Abstract:
The present invention relates to a front filter having a touch screen, and a plasma display apparatus having the same. The front filter installed on a front surface of a panel of a plasma display apparatus, the front filter including: a touch screen for generating a coordinate signal with respect to a touch point.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a plasma display apparatus, and more particularly, to a front filter having a touch screen, and a plasma display apparatus having the same. 
     2. Description of the Related Art 
     Plasma display panel (hereinafter referred to as “PDP”) generally displays an image including character or graphic by generating light from fluorescent substance using ultraviolet rays with a wavelength of 147 nm, which is generated during a gas discharge of an inert mixture gas, such as He+Xe, Ne+Xe, He+Ne+Xe or the like. This PDP has easy slimness and large-sized characteristics, and provides a greatly improved picture quality thanks to the recent technology development. Especially, three-electrode alternating current (AC) surface discharge type PDP has advantages of a low voltage operation and a long life since wall charges stored on a surface in the course of discharge protect electrodes from sputtering generated by the discharge. 
       FIG. 1  is a view illustrating a discharge cell of a conventional three-electrode alternating current (AC) surface discharge type plasma display panel. 
     Referring to  FIG. 1 , a discharge cell of the three-electrode AC surface discharge type PDP includes a scan electrode (Y) and a sustain electrode (Z) formed on an upper substrate  10 , and an address electrode (X) formed on a lower substrate  18 . Each of the scan electrode (Y) and the sustain electrode (z) includes transparent electrodes  12 Y and  12 Z and metal bus electrodes  13 Y and  13 Z having line widths narrower than line widths of the transparent electrodes  12 Y and  12 Z formed at one-sided edge regions of the transparent electrodes  12 Y and  12 Z. 
     The transparent electrodes  12 Y and  12 Z are generally formed of Indium-Tin-Oxide (Hereinafter, referred to as “ITO”) on the upper substrate  10 . The metal bus electrodes  13 Y and  13 Z are generally formed of chrome (Cr) on the transparent electrodes  12 Y and  12 Z to function to reduce a voltage drop caused by the transparent electrodes  12 Y and  12 Z having high resistance. An upper dielectric layer  14  and a passivation film  16  are layered on the upper substrate  10  having the scan electrode (Y) and the sustain electrode (z) formed in parallel with each other. The wall charge generated at the time of plasma discharge is stored in the upper dielectric layer  14 . The passivation film  16  prevents the upper dielectric layer  14  from being damaged due to the sputtering generating at the time of the plasma discharge and also, enhances an emission efficiency of a secondary electron. Magnesium oxide (Mgo) is generally used as the passivation film  16 . A lower dielectric layer  22  and a barrier  24  are formed on the lower substrate  18  having the address electrode (X), and a fluorescent layer  26  is coated on a surface of the lower dielectric layer  22  and the barrier  24 . The address electrode (X) is formed in a direction of crossing with the scan electrode (Y) and the sustain electrode (Z). The barrier  24  is formed in parallel with the address electrode (X) to prevent the visible ray and the ultraviolet ray caused by the discharge from being leaked to an adjacent discharge cell. The fluorescent layer  26  is excited by the ultraviolet ray generated due to the plasma discharge to radiate any one visible ray of red, green or blue. The inert mixed gas for the discharge such as He+Xe, Ne+Xe, He+Ne+Xe and the like is injected into a discharge space of the discharge cell provided between the upper/lower substrates  10  and  18  and the barrier  24 . 
     In the PDP, one frame is divided for time-division driving into several sub-fields having different light-emitting times so as to embody a gray level of the image. Each of the sub-fields is divided into a reset period for which an entire screen is initialized, an address period for which a scan line is selected and a specific cell is selected at the selected scan line, and a sustain period for which the gray level is embodied depending on the light-emitting times. 
