OLED display module structure for reducing visibility of dark spots in rear cover opening area

Abstract

A mobile computing device includes an emissive display panel configured to emit light from a front surface of the display panel, wherein the display panel has a plurality of transparent layers and an opaque back cover layer. The mobile computing device also includes a light sensor located behind the opaque back cover layer, and the opaque back cover layer includes an opening through which light from outside the display that is transmitted through the transparent layer of the display can reach the sensor. An air gap separates the light sensor from the transparent layer of the display panel. The plurality of transparent layers include a reflection attenuation layer on the back of the display panel, the reflection attenuation layer being configured to attenuate reflection of light from an interface between the transparent layer of the display panel and the air gap.

Description

Technical Field

[0001] The present disclosure relates to flat panel displays, and more particularly, to displays that include through-display optics (eg, optical sensors / emitters). Background Art

[0002] At least from a user experience perspective, it may be desirable to extend the display to cover more area of ​​a mobile device (e.g., a phone, tablet, etc.). However, electro-optical devices (e.g., a front-facing camera, a light sensor, a proximity sensor, etc.) located on a side of the mobile device that also includes a display may compete for real estate on the side of the device that includes the display. Therefore, sensors on the display side of the device may be located below the display so that light passes through the display to reach the sensors. However, the presence of the sensors below the display may cause undesirable distortion to the appearance of the display. Summary of the invention

[0003] In a first general aspect, a mobile computing device includes an emissive display panel configured to emit light from a front surface of the display panel, wherein the display panel has a plurality of transparent layers and an opaque back cover layer. The mobile computing device also includes a light sensor located behind the opaque back cover layer, and the opaque back cover layer includes an opening through which light from outside the display that is transmitted through the transparent layer of the display can pass to the sensor. An air gap separates the light sensor from the transparent layer of the display panel. The plurality of transparent layers includes a reflection attenuation layer on the back of the display panel, the reflection attenuation layer being configured to attenuate reflection of light from an interface between the transparent layer of the display panel and the air gap.

[0004] Implementations may include one or more of the following features alone or in combination with each other.

[0005] In an example, the display panel may include an active matrix organic light emitting diode (AMOLED) display.

[0006] In another example, the opaque back cover layer may include a metal layer configured to diffuse heat passing through the metal layer.

[0007] In another example, the reflection attenuating layer may include a first quarter wave plate, a linear polarizer, and a second quarter wave plate, wherein the linear polarizer is located between the first quarter wave plate and the second quarter wave plate.

[0008] In another example, the first quarter wave plate, the linear polarizer, and the second quarter wave plate can be located within the opening of the opaque back cover layer.

[0009] In another example, the first quarter wave plate, the linear polarizer, and the second quarter wave plate may be located between the front surface of the display panel and the back cover layer above the opaque back cover layer.

[0010] In another example, the linear polarizer and the second quarter wave plate may be located within the opening of the opaque rear cover layer, and the first quarter wave plate may be located between the front surface of the display panel and the rear cover layer above the opaque rear cover layer.

[0011] In another example, the first quarter wave plate may include a PET film layer.

[0012] In another example, the first quarter wave plate may include a combination of a PET film layer and a birefringent non-PET film layer.

[0013] In another example, one or more of the first quarter wave plate, the linear polarizer, or the second quarter wave plate can include a partially transmissive, partially opaque layer.

[0014] In another example, the reflection attenuating layer may include a partially transmissive, partially opaque layer that attenuates the intensity of light passing through the layer.

[0015] In another example, the partially transmissive, partially opaque layer may be located within the opening of the opaque back cover layer.

[0016] In another example, the partially transmissive, partially opaque layer may be located between the front surface of the display panel and the back cover layer over the opaque back cover layer.

[0017] In another example, the display panel may include a polarization layer that receives randomly polarized light from outside the display panel and circularly polarizes the light as the light propagates through the polarization layer.

[0018] In another example, the display panel may include an OLED emitter and a semiconductor circuit element configured to control the brightness of light emitted from the OLED emitter, wherein the semiconductor circuit element is shielded by at least some opaque structures in the display panel from direct light received from outside the display module. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1A Depicted is a top (front) surface of a mobile computing device including a display and optics occupying different portions of the front surface.

[0020] Figure 1B Depicted is a top (front) surface of a mobile computing device including a display and a light sensor positioned behind the display area according to a possible implementation of the present disclosure.

[0021] Figure 2A Depicted is a side cross-sectional view of a mobile device including multiple optical devices, each positioned behind a respective through-transmissive region of an emissive (eg, OLED, micro-OLED, or micro-LED) display, according to a possible implementation of the present disclosure.

