IEC 61747-40-1:2013

Liquid crystal display devices - Part 40-1: Mechanical testing of display cover glass for mobile devices - Guidelines

IEC 61747-40-1:2013 is a mechanical performance testing guideline for cover glass used in electronic flat panel displays in mobile devices. This document focuses on key mechanical testing performance parameters and covers mainly strength and damage resistance attributes. The test methods will focus on the cover glass level testing only.

Dispositifs d'affichage à cristaux liquides - Partie 40-1: Essais mécaniques des verres protecteurs des affichages pour les dispositifs mobiles - Lignes directrices

La CEI 61747-40-1:2013 constitue les lignes directrices des essais de performances mécaniques pour les verres protecteurs utilisés dans les dispositifs d'affichages électroniques à écran plat des dispositifs mobiles. Ce document porte essentiellement sur les paramètres clés des performances d'essais mécaniques et il couvre principalement les attributs de résistance et de résistance aux dommages. Les méthodes d'essais seront axées sur les essais du niveau des verres protecteurs uniquement.

General Information

• Status: Published
• Publication Date: 17-Jun-2013
• ICS: 31.120 - Electronic display devices
• Technical Committee: TC 110 - Electronic displays
• Drafting Committee: WG 2 - TC 110/WG 2
• Current Stage: DELPUB - Deleted Publication
• Start Date: 09-Feb-2018
• Completion Date: 17-Apr-2019

Relations

• Revised: IEC 61747-40-1:2019 - Liquid crystal display devices - Part 40-1: Mechanical testing of display cover glass for mobile devices - Guidelines
• Effective Date: 05-Sep-2023

Standards Content (Sample)

IEC 61747-40-1


®


Edition 1.0 2013-06



INTERNATIONAL



STANDARD



NORME
INTERNATIONALE


Liquid crystal display devices –
Part 40-1: Mechanical testing of display cover glass for mobile devices –
Guidelines

Dispositifs d’affichage à cristaux liquides –
Partie 40-1: Essais mécaniques des verres protecteurs des affichages pour les
dispositifs mobiles – Lignes directrices


IEC 61747-40-1:2013

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IEC 61747-40-1



®



Edition 1.0 2013-06







INTERNATIONAL





STANDARD







NORME



INTERNATIONALE











Liquid crystal display devices –

Part 40-1: Mechanical testing of display cover glass for mobile devices –

Guidelines




Dispositifs d’affichage à cristaux liquides –

Partie 40-1: Essais mécaniques des verres protecteurs des affichages pour les


dispositifs mobiles – Lignes directrices














INTERNATIONAL

ELECTROTECHNICAL

COMMISSION


COMMISSION

ELECTROTECHNIQUE

PRICE CODE
INTERNATIONALE

CODE PRIX K


ICS 31.120 ISBN 978-2-83220-862-5



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

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® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale

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CONTENTS


FOREWORD . 3

INTRODUCTION . 5


1 Scope . 6

2 Terms and definitions . 6

3 Mechanical performance testing guidelines . 7

3.1 General . 7

3.2 Mechanical testing guidelines for display cover glass for mobile devices . 8

4 Brief overview of mechanical test methods . 8
Bibliography . 10

Table 1 – Mechanical attributes and measurement methods . 8

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61747-40-1 © IEC:2013 – 3 –



INTERNATIONAL ELECTROTECHNICAL COMMISSION

____________




LIQUID CRYSTAL DISPLAY DEVICES –



Part 40-1: Mechanical testing of display cover glass

for mobile devices – Guidelines



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
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International Standard IEC 61747-40-1 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
110/464/FDIS 110/476/RVD

Full information on the voting for the approval of 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.

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A list of all the parts in the IEC 61747 series, under the general title Liquid crystal display

devices, can be found on the IEC website.


Future standards in this series will carry the new general title as cited above. Titles of existing

standards in this series will be updated at the time of the next edition.


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.

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61747-40-1 © IEC:2013 – 5 –


INTRODUCTION


Mobile electronic devices have become increasingly sophisticated and often incorporate

displays for the purposes of user interface and viewing. Such displays commonly incorporate

a transparent cover glass which aids in protecting the display against the introduction of

damage through routine device transport and use, as well as occasional or accidental misuse.


The purpose of this standard is to provide mechanical testing guidelines for cover glasses

utilized in such applications. Such glasses may or may not be strengthened, for example via

an ion-exchange process, which acts to increase mechanical strength through the introduction

of a surface compressive layer.

It is assumed that all measurements – described in detail in individual test method standards
– are performed by personnel skilled in the general art of mechanical property measurements.
Furthermore, it should be assured that all equipment is suitably calibrated as is known to
skilled personnel and that records of the calibration data and traceability are kept.

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LIQUID CRYSTAL DISPLAY DEVICES –



Part 40-1: Mechanical testing of display cover glass

for mobile devices – Guidelines








1 Scope


This part of IEC 61747 is a mechanical performance testing guideline for cover glass used in
electronic flat panel displays in mobile devices. This document focuses on key mechanical
testing performance parameters and covers mainly strength and damage resistance attributes.
The test methods will focus on the cover glass level testing only.
NOTE The glass used for cover glasses for electronic mobile devices can be chemically strengthened by an ion-
exchange process. This ion exchange process increases the mechanical strength of the glass.
2 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
2.1
abraded
subjected to a defined process which introduces mechanical abrasive damage to a portion of
the specimen to be placed under tension during subsequent flexural strength testing, for
example, biaxial flexure via ring-on-ring
2.2
as-received
representative of standard sample preparation and handling practices, and therefore free of
intentional mechanical damage such as abrasion, scratching, or indentation
Note 1 to entry: The strength of glass is not an intrinsic material property, and like other brittle elastic materials,
is highly dependent upon the surface flaw population. The term “as-received” is meant to represent the surface
condition upon specimen receipt and should be distinguished from a condition where damage has been
intentionally introduced prior to testing.
2.3
central tension
CT
tensile stress generated within the interior of a glass article which serves to counteract (i.e.,

force balance) compressive stress acting at or near the article surface
Note 1 to entry: This note applies to the French language only.
2.4
chemically strengthened
subjected to a molten salt bath containing alkali ions typically larger than those residing in the
glass, resulting in the generation of residual compressive stress (2.5) and central tension (2.3)
2.5
compressive stress
CS
maximum residual stress in compression measured near the glass surface
Note 1 to entry: This note applies to the French language only.

