Patent Publication Number: US-2022229326-A1

Title: Display Device and Method of Manufacturing the Same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of U.S. patent application Ser. No. 16/452,477 filed on Jun. 25, 2019, which claims the benefit of Republic of Korean Patent Application No. 10-2018-0094238, filed on Aug. 13, 2018, each of which is incorporated by reference in its entirety. 
    
    
     BACKGROUND 
     Field of Technology 
     The present disclosure relates to a display device, and more particularly, to a display device equipped with a camera. 
     Discussion of the Related Art 
     In the recent information society, a display device, which is a medium for conveying visual information, is receiving a lot of attention. In order to hold a prominent position in the future, it is desirable for such a display device to satisfy criteria such as low power consumption, reduction of weight and improvement of image quality. 
     Displays may be classified into self-luminescent display devices, which emit light by themselves, such as a cathode ray tube (CRT), an electroluminescence element (EL), a light-emitting diode (LED), a vacuum fluorescent display (VFD), a field emission display (FED) and a plasma display panel (PDP), and non-luminescent display devices, which cannot emit light by themselves, such as a liquid crystal display (LCD). 
     Among these various displays, the liquid crystal display device is intended to display an image using the optical anisotropy of the liquid crystal. Since the liquid crystal display device provides more better visibility than a conventional cathode ray tube and reduces both average power consumption and heat discharge compared to a cathode ray tube having the same screen size, it is attracting a lot of attention as a display. 
     The liquid crystal display device is constructed so as to realize an image in such a way as to control the transmissivity of light emitted from a light source disposed below the liquid crystal by applying an electric field to the liquid crystal and thus controlling the alignment of the liquid crystal. The liquid crystal device is applied to various electronic devices such as smart phones and tablet PCs. In particular, the liquid crystal device includes a cover glass, a liquid crystal panel disposed below the cover glass, a backlight unit disposed below the liquid crystal panel and a cover bottom for accommodating or supporting the liquid crystal panel or the backlight unit. 
     Since the recent display device is intended to have a slim bezel having a small thickness and to have an ultrathin display panel, demand for a slim and light display device is increasing. 
     In the recent mobile devices, it is desirable for a display device to have a narrow bezel, in which the width of a bezel is minimized so as to maximally expand the visible range of a liquid crystal panel, rather than the slim bezel. 
     To this end, when the liquid crystal panel is expanded to the whole front surface of a display device equipped with a camera so as to realize a narrow bezel, the liquid crystal panel may expand into the region to which the camera is mounted. In this case, the camera hole regions of the liquid crystal panel, the polarization plate and the backlight unit, at which the camera is mounted, have to be provided with punched through holes or have to be transparent. 
     SUMMARY 
     Accordingly, the present disclosure is directed to a display device and a method of manufacturing the same that substantially obviate one or more problems due to limitations and disadvantages of the related art. 
     An object of the present disclosure is to provide a display device, which is a narrow-bezel-type display device equipped with a camera and which is able to realize improvement of transparency for image capture by the camera, suppression of creation of air gaps, and improvement of waterproof performance. 
     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, a display device includes a cover glass, a liquid crystal panel disposed below the cover glass and having a transparent portion, an upper polarization plate having a through hole corresponding to the transparent portion and disposed between the cover glass and the liquid crystal panel, an Optically Clear Adhesive (OCA) film disposed between the cover glass and the upper polarization plate and attached thereto, and Optical Clear Resin (OCR) layer charged in the through hole of the upper polarization plate. 
     The OCA film may have a thickness of 150 micrometers (μm) to 250 μm. 
     The OCR layer may have the same thickness as the upper polarization plate. 
     The OCR layer may have a thickness of 100 μm to 150 μm. 
     The display device may further include a backlight light unit providing light to liquid crystal panel and having a first camera hole, and a lower polarization plate having a second camera hole and disposed between the liquid crystal panel and the backlight light unit, wherein the first camera hole and the second camera hole corresponds to the transparent portion of the liquid crystal panel and the through hole of the upper polarization plate. 
