Display device

• US 20060187384A1
• Filed: 04/24/2006
• Published: 08/24/2006
• Est. Priority Date: 10/24/2003
• Status: Abandoned Application

• Current Assignee: Toshiba Matsushita Display Technology (Japan Display Incorporated)
• Original Assignee: Toshiba Matsushita Display Technology (Japan Display Incorporated)
• Inventors: Hisatake, Yuzo
• Application Number:
  US11/409,215
• Publication Number:
  US 20060187384A1
• Time in Patent Office: Days
• US Class Current: 349/113
• CPC Class Codes: H10K 50/8426 Peripheral sealing arrangements, e.g. adhesives, sealants
• CPC Class Codes: H10K 50/846 comprising getter material or desiccants
• 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

Abstract

When a peak wavelength of light emerging from a light-emitting layer is λp(k) (k=1, 2, . . . , m in an order from a smallest wavelength), the peak wavelength λp(k) is less than a value ne(k)P(k) that is obtained by multiplying an extraordinary-ray refractive index ne(k) of a selective reflection layer that forms each selective reflection region by a helical pitch P(k), and is greater than a value no(k)P(k) that is obtained by multiplying an ordinary-ray refractive index no(k) by the helical pitch P(k). A relationship, ne(k−1)P(k−1)<no(k)P(k), is established between the selective reflection layers that form the selective reflection regions.

Claims

1. A display device including a reflecting layer, a light-emitting layer, a ¼

wavelength plate and a polarizer plate, the ¼

wavelength plate being positioned between the polarizer plate and the light-emitting layer, and the light-emitting layer being positioned between the ¼

wavelength plate and the reflecting layer, the display device comprising;

selective reflection layers that are disposed between the ¼

wavelength plate and the light-emitting layer, include liquid crystal molecules that are aligned with a predetermined helical pitch, pass first circularly polarized light, and reflect second circularly polarized light that has a polarity opposite to a polarity of the first circular polarized light and has a predetermined wavelength,

wherein the light-emitting layer has at least one peak wavelength, and the selective reflection layers include an m-number of selective reflection regions when the number of peak wavelengths is m,

when a peak wavelength of light emerging from the light-emitting layer is λ

p(k) (k=1, 2, . . . , m in an order from a smallest wavelength), the peak wavelength λ

p(k) is less than a value ne(k)P(k) that is obtained by multiplying an extraordinary-ray refractive index ne(k) of the selective reflection layer that forms each selective reflection region by a helical pitch P(k), and is greater than a value no(k)P(k) that is obtained by multiplying an ordinary-ray refractive index no(k) by the helical pitch P(k), and

a relationship, ne(k−

1)P(k−

1)<

no(k)P(k), is established between the selective reflection layers that form the selective reflection regions.

3. The display device according to claim 1, wherein a value n(k)P(k), which is obtained by multiplying a mean refractive index n(k) of the selective reflection layers by the helical pitch P(k), is substantially equal to the peak wavelength λ

p(k) of the light-emitting layer.

5. The display device according to claim 1, wherein a reflectance of the second circular polarized light, which is reflected by the selective reflectance layer, is 50% or more at the peak wavelength λ

p(k) of the light-emitting layer.

7. The display device according to claim 1, wherein at least a red pixel with a red peak wavelength, a green pixel with a green peak wavelength and a blue pixel with a blue peak wavelength are arrayed in a planar fashion, and means for individually driving the respective pixels is provided.

9. The display device according to claim 1, wherein the reflecting layer, the light-emitting layer, the selective reflection layer, the ¼

wavelength plate and the polarizer plate are disposed on a substrate in the named order.

11. The display device according to claim 7, wherein the selective reflection layer, the ¼

wavelength layer and the polarizer plate are disposed on one major surface of a substrate in the named order, and the light-emitting layer and the reflecting layer are disposed on the other major surface of the substrate in the named order, and

a thickness of the substrate is not greater than 10 times a pitch of arrangement of the pixels.

13. The display device according to claim 1, wherein the light-emitting layer is held between a pair of electrodes, thus constituting an EL element.

15. The display device according to claim 1, wherein the selective reflection layer is one of a cholesteric liquid crystal layer, a layer obtained by polymerizing a cholesteric liquid crystal layer, and a layer obtained by forming a cholesteric liquid crystal layer in a film shape.

