Waveguide grating adhesives for waveguide-based displays and methods of manufacturing thereof

Abstract

Systems and methods for waveguide gratings with adhesive for waveguide-based displays. The waveguide displays as described herein comprise an adhesive material configured to protect the grating structures from contaminants. The waveguide display as described herein can be manufactured with an inkjet printer.

Description

WAVEGUIDE GRATING ADHESIVES FOR WAVEGUIDE-BASED DISPLAYS AND METHODS OF MANUFACTURING THEREOFCROSS-REFERENCES TO RELATED APPLICATIONS

[0001] The current application claims priority to Provisional Application No. 63 / 664,511 , filed June 26, 2024, the disclosure of which is incorporated herein by reference.FIELD OF THE INVENTION

[0002] The present invention generally relates to waveguide grating adhesive for waveguide-based displays.BACKGROUND

[0003] Waveguides can be referred to as structures with the capability of confining and guiding waves (i.e., restricting the spatial region in which waves can propagate). One subclass includes optical waveguides, which are structures that can guide electromagnetic waves, typically those in the visible spectrum. Waveguide structures can be designed to control the propagation path of waves using a number of different mechanisms. For example, planar waveguides can be designed to utilize diffraction gratings to diffract and couple incident light into the waveguide structure such that the incoupled light can proceed to travel within the planar structure via total internal reflection (TIR).

[0004] Fabrication of waveguides can include the use of material systems that allow for the recording of holographic optical elements within or on the surface of the waveguides. One class of such material includes polymer dispersed liquid crystal (PDLC) mixtures, which are mixtures containing photopolymerizable monomers and liquid crystals. A further subclass of such mixtures includes holographic polymer dispersed liquid crystal (HPDLC) mixtures. Holographic optical elements, such as volume phase gratings, can be recorded in such a liquid mixture by illuminating the material with two mutually coherent laser beams. During the recording process, the monomers polymerize, and the mixture undergoes a photopolymerization-induced phase separation, creatingregions densely populated by liquid crystal (LC) micro-droplets, interspersed with regions of clear polymer. The alternating liquid crystal-rich and liquid crystal-depleted regions form the fringe planes of the grating.

[0005] Waveguide optics, such as those described above, can be considered for a range of display systems and sensor applications. In many applications, waveguides containing one or more grating layers encoding multiple optical functions can be realized using various waveguide architectures and material systems, enabling new innovations in near-eye displays for Augmented Reality (AR) and Virtual Reality (VR), compact Heads Up Displays (HUDs) for aviation and road transport, and sensors for biometric and laser radar (LIDAR) applications. As many of these applications are directed at consumer products, there is a growing requirement for efficient low cost means for manufacturing holographic waveguides in large volumes.

[0006] In near-eye displays and display devices it may be beneficial that the overall system including a waveguide and a projector be compact and light weight to enable the user to wear the near-eye display comfortably and to enable the user to perform different tasks in environments where the user moves.SUMMARY OF THE INVENTION

[0007] Systems and methods in accordance with some embodiments of the invention are directed to waveguide grating adhesive for waveguide-based displays.

[0008] In some aspects, the techniques described herein relate to a method of manufacturing a waveguide display, the method including: printing, using one or more heads of an inkjet printer, one or more holographic materials on a bottom substrate; printing, using a head of the inkjet printer, a photosensitive material on the bottom substrate; positioning a top substrate such that the one or more holographic materials and the photosensitive material are positioned between the bottom substrate and the top substrate; and exposing the one or more holographic materials and the photosensitive material to a recording beam, wherein the exposed one or more holographic materials forms one or more gratings and the exposed photosensitive material forms a sealant surrounding the one or more gratings which prevents moisture from contacting the one or more gratings.

[0009] In some aspects, the techniques described herein relate to a method, wherein the exposure of one or more holographic materials is through a photomask to produce the one or more holographic gratings.

[0010] In some aspects, the techniques described herein relate to a method, wherein printing the one or more holographic materials on the bottom substrate includes: printing, using a first head of an inkjet printer, a first holographic material on the bottom substrate; printing, using a second head of the inkjet printer, a second holographic material on the bottom substrate; and printing, using a third head of the inkjet printer, a third holographic material on the bottom substrate.

