Patent Publication Number: US-2011063532-A1

Title: Image display device

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an image display device for displaying images, such as television images. 
     2. Description of Related Art 
     In recent years, with a reduction in thickness of image display devices for displaying images such as television images, image display devices using a so-called flat display panel such as a plasma display panel and a liquid crystal panel have become mainstream, instead of conventional CRTs. 
       FIG. 6  is a schematic sectional view showing an internal configuration of a plasma display device as an example of such a flat image display device. It should be noted that the upward and downward direction means the upward and downward direction (that is, the vertical direction) of a plasma display device in the normal use position (that is, laterally placed), and the left and right direction means a direction orthogonal to this (that is, the horizontal direction) in the following description. Further, the display screen side is referred to as the forward direction, and the back cover side is referred to as the backward direction. 
     As indicated in  FIG. 6 , a plasma display device  3  is provided with a front cover  200  and a back cover  300 . A PDP  100  (Plasma Display Panel) for displaying images, a chassis  400  supporting the PDP  100  on its front surface, and a plurality of circuit boards  500  that are mounted to the back surface of the chassis  400  for driving the PDP  100  are accommodated inside the space surrounded by the front cover  200  and the back cover  300 . For example, JP 2003-162228 A discloses such a configuration as a conventional example. 
     SUMMARY OF THE INVENTION 
     There is a growing demand for a reduction in thickness of image display devices using a flat display panel such as a plasma display device. In response to this, a visual reduction in thickness can be achieved, for example, by a configuration in which circuit boards are arranged concentrically in the center of the back surface of a chassis so that the thickness of the portion corresponding to the peripheral edge of the back cover can be reduced.  FIG. 7  shows a specific example of a structure with a reduced thickness.  FIG. 7  is a perspective view showing a plasma display device having the structure with a reduced thickness, as viewed from the back side thereof. A step is provided on a back cover  600  for reducing the thickness in the upper portion and the left and right portions of a plasma display device. Thus, a reduction in thickness of the upper portion and the left and right portions that are likely to come into view can yield a design that has a visual effect of thickness reduction. 
     However, such a configuration has a problem in that the strength of the portion having a reduced thickness decreases, which may cause the panel to be damaged if the device is dropped or subjected to an external force. 
     The present invention has been devised in view of the problem described above, and an object thereof is to provide an image display device that can achieve a reduction in thickness while suppressing the decrease in strength. 
     In order to solve the above-mentioned problem, the image display device of the present invention is provided with a panel for displaying images, a chassis supporting the display panel on its front surface, circuit boards arranged within a specific region of the back surface of the chassis, and a back cover having an edge portion that covers the outside of the specific region of the back surface of the chassis, and a projecting portion that projects inside the edge portion toward the side opposite to the chassis and that accommodates the circuit boards. In the image display device, the edge portion includes a plurality of drawn portions extending in a particular direction. 
     “Drawn portion” means a swelled out portion so as to hold a space extending in the particular direction, it may be a concave portion recessed toward the chassis or a convex portion projecting toward the side opposite to the chassis. 
     According to the image display device of the present invention, the circuit boards are arranged concentrically, and these circuit boards are accommodated in the projecting portion of the back cover. Therefore, it is possible to reduce the thickness of the portion defined by the edge portion located outside the projecting portion, thus allowing the apparent thickness to be reduced. Furthermore, it is possible to suppress a decrease in strength by providing the drawn portions in the edge portion. That is, an image display device that can achieve a reduction in thickness, while preventing the strength from decreasing, can be obtained. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view illustrating a configuration of a plasma display device  1  according to the first embodiment. 
         FIG. 2A  is a sectional view taken along the line IIA-IIA in  FIG. 1 , and  FIG. 2B  is a sectional view taken along the line IIB-IIB in  FIG. 1 . 
         FIG. 3  is an enlarged partial view of  FIG. 2A . 
         FIG. 4  is a sectional view showing a plasma display device  2  according to the second embodiment. 
         FIG. 5  is a sectional view taken along the line V-V in  FIG. 4 . 
         FIG. 6  is a schematic sectional view showing the internal configuration of a conventional plasma display device. 
         FIG. 7  is a perspective view showing a plasma display device having the structure with a reduced thickness as viewed from the back side thereof. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Hereinafter, embodiments for carrying out the present invention are described with reference to the drawings. It should be noted that the following descriptions are to be regarded as an example, and the present invention is not limited by these descriptions. Further, an example of a plasma display device is used as an image display device in the following descriptions, as in the conventional example. 
     First Embodiment 
       FIG. 1  is a perspective view illustrating a configuration of a plasma display device  1  according to the first embodiment of the present invention.  FIG. 2A  is a sectional view taken along the line IIA-IIA in  FIG. 1 , and  FIG. 2B  is a sectional view taken along the line IIB-IIB in  FIG. 1 .  FIG. 3  is an enlarged partial view of  FIG. 2A . 
