JP2020513586A - Display with direct backlight unit - Google Patents

Abstract

The array of pixels in the display may be illuminated by a backlight having an array of light emitting diodes in each array of cells. Reflectors are used to reflect the light from the light emitting diodes through the array of pixels. Within the cell, the reflector has a cross-sectional shape that serves to distribute the light emitted from the light emitting diode towards the edge of the cell. The light diffuser layer for the backlight may have a partially reflective layer such as a thin film interference filter having an angle-dependent transmittance. Within each cell, the reflector may have a cross-sectional shape with parabolic or elliptical portions. [Selection diagram] Figure 8

Description

This application is based on International Patent Application No. PCT / US18 / 15776, filed January 29, 2018, US Patent Application No. 15 / 819,085, filed November 21, 2017, and March 2017. Claims priority to U.S. Provisional Patent Application No. 62 / 466,492, filed March 3, which is hereby incorporated by reference in its entirety.
The present invention relates generally to displays, and more specifically to backlit displays.

  Electronic devices often include displays. For example, computers and cellular phones may include backlit liquid crystal displays. The lateral backlight unit has a light emitting diode that emits light into the edge of the light guide plate. The light guide plate then disperses the emitted light laterally across the display to act as backlight illumination. Direct backlight units have an array of light emitting diodes that emit light vertically through the display.

  Direct-type backlights may have locally light and dark tunable light-emitting diodes to allow extended dynamic range. However, if care is not taken, the direct backlight can be thick and can also produce non-uniform backlight illumination.

  The display may have a pixel array, such as a liquid crystal pixel array. The pixel array may be illuminated with backlight illumination from a backlight unit. The backlight unit may include an array of light emitting diodes and a light reflector that serves to reflect light from the light emitting diodes through the pixel array. Each light emitting diode may be placed in a respective cell. In each cell, the light reflector may have a cross-sectional shape that includes a parabolic or elliptical portion.

  A diffuser in the display may be used to homogenize the light from the array of light emitting diodes. The diffuser may be overlaid with a phosphorescent layer and other optical films.

  The light emitting diode may be a blue light emitting diode. A partially reflective layer may be interposed between the diffuser and the array of light emitting diodes. The partially reflective layer may be formed from a stack of dielectric layers on the diffuser. The stack of dielectric layers may form a thin film interference filter having angle-dependent transmittance.

  The light emitting diode may be attached to the printed circuit and may protrude through the opening in the light reflector. The light reflector may be formed from a reflective material such as a reflective white layer or from a dielectric stack forming a thin film interference mirror.

FIG. 8 is a diagram of an exemplary electronic device having a display according to one embodiment.

FIG. 6 is a side cross-sectional view of an exemplary display, according to one embodiment.

FIG. 6 is a top view of an exemplary light emitting diode array for a direct backlight unit, according to one embodiment.

FIG. 3 is a side sectional view of an exemplary light emitting diode, according to one embodiment.

FIG. 6 is a side cross-sectional view of an exemplary light emitting diode within a cavity reflector showing how light can be emitted from the light emitting diode at various angles according to one embodiment.

6 is a graph illustrating how the light emitting diode and the reflective layer of FIG. 5 may be overlaid with a layer having a light transmittance that varies with angle according to one embodiment.

FIG. 6 is a perspective view of a cell of a cavity reflector for a backlight unit, according to one embodiment. FIG. 6 is a perspective view of a cell of a cavity reflector for a backlight unit, according to one embodiment.

FIG. 6 is a top view of a portion of a backlight unit, according to one embodiment.

FIG. 8 is a side cross-sectional view of an exemplary cavity reflector of the type shown in FIG. 7, according to one embodiment.

FIG. 9 is a side sectional view of an exemplary cavity reflector of the type shown in FIG. 8, according to one embodiment.

FIG. 6A is a cross-sectional view of an exemplary cavity reflector including a portion having an elliptical contour, according to one embodiment.

FIG. 6A is a cross-sectional view of an exemplary cavity reflector including a portion having a parabolic contour, according to one embodiment.

FIG. 6 is a side cross-sectional view of an exemplary stack of dielectric layers, such as alternating refractive index dielectric layers, forming a thin film interference filter, according to one embodiment.

FIG. 6 is a side cross-sectional view of an exemplary light interference layer, such as a prism film, according to one embodiment.

FIG. 6 is a side cross-sectional view of an exemplary microlens array layer, according to one embodiment.

FIG. 6 is a side cross-sectional view of an exemplary diffuser layer, according to one embodiment.

FIG. 6 is a side cross-sectional view of an exemplary display, according to one embodiment.

  The electronic device may be equipped with a backlit display. Backlit displays may include liquid crystal pixel arrays or other display structures that are backlit by light from a direct backlight unit. FIG. 1 shows a perspective view of an exemplary electronic device of the type that may include a display with a direct backlight unit. The electronic device 10 of FIG. 1 is a computing device such as a laptop computer, a computer monitor including an embedded computer, a tablet computer, a cellular phone, a media player, or other handheld or portable electronic device, a wristwatch device, a pendant device. Does not include devices, headphones or earphones, devices embedded in glasses or other equipment worn on the user's head, or other smaller devices such as other wearable or miniature devices, televisions, embedded computers Embedded systems such as computer displays, gaming devices, navigation devices, and systems that mount electronic devices with displays on kiosks or automobiles. Temu may be a device or other electronic device, implements two or more functions of these devices.

  As shown in FIG. 1, device 10 may include a display, such as display 14. The display 14 may be mounted within the housing 12. Enclosure 12 may also be referred to as an enclosure or case and may be plastic, glass, ceramic, fiber composite, metal (eg, stainless steel, aluminum, etc.), other suitable material, or any of these materials. It can be formed by a combination of any two or more. The housing 12 may be formed using a unitary construction in which some or all of the housing 12 is machined or molded as a single structure, or multiple structures (eg, an inner frame structure, an outer housing). May be formed using one or more structures that form the surface).

  The housing 12 may have a stand, such as the optional stand 18, and a plurality of parts (eg, housing parts that move relative to each other to form a laptop computer or other device having moving parts). ), May have the shape of a cellular phone or tablet computer (eg, in an arrangement in which the stand 18 is omitted), and / or have other suitable configurations. The configuration of the housing 12 shown in FIG. 1 is exemplary.

