WO2019074501A1

WO2019074501A1 - Display control films

Info

Publication number: WO2019074501A1
Application number: PCT/US2017/056157
Authority: WO
Inventors: Kuan-Ting Wu; Wei-Chung Chen; Chien-Ting Lin
Original assignee: Hewlett-Packard Development Company, L.P.
Priority date: 2017-10-11
Filing date: 2017-10-11
Publication date: 2019-04-18

Abstract

The present subject matter relates to display control films. In an example implementation, a display control film comprises a transparent substrate including an array of cavities through a thickness direction of the transparent substrate. The array of cavities is arranged row-wise and column-wise in a plane of the transparent substrate. The display control film also comprises a graphene layer on surfaces of the transparent substrate along the thickness direction of the transparent substrate.

Description

DISPLAY CONTROL FILMS

BACKGROUND

[0001] Electronic devices, such as laptops, tablets, and mobile phones, may have a display screen lor displaying contents to users. The display screen of such devices may include a liquid crystal display (LCD) screen, a light emitting diode (LED) display screen, an organic LED display screen, a polymer LED display screen, a plasma display screen, and the like.

BRIEF DESCRIPTION OF DRAWINGS

[0002] The following detailed description references the drawings, wherein:

[0003] Fig. 1 illustrates a top view of a display control film, according to an example implementation of the present subject matter;

[0004] Fig. 2(a) illustrates a perspective view of a transparent substrate, according to an example implementation of the present subject matter,

[0005] Fig. 2(b) illustrates a perspective view of the display control film of Fig. 1 , according to an example implementation of the present subject matter;

[0006] Figs.3(a)-3(b) illustrate top views of display control films with cavities of different shapes, according to example implementations of the present subject matter;

[0007] Fig. 4 illustrates a sectional view of a display control film, according to an example implementation of the present subject matter;

[0008] Fig. 5 illustrates a sectional view of a display device, according to an example implementation of the present subject matter; and

[0009] Fig. 6 illustrates a method of fabricating a display control film, according to an example implementation of the present subject matter.

DETAILED DESCRIPTION

[0010] Electronic devices, for example, laptops, tablets, and smartphones, are often utilized by users for performing activities which involve accessing personal data of users. The accessed data may be displayed on a display screen of a display device associated with the electronic device. The activities that Involve accessing of personal data may, for example, include online banking, online trading, insurance, finance, writing exams, accessing medical records, etc. The personal date, displayed on a display screen of a display device, may be sensitive to be viewed by others who are in the vicinity of the display device.

[0011] The display devices generally display contents with wide view angles. A view angle for a display device may be an angle subtended by directions with respect to a perpendicular to the plane of a display screen of the display device up to which the display from the display screen is visible. With wide view angles, displayed contents are visible almost from all directions in front of the display device. The wide view angles of the display device may affect security of personal data of users. Such data may have to be protected from prying eyes in the vicinity of the display device.

[0012] The present subject matter relates to controlling view angles of displays from display devices to protect and maintain privacy of displayed contents from prying eyes. The present subject matter describes examples of display control films which when affixed on a display screen of a display device, enable view angle control for displays from the display screen. The present subject matter also describes examples of display devices which are enabled for view angle control The present subject matter further describes example methods of fabrication of display control films for controlling the view angles.

[0013] In accordance with ah example implementation of the present subject matter, a display control film includes a transparent substrate including an array of cavities through a thickness direction of the transparent substrate. The cavities of the array are empty spaces that pass through-and-th rough the thickness of the transparent substrate. The array of cavities is arranged row-wise and columnwise in a plane of the transparent substrate. The display control film also includes a graphene layer on surfaces of the transparent substrate along the thickness direction of the transparent substrate. The surfaces along the thickness direction of the transparent substrate are inner surfaces of the transparent substrate that surround the cavities. The graphene layer is coated using physical vapor deposition (PVD) technique, and has a thickness in a range of 10 nanometer (nm) to 100 nm.

