WO2021112872A1

WO2021112872A1 - Displays with multiple sizes of lighting elements

Info

Publication number: WO2021112872A1
Application number: PCT/US2019/064936
Authority: WO
Inventors: Te-Yueh LIN; Feng-cheng LIN; Kai-Chun TAI; Yuan-Hsi CHUNG
Original assignee: Hewlett-Packard Development Company, L.P.
Priority date: 2019-12-06
Filing date: 2019-12-06
Publication date: 2021-06-10

Abstract

In one example in accordance with the present disclosure, a display is described. The display includes a plurality of pixels arranged in an array and divided into zones. The display includes a first zone of pixels. In the first zone, first color lighting elements of each pixel of the first zone have a first size. The display includes a second zone of pixels. In the second zone, first color lighting elements of each pixel of the second zone have a second size. The first size is different than the second size.

Description

DISPLAYS WITH MULTIPLE SIZES OF LIGHTING ELEMENTS

BACKGROUND

[0001] Organic light-emitting diodes (OLEDs) are used in different types of displays. OLED displays generate light, generate true black colors, and can be printed. OLED displays have seen increasing use in phones, tablets, and other devices. OLED displays may be able to generate images which are predominantly dark for less energy than other display technologies.

BRIEF DESCRIPTION OF THE DRAWINGS

[0002] The accompanying drawings illustrate various examples of the principles described herein and are a part of the specification. The illustrated examples do not limit the scope of the claims.

[0003] FIG. 1 is a schematic diagram of a display device with pixels having lighting elements of multiple sizes, according to an example of the principles described herein.

[0004] FIG. 2 shows a diagram of two pixels with lighting elements of multiple sizes, according to an example of the principles described herein.

[0005] FIG. 3 shows a layout of two zones on a display in an example of the principles described herein.

[0006] FIG. 4 shows a layout of three zones on a display in an example of the principles described herein.

[0007] FIG. 5 shows a flowchart for a method according to an example of the principles described herein. [0008] FIG. 6 shows a flowchart for a method according to an example of the principles described herein.

[0009] Throughout the drawings, identical reference numbers designate similar, but not necessarily identical, elements. The figures are not necessarily to scale, and the size of some parts may be exaggerated or minimized to more clearly illustrate the example shown. The drawings provide examples and/or implementations consistent with the description. However, the description is not limited to the examples and/or implementations shown in the drawings.

DETAILED DESCRIPTION

[0010] An OLED display is made up of a number of pixels. Each pixel is a region on a display that is colored to form an image. Pixels may be made up of lighting elements. For example, a pixel may include red, green, and blue lighting elements. Lighting elements may be of different sizes from each other. For example, a blue lighting element may experience more rapid decrease in performance over time compared with a red lighting element. Accordingly, a larger blue lighting element may be used to preserve the color balance of the display as the display ages. In some examples, the pixels themselves may have a uniform size across the display. In other examples, the pixels may have varying size across the display.

[0011] In some examples, a pixel may include a white lighting element in addition to the colored lighting elements. Such white lighting elements may enhance the display of white images such as documents or websites. In some displays, the characteristics of the lighting elements are uniform across the display. For example, the blue lighting elements are a constant size across the display and the green lighting elements are a second constant size across the display, etc. However, the present specification describes a varying of the size of the lighting elements across the display. Doing so enhances the lifetime of the display. Specifically, the center of the display includes larger lighting elements and smaller lighting elements (of the same color) are positioned around the periphery of the display. This structure may be coupled with applying a lower power level to the periphery of the display. However, in other examples, a uniform power level is used across the display.

[0012] The performance of OLEDs changes over time. Some factors which may impact the performance of OLEDs over time include the size of the OLEDs and power level applied to the OLEDs. For a display with uniform OLEDs and non-uniform power level applied across the display, the display may exhibit “burn-in” as the OLEDs age. That is, artifacts may result in the display due to the non-uniform aging of the OLEDs. For example, a peripheral zone of pixels which may receive a lower power level may age slower than pixels in a central zone which may receive a higher power level. As a result, the peripheral zone may lighten over time relative to the central zone of the display. When the zones are defined by an abrupt transition, this difference in aging may be readily visible to a user as an artifact. Some users may find this burn-in to be distracting or aesthetically unpleasing. Accordingly, the present specification describes a display that reduces the differences in rates of aging between different portions of the display by varying the size of the lighting elements in different portions of the display.

