Printed electronics - Part 502-2: Quality assessment - Organic light emitting diode (OLED) elements - Combined mechanical and environmental stress test methods for flexible OLED elements

IEC 62899-502-2:2019(E) specifies the combined mechanical and environmental stress test methods for flexible OLED (organic light emitting diode) elements fabricated using the printing method. Mechanical stress tests include the static and cycling vending test, and the dynamic and static rolling test.

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Status
Published
Publication Date
23-Jul-2019
Technical Committee
Current Stage
PPUB - Publication issued
Completion Date
24-Jul-2019
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IEC 62899-502-2
Edition 1.0 2019-07
INTERNATIONAL
STANDARD
colour
inside
Printed electronics –
Part 502-2: Quality assessment – Organic light emitting diode (OLED) elements –
Combined mechanical and environmental stress test methods for flexible OLED
elements
IEC 62899-502-2:2019-07(en)
---------------------- Page: 1 ----------------------
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IEC 62899-502-2
Edition 1.0 2019-07
INTERNATIONAL
STANDARD
colour
inside
Printed electronics –
Part 502-2: Quality assessment – Organic light emitting diode (OLED) elements –
Combined mechanical and environmental stress test methods for flexible OLED
elements
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.035.01; 31.260 ISBN 978-2-8322-7220-6

Warning! Make sure that you obtained this publication from an authorized distributor.

® Registered trademark of the International Electrotechnical Commission
---------------------- Page: 3 ----------------------
– 2 – IEC 62899-502-2:2019  IEC 2019
CONTENTS

FOREWORD ........................................................................................................................... 4

INTRODUCTION ..................................................................................................................... 6

1 Scope .............................................................................................................................. 7

2 Normative references ...................................................................................................... 7

3 Terms and definitions ...................................................................................................... 8

4 General ........................................................................................................................... 8

4.1 Overview................................................................................................................. 8

4.2 Structure of measuring equipment .......................................................................... 8

4.3 Standard conditions ................................................................................................ 8

4.4 Standard atmospheric conditions for referee measurements and tests .................... 8

4.5 Standard atmospheric conditions for measurements and tests ................................ 9

4.6 Recovery conditions ................................................................................................ 9

4.7 Operating conditions ............................................................................................... 9

4.8 Flexible OLED element test configuration................................................................ 9

5 Measurements and analysis ............................................................................................ 9

5.1 General ................................................................................................................... 9

5.2 Sample preparation of OLED element(s) for optical and electrical

measurements ...................................................................................................... 10

5.3 Visual inspection ................................................................................................... 10

5.4 IVL characteristics ................................................................................................ 10

5.5 Luminous flux ....................................................................................................... 10

5.6 Mechanical status ................................................................................................. 10

6 Combined mechanical and environmental stress test ..................................................... 10

6.1 Mechanical stress test (deformation) ..................................................................... 10

6.2 Cyclic bending test ................................................................................................ 11

6.2.1 General ......................................................................................................... 11

6.2.2 Purpose ......................................................................................................... 11

6.2.3 Test apparatus .............................................................................................. 11

6.2.4 Testing conditions ......................................................................................... 11

6.2.5 Test procedure .............................................................................................. 11

6.3 Static bending test ................................................................................................ 12

6.3.1 General ......................................................................................................... 12

6.3.2 Purpose ......................................................................................................... 12

6.3.3 Test apparatus .............................................................................................. 12

6.3.4 Testing conditions ......................................................................................... 13

6.3.5 Test procedure .............................................................................................. 13

6.4 Dynamic and static rolling test .............................................................................. 14

6.4.1 General ......................................................................................................... 14

6.4.2 Purpose ......................................................................................................... 14

6.4.3 Test apparatus .............................................................................................. 14

6.4.4 Testing conditions ......................................................................................... 15

6.4.5 Test procedure .............................................................................................. 16

6.5 Environmental testing methods ............................................................................. 16

6.5.1 General ......................................................................................................... 16

6.5.2 Environmental test at certain temperatures .................................................... 16

7 Reports and results ....................................................................................................... 18

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IEC 62899-502-2:2019  IEC 2019 – 3 –

Annex A (normative) IVL measurement methods .................................................................. 19

A.1 General ................................................................................................................. 19

A.2 Measurement method ........................................................................................... 19

A.2.1 General ......................................................................................................... 19

A.2.2 Measurement apparatus ................................................................................ 19

