Display device

Abstract

Display device comprising the following: a display panel (DP) that has a display area (DA) and a non-display area (NDA) outside the display area (DA); a light source (LS) positioned below the non-display area (NDA) of the display panel (DP) to illuminate the display panel (DP); a Directional Lighting Unit (DLU) located on an upper section of the Display Panel (DP); and an optical sensor (OS) located below the display panel (DP) that receives the light passing through the directional lighting unit (DLU) and the display panel (DP), the Directional Light Unit (DLU) comprises the following: a covering substrate (CS) arranged so that it faces the display panel (DP) which is to be brought into contact with the object; an optical element (OE) that contains the following: a light incidence element (OE_I) arranged between the cover substrate (CS) and the display panel (DP) and overlapping the light source (LS) at a position corresponding to the non-display area, wherein the light incidence element (OE_I) is configured to refract the light supplied by the light source (LS) at a first angle (θ1) to travel by total internal reflection from the non-display area (NDA) to the display area (DA); and a light emission element (OE_E) arranged between the cover substrate (CS) and the display panel (DP) in at least one section of a region where the light travels from the light source (LS), wherein the light emission element (OE_E) is configured to reflect a portion of the totally reflected light at a second angle (θ2) to an object carrying biometric information, and wherein the directional light unit (DLU) is further configured to direct light reflected by the object to the display panel (DP); and a first layer (LR) with low refractive power, which is arranged between the optical element (OE) and the display panel (DP), wherein the refractive indices of the cover substrate (CS) and the optical element (OE) are the same, and wherein the refractive index of the cover substrate (CS) is greater than a refractive index of the first layer (LR1) with low refractive power.

Description

BACKGROUND OF THE INVENTIONField of the invention

[0001] This disclosure relates to a display device, in particular to a display device capable of recognizing a fingerprint using directional light. Description of the state of the art

[0002] In recent years, with the advancement of information and communication technology, various information and communication-based systems have been developed, such as notebook computers, tablet personal computers (PCs), smartphones, personal digital assistants (PDAs), ATMs, and search guidance systems. Since these systems typically store a large amount of confidential data, such as personal information related to privacy, as well as business information and trade secrets, it is necessary to enhance security to protect confidential data.

[0003] For this purpose, a method for increasing security has been proposed using an image sensor capable of recognizing a user's biological information. For example, a fingerprint sensor can increase system security by registering and authenticating a user's fingerprint. The fingerprint sensor is used to recognize the user's fingerprint. An optical fingerprint sensor is widely known as the fingerprint sensor.

[0004] The optical fingerprint sensor operates on the principle of irradiating light using a light source such as a light-emitting diode (LED) and detecting the light reflected by the fingerprint ridges using a complementary metal oxide semiconductor (CMOS) image sensor. Because the optical fingerprint sensor requires scanning the fingerprint using the LED, it is necessary to provide an additional device for scanning the fingerprint. This additional device increases the size of the optical fingerprint sensor, which is why it has limitations in various applications, such as combining it with a display device.

[0005] Conventional optical fingerprint sensors are those disclosed in Republic of Korea Patent No. 10-0608171, filed on June 26, 2006, entitled “Display device having fingerprint recognition sensor,” and in Republic of Korea Patent Laid-Open No. 10-2016-0043216, published on April 21, 2016, entitled “Display device including fingerprint recognizing element.”

[0006] The display devices disclosed in the above-mentioned publications are configured so that display areas of the display devices can be used as touch areas and fingerprint recognition areas. However, the optical fingerprint sensor uses diffuse light with significantly lower directivity than fingerprint recognition light. Therefore, limitations exist in fingerprint recognition.

[0007] US 9 035 909 B2 describes a device for determining a location of at least one object on a touch surface. A light-transmissive panel defines the touch surface and includes a controllable reflective boundary. An illumination assembly introduces light into the panel. A control device selectively controls the reflective boundary so that light can pass through an opening in the reflective boundary between a first layer and a second layer. A light detection assembly measures the light that has passed through the opening and onto the touch surface. In one example, the illumination assembly includes an array of light emitters, the light detection assembly includes an array of light detectors, and each of the light emitters emits light in the form of a beam that is received by an opposing detector.

[0008] US 2012 / 0153134 A1 describes a touch-sensitive device for detecting touches on a surface of a translucent panel.

[0009] US 9 836 166 B2 describes an optical, touch-sensitive device capable of determining the locations of multiple simultaneous touch events.

[0010] Jefferson Y. Han: Low-Cost Multi-Touch Sensing through Frustrated Total Internal Reflection: Proceedings of the 18th annual ACM symposium on User interface software and technology, 2005, pp. 115-118, doi: 10.1145 / 1095034.1095054, describes an example of touch detection based on the attenuation of light passing through a light-conducting plate in total internal reflection, caused by a finger contact.

[0011] US 4,728,186 describes a device for acquiring data from an uneven surface. In one example, an LED is arranged in front of a beveled end face of a light-conducting plate, and a Lippmann hologram is arranged opposite a finger contact portion. An image extraction hologram and a detector are arranged at another portion of the plate.

[0012] As described above, in display devices using conventional optical fingerprint sensors, it is difficult to accurately recognize fingerprints, or a complicated and bulky optical device is required. Accordingly, it is difficult to combine them with a portable display device. SUMMARY

[0013] An object of this disclosure is to provide a display device capable of recognizing a fine fingerprint without a complicated structure such as a bulky optical device.

[0014] Another object of this disclosure is to provide a display device suitable for a display panel having an enlarged display area and a reduced screen frame area.

[0015] The objects are achieved by the features of the independent claim. According to one embodiment, a display device according to this disclosure includes a display panel having: a display surface and a non-display surface outside the display surface; a light source disposed below the non-display surface of the display panel to irradiate the display panel with light; a directional light unit disposed on an upper portion of the display panel, refracts the light supplied from the light source at a first angle to travel from the non-display surface to the display surface by total reflection, refracts a portion of the totally reflected light at a second angle, and then supplies the light reflected by an object having biometric information to the display panel; and an optical sensor disposed below the display panel and receiving the light output from the directional light unit.That is, the directional light unit can be arranged on a front side of the display panel, i.e., on the surface of the display panel capable of displaying an image. The light source and / or the optical sensor can be arranged on a rear side of the display panel, i.e., on the surface opposite the surface of the display panel capable of displaying an image. In other words, the display panel is arranged between the directional light unit and the light source.