2. A display device including a reflecting layer, a light-emitting layer, a color filter, a ¼

wavelength plate and a polarizer plate, the ¼

wavelength plate being positioned between the polarizer plate and the color filter, and the color filter being positioned between the ¼

wavelength plate and the light-emitting layer, the display device comprising;

selective reflection layers that are disposed between the ¼

wavelength plate and the color filter, include liquid crystal molecules that are aligned with a predetermined helical pitch, pass first circularly polarized light, and reflect second circularly polarized light that has a polarity opposite to a polarity of the first circular polarized light and has a predetermined wavelength,

wherein light that is emitted from the light-emitting layer and transmitted through the color filter has at least one peak wavelength, and the selective reflection layers include an m-number of selective reflection regions when the number of peak wavelengths is m,

when a peak wavelength of light emerging from the color filter is λ

p(k) (k=1, 2, . . ., m in an order from a smallest wavelength), the peak wavelength λ

p(k) is less than a value ne(k)P(k) that is obtained by multiplying an extraordinary-ray refractive index ne(k) of the selective reflection layer that forms each selective reflection region by a helical pitch P(k), and is greater than a value no(k)P(k) that is obtained by multiplying an ordinary-ray refractive index no(k) by the helical pitch P(k), and

a relationship, ne(k−

1)P(k−

1)<

no(k)P(k), is established between the selective reflection layers that form the selective reflection regions.

4. The display device according to claim 2, wherein a value n(k)P(k), which is obtained by multiplying a mean refractive index n(k) of the selective reflection layers by the helical pitch P(k), is substantially equal to the peak wavelength λ

p(k) of the light-emitting layer.

6. The display device according to claim 2, wherein a reflectance of the second circular polarized light, which is reflected by the selective reflectance layer, is 50% or more at the peak wavelength λ

p(k) of the light-emitting layer.

8. The display device according to claim 2, wherein at least a red pixel with a red peak wavelength, a green pixel with a green peak wavelength and a blue pixel with a blue peak wavelength are arrayed in a planar fashion, and means for individually driving the respective pixels is provided.

10. The display device according to claim 2, wherein the reflecting layer, the light-emitting layer, the selective reflection layer, the ¼

wavelength plate and the polarizer plate are disposed on a substrate in the named order.

12. The display device according to claim 8, wherein the selective reflection layer, the ¼

wavelength layer and the polarizer plate are disposed on one major surface of a substrate in the named order, and the light-emitting layer and the reflecting layer are disposed on the other major surface of the substrate in the named order, and

a thickness of the substrate is not greater than 10 times a pitch of arrangement of the pixels.

14. The display device according to claim 2, wherein the light-emitting layer is held between a pair of electrodes, thus constituting an EL element.

16. The display device according to claim 2, wherein the selective reflection layer is one of a cholesteric liquid crystal layer, a layer obtained by polymerizing a cholesteric liquid crystal layer, and a layer obtained by forming a cholesteric liquid crystal layer in a film shape.

17. A display device comprising a reflecting layer, a light-emitting layer, a selective reflection layer, a ¼

wavelength plate and a polarizer plate, which are disposed in the named order,

wherein the light-emitting layer includes a first light-emitting layer that emits light with a single first peak wavelength, and a second light-emitting layer that emits light with a single second peak wavelength, and

the selective reflection layer passes first circularly polarized light, reflects second circularly polarized light that has a polarity opposite to a polarity of the first circular polarized light and has a predetermined wavelength, and includes a first reflection layer that includes liquid crystal molecules aligned with a first helical pitch corresponding to the first peak wavelength and reflects the second circularly polarized light of a predetermined wavelength including the first peak wavelength, and a second reflection layer that includes liquid crystal molecules aligned with a second helical pitch corresponding to the wavelength of the second light-emitting layer and reflects the second circularly polarized light of a predetermined wavelength including the second peak wavelength.

18. A display device including a reflecting layer, a light-emitting layer, a ¼

wavelength plate and a polarizer plate, the ¼

wavelength plate being positioned between the polarizer plate and the light-emitting layer, and the light-emitting layer being positioned between the ¼

wavelength plate and the reflecting layer, the display device comprising;

a selective reflection layer that is disposed between the ¼

wavelength plate and the light-emitting layer, passes first circularly polarized light, and reflects second circularly polarized light that has a polarity opposite to a polarity of the first circular polarized light and has a predetermined wavelength,

light that is emitted from the light-emitting layer has at least one peak wavelength λ

p, and

the selective reflection layer reflects light corresponding to a specified wavelength range including the peak wavelength λ

p.