DISPLAY DEVICE

• US 20070120475A1
• Filed: 11/27/2006
• Published: 05/31/2007
• Est. Priority Date: 11/30/2005
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: NISHI, Takeshi, EGI, Yuji, ISHITANI, Tetsuji
• Granted Patent: US 7,804,244 B2
• Time in Patent Office: Days
• US Class Current: 313/506
• CPC Class Codes: H10K 2102/3031 Two-side emission, e.g. transparent OLEDs [TOLED]
• CPC Class Codes: H10K 50/86 Arrangements for improving contrast, e.g. preventing reflection of ambient light
• CPC Class Codes: H10K 59/12 Active-matrix OLED [AMOLED] displays
• CPC Class Codes: H10K 59/8791 Arrangements for improving contrast, e.g. preventing reflection of ambient light
• CPC Class Codes: H10K 85/657 Polycyclic condensed heteroaromatic hydrocarbons

Abstract

It is an object to provide a display device having an electroluminescent element in which a contrast ratio is increased. In a display device having an electroluminescent element between a pair of light transmitting substrates, a circularly polarizing plate having stacked polarizing plates arranged on outer sides thereof is provided. At this time, opposed polarizing plates are arranged to be in a crossed nicol state or in a parallel nicol state. As a result, a display device with a high contrast ratio can be provided.

Claims

1. A display device comprising:

a first light transmitting substrate;

a second light transmitting substrate opposed to the first light transmitting substrate;

a light emitting element provided between the first light transmitting substrate and the second light transmitting substrate;

a first circularly polarizing plate having stacked first linearly polarizing plates arranged on an outer side of the first light transmitting substrate; and

a second circularly polarizing plate having stacked second linearly polarizing plates arranged on an outer side of the second light transmitting substrate,

wherein the light emitting element emits light in both directions of the first light transmitting substrate and the second light transmitting substrate.

2. The display device according to claim 1, wherein the light emitting element comprises an electroluminescent element.

3. The display device according to claim 1, further comprising a thin film transistor formed over the first light transmitting substrate.

4. A display device comprising:

a first light transmitting substrate;

a second light transmitting substrate opposed to the first light transmitting substrate;

a light emitting element provided between a first light transmitting substrate and the second light transmitting substrate;

a first circularly polarizing plate having stacked first linearly polarizing plates arranged on an outer side of the first light transmitting substrate; and

a second circularly polarizing plate having stacked second linearly polarizing plates arranged on an outer side of the second light transmitting substrate,

wherein the light emitting element emits light in both directions of the first light transmitting substrate and the second light transmitting substrate,

wherein transmission axes of the stacked first linearly polarizing plates are arranged to be in a parallel nicol state, transmission axes of the stacked second linearly polarizing plates are arranged to be in a parallel nicol state, and

wherein the transmission axes of the stacked first linearly polarizing plates and the transmission axes of the stacked second linearly polarizing plates are arranged to be in a parallel nicol state.

5. The display device according to claim 4, wherein the light emitting element comprises an electroluminescent element.

6. The display device according to claim 4, further comprising a thin film transistor formed over the first light transmitting substrate.

7. A display device comprising:

a first light transmitting substrate;

a second light transmitting substrate opposed to the first light transmitting substrate;

a light emitting element provided between the first light transmitting substrate and the second light transmitting substrate;

stacked first linearly polarizing plates arranged on an outer side of the first light transmitting substrate;

stacked second linearly polarizing plates arranged on an outer side of the second light transmitting substrate;

a first retardation film provided between the first light transmitting substrate and the first linearly polarizing plate; and

a second retardation film provided between the second light transmitting substrate and the second linearly polarizing plate,

wherein the light emitting element emits light in both directions of the first light transmitting substrate and the second light transmitting substrate,

wherein transmission axes of the stacked first linearly polarizing plates are arranged to be in a parallel nicol state, transmission axes of the stacked second linearly polarizing plates are arranged to be in a parallel nicol state,

wherein the transmission axes of the stacked first linearly polarizing plates and the transmission axes of the stacked second linearly polarizing plates are arranged to be in a parallel nicol state, and

wherein a slow axis of the first retardation film is arranged to be at 45°

with respect to the transmission axis of the first linearly polarizing plate, and a slow axis of the second retardation film is arranged to be at 45°

with respect to the transmission axis of the second linearly polarizing plate.

8. The display device according to claim 7, wherein the light emitting element comprises an electroluminescent element.

9. The display device according to claim 7, further comprising a thin film transistor formed over the first light transmitting substrate.