[0016] The directional light unit includes: a cover substrate arranged to face the display panel to be brought into contact with the object; an optical element including a light exit element; the light exit element may be arranged between the cover substrate and the display panel in at least a portion of a region where the light from the light source travels at a position corresponding to the display surface; a light incident element arranged between the cover substrate and the display panel to be overlapped with the light source at a position corresponding to the non-display surface; and a first low-refractive power layer arranged between the optical element and the display panel.

[0017] The directional light unit further includes a second layer with low refractive power, which is arranged between the optical element and the cover substrate.

[0018] The directional light unit may further include an adhesive layer disposed between the optical element and the cover substrate. The directional light unit may further include a black matrix disposed to correspond to the optical element between the cover substrate and the adhesive layer to block a portion of the light emitted by the light source.

[0019] The directional light unit may further include a black matrix arranged to correspond to the light incident element between the cover substrate and the second low-refractive-power layer to block a portion of the light emitted from the light source.

[0020] The directional light unit may further include an adhesive layer disposed between the optical element and the second low-refractive-power layer. The directional light unit may further include a black matrix disposed to correspond to the light incident element between the adhesive layer and the second low-refractive-power layer to block a portion of the light emitted by the light source.

[0021] The light incident element may be configured to refract a portion of the light incident from the light source at a first angle, causing total internal reflection in the cover substrate, and transmit it to the cover substrate. The light that has been totally reflected from a top surface of the cover substrate and travels toward the light exit element may be reflected by the first low-refractive-power layer at a second angle smaller than the first angle to be transported to the cover substrate, and may travel to the optical sensor after being reflected by the object on the cover substrate.

[0022] The light incident element may be configured to refract a portion of the light incident from the light source at a third angle, causing total internal reflection in the optical element, and transmit it to the optical element. The light that has been totally reflected from a top surface of the optical element and travels toward the light exit element may be reflected at a fourth angle smaller than the third angle to be transported to the cover substrate, and may travel to the optical sensor after being reflected by the object on the cover substrate.

[0023] The light incident element may be configured to refract a portion of the light incident from the light source at a fifth angle, causing total internal reflection in the adhesive layer, and transmit it to the adhesive layer. The light that has been totally reflected from a top surface of the adhesive layer and travels toward the light exit element may be reflected at a sixth angle smaller than the fifth angle to be transported to the cover substrate, and may travel to the optical sensor after being reflected by the object on the cover substrate.

[0024] The refractive indices of the cover substrate, the adhesive layer, and the optical element may be the same. A refractive index of the cover substrate may be higher than a refractive index of the first low-refractive-power layer.

[0025] The refractive indices of the cover substrate and the optical element are the same, a refractive index of the first low-power layer may be the same as that of the second low-power layer, and a refractive index of the cover substrate is larger than that of the first low-power layer.

[0026] The refractive indices of the cover substrate, the adhesive layer, and the optical element may be the same, a refractive index of the first low-power layer may be the same as that of the second low-power layer, and a refractive index of the cover substrate may be larger than that of the first low-power layer.

[0027] The display panel may further comprise a polarizing plate disposed between the display panel and the first low-refractive-power layer. The polarizing plate, the first low-refractive-power layer, and the optical element may be of the same size.

[0028] The display panel may further include signal lines arranged to bypass a region overlapping the light incident element of the optical element and the light source.

[0029] The object may contain a fingerprint in which several papillary ridges and several grooves are arranged alternately.

[0030] In the above-described display device according to this disclosure, it is possible to reconstruct an image captured using a directional light unit and an optical sensor. Therefore, it is possible to recognize a fine fingerprint without a complicated structure such as a bulky optical device.

[0031] Furthermore, it is possible to apply the invention to a display panel having a reduced screen frame area (non-display area) since a light incident element of an optical element and a light source are arranged on the non-display portion of the display panel. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The accompanying drawings, which are included to further the understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. In the drawings: Fig. 1A is a planar view illustrating a display device according to an embodiment of this disclosure; Fig. Figure 1B is an enlarged planar view illustrating a Fig. Region R shown in Figure 1A; Fig. Figure 2 is a planar view illustrating an optical element used in a directional light unit of the invention shown in Fig. 1A; Fig. 3A is a cross-sectional view showing a display device according to a first embodiment of this disclosure along a Fig. 1A and which shows a light path passing through total internal reflection in the directional light unit; Fig. 3B is a cross-sectional view showing a display device according to the first embodiment of this disclosure along a Fig. 1A and showing a light path in which the light refracted by a light exit element of the optical element is converged onto an optical sensor; Fig. 4A is a cross-sectional view showing a display device according to a second embodiment of this disclosure along a Fig. 1A and which shows a light path passing through total internal reflection in the directional light unit; Fig. 4B is a cross-sectional view showing a display device according to the second embodiment of this disclosure along a Fig. 1A and showing a light path in which the light refracted by a light exit element of the optical element is converged onto an optical sensor; Fig. 5A is a cross-sectional view showing a display device according to a third embodiment of this disclosure along a Fig. 1A and which shows a light path passing through total reflection in the directional light unit; and Fig. 5B is a cross-sectional view showing a display device according to the third embodiment of this disclosure along a Fig. 1A and which shows a light path in which the light refracted by a light exit element of the optical element is converged onto an optical sensor. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] Hereinafter, embodiments of this disclosure will be described in detail with reference to the accompanying drawings. Throughout the specification, the same reference numerals denote the same elements. In the following description, a detailed description of well-known functions and configurations will be omitted in case there is a risk of obscuring essential aspects of the embodiments of the present invention. Furthermore, the names of elements used in the following description have been selected solely for the purpose of making this specification easy to read; in reality, they may have other names. Furthermore, as an example of the display device with an integrated touch sensor, a liquid crystal display device with an integrated touch sensor will be described in detail.