[0013] For OLEDs of a given volume which make up the lighting elements, higher power levels correlate with shorter lifetimes. Similarly for OLEDs of a given volume, lower power levels correlate with longer lifetimes. Accordingly, when non-uniform power levels are applied to a display of uniform sized lighting elements, the OLEDs with higher power will age faster and OLEDs with lower power levels will age slower. The result is to burn-in the power non-uniformities into the display. This burn-in is visible to a user as the aging of OLEDs tends to degrade the color of the lighting elements, with blue lighting elements experiencing faster change than green or red lighting elements. Smaller lighting elements experience aging faster than larger lighting elements. Accordingly, blue lighting elements may be larger than green and red lighting elements in a display. This size difference helps counter the faster aging of the blue lighting elements compared with the lower energy green lighting element and red lighting element. [0014] By coordinating the size of the lighting elements with the power level applied, the impact of aging may be made more uniform across the display. That is, larger lighting elements are used with higher power level, for example, in the center of the display. Smaller lighting elements are used with lower power level areas around the periphery of the display. This has the impact of reducing power consumption. This also has the impact of aging the perimeter lighting elements at a rate similar to the lighting elements in the center of the display despite the difference in size of the lighting elements in the respective zones.

[0015] Accordingly, by coordinating the aging rate of the lighting elements across a display, the formation of burn-in artifacts can be reduced. In some examples, the aging rate is controlled by using non-uniform sized lighting elements. For example, smaller lighting elements may be located near the periphery of the display. In another example, the power levels applied to zones of the display are controlled depending on the size of the lighting elements in the respective zones. As discussed above, higher power levels are used to increase the aging rate and lower power level are used to decrease the aging rate.

[0016] As used in this specification and the associated claims, the term “power level” indicates an amount of power provided to a zone of the display. The power level may be provided as a voltage, a current, or a current per unit area of the display.

[0017] Specifically, the present specification describes a display. The display includes a plurality of pixels arranged in an array and divided into zones. The display includes a first zone of pixels, wherein first color lighting elements of each pixel of the first zone have a first size; and a second zone of pixels, wherein first color lighting elements of each pixel of the second zone have a second size. The first size is different than the second size.

[0018] Also described in this specification is an organic light-emitting diode (OLED) display. The OLED display includes a frame and an array of OLEDs affixed to the frame. The array includes a first zone of OLEDs, each OLED of a first color having a first size and a second zone of OLEDs of the first color surrounding the first zone and having a second size. In this example, the first size is greater than the second size.

[0019] The present specification also describes a method. The method includes defining a first, central zone and a second, peripheral zone an organic light-emitting diode (OLED) display, wherein lighting elements of a first color in the central zone are larger than lighting elements of the first color in the peripheral zone. The method also includes applying a first power level to OLEDs in the central zone of the OLED display and applying a second power level to OLEDs in the peripheral zone, wherein lighting elements in the peripheral zone have a lower power level as compared to lighting elements in the central zone.

[0020] Turning to the figures, FIG. 1 is a schematic diagram of a display (100) with pixels (110) having lighting elements (130) of multiple sizes, according to an example of the principles described herein.

[0021] The display (100) has pixels (110) arranged in zones (120-1 and 120-2, collectively 120). Each pixel (110-1 and 110-2, collectively 110) includes a lighting element (130-1 and 130-2, collectively 130) that generates a color displayed on the display (100). Each lighting element (130) may be of a different color. For example, one pixel (110) may include a red, blue, and green lighting element (130). In some examples, the sizes of the lighting elements (130) may vary depending on the color generated by the lighting element (130). For example, in a given zone (120), a blue lighting element (130) may be larger than a green lighting element (130) which is in turn larger than a red lighting element (130).