A.2.3 Measurement procedure ................................................................................ 19

A.2.4 Acceptance .................................................................................................... 19

A.2.5 Items for the relevant specification ................................................................ 19

Annex B (normative) Luminous flux measurement methods ................................................. 21

B.1 General ................................................................................................................. 21

B.2 Measurement method ........................................................................................... 21

B.2.1 General ......................................................................................................... 21

B.2.2 Measurement apparatus ................................................................................ 21

B.2.3 Measurement procedure ................................................................................ 22

B.2.4 Acceptance .................................................................................................... 23

B.2.5 Terms for additional definition ........................................................................ 23

Bibliography .......................................................................................................................... 24

Figure 1 – Apparatus for cyclic bending test .......................................................................... 12

Figure 2 – Apparatus for static bending test .......................................................................... 13

Figure 3 – Example of apparatus for rolling test .................................................................... 15

Figure A.1 – Layout of luminous measurement system .......................................................... 20

Figure B.1 – Example of measurement apparatus for luminous flux using an integral

sphere .................................................................................................................................. 22

Table 1 – Standard conditions for referee measurements and tests ........................................ 8

Table 2 – Examples of the test conditions ............................................................................. 17

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– 4 – IEC 62899-502-2:2019  IEC 2019
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
PRINTED ELECTRONICS –
Part 502-2: Quality assessment –
Organic light emitting diode (OLED) elements –
Combined mechanical and environmental stress
test methods for flexible OLED elements
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

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patent rights. IEC shall not be held responsible for identifying any or all such patent rights.

International Standard IEC 62899-502-2 has been prepared by IEC technical committee 119:

Printed Electronics.
The text of this International Standard is based on the following documents:
FDIS Report on voting
119/271/FDIS 119/278/RVD

Full information on the voting for the approval of this International Standard can be found in

the report on voting indicated in the above table.

This document has been drafted in accordance with the ISO/IEC Directives, Part 2.

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IEC 62899-502-2:2019  IEC 2019 – 5 –

A list of all parts in the IEC 62899 series, published under the general title Printed electronics,

can be found on the IEC website.

The committee has decided that the contents of this document will remain unchanged until the

stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to

the specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
A bilingual version of this publication may be issued at a later date.

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.
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– 6 – IEC 62899-502-2:2019  IEC 2019
INTRODUCTION

Electronic devices made by printing processes have very unique characteristics, as they are

flexible, with foldable, rollable and/or conformable capabilities, compared to the electronic

devices made through conventional non-printing processes that are mostly rigid. Given these

characteristics, these devices can show different phenomena from those by non-printing

processes under some conditions. In order to evaluate these phenomena, several unique

evaluation methods are used for these devices made by the printing process. This document

will provide one of them.
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IEC 62899-502-2:2019  IEC 2019 – 7 –
PRINTED ELECTRONICS –
Part 502-2: Quality assessment –
Organic light emitting diode (OLED) elements –
Combined mechanical and environmental stress
test methods for flexible OLED elements
1 Scope

This part of IEC 62899 specifies the combined mechanical and environmental stress test

methods for flexible OLED (organic light emitting diode) elements fabricated using the printing

method. Mechanical stress tests include the static and cycling vending test, and the dynamic

and static rolling test.
2 Normative references

The following documents are referred to in the text in such a way that some or all of their

content constitutes requirements of this document. For dated references, only the edition

cited applies. For undated references, the latest edition of the referenced document (including

any amendments) applies.
IEC 60068-1:2013, Environmental testing – Part 1: General and guidance
IEC 60068-2-2, Environmental testing – Part 2-2: Tests – Test B: Dry heat

IEC 62341-6-1, Organic light emitting diode (OLED) displays – Part 6-1: Measuring methods

of optical and electro-optical parameters

IEC 62341-6-2, Organic light emitting diode (OLED) displays – Part 6-2: Measuring methods

of visual quality and ambient performance

IEC 62341-6-3, Organic light emitting diode (OLED) displays – Part 6-3: Measuring methods

of image quality
IEC 62715-5-1, Flexible display devices – Part 5-1: Measuring methods of optical
performance

IEC 62715-5-3, Flexible display devices – Part 5-3: Visual assessment of image quality and

defects

IEC 62715-6-1, Flexible display devices – Part 6-1: Mechanical test methods – Deformation

tests

IEC 62899-502-1, Printed electronics – Part 502-1: Quality assessment – Organic light

emitting diode (OLED) elements – Mechanical stress testing of OLED elements formed on

flexible substrates

IEC 62922, Organic light emitting diode (OLED) panels for general lighting – Performance

requirements
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– 8 – IEC 62899-502-2:2019  IEC 2019
3 Terms and definitions

For the purposes of this document, the terms and definitions given in IEC 62899-502-1 apply.

