upper edge of the compartment.

14. The backlighting device according to claim 13, wherein a joint of silicon material joins the upper portion of the light emitting diode to a lower surface of a rounded corner of the printed circuit board, said joint having an intermediate refractive index between the refractive index of the transparent material of the light emitting diode and the refractive index of the light guide plate.

15. A backlighting device for an information display element of a portable object, said device comprising a light guide plate having a front face and a rear face, a light reflector located on the rear face of the light guide plate, and a source of visible light feeding light beams to a boundary or edge of the light guide plate, which spread in the light guide plate between said rear and front faces, wherein the device comprises a layer located between the front face of the light guide plate and a rear face of the display element of the portable object, said layer having at least one zone with partial opacity decreasing from a limit located close to the boundary area of the light guide plate, which receives the light beams of the light source, in order to attenuate the intensity of the light crossing said zone, wherein the light guide plate has on a periphery thereof a rounded corner covered by a light-reflecting layer and a lens arrangement of nanometre size on a section of its front or rear face, and wherein the light source is disposed below the rounded corner in order to feed the light beams in a vertical direction so that said beams are reflected by the reflecting layer at the edge of the light guide plate and spread into the light guide plate between the front and rear faces.

16. A backlighting device for an information display element of a portable object, said device comprising a light guide plate having a front face and a rear face, a light reflector located on the rear face of the light guide plate, and a source of visible light feeding light beams to a boundary or edge of the light guide plate, which spread in the light guide plate between said rear and front faces, wherein the device comprises a layer located above the front face of the light guide plate between the front face of said light guide plate and a rear face of the display element of the portable object, said layer having at least one zone with partial opacity decreasing from a limit located close to a boundary area of the light guide plate, which receives the light beams of the light source, in order to attenuate the intensity of the light crossing said zone, wherein it comprises a crosspiece forming a frame, in which the reflector, the light guide plate and a diffuser are held, and wherein a compartment is cut into a periphery of the crosspiece to house the light source, fixed on a printed circuit board, the crosspiece being detachably mounted and positioned by fitting means on the printed circuit board, and wherein the crosspiece comprises two flexible fingers disposed on side faces of a first inside shoulder to hold the reflector and the light guide plate inserted between a support face of the first shoulder and each flexible finger.

17. A backlighting device for an information display element of a portable object, said device comprising a light guide plate having a front face and a rear face, a light reflector located on the rear face of the light guide plate, and a source of visible light feeding light beams to a boundary or edge of the light guide plate, which spread in the light guide plate and between said rear and front faces,

wherein the device comprises a layer located above the front face of the light guide plate between the front face of said light guide plate and a rear face of the display element of the portable object, said layer having at least one zone with partial opacity decreasing from a limit located close to a boundary area of the light guide plate, which receives the light beams of the light source located below and close to a visible portion of the display element, in order to attenuate the intensity of a light halo crossing said zone, which is caused by the light source;

wherein the light guide plate has on a periphery thereof a rounded corner covered by a light-reflecting layer and a lens arrangement of nanometre size on a section of a front or rear face, and wherein the light source, is disposed below the rounded corner in order to feed the light beams in a vertical direction so that said beams are reflected by the reflecting layer at the edge of the light guide plate and spread into the light guide plate between the front and rear faces.