MXPA99010452A - Acoustic touch position sensor using a low acoustic loss transparent substrate - Google Patents

Abstract

An acoustic touch panel (100) utilizes acoustic waves within a sensor substrate to determine the position of touch. The substrate (1) is made of a glass having an attenuation coefficient of less than or equal to about 0.6 dB/cm as determined at the substrate surface for 5.53 MHz Rayleigh waves as measured by the slope of a plot of amplitude versus distance for a signal through a pair of facing 0.5 inch wide wedge transducers mounted on the glass under test having sufficient thickness to support Rayleigh wave propagation.

Description

ACOUSTIC TOUCH POSITION SENSOR THAT USES A TRANSPARENT SUBSTRATE OF LOW ACOUSTIC LOSS TECHNICAL FIELD OF THE INVENTION The present invention relates to an acoustic touch position sensor, and more particularly to a touch panel of the type wherein an acoustic wave is generated inside a substrate, propagating the acoustic wave in the substrate, which it has a range of characteristic time delays from a transmitted signal, representing the different path lengths associated with each axial displacement along a substrate axis. A touch on the substrate results in a disturbance of the wave, which is detected to determine the axial displacement of the touch on the substrate. Touch panels of this type are used as computer input devices in connection with visual displays of computer images.

BACKGROUND OF THE INVENTION Conventional touch panels are used as input-output devices, applicable in different fields, in combination with a device or visual display unit, such as cathode ray tube (CRT), a liquid crl display ( LCD), or a plasma visual display panel (PDP). Resistive, capacitive, and acoustic touch panels are currently the dominant types of touch panels on the market. The acoustic touch panels provide a more robust touch surface and greater image clarity. resistive and capacitive touch panels. The resistive and capacitive touch panels include a resistance layer formed on a substrate. Due to its strength, optical clarity, and low cost, soda lime glass is generally the preferred substrate material. The resistance layer is essential for the detection of touch position information. In addition, a conventional resistive touch panel includes an overlay plastic cover sheet. For many applications, these additional components to the glass substrate may be susceptible to accidental or malicious damage. In addition, these additional components degrade the visibility of data and images in a visual display device, as a result of the decrease in light transmission and the greater reflection of ambient light. In contrast, conventional acoustic touch panels can be conveniently employed in order to ensure a robust touch surface and better image quality of the visual display. Because ultrasonic acoustic waves are used to detect coordinate data on the input positions, a layer of strength on the glass lime soda substrate is not needed, and a plastic cover sheet is not required. Soda lime glass is very transparent and supports the propagation of acoustic waves at ultrasonic frequencies. Soda lime glass is the substrate material of conventional acoustic touch panels. For the end user, this acoustic touch panel is optically and mechanically little more than a piece of glass for windows. Typically, 4 percent of the incident light is reflected from each glass surface, resulting in a maximum light transmission of approximately 92 percent. The reflection of ambient light reduces the contrast of the image. These reflections are caused by a bad coupling of the refractive index between the air and the glass substrate. The lower transmission of light reduces the brightness of the image. These can be important effects when a touch panel is placed in front of a visual display device having a relatively low luminance (brightness), such as a liquid crl display. The known methods to reduce the reflections and increase the transmission, are optical link or antireflective coatings. These methods resolve the bad coupling of the refractive index between the air and the glass. These methods do not improve the inherent transparency of the substrate material itself.

Soda lime glass is not completely transparent. This is mainly due to the centers of color caused by the impurities of the iron ion. These iron impurities reduce the transmission of light and distort the colors of the images displayed. These are minor effects related to, for example, the different optics between acoustic and resistive touch panels. However, a better transmission in relation to common soda lime glass would provide a useful improvement of the optical advantages of the acoustic touch panels. The technology of visual displays is evolving rapidly. This evolution includes the introduction and acceptance in the market of large display visual products. In turn, this creates a demand for larger touch panels. However, all touch panel technologies encounter problems when scaling to larger sizes. For resistive and capacitive touch panels, it becomes more difficult to maintain sufficient uniformity in the strength layers as the panel sizes increase. For acoustic touch panels, the challenge of larger sizes is to ensure sufficient signal amplitudes. For acoustic touch panels, acoustic signals decrease as panel dimensions increase. This signal loss occurs due to the attenuation or damping of the ultrasonic waves as they propagate through the substrate. Accordingly, large acoustic touch panels may fail to provide a sufficient proportion of the signal to noise in order to reliably determine the entry positions. Accordingly, there is a need for elements to improve the ratio of signal to noise for acoustic touch panels. This is more true, because there are other market pressures for product improvements that reduce the amplitudes of the signals: lower cost controller electronics; reflective arrangements of reduced area; signal absorption seals; etc. Due to the relatively long acoustic trajectory lengths of the acoustic touch panel designs that are commercially successful, the acoustic attenuation properties of the glass substrate are particularly important. To understand the need for long acoustic path lengths, consider this first simpler concept for acoustic touch panels. Conceptually, the simplest acoustic touch position sensor is of the type described in U.S. Patent Number 3,673,327. These touch panels include a plate having an array of transmitters placed along one edge of a substrate to generate parallel beams of acoustic waves. A corresponding array of receivers is placed along the opposite edge of the substrate. Touching the panel at one point causes attenuation in one of the acoustic wave beams. The identification of the corresponding transmitter / receiver pair determines a touch coordinate. The acoustic touch panel disclosed in United States Patent Number 3,673,327 uses a type of acoustic wave known as a "Rayleigh" wave. These Rayleigh waves need to spread only from one edge of the touch panel to the other. However, note that this type of acoustic touch panel requires many transducers, and therefore, associated cable conductors and electronics channels. This type of acoustic sensor has never been commercialized, due to the expense of providing a large number of transducers. Now consider the acoustic touch panels that have been commercially successful. The representative of a representative set of pioneer patents in this field is Adler, United States of America Patent with Reference Number 33151 An acoustic transducer generates a burst of waves that are coupled to a sheet-type substrate. These acoustic waves are diverted 90 ° to an active region of the system, by means of an array of wave redirection grids. The redirection grids are oriented at 45 ° C with the axis of propagation of the waves from the transducer. These grids are analogous to the mirrors partially coated with silver in the optics. The acoustic waves, after traversing the active region, in turn, are redirected by another array of grids, towards an output transducer. A coordinate of the location of a touch is determined by analyzing a selective attenuation of the signal received in the time domain, each characteristic delay corresponding to a coordinate value of the touch on the surface. The use of grid arrangements greatly reduces the required number of transducers, thus making acoustic touch panels possible at commercially competitive prices. On the negative side, this intelligent use of grid arrays increases in a considerable way the maximum distance at which the acoustic waves must propagate through the substrate. The signal amplitudes in the acoustic touch panels are further reduced by the inefficiencies in the dispersion process in the grid arrays. These inefficiencies can be minimized through an appropriate arrangement design. Efficient coherent dispersion is achieved from the arrays by orienting the grid elements at a 45 ° angle, and separating them into integral multiples of the acoustic wavelength. A more efficient use of acoustic energy is provided when the acoustic energy "illuminating" the active area is equalized. Known techniques compensate for the tendency for signal amplitudes to decay exponentially as a function of delay time. As described in lines 37 to 41 of column 11 of U.S. Patent No. 4,746,914, signal equalization with a constant wavelength separation of the gratings, ie, the reflective elements, can be achieved. , providing reflective elements with variable height. An alternative method is to selectively drop grid elements to produce an approximately constant acoustic energy density over the active area. In this case, the separation between the grids decreases when the distance from the transducer increases along the axis of the array. The application of these known methods avoids the unnecessary inefficiencies in the redirection of the acoustic waves. However, the use of grid arrays to redirect acoustic waves twice inevitably leads to signal losses. This increases the importance of the minimum requirements of the signal amplitude in the design of the acoustic touch panel. Electronics for commercially available acoustic touch panel products is based on the basic concepts presented in Brenner et al., United States Patent Number 4,644,100. This patent refers to a refinement of the system according to the US Pat. No. 33,151, wherein the perturbations of a received signal are determined by comparing the received signal with a reference signal profile. stored. By analyzing both the time delays and the signal disturbances, the touch sensitive system employing acoustic waves responds to both the location and the magnitude of a touch. Proper orientation of the touch system requires a sufficiently large ratio of the signal to noise to avoid ambiguities between signal disturbances, due to an acoustic wave absorbent touch, and signal variations due to electronic noise. Electronic noise can be caused by fundamental noise from circuit components, or it may be due to electromagnetic interference. In recent years, the market increasingly expects a fast touch response from the highlights, which requires lower touch disturbance thresholds, and consequently, increases the demand for a higher ratio of signal to noise. A further description of these Adler-type acoustic touch panels can be found in the aforementioned Patents, as well as in the Patents of the United States of North America Nos. 4,642,423; 4,644,100; 4,645,870; 4,700,176; 4,476,914, and 4,791,416. For each detected coordinate axis, acoustic waves are generated, for example, on a glass substrate, by means of a transducer containing a piezoelectric element. Accordingly, a transmitted wave packet is dispersed along the axis of the transmitting reflective array, travels over the substrate, and is recombined into a wave propagating axially through another reflective grid, and directed to a reflective transducer in a anti-parallel direction to the initial transmitted wave. The wave packet is dispersed in time according to the path taken through the substrate. The received waveform is converted to an electrical signal for processing. The time delay of a disturbance of the electrical signal corresponds to a distance traveled by the disturbed component of the wave. Therefore, according to this system, only two transducers are required per axis. Normally both X and Y coordinates are measured; This can be done with a total of only four transducers. Variations of the previous acoustic touch panel systems are possible with additional reductions in the numbers of transducers. The acoustic wave can be reflected by 180 ° near, or at, the edge of the substrate, parallel to the axis of the reflecting transmission grid, and can be reflected back through the substrate to the reflective array, and redraw its trajectory back to the transducer. In this case, the transducer is configured to act both as a transducer and as a receiver at appropriate time periods. A second transducer, reflective array, and reflecting edge are provided for an axis at right angles, to allow the determination of both touch coordinates. Still another system provides a single transducer that produces a wave to detect a touch on two axes, and also receives the wave from both axes. Reducing the number of transducers increases the corresponding acoustic trajectory lengths for a given touch panel size. This increases signal loss due to acoustic damping inside the substrate material. The touch that activates an acoustic touch panel may be due to a finger, gloved or non-gloved, or to a pen that presses against the surface. Optionally, the finger or pen can act indirectly through a cover sheet placed on the surface of the glass substrate. There are several ways that ultrasonic waves can take on glass substrates. The mode referred to as a "Rayleigh" wave is a particular interest for acoustic touch panels. Rayleigh waves are essentially confined to a single surface of a sheet of a uniform non-piezoelectric medium of sufficient finite thickness. Mathematically, Lord Rayleigh calculated the function of the wave for this mode, for a semi-infinite medium. These guided waves near a surface of a medium of finite thickness, are more precisely called "almost-Rayleigh" waves, although these waves are generally referred to as "Rayleigh waves", and are so named in the present. Practical experience with the design and manufacture of touch panels has shown that approximately 4 Rayleigh wavelengths or more is sufficient substrate thickness to successfully propagate Rayleigh waves. Other acoustic modes have been investigated for use in acoustic touch panels. Patents of the United States of North America Nos. 5,260,521; 5,234,148; 5,177,327; 5,162,618, and 5,072,427 disclose the use of horizontally polarized tear waves, and Lamb waves in Adler-type acoustic touch panels. U.S. Patent No. 5,591,945 discloses additional options with respect to the choice of acoustic modes in acoustic touch panels. However, Rayleigh waves have been, and are expected to continue to be, the acoustic mode most commonly used in acoustic touch panels. This is due to the relatively high sensitivity of Rayleigh waves to the touches, and due to its ability to propagate through a simple surface of a homogeneous medium. For commercial acoustic touch panels, the frequency of ultrasonic sound waves is around 5 MHz. For acoustic touch panels employing Rayleigh waves, the thicknesses of the soda lime glass substrates for commercial products up to the date, they are on the scale of 2 millimeters to 12 millimeters. Acoustic touch panel products employing lower-order horizontally polarized tear waves are currently made of 1-millimeter thick soda lime glass. Acoustic touch panels, of the type that has been proven to be commercially viable, make intelligent use of reflective arrays to reduce the number of transducers and electronic channels, and to provide an analog measurement based on the reliable and accurate time of the touch position. This has proven to be essential for the commercialization of acoustic touch panels. However, the resulting relatively long acoustic path lengths, together with the losses from two acoustic scatters, lead to small received signal amplitudes. With these small signal amplitudes, it is difficult to guarantee a sufficient ratio of the signal to the noise for reliable processing of the signals in a touch sensor of the type that transmits ultrasonic sound waves in a glass substrate. Many terms have been used to describe acoustic touch panels: "acoustic sensors", "acoustic touch screens", "ultrasonic touch panels", and so on. Unless otherwise reported, all of these terms are considered to be synonymous herein for a transparent touch sensor that detects ultrasonic sound wave touches using reflective arrays of grids to enable a reduced number of transducers. There is a need for elements to increase the signal amplitudes in the acoustic touch panels.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an acoustic touch panel whose glass substrate has a low attenuation or acoustic damping ratio, and which ensures an acceptable intensity of the transmitted signals. It is a further object of the present invention to provide an acoustic touch panel that is more reliable and robust with respect to electromagnetic interference than the touch position sensors known so far. It is a further object of the present invention to provide an acoustic touch panel that can operate in a reliable manner with a reduced cost controller, with transmission burst amplitudes of approximately 10 volts peak-to-peak, or less. It is a further object of the present invention to provide an acoustic touch panel that includes mechanically compact transducers of reduced signal conversion efficiency.

