Patent Publication Number: US-2015062842-A1

Title: Element substrate, display apparatus and manufacturing method of element substrate

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This Non-provisional application claims priority under 35 U.S.C. §119(a) on Patent Application No(s). 102131278 filed in Taiwan, Republic of China on Aug. 30, 2013, the entire contents of which are hereby incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     The invention relates to an element substrate, a display apparatus and a manufacturing method of the element substrate and, in particular, to a flexible element substrate, a display apparatus and a manufacturing method of the flexible element substrate. 
     2. Related Art 
     With the progress of technologies, display apparatuses have been widely applied to various kinds of fields. Especially, liquid crystal display (LCD) apparatuses, having advantages such as compact structure, low power consumption, less weight and less radiation, gradually take the place of cathode ray tube (CRT) display apparatuses and are widely applied to various electronic products, such as mobile phones, portable multimedia apparatuses, notebook computers, pad computers and other display apparatuses. 
     A conventional liquid crystal display (LCD) apparatus mainly includes an LCD panel. The LCD panel mainly includes a thin film transistor (TFT) substrate, a color filter (CF) substrate and a liquid crystal layer disposed between the two substrates. The CF substrate, the TFT substrate and the LC layer form a plurality of pixels disposed in an array. When the light passes through the LCD panel, the all pixels can display colors forming images accordingly. With regard to the future development of the LCD apparatus and OLED display apparatus, the industry expects that the conventional glass substrate can be replaced by the plastic substrate and the TFT elements, electrodes and capacitors can be made on the plastic substrate so as to bring the light, flexible, shatter-proof and shock-proof characteristics. 
     However, the rigidity of the plastic substrate is scarcely comparable to the glass substrate, so it can not be directly applied to the production line of the TFT elements. Accordingly, the current manner is putting a plastic substrate on a rigid carrier plate (e.g. a glass substrate) and then using the same manufacturing process and equipment as applied to the glass substrate to manufacture the TFT elements or other electronic elements. Nevertheless, an adhesive is required to temporarily stick the plastic substrate on the rigid carrier plate before making the TFT elements, and then a separation is required between the rigid carrier plate and the TFT substrate including the plastic substrate and the TFT elements to bring out the TFT substrate. 
     Because no proper adhesive can be currently applied in the conventional art, the manufacturing process for making the TFT elements on the plastic substrate just can be implemented by a low temperature process. However, the TFT elements made by a low temperature process will be given bad electric property. For example, the carrier mobility of the channel layer of the TFT is slower so as to result in a bad yield rate. Nevertheless, no proper adhesive can be applied when the TFT elements are made by a high temperature process, although the elements can be made capable of better electric property. 
     SUMMARY OF THE INVENTION 
     In view of the foregoing subject, an objective of the invention is to provide an element substrate, a display apparatus and a manufacturing method of the element substrate that have high heat-resistant property so as to be suitable for the high temperature process so that the element substrate and the display apparatus can be made with better electric property and yield rate. 
     To achieve the above objective, an element substrate according to the invention comprises a flexible substrate, an element layer, a buffer layer and an interface layer. The element layer is disposed on the flexible substrate. The buffer layer is disposed on the flexible substrate. The buffer layer and the element layer are disposed on the opposite sides of the flexible substrate. The interface layer is disposed between the flexible substrate and the buffer layer and includes partial material of both of the flexible substrate and the buffer layer. The interface layer is formed by a heat treatment process. 
     To achieve the above objective, a display apparatus according to the invention comprises an element substrate including a flexible substrate, an element layer, a buffer layer and an interface layer. The element layer is disposed on the flexible substrate. The buffer layer is disposed on the flexible substrate. The buffer layer and the element layer are disposed on the opposite sides of the flexible substrate. The interface layer is disposed between the flexible substrate and the buffer layer and includes partial material of both of the flexible substrate and the buffer layer. The interface layer is formed by a heat treatment process. 
