Patent Publication Number: US-2021191192-A1

Title: Optical adjusting film, backlight module and display device

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This is a National Phase Application filed under 35 U.S.C. 371 as a national stage of PCT/CN2020/103434, filed on Jul. 22, 2020, an application claiming priority to Chinese patent application No. 201910712077.4, filed on Aug. 2, 2019, the disclosure of which is incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure belongs to the field of display technology, and particularly relates to an optical adjusting film, a backlight module and a display device. 
     BACKGROUND 
     An anti-peek film may be arranged between a liquid crystal display panel and a backlight module, and may control the light emitted by the backlight module to have a designated directivity, so that other people can be prevented from peeking into the current display content from a relatively inclined visual angle. 
     SUMMARY 
     According to a first aspect of the present disclosure, there is provided an optical adjusting film including: 
     a first substrate and a second substrate opposite to each other; 
     a first electrode layer on a side of the first substrate facing the second substrate; 
     a second electrode layer on a side of the second substrate facing the first substrate; 
     a polymer dispersed liquid crystal layer between the first electrode layer and the second electrode layer; and 
     an anti-adsorption surface layer on a side of the first substrate away from the second substrate, and/or on a side of the second substrate away from the first substrate, the anti-adsorption surface layer being configured to suppress adsorption between the optical adjusting film and a solid surface. 
     In an embodiment, the anti-adsorption surface layer includes a substrate layer and a plurality of anti-adsorption particles, and the plurality of anti-adsorption particles are beyond a surface of the substrate layer away from the polymer dispersed liquid crystal layer. 
     In an embodiment, a diameter of the anti-adsorption particle is greater than a thickness of the substrate layer. 
     In an embodiment, a material of the substrate layer includes an ultraviolet curable resin or a thermosetting resin. 
     In an embodiment, the substrate layer further includes at least one of a photopolymerization initiator, a curing agent, a cross-linking agent, and a photosensitizer. 
     In an embodiment, a material of the anti-adsorption particle includes any one of silicone, polystyrene, polycarbonate, and calcium carbonate. 
     In an embodiment, a height h of the anti-adsorption particle beyond the surface of the substrate layer satisfies: h≥1 μm. 
     In an embodiment, a diameter D of the anti-adsorption particle satisfies: 2 μm≤D≤4 μm. 
     In an embodiment, static friction coefficient k between the anti-adsorption surface layer and a lower polarizer satisfies: k≤0.35. 
     In an embodiment, static friction coefficient k between the anti-adsorption surface layer and an anti-peek film satisfies: k≤0.35. 
     In an embodiment, a contact angle α of distilled water with respect to a surface of the anti-adsorption surface layer away from the polymer dispersed liquid crystal layer satisfies: a≥70°. 
     In an embodiment, the first substrate includes a base material layer, an anti-scratch layer, and an undercoat layer stacked in this order in a direction from the first substrate to the polymer dispersed liquid crystal layer. 
     In an embodiment, the second substrate includes a base material layer, an anti-scratch layer, and an undercoat layer stacked in this order in a direction from the second substrate to the polymer dispersed liquid crystal layer. 
     In an embodiment, materials of the base material layer and the anti-scratch layer include polyethylene terephthalate. 
     In an embodiment, a material of the undercoat layer includes polyester resin or silicone resin. 
     According to a second aspect of the present disclosure, there is provided a backlight module including an optical adjusting film and an anti-peek film stacked with each other, and the optical adjusting film is the optical adjusting film provided according to the first aspect of the present disclosure, 
     the optical adjusting film includes the anti-adsorption surface layer on the side of the second substrate away from the first substrate, and 
     the anti-peek film is on a side of the anti-adsorption surface layer away from the second substrate. 
     In an embodiment, the backlight module further includes an optical film on a side of the anti-peek film away from the anti-adsorption surface layer. 
     In an embodiment, the optical film is a prism sheet, a diffusion sheet, or a light guide plate. 
     According to a third aspect of the present disclosure, there is provided a display device including a display panel and an optical adjusting film stacked with each other, and the optical adjusting film is the optical adjusting film provided according to the first aspect of the present disclosure. 
     In an embodiment, the display device further includes a lower polarizer, an anti-peek film and an optical film, 
     the display panel, the lower polarizer, the optical adjusting film, the anti-peek film and the optical film are sequentially stacked, and 
     the optical adjusting film includes the anti-adsorption surface layer on the side of the first substrate away from the second substrate, and on the side of the second substrate away from the first substrate. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic structural diagram of an optical adjusting film according to an embodiment of the present disclosure; 
         FIG. 2  is a schematic diagram of a detailed structure of part of an optical adjusting film according to an embodiment of the present disclosure; 
         FIG. 3  is a schematic diagram of a detailed structure of part of an optical adjusting film according to an embodiment of the present disclosure; 
         FIG. 4  is a schematic structural diagram of a backlight module according to an embodiment of the present disclosure; and 
         FIG. 5  is a schematic structural diagram of a display device according to an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     To make those skilled in the art better understand the technical solutions of the present disclosure, the present disclosure will be further described in detail with reference to the accompanying drawings and the specific embodiments. 
