Resistive Touch Panel Research Articles

Preview the Products on Display at Display Week 2023

Preview the Products on Display at Display Week 2023

Fabrication of Transparent Conductive Film with Flexible Silver Nanowires Using Roll‐to‐Roll Slot‐Die Coating and Calendering and Its Application to Resistive Touch Panel

AbstractA transparent conductive film incorporating silver nanowires (AgNW TCF) is fabricated through roll‐to‐roll (R2R) slot‐die coating and a subsequent calendering process and applied to a resistive touch panel. To produce a uniform AgNW film on a flexible polyethylene terephthalate substrate, the R2R slot‐die coating is optimized in terms of the solvent, concentration, and flow rate of the AgNW solution, and the length of the AgNWs synthesized using a polyol method. The coated AgNW TCF is calendered between two rolls to produce percolation paths in the film. During the calendering, the roll temperature, applied pressure, and web speed are optimized to yield a low sheet resistance of 28 Ω sq−1 with a transmittance of 86% at 550 nm. To demonstrate the functionality of the AgNW TCF, a coating of SiO2 microspheres is also applied to form a spacer layer, again using R2R slot‐die coating. A resistive touch panel is thus successfully implemented. The effect of the calendering process is confirmed by observing the operation of the touch panel, which is found to be more sensitive and accurate. The integrated manufacturing process for producing an AgNW TCF, presented herein, can be applied to many other major fields.

Epitaxial-Growth-Induced Junction Welding of Silver Nanowire Network Electrodes.

In this study, we developed a roll-to-roll Ag electroplating process for metallic nanowire electrodes using a galvanostatic mode. Electroplating is a low-cost and facile method for deposition of metal onto a target surface with precise control of both the composition and the thickness. Metallic nanowire networks [silver nanowires (AgNWs) and copper nanowires (CuNWs)] coated onto a polyethylene terephthalate (PET) film were immersed directly in an electroplating bath containing AgNO3. Solvated silver ions (Ag+ ions) were deposited onto the nanowire surface through application of a constant current via an external circuit between the nanowire networks (cathode) and a Ag plate (anode). The amount of electroplated Ag was systematically controlled by changing both the applied current density and the electroplating time, which enabled precise control of the sheet resistance and optical transmittance of the metallic nanowire networks. The optimized Ag-electroplated AgNW (Ag-AgNW) films exhibited a sheet resistance of ∼19 Ω/sq at an optical transmittance of 90% (550 nm). A transmission electron microscopy study confirmed that Ag grew epitaxially on the AgNW surface, but a polycrystalline Ag structure was formed on the CuNW surface. The Ag-electroplated metallic nanowire electrodes were successfully applied to various electronic devices such as organic light-emitting diodes, triboelectric nanogenerators, and a resistive touch panel. The proposed roll-to-roll Ag electroplating process provides a simple, low-cost, and scalable method for the fabrication of enhanced transparent conductive electrode materials for next-generation electronic devices.

Buckling and Postbuckling Failure Analyses on a Rectangular Membrane for Touch Panel Applications

Thin conductive polymer membranes are the major sensing structure in resistive touch panels. However, device malfunctions such as early touching and false triggering have been reported during product development and reliability assessment. A surface profile examination has indicated that these membranes have considerable initial warpage, which could be a sign of membrane buckling, since the clamped design of the assembly may cause additional in-plane compression, in turn causing structural buckling. As a result, it is important to analyze the buckling and post-buckling behaviors of conductive polymer membranes due to initial imperfections, residual stress, or assembly issues in order to develop engineering solutions to ensure quality assurance. In this paper, both finite-element analyses and experimental characterizations are performed as the first step toward solving the observed problems. For the buckling analysis, we focus on the correlations between the calculated mode shapes and the observed surface warpage. Post-buckling analysis is also performed for exploring the performance of touch panels with initial warpage. In addition, several experimental investigations are conducted to validate the above mentioned mechanical analyses. The simulation results essentially agree with the observations. Both simulation and experimental investigations indicate that in-plane compression and shear can contribute to the observed failures. Engineering methods to increase buckling rigidity can be helpful for enhancing device reliability.

