IEC TR 62715-6-21:2022

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
IEC TR 62715-6-21:2022-11(en)

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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
























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ELECTROTECHNICAL


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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

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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
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, Technical Reports,
Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC Publication(s)”). Their
preparation is entrusted to technical committees; any IEC National Committee interested in the subject dealt with
may participate in this preparatory work. International, governmental and non-governmental organizations liaising
with the IEC also participate in this preparation. IEC collaborates closely 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
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3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
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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.
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.

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– 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
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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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

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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.

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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
...