[0034] A display device according to an embodiment of this disclosure is described below with reference to the Fig. 1A and Fig. 1B.

[0035] Fig. 1A is a planar view illustrating a display device according to an embodiment of this disclosure, and Fig. Figure 1B is an enlarged planar view illustrating a Fig. Region R shown in Figure 1A.

[0036] As in the Fig. 1A and Fig. 1B, the display device according to the embodiment of this disclosure includes a display panel DP having a display area DA and a non-display area NDA, a directional light unit DLU coupled to the display panel DP, and an optical sensor OS.

[0037] Any display panel can be used as the display panel DP as long as the non-display surface NDA can transmit light. Typically, a display panel of an electroluminescent display device using a flexible translucent substrate can be used. A plurality of signal lines SL for supplying various control signals and data signals to display elements of the display surface DA can be arranged in the non-display surface NDA of the display panel DP. It is preferable that the plurality of signal lines SL be arranged so as to bypass a light source LS of the directional light unit DLU and a light incident element OE_I of an optical element OE so as not to obstruct any path of the light supplied from the light source LS.

[0038] The directional light unit DLU may include the light source LS, the optical element OE and a cover substrate (not shown).

[0039] The light source LS is arranged below the non-display surface NDA of the display panel DP to irradiate the display panel DP with light. It is preferable to use a light source capable of providing collimated light with high collimation, such as an infrared laser.

[0040] The optical element OE refracts the light supplied by the light source LS at a first angle to transport the light from the non-display surface NDA to the display surface DA in total internal reflection, and then reflects a portion of the totally reflected light at a second angle that is smaller than the first angle. The optical element OE then guides the light reflected by an object containing biometric information to the display panel DP.

[0041] The optical element OE includes a light incident element OE_I and a light exit element OE_O, which are separated by a predetermined distance. The light incident element OE_I and the light exit element OE_O are transparent holographic recording films, and the refractive index of each of the light incident element OE_I and the light exit element OE_O can be the same as, or slightly higher than, that of a cover substrate.

[0042] The light incidence element OE_I converts the light supplied from the light source LS into a propagation light. The propagation light is converted to have a constant diffusion angle θ in a horizontal plane consisting of a longitudinal axis and a width axis. In addition, the propagation light maintains its original collimated state in a vertical plane consisting of the longitudinal axis and a thickness direction axis. The diffusion angle θ can be set to be at least as large as an interior angle formed by two line segments connecting an incident point where light is incident and the two endpoints of the other side of the Fig. 2. The propagated light spreads while spreading in a triangular shape having a diffusion angle θ. The triangular area occupied by the diffusion of the propagated light becomes an image detection area (ISA).

[0043] If no object is present on a surface of the cover substrate, the propagation light 100 may be totally reflected in the cover substrate to travel inside the cover substrate. However, if an object is present on the surface of the cover substrate, a portion of the propagation light 100 is refracted by the object and exits to the outside of the cover substrate CS. For example, if an object containing biometric information is brought into contact with the image recognition area ISA of the cover substrate CS, a portion of the light is reflected or absorbed by the object, and a portion of the light is reflected and propagated inside the cover substrate.

[0044] More specifically, the object containing biometric information may include a finger with a fingerprint in which multiple ridges and multiple grooves are arranged alternately. If the object is a finger, the propagation light traveling toward the ridge portion of the fingerprint is absorbed by the ridge of the fingerprint and exits to the outside of the cover substrate. On the other hand, the propagation light traveling toward the groove portion of the fingerprint is reflected in the cover substrate and propagates.

[0045] From the light-emitting element OE_O, a portion of the propagated light 100 traveling inside the cover substrate exits to the display panel DP. If an object containing an image (for example, a human finger with a fingerprint) touches the top surface of the cover substrate CS, the light-emitting element OE_O causes a portion of the light refracted by the finger to be directed to the display panel DP.

[0046] The cover substrate may include a predetermined area capable of recognizing the object having biometric information. The predetermined area may be taken from a section area of ​​the image reading area, as shown in Fig. 2. The cover substrate CS may be made of transparent reinforced glass with a refractive index of approximately 1.5.

[0047] The optical sensor OS receives the light that has exited through the optical element OE and sends the light to a host system (not shown).

[0048] On the other hand, the directional light unit DLU may further include a low-refractive-power layer or the like. The exact configuration of the directional light unit DLU will be described in detail later with reference to the Fig. 3A to 5B.

[0049] In the above-described display device according to this disclosure, it is possible to reconstruct an image captured using the directional light unit DLU and the optical sensor OS. Therefore, it is possible to correctly recognize a fine fingerprint without a complicated structure such as a bulky optical device.

[0050] A display device according to a first embodiment of this disclosure is described below with reference to the Fig. 3A and Fig. 3B described.

[0051] Fig. 3A is a cross-sectional view showing a display device according to a first embodiment of this disclosure along a Fig. 1A and which shows a light path passing through total internal reflection in the directional light unit. Fig. 3B is a cross-sectional view showing a display device according to the first embodiment of this disclosure along a Fig. 1A and which shows a light path in which the light refracted by a light exit element of the optical element is converged onto an optical sensor.

[0052] As in the Fig. 3A and Fig. 3B, the display device according to the first embodiment of this disclosure includes a display panel DP having a display area DA and a non-display area NDA, a light source LS arranged to correspond to the non-display area NDA, a directing light unit coupled to the display panel DP for spreading and emitting the light from the light source LS, and an optical sensor OS that detects or senses the light from the directing light unit DLU.

[0053] Any display panel can be used as the display panel DP as long as the non-display area NDA can transmit light. Typically, a display panel of an electroluminescent display device using a flexible translucent substrate can be used. However, this disclosure is not limited thereto. A liquid crystal display (LCD), a plasma display panel (PDP), a field emission display (FED), or the like can be used in this disclosure if their non-display areas can transmit light. A polarizing plate POL can be attached to a top surface of the display panel DP to improve visibility.

