GB2552809A

GB2552809A - Touch screen display

Info

Publication number: GB2552809A
Application number: GB1613755.6A
Authority: GB
Inventors: Newsome Christopher; Yaacobi-Gross Nir; Grizzi Ilaria
Original assignee: Cambridge Display Technology Ltd; Sumitomo Chemical Co Ltd
Current assignee: Cambridge Display Technology Ltd; Sumitomo Chemical Co Ltd
Priority date: 2016-08-10
Filing date: 2016-08-10
Publication date: 2018-02-14
Also published as: WO2018029442A1

Abstract

The touch screen display comprises a substrate 19; display layer 20 of, for example, red 22, green 23 and blue 24 (RGB) pixels; and a dual sensing layer 26. The dual sensing layer contains a layer of touch sensitive elements 31 and a layer of light sensing elements 27. The light sensing elements 28 are unresponsive to all but one wavelength of light i.e. they are responsive to blue wavelengths and unresponsive to green and red wavelengths. The sensing layers may be coplanar with the light sensing elements interspersed with the touch sensing elements. The light sensing elements 28 may only be positioned over pixels of one particular colour, for example the red pixels 22. The pixels 22, 23, 24 may be organic light emitting diodes (OLEDs) that comprise a colour filter and the light sensing elements 28 may be organic photo diodes (OPDs). The touch sensitive elements may be capacitive in nature and transparent to light of certain wavelengths, for example blue light. Between any of the aforementioned layers there may be optical in/out coupling layers 25, 35, 39. The display can then be encapsulated by a final layer 40. The touch screen display is adapted towards providing fingerprint recognition on computing and portable computing devices.

Description

(71) Applicant(s):

Sumitomo Chemical Co., Ltd.

(Incorporated in Japan)

27-1, Shinkawa 2-chome, Chuo-ku, Tokyo 104-8260, Japan

Cambridge Display Technology Limited Unit 12 Cardinal Park, Cardinal Way, GODMANCHESTER, Cambridgeshire, PE29 2XG, United Kingdom (56) Documents Cited:

WO 2001/069520 A2 US 20140354597 A1

US 20150331508 A1 US 20090074255 A1 (58) Field of Search:

INT CL G06F, G06K, H04W Other: EPODOC, WPI, TXTE (72) Inventor(s):

Christopher Newsome Nir Yaacobi-Gross llaria Grizzi (74) Agent and/or Address for Service:

Venner Shipley LLP

Byron House, Cambridge Business Park,

Cowley Road, Cambridge, CB4 0WZ, United Kingdom (54) Title ofthe Invention: Touch screen display

Abstract Title: A touch screen display with a dual sensor layer (57) The touch screen display comprises a substrate 19; display layer 20 of, for example, red 22, green 23 and blue 24 (RGB) pixels; and a dual sensing layer 26. The dual sensing layer contains a layer of touch sensitive elements 31 and a layer of light sensing elements 27. The light sensing elements 28 are unresponsive to all but one wavelength of light i.e. they are responsive to blue wavelengths and unresponsive to green and red wavelengths. The sensing layers may be coplanar with the light sensing elements interspersed with the touch sensing elements. The light sensing elements 28 may only be positioned over pixels of one particular colour, for example the red pixels 22. The pixels 22, 23, 24 may be organic light emitting diodes (OLEDs) that comprise a colour filter and the light sensing elements 28 may be organic photo diodes (OPDs). The touch sensitive elements may be capacitive in nature and transparent to light of certain wavelengths, for example blue light. Between any of the aforementioned layers there may be optical in/out coupling layers 25, 35, 39. The display can then be encapsulated by a final layer 40. The touch screen display is adapted towards providing fingerprint recognition on computing and portable computing devices.

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Touch screen display

Field of the invention

The present invention relates to a touch screen display.

Background

Touch screen displays are becoming increasingly widespread and can be found in mobile computing and/or communication devices, such as smart phones, smart watches, tablets and laptop computers, as well as displays of other types of devices and appliances such as printers, white goods, and satnav systems.

A touch screen display generally includes a display screen and an overlying touchsensitive array allowing a user to interact with the display screen, for example, by touching an image to select the image.

A touch screen display device such as a smart phone or tablet may be provided with a fingerprint sensor. Such fingerprint sensors tend to be separate from the display screen, that is, the sensing is confined to an area which does not display images.