     To achieve the above objective, a manufacturing method of an element substrate according to the invention comprising steps of: providing a rigid carrier plate; forming a buffer layer on the rigid carrier plate; forming a flexible substrate on the buffer layer; implementing a heat treatment process to form an interface layer between the flexible substrate and the buffer layer; and forming an element layer on the flexible substrate. 
     In one embodiment, the flexible substrate includes organic polymer material. 
     In one embodiment, the buffer layer includes polymer material of polyimide (PI), acrylic or polysiloxane. 
     In one embodiment, the interface layer is formed by an interpenetrating polymer network (IPN) generated after the heat treatment process with a subsequent cooling. 
     In one embodiment, the element substrate further comprises a de-bonding layer disposed on the buffer layer. 
     In one embodiment, the element substrate is a thin film transistor (TFT) substrate, a color filter (CF) substrate, an organic light-emitting diode (OLED) substrate or a touch substrate. 
     In one embodiment, before the step of forming the buffer layer, the manufacturing method further comprises a step of: forming a de-bonding layer on the rigid carrier plate. 
     In one embodiment, the manufacturing method further comprises a step of: separating the de-bonding layer from the buffer layer to obtain the element substrate including the element layer, the flexible substrate, the interface layer and the buffer layer. 
     In one embodiment, the manufacturing method further comprises a step of: separating the de-bonding layer from the rigid carrier plate to obtain the element substrate including the element layer, the flexible substrate, the interface layer, the buffer layer and the de-bonding layer. 
     In one embodiment, the manufacturing method further comprises a step of: separating the buffer layer from the rigid carrier plate to obtain the element substrate including the element layer, the flexible substrate, the interface layer and the buffer layer. 
     In one embodiment, before the step of forming the buffer layer wherein the de-bonding layer has a first surface facing the rigid carrier plate and a second surface which is opposite to the first surface and includes a first part and a second part surrounding the first part, the manufacturing method further comprises a step of: controlling the adhesion of the second surface of the de-bonding layer to make the adhesion of the first part lower than that of the second part. 
     In one embodiment, before the step of forming the buffer layer wherein the de-bonding layer has a first surface facing the rigid carrier plate and a second surface opposite to the first surface, the manufacturing method further comprises a step of: controlling the adhesions of the first and second surfaces of the de-bonding layer to make the adhesion of the second surface lower than that of the first surface. 
     In one embodiment, before the step of forming the buffer layer wherein the de-bonding layer has a first surface facing the rigid carrier plate and a second surface opposite to the first surface, the manufacturing method further comprises a step of: controlling the adhesions of the first and second surfaces of the de-bonding layer to make the adhesion of the first surface lower than that of the second surface. 
     In one embodiment, before the step of forming the buffer layer wherein the rigid carrier plate has a surface including a first part and a second part surrounding the first part, the manufacturing method further comprises a step of: controlling the adhesion of the surface of the rigid carrier plate to make the adhesion of the first part lower than that of the second part. 
     As mentioned above, in the element substrate, the display apparatus and the manufacturing method of the element substrate of the invention, the element substrate includes a flexible substrate, an element layer, a buffer layer and an interface layer, and the interface layer is formed between the flexible substrate and the buffer layer by a heat treatment process. Thereby, in comparison with the prior art, the invention is not limited to the type of the adhesive material and is capable of high heat-resistant property so as to be suitable for the high temperature process. Besides, the IPN phenomenon of the interface layer can make a better adhesion between the flexible substrate and the buffer layer, and therefore the electronic elements of the element substrate and the display apparatus can be made by a high temperature process so that the element substrate and the display apparatus can have better electric property and yield rate. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will become more fully understood from the detailed description and accompanying drawings, which are given for illustration only, and thus are not limitative of the present invention, and wherein: 
         FIG. 1  is a schematic flow chart of a manufacturing method of an element substrate according to an embodiment of the invention; 
         FIGS. 2A to 2I  are schematic diagrams of the manufacturing method of the element substrate according to the first embodiment of the invention; 
         FIG. 2J  is a schematic diagram showing the IPN phenomenon; 
         FIGS. 3A to 3C  are schematic diagrams of the manufacturing method of the element substrate according to the second embodiment of the invention; 
         FIGS. 4A to 4B  are schematic diagrams of the manufacturing method of the element substrate according to the third embodiment of the invention; 
         FIG. 5  is a schematic flow chart of a manufacturing method of an element substrate according to another embodiment of the invention; 
         FIGS. 6A to 6D  are schematic diagrams of the manufacturing method of the element substrate according to the fourth embodiment of the invention; 
         FIG. 7A  is a schematic sectional diagram of the element substrate before the de-bonding; 
         FIG. 7B  is a schematic enlarged diagram of a region in  FIG. 7A ; 
         FIG. 7C  schematically shows the SEM image of the structure of  FIG. 2F  where the flexible substrate is removed by an external force; and 
         FIG. 7D  schematically shows the SEM image of the buffer layer, the de-bonding layer and the rigid carrier plate which are not processed by heat treatment. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention will be apparent from the following detailed description, which proceeds with reference to the accompanying drawings, wherein the same references relate to the same elements. 