  The display 14 includes conductive capacitive touch sensor electrodes or other touch sensor components (eg, resistive touch sensor components, acoustic touch sensor components, force-based touch sensor components, light-based touch). It may be a touch screen display that incorporates layers of sensor components or the like, or it may be a non-touch sensitive display. Capacitive touch screen electrodes may be formed from an array of indium tin oxide pads or other transparent conductive structures.

  Display 14 may include an array of pixels 16 formed from liquid crystal display (LCD) components, or may have an array of pixels based on other display technologies. A side sectional view of the display 14 is shown in FIG.

  As shown in FIG. 2, display 14 may include a pixel array, such as pixel array 24. Pixel array 24 may include an array of pixels, such as pixel 16 of FIG. 1 (eg, an array of pixels having rows and columns of pixels 16). The pixel array 24 may be formed from a liquid crystal display module (sometimes referred to as a liquid crystal display or liquid crystal layer) or other suitable pixel array structure. The liquid crystal display forming the pixel array 24 is, for example, an upper polarizer and a lower polarizer, a thin film transistor layer interposed between the upper polarizer and the lower polarizer, and a color filter layer and a thin film transistor layer. It may include a layer of liquid crystal material. If desired, other types of liquid crystal display structures may be used to form the pixel array 24.

  An image may be displayed on the pixel array 24 during operation of 14. A backlight unit 42 (sometimes referred to as a backlight, backlight layer, backlight structure, backlight module, backlight system, etc.) is used to generate backlight illumination 44 that passes through the pixel array 24. Good. This illumination illuminates any image on pixel array 24 for viewing by an observer, such as observer 20 viewing display 14 in direction 22.

  The backlight unit 42 may include the optical film 26, a light diffuser 34 such as a light diffuser (light diffuser layer), and the light emitting diode array 36. Light emitting diode array 36 may include a two dimensional array of light sources, such as light emitting diodes 38 that produce backlight illumination 44. The light emitting diodes 38 may be arranged in rows and columns, for example, and may be in the XY plane of FIG.

  The light emitting diodes 38 may be collectively controlled by control circuitry within the device 10 or (eg, to implement a local dimming mechanism that helps improve the dynamic range of the image displayed on the pixel array 24). It may be controlled individually. The light generated by each light emitting diode 38 travels upward along the dimension Z through the light diffuser 34 and the optical film 26 and then through the pixel array 24. Light diffuser 34 may include light scattering structures that help diffuse the light from light emitting diode array 36, and thereby provide uniform backlight illumination 44. Optical film 26 may include films such as dichroic filter 32 phosphor layer 30 and film 28. The film 28 may include a brightness enhancement film that helps to collimate the light 44, thereby enhancing the brightness of the display 14 relative to the user 20 and / or other optical film (eg, compensation film).

  The light emitting diode 38 can emit light of any suitable color. In one exemplary configuration, light emitting diode 38 emits blue light. The dichroic filter layer 32 may be configured to pass blue light from the light emitting diode 38 while reflecting light of other colors. The blue light from the light emitting diode 38 is converted to white light by a photoluminescent material such as a phosphor layer 30 (eg, a layer of white phosphor material or other photoluminescent material that converts blue light to white light). May be done. If desired, other photoluminescent materials may be used to convert the blue light into different colored light (eg, red light, green light, white light, etc.). For example, one layer 30 (sometimes referred to as a photoluminescent layer or color conversion layer) may include quantum dots that convert blue light into red and green light (eg, red, green, and blue). Such as to produce white backlight illumination with components etc.). It is also possible to use a configuration in which the light emitting diode 38 emits white light (for example, the layer 30 may be omitted if desired).

  In configurations in which layer 30 emits white light, such as white light produced by the phosphorescent material in layer 30, white light emitted in the downward (−Z) direction from layer 30 is directed by dichroic filter layer 32. , May be reflected back up through the pixel array 24 as backlight illumination (ie, the layer 32 may serve to reflect the backlight outward from the array 36). For example, in a configuration in which layer 30 includes red and green quantum dots, dichroic filter 32 reflects red and green light from red and green quantum dots, respectively, to direct the backlight outward from array 36. It may be configured to help reflect. By placing the photoluminescent material of the backlight 42 (eg, the material of layer 30) over the diffuser layer 34, the light emitting diodes 38 are positioned at the edges of the cells rather than the centers of the light emitting diode cells (tiles) of the array 36. It may be configured to emit more light towards, thereby helping to improve the uniformity of the backlight illumination.

  FIG. 3 is a top view of an exemplary light emitting diode array for the backlight 42. As shown in FIG. 3, the light emitting diode array 36 may include rows and columns of light emitting diodes 38. Each light emitting diode 38 may be associated with a respective cell (tile area) 38C. The length D of the edge of the cell 38C is 2 mm, 18 mm, 1 to 10 mm, 1 to 4 mm, 10 to 30 mm, 5 mm, 10 mm, 15 mm, 20 mm, 25 mm, 20 mm, 15 mm, 10 mm. , Or any other suitable size. If desired, hexagonal tiled arrays and arrays having light emitting diodes 38 configured in other suitable array patterns may be used. In an array with rectangular cells, each cell may have sides of equal length (eg, each cell has a square outline with four equal length cell edges surrounding each light emitting diode). May have) or each cell may have sides of different length (eg, rectangular shape rather than square). The configuration of FIG. 3 in which light emitting diode array 36 has rows and columns of square light emitting diode regions, such as cells 38C, is merely exemplary.

  If desired, each cell 38C is formed from an array of light emitting diode dies (eg, a plurality of individual light emitting diodes 38 arranged in an array such as a cluster of 2 × 2 light emitting diodes in the center of each cell 38C). May have an integrated light source. For example, the light source 38 'in the lower left cell 38C of FIG. 3 is formed from a 2 × 2 array of light emitting diodes 38 (eg, four separate light emitting diode dies). The diodes 38 in the light source 38 'may be mounted on a common package board, mounted on a printed circuit board board that extends across the array 36, or using other suitable arrangements. It may be mounted in the array 36. In general, each cell 38C includes a single light emitting diode 38, a pair of light emitting diodes 38, 2-10 light emitting diodes 38, at least two light emitting diodes 38, at least four light emitting diodes 38, at least eight light emitting diodes 38, It may include a light source 38 'with less than five light emitting diodes 38, or any other suitable number of light emitting diodes. An exemplary configuration in which each cell 38C has a single light emitting diode 38 may be described herein as an example. However, this is merely an example. Each cell 38C may have a light source 38 having any suitable number of one or more light emitting diodes 38.

