Patent Description:
In some aspects of the present description, a glass laminate including first and second glass layers having substantially parallel outermost major surfaces facing away from one another, a reflective film having opposed first and second major surfaces and disposed between the first and second glass layers with the first and second major surfaces facing the respective first and second glass layers, a first adhesive layer disposed between and bonding together the first glass layer and the reflective film, and a second adhesive layer disposed between and bonding together the second glass layer and the reflective film is provided. The reflective film has an average reflectance for a first polarization state in a predetermined visible wavelength range at a predetermined angle of incidence of at least <NUM>% and an average transmittance for an orthogonal second polarization state in the predetermined visible wavelength range at the predetermined angle of incidence of at least <NUM>%. The second adhesive layer is thicker than the first adhesive layer such that the first major surface of the reflective film is separated from the outermost major surface of the first glass layer by a distance d1, the second major surface of the reflective film is separated from the outermost major surface of the second glass layer by a distance d2, and <NUM> ≤ d1/d2 ≤ <NUM>.

In the following description, reference is made to the accompanying drawings that form a part hereof and in which various embodiments are shown by way of illustration. It is to be understood that other embodiments are contemplated and may be made without departing from the scope of the present description. The following detailed description, therefore, is not to be taken in a limiting sense.

Head-up displays typically include a display or projector which projects an image onto a windshield or a combiner which reflects the projected image to a viewer. In some cases, the windshield is a glass laminate which includes a reflective film between two glass layers for reflecting the projected image. Ghost images reflected from outer surfaces of the glass laminate can degrade the image quality of the reflected image. In some cases, a glass laminate has a wedge design that provides a difference in slope between the reflective film and at least one of the outer surfaces of the glass laminate. The difference in slope can be selected to shift the ghost image onto the image reflected by the film so that the ghost does not substantially degrade the sharpness of the reflected image. However, such a wedge design is often not preferred in many embodiments due, at least in part, to the difficulty of providing a desired slope difference in a cost-effective manufacturing process.

According to some embodiments of the present description, it has been found that utilizing a reflective film asymmetrically disposed between glass layers having substantially parallel outermost major surfaces can provide improve perceived image quality by shifting the ghost image that reflects from the front major surface so that it is closer to the primary reflected image. In some embodiments, at least one ghost image substantially overlaps with an image reflected from the reflective film. Traditionally, a relatively thick layer (e.g., <NUM>) of polyvinyl butyral (PVB) has been used to laminate glass layers together in a windshield. In some embodiments, a thin (e.g., <NUM> microns or less) adhesive layer is used to laminate the reflective film to the glass layer facing the projector and a thick a (e.g., <NUM> microns or more) adhesive layer is used to laminate the reflective film to the opposite glass layer. This has been found to sufficiently shift the ghost image such that it is closer to, or substantially overlaps with, the primary reflected image and so does not substantially degrade the sharpness of the reflected image.

The thinner adhesive layer may be a traditional acrylate-based optically clear adhesive (OCA), for example, instead of a PVB layer commonly used in windshield glass laminates. A windshield glass laminate is sometimes included for its improved impact resistance compared to using a single glass layer. For example, one layer can hold glass fragments in place when an object impacts and cracks the other layer. It has been found that using a layer of OCA as the thin adhesive layer and a layer of PVB as the thick adhesive layer provides an impact resistance comparable to a traditional windshield glass laminate. In particular, in some embodiments, when a <NUM>-pound steel ball is dropped on the glass laminate from <NUM> feet onto the glass layer adjacent the thicker adhesive layer, the ball is stopped by the laminate and no glass shards are separated from the glass laminate.

Another advantage of the glass laminates according to some embodiments of the present description is improved fidelity of the reflected image. Utilizing a reflective film between glass layers and using traditional windshield adhesive layers can result in a reduced flatness of the reflective film and this can result in a waviness when a line is projected onto the glass laminate, for example. It has been found that using a thinner adhesive layer on the side of the reflective film facing the projector reduces this waviness.