Direct Chemical-Vapor-Deposition-Fabricated, Large-Scale Graphene Glass with High Carrier Mobility and Uniformity for Touch Panel Applications

In this work, we report the transfer-free measurement of carrier dynamics and transport of direct chemical vapor deposition (CVD) grown graphene on glass with the aid of ultrafast transient absorption microscopy (TAM) and demonstrate the use of such graphene glass for high-performance touch panel applications. The 4.5 in.-sized graphene glass was produced by an optimized CVD procedure, which can readily serve as transparent conducting electrode (TCE) without further treatment. The graphene glass exhibited an intriguing optical transmittance and electrical conductance concurrently, presenting a sheet resistance of 370-510 Ω·sq-1 at a transmittance of 82%, much improved from our previous achievements. Moreover, direct measurement of graphene carrier dynamics and transport by TAM revealed the similar biexponential decay behavior to that of CVD graphene grown on Cu, along with a carrier mobility as high as 4820 cm2·V-1·s-1. Such large-area, highly uniform, transparent conducting graphene glass was assembled to integrate resistive touch panels that demonstrated a high device performance. Briefly, this work aims to present the great feasibility of good quality graphene glass toward scalable and practical TCE applications.

抵抗膜式タッチパネル

抵抗膜式タッチパネル

Effects of Post Annealing Temperatures on Sputtered Indium Tin Oxide Films for the Application to Resistive Touch Panel

Indium tin oxide (ITO) films were deposited on glass substrates by in-line DC sputtering and were annealed at different temperatures in the main chamber of sputter. The post-annealing effects on the optical and electrical properties of the ITO films were investigated and analyzed by various measurement systems. The results show that a higher annealing temperature makes an improvement on the electro-optical properties of the ITO films. The resistivity of the ITO films was reduced from 8.90×10−4Ω·cm to 2.91×10−4Ω·cm and the transmittance was increased from about 76.91% to 82.15% after post annealing at 300 °C in vacuum. The post annealed ITO glass was used in the fabrication of resistive touch panel and it was possible to obtain the better linearity characteristics than those from the touch panel fabricated with non-annealed ITO glass.

Effect of the duty ratio on the indium tin oxide (ITO) film deposited by in-line pulsed DC magnetron sputtering method for resistive touch panel

The indium tin oxide (ITO) film was deposited on PET (polyethylene terephthalate) film using in-line pulsed DC magnetron sputtering system with different duty ratios. The reverse time and the frequency of pulsed DC power were changed to obtain the different duty ratios. From the electrical and optical properties such as the sheet resistance, resistivity, thickness and transmittance, the pulsed DC sputtered ITO/PET films were also superior to the DC sputtered ITO/PET films. The reverse time had little effect on the properties of the ITO/PET film and the frequency of pulsed DC power had an immerse effect on the properties of the ITO/PET films. The optimal ITO/PET film was obtained when the frequency was 200kHz, the reverse time was 1μs, and the duty ratio was about 80%.

38.3: The Structure and Driving Method of Multi‐Touch Resistive Touch Panel

AbstractA highly innovative MT‐RTP (Multi‐Touch Resistive Touch Panel) has been developed. Comparing to the conventional 4‐wired RTP (Resistive Touch Panel), it performs not only high resolution single touch via stylus writing but also multi touch function. In contrast to the projected capacitive touch panel, MT‐RTP is superior to in price and stylus writing capability.

Carbon‐nanotube film on plastic as transparent electrode for resistive touch screens

Abstract— Carbon‐nanotube (CNT) films on plastic are incorporated as the touch electrode in a four‐wire resistive touch panel. Single‐point actuation tests show superior mechanical performance to ITO touch electrodes, with no loss of device functionality up to 3 million actuations. Sliding‐stylus‐pen tests reveal no loss of device linearity after 1 million stylus cycles. A CNT refractive index of ∼1.55 leads to CNT touch panels with low reflection (<9% over the visible range) without costly anti‐reflective coatings. CNT films on PET currently have 86% total transmission (including the PET) over the visible and 600 Ω/□, with lab scale tests giving 88% at 500 Ω/□. CNT films are neutrally colored (a* ∼ 0, b* ∼ 1.5), low haze (<1%), uniform, and both chemically and environmentally stable. Unidym's solution‐based coatings can be printed directly onto both flexible and rigid polycarbonate using solution coating processes. Unidym films can be patterned using subtractive methods such as laser ablation with resolution down to 10 μm, or additive methods such as patterned gravure. CNTs are grown, purified, formulated into inks, and coated using scalable processes, allowing films to be attractive from a cost perspective as well.

32.2: Touch‐Panel Controller Implemented with LTPS TFTs

AbstractA touch panel controller has been implemented with LTPS TFTs on a glass substrate. It induces voltage gradient across either plate of a 4‐wire resistive touch panel and senses the intermediate potential at the touch position via the other plate. Then it converts the acquired analog voltage into digital signal and outputs 3‐bit digital data for the horizontal and vertical positions respectively.

