Electroscopic display device

• US 4,965,562 A
• Filed: 05/06/1988
• Issued: 10/23/1990
• Est. Priority Date: 05/13/1987
• Status: Expired due to Fees

• Current Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Original Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Inventors: Verhulst, Antonius G. H.
• Primary Examiner(s): Oberley, Alvin E.
• Assistant Examiner(s): Hjerpe, Richard
• Application Number:
  US07/191,297
• Time in Patent Office: 900 Days
• Field of Search: 340/763, 340/764, 340/783, 340/788, 350/269, 350/339 F, 350/345, 350/339 R, 313/468, 313/487, 156/644
• US Class Current: 345/85
• CPC Class Codes: G09F 9/372 the positions of the elements being controlled by the application of an electric field

Abstract

Light losses occurring in an electroscopic display device in which UV radiation (9, 10) is converted into visible light (14, 15, 17) are partly annihilated by making the movable electrodes (7) and the fixed electrodes (4) reflective. The electroscopic display device comprises first and second radiation-transparent supporting plates (2, 3), wherein a plurality of display elements are disposed between the supporting plates (2, 3). A luminescent material (12) is disposed on one of the first and second supporting plates (2, 3) at a viewing side, wherein the luminescent material (12) is disposed between the first and second supporting plates (2, 3) adjacent to and facing the electrodes (4, 7) such that the electrodes (4, 7) reflect radiation emitted by the luminescent material (12) to increase the passage of radiation through the viewing side of the display. An extra advantage is that a diffuse light source can then be used.

Claims

1. A display device comprising

(a) first and second separated, radiation-transparent supporting plates,

(b) a plurality of display elements disposed between said supporting plates, each of said display elements including at least one fixed electrode and at least one movable electrode, said movable electrode being movable relative to said fixed electrode by electrostatic forces, and said movable electrode having two end positions determined by abutment faces, said fixed electrodes and movable electrodes defining a pattern of radiation-transparent apertures,

(c) an electrically insulating layer disposed between said fixed electrodes and said movable electrodes,

(d) a pattern of areas being non-transparent to radiation and being disposed on said fixed electrodes, said pattern of areas being substantially identical in size to said pattern of radiation-transparent apertures, wherein coplanar disposition of said pattern of radiation-transparent apertures and said pattern of areas substantially prevents passage of radiation by said fixed and said movable electrodes,

(e) luminescent material disposed on one of said first and second radiation-transparent supporting plates at a viewing side, said luminescent material being disposed between said first and second radiation-transparent supporting plates adjacent to and facing said electrodes,

(f) radiation source means at a side opposite to said viewing side for emitting radiation of a sufficiently short wavelength to excite said luminescent material, and

(g) reflective surfaces disposed on at least one of said fixed electrodes or said movable electrodes at sides facing said luminescent material to reflect radiation emitted by said luminescent material in a direction to increase passage of radiation through said viewing side.

2. A display device according to claim 1, wherein both said fixed electrodes and said movable electrodes have said reflective surfaces to reflect said radiation emitted by said luminescent material.

3. A display device according to claim 1, wherein said fixed electrodes or said movable electrodes disposed closest to said luminescent material have said reflective surfaces on a side remote from said luminescent material.

4. A display device according to claim 1 or claim 2 or claim 3, wherein said radiation source means emits radiation at a central wavelength of 254 nm, and wherein said luminescent material includes at least one of a blue phosphor of BaMg₂ Al₁₆ O₂₇ :

Eu [as a blue phosphor], a green phosphor of CeMgAl₁₁ O₁₉ ;

Tb [as a green phosphor], and a red phosphor of Y₂ O₃ ;

Eu [as a red phosphor].

5. A display device according to claim 1 or claim 2 or claim 3, wherein said radiation source means emits radiation at a wavelength ranging from 360 to 380 nm.

6. A display device according to claim 1 or claim 2 or claim 3, wherein a transparent counter electrode is disposed between said luminescent material and said one of said first and second radiation-transparent supporting plates.

7. A display device according to claim 1 or claim 2 or claim 3, wherein said radiation source means is a diffuse radiation source.

8. A display device according to claim 7, wherein said radiation source means emits radiation at a central wavelength of 254 nm, and wherein said luminescent material includes at least one of a blue phosphor of BaMg₂ Al₁₆ O₂₇ :

Eu [as a blue phosphor], a green phosphor of CeMgAl₁₁ O₁₉ ;

Tb [as a green phosphor], and a red phosphor of Y₂ O₃ ;

Eu [as a red phosphor].

9. A display device according to claim 7, wherein said radiation source means emits radiation at a wavelength ranging from 360 to 380 nm.