  FIG. 4 is a side sectional view of an exemplary light emitting diode. Light emitting diodes, such as light emitting diode 38 of FIG. 4, may have terminals such as contacts 58. The contacts 58 may be electrically coupled to a printed circuit or other substrate with a conductive material such as solder (eg, the light emitting diodes 38 may be soldered to an array such as the array 36 of FIG. 3, or It may be attached in another way). The light emitting diode 38 may have an n-type region 54 and a p-type region 56. Regions 54 and 56 may be formed on substrate 52 from a crystalline semiconductor material such as gallium nitride. Substrate 52 may be formed from a transparent crystalline material such as sapphire or other suitable substrate material. A reflector layer 50 (eg, distributed Bragg reflector) may be formed on the substrate 52 to help laterally direct the light emitted from the diode 38.

  FIG. 5 is a side sectional view of an exemplary light emitting diode. As shown in FIG. 5, each light emitting diode cell (tile) 38C in the light emitting diode array 36 may have a reflector such as a cavity reflector 68. The reflector 68 may have a square outline (ie, a square footprint when viewed from above) or any other suitable shape, and may be sheet metal (eg stamped). Sheet metal), metallized polymer film, metal sheet on plastic carrier, polymer film or dielectric film laminate forming dielectric mirror (thin film interference mirror) on molded plastic carrier, white reflective film (eg gloss coating, diffusion) Glossy white polymer sheet formed from a white ink layer or other white layer on a polymer carrier covered with a glossy coating such as a reflective white reflector or a specular white reflector), or other suitable It may be made from a reflector structure. If desired, the reflector 68 is a cholesteric liquid crystal whose Bragg reflectance is controlled by the birefringence (difference in refractive index) and pitch of the material and can be singular or chirped for bandwidth control. A layer that may be formed from layers or that has a sufficiently large index difference (eg, n> 0.1) between adjacent layers, such as a stack of polymer layers or layers of other materials. It may be an interference filter using the laminated body of. The polymer layer laminate is, for example, a laminate in which polyethylene terephthalate (PET) and polymethyl methacrylate (PMMA) films are alternately laminated, or a polyethylene naphthalate (PEN) and PMMA film is alternately laminated. Good. The light emitting diodes 38 may be soldered or otherwise attached to the metal traces in the printed circuit 60. A central opening in the reflector 68 may receive the light emitting diode 38. The cells in reflector 68 may have a cross-sectional shape with curved portions that serve to reflect light from diode 38 upwards as backlight illumination 44. In one exemplary configuration, a polymer film (eg, a film coated with a dielectric thin film interference mirror surface or a glossy white reflective surface) may be embossed using a roller (eg, a heated roller). The pattern structure above may be used to thermoform the film). The opening of each light emitting diode 38 may be cut with a die cutting tool or other cutting device following a thermoforming operation that forms the curved walls of the reflector 68 within each cell 38C.

  As shown in FIG. 5, a transparent structure, such as a transparent dome structure 70, may be formed on the light emitting diode 38 to help laterally distribute the light from the light emitting diode 38. The dome structure 70 may be formed from beads of transparent silicon or other transparent polymer (as an example). In operation, the light emitting diode 38 emits light refracted away from the Z axis by the dome structure 70. Rays such as ray 80 emitted from light emitting diode 38 may be characterized by an angle A with respect to surface normal n of light emitting diode 38. The light 80 traveling parallel to the Z dimension is parallel to the surface normal n (angle A = 0 °). Light 80 traveling parallel to the XY plane travels perpendicular to the Z dimension and the surface normal n (ie, A = 90 °). Light 80 traveling in other angles towards surface normal n is characterized by an intermediate value of angle A.

  Some rays of light 80 are oriented at a relatively large angle A and are reflected upwards from reflector 68 in direction Z (see, for example, ray 82 reflected from reflector 68 as reflected ray 84). Want). The other rays of light 80 are oriented at a smaller angle A. For example, ray 90 is oriented at a smaller angle A value with respect to surface normal n. Larger angle rays (filtering closer to the edge of cavity 38C while reflecting downward at least some of the vertical rays (A = 0 °) or near-normal rays in the center of cell 38C, such as ray 86). An angle-dependent filter or other layer that is at least partially reflective, such as layer 96, serves to help pass light rays striking 96 onto the reflector 34. It may be interposed between the bodies 68). For example, a ray, such as ray 90, is reflected outwardly and downwardly (-Z direction) by layer 96, as indicated by ray 92, and then upwardly (+ Z direction), as indicated by ray 94. May be returned.

  Layer 96 may be formed from a plurality of dielectric layers 96 '(eg, layer 96 may be a high refractive index formed from layers of silicon oxide, silicon nitride, and / or other inorganic or organic materials). It may be a thin film interference filter formed from dielectric stacks of alternating material and low material, and / or with layers formed from other dielectric materials and / or layers to form a thin film interference filter. May be). In one exemplary configuration, there are 5 layers 96 ', 3 to 6 layers 96', more than 3 layers 96 ', or less than 10 layers 96' within layer 96 ( As an example). A configuration in which layer 96 is formed from one or more layers of reflective material (eg, a single layer of thick material, or two or more layers of material, etc.) without forming a thin film interference filter, or A configuration may be used in which layer 96 includes both a thick coating layer or layers and a thin film interference filter formed from a stack of dielectric layers. If desired, the partially reflective layer 96 is a cholesteric material whose Bragg reflectance is controlled by the birefringence (index difference) and pitch of the material and can be singular or chirped for bandwidth control. It may be formed of a layer of liquid crystal or it may have a sufficiently large index difference (eg, n> 0.1) between adjacent layers, such as a stack of polymer layers or layers of other materials. It may be a bandpass interference filter using a laminated body of layers. The polymer layer laminate is, for example, a laminate in which polyethylene terephthalate (PET) and polymethyl methacrylate (PMMA) films are alternately laminated, or a polyethylene naphthalate (PEN) and PMMA film is alternately laminated. Good.

