Patent Publication Number: US-2023146352-A1

Title: Display device

Description:
TECHNICAL FIELD 
     The present invention relates to a display device. 
     BACKGROUND ART 
     A micro organic light-emitting diode (OLED) display module or a Liquid Crystal On Silicon (LCOS) module is sometimes used as a small display device such as an Electronic View Finder (EVF) or a Head Mounted Display (HMD). Further, from viewpoints of reduction of a footprint in an LCOS display module, reduction of a total height, and improvement of a special shape of an optical member such as a half mirror, or the like, a light-emitting device such as OLED may be arranged right above the LCOS. 
     Patent Document 1 describes a reflective liquid crystal display device. This display device includes the light-emitting device including a light-emitting unit such as an organic electroluminescence element (EL) and a reflective liquid crystal display (LCD). The light-emitting device overlaps the reflective LCD and emits light only toward the reflective LCD side. The light emitted from the light-emitting device is reflected by the reflective LCD and transmitted through a gap of a light shielding layer patterned in a grid shape in the light-emitting device. Thereby, the light which is transmitted through the gap of the light shielding layer patterned in the grid shape is observed by an observer located on the side opposite to the reflective LCD with the light-emitting device therebetween. 
     RELATED ART DOCUMENT 
     Patent Document 
     
         
         [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2006-154402 
       
    
     SUMMARY OF THE INVENTION 
     Technical Problem 
     From a viewpoint of downsizing a display device or the like, a transmission-type light-emitting device such as an OLED may be arranged right above a reflective liquid crystal element such as LCOS. In this case, even when a configuration in which the light-emitting device emits light not only toward a reflective liquid crystal element side but also toward the side opposite to the reflective liquid crystal display device is adopted, it is not possible to distinguish between light emitted toward a reflective liquid crystal display device side from the light-emitting device and light emitted toward the side opposite to the reflective liquid crystal display device from the light-emitting device. Therefore, such a configuration cannot serve as a display device. On the other hand, as described in Patent Document 1, in a case where the light-emitting device emits light only toward the reflective liquid crystal display device side, for an observer located on the side opposite to the reflective liquid crystal display device with the light-emitting device therebetween, there is a possibility that the visibility of an image displayed by the display device may be affected by a light shielding layer provided in the light-emitting device. 
     An example of a problem to be solved by the present invention is to make the visibility of an image displayed by a display device high. 
     Solution to Problem 
     The invention described in claim  1  is a display device including: 
     a light-emitting device including a plurality of light-emitting units and a light-transmitting unit located between the light-emitting units adjacent to each other; 
     a reflective liquid crystal element; and 
     an optical member, 
     in which the light-emitting device is located between the reflective liquid crystal element and the optical member, 
     in which the plurality of light-emitting units emit light toward the reflective liquid crystal element, and 
     in which the light emitted from the plurality of light-emitting units is reflected by the reflective liquid crystal element, transmitted through the light-transmitting unit of the light-emitting device, and formed into an image by the optical member. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a cross-sectional view of a display device according to Embodiment 1. 
         FIG.  2    is a plan view of a light-emitting device of a display device illustrated in  FIG.  1   . 
         FIG.  3    is a cross-sectional view taken along line A-A of  FIG.  2   . 
         FIG.  4    is a cross-sectional view of a detection device according to Embodiment 2. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     In the present specification, the expression “A is located over B” may mean that, for example, A is located directly over B without having another element (for example, layer) located between A and B, or may mean that another element (for example, layer) is partly or wholly located between A and B. In addition, expressions indicating a direction such as “top”, “bottom”, “left”, “right”, “front”, and “rear” or the like are basically used in combination with a direction of a drawing, and it is not limited to be interpreted for, for example, a direction of the use of an invention described in the present specification. 
     In the present specification, unless otherwise noted, the expression “A and B overlap” means that at least a part of A occupies the same area as at least a part of B in an image projected from a certain direction. At this time, a plurality of elements may be in contact with each other, or may be separated from each other. 
     In the present specification, unless otherwise noted, the expression “outside of A” means an area on a side where A is not located with an edge of A as a boundary. 
     In the present specification, an anode indicates an electrode which injects an electron hole into a layer (for example, organic layer) including a light-emitting material, and a cathode indicates an electrode which injects an electron into a layer including the light-emitting material. Further, the expressions “anode” and “cathode” may mean other wordings such as “electron hole injection electrode” and “electron injection electrode”, or “positive electrode” and “negative electrode” or the like. 
