CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority of U.S. Provisional Serial Application No. 62/822,378 filed on March 22, 2019 the contents of which are relied upon and incorporated herein by reference in their entirety as if fully set forth below.

BACKGROUND

FIELD

[0002] The present disclosure is directed to an optical assembly, for example an optical display device, and more particularly an optical assembly comprising features configured to scatter light emitted by electroluminescent elements disposed on a substrate, the features arranged adjacent pixel, subpixel, and/or color conversion volumes.

TECHNICAL BACKGROUND

[0003] Demand for new types of electronic displays, such as electroluminescent displays (e.g., organic light emitting diode - OLED, and micro-LED displays), has resulted in continuing need for improvements to technologies incorporated into these devices. For example, current LED displays can comprise arrays of individually packaged LED chips. To enable close packing of micro-LEDs required to create high resolution displays, multiple LEDs need to be placed on a single substrate, for example a glass substrate.

[0004] LED emission can be Lambertian, and for bottom-emission configurations particularly, a significant amount of the light emitted from a single LED can be trapped in the substrate due to total internal reflection (TIR) of the light intercepting a surface of the substrate at a large angle relative to a surface normal. This phenomenon can be at least partially overcome by roughing the substrate surface. Light extraction enhancements on the order of 50-80% have been reported through such surface modifications.

[0005] However, no surface roughening has achieved 100% extraction efficiency and some light can remain trapped in the substrate. If this trapped light is scattered by a non-planar interface or by other devices on the substrate surface, e.g., electrical traces, etc., light generated from one electroluminescent element can escape the substrate, for example, at the location of another electroluminescent element, and create any one or more of image blurring, non-uniform brightness, or reduced contrast from optical crosstalk.

SUMMARY

[0006] Embodiments of the present disclosure describe an optical assembly configured to direct light from an apparent source of light such that to an observer the light appears to come from an appropriate location on the substrate. For example, display devices can be comprised of a plurality of electroluminescent elements. The electroluminescent elements are turned on and off in a sequence and pattern that forms an image to an observer. For a color image, the various pixels are configured to produce a particular wavelength of light (color) at and appropriate time and position. Since the light sources that generate light are typically Lambertian emitters, light can spread from the electroluminescent element over a broad angular range. Some of that light can appear, through various mechanisms, to come from a location on the display panel (e.g., optical assembly) inconsistent with the color of the light. That is, while the light from that particular location may be designed to be green according to the image displayed, light from that location may appear blue because light from a neighboring blue electroluminescent element leaked to the green location. In other optical assemblies, single color electroluminescent elements may emit light that passes through color conversion layers, e.g., filters, that provide the color information. In such instances, light from the underlying electroluminescent elements may illuminate multiple color conversion layers of different colors. That is, the light emitted by an electroluminescent element, while intended to illuminate a conversion layer of a specific color, instead, illuminates several color conversion layers, thereby producing additional colors. The result of these phenomena can produce blurring, non- uniform brightness, or reduced contrast. To isolate individual pixels, or even individual electroluminescent elements (e.g., subpixels), damage tracks can be disposed in the substrate to scatter the light in a forward direction out of the substrate, while confining the light to be emitted from the substrate at the pixel location where the light was effectively produced. Thus, image brightness can be increased by improving light extraction from the substrate, and optical crosstalk can be minimized, therefore increasing image quality.

[0007] Accordingly, an optical assembly is described comprising a transparent substrate comprising a first major surface and a second major surface opposite the first major surface, the transparent substrate further comprising a damaged layer disposed between a first non- damaged layer including the first major surface and a second non-damaged layer including the second major surface, the transparent substrate still further comprising a pixel comprising a plurality of electroluminescent elements positioned on the first major surface, the pixel defining a pixel volume extending through the damaged layer. A plurality of damage tracks is disposed around the pixel volume within the damaged layer.

[0008] The first plurality of damage tracks can comprise a plurality of substantially parallel rows of damage tracks orthogonal to and crossing a plurality of substantially parallel columns of damage tracks.

[0009] In some embodiments, each electroluminescent element of the plurality of

electroluminescent elements defines a subpixel volume, and a second plurality of damage tracks can be disposed adjacent each subpixel volume defined by the plurality of

electroluminescent elements.

[0010] The second plurality of damage tracks can comprise a plurality of substantially parallel rows of damage tracks orthogonal to and crossing a plurality of substantially parallel columns of damage tracks.

[0011] In some embodiments, one electroluminescent element of the plurality of

electroluminescent elements can be configured to emit a wavelength of light different than a wavelength of light of another electroluminescent element of the plurality of

electroluminescent elements.

[0012] In some embodiments, each electroluminescent element of the plurality of

electroluminescent elements can be configured to emit a wavelength of light the same as a wavelength of light of another electroluminescent element of the plurality of

electroluminescent elements.

[0013] The optical assembly may further comprise a plurality of color conversion layers disposed on the second major surface, wherein individual color conversion layers of the plurality of color conversion layers can be disposed directly opposite a corresponding individual electroluminescent element of the plurality of electroluminescent elements.

[0014] In some embodiments, each damage track of the plurality of damage tracks positioned adjacent a pixel volume or a subpixel volume can comprise a longitudinal axis forming a non-zero angle relative to a normal to one of the first major surface or the second major surface. [0015] In some embodiments, the damaged layer can comprise a plurality of damaged layers stacked between the first non-damaged layer and the second non-damaged layer.

Accordingly, in such embodiments, each damage track can comprise a plurality of damage tracks stacked vertically and arranged within the plurality of damaged layers.

[0016] The transparent substrate can be selected from a group of substrates including glass, fused silica, sapphire, polymers, and glass ceramics.

[0017] In various embodiments, the plurality of electroluminescent elements can comprise microLEDs or organic light emitting diodes.

[0018] In other embodiments, an optical assembly is disclosed comprising a transparent substrate comprising a first major surface and a second major surface opposite the first major surface, the transparent substrate further comprising a damaged layer disposed between a first non-damaged layer including the first major surface and a second non-damaged layer including the second major surface, the transparent substrate still further comprising a pixel defined by a plurality of electroluminescent elements deposited on the first major surface, each electroluminescent element of the plurality of electroluminescent elements defining a subpixel volume extending through the damaged layer. A plurality of damage tracks can be disposed adjacent each subpixel volume, for example around each subpixel volume.

[0019] The optical assembly may further comprise a plurality of color conversion layers positioned on the second major surface, each color conversion layer of the plurality of color conversion layers positioned directly opposite a corresponding electroluminescent element of the plurality of electroluminescent elements.