[0014] The display control films of the present subject matter, when pasted or affixed on a display screen of a display device, control or restrict a view angle of displays from the display device. It may be noted that to return to the unrestricted view angle of displays, the display control film may have to be removed from the display screen of the display device. The display control films of the present subject matter, with thin graphene layers of 10 nm to 100 nm deposited using PVD technique, effectively control the view angle of displays from display screens without significantly reducing the transmittance from the display screens. The transmittance from the display screen with the display control film may be similar to that without the display control film. This facilitates in saving energy utilized for powering tie display screens affixed with the display control film.

[0015] The following detailed description refers to the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the following description to refer to the same or similar parts. While several examples are described in the description, modifications, adaptations, and other implementations are possible. Accordingly, the following detailed description does not limit the disclosed examples. Instead, the proper scope of the disclosed examples may be defined by the appended claims.

[0016] Fig. 1 illustrates a top view of a display control film 100, according to an example implementation of the present subject matter. The display control film 100 includes a transparent substrate 102. The transparent substrate 102 may be like a thin film of a transparent material. The transparent substrate 102, as shown in Fig. 1, includes an array of cavities 104-1, 104-2, .... 104-n. The array of cavities, collectively referred to as cavities 104, is arranged row-wise and columnwise in a plane of the transparent substrate 102. Each of the cavities 104 is an empty space through the thickness of the transparent substrate 102, as illustrated in a perspective view of the transparent substrate 102 in Fig. 2(a).

[0017] In an example implementation, the transparent substrate 102 may have a thickness in a range of 200 micrometer (μπ?) to 500 pm. The transparent substrate 102 with cavities 104 may be fabricated using a mokjing process. The transparent substrate 102 may be of a thermoplastic plastic material which can be molded. The thermoplastic plastic material may include, but is not restricted to, polycarbonate, cyclic olefin copolymer (COC), polyethylene terephthalate (PET), and polyacryiic, such as poly-methyl methacrylate (PMMA).

[0018] The display control film 100 also includes a graphene layer 106-1, 106-2, .... 106-n, on inner surfaces of the transparent substrate 102 that surround the cavities 104. The inner surfaces of the transparent substrate 102 may also be understood as surfaces along a thickness direction of the transparent substrate 102. The graphene layer may be collectively referred to as 106. Fig. 2(b) illustrates a perspective view of the display control film 100 of Fig. 1 , according to an example implementation of the present subject matter. Fig. 2(b) shows the graphene layer 106 coated on the surfaces along the thickness direction 202 of the transparent substrate 102.

[0019] In an example implementation, the graphene layer 106 may be coated using PVD technique and may be of a thickness in a range of 10 nm to 100 nm. Such a thin graphene layer 106 on the surfaces surrounding the cavities 104 of fiie transparent substrate 102 enables controlling view angle of displays from a display device, when the display control film 100 is pasted on a display screen of the display device, without significantly reducing the transmittance from the display screen, in various example implementations, the view angle can be varied by varying the thickness of the graphene layer. The thicker the graphene layer, the smaller is the view angle.

[0020] The cavities 104 in the transparent substrate 102, as shown in Figs. 2(a)-2{b), have a shape of a cuboid, with a square or a rectangular cross-section. Sides of a cross-section of a cuboidai cavity 104 may have lengths in a range of 200 urn to 600 pm. in various example implementations, the view angle can be varied by varying the length of the cross-sectional side of the cavity. The smaller the length of the cross-sectional side of the cavity, the smaller is the view angle.

[0021] Shape of cavities in a transparent substrate for making a display control film of the present subject is not restricted to such a shape. Other shapes are also possible. Figs. 3(a)-3(b) illustrate top views of display control films with cavitiee of different shapes, according to example implementations of the present subject matter.

