EP2490239A1 - Keyswitches with flexible surfaces - Google Patents

Abstract

The keyswitch (100) has light conducting units (160) i.e. LEDs, a front film (105), and an electrically-conducting contact dome (125) arranged on a switching film (120). The front film has a sandwich-layer with a thermoplastic elastomer layer, polyester layer and a polysiloxane layer. The front film is arranged on a carrier element (110) that has a pressure pin (115) acting on the contact dome for transmitting operating force to the contact dome such that an electrical contact between the contact dome and a contact element (150) is closed when the force acts on the front film.

Description

The present invention relates to a surface scanner, in particular a surface scanner with a flexible surface for use in a telecommunication terminal.

Surface probes are used in modern electronic devices in many ways as controls. Your task is usually to implement a mechanical input of a user in an electrical contact closure or an electrical signal. For this purpose, a variety of designs have been developed such controls over time. A frequently used construction of a surface button which can be used as an operating element consists for example of a user interface formed of a silicone rubber, which is arranged on a carrier. The silicone rubber has sufficient flexibility to ensure a key stroke. The carrier has, in corresponding areas, elements which transmit an operating force acting on the silicone surface to a contact foil. The contact foil has a number of contact domes corresponding to the function keys and is separated from a counter contact foil by means of an insulating foil having recesses which are suitable in the region of the contact dome. By the action of a mechanical force such as an operating force on the silicone surface, a contact dome located under the corresponding portion on the silicon surface is brought into contact with an electrically conductive portion on a counter-foil, whereby an electric circuit can be closed. A disadvantage of such a structure of a probe is that the surface button does not resemble in its materiality the rest of the housing of the electronic device and thus visually stands out clearly from the surrounding housing. However, this is often undesirable.

It is therefore an object of the present invention to provide a surface scanner, which does not visually stand out and in its surface structure homogeneously adapts to the surrounding housing.

This object is achieved by a surface scanner according to claim 1. Preferred embodiments and further developments of the surface button according to the invention will become apparent from the dependent claims and the description below.

Thus, a surface scanner is specified, at least comprising a flexible front foil, a switching foil on which at least one electrically conductive contact dome is provided, and a contact element arranged spaced apart from the electrically conductive spacer foil in the region of the conductive contact dome in that the front foil is formed from a sandwich structure consisting of a thermoplastic elastomer layer, a polyester layer and a polysiloxane layer arranged between these layers and is arranged on a carrier element, wherein the carrier element has a pressure pin acting on the contact dome, over which one on the operating force acting on the front foil can be transferred to the contact dome in such a way that an electrical contact between the contact dome and the contact element can be closed when an operating force acts on the front foil.

Advantageously, it is possible by the inventive design of a surface button to form an electrical switching element, which adapts homogeneously in its surface structure of the surrounding housing. In particular, it is with by the invention Removal of a surface button possible to insert an electrical control element gap-free in a housing surface.

In a preferred embodiment of the invention, the thermoplastic elastomer layer is formed from an olefin-based, urethane-based, copolyester-based, styrene-block-polymer-based or copolyamide-based polymer. It is particularly preferred in this case that the elastomer layer is formed from a thermoplastic polyurethane. As a result, it is advantageously possible to take over textures and / or surface structures in a simple manner from mold tools and to transfer them to the stylus surface. The layer thickness of the thermoplastic elastomer layer is preferably in a range between 0.08 mm and 1.0 mm, particularly preferably between ≥ 0.1 mm and 0.35 mm.

In a further embodiment of the invention, the polyester layer is a polycarbonate layer. Polycarbonate provides the front sheet with sufficient stability and sufficient flexibility to allow a key stroke.

In a further embodiment of the invention, the layer thickness of the polyester layer is in a range between 0.05 mm and 1.0 mm, preferably between 0.07 mm and 0.35 mm. In this layer thickness range, the polyester layer imparts very good stability to the front foil sandwich structure without sacrificing the flexibility to allow a sufficient key stroke.

The polysiloxane layer to be provided according to the invention between the thermoplastic elastomer layer and the polyester layer can improve the haptic impression of the surface button and serves as a damping element in the probe structure. The layer thickness of the inventively provided polysiloxane layer is preferably between 0.8 mm and 1 mm, more preferably between ≥ 0.1 mm and 0.7.

