Abstract:
Disclosed is an in-plane switching mode liquid crystal display, in which a pixel electrode and a common electrode are formed on the same substrate. The display includes a first substrate having a first conductive layer and second conductive layer, the first conductive layer and second conductive layer formed on each surface of the first substrate; a second substrate has a transparent pixel electrode and a transparent common electrode formed on one surface of the second substrate, facing the second conductive layer; an electrical connection part is installed to electrically connect the second conductive layer to the transparent common electrode, wherein a common voltage applied to the transparent common electrode is applied to the second conductive layer through the electrical connection part. This arrangement prevents generation of static electricity to suppress a whitening phenomenon due to liquid crystal polarization in a liquid crystal layer, thereby improving display image quality.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates, in general, to an in-plane switching mode liquid crystal display device having a pixel electrode and a common electrode formed on the same substrate, and more particularly, to an in-plane switching mode liquid crystal display device capable of suppressing a liquid crystal polarization due to external static electricity to improve display image quality, by forming an induced electric field between a first conductive layer and a second conductive layer, to which a common voltage is applied through an electrical connection. 
         [0003]    2. Description of the Related Art 
         [0004]    In recent times, research on an in-plane switching mode (IPS) liquid crystal display (LCD) has been widely performed. The IPS LCD includes two electrodes formed on the same substrate such that a voltage is applied between the two electrodes to generate a horizontal electric field or a fringe electric field with respect to the substrate. 
         [0005]    Hereinafter, the structure of a conventional IPS LCD will be described in brief with reference to the accompanying drawings. 
         [0006]      FIG. 1  is a schematic cross-sectional view of a conventional IPS LCD. 
         [0007]    Since the conventional IPS LCD shown in  FIG. 1  includes a pixel array  22  having a pixel electrode and a common electrode and formed at one side of a lower substrate  20 , when static electricity is generated from an upper substrate having no electrode, a liquid crystal polarization may be generated in a liquid crystal layer (LC,  40 ) due to static electricity, thereby deteriorating display image quality. In order to prevent occurrence of the liquid crystal polarization, a method of grounding static electricity introduced from the exterior through an SUS bezel  30  upon introduction of the static electricity by coating a transparent conductive layer  16  on a rear surface of the upper substrate  10 , and connecting a copper tape  32  to the SUS bezel  30  surrounding a mold frame  29  has been used. 
         [0008]    As described above, the transparent conductive layer  16  in contact with the SUS bezel  30  functions as a ground terminal to prevent the upper substrate  10  as a dielectric material from being charged upon introduction of external static electricity, thereby preventing intrusion of the electric field into a liquid crystal  40  due to the static electricity. 
         [0009]    However, when the SUS bezel  30  is removed in order to form a small, lightweight and compact device such as a mobile or portable appliance, the transparent conductive layer  16  formed on the rear surface of the upper substrate  10  must be floated, making it impossible to perfectly shield the static electricity. 
       SUMMARY OF THE INVENTION 
       [0010]    Accordingly, the present invention has been made keeping in mind the above problems occurring in the related art, and an object of the present invention is to provide an in-plane switching mode liquid crystal display capable of suppressing a liquid crystal polarization due to external static electricity to improve display image quality. 
         [0011]    In order to achieve the above object, according to one aspect of the present invention, there is provided an in-plane switching mode liquid crystal display comprising: a first substrate having a first conductive layer and second conductive layer, the first conductive layer and second conductive layer formed on each surface of the first substrate; a second substrate having a transparent pixel electrode and a transparent common electrode formed on one surface of the second substrate, facing the second conductive layer; an electrical connection part is installed to electrically connect the second conductive layer to the transparent common electrode, wherein a common voltage applied to the transparent common electrode is applied to the second conductive layer through the electrical connection part. 
         [0012]    According to another aspect of the present invention, there is provided an in-plane switching mode liquid crystal display comprising: a first substrate having a first conductive layer, second conductive layer, and an insulating layer between the first conductive layer and second conductive layer; a second substrate having a transparent pixel electrode and a transparent common electrode formed on one surface of the second substrate, facing the second conductive layer; an electrical connection part is installed to electrically connect the second conductive layer to the transparent common electrode, wherein a common voltage applied to the transparent common electrode is applied to the second conductive layer through the electrical connection part. 
