Printed appliance component

Abstract

A method for producing an appliance component is provided. The appliance component has an operational front side and back side and has a substrate made of thermally tempered flat glass with a coating. The method includes the steprs of: a) providing a glass substrate made of thermally tempered glass with the dimensions of the appliance component; b) applying a preparation for producing an adhesion promoter layer onto a surface of the glass substrate, wherein the preparation is applied onto the surface of the glass substrate that forms the operational back side of the decorative panel; c) producing the adhesion promoter layer by polymerization of the preparation applied in step b); d) applying a preparation for producing an organic color layer onto the adhesion promoter layer produced in step c) by digital printing; and e) producing the organic color layer by polymerization of the preparation applied in step d).

Claims

1. An appliance component, comprising: a glass substrate having an operational front side that faces a user and an operational back side that faces an inside of the appliance, the glass substrate being made of thermally tempered flat glass; a coating only on the operational back side, wherein the coating comprises at least two coatings, wherein the at least two coatings comprise an intrinsically colored adhesion promoting layer adjacent to the operational back side and an organic color layer applied to the adhesion promoting layer, wherein the organic color layer is a digitally printed layer having a polymer matrix and a colorant; wherein the adhesion promoting layer comprises a polymer matrix with functional groups for bonding to the glass substrate, and wherein the adhesion promoting layer is between the glass substrate and the organic color layer; wherein the adhesion promoting layer has a transmittance of at least 80% for a light wavelength range between 380-780 nm at a layer thickness in a range of between 1-5 m, and wherein the organic color layer is viewable through the adhesion promotor layer and through the glass substrate, from the operational front side of the glass substrate with a mean color coordinate shift E caused by the adhesion promoting layer that is <15 for a color blue, is <5 for a color red, and is <6 for a color green, and wherein: (a) the adhesion promoting layer comprises a copolymer containing the following monomer units: ##STR00004## wherein R1 is an aromatic residue, R2 is an aliphatic residue or an aliphatic acid, R3 is hydrogen or a methyl group, and R4 is an aliphatic or aromatic residue; or (b) the polymer matrix of the adhesion promoter promoting layer is crosslinked by SiOSi bonds and carbon-carbon bonds.

2. The appliance component of claim 1, wherein the glass substrate is selected from a group consisting of a substrate having a thickness of at least 2.5 mm, a substrate having a thickness in a range of 3 to 8 mm, and a substrate having a thickness in a range of 3.5 to 5.5 mm.

3. The appliance component of claim 1, wherein the polymer matrix of the adhesion promoting layer is formed from monomer units of at least one monomer with radically polymerizable groups.

4. The appliance component of claim 1, wherein the polymer matrix of the organic color layer comprises a crosslinked polyacrylic matrix and at least one organic colorant.

5. The appliance component of claim 1, wherein the organic color layer comprises at least one light stabilizer comprising a constituent selected from the group consisting of HALS, piperidine derivatives, and organic aromatic compounds with extended -systems.

6. The appliance component of claim 1, wherein the organic color layer is a single layer having a force required for delamination from the glass substrate of 3.5 to 5 N.

7. The appliance component of claim 1, wherein the organic color layer comprises two layers and that the coating has a force required for delamination from the glass substrate of 5 to 7 N.

8. The appliance component of claim 1, wherein the organic color layer comprises three layers and that the coating has a force required for delamination from the glass substrate of 14 to 16 N.

9. The appliance component of claim 1, wherein the coating further comprises an opaque cover layer arranged on the organic color layer.

10. The appliance component of claim 1, wherein the glass substrate is a soda-lime glass substrate.

11. The appliance component of claim 1, wherein the polymer matrix of the adhesion promoting layer comprises silanes with polymerizable groups, and silsesquioxanes with polymerizable groups.

12. The appliance component of claim 1, wherein the polymer matrix of the adhesion promoting layer comprises pre-hydrolysates of silanes with polymerizable groups as monomer units.

13. The appliance component of claim 1, wherein the polymer matrix of the adhesion promoting layer comprises trialkoxysilanes containing an acrylic or vinyl group.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the following, the invention will be explained in more detail on the basis of examples of embodiment as well as on the basis of FIGS. 1 to 11.

