Display Week 2012 Review: Touch Technology
Contents
1. CF glass that functions as a shield and anti static device this layer can be segmented into sense electrodes Since all sense electrodes except the one being sensed at any given moment are grounded the ITO layer still performs its original function even though it s been seg mented The touch sensor architecture of an IPS LCD is illustrated in Fig 3 Adding in cell touch to an IPS LCD as described in the previous paragraph is some times referred to as no cost because it may require no mask changes The author dis 8 Information Display 9 12 agrees with this viewpoint since it is likely that we are actually talking about creating a new display with embedded touch which rep resents a new development cost that must be amortized The reason it s a new display is that the existing non touch display is unlikely to be made obsolete since the LCD maker probably has OEM customers buying it that use discrete or one glass solution OGS touch screen construction In cell touch in general is likely to add new products to an LCD maker s product line rather than replacing exist ing products The management of this expanded product line adds yet another implicit cost The new development costs to be amortized include not only a new set of masks for the TFT array but also the customization of the combined touch controller and LCD driver TTDI IC and firmware to match the particu lar display resolution being used Non recur ri2. the surface several suppliers Fig 5 Nippon Electric Glass created this 10 8 in curved p cap touch screen reference design on a 50 um glass substrate with elec trodes deposited on both sides and a 100 um cover glass The minimum radius of curva ture is 65 mm Nippon Electric Glass envi sions applications with a curved display in automotive navigation systems tablet PCs and smartphones Source Geoff Walker Information Display 9 12 9 touch technology review e Extensive parameter tunability on Baanto s latest optical touch screens Some of the parameters include touch area detection minimum touch time before a new touch is recognized and shadow touch density e A new laser cutting method for alumino silicate toughened glass that loses only 10 of the glass s strength Asahi Glass e A plug in for Adobe Acrobat that allows four users to simultaneously edit the same drawing or document on a multi user touch table Circle 12 e Re designed spacer dots in a four wire resistive touch screen that reduce the touch force required for activation to only 2 or 3 grams it feels the same as p cap Fujitsu Components e PQ Labs s high finger count infrared touch algorithms licensed to IRTouch and used in a 10 touch 22 in IR touch screen A representative in the IRTouch booth said that there s a lot of interest in the product but that it s not concentrated in any one market i e there isn
3. 70 due to the double sided problem i e whatever you do to one side of the CF glass is likely to damage or affect the other side For example if you do the CF side first it can use organic material when you anneal the ITO on the touch side the high tempera ture damages the organic CF material e One glass solution OGS which Chimei calls window integrated sensor By the way the term OGS seems to be slowly taking hold in the touch industry more than a few booths on the show floor were using it Chimei s yield with CON OOF W Cover Glass Lens Decoration Top Polarizer On Cell Sense Y Electrodes Color Filter Glass Color Filter VCOM Drive X Electrodes Liquid Crystal TFTs TFT Array Glass Fig 4 Synaptics s touch sensor architecture for VA LCDs incorporates an additional layer of segmented ITO row 4 in the graphic that is deposited to form sense electrodes on top of the CF glass The segments of the VCOM plane underneath the CF glass row 7 in the graphic are grouped differently to form drive electrodes when the display is operating in touch sensing mode Source Geoff Walker OGS is also in the 60 70 range because it s a difficult process that the company hasn t done before Other vendors with more experience doing OGS have reported higher yields The touch sensor is a single layer of ITO with bridges Chimei claims that this is lower cost than two
4. Inno vations in Touch Sensing This presenta tion described with excellent clarity all the possible touch sensor architectures that could be used in a smartphone see pages 20 37 of Innovations in Touch Sensing In this presentation Bob also stated that the Sony Xperia P smartphone shown in Fig 2 uses in cell touch electrodes configured as described on page 11 of the Distinguished Paper mentioned above An In Cell Capable Capacitive Touchscreen Controller Ina Synaptics blog it is stated that the HTC EVO Design 4G also uses the same in cell configu ration Both of these smartphones use a 4 in 960 x 540 QHD 275 ppi LTPS LCD However the LCDs are not actually identical visual inspection of the phones reveals that the Sony Xperia P LCD uses RGBW pixels while the HTC EVO Design 4G LCD uses RGB pixels These two shipping products use separate but linked touch controller and LCD driver ICs Synaptics has announced that it has started manufacturing a single IC that includes both functions for 864 x 480 WVGA LCDs it has named this new product TDDI Touch and Display Driver IC This integration reduces component cost of course but it also creates an IC that is unique for a particular LCD If another LCD manufacturer wants the same functionality but is using an LCD with a slightly different resolution there are no stan dards for LCD resolution in the smartphone market like there are in the PC market the