It is a further object of the present invention to provide an acoustic touch panel that allows the use of seals that cause a significant acoustic signal absorption. It is a further object of the present invention to provide a larger acoustic touch panel It is a further object of the present invention to provide a touch panel which presents a reliable and robust touch surface to the user, even when handled roughly. It is a still further object of the invention to provide a quenchable substrate of low acoustic loss for a touch panel, which can be thermally tempered or chemically hardened, thereby making it possible to have large toughened touch panels. invention to increase the ratio of signal to noise in an acoustic touch panel employing Rayleigh waves Another object of the present invention is to provide a touch panel which ensures high light transmission and a clear visual display of the data "by means of the visual display device. Extensive research has led to the achievement of the above objects, and to the discovery that the use of substrates or bases of a specific glass as a means of propagation for ultrasonic sound waves, can suppress the attenuation (damping) of ultrasonic acoustic waves to a great degree, and can also transmit the signals while maintaining its high intensity, until they are received and detected. The present invention is based on the above findings. These objects, as well as other objects that will become clearer from the following discussion, are achieved, in accordance with the present invention, by providing a touch panel having a glass substrate as a propagation medium for acoustic waves. ultrasonic, and that is used to detect the coordinate data on the position touched. In this glass substrate, which comprises SiO2 as the main component, the total content of Na2 ?, CaO, and MgO is 20 weight percent or less, and the total content of Al203, Zr02, Ti02, B203, Y203, Sn02, Pb02, ln203, and K20 is generally 5 weight percent or more. Although this invention was the result of unanticipated experimental work, the following conceptual structure serves to clarify the nature of the invention. The glass is basically silicon dioxide, Si02, to which sufficient amounts of other compounds have been added to alter the formation. of a regular lattice of covalent bonds of Si-O-Si, which would otherwise form crystalline quartz. For example, the addition of Na20 results in the replacement of a Si-O-Si bond of covalent bonds between two silicon atoms with a break in the covalent bond, Si-0 ~ /? ~ Si, plus two Na + ions . In a similar manner, the addition of CaO or MgO results in a break in the covalent bond, Si-O / O-Si, m + as an ion of n i _? Ca or Mg. In this way, the addition of a sufficient amount of "soda" and "lime", results in an amorphous glass instead of crystalline quartz. It is known that the transition from a crystalline material to an amorphous material results in greater damping. For example, consider the following translation of a passage from a textbook of acoustics by Royer and Dieulesaint (Ondes elastisues dans les solides), Volume 1, page XV, editor Masson). The solids used in applications that require relatively high frequency waves (>100 MHz, for example for signal processing), are ^ crystals, because the mechanical vibrations are attenuated less as more materials are ordered in which they propagate. This implies that the use of glass, an amorphous material, instead of a crystalline material such as quartz, inevitably results in increased acoustic losses. The invention unexpectedly discovered that additions of different compounds to silicon dioxide, all sufficient to induce a transition to an amorphous glaze state, vary widely in their effect on acoustic attenuation. Certain glass compositions lead to a significantly lower sound absorption than that which is present in soda lime glass. In addition, a pattern has been observed. Acoustic attenuation is relatively greater if the additions replace the Si-O-Si covalent bonds with the weak ionic ligations, and the acoustic attenuation is relatively smaller if the additions replace the covalent bonds Si-O-Si with covalent bonds alternating, strong ionic bonds, or sterically limited ionic bonds. The addition of B203 leads to B-O-Si bonds. It does not result in breaks in the network of covalent bonds of the material, such as Si-0 ~ / 0 ~ Si. This is an example of the establishment of alternating covalent bonds. Additions that lead to positive ions of high charge states of three or more, for example, Al and Zr, lead to strong ionic bonds. The oxygen ions at the end of the covalent chains, Si-0 ~, will form strong ionic bonds with ions of high charge states. These ionic bonds with high charge state ions are strong, because the electrostatic bonding forces are proportional to the charges of the participating ions. Strong ionic bonds are formed when the covalent Si-O-Si bonds have been broken. For additions of the form 203 or X02, it may not be clear whether the element X forms alternating covalent bonds, X-O-Si, or if the element X forms ions with a high state of charge, X or X. In any case, the result is the same. The network of molecular bonds is reinforced in relation to the additions of the X20 and XO forms. Although this does not make the network more orderly, it is observed empirically that the acoustic attenuation is reduced. Although K20 and BaO are of the same form X20, and XO is formed as 0 and CaO and MgO, the corresponding ion radii are very different. The ionic radius of K + is 1.33 Angstroms, and the ionic radius of Ba is 1.35. In contrast, the ion radii of Na +, Ca, and Mg are 0.95, 0.99, and 0.65, respectively. All these ions will be attracted to the negative charges of the negative oxygen atoms that end the coyalent network. However, the large size of, for example, K + and Ba ions, in relation to, for example, Na +, Ca, and Mg ions, leads to spherical effects due to space filling in the region of broken covalent bonds , Yes-O / O-Yes. The inventors interpret their observations and discoveries, in part, as due to these spherical effects, which result in a suppression of acoustic damping when the ionic radii exceed about 1.1 Angstroms.

