Transparent touch panel and electronic apparatus using the same

#The present invention relates to-a transparent touch panel attached on the display surface of a display device such as an LCD (liquid crystal display), a CRT (cathode ray tube), a plasma display, or the like, as well as to an electronic apparatus using the transparent touch panel. The touch panel is used to input control signals into an electronic apparatus by a user pressing a certain specific region of the display surface corresponding to the signal with a pen or a finger.

#A transparent touch panel (hereinafter referred to as a “TTP”) of the prior art is described below with reference to FIG. 7, which shows a sectional view of a conventional TTP. In FIG. 7, a first transparent conductive layer 2, typically made mainly of indium tin oxide (hereinafter referred to as “ITO”), is formed, typically by a sputtering process, on the upper surface of a fixed substrate 1, typically made of glass. Provided on the first ITO layer 2 is a very small dot spacer 3, typically made of an insulating epoxy resin or the like, disposed at regular intervals. The ITO layer 2 is provided at the perimeter edge with an insulating pattern 4 of a certain specific width. Above the first ITO layer 2, a movable substrate formed of a transparent film, etc. having a second transparent conductive layer 5, typically ITO, on the bottom surface, is provided opposing first ITO layer 2, with insulating pattern 4 interposed between the surfaces. The upper surface of movable substrate 6 is covered with a hard coating layer 7 for protecting movable substrate 6 from getting scratched by a pressing pen or finger. Normally, the surface of movable substrate 6 having said hard coating film 7 is used as the operating surface of a TTP. The first ITO layer 2 and the second ITO layer 5 are connected with an outside circuit (not shown) through a circuit pattern 8A formed on a flexible circuit board 8, via a connection section 9, typically made of silver paste.

#Operation for inputting a control signal is conducted by pushing movable substrate 6 from above in a designated position such that first ITO layer 2 and second ITO layer 5 make contact. Regions not intended for contact between layers 2 and 5 are separated by the dot spacers 3 so that no control signal input can be made from such regions. The location of the designated position is identified by the electrical resistance ratio in the first ITO layer 2 and the second ITO layer 5. In particular, the designated position is identified by an outside circuit that detects the voltage ratio when there is contact at the designated position. The resistance is measured by applying a certain specific voltage on first ITO layer 2 and second ITO layer 5 via electrodes 10A and 10B provided at both edges of the respective layers, as shown in FIG. 8.

#FIG. 1 is a sectional view of a TTP in a first exemplary embodiment of the present invention.

#FIG. 2 is a partially cutaway perspective view of the TTP of FIG. 1. FIG. 3 is a sectional view showing another TTP in the first exemplary embodiment.

#FIG. 4 is a sectional view showing a still other TTP in the first exemplary embodiment.

#Exemplary embodiments of the present invention are described hereunder referring to the drawings. Each of the drawings has been shown magnified in the direction of thickness for an easier illustration of the structure.

#First Embodiment

#FIG. 1 shows a cross sectional view of a TTP in a first exemplary embodiment of the present invention. FIG. 2 is a perspective view of a TTP shown partially cut away. In FIG. 1, a first adhesion layer 12 is provided on the upper surface of substrate 11, such as a polycarbonate substrate about 1.0 mm thick. The first adhesion layer 12 is a highly adhesive layer, such as an epoxy modified acrylic resin, for example formed by printing an epoxy acrylate ink and curing it. First adhesion layer 12 has adhesive properties on both the upper and lower surfaces of the adhesive layer so that the adhesion layer adheres well to substrate 11 and other layers adhere well to it. All adhesion layers discussed herein have similar dual-sided adhesive properties. Provided on first adhesion layer 12 is a first antireflection layer 13. First antireflection layer 13 is preferably a five-layered structure, for example, a laminated structure of silica (referred to as “SiO2”) having a refractive index of about 1.41 and titania (referred to as “TiO2”) having a refractive index of about 2.00, provided by repetitive sputtering. On the first antireflection layer 13, a first transparent conductive layer 14, such as ITO, is formed by sputtering. On ITO layer 14, very small dot spacers 15, such as of an insulating epoxy resin, are provided at regular intervals, and an insulating pattern 16 having a certain specific thickness is provided at the outer perimeter.