Touch-sensitive screen

Abstract

A touch-sensitive screen, in particular for use in a motor vehicle, is described. The screen comprises a rigid cover layer with a roughened surface, a polarization layer arranged beneath the cover layer, a touch sensor layer arranged beneath the polarization layer, and a display of the touch-sensitive screen.

Claims

1. A touch-sensitive screen comprising: a rigid cover layer with a roughened surface formed thereon; a polarization layer arranged beneath the rigid cover layer and comprising a circular polarizer; a λ/2 layer for a light wavelength in the visible range arranged beneath the polarization layer; a touch sensor arranged beneath the polarization layer; and a display of the touch-sensitive screen.

2. The touch-sensitive screen of claim 1, wherein the rigid cover layer is made of glass.

3. The touch-sensitive screen of claim 1, wherein the touch sensor is at least one of an inductive touch sensor, a resistive touch sensor and a capacitive touch sensor.

4. The touch-sensitive screen of claim 1, wherein the touch sensor is bonded to the polarization layer by means of an adhesive layer.

5. The touch-sensitive screen of claim 1, wherein the touch sensor layer is bonded by optical bonding to the polarization layer located above it.

6. A touch-sensitive screen comprising: a rigid cover layer with a roughened surface formed thereon; a touch sensor arranged beneath the rigid cover layer; a polarization layer arranged beneath the touch sensor; a λ/2 layer for a light wavelength in the visible range arranged beneath the polarization layer; and a display of the touch-sensitive screen.

7. The touch-sensitive screen of claim 6, wherein the rigid cover layer is made of glass.

8. The touch-sensitive screen of claim 6, wherein the touch sensor is at least one of an inductive touch sensor, a resistive touch sensor and a capacitive touch sensor.

9. The touch-sensitive screen of claim 6, wherein the polarization layer comprises a circular polarizer.

10. The touch-sensitive layer of claim 6, wherein the polarization layer is embedded by means of a first and a second adhesive layer between the touch sensor layer and the display.

11. A touch-sensitive screen comprising: a rigid cover layer with a roughened surface; a first polarization layer arranged beneath the rigid cover layer; a touch sensor layer arranged beneath the first polarization layer; a second polarization layer arranged beneath the touch sensor layer; and a display of the touch-sensitive screen arranged beneath the second polarization layer.

12. The touch-sensitive layer of claim 11, wherein the rigid cover layer is made of glass.

13. The touch-sensitive layer of claim 12, wherein the rigid cover layer has the roughened surface directly formed thereon.

14. The touch-sensitive layer of claim 11, wherein at least one of the first polarization layer and the second polarization layer comprises a circular polarizer.

15. The touch-sensitive layer of claim 11, wherein a λ/2 layer for a light wavelength in the visible range is arranged beneath the first polarization layer.

16. The touch-sensitive layer of claim 11, wherein the touch sensor layer is bonded to the first polarization layer by means of a first adhesive layer.

17. The touch-sensitive layer of claim 11, wherein the second polarization layer is embedded by means of a second and a third adhesive layer between the touch sensor layer and the display.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further advantages, details and features of the device described herein will become apparent from the following description of exemplary embodiments and from the figures, in which:

(2) FIG. 1 shows a schematic representation of a first exemplary embodiment of a touch-sensitive screen having an uppermost rigid cover layer and an underlying polarizer, the surface of the rigid cover layer being roughened;

(3) FIG. 2 shows a schematic representation of a second exemplary embodiment of a touch-sensitive screen having two polarizers beneath the rigid cover layer;

(4) FIG. 3A shows a schematic representation of a third exemplary embodiment of a touch-sensitive screen having, above the rigid cover layer, a surface composite with a roughened surface;

(5) FIG. 3B shows a schematic illustration of the fracture behavior of the screen according to FIG. 3A;

(6) FIG. 4A shows a schematic representation of a fourth exemplary embodiment of a touch-sensitive screen having, above the rigid cover layer, a surface composite with a roughened surface; and

(7) FIG. 4B shows a schematic illustration of the fracture behavior of the screen according to FIG. 4A.