US 2015/0331508 Al describes an integrated silicon-OLED display and touch sensor panel. The OLED pixels can be arranged side-by-side with the touch sensors.

Summary

According to a first aspect of the present invention there is provided a touch screen display. The touch screen display comprises a substrate and a display layer structure disposed on the substrate. The display layer structure comprises an array of light5 emitting pixels. Each light-emitting pixel comprises a set of first, second, and third subpixels configured to emit light of different first, second, and third colours respectively. The touch screen display further comprises an integrated sensing layer structure disposed over the display layer structure. The integrated sensing layer structure comprises an array of touch-sensitive elements and an array of light-sensing elements. The light-sensing elements are transparent to light of the first colour and are responsive to light of the third colour.

Thus, fingerprint sensing functionality can be provided without necessarily detrimentally affecting the resolution of a touch screen display.

The array of touch-sensitive elements and the array of light-sensing elements maybe coplanar. The light-sensing elements maybe interspersed between the touch-sensitive elements.

The light-sensing elements may be transparent to light of the second colour.

The light-sensing elements may transmit at least 75%, at least 80%, at least 85%, at least 90%, or at least 95% of light of the first colour. The light-sensing elements may transmit at least 75%, at least 80%, at least 85%, at least 90%, or at least 95% of light of the second colour.

The substrate may be planar.

The light-sensing elements and the first subpixels may be in registration. A light30 sensing element may be disposed so as to lie in a light path of light emitted from a subpixel configured to emit light of the first colour. The substrate may extend in a first direction and in a second direction at a first point and the light path may be along a third direction including the first point, the third direction being perpendicular to the first and second directions.

-3The light-emitting pixels may comprise organic light-emitting diodes. The light-sensing elements may comprise organic photodetectors.

The integrated sensing layer structure may comprise a first sensing layer comprising 5 the array of light-sensing elements and a second sensing layer comprising the array of touch-sensitive elements. The integrated sensing layer structure may further comprise an optical out-coupling layer disposed between the first sensing layer and the second sensing layer. The integrated sensing layer structure may further comprise an optical in-coupling layer disposed between the first sensing layer and the second sensing layer.

The touch screen display may comprise an optical out-coupling layer disposed between the display layer structure and the integrated sensing layer structure. The touch screen display may comprise an optical out-coupling layer disposed over the integrated sensing layer structure. The touch screen display may comprise an optical in-coupling layer disposed over the integrated sensing layer structure.

The touch-sensitive elements may be transparent to at least light of the third colour.

The touch-sensitive elements may comprise capacitive touch elements.

The subpixels may comprise colour filters.

The touch screen display may comprise an encapsulation layer disposed over the integrated sensing layer structure.

According to a second aspect of the present invention there is provided a touch screen display device comprising a touch screen display according to the first embodiment and a controller operatively coupled to the touch screen display.

The touch screen display device may be adapted to be a portable computing and/or communications device, for example a smart phone, a tablet computer, a laptop.

According to a third aspect of the present invention there is provided an integrated sensing layer structure. The integrated sensing layer structure comprises an array of touch-sensitive elements and an array of light-sensing elements interspersed between the touch-sensitive elements. The light-sensing

-4elements are transparent to light of a first colour and are responsive to light of a third colour.

-5Brief Description of the Drawings

Certain embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which:

Figure 1 is an electronic device having a touch screen display;

Figure 2 is a schematic cross-section of a part of an optical finger print sensor;

Figure 3a is a schematic cross-section of a part of an optical fingerprint sensor in contact with air;

Figure 3b is a schematic cross-section of a part of an optical fingerprint sensor in contact with a finger;

Figure 4 is a perspective cut-away view of a section of a first touch screen display;

Figure 5 is a cross-sectional view of a section of a first touch screen display through a first plane;

Figure 6 is a cross-sectional view of a section of a first touch screen display and propagation of light through the touch screen display;

Figure 7 is a plan view of a display layer;

Figure 8 is a plan view of a second integrated sensing layer;

Figure 9a is a cross-sectional view of a section of a second touch screen display including the second integrated sensing layer shown in Figure 8 taken along a line A-A’ in Figure 8;

Figure 9b is a cross-sectional view of a section of a second touch screen display including the second integrated sensing layer shown in Figure 8 taken along a line B-B’ in Figure 8;