  The light diffuser 34 and / or other structures within the backlight 42 may comprise any light homogenizing structure to help ensure uniform uniformity of the backlight 44. For example, a pattern of light blocking structures such as structures 88 and reflective structures may be formed on the bottom surface of layer 96. Structure 88 is a dot, ring, square pad, pseudo-random of light-reflecting and blocking pads patterned to block more light emitted at the center of cell 38C than at the edges of cell 38C. It may include patterns or other structures. The structure 88 serves to allow light at the edges of the cell 38C to pass upwards toward the film 26 while reflecting and / or absorbing light emitted axially at the center of the cell 38C. Formed from patterned ink, patterns of reflective protrusions, patterned angle-dependent thin film interference filter layers, and / or other light-reflective and light-scattering structures. This helps to reduce hot spots in the middle of cell 38C and otherwise level out the variations in light intensity that may occur when light from array 36 is diffused by light diffuser 34. The structure 88 may be formed on the lower (inner) surface of the layer 96 and is also used to carry a separate substrate (eg, a different substrate than the layer 96 and / or the substrate support layer 96). ) May be formed above or at any other suitable location within the backlight unit 42.

  During operation, at least a portion of the light from light emitting diode 38 (eg, light 86 in FIG. 5) emitted directly upward at the center of cell 38C is provided by optional structure 88 and / or by layer 96. It is reflected downward. The reflected light is laterally diffused (eg, by reflecting from the cavity reflector 68). Other light, such as light 82 emitted laterally from the light emitting diode 38, may be reflected from the cavity reflector 68 without being reflected from the structure 88 or layer 96 and may pass upward through the diffuser 34. It can function as the backlight 44. Light 90 reflects from layer 96 and reflector 68 before passing upwards as light 94.

  By allowing light near the edge of each cell 38C to pass directly through the diffuser 34 while recirculating light near the center of each cell 38C, the intensity of light near the edge of each cell 38C is adjusted to each cell. It can be increased for the intensity of light near the center of 38C. This helps ensure that the backlight 44 is uniform over the surfaces of the light diffuser 34 and the backlight 42. If desired, light scattering particles 72 (eg, microbeads, hollow microspheres, bubbles, and bubbles) in the polymer or other material forming diffuser layer 34 to help diffuse the emitted light. (Or other light scattering particles) may be embedded. The light scattering particles 72 may have a refractive index different from the refractive index of the polymer forming the diffuser 34. For example, the index of refraction of particles 72 may be higher than the index of refraction of the polymer or other material used in forming layer 34, or it may be lower than the index of refraction of diffuser 34. In addition to, or instead of, including light scattering particles 72 in diffuser 34, light scattering features (projections, ridges, and / or other protrusions on the top and / or bottom surface of light diffuser 34, Grooves, holes, or other depressions) may be formed. In some configurations, the light is in addition to, or instead of, the diffuser 34, a photoluminescent layer within the backlight unit 42 (eg, a photoluminescent layer, which may be formed from phosphors and / or quantum dots). It may be diffused using the sense layer 30).

  In the exemplary configuration of FIG. 5, a single structure 88 (eg, a single pad) is provided above the light emitting diode 38 of each cell 38C. Clusters of pads (round pads, square pads, or other shaped pads) may be formed above each light emitting diode if desired. The density of pads within each cluster (eg, the number of pads per unit area and / or the area consumed by pads per unit area) may vary as a function of position. For example, each pad cluster may have more and / or larger pads near the center of the pad cluster than near the edge of the pad cluster. The use of graded structures, such as pad clusters with graded pad densities (eg, pads centered over diode 38), can help to reduce hotspots in cell 38C smoothly. .. If desired (eg, in a configuration where layer 96, lens 70, and / or other structure in backlight unit 42 is configured to homogenize emitted light without structure 88). ) The structure 88 may be omitted.

  In the exemplary configuration of FIG. 5, a partially reflective layer (eg, a thin metal layer, a stack of dielectric film layers, one or more other portions) between light diffuser 34 and light emitting diode 38, such as layer 96. Reflective layer). Layer 96 may be formed as a coating on the underside of diffuser 34, embedded in diffuser 34, and / or separate from diffuser 34. Light reflected downwards from layer 96 may be reflected upwards back by the cavity reflector 68. Thereby, the presence of layer 96 serves to enhance the number or reflection for each ray, thus enhancing the homogenization of the emitted light from light emitting diode array 36 before it passes through layer 34. If desired, further diffusion may be provided by a diffusion coating on the diffuser 34 and / or other layers within the backlight unit 42 (eg, of the diffuser 34 with embedded light scattering particles 72). A diffusion coating may be formed from the top polymer layer). The density of the light scattering particles 72 may have a gradient if necessary.

  In configurations where the partially reflective layer 96 is formed using a thin film interference filter arrangement, the layer 96 includes a dielectric layer 96 '. Layer 96 ′ of layer 96 may be, for example, a material such as an inorganic layer of various refractive indices (eg, aluminum oxide, silicon oxide, silicon nitride, titanium oxide, other metal oxides, nitrides, and / or oxynitrides). And layers of high refractive index and layers of low refractive index are alternately laminated). Layer 96 ′ may be configured to form a thin film interference filter, where the transmission spectrum of layer 96 varies as a function of angle of incidence. This causes the transmittance T of the light at a given wavelength λ, such as the wavelength λb of FIG. 6, that may be associated with the blue light emitted by the diode 38, to vary depending on the angle of incidence of that light on the layer 96.

  As shown in FIG. 6, layer 96 also exhibits a transmission spectrum 110 when exposed to light from diode 38 at angle A1 (eg, near 0 ° and parallel to surface normal n in FIG. 5). Well, the transmission spectrum 112 may be shown for light traveling at an angle near the angle A2 (for example, 45 °). Due to variations in the transmission spectrum of layer 96 as a function of angle of incidence, blue light at λb is at least partially reflected when characterized by angle of incidence A1 (eg, transmittance T is less than a given amount). , And when characterized by an A2 greater than A1 or an angle of incidence greater than A2, the reflectance is even lower (eg, the transmittance T is greater than a given amount). As shown by the curve in FIG. 6, at least a part of the blue light (for example, the light of wavelength λb) emitted from the light emitting diode 38 at the center of the cell 38C is directly upward (parallel to the surface normal n). ) When emitted, it is reflected and therefore recycled, whereas blue light emitted at a more oblique angle A is able to pass when it hits layer 96. This may help reduce hot spots of light emitted at the center of cell 38C.

  Configuring the shape of the reflector 68 within each cell 38C to help trap light that is diffused laterally outward from the light emitting diode 38 in the center of each cell 38C toward the periphery of each cell 38C. Can further reduce hot spots.

