Abstract:
A coating device includes a coating material source, and at least one substrate disposed opposite to the coating material source. The substrate has a coating surface that receives coating material from the coating material source to form a film thereon. A board is disposed on the coating surface of the substrate. The height and thickness of the board and the angle between the board and the substrate determines gradually changed slope and gradually changed area of the film on the board, whereby the slope and the area can be precisely controlled during the deposition process.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a coating device and a tool used in the coating device, and more particularly to a coating device and a tool for coating an optical film thereon with a precise gradually changed slope and gradually changed area.  
         [0003]     2. Description of the Related Art  
         [0004]     In film-coating filed, coating a film with more than two kinds of thickness on a substrate, in particular, with a specific gradually changed slope, is difficult.  
         [0005]     Conventional methods for coating a film with more than two different thickness in different sections on the same substrate are implemented by regulating the oblique angle of the substrate or using an assistant board during the coating process. Consequently, the thickness of the coating material on the substrate is different on different areas of the substrate. Thus, an optical film with various gradually changed effects is formed by changing the thickness of the film to thereby change the spectrum characteristic of the film. However, the thickness of the coating material cannot be precisely controlled by the above-mentioned methods.  
         [0006]      FIG. 1  is a schematic view of a conventional coating device  5 . The coating device  5  comprises a base  52  and a substrate  51  obliquely set above and spaced from the base  52 . A target  53  is placed on the base  52  for forming a coating film  54  on the substrate  51  by sputtering or vapor-depositing. The substrate  51  is arranged at an oblique angle with respect to the base  52 . The thickness of the coating film  54  is in an inverse proportion to the 1.5 th  to 1.9 th  order of the distance between the base  52  and the substrate  51 . Therefore, the closer a portion of the substrate  51  is to the base  52 , the larger the thickness at the portion of the coating film  54  is.  
         [0007]     Although the oblique angle between the substrate  51  and the base  52  creates the coating film  54  having a gradually changed thickness on the substrate  51 , a gradually changed slope at a specific point on the substrate  51  cannot be defined. When the substrate  51  is tilted at an angle with respected to the base  52 , the gradient slope is pre-determined and the coating film  54  with the desired specific gradually changed slope is prohibited.  
         [0008]      FIG. 2  shows another typical coating device  9  using an assistant board with different shape. The coating device  9  comprises a vacuum chamber  90 , a coating umbrella  91  fixed on an upper portion of the vacuum chamber  90 , an assistant board  92 , and a coating material source  93 . The coating umbrella  91  is pivotally fixed with an axis of a motor  94  and is drove by the motor  94  to rotate about the axis. The coating material source  93  is located opposite to the coating umbrella  91 . The assistant board  92  is located adjacent to the coating umbrella  91  and between the coating material source  93  and the coating umbrella  91 . The coating umbrella  91  has a plurality of coating holes (not shown) in which a plurality of substrates  95  is fixed and a fix hole  910  receiving the axis of the motor  94 . The shape of the assistant board  92  and its position on the coating umbrella  91  will determine the thickness of the film on the substrate  95 . The detailed structure of the coating device  9  can be referred to Taiwan Patent Publication No. 540585.  
         [0009]     During the coating process using the coating device  9 , the plurality of substrates  95  are fixed on the coating umbrella  91 . The motor  94  then drives the coating umbrella  91  to rotate and the coating material source  93  sputters or vapor-deposits coating material on the substrate  95 . After the substrates  95  each are coated with one or more layers of coating material, the substrates  95  are detached from the coating umbrella  91  and other substrates  95  are put in the vacuum chamber  90 . Because there is a long distance between the assistant board  92  and the substrate  95 , it is difficult to precisely control the thickness of the coating on the substrate  95 .  
         [0010]     Taiwan Patent Publication No. M249958 disclosed another coating device. The coating device includes at least two coating material sources and at least two corresponding assistant boards. Similar to the device discussed above with reference to  FIG. 2 , it is also difficult for this coating device to precisely control the film with the gradually changed slope and the gradually changed area.  
       SUMMARY OF THE INVENTION  
       [0011]     Thus, an object of the present invention is to provide a coating device and a tool used in the coating device, the coating device can form a film which gradually changed slope and gradually changed area are precisely controlled.  
