Article Ultrafast Method to Fabricate Gravure Plate for Printed Metal-Mesh Touch Panel:

Weiyuan Chen 1, Wenlang Lai 1, Yuming Wang 1, Kaijun Wang 1, Shengyu Lin 1, Yuli Yen 1,2, Hong Hocheng 2 and Tahsin Chou 1,*

Received: 9 July 2015 ; Accepted: 26 September 2015 ; Published: 5 October 2015 Academic Editor: Maria Farsari

1 Mechanical and System Research Laboratories, Industrial Technology Research Institute, No. 195, Sec. 4, Chung Hsing Road, Chutung, Hsinchu 31040, Taiwan; [email protected] (W.C.); [email protected] (W.L.); [email protected] (Y.W.); [email protected] (K.W.); [email protected] (S.L.); [email protected] (Y.Y.) 2 Department of Power Mechanical Engineering, National Tsing Hua University, No. 101, Sec. 2, Kuang Fu Road, Hsinchu 30013, Taiwan; [email protected] * Correspondence: [email protected]; Tel.: +886-3591-6791; Fax: +886-3582-0043 : This paper is an extended version of our paper published in the 6th International Conference of Asian Society for Precision Engineering and Nanotechnology (ASPEN2015), Harbin, China, 15–19 April 2015.

Abstract: In order to engrave gravure plate with fine lines structures, conventional art used lithography with dry/wet . Lithography with dry/wet etching method allows to engrave lines with smooth concave shape, but its disadvantages include difficulty in controlling aspect ratio, high and uniform in large size process, substrate material limitation due to etching solution availability, and process complexity. We developed ultra-fast laser technology to directly engrave a stainless plate, a gravure plate, to be used for fabricating 23 in. metal-mesh touch panel by gravure offset printing process. The technology employs high energy pulse to ablate materials from a substrate. Because the ultra-fast laser pulse duration is shorter than the energy dissipation time between material lattices, there is no heating issue during the ablation process. Therefore, no volcano-type protrusion on the engraved line edges occurs, leading to good printing quality. After laser engraving, we then reduce surface roughness of the gravure plate using electro-polishing process. Diamond like carbon (DLC) coating layer is then added onto the surface to increase scratch resistance. We show that this procedure can fabricate gravure plate for gravure offset printing process with minimum printing linewidth 10.7 µm. A 23 in. metal-mesh pattern was printed using such gravure plate and fully functional touch panel was demonstrated in this work.

Keywords: ultrafast laser; gravure offset printing; gravure plate; metal-mesh touch panel

1. Introduction Printing process provides a fast, continuous production with low production costs and pollution, and becomes a key process technology in printed electronics [1,2]. These processes need only one-step process to transfer pattern onto target surface, studied by Pudas et al., Lee et al., and Chun et al. [3–5]. Owing to its high line resolution, the gravure offset printing technology may replace the current photolithography process and is considered as the advanced manufacturing technology for next generation electronic products [6]. The key issue of gravure offset printing process is the gravure plate, which transfers the designed pattern to be printed. There are three different engraving methods that can be used for fabricating gravure plate. These methods include wet etching, electroforming [7], and ultra-fast laser direct ablation. Fabricating gravure plate by electroforming is a replication process and not the original