         [0013]    The insulating layer may be over coater layer for improving planarization. 
         [0014]    The color filter layer may be formed on the first substrate, including color filter patterns and the second conductive layer mat be patterned conductive light-shielding layer formed between the color filter patterns. 
         [0015]    The first conductive layer may be patterned in a shape corresponding to the light-shielding layer. 
         [0016]    The color filter layer may be further formed on the first substrate including color filter patterns and a conductive light-shielding layer formed between the color filter patterns, and wherein the second conductive layer is patterned in a shape corresponding to the conductive light-shielding layer. 
         [0017]    The first conductive layer may be replaced with a conductive polarizer. 
         [0018]    Preferably, the in-plane switching mode liquid crystal display further comprises a conductive polarizer on the first conductive layer. 
         [0019]    The first conductive layer may be formed of a metal material or a conductive resin. 
         [0020]    The first conductive layer may be totally formed of a transparent metal material or a transparent conductive resin. 
         [0021]    Preferably, the in-plane switching mode liquid crystal display further comprises a color filter layer formed on the first substrate, including color filter patterns and a light-shielding layer including color filter patterns. 
         [0022]    Preferably, the in-plane switching mode liquid crystal display further comprises an overcoat layer between the first conductive layer and the second conductive layer. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]    The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description when taken in conjunction with the accompanying drawings, in which: 
           [0024]      FIG. 1  is a schematic cross-sectional view of a conventional in-plane switching mode liquid crystal display; 
           [0025]      FIG. 2A  is a schematic cross-sectional view of an in-plane switching mode liquid crystal display in accordance with an exemplary embodiment of the present invention; 
           [0026]      FIG. 25  is a plan view of an in-plane switching mode liquid crystal display including a transfer dotting part of  FIG. 2A ; and 
           [0027]      FIG. 3  is a schematic cross-sectional view of an in-plane switching mode liquid crystal display in accordance with another exemplary embodiment of the present invention. 
           [0028]      FIG. 4  is a schematic cross-sectional view of an in-plane switching mode LCD device according to still another exemplary embodiment of the present invention. 
           [0029]      FIG. 5  is a schematic cross-sectional view of an in-plane switching mode LCD device according to still another exemplary embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0030]    The invention is described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the exemplary embodiments set forth herein. Rather, these exemplary embodiments are provided so that this disclosure is thorough, and will fully convey the scope of the invention to those skilled in the art. 
         [0031]      FIG. 2A  is a schematic cross-sectional view of an in-plane switching mode liquid crystal display in accordance with an exemplary embodiment of the present invention, and  FIG. 2B  is a plan view of an in-plane switching mode liquid crystal display including a transfer dotting part of  FIG. 2A . 
         [0032]    Hereinafter, the in-plane switching mode liquid crystal display in accordance with an exemplary embodiment of the present invention will be described with reference to  FIGS. 2A and 2B . 
         [0033]    The in-plane switching mode liquid crystal display in accordance with an exemplary embodiment of the present invention includes a first substrate  210 , color filter layers  212 R,  212 G, and  212 B, a conductive light-shielding layer  214 , a conductive layer  216 , a second substrate  220 , a pixel array  222  including a transparent pixel electrode and a transparent common electrode, and an electrical connection part  224 . 
         [0034]    The conductive layer  216  is formed on one surface of the first substrate  210 . When the conductive layer  216  is formed on the entire one surface of the first substrate  210 , the conductive layer  216  may be formed of a transparent conductive resin or a transparent conductive metal material such as indium tin oxide (ITO) or indium zinc oxide (IZO) having relatively good light transmissivity. In addition, when the conductive layer  216  is patterned on one surface of the first substrate  210  to correspond to the conductive light-shielding layer  214 , the conductive layer  216  may be formed of metal material and conductive resin of all types including the transparent conductive resin and the transparent conductive metal material. Here, the transparent conductive resin may be formed of a mixture of indium tin oxide powder and acryl (ITO powder +acryl), epoxy, or the like. 
         [0035]    An upper conductive polarizer  219  may be formed on the conductive layer  216 . Otherwise, the upper conductive polarizer  219  may be formed on the first substrate  210  without the conductive layer  216 . 
