IEC 61747-1-2:2014

IEC 61747-1-2 ®
Edition 1.0 2014-08
INTERNATIONAL
STANDARD
Liquid crystal display devices –
Part 1-2: Generic – Terminology and letter symbols

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IEC 61747-1-2 ®
Edition 1.0 2014-08
INTERNATIONAL
STANDARD
Liquid crystal display devices –

Part 1-2: Generic – Terminology and letter symbols

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
PRICE CODE
T
ICS 31.120 ISBN 978-2-8322-1806-8

– 2 – IEC 61747-1-2:2014 © IEC2014
CONTENTS
FOREWORD . 3
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
3.1 Physical concepts . 5
3.2 General terms . 9
3.3 Terms related to specifications, ratings and characteristics, image quality,
reliability test, measurement . 15
3.4 Extra components . 19
4 Units and symbols . 19
Bibliography . 23

Figure 1 – Block diagram for explanation of supply voltages . 21
Figure 2 – Timing chart for explanation of response times . 22

Table 1 – Letter symbols . 19

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
LIQUID CRYSTAL DISPLAY DEVICES –

Part 1-2: Generic – Terminology and letter symbols

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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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
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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 61747-1-2 has been prepared by IEC technical committee 110:
Electronic display devices.
This first edition cancels and replaces the first edition of IEC 61747-1 published in 1998 and
Amendment 1:2003. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) The former IEC 61747-1, Generic specification was divided into IEC 61747-1-1, Liquid
crystal display devices – Part 1-1: Generic – Generic specification and IEC 61747-1-2,
Liquid crystal display devices – Part 1-2: Generic – Terminology and letter symbols.
b) In this part of IEC 61747, new terms have been added and some of the terms and the
definitions have been updated.

– 4 – IEC 61747-1-2:2014 © IEC2014
The text of this standard is based on the following documents:
CDV Report on voting
110/526/CDV 110/562/RVC
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.
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.
NOTE The structure of IEC 61747 series and the changes in the numbering are shown in Annex D of IEC 61747-
30-1:2012.
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.
A bilingual version of this publication may be issued at a later date.

LIQUID CRYSTAL DISPLAY DEVICES –

Part 1-2: Generic – Terminology and letter symbols

1 Scope
This part of IEC 61747 gives the preferred terms, their definitions and symbols for liquid
crystal devices, with the object of using the same terminology when publications are prepared
in different countries.
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 60027 (all parts), Letter symbols to be used in electrical technology
IEC 60050 (all parts), International Electrotechnical Vocabulary (available at
)
IEC 60617, Graphical symbols for diagrams
ISO 80000-1, Quantities and units – Part 1: General
3 Terms and definitions
For the purpose of this document, the following terms and definitions apply.
3.1 Physical concepts
3.1.1
alignment layer
thin layer deposited over the patterned electrodes that determines the direction of the director
at the surface
Note 1 to entry: The alignment layer produces the desired ordering. Alignment such as homeotropic alignment or
planar alignment is achieved by the co-operative ordering of the liquid crystal molecules locally affected by the
surface forces. The alignment layer generates the pretilt angle.
3.1.2
anti-ferroelectric liquid crystal
AFLC
type of smectic liquid crystal having no macroscopic electric polarization at zero external field
Note 1 to entry: An anti-ferroelectric liquid crystal has a paraelectric state with layers of alternating polarity of
permanent dipoles without an external electric field, and it transfers to a ferroelectric state of parallel alignment
when an electric field is applied.
3.1.3
cell gap
thickness of the liquid crystal layer between the two support plates

– 6 – IEC 61747-1-2:2014 © IEC2014
3.1.4
cholesteric phase
liquid crystal phase that exhibits planar nematic ordering in which the directors form a helix
that has its axis perpendicular to the plane
3.1.5
chiral pitch
helical pitch
periodic distance needed for directors to rotate by 360° in a helically structured liquid crystal
3.1.6
chiral nematic phase
liquid crystal phase that exhibits planar nematic ordering in which the directors form a helix
that has its axis perpendicular to the plane
3.1.7
clearing point
phase transition temperature of a liquid crystal for transition toward the isotropic phase
3.1.8
dichroic liquid crystal
liquid crystal exhibiting dichroism, i.e. the property of anisotropic absorption of light
3.1.9
direct addressing
method of addressing by applying a signal to a terminal that corresponds to a single pixel
Note 1 to entry: Hence, all pixels can be addressed individually, in groups or simultaneously
3.1.10
director
axial unit vector describing the local axis of symmetry for the orientational distribution function
of any chosen molecular axis of a liquid crystal
Note 1 to entry: The director co-ordinates define the local alignment of the liquid crystal.
3.1.11
disclination
localized alignment defect (appearing generally in the form of closed or open lines) forming
the boundary between areas exhibiting different alignment states
3.1.12
discotic mesophase
liquid crystal phase of disc-like shaped molecules exhibiting a long range ordering with
respect to the short molecular axis
3.1.13
domain
region having a well-defined boundary in which liquid crystal molecules have the same
director orientation
3.1.14
dynamic scattering
electro-optical effect showing a light scattering caused by turbulent motion in a liquid crystal
layer induced by an electro-hydrodynamic effect

