Abstract:
A vacuum coating apparatus includes at least a chamber, an arc discharge plasma source, a feeding-reeling unit, and a roller set. The first and second openings are connecting with the feeding or reeling unit so as to allow the substrate to enter and leave the chamber therethrough, respectively. The arc discharge plasma source located inside the chamber generates the plasma, which discharges radially from the arc discharge plasma source as its center. The roller set includes a plurality of the first rollers, which are located in the chamber and enclosing the arc discharge plasma source. A first surface of the substrate is facing the plurality of the first rollers and contacts tightly on the periphery of the first rollers so that the first rollers can rotate by the moving of the substrate. The material evaporated and emitted by the plasma is attached onto the first surface of the substrate.

Description:
[0001]    This application claims the benefit of Taiwan Patent Application Serial No. 103131945, filed Sep. 16, 2014, the subject matter of which is incorporated herein by reference. 
       BACKGROUND OF INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The invention relates to a vacuum coating apparatus, and more particularly to a large area roll-to-roll type vacuum coating apparatus. 
         [0004]    2. Description of the Prior Art 
         [0005]    In the art, roll to roll plasma coating method is a high productivity efficiency technology that is capable of continuously and simultaneously performing multi-layer coatings on flexible substrates. By comparing with the traditional batch or in-line plasma coating process, the roll-to-roll plasma coating technology can significantly reduce the production cost. The flexible substrate for the roll-to-roll type process is mainly made of a soft metal plate, a polymer material, which is light, thin, flexible, elastic, workable and transportable. Therefore, such kind of substrates is widely applied to food packing, capacitors, flexible circuit boards, solar cells, 3C products, heat mirrors and so on. 
         [0006]    In particular, the global warming induced by the green house effect has recently become one of crucial issues to nations worldwide. Hence, various renewable energy and energy-saving technologies have been development trends nowadays and are expected to have great contribution to the easing of global warming effect. 
         [0007]    For example, the heat mirror can effectively prevent the solar heat from entering the building and allow portions of the visible light to penetrate therethrough, so the energy consumption from the cooling systems and the illumination systems of the building can be greatly reduced. However, market prices for heat mirror glasses, Low-E glasses or flexible heat-insulation films are so high that they have not been adopted economically by the general public. Thus, a technology for providing low-cost heat mirrors is an unavoidable trend. 
         [0008]    Generally, a heat mirror is a coating film comprising of at least one metal oxide film, and the corresponding manufacturing process can be a reactive magnetron sputtering process employing a metal target in an oxygen atmosphere. However, the reactive magnetron sputtering process is accompanied by a rapid-change hysteresis phenomenon. Also, the target may suffer from toxicity as well as discharging problem. Hence, the stability of the process speed and the coating rate could not be maintained easily. Though the aforesaid shortcomings may be overcome by introducing dual magnetron targets, OES control and plasma power source, yet the investment involved is comparatively high. 
         [0009]    Further, the conventional roll-to-roll type vacuum coating apparatus usually uses a magnetron sputtering source as the plasma source for the coating. While the magnetron sputtering source is at work, the distance between the source and the substrate is about 10 cm and an effective width of about 15 cm hence the plasma is localized within some region, resulting in a local temperature hike on the substrate, causing the deforming of the substrate. Therefore, in the art, a large-capacity cooling cylinder shall be added to the conventional roll-to-roll type vacuum coating apparatus so as to avoid possible over-heating deformation upon the substrate. However, the installation of the cooling cylinder would significantly increase both the facilities cost and the energy consumption. Also, the relative motion between the polymer-made substrate and the cooling cylinder would possibly cause scratches on the substrate. 
         [0010]    In addition, the conventional flexible substrate in manufacturing can have a length of several thousand meters. A batch manufacturing process of the conventional roll-to-roll type vacuum coating apparatus usually takes tens of hours to finish. Also, in the manufacturing, the target material for the magnetron sputtering source is consumed with time, and the magnetic field strength on the target surface would increase gradually with the processing time. Thereupon, the coating speed and the makeup of the coated film vary with time, so a monitoring system is necessary for feedback controlling. 