         [0036]    The conductive light-shielding layer, i.e., black matrices  214  function to prevent light leakage, and may include chrome (Cr). The conductive light-shielding layer  214  is formed on the other surface of the first substrate  210  at predetermined intervals to generally divide the color filter layers  212 R,  212 G and  212 B of red, green and blue. 
         [0037]    The color filter layers  212 R,  212 G and  212 B, generally formed of a photosensitive organic material, are alternately arranged in sequence of red, green and blue color filter patterns between the conductive light-shielding layers  214 . Meanwhile, an overcoat layer  218  may be selectively formed under the color filter layers  212 R,  212 G and  212 B to remove a step difference generated by the color filter layers  212 R,  212 G and  212 B and improve planarity. 
         [0038]    A pixel array  222  including a transparent pixel electrode and a transparent common electrode is formed on one surface of the second substrate  220 . While not specifically shown, each pixel region is defined by gate lines and data lines formed to intersect each other. Switching devices are disposed at the intersection of the gate lines and the data lines. The pixel electrode and the transparent common electrode are spaced apart from each other to overlap a predetermined region, with an insulating layer interposed therebetween, and are disposed in the pixel region in order to apply a voltage to a liquid crystal layer  230  to thereby adjust light transmissivity. 
         [0039]    The electrical connection part  224  is electrically connected to the conductive light-shielding layer  214  and the transparent common electrode of the pixel array  222 , and includes a transfer dotting part including a metal having high conductivity, preferably, silver (Ag), or a conductive sealing member including gold (Au). 
         [0040]    When a common voltage is applied to the transparent common electrode of the pixel array  222 , the common voltage is applied to the conductive light-shielding layer  214  through the electrical connection part  224  to form an induced electric field between the conductive light-shielding layer  214  and the conductive layer  216 , thereby preventing external static electricity from affecting the liquid crystal layer  230 . That is, as bi-directional arrows shown in a vertical direction of the first substrate  210  of  FIG. 2A , the induced electric field is formed between the conductive layer  216  and the conductive light-shielding layer  214  to prevent occurrence of a liquid crystal polarization in the liquid crystal layer  230 . 
         [0041]    In  FIG. 2A , reference numeral  225  designates a sealing member, reference numeral  226  designates a lower polarizer, reference numeral  228  designates a back light unit, and reference numeral  229  designates a mold frame. 
         [0042]    When the electrical connection part  224  is a transfer dotting part, as shown in  FIG. 2B , the transfer dotting part  224  may be formed outside the sealing member  225  surrounding the pixel region. 
         [0043]    Here, when the conductive layer  216  is replaced with only the upper conductive polarizer  219 , the induced electric field is formed between the upper conductive polarizer  219  and the conductive light-shielding layer  214 . 
         [0044]      FIG. 3  is a schematic cross-sectional view of an in-plane switching mode liquid crystal display in accordance with another exemplary embodiment of the present invention. 
         [0045]    Referring to  FIG. 3 , the in-plane switching mode liquid crystal display in accordance with an exemplary embodiment of the present invention includes a first substrate  310 , color filter layers  312 R,  312 G, and  312 B, a light-shielding layer  314 , a first conductive layer  316 , a second conductive layer  317 , a second substrate  320 , a pixel array  322  including a transparent pixel electrode and a transparent common electrode, and an electrical connection part  332 . 
         [0046]    The conductive layer  316  is formed on one surface of the first substrate  310 . When the conductive layer  316  is formed on the entire one surface of the first substrate  310 , the conductive layer  316  may be formed of a transparent conductive resin or a transparent conductive metal material such as indium tin oxide (ITO) or indium zinc oxide (IZO) having relatively good light transmissivity. In addition, when the conductive layer  316  is patterned on one surface of the first substrate  310  to correspond to the light-shielding layer  314 , the conductive layer  216  may be formed of metal material and conductive resin of all types including the transparent conductive resin and the transparent conductive metal material. Here, the transparent conductive resin may be formed of a mixture of indium tin oxide powder and acryl (ITO powder +acryl), epoxy, or the like. 
