MANUFACTURE

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority under 35 U.S.C. § 1 19 of U.S. Provisional Application Serial No. 62/612,848 filed on January 2, 2018 and U.S. Provisional Application Serial No. 62/556,721 filed on September 1 1 , 2017, the contents of each of which are relied upon and incorporated herein by reference in their entireties.

BACKGROUND

[0002] Opaque materials are useful for encasing most products from watches to smart phone chassis, to appliances, to displays. It is often very useful to have a transparent window on these devices to allow light to enter or exit the device. For example, sensor and camera windows should be clear to allow light in, while the display, camera flash, flash light, and sensor detector windows need to be transparent let light out. Currently, transparent and opaque portions of the device are made of different materials which require at least one of complex assembly, painting or other additional decoration steps.

[0003] The display of alphanumeric text, symbols, designs, graphics and information in display products such as instrument consoles, signage, and mobile devices such as tablets and mobile phones may involve the display being visible by viewing the product front surface with an illumination source or light emitter behind the front surface. An example of such display products can be found in vehicle instrument panels, which include such elements as warning lights, graphics, alphanumeric text and symbols that clearly appear when the panel is back-lit, but disappear from view entirely when the panel is only front-lit and not back-lit.

[0004] Such display products may be referred to as "deadfronts" or "dead front" displays, which can be described as a device for conveying visual information and generally comprising a panel which carries information normally invisible to the observer and an illumination source or light emitter to make visible selected information. The panel may carry fixed information visible under any conditions of rear illumination, and the panel may also include information which is selectively illuminated and selectively visible to an observer. This selectively observable information can be provided by using a translucent panel portion which appears opaque without back illumination and an opaque portion on the rear thereof outlining the information to be transmitted. Information transmission occurs when rear illumination lights the opaque and translucent areas and only the translucent areas transmit light. Such dead front displays can be used in automotive, aerospace, signage, mobile devices, and appliance applications for instrument and control panels. Dead front displays can also be used for improved educational or instructional display arrangement where the device combines the normal appearance and usefulness of a blackboard on which words, diagrams, pictures or other indicia may be removably written or applied as with chalk, or permanently or semi-permanently as with paint or ink while presenting a general dead front non- glare dull surface appearance under reflected room light, but which may be selectively energized to display in translucent glowing form against the dead front surface background various patterns of intelligence or information.

[0005] Additionally, the phrase "dead front" has been specifically used to describe a display that conceals both the content that it projects in the on state and also its function as a display such that when switched on the image emanates from a non- obvious or hidden source. These non-obvious or hidden displays can be divided into two categories, "black" and "non-black" dead front displays. Black dead-front displays are considered to have a distinctive, stylish, aesthetically appealing appearance, and they appear black and can be seamlessly integrated into the display bezel, such that there is no visual difference between the bezel and the display. Non-black dead-front displays operate on the same basic principles as black dead front displays and provide similar aesthetic impact, a difference being that the non-black dead front display area and its surroundings (e.g., a bezel) are colored, and are sometimes termed as a hidden display. Other hidden display technologies use semi-transparent, translucent, or semi-opaque plastics with backlit masks or displays mounted beneath their surface, partially reflective films, electrochromic materials, and various types of polarization schemes employing quarter waveplates. Other dead fronting schemes for LCD displays employ various polarization schemes to reduce and/or eliminate light leakage, making the panel appear black.

[0006] Many conventional dead front devices that transmit through partially transparent or translucent materials have a disadvantage in that their optical performance is impaired by the transmission through a partially transparent or translucent material. This causes light scattering, and in-turn, a silhouette of scattered light around the projection, making the image appear fuzzy. Dead front devices that are coated with partially reflective mirrors have an angular dependence to the viewing angle that may also be distracting to the viewer. Moreover, these coatings are not black. In addition, because these devices are generally based on an all-plastic construction, they are susceptible to scratch and wear due to their inherently low mechanical durability.

[0007] Thus, there is a need for the development of new devices, for example dead front and/or hidden devices. There is also a need for devices that can enable new interactive features in a variety of products, such as for automotive interiors, and further enhance the user experience and aesthetics. There also is a need for a material through which light can be transmitted without distortion or scattering, is viewing angle independent, and provides a mechanically robust, scratch resistant, and aesthetically pleasing surface.

SUMMARY

[0008] An embodiment pertains to a device comprising a substrate comprising a glass or glass-ceramic material comprising from about 0.1 % to about 50% by weight crystalline phase; and the substrate comprising an unbleached region having an internal optical transmittance and a bleached discrete region comprising at least partially dissolved crystalline phase, the bleached discrete region having an internal optical transmittance at least twice the internal optical transmittance over at least a 50 nm wide wavelength window in the unbleached region in the visible wavelength range of 300 nm to 1700 nm.

[0009] Another embodiment pertains to a device comprising a substrate comprising a glass or glass-ceramic material the substrate comprising an unbleached region having an internal optical transmittance and a bleached discrete region, wherein the unbleached region is opaque and black and the bleached discrete region comprises a plurality of apertures each having a diameter in a range of from about 10 micrometers to about 1000 micrometers.

[0010] Another embodiment pertains to a method of forming a device comprising: applying thermal energy to discrete regions of a substrate comprising a glass or glass-ceramic material comprising from about 0.1 % to about 50% by weight of a crystalline phase such that there is an unbleached region in the substrate having an internal optical transmittance and a bleached discrete region comprising at least partially dissolved crystalline phase, the bleached discrete region having an internal optical transmittance at least twice the internal optical transmittance over at least a 50 nm wide wavelength window in the unbleached region in the visible wavelength range of 300 nm to 1700 nm.

[0011] Additional features and advantages of the disclosure will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the methods as described herein, including the detailed description which follows, the claims, as well as the appended drawings.

[0012] It is to be understood that both the foregoing general description and the following detailed description present various embodiments of the disclosure, and are intended to provide an overview or framework for understanding the nature and character of the claims. The accompanying drawings are included to provide a further understanding of the disclosure, and are incorporated into and constitute a part of this specification. The drawings illustrate various embodiments of the disclosure and together with the description serve to explain the principles and operations of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The following detailed description can be further understood when read in conjunction with the following drawings, in which:

[0014] FIG. 1 A is a schematic of a device according to one or more embodiments;

[0015] FIG. 1 B is a schematic of a device according to one or more embodiments;

[0016] FIG. 1 C is a schematic of a device according to one or more embodiments; [0017] FIG. 1 D illustrates an electronic device having light sensors for determining a physiological signal according to one or more embodiments;

[0018] FIG. 1 E illustrates an electronic device having light sensors for determining a physiological signal according to one or more embodiments;

[0019] FIG. 2 is a graph of internal optical transmittance spectra of un-bleached base glass and laser bleached regions of samples in accordance with Example 1 ;

[0020] FIG. 3 is a graph of internal optical transmittance spectra of un-bleached base glass and laser bleached regions of samples in accordance with Example 2;

[0021] FIG. 4 is a graph of internal optical transmittance spectra of un-bleached base glass and laser bleached regions of samples in accordance with Example 3;

[0022] FIG. 5 is a graph of internal optical transmittance spectra of un-bleached base glass and laser bleached regions of samples in accordance with Example 6; and

[0023] FIG. 6 is a graph of internal optical transmittance spectra of un-bleached base glass and laser bleached regions of samples in accordance with Example 6.

DETAILED DESCRIPTION

[0024] Embodiments of the disclosure pertain to various devices having transparent and opaque regions. Embodiments pertain to a monolithic material and method of making a material that can have both transparent and opaque regions in the same monolithic material. Some embodiments provide such a material that is strong, scratch resistant, and chemically strengthenable so that dead front displays, watches, sensor windows and many other devices can be made from the same material, greatly reducing manufacturing complexity, while increasing utility and function. Some embodiments pertain to a device comprising a bleached discrete region or a plurality of bleached discrete regions in an opaque glass substrate or opaque glass-ceramic substrate. According to one or more embodiments,

"substrate" refers the physical material upon which a bleached discrete region is made or applied. The substrate can form part of the front of a device that faces a user of the device, a part of the back of a device, or any other portion of a device. The substrate can be a superstrate that overlies another portion of device or overlies another substrate, such as a cover substrate to provide production for the underlying device or substrate. According to one or more embodiments, "device" refers to any type of device that contains discrete bleached regions as defined in this disclosure. Non-limiting examples of devices include signs/signage, mobile devices such as mobile phones, mobile phones with an integrated camera, and tablets, wearable sensors, a watch, a wearable activity tracker, a wearable health monitor (to monitor, e.g., pulse, blood pressure, temperature), a camera, a vehicle display and a sensor window. In some embodiments, the bleached discrete region may comprise an array of bleached discrete regions such as a periodic array or a patterned array.

