IEC 62341-5-3:2013

IEC 62341-5-3 ®
Edition 1.0 2013-08
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Organic light emitting diode (OLED) displays –
Part 5-3: Measuring methods of image sticking and lifetime

Afficheurs à diodes électroluminescentes organiques (OLED) –
Partie 5-3: Méthodes de mesure de la durée de vie et de la rémanence d'images

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IEC 62341-5-3 ®
Edition 1.0 2013-08
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Organic light emitting diode (OLED) displays –

Part 5-3: Measuring methods of image sticking and lifetime

Afficheurs à diodes électroluminescentes organiques (OLED) –

Partie 5-3: Méthodes de mesure de la durée de vie et de la rémanence d'images

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX U
ICS 31.120; 31.260 ISBN 978-2-8322-1045-1

– 2 – 62341-5-3 © IEC:2013
CONTENTS
FOREWORD . 4

1 Scope . 6

2 Normative references . 6

3 Terms and definitions . 6

4 Measuring configuration . 7

4.1 General . 7

4.2 Light measuring device (LMD) . 7

5 Standard measuring conditions . 7
5.1 Standard measuring environmental conditions . 7
5.2 Standard measuring dark-room condition . 7
5.3 Standard setup conditions . 7
5.3.1 General . 7
5.3.2 Adjustment of OLED display modules . 8
5.3.3 Starting conditions of measurements . 8
5.3.4 Test patterns . 8
5.3.5 Conditions of measuring equipment . 9
6 Measuring methods of image sticking . 9
6.1 Purpose. 9
6.2 Measuring method . 9
6.2.1 Measuring equipment . 9
6.2.2 Measuring procedure . 9
6.3 Analysis and report . 10
6.3.1 Analysis . 10
6.3.2 Report . 12
7 Measuring methods of the luminance lifetime . 13
7.1 Purpose. 13
7.2 Measuring method . 13
7.2.1 Measuring equipment . 13
7.2.2 Measuring procedure . 13
7.2.3 Estimation of luminance lifetime . 14
7.3 Analysis and report . 15
Annex A (informative) Calculation method of equivalent signal level . 17

Annex B (informative) Acceleration test of lifetime measurement . 23
Bibliography . 26

Figure 1 – Measuring system and arrangement . 7
Figure 2 – Test pattern for image sticking . 9
Figure 3 – An example of the burn-in image . 10
Figure 4 – An example of luminance behavior in operation for an OLED display panel
or module . 14
Figure 5 – An example of lifetime estimation with the extrapolation method . 15
Figure 6 – An example of estimated lifetime depending on the time elapsed . 15
Figure 7 – An example of Weibull distribution of lifetime . 16
2 2
Figure A.1 – Measured 10 mA/cm to 80 mA/cm OLED degradation values and
corresponding modelled functions with m = 1/1,7 . 18

62341-5-3 © IEC:2013 – 3 –
Figure A.2 – Accumulated colour intensity of IEC 62087:2011 10-min video loop in

RGB subpixel format with equivalent signal distribution chart based on the left images,

respectively . 21

Figure A.3 – Accumulated colour intensity of the IEC 62087:2011 10-min video loop in

W, R, G, and B format, with equivalent signal distribution chart based on the left

images, respectively . 22

Figure B.1 – Examples of Weibull distributions of accelerated lifetime test . 23

Table 1 – An example of measuring distance and radius size. 8

Table 2 – An example of typical value . 12

Table 3 – An example of the image sticking time with reference . 13
Table 4 – An example of the image sticking data at target time . 13
Table 5 – Examples of lifetime measurement . 16
Table A.1 – Examples of the maximum and the minimum equivalent signal levels (8
bits) . 20
Table B.1 – Summary of the acceleration test results in Figure B.1 . 24
Table B.2 – Statistical analysis results of the accelerated lifetime test in Figure B.1 . 24

– 4 – 62341-5-3 © IEC:2013
INTERNATIONAL ELECTROTECHNICAL COMMISSION

____________
ORGANIC LIGHT EMITTING DIODE (OLED) DISPLAYS –

Part 5-3: Measuring methods of image sticking and lifetime

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
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Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
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with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
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4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 62341-5-3 has been prepared by IEC technical committee 110:

Electronic display devices.
The text of this standard is based on the following documents:
FDIS Report on voting
110/474/FDIS 110/501/RVD
Full information on the voting for the approval on this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all the parts in the IEC 62341 series, under the general title Organic light emitting
diode (OLED) displays, can be found on the IEC website.