[0020] In some embodiments, each electroluminescent element of the plurality of

electroluminescent elements can be configured to emit a wavelength of light the same as a wavelength of light of another electroluminescent element of the plurality of

electroluminescent elements.

[0021] The plurality of damage tracks can comprise a plurality of substantially parallel rows of damage tracks orthogonal to and crossing a plurality of substantially parallel columns of damage tracks.

[0022] In some embodiments, each damage track of the plurality of damage tracks can comprise a longitudinal axis forming a non-zero angle relative to a normal to one of the first major surface or the second major surface. [0023] In various embodiments, the plurality of electroluminescent elements can comprise microLEDs or organic light emitting diodes.

[0024] In still other embodiments, an optical assembly is described comprising a first substrate comprising a first major surface and a second major surface opposite the first major surface, the first substrate comprising a pixel defined by a plurality of electroluminescent elements deposited on the second major surface of the first substrate. A transparent second substrate is arranged opposite and substantially parallel to the first substrate, the transparent second substrate comprising a third major surface opposite the second major surface, and a fourth major surface opposite the third major surface, the transparent second substrate further comprising a damaged layer disposed between a first non-damaged layer including the third major surface and a second non-damaged layer including the fourth major surface, the third major surface comprising a plurality of color conversion layers positioned thereon, each color conversion layer of the plurality of color conversion layers defining a color conversion volume extending through the damaged layer. A plurality of damage tracks can be disposed adjacent one or more of the color conversion volumes defined by the plurality of color conversion layers.

[0025] In some embodiments, the plurality of damage tracks can comprise a plurality of substantially parallel rows of damage tracks orthogonal to and crossing a plurality of substantially parallel columns of damage tracks.

[0026] In various embodiments, the transparent second substrate can be selected from a group of substrates including glass, fused silica, sapphire, polymers, and glass ceramics.

[0027] In some embodiments, a black matrix material can be disposed on the third major surface between color conversion layers.

[0028] In some embodiments, each damage track of the plurality of damage tracks can comprise a longitudinal axis forming a non-zero angle relative to a normal to one of the first major surface or the second major surface.

[0029] In various embodiments, each electroluminescent element of the plurality of electroluminescent elements can be configured to emit a wavelength of light the same as a wavelength of light of another electroluminescent element of the plurality of

electroluminescent elements.

[0030] In various embodiments, the transparent second substrate can be selected from a group of substrates including glass, fused silica, sapphire, polymers, and glass ceramics [0031] In some embodiments, the damaged layer can comprise a plurality of damaged layers stacked between the first non-damaged layer and the second non-damaged layer. For example, each damage track of the plurality of damage tracks can comprise more than one damage track, the more than one damage tracks stacked vertically within the plurality of damaged layers.

[0032] In various embodiments, each electroluminescent element of the plurality of electroluminescent elements can comprise a micro-LED or an organic light emitting diode.

[0033] Additional features and advantages will be set forth in the detailed description that follows, and in part will be clear to those skilled in the art from that description or recognized by practicing the embodiments described herein, including the detailed description which follows, the claims, as well as the appended drawings.

[0034] Both the foregoing general description and the following detailed description are merely exemplary and are intended to provide an overview or framework to understanding the nature and character of the claims. The accompanying drawings are included to provide further understanding and are incorporated in and constitute a part of this specification. The drawings illustrate one or more embodiment s), and together with the description, explain principles and operation of the various embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

[0035] FIGS. 1 A and IB are schematic depictions of an apparatus for making a component of an optical assembly in accordance with exemplary embodiments;

[0036] FIG. 2 is a diagrammatic depiction of the optical system used in the apparatus depicted in Figures 1 A and IB;

[0037] FIG. 3 is a flow chart illustrating a method for making a component of an optical assembly in accordance with exemplary embodiments;

[0038] FIG. 4 is a cross-sectional edge view of a substrate with integral damage tracks in accordance with exemplary embodiments;

[0039] FIG. 5 is a cross-sectional view of another substrate with integral damage tracks in accordance with exemplary embodiments;

[0040] FIG. 6 is a cross-sectional view of substrate comprising an electroluminescent element in accordance with exemplary embodiments illustrating potential light paths; [0041] FIG. 7 is a plan view of an exemplary optical assembly in accordance with exemplary embodiments described herein, the optical assembly comprising substrate with a plurality of pixels and pixel volumes, and a plurality of damage tracks extending adjacent the pixel volumes;

[0042] FIG. 8 is a cross-sectional edge view of an optical assembly comprising a substrate with a plurality of pixels and pixel volumes, without a plurality of damage tracks extending adjacent the pixel volumes, and potential light paths without the damage tracks;

[0043] FIG. 9 is a cross-sectional edge view of an optical assembly illustrating pixels and pixel volumes, and damage tracks;

[0044] FIG. 10 is a plan view of a portion of a substrate showing an area pattern of damage tracks in the substrate;

[0045] FIG. 11 is a plan view of a portion of another substrate showing an area pattern of damage tracks in the substrate;

[0046] FIG. 12 is a plan view of a portion of still another substrate showing an area pattern of damage tracks in the substrate, the damage tracks extending adjacent subpixel volumes related to subpixels on the substrate;

[0047] FIG. 13 is a plan view of an exemplary optical assembly in accordance with exemplary embodiments described herein, the optical assembly comprising a substrate with a plurality of subpixels, and related pixel volumes and subpixel volumes, and a plurality of damage tracks extending adjacent the subpixel volumes;

[0048] FIG. 14 is a cross-sectional edge view of a substrate with integral damage tracks, the damage tracks extending at an angle relative the major surfaces of the substrate;

[0049] FIG. 15 is cross-sectional edge view of an optical assembly comprising a substrate with a plurality of subpixels disposed on a first major surface of the substrate, the subpixels defining a plurality of pixel volumes, and a plurality of color conversion layers disposed on a second major surface of the substrate, and a plurality of damage tracks;

[0050] FIG. 16A is cross-sectional edge view of an optical assembly comprising a first substrate and a second substrate, the first substrate comprising a plurality of electroluminescent element and the second substrate comprising a plurality of color conversion layers; and

[0051] FIG. 16B is a close-up view of a portion of the optical assembly of FIG. 16A illustrating color conversion volumes in the second substrate and damage tracks. DETAILED DESCRIPTION

[0052] Reference will now be made in detail to the present embodiments, examples of which are illustrated in the accompanying drawings. Whenever possible, the same reference numerals will be used throughout the drawings to refer to the same or like parts.

