Edit term LOW-E glass
Glass are the essential building materials, with the decoration of buildings requires the improvement of glass in the building industry is also increasing usage. However, today people in the choice of glass doors and windows of buildings, in addition to its aesthetic characteristics and appearance, but also focus on its heat control, cooling costs and the internal projection of sunshine and comfortable balance. This makes coated glass Xingui family - Low-E glass stand out and become the focus of attention.
Low-E glass, also known as Low-E glass, are at multi-storey glass surface plating on metal or other compounds, composed of film products. The coating layer with high visible light through and COSCO highly reflective characteristics of the infrared line with ordinary glass and traditional architecture in comparison with coated glass has the following obvious advantages:
Excellent thermal performance
Outside the glass doors and windows of the heat loss are the main part of the building energy consumption, energy consumption in buildings accounts for more than 50%. The study data indicate that the inner surface of the heat transfer of glass to radiation dominated, accounting for 58 percent, which means that from the change in performance glass to reduce heat loss, the most effective method is to check their inner surface radiation. Ordinary float glass radiation rate of up to 0.84, when plated on a layer of silver-based Low-E film, its radiation rate can be reduced to below 0.1. Thus, Low-E glass windows and doors of buildings, can greatly reduce the radiation caused by interior heat to the outdoor transmission, achieve the desired energy-saving effect.
Reduce interior heat loss caused by another significant environmental protection are effective. Cold season, due to buildings caused by heating CO2, SO2 and other harmful gas emissions are important sources of pollution. If you use Low-E glass, because of the reduction of heat loss can significantly reduce heating fuel consumption, thereby reducing harmful gas emissions.
Good optical properties
Low-E glass for sunlight in the visible light has a high transmission ratio, up to 80%, while the reflectance is very low, which makes them with the traditional coated glass compared to the optical properties of a vastly different situation. Views from the outside, the appearance of a more transparent, clear, namely to ensure the building of good lighting, but also to avoid the previous large-scale glass curtain wall, insulating glass windows light reflection caused by light pollution situation, creating a more soft and comfortable light environment .
Low-E glass of the above-mentioned characteristics make the developed countries was growing at a wide range of applications. China is a relatively energy-poor country, per capita consumption of energy is very low, and building energy consumption has been the total energy consumption of around 27.5%. Therefore, make great efforts to develop Low-E glass production technology and promote its applications, will bring about significant social and economic benefits.
Low-E glass of the application and development
In the United States and Europe, Low-E (Low-E) (translation of said娄义) coated glass because of its superior performance, has been a great deal of concern. Wschvo especially Germany and regulations, so that Low-E glass has the rapid development.
European manufacturers are beginning at the end of 60 laboratory studies "Low-E" of. In 1978, the American-British tepe (interqane) succeeded in "Low-E" glass is applied to buildings.
"Low-E" the superiority is beyond doubt. Since 1990, "Low-E" at the United States to the amount of 5% per year increase. The future, "Low-E" Whether or not to become the dominant position of windows do not know, but the landlord and the windows and doors companies have attached great importance to energy-saving doors and windows. Moreover, the vast majority of this year, buildings are using it to evaluate the merits of energy saving effect of the.
At present, two kinds of Low-E glass production methods
Online high-temperature pyrolysis deposition method:
Online high-temperature pyrolysis deposition "Low-E" glass in the United States has more than the company's products. Such as PPG's Surgate200, Ford Sunglas H. R "P". These products are in the float glass cooling process completed. Liquid metal or metal powder spray directly on to the hot glass surface, with the cooling of glass, metal films become part of the glass. As a result, the film hard and durable. This method produced "Low-E" glass has many advantages: it can be bending, steel, and do not have status in the use of hollow, can be long-term storage. Its disadvantage is the relatively poor thermal properties. Unless the film is very thick, otherwise the "u" ＆#118alue is only sputtering "Low-E" coated glass half. If you want by increasing the thickness to improve its thermal properties, its transparency is very bad.
Offline vacuum sputtering
Off-line production of Low-E glass, are commonly used on the current international magnetron sputtering vacuum coating technology. Sputtering can be produced using "Low-E" glass products manufacturers and the British North America has tepe's "LnplusNetetralR", PPG's Sungatel00, Ford, etc. SunglasHRS. And high-temperature pyrolysis deposition different sputtering are offline. And transmission, according to the location of glass have different horizontal and vertical division.
Sputtering Process "Low-E" glass, take a layer of silver film as a feature film. Silver film at the second floor between the metal oxide film. Metal oxide film on the silver membrane to provide protection, and as a middle layer between the color layer to increase the degree of purity and light transmission.
Vertical production process, glass placed in the rack on the vertical, into the number of class 10-1 Pa vacuum environment, access to an appropriate amount of process gases (Ar inert gas or reaction gas O2, N2), and maintain a stable vacuum. The target Ag, Si, etc. embedded in the cathode, and with the cathode placed in the horizontal direction perpendicular to the magnetic field and thus constitute a magnetron target. Target for a magnetron cathode, together with the DC or AC power, in the role of high-voltage, the process gas ionization, the formation of plasma. Among them, the electron in the electric and magnetic fields under a common, high-speed spiral movement, the collision gas molecules, resulting in more positive ions and electrons; positive ions at the role of the electric field, the energy reaches a certain target cathode after the crash, was splashed Injection of the target deposited on glass substrates on the formation of thin films. In order to form a uniform layer, the cathode target moving back and forth near the glass surface. In order to obtain multilayer films, we must use more than one cathode, each cathode are moving back and forth in the glass surface to form a certain thickness.
