GAP FILLING OF AN EMBOSSED STRUCTURE WITH A ROTATIONALLY COATED MATERIAL WITH A HIGH REFRONTATE INDEX FOR OPTICAL COMPONENTS

Description

BACKGROUND Field

[0001] Embodiments of the present disclosure generally relate to display devices for augmented, virtual, and mixed reality. More specifically, embodiments described herein provide a method for forming an optical component for a display device.Description of the Related Art

[0002] Virtual reality is generally considered to be a computer generated simulated environment in which a user has an apparent physical presence. A virtual reality experience can be generated in 3D and viewed with a head-mounted display (HMD), such as glasses or other wearable display devices that have near-eye display panels as lenses to display a virtual reality environment that replaces an actual environment.

[0003] Augmented reality enables an experience in which a user can still see through the display lenses of the glasses or other HMD device to view the surrounding environment, yet also see images of virtual objects that are generated for display and appear as part of the environment. Augmented reality can include any type of input, such as audio and haptic inputs, as well as virtual images, graphics, and video that enhances or augments the environment that the user experiences.

[0004] EP 3 094 160 A1 relates to an optical substrate having shapes of projections and depressions formed on the surface thereof. An optical substrate comprises a support substrate and a projection-depression structure layer on a surface of which shapes of projections and depressions are formed, the projection-depression structure layer being laminated on the support substrate, A coating layer may be formed on the projection-depression structure layer. A coating layer can be formed by a sol-gel method of applying a sol gel solution by spin coating. An optical functional layer may be formed on a surface of a support substrate opposite to a surface of the support substrate on which the projection-depression structure layer is formed. An optical functional layer may have a protective layer. US 6 144 795 A relates to a hybrid organic-inorganic planar optical waveguide device. EP 2 717 102 A1 relates to a colored counterfeit prevention structure.

[0005] Both virtual reality and augmented reality display devices utilize optical components, such as waveguides or flat lens / meta surfaces, including a patterned layer having high refractive index (RI), such as 1.7 or higher. The refractive index is a ratio of the speed of light in a vacuum to the speed of light in the medium. Conventional method for forming the patterned high RI layer includes pressing a stamp having the pattern onto a layer of nanoparticles of the high RI material to transfer the pattern to the layer of nanoparticles. The resulting patterned high RI layer has either non-uniform dispersion of the nanoparticles in the patterned high RI layer or brittle structure due to weak bonding between nanoparticles.

[0006] Accordingly, an improved method for forming optical components for virtual reality or augmented reality display devices is needed.SUMMARY

[0007] Embodiments of the present disclosure generally relate to a method for forming an optical component, for example, for a virtual reality or augmented reality display device.

[0008] According to an aspect, a method according to independent claim 1 is provided. In one embodiment, a method includes forming a first layer having a first refractive index on a first surface of a substrate, pressing a stamp having a pattern onto the first layer, transferring the pattern to the first layer to form a patterned first layer, and forming a second layer having a second refractive index greater than the first refractive index on the patterned first layer by spin coating. The method includes forming a third layer having a third refractive index on a second surface of the substrate, the second surface being opposite the first surface of the substrate.

[0009] In an embodiment, the first refractive index ranges from about 1.1 to about 1.5, and the second refractive index ranges from about 1.7 to about 2.4.

[0010] In another embodiment, a method includes forming a first layer having a first refractive index on a first surface of a substrate, pressing a first stamp having a first pattern onto the first layer, transferring the first pattern to the first layer to form a patterned first layer, and forming a second layer having a second refractive index ranging from about 1.7 to about 2.4 on the patterned first layer by spin coating. The second layer includes a metal oxide. The method includes forming a third layer having a third refractive index on a second surface of the substrate, the second surface being opposite the first surface of the substrate.BRIEF DESCRIPTION OF THE DRAWINGS

[0011] So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only exemplary embodiments and are therefore not to be considered limiting of its scope, and may admit to other equally effective embodiments. Figure 1 is a flow diagram of a method for forming an optical component according to one embodiment described herein. Figures 2A - 2D illustrate schematic cross-sectional views of the optical component during different stages of the method of Figure 1 according to one example not falling under the scope of protection described herein. Figures 3A - 3D illustrate schematic cross-sectional views of an optical component during different stages according to one embodiment described herein. Figures 4A - 4D illustrate schematic cross-sectional views of an optical component according to embodiments described herein.