According to one or more embodiments opaque refers to a material or a region that has an internal transmittance of less than 1 %. According to some embodiments a region or a material that is opaque has a strong absorbance, and in specific embodiments the region of material that is opaque is not due to scattering of light. According to one or more embodiments, a region that is referred to as "black," the black is determined by CIELAB color space coordinates determined from specular reflectance measurements using a spectrophotometer with illuminant D65, and the region exhibits CIELAB color space coordinates of: 0< L ^* <10, -10< a ^* <10, -10< b ^* <10

[0025] According to one or more embodiments, "array" means an ordered series or arrangement of discrete regions. A "periodic array" is an array in which the discrete regions occur in regular intervals or spacings. For example, in a linear periodic array of bleached discrete regions that are circles, the center-to-center spacing of each discrete region may be equal for a particular interval. A "patterned array" refers to a repeated decorative design of discrete regions, for example in a geometric pattern or other pattern. The center-to-center spacing may also be referred to as "pitch." The pitch of bleached discrete regions can be measured using a conventional optical microscope, collecting images of the bleached discrete region, and using image processing software to calculate the center-to-center distance of adjacent bleached discrete regions. The center is the geometrical middle point of a bleached discrete region. If bleached discrete regions are less than 0.2 micrometers in diameter, a scanning electron microscope can be used, the images can be collected, and image processing software can be utilized to determine the center-to-center spacing of adjacent bleached discrete regions. [0026] In some embodiments, the bleached discrete regions may be in the form of apertures, graphics, alphanumeric text and/or symbols. In some embodiments, the apertures, graphics, alphanumeric text and/or symbols can be arranged to present visual information to an observer. According to one or more embodiments,

"aperture" refers to an opening through which light travels. In some embodiments, an aperture can be round, elliptical or any suitable polygonal geometric shape, such as rectangular, square or triangular. In some embodiments where an aperture is formed through the thickness of a material defined by a first surface and a second surface, the aperture may have a cross-sectional dimension that is the same through the thickness of the material or different through the thickness of the material. As a non-limiting example, for an aperture that is circular in cross-section, the aperture may be cylindrical and have the same cross-sectional diameter at the first surface and second surface of the material. In other embodiments, the aperture cross- sectional dimension is larger at first surface of the material than the second surface of the material. For example, the aperture may be conical in shape. In one or more embodiments, the term "diameter" should not be limited to a circular shape. Thus, in some embodiments, "diameter" may refer to a distance between edges of an aperture which can be square, rectangular, polygonal or any suitable geometric shape for a particular end use. For apertures that are polygonal, the diameter refers to a straight line passing from side to side through the center of the aperture. In the case of a rectangle, the diameter refers to the smallest cross-sectional dimension of the rectangle. In the case of a triangle, diameter refers to the smallest height of the triangle. In the case of an elliptical aperture, the diameter refers to the smallest cross-sectional dimension passing through the center of the ellipse. In some embodiments, the bleached discrete regions comprise a plurality of apertures, each aperture having a diameter in a range of from about 10 micrometers to about 10,000 micrometers, or in a range of from about 10 micrometers to about 5,000 micrometers or in a range of from about 10 micrometers to about 1 ,000 micrometers, or in a range of from about 10 micrometers to about 500 micrometers, or in a range of from about 50 micrometers to about 10,000 micrometers, or in a range of from about 50 micrometers to about 5,000 micrometers or in a range of from about 50 micrometers to about 1 ,000 micrometers, or in a range of from about 50 micrometers to about 500 micrometers, or in a range of from about 50 micrometers to about 300 micrometers, or in a range of from about 50 micrometers to about 200 micrometers, or in a range of from about 50 micrometers to about 100 micrometers, or in a range of from about 10 micrometers to about 90 micrometers, or in a range of from about 10 micrometers to about 80 micrometers, or in a range of from about 10 micrometers to about 70 micrometers, or in a range of from about 10 micrometers to about 60 micrometers, or in a range of from about 10 micrometers to about 50 micrometers. In some embodiments, the apertures have a center-to-center spacing in a range of from about 20 micrometers to about 200 micrometers or from 20 micrometers to about 100 micrometers.

[0027] In some embodiments, with reference to FIG. 1A, a device 100 comprises a dead front display comprising back lighting. Back lighting can include an illumination source or light emitter 130 positioned on a side 124 of substrate (or panel) 120 opposite a side 122 facing an observer of the device. The side 124 and side 124 define a thickness "T". Back lighting can comprise a light emitting diode (LED), a laser, an organic light emitting diode (OLED) or liquid crystal display (LCD).

Bleached discrete regions 140 allow radiation 132 to be transmitted through the bleached discrete regions. In some embodiments, the device comprises a dead front display comprising a panel or substrate which carries information normally invisible to an observer and an illumination source or light emitter 130, which provides back lighting and when illuminated, makes selected information visible to an observer. In some embodiments, a dead front display device comprises a panel or substrate which may carry fixed information visible under any conditions of rear illumination, and the panel or substrate may also include information which is selectively illuminated and selectively visible to an observer. In some embodiments, this selectively observable information can be provided by using a translucent panel or substrate portion which appears opaque without back illumination and an opaque portion on the rear thereof outlining the information to be transmitted. In some embodiments, a device comprises a dead front display that conceals both the content that it projects in the on state and also its function as a display such that when the display is switched on, an image emanates from a non-obvious or hidden source. In some embodiments, a device comprising a black dead-front display is provided, and the black dead-front display appears black and can be seamlessly integrated into a display bezel, such that there is no visual difference between the bezel and the display. Some embodiments provide a non-black dead front display. In some embodiments, a device is provided comprising a non-black dead-front display comprising a substrate including a colored display area and a colored surrounding area (e.g., a bezel). FIG 1 B shows an example of a black dead front display 200 having a plurality of bleached discrete regions 210 in the form of apertures. FIG 1 C shows an example of a black dead front display 200 having a plurality of bleached discrete regions 210 in the form of symbols and alphanumeric characters (shown as 10:31 P.M.).

[0028] According to one or more embodiments, the term "bleaching" and the phrase "optical bleaching" refer to the direction of thermal energy to discrete regions or thermally treating discrete regions of a glass or glass-ceramic substrate to increase the internal optical transmittance in the discrete regions by partial or complete decomposition of crystalline phases in the discrete regions compared to portions of the substrate that have not been thermally treated. Thus, the thermally treated discrete regions that have been "bleached" or optically bleached exhibit an increased internal optical transmittance compared to the portions of the substrate that have not been thermally treated. In some embodiments, the thermally treated discrete regions have an absorbance in a specific wavelength range (e.g., an infrared wavelength range, an ultraviolet wavelength range and/or an ultraviolet wavelength range) that is reduced compared to portions of the substrate that have not been bleached. In some embodiments, for example, if a laser operating in the near infrared (NIR) wavelength range is used to bleach a discrete region of the substrate, thermal decomposition of the crystalline phase that absorbs radiation in the NIR wavelength range occurs in the bleached discrete region, and absorption in the NIR is reduced compared to portion of the substrate that have not been bleached. In some embodiments, exposure to a NIR laser would cause the absorbance of both the NIR and visible wavelengths to be reduced.

[0029] According to one or more embodiments of the devices described in this disclosure, the device does not comprise a volume-colored glass-ceramic material in which coloring ions are distributed throughout the material. Instead, in one or more embodiments, a device comprises a substrate comprising a colored crystalline phase, for example, in the form of colored crystallites that absorb radiation in a visible, infrared, near infrared and/or ultraviolet wavelength range and result in the glass substrate or glass-ceramic substrate exhibiting color.

[0030] Empirical measurement of a glass substrate or a glass-ceramic substrate to determine the change in optical absorbance in a discrete region which has been bleached can be achieved using a UV/VIS/N I R wavelength spectrophotometer (sometimes called an absorbance spectrometer or simply a spectrometer), which measures a light beam's intensity as a function of its color (wavelength). An example of a suitable spectrophotometer is a LAMBDA 950 UV/Vis

Spectrophotometer, available from PerkinElmer, Inc., Waltham, MA

(http://www.perkinelmer.com/produ^

). Absorbance of regions, including a bleached discrete region, can be measured at particular wavelengths or across the whole UV, VIS, and NIR wavelength ranges of the electromagnetic spectrum.

[0031] Depending on the size of the bleached discrete region, a conventional spectrometer can be used to measure the change in absorption of radiation of a bleached discrete region of a glass substrate or glass-ceramic substrate at a particular wavelength or in a range of wavelengths in the UV/VIS/NIR wavelength ranges. The change in absorption can be determined by measuring absorbance before bleaching and after bleaching. If the bleached discrete region is very small (e.g., about 10 micrometers) a spectrometer with an optical fiber coupled probe can be used to measure changes in absorption of radiation over small bleached discrete region.

[0032] The spectrometer can measure absorbance in units of optical density per millimeter (OD/mm) of thickness of a sample. The spectrometer can also measure peak internal optical transmittance and average internal optical transmittance over a given wavelength range. Internal optical transmittance of materials is dependent on composition and heat treatment. Thus, a particular composition has an intrinsic dynamic range of internal optical transmittance (or absorbance). For a particular glass or glass-ceramic material, maximum internal optical transmittance (or lowest absorbance) will be observed when the material has been formed and cooled without a heat treatment that promotes the formation (nucleation and growth) of any absorptive crystallites. The lowest internal optical transmittance (i.e., highest absorbance) for a particular glass or glass-ceramic material is dependent on both the composition of the glass or glass-ceramic material and on the heat treatment time and temperature. For example, a glass or glass-ceramic that has a maximum average internal optical transmittance of 70% and a minimum average internal optical transmittance of 1 % (over some wavelength range at a particular thickness) could be heat treated at a particular temperature and time that would produce an average internal optical transmittance(t) 1 %≤ t≤ 70%.