     The plasma display device  1  is provided with a front cover  20  and a back cover  30 . A PDP  10  as a display panel for displaying images, a chassis  40  supporting the PDP  10  on its front surface, and a plurality of circuit boards  50  that are mounted to the back surface of the chassis  40  for driving the PDP  10  are accommodated inside the space surrounded by the front cover  20  and the back cover  30 . The plasma display device  1  has an elongated shape, viewed from the image display screen side, and generally is positioned such that the longitudinal direction is the horizontal direction and the short direction is the vertical direction (that is, the PDP  10  is in an upright position). 
     As indicated in  FIG. 3 , the PDP  10  has a front panel  11 , a back panel  12  and a sealing member  13  formed along the periphery thereof. The front panel  11  and back panel  12  are bonded to each other with the sealing member  13  arranged on the edge portion of the main surface of each panel, and are spaced apart by the thickness of the sealing member  13 . The front panel  11  and back panel  12  are formed of glass substrates and the like. The enclosed space that is sealed by the sealing member  13  between the front panel  11  and back panel  12  is filled with a rare gas such as Ne and Xe. An electric field is applied to the enclosed space, thereby causing electric discharge and light emission. 
     A front filter  14  is attached to the front surface of the PDP  10 . The front filter  14  is formed of various filters such as an anti-reflection filter for preventing the reflection of outside light, and an electromagnetic wave shielding filter. 
     The front cover  20  is formed into a shape to constitute the front surface and the upper, lower, left and right side surfaces of the plasma display device  1 . The portion of the front cover  20  constituting the front surface of the device  1  is provided with an opening so that the image display area of the PDP  10  should be exposed. The front cover  20  is made, for example, of a conductive member, such as aluminium with a thickness of about 1 mm. The front cover  20  is connected electrically to the electromagnetic wave shielding filter of the front filter  14 . Further, the front cover  20  is connected to the back cover  30  that also is made of a conductive member as well. That is, the front cover  20 , the back cover  30 , and the front filter  14  form a shield housing that surrounds the PDP  10 . The front cover  20  serves also as an escutcheon frame that covers the periphery of the image display screen of the PDP  10 . 
     The chassis  40  is made of a metal having both good mechanical rigidity and good heat conductivity, such as aluminium. The chassis  40  has almost the same shape and area as the PDP  10  as viewed from the front and has a thickness, for example, of about 1.0 to 2.0 mm. As indicated in  FIG. 3 , the chassis  40  is bonded to the back surface of the back panel  12  in the PDP  10  over the entire surface thereof via an adhesive sheet  41  with heat conductivity. That is, the chassis  40  supports the PDP  10  that serves as a display panel, on its front surface. The chassis  40  is fixed to the front cover  20  via a fixing member  21  provided around the chassis  40 . 
     The adhesive sheet  41  has an elongated shape and almost the same area as the PDP  10  as viewed from the front and has a thickness, for example, of about 0.5 to 2.0 mm. The adhesive sheet  41  interposed between the PDP  10  and the chassis  40  allows the PDP  10  basically made of glass substrates to be in close contact with the chassis  40  that is metal. Thus, the effect of heat conduction from the PDP  10  to the chassis  40  is enhanced. Therefore, the adhesive sheet  41  is preferably made of silicon or the like having both flexibility and heat conductivity. 
     The circuit boards  50  are constituted by a drive circuit board for driving the PDP  10 , a signal processing circuit board for transmitting image signals to the PDP  10 , and the like. The circuit boards  50  are fixed to a back surface of the chassis  40  with fixing members such as screws. In this embodiment, the circuit boards  50  are arranged within a specific region of the back surface of the chassis  40  so that they concentrate in the lower center of the back surface. That is, the specific region is the lower center region of the back surface of the chassis  40 . It should be noted that the specific region is covered by a later-mentioned projecting portion  31  of the back cover  30 . 
     The back cover  30  covers the chassis  40  and the circuit boards  50  from the back side thereof, and is connected to the front cover  20  at its peripheral edge portion. The back cover  30  is made, for example, of steel with a thickness of about 0.5 mm. The back cover  30  has an edge portion  32  that covers the outside of the specific region of the back surface of the chassis  40 , and a projecting portion  31  that projects inside the edge portion  32  toward the side opposite to the chassis  40  and that accommodates the circuit boards  50 . The plasma display device  1  has a thickness, for example, of about 1 cm in the portion corresponding to the edge portion  32  of the back cover  30 . Further, the plasma display device  1  has a thickness, for example, of about 5 cm in the portion corresponding to the projecting portion  31  of the back cover  30 . 
