OLED display residual image time evaluation method in practical application environment

Abstract

The OLED display actual application environment under the residual image time evaluation method belongs to the OLED display residual image evaluation technical field, and specifically is an OLED display actual application environment under the residual image time evaluation method.The method is based on the residual image appearance time under the black and white checkerboard display, and the actual application environment under the device residual image time is calculated by combining the actual use mode of the OLED display and the external temperature.The method solves the problem that the existing OLED display residual image appearance time evaluation method is deviated from the actual application environment, and a scientific and reasonable residual image appearance time evaluation method considering the influence of the actual application environment is provided.

Description

Technical Field

[0001] This invention belongs to the field of OLED display performance evaluation technology, specifically a method for evaluating image retention time in a real-world application environment of OLED displays. Background Technology

[0002] OLED, or Organic Light-Emitting Diode, is a rapidly developing emerging display technology that achieves display through the self-illumination of organic materials. This display technology has a series of characteristics such as self-illumination, low-voltage DC drive, all-solid-state, wide viewing angle, light weight, energy saving, and simple process. It is recognized by the industry as the third generation of display technology after LCD and is now increasingly used in portable products such as mobile phones and digital cameras.

[0003] Due to the self-emissive nature of OLED displays, the organic materials in OLED screens age faster due to continuous light emission after displaying static or high-brightness images for an extended period. This results in image retention on the display screen, affecting the usability of the OLED display. The time from when the display is first used until the image retention appears is defined as the retention time.

[0004] According to the conventional evaluation method for afterimage time published in the paper by Wang Junsheng et al., the starting time point is T1, and the OLED display starts and continuously plays the image of the difference color block; at time intervals t, the display switches to playing the image of the pure color block, and the brightness of the pure color block area is tested using a color analyzer; when the brightness difference between the first and second areas of the color block reaches 5%, the time is recorded as T. n If we assume that afterimages are generated, then the afterimage duration is T. n ~T1; otherwise, continue the above process until ghosting occurs. This conventional testing method generally requires tens of thousands of hours. The brightness difference of the color patch image used in this testing method is small, and the color patch image only occupies a small area of ​​the entire display. It does not perform full-screen differential image testing of the display. This testing method cannot characterize the ghosting data under the extreme test conditions of the display. In addition, this testing method only evaluates the ghosting time under the enumeration method and does not introduce relevant factors that affect the ghosting time. Summary of the Invention

[0005] The purpose of this invention is to propose a method for evaluating image retention in a near-real-world application environment, which can be used to comprehensively evaluate image retention time in a near-real-world application environment.

[0006] The present invention discloses a method for evaluating the ghosting time of an OLED display in a practical application environment. The method is characterized by: using a full-screen black-and-white checkerboard display, which establishes extreme conditions for differentiated image brightness differences; confirming the ghosting occurrence time under the checkerboard conditions by displaying a full-screen black-and-white image; and calculating the ghosting time in the actual application environment by combining the actual usage mode of the OLED display and the ambient temperature. Specifically:

[0007] ①RI act =RI model ×f temp ;

[0008] ②RI model =f model ×RI pattern ;

[0009] ③f model =f diff ×f work ;

[0010] ④f diff =[1 / (L diff / L pattern ) 1.7 ];

[0011] Combining the above formulas, we get:

[0012] RI act =RI model ×f temp =f model ×RI pattern ×f temp =f diff ×f work ×RI pattern ×f temp =[1 / (L diff / L pattern ) 1.7 ]×f work

[0013] ×RI pattern ×f temp ;

[0014] In formula ①, RI act RI represents the ghosting time in practical application environments. model f represents the afterimage time in actual usage mode. temp The ambient temperature coefficient is used, with a value range of 0 to 1.

