UV-curable enamel composition

Abstract

The enamel composition includes a glass frit, a pigment, and an organic carrier medium, the organic carrier medium including a UV curable composition, the UV curable composition including at least one monofunctional acrylate monomer, the at least one monofunctional acrylate monomer having Formula (I): TIFF2024539062000017.tif2265 or formula (II): TIFF2024539062000018.tif2265 (wherein n is 0 or 1.) This includes compounds of the formula:

Description

[Technical field]

[0001] The present specification relates to a UV curable enamel ink composition for screen printing on glass. [Background technology]

[0002] In the automotive glazing industry, it is common to decorate windshields, backlights, sidelights, and other glass components with a black band of hiding enamel that extends around the peripheral area of ​​the component. Its primary function is to protect the adhesive that secures the glass components from ultraviolet light that would break down the adhesive. A secondary function is to provide a clean aesthetic by covering the electrical circuits, wires, and connectors that ensure the functionality of the electrical and electronic components attached to or embedded in the glass components.

[0003] The enamel is applied as a paste or ink to a flat glass substrate by screen printing or inkjet printing, then fired at high temperatures, softening the substrate so that it can be bent into its final shape.

[0004] It is known in the art to provide a curable vehicle for an enamel composition. For example, U.S. Pat. No. 4,649,062 (Kosiorek et al.; Patent Document 1) and U.S. Pat. No. 4,900,763 (Kraushaar; Patent Document 2) disclose an ultraviolet-curable organic vehicle that is introduced into the composition to provide a thick-film ceramic color. In Patent Document 1, the curable vehicle includes: (a) at least one polymerizable liquid oligomer that includes a backbone that includes at least two acrylate or methacrylate functional end groups; (b) at least one photopolymerizable liquid monomer that includes an acrylate or methacrylate functional group, the functionality of the monomer component (b) being in the range of 1 to 6; and (c) a photoinitiator. In US Patent No. 5,399,933, the vehicle comprises: (a) at least two polymerizable liquid oligomers containing acrylate or methacrylate functional end groups and selected from di- or tri-functional polyester acrylates or methacrylates and di- or tri-functional polyurethane acrylates or methacrylates; (b) at least one monofunctional polyether acrylate or methacrylate; (c) at least one pentafunctional aliphatic pentaacrylate or pentamethacrylate; and (d) a photoinitiator.

[0005] In another example, WO 2017 / 009184 (Jain et al.) discloses a curable composition that includes (a) at least one (meth)acrylate monomer or oligomer; and (b) at least one monofunctional (meth)acrylate monomer that includes a polycyclic moiety having at least three rings that are fused or condensed. However, WO 2017 / 009184 is not in the field of enamel compositions or screen printing on glass substrates.

[0006] Canadian Patent No. 2,807,541 (Brown et al.) discloses a heat-curable acrylate-based print medium. As an example, this patent discloses a method for forming a decorative glass structure, which includes applying to a first glass substrate an enamel paste composition that includes (i) a glass component and (ii) a low-VOC heat-curable medium. The heat-curable medium includes a functional acrylate monomer having at least one functionality. However, the medium is not UV-curable.

[0007] A problem with some of the prior art compositions is that under certain application conditions they tend to exhibit a high increase in ink viscosity upon application, which is undesirable. Such conditions include screen printing conditions, whereby the ink is applied to the backside of a printing screen and then a blade is used to push the ink through the holes or openings in the screen (which define the printing pattern). A squeegee or rubber blade is used to contact the screen with the substrate, thereby transferring the ink to the substrate. This process includes several steps that can affect the rheology of the ink, such as, for example, applying a thin layer of ink using a blade and removing excess ink using a vacuum or suction device.

[0008] Another problem with the prior art is that some ink compositions may not exhibit a satisfactory level of hardness or structural integrity after application, e.g., by screen printing. This can be problematic if the enamel ink is subjected to further processing before the firing step, e.g., overprinted with a conductive metal (e.g., silver) layer that may form the busbar and / or wiring connections of a backlight defrost system. For example, a cured enamel ink layer may typically be overprinted with a silver paste that forms a conductive metal ink in a subsequent firing step. Because the silver paste is typically a solvent-based ink formulation, some components of the paste, especially the solvent, may penetrate the UV-cured enamel layer after overprinting and before drying of the silver overprint. Thus, insufficient hardness, structural integrity, and / or degree of chemical resistance (or chemical resistance) of the enamel ink layer may damage the enamel ink layer, and / or substances of the overprint layer, e.g., solvents, may penetrate the enamel layer and cause chemical breakdown in the ink layer, both of which may result in a deterioration of the quality of the enamel layer by adversely affecting its adhesion on a substrate, such as glass.