[0054] The light source LS is arranged under the non-display surface NDA of the display panel DP to irradiate the display panel DP with light. It is preferable to use a light source capable of providing collimated light, such as an infrared laser.

[0055] The directional light unit may include a cover substrate CS, a low-refractive-power layer LR, and the light source LS. The directional light unit refracts the light supplied by the light source LS to propagate it from the non-display surface NDA to the display surface DA in total internal reflection, reflects a portion of the total internal reflection, and transmits the light reflected by the object containing biometric information to the display panel DP and the optical sensor OS.

[0056] The cover substrate CS may contain a predetermined area capable of detecting the object containing biometric information. The cover substrate CS may be made of transparent reinforced glass with a refractive index of approximately 1.5. A black matrix BM may be attached to the edge of the cover substrate CS so that it corresponds to the light source LS. The object containing biometric information may include a finger having a fingerprint F in which several grooves V and several papillary ridges R are alternately arranged.

[0057] The low-refractive-power layer LR is disposed between the cover substrate CS and the display panel DP. It is preferable that the low-refractive-power layer LR has a refractive index lower than that of the cover substrate CS. The refractive index of the low-refractive-power layer LR preferably resembles the refractive index of the object to be recognized. For example, if the display device of this disclosure is applied to fingerprint recognition, the low-refractive-power layer LR may have a refractive index of approximately 1.4, similar to the refractive index of human skin of 1.39.

[0058] The optical element OE is arranged between the cover substrate CS and the low-refractive-power layer LR and can include the light-incidence element OE_I and the light-outcidence element OE_O. The light-incidence element OE_I and the light-outcidence element OE_O are transparent holographic recording films. The refractive index of the light-incidence element OE_I and the light-outcidence element OE_O can be the same as, or slightly higher than, that of the cover substrate.

[0059] The light incident element OE_I is arranged to correspond to the non-display area NDA and is arranged to overlap the black matrix BM and the light source LS. The light incident element OE_I refracts a portion of the light incident from the light source LS at a first angle θ1, causing total internal reflection in the cover substrate CS, and transmits it to the cover substrate CS. Since the propagation light is already reflected with respect to Fig. 2, further explanations are omitted.

[0060] The light-output element OE_O may be arranged in at least a portion of an area where light from the light source LS travels at a position corresponding to at least a portion of the image recognition area ISA defined by the propagated light. In this case, the light-output element OE_O may be arranged at a predetermined distance from the light-input element OE_I. The light-output element OE_O reflects the incident light at a second angle θ2 smaller than the first angle θ1 and exits the reflected light at the cover substrate CS. The light is reflected by the object and propagated to the display panel DP and an optical sensor OS.

[0061] The optical sensor OS is located outside the display panel DP at a position corresponding to the light-emitting element OE_O of the optical element OE. The optical sensor OS detects the amount of light transmitted through the display panel DP.

[0062] An adhesive layer AD can further be arranged between the cover substrate CS and the optical element OE. The adhesive layer AD serves to couple the cover substrate CS to the optical element OE. The refractive index of the adhesive layer AD can be substantially the same as that of the cover substrate CS.

[0063] In the embodiment of the Fig. 3A and Fig. 3B, it is possible to integrate the polarizing plate POL, the low-refractive-power layer LR, and the optical element OE in a single process because they are essentially the same size.

[0064] Next, as in the Fig. 3A and Fig. 3B, a case will be described in which light emitted from the light source is converted into the propagation light by the optical element to move in the display area, and a case in which, after the propagation light is reflected by the object, the reflected light is converged to the optical sensor to capture an image of the object.

[0065] As in Fig. As shown in Figure 3A, the light emitted from the light source LS passes through the display panel DP, the polarizing plate POL, and the low-refractive-power layer LR, and is incident on the light incident element OE_I of the optical element OE. The light incident element OE_I refracts the incident light at a first angle θ1 to induce total internal reflection in the cover substrate CS. A portion of the light that has passed through the light incident element OE_I travels to the black matrix BM, and the remaining light is refracted at the first angle θ1 to travel from the non-display surface NDA to the display surface DA. Accordingly, it is possible to prevent the light from leaking into the non-display surface NDA because the light arriving at the black matrix BM is blocked by the black matrix BM.The adhesive layer AD and the cover substrate CS arranged on the optical element OE have essentially the same refractive index, so that the light refracted by the light incident element OE_I and then propagating into the display surface DA reaches the top surface of the cover substrate CS and is totally reflected. The totally reflected light is transmitted through the cover substrate CS and the adhesive layer AD and is totally reflected back onto the bottom surface of the optical element OE.That is, since the refractive index of the optical element OE is substantially similar to that of the cover substrate and the adhesive layer, and the refractive index of the low-refractive-power layer LR disposed under the optical element OE is smaller than that of the cover substrate, the light totally reflected at the top surface of the cover substrate CS is not transmitted through the low-refractive-power layer LR, but is totally reflected by the low-refractive-power layer LR, thereby moving back to the cover substrate CS. In this way, a part of the light emitted from the light source LS and refracted by the light incident element OE_I is reflected by total internal reflection between the top surface of the cover substrate CS and the bottom surface of the optical element OE, thereby moving to the region corresponding to the display area DA, as shown in FIG. Fig. 3A. In Fig. 3A, in the case where an object (e.g., a finger) having a fingerprint F with biometric information touches the top surface of the cover substrate CS, the light is absorbed when it hits the papillary ridge R of the fingerprint F, but the light is reflected when it hits the groove V of the fingerprint F. Accordingly, the light traveling to the top surface of the cover substrate CS maintains a total reflection state and propagates into the display surface DA.