         [0012]     In order to achieve the above-mentioned object, the coating device in accordance with the present invention comprises a coating material source that supplies a coating material, and a substrate opposite to the coating material source. The substrate has a coating surface, which receives the coating material to form a film thereon. A board having predetermined height and thickness is arranged between the coating surface of the substrate and the coating material source. The board is rotatable with respect to the coating surface to selectively set an included angle between the board and the coating surface. By changing the height and thickness of the board and the included angle, the film is formed with a gradually changed slope and a gradually changed area.  
         [0013]     The substrate is arranged to be rotatable about an axis. A coating umbrella is rotatable about the axis and defines a hole for receiving and fixing the substrate therein. The substrate is surrounded by a frame having opposite sides between which the board is rotatably mounted. The coating device further comprises a vacuum chamber in an upper portion of which the coating umbrella is arranged, and the coating umbrella is coupled to and driven by a motor to rotate about the axis.  
         [0014]     The present invention also provides a tool used in the coating device. The tool comprises a frame adapted to receive and removably retain a substrate therein with a coating surface of the substrate receiving a coating material from a coating material source to form a film thereon; and a board having a height and thickness adjustably mounted on the frame and between the coating surface of the substrate and the coating material source, whereby by changing the height and thickness of the board and an included angle between the board and the coating surface, the film is formed with a gradually changed slope and a gradually changed area.  
         [0015]     The gradually changed slope and area of the film are precisely controlled by the coating device according to the invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]      FIG. 1  is a schematic view showing a conventional coating device;  
         [0017]      FIG. 2  is a schematic view showing another conventional coating device;  
         [0018]      FIG. 3  is a schematic view of a coating device according to a preferred embodiment of the invention;  
         [0019]      FIG. 4  is a schematic view of a tool used in the coating device shown in  FIG. 3 ; and  
         [0020]      FIG. 5  is a schematic view of a tool according to a second preferred embodiment of the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0021]     It will be understood that the illustration is for the purpose of describing preferred embodiments of the invention and is not intended to limit the invention thereto.  
         [0022]     Referring to  FIG. 3 , a coating device constructed in accordance with the present invention comprises a vacuum chamber  10 , which can be evacuated by a vacuum pump, a coating umbrella  11  fixed in an upper portion of the vacuum chamber  10 , a plurality of tools  2  (only one shown in the drawings) installed on the coating umbrella  11 , and a coating material source  13  arranged in a lower portion of the vacuum chamber  10 .  
         [0023]     The coating umbrella  11  is coupled to and driven by a motor  14  to rotate about an axis that is shown in dashed line in  FIG. 3 . The coating material source  93  is located opposite to the coating umbrella  11  and preferably offsets from a vertical center line of the coating umbrella  11 , which can be coincident with the rotation axis of the umbrella  11 . The coating umbrella  11  forms a plurality of coating holes (not shown) for fixing the tools  2  therein, respectively.  
         [0024]     Referring to  FIG. 4 , the tool  2  is constructed to receive and retain a rectangular substrate  23  therein. The substrate  23  has a surface  231 , which will be referred to as “coating surface” hereinafter, to receive a coating material from the coating material source  13  to form a film thereon. The tool  2  comprises a frame  21  surrounding the substrate  23 . In the embodiment illustrated, the frame  12  is rectangular, corresponding to the rectangular shape of the substrate  23 . A board  22  is mounted to the frame  21 , and preferably straddling between opposite sides of the frame  21  and opposing the coating surface  231  of the substrate  23 . The board  22  is allowed to rotate with respect to the frame  21 . The board  22  has predetermined height and thickness and is inclined with respect to the frame. 21  and the substrate  23  at a predetermined oblique angle that is denoted by symbol “θ” in  FIG. 4 .  
         [0025]     The tool  2  is mounted on the coating umbrella  11  in such a way that the substrate  23  is located on an outer surface of the coating umbrella  11  and that the board  22  partially extends through the coating hole of the coating umbrella  11  and into an interior of the coating umbrella  11 . Thus, the coating surface  231  of the substrate  23  faces the coating material source  13  through the coating hole. The coating material emitted from the coating material source  13  travels through the coating hole of the coating umbrella  11  and reaches and deposits on the coating surface  231  of the substrate  23  to form the coating film.  
