Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G77/00—Macromolecular compounds obtained by reactions forming a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon in the main chain of the macromolecule
  • C08G77/04—Polysiloxanes
  • C08G77/14—Polysiloxanes containing silicon bound to oxygen-containing groups
  • C08G77/18—Polysiloxanes containing silicon bound to oxygen-containing groups to alkoxy or aryloxy groups
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G77/00—Macromolecular compounds obtained by reactions forming a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon in the main chain of the macromolecule
  • C08G77/80—Siloxanes having aromatic substituents, e.g. phenyl side groups
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D183/00—Coating compositions based on macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing silicon, with or without sulfur, nitrogen, oxygen, or carbon only; Coating compositions based on derivatives of such polymers
  • C09D183/04—Polysiloxanes
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D5/00—Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes
  • C09D5/16—Antifouling paints; Underwater paints
  • C09D5/1656—Antifouling paints; Underwater paints characterised by the film-forming substance
  • C09D5/1662—Synthetic film-forming substance
  • C09D5/1675—Polyorganosiloxane-containing compositions
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
  • G02B1/10—Optical coatings produced by application to, or surface treatment of, optical elements
  • G02B1/18—Coatings for keeping optical surfaces clean, e.g. hydrophobic or photo-catalytic films
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
  • G02B27/0006—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 with means to keep optical surfaces clean, e.g. by preventing or removing dirt, stains, contamination, condensation

Definitions

• the present invention relates to a coating composition
• a coating composition comprising an organosilane compound according to formula (I) or (II) as described herein or mixtures thereof, an invisible-fingerprint film comprising said organosilane compound, a method of forming said invisible-fingerprint film and an article comprising said invisible-fingerprint film.
• digital telecommunication devices such as mobile phones, personal computers, navigators, and cash dispensers
• displays and touch panels installed in input/output units.
• These displays and touch panels are usually controlled by finger contact so that fingerprints are deposited on the surfaces of the displays and touch panels.
• Fingerprints consists of an aqueous fraction, i.e., sweat, and an oily fraction, i.e., sebum (B. Stoehr et al., Unusual Nature of Fingerprints and the Implications for Easy-to-Clean Coatings, Langmuir 2016, 32, 2, 619-625).
• the oily components of the sebum e.g.
• a film coating onto the surfaces of the displays and touch panels.
• monofunctional coating layers include anti-glare (AG) coatings, anti-fingerprint (AF) coatings and invisible-fingerprint (IF) coatings.
• AG coating is a technology based on fine irregularities on a display or touch panel surface that reduce specular reflection and may obscure fingerprints to a minor extent.
• AF coating is a method of forming an omniphobic layer on the surface of the display or touch panel, e.g., by spraying or vapor deposition of perfluorinated molecules to provide easy to clean and smooth surfaces with a slippery touch feel.
• IF coating is a method of spreading the fatty fingerprint component during or after fingerprint application to reduce scattered reflection and thereby render fingerprint residues inconspicuous.
• IF coatings are strongly oleophilic coatings that cause oils to be invisible, or nearly invisible, by causing the oils, e.g., from fingerprints, to spread along the screen surface.
• oils having an index of refraction ⁇ 1 .46 (Jaime Wisniak, The Chemistry and Technology of Jojoba Oil, 1987, page 253) comparable to or slightly lower than that of standard screen materials, e.g., glass (1 .46-1 .52)
• light will pass through the flattened sebum layer without significant scattering. Even though the fingerprints are still physically present, one cannot see them without close inspection.
• coatings and coating materials displaying good IF properties need to be hydrophobic enough in order to prevent the deposition of the aqueous component of fingerprint liquid, i.e., sweat.
• fingerprint liquid i.e., sweat
• the overall amount of deposited fingerprint liquid can be minimized to an extend comparable to standard AF coatings, while rendering unavoidable residual fat deposits largely invisible.
• Feasible IF coatings are thus characterized by high water (H 2 0) contact angles and low contact angles of hydrophobic liquids with high surface tension, such as diiodomethane (DIM), a high transparency, a low initial haze before application of the fingerprint as well as low haze with the fingerprint.
• the IF coatings should also have a high abrasion resistance and a low coefficient of friction, which indicates a smooth surface that is pleasant to touch when wiping over the coated surface.