         [0011]    Hence, how to provide a vacuum coating apparatus, that can perform various continuous vacuum coatings on the flexible substrate with modular designed chambers, that is capable of being arranged for different applications, of finishing the manufacturing process in a single run, so as to increase the yield effectively, lower the cost as well as enhance the product competitiveness, is an important subject. 
       SUMMARY OF THE INVENTION 
       [0012]    Accordingly, it is the primary object of the present invention to provide a vacuum coating apparatus, which can perform various continuous vacuum coating processes upon a flexible substrate with modular designed chambers, that is able to be re-assembled for different applications, capable of finishing the manufacturing process in a single run, so as to increase the yield effectively, lower the cost as well as enhance the product competitiveness. 
         [0013]    In the present invention, the vacuum coating apparatus includes at least one chamber, at least one arc discharge plasma source, a feeding-reeling unit and a roller set. The chamber has a first opening and a second opening connecting with the feeding or reeling unit respectively so as to allow the substrate to move in and out of the chamber. The substrate has a first surface and a second surface, which is opposing to the first surface. The arc discharge plasma source locating inside the chamber is to generate the plasma, which discharges radially from the arc discharge plasma source in the chamber. The roller set includes a plurality of first rollers circling the arc plasma discharge source. The first surface of the substrate faces the first rollers and contacts tightly on the periphery of the first rollers so that the first rollers can rotate by the moving of the substrate. The material evaporated and emitted by the plasma is attached onto the first surface of the substrate. 
         [0014]    In one embodiment of the present invention, the vacuum coating apparatus includes a plurality of chambers, each of which has a corresponding arc discharge plasma source. The substrate is detoured into each of the plurality of chambers. Each arc discharge plasma source in the respective chamber can generate plasma individually. 
         [0015]    All these objects are achieved by the vacuum coating apparatus described below. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    The present invention will now be specified with reference to its preferred embodiment illustrated in the drawings, in which: 
           [0017]      FIG. 1  is a schematic view of a preferred embodiment of the vacuum coating apparatus in accordance with the present invention; 
           [0018]      FIG. 2  is an enlarged view of the chamber of  FIG. 1 ; and 
           [0019]      FIG. 3  is a schematic view of another embodiment of the vacuum coating apparatus in accordance with the present invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0020]    The invention disclosed herein is directed to a vacuum coating apparatus. In the following description, numerous details are set forth in order to provide a thorough understanding of the present invention. It will be appreciated by one skilled in the art that variations of these specific details are possible while still achieving the results of the present invention. In other instance, well-known components are not described in detail in order not to unnecessarily obscure the present invention. 
         [0021]    Referring now to  FIG. 1  and  FIG. 2 , a schematic view of a preferred embodiment of the vacuum coating apparatus. The vacuum coating apparatus  100  includes a cylinder-shaped vacuum chamber  110 . The radial cross section view of the chamber  110  is shown in  FIG. 1  and  FIG. 2 . The chamber  110  has a first opening  111  and a second opening  112  located opposing to the first opening  111  inside the chamber  110 . A first feeding unit  120  located outside the chamber  110  is mounted at a position close to the first opening  111  and is connecting with the first opening  111 . At the other side of the chamber  110 , a second feeding unit  130  is mounted close to the second opening  112  and is connecting with the second opening  112 . One of the first feeding unit  120  and the second feeding unit  130  is to feed the substrate  180  into the chamber  110 , while the other thereof is to reel the substrate  180  leaving the chamber  110 . For example, by having the second feeding unit  130  as the unit to reel the substrate  180 , the first feeding unit  120  is to feed the substrate  180  to the chamber  110 . The substrate  180  enters the chamber  110  through the first opening  111 , and leaves the chamber  110  via the second opening  112 . In another example, the first feeding unit  120  can be applied as the unit to reel the substrate  180  and the second feeding unit  130  as the unit to feed the substrate  180 . In the present invention, the substrate  180  is a flexible coiled material having a specific width with unlimited choices of the materials. The flexible material is chosen according to manufacturing needs. Also, the embodiment of the feeding units in accordance with the present invention is not limited to the aforesaid two opposing feeding/reeling units. In other embodiment not shown here, the two feeding units  120 ,  130  can be integrated into one single unit capable of feeding and reeling the flexible substrate  180 . 
