Patent Publication Number: US-11036091-B2

Title: Display panel

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present disclosure generally relates to an electronic device, in particular, to a display panel. 
     2. Description of Related Art 
     In a typical display panel, a display medium layer is sandwiched between a first substrate and a second substrate. The two substrates are kept together via a sealant to form a display cell. A thickness of the display medium layer may influence the optical properties of the display panel. The sealant might assist to maintain a certain distance between the first substrate and the second substrate. Structural requirements of other components of the display panel might have to be considered when designing display panels with thin display medium layers. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present disclosure is directed to a display panel including a substrate having a recess, and a sealant received by the recess. 
     According to an embodiment, a display panel may have a first region and a second region encircled by the first region. The display panel may include a first substrate, a second substrate, a sealant, a conductive layer, and a display medium layer. The first substrate may have a first recess in the first region. The second substrate may be disposed opposite to the first substrate. The sealant may be disposed between the first substrate and the second substrate, and may be received by the first recess. The conductive layer may be disposed on the first substrate, may cover the first recess in a conformal manner, and may be interposed between the first substrate and the sealant. The display medium layer may be disposed between the first substrate and the second substrate and may be encircled by the sealant. A thickness of the sealant may be larger than a distance between the first substrate and the second substrate in the second region of the display panel. 
     According to an embodiment, a width of the first recess may be greater than a width of the sealant. 
     According to an embodiment, the display panel may further have a third region. The first region may be positioned between the third region and the second region, and the conductive layer disposed on the first substrate may continuously extend from the second region, pass through the first region and reach the third region to cover the first recess in a conformal manner. 
     According to an embodiment, the first substrate may have a first thickness at the first region, a second thickness at the second region and a third thickness at the third region, and the first thickness may be smaller than either the second thickness or the third thickness. 
     According to an embodiment, side surfaces of the first recess may be tapered. 
     According to an embodiment, a display panel may further include a light shielding layer disposed on an outer surface of the first substrate further away from the display medium layer. A vertical projection of the first recess may fall on the light shielding layer. 
     According to an embodiment, a width of the light shielding layer may be larger than a maximum width of the first recess. 
     According to an embodiment, a depth of the first recess may be smaller than a half of the thickness of the first substrate at the second region. 
     According to an embodiment, a thickness of the display medium layer may be smaller than 2 μm. 
     According to an embodiment, the second substrate may include a base plate and a passivation layer disposed over the base plate, a second recess may be formed in the passivation layer at the first region, and the sealant may be received by the second recess. 
     According to an embodiment, the second substrate may further include an active device layer covered by the passivation layer. The passivation layer may be interposed between the sealant and a portion of the active device layer. 
     According to an embodiment, the base plate may be a silicon bulk and the active device layer may include a plurality of complementary metal-oxide-semiconductor devices formed in the silicon bulk. 
     According to an embodiment, the sealant may include a sealing material and a plurality of fillers distributed in the sealing material. 
     According to an embodiment, the display panel may further include a first alignment layer disposed between the display medium layer and the first substrate and a second alignment layer disposed between the display medium layer and the second substrate. 
     According to an embodiment, one or both of the first alignment layer and the second alignment layer may include an inorganic alignment layer and an organic alignment layer, the inorganic alignment layer may be spaced from the sealant by a gap, and the organic alignment layer may be located in the gap to be in contact with the sealant. 
     According to an embodiment, a display panel may have a first region and a second region encircled by the first region. The display panel may include a first substrate, a second substrate, a sealant, and a display medium layer. The second substrate may be disposed opposite to the first substrate. The second substrate may include a silicon bulk and a passivation layer disposed on the silicon bulk. A recess may be formed in the passivation layer at the first region. The sealant may be disposed between the first substrate and the second substrate, and be received by the recess. A display medium layer may be disposed between the first substrate and the second substrate, and be encircled by the sealant. A thickness of the sealant may be larger than a distance between the first substrate and the second substrate in the second region of the display panel. 
     According to an embodiment, the second substrate may further include an active device layer formed in the silicon bulk and covered by the passivation layer, and the passivation layer may be interposed between the sealant and a portion of the active device layer. 
     According to an embodiment, the passivation layer may include a first insulation layer and a second insulation layer stacked on the first insulation layer. 
     According to an embodiment, a depth of the recess may be insufficient to pass throughout a thickness of the first insulation layer. 
     According to an embodiment, the display panel may further include a first alignment layer disposed between the display medium layer and the first substrate and a second alignment layer disposed between the display medium layer and the second substrate. 
     According to an embodiment, one or both of the first alignment layer and the second alignment layer may include an inorganic alignment layer and an organic alignment layer, the inorganic alignment layer may be spaced from the sealant by a gap, and the organic alignment layer may be located in the gap to be in contact with the sealant. 
     According to an embodiment, the display panel may further have a third region. The first region may be positioned between the third region and the second region, and the first alignment layer and the second alignment layer may be absent in the third region. 
     According to an embodiment, a thickness of the display medium layer is smaller than 2 μm. 
     In view of the above, a display panel in accordance with some embodiments of the disclosure has a first region surrounding a second region, and includes one or both of a first substrate and a second substrate having a recess in the first region. A sealant is disposed between the first substrate and the second substrate and is received in the recess. A distance between the first substrate and the second substrate in the second region may be smaller than a thickness of the sealant. Accordingly, sealing with low compressibility may be used even in the display panels requiring a small thickness of the display medium layer. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings are included to provide further understanding of the disclosure, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the disclosure and, together with the description, serve to explain the principles of the disclosure. 