• Organosilanes have been identified as suitable components for providing a good IF coating.
• EP 2474 577 A1 discloses IF coating compositions comprising organosilane compounds with at least one hydrolysable group and at least one hydrophobic group which comprises alkyl groups and optionally ethoxy-based groups. These IF coatings show high H 2 0 contact angles and low DIM contact angles but are not tested with regard to transparency, haze, abrasion resistance and coefficient of friction.
• US 2019/0367773 A1 discloses IF coating compositions comprising alkylsilane compounds, POSS compounds or mixtures thereof, wherein the alkylsilane compounds comprise at least one alkyloxy group and at least one hydrophobic group which comprises alkyl groups. These IF coatings show acceptable H 2 0 contact angles, low DIM contact angles and good abrasion resistance but are not tested with regard to transparency, haze and coefficient of friction.
• JP 2011/006653 A, JP 2010/100819 A and JP 2011/068000 A all relate to copolymerizable compositions suitable for IF coatings which comprise as one copolymer a hydrolysable organosilane and as a second copolymer a hydrolysable organosilane having a tt-electron conjugated structure such as an aryl group which in some embodiments can be bonded to the Si-atom via a short alkyl group of up to 5 carbon atoms.
• the cured and copolymerized films show rather low haze and surface roughness but were not tested in behalf of contact angles and abrasion resistance.
• the present invention relates to a coating composition
• a coating composition comprising an organosilane compound represented by formula (I) or (II)
• R 1 is a hydrolysable group, independently selected from halogen or -OR 4 ; preferably independently selected from -OR 4 ;
• R 4 is independently selected from H or linear or branched alkyl groups having from 1 to 4 carbon atoms;
• R 2 is independently H or a linear or branched alkyl group having from 1 to 4 carbon atoms; n is 0, 1 or 2, preferably 0 or 1 , most preferably 0;
• R 3 is independently H or a linear or branched alkyl group having from 1 to 4 carbon atoms
• Ar is a substituted or non-substituted aryl group having from 5 to 10 carbon atoms, wherein the optional substituent(s) is/are independently selected from linear or branched alkyl groups, linear or branched halogenated alkyl groups, such as linear or branched fluorinated or chlorinated alkyl groups, -OR 5 , -N(R 5 ) 2 , and halogen, such as F or Cl, preferably Ar being a non-substituted aryl group having from 5 to 10 carbon atoms; most preferably Ar being a non-substituted phenyl group;
• R 5 is independently H or a linear or branched alkyl group having from 1 to 4 carbon atoms; and x is 6 to 16, preferably 8 to 14; or mixtures thereof; and an optional solvent.
• the present invention relates to an invisible-fingerprint film originating from a composition comprising an organosilane compound represented by formula (I) or (II)
• RVnR 2 nSi-(CH 2 ) x -Ar R 1 3-n R 2 n Si-(CH 2 ) x -Si(R 3 ) 2 -Ar (II) wherein
• R 1 is a hydrolysable group, independently selected from halogen or -OR 4 ; preferably independently selected from -OR 4 ;
• R 4 is independently selected from H or linear or branched alkyl groups having from 1 to 4 carbon atoms;
• R 2 is independently H or a linear or branched alkyl group having from 1 to 4 carbon atoms; n is 0, 1 or 2, preferably 0 or 1 , most preferably 0;
• R 3 is independently H or a linear or branched alkyl group having from 1 to 4 carbon atoms
• Ar is a substituted or non-substituted aryl group having from 5 to 10 carbon atoms, wherein the optional substituent(s) is/are independently selected from linear or branched alkyl groups, linear or branched halogenated alkyl groups, such as linear or branched fluorinated or chlorinated alkyl groups, -OR 5 , -N(R 5 ) 2 , and halogen, such as F or Cl, preferably Ar being a non-substituted aryl group having from 5 to 10 carbon atoms; most preferably Ar being a non-substituted phenyl group;
• R 5 is independently H or a linear or branched alkyl group having from 1 to 4 carbon atoms; and x is 6 to 16, preferably 8 to 14; or mixtures thereof.
• the present invention relates to a method of forming an invisible-fingerprint film comprising the steps of:
• the present invention relates to an article comprising the invisible-fingerprint film as described above or below on at least one outermost surface thereof.
