Patent Description:
Advancements in precision micromachining and related process improvements made to reduce size, weight and material costs have facilitated fast pace growth of products such as, but not limited to, flat panel displays for touch screens, tablets, smartphones and televisions. As a result of these advancements, ultrafast industrial lasers have become important tools for applications requiring high precision micromachining. Laser cutting processes utilizing such lasers are expected to separate substrates in a controllable fashion, to form negligible debris and to cause minimal defects and low subsurface damage to the substrate. Coatings on surfaces of substrates can reduce the effectiveness of laser cutting processes. For example, a coating may absorb some of a laser beam, altering propagation of the laser beam to an interior portion of the substrate. Additionally, separation of the coated substrate may form unacceptable amounts of debris, and also may cause defects or subsurface damage to the separated portions of the substrate.

Accordingly, a need exists for alternative improved methods for separating coated substrates.

According to a first aspect of the present disclosure, a method of separating a coated substrate includes directing an infrared laser beam onto a first surface of the coated substrate. The coated substrate includes a coating layer disposed on a transparent workpiece, a plurality of defects is disposed within the coated substrate, extending into both the coating layer and the transparent workpiece and disposed along a contour line that divides a primary region of the coated substrate from a dummy region of the coated substrate, and the infrared laser beam projects an infrared beam spot onto the first surface of the coated substrate. The method also includes translating at least one of the coated substrate and the infrared laser beam relative to each other such that the infrared beam spot traces an oscillating pathway. The oscillating pathway follows an offset line in a translation direction and oscillates between an inner track line and an outer track line, the oscillating pathway is disposed on the dummy region of the coated substrate, and the infrared laser beam applies thermal energy to the plurality of defects disposed in the coated substrate and inducing separation of the coated substrate along the contour line.

A second aspect of the present disclosure includes the method of the first aspect, wherein when tracing the oscillating pathway, the infrared beam spot applies thermal energy to the dummy region of the coated substrate without melting or ablating the coating layer of the primary region of the coated substrate.

A third aspect of the present disclosure includes the method of the first aspect or the second aspect, wherein the infrared beam spot has a Gaussian energy distribution.

A fourth aspect of the present disclosure includes the method of any of the previous aspects, wherein the oscillating pathway follows a linear oscillation in which the oscillating pathway oscillates along a transverse axis that is orthogonal to the offset line and the offset line is parallel to and offset from the contour line.

A fifth aspect of the present disclosure includes the method of the fifth aspect, wherein the oscillating pathway has a plurality of straight portions and a plurality of rounded portions, each of the plurality of straight portions extends along the transverse axis between the plurality of rounded portions and each of the plurality of straight portions have a length of from <NUM> to <NUM>, and each of the plurality of rounded portions have a radius of curvature of from <NUM> to <NUM>.

A sixth aspect of the present disclosure includes the method of any of the first aspect through the third aspect, wherein the oscillating pathway follows a wobbling oscillation in which the oscillating pathway rotationally oscillates between the inner track line and the outer track line while following the offset line in the translation direction.

A seventh aspect of the present disclosure includes the method of any of the first aspect through the third aspect, wherein the oscillating pathway is a sawtooth pathway having angular turns at or between the inner track line and the outer track line while following the offset line in the translation direction.

An eighth aspect of the present disclosure includes the method of any of the previous aspects, wherein the offset line is spaced a distance of from <NUM> to <NUM> from the contour line, the inner track line is spaced a distance of from <NUM> to <NUM> from the contour line, and the outer track line is spaced a distance of from <NUM> to <NUM> from the contour line.

A ninth aspect of the present disclosure includes the method of any of the previous aspects, wherein the infrared laser beam is generated by an infrared beam source and the infrared beam source is coupled to a scanner configured to translate the infrared laser beam such that the infrared beam spot traces the oscillating pathway.

A tenth aspect of the present disclosure includes the method of any of the previous aspects, wherein the infrared laser beam has a <NUM>/e<NUM> diameter in a range of from <NUM> to <NUM>.

An eleventh aspect of the present disclosure includes the method of any of the previous aspects, wherein the coating layer is a polymer or a metal oxide.

A twelfth aspect of the present disclosure includes the method of any of the previous aspects, wherein the transparent workpiece comprises borosilicate glass, soda-lime glass, aluminosilicate glass, alkali aluminosilicate glass, alkaline earth aluminosilicate glass, alkaline earth boro-aluminosilicate glass, fused silica, sapphire, silicon, or gallium arsenide.

A thirteenth aspect of the present disclosure includes the method of any of the previous aspects, further including, prior to directing the infrared laser beam onto the first surface the coated substrate, forming the plurality of defects in the coated substrate.

A fourteenth aspect of the present disclosure includes the method of the thirteenth aspect, wherein forming the plurality of defects includes directing a pulsed laser beam into the coated substrate. The pulsed laser beam forms a pulsed laser beam focal line extending into the coating layer and the transparent workpiece, the pulsed laser beam focal line inducing absorption in the coating layer and the transparent workpiece, the induced absorption producing an individual defect in the coated substrate and the pulsed laser beam focal line includes a wavelength λ, a spot size wo, and a Rayleigh range ZR that is greater than <MAT>, where FD is a dimensionless divergence factor comprising a value of <NUM> or greater. The method further includes translating at least one of the coated substrate and the pulsed laser beam relative to each other along the contour line to form the plurality of defects in the coated substrate.

A fifteenth aspect of the present disclosure includes the method of the fourteenth aspect, wherein the coating layer includes a transmission of greater than <NUM>% per mm of material depth of the wavelength λ of the pulsed laser beam focal line.

A sixteenth aspect of the present disclosure includes the method of the fourteenth aspect or the fifteenth aspect, wherein a spacing between adjacent defects of the plurality of defects is about <NUM> or less, each pulse burst of the pulsed laser beam has a pulse burst energy of greater than <NUM>µJ, and the dimensionless divergence factor FD has a value of from <NUM> to <NUM>.

A seventeenth aspect of the present disclosure includes the method of the fourteenth aspect or the fifteenth aspect, wherein the pulsed laser beam traverses an aspheric optical element before irradiating the coated substrate.

According to an eighteenth aspect of the present disclosure, a method of separating a coated substrate includes directing an infrared laser beam onto a first surface of the coated substrate. The coated substrate includes a coating layer disposed on a transparent workpiece, a plurality of defects is disposed within the coated substrate, extending into both the coating layer and the transparent workpiece and disposed along a contour line that divides a primary region of the coated substrate from a dummy region of the coated substrate, the infrared laser beam projects an infrared beam spot onto the first surface of the coated substrate, and the infrared beam spot includes an energy distribution in which <NUM>% or less of a total energy of the infrared beam spot has a fluence less than <NUM>% of a maximum fluence of the infrared beam spot. The method also includes translating at least one of the coated substrate and the infrared laser beam relative to each other such that the infrared beam spot follows an offset line, wherein the offset line is disposed on the dummy region of the coated substrate and is offset from the contour line such that the inner region of the infrared beam spot is projected onto the dummy region and the infrared laser beam applies thermal energy to the plurality of defects disposed in the coated substrate and inducing separation of the coated substrate along the contour line.

A nineteenth aspect of the present disclosure includes the method of the eighteenth aspect, wherein when following the offset line, the infrared beam spot applies thermal energy to the dummy region of the coated substrate without melting or ablating the coating layer of the primary region of the coated substrate.

A twentieth aspect of the present disclosure includes the method of the eighteenth aspect or the nineteenth aspect, wherein at least one of the coated substrate and the infrared laser beam are translated relative to each other such that the infrared beam spot traces an oscillating pathway that follows the offset line in a translation direction and oscillates between an inner track line and an outer track line and the oscillating pathway is disposed on the dummy region of the coated substrate.

A twenty-first aspect of the present disclosure includes the method of any of the eighteenth through twentieth aspects, wherein the entirety of the inner region of the infrared beam spot is projected onto the dummy region of the coated substrate.

A twenty-second aspect of the present disclosure includes the method of any of the eighteenth through twenty-first aspects, wherein the infrared laser beam traverses a diffractive optical element before irradiating the coated substrate.

A twenty-third aspect of the present disclosure includes the method of any of the eighteenth through twenty-second aspects, wherein <NUM>% or less of the total energy of the infrared beam spot has less than <NUM>% of the maximum fluence of the infrared beam spot.

A twenty-fourth aspect of the present disclosure includes the method of any of the eighteenth through twenty-third aspects, wherein <NUM>% or less of the total energy of the infrared beam spot has less than <NUM>% of the maximum fluence of the infrared beam spot.

A twenty-fifth aspect of the present disclosure includes the method of any of the eighteenth through twenty-fourth aspects, wherein the offset line is parallel to the contour line.

A twenty-sixth aspect of the present disclosure includes the method of any of the eighteenth through twenty-fifth aspects, wherein the coating layer is a polymer or a metal oxide.

A twenty-seventh aspect of the present disclosure includes the method of any of the eighteenth through twenty-sixth aspects, wherein the transparent workpiece is borosilicate glass, soda-lime glass, aluminosilicate glass, alkali aluminosilicate glass, alkaline earth aluminosilicate glass, alkaline earth boro-aluminosilicate glass, fused silica, sapphire, silicon, or gallium arsenide.

A twenty-eighth aspect of the present disclosure includes the method of any of the eighteenth through twenty-seventh aspects, further including, prior to directing the infrared laser beam onto the first surface the coated substrate, forming the plurality of defects in the coated substrate.

A twenty-ninth aspect of the present disclosure includes the method of the twenty-eighth aspect, further including, wherein forming the plurality of defects includes directing a pulsed laser beam into the coated substrate, wherein the pulsed laser beam forms a pulsed laser beam focal line extending into the coating layer and the transparent workpiece, the pulsed laser beam focal line inducing absorption in the coating layer and the transparent workpiece, the induced absorption producing an individual defect in the coated substrate. The pulsed laser beam focal line includes a wavelength λ, a spot size wo, and a Rayleigh range ZR that is greater than <MAT>, where FD is a dimensionless divergence factor comprising a value of <NUM> or greater. The method also includes translating at least one of the coated substrate and the pulsed laser beam relative to each other along the contour line to form the plurality of defects in the coating layer.

A thirtieth aspect of the present disclosure includes the method of the twenty-ninth aspect, wherein the coating layer includes a transmission of greater than <NUM>% per mm of material depth of the wavelength λ of the pulsed laser beam focal line.

