Low-E glass, also known as low-emissivity glass, is a film-based product that is coated with multiple layers of metal or other compounds on the surface of the glass. The coating layer has high transmission of visible light and high reflection of mid-range infrared rays, which has the following obvious advantages compared with ordinary glass and traditional coated glass for construction:
The heat loss of the outer door and window glass is the main part of the building’s energy consumption, accounting for more than 50% of the building’s energy consumption. Relevant research data show that the heat transfer on the inner surface of the glass is mainly radiation, accounting for 58%, which means that the heat loss can be reduced by changing the performance of the glass. The most effective method is to suppress the radiation on the inner surface. Ordinary float glass has an emissivity of up to 0.84. When a low-emissivity film based on silver is applied, the emissivity can be reduced to less than 0.1. Therefore, the use of Low-E glass to manufacture building doors and windows can greatly reduce the transfer of indoor thermal energy to the outside due to radiation, achieving an ideal energy saving effect.
Another significant benefit of reduced indoor heat loss is environmental protection. In the cold season, the emission of harmful gases such as CO2 and SO2 caused by building heating is an important source of pollution. If Low-E glass is used, the fuel consumed by heating can be greatly reduced due to the reduction in heat loss, thereby reducing harmful gas emissions.
Low-E glass has a high transmittance for visible light in sunlight, up to 80%, and a low reflectance, which makes the optical performance much better than conventional coated glass. When viewed from the outside, the appearance is more transparent and clear, which ensures the good lighting of the building, and avoids the light pollution caused by the light reflection of the large-area glass curtain wall and the insulated glass factory door and window, thus creating a softer and more comfortable light environment.
According to the different characteristics of the products, coated glass can be divided into the following categories: heat reflective glass, low-emissive glass (Low-E), conductive film glass and so on. Heat-reflecting glass is generally coated with one or more layers of a metal such as chromium, titanium or stainless steel or a compound thereof on the surface of the glass to make the product rich in color, suitable for visible light, and high in infrared light. Reflectivity, high absorption rate of ultraviolet light, therefore, also known as solar control glass, mainly used in construction and glass curtain wall; low-emissivity glass is coated on the surface of glass by a layer of metal such as silver, copper or tin or its compounds The film system has high transmittance to visible light, high reflectivity to infrared rays, and good thermal insulation performance. It is mainly used in construction and transportation of automobiles and ships. Due to the poor strength of the film layer, it is generally They are all made of insulating glass. Conductive film glass is coated with conductive film such as indium tin oxide on the surface of glass. It can be used for heating, defrosting, defogging and liquid crystal display of glass.
The current two Low-E glass production methods are online high temperature pyrolysis deposition:
Online high temperature pyrolysis deposition
“Low-E” glass has products from several companies in the United States. Such as PPG’s Surgate200, Ford’s SunglasH. R”P”. These products are completed during the float glass cooling process. The liquid metal or metal powder is sprayed directly onto the surface of the hot glass, and as the glass cools, the metal film becomes part of the glass. Therefore, the film layer is hard and durable. The “Low-E” glass produced by this method has many advantages: it can be bent and tempered, does not have to be used in a hollow state, and can be stored for a long period of time. Its disadvantage is that the thermal performance is relatively poor. Unless the film is very thick, its “u” value is only half that of the “Low-E” coated glass by sputtering. If you want to improve the thermal properties by increasing the film thickness, the transparency is very poor.
Off-line vacuum sputtering
The offline production of Low-E glass is currently widely used in the world by vacuum magnetron sputtering coating technology. Manufacturers and products of “Low-E” glass which can be produced by sputtering method include “LnplusNetetralR” of Intertek of North America, Sungatel00 of PPG, and SunglasHRS of Ford. Unlike the high temperature pyrolysis deposition method, the sputtering method is off-line. And according to the difference of the glass transmission position, there are horizontal and vertical points. The “Low-E” glass is produced by a sputtering process, and a layer of pure silver film is required as a functional film. The pure silver film is between the two metal oxide films. The metal oxide film provides protection to the pure silver film and increases the color purity and light transmittance as an intermediate layer between the film layers.