[0015] In equation ②, f model To utilize the mode factor, which is related to differences in display brightness and continuous operation of the monitor, RIpattern The RI is the afterimage time of the black and white checkerboard pattern under actual operating brightness. pattern The calculation method starts with timing the black and white checkerboard display of the OLED display at a set brightness. After a certain time interval, the display is switched to a full white screen. A luminance meter is used to test the brightness difference between adjacent areas of the display area. If the brightness difference is greater than 3%, it is considered that ghosting occurs. The time period from the start of timing to the appearance of ghosting is the ghosting time of the black and white checkerboard display at the actual used brightness.

[0016] In equation ③, f diff To represent the image retention difference caused by the difference in brightness between the displayed image and the checkerboard pattern, a factor is introduced; f work This is the continuous operating factor of the display.

[0017] In formula ④, L diff L represents the ratio of the brightness of the brightest area to the brightness of the darkest area in a real-world display scenario. pattern This represents the brightness ratio of the white area to the black area of ​​the black and white checkerboard pattern under actual usage brightness. The process of establishing Equation ④ is shown below:

[0018] The first step is to establish the relationship between the brightness and lifespan of an OLED device as L. n ×t x =const, where L is the device brightness, t x It is the display lifetime, which is the time it takes for the pixel brightness of an OLED device to decay to half of its original initial brightness. n is 1.7, see the literature "OLED degradation described by using a time-dependent local relaxation model".

[0019] The second step is that because the brightness of display pixels decays at different rates, image burning occurs, also known as image retention (see the book "OLED Organic Electroluminescent Materials and Devices" by Chen Jinxin and Huang Xiaowen, 2007). Therefore, the decay of device pixel brightness, i.e., its lifespan, is closely related to the occurrence of image retention. Based on this conclusion, the relationship between brightness and lifespan can be considered as L... n ×t x =const can also represent the relationship between afterimage time and brightness.

[0020] Thirdly, as mentioned above, we believe L n ×t x =const can also characterize the relationship between afterimage time and brightness, thus establishing the relationship L 使用 n ×t x使用 =const and L棋盘格 n ×t x棋盘格 =const, where L 使用 To use the brightness shown on the screen, L 棋盘格 The brightness of the chessboard pattern image, t x使用 To utilize the device ghosting time under the displayed screen, t x棋盘格 The time of device afterimage under the chessboard grid is n, which takes the value 1.7.

[0021] Fourthly, as mentioned above, device ghosting occurs due to varying degrees of brightness decay among display pixels. For example, the black and white checkerboard pattern uses maximized image brightness differences to represent these differences in pixel brightness decay, thus achieving ghosting testing under checkerboard display conditions. Similarly, under normal display conditions, brightness differences exist between images, leading to ghosting. Because this patent maintains consistent brightness between the displayed image and the checkerboard test image, f is introduced. diff A brightness difference factor is introduced to represent the afterimage difference caused by the relationship between the brightness difference of the display screen and the brightness difference of the checkerboard pattern. A relation f can be established. diff =t x使用 / t x棋盘格 =[1 / (L 使用 / L 棋盘格 ) n ] = [1 / (L diff / L pattern ) n ], where L diff L represents the ratio of the brightness of the brightest area to the brightness of the darkest area in a displayed image. pattern The value of n represents the ratio of the brightness of the white area to the black area of ​​the black and white checkerboard pattern under actual usage brightness, where n takes the value of 1.7.

[0022] Specifically, the image retention time of OLED displays varies under different ambient temperatures, especially at high or low temperatures, where it decreases compared to room temperature. The difference is particularly pronounced at high temperatures, where the image retention time differs significantly from that at room temperature. Therefore, the coefficient of performance (f) for ambient temperature varies with the ambient temperature. temp The associated assignments are shown in Table 1:

[0023] outside temperature <![CDATA[f temp ]]> -45～-30℃ 1 / 3 -29～-15℃ 1 / 2 -14～0℃ 2 / 3 0-14℃ 2 / 3 15-29℃ 1 30-45℃ 1 / 5 45-60℃ 1 / 10

[0024] Table 1.

