HK1169823B - Coated glass sheet - Google Patents

Description

Coated glass sheet

Technical Field

The present invention relates to coated glass sheets, in particular glass sheets having a lacquer layer formed on the surface thereof, and to such glass sheets which can be heat treated and which can be handled prior to such possible heat treatment. By "lacquer layer" is meant herein paint (paint), glaze (enamel), lacquer (lacquer) or other type of decorative color layer.

Background

The glass sheet according to the invention may have various applications. The lacquered glass sheets may for example be used for decorative purposes in furniture, wardrobe, as doors of furniture, as partitions, in tables, shelves, in bathrooms, in shop displays, as wall coverings, in outdoor environments, and as spandrels. The lacquer can also be used on the panes of automotive glazings or on at least a part of these glazings, for example on the peripheral part of a windscreen. More and more of these applications necessitate tempered glass sheets, which have the advantage of being more resistant to breakage. Other heat treatments are also becoming common: such as bending.

Traditionally, painted glass sheets can be produced according to various methods.

In one known method, a glass sheet is covered with a layer of an organic-based paint, which is then dried and/or cured in an oven, for example at about 150 ℃ for about 10 minutes. The organic-based paint may comprise, for example, a polyurethane resin, an alkyd resin, or an acrylic resin. The glass may be treated with silane prior to application of the paint layer. When conventional painted glass sheets covered with a layer of organic based paint are heat treated at high temperatures, the paint burns, is degraded or can be completely destroyed. These conventional painted glass sheets will generally not be able to withstand temperatures above 200 ℃ without degradation. When the glass sheets are tempered before painting, this necessitates that the glass sheets are already at their final size, since it is not possible to cut and grind the tempered glass sheets. This makes it impossible to perform mass and continuous production.

In another known method, a glass plate is covered with an infrared or ultraviolet curable glaze layer, then cured, and finally subjected to a heat treatment at about 600 ℃. This curing step provides the coated glass sheet with limited mechanical resistance (Clemen test results less than 50g), allowing it to be handled on a production line until it reaches the oven where the heat treatment takes place. However, prior to the heat treatment step, the curing step does not provide the coated glass sheet with sufficient mechanical and water resistance to withstand transport, for example by truck, for cutting, edging or storage. For these traditionally glazed glasses, a heat treatment has to be carried out immediately after production and on the same production line.

Recently, painted glass sheets have been developed by providing a coating on the glass sheet, said coating comprising, in sequence, a first layer comprising an enamel and a second layer comprising a resin (WO 2007104752). The glass sheet can be handled and transported before heat treatment without damaging the coating; they can be cut and ground prior to heat treatment without causing the coating to peel off or be damaged at the edges of the cut line; in addition, they can provide good resistance to running water prior to heat treatment. In general, the second layer is temporary to give resistance to the painted glass sheet before the heat treatment; it is intended to be removed or destroyed after heat treatment. However, although such a two layer system may provide good scratch resistance prior to heat treatment, we note that during production the resistance of the first layer prior to deposition of the second layer may be poor and that handling tools such as conveyor rollers or suction devices may damage the first layer before it is protected by the second layer, leading to defects in the final product.

Unless otherwise indicated, the temperatures referred to herein refer to the oven (oven) temperature, i.e., the temperature of the atmosphere in which the heating or heat treatment is carried out. "Heat treatment" refers to bending and/or thermal tempering and/or thermal hardening operations and/or other similar heating processes. Such heat treatment may involve heating or exposing the painted glass sheet to a temperature greater than about 560 ℃, e.g., 560 ℃ to 750 ℃, in an atmosphere for 2 minutes to 20 minutes, preferably a maximum of 15 minutes, depending on the thickness of the glass sheet and the oven used. The term "heat treated glass sheet" as used herein means that the glass sheet has undergone a heat treatment. The term "curing" means a step that allows the liquid paint, lacquer or enamel coating to harden. Curing typically involves at least drying (solvent evaporation), but may also involve chemical reactions such as cross-linking of polymer chains.

Disclosure of Invention

According to one aspect, the present invention provides a glass sheet having a coating of enamel provided on at least one surface of the glass sheet. Advantageously, the enamel coating according to the invention comprises 11-40% of organic substances.

This increased content of organic substances in the enamel coating can provide advantageous mechanical resistance properties prior to heat treatment. The glass sheets according to the invention can be handled and transported before the heat treatment with common handling tools (e.g. rollers, suction devices) without damaging the coating, e.g. without producing scratches. They can be cut and ground prior to heat treatment without causing the coating to peel off or be damaged at the edges of the cut line. Furthermore, they can provide good resistance to running water before the heat treatment, so that peeling or destruction of the coating is avoided, for example, when washing glass plates or edging. Furthermore, these properties can be achieved with a single layer coated on a glass plate, which can be easier, cheaper and less time consuming than previously known methods that require two layers.