     A plurality of drawn portions extending in a particular direction are provided in the edge portion  32  of the back cover  30 . In this embodiment, each drawn portion is a concave portion  320  recessed toward the chassis  40 . The concave portions  320  are provided above and on both sides of the projecting portion  31 , extending in the vertical direction while aligning in the horizontal direction. The concave portion  320  has a depth of about 2 to 5 mm, and a width of about 10 to 15 mm, for example. The concave portions  320  can be formed by concaving the edge portion  32  of a planar shape using a drawing process. In this embodiment, the concave portions  320  are formed at 10 points at equal intervals in the horizontal direction. Specifically, the concave portions  320  are formed at 6 points in the above portion of the projecting portion  31  and at 2 points for each of both sides thereof. 
     The length of the concave portions  320  is not limited specifically, and can be determined appropriately. In this embodiment, the concave portions  320  located above the projecting portion  31  and the concave portions  320  located lateral to the projecting portion  31  both have a length slightly shorter than the height of the edge portion  32  corresponding to each position. 
     A plurality of fans  60  are provided inside the projecting portion  31 . The fans  60  are mounted to the chassis  40  via a mounting member, which is not illustrated. Air inlets  34  are provided in the upper portion of the edge portion  32  so as to be located at a position between adjacent pairs of the concave portions  320 . Air outlets  33  are provided in the upper portion of the projecting portion  31  at a position corresponding to the middle between adjacent pairs of the concave portions  320 . Furthermore, air inlets  34  are provided also in the lower portion of the projecting portion  31  in this embodiment. When the fans  60  are operated, airflow from the air inlets  34  to the air outlets  33  occurs between the chassis  40  and back cover  50 , and the air in the space between the chassis  40  and the back cover  30  is emitted through the air outlets  33  to the outside. 
     It should be noted that the air inlets  34  and the air outlets  33  are not necessarily provided in the position illustrated in the figure. For example, in the case where the edge portion  32  of the back cover  30  has an outer peripheral edge portion that is bent forward, the air inlets  34  may be provided in the bent portion. Further, the air inlets  34  and the air outlets  33  may be provided, not on the main wall of the projecting portion  31  that faces the chassis  40 , but on the peripheral wall thereof that broadens and extends from the peripheral edge of the main wall toward the chassis  40 . 
     In this embodiment, a centrifugal fan is employed as the fans  60 . Five fans  60  are provided in the upper region inside the projecting portion  31  at equal intervals in the horizontal direction so that air can be blown straight toward the air outlets  33 . More specifically, the fans  60  each are arranged at a position corresponding to the middle between adjacent pairs of the concave portions  320  in the back cover  30 . That is, the five fans  60  each are provided so as to be located between adjacent pairs of the concave portions  320  that are located above the projecting portion  31  among the concave portions  320  that are provided in the edge portion  32 . 
     Descriptions for the configuration of the plasma display device  1  according to this embodiment have been given hereinbefore. Next, the operation of the plasma display device  1  is described. 
     As mentioned above, the plasma display device  1  has a reduced thickness in the upper portion and the left and right portions corresponding to the edge portion  32  of the back cover  30 . Generally, the plasma display device  1  is positioned such that the back side thereof (the side of the back cover  30 ) faces the wall or the like. Therefore, a visual effect of reduced thickness can be obtained by reducing the thickness of the upper portion and the left and right portions that are likely to come into view. 
     However, a decrease in the strength of the plasma display device is caused by just simply providing the portions with reduced thickness. In this embodiment, a plurality of the concave portions  320  therefore are provided in the edge portion  32  of the back cover  30 . The deformation of the back cover  30  due to stress can be prevented and the strength thereof can be enhanced by providing the concave portions  320 . With such a configuration, it is possible to improve the strength in the thin portions of the plasma display device  1  and to prevent the damages of the plasma display device  1  such as breakage of the display panel when the device is dropped or subjected to an external force. 
     Further, the concave portions  320  are provided extending along the upright direction of the plasma display device  1 , that is, the vertical direction, in this embodiment. Therefore, the space between the chassis  40  and the back cover  30  is partitioned by the concave portions  320 . Thus, airflow paths are formed in the vertical direction. The fans  60  each are provided so as to correspond to the middle between adjacent pairs of the concave portions  320  in the back cover  30 , that is, the above-mentioned airflow paths. Such a configuration allows the heat that has been generated from the PDP  10  and transferred to the chassis  40  to be dissipated efficiently by the fans  60 . Specifically, air flows through the flow path as indicated by the arrow A in  FIG. 2B , and the air is emitted through the air outlets  33 , so that the heat is dissipated. Of course, the fans  60  also have the effect of dissipating the heat that has been generated from the circuit boards  50  inside the projecting portion  31  as well, owing to the air drawn through the air inlets  34  provided in the lower portion of the projecting portion  31 . 