[0053] As used herein, the term“about” means that amounts, sizes, formulations, parameters, and other quantities and characteristics are not and need not be exact, but may be approximate and/or larger or smaller, as desired, reflecting tolerances, conversion factors, rounding off, measurement error and the like, and other factors known to those of skill in the art.

[0054] Ranges can be expressed herein as from“about” one particular value, and/or to“about” another particular value. When such a range is expressed, another embodiment includes from the one particular value to the other particular value. Similarly, when values are expressed as approximations by use of the antecedent“about,” it will be understood that the particular value forms another embodiment. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.

[0055] Directional terms as used herein - for example up, down, right, left, front, back, top, bottom - are made only with reference to the figures as drawn and are not intended to imply absolute orientation.

[0056] Unless otherwise expressly stated, it is in no way intended that any method set forth herein be construed as requiring that its steps be performed in a specific order, nor that with any apparatus, specific orientations be required. Accordingly, where a method claim does not actually recite an order to be followed by its steps, or that any apparatus claim does not actually recite an order or orientation to individual components, or it is not otherwise specifically stated in the claims or description that the steps are to be limited to a specific order, or that a specific order or orientation to components of an apparatus is not recited, it is in no way intended that an order or orientation be inferred in any respect. This holds for any possible non-express basis for interpretation, including: matters of logic with respect to arrangement of steps, operational flow, order of components, or orientation of components; plain meaning derived from grammatical organization or punctuation, and; the number or type of embodiments described in the specification. [0057] As used herein, the singular forms "a," "an" and "the" include plural references unless the context clearly dictates otherwise. Thus, for example, reference to“a” component includes aspects having two or more such components, unless the context clearly indicates otherwise.

[0058] The word“exemplary,”“example,” or various forms thereof are used herein to mean serving as an example, instance, or illustration. Any aspect or design described herein as “exemplary” or as an“example” should not be construed as preferred or advantageous over other aspects or designs. Furthermore, examples are provided solely for purposes of clarity and understanding and are not meant to limit or restrict the disclosed subject matter or relevant portions of this disclosure in any manner. It can be appreciated that a myriad of additional or alternate examples of varying scope could have been presented but have been omitted for purposes of brevity.

[0059] As used herein, the terms“comprising” and“including”, and variations thereof, shall be construed as synonymous, open-ended, and interchangeable, unless otherwise indicated. A list of elements following the transitional phrases comprising or including is a non-exclusive list, such that elements in addition to those specifically recited in the list may also be present.

[0060] The terms“substantial,”“substantially,” and variations thereof as used herein are intended to note that a described feature is equal or approximately equal to a value or description. For example, a“substantially planar” surface is intended to denote a surface that is planar or approximately planar. Moreover,“substantially” is intended to denote that two values are equal or approximately equal. In some embodiments,“substantially” may denote values within about 10% of each other, such as within about 5% of each other, or within about 2% of each other.

[0061] As used herein, micro-LED refers to a light emitting diode with a light emission area with dimensions on the order of less than about 100 micrometers (pm) x about 100 pm (10,000 pm ² ), such as less than about 50 pm x about 50 pm (2,500 pm ² ), for example, less than about 10 pm x about 10 pm (100 pm ² ).

[0062] FIGS. 1A and IB are diagrammatic depictions of an exemplary apparatus 10 for making subsurface defects in a transparent substrate 12. As described herein, substrate 12 may be glass, fused silica, sapphire, a polymer, or any other suitable material. Figures 1 A-1B show substrate 12 disposed on platform 14. Briefly, imaging assembly 16 can be employed to generate a focal line to provide laser-induced scattering features within substrate 12 with a pulsed line-focus laser beam under the direction of controller 18. Substrate 12 is essentially transparent with respect to single photon absorption of the pulsed line-focus laser beam when propagating through substrate 12. Imaging assembly 16 can include laser light source 20 providing a pulsed laser beam, and optical system 22 that guides the pulsed laser beam from laser light source 20 to substrate 12 and forms a line focus within the substrate. Platform 14 may, in some embodiments, be employed as a translation mechanism for positioning substrate 12 relative to the focal line formed by optical system 22, although, as described below, other alternate embodiments are possible.

[0063] While traditional Gaussian optical beams can be used to create modified regions inside a transparent material, the length of the interaction region within that material is governed by diffraction of the beam and can be short. When Gaussian beams are focused to spot sizes small enough to generate optical intensities sufficient to produce an interaction response, they can have Rayleigh (depth of focus) ranges on the order of tens of micrometers. However, for Bessel beams, the length of interaction over which a small spot size is maintained can be much longer, easily over distances on the order of millimeters. Thus, a Bessel-like beam, or line focus, can modify the substrate material over a much longer distance in the substrate, in a single pass, than a standard Gaussian beam. Processing speeds with Bessel-like beams can be multiple orders of magnitude faster than with typical Gaussian beams.

[0064] The modified regions of the substrate, configured to scatter light propagating in the substrate, can incorporate micro cracks, substrate material that has melted and re-solidified, substrate material that has undergone a phase change, substrate material that has undergone a compositional change, substrate material that has changed amorphous or crystalline structure, substrate material that has undergone a change in refractive index, or combinations thereof. In some embodiments, such a modified region can comprise a tube-like region (when viewed in plane with or parallel to the substrate surrounded by radial micro cracks. As used hereinafter, modified regions in the substrate (e.g., scattering features) are broadly referred to as damage tracks. Damage tracks can be described as having a diameter L (see FIG. 4, for example), wherein the diameter L describes the roughly circular area of the substrate modified by the laser when the substrate is viewed from the top-down (i.e., orthogonal to the largest dimensions). Damage tracks can have a diameter L from about 0.5 pm to about 150 pm, about 10 pm to about 120 pm, about 10 pm to about 100 pm, or about 20 pm to about 80 pm. In the case where a damage track comprises a tube-like region surrounded by radial micro cracks, the tube-like region may have a diameter L of from about 0.5 pm to about 20 pm or about 3 pm to about 10 mih and the damage track (the tube-like region and the micro cracks) can have a diameter from about 10 mih to about 120 mih. In some embodiments, the damage tracks can have a diameter of about 10, 20, 30, 40, 50, 60, 70, 80, 90, or 100 mih.

[0065] It is also possible to form a long thin damage track through a process known as “filamentation”. In this method, a very short laser pulse of sufficient intensity is directed into a material to produce an optical Kerr effect, wherein the refractive index of the substrate material is locally modified by the high electric field strength of the laser pulse. This makes the beam self-focus and can create beams that propagate in long thin channels through many millimeters of substrate material. This process requires power in the laser pulse to exceed a threshold, Pcmicai (which for glass is typically about 5 MW). Hence, high energy lasers producing very short pulses (e.g., femtosecond pulses) are needed for filamentation.