     “Light-emitting device” in the present specification includes a device including a light-emitting element, such as a display or illumination. Further, there may be a case where a wiring directly, indirectly, or electrically connected to a light-emitting element, an integrated circuit (IC), or a housing or the like is also included in “light-emitting device”. 
     In the present specification, “connection” indicates a state in which a plurality of elements are being connected regardless of whether they are directly or indirectly connected. For example, a case where the plurality of elements are connected with an adhesive or a connecting member therebetween may also be expressed simply as “a plurality of elements are connected”. Further, a case where a member which is capable of supplying or transmitting current, voltage, or electrical potential exists between the plurality of elements and “the plurality of elements are electrically connected” may also be expressed simply as “a plurality of elements are connected”. 
     In the present specification, unless otherwise noted, expressions such as “first, second, A, B, (a), (b)” or the like are intended to distinguish an element, and an essence, an order, a sequence, or a quantity or the like of the element is not limited by the expressions. 
     In the present specification, each member and each element may be singular, or plural. However, when “singular” or “plural” is clear in a context, it is not limited to this. 
     In the present specification, unless otherwise noted, a meaning of the expression “A includes B” is not limited to that A is configured only with B, but that A can be configured with elements other than B. 
     In the present specification, unless otherwise noted, “section” means a surface which appears when the light-emitting device is cut in a direction of a pixel or a light-emitting material or the like being laminated. 
     In the present specification, expressions such as “does not have”, “does not include”, and “is not positioned” or the like may mean that a certain element is completely excluded or that a certain element exists to a degree at which the element does not have a technical effect. 
     In the present specification, expressions for explaining a temporal before-after relationship, such as “after”, “subsequently to”, “next to”, and “before” or the like express a relative temporal relationship, and elements for which the temporal before-after relationship is used are not necessarily continuous. In order to express that elements are continuous, an expression such as “immediately” or “directly” or the like may be used. 
     Embodiments of the present invention will be described below by referring to the drawings. Moreover, in all the drawings, the same constituent elements are given the same reference numerals, and descriptions thereof will not be repeated. 
     Embodiment 1 
       FIG.  1    is a cross-sectional view of a display device  1  according to Embodiment 1.  FIG.  2    is a plan view of a light-emitting device  10  of the display device  1  illustrated in  FIG.  1   .  FIG.  3    is a cross-sectional view taken along line A-A of  FIG.  2   .  FIG.  1    illustrates one cross section perpendicular to a height direction of the display device  1 . 
     The display device  1  includes the light-emitting device  10 , a reflective liquid crystal element  20 , and an optical member  30 . The light-emitting device  10  includes a substrate  100 , a plurality of light-emitting units  142 , and a plurality of light-transmitting units  144 . Each light-emitting unit  142  includes an organic EL element. Each light-transmitting unit  144  is located between the light-emitting units  142  adjacent to each other. The reflective liquid crystal element  20  includes a spatial light modulation element  210  and a polarizer  220  (polarizing plate). 
     In  FIG.  1   , an arrow extending from the light-emitting unit  142  toward the spatial light modulation element  210  represents light emitted from the light-emitting unit  142 . Further, an arrow extending from the spatial light modulation element  210  toward the polarizer  220  represents light reflected by the spatial light modulation element  210  and shielded by the polarizer  220 . Further, an arrow which extends from the spatial light modulation element  210  passing through the polarizer  220 , the substrate  100 , and the optical member  30  represents light which is reflected by the spatial light modulation element  210  and is transmitted through the polarizer  220 , the substrate  100 , and the optical member  30 . 
     The display device  1  will be explained by referring to  FIGS.  1  to  3   . 
     The light-emitting device  10  is located between the reflective liquid crystal element  20  and the optical member  30 . 
     The substrate  100  includes a first surface  102  and a second surface  104 . The plurality of light-emitting units  142  are located over the first surface  102  of the substrate  100 . It is possible to supply driving power to the plurality of light-emitting units  142  from the outside of the light-emitting device  10  through a wiring member  150  such as a Flexible Printed Circuit (FPC) or the like. The second surface  104  is on the opposite side to the first surface  102 . 
     As shown in  FIG.  3   , each light-emitting unit  142  includes a first electrode  110 , an organic layer  120 , and a second electrode  130 . The first electrode  110 , the organic layer  120 , and the second electrode  130  are stacked in order from the first surface  102  side of the substrate  100 . 
     The substrate  100  may be single-layered or multi-layered. The substrate  100  is, for example, a glass substrate. The substrate  100  may be a resin substrate including an organic material (for example, polyethylene naphthalate (PEN), polyether sulphone (PES), polyethylene terephthalate (PET), or polyimide). When the substrate  100  is a resin substrate, an inorganic barrier layer (for example, SiN or SiON) may be positioned over at least one of the first surface  102  and the second surface  104  of the substrate  100 . 
