Liquid Crystal Displays With Minimized Transmission Loss and Enhanced Off-Axis Color Fidelity

• US 20160209691A1
• Filed: 09/10/2015
• Published: 07/21/2016
• Est. Priority Date: 01/19/2015
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Chen, Yuan, Yang, Byung Duk, Tai, Chia Hsuan, Osawa, Hiroshi, Kim, Kyung Wook, Hung, Ming-Chin, Lin, Shang-Chih, Chang, Shih Chang, Chen, Yu Cheng
• Granted Patent: US 9,645,464 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G02B 6/00 Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
• CPC Class Codes: G02B 6/005 provided by one optical element, or plurality thereof, placed on the light output side of the light guide
• CPC Class Codes: G02F 1/133345 Insulating layers G02F1/1335, G02F1/1337, G02F1/135, G02F1/136 take precedence
• CPC Class Codes: G02F 1/13338 Input devices, e.g. touch panels
• CPC Class Codes: G02F 1/133514 Colour filters
• CPC Class Codes: G02F 1/133521 Interference filters
• CPC Class Codes: G02F 1/133528 Polarisers
• CPC Class Codes: G02F 1/1362 Active matrix addressed cells G02F1/134336, G02F1/134363 take precedence
• CPC Class Codes: G02F 1/136209 Light shielding layers, e.g. black matrix, incorporated in the active matrix substrate, e.g. structurally associated with the switching element
• CPC Class Codes: G02F 1/136222 Colour filters incorporated in the active matrix substrate
• CPC Class Codes: G02F 1/1368 in which the switching element is a three-electrode device G02F1/136277 takes precedence
• CPC Class Codes: H01L 29/518 the insulating material containing nitrogen, e.g. nitride, oxynitride, nitrogen-doped material
• CPC Class Codes: H01L 29/78606 with supplementary region or layer in the thin film or in the insulated bulk substrate supporting it for controlling or increasing the safety of the device H01L29/78642, H01L29/78645 take precedence

Abstract

A display may have upper and lower display layers. A layer of liquid crystal material may be interposed between the upper and lower display layers. The display layers may have substrates. The display layers may include a color filter layer having an array of color filter elements on a glass substrate and a thin-film transistor layer having a layer of thin-film transistor circuitry on a glass substrate. Dielectric layers within the display layers such as dielectric layers within the thin-film transistor layer may have differing indices of refraction. Reflections and color shifts due to index of refraction discontinuities may be minimized by interposing graded index dielectric layers between adjacent layers with different indices. The graded index layers may be formed from structures with a continuously varying index of refraction or structures with a step-wise varying index of refraction.

Claims

1. A liquid crystal display having an array of pixels;

an upper polarizer;

a lower polarizer

a layer of liquid crystal material;

a color filter layer between the lower polarizer and the layer of liquid crystal material; and

a thin-film transistor layer between the layer of liquid crystal material and the upper polarizer, wherein the thin-film transistor layer comprises;

a substrate layer;

a patterned layer of opaque masking material with openings for the pixels;

a first dielectric layer that covers the patterned layer of opaque masking material;

a second dielectric layer; and

a third dielectric layer interposed between the first and second dielectric layers, wherein the first dielectric layer has a first index of refraction, wherein the second dielectric layer has a second index of refraction that is different than the first index of refraction, and wherein the third dielectric layer has a graded index of refraction to minimize reflections arising from a difference between the first and second indices of refraction.

2. The liquid crystal display defined in claim 1 wherein the first dielectric layer comprises spin-on glass that planarizes the patterned layer of opaque masking material.

3. The liquid crystal display defined in claim 2 wherein the second dielectric layer comprises a thin-film transistor gate insulator layer.

4. The liquid crystal display defined in claim 3 wherein the spin-on glass layer includes silicon dioxide.

5. The liquid crystal display defined in claim 4 wherein the second dielectric layer includes silicon nitride.

6. The liquid crystal display defined in claim 5 wherein the third dielectric layer comprises silicon oxynitride.

7. The liquid crystal display defined in claim 6 wherein the third dielectric layer comprises a plurality of sublayers with different respective index of refraction values so that the third dielectric layer has a step-wise varying index of refraction profile.