Micromachines 2015, 6, 1483–1489; doi:10.3390/mi6101433 www.mdpi.com/journal/micromachines Micromachines 2015, 6, 1483–1489 structuring process. Fabricating gravure plate by wet etching process after lithography is popular in industry. However, the major disadvantage of wet etching process is isotropic etching phenomenon. It is difficult to make the high aspect ratio of the groove substrate. Furthermore, the etchant chemicals have to be continuously replaced in order to keep the same initial etching rate, and the choice of substrateMicromachines material 2015 is, 6 limited, page–page by the availability of the etchant chemicals. The method to fabricate gravure plates described in this research is ultra-fast laser direct ablation. A laser beam is focused onto popular in industry. However, the major disadvantage of wet etching process is isotropic etching the surfacephenomenon. of the gravure It is difficult plate to to make fabricate the high the aspect pattern. ratio Comparingof the groove with substrate. ablation Furthermore, using nanosecond the pulses laser,etchant the chemicals ultra-fast have laserto be ablationcontinuously has replaced little or in noorder collateral to keep the damage same initial from etching shock rate, waves and heat conductionand the choice produced of substrate during material the material is limited being by the processed availability [8 ].of Usingthe etchant dimensional chemicals analysis,. The the conductionmethod time to infabricat SUS304e gravure steel plateplates isdescribed at the range in this of research millisecond is ultra and-fast nanosecond. laser direct ablation. Comparing to the twoA methods laser beam mentioned is focused before,onto the ultra-fast surface of laserthe gravure direct ablationplate to fabricate has advantages the pattern. of Compar short productioning with ablation using nanosecond pulses laser, the ultra-fast has little or no collateral time and well uniformity [8–10]. damage from shock waves and heat conduction produced during the material being processed [8]. TheUsing great dimensional demand foranalysis, alternative the conduction solutions time for in SUS304 indium steel tin plate oxide is (ITO)at the range has arisen of millisecond due to several intrinsicand drawbacks nanosecond. ITO’s. Compar Theing transparentto the two methods conducting mentioned electrodes before, ultr cana-fast be laser made direct by metalablation material throughhas by advantages laser ablation of short [production11], lithography, time and well and uniform printingity [8 process.–10]. The printing process has the advantage inThe cost great and demand throughput. for alternative solutions for indium tin oxide (ITO) has arisen due to several intrinsic drawbacks ITO’s. The transparent conducting electrodes can be made by metal material In this study, an ultra-fast laser engraving system is established to fabricate 23 in. metal-mesh through by laser ablation [11], lithography, and printing process. The printing process has the gravuread plate.vantage In in ordercost and to throughput. enhance the ink transfer rate, electrolytic polished process [12] is used to decreaseIn the this roughness study, an of ultra groove-fast engravedlaser engraving by laser. system Then, is established