(2) FIG. 1 shows a schematic representation of an embodiment of the production process according to the invention;

(3) FIG. 2 shows a schematic representation of an embodiment of an excerpt from an appliance component according to the invention;

(4) FIG. 3 shows a schematic representation of another embodiment of an appliance component according to the invention, wherein the coloring layer contains two different colorants;

(5) FIG. 4 shows a schematic representation of a comparative example without an adhesion promoter layer;

(6) FIG. 5 shows a schematic representation of an exemplary embodiment of an appliance component according to the invention, the coating of which has an additional cover layer;

(7) FIG. 6 shows a schematic representation of an exemplary embodiment, in which the coating comprises two coloring layers;

(8) FIG. 7 shows a schematic representation of an exemplary embodiment, in which the coating comprises two coloring layers and a cover layer;

(9) FIG. 8 shows a schematic representation of an exemplary embodiment with a laterally structured coating;

(10) FIG. 9 shows a schematic representation of an embodiment of an appliance component according to the invention in top view;

(11) FIG. 10 shows a photograph of a coated appliance component according to the invention in the form of a decorative panel; and

(12) FIG. 11 shows the transmittance of a glass substrate coated with an adhesion promoter layer according to the invention and of an uncoated glass substrate for comparison.

DETAILED DESCRIPTION

(13) In FIG. 1, an embodiment of the method according to the invention is shown schematically. In step a), a thermally tempered flat glass 1 as well as a preparation 2 for producing the adhesion promoter layer are provided. The flat glass 1 serves as a substrate for the coating applied in the following method steps and has a thickness of at least 2.5 mm. According to a first exemplary embodiment, the preparation 2 contains at least the following components in wt. %:

(14) TABLE-US-00005 Acrylic acid isobornyl ester, IBA 46.10% 5-Hexenoic acid 10.40% Benzyl acrylate 17.40% CN131B from Sartomer USA, LLC 11.10% Triphenylphosphine oxide 2.50% 2-Hydroxy-3-phenoxypropyl acrylate 8.10% Glycidyl phenyl ether 0.80% 3,4-bis-2-methoxyethylidene-2,4-hexadione 2.40% Butylhydroxytoluene 0.80% 2,2-Methylenebis (4-methyl-6-tert-butylphenol) 0.40% Total 100.0%

(15) In step b), the preparation 2 is applied onto the surface of one side face of the flat glass 1. The side face of the flat glass 1, which is coated with the preparation 2, forms here the operational back side of the appliance component being produced. Correspondingly, the side face of the flat glass that forms the operational front side of the appliance component remains uncoated.

(16) The viscosity of the preparation 2 can be adjusted via the percentage of reactive diluent as well as the percentage of oligomers with polymerizable groups. Since the preparation 2 of this exemplary embodiment contains a relatively high percentage of reactive diluents of more than 60 wt. %, the preparation 2 has a relatively low viscosity, so that it can be applied in step b) by employing a spraying method. The percentage of oligomers with polymerizable groups, also referred to as pre-polymers amounts to 11 wt. %.

(17) In step c) a hardening by UV light of the layer 20 applied in step b) takes place. The preparation 2 in this case contains a photoinitiator. By irradiation with light having a wavelength of 200-450 nm, preferably 250-380 nm, therefore, a polymerization of the monomers takes place, leading to a crosslinking in the applied layer 20.

(18) In the case of the preparation 2 of the first exemplary embodiment, the percentage of aromatic monomers amounts to 36 wt. %. Additionally, the preparation containing 46 wt. % acrylic acid isobornyl ester contains a high percentage of an aliphatic acrylate with a sterically demanding residue, so that the polymerization shrinkage occurring in step c) is small.

(19) The preparation 2 contains a monomer that has an acid function in addition to a polymerizable group. This acid function is contained in the preparation in a percentage of 10 wt. % This acid functionality of the corresponding monomer forms a covalent compound with free hydroxy groups, so that a good adhesion of the monomer to the glass surface is ensured. Due to the polymerization of the monomers in step c), the incorporation of the corresponding monomers in the polymer of the adhesion promoter layer 3 leads to a good adhesion of the layer 3 to the surface of the glass substrate 1. This is shown schematically in FIG. 11. Thus, the polymer 30 of the adhesion promoter layer 3 is bonded covalently via carboxyl groups 31 to the glass surface 1.