Furthermore, the inventors have surprisingly found that the coating composition according to the invention can be cured at lower temperatures and/or more rapidly than previously known coatings for painting glass sheets.

The invention has particular advantages in the heat-treatable lacquered glass sheets. The term "heat treatable glass sheet" as used herein means that the painted glass sheet according to the present invention is suitable for heat treatment without defects (e.g. aesthetic defects of the paint) and still has good adhesion between the glass sheet and the paint.

Preferably, the enamel coating according to the invention comprises 11-25% of organic substances. This upper limit of organic matter in the enamel coating makes it possible to avoid the so-called "starring" phenomenon, which can be observed on painted glass through light transmission. It appears when the paint coating is not completely uniform and shows some (microscopic) pores. These holes allow light to pass through the coating and are thus visible when viewed from the glass side, appearing as small spots.

To measure this content of organic matter, the amount of coating material scratched from a cured but non-heat treated coated glass plate (typically about 1-2 grams) was analyzed by thermogravimetric analysis (TGA). TGA was performed in air at a temperature rise of 10 ℃/min from 20 ℃ to 1000 ℃. The content of organic substances was determined as follows: the material that burned during the TGA process (removing possible residual solvent) was quantified until no further weight loss was observed. Typically, the organic matter is completely combusted upon reaching 500 ℃.

The glass sheet according to the invention, untreated or once heat treated, can also advantageously provide similar properties to conventional non-heat treatable lacquered glass sheets in terms of adhesion of the coating to the glass, chemical resistance, mechanical resistance and resistance to adhesives (glue resistance). In particular, the untreated or heat treated glass sheet according to the invention may have one or more of the following properties:

abrasion test, Clemen test, Persoz test, UV test and setting test are all described below.

According to the invention, a coating of enamel is provided on at least one surface of the glass sheet. The term "glaze" is used herein equally for glaze compositions prior to any curing or heat treatment, or glaze compositions that are dried or cured but have not yet been sintered. Glazes generally comprise a pigment and a frit (frit). Glazes generally comprise a medium. The medium ensures that the solid particles are in proper suspension and allows the application and temporary attachment of the glaze to the substrate. The medium is preferably organic. Examples of glazes suitable for the coating according to the invention are the 144001 black 801029 glazes from the company FERRO, the AF2600-65-96 glazes from the company JOHNON MATTHEY and the TEMPVER bionco 3400-06-011 or 3400-.

According to the invention, the coating contains 11 to 40% of organic substances. Such organic substances may come from the initial medium of commercial glazes, to which additional organic compounds are added to achieve the desired amount of organic substance in the coating. Alternatively, the enamel coating of the invention can be prepared as follows: in particular, glass frits, pigments and organic compounds are mixed to obtain an enamel coating having the desired organic quality.

Preferably, the organic substance has a softening temperature of at least 20 ℃, preferably at least 25, 30, 35 or 40 ℃ after curing. These values may also help to provide advantageous mechanical resistance prior to heat treatment. This softening temperature may be equal to the Tg (glass transition temperature) in the case where the organic substance consists essentially of a polymer, or the melting point if other compounds are present. These softening temperature values ensure that the coating is not too soft before curing and at the usual temperatures involved in the production process, otherwise scratches are very easily produced in the coating.

Preferably, the organic substance of the coating (i.e. once cured) comprises or more preferably consists of at least one substance selected from the group consisting of: polyols, alkyds, acrylics, polyacrylics, polyacrylates, polymethacrylates, acrylamides, melamines, polycarbonates, acrylic-styrenes, vinyl-acrylics, urethanes, polyurethanes, polyesters, polyolefins, urethane alkyds, polyureas, amino resins, polyamides, epoxy resins, epoxy esters, phenolic resins, silicone resins, PVC, PVB, and water-based resins, as well as reaction products of photocurable chemicals. The organic substance of the coating may advantageously also comprise conventional paint additives such as dispersing agents, levelling agents, flow agents, UV-protection agents, catalysts, wetting agents, adhesion promoters, matting agents and/or structuring agents. More preferably, the organic substance of the coating comprises a polyol and melamine.