The spherical effects are more pronounced for large radius ions simply charged from additions of the X20 form. This is because there are two X + ions by broken covalent bond _Si-0 ~ / 0 ~ Si. K + is the most important example for X +. The spherical effects of K + ions in glass are known, and are the basis for the chemical hardening of glass. The double-charged ions of larger radii, for example, Ba and Sr, will have stronger spherical effects than the smaller double-charged ions Mg and Ca, but will have weaker spherical effects than the simply charged large ion pairs such as K + , and Ba and Sr are more neutral in their acoustic effects. The above conceptual structure provides a context for the invention specified below. The touch panel of the present invention is provided with a glass substrate as a propagation medium for the ultrasonic acoustic waves, which is used to detect the coordinate data on a touched position, whose total content of p Na O, CaO, and MgO in the glass substrate is 20 weight percent or less, and whose total content of Al203, Zr02, Ti0, B2 ° 3 '? 2 ° 3' Sn ° 2 'Pb02, ln203, and K20 is in general 5 percent by weight or more. The use of this glass substrate as a propagation medium for ultrasonic acoustic waves, suppresses the attenuation or damping of ultrasonic acoustic waves, and ensures that a high or acceptable signal strength is received. The touch panel of the present invention is also provided with a glass substrate as a propagation medium for the ultrasonic acoustic waves, which is used to detect the coordinate data on a touched position, and wherein the glass substrate has a transmission of light higher than a glass of soda lime in the region of visible rays. These objects are further achieved, in accordance with the present invention, by providing an acoustic touch position sensor of the type described above, with a substrate made of a transparent material, such as a tempered or tempered glass, preferably a glass that contains barium, which exhibits a substantially lower acoustic absorption than conventional soda lime glass. "Tempered glass" means a glass that can be thermally hardened, or substantially chemically hardened. The thermal tempering occurs when the glass is heated until it is hot bright red and then cooled rapidly, thus putting the glass on both surfaces under very high compression because they cooled so quickly. For fully tempered glass, this can be approximately 1,050 kg / cm2. It is also possible to thermally temper the glass in a partial manner to, for example, approximately 700 kg / cm. The inner portion of the glass cools more slowly, and is under tension, stretching parallel to the surfaces on both surfaces. The glass can only be heat tempered if it has a sufficiently large coefficient of thermal expansion, that is, it has a coefficient of thermal expansion greater than about 6'x 10 / K before being annealed. The chemical hardening of the glass takes place by replacing some of the lower alkali metal ions present on the surface of the glass, with higher alkali metal ions, for example, the replacement of lithium and / or sodium ions with potassium ions. The chemical hardening process is generally disclosed in U.S. Patent No. 3,954,487, which is incorporated herein by reference. Here, we are interested in glasses that can be hardened "substantially" in a chemical way, that is, up to an increase in strength of at least approximately 50 percent, preferably up to an increase in strength of at least about 100 percent. In a very unexpected way, it has been discovered that the use of a glass containing temptable barium as a substrate for acoustic touch panels employing Rayleigh waves, adds between 10 and 30 dB to the ratio of the signal to noise, compared with equivalent acoustic touch panels that they use soda lime glass as the substrate. On a tonnage basis, the volume of glass produced in the world is soda lime glass. For example, window glass is soda lime glass. The windows and mirrors for cars are made with soda lime glass. Being the most inexpensive glass material, soda lime glass is the natural choice for a transparent substrate material. Accordingly, all Adler type acoustic touch panels known until recently, with the exception of this invention, have been based on a glass substrate formed of soda lime glass. The borosilicate glass was originally developed by Dow Corning, and traded by Corning under the brand name "Pyrex". This glass, although a bit more expensive than soda lime glass, has found a massive market, mainly due to its small coefficient of thermal expansion, which makes it possible to withstand large temperature gradients without cracking. Schott Glass also currently markets a borosilicate glass under the brand names "Tempax" and "BoroFloat". In a simple experiment, it has been shown that borosilicate glass is about half as absorbent of Rayleigh waves as glass of soda lime. Figure 3 illustrates the measurement method used to determine the attenuation of Rayleigh waves in the glass. A transmitting and receiving transducer pair 2 and 4, respectively, was placed on the glass, and the distance between them was varied, between 5.08 centimeters, 10.16 centimeters, and 15.24 centimeters. Measurements were taken with two glass samples of soda lime, and two samples of borosilicate glass in each of the distances. In this case, the borosilicate glass was a Tempax glass sheet manufactured by Schott. The results are illustrated graphically in Figure 4. As can be seen in Figure 4, the attenuation in the glass of soda lime was approximately twice the attenuation measured for the borosilicate glass. The glass of soda lime exhibited an attenuation of 1.44 dB by 2.54 centimeters; Boron silicate glass attenuated the same signal by 0.74 dB by 2.54 centimeters. In relation to the glass of soda lime, these data imply that the borosilicate glass has 0.70 dB of additional signal by 2.54 centimeters of acoustic trajectory. For a maximum acoustic path length of 50.8 centimeters to 101.6 centimeters. This implies 14 to 28 dB of additional signal. Follow-up measurements were made with Schott Boroficate silicate glass "Borofloat", and soda lime glass from a variety of sources. The results confirm the advantage of borosilicate on soda lime glass. In the experiments, all glasses containing barium tested, share the characteristics of low acoustic loss of borosilicate glass. -An example of a glass containing barium is the structural element of the dial plate used in the manufacture of the Zenith 1490 FTM monitor (flat tension mask). It was observed that the measured samples had an acoustic attenuation of approximately 0.6 dB / 2.54 centimeters. Similar low noise attenuation was observed in the face plates of a variety of cathode ray tubes from a variety of monitor products: MiniMicro MM1453M; Mitsubishi AUM-1371; Quimax DM-14 +; NEC A4040; and Golstar 1420-Plus. Another example of a glass containing barium is Schott B270 glass, which is reported to have the approximate composition (weight percent on an oxide basis) of SiO2: 69.5, a20: 8.1, K20: 8.3, CaO: 7.1, BaO : 2.1, ZnO: 4.2, Ti02: 0.5, Sb203: 0.5. Accordingly, the use of a low loss glass in an acoustic touch panel according to the invention, provides an extra measure of "accumulation" of signal, due to the greater proportion of the signal to noise. This increased accumulation makes it possible to achieve many objectives that, at least superficially, do not seem to be related to the choice of substrate material. These are listed below: (1) The greater proportion of the signal to noise makes it possible to reduce the cost of the electronic controller associated with the touch panel. In particular, the burst circuit of the controller, which sends a tone burst to the transmitting transducers of the touch panel, can be simplified by reducing the amplitude of the burst to, for example, the logic voltage levels. Transistor-transistor (TTL), making it possible to use lower cost circuits in the output stage. Reducing the burst's amplitude also has the advantage of reducing EMI emissions from the controller. (2) Acoustic touch panels of the type disclosed in US Pat. No. 33,151, use reflective arrays to minimize the noise of transducers and electronic channels, and to provide an analog measurement based on the Reliable and accurate time of touch precision. However, the resulting relatively long acoustic wavelength path lengths, together with the losses from the two acoustic wave scatters, lead to small received signal amplitudes, and limit the overall size of the touch panel. An increase in the ratio of signal to noise, resulting from the use of borosilicate glass or barium-containing glass, makes it possible to increase the overall size of this type of touch panel. For example, rectangular touch panels can have a diagonal dimension of at least 53.34 centimeters. (3) It is often necessary to allow contact between the sensitive portion of the touch panel and adjacent objects. For example, a cathode ray tube housing can make contact with an acoustic touch panel in such a way as to protect and enclose the reflective arrays and transducers. This contact can be made by means of an elastic and waterproof seal, such as an RTV seal, between the substrate of the touch panel and the adjacent object. These seals absorb the energy of the acoustic wave, making it highly desirable to increase the ratio of the signal to the noise before the application of the seal. (4) For many applications, ensuring proper mechanical adjustment of a touch panel in a visual touch / display system involves optimizing the mechanical design at the expense of the amplitudes of the acoustic signals. Mechanically compact transducers with less than optimal acoustic performance can be designed. Mirror arrays that are narrower than optimal can be designed so that signal operation accommodates mechanical limitations. The less signal is lost due to cushioning in the substrate material, the more flexibility the design engineer has to improve the mechanical adjustment at the expense of the amplitude of the signal.