[0025] Specifically, f work This mainly reflects the continuous working time and RI of the OLED display under the black and white checkerboard pattern. pattern The relationship, f work The associated assignments are shown in Table 2:

[0026]

[0027]

[0028] Table 2.

[0029] Specifically, for OLED displays operating under various ambient temperatures, the specific calculation formula is as follows:

[0030] RI act =[1 / (L diff / L pattern ) 1.7 ]×f work ×RI pattern ×f temp =[1 / (L diff / L pattern ) 1.7 ]×f work ×RI pattern ×f temp1 +[1 / (L diff / L pattern ) 1.7 ]×f work ×RI pattern ×f temp2 +...+[1 / (L diff / L pattern ) 1.7 ]×f work ×RI pattern ×f tempN

[0031] Where N represents the number of temperatures at which the OLED display operates.

[0032] Specifically, for OLED displays with multiple usage modes, the specific calculation formula is as follows:

[0033] RI act =[1 / (L diff / L pattern ) 1.7 ]×f work ×RI pattern ×f temp =[1 / (L diff1 / L pattern1 ) 1.7 ]×f work1 ×RI pattern1 ×f temp + [1 / (L diff2 / L pattern2 ) 1.7 ]×f work2 ×RIpattern2 ×f temp +...+[1 / (L diffM / L patternM ) 1.7 ]×f workM ×RI patternM ×f temp

[0034] Where M represents the number of multiple usage modes of the OLED display.

[0035] Specifically, for OLED displays operating under multiple ambient temperatures and usage modes simultaneously, the specific calculation formula is as follows:

[0036] RI act =[1 / (L diff / L pattern ) 1.7 ]×f work ×RI pattern ×f temp =[1 / (L diff1 / L pattern1 ) 1.7 ]×f work1 ×RI pattern1 ×f temp1 + [1 / (L diff2 / L pattern2 ) 1.7 ]×f work2 ×RI pattern2 ×f temp2 +......+[1 / (L diffM / L patternM ) 1.7 ]×f workM ×RI patternM ×f tempN

[0037] Where N represents the number of temperatures in various temperature environments for the OLED display, and M represents the number of usage modes for the OLED display.

[0038] In actual use of OLED displays, usage patterns and ambient temperature have an impact. The method of this invention takes into account these factors and proposes a scientific and reasonable method for evaluating OLED display image retention. This solves the problem that existing methods for evaluating the time of image retention in OLED displays are detached from the actual application environment, and provides a basis for evaluating the image retention time of OLED display products. Detailed Implementation Plan

[0039] Example 1: The specific usage mode conditions for the OLED display are a brightness of 100 cd / m². 2The test showed that L was displayed on the screen. diff The ratio is 100:1. The ambient temperature and time conditions are: 1 hour at room temperature and 2 hours at 40 degrees Celsius. The calculation of the image retention time of the monitor under actual application conditions is as follows:

[0040] S1: Using a black and white checkerboard pattern, confirm the black and white checkerboard ghosting time (RI) at the specified brightness. pattern When using a brightness of 100 cd / m 2 The black and white checkerboard afterimage time RI pattern The test lasted 6 hours; under these conditions, the black and white checkerboard grid L... pattern The ratio is 10000:1;

[0041] S2: RI was not achieved after 1 hour of use at room temperature. pattern Half of the test time, f work The value is 1.2. Similarly, after 2 hours of use at 40 degrees Celsius, the RI (Recovery Rate) was not reached during the 20-hour usage time at 40 degrees Celsius. pattern Half of the test time, f work It is also 1.2.

[0042] S3: Calculate the afterimage time by combining usage mode conditions and ambient temperature conditions.

