CROSS REFERENCE TO RELATED APPLICATIONS
This is a continuation of PCT application No. PCT/EP2010/006397, entitled “DEVICE HAVING REDUCED FRICTION PROPERTIES”, filed Oct. 20, 2010, which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a device, in particular to a cover panel for a display device or a monitor front panel or a surface for inputs including a substrate and a coating applied onto the substrate, use of such a device, as well as a method to produce such a device.
2. Description of the Related Art
From DE 198 48 591 A1 an optical glass panel has become known which is provided with a fluoro-organic compound. According to DE 198 48 591 A1, through the coating with a fluoro-organic compound, glass panels, in particular wind shields, window panes or headlight lenses of vehicles are provided which distinguish themselves through high scratch resistance, reduced air friction, improved sliding of windshield wipers as well as dirt repellence. DE 198 48 591 A1 is restricted to the field of conventional glass panels. In particular the importance of avoiding fingerprints in the field of display panels is not described.
A special coating system for a substrate has become known from U.S. Pat. No. 6,472,017 B2 which includes a diamond-like carbon layer and one layer of fluoro-alkyl-silane. The diamond-like carbon layer provides durability and/or hydrophobicity. The fluoro-alkyl-silane layer also serves to provide a high contact angle of the coating system. U.S. Pat. No. 6,472,017 B2 also does not describe avoidance of finger prints.
From DE 10 2007 058 927 A1 a substrate comprising a sol-gel-layer and a barrier layer as well as an anti-reflective layer has become known. The anti-reflective layer can be applied in the sol-gel-process. The coating described in DE 10 2007 058 927 A1 finds use as an abrasion resistant laminate material in the field of solar cells. Coefficients of friction, in particular values of the initial friction, are not described in DE 10 2007 058 927 A1.
From DE 39 41 797 A1 a coating system with a high anti-reflective effect for a substrate has become known, whereby the coating is applied with the assistance of chemical vapor deposition (CVD) or reactive sputtering. Further, DE 102 13 036 A1 describes the coating of a synthetic film with a multi-layer interference coating, whereby the multi-layer interference coating can also find use for an anti-reflection system. Neither in DE 30 41 797 A1 nor in DE 102 13 036A1 are coefficients of friction stated for the coating systems.
Coated substrates, according to those described above often have the problem that the surfaces of these coatings are often very rough in spite of high contact angles. This results in that glass panels, which for example find use in the field of displays, are scratched by ball pens or pens which leads to an unsteady character image and in addition affects the surface. Especially in the use of glass panels in display products which include a touch-panel application, namely a surface whereby through touching of certain areas of the surface the program sequence of a technical device can be directly controlled, the top (glass) surface and its properties is important. However, due to the previously cited problems according to the current state of the art the top glass surface was not able to recognize writing with certainty.
Moreover, the glass surfaces according to the current state of the art were susceptible to contamination for example through finger prints. Therefore, according to the current state of the art, cleaning solutions containing professional and commercial glass cleaning agents had to be used to clean the glass surfaces.
What is needed in the art is a device which can be used for example for touch-panel applications which is dirt repellent and scratch resistant. Fingerprints in particular should be avoided as far as possible on the surface, or should be visible as little as possible.
SUMMARY OF THE INVENTION
The present invention provides a device including a substrate, as well as a coating applied onto the substrate, wherein the coating on the surface exhibits a a coefficient of friction (tan α) in the range between approximately 0.01 and 0.12, for example between 0.02 and 0.1, or between 0.03 and 0.09. The coefficient of friction is a coefficient of friction which is determined on a slanted plane which is tilted at an angle α. Angle α at which a weight arranged on the plane will slide determines the coefficient of friction. The coefficient of friction according to the current invention is a coefficient of friction of rest or static friction or a starting coefficient of friction, in contrast to the coefficient of sliding friction or dynamic coefficient of friction.
The inventive coating ensures that the surface appears smooth, or respectively is smoothed, and that the coefficient of friction of the surface of the substrate is reduced.
If a surface is provided with a coating according to the present invention, then it is, for example, possible to move an input device on this surface without “scratching” or undesirable “sticking”, as is typically the case, for example, with a pen having a synthetic tip or a finger on normal glass surfaces. Moreover, the adherence of dirt or fingerprints on the surface is substantially reduced, so that dry cleaning of these contaminants on a surface with reduced adhesion is possible. This is especially advantageous with touch-panel applications.
In addition, the adherence, or respectively sticking of organic substances, for example oils, such as skin oil, is substantially reduced or respectively practically completely prevented on a substrate provided with the inventive coating, so that fingerprints are largely avoided or respectively are far less visible. Since the skin oil adheres less or practically not at all on the coating, cleaning of the substrate with an inventive coating is also easier. In one embodiment of the present invention the contaminations from organic substances or respectively skin oil can even be wiped off dry. This means that, for example on displays or touch screen panels, the obligatory cleaning agents for organic contaminants can be relinquished.