     The display device may further include a cover bottom having a third camera hole corresponding to the first and second camera holes and holding the backlight light unit and the liquid crystal panel, and a camera disposed in the first to third camera hole. 
     The backlight light unit may include optical sheets, a light guide plate, and a reflective plate. The first camera hole may penetrate the optical sheets, the light guide plate, and the reflective plate. 
     The cover glass may further include a touch panel. 
     In another aspect of the present disclosure, a display device includes a display panel having a transparent portion, a cover substrate on the display panel, a polarization plate having a through hole corresponding to the transparent portion of the display panel and disposed between the cover substrate and the display panel, an OCA film disposed between the cover substrate and the polarization plate and attached thereto, and an OCR layer disposed in the through hole of the polarization plate. The cover substrate may further include a touch panel. 
     The OCR layer in the through hole of the polarization plate and the transparent portion of the display panel may correspond to at least one optical module including at least one of cameras and optical sensors. 
     In another aspect of the present disclosure, a method of manufacturing a display device includes preparing a display panel and a polarization plate on the display panel, the display panel having a transparent portion and the polarization plate having a through hole corresponding to the transparent portion of the display panel, disposing an OCR layer in the through hole of the polarization plate, attaching an OCA film to a cover substrate, and closely combining the polarization plate with the OCA film attached to the cover substrate. 
     The disposing the OCR layer in the through hole may comprise spraying OCR spray liquid onto the transparent portion of the display panel so as to charge the OCR layer in the through hole of the polarization plate, and curing the OCR layer. The OCR layer may be charged in the through hole of the polarization plate in such a manner that the OCR spray liquid is sprayed onto a plurality of dots on the transparent portion of the display panel, the dots being spaced apart from each other at regular intervals, and the OCR spray liquid spreads out on the transparent portion of the display panel. 
     The OCR layer charged in the through hole may be cured by ultraviolet light. 
     It is to be understood that both the foregoing general description and the following detailed 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 disclosure and are incorporated in and constitute a part of this application, illustrate embodiment(s), and together with the description serve to explain the principle of the invention. In the drawings: 
         FIGS. 1A and 1B  illustrate a display device equipped with a camera according to an embodiment, in which  FIG. 1A  is a front view of the display device, and  FIG. 1B  is a front view of the display device, from which a cover glass and an upper cover are removed; 
         FIG. 2  is a perspective view taken along line A-A in  FIG. 1B , according to an embodiment; 
         FIG. 3  is a cross-sectional view of a substantial part of the display device according to an embodiment; 
         FIG. 4  is a view showing a procedure in which the OCR resin shown in  FIG. 3  is applied to a through hole, according to an embodiment; 
         FIGS. 5A and 5B  are views showing the region in the through hole in  FIG. 4  to which the OCR spray liquid is sprayed, according to an embodiment; 
         FIG. 6  is a view showing a procedure in which the OCR layer is cured by an ultraviolet lamp, according to an embodiment; 
         FIG. 7  is a view showing a procedure in which an OCA film is attached to the cover glass in  FIG. 3 , according to an embodiment; 
         FIG. 8  is a view showing a comparative example in which only an OCA film is attached to the through hole, according to an embodiment; and 
         FIG. 9  is a flowchart illustrating a method of manufacturing the display device according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, embodiments will be clearly revealed via description thereof with reference to the accompanying drawings. In the following description of the embodiments, it will be understood that, when an element such as a layer, film, region, pattern, or structure is referred to as being “on” or “under” another element, it can be “directly” on or under another element or can be “indirectly” formed such that an intervening element may also be present. In addition, it will also be understood that the criteria for “on” or “under” are determined on the basis of the drawings. 
     In the drawings, the size of each constituent element is exaggerated, omitted, or schematically illustrated for convenience of description and clarity. Also, the size of each constituent element does not entirely reflect the actual size thereof. The same reference numbers will be used throughout the drawings to refer to the same or like parts. 
     Hereinafter, embodiments will be described with reference to the accompanying drawings. 