         [0022]    Inside the chamber  110 , a long cylindrical arc discharge plasma source  140  is placed. The arc discharge plasma source  140  is mounted coaxially with the chamber  110 .  FIG. 1  and  FIG. 2  show the radial cross section of the arc discharge plasma source  140 . The arc discharge plasma source  140  is inside the chamber  110  and is to generate the plasma  141 . The plasma  141  produced by the arc discharge plasma source is outwardly emitted radially from the arc discharge plasma source  140  as the center. 
         [0023]    The chamber  110  further includes a roller set for guiding the moving of the substrate  180  inside the chamber  110 . In this embodiment, the roller set consists a plurality of first rollers  150  and a plurality of second rollers  160 . Both the first rollers  150  and the second rollers  160  are driven to rotate. The first rollers  150  locate inside the chamber  110  and are mounted around the periphery of arc discharge plasma source  140 . Each of the first rollers  150  keeps the same distance d to the arc discharge plasma source  140 . The magnitude of the distance d is chosen depending on the manufacturing requirements. For example, the distance d may be within a range of 30-200 cm for typical processes. As shown in  FIG. 2 , inside the chamber  110 , two of the second rollers  160  are mounted close to the first opening  111 , while another two thereof are mounted close to the second opening  112 . It shall be understood to the ordinary skilled in the art that the arrangement of the first rollers  150  and the second rollers  160  is various, not limited to the pattern shown in this embodiment. For example, in other embodiments, the number of the first rollers  150  is not limited to four as shown in the embodiment. The first rollers  150  might be more than four. And the second rollers  160  may not be limited to a pair of two as shown in this embodiment. Moreover, the second rollers  160  may have one or more than two rollers mounted near the first or second opening  111  or  112 , respectively. 
         [0024]    Further, in this embodiment, each of the first rollers  150  is paired by a roller shield  170 , which is located between the respective first roller  150  and the arc discharge plasma source  140  and closer to the corresponding first roller. By providing the roller shield  170 , the respective first roller  150  can have a protection from the adhesion of the evaporated material generated by the plasma  141 . In the present invention, the material for the roller shield  170  is not strictly limited, such as stainless steel or other metallic materials. 
         [0025]    As shown in  FIG. 2 , the substrate  180  has a first surface  181 , a second surface  182  opposing to the first surface  181 , and two opposing ends  183 ,  184 . The first surface  181  of the substrate  180  faces and contacts the plurality of the first rollers  150 , and thus the first surface  181  is rolled over and tensed by the first rollers  150  as a polygon due to the flexibility of the substrate  180 . The opposing ends  183 ,  184  of the surface  182  of the substrate  180  are in contact with the second rollers  160  near the first opening  111  and second opening  112  respectively. And the two ends  183 ,  184  are further extended out of the chamber  110  through the first opening  111  and the second opening  112 , respectively. 
         [0026]    The operation of the present invention is as follows: While the substrate  180  is driven to move forward by the first feeding unit  120  and the second feeding unit  130 , the first rollers  150  are driven to rotate by the passing of the substrate  180  simultaneously. The evaporated material emitted by the plasma  141  from the plasma source  140  is adhered to and thus coated onto the first surface  181  of the substrate  180 . By providing the roller shield  170  to each of the first rollers  150 , the first rollers  150  can then be prevented from contamination of the evaporated material of the plasma  141 . This not only keeps the first roller  150  clean so as to avoid the damage to the substrate  180  caused by the contaminated unshielded first rollers  150 , but also protects the first rollers  150  from the high temperature of the plasma  141 . 
         [0027]    As mentioned above, the substrate  180  is a coiled material with a specific width. In the embodiment structure of the present invention, the effective area of the substrate  180  for coating is about (1.3-1.6)πdW, in which the d is the distance between the individual first roller  150  and the arc discharge plasma source  140  (equal substantially to the distance between the arc discharge plasma source  140  and the substrate  180 ), and the W is the width of the substrate  180 . 