Figure 10 is a cross-sectional view of a section of a second touch screen display and propagation of light through the third touch screen display;

Figure 11 is a plan view of a modified display layer;

Figure 12 is a plan view of a third integrated sensing layer;

Figure 13 is a cross-sectional view of a section of a third touch screen display including the third integrated sensing layer shown in Figure 12 taken along a line C-C’ in Figure 13;

Figure 14 is a cross-sectional view of a section of a third touch screen display and propagation of light through the third touch screen display;

Figure 15 is an example absorption spectrum for a material included in a photodetector; Figure 16 is a block diagram of a touch screen display coupled to a controller; and Figure 17 is a process flow diagram of a method of fabricating a touch screen display.

-6Detailed Description of Certain Embodiments

In the following, like parts are denoted by like reference numerals.

Referring to Figure l, an electronic device l having a touch screen display 2 is shown.

The touch screen display is capable of reading a fingerprint.

Referring to Figure 2, an optical fingerprint reader 3 includes a transparent layer 4 having a refractive index m and first and second opposite faces 5, 6. A light-emitting element 7, for example an organic light-emitting diode, is disposed on the first face 5 and emits light 8 towards the second face 6. The second face 6 has an interface 9 with a medium 10 which is in contact with the second face 6.

Light 8 may be partially reflected at the interface 9, in dependence upon the refractive index of the medium 10 in contact with the second face 6 at the point of incidence of a light ray at the interface 9. A light-detecting element 11 disposed on the first face 5, for example an organic photodetector, detects light 12 reflected at the interface 9. The fingerprint sensor comprises an array of light-emitting elements 7 and light-detecting elements 11. As will be described hereinafter, when a finger 13 is in contact with the second face 6, the light detected by the light-detecting elements 11 can be used to locate the features of a fingerprint of the finger 13.

Referring to Figure 3a, the optical fingerprint sensor 3 is shown in more detail. First and second light-emitting elements 71, 72 emit first and second rays 81, 82 respectively towards the interface 9. The medium in contact with the second face 6 is air. The refractive index m of the transparent layer 4 into which the first and second emitted rays 81, 8₂ are emitted is greater than the refractive index of air, and thus the first and second emitted rays 81, 8₂ are partially internally reflected at the interface 9. First and second detectors ill, ii₂ detect first and second reflected rays 121,12₂ respectively.

Referring to Figure 3b, the optical fingerprint sensor 3 is shown, along with a section 14 of a finger 13 which is in contact with the interface. The finger section 14 has first, second, and third ridges 151,152,153, which contact the second face 6 at first, second, and third points of contact 161,162,163 respectively. First and second valleys 171,172, which do not contact the second face 6, are present between ridges 151 and 152, and 152 and 153, respectively. Thus, first and second air gaps 181,182 are formed between the second face 6 and first and second valleys 171,172 respectively.

-ΊΑ third emitted ray 8₃, which is incident at the interface 9 at the first point 161 where the first ridge 151 is in contact with the second face 6, is scattered and/or absorbed. A portion 12₃ of scattered light may be detected by the first detector 91.

A fourth emitted ray 84 is incident at the second face 6 at a fourth point 164 which lies between second and third points 162, i6₃ and is in contact with an air gap 182. At point 164, the second face 6 is not in contact with the finger 13. The fourth emitted ray 84 is partially internally reflected at the interface 9 and a fourth reflected ray 12₄ may be detected by the second detector 9₂.

Thus, by analysing output signals from light detectors 9, points of contact and noncontact with the second face 6 can be located and ridges and valleys of a fingerprint of a finger 13 can be mapped.

Referring to Figures 4 and 5, a first touch screen display 2 is shown in more detail.

The first touch screen display 2 comprises a substrate 19 which may be transparent or opaque. A display layer structure 20 is disposed on the substrate 19. The display layer structure 20 comprises an array of light-emitting pixels 21, each light-emitting pixel comprising a set of first, second, and third subpixels 22, 23, 24. The first, second, and third subpixels 22, 23, 24 emit light of first, second, and third colours respectively. Preferably, the first colour is red (R), the second colour is green (G), and the third colour is blue (B).

Each subpixel 22, 23, 24 is individually addressable, that is, capable of being turned on and off independently of any other subpixel 22, 23, 24.