<FIG> is a schematic cross-sectional view of a glass laminate <NUM> and a light source <NUM>. The glass laminate <NUM> includes first and second glass layers <NUM> and <NUM> having substantially parallel outermost major surfaces <NUM> and <NUM> facing away from one another, and a reflective film <NUM> having opposed first and second major surfaces <NUM> and <NUM> and disposed between the first and second glass layers <NUM> and <NUM> with the first and second major surfaces <NUM> and <NUM> facing the respective first and second glass layers <NUM> and <NUM>. The reflective film <NUM> has an average reflectance for a first polarization state (e.g., polarization state <NUM> depicted in <FIG> which is a p-polarization state in the illustrated embodiment) in a predetermined visible wavelength range at a predetermined angle of incidence of at least <NUM>% (e.g., in a range of <NUM>%-<NUM>%, or about <NUM>%) and an average transmittance for an orthogonal second polarization state (e.g., polarization state <NUM> depicted in <FIG> which is an s-polarization state in the illustrated embodiment) in the predetermined visible wavelength range at the predetermined angle of incidence of at least <NUM>%. In some embodiments, the reflective film <NUM> includes a plurality of alternating polymeric interference layers as described further elsewhere herein. The glass laminate <NUM> includes a first adhesive layer <NUM> disposed between and bonding together the first glass layer <NUM> and the reflective film <NUM>, and a second adhesive layer <NUM> disposed between and bonding together the second glass layer <NUM> and the reflective film <NUM>. The second adhesive layer <NUM> can optionally include an optically absorbing material <NUM> as described further elsewhere herein.

The second adhesive layer <NUM> is thicker than the first adhesive layer <NUM> such that the first major surface <NUM> of the reflective film <NUM> is separated from the outermost major surface <NUM> of the first glass layer <NUM> by a distance d1, the second major surface <NUM> of the reflective film <NUM> is separated from the outermost major surface <NUM> of the second glass layer <NUM> by a distance d2, and <NUM> ≤ d1/d2 ≤ <NUM>. In some embodiments, <NUM> ≤ d1/d2 ≤ <NUM>, or <NUM> ≤ d1/d2 ≤ <NUM>, or <NUM> ≤ d1/d2 ≤ <NUM>. In some embodiments, the second adhesive layer <NUM> is at least <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM> times thicker than the first adhesive layer <NUM>. In some embodiments, the first adhesive layer <NUM> has a thickness in a range of <NUM> micron to <NUM> microns and the second adhesive layer <NUM> has a thickness in a range of <NUM> microns to <NUM> microns. In some embodiments, the first adhesive layer <NUM> has a thickness in a range of <NUM> micron to <NUM> microns and the second adhesive layer <NUM> has a thickness in a range of <NUM> microns to <NUM> microns.

In some embodiments, the first and second glass layers <NUM> and <NUM> have a substantially same thickness. In this context, substantially same thickness means within <NUM>% of one another. In some embodiments, the first glass layer <NUM> has a thickness in a range of <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM> times a thickness of the second glass layer <NUM>. In some embodiments, the second glass layer <NUM> is thicker than the first glass layer <NUM>. In some embodiments, the second glass layer <NUM> is at least <NUM> times, or <NUM> times, or <NUM> times, or <NUM> times thicker than the first glass layer <NUM>. In some embodiments, the second glass layer <NUM> is no more than <NUM> times, or <NUM> times or <NUM> times thicker than the first glass layer <NUM>. Using a thinner first glass layer <NUM> positions a first ghost image closer to a primary reflected image but using a thicker first glass layer <NUM> (e.g., having a thickness similar to that of the second glass layer <NUM>) improves impact resistance. In some embodiments, the first glass layer <NUM> has a thickness less than <NUM>, or less than <NUM>, or less than <NUM>, or less than <NUM>. In some embodiments, the first glass layer <NUM> has a thickness greater than <NUM>, or greater than <NUM>.

In some embodiments, the light source <NUM> emits or projects an image of a line having a projected luminance distribution about a centerline of the projected line having a full width at half maximum σ. The luminance distribution may be expressed as a function of the x-coordinate illustrated in <FIG> or in terms of an angle from a peak luminance direction or from a central ray <NUM> as schematically illustrated in <FIG>. Non-central rays 129a and 129b are also illustrated in <FIG>. Ray 129b makes an angle φ with the central ray <NUM>. The luminance distribution can be expressed in terms of the angle φ, where positive φ in <FIG> corresponds to positive x-coordinate in <FIG>. The luminance distribution can be determined using a detector having an input aperture in a plane perpendicular to a central ray reflected from the reflective film <NUM> (e.g., the x-y plane referring to the x-y-z coordinate system of <FIG>). Suitable detectors include the PROMETRIC I8 imaging colorimeter available from Radiant Vision Systems (Redmond, WA). The luminosity, which may also be referred to a brightness, can be defined as an integral over wavelengths of the radiance times the photopic luminosity function defined by the Commission Internationale de l'Éclairage (CIE) in the CIE <NUM> color space. Any relations described herein regarding luminance or luminance distribution may also hold for radiance or radiance distribution or for intensity or intensity distribution.

