Patent Publication Number: US-2020301192-A1

Title: Flexible liquid crystal display device

Description:
BACKGROUND OF THE DISCLOSURE 
     1. Field of the Disclosure 
     The present disclosure relates to a liquid crystal display device, and more particularly to a flexible liquid crystal display device. 
     2. Description of the Prior Art 
     A flexible electronic device is a novel technology of manufacturing electronic components and elements on foldable (or bendable, stretchable or flexible) substrates. In comparison with a rigid electronic device, the flexible electronic device provides many advantages including small size, cost effectiveness, light weight, durability, flexibility and portability. This technology becomes more and more popular because of the potential uses in electronic applications, including flexible displays, flexible touch panels, wearable electronic devices, etc. 
     Currently, extensive studies have been conducted on the research and development of flexible displays. However, even so, there are still many technical defects to be overcome. For example, for the flexible displays, especially for flexible liquid crystal displays, after using a certain period of time, the side of the flexible substrate (such as a color filter substrate and/or a thin film transistor substrate) in the display may be peeled off from the cover layer (such as a glass cover). This defect not only may cause abnormal displaying images at the peripheral portion of the flexible display, but also may cause the flexible display to occur a large area of the abnormal displayed images because the irruption of external matters from the peeling regions, which reduces the reliability or lifetime of the flexible display. 
     SUMMARY OF THE DISCLOSURE 
     Accordingly, it is necessary to provide an improved flexible liquid crystal display device to solve the problems encountered by current flexible liquid crystal display devices. 
     According to an embodiment, the present disclosure provides a flexible liquid crystal display device including a first flexible substrate, a second flexible substrate, a liquid crystal layer, a cover layer and a waterproof glue. The second flexible substrate is disposed opposite to the first flexible substrate, and the liquid crystal layer is disposed between the first flexible substrate and the second flexible substrate. The cover layer has a surface facing the second flexible substrate, and the waterproof glue is adhered to the surface of the cover layer and a side of the second flexible substrate. 
     According to the flexible liquid crystal display device of this embodiment in the present disclosure, since the waterproof glue is adhered to the surface of the cover layer and the side of the second flexible substrate, the probability of the second flexible substrate, especially the side thereof, peeling off from the surface of the cover layer may be reduced, and thus the reliability or lifetime of the flexible liquid crystal display device may be increased. 
     These and other objectives of the present disclosure will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the embodiment that is illustrated in the various figures and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a top view schematic diagram of a flexible liquid crystal display device according to a first embodiment of the present disclosure. 
         FIG. 2  is a cross-sectional view schematic diagram of a flexible liquid crystal display device according to a first embodiment of the present disclosure. 
         FIG. 3  is a cross-sectional view schematic diagram of a flexible liquid crystal display device according to a second embodiment of the present disclosure. 
         FIG. 4  is a cross-sectional view schematic diagram of a flexible liquid crystal display device according to a third embodiment of the present disclosure. 
         FIG. 5  is a top view schematic diagram of a flexible liquid crystal display device according to a fourth embodiment of the present disclosure. 
         FIG. 6  is a top view schematic diagram of a flexible liquid crystal display device according to a fifth embodiment of the present disclosure. 
         FIG. 7  is a cross-sectional view schematic diagram of a flexible liquid crystal display device according to an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure may be understood by reference to the following detailed description, taken in conjunction with the drawings as described below. It is noted that, for purposes of conciseness of the drawings and being easily understood by one skilled in the art, the components in the drawings may not be drawn to practical scale. In addition, the number and dimension of each component shown in drawings are only illustrative and are not intended to limit the scope of the present disclosure. 
     Certain terms are used throughout the description and following claims to refer to particular components. As one skilled in the art will understand, electronic equipment manufacturers may refer to a component by different names. This document does not intend to distinguish between components that differ in name but not function. The terms “include”, “comprise” and/or “have” used in the description of the present disclosure are open-ended terms, so it should be interpreted as the meaning of “including but not limited to . . . .” 
     When a component or a layer is referred to “disposed on another component or another layer” or “connected to another component or another layer”, it may represent that the component or the layer is directly disposed on another component or layer or directly connected to another component or layer, or other intermediate component or layer may exist between them. By comparison, when a component is referred to “directly disposed on another component or layer” or “directly connected to another component or another layer”, any intermediate component or layer does not exist between them. 