[0033] Embodiments of the disclosure provide a device comprising a substrate or panel including an optically bleached discrete region in an opaque glass or glass- ceramic substrate. The substrate in some embodiments comprises a strengthenable glass or glass-ceramic material to form the outer surface of device. In some embodiments, the substrate comprises a strengthenable and scratch-resistant glass or glass-ceramic material to form the outer surface of the device. As used herein, "strengthenable" refers to a glass that can be strengthened by thermal treatment (.e.g., tempering) and/or chemically strengthened, such as by ion exchange. In specific embodiments, substrates used as panels in displays are chemically strengthenable. Non-limiting examples of chemically strengthenable glasses comprise alkali aluminosilicates, for example, Gorilla® Glass available from Corning, Inc., Corning, NY. Ion-exchanged glasses provide high strength and scratch resistance to protect portable electronic devices, and are transparent to visible, microwave, and radio frequency radiation. In some embodiments, the device comprises a hidden "dead front" display panel comprising a glass or glass-ceramic substrate. In some embodiments, panels formed from the substrates described in this disclosure would enable the emission from small, addressable light sources (e.g., light emitting diodes (LEDs) or a pixel on a display) to be transmitted through the small (80-100 micrometer in diameter) optically bleached apertures. Because of the small size of these optically bleached discrete regions, they would not be observable to the naked eye (that is, without the aid of magnification from a microscope or the like), and the panel comprising such a substrate would appear black, or the chosen color of the bleachable opaque material. When the light source(s) directly behind the bleached aperture(s) is/are illuminated the viewer would realize that it is a display. [0034] Moreover, according to one or more embodiments, because the bleached discrete region is highly transparent at visible wavelengths and sized to match the emission of the illumination source or light emitter, a device can be provided where there is no silhouette around the image like what is observed with the current 'hidden displays' that employ semi-transparent, translucent, or semi-opaque plastics.

Additionally, because the bleached apertures can be made sufficiently small and in close enough proximity to overlap individual pixels on a display, an undistorted, high resolution image could be projected through this patterned material. These apertures can also be made in the shape of various symbols and back-lit in the conventional manner used for dead front displays. In some embodiments, because the devices described herein do not rely on printed coatings or graphics, the devices may be less expensive to produce than existing devices with dead front displays. This is because a bleachable opaque glass or glass-ceramic combines the functionality of the panel (e.g., cover or substrate) with that of a mask, which in current dead front devices is printed on the inner surface of the cover or is an entirely separate layer within a stack used to form a dead front display.

[0035] In addition to superior optical properties, glass and glass-ceramic substrates, as noted above, exhibit better scratch resistance and mechanical durability compared to plastic panels. Additionally, glass and glass-ceramic substrates provide a superior aesthetics and tactile experience, which is in demand for automotive interiors. Furthermore the surface can be textured to provide antiglare, aesthetic, or tactile features or decoration.

[0036] Embodiments of the disclosure provide mechanically robust, optically and aesthetically superior hidden or dead front displays, which can be used for a variety of applications, including signs/signage, mobile devices such as mobile phones and tablets, wearable sensors, a watch, a wearable activity tracker, a wearable health monitor (to monitor, e.g., pulse, blood pressure, temperature), a camera and vehicle displays.

[0037] Bleached discrete regions in opaque glass and glass-ceramic substrates according to one or more embodiments allows a clear, high resolution image to be projected through a material that appears 'black' or 'dead fronted'. The devices described herein are superior to commercialized hidden/dead front displays that employ partially transparent or translucent plastics that cause the projected light to scatter, creating a silhouette around the image. This is because bleached discrete regions in opaque glass can be made over a broad range of sizes and geometries, allowing a close match in size and registration between the light-source and the discrete region, facilitating minimal light leakage.

[0038] In some embodiments, opaque bleachable glass or glass-ceramic substrates can be formed in three dimensions (3D-formed) and or sagged before bleaching, allowing displays to be put within complex shaped parts having bends and/or curvature in three planes (e.g. X, Y and Z). According to some

embodiments, a device comprising hidden/dead front display is provided that does not employ partially reflective films, coatings, or printed layers that contain patterned discrete regions such as features or apertures. Thus, embodiments provide lower- cost, more robust, and versatile devices. Lower cost arises from the fact that while printing and coating technologies are widespread, they are expensive ($1 -$2 per square foot). Superior robustness in some embodiments can be due to the fact that coatings can be atmospherically sensitive and degrade over time and may exhibit inferior mechanical properties compared to glass or glass-ceramic substrates.

Enhanced versatility according to some embodiments is due to the fact that complex 3D-formed polymer-based displays relying on coatings or printed features could not necessarily be produced over a wide range of shapes due to limited coating techniques and cost.

[0039] Some watch backs are made with opaque metal or zirconia with glass or sapphire windows that are co-finished with the back to produce a seamless finish. Embodiments of devices described herein allow for a device comprising transparent and opaque regions comprised of a monolithic substrate without the need to attach multiple materials together, which simplifies assembly and lowers cost, and enables the creation of fine or angled feature that otherwise would not be possible.

[0040] In some embodiments, devices are provided that do not employ partially reflective coatings. Reflective coatings can lead to angular dependent optical aberrations and reduced brightness. Additionally, reflective coatings such as metallic films can prevent the transmission of radio frequencies (RF), which are emitted (and/or received by certain devices). Thus, embodiments of this disclosure provide devices having an RF transparent dead front display, which can allow superior transmission at these frequencies.

[0041] In some embodiments, the devices described herein offer the potential for superior brightness due to the fact that the bleached discrete region is highly transparent at visible wavelengths. In contrast, existing hidden/dead front displays that use translucent plastics reduce brightness by scattering the light. In some embodiments, the devices provide a unique potential to control the emission from the source by size and shape of the bleached discrete regions. For example, in one or more embodiments, conically shaped or angled bleached apertures through the thickness of the material could be formed. Also, in a glass or glass-ceramic substrate, the surface of the bleachable material could be deformed to form a lens to focus/defocus/steer the emission from the light source. This could enable modulation of the display's etendue. The term "etendue" refers to a property of light in an optical system, which characterizes how "spread out" the light is in area and angle. From the source point of view, it is the product of the area of the source and the solid angle that the system's entrance pupil subtends as seen from the source.

Equivalently, from the system point of view, the etendue equals the area of the entrance pupil multiplied by the solid angle the source subtends as seen from the pupil, (see http://en.wikipedia.org/wiki/Etendue).

[0042] In some embodiments, because the optically bleached apertures could be made smaller than what can be resolved by the un-aided eye (e.g., using a microscope), such displays may have an aesthetic advantage, because the display 'screen' or 'area' would appear to be a homogenous/uniform color and texture.

Moreover, the surrounding area of the screen could be made of the same laser- bleached sheet, such that the display appears to be bezel-less.

[0043] In embodiments, in which devices are used herein to form sensor windows and/or sensors, and the devices according to some embodiments provide both opaque and clear apertures that prevent sensor crosstalk between adjacent apertures. In embodiments that use the substrates described herein to form a camera housing or cover, the substrates can be strengthened and have both opaque and clear apertures to prevent camera flash from washing out photos without the need for multiple materials and optical isolators. [0044] In one or more embodiments, optically bleachable glass and/or glass- ceramic materials as described herein may be utilized for portable electronic devices and wearable electronic devices. According to some embodiments, a device can comprise a smart watch or other wearable have light sources and sensors mounted to the back side of the watch for sensing heart rate, photoplethysmography (PPG), and glucose and oximetry sensors. A photoplethysmogram (PPG) is an optically obtained plethysmogram, which is in some embodiments a volumetric measurement of an organ or whole body. A PPG is often obtained by using a pulse oximeter which illuminates the skin and measures changes in light absorption. A conventional pulse oximeter monitors the perfusion of blood to the dermis and subcutaneous tissue of the skin.

[0045] According to one or more embodiments, of a wearable device, a light source is optically isolated from a sensor, and therefore, multiple apertures are needed in an otherwise black or opaque material. Exemplary materials and processes enable a monolithic black back (i.e., facing the skin of the subject wearing the device) of such a wearable device with optically bleached apertures as described herein. In other embodiments, multiple apertures as described herein can be incorporated in a mobile phone camera where the flash is transmitted through a first aperture in close proximity to the camera aperture. The black or opaque material prevents light from the flash wave guiding through the substrate containing the apertures, entering the camera and washing out the photo image, while the laser bleached apertures enable the flash to illuminate the subject and then pass into the camera as desired

[0046] According to one or more embodiments of the present disclosure, devices can receive light information from each of two light guides, one in contact with the tissue of the subject (e.g. person) wearing the device and one not in contact with the tissue of the subject. First light information can be obtained from the first light guide, and second light information can be obtained from the second light guide. A heart rate signal can then be computed from the first and second light information, for example, by using blind source separation and/or cross-correlation. Although examples disclosed herein may be described and illustrated herein in terms of two sensors, emitters, and light guides, it should be understood that the examples are not so limited, but are additionally applicable to devices including any number and configuration of sensors, emitters, and light guides.

[0047] Exemplary embodiments of the disclosure are directed to a device or system for sensing and measurement of physiological signals. Multiple signals may be obtained, and each signal may contain a physiological signal of interest (e.g., a heart rate signal). Sensing may include detection of physiological signals from optical sensors, force and pressure sensors, temperature sensors, accelerometers, proximity detectors, and/or impedance sensors, among other possibilities. In some examples, sensing devices and systems may include optical sensors including light guides in contact and not in contact with tissue of a user or subject wearing the device.

[0048] FIG. 1 D illustrates an exemplary embodiment of an electronic device 300 having light sensors for determining a physiological conditions such as a heart rate signal according to examples of the disclosure. A first light sensor 310 may be co- located with a contacting bleached discrete region 302 and a first light emitter 306. The contacting bleached discrete region 302 may be configured so as to be adjacent to, in close proximity (e.g., within 1-5 cm) or in contact with tissue 314 of a user or wearer of the device (e.g., a person), such as skin. In one or more embodiments, the contacting bleached discrete region 302 may be curved such that the surface is configured to contact tissue 314 of the user. A second light sensor 312 may be co- located with a non-contacting bleached discrete region 304 and a second light emitter 308. The non-contacting bleached discrete region 304 may be configured so as to not be in contact with tissue 314 of the user or wearer of the device 300. In some examples, the non-contacting bleached discrete region 304 may be recessed with respect to the body of the electronic device 300 such that it is configured not to contact tissue 314 of the user or wearer of the device.