[0011] In some aspects, the techniques described herein relate to a method, wherein the exposed one or more holographic materials forms an input grating, a fold grating, and an output grating.

[0012] In some aspects, the techniques described herein relate to a method, wherein the head that prints the photosensitive material is different from the one or more heads that print the holographic materials.

[0013] In some aspects, the techniques described herein relate to a method, wherein exposing the one or more holographic materials and the photosensitive material to a recording beam includes: exposing the edges of the photosensitive material which surrounds the one or more holographic materials; exposing the one or more holographic materials; and exposing the remaining photosensitive material which surrounds the one or more holographic materials.

[0014] In some aspects, the techniques described herein relate to a method, wherein exposing the edges of the photosensitive material includes masking the one or more holographic materials and the remaining photosensitive material while exposing the edges of the photosensitive material.

[0015] In some aspects, the techniques described herein relate to a method, wherein exposing the photosensitive material cures the photosensitive material.

[0016] In some aspects, the techniques described herein relate to a method, wherein the photosensitive material includes monomers, photoinitiators, diluents, and solvents.

[0017] In some aspects, the techniques described herein relate to a method, wherein the monomers are acrylates.

[0018] In some aspects, the techniques described herein relate to a method, wherein the monomers include alicyclic, aromatic, and aliphatic groups.

[0019] In some aspects, the techniques described herein relate to a method, wherein the monomers include cage-like structures.

[0020] In some aspects, the techniques described herein relate to a method, wherein the one or more holographic materials each include monomers, an inert material, and a photoinitiator.

[0021] In some aspects, the techniques described herein relate to a method, wherein the inert material includes a liquid crystal.

[0022] In some aspects, the techniques described herein relate to a waveguide display including: an input grating, wherein the input grating inputs a light in total internal reflection within the waveguide; an output grating, wherein the output grating outputs the light towards a user; an adhesive material, wherein the adhesive material is disposed between the input grating and the output grating.

[0023] In some aspects, the techniques described herein relate to a waveguide display, further including a fold grating, wherein the input grating directs the light in total internal reflection towards to the fold grating, wherein the fold grating provides beam expansion on the light, wherein the fold grating directs the light towards the output grating.

[0024] In some aspects, the techniques described herein relate to a waveguide display, wherein the adhesive material is disposed between the input grating, the fold grating, and the output grating.

[0025] In some aspects, the techniques described herein relate to a waveguide display, wherein the adhesive material protects each grating from a contaminant.

[0026] In some aspects, the techniques described herein relate to a waveguide display, wherein the adhesive material includes a small molecular weight monomer, a photoinitators, an adhesion promoter, and a filler.

[0027] In some aspects, the techniques described herein relate to a waveguide display, wherein the filler is selected from a non-reactive or a reactive material.

[0028] Additional embodiments and features are set forth in part in the description that follows, and in part will become apparent to those skilled in the art upon examination of the specification or may be learned by the practice of the disclosure. A furtherunderstanding of the nature and advantages of the present disclosure may be realized by reference to the remaining portions of the specification and the drawings, which forms a part of this disclosure.BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The description will be more fully understood with reference to the following figures, which are presented as embodiments of the invention and should not be construed as a complete recitation of the scope of the invention, wherein:

[0030] Figure 1A schematically illustrates a plain view of a waveguide display in accordance with an embodiment.

[0031] Figure 1 B schematically illustrates a cross-sectional view of a waveguide display in accordance with an embodiment.

[0032] Figures 2A to 2E schematically illustrate a process of manufacturing a waveguide display in accordance with an embodiment.