[0009] It is an object of the present invention to address or alleviate one or more of the problems in the prior art.

[0010] It is an object of the present invention to provide a UV curable enamel ink composition that exhibits minimal or reduced viscosity change in screen printing applications. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] U.S. Pat. No. 4,649,062 [Patent Document 2] U.S. Pat. No. 4,900,763 [Patent Document 3] International Publication No. 2017 / 009184 [Patent Document 4] Canadian Patent No. 2807541 Summary of the Invention

[0012] The inventors have found that some enamel ink compositions are prone to exhibit an increase in viscosity during screen printing. The inventors have found a solution that advantageously provides a UV curable composition as a vehicle for the enamel ink, which exhibits minimal or reduced viscosity change in screen printing applications.

[0013] According to one aspect of the present specification, Glass frit, Pigments, and Organic Carrier Media Including, The organic carrier medium comprises a UV curable composition, the UV curable composition comprises at least one monofunctional acrylate monomer, the at least one monofunctional acrylate monomer having Formula (I): TIFF2024539062000002.tif2265 or formula (II): TIFF2024539062000003.tif2265 (wherein n is 0 or 1.) An enamel composition is provided comprising the compound of formula (I).

[0014] The at least one monofunctional acrylate monomer has formula (Ia): TIFF2024539062000004.tif2954 formula (Ia) The compound may include:

[0015] The compound of formula (Ia) may be generically named as tricyclodecane methanol monoacrylate.

[0016] The at least one monofunctional acrylate monomer has the formula (IIa): TIFF2024539062000005.tif3051 formula (IIa) The compound may include:

[0017] The compound of formula (IIa) may be generally named hexahydro-4,7-methano-1H-indenyl acrylate.

[0018] Advantageously, the enamel composition may have minimal changes in viscosity, for example after about 30 minutes, for example after about 1 hour, for example after about 2 hours. Advantageously, the enamel composition may have minimal changes in viscosity before, during or after application, typically by screen printing. The change in viscosity of the enamel composition may be less than 50%, for example less than 25%, for example less than 10%, for example less than 5%, typically less than 2%. It is understood that the observed change in viscosity may depend on other parameters, such as the thickness of the enamel composition layer applied by screen printing. However, the inventors have found that advantageously, the use of one of the claimed compounds (such as tricyclodecane methanol monoacrylate) as a monofunctional acrylate monomer in the UV-curable composition may help to reduce the change in viscosity during the screen printing process, compared to other compositions, such as compositions using isobornyl acrylate. Without wishing to be bound by theory, it is believed that providing a compound of formula I or formula II (such as tricyclodecane methanol monoacrylate) as a monofunctional acrylate monomer in a UV curable composition can stabilize the viscosity of the UV curable composition by exhibiting a low evaporation rate. For example, tricyclodecane methanol monoacrylate may exhibit a lower evaporation rate than, for example, isobornyl acrylate. Furthermore, it is believed that providing a claimed compound (e.g., tricyclodecane methanol monoacrylate) as a monofunctional acrylate monomer in a UV curable composition can provide the resulting coating with excellent hardness, structural integrity, and / or chemical resistance.

[0019] Thus, according to another aspect of the present disclosure, Glass frit, Pigments, and Organic Carrier Media Including, the organic carrier medium comprises a UV curable composition; An enamel composition is provided, wherein the change in viscosity of the enamel composition after application by screen printing is less than 50%, such as less than 25%, such as less than 10%, such as less than 5%, typically less than 2%.

[0020] The change in viscosity of the enamel composition may be measured after application by screen printing, for example after about 30 minutes, for example after about 1 hour, for example after about 2 hours.

[0021] Preferably, the UV curable composition may comprise at least one monofunctional acrylate monomer, which may comprise a compound of formula (I), (Ia), (II), or (IIa).