[0022] In an example implementation of the present subject matter, a display control film may have a transparent substrate with an array of cavities, where each cavity of the array of cavities has a shape of a cylinder with a polygonal cross-section. The cylindrical cavity has a height equal to the thickness of the transparent substrate. Fig.3(a) illustrates a top view of an example display control film 300 having a transparent substrate 302 with an array of cavities 304, where each cavity of the array of cavities 304 has a shape of cylinder with a hexagonal cross-section. The surfaces of the transparent substrate 302 that are along the thickness direction of the transparent substrate and surrounding fine cavities 304 are coated with a graphene layer 306 of thickness in a range of 10 nm to 100 nm.

[0023] Fig. 3(b) illustrates a top view of an example display control film 310 having a transparent substrate 312 with an array of cavities 314, where each cavity of the array of cavities 314 has a shape of a cylinder with a circular cross- section. The surfaces of the transparent substrate 312 that are along the thickness direction of the transparent substrate and surrounding the cavities 314 are coated with a graphene layer 316 of thickness in a range of 10 nm to 100 nm.

[0024] In an example implementation, adjacent cavities of the array of cavities in the transparent substrate of the display control film of the present subject matter may be separated by a distance in a range of 200 pm to 500 pm. In various example implementations, the view angle can be varied by varying the distance between the adjacent cavities. The smaller the distance between the adjacent cavities, the smaller is the view angle.

[0025] The display control films described above enable 4-way view angle control, i.e., restricting the view angle of displays about axes along rows and columns of cavities in the transparent substrate. 4-way view angle control can provide privacy of displays when viewed from either of left, right, top and bottom of the display screen. In an example implementation, the display control film when pasted on a display screen of a display device may restrict the view angle to within ±30° to ±60°. It may be noted that for a display control film with a view angle of ±6°, the display from a display screen having the display control film is visible from directions within θ° on any side of a perpendicular to the display screen and not visible from direction outside 6°.

[0026] Fig. 4 illustrates a sectional view of a display control film 400, according to an example implementation of the present subject matter. The display control film 400 includes a transparent substrate 402 having cavities through a thickness direction 404 of the transparent substrate 402. Surfaces of the transparent substrate 402 that are along the thickness direction 404 are coated with a graphene layer 406 of thickness in a range of 10 nm to 100 nm. The graphene layer 406 is coated using PVD technique. Since the sectional view of the display control film 400 is shown in Fig. 4, the cavities are not visible. The graphene layer 406 coated on the surfaces surrounding the cavities is visible in Fig.4. The dimensions and shapes of the transparent substrate 402, cavities, and the graphene layer 406 may be the same as described earlier in accordance with implementations of the present subject matter. The material of the transparent substrate 402 may also be the same as described earlier. The transparent substrate 402 with the cavities and with the graphene layer 406 coated on the surfaces surrounding the cavities may also be referred to as a display control layer of the display control film 400.

[0027] The display control film 400 also includes an optically clear adhesive layer covering the transparent substrate 402 from each planar side. As shown in Fig.4, the display control film 400 has two optically dear adhesive layers 408 and 410, A first optically clear adhesive layer 408 covers the transparent substrate 402 from a first planar side, and a second optically clear adhesive layer 410 covers the transparent substrate 402 from a second planar side. It may be noted each of the optically dear adhesive layers 408 and 410 covers the entire planar surface of the transparent substrate 402. The optically dear adhesive layers 408 and 410 provide durability to the graphene layer 406.

[0028] In an example implementation, each of the optically clear adhesive layers 408 and 410 may have a thickness in a range of 100 pm to 250 pm. The optically clear adhesive layers 408 and 410 may be of a material including, but not restricted to, one of polyacry!ic, polycarbonate, COC, and polyester. In an example implementation, the optically dear adhesive layers 408 and 410 may be laminated on the transparent substrate 402. In an example implementation, the optically clear adhesive layers 408 and 410 may be spray coated on the transparent substrate 402 followed by curing using ultraviolet (UV) radiations.

