BACKGROUND

[0001] Electronic devices, such as laptops, tablets, and mobile phones, may have a display screen for 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 iRustrates 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 data, 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 generafly 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 an 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 an opaque layer on surfaces of the transparent substrate along the thickness direction of the transparent substrate. The surface along the thickness direction of the transparent substrate are inner surfaces of the transparent substrate that surround the cavities. The opaque layer may be made of a material including one or more of graphene, carbon-black, black dye, graphite, and carbon nanotubes.

[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.

[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 (pm) to 500 pm. The transparent substrate 102 with cavities 104 may be fabricated using a molding 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 polyacrylic, such as poly-methyl methacrylate (PMMA).

[0018] The display control film 100 also includes an opaque 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 opaque 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 opaque layer 106 coated on the surfaces along the thickness direction 202 of the transparent substrate 102.

[0019] in an example implementation, the opaque layer may be made of a material including one or more of graphene, carbon-black, black dye, graphite, and carbon nanotubes. The opaque layer 106 may be of a thickness in a range of 1 pm to 5 Mm. The opaque layer 106 on the surfaces surrounding the cavities 104 of the 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, in various example implementations, the view angle can be varied by varying the thickness of the opaque layer. The thicker the opaque layer, the smaller is the view angle.

[0020] The cavities 104 in the transparent substrate 102, as shown in Fig. 2, have a shape of a cuboid, with a square or a rectangular cross-section. Sides of a cross-section of a cuboidal cavity 104 may have lengths in a range of 200 pm 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 tlm 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 cavities 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 the cavities 304 are coated with an opaque layer 306.

[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 an opaque layer 316.

[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 \im 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 ±θ', the display from a display screen having the display control film is visible from directions within 6° on any side of a perpendicular to the display screen.

[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 an opaque layer 406. Since the sectional view of the display control film 400 is shown in Fig. 4, the cavities are not visible. The opaque 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 opaque 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 and the opaque layer 406 may also be the same as described earlier. The transparent substrate 402 with the cavities and with the opaque 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 layer covering the transparent substrate 402 from each planar side. As shown in Fig. 4, the display control film 400 has two optically clear layers 408 and 410. A first optically clear layer 406 covers the transparent substrate 402 from a first planar side, and a second optically dear layer 410 covers the transparent substrate 402 from a second planar side. It may be noted each of the optically dear layers 408 and 410 covers the entire planar surface of the transparent substrate 402. The optically dear layers 408 and 410 provide durability to the opaque layer 406.

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

[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 layers 408 and 410. A first surface protection layer may cover the first optically clear layer 408. A second surface protection layer may cover the second optically dear layer 410. The 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 Mm 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 clear layer. In an example implementation, the surface protection layer may be spray coated on the optically clear layer followed by curing using UV light.

[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, polyamide, polyoiefin. 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, for 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. 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. An opaque layer 510 is coated 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 opaque layer 510 is visible in Fig. 5. The dimensions and shapes of the transparent substrate 506, cavities, and the opaque layer 510 may be the same as described earlier. The materiel of the transparent substrate 506 and the opaque layer 510 may also be the same as described earlier.

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

[0036] As shown in Fig. 5, the display control film 504 interfaces with the display screen 502 through the optically dear 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] The 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 indude a cover layer (not shown) over the optically dear 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 po!yacryHc and polycarbonate. The hard transparent layer may be spray coated followed by curing using UV light. The hard transparent layer may have a thickness in a range of about 1 pm to about 10 pm. The plastic layer may be of a thickness in a range of about 100 pm to about 500 pm. 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 dear 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, ethylene- vinyl acetate copolymer, polyamide, polyolefin, 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 columnwise 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 hydrophobic layer is coated on each planar side of the transparent substrate. In an example implementation, the hydrophobic layer may be roller coated. For roller coating the hydrophobic layer, the transparent substrate may be passed between two rollers of a roller coating machine and the two rollers are supplied with a solution of a hydrophobic material. The hydrophobic material may include, but not restricted to, ethylene vinyl acetate, ethyiene-ethyl acryiate, ionomer, ethylene acrylate, phenoxy compounds, polyamide, polyester, polyvinyl acetate, polyvinyl butyral and polyvinyl ether having ftouiOpolymers. The solution of the hydrophobic material may have a viscosity in a range of 3,000 centiPoise (cp) to 40,000 op. In an example implementation, the hydrophobic layer may have a thickness in a range of 3 urn to 15 pm> After roller coating the hydrophobic layer on the transparent substrate, the hydrophobic layer is exposed to UV radiations of an energy dose of 1.2 Joules/centimeter ² (J/cm ² ) to 5 J/cm ² for a time duration in a range of 10 seconds to 45 seconds.

