Patent Publication Number: US-2019187515-A1

Title: Method for producing display panel

Description:
This Nonprovisional application claims priority under 35 U.S.C. § 119 on Patent Application No. 2017-242982 filed in Japan on Dec. 19, 2017, the entire contents of which is hereby incorporated by reference. 
     TECHNICAL FIELD 
     The present invention relates to a method for producing a display panel. 
     BACKGROUND ART 
     A method for producing a display panel includes many steps. Various techniques have been conventionally proposed for reducing the number of steps included in the method for producing a display panel. 
     Patent Document 1 discloses a method for producing a liquid crystal panel, characterized in that a display panel and two electrode substrate members, which include a plurality of electrode substrates preferably made of plastic, are bonded so as to face each other, polarizing plates are bonded to corresponding back surfaces of the electrode substrate members, and thereafter, an end portion of one of the electrode substrate members is cut together with the polarizing plates to provide a terminal area at a time. 
     Patent Document 2 discloses a method for producing a liquid crystal device, characterized by including the step of bonding an optical film to an outer surface of at least one of a first base substrate and a second base substrate before a large-sized panel is divided into separate panels. 
     Patent Document 3 discloses a method for producing a display device, including the steps of: bonding a first base substrate and a second base substrate to each other; bonding a first polarizing plate to the first base substrate; bonding a second polarizing plate to the second base substrate; and subjecting the first polarizing plate, the first base substrate, the second base substrate, and the second polarizing plate to dicing by batch. 
     CITATION LIST 
     Patent Literatures 
     [Patent Literature 1] 
     Japanese Patent Application Publication Tokukai No. 2002-277860 
     [Patent Literature 2] 
     Japanese Patent Application Publication Tokukai No. 2007-248594 
     [Patent Literature 3] 
     Japanese Patent Application Publication Tokukai No. 2016-90855 
     SUMMARY OF INVENTION 
     Technical Problem 
     In recent years, a panel incorporated into a smart phone and a wearable device has had a narrower frame, and there has been a growing demand for a display panel having not only a narrower frame but also an irregular shape (circular shape, cutout, cut at corners, etc.). Applying the techniques disclosed in Patent Documents 1 to 3 to a method for producing a display panel including a glass substrate and having a narrow frame and an irregular shape gives rise to the following problems. 
     The technique disclosed in Patent Document 1 is applied to processing of an electrode substrate made of plastic, but is not applied to processing of a glass substrate. 
     The technique disclosed in Patent Document 2 is applicable to rectangular shape splitting of a glass substrate, but is not applicable to irregular shape processing of a glass substrate. The technique disclosed in Patent Document 3 requires performing the processing of the polarizing plates and the processing of a glass substrate at different times. Accordingly, it is necessary for a glass substrate maker and a polarizing plate maker to perform irregular shape processing of a glass substrate and irregular shape processing of the polarizing plates at different times. This increases the number of steps in the production method. 
     Furthermore, the techniques disclosed in Patent Documents 1 and 3 fail to make the end faces of the polarizing plates and the end faces of the glass substrate flush with each other. 
     The present invention has been attained to solve the above problems, and it is an object of the present invention to produce a display panel having a narrow frame and having an irregular shape by a fewer number of steps and to make the end faces of the polarizing plates flush with the end face of the glass substrate. 
     Solution to Problem 
     A method for producing a display panel in accordance with an aspect of the present invention includes the steps of: bonding a polarizing plate having a rectangular shape to a separate glass substrate, the separate glass substrate having a rectangular shape and including a display region having at least one cutout; and simultaneously cutting a contour of the separate glass substrate and a contour of the polarizing plate with use of an end mill or a laser. 
     Advantageous Effects of Invention 
     An aspect of the present invention yields the effect of processing a display panel having a narrow frame and having an irregular shape so that the end faces of the polarizing plates are made flush with the end face of the glass substrate and producing such a display panel having a narrow frame and having an irregular shape by a fewer number of steps. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a view illustrating a large-sized glass substrate including a plurality of display regions with respective ones of cutouts, in accordance with an embodiment of the present invention. 