  The perspective view of FIG. 7 illustrates an exemplary configuration of a portion of the reflector 68 that covers the exemplary cell 38C. As shown in the example of FIG. 7, the reflectors 68 of the cells 38C are such that each of the walls of the reflectors 68 is flush with the printed circuit 60 along the peripheral edge 38E of the cell 38C (eg, The height may be increased to the height H in FIG. 5). As a result, the height of the reflector 68 along each edge 38E between the opposing cell corners 38D (the distance between the point on the edge 38E and the printed circuit 60) is constant and the reflector 68's Each edge follows a straight line along each linear cell edge 38E. In this configuration, the contours of cells 38C (eg, edge-to-edge contour 152) taken along the X or Y dimension are at midpoints along the cell edges 38E (eg, opposite corners of edge 38E). At the point of half the distance between the end points of the section), go up to the vertex 38E '. The cross-sectional shape of the cell 38C taken along the diagonal direction (between the respective corner portions 38D) such as the contour 154 between the corner portions rises to the apex at the cell corner portion 38D. Each vertex of the contour between the cell edges (eg, the midpoint 38E ′ of the edge) corresponds to each vertex of the contour between the cell corners above the printed circuit 60 (the end point of the edge 38E, It is located at the same distance (the height H in FIG. 5) as the corner point 38D).

  In the example of FIG. 8, the reflector 68 of the cell 38C is configured so that the reflector 68 does not rise to the same height H at each point along the edge portion 38E. Rather, the edges 38E have a curvilinear shape that descends toward their midpoints. Specifically, each edge 38E is characterized by a maximum height H at a corner 38D (the end of the curved edge 38E) and a minimum height that is less than H at the center of that edge 38E. Is characterized by Therefore, the height of the reflector 68 along each edge 38E between the opposing cell corners 38D is not constant, and each edge of the reflector 68 follows a curve that hangs along the cell edge 38E. The cross-sectional shape of the reflector 68 of the cell 38C of FIG. 8 taken along the X or Y dimension (eg, the contour 152 between the cell edges) is less than H at a midpoint along the cell edge 38E. Of the cell 38C taken along the diagonal direction between the corners 38D, such as the contour 154 between the respective parts, is the same as that of the reflector 68 of the cell 38C in FIG. (Similarly) The cell corner 38D rises to the top of height H. Therefore, each vertex of the contour between the cell edge portions (point 38E ′) is located closer to the printed circuit 60 than each vertex of the contour between the cell corner portions (point 38D).

  FIG. 9 is a top view of a portion of array 36. The cross-sectional shape between the edges of the reflector 68, such as contour 152 in FIGS. 7 and 8, is taken along line 204 and the line of sight is at 206. The cross-sectional shape between each portion of the reflector 68, such as the contour 154 of FIGS. 7 and 8, is taken along line 200 and the direction of the line of sight is 202. The edge point 38E ′ is located at a distance ED in the X and Y directions from the light emitting diode 38, where ED is half the cell dimension (cell edge length) D. Corner point 38D is located a distance DD from light emitting diode 38 along dimension 208, which dimension is defined by an axis oriented at an angle of 45 ° with respect to both the X and Y axes of FIG. ..

  10 and 11 are side cross-sectional views of exemplary reflector configurations of cells 38C in array 36.

  The arrangement shown in FIG. 10 corresponds to an arrangement of the type shown in FIG. 7, in which the edge 38E is straight. The reflector portion 68-1 corresponds to a portion of the reflector 68 that extends between the light emitting diode 38 and the corner 38D of the cell 38C and has a curved shape that matches the contour 154 of the reflector 68 of the cell 38C of FIG. Has a contour. The reflector portion 68-2 corresponds to a portion of the reflector 68 extending between the light emitting diode 38 and the edge midpoint 38E ′ of the cell 38C, and has a curved contour corresponding to the contour 152 of the cell 38C of FIG. Have. As shown in FIG. 10, both points 38E ′ and 38D in this type of arrangement are located at a distance H from the plane in which the printed circuit 60 resides.

  The arrangement shown in FIG. 11 corresponds to a configuration of the type shown in FIG. 8 in which the edges 38E are curved and hang down toward the printed circuit 60 at the location between the corners 38D. The reflector portion 68-1 of FIG. 11 corresponds to the portion of the reflector 68 extending between the light emitting diode 38 and the corner 38D of the cell 38C and matches the contour 154 of the reflector 68 of the cell 38C of FIG. It has a curved contour. The reflector portion 68-2 corresponds to a portion of the reflector 68 extending between the light emitting diode 38 and the edge midpoint 38E ′ of the cell 38C, and has a curved contour corresponding to the contour 152 of the cell 38C of FIG. Have. The point 38D at the corner of the cell 38C in this type of arrangement is located a distance H from the plane in which the printed circuit 60 resides, and the edge midpoint, such as point 38E ', is less than H from the plane in which the printed circuit 60 resides. It is located at a distance of H '.

  If desired, the reflector 68 may have a Fresnel shape, in which the reflector 68 has a series of concentric circles each having a contour that corresponds to a corresponding portion of the contour, such as contour 152 or 154. Ring 68-3 of. When a Fresnel reflector structure (reflection Fresnel lens structure) is used for the reflector 68, the maximum separation between the reflector 68 and the printed circuit 60 in this type of arrangement is in the type of configuration shown in FIGS. 7 and 8. The distance between the printed circuit 60 and the layer 96 can be minimized since it can be less than the maximum separation between the reflector 68 and the printed circuit 60.

  12 and 13 show that the cross-sectional shape of the reflector 68 may have elliptical or parabolic portions to enhance the homogeneity of the emitted light 44.

  FIG. 12 shows an example in which an elliptical shape is used for the cross-sectional shape portion of the reflector 68 in the cell 38C. As shown in FIG. 12, the light emitting diode 38 is associated with a virtual image at position F1 (position of reflection of the light emitting diode 38 on the layer 96). This position may form one of the two foci of the ellipse used to define a portion of the contour of the reflector 68. Two exemplary ellipses are shown in the example of FIG. The ellipse 220 has a first focus F1 and a second focus F2. The ellipse 222 has a first focus F1 and a second focus F2 ′. The focal points F2 and F2 ′ may be in the plane of the layer 96. The portion 220 'of the ellipse 220 may form a contour between the edges of the reflector 68, such as the contour 152 of FIGS. The portion 222 ′ of the ellipse 222 may form a contour between the edges of the reflector 68, such as the contour 154 of FIGS. 7 and 8.