62341-5-3 © IEC:2013 – 5 –
The committee has decided that the contents of this publication will remain unchanged until

the stability date indicated on the IEC web site under "http://webstore.iec.ch" in the data

related to the specific publication. At this date, the publication will be

• reconfirmed;
• withdrawn;
• replaced by a revised edition, or

• amended.
IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct
understanding of its contents. Users should therefore print this document using a
colour printer.
– 6 – 62341-5-3 © IEC:2013
ORGANIC LIGHT EMITTING DIODE (OLED) DISPLAYS –

Part 5-3: Measuring methods of image sticking and lifetime

1 Scope
This part of IEC 62341 specifies the standard measurement conditions and measurement

methods for determining the image sticking and lifetime of organic light emitting diode (OLED)
display panels and modules. It mainly applies to modules.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and
are indispensable for its application. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 60050 (all parts), International Electrotechnical Vocabulary (available at
)
IEC 62087:2011, Methods of measurement for the power consumption of audio, video and
related equipment
IEC 62341-1-2:2007, Organic light emitting diode (OLED) displays – Part 1-2: Terminology
and letter symbols
IEC 62341-6-1:2009, Organic light emitting diode (OLED) displays – Part 6-1: Measuring
methods of optical and electro-optical parameters
IEC 61966-2-1:1999, Multimedia systems and equipment – Colour measurement and
management – Part 2-1: Colour management –Default RGB colour space – sRGB
CIE 15-2004, Colorimetry
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 62341-1-2:2007 and
IEC 60050-845:1987, as well as the following apply.
3.1
equivalent current density
average current density of a certain pixel calculated from a varying luminance per frame
image in a moving picture so that luminance degradation becomes similar at the same time
Note 1 to entry: See Annex A.
3.2
equivalent signal level
digital code value from 0 to 255 (in the case of 8 bits) transformed from the normalized
luminance of a certain pixel by a gamma function
Note 1 to entry: See Annex A.
62341-5-3 © IEC:2013 – 7 –
4 Measuring configuration
4.1 General
The system diagrams and/or operating conditions of the measuring equipment shall comply

with the structure specified in each item. The measuring system and its arrangement are

shown in Figure 1. The details are referred to in Clause 5.

OLED
display
Display surface
module
Light measuring device
Driving
Driving
power
signal
source
IEC  2151/13
Figure 1 – Measuring system and arrangement
4.2 Light measuring device (LMD)
The LMD as defined in IEC 62341-6-1:2009 shall be used. Specifically, the accuracy of the
LMD at 1 degree of the measurement field angle is recommended as being ≤ ±3%, and with a
repeatability ≤ ±0,5%.
5 Standard measuring conditions
5.1 Standard measuring environmental conditions
The standard measuring environmental conditions specified in IEC 62341-6-1:2009, 5.1, shall
be applied. For image sticking measurements, the environmental temperature shall be
controlled at 25 °C ± 2 °C, otherwise a temperature controlled detector shall be used. (The
stability of the LMD shall be less than 1/5 of the intended detecting difference levels of
luminance and colour.)
5.2 Standard measuring dark-room condition

The standard measuring dark-room conditions specified in IEC 62341-6-1:2009, 5.2, shall be
applied.
5.3 Standard setup conditions
5.3.1 General
For the measurement area, the minimum radius for measurement with the distance and
aperture angle is explained in Table 1.

– 8 – 62341-5-3 © IEC:2013
Table 1 – An example of measuring distance and radius size

