Patent Publication Number: US-2021181565-A1

Title: Liquid crystal display device

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device having a structure for cooling a glass in the liquid crystal display device to which the glass is applied. 
     2. Description of the Related Art 
     Liquid crystal display devices are devices for displaying image data by adjusting an amount of passing light by using a characteristic that an arrangement state of liquid crystal molecules varies according to an applied voltage. 
     Such liquid crystal display devices may be classified into a liquid crystal display device adopting a simple matrix scheme and a liquid crystal display device adopting an active matrix scheme according to a liquid crystal display matrix. 
     The simple matrix scheme is configured such that active elements such as transistors are attached to a glass substrate. Although the performance of the simple matrix scheme is excellent, a process may be complicated, and it may be difficult to increase a size. 
     The active matrix scheme has a structure in which one transistor for controlling a voltage is connected to one liquid crystal dot, and may have a strong contrast so as not to cause smears, so that the active matrix scheme may be used for a color type. 
     Such a liquid crystal display device adopting the active matrix scheme has been widely used in flat panel TVs, portable computers, monitors, and the like as the performance of the liquid crystal display device adopting the active matrix scheme rapidly develops. 
     For example, the applicant of the present invention has disclosed the technique of the liquid crystal display device in various patent documents such as the following patent documents 1 to 3, which have been filed and registered now. 
     Meanwhile, a glass for protecting a liquid crystal display panel may be applied to the liquid crystal display device. 
     In general, the glass may be spaced apart from the liquid crystal display panel by a predetermined interval. 
     However, in recent years, in order to prevent deterioration of image quality due to separation between the liquid crystal display panel and the glass, a technique for directly bonding the glass and the liquid crystal display panel has been developed. 
     Such a technique is referred to as ‘direct bonding’ or ‘optical bonding’ (hereinafter abbreviated as “direct bonding”). 
     In a case of using a display module to which the direct bonding technique is applied, when the display module is used in an environment exposed to direct sunlight or other high-temperature heat sources for a predetermined time, high-temperature radiant heat may be generated in the glass attached to a front surface of the liquid crystal display panel. Therefore, the high-temperature radiant heat may be transferred to the liquid crystal display panel attached to the glass, so that thermal deformation may occur in the liquid crystal display panel. 
     Accordingly, the damage to the liquid crystal display panel that is thermally deformed may be shown in the form of a smear or a bruise called ‘mura’ at a lower end of the display module, and yellow deformation may be mainly and distinctively recognized. 
     Such damage to the liquid crystal display panel may be particularly severe at the lower end due to the influence of gravity acting on the liquid crystal display panel and the glass, and may also be shown on left and right sides. 
       FIGS. 1 and 2  are views illustrating configurations of liquid crystal display devices according to the related art. 
     In the liquid crystal display device according to the related art, as shown in  FIG. 1 , a backlight unit  2  may be installed on a rear surface of a liquid crystal display panel  1 , and the liquid crystal display panel  1  and a glass  3  may be spaced apart from each other by a predetermined interval. 
     When the liquid crystal display device according to the related art configured as described above is used in an environment exposed to direct sunlight or other high-temperature heat sources for a predetermined time, the liquid crystal display panel  1  may be cooled by moving air through a space between the glass  3  and the liquid crystal display panel  1 . 
     However, as shown in  FIG. 1 , when the liquid crystal display panel  1  and the glass  3  are spaced apart from each other, due to causes such as double image formation on the glass  3  and the liquid crystal display panel  1  because of a separation interval, there has been a problem that image quality may be deteriorated. 
     In order to solve such a problem, as shown in  FIG. 2 , a technique in which the glass  3  is attached to the liquid crystal display panel  1  by a direct bonding scheme, and an additional glass  4  is installed on a front side of the glass  3  directly attached to the liquid crystal display panel  1  while being spaced apart from the glass  3  by a predetermined interval has been proposed. 
     However, since the liquid crystal display device shown in  FIG. 2  requires two glasses  3  and  4 , there has been a problem that a manufacturing cost may be increased, and workability may be reduced. 
     In particular, since the liquid crystal display device shown in  FIG. 2  has a structure that air circulated by the driving of a blower fan  5  installed in a cover bottom is transferred to the glass  3  and the backlight unit  2 , which are installed on front and rear surfaces of the liquid crystal display panel  1 , respectively, and indirectly cools the liquid crystal display panel  1 , there has been a problem that cooling efficiency may be reduced. 