  FIG. 13 shows an example in which a parabolic shape is used for the cross-sectional shape portion of the reflector 68 in the cell 38C. As shown in FIG. 13, the reflector 68 may have a cross-sectional shape including a parabolic portion (for example, a cross-sectional shape between edges and / or a cross-sectional shape between corners). The point PF1 may be associated with a parabolic focus defining the shape of part of the contour of the reflector 68. The axis of symmetry of the parabola may be oriented at a non-zero angle with respect to the X axis (as shown by axis 242) or have any other suitable orientation (eg, horizontal axis 240). See). If desired, the parabolic axis of symmetry and the parabolic focus may have other suitable positions (see, for example, focus PF2).

  The elliptical and parabolic contours of the reflector 68 may help distribute the light from the light emitting diodes 38 evenly over the surface of each cell 38C, each cell 38C emitting uniform backlight illumination 44. This is demonstrated by the ray trace model. The reflector 68 may have other shapes if desired. The use of elliptical and parabolic contours on the portion of reflector 68 is exemplary.

  14, 15, 16 and 17 show exemplary layers that may be incorporated into the backlight 42.

  Optical layers such as the optical film 26 in the backlight 42 may include thin film interference filter layers. These layers may be formed from a stack of inorganic and / or organic dielectric layers of alternating refractive index (see, for example, the dielectric stack of layer 300 in FIG. 14). Thin film interference filters may form broadband (white light) reflectors (sometimes called mirrors or partial mirrors) and / or filters that reflect some colors of light more than others. May be formed (eg, forming a filter having a non-flat visible light reflectance spectrum). The thin film interference filter may be configured to transmit non-reflected light (eg, have high light transmittance at non-reflected wavelengths). A dielectric stack, such as the stack of layers 300 of FIG. 14, may be formed on a polymer or glass substrate and / or a layer of material that performs other functions (eg, as a thin film interference filter coating layer). May be combined with.

  If desired, a brightness enhancement film (sometimes referred to as a prism film, a light collimating layer, or a light collimating prism layer) may be used in collimating the light 44. FIG. 15 is a side sectional view of an exemplary prism film. As shown in FIG. 15, the prism film 302 has a series of parallel ridges 304 extending in the plane of the drawing and having a triangular cross-sectional shape. The ridges 304 may face upward (outward) toward the viewer to help collimate the light 44 toward the viewer.

  A microlens array layer, such as the exemplary microlens array layer 306 of FIG. 16, can be used to diffuse and homogenize light 44. Layer 306 may be relatively thin so as not to excessively increase the thickness of display 14. For example, layer 306 may be 5 to 100 micrometers thick, 10 micrometers or more thick, or less than 150 micrometers thick. In the example of FIG. 16, the upper (outward) surface 309 of layer 306 has an array of convex lenses, such as convex microlens 308, and the lower (inward) surface 311 of layer 306 is concave microlens 308. With an array of concave lenses such as. In general, any of the surfaces of layer 306 may be planar, any of the surfaces of layer 306 may have a convex lens, and / or any of the surfaces of layer 306 may have a concave lens. Good. The configuration of FIG. 16 is merely an example. Microlenses 308 may have about 15-25 micrometers, 10 micrometers or more, less than 30 micrometers, or other suitable lateral dimension, and have a height of about 3-20 micrometers. Good. A non-uniform pattern may be used for the microlenses 308 to reduce moiré effects.

  Optical layer 26 may include one or more light diffuser layers. In the exemplary configuration of FIG. 17, the light diffuser layer 310, which may also be referred to as a diffuser or diffuser layer, comprises a polymeric substrate, such as a substrate 312 having light scattering particles 314 (eg, titanium oxide particles) embedded therein. .. A diffuser configuration may be used if desired.

  An exemplary configuration of the display 14 with one or more layers, such as these layers, incorporated into the backlight 42 is shown in FIG. As shown in the exemplary configuration of FIG. 18, the backlight unit 42 may include a light source such as the light emitting diode array 36. Light from array 36 (eg, blue light from a blue light emitting diode in array 36) passes upward in the + Z direction through the layers stacked on array 36 and backlight illumination 44 of pixel array 24. As it goes out from the backlight unit 42.

  The backlight 42 of the display 14 of FIG. 18 may have a diffuser, such as the diffuser layer 310. The diffuser layer 310 may be located above the array 36. The lower surface of the diffuser layer 310 may be coated with a thin film interference filter 320. A filter 320 is constructed from a stack of dielectric layers of alternating refractive index (see, eg, the dielectric stack in FIG. 14) configured to partially transmit and partially reflect blue light. It may be formed. For example, the reflectance of the filter 320 (sometimes referred to as a blue light reflection filter or a partial reflection filter) at the blue wavelength is between 50% and 90%, 60% or more, less than 80%, or any other suitable value. (Eg, the filter may be a partially transmissive blue reflective filter, ie, partially transmissive for blue light). The filter may have higher or lower reflectivity for red and green wavelengths than for blue wavelengths.

  A photoluminescent layer, such as yellow phosphor layer 316, is used to cause at least some of the light from the light emitting diodes of array 36 (eg, at least some of the blue light from the blue light emitting diodes in array 36) to be red. It may be converted to green light, which allows layer 316 to emit white light backlight illumination 44. Some of the red and green light may be emitted downward. A thin film interference filter, such as filter 318, may be formed on the lower surface of layer 316 to prevent lateral leakage of red and green light. Filter 318 may be formed from a dielectric stack (eg, dielectric stack 300 of FIG. 14) configured to reflect red and green light while passing blue light (eg, filter 318 is , A blue transmissive, red and green reflective thin film interference filter).

  Microlens array layer 306 (FIG. 16) may be located above layer 316 and may be used to diffuse light 44 and prevent hot spots.

  The light 44 may be collimated towards the viewer 20 using one or more prism films 302. In the example of FIG. 18, the display 14 has two prism films 302. The prisms of film 302 may be oriented at right angles to each other. For example, if the prism of the lower prism film is parallel to the X axis, the prism of the upper prism film may be parallel to the Y axis. A reflective polarizer 322 may be positioned above the prismatic film 302 to help recirculate light and thereby improve backlight efficiency. The reflective polarizer 322 may reflect (recycle) orthogonal polarizations while allowing linearly polarized light to pass along a given axis.

