IEC TR 62715-6-21:2022

Flexible display devices - Part 6-21: Mechanical test methods - Foldable durability test for foldable display set

IEC TR 62715-6-21:2022, which is a technical report, provides information about various folding types and hinge structures of foldable products which can affect the durability of a foldable panel. This document focuses only on the issues concerning the foldable products and will not include product parts that do not affect display durability such as speakers, batteries, communication ports.

General Information

• Status: Published
• Publication Date: 03-Nov-2022
• ICS: 31.120 - Electronic display devices
• Technical Committee: TC 110 - Electronic displays
• Drafting Committee: WG 8 - TC 110/WG 8
• Current Stage: PPUB - Publication issued
• Start Date: 04-Nov-2022
• Completion Date: 05-Dec-2022

Overview

IEC TR 62715-6-21:2022 is an International Electrotechnical Commission (IEC) technical report that addresses the mechanical durability of foldable display devices. Specifically, this report provides detailed information about various folding methods and hinge structures in foldable products, which play a critical role in the durability and reliability of foldable display panels. It focuses on aspects that directly affect the longevity and mechanical performance of the display component, excluding unrelated parts such as speakers, batteries, or communication ports. As flexible and foldable display technology is increasingly adopted in consumer electronics, this guidance is vital for manufacturers, testers, and quality control professionals.

Key Topics

• Folding Types:
  The report categorizes foldable products based on folding method:

  • In-folding: The light-emitting surface folds inward, protecting the display but increasing folding stress due to a smaller radius of curvature (R value).
  • Out-folding: The light-emitting surface folds outward, making the display more vulnerable but experiencing less folding stress.
  • Multi-folding: Panels that fold at multiple points (e.g., "Z-type" in-out folding or "G-type" in-in folding), anticipated for future product generations.
  • In and out-folding: Products designed to fold both inward and outward, providing greater flexibility.

• Hinge Structures:
  Comprehensive analysis of hinge designs and their impact on durability:

  • Constant R type: Maintains a relatively consistent radius of curvature during folding.
  • Varying R type: Features a changing radius for improved stress distribution and reduced crease formation.
  • The hinge structure influences product thickness, weight, folding angle, and the unfolding experience.

• Durability Testing:
  Guidance on key parameters influencing mechanical durability:

  • Angle of folding and unfolding: Consistent maintenance of folding angles (typically 0°–180°, potentially up to 360° for advanced designs) is crucial.
  • Radius of curvature (R value): Consistent R value ensures reliable durability testing.
  • Folding angular speed: Speed and intervals of folding directly affect applied mechanical stress and are standardized in durability assessments.

Applications

• Consumer Electronics:
  Manufacturers of foldable smartphones, tablets, and laptops benefit from standardized test methods, ensuring product reliability during real-world handling.
• Product Design and Development:
  Engineers and designers use this report to optimize hinge structures and folding mechanisms, reducing failure rates and improving user experience.
• Quality Assurance and Testing:
  Testing laboratories apply the durability test methods detailed in this report to validate the mechanical integrity of foldable display panels.
• Innovation and Future Products:
  By classifying future folding types (multi-folding and bi-directional folding), the standard supports the development of novel flexible display devices.

Related Standards

• IEC 62715-6-1:
  Addresses mechanical test methods for flexible display devices, including deformation and cyclic bend tests referenced in this report.
• IEC 62715-6-22:
  (Under development) Will specify methods for measuring crease and waviness in foldable panels, complementing durability testing covered in IEC TR 62715-6-21.
• IEC 62715 Series:
  A comprehensive series covering mechanical, optical, and environmental test methods applicable to flexible and foldable display device technologies.

Practical Value

Implementing IEC TR 62715-6-21:2022 enables organizations to:

• Increase product lifespan and customer satisfaction by ensuring robust folding mechanisms.
• Benchmark durability across manufacturers with harmonized testing practices.
• Identify and avoid design pitfalls that compromise display durability in foldable devices.
• Prepare for evolving consumer expectations and advance the state of foldable electronic devices through standardized engineering practices.

This technical report serves as a foundation for developing reliable, high-performance foldable display products in a rapidly growing market.

Standards Content (Sample)

IEC TR 62715-6-21 ®
Edition 1.0 2022-11
TECHNICAL
REPORT
colour
inside
Flexible display devices –
Part 6-21: Mechanical test methods – Foldable durability test for foldable display
set
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IEC TR 62715-6-21 ®
Edition 1.0 2022-11
TECHNICAL
REPORT
colour
inside
Flexible display devices –
Part 6-21: Mechanical test methods – Foldable durability test for foldable

display set
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 31.120 ISBN 978-2-8322-6013-5