     Therefore, when a liquid crystal display device adopting the direct bonding technique is used, there has been a demand for developing a technique capable of preventing the thermal deformation of the liquid crystal display panel in a high-temperature environment. 
     DOCUMENTS OF RELATED ART 
     Patent Documents 
     (Patent document 1) Korean Patent Registration No. 10-1598056 (published on Feb. 26, 2016) 
     (Patent document 2) Korean Patent Registration No. 10-1763308 (published on Aug. 4, 2017) 
     (Patent document 3) Korean Patent Registration No. 10-1987812 (published on Jun. 12, 2019) 
     SUMMARY OF THE INVENTION 
     To solve the problems described above, one object of the present invention is to provide a liquid crystal display device capable of cooling a liquid crystal display panel and a glass by applying an air flow structure using external air to the liquid crystal display panel that has a front surface to which the glass is attached by a direct bonding scheme. 
     Another object of the present invention is to provide a liquid crystal display device capable of preventing thermal deformation due to high-temperature radiant heat by cooling the liquid crystal display panel to which the glass is attached by the direct bonding scheme. 
     To achieve the objects described above, according to the present invention, there is provided a liquid crystal display device including: a liquid crystal display panel for displaying an image; a backlight unit for irradiating light toward a rear surface of the liquid crystal display panel; a cover bottom formed therein with a space in which the liquid crystal display panel and the backlight unit are installed; and a glass attached to a front surface of the liquid crystal display panel by a direct bonding scheme to protect the liquid crystal display panel, wherein the liquid crystal display panel and the backlight unit are spaced apart from each other so that air moves through a space between the liquid crystal display panel and the backlight unit. 
     As described above, according to the liquid crystal display device of the present invention, the liquid crystal display panel is attached to the glass by the direct bonding scheme, and the backlight unit is installed on a rear side of the liquid crystal display panel while being spaced apart from the liquid crystal display panel by a preset interval to allow the air to move through a separation space, so that the liquid crystal display panel can be directly cooled. 
     Therefore, according to the present invention, when the liquid crystal display device is used in an environment exposed to direct sunlight or other high-temperature heat sources for a predetermined time, the thermal deformation of the liquid crystal display panel due to the high-temperature radiant heat generated from the glass can be prevented. 
     In addition, according to the present invention, air cooled by using a thermoelectric element is circulated through a movement space between the panel and the backlight unit, so that the panel and the glass can be effectively cooled. 
     Therefore, according to the present invention, an air circulation structure using the thermoelectric element is applied, so that heat dissipation can be performed by circulating internal air without introduction of external air. 
     As a result, according to the present invention, the liquid crystal display panel is directly attached to the glass through the direct bonding scheme, so that image quality of a screen can be maximized, and damage due to the thermal deformation of the liquid crystal display panel can be effectively prevented. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1 and 2  are views illustrating configurations of liquid crystal display devices according to the related art. 
         FIG. 3  is a view showing a configuration of a liquid crystal display device according to an exemplary embodiment of the present invention. 
         FIG. 4  is a rear view showing the liquid crystal display device shown in  FIG. 3 . 
         FIG. 5  is a view showing a liquid crystal display device according to another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Hereinafter, a liquid crystal display device according to an exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawings. 
     First, prior to describing a configuration of the liquid crystal display device according to the exemplary embodiment of the present invention, configurations of liquid crystal display devices according to the related art will be schematically described with reference to  FIGS. 1 and 2 . 
     Hereinafter, a direction in which a glass is installed based on a liquid crystal display panel is referred to as a ‘front side’, and an opposite direction thereof is referred to as a ‘rear side’. 
     In addition, terms indicating directions such as ‘left’, ‘right, ‘upward’, and ‘downward’ are defined as indicating respective directions based on the above-described front and rear sides. 
     In order to solve problems as described in the related art, according to the present invention, in a state in which the liquid crystal display panel is attached to the glass by a direct bonding scheme, a separation space may be formed between the liquid crystal display panel and the backlight unit, and air may move through the separation space, so that the liquid crystal display panel may be directly cooled. 
     Next, a configuration of the liquid crystal display device according to the exemplary embodiment of the present invention will be described in detail with reference to  FIG. 3 . 
       FIG. 3  is a view showing a configuration of a liquid crystal display device according to an exemplary embodiment of the present invention, and  FIG. 4  is a rear view showing the liquid crystal display device shown in  FIG. 3 . 