[0066] The use of line-focus optics and Bessel-like beams with short-pulse lasers may be a preferred method to fabricate defect lines in the substrate. But the above-mentioned other methods can also be used to generate long thin defect lines, for example inside glass, albeit with trade-offs in either increased system cost or decreased reliability (from very short pulse and high energy lasers) or overall processing time (with Gaussian beams and many focus passes). Additionally, a series of short-length closely spaced features can approximate a line defect and can be made by a series of translations of the optical focus along the optical beam path.

[0067] Specifically, controller 18 can be configured as a highly automated apparatus substantially controlled by a computer-aided manufacturing program 24. In various embodiments, computer-aided manufacturing program 24 can use an executable file that directs relative motion between platform 14 and imaging assembly 16. Figure 1A illustrates relative movement between imaging assembly 16 and substrate 12 in the x-y plane, represented by double arrows 26 and 28, respectively. Figure IB is a side view illustrating relative movement between imaging assembly 16 and substrate 12 in the z-direction, orthogonal to the x-y plane, and represented by double arrow 30, and optionally in angular direction (Q).

[0068] In some embodiments, apparatus 10 can feature a stationary imaging assembly 16. In this instance, platform 14 can be configured to move beneath imaging assembly 16. The use of a hybrid apparatus 10 incorporating both platform 14 movements as well as imaging assembly 16 movements is contemplated. Platform 14 may comprise, for example, a programmable numerical control (CNC) apparatus. In some embodiments, platform 14 can be configured to move in one axial direction, whereas imaging assembly 16 can move in the remaining axes. The present disclosure also contemplates the use of a stationary platform 14, and an imaging assembly 16 configured to move in three-dimensional space over substrate 12 as dictated by computer-aided manufacturing program 24. An embodiment of computer-aided manufacturing program 24 is shown at FIG. 3 and described in the related text. The computer- aided manufacturing program 24 can also be configured to control laser and other optical parameters of imaging assembly 16.

[0069] Controller 18 can be configured to operate imaging assembly 16 to form a laser beam focal line at a precise location in three dimensions within substrate 12. Imaging assembly 16 can include laser light source 20 that operates in conjunction with optical system 22. For example, in various embodiments, laser light source 20 can be a pulsed laser. Specifically, controller 18 can be configured to control optical system 22 and laser light source 20 so a laser beam with predetermined laser characteristics traverses an optical beam path to generate an elongated laser-induced region of damage in substrate 12. For example, imaging assembly 16, under the control of controller 18, can generate a single laser pulse, or a burst of pulses, to produce a pulsed line focus laser beam to interact with substrate 12. The laser beam produces a focal line that generates an induced absorption within the substrate to produce a material modification along the laser beam focal line. This material modification is referred to herein as a laser-induced damage track, or damage track for short. Controller 18 may be implemented using a programmable numerical control (CNC) apparatus.

[0070] As noted briefly above, the wavelength of laser light source 20 can be selected such that substrate 12 is substantially transparent at the selected wavelength (e.g., absorption less than about 15% per millimeter (mm) of material depth > g « 1/centimeter (1/cm), where g is the Lambert-Beer absorption coefficient). The pulse duration of laser light source 20 can be selected such that no significant heat transport (e.g., heat diffusion) out of the zone of interaction can take place within the time of interaction (for example: t « d ² /a, where d is the focus diameter of the laser beam, t is the laser pulse duration, and a is the heat diffusion constant of the substrate material). The pulse energy of laser light source 20 can be selected such that the intensity of the laser beam in the zone of interaction, e.g., along the focal line, produces an induced absorption that leads to formation of a damage track corresponding to the focal line location. [0071] The polarization state of the laser beam produced by laser light source 20 may influence both interaction between the laser beam and the substrate at the surface of the substrate (e.g., reflectivity) and the type of interaction within the substrate (e.g., induced absorption). Induced absorption may take place by way of induced, free-charge carriers (typically electrons), either after thermal excitation, or by way of multiphoton absorption and internal photoionization, or by way of direct field ionization (where field strength of the light breaks electron bonding directly). For certain substrate materials (for example birefringent materials), further absorption and/or transmission of the laser light may depend on the polarization of the light. Consequently, the polarization, by way of suitable optics (e.g., phase plates), should be selected by the user to be conducive for modifying the respective substrate material. Therefore, if the substrate material is not optically isotropic, but for example birefringent, propagation of laser light in the substrate can be also influenced by polarization. Thus, laser beam polarization and orientation of the polarization vector may be selected such that one focal line is formed, not two (e.g., ordinary and extraordinary rays). In the case of optically isotropic substrate materials, this does not play any role.

[0072] Furthermore, optical intensity of the laser beam should be selected based on pulse duration, pulse energy, and focal line diameter such that there is preferably no significant ablation or significant melting of the substrate material, but rather damage track formation in the microstructure of the substrate. For typical substrate materials such as glass or transparent crystals, this requirement can be most easily satisfied with pulsed lasers in the sub-nanosecond range, for example with pulse durations of between about 0.1 picoseconds (ps) and 100 ps, and preferably less than 15 ps.

[0073] In some embodiments, the average diameter d of the laser beam focal line can be in a range from about 0.3 micrometers (pm) to about 5.0 pm, for example in a range from about 1.0 pm to about 3.0 pm, from about 0.4 pm to about 4.0 pm, or about 2.0 pm, and/or in that pulse duration t of laser light source 20 is selected such that, within the time of interaction with the material of substrate 12, heat diffusion in the material is negligible. Preferably no heat diffusion takes place. Accordingly, t, d, and the heat diffusion constant a of the substrate material can be set according to t « d ² /a and/or t can be selected to be less than about 10 nanoseconds (ns), for example less than about 100 ps, and/or in that the pulse repetition rate of laser light source 20 is between about 10 kHz and about 1000 kHz (e.g., about 100 kHz), and/or in that laser light source 20 is operated as a single-pulse laser or as a burst-pulse laser, with energies per burst pulse between about 40 microJoules (pJ) and about 1000 pj, and/or in that the average laser power, measured directly on the output side of the beam of laser light source 20, is in a range from about 10 watts to about 100 watts (e.g., in a range from about 30 watts to about 50 watts).