     It should be noted that although the projecting portion  31  is formed in the lower center of the back cover  30  in this embodiment, the formation of the projecting portion  31  is not limited thereto. A configuration in which the edge portion  32  is formed also in the lower portion and the projecting portion  31  is formed in the center portion is possible. With such a configuration, a visual effect of thin appearance can be achieved also in the case where the lower portion comes into the view, for example, when the plasma display device  1  is used in a wall mounted position. 
     Further, the concave portions  320  are provided at 10 points, and the five fans are provided in this embodiment. However, the number of them is not limited thereto and can be selected appropriately. Further, the length, the thickness (depth), and the width, etc. of the concave portions  320  can be selected appropriately, and it also is possible to form the concave portions  320  in various shapes in the same device. 
     Second Embodiment 
     Next, the second embodiment of the present invention is described with reference to  FIG. 4  and  FIG. 5 . The second embodiment differs from the first embodiment in that the concave portions  320  are in contact with the back surface of the chassis  40 . Other configurations are the same as those in the first embodiment and thus descriptions thereof are omitted. 
       FIG. 4  is a sectional view including the concave portions  320  in the plasma display device  2  according to the second embodiment, and corresponds to  FIG. 2A  in the first embodiment. 
     In the plasma display device  2 , the concave portions  320  provided in the edge portion  32  of the back cover  30  are in contact with the back surface of the chassis  40  via heat transfer sheets  70  with heat conductivity. As a material to form the heat transfer sheet  70 , silicon, acrylic, or the like can be used, for example. 
     Each of the heat transfer sheets  70  has a strip shape with about the same length and width as the concave portions  320 , and is arranged at a position corresponding to each concave portion  320 , as indicated in  FIG. 5 . That is, each concave portion  320  is in contact with the back surface of the chassis  40  via the heat transfer sheet  70  across its full length. 
     Here, the necessity of heat dissipation in the PDP  10  is described. The PDP  10  is likely to have a high temperature because of the operational principle that uses gas discharge for displaying images. When the PDP  10  has a high temperature exceeding its limit due to insufficient heat dissipation thereof, the electrical capacity of the electrodes formed inside the PDP  10  changes, thus causing adverse effects such as the failure of normal discharge. For this reason, the PDP  10  needs to be maintained at a certain temperature (for example, 70 to 80° C.) or less. The heat-dissipation performance decreases particularly in the configuration in which the periphery of the device has a reduced thickness by providing the edge portion  32  in the back cover  30 , since it also is difficult to add a heat dissipation member on the back side of the chassis  40 . 
     In this embodiment, the use of the above-mentioned heat transfer sheets  70  enables the heat transferred from the PDP  10  to the chassis  40  to be transferred to the back cover  30  by heat conduction. That is, it is possible to enhance the heat dissipation effect on the PDP  10  further. 
     It should be noted that, although the concave portions  320  are brought into contact with the back surface of the chassis  40  via the heat transfer sheets  70  in this embodiment, they may be in contact directly with each other, or may be in contact via another heat conductive member (for example, screws). Such contact structures can be achieved at low cost. Further, a spring member and the like may be employed as a heat conductive member that brings the concave portions  320  into contact with the back surface of the chassis  40 . In short, any contact structure can be employed as long as it allows heat to be conducted. The use of the heat transfer sheet  70  facilitates thin and broad contact, and therefore is advantageous in view of the productivity and the heat dissipation effect. 
     Other Embodiments 
     The concave portions  320  extending in the vertical direction are provided also in the lateral sides of the projecting portion  31  in the above-described embodiment. However, the concave portions  320  may extend in an oblique direction or the horizontal direction in the lateral sides of the projecting portion  31 . Alternatively, the concave portion  320  may be omitted in the lateral sides of the projecting portion  31 . That is, the concave portions  320  are provided preferably at least above the projecting portion  31  so as to extend in the vertical direction and align in the horizontal direction. 
     Further, the concave portions  320  are not necessarily provided in parallel to each other, and may be provided spreading radially from the projecting portion  31 , for example. 
     Furthermore, the drawn portion extending in a particular direction is not necessarily a concave portion recessed toward the chassis  40 , and may be a convex portion projecting toward the side opposite to the chassis  40 . 
     Further, it also is possible to form the back cover  30  using a molded resin with a conductive film formed thereon. That is, the “drawn portion” of the present invention is not restricted to being formed by drawing a metal plate, and may be a material that has been molded into the shape in advance. 
     The present invention is suitable for thin image display devices such as a plasma display device. 
     The present invention may be embodied in other forms without departing from the spirit or essential characteristics thereof. The embodiments described in this specification are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.