Patent Publication Number: US-2023147590-A1

Title: Touch panel and touch display device

Description:
FIELD OF THE INVENTION 
     The present invention relates to a display technique, and more particularly, to a touch panel and a touch display device. 
     BACKGROUND 
     In general, the touch display device has a wide view angle such that multiple viewers could watch the touch display device at the same time. However, in some scenarios, the wide angle may introduce some issues. For example, when a user is viewing a private website/information or inputting a password, the wide angle may allow another user to know the confidential information. For the privacy reason, a privacy protection film is also positioned in front of the display to reduce the view angle by filtering out large-angle light. 
     As shown in  FIG.  1   , the conventional privacy protection film  10  adopts the shutter mechanism. That is, the privacy protection film  10  has a shutter structure, which comprises a plurality of parallel grids  11 . The light could pass through the gaps  12  between two adjacent grids  11 . Through adjusting the shape of the grids  11  and the size of the gaps  12 , the large-angle light could be filtered out. 
     However, the conventional privacy protection film  10  has a certain thickness and thus increases the entire thickness of the display device. In this way, the user experience is reduced. 
     SUMMARY 
     The conventional privacy protection film  10  has a certain thickness and thus increases the entire thickness of the display device. In this way, the user experience is reduced. One objective of an embodiment of the present invention is to provide a touch panel and a touch display device to solve the above issue. 
     According to an embodiment of the present invention, a touch panel is disclosed. The touch panel comprises: a display module, a package cover plate, placed on a light-emitting side of the display module. The display module comprises a display screen and a first polarizer placed on a side of the display screen, which is close to the package cover plate. A first frame glue is placed between the package cover plate and the display module, and the first frame glue, the package cover plate and the display module form a cavity. A first liquid crystal (LC) is filled in the cavity; the first liquid crystal comprises a plurality of first liquid crystal molecules, and orthogonal projections of light axes of some of the first liquid crystal molecules intersect a polarization direction of the first polarizer. 
     In some embodiments of the present disclosure, the orthogonal projections of the light axes of some of the first liquid crystal molecules are perpendicular to the polarization direction of the first polarizer. 
     In some embodiments of the present disclosure, a second polarizer is placed on a side of the package cover plate, which is comparatively far from the display module, and a polarization direction of the second polarizer is perpendicular to the polarization direction of the first polarizer. 
     In some embodiments of the present disclosure, a first alignment film layer is placed between the display module and the first LC. A second alignment film layer is placed between the first LC and the package cover plate. The first alignment film layer and the second alignment film are oppositely arranged. 
     In some embodiments of the present disclosure, a first electrode layer is placed between the display module and the first LC. A second electrode layer is placed between the first LC and the package cover plate. 
     In some embodiments of the present disclosure, the display module further comprises a touch layer placed on a side of the display screen, which is close to the package cover plate. 
     In some embodiments of the present disclosure, the touch layer is placed between the display screen and the package cover plate. The first polarizer is placed between the touch layer and the package cover plate. The first frame glue, the package cover plate and the touch layer form the cavity. 
     In some embodiments of the present disclosure, the display module further comprises a third polarizer placed on a side of the package cover plate, which is comparatively far away from the display screen. A polarization direction of the third polarizer is perpendicular to the polarization direction of the first polarizer. 
     In some embodiments of the present disclosure, a light blocking layer is placed at an edge of the package cover plate, and an orthogonal projection of the light blocking layer on the package cover plate covers an orthogonal projection of the first frame glue on the package cover plate. 
     According to an embodiment of the present invention, a touch display device is disclosed. The touch display device comprises a backlight module and a touch panel. The backlight module is placed on a back side of the touch panel. The touch panel comprises: a display module; a package cover plate, placed on a light-emitting side of the display module; wherein the display module comprises a display screen and a first polarizer placed on a side of the display screen, which is close to the package cover plate; wherein a first frame glue is placed between the package cover plate and the display module, and the first frame glue, the package cover plate and the display module form a cavity; a first liquid crystal (LC) is filled in the cavity; the first liquid crystal comprises a plurality of first liquid crystal molecules, and orthogonal projections of light axes of some of the first liquid crystal molecules intersect a polarization direction of the first polarizer. 
     In some embodiments of the present disclosure, the orthogonal projections of the light axes of some of the first liquid crystal molecules are perpendicular to the polarization direction of the first polarizer. 
     In some embodiments of the present disclosure, a second polarizer is placed on a side of the package cover plate, which is comparatively far from the display module, and a polarization direction of the second polarizer is perpendicular to the polarization direction of the first polarizer. 
