FIELD OF THE INVENTION 
       [0001]    The present disclosure relates to a mask, especially to a thin-film mask, fitting aids, fitting and exposure assistant device and fitting method for the thin-film mask pasted on a curved substrate. 
       BACKGROUND 
       [0002]    Nowadays, the smart device, such as smart phone, smart watch or smart medical devices, with large-screen monitor is common and makes user receiving messages easier than before. Moreover, not only the size and the function are important for the large-screen monitors, the visual appearance including the shape, the contour and the color is also a part which is paid attention to. A stellar exterior design and the manufacturing process thereof makes the large-screen monitor having individuation and attractive appearance in the same time. Among them, the large-screen monitor with curved shell is the most popular and attractive one which might lead the fashion and tread of future. 
         [0003]    Currently used methods for manufacturing the curved shell and the pattern thereon of the smart device are described as follows: transfer printing and laser engraving after ink jet. Said transfer printing is preparing the pattern first and transferring the pattern to the target curved surface. Though the processing cost of transfer printing is low, however, the transfer printing technique has some drawback such as the slow processing speed, costly material, and the low resolution of printing. On the other side, as the name suggests, said laser engraving after ink jet is jetting the ink to the target curved surface first and then engraving the target curved surface to get the pattern by laser. This method costs high in material, equipment and processing and processes slow but with high printing resolution. The minimum resolution is up from 20 um. 
         [0004]    Accordingly, how to provide a method to manufacture the curved shell and the pattern thereon with low processing and material cost, high processing speed and high printing resolution and a method to make colorful patterns on a curved and solid shell has become the major emphasis of the smart device firm. One technique is called photolithography which coats a photoresist layer on the curved shell and uses light to transfer a geometric pattern to the resist layer on the curved shell. However, how to etch the curved shell by photo mask is the major direction of the related field. 
       SUMMARY 
       [0005]    In order to achieve the above objective and other purposes, the present disclosure provide a thin-film mask, fitting aids, fitting and exposure device and fitting method for the thin-film mask pasted on a curved substrate. Applying a fitting aid to curve the thin-film mask and to make the thin-film mask pasting on the curved substrate, therefore, a curve surface pattern could be patterned on a curved substrate. By using the apparatus and method of present disclosure, the curved surface patterns on the curved substrate can be mass production by the light resist technique, and increase the quality, the precision and the yield of the products. 
         [0006]    The present disclosure provides a thin-film mask for attaching to a curved substrate to form a photoresist layer on the curved substrate, and comprising: a thin-film substrate, composed of a flexible material; and a thin-film mask layer, formed on the thin-film substrate, having a visible pattern and used to attach to the photoresist layer of the curved substrate; wherein the thickness of the thin-film substrate is between 1 micrometer and 100 micrometers, the thickness of the thin-film mask layer is between 10 nanometers and 3000 nanometers. 
         [0007]    The present disclosure also provides a fitting aid for which assists the thin-film mask to paste on the curved substrate when applying a pressure and acts as an interface between the thin-film mask and a exposure device, which comprising: a flexible sheet, composed of an elastic material with high transmittance, passed through by the light having a wavelength between 300 nanometers and 500 nanometers, deformed by an outer force to make the thin-film mask pasting closely on the photoresist layer of the curved substrate while the thin-film mask is attached to the curved substrate, and curved the thin-film mask. 
         [0008]    The present disclosure provides a fitting and exposure assistant device for forming a photoresist layer with a curved surface pattern on a curved substrate, comprising: a thin-film mask which comprising a thin-film substrate, composed of a flexible material, disposing a plurality of positioning holes which is positioning and aligning the thin-film substrate to the curved substrate by a fitting aid, and a thin-film mask layer, formed on the thin-film substrate, having a visible pattern, wherein the thickness of the thin-film substrate is between 1 micrometer and 100 micrometers, the thickness of the thin-film mask layer is between 10 nanometers and 3000 nanometers; a flexible sheet, composed by a elastic material with high transmittance, passed through by the light having a wavelength between 300 nanometers and 500 nanometers, wherein the flexible sheet is deformed by an outer force to make the thin-film mask pasting on the photoresist layer of the curved substrate closely while the thin-film mask is attached to the curved substrate, and curves the surface of the thin-film mask; wherein the flexible sheet, the thin-film mask layer and the curved substrate are piled up in order, and exposed together in a exposure device to formed the curved pattern on the photoresist layer. 