[0012] To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.DETAILED DESCRIPTION

[0013] Embodiments of the present disclosure generally relate to a method for forming an optical component, for example, for a virtual reality or augmented reality display device. In one example not falling under the scope of protection, the method includes forming a first layer on a substrate, and the first layer has a first refractive index. The method further includes pressing a stamp having a pattern onto the first layer, and the pattern of the stamp is transferred to the first layer to form a patterned first layer. The method further includes forming a second layer on the patterned first layer by spin coating, and the second layer has a second refractive index greater than the first refractive index. The second layer having the high refractive index is formed by spin coating, leading to improved nanoparticle uniformity in the second layer.

[0014] Figure 1 is a flow diagram of a method 100 for forming an optical component 200 according to one example not falling under the scope of protection described herein. Figures 2A - 2D illustrate schematic cross-sectional views of the optical component 200 during different stages of the method 100 of Figure 1 according to the example described herein. The method 100 starts at block 102 by forming a first layer 204 having a first RI on a substrate 202, as shown in Figure 2A. In one embodiment, the substrate 202 is fabricated from a visually transparent material, such as glass. The substrate 202 has a RI ranging from about 1.4 to about 2.0. The first layer 204 is fabricated from a transparent material, and the first RI ranges from about 1.1 to about 1.5. In one embodiment, the RI of the substrate 202 is the same as the first RI of the first layer 204. In another embodiment, the RI of the substrate 202 is different from the first RI of the first layer 204. The first layer 204 is fabricated from porous silicon dioxide, quartz, or any suitable material. In one embodiment, the first layer 204 is formed on the substrate 202 by spin coating. For example, a solution including a silicon precursor is spin-coated onto the substrate 202 and then heated in oxygen environment to form the first layer 204. In some embodiments, there are no nanoparticles dispersed in the solution. The silicon precursor is dissolved in the solution.

[0015] Next, at block 104, a stamp 206 having a pattern 208 is pressed onto the first layer 204, as shown in Figure 2B. The stamp 206 is fabricated from any suitable material, such as silicon, quartz, glass, or a polymer. The polymer may be polyurethane, polybutadiene, polyisoprene, or poly(dimethylsiloxane) (PDMS). The pattern 208 formed on the stamp 206 may include a plurality of protrusions 210 and a plurality of gaps 212. Adjacent protrusions 210 are separated by a gap 212. The protrusions 210 may have any suitable shape. After the stamp 206 is pressed onto the first layer 204, a curing process may be performed to cure the first layer 204. The curing process may utilize UV light or thermal energy to cure the first layer 204.

[0016] After the first layer 204 is cured, the stamp 206 is removed from the cured first layer 204, and the pattern 208 of the stamp 206 is transferred to the cured first layer 204 to form a patterned first layer 214, as shown at block 106 in Figure 1 and in Figure 2C. The pattern 208 of the patterned first layer 214 includes a plurality of protrusions 216 and a plurality of gaps 218. Adjacent protrusions 216 are separated by a gap 218. As shown in Figure 2C, the protrusion 216 has a rectangular shape. The protrusion 216 may have any other suitable shape. Examples of the protrusion 216 having different shapes are shown in Figures 4A - 4D. In one embodiment, the protrusions 216 are gratings. Gratings are a plurality of parallel elongated structures that splits and diffracts light into several beams traveling in different directions. Gratings may have different shapes, such as sine, square, triangle, or sawtooth gratings. Because the first layer 204, or the patterned first layer 214, does not contain any nanoparticles, there are no non-uniformity issues. Furthermore, the removal of the stamp 206 from the patterned first layer 214 does not damage the patterned first layer 214, because the patterned first layer 214 is not formed by packing nanoparticles.

[0017] Next, at block 108, a second layer 220 having a refractive index greater than that of the first layer 204 is formed on the patterned first layer 214 by spin coating, as shown in Figure 2D. The second layer 220 includes metal oxides, such as titanium oxide (TiO x ), tantalum oxide (TaO x ), zirconium oxide (ZrO x ), hafnium oxide (HfO x ), or niobium oxide (NbO x ). In one embodiment, the second layer 220 has a RI ranging from about 1.7 to about 2.4. In one embodiment, the second layer 220 includes nanoparticles of the metal oxides dispersed in a polymer matrix or a carrier liquid, and the nanoparticles are uniformly distributed throughout the second layer 220 due to the spin coating method. Furthermore, because the patterned first layer 214 has the pattern 208 formed thereon, the second layer 220 is also patterned as the second layer 220 is spin coated on the patterned first layer 214. As shown in Figure 2D, the second layer 220 includes a plurality of protrusions 222, and each protrusion 222 is formed in a corresponding gap 218 (as shown in Figure 2C) of the patterned first layer 214. The protrusions 216 of the patterned first layer 214 and the protrusions 222 of the second layer 220 are alternately positioned. Because the pattern of the second layer 220, i.e., the protrusions 222, are formed without using a stamp to press thereonto, the pattern of the second layer 220 is not damaged and the nanoparticles of the metal oxide material are uniformly distributed in the second layer 220.