the gravure to platefabricate is deposited23-inch with diamondmetal like-mesh carbon gravure (DLC) plate. to In protect order to the enhance surface the against ink transfer scratches rate, electrolytic and abrasion polished by process the doctor [12] blade duringis printing used to decrease process. the Finally,roughness the of groove gravure engraved plate by can laser. be Then, manufactured the gravure byplate optimal is deposited machining parameterswith diamond and successfully like carbon used(DLC) forto protect printing the surface the 23 against in. metal-meshscratches and abrasion touch sensor by the doctor circuits with blade during printing process. Finally, the gravure plate can be manufactured by optimal linewidth of approximately 10 µm. machining parameters and successfully used for printing the 23 in. metal-mesh touch sensor circuits with linewidth of approximately 10 μm. 2. Femtosecond Laser System and Machining Process Figure2. Femtosecond1 shows the Laser schematic System and diagram Machining of the Process ultra-fast laser engraving system used to engrave 23 in. metal-meshFigure 1 circuitshows the patterns schematic on diagram the steel of substrate.the ultra-fast The laser laser engraving source system is a commercial used to engrave ytterbium laser (HIGH23 in. metal Q LASER,-mesh circuit FemtoREGEN, patterns on the Rankweil, steel substrate. Austria), The laser that source generates is a commercial 350 fs laser ytterbium pulses with a maximumlaser pulse (HIGH energy Q LASER, of20 FemtoREGENµJ at a 100, kHzRankweil, repetition Austria rate), that and generates central 350 wavelength fs laser pulses of withλ = 1035a nm. maximum pulse energy of 20 μJ at a 100 kHz repetition rate and central wavelength of λ = 1035 nm. A galvoA scannergalvo scanner system system is embodied is embodied in in the the laserlaser machining system, system, which which makes makes the process the process speed speed up to 3000up to mm/s. 3000 mm/s. The The diameter diameter of of laser laser beambeam spot size size is is1313 μmµ, m,and and the beam the beam quality quality is M2 < is 1.2. M2 < 1.2. The workpieceThe workpiece is placed is placed on theon the vacuum vacuum chuck chuck and machined machined by bygalvo galvo scanner scanner system system at various at various feed rates.feed Afterrates. After machining machining process, process, the the workpiece workpiece is is rinsed rinsed for for 10 10min min with with alcoh alcoholol in an ultrasonic in an ultrasonic cleanercleaner to remove to remove any debrisany debris from from the the ablation ablation processprocess and and finally finally electrolytic electrolytic polished polished process. process. In this study, a gravure plate which has 15 μm of inner metal-mesh circuits and 70 μm outer In this study, a gravure plate which has 15 µm of inner metal-mesh circuits and 70 µm outer circuit. Due to the difference of line width between inner metal-mesh and outer circuit, this study circuits.utilizes Due tothe the spiral difference feeding ofmachining line width method between to engrave inner metal-meshthe groove with and various outer circuit, widths thisis study utilizesproposed the spiral. feeding machining method to engrave the groove with various widths is proposed.