[0029] Further, in an example implementation, the display control film 400 may include a surface protection layer (not shown in Fig.4) covering at least one of the optically clear adhesive layers 408 and 410. A first surface protection layer may cover the first optically dear adhesive layer 408. A second surface protection layer may cover the second optically dear adhesive layer 410. Hie surface protection layer enhances the durability and structural strength of the display control film 400.

[0030] In an example implementation, the surface protection layer may have a thickness in a range of 3 pm to 30 pm. The surface protection layer may be of a material including, but not restricted to, polyacrylic, polycarbonate, and polyester. In an example implementation, the surface protection layer may be laminated on the optically dear adhesive layer. In an example implementation, the surface protection layer may be spray coated on the optically dear adhesive layer followed by curing using UV radiations.

[0031] Further, in an example implementation, the display control film 400 may include an adhesive layer (not shown) on one side of the display control film 400, through which the display control film 400 may be pasted on a display screen of a display device. The adhesive layer may be of a material including, but not restricted to, an optical clear adhesive or a UV curable adhesive. The UV curable adhesive may include, but is not restricted to, an isocyanate based polymer, epoxy, acrylic, hot melt adhesive, ethylene-vinyl acetate copolymer, polyamtde, polyolefin, styrene copolymer, polyester, and polyurethane.

[0032] A procedure to fabricate a display control film of the present subject matter is described with reference to Fig. 6.

[0033] Fig. 5 illustrates a sectional view of a display device 500, according to an example implementation of the present subject matter. The display device 500 may be implemented in various ways. For example, the display device 500 may be implemented as monitors for desktop computers, and display units of laptops, mobile phones, tablets, electronic readers, televisions, etc. The display device 500 includes a display screen 502. The display screen 502 may, fix example, include a liquid crystal display (LCD) screen, a light emitting diode (LED) display screen, an organic LED display screen, a polymer LED display screen, a plasma display screen, and such.

[0034] The display device 500 includes a display control film 504 over the display screen 502, as shown in an exploded view of the encircle region of the display screen 502. The display control film 504 includes a transparent substrate 506 having cavities through a thickness direction 508 of the transparent substrate 506 and arranged row-wise and column-wise in a place of the transparent substrate 506. The display control film 504 also includes a physical vapor deposited graphene layer 510 on surfaces of the transparent substrate 506 that are along the thickness direction 508. Since the sectional view is shown in Fig.5, the cavities in the transparent substrate 506 are not visible, but the physical vapor deposited graphene layer 510 is visible in Fig. 5. The dimensions and shapes of the transparent substrate 506, cavities, and the graphene layer 510 may be the same as described earlier. The material of the transparent substrate 506 may also be the same as described earlier.

[0035] The display control film 504 also includes two optically clear adhesive layers, one each on each planar side of the transparent substrate 506. As shown in Fig. 5, a first optically clear adhesive layer 512 is on a top planar side of the transparent substrate 506, and a second optically clear adhesive layer 514 is on a bottom planar side of the transparent substrate 506. The thickness and tine material of the optically clear adhesive layers 512 and 514 may be file same as described earlier.

[0036] As shown in Fig. 5, the display control film 504 interfaces With the display screen 502 through the optically clear adhesive layer 514 on one side of the display control film 504. In an example implementation, the display control film 504 may also include a surface protection layer (not shown in Fig. 5) on at least one of the optically clear layers 512 and 514. in such example implementations, the display control film 504 may interface with the display screen 502 through the surface protection layer. [0037] Hie display control film 504 on the display screen 502 restricts the view angle of displays from the display screen 502. In an example implementation, the display control film 504 may also Include a cover layer (not shown) over the optically clear adhesive layer 512 or over the surface protection layer, as the case may be. The cover layer may provide durability and structural strength to the display control film 504. The cover layer may be one of a hard transparent layer and a plastic layer. The hard transparent layer may be of a material including, but not restricted to, one of pofyacrytic and polycarbonate. The hard transparent layer may be spray coated followed by airing using UV radiations. The hard transparent layer may have a thickness in a range of about 1 pm to about 10 μιη. The plastic layer may be of a thickness in a range of about 100 urn to about 500 μιη. The plastic layer may be spray coated.

