Abstract:
An electromagnetic interference (EMI) shielding filter includes a conductive pattern for shielding electromagnetic waves; and blackened layers formed on a surface of the conductive pattern. The electromagnetic interference (EMI) shielding filter is manufactured by preparing a base film; forming on the base film a first blackened layer, a conductive layer, and a second blackened layer in sequence; and patterning the first blackened layer, the conductive layer, and the second blackened layer by using a same mask, and forming on front and rear surfaces of an EMI shielding layer a conductive pattern comprising the first and second blackened layers.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to an electromagnetic interference shielding filter and a manufacturing method thereof, in which the surface of an electromagnetic interference shielding layer is melanized (or blackened) to improve contrast ratio.  
         [0003]     2. Discussion of the Background Art  
         [0004]     In general, image display devices have an electromagnetic interference (EMI) shielding filter on the front surface to shield emission of electromagnetic waves to outside. The EMI filters not only shield electromagnetic waves but also transmit visible rays, so they usually have a conductive mesh pattern. A related art conductive mesh pattern, however, reflected an external light or a visible ray from a display panel. As a result, contrast was deteriorated. This problem is apparent in a plasma display panel (hereinafter it is referred to as “PDP”) that displays images by using a gas discharge.  
         [0005]     PDPs regulate gas discharge time of each pixel on the basis of digital video data, and display an image. Typical examples of these PDPs are AC PDPS, as shown in  FIG. 1 , which includes three electrodes and are driven by an AC voltage.  
         [0006]      FIG. 1  is a perspective view of a related art AC PDP. More particularly,  FIG. 1  illustrates the structure of a discharge cell corresponding to a sub-pixel.  
         [0007]     As shown in  FIG. 1 , the discharge cell is divided into an upper plate  15  and a lower plate  25 . The upper plate  15  includes an upper substrate  10  where a sustain electrode pair  12 A and  12 B, an upper dielectric layer  14 , and a protective film  16  are formed in sequence. The lower plate  25  includes a lower substrate  18  where an address electrode  20 , a lower dielectric layer  22 , a barrier rib  24 , and fluorescent layers  26 .  
         [0008]     The upper substrate  10  and the lower substrate  18  are spaced out in parallel by the barrier rib  24 . The sustain electrode pair  12 A and  12 B respectively includes a transparent electrode for transmitting visible rays, and a metal electrode for compensating resistance of the transparent electrode. The transparent electrode is relatively wider than the metal electrode. The sustain electrode pair  12 A and  12 B includes a scan electrode  12 A and a sustain electrode  12 B. The scan electrode  12 A provides scan signals for determining data supply time, and sustain signals for sustaining the gas discharge. On the other hand, the sustain electrode  12 B mainly provides sustain signals for sustaining the discharge. The upper dielectric layer  14  and the lower dielectric layer  22  are piled up with charges from the gas discharge. The protective film  16  protects the upper dielectric layer  14  from damages caused by a sputtering of plasma and thus, extends lifespan of the PDP and improves the emission efficiency of secondary electrons. The protective film  16  is usually made from magnesium oxide NgO). The dielectric layers  14  and  22  and the protective film  16  lower an externally applied discharge voltage. The address electrode  20  is formed at tight angles to the sustain electrode pair  12 A and  12 B. The address electrode  20  provides data signals for selecting cells to be displayed. The barrier rib  24  together with the upper and lower substrates  10  and  18  create a discharge space. The barrier rib  24  is formed in parallel with the address electrode  20 , and prevents ultraviolet rays generated by the gas discharge from being leaked to the adjacent discharge cells. The fluorescent layer  26  is applied to the surface of the lower dielectric layer  22  and barrier rib  24 , and generate one of visible rays in red, blue, or blue. The discharge space is filled with different compositions of inert gas mixtures including He, Ne, Ar, Xe, and Kr, or Excimer gas for generating ultraviolet rays.  
         [0009]     Thusly structured discharge cell is selected by an opposing electrode discharge between the address electrode  20  and the scan electrode  12 A, and sustained by a surface discharge between the scan electrode  12 A and the sustain electrode  12 B. Therefore, the fluorescent layer  26  is excited by ultraviolet rays generated during the sustain discharge, and visible rays are emitted to the outside of the cell. In this case, the discharge cell controls the cell&#39;s discharge sustain period, namely frequency of the sustain discharge, according to video data, and emits a light at a gray scale level.  