         [0026]     During the coating process, the motor  14  rotates the coating umbrella  11 , while the coating material source  13  emits the coating material that is sputtered onto or vapor-deposited onto the coating surface  231  of the substrate  23  in a vacuum. After the coating surface  231  is coated with one or more layers of coating material, which form the coating film, the tool  2  is detached from the coating umbrella and removed out of the vacuum chamber  10 . Other sets of tools retaining new substrates  23  are put in the vacuum chamber  10  for the next cycle of coating operation.  
         [0027]     Because the distance between the board  22  and the substrate  23  is short, the thickness of the film on the substrate  23  can be precisely controlled by the board  22 . The height and thickness of the board  22  and the included angle between the board  22  and the substrate  23  are selected to precisely control the amount of the coating material adhered to the substrate  23  and thus the thickness at different areas of the film formed on the substrate  23 . This will be further described. Thus, the optical film with different gradually change effects can be formed by changing the thickness of the film to thereby change the spectrum characteristic of the film. Due to the board  22  of the tool  2 , the coating material emitted from different positions of the coating material source  23  forms different amount of the coating on the coating surface  231 , thus the thickness of the coating film on the substrate  23  gradually changes. Furthermore, the substrate  23  has a movement relative to the coating material source  13  when the coating umbrella  11  rotates, so the gradually changed area of the film is increased, and the gradually changed slope is altered. Therefore, to precisely control the gradually changed slope and the gradually changed area, the tool must be designed according to specific parameters, such as the gradually changed slope and gradually changed area of the film.  
         [0028]     The height and thickness of the board  22  and angle between the board  22  and the substrate  23  influence the gradually changed slope and gradually changed area of the coating film on the substrate  23  and are described as follows:  
         [0000]     1. Height of the Board  22  (H)  
         [0029]     The greater the height of the board  22  is, the larger the gradually changed area is. The smaller the height of the board  22  is, the less the gradually changed area is. The height of the board  22  also influences the gradually changed slope. 
 
 H=K·D  
 
 where “K” is a constant determined by the material of the coating material source, curvature of the coating umbrella  11 , and parameters of the vaporization and “D” represents the gradually changed area. 
 
 2. Angle Between the Board  22  and the Substrate  23  (θ) 
 
         [0030]     The angle between the board  22  and the substrate  23  is an angle from 0° to 180°. It is preferred that the angle is selected from the range between 45° to 135°. For the board  22  of a given height, the larger the absolute value of the difference |90−θ| is, the larger the gradually changed area is. For instance, assuming the height of the board  22  is 22 mm, when θ=90°, the gradually changed area is 6.3 mm, and when θ=70°, the gradually changed area is 8.5 mm.  
         [0031]     3. The thickness of the board  22  influences the area without film. The larger the thickness of the board  22  is, the larger the area without film is.  
         [0032]     4. The substrate  23  located on different circles of the coating umbrella  11  has different angles with respect to the coating material source  13 . Thus, the height of the board  22  and the angle between the board  22  and the substrate  23  should be properly designed to achieve the substrates having the same gradually changed area and gradually changed slope.  
         [0033]     Thus, considering all of the above-mentioned factors, a gradually changed film with predetermined gradually changed slope and area can be designed. The gradually changed slope and area are precisely controlled.  
         [0034]     Referring to  FIG. 5 , a tool  3  according to a second preferred embodiment comprises a rectangular substrate  33 . The substrate  33  has a coating surface  331  adapted to receive coating material from the coating material source to form a film thereon. A frame  31  surrounds the substrate  33  along four sides thereof. A number of parallel boards  32  are mounted to the frame  31 , straddling between opposite sides of the frame  31 . The boards  32  are rotatable relative to the frame  31 . The board  32  locates on the coating surface  331  of the substrate  33 . The board  32  has predetermined height, thickness, and angle with respect to the substrate  23 .  
         [0035]     Thus, similar to the illustration with reference to the first embodiment, by changing the angular position of each board  32  with respect to the substrate, the film formed of the coating material on the coating surface  331  can be regulated. Further, by setting the height and thickness of each board  32 , the film can also be regulated.