After UV LED Spot Light Source, linear UV LED curing machine emerges in IT electronics industry. This paper introduces the principle, structure, characteristics and application of Linear UV LED Light Source. Linear UV LED light source is different from the scattered light emitted by mercury lamp. The ultraviolet light emitted by UV LED linear light source is a narrow linear light nearly parallel to the light, with high energy concentration, irradiation intensity and curing efficiency. It is to avoid UV damage outside the work area and can also form a curvilinear light source. It is used in LCD panel, touch screen and printing.
1.Introduction of UV Curing
In the special formulation of resin to add photo-initiator, absorption of UV Curing Equipment in the high intensity of UV light, the generation of active free radicals or ion group, which triggered polymerization, cross-linking and grafting reaction, so that the resin (UV coating, ink, adhesive, etc.) in a few seconds (ranging from liquid to solid). This process is called “UV Curing”. UV curing is widely used in adhesive, paints, inks, coatings and other fields.
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| 100*100mm High Power Surface UV Curing Machine |
2.The characteristics of UV LED
The UV LED (UV light emitting diode) is a solid-state semiconductor device that can directly convert electrical energy into ultraviolet light. UV LED spot light source working temperature under 100℃, and usually has a long service life, high reliability, high luminous efficiency, less power consumption, no radiation, beneficial to environmental protection and other features. In recent years, it have been applied gradually in the UV curing.
- Long service life : over 20,000 hours
- Energy saving effect is significant, up to 90%
- No infrared radiation : will not cause thermal stress and thermal deformation of the work-piece
- Compact size, flexible configuration : volume is only 0.1cm3
- Energy concentration : more than 98% of the light output is in the ultraviolet band
- The main peak is narrow and single : over 90% of the light output is concentrated in the range of 10nm near the main wave peak
- Dc low voltage drive : suitable for portable UV equipment
- The output power is stable and continuously adjustable
- Flash : no preheating time is required, and the response time is in microseconds
- The opening and closing times do not affect the service life. No shutter is required
- Environmental protection : RoHS compliant, mercury free
3.Situation of UV Curing Equipment Application
UV curing equipment and mercury lamp can provide the same UV light, but also has a long life, no heat radiation, low consumption, low cost, accurate and adjustable power, small size, light source shape can be customized, mercury lamp does not have the characteristics. It has been successfully applied in many fields of industrial assembly : LCD manufacturing, camera and other optical products manufacturing, optical disc manufacturing, watch manufacturing, buzzer, mobile phone keypad assembly, electronic circuit board manufacturing, polarizing parts manufacturing, micro-motor assembly and other electronic parts manufacturing.
The application of UV curing equipment for civil use is also gradually developing :
In the field of daily necessities, it is mainly used in production of household goods, furniture and toys. The the field of glass technology, the assembly of glass crafts. Jewelry and other accessories of the assembly, Mosaic, positioning and printing areas.
4.Structure and Features of Linear UV Curing Light Source
UV LED has many advantages, but there are still many restrictions on the popularity of UV LED. The current linear UV LED light source has high cost, small single power, complex optical path system, narrow crest and poor matching of photo-initiator and other problems.
The first application to gain acceptance and popularity is UV LED Spot Light Source :
The size of UV LED light emitting unit is only a few millimeters, and the luminous body is mostly a cube with a side length of 1mm, with small luminous point, which is very suitable for achieving good focusing effect through the optical path system and realizing small light spot and high intensity ultraviolet irradiation.
UV Spot Light Source is suitable for curing only a few millimeters of area, but also requires high intensity of ultraviolet radiation spot curing occasions, such as : laser head, optical fiber connector, optical fiber coupler, LCD, OLED, hard disk, smart card, sensor, micro motor, encoder manufacturing, solder joint reinforcement, etc.
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| 1+4 Portable UV Spot Light Source |
5.The application of linear UV curing Light Source
Linear UV Light Source is mostly narrow and slender linear light. It is necessary to design special optical path system to converge multiple light spots emitted by a row of UV LED into narrow, uniform and high intensity linear light.
At present, there are several types of linear UV light sources :
(1)This kind of line UV light source is suitable for the long and thin work-piece to carry on the solidification irradiation occasion. The energy is high, the solidification efficiency is high. But on the other hand, the working distance is sensitive, has the strict request to the irradiation distance, generally only has several millimeters to ten millimeters working distance.
(2)This kind of line illuminant illuminate is even, not sensitive to working distance, general radial width is controlled in millimeter, but energy is a bit weak.
(3)The irradiation range of this kind of linear UV light source is large and working distance is not sensitive, but compared with the first two kinds, the irradiation intensity is the weakest.
(4)The curvilinear UV light source is composed of several linear UV light source, which can form a special shape and meet the needs of special stations.
Cost and luminous intensity are the main constrains to the popularity and application of UV LED. The development and design ideas of line UV light source should follow the following points :
Optical path system is the key. A good optical path system should be concentrated and uniform energy, so as to reduce the deformation of the solidified work-piece and reduce the solidification stress, improve the solidification accuracy. High irradiation intensity makes curing more efficient. Special shape linear UV light source, more adaptability, meet station needs, make its application more popular. More energy saving and environmental protection and lower cost.
(1)Linear UV light source and dispensing machine cooperate to realize rapid sealing and streamline operation of the chip. Due to high energy of UV LED, stable light output and even irradiation, the production is more efficient.
(2)Since UV LED is a cold light source without thermal radiation and with small temperature rise, it can meet the requirement of LCD production. In the manufacturing process of LCD, the UV LED Line Light Source is used to seal the edge of LCD, and the connection between FPC and LCD is reinforced with cables, which is simple, fast and efficient.
(3)Linear UV curing light source with UV ink can be used in the printing field.
(4)Manufacture of syringes and needles.
(5)Headphones, mike manufacturing.
(6)Sensor encapsulation.
6.Large Area UV Curing Light Source
UV LED surface light source also has no thermal radiation, and the temperature in the curing furnace can be controlled at room temperature, many LED luminous points are evenly distributed, and many groups of professional lens optimized for UV irradiation have good irradiation uniformity and excellent uniformity of irradiation intensity between edge and center. The shape and size of the luminescent area can be customized according to user requirement.
Large area UV curing light source in the same input power, compared with mercury lamps, irradiation cost is more expensive. In the terms of output power, the cost is more expensive than mercury lamps.
At present, the main breakthrough of UV LED surface light source application and popularization is small surface light source. Now, the irradiation intensity of small surface light source can reach more than a few hundred to a thousand milliwaittts per square centimeter. High irradiation intensity brings higher production efficiency. On the other hand, small surface light source energy concentration and no heat radiation, so its cooling system and the entire irradiation system tend to miniaturization, more convenient application.
Compared with UV spot light source and linear UV light source, the cost of UV surface light source is high, which restricts the application and development of surface UV curing light source.
7.Brief Summary
With the continuous reduction of UV LED cost, the popularity of UV LED is transiting from UV spot light source to line UV curing light source (it will take some time for the popularity of surface UV light source). In the field of industrial assembly and daily necessities, line UV light source will get more attention.
At the same time, with the adaptive development of UV LED photo-initiator, the application of UV LED will be more extensive and its advantages will be more and more obvious.
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