This invention relates to systems and methods for curing a curable coating with electromagnetic radiation. More specifically, embodiments of the present invention relate to a system for focusing electromagnetic radiation onto a curing surface. Even more specifically, embodiments of the present invention relate to a system for focusing electromagnetic radiation emitted by an array of UV LEDs onto a curing surface.
Adhesives are used widely in many industries as an efficient means of joining two or more elements. In the electronics industry, adhesives are particularly used for supporting components on printed circuit boards. The inherent disadvantage of the use of adhesive is the time factor required for setting or curing the adhesive. This time problem has been solved to some extent by the use of electromagnetic radiation curing. Exposure to electromagnetic radiation, including the ultraviolet (UV) and infrared (IR) spectrums, promotes curing through polymerization, or cross-linking of monomers in the adhesive. In addition to a substantial saving of time, there is also a considerable saving in plant space, since an electromagnetic curing line is considerably shorter than previous systems, which for example, utilized heated gas ovens. Another advantage of electromagnetic curing is that there are no solvents to be discharged into the atmosphere.
One of the most efficient electromagnetic radiation curing systems employs a tubular quartz lamp which includes mercury and argon and produces a high temperature electric arc. The light emitted from the exited mercury plasma is in 360 degrees with respect to the longitudinal axis of lamp. Lamp may be positioned near a curing surface so as to project radiation thereon to effect curing. However, the majority of emitted radiation does not directly strike the curing surface. In order to focus the light into a uniform and narrow line of irradiance and capture substantial portion of the light required for curing UV-curable material, complex and large systems utilizing multiple reflectors and lenses have been used in the prior art. Such systems are not efficient due to loss of the escaped light not being fully focused by the optical elements. In addition, such systems require utilization of bigger reflectors and bulky cooling systems because of the heat generated by mercury lamps, and as a result, the weight of such systems limiting the speed of the curing apparatus. Moreover, curing systems utilizing mercury lamps do not allow placing a curing surface close to a reflector due to the nature of lamp illumination, which requires focusing optics to be placed far from the curing surface in order to capture more light emitted in 360 degrees from the mercury lamp. Another limitation is the heat generated by the mercury lamp: placing a lamp too close to a curing surface or to a reflector will result in overheating and deforming the curing surface or the reflector, or both. Higher curing system efficiency, or more complete use of emitted radiation, means less radiation needs to be emitted to effect curing. Higher curing system efficiency will result in less power required to effect curing of the adhesive on the curing surface. More efficient systems characterized by a highly uniform focused beam of irradiance are needed for efficient curing applications.
Systems and methods for curing a curable coating with electromagnetic radiation are provided.
In one set of embodiments, a system for focusing electromagnetic radiation onto an illumination area is provided. The system includes a reflector having a focusing reflective surface, a source focal region, and an object focal region. The system further includes an electromagnetic radiation source for emitting electromagnetic radiation onto said illumination area; wherein said source of electromagnetic radiation is disposed at the source focal region, and the focusing reflective surface reflects an electromagnetic radiation toward the illumination area disposed at the object focal region.
In one set of embodiments, a system for focusing electromagnetic radiation onto an illumination area is provided. The system includes a first reflector having a first focusing reflective surface, a first source focal region, and a first object focal region. The system further includes a first electromagnetic radiation source for emitting electromagnetic radiation onto said illumination area; wherein said source of electromagnetic radiation is disposed at the first source focal region of the first reflector, and the first focusing reflective surface reflects an electromagnetic radiation toward said illumination area. The system further includes a second reflector having a second focusing reflective surface, a second source focal region, and a second object focal region. The system further includes a second source of electromagnetic radiation for emitting electromagnetic radiation onto said illumination area; wherein said source of electromagnetic radiation is disposed at the second source focal region of the second reflector, and the second focusing reflective surface reflects an electromagnetic radiation toward said illumination area.
In one set of embodiments, a method of curing an electromagnetic radiation-curable coating on a substrate using electromagnetic radiation is provided. The method comprises the steps of providing a coated substrate; locating an electromagnetic radiation reflector at a position spaced from said coated substrate; and positioning an electromagnetic radiation source between said coated substrate and said electromagnetic radiation reflector such that said rays being emitted by said source onto reflector and reflected onto said coated substrate.
Other aspects, embodiments and features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying figures. The accompanying figures are schematic and are not intended to be drawn to scale. In the figures, each identical or substantially similar component that is illustrated in various figures is represented by a single numeral or notation.
For purposes of clarity, not every component is labeled in every figure. Nor is every component of each embodiment of the invention shown where illustration is not necessary to allow those of ordinary skill in the art to understand the invention. All patent applications and patents incorporated herein by reference are incorporated by reference in their entirety. In case of conflict, the present specification, including definitions, will control.
The preceding summary, as well as the following detailed description of the invention, will be better understood when read in conjunction with the attached drawings. For the purpose of illustration the invention, presently preferred embodiments are shown in the drawings. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown.
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The following embodiments of the proposed invention are designed to solve mentioned above problems associated with the prior art optical systems for curing by utilizing an array of light emitting devices (LEDs) emitting light in about 120 degrees in case of Lambertian emission LEDs, and in about 80 degrees in case of collimating emission LEDs, resulting in the optical systems characterized by high efficiency, uniform narrow-line high intensity irradiance, and compact designs without need to employ an elaborate optical and bulky cooling systems.
Some embodiments involve maximizing the intensity of electromagnetic spectrum emitted by a radiation source during the process of curing an adhesive by utilizing an array of LEDs and reflector and to provide an apparatus for curing an adhesive on a curing surface of varying dimensions.
In some embodiments, the proposed invention utilizes an array of LEDs instead of mercury lamp as a source of electromagnetic radiation. The light emitted form a Lambertian emission LED is in approximately 120 degrees, and is in approximately 80 degrees in case of an LED having a collimating emission characteristic. Only one reflector may be needed to effectively focus the light from an LED array into a uniform and narrow line of irradiance utilizing a Lambertian emission LED; more compact reflector may be needed in case of an LED with collimating emission. Two reflectors with shared object focal point could be used to double the intensity of irradiation. The width of irradiance line is controlled by optimizing the reflector, i.e. the distance between a reflective surface, a source focal region, and an object focal region. The following are examples of advantage of the proposed invention over prior art: no need for collection optics such as light pipes or the need for a focusing lens, elimination of a bulky cooling system for a reflector, more efficient system with highly uniform focused beam of irradiance, smaller size of reflector, ability to focus the light into the narrow line while maintaining close proximity of curing surface and the reflector resulting in a much more compact design.
Referring to
Any suitable LEDs may be used in connection with the invention. Examples of suitable LEDs have been described, for example, in U.S. Pat. Nos. 6,831,302 and 7,417,367 which are incorporated herein in their entireties.
It will be understood that the invention may be embodied in other specific forms without departing from the spirit or central characteristics thereof. The present examples and embodiments, therefore, are to be considered in all respects as illustrative and not restrictive, and the invention is not to be limited to the details given herein.
This application claims priority to U.S. Provisional Patent Application Ser. No. 61/152,416, filed Feb. 13, 2009 which is incorporated herein by reference in its entirety.
Number | Date | Country | |
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61152416 | Feb 2009 | US |