Patent Publication Number: US-2023138640-A1

Title: Display device and manufacturing method thereof

Description:
CLAIM OF PRIORITY 
     The present application claims priority from Japanese Patent Application JP 2012-219420 filed on Oct. 1, 2012, the content of which is hereby incorporated by reference into this application. 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a display device, built up by adhering 2 pieces of substrates with using a seal, and a method, as well, for manufacturing the same. 
     Description of the Related Art 
     A display devices, such as, a liquid crystal display device, for example, is spreading application thereof, widely, in various technical fields, because of a flat configuration, a light-weight and an electric power saving thereof. Onto a portable phone (e.g., a mobile phone) and/or a DSC (Digital Still Camera), etc., for example, are applied the small-sized liquid crystal display devices, widely. The display devices, being built up by adhering 2 pieces of substrates with using a seal member therebetween, in particular, relating to the liquid crystal display device, are described in the following Japanese Patent Laid-Open No. 2007-304452; and Japanese Patent Laid-Open No. 2007-148449. 
     In the Japanese Patent Laid-Open No. 2007-304452 is disclosed a liquid crystal display device, spreading an area of a seal member, which is in contact with a groundwork, by forming a structure provided for excluding an alignment film in an area where the seal member contacts with the alignment film, while forming an end portion of the alignment film within an inside of the seal member, in a terminal connector portion where other substrate extends directing outside from one substrate, and also forming the alignment film in an outside of the seal member, on a side where the end portions those 2 pieces of the substrates are aligned with, for the purpose of maintaining the bonding strength of the seal member, in the liquid crystal display device, being built up with 2 pieces of substrates adhered by the seal member on the periphery of the substrates. 
     Also, in the Japanese Patent Laid-Open No. 2007-148449 is disclosed a liquid crystal display device, which is manufactured by disposing and baking the seal member, provisionally, on a transparent substrate made of a plastic, and forming a column-like spacer(s) within the seal on a transparent substrate of the plastic, wherein the transparent substrate disposing the seal member and the transparent substrate forming the column-like spacer(s) within the seal are put on each other in such a manner that the column-like spacer(s) within the seal is/are buried into the seal members, and are baked under heating/suppression, to be sealed up on the seal portion thereof, for providing the liquid crystal display device improved in the reliability with respect to sealing thereof, in particular, in a device necessitating a low-temperature manufacturing process, being equal to or lower than 160° C., such as, a STN liquid crystal display device applying a plastic substrate therein, etc. 
     SUMMARY OF THE INVENTION 
     Within the display device, such as, the liquid crystal display device, etc., so-called a narrow framing is advanced, i.e., narrowing the frame portion, starting from a panel end portion up to a pixel region (i.e., an effective display region), for the purpose of widening a display screen with respect to an outer configuration thereof, in particular, in the liquid crystal display panel. 
       FIG.  6 A  shows a plane view of an outlook of the conventional liquid crystal display panel (before being cut out). As is shown in this figure, an alignment film  310  is formed in a region larger than that of an effective display region  410 . Also,  FIG.  6 B  is a cross-sectional view of A-B portion of the liquid crystal panel shown in  FIG.  6 A . A seal  301  is formed between a color filter (CF) side substrate  201 , on which a black matrix film (BM)  202  and an over coating film (OC), etc., and a TFT side substrate (made of glass)  101 , on which are formed a silicon nitride film  102  for forming a gate insulation film, an inorganic passivation film (PAS)  103 , an upper layer passivation film (UPS)  104  or an organic passivation film (FPS)  104 , a gate wiring (GAL)  110 , a drain wiring (DCR)  111 , etc. Also, the alignment film  310  is formed by printing, on the CF side substrate  201  and the TFT side substrate. A reference numeral  305  denotes a SOC (Space on color filter), which is disposed within the effective display region for the purpose of defining a gap distance between those substrates, while a reference numeral  306  denotes a sub SOC within the effective display region. Also, the same reference numerals denote the same constituent elements, respectively. 