[0022] Lighting elements (130) of a given color may vary in size between zones (120). For example, in the first zone (120-1), the lighting elements (130) of the first color have a first size. These same color lighting elements (130), e.g., red, in the second zone (120-2) have a second, different size. In some examples, each of the colors of lighting elements (130) has the same size ratio between the first zone (120-1) and second zone (120-2). For example, each lighting element (130-2) in the second zone (120-2) may be 86% of the size of the same color lighting element (130-1) in the first zone (120-1). In other examples, the different colors of lighting elements (130) have different relative size ratios in different zones (120). For example, the blue lighting element (130-2) in the second zone (120-2) may be 86% of the size of the blue lighting element (130- 1) in the first zone while the green lighting element (130-2) in the second zone (120-2) may be 82% of the size of the green lighting element (130-1) in the first zone, and the red lighting element (130-2) of the second zone (120-2) may be 90% of the size of the red lighting element (130-1 ) of the first zone (120-1). Put another way, a blue lighting element (130-1 ) in the first zone (120-1) may be 20% larger than a green lighting element (130-1) in the first zone (120-1), but a blue lighting element (130-2) in the second zone (120-2) may be 25% percent larger than a green lighting element (130) in the second zone (120-2).

[0023] In some examples, the second zone (120-2) surrounds the first zone (120-1 ). That is, the first color lighting elements (130-1 ) of the first size of the first zone (120-1) may be located in a center of the display (100). Accordingly, the first color lighting elements (130-2) of the second size of the second zone (120-2) may be located towards a periphery of the display (100), for example, along the edges of the display (100). In contrast to the lighting elements (130-1) of a given color which vary in size between the first zone (120-1) and the second zone (120-2), the pixels (110) in the first zone (120-1) and second zone (120-2) may be of roughly equal size in both zones (120).

[0024] In some examples, the ratio of the sizes of the lighting elements that make up a pixel (110) may be the same, within a given manufacturing tolerance, for the pixels (110) in the first zone (120-1) and pixels (110) in the second zone (120-2). In an example, the pixel dimensions are +/- 20%. In other examples, the relative sizes of the lighting elements (130) are varied as a function of the zone (120). For example, pixels (110-1) in the first zone (120-1) may have a larger blue lighting element (130-1) as compared to red lighting element (130-1) than pixels (110) in the second zone (120-2). The pixels (110) may be uniform across the zones (120). In another example, the pixels (110) also vary in size across the zones (120). Varying the pixel (110) size may be accompanied by remapping the images provided to the display (100). [0025] In some examples, the size of lighting elements (130-2) of a given color in the second zone (120-2) is 80% to 90% of the size of lighting elements (130- 1) of the same color in the first zone (120-1). In another example, the size of lighting elements (130-2) of a first color in the second zone (120-2) is 86% of the size of lighting elements (130-1) of the same color in the first zone (120-1). In an example with a third zone around the second zone (120-2), the size of lighting elements (130) of the first color in the third zone may be 65% to 75% of the size of lighting elements (130-1) of the first color in the first zone (120-1). In an example, the size of lighting elements (130) of a first color in the third zone is 72% of the size of lighting elements (130-1 ) of the same first color in the first zone (120-1).

[0026] In some examples, the sizes of the lighting elements (130) may change continuously from the center to the periphery of the display (100). That is, there may be a gradual and continuous decrease in lighting element (130) size going away from the center of the display (100). In other examples, the size of the lighting elements (130) within each zone (120) is uniform and the boundaries between the zones (120) represent stepwise changes in a size of lighting element (130) of a first color. Such uniform zones (120) may simplify manufacturing of the display (100).

[0027] The use of smaller lighting elements (130-2) around the periphery and larger lighting elements (130-1) toward the center may make the lifetime of the lighting elements (130) more uniform across the display (100). This may be especially true if the periphery, e.g., the second zone (120-2), is powered at a lower power level than the center of the display (100), e.g., the first zone (120- 1)·

[0028] That is, operating a lighting element (130-1) at a higher power level tends to decrease the lifetime of the lighting element (130) and smaller lighting elements (130-2) have a shorter lifetime than larger lighting elements (130). Accordingly, correlating the size of the lighting elements (130) with the power level allows a more uniform lifetime to be achieved across the display (100).

