Electroluminescent device and apparatus

• US 6,441,551 B1
• Filed: 01/03/2000
• Issued: 08/27/2002
• Est. Priority Date: 07/14/1997
• Status: Expired due to Term

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Araki, Yoshinori, Abe, Hidetoshi
• Primary Examiner(s): Patel, Nimeshkumar D.
• Assistant Examiner(s): Santiago, Mariceli
• Application Number:
  US09/462,119
• Time in Patent Office: 967 Days
• Field of Search: 313/506, 313/498-512, 349/19, 349/33, 349/69, 349/88, 349/86, 315/169.3, 315/169.1
• US Class Current: 313/503
• CPC Class Codes: H05B 33/12 Light sources with substantially two-dimensional radiating surfaces
• CPC Class Codes: H05B 33/22 characterised by the chemical or physical composition or the arrangement of auxiliary dielectric or reflective layers

Abstract

The present invention provides the EL device and apparatus each of which has a white appearance in the non-light-emitting state, and can emit white light with high luminance in the light-emitting state. When such an EL device or apparatus is used, the light-emitting surface provides a background with high whiteness both in the light-emitting and non-light-emitting state, and can highlight a light-transmitting printed layer formed on the light-emitting surface.

Claims

1. An electroluminescent device comprising:

an electroluminescent element having a light-emitting surface which emits white light, and

a liquid crystal layer which is placed on said light-emitting surface, has a haze of 20% or less when a voltage is applied, and assumes a white color and has a haze of 70% or larger when no voltage is applied,

wherein said device presents a white appearance both in the light-emitting and non-light-emitting states of the electroluminescent element, wherein said electroluminescent element comprises a color filter layer containing a colorant which develops a complementary color to a color of light emitted by a luminescent layer, and a surface of the color filter layer forms the light-emitting surface, and wherein the color filter layer includes an additive selected from the following group of additives;

surfactants, antioxidants, antifungus agents, rust-preventives, moisture absorbents, and cross-linking agents.

2. An electroluminescent apparatus comprising:

(a) a power source

(b) an electroluminescent element having a light-emitting surface which emits white light, and being electrically connected with said power source, and

(c) a liquid crystal layer which is placed on said light-emitting surface, has a haze of 20% or less when a voltage is applied, and assumes a white color and has a haze of 70% or larger when no voltage is applied, and which is electrically connected with said power source,

wherein said device presents a white appearance both in the light-emitting and non-light-emitting states of the electroluminescent element, and wherein said electroluminescent element and said liquid crystal layer are connected with said power source so as to be activated such that said electroluminescent element simultaneously emits white light and the liquid crystal layer becomes transparent to maintain a substantially constant white appearance when transitioning from the non-light-emitting state to the light-emitting state.

3. The electroluminescent device of claim 2, wherein the electroluminescent element and the liquid crystal layer are connected in series with the power source so that the voltage is applied to them at the same time.

4. The electroluminescent device of claim 2, wherein the electroluminescent element and the liquid crystal layer are connected in parallel with the power source so that the voltage is applied to them at the same time.

5. An electroluminescent device comprising:

an electroluminescent element having a light-emitting surface which emits white light, the electroluminescent element including a luminescent layer and a color filter layer containing a colorant which emits light of a complimentary color to that emitted from the luminescent layer, wherein the color filter layer includes an additive selected from the following group of additives;

surfactants, antioxidants, antifungus agents, rust-preventives, moisture absorbents, and cross-linking agents, and

a liquid crystal layer which is placed on said light-emitting surface, has a haze of 20% or less when a voltage is applied, and assumes a white color and has a haze of 70% or larger when no voltage is applied, wherein said device presents a white appearance both in the light-emitting and non-light-emitting states of the electroluminescent element.

6. The electroluminescent device of claim 5, wherein the colorant in the color filter layer is a fluorescent colorant which emits fluorescent light by inducement of light from the luminescent layer.

7. The electroluminescent device of claim 5, wherein the color filter layer includes a resin comprising a pressure sensitive adhesive.

8. The electroluminescent device of claim 6, wherein the pressure sensitive adhesive adheres the electroluminescent element to the liquid crystal layer.

9. (New) The electroluminescent device of claim 8, wherein the pressure sensitive adhesive increases luminance of the electroluminescent device.

10. The electroluminescent device of claim 5, further comprising a prismatic film between the electroluminescent element and the liquid crystal layer.

11. The electroluminescent device of claim 10, wherein the prismatic film and the liquid crystal layer are physically spaced so as not to contact each other.

12. The electroluminescent device of claim 11, wherein the color filter layer includes a resin comprising a pressure sensitive adhesive that adheres the prismatic film to the electroluminescent device.

13. An electroluminescent device comprising:

an electroluminescent element having a light-emitting surface which emits white light, the electroluminescent element including a luminescent layer and a color filter layer containing a colorant which emits light of a complimentary color to that emitted from the luminescent layer;

a liquid crystal layer that has a haze of 20% or less when a voltage is applied, and assumes a white color and has a haze of 70% or larger when no voltage is applied, wherein said device presents a white appearance both in the light-emitting and non-light-emitting states of the electroluminescent element; and

a prismatic film between the electroluminescent element and the liquid crystal layer.

14. The electroluminescent device of claim 13, wherein the prismatic film and the liquid crystal layer are physically spaced so as not to contact each other.

15. The electroluminescent device of claim 13, wherein the color filter layer includes a resin comprising a pressure sensitive adhesive that adheres the prismatic film to the electroluminescent device.

16. A method comprising:

simultaneously applying power to an electroluminescent (EL) device and a liquid crystal display (LCD) to cause the EL device to emit white light and the LCD to become transparent; and

simultaneously deactivating the power from the EL device and the LCD to cause the LCD to assume white color having a haze of 70% or larger.