[0066] As in Fig. As shown in Figure 3B, a portion of the light totally reflected from the upper surface of the cover substrate CS reaches the light-exiting element OE_O. The light, which—from the light reaching the light-exiting element OE_O—is scattered by patterns of the light-exiting element OE_O, is reflected at a second angle θ2 smaller than the first angle θ1, and maintains total reflection, and propagates into the cover substrate CS via the adhesive layer AD. At this time, when the finger touches the cover substrate CS, the light reaching the ridge R of the fingerprint F is absorbed, and the light reaching the groove V of the fingerprint F is reflected to pass through the adhesive layer AD, the optical element OE, the low-refractive-power layer LR, the polarizing plate POL, and the display panel DP.The optical sensor OS, located under the display panel DP, detects the amount of light reflected by the papillary ridge R and the groove V of the fingerprint F. The light detected by the optical sensor OS can be used to reconstruct the fingerprint pattern of the finger after being transmitted through output lines to an image capture IC (not shown).

[0067] In the display device according to the embodiment of the Fig. 3A and Fig. 3B of this disclosure, it is possible to reconstruct an image captured using the directional light unit and the optical sensor. Therefore, it is possible to correctly recognize a fine fingerprint without a complicated structure such as a bulky optical device.

[0068] In addition, it is possible to easily apply the invention to a display panel having a reduced screen frame area because a light incident element of an optical element and a light source are arranged on the non-display portion of the display panel.

[0069] Hereinafter, a display device according to a second embodiment of this disclosure will be described with reference to the Fig. 4A and Fig. 4B.

[0070] Fig. 4A is a cross-sectional view showing a display device according to a second embodiment of this disclosure along a Fig. 1A and which shows a light path passing through total internal reflection in the directional light unit. Fig. 4B is a cross-sectional view showing a display device according to the second embodiment of this disclosure along a Fig. 1A and which shows a light path in which the light refracted by a light exit element of the optical element is converged onto an optical sensor.

[0071] As in the Fig. 4A and Fig. 4B, the display device according to the second embodiment of this disclosure includes a display panel DP having a display area DA and a non-display area NDA, a light source LS arranged to correspond to the non-display area NDA, a directing light unit coupled to the display panel DP for spreading and exiting the light from the light source LS, and an optical sensor OS that detects or senses the light from the directing light unit DLU.

[0072] Any display panel can be used as the display panel DP as long as the non-display area NDA can transmit light. Typically, a display panel of an electroluminescent display device using a flexible translucent substrate can be used. However, this disclosure is not limited thereto. A liquid crystal display (LCD), a plasma display panel (PDP), a field emission display (FED), or the like can be used in this disclosure if their non-display areas can transmit light. A polarizing plate POL can be attached to a top surface of the display panel DP to improve visibility.

[0073] The light source LS is arranged under the non-display surface NDA of the display panel DP to irradiate the display panel DP with light. It is preferable to use a light source capable of providing collimated light, such as an infrared laser.

[0074] The directional light unit may include a first low-refractive-power layer LR1, an optical element OE, a second low-refractive-power layer LR2, and a cover substrate CS. The directional light unit refracts the light supplied from the light source LS to propagate it from the non-display surface NDA to the display surface DA in total internal reflection, reflects a portion of the total internal reflection, and transmits the light reflected by an object containing biometric information to the display panel DP and the optical sensor OS.

[0075] The cover substrate CS may contain a predetermined area capable of detecting the object containing biometric information. The cover substrate CS may be made of transparent reinforced glass with a refractive index of approximately 1.5. A black matrix BM may be attached to the edge of the cover substrate CS so that it corresponds to the light source LS. The object containing biometric information may include a finger having a fingerprint F in which several grooves V and several papillary ridges R are alternately arranged.

[0076] The first low-refractive-power layer LR1 is disposed between the cover substrate CS and the display panel DP. The second low-refractive-power layer LR2 is disposed between the cover substrate CS and the optical element OE. It is preferable that the first and second low-refractive-power layers LR1 and LR2 have a refractive index lower than that of the cover substrate CS. The refractive index of the first and second low-refractive-power layers LR1 and LR2 is preferably similar to the refractive index of the object to be recognized. For example, when the display device of this disclosure is applied to fingerprint recognition, the first and second low-refractive-power layers LR1 and LR2 may have a refractive index of about 1.4, similar to the refractive index of human skin of 1.39.

[0077] The optical element OE, arranged between the first and second low-refractive-power layers LR1 and LR2, includes a light incident element OE_I and a light exit element OE_O. The light incident element OE_I and the light exit element OE_O are transparent holographic recording films. The refractive index of the light incident element OE_I and the light exit element OE_O can be the same as, or slightly higher than, that of the cover substrate.

[0078] The light incident element OE_I is arranged to correspond to the non-display surface NDA and is arranged to overlap the black matrix BM and the light source LS. The light incident element OE_I refracts a portion of the light incident from the light source LS at a first angle θ1, causing total internal reflection in the optical element OE, and propagates it to the optical element OE. Since the first low-refractive-power layer LR1, which has a refractive index lower than that of the optical element OE, is arranged on the bottom surface of the optical element OE and the second low-refractive-power layer LR2, which has a refractive index lower than that of the optical element OE, is arranged on the top surface of the optical element OE, the light traveling into the optical element OE does not escape from the optical element OE but propagates into the optical element OE in total internal reflection.

[0079] The light-output element OE_O may be arranged in at least a portion of an area where light from the light source LS travels at a position corresponding to at least a portion of the image recognition area ISA defined by the propagation light. In this case, the light-output element OE_O may be separated from the light-input element OE_I by a predetermined distance. The light-output element OE_O reflects the incident light at a second angle θ2 smaller than the first angle θ1 and exits the reflected light at the cover substrate CS. The light is reflected by the object, thereby propagating to the display panel DP and an optical sensor OS.

[0080] The optical sensor OS is located outside the display panel DP at a position corresponding to the light-emitting element OE_O of the optical element OE. The optical sensor OS detects the amount of light transmitted through the display panel DP.

[0081] In the embodiment of the Fig. 4A and Fig. 4B, it is possible to integrate the polarizing plate POL, the first low-refractive-power layer LR1, and the optical element OE in a single process because they are essentially the same size.

[0082] Next, as in the Fig. 4A and Fig. 4B, a case will be described in which light emitted from the light source is converted into the propagation light by the optical element to move in the display area, and a case in which, after the propagation light is reflected by the object, the reflected light is converged to the optical sensor to capture an image of the object.