     As below, the element substrate and the display apparatus including the element substrate can be obtained by the clear illustration of the manufacturing method of the element substrate. 
       FIG. 1  is a schematic flow chart of a manufacturing method of an element substrate according to an embodiment of the invention, and  FIGS. 2A to 2I  are schematic diagrams of the manufacturing method of the element substrate according to the first embodiment of the invention. 
     As shown in  FIG. 1 , the manufacturing method of the element substrate includes the steps S 01  to S 07 . 
     First, as shown in  FIGS. 1 and 2A , the step S 01  is providing a rigid carrier plate  11 . Herein for example, the rigid carrier plate  11  is a glass plate, metal plate, fiberglass plate, thick plastic plate, or metal/organic composite plate. 
     As shown in  FIG. 2B  (side view) and  FIG. 2C  (top view of  FIG. 2B ), the step S 02  is forming a de-bonding layer  12  on the rigid carrier plate  11 . One of the surfaces of the de-bonding layer  12  is used as the separation interface between the element substrate  1  and the rigid carrier plate  11 . In this embodiment, the de-bonding layer  12  can be formed on the rigid carrier plate  11  by the method of spin coating, spray coating or slit coating, so that the de-bonding layer  12  substantially have the same area as the rigid carrier plate  11 . The de-bonding layer  12  has a first surface  121  and a second surface  122  opposite to the first surface  121 , and the first surface  121  faces the rigid carrier plate  11 . The second surface  122  includes a first part P 1  and a second part P 2  surrounding the first part P 1 . The area of the first part P 1  is greater than or equal to that of the element substrate. The material of the de-bonding layer  12  can include polysiloxane, polyimide (PI), polyamic acid (PAA) or fluoro-polymer for example. In this embodiment, the de-bonding layer  12  includes polysiloxane material for example. 
     After forming the de-bonding layer  12  and before forming the buffer layer in the step S 03 , the manufacturing method can further include a step of controlling the adhesion of the second surface  122  of the de-bonding layer  12  to make the adhesion of the first part P 1  of the second surface  122  lower than that of the second part P 2 . The higher adhesion of the second part P 2  can firmly fix the substrate to the carrier plate during the process, and the lower adhesion of the first part P 1  can be applied to the separation interface between the substrate and the carrier plate. As an embodiment, the property of the second surface  122  of the de-bonding layer  12  is modified by UV illumination or plasma bombardment (e.g. the functional groups of the surface are broken or oxidized to change the adhesion), so that the adhesion of the first part P 1  is lower than that of the second part P 2 . In other words, the adhesion of the second surface  122  is patterned. 
     Then, as shown in  FIG. 2D , the step S 03  is forming a buffer layer  13  on the rigid carrier plate  11 . In this embodiment, the buffer layer  13  also can be formed on the rigid carrier plate  11  and the de-bonding layer  12  by the method of spin coating, spray coating or slit coating. In a top view, the buffer layer  13 , the de-bonding layer  12  and the rigid carrier plate  11  approximately have the same size. The material of the buffer layer  13  can include PI, polyamic acid (PAA), acrylic, polysiloxane or other organic or inorganic polymers for example. Herein, the buffer layer  13  includes PI material for example. 
