Edge-lit transflective non-emissive display with angled interface means on both sides of light conducting panel

• US 5,339,179 A
• Filed: 10/01/1992
• Issued: 08/16/1994
• Est. Priority Date: 10/01/1992
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Whittle, Daniel J., Rudisill, Charles A.
• Primary Examiner(s): Gross, Anita P.
• Application Number:
  US07/955,524
• Time in Patent Office: 684 Days
• Field of Search: 359/48, 359/49, 385/129, 385/146, 385/901, 362/31, 362/26, 362/297
• US Class Current: 349/65
• CPC Class Codes: F21V 7/00 Reflectors for light sources characterised by cooling arrangements F21V29/505
• CPC Class Codes: G02B 6/0038 Linear indentations or grooves, e.g. arc-shaped grooves or meandering grooves, extending over the full length or width of the light guide
• CPC Class Codes: G02B 6/0055 Reflecting element, 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
• CPC Class Codes: Y10S 385/901 Illuminating or display apparatus

Abstract

A transflective liquid crystal display (LCD) uses the reflective and refractive characteristics of an edge-lit flat light pipe as a backlight panel behind the liquid crystal layer. The front and/or back surfaces of the edge-lit backlight panel are textured to enhance reflectivity of ambient light and transmission of edge light. The front surface of the panel is textured with pits that have walls at an angle to enhance reflectivity over a range of viewing angles. Further, the back surface of the panel is textured with pits having wall angles, and a pattern to enhance the uniform reflection of edge light toward and through the front surface of the backlight panel. The indentations may be conical, triangular or random. The pit wall angles lie within a preferred range of angles to optimize the amount of light within the useable viewing angle for the LCD. Alternative embodiments include backlight panel where only the front surface has indentations and the back surface is flat and mirrored, or where only the back surface of the panel has indentations and the front surface is flat.

Claims

1. A transflective non-emissive display apparatus for generating a display with ambient light from in front of the display and with artificial light from within the display, said apparatus comprising:

a non-emissive light means for selectively passing light whereby the display appears light or dark to a viewer in front of the display depending on whether light is passed, or not passed, by said light means;

artificial light means behind said non-emissive light means, said artificial light means for generating light for selective passage through the non-emissive light means;

a backlight means behind said non-emissive light means and responsive to ambient light and to said artificial light means, said backlight means for reflecting ambient light that has passed through said non-emissive light means from the front of the display towards the non-emissive light means, and said backlight means for reflecting and refracting light from said artificial light means towards the non-emissive light means,

said backlight means having front and back walls; and

interface means in at least one of said front and back walls, said interface means being positioned at an angle relative to incident ambient light and artificial light for reflecting and refracting ambient light and artificial light towards said non-emissive light means at a useable viewing angle for the viewer,

wherein said interface means comprises

a first light interface means in said front wall positioned at an angle for reflecting the ambient light at a useable viewing angle towards said non-emissive light means; and

a second light interface means in the back wall positioned at an angle for reflecting artificial light out the front wall and toward said non-emissive light means.

2. The apparatus of claim 1 wherein:

said second light interface means is in portions of the back wall and

the remaining portions of the back wall reflect ambient light refracted by said front wall back towards said non-emissive light means.

3. The apparatus of claim 1 wherein said non-emissive light means comprises:

liquid crystal means for rotating polarized light when in a first state and not rotating polarized light when in a second state;

a first polarizing means in front of said crystal means for linearly polarizing light; and

a second polarizing means behind said crystal means for linearly polarizing light, said first and second polarizing means oriented relative to each other whereby light is passed by said non-emissive means when said crystal means is in the one of the first or second state and light is not passed by said non-emissive means when said crystal means is in the other state.

