Coating & Dispensing Technology Glossary

Term Meaning
A
Adhesive residue Adhesive residue is caused by fracturing of the adhesive (glue) layer. There are three major types of fractures. An anchor fracture is a phenomenon where an adhesive layer is separated from the substrate and transferred to the target. A cohesive fracture is a phenomenon where an adhesive layer is divided and adhered to both the substrate and target. An interfacial fracture is a normal (clean peeling) state.
Air entrainment A defect where air gets trapped in the coating. This occurs when coating is applied too quickly and air gets trapped between the substrate and the coating.
All-solid-state battery Also known as all solid type, these batteries use inorganic solid electrolytes instead of the organic liquid electrolytes and separators used in current lithium-ion batteries (LiB). Solid electrolytes offer greater flame resistance and thermal and chemical stability, which ensures safety and durability even when the energy density is increased. This technology is a promising option for ultra-fast recharging, and structures without liquid electrolyte allow for a higher degree of design flexibility. Research and development efforts toward practical use in electric vehicles (EVs) and other applications are currently underway.
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Anchor effect (Fastener effect) An effect where adhesive hardens on the uneven surfaces of a target to form nail or wedge-like shapes. Also called the fastener effect.
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Aspect ratio For rectangles, the aspect ratio is the ratio between the lengths of two neighboring sides. For cylindrical objects, the aspect ratio refers to the ratio between the diameter and height. For 3D structures, the aspect ratio is determined from the shape of a cross-sectional view. In linear coating, the state where the thickness is large with respect to the line width is called a high aspect ratio.
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B
Barrel In coating equipment, a barrel is a container for storing coating fluid.
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Bead Coating material applied in a long continuous shape as if squeezed from a tube.
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Blade A tool that works as a spatula to achieve the desired film thickness by removing any portion beyond what is necessary from excessively applied coating fluid.
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Bonding In industry, bonding refers to the process of joining two workpieces using liquid or semi-liquid (paste or cream) adhesive to ensure a long-term bond.
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C
CFRP An abbreviation for Carbon Fiber Reinforced Plastic. CFRP refers to composite materials made of carbon fiber and resin. These materials have lower density, less weight, and higher strength than iron or aluminum. Unlike metals, CFRP offers high elasticity and strength in the fiber direction, which enables stronger designs based on the proportion of the fiber direction. CFRP has been used for applications that take advantage of the lightweight, high-strength, and high-rigidity (hard to bend) characteristics, such as in aerospace industry, automotives, and sports gear/equipment.
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Cascading A coating defect that looks like ripples on a coated surface. Contrary to "ribbing (longitudinal raised streaks)" caused by the fast speed of the substrate, cascading often occurs when the speed of the substrate is slow.
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Cell pattern transfer When a gravure coater is used for thick film coating and the inner volume of the gravure cells—the cells on the roller that create the coating pattern—is increased, the cell pattern becomes coarse and the pattern of the cells themselves is transferred onto the target surface. This coating defect is called cell pattern transfer.
Chamber An enclosed area where coating fluid is applied to a rotating applicator roll using a tank or pump. Chambers prevent the coating fluid from being exposed to air prior to coating. A unit that features a doctor blade at the end of the chamber is called a doctor chamber.
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Changeover Changeover refers to the preparation before a process begins where the type of product or the manufacturing method is changed. This preparation includes changing tools, performing reference adjustments of equipment and tools, and changing the materials or components.
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Coating nozzle, coating needle The part of a dispenser where the solution is dispensed. A wide variety of coating nozzles/needles are available to suit various coating fluids, purposes, and conditions. In terms of material, for example, metal and plastic needles are used for general purposes, and PTFE nozzles are used for anaerobic solutions. In terms of mechanism, double-threaded screw needles are used for improved stability of the syringe attachment. As for size and shape, precision nozzles and high-resolution nozzles support precision coating, and curved nozzles allow coating on the sides of targets. Various other nozzles and needles are also available.
Contact angle θ References the interior angle between the sidewall of a drop of liquid and the surface it sits on. It can be expressed through Young's equation and represented by θ (Contact Angle). The solid surface is considered wet when the surface tensions of the liquid and solid surface are balanced (the contact angle θ approaches 0).
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D
Die A die is a specially shaped block used to shape an object from a solid material. A mold is used for the same purpose, but instead using molten material. A slot die coater is a coating system that uses a die. Such systems are categorized as pre-metered coating systems that control flow rate through a metering pump before coating. Because these systems ensure a uniform flow rate, width, and speed for coating film forming, they are often used for coating optical films, which require highly accurate film thickness. There are also multi-layer slot die coaters that create multiple layers of coating films simultaneously.