Due to its durability, scratch resistance, and optical clarity, soda lime glass has been the material of choice for acoustic touch panels. As noted above, glasses containing borosilicate and barium silicate provide these mechanical and optical advantages, and at the same time, increase the ratio of signal to noise. The experiments referred to above show a pronounced improvement over soda lime glass. Experiments were performed using the most important acoustic glass for acoustic touch panels: Rayleigh waves. As with soda lime glass, other acoustic modes, such as Lamb waves and ripples, can be made to propagate on glass substrates containing borosilicate or barium silicate. A pattern of reduced acoustic attenuation in glasses has been observed with compositions that minimize the number of unrestricted broken bonds Si-0_ / 0 ~ Si. There are reasons to believe that this general pattern is independent of the acoustic mode. The energy of Rayleigh waves is in the form of tensions, tractions, and both tear and longitudinal movements, and consequently, Rayleigh waves are subject to the damping mechanisms corresponding to these forms of energy. Tear waves have energy only in the form of tractions, tensions, and tear motions, and consequently, the damping mechanisms for tear waves are a subset of the damping mechanisms for Rayleigh waves. With the exception of a flexural wave, which contains only tear energy, Lamb waves have energy in both the tear and longitudinal form, and therefore share the same damping mechanisms, albeit in different proportions, than Rayleigh waves. Due to the shared damping mechanisms, glasses containing borosilicate and barium silicate have a reduced attenuation in relation to soda lime glass for all acoustic modes. For a complete understanding of the present invention, reference should now be made to the following detailed description of the preferred embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic plan view showing an embodiment of the acoustic touch panel of the present invention. Figure 2 is a wave profile showing the envelope of the signals received in Example 1. Figure 3 is a diagram illustrating a method for measuring the attenuation of acoustic waves in a substrate. Figure 4 is a graph of the actual results of Rayleigh wave measurements, using the method illustrated in Figure 3, for a glass lime soda substrate and a borosilicate glass substrate. Figure 5 is a cross-sectional view of a touch panel mounted on a visual display monitor of cathode ray tube. Figure 6 is a cross-sectional view of a touch panel used to receive a projected image. Figure 7 is a cross-sectional view of a safety glass lamination, wherein the outer glass layer serves as a touch panel substrate.