Figure 1. (a) The ultra-fast laser engraving system; (b) profile of the ultra-fast laser. Figure 1. (a) The ultra-fast laser engraving system; and (b) Gaussian beam profile of the ultra-fast laser. 2

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3. FabricationMicromachines of2015 23, 6, In.page Metal-Mesh–page Circuits Gravure Plate Micromachines 2015, 6, page–page The3. Fabrication dimensions of 23 of In. groove Metal- onMesh gravure Circuits plate Gravure machined Plate by ultra-fast laser engraving system are related3. Fabrication toT thehe dimensions parameters of 23 In. of ofMetal groove laser-Mesh fluence,on gravure Circuits spiral plate Gravure width, machined Plate and by cover ultra rate-fast of laser spiral engraving path. system are Figurerelated 2to showsthe parameters the relationship of laser fluence, between spiral thewidth, groove and cover width rate andof spiral laser path. fluence varied from The dimensions of groove on gravure plate machined by ultra-fast laser engraving system are 1.2 to 2.7Figure J/cm2 .2 Theshows groove the relationship width is increased between linearlythe groove with width the laserand laser fluence. fluence Figure varied2 also from shows related to the parameters of laser fluence, spiral width, and cover rate of spiral path. 1.2 to 2.7 J/cm2. The groove width is increased linearly with the laser fluence. Figure 2 also shows the relationshipFigure 2 betweenshows the the relationship groove width between and the the groove cover width rate atand the laser spiral fluence width varied of 5 fromµm, and the relationship between the groove width and the cover rate at the spiral width of 5 μm, and machining1.2 to 2.7 speed J/cm2 with. The 20groove mm/s. width Three is increased levels of linearly cover with rate, the included laser fluence 50%,. 65%,Figure and 2 also 80%, shows are used machining speed with 20 mm/s. Three levels of cover rate, included 50%, 65%, and 80%, are used for experiments.the relationship When between the coverthe groove rate reacheswidth and 80%, the the cover width rate of at groove the spiral is clearlywidth of wider 5 μm, than and lower for experiments. When the cover rate reaches 80%, the width of groove is clearly wider than lower covermachining rates. The speed results with in20 moremm/s. energy Three levels accumulated of cover rate at high, included cover 50%, rate. 65%, Due and to 80%, the twoare used different cover rates. The results in more energy accumulated at high cover rate. Due to the two different for experiments. When the cover rate reaches 80%, the width of groove is clearly wider than lower groovegroove widths width betweens between outer outer circuit circuit and and inner inner mesh mesh structure, structure, we we can can adjust adjust spiral spiral width width to achieveto cover rates. The results in more energy accumulated at high cover rate. Due to the two different the purpose.achieve the There purpose. are twoThere types are oftwo spiral types widths of spiral (Ω 1width = 5 sµ (m;Ω1 Ω = 2 5 = μ 10m; µΩm)2 = used10 μm) in experiments,used in groove widths between outer circuit and inner mesh structure, we can adjust spiral width to as shownexperiments, in Figure as 3shown, and thein Figure experimental 3, and the result experimental showsthat result the shows wider that spiral the wider width spiral leads width to wider achieve the purpose. There are two types of spiral widths (Ω1 = 5 μm; Ω2 = 10 μm) used in grooveleads width. to wider groove width. experiments, as shown in Figure 3, and the experimental result shows that the wider spiral width TheT experimentalhe experimental results results show show that that thethe covercover rate rate and and spiral spiral width width do donot nothave have an obvious an obviouslyly leads to wider groove width. affect for the groove depth. Figure 4 shows the relationship between the depth of groove and affect forT thehe grooveexperimental depth. results Figure show4 shows that the cover relationship rate and between spiral width the depthdo not of have groove an obvious and thely laser the laser fluence under the condition of spiral width of 5 μm, engraving speed of 20 mm/s, and fluenceaffect under for the the groove condition depth. of spiral Figure width 4 shows of 5theµm, relationship engraving between speed of the 20 depth mm/s, ofand groove cover and rate of cover rate of 50%. When the laser fluence and cover rate are increased, the depths of groove are 50%.the When laser the fluence laser under fluence the and condition cover rate of spiral are increased, width of 5 the μm, depths engraving of groove speed are of increased20 mm/s, and linearly. increased linearly. coverFigure rate5 shows of 50%. the When linewidth the laser of groovefluence isand measured cover rate by are optical increased, microscope the depths and of sampled groove byare nine Figure 5 shows the linewidth of groove is measured by optical microscope and sampled by increased linearly. pointsnine on points gravure on plate.gravure The plate. average The average linewidth line ofwidth groove of groove is 14.7 isµ m,14.7 and μm, the and standard the standard deviation Figure 5 shows the linewidth of groove is measured by optical microscope and sampled by is 0.266deviationµm. Theis 0.266 result μm. of standardThe result deviationof standard shows deviation that theshows gravure that the plate gravure made plate by ultra-fast made by laser nine points on gravure plate. The average linewidth of groove is 14.7 μm, and the standard engravingultra-fast system laser isengraving uniform. system is uniform. deviation is 0.266 μm. The result of standard deviation shows that the gravure plate made by ultra-fast laser engraving system is uniform.

