Method for making interactive information devices with spacer elements

[0002] This is a division of U.S. patent application Ser. No. 09/954,139, filed Sep. 17, 2001, now U.S. Pat. No. 6,627,918 by Catherine A. Getz and Martin Mennig for SPACER ELEMENTS FOR INTERACTIVE INFORMATION DEVICES AND METHOD FOR MAKING SAME, which claims priority from U.S. Provisional Patent Application No. 60/234,867, filed Sep. 22, 2000, the disclosures of which are hereby incorporated by reference herein.

[0003] This invention relates to an improved technology for the separation of a rigid, transparent, conductively coated substrate and a flexible, transparent, conductively coated top sheet as used in an interactive information device such as a computer touch panel, a digitizer panel, a personal digital assistant known as a PDA, or a computer pen input device.

[0004] In an interactive information device having opposing conductive surfaces on a flexible top sheet and a rigid bottom sheet, “spacer dots”, or the like, are non-conductive insulating islands or spacer elements that separate the transparent conductively coated rigid substrate from the flexible transparent conductively coated top sheet in a touch input device when in its normal, untouched condition. When a user presses on the top sheet, such as with a finger or stylus, the flexible transparent conductive substrate is forced to make contact with the transparent conductively coated rigid substrate creating an electrical circuit for touch detection. When the device is not being touched, it is important that the flexible top sheet and the rigid back substrate do not come into contact so as to avoid creating a false touch. It is also desired that the spacer dots or elements be of minimal visibility for optimal optical performance of the information device.

[0005] The present invention includes an improved process and improved materials for producing uniformly dispersed, consistent, durable, essentially non-visible, fixed substrate-interpane-spacer elements (for example “spacer dots”) for spacing the opposing conductive surfaces of the flexible top sheet and rigid bottom sheet of an interactive information device.

[0006] The invention is most effectively accomplished by the application of the non-conducting spacer dots or elements on the rigid substrate of the interactive information device using appropriately tall dots or elements separating the sheets well apart for optimum electrical performance (non false—touch) while minimizing visibility for optimum optical performance (such as by rendering the dots invisible such as by index matching the dot material to the surrounding interpane medium and/or by having a small dot diameter and/or by having few, well spaced dots). It is preferred that the performance be further improved by the use of spacer dot materials that are optically matched to the transparent conductors, typically indium tin oxide. It is preferred that the registration and/or orientation of the dots on the glass be matched to the particular touch screen design. It is preferred that the placement of the dots on the glass allow for manufacturability of more than one touch device per coated stock sheet, known as “stock sheet” or “stock lite” form substrates. It is also preferred that the spacer dots be durable to withstand post-processing requirements such as washing, cutting, baking, and the like, for the manufacturing of the touch devices.

[0007] FIG. 1 is a sectional, side elevation of an interactive information device incorporating the improved spacer elements of the present invention;

[0008] FIG. 1A is a sectional, side elevation of a second embodiment of the interactive information device of the present invention;

[0009] FIG. 1B is a sectional, side elevation of a third embodiment of the interactive information device of the present invention;

[0010] FIG. 2 is a flow diagram of a preferred method for making the interactive information device of FIG. 1 incorporating the present invention; and

[0011] FIG. 3 is a photograph of exemplary spacer elements in accordance with the present invention.

[0012] More specifically, and as shown in FIG. 1, this invention relates to the improved process and materials resulting in an interactive information device such as a resistive touch device 60 comprising rigid substrate 10 such as soda lime glass with a transparent conductive thin film 20. The spacer dots or elements 30 are deposited most preferably by silk screen methods on thin film 20. The flexible substrate 40 with transparent conductive thin film 50 provides the top sheet of the resistive touch device 60. Optionally, the transparent substrate 10 of the present invention may be an optical plastic comprising a conductively coated cyclic olefin copolymer plastic substrate as disclosed in U.S. patent application Ser. No. 09/946,228, filed Sep. 5, 2001, entitled IMPROVED PLASTIC SUBSTRATE FOR INFORMATION DEVICES AND METHOD FOR MAKING SAME, the disclosure of which is hereby incorporated by reference herein in its entirety. Such rigid plastic substrate may be formed from a cyclic olefin copolymer (COC) such as is available from Ticonca of Summit, N.J., under the trade name “Topas.” Cyclic olefin-containing resins provide an improved material for a rigid, transparent conductively coated substrate suitable for use in an information display. The improved information display incorporating the improved plastic substrate is lightweight, durable, flex resistant, dimensionally stable and break resistant as compared to other, more conventional substrates. A rigid plastic substrate can be formed by extrusion, casting or injection molding. When inject on molding is used such as when forming a substrate from a cyclic olefin copolymer (COC), a non-planar curved (spherical or multiradius) part can be formed, optionally with at least one surface roughened (such as by roughening/patterning a surface of the tool cavity used for injection molding) so as to have a light-diffusing, anti-glare property.