         FIG. 1  shows a schematic cross-sectional view of a display panel according to an embodiment of the present disclosure. 
         FIG. 2A  to  FIG. 2D  show schematic cross-sectional views of a first substrate undergoing a portion of the steps of a fabricating method in accordance with an embodiment of the present disclosure. 
         FIG. 3A  to  FIG. 3D  show schematic cross-sectional views of a display panel according to some embodiments of the present disclosure. 
         FIG. 4A  shows a schematic cross-sectional view of a display panel according to an embodiment of the present disclosure. 
         FIG. 4B  and  FIG. 4C  show schematic cross-sectional views of an enlarged portion of a display panel according to an embodiment of the present disclosure. 
         FIG. 5  shows a schematic cross-sectional view of a display panel according to some embodiments of the present disclosure. 
     
    
    
     In the drawings, the relative dimensions of the illustrated components might have been altered for the sake of clarity. 
     DESCRIPTION OF THE EMBODIMENTS 
     Reference will now be made in detail to the present preferred embodiments of the disclosure, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the descriptions to refer to the same or like parts. 
     In the disclosure, the locution “an element A is disposed on an element B”, used to describe a positional relationship, encompasses the possibilities of one or multiple other elements disposed between the element A and the element B, as well as the case of no other elements existing between the element A and the element B. 
       FIG. 1  shows a cross-sectional view of a display panel  100 A according to some embodiments of the present disclosure. As shown in the cross-sectional view of  FIG. 1 , the display panel  100 A includes a first substrate  110 , a second substrate  120  opposite to the first substrate  110 , a display medium layer  130 , and a sealant  140 . The first substrate  110  and the second substrate  120  are assembled via the sealant  140 . The display medium layer  130  is sandwiched between the first substrate  110  and the second substrate  120  and is surrounded by the sealant  140 . The display medium layer  130  may be made of liquid crystals, so that the first substrate  110 , the second substrate  120 , the display medium layer  130 , and the sealant  140  may serve as a liquid crystal cell, but the disclosure is not limited thereto. In some embodiments, a first alignment layer  150  may be selectively disposed between the first substrate  110  and the display medium layer  130 , and a second alignment layer  160  may be selectively disposed between the display medium layer  130  and the second substrate  120 . 
     In some embodiments, the display panel  100 A further includes an anti-reflective layer  114  and a light shielding layer  116  disposed on a first surface  110   a  of the first substrate  110 . In some embodiments, the first substrate  110  may be made of glass, but the disclosure is not limited thereto. In some embodiments, the first surface  110   a  of the first substrate  110  is a surface farther away from the display medium layer  130 . A material of the anti-reflective layer  114  may include silicon oxide, titanium oxide, or a combination of both. 
     In some embodiments, the light shielding layer  116  has a frame-like pattern when viewed from top, but the disclosure is not limited thereto. In some alternative embodiments, the light shielding layer  116  may be disposed following other patterns or layers, according to the requirements of the design. In some embodiments, both the anti-reflective layer  114  and the light shielding layer  116  may be in physical contact with the first substrate  110  and bottom surfaces of the anti-reflective layer  114  and the light shielding layer  116  may be coplanar. In other words, the anti-reflective layer  114  may be absent from the regions where the light shielding layer  116  is disposed, but the disclosure is not limited thereto. In some alternative embodiments, the anti-reflective layer  114  may extend over the whole first surface  110   a  of the first substrate  110 , and be disposed between the light shielding layer  116  and the first substrate  110 . Namely, the anti-reflective layer  114  may be sandwiched between the light shielding layer  116  and the first substrate  110 . 
     The light shielding layer  116  has a light shielding effect. The display light of the display panel  100 A may be obstructed or shielded by the light shielding layer  116  in a first region  102  of the display panel  100 A, so that a displayed image may be presented in a second region  104  beside the first region  102 . In other words, the second region  104  may be a display area of the display panel  100 A. In some embodiments, the first region  102  has a frame-like pattern when viewed from the top, and surrounds the second region  104 . A boundary between the first region  102  and the second region  104  of the display panel  100 A may be defined by an inner edge  116   i  of the light shielding layer  116 . Another boundary of the first region  102  may be defined by an outer edge  116   o  opposite to the inner edge  116   i  of the light shielding layer  116 . In some embodiments, the outer edge  116   o  defines the boundary of the first region  102  and a third region  106  of the display panel  100 A. The third region  106  may be considered an outermost peripheral region of the display panel  100 A, and may be omitted in some embodiments. The light shielding layer  116  may present a sharp pattern, with the inner edge  116   i  and the outer edge  116   o  showing good linearity. A material for the light shielding layer  116  may include organic inks, but the disclosure is not limited thereto. 
     In some embodiments, the first substrate  110  may present a first recess R 1  in the first region  102  of the display panel  100 A. The first recess R 1  is formed in the first region  102  in a second surface  110   b  of the first substrate  110  opposite to the first surface  110   a , so that the second surface  110   b  of the first substrate  110  presents an uneven profile. In some embodiments, a cross section of the first recess R 1  may have a trapezoidal shape. That is, the first recess R 1  may present a minimum width W min  at a bottom of the first recess R 1  deep within the first substrate  110 , and a maximum width W max  greater than the minimum width W min  where the first recess R 1  starts recessing into the first substrate  110 . In other words, the side surfaces of the first recess R 1  may be tapered. In some alternative embodiments, the side surfaces of the first recess R 1  may not be tapered and thus the maximum width W max  and the minimum width W min  may be the same. The first recess R 1  may have a frame-like pattern when viewed from top, similar to the pattern of the light shielding layer  116 . In some embodiments, the light shielding layer  116  may be deposited following the pattern of the first recess R 1 , so that a vertical projection of the first recess R 1  falls on the light shielding layer  116 . In some embodiments, the first recess R 1  is entirely contained within the first region  102  of the display panel  100 A. That is, in some embodiments, the vertical projection of the first recess R 1  falls completely within a span of the light shielding layer  116 . In some embodiments, a width W 116  of the light shielding layer  116  is not smaller than a maximum width W max  of the first recess R 1 . 