     For example, in case that the image is expressed using a 256 gray level as in  FIG. 2 , a frame period (16.67 ms) corresponding to 1/60 second is divided into eight sub-fields (SF 1  to SF 8 ). Also, each of the eight sub-fields (SF 1  to SF 8 ) is again divided into a reset period, an address period and a sustain period. Herein, the reset and address periods of each sub-field are identical every sub-field, while as the sustain period is increased in a ratio of 2 n  (n=0, 1, 2, 3, 4, 5, 6, 7) at each of the sub-fields. 
     In the above-driven PDP, a front filter for shielding an electronic wave and also preventing an external light from being reflected is installed on a front surface of the upper substrate  10 . 
       FIG. 3  is a schematic section view illustrating a portion of a conventional plasma display apparatus. 
     Referring to  FIG. 3 , the conventional plasma display apparatus includes a panel  32  where the upper substrate  10  and the lower substrate  18  are attached to each other with a gap therebetween, a front filter  30  installed at a front surface of the panel  32 , a chassis base  36  for supporting the panel  32  and also mounting a printed circuit board thereon, a heat sink plate  34  attached to a front surface of the chassis base  36 , a back cover  38  installed on a rear surface of the panel  32 , and a front cabinet  45  for electrically connecting the back cover  38  and the front filter  30 . 
     The front cabinet  45  includes a filter support portion  40  for electrically connecting the front filter  30  and the back cover  38 , and a support member  42  for fixing and supporting the front filter  30  and the back cover  38 . The filter support portion  40  supports the front filter  30  such that a rear surface of the front filter  30  is spaced away from the panel  32 . Further, the filter support portion  40  electrically connects the EMI shield film included in the front filter  30  to the back cover  38  grounded to a ground voltage source to discharge an EMI signal from the EMI shield film. Also, the filter support portion  40  prevents the EMI from being laterally emitted. 
     The printed circuit board mounted on the chassis base  36  supplies a driving signal to electrodes (for example, a scan electrode, a sustain electrode and an address electrode) of the panel  32 . For this, the printed circuit board includes various driving portions not shown. The panel  32  displays a certain image in response to the driving signal supplied from the printed circuit board. The heat sink plate  34  dissipates heat generated from the panel  32  and the printed circuit board. The back cover  38  protects the panel  32  from an external impact, and also shields an electromagnetic interference (Hereinafter, referred to as “EMI”) laterally emitted. 
     The front filter  30  shields the EMI and also, prevents an external light from being reflected. For this, the front filter  30  includes a antireflection coating  50 , an optical characteristic film  52 , a touch screen  56 , and a near infrared ray (Hereinafter, referred to as “NIR”) shield film  58 . Herein, an adhesive layer is formed between respective films  50 ,  52 ,  56  and  58  of the front filter  30  to adhere respective films  50 ,  52 ,  56  and  58  to one another. Generally, a specific substance is added to the adhesive layer to form the optical characteristic film  52 . At this time, a structure of the front filter is a little varied depending on a manufacture enterprise. 
     The antireflection coating  50  prevents an external incident light from being reflected toward an external to improve a contrast of a plasma display panel (PDP). The antireflection coating So is formed on a surface of the front filter  30 . Meanwhile, the antireflection coating  50  can be additionally formed on a rear surface of the front filter  30 . 
     The optical characteristic film  52  functions to decrease brightness of red (R) and green (G) of visible ray incident from the panel, while it functions to increase brightness of blue (B) to improve an optical characteristic of the PDP. 
     The glass  54  prevents the front filter  30  from being damaged by the external impact. That is, the glass  54  supports the front filter  30  to prevent the front filter  30  from being damaged by the external impact. 
     The EMI shield film  56  shields the EMI to prevent the EMS incident from the panel  32  from being emitted to the external. In the above structure of the EMI shield film  56 , a plurality of first electrode lines  61   a  and a plurality of second electrode lines  61   b  are crossed with one another for an integral structure. Since the plurality of electrode lines is finely constructed like a black matrix, it does not influence the picture quality. 