Figure 2. The relationship between the groove width and laser fluence at different cover rate. Figure 2. The relationship between the groove width and laser fluence at different cover rate. Figure 2. The relationship between the groove width and laser fluence at different cover rate.

Figure 3. The relationship between the groove width and laser fluence at different spiral width. 3 FigureFigure 3. The 3. The relationship relationship between between the the groovegroove width and and laser laser fluence fluence at different at different spiral spiral width width.. 3

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Figure 4. The relationship between the groove depth and laser fluence. Figure 4. The relationship between the groove depth and laser fluence. Figure 4. The relationship between the groove depth and laser fluence.

Figure 4. The relationship between the groove depth and laser fluence.

Figure 5. 9 points measurement and picture of gravure plate. Figure 5. 9 points measurement and picture of gravure plate. After engravingFigure process 5. 9 by points ultra measurement-fast laser engraving and picture system, of gravure the gravure plate. plate is rinsed for 10 min with alcohol in an ultrasonic cleaner to remove any debris from the ablation process. Owing to After engraving processFigure 5. by 9 point ultras -measurementfast laser engraving and picture system, of gravure the plategravure. plate is rinsed for enhance the ink transfer rate, the gravure plate needs another surface treatment, electrolytic polish. After10 min engravingwith alcohol process in an ultrasonic by ultra-fast cleaner laserto remove engraving any debris system, from the the ablation gravure process. plate O iswing rinsed to for After the polished process, the roughness of the inner groove is reduced and suitable for printing 10 minenhance withAfteralcohol the engraving ink intransfer an process ultrasonic rate, theby ultragravure cleaner-fast plate tolaser remove needs engraving anyanother debris system, surface from the treatment, thegravure ablation plateelectrolytic process. is rinsed polish. Owing for to process, as shown in Figure 6. The gravure plate is ready for gravure offset printing process. enhance10After min the the with ink polished alcohol transfer process,in rate,an ultrasonic the roughness gravure cleaner plate toof removethe needs inner any anothergroove debris is surfacefrom reduced the treatment,ablation and suitable process. electrolytic for O printingwing to polish. In order to protect the gravure plate from scratching in the doctor blade during the printing Afterenhanceprocess, the polished asthe shown ink process,transfer in Figure rate, the 6. the roughnessThe gravure gravure plate of plate the needs is inner ready another groovefor gravure surface is reduced offset treatment, printing and electrolytic suitable process. forpolish. printing Afterprocess, the thepolished diamond process, like carbon the roughness (DLC) material of the inner is deposited groove ison reduced the surface and ofsuitable gravure for plate. printing The process, asIn shownorder to in protect Figure the6. The gravure gravure plate plate from is scratching ready for in gravure the doctor offset blade printing during process. the printing process,DLC material as shown is the in high Figure hardness 6. The gravurematerial plate and usedis ready for formany gravure application offset sprinting [13]. Figure process. 7 shows the Inprocess, order the to diamond protect thelike gravurecarbon (DLC) plate material from scratching is deposited in on the the doctor surface blade of gravure during plate. the The printing 23 in.In metal order-mesh to protect circuits the gravure gravure plate plate with from 2 μ mscratching thickness in DLC the coatingdoctor bladelayer. during the printing process,DLC the material diamond is thelike high carbon hardness (DLC) material material and used is depositedfor many application on the surfaces [13]. Figure of gravure 7 shows plate. the The process,23 in. metal the- meshdiamond circuits like gravurecarbon (DLC)plate with material 2 μm is thickness deposited DLC on coatingthe surface layer. of gravure plate. The DLCDLC material material is the is the high high hardness hardness material material andand used for for many many application applicationss [13]. [13 Figure]. Figure 7 shows7 shows the the 23 in.23 metal-mesh in. metal-mesh circuits circuits gravure gravure plate plate with with 22 µμm thickness DLC DLC coating coating layer. layer.

Figure 6. The gravure plate without and with surface treatment of (a) before electrolytic polishing, (b) bad ink transfer rate of non-treatment gravure plate, (c) after electrolytic polishing, and (d) good Figure 6. The gravure plate without and with surface treatment of (a) before electrolytic polishing, ink transfer rate of electro-polished gravure plate. (b) bad ink transfer rate of non-treatment gravure plate, (c) after electrolytic polishing, and (d) good Figure 6. The gravure plate without and with surface4 treatment of (a) before electrolytic polishing, Figureink 6. transferThe gravure rate of electro plate-polished without gravure and with plate surface. treatment of (a) before electrolytic polishing; (b) bad ink transfer rate of non-treatment gravure plate, (c) after electrolytic polishing, and (d) good (b) bad ink transfer rate of non-treatment gravure4 plate; (c) after electrolytic polishing; and (d) good ink transfer rate of electro-polished gravure plate. ink transfer rate of electro-polished gravure plate. 4

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Figure 7. The Scanning electron microscope (SEM) cross-section picture of diamond like carbon (DLC) coating layer. Figure 7.7.The The Scanning Scanning electron electron microscope microscope (SEM) (SEM cross-section) cross-section picture picture of diamond of diamond like carbon like carbon (DLC) 4. Gravurecoating(DLC) coatingOffset layer. layerPrinting. Process of 23 In. Metal-Mesh Touch Sensor