       FIG. 1A  illustrates a front view of a display device equipped with a camera according to an embodiment, and  FIG. 1B  is a front view of the display device from which a cover glass and an upper cover are removed.  FIG. 2  is a perspective view taken along line A-A in  FIG. 1B . 
     Referring to  FIGS. 1A and 1B , the display device  1  according to the embodiment includes the camera  2  provided on the front surface thereof, and is constructed so as to realize a narrow bezel, the bezel having a reduced width so as to expand the visible range of a liquid crystal panel  200 , covered by a cover glass (substrate)  10 , as wide as possible. 
     The cover glass  10  may include a protective film (not shown) provided on the upper surface thereof. Furthermore, the cover glass  10  may include a touch panel (not shown). The touch panel may be classified into a pressure-sensitive type, in which sensor lines, which are adapted to respond to pressure applied to the surface thereof, are densely arranged so as to recognize the coordinates of a location to which pressure is applied, and an electrostatic type, in which an electric charge is applied to the surface of the cover glass  10  and sensors are provided therearound so as to recognize a contact location on the surface by detecting the extent to which the charge is lost in the event of contact. 
     As illustrated in  FIG. 1B , an upper polarization plate  110  is disposed beneath the cover glass  10 , and a through hole H is formed in the upper polarization plate  110  through punching so as to allow operation of the camera  2 . 
     As illustrated in  FIG. 2 , the through hole H, which is formed in the upper polarization plate  110 , may have a location and size corresponding to those of a camera hole CH in which the camera (not shown in  FIG. 2 ) is mounted. 
     The liquid crystal panel  200  may be disposed between the through hole H and the camera hole CH, and may have a transparent portion  230 , which is disposed between the through hole H and the camera hole CH. 
     The liquid crystal panel  200  includes a color filter substrate  210 , in which pixels are arranged in a matrix pattern so as to output an image, an array substrate  220  combined with the color filter substrate  210  so as to form a cell gap therebetween, and a liquid crystal layer (not shown) formed in the cell gap between the color filter substrate  210  and the array substrate  220 . 
     The color filter substrate  210  may be composed of a color filter, which is constituted by a plurality of sub color filters for realizing red, green and blue (RGB) colors, a black matrix for isolating the sub color filters from each other and blocking the light transmitted through the liquid crystal layer, and an overcoat layer formed on the color filter and the black matrix. 
     The array substrate  220  is provided with gate lines and data lines, which are arranged in horizontal and vertical directions so as to form pixel regions, and thin film transistors (TFT), which are switching elements, are formed on the cross regions between the gate lines and the data lines. Each of the thin film transistors is composed of a gate electrode connected to the gate line, a source electrode connected to the data line, and a drain electrode connected to a pixel electrode. Any one of the array substrate  220  and the color filter substrate  210  includes a common electrode. 
     The liquid crystal panel  200 , in which the color filter substrate  210  and the array substrate  220  are combined with each other, is provided with the common electrode and the pixel electrode so as to apply an electric field to the liquid crystal layer and to control the voltage of a data signal applied to the pixel electrode in the state in which voltage is applied to the common electrode. Therefore, the liquid crystal in the liquid crystal layer is rotated due to the dielectric anisotropy according to an electric field between the common electrode and the pixel electrode so as to allow or block the transmission of light from the pixels, thereby displaying a character or an image. Here, in order to independently control the voltage of a data signal applied to the pixel electrodes, the switching elements, such as the thin film transistors, are respectively provided at the pixels. 
     The transparent portion  230  of the liquid crystal panel  200  may be configured to have a shape and size corresponding to those of the camera hole CH and the through hole H, and may be maintained in the transparent state so as to allow image capture by the camera  2 . For example, the transparent portion  230  may perform control so as to make a partial region of the liquid crystal panel  200  transparent in a manner of controlling or removing the sub filters in the color filter substrate  210 . 
     The polarization plates  110  and  120  may be respectively attached to the upper surface of the color filter substrate  210  and the lower surface of the array substrate  220 . Here, the lower polarization plate  120  functions to polarize light that has passed through a backlight unit  300  toward the array substrate  220 , and the upper polarization plate  110  functions to polarize light that has passed through the liquid crystal panel  200 . 