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Dip coating A coating method that involves immersing a workpiece (coating target) in solution. After immersion, the workpiece is removed with consideration of the viscous force and surface tension of the solution, gravity, and the removal speed. Any remaining solution on the workpiece is removed through drying or sintering to form a uniform thin film.
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Doctor blade A device for removing dirt or foreign particles on the surface of coater rollers that may cause defective coating. Some applications involve intentionally applying more coating fluid than necessary, and a blade removes the excess fluid to control the film thickness to a uniform amount. This blade is also called a doctor blade.
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Drying curve (drying characteristic curve) A material property indicated as the amount of moisture evaporation over time per unit of surface area to be dried (or per unit of anhydrous material weight).
F
FPC An abbreviation for Flexible Printed Circuit, which can also be called flexible PCB, flexible circuit board, flexible printed board, or flexible printed wiring board. An electronic circuit is formed on a substrate consisting of a thin base film which works as an insulator (plastic, polyimide, PET, etc.) and conductive metal such as a copper foil bonded on it. FPCs have been used for smartphones, LCDs, and other electronics because of they are thin and flexible. Major applications include moving parts, bending parts, and cables connecting PCBs, or for units that require thinner and lightweight designs.
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Filler Fine inorganic or organic particles that will be added to a resin to improve the functionality. As developments in nano technology continue to arise, fillers of ultrafine particles with micrometer-scale or nanometer-scale diameters have become more popular.
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H
Hard coat A hard coat is used for surface protection of screens on smartphones and game consoles, automobile surfaces, and construction materials. In general, a hard coat is required to provide high surface hardness (H or higher pencil hardness) and transparency (90% or higher light transmission ratio in the visible range). In fields where improved hardness and coating properties are required, the hard coat will use coating materials that can be classified into three types. "Organic" coats provide a lower hardness compared with the other two types, but the coats are easier to handle and recoating is possible. "Silicon" coats provide the highest hardness and high durability, but such coats are not suitable for recoating. "Metallic" coats provide high hardness, but the coating condition is limited because sintering is required for coating film forming.
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High edge A coating defect where one edge or both edges of a coated sheet become thicker than other sections due to irregularities in the coated surface.
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I
ITO film An ITO film is a transparent film with electrical conductivity. It is also called a transparent conductive film. Due to the high electrical characteristics and transparency, ITO film has been widely used for touch panels and LCDs. ITO is an abbreviation for indium tin oxide. The film is a composition of indium oxide (In₂O₃) and tin oxide (SnO₂). The composition ratio affects the resistance and transparency of the ITO film. ITO films are formed through several methods depending on the purpose, including PVD (Physical Vapor Deposition) such as sputtering and vacuum deposition; CVD (Chemical Vapor Deposition); and coating.
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Interfacial tension A force that makes a substance shrink its interfacial surface through the force of attraction between molecules. This is the force that makes mercury or water form drops in the atmosphere. The term "surface tension" is generally used for liquids.
K
Knurling When a film coated with adhesive material is wound into a roll, the stress gradually increases. The stress especially concentrates on the thicker sections called "gauge bands”, and winding in multiple layers causes deformation or deterioration of the coated surface or substrate. Embossing both ends of the substrate after coating to make the ends higher (knurling) reduces the adhesiveness at the center of the roll during winding and prevents damage to the coated surface and substrate.
L
Liquid gasket A flowable material applied on surfaces to be joined to form an elastic film or adhesive layer. Liquid gaskets provide oil-tightness, water-tightness, and airtightness to the joined section to prevent leakage or add pressure resistance.
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M
MEMS An abbreviation for Micro Electro Mechanical Systems. Typical MEMS have a total length in the order of mm or less, and the components are in the order of μm. The technological scope of MEMS includes mechanical components, sensors, actuators, and devices integrated on silicon substrates, glass substrates, and organic materials of electronic circuits. The core part is fabricated based on semiconductor integrated circuit manufacturing technologies, but etching processes for forming 3D shapes and movable structures are also used.
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Meniscus Meniscus is the curve in the upper surface of liquid in a capillary (narrow tube), as compared with the flat surface caused by surface tension. When adhesion between the liquid and the tube is strong—such as with water and glass—a concave meniscus occurs. When the liquid does not wet the tube wall, such as with mercury, a convex meniscus occurs.
O
Organic EL Organic EL is a technology that uses OLEDs (Organic Light-Emitting Diodes)—light-emitting elements made of organic matter that emits light in response to an electric current. Displays using organic EL, or OELDs (Organic Electro Luminescence Displays), do not require backlight and are characterized by low power consumption, high brightness, a thin profile, and lightweight design. Such displays are often used for smartphones, tablets, and low-profile display units.