     According to the exemplary embodiment of the present invention, as shown in  FIG. 3 , a liquid crystal display device  10  may include: a liquid crystal display panel  20  (hereinafter referred to as “panel”) for displaying an image; a backlight unit  30  for irradiating light toward a rear surface of the panel  20 ; a cover bottom  11  formed therein with a space in which the panel  20  and the backlight unit  30  are installed; and a glass  40  attached to a front surface of the panel  20  by a direct bonding scheme to protect the panel  20 . 
     A structure in which a cover bottom and a case top manufactured by using a metal material are coupled to each other is applied to a liquid crystal display device according to the related art. 
     Recently, in order to improve an immersion level and differentiate a design by minimizing a bezel of the liquid crystal display device  10 , the case top formed of a metal material has been removed, and a glass  40  manufactured by using a glass material has been applied to a front surface of the liquid crystal display device  10 . 
     To this end, the cover bottom  11  may have a substantially hexahedral shape with an open front surface, and the glass  40  may be installed on a front surface of the cover bottom  11 . 
     A panel guide having a rectangular frame shape on which the panel  20  is seated may be installed on an inner surface of an edge of the cover bottom  11 . 
     However, in the present embodiment, the cover bottom  11  and the panel guide are not separated, and are collectively referred to as the cover bottom  11 . 
     A support part  12  having a front surface on which the glass  40  is seated and configured to support the panel  20  that is coupled to an inside of the support part  12  may be formed on the inner surface of the edge of the cover bottom. In other words, the support part  12  may perform a function of the panel guide. 
     The glass  40  may have a sectional area greater than a sectional area of the panel  20 , and may be disposed on a front side of a space formed inside the cover bottom  11 . 
     The panel  20  may be attached to the glass  40  by the direct bonding scheme, and may have a sectional area corresponding to a space formed inside the support part  12 . 
     Therefore, the glass  40  may be supported by the cover bottom  11 , and the panel  20  may be stably supported by the support  12  of the cover bottom  11 . 
     The backlight unit  30  may be installed on a rear side of the panel  20  while being spaced apart from the panel  20  by a preset interval. 
     In other words, the panel  20  and the backlight unit  30  may be spaced apart from each other by the preset interval, and a movement space through which air moves by a fan  50  that will be described below may be formed between the panel  20  and the backlight unit  30 . 
     The preset interval may be set based on a test result obtained by measuring surface temperatures of the glass  40  and the panel  20  under a sunlight condition. 
     For example, in the present embodiment, the preset interval may be set to about 10.0 mm±2.0 mm. 
     However, the present invention is not necessarily limited to the above configuration, and the preset interval may vary according to various conditions such as a standard of each component applied to the liquid crystal display device. 
     Meanwhile, the cover bottom  11  may be formed at a lower end thereof with an inlet hole  13  through which external air is introduced through the cover bottom  11 , and the cover bottom  11  may be formed at an upper end thereof with an outlet hole  14  through which air that is heated through heat exchange with the panel  20  in a process of moving through the movement space is discharged to an outside. 
     An air filter  51  for filtering dust or foreign substances included in the external air may be installed in the inlet hole  13 , and a fan  50  for sucking the air inside the cover bottom  11  to discharge the sucked air to the outside may be installed in the outlet hole  14 . 
     In addition, a blocking plate  15  for preventing the air introduced through the inlet hole  13  from directly moving to the outlet hole  14  along a rear space of the backlight unit  30  may be formed at a rear wall of the cover bottom  11 . 
     The blocking plate  15  may have a width corresponding to a distance between the cover bottom  11  and the backlight unit  30  to perform a function of supporting the backlight unit  30 . 
     As described above, according to the present invention, the liquid crystal display panel is attached to the glass by the direct bonding scheme, and the backlight unit is installed on the rear side of the liquid crystal display panel while being spaced apart from the liquid crystal display panel by a preset interval to allow the air to move through the separation space, so that the liquid crystal display panel can be directly cooled. 
     Therefore, when the present invention is used in an environment exposed to direct sunlight or other high-temperature heat sources for a predetermined time, thermal deformation of the liquid crystal display panel due to high-temperature radiant heat generated from the glass can be prevented. 
     Accordingly, according to the present invention, damage due to the thermal deformation of the liquid crystal display panel can be effectively prevented. 
     In addition, according to the present invention, the liquid crystal display panel is directly attached to the glass through the direct bonding scheme, so that image quality of a screen can be maximized. 
     Next, a coupling relation and an operating method of the liquid crystal display device according to the exemplary embodiment of the present invention will be described in detail. 