     Explanation will be given about a manufacturing method by referring to  FIG.  8   . On the CF side substrate, after forming the over coating film (OC), etc., thereon, the alignment film  310  is printed for each liquid crystal display panel, and a surface of the alignment film is rubbed in a certain direction (i.e., rubbing). Next, a seal  301  is applied on for each liquid crystal display panel. The seal  301  may be applied on the TFT side substrate. On the TFT side substrate, after forming UPS or FPS thereon, the alignment film is printed for each liquid crystal display panel, and the rubbing is made thereon. Thereafter, the CF and the TFT side substrates, on each of which is applied the seal, are piled up with, so that the surfaces, being formed the alignment films thereon, are opposite with each other, and they are bonded. 
     If the narrow framing is advanced, it is very difficult to keep an effective seal width and a tolerance of size of printing the alignment film. Thus, conventionally, the printing position of the alignment film does not overlap the region where the seal  301  is formed, or a very little if it overlaps, including an error of the printing position of the alignment film; thus, it is possible to maintain the effective seal region (i.e., the region shown by arrows in both directions within the seal  301 ). However, narrowing the distance between the end portion (i.e., the cutting plane) and an end portion of the effective display region  410  brings a permissible error (i.e., a size tolerance) in the printing position of the alignment film  310  to be restrictive. 
     The inventors made studies upon the permissible error of the printing position, and reach to a solution of the problem of the permissible error, by forming the alignment films, each of which is printed for each liquid crystal display panel, conventionally, but covering over plural numbers of the liquid crystal panels. Then, the inventors manufactured a liquid crystal display device having such unique structure as mentioned above.  FIG.  7 A  shows a plane view of an outlook of the liquid crystal display panel (before cutting), which the inventors studied. As is shown in this figure, the alignment film  310  is formed covering over every liquid crystal display panel. Also,  FIG.  7 B  is a cross-sectional view of A-B portion of the liquid crystal display panel shown in  FIG.  7 A . Forming the alignment film  310  covering over the every liquid crystal display panel (i.e., a solid pattern) does not brings about a fluctuation within the region where the alignment film  310  and the seal  301  are overlapping on each other. In those Japanese Patent Laid-Open No. 2007-304452 and Japanese Patent Laid-Open No. 2007-148449 mentioned above, it is not apparent if the alignment film is formed or not, covering over the plural numbers of the liquid crystal display panels. 
     However, as a result of such structure as mentioned above, so-called a black unevenness or spot is generated, and then it is apparent that the reliability thereof is deteriorated. 
     An object of the present invention lies to provide a display device having high reliability even if being narrowed with the frame thereof, and a method for manufacturing the same. 
     According to the present invention, as an embodiment for accomplishing the object mentioned above, there is provided a display device, having a display panel, being constructed by adhering a first substrate and a second substrate with using a seal, wherein a main SOC for use of adjusting a gap distance is disposed like a wall, on a peripheral end portion of the first and second substrates, and the seal is disposed inwardly of the main SOC. 
     Also, according to the present invention, there is also provided a method for manufacturing a display device, comprising the following steps of:
         a step for preparing a first substrate having plural numbers of display panel regions, each having an effective display region;   a step for forming a first organic film covering over the plural numbers of display panel regions on the first substrate;   a step for preparing a second substrate, having plural numbers of display panel regions, each having an effective display region, and being formed with a main SCO for use of adjusting a gap distance in a region including a cutting plane of the display panel region;   a step for forming a second organic film covering over the plural numbers of display panel regions on the second substrate;   a step for applying a seal on a region of the second substrate, including a region where the main SOC is formed and/or a region including a cutting plane of the display panel region of the first substrate;   a step for laminating the first substrate and the second substrate, so that the first organic film of the first substrate faces to the second organic film of the second substrate, and thereby adhering those to each other by the seal; and   a step for cutting out the display panel region on the cutting plane, so that the main SOC is separated.       