[0083] As in Fig. As shown in Figure 4A, the light emitted from the light source LS passes through the display panel DP, the polarizing plate POL, and the first low-refractive-power layer LR1, and is incident on the light incident element OE_I of the optical element OE. The light incident element OE_I refracts the incident light at a first angle θ1 to induce total internal reflection in the optical element OE. A portion of the light that has passed through the light incident element OE_I travels to the black matrix BM, and the remaining light is refracted at the first angle θ1 to travel from the non-display surface NDA to the display surface DA. Accordingly, it is possible to prevent the light from leaking into the non-display surface NDA because the light arriving at the black matrix BM is blocked by the black matrix BM.The light refracted by the light incident element OE_I and then propagated into the display surface DA is totally reflected in the optical element OE because the first and second low-refractive-power layers LR1 and LR2 are disposed on the bottom and top surfaces of the optical element OE, respectively. That is, the light that was totally reflected on the top surface of the optical element OE is totally reflected again onto the bottom surface of the optical element OE, thereby propagating in a total reflection state in the optical element OE. In this way, a part of the light emitted from the light source LS and refracted by the light incident element OE_I is incident on a region corresponding to the display surface DA by the total reflection between the top surface of the optical element OE and the bottom surface of the optical element OE, as shown in FIG. Fig. 4A shown.

[0084] As in Fig. As shown in Figure 4B, the light propagating in total internal reflection in the optical element OE reaches the light-exiting element OE_O. The light reaching the light-exiting element OE_O is scattered by patterns of the light-exiting element OE_O and reflected at a second angle θ2 smaller than the first angle θ1. The light reflected at the second angle θ2 passes through the light-exiting element OE_O and then travels to the cover substrate CS via the second low-refractive-power layer LR2. At this time, when the finger touches the cover substrate CS, the light reaching the ridge R of the fingerprint F is absorbed, and the light reaching the groove V of the fingerprint F is reflected to the second low-refractive-power layer LR2, the optical element OE, the first low-refractive-power layer LR1, the polarizing plate POL, and the display panel DP.The optical sensor OS, located under the display panel DP, detects the amount of light reflected by the papillary ridge R and the groove V of the fingerprint F. The light detected by the optical sensor OS can be used to reconstruct the fingerprint pattern of the finger after being transmitted through output lines to an image capture IC (not shown).

[0085] In the display device according to the embodiment of the Fig. 4A and Fig. 4B of this disclosure, it is possible to reconstruct an image captured using the directional light unit and the optical sensor. Therefore, it is possible to correctly recognize a fine fingerprint without a complicated structure such as a bulky optical device.

[0086] In addition, it is possible to easily apply the invention to a display panel having a reduced screen frame area because a light incident element of an optical element and a light source are arranged on a non-display portion of a display panel.

[0087] In the display device according to the embodiment of the Fig. 4A and Fig. 4B of this disclosure, the optical element is arranged between the first low-power layer and the second low-power layer. Therefore, compared to the embodiment of Fig. 3A and Fig. 3B, in which the second low-refractive-power layer is absent, reduces the scattered light, thereby improving the resolution of the image captured from the object without being affected by the scattered light.

[0088] Hereinafter, a display device according to a third embodiment of this disclosure will be described with reference to the Fig. 5A and Fig. 5B.

[0089] Fig. 5A is a cross-sectional view showing a display device according to a third embodiment of this disclosure along a Fig. 1A and which shows a light path passing through total internal reflection in the directional light unit. Fig. 5B is a cross-sectional view showing a display device according to the third embodiment of this disclosure along a Fig. 1A and which shows a light path in which the light refracted by a light exit element of the optical element is converged onto an optical sensor.

[0090] As in the Fig. 5A and Fig. 5B, the display device according to the third embodiment of this disclosure includes a display panel DP having a display area DA and a non-display area NDA, a light source LS arranged to correspond to the non-display area NDA, a directing light unit coupled to the display panel DP for spreading and exiting the light from the light source LS, and an optical sensor OS that detects or senses the light from the directing light unit DLU.

[0091] Any display panel can be used as the display panel DP as long as the non-display area NDA can transmit light. Typically, a display panel of an electroluminescent display device using a flexible translucent substrate can be used. However, this disclosure is not limited thereto. A liquid crystal display (LCD), a plasma display panel (PDP), a field emission display (FED), or the like can be used in this disclosure if their non-display areas can transmit light. A polarizing plate POL can be attached to a top surface of the display panel DP to improve visibility.

[0092] The light source LS is arranged under the non-display surface NDA of the display panel DP to irradiate the display panel DP with light. It is preferable to use a light source capable of providing collimated light, such as an infrared laser.

[0093] The directional light unit may include a first low-refractive-power layer LR1, an optical element OE, an adhesive layer AD, a second low-refractive-power layer LR2, and a cover substrate CS. The directional light unit refracts the light supplied from the light source LS to propagate it from the non-display surface NDA to the display surface DA in total internal reflection, reflects a portion of the total internal reflection, and transmits the light reflected by an object containing biometric information to the display panel DP and the optical sensor OS.

[0094] The cover substrate CS may contain a predetermined area capable of recognizing the object containing biometric information. The cover substrate CS may be made of transparent reinforced glass with a refractive index of approximately 1.5. The object containing biometric information may include a finger having a fingerprint F in which a plurality of grooves V and a plurality of papillary ridges R are alternately arranged.

[0095] The first low-refractive-power layer LR1 is arranged between the cover substrate CS and the display panel DP.

[0096] The second low-refractive-power layer LR2 is attached to a bottom surface of the cover substrate CS, between the cover substrate CS and the optical element OE. A black matrix BM can be attached to the edge of the second low-refractive-power layer LR2 in such a way that it corresponds to the light source LS.