DESCRIPTION OF THE PREFERRED MODALITIES In the present invention, the propagation medium for the ultrasonic acoustic waves comprises a specific glass substrate or base. A "touch type panel composed of the glass substrate" serves to provide coordinate data of a touch position.A characteristic of the touch panel of the present invention resides in the use of a glass substrate on which information is inserted. by a touch, this glass being comprised of Si02 as the main component, with a total low content of Na20, CaO, and MgO (hereinafter, these three compounds can be generically referred to as the first component).The content is about 55 to 90 percent by weight, and preferably about 60 to 85 percent by weight (eg, 65 to 85 percent by weight). When the content of the first component is larger, the attenuation or damping ratio of the ultrasonic acoustic waves increases on the one hand, and the intensity of the received signal decreases on the other, presumably because the first component contained in the glass breaks the covalent bonds of Si-O-Si in the covalent network of Si02 without replacing these broken bonds with alternating covalent bonds, strong ionic bonds, or sterically limited ionic bonds.Therefore, the total content of the first component must be kept low. Particularly desirable is a glass substrate having a lower total content of the first component than that of soda lime glass, which is a conventional and common glass. , it is preferable to use a glass substrate with a total content of the first component of 20 weight percent or less (i.e., from 0 to 20 weight percent). A preferable glass substrate comprises a glass having a total content of the first component of about 0 to 18 weight percent (eg, 1 to 17 weight percent), and especially about 0 to 17 percent by weight by weight (for example, from 2 to 16 weight percent). The increase in the content of a component that avoids covalent Si-O-Si bonds that are poorly limited, causes a lower attenuation or damping of the ultrasonic acoustic waves. An elevation of an attenuation or damping, as well as a drop in the intensity of the received signals, can be prevented by using a glass substrate having a high total content of Al203, Zr03, Ti02, B2 ° 3 'Y2 ° 3' Sn03 'Pb02' In2 ° 3 'and K2 ° (later on, these components can simply be referred to as the second component). It is particularly preferable that the second component is present in a higher total content than what is present in the soda lime glass, ie the total content of the second component should be 5 weight percent or more (e.g. , from 5 to 25 weight percent). A desirable glass substrate contains the second component at about 5 to 20 weight percent, and particularly about 7 to 20 weight percent (e.g., 7 to 18 weight percent) accumulated. Provided that the total content of the first component and that of the second component are in the above ranges, the glass substrate does not need to contain all the first components or the second components, respectively. To be specific, the glass substrate may comprise at least one compound, or even no compound, between the first component (Na20, CaO, MgO), or may comprise at least one compound between the second component (A1203, Zr02, Ti02, etc) . The glass substrate may also contain different components, such as an oxide (for example, BaO, ZnO, BeO, Li20, Te02, v2 ° 5 'p2 ° 5 ^' a melting agent, a lightener, a coloring agent, a decolorizing, or other components The glass substrate of the touch panel of this invention in which "the data is to be entered by a touch, is arranged on the visual display device, and the data is only displayed by the display device. visual, being visible through the touch panel It is therefore desirable that the glass substrate constituting the touch panel has excellent light transmission in the region of visible rays (wavelength of approximately 400 to 700 nanometers) In terms of noise inhibition, it is desirable that the glass substrate exhibiting a high transmission in the region of visible rays has a higher intensity of the received signal than the glass of soda lime. A high rate of transmission can be formed from a glass comprising Si02 as the main component, and also containing the first component and the second component, or other glasses (for example, a glass without rust). "In optically demanding applications, the acoustic touch panel can be optically linked to the visual display device, thereby eliminating reflections and transmission losses from the back surface of the touch panel and from the front surface of the visual display. avoid distracting reflexes from an acoustic touch panel, a gloss treatment may be applied, for example, an uneven coating using a silica or a chemical etching.Another way (if fingerprints are not a problem), it can apply an anti-reflective coating In both cases, the surface treatment is very superficial compared to the acoustic wavelength, and the glass substrate still determines the relevant acoustic properties of the panel.As the glass for the substrate of this invention, it is they can mention other glasses that have the composition or the previous characteristics s, such as a lead glass, an aluminoborosilicate glass, an aluminum silicate glass, a borosilicate glass, and the like. The touch panel of this invention, disposed on the visual display device, may be used in combination with a liquid crystal display device, a plasma display panel device, or the like. Figure 1 is a schematic plan view showing a modality of the touch panel in accordance with the present invention. The touch panel shown in Figure 1 comprises the glass substrate 1 as a propagation medium having a visual display area (an image display area) 2, which can be touched, and which is laterally symmetrical in the directions of the X axis and the Y axis formed on its surface. The acoustic waves propagating in the substrate have sufficient power density at the surface to be measurably attenuated by touches on the surface. The transmission elements 3a and 3b transmit the acoustic waves in the directions of the X axis and the Y axis of the glass substrate. These transmission elements comprise electroacoustic transducers, for example ceramic piezoelectric elements, and perhaps also mode converting elements, such as a plastic wedge of a wedge transducer. These transducing elements are arranged in previously determined positions on the glass substrate 1, to direct the acoustic beams towards the transmitting reflective grid arrays 4a and 5a. The acoustic waves from the transmission elements in the directions of the X axis and the Y axis are redirected and propagated in the directions of the Y axis and the X axis over the entire visual display area 2 by means of a reflective element comprising first arrays reflective (first reflective elements) 4a and 4b formed on both edges in the direction of the Y axis, and the second reflective arrays (second reflective elements) 5a and 5b formed on both edges in the X axis direction, and the acoustic waves become to direct or converge on the directions of the X axis and the Y axis, to be received by the receiving elements. The receiving elements 6a and 6b comprise the same members as the transmitting elements. The distinction between the transmitting elements and the receiving elements is largely determined by the connections with the electronics. If the items 6a and 6b are connected to the excitation circuit, and 3a and 3b are connected to the receiving circuit, then 6a and 6b will serve as transmitting elements, and 3a and 3b will serve as receiving elements. The signal cables 7a and 7b are connected to the transmitter elements, while the signal cables 8a and 8b are connected to the receiver elements. In this device, when an excitation signal is transmitted intermittently, such as a tone burst of a few dozen cycles, by means of the cables 7a (or 7b) to the transmitter elements 3a (or 3b), the ultrasonic sound waves are reflected by the reflective arrays 4a (or 5a), propagate through the surface of the glass substrate 1, are reflected by the reflective arrays 4b (or 5b), to be received by the receiving elements 6a (or 6b). The total acoustic delay is well below 1 millisecond, and therefore, there is time within the time of the human reaction, to excite in sequence the measurement subsystems of the X and Y coordinates. The received signal is sent to a processing controller of signals by means of the signal cables 8a (or 8b), wherein the controller recognizes the received signal and detects its intensity. The touch panel of Figure 1 is typically intended to be placed in front of a visual display device, and to serve as a computer peripheral, for the same central computer that controls the visual display device, and perhaps other output devices , such as a sound system. Normally, the application software of the central computer provides feedback to the human user when a touch has been detected. This feedback can take many forms. Examples are enhancing the Icon in the displayed image, an audible click or a ringing sound from a speaker, or simply performing the desired touch control function. Of course, all this desired performance depends on the acoustic touch panel system correctly detecting a touch, which in turn depends on maintaining an acceptable ratio of signal to noise. The acoustic waves lose intensity as they propagate through the glass substrate of a touch panel. This physical effect, the attenuation of the acoustic energy by the substrate is a key factor in the determination of the signal amplitudes for an acoustic touch panel system. In the touch panel of the present invention, the use of selected glass substrates reduces the attenuation or damping of ultrasonic acoustic waves, and ensures detection of the received signal with sufficient intensity. Touch positions reliably and accurately. Tests were conducted using transmission transducers and piezoelectric reception transducers mounted on glass sheets of soda lime and borosilicate glass at different distances to measure acoustic attenuation. See Figure 3 and Figure 4. Two glass sheets of soda lime (soda lime number 1 and soda lime number 2) and two sheets of borosilicate glass were tested. (borosilicate number 1 and boron silicate number 2). Boron silicate glass was manufactured by Schott Glass Co. and sold under the trademark "Tempax". The data clearly reveal that Rayleigh waves are subject to approximately 50 percent less attenuation in boron silicate than in soda lime glass. The average attenuation for borosilicate glass was 0.74 dB / 2.54 centimeters, while the average attenuation for soda lime glass was 1.44 dB / 2.54 centimeters. The signal gain due to the use of borosilicate glass instead of soda lime glass depends on the distance in which the acoustic waves propagate in the substrate. The maximum path length from the transmission transducer, for example 3a, to the receiving transducer, is approximately the total length of the transmitting reflective array, for example 4a, plus the internal separation between the mirror arrays, plus the total length of the reflective arrangement 4b. For the present commercial products, this maximum path length is normally in the range of 50.8 to 101.6 centimeters. For a maximum path length on a scale of 50.8 to 101.6 centimeters, and an attenuation (for Rayleigh waves of 5.53 MHz in soda lime glass) of approximately 1.5 dB / 2.54 centimeters, the signal loss due to the attenuation of the substrate is on the scale of 30 to 60 dB. Because the total attenuation for the touch panels is normally in the range of 80 to 100 dB, the loss due to attenuation of the substrate is a substantial percentage (approximately 50 percent) of this total value. Accordingly, if boron silicate glass, or some other transparent material with substantially less sound absorption than soda lime glass, is used as the substrate, instead of soda lime glass, it is possible to substantially increase the signal available received by the receiving transducer. In particular, the above data imply an additional 0.7 dB of signal per 2.54 centimeters of acoustic path length. For a maximum acoustic path scale of 50.8 to 101.6 centimeters, this implies 14 to 28 dB of additional signal. For acoustic touch panels of sizes larger than the commercial products of today, the signal gain is greater. Acoustic attenuation is a growing function of frequency. Quantitative measurements and previous calculations were performed with a test frequency of 5.53 MHz. If a product is designed for a higher operating frequency, the acoustic attenuation will be greater, and the gain of using a glass of more acoustic loss will also be greater. If a product is designed for a lower frequency, the opposite will be true. Although the quantitative numbers will change, the qualitative advantages of a glass substrate with low acoustic loss will remain. Acoustic damping test measurements at 5.53 MHz are relevant for identifying low-loss acoustic glass substrates for use in products with operating frequencies anywhere within a wide range, for example, from 3 to 10 MHz. explicit, we can define the "glass of low acoustic loss" as follows: less than 0.5 dB / cm of acoustic attenuation for 5.53 MHz Rayleigh waves, measured by the inclination of a graph of the amplitude versus the distance for a signal through a pair of wide wedge transducers of 1.27 centimeters faced mounted on the glass under test. The data of the touch panels assembled with borosilicate borosilicate glass show markedly increased signal amplitudes. This shows that both the borosilicate glass borofloat and Tempax provide similar acoustic advantages. For some applications, it is desirable to use a tempered glass substrate. Due to its low coefficient of thermal expansion, the borosilicate glass can not be heat tempered. Due to a low percentage, and even a lack of sodium ions that can be replaced by potassium ions, the common borosilicate glass can be chemically hardened only to a very limited extent. For applications that demand tempered glass substrates, it is preferable to use a tempered glass with low acoustic losses. It has been found that this is made possible by the selection of glass containing barium as the substrate material for the acoustic touch panels. The discovery that acoustic wave losses are much less for borosilicate glass and for barium-containing glass than for soda lime glass, forms the basis for International Application of TCP Number 096/23292, which It was published on August 1, 1996. In addition, it has been discovered that Schott Glass's B270MR glass is an example of glass containing barium (2.1 percent BaO) with low sound loss, which can be acquired in a easy and economical in sheet form, and which can optionally be heat tempered, or chemically hardened. The additional signal amplitude provided by the use of a borosilicate glass or a glass substrate containing barium, makes possible a number of product improvements which, by themselves, lead to undesirable losses in the proportion of the signal to noise. Now several of these product improvements will be described. In the design of transducers, for example, articles 3a, 3b, 6a, and 6b, the design engineer often faces a distance between the amplitude of the signal and the mechanical adjustment of the touch panel inside the housing of the visual display device . In some cases, the design engineer can avoid mechanical interference by reducing the width of the transducer from, for example, 1.27 centimeters to 0.635 centimeters. The reduced-width transducer leads to signal losses, in part due to the greater angular divergence of an acoustic beam from a narrower transducer. In other cases, the design engineer may include a beveled surface on the edge of the glass substrate on which to mount, for example, a wedge transducer. If the angle of the bevel is sharp enough to equal or exceed the angle of the wedge, for example 33 °, the wedge transducer will conveniently be below the plane of the touch surface. However, the intersection of the touch surface with this steep beveled surface leads to an acoustic discontinuity, which results in significant signal losses. In these and other cases, a touch panel with a better mechanical fit is possible if a low acoustic loss substrate allows the design engineer to make distances that compromise the efficiency of the transducer. The design engineer faces another drawback between electronic and mechanical design, when there is a need for a seal between the touch surface and a housing of the visual display device. For example, see Figure 5. This illustrates how a touch panel 100 can be attached to the cover plate of a cathode ray tube (CRT) 102. Touch panel 100 and cathode ray tube 102 they are limited within the housing of the cathode ray tube 104. The touch panel 100 is held in place by a spacer / adhesive system 106, both of which follow the curved profile of the dial plate of the cathode ray tube. The enclosure partially defined by the touch panel 100 and the cathode ray tube housing 104 is completed by means of an elastic circumferential seal 108 positioned in or near the gap between the housing 104 and the touch panel 100. The seal 108 it is in contact with the sensitive touch surfaces of the touch panel 100, and absorbs the acoustic wave energy. Due to the greater signal accumulation provided by the present invention, seal 108 can cause a loss of acoustic wave energy of at least 6 dB, and even up to 12 dB, without reducing the ratio of signal to noise to unintelligible levels. The design engineer faces yet another inconvenience in the design of the electronics. The current control products used with the acoustic touch panels generate excitation signals of many tens of volts from peak to peak. This relatively large excitation voltage is added to the cost of the electronic circuit, and may additionally have the side effect of contributing to the generation of unacceptable levels of EMI emissions. Much can be gained by reducing the excitation voltage by, for example, 15 dB. However, a 15 dB reduction in the excitation voltage will result in a corresponding loss of 15 dB in the received signal. The replacement of soda lime glass with boron silicate or glass containing barium provides sufficient signal buildup to enable this excitation voltage reduction. Perhaps the most dramatic product improvement made possible by the glass substrate of low acoustic loss, is a significant increase in the maximum size of the sensor. Elo TouchSystems, Inc. has recently introduced acoustic touch panel products, based on borosilicate glass. These are large touch panels with a diagonal dimension of 53.34 centimeters. Elo initially. He tried to introduce a glass product of soda lime of 53.34 centimeters, but canceled the effort because the signal amplitudes were insufficient to guarantee reliable quality performance. The sensitivity of the signals to the increasing size of a soda lime touch panel can be seen from the following calculations. Assuming a standard video display aspect ratio of 3: 4, an increase of 2.54 centimeters in the diagonal dimension will increase the maximum length of the acoustic path (maximum acoustic path length = constant + twice the length of the array X + the internal separation between arrangements X) by 5,588 centimeters. For an attenuation of 1.5 dB / 2.54 centimeters, every 2.54 centimeters of added diagonal increases the absorption in the substrate by 3.3 dB. The addition of 7.62 centimeters to the diagonal will lower the signal by 10 dB. As a result, acoustic soda lime panels of larger size quickly become more difficult. Many larger sizes are possible with borosilicate glass, as demonstrated by Elo TouchSystems with a 78.74-centimeter-diagonal touch panel in operation, which has a laminated inverse projection screen, and illuminated with a projective visual display, at the Comdex show in November 1996 in Las Vegas. This example illustrates the use of large touch panels in a projected image configuration. See Figure 5. A projector 118 and lens 120 projects a video image in real time on a reverse projection screen 110, which can be laminated to the back of the substrate of an acoustic touch panel 122. There is increasing interest in the market in very large touch panels, to be used in audiovisual applications. The use of large pieces of glass in an application that involves frequent contact may present concerns for safety and resistance. As this niche of the emerging market matures, there may be a demand for tempered versions of very large acoustic touch panels. Boron silicate glass can not be tempered. Boron silicate glass has a small coefficient of thermal expansion. For example, the data sheet for Schott's BoroFloat glass gives a thermal expansion coefficient of 3.25 x 10 / K. This makes the borosilicate glass, for example Pyrex, difficult to break with a thermal shock. It also makes it difficult to create the tension pattern of the tempered glass by rapid cooling of the heated glass. Although the borosilicate glass can not be tempered, glass containing barium of low acoustic loss is available, such as Schott B270 glass, which can be tempered. The acoustic touch panels made of glass B270, can be as large as they can be tempered with heat or can be chemically hardened. The fact that B270 glass can be tempered can be understood as the result of the coefficient of thermal expansion of the B270. The technical data sheet of the B270 gives an average coefficient of expansion (from 20 ° C to 300 ° C) of 9.5 x 10 / K. This is similar to soda lime glass, and very different from boron silicate glass, such as BoroFloat, whose coefficient of thermal expansion is 3.25 x 10 / K. ESL 4022C glass frit, which has a coefficient of thermal expansion of 8.8 x 10 / K, is used because its coefficient of thermal expansion matches the thermal expansion coefficients typical of soda lime glass. For example, Starphire soda lime glass has a specified thermal expansion coefficient of 9.0 x 10 / K. The use of tempered glass substrates requires the use of a reflective fixation material and a curing process that does not temper the glass. For example, reflective materials that cure at low temperature can be used. Polymeric materials dampen acoustic power more quickly than conventional glass frit reflector materials, and therefore, increase the need for a low acoustic loss substrate. It is also feasible to build large touch panels as part of a safety glass assembly, that is, a lamination of two sheets of glass. See Figure 7. Optionally, one or both of the glass sheets can be heat hardened or chemically hardened. For example, a substrate for a Rayleigh sound acoustic touch panel operating at 5.53 MHz, may be a 3-millimeter thick layer of tempered B270 glass, which may be laminated onto a second layer of tempered B270 glass of 3 mm. thickness. For a load or impact applied to the upper surface of the safety glass substrate, a lot of force is added, even if only the lower glass layer is hardened. When deflected, the safety glass substrate under load, the upper glass layer is under compression, and the lower glass layer is under tension. Glass is much stronger under compression than under tension. It is "more important that the tensioned glass layer is tempered." A prototype touch panel on an un-tempered laminated glass broke with a heavy impact on the upper touch surface, and it was the lower layer of glass that fractured. However, the upper glass layer did not break, despite the cracks clearly visible in the lower glass layer, and the prototype touch panel still worked.This is experimental evidence that the lower glass layer is The most important layer to be tempered A safety glass substrate can be composed of a top layer of 3 mm non-tempered BoroFloat glass, in a 3 mm thick tempered soda lime glass bottom layer (or thicker.) However, for applications with a sufficiently wide operating temperature scale, this is not a practical design, due to the very different thermal expansion coefficients of the glass Boron silicate and soda lime glass. Changes in temperature will cause the substrate to deform as a bi-metal strip on a thermostat. This deformation effect has been observed experimentally. A sample of borosilicate glass was adhered to a glass sample of un-tempered soda lime. Both samples had a nominal size of 15.24 centimeters by 22.86 centimeters. This lamination was put in an oven. A change of 30 ° C in the temperature resulted in a very visible deformation of this small laminated sample. The deformation due to temperature changes will be much less a problem for a lamination of, for example, glass B270 of 3 millimeters of unhardened thickness and tempered soda lime glass. Note the advantage of having a low acoustic loss glass with a coefficient of thermal expansion similar to that of standard soda lime glass, even when the low tempered acoustic loss glass is not really tempered. There are additional advantages to a low-loss tempered glass with a thermal expansion coefficient similar to standard soda lime glass, for example between 6 x 10.6 / K and 12 x 10.6 / K. It has been observed that the bond between the cbmún glass frit, currently used as a reflector material for most commercial touch panel products, and the boron silicate substrates, is of a lower quality than the bond of the glass frit reflectors on soda lime glass substrates. This is due to the poor coupling of the coefficients of thermal expansion between the frit and the borosilicate glass. The frit compositions exist with a better coupling to the coefficient of thermal expansion of the borosilicate glass, but only at the expense of a higher curing temperature higher than 500 ° C. An advantage of low temperature heat-curable acoustic glass over borosilicate glass is its coefficient of thermal expansion that is well coupled with standard glass frit products with low sintering temperatures. As described in U.S. Patent No. 5,591,945, it is possible to design acoustic touch panels where Rayleigh waves propagate along the reflective arrays, while horizontally polarized tear waves detect the touches in the active area of the sensor (hereinafter referred to as a Rayleigh-Rayleigh-tear sensor). This sensor can detect a touch even when the sensor is sealed with silicone rubber (RTV). This sensor can detect a touch when the active area is covered with water. A large Rayleigh-tear-Rayleigh sensor can be constructed using a glass of low acoustic loss, such as B270 glass. For an operating frequency of 5.53 MHz, the wave mechanics of a Rayleigh-Rayleigh tear sensor limits the thickness of the glass to approximately 3 millimeters. In addition, because a Rayleigh-Rayleigh tear sensor is sensitive to touch on both the upper and lower surface of the glass, it can not be laminated as part of a safety glass substrate using conventional safety glass adhesives. (Adhesives are required as silicone rubber with low viscous damping). These wavelength requirements of the Rayleigh-tear-Rayleigh touch panels make a glass containing low-loss acoustic-tempered barium such as the B270, be particularly interesting for large Rayleigh-tear-Rayleigh touch panels. The following examples are intended to describe the present invention in greater detail, and by no means should be construed to define the scope of the invention.