The level of law at a large extent, and vertical method are similar. The main difference at the place of glass, glass wheels arranged by the level of transmission, through the cathode, glass valve through a series of sales is scheduled after the vacuum shift. When the glass Get the main sputtering chamber, the coating stress to achieve the target fixed cathode metal, glass mobile. At the glass through the cathode process, the film formation.
At present, the vast majority of domestic and imported production line of magnetron sputtering of the target products are based on single-coated membrane and the metal film-based solar control glass membrane. Such products are relatively simple process, requiring a lower level of the equipment. Therefore, these lines can not meet the coating LOW-E glass requirements.
Sputtering production "Low-E" glass, with the following characteristics:
Because there is a wide range of metal target selection, and a variety of metal target combinations, therefore, sputtering production "Low-E" glass can have a variety of configurations. In color and purity, the sputtering Electroless plating is better than hot, and are offline because of law, in the new product development is also more flexible. The main advantage of sputtering is also produced "Low-E" insulating glass its "u" ＆#118alue of pyrolysis products is better than "u" ＆#118alue, but its disadvantage is the silver oxide layer is very fragile, so it can not as Like the use of ordinary glass. It must be made of insulating glass, and not make hollow Products ago, is also not suitable for long-distance transportation.
Low-E glass features and functions of
Solar radiation energy at 97% concentration of 0.3-2.5um wavelength of scope, and this is part of the energy from the outdoors; 100 ℃ the following objects of radiation energy concentrated in the 2.5um band above, this part of the energy mainly from the interior.
If the room window for the sector, then the winter or at high latitudes we hope to come in outdoor radiation energy, while the interior not to release the radiation energy. If the wavelength of the radiation field, the indoor and outdoor radiation cut-off point on the wavelength at 2.5um. Therefore, the selection must function room with a window on the key.
3mm thick ordinary transparent glass with solar radiation transmittance of 87% during the day from outside the radiation energy can be most through; but at night or cloudy weather, the interior of objects from the thermal radiation energy absorbed by their 89% so that the glass temperature, and then through the indoor and outdoor radiation and convection to distribute its heat exchange and therefore unable to effectively block the interior heat vent to the outdoors.
Low-E insulating glass for 0.3-2.5um solar radiation transmittance of more than 60 percent during the day from outside the majority of radiation energy can be through, but the night and cloudy weather, the interior of objects from the thermal radiation of about 50 % more than by its reflection back interior, only less than 15% of the thermal radiation is absorbed by his re-radiation and convection through the exchange of loss, it can effectively prevent the interior of the heat vent to the outdoors. Low-E glass of this feature so that it will have to control one-way flow of heat role interior.
Shortwave sunlight through the window, the exposure to the items on the interior. These items were heated, will be the form of longwave radiation once again. These long-wave has been "Low-E" window glass block, back to the interior. In fact the radiation through the window once again been reduced to 85 percent, significantly improving the insulation properties of window glass.
Insulation properties of window glass is generally used "u" ＆#118alue to express, and "u" ＆#118alue and the emissivity glass has a direct relationship.
"u" ＆#118alue is defined as: ASHRAE standard conditions, because of the glass thermal conductivity and the temperature difference between indoor and outdoor, the formation of air to air heat transfer. Its Imperial units as follows: British thermal units per square foot per hour per Fahrenheit, metric units: watts per square meter per Celsius, "u" ＆#118alue of less heat transfer through the glass also lower the insulation properties of window glass the better. Emissivity are objects of a heat radiation per unit area per unit area with the blackbody at the same temperature, under the same conditions, the ratio of radiation heat. Emissivity is defined as an object to absorb or reflect heat capacity. Theoretically completely blackbody for all wavelengths with 100% absorption. That is, zero reflectivity. Therefore, the blackbody radiation rate of 1.0.
Typically, the float glass of white radiation rate was 0.84. The majority of online thermal polymerization "Low-E" coated glass radiation rate at between 0.35 to 0.5. Vacuum magnetron sputtering "Low-E" coated glass radiation rate at between 0.08 to 0.15. It is worth noting that low rates of direct radiation corresponds to a low "u" ＆#118alue. Emissivity glass more close to zero, and its insulation performance, the better.
An "energy-saving lighting system" must be reflected in the superiority of the highest possible total energy of the sun through, while at the same time with a minimum of "u" ＆#118alue. Through taking into account the availability and thermal energy loss, the energy balance equation is set up, Ueg = UF-RFg. The best energy balance characteristics of lighting systems are vacuum magnetron sputtering "Low-E" insulating glass coating. Single layer of glass even though its transmission to the largest solar power, but it's "u" ＆#118alue and "Ueg" ＆#118alue is the worst. Therefore, we can not meet the demand for good energy balance.
Simple transmission of high solar power, can effectively maintain their energy, we can not think it is the energy-saving materials. "Low-E" insulating glass coating is a good energy-saving lighting materials. It has a high solar energy transmission, very low "u" ＆#118alue, and, because of the effect of coated, "Low-E" glass reflection of heat back to interior, making a high temperature near the window, people at windows the vicinity will not feel too much discomfort. And the application of "Low-E" windows of the building of its interior temperature is relatively high, so in the winter to maintain a relatively high interior temperature, rather than frost, so that people will be at the interior comfort. "Low-E" glass is also able to block many UV transmission to prevent bleaching interior items.