[0074] In certain embodiments, wavelength l of laser light source 20 can be selected such that the material of substrate 12 is transparent or substantially transparent to the selected wavelength, the latter meaning that any decrease in intensity of the laser beam taking place along the direction of the laser beam in the material of substrate 12 per millimeter of the depth of penetration of the laser beam is about 15% or less. For glasses or crystal substrates 12 that are transparent in the visible wavelength range, laser light source 20 can be, for example, an Nd:YAG laser with a wavelength l of 1064 nm or a Yb: YAG laser with a wavelength l of 1030 nm. For semiconductor substrates 12 that are transparent in the infrared wavelength range, laser light source 20 can be, for example, an EnYAG laser with a wavelength l in a range from about 1.5 pm to about 1.8 pm.

[0075] Reference is made to U.S. Published Patent Application No. US20140199519 or International Published Patent Application No. W02014/079570, which provide a more detailed explanation of an exemplary imaging assembly 16 and laser light source 20.

[0076] FIG. 2 is a schematic depiction of exemplary embodiments of optical system 22 shown in FIGS. 1 A and IB and used to form a focal line in an exemplary substrate 12. Substrate 12 is shown comprising a first major surface 32 on which the laser beam is incident, and an opposing second major surface 34. In various embodiments, optical system 22 can include an optical element 36 positioned in the path of laser beam 38. Optical element 36 can comprise a non-spherical free surface and can be implemented as an axicon with a 5° cone angle, which is positioned parallel to the direction 40 of laser beam 38 and centered thereon. The axicon cone tip in this case points counter to direction 40 of laser beam 38. The distance of the plano convex collimation lens 42 from optical element 36 is denoted by zla, the distance of focusing lens 44 from collimation lens 42 is denoted by zl b, and the distance of focal line 2b produced by focusing lens 44 is denoted by z2 (seen in each case in the direction of the beam). The annular transformation of laser beam 38 by optical element 36 is shown with the reference sign SR. The annular radiation SR formed by optical element 36 and incident on collimation lens 42 in a divergent manner, and with a ring diameter dr, has the ring diameter dr remaining at least approximately constant along distance zl b and is set to the desired ring width br at the location of focusing lens 44. As a result, a short focal line 2b is produced so that the ring width br of about 4.0 mm at the location of collimation lens 42 is reduced by the focusing properties of the latter at the location of focusing lens 44 to about 0.5 mm.

[0077] A focal line length 2b of about 0.5 mm or less can be achieved with a typical laser beam diameter of about 2.0 mm, a focusing lens 44 of f = 25 mm focal length, and a collimation lens 42 of f '= 150 mm focal length. Furthermore, in this example, z 1 a is substantially equal to zl b (140 mm) and z2 is substantially equal to about 15 mm.

[0078] As embodied herein and depicted in FIG. 3, a flow chart illustrating a method 100 for making a substrate 12 with integral defect lines is disclosed. In step 102, substrate 12 is selected. Substrate 12 may be glass, fused silica, sapphire, a polymer, or any suitable transparent substrate. Suitable glass materials can include various glass substrates such as quartz, borosilicate, aluminosilicate, aluminoborosilicate, sapphire or soda-lime glass, sodium- containing glass, hardened glass or unhardened glass.

[0079] In step 104, imaging assembly 16 parameters are selected in accordance with the selected material. As described above, some of these specifications (including ranges, if applicable) can include the laser wavelength, pulse width, spot size, pulse energy, scan speed and depth of focus for different substrate materials (e.g., glass compositions). As noted above, the“line-focus optics” (e.g. Gauss-Bessel or Bessel-like beams) used to create defect structures are advantageous because they can form elongated damage tracks in a single laser pass, as opposed to multiple passes that would be required using traditional laser beams. Moreover, since the combination of a short-pulse (< 100 ps) laser with Bessel beams forms focal lines producing no significant ablation or melting of the substrate material, they can be employed herein so that damage tracks are formed in the microstructure of substrate 12.

[0080] In step 106, the area pattern map to be formed in substrate 12 is provided to controller 18. As disclosed herein, the area pattern map may specify display device viewing angles and the size and position of pixel locations. In step 108, the focal length and the position of the focal length within the substrate may also be provided to controller 18. Determination of the x-y area pattern map, the focal line length, and other laser parameters described herein specify the formation and positioning of the damage tracks within substrate 12. In step 110, the angle Q for damage tracks (e.g., longitudinal axes thereof) is selected. If the damage tracks are designed to be normal to a first major surface 32 (10-1), of substrate 12, e.g., the major surface on which the laser beam is incident, then angle Q of imaging assembly 16 relative to substrate 12 selected in step 110 should be zero.

[0081] In steps 112-114, imaging assembly 16 laser-induces damage tracks within substrate 12 in accordance with the predetermined plan specified in steps 102-110. As shown in FIG. 5, the predetermined plan may call for multiple layers of tracks, in which case, decision diamond 116 would redirect the process flow to step 106. In such a case, it is generally preferred to form the lowest layer first (the layer farthest from the incident major surface), and then progress to layers above that, so that pre-existing damage tracks above the desired layer do not block the rays of the high numerical aperture beam from forming a line focus. Once the last damage layer is formed in substrate 12, the process may be terminated (step 118). Alternatively, the fabricated substrate can be strengthened in subsequent steps using thermal or chemical methods.

[0082] FIG. 4 is a cross-sectional view of an exemplary substrate 12 comprising first major surface 32 and second major surface 34, and a plurality of damage tracks 50 produced by the method 100 described above disposed between the first and second major surfaces. The integral damage tracks 50 can be implemented by multiple parallel transverse rows of damage tracks 50 periodically spaced and disposed in at least one vertical layer, i.e., a layer extending in a thickness direction of substrate 12. Damage tracks 50 extend over a thickness TL in the substrate and are disposed within a damage layer in the interior of substrate 12 between a top layer 46 of undamaged material with a thickness TGT and a bottom layer 48 of undamaged substrate material with a thickness TGB. Thus, the substrate thickness is TG = TGT + TL + TGB. The length TL of the damage tracks substantially corresponds to the focal line length generated by imaging assembly 16. The thickness of top and bottom layers 46, 48, where the glass is unmodified by the damage tracks, is selected to prevent cracks that might extend from a damage track from propagating to the major surfaces of the glass, and to provide substrate 12 with enough structural integrity to resist shear forces. Ensuring damage tracks 50 do not extend all the way to the glass surface can be preferred. When a crack reaches the glass surface, it creates a path for water or humidity ingress, which can promote rapid crack growth and cause failure of the part. In practice, keeping the thicknesses TGT and TGB > 50 pm, and more preferably > 100 pm, has been found sufficient to prevent part failure. For thin glass, e.g., < 1 mm, ensuring this stand-off distance from the major surfaces of the substrate can require precise control of the system focus and the energy density distribution within the laser line focus. However, in the case of thicker glass, e.g., > 3 mm, which is a common display glass thickness, larger stand- off distances may be employed (e.g. 250 pm or more) without significantly sacrificing optical performance. In some embodiments, as depicted in FIG. 5, damage tracks 50 can comprise multiple damage tracks stacked vertically over each other. For example, FIG. 5 illustrates three damage tracks disposed within distance TL in each vertical array of damage tracks.