According to a thirty-first aspect of the present disclosure, a method of separating a coated substrate includes directing an infrared laser beam onto a first surface of the coated substrate. The coated substrate includes a coating layer disposed on a transparent workpiece, a plurality of defects is disposed within the coated substrate, extending into both the coating layer and the transparent workpiece and disposed along a contour line that divides a primary region of the coated substrate from a dummy region of the coated substrate, and the infrared laser beam projects an infrared beam spot onto the first surface of the coated substrate. The infrared beam spot comprises includes annular shape. The method also includes translating at least one of the coated substrate and the infrared laser beam relative to each other such that the infrared beam spot follows an offset line, wherein the offset line is disposed on the dummy region of the coated substrate and is offset from the contour line such that the infrared beam spot is projected onto the dummy region and the infrared laser beam applies thermal energy to the coated substrate thereby inducing separation of the coated substrate along the contour line.

A thirty-second aspect of the present disclosure includes the method of the thirty-first aspect, wherein when following the offset line, the infrared beam spot applies thermal energy to the dummy region of the coated substrate without melting or ablating the coating layer of the primary region of the coated substrate.

A thirty-third aspect of the present disclosure includes the method of the thirty-first aspect or the thirty-second aspect, wherein at least one of the coated substrate and the infrared laser beam are translated relative to each other such that the infrared beam spot traces an oscillating pathway that follows the offset line in a translation direction and oscillates between an inner track line and an outer track line and the oscillating pathway is disposed on the dummy region of the coated substrate.

A thirty-fourth aspect of the present disclosure includes the method of any of the thirty-first through thirty-third aspects, wherein the infrared laser beam traverses an aspheric optical element before irradiating the coated substrate.

A thirty-fifth aspect of the present disclosure includes the method of any of the thirty-first through thirty-fourth aspects, wherein the infrared laser beam traverses a focusing lens before irradiating the coated substrate, the focusing lens comprises a focal plane at a focal length from the focusing lens, and the first surface of the coated substrate is positioned relative to the focusing lens such that the focal plane is offset from the first surface of the coated substrate.

A thirty-sixth aspect of the present disclosure includes the method of any of the thirty-first through thirty-fifth aspects, wherein the infrared laser beam comprises a pulsed infrared laser beam and when translating at least one of the coated substrate and the pulsed infrared laser beam relative to each other, the pulsed infrared laser beam impinges the first surface of the coated substrate at impingement locations along the offset line spaced apart a distance of from ¼ a diameter of the infrared beam spot to ½ the diameter of the infrared beam spot.

A thirty-seventh aspect of the present disclosure includes the method of any of the thirty-first through thirty-sixth aspects, further including forming the plurality of defects in the coated substrate prior to directing the infrared laser beam onto the first surface the coated substrate by directing a pulsed laser beam into the coated substrate. The pulsed laser beam forms a pulsed laser beam focal line extending into the coating layer and the transparent workpiece, the pulsed laser beam focal line inducing absorption in the coating layer and the transparent workpiece, the induced absorption producing an individual defect in the coated substrate. The pulsed laser beam focal line includes a wavelength λ, a spot size wo, and a Rayleigh range ZR that is greater than <MAT>, where FD is a dimensionless divergence factor has a value of <NUM> or greater. The method further includes translating at least one of the coated substrate and the pulsed laser beam relative to each other along the contour line to form the plurality of defects in the coating layer.

A thirty-eighth aspect of the present disclosure includes the method of the thirty-seventh aspect, wherein the coating layer includes a transmission of greater than <NUM>% per mm of material depth of the wavelength λ of the pulsed laser beam focal line.

Additional features and advantages of the processes and systems described herein 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 embodiments described herein, including the detailed description which follows, the claims, as well as the appended drawings.

Reference will now be made in detail to embodiments of separating a substrate, such as a coated substrate comprising a transparent workpiece and a coating layer. The coated substrate includes a primary region and a dummy region. The primary region is a portion of the coated substrate that is to be used as a resultant product, such as a screen or other substrate in a consumer electronics product, and the dummy region is a scrap region. Because the primary region is to be used as a product, it is desirable to separate the primary region from the dummy region while limiting or preventing damage to the primary region. The methods described herein include using a pulsed laser beam to form a series of defects in the coated substrate and an infrared laser beam to separate the transparent workpiece and the coating layer along the series of defects, which are formed along a boundary between the primary region and the dummy region.

In particular, the methods described herein direct thermal energy onto the dummy region of the coated substrate using techniques sufficient to both induce separation of the defects disposed in the coated substrate along the boundary between the primary region and the dummy region in a single process step. One method described herein includes translating an infrared laser beam along an oscillating pathway on the dummy region. Another method described herein includes modifying the energy distribution of an infrared laser beam into a top hat energy distribution and directing this modified laser beam onto the dummy region. Yet another method described herein includes forming the infrared laser beam into an annular shape and directing this annular infrared laser beam onto the dummy region. While the methods and systems are primarily described herein with respect to a coated substrate comprising a transparent workpiece and a coating layer, it should be understood that these methods and systems are also applicable to the separation of single substrates, such as uncoated transparent workpieces, which may benefit from the decrease in chipping and heat cracks and thus a higher release speed. Various embodiments of separating a coated substrate using laser processing techniques will be described herein with specific reference to the appended drawings. Whenever possible, the same reference numerals will be used throughout the drawings to refer to the same or like parts.

As used herein, "laser processing" comprises directing a laser beam onto and/or into a substrate, such as a coated substrate comprising a transparent workpiece with a coating layer. In some embodiments, laser processing further comprises translating the laser beam relative to the coated substrate, for example, along a contour line or other pathway. Examples of laser processing include using a laser beam to form a contour comprising a series of defects that extend into the transparent workpiece and using an infrared laser beam to heat both the transparent workpiece and the coating layer. Laser processing may separate the coated substrate along one or more desired lines of separation.

As used herein, "beam spot" refers to a cross section of a laser beam (e.g., a beam cross section) at the impingement location of the laser beam at an impingement surface of a substrate (e.g., the coated substrate). The impingement surface is the surface of a coated substrate upon which the laser beam is first incident. The beam spot is the cross-section at the impingement location. In the embodiments described herein, the beam spot is sometimes referred to as being "axisymmetric" or "non-axisymmetric. " As used herein, axisymmetric refers to a shape that is symmetric, or appears the same, for any arbitrary rotation angle made about a central axis, and "non-axisymmetric" refers to a shape that is not symmetric for any arbitrary rotation angle made about a central axis. The rotation axis (e.g., the central axis) is most often taken as being the optical axis (axis of propagation) of the laser beam, which is the axis extending in the beam propagation direction, which is referred to herein as the z-direction.

As used herein, "upstream" and "downstream" refer to the relative position of two locations or components along a beam pathway with respect to a beam source. For example, a first component is upstream from a second component if the first component is closer to the beam source along the path traversed by the laser beam than the second component.

As used herein, "pulsed laser beam focal line," refers to a pattern of interacting (e.g., crossing) light rays of a pulsed laser beam that forms a focal region elongated in the beam propagation direction. In conventional laser processing, a pulsed laser beam is tightly focused to a focal point. The focal point is the point of maximum intensity of the pulsed laser beam and is situated at a focal plane in a substrate, such as the transparent workpiece. In the elongated focal region of a pulsed laser beam focal line, in contrast, the region of maximum intensity of the pulsed laser beam extends beyond a point to a line aligned with the beam propagation direction. A pulsed laser beam focal line is formed by converging light rays of a pulsed laser beam that intersect (e.g., cross) to form a continuous series of focal points aligned with the beam propagation direction. The pulsed laser beam focal lines described herein are formed using a quasi-non-diffracting beam, mathematically defined in detail below.

As used herein, "contour line," corresponds to the set of intersection points of the laser beam with the incident surface of a substrate (e.g., the coated substrate) resulting from relative motion of the laser beam and the substrate. A contour line can be a linear, angled, polygonal or curved in shape. A contour line can be closed (i.e. defining an enclosed region on the surface of the substrate) or open (i.e. not defining an enclosed region on the surface of the substrate). The contour line represents a boundary along which separation of the substrate into two or more parts is facilitated. For example, in the embodiments described herein, the contour line represents a boundary between a dummy region of the coated substrate and a primary region of the coated substrate.

As used herein, "contour," refers to a set of defects in a substrate (e.g., in the transparent workpiece of the coated substrate) formed by a laser beam through relative motion of a laser beam and the substrate along a contour line. The defects are spaced apart along the contour line and are wholly contained within the interior of the substrate or extend through one or more surfaces into the interior of the substrate. Defects may also extend through the entire thickness of the substrate. Separation of the substrate (e.g., the transparent workpiece) occurs by connecting defects, such as, for example, through propagation of a crack.

As used herein, a "defect" refers to a region of a transparent workpiece that has been modified by a laser beam. Defects include regions of a transparent workpiece having a modified refractive index relative to surrounding unmodified regions of the transparent workpiece. Common defects include structurally modified regions such as void spaces, cracks, scratches, flaws, holes, perforations, densifications, or other deformities in the transparent workpiece produced by a pulsed laser beam focal line. Defects may also be referred to, in various embodiments herein, as defect lines or damage tracks. A defect or damage track is formed through interaction of a pulsed laser beam focal line with the transparent workpiece. As described more fully below, the pulsed laser beam focal line is produced by a pulsed laser. A defect at a particular location along the contour line is formed from a pulsed laser beam focal line produced by a single laser pulse at the particular location, a pulse burst of sub-pulses at the particular location, or multiple laser pulses at the particular location. Relative motion of the laser beam and transparent workpiece along the contour line results in multiple defects that form a contour.