         [0009]    The present disclosure also provides a fitting and exposure assistant device for forming a photoresist layer with a curved surface pattern on a curved substrate, comprising: a thin-film mask comprising a thin-film substrate, composed of a flexible material, disposing a plurality of positioning holes for positioning and aligning the thin-film substrate to the curved substrate by a fitting aid, and a thin-film mask layer, formed on the thin-film substrate, having a visible pattern, wherein the thickness of the thin-film substrate is between 1 micrometer and 100 micrometers, the thickness of the thin-film mask layer is between 10 nanometers and 3000 nanometers; a hard sheet, having a curved surface matching with the curved substrate for pressing and pasting the thin-film mask to the photoresist layer of the curved substrate closely while the thin-film mask is attached to the curved substrate, and curves the surface of the thin-film mask; wherein the curved substrate fitting with the thin-film mask layer is exposed in the exposure assistant device to formed the curved surface pattern on the photoresist layer. 
         [0010]    The present disclosure further provides a method for fitting a thin-film mask to a curved substrate, comprising the steps of: providing a curved substrate, a thin-film mask and a fitting aid, wherein the curved substrate having a photoresist layer; setting the thin-film mask between the curved substrate and the fitting aid; and pressing and fitting the thin-film mask to the curved substrate by using the fitting aid. 
         [0011]    In order to make the structure and characteristics as well as the effectiveness of the present disclosure to be further understood and recognized, the detailed description of the present disclosure is provided as follows along with embodiments and accompanying figures. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1A to 1D  show a flow chart of steps for fitting a thin-film mask to a curved substrate according to various embodiments of the present disclosure; 
           [0013]      FIGS. 2A and 2B  show a top view and a cross-sectional view of the curved shell fabricated by the method of the present disclosure; 
           [0014]      FIGS. 3A and 3B  show a top view and a cross-sectional view of the thin-film mask applying on the positive resist according to an embodiment of the present disclosure; 
           [0015]      FIGS. 4A and 4B  show a top view and a cross-sectional view of the thin-film mask applying on the negative resist according to another embodiment of the present disclosure; 
           [0016]      FIGS. 5A and 5B  show a top view and a cross-sectional view of the fitting fixture according to an embodiment of the present disclosure; 
           [0017]      FIG. 6A  shows a top view of the fitting aid according to an embodiment of the present disclosure; 
           [0018]      FIG. 6B to 6D  show cross-sectional views along the A-A cut of the fitting aid according to various embodiments of the present disclosure; 
           [0019]      FIG. 7A to 7E  show a flow chart in cross-sectional view of fitting a thin-film mask to a curved substrate according to an embodiment of  FIG. 1B  of the present disclosure; 
           [0020]      FIG. 8A to 8E  show a flow chart in cross-sectional view of fitting a thin-film mask to a curved substrate according to another embodiment of  FIG. 1B  of the present disclosure; 
           [0021]      FIG. 9A to 9E  show a flow chart in cross-sectional view of fitting a thin-film mask to a curved substrate according to further another embodiment of  FIG. 1B  of the present disclosure; 
           [0022]      FIG. 10A  shows a top view of the fitting aid according to another embodiment of the present disclosure; 
           [0023]      FIG. 10B  shows a cross-sectional view along A-A cut of the  FIG. 10A  of the present disclosure; and 
           [0024]      FIGS. 11  A to  11 E show a flow chart in cross-sectional view of fitting a thin-film mask to a curved substrate according to an embodiment of  FIG. 1D  of the present disclosure 
       
    
    
     DETAILED DESCRIPTION 
       [0025]    According to the embodiments of the present disclosure, they provide a flexible material fitting aid and a hard material fitting aid to make the thin-film mask being curved and paste and fit the thin-film mask on a curved substrate closely. Therefore, the curved substrate with the thin-film mask could fabricate curved surface patterns on it by processing a lithography process. 
         [0026]    Next, please refer to  FIG. 1A to 1D , the methods how a thin-film mask paste to a curved substrate according to various embodiments are disclosed. 
         [0027]    First, as shown in  FIG. 1A , it is a flow chart of steps for pasting a thin-film mask to a curved substrate according an embodiment of present disclosure, the steps comprising: 
         [0028]    Step  101 : providing a curved substrate having a photoresist layer, a thin-film mask and a fitting aid. 
         [0029]    Step  102 : setting the thin-film mask between the curved substrate and the fitting aid. 
         [0030]    Step  103 : pressing and fitting the thin-film mask to the curved substrate by using fitting aid. 
         [0031]    The relative content of embodiment of  FIG. 1A  would be illustrated with  FIG. 3A  to  FIG. 7E  later. 