4. GravureIn this Offsetstudy, Printinggravure Processoffset printing of 23 In. process Metal -isMesh used Touch to fabricate Sensor the 23 in. metal-mesh touch 4. Gravure Offset Printing Process of 23 In. Metal-Mesh Touch Sensor panel, as shown in Figure 8. First, the ink is scratched into the grooves of a gravure plate by the In this study, gravure offset printing process is used to fabricate the 23 in. metal-mesh touch doctorIn blade. this study, During gravure the optimum offset printing parameters, process the isgrooves used to ar fabricatee filled completely the 23 in. and metal-mesh all of the touchink is panel, as shown in Figure 8. First, the ink is scratched into the grooves of a gravure plate by the removedpanel, as from shown non in- Figurepatterned8. First,areas. the Second, ink is scratchedthe ink is intopicked the up grooves from the of a gravure gravure plate plate grooves by the doctor blade. During the optimum parameters, the grooves are filled completely and all of the ink is withdoctor an blade. offset Duringmaterial the called optimum blanket. parameters, The blanket the is grooves fixed on are a roller filled completelycalled blanket and roller. all of When the ink the is removed from non-patterned areas. Second, the ink is picked up from the gravure plate grooves inkremoved is picked from u non-patternedp on the blanket, areas. the Second, roller rotates the ink forward is picked and up frompresses the the gravure ink onto plate the grooves substrate. with with an offset material called blanket. The blanket is fixed on a roller called blanket roller. When the Inan offsetthis study, material the called blanket. nanoparticle The blanket ink developed is fixed on in a rollerour laboratory called blanket is used roller. for When the gravure the ink ink is picked up on the blanket, the roller rotates forward and presses the ink onto the substrate. offsetis picked printing. up on the blanket, the roller rotates forward and presses the ink onto the substrate. In this In this study, the silver nanoparticle ink developed in our laboratory is used for the gravure study,The the printed silver nanoparticlesilver fine lines ink are developed used for inmetal our- laboratorymesh touch is sensor, used for as theshown gravure in Figures offset printing.9 and 10. offset printing. The optimalThe printed laser silver machining fine lines parameters are used forused metal-mesh to fabricate touch the pattern sensor, ason shown SUS304 in gravure Figures 9plate and 10are. The printed silver fine lines are used for metal-mesh touch sensor, as shown in Figures 9 and 10. atThe specific optimal laser laser power machining of 180 parametersmW, spiral usedwidth to of fabricate 40 μm, theand pattern cover rate on SUS304 of 50% gravurefor outer plate circuit. are The optimal laser machining parameters used to fabricate the pattern on SUS304 gravure plate are Theat specific parameters laser powerat spiral of width 180 mW, of 5 spiralμm and width cover of rate 40 µ 50%m, and are coverused for rate inner of 50% circuit. for outerThe average circuit. at specific laser power of 180 mW, spiral width of 40 μm, and cover rate of 50% for outer circuit. lineThe parameterswidth for printed at spiral inner width circuits of 5 µ measuredm and cover by rateoptical 50% microscope are used for and inner sampled circuit. by The nine average points line on The parameters at spiral width of 5 μm and cover rate 50% are used for inner circuit. The average thewidth gravure for printed plate inneris 10.7 circuits μm, and measured the standard by optical deviation microscope is approximately and sampled 0.7 by nineμm, pointsas shown on thein line width for printed inner circuits measured by optical microscope and sampled by nine points on Figuregravure 9. plate The average is 10.7 µ linem, and width the of standard outer circuit deviation is nearly is approximately 70 μm. The 23 0.7 in.µ metalm, as- shownmesh touch in Figure sensor9. the gravure plate is 10.7 μm, and the standard deviation is approximately 0.7 μm, as shown in isThe finally average fabricated line width by gravure of outer offset circuit printing is nearly process 70 µm. and The assembled 23 in. metal-mesh for touch touch panel sensor in this is finallystudy. Figure 9. The average line width of outer circuit is nearly 70 μm. The 23 in. metal-mesh touch sensor Thefabricated 23 in. bymetal gravure-mesh offset touch printing panel is process demonstrated and assembled the touch for touchfunction panel successfully, in this study. as Theshown 23 in.in is finally fabricated by gravure offset printing process and assembled for touch panel in this study. Figuremetal-mesh 10. touch panel is demonstrated the touch function successfully, as shown in Figure 10. The 23 in. metal-mesh touch panel is demonstrated the touch function successfully, as shown in Figure 10.

Figure 8. Schematic diagram of gravure offset printing process.process. Figure 8. Schematic diagram of gravure offset printing process.

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Figure 9. (a) The picture of 23 in. metal-mesh printed sample. (b) Picture of inner metal mesh of Figure 9. ((aa)) The The p pictureicture of of 23 in. metal metal-mesh-mesh printed printed sample sample;. ( (bb)) Picture Picture of of inner inner metal mesh of printing sample. (c) Picture of outer circuit of printing sample. printing sample sample;. and(c) Picture (c) Picture of outer of outer circuit circuit of printing of printing sample. sample.