     In some embodiments of the present disclosure, a first alignment film layer is placed between the display module and the first LC. A second alignment film layer is placed between the first LC and the package cover plate. The first alignment film layer and the second alignment film are oppositely arranged. 
     In some embodiments of the present disclosure, a first electrode layer is placed between the display module and the first LC. A second electrode layer is placed between the first LC and the package cover plate. 
     In some embodiments of the present disclosure, the display module further comprises a touch layer placed on a side of the display screen, which is close to the package cover plate. 
     In some embodiments of the present disclosure, the touch layer is placed between the display screen and the package cover plate. The first polarizer is placed between the touch layer and the package cover plate. The first frame glue, the package cover plate and the touch layer form the cavity. 
     In some embodiments of the present disclosure, the display module further comprises a third polarizer placed on a side of the package cover plate, which is comparatively far away from the display screen. A polarization direction of the third polarizer is perpendicular to the polarization direction of the first polarizer. 
     In some embodiments of the present disclosure, a light blocking layer is placed at an edge of the package cover plate, and an orthogonal projection of the light blocking layer on the package cover plate covers an orthogonal projection of the first frame glue on the package cover plate. 
     In some embodiments of the present disclosure, an orthogonal projection of the display module on the package cover plate lies in the package cover plate. 
     In some embodiments of the present disclosure, the first frame glue is placed at an edge of the display module and surrounding a lighting area of the display module. 
     The first liquid crystal (LC) is filled in the cavity and is used to adjust the polarization direction and the transmission direction of the incident light. Light with different incident angles will be differently changed by the first LC such that the light with larger incident angle could be filtered out to protect the privacy. In contrast to the privacy protection film, the first LC could achieve the same purpose without increasing the thickness of the display device. Furthermore, when the user is viewing the touch panel, the luminance of the outgoing light will not be enormously reduced and the color will not be distorted. Thus, the user experience could be raised. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       To help a person skilled in the art better understand the solutions of the present disclosure, the following clearly and completely describes the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are a part rather than all of the embodiments of the present invention. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present disclosure. 
         FIG.  1    is a diagram of a conventional privacy protection film. 
         FIG.  2    is a diagram of a touch panel of a first structure according to the first embodiment of the present invention. 
         FIG.  3    is a diagram of a touch panel of a second structure according to the first embodiment of the present invention. 
         FIG.  4    is a diagram of a touch panel of a third structure according to the first embodiment of the present invention. 
         FIG.  5    is a diagram of a touch panel according to the second embodiment of the present invention. 
         FIG.  6    is a diagram of a touch panel when the touch panel is in a large view angle mode according to the second embodiment of the present invention. 
         FIG.  7    is a diagram of a touch panel when the touch panel is in a privacy protection mode according to the second embodiment of the present invention. 
         FIG.  8    is a diagram of a touch display device according to an embodiment of the present invention. 
     
    
    
     REFERENCE SIGNS OF ELEMENTS 
       10  protection film;  11  grid;  12  gap;  20  touch panel;  21  display module;  211  display screen;  211   a  array substrate;  211   b  color film substrate;  211   c  second frame glue;  211   d  second LC;  212  first polarizer;  213  third polarizer;  214  optical glue;  215  touch layer;  22  package cover plate;  23  first frame glue;  24  cavity;  25  first LC;  261  first alignment film layer;  262  second alignment film layer;  271  first electrode layer;  272  second electrode layer;  273  third electrode layer;  274  fourth electrode layer;  28  second polarizer;  29  light blocking layer;  31  incident light;  32  outgoing light;  40  backlight module. 
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Spatially relative terms, such as “beneath”, “below”, “lower”, “above”, “upper” and the like, may be used herein for ease of description to describe one element or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the exemplary term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. 
     The conventional privacy protection film  10  has a certain thickness and thus increases the entire thickness of the display device. In this way, the user experience is reduced. One objective of an embodiment of the present invention is to solve the above issue. 
     Embodiment 1 
     As shown in  FIG.  2   , the touch panel  20  comprises a display module  21  and a package cover plate  22 . The package cover plate  22  is placed on a light-emitting side of the display module  21 . 
     The display module  21  could be an LCD module  21 . The package cover plate  22  could be a transparent plastic cover plate or a transparent glass cover plate. The orthogonal projection of the display module  21  on the package cover plate  22  lies in the package cover plate  22 . That is, the size of the package cover plate  22  is larger than the size of the display module  21 . The package cover plate  22  is used to protect the display module  21  from being squeezed or hit and moisture. 