     First, a worker may install the backlight unit  30  while a rear surface of the cover bottom  11  is seated on a worktable. 
     In this case, the air filter  51  and the fan  50  may be installed in the inlet hole  13  and the outlet hole  14  that are formed at the lower and upper ends of the cover bottom  11 , respectively. 
     Subsequently, the glass  40  may be attached to the front surface of the panel  20  by the direct bonding scheme. 
     The glass  40  and the panel  20  attached to each other as described above may be coupled to an inside of the cover bottom  11 . 
     Then, the panel  20  may be coupled to an inner space of the support part  12  formed in a rectangular frame shape on the inner surface of the edge of the cover bottom  11  so as to be supported by the support part  12 , and the glass  40  may be seated on a front surface of the support part  12 . 
     When the liquid crystal display device  10  assembled through a process described above is used in the environment exposed to direct sunlight or other high-temperature heat sources for a predetermined time, the fan  50  may be driven to directly cool the panel  20 . 
     In other words, a main controller (not shown) for controlling driving of each device provided in the liquid crystal display device  10  may generate a control signal for controlling the driving of the fan  50  based on a temperature detected by a temperature sensor (not shown) for detecting a temperature inside the liquid crystal display device  10  or a temperature of the panel  20 . 
     When the fan  50  is driven by the control signal of the main controller, the external air from which the dust or the foreign substances have been filtered in a process of passing through the air filter  51  installed at the lower end of the cover bottom  11  may be introduced into the cover bottom  11 . 
     Since the blocking plate  15  is installed between the rear wall of the cover bottom  11  and the backlight unit  30 , the introduced air may move upward along the movement space between the panel  20  and the backlight unit  30  without being directly discharged through the outlet hole. At this time, the panel  20  and the glass  40  may be cooled through the heat exchange with the panel  20 . 
     The air heated while cooling the panel  20  as described above may move upward so as to be discharged to the outside through the outlet hole  14  formed at the upper end of the cover bottom  11 . 
     Table 1 is a table of test results obtained by measuring a glass surface temperature and a panel surface temperature of the liquid crystal display devices according to the related art and the present invention according to external temperature conditions. 

 
     Table 1 shows the results of measuring the glass surface temperature until an abnormal phenomenon of the panel occurs by applying conditions similar to the direct sunlight. 
     In other words, Table 1 shows the result of measuring an external surface temperature of the glass  40  and an internal surface temperature of the panel  20  of the liquid crystal display device  10  according to the present invention compared to the liquid crystal display device according to the related art shown in  FIG. 1  under the same conditions when 5 minutes have elapsed from the start of a test and in a unit of 30 minutes from the start of the test. 
     In addition, Table 1 shows a temperature and a time at which yellow deformation (hereinafter referred to as “yellowing”) due to gravity acting on the glass  40  and the panel  20  starts to occur. 
     The test was performed under the same conditions until a time at which a blackening phenomenon due to deformation of liquid crystals of the panel  20  occurs. 
     As a result of performing the test under the above conditions, it was found that the liquid crystal display device  10  according to the present invention may extend a yellowing occurrence time from about 2 hours to about 4 hours and 30 minutes that is twice or more as compared with the liquid crystal display device according to the related art, and may also extend an occurrence time of the blackening phenomenon that causes the deformation of the liquid crystals of the panel  20  from about 3 hours to about 7 hours or more as compared with the liquid crystal display device according to the related art. 
     In this case, unless yellowing due to gravity is continuously accumulated to cause the blackening phenomenon, a yellowing phenomenon may disappear when heat applied from the outside is removed. 
     In general, a liquid crystal display device installed outdoors may not be directly exposed to the direct sunlight for 4 hours or more. 
     Therefore, the above test conditions are extreme conditions, and the test was performed under severe conditions than actual sunlight conditions. When the liquid crystal display device according to the related art is used for 4 hours or more under a direct sunlight condition while being installed outdoors, the yellowing occurred in about 20% to 30%. 
     Therefore, it may be determined by merging the above test results and actual conditions of use that the liquid crystal display device  10  according to the present invention has a heat dissipation effect of twice or more as compared with the liquid crystal display device according to the related art. 
     Through a process as described above, according to the present invention, in the state in which the liquid crystal display panel is attached to the glass by the direct bonding scheme, the separation space may be formed between the liquid crystal display panel and the backlight unit, and the air may move through the separation space, so that the liquid crystal display panel may be directly cooled. 