• Fig 1 shows the abrasion resistance of the coated float glass substrates of the examples by measuring the water contact angle before applying extensive linear abrasion, after 500 cycles of extensive linear abrasion, after 1000 cycles of extensive linear abrasion, after 2000 cycles of extensive linear abrasion and after 3000 cycles of extensive linear abrasion from left to right for the coated substrates 2-CS-F, 1-IS-F, 2-IS-F, 3-IS-F, and 4-IS-F.
• Fig 2 shows the abrasion resistance of the coated Gorilla® glass substrates of the examples by measuring the water contact angle before applying extensive linear abrasion, after 500 cycles of extensive linear abrasion, after 1000 cycles of extensive linear abrasion, after 2000 cycles of extensive linear abrasion and after 3000 cycles of extensive linear abrasion from left to right for the coated substrates 2-CS-G, 1-IS-G, 2-IS-G, 3-IS-G, and 4-IS-G.
• the present invention relates to a coating composition
• a coating composition comprising an organosilane compound represented by formula (I) or (II)
• R 1 is a hydrolysable group, independently selected from halogen or -OR 4 ; preferred halogens are F and Cl, more preferably Cl; it is however preferred that R 1 is independently selected from -OR 4 ;
• R 4 is independently selected from H or linear or branched alkyl groups having from 1 to 4 carbon atoms;
• R 2 is independently H or a linear or branched alkyl group having from 1 to 4 carbon atoms; n is 0, 1 or 2, preferably 0 or 1 , most preferably 0;
• R 3 is independently H or a linear or branched alkyl group having from 1 to 4 carbon atoms
• Ar is a substituted or non-substituted aryl group having from 5 to 10 carbon atoms, wherein the optional substituent(s) is/are independently selected from linear or branched alkyl groups, linear or branched halogenated alkyl groups, such as linear or branched fluorinated or chlorinated alkyl groups, -OR 5 , -N(R 5 ) 2 , and halogen, such as F or Cl, preferably Ar being a non-substituted aryl group having from 5 to 10 carbon atoms; most preferably Ar being a non-substituted phenyl group;
• R 5 is independently H or a linear or branched alkyl group having from 1 to 4 carbon atoms; and x is 6 to 16, preferably 8 to 14; or mixtures thereof; and an optional solvent.
• the coating composition can comprise one organosilane compound represented by formula (I) or (II) or mixtures of two or more organosilane compounds represented by formula (I), mixtures of two or more organosilane compounds represented by formula (II) or mixtures of two or more organosilane compounds represented by formula (I) and (II).
• R 1 is independently selected from -OR 4 ;
• R 4 is independently selected from linear or branched alkyl groups having from 1 to 4 carbon atoms; preferably from methyl, ethyl or isopropyl; more preferably from methyl or ethyl; n is 0;
• R 3 is independently a linear or branched alkyl group having from 1 to 4 carbon atoms; preferably from methyl, ethyl or isopropyl; more preferably from methyl;
• Ar is a non-substituted aryl group having from 5 to 10 carbon atoms; more preferably Ar being a non-substituted phenyl group; and n is 8 to 14, preferably 10 to 12, more preferably 11 or 12.
• organosilane compound represented by formula (I) or (II) is especially preferred.
• R 1 is independently selected from a methoxy group, an ethoxy group, or an isopropyloxy group, preferably a methoxy group or an ethoxy group; n is 0;
• R 3 is independently a C 2 H 5 group or CH 3 group, preferably a CH 3 group;
• Ar is a non-substituted aryl group having from 5 to 10 carbon atoms, preferably a non- substituted phenyl group; and x is 8 to 14, preferably 10 to 12, more preferably 11 or 12.
• R 1 is the same and selected from a methoxy group or an ethoxy group; n is 0;
• R 3 is a CH 3 group
• Ar is a non-substituted phenyl group; and n is 11 or 12.
• organosilane compound represented by formula (I) are phenyldodecyltrimethoxysilane, and phenyldodecyltriethoxysilane, most preferably phenyldodecyltriethoxysilane.