     The first frame glue  23  is placed between the package cover plate  22  and the display module  21 . The first frame glue  23  is placed at the edge of the display module  21  and surrounding the lighting area of the display module. In contrast to apply the optical glue to the entire surface of the package cover plate  22  to paste the package cover plate  22  on the display module  21 , the manufacturing process in this embodiment is more mature and the operation is more simple. Furthermore, the first frame glue  23 , the package cover plate  22  and the display module  22  form a cavity  24  and the first liquid crystal (LC)  25  is filled in the cavity. This could prevent the package cover plate  22  from sinking into the cavity  24  due to the atmospheric pressure. 
     As shown in  FIG.  3   , the display module  21  comprises a display screen  211  and a first polarizer  212  placed on a side of the display screen  211 , where the side is comparatively close to the package cover plate  22 . The first LC  25  has a first state. When the first LC  25  is in the first state, the orthogonal projections of light axes of at least some of the first LC molecules on the first polarizer  212  are perpendicular to the polarization direction of the first polarizer  212 . 
     The first LC  25  could comprise twisted nematic (TN) liquid crystals. Through filling the first LC  25  in the cavity  24 , the first LC  25  could be used to adjust the polarization direction and the transmission direction of the incident light. In this way, light with different incident angles will be differently adjusted such that the outgoing light of the display module  21 , which has a larger outgoing angle, could be filtered out to achieve the privacy protection. In contrast to the display panel using the conventional privacy protection film, filling the first LC  25  into the cavity  24  to achieve the same privacy protection does not increase the thickness of the touch display device. Furthermore, when the user is viewing the touch panel  20  (for example, the angle between the viewing direction of the user and the normal direction of the touch panel is equal to or less than 10 degrees), the luminance of the outgoing light of the touch panel  20  will not be enormously reduced and the color will not be distorted. Thus, the user experience could be raised. 
     The first LC  25  could comprise twisted nematic (TN) liquid crystals. The TN liquid crystals have the polarization rotation characteristic, which is used to adjust the polarization direction of the first outgoing light of the display module. Furthermore, light passing through the first LC  25  with different incident angles will have different degrees of phase delays and thus the outgoing light corresponding to the incident light will be differently adjusted. In this way, the first LC  25  could be determined to filter out the first outgoing light having larger outgoing angle, of the display module, such that the privacy protection could be accomplished. 
     When the first LC  25  comprises the TN liquid crystals, the orthogonal projections of light axes of at least some of the first LC molecules on the first polarizer  212  are perpendicular to the polarization direction of the first polarizer  212 . 
     The refractive index of the liquid crystal changes according to its direction such that the variance of the polarization direction of the incident light of the first LC  25  is related to the distribution of the liquid crystal molecules. In this way, the outgoing light of the first LC  25  has different transmission routes. Because the twisting pitch of the TN LC molecule is much larger than the wavelength of the outgoing light of the display module  21 , when the light axes of some of the LC molecules are perpendicular to the polarization direction of the first polarizer  212  within the same plane, the polarization direction of the incident light will be rotated by 90 degrees by the first LC  25 . Therefore, the better privacy protection could be achieved. 
     When the first LC comprises the TN liquid crystals, a second polarizer  28  could be further placed on a side of the package cover plate  22 , where the side is comparatively far away from the display module  21 . The polarization direction of the second polarizer  28  is perpendicular to the polarization direction of the first polarizer  212 . 
     The polarization direction of the outgoing light of the display module  21  will be rotated by 90 degrees after passing through the LC molecules of the first LC  25 . At this time, the polarization direction of the outgoing light is perpendicular to the polarization direction of the first polarizer  212 . The second polarizer  28  could be used to analyze the light passing through the first LC  25 . The light having the same polarization direction of the second polarizer  28  is able to pass through the second polarizer  28 . The light having different polarization directions from the polarization direction of the second polarizer  28  will be blocked by the second polarizer  28  to prevent the light from influencing the normal display of the touch panel  20 . 
     The second polarizer  28  is a linear polarizer. The ambient light is basically similar to the circularly polarized light. When the ambient light tries to pass through the second polarizer  28 , about a half of the ambient light will be blocked by the second polarizer  28 . This means that only a part of the ambient light could pass through the second polarizer  28  and enters the cavity  24 . The passing ambient light is reflected between the package cover plate  22  and the display module  21 . By using the second polarizer  28  to reduce the amount of ambient light entering the cavity  24 , the user may not view a whitening phenomenon on the touch panel  20  when the user views the touch panel  20  in a reflecting view angle (such as a large view angle). Thus, this increases the viewable angle of the touch panel and raises the user experience. 