     The backlight unit  300  may include a light guide plate  320  disposed below the liquid crystal panel  200 , a plurality of optical sheets  310  for radiating light exiting the light guide plate  320  to the liquid crystal panel  200  with improved efficiency, and a reflective plate  330 . 
     The light guide plate  320  receives light from a light source (not shown) and guides the light toward the liquid crystal panel  200 . The light guide plate  320  may be made of a plastic material of polymethylmethacrylate (PMMA) or polycarbonate (PC). 
     The optical sheet  310  may include a diffusion sheet and a prism sheet, and may further include a brightness enhancement film and a protective sheet, such as dual brightness enhancement film (DBEF). The optical sheet  310  may be disposed between the upper surface of the light guide plate  320  and the rear surface of the liquid crystal panel  200 . 
     The reflective plate  330  is disposed between a cover bottom  400  and the rear surface of the light guide plate  320 . The reflective plate  330  reflects both light emitted from the light source and light reflected by the light guide plate  320  toward the liquid crystal panel  200 . The light emitted from the light source enters the lateral surface of the light guide plate  320 , which is made of a transparent material, and the reflective plate  330 , which is disposed on the rear surface of the light guide plate  320 , reflects the light that exits the rear surface of the light guide plate  320  toward the optical sheet  310  on the light guide plate  320 , thereby realizing reduction of light loss and improvement in uniformity of luminance. 
     The backlight unit  300 , which includes the above-mentioned components, is received in the cover bottom  400 . The backlight unit  300  is not limited to the above-described structure, and any of backlight units  300  having other structures may be applied to the display device  1 . 
     The cover bottom  400  may receive therein the backlight unit  300  and a guide panel, and may support the liquid crystal panel  200 . For example, the cover bottom  400  may be composed only of a bottom part and a lateral part in order to realize a minimized slim bezel region. Specifically, the cover bottom  400  may include the bottom part having a rectangular shape and the lateral part projecting upwards from one side of the bottom part by a predetermined height. The cover bottom  400  is only for illustrative purposes, and any of cover bottoms  400  having various shapes may be applied to the display device  1 . 
     In the display device  1  according to the embodiment, the through hole H is formed through the upper polarization plate  110 , and the camera hole CH, in which the camera  2  is mounted, is formed though the backlight unit  300  and the cover bottom  400 . The transparent portion  230  in the liquid crystal panel  200  is disposed between the through hole H and the camera hole CH. 
       FIG. 3  is a cross-sectional view of a substantial part of the display device according to the embodiment.  FIG. 4  is a view showing a procedure in which OCR spray liquid shown in FIG. is applied to the through hole H formed in the upper polarization plate.  FIG. 5  is a view showing a region in the through hole H in  FIG. 4  to which the OCR spray liquid is sprayed.  FIG. 6  is a view showing a procedure in which an OCR layer is cured by an ultraviolet lamp.  FIG. 7  is a view showing a procedure in which an optical clear adhesive (OCA) film is attached to the cover glass in  FIG. 3 .  FIG. 8  is a view showing a comparative example in which only an OCA film is attached to the through hole. 
     Referring to  FIGS. 3 to 8 , the realization of improvement of transparency for image capture by the camera  1 , suppression of air gaps in the through hole H and enhancement of waterproof performance, which are achieved by the display device  1  according to some embodiments, will be described. 
     The display device  1  according to the embodiment may include an OCA film  500 , disposed between the cover glass  10  and the upper polarization plate  110  and attached thereto, and an OCR layer  600  disposed in the through hole H in the upper polarization plate  110 . 
     The OCA film  500  may be disposed between the cover glass  10  and the upper polarization plate  110  and attached thereto so as to improve luminance. 
     The Optical clear adhesive (OCA) film is an optically transparent adhesive. The OCA film has an advantage of allowing 97% or more of incident light to pass therethrough, like glass, and of improving definition of a screen compared to a piece of double-faced adhesive tape. The OCA film  500  is present in a solid state before and after attachment of the cover glass  10  to the upper polarization plate  110 . The OCA film  500  may also be referred to as an optical adhesive film, an OCA sheet or an OCA. 
