High output flat-panel display back light module

• US 6,341,879 B1
• Filed: 09/28/1999
• Issued: 01/29/2002
• Est. Priority Date: 09/28/1999
• Status: Expired due to Fees

• Current Assignee: Performance Display Systems, Inc., TransPacific Exchange, LLC
• Original Assignee: Rainbow Displays, Inc.
• Inventors: Guzowski, Lawrence T., Skinner, Dean W.
• Primary Examiner(s): CARIASO, ALAN B
• Application Number:
  US09/407,620
• Time in Patent Office: 854 Days
• Field of Search: 362/216, 362/222, 362/225, 362/247, 362/251, 362/260, 362/295, 362/394, 362/395, 362/411, 362/294, 362/218, 362/273, 362/242-246, 349/67, 349/70
• US Class Current: 362/295
• CPC Class Codes: F21S 8/00 Lighting devices intended for fixed installation F21S9/00, F21S10/00 take precedence; using a string or strip of light sources F21S4/00
• CPC Class Codes: F21V 29/74 with fins or blades
• CPC Class Codes: F21V 29/76 with essentially identical parallel planar fins or blades, e.g. with comb-like cross-section
• CPC Class Codes: F21V 29/83 the elements having apertures, ducts or channels, e.g. heat radiation holes
• CPC Class Codes: F21V 7/28 characterised by coatings
• CPC Class Codes: F21Y 2103/00 Elongate light sources, e.g. fluorescent tubes
• CPC Class Codes: G02F 1/13336 Combining plural substrates to produce large-area displays, e.g. tiled displays
• CPC Class Codes: G02F 1/133512 Light shielding layers, e.g. black matrix G02F1/136209 takes precedence
• CPC Class Codes: G02F 1/133524 Light-guides, e.g. fibre-optic bundles, louvered or jalousie light-guides
• CPC Class Codes: G02F 1/133604 with lamps
• CPC Class Codes: G02F 1/133605 including specially adapted reflectors
• CPC Class Codes: G02F 1/133613 characterized by the sequence of light sources
• CPC Class Codes: G02F 1/133628 with cooling means
• CPC Class Codes: G02F 2201/36 Airflow channels, e.g. constructional arrangements facilitating the flow of air
• CPC Class Codes: H05B 41/40 discontinuously

Abstract

The present invention features a system for uniformly distributing luminance and a high degree of collimation from a back light module for a flat-panel, liquid crystal display (LCD). A constant and uniform luminance output of the back light module is obtained through appropriate selection of lamps, geometry and optical components. An appropriate balance of lamps, lamp spacing, reflective light back plane, and diffuser and collimating optics are chosen to produce a high brightness back light module with very high intensity output over very large surfaces. Variations in intensity over the illuminated area are minimized using light recycling in conjunction with the collimating optics. Optimum geometries are determined for the purpose of maximizing light output at high efficiencies, while minimizing luminance gradients across the display. Finally, a precise collimator eliminates light beyond a defined angle, as required in a tiled, flat-panel LCD.

Claims

1. A high-output back light module for use with a tiled, flat-panel display having visually imperceptible seams, comprising:

a) a housing defining a lamp cavity having optically-reflective interior side surfaces, a highly optically reflective, substantially planar rear surface and an open, front light-emitting surface defining an illuminated area;

b) an array of fluorescent lamps disposed horizontally within said cavity; and

c) lamp control means comprising an electronic ballast circuit operatively connected to said array of lamps to selectively provide power thereto;

whereby said power is selectively provided to said lamp array so as to maximize light output therefrom.

2. The high-output back light module for use with a tiled, flat-panel display having visually imperceptible seams as recited in claim 1, further comprising a highly reflective rear surface that further comprises:

d) a back plane having a highly spectrally reflective coating thereupon;

e) a layer of textured, diffusing, reflective paint disposed upon said highly spectrally reflective coating; and

f) a layer of Teflon®

material impregnated with titanium dioxide and having a thickness chosen to maximize reflectivity of said Teflon®

layer, disposed over said layer of textured, reflective paint.