         [0032]    Please refer to  FIG. 1B , which shows a flow chart of steps for pasting a thin-film mask to a curved substrate according another embodiment of present disclosure, the steps comprising: 
         [0033]    Step  111 : providing a curved substrate having a photoresist layer, a thin-film mask and a fitting aid composed by flexible material. 
         [0034]    Step  112 : setting the thin-film mask between the curved substrate and the fitting aid. 
         [0035]    Step  113 : pressing and fitting the thin-film mask to the curved substrate by using fitting aid. 
         [0036]    Step  114 : vacuum pumping to remove the air between the thin-film mask and the curved substrate. 
         [0037]    In the embodiment of  FIG. 1B , it provides a fitting aid composed of flexible materials, such as the silica gel with lamination bonding or other flexible materials with porous property, to help the thin-film mask fit on the curved substrate having photoresist layer. Besides, in the embodiment of  FIG. 1B , it also provides a vacuum pumping step to remove the air between the thin-film mask and the curved substrate to make the thin-film mask and the curved substrate fitting closely. Base on the characteristics mentioned above, the fitting aid could paste on the thin-film mask closely and forming a three-layer structure is composed of the fitting aid, the thin-film mask and the curved substrate to process a lithography process. Also, if the refractive index of the material of fitting aid is greater than the air, the effect of the exposure will be better because of the collimation of the light incident to the curved substrate is raised during the lithography process. 
         [0038]    Refer to  FIGS. 2A and 2B , which are a top view and a cross-sectional view of the curved shell  1  which fabricated by the skill of the present disclosure, wherein  FIG. 2B  is a cross-sectional view along the A-A cut of the  FIG. 2A . According to the figures, the curved substrate  10  has a photoresist layer  20  on which a curved surface pattern has been prepared. However, the preparation of the curved surface pattern is quite difficult. The lack of the precision of traditional screen printing results in a poor resolution of the curved surface pattern and fails to meet the high resolution need of consumer electronics. Comparatively speaking, the present disclosure provides a thin-film mask fitting perfectly on the photoresist layer of the curved substrate  10  formed by a high precision curved thin-film mask. After that, processing a lithography process on the curved substrate having the thin-film mask to get the high resolution curved surface patterns of the  FIG. 2A . 
         [0039]    Next, referring to  FIG. 3A  to  FIG. 7E  of the present disclosure to illustrate the fitting apparatus and methods of the present disclosure, especially the thin-film mask, the fitting aid and the fitting fixture used to paste the thin-film mask precisely and closely. 
         [0040]    Refer to  FIG. 3A  and  FIG. 3B  of the present disclosure, wherein  FIG. 3B  is a cross-sectional view along the A-A cut of  FIG. 3A , which show a thin-film mask example used for the positive resists. In the other side,  FIG. 4A  and  FIG. 4B  show an example that the thin-film mask is used for the positive resists, wherein  FIG. 4B  is a cross-sectional view along the A-A cut of  FIG. 4A . As the figures tell, the thin-film masks cover areas of two embodiments are in direction opposition. 
         [0041]    The thin-film mask  30 A of  FIG. 3A  and  FIG. 3B  comprising a thin-film substrate  39  and a thin-film mask layer  32  formed thereon. The thin-film mask  30 A of  FIG. 4A  and  FIG. 4B  comprising a thin-film substrate  39  and a thin-film mask layer  35  formed thereon. Said thin-film substrate  39  is composed of a flexible material, such as PET. And the thin-film mask layer  32 ,  35  formed on the thin-film substrate  39 , having a visible pattern and used to attach to the photoresist layer of the curved substrate, wherein the thickness of the thin-film substrate  39  is between 1 micrometer and 100 micrometers, the thickness of the thin-film mask layer is between 10 nanometers and 3000 nanometers. The thin-film mask layer  32 ,  35  is composed of the metal materials and has high flexibility when the thickness is ranged from 10 micrometers to 3000 micrometers, thus it is suitable for applying on the curved surface. In addition, the thin-film substrate  39  comprising a plurality of positioning holes for positioning and aligning the thin-film substrate to the curved substrate. 
         [0042]    Next, please refer to  FIG. 5A  and  FIG. 5B , which shows top view and a cross-sectional view of a fitting fixture according to an embodiment of the present disclosure. As shown in the figure, the fitting fixture  50  having a plurality of position latch  51  corresponding to the position holes  34  of the thin-film mask  30 A,  30 B. Therefore, the fitting fixture  50  can hold the thin-film mask  30 A,  30 B truly and help them position precisely. 