For example, in the present display (100), larger lighting elements (130-1) are operated at higher power level in the first zone (120-1) of the display (100) and smaller lighting elements (130-2) are operated at lower power level in the second zone (120-2) of the display (100). This may provide a more uniform aging profile across the display (100). That is, in this example, the OLED display (100) is operated at a non-uniform power level where the power level applied locally depends on the size of the OLED lighting elements (130). Operating the second zone (120-2) at a lower power level may reduce power consumption for the display (100) compared with operating the entire display (100) at a uniform, higher power level. However, in another example, regardless of the lighting element (130) size, the OLED display (100) is operated at a uniform power level.

[0029] FIG. 2 shows a diagram of two pixels (110) with lighting elements (130) of multiple sizes, in an example of the principles described herein. In the example depicted in Fig. 2, the lighting elements (130) are, in increasing size, red (131), green (132), and blue (133). Note that lighting elements (130) in the pixel (110-1) from the first zone (120-1) are larger than the corresponding lighting elements (130) in the pixel (110-2) from the second zone (120-2). [0030] In this example, the lighting elements (130) retain the same relative proportions in both zones (120). However, in other examples the ratio of the lighting elements (130) sizes may vary between the zones (120). For example, the red lighting element (131) may be smaller by a first percentage, the green lighting element (132) smaller by a second percentage, and the blue lighting element (133) smaller by a third percentage when comparing the lighting elements (130) of the second zone (120-2) to the corresponding lighting elements (130) in the pixel (110-1) of the first zone (120-1).

[0031] The red lighting element (131-1) of the first zone (120-1) may be larger than the red lighting element (131-2) of the second zone (120-2). The green lighting element (132-1 ) of the first zone (120-1 ) may be larger than the green lighting element (132-2) of the second zone (120-2). The blue lighting element (133-1 ) of the first zone (120-1) may be larger than the blue lighting element (133-2) of the second zone (120-1 ).

[0032] FIG. 3 shows a layout of two zones (120) on a display (300), accordingly to an example of the principles described herein. The first zone (120-1) is located in the center of the display (300) (e.g., the first zone (120-1) includes the centermost pixels (110-1) of the display (100)) and the second zone (120-2) is located in the periphery of the display (300) (e.g., the second zone (120-2) does not include the centermost pixels (110-1) of the display (100) and may include the outermost pixels (110-2) of the display (100)).

[0033] In an example, the pixels (Fig. 1 , 110) with the larger lighting elements (130) are located in the first zone (120-1) and the pixels (110) in the second zone (120-2) have smaller lighting elements (130). When a uniform power level is applied to the first zone (120-1) and second zone (120-2), the first zone (120- 1) consumes more power and releases more light than an equal area of the second zone (120-1). Accordingly, the lighting elements (130) in the first zone (120-1) age at roughly the same rate as the smaller lighting elements (130) in the second zone (120-2). This uniform aging keeps the display (300) from developing burn-in artifacts that result from unequal aging of the display (300). [0034] FIG. 4 shows a layout of three zones (120) on a display (400), according to an example of the principles described herein. In this example, the first zone (120-1) is surrounded by a second zone (120-2) which is surrounded by a third zone (120-3).

[0035] As described above, the size of the lighting elements (130) of the pixels (110) of the zones (120) may depend on the zone (120). For example, the first zone (120-1 ) has the largest lighting elements (130) of a first color, the second zone (120-2) has middle sized lighting elements (130) of the first color and the third zone (120-3) has the smallest lighting elements (130) of the first color.

This pattern may hold for all the colors of the lighting elements (130). In other examples, a second color lighting element (130) and/or a third color lighting element (130) may have uniform size across the three zones (120). For example, the blue lighting element (133) may be substantially uniform in size across the three zones (120) while the red or green lighting element (131) varies in size depending on the zone (120). Similarly, the green lighting element (132) may vary to the same degree as the other pixels (110), vary to a different degree, or be of uniform size across the display (100). In this example, the first, central zone (120-1 ) includes the centermost pixels (110-1 ) of the display (100). The second zone (120-2) surrounds the first zone (120-1) and includes pixels (110) which are not the centermost and which are not the most peripheral. The third zone (120-3) is the peripheral or outermost zone (120) and surrounds the second zone (120-2). The third zone (120-3) includes the peripheral pixels (110) located near the edge of the display (100) and does not include the pixels (110-1) located in the center of the display (100).