[0043] RI act =[1 / (L diff / L pattern ) 1.7 ]×f work ×RI pattern ×f temp =[1 / (L diff / L pattern ) 1.7 ]×f work ×RI pattern ×f temp1 +[1 / (L diff / L pattern ) 1.7 ]×f work ×RI pattern ×f temp2 = [1 / (100 / 10000)] 1.7 ]×1.2×6×1+[1 / (100 / 10000) 1.7 ]×1.2×6 ×(1 / 5)=21700h

[0044] Example 2: The specific usage mode of the OLED display has two stages. The first stage is using a brightness of 100 cd / m². 2 L under the display screen diff The initial contrast ratio is 100:1, with a display time of 1 hour. The second stage uses a brightness of 200 cd / m².2 L under the display screen diff The contrast ratio is 200:1, the display time is 4 hours, and the entire time is used at room temperature. The specific steps to calculate the image retention time of the monitor under real-world application conditions are as follows:

[0045] S1: Using a black and white checkerboard pattern, confirm the black and white checkerboard ghosting time (RI) at the specified brightness. pattern When using a brightness of 100 cd / m 2 The black and white checkerboard afterimage time RI pattern1 The test lasted for 6 hours, using a brightness of 200 cd / m². 2 The black and white checkerboard afterimage time RI pattern2 The test lasted for 3 hours; the brightness was 100 cd / m². 2 Play the black and white checkerboard L pattern1 The ratio is 10000:1, using a brightness of 200 cd / m². 2 Play the black and white checkerboard L pattern2 The ratio is 20000:1;

[0046] S2: The first phase display time is 1 hour, which does not exceed RI. pattern1 Half of the test time, f work1 The value is 1.2, and the second stage uses a brightness of 200 cd / m². 2 The displayed time is 4 hours, exceeding RI. pattern2 Test time, f work2 It is 0.6.

[0047] S3: Calculate the afterimage time by combining usage mode conditions and ambient temperature conditions.

[0048] RI act =[1 / (L diff / L pattern ) 1.7 ]×f work ×RI pattern ×f temp =[1 / (L diff1 / L pattern1 ) 1.7 ]×f work1 ×RI pattern1 ×f temp + [1 / (L diff2 / L pattern2 ) 1.7 ]×f work2 ×RI pattern2 ×f temp = [1 / (100 / 10000)] 1.7 ]×1.2×6×1+[1 / (100 / 10000) 1.7 ] × 0.6 × 3 × 1 = 22606h

[0049] Example 3: The specific usage mode of the OLED display has two stages. The first stage is using it at room temperature with a brightness of 100 cd / m². 2 L under the display screen diff The initial contrast ratio is 100:1, with a display time of 4 hours. The second stage uses a brightness of 200 cd / m². 2 L under the display screen diff With a contrast ratio of 200:1, the display time is 4 hours at a high temperature of 40 degrees Celsius. The specific steps for calculating the image retention time of the monitor in real-world application environments are as follows:

[0050] S1: Using a black and white checkerboard pattern, confirm the black and white checkerboard ghosting time (RI) at the specified brightness. pattern When using a brightness of 100 cd / m 2 The black and white checkerboard afterimage time RI pattern1 The test lasted for 6 hours, using a brightness of 200 cd / m². 2 The black and white checkerboard afterimage time RI pattern2 The test lasted for 3 hours; the brightness was 100 cd / m². 2 Play the black and white checkerboard L pattern1 The ratio is 10000:1, using a brightness of 200 cd / m². 2 Play the black and white checkerboard L pattern2 The ratio is 20000:1;

[0051] S2: The first phase display time is 4 hours, exceeding RI. pattern1 Half of the test time but not more than RI pattern1 Test time, f work1 The value is 1.05, and the second phase display time is 4 hours, exceeding the RI. pattern2 Test time but not exceeding RI pattern2 Twice the test time, f work2 It is 0.6.

[0052] S3: Calculate the afterimage time by combining usage mode conditions and ambient temperature conditions.