     The NIR shield film  58  shields a NIR (Near Infrared Ray) emitted from the panel  32  to prevent the NIR exceeding a reference value from being emitted toward the external such that a signal transmitting device using IR (Infrared Ray) can normally transmit a signal such as a remote controller and the like. Meanwhile, the EMI shield film  56  and the NIR shield film  58  can be constructed as one layer. 
     As shown in  FIG. 6 , the front filter  30  is electrically connected with the back cover  38  through the filter support portion  40 . Describing this in detail, the filter support portion  40  is connected to the rear surface of the front filter  30  at one end of the front filter  30 . At this time, the filter support portion  40  is electrically connected with at least one of the EMI shield film  56  and the NIR shield film  58 . That is, the filter support portion  40  connects the front filter  30  to the back cover  38  to shield the EMI and/or the NIR. 
     The conventional front filter  30  uses the glass  54  so as to prevent the front filter  30  from being damaged by the external impact. This front filter is called a glass typed front filter. However, if the glass  54  is inserted into the front filter  30 , there is a disadvantage in that the front filter  30  is thickened. Further, if the glass  54  is inserted into the front filter  30 , there is a drawback in that the front filter  30  is increased in weight and also a manufacture cost. 
     In order to solve the above drawback, the front filter without the glass has been proposed. 
     On the other hand, as means for inputting any command on a screen of a display device, a touch screen is widely used. 
       FIG. 7  is a view illustrating a structure of a conventional touch screen. 
     The touch screen  70  includes an upper film  72  forming a first transparent conductive layer  74  thereon, and a lower film  76  forming a second transparent conductive layer  78  thereon and being spaced away from the upper film  72 . 
     The upper film  72  and the lower film  76  are united by a sealant  73  coated along an edge portion being a non-touch area and are spaced away from each other as much as a height of the sealant  73 . Further, a plurality of spacers (not shown) (for example, dot spacer and the like) is additionally formed on the first transparent conductive layer  74  of the upper film  72  or the second transparent conductive layer  78  of the lower film  76  at a touch area excepting for the non-touch area to separate the upper film  72  from the lower film  76 . 
     A transparent film formed of polyethylene terephthalate (PET) is mainly used as the upper film  72  pressed by a pen or a finger, and a transparent film formed of a material like the upper film  72  is used as the lower film  76 . As first and second transparent conductive layers  74  and  78 , any one of ITO (Indium-Tin-Oxide), IZO (Indium-Zinc-Oxide) and ITZO (Indium-Tin-Zinc-Oxide) is used. 
     If the first transparent conductive layer  74  is in contact with the second transparent conductive layer  78  by the upper film  72  pressed by the pen or the finger, a resistance value of the touch screen  70  is varied depending on its contact position. Additionally, since current or voltage is different depending on the varied resistance value, the touch screen  70  output the varied current or voltage as an X-axis coordinate signal through an X electrode bar  75 , that is, fist and second X electrode bars  75 A and  75 B connected to the first transparent conductive layer  74 , and outputs as a Y-axis coordinate signal through a Y electrode bar  79 , that is, first and second Y electrode bar  79 A and  79 B connected to the second transparent conductive layer  78 . In this case, the touch screen  70  sequentially outputs the X-axis coordinate signal and the Y-axis coordinate signal under control of a touch screen controller (not shown). 
     As described above, the front filter of the PDP performs an electromagnetic wave shielding function, a color adjustment function, a near infrared absorption function and the like. The touch screen performs a computer function, a home networking function, an automatic power-off function, an internet function and the like. 
     Accordingly, if the above touch screen is equipped with the plasma display apparatus, the plasma display apparatus does not require an external separate input device, and further can not only appeal to consumer&#39;s mentality, but also can enhance a value of a high-class brand. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention is directed to a front filter, and a plasma display apparatus having the same, that substantially obviate one or more problems due to limitations and disadvantages of the related art. 
     An object of the present invention is to provide a front filter with a touch screen, and a plasma display apparatus having the same. 
     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 objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings. 