[0033] Figure 3 illustrates a method for forming a waveguide display in accordance with an embodiment.DETAILED DESCRIPTION

[0034] Waveguide displays may include a waveguide with various gratings which may be manufactured using a holographic exposure process to create various grating structures such as volume Bragg gratings (VBG) and / or evacuated periodic structures (EPS). A holographic polymer dispersed liquid crystal (HPDLC) mixture or reactive monomer liquid crystal mixture (RMLCM) may be exposed to a holographic recording beam to form the grating. The HPDLC may include a mixture of monomer and liquid crystal (LC). Examples of this process and the formed gratings are discussed in U.S. Pat. Pub. No. 2021 / 0063634, entitled “Evacuating Bragg gratings and methods of manufacturing” and filed on Aug. 28, 2020, which is hereby incorporated by reference in its entirety for all purposes. After exposure, the formed grating includes alternating LC rich regions and polymer rich regions. Both the LC rich regions and the polymer rich regions contain at least some LC. LC may be used in HPDLCs to provide index difference between LC rich regions and polymer rich regions. Differences in effective refractiveindices may define grating structures and thereby Bragg response or optical diffraction efficiency in waveguide-based displays. High refractive index nanoparticles can also be used to create grating structures with varying refractive indices where nanoparticle rich regions create domains of higher refractive indices compared to polymer rich regions. Examples of nanoparticle-based holographic structures as described in U.S. Pat. Pub. No. 2023 / 0266512, entitled “Nanoparticle-based Holographic Photopolymer Materials and Related Applications” and filed on Jul. 14, 2020, which also incorporated by reference in entirety for all purposes.

[0035] Water molecules can react with LCs or inorganic ligand coordination sites in nanoparticles and their derivatives. These reactions can be permanent or temporary resulting in physical transformation. External molecules (e.g. water) can affect inter / intra molecular interactions in LCs leading to significant modification of optical performance of nematic droplets. For example, aggregation or precipitation of liquid crystalline molecules can increase haze; therefore, LCs need to be shielded from contamination of water molecules. The HPDLC mixture may include aromatic components such as biphenyls, tolanes or terphenyls which can precipitate on exposure to moisture, due to insolubility of these components in aqueous medium. Moisture can result in hazy or opaque material hindering the see-through transparency, especially when used in transparent display device. Desiccants in formulations can preferentially react with moisture before any reaction between water & liquid crystals and thereby providing nano-barrier protection for sensitive optical components. Examples of holographic mixtures including moisture absorbing materials are described in Int. App. No. PCT / US2023 / 078846, entitled “Holographic Mixtures Including Moisture Absorbing Materials” and filed Nov. 6, 2023 which is hereby incorporated by reference in its entirety for all purposes. One example is high modulation domains of LC droplets in their nematic phase in HPDLCs. Such desiccants in grating regions can stop water vapors. Hence, chemically reactive materials like desiccants can protect sensitive optical components such as domains of HPDLCs from degradation due to moisture. While described in the context of liquid crystal, the invention also includes holographic mixtures including photopolymerizable monomers mixed with an inert fluid which may be sensitive to moisture.

[0036] Disclosed herein are waveguide-based displays which perform even whenexposed to harsh conditions which includes one or many external stimuli such as high temperature, & humidity. The waveguide-based displays may include gratings (e.g. input gratings, output gratings, and / or fold gratings) which may include HPDLC mixtures and are fabricated utilizing exposure techniques as described above. Sealing of such displays may protect against moisture exposure as well as prevent LC diffusion outside of the grating region when subjected to storage temperatures above LC melting temperature. The gratings may be surrounded within an adhesive material which may act as a sealant material. Gratings surrounded with this adhesive material can be used to manufacture stable displays with no degradation or acceptable reduction in performance under various conditions including continuous usage at ambient environments, during extended storage, and upon exposure to high humidity, and temperature. The stable displays may be integrated into lenses or head worn displays. Very low reduction or change in optical efficiency at elevated temperatures and high humidity is desirable in such devices.

[0037] The gratings may include ester linkages as part of the polymer backbones such as polyesters or polylactic acids (PLAs) . During the lifetime of such products, the hydrolytic chain scission of ester bonds that randomly takes place in the polymer might be considered a primary cause of reduction in molecular weight and the related deterioration of mechanical and physical properties of PLA. Water molecules may penetrate the polymer matrix and simultaneously convert the long polymer chain to low- molecular-weight, water-soluble oligomers and the given monomer. It follows that an effective suppression of the degradation may include diminishing the hydrolysis process, either to prevent the water penetration or to slow down the rate of hydrolytical reactions.