(20) In step d), the application of the preparations 4a, 4b, 4c and 4d is produced by an ink-jet printing method, wherein the preparations 4a to 4d differ by the colorants contained in them. The percentage of colorant in the preparations 4a to 4d lies in the range of 2.5 to 3 wt. %.

(21) In order to produce the desired color hue for the particular print region, in this case, preparations 4a, 4b, 4c and 4d can be applied individually or in different mixing ratios. Since the preparations 4a to 4d differ essentially only with respect to the colorant contained in them; a mixing of the preparations 4a to 4d in the layer 4 is possible, independently of the particular mixing ratio. In this case, the particular mixing ratios at different local regions of the layer 4 are determined by the color hue to be obtained.

(22) In one embodiment, hardening can be produced line by line or row by row at the printhead. Alternatively, hardening can take place after the application of the entire layer.

(23) The preparations 4a to 4d contain the following components:

(24) TABLE-US-00006 Colorant 1 to 5 wt. % 1,6-hexanediol diacrylate 20 to 33 wt. % (Tetrahydro-2-furanyl)methyl 20 to 35 wt. % 2-propenoate Sartomer sr44 15 to 25 wt. % Photoinitiator 8 to 15 wt. % 1-Mesityl-2-methyl-1-propanone 0 to 20 wt. % Dipentyl erythritol hexaacrylate 10 to 25 wt. % Oxygen inhibitor <1 wt. %

(25) Due to the use of 1,6-hexanediol diacrylate as a difunctional reactive diluent, i.e., a reactive diluent with two polymerizable acrylic functionalities, the preparations 4a, 4b, 4c and 4d have low viscosities, so that the preparations 4a, 4b, 4c and 4d can be applied by means of ink-jet printing. At the same time, due to the difunctionality of the reactive diluent as well as by use of a hexafunctional acrylate in the preparations 4a, 4b, 4c and 4d in the polymerization occurring in step e), a high degree of crosslinking is ensured within the coloring layer 5. The coloring layer thus has a high mechanical stability.

(26) In the exemplary embodiment shown in FIG. 1, after the hardening of the coloring layer 5 in steps f) and g), a cover layer 7 is applied. In this case, the cover layer 7 can be a coloring layer with a high percentage of pigment or colorant. Preferably, the cover layer contains a white pigment, for example TiO2. The percentage of pigment of the cover layer 7 in the exemplary embodiment is 15 wt. % in this case, and is thus essentially higher than the percentage of colorant in the coloring layer 5. The preparation 7 has the following composition in this case:

(27) TABLE-US-00007 1,6-hexanediol diacrylate 20 to 30 wt. % (Tetrahydro-2-furanyl)methyl 2-propenoate 15 to 25 wt. % Sartomer sr44 15 to 25 wt. % Diphenyl(2,4,6-trimethylbenzoyl) 7 to 15 wt. % Colorant or pigment 10 to 20 wt. % 1-Mesityl-2-methyl-1-propanone 8 to 13 wt. %

(28) In this case, the preparation 7 can be applied with an ink-jet method or by means of a screen printing. In step g) the hardening of layer 70 to the cover layer 7 is produced by means of UV light.

(29) In a second exemplary embodiment, a preparation 2 with the following composition is provided in step a):

(30) TABLE-US-00008 2-Propanol 5 to 10 wt. % Dipropylene glycol monomethyl ether 75 to 90 wt. % Methanol 1 to 5 wt. % 3-Methacryloxypropyltriethoxysilane 2 to 8 wt. %

(31) In the second exemplary embodiment, the hardening of the adhesion promoter layer 3 in step c) is produced by hydrolysis of the silanes, so that the monomer units of the polymer of the adhesion promoter layer 3 are linked together via SiO bonds. The bonding of the adhesion promoter layer 3 to the surface of the glass substrate also takes place by way of SiO bonds.

