Black electrode TFEL display

• US 5,504,389 A
• Filed: 03/08/1994
• Issued: 04/02/1996
• Est. Priority Date: 03/08/1994
• Status: Expired due to Term

• Current Assignee: Beneq Oy (Qingdao Sifang SRI & Intellectual Co., Ltd.)
• Original Assignee: Planar Systems Incorporated (Leyard Optoelectronic Co., Ltd.)
• Inventors: Dickey, Eric R.
• Primary Examiner(s): O'Shea, Sandra L.
• Assistant Examiner(s): Patel, Ashok
• Application Number:
  US08/208,732
• Time in Patent Office: 756 Days
• Field of Search: 313/506, 313/509, 313/512, 313/505, 313/112, 315/169.3, 345/76, 345/36, 345/45, 428/917
• US Class Current: 313/506
• CPC Class Codes: H05B 33/10 Apparatus or processes specially adapted to the manufacture of electroluminescent light sources
• CPC Class Codes: H05B 33/22 characterised by the chemical or physical composition or the arrangement of auxiliary dielectric or reflective layers
• CPC Class Codes: H10K 50/822 characterised by their shape
• CPC Class Codes: H10K 50/854 comprising scattering means
• CPC Class Codes: H10K 50/856 comprising reflective means
• CPC Class Codes: H10K 50/865 comprising light absorbing layers, e.g. light-blocking layers
• CPC Class Codes: Y10S 428/917 Electroluminescent

Abstract

An electroluminescent display having a plurality of layers including at least a transparent electrode layer, a rear electrode layer, and at least three layers including an electroluminescent layer sandwiched between front and rear dielectric layers. All three layers thereof are disposed between the rear electrode layer and the transparent electrode layer wherein the transparent electrode layer is formed on a transparent substrate, so as to emit light upon the application of an electric field between the transparent electrode layer and the rear electrode layer. A thin-film absorption layer that absorbs a substantial percentage of light incident thereon is disposed between the rear electrode layer and the rear dielectric layer. The thin-film light absorption layer includes a first absorption portion having a complex refractive index that substantially matches the complex refractive index of the rear dielectric layer where they are adjacent and a second absorption portion having a complex refractive index that substantially matches the complex refractive index of the rear electrode layer where they are adjacent. In one embodiment the thin-film light absorption layer is a single layer having a complex refractive index which gradually changes. In an alternate embodiment the thin-film light absorption layer is composed of a plurality of discrete layers.

Claims

1. An electroluminescent device comprising:

(a) a plurality of layers including at least a transparent electrode layer, a rear electrode layer, and at least three layers including an electroluminescent layer sandwiched between front and rear dielectric layers, all three layers thereof disposed between said rear electrode layer and said transparent electrode layer so as to emit light upon the application of an electric field between said transparent electrode layer and said rear electrode layer; and

(b) a thin-film light absorption layer that absorbs a substantial percentage of light incident thereon and which is disposed between said rear electrode layer and said rear dielectric layer, said light having a wavelength, said thin-film light absorption layer comprising;

(i) a first absorption portion having a first complex refractive index at a side adjacent said rear dielectric layer, said rear dielectric layer having an initial complex refractive index that substantially matches said first complex refractive index at a side adjacent said first absorption portion; and

(ii) a second absorption portion having a second complex refractive index at a side adjacent said rear electrode layer, said rear electrode layer having a complex refractive index that substantially matches said second complex refractive index at a side adjacent said second absorption portion.

2. The electroluminescent device of claim 1 wherein said first absorption portion of said light absorption layer is transparent and said second absorption portion is substantially opaque.

3. The electroluminescent device of claim 1 wherein said first complex refractive index changes from said first absorption portion of said light absorption layer with a gradual gradient to said second complex refractive index at said second absorption portion of said light absorption layer.

4. The electroluminescent device of claim 1 wherein said first complex refractive index monotonically changes to said second complex refractive index and wherein:

(a) said thin-film light absorption layer is composed of a plurality of discrete layers that are thin relative to said light'"'"'s wavelength, wherein a first layer of said discrete layers is said first absorption portion and a last layer of said discrete layers is said second absorption portion; and

(b) said thin-film layer'"'"'s average optical thickness is at least large enough to be on the order of said light'"'"'s wavelength.