• organosilane compound represented by formula (II) are (trimethoxysilyl)(dimethylphenylsilyl)undecane, (triethoxysilyl)(dimethylphenylsilyl)undecane; (trimethoxysilyl)(dimethylphenylsilyl)dodecane; (triethoxysilyl)(dimethylphenylsilyl)dodecane; (trimethoxysilyl)(dimethylphenylsilyl)octane; (triethoxysilyl)(dimethylphenylsilyl)octane, more preferably (trimethoxysilyl)(dimethylphenylsilyl)undecane,
• the organosilane compound preferably is selected from phenyldodecyltriethoxysilane, (trimethoxysilyl)(dimethylphenylsilyl)undecane or mixtures thereof.
• the organosilane compound is phenyldodecyltriethoxysilane.
• the organosilane compound is (trimethoxysilyl)(dimethylphenylsilyl)undecane.
• the organosilane compound as described herein is preferably present in the coating composition in an amount of from 0.01 wt% to 25.0 wt%, more preferably from 0.02 to 20.0 wt%, still more preferably from 0.05 wt% to 15.0 wt%, even more preferably from 0.07 wt% to 10.0 wt% and most preferably from 0.10 wt% to 5.0 wt%, based on the total amount of the coating composition.
• the coating composition preferably further comprises a solvent.
• Said solvent is preferably selected from a group consisting of methanol, ethanol, isopropanol, butanol, 1 -methoxy-2-propyl-acetate (PGMEA), 1-methoxy-2-propanol (PGME), 2-butanon (MEK), hexadecane, octane, hexane, cyclohexane, cyclopentane, toluene, xylene, benzene, carbontetrachloride, chloroform, methylene chloride, and ethylene glycol or mixtures thereof.
• PMEA 1 -methoxy-2-propyl-acetate
• MEK 2-butanon
• hexadecane octane, hexane, cyclohexane, cyclopentane, toluene, xylene, benzene, carbontetrachloride, chloroform, methylene chloride, and
• Especially preferred solvents are alcohols selected from the group of methanol, ethanol, isopropanol, 1 -methoxy-2-propyl-acetate (PGMEA), 1-methoxy-2-propanol (PGME), 2-butanon (MEK) or mixtures thereof.
• the solvent as described herein is preferably present in the coating composition in an amount of from 75.0 wt% to 99.99 wt%, more preferably from 80.0 to 99.98 wt%, still more preferably from 85.0 wt% to 99.95 wt%, even more preferably from 90.0 wt% to 99.93 wt% and most preferably from 95.0 wt% to 99.90 wt%, based on the total amount of the coating composition.
• the coating composition can further comprise additives such as a lubricant for imparting lubricating properties to a film formed from said coating composition.
• Suitable lubricants not particularly limited.
• Non-limiting examples can be e.g. unsaturated fatty acids, such as myristoleic acid, palmitoleic acid and oleic acid, saturated fatty acids, such as lauric acid, palmitic acid and stearic acid, and hydrocarbon materials, such as hydrocarbon oils, like squalene, triolein and jojoba oil, or mixtures thereof.
• the lubricant can be present in the solvent in an amount of up to 50 wt%, such as from 0.05 wt% to 50 wt%, preferably from 0.1 to 25.0 wt%, based on the total amount of solvent present in the coating composition.
• suitable additives can be include from antioxidants, UV absorbers, light stabilizers and clarifiers.
• the amount of these additives, if present, usually does not exceed 5 wt%, preferably 2 wt% and most preferably 1 wt% of the total amount of the coating composition.
• the present invention relates to an invisible-fingerprint film originating from an organosilane compound represented by formula (I) or (II)
• R 1 is a hydrolysable group, independently selected from halogen or -OR 4 ; preferably independently selected from -OR 4 ;
• R 4 is independently selected from H or linear or branched alkyl groups having from 1 to 4 carbon atoms;
• R 2 is independently H or a linear or branched alkyl group having from 1 to 4 carbon atoms; n is 0, 1 or 2, preferably 0 or 1 , most preferably 0;
• R 3 is independently H or a linear or branched alkyl group having from 1 to 4 carbon atoms
• Ar is a substituted or non-substituted aryl group having from 5 to 10 carbon atoms, wherein the optional substituent(s) is/are independently selected from linear or branched alkyl groups, linear or branched halogenated alkyl groups, such as linear or branched fluorinated or chlorinated alkyl groups, -OR 5 , -N(R 5 ) 2 , and halogen, such as F or Cl, preferably Ar being a non-substituted aryl group having from 5 to 10 carbon atoms; most preferably Ar being a non-substituted phenyl group;
• R 5 is independently H or a linear or branched alkyl group having from 1 to 4 carbon atoms; and x is 6 to 16, preferably 8 to 14; or mixtures thereof.