ISO and IEC maintain terminological databases for use in standardization at the following

addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
4 General
4.1 Overview

The flexible OLED elements can show some level of property variation applied by mechanical

stress in certain environmental conditions such as a hot or cool atmosphere. In order to

evaluate adequately these variations, environmental test conditions combined with a

mechanical test are introduced.
4.2 Structure of measuring equipment

The system diagrams and/or operating conditions of the measuring equipment shall comply

with the structure specification of each item.
4.3 Standard conditions
The standard testing conditions shall be as follows:
– temperature: 25 °C
– atmosphere: 101,3 kPa

If the parameters to be measured depend on temperature and/or pressure, and their

dependence on temperature and pressure is known, the parameter values can be measured

under the conditions specified in 4.5 and corrected by calculation to the standard reference

atmosphere above.
4.4 Standard atmospheric conditions for referee measurements and tests

If the parameters to be measured depend on temperature, pressure and humidity and their

dependence on temperature, pressure and humidity is unknown, the atmospheres to be

specified shall be selected from the following values, as shown in Table 1. The selected

values shall be noted in the relevant specifications.
Table 1 – Standard conditions for referee measurements and tests
a b b
Temperature Relative humidity Air pressure
°C % RH kPa
20 ± 1 (close)/ ± 2 (wide) 63 to 67 (close), 60 to 70 (wide) 86 to 106
25 ± 1 (close)/ ± 2 (wide) 48 to 52 (close), 45 to 55 (wide) 86 to 106
30 ± 1 (close)/ ± 2 (wide)
45 to 75 86 to 106
35 ± 1 (close)2/ ± 2 (wide)

The close tolerances may be used for the referee measurements. The wider tolerances

may be used only when allowed by the relevant specification.
Inclusive values.
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IEC 62899-502-2:2019  IEC 2019 – 9 –
4.5 Standard atmospheric conditions for measurements and tests

Unless otherwise specified, all tests and measurements shall be carried out under standard

atmospheric conditions:
– temperature: (25 ± 5) °C
– relative humidity: (60 ± 15) %
– atmospheric pressure: (96 ± 10) kPa
4.6 Recovery conditions
The recovery conditions specified in IEC 60068-1:2013, 4.4 shall be applied.

The OLED element shall be subjected to the recovery procedure in the chamber or otherwise

as appropriate.

The OLED element shall then remain under standard atmospheric conditions for recovery for

a period adequate for the attainment of temperature stability, for a minimum of 1 h.

If required by the relevant specification, the element shall be switched on or loaded and

measured continuously during the recovery period.

If the standard conditions given above are not appropriate for the device to be tested, the

relevant specification may call for other recovery conditions.
4.7 Operating conditions

Apply the proper driving current and voltage to the OLED element to provide luminosity at

normal intended operation.
4.8 Flexible OLED element test configuration

Unless otherwise specified, the OLED element shall be tested in a state that is ready for

normal operation without any protective elements added, nor voltage applied.
5 Measurements and analysis
5.1 General

Both before and after the combined stress testing in Clause 6, the following measurements on

the electrical, optical and mechanical characteristics of OLED element(s) shall be performed

in the standard environmental conditions defined in Clause 4. Measurement samples shall be

prepared according to 5.2 before the measurements defined in 5.3 and 5.4. Both IEC 62922

and IEC 62341-6-1 are applied to measure the optical and electro-optical parameters.

a) Visual inspection (see 5.3): Visual inspection shall be performed according to IEC 62715-

5-3.

b) IVL (intensity of electric current, voltage, luminance) characteristics (see 5.4).

c) Luminous flux (see 5.5): Optical performance measurement shall refer to IEC 62715-5-1.

d) Mechanical status (5.6).

e) Image quality: Image quality measurement shall refer to IEC 62341-6-2 and IEC 62341-6-3.

Depending on the purpose of the test, only one, some, or all of the methods shall be used.