A first optical out-coupling layer 25 is disposed over the display layer structure 20. The first optical out-coupling layer 25 is substantially transparent and may be patterned to as to allow light emitted by the subpixels 22, 23, 24 to be coupled out of the display layer structure 20 in a direction away from the substrate 19. For example, the first optical out-coupling layer 25 may comprise a microlens array.

A first integrated sensing layer structure 26 is disposed over the first optical outcoupling layer 25. The first integrated sensing layer structure 26 comprises a light-8sensing layer 27 comprising an array of spaced apart photodetectors 28, for example, organic photodetectors. The photodetectors 28 are substantially transparent to light of the first colour and responsive to light of the third colour. The light-sensing layer 27 comprises a substantially transparent material 29 disposed between the photodetectors

28 in the plane of the light-sensing layer 27.

The array of photodetectors 28 is disposed such that the photodetectors 28 overlie the subpixels 22 which emit light of the first colour and do not overlie the subpixels 24 which emit light of the third colour. The photodetectors 28 are substantially transparent to light of the first colour emitted by subpixels 22, and so light of the first colour emitted by subpixels 22 is not blocked by photodetectors 28.

A second optical out-coupling layer 30 is disposed over the light-sensing layer 27. The second optical out-coupling layer 30 may also function as an optical in-coupling layer.

The first integrated sensing layer structure 26 further comprises a touch-sensing layer structure 31. The touch sensing layer structure 31 comprises first and second touch sensing layers 32, 34 spaced apart by a transparent insulating layer 33. The first touch sensing layer 32 comprises a first set of touch sensing electrodes 35 extending in a first direction and spaced apart by transparent insulating sections 36 in a second direction which is perpendicular to the first direction, the first and second directions being in the plane of the touch sensing layer structure 31. The second touch sensing layer 34 comprises a second set of touch sensing electrodes 37 extending in the second direction and spaced apart by transparent insulating sections 38 in the first direction. The touch sensing electrodes 35,37 preferably comprise a substantially transparent material, for example, indium tin oxide (ITO). The transparent insulating sections 33, 36, 38 may comprise, for example, air, polystyrene, Poly(methyl methacrylate) (PMMA), ORG series or PGI series dielectrics available from Sumitomo Chemical Co.

A third optical out-coupling layer 39 is disposed over the first integrated sensing layer structure 26. The third optical out-coupling layer 39 may also function as an optical incoupling layer.

The first touch screen display 2 further comprises a capping layer (or encapsulation layer) 40 overlying the third optical out-coupling layer 39. The capping layer 40 comprises a substantially transparent material, for example, plastic or glass. The

-9capping layer has a first interface 41 with the third out-coupling layer 39 and a second interface 42 opposite the first interface 41.

Referring to Figure 6, the first touch screen display 2 is shown. A section 14 of a finger 5 13 contacts the second interface 42 of the capping layer 40. As described previously, the features of a fingerprint in contact with an interface may be determined by monitoring the amount of light reflected from the side of the interface opposite to the finger.

First and second light rays 431, 432 are emitted by first and second subpixels 24,, 242.

The first and second subpixels 24,, 242 are subpixels of the third type, that is, subpixels which emit light of the third colour.

The first and second emitted light rays 431, 432 propagate through the first optical outcoupling layer 25, the first integrated sensing layer structure 26, the second optical out15 coupling layer 30, the touch-sensing layer structure 31, and the third optical outcoupling layer 39, and are incident at the second interface 42.

The first emitted light ray 431 is incident at the interface 42 at a fifth point i6₅. The fifth point i6₅ lies between second and third adjacent points of contact 162,163 and is in contact with an air gap 181. The first emitted ray 431 is partially internally reflected at the second interface 42 and a first reflected ray 491 is directed at a first photodetector 281. The photodetectors 28 are sensitive to light of the third colour and thus the first photodetector 281 outputs a signal in response to receiving a first reflected light ray 491.

The second emitted light ray 432 is incident at a sixth point 160 which is in contact with a third ridge 153. The second emitted ray 432 is scattered and/or absorbed and a second scattered light ray 492 may be directed at a second photodetector 282. The second photodetector 282 measures a reduced amount of light compared to with the first photodetector 281. Thus, the features of a fingerprint carried by a finger in contact with the second interface 42 may be determined.