Radius of measurement
Distance Aperture angle
field
(mm) (degree)
(mm)
2 10
1 5
0,2 1
0,1 0,5
5.3.2 Adjustment of OLED display modules
The adjustment of OLED display modules specified in IEC 62341-6-1:2009, 5.3.1, shall be
applied.
5.3.3 Starting conditions of measurements
Warm-up time is defined as the time elapsed from the moment of switching on the supply
voltage until repeated measurements of the display show a variation in luminance of less than
2 % per minute. Repeated measurements shall be taken for at least a period of 15 minutes
after starting. The luminance variations shall also not exceed 5 % during the total
measurement.
5.3.4 Test patterns
The test patterns for display devices such as mobile phones, table PCs, monitors and TVs are
shown in Figure 2. In the case of mobiles and tablet PCs, depending on the size of the OLED
display panels or modules and measurement distance between the display and the LMD, if the
pattern size is a smaller area than a 10 mm radius at a 500 mm measurement distance with a
2-degree aperture angle of the LMD, then the aperture angle of the LMD should be set to
cover the pattern area as set in Table 1. The measuring distance and the aperture angle may
be adjusted to achieve a measuring field greater than 500 pixels if the setting of the aperture
angle is difficult. For all applications, the test pattern is used in Figure 2a), and usage method
case for monitors and TVs such as Figure 2b) may be used. In order to get repeatability of
measurement, the measuring location from P to P for TVs type as shown in Figure 2c) are
0 4
set, considering the uniformity of the OLED display panels or modules.

62341-5-3 © IEC:2013 – 9 –
IEC  2152/13 IEC  2153/13
a) – The test pattern for display b) – The test pattern for monitor
devices except monitors and TV devices
and TVs
IEC  215413
c) – Image sticking measuring location
Figure 2 – Test pattern for image sticking
5.3.5 Conditions of measuring equipment
The general conditions in IEC 62341-6-1:2009, 5.3.3.1, shall be applied.
6 Measuring methods of image sticking
6.1 Purpose
The purpose of this method is to measure the image sticking of OLED display panels or
modules.
6.2 Measuring method
6.2.1 Measuring equipment
The following equipment defined in IEC 62341-6-1:2009, 6.1.2, shall be used:
a) power supplies and signal sources for driving,
b) LMD.
6.2.2 Measuring procedure
The OLED display modules shall be set in dark-room conditions for measurement.
1) Initial measurements on full screen pattern

– 10 – 62341-5-3 © IEC:2013
Apply a full white screen driving signal to the OLED display modules over the full screen,

and set all power supplies to the standard operation conditions. However, for some display

applications, the full screen luminance can be reduced, according to 7.3.1 of IEC 62341-6-

1:2009.
Measure the initial spectral radiance or tristimulus values of white at P to P as shown in
0 4
Figure 2c). The initial spectra radiance or tristrimulus values of the primary colours may

also be measured individually.

2) Image burn-in using test pattern

For the test pattern for display devices (except monitors and TVs), set the test input signal
to the OLED display modules to generate a 0 % luminance level over the full screen and a

peak luminance at the test pattern which is located at the centre of the display as shown in

Figure 2a). For monitor and TV, set the peak luminance level over the 4 % window pattern
located in the centre of the display with a 15 % luminance level of the peak luminance
over the background area. For information about guidance, see Annex C of
IEC 62087:2011. If the other pattern is used, it should be based on Annex A of this
document and reported.
Keep the test pattern until the specified time, considering the luminance degradation curve.
For example, the measurement time can be every 1 hour during the first 6 hours, and
every 24 hours during the first 120 hours; then every 72 hours until the target time in the
standard measurement condition. Alternatively keep the test pattern until the target time in
the standard measurement condition.
3) Measurements on full screen pattern
Apply a full white screen driving signal to the OLED display modules over the full screen.
Measure the spectral radiance or the tristimulus values at the same measuring location as
the initial measurement. The initial and final spectra radiance or tristrimulus values of the
individual primary colours may also be measured and reported.
All measurements shall be done at the target time of 400 and 500 hours and shall be reported.
In Figure 3, an example of the burn-in image is shown.

IEC  2155/13
Figure 3 – An example of the burn-in image
6.3 Analysis and report
6.3.1 Analysis
6.3.1.1 Luminance and chromatic deviation method
Image sticking can be characterized by luminance and chromatic deviation.
The image sticking of luminance IS(t) for white is calculated as follows:

62341-5-3 © IEC:2013 – 11 –
 
 
L t) / L (t)
 
i 0
∑
 
i=1
 
(1)
IS(t)= 1− ×100(%)
 
 
L (t ) / L (t )
 
i 0 0 0
∑
 
i=1
 
where
t is the specified measurement time;

t is the initial measurement time;