P‐87: Carbon Nanotube Film on Plastic as the Touch Electrode in a Resistive Touch Screen

AbstractCarbon nanotube (CNT) films on plastic are incorporated as the touch electrode in a four‐wire resistive touch panel. Touch actuation testing shows superior mechanical performance to ITO touch electrodes. Refractive index matching leads to CNT panels with lower reflection. Direct printing on polycarbonate is demonstrated. Patterning options are discussed.

PET 기판 위에 SiO2버퍼층 증착에 따른 ITO 박막의 부착 및 전기적 광학적 특성 연구

Using an evaporation system, <TEX>$SiO_2$</TEX> was deposited as a buffer layer between a PET substrate and a ITO layer and then ITO/<TEX>$SiO_2$</TEX>/PET layers were annealed for 1.5 hours at the temperature of <TEX>$180^{\circ}C$</TEX>. Adhesion and electro-optical properties of ITO films were studied with thickness variance of a <TEX>$SiO_2$</TEX> buffer layer. As a result of introduction of the <TEX>$SiO_2$</TEX> buffer layer, sheet resistance and resistivity increased and a ITO film with optimum sheet resistance (<TEX>$529.3{\Omega}/square$</TEX>) for an upper ITO film of resistive type touch panel could be obtained when <TEX>$SiO_2$</TEX> of <TEX>$50{\AA}$</TEX> was deposited. And it was found that ITO films with <TEX>$SiO_2$</TEX> buffer layer have higher transmittance of <TEX>$88{\sim}90%$</TEX> at 550 nm wavelength than ITO films with no buffer layers and the transmittance was enhanced as <TEX>$SiO_2$</TEX> thickness increased from <TEX>$50{\AA}$</TEX> to <TEX>$100{\AA}$</TEX>. Adhesion property of ITO films with <TEX>$SiO_2$</TEX> buffer layers became better than ITO films with no buffer layers and this property was independent of <TEX>$SiO_2$</TEX> thickness variance (<TEX>$50{\sim}100{\AA}$</TEX>). By depositing a <TEX>$SiO_2$</TEX> buffer layer of <TEX>$50{\AA}$</TEX> on the PET substrate and sputtering a ITO thin film on the layer, a ITO film with enhanced adhesion, electro-optical properties could be obtained.

Balance and Tracking Control of Ball and Plate Systems

In this video, the digital signal processor based (DSP-based) ball and plate control system is introduced. The plate is actuated by two DC motors. To sense the position of the ball, a resistive touch panel is utilized. The optical encoder with resolution 1000 pluses/rev attached to the shaft of the DC motor is used to measure the angular displacement of the motor. The system is controlled by a DSP (150MHz/32-bit) board equipped with a 12-bit D/A converter. The sampling frequency of the system is chosen to be 1 kHz. The voltage signals are generated according to the designed control law and are also supplied to power amplifiers that derive the DC motors. The signal from the touch panel is passed through a digital low-pass filter to reduce the effect of sensor noise. The ball and plate system is a highly nonlinear and coupled system. Due to existence of the centrifugal force, the system relative degree is not well defined. Moreover, the centrifugal force provides a strong positive feedback and easily leads to the peaking phenomenon. The system model is approximated as two decoupled systems. The backstepping control design approach is used to design the controller for balance and tracking control. The video shows the effectiveness of the designed control system.

Production of transparent conductive films with inserted SiO2 anchor layer, and application to a resistive touch panel

AbstractIn order to reduce light reflectivity and enhance the durability of resistive touch panels used for pen input, a transparent conductive film consisting of an inserted SiO2 anchor layer between PET and ITO layers (ITO/SiO2/PET) was produced and its application to resistive touch panels was attempted.The luminous reflectance of the ITO/SiO2/PET structure was found to be about 4% lower than that of ITO/PET. The durability was estimated by the resistance change ratio of the ITO layer caused by damage due to scribbling; the decrease in resistance of the ITO/SiO2/PET structure was less than half that of the ITO/PET structure. Furthermore, the resistivity of the ITO layer in ITO/SiO2/PET was 8.4 × 10–4 Ω‐cm, lower than the value of 1.3 × 10–3 Ω‐cm in ITO/PET. This demonstrates the conductivity‐increasing effect of the insertion of a SiO2 layer into the transparent conductive film. © 2001 Scripta Technica, Electron Comm Jpn Pt 2, 84(7): 39–45, 2001