         [0028]    In the embodiment of  FIG. 1 , if it is needed to coat more than two layers of films onto the substrate  180 , a backward-forward control upon the substrate  180  inside the chamber  110  can do this job. The determination of the speeds of the first rollers  150  and the second rollers  160  (if not free rotation), the tension of the substrate  180 , and the related parameters are up to the selection of the material of the substrate  180  and the requirement of the coating. 
         [0029]    Referring now to  FIG. 3 , a schematic view of another embodiment of the vacuum coating apparatus in accordance with the present invention is shown. The major difference between this embodiment to the aforesaid embodiment of  FIG. 1  is that this embodiment includes a plurality of chambers  110 A˜ 110 C, each of which has an individual arc discharge plasma source  140 A˜ 140 C. Similar to the aforesaid embodiment, the vacuum coating apparatus of  FIG. 3  also includes a first feeding unit  120  and a second feeding unit  130  (to be mounted to the opposing ends of the plurality of the chambers  140 A˜ 140 C). The substrate  180  is to go through, in order, each of the chambers  110 A˜ 110 C. The setup of this embodiment for the vacuum coating apparatus can be applied to relevant manufacturing processes for continuous vacuum multi-layer coating upon a flexible substrate. In the respective chambers  110 A˜ 110 C, the arc discharge plasma sources  140 A˜ 140 C can provide the same plasma, or different plasmas. For example, while the arc discharge plasma sources  140 A˜ 140 C produce the same plasma, then the vacuum coating apparatus of  FIG. 3  can be used to form three same layers onto the substrate  180  to meet the thickness requirement. In another example, while the arc discharge plasma sources  140 A˜ 140 C produce different plasmas, then three different films can be coated in order onto the substrate  180 . The chambers of the present invention are modular designed. This design is capable of being arranged for different applications, of finishing the manufacturing process in a single run, so as to increase the yield effectively, lower the cost as well as enhance the product competitiveness. It is also applicable to perform a backward-forward control of the substrate  180  in between the three chambers  110 A˜ 110 C to obtain thicker or more layers to be coated on the substrate  180 . In addition, in the embodiment of  FIG. 3 , air blocking chambers can be constructed between neighboring chambers (not shown here) to block gaseous molecules in different chambers hence the production stability and the product quality can be enhanced. 
         [0030]    In summary, by comparing to the conventional roll-to-roll type vacuum coating apparatus, the vacuum coating apparatus in accordance with the present invention has at least the following advantages. 
         [0031]    The vacuum coating apparatus of the present invention has a larger distance between the arc discharge plasma source and the substrate, where the conventional distance is about 10 cm. However the distance of the present invention can be up to 30-200 cm. In addition, the plasma of the present invention is emitted radial-outwardly at omni-ranged (360°) directions. The effective width of the present invention can be up to meters. Also for the polymer substrate of the present invention, it does not have a significant temperature hike during the manufacturing, so no cooling device is needed, such that the cooling device can be removed and thus the production cost can be reduced. 
         [0032]    In the present invention, for the distance between the arc discharge plasma source and the substrate is larger, the required amount of the reaction air can be reduced so that the possible toxicity on the target material during the plasma reactive deposition manufacturing process can be effectively prohibited. 
         [0033]    In the present invention, it is a large area roll-to-roll type vacuum coating apparatus. The chambers are modular-designed and the structures are simple, with the feature that is capable of performing backward and forward coating manufacturing processes in a single chamber or being reassembled to meet various applicable needs. 
         [0034]    In the present invention, the arc plasma discharge source works by arc discharging without the need of any magnets. When working for long periods, the coating rate and the film composition can be maintained and unaffected by the time. 
         [0035]    By utilizing the present invention for coating a three-layer film of TiO 2 /TiN/TiO 2  on a 1000 m PET substrate at respective coating speeds of 2/3/2 m/min., the process time is no more than 25 hours. It is thus proved that the present invention can perform a more-desired productivity. Importantly, the apparatus of the present invention is simply structured, at lower equipment cost and free of the risk of overheating and toxicity. 
         [0036]    The aforesaid embodiment is an example for explaining the feature and effect of the present invention. The embodiment is not a limitation to the realization of the present invention. Without departing from the spirit and scope of the present invention, any change or modification referring to the present invention for making equivalent effects are covered by claims as follows.