5. The electroluminescent device of claim 1 wherein:

(a) a first index of refraction of said first complex refractive index decreases in value toward a second index of refraction of said second complex refractive index; and

(b) a first extinction coefficient of said first complex refractive index increases in value toward a second extinction coefficient of said second complex refractive index.

6. The electroluminescent device of claim 5 wherein:

(a) said first index of refraction and said first extinction coefficient are, respectively, approximately 0.0 and 1.75; and

(b) said second index of refraction and said second extinction coefficient are, respectively,

approximately 6.0 and 0.8.

7. In a TFEL device for providing an optical display, a substrate supporting a laminar thin film which includes a set of transparent front electrodes, a set of rear electrodes, and a phosphor layer sandwiched between front and rear dielectric layers, and disposed between said front and rear electrodes the improvement comprising:

(a) a thin-film light absorption layer that absorbs a substantial percentage of light incident thereon; and

(b) said light absorption layer disposed between said rear dielectric layer and said set of rear electrodes; and

(c) said thin-film light absorption layer comprising;

(i) a first absorption portion having a first complex refractive index at a side adjacent said rear dielectric layer, said rear dielectric layer having an initial complex refractive index that substantially matches said first complex refractive index at a side adjacent said first absorption portion; and

(ii) a second absorption portion having a second complex refractive index at a side adjacent said rear electrode layer, said rear electrode layer having a complex refractive index that substantially matches said second complex refractive index at a side adjacent said second absorption portion.

8. The electroluminescent device of claim 7 wherein said first complex refractive index changes from said first absorption portion of said light absorption layer with a gradual gradient to said second complex refractive index at said second absorption portion of said light absorption layer.

9. The electroluminescent device of claim 7 wherein said first complex refractive index monotonically changes to said second complex refractive index and wherein:

(a) said thin-film light absorption layer is composed of a plurality of discrete layers that are thin relative to said light'"'"'s wavelength, wherein a first layer of said discrete layers is said first absorption portion and a last layer of said discrete layers is said second absorption portion; and

(b) said thin-film layer'"'"'s average optical thickness is at least large enough to be on the order of said light'"'"'s wavelength.

10. An electroluminescent device comprising:

(a) a plurality of layers including at least a transparent electrode layer, a rear electrode layer, and at least three layers including an electroluminescent layer sandwiched between front and rear dielectric layers, all three layers thereof disposed between said rear electrode layer and said transparent electrode layer so as to emit light upon the application of an electric field between said transparent electrode layer and said rear electrode layer; and

(b) a thin-film light absorption layer that absorbs a substantial percentage of light incident thereon and which is disposed between said rear electrode layer and said rear dielectric layer, said thin-film light absorption layer comprising;

(i) a first absorption portion having a first complex refractive index at a side adjacent a first adjacent layer, said first adjacent layer having an initial complex refractive index that substantially matches said first complex refractive index at a side adjacent said first absorption portion; and

(ii) a second absorption portion having a second complex refractive index at a side adjacent a second adjacent layer, said second adjacent layer having a complex refractive index that substantially matches said second complex refractive index at a side adjacent said second absorption portion.

11. The electrolumininescent device of claim 10 wherein said first adjacent layer is said rear dielectric layer and said second adjacent layer is said rear electrode layer.

12. The electroluminescent device of claim 10 wherein said first complex refractive index changes from said first absorption portion of said light absorption layer with a gradual gradient to said second complex refractive index at said second absorption portion of said light absorption layer.

13. The electroluminescent device of claim 10 wherein said first complex refractive index monotonically changes to said second complex refractive index and wherein:

(a) said thin-film light absorption layer is composed of a plurality of discrete layers that are thin relative to said light'"'"'s wavelength, wherein a first layer of said discrete layers is said first absorption portion and a last layer of said discrete layers is said second absorption portion; and

(b) said thin-film layer'"'"'s average optical thickness is at least large enough to be on the order of said light'"'"'s wavelength.