     The OCA film  500  may have, for example, a thickness of 150 μm to 250 μm. 
     When only an OCA film  501  is attached to the cover glass  10  and the upper polarization plate  110  as illustrated in  FIG. 8 , a portion of the OCA film  500  may droop toward the through hole H due to the through hole H in the polarization plate  110 , with the result that a stepped portion is created in the OCA film  501 , thereby generating air gaps (e.g., bubbles) between the layers such as between the OCA film  501  and the upper polarization plate  110 , between the OCA film  501  and the transparent portion  230  of the liquid crystal panel  200 , and/or between the cover glass  10  and the OCA film  501 . Because the air gaps deteriorate the transparency and impair the waterproof performance, the image capture performance of the camera  2  may be deteriorated. 
     To solve this, the OCR layer  600  is disposed in the through hole H in the upper polarization plate  110  without voids. 
     The OCR, which is an ultraviolet curing agent for improving luminance, is excellent in transparency, adhesive force and weather resistance. The OCR layer  600 , which is disposed in the through hole H, enhances the light transmissivity of the camera  2 , and improves luminance and brightness, thereby improving visibility. In addition, the enhancement of light transmissivity offers additional effects of reducing the amount of power consumed for operation of the display and thus heat generation and of improving shock resistance. 
     When the OCR layer  600  is disposed in the through hole H, the contrast ratio is improved by 400% or more, with the result that there are advantages of realization of a clear image or prevention of a phenomenon whereby the liquid crystal display is not clearly visible under daylight condition. The OCR layer  600  may also be referred to as OCR direct bonding adhesive or simply as OCR. The OCR layer  600  is present in a liquid state before application but is present in a solid state after application and UV curing. 
     Since the OCR layer  600  is applied to the through hole H in the polarization plate  110  in such a way that an optical resin is densely charged, it is possible to make the display device  1  slim and to prevent the generation of air gaps attributable to voids. 
     For example, the OCR layer  600  may have a small thickness corresponding to the thickness of the upper polarization plate  110 , that is, a thickness of 100 μm to 150 μm, which is smaller than the thickness of the OCA film  500 . 
     As illustrated in  FIGS. 4 and 5 , the OCR layer  600  may be applied and charged in the through hole H in such a manner as to be sprayed toward a plurality of dots, which are spaced apart from each other at regular intervals. Here, the plurality of dots may be imaginary dots, which are located so as to enable the OCR layer  600  to be densely charged without gaps. The OCR may be sprayed as OCR spray liquid  610  in dot units through a jetting valve  700 . Here, the OCR, which is sprayed in dot units through the jetting valve  700 , will be referred to as the OCR spray liquid  610 . 
     The plurality of dots for the OCR spray liquid  610  may be nine dots P 1 -P 9 , which are spaced apart from each other at regular intervals in the through hole H, as illustrated in  FIG. 5A , or may be ten dots P 1 -P 10 , as illustrated in  FIG. 5B . The above-described arrangement of the dots is merely an illustrative example, and the dots may be arranged in various numbers and dispositions as necessary. 
     The jetting valve  700  may be configured to be movable on the through hole H, and may discharge the OCT spray liquid  610  in an amount of 0.032 mg per one dot. The OCR spray liquid  610 , which is sprayed to the dots, spreads out on the transparent portion  230  of the liquid crystal panel  200 . Consequently, the OCR spray liquid  610  on the dots may be connected to each other, and thus may be densely charged in the through hole H. 
     The jetting valve  700  may spray the OCR spray liquid  610  once at each of the dots while moving on the through hole H. Alternatively, the jetting valve  700  may spray the OCR spray liquid  610  twice or more at each of the dots as necessary. 
     In order to allow the OCR spray liquid  610  to have a predetermined viscosity and to allow the OCR spray liquid sprayed on the dots to be connected to each other, the jetting valve  700  may spray the OCR spray liquid  610  at a temperature of 70° C. 
