Field of the Invention

The present invention relates to a bifacial decorated coloured glass plate and to a method of its production.

Background of the Invention

Coloured glass plates coloured in their mass are known. However, such plates are expensive. Therefore, they are substituted by cheaper alternatives of coloured one-face coatings on glass plates .

Methods of decorating are disclosed, where coloured coating, made of organic or inorganic colours, is applied to one side of the glass plate, for example by spraying, printing or applied by a roller.

It is known to fix coloured film to one side of a glass plate.

A disadvantage of such methods is that such glass plate has different visual properties on both sides, the front side and the underside.

The same disadvantage has also the combined coloured coating with chemical or abrasive erosion of the glass plate surface on one or the other plate side.

During decorating of the glass plate surface by erosion covering masks are used.

It is known to carry out chemical erosion of the glass surface for decorative purposes by etching (frosting) by means of sulphuric acid and hydrofluoric acid fluoride salt composition.

Representation of individual components influences the final effect regarding the roughness, the etched layer depth, and the refraction of light. On places not to be etched (frosted), the glass plate is covered by a suitable covering mask, which mask

is in the form of a film or it is printed. The mask is made of a material resistant to the etching solution (paste) . The plate is immersed into the etching (frosting) solution (paste) for a certain time. Thereafter, the covering mask is washed off and removed. In this method it is expected that the covering plate material is sufficiently resistant to the chemical solution and at the same time that the material does not influence this solution chemically.

A disadvantage of using this covering mask and immersing bath is the relatively high price of the covering mask and of its application. Another disadvantage is its low accuracy in using a decor utilising size of individual elements, printing dots, of the diameter 0.05 mm. The so called running of the ink into sides brings about qualitative problems that disqualify this technology in use for decors utilising individual printing dots being of diameter about 0.05 mm.

To obtain coloured glass plates, it is also known to stick a coloured film between two glass plates, or to create a bifacial coloured decor on a glass plate by spraying or printing it, etc. A disadvantage of such methods is that after the subsequent treatment, the plates cannot be thermally treated by thermal curing or bending because the decor would suffer in the place of contact with the thermal treatment equipment .

Summary of the Invention

Disadvantages of the existing methods of obtaining coloured decorated plates, and this obtaining of a front side or of an underside, and limited application resulting from the impossibility of a subsequent thermal after treatment, are removed by a bifacial decorated coloured glass plate and by a method of producing of its coloured decor according to the invention, which decor allows obtaining of a coloured glass plate, where there is no visual difference between one and the

other side (there is no front side and underside) , and at the same time, the plate is able to be moved on one determined side on rollers of the thermal boxes to be thermally cured or bent without being damaged at high temperatures above 600 ⁰ C.

The invention consists in that light diffusion and light reflection from individual small elements of decor, and leaving of certain areas of the glass plate without any decor for direct light passage, but influenced by light decomposition at edges of individual elements of the decor on both sides of the plate, are used. In case of a suitable size of individual decor elements or in case of their alignment into continual patterns and their density, optical phenomena similar to light passage through a narrow slit can take place.

The resulting light effect consisting of individual optical phenomena so as reflection, decomposition, partial transmittance through the decorated element, and light diffusion appear to be light transmittance in mass through a coloured glass plate, and this identically from both sides.

On one side of the plate is a decor with pattern, formed by a system of individual coloured elements (dots) of size 0.02 to 2 mm that can be arranged continually into patterns, e.g. lines. Between individual elements or continual patterns, there are slits having the size of 0.001 to 2 mm, whereby the whole area of the slits makes 5 % maximally of the decorated area. Therefore, 95 % maximally of the original area is covered to allow partial light transmittance through the free area. The decor with pattern, formed by a system of individual coloured elements, can be covered by non-transparent or semitransparent coating or film up to 100 % of the area.

By selecting the density and size of elements on the plate, it is possible to obtain various transparency and colouring of the glass plate, and this also selectively. Eventually, both sides of the plate can have different arrangement of the elements.

Said elements are preferably made of a paint resistant to temperature above 600 ⁰ C (paints used in glass, ceramic, metal, enamel making industries, etc.) to allow subsequent thermal treatment. Said paints are applied by standard technologies, for example by serigraphy, spraying across a template, applying by a roller, etc.

The decorating elements can be of one colour or of more colours, they can form multicoloured patterns and the slits between them can by covered by a transparent coating. They can be made of a paint, which paint can be one-component or multi-component, not resisting to high temperature.

The coloured decor can be formed by a combination of elements, a paint and a coloured patterned or non-patterned film, or it is made of a patterned printed coloured film.

On the other side of the glass plate a decor is formed with a pattern formed also by a system of individual elements of the size from 0.02 to 2 mm that can be arranged into continuous formations that can be different from the decor of the first side. However, said elements are formed by chemical erosion of the glass surface, for example by etching or by abrasive erosion of the glass surface, for example by sanding. Both methods can be provided by standard methods, for example by etching paste or by etching or sanding across a covering mask. Covering of the original area is maximally 95 % to provide partial passage of light through the free area.

The percentage of coverage of the original plate side areas influences the obtained colouring and transparency of the glass plate.

At the same time, the other side of the plate is able to be in contact with rollers of the thermal equipment without any damage and also at temperatures above 600 ⁰ C.

By the solution according to the invention it is possible to obtain a semi-lustre (according to the percents of the surface covered by decor) coloured transparent glass plate, suitable for

next processing - formatting, grinding, drilling, final thermal treating (thermal curing, bending) .