Overcoating A process of coating a material to create an overcoat layer for the purpose of smoothing any unevenness on the surface. A typical overcoating application is smoothing unevenness on the surface of LCD color filters.
P
Photolithography A technology where a coat of light-sensitive resist is applied to a substrate before the substrate is exposed to light to form the desired pattern of exposed and unexposed areas. Photolithography is used for nano-order wiring and microfabrication, such as wiring on semiconductor ICs.
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Polymer molecule (Macromolecule) A very large molecule. The size of a molecule is expressed by the molecular weight, with larger molecules having a high molecular weight, and smaller molecules having a low molecular weight. In general, a molecule with a molecular weight of several thousands or more is called a polymer molecule or a macromolecule.
Potting In general, potting is a process of filling a case with insulation material such as urethane, silicon, or epoxy in order to protect the electronic circuit mounted inside. Three-dimensional coating using urethane resin for design purposes is also called potting.
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Primary bonding force This term is used for adhesive-based adhesion and refers to the force of the chemical bond (such as the covalent bond, metallic bond, or ionic bond).
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R
Ribbing A type of coating defect. Ribbing refers to the repeated ribs (longitudinal raised streaks) that appear on a coated surface along the moving direction of the substrate. This often occurs when the substrate moves too fast.
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Roping A streaky coating defect appearing along the circumferential direction of an applicator roll (the roll that applies coating material). Roping often occurs when the viscosity of the fluid is high or when the circumferential velocity of the roll is fast.
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Rotational centrifugal force An apparent force (inertial force) working on an rotating (circular motion) object in the opposite direction from the center.
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S
Sealant Also called sealing material or sealing agent. This paste-like material is made of synthetic resin or synthetic rubber and is used to fill seams or gaps for the purpose of adding water resistance or airtightness. In the sealant coating process, some base coating materials are often used together, such as a sealer—which improves adhesion to the target surface—and primer,—which increases adhesion. Consequently, in the field of automotive manufacturing or construction painting, sealer or primer may be used as a term for sealants.
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Shearing An operation similar to cutting an object with scissors. Shearing occurs when two forces parallel to the cross sectional surface of an object are applied in opposite directions.
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Slurry A muddy or gruel-like mixture of solid particles suspended in liquid. Also called a slip.
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Solidification A process where a liquid or gas turns into a solid. Solidification is synonymous with “coagulation”. The process is generally differentiated for gases under the term “sublimation”.
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Streak A defect that appears on a coated surface (also known as linear defects). Many causes may contribute to this type of defect. For example, when a large particle is caught on part of the coating equipment, such as a blade for adjusting the coating amount, a linear defect will be created on the coated surface.
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Substrate A base material used for making products or compounds. A smooth film or sheet substrate wound into a roll is called a web.
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Surface tension Surface tension is the force operating on a liquid to continually minimize its surface area. It is caused by the attraction among the molecules to pull surface molecules inward.
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Syringe For industrial use, a syringe refers to a type of pump that continuously feeds liquid such as adhesive, silver, solder paste, grease, or solution from a container.
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T
TFT An abbreviation for Thin Film Transistor. TFTs are one type of field-effect transistor and refer to transistors made by depositing only thin films on an insulation substrate. TFTs consist of a semiconductor film (such as CdS or CdSe, with a film thickness of 1 μm or less), an insulation film (such as SiO or CaF₂, with a film thickness of 0.1 μm or less), and electrodes (such as Al or Au). TFTs are typically used for LCDs.
Teaching The process of loading complex programs onto an industrial robot and configuring the settings to ensure proper playback and operation (teaching playback). Online teaching is a method that uses a teach pendant to make the robot remember an operation and then play it back on the site to allow for further fine adjustments. Offline teaching is the method of transferring an operation program—complete with CAD data—from a computer to the robot in order to make the robot remember the complicated operation.
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V
Van der Waals force Molecules that remain in a gas state at room temperature are stable by themselves and do not cause chemical bonds even when molecular motion weakens at lower temperatures to make the molecules closer to each other. The van der Waals force is an attraction force that operates between molecules in close proximity to bind them together (into liquid or solid). This force is also called a "secondary bonding force."
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W
Web A smooth, thin, continuous, and flexible substrate such as a film, sheet, paper, or metal foil that is not cut into pieces but is typically wound into a roll. The roll-to-roll transfer of a substrate is called web handling or web transfer.
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Wettability Wettability can be determined from the contact angle θ between a solid surface and a drop of liquid on the surface. A smaller contact angle indicates a higher wettability, which implies better coating of the liquid over the solid surface. On the contrary, a larger contact angle indicates a state where the solid surface will repel the liquid, referred to as a lower wettability.
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