L  is the luminance of measurement location from P .
i i
∆u’v’(t) caused by image sticking at P over time for white is calculated
Chromatic deviation
0 0
as follows:
2 2
∆u'v'(t) = {u'(t)− u'(t )} +{v'(t)− v'(t )}
(2)
0 0 0
where
t is the specified measurement time;
t is the initial measurement time;
(u’(t), v’(t)) is the white chromaticity value at the specified time;
(u’(t ),v’(t )) is the white chromaticity value at the initial time.
0 0
The average of chromatic deviation ∆u’v’(t) caused by image sticking between different
AVG
measuring locations from P to P for white is calculated as follows:
1 4
 
2 2
 
∆u'v'(t) = {u' (t)− u' (t)} +{v' (t)− v' (t)} / 4 (3)
AVG ∑ i 0 i 0
 
 i=1 
where
t is the specified measurement time;
(u’ (t), v’ (t)) is the chromaticity coordinates of measuring locations of P (i = 1, 2, 3, 4).
i i i
The value of u' and v' can be calculated from the tristimulus value X, Y, and Z using the
following equations:
u'= 4X /(X+ 15Y+ 3Z)
(4)
v'= 9Y /(X+ 15Y+ 3Z)
6.3.1.2 Colour difference method
The image sticking shall be analyzed with ∆E* of the three-dimensional, CIE 1976 L*a*b*
ab
colour space (see CIE 15-2004) following the procedure in 6.2.2. Additional three-dimensional
uniform colour spaces and colour spaces may also be used and identified in the test report.
Each colour point can be plotted on the L*, a*, and b* axes of the CIE L*a*b* colour space by
referencing the peak white tristimulus value (X , Y , Z ) in measuring location P at initial time
n n n 0
t and using the following transformation equations:
– 12 – 62341-5-3 © IEC:2013
L * (t)= 116 f (Y (t)/ Y )−16
i i n
a * (t)= 500[f (X (t)/ X )− f (Y (t)/ Y )] (5)
i i n i n
b * (t)= 200[f (Y (t)/ Y )− f (Z (t)/ Z )]
i i n i n
where
1/ 3 3

x x> (6 / 29)

f (x)=

1 29 4
( ) x+ otherwise

3 6 29
t is the specified measurement time;
L*a*b* is the CIELAB colour coordinates of measuring locations of P (i = 0, 1, 2, 3, 4);
i i
(X , Y , Z ) is the tristimulus value of reference white in measuring location P at initial
n n n 0
time t .
Colour difference formula ∆E* (t) caused by image sticking at P over time for white is
ab 0 0
calculated as follows:
2 2 2
(6)
∆E * (t) = {L * (t)− L * (t )} + {a * (t)− a * (t )} + {b * (t)− b * (t )}
ab 0 0 0 0 0 0 0 0 0 0
where
t is the specified measurement time;
t is the initial measurement time;
is the CIELAB colour coordinates of measuring locations of P .
L*a*b*
0 0
Average of colour difference formula ∆E* (t) caused by image sticking between different
ab AVG
measuring locations from P to P for white is calculated as follows:
1 4
 
2 2 2
  (7)
∆E * (t) = {L * (t)− L * (t )} + {a * (t)− a * (t )} + {b * (t)− b * (t )} / 4
ab AVG ∑ i 0 0 i 0 0 i 0 0
 
i=1
 
where
t is the specified measurement time;
L*a*b* is the chromaticity coordinates of measuring locations of P (i = 1, 2, 3, 4).
i i
6.3.2 Report
6.3.2.1 General
The typical value of image sticking can be reported with specified time, as shown in Table 2. If
other primary colours are used such as red, green and blue, it should be reported.
Table 2 – An example of typical value
Measurement data
time
P Average of P ~ P
Colour
0 1 4
(hour)
X Y Z X Y Z
0 White
1 White
62341-5-3 © IEC:2013 – 13 –
6.3.2.2 Image sticking time
The estimated time of image sticking can be reported with the result of the comparison

between the reference luminance ratio, the chromatic deviation, and the colour difference, as