     Then, as shown in  FIG. 2E , the step S 04  is forming a flexible substrate  14  on the buffer layer  13 . Herein, the flexible substrate  14  is a flexible film and attached to the buffer layer  13  as a lamination structure through a rolling wheel. The flexible substrate  14  includes organic polymer material, which is also thermoplastic material, such as PI, polyethylene (PE), polyvinylchloride (PVC), PS, acrylic, fluoro-polymer, polyester, or nylon. In this embodiment, the flexible substrate  14  includes PI material for example. 
     Then, as shown in  FIG. 2F , the step S 05  is implementing a heat treatment process to form an interface layer  15  between the flexible substrate  14  and the buffer layer  13 . In this embodiment, since the flexible substrate  14  and the buffer layer  13  are both PI-contained material, the temperature of the heat treatment process is about between 300° C. and 500° C., and is 400° C. herein for example. Nevertheless, the temperature of the heat treatment may be different according to different material. For example, when the flexible substrate  14  and the buffer layer  13  include PI and acrylic material, the temperature of the heat treatment may be lower than 200° C. After the heat treatment process and a subsequent cooling, an interpenetrating polymer network (IPN) phenomenon will occur between the flexible substrate  14  and the buffer layer  13  to form an interface layer  15 . 
       FIG. 2J  is a schematic diagram showing the IPN phenomenon. The IPN phenomenon means two polymer materials (left and middle patterns in  FIG. 2J ) are bonded to each other by van der Waals&#39; force or hydrogen bond. In this embodiment, because the temperature 400° C. of the heat treatment is closer to or even higher than one of the glass transition temperatures (Tg) of the flexible substrate  14  and the buffer layer  13 , the polymer chain (network) of the flexible substrate  14  and the buffer layer  13  will partially dissolve and interpenetrate at their connection interface to form an interface layer  15  having higher adhesion by the IPN phenomenon (right pattern in  FIG. 2J ), and therefore the interface layer  15  includes partial material of the flexible substrate  14  and partial material of the buffer layer  13 . 
     As shown in  FIG. 2G , the step S 06  is forming an element layer  16  on the flexible substrate  14 . The buffer layer  13  and the element layer  16  are disposed on the opposite sides of the flexible substrate  14 . In this embodiment, a high temperature process is implemented to make the elements of the TFT substrate on the flexible substrate  14  to form an element layer  16 . Herein, the element layer  16  can include electronic elements such as TFTs, capacitors, conductive layers, transparent electrodes. In other embodiments, the element layer  16  may include a filter layer, a black matrix (BM), a transparent electrode, etc. for making a color filter substrate; the element layer  16  may include TFTs, light-emitting diodes, etc. for making an OLED substrate; or the element layer  16  may include a patterned transparent electrode for making a touch substrate. Therefore, the element substrate  1  made by the manufacturing method of the element substrate of the invention is not limited to a TFT substrate, a CF substrate, an OLED substrate or a touch substrate. 
     As shown in  FIGS. 2H and 2I , the step S 07  is separating the de-bonding layer  12  from the buffer layer  13  to obtain the element substrate  1  including the element layer  16 , the flexible substrate  14 , the interface layer  15  and the buffer layer  13 . To be noted, the property of the second surface  122  of the de-bonding layer  12  is modified after the step S 02 , so that the adhesion of the first part P 1  of the second surface  122  is lower than that of the second part P 2 . So, when the cutting is implemented as shown in  FIG. 2H  along two cutting lines C which are at the edge of the element substrate  1  and go deep into the de-bonding layer  12 , the element substrate  1  as shown in  FIG. 2I  can be obtained by the separation between the buffer layer  13  and the de-bonding layer  12  at the first part P 1 . 
       FIGS. 3A to 3C  are schematic diagrams of the manufacturing method of the element substrate according to the second embodiment of the invention. 