Example 1 (prior art) An ultrasonic acoustic touch panel was produced as shown in Figure 1, using a flat soda lime glass substrate (manufactured by Central Glass Co., Ltd., Japan: 488 millimeters (width) x 403 millimeters (length) x 3.3 mm (thickness)). Ripples were excited Rayleigh, and they propagated in this acoustic touch panel. The operation of the touch panel was observed using a controller (5810E100 manufactured by Touch Panel Systems Co., Ltd.). The glass of soda lime comprised SiO2 (71 weight percent), Na20 (13 weight percent), K20 (1 weight percent), CaO (11 weight percent), MgO (2 weight percent) ), and Al20 (2 percent by weight). The total content of the first component (Na20, CaO, MgO) was 26 percent by weight, while the total content of the second component (Al20, Zr02, Ti02, B203, Y2 ° 3 'Sn02' P 02 'In2 ° 3' K20 ^ was 3 weight percent. The transmission of light from the glass substrate in the region of visible rays measured 91.8 percent (using a haze computer, HGM-2D, manufactured by Suga Testing Apparatus Co., Ltd.). There is some uncertainty in the absolute calibration of this measurement. However, this measurement will serve well for comparisons with other glass (92 percent transmission is a theoretical upper limit given by a 4 percent reflection on both the front and the rear surface of the glass). The reflection is caused by the bad coupling of the refractive index between the air and the glass. The refractive index for glass is normally approximately N = 1.5, such that the reflection on a single surface (n-l / n + 1) is approximately 4 percent. The propagation velocity of the acoustic waves was measured according to the method described below. The propagation speed of the acoustic waves was determined by varying the separation or spacing of the reflector array elements, and observing when the amplitude of the received signal is more intense. The amplitude of the received signal is more intense when the spacing or spacing is equal to an integral multiple of the acoustic wavelength corresponding to the fixed operating frequency. A set of samples was made where the reflector spacing was varied by small degrees. Having determined the wavelength from the separation, giving the maximum amplitude received, the velocity is determined from the product of the wavelength and the frequency (5.53 MHz). As with the commercial Rayleigh wave touch panel products, acoustic signals were transmitted on, and received from, the glass surface, with wedge transducers. The wedge transducers are composed of a ceramic piezoelectric element bonded to a plastic wedge, which in turn is bonded to the glass surface. The wedge couples the acoustic waves in the pressure mode from the piezoelectric element to the Rayleigh waves on the glass substrate. The transmitted transducer was excited by a 5.53 MHz tone burst of an amplitude of 50 volts. In this manner, the propagation velocity of the soda lime glass substrate was measured at 317,500 centimeters / second in the receiving transducers. Measurements were made for both the subsystems of the X axis and the Y axis of the touch panel. The intensities measured were 1.41 mV and 1.69 mV, respectively. It is interesting to identify glass substrate materials that lead to amplitudes of larger received signals.