     The term “face” mentioned in the present disclosure refers to a component being close to another component, and the term “face away from” refers to a component being away from another component. The term “flexible device” means that the device can be bent, folded, curled, flexed or other similarly actuated along at least one bending axis, but not limited thereto. According to some embodiments, the device may also be respectively bent along more than two bending axes. 
     It should be noted that the technical features in different embodiments described in the following description can be replaced, recombined or mixed with one another to constitute another embodiment without departing from the spirit of the present disclosure. 
     Please refer to  FIG. 1  and  FIG. 2 .  FIG. 1  is a top-view schematic diagram of a flexible liquid crystal display device according to a first embodiment of the present disclosure.  FIG. 2  is a cross-sectional view schematic diagram of a flexible liquid crystal display device according to a first embodiment of the present disclosure. The flexible liquid crystal display device  100  includes a cover layer  110 , a waterproof glue  120  and an adhesive material  122 , and the adhesive material  122  may surround the waterproof glue  120 . The flexible liquid crystal display device  100  may be divided into a display region  102  and a peripheral region  104 . The display region  102  refers to a region where the display device presents images, and the peripheral region  104  refers to a region that does not present images or refers to a region for accommodating peripheral circuits. The waterproof glue  120  and the adhesive material  122  may be respectively disposed along an edge P 1  of the display region  102  to make the waterproof glue  120  and the adhesive material  122  surround the display region  102 . For not affecting the presentation of the images, the waterproof glue  120  and the adhesive material  122  may not be disposed in the display region  102 , and may be just disposed in the peripheral region  104 . The waterproof glue  120  has a width TK 1 , and the adhesive material  122  has a width TK 2  (which are measured along the same direction such as the direction X, or a horizontal direction of the cover layer  100 ). The width TK 1  and the width TK 2  can be identical, or can be different, but not limited thereto. In this embodiment, the width TK 1  and the width TK 2  are both 2 mm. Besides, in a top view, the waterproof glue  120  may be disposed between the edge P 1  of the display region  102  and an edge P 2  of the adhesive material  122  which is away from the display region  102 , and the waterproof glue  120  is close to the display region  102 , and the protection effect is increased. A distance d between the edge P 2  of the adhesive material  122  and an edge P 3  of the cover layer  110  can be reserved according to the design requirement. In this embodiment, the distance d may be 1.5 cm to 3 mm, but not limited thereto. In other embodiment, the edge P 2  of the adhesive material  122  may also be aligned with the edge P 3  of the cover layer  110 . In order to describe the present disclosure more clearly, the structure of the device shown in  FIG. 1  is described in the following. Please noted that  FIG. 1  is a top view of the flexible liquid crystal display device  100  through the liquid crystal layer, and is a top view through the section plane BB′ of the liquid crystal layer  116  in  FIG. 2  for example. 
       FIG. 2  is a cross-sectional view schematic diagram of a flexible liquid crystal display device according to a first embodiment of the present disclosure, which can be a flexible liquid crystal display device that is drawn along the section line A-A′ of  FIG. 1 . The flexible liquid crystal display device  100  further includes a first flexible substrate  112 , a second flexible substrate  114  and a liquid crystal layer  116 . Wherein, the second flexible substrate  114  is disposed opposite to the first flexible substrate  112 , and the liquid crystal layer  116  is disposed between the first flexible substrate  112  and the second flexible substrate  114 . The cover layer  110  is disposed on the second flexible substrate  114 , and the cover layer  110  has a first surface  110   b  facing away from the second flexible substrate  114  and a second surface  110   a  facing the second flexible substrate  114 . The first flexible substrate  112  may include a first surface  112   b  and a second surface  112   a  opposite to each other, and the first surface  112   b  faces the second flexible substrate  114 . The second flexible substrate  114  may include a first surface  114   b  and a second surface  114   a  opposite to each other, and the first surface  114   b  faces the cover layer  110 , while the second surface  114   a  faces the first flexible substrate  112 . 