     To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, there is provided a front filter installed on a front surface of a panel of a plasma display apparatus, the front filter including: a touch screen for generating a coordinate signal with respect to a touch point. 
     At this time, the touch screen can shield electromagnetic interference (EMI). Further, the front filter is preferably a film type filter. 
     According to the inventive the front filter, the touch screen can include: an upper film on which a plurality of first electrode lines are formed; a lower film on which a plurality of second electrode lines crossing the plurality of first electrode lines are formed; and a plurality of dot spacers formed at a touch area such that the upper film and the lower film are spaced away from each other. 
     At this time, at least one of the plurality of first and second electrode lines can be formed of a dual layer of silver (Ag) and Indium-Tin-Oxide (ITO). Further, at least one of the plurality of first and second electrode lines may be formed of silver (Ag). Also, at least one of the plurality of first and second electrode lines may be formed of Indium-Tin-Oxide (ITO). 
     The upper film and the lower film can be formed of PolyEthylene Terephthalate (PET). 
     According to the inventive front filter, the touch screen can include: an upper film on which a first transparent conductive layer is formed; a lower film on which a second transparent conductive layer facing the first transparent conductive layer is formed; and a plurality of dot spacers formed at the touch area such that the upper film and the lower film are spaced away from each other. 
     At this time, the first and second transparent conductive layers are formed of Indium-Tin-Oxide (ITO). 
     The inventive front filter further includes: an antireflection coating for preventing an external incident light from being again reflected toward an external; an optical characteristic film for decreasing brightness of red and green of visible ray incident from the panel and at the same time, increasing brightness of blue; and a near infrared ray shielding film for shielding near infrared ray radiated from the panel. 
     In another aspect of the present invention, there is provided a plasma display apparatus including: a panel formed by attaching an upper substrate and a lower substrate to each other; a front filter installed on a front surface of the panel, and having a touch screen for generating a coordinate signal with respect to a touch point; a chassis base for fixing the panel; a back cover installed on a rear surface of the panel; and a front cabinet for electrically connecting the front filter and the back cover. 
     It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principle of the invention. In the drawings: 
         FIG. 1  is a perspective view illustrating a structure of a discharge cell of a conventional plasma display panel; 
         FIG. 2  is a view illustrating a frame at which a 256 gray level is expressed in a conventional plasma display panel; 
         FIG. 3  is a schematic section view illustrating a portion of a conventional plasma display apparatus; 
         FIG. 4  is a schematic section view illustrating a front filter shown in  FIG. 3 ; 
         FIG. 5  is a detailed view illustrating an EMI shield film shown in  FIG. 4 ; 
         FIG. 6  is a detailed view illustrating a grounding procedure of a front filter and a filter support portion shown in  FIG. 3 ; 
         FIG. 7  is a view illustrating a structure of a conventional touch screen; 
         FIG. 8  is a view illustrating a front filter, of a plasma display apparatus according to a first embodiment of the present invention; 
         FIG. 9  is a detailed view illustrating a touch screen of  FIG. 8 ; 
         FIG. 10  is a view illustrating a front filter of a plasma display apparatus according to a second embodiment of the present invention; and 
         FIG. 11  is a detailed view illustrating a touch screen shown in  FIG. 10 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. 
       FIG. 8  is a view illustrating a front filter of a plasma display apparatus according to a first embodiment of the present invention. 
     Referring to  FIG. 8 , the front filter  130  includes an antireflection coating  150 , an optical characteristic film  152 , a touch screen  156 , and a Near Infrared Ray (Hereinafter, referred to as “NIR”) shield film  158 . Herein, it is desirable that the front filter  130  is a film type filter without a glass for support. 
     An adhesive layer is formed between respective films  150 ,  152 ,  156  and  158  of the front filter  130  to adhere respective films  150 ,  152 ,  156  and  158  to one another. Generally, a specific substance is added to the adhesive layer to form the optical characteristic-film  152 . 