     In the present embodiment, the light-emitting device  10  emits light from the second surface  104  side of the substrate  100 . That is, the light-emitting device  10  has a bottom-emission structure. In this case, the substrate  100  has light-transmitting properties. Transmittance of visible light of the substrate  100  is, for example, equal to or greater than 75% and equal to or less than 100%. 
     The first electrode  110  has light-transmitting properties. Transmittance of visible light of the first electrode  110  is, for example, equal to or greater than 75% and equal to or less than 100%. The first electrode  110  can function as an anode. In one example, the first electrode  110  includes a metal or an alloy. The metal or the alloy is, for example, silver or a silver alloy. In this example, the thickness of the first electrode  110  may be, for example, equal to or greater than 5 nm and equal to or less than 50 nm. When the thickness of the first electrode  110  is equal to or greater than the lower limit, it is possible to lower electric resistance of the first electrode  110 , and when the thickness of the first electrode  110  is equal to or less than the upper limit, it is possible to increase transmittance of the first electrode  110 . In another example, the first electrode  110  may include an oxide semiconductor. The oxide semiconductor is, for example, Indium Tin Oxide (ITO), Indium Zinc Oxide (IZO), Indium Tungsten Zinc Oxide (IWZO), Zinc Oxide (ZnO), or Indium Gallium Zinc Oxide (IGZO). 
     The organic layer  120  is located over the first electrode  110 . The organic layer  120  may include, for example, a hole injection layer (HIL), a hole transport layer (HTL), a light-emitting layer (EML), an electron transport layer (ETL), and an electron injection layer (EIL) in this order from the first electrode  110  toward the second electrode  130 . However, an example of a layer included in respective organic layers  120  is not limited to the example explained here. 
     The second electrode  130  has light shielding properties, specifically, light reflectivity. Transmittance of visible light of the second electrode  130  is, for example, equal to or greater than 0% and equal to or less than 20%. The second electrode  130  is located over the organic layer  120 . The second electrode  130  can function as a cathode. In one example, the second electrode  130  may include a metal or an alloy. The metal or the alloy is, for example, at least one metal selected from a group formed of Al, Au, Ag, Pt, Mg, Sn, Zn, and In, or an alloy of a metal selected from this group. 
     In the present embodiment, the plurality of light-emitting units  142  are arranged in a stripe pattern. A light shielding member such as the second electrode  130  is not positioned in a region between light-emitting units  142  adjacent to each other. Therefore, the region between the light-emitting units  142  adjacent to each other is a light-transmitting unit  144 . Transmittance of visible light of the light-transmitting unit  144  is, for example, equal to or greater than 40% and equal to or less than 100%. 
     Further, the plurality of light-emitting units  142  include a plurality of R (red) light sources  142   a , a plurality of G (green) light sources  142   b , and a plurality of B (blue) light sources  142   c . Each R light source  142   a , each G light source  142   b , and each B light source  142   c  is repeatedly arranged along a direction intersecting the extending direction of the stripe. However, the R light sources  142   a , the G light sources  142   b , and the B light sources  142   c  may have a dot shape arranged in a matrix. In a case where the plurality of light-emitting units  142  include the R light source  142   a , the G light source  142   b , and the B light source  142   c , the display device  1  can display a color image by a field sequential color (FSC) method of the spatial light modulation element  210 . 
     The plurality of light-emitting units  142  emit light toward the reflective liquid crystal element  20 . Specifically, the light-emitting device  10  emits the light to the second surface  104  side, the second surface being one surface of both surfaces of the light-emitting device  10 , and substantially does not emit the light to a first surface  102  side, the first surface being the other surface of the both surfaces of the light-emitting device  10 . This is due to that almost all or an entirety of the light emitted from the organic layer  120  is reflected by the second electrode  130  having the light reflectivity and is not transmitted through the second electrode  130 . For example, the maximum luminous intensity on the first surface  102  side of the light-emitting device  10  is equal to or greater than 0% and equal to or less than 10° of the maximum luminous intensity on the second surface  104  side of the light-emitting device  10 . 
     The spatial light modulation element  210  includes liquid crystal, for example, LCOS. 
     Light emitted from the light-emitting device  10  is transmitted through the polarizer  220 . The light transmitted through the polarizer  220  becomes linearly polarized light. This linearly polarized light is incident on the spatial light modulation element  210  and rotates depending on a pixel of the spatial light modulation element  210 . The linearly polarized light rotated and reflected by the spatial light modulation element  210  is shielded by the polarizer  220 . In contrast, the linearly polarized light which is reflected without being rotated by the spatial light modulation element  210  is transmitted through the polarizer  220 . 