The thickness of the coating once dried and/or cured but before heat treatment is at least 10 μm and it is at most 150 μm. Preferably, the thickness of the coating is at least 15 μm, and it is at most 100 μm. If the thickness of the coating is too low, it may not be sufficient to form a painted glass sheet with the desired mechanical and water resistance; if the thickness of the coating is too great, curing may be poor and separation may occur. Such thicknesses may be achieved by one or more applications during the manufacturing process. The layer thickness referred to herein means the average geometric thickness of the layer.

Preferably, the coating is in direct contact with the glass substrate. The glass substrate may be surface treated with an adhesion promoter prior to coating to improve adhesion of the coating to the glass without departing from this embodiment. Such adhesion promoters may include silanes.

In other embodiments, there may be a continuous layer between the coating and the glass sheet. These preferred structures can provide particularly good mechanical resistance properties for transportation, for cutting and grinding, and for resistance under running water, prior to any heat treatment. In such embodiments, the glass substrate may also be surface treated with an adhesion promoter prior to any coating to improve adhesion of the first coating to the glass.

In a preferred embodiment, the coating of the invention may be continuous and extend over almost the entire surface of the glass sheet, i.e. over more than 90% of the surface of the glass sheet, preferably over more than 95% of the surface of the glass sheet.

The coating may be colored for decorative purposes. If the glass sheet is heat treated, the color may change during the heat treatment depending on the composition of the coating. If this occurs, this should be taken into account for the heat treatable product to ensure that the final colour after heat treatment is desired. Alternatively, if the glass sheet is heat treated, the color may not change during the heat treatment.

The coating may be opaque or translucent for decorative purposes. It may also be structured or matt.

The substrate used may be flat glass, in particular float glass of various thicknesses (for example 1.8-10.2 mm); it may be soda-lime glass and may be clear, ultra-clear, tinted, etched or sandblasted glass. The glass sheet according to the invention may have dimensions greater than 1m x 1 m. They may have dimensions of, for example, 3.21m × 6m or 3.21m × 5.50m or 3.21m × 5.10m or 3.21m × 4.50m, known as PLF, or of, for example, 3.21m × 2.50m or 3.21m × 2.25m, known as DLF. Although the present invention is described mainly in terms of a glass substrate, it can also be applied to a metal substrate or a plastic substrate.

According to some embodiments, the coated glass sheet of the present invention may comprise an additional coating layer applied over the enamel coating layer further from the glass sheet. This contributes to further increasing the mechanical resistance of the painted glass sheet. Such additional coating may be of the second layer type described in WO2007104752, i.e. a layer comprising a resin and optionally a filler of enamel. Such a resin may comprise at least one material selected from the group consisting of: photocurable chemicals, polyester resins, alkyd resins, acrylics, acrylamides, acrylic-styrenes, vinyl-acrylics, urethanes, polyurethanes, polyesters, urethane alkyds, amino resins, polyamides, epoxy resins, epoxy esters, phenolic resins, silicone resins, PVC, PVB, and water-based resins. Such additional coating layers may have a thickness of 5-50 μm once cured.

According to another aspect, the invention provides a process for producing heat-treatable lacquered glass sheets, comprising the following steps in the order recited:

-providing a glass sheet;

-applying on at least one surface of the glass sheet a coating of enamel comprising 11-40% of organic substances, expressed in weight percentage; and is

-curing the coating so that the enamel hardens and adheres to the glass but has not yet been melted or sintered.

Curing of the coating may be carried out by temperature, UV, IR or NIR irradiation, by electron beam, and/or by induction heating.

When curing under IR irradiation is considered, preferably the coating is cured at a temperature of at least 150 ℃ or at least 175 ℃ and/or not more than 300 ℃, preferably not more than 275 ℃; this may be done for about 1-20 minutes, preferably 2-15 minutes (in a static oven); alternatively, in an industrial oven, this is about 200 ℃ and 250 ℃ measured on glassThe maximum temperature may last for about 5-10 minutes. When curing by electron beam is considered, this may require at least 40 keV. When curing by UV is considered, this may require at least 250mJ/m²。

The coating may be applied by any method known in the art, such as roll or curtain coating, spray coating, or flow coating. Silk screening may also be used, especially if only a portion of the glass sheet is coated.

When the glass sheet according to the invention is heat treated, the coating melts and sinters and the organic substance burns. Sintering may be performed at a temperature of about 600-700 c or higher.

Preferably, the glass sheet according to the invention, once thermally tempered or toughened, is then laminated according to standard EN 12150-1: 2000 may be used as safety glass in buildings. Preferably, the glass sheet according to the invention, once thermally tempered or toughened, is subjected to a tempering according to the standard prEN 14-179-1: 2001 or EN 1863-1: the fracture test of 2000 was broken.