The phrase "transparent workpiece," as used herein, means a workpiece formed from glass, glass-ceramic or other material which is transparent, where the term "transparent," as used herein, means that the material has a linear optical absorption of less than <NUM>% per mm of material depth, such as less than <NUM>% per mm of material depth for the specified pulsed laser wavelength, or such as less than <NUM>% per mm of material depth for the specified pulsed laser wavelength. Unless otherwise specified, the material has a linear optical absorption of less than about <NUM>% per mm of material depth. The transparent workpiece may have a depth (e.g., thickness) of from about <NUM> microns (µm) to about <NUM> (such as from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>). Transparent workpieces may comprise glass workpieces formed from glass compositions, such as borosilicate glass, soda-lime glass, aluminosilicate glass, alkali aluminosilicate, alkaline earth aluminosilicate glass, alkaline earth boro-aluminosilicate glass, fused silica, or crystalline materials such as sapphire, silicon, gallium arsenide, or combinations thereof. In some embodiments, the glass may be ion-exchangeable, such that the glass composition can undergo ion-exchange for glass strengthening before or after laser processing the transparent workpiece. For example, the transparent workpiece may comprise ion exchanged and ion exchangeable glass, such as Corning® Gorilla® Glass available from Corning Incorporated of Corning, NY (e.g., code <NUM>, code <NUM>, and code <NUM>). Further, these ion-exchanged glasses may have coefficients of thermal expansion (CTE) of from about <NUM> ppm/°C to about <NUM> ppm/°C. Other example transparent workpieces may comprise EAGLE XG® and CORNING LOTUS™ glass available from Corning Incorporated of Corning, NY. Moreover, the transparent workpiece may comprise other components, which are transparent to the wavelength of the laser, for example, glass ceramics or crystals such as sapphire or zinc selenide. Furthermore, in the embodiments described herein, a coating layer is disposed on the transparent workpiece forming a coated substrate.

In an ion exchange process, ions in a surface layer of the transparent workpiece are replaced by larger ions having the same valence or oxidation state, for example, by partially or fully submerging the transparent workpiece in an ion exchange bath. Replacing smaller ions with larger ions causes a layer of compressive stress to extend from one or more surfaces of the transparent workpiece to a certain depth within the transparent workpiece, referred to as the depth of layer. The compressive stresses are balanced by a layer of tensile stresses (referred to as central tension) such that the net stress in the glass sheet is zero. The formation of compressive stresses at the surface of the glass sheet makes the glass strong and resistant to mechanical damage and, as such, mitigates catastrophic failure of the glass sheet for flaws, which do not extend through the depth of layer. In some embodiments, smaller sodium ions in the surface layer of the transparent workpiece are exchanged with larger potassium ions. In some embodiments, the ions in the surface layer and the larger ions are monovalent alkali metal cations, such as Li+ (when present in the glass), Na+, K+, Rb+, and Cs+. Alternatively, monovalent cations in the surface layer may be replaced with monovalent cations other than alkali metal cations, such as Ag+, Tl+, Cu+, or the like.

As used herein, the term "quasi-non-diffracting beam" is used to describe a laser beam having low beam divergence as mathematically described below. In particular, the laser beam used to form a contour of defects in the embodiments described herein. The laser beam has an intensity distribution I(X,Y,Z), where Z is the beam propagation direction of the laser beam, and X and Y are directions orthogonal to the beam propagation direction, as depicted in the figures. The X-direction and Y-direction may also be referred to as cross-sectional directions and the X-Y plane may be referred to as a cross-sectional plane. The coordinates and directions X, Y, and Z are also referred to herein as x, y, and z; respectively. The intensity distribution of the laser beam in a cross-sectional plane may be referred to as a cross-sectional intensity distribution.

The quasi-non-diffracting laser beam may be formed by impinging a diffracting laser beam (such as a Gaussian beam) into, onto, and/or thorough a phase-altering optical element, such as an adaptive phase-altering optical element (e.g., a spatial light modulator, an adaptive phase plate, a deformable mirror, or the like), a static phase-altering optical element (e.g., a static phase plate, an aspheric optical element, such as an axicon, or the like), to modify the phase of the beam, to reduce beam divergence, and to increase Rayleigh range, as mathematically defined below. Example quasi-non-diffracting beams include Gauss-Bessel beams, Airy beams, Weber beams, and Bessel beams.

Referring to <FIG> and <FIG> and <FIG>, the pulsed laser beam <NUM> used to form the defects further has an intensity distribution I(X,Y,Z), where Z is the beam propagation direction of the pulsed laser beam <NUM>, and X and Y are directions orthogonal to the direction of propagation, as depicted in the figures. The X-direction and Y-direction may also be referred to as cross-sectional directions and the X-Y plane may be referred to as a cross-sectional plane. The intensity distribution of the pulsed laser beam <NUM> in a cross-sectional plane may be referred to as a cross-sectional intensity distribution.

The pulsed laser beam <NUM> at the beam spot <NUM> or other cross sections may comprise a quasi-non-diffracting beam, for example, a beam having low beam divergence as mathematically defined below, by propagating the pulsed laser beam <NUM> (e.g., outputting the pulsed laser beam <NUM>, such as a Gaussian beam, using a beam source <NUM>) through an aspheric optical element <NUM>, as described in more detail below with respect to the optical assembly <NUM> depicted in <FIG>. Beam divergence refers to the rate of enlargement of the beam cross section in the direction of beam propagation (i.e., the Z direction). As used herein, the phrase "beam cross section" refers to the cross section of the pulsed laser beam <NUM> along a plane perpendicular to the beam propagation direction of the pulsed laser beam <NUM>, for example, along the X-Y plane. One example beam cross section discussed herein is the beam spot <NUM> of the pulsed laser beam <NUM> projected onto the coated substrate <NUM>.

The length of the pulsed laser beam focal line produced from a quasi-non-diffracting beam is determined by the Rayleigh range of the quasi-non-diffracting beam. Particularly, the quasi-non-diffracting beam defines a pulsed laser beam focal line <NUM> having a first end point and a second end point each defined by locations where the quasi-non-diffracting beam has propagated a distance from the beam waist equal to a Rayleigh range of the quasi-non-diffracting beam. The length of the laser beam focal line corresponds to twice the Rayleigh range of the quasi-non-diffracting beam. A detailed description of the formation of quasi-non-diffracting beams and determining their length, including a generalization of the description of such beams to asymmetric (such as non-axisymmetric) beam cross sectional profiles, is provided in <CIT> and <CIT>, which are incorporated by reference in their entireties.

The Rayleigh range corresponds to the distance (relative to the position of the beam waist as defined in Section <NUM> of ISO <NUM>-<NUM>:<NUM>(E)) over which the variance of the laser beam doubles (relative to the variance at the position of the beam waist) and is a measure of the divergence of the cross sectional area of the laser beam. The Rayleigh range can also be observed as the distance along the beam axis at which the peak optical intensity observed in a cross sectional profile of the beam decays to one half of its value observed in a cross sectional profile of the beam at the beam waist location (location of maximum intensity). Laser beams with large Rayleigh ranges have low divergence and expand more slowly with distance in the beam propagation direction than laser beams with small Rayleigh ranges.

Beam cross section is characterized by shape and dimensions. The dimensions of the beam cross section are characterized by a spot size of the beam. For a Gaussian beam, spot size is frequently defined as the radial extent at which the intensity of the beam decreases to <NUM>/e<NUM> of its maximum value. The maximum intensity of a Gaussian beam occurs at the center (x = <NUM> and y = <NUM> (Cartesian) or r = <NUM> (cylindrical)) of the intensity distribution and radial extent used to determine spot size is measured relative to the center.

Beams with Gaussian intensity profiles may be less preferred for laser processing to form a contour of defects because, when focused to small enough spot sizes (such as spot sizes in the range of microns, such as about <NUM>-<NUM> or about <NUM>-<NUM>) to enable available laser pulse energies to modify materials such as glass, they are highly diffracting and diverge significantly over short propagation distances (low Rayleigh range). To achieve low divergence (high Rayleigh range), it is desirable to control or optimize the intensity distribution of the pulsed laser beam to reduce diffraction. Pulsed laser beams may be non-diffracting or weakly diffracting. Weakly diffracting laser beams include quasi-non-diffracting laser beams. Representative weakly diffracting laser beams include Bessel beams, Gauss-Bessel beams, Airy beams, Weber beams, and Mathieu beams.

Non-diffracting or quasi-non-diffracting beams generally have complicated intensity profiles, such as those that decrease non-monotonically vs. radius. By analogy to a Gaussian beam, an effective spot size wo,eff can be defined for any beam, even non-axisymmetric beams, as the shortest radial distance, in any direction, from the radial position of the maximum intensity (r = <NUM>) at which the intensity decreases to <NUM>/e<NUM> of the maximum intensity. Further, for axisymmetric beams wo,eff is the radial distance from the radial position of the maximum intensity (r = <NUM>) at which the intensity decreases to <NUM>/e<NUM> of the maximum intensity. A criterion for Rayleigh range ZR based on the effective spot size wo,eff for axisymmetric beams can be specified as non-diffracting or quasi-non-diffracting beams for forming damage regions in Equation (<NUM>), below: where FD is a dimensionless divergence factor having a value of at least <NUM>, in an embodiment at least <NUM>, in an embodiment at least <NUM>, in an embodiment at least <NUM>, in particular at least <NUM> and in another embodiment at least <NUM>. In a further embodiment FD can be in the range from <NUM> to <NUM>, in particular in the range from <NUM> to <NUM> and furthermore in particular in the range from <NUM> to <NUM>. For a non-diffracting or quasi-non-diffracting beam the distance (Rayleigh range), ZR in Equation (<NUM>), over which the effective spot size doubles, is FD times the distance expected if a typical Gaussian beam profile were used. The dimensionless divergence factor FD provides a criterion for determining whether or not a laser beam is quasi-non-diffracting. As used herein, the pulsed laser beam <NUM> is considered quasi-non-diffracting if the characteristics of the laser beam satisfy Equation (<NUM>) with a value of FD ≥ <NUM>. As the value of FD increases, the pulsed laser beam <NUM> approaches a more nearly perfectly non-diffracting state. Thus, as the value of FD increases, the length of the laser beam focal line increases, facilitating the formation of longer defects.

Additional information about Rayleigh range, beam divergence, intensity distribution, axisymmetric and non-axisymmetric beams, and spot size as used herein can also be found in the international standards ISO <NUM>-<NUM>:<NUM>(E) entitled "Lasers and laser-related equipment-Test methods for laser beam widths, divergence angles and beam propagation ratios-Part <NUM>: Stigmatic and simple astigmatic beams", ISO <NUM>-<NUM>:<NUM>(E) entitled "Lasers and laser-related equipment-Test methods for laser beam widths, divergence angles and beam propagation ratios-Part <NUM>: General astigmatic beams", and ISO <NUM>-<NUM>:<NUM>(E) entitled "Lasers and laser-related equipment - Test methods for laser beam widths, divergence angles and beam propagation ratios - Part <NUM>: Intrinsic and geometrical laser beam classification, propagation and details of test methods".