In a further embodiment of the invention, the front foil has a survey. This survey can be used to haptically and / or visually perceptible representation of a symbol on the front panel of the surface button. Thus, for example, the activatable by the surface button functions of an electrical or electronic device can be displayed as a raised icon, so that a user readily recognizes the functionality of the surface scanner. An example of such a pictogram is the raised representation of a pictographs symbolizing a picked-up telephone receiver, by which a user immediately recognizes that the area button is used for activating a telecommunication terminal or for accepting calls on such a device. In a preferred embodiment of the invention, the elevation which can be perceived optically and / or haptically is due to a thickening in the layer thickness of the polysiloxane layer. This thickening is then taken over by the overlying thermoplastic elastomer layer, so that an observable on the front foil pictogram arises. In this case, it is provided in particular that the layer thickness of the thermoplastic elastomer layer orthogonal to the polysiloxane layer above the thickening of the polysiloxane layer substantially corresponds to the layer thickness of the thermoplastic elastomer layer orthogonal to the polysiloxane layer in the remaining regions of the front foil.

In a further preferred embodiment of the invention, the survey in the front film on a height-to-width ratio of 1: 1. In this way, in particular cracking in the thermoplastic elastomer layer can be avoided.

In a further embodiment of the invention, it can be provided that the front foil is printed at least in partial areas and / or metallized. This printing and / or metallization can be used, in particular, to change the external appearance of the front foil, for example to display graphics, numbers and / or letters. In particular, it may be provided according to the invention that the front film is partially or metallized over the entire surface to give the surface button a decorative metallic appearance.

In a further preferred embodiment of the invention, the front film is formed from a composite film structure of a thermoplastic polyurethane film, a polycarbonate film and a silicone film arranged therebetween. The shaping of the film structure, for example by means of hot-forming presses, in a suitable form permits a cost-effective and precise production of the front film in a simple manner.

In a further embodiment of the invention, the carrier element consists essentially of a polycarbonate and / or ABS copolymer. In this way, a sufficiently stable substructure of the surface scanner can be achieved with a low construction height.

In a further embodiment of the invention, the carrier element and the pressure pin are integrally formed. As a result, the carrier element can be produced inexpensively by conventional injection molding in an advantageous manner.

In a further preferred embodiment of the invention, the pressure pin is arranged by means of a web, flip-hinge and / or a tongue flexibly within the support element. As a result, a sufficient mobility of the pressure pin is achieved in the direction of the acting operating force, at the same time a sufficient restoring force is ensured to avoid an unwanted contact closure between the switching film and the contact element.

In a further embodiment of the invention, it can be provided that the surface scanner has light-guiding elements, by means of which of corresponding components, such as LEDs, emitted on the user interface of the membrane switch by a user perceptible is. This can serve, for example, for signaling an operating state of the electrical or electronic device in which the surface button according to the invention is installed. For this purpose, it can be provided, in particular, that the front film has translucent areas, through which light guided via the light-guiding elements can exit.

With this in mind, the present invention also relates to the use of a composite film structure consisting of a thermoplastic polyurethane film, a polycarbonate film, and a silicone film interposed therebetween as a front sheet in an electrical switching element.

Fig. 1

zeigt den schematischen Aufbau einer Ausgestaltung eines erfindungsgemäßen Flächentasters;

Fig. 2

zeigt den schematischen Aufbau einer in einem erfindungsgemäßen Flächentaster einsetzbaren Frontfolie.

The invention will be further explained with reference to figures.

Fig. 1

shows the schematic structure of an embodiment of a surface button according to the invention;

Fig. 2

shows the schematic structure of an insertable in a surface scanner front panel according to the invention.

Fig. 1 shows the schematic structure of an embodiment of a surface button 100 according to the invention. The surface scanner has a flexible front foil 105, which is arranged on a support member 110 and connected via an adhesive layer 170 with this. The support member 110 is formed as an injection molded part of a suitable plastic material, such as polycarbonate. The carrier element 110 has a pressure pin 115 which allows an operating force acting on the front foil 105 to act on a contact dome 125 of a switching foil 120. The switching foil 120 is connected to the carrier element 110 via an adhesive layer 180. The operating force acting on the contact dome 125 of the switching foil 120 via the pressure pin 115 presses the contact dome 125 in the direction of a contact element 150 arranged spaced apart from the switching foil 120 by an insulating spacer foil 140. This produces an electrically conductive connection between the switching foil 120 and the contact element 150 realized. With appropriate electrical contacting of the switching film 120 and the contact element 150, we thus achieved the functionality of a button. The illustrated embodiment of a surface scanner according to the invention also has light-guiding elements 160, by means of which light emitted by a corresponding component, such as, for example, an LED, can be perceptible to the user. For this purpose, the front foil 105 has a translucent region 165, through which the light of a light source brought in via the light-guiding elements 160 to the front foil can be perceived.