Detailed Description

Embodiments of the present invention will now be further described, by way of example only, and in conjunction with some comparative examples which do not conform to the present invention. Table I summarizes all examples and comparative examples.

Examples 1 to 17

Various mixtures were produced comprising commercially available glazes and commercially available paints. According to the invention, a paint is added to provide an increased organic matter content to the glaze.

The glazes used in all examples 1 to 17 are shown in table I. For example, the white glaze TEMPVER bianco 3400-.

In examples 1-3, 7-11 and 16-17, GLASOREX paint from FENZI corporation was used, having various colors as defined by the RAL system. These paints generally contain about pigments, solvents, methacrylic resins, melamine resins and epoxy resins. In examples 4-5 and 12-15, clear coat (clearcoat) containing UV resistant additive from FENZI corporation was used; in example 6, the clear coat did not contain an anti-UV additive. The clear coat may also contain methacrylic resins, melamine resins, and epoxy resins.

The glaze and paint were mixed in various proportions as given in columns 2 and 4 of table I. In some embodiments, the amount of organic matter measured by TGA is given in% by weight (column 6 of table I).

A float glass sheet having a thickness of 4mm was conveyed along a certain path by a roller conveyor. They are first washed in a conventional manner. They are then passed under a curtain coater where they are coated with a mixture comprising commercial glaze and paint. Different mixtures have been used for the examples as given in columns 2 and 6 of table I and as explained above. The coating is then cured at moderate temperatures according to the parameters given in column 9 of table I.

The thickness of the coating once dried and before heat treatment is given in column 7 of table I. The products after curing but before heat treatment (columns 10-12 of table I) show good water resistance under running water. The coating has good adhesion to the glass; this may allow good grinding without defects on the edges. Persoz and Clemen gave good results. No excess coating was removed after the 1000-revolution abrasion test, indicating that such a coating is resistant to handling and shipping.

The product has resistance to heat treatment and has shown good Persoz results after heat treatment (180 seconds at 680 c) (column 13 of table I).

Comparative examples 1 to 3

In comparative examples 1 to 3, the coating layer was composed of only glaze and the content of organic matter was less than 11%. The resistance of such a coating before heat treatment is much lower: there was no resistance to abrasion testing and Persoz and Clemen results were lower. Their resistance under running water is unacceptable, edging is not possible and unacceptable scratches occur during handling and/or transport.

Comparative examples 4 and 5

In comparative examples 4 and 5, the coating did not contain a glaze; the coating consists only of colored paint. The content of organic substances in the coating is higher than 40%. Such coatings have good resistance to running water, edging or scratching, but are not heat treatable. The coating is hardly damaged.

Examples 18 to 28

The various coated and cured glasses according to the first set of examples were coated with additional coatings by passing under a curtain coater, where a polyurethane paint from FENZI corporation containing approximately 50% by weight of enamel filler was applied over the first coating containing enamel and paint. This second coating was dried directly after application at 200 ℃ during about 20 minutes.

The thickness of this additional layer once cured and before heat treatment of the product is given in column 8 of table I. The product, once cured and before heat treatment, shows an enhanced resistance compared to a product having a single layer comprising a glaze and a paint (columns 10-12 of table I).

Comparative example 6

This comparative example corresponds to the product according to WO 2007104752. Although the resistance of the 2-layer product before heat treatment is good, the resistance of the first coating before coating with the second protective coating is insufficient: scratches may occur during operation on a production line.

Testing

Abrasion tests can be used to predict the performance of the painted glass sheets of the present invention when edge-finished, shipped, washed and/or heat treated. A10X 10cm square sample was mounted on a steel plate rotating at a speed of 65-75 rpm. Each of the two parallel weighted arms carries a special grinding wheel (CS10F) that rotates freely about a horizontal axis. Each wheel is placed on the sample to be tested under a weight applied to each arm, which is a mass of 500 g. The combination of the rotating support disk and the abrasive wheel produced an abrasive crown (crown) on the sample, which was more or less large depending on the hardness of the coating.

The amount of coating removed after subjecting the coated glass sheet to 1000 revolutions in the abrasion test defined herein is calculated as follows:

-determining the weight of the coated glass sheet: wtpainted glass.

-the weight of the same uncoated glass sheet is also determined: wtglass.

The weight of the coating itself is then calculated: wtpaint ═ Wtpainted glass-Wtglass.

-the "paint ratio" p.r. can also be calculated; in a preferred embodiment of the present invention, the paint ratio may be about 1-2% by weight.

-then providing and weighing a 10cm x 10cm square sample of such a coated glass plate: wtpainted sample.