shown in Table 3.
Table 3 – An example of the image sticking time with reference

Factor Threshold Estimated time

Luminance ratio (IS) 3 %
Chromatic deviation ∆u’v’(t) at P
0 0
0,004
Average of chromatic deviation ∆u’v’(t)
AVG
Colour difference ∆E* (t) at P
ab 0 0
Average of colour difference ∆E* (t)
ab AVG
6.3.2.3 Image sticking data
The image sticking can be reported after target time, as shown in Table 4.
Table 4 – An example of the image sticking data at target time
Time
Factor Result data
(hours)
Luminance ratio (IS)
Chromatic deviation ∆u’v’(t) at P
0 0
Average of chromatic deviation ∆u’v’(t)
AVG
Colour difference ∆E* (t) at P
ab 0 0
Average of colour difference ∆E* (t)
ab AVG
7 Measuring methods of the luminance lifetime
7.1 Purpose
The purpose of this method is to measure the luminance lifetime of the OLED display panels
or modules. The lifetime is the elapsed time required for the luminance to decrease to the

specified fraction of the initial luminance in operation. Unless otherwise specified, the half
luminance lifetime shall be used for lifetime measurements.
7.2 Measuring method
7.2.1 Measuring equipment
The following equipment shall be used:
a) power supplies and signal sources for driving,
b) LMD
7.2.2 Measuring procedure
The OLED display panels or modules shall be set in the standard measuring conditions. The
dark-room conditions shall be applied when the luminance is measured. Apply a full white
screen driving signal to the OLED display panel or module at 100 % grey level, and set all

– 14 – 62341-5-3 © IEC:2013
power supplies to the standard operation conditions. However, for some display applications,

the full screen luminance can be reduced, according to 7.3.1 of IEC 62341-6-1:2009.

Measure the initial luminance and keep the above operating conditions and measure the

luminance of the device under test (DUT) at the specified time. The specified time can be 1, 2,

5, 10, 20, 50, 100, 200, 500, 1 000 and 2 000 days. In Figure 4, an example of the luminance

behavior in operation is shown. When measuring the luminance lifetime, an acceleration

method may be acceptable (see Annex B). If an acceleration method is applied, the

acceleration condition, the acceleration ratio and the theoretical basis of the method shall be

reported.
0 10 000 20 000 30 000 40 000 50 000 60 000
Time  (h)
IEC  2156/13
Figure 4 – An example of luminance behavior in operation
for an OLED display panel or module
7.2.3 Estimation of luminance lifetime
The direct measurement of luminance lifetime would typically take an impractically long time,
exceeding several tens of thousands of hours of panel operation. Extrapolation methods are
applied to shorten the measuring period. Luminance lifetime is a degradation phenomenon of
the light emission from OLED displays. An extrapolation method can be applied to estimate
the lifetime by using a formula which models the degradation with time. This method is based
on the knowledge of the degradation phenomenon.
The degradation phenomenon shows exponential degradation as follows [1] :

1/ n
 
 t
 
L(t)= L(0)exp− (8)
 
a
 
 
 
where
t is the operating time;
L(t) is the luminance value of the degradation phenomena at time t;
L(0) is the initial luminance value of L(t);
a is the constant (relaxation time);
n is the acceleration factor.
—————————
Numbers in square brackets refer to the Bibliography.
Relative luminance  (%)
62341-5-3 © IEC:2013 – 15 –
However, in the case of luminance degradation of OLED displays, this formula does not

coincide with the observed result. Other formulae should be chosen.

In Equation (9), there is a linear relation between ln(L(0) /L(t)) and ln(t).

ln[ln(L(0) / L(t))]= 1/ nln(t)−1/ nln(a) (9)

–0,4
–0,5
–0,6
–0,7
–0,8
–0,9
y = 0,555 6 x – 2,584 4
–1,0
–1,1
–1,2
–1,3
–1,4
–1,5
–1,6
2,0 2,2 2,4 2,6 2,8 3,0 3,2 3,4 3,6 3,8 4,0
ln{ln(t)}
IEC  2157/13
Figure 5 – An example of lifetime estimation with the extrapolation method
With the linear relation, the lifetime may be estimated, using the extrapolation method (Figure
5). To check the suitability of the degradation equation, the drift of the estimated lifetime
should be used. If the formula is appropriate, there will be no significant drift of the estimated
value with the driven time. Examples are shown in Figure 6.