     According to the present invention, it is possible to provide a display device having high reliability even if being narrowed with the frame thereof, and a method for manufacturing the same. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Those and other objects, features and advantages of the present invention will become more readily apparent from the following detailed description when taken in conjunction with the accompanying drawings wherein: 
         FIG.  1    is a cross-sectional view of a principle portion (i.e., a seal portion) of a liquid crystal display device, according to a first embodiment of the present invention; 
         FIG.  2 A  is an entire plane view of the outlook of the liquid crystal display device, according to the first embodiment of the present invention; 
         FIG.  2 B  is an entire plane view of the outlook thereof, for explaining the positions where a main SOC and a seal are disposed, within the liquid crystal display device, according to the first embodiment of the present invention; 
         FIG.  3    is an outlook plane view (before cutting) for explaining a region where an alignment film is formed, within the liquid crystal display device, according to the first embodiment of the present invention; 
         FIG.  4    is an outlook plane view (before cutting) for explaining a region where an alignment film is formed, within other liquid crystal display device, according to the first embodiment of the present invention; 
         FIG.  5    is a cross-sectional view of a principle portion (i.e., a seal portion) of a liquid crystal display device, according to a second embodiment of the present invention; 
         FIG.  6 A  is an outlook plane view of the conventional liquid crystal display panel (before cutting); 
         FIG.  6 B  is an outlook cross-sectional view of A-B portion of the liquid crystal display panel shown in  FIG.  6 A ; 
         FIG.  7 A  is an outlook plane view of the liquid crystal display panel (before cutting), in relation with the studies made by the inventors and so on; 
         FIG.  7 B  is an outlook cross-sectional view of A-B portion of the liquid crystal display panel shown in  FIG.  7 A ; 
         FIG.  7 C  is an outlook cross-sectional view, for explaining deterioration of reliability of the liquid crystal display panel (after cutting), in relation with the studies made by the inventors and so on; and 
         FIG.  8    is a flowchart of an outlook of steps, for explaining a method for manufacturing the liquid crystal display panel. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The inventors studied the reason of generating the black spots. As a result thereof, the followings come to be apparent on the cross-sectional view of the liquid crystal display panel shown in  FIG.  7 C ; i.e., that an adhesiveness is deteriorated between the alignment film  310  and the seal  301 , and that moisture intrudes therein from a boundary surface defined between the alignment film  310  and the over coating film (OC)  203  and also a boundary surface defined between the alignment film  310  and the seal  301 , and this affects ill influences to the effective display region. Then, a main SOC (Space on color filter) is disposed like a wall in a region including the cutting plane of the liquid crystal display panel. With this, the narrow framing can be achieved, as well as, reducing/preventing the moisture from intruding therein, i.e., reducing/preventing of the black spots, and therefore it is possible to maintain the reliability for a long time-period. The main SOC can be formed only on one side of the four sides of the liquid crystal display panel, thereby obtaining an effect of reducing the black spots, but preferably, it is formed on all of those four sides. Also, a management can be omitted upon the printing size of the alignment film, and therefore it is possible to reduce the manufacturing cost thereof. Further, in the Japanese Patent Laid-Open No. 2007-304452, there is formed the alignment film in an outside of the structure provided for excluding the alignment film, then it is difficult to achieve the narrow framing, fully. Also, with the structure of the Japanese Patent Laid-Open No. 2007-148449, since the spacer within the seal is column-like, therefore it is impossible to prevent the moisture from intruding therein, fully. 
     Hereinafter, explanation will be given by referring to the embodiments. Although the explanation will be given on an example of liquid crystal display device; the present invention is also applicable to a display device, being construed by adhering 2 pieces of substrates with using a seal, and a method for manufacturing the same. 