[0053] RI act =[1 / (L diff / L pattern ) 1.7 ]×f work ×RI pattern ×f temp =[1 / (L diff1 / L pattern1 ) 1.7 ]×f work1 ×RI pattern1 ×f temp1 + [1 / (Ldiff2 / L pattern2 ) 1.7 ]×f work2 ×RI pattern2 ×f temp2 =[1 / (100 / 10000) 1.7 ]×1.05×6×1+[1 / (100 / 10000) 1.7 ]×0.6×3×(1 / 5)=16728h

Claims

1. A method for evaluating image retention time in practical applications of OLED displays, characterized by: Using a full-screen black-and-white checkerboard display, extreme conditions of differentiated image brightness differences are established. The time of image retention under these checkerboard conditions is determined by displaying a full-screen black-and-white image. Combined with actual OLED display usage patterns and ambient temperature, the image retention time in real-world application environments is calculated. Specifically: RI act =RI model ×f temp =f model ×RI pattern ×f temp =f diff ×f work ×RI pattern ×f temp =[1 / (L diff / L pattern ) 1.7 ]×f work ×RI pattern ×f temp ; Among them, RI act RI represents the ghosting time in practical application environments. model f represents the afterimage time in actual usage mode. temp The ambient temperature coefficient is used, with a value range of 0 to 1; f model To use mode coefficients; RI pattern f is the afterimage time of the black and white checkerboard pattern under actual operating brightness. diff f is the brightness difference factor for the displayed image; work L is the continuous operating factor of the display. diff L represents the ratio of the brightness of the brightest area to the brightness of the darkest area in a real-world display scenario. pattern This represents the brightness ratio between the white and black areas of the black and white checkerboard pattern under actual usage brightness.

2. The method for evaluating image retention time in a real-world application environment of an OLED display as described in claim 1, characterized in that... External temperature and ambient temperature coefficient f temp The associated assignments are shown in the table below:

3. The method for evaluating image retention time in a real-world application environment of an OLED display as described in claim 1, characterized in that... f work The associated assignments are shown in the table below:

4. The method for evaluating image retention time in a real-world application environment of an OLED display as described in claim 1, characterized in that... When an OLED display is used under various ambient temperatures, the specific calculation formula is as follows: RI act =[1 / (L diff / L pattern ) 1.7 ]×f work ×RI pattern ×f temp =[1 / (L diff / L pattern ) 1.7 ]×f work ×RI pattern ×f temp1 +[1 / (L diff / L pattern ) 1.7 ]×f work ×RI pattern ×f temp2 +...+[1 / (L diff / L pattern ) 1.7 ]×f work ×RI pattern ×f tempN Where N represents the number of temperatures at which the OLED display operates.

5. The method for evaluating image retention time in a real-world application environment of an OLED display as described in claim 1, characterized in that... When an OLED display has multiple usage modes, the specific calculation formula is as follows: RI act =[1 / (L diff / L pattern ) 1.7 ]×f work ×RI pattern ×f temp =[1 / (L diff1 / L pattern1 ) 1.7 ]×f work1 ×RI pattern1 ×f temp +[1 / (L diff2 / L pattern2 ) 1.7 ]×f work2 ×RI pattern2 ×f temp +...+[1 / (L diffM / L patternM ) 1.7 ]×f workM ×RI patternM ×f temp Where M represents the number of multiple usage modes of the OLED display.

6. The method for evaluating image retention time in a real-world application environment of an OLED display as described in claim 1, characterized in that... When an OLED display is subjected to multiple ambient temperatures and multiple usage modes simultaneously, the specific calculation formula is as follows: RI act =[1 / (L diff / L pattern ) 1.7 ]×f work ×RI pattern ×f temp =[1 / (L diff1 / L pattern1 ) 1.7 ]×f work1 ×RI pattern1 ×f temp1 +[1 / (L diff2 / L pattern2 ) 1.7 ]×f work2 ×RI pattern2 ×f temp2 +......+[1 / (L diffM / L patternM ) 1.7 ]×f workM ×RI patternM ×f tempN Where N represents the number of temperatures in various temperature environments for the OLED display, and M represents the number of usage modes for the OLED display.

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