[0018] After the spin coating of the second layer 220, a curing process may be performed to cure the second layer 220. The curing process of the second layer 220 may be the same as the curing process of the patterned first layer 214. The optical component 200 including layers having different Rls may be used in any suitable display devices. For example, in one embodiment, the optical component 200 is used as a waveguide or waveguide combiner in augmented reality display devices. Waveguides are structures that guide optical waves. Waveguide combiners are used in augmented reality display devices that combine real world images with virtual images. In another embodiment, the optical component 200 is used as a flat lens / meta surfaces in augmented and virtual reality display devices and 3D sensing devices, such as face ID and LIDAR.

[0019] Figures 2A - 2D illustrate the method 100 for forming the optical component 200 including layers having different Rls on one side of the substrate 202. In the present invention, both sides of the substrate 202 are utilized to form layers having different Rls thereon. Figures 3A - 3D illustrate schematic cross-sectional views of an optical component 300 during different stages according to one embodiment described herein. As shown in Figure 3A, the substrate 202 includes a first surface 302 and a second surface 304 opposite the first surface 302. The patterned first layer 214 and the second layer 220 are formed on the first surface 302 of the substrate 202, as described in Figures 2A - 2D. Next, a third layer 306 is formed on the second surface 304 of the substrate 202, and the third layer 306 is patterned by the stamp 206, as shown in Figure 3B. The third layer 306 may be fabricated from the same materials as the first layer 204 (as shown in Figure 2A). The third layer 306 may be formed by the same process as the first layer 204. The stamp 206 includes the pattern 208.

[0020] Next, as shown in Figure 3C, the pattern 208 of the stamp 206 is transferred to the third layer 306 to form a patterned third layer 308, and the stamp 206 is removed from the patterned third layer 308. The patterned third layer 308 is cured by a curing process similar to the curing process performed on the patterned first layer 214 prior to removal of the stamp 206. The patterned third layer 308 includes a plurality of protrusions 310 and a plurality of gaps 312. Adjacent protrusions 310 are separated by a gap 312. The patterned third layer 308 may be fabricated from the same material as the patterned first layer 214 and may have the same pattern as the patterned first layer 214. In other words, the patterned third layer 308 may be identical to the patterned first layer 214. In some embodiments, the patterned third layer 308 has a different pattern than the patterned first layer 214. Next, as shown in Figure 3D, a fourth layer 316 is formed on the patterned third layer 308 by spin coating. The fourth layer 316 may be identical to the second layer 220 and may be fabricated by the same method as the second layer 220. The fourth layer 316 includes a pattern, such as the plurality of protrusions 318. The protrusions 310 of the patterned third layer 308 and the protrusions 318 of the fourth layer 316 are alternately positioned. The optical component 300 includes layers having different Rls formed on two surfaces of the substrate 202. The optical component 300 may be used in any suitable display devices. For example, in one embodiment, the optical component 300 is used as a waveguide or waveguide combiner in augmented reality display devices. In another embodiment, the optical component 300 is used as a flat lens / meta surfaces in augmented and virtual reality display devices and 3D sensing devices, such as face ID and LIDAR.

[0021] Figures 4A - 4D illustrate schematic cross-sectional views of an optical component 400 according to examples described herein - only figures 4C & 4D concern embodiments falling under the scope of protection. As shown in Figure 4A, the optical component 400 includes the substrate 202, the patterned first layer 214 disposed on the substrate 202, and the second layer 220 disposed on the patterned first layer 214. The patterned first layer 214 includes a plurality of protrusions 402, and the second layer 220 includes a plurality of protrusions 403. Each of the protrusions 402, 403 has a parallelogramical cross-sectional area, as shown in Figure 4A. The protrusions 402, 403 may be gratings.

[0022] As shown in Figure 4B, the optical component 400 includes the substrate 202, the patterned first layer 214 disposed on the substrate 202, and the second layer 220 disposed on the patterned first layer 214. The patterned first layer 214 includes a plurality of protrusions 404, and the second layer 220 includes a plurality of protrusions 405. Each of the protrusions 404, 405 has a triangular cross-sectional area, as shown in Figure 4B. The protrusions 404, 405 may be gratings.

