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4767
Background Statement for SEMI Draft Document 4767
New Standard: Terminology of Plastic Substrate for Flexible Display
Note: This background statement is not part of the balloted item. It is provided solely to assist the recipient in reaching an informed decision based on the rationale of the activity that preceded the creation of this document.
Note: Recipients of this document are invited to submit, with their comments, notification of any relevant patented technology or copyrighted items of which they are aware and to provide supporting documentation. In this context, “patented technology” is defined as technology for which a patent has issued or has been applied for. In the latter case, only publicly available information on the contents of the patent application is to be provided.
Background Statement
Flexible displays are one of the styles of displays, and the general term for the displays which display area can turn.
And these displays have a possibility of creating very unique new applications, such as paper-like , wearable , and a rollup.
One of the important components which constitute flexible displays is a plastic substrate.
The standard purpose is to unify the term of a plastic substrate used for flexible displays.
Responses to this letter ballot will be reviewed by the Polarizing Film Task Force.
If you have any questions, please contact the Flexible Display Task co-leaders:
Tadahiro Furukawa (Kyodo Printing),
Takashi Shiro (Teijin), ,
or SEMI Staff, Hiro’fumi Kanno at
SEMI Draft Document 4767
New Standard: Terminology for Plastic Substrates of Flexible Display
1 Purpose
1.1 In this standard, definition and interpretation of each term provides characteristics of materials used for Flexible Display manufacturing. This standard benefits unification of terminologies generally used for Plastic substrates of Flexible Display manufacturing.
2 Scope
2.1 This standard is applicable for Plastic substrates of Flexible Display manufacturing. It covers terminologies related to Plastic substrates of Flexible Display, used in the area of material, structure, inspection, and measurement.
NOTICE: This standard does not purport to address safety issues, if any, associated with its use. It is the responsibility of the users of this standard to establish appropriate safety and health practices and determine the applicability of regulatory or other limitations prior to use.
3 Limitations
3.1 This standard does not include thin glass substrate and metal foil
NOTICE: This standard does not purport to address safety issues, if any, associated with its use. It is the responsibility of the users of this standard to establish appropriate safety and health practices and determine the applicability of regulatory or other limitations prior to use.
4 Referenced Standards
4.1 None
5 Abbreviations and Acronyms
5.1 None
6 Definitions
6.1 Elements of Plastic substrate of Flexible Display — See Figure 1. Plastic substrate of Flexible Display is composed of Base film and, if need arises, Coating layer that implements and/or complements the requirements for specification. Several layers may be coated on Base film.
6.1.1 Base Film — the base film that defines shape of Flexible Display. It generally provides the thermal properties and mechanical properties of the display.
6.1.2 Coating Layer — the layers that are deposited on Base film by wet process and/or dry process. They generally provide high Gas/Water barrier, good adhesion between Base film and other layer, a smooth surface, a hard surface, and a resistance against chemicals respectively. The layer may have several properties above.
6.1.3 Electrical Conductive layer (option) — the layer that is deposited by wet process and/or dry process. It generally supplies electric voltage or electric current to an active layer such as liquid crystal layer or light emitter layer or electrophoretic layer. Generally, a transparent conductive film is used.
Figure 1
Plastic Substrates of Flexible Display
6.2 Optical Properties
6.2.1 Transmittance — The ratio of the light intensity passes through the plastic substrate to the incident. The incident intensity I0, and the transmission intensity I, transmittance T is represented by the formula below.
T=I/I0 × 100 (%) (1)
Transmittance is affected by the composition, temperature, thickness of the material, and wavelength of light.
6.2.2 Retardation —A representation of the optical path difference caused by the difference between the fast axis (axis of lower refractive index) and the slow axis (axis of higher refractive index). Its value is expressed as follows.
(Retardation) = (refractive index difference Δn) × (pathlength) (2)
Retardation is affected by the composition, temperature, thickness of the material, and wavelength of light.
6.2.3 Reflectance — The ratio of reflected light intensity to the incident wave intensity, when the light reflected at the boundary of the plastic substrate. At the substrate surface, the light beam incident on the surface "Φ", the light beam reflected from the surface "Φr", reflectance R is represented by the formula below.