[0049] The electronic device 300 may be situated such that the first light sensor 310 and second light sensor 312, the first light emitter 306 and second light emitter 308, and the contacting bleached discrete region 302 and non-contacting bleached discrete region 304 are proximate the tissue 314 of the user, so that light from a light emitter may be directed through a bleached discrete region and be incident on the tissue. For example, the electronic device 300 may be held in a user's hand or strapped to a user's wrist, among other possibilities. A portion of the light from a light emitter may be absorbed by the skin, vasculature, and/or blood, among other possibilities, and a portion may be reflected back to a light sensor co-located with the light emitter. In some examples, light guides may direct light to tissue and/or back to a light sensor, and some emitters and sensors may direct light to and from tissue without a light guide.

[0050] A controller 318 may be provided and coupled to various components of the device 300 to control the operation thereof. The controller 318 according to some embodiments includes a central processing unit (CPU) 322, a memory 324, and support circuits 326. The controller 318 may control the device 300 directly, or via computers (or controllers) associated with particular monitoring system and/or support system components. The controller 318 may be one of any form of general- purpose computer processor that can be used in an industrial setting for controlling various chambers and sub-processors. The memory, or computer readable medium, 324 of the controller 328 may be one or more of readily available memory such as random access memory (RAM), read only memory (ROM), floppy disk, hard disk, optical storage media (e.g., compact disc or digital video disc), flash drive, or any other form of digital storage, local or remote. The support circuits 326 are coupled to the CPU 322 for supporting the processor in a conventional manner. These circuits include cache, power supplies, clock circuits, input/output circuitry and subsystems, and the like. One or more processes may be stored in the memory 324 as software routine that may be executed or invoked to control the operation of the device 300. The software routine may also be stored and/or executed by a second CPU (not shown) that is remotely located from the hardware being controlled by the CPU 322. The controller 318 may be linked via a hard wired connection or wirelessly, for example, using a blue tooth or other suitable wireless connection.

[0051] Referring now to FIG. 1 E, another embodiment of a electronic device 400 (or system) for sensing comprises a substrate 401 having a plurality of bleached discrete regions 402 that are angled with respect to the substrate 401 comprised of an opaque or black material. A light emitter 406 transmits light 405 though a bleached discrete region 402. The angled bleached discrete regions 402 can reject stray light from signal light 407 transmitted to detector 412 while enabling the signal light 407 coming from the light emitter 406. The signal light may be received from the epidermis 500 of a subject or wearer of the device 400 or off of blood vessels 518 deep in the skin of the subject to enter the detector 412. Rejection of stray light can increase the signal to noise and improve accuracy of the device 400. The device shown in FIG. 1 E can also include a controller, CPU, memory and support circuits configured similarly to the (CPU) 322, a memory 324, and support circuits 326 described with respect to FIG. 1 D, which can be connected to the device 400 via a wired or wireless connection.

[0052] The devices shown in FIGS. 1 D and 1 E are exemplary, and it will be understood that according to embodiments of the disclosure, the devices can comprise a substrate comprising a glass or glass-ceramic material comprising from about 0.1 % to about 50% by weight crystalline phase and the substrate comprising an unbleached region having an internal optical transmittance and a bleached discrete region as described herein. Thus, the devices in FIGS. 1 D and 1 E can minimally comprise such a substrate that provides a sensor window. An electronic device for sensing according to one or more embodiments can comprise the additional components of the light emitters, a detector (or multiple detectors and/or a sensor (or multiple sensors) as described with respect to FIGS. 1 D and 1 E.

[0053] Thus according to one or more embodiments, a device as shown according to FIGS. 1 E or 1 E comprises a substrate comprising a glass or glass-ceramic material comprising from about 0.1 % to about 50% by weight crystalline phase; and the substrate comprises an unbleached region having an internal optical

transmittance and a bleached discrete region comprising at least partially dissolved crystalline phase, the bleached discrete region having an internal optical

transmittance at least twice the internal optical transmittance over at least a 50 nm wide wavelength window in the unbleached region in the visible wavelength range of 300 nm to 1700 nm. The device according to some embodiments may further comprise a light emitter (e.g. a LED, an OLED, a laser, etc.) and a sensor, wherein the substrate comprises at least a first bleached discrete region and a second bleached discrete region and radiation from the light emitter is emitted through the first discrete bleached region and the sensor captures light emitted through the second bleached discrete region. In the device according to some embodiments, the unbleached region is opaque (black) and the first bleached discrete region is optically isolated from the second bleached discrete region. In the device according to some embodiments, the sensor is selected from the group consisting of a heart rate sensor, a glucose sensor, a temperature sensor and an oximetry sensor. In the device according to some embodiments, the device is wearable by a subject. In the device according to some embodiments, the device has a thickness, a first side and a second side opposite the first side, wherein the first bleached discrete region and the second bleached discrete region are located on the first side and a dead front display is located on the second side. In the device according to some

embodiments, the device comprises a mobile phone with an integrated camera comprising two adjacent bleached discrete regions.

[0054] In the device according to some embodiments of FIGS. 1 D or 1 E, the device comprises a sensor window comprising two discrete bleached regions. In the device according to some embodiments, the discrete bleached regions are angled with respect to a major surface of the substrate. In the device according to some embodiments, the device comprises a sensor comprising a first discrete bleached region and a light emitter positioned to direct light through the first discrete bleached region and a sensor positioned to receive signal light emitted through a second discrete bleached region.

[0055] In one or more embodiments, a device according to FIGS. 1 D or 1 E comprises a substrate comprising a glass or glass-ceramic material the substrate comprising an unbleached region having an internal optical transmittance and a bleached discrete region, wherein the unbleached region is opaque and black and the bleached discrete region comprises a plurality of apertures each having a diameter in a range of from about 10 micrometers to about 1000 micrometers. The device according to some embodiments may further comprise a light emitter (e.g. a LED, an OLED, a laser, etc.) and a sensor, wherein the substrate comprises at least a first bleached discrete region and a second bleached discrete region and radiation from the light emitter is emitted through the first discrete bleached region and the sensor captures light emitted through the second bleached discrete region. In the device according to some embodiments, the unbleached region is opaque (black) and the first bleached discrete region is optically isolated from the second bleached discrete region. In the device according to some embodiments, the sensor is selected from the group consisting of a heart rate sensor, a glucose sensor, a temperature sensor and an oximetry sensor. In the device according to some embodiments, the device is wearable by a subject. In the device according to some embodiments, the device has a thickness, a first side and a second side opposite the first side, wherein the first bleached discrete region and the second bleached discrete region are located on the first side and a dead front display is located on the second side. In the device according to some embodiments, the device comprises a mobile phone with an integrated camera comprising two adjacent bleached discrete regions.

[0056] In the device according to some embodiments of FIGS. 1 D or 1 E, the device comprises a sensor window comprising two discrete bleached regions. In the device according to some embodiments, the discrete bleached regions are angled with respect to a major surface of the substrate. In the device according to some embodiments, the device comprises a sensor comprising a first discrete bleached region and a light emitter positioned to direct light through the first discrete bleached region and a sensor positioned to receive signal light emitted through a second discrete bleached region.

[0057] Bleaching Techniques

[0058] According to one or more embodiments, glass or glass-ceramic substrates are processed in a way to optically bleach at least one discrete region in the substrate as described above. In some embodiments, localized thermal heating by various laser light sources can be used to dissolve or re-solubilize various small crystalline phases (e.g., crystallites, micrometer-sized crystals (10 micrometers or less in cross-sectional dimension) or nanometer-sized crystals (100 nanometers or less in cross sectional dimension)) in discrete regions of glass or glass-ceramic substrates. While the disclosure is not to be limited by a scientific principle or theory, in one or more embodiments, localized heating of discrete regions of substrates results in a reversible redox reaction within the glass or glass-ceramic material that erases a chromophore(s) in the form of small crystals that gives rise to visible absorbance. When the chromophores are erased, absorbance is reduced in the substrate, and internal optical transmittance is increased.

[0059] Bleaching can be achieved using any suitable apparatus or system to increase internal optical transmittance in the discrete region. In one or more embodiments, bleaching is achieved by thermally treating the discrete region. Such thermal treatment may be performed using those energy sources known in the art, such as, but not limited to, furnaces, flames such as gas flames, resistance furnaces, lasers, microwaves, or the like. Laser bleaching has been determined to provide substrates with discrete regions having increased internal optical transmittance after bleaching. Preliminary bleaching experiments were conducted using a single-mode multimode fiber bundle coupled laser operating at 60 watts of power at 810 nm with both flat top and Gaussian beam profiles. A smaller bleached area was achieved with the Gaussian optics, which was focused to a 0.7 mm spot size.