5. al world Connecting a noisy AC adapter to a smart phone can raise the system noise floor by a factor of 10 causing that touch screen to become completely inoperative The use of a fine tipped passive stylus which will become much more important with the launch of Windows 8 requires a much higher SNR Based on Synaptics work a realistic minimum SNR target for an excellent user experience in the real world is 50 dB a little over 300 1 Even higher is better for a passive stylus In order to accomplish a 50 dB SNR Synaptics concluded that a the basic touch architecture must be true mutual capacitive rather than any of the existing in cell capaci tive variations b the touch controller and the LCD driver must communicate with each other and c the LCD driver timing must be modified to support both a display mode and a touch mode The Distinguished Paper entitled An In Cell Capable Capacitive Touchscreen Controller with High SNR and Integrated Display Driver IC for WVGA LTPS Displays by Synaptics is the key document that describes this technique Among other details the paper describes segmenting the VCOM plane in an LCD to allow dual purpose operation as drive electrodes for true mutual capacitive touch sensing while still functioning as a proper VCOM plane for display operation Re purposing the VCOM plane as touch screen drive electrodes also produces a highly desirable advantage it moves th
6. an early sample of Synaptics s integrated touch controller and LCD driver TDDI IC The Chimei represen tatives said that their drive electrodes VCOM segments use existing traces on the TFT array this is possible because the Synaptics TDDI IC allows each row and column of the LCD to be addressed individually They also said that they had not yet measured the SNR of their prototype but that they expected the value to be similar to that reported by Synaptics Other Chimei Innolux Embedded Touch Architectures Chimei had the most extensive display of embedded touch products on the show floor In addition to the IPS in cell touch mentioned in the previous paragraph the company was also showing or talking about the following e A self capacitive set of electrodes on top of the CF glass in a diamond pattern with true multi touch and as many as 300 pads A VP at Chimei told the author that they had started this project a long time ago when Chimei had a restricted manufacturing capacity They did not want to add more machines to do multiple layers so they challenged their engineering team to add touch using the existing equipment From such challenges innovation is born e Standard on cell mutual capacitive which Chimei calls OTS on cell touch screen This is a single layer of ITO with bridges using the standard Synaptics controller This configuration is not in volume pro duction yet at Chimei because the yield is only 60
7. e typical 10 V VCOM signal from the denominator of the SNR into the numerator i e instead of being considered noise that detracts from the operation of the touch screen the VCOM signal becomes part of the touch screen operation Even better higher VCOM voltages result in a higher SNR The sense electrodes are deposited in a single layer of ITO on top of the color filter CF glass This touch sensor architecture is shown in Fig 1 taken from the aforemen tioned Synaptics Distinguished Paper Note that technically this architecture is a hybrid of in cell and on cell since one set of electrodes is inside the cell the segmented VCOM plane and one set of electrodes is outside the cell deposited on top of the CF glass However the LCD industry is rapidly moving towards calling all forms of embed ded touch in cell on the grounds that it s all inside the LCD module For example Chimei Innolux announced at Display Week 2012 that it is going to brand all of its embedded touch products from now on as Touch On Display TOD intentionally obscuring the specific touch sensor architecture that s used in a given product After all why should anyone care what touch sensor architecture is used other than the manufacturer of course New Shipping In Cell Products The Next Piece of the Puzzle On Monday of Display Week 2012 Bob Mackey Synaptics s Principal Scientist presented a Technical Seminar entitled