In some embodiments, the light source <NUM> projects polarized light having a first polarization state <NUM>. An ambient light ray <NUM> having a second polarization state <NUM> is illustrated in <FIG> as being transmitted through reflective film <NUM> which may be a reflective polarizer. The light source <NUM> may be or include a display such as a liquid crystal display (LCD) or an organic light emitting diode (OLED) display. In some embodiments, various optical components (e.g., curved mirror(s) and/or optical lens(es)) are included in the light source <NUM> to provide the desired light output to the glass laminate <NUM>.

<FIG> is a schematic cross-sectional view of a reflective film <NUM>, which may correspond to reflective film <NUM>. Reflective film <NUM> includes a plurality of alternating polymeric interference layers <NUM> and <NUM>. In the illustrated embodiments, the plurality of alternating polymeric interference layers <NUM> and <NUM> is disposed on an optional skin layer <NUM>. In some embodiments, a second skin layer is disposed adjacent the plurality of alternating polymeric interference layers <NUM> and <NUM> opposite the skin layer <NUM>. The skin layer <NUM> may optionally include optically absorbing material <NUM>. Optically absorbing material <NUM> may be dyes, pigments, or a combination thereof which may be dispersed in a polymeric material of the skin layer <NUM>. In some embodiments, at least one of the inference layers <NUM> or <NUM> is oriented along a first direction (e.g., x1-direction), and the optically absorbing material <NUM> is or includes a dichroic dye at least partially oriented along the first direction. Any of these optically absorbing materials may optionally be included in second adhesive layer <NUM> instead of or in addition to be including in the skin layer <NUM>. The optically absorbing material may be included to reduce the brightness of a ghost image reflected from the outermost major surface <NUM> as described further elsewhere herein.

Interference layers reflect and transmit light primarily by optical interference. Reflecting and transmitting light primarily by optical interference means that the reflectance and transmittance of the interference layers can be reasonably described by optical interference or reasonably accurately modeled as resulting from optical interference. Adjacent pairs of interference layers having differing refractive indices reflect light by optical interference when the pair has a combined optical thickness (refractive index times physical thickness) of ½ the wavelength of the light. Interference layers typically have a physical thickness of less <NUM> or less than <NUM>. Skin layers are typically noninterference layers which have an optical thickness too large to reflect and transmit light primarily by optical interference and typically have a physical thickness of greater than <NUM> micron or greater than <NUM> microns. The reflective film <NUM> can include many more interference layers than schematically illustrated in <FIG>. For example, the reflective film <NUM> can include between <NUM> and <NUM> interference layers.

Suitable materials for the alternating interference layers <NUM> and <NUM> and for the skin layer <NUM> include, for example, polyethylene naphthalate (PEN), copolymers containing PEN and polyesters (e.g., polyethylene terephthalate (PET) or dibenzoic acid), glycol modified polyethylene terephthalate (PETg), polycarbonate (PC), poly(methyl methacrylate) (PMMA), or blends of these classes of materials.

Exemplary reflective films composed of polymer materials may be fabricated using coextruding, casting, and orienting processes. Methods of making such films are described in <CIT>) "Optical Film", <CIT>) "Optical Film and Process for Manufacture Thereof", <CIT>) "Apparatus for Making Multilayer Optical Films", and patent application publication <CIT>) "Feedblock for Manufacturing Multilayer Polymeric Films". Useful reflective films for use in head-up displays are described in <CIT>).

The reflective film may be a partial mirror or a partial reflective polarizer, for example. In some embodiments, the reflective film is oriented primarily along the x1 direction and has a stronger reflectivity for a first polarization state having the electric field along the x1 direction and a lower reflectivity for a second polarization state having the electric field along the x2 direction, referring to the x1-x2-x3 coordinate system illustrated in <FIG>.