[0060] Laser Bleachable Glass and Glass-Ceramic Materials and Substrates

[0061] Devices according to one or more embodiments comprise a substrate including a bleached discrete region or a plurality of bleached discrete regions. The bleached discrete regions in one or more embodiments are in arrays such as periodic arrays or patterned arrays, the bleached discrete regions may be in the form of apertures, graphics, alphanumeric text and/or symbols. In some embodiments, the apertures, graphics, alphanumeric text and/or symbols can be arranged to present visual information to an observer. The substrate according to one or more embodiments comprises bleached discrete regions and a glass or a glass-ceramic composition comprising a glass phase and further comprising a crystalline phase that permits a discrete region to be selectively bleached by the application of thermal energy. In some embodiments, a device comprises a substrate including bleached discrete regions and a glass or a glass-ceramic composition comprising a glass phase and further comprising a crystalline phase in a range of from about 0.1 % to about 50% by weight, from about 0.1 % to about 45% by weight, from about 0.1 % to about 40% by weight, from about 0.1 % to about 35% by weight, from about 0.1 % to about 30% by weight, from about 0.1 % to about 25% by weight, from about 0.1 % to about 20% by weight, from about 0.1 % to about 15% by weight, from about 0.3% to about 10% by weight, from about 0.3% to about 9% by weight, from about 0.3% to about 8% by weight, from about 0.3% to about 7% by weight, from about 0.3% to about 6% by weight, from about 0.3% to about 5% by weight, from about 0.3% to about 4% by weight, from about 0.3% to about 3% by weight, or from about 0.3% to about 2% by weight, from about 0.1 % to about 10% by weight, from about 0.1 % to about 9% by weight, from about 0.1 % to about 8% by weight, from about 0.1 % to about 7% by weight, from about 0.1 % to about 6% by weight, from about 0.1 % to about 5% by weight, from about 0.1 % to about 4% by weight, from about 0.1 % to about 3% by weight, or from about 0.1 % to about 2% by weight. In some

embodiments, the device comprises a substrate that has any of the above compositions and has crystallites that have an average crystallite size in a range of from about 5 nm to about 500 nm, of from about 5 nm to about 450 nm, of from about 5 nm to about 400 nm, of from about 5 nm to about 380 nm, of from about 5 nm to about 300 nm, of from about 5 nm to about 250 nm, of from about 5 nm to about 200 nm, of from about 5 nm to about 150 nm, of from about 5 nm to about 100 nm, of from about 5 nm to about 90 nm, of from about 5 nm to about 80 nm, of from about 5 nm to about 70 nm, of from about 5 nm to about 60 nm, of from about 5 nm to about 50 nm, of from about 10 nm to about 380 nm, in a range of from about 10 nm to about 300 nm, in a range of from about 10 nm to about 250 nm, in a range of from about 10 nm to about 200 nm, in a range of from about 10 nm to about 150 nm, in a range of from about 10 nm to about 100 nm, in a range of from about 10 nm to about 90 nm, in a range of from about 10 nm to about 80 nm, in a range of from about 10 nm to about 70 nm, in a range of from about 10 nm to about 60 nm, or in a range of from about 10 nm to about 50 nm. In one or more embodiments, the glass or glass-ceramic substrate is ion exchangeable and comprises at least one surface under a compressive stress (as) of at least about 200 MPa in a compressively stressed layer having a depth of layer (DOL) of at least about 20 μιη of the substrate; or at least one compressively stressed layer having a DOL of 20 μιη up to about 150 μιη for a substrate thickness of from about 0.1 millimeter (mm) up 5 mm, 0.1 millimeter (mm) to 2 mm, 0.1 millimeter (mm) to 1 .3 mm, or 0.1 millimeter (mm) to 0.7 mm.

[0062] In some embodiments, a device comprises a substrate including a bleached discrete region or a plurality of bleached discrete regions and an opaque black glass or an opaque black glass-ceramic composition comprising a glass phase and further comprising a crystalline phase in a range from about 0.3% to about 10% by weight, from about 0.3% to about 9% by weight, from about 0.3% to about 8% by weight, from about 0.3% to about 7% by weight, from about 0.3% to about 6% by weight, from about 0.3% to about 5% by weight, from about 0.3% to about 4% by weight, from about 0.3% to about 3% by weight, or from about 0.3% to about 2% by weight, from about 0.1 % to about 10% by weight, from about 0.1 % to about 9% by weight, from about 0.1 % to about 8% by weight, from about 0.1 % to about 7% by weight, from about 0.1 % to about 6% by weight, from about 0.1 % to about 5% by weight, from about 0.1 % to about 4% by weight, from about 0.1 % to about 3% by weight, or from about 0.1 % to about 2% by weight. In some embodiments, the device comprises a substrate that has any of the above compositions and has crystallites that have an average crystallite size in a range of from about 10 nanometers (nm) to about 380 nm, in a range of from about 10 nm to about 300 nm, in a range of from about 10 nm to about 250 nm, in a range of from about 10 nm to about 200 nm, in a range of from about 10 nm to about 150 nm, in a range of from about 10 nm to about 100 nm, in a range of from about 10 nm to about 90 nm, in a range of from about 10 nm to about 80 nm, in a range of from about 10 nm to about 70 nm, in a range of from about 10 nm to about 60 nm, or in a range of from about 10 nm to about 50 nm. In one or more embodiments, the glass or glass-ceramic substrate is ion exchangeable and comprises at least one surface under a compressive stress (as) of at least about 200 MegaPascals (MPa) in a

compressively stressed layer having a depth of layer (DOL) of at least about 20 micrometers (μιη) of the substrate; or at least one compressively stressed layer having a DOL of 20 μιη up to about 150 μιη for a substrate thickness of from about 0.1 millimeter (mm) up to about 5 mm, 0.1 millimeter (mm) up to about 2 mm, 0.1 millimeter (mm) up to about 1.3 mm, or 0.1 millimeter (mm) up to about 0.7 mm.

[0063] In some embodiments, a device comprises a substrate including a bleached discrete region of a plurality of bleached discrete regions and a glass or glass- ceramic composition comprising a glass phase and further comprising a comprises a crystalline tungsten bronze phase, a molybdenum bronze phase, a mixed tungsten- molybdenum bronze phase comprising nanoparticles and having the formula M _X A03 or MxAC , where A is at least one of W and Mo, and where M includes at least one of H, Li, Na, K, Rb, Cs, Mg, Ca, Sr, Sn, P, S, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Ga, Se, Zr, Nb, Ru, Rh, Pd, Ag, Cd, In, Sb, Te, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Ta, Os, Ir, Pt, Au, TI, Pb, Bi, and U,, and where 0 < x < 1 , or a mixed tungsten-molybdenum bronze phase comprising nanoparticles and having the formula MxAC , where A is at least one of W and Mo, and where M includes at least one of H, Li, Na, K, Rb, Cs, Mg, Ca, Sr, Sn, P, S, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Ga, Se, Zr, Nb, Ru, Rh, Pd, Ag, Cd, In, Sb, Te, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Ta, Os, Ir, Pt, Au, TI, Pb, Bi, and U„ and where 1 < x < 2. The crystalline tungsten bronze phase is present in a range of from about 0.3% to about 10% by weight, from about 0.3% to about 9% by weight, from about 0.3% to about 8% by weight, from about 0.3% to about 7% by weight, from about 0.3% to about 6% by weight, from about 0.3% to about 5% by weight, from about 0.3% to about 4% by weight, from about 0.3% to about 3% by weight, or from about 0.3% to about 2% by weigh, from about 0.1 % to about 10% by weight, from about 0.1 % to about 9% by weight, from about 0.1 % to about 8% by weight, from about 0.1 % to about 7% by weight, from about 0.1 % to about 6% by weight, from about 0.1 % to about 5% by weight, from about 0.1 % to about 4% by weight, from about 0.1 % to about 3% by weight, or from about 0.1 % to about 2% by weight. In some embodiments, the device comprises a substrate that has any of the above compositions and has crystallites that have an average crystallite size in a range of from about 5 nm to about 500 nm, of from about 5 nm to about 450 nm, of from about 5 nm to about 400 nm, of from about 5 nm to about 380 nm, of from about 5 nm to about 300 nm, of from about 5 nm to about 250 nm, of from about 5 nm to about 200 nm, of from about 5 nm to about 150 nm, of from about 5 nm to about 100 nm, of from about 5 nm to about 90 nm, of from about 5 nm to about 80 nm, of from about 5 nm to about 70 nm, of from about 5 nm to about 60 nm, of from about 5 nm to about 50 nm, of from about 10 nm to about 380 nm, in a range of from about 10 nm to about 300 nm, in a range of from about 10 nm to about 250 nm, in a range of from about 10 nm to about 200 nm, in a range of from about 10 nm to about 150 nm, in a range of from about 10 nm to about 100 nm, in a range of from about 10 nm to about 90 nm, in a range of from about 10 nm to about 80 nm, in a range of from about 10 nm to about 70 nm, in a range of from about 10 nm to about 60 nm, or in a range of from about 10 nm to about 50 nm. In one or more embodiments, the glass or glass-ceramic substrate is ion exchangeable and comprises at least one surface under a compressive stress (as) of at least about 200 MPa in a compressively stressed layer having a depth of layer (DOL) of at least about 20 μιη of the substrate; or at least one compressively stressed layer having a DOL of 20 μιη up to about 150 μιη for a substrate thickness of from about 0.1 millimeter (mm) up to about 5 mm, 0.1 millimeter (mm) up to about 2 mm, 0.1 millimeter (mm) up to about 1.3 mm, or 0.1 millimeter (mm) to up to about 0.7 mm.