8. e functional differ ence between the VA and IPS configurations VA LCDs do not use a shield layer on top of the CF glass so one additional ITO mask is required in order to deposit a layer of seg mented ITO to form sense electrodes on top of the CF glass The position of the drive elec trodes in a VA LCD is fixed by the VCOM mask while the position of the drive elec trodes in an IPS LCD is determined by the LCD drive electronics The touch sensor architecture of a VA LCD is illustrated in Fig 4 Chimei Innolux s In Cell Prototype The Final Piece of the Puzzle The final piece of the puzzle came from the author talking with several company represen Cover Glass Lens Decoration Top Polarizer Shield Sense Y Electrodes Color Filter Glass Color Filter Liquid Crystal Fig 3 Synaptics s touch sensor architecture for IPS LCDs uses an ITO shield layer on top of the CF glass row 4 in the graphic The shield layer is segmented to form sense electrodes while still retaining its function as a shield Similarly the segments of the VCOM plane in the TFT array row 8 in the graphic are grouped differently to form drive electrodes when the display is operating in touch sensing mode Source Geoff Walker tatives in Chimei Innolux s booth on the show floor The Chimei representatives said that they have recently prototyped in cell touch in one of their IPS LCDs using Synaptics s touch sensor architecture and
9. enior Touch Technologist at Intel He can be contacted at geoff walker intel com 408 765 0056 office or 408 506 7556 mobile 6 Information Display 9 12 touch related materials and equipment market research and touch related services such as bonding optical enhancement and integration As the likely result of projected capacitive p cap and resistive touch technologies accounting for more than 90 of the number of touch screens shipped in 2011 according to DisplaySearch s latest 2012 data the total number of touch technologies exhibited at Display Week 2012 decreased While 12 technologies were shown in 2011 this year there were only six p cap single touch and multi touch resistive infrared embedded in cell on cell hybrid and optical If you looked closely you could find one company that sells but wasn t exhibiting surface acoustic wave another that sells but wasn t exhibiting surface capacitive and a third that sells but wasn t exhibiting electromagnetic digitizers Bending wave from Elo Touch Systems and 3M and force sensing e g from F Origin were nowhere to be found Projected Capacitive P Cap The key difference in the p cap suppliers at Display Week this year was the number of touch module suppliers focused specifically on meeting the needs of commercial applica tions in the U S The 15 suppliers in this group included 3M AMT Bergquist Dawar EETI Emerging Display Techn
10. inting have partnered to produce a line of Fine Touch Z touch screens in sizes 5 12 in Source Geoff Walker module suppliers at Display Week this year that are focused specifically on meeting the needs of commercial applications in the U S It seems clear that the exhibition conference portion of Display Week has become the number one place for U S based commercial touch prospects to look for suppliers and new Fig 7 A 7 in p cap touch screen from Emerging Display Technologies supports a passive Stylus with a 2 mm tip The author wrote his name on the screen with palm con tact there were no spurious points recorded and the ink was noise free with normal stair stepping that software could easily smooth Source Geoff Walker technology The majority of the 31 presenta tions on touch in the bulleted list at the begin ning of this article presentations made in the Market Focus Conference Investors Conference Exhibitors Forum Technology Seminars and Short Course were made by American companies In contrast the touch portion of the Sympo sium is dominated by the Asia centric display industry Of the 19 papers and posters on touch presented in the Symposium 10 were written from a display industry perspective reflecting the very strong interest of the dis play industry in embedded touch five were written from a touch screen industry perspec tive and four were written from an other perspective glas
11. layers with an insulator One of the difficulties is the temperature limit of the black mask decoration material if the ITO needs to be annealed the current black mask material cannot handle the high temperature Some Other Interesting Exhibits The Display Week exhibition is so chock full of interesting things to see that it s almost impossible to see it all Here is a sampling of exhibit offerings that the author found particu larly interesting e A very clever method of having touch buttons on a display without actually using a touch screen This is accomplished by positioning long range proximity sensors in the bezel below the display and con trolling their sensing pattern Azoteq e A Specific Absorption Rate SAR prox imity sensor with optimization for human detection vs inanimate objects This is accomplished using two capacitive proximity sensors and digital signal processing Semtech e A curved touch screen shown in Fig 5 built on a 50 um glass substrate with a 100 um cover glass Nippon Electric Glass e A new method of making ITO invisible by depositing the ITO on top of a 3 D moth eye nanostructure The nano structure makes the difference between the I TO coated and uncoated surfaces reflectivity and also transmittance almost zero Sony Chemical e A 3H hardcoat film with more abrasion resistance than an 8H hardcoat film Oike e P cap touch screens that work well with water on