The reflective film <NUM> or <NUM> has an average reflectance for a first polarization state in a predetermined visible wavelength range at a predetermined angle of incidence of at least <NUM>% and an average transmittance for an orthogonal second polarization state in the predetermined visible wavelength range at the predetermined angle of incidence of at least <NUM>%. The predetermined visible wavelength range may be the entire visible wavelength range (about <NUM> to about <NUM>) or a portion of the visible wavelength range. In some embodiments, the predetermined visible wavelength range extends at least from <NUM> to <NUM>. In some embodiments, the predetermined visible wavelength range extends from <NUM> to <NUM>. In some embodiments, the reflective film <NUM> or <NUM> is reflective in narrow bands corresponding to wavelengths transmitted by red, green, and blue subpixels of a display, for example. In this case, the predetermined wavelength range may be a disjoint union of a red range, a green range, and a blue range. This can allow the reflective film to be transmissive for both polarization states for wavelengths between the red range and the green range and between the green range and the blue range and so can increase the transparency of the reflective film for ambient light.

The predetermined angle of incidence may be the angle θ (see <FIG>) where a light source <NUM> is adapted to project onto the glass laminate. The predetermined angle of incidence and/or the angle θ may be in a range of <NUM> degrees to <NUM> degrees, or in a range of <NUM> degrees to <NUM> degrees, or in a range of <NUM> degrees to <NUM> degrees, or in a range of <NUM> degrees to <NUM> degrees, or in a range of <NUM> degrees to <NUM> degrees, or in a range of <NUM> degrees to <NUM> degrees, or in a range of <NUM> degrees to <NUM> degrees, or the predetermined angle may be about <NUM> degrees (e.g., <NUM> to <NUM> degrees, or <NUM> to <NUM> degrees), about <NUM> degrees (e.g., <NUM> to <NUM> degrees, or <NUM> to <NUM> degrees) or about <NUM> degrees (e.g., <NUM> to <NUM> degrees, or <NUM> to <NUM> degrees), for example.

In some embodiments, the average reflectance of the reflective film <NUM> or <NUM> for the first polarization state in the predetermined visible wavelength range at the predetermined angle of incidence is at least <NUM>%, or at least <NUM>%, or at least <NUM>%. In some embodiments, the average transmittance if the reflective film <NUM> or <NUM> for the second polarization state in the predetermined visible wavelength range at the predetermined angle of incidence is at least <NUM>%, or at least <NUM>%.

The average reflectance and average transmittance in the predetermined wavelength range refers to the reflectance and transmittance averaged (unweighted) over wavelengths in the predetermined wavelength range. The reflectance and transmittance are determined for light incident on the reflective film in air, unless indicated differently.

In some embodiments, the reflective film includes absorbing material on one side of the film (e.g., in a skin layer) and not on the other or includes more absorbing material on one side than the other. In this case, the reflectance and transmittance are determined for light incident on the reflective film on the side of the film opposite the absorbing material or opposite the side that is more absorbing. In some embodiments, the reflective film <NUM> is disposed between the first and second glass layers <NUM> and <NUM> with the skin layer <NUM> facing the second glass layer <NUM> and with absorbing material included in the skin layer <NUM>. As described further elsewhere herein, this may be done to reduce the luminance of a ghost image reflected from the outermost major surface <NUM> of the second glass layer <NUM>.

When a reflective film is included in a glass laminate using PVB layers having thicknesses traditionally used in glass laminates of windshields, a distortion of an image reflected from the reflective film can occur due to a reduced flatness of the film. According to the present description, when a thin adhesive layer, such as a thin layer of optically clear adhesive (e.g., an optically clear adhesive (e.g., acrylate based) commonly used in optical components), is used in place of a PVB layer having a thickness traditionally used in windshield laminates, that this distortion can be substantially reduced.

<FIG> is a schematic illustration of a plurality of parallel lines <NUM> which can be projected by a light source <NUM> onto the glass laminate <NUM>. <FIG> is a schematic illustration of reflected image <NUM> of the plurality of parallel lines <NUM>. <FIG> is a schematic illustration of a distribution <NUM> of an angle α between centerlines <NUM> of the reflected images <NUM> and the y-direction (see <FIG>). The distribution <NUM> has a full width at half maximum <NUM> which may be less than <NUM> degrees, for example.

The light source <NUM> projects a light <NUM> onto the glass laminate <NUM>. Portions <NUM>, <NUM> and <NUM> of the light reflect from the glass laminate <NUM>. The projected light <NUM> may be a projected line or a plurality of projected lines, for example. The portions <NUM>, <NUM>, and <NUM> can refer to portions of a projected line or portions of a plurality of projected lines as will be clear from the context. In some embodiments, the projected line(s) is in the first polarization state (e.g., a p-polarization state). In other embodiments, the projected line(s) are unpolarized.