[0038] In various embodiments, a pair of substrates may sandwich an unexposed holographic mixture. The holographic mixture may be exposed in order to produce one or more volume gratings such as volume Bragg gratings. Different unexposed holographic mixtures may be inkjet printed on different portions of a substrate in order to produce different gratings such as an input grating, a fold grating, and an output grating. As an example, different print heads on a single printer may store the different holographic mixtures such that a first print head may print a first mixture which is used to produce an input grating, a second print head may print a second mixture which is used to produce a fold grating, and a third print head may print a third mixture which is used to produce anoutput grating. A fourth print head may print a fourth mixture which may surround the printed first mixture, the printed second mixture, and the printed third mixture and may be exposed to produce the sealant. Inkjet printing may be considered as an example of various deposition techniques, but waveguides with these multiple material types may also be manufactured by other deposition techniques.

[0039] Fig. 1A is a schematic plain view of an example waveguide which may be utilized in a waveguide based display in accordance with an embodiment of the invention. The waveguide includes one or more gratings. As illustrated, there may be an input grating 108, a fold grating 106, and / or an output grating 104. The input grating 108 inputs light into total internal reflection in the waveguide and towards the fold grating 106. The fold grating 106 performs beam expansion on the light and directs the light to the output grating 104. The output grating 104 outputs light towards a user. In some examples, the output grating 104 may also perform beam expansion on the light. The waveguide may include more or less gratings. For example, the waveguide may include an input grating 108 and an output grating 104. The input grating 108 may input light into total internal reflection in the waveguide and towards the output grating 104. The output grating 104 may provide beam expansion and output light. Furthermore, there may be more than one of at least one of the input, fold, or output gratings, according to the waveguide architecture, to provide paths for different angular ranges colors, and polarizations or different beam expansions in the case of more than one fold grating.

[0040] There may be an adhesive material 102 separating the gratings 104, 106, 108. The adhesive material 102 may adhere two separated substrates. The adhesive material 102 may be positioned on the same layer as the gratings 104, 106, 108. The adhesive material 102 may be a sealant. The adhesive material 102 protects the gratings 104, 106, 108 from various contaminants 110 such as moisture.

[0041] Fig. 1 B is a schematic cross-sectional view of an example waveguide which may be utilized in a waveguide-based display in accordance with an embodiment of the invention. The waveguide includes various gratings 152 supported by a bottom substrate 154. The gratings 152 are positioned between the bottom substrate 154 and a top substrate 156. An adhesive 158 occupies areas around the gratings 152. The adhesive 158 adheres the top substrate 156 to the bottom substrate 154. The adhesive 158protects the gratings 152 from various contaminants such as moisture. While the gratings 152 are illustrated to contact both the bottom substrate 154 and the top substrate 156, in some embodiments, the gratings 152 may be separated from the top substrate 156 and merely contact the bottom substrate 154. In some embodiments, the gratings 152 may be supported by the top substrate 156 and merely contact the top substrate 156 and be spaced apart from the bottom substrate 154. The gratings 152 may include one or more input gratings, one or more output gratings, and / or one or more fold gratings.

[0042] The adhesive may be applied utilizing a formulation including small molecular weight monomers or oligomers, photoinitiators, adhesion promoters along with diluents or solvents and other filler-like components based on non-reactive (or inert in a monomer rich medium) or reactive (aka with monomeric functional substituents) materials such as nanoparticles and polymeric barriers. Examples of fillers are functionalized nanoparticles based on Ti, Zr, Si, or similar, and non-reactive fillers including poly-isobutylene (PIB) or similar hydrophobic materials. Monomers with higher functionality ratio may be stronger, but higher degree of cross-linking may hinder phase separation. Monomers or oligomers with higher reactive functionality may result in rigid structures because of increased crosslinking density. Active holographic formulations may include lesser cross-linked structures. Reduced cross linked structures are soft and flexible, may contain higher ‘free- volume’ or ‘voids’ in the polymer network. Hence, foreign molecules like water can be penetrated through polymer networks. Water molecules can reduce optical performance by degrading the structural integrity of the HPDLCs. Adhesive and / or sealant formulations with higher cross-linking can be used protect sensitive structures such as LCs in HPDLCs.