12. n it requires a new custom IC This problem was pointed out in a presentation entitled Chal lenges and Opportunities in Touch Controller Semiconductors made by Randy Lawson a Senior Principal Analyst at IHS during Thursday s Market Focus touch conference In Cell Touch in IPS LCDs In an IPS LCD the VCOM plane is located in the TFT array and it s already segmented by design Without changing the various metal Towch Receivers M0 Receiver on CF glass Segmented VOOM Plane Fig I Synaptics s true mutual capacitive LCD in cell touch sensor architecture incor porates a VCOM plane that is segmented to allow dual purpose operation as drive elec trodes for touch sensing while still functioning as a proper VCOM plane for display opera tion Sense electrodes are deposited on top of the color filter glass Source Synaptics Information Display 9 12 7 touch technology review APERLA Fig 2 The Sony Xperia P smartphone uses Synaptics s true mutual capacitive in cell touch sensor architecture as described in the company s Distinguished Paper Like most current mobile devices this smartphone uses an IPS LCD the touch sensor is therefore configured as shown in Fig 3 Image source Sony and ITO masks used to create the VCOM plane the VCOM segments can be grouped differently to form touch sensing drive elec trodes In most IPS LCDs there is also a grounded layer of ITO on top of the
13. ng engineering NRE costs such as the latter can be justified by the reduction in com ponent cost achieved by the TTDI IC but the primary factor that justifies the development of a new display with embedded touch is very high sales volume In the author s opinion it therefore seems unlikely that in cell touch is going to spread into every LCD in an LCD maker s product line it s more likely that it will be used only in the highest volume models at least in the next several years Over the long term as the overall penetration of touch increases it is possible that the majority of mobile LCDs could include in cell touch Usable in cell capacitive touch in IPS LCD ll E E D a a a tts amp VCOMDrive X Electrodes TFT Array Glass larger than mobile LCDs is still under devel opment ITO replacement materials such as micro scale metal mesh or silver nanowires are probably the most significant enabler In Cell Touch in VA LCDs The differences in touch sensing architecture between an IPS LCD and a VA LCD are minor The main difference is the location of the VCOM electrode In a VA LCD the VCOM signal is applied to the ITO on the inner surface of the CF glass Again the ITO mask used to create the VCOM plane is changed so that the VCOM segments can be grouped differently to form drive electrodes Since the inner surface of the CF glass and the top surface of the TFT array are only a few microns apart there is littl
14. ologies Gunze USA Mitsubishi Electric NLT Tech nologies Ocular Panjit RitFast SMK Touch 0362 0972 09 2012 006 1 00 00 SID 2012 International UICO and Zytronic there may be others that the author missed Prior to Display Week it was not unusual to hear a p cap touch screen prospect say Well who else IS there besides Ocular and Touch Inter national Several of 15 are first time exhibi tors at Display Week others have changed their product focus from resistive to p cap There s beginning to be a significant amount of product differentiation between these suppliers Some of their differentiation points include quick turn prototypes large screens e g 17 and 22 in a wide range of screen sizes cover glass decoration printing shaping drilling light pipes efc lamination extended operating temperatures working with wet hands or gloves stylus support a large number of simultaneous touch points operation in rain or saltwater spray and embedded GUI solutions In Cell Touch The Real Surprise at Display Week 2012 Prior to Display Week 2012 it seemed as though in cell touch wasn t making any sig nificant progress The number of shipping products with in cell touch could be counted on just a few fingers 1 The line of Samsung digital cameras that use pressed capacitive with a user experience significantly inferior to that of the typical smartphone 2 The 21 5 in monitors fr
15. om Integrated Digital Technologies IDTI that use in cell optical 3 The Microsoft Surface 2 0 that uses Samsung s SUR40 LCD with in cell optical but requires severely limiting ambient light e g 50 lux maximum of incandescent light due to the touch system s very high sensitivity to ambient IR While these products are all shipping they cannot be seen as successful mainstream applications of in cell touch What changed and was reported in bits and pieces at Display Week 2012 was that Synaptics made a breakthrough Working with multiple LCD manufacturers with the lead most likely being Sony for the last year Synaptics determined that the only way to create a smartphone like touch experience with in cell touch is to use the same mutual capacitive sensor architecture that has become so successful in external touch screens but move at least one set of electrodes into the LCD cell and find a way to significantly increase the touch system s signal to noise ratio SNR Most of the papers published mostly by the display industry on all forms of in cell touch optical voltage sensing pressed capac itive and self capacitive have reported SNRs in the range of 10 1 3 dB or 20 1 10 dB For example there is a touch paper from this year s Symposium that claims an SNR of 10 1 is enough to meet the needs of a smartphone That may be acceptable in the lab but it s certainly not acceptable in the re