The term "parallel lines" should be understood to refer to straight lines that are parallel to one another unless indicated differently. The term "projected line" should be understood to refer to a projected straight line unless indicated differently. However, the term "centerline" is used to refer to a curve or line which may or may not be a straight line (e.g., the centerlines may be curved and/or irregular).

In some embodiments, a glass laminate <NUM> includes first and second glass layers <NUM> and <NUM> having substantially parallel outermost major surfaces <NUM> and <NUM>; and a reflective film <NUM> or <NUM> including a plurality of alternating polymeric interference layers <NUM> and <NUM> and disposed between and adhered to the first and second glass layers <NUM> and <NUM> through respective first and second adhesive layers <NUM> and <NUM>, where the first adhesive layer <NUM> has a thickness no more than <NUM> times (or no more than <NUM> times, or no more than <NUM> times, or no more than <NUM> times, or no more than <NUM> times) a thickness of the second adhesive layer <NUM>, such that when a light source <NUM> projects a plurality of parallel lines <NUM> onto the outermost major surface <NUM> of the first glass layer <NUM> (and through the first glass layer to the reflective film) along a first direction (z' direction) making an angle θ in a range of <NUM> degrees to <NUM> degrees with respect to a normal <NUM> to the glass laminate <NUM> so that the plurality of parallel lines <NUM> extend along a second direction (y direction) orthogonal to a first plane (x'-z' plane) defined by the first direction and the normal <NUM> and are spaced apart along a third direction (x'-direction) in the first plane and orthogonal to the first direction, a first portion <NUM> of each projected line reflects from the reflective film <NUM> or <NUM>, where a reflected image <NUM> of each line includes the reflected first portion <NUM>, each reflected image <NUM> has a luminance distribution defining a centerline <NUM> of the reflected image <NUM>, and a distribution <NUM> of an angle α between the centerlines <NUM> of the reflected images <NUM> and the second direction (y-direction) has a full width at half maximum <NUM> of less than <NUM> degrees. The distribution <NUM> can be obtained by determining the angle α between the centerline <NUM> and the second direction at a plurality of locations along each line to determine the overall distribution of α. The plurality of locations can be selected at uniform intervals along the second direction and the number of locations can be increased until a statistical measure of the distribution, such as the full width at half maximum <NUM>, converges. Related image analysis procedures which can be used to determine the distribution of the orientation of the centerline tangent angle α are described in "<NPL>. In some embodiments, the full width at half maximum <NUM> of the distribution <NUM> of the angle α is less than <NUM> degrees, or less than <NUM> degrees, or less than <NUM> degrees, or less than <NUM> degrees.

In some embodiments, the light source <NUM> is positioned within <NUM>, <NUM>, <NUM>, or <NUM> of the glass laminate <NUM>. The distance between the light source <NUM> and the glass laminate <NUM> is the distance along a central light ray from the light source <NUM> to the glass laminate <NUM> (e.g., the distance between the light source <NUM> and the glass laminate <NUM> along the light <NUM>).

<FIG> is a schematic illustration of a reflected luminance distribution <NUM> of a reflected image. The distribution may be expressed in terms of a lateral dimension (x-dimension) at a detector location or in terms of an angle from a peak luminance direction (see, e.g., the angle φ illustrated in <FIG>). The distribution can be determined over a length of the line and so a non-zero angle α (see <FIG>) to the y-direction can increase the width of the distribution.

In some embodiments, a glass laminate <NUM> includes first and second glass layers <NUM> and <NUM> having substantially parallel outermost major surfaces <NUM> and <NUM>; and a reflective film <NUM> or <NUM> including a plurality of alternating polymeric interference layers <NUM> and <NUM> and disposed asymmetrically between the outermost major surfaces <NUM> and <NUM> such that when a light source <NUM> positioned within <NUM> of the glass laminate <NUM> projects a line 350a onto the outermost major surface <NUM> of the first glass layer <NUM> (and through the first glass layer to the reflective film) along a first direction (z' direction) making an angle θ in a range of <NUM> degrees to <NUM> degrees with respect to a normal <NUM> to the glass laminate <NUM> so that the line extends along a second direction (y direction) orthogonal to a first plane (x'-z' plane) defined by the first direction and the normal <NUM> and has a projected luminance distribution about a centerline of the projected line having a full width at half maximum σ of no more than <NUM> degrees, a first portion <NUM> of the projected line 350a reflects from the reflective film and a second portion <NUM> of the projected line 350a reflects from the outermost major surface <NUM> of the first glass layer <NUM>, a reflected image 352a of the line including a primary reflected image portion <NUM> (portion under dotted line in <FIG>) defined by the reflected first portion <NUM> and a first ghost portion <NUM> (a portion between the dotted line and the solid line in <FIG>) defined by the reflected second portion <NUM>. The first ghost portion <NUM> substantially overlaps with the primary reflected image portion <NUM>.