In the vertical production process, the glass is placed vertically on the shelf, fed into a vacuum environment of the order of 10-1 Pa, and an appropriate amount of process gas (inert gas Ar or reactive gases O2, N2) is passed through, and the vacuum is kept stable. A target Ag, Si, or the like is embedded in the cathode, and a magnetic field is placed in a horizontal direction perpendicular to the cathode to constitute a magnetron target. The magnetron target is used as a cathode, and a direct current or an alternating current power source is applied. Under the action of a high voltage, the process gas is ionized to form a plasma. Among them, under the joint action of electric field and magnetic field, electrons undergo high-speed spiral motion, colliding with gas molecules to generate more positive ions and electrons; positive ions under the action of electric field, after reaching a certain energy, they hit the cathode target and are splashed. The projected target is deposited on a glass substrate to form a film. In order to form a uniform film layer, the cathode target moves back and forth close to the glass surface. In order to obtain a multilayer film, it is necessary to use a plurality of cathodes, each of which moves back and forth on the surface of the glass to form a certain film thickness.
The horizontal method is largely similar to the vertical method. The main difference is in the placement of the glass. The glass is transported by horizontally aligned wheels. Through the cathode, the glass changes through a series of pins. When the glass reaches the main sputtering chamber, the coating pressure is reached, the metal cathode target is fixed, and the glass moves. The film layer is formed during the passage of the glass through the cathode. At present, the target products of domestic and most imported magnetron sputtering coating production lines are solar control film glass mainly composed of single film and metal film. This type of product is relatively simple in process and requires less equipment. Therefore, these production lines cannot meet the requirements for plating LOW-E glass.
How to distinguish low-e glass
Use one side of the glass to illuminate with an infrared light (Yuba light) and feel the burning sensation from the other side. Some are not Low-E, only a slight heat is.
Low-E insulating glass blocks 80% of infrared radiation, which is essential for it. No infrared light can be replaced by a high wattage incandescent lamp, but ordinary glass is required for comparative testing.
Other identification methods: (In fact, through the universal meter is to test the current to know that low-e is a layer of metal film)
1. The single-piece Low-E is well identified. Just use a multimeter to measure the surface resistance of the glass. If it is tens of ohms (related to the distance between the measuring pen tips), it is Low-E.
2, there is no window frame of insulating glass, such as curtain wall glass, if it is used in the online Low-E glass, you can use a multimeter to measure where the edge of the glass is not stained with a sealant. If it is offline Low-E, it can not be measured in this way, because the Low-E film on the side has been removed, and it can be observed whether there is any trace of film removal;
3, the method of looking at the shadow with a lighter flame is not accurate, only in the case of the known Low-E insulating glass, the position of the film surface is roughly discriminated.
4, the most accurate method, can not only determine whether Low-E is hollow, but also can judge whether it is high-quality Low-E or low-quality Low-E method – remove the glass surface resistance or spectral data
Building insulation glass film (how to identify glass LOW-E film and solar control film) building insulation film for energy saving as the main purpose, with UV and safety explosion-proof function, this building insulation film is divided into heat-reflecting film and low Radiation film.
The heat reflective film (also known as the solar control film) is attached to the surface of the glass to allow a certain amount of visible light to pass through the room. The high infrared reflectance IR and the low solar heat gain coefficient SHGC can keep the indoor temperature from rising in the hot summer. Too much, thus reducing the cost of electricity for indoor air conditioning.
Low-emission film (also known as LOW-E film) can transmit a certain amount of short-wave solar radiant energy, allowing solar radiant heat (near-infrared) to enter the room, while at the same time radiating more than 90% of indoor object heat sources (such as heating equipment) The long-wave infrared (far infrared) is reflected back into the room, so it can be used in heating buildings in cold areas to achieve the obvious effect of heat preservation and energy saving.
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