         [0010]      FIG. 2  is a schematic perspective view of a PDP set including the PDP  30  of  FIG. 1 .  
         [0011]     As shown in  FIG. 2 , the PDP set includes a case  60 , a printed circuit board  50  (hereinafter, it is referred to as (“PCB”) housed in the case  60 , a PDP  30 , a glass type front filter  40 , and a cover  70  connected to the case  60  and encompassing the glass type front filter  40 .  
         [0012]     As discussed before with reference to  FIG. 1 , the PDP  30  includes an upper plate  15  and a lower plate  25  connected to the upper plate  15 .  
         [0013]     The PCB  50  disposed on the rear surface of the PDP  30  includes a plurality of driving and control circuits for driving the sustain electrode pair  12 A and  12 B and the address electrode  20  formed on the PDP  30 . Situate between the PCB  50  and the PDP  30  is a heat radiation plate (not shown) for radiating heat emitted from the PDP  30  and the PCB  50 .  
         [0014]     The glass type front filter  40  shields electromagnetic waves generated from the PDP  30  towards the front surface, prevents external light reflection, blocks near-infrared rays, and corrects colors. To this end, the glass type front filter  40  includes, as shown in  FIG. 3 , a first antireflection coating  44  attached to a front surface of a glass substrate  42 , an EMI shielding filter  46 , a NIR (near infrared ray) blocking film  48 , a color correcting film  52 , and a second antireflection coating  54 , the EMI shielding film  46 , the NIR blocking film  48 , the color correcting film  52  and the second antireflection coating  54  being layered in cited order on the rear surface of the glass substrate  42 .  
         [0015]     The glass substrate  42  is made from a reinforced glass to support the glass type front filter  40  and to protect the front filter  42  and the PDP  30  from damages caused by external impacts. The first and second antireflection coatings  44  and  54  prevent incident light rays from outside from being reflected back to the outside and thus, improve contrast effects. The EMI shielding filter  46  absorbs electromagnetic waves generated from the PDP  30 , and shields the emission of the electromagnetic waves to outside. The NIR blocking film  48  absorbs near infrared rays at a wavelength band of 800-1000 nm that are generated from the PDP  30 , and blocks the emission of the near infrared rays to outside. This is how infrared rays (approximately 947 nm) generated from a remote controller are normally input to an infrared ray receiver built in the PDP set. The color correcting film  52  contains a color dye, which is used to adjust or correct colors, whereby color purity can be improved. These films  44 ,  46 ,  48 ,  52 , and  54  are adhered to the glass substrate  42  through an adhesive or glue.  
         [0016]     The case  60  protects the PCB  50 , the glass type front filter  40  and the PDP  30  from external shocks, and shields electromagnetic waves emitted from side and rear surfaces of the PDP  30 . Also, to ensure that the glass type front filter  40  is separated from the PDP  30 , the case  60  is electrically connected to the EMI shielding filter  46  of the glass type front filter  40  through a support member (not shown) that supports from the rear surface of the case  60 . Therefore, the case  60  and the EMI shielding filter  46  of the glass type front filter  40  are both earthed to a ground voltage, and absorb electromagnetic waves emitted from the PDP  30  and discharge them. This is how the emission of the electromagnetic waves to outside is blocked.  
         [0017]     Lastly, the cover  70  encompasses the outside of the glass type front filter  40 , and is connected to the case  60 .  
         [0018]     As discussed above, the related art PDP set includes the glass type front filter  40  for shielding electromagnetic waves and correcting optical characteristics. However, because the glass type front filter  40  includes a glass substrate made from the reinforced glass, which is relatively thick, the thickness and weight of the PDP set were increased, and the cost of manufacture was also increased.  
         [0019]     As an attempt to solve the above-described problems, a film type front filter without a glass substrate, as shown in  FIG. 4 , has been suggested. The film type front filter  65  shown in  FIG. 4  includes a color correcting film  68 , a NIR blocking film  66 , an EMI shielding filter  64 , and an antireflection layer  62 , each being sequentially adhered to an upper plate  15  of the PDP  30 .  