[0022] Figure 2B Depicting a side cross-sectional view of a mobile device including multiple optical devices positioned by a single through-transmissive region of an emissive display in accordance with a possible implementation of the present disclosure.

[0023] Figure 3 Depicts a possible side cross-sectional view of an emissive display.

[0024] Figure 4 is a schematic diagram of a display panel and a sensor located below the display panel that interacts with an object at a distance from the front surface of the display panel.

[0025] Figure 5 is a schematic diagram of an embodiment of a display panel and a sensor located below the display panel, showing light propagating through the display panel to the sensor.

[0026] Figure 6 is a schematic diagram of another embodiment of a display panel and a sensor located below the display panel, showing light propagating through the display panel to the sensor.

[0027] Figure 7 is a schematic diagram of another embodiment of a display panel and a sensor located below the display panel, showing light propagating through the display panel to the sensor, including the polarization state of the light.

[0028] Figure 8 is a schematic diagram of another embodiment of a display panel and a sensor located below the display panel, showing light propagating through the display panel to the sensor, including the polarization state of the light.

[0029] Fig. 9A is a schematic diagram of another embodiment of a display panel and a sensor located below the display panel, showing light propagating through the display panel to the sensor.

[0030] Fig. 9B is a schematic diagram of another embodiment of a display panel and a sensor located below the display panel, showing light propagating through the display panel to the sensor.

[0031] The components in the drawings are not necessarily drawn to scale and may not be drawn to scale with respect to each other. Like reference numerals designate corresponding parts throughout the several views. DETAILED DESCRIPTION

[0032] The present disclosure describes a flat panel display (i.e., display) that can be used with a computing device (e.g., a mobile phone, a tablet computer, etc.). The front surface of the mobile device includes a display that typically operates as a graphical user interface (GUI), and one or more optical devices that operate as sensors / emitters in an area below the display and facing the front surface. The one or more optical devices can be configured for a variety of functions, including (but not limited to) sensing lighting conditions (e.g., an ambient light sensor), sensing the proximity of an object near the display (e.g., an electromagnetic sensor), and capturing images (e.g., a fingerprint sensor).

[0033] The proximity sensor may include a transmitter of electromagnetic radiation and a receiver for determining the proximity of the display to an object that reflects electromagnetic radiation transmitted by the transmitter, which is then reflected by the object and received by the receiver. For example, when a percentage of the intensity of the transmitted radiation received at the receiver after being reflected by the object exceeds a threshold, a signal from the proximity sensor may determine that the object is closer to the display than the threshold distance.

[0034] The fingerprint sensor may also include a transmitter and receiver of electromagnetic radiation for imaging a fingerprint pressed against a finger on the display. For example, radiation may be transmitted from the transmitter of the fingerprint sensor, reflected from the finger, and then detected by the receiver. The fingerprint pattern may be determined based on the reflected light received at the receiver and may be compared with stored data associated with the fingerprint.

[0035] An ambient light sensor may include a receiver of light and may determine an amount of ambient light received by the sensor.

[0036] Light sensors are used in many mobile devices. Recent advances in emissive display technology (e.g., active-matrix organic light-emitting diodes (AMOLEDs)) facilitate extending the emissive (i.e., active) area of ​​a display toward (e.g., to) the edge of a mobile device. By extending the active area of ​​a display toward the edge of a mobile device, a user can experience the advantages of a larger display without the disadvantages of a larger device. However, this may leave insufficient space for light sensors or other optical devices outside the area of ​​the emissive display on the front side of the mobile device.

[0037] The emissive displays disclosed herein are configured to share the front surface of a mobile device with one or more sensors so that the active area of ​​the display can extend to the edge without requiring gaps in the display or in the space around the display for the light sensors. Thus, one or more portions of the disclosed displays covering the light sensors can be configured so that the light sensors positioned behind the display can transmit and receive electromagnetic radiation through the display. Typically, an air gap separates the back of the display panel from the light sensors.

[0038] Ideally, when the light sensor is located below the display panel, light will pass through the display panel unimpeded to the sensor. However, in practice, light is scattered, absorbed, and reflected by elements within the display panel. Some reflected and / or scattered light may interfere with the operation of the pixel circuits in the display panel, resulting in unintended operation of at least some of the pixel circuits. Specifically, light (e.g., ambient light passing through the display) may reflect from the interface between the back of the display panel and the air gap between the panel and the light sensor, and then hit the semiconductor circuit that controls the pixel brightness of the OLED above the air gap. This reflected light may interfere with the expected brightness of the OLED, causing the OLED to have an intensity and / or color that is different from the intensity and / or color it is programmed to produce.