     At this time, a structure of the front filter is a little varied depending on a manufacture enterprise. The present invention does not illustrate the adhesive layer for description convenience, and exemplifies the structure of the front filter  130  widely generally used at present. 
     The antireflection coating  150  prevents an external incident light from being reflected toward an external to improve a contrast of a plasma display panel (PDP). The antireflection coating  150  is formed on a surface of the front filter  130 . Meanwhile, the antireflection coating  150  can be additionally formed on a rear surface of the front filter  130 . 
     The optical characteristic film  152  functions to decrease brightness of red (R) and green (G) of visible ray incident from a panel, while it functions to increase brightness of blue (B) to improve an optical characteristic of the PDP. 
     The touch screen  156  shields EMI (Electromagnetic interference) to prevent the EMI incident from the panel from being emitted to the external. Describing a structure of the touch screen with reference to  FIG. 9 , the touch screen  156  includes an upper film  160   a  on which a plurality of first electrode lines  161   a  are formed, and a lower film  160   b  on which a plurality of second electrode lines  161   b  are formed in a direction of crossing with the plurality of first electrode lines  161   a  to face the upper film  160   a . At this time, since the plurality of electrode lines is finely structured like a black matrix, it does not influence a picture quality. Further, the plurality of first and second electrode lines  161   a  and  161   b  arranged in a format of the black matrix as described above shields the EMI. 
     The upper film  160   a  and the lower film  160   b  are united by a sealant (not shown) coated along an edge portion being a non-touch area, and are spaced away from each other as much as a height of the sealant. Further, a plurality of dot spacers  162  is additionally formed on the plurality of first electrode lines  161   a  of the upper film  160   a  or the plurality of second electrode lines  161   b  of the lower film  160   b  at a touch area excepting for the non-touch area to separate the upper film  160   a  from the lower film  160   b.    
     A transparent film formed of polyethylene terephthalate (PET) is mainly used as the upper film  160   a  pressed by a pen or a finger, and a transparent film formed of a material like the upper film  160   a  is used as the lower film  160   b . At least one of the first and second electrode lines  161   a  and  161   b  is formed of a dual layer of silver (Ag) and Indium-Tin-Oxide (ITO). Further, at least one of the first and second electrode lines  161   a  and  161   b  is formed of silver (Ag) or Indium-Tin-oxide (ITO). 
     If the first electrode line  161   a  is in contact with the second electrode line  161   b  by the upper film  160   a  pressed by the pen or the finger, a resistance value of the touch screen  156  is varied depending on its contact position. Additionally, since current or voltage is different depending on the varied resistance value, the varied current or voltage is outputted as x-axis and Y-axis coordinate signals through an external electrode not shown connected to the first and second electrode lines  161   a  and  161   b.    
     In other words, in a conventional structure of an EMI shield film having crossed and integrated first and second electrode lines, the inventive touch screen  156  separates the first electrode line  161   a  and the second electrode line  161   b  from each other to respectively form the first and second electrode lines  161   a  and  161   b  on the upper/lower films  160   a  and  160   b . And then, the plurality of dot spacers  162  is formed between the upper film  160   a  and the lower film  160   b . Accordingly, the touch screen  156  shields the EMI to not only prevent the EMI incident from the panel from being emitted to the external but to also perform a function of the touch screen. 
     The NIR shield film  158  shields the NIR radiated from the panel to prevent the NIR exceeding a reference value from being emitted to the external such that a signal transmitting device using IR (Infrared Ray) can normally transmit a signal such as a remote controller and the like. 
       FIG. 10  is a view illustrating a front filter of a plasma display apparatus according to a second embodiment of the present invention. 
     Referring to  FIG. 10 , the front filter  230  includes an antireflection coating  250 , an optical characteristic film  252 , a touch screen  256 , and a Near Infrared Ray (Hereinafter, referred to as “NIR”) shield film  258 . Herein, it is desirable that the front filter  230  is a film type filter without a glass for support. 