         FIG. 2  is a view illustrating a separate glass substrate including one display region with a cutout, in accordance with an embodiment of the present invention. 
         FIG. 3  is a view illustrating polarizing plates in accordance with an embodiment of the present invention. 
         FIG. 4  is a view illustrating the separate glass substrate with the polarizing plates bonded thereto, in accordance with an embodiment of the present invention. 
         FIG. 5  is a view illustrating a display panel obtained by irregular shape processing, in accordance with an embodiment of the present invention. 
         FIG. 6  is an explanatory view illustrating other example method for producing a display panel in accordance with an embodiment of the present invention. 
         FIG. 7  is an explanatory view illustrating the advantages of the display panel produced by the production method in accordance with an embodiment of the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     (Large-Sized Glass Substrate  1 ) 
       FIG. 1  is a view illustrating a large-sized glass substrate  1  including a plurality of display regions  21  with respective ones of cutouts  31 , in accordance with an embodiment of the present invention. (a) of  FIG. 1  illustrates the large-sized glass substrate  1  when viewed from above, and (b) of  FIG. 1  illustrates a cross section of the large-sized glass substrate  1  when viewed along a line A-A′ in (a) of  FIG. 1 . 
     In carrying out a method for producing a display panel, a display panel maker first prepares a large-sized glass substrate  1  like the one illustrated in  FIG. 1 . The large-sized glass substrate  1  includes a color filter (CF) substrate  11  and a thin film transistor (TFT) substrate  12 . The CF substrate  11  and the TFT substrate  12  are glass substrates. As illustrated in (b) of  FIG. 1 , the large-sized glass substrate  1  has a laminated structure of the CF substrate  11  and the TFT substrate  12 . 
     The large-sized glass substrate  1  includes a plurality of display regions  21  each having an irregular shape. The irregular shape means a non-rectangular shape. The display regions  21  each have cutouts  31 . Each of the display regions  21  has at least one cutout and may alternatively have other cutout which is different from the cutouts  31 . The display regions  21  are surrounded by respective ones of frame regions  22 . A connection region  23  is located on a lower side of the frame region  22  in a paper sheet of  FIG. 1 . The connection region  23  is a region where a driver for driving the display region  21  is provided. The connection region  23  is also a region where a wiring to be connected to one end of a flexible printed circuit board (FPC) is formed. The FPC is a substrate for connecting the display panel to an external device. A place where the driver is mounted is not limited to the connection region  23 . The connection region  23  can alternatively be mounted on the FPC or on an external substrate. 
     On a surface of the CF substrate  11  which surface faces the TFT substrate  12 , various resin thin films are formed. Examples of the resin thin films include black matrix, a red color filter, a green color filter, and a blue color filter. These resin thin films are formed on the surface of the CF substrate in an area corresponding to the display region  21 . 
     On a surface of the TFT substrate  12  which surface faces the CF substrate  11 , TFTs and a wiring are formed. The TFTs are formed on the surface of the CF substrate  11  in an area corresponding to the display region  21 . The wiring is formed on the surface of the CF substrate  11  in areas corresponding to the display region  21 , the frame region  22 , and the connection region  23 . 
     Liquid crystal is injected into a space, provided between the CF substrate  11  and the TFT substrate  12 , corresponding to the display region  21 . Thus, the display region  21  is equivalent to a display region of a liquid crystal display section. The display region  21 , however, is not limited to such a display region, and can alternatively be a display region of an organic EL display section or a display region of other display section. 
     The rim of the frame region  22  coincides with contours  41  of the CF substrate  11  and the TFT substrate  12  in the display panel. As described in detail later, the contour  41  of the CF substrate  11  and the contour  41  of the TFT substrate  12  are simultaneously cut. 