In some embodiments, a third portion <NUM> of the projected line <NUM> reflects from the outermost major surface <NUM> of the second glass layer <NUM>, and the reflected image <NUM> of the line further includes a second ghost portion <NUM> (a portion between the dotted line and the solid line in <FIG>) defined by the reflected third portion <NUM>, where the second ghost portion <NUM> substantially overlaps with the primary reflected image portion <NUM>.

In some embodiments, the reflected image 352a has a reflected luminance distribution <NUM> having a maximum at a peak <NUM> of the reflected luminance distribution <NUM> and decreasing monotonically in at least one lateral direction (+x direction) away from the peak <NUM> to an edge <NUM> of the reflected image 352a. The edge <NUM> can be taken to be where the luminance drops to <NUM>% of the maximum luminance.

In some embodiments, the reflected image 352a has a reflected luminance distribution <NUM>, where a contribution to the reflected luminance distribution <NUM> from the first ghost portion <NUM> is not separately resolvable from a contribution to the reflected luminance distribution <NUM> from the primary reflected image portion <NUM> in a plot of the reflected luminance distribution <NUM>. The contribution from the first ghost portion <NUM> is not separately resolvable from the contribution from the primary reflected image portion <NUM> when there are no features in the distribution <NUM> that can be attributed to the first ghost portion <NUM> without reference to the primary reflected image portion <NUM>. For example, there are no local maxima or inflection points that can be attributed to the first ghost portion <NUM>. The first ghost portion <NUM> can be determined once the primary reflected portion <NUM> is determined. The primary reflected portion <NUM> can be determined from known luminance distribution of the projected line which allows the reflected luminance distribution to be determined when no ghosts are present. In the illustrated embodiment, the second ghost portion <NUM> is separately resolvable from the contribution from the primary reflected image portion <NUM> due to the presence of a local maxima and an inflection point on the left-hand side of the distribution <NUM>.

In some embodiments, the full width at half maximum of the projected line is no more than <NUM> degrees, or no more than <NUM> degrees. In some embodiments, the reflected image has an angular distribution of luminance having a full width at half maximum of no more than <NUM> degrees, or no more than <NUM> degrees, or no more than <NUM> degrees.

A portion of the reflected image substantially overlaps with another portion of the reflected image if the luminance of the portion having a larger maximum luminance is at least as large as the luminance of the other portion at the position (angular or linear) of a quarter maximum of the other portion. This is schematically illustrated in <FIG>. In <FIG>, the luminance of the primary reflected image portion <NUM> is substantially less than the luminance <NUM> at a quarter maximum of the first ghost portion <NUM> at the position 579a of the quarter maximum. The full width at quarter maximum <NUM> of the first ghost portion <NUM> is indicated. The position 579a is the quarter maximum position closest to the primary reflected image portion <NUM>. In <FIG>, the luminance of the primary reflected image portion <NUM> is equal to the luminance <NUM> at a quarter maximum of the first ghost portion <NUM> at the position 579b of the quarter maximum. In <FIG>, the luminance of the primary reflected image portion <NUM> is greater than the luminance <NUM> at a quarter maximum of the first ghost portion <NUM> at the position 579c of the quarter maximum. In the case illustrated in <FIG>, the luminance of the primary reflected image portion <NUM> is greater than the luminance at a half maximum of the first ghost portion <NUM> at a position of the half maximum. The full width at half maximum <NUM> of the first ghost portion <NUM> is indicated in <FIG>. The first ghost portion <NUM> substantially overlaps with the primary reflected image portion <NUM> in the cases illustrated in <FIG> and <FIG>, but not in the case illustrated in <FIG>. Overlap of the second ghost portion with the primary reflected image portion is defined similarly. In some embodiments where a portion of the reflected image is described as substantially overlapping with another portion of the reflected image, the luminance of the portion having a larger maximum luminance is at least as large as the luminance of the other portion at the position (angular or linear) of a half maximum of the other portion.