The same samples were then weighed after being subjected to a wear test of 1000 revolutions with two wheels CS10 each loaded with 500 g: wttested sample. The coating is removed in accordance with the shape of the abrasive crown (i.e., 2-D circle loop).

The amount of coating removed can then be calculated.

The maximum amount of coating that can be removed is about 25%. This is due to the size of the ground crown surface on a 10 x 10cm square sample and the paint ratio typically applied.

The glass thickness of the samples tested must be the same as the glass thickness used in the p.r. calculation.

The Clemen test is used to evaluate the scratch resistance of the coating. The tungsten carbide tipped needle is pressed onto the coating by applying a load on the needle. The needle was used to scratch the coating over a distance of about 60 mm. Multiple weights (from 250g at 250g intervals up to 2500g) can be applied to the same sample with a distance between each scratch. A series of parallel scratches can be created in the sample. The full details of this test are described in international standard ISO 1518-.

The UV test was used to simulate the degradation caused by sunlight. Full details of this test are described in ASTM Standard G53-88. The sample was exposed to uv light. The exposure conditions used here were: UVA lamp at 340 nm; power of the UV lamp: 300W; timing of UV exposure: 1000 hours; UV exposure temperature: 60 ℃; no coagulation exposure was performed. No color change occurred after the test, preferably a color change Δ Ε^＊Should be less than 2. Delta E^＊Calculated as follows: delta E^＊＝√(ΔL^＊2+Δa^＊2+Δb^＊2) Wherein L is measured according to the CIElab scale^＊a^＊b^＊。

The coagulation test is used to evaluate the performance of the sample in a humid ambient atmosphere and to pinpoint any defects in the protection of the sample against corrosion. The complete details of this test are described in the standard DIN 50017. The conditions used here are: 98% relative humidity; a temperature of 40 ℃; lasting for 20 days. No blistering, i.e. local peeling of the lacquer, should be seen after the test.

Coating hardness can be measured using a Persoz pendulum. The samples were conditioned at a temperature of 20 ℃ for at least 24 hours before the hardness measurements were made. The pendulum hardness test is based on the following principle: the amplitude of the pendulum vibration will drop more rapidly when supported on softer surfaces. The Persoz test measures the time for the amplitude to drop from 12 ° to 4 °. The full details of this test are given in international standard ISO 1522-1998.

Claims (11)

1. Glass sheet having a coating of enamel provided on at least one surface of said glass sheet, characterized in that the coating comprises 11-25% of organic substances, expressed in weight percentage, analyzed by thermogravimetric analysis measuring the amount of coating substance scratched from the cured but not heat-treated coated glass sheet, and in that the coating is in direct contact with the glass sheet,

wherein the coating extends over greater than 90% of the surface of the glass sheet.

2. Glass sheet according to claim 1, characterized in that the coating comprises pigments and glass frits.

3. Glass sheet according to any preceding claim, characterized in that the organic substance of the coating comprises at least one substance selected from the group consisting of: the reaction products of polyols, alkyds, acrylics, polyacrylics, polyacrylates, polymethacrylates, acrylamides, melamines, polycarbonates, acrylic-styrenes, vinyl-acrylics, urethanes, polyurethanes, polyesters, polyolefins, urethane alkyds, polyureas, amino resins, polyamides, epoxies, phenolics, silicones, PVC, PVB, water-based resins, and photo-curable chemicals.

4. Glass sheet according to claim 3, characterized in that the organic substance of the coating comprises a polyol and melamine.

5. Glass sheet according to claim 1, characterized in that the coating has a thickness of 10 to 150 μm.

6. Glass sheet according to claim 5, characterized in that the coating has a thickness of 15 to 100 μm.

7. Glass sheet according to claim 1, characterized in that an adhesion promoter is present at the surface of the glass sheet.

8. Glass sheet according to claim 1, characterized in that the glass sheet comprises a further coating applied on top of the enamel coating, further from the glass sheet.

9. Glass sheet according to claim 1, characterized in that the glass sheet is heat treatable.

10. Glass sheet according to claim 1, characterized in that the organic substance of the coating has a softening temperature of at least 20 ℃.

11. A method for producing heat-treatable lacquered glass sheets comprising the following steps in the order recited:

-providing a glass sheet;

-applying on at least one surface of the glass sheet a coating of enamel containing 11-25% of organic substances, expressed in weight percentage, wherein the coating extends over more than 90% of the surface of the glass sheet; and is

-curing the coating so that the enamel hardens and adheres to the glass but has not yet been melted or sintered.