     In some embodiments, the first substrate  110  presents a first thickness T 102  at the first region  102 , a second thickness T 104  at the second region  104 , and a third thickness T 106  at the third region  106 . Because of the first recess R 1 , the first thickness T 102  may be smaller than either the second thickness T 104  or the third thickness T 106 . In some embodiments, the first thickness T 102  is not less than a half of the second thickness T 104 . In other words, a depth D R1  of the first recess R 1  is smaller than a half of the second thickness T 104  of the first substrate  110  at the second region  104 . 
     The display panel  100 A further includes a conductive layer  118  disposed on a second surface  110   b  of the first substrate  110 . The second surface  110   b  may be the surface of the first substrate  110  closer to the display medium layer  130 . In some embodiments, the conductive layer  118  may extend over the entire second surface  110   b  of the first substrate  110 . In some embodiments, the conductive layer  118  is disposed conformally over the second surface  110   b  of the first substrate  110 . That is, a profile of the conductive layer  118  follows a profile of the second surface  110   b  of the first substrate  110 , so that the conductive layer  118  conforms to the first recess R 1 . In other words, the conductive layer  118  is disposed on the first substrate  110 , and continuously extends from the second region  104 , passes through the first region  102  and reaches the third region  106  to cover the first recess R 1  in a conformal manner. In the first region  102  of the display panel  100 A, the conductive layer  118  is disposed between the first substrate  110  and the sealant  140 . In the second region  104  of the display panel  100 A, the conductive layer  118  is disposed between the first substrate  110  and the display medium layer  130 . In some embodiments, a material of the conductive layer  118  includes ITO or any other material that is conductive and transparent to the display light. 
     The second substrate  120  may be a transistor array substrate comprising a base plate  122 , such as a glass plate or a silicon backplane formed of a silicon bulk, and an active device layer  124  disposed thereon. In some embodiments, the active device layer  124  and the conductive layer  118  may be used for providing the driving electric field to drive the display medium layer  130 . In some embodiments, the second substrate  120  may further optionally include a passivation layer  126  disposed over the active device layer  124 . The active device layer  124  may be a thin film transistor array, a CMOS (Complementary Metal-Oxide Semiconductor) device array, or the like. Accordingly, the display panel  100 A may be a Thin Film Transistor Liquid Crystal Display (TFT-LCD) panel or an LCoS (Liquid Crystal on Silicon) display panel. 
     In some embodiments, the display medium layer  130  may be disposed between the first substrate  110  and the second substrate  120  and fill the space surrounded by the first substrate  110 , the second substrate  120  and the sealant  140 . The display medium layer  130  may further extend from the second region  104  into the first region  102 . That is, a small portion of the display medium layer  130  may be covered by the light shielding layer  116 . A thickness T 130  of the display medium layer  130  is referred to as a “cell gap”. Some optical properties of the display medium layer  130  such as the phase retardation may be influenced by the cell gap and the light transmittance of the display panel  100 A is generally related to the phase retardation of the display medium layer  130 . For some applications, it might be preferable to use a thinner display medium layer. For example, a reflective liquid crystal display panel generally requires a smaller cell gap than a transmissive liquid crystal display panel. Or, the display medium layer having higher value of birefringence may require a smaller cell gap to achieve the desired phase retardation. In some embodiment, a thickness T 130  of the display medium layer  130  may be smaller than 2 μm. To achieve a small cell gap, a distance D S  between the first substrate  110  and the second substrate  120  in the second region  104  may be comparably small. In the present embodiment, the distance D S  is measured as the distance between the second surface  110   b  of the first substrate  110  and a surface  126   a  of the passivation layer  126  closer to the display medium layer  130 . In some embodiments in which the passivation layer  126  is not included, the distance D S  is measured between the second surface  110   b  of the first substrate  110  and a surface  124   a  of the active device layer  124  closer to the display medium layer  130 . 
     The sealant  140  is disposed in the first region  102  of the display panel  100 A and is sandwiched between the first substrate  110  and the second substrate  120 . In some embodiments, the sealant  140  may contact the conductive layer  118  on the first substrate  110 , and the passivation layer  126  (if included) on the second substrate  120 . In some embodiments, by leaning against the first substrate  110  at one end and the second substrate  120  at the other end, the sealant  140  may contribute to the stabilization of the distance D S  between the first substrate  110  and the second substrate  120 . In some embodiments, the sealant  140  encircles the display medium layer  130 . In some embodiments, the sealant  140  has a frame-like structure surrounding the display medium layer  130  when viewed from top. In some embodiments, the sealant  140  is received in the first recess R 1  of the first substrate  110 . In some embodiments, the maximum width W max  and the minimum width W min  of the first recess R 1  are greater than a width W 140  of the sealant  140 , but the disclosure is not limited thereto. In some embodiments, the width W 140  of the sealant  140  is comparable to the minimum width W min  of the first recess R 1 . That is, the sealant  140  may fill the bottom of the first recess R 1 . In some alternative embodiments, the first recess R 1  may have a constant width and the sealant  140  may have the width W 140  not greater than the first recess R 1  so as to be received in the first recess R 1 . In some embodiments, the light shielding layer  116  may be disposed in such a way to completely shield the sealant  140 . 