The touch sensing layer may alternatively be coplanar with the light sensing layer. A second touch screen display 2’ comprising the display layer structure 20 and a second integrated sensing layer structure 26’ will now be described.

- 10 Referring to Figure 7, a display layer structure 20 of a second touch screen display 2’ is shown. The subpixels 22, 23, 24 are arranged in a repeating two-dimensional array.

The first subpixels 22 have first and second side lengths x_i5 y_x in the plane of the display layer.

Referring to Figure 8, the second integrated sensing layer structure 26’ comprises photodetectors 44, which may be organic photodetectors. The photodetectors 44, each having first and second side lengths x₂, y₂ in the plane of the second integrated sensing layer structure 26’, are disposed in an array. The first photodetector side length x₂ is smaller than the first side length x_x of the first subpixel 22 and the second photodetector side length y₂ is smaller than the second side length y_x of the first subpixel 22. The photodetectors 44 are substantially transparent to light of the first colour and responsive to light of the third colour.

A first set of touch sensing electrodes 35’ are spaced apart and interspersed with the photodetectors 44 in a first direction (for example, the y direction) and extend in a second direction (for example, the x direction) which is perpendicular to the first direction. The electrodes comprising the first set 35’ are spaced apart from each other and from the photodetectors 28’ by insulating material 45 which is substantially transparent.

A second set of touch sensing electrodes 37’ are spaced apart and interspersed with the photodetectors 44 in the second direction and extend in the first direction. The electrodes comprising the first set 35’ are spaced apart from each other and from the photodetectors 44 by insulating material (not shown) which is substantially transparent. The first and second sets of touch sensing electrodes 35’, 37’ are spaced apart by an insulating layer (not shown) in a third direction perpendicular to the first and second directions. The insulating material 45 and insulating layer may comprise, for example, air, polystyrene, Poly(methyl methacrylate) (PMMA), ORG series or PGI series dielectrics available from Sumitomo Chemical Co.

Figure 9a shows a first cross-sectional view of a second touch screen display 2’ comprising the display layer structure 20 and the second integrated sensing layer structure 26’.

- 11 The second touch screen display 2’ comprises a substrate 19 and a display layer structure 20 disposed on the substrate 19. A first optical out-coupling layer 25 is disposed over the display layer structure.

The second integrated sensing layer structure 26’ is disposed over the first optical outcoupling layer 25. The array of photodetectors 44 is disposed such that the photodetectors 44 partially overlie the subpixels 22 which emit light of the first colour and do not overlie the subpixels 24 which emit light of the third colour. The photodetectors 44 are substantially transparent to light of the first colour emitted by subpixels 22, and so light of the first colour emitted by subpixels 22 is not blocked by photodetectors 44.

As described hereinbefore, the second integrated sensing layer structure 26’ further comprises first and second sets of touch sensing electrodes 35’, 37’ spaced apart by an insulating layer 33’ which is substantially transparent. Thus, in this embodiment, the touching sensing elements are coplanar with the light sensing elements.

The electrodes comprising the first set 35’ are spaced apart from each other and from the photodetectors 44 by insulating material 45 which is substantially transparent. The electrodes comprising the second set 37’ are spaced apart from each other and from the photodetectors 44 by insulating material 46 which is substantially transparent.

The insulating layer 33’ and insulating material 45, 46 may comprise, for example, air, polystyrene, Poly(methyl methacrylate) (PMMA), ORG series or PGI series dielectrics available from Sumitomo Chemical Co.

A third optical out-coupling layer 39 is disposed over the second integrated sensing layer structure 26’. The third optical out-coupling layer 39 may also function as an optical in-coupling layer.

The second touch screen display 2’ further comprises a capping layer 40 overlying the third optical out-coupling layer 39. The capping layer 40 comprises a substantially transparent material, for example, plastic or glass. The capping layer 40 has a first interface 41 with the third out-coupling layer 39 and a second interface 42 opposite the first interface 41.

- 12 Figure 10 shows third and fourth light rays 43₃, 434 emitted by third and fourth subpixels 243, 244 of second touch screen display 2’. The third and fourth subpixels 243, 244 are subpixels of the third type, that is, subpixels which emit light of the third colour.

The third and fourth light rays 433, 434 propagate through the first optical out-coupling layer 25, the second integrated sensing layer structure 26’, and the third optical outcoupling layer 39, and are incident at the second interface 42.