Referring now to <FIG> and <FIG>, a coated substrate <NUM> comprising a transparent workpiece <NUM> and a coating layer <NUM> disposed on the transparent workpiece <NUM> is schematically depicted undergoing laser processing according to the methods described herein. In particular, <FIG> and <FIG> schematically depict directing a pulsed laser beam <NUM> that is output by a pulsed beam source <NUM>, such as a Gaussian pulsed beam source, and oriented along a beam pathway <NUM> into the coated substrate <NUM> to form a defect <NUM> in the coated substrate <NUM>, for example, extending into both the coating layer <NUM> and the transparent workpiece <NUM>. The pulsed laser beam <NUM> propagates along the beam pathway <NUM> and is oriented such that the pulsed laser beam <NUM> may be focused into a pulsed laser beam focal line <NUM> within the coated substrate <NUM>, for example, using an aspheric optical element <NUM> and one or more lenses (<FIG>). The pulsed laser beam focal line <NUM> generates an induced absorption within the transparent workpiece <NUM> and, in some embodiments, the coating layer <NUM>, to produce the defect <NUM> within the coated substrate <NUM> that may extend into both the coating layer <NUM> and the transparent workpiece <NUM>. Furthermore, a contour <NUM> of defects <NUM> may be formed in the coated substrate <NUM> by translating at least one of the pulsed laser beam <NUM> and the coated substrate <NUM> relative to one another such that the pulsed laser beam <NUM> translates relative to the coated substrate <NUM> in a translation direction <NUM>.

As also shown in <FIG>, the pulsed laser beam <NUM> forms a beam spot <NUM> projected onto a first surface <NUM> of the coated substrate <NUM>. In <FIG>, the first surface <NUM> is a surface of the coating layer <NUM>. The coating layer <NUM> may comprise any material comprising a transmission of greater than <NUM>% per mm of material depth of the wavelength λ of the pulsed laser beam <NUM>. Without intending to be limited by theory, transmission losses are due to scattering or absorption and minimizing transmission losses minimizes disruption of the formation of the pulsed laser beam focal line <NUM> in the coating layer <NUM> and the transparent workpiece <NUM>. In some embodiments, the transmission is greater than <NUM>% per mm of material depth, such as greater than <NUM>% per mm of material depth. In addition, material of the coating layer <NUM> has a homogenous phase alteration (e.g., a phase alteration caused by refractive index). Without intending to be limited by theory, any step in phase alteration will result in a loss of focus on a one digit µm scale. Indeed, inhomogeneous alteration of the phase or direction of the light causes scattering, which reduces transmission. While the coating layer <NUM> may comprise any material having a transmission of greater than <NUM>% per mm of material depth of the wavelength λ of the pulsed laser beam <NUM>, example materials include a metal oxide and a polymer.

Referring also to <FIG>, the pulsed laser beam <NUM> may be focused into the pulsed laser beam focal line <NUM> using a lens <NUM>, which is the final focusing element in an optical assembly <NUM>. While a single lens <NUM> is depicted in <FIG> and <FIG>, the optical assembly <NUM> further comprises an aspheric optical element <NUM>, which modifies the pulsed laser beam <NUM> such that the pulsed laser beam <NUM> has a quasi-non-diffracting character downstream the aspheric optical element <NUM>. Thus, when the portion of the pulsed laser beam <NUM> shown in <FIG> and <FIG> impinges the lens <NUM>, the pulsed laser beam <NUM> has a quasi-non-diffracting character. Furthermore, some embodiments may include a lens assembly <NUM> including, for example a first lens <NUM> and a second lens <NUM>, and repetitions thereof (<FIG>) to focus the pulsed laser beam <NUM> into the pulsed laser beam focal line <NUM>. Other standard optical elements (e.g. prisms, beam splitters etc.) may also be included in lens assembly <NUM>.

As depicted in <FIG>, the pulsed laser beam <NUM> may comprise an annular shape when impinging the lens <NUM>. While the lens <NUM> is depicted focusing the pulsed laser beam <NUM> into the pulsed laser beam focal line <NUM> in <FIG>, other embodiments may use the aspheric optical element <NUM> (<FIG>), which modifies the pulsed laser beam <NUM> such that the pulsed laser beam <NUM> has a quasi-non-diffracting character downstream the aspheric optical element <NUM>, to also focus the pulsed laser beam <NUM> into the pulsed laser beam focal line <NUM>. In other words, in some embodiments, the lens <NUM> may be the final focusing element and in other embodiments, the aspheric optical element <NUM> may be the final focusing element. The pulsed laser beam focal line <NUM> may have a length in a range of from about <NUM> to about <NUM> or in a range of from about <NUM> to about <NUM>. Various embodiments may be configured to have a pulsed laser beam focal line <NUM> with a length l of about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, or about <NUM> e.g., from about <NUM> to about <NUM>. The length of the pulsed laser beam focal line <NUM> may be selected based on the particular laser processing goals. As one example, for thicker coated substrates <NUM> it may be advantageous to form longer pulsed laser beam focal lines <NUM>. As another example, if defects <NUM> extending into only discrete depth sections of the coated substrate <NUM> is desired, it may be advantageous to form shorter pulsed laser beam focal lines <NUM>.

Referring now to <FIG>, the optical assembly <NUM> for producing a pulsed laser beam <NUM> that is quasi-non-diffracting and forms the pulsed laser beam focal line <NUM> at the coated substrate <NUM> inclusive of the coating layer <NUM> and transparent workpiece <NUM> using the aspheric optical element <NUM> (e.g., an axicon <NUM>) is schematically depicted. The optical assembly <NUM> includes a pulsed beam source <NUM> that outputs the pulsed laser beam <NUM>, and the lens assembly <NUM> comprising the first lens <NUM> and the second lens <NUM>. The coated substrate <NUM> may be positioned such that the pulsed laser beam <NUM> output by the pulsed beam source <NUM> irradiates the coating layer <NUM> and transparent workpiece <NUM>, for example, after traversing the aspheric optical element <NUM> and thereafter, both the first lens <NUM> and the second lens <NUM>.

The aspheric optical element <NUM> is positioned within the beam pathway <NUM> between the pulsed beam source <NUM> and the coated substrate <NUM>. In operation, propagating the pulsed laser beam <NUM>, e.g., an incoming Gaussian beam, through the aspheric optical element <NUM> may alter, for example, phase alter, the pulsed laser beam <NUM> such that the portion of the pulsed laser beam <NUM> propagating beyond the aspheric optical element <NUM> is quasi-non-diffracting, as described above. The aspheric optical element <NUM> may comprise any optical element comprising an aspherical shape. In some embodiments, the aspheric optical element <NUM> may comprise a conical wavefront producing optical element, such as an axicon lens, for example, a negative refractive axicon lens (e.g., negative axicon), a positive refractive axicon lens, a reflective axicon lens, a diffractive axicon lens, a phase axicon, a diffractive optic, a cubically shaped optical element, or the like.

While the optical assembly <NUM> is primarily described as altering the pulsed laser beam <NUM> into a quasi-non-diffracting beam using the aspheric optical element <NUM>, it should be understood that a quasi-non-diffracting beam also be formed by other phase-altering optical elements, such as a spatial light modulator, an adaptive phase plate, a static phase plate, a deformable mirror, diffractive optical grating, or the like. Each of these phase-altering optical elements, including the aspheric optical element <NUM>, modify the phase of the pulsed laser beam <NUM>, to reduce beam divergence, increase Rayleigh range, and form a quasi-non-diffracting beam as mathematically defined above.

Referring still to <FIG>, the lens assembly <NUM> comprises two lenses, with the first lens <NUM> positioned upstream the second lens <NUM>. The first lens <NUM> may collimate the pulsed laser beam <NUM> within a collimation space <NUM> between the first lens <NUM> and the second lens <NUM>. Further, the most downstream positioned second lens <NUM> of the lens assembly <NUM> may focus the pulsed laser beam <NUM> into the transparent workpiece <NUM>. In some embodiments, the first lens <NUM> and the second lens <NUM> each comprise plano-convex lenses. When the first lens <NUM> and the second lens <NUM> each comprise plano-convex lenses, the curvature of the first lens <NUM> and the second lens <NUM> may each be oriented toward the collimation space <NUM>. In other embodiments, the first lens <NUM> may comprise a collimating lens and the second lens <NUM> may comprise a meniscus lens, an asphere, or another higher-order corrected focusing lens. In operation, the lens assembly <NUM> may control the position of the pulsed laser beam focal line <NUM> along the beam pathway <NUM>. In further embodiments, the lens assembly <NUM> may comprise an 8F lens assembly, a 4F lens assembly comprising a single set of first and second lenses <NUM>, <NUM>, or any other known or yet to be developed lens assembly <NUM> for focusing the pulsed laser beam <NUM> into the pulsed laser beam focal line <NUM>. Moreover, it should be understood that some embodiments may not include the lens assembly <NUM> and instead, the aspheric optical element <NUM> may focus the pulsed laser beam <NUM> into the pulsed laser beam focal line <NUM>. For example, aspheric optical element <NUM> may both transform pulsed laser beam <NUM> into a quasi-non-diffracting laser beam and focus the quasi-non-diffracting laser beam into pulsed laser beam focal line <NUM>.

Referring again to <FIG>, the pulsed beam source <NUM> is configured to output pulsed laser beam <NUM>. In operation, the defects <NUM> of the contour <NUM> are produced by interaction of the transparent workpiece <NUM> with the pulsed laser beam <NUM> output by the pulsed beam source <NUM> as modified by the aspheric optical element <NUM> and/or lens assembly <NUM>. In operation, the pulsed laser beam <NUM> output by the pulsed beam source <NUM> may create multi-photon absorption (MPA) in the transparent workpiece <NUM>. MPA is the simultaneous absorption of two or more photons of identical or different frequencies that excites a molecule from one state (usually the ground state) to a higher energy electronic state (i.e., ionization). The energy difference between the involved lower and upper states of the molecule is equal to the sum of the energies of the involved photons. MPA, also called induced absorption, can be a second-order or third-order process (or higher order), for example, that is several orders of magnitude weaker than linear absorption. It differs from linear absorption in that the strength of second-order induced absorption may be proportional to the square of the light intensity, for example, and thus it is a nonlinear optical process.

