LCD display with microtextured back reflector and method for making same

• US 5,245,454 A
• Filed: 12/31/1991
• Issued: 09/14/1993
• Est. Priority Date: 12/31/1991
• Status: Expired due to Term

• Current Assignee: American Telephone & Telegraph Company (AT&T, Inc.)
• Original Assignee: AT&T, Inc.
• Inventors: Blonder, Greg E.
• Primary Examiner(s): Arnold, Bruce Y.
• Assistant Examiner(s): RYAN, JAY
• Application Number:
  US07/816,405
• Time in Patent Office: 623 Days
• Field of Search: 359/70, 359/530, 359/546, 359/850, 359/851, 359/627
• US Class Current: 349/113
• CPC Class Codes: G02F 1/133553 Reflecting elements associated to illuminating devices G02F1/133605
• CPC Class Codes: Y10S 359/90 Methods

Abstract

Applicant has discovered a method for microembossing reflector surfaces with controlled reflecting patterns too small to be resolved by the unaided eye but capable of providing controlled reflection characteristics superior to uncontrolled random deformation. The result is a microtextured reflector of having dispersion characteristics of enhanced uniformity and a display device which can be read over an enhanced range of viewing angles. Specifically, a reflector in accordance with the invention comprises a base plane and a pattern of microelements having maximum lateral dimensions less than 125 micrometers and smooth, continuous mold-formed surfaces arising from the base plane. Such a reflector surface can be made using a master formed by covering a substrate with photoresist, exposing the resist to define a pattern of microelements having maximum lateral dimensions less than about 125 micrometers and heating the substrate to partially melt the resist elements thereby obtaining smooth-surfaced microelements. The master can be used to form an embossing surface or mold, which, in turn, can be used to make a microtextured reflecting surfaces. A preferred reflecting surface is composed of closely packed, smooth-surfaced spherical segments having diameters of twenty-five microns, altitudes of four microns. Advantageously random segments are disposed between successive spherical segments. The preferred reflector possesses reflecting characteristics superior to conventional isotropic reflectors.

Claims

1. A transparent display device comprising:

a transparent display cell having front and back sides,

a back reflector disposed adjacent the back side of said cell, said back reflector having a microtextured reflecting surface comprising a base plane and a pattern of spherical segment reflecting surfaces having maximum lateral dimensions less than 125 micrometers and smooth, continuous mold-formed surfaces rising from said base plane.

2. The display device of claim 1 wherein said pattern of microelements comprises a plurality of spherical segment reflecting surfaces having bases in the range 10-125 micrometers in diameter.

3. The display device of claim 2 further comprising segments of irregular base having smooth, continuous reflecting surfaces disposed between successive spherical segments.

4. The display device of claim 2, wherein the altitudes of said spherical segments are 10 to 20% of their diameters.

5. The display device of claim 2, wherein the combined areas of the spherical bases comprise 50 to 90% of the area of said reflector.

6. The display device of claim 2, wherein said spherical segments are disposed in a hexagonal array.

7. A microtextured reflecting layer comprising:

a layer of material having a surface comprising a plurality of reflecting spherical segments having smooth, continuous mold-formed surfaces and bases in the range 10-125 micrometers in diameter.

8. The reflecting layer of claim 7 further comprising segments of irregular base having smooth, continuous surfaces disposed between successive spherical segments.

9. The reflecting layer of claim 7, wherein the altitudes of said spherical segments are 10% to 20% of the diameters.

10. The reflecting layer of claim 7, wherein the combined areas of the spherical segment bases comprise 50 to 90% of the area of said reflecting element.

11. The reflecting layer of claim 7, wherein said material is transparent.