• organosilane compound is the same in all embodiments as described above or below for the coating composition according to the present invention.
• the term “originating” means that upon film formation the organosilane compound represented by formula (I) or (II) can undergo chemical modifications such as hydolyzation, crosslinking etc so that the invisible-fingerprint film can comprise non-modified organosilane compounds and/or modified organosilane compounds.
• the invisible-fingerprint film originating from a composition comprising an organosilane compound represented by formula (I) or (II) as described above or below shows an improved balance of properties in regard of high water (H 2 0) contact angles, low contact angles of hydrophobic liquids with high surface tension such as diiodomethane (DIM contact angles), a high transparency, a low initial haze (before application of the fingerprint) as well as low haze with the fingerprint, high abrasion resistance and a low coefficient of friction.
• Such a profile of properties qualifies said invisible-fingerprint film as a coating which spreads hydrophobic liquids such as sebum so that e.g. fingerprints are nearly invisible. This can be seen e.g.
• the film further shows good optical properties with high transparency and low initial haze, which qualifies the film as a coating for displays and touch panels. Additionally, the films show a low coefficient of friction both when sliding a metal weight and a paper covered weight across glass coated with the inventive film. Said low coefficient of friction allows a smooth surface and reduces the sticky feeling when sliding a finger over a display or touch panel. Still further, the film shows a high abrasion resistance which can be seen in high water contact angles maintained after up to 3000 cycles of extensive linear abrasion. The high abrasion resistance shows a high durability of the films even under high stress.
• the invisible-fingerprint film according to the present invention preferably has a water contact angle of more than 70°, more preferably at least 80°, still more preferably of at least 85° and most preferably of at least 90° when coated onto Gorilla ⁇ glass or other chemically strengthened glasses.
• the upper limit of the water contact angle of the invisible-fingerprint film when coated on Gorilla® glass or other chemically strengthened glasses is usually not higher than 120°, more preferably not higher than 110°.
• the invisible-fingerprint film according to the present invention preferably has a water contact angle of more than 70°, more preferably at least 80°, still more preferably of at least 85° and most preferably of at least 90° when coated on float glass.
• the upper limit of the water contact angle of the invisible-fingerprint film when coated on float glass is usually not higher than 120°, more preferably not higher than 110°.
• the invisible-fingerprint film according to the present invention preferably has a diiodomethane contact angle of not more than 55°, more preferably not more than 52°, still more preferably not more than 50° and most preferably not more than 48 when coated on Gorilla® glass or other chemically strengthened glasses.
• the lower limit of the diiodomethane contact angle of the invisible-fingerprint film when coated on Gorilla® glass or other chemically strengthened glasses is usually at least 15°, more preferably at least 20°.
• the invisible-fingerprint film according to the present invention preferably has a diiodomethane contact angle of not more than 57°, more preferably not more than 55°, still more preferably not more than 52° and most preferably not more than 50° when coated on float glass.
• the lower limit of the diiodomethane contact angle of the invisible-fingerprint film when coated on float glass is usually at least 15°, more preferably at least 20°.
• a high water contact angle and low diiodomethane contact angle show a pronounced hydrophobicity and a high oleophilicity of the film according to the invention.
• the invisible fingerprint film preferably shows good abrasion resistance:
• the invisible-fingerprint film as described herein preferably has a water contact angle when coated on Gorilla® glass or other chemically strengthened glasses after 500 cycles of extensive linear abrasion of at least 60°, more preferably at least 65° and most preferably at least 70°.
• the upper limit of the water contact angle of the invisible-fingerprint film when coated on Gorilla® glass or other chemically strengthened glasses after 500 cycles of extensive linear abrasion usually is not higher than 105°, preferably not higher than 95°.