     Meanwhile, although the present embodiment has been described that the inlet hole  13  and the outlet hole  14  are formed at the lower and upper ends of the cover bottom  11 , respectively, and the air filter  51  and the fan  50  are installed in the inlet hole  13  and the outlet hole  14 , respectively, the present invention is not necessarily limited thereto. 
     In other words, the present invention may be modified such that the air filter  51  and the fan  50  are installed in the inlet hole  13  to suck the external air and supply the sucked air to the panel  20 , and the air heated through the heat exchange is discharged through the outlet hole  14 . 
     In addition, the present invention may be modified such that a plurality of outlet holes  14  are formed at the upper end and a center portion of the cover bottom  11 , the air filter  51  is installed in both the inlet hole  13  and the outlet hole  14 , and the fan  50  is installed in at least one of the inlet hole  13  and the outlet hole  14 . 
     In addition, although eight fans are shown in  FIG. 4 , a number, a capacity, and the like of installed fans  50  may vary according to various conditions such as a size, a shape, and the like of a position where the fan  50  is installed, that is, the outlet hole  14  or the inlet hole  13 . 
       FIG. 5  is a view showing a liquid crystal display device according to another embodiment of the present invention. 
     As shown in  FIG. 5 , a liquid crystal display device  10  according to another embodiment of the present invention has a configuration similar to the above-described configuration of the liquid crystal display device described with reference to  FIGS. 3 and 4  except that the liquid crystal display device  10  according to another embodiment of the present invention includes a thermoelectric element  60  for cooling internal air of the liquid crystal display device  10 . 
     Therefore, redundant descriptions of components that are identical to the components of the above-described embodiment will be omitted. 
     The thermoelectric element  60  may provide an electronic cooling effect by using heat absorption and heat generation due to a Peltier effect. 
     For example, the thermoelectric element  60  may use a pn junction configured by a semiconductor such as a compound of bismuth and tellurium (Bi 2 Te 3 ), and may be installed on the upper end of the cover bottom  11 . 
     A cooling unit  61  of the thermoelectric element  60  may be installed inside the cover bottom  11  of the liquid crystal display device  10 , and a heat dissipation unit  62  of the thermoelectric device  60  may be installed outside the cover bottom  11 . 
     Therefore, the internal air of the liquid crystal display device  10  may be cooled through the heat exchange with the cooling unit  61  of the thermoelectric element  60 , and the cooling unit  61  of the thermoelectric element  60  may transfer heat, which is transferred from the internal air, to the heat dissipation unit  62 . 
     Accordingly, the heat dissipation unit  62  of the thermoelectric element  60  may radiate the heat transferred from the cooling unit  61  to the outside through the heat exchange with external air of the liquid crystal display device  10 . 
     In addition, the liquid crystal display device  10  may further include: a first fan  52  for blowing the external air toward the heat dissipation unit  62 ; and second and third fans  53  and  54  for circulating the internal air of the liquid crystal display device  10 . 
     For example, the first fan  52  may be installed on the rear surface of the cover bottom  11 , and the second fan  53  and the third fan  54  may be installed at lower and upper ends of an inner space of the liquid crystal display device  10 , respectively. 
     Therefore, the second fan  53  may blow the air cooled by the cooling unit  61  of the thermoelectric element  60  toward the movement space between the panel  20  and the backlight unit  30 , and the third fan  54  may blow air, which is heated while rising through the movement space between the panel  20  and the backlight unit  30 , toward the cooling unit  61  of the thermoelectric element  60 . 
     However, the present invention is not necessarily limited to the above configuration, and the present invention may be modified such that a plurality of first fans  52  are installed, or one fan or three or more fans are installed inside the liquid crystal display device  10 . 
     As described above, according to the present invention, the air cooled by using the thermoelectric element is circulated through the movement space between the panel and the backlight unit, so that the panel and the glass can be effectively cooled. 
     In addition, according to the present invention, since an air circulation structure using the thermoelectric element is applied, heat dissipation is performed by circulating the internal air without introduction of the external air, so that an effect identical to the effect of the above-described embodiment can be obtained. 
     Although the present invention invented by the present inventor has been described in detail with reference to the embodiments, the present invention is not limited to the above embodiments, and various modifications are possible without departing from the gist of the present invention. 
     The present invention may be applied to a liquid crystal display device technique in which, in a state in which a liquid crystal display panel is attached to a glass by a direct bonding scheme, a separation space is formed between the liquid crystal display panel and a backlight unit, and air moves through the separation space, so that the liquid crystal display panel may be directly cooled.