100 000
Underestimated
90 000
Proper model
80 000
Overestimated
70 000
60 000
50 000
40 000
30 000
20 000
10 000
0 2 000 4 000 6 000 8 000 10 000
Time elapsed for lifetime measurement  (h)
IEC  2158/13
Figure 6 – An example of estimated lifetime depending on the time elapsed
7.3 Analysis and report
Generally, the lifetime follows the Weibull distribution, and the lifetime can be expressed with
statistical parameters which represent the Weibull distribution.
ln[ln{L(0)/L(t)}]
Estimated ifetime  (h)
– 16 – 62341-5-3 © IEC:2013
Shape factor: 7,10
Scale factor: 27 426,6
5     Average: 25 674,7
Std. dev.: 4 257,51
15 000 20 000 30 000
Lifetime  (h)
IEC  2159/13
Figure 7 – An example of Weibull distribution of lifetime
The typical value and deviation should be reported for the lifetime. The typical value of the
lifetime can be reported with the average mean time to failure (MTTF) or scale factor of the
Weibull distribution, and the deviation can be reported with the standard deviation or shape
factor of the Weibull distribution. Furthermore, the lifetime may be reported with the value at
the lower 10 % position (B ) in the Weibull distribution [2] (see Table 5).
Table 5 – Examples of lifetime measurement
Items Data
Number of samples 20
MTTF 25 674
Typical values
Scale factor 27 427
Standard deviation 4 258
Deviations
7,10
Shape factor
B 19 977
Percentage  (%)
62341-5-3 © IEC:2013 – 17 –
Annex A
(informative)
Calculation method of equivalent signal level

A.1 Purpose
The purpose of this method is to define the procedure to calculate the equivalent signal level

for the image sticking of a TV type.

A.2 Determining the equivalent signal level
A.2.1 General
Since OLED degradation is not proportional to current density generally, the quantities of
normalized luminance intensity and equivalent current density, which are proportional to
OLED degradation, are defined. It is possible to apply this quantity to the usage model-based
image sticking measuring method. The normalized luminance intensity is in the RGB linear
space and can be converted to the equivalent signal level to apply linear to non-linear
conversion. Further, accurate image sticking simulation for a specific application can be
achieved by computing one image in terms of normalized luminance intensity or equivalent
current density from various kinds of actual usage images and image sources.
A.2.2 Calculation of the normalized luminance intensity
The equivalent current density is calculated using the OLED degradation function. The OLED
degradation function that is normalized by initial luminance is given empirically by the
stretched exponential function:
L(t)
m
∝ Aexp(−KJt ) (A.1)
L(0)
Where L(0) is initial luminance, A, K and m are fitting coefficients depending on the device, J
is current density of the OLED device in subpixel, and t is time of test duration. K and m are
determined from the measurement data. m=1/n, n is the acceleration factor according to
Equations (8) and (9). Figure A.1 shows the measured luminance degradations and fitted
lines according to Equation (A.1).

– 18 – 62341-5-3 © IEC:2013
Degradation time
2 2
1,00
t
f 10 mA/cm 40 mA/cm
P (t , D )
1 f 1
80 mA/cm
20 mA/cm
0,98
t
P (t + t , D )
2 2 f 1
J
0,96
t
t
f
0,94
P (t + t , D )
3 3 f 3
J
0,92
P (3t , D )
eff f eff
t t
f f
t
f J
eff
J J
4 3
0,90
Time
IEC  2160/13
2 2
Figure A.1 – Measured 10 mA/cm to 80 mA/cm OLED degradation values
and corresponding modelled functions with m = 1/1,7
As shown in Figure A.1, this model accurately accounts for the degradation of the OLED as a
function of both time and current density for a typical OLED. By applying this model and
assuming that degradation is additive, one can derive a degradation function for a subpixel
which is degraded by exposure to multiple current densities over time. Therefore, we define
D which is the degradation of a pixel by the temporal sequence of current densities
n
J .J .J …J and N over a time period t . D is calculated as follows.
1 2 3 n f n
1) Consider a first degradation of an OLED, resulting from exposure to current density J
. This degradation is expressed as:
over a time period t
f
m
D = Aexp(− KJ t ) (A.2)
1 1 f
2) Consider an alternate degradation D of an OLED resulting from current density J over a
A 2
time period t . This degradation is expressed as:
m
D = Aexp(− KJ t ) (A.3)
A 2 2
We can now define t , such that it is the time required to make D equal to D .
2 1 A
Accordingly t can be calculated from (A.2) and (A.3) and is expressed as:
m
 J 
t = t (A.4)
2   f
J
 2
Using Equation (A.4), time period t can be scaled to account for differences between
current densities J and J . Therefore, after an OLED is exposed to J for a first time
1 2 1
period and J for a second time period, the resulting degradation can be expressed as:
m
 