     First Embodiment 
     A first embodiment of the present invention will be explained by referring to  FIGS.  1  to  4   . Herein,  FIG.  2 A  is an entire plane view of the outlook of the liquid crystal display device according to the present embodiment. The present liquid crystal display device is constructed with a display region  400  and a driver circuit region  450 .  FIG.  2 B  is an entire plane view of the outlook thereof, for explaining the positions where a main SOC and a seal are disposed, within the liquid crystal display device, according to the first embodiment of the present invention. The main SOC is formed like a wall, surrounding the periphery of a liquid crystal display panel, and the seal  301  is disposed in a side of an effective display region (hereinafter, “inside”) of the liquid crystal display panel, with respect to the main SOC. In the present embodiment, a sub SOC is further disposed inside the main SOC  302 . 
       FIG.  1    is a cross-sectional view of a principle portion (i.e., a seal portion) of the liquid crystal display device according to the present embodiment. Within the present embodiment, the main SOC  302  having height of 3 μm and width of 0.2 mm is formed in a region including the cutting plane of the liquid crystal display panel, facing to a CF substrate. With this, after cutting into each liquid crystal display panel, since the main SOC  302  comes to be disposed on an outermost peripheral portion between the TFT side substrate  101  and the CF side substrate  201 , it is possible to reduce/prevent the moisture from intruding into the effective display region  410 . The main SOC  302  can be formed in a step same to that for forming a SOC  305  within the effective display region. In that instance, though it may be made at the same height, but with forming the SOC  305  within the effective display region to be lower than the height of the min SOC  302  in the height thereof, it is possible to reduce/prevent defects of periphery gaps due to bulging of the seal. The main SOC  302  can be formed of an organic material, such as, an acryl or an epoxy, etc., similar to the SOC  305  formed within the effective display region. 
     Also, in the present embodiment, plural numbers of sub SOCs  303  for use of interruption or stop are disposed within an inside of the main SOC  302 . With this, even if the moisture passes through the main SOC  302 , since the sub SOC  303  can elongate a route of intrusion of the moisture, then it is possible to increase the reliability thereof, further. Lowering the height of the sub SOCs  303  than that of the main SOC  302  enables the seal  301 , which is applied in the vicinity of the cutting plane of the liquid crystal display panel, to flow inside, if it is pushed out by the main SOC  302  when the TFT side substrate and the CF side substrate are piled up (i.e., enabling the seal to escape from). For the seal between the main SOC  302  and the alignment film  310  on the substrate facing to TFT, it is preferable to be pushed out, entirely, into inside. Even if remaining a little bit thereof, it does not matter, from a practical viewpoint. Also, those sub SOCs  303  are formed in the same step and of the same material to that of the main SOC  302 . Also, in the present embodiment, plural numbers of grooves are formed on the upper layer passivation film (UPS)  104  or the organic passivation film (FPS)  104  of the TFT side substrate, to be the interruption or stop. Thickness of the FPS, etc., is determined to 2 μm. With this, even in case where the moisture passes through the main SOC  302  by any change, since the route of intrusion of the moisture can be elongated by the grooves formed on the UPS  104  or the FPS  104 , therefore it is possible to increase the reliability, further. Moreover, with such an arrangement thereof that those sub SOCs  303  and the grooves formed on the UPS  104  or the FPS  104  are piled up on each other, when seeing them from the above, vertically, since the alignment film, being pushed by the sub SOC, tries to enter into the groove portion, then it is possible to increase the adhesiveness between a groundwork film thereof. 
     Also, for the drain wiring (DCR)  111  and the gate wiring (GAL)  110 , it is preferable to be disposed within inside (i.e., in a side of the effective display region) than the sub SOC  303 . Also, it is preferable that the drain wiring (DCR)  111  and the gate wiring (GAL)  110  are disposed, not to be piled up on the sub SOC  303 , when seeing them from the above, vertically. The drain wiring (DCR)  111  and the gate wiring (GAL)  110  are disposed, inside, separating by about 0.2 mm from the cutting plane. 