In some embodiments, the pulsed beam source <NUM> may output a pulsed laser beam <NUM> comprising a wavelength of, for example, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM>, or <NUM>. Further, the pulsed laser beam <NUM> used to form defects <NUM> in the transparent workpiece <NUM> may be well suited for materials that are transparent to the selected pulsed laser wavelength. Suitable laser wavelengths for forming defects <NUM> are wavelengths at which the combined losses of linear absorption and scattering by the transparent workpiece <NUM> are sufficiently low. In embodiments, the combined losses due to linear absorption and scattering by the transparent workpiece <NUM> and the coating layer <NUM> at the laser wavelength are less than <NUM>%/mm, or less than <NUM>%/mm, or less than <NUM>%/mm, or less than <NUM>%/mm, or less than <NUM>%/mm, such as <NUM>%/mm to <NUM>%/mm, <NUM>%/mm to <NUM>%/mm, or <NUM>%/mm to <NUM>%/mm, for example, <NUM>%/mm, <NUM>%/mm, <NUM>%/mm, <NUM>%/mm, <NUM>%/mm, or any range having any two of these values as endpoints, or any open-ended range having any of these values as a lower bound. As used herein, the dimension "/mm" means per millimeter of distance within the transparent workpiece <NUM> in the beam propagation direction of the pulsed laser beam <NUM> (i.e., the Z direction). Representative laser wavelengths for many glass workpieces include fundamental and harmonic wavelengths of Nd<NUM>+ (e.g. Nd<NUM>+:YAG or Nd<NUM>+:YVO<NUM> having fundamental wavelength near <NUM> and higher order harmonic wavelengths near <NUM>, <NUM>, and <NUM>). Other laser wavelengths in the ultraviolet, visible, and infrared portions of the spectrum that satisfy the combined linear absorption and scattering loss requirement for a given substrate material can also be used.

Referring still to <FIG>, in operation, the contour <NUM> may be formed in the coated substrate <NUM> by irradiating a contour line <NUM> with the pulsed laser beam <NUM> and translating at least one of the pulsed laser beam <NUM> and the coated substrate <NUM> relative to each other along the contour line <NUM> in the translation direction <NUM> to form the defects <NUM> of the contour <NUM>. While the contour <NUM> depicted in <FIG> is linear, it should be understood that the contour <NUM> may be non-linear, for example, curved. Further, in some embodiments, the contour <NUM> may be a closed contour, such as a circle, rectangles, ellipses, squares, hexagons, ovals, regular geometric shapes, irregular shapes, polygonal shapes, arbitrary shapes, and the like. The contour line <NUM> represents a boundary between a primary region <NUM> and a dummy region <NUM> of the coated substrate <NUM>. The primary region <NUM> is the region of the coated substrate <NUM> that is to be used as a resultant product and the dummy region <NUM> is a scrap region.

Directing or localizing the pulsed laser beam <NUM> into the coated substrate <NUM> generates an induced absorption (e.g., MPA) within the coating layer <NUM>, the transparent workpiece <NUM>, or both (depending on whether the pulsed laser beam focal line <NUM> extends into the coating layer <NUM>, the transparent workpiece <NUM>, or both) deposits enough energy to break chemical bonds in the coating layer <NUM> and/or the transparent workpiece <NUM> at spaced locations along the contour line <NUM> to form the defects <NUM>. According to one or more embodiments, the pulsed laser beam <NUM> may be translated across the coated substrate <NUM> by motion of the coated substrate <NUM> (e.g., motion of a translation stage <NUM> coupled to the coated substrate <NUM>), motion of the pulsed laser beam <NUM> (e.g., motion of the pulsed laser beam focal line <NUM>), or motion of both the coated substrate <NUM> and the pulsed laser beam focal line <NUM>. By translating at least one of the pulsed laser beam focal line <NUM> relative to the coated substrate <NUM>, the plurality of defects <NUM> may be formed in the coated substrate <NUM>.

In some embodiments, the defects <NUM> may generally be spaced apart from one another by a distance along the contour <NUM> of from <NUM> to <NUM>, such as, <NUM> to <NUM>, <NUM> to <NUM>, or <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, or <NUM> to <NUM>, such as <NUM> or less, <NUM> or less, <NUM> or less, <NUM> or less, <NUM> or less, <NUM> or less, <NUM> or less, <NUM> or less, <NUM> or less, such as <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or any range having any two of these values as endpoints, or any open-ended range having any of these values as a lower bound. While not intending to be limited by theory, increasing the spacing distance between adjacent defects <NUM> may increase the processing speed (i.e., reducing processing time) and decreasing the spacing distance between adjacent defects <NUM> may reduce the break resistance of the contour <NUM> of defects <NUM>. Further, the translation of the coated substrate <NUM> relative to the pulsed laser beam <NUM> may be performed by moving the coated substrate <NUM> and/or the pulsed beam source <NUM> using one or more translation stages <NUM>.

Referring now to <FIG>, when the defects <NUM> of the one or more contours <NUM> are formed with pulse bursts <NUM> having at least two sub-pulses <NUM>, the force necessary to separate the coated substrate <NUM> along contour <NUM> (i.e. the break resistance) is reduced compared to the break resistance of a contour <NUM> of the same shape with the same spacing between adjacent defects <NUM> in an identical coated substrate <NUM> that is formed using a single pulse laser having the same energy as the combined energies of the sub-pulses of the pulse burst <NUM>. A pulse burst (such as pulse burst <NUM>) is a short and fast grouping of sub-pulses (i.e., a tight cluster of sub-pulses, such as sub-pulses <NUM>) that are emitted by the laser and interact with the material (i.e. MPA in the material of the coating layer <NUM> and/or the transparent workpiece <NUM>). The use of pulse bursts <NUM> (as opposed to a single pulse operation) increases the size (e.g., the cross-sectional size) of the defects <NUM>, which facilitates the connection of adjacent defects <NUM> when separating the coated substrate <NUM> along the contour <NUM>, thereby minimizing crack formation away from contour <NUM> in the separated sections of the coated substrate <NUM>.

Referring still to <FIG>, in some embodiments, pulses produced by the pulsed beam source <NUM> are produced in pulse bursts <NUM> of two sub-pulses <NUM> or more per pulse burst <NUM>, such as from <NUM> to <NUM> sub-pulses <NUM> per pulse burst <NUM> or from <NUM> to <NUM> sub-pulses <NUM> per pulse burst <NUM>. Furthermore, the energy required to modify the coating layer <NUM> and/or the transparent workpiece <NUM> is the pulse energy, which may be described in terms of pulse burst energy (i.e., the energy contained within a pulse burst <NUM> where each pulse burst <NUM> contains a series of sub-pulses <NUM>; that is, the pulse burst energy is the combined energy of all sub-pulses within the pulse burst). The pulse energy (for example, pulse burst energy) may be from <NUM>µJ to <NUM>µJ or <NUM>µJ to <NUM>µJ, such as from <NUM>µJ to <NUM>µJ, <NUM>µJ to <NUM>µJ, or from <NUM>µJ to <NUM>µJ, for example, <NUM>µJ, <NUM>µJ, <NUM>µJ, <NUM>µJ, <NUM>µJ, <NUM>µJ, <NUM>µJ, <NUM>µJ, <NUM>µJ, <NUM>µJ, <NUM>µJ, or any range having any two of these values as endpoints, or any open-ended range having any of these values as a lower bound.

Referring now to <FIG>, after forming the contour <NUM> of defects <NUM> along the contour line <NUM> in the coated substrate <NUM> using, for example, one of the embodiments according <FIG>, the coated substrate <NUM> may be further acted upon in a subsequent separating step to induce separation of the transparent workpiece <NUM> and the coating layer <NUM> along the contour line <NUM> (i.e., along the contour <NUM> of defects <NUM>). The subsequent separating step includes directing an infrared laser beam <NUM> onto the coated substrate <NUM> to apply a thermal stress to the coating layer <NUM> and the transparent workpiece <NUM>. The applied thermal stress induces separation that extends between adjacent defects <NUM> in the coated substrate <NUM> along the contour line <NUM>. In the transparent workpiece <NUM>, this separating may include propagation of a crack along the contour line <NUM>.

Without being bound by theory, the infrared laser beam <NUM> is a controlled heat source that rapidly increases the temperature of the coating layer <NUM> at or near the contour line <NUM>, modifying material of the coating layer <NUM> along or near the contour line <NUM> to induce separation of the material of the coating layer <NUM> extending between adjacent defects <NUM>. In addition, this rapid heating may build compressive stress in the transparent workpiece <NUM> on or adjacent to the contour <NUM>. Since the area of the heated surface of transparent workpiece <NUM> is relatively small and shallow when compared to the overall surface area of the transparent workpiece <NUM>, the heated area cools relatively rapidly. The resultant temperature gradient induces tensile stress in the transparent workpiece <NUM> sufficient to propagate a crack along the contour <NUM> and through the depth of the transparent workpiece <NUM>, resulting in full separation of the transparent workpiece <NUM> along the contour <NUM>. Without being bound by theory, it is believed that the tensile stress may be caused by expansion of the glass (i.e., changed density) in portions of the workpiece with higher local temperature induced by infrared laser beam <NUM>. By inducing separation of both the coating layer <NUM> and the transparent workpiece <NUM>, the infrared laser beam <NUM> induces separation of the coated substrate <NUM> along the contour line <NUM>.

<FIG> depicts an optical assembly <NUM> comprising an infrared beam source <NUM> configured to generate the infrared laser beam <NUM>. The infrared beam source <NUM>, which may comprise a carbon dioxide laser (a "CO<NUM> laser"), a carbon monoxide laser (a "CO laser"), a solid-state laser, a laser diode, or combinations thereof. The infrared laser beam <NUM> comprises a wavelength that is readily absorbed by the transparent workpiece <NUM>, for example, a wavelength ranging from <NUM> to <NUM>, such as, a range of <NUM> to <NUM>. The power of the infrared laser beam <NUM> may be from about <NUM> W to about <NUM> W, for example <NUM> W, <NUM> W, <NUM> W, <NUM> W, <NUM> W, or the like. Further, the infrared beam source <NUM> may comprises a continuous wave laser or a pulsed laser. The optical assembly <NUM> further comprises a lens assembly <NUM> that includes a lens <NUM> for focusing the infrared laser beam <NUM> onto the coated substrate <NUM>. In operation, the infrared laser beam <NUM> propagates along an infrared beam pathway <NUM> and is oriented such that the infrared laser beam <NUM> may be directed onto the coated substrate <NUM>, for example, focused onto the first surface <NUM> of the coated substrate <NUM> using the lens <NUM>.