[0022] According to another aspect of the present disclosure, depositing an enamel composition as described herein onto a substrate; hardening the enamel composition; and Firing the hardened enamel composition A method for forming an enamel coating is provided, comprising:

[0023] Preferably, the enamel composition is applied by screen printing. Preferably, the curing step may include curing a UV-curable composition of the enamel composition. The method may include curing the enamel composition by exposing the composition to a radiation source, for example by irradiating the composition with UV light.

[0024] Following the curing step, the method may include coating, for example printing, at least a portion of the enamel composition with an outer coating. Typically, the outer coating includes or may be a conductive metal (e.g. silver) layer, for example forming the busbars and / or wiring connections of a backlight defrosting system. Advantageously, the enamel composition of the invention may have good hardness and / or chemical resistance, which makes it particularly suitable for carrying out such overprinting processes. [Brief description of the drawings]

[0025] For a better understanding of the invention, and to show how it may be carried into effect, certain embodiments thereof will now be described, by way of example only, with reference to the accompanying drawings, in which: [Figure 1] 1 is a graph showing the change in viscosity of compositions described herein. [Diagram 2] 1 is a graph showing the viscosity change of alternative compositions. [Diagram 3] 1 is a graph showing the viscosity change of alternative compositions. [Figure 4] 4 shows a graph plotting the viscosity increase of the compositions of FIGS. 1 to 3. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] As discussed above, the present specification provides an enamel composition comprising a glass frit, a pigment, and an organic carrier, which advantageously exhibits good viscosity stability after being applied by screen printing, and further exhibits good adhesion on glass, and high hardness, structural integrity, and / or chemical resistance, as compared to existing enamel compositions.

[0027] Typically, the organic carrier medium comprises a UV curable composition comprising a monofunctional acrylate monomer, the monofunctional acrylate monomer comprising a compound of formula (I) or formula (II), such as tricyclodecane methanol monoacrylate or hexahydro-4,7-methano-1H-indenyl acrylate.

[0028] Without wishing to be bound by theory, it is believed that providing tricyclodecane methanol monoacrylate as a monofunctional acrylate monomer in a UV curable composition can stabilize the viscosity of the UV curable composition by exhibiting a low evaporation rate. For example, tricyclodecane methanol monoacrylate can exhibit a lower evaporation rate than, for example, isobornyl acrylate. Furthermore, it is believed that providing tricyclodecane methanol monoacrylate as a monofunctional acrylate monomer in a UV curable composition can provide the resulting coating with excellent hardness, structural integrity, and / or chemical resistance.

[0029] The organic carrier medium may comprise the UV curable composition. The organic carrier medium, e.g., the UV curable composition, may comprise one or more binders. Typically, the binder may comprise or be a polymer. The binder may comprise an acrylic resin, a cellulosic resin, and the like. The binder may comprise one or more resins selected from the list consisting of cellulose acetate butyrate resin, acrylic resin, and the like. The binder or combination of binders may be selected to provide a composition having a desired viscosity or rheology and / or having a desired level of hardness. The organic carrier medium, e.g., the UV curable composition, may comprise the binder in an amount of about 0.1-20% by weight, e.g., about 1-10% by weight, e.g., about 2-6% by weight.

[0030] The organic carrier medium, e.g., the UV curable composition, may comprise one or more curable polymers. The curable polymer may comprise an unsaturated polymer or oligomer, e.g., an acrylated polymer or oligomer. The curable polymer may comprise an aliphatic polyurethane acrylate. The organic carrier medium, e.g., the UV curable composition, may comprise one or more curable polymers in an amount of about 5-60% by weight, e.g., about 10-50% by weight, e.g., about 20-40% by weight.

[0031] The organic carrier medium, e.g., the UV curable composition, may include one or more acrylic monomers. The one or more acrylic monomers may include at least one monofunctional acrylate monomer. The organic carrier medium, e.g., the UV curable composition, may include one or more acrylic monomers in an amount of about 20-70% by weight, e.g., about 30-60% by weight, e.g., about 40-50% by weight.