     The optical member  30  is a condensing element. In the present embodiment, the optical member  30  includes at least one lens. Light emitted from the plurality of light-emitting units  142  is reflected by the reflective liquid crystal element  20 , transmitted through the light-transmitting unit  144  of the light-emitting device  10  and the optical member  30 , and emitted. That is, the light emitted from the plurality of light-emitting units  142  is reflected by the reflective liquid crystal element  20 , transmitted through the light-transmitting unit  144  of the light-emitting device  10 , and formed into an image by the optical member  30 . Note that the optical member  30  may include, for example, a diffraction grating instead of the lens. 
     The reflective liquid crystal element  20  is located within a depth of field of the optical member  30 . In contrast, the light-emitting unit  142  of the light-emitting device  10 , more specifically, the second electrode  130  is located outside the depth of field of the optical member  30 . Therefore, in the present embodiment, when an observer observes an image displayed by the display device  1  from the above of the display device  1 , the second electrode  130  looks blurred. Therefore, it is possible to make the second electrode  130  unnoticeable to the observer of the image of the light-emitting device  10 . That is, in the present embodiment, in comparison with a case where the optical member  30  is not provided, it is possible to make the visibility of an image displayed by the display device  1  high. 
     Embodiment 2 
       FIG.  4    is a cross-sectional view of a detection device  2  according to Embodiment 2.  FIG.  4    illustrates one cross section perpendicular to a height direction of the detection device  2 . 
     The detection device  2  includes a light-emitting device  10 , an optical member  30 , and an imaging element  40 . In the present embodiment, the detection device  2  detects a fingerprint of a finger F as an object. However, the object which can be detected by the detection device  2  is not limited to the example according to the present embodiment. 
     In  FIG.  4   , an arrow extending from a light-emitting unit  142  toward a side on which the finger F is located represents light emitted from the light-emitting unit  142 . In addition, an arrow extending from the finger F toward a side on which the light-emitting device  10 , the optical member  30 , and the imaging element  40  are located represents light reflected by the finger F. 
     A summary of the detection device  2  is explained using  FIG.  4   . The optical member  30  is located between the light-emitting device  10  and the imaging element  40 . A plurality of light-emitting units  142  emit light toward a side opposite to a side on which the optical member  30  is located. The light emitted from the plurality of light-emitting units  142  is reflected by the finger F, transmitted through the light-transmitting unit  144  of the light-emitting device  10 , and formed into an image on the imaging element  40  by the optical member  30 . Thereby, the fingerprint of the finger F is detected. 
     As is the case with Embodiment 1, the light-emitting device  10  includes a substrate  100 , the plurality of light-emitting units  142 , and a plurality of light-transmitting units  144 . The plurality of light-emitting units  142  are, for example, monochrome light sources. The light-emitting device  10  has a bottom-emission structure. The plurality of light-emitting units  142  of the light-emitting device  10  emit light toward a side opposite to a side on which the optical member  30  and the imaging element  40  are located. In other words, the light-emitting device  10  is arranged such that a first surface  102  of the substrate  100  faces the optical member  30  and the imaging element  40 . 
     The optical member  30  is a condensing element, and includes at least one lens. In the present embodiment, the optical member  30  includes a focus lens. 
     The imaging element  40  is an image sensor, such as, for example, a Complementary MOS (CMOS) image sensor, a Charge-Coupled Device (CCD) image sensor. 
     In the present embodiment, the imaging element  40 , the optical member  30 , and the light-emitting device  10  are stacked along one direction, specifically, a height direction of the detection device  2 . In this case, for example, in comparison with a case where a light source to irradiate light to the finger F and a sensor which detects light reflected by the finger F are aligned in a direction perpendicular to the height direction of the detection device  2 , a size of the detection device  2  in the direction perpendicular to the height direction of the detection device  2  can be reduced. 
     As described above, although the embodiments of the present invention have been set forth with reference to the accompanying drawings, they are merely illustrative of the present invention, and various configurations other than those stated above can be adopted. 
     For example, in respective embodiments, the light-emitting device  10  has a bottom-emission structure. However, the light-emitting device  10  may has a top-emission structure. 
     Further, in Embodiment 1, the plurality of light-emitting units  142  include light sources of different colors. However, the plurality of light-emitting units  142  may be the monochrome light sources. Even in such a case, the display device  1  can display a monochrome image. 