<FIG> schematically illustrates a luminance distribution of a primary reflected image portion <NUM> substantially overlapping with first and second ghost portions <NUM> and <NUM>. <FIG> schematically illustrates the reflected luminance distribution <NUM> which includes contributions from the primary reflected image portion <NUM> and the first and second ghost portions <NUM> and <NUM>. The dotted lines indicate locations of peaks in the primary reflected image portion <NUM> and the first and second ghost portions <NUM> and <NUM>. The vertical direction (direction along the dotted lines) represents luminance in arbitrary units and the horizontal direction represents angular or linear displacement.

In some embodiments, the glass laminate <NUM> includes optically absorbing material disposed between the first glass layer <NUM> and the outermost major surface <NUM> of the second glass layer <NUM>. In some embodiments, the optically absorbing material is disposed between the reflective film <NUM> and the outermost major surface <NUM> of the second glass layer <NUM>, or between alternating polymeric interference layers of the reflective film <NUM> and the outermost major surface <NUM> of the second glass layer <NUM>. In some embodiments, the second glass layer <NUM> is optically absorbing (e.g., having an optically absorbing band in the near infrared which extends into the red portion of the visible spectrum). As described further elsewhere herein, the optically absorbing material can be included in a skin layer <NUM> or in an adhesive layer <NUM>, for example. The optically absorbing material may be included to reduce the brightness of the second ghost compared to the first ghost. In some embodiments, the second ghost portion <NUM> has a brightness less than a brightness of first ghost portion <NUM>. In some embodiments, the second ghost portion <NUM> has a brightness less than <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM> times a brightness of first ghost portion <NUM>. The brightness of the first and second ghost portions are the peak values of the luminance distributions of the first and second ghost portions.

In some embodiments, the optically absorbing material has an absorbance depending on polarization. For example, in some embodiments, the reflective film has an average reflectance for a first polarization state in a predetermined visible wavelength range at a predetermined angle of incidence of at least <NUM>% (or at least <NUM>%, or at least <NUM>% or at least <NUM>%) and an average transmittance for an orthogonal second polarization state in the predetermined visible wavelength range at the predetermined angle of incidence of at least <NUM>% (or at least <NUM>%, or at least <NUM>%), and the optically absorbing material is optically absorptive for light having the first polarization sate and substantially optically transmissive for light having the second polarization state (e.g., the absorbance for the second polarizations state may be less than <NUM>, or less than <NUM> times the absorbance for the first polarization state).

As used herein, "substantially parallel" outermost major surfaces are sufficiently close to parallel that any deviation from parallel results in a shift in a relative position of the peaks of the first and second ghost portions of less than <NUM> percent. Substantially parallel outermost major surfaces may be parallel or nominally parallel. <FIG> is a schematic illustration of a glass laminate <NUM> having outermost major surfaces <NUM> and <NUM> defining an angle δ therebetween. In some embodiments, substantially parallel outermost major surfaces define an angle δ therebetween of less than <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM> degrees. The angle δ is an angle between tangent planes at the opposing outermost major surfaces a location on the glass laminate. In some embodiments, δ is in any of the above ranges for each location on the glass laminate or for each location over at least <NUM>% or <NUM>% of an area of the glass laminate. In some embodiments, the reflective film <NUM> is substantially parallel with the outermost major surface <NUM> in the sense that any deviation from parallel results in a shift in a relative position of the peaks of the first ghost and primary reflected image portions of less than <NUM> percent. Similarly, in some embodiments, the reflective film <NUM> is substantially parallel with the outermost major surface <NUM> in the sense that any deviation from parallel results in a shift in a relative position of the peaks of the second ghost and primary reflected image portions of less than <NUM> percent.

<FIG> is a schematic front view of a windshield <NUM> which may be or include the glass laminate <NUM>, for example. In some embodiments, the reflective film covers substantially the entire windshield <NUM> (e.g., at least <NUM>% or at least <NUM>% of a surface area of the windshield). In some embodiments, the reflective film and the first and second glass layers are substantially coextensive with one another (e.g., any of the first and second glass layers and the reflective film may cover at least <NUM>% or at least <NUM>% of a surface area of any other of the first and second glass layers and the reflective film).

A reflective film, referred to as windshield combiner film (WCF), was made by extruding and uniaxially orienting <NUM> alternating polymer layers plus two outermost skin layers as generally described in <CIT>). The alternating polymer layers were oriented PET as the higher index layers and crystalline PETg as the lower index layers. The layer thicknesses were selected to produce reflectivity throughout the visible wavelength range of <NUM> to <NUM>. The film had an average reflectance in the visible range at an angle of incidence of <NUM> degrees of about <NUM>% for p-polarized light and was substantially transmissive for s-polarized light.