     In some embodiments, the sealant  140  may include a sealing material  142  and a plurality of fillers  144  dispersed in the sealing material  142 , but the disclosure is not limited thereto. In some embodiments, the sealant  140  may include only the sealing material  142  without the fillers  144 . In some embodiments, the sealing material  142  may be a thermally curable material, a photochemically curable material, or a thermo-photocurable material. The sealing material  142  may include organic resins such as epoxy resin, polyurethane resins, furan-based resins, acrylate resins, or the like. A material of the fillers  144  may include glass fiber, plastics, siliconates, mica, or the like. The fillers  144 , by being dispersed into the sealing material  142 , may increase the structural stability of the sealant  140 , and, as such, of the entire display panel  100 A. When designing a display panel according to some embodiments of the disclosure, the cell gap T 130  and the distance D S  have to be taken into account when choosing the material for the sealant  140 . For example, one of the factors to be considered is how thin a material can be pressed. In some embodiments, by accommodating the sealant  140  into the first recess R 1 , a thickness T 140  of the sealant  140  may be greater than the distance D S  between the first substrate  110  and the second substrate  120  in the second region  104 , so that even less compressible materials can be used for the sealant  140 . In some embodiments, the depth D R1  of the first recess R 1  and a concentration and a size of the fillers  144  may be adjusted to reach the desired thickness T 130  for the display medium layer  130 . As such, when designing a display panel according to some embodiments of the disclosure, a material of the sealant  140  can be chosen from a wider range of candidate materials and small cell gaps (the thickness T 130 ), if so desired, are achievable without difficulty. 
     In some embodiments, the first alignment layer  150  and the second alignment layer  160  may be disposed between the display medium layer  130  and the first substrate  110  and between the display medium layer  130  and the second substrate  120 , respectively. The first and second alignment layers  150  and  160  may be disposed within the enclosure formed by the sealant  140 , and may extend in the second region  104  of the display panel  110 A and at least part of the first region  102 . The first and second alignment layers  150  and  160  may be absent from the third region  106  of the display panel  100 A. The first and second alignment layers  150  and  160  may be respective an organic alignment layer or an inorganic alignment layer. A material used for the organic alignment layer may include polyimide, e.g. thermally curable polyimide or UV-curable polyimide. A material of the inorganic alignment layer may include silicon oxide (SiO x ), zinc oxide (ZnO) or nanoporous anodic aluminum oxide. In some embodiments, the first and second alignment layers  150  and  160  may extend to partially overlap the sealant  140  and be in contact with the sealant  140 . The first alignment layer  150  is disposed on the conductive layer  118 , and interposed between the conductive layer  118  and the display medium layer  130 . 
     The fabrication process of the display panel  100 A of  FIG. 1  may include the following steps, but is not limited thereto, and the order of the steps is also not limited to the order presented here. Cross-sectional views of some manufacturing intermediates according to some embodiments of the disclosure are shown in  FIG. 2A-2E . As shown in  FIG. 2A , a surface of the first substrate  110  is etched to be partially removed to form the first recess R 1 , where the etched surface is defined as the surface ( 110   b ) facing the display medium layer  140  in the finished display panel  100 A as depicted in  FIG. 1 . The etching step may involve a wet etching step (for example with hydrofluoric acid) or a dry etching step (for example with plasma). In some embodiments, either anisotropic or isotropic etching conditions may be used. Specifically, a patterned photoresist PR may be used to shield from the etching agent portions of the first substrate  110  that are not be removed according to the intended design and may be removed from the first substrate  110  after the first recess R 1  with the desired size and shape is formed. 
     Subsequently, as shown in  FIG. 2B , on the first surface  110   a  opposite to the surface  110   b  presenting the first recess R 1 , the anti-reflective layer  114  and the light shielding layer  116  may be formed (not necessarily in the recited order) and the conductive layer  118  is formed on the second surface  110   b  presenting the first recess R 1  in a conformal manner. In some embodiments, the anti-reflective layer  114  is formed by the thermal deposition, and, if required, a pattern may be generated through auxiliary masks (not shown) either during the deposition step or during a subsequent etching step, but the disclosure is not limited thereto. In some embodiments, the light shielding layer  116  is formed by inkjet printing or super-inkjet printing. 
     In  FIG. 2C , the first alignment layer  150  is formed on top of the conductive layer  118 . As shown in  FIG. 2D , the sealing material  142   a  is dispensed in the first recess R 1  of the first substrate  110 . In some embodiments, the sealing material  142   a  is premixed with the fillers  144 . In some embodiments, the sealing material  142   a  may be provided by dispensing, printing, or APR printing technology, but the disclosure is not limited thereto. The sealing material  142   a  though is not yet cured, has a certain viscosity to maintain the thickness without significantly spreading and extending outwardly. A display medium material  130   a  is dispensed on the first alignment layer  150  in the region surrounded by the sealing material  142   a.    