     Further, in respective embodiments, the light-emitting unit  142  includes an organic EL element. However, the light-emitting unit  142  may include a light-emitting element which is different from the organic EL element, such as an inorganic EL element or the like. 
     According to Embodiment 1, following aspects are provided. 
     (Aspect 1-1) A display device including: 
     a light-emitting device including a plurality of light-emitting units and a light-transmitting unit located between the light-emitting units adjacent to each other; 
     a reflective liquid crystal element; and 
     an optical member, 
     in which the light-emitting device is located between the reflective liquid crystal element and the optical member, 
     in which the plurality of light-emitting units emit light toward the reflective liquid crystal element, and 
     in which the light emitted from the plurality of light-emitting units is reflected by the reflective liquid crystal element, transmitted through the light-transmitting unit of the light-emitting device, and formed into an image by the optical member. 
     (Aspect 1-2) 
     The display device according to aspect 1-1, in which the optical member includes a lens. 
     (Aspect 1-3) 
     The display device according to aspect 1-1 or 1-2, 
     in which the reflective liquid crystal element is located within a depth of field of the optical member, and 
     in which the plurality of light-emitting units of the light-emitting device are located outside the depth of field of the optical member. 
     (Aspect 1-4) 
     The display device according to any one of aspects 1-1 to 1-3, 
     in which each of the plurality of light-emitting units includes an organic EL element. 
     (Aspect 1-5) 
     The display device according to any one of aspects 1-1 to 1-4, 
     in which the plurality of light-emitting units include a R light source, a G light source, and a B light source. 
     (Aspect 1-6) 
     A display device including: 
     a light-emitting device including a plurality of light-emitting units and a light-transmitting unit located between the light-emitting units adjacent to each other; 
     a reflective liquid crystal element; and 
     a condensing element, 
     in which the light-emitting device is located between the reflective liquid crystal element and the condensing element, 
     in which the plurality of light-emitting units emit light toward the reflective liquid crystal element, and 
     in which the light emitted from the plurality of light-emitting units is reflected by the reflective liquid crystal element, transmitted through the light-transmitting unit of the light-emitting device and the condensing element, and emitted. 
     (Aspect 1-7) 
     The display device according to aspect 1-6, 
     in which the condensing element includes a lens. 
     (Aspect 1-8) 
     The display device according to aspect 1-6 or 1-7, 
     in which the reflective liquid crystal element is located within a depth of field of the condensing element, and 
     in which the plurality of light-emitting units of the light-emitting device are located outside the depth of field of the condensing element. 
     (Aspect 1-9) 
     The display device according to any one of aspects 1-6 to 1-8, in which each of the plurality of light-emitting units includes an organic EL element. 
     (Aspect 1-10) 
     The display device according to any one of aspects 1-6 to 1-9, 
     in which the plurality of light-emitting units include a R light source, a G light source, and a B light source. 
     According to Embodiment 2, following aspects are provided. 
     (Aspect 2-1) 
     A detection device detecting an object, the detection device including: 
     a light-emitting device including a plurality of light-emitting units and a light-transmitting unit located between the light-emitting units adjacent to each other; 
     an imaging element; and 
     an optical member, 
     in which the optical member is located between the light-emitting device and the imaging element, 
     in which the plurality of light-emitting units emit light toward a side opposite to a side on which the optical member is located, and 
     in which the light emitted from the plurality of light-emitting units is reflected by the object, transmitted through a plurality of transmission units of the light-emitting device, and formed into an image on the imaging element by the optical member. 
     (Aspect 2-2) 
     The detection device according to aspect 2-1, 
     in which the optical member includes a lens. 
     (Aspect 2-3) 
     The detection device according to aspect 2-1 or 2-2, 
     in which each of the plurality of light-emitting units includes an organic EL element. 
     (Aspect 2-4) 
     The detection device according to any one of aspects 2-1 to 2-3, 
     in which the plurality of light-emitting units are monochrome light sources. 
     This application claims priority from Japanese Patent Application No. 2020-057520, filed on Mar. 27, 2020, the disclosure of which is incorporated by reference in its entirety. 
     REFERENCE SIGNS LIST 
     
         
           1  display device 
           2  detection device 
           10  light-emitting device 
           20  reflective liquid crystal element 
           30  optical member 
           40  imaging element 
           100  substrate 
           102  first surface 
           104  second surface 
           110  first electrode 
           120  organic layer 
           130  second electrode 
           142  light-emitting unit 
           142   a  R light source 
           142   b  G light source 
           142   c  B light source 
           144  light-transmitting unit 
           150  wiring member 
           210  spatial light modulation element 
           220  polarizer