The third emitted light ray 43₃ is incident at the interface 42 at a seventh point i6₇. The 10 seventh point i6₇ lies between second and third adjacent points of contact 162,163 and is in contact with an air gap 181. The third emitted ray 433 is partially internally reflected at the second interface 42 and a third reflected ray 493 is directed at a third photodetector 443. The photodetectors 44 are sensitive to light of the third colour and thus the third photodetector 443 outputs a signal in response to receiving a third reflected light ray 493.

The fourth emitted light ray 434 is incident at an eighth point 16s which is in contact with a third ridge i5₃.The fourth emitted ray 432 is scattered and/or absorbed and a fourth scattered light ray 494 may be directed at a fourth photodetector 444. The fourth photodetector 444 measures a reduced amount of light compared to with the third photodetector 443. Thus, the features of a fingerprint carried by a finger in contact with the second interface 42 may be determined.

Referring to Figure 11, a modified display layer structure 20’ is shown. The first subpixels 22 are arranged in columns interspersed with columns of second subpixels 23 and columns of third pixels 24.

Referring to Figure 12, a third integrated sensing layer structure 26” is shown. The third integrated sensing layer structure 26” comprises a plurality of spaced apart columns of photodetectors 28, for example, organic photodetectors. The columns extend in a first direction in the plane of the third integrated sensing layer structure 26”, for example, the y direction and are spaced apart in a second, perpendicular direction in the plane of the third integrated sensing layer structure 26”, for example, the x direction. The photodetectors 28 are substantially transparent to light of the first colour and responsive to light of the third colour.

-13The third integrated sensing layer structure 26” comprises a plurality of spaced apart columns of touch sensing elements 47 interspersed with the columns of photodetectors 28. The touch sensing elements 47 are coplanar with the photodetectors 28.

The columns of touch sensing elements 47 extend in the first direction, that is, the direction the plane of the third integrated sensing layer structure 26” parallel to the columns of photodetectors 28, and are spaced apart in the first direction by transparent insulating material 48. The columns of touch sensing elements 47 are spaced apart in the second direction, that is, the direction in the plane of the third integrated sensing layer structure 26” parallel to the columns of photodetectors 28 which is perpendicular to the first direction, by transparent insulating material 48 and by photodetectors 28. The transparent insulating material 48 may comprise, for example, air, polystyrene, Poly(methyl methacrylate) (PMMA), ORG series or PGI series dielectrics available from Sumitomo Chemical Co.

Referring to Figure 13, a third touch screen display 2” comprising the third integrated sensing layer structure 26” is shown.

The third touch screen display 2 comprises a substrate 19 which may be transparent or opaque. The modified display layer structure 20’ is disposed on the substrate 19.

A first optical out-coupling layer 25 is disposed over the modified display layer structure 20’. The first optical out-coupling layer is substantially transparent and may be patterned to as to allow light emitted by the subpixels 22, 23, 24 to be coupled out of the modified display layer structure 20’ in a direction away from the substrate 19. For example, the first optical out-coupling layer 25 may comprise a microlens array.

The third integrated sensing layer structure 26” is disposed over the first optical outcoupling layer 25 such that photodetectors 28 overlie first subpixels 22 which emit light of the first colour and do not overlie third subpixels 24 which emit light of the third colour. The photodetectors 28 are substantially transparent to light of the first colour emitted by subpixels 22, and so light of the first colour emitted by subpixels 22 is not blocked by photodetectors 28.

-14A third optical out-coupling layer 39 is disposed over the third integrated sensing layer structure 26”. The third optical out-coupling layer 39 may also function as an optical in-coupling layer.

The third touch screen display 2” further comprises a capping layer 40 overlying the second optical out-coupling layer 30. The capping layer 40 comprises a substantially transparent material, for example, plastic or glass. The capping layer 40 has a first interface 41 with the second out-coupling layer 30 and a second interface 42 opposite the first interface 41.

Figure 14 shows fifth and sixth light rays 43₅,430 emitted by fifth and sixth subpixels 24₅, 246 of third touch screen display 2”. The fifth and sixth subpixels 24₅, 246 are subpixels of the third type, that is, subpixels which emit light of the third colour.

The fifth and sixth light rays 43₅, 430 propagate through the first optical out-coupling layer 25, the third integrated sensing layer structure 26”, and the third optical outcoupling layer 39, and are incident at the second interface 42.