     In order to enable the liquid crystal display device to switch between an anti-peek display mode and a non-anti-peek display mode, an optical adjusting film is provided between the liquid crystal display panel and the anti-peek film in the related art. The optical adjusting film has the function of changing the divergence degree of light, so that light with strong directivity emitted from the anti-peek film has controllable divergence characteristics after passing through the optical adjusting film. 
     There is a problem of adsorption between the optical adjusting film and the anti-peek film and a problem of adsorption between the optical adjusting film and display panel or the lower polarizer on the display panel, which may cause a poor display of water stain type. 
     Referring to  FIGS. 1 to 3 , the present embodiment provides an optical adjusting film including a first substrate  13  and a second substrate  16  opposite to each other, a first electrode layer  12  on a side of the first substrate  13  facing the second substrate  16 , a second electrode layer  15  on a side of the second substrate  16  facing the first substrate  13 , and a polymer dispersed liquid crystal layer  11  between the first electrode layer  12  and the second electrode layer  15 . 
     In an embodiment, the polymer dispersed liquid crystal layer  11  may be formed by mixing a liquid crystal and a high-molecular polymer. 
     In practical applications, the polymer dispersed liquid crystal layer  11  between the first electrode layer  12  and the second electrode layer  15  is controlled to be in an ordered state or a disordered state by applying different voltages between the first electrode layer  12  and the second electrode layer  15 . When the polymer dispersed liquid crystal layer  11  is in the ordered state, it has no scattering effect on light, and the collimated light emitted to the optical adjusting film still maintains a collimated state when having passed through the optical adjusting film. When the polymer dispersed liquid crystal layer  11  is in the disordered state, it has a scattering effect on light, and the collimated light emitted to the optical adjusting film has a large divergence angle when having passed through the optical adjusting film. 
     With reference to  FIGS. 4 and 5 , the optical adjusting film may be applied to a backlight module or a display device, with one surface facing the anti-peek film  21  and the other surface facing the display panel  32 . By taking the liquid crystal display panel as an example, a lower surface of the liquid crystal display panel is usually attached with a lower polarizer  31 . In order to avoid the adsorption between the optical adjusting film and the anti-peek film  21  or the lower polarizer  31 , the optical adjusting film according to the embodiment is further provided with an anti-adsorption surface layer  14 . 
     That is, the optical adjusting film further includes the anti-adsorption surface layer  14  on a side of the first substrate  13  away from the second substrate  16  and/or a side of the second substrate  16  away from the first substrate  13 , and the anti-adsorption surface layer  14  is configured to suppress adsorption between the optical adjusting film and a solid surface. 
     In an embodiment, the anti-adsorption surface layer  14  includes a substrate layer  141  and a plurality of anti-adsorption particles  142 , and the anti-adsorption particles  142  are beyond a surface of the substrate layer  141  away from the polymer dispersed liquid crystal layer  11 . That is, the surface of the optical adjusting film is rendered to be a relatively rough surface by the anti-adsorption particles  142  (specifically, hard tiny particles), so that the adsorption effect between the optical adjusting film and the solid surface can be suppressed. 
     In an embodiment, a diameter of the anti-adsorption particle  142  is greater than a thickness of the substrate layer  141 . In this manner, it can be ensured that the anti-adsorption particles  142  can go beyond the surface of the substrate layer  141  away from the polymer dispersed liquid crystal layer  11  in a case where the anti-adsorption particles  142  and the substrate layer  141  are formed as a single piece. 
     In an embodiment, the material of the substrate layer  141  includes an ultraviolet curable resin or a thermosetting resin, for example, ultraviolet curing resin materials such as acrylic resins, urethane acrylate resins, and polyester acrylate (PEA) resins, and thermosetting resin materials such as urethane resins and polyurethane (PU) resins. In an embodiment, other additives may be included in the substrate layer  141 , such as photopolymerization initiators, curing agents, crosslinking agents, photosensitizers, and the like, or combinations thereof. In this embodiment, the substrate layer  141  also serves as a hard coat. The anti-adsorption surface layer  14  may be prepared by incorporating the anti-adsorption particles  142  into these materials and then hardening them. Note that, in this embodiment, the surface of the finally prepared anti-adsorption surface layer  14 , on which the substrate layer  141  and the anti-adsorption particles  142  are exposed, is usually adhered with a very thin layer of the material of the substrate layer  141 . 
     In an embodiment, the material of the anti-adsorption particles  142  includes any one of silicone, polystyrene (PS), polycarbonate (PC), calcium carbonate (CaCO 3 ). The anti-adsorption particles  142  made of these materials are commercially available. 
     In an embodiment, the height h of the anti-adsorption particle  142  beyond the surface of the substrate layer  141  satisfies: h≥1 μm. Inventors found that if the height of the anti-adsorption particle  142  beyond the surface of the substrate layer  141  is too small, the anti-adsorption effect between the optical adjusting film and the lower polarizer  31  or the anti-peek film  21  is not significant. Table 1 below shows specific experimental results. 
     TABLE 1 influence of the size of the anti-adsorption particle on the adsorption and display effects 
     
