Light emitting device with translucent semi-reflection layer and electronic apparatus

• US 7,868,528 B2
• Filed: 09/17/2008
• Issued: 01/11/2011
• Est. Priority Date: 10/18/2007
• Status: Active Grant

• Current Assignee: Element Capital Commercial Company Pte. Ltd.
• Original Assignee: Seiko Epson Corporation (Seiko Group)
• Inventors: Kobayashi, Hidekazu
• Primary Examiner(s): Guharay; Karabi
• Assistant Examiner(s): QUARTERMAN, KEVIN J
• Application Number:
  US12/212,175
• Publication Number:
  US 20090103304A1
• Time in Patent Office: 846 Days
• Field of Search: 313498-512, 313/112, 313/113
• US Class Current: 313/112
• CPC Class Codes: H10K 50/86 Arrangements for improving contrast, e.g. preventing reflection of ambient light

Abstract

A light emitting device includes: a light emitting element which includes a first electrode layer, a second electrode layer, and a light emitting function layer disposed between the first electrode and the second electrode; a reflection layer which reflects light emitted from the light emitting function layer toward the light emitting function layer; and a translucent semi-reflection layer which is disposed opposite the reflection layer with the light emitting function layer interposed therebetween to reflect some of the light emitted from the light emitting function layer toward the light emitting function layer and to transmit the remainder of the light, wherein the translucent semi-reflection layer has a refractive index of 1 or more.

Claims

1. A light emitting device comprising:

a light emitting element which includes a first electrode layer, a translucent semi-reflection layer, and a light emitting function layer disposed between the first electrode and the translucent semi-reflection layer;

a reflection layer which reflects light emitted from the light emitting function layer toward the light emitting function layer;

the translucent semi-reflection layer, which is disposed opposite the reflection layer with the light emitting function layer interposed therebetween to reflect some of the light emitted from the light emitting function layer toward the light emitting function layer and to transmit the remainder of the light, the translucent semi-reflection layer having a refractive index of 1 or more;

a plurality of separators sandwiching the first electrode layer;

a color filter which is disposed opposite the light emitting function layer with the translucent semi-reflection layer interposed between the color filter and the light emitting function layer to transmit the light transmitted through the translucent semi-reflection layer,

wherein an optical distance between the reflection layer and an interface which is not opposite to the reflection layer in the translucent semi-reflection layer is determined on the basis of d₁ calculated from Formula (1);

d₂=(p+1/2)·

λ

/2−

(φ

₁−

φ

₂)·

λ

/4π

 

 

(1),

where λ

is a wavelength corresponding to a peak of transmissivity of the color filter,

φ

₁ is a phase variation occurring when light having a wavelength λ

traveling from an opposite side of the light emitting function layer to the translucent semi-reflection layer reflects from an interface opposite the light emitting function layer of the translucent semi-reflection layer,

φ

₂ is a phase variation occurring when light having a wavelength λ

traveling from the light emitting function layer to the reflection layer reflects from the reflection layer, and

p is a positive integer.

2. The light emitting device according to claim 1, further comprising:

a color filter which is disposed opposite the light emitting function layer with the translucent semi-reflection layer interposed therebetween to transmit the light transmitted through the translucent semi-reflection layer,

wherein the translucent semi-reflection layer has a predetermined physical thickness t_z, and

wherein an optical distance between the reflection layer and an interface which is opposite to the reflection layer in the translucent semi-reflection layer is determined on the basis of d₁ calculated from Formula (2);

d₂=(p+1/2)·

λ

/2−

(φ

₁−

φ

₂)·

λ

/4π

−

n_z·

t_z 

 

(2),

where λ

is a wavelength corresponding to a peak of transmissivity of the color filter,

φ

₁ is a phase variation occurring when light having a wavelength λ

traveling from an opposite side of the light emitting function layer to the translucent semi-reflection layer reflects from an interface opposite the light emitting function layer of the translucent semi-reflection layer,

φ

₂ is a phase variation occurring when light having a wavelength λ

traveling from the light emitting function layer to the reflection layer reflects from the reflection layer,

p is a positive integer, and

n_z is a refractive index for a wavelength λ

of the translucent semi-reflection layer.

3. The light emitting device according to claim 1,

wherein the translucent semi-reflection layer contains an alloy of at least two kinds of unit elements, and

wherein an alloy composition of the translucent semi-reflection layer is determined depending on a physical thickness of the translucent semi-reflection layer or the physical thickness of the translucent semi-reflection layer is determined depending on the alloy composition, when the refractive index varies depending on a variation in a composition ratio of one element of the unit elements and a variation in the physical thickness of the translucent semi-reflection layer.

4. The light emitting device according to claim 1, wherein the translucent semi-reflection layer contains MgAg.

5. An electronic apparatus comprising the light emitting device according to claim 1.

6. The light emitting device according to claim 1, further comprising:

a plurality of first electrode layers, wherein the plurality of separators are disposed between the plurality of first electrode layers.