[0038] It may be noted that the display control film 504 has to be affixed on the display screen 502 of the display device 500 to enable view angle control of displays from the display screen 502 in accordance with the present subject matter. In an example implementation, the display control film 504 may be pasted on the display screen 502 using an optical clear adhesive, such that the display control film 504 is detachable from the display screen 502. In an example implementation, the display control film 504 may be permanently pasted on the display screen 502 using a UV curable adhesive. The UV curable adhesive may include, but is not restricted to, an isocyanate based polymer, epoxy, acrylic, hot melt adhesive, ethy!ene-vinyl acetate copolymer, polyamide, poiyolefin, styrene copolymer, polyester, and polyurethane.

[0039] Fig. 6 illustrates a method 600 of fabricating a display control film, according to an example implementation of the present subject matter. For fabricating the display control film, a transparent substrate having an array of cavities is prepared. As mentioned earlier, cavities of the array pass through a thickness direction of the transparent substrate. The transparent substrate may be prepared by a molding a transparent thermoplastic plastic material. The transparent thermoplastic plastic material may be poured in a mold having protrusions of a suitable shape and height and arranged row-wise and column- wise in a plane which leads to formation of the array of cavities. The transparent substrate may be cleaned prior to coating any layer thereon.

[0040] At block 602, a shielding film is laminated on each planar side of the transparent substrate. The shielding film for lamination may have a surface profile same as that of the transparent substrate, such that the shielding film covers the material portion of the transparent substrate and not the cavities in the transparent substrate. The shielding film may be of a material including, but not restricted to, ethylene vinyl acetate, ethylene-ethyl acrylate, ionomer, ethylene acrylate, polyester, and polyvinyl acetate, in an example implementation, the shielding film may have a thickness in a range of 3 pm to 20 pm.

[0041] At block 604, a graphene layer is coated, by PVD, on surfaces of the transparent substrate lying along the thickness direction of the transparent substrate. For coating the graphene layer using PVD, the transparent substrate is placed in a vacuum chamber maintained at about 10 miliTorr at a temperature in a range of 120°C to 150°C. A graphite target is placed in the vacuum chamber. The graphite target is bombarded by argon (Ar+) ions. The Ar+ ions knock graphene atoms out from the graphite target The graphene atoms move towards the transparent substrate to coat a graphene layer on the transparent substrate. The transparent substrate is placed in the vacuum chamber for a time duration in a range of 7 minutes to 10 minutes to obtain the graphene layer of a thickness in a range of 10 nm to 100 nm. It may be noted that the graphene layer may get deposited on the shielding film and oh the surfaces along the- thickness direction of the transparent substrate.

[0042] At block 606. the shielding film is removed from each planar side of the transparent substrate. Removal of the shielding film from each planar side of the transparent substrate results in the display control film having the transparent substrate with the graphene layer coated on the surfaces along the thickness direction of the transparent substrate. In an example implementation, the shielding film may be peeled off from the transparent substrate.

[0043] In an example implementation, after removing the shielding film, an optically clear adhesive layer may be provided on each planar side of the transparent substrate. The optically clear adhesive layer may be laminated or spray coated on the transparent substrate, as described earlier. After providing the optically clear adhesive layer, the optically clear adhesive iayer is exposed to UV radiations of art energy dose of 2 Joules/centimeter² (J/cm²) to 20 J/cm² for a time duration in a range of 10 seconds to 60 seconds.