       
         
           
               
               
               
               
               
             
               
                   
               
             
            
               
                 Height of the 
                 Less than 
                 1 μm-1.5 μm 
                 1.5 μm-2 μm 
                 More than 
               
               
                 anti-adsorption 
                 1 μm 
                   
                   
                 2 μm 
               
               
                 particle 142 beyond 
               
               
                 the surface of the 
               
               
                 substrate layer 141 
               
               
                 Adsorption degree 
                 Serious 
                 No 
                 No 
                 No 
               
               
                 between the optical 
                 adsorption 
                 adsorption 
                 adsorption 
                 adsorption 
               
               
                 adjusting film and 
               
               
                 the lower polarizer 
               
               
                 31 
               
               
                 Adsorption degree 
                 Serious 
                 Moderate 
                 Slight 
                 Slight 
               
               
                 between the optical 
                 adsorption 
                 adsorption 
                 adsorption 
                 adsorption 
               
               
                 adjusting film and 
               
               
                 the anti-peek film 
               
               
                 21 
               
               
                 Status and effect of 
                 Failure 
                 Large area of 
                 Slight 
                 Slight 
               
               
                 the backlight 
                   
                 Newton&#39;s 
                 Newton&#39;s 
                 Newton&#39;s 
               
               
                 module 
                   
                 rings are 
                 rings are 
                 rings are 
               
               
                   
                   
                 visible 
                 visible 
                 visible 
               
               
                 Status and effect of 
                 Failure 
                 Qualified 
                 Qualified 
                 Qualified 
               
               
                 the display module 
                   
                 picture 
                 picture 
                 picture 
               
               
                   
                   
                 quality 
                 quality 
                 quality 
               
               
                   
               
            
           
         
       
     