[0083] The rows of damage tracks 50 can be separated by a row spacing D. Additionally, as previously described, individual damage tracks 50 can have a diameter L. As described in more detail following, rows, and columns, of damage tracks can be produced in a substrate such that damage tracks surround an electroluminescent picture elements (pixels) comprising an electroluminescent display panel. Such electroluminescent display panels can include, but are not limited to, micro-LED display panels or organic light emitting LED display panels. The region of substrate 12 that can be laser processed can be selected to include all or a portion of substrate 12. In one embodiment, for example, the damage tracks can feature a row (column) spacing D of about 50 pm to about 2000 pm, a pitch between individual damage tracks of about 3.0 microns to about 50 microns, and a damage track depth TL of about 0.2 mm to about 10 mm. As noted previously, diameter A and damage track thickness TL is determined at least by the spot diameter and the line-focus parameters of imaging assembly 16. Of course, the present disclosure should not be construed as being limited to the above stated values. These values and ranges are merely exemplary.

[0084] FIG. 6 depicts a cross-sectional side view of an exemplary optical assembly 200 comprising transparent substrate 202 including first major surface 204 and second major surface 206 opposite first major surface 204, and an electroluminescent element 208 (e.g., micro-LED, organic light emitting diode, or the like) deposited on first major surface 204. First major surface 204 may be parallel or substantially parallel to second major surface 206. Substrate 202 further comprises a thickness defined between first major surface 204 and second major surface 206. As used herein, deposited or positioned“on” refers to being coupled to substrate 202, but not necessarily in direct intimate contact with substrate 202. Substrate 202 may comprise any suitable material for the manufacture of an optical assembly, but in exemplary embodiments, may comprise a glass material, for example a borosilicate glass, an alumino-borosilicate glass, an alkali borosilicate glass, or the like. In other embodiments, substrate 12 may comprise fused silica, sapphire, a polymer, or any other suitable material. Optical assembly 200 may further include one or more electrode and/or semiconductor layers 210, such as transparent electrodes (e.g., transparent conductive oxides such as indium tin oxide, conductive polymers, carbon nanotubes, graphene, nanowire meshes, ultrathin metal films, and so forth), disposed on electroluminescent element 208, and/or between substrate 202 and the electroluminescent element 208. For example, while FIG. 6 illustrates two electrodes 210 positioned overtop electroluminescent element 208, in some embodiments, electroluminescent element 208 may comprise an electrode in contact with an“upper” surface of the electroluminescent element, and another electrode in contact with an opposing“lower” surface of the electroluminescent element. Electrodes may be positioned in contact with electroluminescent element 208 in any location or position necessary for the operation of the electroluminescent element

[0085] In some embodiments, one or more additional layers may be disposed on substrate 202, for example a planarization layer or encapsulation layer 212 disposed over first major surface 204. FIG. 6 illustrates an electroluminescent element 208 configured for bottom-emission, wherein light is directed from electroluminescent element 208 through first major surface 204, propagates through substrate 202, and is emitted from second major surface 206. Some light rays, like light ray 220, propagate through substrate 202 and are refracted at second surface 206, for example the substrate - air interface. For some light rays, like light ray 222, the light rays are incident at second major surface 206 perpendicularly and experience little or no refraction. However, other light rays, like light ray 224, are incident at the substrate - air interface (e.g., second major surface 206) at a sufficiently large angle Q relative to surface normal 226 that the light rays are totally internally reflected, thereby trapping the light within the substrate until the light ray is acted upon in such a way that, for example, the angle of incidence Q is sufficiently decreased that light can escape through second surface 206. The angle at which total internal reflection (TIR) occurs is known as the critical angle 0 _C , and depends on the index of refraction of substrate 202 and the index of refraction of the medium on the other side of second major surface 206, e.g., air.

[0086] In various embodiments, optical assembly 200 may comprise, for example, a display device, wherein substrate 202 comprises a plurality of electroluminescent elements 208 disposed thereon, wherein substrate 202 and components disposed thereon comprise a display panel. Accordingly, in some embodiments, such as shown in FIG. 7, electroluminescent elements 208 can be arranged as picture elements (pixels) 232 of the display panel, wherein individual subpixels, of different emission wavelengths (e.g., colors) may comprise a given pixel 232, each sub-pixel comprising an individual electroluminescent element 208. For example, in some embodiments, each pixel 232 may comprise three sub-pixels, each electroluminescent element 208 of the three subpixels selected to emit light of a different color. That is, each subpixel comprises an electroluminescent element 208, in the present example, and each pixel therefore comprises three electroluminescent elements 208. In various embodiments, for example, each electroluminescent element 208 of the three electroluminescent elements comprising pixel 232, can be selected to emit one of the three colors blue, green or red comprising the RGB additive color model. However, in further embodiments, pixels 232 may comprise more than three colors, and the selected colors can be other colors as are necessary or desired. Pixels 232 can be arranged as electrically-addressable rows and columns of pixels. For example, in the embodiment shown in FIG. 7, optical assembly 200 comprises 4 columns of pixels, e.g., pixel columns Cl through C4, and 6 rows of pixels 232, e.g., pixel rows R1 through R6, arranged orthogonal to each other, each pixel of the resultant 6 x 4 = 24 pixels comprising three subpixels. Commercially-available display panels may comprise many millions of pixels, and the illustrated optical assembly 200 shown in FIG. 7 is for purposes of explanation and not limitation.