[0013] A transparent, plastic substrate such as one formed from cyclic olefin polymer resin can be used to form a rigid panel or back plate for use in a resistive membrane touch device where the cyclic olefin panel functions as a transparent back plate for a flexible, conductive, transparent touch member assembly as is also described in U.S. patent application Ser. No. 09/946,228 filed Sep. 5, 2001, incorporated by reference above.

[0014] The transparent thin film conductors 20 and 50 are typically metal oxides such as indium tin oxide, tin antimony oxide, fluorine doped tin oxide, or tin oxide. The spacer dots 30 preferably consist of organic-inorganic nanocomposites (Nanomeres®) utilizing methyl tetraethylorthosilicate, tetraethylorthosilicate, or glycidoxypropyltrimethoxysilane as network formers hydrolyzed using hydrochloric acid prepared initially in a paste form. Silica sols, silica powders, ethyl cellulose, and hydroxypropyl cellulose may be utilized as additives to adjust viscosity. Cyracure, (Union Carbide, UV 6974) serves as the photoinitiator allowing for the use of ultraviolet light for curing. The resulting improved spacer dots 30 can be enhanced optically by nano-paricle metal oxides and pigments such as titanium dioxide (TiO₂), barium titanium oxide BaTiO), silver (Ag), nickle (Ni), molybdenum (Mo), and platinum (Pt). The resulting index of refraction of the dots 30 for substantial optical matching to the transparent conductor is referably about 1.49 to about 2.0, most preferably about 1.75 to about 1.95 (for light having a wavelength at the sodium D line, i.e., at about 589 nanometers).

[0015] The preferred spacer dots, such as those shown in FIG. 3, are produced by silk screen printing using fine mesh sieves with appropriate hole patterns. The nanoparticles can be used to adjust the refractive index of the dots easily; for example, the nanoparticles can include silicon dioxide for decreasing the index; or zirconium dioxide, titanium dioxide, and tantalum pentoxide for increasing the refractive index. The nanoparticles can be used to adjust the viscosity of the paste. The incorporation of nanoparticles leads to reduced shrinkage during the curing of the spacer dots. The ultraviolet (UV) curable silk screen printing paste is preferably synthesized using a nanocomposite material as described in U.S. Pat. No. 5,910,522 “Composite Adhesive for Optical and Opto-Electronic Applications” by Institut fur Neue Materialien gemeinnutzige GmbH, Saarbrucken Germany, invented by Helmut Schmidt, Saarbrucken-Gudingen et al, dated Jun. 8, 1999, the entire disclosure of which is hereby incorporated by reference herein. The preferred screening paste contains the following:

[0016] a) transparent polymers and/or polymerizable oligomers and/or monomers,

[0017] b) nanoscale inorganic particles,

[0018] c) optionally, compounds for the surface modification of said inorganic particles,

[0019] d) optionally, a crosslinking initiator.

[0020] In some forms of the invention, it may be useful to incorporate a reduced glare, conductive coated panel having increased visible light transmission and suitable for use as a touch screen, digitizer panel or substrate in an information display and incorporating one or more thin film interference layers forming a thin film stack on opposite surfaces of a substrate such as that described herein and a transparent electrically conductive coating on the outer most layer of one or both of the thin film stacks, such as described in U.S. patent application Ser. No. 09/883,654, filed Jun. 18, 2001 entitled ENHANCED LIGHT TRANSMISSION CONDUCTIVE COATED TRANSPARENT SUBSTRATE AND METHOD FOR MAKING SAME, the disclosure of which is hereby incorporated by reference herein.

[0021] The present invention may also include the use of a reduced contrast, increased transmission, conductively coated panel wherein optical in-homogeneity is reduced between the transparent conductively coated regions and the non-coated regions rendering these delineation regions essentially visually indistinguishable when viewed so that there is no substantial contrast apparent when viewed in reflected light as described in U.S. provisional patent application Serial No. 60/239,788, filed Oct. 12, 2000, entitled REDUCED CONTRAST IMPROVED TRANSMISSION CONDUCTIVELY COATED TRANSPARENT SUBSTRATE, the disclosure of which is hereby incorporated by reference in its entirety.