     Although the larger the height of the anti-adsorption particle  142  beyond the substrate layer  141 , the better the adsorption effect between the optical adjusting film and the structure above or below it is suppressed, the too large height of the anti-adsorption particle  142  beyond the substrate layer  141  may affect the transmittance of the entire display. 
     Inventors found that the height of the anti-adsorption particle  142  beyond the substrate layer  141  is generally not much different from the size of the radius thereof. Therefore, based on the above considerations, in the embodiment, a diameter D of the anti-adsorption particle  142  satisfies: 2 μm≤D≤4 μm. 
     It should be noted that the density of the anti-adsorption particle  142  distributed on the surface of the substrate layer  141  has little influence on the anti-adsorption effect. By taking the radius of the anti-adsorption particle  142  being 1.5 μm as an example, there is not much difference in the anti-adsorption effect between the cases of 45, 50, and 60 anti-adsorption particles  142  distributed in an area of 1 mm 2 . Similarly, by taking the radius of the anti-adsorption particles  142  being 3 μm as an example, there is not much difference in the anti-adsorption effect between the cases of 45, 50, and 60 anti-adsorption particles  142  distributed in an area of 1 mm 2 . 
     In an embodiment, static friction coefficient k between the anti-adsorption surface layer  14  and the lower polarizer  31  satisfies: k≤0.35. In an embodiment, static friction coefficient k between the anti-adsorption surface layer  14  and the anti-peek film  21  satisfies: k≤0.35. Inventors found that the smaller the static friction coefficient between the anti-adsorption surface layer  14  and another solid surface, the more favorable it is to suppress the adsorption effect. 
     In an embodiment, a contact angle α of distilled water with respect to a surface of the anti-adsorption surface layer  14  away from the polymer dispersed liquid crystal layer  11  satisfies: a≥70°. Inventors found that the larger the contact angle of distilled water with respect to the surface of the anti-adsorption surface layer  14  away from the polymer dispersed liquid crystal layer  11  is, the more favorable it is to suppress the adsorption effect. 
     In an embodiment, the first substrate  13  includes a base material layer  131 , an anti-scratch layer  132 , and an undercoat layer  133  stacked in this order in a direction from the first substrate  13  to the polymer dispersed liquid crystal layer  11 . In an embodiment, the second substrate  16  includes a base material layer  161 , an anti-scratch layer  162 , and an undercoat layer  163  stacked in this order in a direction from the second substrate  16  to the polymer dispersed liquid crystal layer  11 . 
     The material of the base material layers  131 ,  161  may usually be polyethylene terephthalate (PET), which has characteristics of high light transmittance, less rainbow patterns caused by surface hardening treatment, and low heat shrinkage. The materials of the anti-scratch layers  132 ,  162  may be the same as that of the substrate layer  141 . The materials of the undercoat layers  133 ,  163  are, for example, polyester resin, silicone resin (DC resin), or the like. The function of the undercoat layers  133 ,  163  is to provide flat surfaces for the first electrode layer  12  and the second electrode layer  15  described above. 
     Referring to  FIG. 4 , the embodiment provides a backlight module, which includes an optical adjusting film and an anti-peek film  21  stacked with each other, and the optical adjusting film is the optical adjusting film according to the above embodiment. Also shown in  FIG. 4  is an optical film  22  on a side of the anti-peek film  21  away from the optical adjusting film. The optical film  22  is, for example, a prism sheet, a diffusion sheet, a light guide plate, or the like. Other parts of the backlight module may be designed according to conventional schemes, and are not shown. 
     The adsorption effect between the optical adjusting film and the anti-peek film  21  in the backlight module or between the optical adjusting film and the lower polarizer  31  after assembled to form the display device in a subsequent process is suppressed or eliminated, so that the display quality can be ensured. 
     Referring to  FIG. 5 , the embodiment provides a display device including a display panel  32  and an optical adjusting film stacked with each other, and the optical adjusting film is the optical adjusting film according to the above embodiment. 
     In an embodiment, the display device may be any product or component having a display function, such as a device formed by attaching the liquid crystal display panel  32  and an optical adjusting film, a liquid crystal display module, a mobile phone, a tablet computer, a television, a display, a notebook computer, a digital photo frame, and a navigator. 
     The adsorption effect between the optical adjusting film and the anti-peek film  21  (if any) or the lower polarizer  31  (if any) in the display device is suppressed or eliminated, thereby ensuring the display quality. 
     In an embodiment, the lower polarizer  31  shown in  FIG. 5  may be a wire grating polarizer integrated inside the display panel  32 . In this case, the adsorption effect between the optical adjusting film and the display panel  32  can be suppressed or eliminated. 
     It will be understood that the above embodiments are merely exemplary embodiments employed to illustrate the principles of the present disclosure, and the present disclosure is not limited thereto. It will be apparent to those skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope of the disclosure, and these changes and modifications are to be considered within the scope of the disclosure.