     (Rectangular Shape Division of Large-Sized Glass Substrate  1 ) 
       FIG. 2  is a view illustrating a separate glass substrate  2  including one display region  21  with a cutout  31 , in accordance with an embodiment of the present invention. (a) of  FIG. 2  illustrates the separate glass substrate  2  when viewed from above, and (b) of  FIG. 2  illustrates a cross section of the separate glass substrate  2  when viewed along a line A-A′ in (a) of  FIG. 2 . A display panel maker divides the large-sized glass substrate  1  illustrated in  FIG. 1  into a plurality of separate glass substrates  2  in cell units as illustrated in  FIG. 2 . The separate glass substrate  2  in cell unit means a separate glass substrate  2  including one display region  21  with a cutout  31 . In other words, the separate glass substrate  2  includes one display region  21 , one frame region  22 , and one connection region  23 . 
     The separate glass substrate  2  illustrated in  FIG. 2  is rectangular in shape. At this stage, a display panel maker cuts the separate glass substrate  2  at a part corresponding to the connection region  23 . Accordingly, in the connection region  23  of the separate glass substrate  2 , the TFT substrate  12  is present, but the CF substrate  11  is not present (as illustrated in (b) of  FIG. 2 ). Such exposure of the connection region  23  allows the driver to be provided in the connection region  23  and allows for connection to the FPC. 
     At this stage, the display panel maker does not perform irregular shape processing on the separate glass substrate  2 . In other words, in the separate glass substrate  2 , the contour  41  of the CF substrate  11  and the contour  41  of the TFT substrate  12  are not cut. 
     (Polarizing Plates  51  and  52 ) 
       FIG. 3  is a view illustrating polarizing plates  51  and  52  in accordance with an embodiment of the present invention. The polarizing plates  51  and  52  are prepared by a polarizing plate maker. Each of the polarizing plates  51  and  52  illustrated in  FIG. 3  has a cell unit size that accommodates the size of the separate glass substrate  2  into which the large-sized glass substrate  1  is divided in cell unit as illustrated in  FIG. 2 . The maker of the polarizing plates  51  and  52  first produces one or more large-sized polarizing plates and divides them into separate polarizing plates in cell units. Consequently, the polarizing plates  51  and  52  of a size illustrated in  FIG. 3  are produced. In an example case illustrated in  FIG. 3 , the polarizing plates  51  and  52  are larger in size than the display region  21  illustrated in  FIG. 2 . Before bonded to the large-sized glass substrate  1 , the polarizing plates  51  and  52  are rectangular in shape. In other words, the maker of the polarizing plates  51  and  52  does not perform irregular shape processing on the polarizing plates  51  and  52  in cell units. 
     The maker of the polarizing plates  51  and  52  delivers, to the display panel maker, the polarizing plates  51  and  52  in cell units illustrated in  FIG. 3 . Alternatively, the maker of the polarizing plates  51  and  52  can deliver one or more large-sized polarizing plates to the display panel maker, and the display panel maker can divide the one or more large-sized polarizing plates thus delivered into the polarizing plates  51  and  52  in cell units. 
     (Bonding of Polarizing Plates  51  and  52 ) 
       FIG. 4  is a view illustrating the separate glass substrate  2  with the polarizing plates  51  and  52  bonded thereto, in accordance with an embodiment of the present invention. (a) of  FIG. 4  illustrates a top surface of the separate glass substrate  2  with the polarizing plates  51  and  52  bonded thereto, and (b) of  FIG. 4  illustrates a cross section of the separate glass substrate  2  when viewed along a line A-A′ in (a) of  FIG. 4 . The display panel maker bonds the rectangular polarizing plate  51  illustrated in  FIG. 3  to the surface of the rectangular separate glass substrate  2  illustrated in  FIG. 2  on the CF substrate  11  side. The polarizing plate  51  is disposed on the surface of the CF substrate  11  in such a manner that the display region  21  is overlaid in whole with the polarizing plate  51 . The display panel maker further bonds the rectangular polarizing plate  52  illustrated in  FIG. 3  to the surface of the TFT substrate  12  in the rectangular separate glass substrate  2  illustrated in  FIG. 2 . The polarizing plate  52  is disposed on the surface of the TFT substrate  12  in such a manner that the display region  21  is overlaid in whole with the polarizing plate  52 . 