• the invisible-fingerprint film preferably has a water contact angle when coated on Gorilla® glass or other chemically strengthened glasses after 3000 cycles of extensive linear abrasion of at least 50°, more preferably at least 55° and most preferably at least 60°.
• the upper limit of the water contact angle when coated on Gorilla® glass or other chemically strengthened glasses after 3000 cycles of extensive linear abrasion usually is not higher than 105°, preferably not higher than 95°.
• the invisible-fingerprint film has a water contact angle on coated float glass after 500 cycles of extensive linear abrasion of at least 55°, more preferably at least 65° and most preferably at least 75°.
• the upper limit of the water contact angle of the invisible-fingerprint film when coated on float glass after 500 cycles of extensive linear abrasion usually is not higher than 105°, preferably not higher than 95°.
• the invisible-fingerprint film preferably has a water contact angle when coated on float glass after 3000 cycles of extensive linear abrasion of at least 50°, more preferably at least 55° and most preferably at least 60°.
• the upper limit of the water contact angle of the invisible- fingerprint film when coated on float glass after 3000 cycles of extensive linear abrasion usually is not higher than 105°, preferably not higher than 95°.
• Extensive linear abrasion in this regard means an abrasion test as described below in the chapter of measurement methods.
• One cycle thereby means one run of the described regime, 500 cycles mean 500 runs of the described regime and 3000 cycles mean 3000 runs of the described regime.
• a high water contact angle after 500 or even 3000 cycles of extensive linear abrasion indicates that after the abrasion regime the hydrophobicity of the film is still high, which indicated that the film is not overtly destroyed and abraded.
• the difference of water contact angle on coated Gorilla® glass or other chemically strengthened glasses being the initial contact angle before staring the abrasion test minus the water contact angle after 3000 cycles of extensive linear abrasion, each on coated Gorilla® glass or other chemically strengthened glasses, is not higher than 45°, more preferably not higher than 35°, most preferably not higher than 30°.
• the difference of water contact angle on coated float glass being the initial contact angle before staring the abrasion test minus the water contact angle after 3000 cycles of extensive linear abrasion, each on coated float glass, is not higher than 45°, more preferably not higher than 30°, most preferably not higher than 20°.
• the invisible-fingerprint film according to the present invention shows good optical properties:
• 0° Gorilla® glass or other chemically strengthened glasses coated with the invisible-fingerprint film has a transparency of at least 90%, more preferably at least 91% and most preferably at least 92%, when measured in air as the surrounding medium.
• the upper limit of the transparency of coated Gorilla® glass or other chemically strengthened glasses is usually 94%, preferably 93.6%.
• an angle of incidence of 0° float glass coated with the invisible-fingerprint film preferably has a transparency of at least 90%, more preferably at least 91 % and most preferably at least 92%, when measured in air as the surrounding medium.
• the upper limit of the transparency of coated float glass is usually 93%, preferably 92.6%.
• the invisible-fingerprint film preferably has a haze of not more than 1.0%, more preferably not more than 0.9% and most preferably not more than 0.8%, when measured on coated Gorilla® glass or other chemically strengthened glasses.
• the lower limit of the haze of coated Gorilla® glass or other chemically strengthened glasses is usually 0.01%, preferably 0.03%.
• the invisible-fingerprint film preferably has a haze of not more than 1 .0%, more preferably not more than 0.9% and most preferably not more than 0.8%, when measured on coated float glass.
• the lower limit of the haze of coated float glass is usually 0.01 %, preferably 0.03%.
• the invisible-fingerprint film After application of a fingerprint, the invisible-fingerprint film preferably has a haze of not more than 8.0%, more preferably not more than 6.0% and most preferably not more than 5.0%, when measured on coated float glass.
• the lower limit of the haze of coated float glass after applying a fingerprint is usually 1.0%, preferably 2.0%.
• the invisible-fingerprint film has a difference in haze on float glass, being the difference of the haze with fingerprint minus the initial haze, of not more than 7.5%, more preferably not more than 6.0% and most preferably not more than 5.0%.
• the invisible-fingerprint film according to the present invention preferably shows a low coefficient of friction measured using a stainless-steel foil or glassine paper covered metal, which indicates a smooth surface of a glass substrate coated with the film of the invention:
• the invisible-fingerprint film preferably has a coefficient of friction (stainless steel foil against coated Gorilla® glass or other chemically strengthened glasses) of not more than 0.30, more preferably not more than 0.27 and most preferably not more than 0.25.