[0032] The organic carrier medium, e.g., the UV curable composition, may include one or more difunctional acrylic monomers, e.g., tripropylene glycol diacrylate (TPGDA). The organic carrier medium, e.g., the UV curable composition, may include one or more difunctional acrylic monomers in an amount of about 5-30% by weight, e.g., about 10-20% by weight.

[0033] As mentioned above, preferably, the UV curable composition may comprise a compound of formula (I) or formula (II), such as tricyclodecanemethanol monoacrylate (TCDA) or hexahydro-4,7-methano-1H-indenyl acrylate. The organic carrier medium, such as the UV curable composition, may comprise one or more monofunctional acrylic monomers, such as TCDA, in an amount of about 10-50% by weight, such as about 20-40% by weight.

[0034] The organic carrier medium, such as the UV curable composition, may further include one or more surfactants or dispersing agents (eg, soy lecithin).

[0035] The organic carrier medium, for example the UV curable composition, may further include one or more photoinitiators and / or photosensitizers.

[0036] The organic carrier medium, for example the UV curable composition, may further comprise one or more additives selected from the list consisting of UV stabilizers (eg 4-tert-butylcatechol), adhesion promoters, thickeners, defoamers, and the like.

[0037] The enamel composition, e.g., its organic carrier medium, may further comprise one or more diluents, e.g., solvents. Alternatively, the enamel composition, e.g., its organic carrier medium, may not comprise a diluent, e.g., solvent. A solvent may not be required, for example, if one of the components of the composition, e.g., one or more acrylic monomers, acts as a reactive diluent for the composition.

[0038] For example, the viscosity of the enamel composition before hardening may be in the range of about 5-25 Pa·s, such as about 10-20 Pa·s, such as about 15-18 Pa·s, such as about 16-17 Pa·s. Typically, the viscosity is measured at 21°C using a cone-plate geometry (CP 40 mm, 1°) with a continuous shear rate measurement program (0.10-50 s -1 ) at a shear rate of 10 s -1 The viscosity may be recorded as the paste viscosity at

[0039] The enamel composition according to the invention may be deposited on a substrate, preferably by means of screen printing, and then the composition is cured, for example by exposure to UV light.

[0040] If desired, a portion of the enamel composition may be coated, e.g., printed, with an outer coating, such as, for example, a conductive metal (e.g., silver) layer that may form the busbar and / or wiring connections of a backlight defrost system. Advantageously, the enamel composition of the present invention may have excellent hardness and / or chemical resistance that is particularly suitable for carrying out such overprinting processes. EXAMPLES

[0041] A number of more detailed examples are provided below to illustrate different embodiments of the invention.

[0042] Example 1 Preparation of a composition according to the first embodiment combination One embodiment of a formulation for an enamel ink composition is shown in Table 1. TIFF2024539062000006.tif126158

[0043] Preparation of the Composition Table 2 shows the formula for preparing the compositions of Table 1. TIFF2024539062000007.tif100159

[0044] This formulation is based on the preparation of 100 g of enamel ink composition. The composition is prepared using intermediate components #1 through #7. Some of these components, namely #1, 3, 4, and 5, are provided as intermediate components identified as A, B, C, and D, respectively. The formulations of each of the intermediate components A, B, C, and D are provided below in Tables 2a, 2b, 2c, and 2d.

[0045] TIFF2024539062000008.tif34161

[0046] TIFF2024539062000009.tif86164

[0047] TIFF2024539062000010.tif44164

[0048] TIFF2024539062000011.tif38164

[0049] Ingredients #1-7 were weighed into a plastic container and mixed at high speed to obtain a homogenous solution. Enamel powder (ingredient #8) and Thixatrol Max (ingredient #9) were added and the mixture was mixed at high speed for 20 seconds at 3000 rpm. The paste mixture was homogenized twice on a three-roll mill. The paste was diluted with a medium based on mixtures #1-7 to a viscosity of approximately 15 Pa·s.

[0050] Viscosity Analysis The change in viscosity of the enamel paste over time was evaluated using the following test method.

[0051] The viscosity stability of the paste was evaluated by applying a thin film of the paste (200 μm) onto a glass plate and measuring the viscosity and weight loss of the thin film after exposure to a thermostatic chamber at 30°C and 65% RH for intervals of 0.5, 1.0, 1.5, and 2.0 h.