(32) FIG. 2 shows a schematic representation of an excerpt of an appliance component in cross section. The adhesion promoter layer 3 in this case is applied onto the side face 12 of the flat glass 1, which forms the operational back side of the appliance component. The side face 13 of the flat glass 1 that forms the operational front side, in contrast, does not have a coating. The coloring layer 5 is arranged on the adhesion promoter layer 3 and comprises an organic polymer matrix 50 and a colorant 6 embedded therein. FIG. 2 shows here an exemplary embodiment with a monochromic coloring layer 5, i.e., the coloring layer 5 only has one colorant 6. The adhesion promoter layer 3 has a layer thickness of 4 to 5 m.

(33) FIG. 3, in contrast, shows an exemplary embodiment in which the coloring layer 5 has two different colorants 60 and 61 in the excerpt shown. The comparative example shown in FIG. 4 is distinguished from the embodiment according to the invention shown in FIG. 3 by the fact that the comparative example does not have an adhesion promoter layer. The coloring layer 5 is thus applied directly onto the glass surface.

(34) In FIG. 5, an embodiment of the invention is shown, in which a cover layer 7 is applied over the coloring layer 5.

(35) FIG. 6 shows an exemplary embodiment comprising two coloring layers 51 and 52. In this case, the second coloring layer was applied after the hardening of the first coloring layer 51. In the exemplary embodiment shown in FIG. 6, the two coloring layers 51 and 52 are distinguished by the colorants 60 and 61 contained in the excerpt shown.

(36) The embodiment shown in FIG. 7 essentially corresponds to the embodiment shown in FIG. 6. In addition, a cover layer 7 is arranged on the second coloring layer 52.

(37) In order to determine the mechanical and chemical resistance of the appliance components according to the invention, the following samples were investigated.

(38) Sample 1: Flat glass substrate with adhesion promoter layer and one coloring layer (see FIG. 3);

(39) Sample 2: Glass substrate with adhesion promoter layer, a coloring layer and a cover layer (see FIG. 5).

(40) Sample 3: Glass substrate with adhesion promoter layer, two coloring layers and a cover layer (see FIG. 7);

(41) Sample 4: Comparative sample comprising a glass substrate and a coloring layer (see FIG. 4).

(42) As the comparative example, sample 4 has no adhesion promoter layer. Here, the glass substrate was pretreated with a plasma method prior to the application of the coloring layer.

(43) The scratch resistance of the coating, the stability of the coating relative to water and moisture, the temperature stability of the coating, as well as the chemical stability of the coating were determined.

(44) To determine the adhesion of the coating, the samples were investigated according to the measurement standard ASTM D 3359. For this purpose, the samples were first left to stand for at least 24 hours after printing. Subsequently, a cross-cut grid test was conducted on the samples. For this purpose, a cross-cut grid made of 6 parallel cuts was introduced on the samples. Subsequently, an adhesive film was applied on the cross-cut grid, then pulled off, and the number of fields of the cross-cut grid in which the coating was detached was determined. The test was carried out 90 times for each sample. Table 1 shows the results of the cross-cut grid test.

(45) TABLE-US-00009 TABLE 1 Results of the cross-cut grid test. Percentage of the Classification according detached coating to ASTM D 3359 Sample 1 0.4% 4B Sample 2 1.9% 4B Sample 3 2% 4B Sample 4 75%

(46) It is clear that for all investigated examples of embodiment of the invention, only a very small percentage of the coating is stripped off, and the coating thus displays a good adhesion to the glass surface. Thus, the detached percentage in the case of all samples is less than 5% in the cross-cut grid test. This is attributed to the adhesion promoter layer. Thus, in the cross-cut grid test of the comparative example (sample 4) without an adhesion promoter layer, a substantially higher percentage of the coating is detached.

(47) The force required for delaminating the coating was determined with the aid of a scratching-tool Elcometer 3092 Sclerometer Hardness Tester with a round test tip made of tungsten carbide with a test tip radius of 1.0 mm (model designation KT003092P003) according to the measurement standard AS 3894.4. Here, 24 hours after the printing of the glass substrate, the tool was guided over a path of 10 mm at a constant speed over the surface of the samples, and the force required for the delamination of the coating was determined. The test was carried out three times for each sample. Table 2 compiles the results of the scratch test.