Use 2 Instead of the glass lime soda substrate of Example 1, a flat boron silicate glass substrate (sold by Schott Co. Ltd. under the trade name Tempax; 488 millimeters (width)) was used in this example. x 403 millimeters (length) x 3.3 millimeters (thickness)). The glass substrate comprised Si02 (81 weight percent), Na20 (3 percent by weight), K20 (1 percent by weight), B20 (13 percent by weight), and Al203 (2 percent by weight), with the total content of the first component (Na20, CaO, MgO) of 3 percent by weight, and the total content of the second component (Al203, Zr02, Ti02, B203, Y203, Sn20, Pb02, ln203, K20) being 16 percent by weight. The light transmission of the glass substrate in the visible ray region measured 93.0 percent by the method described in Example 1. This is about 1 percent higher than for the soda lime glass of Example 1. In addition , when looking at the shore above, this glass has a pale yellow-green color, instead of the dark green of the common soda lime glass; This glass has a better transmission of light. Using the test methods of Example 1, the propagation velocity of the glass substrate was measured as 310.611.52 centimeters / second. For the designed touch panel to have a propagation velocity of 310.611.52 centimeters / second, the intensity of the received signal was measured, using the methods of Example 1, both for the X axis and for the Y axis. The intensity in the axis X (the horizontal axis in Figure 1) was 6.66 mV, and that on the Y axis (the vertical axis in Figure 1) was 8.39 mV. This is a gain greater than 12 decibels in the amplitude of the received signal. Prototype touch panels have been constructed from both boron silicate glass TEMPAXMR and BoroFloat borosilicate. In both cases, a dramatic increase in the intensity of the received signal is observed in relation to the touch panels that use soda lime glass. The degree of increment of the 'signal depends on the details of the touch panel design; the received signals normally increase between 10 and 30 decibels. The observed effect is more dramatic for the larger touch panels, where the acoustic waves propagate for longer distances. The touch panel was connected to a controller to detect the coordinates of a touch position. As in Figure 2, the signal received when the panel was touched showed a pronounced drop Dt in the received signal intensity D, thus making it possible to clearly recognize the touch position. The desired functionality of the touch panel is well provided, eg 3 Instead of the "lime" glass substrate used in Example 1, a flat glass substrate was used (Schott or Desag Co., Ltd., trade name). B270-SUPER ITE or B270MR, 488 millimeters (width) x 403 millimeters (length) x 3.3 millimeters (thickness)) .The glass substrate comprised Si02 (69 percent by weight), Na20 (8 percent by weight), K20 (8 percent by weight), CaO (7 percent by weight), BaO (2 percent by weight), ZnO (4 percent by weight), Ti02 (1 percent by weight), and 203 (1 percent) by weight) The total content of the first component (Na20, CaO, MgO) was 15 weight percent, and the total content of the second component (Al20, Zr02, Ti02, B203, Y 03, Sn02, Pb02, ln203, K20) was 9 weight percent The light transmission of the glass substrate in the region of visible rays measured 92.8 percent by the same method described in Example 1. This measurement is 1 percent higher than for the soda lime glass of Example 1. When viewed with the edge above, a pale yellow-green color is seen as the borosilicate glass of Example 2, and unlike the deep green of the soda lime glass of Example 1. Using the test methods of Example 1, it was observed that the glass substrate has a Rayleigh wave propagation velocity of 308,886.86 centimeters / second. The intensity of the signal received from a touch panel was measured with a propagation velocity of 308,886.86 centimeters / second with respect to the X axis and the Y axis, using the methods of Example 1. The intensities of the received signals were 7.69 mV on the X axis, and 7.50 Mv on the Y axis. Like the borosilicate glasses of Example 2, this was an increase in the amplitude of the received signal greater than 12 decibels with respect to standard soda lime glass. A touch was detected using the touch panel connected to the controller. The touch position could be determined precisely from the pronounced subsidence in the received signal. Glass suppliers can heat temper or chemically harden B270 glass using conventional industrial processes. Example 4 STARPHIREMR glass manufactured by PPG, like B270 glass, is a "white" glass that serves markets that require high transmission glass with minimal color dependence. In this sense, STARPHIREMR y_B270MR are optical equivalents. It is interesting that they are not acoustic equivalents. The STARPHIRE glass does not provide the benefits of low acoustic loss provided by the B270 glass, as seen in Example 3. Within the measurement errors, it is observed that the STARPHIRE glass has the same acoustic attenuation as the lime glass in the glass. common soda The STARPHIREMR glass composition is Si02 (73 weight percent), Na20 (15 weight percent), CaO (10 weight percent), unspecified (2 percent). The total content of the first component (Na20, CaO, MgO) is at least 25 weight percent, while the total content of the second component (Al203, Zr03, Ti02, B203, 203, Sn03, Pb02, ln203, K20 ) is at most 2 percent by weight. Example 5 The glass B270 of Example 3 is an example of a glass containing barium. Another example of a glass containing barium is the glass used in the cover plate of the color monitors or the visual displays of cathode ray tube television. Acoustic measurements of the type shown in Figure 4 were made on the cover plates of several color monitors from different sources: Zenith 1490 FTM monitor (flat tension mask); MiniMicro MM1453M; Mitsubishi AUM-1371; Quimax DM-14 +; NEC A4040; and Goldstar 1420-Plus. It was observed that the measured samples had an acoustic attenuation of approximately 0.6 dB / 2.54 centimeters. This is very similar to the borosilicate data of Figure 4. The composition of a representative dial plate glass is as follows: SiO2 (65 weight percent), Na20 (7 weight percent), CaO ( 2 percent by weight), MgO (1 percent by weight), A1203 (2 percent by weight), SrO (10 percent by weight), BaO (2 percent by weight), Pb02 (2 percent by weight ), K20 (9 percent by weight). In the above examples, it is clearly demonstrated that the touch panel substrates of Examples 2, 3, and 5, compared to the touch panel substrates of Examples 1 and 4, can prevent attenuation or damping of the waves. acoustics in a more effective manner, and consequently, can provide better ratios of the signal to noise. Having described and shown the above specification and accompanying figures in this manner, a novel acoustic touch position sensor is provided which utilizes a glass substrate of low acoustic loss that satisfies all the objects and advantages sought for it. However, those skilled in the art will be able to see that different changes, modifications, variations, and other uses and applications of the present invention can be made, after considering this specification and the accompanying drawings, which disclose the preferred embodiments of the invention. the same. It is considered that all changes, modifications, variations, and other uses and applications that do not depart from the spirit and scope of the invention, are covered by the invention, which should be limited only by the following claims.

Claims (47)

1. A touch panel provided with a glass substrate as a propagation medium for Rayleigh waves, and which is used to detect the coordinate data on a touch position, wherein the composition of the glass substrate comprises Si0 as the main component, comprises additional components that prevent Si02 from forming a regular crystalline lattice by the alteration of the Si-O-Si covalent bonds, and wherein the additional components provide sufficient strong alternating bonds through strong ionic bond, alternating covalent bond, or limitations spherical, to produce an attenuation coefficient less than, or equal to, approximately 0.5 dB / cm, as determined on the substrate surface for 5.53 MHz Rayleigh waves, as measured by the slope of an amplitude versus distance plot for a signal through a pair of wedge transducers of 1.27 centimeters wide faced mounted on a sample of the type of glass under test, which has sufficient thickness to withstand the propagation of Rayleigh waves.

2. A touch panel provided with a glass substrate as a propagation medium for Rayleigh waves, and which is used to detect coordinate data on a touch position, wherein the composition of the glass substrate comprises Si02 as the component primary, and the total content of Na20, CaO, and MgO in the glass substrate is 20 weight percent or less.