[0097] It is preferable that the first and second low-refractive-power layers LR1 and LR2 have a refractive index lower than that of the cover substrate CS. The refractive index of the first and second low-refractive-power layers LR1 and LR2 is preferably similar to the refractive index of the object to be recognized. For example, when the display device of this disclosure is applied to fingerprint recognition, the first and second low-refractive-power layers LR1 and LR2 may have a refractive index of approximately 1.4, similar to the refractive index of human skin of 1.39.

[0098] The optical element OE is arranged between the first and second low-refractive-power layers LR1 and LR2. An adhesive layer AD can be arranged between the optical element OE and the second low-refractive-power layer LR2 to couple the optical element OE to the second low-refractive-power layer LR2.

[0099] The optical element OE, arranged between the adhesive layer AD and the low-refractive-power layer LR1, includes a light incident element OE_I and a light exit element OE_O. The light incident element OE_I and the light exit element OE_O are transparent holographic recording films. The refractive index of the light incident element OE_I and the light exit element OE_O can be the same as, or slightly higher than, that of the cover substrate.

[0100] The light incidence element OE_I is arranged to correspond to the non-display area NDA and is arranged to overlap the black matrix BM and the light source LS. The light incidence element OE_I refracts a portion of the light incident from the light source LS at a first angle θ1, causing total internal reflection in the adhesive layer AD, and propagates it to the optical element OE.Since the first low-refractive-power layer LR1, which has a refractive index smaller than that of the optical element OE, is arranged on the underside of the optical element OE and the second low-refractive-power layer LR2, which has a refractive index smaller than that of the optical element OE, is arranged on the top side of the adhesive layer AD, the light traveling from the light incident element OE_I to the display surface DA propagates in total reflection between the top side of the adhesive layer AD and the underside of the optical element OE.

[0101] The light-output element OE_O may be arranged in at least a portion of an area where light from the light source LS travels at a position corresponding to at least a portion of the image recognition area ISA defined by the propagation light. In this case, the light-output element OE_O may be separated from the light-input element OE_I by a predetermined distance. The light-output element OE_O reflects the incident light at a second angle θ2 smaller than the first angle θ1 and exits the reflected light at the cover substrate CS. The light is reflected by the object, thereby propagating to the display panel DP and an optical sensor OS.

[0102] The optical sensor OS is located outside the display panel DP at a position corresponding to the light-emitting element OE_O of the optical element OE. The optical sensor OS detects the amount of light transmitted through the display panel DP.

[0103] In the embodiment of the Fig. 5A and Fig. 5B, it is possible to integrate the polarizing plate POL, the first low-refractive-power layer LR1, and the optical element OE in a single process because they are essentially the same size.

[0104] Next, as in the Fig. 5A and Fig. 5B, a case will be described where light emitted from the light source is converted into the propagation light by the optical element to move in the display area, and a case where, after the propagation light is reflected by the object, the reflected light is converged to the optical sensor to capture an image of the object.

[0105] As in Fig. As shown in Figure 5A, the light emitted by the light source LS passes through the display panel DP, the polarizing plate POL, and the first low-refractive-power layer LR1 and is incident on the light incident element OE_I of the optical element OE. The light incident element OE_I refracts the incident light at a first angle θ1 to induce total internal reflection in the adhesive layer AD.

[0106] Part of the light that has passed through the light incident element OE_I travels to the black matrix BM, and the remaining light is refracted to travel from the non-display area NDA to the display area DA. Accordingly, it is possible to prevent the light from escaping into the non-display area NDA because the light arriving at the black matrix BM is blocked by the black matrix BM.

[0107] The light refracted by the light incident element OE_I and then propagating into the display surface DA is totally reflected between the upper surface of the adhesive layer AD and the lower surface of the optical element OE, because the first low-refractive-power layer LR1 is disposed on the lower surface of the optical element OE and the second low-refractive-power layer LR2 is disposed on the upper surface of the adhesive layer AD. The light that was totally reflected on the upper surface of the adhesive layer AD is totally reflected again on the lower surface of the optical element OE, thereby propagating in a total reflection state in the adhesive layer AD and the optical element OE.In this way, a part of the light emitted from the light source LS and refracted by the light incident element OE_I moves to a region corresponding to the display area DA by total internal reflection between the top surface of the adhesive layer AD and the bottom surface of the optical element OE, as shown in . Fig. 5A shown.

[0108] As in Fig. As shown in Figure 5B, the light propagating in total internal reflection through the adhesive layer AD and the optical element OE reaches the light-exiting element OE_O. The light reaching the light-exiting element OE_O is scattered by patterns of the light-exiting element OE_O and is reflected at a second angle θ2 that is smaller than the first angle θ1. The light reflected in the light-exiting element OE_O propagates in the cover substrate CS via the adhesive layer AD and the second low-refractive-power layer LR2. At this time, when the finger touches the cover substrate CS, the light reaching the papillary ridge R of the fingerprint F is absorbed, and the light reaching the groove V of the fingerprint F is reflected, thereby passing through the second low-refractive power layer LR2, the adhesive layer AD, the optical element OE, the first low-refractive power layer LR1, the polarizing plate POL, and the display panel DP.The optical sensor OS, located under the display panel DP, detects the amount of light reflected by the papillary ridge R and the groove V of the fingerprint F. The light detected by the optical sensor OS can be used to reconstruct the fingerprint pattern of the finger after being transmitted through output lines to an image capture IC (not shown).

[0109] In the display device according to the embodiment of the Fig. 5A and Fig. 5B of this disclosure, it is possible to reconstruct an image captured using the directional light unit and the optical sensor. Therefore, it is possible to correctly recognize a fine fingerprint without a complicated structure such as a bulky optical device.

[0110] In addition, it is possible to easily apply the invention to a display panel having a reduced screen frame area because the light incident element of the optical element and the light source are arranged on the non-display portion of the display panel.

[0111] In the display device according to the embodiment of the Fig. 5A and Fig. 5B of this disclosure, the display device may be provided with the adhesive layer between the second low-refractive-power layer and the optical element, thereby increasing a distance of the propagating light traveling between the first low-refractive-power layer and the second low-refractive-power layer. Therefore, compared to the embodiment of Fig. 4A and Fig. 4B, it is possible to improve the resolution of the image captured from the object by further reducing the influence of the scattered light.

