METHOD FOR PRODUCING A HEAT-STABLE COATING BY DIGITAL PRINTING

Abstract

A method for producing a small heating household appliance article having a substrate with at least two opposite faces, includes providing the substrate and obtaining a heat-stable coating on the substrate. The procedure for obtaining a coating includes depositing by digital printing, on at least one of the two opposite faces of the substrate and through at least one nozzle having an aperture of at least 80 m, at least one layer of a composition including at least one binder and having a dry extract of at least 15% by weight, and curing the coated substrate.

Claims

1. A process for producing a small heating household equipment article comprising a substrate with at least two opposite faces, the process comprising: providing said substrate; and obtaining a heat-stable coating on said substrate, said obtaining step comprising: depositing on at least one of the two opposite faces of said substrate at least one layer of a composition comprising at least one binder; and curing said coated substrate, wherein the composition comprising at least one binder has a dry matter content greater than or equal to 15% by weight, and wherein said deposition is carried out through digital printing via at least one nozzle having an aperture greater than or equal to 80 m in size.

2. The process according to claim 1, wherein said composition has a dry matter content greater than or equal to 20% by weight.

3. The process according to claim 1, wherein the binder comprises at least one of a bonding resin, a fluorocarbon resin, a sol-gel composition, an enamel frit slip, a lacquer, and a condensed tannin.

4. The process according to claim 1, wherein the substrate is chosen from among metallic material substrates, glass substrates, ceramic substrates, terracotta substrates, and plastic substrates.

5. The process according to claim 1, wherein the small heating household equipment article is a culinary article or a small household appliance article.

6. The process according to claim 1, wherein the size of the nozzle aperture is less than or equal to 1.5 mm.

7. The process according to claim 1, wherein the composition further comprises functional fillers.

8. The process according to claim 1, wherein the a thickness of the layer printed by digital printing is greater than 0.1 m and less than or equal to 1000 m.

9. The process according to claim , wherein a thickness of the heat-stable coating, after curing of the coated substrate, is greater than 0.1 m and less than or equal to 1000 m.

10. The process according to claim 1, wherein the heat-stable coating further comprises at least one decoration and/or at least one other layer.

11. The process according to claim 1, wherein said deposition is carried out through digital printing using the ink jet process.

12. The process according to claim 10, wherein the at least one other layer is an undercoat, a primer layer or a protective layer.

Description

EXAMPLES

Tests

Determination of the Dry Matter Content of a Composition

Principle

[0124] The dry matter content of a product is the residual solid part remaining after evaporation of the volatile materials it contains. The temperature and duration of drying play a major role, because high-boiling-point solvents, monomer fractions, reactive diluents and reaction by-products (according to their degree of retention) leave the film in formation very slowly. It is therefore very important to define standardized drying conditions in a very conventional manner, as close as possible to practice.

Procedure

[0125] To measure this dry matter content, we proceed as follows: [0126] weigh an aluminum cup: m.sub.0=mass of the cup; [0127] place in this cup between 0.5 g and 3 g of product to be studied; [0128] weigh the filled cup: m.sub.1=mass of the filled cup; [0129] place the cup in a 210 C. oven for two hours; [0130] after curing and after cooling, weigh the cup: m.sub.2=mass of the filled cup after curing and cooking; [0131] the dry matter content is given by the below formula:

Dry matter content=100*[(m.sub.2m.sub.0)/(m.sub.1m.sub.0)]

[0132] Examples 1 to 14 are examples according to the invention. Comparative examples 1 and 2 are not examples according to the invention.

Example 1

Substrate with Non-Stick Coatings and Decoration Based on Fluorocarbon Resin

[0133] The substrate is a chemically cleaned aluminum disk.

[0134] A coating based on fluorocarbon resin, bonding resin and mineral reinforcing fillers is applied by screen printing in successive layers on the first face of the disk.

[0135] The whole is precured at a temperature of 350 C.

[0136] The second face of the disk receives by screen printing an undercoat of white composition based on fluorocarbon resin.

[0137] A photo-realistic decoration is made by printing a decoration composition, based on colored particulate pigments and free of binder, by ink jet process using a printing system equipped with standard Drop-on-Demand printheads, type Xaar 1001, whose nozzles have an aperture of about 1 m, at a resolution of 360 DPI on the white undercoat. The thickness of the wet decoration thus obtained is between 0.5 m and 5 m.