[0039] To mitigate this effect, structures are disclosed herein that reduce the amount of light reflected from the interface between the back of the display panel and the air gap between the panel and the light sensor. For example, an anti-reflective polarizer or attenuator can be placed at the interface to reduce reflections.

[0040] Traditionally, the display and the optical devices located on the surface of the device including the display have occupied separate areas of the front surface. For example, Figure 1A A mobile device 101 is depicted having a display 110 and a light sensor (eg, an ambient light sensor, a proximity sensor, etc.) 111 occupying different portions of a front surface.

[0041] Figure 1B A mobile device 102 is shown having a display 112 that extends toward an edge of the device and occupies a larger portion of the surface of the device 102 than the display 110 of the device 101. Unlike mobile devices in which the display is excluded from the area reserved for the optical device, the light emitting (i.e., active) area of ​​the display 112 extends substantially over the entire front surface. Thus, nearly the entire front surface of the mobile device 102 can be used to present color, black and white, or grayscale images, graphics, and / or characters. In some embodiments, the display 112 can include one or more areas 120, and the light sensor or emitter can be disposed behind (i.e., below) the area 120.

[0042] The size, shape and / or location of region 120 may be implemented in different ways. For example, Figure 1B The region 120 shown in FIG. 1 has a rounded (eg, circular) shape and is positioned separately from the edge of the display 112 , but this need not be the case. For example, the region 120 may have a rectangular shape and may be positioned along the edge of the display 112 .

[0043] Figure 2A Depicted is a side cross-sectional view of a mobile device having a display 112 having regions 120A, 120B through which electromagnetic radiation can be transmitted to an underlying optical device, such as a fingerprint sensor, an ambient light sensor, or a proximity sensor. The mobile device can include multiple optical devices 140A, 140B, each positioned behind a different region 120A, 120B. Figure 2B Depicted is a side cross-sectional view of a mobile device having a display 112 with a single region 120C for use by multiple optical devices 140A, 140B. The optical devices 140A, 140B can transmit and / or receive electromagnetic radiation 125 through the regions 120A, 120B, 120C.

[0044] Figure 3 A side cross-sectional view of an emissive display (eg, an AMOLED display) suitable for use with the mobile device of Figure 1 is shown. Although the principles of the present disclosure may be applied to display technologies other than AMOLED displays, implementations of AMOLED displays will be considered throughout this disclosure.

[0045] like Figure 3As shown, the AMOLED display 300 includes multiple layers that make up a display panel 360. These layers include a cover glass layer 310 that can form the front surface of the mobile device 102. In a possible embodiment, the display 300 can include a polarizer film layer 315. The display 300 can also include a touch sensor layer 320, which includes touch sensor electrodes 322. The pixels 337 of the display are formed by separate elements of the cathode layer 330, the OLED emitter stack 335, and the anode layer 336. The elements of the anode layer 336 can be reflective so that light emitted from the OLED emitter stack 335 is guided from the anode layer 336 in the vertical (z) direction. The elements of the anode layer 336 can be coupled to a thin film transistor (TFT) semiconductor structure 340 including a source, a gate, and a drain, and the TFT semiconductor structure 340 can be controlled by an electrical signal transmitted through a signal line 342. The display 300 may further include a transparent barrier layer 345 including, for example, SiNx or SiONx, and a transparent substrate layer 350 including, for example, polyimide (PI) and / or polyethylene terephthalate (PET). An opaque layer / film 370 for mechanical support, heat diffusion, and electrical shielding may be located below the display panel 360 to protect the display from local hot spots caused by heat generating components such as, for example, CPU, GPU, etc. in the mobile device, and from electrical signals / electrical noise from electrical components in the device located below the display 300.

[0046] The layers of display 300 may include transparent and non-transparent circuit elements. For example, TFT structures 340, pixels 337, signal lines 342, and / or touch sensor electrodes 322 may block light from propagating through display 300. Light may be reflected or absorbed by non-transparent (i.e., opaque) circuit elements.