[0064] In some embodiments, a device comprises a substrate including a bleached discrete region and a plurality of bleached discrete regions and a glass or glass- ceramic composition comprising a glass phase and further comprising a crystalline phase containing molybdenum or mixed molybdenum-tungsten bronze, the crystalline phase in a range of from about 0.3% to about 10% by weight, from about 0.3% to about 9% by weight, from about 0.3% to about 8% by weight, from about 0.3% to about 7% by weight, from about 0.3% to about 6% by weight, from about 0.3% to about 5% by weight, from about 0.3% to about 4% by weight, from about 0.3% to about 3% by weight, or from about 0.3% to about 2% by weight, from about 0.1 % to about 10% by weight, from about 0.1 % to about 9% by weight, from about 0.1 % to about 8% by weight, from about 0.1 % to about 7% by weight, from about 0.1 % to about 6% by weight, from about 0.1 % to about 5% by weight, from about 0.1 % to about 4% by weight, from about 0.1 % to about 3% by weight, or from about 0.1 % to about 2% by weight. In some embodiments, the device comprises a substrate that has any of the above compositions and has crystallites that have an average crystallite size in a range of from about 5 nm to about 500 nm, of from about 5 nm to about 450 nm, of from about 5 nm to about 400 nm, of from about 5 nm to about 380 nm, of from about 5 nm to about 300 nm, of from about 5 nm to about 250 nm, of from about 5 nm to about 200 nm, of from about 5 nm to about 150 nm, of from about 5 nm to about 100 nm, of from about 5 nm to about 90 nm, of from about 5 nm to about 80 nm, of from about 5 nm to about 70 nm, of from about 5 nm to about 60 nm, of from about 5 nm to about 50 nm, of from about 10 nm to about 380 nm, in a range of from about 10 nm to about 300 nm, in a range of from about 10 nm to about 250 nm, in a range of from about 10 nm to about 200 nm, in a range of from about 10 nm to about 150 nm, in a range of from about 10 nm to about 100 nm, in a range of from about 10 nm to about 90 nm, in a range of from about 10 nm to about 80 nm, in a range of from about 10 nm to about 70 nm, in a range of from about 10 nm to about 60 nm, or in a range of from about 10 nm to about 50 nm.

[0065] The crystalline phase content can be determined by x-ray diffraction and/or Raman spectroscopy. [0066] In some embodiments, a device comprises a substrate including a bleached discrete region or a plurality of bleached discrete regions and a glass or glass- ceramic composition having crystallites that have an average crystallite size in a range of from about 5 nm to about 500 nm, of from about 5 nm to about 450 nm, of from about 5 nm to about 400 nm, of from about 5 nm to about 380 nm, of from about 5 nm to about 300 nm, of from about 5 nm to about 250 nm, of from about 5 nm to about 200 nm, of from about 5 nm to about 150 nm, of from about 5 nm to about 100 nm, of from about 5 nm to about 90 nm, of from about 5 nm to about 80 nm, of from about 5 nm to about 70 nm, of from about 5 nm to about 60 nm, of from about 5 nm to about 50 nm, of from about 10 nm to about 380 nm, in a range of from about 10 nm to about 300 nm, in a range of from about 10 nm to about 250 nm, in a range of from about 10 nm to about 200 nm, in a range of from about 10 nm to about 150 nm, in a range of from about 10 nm to about 100 nm, in a range of from about 10 nm to about 90 nm, in a range of from about 10 nm to about 80 nm, in a range of from about 10 nm to about 70 nm, in a range of from about 10 nm to about 60 nm, or in a range of from about 10 nm to about 50 nm. In one or more embodiments, the glass or glass-ceramic substrate is ion exchangeable and comprises at least one surface under a compressive stress (as) of at least about 200 MPa in a

compressively stressed layer having a depth of layer (DOL) of at least about 20 μιη of the substrate; or at least one compressively stressed layer having a DOL of 20 μιη up to about 150 μιη for a substrate thickness of from about 0.1 millimeter (mm) up to about 5 mm, 0.1 millimeter (mm) up to about 2 mm, 0.1 millimeter (mm) up to about 1.3 mm, or 0.1 millimeter (mm) up to about 0.7 mm.

[0067] Additional bleachable glass or glass-ceramic materials that can be used as part of a device comprising a substrate including a bleached discrete region or a plurality of bleached discrete regions that provide a hidden/dead front display are provided below. The bleached discrete regions in one or more embodiments are in arrays such as periodic arrays or patterned arrays, the bleached discrete regions may be in the form of apertures, graphics, alphanumeric text and/or symbols. In some embodiments, the apertures, graphics, alphanumeric text and/or symbols can be arranged to present visual information to an observer. [0068] According to one or more embodiments, a device comprises a substrate including a bleached discrete region or a plurality of bleached discrete regions and a glass or glass-ceramic materials selected from the group consisting of a glass formulated to be formable and/or color-tunable and formulated to be crystallizable to formed and/or color-tuned glass-ceramics (hereinafter "formable and crystallizable glass" or "formable and crystallizable glasses" or "formable, crystallizable glass" or "formable, crystallizable glasses" "color-tunable and crystallizable glass" or "color- tunable and crystallizable glasses" or "color-tunable, crystallizable glass" or "color- tunable, crystallizable glasses" or "formable and/or color-tunable and crystallizable glass" or "formable and/or color-tunable and crystallizable glasses" or "formable and/or color-tunable, crystallizable glass" or "formable and/or color-tunable, crystallizable glasses" or "crystallizable glass" or "crystallizable glasses"); or a glass- ceramic (hereinafter "formed glass-ceramic" or "formed glass-ceramics" or "color- tuned glass-ceramic" or "color-tuned glass-ceramics" or "formed and/or color-tuned glass-ceramic" or "formed and/or color-tuned glass-ceramics" or "formed, color-tuned glass-ceramic" or "formed, color-tuned glass-ceramics" or "color-tuned, formed glass-ceramic" or "color-tuned, formed glass-ceramics" or "glass-ceramic" or "glass- ceramics"); or an ion exchangeable ("IXable"), glass-ceramic subjectable to an ion exchange (IX) surface treatment (hereinafter "ion exchangeable (IXable) glass- ceramic" or "IXable, glass-ceramics" or "IXable, formed glass-ceramic" or "IXable, formed glass-ceramics" or "IXable, color-tuned glass-ceramic" or "IXable, color-tuned glass-ceramics" or "IXable, formed and/or color-tuned glass-ceramic" or "IXable, formed and/or color-tuned glass-ceramics" or "IXable, formed, color-tuned glass- ceramic" or "IXable, formed, color-tuned glass-ceramics" or "IXable, color-tuned, formed glass-ceramic" or "IXable, color-tuned, formed glass-ceramics" or "glass- ceramic" or "glass-ceramics"); or

an ion exchanged (IX) glass-ceramic (hereinafter "ion exchanged (IX) glass-ceramic" or "ion exchanged (IX) glass-ceramics" or "ion exchanged (IX) glass-ceramic" or "IX, glass-ceramics" or "IX, formed glass-ceramic" or "IX, formed glass-ceramics" or "IX, color-tuned glass-ceramic" or "IX, color-tuned glass-ceramics" or "IX, formed and/or color-tuned glass-ceramic" or "IX, formed and/or color-tuned glass-ceramics" or "IX, formed, color-tuned glass-ceramic" or "IX, formed, color-tuned glass-ceramics" or "IX, color-tuned, formed glass-ceramic" or "IX, color-tuned, formed glass-ceramics" or "glass-ceramic" or "glass-ceramics").

[0069] According to one or more embodiments, a device comprises a substrate including a bleached discrete region or a plurality of bleached discrete regions and a composition selected from the group consisting of low crystallinity (in the range of from 0.1 % to 50% by weight crystal content) magnetite, pseudobrookite, and/or ε- Fe203 solid solution glass-ceramics disclosed in United States Patent Number 9,403,716, the entire content of which is incorporated herein by reference. In specific embodiments, the substrate comprises a glass-ceramic composition comprising less than about 15 wt % of one or more crystalline oxide phases; and a composition comprising on an oxide basis in mol %: about 50-76 S1O2; about 4-25 AI2O3; greater than 0 to about I 4P2O5+B2O3; greater than 0 to about 33 R2O, wherein R2O comprises one or more of U2O, Na20, K2O, Rb20, CS2O, CU2O, and Ag20; and greater than 0 to about 5 of one or more nucleating agents; and optionally, from 0 to about 20 RO, wherein RO comprises one or more of MgO, CaO, SrO, BaO, and ZnO. In one or more embodiments, such compositions contain Fe203 in a range of from about 0.5 mol% to about 3 mol% or from about 1 mol% to 3 mol%. In one or more embodiments, the glass or glass-ceramic substrate has a composition that is ion exchangeable and comprises at least one surface under a compressive stress (as) of at least about 200 MPa in a compressively stressed layer having a depth of layer (DOL) of at least about 20 μιη of the substrate; or at least one compressively stressed layer having a DOL of about20 μιη up to about 150 μιη for a substrate thickness of from about 0.1 millimeter (mm) up to about 5 mm, 0.1 millimeter (mm) up to about 2 mm, 0.1 millimeter (mm) up to about 1.3 mm, or 0.1 millimeter (mm) up to about 0.7 mm. In one or more embodiments, one or more nucleating agents comprises on an oxide basis in mol %: up to about 5 ΤΊΟ2; or alternatively, up to about 3 Zr02; or TiC and Zr02, wherein Ti02+Zr02 comprises up to about 5 and Zr02 comprises up to about 3. In one or more embodiments, substrates comprising black glass-ceramics are provided, the glass-ceramic having a liquidus viscosity greater than about 20 kiloPascal ^* seconds (kPa ^* s), making the glass-ceramic suitable for downdraw forming (e.g., fusion downdraw forming or slot downdraw forming). In one or more embodiments, substrates comprise sodium aluminosilicate base glasses that ion exchange with potassium ions and contain a crystalline phase. For black materials, a crystalline phase with high absorption and low scattering across the visible was desired so target crystalline phases included highly absorbing compounds in the Fe203-Ti02-MgO system. For a deep rich black color, the crystals in the glass-ceramic should be as small as possible or index matched to the glass to prevent optical scattering which would turn an otherwise black glass-ceramic to grey. In one or more embodiments, such glass-ceramics have an average crystallite size in a range of 10-20 nm.