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61747-40-1 © IEC:2013 – 7 –


2.6

cover glass

cover lens

glass that typically protects an optical component such as a display from damage


2.7

damage resistance

ability to resist certain potential damage-inducing events such as abrasion, indentation or

scratching


2.8

depth of layer
DOL
distance from the surface of a strengthened glass to the depth of zero stress or the depth of
transition from compressive to tensile stress
Note 1 to entry: The ability to approximate this depth is dependent upon the measurement methodology chosen.
Note 2 to entry: This note applies to the French language only.
2.9
edge strength
measured stress at failure in the case where failure is known to have originated from a
specimen edge
2.10
mobile device
electronic device that includes a battery and is designed to be carried about by consumers
2.11
retained surface strength
abraded surface strength
measured stress at failure in the case where failure is known to have originated from a
specimen surface which has experienced a prescribed abrasion or mechanical damage event
2.12
strength
stress at which a specimen fails for a given loading condition
2.13
thermally strengthened
subjected to fast cooling of the glass exterior relative to the glass interior, resulting in the
generation of residual compressive stress (2.5) and central tension (2.3)

3 Mechanical performance testing guidelines
3.1 General
The appropriate attribute(s) and test method(s) shall be selected based on the detail
specification or depending on the purpose of the evaluation.
The standard environment for testing shall be 23 °C ± 3 °C for temperature and 50 % ± 5 %
for relative humidity, unless otherwise specified in the detail specification. These standard
requirements are established to control fatigue effects when performing mechanical testing on
glass. If environmental conditions differ from the standard environment, the conditions shall
be reported with the test data.

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3.2 Mechanical testing guidelines for display cover glass for mobile devices


The mechanical attributes and measurement methods are given in Table 1.


Table 1 – Mechanical attributes and measurement methods


Category Attributes Unit Test method

Strength (as-received) Edge strength MPa Uniaxial flexural strength (4-point bend)

Strength (as-received) Surface strength N Biaxial flexural strength (ring-on-ring)

Impact resistance Surface energy-to-failure Joules Biaxial flexural energy-to-failure (ball drop)

Surface damage Scratch performance gF Scratch lateral crack visibility/retained
resistance N strength
Surface damage Retained surface strength N Abraded biaxial flexural strength (ring-on-
resistance ring)
Surface damage Resistance to indentation gF Visual median radial crack
resistance cracking N resistance/retained strength

In case the samples to be tested are that of strengthened glass – for example, via chemical or
thermal means – the results of mechanical testing will depend on the degree of strengthening.
This degree of strengthening may be characterized by attributes such as compressive stress,
depth of layer, or other. While these are to be stated with any test reports, the measurement
methods for these parameters are outside the scope of this guideline document.
Strengthened glasses may result in non-linearities (such as in load to stress conversion) due
to high deformations and the formation of membrane stresses, which shall be taken into
consideration during data analysis and reporting.
4 Brief overview of mechanical test methods
a) Edge strength
Uniaxial flexural strength (4-point bend)
A uniaxial flexural test via a 4-point bend has been selected as the best representative
test for edge strength. This is related to the observations of failures occurring from edge
flaws rather than surface flaws in the specimen.
b) Surface strength
Biaxial flexural strength (ring-on-ring)
A biaxial flexural test via a ring-on-ring methodology is designed to test surface strength.
A note of caution: when the specimen deflects more than 1/2 its thickness, the load-to-

stress relationship is no longer linear, and non-linear effects shall be taken into account to
properly convert load to stress.
c) Surface impact resistance (energy to failure)
Biaxial flexural energy-to-failure (ball drop)
A biaxial flexural test via a ball drop provides an indirect measurement of surface strength
by applying a biaxial stress to the glass surface upon ball impact. Measurement of the
impact energy is used to approximate equivalent performance for different ball sizes,
weights and drop heights.
d) Scratch performance
Scratch lateral crack visibility/retained strength
Lateral cracks are cracks originating from the sub-surface of the glass (not from the
surface) which initially extend nearly parallel to the surface. These cracks may ultimately
propagate to intersect the surface of the glass resulting in visible chipping. The test is
performed in a step-load manner utilizing sliding indentation with, for example, a Knoop or

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61747-40-1 © IEC:2013 – 9 –


Vickers diamond tip. Retained strength after sliding indentation may be measured via

biaxial flexure (ring-on-ring) with the indentation site oriented in tension.

e) Retained surface strength


Abraded biaxial flexural strength (ring-on-ring)

An abraded biaxial flexural test (via ring-on-ring) can be an effective measure of the

retained surface strength of a test specimen. Development of an abrasion method for

standardization is currently under evaluation.

f) Resistance to indentation cracking

Visual median/radial crack resistance/retained strength


Median/radial cracks extend from the corners of the indent impression and are oriented
perpendicular to the surface so that they have the greatest strength-limiting effect in
bending. The test is performed in a step-load manner with, for example, a Vickers
diamond tip until the cracks form. Retained strength after indentation may be measured
via biaxial fle
...