According to an embodiment of the present invention the coating includes an anti-reflective coating. The coating including the anti-reflective coating or respectively the anti-reflection coating has, for example, a coefficient of friction (tan α) or respectively a static coefficient of friction on the surface in the range of between approximately 0.01 and 0.12, for example between 0.02 and 0.1, or between 0.03 and 0.09. As a rule this is achieved by a cover layer applied on the anti-reflective or respectively anti-reflection coating. The thickness of the cover layer which reduces the coefficient of friction is in the range of between 0.1 nanometers (nm) to 10 nm.
The substrate is, for example, a glass panel, such as a soda-lime glass panel or a borosilicate glass panel which is obtained, for example in a draw method, for example up-draw or down-draw method, or in the float technology or from a cast glass or rolled glass. In particular with the latter method, namely the cast or roll method it is feasible that the necessary optical quality of the surface may be obtained through a polishing method which is required, for example, for a display front panel. The substrate may alternatively also be a synthetic substrate.
For application in display glasses, such as touch-panels or touch screens of small formats the substrate is, for example ≦1 mm thick and is an ultra-thin substrate. Exemplary materials are the ultra-thin glasses D263, B270 or Borofloat by SCHOTT AG.
If the devices are used for cover panels for displays, optionally also as touch-panels or touch screens, for larger surfaces, for example surfaces larger than 1 square meter (m2), then substrates having a thickness of between approximately 4 to 6 millimeters (mm) are used, so that a mechanical protective function of the displays is also assumed.
The panels can be single panels as well as laminated panels. A laminated panel for example includes two panels, a first and a second panel, which are laminated for example with a polyvinyl butyral (PVB) film. Of the outward facing surfaces of the laminated panel at least one surface is provided with an inventive, friction reduced surface having a coefficient of friction or respectively a static coefficient of friction (tan α), in the range of between approximately 0.01 and 0.12, for example between 0.02 and 0.1 or between 0.03 and 0.09.
In order to provide not only extreme smoothness of the surface, but also a surface which can be easily cleaned with liquid cleaning agents, the inventive layers have contact angles >approximately 50 degrees, for example >70 degrees. Layers having contact angles >50 degrees, for example >70 degrees allow, in addition to the previously described dry cleaning, simple cleaning of the glass surface from contaminants using liquid cleaning agents such as glass cleaners or water. The reduced adherence mechanism which, for example is distinguished by a low coefficient of friction, is substantially responsible for the good cleanability, in particular dry cleaning of the inventive layers or respectively coatings. The inventive layer or respectively coating however, also has a high contact angle which can even reach more than 100°; however decisive for the dry-cleanability is the low adherence of contaminants, such as organic contaminants on the surface of the coating, and not the high angle of contact.
The primary application for the herein described devices with a substrate and a coating applied thereto, having a low coefficient of friction is in the use of a cover panel providing a mechanical protective function and/or a surface for inputs, for example input devices or so-called displays. The device finds use in areas where technical devices can be operated by touching of parts on the surface of the device, namely in the area of touch-panel applications with interactive input. Since a panel of this type also introduces additional interfaces into the total optical system of the display, a reflectivity of approximately 8% is achieved on the display when using only a conventional float glass panel as substrate material without anti-reflective coating. This reflectivity interferes with the effective contrast of the display since reflections compete with the useful signal of the display. For this reason, it is especially advantageous for this application to incorporate an anti-reflective coating or respectively an anti-reflection coating onto the substrate, namely to use a panel provided with an anti-reflective coating, whose reflectivity RVIS clearly reduces in the visible wavelength range at standard light D65 and is, for example lower than approximately 4%, or <2%. This glass or synthetic panel then includes an anti-reflective coating which is also referred to as anti-reflection coating and which is applied according to one of the following application methods:
a) The anti-reflective coating or respectively the anti-reflection coating is applied with the assistance of liquid technology, whereby the coating applied with the assistance of the liquid technology is provided with the assistance of one of the following techniques:
The anti-reflective coating is applied using the sol-gel technology;
The anti-reflective coating is produced as single-layer interference coating in the sol-gel-technology;
The anti-reflective coating is produced as multi-layer interference coating in the sol-gel technology, wherein the multi-layer interference coating is, for example, a three- to seven-layer interference coating; or
The anti-reflective coating is produced as a three-layer interference coating in the sol-gel technology, whereby the first layer has a refractive index between approximately 1.6 and 1.8, the second layer has a refractive index between approximately 1.9 and 2.5 and the third layer has a refractive index between approximately 1.4 and 1.5.