The measuring frequency and evaluation criteria shall be specified in the detailed

specifications.
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– 10 – IEC 62899-502-2:2019  IEC 2019

NOTE Measurements of luminous intensity distribution and maintenance of luminous flux are important

parameters for OLED elements, however these measurements, in particular for maintenance of luminous flux, can

cause degradation of OLED elements which will disturb evaluation of the mechanical stress testing of OLED

elements. Since these measurements would be applicable for an evaluation as a final product, but not practically

suitable for an evaluation as an element for this case, they are eliminated for evaluating the OLED elements both

before and after the mechanical stress testing.

5.2 Sample preparation of OLED element(s) for optical and electrical measurements

Before and after the combined stress test, the specimens are evaluated by putting them on a

flat surface with appropriate support. In addition, the specimens used for the measurement

shall be of appropriate geometry for mechanical stress testing. If some are small or have a

narrow edge that will make clamping impossible for mechanical testing, they should be fixed

on a bendable support substrate with a suitable adhesive strip or glue. Both adhesive strip

and glue should not influence the measurement.

For precise optical measurements, it is very important to define the alignment of the

measurement specimen because flexible printed OLED element(s) can be easily deformed by

an external force. Measurements of the optical and electrical characteristics of flexible

element(s) shall be made with the light emitting area aligned in a flat state. If flexible

element(s) are aligned in a curved state, it will be difficult to make precise optical

measurements. The measurement element(s) shall be supported or fixed to be flat.

The flatness and size of the sample(s) shall be separately agreed in writing between supplier

and customer.

NOTE In some cases, the testing sample might be short or have a very narrow clamping edge for the mechanical

stress testing.
5.3 Visual inspection

As stated in 5.1 a), visual inspection shall be performed according to IEC 62715-5-3.

5.4 IVL characteristics

Measurements of IVL characteristics shall be performed using the electrical testing method as

shown in Annex A. Measurements are considered to have failed when the sample is

electrically leaky due to a short circuit. A short circuit of the element(s) can be caused by the

extraordinarily large current flowing between the anode and cathode on the element(s).

5.5 Luminous flux

Measurement of the luminous flux, namely the light intensity of the light source, is performed

according to Annex B.
5.6 Mechanical status
Measure the shape of the OLED element based upon the requirements.
6 Combined mechanical and environmental stress test
6.1 Mechanical stress test (deformation)

There are several mechanical stress test methods described in IEC 62715-6-1. Depending on

the requirement(s), one or more proper mechanical stress test(s) is chosen, and the test

equipment is prepared accordingly. The mechanical stress test apparatus shall work properly

in an environmental chamber. Environmental stress is described in 6.5.

NOTE In order to avoid redundancy of description, this document only describes the cyclic bending test as an

example of mechanical stress.
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IEC 62899-502-2:2019  IEC 2019 – 11 –
6.2 Cyclic bending test
6.2.1 General

This procedure is for conditioning the sample under mechanical stress by repeated bending.

6.2.2 Purpose

The purpose of this test is to provide a standard procedure for evaluating the robustness of a

flexible display against a cyclic bending stress which might typically happen in application.

The bending properties might cover several typical parameters of the characteristics of the

quality of the OLED elements.
6.2.3 Test apparatus

The cyclic bending test equipment includes the clamp to hold a bending test sample, the

moving part, the control system which regulates the number of cyclic bendings, the moving

distance, and the moving speed while testing. The specimen shall be securely clamped with a

gripping part during the test. An example of cyclic bending test equipment is shown

in Figure 1.

To evaluate cyclic bending without putting another force, such as tension, U-shaped cyclic

bending equipment can be preferable.
6.2.4 Testing conditions
Testing conditions are specified as follows:
– bending radius
r (bending radius): 50 mm, 40 mm, 20 mm, 10 mm
– bending velocity, procedure for one cycle
t ( time for one bend and interval ): 0,5 s, 1 s, 2 s, 3 s, 5 s, 10 s
– load
– number of repeating cycles
– criteria for acceptance
– number of samples

– the bending inner surface is the top surface (face-up) or the back side surface (face-down)

– bending direction: either X (bending along the longer edge) or Y (bending along the

shorter edge) of the specimen
NOTE 1 The numerical values of the test conditions are examples.

NOTE 2 The criteria for acceptance include the visual performance and sample geometry both before and after

the stressing.
All conditions shall be reported i
...

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