     Subsequently, the first substrate  110  is assembled with the second substrate  120  (shown in  FIG. 1 ) having the second alignment layer  160  (shown in  FIG. 1 ) formed thereon. The second alignment layer  160  may have been formed on the second substrate  120  before the assembling step with the first substrate  110 . During the assembling step, the sealing material  142   a  may be compressed. After assembling the second substrate  120  with the first substrate  110 , a curing step may be performed to cure the compressed sealing material  142   a . In some embodiments, the sealing material  142   a  may be a UV-curable sealant. In other words, an irradiation with a curing light having wavelength below about 400 nm (UV light) may be required. The curing light may have maximum intensity around 365 nm, depending on the material used for the sealing material  142   a . Alternatively, the sealing material  142   a  may be mainly cured with UV light of wavelength of 365 nm. In some other embodiments, the sealing material  142   a  may be cured by heat, and a baking step may be performed. The temperature and the duration of the baking step may be selected according to the material used. Upon curing, formation of the display panel  100 A shown in  FIG. 1  may be complete. 
     As shown in  FIG. 1 , in some embodiments, after the assembly of the first substrate  110  with the second substrate  120  and the curing step, the thickness T 140  of the sealant  140  may be greater than the thickness T 130  of the display medium layer  130 . Furthermore, the thickness T 140  of the sealant  140  may be greater than the distance D S  between the first substrate  110  and the second substrate  120  in the second region  104 . 
     In  FIG. 3A  is shown a cross-sectional view of a display panel  100 B according to another embodiment of the present disclosure. The structure of the display panel  100 B shown in  FIG. 3A  may be an implementing example of an embodiment of the present disclosure. The display panel  100 B shown in  FIG. 3A  is similar to the display panel  100 A shown in  FIG. 1 , and the same or similar reference numbers in the two embodiments represent the same or similar elements or components. The display panel  100 B may include the first substrate  110 , the anti-reflective layer  114 , the light shielding layer  116 , the conductive layer  118 , the second substrate  120 , the display medium layer  130 , the sealant  140 , the first alignment layer  150 A, and the second alignment layer  160 A. In the embodiment, the first alignment layer  150 A includes a first organic alignment layer  152  and a first inorganic alignment layer  154 , and the second alignment layer  160 A includes a second organic alignment layer  162  and a second inorganic alignment layer  164 . 
     In some embodiments, the first inorganic alignment layer  154  is stacked on top of the first organic alignment layer  152 . That is, the first inorganic alignment layer  154  is disposed between the first organic alignment layer  152  and the display medium layer  130 . In some alternative embodiments, the first organic alignment layer  152  and the first inorganic alignment layer  154  may be disposed on the first substrate  110  in a coplanar manner. Accordingly, the first organic alignment layer  152  may not be interposed between the first inorganic alignment layer  154  and the first substrate  110 . 
     In some embodiments, the second inorganic alignment layer  164  is stacked on top of the second organic alignment layer  162 . That is, the second inorganic alignment layer  164  is disposed between the second organic alignment layer  162  and the display medium layer  130 . In some alternative embodiments, the second organic alignment layer  162  and the second inorganic alignment layer  164  may be disposed on the second substrate  120  in a coplanar manner. Accordingly, the second organic alignment layer  162  may not be interposed between the second inorganic alignment layer  164  and the second substrate  120 . 
     The organic alignment layers  152  and  162  may extend continuously from the second region  104  to a part of the first region  102  within an inner perimeter of the sealant  140 , and physically contact the inner edge of the sealant  140 . The first and second inorganic alignment layers  154  and  164  may respectively be spaced apart from the sealant  140  by a gap G. That is, the first and second organic alignment layers  152  and  162  may be disposed in the gap G, whilst the inorganic alignment layers  154  and  164  may not extend within the gap G. The first and second organic alignment layers  152  and  162  and the first and second inorganic alignment layers  154  and  164  are in contact with the display medium layer  130 . When the display medium layer  130  contains a liquid crystal material, the two alignment layers  150 A and  160 A are used for orientating the liquid crystal molecules and inducing a pre-tilt angle in the liquid crystal molecules. 
     A material used for the first and second organic alignment layers  152  and  162  may include polyimide. In some embodiments, the material of the first and second organic alignment layers  152  and  162  may include thermally curable polyimide or UV-curable polyimide. The first and second organic alignment layers  152  and  162  may have a thickness in a range of a couple of hundreds to a couple of thousands of angstroms. A material of the first and second inorganic alignment layers  154  and  164  may include silicon oxide (SiO x ), zinc oxide (ZnO) or nanoporous anodic aluminum oxide, but the disclosure is not limited thereto. Each of the first and second inorganic alignment layers  154  and  164  may have a thickness in the range from 200 to 2000 angstroms. 
     In  FIG. 3B  is shown a cross-sectional view of a display panel  100 C according to another embodiment of the present disclosure. The structure of the display panel  100 C shown in  FIG. 3B  may be an implementing example of an embodiment of the present disclosure. The display panel  100 C shown in  FIG. 3B  is similar to the display panel  100 B shown in  FIG. 3A , and the same or similar reference numbers in the two embodiments represent the same or similar elements or components. The display panel  100 C may include the first substrate  110 , the anti-reflective layer  114 , the light shielding layer  116 , the conductive layer  118 , the second substrate  120 , the display medium layer  130 , the sealant  140 A, the first alignment layer  150 B, and the second alignment layer  160 B. The first substrate  110  may present the first recess R 1  in the first region  102  of the display panel  100 C, where the sealant  140 A is located. As for the display panel  100 B of  FIG. 3 , also in the display panel  100 C, the sealant  140 A is disposed in the first recess R 1 . A difference between the display panel  100 C shown in  FIG. 3B  and the display panel  100 B shown in  FIG. 3A  is that the sealant  140 A partly covers the first and second organic alignment layers  152 A and  162 A. That is, the first and second organic alignment layers  152 A and  162 A extend further into the recess R 1  or over the bottom substrate  120  than the first and second organic alignment layers  152  and  162  of the display panel  100 B shown in  FIG. 3A . Another difference between the display panel  100 C of  FIG. 3B  and the display panel  100 B of  FIG. 3A  is that the first alignment layer  150 B may further include a first hydrophobic material layer  156  formed on the first inorganic alignment layer  154  and the second alignment layers  160 B may further include a second hydrophobic material layer  166  formed on the second inorganic alignment layer  164 . 