[0022] The preferred process, and as shown in FIG. 2, for the application of the spacer dots 30 starts with the use of conventional glass cleaning techniques for preparation of the transparent conductively coated rigid substrate or lite 10. The substrate is in the form known as stocksheet allowing for the subsequent cutting from and manufacture of multiple touch devices from one lite. Lites can be processed in the flat or bent product configuration. Prior to the deposition of the transparent conductor thin film 20, a pattern of a mask material may be applied to the raw glass using a silk screen coating method, 325-mesh stainless steel screen. This allows removal of the thin film conductor, indium tin oxide for example, in the areas coated with the mask material following the deposition of the conductive film. The conductive thin film 20, indium tin oxide, is then deposited on surface 24 of the lite, over any mask material, preferably by the sputtering physical vapor deposition technique or evaporation physical vapor deposition technique. A thick film conductive electrode pattern, typically a silver frit such as Dupont 7713, is then applied using a silk screen coating method, 325 stainless steel mesh silk screen with glass frit as required based on the touch screen design. The thin film conductor 20 and the thick film conductor are then cured using a conventional baking process, such as 480 degrees C. for 60 minutes. The thin film may be chemically reduced in an inert forming gas curing environment. Following curing of the thick film and thin film conductors, the coated lite is washed using conventional glass washing techniques. This prepares the lite for the application of the spacer dots and removes residual mask material for the deletion of specific areas of the thin film conductor as required by the touch screen design. The transparent conductor may also be deleted in selected areas following curing using photolithography or laser deletion methods.

[0023] The spacer dots 30 are then applied to the transparent conductor 20 on substrate or lite 10 using conventional silk screening techniques using a 400-mesh stainless steel. Alternately, the dots 30a,may be applied to surface 51 of transparent conductor 50 or to both conductors 20 and 50 as described below. The dots are arranged in an orientation based on the design of the touch screen. Optimum design calls for dots 30 to be non-visible minimizing diameter with maximum height for electrical functionality. Spacer dot dimensions for width are about 125 microns to about 15 microns, preferably about 100 microns to about 25 microns, most preferably about 80 microns to about 40 microns in diameter. Spacer dot dimensions for height are about 25 microns to about 3 microns, preferably about 15 microns to about 5 microns, most preferably about 12 microns to about 8 microns. The spacer dots are then cured using ultraviolet light energy level of less than about 1000 mJ/cm2, preferably less than about 500 mJ/cm2, most preferably less than about 400 mJ/cm2 and/or drying at less than about 300 degrees C. for less than about 40 minutes, preferably less than about 200 degrees C. for less than about 20 minutes, most preferably less than about 100 degrees C. for less than about 10 minutes. The coated lites with dots 30 thereon are then washed using conventional glass washing techniques, inspected, and cut to final touch screen dimensions using conventional glass cutting techniques. Dielectric materials and adhesives are applied to the resulting rigid glass coated substrate. The flexible conductive top sheet 40 is then bonded to the conductive glass substrate 10 with the spacer dots 30 separating the top sheet from the coated glass substrate. A flexible electric connector is electrically connected to the complete assembly for attachment to the information device. The device is then inspected and tested electronically. The resulting product is the complete interactive information device 60.

[0024] Alternately, as shown in embodiment 60′ in FIG. 1A, transparent, insulating spacer members or dots 30a,which are substantially similar to spacer dots 30 described above, may be arranged and located on surface 51 of conductive thin film coating 50 in the same manner as described above for dots 30 on surface 22 also to avoid false-touch sensing of the touch screen.

[0025] In yet another embodiment 60″, shown in FIG. 1B, spacer members or dots 30bmay be located and arranged on surface 22 of conductive coating 20 while spacer members 30cmay be arranged and located on surface 51 of conductive thin film coating 50. Spacer members or dots 30band 30care substantially similar to spacer members or dots 30 described above. In embodiment 60″, however, spacer dots 30b,30calternate on opposite sides of the gap on coatings 20, 50 and are spaced at greater a distance from one another on each of the opposing surfaces so as not to be aligned with or engage one another but allow the conductive coatings 20, 50 to engage one another between the spacer dots when flexible film 40 is touched or pressed.

[0026] A preferred synthesis for the spacer dot paste was produced with a mixture of 118.2 g glycidoxypropyltrimethoxysilane, 13.5 g bidistilled water and 4 g hydroxypropyl cellulose refluxed for 24 hours. The mixture was filtered afterwards. In addition, a mixture of 10 g of 30% by weight colloidal silicon dioxide in isopropanol and 2.4 mg 40% by weight tetrahexylammoniumhydroxide in water was produced under stirring. 20 g of glycidoxypropyltrimethoxysilane and 3 g of 30% by weight colloidal silicon dioxide in isopropanol/40% by weight tetrahexylammoniumhydroxide in water mixture were mixed, water and alcohol were removed by distillation (temperature at 60 degrees C., pressure at 200 mbar, removal of 25.4% of the mixture). Afterwards 2 weight percent of the photoinitiator Union Carbide Cyracure UVI 6974 were added.

[0027] While several forms of the invention has been shown and described, other forms will now be apparent to those skilled in the art. Therefore, it will be understood that the embodiments shown in the drawings and described above are merely for illustrative purposes, and are not intended to limit the scope of the invention which is defined by the claims which following including the doctrine of equivalents.