1 1
 
 
J m+ J m
m   m
1 2
D = Aexp(− KJ (t + t ) ) = Aexp− K (2t )   (A.5)
2 2 2 f f
 
  

 
 
 
3) Consider the degradation of an OLED over a third time interval t with exposure to current
density J . Degradation D can then be expressed as:
3 2A
L(t)
L(0)
62341-5-3 © IEC:2013 – 19 –
m
D = Aexp(− KJ t ) (A.6)
2A 3 3
Again, defining t such that it is the time required to make D and D equal, t is

3 2 2A 3
calculated from (A.5) and (A.6) and is expressed as:

1 1
 
J m+ J m
 
1 2
t = (2t ) (A.7)
3 f
 
 
J m
  3
Therefore after the third time interval, the degradation D is expressed as:

m
 
1 1 1
 
 
m m m
J + J + J
 
m 1 2 3 m
D = Aexp(− KJ (t + t ) ) = Aexp− K (3t )  (A.8)
3 3 3 f f
 
 3 
 
 
 
 
Thus, after N intervals, D is expressed as:
n
m
D = Aexp(− KJ (Nt ) ) (A.9)
n eff f
is the equivalent current density and is expressed as:
where J
eff
m
 
(J ) m
 
n
J =  (A.10)
eff
∑
 
 N 
n
 
Similarly, since intensity is proportional to current density (i.e., current density can be
computed by scaling intensity by the efficiency, luminance, and area of the OLED), we
can also express normalized luminance intensity I in RGB linear space as:
eff
m
 
m
(I )
 
n
I =  (A.11)
eff ∑
 
N
 
n
 
The normalized luminance intensity I can be transformed to the equivalent signal level
eff
I’ by using the equation specified in IEC 61966-2-1:1999 as follows:
eff
If
I ≤ 0,0031308
eff
I' = 12,92× I (A.12)
eff eff
or if I > 0,0031308
eff
1,0
I' = 1,055× I 2,4− 0,055  (A.13)
eff eff
where signal level I’ is the normalized value from 0 to 1.
eff
Another linear to non-linear conversion can also be used for the normalized luminance
intensity to the equivalent signal level transformation.

– 20 – 62341-5-3 © IEC:2013
A.2.3 Extraction of the equivalent signal level from the IEC 62087:2011 10-min video

loop
The extraction of the maximum and the minimum equivalent signal levels are demonstrated by

using the IEC 62087:2011, 10-min video loop. Assuming the experimental data of m = 1/1,7,

and the transformation equation specified in IEC 61966-2-1 for non-linear to linear and linear
to non-linear conversion, OLED device primaries are the same as that in IEC 61966-2-1, and

take both the RGB and RGBW formats. The maximum and the minimum equivalent signal

levels are summarized in Table A.1. For example, the values are shown in the case where m =

1/1,7, gamma is 2,2, the white point is D65 and the signal is 8 bits. m is the experimental

value, so the maximum and the minimum equivalent signal levels are recalculated from (A.10)

or (A.11) in the case of another m value. They are also recalculated from (A.12) and (A.13) in

case of another gamma value. The images and distribution of signal levels are shown in
Figures A.2 and A.3. In the case of an RGB pixel format display, the test input signal to the
OLED display panels or modules can be set to generate 165, 160, and 163, respectively, as
the maximum equivalent signal level over the 4 % window located in the centre of the display
and 66, 65, and 65, respectively, as the minimum equivalent signal level over the remaining
area simultaneously. However, for the case where the OLED display panels or modules have
more than 3 primaries (i.e. RGBW), the procedure should be separated into multiple
procedures with the multiple combination of the equivalent signals as follows:
Procedure A: 108,0,0 as the maximum signal level, 22,0,0 as the minimum signal level.
Procedure B: 0,85,0 as the maximum signal level, 0,21,0 as the minimum signal level.
Procedure C: 0,0,89, as the maximum signal level,0,0,27 as the minimum signal level.
Procedure D: 151,151,151 as the maximum signal level, 66,66,66 as the minimum signal level.
Table A.1 – Examples of the maximum and the minimum equivalent signal levels (8 bits)
RGB pixe
...