R = Φr / Φ × 100 (%) (3)
Reflectance is affected by the composition, temperature, thickness of the material, and wavelength of light.
6.2.4 Chromaticity — Quantitative representation of the color. For example, commonly used in the plastic substrate in L * a * b * color system, "Lightness index" represented by the L *, "Hue" and "saturation" value of a * b * represented.
6.3 Physical Properties
6.3.1 Elastic Modulus — Physical properties represented by the difficulty of the deformation. Within the elastic limit, stress divided by strain. Also called modulus or bounce factor. In thus field, tensile modulus and flexural modulus are important.
6.3.2 Strength of Rupture — Maximum strength of the plastic substrate without break, when it is pulled in a fixed direction.
6.3.3 Elongation of Rupture — When the plastic substrate is pulled in a certain direction, the maximum amount of elongation without break.
6.3.4 Surface roughness — the criterion for the smoothness of the plastic substrate surface. Usually the randomly selected areas on the plastic substrate surface are measured by a surface analyzer.
6.3.5 Curl — Unidirectional deformation of the plastic substrate. Those defined by the maximum distance from the reference plane and the backside or surface of plastic substrate. It includes all the twist or some part of the rise and fall of the plastic substrate on the reference plane.
6.3.6 Waviness, Undulation — Cyclic deformation of the plastic substrate. It is represented by the residual roughness after removing the long wavelength component (Curl) of short wavelength components (surface roughness).
6.3.7 Distortion — Two axial deformation of the plastic substrate.
6.3.8 Coefficient of Thermal Expansion (CTE) — The deformation of the plastic substrate by temperature variation. The rate of inflation of one-way to expand the plastic substrate by raising the temperature 1K (℃).
6.3.9 Coefficient of Humidity Expansion — The deformation of the plastic substrate by humidity variation. The rate of inflation of one-way to expand the plastic substrate by a rise in humidity, rate of change of relative humidity (%) per size of deformation rate (%) shown in (in% /% RH).
6.3.10 Thermal Shrinkage — Deformation amount of the plastic substrate before and after heat treatment. The ratio is shown in ΔL/L0. ΔL is the amount of change, L0-L as indicated. L0 is the length of the substrate before heat treatment. L is the length of the material after heat treatment.
Thermal Shrinkage = ΔL/L0× 100 (%) (4)
6.3.11 Oxygen Transmission Rate — Time rate of oxygen gas transmission through a unit area (1ｍ２) of parallel surfaces of a plastic film per unit time (24hr) under specified temperature and humidity conditions.
NOTE 1: See ISO 15105-1,2
6.3.12 Water Vapor Transmission Rate — Time rate of water vapor transmission through a unit area (1ｍ２) of parallel surfaces of a plastic film per unit time (24hr) under specified temperature and humidity conditions.
NOTE 2: See ISO 15106-1,2,3,4
6.4 Thermal Properties
6.4.1 Glass transition temperature — Glass transition temperature (Tg) is the temperature at which a polymer ceases to be brittle and glassy, becomes less rigid and rubbery.
6.4.2 Melting temperature — Melting temperature(Tm) of a polymer corresponds to a change from the solid to liquid state. Melting point of a solid is the temperature at which the vapor pressure of the solid and the liquid are equal. At the melting point the solid and liquid phase exist in equilibrium.
6.4.3 Heat deflection temperature (Heat distortion temperature) — Heat deflection temperature or heat distortion temperature is the temperature at which a plastic substrate deforms under a specified load.
NOTE 3: See ISO 75-1,2,3
6.4.4 Chemical resistance — Chemical resistance is level of resistance to chemicals.
6.5 Defects
6.5.1 Surface Defect
6.5.1.1 Foreign material — a defect that appears as foreign material. Allowable foreign material size is determined by display panel pixel size.
6.5.1.2 Scratch — a surface fissure. Scratch on the device side may cause device failure. Allowable width or depth of scratch is determined by display panel pixel size or structure of device.