[0138] A colorless protective layer is made, on the decoration and the white undercoat, by printing a composition comprising a PTFE dispersion, solvents and conventional additives. Said composition has a dry matter content of about 50-55% by weight. This composition is deposited by means of a digital printing machine equipped with valve-jet technology printheads whose nozzles have an aperture of 100 m. The thickness of the wet layer thus deposited is about 20 m.

[0139] The disk coated on its two faces is cured at 430 C. for 10 minutes.

[0140] The thickness of the cured coating thus obtained on the second face of the disk is about 30 m.

Example 2

Substrate with Non-Stick Coatings and Decoration Based on Fluorocarbon Resin

[0141] The substrate is a chemically cleaned aluminum disk.

[0142] A coating based on fluorocarbon resin, bonding resin and mineral reinforcing fillers is applied by screen printing in successive layers on the first face of the disk.

[0143] The whole is precured at a temperature of 350 C.

[0144] The second face of the disk receives by screen printing an undercoat of white composition based on fluorocarbon resin.

[0145] A photo-realistic decoration is made by printing a decoration composition, based on colored particulate pigments and free of binder, by ink jet process using a printing system equipped with standard Drop-on-Demand printheads, type Xaar 1001, whose nozzles have an aperture of about 1 m, at a resolution of 360 DPI on the white undercoat. The thickness of the wet decoration thus obtained is between 0.5 m and 5 m.

[0146] A colorless protective layer is made, on the decoration and the white undercoat, by printing a composition comprising a PTFE dispersion, solvents, conventional additives and flakes of which the largest characteristic dimension is about 100 m. Said composition has a dry matter content of about 50-55% by weight. This composition is deposited by means of a digital printing machine equipped with valve-jet technology printheads whose nozzles have an aperture of 200 m. The thickness of the wet layer thus deposited is about 20 m.

[0147] The disk coated on its two faces is cured at 430 C. for 10 minutes.

[0148] The thickness of the cured coating thus obtained on the second face of the disk is about 30 m.

Example 3

Substrate with a Non-Stick Coating Based on Fluorocarbon Resin

[0149] The substrate is a chemically cleaned aluminum disk.

[0150] A primer composition based on a mixture of PTFE and PFA dispersions, a bonding resin (PAI), colloidal silica and carbon black dispersion, is applied by digital printing on one of the faces of the disk. Said composition has a dry matter content of about 20-25% by weight.

[0151] This digital printing is performed by means of a digital printing machine using the ink jet process, the machine being equipped with valve-jet technology printheads whose nozzles have an aperture of 100 m. The thickness of the wet layer thus deposited is about 30 m.

[0152] The primer layer is dried at about 100 C.

[0153] A colorless protective layer is then made on the primer layer. A colorless protective composition based on a PTFE dispersion, solvent and conventional additives is deposited by means of a digital printing machine using the ink jet process, the machine being equipped with valve-jet technology printheads whose nozzles have an aperture of 100 m. Said composition has a dry matter content of about 50-55% by weight. The thickness of the wet layer thus deposited is about 20 m.

[0154] The disk thus coated is cured at 430 C. for 10 minutes.

[0155] The thickness of the cured coating thus obtained is about 30 m.

Example 4

Substrate with a Non-Stick Coating Based on Fluorocarbon Resin

[0156] The substrate is a chemically cleaned aluminum disk.

[0157] A primer composition based on a mixture of PTFE and PFA dispersions, a bonding resin (PAI), colloidal silica, mineral reinforcing fillers (alumina powder with particle size of 3-50 m) and carbon black dispersion, is applied by digital printing on one of the faces of the disk. Said primer composition has a dry matter content of about 20-25% by weight.

[0158] This digital printing is performed by means of a digital printing machine using the ink jet process, the machine being equipped with valve-jet technology printheads whose nozzles have an aperture of 150 m. The thickness of the wet layer thus deposited is about 30 m.

[0159] The primer layer is dried at about 100 C.

[0160] A colorless protective layer is then made on the primer layer. A colorless protective composition based on a PTFE dispersion, solvent and conventional additives is deposited by means of a digital printing machine using the ink jet process, the machine being equipped with valve-jet technology printheads whose nozzles have an aperture of 100 m. Said protective composition has a dry matter content of about 50-55% by weight. The thickness of the wet layer thus deposited is about 20 m.

[0161] The disk thus coated is cured at 430 C. for 10 minutes.

[0162] The thickness of the cured coating thus obtained is about 30 m.