[0044] Further, in an example implementation, a surface protection iayer may be provided on the optically clear adhesive Iayer on at least one planer side. The surface protection iayer may be laminated or spray coated on the optically clear adhesive Iayer, as described earlier.

[0045] Further, in an example implementation, an adhesive iayer may be provided on one side of the display control film for pasting the display control film on a display screen of a display device. The adhesive Iayer may be of a materia! including, but not restricted to, an optical clear adhesive or a UV curable adhesive.

[0046] Although implementations for display control films, display devices, and methods of fabrication of display control films have been described in language specific to structural and functional features, it is to be understood that the present subject matter is not limited to the specific features described. Rather, the specific features are disclosed and explained as example implementations for display control films, display devices, and methods of fabrication of display control films.

Claims

We claim:

1. A display control film comprising:

a transparent substrate Including an array of cavities through a thickness direction of the transparent substrate, the array of cavities being arranged rowwise and column-wise in a plane of the transparent substrate; and

a graphene layer on surfaces of the transparent substrate along the thickness direction of the transparent substrate, the graphene layer having a thickness in a range of 10 nm to 100 nm.

2. The display control film as claimed in claim 1, wherein each cavity of the array of cavities has a shape of one of a cylinder with a polygonal cross-section and a cylinder with a circular cross-section.

3. The display control film as claimed in claim 1 , wherein each cavity of the array of cavities has a shape of a cuboid, wherein sides of a cross-section of the cuboid have lengths in a range of 200 urn to 600 μητ

4. The display control film as claimed in claim 1 , wherein the transparent substrate has a thickness in a range of 200 pm to 500 pm.

5. The display control film as claimed in claim 1 , wherein adjacent cavities of the array of cavities are separated by a distance in a range of 200 pm to 500 pm.

6. The display control film as claimed in claim 1, comprising an optically dear adhesive layer covering the transparent substrate from each planar side.

7. The display control film as claimed in claim 6, comprising a surface protection layer covering the optically dear adhesive layer.

8. A display device comprising:

a display screen; and a display control film over the display screen, the display control film comprising:

a transparent substrate including an array of cavities through a thickness direction of the transparent substrate, the array of cavities being arranged row-wise and column-wise in a plane of the transparent substrate;

a physical vapor deposited graphene layer on surfaces of the transparent substrate along the thickness direction of the transparent substrate to control a view angle of a display from the display device, the physical vapor deposited graphene layer having a thickness in a range of 10 nm to 100 nm; and

an optically clear adhesive layer on each planar side of the transparent substrate.

9. The display device as claimed in claim 8, wherein the display control film comprising a surface protection layer covering the optically clear adhesive layer.

10. The display device as claimed in claim 8, wherein each cavity of the array of cavities has a shape of one of a cylinder with a polygonal cross-section and a cylinder with a circular cross-section.

11. The display device as claimed in claim 8, wherein each cavity of the array of cavities has a shape of a cuboid, wherein sides of a cross-section of the cuboid have lengths in a range of 200 pm to 600 pm.

12. A method of fabricating a display control film, the method comprising:

laminating a shielding film on each planar side of a transparent substrate, the transparent substrate including an array of cavities passing through a thickness direction of the transparent substrate, wherein the array of cavities is arranged row-wise and column-wise in a plane of the transparent substrate; coating, by physical vapor deposition, a graphene layer on surfaces of the transparent substrate lying along the thickness direction of the transparent substrate; and

removing the shielding film from each planar side of the transparent substrate.

13. The method as claimed in claim 12, wherein the graphene layer is of a thickness in a range of 10 nm to 100 nm.

14. The method as claimed in claim 12, further comprising:

providing an optically clear adhesive layer on each planar side of the transparent substrate.

15. The method as claimed in claim 14, further comprising:

exposing the optically clear adhesive layer to ultraviolet radiations of an energy dose of 2 J/cm² to 20 J/cm² for a time duration in a range of 10 seconds to 60 seconds.