3. A touch panel as claimed in claim 2, wherein the total content of Al203, r03, Ti02, B203, Y3, Sn03, Pb02, ln203, and K20 on the glass substrate, is 5 weight percent or more.

4. A touch panel provided with a glass substrate as a propagation medium for Rayleigh waves, and which is used to detect the coordinate data on a touch position, wherein the glass substrate is comprised of Si02 as the component main, and the glass substrate has a higher light transmission than a glass of soda lime in the region of visible rays.

5. A touch panel provided with a glass substrate as a propagation medium for Rayleigh waves, and which is used to detect the coordinate data on a touch position, wherein the glass substrate is comprised of Si02 as the component main, being the total content of Na20, CaO, and MgO 20 percent by weight or less, and the total content being 1203, Zr03, Ti02, B203, Y203, Sn03, Pb02, ln203, and K20 of 5 percent by weight or more, and wherein the substrate comprises a glass having a higher light transmission than a glass of soda lime in the region of visible rays.

6. A touch panel as claimed in claim 5, provided with a glass substrate as a propagation medium for Rayleigh waves, and which is used to detect the coordinate data on a touch position, wherein the glass substrate comprises from 1 to 17 weight percent of the total content of Na20, CaO, and MgO, and from 5 to 20 weight percent of the total content of A1203, Zr03, Ti02, B2 ° 3 'Y2 ° 3' Sn03 'Pb02, ln203, and K20.

7. A touch panel as claimed in claim 5, wherein the substrate has the approximate composition (weight percent on an oxide base) of SiO2: 69, Na20: 8, K20: 8, CaO: 7, BaO : 2, ZnO: 4, Ti02: 1, Sb203: 1.

8. In a touch panel system comprising a substrate capable of supporting the propagation of acoustic waves, and elements to be inserted into the substrate, the improves that the sustrato.se is made of a tempered glass that has a coefficient of attenuation less than, or equal to, approximately 0.4 dB / cm, determined in the surface of the substrate for Rayleigh waves of 5.53 MHz, measured by the inclination of a graph of amplitude against distance for a signal through a pair of wedge transducers of 1.27 centimeters wide faced mounted on a sample of the type of glass under test, which has sufficient thickness to withstand the propagation of Rayleigh waves.

9. A touch panel as claimed in claim 8, wherein the ultrasonic sound waves are Rayleigh waves.

The touch panel according to claim 8, wherein the glass has a coefficient of thermal expansion greater than about 6 x 10 / K before being quenched.

The touch panel according to claim 8, wherein the substrate is heat tempered, and has a coefficient of thermal expansion of between about 6 x 10 / K and about 12 x 10 / K before being quenched.

The touch panel according to claim 10, wherein the substrate is heat tempered, and has a coefficient of expansion. thermal from about 8 x 10 / K to about 10 x 10 / K before being annealed.

The touch panel according to claim 8, wherein the attenuation coefficient is equal to, or less than, approximately 0.45 dB / cm.

The touch panel according to claim 8, wherein the substrate is thermally quenched, and has an attenuation coefficient less than or equal to about 0.5 dB / cm.

15. A touch panel according to claim 8, wherein the substrate is comprised of SiO2 as the main component, and the total content of Na20, CaO, and MgO in the glass substrate is 20 weight percent or less .

16. A touch panel as claimed in claim 15, wherein the total content of 120, Zr0, Ti02, B203, 03, Sn03, Pb02, ln203, and K20 on the glass substrate is 5 weight percent or more.

17. A touch panel as claimed in claim 8, wherein the glass substrate is comprised of Si02 as the main component, and the glass substrate has a higher light transmission than a glass of soda lime in the region of visible rays.

18. A touch panel as claimed in claim 8, wherein the glass substrate is comprised of Si02 as the main component, the total content of Na20, CaO, and MgO being 20 weight percent or less, and the total content of A1203, Zr03, Ti02, B20, Y20, Sn0, Pb02, ln 03, and K20 of 5 weight percent or more, and wherein the substrate comprises a glass having a higher light transmission than a glass of soda lime in the region of visible rays.

19. A touch panel as claimed in claim 8, wherein the glass substrate comprises from 1 to 17 weight percent of the total content of Na20, CaO, and MgO, and from 5 to 20 weight percent of the total content of Al203, Zr03, Ti02, B203, 03, Sn03, Pb02, ln203, and K20.

20. The touch panel according to claim 8, wherein the substrate is a glass containing barium.

21. The touch panel according to claim 8, wherein the substrate is a glass containing at least about 1 percent by weight of barium oxide.

22. The touch panel according to claim 8, wherein the substrate is a glass containing at least about 2 percent by weight of barium oxide.

23. The touch panel according to claim 8, wherein the substrate has the approximate composition (weight percent on an oxide base) of YES02: 69, Na20: 8, K20: 8, CaO: 7, BaO: 2, ZnO: 4, Ti02: 1, Sb203: 1.

24. The touch panel according to claim 8, wherein the substrate is Adapt to propagate Rayleigh waves.

25. The touch panel according to claim 8, wherein the substrate is adapted to propagate horizontally polarized tear waves.

26. The touch panel according to claim 8, wherein the substrate is adapted to propagate horizontally polarized tear waves of a higher order.

27. The touch panel according to claim 8, wherein the substrate is adapted to propagate horizontally polarized tear waves of zero order.

28. The touch panel according to claim 8, wherein the substrate is adapted to propagate Love waves.

29. The touch panel according to claim 8, wherein the touch sensor comprises: a substrate having at least one touch surface, and which is capable of propagating an acoustic wave; a transducer for producing an acoustic wave along a first axis in the substrate, this first axis being parallel to the mentioned surface; and a first reflective array having a length, and disposed along the first axis, to reflect, along the length of the array, a first reflected wave, this first reflected wave being directed over a second axis in the substrate, different from the first eJe, and having a component parallel to the mentioned surface; "whereby a proximity of an object to the substrate causes a disturbance in the energy carried by this first reflected wave

30. The touch panel according to claim 8, wherein glass frit is present as a reflective material.

31. The touch panel according to claim 8, wherein a reflective ink that is cured at a temperature less than the tempering temperature of the glass is present as a reflective material

32. The touch panel according to claim 8, wherein the substrate is a lamination of two sheets of glass comprising an inner layer and an outer layer, wherein the outer layer has an attenuation coefficient less than or equal to about 0.5 dB / cm. "

33 . The touch panel according to claim 31, wherein the inner layer is a tempered glass.

34. The touch panel according to claim 31, wherein the lamination of safety glass, both the inner cap and the outer layer, is tempered glass.

35. The touch panel according to claim 31, wherein the outer layer is comprised of a glass having the approximate composition (weight percent on an oxide base) of SiO2: 69.5, Na20: 8.1, K20:

8. 3, CaO: 7.1, BaO: 2.1, ZnO: 4.2, Ti02: 0.5, Sb203: 0.5.

36. The touch panel according to claim 31, wherein the outer layer has a coefficient of thermal expansion greater than 6 x 10 / K.

37. The touch panel according to claim 31, wherein the inner layer is tempered soda lime glass.

38. The touch panel according to claim 8, wherein the substrate is of a generally rectangular shape, in the face view, and has four substantially straight edges, the diagonal dimension of the substrate being greater than 53.34 centimeters.

39. A touch panel according to claim 8, wherein the substrate has a coating on the surface to substantially eliminate the brightness of the reflection.

40. A touch panel according to claim 8, wherein the substrate is laminated to the reverse projection screen material.

41. A touch panel according to claim 2, wherein the substrate is laminated to the reverse projection screen material.

42. A touch panel according to claim 8, wherein the substrate is of a curved profile.

43. A touch panel according to claim 2, wherein the substrate is of a curved profile.

44. In a touch sensing system comprising a substrate capable of supporting the propagation of acoustic waves, and elements for introducing these waves into the substrate, the improvement comprises that the substrate is made of a glass containing chemically hardened barium, which has a attenuation coefficient less than, or equal to, approximately 0.5 dB / cm, determined at the substrate surface for Rayleigh waves of 5.53 MHz, measured by the slope of an amplitude versus distance plot for a signal through a pair of transducers 1.27 cm wide wedge wedges mounted on a sample of the type of glass under test, which has sufficient thickness to withstand the propagation of Rayleigh waves.

45. The touch panel according to claim 43, wherein the substrate is a glass containing at least about 1 percent by weight of barium oxide.

46. The touch panel according to claim 43, wherein the substrate is a glass containing at least about 2 weight percent barium oxide.

47. The touch panel according to claim 43, wherein the substrate has the approximate composition (weight percent on an oxide base) of SiO2: 69, Na20: 8, K20: 8, CaO: 7, BaO: 2, ZnO: 4, Ti02: 1, Sb203: 1.