Example 5

Substrate with a Non-Stick Coating Based on Fluorocarbon Resin

[0163] The substrate is a chemically cleaned aluminum disk.

[0164] A primer composition based on a mixture of PTFE and PFA dispersions, a bonding resin (PAI), colloidal silica, mineral reinforcing fillers (alumina powder with particle size of 3-50 m) and carbon black dispersion, is applied by digital printing on one of the faces of the disk. Said primer composition has a dry matter content of about 20-25% by weight.

[0165] This digital printing is performed by means of a digital printing machine using the ink jet process, the machine being equipped with valve-jet technology printheads whose nozzles have an aperture of 150 m. The thickness of the wet layer thus deposited is about 30 m.

[0166] The primer layer is dried at about 100 C.

[0167] The following compositions are deposited successively by digital printing on the primer layer: [0168] a red heat-stable decoration composition based on a PTFE dispersion and a mixture of perylene red and black pigment. Said composition has a dry matter content of about 50% by weight. This composition is printed, following a solid disk shape, by means of a digital printing machine using the ink jet process, the machine being equipped with valve-jet technology printheads whose nozzles have an aperture of 100 m. The thickness of the wet layer thus deposited is about 5 m; [0169] a red thermochromic decoration composition based on a PTFE dispersion and iron oxide. Said composition has a dry matter content of about 50% by weight. This composition is printed, following a discontinuous pattern at least partially covering the red heat-stable decoration layer, by means of a digital printing machine using the ink jet process, the machine being equipped with valve-jet technology printheads whose nozzles have an aperture of 100 m. The thickness of the wet layer thus deposited is about 5 m; [0170] a decoration composition in a color clearly distinct from the color of the primer layer, free of binder and comprising flakes of which the largest characteristic dimension is about 100 m. Said composition has a dry matter content of about 20% by weight. This composition is printed, following a discontinuous pattern at least partially covering the red decoration layers, by means of a printing machine equipped with valve-jet technology printheads whose nozzles have an aperture of 200 m. The thickness of the wet layer thus deposited is about 5 m.

[0171] A colorless protective layer is made, on the primer layer and the decoration layers, by printing a composition comprising a PTFE dispersion, solvents, conventional additives and flakes of which the largest characteristic dimension is about 100 m. Said composition has a dry matter content of about 50-55% by weight. This composition is deposited by means of a digital printing machine using the ink jet process, the machine being equipped with valve-jet technology printheads whose nozzles have an aperture of 200 m. The thickness of the wet layer thus deposited is about 20 m.

[0172] The disk thus coated is cured at 430 C. for 10 minutes. The thickness of the cured coating thus obtained is about 35 m.

Example 6

Substrate with a Non-Stick Coating Based on Fluorocarbon Resin

[0173] The substrate is a chemically cleaned aluminum disk.

[0174] A composition based on a mixture of PTFE and PFA dispersions and a cobalt blue pigment dispersion having particles of about 5 m, is applied by digital printing on one of the faces of the disk. Said primer composition has a dry matter content of about 40% by weight.

[0175] This digital printing is performed by means of a digital printing machine using the ink jet process, the machine being equipped with valve-jet technology printheads whose nozzles have an aperture of 100 m. The thickness of the wet layer thus deposited is about 30 m.

[0176] The disk thus coated is cured at 430 C. for 10 minutes.

[0177] The thickness of the cured coating thus obtained is about 15-20 m.

Example 7

Cap with a Non-Stick Coating Presenting Improved Scratch Resistance

[0178] From an aluminum disk, a press is used to obtain a cap form.

[0179] On the bottom of the concave part of the cap, a discontinuous layer of a composition based on enamel frit slip and inorganic reinforcing fillers (alumina powder with particle size of about 25 m) is deposited by means of a digital printing machine using the ink jet process, the machine being equipped with valve-jet technology printheads whose nozzles have an aperture of 400 m. Said composition has a dry matter content of about 65% by weight. The thickness of the discontinuous wet layer thus obtained is about 20 m.

[0180] The cap thus coated is cured at 560 C. for 10 minutes.

[0181] On the entire concave part of the cap, several successive PTFE-based layers are applied by spraying.

[0182] The cap thus coated is then cured at 430 C. for 10 minutes.

[0183] The thickness of the cured coating obtained is about 35 m.

Example 8

Substrate with an Easy-to-Clean Lacquer Coating

[0184] The substrate is a chemically cleaned aluminum disk.