[0043] Edge sealants may be utilized to prevent moisture from penetrating into the waveguide. Edge sealants with very low water vapor transition rate (WVTR) can stop moisture. The efficacy of low WVTR sealants may come from several material characteristics such as cross-linking (physical or chemical), glass transition temperature (Tg), and / or porosity of polymer network. However, these edge sealants may not be the best option due to aesthetic reasons and thus may not be a good option for waveguide based displays. Various embodiments may include ink jet printable adhesive monomers. These printable monomers may include reactive formulation which may be utilized to form sealants. Sealants may be utilized in waveguides to bond substrates and keep lensesintact and protect lens from moisture ingress. Sealants may be on the same film plane and in contact with the holographic photopolymers utilized for the gratings.

[0044] Various embodiments of the sealant formulation include photoinitiators, diluents, solvents, adhesion promoters, and photocurable monomers. The photoinitiators may also be photosensitizers. Diluents and / or solvents may be reagents to reduce viscosity. The monomers may include various reactive monomer types. The reactive group in monomers may each be acrylates or similar monomers with compatible functional groups. Incompatibility may arise from differences in chemical polarity or miscibility of components which can lead to non-continuous films adversely affecting optical characteristics such as haze, contrast or resolution. The photoinitiators may include dyes and co-initiators. The photoinitiators for each of the examples may be between 0.001 wt% and 10 wt%. The diluents and / or solvents for each of the examples may be between 0.1 and 10 wt%. The diluents and / or solvents may be higher than 10 wt% as needed to reduce viscosity. There may be different types of reactive monomers utilized as monomers. These reactive monomers may include monofunctional aliphatic groups including alicyclics or aromatic groups, and their functionality may be 2 or more. These monomers may also be blended with other reactive molecules having rigid cyclic structures. In some embodiments, monomers with cyclic groups include cage-like compounds. In some embodiments, the amount of alicyclic monofunctional reactive monomers may be between 5 and 15 wt%. The amount of aromatic, monofunctional reactive monomers may be between 10 and 20 wt%. Some of the alicyclic, caged / rigid monomers are designed to have higher Tgfor the resultant adhesive polymer backbone.

[0045] In a first specific embodiment, the sealant formulation may contain aliphatic bifunctional reactive monomers. The amount of aliphatic, bifunctional reactive monomers may be greater than 40% by weight and / or be largest in composition of one of the bifunctional components may be as high as ~50 wt% or similar in addition to other monofunctional monomers, photoinitiator solutions and diluents.

[0046] In a second specific embodiment, the sealant formulation may contain a combination of bifunctional, multifunctional (e.g. >3), and cyclic / caged / rigid aliphatic reactive monomers along with photoinitiator solutions and diluents. In some examples, the amount of aliphatic, bifunctional reactive monomers may be greater than 10 wt%and / or less than ~50 wt%. In some examples, the amount of aliphatic multi-functional (e.g. >3) monomers may be more than 10 wt%. In some examples, the sealant formulation may contain cylic / caged / rigid-like molecules. The amount of reactive cycl ic / cage / rig id-l ike molecules may be greater than 3 wt% or 5 wt%.

[0047] In a third specific embodiment, the sealant formulation may contain a combination of aliphatic bifunctional, aliphatic multifunctional (e.g. >3), and alicyclic reactive monomers along with photoinitiator solutions and diluents. In some examples, the amount of aliphatic, bifunctional reactive monomers may be greater than 10 wt%, the amount of aliphatic, multi-functional reactive monomers may be greater than 10 wt%, the amount of alicyclic, reactive monomer may be greater than 5 wt% or 15 wt%.

[0048] In some embodiments, the reactive monomers and oligomers include (meth)acrylate groups. In some embodiments, the reactive monomers and oligomers include urethane, epoxy, polyester, siloxanes and silsesquioxanes (SSQs) groups.