     After the OCR layer  600  is completely charged in the through hole H in the above manner, an operation of curing the OCR layer  600  is performed as illustrated in  FIG. 6 . In order to cure the OCR layer  600 , an ultraviolet lamp  800  may be used. 
     After the OCR layer  600  is cured in the through hole H, an operation of attaching the OCA film  500  to the cover glass  10  is performed as illustrated in  FIG. 7 . Here, the OCA film  500  may be attached to the lower surface of the cover glass  10  using a jig  900  so as not to create an air gap. 
     After the OCA film  500  is attached to the lower surface of the cover glass  10 , the upper polarization plate  110  with the through hole H being filled with the OCR layer  600  is closely combined with the OCA film  500  attached to the cover glass  10 , as illustrated in  FIG. 3 . 
     In the narrow-bezel-type display device according to the embodiment, it is possible to realize improvement of transparency for image capture by the camera, suppression of creation of air gaps and improvement of waterproof performance by virtue of adoption of the OCA film  500  and the OCR layer  600 . 
       FIG. 9  is a flowchart of the method of manufacturing the display device according to an embodiment. 
     Referring to  FIG. 9 , the method of manufacturing the display device according to the embodiment is carried out so as to firstly perform an operation (S 100 ) of spraying the OCR spray liquid  610  to the through hole H in the upper polarization plate  110 . 
     In the operation (S 100 ), more specifically, the OCR spray liquid  610  is sprayed onto the transparent portion  230  of the liquid crystal panel  200  so as to fill the through hole H formed in the upper polarization plate  110  with the OCR layer  600 . Here, the OCR layer  600  may be charged into the through hole H in such a manner that the OCR spray liquid  610  is sprayed to a plurality of dots on the transparent portion  230 , which are spaced apart from each other at regular intervals. The number of the plurality of dots may be nine or ten. The OCR spray liquid  610  may be sprayed and charged while the jetting valve  700  moves along the plurality of dots. 
     The OCR layer  600  may be applied to an extent that corresponds to the thickness of the upper polarization plate  110 . The applied OCR layer  600  may have, for example, a thickness of 100 μm to 150 μm. 
     Subsequently, an operation (S 200 ) of curing the OCR layer  600  charged in the through hole H is performed. 
     Here, the OCR layer  600  charged in the through hole H may be cured using an ultraviolet lamp  800 . 
     After the OCR layer  600  is cured, an operation (S 300 ) of attaching the OCA film  500  to the cover glass  10  is performed. The OCA film  500  may have a thickness of 150 μm to 250 μm, and may be attached to the cover glass  10  using the jig. 
     After the OCA film  500  is attached to the cover glass  10 , an operation (S 400 ) of closely combining the upper polarization plate  110  with the OCA film  500  attached to the cover glass  10  is performed. 
     According to the method of manufacturing the narrow-bezel-type display device according to the embodiment, it is possible to realize improvement of transparency for image capture by the camera, suppression of creation of air gaps and improvement of waterproof performance by virtue of adoption of the OCA film  500  and the OCR layer  600 . 
     The display device according to an embodiment may include a display panel such as an electroluminescence (EL) panel, a light-emitting diode (LED) panel, etc. The transparent portion of the display panel and the OCR layer disposed in the through hole H of the upper polarization plate on the display panel may correspond to each of optical modules. The optical modules may include cameras and various types of optical sensors, such as an infrared sensor, an illumination sensor, etc. 
     The display device according to an embodiment may be applied to various electronic devices, such as TVs, smart phones and tablet PCs. 
     As described above, according to the display device and the method of manufacturing the same according to an embodiment, it is possible to realize a narrow bezel, which offers improvement of transparency for image capture by the camera, suppression of creation of air gaps and improvement of waterproof performance by virtue of adoption of the OCA film and the OCR layer. 
     The features, configurations, effects and the like described above in the embodiments are included in at least one embodiment, but do not need to be limited only to the at least one embodiment. In addition, the features, configuration, effects and the like exemplified in the respective embodiments may be combined with other embodiments or modified by those skilled in the art. Accordingly, the content related to such combinations and modifications should be understood to fall within the scope of the embodiments.