  According to one embodiment, a display is provided that includes a plurality of pixels and a backlight configured to generate backlight illumination for the plurality of pixels, the backlight configured to emit light. And a reflector for reflecting the light from the light source through the plurality of pixels, the reflector being selected from the group consisting of a parabolic portion and an elliptical portion. Each cell has a cross-sectional shape.

  According to another embodiment, the pixel comprises an array of pixels and the light source comprises a two-dimensional array of light sources arranged in a two-dimensional array of respective cells.

  According to another embodiment, each light source comprises at least one light emitting diode.

  According to another embodiment, a display includes a light diffuser layer interposed between an array of light emitting diodes and an array of pixels and a partially reflective layer interposed between the light diffuser layer and the array of light emitting diodes. Including and

  According to another embodiment, the partially reflective layer is selected from the group consisting of a thin film interference filter with angle-dependent light transmission properties, a cholesteric liquid crystal layer, and a stack of alternating refractive index polymer films. Includes a partially reflective layer.

  According to another embodiment, the display comprises a printed circuit, a light emitting diode is mounted on the printed circuit, and within each cell a reflector has four straight edges surrounding each one of the light emitting diodes. However, the points along each of the four edges are separated from the printed circuit by a common distance.

  According to another embodiment, the display includes a printed circuit, the light emitting diode is mounted on the printed circuit, and within each cell, the reflector is between four corners and each pair of four corners. With four curvilinear edges extending to each of the four curvilinear edges, each of the four curvilinear edges having a first distance from the printed circuit and a first distance from the printed circuit. Also have midpoints that are a short second distance apart.

  According to another embodiment, a display includes a light diffuser layer interposed between an array of pixels and an array of light emitting diodes, the partially reflective layer including a coating on the light diffuser layer and the reflector , A glossy white reflector, a diffuse white reflector, a specular white reflector, a stack of thin film dielectric layers forming a thin film interference mirror, a cholesteric liquid crystal layer, and a stack of polymer films with alternating refractive indices. Including a reflector selected from the group consisting of:

  According to another embodiment, the reflector comprises a reflector selected from the group consisting of a gloss white reflector, a diffuse white reflector, or a specular white reflector.

  According to another embodiment, the reflector is a reflection selected from the group consisting of a stack of thin film dielectric layers forming a thin film interference mirror, a cholesteric liquid crystal layer, and a stack of alternating refractive index polymer films. Including the body.

  According to another embodiment, the light emitting diode comprises a blue light emitting diode and the display comprises a partially reflective layer interposed between the light emitting diode and the array of pixels.

  According to another embodiment, the light source comprises at least two light emitting diodes.

  According to one embodiment, there is provided a display comprising an array of pixels and a backlight configured to generate backlight illumination for the array of pixels, the backlight configured to emit light. A two-dimensional array of light emitting diode cells, each of which includes at least one light emitting diode, and a reflector that reflects light from the light emitting diode through the array of pixels, the reflector having a parabolic portion. Each cell has a cross-sectional shape.

  According to another embodiment, a display is a light diffuser layer interposed between an array of pixels and an array of light emitting diodes, the light emitting diodes being configured to emit blue light. It further includes a body layer and a coating on the light diffuser layer that forms a thin film interference filter having an angle dependent transmission.

  According to another embodiment, the light emitting diode is configured to emit blue light.

  According to another embodiment, the display includes a printed circuit, the light emitting diode is mounted on the printed circuit, and within each cell the reflector has four corners and four extending between the corners. And each point along each of the four linear edges is separated from the printed circuit by a common distance.

  According to another embodiment, the display includes a printed circuit, the light emitting diode is mounted on the printed circuit, and within each cell, the reflector is between four corners and each pair of four corners. With four curvilinear edges extending to each of the four curvilinear edges, each of the four curvilinear edges having a first distance from the printed circuit and a first distance from the printed circuit. Also have midpoints that are a short second distance apart.

  According to another embodiment, the reflector comprises a layer selected from the group consisting of a layer having a stack of dielectric layers forming a thin film interference mirror and a gloss white layer.

  According to another embodiment, the light emitting diode comprises a white light emitting diode.

  According to one embodiment, there is provided a display comprising an array of pixels and a backlight configured to generate backlight illumination for the array of pixels, the backlight configured to emit light. And arranged in a two-dimensional array of cells, each including a two-dimensional array of light emitting diodes and a reflector that reflects light from the light emitting diodes through the array of pixels, the reflector having an elliptical shape. Each cell has a cross-sectional shape having a portion.

  According to another embodiment, the light emitting diode comprises a blue light emitting diode and the display comprises a light diffuser layer interposed between the array of pixels and the array of light emitting diodes and a thin film interference having an angle-dependent transmittance. And a coating on the light diffuser layer to form a filter, the reflector comprising a layer having a stack of dielectric layers forming a thin film interference mirror and a layer selected from the group consisting of a gloss white layer.

  According to one embodiment, a display is provided that includes a pixel configured to display an image and a backlight configured to generate backlight illumination for the pixel, the backlight emitting light. A two-dimensional array of light emitting diode cells each including at least one light emitting diode configured to emit light; a reflector having a curvilinear cross-sectional shape for reflecting light from the light emitting diodes through the array of pixels; A microlens array layer between the pixel and the two-dimensional array of light emitting diode cells.

  According to another embodiment, the backlight comprises a phosphor layer between the microlens array layer and the two-dimensional array of light emitting diode cells and a diffuser between the phosphor layer and the two-dimensional array of light emitting diode cells. A layer and a first thin film interference filter on the diffuser layer and a second thin film interference filter on the phosphor layer.

  According to another embodiment, the backlight includes a diffuser layer between the phosphor layer and the two-dimensional array of light emitting diode cells.

  According to another embodiment, the backlight includes a first thin film interference filter on the diffuser layer and a second thin film interference filter on the phosphor layer.

  According to one embodiment, the light emitting diode comprises a blue light emitting diode configured to emit blue light, wherein the first thin film interference filter is configured to partially transmit blue light and the second thin film The interference filter is configured to transmit blue light and reflect red and green light generated in the phosphor layer in response to the blue light, and the backlight includes pixels and a microlens array layer. And a reflective prism between the second prism film and the pixel.

  According to another embodiment, the first thin film interference filter is configured to partially transmit blue light.

  According to another embodiment, the second thin film interference filter is configured to transmit blue light and reflect the red and green light generated in the phosphor layer in response to blue light.