3. The high-output back light module for use with a tiled, flat-panel display having visually imperceptible seams as recited in claim 2, wherein said array of fluorescent lamps is located at a predetermined, optimized distance from said reflective rear surface.

4. The high-output back light module for use with a tiled, flat-panel display having visually imperceptible seams as recited in claim 3, wherein said array of fluorescent lamps comprises a predetermined number of fluorescent lamps of a predetermined type, each having a lamp diameter, chosen to maximize the light output of said back light module and to establish substantially full efficacy in said lamp cavity.

5. The high-output back light module for use with a tiled, flat-panel display having visually imperceptible seams as recited in claim 4, wherein said fluorescent lamps are spaced apart from one from another at a predetermined, inter-lamp spacing;

said array of lamps being located a predetermined, optimized distance from said back plane, said distance being functionally related to at least one of the parameters;

said lamp diameter, said lamp type and said inter-lamp spacing.

6. The high-output back light module for use with a tiled, flat-panel display having visually imperceptible seams as recited in claim 5, wherein said inter-lamp spacing between each lamp of said array of fluorescent lamps is substantially equal.

7. The high-output back light module for use with a tiled, flat-panel display having visually imperceptible seams as recited in claim 5, further comprising a high-transmittance exit diffuser placed proximate said open, front light-emitting surface.

8. The high-output back light module for use with a tiled, flat-panel display having visually imperceptible seams as recited in claim 7, wherein said high-transmittance exit diffuser produces a substantially Lambertian distribution.

9. The high-output back light module for use with a tiled, flat-panel display having visually imperceptible seams as recited in claim 7, further comprising light collimating means placed proximate said open, front light-emitting surface and said exit diffuser, whereby the light output of said back light module is maximized while reducing luminance gradients across said illuminated area below a predetermined value.

10. The high-output back light module for use with a tiled, flat-panel display having visually imperceptible seams as recited in claim 9, further comprising brightness-enhancing means disposed proximate said light collimating means.

11. The high-output back light module for use with a tiled, flat-panel display having visually imperceptible seams as recited in claim 10, wherein said brightness-enhancing means comprises two brightness-enhancing films (BEFs), each having an operational orientation, said BEFs being arranged such that their respective operational orientations are in an orthogonal relationship to one another.

12. The high-output back light module for use with a tiled, flat-panel display having visually imperceptible seams as recited in claim 9, wherein said collimating means comprises an array of open cells having a regular, repeating cell geometry and a thickness defining a cell depth.

13. The high-output back light module for use with a tiled, flat-panel display having visually imperceptible seams as recited in claim 12, wherein said cell geometry and said thickness define a cell width and a cell depth.

14. The high-output back light module for use with a tiled, flat-panel display having visually imperceptible seams as recited in claim 13, wherein said cell width and said cell depth have an aspect ratio therebetween, said aspect ratio defining a cut-off angle.

15. The high-output back light module for use with a tiled, flat-panel display having visually imperceptible seams as recited in claim 13, wherein said cell width and said cell depth define cell walls.

16. The high-output back light module for use with a tiled, flat-panel display having visually imperceptible seams as recited in claim 13, wherein said cell walls are coated with a light-absorbing coating.

17. The high-output back light module for use with a tiled, flat-panel display having visually imperceptible seams as recited in claim 16, wherein said light-absorbing coating comprises flat, black paint.

18. The high-output back light module for use with a tiled, flat-panel display having visually imperceptible seams as recited in claim 1, wherein said lamp control means comprises lamp temperature regulation means whereby the surface temperature of each of said lamps of said array of fluorescent lamps is maintained substantially within a predetermined range of operating temperatures.

19. The high-output back light module for use with a tiled, flat-panel display having visually imperceptible seams as recited in claim 18, wherein said lamp temperature regulation means comprises at least one from the group:

heat sinks, dimming controls and louvers.