         [0043]    Please refer to  FIG. 6A , which shows a top view of the fitting aid according to an embodiment, and  FIG. 6B  to  FIG. 6D  are the cross-sectional views along the A-A cut of various type of fitting aid of the present disclosure. As shown in  FIG. 6B , the shape of fitting aid comprising a forming bottom  41 , a first curved side  42  and a second curved side  43  is prepared previously to fit the curved substrate  10  for enhancing the processing speed. In other preferred embodiments, as shown in  FIGS. 6C and 6D , the fitting aid could be a planar structure ( 40 B) or a designed structure having a curved bottom matching with the curved substrate  10  ( 40 C). The fitting aid is composed of single material, however, it could also be formed in different shapes by other different materials, such as silicone, silicone oil coated soft outer layer material, silicon organic material, fluorine-containing organic material or the mixture thereof. Base on the properties of those materials, the fitting aid could be a well deformation to help the thin-film mask fit on the curved surface  10 . 
         [0044]    It can be seen from the embodiments mentioned above that the efficiency will increase if the fitting aid is composed of an elastic material with high transmittance, such as could be passed through by the light having a wavelength between 300 nanometers and 500 nanometers. The collimation of the following exposure process increases as the material properties of the high transmittance elastic material, jointly, the printing resolution of the exposure process increases as well. 
         [0045]    Next, please refer to  FIG. 7A  to  FIG. 7E , which show a flow chart in cross-sectional view of fitting a thin-film mask to a curved substrate according to an embodiment of  FIG. 1B  of the present disclosure. In the embodiment, the fitting aid  40 A and the thin-film mask  30 A for positive resists layer  20 A are used. 
         [0046]    First, as shown in  FIG. 7A , the fitting fixture  50  hold the thin-film mask  30 A to position precisely to the curved surface  10  with positive photoresist layer  20 A, and the fitting aid  40 A is prepared to press and to fit after that. The figure illustrates the step  111  and step  112  of  FIG. 1B  which says providing a curved substrate having a photoresist layer, a thin-film mask and a fitting aid, wherein the fitting aid is composed by flexible material, and setting the thin-film mask between the curved substrate and the fitting aid. 
         [0047]    Next, as shown in  FIGS. 7B and 7C , the thin-film mask  30 A becomes deformed and fits to the curved surface  10  while the fitting aid  40 A keeps pressing on them. At this time, the positive photoresist layer  20 A of the curved substrate  10  and the thin-film mask layer  32  of the thin-film mask  30 A are fitting together, and supported by the air of the hollow area  31  which formed between the thin-film mask  30 A and the positive photoresist layer  20 A, which exactly express the meaning of step  113   FIG. 1B  that pressing and fitting the thin-film mask to the thin-film mask on the curved substrate by using fitting aid. 
         [0048]    Next, as mentioned in step  114  of  FIG. 1B , it processes a vacuum pumping method to remove the air between the thin-film mask and the curved substrate. Refer to  FIG. 7D , the air of the hollow area  31  between the thin-film mask  30 A and the positive photoresist layer  20 A in  FIG. 7C  would be removed, which results in the fitting aid  40 A with flexible material deformed again to fill the space. Therefore, the fitting aid  40 A, the thin-film mask  30 A and the positive photoresist layer  20 A would tightly fit to each other temporarily. It would bring the advantages for the following lithography process. 
         [0049]    At last, removing the fitting fixture  50  as shown in  FIG. 7E , then the exposure device could process the lithography by applying the ultraviolet light. 
         [0050]    All everything else equal,  FIG. 8A  to  FIG. 8E  show a embodiment using a negative photoresist layer  20 B and a corresponding thin-film mask  30 B thereof to forming a curved surface pattern. The process and the remarkable fact of negative resist embodiment is similar to the positive resist one shown on  FIG. 7A  to  FIG. 7E , thus, no more tautology here. The different between those two embodiments is the positions where the thin-film mask  30 A,  30 B having a deformation is different which results from the thin-film mask layer  35  and the thin-film mask layer  32  are locating on the different position. However, though the deformation part is different, the thin-film mask  30 B could still having a corresponding deformation suitable for negative resist use after the pressing pressure of the flexible fitting aid  40 A and the air removing by vacuum pumping step. 
         [0051]    Next, please refer to  FIG. 9A  to  FIG. 9E , they illustrate a different embodiment which applying other kind of the fitting aid  40 B to help the thin-film mask  30 A paste on the curved surface closely. In the embodiment, the fitting aid  40 B is a simply planar structure and the exterior of the fitting aid is not adjusted before use. However, it does not affect the effect of the fitting aid. Base on the characteristics of the flexible material of the fitting aid  40 B, a planar structure fitting aid  40 B could still have a corresponding deformation by an outer force to help the thin-film mask  30 A pasting closely to the curved substrate  10  while the thin-film mask is attached to the curved substrate. 