(48) TABLE-US-00010 TABLE 2 Results of the scratch test Sample Force required for delamination Sample 1 3.5N to 5N Sample 2 5N to 7N Sample 3 14N to 16N Sample 4 <0.5N

(49) The samples according to the invention display here a very high scratch resistance, whereby the scratch resistance increases with increasing number of layers. We proceed from the fact that the cover layer and the coloring layers, in particular, contribute to the high scratch resistance based on their composition.

(50) In order to determine the stability of the coatings against water, the samples were placed in water at a temperature of 20 C. for 24 hours. After a drying time of at least 24 hours, subsequently a cross-cut grid test, a test for determining the scratch resistance, as well as a visual inspection were conducted. Table 3 compiles the results of the tests.

(51) TABLE-US-00011 TABLE 3 Test results after immersion in water Percentage of Force detached required coating (cross- for Sample cut grid test) delamination Visual inspection Sample 1 <1% 4.5 to 6N No optical change Sample 2 <5% 9.5 to 11N No optical change Sample 3 5% to 15% 11.5 to 14N Visible detachments at the edges of the coating Sample 4 >75% <0.5N Film almost completely detached as a layer

(52) It is clear that the coatings according to the invention also display good adhesion and scratch resistance even after immersion in water. The stability decreases in this case, after water immersion, with increasing number of coloring layers.

(53) In addition, the stability of the samples against moisture was tested. In this case, the samples were exposed to an atmosphere with a relative air humidity of at least 95% at a temperature of 49 C. for 120 C. After a drying time of at least 24 hours, a test for determining the scratch resistance, a cross-cut grid test, as well as a visual inspection of the sample were conducted. Table 4 shows the respective test results.

(54) TABLE-US-00012 TABLE 4 Test results after placement in moist environment Percentage of Force detached required coating (cross- for Sample cut grid test) delamination Visual inspection Sample 1 <5% 4.5 to 7N No optical change Sample 2 <22% 9.5 to 11N No optical change Sample 3 <30% 14 to 14.5N Partial regions appear transparent based on a partial detachment of the coating from the glass Sample 4 >75% <0.5N Film almost completely detached as a layer

(55) The temperature stability of the coating was tested by subjecting the samples to 10 temperature cycles, in which the samples were stored each time for one hour at 57 C. and one hour at 23 C. Subsequently, the adhesion and the scratch resistance of the samples were determined and an optical inspection was conducted. Table 5 compiles the results of the tests.

(56) TABLE-US-00013 TABLE 5 Test results after 10 temperature cycles Percentage of Force detached required coating (cross- for Sample cut grid test) delamination Visual inspection Sample 1 <1% 4.5 to 7.5N No optical change Sample 2 8.5% 10.5 to 12.5N No optical change Sample 3 2% 15.5N No optical change Sample 4 >15% <0.5N No optical change

(57) In addition, the samples were subjected to permanently increased temperatures of 57 C., 65 C. and 74 C. for 7 days, and subsequently investigated for cracks in the coating. The results are shown in Table 6.

(58) TABLE-US-00014 TABLE 6 Temperature stability Stored Stored Stored Sample at 57 C. at 65 C. at 74 C. Sample 1 No cracks No cracks Crack formation on the entire surface of the coating Sample 2 No cracks No cracks No cracks Sample 3 No cracks No cracks Cracks in the edge regions of the coating Sample 4 No cracks No cracks No cracks

(59) All examples of embodiment display a high temperature resistance. Cracks thus first occur at temperatures above 65 C. In this case, the crack formation may be attributed to different thermal expansion coefficients of the adhesion promoter layer and the coloring layers.

(60) In order to determine the chemical resistance of the samples, the chemicals or substances listed in Table 7 were applied onto the surface of the coating, the samples were then stored at room temperature for six cycles for up to 7 hours, and subsequently the optical change of the samples was evaluated. Here, the evaluation of the visual changes of the samples was conducted according to the following grading: 0no optical changes, such as visually recognizable shadows or spots 1slight optical changes that can be recognized depending on the angle of observation 2optical changes also recognizable under various angles of observation 3clear changes that can be recognized independently from the particular angle of observation

(61) In this case, the chemical stability of one sample 1 with different colorants in the coloring layer was tested. Table 7 compiles the results of the test with different print colors.