[0185] One of the faces of the substrate is coated with a layer of a composition based on silicone-polyester lacquer by means of a digital printing machine using the ink jet process, the machine being equipped with valve-jet technology printheads whose nozzles have an aperture of 100 m. Said composition comprises the silicone-polyester lacquer, pigments and solvents, and has a dry matter content of about 50% by weight. The thickness of the wet layer thus deposited is about 20 m.

[0186] The disk thus coated is cured at 250 C. for 10 minutes.

[0187] The thickness of the cured coating obtained is about 10 m.

Example 9

Cap with an Anti-Scratch Protective Coating

[0188] From an aluminum disk, a press is used to obtain a cap form.

[0189] On the bottom of the convex part of the cap, a layer of a composition based on enamel frit slip containing stainless steel beads of about 45 m is deposited by means of a digital printing machine using the ink jet process, the machine being equipped with valve-jet technology printheads whose nozzles have an aperture of 200 m. These stainless steel beads are selected so as to form a protuberance and remain in direct contact with the heating surface once the coating is cured. Said composition has a dry matter content of about 70% by weight.

[0190] The thickness of the wet layer thus deposited is about 50 m.

[0191] The cap is then cured at 560 C. for 10 minutes.

[0192] The thickness of the cured coating obtained in the end is about 30 m with the top of the stainless steel beads visible.

Example 10

Cap with an Anti-Scratch Protective Coating

[0193] From an aluminum disk, a press is used to obtain a cap form.

[0194] On the bottom of the convex part of the cap, a layer of a colored composition based on silane precursors containing stainless steel beads of about 45 m is deposited by means of a digital printing machine using the ink jet process, the machine being equipped with valve-jet technology printheads whose nozzles have an aperture of 200 m. These stainless steel beads are selected so as to form a protuberance and remain in direct contact with the heating surface once the coating is cured. Said composition has a dry matter content of about 70% by weight.

[0195] The thickness of the wet layer thus deposited is about 50 m.

[0196] The cap is then cured at 250 C. for 20 minutes.

[0197] The thickness of the cured coating obtained in the end is about 30 m with the top of the stainless steel beads visible.

Example 11

Cap with a Sol-Gel-Based Non-Stick Coating

[0198] From an aluminum disk, a press is used to obtain a cap form.

[0199] On the entire concave face of the cap, a first layer of a colored composition based on silane precursors is applied by spraying.

[0200] On the bottom of the concave part of the cap, the following compositions are deposited successively by digital printing: [0201] a red (mixture of perylene red and black pigment) heat-stable decoration composition free of binder. Said composition has a dry matter content of about 50% by weight. This printing is performed, following a solid disk shape, by means of a digital printing machine using the ink jet process, the machine being equipped with valve-jet technology printheads whose nozzles have an aperture of 100 m. The thickness of the wet layer thus deposited is about 10 m; [0202] a red thermochromic decoration composition based on iron oxide and free of binder. Said composition has a dry matter content of about 50% by weight. This printing is performed, following a discontinuous pattern at least partially covering the red heat-stable decoration layer, by means of a digital printing machine using the ink jet process, the machine being equipped with valve-jet technology printheads whose nozzles have an aperture of 100 m. The thickness of the wet layer thus deposited is about 10 m; [0203] a decoration composition in a color clearly distinct from the color of the first layer coated by spraying, free of binder and comprising flakes of which the largest characteristic dimension is about 100 m. Said composition has a dry matter content of about 20% by weight. This printing is performed, following a discontinuous pattern at least partially covering the red decoration layers, by means of a digital printing machine using the ink jet process, the machine being equipped with valve-jet technology printheads whose nozzles have an aperture of 200 m. The thickness of the wet layer thus deposited is about 10 m.

[0204] On the entire concave face of the cap, a last layer of a colorless composition based on silane precursors is applied by spraying.

[0205] The cap is then cured at 250 C. for 15 minutes.

[0206] The thickness of the cured coating thus obtained is about 30 m.

Example 12

Substrate with a Non-Stick Coating Based on Fluorocarbon Resin

[0207] The substrate is a mechanically brushed aluminum disk.

[0208] A primer composition based on a mixture of PTFE and FEP dispersions, a bonding resin (PAI), colloidal silica, mineral reinforcing fillers (silicon carbide with particle size of 3-50 m) and carbon black dispersion, is applied by digital printing on one of the faces of the disk. Said primer composition has a dry matter content of about 35-40% by weight.