         [0052]    Besides, the fitting aid of present disclosure could also be formed as the type which the outside of the fitting aid is solid silicone gel and the liquid solid gel is contained inside of the fitting aid. This type of the fitting aid provides the same feature that it would have a corresponding deformation during the pressing and fitting process. Further, the material of fitting aid also extends the reach of other non-silicone flexible materials, such as an elastic material with high transmittance. 
         [0053]    The embodiments mentioned above fully illustrate all the aspect of the fitting aid composed of the flexible materials. Next, please refer to the figures and the following description, the characteristics of the fitting aid composed of hard materials is disclosed. 
         [0054]    Please refer to  FIG. 1C , which shows a flow chart of steps for pasting a thin-film mask to a curved substrate according another embodiment of present disclosure, where in the fitting aid is composed by hard material, the steps comprising: 
         [0055]    Step  121 : providing a curved substrate having a photoresist layer, a thin-film mask and a fitting aid composed by hard material. 
         [0056]    Step  122 : setting the thin-film mask between the curved substrate and the fitting aid. 
         [0057]    Step  123 : pressing and fitting the thin-film mask to the curved substrate by using fitting aid. 
         [0058]    Step  124 : vacuum pumping to remove the air between the thin-film mask and the curved substrate. 
         [0059]    Step  125 : removing the fitting aid. 
         [0060]    Please refer to  FIG. 1D , which shows a flow chart of steps for pasting a thin-film mask to a curved substrate according further another embodiment of present disclosure, where in the fitting aid is composed by hard material, the steps comprising: 
         [0061]    Step  131 : providing a curved substrate having a photoresist layer, a thin-film mask and a fitting aid composed by hard material. 
         [0062]    Step  132 : setting the thin-film mask between the curved substrate and the fitting aid. 
         [0063]    Step  133 : pressing and fitting the thin-film mask to the curved substrate by using fitting aid. 
         [0064]    Step  134 : removing the fitting aid. 
         [0065]    Next, refer to  FIG. 10A ,  FIG. 10B  and  FIG. 11A to 11E , the shape of fitting aid  60  composed of a hard material is prepared previously and fit on the curved substrate  10 , as  FIG. 10B  shows, fitting aid  60  comprising a bottom  61 , a first curved site  62 , a second curved site  63  and a supporting rib  64 . The supporting rib  64  is used to help position the fitting aid  60  because of the less flexibility of hard material. Also, on the bottom of the fitting aid  60  where contact to the thin-film mask can set up a flexible thin-film to enhance the effect of fitting and pasting. 
         [0066]    Refer to  FIG. 11A  to  FIG. 11E , the process is the same as the process of  FIG. 1C  and  FIG. 1D .  FIG. 11A  shows that providing a curved substrate having a photoresist layer, a thin-film mask and a fitting aid composed of hard material, and setting the thin-film mask between the curved substrate and the fitting aid which is described in steps  121  to  122  and steps  131  to  132 . 
         [0067]      FIG. 11B  to  FIG. 11C  show the step of pressing and fitting the thin-film mask to the curved substrate by using fitting aid which described in step  123  and step  133 . 
         [0068]      FIG. 11D  shows the step of removing the fitting aid which described in step  125  and step  134 . Though the step  124  does not show in the figures, however, it would be obviously the thin-film substrate  39  will deform and fit on the positive photoresist layer  20 A on the curved substrate  10  if the vacuum pumping is executed. 
         [0069]    To sum up, by the methods and the apparatus of present disclosure, the tools could easily to match each other, and the curved surface patterns on the curved substrate can be mass production by the light resist technique, and increase the quality, the product precision and the yield of products. 
         [0070]    Accordingly, the present disclosure conforms to the legal requirements owing to its novelty, non-obviousness, and utility. However, the foregoing description is only embodiments of the present disclosure, not used to limit the scope and range of the present disclosure. Those equivalent changes or modifications made according to the shape, structure, feature, or spirit described in the claims of the present disclosure are included in the appended claims of the present disclosure.
A thin-film mask, fitting aids, fitting and exposure assistant device and fitting method for the thin-film mask paste on a curved substrate is disclosed. The disclosure uses the fitting aids to apply pressure on the thin-film mask to paste on the curved substrate. After the template device had formed, send the template device to the exposure machine, and the high resolution color photoresist pattern is made on the curved substrate.