[0023] As shown in Figure 4C, the optical component 400 includes the substrate 202, the patterned first layer 214 disposed on the first surface 302 of the substrate 202, and the second layer 220 disposed on the patterned first layer 214. The patterned first layer 214 includes the plurality of protrusions 402, and the second layer 220 includes the plurality of protrusions 403. The optical component 400 further includes the patterned third layer 308 disposed on the second surface 304 of the substrate 202 and the fourth layer 316 disposed on the patterned third layer 308. The patterned third layer 308 includes a plurality of protrusions 406, and the fourth layer 316 includes a plurality of protrusions 407. The protrusions 406, 407 may be substantially the same as the protrusions 402, 403, respectively. The protrusions 402, 403, 406, 407 may be gratings.

[0024] As shown in Figure 4D, the optical component 400 includes the substrate 202, the patterned first layer 214 disposed on the first surface 302 of the substrate 202, and the second layer 220 disposed on the patterned first layer 214. The patterned first layer 214 includes the plurality of protrusions 404, and the second layer 220 includes the plurality of protrusions 405. The optical component 400 further includes the patterned third layer 308 disposed on the second surface 304 of the substrate 202 and the fourth layer 316 disposed on the patterned third layer 308. The patterned third layer 308 includes a plurality of protrusions 408, and the fourth layer 316 includes a plurality of protrusions 409. The protrusions 408, 409 may be substantially the same as the protrusions 404, 405, respectively. The protrusions 404, 405, 408, 409 may be gratings. The optical component 400 may be used in any suitable display devices. For example, in one embodiment, the optical component 400 is used as a waveguide or waveguide combiner in augmented reality display devices. In another embodiment, the optical component 400 is used as a flat lens / meta surfaces in augmented and virtual reality display devices and 3D sensing devices, such as face ID and LIDAR.

[0025] A method for forming an optical component including layers having different Rls is disclosed. A pattern is formed in the layer having a lower RI, and the layer having a higher RI is spin coated on the patterned layer with the lower RI. The spin coated layer having the higher RI has improved uniformity of nanoparticles of the high RI material. Furthermore, the layer having the higher RI is not damaged because imprinting of the layer having the higher RI using a stamp is avoided. The application of the optical component is not limited to augmented and virtual reality display devices and 3D sensing devices. The optical component can be used in any suitable applications.

[0026] While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Claims

1. A method (100), comprising: forming a first layer (204) having a first refractive index on a first surface (302) of a substrate (202); pressing a stamp (206) having a first pattern (208) onto the first layer (204); transferring the first pattern (208) to the first layer (204) to form a patterned first layer (214); forming a second layer (220) having a second refractive index greater than the first refractive index on the patterned first layer (214) by spin coating; forming a third layer (306) having a third refractive index on a second surface (304) of the substrate (202), the second surface (304) being opposite the first surface (302) of the substrate (202); pressing a second stamp having a second pattern onto the third layer (306); transferring the second pattern to the third layer (306) to form a patterned third layer (308); and forming a fourth layer (316) having a fourth refractive index greater than the third refractive index on the patterned third layer (308) by spin coating.

2. The method (100) of claim 1, wherein the first refractive index ranges from about 1.1 to about 1.5.

3. The method (100) of claim 1, wherein the first layer (204) comprises porous silicon dioxide or quartz.

4. The method (100) of claim 1, wherein the second layer (220) comprises a metal oxide.

5. The method (100) of claim 1, wherein the second layer (220) comprises titanium oxide, tantalum oxide, zirconium oxide, hafnium oxide, or niobium oxide.

6. The method (100) of claim 1, wherein the first layer (204) is formed on the substrate (202) by spin coating.

7. The method (100) of claim 1, wherein the first refractive index ranges from about 1.1 to about 1.5; and wherein the second refractive index ranges from about 1.7 to about 2.4.

8. The method (100) of claim 7, wherein the second layer (220) comprises titanium oxide, tantalum oxide, zirconium oxide, hafnium oxide, or niobium oxide.

9. The method (100) of claim 7, wherein transferring the first pattern (208) to the first layer (204) comprises curing the first layer (204) with the stamp (206) on the first layer (204).

10. The method (100) of claim 9, wherein the curing the first layer (204) comprises UV curing or thermal curing.

11. The method (100) of claim 1, wherein the second refractive index ranges from about 1.7 to about 2.4, and wherein the second layer (220) comprises a metal oxide.

12. The method (100) of claim 11, wherein the first layer (204) is formed on the first surface (302) of the substrate (202) by spin coating.

13. The method (100) of claim 1, wherein the second pattern is different from the first pattern.