     The first LC  25  could comprise Polymer Dispersed Liquid Crystal (PDLC). The PDLC could perform a scattering operation on the incident light of the first LC  25  to change the transmission direction of the incident light. Thus, by arranging the distribution of the first LC molecules, the light having a larger view angle could be shifted to the central area of the touch panel. In this way, the privacy protection could be accomplished as well. 
     The display module  21  further comprises a third polarizer  213 . The third polarizer  213  is placed on a side of the package cover plate  22 , where the side is comparatively far away from the display screen  211 . The polarization direction of the first polarizer  212  is perpendicular to the polarization direction of the third polarizer  213 . The third polarizer  213  is used to convert the light generated by the light source of the touch panel  20  into the polarized light. 
     The display module  21  further comprises a touch layer  215  placed on a side of the package cover plate  22 , where the side is comparatively close to the display screen  211  such that the touch panel  20  has the touch control function. 
     The touch layer  215  could comprise one or more types of capacitor-type touch sensing components, resistor-type touch sensing components, acoustics-type touch sensing components, mechanic-type touch sensing components, and optical-type touch sensing components. The touch layer  215  could be pasted on the display screen  212  through the frame glue frame. The touch layer  215  could be totally pasted on display screen  211  through the optical glue  214 . 
     The touch layer  215  is placed between the display screen  211  and the package cover plate  22 . The first frame glue  23 , the package cover plate  22  and the touch layer  215  form the cavity  24 . The first polarizer  212  is placed between the touch layer  215  and the package cover plate  22  to prevent the first polarizer  212  from influencing the sensitivity of the touch layer  215 . 
     The first alignment film layer  261  is placed on a side of the display module  12 , where the side is comparatively close to the package cover plate  22 . The second alignment film layer  262  is placed on a side of the package cover plate  22 , where the side is comparatively close to the display module  21 . The first alignment film layer  261  and the second alignment film layer  262  are oppositely arranged. 
     When the first LC  25  is formed, the first alignment film layer  261  and the second alignment film layer  262  could be used to arrange the LC molecules of the first LC  25  in a specific direction such that the LC molecules of the first LC  25  could be always distributed in the specific direction. In this way, the touch panel  20  is always in the privacy-protection mode. 
     As shown in  FIG.  4   , the display screen  211  comprises an array substrate  211   a  and a color film substrate  211   b . The array substrate  211   a  and the color film substrate  211   b  are oppositely arranged. A second frame glue  211   c  is placed between the array substrate  211   a  and the color film substrate  211   b . The second frame glue  211   c , the array substrate  211   a  and the color film substrate  211   b  form a storage cavity. A second LC  211   d  is placed in the storage cavity. 
     The first polarizer  212  is placed on a side of the array substrate  211   a , where the side is comparatively far away from the color film substrate  211   b . The third polarizer  211  is placed on a side of the color film substrate  211   b , where the side is comparatively far away from the array substrate  211   a.    
     The materials of the first frame glue  22  and the second frame glue  211   c  could be the same or different. The orthogonal projection of the first frame glue  23  on the second frame glue  211   c  lies in the second frame glue  211 . This could prevent the second frame glue  211   c  from influencing the normal display of the touch panel  20 . 
     The materials of the second LC  211   d  and the first LC  25  could be the same or different. 
     A light blocking layer  29  is placed at the edge of the package cover plate  22 . The orthogonal projection of the light blocking layer  29  on the package cover plate  22  covers the orthogonal projection of the first frame glue  23  on the package cover plate  22  to prevent the leakage light at the edge. 
     As shown in  FIG.  5   , a first electrode layer  271  is placed between the display module  21  and the first LC  25 . A second electrode layer  272  is placed between the package cover plate  22  and the first LC  25 . 
     The materials of the first electrode layer  271  and the second electrode layer  272  could be metal oxide or any other transparent conductive material. 
     The electric field between the first electrode layer  271  and the second electrode layer  272  could be used to rotate the LC molecules to arrange the first LC molecules of the first LC  25  distribute according to different angles. In this way, the touch panel  20  could be easily switched between the large-view-angle mode (for example, the angle between the viewing direction of the user and the normal direction of the touch panel is larger than or equal to 40 degrees and the user could still clearly view the image shown on the touch panel  20 ) and the privacy protection mode (for example, the angle between the viewing direction of the user and the normal direction of the touch panel is equal to or less than 10 degrees and the user cannot view the display image on the touch panel  20 ) without installing or removing the privacy protection film. This is more efficient and convenient and is more easily used in the full-screen touch panel. 