     An adhesive layer is formed between respective films  250 ,  252 ,  256  and  258  of the front filter  230  to adhere respective films  250 ,  252 ,  256  and  258  to one another. Generally, a specific substance is added to the adhesive layer to form the optical characteristic film  252 . 
     The antireflection coating  250  prevents an external incident light from being reflected toward an external to improve a contrast of a plasma display panel (PDP). The antireflection coating  250  is formed on a surface of the front filter  230 . Meanwhile, the antireflection coating  250  can be additionally formed on the rear surface of the front filter  230 . 
     The optical characteristic film  252  functions to decrease brightness of red (R) and green (G) of visible ray incident from a panel, while it functions to increase brightness of blue (B) to improve an optical characteristic of the PDP. 
     The touch screen  256  shields  8 MI (Electromagnetic interference) to prevent the EMI incident from the panel from being emitted to the external. Describing a structure of the touch screen with reference to  FIG. 11 , the touch screen  256  includes an upper film  260   a  on which a plurality of first transparent conductive layers  261   a  are formed, and a lower film  260   b  on which a plurality of second transparent conductive layers  261   b  are formed in a direction of crossing with the plurality of first transparent conductive layers  261   a  to face the upper film  260   a.    
     The upper film  260   a  and the lower film  260   b  are united by a sealant (not shown) coated along an edge portion being a non-touch area and are spaced away from each other as much as a height of the sealant. Further, a plurality of dot spacers  262  is additionally formed on the plurality of first transparent conductive layers  261   a  of the upper film  260   a  or the plurality of second transparent conductive layers  261   b  of the lower film  260   b  at a touch area excepting for the non-touch area to separate the upper film  260   a  from the lower film  260   b.    
     A transparent film formed of polyethylene terephthalate (PET) is mainly used as the upper film  260   a  pressed by a pen or a finger, and a transparent film formed of a material like the upper film  260   a  is used as the lower film  260   b . As first and second transparent conductive layers  261   a  and  261   b , indium-tin-oxide (ITO) is used. 
     If the first transparent conductive layer  261   a  is in contact with the second transparent conductive layer  261   b  by the upper film  260   a  pressed by the pen or the finger, a resistance value of the touch screen  256  is varied depending on its contact position. Additionally, since current or voltage is different depending on the varied resistance value, the varied current or voltage is outputted as X-axis and Y-axis coordinate signals through an external electrode not shown connected to the first and second transparent conductive layers  261   a  and  261   b.    
     In other words, in a conventional structure of an EMI shield film having crossed and integrated first and second transparent conductive layers, the inventive touch screen  256  separates the first transparent conductive layer  261   a  and the second transparent conductive layer  261   b  from each other to respectively form the first and second transparent conductive layers  261   a  and  261   b  on the upper/lower films  260   a  and  260   b . And then, the plurality of dot spacers  262  is formed between the upper film  260   a  and the lower film  260   b . Accordingly, the touch screen  256  shields the EMI to not only prevent the EMI incident from the panel from being emitted to the external, but to also perform a function of the touch screen. 
     The NIR shield film  258  shields the NIR radiated from the panel to prevent the NIP exceeding a reference value from being emitted to the external such that a signal transmitting device using IR (Infrared Ray) can normally transmit a signal such as a remote controller and the like. 
     The above-described film typed front filter has an advantage of light weight and also slim in comparison to a glass typed front filter. Further, the film typed front filter can reduce a manufacture cost in comparison to the glass typed front filter. 
     Since the plasma display apparatus is provided with the various-functional touch screen formed on the front filter, the present invention does not require an external separate input unit. Further, the present invention not only appeals to consumer&#39;s mentality, but also enhances a value of a high-class brand. 
     The present invention can also use the touch screen to add an automatic positioning and screen adjustment function, and an additional function such as color depth adjustment, resolution adjustment and brightness adjustment. 
     As described above, the present invention can provide the touch screen for the front filter installed in the plasma display apparatus to not only add various functions, but to also appeal to the consumer&#39;s mentality and enhance the value of the high-class brand. 
     It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.