     Mainly different from the first embodiment, the de-bonding layer  12  of this embodiment is formed and patterned on the rigid carrier plate  11  as shown in  FIGS. 3A and 3B , so that the de-bonding layer  12  is located on the central portion of the rigid carrier plate  11  instead of on the entire corresponding surface of the rigid carrier plate  11 . The area of the de-bonding layer  12  is greater than or equal to that of the obtained element substrate, and is less than the area of the rigid carrier plate  11 . 
     In  FIG. 3A , the de-bonding layer  12  also has a first surface  121  and a second surface  122  opposite to the first surface  121 , and the first surface  121  faces the rigid carrier plate  11 . Besides, in this embodiment, the de-bonding layer  12  is controlled so that the adhesion of the second surface  122  can be lower than that of the first surface  121 . In other words, the adhesion of the first surface  121  of the de-bonding layer  12  is greater than that of the second surface  122 . Moreover, since the de-bonding layer  12  is just formed on the central portion of the rigid carrier plate  11 , the buffer layer  13  formed in the step S 03  as shown in  FIG. 3C  is not only located on the de-bonding layer  12  but also surrounds and covers the de-bonding layer  12 , and also directly contacts the rigid carrier plate  11 . 
     In the de-bonding process of the step S 07 , like the first embodiment, because the adhesion of the first surface  121  is greater than that of the second surface  122 , the element substrate  1  can be obtained by separating the buffer layer  13  from the de-bonding layer  12  with the second surface  122  (referring to  FIGS. 2H and 2I ), and the element substrate  1  also includes the element layer  16 , the flexible substrate  14 , the interface layer  15  and the buffer layer  13 . 
     Since the other technical features and processes of the manufacturing method of the element substrate of the second embodiment can be comprehended by referring to the first embodiment, they are not described here for conciseness. 
       FIGS. 4A to 4B  are schematic diagrams of the manufacturing method of the element substrate according to the third embodiment of the invention. 
     The de-bonding layer  12  of the third embodiment also has a first surface  121  and a second surface  122  opposite to the first surface  121 , and the first surface  121  faces the rigid carrier plate  11 . In this embodiment, the adhesions of the first and second surfaces  121  and  122  also need to be controlled. However, mainly different from the second embodiment, the adhesions of the first and second surfaces  121  and  122   a  are controlled so that the first surface  121  can have a lower adhesion than the second surface  122 . In other words, the adhesion of the first surface  121  is less than that of the second surface  122 . 
     Accordingly, in the de-bonding process of the step S 07 , since the adhesion of the first surface  121  is less than that of the second surface  122 , which is different from the second embodiment, the separation interface is the first surface  121  between the de-bonding layer  12  and the rigid carrier plate  11  as shown in  FIG. 4A , and the element substrate  1  a can be obtained thereby in  FIG. 4B , including the element layer  16 , the flexible substrate  14 , the interface layer  15 , the buffer layer  13  and the de-bonding layer  12 . 
     Since the other technical features and processes of the manufacturing method of the element substrate of the third embodiment can be comprehended by referring to the second embodiment, they are not described here for conciseness. 
       FIG. 5  is a schematic flow chart of a manufacturing method of an element substrate according to another embodiment of the invention, and  FIGS. 6A to 6D  are schematic diagrams of the manufacturing method of the element substrate according to the fourth embodiment of the invention. 
     Mainly different from the case of  FIG. 1 , the case of  FIG. 5  is without the step S 02 . In other words, the main difference between the first and fourth embodiments is that the fourth embodiment is without the step S 02 , so the buffer layer is directly formed on the rigid carrier plate  11  as shown in  FIG. 6B . Before forming the buffer layer  13 , the surface of the rigid carrier plate  11  needs to be modified in property. The rigid carrier plate  11  has a surface  111 . The surface  111  includes a first part P 1  and a second part P 2 , and the second part P 2  surrounds the first part P 1 . The adhesion of the surface  111  of the rigid carrier plate  11  needs to be adjusted so that the first part P 1  has a lower adhesion than the second part P 2 . As an embodiment, the adhesion of the surface of the outer part (i.e. the second part P 2 ) is made greater than that of the central part (i.e. the first part P 1 ) by patterned UV illumination or plasma bombardment. Then, a buffer layer  13  is formed on the modified rigid carrier plate  11 . 