(62) TABLE-US-00015 TABLE 7 Chemical stability Clear Substance Cyan Magenta Yellow Black White (no color) Average Lemon 0 0 0 0 0 0 0 Vinegar 2 1 1 2 1 0 1 Window 0 0 1 0 0 0 0 cleaner Ketchup 0 0 0 0 1 0 0 Mustard 0 1 0 0 0 0 0 Scouring 1 1 0 2 1 0 1 agent Household 1 1 1 1 1 0 1 cleaner Drain 3 3 3 3 3 3 3 cleaner

(63) As can be recognized from Table 7, the coloring layer has a high chemical stability against a plurality of substances. Slight optical changes occur in the case of vinegar scouring agent, as well as for household cleaner. Here, the extent of optical visibility of the changes is mainly influenced by the particular print colors. Thus, in a clear layer without colorant, the changes are less striking. In all cases, drain cleaner leads to strong optical changes.

(64) FIG. 8 shows a schematic representation of an embodiment, in which the coating is applied laterally structured onto the side face of the glass substrate 1, i.e., partial regions 1a of the glass surface of the operational back side have neither an adhesion promoter layer 3 nor a coloring layer 5.

(65) FIG. 9 shows a view of an appliance component that has the uncoated partial regions 9. These partial regions 9 can be formed, for example, as windows for indications or displays. The coating 8 can additionally also comprise regions 80 with decorative logos, illustrations, and/or symbols such as letters or numbers.

(66) FIG. 10 shows a photograph of an appliance component according to the invention.

(67) FIG. 11 shows the representation of the transmittance curves of a glass substrate 30 coated with an adhesion promoter layer according to the invention, as well as of an uncoated glass substrate 10 as a reference sample. The adhesion promoter layer here has a thickness of 3.8 m. From FIG. 11 it can be seen that the transmittance experiences only a very slight change due to the adhesion promoter layer. Here, particularly for the smaller wavelengths in the VIS range, the adhesion promoter layer leads to a reduction in the transmittance, whereas the transmittance at the higher wavelengths in the VIS range is not influenced or almost not influenced. This transmittance behavior of the adhesion promoter layer at different wavelengths also leads to the fact that the shift of color coordinates E is dependent on the particular wavelength. Table 8 shows the results here of the shift of color coordinates in the case of various print colors.

(68) TABLE-US-00016 TABLE 8 Results of the lab measurement Adhesion promoter layer on glass substrate Glass substrate Color L a b L a b E Blue 27.35 14.77 29.51 26.52 10.12 21.72 9.11 Green 47.9 66.03 20.18 46.61 63.28 18.88 3.3 Red 41.78 48.2 25.73 41.44 48.58 25.72 0.51 Black 38.01 1.15 4.95 33.33 1.96 6.35 4.95 Yellow 81.02 10.997 70.72 81.99 11.28 75.82 5.2 Magenta 43.23 57.47 13.57 43.01 57.12 10.77 2.83 Cyan blue 55.28 38.71 35.97 54 38.54 35.02 1.6

(69) The measurement values listed in Table 8 were determined by lab measurements according to the standard ASTM E-1164 with a spectrophotometer of the kind Konica Minolta cm-700 d. Here, first of all, an adhesion promoter layer according to the invention was applied onto a soda-lime glass, wherein the layer thickness of the adhesion promoter layer amounted to 5 m+/1 m. A coloring layer that had discrete regions with the colors listed in Table 8 was applied onto the adhesion promoter layer. The thus-printed substrate was placed with the coated side onto a white sheet of paper and the color coordinates of the individual colors were determined in the lab system from the uncoated side of the glass substrate. As the reference sample, a glass substrate without an adhesion promoter layer, but with a corresponding coloring layer was provided, and the color coordinates of the individual print colors were determined. The shift of color coordinates E results from the difference between the particular color coordinates of the sample with the adhesion promoter layer and the reference sample. The shift of color coordinates E thus shows the influence of the adhesion promoter layer on the color coordinates of a print color of the coloring layer by the user. It is clear here that the shift of color coordinates through the adhesion promoter layer in the case of blue color hues is clearly greater than in the case of red color hues. In particular, with a view from the glass side, blue color hues appear as yellowish to the user.