The fifth emitted light ray 43₅ is incident at the interface 42 at a ninth point i6_g. The ninth point i6_g lies between second and third adjacent points of contact 162,163 and is in contact with an air gap 181. The fifth emitted ray 43₅ is partially internally reflected at the second interface 42 and a fifth reflected ray 49₅ is directed at a fifth photodetector 285. The photodetectors 28 are sensitive to light of the third colour and thus the fifth photodetector 285 outputs a signal in response to receiving a fifth reflected light ray

49sThe sixth emitted light ray 430 is incident at a tenth point 1610 which is in contact with a third ridge i5₃.The sixth emitted ray 430 is scattered and/or absorbed and a sixth scattered light ray 490 maybe directed at a sixth photodetector 282. The sixth photodetector 280 measures a reduced amount of light compared to with the fifth photodetector 285. Thus, the features of a fingerprint carried by a finger in contact with the second interface 42 may be determined.

The subpixels 22, 23, 24 of the display layer structure 20 and the modified display layer structure 20’ are preferably organic light-emitting diodes (OLEDs).

-15OLEDs comprise an anode, a cathode and a light-emitting layer comprising an organic light-emitting material between the anode and the cathode. One or more further layers may be provided between the anode and the cathode, optionally one or more chargetransporting, charge injecting or charge-blocking layers. Upon application of a bias between the anode and cathode, light is emitted from the organic light-emitting material. OLEDs may be as described in Organic Light-Emitting Materials and Devices, Editors Zhigang Li and Hong Meng, CRC Press, 2007, the contents of which are incorporated herein by reference.

Light-emitting materials may emit in any part of the visible spectrum and include red, green, and blue light-emitting materials.

A blue emitting material may have a photoluminescent spectrum with a peak in the range of 4OO-49Onm, optionally 420-490nm. A green emitting material may have a photoluminescent spectrum with a peak in the range of more than 490nm up to

58onm, optionally more than 490nm up to 540nm. A red emitting material may have a photoluminescent spectrum with a peak in the range of more than 58onm up to 630nm, optionally more than 585nm up to 625nm.

The photodetectors 28, 28’, 44 are preferably organic photodetectors (OPDs).

An OPD comprises an anode, a cathode and an organic semiconducting region between the anode and cathode. The organic semiconducting region may comprise adjacent electron-donating and electron-accepting layers or may comprise a single layer comprising a mixture of an electron-accepting material and an electron-donating material. One or more further layers may be provided between the anode and the cathode. Conversion of light incident into electrical current maybe detected in zero bias (photovoltaic) mode or reverse bias mode.

Figure 15 illustrates example absorbance spectra for first and second organic materials suitable for use in an OPD in a touch screen display device according to the present invention. The first material, having a first absorbance spectrum 51, is Poly(9,9-di-noctylfluorenyl-2,7-diyl), also known as F8. The first material is absorbing in the blue region of the spectrum and is transparent to red and green light. The second material, having a second absorbance spectrum 52, is Poly(9,9-dioctylfluorene-alt-16benzothiadiazole), also known as F8BT. The second material is absorbing in the blue region and is transparent to red light.

Either of the first and second materials may act as the donor material in a photodiode combined with a C6o derivative, for example, [6,6]-phenyl-C6i-butyric acid methyl ester, also known as PCBM, as an acceptor. The choice of C6o derivative is made such that there is a sufficient energy level offset in the donor: acceptor interface to allow efficient exciton dissociation. For example, the energy level offset maybe approximately 0.2 eV.

Referring to Figure 16, the first touch screen display 2 comprising display layer 20, light sensing elements 28, and touch sensing elements 35, 37 may be coupled to a controller 50.

The controller 50 may be adapted to output a signal or command in response to receiving a signal from one or more of the light sensing elements 28. The controller 50 maybe adapted to apply a signal to one or more of the light sensing elements 28.

The controller 50 may be adapted to output a signal or command in response to receiving a signal from one or more of the touch sensing elements 35, 37. The controller may be adapted to apply a signal to one or more of the touch sensing elements 35,37.

The controller 50 may be adapted to apply a signal to one or more of the light-emitting pixels 21 or subpixels 22, 23, 24.

The second and third touch screen displays 2’, 2” may be coupled to a controller 50 in a similar manner.