     The first and second hydrophobic material layers  156  and  166  are respectively disposed on the surfaces  154   a  and  164   a  of the first and second inorganic alignment layers  154  and  164 . The surfaces  154   a  and  164   a  are the surfaces of the first and second inorganic alignment layers  154  and  164  which interface with the display medium layer  130 . The first and second hydrophobic material layers  156  and  166  may include hydrophobic molecules, such as silanes, fluorinated silanes, acids, or long-chain alcohols. In some embodiments, if the material of the first and second inorganic alignment layers  154  and  164  is obliquely deposited silicon oxide, a resulting silane sidechain attached to silicon atoms at the surfaces  154   a  and  164   a  may be Si—O—Si(ROH) 2 —R′—CH 3  or Si—O—Si(ROH) 2 —(CF 2 ) n —CF 3 , where R and R′ are alkyl chains which may be different from each other and n, an integer number, represents the number of the carbon atoms of the alkyl chain. In some embodiments including the aforementioned silane or a similar coating, the coated surfaces  154   a  and  164   a  of the first and second inorganic alignment layers  154  and  164  may have a water contact angle greater than 60 degrees. Because of the attached hydrophobic molecules, the increased hydrophobicity of the surfaces  154   a  and  164   a  may further facilitate pre-tilting and vertical alignment of the material of the display medium layer  130 . 
     The fabrication process of the display panels  100 B and  100 C differ from the fabrication process of the display panel  100 A in that, prior to assembly of the display panel, the first organic alignment layer  152  or  152 A and the first inorganic alignment layer  154  may be formed on top of the conductive layer  118 . The method of forming the first organic alignment layer  152  or  152 A (and the second organic alignment layer  162  or  162 A on the second substrate  120  shown in  FIG. 3A ) may include ink-jet printing or spin-coating and may further include patterning to form the desired pattern, but the method is not limited thereto. The method of forming the first inorganic alignment layer  154  (or the second inorganic alignment layer  164  shown in  FIG. 1 ) may include thermal evaporation of the desired material, but the method is not limited thereto. 
     For the display panel  100 C, the first and second hydrophobic material layers  156  and  166  are further respectively formed on the surfaces  154   a  and  164   a  of the first and second inorganic alignment layers  154   a  and  164   a . The disposing of the first and second hydrophobic material layers  156  and  166  on the surfaces  154   a  and  164   a  of the first and second inorganic alignment layers  154  and  164  may involve a surface treatment or modification process, such as a silane surface treatment process through, for example, chemical vapor deposition. The surfaces  154   a  and  164   a  may be treated in isolation by shielding other areas beyond the first and second inorganic alignment layers  154  and  164  with the use of a mask (not shown) or by other selective deposition techniques. In some embodiments, a region corresponding to the gap G, or, in general, to the portions of the first and second organic alignment layers  152 A and  162 A left exposed by the first and second inorganic alignment layers  154  and  164 , may be shielded during the formation of the first and second hydrophobic material layers  156  and  166 , such that the first and second organic alignment layers  152 A and  162 A may not be subjected to the hydrophobic treatment. 
     In  FIG. 3C  is shown a cross-sectional view of a display panel  100 D according to another embodiment of the present disclosure. The structure of the display panel  100 D shown in  FIG. 3C  may be an implementing example of an embodiment of the present disclosure. The display panel  100 D shown in  FIG. 3C  is similar to the display panel  100 A shown in  FIG. 1 , and the same or similar reference numbers in the two embodiments represent the same or similar elements or components. The display panel  100 D having the first region  102  surrounding the second region  104  served as the display region may include the first substrate  110 , the anti-reflective layer  114 , the light shielding layer  116 , the conductive layer  118 , the second substrate  120 , the display medium layer  130 , the sealant  140 , the first alignment layer  150 , and the second alignment layer  160 . The first substrate  110  may present the first recess R 1  in the first region  102  of the display panel  100 D, where the sealant  140  is located. As for the display panel  100 A of  FIG. 1 , also in the display panel  100 D the sealant  140  is disposed in the first recess R 1 . The display panel  100 D of  FIG. 3C  differs from the display panel  100 A of  FIG. 1  as a color filter  170  is disposed between the second alignment layer  160  and the second substrate  120  in the second region  104  of the display panel  100 D. In some embodiments, a peripheral portion of the color filter  170  may be disposed within the first region  102  of the display panel  100 D. In some alternative embodiments, a span of the color filter  170  may match or slightly exceed a span of the second alignment layer  160 , but the disclosure is not limited thereto. 