[0047] Figure 44 is a schematic diagram of a mobile device 400 including a light sensor (e.g., a proximity sensor) 402 located below a display panel 404 that interacts with an object 406 at a distance D from a front surface of the display panel 404. The light sensor 402 may include a transmitter 408 and a receiver 410 of electromagnetic radiation (e.g., infrared light). An opaque layer 412 for heat diffusion and / or electrical shielding may be disposed between the display panel 404 and the proximity sensor 402, and / or the opaque layer 412 may be disposed between a layer including an OLED emitter of the display and the proximity sensor 402. The opaque layer 412 may include one or more openings through which electromagnetic radiation may pass when electromagnetic radiation is transmitted to and received from the object 406. In some embodiments, the electromagnetic radiation transmitted to and received from the object 406 may pass through different openings in the opaque layer 412 that are spatially separated from each other, and in some embodiments, the electromagnetic radiation transmitted to and received from the object may pass through the same opening. The proximity sensor 402 may operate by determining the amount (e.g., intensity) of electromagnetic radiation emitted from the transmitter 408, reflected from the object 406, and then received by the receiver 410. Under the assumption that the amount of light received, as measured by the intensity of the received light, increases monotonically as the distance D between the display panel 404 and the object 406 decreases, the amount of light received by the receiver 410 may be used as a signal of how close the front surface of the display panel 404 is to the object 406. The amount of light received at the receiver may be correlated with the distance between the object and the display panel, where the correlation is based on an empirical calibration between the received intensity and the distance, or based on a theoretical model of light propagation from the transmitter 408 to the object 406 and from the object 406 to the receiver 410, or a combination of both.

[0048] Figure 5 is a schematic diagram of an embodiment of a display panel 500 and a sensor 502 located below the display panel 500, showing light propagating through the display panel to the sensor. The sensor 502 may be coupled to a sensor module 503 that contains control electronics for operating the sensor.

[0049] The display panel may include multiple layers. For example, the display panel 500 may include: a cover glass layer 506; a polarizer layer, which may include a linear polarizer 508a and a quarter wave plate 508b that may reduce the amount of light reflected from the OLED layer in the panel that exits the front surface of the display; an encapsulation / touch sensor layer 510 containing touch sensor electrodes; a cathode layer 512; an OLED layer 514; a pixel circuit layer 516 containing an anode 518 for supplying current to the OLED; and semiconductor circuit elements 520, a PI layer 522, a PET layer 524, and an opaque back cover layer 526 for controlling the current supplied to the anode. The openings in the back cover layer 526 allow light from outside the display panel to pass through the panel and through the openings 528 to the sensor.

[0050] Figure 5 530 , 532 for light passing through the display panel 500 are shown, each of which shows possible reflections of the light within the panel. In one path 532, the light can traverse the transparent elements of the display panel and be reflected by the top surface of the back cover 526, so that the light is then directed back into the panel 500. However, due to the low reflectivity of the back cover 526 (e.g., 0.1% of the light in the incident light), the amount of light reflected from the top surface of the back cover 526 from the beam path 532 may be relatively small. In the other path 530, the light can traverse the transparent elements of the display panel and be reflected by the interface between the transparent layer (e.g., PET layer 524) and the air gap between the panel and the light sensor located below the opening 528 in the back cover 526 (i.e., due to the refractive index mismatch between the air and the transparent layer), which also causes light to be reflected from the interface back to the panel 500. Reflection from the interface of light path 530 can be significantly higher (e.g., 4% of the incident light) than reflection of light from the top surface of back cover layer 526 along path 532, and the difference results in more reflected light being exposed to the bottom surface of the semiconductor layer of the display pixel circuitry compared to the remainder of the display area covered by back cover 526.

[0051] In some cases, reflected light that strikes the semiconductor circuit element 520 can cause a reduction in light emission from the pixel, which in turn causes unexpected black spots in the display. For example, although the semiconductor circuit element 520 is shielded to avoid direct light that enters the front surface of the panel through the cover window layer 506 (e.g., through the anode 518 or the OLED itself), the reflected light (e.g., high-intensity short-wavelength light) that strikes the semiconductor circuit element 520 can increase the TFT leakage current of the circuit that controls the emission of light from the pixel. In some cases, the increase in leakage current may be due to the photoelectric effect caused by the reflected light on the circuit. The increase in the TFT leakage current of the circuit may cause the pixel controlled by the circuit to appear darker than expected. Since the semiconductor layer and the associated pixel circuit located above the opening 528 in the back cover 526 are hit by the higher intensity reflected light, the display panel 500 may appear to have an odd number of black spots above the location of the light sensor below the display compared to the remaining display area covered by the back cover 526.

[0052] Figure 6 is a schematic diagram of another embodiment of a display panel 600 and a sensor 602 located below the display panel 600, showing light propagating through the display panel to the sensor. The sensor 602 may be coupled to a sensor module 603 that contains control electronics for operating the sensor.