[0087] As previously noted, light intersecting the substrate-air interface at high angles of incidence relative to normal 226 can remain trapped in the substrate. If this trapped light is scattered at the substrate-air interface, or by other electroluminescent elements, electrical traces, etc., the scattered light can escape the substrate at the location of another pixel 232 and create image blurring (e.g., crosstalk), non-uniform brightness, and/or reduced contrast, or other optical effects. Crosstalk can be visualized with the aid of FIG. 8, which illustrates rays of light emitted from a pixel 232 of optical assembly 200. As shown, light rays emitted from a given pixel (e.g., at pixel coordinate Cl, Rl) that intercept the interface at second major surface 206 at a large angle relative to normal 226, such as light ray 224 that undergoes TIR at the substrate-air interface, can propagate laterally within the substrate, but may intercept a scattering location positioned away from the originating pixel such that the scattered light exits the substrate through second major surface 206 at a location of an adjacent pixel (e.g., at pixel coordinate C2, Rl), or a pixel positioned even farther from the originating pixel. In this instance, the viewer might see, for example, blue light emitted from the subpixel of one pixel coming from the general location of a red subpixel of a neighboring pixel, or a mixture of the blue and red light. Thus, steps should be taken to confine scattering of internally-reflected light propagating in the substrate to the location of the pixel from which the light originated. [0088] Referring to FIG. 9, in various embodiments, damage tracks 50 may be formed in substrate 202 as previously described, in an area pattern such that damage tracks 50 are formed adjacent, for example around, individual pixel volumes 240 of optical assembly 200. As used herein, pixel volume refers to the volume of a footprint of a pixel 232 extended through the substrate, and a pixel footprint refers to the outline of a pixel periphery on the substrate, e.g., an outline of the light emitting area of a pixel on first surface 204 of substrate 12. A pixel volume is the volume of the substrate resulting from a projection of that footprint through the substrate in a direction of the thickness of the substrate, e.g., orthogonal to the first and/or second major surface. Referring again to FIG. 7, in various embodiments, lines of damage tracks can be arranged in a grid pattern comprising rows 234 of damage tracks and columns 236 of damage tracks that extend adjacent and/or between individual pixels 232. The rows 234 and columns 236 of damage tracks 50 are shown as dashed lines in FIG. 7. For example, in some embodiments, rows 234 and columns 236 of damage tracks 50 can be arranged orthogonal to each other, mimicking the arrangement of pixels 232. Such lines of damage tracks can comprise a single line of damage tracks per row 234 or column 236 of damage tracks, or damage tracks can comprise multiple lines of damage tracks arranged in geometric patterns (e.g., FIG. 10) or as randomly distributed damage tracks along a line (FIG. 11).

[0089] In some embodiments, as shown in FIG. 12, damage tracks 50 may be formed in substrate 202 by methods previously described, but in an area pattern such that the damage tracks are formed adjacent individual subpixel volumes of the display panel. For example, in some embodiments, damage tracks 50 may be formed in substrate 202 in an area pattern such that the damage tracks are formed around individual subpixel volumes of the display panel. Subpixel volumes are similar to pixel volumes, except the term subpixel volume refers to the projected volume of a subpixel (e.g., individual electroluminescent element) rather than a pixel. FIG. 12 is a plan view of substrate 12 illustrating placement of individual subpixels (e.g., electroluminescent elements 208) and damage tracks arranged in crossing (e.g., intersecting) rows 234 and columns 236 of damage tracks such that rows and/or columns of damage tracks are adjacent individual subpixels (e.g., electroluminescent elements 208). In various embodiments, the individual subpixels may be surrounded by rows and columns of damage tracks.

[0090] In still other embodiments, shown in FIG. 13, damage tracks 50 may be formed in substrate 202 in an area pattern such that the damage tracks are formed in rows 234 and/or columns 236 adjacent both individual pixel volumes and individual subpixel volumes. For example, damage tracks 50 may be formed in substrate 202 in an area pattern such that the damage tracks are formed in rows 234 and/or columns 236 that surround both individual pixel volumes and individual subpixel volumes.

[0091] While in some embodiments damage tracks 50 can be arranged such that longitudinal axes of the damage tracks are orthogonal to the first major surface 204 of substrate 202 or the second major surface 206 of substrate 202, in some embodiments damage tracks 50 can be arranged such that longitudinal axes 238 of the damage tracks form an angle f normal to the first major surface 204 or the second major surface 206. FIG. 14 is a cross-sectional edge view of a portion of an optical assembly 200 illustrating damage tracks positioned adjacent pixel volumes 240 and extending at an angle f relative to first and/or second major surfaces 204, 206. In other embodiments, angularly-extending damage tracks can be positioned adjacent individual subpixel volumes. For example, angularly-extending damage tracks can be positioned around, such as surrounding, individual subpixel volumes. As shown, light rays 220 emitted by a pixel 232 (e.g., emitted from an electroluminescent element 208 comprising a subpixel of the pixel) can be scattered upon intercepting a damage track 50, thereby confining the light ray, and the light scattered by the interception, to the location of the pixel as would be seen by an observer facing second major surface 206.

[0092] In some embodiments, such as shown in FIG. 15, optical assembly 200 can comprise a plurality of electroluminescent elements 208 positioned on first major surface 204 of substrate 12, wherein each electroluminescent element 208 emits light of the same wavelength (e.g., color) as other electroluminescent elements 208 of the plurality of electroluminescent elements. For example, the plurality of electroluminescent elements 208 may emit a bluish light. In such instances, a color conversion layer 242 may be positioned on second major surface 206 such that light emitted from the plurality of electroluminescent elements 208 is transformed by the color conversion layer 242 into light of a different color, e.g., white light. For example, color conversion layer 242 may comprise a plurality of discrete (e.g., separated) layers, wherein each discrete color conversion layer 242 is positioned opposite a corresponding electroluminescent element 208. Color conversion layers 242 can be segregated into blue color conversion layers, green color conversion layers, and red color conversion layers. Thus, in a facsimile of the foregoing embodiment comprising blue light-emitting electroluminescent elements, green light-emitting electroluminescent elements, and red light-emitting electroluminescent elements, the blue, green, and red color conversion layers 242, can be incorporated into pixels 232, each pixel 232 comprising a plurality of electroluminescent elements 208 and a plurality of corresponding color conversion layers 242. Accordingly, a color conversion layer 242 of one color, paired with an electroluminescent element 208, can represent one subpixel. For example, a pixel 232 in accordance with the present embodiment can comprise three electroluminescent elements 208 of a single color positioned on first major surface 204, and three color-conversion layers 242 of different colors positioned on second major surface 206: e.g., a blue color conversion layer, a green color conversion layer, and a red color conversion layer, each color conversion layer paired with a corresponding electroluminescent element 208. Color conversion layers 242 can comprise, for example, a phosphor material (e.g., cerium- doped YAG) or a semiconductor material (e.g., quantum dot).