– 2 – IEC 62715-6-21:2022 © IEC:2022
CONTENTS
FOREWORD . 3
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 Foldable devices technology . 6
4.1 General . 6
4.2 Classification of folding product . 6
4.2.1 General . 6
4.2.2 In-folding products . 6
4.2.3 Out-folding products . 7
4.2.4 Multi-folding products . 7
4.2.5 In and out-folding products . 8
4.3 Hinge structure . 8
4.3.1 General . 8
4.3.2 Role of the hinge structure . 9
4.3.3 Types of hinge structure . 12
5 Durability items of folding products . 12
5.1 General . 12
5.2 Angle of folding and unfolding . 13
5.3 Radius of curvature of folding area . 13
5.4 Folding angular speed . 13
Bibliography . 14

Figure 1 – Example of in-folding product . 6
Figure 2 – Example of out-folding product . 7
Figure 3 – R comparison of in-folding versus out-folding . 7
Figure 4 – Example of multi-folding Z-type product . 8
Figure 5 – Example of multi-folding G-type product . 8
Figure 6 – In and out-folding products . 8
Figure 7 – General hinge structure . 9
Figure 8 – Flip phone . 9
Figure 9 – Angle of folding and unfolding . 10
Figure 10 – Constant R type hinge . 12
Figure 11 – Varying R type hinge . 12

IEC 62715-6-21:2022 © IEC:2022 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
FLEXIBLE DISPLAY DEVICES –
Part 6-21: Mechanical test methods –
Foldable durability test for foldable display set

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
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rights. IEC shall not be held responsible for identifying any or all such patent rights.
IEC TR 62715-6-21 has been prepared by IEC technical committee 110: Electronic displays. It
is a Technical Report.
The text of this Technical Report is based on the following documents:
Draft Report on voting
110/1426/DTR 110/1435A/RVDTR
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this Technical Report is English.

– 4 – IEC 62715-6-21:2022 © IEC:2022
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/standardsdev/publications.
A list of all parts in the IEC 62715 series, published under the general title Flexible display
devices, 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.

IMPORTANT – The "colour inside" logo on the cover page of this document indicates that it
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contents. Users should therefore print this document using a colour printer.

IEC 62715-6-21:2022 © IEC:2022 – 5 –
FLEXIBLE DISPLAY DEVICES –
Part 6-21: Mechanical test methods –
Foldable durability test for foldable display set

1 Scope
This part of IEC 62715, which is a technical report, provides information about various folding
types and hinge structures of foldable products which can affect the durability of a foldable
panel. This document focuses only on the issues concerning the foldable products and will not
include product parts that do not affect display durability such as speakers, batteries,
communication ports.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions 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
3.1
foldable panel
flexible display panel which can be folded
3.2
foldable display set
foldable product
device to which a foldable panel is applied
3.3
in-folding
method used to fold the light emitting surface inward
3.4
out-folding
method used to fold the light emitting surface outward
3.5
multi-folding
method used to fold more than once in different positions
EXAMPLE The different folding positions can be in-out Z type or in-in G type.
3.6
in and out-folding
method used to fold in both the inward and outward direction

– 6 – IEC 62715-6-21:2022 © IEC:2022
3.7
R value
radius of curvature of the folding area
3.8
folding area
curved section of the panel due to folding
4 Foldable devices technology
4.1 General
The foldable product market has been growing steadily and the demand for foldable display
panels is expected to increase in the future. The first foldable product was launched in 2019
and since then, various types of foldable products have been released during the past three
years.
In 4.2, some of the techniques of the foldable product which affect the durability of the foldable
panels are discussed.
4.2 Classification of folding product
4.2.1 General
The foldable product can be classified according to the folding method. The types of products
released so far include in-folding and out-folding. Multi-folding (in-in folding, in-out folding) is
expected in the future.
4.2.2 In-folding products
Figure 1 – Example of in-folding product
A foldable panel with the light emitting surface folded inward is called “in-folding” panel, and an
“in-folding” product means a device to which the in-folding panel is applied. Figure 1 shows the
most common type of the in-folding products. Such in-folding products have an advantage in
that the panel surface can be protected in terms of durability because the panel is located inside
the foldable product when folded.
On the other hand, since the R value for in-folding is smaller, more sophisticated technology is
needed to ensure device durability.
As the R value becomes smaller, the folding stress that the panel experiences increases. To
mitigate this stress, the technology of the material, stack structure and module design will be
optimized so that it can buffer against the folding stress.

IEC 62715-6-21:2022 © IEC:2022 – 7 –
4.2.3 Out-folding products
The “out-folding” panel has a light emitting surface on the outside of the panel when folded, and
an “out-folding” product means the device to which the out-folding panel is applied as shown in
Figure 2.
Figure 2 – Example of out-folding product
These out-folding products have a disadvantage with respect to durability because the surface
of the foldable panel is exposed outward when folded so it is easily damaged. It is also more
difficult to manage the flatness of the display surfaces when users configure the product in the
unfolded state. This can cause distortion and bend of the display when viewed by the user. In
addition, the screen can malfunction if it is unintentionally touched in the folded state.
On the other hand, compared to in-folding products, the R value for out-folding products is larger
and results in a reduction of the folding stress. Figure 3 shows the R comparison between in-
folding and out-folding products.

Figure 3 – R comparison of in-folding versus out-folding
4.2.4 Multi-folding products
Although they have not been released yet, it is expected
...