     Through the bonding of the polarizing plates  51  and  52 , the outlines  61  of the polarizing plates  51  and  52  are determined with respect to the separate glass substrate  2 . In the separate glass substrate  2 , the contour  61  coincides with the contours  41 . At this stage, the separate glass substrate  2  is not subjected to irregular shape processing. 
     (Simultaneous Irregular Shape Processing) 
       FIG. 5  is a view illustrating the display panel  3  obtained by irregular shape processing, in accordance with an embodiment of the present invention. (a) of  FIG. 5  illustrates the display panel  3  when viewed from above, and (b) of  FIG. 5  illustrates a cross section of the display panel  3  when viewed along a line A-A′ in (a) of  FIG. 5 . 
     The display panel maker performs irregular shape processing simultaneously on the constituent components of the separate glass substrate  2  illustrated in  FIG. 4 , i.e., the CF substrate  11 , the TFT substrate  12 , the polarizing plate  51 , and the polarizing plate  52 . Specifically, contours  41  of the CF substrate  11  and the TFT substrate  12  and contours  61  of the polarizing plates  51  and  52  are simultaneously cut with use of an end mill or a laser. This produces a display panel  3 , as illustrated in  FIG. 5 , having a narrow frame and having an irregular shape. 
     Thereafter, to the irregularly-shaped display panel  3 , components such as a backlight module, a driver IC, and a flexible printed circuit board are mounted sequentially. This produces a display panel  3  in finished form. Note that a light guide plate contained in the backlight module has an irregular shape similarly to the irregular shape of the display region  21  and other components. However, the light guide plate, which is produced by injection molding with a plastic frame mold, is not subjected to irregular shape processing simultaneously with the CF substrate  11 , the TFT substrate  12 , the polarizing plate  51 , and the polarizing plate  52 . 
     As described above, according to a production method in accordance with an embodiment of the present invention, the polarizing plates  51  and  52  before subjected to irregular shape processing are bonded to the separate glass substrate before subjected to irregular shape processing, and thereafter, the separate glass substrate  2  and the polarizing plates  51  and  52  are simultaneously subjected to irregular shape processing with use of an end mill or a laser. Thus, it is possible to reduce the steps for the irregular shape processing process by one step, in comparison with the conventional technique of individually subjecting the separate glass substrate  2  and the polarizing plates  51  and  52  to irregular shape processing. This eliminates the maker of the polarizing plates  51  and  52  having to make a capital investment for irregular shape processing of the polarizing plates  51  and  52 . Furthermore, it is possible to reduce the time for producing the polarizing plates  51  and  52 . This consequently achieves reduction in cost of the polarizing plates  51  and  52  and securement of the capacity. 
     Moreover, by simultaneously subjecting the separate glass substrate  2  and the polarizing plates  51  and  52  to irregular shape processing with use of an end mill or a laser, it is possible to make the end faces of the polarizing plates  51  and  52 , the end face of the CF substrate  11 , and the end face of the TFT substrate  12  flush with one another in the produced display panel  3 . 
     (Other Example Production Method) 
       FIG. 6  is an explanatory view illustrating other example method for producing a display panel in accordance with an embodiment of the present invention. In carrying out the production method illustrated in  FIG. 6 , the display panel maker first prepares a large-sized glass substrate  1 , as illustrated in  FIG. 1 , including a plurality of display regions  21  having respective ones of cutouts  31 . Subsequently, as illustrated in (a) of  FIG. 6 , the display panel maker divides the large-sized glass substrate  1  into medium-sized glass substrates  4  each including display regions which are fewer than the display regions of the large-sized glass substrate  1  and have respective ones of cutouts  31 . In (a) of  FIG. 6 , the large-sized glass substrate  1  is divided into medium-sized glass substrates  4  each including three display regions  21  which have respective ones of the cutouts  31 . At this stage, the display panel maker does not subject the medium-sized glass substrate  4  to irregular shape processing. 
