The present invention relates to a capacitive touchscreen structure, particularly to a durable capacitive touchscreen structure.
Display devices are widely used in various electronic products to function as media between users and information. Among them, LCD (Liquid Crystal Display) is the mainstream display device because of its slimness, low power consumption and low radiation. Common display devices can only present information to users.
Users still need input devices, such as mice or keyboards, to operate electronic products or input instructions into electronic products, such as personal computers or notebooks. Usually, operating input devices is a barrier for beginners to use electronic devices. Thus, touchscreens, which integrate a touch-control module with a display device, have been developed to realize intuitive operation. As touchscreens simultaneously have functions of information presentation and intuitive operation, they can effectively lower the threshold of operation and also promote the efficiency of input operation. Further, the technology of manufacturing touchscreens is growing sophisticatedly, aside from promoting performance and quality of the products, the manufacture cost thereof also can be greatly reduced. Therefore, touchscreens have been widely applied to common consumer electronics, such as mobile communication devices, tablet computers, digital cameras, digital music players, personal digital assistants (PDA), and global positioning systems (GPS).
The current touchscreens can be categorized into the resistive type, the capacitive type, the sonic type, and the optical type. Among them, the resistive type and the capacitive type are more widely used.
The resistive touchscreen is formed of two ITO (Indium Tin Oxide) conductive layers joined vertically. Applying pressure to the touchscreen enables the conduction between the upper and lower electrodes. The controller detects the voltage variation and then works out the touched position to obtain the signal of the input position. For example, a U.S. Pat. No. 4,822,957 has been widely applied to a five-wire resistive touchscreen of Elo Touch Company. The resistive touchscreen is the cheapest and most popular one on the current market. However, mechanically pressing action in operation causes friction between components and shortens the service life of the resistive touchscreen. Besides, the resistive touchscreen is unlikely to perform complicated instructions.
In a common capacitive touchscreen structure, a conductive layer, such as an ITO layer, is formed on a glass substrate, and electrode patterns are formed on the surface thereof, and then a protective film or an insulating layer is coated on the surface. Sometimes, an anti-noise layer can be arranged below the glass substrate to reduce environment interference. In a common capacitive touchscreen, the voltage is supplied from four corners of the screen, and the electrode patterns form an electric field on the surface of the glass substrate. Touching the screen induces current and causes voltage drop in the touched position. According to the ratio of induced current from the touched position to the four corners that is detected by the controller, the controller can work out the touched position. U.S. Pat. No. 4,198,539, No. 4,293,734, No. 4,371,746, and No. 6,781,579, and a U.S. application Ser. No. 11/409,425 respectively disclosed technologies of capacitive touchscreens.
The capacitive touchscreen can be operated more smoothly than the resistive touchscreen. Further, the capacitive touchscreen is exempted from pressing action for instruction input and has a longer service life. However, the electrode patterns, which are arranged around the conductive layer, protrude from the conductive layer, thus a panel has to be used to cover the electrode patterns. However, such a measure impairs the realization of a full-planar capacitive touchscreen. Limited by material and thickness, the protective film or insulating layer sputter-coated on the outmost layer of the conventional capacitive touchscreen is less likely to promote durability. Although the capacitive touchscreen may adopt a thicker protective film, a protective film thicker than 50 μm disables the operation of the capacitive touchscreen.
The primary objective of the present invention is to solve the problems that the conventional capacitive touchscreen can neither achieve durability nor realize a full-planar design. To achieve the abovementioned objective, the present invention proposes a capacitive touchscreen structure, which comprises a surface substrate and a transparent conductive layer in sequence. The surface substrate includes a top surface having a touch area and a bottom surface opposite to the top surface. The transparent conductive layer further comprises at least one electrode pattern arranged on the lateral side of the transparent conductive layer. When an external voltage is applied to the electrode pattern, a surface capacitance is generated on the touch area and variation of the surface capacitance is detected to determine a position where a user touches. A terminal impedance exists between the electrode patterns and has a value of 800-2000Ω.
In one aspect, the surface substrate has a thickness equal to or less than 0.55 mm.
In one aspect, the surface substrate has a dielectric constant of 2.5-4, and the surface substrate is made of a material selected from a group consisting of glass, PMMA (Polymethylmethacrylate), PVC (Polyvinylchloride), Nylon, PC (Polycarbonate), PET (Polyethylene terephthalate), PI (Polyimide), COC (Cyclic Olefin Copolymer), and organic glass.
In one aspect, the transparent conductive layer is sputter-coated on the bottom surface of the surface substrate; alternatively, the transparent conductive layer is an independent film coated on the bottom surface of the surface substrate.
In one aspect, an insulating layer is arranged on one surface of the transparent conductive layer, which is opposite to the surface substrate.
In one aspect, the capacitive touchscreen structure further comprises an optical film arranged on the top surface of the surface substrate and/or on one surface of the transparent conductive layer, which is opposite to the surface substrate.
In one aspect, the capacitive touchscreen structure further comprises an explosion-proof film arranged on the top surface of the surface substrate and/or on one surface of the transparent conductive layer, which is opposite to the surface substrate.
In the present invention, the surface substrate is arranged above the transparent conductive layer and the electrode patterns to replace the protective film or insulating layer, which is sputter-coated on the outer layer of the conventional capacitive touchscreen. Therefore, the capacitive touchscreen structure of the present invention has higher durability. In the present invention, the outer layer is the surface substrate and the electrode patterns are covered by the surface substrate, hence the present invention can realize a full-planar design.
The technical contents of the present invention are described in detail in cooperation with the drawings below.
Refer to
In this embodiment, the transparent conductive layer 12 is sputter-coated on the bottom surface 112 of the surface substrate 11, whereby the transparent conductive layer 12 and the surface substrate 11 are integrated into a single piece of conductive substrate. In this embodiment, the transparent conductive layer 12 is formed in a rectangle shape, and each lateral side thereof has an electrode pattern 13. Two terminals of the electrode pattern 13 have terminal impedance R1. In the present invention, the terminal impedance R1 has a value of 800-2000Ω. The transparent conductive layer 12 has an insulating layer 14 on one surface opposite to the surface substrate 11. The insulating layer 14 is made of a non-polar material or a weak-polar material. The non-polar material (μ=0) is selected from a group consisting of polyethylene, polypropylene, polybutadiene, and polytetrafluoroethylene. The weak-polar material (μ≦0.5) may be polystyrene or natural rubber.
The capacitive touchscreen structure of the present invention may further comprise at least one auxiliary functional film to meet design requirements, such as an optical film or an explosion-proof film. Refer to
Refer to
In the capacitive touchscreen structure of the present invention, the surface substrate is arranged above the transparent conductive layer and the electrode patterns to replace the protective film or insulating layer sputter-coated on the outer layer in the conventional techniques, so as to improve transparency and durability. Further, the present invention can realize a full-planar design because the electrode patterns are covered by the surface substrate.
The present invention possesses utility, novelty and non-obviousness and meets the condition for a patent. Thus, the Inventors file the application. It is appreciated if the patent is approved fast.
The embodiments described above are only to exemplify the present invention but not to limit the scope of the present invention. Any equivalent modification or variation according to the spirit of the present invention is to be also included within the scope of the present invention.