[0049] Exemplary useful reactive monomers / oligomers include benzyl (meth) acrylate, phenoxy ethyl (meth) acrylate, phenoxy-2-methylethyl(meth)acrylate, phenoxyethoxyethyl (meth)acrylate, 3 - hydroxy - 2 - hydroxypropyl (meth)acrylate, phenylthio ethyl (meth) acrylate, lauryl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentadienyl (meth)acrylate, dicyclopentanyl acrylate, 1 - adamantyl (meth)acrylate, 2-adamantyl (meth)acrylate, cyclohexyl (meth)acrylate, butyl (metha)crylate, 3,3,5 - trimethyl cyclohexyl (meth)acrylate, tricyclodecanedimethanol di (meth)acrylate, tris (2 - hydroxyethyl) iso cyanurate tri (meth) acrylate, cyclohexanedimethanol di (meth)acrylate), hexane diol di(meth)acrylate, 1 ,6-hexanediol di(meth)acrylate, propone di(meth)acrylate, butane diol di(meth)acrylate, tripropylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, bisphenol A di(meth)acrylate, ethoxylated and propoxylated bisphenol A di(meth)acrylates, beta carboxy ethyl (meth)acrylate, urethane (meth)acrylate oligomers, (meth)acrylated polysiloxanes or combinations thereof.

[0050] In some embodiments, the cured monomer / oligomer used as the sealant has a glass transition temperature (Tg) higher than expected device reliability / ageing temperatures.

[0051] The Waveguides (WGs) were fabricated using inkjet printed holographicmaterials and sealants. The WGs may contain adhesive materials that include high refractive index (Rl) components such as liquid crystals and / or nanoparticles.

[0052] As discussed above, moisture penetrates through the edges of the waveguides and interacts with the gratings within the waveguide. The moisture may react with polymer chains or high Rl components in the gratings resulting in loss in optical efficiency or increase in haze and damage of polymer chains resulting in delamination or cracking of polymer films. One example of high refractive index components is TiO2 based nanocrystals. Ligand capped nanocrystals are used in formulations, especially for inkjet printable materials. Such components may be synthesized by reacting ligands with nanocrystal cores (Ti, as an example). Moisture ingress can affect metal-ligand bonds, hence resulting in a change of refractive index & diffraction efficiency. This may be a major problem in waveguides as this can result in changes of diffraction efficiency affecting light extraction, color uniformity, etc.

[0053] All of the first specific embodiment, second specific embodiment, and third specific embodiment were evaluated. Optical properties were measured after storing at 70 degrees C and 90% relative humidity for extended (e.g. days / weeks) as one of the test conditions. While all of these embodiments showed good optical properties, the second specific embodiment and the third specific embodiment shows superior optical efficiency, optical contrast, and adhesion in comparison with the first specific embodiment.

[0054] Figs. 2A-2E are schematics of an example manufacturing process for a waveguide based display. Fig. 2A is a plan view of an example. An inkjet printer may include four print heads. A first print head may print a first holographic material on a substrate. A second print head may print a second holographic material on the substrate. A third print head may print a third holographic material on the substrate. A fourth print head may print a photosensitive material on the substrate. The photosensitive material may be utilized to form the sealant / adhesive. The first holographic material may be used to produce an input grating, the second holographic material may be used to produce a fold grating, and the third holographic material may be used to produce an output grating. The photosensitive material may be used to produce a sealant and may surround the first holographic material, the second holographic material, and the third holographic material. The first holographic material, the second holographic material, and the third holographicmaterial may include a monomer and an inert material. When exposed, the monomer and inert material may phase separate to produce a polymer matrix and inert material rich regions. The first holographic material, the second holographic material, and the third holographic material may be different. For example, the first holographic material, the second holographic material, and the third holographic material may have different concentrations of monomer and inert material. The inert material may be liquid crystal.

[0055] The photosensitive material is described in detail above and may contain photoinitiators, diluents, solvents, adhesion promoters and / or monomers.

[0056] Fig. 2B is a cross sectional schematic of a step in manufacturing the waveguide display. The step includes placing a top substrate on top of the first holographic material, the second holographic material, and the third holographic material and the photosensitive material.