     The maker of the polarizing plates  51  and  52  first produces one or more large-sized polarizing plates. Thereafter, as illustrated in (b) of  FIG. 6 , the maker of the polarizing plates  51  and  52  divides the one or more large-sized polarizing plates into rectangular polarizing plates  51  and  52  having a size that accommodates the size of the separate medium-sized glass substrates  4  illustrated in (a) of  FIG. 6 . The maker of the polarizing plates  51  and  52  delivers, to the display panel maker, the polarizing plates  51  and  52  after the division, without subjecting them to irregular shape processing. Alternatively, the maker of the polarizing plates  51  and  52  can deliver one or more large-sized polarizing plates to the display panel maker, and the display panel maker can divide the one or more large-sized polarizing plates thus delivered into the polarizing plates  51  and  52  of a size illustrated in (b) of  FIG. 6 . 
     (Bonding of Polarizing Plates  51  and  52 ) 
     The display panel maker bonds the rectangular polarizing plate  51  illustrated in (b) of  FIG. 6  to the surface of the rectangular medium-sized glass substrate  4  illustrated in (a) of  FIG. 6  on the CF substrate  11  side. The polarizing plate  51  is disposed on the surface of the CF substrate  11  in such a manner that three display regions  21  are overlaid in whole with the polarizing plate  51 . The display panel maker further bonds the rectangular polarizing plate  52  illustrated in (b) of  FIG. 6  to the surface of the TFT substrate  12  in the rectangular separate glass substrate  2  illustrated in (a) of  FIG. 6 . The polarizing plate  52  is disposed on the surface of the TFT substrate  12  in such a manner that the three display regions  21  are overlaid in whole with the polarizing plate  52 . This produces a medium-sized glass substrate  4 , as illustrated in (c) of  FIG. 6 , including three display regions  21  with cutouts  31  and having the polarizing plates  51  and  52  bonded thereto. 
     The display panel maker does not subject the medium-sized glass substrate  4  illustrated in (c) of  FIG. 6  to rectangular shape division into three separate glass substrates  2  in cell units. Instead, the display panel maker performs irregular shape processing simultaneously on the constituent components of the medium-sized glass substrate  4  illustrated in (c) of  FIG. 6 , i.e., the CF substrate  11 , the TFT substrate  12 , the polarizing plate  51 , and the polarizing plate  52 . Specifically, contours  41  of the CF substrate  11  and the TFT substrate  12  and contours  61  of the polarizing plates  51  and  52  are simultaneously cut with use of an end mill or a laser. The display panel maker applies such simultaneous cutting to the contours  41  and the contours  61  at three different positions. This produces, from the medium-sized glass substrate  4 , three display panels  3 , as illustrated in  FIG. 5 , each having a narrow frame and having an irregular shape. 
     In the example case illustrated in  FIG. 6 , a display panel  3  having a narrow frame and having an irregular shape is obtained as in the example cases illustrated in  FIGS. 1 to 5 . Furthermore, the example case illustrated in  FIG. 6  achieves reduction in effort required to perform bonding of the polarizing plates  51  and  52 , in comparison with the case where the polarizing plates  51  and  52  are bonded to an individual separate glass substrate  2  in cell unit. 
     (Advantages of Display Panel  3 ) 
       FIG. 7  is an explanatory view illustrating the advantages of the display panel  3  produced by the production method in accordance with an embodiment of the present invention. (a) of  FIG. 7  illustrates a cross section of the display panel  3  produced by the production method in accordance with an embodiment of the present invention. (b) of  FIG. 7  illustrates a cross section of a display panel  3  produced by the conventional production method. In an example case illustrated in  FIG. 7 , the display panel  3  is a liquid crystal display panel. The display panel  3  includes a reflecting sheet  71 , a light guide plate  72 , a diffusing sheet  73 , an upper lens sheet  74 , a lower lens sheet  75 , a plastic frame  76 , a double-sided tape  77 , a polarizing plate  52 , a TFT substrate  12 , a CF substrate  11 , and a polarizing plate  52 . The reflecting sheet  71 , the light guide plate  72 , the diffusing sheet  73 , the upper lens sheet  74 , the lower lens sheet  75 , and the plastic frame  76  constitutes a backlight module. The polarizing plate  52  and the plastic frame  76  are adhered to each other with the double-sided tape  77 . 