[0052] Viscosity measurements were performed at 21 °C using a cone-plate geometry (CP 40 mm, 1°) with a continuous shear rate measurement program (0.10–50 s -1 ) at a shear rate of 10 s -1 The viscosity at this point was recorded as the paste viscosity.

[0053] The formulation details of the three different compositions are given below in Table 3. Composition 1 corresponds to the composition in Table 1. Compositions 2-4 are similar UV-curable compositions but based on different acrylate monomers. TIFF2024539062000012.tif204150

[0054] In Composition 1, the organic carrier medium includes three acrylic monomer components: a difunctional acrylic monomer in the form of tripropylene glycol diacrylate (TPGDA), and two monofunctional acrylic monomers in the form of tricyclodecane methanol monoacrylate (TCDA) and a monofunctional urethane acrylate.

[0055] In contrast, Composition 2 contains TPGDA and a monofunctional urethane acrylate as acrylic monomer components, i.e., Composition 2 does not contain tricyclodecane methanol monoacrylate (TCDA).

[0056] In composition 3, the organic carrier medium comprises a mixture of TPGDA, isobornyl acrylate (IBOA) and a monofunctional urethane acrylate, i.e., similar to composition 1, but substituting IBOA for TCDA.

[0057] Composition 4 is similar to composition 3 (both use isobornyl acrylate as the monofunctional acrylic monomer), and the only difference is the photopolymerization initiator used, which does not qualitatively affect the viscosity behavior or hardness.

[0058] The viscosities measured over time for compositions 1, 2 and 3 in Table 3 are shown in Figs. 1 to 3.

[0059] As can be seen from FIG. 1, the viscosity of UV-curable composition 1 using tricyclodecane methanol monoacrylate (TCDA) as the monofunctional acrylic monomer was substantially stable over a period of 2 hours.

[0060] 2, the viscosity of UV-curable Composition 2 was also relatively constant over time. However, because Composition 2 contains TPGDA and a monofunctional urethane acrylate as the acrylic monomer components, the solvent resistance of the resulting coating was found to be of poor quality (see Table 5 below) and therefore not optimal for subsequent overprinting with, for example, a metal bus bar.

[0061] In contrast, the viscosity of UV-curable composition 3, which uses only tripropylene glycol diacrylate (TPGDA) as the acrylic monomer component, showed a significant increase over the same period of time. Without wishing to be bound by theory, this is believed to be due, at least in part, to the relatively faster evaporation rate of isobornyl acrylate compared to tricyclodecane methanol monoacrylate.

[0062] FIG. 4 is a graph plotting the viscosity increase of Compositions 1, 2 and 3, respectively, further illustrating the above observations with respect to FIGS.

[0063] A comparison of the viscosity change over time for Compositions 1 and 4 is shown in Table 4. TIFF2024539062000013.tif41142

[0064] As can be observed from Table 4, the viscosity of UV-curable composition 1, which uses tricyclodecane methanol monoacrylate (TCDA) as the monofunctional acrylic monomer, remained substantially stable over a two-hour period. In contrast, the viscosity of UV-curable composition 4, which uses only tripropylene glycol diacrylate (TPGDA) as the acrylic monomer component, showed a significant increase over the same period.

[0065] This is consistent with the observations made for composition 3, since composition 4 is similar to composition 3 (both use isobornyl acrylate as the monofunctional acrylic monomer) and differs only in the photoinitiator used, which is not expected to affect either the viscosity behavior or hardness.

[0066] Solvent resistance evaluation Films were prepared using the above compositions #1 (containing TCDA as a monofunctional monomer) and #2 (containing no TCDA), which were cured and then exposed to a solvent using butyl diglycol acrylate (BDGA). A qualitative evaluation of the solvent resistance was performed, and the results are shown in Table 5. TIFF2024539062000014.tif151147

[0067] As shown in Table 5, it can be seen that UV-curable composition 1, which uses tricyclodecane methanol monoacrylate (TCDA) as a monofunctional acrylic monomer, has improved solvent resistance to BDGA compared to composition 2, which does not contain TCDA.