b) The anti-reflective coating or respectively anti-reflection coating is produced with the assistance of a high-vacuum technology, whereby the coating applied with the assistance of high-vacuum technology is provided in one of the following techniques:
The anti-reflective coating is produced with the assistance of a high-vacuum technology as a multi-layer interference coating system, wherein the multi-layer interference coating is, for example, a three-layer to seven-layer interference coating;
The anti-reflective coating is produced with the assistance of a high-vacuum technology as a single layer system;
The anti-reflective coating is produced in a sputtering process under high vacuum; or
The anti-reflective coating is produced in a high-vacuum coating process by thermal evaporation;
c) The anti-reflective coating or respectively anti-reflection coating is produced with the assistance of a CVD process, whereby the layer applied with the assistance of a CVD process is provided in one of the following techniques:
The anti-reflective coating is produced in an online-CVD process; or
The anti-reflective coating is produced in an offline-CVD process;
d) The anti-reflective coating or respectively anti-reflection coating is produced with the assistance of an etching process, whereby the layer applied with the assistance of an etching process is provided in one of the following techniques:
The anti-reflective coating is produced with the assistance of an etching process as a porous layer; or
The anti-reflective coating is produced with the assistance of an etching process as a light-scattering surface.
If an anti-reflective coating is applied, and the anti-reflective coating is provided with a cover layer which has a static coefficient of friction (tan α) in the range between approximately 0.01 and 0.12, for example between 0.02 and 0.1, or between 0.03 and 0.09, then the anti-reflective coating is optically adapted to the cover layer, for example through addition of precursor materials or polymers, so that an anti-reflective effect is provided. The anti-reflective effect is such that, with one- or two-sided application the reflectivity of the entire system is between approximately 0.1% and 7%, for example between 0.1% and 6%, between 0.1% and 5.5%, between 0.1% and 4%, between 0.1% and 2%, or between 0.1% and 1.5% in the visible wavelength range at standard light D65.
According to one embodiment of the present invention, the substrate with coating is used in one of the following areas or for one of the following products:
a protective cover for displays or respectively display devices;
a cover panel for displays;
a cover panel for touch panels,
a part of the touchscreen with optical scanning; or
within a display system as a touchpad for interactive input of signals, or as cover or protective panel.
In addition to the device, the present invention also provides a method to produce a coating having a coefficient of friction between approximately 0.01 and 0.12, for example between 0.02 and 0.1, or between 0.03 and 0.09 on a substrate which, includes the following steps:
A coating, in particular an anti-reflection coating is applied according to a liquid technology, such as with sol-gel technology, or with high-vacuum technology onto a substrate;
The coated substrate is introduced into a pressure vessel which is evacuated at low vacuum;
The coating applied onto the substrate is processed in a further step, for example smoothed locally in such a way that the coefficient of friction is between approximately 0.01 and 0.12, for example between 0.02 and 0.1, or between 0.03 and 0.09.
According to a second embodiment of the method according to the present invention:
The coated substrate is introduced into a pressure vessel which is set to a vacuum in the range of between approximately 10 Pascals (Pa) to 1050 hectopascals (hPa), for example between 10 hPa to 500 hPa, wherein for example a vacuum in the form of a fine vacuum in the range between 10 Pa and 100 Pa or a low vacuum above 100 Pa is evacuated;
A cover layer is applied onto the coating in such a manner that the coefficient of friction is between approximately 0.01 and 0.12, for example between 0.02 and 0.1, or between 0.03 and 0.09. The coating is hereby for example smoothed, at least locally.
In order to adjust the coefficient of friction the ultra-hydrophobic coating material “Duralon Ultratec” produced by Cotec GmbH., Frankenstraβe 19, D-63791, Karlstein, Germany can for example, in the form of a tablet (14 mm diameter, 5 mm height) be put into a vaporizer which is located in the aforementioned pressure vessel. From this vaporizer the coating material is then evaporated from the filling of the tablet at temperatures of between approximately 100° C. to 400° C. and precipitates onto the surface of the substrate or onto a previously applied coating, for example onto an anti-reflection coating or respectively anti-reflex coating as a cover layer. For distribution of the coating material a device for general coating of objects is used, as disclosed in EP-A-1816232, the disclosure content of which is incorporated into the current application in its entirety. The time- and temperature profiles are set as provided by Cotec GmbH, FrankenstraBe 19, D-63791, Karlstein, Germany for evaporation of the “Duralon Ultratec” material tablet. The substrates (non-coated and/or with anti-reflection coating) reach a slightly elevated temperature during the process which is in the range of between approximately 300K to 370K.