[0112] It will be apparent to those skilled in the art that the disclosure may be altered and modified in various ways without departing from the scope of the disclosure discussed above. Accordingly, the technical scope of the disclosure is not limited to the content described in the detailed description of the specification, but is determined by the claims.

[0113] The following list of embodiments forms part of the description. These features may be combined in any suitable manner beyond the expressly described forms.

Claims

[1] Display device comprising: a display panel (DP) having a display area (DA) and a non-display area (NDA) outside the display area (DA); a light source (LS) arranged under the non-display area (NDA) of the display panel (DP) for irradiating the display panel (DP) with light; a directional light unit (DLU) arranged on an upper portion of the display panel (DP); and an optical sensor (OS) located under the display panel (DP) and receiving the light passing through the directional light unit (DLU) and the display panel (DP), wherein the directional light unit (DLU) comprises: a cover substrate (CS) arranged to face the display panel (DP) to be brought into contact with the object; an optical element (OE) containing: a light incident element (OE_I) arranged between the cover substrate (CS) and the display panel (DP) and overlapping with the light source (LS) at a position corresponding to the non-display surface, wherein the light incident element (OE_I) is configured to refract the light supplied from the light source (LS) at a first angle (θ1) to move from the non-display surface (NDA) to the display surface (DA) by total internal reflection; and a light exit element (OE_E) arranged between the cover substrate (CS) and the display panel (DP) in at least a portion of a region where the light from the light source (LS) travels, and wherein the light exit element (OE_E) is configured to reflect a portion of the totally reflected light at a second angle (θ2) toward an object having biometric information, wherein the directional light unit (DLU) is further configured to supply light reflected by the object to the display panel (DP); and a first layer (LR) with low refractive power arranged between the optical element (OE) and the display panel (DP), wherein the refractive indices of the cover substrate (CS) and the optical element (OE) are the same, and wherein the refractive index of the cover substrate (CS) is greater than a refractive index of the first layer (LR1) with low refractive power. [2] The display device according to claim 1, wherein the directional light unit (DLU) further comprises a second low-refractive-power layer (LR2) disposed between the optical element (OE) and the cover substrate (CS). [3] The display device according to claim 1, wherein the directional light unit (DLU) further comprises: an adhesive layer (AD) arranged between the optical element (OE) and the cover substrate (CS); and a black matrix (BM) arranged to overlap the light incident element (OE_I) and arranged between the cover substrate (CS) and the adhesive layer to block part of the light emitted by the light source (LS). [4] The display device according to claim 2, wherein the directional light unit (DLU) further comprises a black matrix (BM) arranged to correspond to the light incident element (OE_I) and disposed between the cover substrate (CS) and the second low-refractive power layer (LR2) to block a part of the light emitted from the light source (LS). [5] A display device according to claim 2, wherein the directional light unit (DLU) further comprises: an adhesive layer (AD) arranged between the optical element (OE) and the second layer (LR2) with low refractive power; and a black matrix (BM) arranged to overlap the light incident element (OE_I) between the adhesive layer (AD) and the second layer (LR2) with low refractive power in order to block part of the light emitted by the light source (LS). [6] The display device according to claim 3, wherein the light incident element (DLU) refracts a part of the light incident from the light source (LS) at the first angle (θ1) to induce total reflection in the cover substrate (CS) and cause the part of the light to move into the cover substrate (CS), and wherein the light that has been totally reflected from an upper surface of the cover substrate (CS) and moves to the light exit element (OE_O) is reflected at the second angle (θ2) smaller than the first angle (θ1) by the first low-refractive-power layer (LR) to be transported to the cover substrate (CS), and moves to the optical sensor (OS) after being reflected by the object on the cover substrate (CS). [7] The display device according to claim 4, wherein the light incident element (DLU) refracts a part of the light incident from the light source (LS) at the first angle (θ1) to cause total reflection in the optical element (OE) and cause the part of the light to move into the optical element (OE), and wherein the light that has been totally reflected from a top surface of the optical element (OE) and moves to the light exit element (OE_O) is reflected at the second angle (θ2) smaller than the first angle (θ1) to be transported to the cover substrate (CS), and moves to the optical sensor (OS) after being reflected by the object on the cover substrate (CS). [8] The display device according to claim 5, wherein the light incident element (DLU) refracts a part of the light incident from the light source (LS) at the first angle (θ1) to induce total reflection in the adhesive layer (AD) and cause the part of the light to move into the adhesive layer (AD), and wherein the light that has been totally reflected from an upper surface of the adhesive layer (AD) and moves to the light exit element (OE_O) is reflected at the second angle (θ2) smaller than the first angle (θ1) to be transported to the cover substrate (CS), and moves to the optical sensor (OS) after being reflected by the object on the cover substrate (CS). [9] The display device according to claim 5, wherein a refractive index of the adhesive layer (AD) is the same as the refractive indices of the cover substrate (CS) and the optical element (OE). [10] A display device according to claim 7, wherein the refractive index of the first low-power layer (LR1) is the same as that of the second low-power layer (LR2). [11] The display device according to claim 8, wherein a refractive index of the adhesive layer (AD) is the same as the refractive indices of the cover substrate (CS) and the optical element (OE), and wherein the refractive index of the first low-refractive power layer (LR1) is the same as that of the second low-refractive power layer (LR2). [12] A display device according to any one of claims 1 to 11, wherein the display panel (DP) further comprises: a polarizing plate (POL) disposed between the display panel (DP) and the first low-refractive-power layer (LR; LR1), and wherein the polarizing plate (POL), the first low-refractive-power layer (LR; LR1) and the optical element (OE) have the same size. [13] The display device according to any one of claims 1 to 11, wherein the display panel (DP) further comprises signal lines (SL) arranged to bypass a region overlapping the light incident element (OE_I) of the optical element (OE) and the light source (LS). [14] Display device according to one of claims 1 to 11, wherein the object contains a fingerprint in which a plurality of papillary ridges (R) and a plurality of grooves (V) are arranged alternately.

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