DISPLAY DEVICE

• US 20070200977A1
• Filed: 02/21/2007
• Published: 08/30/2007
• Est. Priority Date: 02/24/2006
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Egi, Yuji, Nishi, Takeshi, Ishitani, Tetsuji
• Granted Patent: US 7,864,268 B2
• Time in Patent Office: Days
• US Class Current: 349/96
• CPC Class Codes: G02F 1/133531 characterised by the arrangement of polariser or analyser axes
• CPC Class Codes: G02F 1/133533 Colour selective polarisers G02F1/1347 takes precedence

Abstract

An object of the invention is to provide a display device having a high contrast ratio. Another object of the invention is to manufacture such a high-performance display device at low cost. In a display device having a display element between a pair of light-transmissive substrates, polarizer-including layers, which have different wavelength distributions of extinction coefficients, are stacked so that absorption axes are in a parallel nicol state, over each light-transmissive substrate. Absorption axes of one of a pair of stacks of polarizers and the other together which interpose the display element are deviated from a cross nicol state. A retardation plate may be provided between the stack of polarizing plates and the substrate.

Claims

1. A display device comprising:

a first light-transmissive substrate and a second light-transmissive substrate which are provided so as to face each other;

a display element provided between the first light-transmissive substrate and the second light-transmissive substrate;

a first layer including first stack of polarizers outside the first light-transmissive substrate; and

a second layer including second stack of polarizers outside the second light-transmissive substrate,

wherein polarizers in each of the first stack of polarizers and the second stack of polarizers have different wavelength distributions of extinction coefficients of absorption axes,

absorption axes of polarizers in the first stack of polarizers are in a parallel nicol state,

absorption axes of polarizers in the second stack of polarizers are in a parallel nicol state, and

absorption axis of a polarizer in the first stack of polarizers and that of a polarizer in the second stack of polarizers are deviated from a cross nicol state.

2. A display device according to claim 1 wherein the first light-transmissive substrate is provided over the first layer, and the display element is provided over the first light-transmissive substrate, and the second light-transmissive substrate is provided over the display element, and the second layer is provided over the second light-transmissive substrate.

3. A display device according to claim 1, wherein a polarizer is provided between a pair of protective layers in each of the first layer and the second layer.

4. A display device according to claim 1, wherein a light source is provided outside the second stack of polarizers.

5. A display device according to claim 1, wherein the display element is a liquid crystal element.

6. A display device acccording to claim 1 wherein the display device is incorporated into one selected from the group consisting of a portable information terminal, a digital video camera, a mobile phone, a television set and a portable computer.

7. A display device comprising:

a first light-transmissive substrate and a second light-transmissive substrate which are provided so as to face each other;

a display element provided between the first light-transmissive substrate and the second light-transmissive substrate;

a first layer including first stack of polarizers outside the first light-transmissive substrate;

a second layer including second stack of polarizers outside the second light-transmissive substrate;

a first retardation plate between the first light-transmissive substrate and the first layer including the first stack of polarizers; and

a second retardation plate between the second light-transmissive substrate and the second layer including the second stack of polarizers,

wherein polarizers in each of the first stack of polarizers and the second stack of polarizers has a different wavelength distribution of extinction coefficient of an absorption axis,

absorption axes of polarizers in the first stack of polarizers are in a parallel nicol state, and

absorption axes of polarizers in the second stack of polarizers are in a parallel nicol state,

absorption axis of a polarizer in the first stack of polarizers and that of a polarizer in the second stack of polarizers are deviated from a cross nicol state.

8. A display device according to claim 7 wherein the first light-transmissive substrate is provided over the first layer, and the display element is provided over the first light-transmissive substrate, and the second light-transmissive substrate is provided over the display element, and the second layer is provided over the second light-transmissive substrate.

9. A display device according to claim 7, wherein a polarizer is provided between a pair of protective layers in each of the first layer and the second layer.

10. A display device according to claim 7, wherein a light source is provided outside the second stack of polarizers.

11. A display device according to claim 7, wherein the display element is a liquid crystal element.

12. A display device acccording to claim 7 wherein the display device is incorporated into one selected from the group consisting of a portable information terminal, a digital video camera, a mobile phone, a television set and a portable computer.

13. A display device comprising:

a first light-transmissive substrate and a second light-transmissive substrate which are provided so as to face each other;

a display element provided between the first light-transmissive substrate and the second light-transmissive substrate;

a first layer including first stack of polarizers outside the first light-transmissive substrate; and

a second layer including second stack of polarizers outside the second light-transmissive substrate,

wherein a first polarizer, a second polarizer, and a third polarizer are stacked in this order on a side of the first light-transmissive substrate to form the first stack of polarizers,

polarizers in each of the first stack of polarizers and the second stack of polarizers have different wavelength distributions of extinction coefficients of absorption axes,

absorption axes of polarizers in the first stack of polarizers are in a parallel nicol state,

absorption axes of polarizers in the second stack of polarizers are in a parallel nicol state, and

absorption axis of a polarizer in the first stack of polarizers and that of a polarizer in the second stack of polarizers are deviated from a cross nicol state.

14. A display device according to claim 13 wherein the first light-transmissive substrate is provided over the first layer, and the display element is provided over the first light-transmissive substrate, and the second light-transmissive substrate is provided over the display element, and the second layer is provided over the second light-transmissive substrate.

15. A display device according to claim 13, wherein a polarizer is provided between a pair of protective layers in each of the first layer and the second layer.

16. A display device according to claim 13, wherein a light source is provided outside the second stack of polarizers.

17. A display device according to claim 13, wherein the display element is a liquid crystal element.

18. A display device acccording to claim 13 wherein the display device is incorporated into one selected from the group consisting of a portable information terminal, a digital video camera, a mobile phone, a television set and a portable computer.

19. A display device comprising:

a first light-transmissive substrate and a second light-transmissive substrate which are provided so as to face each other;

a display element provided between the first light-transmissive substrate and the second light-transmissive substrate;

a first layer including first stack of polarizers outside the first light-transmissive substrate;

a second layer including second stack of polarizers outside the second light-transmissive substrate;

a first retardation plate between the first light-transmissive substrate and the first layer including the first stack of polarizers; and

a second retardation plate between the second light-transmissive substrate and the second layer including the second stack of polarizers,

wherein a first polarizer, a second polarizer, and a third polarizer are stacked in this order on a side of the first light-transmissive substrate to form the first stack of polarizers,

polarizers in each of the first stack of polarizers and the second stack of polarizers have different wavelength distributions of extinction coefficients of absorption axes,

absorption axes of polarizers in the first stack of polarizers are in a parallel nicol state,

absorption axes of polarizers in the second stack of polarizers are in a parallel nicol state, and

absorption axis of a polarizer in the first stack of polarizers and that of a polarizer in the second stack of polarizers are deviated from a cross nicol state.

20. A display device according to claim 19 wherein the first light-transmissive substrate is provided over the first layer, and the display element is provided over the first light-transmissive substrate, and the second light-transmissive substrate is provided over the display element, and the second layer is provided over the second light-transmissive substrate.

21. A display device according to claim 19, wherein a polarizer is provided between a pair of protective layers in each of the first layer and the second layer.

22. A display device according to claim 19, wherein a light source is provided outside the second stack of polarizers.

23. A display device according to claim 19, wherein the display element is a liquid crystal element.

24. A display device acccording to claim 19 wherein the display device is incorporated into one selected from the group consisting of a portable information terminal, a digital video camera, a mobile phone, a television set and a portable computer.