     An optical adhesive  118  is disposed between the second flexible substrate  114  and the cover layer  110 , and fixed the second flexible substrate  114  and the cover layer  110 . The waterproof glue  120  is adhered to a portion of the second surface  110   a  of the cover layer  110  and a side  114   c  of the second flexible substrate  114 . In this embodiment, the waterproof glue  120  can be further adhered to a portion of a side  112   c  of the first flexible substrate  112 . The adhesive material  122  is adhered to a portion of the second surface  110   a  of the cover layer  110  and a portion of the first flexible substrate  112 . In this embodiment, the adhesive material  122  is not only adhered to the side  112   c  of the first flexible substrate  112  and the second surface  112   a  of the first flexible substrate  112 , but also can be directly in contact with the waterproof glue  120 . As a result, in addition to strengthening the integral firmness of the flexible liquid crystal display device  100 , and the risk of the adhesive material  122  peeling from the first flexible substrate  112  may also be reduced. 
     According to this embodiment, the waterproof glue  120  is disposed between the adhesive material  122  and the first flexible substrate  112  and disposed between the adhesive material  122  and the second flexible substrate  114 , and the waterproof glue  120  can attach to the first flexible substrate  112  and the second flexible substrate  114 . According to the test results, disposing the waterproof glue  120 , for example, to at least cover the side  114   c  of the second flexible substrate  114  may reduce the moisture to be absorbed by the edge portion of the second flexible substrate  114 . Therefore, it can reduce the chance that the second flexible substrate  114  is peeling off from the cover layer  110 . For example, when taking the bending axis FL shown in  FIG. 2  as a center and applying force in the directions of the double arrows to flex the first flexible substrate  112  and the second flexible substrate  114 , peeling off of the second flexible substrate  114  from the portion marked with the regions A may be reduced. Therefore, the reliability or lifetime of the flexible liquid crystal display device  100  may be enhanced. It is noted that, the number of the folding axis FL can be more than one and is not limited to one, and the location thereof can be arbitrarily defined according to a user&#39;s manner. In addition, the directions of the double arrows in the drawing are merely illustrative and are not intended to restrict the practical direction of force application. 
     The waterproof glue  120  may be materials having waterproof properties, such as silicone gel, polyurethane (PU), polyethylene terephthalate (PET), polycarbonate (PC), polymethyl methacrylate (PMMA), etc. The adhesive material  122  may be materials having higher adhesion such as polymer material having adhesion, and to make the waterproof glue  120  to more closely and firmly attach to the side  114   c  of the second flexible substrate  114 , and reduce the waterproof glue  120  from peeling off from the side  114   c  of the second flexible substrate  114 . The adhesion of the adhesive material  122  described above is the result of comparison with the adhesion of the optical adhesive  118 , which means the adhesive material  122  has an adhesion better than the optical adhesive  118 . In particular, in addition to fixing the second flexible substrate  114  and the cover layer  110 , the optical adhesive  118  also need to have the function of light transmission, and by comparison, the adhesive material  122  is mainly used to strengthen the integral firmness of the flexible liquid crystal display device  100 , so it has higher requirement for adhesion. In this embodiment, the waterproof glue  120  is fluid, so it can be coated by a nozzle and then placed stand to make the waterproof glue  120  dry and solidify. The adhesive material  122  is disposed in the form of a sheet. In other embodiments, the adhesive material  122  also can present as fluid glue, and be disposed through a coating method, but not limited thereto. Besides, according to an embodiment of the present disclosure, since the waterproof glue  120  and the adhesive material  122  may be located at the peripheral region  104  of the flexible liquid crystal display device  100  (as shown in  FIG. 1  for example) and may not be disposed in the display region  102  of the flexible liquid crystal display device  100 , it is not necessary to consider the transmittance of the waterproof glue  120  and the adhesive material  122  when choosing the materials. 
     In addition, the main body of the cover layer  100  can be a cover glass, a protecting layer or a plastic substrate. The main body of the first flexible substrate  112  and the main body of the second flexible substrate  114  can be a plastic substrate respectively, and the water absorption rate of the first flexible substrate  112  and the second flexible substrate  114  may be higher than the water absorption rate of the cover layer  110 . In regard to the condition that the water absorption rate of the first flexible substrate  112  and the water absorption rate of the second flexible substrate  114  is higher than the water absorption rate of the cover layer  110 . The main body of the first flexible substrate  112  and/or the main body of the second flexible substrate  114  can be polyimide resin, polyester resin, polyethersulfone resin, cellulose resin, polyacrylate resin, polystyrene resin, polyolefin resin, polycarbonate resin and polysulfone resin, but not limited thereto. The main body of the cover layer  110  can be glass or the above described resin having lower water absorption rate than the first flexible substrate  112  and/or the second flexible substrate  114 . In this embodiment, the polyimide resin is used mainly. It is noted that, the cover layer  110 , the first flexible substrate  112  and the second flexible substrate  114  described above are rectangles for example, but not limited thereto, and they can also be presented in any other suitable shapes, such as triangles, rhombuses, trapezoids, wedges, other polygons or irregular shapes with arc edges. 