DETAILED DESCRIPTION

(8) FIG. 1 shows a schematic view of an exemplary embodiment of a touch-sensitive screen 100, e.g., for use in a motor vehicle. The motor vehicle can be a car, but also a railway vehicle or aircraft.

(9) In the exemplary embodiment shown in FIG. 1, the touch-sensitive screen 100 comprises a rigid cover layer 102 with a roughened surface 101 and a layer thickness of approximately 0.8 or 1.0 millimeter, a polarization layer 104 with a thickness of 375 micrometers arranged beneath the rigid cover layer 102, a touch sensor layer 106 arranged beneath the polarization layer 104, and a display 108 of the touch-sensitive screen 100. The mentioned layers are bonded together by adhesive layers, comprising a first 103, a second 105 and a third adhesive layer 107.

(10) In order to avoid reflections, the surface 101 of the rigid cover layer 102 is roughened. This additionally leads to an improvement in the haptic properties of the surface 101 because, on touching the screen, a finger moves more easily over a roughened surface (and more precise control of the touch function is accordingly possible) than over a high-gloss, that is to say smooth, surface optionally provided with an optical coating, to which a finger often appears to stick when it is moved.

(11) Because the roughening of the surface 101 also affects the transmitted light of the display 108, the chosen roughness is in one variant adapted to the resolution of the display 108 in order to optimize the screen display. An average roughness in the range between S.sub.a=0.17 and 0.25 micrometers, e.g., between 0.188 and 0.192 micrometers, with −0.2<S.sub.sk<0.2 and with 2.8<S.sub.ku<3.2, optionally with an at least approximately Gaussian distribution, has been found to be suitable, but positive results are to be achieved for a broader roughness range of approximately between S.sub.a=0.1 and 2 micrometers with −2<S.sub.sk<2 and/or with 0<S.sub.ku<4.0 as well as for a profile depth S.sub.z between 2 and 30 micrometers.

(12) The average roughness can be adapted to the (e.g., target or maximum) resolution of the screen display according to subjective judgement on the basis of the surface gloss. Thus, a higher resolution is usually accompanied by a lower roughness. A roughness corresponding to a gloss between 20 and 150 gloss units, GU, e.g., around 40 GU, has been found to be suitable. Moreover, in connection with the sparkling characteristics of the surface, a Gaussian distribution of the roughness parameters was found to be advantageous.

(13) In the exemplary embodiment, this roughness is achieved by etching the rigid cover layer 102. In that case the roughness of the surface typically increases, and its GU drops, with an increasing duration of the etching process. Sandblasting and/or molding of the rigid cover layer 102 from a production mold having a roughened surface are, however, also possible production processes. The haptic properties of the rough surface 101 can additionally be improved further by applying an anti-fingerprint coating (not shown).

(14) Because the rigid cover layer 102 is uppermost, the touch-sensitive screen 100 may pose a risk of injury when installed in the motor vehicle if the rigid cover layer 102 consists of conventional glass. The safety of the screen 100 can effectively be increased if plastic (such as, for example, polycarbonate, polyethylene terephthalate or polymethyl methacrylate), laminated glass or chemically toughened glass is used as the material for the rigid cover layer 102. In the case of chemically strengthened glass, for example, a depth of layer, DOL, of approximately 30 micrometers was found compatible with the roughness characteristics as described above without causing unacceptable bending of the surface. The glass was also found to satisfy the requirements of common head impact tests and thus to be crash safe. The fracture properties of the rigid cover layer 102 can at the same time be influenced by the chosen thickness of the rigid cover layer 102.

(15) It has been shown that, by means of the described roughness of the surface layer 101 and by application of an anti-fingerprint coating (e.g. with a layer thickness of approximately 10 nanometers), very good haptic properties can be achieved even when plastic is used as the material for the rigid cover layer 102.