[0053] The display panel may include multiple layers. For example, the display panel 600 may include: a cover glass layer 606; a polarizer layer, which may include a linear polarizer 608a and a quarter wave plate 608b; an encapsulation / touch sensor layer 610 containing touch sensor electrodes; a cathode layer 612; an OLED layer 614; a pixel circuit layer 616 containing an anode 618 for supplying current to the OLED; and a semiconductor circuit element 620, a PI layer 622, a PET layer 624, and an opaque back cover layer 626 for controlling the current supplied to the anode. The opening 628 in the back cover layer 626 allows light from outside the display panel to pass through the panel and through the opening 628 to the sensor. The opening 628 may include a reflection attenuation layer on the back of the display panel, which includes a first film layer 630, a linear polarizer 632, and another quarter wave plate layer 634.

[0054] Figure 6Path 640 of light passing through display panel 600 is shown in FIG. 6. The structure of additional layers 630, 632, 634 in display panel 600 can be used to reduce the amount of light reflected from the interface between the panel and the air gap between the panel and light sensor 602 as compared to panel 500. For example, when light enters panel 600 through cover window layer 606, the light can be randomly polarized. Then, after passing through linear polarizer layer 608a that is polarized in a first direction in the plane of layer 608a, the light can be linearly polarized in the first direction. Then, after passing through quarter wave plate 610, the light can be circularly polarized in a first chirality (e.g., right circularly polarized).

[0055] In some embodiments, the first film layer 630 can include a birefringent material so that the layer 630 acts as a quarter wave plate for light transmitted through the layer. Thus, after passing through the first film layer 630 in the opening 628, the light can be linearly polarized in a second linear polarization direction, where the second linear polarization direction is orthogonal to the first linear polarization direction due to the film 608a. This second linear polarization direction of the light can be transmitted with near zero attenuation through the linear polarization layer 632, the polarization axis of the linear polarization layer 632 being aligned with the second linear polarization direction of the light. Then, after passing through the second quarter wave plate layer 634 in the opening 628, the light can be circularly polarized (e.g., left circularly polarized) with a second chirality opposite to the first chirality. When the light interacts with the interface between the bottom transparent layer 634 of the panel and the interface between the panel and the air gap between the light sensor 602, a first portion 642 of the light is transmitted through the interface and a second portion 644 is reflected from the interface. The reflected portion of the light has the chirality of its polarization reversed so that it is circularly polarized with the first chirality. Then, after passing through the quarter wave plate 634 again, the reflected light is linearly polarized in the first direction. Because the first linear polarization direction is orthogonal to the polarization axis of the linear polarization layer 632, the reflected light is sharply attenuated by the layer 632, and very little light 646 is transmitted through the layer 632 in the direction from the back of the panel toward the front of the panel. Therefore, very little reflected light reaches the pixel circuit layer 616 containing the semiconductor circuit element 620 for controlling the current provided to the anode 618 of the OLED. Therefore, the TFT leakage current of the pixel circuit is not increased, and the OLED emits its designed amount of light, so that black spots in the display above the opening 628 of the sensor 602 can be avoided.

[0056] In some embodiments, the transparent PET layer 624 of the display panel can introduce some polarization rotation to light passing through the layer 624. Therefore, the thickness, composition, and other material properties of the first film layer 630 can be selected so that the combination of the PET layer 630, which can include birefringent PET or non-PET materials, and the first film layer 630 acts as a quarter wave plate for light passing through the layer combination. In some embodiments, one or more of the layers 630, 632, 634 can be applied to the display panel 600 as a coating.

[0057] Figure 7 is a schematic diagram of another embodiment of a display panel 700 and a sensor 702 located below the display panel 700, showing light propagating through the display panel to the sensor. The sensor 702 may be coupled to a sensor module 703 containing control electronics for operating the sensor.

[0058] The display panel may include multiple layers. For example, the display panel 700 may include: a cover glass layer 706; a polarizer layer, which may include a linear polarizer 708a and a quarter wave plate 708b; an encapsulation / touch sensor layer 710 including touch sensor electrodes; a cathode layer 712; an OLED layer 714; a pixel circuit layer 716 including an anode 718 for supplying current to the OLED; and a semiconductor circuit element 720, a PI layer 722, a first film layer (e.g., a PET film layer) 724, and an opaque back cover layer 726 for controlling the current provided to the anode. The opening 728 in the back cover layer 726 allows light from outside the display panel to pass through the panel and through the opening 728 to the sensor. The reflection attenuation layer on the back of the display panel includes a first film layer 724, a linear polarizer 730, and a quarter wave plate layer 732, wherein at least some layers of the reflection attenuation layer are included in the opening 728. In some embodiments, one or more of the layers 724, 730, 732 may be applied to the display panel 700 as a coating.