     Besides, the liquid crystal material in the liquid crystal layer  116  can be nematic liquid crystal, smectic liquid crystal, cholesteric liquid crystal, etc., but not limited thereto. In addition, the first flexible substrate  112  can include components or layers, such as switch elements (thin film transistors for example), a polarizer, conductive lines, etc. The second flexible substrate  114  can include components or layers, such as a color filter, a polarizer, a light shielding layer, conductive lines, etc., and they are not shown herein for conciseness. 
     The flexible liquid crystal display device is not limited to the above embodiments, and there may be different variation embodiments. For simplifying the description, the different variation embodiments in the following will use the same reference numerals as the first embodiment to symbol the same elements. In order to easily compare the differences between the first embodiment and the different variation embodiments, the following description will emphasize the differences of the different variation embodiments, and the repeated part will not be described redundantly. 
       FIG. 3  is a cross-sectional view schematic diagram of a flexible liquid crystal display device according to a second embodiment of the present disclosure. According to this embodiment, the waterproof glue  120  may be further adhered to the second surface  112   a  of the first flexible substrate  112 . By adhering the waterproof glue  120  to the second surface  112   a  of the first flexible substrate  112 , the moisture can be more resisted from entering the flexible liquid crystal display device  100 , and therefore the risk of peeling off of the second flexible substrate  114  at the regions A or adjacent the regions A can be reduced. In this embodiment, the portions of the waterproof glue  120  and the adhesive material  122  that are adhered to the second surface  110   a  of the cover layer  110  have a shape of curved surface. In addition, the portions of the waterproof glue  120  and the adhesive material  122  that are adhered to the second surface  112   a  of the first flexible substrate  112  (that is, the bottom regions R 1 ) have a shape of curved surface, and in addition to increasing the aesthetic effect of the appearance, it can also reduce the user be wounded when using the device, but the present disclosure is not limited thereto. 
       FIG. 4  is a cross-sectional view schematic diagram of a flexible liquid crystal display device according to a third embodiment of the present disclosure. According to this embodiment, the width of the first flexible substrate  112  in the direction X is greater than that of the second flexible substrate  114 , but not limited thereto. Furthermore, the waterproof glue  120  is adhered to a portion of the first surface  112   b  of the first flexible substrate  112 , and the adhesive material  122  is adhered to the side  112   c  of the first flexible substrate  112  and the second surface  112   a  of the first flexible substrate  112 . 
       FIG. 5  is a top view schematic diagram of a flexible liquid crystal display device according to a fourth embodiment of the present disclosure. The waterproof glue  120  and the adhesive material  122  are respectively disposed along the edge P 1  of the display region  102 , and the adhesive material  122  of this embodiment presents as a pattern of interrupted lines in a top view, and a portion of the edge P 1  of the display region  102  may not be covered by the adhesive material  122 . The interrupted lines can present as an arrangement of dashed lines or dash dotted lines, and there is a space S 1  between adjacent segments of the adhesive material  122 , but not limited thereto. The spaces S 1  can be equal or not equal to each other according to the design, and are not limited. In this embodiment, the waterproof glue  120  is disposed along the edge P 1  of the display region  102  and does not has a pattern of interrupted lines, and the resisting ability of the moisture from entering the flexible liquid crystal display device  100  is increased. 