3.1.15
electrically controlled birefringence
electro-optical effect caused by the birefringence of a liquid crystal layer which can be
modulated (varied) by an electric field
Note 1 to entry: It is also called “tunable birefringence”.
3.1.16
electrode layer
electrically conductive layer, usually transparent, covering the support plates and patterned to
establish the display and electric contact configuration
Note 1 to entry: The electrode layer may be made, for example, of indium tin oxide (ITO).
3.1.17
ferroelectric liquid crystal
liquid crystal phase exhibiting a spontaneous electric polarization
Note 1 to entry: The ferroelectric liquid crystal effect is commonly exhibited in chiral smectic liquid crystal.
3.1.18
film compensated super twisted nematic liquid crystal
FSTN
liquid crystal which changes the background colour of an STN-LCD to black-and-white, by
adding a special layer of compensation film
3.1.19
guest-host effect
anisotropic optical absorption effect occurring in a dichroic liquid crystal layer containing a
dissolved dye
3.1.20
highly twisted nematic liquid crystal cell
nematic liquid crystal which has a twisted angle structure of 90° to 180° between two
substrates
3.1.21
homeotropic alignment
alignment state of a liquid crystal layer for which the director is at all points nominally
perpendicular to a support plate surface
3.1.22
liquid crystal
material that exhibits a mesophase consisting of elongated (rod-like) or disc-like (discotic)
molecules and that possesses at least one long range orientational ordering with respect to
one molecular axis
3.1.23
mesophase
mesomorphic phase
ordered state of matter between the crystalline and isotropic liquid phases, exhibiting some of
the properties of the neighbouring phases, for example in respect of fluidity and birefringence
3.1.24
nematic phase
liquid crystal phase in which the molecules possess a long-range orientational ordering of one
molecular axis (uniaxial nematic liquid crystal) or two molecular axes (biaxial nematic liquid
crystal)
– 8 – IEC 61747-1-2:2014 © IEC2014
3.1.25
phase transition
phenomenon in which liquid crystal changes from one phase to another
EXAMPLE From the smectic to the nematic phase, the solid to the smectic phase, or the nematic to the isotropic
liquid phase
3.1.26
planar alignment
alignment state of a liquid crystal layer for which the director is everywhere nominally parallel
to a support plate surface
Note 1 to entry: This alignment is also referred to as homogeneous alignment.
3.1.27
polymer dispersed liquid crystal
liquid crystal polymer composites within which there exists at least two different phases
3.1.28
pretilt angle
angle between the plane of a support plate and the adjacent liquid crystal director
3.1.29
rubbing axis
rubbing direction
direction or axis of rubbing of the alignment layer in order to align liquid crystal molecules
3.1.30
smectic phase
liquid crystalline phase characterized by at least one one-dimensional long range transitional
ordering of the molecules and a long-range orientational ordering for one molecular axis
3.1.31
spacer
material (e.g. calibrated spheres or cylinders) incorporated into a liquid crystal cell to ensure
a constant distance between the support plates
3.1.32
storage capacitor
capacitor, parallel to a liquid crystal element, holding a signal voltage applied to each pixel or
subpixel in an active matrix display
3.1.33
storage effect
property of a picture element in which the visual information is retained after the activation
has been removed
3.1.34
super twisted nematic liquid crystal
STN
nematic liquid crystal which possesses a twisted structure from 180° to 270° between the
support plates
3.1.35
thermotropic liquid crystal
material whose liquid crystalline phase changes as the temperature changes in a certain
range
3.1.36
thin film transistor liquid crystal display
TFT-LCD
active matrix liquid crystal display with thin film transistors, in which every pixel is controlled
by one or more thin film transistor switches
3.1.37
twist angle
oriented angle between the projections of the respective surface directors at the support
plates on to one of the support plates of a twisted nematic cell
3.1.38
twisted nematic liquid crystal
TN
nematic liquid crystal which possesses a twisted structure of around 90° between the support
plates
3.1.39
twisted nematic structure
nematic liquid crystal state characterized by a twisted structure
3.1.40
voltage holding ratio
ratio of the holding voltage to the signal voltage initially applied at opposed electrodes in a
liquid crystal cell
3.2 General terms
3.2.1
achromatic display
display that generates an image which is devoid of hue
3.2.2
active area
part of a display screen area delimited by picture elements
3.2.3
active matrix display
matrix-addressed display device in which each picture element has at least one switching
element (e.g. diode or transistor)
3.2.4
addressing
selection of the pixels in space and/or time for activation or deactivation
3.2.5
alphanumeric display
display that is able to show a limited set of characters comprising at least letters and Arabic
numerals
3.2.6
backlight
light source system that illuminates light uniformly onto a liquid crystal display cell from
behind
– 10 – IEC 61747-1-2:2014 © IEC2014
3.2.7
black matrix
film-like structure that prevents unwanted light from passing between the dot electrodes in a
matrix display
Note 1 to entry: A black matrix is normally formed with a metal or organic film patterned on the substrate.
3.2.8
built in driver
monolithic driver
IC driver built in the same substrate as the active elements of pixels in an active matrix LCD
3.2.9
chip on glass
joint of liquid crystal module that mounts the IC chip directly on to the glass substrate of a
liquid crystal cell
3.2.10
chip on film
binding of the IC chip on the flexible printed circui
...