  According to another embodiment, the backlight includes first and second prism films between the pixels and the microlens array layer.

  According to another embodiment, the backlight includes a reflective polarizer between the second prism film and the pixel.

  The foregoing is merely exemplary and various changes may be made to the described embodiments. The embodiments described above may be implemented individually or in any combination.

Claims (30)

Multiple pixels,
A backlight configured to generate backlight illumination for the plurality of pixels, the display comprising:
The backlight is
A light source configured to emit light, and disposed within each of the plurality of cells,
A reflector that reflects light from the light source through the plurality of pixels,
A display wherein the reflector has a cross-sectional shape within each cell having a portion, the portion selected from the group consisting of a parabolic portion and an elliptical portion.   The display of claim 1, wherein the pixel comprises an array of pixels and the light source comprises a two-dimensional array of the light sources arranged within a two-dimensional array of the respective cells.   The display of claim 2, wherein each light source comprises at least one light emitting diode. A light diffuser layer interposed between the array of light emitting diodes and the array of pixels;
The display of claim 3, further comprising a partially reflective layer interposed between the light diffuser layer and the array of light emitting diodes.   The partially reflective layer comprises a thin film interference filter having angle-dependent light transmission properties, a cholesteric liquid crystal layer, and a partially reflective layer selected from the group consisting of a stack of polymer films with alternating refractive indices, The display according to claim 4.   A printed circuit is further provided, wherein the light emitting diode is mounted to the printed circuit, and in each cell the reflector has four linear edges surrounding each one of the light emitting diodes; 6. The display of claim 5, wherein points along each of the edges of the display are spaced a common distance from the printed circuit.   A printed circuit, wherein the light emitting diode is mounted to the printed circuit, and the reflector in each cell extends between four corners and four reflectors each extending between each pair of the four corners. A curved edge, each of the four curved edges having a first distance from the printed circuit at a first distance and a second distance shorter than the first distance from the printed circuit. 6. The display of claim 5, having a midpoint separated by a distance of.   6. The display of claim 5, further comprising a light diffuser layer interposed between the array of pixels and the array of light emitting diodes, the partially reflective layer including a coating on the light diffuser layer.   9. The display of claim 8, wherein the reflector comprises a reflector selected from the group consisting of a gloss white reflector, a diffuse white reflector, and a specular white reflector.   9. The display of claim 8 including a reflector selected from the group consisting of a stack of thin film dielectric layers forming a thin film interference mirror, a cholesteric liquid crystal layer, and a stack of polymer films of alternating refractive index.   4. The display of claim 3, wherein the light emitting diode comprises a blue light emitting diode, and the display further comprises a partially reflective layer interposed between the light emitting diode and the array of pixels.   The display according to claim 2, wherein each light source has at least two light emitting diodes. An array of pixels,
A backlight configured to generate backlight illumination for the array of pixels, the display comprising:
The backlight is
A two-dimensional array of light emitting diode cells each including at least one light emitting diode configured to emit light;
A reflector for reflecting light from the light emitting diode through the array of pixels,
A display in which the reflector has a cross-sectional shape having a parabolic portion in each cell. A light diffuser layer interposed between the array of pixels and the array of light emitting diodes;
14. The display of claim 13, further comprising: a coating on the light diffuser layer that forms a thin film interference filter having an angle-dependent transmission.   15. The display of claim 14, wherein the light emitting diode is configured to emit blue light.   A printed circuit further comprising the light emitting diode mounted to the printed circuit, the reflector having four corners in each cell, and four straight edges extending between the corners. 16. The display of claim 15 having a portion, wherein each point along each of the four straight edges is a common distance from the printed circuit.   A printed circuit is further provided, wherein the light emitting diode is mounted on the printed circuit, and in each cell the reflector extends between four corners and each of the four corners has a respective pair of four corners. A plurality of curvilinear edges, each of the four curvilinear edges being at a first distance from the printed circuit and a distance from the printed circuit being greater than the first distance. 16. The display of claim 15, having midpoints separated by a second short distance.   16. The display of claim 15, wherein the reflector comprises a layer selected from the group consisting of a layer having a stack of dielectric layers forming a thin film interference mirror and a gloss white layer.   14. The display of claim 13, wherein the light emitting diodes include white light emitting diodes. A display comprising an array of pixels and a backlight configured to generate backlight illumination for the array of pixels, comprising:
The backlight is
A two-dimensional array of light emitting diodes configured to emit light and disposed within a two-dimensional array of cells,
A reflector for reflecting light from the light emitting diode through the array of pixels,
A display, wherein the reflector has a cross-sectional shape within each cell having an elliptical portion. The light emitting diode comprises a blue light emitting diode,
The display is
A light diffuser layer interposed between the array of pixels and the array of light emitting diodes;
A coating on the light diffuser layer to form a thin film interference filter having angle-dependent transmittance,
21. The display of claim 20, wherein the reflector comprises a layer selected from the group consisting of a layer having a stack of dielectric layers forming a thin film interference mirror and a gloss white layer. A pixel configured to display an image,
A backlight configured to generate backlight illumination for the pixels, the display comprising:
The backlight is
A two-dimensional array of light emitting diode cells each including at least one light emitting diode configured to emit light;
A reflector having a curved cross-sectional shape for reflecting light from the light emitting diode through the array of pixels;
A microlens array layer between the pixel and the two-dimensional array of light emitting diode cells;
Including the display.   23. The display of claim 22, wherein the backlight further comprises a phosphor layer between the microlens array layer and the two-dimensional array of light emitting diode cells.   24. The display of claim 23, wherein the backlight further comprises a diffuser layer between the phosphor layer and the two-dimensional array of light emitting diode cells.   25. The display of claim 24, wherein the backlight further comprises a first thin film interference filter on the diffuser layer and a second thin film interference filter on the phosphor layer.   26. The display of claim 25, wherein the light emitting diode comprises a blue light emitting diode configured to emit blue light.   27. The display of claim 26, wherein the first thin film interference filter is configured to partially transmit the blue light. 28. The second thin film interference filter is configured to transmit the blue light and reflect the red and green light generated by the phosphor layer in response to the blue light. Display described in. 29. The display of claim 28, wherein the backlight further comprises first and second prism films between the pixels and the microlens array layer.   30. The display of claim 29, wherein the backlight further comprises a reflective polarizer between the second prism film and the pixels.

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