• the lower limit for the coefficient of friction (stainless steel foil against coated Gorilla® glass) is usually 0.05, preferably 0.10.
• the invisible-fingerprint film preferably has a coefficient of friction (glassine paper against coated Gorilla® glass or other chemically strengthened glasses) of not more than 0.40, more preferably not more than 0.35 and most preferably not more than 0.30.
• the lower limit for the coefficient of friction (glassine paper against coated Gorilla® glass or other chemically strengthened glasses) is usually 0.05, preferably 0.10.
• the invisible-fingerprint film preferably has a coefficient of friction (stainless steel foil against coated float glass) of not more than 0.30, more preferably not more than 0.25 and most preferably not more than 0.20.
• the lower limit for the coefficient of friction (stainless steel foil against coated float glass) is usually 0.05, preferably 0.10.
• the invisible-fingerprint film preferably has a coefficient of friction (glassine paper against coated float glass) of not more than 0.40, more preferably not more than 0.30 and most preferably not more than 0.25.
• the lower limit for the coefficient of friction (glassine paper against coated float glass) is usually 0.05, preferably 0.10.
• a further aspect of the present invention is a method of forming an invisible-fingerprint film comprising the steps of:
• the coating composition and the invisible-fingerprint film preferably relate to all embodiments of the coating composition and the invisible-fingerprint film of the present invention as described above or below.
• the substrate preferably is a substrate, which is prone to being contaminated with fingerprints, such as glass, metal, ceramic, plastic, wood, stone and the like.
• the coating composition can be applied to only one surface of the substrate or all surfaces of the substrate or any number of surfaces of the substrate.
• the at least one surface of the substrate can have functional groups such as hydroxyl groups, carboxyl groups, thiol groups sulfonic acid groups or the like. If no functional groups are present on the at least one surface, said at least one surface can be pretreated in order to introduce such functional groups.
• Suitable pretreatment methods are e.g. corona discharge treatment, UV/ozone treatment, oxygen or air plasma treatment, a treatment involving a chemical oxidizing agent, such as potassium permanganate or other comparable treatments as known in the art, e.g. sulfuric or nitric acid treatment, acidic or basic piranha cleaning with hydrogen peroxide, RCA cleaning, or aqua regia treatment.
• the coating composition can be applied onto at least one surface of the substrate by any suitable manner known in the art such as an immersion method, an application method or a vacuum deposition method.
• the substrate is usually immersed into the liquid coating composition e.g. by dip coating, so that at least one surface of the substrate is coated with the liquid coating composition.
• the coating composition is usually dried e.g. by evaporating the solvent and the invisible-fingerprint film is formed.
• the liquid coating composition is usually applied onto at least one surface of the substrate by e.g. spray coating or spin coating as well as other device controlled methods like printing or bar coating. After that, the coating composition is usually dried e.g. by evaporating the solvent and the invisible-fingerprint film is formed.
• the coating composition is usually evaporated and then deposited onto at least one surface of the substrate. After that, the coating composition is usually dried e.g. by evaporating the solvent and the invisible- fingerprint film is formed.
• a coating composition comprising a higher amount of organosilane compound of up to 20.0 wt% or even up to 100 wt% is used, whereas for the other methods coating composition comprising a lower amount of organosilane compound of not more than 5.0 wt% or even not more than 1 .5 wt% is used.
• the drying step in all application methods is usually performed at increased temperatures such as e.g. 80°C to 200°C, preferably 100°C to 175°C most preferably 120°C to 150°C, depending on the components of the coating composition.
• unbound silane molecules may be removed by washing the treated surface with an organic solvent or wiping with a solvent-soaked cloth, or a polishing device.
• Still another aspect of the present invention relates to an article comprising the invisible- fingerprint film as described above or below on at least one outermost surface thereof.
• the coating composition and the invisible-fingerprint film preferably relate to all embodiments of the coating composition and the invisible-fingerprint film of the present invention as described above or below.
• the invisible-fingerprint film is preferably applied onto the at least one surface of the article using the method of forming an invisible-fingerprint film according to the invention in all embodiments as described above or below.