[0057] Fig. 2C-1 is a cross sectional schematic of a step in manufacturing the waveguide display. Fig. 2C-2 is a plain view of the step in manufacturing the waveguide display. The step includes using a mask and exposing the sealant at the edge to create an edge sealant. During the waveguide manufacturing, index fluids or liquids may be used to copy the grating structures from the master to the photopolymers. Such index fluids can penetrate between substrates and dilute or corrupt materials along the edge of the substrate. Edge sealing is the first process to create a barrier so that materials are not contaminated during contact copy process. During edge cure, sealant material is partially cured or gelled. Full cure happens only at the end along with other exposed holographic materials, which is a post-cure. Excessive exposure during precure may corrupt holographic material, which makes this partial cure advantageous.

[0058] Fig. 2D is a cross sectional schematic of a step in manufacturing the waveguide display. The step includes exposing the first holographic material, the second holographic material, and the third holographic material with one or more holographic recording beams. The holographic recording beams may interfere to form a fringe pattern which creates an input grating, a fold grating, and an output grating.

[0059] Fig. 2E is a plain view of a schematic of a step in manufacturing the waveguide display. The step includes curing the photosensitive material through exposure to light to produce the sealant. The exposure may be the same exposure as the holographicrecording beams. For example, a photomask may be used to create the interference pattern to expose the first holographic material, the second holographic material, and the third holographic material whereas the photomask may be absent in the sections of the photosensitive material.

[0060] Fig. 3 is an example method for forming a waveguide display in accordance with an embodiment of the invention. The method includes printing (302) one or more holographic materials on a bottom substrate. The printing may be performed using one or more heads of an inkjet printer. The method further includes printing (304) a photosensitive material on the bottom substrate. The printing may be performed using a head of the inkjet printer. The method further includes positioning (306) a top substrate such that the one or more holographic materials and the photosensitive material are positioned between the bottom substrate and the top substrate. The top substrate may be a cover substrate. The bottom substrate and / or the top substrate may be glass or plastic. The method further includes exposing (308) the one or more holographic materials and the photosensitive material to a recording beam. The exposed one or more holographic materials forms one or more gratings. The exposed photosensitive material forms a sealant surrounding the one or more gratings which prevents moisture from contacting the one or more gratings.

[0061] The exposure of one or more holographic materials may be performed through a photomask to produce one or more holographic gratings. The photomask may produce an interference pattern which may expose one or more holographic materials. Printing the one or more holographic materials on the bottom substrate may include: printing, using a first head of an inkjet printer, a first holographic material on the bottom substrate; printing, using a second head of the inkjet printer, a second holographic material on the bottom substrate; and printing, using a third head of the inkjet printer, a third holographic material on the bottom substrate.

[0062] The exposed one or more holographic materials forms an input grating, a fold grating, and an output grating. The head that prints the photosensitive material is different from the one or more heads that print the holographic materials.DOCTRINE OF EQUIVALENTS

[0063] While the above description contains many specific embodiments of the invention, these should not be construed as limitations on the scope of the invention, but rather as an example of one embodiment thereof. It is therefore to be understood that the present invention may be practiced in ways other than specifically described, without departing from the scope and spirit of the present invention. Thus, embodiments of the present invention should be considered in all respects as illustrative and not restrictive. Accordingly, the scope of the invention should be determined not by the embodiments illustrated, but by the appended claims and their equivalents.

[0064] As used herein, the singular terms “a,” “an,” and “the,” may include plural referents unless the context clearly dictates otherwise. Reference to an object in the singular is not intended to mean “one and only one” unless explicitly so stated, but rather “one or more.”

[0065] As used herein, the terms “approximately” and “about” are used to describe and account for small variations. When used in conjunction with an event or circumstance, the terms can refer to instances in which the event or circumstance occurs precisely as well as instances in which the event or circumstance occurs to a close approximation. When used in conjunction with a numerical value, the terms can refer to a range of variation of less than or equal to ± 10% of that numerical value, such as less than or equal to ±5%, less than or equal to ±4%, less than or equal to ±3%, less than or equal to ±2%, less than or equal to ±1 %, less than or equal to ±0.5%, less than or equal to ±0.1 %, or less than or equal to ±0.05%.