Fig. 2 1 shows the schematic structure of a front foil 105 which can be used in a surface feeler according to the invention. The front foil 105 has a sandwich structure formed from a thermoplastic elastomer layer 200, a polyester layer 220 and a polysiloxane layer 210 arranged between these layers. The thermoplastic elastomer layer 200 is preferably formed from a thermoplastic polyurethane film. The polyester layer 220 is preferably formed on a polycarbonate film. The front foil 105 may have elevations 300, which may serve for the haptic and / or visual perception of symbols on the surface of the front foil 105. The elevation 300 is preferably formed in the polysiloxane layer 210 by a thickening 310 of this layer at the appropriate location, while the overlying thermoplastic elastomer layer in the orthogonal direction to the polysiloxane layer has a substantially uniform thickness. The ratio of the width of the elevation 300 to its height is preferably 1: 1. The layer thickness of the thermoplastic elastomer layer is preferably between ≥ 0.1 mm and 0.35 mm, while the layer thickness of the polysiloxane layer is between ≥ 0.1 mm and 0.7 mm and the layer thickness of the polyester layer between 0.07 mm and 0.35 mm lies.

Claims (13)

Surface probe (100), at least comprising a flexible front foil (105), a switching foil (120) on which at least one electrically conductive contact dome (125) is provided, and a recess (130) in the region of the conductive contact dome (125) comprising electrically insulating spacer film (140) to the switching film (120) spaced contact element (150), characterized in that the front film (105) of a sandwich structure consisting of a thermoplastic elastomer layer (200), a polyester layer (220) and a between these layers arranged polysiloxane layer (210), is formed and arranged on a carrier element (110), wherein the carrier element (110) on the contact dome (125) acting pressure pin (115) via which a on the front foil (105) acting operating force in such a way on the contact dome (125) is transferable, which upon exposure to an operating force on the front sheet (105) an electric Her contact between the contact dome (125) and the contact element (150) is closable. A surface probe according to claim 1, wherein the thermoplastic elastomer layer (200) is formed of an olefin-based, urethane-based, copolyester-based, styrenic block polymer-based or copolyamide-based polymer. Surface scanner according to one of the preceding claims, wherein the polyester layer (220) is a polycarbonate layer. Surface scanner according to one of the preceding claims, wherein the thermoplastic elastomer layer (200) has a layer thickness between 0.08 mm and 1.0 mm, preferably ≥ 0.1 mm and 0.35 mm. Surface scanner according to one of the preceding claims, wherein the polyester layer (220) has a layer thickness between 0.05 mm and 1.0 mm, preferably between 0.07 mm and 0.35 mm. Surface scanner according to one of the preceding claims, wherein the polysiloxane layer (210) has a layer thickness between 0.8 mm and 1 mm, preferably ≥ 0.1 mm and 0.7 mm. Surface scanner according to one of the preceding claims, wherein the front foil (105) has a protrusion (300), this being formed from a layer thickening (310) of the polysiloxane layer (210). A surface scanner according to claim 7, wherein the bump (300) has a height-to-width ratio of 1: 1. A surface scanner according to any one of the preceding claims, wherein the front sheet (105) is formed of a composite film structure of a thermoplastic polyurethane film, a polycarbonate film and a silicone film interposed therebetween. Surface scanner according to one of the preceding claims, wherein the carrier element (110) consists of a polycarbonate and / or ABS copolymer. Surface probe according to one of the preceding claims, wherein the carrier element (110) and the pressure pin (115) are integrally formed. Surface button according to claim 11, wherein the pressure pin (115) by means of a web, flip-hinge and / or a tongue flexible within the support element (110) is arranged. Use of a composite film structure consisting of a thermoplastic polyurethane film, a polycarbonate film and an interposed silicone film as a front foil in an electrical switching element.

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