     Furthermore, the first alignment film layer  261  could be placed on the display module  21  and the second alignment film layer  262  is placed on the package cover plate  22 . Or, the first alignment film layer  261  and the second alignment film layer  262  do not need to be used. 
     Under the condition that the first alignment film layer  261  could be placed on the display module  21  and the second alignment film layer  262  is placed on the package cover plate  22 , the first alignment film layer  261  covers the first electrode layer  271  and the second alignment film layer  262  covers the second electrode layer  272 . 
     In an embodiment, the first LC  25  comprises the TN LC. When the user needs to use the large-view-angle mode of the touch panel  20 , the first electrode layer  271  and the second electrode layer  272  are powered. The LC molecules in the first LC  25  are distributed according to the electric field between the first electrode layer  271  and the second electrode layer  272 . The light axes of all the first LC molecules are perpendicular to the surface of the touch panel  20 . The first LC loses its optical rotation function and the outgoing light from the display module  21  follows its original route to pass through the first LC  25 . At this time, the view angle of the touch panel  20  is larger. When the user needs to use the privacy protection mode of the touch panel  20 , the first electrode layer  271  and the second electrode layer  272  are not powered. The LC molecules in the first LC  25  are distributed according to predetermined angles. The polarization direction of the outgoing light from the display module  21  is rotated when the outgoing light passes through the first LC such that the touch panel  20  enters the privacy protection mode. 
     In another embodiment, the first LC comprises PDLC. As shown in  FIG.  6   , when the user needs to use the large-view-angle mode of the touch panel  20 , the first electrode layer  271  and the second electrode layer  272  are not powered. Without any applied voltage, the light axis of each of the first LC molecules is distributed in its prioritized trend. That is, the light axes of all the first LC molecules are distributed in disorder and at least the light axes of some of the first LC molecules are different. Because the PDLC is a dielectric anisotropy material, the incident light  31  incident into the first LC  25  will be scattered and become outgoing light  32  direct to different directions. This increases the luminance view angle of the touch panel  20  and thus makes the touch panel  20  enter the large-view-angle mode. 
     As shown in  FIG.  7   , when the user needs to use the privacy protection mode of the touch panel  20 , the first electrode layer  271  and the second electrode layer  272  are powered. The LC molecules in the first LC  25  are orderly distributed according to the electric field and the light axes of all the LC molecules along the electric field. After the incident light  31  into the first LC  25  passes through the first LC  25 , the route of the outgoing light  25  is parallel to the route of the incident light  31 . At this time, the view angle of the touch panel  20  is small and thus the touch panel  20  enters the privacy protection mode. 
     Under the condition that the first LC  25  comprises PDLC, the PDLC could be set to be arranged in predetermined angles when the first electrode layer  271  and the second electrode layer  272  are not powered. This makes the light having a large view angle is deflected toward to the center area of the touch panel  20  after passing through the first LC  25  such that the touch panel  20  enters the privacy protection mode. Furthermore, when the first electrode layer  271  and the second electrode layer  272  are powered, the luminance view angle of the touch panel  20  is larger and thus the touch panel  20  enters the large-view-angle mode. 
     The first liquid crystal (LC)  25  is filled in the cavity  24  and is used to adjust the polarization direction and the transmission direction of the incident light. Light with different incident angles will be differently changed by the first LC  25  such that the light with larger incident angle could be filtered out to protect the privacy. In contrast to the privacy protection film, the first LC could achieve the same purpose without increasing the thickness of the display device. Furthermore, when the user is viewing the touch panel  20 , the luminance of the outgoing light will not be enormously reduced and the color will not be distorted. Thus, the user experience could be raised. 
     Based on the above-mentioned touch panel  20 , a touch display device is disclosed. As shown in  FIG.  8   , the touch display device comprises a backlight module  40  and a touch panel  20  according to any one of the above-mentioned embodiments. The backlight module  40  is placed on the back side of the touch panel  20 . 
     Above are embodiments of the present invention, which does not limit the scope of the present invention. Any modifications, equivalent replacements or improvements within the spirit and principles of the embodiment described above should be covered by the protected scope of the invention. In addition, the above embodiments might have different focuses and thus might not be illustrated in details. For those not illustrated in details, a person having ordinary skills in the art could refer to any related description regarding another embodiment.