Referring now to <FIG>, a cross section of the coated substrate <NUM> with a contour <NUM> of defects <NUM> during laser processing with the infrared laser beam <NUM> is schematically depicted. In <FIG>, the infrared laser beam <NUM> is directed onto the coated substrate <NUM> using the optical assembly <NUM> of <FIG> and comprises a Gaussian intensity profile at the coated substrate <NUM>. In addition, in <FIG>, the infrared laser beam <NUM> is directed onto the coated substrate <NUM> in alignment with the contour <NUM> of defects <NUM> and thus in alignment with the contour line <NUM>. Because the infrared laser beam <NUM> comprises a Gaussian energy distribution, interaction of the infrared laser beam <NUM> with the coated substrate <NUM> forms a thermal affected area <NUM> having a Gaussian shape. The thermal affected area <NUM> corresponds to the portions of coated substrate <NUM> that receive sufficient energy from the Gaussian energy distribution of infrared laser beam <NUM> to produce thermal stresses sufficient to induce separation of coated substrate <NUM> along the contour <NUM>. That is, the thermal affected area <NUM> comprises a portion of the coating layer <NUM> and a portion of the transparent workpiece <NUM> into which thermal energy sufficient to induce separation of the contour <NUM> of defects <NUM> is applied. However, when the infrared laser beam <NUM> is directed onto the coated substrate <NUM> in alignment with the contour <NUM> of defects <NUM>, as shown in <FIG>, the thermal affected area <NUM> is formed symmetrically in both the dummy region <NUM> and the primary region <NUM>, which damages the primary region <NUM>, for example, by causing some melt and ablation by melting or ablating the coating layer <NUM> on the primary region <NUM>. Indeed, <FIG> shows a top view of the coated substrate <NUM> of <FIG> with a series of defects <NUM> separated using the laser processing technique shown in <FIG>. As shown in <FIG>, the thermal affected areas <NUM> extend into the primary region <NUM>, showing that unwanted damage is generated in the primary region <NUM> using the technique of <FIG>. As noted above, the primary region <NUM> is the region of the coated substrate <NUM> that is to be used as a resultant product and thus any damage to the primary region <NUM> is undesired. In contrast, the dummy region <NUM> is a scrap region.

Referring now to <FIG>, one potential solution to preventing damage to the primary region <NUM> is to offset the infrared laser beam <NUM> from the defects <NUM> and direct the infrared laser beam <NUM> predominately onto the dummy region <NUM> of the coated substrate <NUM> offset from the contour <NUM> of defects <NUM> and away from the primary region <NUM>. In <FIG>, the infrared laser beam <NUM> is directed onto the coated substrate <NUM> using the optical assembly <NUM> of <FIG> and comprises a Gaussian intensity profile at the coated substrate <NUM>. Directing the infrared laser beam <NUM> onto the dummy region <NUM> away from the primary region <NUM> modifies the coating layer <NUM> on the dummy region <NUM> adjacent and along the contour <NUM> of defects <NUM> without ablation, melting, colorization, surface alteration and/ or change in conductivity, of the coating layer <NUM> on the primary region <NUM>. That is, placement of infrared laser beam <NUM> away from contour <NUM> into dummy region <NUM> reduces the thermal energy from the Gaussian energy distribution of infrared laser beam <NUM> transferred to the portion of coating layer <NUM> in primary region <NUM> to a degree sufficient to avoid damage. However, because the infrared laser beam <NUM> comprises a Gaussian intensity profile at the coated substrate <NUM>, positioning the infrared laser beam <NUM> far enough offset from the contour <NUM> of defects <NUM> to prevent damage to the primary region <NUM> may fail to induce separation of the materials of the coated substrate <NUM> between adjacent defects <NUM> since it reduce the resultant temperature gradient in proximity to the defects <NUM>. For example, positioning the infrared laser beam <NUM> far enough offset from the contour <NUM> of defects <NUM> to prevent damage to the primary region <NUM> may fail to induce tensile stress in the transparent workpiece <NUM> sufficient to propagate a crack along the contour <NUM> and through the depth of the transparent workpiece <NUM>, since it reduces the resultant temperature gradient in proximity to the defects <NUM>. Thus, alternative techniques for separating the coated substrate <NUM> (i.e., separating the primary region <NUM> from the dummy region <NUM>) while minimizing or preventing damage to the primary region <NUM> are desired.

Referring still to <FIG>, one technique to separate the coated substrate <NUM> while minimizing damage to the primary region <NUM> is to translate the infrared laser beam <NUM> offset from the contour line <NUM> along multiple passes, where each individual pass does not apply enough thermal energy to damage the primary region <NUM>. While a single pass may not be sufficient to separate the contour <NUM> of defects <NUM>, particularly the portions of the contour <NUM> of defects <NUM> that extend into the transparent workpiece <NUM>, thermal energy accumulates in the transparent workpiece <NUM> upon multiple passes, inducing separation the coated substrate <NUM> along contour <NUM> of defects <NUM> without damaging primary region <NUM>. Further, each pass may follow the same path or offset paths, each located along the dummy region <NUM>.

Referring now to <FIG>, additional techniques to generate sufficient thermal stress to induce separation of the series of defects <NUM> of the coated substrate <NUM> along the contour line <NUM> while limiting or preventing damage to the primary region <NUM> of the coated substrate <NUM> will now be described. In particular, <FIG> depict a method of laser processing the coated substrate <NUM> along an oscillating pathway <NUM> using the infrared laser beam <NUM> of <FIG> having a Gaussian intensity profile, <FIG> depict methods of laser processing the coated substrate <NUM> using an infrared laser beam <NUM>' having a modified energy distribution, and <FIG> and <FIG> depict a method of laser processing the coated substrate <NUM> using an infrared laser beam <NUM>" formed into an annulus and directed onto the first surface <NUM> of the coated substrate <NUM> offset from a focal plane <NUM> of a final focusing element. Each of these techniques induce separation of the contour <NUM> of defects <NUM> in the coated substrate <NUM> in a single pass while limiting or preventing damage to the primary region <NUM> of the coated substrate <NUM>. Indeed, the techniques described herein reduce tact time, reduce debris generated during the process, and reduce the complexity of the optical system. Furthermore, while these techniques are primarily described herein with respect to the coated substrate <NUM> comprising the transparent workpiece <NUM> and the coating layer <NUM>, it should be understood that these techniques are also applicable to the separation of single substrates, such as uncoated transparent workpieces, which may benefit from the decrease in chipping and heat cracks and thus a higher release speed.

Referring now to <FIG>, a schematic top view of the coated substrate <NUM> comprising a plurality of defects <NUM> positioned along the contour line <NUM> undergoing a separating step using the infrared laser beam <NUM> is depicted. In the method depicted in <FIG>, the infrared laser beam <NUM> follows the oscillating pathway <NUM>. In particular, at least one of the coated substrate <NUM> and the infrared laser beam <NUM> are translated relative to each other such that an infrared beam spot <NUM> traces the oscillating pathway <NUM>. The infrared beam spot <NUM> is projected by the infrared laser beam <NUM> on the first surface <NUM> of the coated substrate <NUM>. The oscillating pathway <NUM> is disposed on the dummy region <NUM> such that infrared laser beam <NUM> generates minimal to no damage on the primary region <NUM>. Similar to the embodiment of <FIG>, above, the infrared laser beam <NUM> comprises a Gaussian energy distribution; however, the oscillating pathway <NUM> facilitates the application of enough thermal energy to the dummy region <NUM> of the coated substrate <NUM> to induce separation of the coated substrate <NUM> along the contour line <NUM> while avoiding damage to primary region <NUM>. Traversal of infrared laser beam <NUM> along the oscillating pathway <NUM> provides a mechanism to control the amount of thermal energy transferred to primary region <NUM>. As infrared laser beam <NUM> moves closer to contour line <NUM>, more thermal energy is transferred to the vicinity of defects <NUM> and thermal energy sufficient to induce separation of transparent workpiece <NUM> is available. To prevent damage to the coating layer <NUM> in primary region <NUM>, the motion of infrared laser beam <NUM> is reversed and moved away from contour line <NUM> to prevent excess transfer of thermal energy to primary region <NUM>. By controlling the power of infrared laser beam <NUM>, the speed of traversal of infrared laser beam <NUM> along oscillating pathway <NUM> and the proximity of closest approach of infrared laser beam <NUM> to contour line <NUM>, as well as the number of times the infrared laser beam <NUM> reaches the distance of closest approach to the contour line <NUM>, transfer of thermal energy is controlled and separation of primary region <NUM> from dummy region <NUM> without damage to the coating layer <NUM> in primary region <NUM> is achievable.

As depicted in <FIG>, the oscillating pathway <NUM> follows an offset line <NUM> in a translation direction while oscillating between an inner track line <NUM> and an outer track line <NUM>. In the embodiments depicted in <FIG>, each oscillation extends from one of the inner track line <NUM> or the outer track line <NUM> to the other. However, it should be understood that, in some embodiments, the oscillating pathway <NUM> may oscillate between the inner track line <NUM> and the outer track line <NUM> without reaching the inner track line <NUM>, the outer track line <NUM>, or both, during some or all of the oscillations. Each of the offset line <NUM>, the inner track line <NUM>, and the outer track line <NUM> are disposed on the dummy region <NUM> of the coated substrate <NUM>. In particular, each of the offset line <NUM>, the inner track line <NUM> and the outer track line <NUM> are parallel pathways on the dummy region <NUM> of the coated substrate <NUM> and are each parallel to the contour line <NUM>. For example, in the embodiment depicted in <FIG>, the contour line <NUM> is linear along the Y axis and the transverse axis is the X axis. However, it should be understood that the contour line <NUM> and the offset line <NUM> may be curved or otherwise non-linear and thus the transverse axis may change at points along the offset line <NUM> to retain orthogonality with the offset line <NUM>.

The offset line <NUM> may be spaced a distance of <NUM> to <NUM> from the contour line <NUM>, such as from <NUM> to <NUM> from the contour line <NUM>, for example, the offset line <NUM> may be spaced from the contour line <NUM> by a distance of <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or any range having any two of these values as endpoints. The inner track line <NUM> may be spaced a distance of <NUM> to <NUM> from the contour line <NUM>, such as a distance of from <NUM> to <NUM> from the contour line <NUM>, for example, the inner track line <NUM> may be spaced from the contour line <NUM> by a distance of <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or any range having any two of these values as endpoints. The outer track line <NUM> may be spaced a distance of <NUM> to <NUM> from the contour line <NUM>, such as a distance of from <NUM> to <NUM> from the contour line <NUM>, for example, the outer track line <NUM> may be spaced from the contour line <NUM> by a distance of <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or any range having any two of these values as endpoints. Furthermore, the offset line <NUM> may be equally spaced from both the inner track line <NUM> and the outer track line <NUM>. In addition, the spacing distance between the offset line <NUM> and each of the inner track line <NUM> and the outer track line <NUM> may be the same as the distance between the inner track line <NUM> and the contour line <NUM>.