Referring to Figure 17, a process flow diagram of a method of fabricating the touch screen display 2 is shown.

The substrate 19 is provided (step Si). The display layer structure is formed (step S2). Intermediate layer(s) is formed (step S3). The sensing layer is formed (step S4).

-17Step S3 may alternatively comprise providing a pre-formed intermediate layer, for example an optical out-coupling and/or in-coupling layer, and attaching the intermediate layer to the display layer structure.

Step S4 may alternatively comprise providing a pre-formed integrated sensing layer structure and attaching the integrated sensing layer structure to the intermediate layer(s).

Modifications

It will be appreciated that various modifications may be made to the embodiments hereinbefore described. Such modifications may involve equivalent and other features which are already known in the design, manufacture and use of touch screen displays and which may be used instead of or in addition to features already described herein. Features of one embodiment maybe replaced or supplemented by features of another embodiment.

The arrangement of subpixels may be other than the arrangements shown in Figures 7 and 11. A subpixel may include a colour filter.

Any of the optical out-coupling/in-coupling layers may be omitted. Further outcoupling/in-coupling layers maybe present.

Claims

Claims

l. A touch screen display comprising: a substrate;

5 a display layer structure disposed on the substrate, the display layer structure comprising an array of light-emitting pixels, each light-emitting pixel comprising a set of first, second, and third subpixels configured to emit light of different first, second, and third colours respectively; and an integrated sensing layer structure disposed over the display layer structure, 10 the integrated sensing layer structure comprising an array of touch-sensitive elements and an array of light-sensing elements;

wherein the light-sensing elements are transparent to light of the first colour and are responsive to light of the third colour.

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2. A touch screen display according to claim 1, wherein the array of touch-sensitive elements and the array of light-sensing elements are coplanar.
3. A touch screen display according to claim 1 or 2, wherein the light-sensing elements are interspersed between the touch-sensitive elements.
4. A touch screen display according to any preceding claim, wherein the lightsensing elements are transparent to light at the second colour.
5. A touch screen display according to any preceding claim, wherein the light25 sensing elements are not responsive to light at the second colour.
6. A touch screen display according to any preceding claim, wherein the lightsensing elements and the first subpixels are in registration.

30
7. A touch screen display according to any preceding claim, wherein the substrate extends in first and second directions at a first point, wherein a light-sensing element is disposed so as to lie in a light path of light emitted from a subpixel configured to emit light of the first wavelength, the light path being along a third direction including the first point, the third direction being perpendicular to the first and second directions.
-198. A touch screen display according to any preceding claim, wherein the lightemitting pixels comprise organic light emitting diodes.
9. A touch screen display according to any preceding claim, wherein the light5 sensing elements comprise organic photodetectors.

10. A touch screen display according to any preceding claim, wherein the integrated sensing layer structure comprises a first sensing layer comprising the array of lightsensing elements and a second sensing layer comprising the array of touch-sensitive
10 elements.
11. A touch screen display according to claim 10, further comprising an optical outcoupling layer disposed between the first sensing layer and the second sensing layer.

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12. A touch screen display according to claim 10 or 11, further comprising an optical in-coupling layer disposed between the first sensing layer and the second sensing layer.
13. A touch screen display according to any preceding claim, further comprising an optical out-coupling layer disposed between the display layer structure and the

20 integrated sensing layer structure.
14. A touch screen display according to any preceding claim, further comprising an optical out-coupling layer disposed over the integrated sensing layer structure.

25
15. A touch screen display according to any preceding claim, further comprising an optical in-coupling layer disposed over the integrated sensing layer structure.
16. A touch screen display according to any preceding claim, wherein the touchsensitive elements are transparent to at least light at the third colour.
17. A touch screen display according to any preceding claim, wherein the touchsensitive elements comprise capacitive touch elements.
18. A touch screen display according to any preceding claim, wherein each subpixel 35 comprises a colour filter.

- 20
19· A touch screen display according to any preceding claim, further comprising an encapsulation layer disposed over the integrated sensing layer structure.
20. A touch screen display device comprising a touch screen display according to 5 any preceding claim and a controller operatively coupled to the touch screen display.
21. A touch screen display device according to claim 20, which is adapted to be a portable computing device.

Intellectual

Property

Office

Application No: GB1613755.6 Examiner: Mr Chris Davidson