[0070] According to one or more embodiments, a device is provided comprising a substrate comprising a glass or glass-ceramic material comprising from about 0.1 % to about 50% by weight crystalline phase; and

the substrate comprises an unbleached region having an internal optical

transmittance and a bleached discrete region comprising at least partially dissolved crystalline phase, the bleached discrete region having an internal optical

transmittance at least twice the internal optical transmittance over at least a 50 nm wide wavelength window in the unbleached region in the visible wavelength range of 300 nm to 1700 nm, wherein the unbleached regions contains a crystalline phase comprising at least one of Fe203, ΤΊΟ2, and MgO, or the unbleached regions contain a crystalline phase comprising any combination of Cr, Fe, Co, Ni, or Cu , or the unbleached regions contain a crystalline phase comprising any combination of W and Mo.

[0071] As described in the background, the earliest dead front display designs employ transparent overlays made of glass but more commonly plastic with opaque graphics that form a mask with symbols and or text. When these masks are backlit, the graphic becomes visible. Such graphics can be screen printed inks, vapor deposited metallic coatings, or stamped (cut-out) semi- or fully-opaque films that are laminated to the overlay. Exemplary embodiments differ from these concepts because instead of using a printed or deposited mask layer on a glass or plastic overlay, an opaque glass or glass-ceramic is employed with thermally modulatable internal optical transmittance or thermally modulatable optical absorbance. This enables one to locally tune the internal optical transmittance of these exemplary materials by local heating with an energy source, for example, a laser, facilitating the creation of optically transparent discrete regions, e.g., apertures, symbols, and or text. Thus, with exemplary embodiments described herein, a single layer of glass and/or glass-ceramic material can serve doubly as a cover material for a display and the mask of a hidden/dead front display.

[0072] Embodiments also provide devices with hidden or dead front displays that differ from those that employ semi-transparent, translucent, or semi-opaque materials, and those that employ transparent materials coated with partially reflective films. In one or more embodiments the difference is due to an opaque glass or glass-ceramic with optically transparent apertures that allow light transmission. According to one or more embodiments, opaque refers to the inability for the light from the display or light-source behind the panel to transmit through the substrate or layer that forms the panel, which is determined by the absorption coefficient of the material and its thickness. Moreover, exemplary embodiments do not necessarily utilize partially reflective coatings to produce the appearance of opacity in reflected light, however, in some embodiments reflective coatings could be used to further enhance/alter the appearance of a device. Compared to devices made from translucent or semi opaque materials that are not bleachable (whether they are plastic or glass) the devices described herein do not distort the image due to scattering.

[0073] Exemplary embodiments also differ from conventional dead front displays employing various polarization schemes (e.g., quarter waveplates) to gate/prevent light leakage to give the appearance of a completely black or 'dead' screen as such embodiments do not use polarizers, light gates, or quarter waveplates to control, modulate, or eliminate light leakage.

[0074] Photo-sensitive glasses and glass-ceramics as described above are also capable of producing small optically transparent windows or 'apertures' within an opaque layer. These include noble metal-doped glasses that produce color upon UV irradiation followed by thermal treatment, and a certain photosensitive glass- ceramics (e.g., Fotoform and Fota-lite) that become various shades of opal white or pastel colors when UV irradiated and subsequently heat treated. While

photosensitive glasses and glass-ceramics offer some advantages for dead-front or hidden displays including that they do not require lasers to pattern them, instead using facile masks and mercury vapor flood lamps and that they can produce fine features with high resolution (on the order of micrometers) that is superior to thermally bleached materials that are limited by thermal diffusion. In addition, these materials can produce a host of different opaque colors, opal white, and opaque grayscale tones. However, such photosensitive glass and glass-ceramic materials are intrinsically poor candidates for dead front display applications (especially those including but not limited to hand-held devices and automotive applications that require scratch resistance and high strength). Also, such photosensitive glass and glass-ceramic materials are not compatible with downdraw processes such as slot downdraw or fusion downdraw processes for forming thin glass sheets, as they have inherently low chemical and mechanical durability, and they have high cost because they contain noble metals. In addition, such photosensitive glass and glass-ceramic materials are difficult to melt (due to volatile species (e.g., halogens), and they cannot produce a true black substrate, which is considered most desirable and congruent with the contemporary definition of a dead front display.

[0075] It is for these reasons that such photosentive glass and glass-ceramics are not considered suitable for dead-front display applications, despite their capabilities. Moreover, exemplary embodiments described herein differ from photosensitive materials because one or more embodiments utilize a fundamentally different mechanism to create optically transparent apertures, namely, bleaching of the glass or glass-ceramic material to dissolve crystalline phase in the glass or glass-ceramic. In one or more embodiments, the crystalline phase is at least partially decomposed or completely decomposed. In one or more embodiments, dissolving or

decomposing the crystalline phases can allow modulation of the optical extinction in the UV, VIS, and NIR wavelength ranges. In one or more embodiments, the crystalline phase of the glass or glass-ceramic material that forms the substrate of the device has discrete regions in which the crystalline phase has been heated such that the crystalline phase is re-solubilized or placed back in solution such that internal optical transmittance in the bleached discrete region is increased compared to regions of the substrate that have not been bleached. In some embodiments, the bleached discrete regions of a substrate have more than twice the internal optical transmittance of the unbleached region in at least a 50 nm wide wavelength window in the visible wavelength range of 300 nm to 1700 nm (e.g., 380 nm to 780 nm), and in some embodiments, more than 10 times the internal optical transmittance of an unbleached region in the visible wavelength range of 300 nm to 1700 nm (e.g., 380 nm to 780 nm) and in some embodiments, more than 20 times, 30 times, 40 times, 50 times, 60 times, 70 times, 80 times, 90 times, 100 times, 200 times, 300 times, 400 times, 500 times, 1000 times, 2000 times, 3000 times, 4000 times, 5000 times, 6000 times, 7000 times, 8000 times, 9000 times or 10000 times the internal optical transmittance of an unbleached region in the visible wavelength range of 300 nm to 1700 nm (e.g., 380 nm to 780 nm). Reference to bleached discrete region a having a specific internal optical transmittance value times the internal optical transmittance of an unbleached region means that the internal optical transmittance is measured with respect to a sample having the same thickness in the bleached discrete region and unbleached region. While the disclosure is not to be limited by a scientific principle or theory, in one or more embodiments, localized heating of discrete regions of substrates results in a reversible redox reaction within the glass or glass- ceramic material that erases a chromophore(s) in the form of small crystals or metallic nanoparticles that gives rise to visible absorbance. In some embodiments, when the chromophores are erased or their oxidation state is shifted to an oxidation state that does not strongly attenuate, absorbance is reduced in the substrate, and internal optical transmittance is increased. In one or more embodiments, complete dissolution of the crystalline phase results in the crystalline phase returning to the glassy phase, resulting in a reduction in the optical absorbance of the material, and increasing the internal optical transmittance of the material in the bleached discrete regions. In one or more embodiments, bleaching is achieved by thermally treating the discrete region. Such thermal treatment may be performed using those energy sources known in the art, such as, but not limited to, furnaces (e.g., resistance furnace), lasers, microwaves, or the like.

[0076] In one or more embodiments, a device comprises a substrate including bleached discrete regions and a glass or glass-ceramic composition comprising a glass phase and further comprising a crystalline phase wherein the composition is free of silver, gold and/or vanadium.

[0077] In one or more embodiments, a device comprises a substrate including a bleached discrete region or a plurality of bleached discrete regions and a glass or glass-ceramic composition that provides suitable combination of physical properties and a liquidus temperature (liquidus viscosity), which allows the glass to be formed by a downdraw process (e.g., a fusion downdraw process or slot downdraw process). The downdraw sheet drawing processes and, in particular, the fusion downdraw process described in U.S. Pat. Nos. 3,338,696 and 3,682,609, both to Dockerty, are capable of producing glass sheets that can be used as substrates without requiring costly post-forming finishing operations such as lapping and polishing. Unfortunately, the fusion downdraw process places rather severe restrictions on the glass properties, which require relatively high liquidus viscosities. According to one or more embodiments, glass or glass-ceramic compositions to form the substrates used in the devices have a liquidus viscosity greater than about 10 ⁵ Poise.

[0078] Additional embodiments comprise a method of forming a device comprising applying thermal energy to discrete regions of a substrate comprising a glass or glass-ceramic material comprising from about 0.1 % to about 50% by weight crystalline phase such that there is an unbleached region in the substrate having an internal optical transmittance and a bleached discrete region comprising at least partially dissolved crystalline phase, the bleached discrete region having an internal optical transmittance at least twice the internal optical transmittance over at least a 50 nm wide wavelength window in the unbleached region in the visible wavelength range of 300 nm to 1700 nm (e.g., 380 nm to 780 nm). In some embodiments, applying thermal energy causes the crystalline phase to be re-solubilized or placed back in solution such that internal optical transmittance in the bleached discrete region is increased compared to regions of the substrate that have not been bleached.

[0079] In some embodiments, applying thermal energy comprises using a furnace (e.g., a resistance furnace), a flame (e.g., a gas flame), a laser, or microwaves. In some embodiments, applying thermal energy comprises directing a laser toward the discrete regions.