     Since the steps S 04  to S 06  are similar to the foregoing embodiment, they are not described here again for conciseness. In the de-bonding process of the step S 071 , because the first part P 1  of the surface  111  of the rigid carrier plate  11  has a lower adhesion than the second part P 2 , the element substrate  1  can be obtained by separating the buffer layer  13  from the rigid carrier plate  11  as shown in  FIGS. 6C and 6D . Like the first embodiment, the element substrate  1  includes the element layer  16 , the flexible substrate  14 , the interface layer  15  and the buffer layer  13 . 
     Since the other technical features and processes of the manufacturing method of the element substrate of the fourth embodiment can be comprehended by referring to the first embodiment, they are not described here for conciseness. 
     Moreover, by referring to the related SEM (scanning electron microscope) images, the evidence of the IPN generated between the flexible substrate  14  and the buffer layer  13  to form an interface layer  15  can be shown.  FIGS. 7A to 7D  are schematic SEM images according to the invention.  FIG. 7A  is a sectional diagram of the element substrate before the de-bonding, and  FIG. 7B  is an enlarged diagram of the region A in  FIG. 7A .  FIG. 7C  shows the SEM image of the structure of  FIG. 2F  which undergoes the heat treatment but with the flexible substrate  14  removed by an external force, and  FIG. 7D  shows the SEM image of the buffer layer  13 , the de-bonding layer  12  and the rigid carrier plate  11  which are not processed by heat treatment. Besides, the de-bonding layer  12  is not specifically shown in  FIGS. 7A to 7D  due to its thinness, and the interface layer  15  is also not shown in  FIG. 7A . 
     It can be found from  FIG. 7B  that the IPN is generated between the flexible substrate  14  and the buffer layer  13  to form an interface layer  15 . Besides, it can be found that the interface layer  15  includes partial material of both of the flexible substrate  14  and the buffer layer  13 . In other words, the flexible substrate  14  and the buffer layer  13  dissolve and interpenetrate at their connection interface to form the interface layer  15  so as to have higher adhesion. 
     Moreover, the left parts of  FIG. 7C and 7D  are both sectional diagrams, the right part of  FIG. 7C  is the top view of the left part of  FIG. 7C , and the right part of  FIG. 7D  is the top view of the left part of  FIG. 7D . By comparing the right part of  FIG. 7C  and the right part of  FIG. 7D , it can be found that the polymer network of the flexible substrate  14  (denoted by white color) and the polymer network of the buffer layer  13  (denoted by gray color) dissolve mutually and interpenetrate at the connection interface, giving the evidence that the IPN phenomenon exists. 
     A display apparatus of the invention includes the above-mentioned element substrate  1  or  1   a . Since the structures of the element substrates  1  and  1   a  are clearly illustrated as above, they are not described here for conciseness. When the display apparatus is an LCD apparatus, the element substrate  1  or  1   a  can be a TFT substrate or a CF substrate. When the display apparatus is an OLED display apparatus, the element substrate  1  or  1   a  can be an OLED substrate. When the display apparatus is a touch panel, the element substrate  1  or  1   a  can be a touch substrate. 
     Summarily, in the element substrate, the display apparatus and the manufacturing method of the element substrate of the invention, the element substrate includes a flexible substrate, an element layer, a buffer layer and an interface layer, and the interface layer is formed between the flexible substrate and the buffer layer by a heat treatment process. Thereby, in comparison with the prior art, the invention is not limited to the type of the adhesive material and is capable of high heat-resistant property so as to be suitable for the high temperature process. Besides, the IPN phenomenon of the interface layer can make a better adhesion between the flexible substrate and the buffer layer, and therefore the electronic elements of the element substrate and the display apparatus can be made by a high temperature process so that the element substrate and the display apparatus can have better electric property and yield rate. 
     Although the invention has been described with reference to specific embodiments, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiments, as well as alternative embodiments, will be apparent to persons skilled in the art. It is, therefore, contemplated that the appended claims will cover all modifications that fall within the true scope of the invention.