[0209] The digital printing is performed by means of a digital printing machine using the ink jet process, the machine being equipped with printheads of a technology as described in U.S. Pat. No. 6,460,980 and whose discharge channel has a diameter of 500 m. The thickness of the wet layer thus deposited is about 30 m.

[0210] The primer layer is dried at about 100 C.

[0211] A colorless protective layer is made, on the primer layer and the decoration layers, by printing a composition comprising a mixture of PTFE, PFA and FEP dispersions, solvents, conventional additives and flakes of which the largest characteristic dimension is about 100 m. Said composition has a dry matter content of about 45-50% by weight.

[0212] This composition is deposited by means of a digital printing machine equipped with printheads of a technology as described in U.S. Pat. NO. 6,460,980 and whose discharge channel has a diameter of 500 m. The thickness of the wet layer thus deposited is about 30 m.

[0213] The disk thus coated is cured at 430 C. for 10 minutes.

[0214] The thickness of the cured coating thus obtained is about 25 m.

Example 13

Substrate with a Non-Stick Coating Based on Fluorocarbon Resin

[0215] The substrate is a mechanically brushed aluminum disk.

[0216] A primer composition based on a mixture of PTFE and FEP dispersions, a bonding resin (PAI), colloidal silica, mineral reinforcing fillers (spherical alumina with particle size of 3-50 m) and carbon black dispersion, is applied by digital printing on one of the faces of the disk. Said primer composition has a dry matter content of about 35-40% by weight.

[0217] The digital printing is performed by means of a printing machine equipped with printheads of a technology as described in the patent WO2010/146473 and whose discharge channel has a diameter of 120 m. The thickness of the wet layer thus deposited is about 30 m.

[0218] The primer layer is dried at about 100 C.

[0219] The following compositions are deposited successively by digital printing on the primer layer: [0220] a red heat-stable decoration composition based on a PTFE dispersion and a mixture of perylene red and black pigment. Said composition has a dry matter content of about 50% by weight. This composition is printed, following a solid disk shape, by means of a digital printing machine using the ink jet process, the machine being equipped with valve-jet technology printheads whose nozzles have an aperture of 100 m. The thickness of the wet layer thus deposited is about 5 m; [0221] a red thermochromic decoration composition based on a PTFE dispersion and iron oxide. Said composition has a dry matter content of about 50% by weight. This composition is printed, following a discontinuous pattern at least partially covering the red heat-stable decoration layer, by means of a digital printing machine using the ink jet process, the machine being equipped with valve-jet technology printheads whose nozzles have an aperture of 100 m. The thickness of the wet layer thus deposited is about 5 m; [0222] a decoration composition in a color clearly distinct from the color of the primer layer, free of binder and comprising flakes of which the largest characteristic dimension is about 100 m and spherical alumina fillers 15-50 m in size. Said composition has a dry matter content of about 20% by weight. This composition is printed, following a discontinuous pattern at least partially covering the red decoration layers, by means of a digital printing machine using the ink jet process, the machine being equipped with valve-jet technology printheads whose nozzles have an aperture of 200 m. The thickness of the wet layer thus deposited is about 5 m.

[0223] A colorless protective layer is made, on the primer layer and the decoration layers, by printing a composition comprising a mixture of PTFE, PFA and FEP dispersions, solvents, conventional additives and flakes of which the largest characteristic dimension is about 100 m. Said composition has a dry matter content of about 50-55% by weight. This composition is deposited by means of a digital printing machine using the ink jet process, the machine being equipped with valve-jet technology printheads whose nozzles have an aperture of 200 m. The thickness of the wet layer thus deposited is about 20 m.

[0224] The disk thus coated is cured at 430 C. for 10 minutes.

[0225] The thickness of the cured coating thus obtained is about 20 m.

Example 14

Substrate with a Non-Stick Coating Based on Fluorocarbon Resin

[0226] The substrate is a mechanically brushed aluminum disk.

[0227] A composition based on a mixture of PTFE and PFA dispersions and a pigment dispersion, mixture of cobalt blue and bismuth vanadate, having particles of about 5 m, is applied by digital printing on one of the faces of the disk. Said primer composition has a dry matter content of about 40% by weight.

[0228] The digital printing is performed by means of a digital printing machine using the ink jet process, the machine being equipped with printheads of a technology as described in U.S. Pat. No. 6,460,980 and whose discharge channel has a diameter of 500 m. The thickness of the wet layer thus deposited is about 30 m.

