Organic electroluminescent device, polarizing surface light source, and liquid-crystal display

• US 20020008807A1
• Filed: 01/16/2001
• Published: 01/24/2002
• Est. Priority Date: 01/17/2000
• Status: Active Grant

• Current Assignee: Nitto Denko Corporation
• Original Assignee: Nitto Denko Corporation
• Inventors: Miyatake, Minoru, Nagatsuka, Tatsuki
• Granted Patent: US 6,947,105 B2
• Time in Patent Office: Days
• US Class Current: 349/65
• CPC Class Codes: G02B 5/3016 involving passive liquid crystal elements optical properties of liquid crystals G02F1/0063; polarising elements associated with active liquid crystal devices G02F1/133528
• CPC Class Codes: G02F 1/133603 with LEDs
• CPC Class Codes: G02F 1/13362 providing polarized light, e.g. by converting a polarisation component into another one
• CPC Class Codes: H10K 50/868 Arrangements for polarized light emission H10K50/86 takes precedence
• CPC Class Codes: H10K 85/141 comprising aliphatic or olefinic chains, e.g. poly N-vinylcarbazol, PVC or PTFE

Abstract

An organic electroluminescent device is disclosed which has a simple constitution, is excellent in device stability and emission efficiency, and attains high brightness. The organic electroluminescent device comprises an organic electroluminescent element (2) and a polarized-light scattering film (1) which comprises a light-transmitting resin (11) and dispersedly contained therein minute regions (12) differing from the light-transmitting resin in birefringent characteristics and in which the difference in refractive index between the minute regions and the light-transmitting resin in the axis direction in which a linearly polarized light has a maximum transmittance, Δn¹, is smaller than 0.03 and that in a direction perpendicular to the Δn¹ direction, Δn², is from 0.03 to 0.5, the light produced by the organic electroluminescent element being emitted from the device through the polarized-light scattering film. Also disclosed are: a polarizing surface light source which comprises the organic electroluminescent device and which has an illuminating planar surface and emits a polarized light; and a liquid-crystal display which comprises the polarizing surface light source and a liquid-crystal cell disposed on the light emission side of the light source.

Claims

1. An organic electroluminescent device comprising an organic electroluminescent element and a polarized-light scattering film which comprises a light-transmitting resin and dispersedly contained therein minute regions differing from the light-transmitting resin in birefringent characteristics and in which the difference in refractive index between the minute regions and the light-transmitting resin in the axis direction in which a linearly polarized light has a maximum transmittance, Δ

n¹, is smaller than 0.03 and that in a direction perpendicular to the Δ

n¹ direction, Δ

n², is from 0.03 to 0.5, the light produced by the organic electroluminescent element being emitted from the device through the polarized-light scattering film.

2. The organic electroluminescent device of claim 1, wherein the polarized-light scattering film constitutes an electrode substrate for the organic electroluminescent element or is superposed on the electrode substrate.

3. The organic electroluminescent device of claim 1, wherein the minute regions of the polarized-light scattering film comprise a thermoplastic resin which has a glass transition temperature of 50°

C. or higher and shows a nematic liquid-crystal phase in a range of temperatures lower than the glass transition temperature of the light-transmitting resin.

4. The organic electroluminescent device of claim 1, wherein the minute regions of the polarized-light scattering film which are dispersedly contained in the light-transmitting resin are formed by phase separation and have a Δ

n²-direction length of from 0.5 to 50 μ

m.

5. The organic electroluminescent device of claim 1, wherein the light-transmitting resin of the polarized-light scattering film has a deformation-under-load temperature of 80°

C. or higher and a glass transition temperature of 110°

C. or higher.

6. A polarizing surface light source comprising the organic electroluminescent device of claim 1, which has an illuminating planar surface and emits a polarized light.

7. The polarizing surface light source of claim 6, which has at least one of a polarizing film and a retardation film on the light emission side or opposite side of the organic electroluminescent device.

8. The polarizing surface light source of claim 7, wherein the axis of transmission of the polarizing film or the axis of retardation of the retardation film is parallel or perpendicular to the Δ

n² direction of the polarized-light scattering film.

9. The polarizing surface light source of claim 6, which has on the light emission side at least one of a light diffuser film and a lens sheet each having the property of maintaining polarization.

10. A liquid-crystal display which comprises the polarizing surface light source of claim 6 and a liquid-crystal cell disposed on the light emission side of the light source.