       FIG. 6  is a top view schematic diagram of a flexible liquid crystal display device according to a fifth embodiment of the present disclosure. The waterproof glue  120  of this embodiment presents as a pattern of interrupted lines in a top view. Furthermore, the waterproof glue  120  of this embodiment is double layered structured, which has a plurality segments of inner waterproof glue  120 - 1  at the inner layer and a plurality segments of outer waterproof glue  120 - 2  at the outer layer, but not limited thereto. There may be a space S 1  between any two adjacent segments of the inner waterproof glue  120 - 1 , and there may be a space S 2  between any two adjacent segments of the outer waterproof glue  120 - 2 . The spaces S 1  and the spaces S 2  can be adjusted moderately according to the requirement. It is noted that, the inner waterproof glue  120 - 1  and the outer waterproof glue  120 - 2  may be connected with each other to surround the entire display region  102 . In such design, there is a larger contact area between the water proof glue  120  and the adhesive material  122 , and the adhesion is enhanced. And the waterproof glue  120  can be more closely disposed at the edge P 1  of the display region  102 . Furthermore, since the flexible liquid crystal display device  100  may be flexed during using, the moisture may easily be permeated from the turning positions of the peripheral region  104  (such as the corner regions C 1 , C 2 , C 3 , C 4 ). Therefore, in this embodiment, at the corner regions C 1 , C 2 , C 3 , C 4  in the peripheral region  104 , the locations close to the display region  102  are all disposed with the waterproof glue  120  to strengthen the waterproof function at the turning positions. 
       FIG. 7  is a cross-sectional view schematic diagram of a flexible liquid crystal display device according to an embodiment of the present disclosure. More components in the flexible liquid crystal display device  100  are further drawn in this embodiment, and more particular to the components in the first flexible substrate  112  and the second flexible substrate  114 . Referring to  FIG. 7 , the first flexible substrate  112  may include a polarizer  1121 , a substrate  1122 , and a switch element layer  1123 , wherein the polarizer  1121  and the switch element layer  1123  can be respectively disposed on the two opposite surfaces of the substrate  1122 , but not limited thereto. Furthermore, there are a plurality of switch elements  1124  such as thin film transistors having a bottom gate in the switch element layer  1123 . Referring to the lower right figure in  FIG. 7 , each switch element  1124  can include a bottom gate  1124 - 1  disposed on the substrate  1122 , a gate dielectric layer  1124 - 2  disposed above the bottom gate  1124 - 1 , a source/drain  1124 - 3  disposed on both sides above the bottom gate  1124 - 1  and a semiconductor layer  1124 - 4  sandwiched between the gate dielectric layer  1124 - 2  and the source/drain  1124 - 3 . The second flexible substrate  114  selectively includes a polarizer  1141 , a substrate  1142 , a light shielding layer  1143  and a color filter  1144 . The polarizer  1141  and the color filter  1144  can be respectively disposed on the two opposite surfaces of the substrate  1142 . The liquid crystal layer  116  can further include liquid crystal material  1161  and a sealant  1162 , wherein the sealant  1162 , the first flexible substrate  112  and the second flexible substrate  114  may enclose the liquid crystal material  1161  in a space. The flexible liquid crystal display device  100  further includes an outer frame  130  and a backlight device  132 . The light from the backlight device  132  cannot transmit through the regions blocked by the light shielding layer  1143 , so a plurality of pixel illuminating regions  140  are defined in the display region  102  by the light shielding layer  1143 . 
     The cover layer  110  can be exposed from an opening S of the outer frame  130 , and the presented images of the display region  102  can be viewed from this opening S. The backlight device  132  is disposed between the outer frame  130  and the first flexible substrate  112  to provide the light required for presenting images. According to this embodiment, the waterproof glue  120  and the adhesive material  122  are not directly in contact with the outer frame  130  and the backlight device  132 . However, the waterproof glue  120  or the adhesive material  122  can be directly in contact with the outer frame  130  or the backlight device  132  in other embodiments. In particular, a polarized light may be formed from the light produced by the backlight device  132  through the polarizer  1121  first, and the turning directions of the liquid crystal material  1161  at corresponding regions are controlled by the switch elements  1124  to rotate the polarization direction of partial of the polarized light, and the partial of the polarized light can sequentially pass through the components or layers such as the color filter  1144  and the polarizer  1141 , and to present the images. It is noted that, a portion of the light shielding layer  1143  is disposed in the peripheral region  104  and disposed closely adjacent to the edge P 1  of the display region  102 , so an edge  1143 S of the portion of the light shielding layer  1143  may be aligned with the edge P 1  of the display region  102 , or also be aligned with an edge  130 S of the outer frame  130  simultaneously. 
     According to the flexible liquid crystal display device  100  disclosed by the embodiments described above, since the waterproof glue  120  may at least attach to the side  114   c  of the second flexible substrate  114 , peeling off of the second flexible substrate  114 , especially the side  114   c  of the second flexible substrate  114  from the surface of the cover layer  110  may be mitigated, and the reliability or lifetime of the flexible liquid crystal display device  100  may be increased. 
     Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the disclosure. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.