(16) In the exemplary embodiment according to FIG. 1, the polarization layer 104 beneath the rigid cover layer 102 serves to absorb incident light. The use of circular polarizers, comprising a linear polarizer in conjunction with an underlying λ/4 layer for a wavelength in the middle visible light spectrum, already shows very good results. These can be improved further, e.g., in relation to a broadened absorption spectrum, if a λ/2 layer is additionally arranged beneath the λ/4 layer of the polarization layer 104. For example, the usual red or blue sheen of screens when the display 108 is switched off can thereby be reduced in particular.

(17) The touch sensor layer 106, in dependence on the polarization layer 104 used, can be applied to an isotropic plastics film. In the exemplary embodiment according to FIG. 1, the touch sensor layer 106 is firmly embedded by means of a second 105 and third adhesive layer 107 between the polarization layer 104 and the display 108 of the touch-sensitive screen 100. While such bonding of the touch sensor layer 106 both at the top and at the bottom is advantageous for the optical and mechanical properties of the screen 100, it would also be possible in an alternative embodiment to omit the third adhesive layer 107 and replace it with an air gap. This would simplify the production of the touch-sensitive screen 100. In addition, in order to improve the optical properties, each of the adhesive layers 105, 107 used can be produced by optical bonding, that is to say by a bond that minimizes disruptive optical interface phenomena between the layers.

(18) In the exemplary embodiment, the touch sensor layer 106 comprises a capacitive touch sensor. However, alternative embodiments can also provide different types of sensor. In addition, the display 108 is a conventional liquid crystal panel. Here too, however, alternative embodiments can provide different display systems, such as a liquid crystal panel with an OLED backlight unit or an OLED display panel.

(19) A use of the touch-sensitive screen 100 shown in FIG. 1 for installation in a motor vehicle requires high resistance to extreme temperatures and temperature variations as well as to humidity and humidity variations. Requirements made of screens for installation as standard in motor vehicles provide that the optical and mechanical properties of the screen and its components, e.g., the polarizers, do not exhibit noticeable impairment even after at least 500 hours' continuous exposure to an ambient temperature of 60° Celsius at a relative humidity between 92 and 95 percent or after at least 500 hours' continuous exposure to an ambient temperature of 95° Celsius. For an installation of the touch-sensitive screen 100 in a motor vehicle, therefore, the screen components and the processing thereof to form the screen 100 can be so chosen that they satisfy the mentioned requirements. It will be appreciated that alternative or additional requirements can also be made.

(20) On account of the haptic preferences, the touch-sensitive screen 100 shown in FIG. 1 is based on a screen structure with the rigid cover layer 102 uppermost, while the known disadvantages of this structural design of high surface reflectivity are at the same time eliminated by an appropriate roughening of the surface. While risks of injury when this screen 100 is used in a motor vehicle are excluded by a particular choice of material for the rigid cover layer 102, it has at the same time been shown that, as a result of the mentioned structuring of the surface 101, these materials do not strongly affect the haptic perception when the touch function of the screen 100 is used. In fact, in particular by the additional application of an anti-fingerprint coating, considerably easier gliding of the finger over the surface 101 can be achieved than is the case with high-gloss screen surfaces. In addition, it has been shown that the combination of the roughened surface 101 with an underlying circular polarizer (see layer 104), which can additionally be supplemented by an underlying λ/2 layer, leads to a deep-black appearance of the touch-sensitive screen 100 when the display 108 is switched off.

(21) As a result of the described properties of the touch-sensitive screen 100, it is suitable, e.g., as part of an instrument or instrument system in a motor vehicle, such as, for example, an infotainment system or a navigation system. The screen 100 is also suitable as part of a motor vehicle cockpit system (e.g. for displaying the speed and/or engine speed) and/or tablet PC for installation in a motor vehicle. The safety of the screen 100 permits installation in the preferred visual range, directly in front of the seat of a vehicle occupant (e.g. on the back of a driver's seat and/or passenger seat). Further fields of application of the touch-sensitive screen 100 are, however, not excluded.