[0229] The primer layer is dried at about 100 C.

[0230] A composition in a color clearly distinct from the color of the primer layer, based on a mixture of PTFE and PFA dispersions and an iron oxide pigment dispersion, having particles of about 5 m. Said composition has a dry matter content of about 40% by weight. This composition is printed, following a discontinuous pattern at least partially covering the first green layer, by means of a printing machine equipped with printheads as described in the patent WO2010/146473 and whose discharge channel has a diameter of 120 m. The thickness of the wet layer thus deposited is about 20 m.

[0231] The disk thus coated is cured at 430 C. for 10 minutes.

[0232] The cured coating thus obtained is about 20 m in thickness and presents a red decorative pattern on a green background.

Comparative Example 1

[0233] The substrate is a chemically cleaned aluminum disk.

[0234] A coating based on fluorocarbon resin, bonding resin and mineral reinforcing fillers is applied by screen printing in successive layers on the first face of the disk.

[0235] The whole is precured at a temperature of 350 C.

[0236] The second face of the disk receives by screen printing an undercoat of white composition based on fluorocarbon resin.

[0237] A photo-realistic decoration is made by printing a decoration composition, based on colored particulate pigments and free of binder, by ink jet using a printing system equipped with standard Drop-on-Demand printheads, type Xaar 1001, whose nozzles have an aperture of about 1 m, at a resolution of 360 DPI on the white undercoat. The thickness of the wet decoration thus obtained is between 0.5 m and 5 m.

[0238] A colorless protective layer is made, on the decoration and the white undercoat, by printing a composition comprising a PTFE dispersion, solvents and conventional additives. Said composition has a dry matter content of about 10% by weight. This composition is deposited by ink jet using a digital printing system equipped with standard Drop-on-Demand printheads, type Xaar 1001, whose nozzles have an aperture of about 1 m, at a resolution of 360 DPI. The thickness of the wet layer thus deposited is about 10 m.

[0239] This layer is dried for 1 minute at 100 C. After drying, the thickness of the layer is about 1 m.

[0240] To achieve a minimum final dry thickness of protective layer (that is, about 10 m) to ensure good non-stick quality of the final coating, it is then necessary to multiply by at least 10 times the step of printing the colorless protective composition followed by a drying.

[0241] The disk coated on its two faces is cured at 430 C. for 10 minutes. The thickness of the cured coating thus obtained on the second face of the disk is about 30 m.

[0242] The final coating thus obtained is similar to the one made in example 1, but 10 times as many printing and drying steps were necessary, which is not a reasonable industrial process.

Comparative Example 2

[0243] The substrate is a chemically cleaned aluminum disk.

[0244] A coating based on fluorocarbon resin, bonding resin and mineral reinforcing fillers is applied by screen printing in successive layers on the first face of the disk.

[0245] The whole is precured at a temperature of 350 C.

[0246] The second face of the disk receives by screen printing an undercoat of white composition based on fluorocarbon resin.

[0247] A photo-realistic decoration is made by printing a decoration composition, based on colored particulate pigments and free of binder, by ink jet process using a printing system equipped with standard Drop-on-Demand printheads, type Xaar 1001, whose nozzles have an aperture of about 1 m, at a resolution of 360 DPI on the white undercoat. The thickness of the wet decoration thus obtained is between 0.5 m and 5 m.

[0248] A colorless protective layer is made, on the decoration and the white undercoat, by printing a composition comprising a PTFE dispersion, solvents and conventional additives. Said composition has a dry matter content of about 10% by weight. This composition is deposited by ink jet process using a digital printing system equipped with standard Drop-on-Demand printheads, type Xaar 1001, whose nozzles have an aperture of about 1 m, at a resolution of 360 DPI. The thickness of the wet layer thus deposited is about 10 m.

[0249] To achieve a minimum final dry thickness of protective layer (that is, about 10 m) to ensure good non-stick quality of the final coating, it is then necessary to multiply by at least 10 times the step of printing the colorless protective composition.

[0250] The thickness of the wet layer thus deposited is about 100 m. Such a wet layer does not permit maintaining homogeneity of component distribution.

[0251] The disk coated on its two faces is cured at 430 C. for 10 minutes.

[0252] The thickness of the cured coating thus obtained on the second face of the disk is about 30 m.

[0253] The final coating thus obtained has a non-homogeneous protective layer, the added thicknesses formed are very yellow and cracked and there are areas of very low thicknesses where the non-stick quality is insufficient.