Light guides suitable for illuminated displays

• US 20030223217A1
• Filed: 09/12/2002
• Published: 12/04/2003
• Est. Priority Date: 03/16/2000
• Status: Active Grant

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Wright, John C., Hicks, Andrew M., Mueller, Bruno
• Granted Patent: US 6,893,135 B2
• Time in Patent Office: Days
• US Class Current: 362/31
• CPC Class Codes: G02B 6/004 Scattering dots or dot-like elements, e.g. microbeads, scattering particles, nanoparticles
• CPC Class Codes: G02B 6/005 provided by one optical element, or plurality thereof, placed on the light output side of the light guide
• CPC Class Codes: G02B 6/0053 Prismatic sheet or layer; Brightness enhancement element, sheet or layer
• CPC Class Codes: G02B 6/0055 Reflecting element, sheet or layer
• CPC Class Codes: G02B 6/0071 with elongated shape, e.g. tube

Abstract

A light guide (1) comprises a housing (3) defining a light-guiding optical cavity having first and second opposed major faces (5, 6), and a light source (11) arranged to direct light into the cavity from one end, to be guided between the major faces. The first major face (5) comprises a window through which light can be emitted from the optical cavity to be used, for example, for illuminating a graphic display. To improve the light distribution across that first major face (5), the second major face (6) comprises a sheet material (23) having a specularly-reflecting surface (24) that faces into the optical cavity and has diffusely-reflecting light-extraction elements (27) applied thereto in a predetermined configuration for causing light to be emitted from the optical cavity through the said window.

Claims

1. A light guide comprising a housing defining a light-guiding optical cavity having first and second opposed major faces, and at least one light source arranged to direct light into the cavity from one end, to be guided between the major faces;

wherein the first major face comprises a window through which light can be emitted from the optical cavity, and the second major face comprises a sheet material having a specularly-reflecting surface that faces into the cavity and has diffusely-reflecting light-extraction elements applied thereto in a predetermined configuration for causing light to be emitted from the optical cavity through the said window.

2. A light guide as claimed in claim 1, in which the specularly-reflective surface has a reflectivity of at least 90% for light incident on the surface at any angle.

3. A light guide as claimed in claim 1 or claim 2, in which the sheet material having the specularly-reflecting surface is laminated to an internal surface of the housing

4. A light guide as claimed in any one of the preceding claims, in which the light-extraction elements are printed elements formed in a diffusely-reflecting material.

5. A light guide as claimed in claim 4, in which the light-extraction elements are printed directly on the specularly-reflecting surface.

6. A light guide as claimed in any one of the preceding claims, in which the percentage area of the specularly-reflecting surface that is covered by light extracting-elements is not constant over the whole area second major face.

7. A light guide as claimed in claim 6, in which, in any region of the second major surface, the percentage area of the specularly-reflecting surface that is covered by light extracting-elements varies with the distance of that region from the light source.

8. A light guide as claimed in any one of the preceding claims, including a second light source arranged to direct light into the cavity from the end opposite the first-mentioned light source, to be guided between the major faces.

9. A light guide as claimed in any one of the preceding claims, in which the first major face has a structured surface comprising a plurality of parallel prisms on the side remote from the optical cavity.

10. A light guide as claimed in any one of the preceding claims, in which a display that is to be illuminated is positioned in front of the window.

11. A light guide as claimed in claim 10, in which at least some of the diffusely-reflecting light-extraction elements are applied to the specularly-reflecting surface in a configuration that is related to the display.

12. A light guide as claimed in claim 10, including diffusely-reflecting light-extraction elements applied to the window, on the side facing into the optical cavity, in a configuration that is related to the display.

13. A light guide substantially as described herein with reference to, and as illustrated by, FIGS. 1 to 5;

or FIGS. 6 to 8;

or FIGS. 1 to 5, as modified by FIG. 9;

or FIGS. 6 to 8 as modified by FIG. 9, of the accompanying drawings.