6.5.1.3 Stain — a defect that found by a different color and contrast locally, but can have different names depending upon color and shape.
6.5.1.4 Streak — a linier defect with a very small undulation on the plastic substrate surface.
6.5.1.5 Crack — a defect that appears as a crack on surface or edge of the plastic substrate.
6.5.1.6 Bump — a small protuberance on the plastic substrate.
6.5.1.7 Dimple —surface defect that appears as a dimple.
6.5.1.8 Fish eye — a defect as a fish-eye-shaped bump caused by gel material and foreign particle.
6.5.1.9 Dent — an impression on the surface caused by external force.
6.5.1.10 Delamination — a defect on surface or edge of the plastic substrate that appears as detachment coating layer and base film, or nearby coating layer.
6.5.1.11 Pin Hole — a small hole on surface of the coating layer.
6.5.2 Internal Defect
6.5.2.1 Bubble — a small gaseous inclusion. Allowable bubble size is determined by display panel pixel size.
6.5.2.2 Foreign material — a internal defect that appears as foreign material. Allowable foreign material size is determined by display panel pixel size.
6.5.2.3 Pin hole — a small hole through the base film or the inside coating layer.
6.5.3 Optical defect
6.5.3.1 Mura — variation in visual appearance (transparency, haze, color, and other optical）
6.5.3.2 Retardation uniformity — uniformity of phase difference and optical axis, retardation uniformity may cause failure of display that used polarized light.
7 Symbols
7.1 [symbol 1] — definition.
7.2 [symbol 2] — definition.
7.3 [symbol 3] — definition.
8 Related Documents
8.1 ISO Standards[1]
ISO 15105-1:2007 — Plastics - Film and sheeting - Determination of gas-transmission rate - Part 1: Differential-pressure methods
ISO 15105-2:2003 — Plastics - Film and sheeting - Determination of gas-transmission rate - Part 2: Equal-pressure method
ISO 15106-1:2003 — Plastics - Film and sheeting - Determination of water vapour transmission rate - Part 1: Humidity detection sensor method
ISO 15106-2:2003 — Plastics - Film and sheeting - Determination of water vapour transmission rate - Part 2: Infrared detection sensor method
ISO 15106-3:2003 — Plastics - Film and sheeting - Determination of water vapour transmission rate - Part 3: Electrolytic detection sensor method
ISO 15106-4:2008 — Plastics - Film and sheeting - Determination of water vapour transmission rate - Part 4: Gas-chromatographic detection sensor method
ISO 75-1:2004 — Plastics - Determination of temperature of deflection under load - Part 1: General test method
ISO 75-2:2004 — Plastics - Determination of temperature of deflection under load - Part 2: Plastics and ebonite
ISO 75-3:2004 — Plastics - Determination of temperature of deflection under load - Part 3: High-strength thermosetting laminates and long-fibre-reinforced plastics
NOTICE: SEMI makes no warranties or representations as to the suitability of the standards set forth herein for any particular application. The determination of the suitability of the standard is solely the responsibility of the user. Users are cautioned to refer to manufacturer's instructions, product labels, product data sheets, and other relevant literature, respecting any materials or equipment mentioned herein. These standards are subject to change without notice.
By publication of this standard, Semiconductor Equipment and Materials International (SEMI) takes no position respecting the validity of any patent rights or copyrights asserted in connection with any items mentioned in this standard. Users of this standard are expressly advised that determination of any such patent rights or copyrights, and the risk of infringement of such rights are entirely their own responsibility.
This is a draft document of the SEMI International Standards program. No material on this page is to be construed as an official or adopted standard. Permission is granted to reproduce and/or distribute this document, in whole or in part, only within the scope of SEMI International Standards committee (document development) activity. All other reproduction and/or distribution without the prior written consent of SEMI is prohibited.
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[1] International Organization for Standardization, ISO Central Secretariat, 1 rue de Varembé, Case postale 56, CH-1211 Geneva 20, Switzerland. Telephone: 41.22.749.01.11; Fax: 41.22.733.34.30; http://www.iso.ch