16. s 2 bonding and proximity sensing While this difference between the exhibition conference and the Symposium parts of Display Week is not necessarily a problem the author would definitely like to encourage the touch screen industry to write more higher quality papers or posters for the Symposium In that way the touch portion of Display Week will become all it can be References DisplaySearch Touch Panel Market Analysis 2012 Annual Report July 2012 J Lee et al Hybrid Touch Screen Panel Inte grated in TFT LCD SID Symposium Digest paper 24 3 2007 3Samsung Electronics America Inc User Manual ST700 version 1 3 pp 21 22 March 2011 http www idti com tw solution php retrieved 7 13 12 http ntuzhchen blogspot com 201 1 03 idti in cell touch panel html retrieved 7 13 12 Samsung Electronics Co Ltd Samsung SUR40 for Microsoft Surface Venue Readiness Guide pp 7 13 December 2011 TM Ozbas et al An In Cell Capable Capaci tive Touchscreen Controller with High SNR and Integrated Display Driver IC for WVGA LTPS Displays ISSN 0097 966X 12 4301 0485 paper 37 1 SID Symposium Digest 49 485 488 2012 8B Mackey Innovations in Touch Sensing presented as Seminar M 3 at SID Display Week Conference Boston MA June 2012 download able from http blog synaptics com wp content uploads 2012 06 SID_2012_Seminar M 3_CapacitiveTouch_Mackey_Present pdf h
17. t one common application e Stantum s latest digital resistive touch screen made by Nissha Printing and shown in Fig 6 with Peratech s quan tum tunneling pressure sensing material in a layer only a few microns thick between the film and the glass e A p cap mutual capacitive sensor in 3 5 5 and 7 in sizes that uses a single layer of ITO without bridges or metal routing traces This is accomplished by running drive electrodes vertically down the sensor and forming individual sense pads in a column beside each drive elec trode This layout also allows the sensor to be borderless on three sides The sen sor is built on a substrate of Corning s 0 1 mm Willow glass and laminated to a 0 5 mm cover glass with 0 1 mm of OCA for a total stack up of 0 7 mm This is about the same thickness as an OGS configuration but without the asso ciated yield problems TouchTurns e An ordinary 7 in p cap touch screen shown in Fig 7 that works very well with a passive 2 mm tip stylus Emerg ing Display Technologies Touch at Display Week is Evolving In the beginning of this article there was a mention of the increased number of p cap 10 Information Display 9 12 Fig 6 Stantum s latest digital resistive tVSM touch screen uses Peratech s quan tum tunneling pressure sensing material in a layer only a few microns thick between the film and the glass Note the Nissha branding Stantum and Nissha Pr
18. touch technology review Display Week 2012 Review Touch Technology 2012 was the year that in cell capacitive touch became real It didn t happen with big fanfare in fact you had to put together pieces from the Symposium the Monday Technology Seminars the Thursday Market Focus touch conference and the exhibits to get the full picture But it was there and it s significant by Geoff Walker L you missed Display Week 2012 you missed the most important event of the year in the touch industry anywhere on the planet The amount of concentrated information about touch available at Display Week 2012 was and will be unsurpassed by any other conference anywhere this year e A 4 hour Short Course on Sunday e Two 90 minute Technology Seminars on Monday e Three presentations at Tuesday s Investors Conference e Six presentations at the Exhibitors Forum on Tuesday e 12 papers in the Symposium mostly on Wednesday e Seven posters in Thursday s Poster Session e 19 presentations in Thursday s Market Focus Conference e Almost half of the 195 companies exhibiting on the show floor including suppliers of touch screens controllers At the time he wrote this article Geoff Walker was the Owner amp Principal Consul tant at Walker Mobile LLC a technical mar keting consulting firm He has also been Information Display s Guest Editor for Touch since 2007 By the time this article will be published Geoff will be a S
19. ttp blog synaptics com p 104 retrieved 6 20 12 IOR Lawson Challenges and Opportunities in Touch Controller Semiconductors presented at SID IMS Future of Touch and Interactivity 2012 Conference Boston MA June 2012 E
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