[0059] Figure 7 Path 740 of light passing through display panel 700 is shown in FIG. A reflection attenuation layer in display panel 700 may be used to reduce the amount of light reflected from the interface between the panel and the air gap between the panel and light sensor 702. For example, when light enters panel 700 through cover window layer 706, the light may be randomly polarized. Then, after passing through linear polarizer layer 708a that is polarized in a first direction in the plane of layer 708a, the light may be linearly polarized in the first direction. Then, after passing through quarter wave plate 710, the light may be circularly polarized (e.g., right circularly polarized) with a first chirality.

[0060] In some embodiments, the first film layer 724, which may include a PET film in some embodiments, may include a birefringent material such that the layer 724 acts as a quarter wave plate for light transmitted through the layer. Thus, after passing through the first film layer 724, the light may be linearly polarized in a second linear polarization direction, wherein the second linear polarization direction is perpendicular to the first linear polarization direction. This second linear polarization direction of the light may be transmitted with near zero attenuation through the linear polarization layer 730, the polarization axis of which is aligned with the second linear polarization direction of the light. Then, after passing through the quarter wave plate layer 732 in the opening 728, the light may be circularly polarized in a second chirality opposite to the first chirality (e.g., left circular polarization). When the light interacts with the interface between the bottom transparent layer 732 of the panel and the interface between the panel and the air gap between the light sensor 702, a first portion 742 of the light is transmitted through the interface, and a second portion 744 is reflected from the interface. The reflected portion of the light has the chirality of its polarization reversed, such that it is circularly polarized in the first chirality. Then, after passing through the quarter wave plate 732 again, the reflected light is linearly polarized in the first direction. Because the first linear polarization direction is orthogonal to the polarization axis of the linear polarization layer 730, the reflected light is sharply attenuated by the layer 730, and very little light 746 is transmitted through the layer 730 in the direction from the back of the panel toward the front of the panel. Therefore, little reflected light reaches the pixel circuit layer 716 containing the semiconductor circuit element 720 for controlling the current provided to the anode 718 of the OLED. Therefore, the TFT leakage current of the pixel circuit is not increased, and the OLED emits its designed amount of light, so that black spots in the display above the opening 728 of the sensor 702 can be avoided.

[0061] Figure 8 800 and a sensor 802 located below the display panel 800, showing light propagating through the display panel to the sensor. The sensor 802 can be coupled to a sensor module 803 that contains control electronics for operating the sensor. Figure 6 and 7 The display panel 800 may include a reflection attenuation layer on the back of the panel, but unlike Figure 6 and 7 Unlike the display panel of FIG. 80 , the reflection attenuation layer in the panel 800 may be located above the opaque rear cover layer 826 .

[0062] Thus, the display panel may include multiple layers, such as a cover glass layer 806; a polarizer layer, which may include a linear polarizer 808a and a quarter wave plate 808b; an encapsulation / touch sensor layer 810 including touch sensor electrodes; a cathode layer 812; an OLED layer 814; a pixel circuit layer 816 including an anode 818 for supplying current to the OLED; and a semiconductor circuit element 820 for controlling the current supplied to the anode, a PI layer 822, a first film layer (e.g., a PET film layer) 824, a linear polarizer layer 830, a quarter wave plate layer 832, and an opaque back cover layer 826. The opening 828 in the back cover layer 826 allows light from outside the display panel to pass through the panel and through the opening 828 to the sensor. The reflection attenuation layer on the back of the display panel 800 above the opaque back cover layer 826 may include a first film layer 824, a linear polarizer layer 830, and a quarter wave plate layer 832. In some embodiments, one or more of the layers 824 , 830 , 832 can be applied to the display panel 800 as a coating.