The reflective film WCF was laminated between first and second <NUM> thick glass layers with a <NUM> mil thick layer of <NUM> <NUM> bonding the reflective film to the first glass layer and a <NUM> thick PVB layer (formed from two <NUM> thick PVB layers) bonding the reflective film to the second glass layer.

An Apple Inc. (Cupertino, CA) IPAD (first generation) was used to project a line onto the first glass layer of the glass laminate at an angle of incidence of about <NUM> degrees. The line image was <NUM> pixels wide. The reflected luminance distribution was determined using a PROMETRIC I8 imaging colorimeter available from Radiant Vision Systems (Redmond, WA) as a function of angle (e.g., the angle φ of <FIG>) from a central peak of the primary reflected image and is shown in <FIG>. The primary reflected image had a full width at half maximum of about <NUM> degrees. A first ghost image was present at about <NUM> degrees from the primary reflected image and a second ghost image was present at about -<NUM> degrees from the primary reflected image.

Example <NUM> was prepared and tested as described for Example <NUM> except that the first and second glass layers were each <NUM> thick. The resulting reflected luminance distribution is shown in <FIG> as a function of angle (e.g., the angle φ of <FIG>) and location (e.g., the x-coordinate of <FIG>), respectively. The first and second ghost images substantially overlap with the primary reflected image.

Comparative Example C1 was prepared and tested as described for Example <NUM> except that the first adhesive layer was a <NUM> thick PVB layer. The resulting reflected luminance distribution is shown in <FIG> as a function of location (x-coordinate of <FIG>). The first and second ghost images has a sufficiently high luminance and were sufficiently displaced from the primary reflected image to cause objectionable loss of image fidelity.

Example <NUM> was prepared as described for Example <NUM> except that the first adhesive layer was a <NUM> thick PVB layer. Example <NUM> was prepared as described for Example <NUM> except that the first glass layer was <NUM> thick. Using a thicker glass layer is expected to affect the position of the ghost image but is expected to have a negligible effect on line waviness.

A plurality of parallel lines was projected onto the reflective film through the first glass layer of the glass laminate of Comparative Example C1, Example <NUM> and Example <NUM> at an angle of incidence on the glass laminate of about <NUM> degrees and the reflected image was analyzed using the PROMETRIC colorimeter. The reflected images for Comparative Example C1, Example <NUM> and Example <NUM> are shown in <FIG>, respectively. A centerline tangent to each line was determined at a sufficient number of locations along each line to determine a distribution of orientation of the centerline tangent using an image analysis procedure generally described in "<NPL>. The resulting distribution is plotted in <FIG>. The full width at half maximum for each distribution was determined and found to be <NUM> degrees, <NUM> degrees, and <NUM> degrees for Comparative Example C1, Example <NUM> and Example <NUM>, respectively.

Claim 1:
A glass laminate (<NUM>) comprising:
first and second glass layers (<NUM>, <NUM>) having substantially parallel outermost major surfaces (<NUM>, <NUM>) facing away from one another;
a reflective film (<NUM>) having opposed first and second major surfaces (<NUM>, <NUM>) and disposed between the first and second glass layers (<NUM>, <NUM>) with the first and second major surfaces (<NUM>, <NUM>) facing the respective first and second glass layers (<NUM>, <NUM>), the reflective film (<NUM>) having an average reflectance for a first polarization state in a predetermined visible wavelength range at a predetermined angle of incidence of at least <NUM>% and an average transmittance for an orthogonal second polarization state in the predetermined visible wavelength range at the predetermined angle of incidence of at least <NUM>%;
a first adhesive layer (<NUM>) disposed between and bonding together the first glass layer (<NUM>) and the reflective film (<NUM>); and
a second adhesive layer (<NUM>) disposed between and bonding together the second glass layer (<NUM>) and the reflective film (<NUM>), the second adhesive layer (<NUM>) being thicker than the first adhesive layer (<NUM>) such that the first major surface (<NUM>) of the reflective film (<NUM>) is separated from the outermost major surface (<NUM>) of the first glass layer (<NUM>) by a distance d1, the second major surface (<NUM>) of the reflective film (<NUM>) is separated from the outermost major surface (<NUM>) of the second glass layer (<NUM>) by a distance d2, and <NUM> ≤ d1/d2 ≤ <NUM>.