         [0020]     The antireflection coating  62  prevents incident light rays from outside from being reflected back to the outside. The EMI shielding filter  64  absorbs electromagnetic waves generated from the PDP  30 , and shields the emission of the electromagnetic waves to outside. The NIR blocking film  66  absorbs near infrared rays that are generated from the PDP  30 , and blocks the emission of the near infrared rays to outside. The color correcting film  68  contains a color dye, which is used to adjust or correct colors, whereby color purity can be improved. These films  62 ,  64 ,  66 , and  68  are adhered to the PDP  30  through an adhesive or glue.  
         [0021]     Both the glass type front filter  40  of  FIG. 3  and the film type front filter  65  include an EMI shielding filter  46  or  64  for shielding EMI from the PDP  30 . As shown in  FIGS. 5 and 6 , the EMI filter  46  or  64  includes an EMI shielding layer  75  formed of conductive meshes  74  and frames  72  for supporting the conductive meshes  74 , and a base film  75  formed on the EMI shielding layer  75 .  
         [0022]     Referring to  FIGS. 5 and 6 , to form the conductive meshes  74  and the frames  72  a metal layer made from silver (Ag) or copper (Cu) for example undergoes photolithography and etching processes to be patterned. To be more specific, a metal foil is formed on the base film  76 , and the metal foil is coated with a photoresist. Later, the photoresist coating is patterned by using a mask and thus, the frame and a photoresist pattern in mesh type are formed. The metal foil is patterned by using the photoresist pattern as a mask, and as a result, the EMI shielding layer  75  including the frames  72  and the conductive meshes  74  is formed on the base film  76 , as illustrated in  FIG. 6 . Any photoresist patterns remaining on the frames  72  and the conductive meshes  74  are removed through a strip process.  
         [0023]     The EMI shielding layer  75 , namely the conductive meshes  74  and the frames  72 , of the related art EMI shielding filter  46  or  64  is usually made from highly lustrous metals. Thus, an externally incident lights R 1  or display lights R 2  emitted from the PDP  30  are reflected by the metallic conductive meshes  74  and frames  72 . These reflected lights by the EMI shielding filter  75  increases overall black level or brightness of the PDP  30 , resulting in deterioration of contrast ratio.  
       SUMMARY OF THE INVENTION  
       [0024]     An object of the invention is to solve at least the above problems and/or disadvantages and to provide at least the advantages described hereinafter.  
         [0025]     Accordingly, one object of the present invention is to solve the foregoing problems by providing an electromagnetic interference shielding filter and a manufacturing method thereof, in which the surface of an electromagnetic interference shielding layer is melanized (or blackened) to improve contrast ratio.  
         [0026]     The foregoing and other objects and advantages are realized by providing an electromagnetic interference (EMI) shielding filter, including: a conductive pattern for shielding electromagnetic waves; and blackened layers formed on a surface of the conductive pattern.  
         [0027]     Another aspect of the invention provides a manufacturing method of an electromagnetic interference (EMI) shielding filter, the method including the steps of preparing a base film; forming on the base film a first blackened layer, a conductive layer, and a second blackened layer in sequence; and patterning the first blackened layer, the conductive layer, and the second blackened layer by using a same mask, and forming on front and rear surfaces of an EMI shielding layer a conductive pattern comprising the first and second blackened layers.  
         [0028]     Still another aspect of the invention provides a manufacturing method of an electromagnetic interference (EMI) shielding filter, the method including the steps of: preparing a base film; forming on the base film a first blackened layer and a conductive layer; patterning the first blackened layer and the conductive layer by using a same mask, and forming on the rear surface of an EMI shielding layer a conductive pattern comprising the first blackened layer; and forming a second, third, and fourth blackened layer for encompassing a front surface and both side surfaces of the conductive pattern.  
         [0029]     Another aspect of the invention provides a front filter of a plasma display panel, in which the front filter includes a conductive pattern for shielding electromagnetic waves, and a base film for supporting the conductive pattern, and blacked layers are formed on a part of the conductive pattern.  