[0041] In an example implementation, the hydrophobic layer may be laminated on the transparent substrate. For laminating the transparent substrate with the hydrophobic layer, a prefabricated hydrophobic layer of a thickness in a range of 3 pm to 15 pm is pasted on the transparent substrate. The hydrophobic layer for lamination may have a surface profile same as that of the transparent substrate, such that the hydrophobic layer covers the material portion of the transparent substrate and not the cavities in the transparent substrate.

[0042] At block 604, an opaque layer is coated on surfaces of the transparent substrate lying along the thickness direction of the transparent substrate. In an example implementation, the opaque layer may be immersion coated. For immersion coating of the opaque layer, the transparent substrate with hydrophobic layers is immersed in a solution having opaque material, such as graphene, carbon-black, black dye, graphite, carbon nanotubes, and a combination thereof. The opaque material may have a concentration in a range of 5 weight% (wt%) to SO wt%. The transparent substrate may be immersed in the solution having the opaque material for a time duration in a range of 15 seconds to 30 seconds. In an example implementation, the solution having the opaque material may be provided with an ultrasonic treatment while the transparent substrate in immersed therein. After immersing the transparent substrate for the mentioned time duration, the transparent substrate is removed from the solution and the opaque layer is exposed to UV radiations of an energy dose of 2 J/cm ² to 20 J/cm ² for a time duration in a range of 10 seconds to 60 seconds. In an example implementation, the opaque layer may have a thickness in a range of 1 pm to 5 pm.

[0043] it may be noted that the hydrophobic layer is coated, through roller coating or lamination, on the planar sides of the transparent substrate and not coated on the surfaces along the thickness direction of the transparent substrate. Since the solution in which the transparent substrate is immersed for coating the opaque layer repels the hydrophobic layer, the opaque layer gets coated on the surfaces along the thickness direction of the transparent substrate. [0044] At block 606, the hydrophobic layer is removed from each planar side of the transparent substrate. Removal of the hydrophobic layer from each planar side of the transparent substrate results in the display control film having the transparent substrate with the opaque layer coated on the surfaces along the thickness direction of the transparent substrate.

[0045] in an example implementation, the hydrophobic layer may be removed using a release film of thickness in a range of 5 pm to 30 pm. The release film may include a polyester base layer and an adhesive coating on one side of the polyester base layer. The adhesive coating may be made of isocyanate based polymers (PMDI, urethanes. urea), epoxies, acrylics, hot melt adhesives, ethylene-vinyl acetate copolymers, polyamides, poiyotefins, styrene copolymers, polyester, poEyurethane and rubber-based adhesives containing fluoropolymers such as fluorinated olefin-based polymers, fluoroacryiates, ftuorosilicone acrylates, fluorourethanes, perfluoropofyethers/ perfiuoropolyoxetanes, fiuorotelomers (C-6 or lower), polytetrafiuoroethylene (PTFE), poiyvinylidenefluourtde (PVDF), fluorosiloxarte, fluoro UV polymers and hydrophobic polymers (C-7 or longer). The release film may be pasted on the hydrophobic layer and then peeled off to remove the hydrophobic layer along with the release film.

[0046] in an example implementatJon, after removing the hydrophobic layer, an optically clear layer may be provided on each planar side of the transparent substrate. The optically clear layer may be laminated or spray coated on the transparent substrate, as described earlier. Further, in an example implementation, a surface protection layer may be provided on the optically clear layer on at least one planer side. The surface protection layer may be laminated or spray coated on the optically clear layer, as described earlier.

[0047] Further, in an example implementation, an adhesive layer 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 layer may be of a material 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. Rattier, the specific features are disclosed and explained as example implementations for display control films, display devices, and methods of fabrication of display control films.