     In  FIG. 3D  is shown a cross-sectional view of a display panel  100 E according to another embodiment of the present disclosure. The structure of the display panel  100 E shown in  FIG. 3D  may be an implementing example of an embodiment of the present disclosure. The display panel  100 E shown in  FIG. 3D  is similar to the display panel  100 C shown in  FIG. 3B , and the same or similar reference numbers in the two embodiments represent the same or similar elements or components. The display panel  100 E having the first region  102  surrounding the second region  104  served as the display region may include the first substrate  110 , the anti-reflective layer  114 , the light shielding layer  116 , the conductive layer  118 , the second substrate  120 , the display medium layer  130 , the sealant  140 , the first alignment layer  150 C, and the second alignment layer  160 C. In the display panel  100 E, the first and second organic alignment layers  152  and  162  extend up to the sealant  140 , without overlapping it, as discussed with reference to the display panel  100 B of  FIG. 3A . The first and second hydrophobic material layers  156  and  166  are formed on the first and second inorganic alignment layer  154  and  164 , respectively, similarly to what discussed with reference to the display panel  100 C of  FIG. 3B . Furthermore, the display panel  100 E of  FIG. 3D  further includes the color filter  170  disposed between the second organic alignment layer  162  and the second substrate  120  in the second region  104 , similarly to what discussed with reference to the display panel  100 D of  FIG. 3C . In some embodiments, the span of the color filter  170  matches or slightly exceed the span of the second hydrophobic material layer  166 . 
     It is to be understood that, in some embodiments, all the display panels of the present disclosure may include one or both of the first and second hydrophobic material layers  156  and  166 . According to some embodiments, overlap between the sealant  140 A and the first and second organic alignment layers  152 A and  162 A is possible for all the display panels of the present disclosure. Furthermore, in some embodiments, all the display panels of the present disclosure may include the color filter  170 . 
     In  FIG. 4A  is shown a cross section of a display panel  200  according to another embodiment of the present disclosure. The structure of the display panel  200  shown in  FIG. 4A  may be an implementing example of an embodiment of the present disclosure. The display panel  200  shown in  FIG. 4A  is similar to the display panel  100  shown in  FIG. 1 , and the same or similar reference numbers in the two embodiments represent the same or similar elements or components. The display panel  200  may include the first substrate  210 , the anti-reflective layer  114 , the light shielding layer  116 , the conductive layer  218 , the second substrate  220 , the display medium layer  130 , the sealant  140 , the first alignment layer  150 , and the second alignment layer  160 . In some embodiments, the anti-reflective layer  114  and the light shielding layer  116  are formed on the first surface  210   a  of the first substrate  210  further away from the display medium layer  130 . A difference between the display panel  200  of  FIG. 4A  and the display panel  100 A of  FIG. 1  is that the first substrate  210  does not include a recess. In some embodiments, portions of the second surface  210   b  of the first substrate  210  closer to the display medium layer  130  in the first region  102 , in the second region  104 , and in the third region  106  are substantially coplanar. In other words, no first recess is formed in the first substrate  210 . The conductive layer  218  is conformally disposed on the second surface  210   b  of the first substrate  210 . In other words, the conductive layer  218  may be a flat layer. 
     In some embodiments, the second substrate  220  includes the base plate  222  having an active device layer  224  formed thereon, and a passivation layer  226  disposed on the active device layer  224 . In some embodiments, the base plate  222  includes a silicon bulk, and the active device layer  224  includes a plurality of complementary metal-oxide semiconductor devices formed in the silicon bulk. In some embodiments, the active device layer  224  may include a thin film transistor array. In some embodiments, the active device layer  224  may be formed on a surface  222   a  of the base plate  222  closer to the display medium layer  130 , and extends continuously within the first region  102  and the second region  104 . In some embodiments, the active device layer  224  further extends within the third region  106 . 
     In the present embodiment, the passivation layer  226  covers the active device layer  224 . The passivation layer  226  is interposed between the sealant  140  and the active device layer  224  in the first region  102 , and between the active device layer  224  and the second alignment layer  160  in the second region  104 . In some embodiments, a material of the passivation layer  226  includes organic insulating materials, such as polymer-based insulating materials, or inorganic insulating materials such as oxides or nitrides. In some embodiments, the passivation layer  226  may be formed by spin-on coating, chemical vapor deposition (CVD), plasma-enhanced chemical vapor deposition (PECVD), or the like, but the disclosure is not limited thereto. 
     In addition, a second recess R 2  is formed within the second substrate  220 , and the sealant  140  is received in the second recess R 2 . In some embodiments, as the sealant  140  is received in the second recess R 2 , the thickness T 140  of the sealant  140  may be larger than the distance D S  between the first substrate  210  and the second substrate  220  in the second region  104  of the display panel  200 . In the present embodiment, the distance D S  is measured as the distance between the second surface  210   b  of the first substrate  210  and a surface  226   a  of the passivation layer  226  closer to the display medium layer  130 . In some embodiments, the thickness T 140  of the sealant  140  is greater than the thickness T 130  of the display medium layer  130 . In some embodiments, the thickness T 130  of the display medium layer  130  may be smaller than 2 μm. The sealant  140  is received in the second recess R 2  so that sealing with low compressibility may be used even in the display panels requiring a small thickness of the display medium layer  130 . 