[0066] Additionally, amounts, ratios, and other numerical values may sometimes be presented herein in a range format. It is to be understood that such range format is used for convenience and brevity and should be understood flexibly to include numerical values explicitly specified as limits of a range, but also to include all individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly specified. Where ranges are described, the range should be understood to include the endpoints of the ranges, and the endpoints of such ranges are also contemplated to stand on their own as inventive, individual data points and to form the endpoints of other ranges. For example, a ratio in the range of about 1 to about 200 should be understood to include the explicitly recited limits of about 1 and about 200, butalso to include individual ratios such as about 2, about 3, and about 4, sub-ranges such as about 1 to about 10, about 10 to about 50, about 20 to about 100, about 100 to about 200, and so forth, and related ranges such as greater than about 1 or less than about 200.

Claims

WHAT IS CLAIMED IS:1 . A method of manufacturing a waveguide display, the method comprising: printing, using one or more heads of an inkjet printer, one or more holographic materials on a bottom substrate; printing, using a head of the inkjet printer, a photosensitive material on the bottom substrate; positioning a top substrate such that the one or more holographic materials and the photosensitive material are positioned between the bottom substrate and the top substrate; and exposing the one or more holographic materials and the photosensitive material to a recording beam, wherein the exposed one or more holographic materials forms one or more gratings and the exposed photosensitive material forms a sealant surrounding the one or more gratings which prevents moisture from contacting the one or more gratings.

2. The method of claim 1 , wherein the exposure of one or more holographic materials is through a photomask to produce the one or more holographic gratings.

3. The method of claim 1 , wherein printing the one or more holographic materials on the bottom substrate comprises: printing, using a first head of an inkjet printer, a first holographic material on the bottom substrate; printing, using a second head of the inkjet printer, a second holographic material on the bottom substrate; and printing, using a third head of the inkjet printer, a third holographic material on the bottom substrate.

4. The method of claim 1 , wherein the exposed one or more holographic materials forms an input grating, a fold grating, and an output grating.

5. The method of claim 1 , wherein the head that prints the photosensitive material is different from the one or more heads that print the holographic materials.

6. The method of claim 1 , wherein exposing the one or more holographic materials and the photosensitive material to a recording beam comprises: exposing the edges of the photosensitive material which surrounds the one or more holographic materials; exposing the one or more holographic materials; and exposing the remaining photosensitive material which surrounds the one or more holographic materials.

7. The method of claim 6, wherein exposing the edges of the photosensitive material comprises masking the one or more holographic materials and the remaining photosensitive material while exposing the edges of the photosensitive material.

8. The method of claim 1 , wherein exposing the photosensitive material cures the photosensitive material.

9. The method of claim 1 , wherein the photosensitive material comprises monomers, photoinitiators, diluents, and solvents.

10. The method of claim 9, wherein the monomers are acrylates.

11. The method of claim 10, wherein the monomers comprise alicyclic, aromatic, and aliphatic groups.

12. The method of claim 11 , wherein the monomers comprise cage-like structures.

13. The method of claim 1 , wherein the one or more holographic materials each include monomers, an inert material, and a photoinitiator.

14. The method of claim 13, wherein the inert material comprises a liquid crystal.

15. A waveguide display comprising: an input grating, wherein the input grating inputs a light in total internal reflection within the waveguide; an output grating, wherein the output grating outputs the light towards a user; an adhesive material, wherein the adhesive material is disposed between the input grating and the output grating.

16. The waveguide display of claim 15, further comprising a fold grating, wherein the input grating directs the light in total internal reflection towards to the fold grating, wherein the fold grating provides beam expansion on the light, wherein the fold grating directs the light towards the output grating.

17. The waveguide display of claim 16, wherein the adhesive material is disposed between the input grating, the fold grating, and the output grating.

18. The waveguide display of claim 15, wherein the adhesive material protects each grating from a contaminant.

19. The waveguide display of claim 15, wherein the adhesive material comprises a small molecular weight monomer, a photoinitators, an adhesion promoter, and a filler.

20. The waveguide display of claim 19, wherein the filler is selected from a non- reactive or a reactive material.

Images