Furthermore, the spacing distances between the contour line <NUM>, the offset line <NUM>, the inner track line <NUM>, and the outer track line <NUM> may be a function of the <NUM>/e<NUM> beam diameter of the infrared beam spot <NUM>. For example, the spacing distances between the contour line <NUM>, the offset line <NUM>, the inner track line <NUM>, and the outer track line <NUM> may be at least half the <NUM>/e<NUM> beam diameter of the infrared beam spot <NUM>. The <NUM>/e<NUM> beam diameter of the infrared beam spot <NUM> is in a range of from <NUM> to <NUM>, such as from <NUM> to <NUM>, or from <NUM> to <NUM>, for example, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or any range having any two of these values as endpoints. In operation, a <NUM>/e<NUM> beam diameter of the infrared beam spot <NUM> in the above ranges may facilitate high precision application of thermal energy to the coated substrate <NUM> and allows the infrared beam spot <NUM> to oscillate along the oscillating pathway <NUM> without impinging the primary region <NUM>.

In operation, as the infrared laser beam <NUM> is translated such that the infrared beam spot <NUM> traces the oscillating pathway <NUM>, the infrared laser beam <NUM> applies thermal energy to the coated substrate <NUM> to induce separation of the series of defects <NUM> of the coated substrate <NUM> along the contour line <NUM> while limiting or preventing damage to the primary region <NUM> of the coated substrate <NUM>. For example, as depicted in <FIG>, a scanner <NUM> is coupled to the infrared beam source <NUM> and is configured to translate the infrared beam source <NUM> and infrared laser beam <NUM> such that the infrared beam spot <NUM> traces the oscillating pathway <NUM>. In particular, the scanner <NUM> may both oscillate the infrared laser beam <NUM> while linearly translating the infrared laser beam <NUM>. The speed of motion of infrared laser beam <NUM> is preferably greater than or equal to <NUM>/s, such as between <NUM>/s and <NUM>/s, or between <NUM>/s and <NUM>/s, or between <NUM>/s and <NUM>/s, or between <NUM>/s and <NUM>/s, or between <NUM>/s and <NUM>/s, or between <NUM>/s and <NUM>/s.

Furthermore, each of <FIG> depict different embodiments of the oscillating pathway <NUM>. For example, <FIG> depicts an embodiment of the oscillating pathway <NUM> that is a pendulum pathway <NUM>, <FIG> depicts an embodiment of the oscillating pathway <NUM> that is a wobbling pathway <NUM>, and <FIG> depicts an embodiment of the oscillating pathway <NUM> that is a sawtooth pathway <NUM>.

Referring now to <FIG>, in some embodiments the oscillating pathway <NUM> is a pendulum pathway <NUM> that follows the offset line <NUM> in a translation direction while oscillating along a transverse axis between an inner track line <NUM> and an outer track line <NUM>, where the transverse axis is orthogonal the offset line <NUM>. For example, the pendulum pathway <NUM> has a plurality of rounded portions <NUM> and a plurality of straight portions <NUM>. The plurality of rounded portions <NUM> each reach either the inner track line <NUM> or the outer track line <NUM>. Further, the straight portions <NUM> each extend between two rounded portions <NUM> and traverse the offset line <NUM>. Indeed, as depicted in <FIG>, the straight portions <NUM> extend along the transverse axis, which is orthogonal to the offset line <NUM>. In some embodiments, the plurality of straight portions <NUM> each comprise a length of from <NUM> to <NUM>, such as from <NUM> to <NUM>, for example, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or any range having any two of these values as endpoints. In some embodiments, the plurality of rounded portions <NUM> each comprise a radius of curvature of from <NUM> to <NUM>, such as from <NUM> to <NUM>, for example, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or any range having any two of these values as endpoints.

Referring now to <FIG>, in some embodiments the oscillating pathway <NUM> is a wobbling pathway <NUM> that rotationally oscillates between the inner track line <NUM> and the outer track line <NUM> while following the offset line <NUM> in the translation direction. In operation, the wobbling pathway <NUM> may be achieved using the scanner <NUM>. In particular, the scanner <NUM> may rotate the infrared laser beam <NUM> (e.g., rotate the infrared beam source <NUM>) in a rounded pattern around a central axis of the scanner <NUM> while linearly translating the infrared laser beam <NUM> along the translation direction to follow the offset line <NUM>. In some embodiments, the rounded pattern is a circle or ellipse and in some embodiments, the rounded pattern may be a Lissajou pattern. Referring now to <FIG>, in some embodiments, the oscillating pathway <NUM> is a sawtooth pathway <NUM> having a plurality of straight portions connected angular turns at or between the inner track line <NUM> and the outer track line <NUM> while following the offset line <NUM> in the translation direction.

Referring now to <FIG>, by irradiating the dummy region <NUM> of the coated substrate <NUM> with the infrared laser beam <NUM> along the oscillating pathway <NUM> of <FIG>, the accumulated fluence applied by the infrared laser beam <NUM> onto the dummy region <NUM> of the coated substrate <NUM> follows a top hat accumulated fluence distribution in which <NUM>% or less of the total energy applied to the dummy region <NUM> is applied to portions of the dummy region <NUM> not located between the inner track line <NUM> and the outer track line <NUM> and that portions of the dummy region <NUM> between the inner track line <NUM> and the outer track line <NUM> are impinged by an accumulated fluence of greater than <NUM>% of the maximum accumulated fluence applied any portion of the dummy region <NUM>. This top hat accumulated fluence distribution is graphically depicted in <FIG>, in which line <NUM> of graph <NUM> depicts the relative accumulated fluence as a function of position along a portion of the dummy region <NUM>. The relative accumulated fluence at the peak of the accumulated fluence distribution is normalized to <NUM> and the balance of the accumulated fluence distribution is scaled proportionally.

Referring now to <FIG>, another method of laser processing the coated substrate <NUM> using an infrared laser beam <NUM>' having a modified energy distribution is schematically depicted. <FIG> schematically depicts an optical assembly <NUM>' and lens assembly <NUM>', which includes the optical assembly <NUM> of <FIG> with the addition of a diffractive optical element <NUM> for modifying the intensity profile of the infrared laser beam <NUM>. In particular, the infrared laser beam <NUM> output by the infrared beam source <NUM> comprises a Gaussian energy distribution and after traversing the diffractive optical element <NUM> and reaching the coated substrate <NUM>, the infrared laser beam <NUM> (now infrared laser beam <NUM>') comprises a modified, top hat energy distribution. Thus, an infrared beam spot <NUM>' (<FIG>) projected by the infrared laser beam <NUM>' onto the first surface <NUM> of the coated substrate <NUM> comprises a top hat energy distribution. As used herein, a "top hat energy distribution" refers to an energy distribution in which <NUM>% of the total energy of infrared beam spot (e.g., infrared beam spot <NUM>' of <FIG>) has a fluence less than <NUM>% of the maximum fluence. In the illustrative example of <FIG>, <NUM>% or more of the total energy of the infrared beam spot <NUM>' is within an inner region (e.g., inner region <NUM>) bounded at <NUM>% of a maximum fluence of the infrared beam spot <NUM>'.

Referring now to <FIG>, the infrared beam spot <NUM>' formed using the optical assembly <NUM>' of <FIG> is schematically depicted in association with a graph <NUM>, which includes line <NUM> showing the relative fluence as a function of the relative radial position within the infrared beam spot <NUM>'. The relative fluence at the peak of the fluence distribution is normalized to <NUM> and the balance of the fluence distribution is scaled proportionally. As shown in <FIG>, the infrared beam spot <NUM>' includes an outer perimeter <NUM>, an inner perimeter <NUM>, and an inner region <NUM> bounded by the inner perimeter <NUM>, which is defined by a particular relative fluence, such as <NUM>% of the maximum fluence of the infrared beam spot <NUM>'. In some embodiments, the infrared beam spot <NUM>' comprises an energy distribution in which <NUM>% or less of the total energy of the infrared beam spot <NUM>' has less than <NUM>% of the maximum fluence. In some embodiments, the infrared beam spot <NUM>' comprises an energy distribution in which less than <NUM>% of the total energy of the infrared beam spot <NUM>' has a fluence less than <NUM>% of the maximum fluence. In some embodiments, the infrared beam spot <NUM>' comprises an energy distribution in which less than <NUM>% of the total energy of the infrared beam spot <NUM>' has a fluence less than <NUM>% of the maximum fluence.

Referring now to <FIG>, a cross section of the coated substrate <NUM> during laser processing with the infrared laser beam <NUM>' of <FIG> is schematically depicted. Because the infrared beam spot <NUM>' comprises a top hat energy distribution, the resultant thermal affected area <NUM> formed in the coated substrate <NUM> comprises a substantially rectilinear shape. The substantially rectilinear shape means that the decrease in fluence from a relative fluence of <NUM>% of the maximum fluence to <NUM>%, <NUM>%, or even <NUM>% of the maximum fluence is steep so that, relative to a Gaussian distribution centered at the same position, a significantly reduced overlap of the wings of the distribution with the primary region <NUM> occurs. As a result, the region of high fluence of the top hat energy distribution can be placed closer to defects <NUM> to promote thermal separation without inducing damage to the coating layer <NUM> in primary region <NUM>. In operation, the infrared laser beam <NUM>' projects the infrared beam spot <NUM>' onto the first surface <NUM> of the coated substrate <NUM> in the dummy region <NUM> of the coated substrate <NUM>. In particular, the infrared beam spot <NUM>' is projected onto the offset line <NUM> such that the infrared beam spot <NUM>' is offset from the contour line <NUM>. For example, the infrared beam spot <NUM>' may be centered onto the offset line <NUM> such that the offset line <NUM> bisects the infrared beam spot <NUM>'. In some embodiments, the inner perimeter <NUM> of the infrared beam spot <NUM>' may be disposed at the inner track line <NUM> and the outer track line <NUM> or between the inner track line <NUM> and the outer track line <NUM>.