     In  FIG. 4B  is shown an enlarged view of a portion of a display panel according to some embodiments of the present disclosure. The enlarged portion shown in  FIG. 4B  corresponds to the portion inscribed in the area A shown in  FIG. 4A .  FIG. 4B  only illustrates the second substrate  220  and the sealant  140  for descriptive purpose. In some embodiments the passivation layer  226  may include a plurality of insulation layers. As shown in  FIG. 4B , in some embodiments the passivation layer  226  may include a first insulation layer  2261  and a second insulation layer  2262  stacked on the first insulation layer  2261 . In some embodiments, the second recess R 2  is formed by patterning the passivation layer  226 . In some embodiments, a portion of the second insulation layer  2262  is removed by an etching step. In some embodiments, a corresponding portion of the first insulation layer  2261  may also be removed, but the etching step is carried out in such a way that a depth D R2  of the second recess R 2  is insufficient to pass throughout a thickness T 2261  of the first insulation layer  2261 . In other words, at least a portion of the first insulation layer  2261  is interposed between the active device layer  224  and the sealant  140 . In some alternative embodiments as shown in  FIG. 4C , only a portion of the second insulation layer  2262  is removed to form the second recess R 2 . In some embodiments, a material of the first insulation layer  2261  is different than a material of the second insulation layer  2262 , so that selective etching conditions may be applied to form the second recess R 2  of the desired depth D R2 . 
     According to some embodiments, the display panel in accordance with any of the embodiments of the present disclosure may have a multi-layered passivation layer  226 . Furthermore, the display panel  200  may further include a color filter (not shown in  FIG. 4A ), as discussed with reference to the display panel  100 D of  FIG. 3C . The display panel  200  may further include hydrophobic material layers (not shown in  FIG. 4A ) formed on one or both of the alignment layers  150  and  160 , as discussed with reference to the display panel  100 C shown in  FIG. 3B . In addition, the display panel  200  may include both the color filter and the hydrophobic material layers, as discussed with reference to the display panel  100 E of  FIG. 3D . 
     In  FIG. 5  is shown a cross section of a display panel  300  according to another embodiment of the present disclosure. The structure of the display panel  300  shown in  FIG. 5  may be an implementing example of an embodiment of the present disclosure. The display panel  300  shown in  FIG. 5  includes features similar to the display panel  100 A shown in  FIG. 1 , and features similar to the display panel  200  shown in  FIG. 4A , and the same or similar reference numbers in the three embodiments represent the same or similar elements or components. The display panel  300  of  FIG. 5  may include a first substrate  110  having a first recess R 1  formed therein as the display panel  100 A of  FIG. 1 , and a second substrate  220  having a second recess R 2  formed therein as the display panel  200  of  FIG. 4A . The display panel  300  may further include the anti-reflective layer  114 , the light shielding layer  116 , the conductive layer  118 , the display medium layer  130 , the sealant  140 , the first alignment layer  150  and the second alignment layer  160 . The anti-reflective layer  114  and the light shielding layer  116  may be disposed on the surface  110   a  of the first substrate  110  further away from the display medium layer  130 . The second substrate  220  may include the base plate  222 , the active device layer  224  and the passivation layer  226 . The conductive layer  118  is conformally disposed over the second surface  110   b  of the first substrate  110 , and follows the profile of the first recess R 1  in the first region  102  of the display panel  300 . The sealant  140  encircles the display medium layer  130  and is received in the first recess R 1  of the first substrate  110  and the second recess R 2  of the second substrate  220 . In other words, a vertical projection of the first recess R 1  falls over a span of the second recess R 2 , so that the sealant  140  may be simultaneously disposed in both recesses R 1  and R 2 . By having the sealant  140  disposed in the recesses R 1  and R 2  in the first region  102  of the display panel  300 , the thickness T 140  of the sealant  140  may be greater than the distance D S  between the first substrate  110  and the second substrate  220  in the second region  104  of the display panel  300 . In some embodiments, the distance D S  is measured as the distance between the second surface  110   b  of the first substrate  110  and the surface  226   a  of the passivation layer  226  closer to the display medium layer  130  in the second region  104  of the display panel  300 . In some embodiments, the thickness T 140  of the sealant  140  is greater than the thickness T 130  of the display medium layer  130 . In some embodiments, the thickness T 130  of the display medium layer  130  may be smaller than 2 μm. 
     In some embodiments, the conductive layer  118  is disposed between the sealant  140  and the first substrate  110 . In some embodiments, at least a portion of the passivation layer  226  is disposed between the sealant  140  and the active device layer  224  while the portion of the passivation layer  226  may be thinner than the other portions of the passivation layer  226 . In some embodiments, the passivation layer  226  may have a multi-layered structure as previously discussed with reference to  FIG. 4B  and  FIG. 4C . Furthermore, the display panel  300  may further include a color filter (not shown in  FIG. 5 ), as discussed with reference to the display panel  100 D of  FIG. 3C . The display panel  300  may further include hydrophobic material layers (not shown in  FIG. 5 ) formed on one or both of the alignment layers  150  and  160 , as discussed with reference to the display panel  100 C shown in  FIG. 3B . In addition, the display panel  300  may include both the color filter and the hydrophobic material layers, as discussed with reference to the display panel  100 E of  FIG. 3D . 
     In light of the foregoing, a display panel according to an embodiment of the disclosure includes a sealant disposed between a first substrate and a second substrate in a first region of the display panel. One or both of the first substrate and the second substrate may present a recess in the first region where the sealant is received. By having the sealant disposed within the recess of the first substrate or the second substrate, a thickness of the sealant may be greater than a distance between the first substrate and the second substrate in a second region of the display panel. The second region of the display panel may be surrounded by the first region, and may act as a display area for the display panel. The possibility of having a thicker sealant in the first region expands the range of possible materials usable for the sealant even when designing display panel having a particularly thin display medium layer (small gap) disposed between the first substrate and the second substrate in the second region of the display panel. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present disclosure without departing from the scope or spirit of the disclosure. In view of the foregoing, it is intended that the present disclosure covers modifications and variations of this disclosure, provided these falls within the scope of the following claims and their equivalents.