10. A display device comprising:

a first light transmitting substrate;

a second light transmitting substrate opposed to the first light transmitting substrate;

a light emitting element provided between the first light transmitting substrate and the second light transmitting substrate;

stacked first linearly polarizing plates arranged on an outer side of the first light transmitting substrate;

a second linearly polarizing plate arranged on an outer side of the second light transmitting substrate;

a first retardation film provided between the first light transmitting substrate and the first linearly polarizing plate; and

a second retardation film provided between the second light transmitting substrate and the second linearly polarizing plate,

wherein the light emitting element emits light in both directions of the first light transmitting substrate and the second light transmitting substrate,

wherein transmission axes of the stacked first linearly polarizing plates are arranged to be in a parallel nicol state,

wherein the transmission axes of the stacked first linearly polarizing plates and a transmission axis of the second linearly polarizing plate are arranged to be in a parallel nicol state, and

wherein a slow axis of the first retardation film is arranged to be at 45°

with respect to the transmission axis of the first linearly polarizing plate, and a slow axis of the second retardation film is arranged to be at 45°

with respect to the transmission axis of the second linearly polarizing plate.

11. The display device according to claim 10, wherein the light emitting element comprises an electroluminescent element.

12. The display device according to claim 10, further comprising a thin film transistor formed over the first light transmitting substrate.

13. A display device comprising:

a first light transmitting substrate;

a second light transmitting substrate opposed to the first light transmitting substrate;

a light emitting element provided between the first light transmitting substrate and the second light transmitting substrate;

a first circularly polarizing plate having stacked first linearly polarizing plates arranged on an outer side of the first light transmitting substrate; and

a second circularly polarizing plate having stacked second linearly polarizing plates arranged on an outer side of the second light transmitting substrate,

wherein the light emitting element emits light in both directions of the first light transmitting substrate and the second light transmitting substrate,

wherein transmission axes of the stacked first linearly polarizing plates are arranged to be in a parallel nicol state, transmission axes of the stacked second linearly polarizing plates are arranged to be in a parallel nicol state, and

wherein the transmission axes of the stacked first linearly polarizing plates and the transmission axes of the stacked second linearly polarizing plates are arranged to be in a crossed nicol state.

14. The display device according to claim 13, wherein the light emitting element comprises an electroluminescent element.

15. The display device according to claim 13, further comprising a thin film transistor formed over the first light transmitting substrate.

16. A display device comprising:

a first light transmitting substrate;

a second light transmitting substrate;

a light emitting element provided between the first light transmitting substrate and the second light transmitting substrate;

stacked first linearly polarizing plates arranged on an outer side of the first light transmitting substrate;

stacked second linearly polarizing plates arranged on an outer side of the second light transmitting substrate;

a first retardation film provided between the first light transmitting substrate and the first linearly polarizing plate; and

a second retardation film provided between the second light transmitting substrate and the second linearly polarizing plate,

wherein the light emitting element emits light in both directions of the first light transmitting substrate and the second light transmitting substrate,

wherein transmission axes of the stacked first linearly polarizing plates are arranged to be in a parallel nicol state, transmission axes of the stacked second linearly polarizing plates are arranged to be in a parallel nicol state,

wherein the transmission axes of the stacked first linearly polarizing plates and the transmission axes of the stacked second linearly polarizing plates are arranged to be in a crossed nicol state,

wherein a slow axis of the first retardation film is arranged to be at 45°

with respect to the transmission axis of the first linearly polarizing plate, and a slow axis of the second retardation film is arranged to be at 45°

with respect to the transmission axis of the second linearly polarizing plate.

17. The display device according to claim 16, wherein the light emitting element comprises an electroluminescent element.

18. The display device according to claim 16, further comprising a thin film transistor formed over the first light transmitting substrate.

19. A display device comprising:

a first light transmitting substrate;

a second light transmitting substrate opposed to the first light transmitting substrate;

a light emitting element provided between the first light transmitting substrate and the second light transmitting substrate;

stacked first linearly polarizing plates arranged on an outer side of the first light transmitting substrate;

a second linearly polarizing plate arranged on an outer side of the second light transmitting substrate;

a first retardation film provided between the first light transmitting substrate and the first linearly polarizing plate; and

a second retardation film provided between the second light transmitting substrate and the second linearly polarizing plate,

wherein the light emitting element emits light in both directions of the first light transmitting substrate and the second light transmitting substrate,

wherein transmission axes of the stacked first linearly polarizing plates are arranged to be in a parallel nicol state, the transmission axes of the stacked first linearly polarizing plates and a transmission axis of the second linearly polarizing plate are arranged to be in a crossed nicol state, and

wherein a slow axis of the first retardation film is arranged to be at 45°

with respect to the transmission axis of the first linearly polarizing plate, and a slow axis of the second retardation film is arranged to be at 45°

with respect to the transmission axis of the second linearly polarizing plate.

20. The display device according to claim 19, wherein the light emitting element comprises an electroluminescent element.

21. The display device according to claim 19, further comprising a thin film transistor formed over the first light transmitting substrate.