         [0047]    An upper conductive polarizer  319  may be formed on the first transparent conductive layer  316 . On the other hand, the upper conductive polarizer  319  may be formed on the first substrate  310 , without the first transparent conductive layer  316 . 
         [0048]    The light-shielding layer  314  functions to prevent light leakage, and may include resin. The light-shielding layer  314  formed of resin can implement clear display even in an outdoor environment because the light-shielding layer  314  does not reflect external incident light. In addition, a reddish coloring problem generated by the internal reflection upon implementation of ultra-high brightness can be readily solved, and design of the liquid crystal display and a manufacturing process thereof can be simplified. 
         [0049]    The light-shielding layers  314  are formed on the other surface of the first substrate  310  at predetermined intervals, lo and generally divide the red, green and blue color filter layers  312 R,  312 G and  312 B. 
         [0050]    The color filter layers  312 R,  312 G and  312 B, generally formed of a photosensitive organic material, are alternately arranged in sequence of red, green and blue color filter patterns between the light-shielding layers  314 . 
         [0051]    The second conductive layer  317  substantially patterned under the light-shielding layer  314  in a shape corresponding to the light-shielding layer  314 . 
         [0052]    Meanwhile, an overcoat layer  318  may be selectively formed under the color filter layers  312 R,  312 G and  312 B to remove a step difference generated by the color filter layers  312 R,  312 G and  312 B and improve planarity. This case, the second conductive layer  317  may be formed under the overcoat layer  318 . Here, the overcoat layer  318  may include a thermosetting material. 
         [0053]    The second conductive layer  317  may be formed between the second substrate  320  and the light-shielding layer  314 . This case, the second conductive layer  317  is patterned in a shape corresponding to the light-shielding layer  314  or on the entire of the second substrate  320 . 
         [0054]    The pixel array  322  including a transparent pixel electrode and a transparent common electrode is formed on one surface of the second substrate  320 . Meanwhile, each pixel region is defined by gate lines and data lines formed to intersect each other. Switching devices are disposed at the intersection of the gate lines and the data lines (not shown). The pixel electrode and the transparent common electrode are spaced apart from each other to overlap a predetermined region, with an insulating layer (not shown) interposed therebetween, and are disposed in the pixel region in order to apply a voltage to a liquid crystal layer  330  to thereby adjust light transmissivity. 
         [0055]    The electrical connection part  332  is electrically connected to the second conductive layer  317  and the transparent common electrode of the pixel array  322 , and includes a transfer dotting part including a metal having high conductivity, preferably, silver (Ag), or a conductive sealing member including gold (Au). 
         [0056]    When a common voltage is applied to the transparent common electrode of the pixel array  322 , the common voltage is applied to the second conductive layer  317  through the electrical connection part  332  to form an induced electric field between the second conductive layer  317  and the first conductive layer  316 , thereby preventing external static electricity from affecting the liquid crystal layer  330 . That is, as shown by arrows, the induced electric field is formed between the first conductive layer  316  and the second conductive layer  317  to prevent occurrence of a liquid crystal polarization in the liquid crystal layer  330 . 
         [0057]    Meanwhile, as shown in  FIG. 3 , the IPS LCD further includes a sealing member  325 , a lower polarizer  326 , a back light unit  328 , and a mold frame  329 . 
         [0058]    Here, when the first conductive layer  316  is replaced with the upper conductive polarizer  319 , an induced electric field is formed between the upper conductive polarizer  319  and the second conductive layer  317 . 
         [0059]    Meanwhile, since basic components of the LCD, which are not specifically described, for example, a thin film transistor, a substrate, a liquid crystal layer, and so on, are the same as in the conventional LCD, detailed descriptions thereof will be omitted. 
         [0060]      FIG. 4  is a schematic cross-sectional view of an in-plane switching mode LCD device according to still another exemplary embodiment of the present invention. 
         [0061]    Referring to  FIG. 4 , the in-plane switching mode LCD device according to this exemplary embodiment will be described. 
         [0062]    The in-plane switching mode LCD device according to this exemplary embodiment includes a first substrate  410 , color filter layers  412 R,  412 G, and  412 B, a conductive light-shielding layer  414 , a conductive layer  416 , a first overcoat layer  417 , a second substrate  420 , a pixel array  422  including a transparent pixel electrode and a transparent common electrode, and an electrical connection part  424 . 