[0080] In some method embodiments, the discrete region is selected from the group consisting of a periodic array of apertures, a patterned array of apertures, graphics, alphanumeric text and symbols. In some embodiments, the bleached discrete region is arranged to present visual information to an observer. In some method embodiments, the bleached discrete region comprises a plurality of apertures each having a diameter in a range of from about 10 micrometers to about 100 micrometers. In some method embodiments, the apertures have a center-to- center spacing in a range of from about 20 micrometers to about 200 micrometers or from about 20 micrometers to about 100 micrometers. In some method

embodiments, the device comprises a sign a mobile phone, a tablet, a wearable sensor, a wearable activity tracker, a wearable health monitor, a watch, a camera and a vehicle display. The method of claim 36, wherein the glass or glass-ceramic has a liquidus viscosity greater than about 10 ⁵ Poise.

[0081] Some method embodiments further comprise forming the substrate using a downdraw forming process to form the substrate as a sheet. Some method embodiments further comprise using a fusion downdraw forming process to form the substrate as a sheet.

[0082] Additional embodiments include laser-bleaching glass or glass-ceramic on a hot-stage such that the glass or glass-ceramic material is pre-heated to

temperatures near or around the strain or anneal point (near or at the glass transition temperature (Tg). This would allow the material to relax as it is bleached such that the surfaces remain smooth (un-distorted/non-textured). It was observed that the smaller size of the bleached area obtained from laser bleaching, the smaller deformation ('laser bumps"), and it is possible to put pressure on the surface with transparent "non-sticking material" to prevent "bump" formation, or deform bump to flat top raised feature.

[0083] One or more embodiments can include tuning the laser bleaching and process conditions (wavelength, beam profile, exposure time, power density, and substrate temperature) such that the glass or glass-ceramic is locally heated and a small spherical deformation is induced at the surface of the laser-bleached aperture. Such a feature could act as a lens, enabling focusing or defocusing from the addressable light source (LED or pixel on a display)..

[0084] Further embodiments may form a non-symmetrical conically shaped aperture to further collect and or steer the emission from the addressable light source.

[0085] Additional embodiments may include a glass-glass laminate comprised of a transparent substrate with an ultra-thin (e.g., <100 micrometer) cladding of a highly absorptive bleachable glass or glass-ceramic. This thin, bleachable layer may offer greater control of the size or resolution of the aperture as there would be less material to bleach.

[0086] Some embodiments of laser-bleached apertures can be used for camera windows and sensors, allowing discrete placement of such components within a device, and or behind the display screen.

[0087] Further embodiments may texture the surfaces of the laser bleached opaque glass and glass-ceramics to alter the reflectivity and or tactile experience by methods including but not limited to: sandblasting, media blasting, and or chemical etching.

[0088] Some embodiments may produce dead front displays or opaque printing on glass or glass-ceramic by locally laser bonding/welding/melting an opaque pigment such as a glass frit or a carbonaceous material to the surface of the glass or glass- ceramic.

[0089] Various embodiments of the present disclosure are further illustrated by the following non-limiting examples.

[0090] EXAMPLES

[0091] Bleaching experiments were first conducted using a multimode fiber bundle coupled laser operating at 60 Watts of power at 810 nm with both flat top and Gaussian beam profiles.

[0092] Transmission spectra were measured using a PerkinElmer Lambda 950 with a 60 mm integrating sphere. Measurements were obtained over a spectral range of 300 nm to 2500 nm at 2 nm data intervals. Prior to measurement, the samples were cleaned using a TX® 609 Technicloth® wiper dampened with H PLC grade reagent alcohol and wiped across the flat substrates. A 1.5 mm diameter aperture was first placed onto the integrating sphere's transmittance port opening. Samples were measured for total internal optical transmittance with the sample mounted at sphere's entrance port hole, allowing for collection of wide angle scattered light. Total internal optical transmittance data was collected with a reference reflectance disc (Spectralon) positioned over integrating sphere's exit port hole. The exposure times were manually controlled by turning on and off the laser. [0093] A smaller bleached area was achieved with the Gaussian optics, which was focused to a 0.7 mm spot size. Internal optical transmittance spectra were measured as follows

[0094] Example 1

[0095] A multimode fiber bundle coupled laser with a Gaussian beam profile at powers of 15 watts and 20 watts at 810 nm was used to form apertures on a 0.5 mm thick black glass substrate, product code 4318 available from Corning, Inc., Corning, NY. Exposure times at each power were 1 second, 2 seconds, 3 seconds, 4 seconds and 5 seconds.

[0096] Internal optical transmittance was measured as described above. FIG. 2 shows the internal optical transmittance over the wavelength range of 350 nm to 800 nm. As the laser power and exposure time increased, the internal internal optical transmittance across these wavelengths increased.

[0097] Example 2

[0098] A multimode fiber bundle coupled laser with a Gaussian beam profile at powers of 15 watts and 20 watts at 810 nm was used to form apertures on a 0.5 mm thick vanadium-doped glass glass-ceramic substrate comprising a crystalline tungsten bronze phase comprising nanoparticles and a crystalline tungsten bronze phase comprising nanoparticles and having the formula MxWC , where M includes at least one of H, Li, Na, K, Rb, Cs, Mg, Ca, Sr, Sn, P, S, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Ga, Se, Zr, Nb, Ru, Rh, Pd, Ag, Cd, In, Sb, Te, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Ta, Os, Ir, Pt, Au, TI, Pb, Bi, and/ U, and where 0 < x < 1.

Exposure times at each power were 1 second, 2 seconds, 3 seconds, 4 seconds and 5 seconds.

[0099] Internal optical transmittance was measured as described above. FIG. 3 shows the internal optical transmittance over the wavelength range of 350 nm to 800 nm. As the laser power and exposure time increased, the internal optical

transmittance across these wavelengths increased.

[00100] Example 3

[00101] A multimode fiber bundle coupled laser with a Gaussian beam profile at a powers of 15 watts and 20 watts at 810 nm was used to form apertures on a 0.78 mm thick glass glass-ceramic Corning glass code 174CUS, available from Corning, Inc., Corning, NY. Exposure times at each power were 1 second, 2 seconds, 3 seconds, 4 seconds and 5 seconds.

[00102] Internal optical transmittance was measured as described above. FIG. 4 shows the internal optical transmittance over the wavelength range of 350 nm to 800 nm. The data indicates that higher laser power (compare 20W-1 sec vs 15W-1 sec) results in higher internal internal optical transmittance.

[00103] Example 4

[00104] A glass-ceramic substrate having the following composition in mol% was prepared.

[00105] The glass was melted, poured onto a steel table, and annealed. Samples that were 0.5 mm thick were made from the annealed melt and polished. These samples were heat treated at 550°C for 12 hours, cooled to 475°C at 1 °C per minute, and then cooled at a furnace rate to room temperature (approximately 10° C per minute). The bleached sample was derived from the unbleached sample, but subjected to further high energy processing according to the following conditions: a five (5) second exposure to a high intensity infrared lamp (a Research, Inc. Spot Heater Model 4085 infrared heat lamp). As is evident from the spectra in FIG. 5 and FIG. 6, the unbleached samples demonstrated low internal optical transmittance and high absorbance levels across the UV, visible and NIR regimes. Conversely, the bleached samples demonstrated high internal optical transmittance and low absorbance levels across the UV, visible and NIR regimes. As such, it is apparent that the bleaching process drives the crystalline phases present in the unbleached samples back into solution, thus significantly changing the optical properties of the substrates.

[00106] Example 5

[00107] A multimode fiber bundle coupled laser with a Gaussian beam profile at a powers of 53 watts at 810 nm was used on a 0.5 mm thick black glass substrate, product code 4318 available from Corning, Inc., Corning, NY, the laser in a translating mode through a cordierite cellular ceramic mask having openings of 196 cells per square inch available from Corning, Inc. at a speed of 2 mm/s. A pattern of bleached discrete regions corresponding to the cellular structure of the honeycomb substrate was formed, as the internal optical transmittance in the bleached discrete regions was greater than the internal optical transmittance in the non-bleached regions.

[00108] Some experiments were conducted by heating the glass on a hot plate at 270°C and held there for the duration of the bleaching process. This was an attempt to reduce the temperature delta required to bleach the sample and alleviate thermal stress. Following the bleaching process the hot plate was turned off and the samples were allowed to cool to room temperature.

[00109] Example 6

[00110] A single mode fiber laser with a Gaussian beam profile at a power of 3 watts at 1480 nm (Spectra Physics Integra) and a spot size of 30 micrometers was used to optically bleach apertures in a 0.5 mm thick black glass substrate, product code 4318 available from Corning, Inc., Corning, NY. Exposure time was 300

milliseconds, controlled by mechanical shutter. Transmission increased in the optically bleached areas.

[00111] Further laser bleaching experiments were conducted s single TEM00 mode laser with a Gaussian beam profile at an average power of 0.3 watts at 355 nm, repetition rate 30 kHz, and pulse width 15 ns, and a spot size of 30 micrometers was used to optically bleach apertures in a 0.5 mm thick black glass substrate, product code 4318 available from Corning, Inc., Corning, NY. It was observed that it took a significant amount of time 1000-2000 milliseconds at the 355 nm wavelength for the substrate to bleach because of the material's strong UV absorbance. Thus, it took longer for the light to penetrate the sample and the spots that were exposed to 355 nm laser light were not highly transparent even after prolonged exposure. In contrast, samples exposed to the 1480 nm 4W continuous wave laser with single mode fiber delivery, bleached rapidly (300 ms) and were highly transparent. In this experiment the exposure time of 300 ms was the shortest time possible with a mechanical shutter on the apparatus. It is conceivable that by optimizing laser power full optical bleaching could be achieved with a shorter exposure time. This accelerated bleaching occurred because the NIR penetration is much greater and since it is a self-limiting process, through-thickness bleaching is more efficient. Resolution is also better because there is less thermal diffusion with shorter bleach times.

[00112] While the foregoing is directed to various embodiments, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope thereof is determined by the embodiments that follow.