• the article can be any article prone to being contaminated with fingerprints such as articles comprising displays, touch panels and/or smooth and glossy housings, like digital communication devices, such as mobile phones, personal computers, note books, navigators, cash dispensers, security systems or information terminals.
• articles comprising displays, touch panels and/or smooth and glossy housings, like digital communication devices, such as mobile phones, personal computers, note books, navigators, cash dispensers, security systems or information terminals.
• Such displays can be CRT, LCD, PDP LED or FED displays.
• Such housings can be plastic, glass, ceramic or metal housings.
• the at least one surface of the article comprising the invisible-fingerprint film according to the invention can be at least one of a display, touch panel or housing surface.
• Static contact angles were determined via application of droplets (2-5 pL) of deionized water or diiodomethane, subsequent optical characterization via a digital imaging system, and software- assisted analysis using an ellipse fitting function. Both common optical contact angle measurement setups based on syringe dosing and integrated systems using liquid needle dosing were found to give comparable results. The method is described in detail in Ming Jin, Raymond Sanedrin, Daniel Frese, Carsten Scheithauer, -Thomas Willers, Replacing the solid needle by a liquid one when measuring static and advancing contact angles, Colloid Polym Sci (2016) 294:657-665. c) Extensive linear abrasion
• Dynamic coefficients of friction were measured with a procedure adapted from ASTM D1894 using a ForceBoardTM friction measurement setup by INDUSTRIAL DYNAMICS SWEDEN AB. For this, a square shaped weight (64x64 mm 2 ) covered either with polished, stainless steel foil (thickness around 0.1 mm) or glassine paper was pulled over the coated glass plates for 50 mm with a pulling speed of 2.5 mm/s applying a pressure of 1.3 mN/mm 2 .
• Comparative Composition 1 (CC-1): 1.0 wt% phenyltrimethoxysilane in ethanol
• Comparative Composition 2 (CC-2): 1.0 wt% phenethyltrimethoxysilane in ethanol
• Inventive Composition 1 (IC-1): 1.0 wt%
• Inventive Composition 3 (IC-3): 1.0 wt% phenyldodecyltriethoxysilane in ethanol
• Inventive Composition 4 (IC-4): 0.5 wt%(trimethoxysilyl)(dimethylphenylsilyl)undecane and 0.5 wt% phenyldodecyltriethoxysilane in ethanol b) Forming of invisible-fingerprint films on glass substrates
• the above disclosed coating compositions are acidified with nitric acid (3 mg/ml_) and then directly applied onto float glass and Gorilla® glass substrates by spin coating.
• the coated substrates are dried in an oven at 120 °C for 20 min.
• Comparative substrate 1-CS-F float glass substrate coated with CC-1 Comparative substrate 2-CS-F: float glass substrate coated with CC-2 Inventive substrate 1-IS-F: float glass substrate coated with IC-1 Inventive substrate 2-IS-F: float glass substrate coated with IC-2 Inventive substrate 3-IS-F: float glass substrate coated with IC-3 Inventive substrate 4-IS-F: float glass substrate coated with IC-4
• the haze of the coated float glass substrates was also measured after applying a fingerprint.
• Table 3 the haze measurements before application of the fingerprint (initial haze), after application of a fingerprint (Haze with FP) and the difference of the Haze with FP - initial haze (dHaze) are listed.
• Table 3 Haze measurement before and after application of a fingerprint All films show sufficiently low haze after applying a fingerprint.
• Table 4 Coefficient of friction of the coated glass substrates The results in coefficient of friction of the films on float glass and Gorilla® glass substrates are comparable. The best results are obtained for films comprising the organosilanes with the longest (CH 2 )-spacers (IC-2 and IC-3) and the mixture thereof (IC-4). Finally, the abrasion resistance of the coated glass substrates are determined by measuring the water contact angle before applying extensive linear abrasion, after 500 cycles of extensive linear abrasion, after 1000 cycles of extensive linear abrasion, after 2000 cycles of extensive linear abrasion and after 3000 cycles of extensive linear abrasion.
• the best abrasion resistance clearly shows the films comprising the organosilanes with the longest (CH 2 )-spacers (IC-2, IC-3 and IC-4).

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