§
Luxuse
Patent Intelligence
Sign In
← Back to Patent Explorer
US3860424A Expired / Lapsed US ⏱️ 0.0 years remaining

Led display

Assignee: AT&T Inc
•
Filing: 1973-10-18
•
Granted: 1975-01-14
•
Expires: 1993-10-18
📄 Original PDF 🌐 Google Patents 🔄 Sync Now

Abstract

Abstract LED displays with integrated logic are typically formed by bonding the LED devices and often the logic chips to large alumina or other ceramic substrates, lead frame substrates or other substrates. Typically the arrangement has a large area of uncovered substrate due to the large display area compared with the smaller chip size. Reflection of bright light from the substrate detracts from the contrast of the display. It has been found that photoresist materials conventionally in use turn black when heated to temperatures in excess of those recommended for post-baking (e.g., > 200* C). It is convenient to cover the inactive portion of the substrate with a patterned layer of photoresist (leaving windows for chip and circuit bonding) and then, through a heat treatment, which may already exist in the IC process, to blacken the photoresist layer. The photoresist layer forms a part of the finished device. Adhesion of the photoresist is surprisingly tenacious.

Inventors

  • 👤 Bertrand Harold Johnson

Bibliographic Details

Application Number —
Jurisdiction US
Data Source google_patents
Last Synchronized 2026-10-26 12:29
CPC Classifications
H; H05; H05B; H05B33/00; H05B33/12; H05B33/26; H05B33/22

Claims Analysis

Total Claims: 11
Claim 1
Independent Claim 100 words
A METHOD FOR ENHANCING THE CONTRAST OF AN ELECTROLUMINESCENT DISPLAY DEVICE IN WHICH LIGHT-EMITTING DEVICES ARE AFFIXED TO PORTIONS OF A SUBSTRATE AND IN WHICH OTHER PORTIONS OF THE SUBSTRATE NOT COVERED WITH LIGHT-EMITTING DEVICES ARE REFLECTIVE AND TEND TO REDUCE THE CONTRAST OF THE LIGHT-EMITTING REGIONS WITH RESPECT TO THE BACKGROUND OF THE DISPLAY, THE METHOD CHARACTERIZED BY PHOTOLITHOGRAPHICALLY APPLYING SELECTIVELY TO THE LIGHT-REFLECTING PORTIONS A PHOTORESIST, AND BAKING THE PHOTORESIST AT A TEMPERATURE SUFFICIENT TO DARKEN THE PHOTORESIST SIGNIFICANTLY AND CAUSE IT TO ADHERE PERMANENTLY TO THOSE PORTIONS SO AS TO REMAIN A PART OF THE FINISHED DEVICE.
Claim 2
Independent Claim 100 words
A METHOD FOR ENHANCING THE CONTRAST OF AN ELECTROLUMINESCENT DISPLAY DEVICE IN WHICH LIGHT-EMITTING DEVICES ARE AFFIXED TO PORTIONS OF A SUBSTRATE AND IN WHICH OTHER PORTIONS OF THE SUBSTRATE NOT COVERED WITH LIGHT-EMITTING DEVICES ARE REFLECTIVE AND TEND TO REDUCE THE CONTRAST OF THE LIGHT-EMITTING REGIONS WITH RESPECT TO THE BACKGROUND OF THE DISPLAY, THE METHOD CHARACTERIZED BY PHOTOLITHOGRAPHICALLY APPLYING SELECTIVELY TO THE LIGHT-REFLECTING PORTIONS A PHOTORESIST, AND BAKING THE PHOTORESIST AT A TEMPERATURE SUFFICIENT TO DARKEN THE PHOTORESIST SIGNIFICANTLY AND CAUSE IT TO ADHERE PERMANENTLY TO THOSE PORTIONS SO AS TO REMAIN A PART OF THE FINISHED DEVICE.
Claim 3
Dependent Claim 24 words
The method of claim 1 in which the reflecting portions over which the photoresist is applied include portions of a highly reflecting ceramic substrate.
Claim 4
Dependent Claim 23 words
The method of claim 1 in which the reflecting portions over which the photoresist is applied include conductor patterns of highly reflecting metallization.
Claim 5
Dependent Claim 16 words
The method of claim 1 in which the photoresist is baked at a temperature exceeding 200*C.
Claim 6
Dependent Claim 16 words
The method of claim 1 in which the photoresist is baked at a temperature exceeding 300*C.
Claim 7
Dependent Claim 15 words
The method of claim 1 in which the light-emitting devices are gallium compound semiconductor diodes.
Claim 8
Dependent Claim 22 words
The method of claim 1 in which the photoresist is applied with a thickness in the range of 0.1 to 10 microns.
Claim 9
Dependent Claim 42 words
The method of claim 1 in which at least parts of the light-emitting devices are affixed to the substrate by a bonding technique that uses a heat treatment step, and the photoresist is darkened as a result of this heat treatment step.
Claim 10
Dependent Claim 14 words
The method of claim 1 in which the substrate is a metal lead frame.
Claim 11
Dependent Claim 18 words
The method of claim 1 in which the photoresist is applied also to portions of the light-emitting devices.

References Cited (Backward Citations)

US3397334A Cited
US3758304A Cited
US3672925A Cited

USPTO Annuity & Maintenance Windows

Annuity Stage Window Opens Payment Deadline Surcharge Period Until Estimated Fee Status
3.5 Years (Year 4) 1978-01-13 1978-07-15 1979-01-14 $2000.00 Window Closed / Lapsed
7.5 Years (Year 8) 1982-01-13 1982-07-15 1983-01-14 $3760.00 Window Closed / Lapsed
11.5 Years (Year 12) 1986-01-13 1986-07-15 1987-01-14 $7700.00 Window Closed / Lapsed

Assigned Categories & Tags

No categories assigned to this patent yet.

Assign Category Tag