Colour Electroluminescent Display Device and its Driving Method

• US 20070222800A1
• Filed: 04/15/2005
• Published: 09/27/2007
• Est. Priority Date: 04/16/2004
• Status: Active Grant

• Current Assignee: Innolux Hong Kong Holding Ltd (InnoLux Corporation)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Van Woudenberg, Roel, Fish, David, Hoppenbrouwers, Jurgen, Van Der Vaart, Nijs, Budzelaar, Franciscus, Childs, Mark
• Granted Patent: US 7,791,565 B2
• Time in Patent Office: Days
• US Class Current: 345/694
• CPC Class Codes: G09G 2300/0452 Details of colour pixel setup, e.g. pixel composed of a red, a blue and two green components
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2320/043 Preventing or counteracting the effects of ageing
• CPC Class Codes: G09G 2320/0666 for control of colour parameters, e.g. colour temperature
• CPC Class Codes: G09G 3/3233 with pixel circuitry controlling the current through the light-emitting element
• CPC Class Codes: H01L 27/156 two-dimensional arrays
• CPC Class Codes: H10K 59/12 Active-matrix OLED [AMOLED] displays
• CPC Class Codes: H10K 59/351 comprising more than three subpixels, e.g. red-green-blue-white [RGBW]

Abstract

A colour electroluminescent, EL, display device comprising an array of pixels (11) each comprising sub-pixels (1) of two or more colours (R, G, B). For at least one of the colours (R, G, B), the pixel (11) comprises a first sub-pixel (R_L, G_L, B_L) comprising a first EL material and a second sub-pixel (R_c, G_c, B_c) comprising a second EL material. The first EL material is of higher lifetime than the second EL material; the second EL material has better colour points and/or better colour rendition properties than the first EL material. In some embodiments a pixel comprises two red sub-pixels (R_L, R_c), two green subpixels (G_L, G_c) and two blue sub-pixels (B_L, Bc), one sub-pixel of each colour (R_L, G_L, B_L) comprising relatively high lifetime EL material and the other sub pixel of each colour (R_c, G_c, B_c) comprising relatively good colour points EL material. In other embodiments a pixel comprises two blue sub-pixels (B_L, B_c) but only one red sub-pixel and one green sub-pixel.

Claims

1. A colour electroluminescent, EL, display device comprising an array of pixels (11);

wherein;

each pixel (11) comprises sub-pixels (1) of two or more main colours;

for at least one of the main colours, the pixels (11) comprise first sub-pixels (R_L, G_L, B_L) of the main colour comprising a first EL material and second sub-pixels (R_C, G_C, B_C) of the main colour comprising a second EL material;

the first EL material is of a higher lifetime than the second EL material; and

the second EL material has a better colour point and/or better colour rendition properties than the first EL material.

2. A display device according to claim 1, wherein each pixel (11) comprises a said first sub-pixel (R_L, G_L, B_L) of the main colour comprising a first EL material and a said second sub-pixel (R_C, G_C, B_C) of the main colour comprising a second EL material.

3. A display device according to claim 2, further comprising circuitry (12) arranged to drive the display device such that when a colour or colour hue to be displayed by the pixel can be provided with a sufficient colour contribution of the main colour of the first and second sub-pixels by driving the first sub-pixel (R_L, G_L, B_L) without driving the second sub-pixel (R_C, G_C, B_C), then the first sub-pixel (R_L, G_L, B_L) is driven but not the second sub-pixel (R_C, G_C, B_C);

and further arranged such that when the colour or colour hue to be displayed cannot be provided with a sufficient colour contribution of the main colour of the first and second sub-pixels by driving the first sub-pixel (R_L, G_L, B_L) without driving the second sub-pixel (R_C, G_C, B_C) then the second sub-pixel (R_C, G_C, B_C) is driven.

4. A display device according to claim 3, wherein the driving circuitry (12) is arranged such that, when the colour or colour hue to be displayed cannot be provided with a sufficient colour contribution of the main colour of the first and second sub-pixels by driving the first sub-pixel (R_L, G_L, B_L) without driving the second sub-pixel (R_C, G_C, B_C), then the second sub-pixel (R_C, G_C, B_C) is driven in addition to driving the first sub-pixel (R_L, G_L, B_L).

5. A display device according to claim 3, wherein the driving circuitry (12) is arranged such that, when the colour or colour hue to be displayed cannot be provided with a sufficient colour contribution of the main colour of the first and second sub-pixels by driving the first sub-pixel (R_L, G_L, B_L) without driving the second sub-pixel (R_C, G_C, B_C), then the second sub-pixel (R_C, G_C, B_C) is driven instead of driving the first sub-pixel (R_L, G_L, B_L).

6. A display device according to claim 1, wherein, for each of the main colours, the pixels comprise first sub-pixels (R_L, G_L, B_L) of the main colour comprising a first EL material and second sub-pixels (R_C, G_C, B_C) of the main colour comprising a second EL material;

the first EL material is of a higher lifetime than the second EL material; and

the second EL material has a better colour point and/or better colour rendition properties than the first EL material.

7. A display device according to claim 1, wherein, for only the main colour blue, the pixels comprise first blue sub-pixels (B_L) comprising a first EL material and second blue sub-pixels (B_C) comprising a second EL material;

the first EL material is of a higher lifetime than the second EL material; and

the second EL material has a better colour point and/or better colour rendition properties than the first EL material.

8. A display device according to claim 7 when dependent from claim 1, wherein some of the pixels comprise a said first blue sub-pixel (B_L) and not a said second blue sub-pixel (B_C);

and the remaining pixels comprise a said second blue sub-pixel (B_C) and not a said first blue sub-pixel (B_L).

9. A display device according to claim 1, wherein the main colours are red, green and blue.

10. A method of driving a colour electroluminescent, EL, display device, comprising:

determining whether a sufficient colour contribution to a colour hue to be displayed can be provided by a first sub-pixel (R_L, G_L, B_L) of a pair of colour sub-pixels of a given colour, wherein the first sub-pixel (R_L, G_L, B_L) of the pair comprises a first EL material and the second sub-pixel (R_C, G_C, B_C) of the pair comprises a second EL material, the first EL material being of a higher lifetime than the second EL material, and the second EL material having better colour points and/or better colour rendition properties than the first EL material;

if a sufficient colour contribution can be provided, driving the first sub-pixel (R_L, G_L, B_L) but not the second sub-pixel (R_C, G_C, B_C); and

if a sufficient colour contribution cannot be provided, driving the second sub-pixel (R_C, G_C, B_C).

11. A method according to claim 10, wherein, if a sufficient colour cannot be provided, the step of driving the second sub-pixel (R_C, G_C, B_C) is performed in addition to driving the first sub-pixel (R_L, G_L, B_L) such that both the first and second sub-pixel make a colour contribution to the colour hue to be displayed.

12. A method according to claim 10, wherein, if a sufficient colour cannot be provided, the step of driving the second sub-pixel (R_C, G_C, B_C) is performed instead of driving the first sub-pixel (R_L, G_L, B_L) such that the second sub-pixel (R_C, G_C, B_C) makes a colour contribution to the colour hue to be displayed but the first sub-pixel (R_L, G_L, B_L) does not make a contribution to the colour hue to be displayed.