[0093] In the embodiment of FIG. 15, light emitted from one electroluminescent element 208 in one pixel 232, in the absence of damage tracks 50, may intersect the color conversion layer of an adjacent pixel, or even the color conversion layer of an adjacent electroluminescent element (e.g., subpixel) within the same pixel. When this occurs, light emitted from one electroluminescent element 208 intended for the corresponding color conversion layer may instead at least partially illuminate an adjacent color conversion layer, thereby emitting a color light toward the viewer different than what was intended by the apparatus designer. For example, consider that an electroluminescent element 208 of a pixel in column Cl of FIG. 15 is activated and intended to direct light toward the green color conversion layer 242G. In the absence of damage tracks 50, light from the electroluminescent element may also illuminate the red color conversion layer 242R or the blue color conversion layer 242B. Accordingly, damage tracks positioned in rows 234 and columns 236 between individual subpixel volumes and/or pixel volumes can mitigate crosstalk between individual subpixels and/or pixels.

[0094] In still other embodiments, for example as illustrated by the exemplary optical assembly 300 shown in FIG. 16A, the optical assembly may comprise a first substrate 302 and a transparent second substrate 304. First substrate 302 comprises a first major surface 306 and a second major surface 308. A plurality of electroluminescent elements 208 can be disposed on second major surface 308, the plurality of electroluminescent elements 208 defining a pixel 232. As in other embodiments, pixels 232 can be arranged in specific patterns, for example an array of rows and/or columns (a single row of columns Cl - C4 is shown in FIG. 16A). Transparent second substrate 304 comprises a third major surface 310 (see FIG. 16B) and a fourth major surface 312. Transparent second substrate 304 is spaced apart from first substrate 302 and positioned such that third major surface 310 is opposite from and faces second major surface 308. Third major surface 310 may further comprise a plurality of color conversion layers 314 positioned thereon. A gap 316 may exist between the plurality of electroluminescent elements 208 and the plurality of color conversion layers 314. Because the plurality of electroluminescent elements 208 in accordance with the present embodiment are top-emitting, first substrate 302 need not be transparent, and an electrode layer that may be positioned between the plurality of electroluminescent elements 208 and first substrate 302 need also not be transparent. A planarization layer (not shown) may be positioned over the electroluminescent elements 208. In addition, an additional layer, for example a transparent electrode layer (not shown), may be positioned over the plurality of electroluminescent elements 208.

[0095] The color conversion layers 314 may, in some embodiments, be distributed in an area pattern, e.g., array, corresponding to an area pattern of electroluminescent elements 208 on second major surface 308 of first substrate 302. That is, if the electroluminescent elements 208 are arranged on second major surface 308 of first substrate 302 in a rectangular array of rows and columns of electroluminescent elements, color conversion layers 314 can also be arranged in a rectangular array of rows and columns, wherein individual color conversion layers 314 are positioned directly opposite a corresponding electroluminescent element 208. Such rectangular arrays of rows and columns can apply to either one or both of pixels or individual electroluminescent elements (e.g., subpixels). Analogous to preceding embodiments, each color conversion layer 314 can define a color conversion volume 318 extending through a thickness (e.g., through a damaged layer 320) of transparent second substrate 302. As used herein, color conversion volume refers to the volume of a footprint of a color conversion layer extended through transparent second substrate 304. That is, a color conversion layer footprint refers to the outline of a color conversion layer as projected onto transparent second substrate 304, e.g., an outline of the color conversion layer on third major surface 310 of transparent second substrate 304. A color conversion volume 318 is the volume within transparent second substrate 304 represented when a color conversion footprint is projected through transparent second substrate 304 in a direction of a thickness of the second substrate, e.g., orthogonal to the third or fourth major surface of the second substrate. A black matrix material 322, for example an opaque polymer material, may be deposited on third major surface 310 to optically isolate each color conversion layer from other color conversion layers in the array of color conversion layers at third major surface 310.

[0096] As described above and as shown in FIG. 16 A, an electroluminescent element 208 of a pixel in column C 1 can be activated and intended to direct light toward, for example, blue color conversion layer 314B. Some light rays, like light ray 324, may propagate through transparent second substrate 304 and be refracted at fourth surface 312, for example the substrate - air interface. In certain instances, best seen at detail A of FIG. 16 A, light from the electroluminescent element 208 directly opposite a blue color conversion layer 314B may propagate through transparent second substrate 304 at such an angle that blue light emitted from blue color conversion layer 314B may exit fourth major surface 312 in the general location of, for example, a red color conversion layer 314R, such as a red color conversion layer corresponding to an adjacent pixel.

[0097] Accordingly, in various embodiments and as shown in FIG. 16B and region A’, which is an enlargement of the region of detail A in FIG. 16A, but in an alternative embodiment, damage tracks 50 may be formed in transparent second substrate 304 in an area pattern, e.g., orthogonal rows and/or columns, such that damage tracks 50 are formed adjacent individual color conversion volumes 318 of transparent second substrate 304, or groups of color conversion volumes. For example, damage tracks 50 may be formed in transparent second substrate 304 in an area pattern such that damage tracks 50 are formed between and around individual color conversion volumes 318 of transparent second substrate 304, or groups of color conversion volumes. Thus, in the example illustrated in FIG. 16B, blue light emitted from blue color conversion layer 314B can intercept damage tracks 50 and be scattered by damage tracks 50 in a direction toward and through fourth major surface 312. Accordingly, blue light from blue color conversion layer 314B can exit fourth major surface 312 in the general location of blue color conversion layer 314B and not appear to an observer to be emitted from the location of green color conversion layer 314R. As described above, damage tracks 50 can be arranged adjacent, for example around, groups of color conversion volumes, for example a group of three color-conversion volumes directly opposite a corresponding pixel comprised of three electroluminescent elements 208, although it should be noted that the group of color conversion volumes may include fewer than three color conversion volumes or more than three color conversion volumes. Thus, referring to FIG. 16A, damage tracks 50 could be arranged adjacent the color conversion layers corresponding to any one or more of the color conversion volumes corresponding to the pixels Cl - C4. For example, in some embodiments, damage tracks 50 could be arranged around the color conversion layers corresponding to any one or more of the color conversion volumes corresponding to the pixels Cl - C4. In some embodiments, color mixing at the pixeldevel may be beneficial. Accordingly, in some embodiments, damage tracks 50 may be arranged adjacent, for example around, groups of color conversion volumes corresponding to individual pixels, and not individual color conversion volumes.

[0098] As described in respect of FIG. 14 and transparent substrate 202, damage tracks 50 disposed within damaged layer 320 of transparent second substrate 304 can be tilted by an angle f relative to a normal to either one or both of third or fourth major surfaces 310 or 312, respectively.

[0099] It will be apparent to those skilled in the art that various modifications and variations can be made without departing from the spirit or scope of the claims.