(22) FIG. 2 shows a schematic view of a second exemplary embodiment of a touch-sensitive screen 200 for use in a motor vehicle. Corresponding to the touch-sensitive screen 100 of FIG. 1, the touch-sensitive screen 200 of FIG. 2 also comprises a rigid cover layer 202 with a roughened surface 201, which is bonded by means of a first adhesive layer 203 to an underlying polarization layer 204, which in turn is bonded by means of a second adhesive layer 205 to a touch sensor layer 206. Unlike the touch-sensitive screen 100 according to FIG. 1, however, the screen 200 of FIG. 2 also comprises beneath the touch sensor layer 206 a second polarization layer 209, which is embedded by means of a third 207 and fourth adhesive layer 210 between the touch sensor layer 206 and the display 208 of the screen 200.

(23) It has been shown that the second polarization layer 209, which can in turn comprise a circular polarizer, further improves the reflection properties as compared with the screen 100 of FIG. 1 to the effect that the screen 200 has a deep-black appearance when the display 208 is switched off. For example, the shimmering colors that are otherwise usual are reduced to such an extent that they are no longer noticeable.

(24) The mode of operation of the described touch-sensitive screens 100, 200 is based inter alia on an interaction between the nature (e.g. roughness) of the surface 101, 201 and the material of the rigid cover layer 102, 202 with absorption properties of underlying polarization layers 104, 204, 209 as well as the combination of the layers with one another. It is clear that, in a departure from the described exemplary embodiments, the described mode of operation can also be achieved by alternative embodiments, e.g., by incorporating further material layers into the screen structure.

(25) FIG. 3A shows a schematic view of a third exemplary embodiment of a touch-sensitive screen 300. The screen 300 is optimized for good haptic and aesthetic properties in combination with low reflection of ambient light, while also fulfilling the durability and safety requirements as posed by the use in for example a motor vehicle.

(26) Similar to the touch-sensitive screen 100 of FIG. 1, the touch-sensitive screen 300 of FIG. 3A comprises a rigid cover layer 302 bonded by means of a first adhesive layer 303 to an underlying polarization layer 304, which in turn is bonded by means of a second adhesive layer 305 to a touch sensor layer 306. Further in correspondence to the previous examples, a third adhesive layer 307 connects the touch sensor layer 306 to a display 308. Unlike the previous examples of the touch-sensitive screens 100, 200, the screen 300 of FIG. 3A further comprises a transparent glass layer 301a with a roughened surface and a surface adhesive layer 301b which connects the glass layer 301a to the rigid cover layer 302. Moreover, the rigid cover layer 302 does not necessarily have a roughened surface.

(27) Although the shown components 303-308 underneath the rigid cover layer 302 resemble those of the screen 100 of FIG. 1, it will be appreciated that the described variation in the upper layers of the screen 300 can be applied also to the screen 200 of FIG. 2.

(28) In connection with the above described touch-sensitive screens 100, 200, it has been said that the rigid cover layer 102, 202 can be made of a variety of materials, such as glass or plastic. For devices used for example in vehicles, use is mostly made of non-splintering plastic instead of glass for the cover layer, in order to fulfil safety requirements. It is further possible to cover the cover glass of the display with a cut-resistant plastic film. In the event of a fracture of the cover glass, for instance by virtue of the impingement of an occupant of the vehicle in the event of an accident, this plastic film serves to reliably hold in check the shards and fragments arising underneath.

(29) Plastic surfaces are sometimes considered to be less visually appealing and inferior in comparison with glass. In addition, plastic surfaces may not be sufficiently scratch-resistant, especially in the case of a touch function of the display. With the use of restraining plastic films by way of covering, a further factor is that such surfaces wear out easily and an optical antireflection coating of the films is costly or, once again, is not compatible with a touch function of the display.

(30) The screen 300 of FIG. 3A combines the advantages of a glass surface while keeping the risk of injuries at a minimum. In addition, the previously described optical advantages of a roughened surface in combination with a polarizer and further elements underneath the cover layer can also be realized for the screen 300. Given sufficiently thin design of the glass layer 301a, said layer exhibits a relatively high flexibility and hence pliability. Hence the risk of damage to the glass layer 301a by the customary operational loading (for instance, for a video screen with touch function) falls. At the same time, in the event of a possible fracture of the glass layer 301a as a result of an impingement a risk of injury by the fragments arising is diminished by reason of the pliability thereof. In addition, given sufficiently low rigidity of the glass layer 301a and, at the same time, sufficiently firm adhesion of the glass layer 301a to the rigid cover layer 302 with the aid of the surface adhesive layer 301b, in the event of a smashing of the glass layer 301a the fracture edges of the glass layer 301a cannot project far from the surface in a manner entailing a risk of injury. Further, on account of the thin design of the glass layer 301a it is not possible for shards of a thickness entailing a risk of injury to erupt from the material thickness of the glass layer 301a.