         [0030]     Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objects and advantages of the invention may be realized and attained as particularly pointed out in the appended claims. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0031]     The invention will be described in detail with reference to the following drawings in which like reference numerals refer to like elements wherein:  
         [0032]      FIG. 1  is a perspective view of a related art three-electrode AC surface discharge plasma display panel (PDP);  
         [0033]      FIG. 2  is a schematic perspective view of a PDP set including a PDP of  FIG. 1 ;  
         [0034]      FIG. 3  is a cross-sectional view showing a vertical structure of a glass type front filter and PDP of  FIG. 2 , respectively;  
         [0035]      FIG. 4  is a cross-sectional view showing a vertical structure of a PDP to which a related art film type front filter is attached;  
         [0036]      FIG. 5  is a plan view showing a detailed structure of a related art electromagnetic interference (EMI) shielding filter of  FIG. 3  and  FIG. 4 ;  
         [0037]      FIG. 6  is a cross-sectional view of a related art EMI shielding filter, taken along line A-A′ in  FIG. 5 ;  
         [0038]      FIG. 7  is a cross-sectional view showing a structure of an EMI shielding filter according to a first embodiment of the present invention,  
         [0039]      FIGS. 8A and 8B  are cross-sectional views showing a step-by-step procedure for manufacturing an EMI shielding filter according to the present invention;  
         [0040]      FIG. 9  is a cross-sectional view showing a structure of an EMI shielding filter according to a second embodiment of the present invention; and  
         [0041]      FIGS. 10A through 10C  are cross-sectional views showing a step-by-step procedure for manufacturing an EMI shielding filter according to the present invention. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0042]     The following detailed description will present an electromagnetic interference (EMI) shielding filter and a manufacturing method thereof according to a preferred embodiment of the invention in reference to the accompanying drawings.  
         [0043]      FIG. 7  is a cross-sectional view showing a structure of an EMI shielding filter according to a first embodiment of the present invention. As shown in  FIG. 7 , the EMI shielding filter includes an EMI shielding layer  83  formed of conductive meshes  84  and frames  86  for supporting the conductive meshes  84 , and a base film  82  on which the EMI shielding layer  83  is formed.  
         [0044]     The conductive meshes  84  of the EMI shielding layer  83  are positioned at an area where light (visible rays) from a display panel (e.g., a PDP) is transmitted, and secure transmittance and absorb electromagnetic waves emitted from the display panel. The frames  86  encompasses outside of the conductive meshes  84  to support the conductive meshes  84  and to form a discharge path for absorbed electromagnetic waves. The EMI shielding layer  83  formed of the conductive meshes  84  and the frames  86  are made from metals including silver (Ag) or copper (Cu).  
         [0045]     The base film  82  supports the EMI shielding layer  83 .  
         [0046]     Also, a blackened layer  88  is formed on the surface of the metallic EMI shielding layer  83  to prevent light reflection. More specifically, the blackened layer  88  includes a first blackened layer  88 A formed on a rear surface of the EMI shielding layer  83  to absorb a display light from the display panel, and a second blackened layer  88 B formed on a front surface of the EMI shielding layer  83  to absorb an externally incident light. Therefore, the blackened layer  88  is useful for preventing the external light reflection and display light reflection by the EMI shielding layer  83 , and as a result thereof, contrast ratio can be improved.  
         [0047]     Here, the blackened layer  88  can be formed by oxidizing metals like Cu or Ni or oxidizing an alloy.  
         [0048]     In addition, at least one of the first and second blackened layers  88 A and  88 B can be formed by oxidizing the EMI shielding layer  83 .  
         [0049]     A manufacturing method of the EMI shielding filter with the above structure will be now explained.  
         [0050]     As shown in  FIG. 8A , a base film  82  is first prepared, and then the first blackened layer  88 A, a conductive layer  85  and the second blackened layer  88 B are sequentially formed on the top of the base film  82 . Here, the conductive layer  85  is formed trough a deposition process like a sputtering. The first and second blackened layers  88 A and  88 B are formed through a screen printing, compound thin film coating, or electrochemical blackening process.  
         [0051]     The second blackened layer  88 B is coated with a photo-resist, and the photoresist is patterned through a mask. In this manner, a photoresist pattern is formed on the frames and meshes. Using the photoresist pattern as a mask, the second blackened layer  88 B, the conductive layer  85 , and the first blackened layer  88 A are patterned in like manner. Hence, as shown in  FIG. 8B , the first and second blackened layers  88 A and  88 B are formed on the rear and front surfaces of the EMI shielding layer, that is on the rear and front surfaces of the conductive meshes  84  and frames  86 , respectively. Lastly, any photoresist patterns remaining on the second blackened layer  88 B are removed through a strip process.  