Figure 10. Demonstration of 23 in. metal-mesh touch sensor. Figure 10. Demonstration of 23 in. metal-mesh touch sensor. Figure 10. Demonstration of 23 in. metal-mesh touch sensor. 5. Conclusions 5. Conclusions 5. ConclusionsIn this study, the 23 in. gravure plate has been completed by using ultra-fast laser engraving In this study, the 23 in. gravure plate has been completed by using ultra-fast laser engraving system,In thisand study, used theto 23print in. gravurethe metal plate-mesh has circuits been completed on . by The using touch ultra-fast panel laser with engraving printed system, and used to print the metal-mesh circuits on glass. The touch panel with printed metalsystem,-mesh and usedcircuits to printon glass the metal-meshhas been successfully circuits on glass. demonstrated The touch panel touch withfunction printed after metal-mesh bonding metal-mesh circuits on glass has been successfully demonstrated touch function after bonding integratedcircuits on circuit glass has chips been. Using successfully spiral feed demonstrated of laser beam touch produces function higher after bondingaspect ratio integrated of the groove circuit integrated circuit chips. Using spiral feed of laser beam produces higher aspect ratio of the groove onchips. gravure Using plate, spiral which feed is considered of laser beam advantageous produces higherfor the aspectprinted ratio lines ofto thebe narrow groove and on thick gravure to on gravure plate, which is considered advantageous for the printed lines to be narrow and thick to meetplate, the which requirements is considered of advantageousfine pattern as for well the printedas electrical lines toconduction. be narrow In and the thick current to meet study, the meet the requirements of fine pattern as well as electrical conduction. In the current study, therequirements width of groove of fine patternin gravure as well plate as electricalis 14.7 μm, conduction. and the width In the of current printed study, line theis 10.7 width μm, of groovewhich the width of groove in gravure plate is 14.7 μm, and the width of printed line is 10.7 μm, which isin gravurewithin platethe required is 14.7 µ m,specifications and the width of ofthe printed metal line-mesh is 10.7 circuitsµm, whichon touch is within sens theor requiredin the is within the required specifications of the metal-mesh circuits on touch sensor in the displayspecifications industry. of the metal-mesh circuits on touch sensor in the display industry. display industry. Acknowledgments: This work was supported by the Ministry of Economic Affairs (MOEA) of Taiwan (under Acknowledgments: This work was was supported by the Ministry Ministry of Economic Affairs (MOEA) of Taiwan (under(under thethe grant grant number number of of E353C11100) E353C11100).. the grant number of E353C11100). Author Contributions: Tahsin Chou, Yuming Wang, Weiyuan Chen and Wenlang Lai proposed the idea; WeiyuanAuthor Contributions Chen and Wenlang: Tahsin Lai Chou, performed Yuming ultrafast Wang, laser Weiyuan engraving Chen experiment and Wenlang and analysis; Lai proposed Yuming the Wang, idea; KaijunWeiyuan Wang, Chen Shengyuand Wenlang Lin, Laiand performed Yuli Yen ultrafast performed laser gravure engraving offset experiment printing and process analysis; and Yuming touch sensorWang, verificationKaijun Wang,. Weiyuan Shengyu Chen Lin, and and Tahsi Yulin ChouYen performed prepared thegravure manuscript; offset printingHong Hocheng process contributed and touch tosensor give valuableverification suggestions. Weiyuan on Chen the experimental and Tahsin Choumethods. prepared the manuscript; Hong Hocheng contributed to give valuable suggestions on the experimental methods. 1488 6 6 Micromachines 2015, 6, 1483–1489

Author Contributions: Tahsin Chou, Yuming Wang, Weiyuan Chen and Wenlang Lai proposed the idea; Weiyuan Chen and Wenlang Lai performed ultrafast laser engraving experiment and analysis; Yuming Wang, Kaijun Wang, Shengyu Lin, and Yuli Yen performed gravure offset printing process and touch sensor verification. Weiyuan Chen and Tahsin Chou prepared the manuscript; Hong Hocheng contributed to give valuable suggestions on the experimental methods. Conflicts of Interest: The authors declare no conflict of interest.

References

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