[0068] Application of the enamel layer To mimic the viscosity stability of the paste during the screen printing process, a thin film of the paste (wet thickness: 50 microns) was cast onto a glass substrate and exposed to 30°C and 60% RH in a temperature chamber with controlled air circulation. The results shown in Table 4 show that the viscosity change of the paste made according to composition 1 was almost negligible, while the isobornyl acrylate-based UV paste (composition 4) showed a significantly higher viscosity increase.

[0069] The UV curable paste (Composition 1) was screen printed onto a glass sheet using screen mesh sizes (77T, 90T). It is understood that the glass substrate may be any glass suitable for use in the automotive industry, such as clear, green or dark tinted (i.e. privacy glass) float glass. The screen printed film (wet film thickness approximately 20-22 microns) was UV cured using an industrial UV curing machine.

[0070] The cured film was overprinted with silver paste (AG330L-80) in the shape of a busbar (wet film thickness: 25-30 microns) and dried in an industrial IR belt dryer. The cured black enamel with silver overprint was placed in a roller kiln following a suitable firing cycle to strengthen the backlight enamel.

[0071] Although the present invention has been described with reference to specific examples and embodiments, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention as defined by the appended claims.

Claims

1. Glass frit, pigments, and Organic Carrier Medium Including, The organic carrier medium comprises a UV curable composition, the UV curable composition comprises at least one monofunctional acrylate monomer, the at least one monofunctional acrylate monomer having Formula (I): Or formula (II): (In the formula, n is 0 or 1.) 1. An enamel composition comprising a compound of formula (I).

2. The composition of claim 1 , wherein the at least one monofunctional acrylate monomer comprises tricyclodecane methanol monoacrylate or hexahydro-4,7-methano-1H-indenyl acrylate.

3. The composition of claim 1 , wherein the enamel composition exhibits a viscosity change of less than 25% after 2 hours.

4. 4. The composition of claim 3, wherein the change in viscosity is less than 2%.

5. 10. The enamel composition of claim 1, wherein the viscosity of the enamel composition changes by less than about 25% after application by screen printing.

6. 6. The composition of claim 5, wherein the viscosity changes by less than 2% after 2 hours.

7. 7. The composition of claim 5 or 6, wherein the at least one monofunctional acrylate monomer comprises tricyclodecanemethanol monoacrylate or hexahydro-4,7-methano-1H-indenyl acrylate.

8. The composition of claim 1 , wherein the UV curable composition comprises one or more polymeric binders.

9. The composition of claim 1 , wherein the UV curable composition comprises one or more curable polymers.

10. The composition of claim 9 , wherein the curable polymer comprises an acrylated polymer or oligomer.

11. The composition of claim 1 or 6, wherein the UV curable composition further comprises one or more difunctional acrylic monomers.

12. The composition of claim 11 , wherein the one or more difunctional acrylic monomers comprise tripropylene glycol diacrylate (TPGDA).

13. The composition of claim 11, wherein the UV curable composition comprises one or more difunctional acrylic monomers in an amount of 10 to 20% by weight.

14. The composition of claim 1 or 6, wherein the UV curable composition comprises at least one monofunctional acrylic monomer in an amount of 20 to 40 wt %.

15. The composition of claim 1 , wherein the UV curable composition further comprises one or more surfactants or dispersants.

16. The composition of claim 1 , wherein the UV-curable composition further comprises one or more photoinitiators and / or photosensitizers.

17. 10. The composition of claim 1, wherein the UV curable composition further comprises one or more additives selected from the list consisting of UV stabilizers, adhesion promoters, thickeners, and antifoaming agents.

18. The composition of claim 1 , wherein the organic carrier medium further comprises one or more diluents or solvents.

19. The composition of claim 1, wherein the viscosity of the composition before curing is in the range of 10 to 20 Pa·s.

20. A step of depositing the enamel composition of claim 1 onto a substrate; curing the enamel composition; and Firing the hardened enamel composition 1. A method for forming an enamel coating, comprising:

21. 21. The method of claim 20, including applying the enamel composition by screen printing.

22. 22. The method of claim 20 or 21, wherein the curing step comprises curing a UV-curable composition of the enamel composition by exposing it to an ultraviolet light source.

23. 21. The method of claim 20, further comprising printing at least a portion of the enamel composition with an outer metallic layer after the curing step.

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