8. The liquid crystal display defined in claim 7 wherein the third dielectric layer has only two of the sublayers.

9. The liquid crystal display defined in claim 7 wherein the third dielectric layer has at least three of the sublayers.

10. The liquid crystal display defined in claim 6 wherein the third dielectric layer comprises a silicon oxynitride layer having a continuously varying index of refraction value.

11. The liquid crystal display defined in claim 10 further comprising backlight structures that supply backlight that passes through the lower polarizer before passing through the liquid crystal layer.

12. A liquid crystal display having an array of pixels;

an upper polarizer;

a lower polarizer

a layer of liquid crystal material;

a color filter layer between the upper polarizer and the layer of liquid crystal material; and

a thin-film transistor layer between the layer of liquid crystal material and the lower polarizer, wherein the thin-film transistor layer comprises;

a substrate layer;

a first dielectric layer having a first index of refraction; and

a second dielectric layer having a second index of refraction; and

a graded index dielectric layer that is interposed between the first and second dielectric layers.

13. The liquid crystal display defined in claim 12 wherein the first dielectric layer comprises a silicon dioxide interlayer dielectric layer, wherein the second dielectric layer comprises a silicon nitride interlayer dielectric layer, and wherein the graded index dielectric layer comprises a silicon oxynitride layer with a continuously varying index of refraction.

14. The liquid crystal display defined in claim 12 wherein the first dielectric layer comprises a silicon dioxide interlayer dielectric layer, wherein the second dielectric layer comprises a silicon nitride interlayer dielectric layer, and wherein the graded index dielectric layer comprises a silicon oxynitride layer with a step-wise varying index of refraction produced by multiple sublayers having different indices of refraction.

15. The liquid crystal display defined in claim 12 wherein the first dielectric layer comprises a silicon nitride interlayer dielectric layer, wherein the second dielectric layer comprises a silicon oxide thin-film transistor gate insulator layer, and wherein the graded index dielectric layer comprises a silicon oxynitride layer with a continuously varying index of refraction.

16. The liquid crystal display defined in claim 12 wherein the first dielectric layer comprises a silicon nitride interlayer dielectric layer, wherein the second dielectric layer comprises a silicon oxide thin-film transistor gate insulator layer, and wherein the graded index dielectric layer comprises a silicon oxynitride layer with a step-wise varying index of refraction produced by multiple sublayers having different indices of refraction.

17. The liquid crystal display defined in claim 12 wherein the first dielectric layer comprises a silicon oxide buffer layer formed adjacent to a silicon oxide gate insulator layer, wherein the second dielectric layer comprises a silicon nitride buffer layer, and wherein the graded index dielectric layer comprises a silicon oxynitride layer with a continuously varying index of refraction.

18. The liquid crystal display defined in claim 12 wherein the first dielectric layer comprises a silicon oxide buffer dielectric layer formed adjacent to a silicon oxide gate insulator layer, wherein the second dielectric layer comprises a silicon nitride buffer dielectric layer, and wherein the graded index dielectric layer comprises a silicon oxynitride layer with a step-wise varying index of refraction produced by multiple sublayers having different indices of refraction.

19. A liquid crystal display having an array of pixels;

an upper polarizer;

a lower polarizer

a layer of liquid crystal material;

a color filter layer between the upper polarizer and the layer of liquid crystal material; and

a thin-film transistor layer between the layer of liquid crystal material and the lower polarizer, wherein the thin-film transistor layer comprises;

a substrate layer having a first index of refraction;

a dielectric buffer layer having a second index of refraction that is different than the first index of refraction; and

a graded index dielectric layer that is interposed between the substrate and the dielectric buffer layers.

20. The liquid crystal display defined in claim 19 wherein the dielectric buffer layer comprises a silicon nitride layer and wherein the graded index dielectric layer comprises a silicon oxynitride layer with a continuously varying index of refraction.

21. The liquid crystal display defined in claim 19 wherein the dielectric buffer layer comprises a silicon nitride layer and wherein the graded index dielectric layer comprises a silicon oxynitride layer with a step-wise varying index of refraction produced by multiple sublayers having different indices of refraction.

22. The liquid crystal display defined in claim 19 further comprising:

a conductive oxide layer; and

an index matching layer between the conductive oxide layer and the substrate layer, wherein the conductive oxide layer has a third index of refraction and wherein the index matching layer has an index of refraction that is between the first and second indices of refraction.