4. A transflective non-emissive display apparatus comprising:

a non-emissive light means for controlling the passage of light whereby portions of said display appear light or dark to a viewer in front of the display depending on whether light is passed or not passed by corresponding portions of said light means;

a light conducting panel behind said non-emissive light means, said light conducting panel having front, back and side walls, said front and back walls oriented for reflecting ambient light that has passed through said light means;

an edge light source for introducing light in one of the side walls of said light conducting panel;

at least one of said front and back walls having surface indentations in the wall;

a plurality of said indentations having indentation wall angles oriented relative to incident ambient light to refract and reflect the ambient light towards said non-emissive light means at a useable viewing angle for the viewer; and

a plurality of said indentations having indentation wall angles oriented relative to incident edge light to refract and reflect the edge light towards said non-emissive light means at a useable viewing angle,

wherein said indentations comprise;

indentations in said front wall having wall angles for reflecting the ambient light that passed through said non-emissive light means back through said non-emissive light means at a useable viewing angle and for reflecting edge light inside the light conducting panel towards the back wall;

indentations in the back wall having wall angles for reflecting ambient light, refracted through the front wall, and edge light out the front wall and toward said non-emissive light means.

5. The apparatus of claim 4 wherein:

said front wall indentations are distributed uniformly through out the surface of the front wall; and

said back wall indentations are distributed such that the areal density of the indentations in the back wall increases as a function of the distance from the side wall through which the edge light is introduced.

6. The apparatus of claim 5 wherein:

said front wall indentations are conical; and

said back wall indentations are triangular in cross-sectional shape with one wall facing the edge-lit side wall.

7. The apparatus of claim 6 wherein:

pluralities of said back wall indentations have edge light facing walls oriented at one of a plurality of angles, said one angle being one of approximately 15°

, 30°

, or 45°

relative to the back wall.

8. The apparatus of claim 4 wherein said front wall indentations are conical.

9. The apparatus of claim 4 wherein:

pluralities of said front wall indentations primarily have walls oriented at one or more of a plurality of angles relative to a line normal to the front wall surface, the plurality of wall angles being between 15° and

60°

.

10. The apparatus of claim 4 wherein:

said front wall indentations are distributed such that the areal density of the indentations in the front wall increases as a function of the distance from the side wall through which the edge light is introduced.

11. The apparatus of claim 4 wherein:

pluralities of said back wall indentations have edge light facing walls oriented at one of a plurality of angles, said one angle being one of approximately 15°

, 30° and

45°

relative to the back wall.

12. The apparatus of claim 11 wherein:

said back wall indentations are distributed such that the areal density of the indentations in the back wall increases as a function of the distance from the side wall through which the edge light is introduced.

13. A transflective non-emissive display apparatus comprising:

liquid crystal layer for rotating polarized light when in a first state and not rotating polarized light when in a second state;

a first polarizer in front of said crystal layer for linearly polarizing light;

a second polarizer behind said crystal layer for linearly polarizing light, said first and second polarizers oriented relative to each other whereby light is passed by said polarizers when said crystal layer is in one of the first or second states and light is not passed by said polarizers when said crystal layer is in the other state;

a light conducting panel behind said liquid crystal layer, said light conducting panel having front, back and side walls, said front and back walls oriented for reflecting ambient light that has passed through said layer;

an edge light source for introducing light in one of the side walls of said light conducting panel;

said front and back walls having surface indentations in the wall;

indentations in said front wall having wall angles for reflecting the ambient light that passed through said liquid crystal layer back through said layer at a useable viewing angle and for reflecting edge light inside the light panel towards the back wall; and

indentations in the back wall having wall angles for reflecting ambient light, refracted through the front wall, and edge light toward said liquid crystal layer.

14. The apparatus of claim 13 wherein:

said front wall indentations are distributed uniformly through out the surface of the front wall; and

said back wall indentations are distributed such that the areal density of the indentations in the back wall increases as a function of the distance from the side wall through which the edge light is introduced.

15. The apparatus of claim 14 wherein:

pluralities of said front wall indentations primarily have walls oriented at one or more of a plurality of angles relative to a line normal to the front wall surface, the plurality of wall angles being between 15° and

60°

.