         [0063]    The conductive layer  416  is formed between the first substrate  410  and a first overcoat layer  417 . When the conductive layer  416  is formed on the entire lower surface of the first substrate  410 , the conductive layer  416  may be formed of a transparent conductive resin or a transparent conductive metal material such as ITO or IZO having relatively excellent light transmissivity. Further, when the conductive layer  416  is formed under the first substrate  410  and patterned to correspond to the conductive light-shielding layer  414 , the conductive layer  416  may be formed of metal material and conductive resin of all types including the transparent conductive resin and the transparent conductive metal material. 
         [0064]    The transparent conductive resin may be composed of a mixture (ITO Powder +Acryl) of ITO powder and acryl or epoxy. Further, an upper conductive polarizer  419  may be formed on the first substrate  410 . 
         [0065]    The conductive light-shielding layer  414  serves to prevent light leakage, and may include Cr. The conductive light-shielding layers  414  are formed under the first overcoat layer  417  to be spaced a predetermined distance from each other. In general, the conductive light-shielding layer  414  divide the red, green, and blue color filter layers  412 R,  412 G, and  4123 . 
         [0066]    The filter layers  412 R,  412 G, and  4123 , formed of a photosensitive organic material, are alternately arranged in sequence of red, green, and blue color filter patterns between the respective conductive light-shielding layers  414 . Meanwhile, the second overcoat layers  418  may be selectively formed under the color filter layers  412 R,  412 G, and  412 B so as to remove a step difference formed by the color filter layers  412 R,  412 G, and  412 B and improve planarity. 
         [0067]    The pixel array  422  including a pixel electrode and a transparent common electrode is formed on one surface of the second substrate  420 . Meanwhile, although not shown, the respective pixel regions are defined by gate lines and data lines formed in directions crossing each other, and switching devices are formed at intersections of the gate lines and the data lines. Further, the pixel electrode and the transparent common electrode are spaced apart from each other to overlap a predetermined region, with an insulating layer interposed therebetween, and are formed in the pixel region in order to apply a voltage to a liquid crystal layer  430  to thereby adjust light transmissivity. 
         [0068]    The electrical connection part  424  is electrically connected to the conductive light-shielding layer  414  and the transparent common electrode of the pixel array  422 . The electrical connection part  424  includes a transfer dotting part including a metal having high conductivity, preferably, silver (Ag), or a conductive sealing member including gold (Au). 
         [0069]    When a common voltage is applied to the transparent common electrode of the pixel array  422 , the common voltage is applied lo to the conductive light-shielding layer  414  through the electrical connection part  424  so as to form an induced electric field between the conductive light-shielding layer  414  and the conductive layer  416 , thereby preventing external static electricity from affecting the LC layer  430 . That is, as indicated by arrows which are represented in the first overcoat layer  417 , the induced electric field is formed between the conductive layer  416  and the conductive light-shielding layer  414 , thereby preventing liquid crystal polarization from occurring in the liquid crystal layer. 
         [0070]    In  FIG. 4 , reference numerals  425 ,  426 ,  428 , and  429  represent a sealing member, a lower polarizer, a backlight unit, and a mold frame, respectively. 
         [0071]      FIG. 5  is a schematic cross-sectional view of an in-plane switching mode LCD device according to still another exemplary embodiment of the present invention. 
         [0072]    Referring to  FIG. 5 , the in-plane switching mode liquid crystal display in accordance with an exemplary embodiment of the present invention includes includes a first substrate  510 , color filter layers  512 R,  512 G, and  512 B, a light-shielding layer  514 , a first conductive layer  516   a , a second conductive layer  516   b , a second substrate  520 , a pixel array  522  including a transparent pixel electrode and a transparent common electrode, and an electrical connection part  532 . 