[0063] exist Figure 8 In the illustrated embodiment, the first film layer 824, which may include a PET film in some embodiments, may include a birefringent material such that the layer 824 acts as a quarter wave plate for light transmitted through the layer. Thus, after passing through the first film layer 824, the light may be linearly polarized in a second linear polarization direction, wherein the second linear polarization direction is perpendicular to the first linear polarization direction. This second linear polarization direction of the light may be transmitted with near zero attenuation through the linear polarization layer 830, the polarization axis of the linear polarization layer being aligned with the second linear polarization direction of the light. Then, after passing through the quarter wave plate layer 832, the light may be circularly polarized (e.g., left circularly polarized) with a second chirality opposite to the first chirality. When the light interacts with the interface between the bottom transparent layer 832 of the panel and the interface between the panel and the air gap between the light sensor 802, a first portion 842 of the light is transmitted through the interface, and a second portion 844 is reflected from the interface. The reflected portion of the light has the chirality of its polarization reversed, so it is circularly polarized with the first chirality. Then, after passing through the quarter wave plate 832 again, the reflected light is linearly polarized in the first direction. Because the first linear polarization direction is orthogonal to the polarization axis of the linear polarization layer 830, the reflected light is sharply attenuated by the layer 830, and very little light 846 is transmitted through the layer 830 in the direction from the back of the panel toward the front of the panel. Therefore, very little reflected light reaches the pixel circuit layer 816 containing the semiconductor circuit element 820 for controlling the current provided to the anode 818 of the OLED. Therefore, the TFT leakage current of the pixel circuit is not increased, and the OLED emits its designed amount of light, so that black spots in the display above the opening 828 of the sensor 802 can be avoided.

[0064] In some cases, where the reflection attenuating layer is located above the opening 828 rather than at least partially within the opening Figure 8 Embodiments of may be easier to manufacture than embodiments in which a portion of the reflection attenuating layer is located in the opening 828, but the cost of materials (eg, for polarizing layers 824, 830, 832 that span the width of the display) may be higher.

[0065] Fig. 9A is a schematic diagram of another embodiment of a display panel 900 and a sensor 902 located below the display panel 900, showing light propagating through the display panel to the sensor. The sensor 902 can be coupled to a sensor module 903 containing control electronics for operating the sensor. The display panel 900 can include a reflection attenuating layer on the back side of the panel, wherein the reflection attenuating layer includes a partially transmissive, partially opaque layer or coating that attenuates the intensity of light passing through the reflection attenuating layer.

[0066] The display panel 900 may include multiple layers, such as a cover glass layer 906; a polarizer layer, which may include a linear polarizer 908a and a quarter wave plate 908b; an encapsulation / touch sensor layer 910 containing touch sensor electrodes; a cathode layer 912; an OLED layer 914; a pixel circuit layer 916 containing an anode 918 for supplying current to the OLED; and a semiconductor circuit element 920, a PI layer 922, and a clear PET film layer 924 for controlling the current supplied to the anode. An opening 928 in the back cover layer 926 allows light from outside the display panel 900 to pass through the panel and through the opening 928 to the sensor 902. The reflection attenuation layer on the back side of the display panel 900 within the opening 928 in the opaque back cover layer 926 may include a partially transmissive, partially opaque material layer 930 (e.g., a neutral density filter) that attenuates light passing through the reflection attenuation layer.

[0067] exist Fig. 9A In the illustrated embodiment, the transmittance of the partially transmissive, partially opaque material layer 930 can be selected so that sufficient transmitted light 942 passes through the layer 930 for the sensor 902 to function as designed, but so that when the light is transmitted through the layer twice (i.e., once in a direction toward the sensor 902 and once in a direction away from the sensor 902 after reflection from an interface with the air gap), the intensity of light 944 reflected from the air gap is sufficiently attenuated so that the reflected light 944 does not significantly interfere with the operation of the semiconductor circuit element 920 used to control the current provided to the anode 918 of the OLED emitter.

[0068] Fig. 9Bis a schematic diagram of another embodiment of a display panel and a sensor located below the display panel, showing light propagating through the display panel to the sensor, wherein the embodiment is similar to Fig. 9A 900, except that a partially transmissive, partially opaque layer 930 of material is located over the opaque back cover layer 926. In some embodiments, layer 930 can be applied to the display panel 900 as a coating.

[0069] In some embodiments, one or more of the reflection attenuation layers of the display panel 600, 700, or 800 may include a partially transmissive, partially opaque layer that attenuates the intensity of light passing through the reflection attenuation layer. For example, a quarter wave plate layer or a linear polarizer layer of the reflection attenuation layer of the display panel 600, 700, or 800 may include a partially transmissive, partially opaque layer.

[0070] The disclosed display has been presented in the context of a mobile device such as a tablet or smartphone. However, the disclosed principles and techniques may be more generally applied to any display where it is desirable to position a sensor behind the display. For example, a virtual agent home terminal, a television, or an automated teller machine (ATM) are a non-limiting set of alternative applications that may utilize a light sensor located behind the active area of ​​the display. Furthermore, the purpose of placing the light sensor behind the display is not limited to extending the display to the edge of the device. For example, it may be desirable to place the light sensor behind the display for aesthetic or stealth reasons.