Forming the thermal affected area <NUM> using the infrared laser beam <NUM>' of <FIG> further comprises translating at least one of the coated substrate <NUM> and the infrared laser beam <NUM>' relative to each other such that the infrared beam spot <NUM>' follows the offset line <NUM>. Without intending to be limited by theory, the infrared laser beam <NUM>' applies thermal energy to the coated substrate <NUM> to induce separation of the series of defects <NUM> of the coated substrate <NUM> along the contour line <NUM> while limiting or preventing damage to the primary region <NUM> of the coated substrate <NUM>. Indeed, because the infrared beam spot <NUM>' comprises a modified energy distribution that sharply drops at a particular radial location (e.g., a top hat energy distribution), the infrared laser beam <NUM>' applies thermal energy sufficient to damage the coated substrate <NUM> to the dummy region <NUM> and not to the primary region <NUM>. Furthermore, it should be understood that in some embodiments, the infrared beam spot <NUM>' of <FIG> having a top hat energy distribution may be traversed along the oscillating pathway <NUM> of <FIG>.

Referring now to <FIG>, an optical assembly <NUM>" for laser processing with an infrared laser beam <NUM>" formed into an annulus using an aspheric optical element <NUM> (such as an axicon <NUM>) is schematically depicted. The aspheric optical element <NUM> may comprise any of the embodiments of the aspheric optical element <NUM> described above with respect to <FIG>. Indeed, the aspheric optical element <NUM> may modify the infrared laser beam <NUM> output by the infrared beam source <NUM> into a phase modified infrared laser beam <NUM>" having an annular shape. Without intending to be limited by theory, the infrared laser beam <NUM>" comprises the phase characteristics that form the pulsed laser beam <NUM> of <FIG> into a quasi-non-diffracting beam. However, in the embodiment depicted in <FIG>, the infrared laser beam <NUM>" impinges the coated substrate <NUM> while having an annular shape (e.g., upstream a focal plane of a final focusing element).

Further, as shown in <FIG>, the optical assembly <NUM>" comprises a lens assembly <NUM>", which may further comprise one or more lenses <NUM>, <NUM>, which may comprise the same lenses as lenses <NUM>, <NUM> of the lens assembly <NUM> of <FIG>. Further, in the embodiment of the optical assembly <NUM>" depicted in <FIG>, the lens <NUM> operates as the final focusing element, that is, the final focusing element the infrared laser beam <NUM>" traverses before impinging the coated substrate <NUM>. While lens <NUM> is depicted as the final focusing element, it should be understood that the aspheric optical element <NUM> may alternatively be positioned as the final focusing element. The final focusing element comprises a focal length that extends from the final focusing element to a focal plane <NUM>. As shown in <FIG>, the final focusing element (i.e., the second lens <NUM>) and the first surface <NUM> of the coated substrate are positioned relative to one another such that the focal plane <NUM> is offset from the first surface <NUM> of the coated substrate <NUM> may an offset length OL.

Referring now to <FIG>, a caustic <NUM> of the infrared laser beam <NUM>" downstream the final focusing element (i.e., the second lens <NUM>). As used herein, a "caustic" refers to an envelope of light of a laser beam refracted by an optical component and thereafter directed onto and/or a substrate. For example, the caustic may comprise the envelope of light of a laser beam extending from the most downstream optical component of an optical system onto and/or into a substrate. As shown by its caustic <NUM>, the annular shaped infrared laser beam <NUM>" impinged the coated substrate <NUM> at locations at or between the inner track line <NUM> and the outer track line <NUM>. Indeed, in some embodiments, the offset line <NUM> bisects the caustic <NUM> of the infrared laser beam <NUM>". Furthermore, it should be understood that in some embodiments, the infrared laser beam of <FIG> and <FIG> having a annular shape may be traversed along the oscillating pathway <NUM> of <FIG>.

Referring now to <FIG>, because the infrared laser beam <NUM>" impinges the first surface <NUM> offset from the focal plane <NUM>, the infrared laser beam <NUM>" projects an infrared beam spot <NUM>" onto the first surface of the coated substrate that comprises an annular shape. <FIG> schematically depicts a top view of the coated substrate <NUM> of <FIG> during laser processing using the infrared laser beam <NUM>" of <FIG>. In operation, laser processing the coated substrate <NUM> using the infrared laser beam <NUM>" comprises translating at least one of the coated substrate <NUM> and the infrared laser beam <NUM>" relative to each other such that the infrared beam spot <NUM>" follows the offset line <NUM>. For example, the offset line <NUM> may bisect the infrared beam spot <NUM>". Further, the infrared beam spot <NUM>" may projected onto the dummy region <NUM> without impinging the primary region <NUM>.

Further, in some embodiments, the infrared laser beam <NUM>" comprises a pulsed infrared laser beam (i.e., in some embodiments, the infrared beam source <NUM> may be a pulsed infrared beam source). In embodiments in which the infrared laser beam <NUM>" is pulsed, when translating at least one of the coated substrate <NUM> and the infrared laser beam <NUM>" relative to each other, the infrared laser beam <NUM>" impinges the first surface of the coating substrate at locations (i.e., impingement locations <NUM>) along the offset line spaced apart from one another by a distance of from ¼ a diameter of the infrared beam spot <NUM>" to ½ the diameter of the infrared beam spot <NUM>", for example, ⅓ the diameter of the infrared beam spot <NUM>". This spacing distance between impingement locations <NUM> may be altered by altering the pulse rate of the infrared laser beam <NUM>", the translation rate of the infrared laser beam <NUM>" and the coated substrate <NUM> relative to one another, or both. Without intending to be limited by theory, a ¼ to ½ overlap between adjacent impingement locations <NUM> causes more continuous damage along the offset line <NUM> than fully spacing the impingement locations <NUM> apart. Similar to the embodiments, of 7A-7D and the embodiments of 8A-8C, the infrared laser beam <NUM>" applies thermal energy to the coated substrate <NUM> thereby inducing crack propagation within the coated substrate <NUM> along the plurality of defects <NUM>, thereby separating the coated substrate <NUM> along the contour line <NUM>.

Indeed, by irradiating the dummy region <NUM> of the coated substrate <NUM> with the annulus of the infrared laser beam <NUM>" along the offset line <NUM>, as depicted in <FIG>, the accumulated fluence applied by the infrared laser beam <NUM>" onto the dummy region <NUM> of the coated substrate <NUM> follows a top hat accumulated fluence distribution in which <NUM>% or less of the total energy applied to the dummy region <NUM> is applied to portions of the dummy region <NUM> not located between the inner track line <NUM> and the outer track line <NUM> and that portions of the dummy region <NUM> between the inner track line <NUM> and the outer track line <NUM> are impinged by an accumulated fluence of greater than <NUM>% of the maximum accumulated fluence applied any portion of the dummy region <NUM>. This top hat accumulated fluence distribution is graphically depicted in <FIG>, in which line <NUM> of graph <NUM> depicts the relative accumulated fluence as a function of position along a portion of the dummy region <NUM>. The relative accumulated fluence at the peak of the accumulated fluence distribution is normalized to <NUM> and the balance of the accumulated fluence distribution is scaled proportionally.

In view of the foregoing description, it should be understood that a coated substrate comprising a transparent workpiece and a coating layer may be laser separated while limiting or preventing damage to a primary region of the coated substrate. The methods described herein include using a pulsed laser beam to form a series of defects in the transparent workpiece and an infrared laser beam to separate the transparent workpiece and the coating layer along the series of defects, which are formed along a boundary between the primary region and a dummy region. Methods described herein include translating an infrared laser beam along an oscillating pathway on the dummy region to separate the coated substrate, modifying the energy distribution of an infrared laser beam into a top hat energy distribution and directing this modified laser beam onto the dummy region to separate the coated substrate, and forming the infrared laser beam into an annular shape and directing this annular infrared laser beam onto the dummy region to separate the coated substrate. As described herein, these methods direct thermal energy onto the dummy region of the coated substrate using techniques sufficient to both induce crack propagation of the defects disposed in the coated substrate along the boundary between the primary region and the dummy region in a single process step.

As used herein, the term "about" means that amounts, sizes, formulations, parameters, and other quantities and characteristics are not and need not be exact, but may be approximate and/or larger or smaller, as desired, reflecting tolerances, conversion factors, rounding off, measurement error and the like, and other factors known to those of skill in the art. When the term "about" is used in describing a value or an end-point of a range, the specific value or end-point referred to is included. Whether or not a numerical value or end-point of a range in the specification recites "about," two embodiments are described: one modified by "about," and one not modified by "about. " It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.

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

Unless otherwise expressly stated, it is in no way intended that any method set forth herein be construed as requiring that its steps be performed in a specific order, nor that with any apparatus specific orientations be required. Accordingly, where a method claim does not actually recite an order to be followed by its steps, or that any apparatus claim does not actually recite an order or orientation to individual components, or it is not otherwise specifically stated in the claims or description that the steps are to be limited to a specific order, or that a specific order or orientation to components of an apparatus is not recited, it is in no way intended that an order or orientation be inferred, in any respect. This holds for any possible non-express basis for interpretation, including: matters of logic with respect to arrangement of steps, operational flow, order of components, or orientation of components; plain meaning derived from grammatical organization or punctuation, and; the number or type of embodiments described in the specification.

As used herein, the singular forms "a," "an" and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to "a" component includes aspects having two or more such components, unless the context clearly indicates otherwise.

Claim 1:
A method of separating a coated substrate (<NUM>), the method comprising:
directing an infrared laser beam (<NUM>) onto a first surface (<NUM>) of the coated substrate (<NUM>) wherein:
the coated substrate (<NUM>) comprises a coating layer (<NUM>) disposed on a transparent workpiece (<NUM>);
a plurality of defects (<NUM>) is disposed within the coated substrate (<NUM>), extending into both the coating layer (<NUM>) and the transparent workpiece (<NUM>) and disposed along a contour line (<NUM>) that divides a primary region (<NUM>) of the coated substrate (<NUM>) from a dummy region (<NUM>) of the coated substrate (<NUM>); and
the infrared laser beam (<NUM>) projects an infrared beam spot (<NUM>) onto the first surface (<NUM>) of the coated substrate (<NUM>); and characterized by:
translating at least one of the coated substrate (<NUM>) and the infrared laser beam (<NUM>) relative to each other such that the infrared beam spot (<NUM>) traces an oscillating pathway (<NUM>), wherein:
the oscillating pathway (<NUM>) follows an offset line (<NUM>) in a translation direction (<NUM>) and oscillates between an inner track line (<NUM>) and an outer track line (<NUM>);
the oscillating pathway (<NUM>) is disposed on the dummy region (<NUM>) of the coated substrate (<NUM>); and
the infrared laser beam (<NUM>) applies thermal energy to the plurality of defects (<NUM>) disposed in the coated substrate (<NUM>) and inducing separation of the coated substrate (<NUM>) along the contour line (<NUM>).