     The cross section illustrated in (a) of  FIG. 7  contains the cross section when viewed along the line A-A′ in  FIG. 5 . In (a) of  FIG. 7 , all of the respective end portions of the polarizing plate  52 , the TFT substrate  12 , the CF substrate  11 , and the polarizing plate  51  are located identically at the position  81 . This allows an area where the polarizing plate  52 , the double-sided tape  77 , and the plastic frame  76  are close to one another in the display panel  3  to be kept away from a boundary  83  of the display region  21 . This allows the inner wall of the plastic frame  76  to be kept away from the boundary  83  of an active region. Thus, light  73  having traveled through the light guide plate  72  and having been reflected by the inner wall of the plastic frame  76  is blocked by a hood-like portion of the double-sided tape  77 . Consequently, it is possible to prevent the light  73  from leaking to the display region  21 . 
     The display panel  3  illustrated in (b) of  FIG. 7  is produced by a production method according to the conventional technique. The following will gives a brief explanation of the procedure of the production method. The maker of the display panel  3  performs irregular shape processing on the separate glass substrate  2  including the TFT substrate  12  and the CF substrate  11 . The maker of the polarizing plates  51  and  52  performs irregular shape processing on each of the polarizing plates  51  and  52  individually. The maker of the display panel  3  bonds the polarizing plate  51  having undergone irregular shape processing to the CF substrate  11  and bonds the polarizing plate  52  having undergone irregular shape processing to the TFT substrate  12 . 
     In (b) of  FIG. 7 , the respective ends of the TFT substrate  12  and the CF substrate  11  and the respective ends of the polarizing plates  51  and  52  are not located identically at the position  81  and are displaced individually from the position  81 . Thus, the inner wall of the plastic frame  76  cannot be kept away from the boundary  83  of the active region. This does not allow light  73  having traveled through the light guide plate  72  and having been reflected by the inner wall of the plastic frame  76  to be blocked by the hood-like portion of the double-sided tape  77 . This may leak the light  73  from outside the double-sided tape  77  toward the display region  21 . 
     The display panel produced in accordance with an embodiment of the present invention is not limited to a liquid crystal display panel and can be other kinds of display panels. 
     [Recap] 
     First aspect: A method for producing a display panel, including the steps of: bonding a polarizing plate having a rectangular shape to a separate glass substrate, the separate glass substrate having a rectangular shape and including a display region having at least one cutout; and simultaneously cutting a contour of the separate glass substrate and a contour of the polarizing plate with use of an end mill or a laser. 
     Second aspect: The method according to the first aspect, wherein the display region comprises a plurality of display regions, the method further including the step of: dividing a glass substrate including the plurality of display regions each having the at least one cutout into separate glass substrates, the separate glass substrates each having a rectangular shape and each including a respective one of the plurality of display regions, in the bonding step, bonding the polarizing plate to each of the separate glass substrates into which the glass substrate has been divided. 
     The present invention is not limited to the embodiments, but can be altered by a skilled person in the art within the scope of the claims. The present invention also encompasses, in its technical scope, any embodiment derived by combining technical means disclosed in differing embodiments. Further, it is possible to form a new technical feature by combining the technical means disclosed in the respective embodiments. 
     REFERENCE SIGNS LIST 
     
         
           1 : Large-sized glass substrate 
           2 : Separate glass substrate 
           3 : Display panel 
           4 : Medium-sized glass substrate 
           11 : CF substrate 
           12 : TFT substrate 
           21 : Display region 
           22 : Frame region 
           23 : Connection region 
           31 : Cutout 
           41 : Contour 
           51 : Polarizing plate 
           52 : Polarizing plate 
           61 : Contour