         [0073]    The first conductive layer  516   a  is formed under the first substrate  510 . When the conductive layer  516   a  is formed on the entire on one surface of the first substrate  510 , the first conductive layer  516   a  may be formed of a transparent conductive resin or a transparent conductive metal material such as ITO or IZO having relatively excellent light transmissivity. Further, when the first conductive layer  516   a  is formed under the first substrate  510  and patterned to correspond to the light-shielding layer  514 , the first conductive layer  516   a  may be formed of metal material and conductive resin of all types including the transparent conductive resin and the transparent conductive metal material. The transparent conductive resin may be composed of a mixture (ITO Powder+Acryl) of ITO powder and acryl or epoxy. Further, an conductive polarizer  519  may be formed on the first substrate  510 . 
         [0074]    The light-shielding layers  514  are formed under the first conductive layer  516   a  to be spaced a predetermined distance from each other. In general, the light-shielding layer  514  divide the red, green, and blue color filter layers  512 R,  512 G, and  512 B. 
         [0075]    The filter layers  512 R,  512 G, and  512 B, formed of a photosensitive organic material, are alternately arranged in sequence of red, green, and blue color filter patterns between the respective light-shielding layers  514 . Meanwhile, the first overcoat layers  517  may be selectively formed between the first conductive layer  516   a , the color filter layers  512 R,  512 G, and  512 B and the light-shielding layer  514 . 
         [0076]    The second conductive layer  516   b  substantially patterned under the light-shielding layer  514  in a shape corresponding to the light-shielding layer  514 . 
         [0077]    Meanwhile, an overcoat layer  518  may be selectively formed under the color filter layers  512 R,  512 G and  512 B to remove a step difference generated by the color filter layers  512 R,  512 G and  512 B and improve planarity. The second conductive layer  516   b  may be formed under the overcoat layer  518 . 
         [0078]    The second conductive layer  516   b  may be formed between the first overcoat layer  517  and the light-shielding layer  514 . The second conductive layer  516   b  may be formed on the entire upper one surface of the first overcoat layer  517 . 
         [0079]    The pixel array  522  including a transparent pixel electrode and a transparent common electrode is formed on one surface of the second substrate  520 . Meanwhile, although not shown, the respective pixel regions are defined by gate lines and data lines formed in directions crossing each other, and switching devices are formed at intersections of the gate lines and the data lines. Further, the pixel electrode and the transparent common electrode are spaced apart from each other to overlap a predetermined region, with an insulating layer interposed therebetween, and are formed in the pixel region in order to apply a voltage to a liquid crystal layer  530  to thereby adjust light transmissivity. 
         [0080]    The electrical connection part  532  is electrically connected to the second conductive layer  516   b  and the transparent common electrode of the pixel array  522 . The electrical connection part  532  includes a transfer dotting part including a metal having high conductivity, preferably, silver (Ag), or a conductive sealing member including gold (Au). 
         [0081]    When a common voltage is applied to the transparent common electrode of the pixel array  522 , the common voltage is applied to the second conductive layer  516   b  through the electrical connection part  532  so as to form an induced electric field between the first conductive layer  516   a  and the second conductive layer  516   b , thereby preventing external static electricity from affecting the LC layer  530 . That is, as indicated by arrows which are represented, the induced electric field is formed between the first conductive layer  516   a  and the second conductive layer  516   b , thereby preventing liquid crystal polarization from occurring in the liquid crystal layer. 
         [0082]    Meanwhile, as shown in  FIG. 5 , the IPS LCD further includes a sealing member  525 , a lower polarizer  526 , a back light unit  528 , and a mold frame  529 . 
         [0083]    In addition, although the exemplary embodiments of the IPS LCD of the present invention have been described, not being limited thereto, the present invention may be adapted to all LCDs using optical anisotropy and polarizing characteristics of liquid crystal. 
         [0084]    As can be seen from the foregoing, a common electric potential is applied to a conductive light-shielding layer formed on the other side of a first substrate through an electrical connection part to form an induced electric field with respect to a conductive layer formed on one side of the first substrate, thereby suppressing a liquid crystal polarization due to external static electricity to improve display image quality. 
         [0085]    Further, according to the present invention, a common potential is applied to a second conductive layer formed on the other surface of the first substrate through an electrical connection part to form an induced electric field with respect to a first conductive layer formed on one side of the first substrate, thereby suppressing a liquid crystal polarization due to external static electricity to improve display image quality. 
         [0086]    Although exemplary embodiments of the present invention have been described for illustrative purposes, not being limited thereto, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.