         [0052]      FIG. 9  is a cross-sectional view showing a structure of an EMI shielding filter according to a second embodiment of the present invention. As shown in  FIG. 9 , the EMI shielding filter includes an EMI shielding layer  93  formed of conductive meshes  94  and frames  96  for supporting the conductive meshes  94 , and a base film  92  on which the EMI shielding layer  83  is formed.  
         [0053]     The conductive meshes  94  of the EMI shielding layer  93  are positioned at an area where light (visible rays) from a display panel (e.g., a PDP) is transmitted, and secure transmittance and absorb electromagnetic waves emitted from the display panel. The frames  96  encompasses outside of the conductive meshes  94  to support the conductive meshes  94  and to form a discharge path for absorbed electromagnetic waves. The EMI shielding layer  93  formed of the conductive meshes  94  and the frames  96  are made from metals including silver (Ag) or copper (Cu).  
         [0054]     The base film  92  supports the EMI shielding layer  93 .  
         [0055]     Also, a blackened layer  98  is formed on the surface of the metallic EMI shielding layer  93  to prevent light reflection. More specifically, the blackened layer  98  includes first through fourth blackened layers  98 A through  98 D that are formed on the front, rear and both side surfaces of the EMI shielding layer  93 , respectively. The second blackened layer  98 B formed on the front surface of the EMI shielding layer  93  absorbs an externally incident light, the first blackened layer  98 A formed on the rear surface of the EMI shielding layer  93  absorbs a display light from the display panel, and the third and fourth blackened layers  98 C and  98 D formed on both sides of the EMI shielding layer  93  absorb the external light and the display light, respectively. Therefore, the blackened layer  98  is useful for preventing the external light reflection and display light reflection by the EMI shielding layer  93 , and as a result thereof, contrast ratio can be improved.  
         [0056]     A manufacturing method of the EMI shielding filter with the above structure will be now explained.  
         [0057]     As shown in  FIG. 10A , a base film  92  is first prepared, and then the first blackened layer  98 A, and a conductive layer  95  are sequentially formed on the top of the base film  92 . Here, the conductive layer  95  is formed through a deposition process like a sputtering. The first blackened layers  88 A is formed through a screen printing or compound thin film coating process.  
         [0058]     The conductive layer  95  is coated with a photoresist, and the photoresist is patterned through a mask. In this manner, a photoresist pattern is formed on the frames and meshes. Using the photoresist pattern as a mask, the conductive layer  95  and the first blackened layer  98 A ate patterned in like manner. Hence, as shown in  FIG. 10B , the EMI shielding layer, that is, the conductive meshes  94  and frames  96 , is formed on the base film  92 , and the first blackened layer  98 A is formed on the rear surfaces of the conductive meshes  94  and frames  96 , respectively. Any photoresist patterns remaining on the conductive meshes  94  and frames  96  are removed through a strip process.  
         [0059]     Referring to  FIG. 10C , after the first blackened layer  98 A is formed, the second through fourth blackened layers  98 B through  98 D are formed on the surface of the EMI shielding layer  93  formed of the conductive meshes  94  and frames  96 . The second through fourth blackened layers  98 B through  98 D can be formed on the front and both side surfaces of the conductive meshes  94  and frames  96  through an electrochemical blackening, e.g., electroless plating, or screen printing or compound thin film coating process.  
         [0060]     In conclusion, the EMI shielding filter and manufacturing method thereof can be advantageously used for preventing external light reflection and display light reflection by blackening the surface of the EMI shielding filter and thus, can improve contrast ratio of the display device.  
         [0061]     While the invention has been shown and described with reference to certain preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.  
         [0062]     The foregoing embodiments and advantages are merely exemplary and are not to be construed as limiting the present invention. The present teaching can be readily applied to other types of apparatuses. The description of the present invention is intended to be illustrative, and not to limit the scope of the claims. Many alternatives, modifications, and variations will be apparent to those skilled in the art. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents but also equivalent structures.