     Also, the SOC is formed on the color filter substrate (the CF substrate) side in  FIG.  1   , it may be formed on the TFT substrate side. Further, the color filter may be formed on the TFT substrate side. In consideration that the color filter is formed on the TFT substrate side, the CF substrate may be referred to as a counter substrate. 
     Next, an explanation will be given on a method for manufacturing the present liquid crystal display device, by referring to  FIG.  8   . First of all, in the same step that for forming the SOC  305  and the sub SOC  306  within the effective display region is prepared the CF side substrate, which is formed with the main SOC  302  and the sub SOCs  303  thereon. Next, in the present embodiment, on the TFT side substrate and the CF side substrate are formed the alignment films  310 , not for each liquid crystal display panel, but covering over the plural numbers of the liquid crystal display panels. Thickness of the alignment film is determined to be 110 nm. Next, on the USP 104 or the FPS  104  of the TFT side substrate are formed the grooves through the alignment film  310 . The process upon the TFT side substrate and the process upon the CF side substrate may be conducted, time-sequentially or in parallel with, simultaneously, and on the contrary thereto, the process upon the TFT side substrate may be conducted first. Next, the seal  301  is applied in the region, including the cutting plane of the CF side substrate therein. Width of the seal is determined to be 0.8 mm. The seal may be also applied on the TFT side substrate. Also, it may be applied on both the TFT side substrate and the CF side substrate. Following to this, the CF side substrate and the TFT side substrate are piled up, so that the surfaces, on which the alignment films are formed, are facing to each other, and they are adhered by the seal. When laminating each substrate, the seal  301  applied in the vicinity of the cutting plane of the liquid crystal display panel pushes the seal, which is pushed out by the main SOC  302 , when the TFT side substrate and the CF side substrate are piled up, to flow inside, and thereby adjusts a gap distance between the substrates. Thereafter, it is cut into each liquid crystal display panel, and thereby completing the liquid crystal devices. 
     In relation with the disposition or arrangement before cutting out the liquid crystal display panels, as is shown in  FIG.  3   , other than the case where there is a distance between the liquid crystal display panels neighboring with (i.e., the conventional arrangement), there can be considered the case where there is no distance between the liquid crystal display panels neighboring with (i.e., a full-just arrangement), as is shown in  FIG.  4   . The present embodiment can be applied, not only into such arrangement as shown in  FIG.  3   , but also into such arrangement as shown in  FIG.  4   . 
     With such arrangement of the liquid crystal display panels as shown in  FIG.  4   , the liquid crystal display device, having such the cross-section structure as shown in  FIG.  1   , is manufactured with applying the manufacturing method mentioned above, and as a result thereof, there is no generation of the black spot, and therefore, it is possible to obtain the liquid crystal display device having high reliability thereof. 
     As was mentioned above, according to the present embodiment, with provision of the main SOC in the region including the liquid crystal display panel, it is possible to provide a display device having high reliability and a method for manufacturing the same, even if it is the narrow framing type. Also, with such arrangement of the plural numbers of the sub SOCs inside the main SOC, it is possible to increase the reliability thereof, further. Also, with forming the plural numbers of grooves on the UPS or the FPS inside the main SOC through the alignment film, it is possible to increase the reliability thereof, much more. Also, with printing the alignment film covering over the plural numbers of liquid crystal display panels, there is no necessity of the management of printing size of the alignment film. 
     Second Embodiment 
     An explanation will be given on a second embodiment of the present invention, by referring to  FIG.  5   . What is described in the first embodiment but not described in this embodiment may also be applied to this embodiment as long as there is no particular circumstance.  FIG.  5    is a cross-sectional view of a principle portion (i.e., the seal portion) of the liquid crystal display device, according to the present embodiment. The difference between the present embodiment and the embodiment 1 lies in an aspect that, comparing to the fact that the upper layer passivation film (UPS)  104  or the organic passivation film (FPS)  104  is formed on the TFT side substrate in the embodiment 1, but according to the present embodiment, it does not have such UPS or FPS. Accompanying this, on the TFT side substrate, the alignment film  310  is formed on the inorganic passivation film (PAS). Other structural elements are same to those of the embodiment 1, and therefore the explanation thereof will be omitted herein. 