[0036] FIG. 5 shows a flowchart for a method (500), according to an example of the principles described herein. The method (500) reduces image sticking in an OLED display (Fig. 1 , 100). That is, when the pixels (Fig. 1 , 110) in a display (Fig. 1 , 100) age at non-uniform rates, it can produce artifacts which are visible in the display (Fig. 1 , 100). Specifically, using lower power level near the periphery of the display (Fig. 1 , 100) produces slower aging of the lighting elements (Fig. 1 , 130) that receive the lower power level. The associated pixels (Fig. 1 , 110) and lighting elements (Fig. 1 , 130) then appear brighter than areas which received higher power levels. The boundary between these areas can appear as a line or other artifact in the display (Fig. 1 , 100). To address this, smaller lighting elements (Fig. 1 , 130) are formed in a lower power level region to reduce the disparity in aging of the pixels. This allows a more uniform power level between the first zone (120-1) and the second zone (120-2). The smaller lighting elements (130) may produce a desired reduction in power consumption in the periphery zone (Fig. 1 , 120-2) compared with the center zone (Fig. 1 , 120- 1 ) of the display (Fig. 1 , 100). In addition to the placement of differently sized lighting elements (Fig. 1, 130), power level may be regulated to the different zones (Fig. 1 , 120) to equalize aging across the zones (Fig. 1 , 120).

[0037] According to the method (500), a first, central zone (FIG. 1 , 120-1) and a second, periphery zone (FIG. 1 , 120-2) are defined (block 540) in the OLED display (Fig. 1 , 100). In one example, lighting elements (FIG.12, 130) of a first color in the first, central zone (Fig. 1 , 120-1 ) are larger than lighting elements (Fig. 1 , 130) of the first color in the second, peripheral zone (Fig. 1 , 120-2). The use of larger lighting elements (Fig. 1 , 130) in the central zone (Fig. 1 , 120-1) and smaller lighting elements (Fig. 1 , 130) in the peripheral zone (Fig. 1 , 120-2) provides reduced power consumption compared with uniformly sized lighting elements (Fig. 1 , 130) across the zones (Fig. 1 , 120). The lighting elements (Fig. 1 , 130) of the first color may be blue (Fig. 2, 133), red (Fig. 2, 131), green (Fig. 2, 132), or white lighting elements (Fig. 1 , 130).

[0038] A first power level is applied (block 542) to OLEDs in the central zone (Fig. 1 , 120-1) of the OLED display (Fig. 1 , 100). The first power level powers the OLEDs and causes the OLEDs to illuminate. A byproduct of applying this power level is that the OLEDs’ age, meaning the material which makes up the OLED functions less efficiently. Accordingly, control of the power level allows regulation of the illumination and the aging of the OLEDs in the central zone (Fig. 1 , 120-1).

[0039] A second power level is applied (block 544) to OLEDs in the peripheral zone (Fig. 1 , 120-2). The lighting elements (Fig. 1 , 130) of the first color in the peripheral zone (Fig. 1 , 120-2) have a lower power level as compared to lighting elements (Fig. 1 , 130) of the first color in the central zone (Fig. 1, 120-1). The lower power level in the second, peripheral zone (Fig. 1 , 120-2) allows control over the illumination and aging of the OLEDs which make up the lighting elements (Fig. 1, 130) in the pixels (Fig. 1 , 110) of the second, peripheral zone (Fig. 1 , 120-2).

[0040] In some examples, the pixels (Fig. 1 , 110-1) in the central zone (Fig. 1 , 120-1) of the display (Fig. 1, 100) are brighter than pixels (Fig. 1 , 110-2) in the periphery zone (Fig. 1 , 120-2). In an example, the lighting elements (Fig. 1 ,

130) of the first color in the periphery of the display (Fig. 1 , 100) are 86% of a size of lighting elements (Fig. 1 , 130) of the first color in the center of the display (Fig. 1 , 100). The ratio allows differences in brightness of the lighting elements (Fig. 1 , 130) between the first zone (Fig. 1 , 120-1) and second zone (Fig. 1 , 120-2) while minimizing the power level difference with its associated impact on aging between the two zones (Fig. 1 , 120).