[0071] In the specification and / or drawings, typical embodiments have been disclosed. The present disclosure is not limited to such exemplary embodiments. The use of the term "and / or" includes any and all combinations of one or more associated listed items. Unless otherwise specified, specific terms have been used in a general and descriptive sense, not for limiting purposes. As used in this specification, spatial relative terms (e.g., front, back, above, below, etc.) are intended to cover different orientations of the device in use or operation other than the orientation shown in the figures. For example, the "front surface" of a mobile computing device may be a surface facing the user, in which case the phrase "in front" means closer to the user. Additionally, the "top surface" of a display may be a surface facing the user, in which case the phrase "below" means deeper into the interior of the mobile computing device.

[0072] Although certain features of the described embodiments have been shown as described herein, many modifications, substitutions, changes and equivalents will now be apparent to those skilled in the art. Therefore, it should be understood that the appended claims are intended to cover all such modifications and changes that fall within the scope of the embodiments. It should be understood that they have been presented only by way of example and not limitation, and that various changes in form and detail may be made. Any part of the apparatus and / or method described herein may be combined in any combination, except mutually exclusive combinations. The embodiments described herein may include various combinations and / or sub-combinations of the functions, components and / or features of the different embodiments described.

Claims

1. A mobile computing device, comprising: an emissive display panel configured to emit light from a front surface of the display panel, the display panel having a plurality of transparent layers and an opaque back cover layer; a light sensor located behind the opaque back cover layer, wherein the opaque back cover layer includes an opening through which light from outside the display panel that is transmitted through the plurality of transparent layers of the display panel can pass to the sensor, wherein an air gap separates the light sensor from the plurality of transparent layers of the display panel, the light sensor being located behind an active area of ​​the display panel; in The plurality of transparent layers include a reflection attenuating layer on a back surface of the display panel, the reflection attenuating layer being configured to attenuate reflection of light from an interface between a transparent layer of the display panel and the air gap, The active area of ​​the display panel includes an OLED emitter and a semiconductor circuit element configured to control the brightness of light emitted from the OLED emitter, wherein the semiconductor circuit element is shielded from direct light received from outside the display panel by at least some opaque structures in the display panel.

2. The mobile computing device of claim 1, wherein: The display panel includes an active matrix organic light emitting diode (AMOLED) display.

3. The mobile computing device of claim 1 , wherein: The opaque back cover layer includes a metal layer configured to diffuse heat passing through the metal layer.

4. The mobile computing device of claim 1 , wherein: The reflection attenuation layer includes a first quarter wave plate, a linear polarizer, and a second quarter wave plate, wherein the linear polarizer is located between the first quarter wave plate and the second quarter wave plate.

5. The mobile computing device of claim 4, wherein: The first quarter wave plate, the linear polarizer, and the second quarter wave plate are positioned within the opening of the opaque back cover layer.

6. The mobile computing device of claim 4, wherein: The first quarter wave plate, the linear polarizer, and the second quarter wave plate are located between the front surface of the display panel and the back cover layer above the opaque back cover layer.

7. The mobile computing device of claim 4, wherein: The linear polarizer and the second quarter wave plate are located within the opening of the opaque back cover layer, and wherein the first quarter wave plate is located between the front surface of the display panel and the back cover layer above the opaque back cover layer.

8. The mobile computing device of claim 4, wherein: The first quarter wave plate includes a PET film layer.

9. The mobile computing device of claim 4, wherein: The first quarter wave plate includes a combination of a PET film layer and a birefringent non-PET film layer.

10. The mobile computing device of claim 4, wherein: One or more of the first quarter wave plate, the linear polarizer, and the second quarter wave plate include a partially transmissive, partially opaque layer.

11. The mobile computing device of claim 1 , wherein: The reflection attenuating layer includes a partially transmissive, partially opaque layer that attenuates the intensity of light passing through the layer.

12. The mobile computing device of claim 11, wherein: The partially transmissive partially opaque layer is located within the opening of the opaque back cover layer.

13. The mobile computing device of claim 11, wherein: The partially transmissive partially opaque layer is located between the front surface of the display panel and the back cover layer over the opaque back cover layer.

14. A mobile computing device according to any one of claims 1 to 13, wherein: The display panel includes a polarization layer that receives randomly polarized light from outside the display panel and circularly polarizes the light as a result of the light propagating through the polarization layer.

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