     In the present embodiment, plural numbers of grooves are formed on the inorganic passivation film (PAS), to be the interruption or stop. With this, even in the case where the moisture passes through the main SOC  302 , since the grooves formed on the PAS  103  is able to elongate the route of intrusion of the moisture, it is possible to increase the reliability thereof, further. Moreover, with such an arrangement thereof that the sub SOCs  303  and the grooves formed on the PAS  103  are piled up on each other, when seeing them from the above, vertically, since the alignment film, being pushed by the sub SOC, tries to enter into the groove portion, therefore it is possible to increase the adhesiveness between a groundwork film thereof. 
     Next, an explanation will be given on a method for manufacturing the present liquid crystal display device, by referring to  FIG.  8   . However, neither UPS nor FPS is formed on the TFT side substrate. First of all, in the same step for forming the SOC  305  and the sub SOC  306  within the effective display region is prepared the CF side substrate, which is formed with the main SOC  302  and the sub SOCs  303  thereon. Next, in the present embodiment, on the TFT side substrate and the CF side substrate are formed the alignment films  310 , not for each liquid crystal display panel, covering over the plural numbers of the liquid crystal display panels. Thickness of the alignment film is determined to be 110 nm. Next, on the PAS  103  of the TFT side substrate are formed the grooves through the alignment film  310 . The process upon the TFT side substrate and the process upon the CF side substrate may be conducted, time-sequentially or in parallel with, simultaneously, and on the contrary thereto, the process upon the TFT side substrate may be conducted first. Next, the seal  301  is applied in the region, including the cutting plane of the CF side substrate therein. Width of the seal is determined to be 0.8 mm. Following to the above, the CF side substrate and the TFT side substrate are piled up, so that the surfaces, on which the alignment films are formed, are facing to each other, and they are adhered by the seal. When laminating each substrate, the seal  301  applied in the vicinity of the cutting plane of the liquid crystal display panel pushes the seal, which is pushed out by the main SOC  302 , when the TFT side substrate and the CF side substrate are piled up, to flow inside, and thereby adjusts a gap distance between the substrates. Thereafter, it is cut into each liquid crystal display panel, and thereby completing the liquid crystal devices. 
     With such arrangement of the liquid crystal display panels as shown in  FIG.  4   , the liquid crystal display device, having such cross-section structure as shown in  FIG.  5   , is manufactured with applying the manufacturing method mentioned above, and as a result thereof, there is no generation of the black spot, and therefore it is possible to obtain the liquid crystal display device having high reliability thereof. 
     As was mentioned above, according to the present embodiment, with provision of the main SOC in the region including the liquid crystal display panel, it is possible to provide a display device having high reliability and a method for manufacturing the same, even if it is the narrow framing type. Also, with the arrangement of the plural numbers of the sub SOCs inside the main SOC, it is possible to increase the reliability thereof, further. Also, with forming the plural numbers of grooves on the PAS inside the main SOC through the alignment film, it is possible to increase the reliability therefore, much more. Also, with printing the alignment film covering over the plural numbers of liquid crystal display panels, there is no necessity of the management of printing size of the alignment film. 
     The present invention should not be limited to those embodiments mentioned above, but may includes various modifications thereof. For example, the embodiments mentioned above are explained in the details thereof, for the purpose of easy understanding of the present invention, and the present invention should not be necessarily restricted to that comprising all of the constituent elements mentioned above. Also, a part of constituent element(s) of a certain embodiment can be replaced by the constituent element(s) of the other embodiment, or the constituent element(s) of the other embodiment can be added to the constituent element (s) of the certain embodiment. Also, a part of the constituent element (s) of each embodiment can be added/deleted/replaced by other constituent element(s).