[0041] FIG. 6 shows a flowchart for a method (600) according to an example of the principles described herein. The method (600) includes to define (block 640) a central zone (Fig. 1 , 120-1) and a peripheral zone (Fig. 1 , 120-2) of the OLED display (Fig. 1 , 100), wherein red lighting elements (Fig. 2, 131-1) in the central zone (Fig. 1, 120-1) are larger than red lighting elements (Fig. 2, 131-2) in the peripheral zone (Fig. 1 , 120-2).

[0042] The method (600) includes a first voltage being applied (block 642) to OLEDs in the central zone (Fig. 1 , 120-1 ) of the OLED display (Fig. 1 , 100).

The first voltage powers the OLEDs and causes the OLEDs to illuminate. A byproduct of applying this voltage is that the OLEDs age, meaning the material which makes up the OLED functions less efficiently. Accordingly, control of the voltage allows regulation of the illumination and the aging of the OLEDs in the central zone (Fig. 1, 120-1).

[0043] The method (600) includes a second voltage being applied (block 644) to OLEDs in the peripheral zone (Fig. 1 , 120-2). The red lighting elements (Fig. 2, 131-2) in the peripheral zone (Fig. 1 , 120-2) have a lower voltage as compared to red lighting elements (Fig. 2, 131-1) in the central zone (Fig. 1 , 120-1). The lower voltage in the second, peripheral zone (Fig. 1 , 120-2) allows control over the illumination and aging of the OLEDs which make up the red lighting elements (Fig. 2, 131-2) in the pixels (Fig. 1 , 110-2) of the second, peripheral zone (Fig. 1 , 120-2).

[0044] It will be appreciated that, within the principles described by this specification, a vast number of variations exist. It should also be appreciated that the examples described are examples, and are not intended to limit the scope, applicability, or construction of the claims in any way.

Claims

CLAIMS WHAT IS CLAIMED IS:

1. A display comprising: a plurality of pixels arranged in an array and divided into zones; a first zone of pixels, wherein first color lighting elements of each pixel of the first zone have a first size; and a second zone of pixels, wherein first color lighting elements of each pixel of the second zone have a second size, wherein the first size is different than the second size.

2. The display of claim 1 , wherein the second zone surrounds the first zone.

3. The display of claim 1 , wherein the lighting elements are organic light emitting diodes (OLEDs).

4. The display of claim 1, wherein each pixel comprises a blue, red, and green lighting element.

5. The display of claim 4, wherein the first color is red.

6. The display of claim 4, wherein a pixel in the first zone has a larger ratio of blue lighting element size to red lighting element size than a pixel in the second zone.

7. The display of claim 4, wherein the second size is 80% to 90% of the first size.

8. The display of claim 1 , wherein a size of the first color lighting elements changes continuously from a center of the display towards a periphery of the display.

9. The display of claim 1 , wherein a size of the first color lighting elements are uniform within each zone.

10. An organic light-emitting diode (OLED) display, comprising: a frame; and an array of organic light-emitting diodes (OLEDs) affixed to the frame, the array comprising: a first zone of OLEDs, each OLED of a first color in the first zone having a first size; and a second zone of OLEDs surrounding the first zone, each OLED of the first color in the second zone having a second size, wherein the first size is greater than the second size.

11. The display of claim 10, wherein a size of OLEDs of the first color within each zone are uniform.

12. The display of claim 10, further comprising a third zone of OLEDs surrounding the second zone, wherein:

OLEDs of the first color in the third zone have a third size; the second size is 80 % to 90 % of the first size; and the third size is 65 % to 75 % of the first size.

13. A method, comprising: defining a first, central zone and a second, peripheral zone of an organic light-emitting diode (OLED) display, wherein lighting elements of a first color in the central zone are larger than lighting elements of the first color in the peripheral zone; applying a first power level to OLEDs in the central zone of the OLED display; and applying a second power level to OLEDs in the peripheral zone, wherein OLEDs in the peripheral zone have a lower power density as compared to OLEDs in the central zone.

14. The method of claim 13, wherein pixels formed by the OLEDs in the central zone of the display are brighter than pixels formed by the OLEDs in the peripheral zone.

15. The method of claim 13, wherein a size of OLEDs of the first color in the peripheral zone of the display are 86% of a size of OLEDs of the first color in the central zone of the display.