(31) FIG. 3B shows a schematic representation of the fracture behavior of the screen 300 according to FIG. 3A under the influence of the force represented by the arrow in FIG. 3A. Instead of protruding shards and edges, the smashed glass layer 301a exhibits, very largely, vertical fractures or cracks through the entire layer thickness, the fragments of the glass layer 301a that are formed being effectively held in the surface composite 300 by the surface adhesive layer 301b situated below said glass layer 301a.

(32) In one variation the screen 300 further comprises a flexible backing layer embedded into the surface adhesive layer 301b. Given that the flexible backing layer has tear-resistant and cut-resistant properties, it will serve to better prevent a protrusion of fracture edges in the event of a fracture of the rigid cover layer 302. This happens by virtue of the fact that shards and fracture edges of the smashed rigid cover layer 302 are held in check with the aid of the affixed tear-resistant and cut-resistant backing layer. For the backing layer, a thickness between 50 μm and 500 μm, e.g., between 100 μm and 300 μm, proved appropriate.

(33) For the described fracture behavior of the glass surface the Interaction of low rigidity of the glass layer 301a and high strength of the underlying adhesive bond with the aid of the surface adhesive layer 301b is essential. In order to guarantee sufficient accident safety, the glass layer 301a has been designed to be sufficiently thin. At the same time, the use of the screen 300 with touch function makes demands as regards a mechanical minimal load-bearing capacity of the glass layer 301a.

(34) A layer thickness between 50 μm and 200 μm for the glass layer 301a has proved expedient. Whereas, in addition, the use of borosilicate glass has proved worthwhile, other glasses, e.g., chemically hardened glasses, can also be used for the glass layer 301a. Generally suited are, for example, glass types Schott D263, Schott Xensation, Asahi Dragontrail and Corning Gorilla I/II/III.

(35) The specifications of the surface adhesive layer 301b also result from the properties of the glass layer 301a being used. In this connection, a hardness of the surface adhesive layer 301b between 0 Shore A and 60 Shore A, for example between 15 Shore A and 45 Shore A, and also a thickness of the surface adhesive layer 301b of about 100 μm to 400 μm has been shown to be advantageous. Positive results can, however, be achieved for a thickness of the surface adhesive layer 301b within the range between 5 μm and 500 μm. Suitable as adhesive are adhesives based on acrylic or silicone. Furthermore, the first adhesive layer may take the form of a composite consisting of two or more adhesive laminations.

(36) FIG. 4A shows a schematic view of a fourth exemplary embodiment of a touch-sensitive screen 400 suitable for use in a motor vehicle. The components 402-408 in the lower parts of the screen 400 correspond to the components 302-308 of the screen 300 of FIG. 3A, respectively. Moreover, similar to the screen 300 of FIG. 3A the screen 400 of FIG. 4A comprises a transparent glass layer 401a with a roughened surface and a first surface adhesive layer 401b which connects the glass layer 301a to a surface beneath. What has been said above with respect to these components therefore equally applies to the screen 400 of FIG. 4A. However, the screen 400 differs from the screen 300 as it further comprises a transparent flexible backing layer 401c embedded between the first surface adhesive layer 401a and a second surface adhesive layer 401d underneath the flexible backing layer 401c.

(37) FIG. 4B shows a schematic representation of the fracture behavior of the screen 400 according to FIG. 4A under the influence of the force represented by the arrow in FIG. 4A. Different from the screen 300 of FIG. 3B, in the present case the backing layer 401c further helps to prevent shards of the broken rigid cover glass 402 to penetrate through the surface of the screen 400.