The method of producing a bifacial coloured glass plate comprises that one side of the plate is coated with a coloured decor with a pattern formed by a system of individual coloured elements having the size of 0.02 to 2 mm or arranged into continuous formations, for example lines, so that between individual elements or continuous formations there are slits having the size from 0.001 to 2 mm, and the total area of the slits between the elements is minimally 5 % of the decorated area, eventually, the colour decor with pattern is covered by non-transparent or semitransparent coating or film up to 100 % of the area, and further providing of the other side of the plate also by a decor of said pattern from elements that are created by chemical erosion of the glass surface, e.g. by etching or by abrasive erosion of the glass surface, e.g. by sanding, and after the time necessary for etching or abrasion the surface is washed off by water.

Said system of elements on the other side of the plate is formed preferably by etching using a covering mask, which mask consists of a basic compound mixed with a curable liquid carrier at a given ratio and chemically reacting with the etching solution by neutralization, and after its curing (by time, heat, UV lamp, etc.) the etching solution is applied to the whole area, which etching solution is washed off by water together with the covering mask after the period of time necessary for the etching.

Elements can be formed in various density, size, and arrangement from one or more colours and so multicoloured patterns can be formed and the slits can be covered by a transparent coating. They can be formed by a paint resistant to high temperatures or by one-component or multi-component paint non-resistant to high temperature .

The coloured decor is preferably formed by a combination of a paint and a coloured film or it is formed by a coloured printed film.

The covering mask is particularly preferable because of its very fine patterns with printing dots having diameter about 0.05 mm. It is from a solution - liquid that can be cured by time, heat, or UV lamp, etc. and some of the technically available bases (hydroxides) . For example, mixtures of paraffin and calcium hydroxide or solution of with UV lamp cured lacquers, paints or inks, mixed with calcium hydroxide or another basic compound. Components ratio in this mixture is adjusted so that the mixture is applicable by a suitable technology, for example by printing, to the surfaces of glass to the places to be without any decor. After curing, etching (frosting) solution (paste) , prepared by standard method used in the existing technologies, is applied to the whole surface of the glass. Application can be made by a roller, serigraphy, or by spraying. After application of the etching (frosting) solution (paste), both components, the solution (paste) and the basic covering mask are partially neutralized in the place of contact, whereby, neutralization boundary is formed. Thereby, action of the etching (frosting) solution (paste) exactly and distinctly limited only to the places without the basic mask is obtained. Owing to the chemical reaction (neutralization) , no running of the etching process under the covering mask, so as it is the case in case of the standard methods, is observed. After the time necessary to carry out the etching process, the glass surface is washed off by a strong flow of water, which water washes off both the etching (frosting) solution (paste) and the mask used. The resulting effect of using such mask is exceptionally sharp outline of the pattern.

Examples of invention embodiments

The starting material for making of a coloured glass plate is a planar glass plate of the size 6 x 5 m, with thickness 2 to 25 mm, which plate is transparent or slightly coloured. Coloured decor with a pattern formed by a system of individual colour elements, having the size from 0.02 to 2 mm is applied on a clean surface of one side of the plate so that there are slits having the size from 0.01 to 2 mm between the individual elements. The elements are made of an inorganic paint, resistant to temperatures above 600 ⁰ C, in such density that minimally 5 % of the original area remains free . Serigraphy or other standard technologies, e.g. spraying across a template, injecting, etc., are used to apply the paint. After curing of the paint, this layer can be covered also by non-transparent or semitransparent coating or film up to 100 % of its area.

After curing of the paint, the other side of the plate is decorated by a semi-transparent decor comprised of elements having the size from 0.02 to 2 mm, with spacing between dots from 0.001 to 2 mm, uniformly up to the maximum coverage 95 % of the original area. Individual elements can be continuously arranged into formations.

But they are always arranged so that they optically cooperate with the first plate side and they are coloured according to the first side. Thereby, the same visual perception is obtained both for the front side and the underside of the plate, and at the same time, the other side is able to be in contact with rollers of the heat producing equipment without any damage even at temperatures above 600 ⁰ C. The semitransparent decor is formed by printing of the etching paste on glass or by printing of the covering template for standard methods of etching by etching solutions or by abrasive sanding. Places not to be etched are covered by a covering mask.

In this case the covering mask is formed so that for two parts of the standard UV-lamp curable ink 1 part of calcium hydroxide is added, and this mixture is kneaded to form thick paste, which

paste is then applied to the glass plate in a serigraph machine in places that are to be without any decor and the paste is cured by UV lamp.

On a roller line the plate is transported under the spraying platform, where the etching (frosting) solution or paste is sprayed on one side. The solution or paste is of such viscosity that it holds uniformly on the sprayed surface. The bottom side of the plate does not require to be protected.

After the time necessary for etching (frosting) the plate is transported into a washing box and the surface is washed off by a flow of pressurized water, which water washes off both the etching solution and the covering mask.

The plate is transported into a box for final washing and drying. Then, the glass plate is prepared for further use.

To obtain the required visual results the solution according to the invention allows a number of combinations, all being within the scope of the claims.

The smaller the elements are, i.e. nearer to the size 0.02 mm, and the smaller is the distance between them, or between the continuous parts of formations from them, the better the originally uncoloured elements absorb the colour spectrum coming out from the coloured elements. By selection of the density and the size of elements, and this also selectively within the plate, it is possible to obtain various transparency and colour of the plate. Sometimes, it is preferable to use also different arrangement of elements on both sides of the plate.

Standard technological methods of applying coloured decor are used, e.g. serigraphy, spraying across a template, applying by a roller, Rotocolor, etc. For the chemical treatment of the surface, for example etching by an etching paste or across a covering template by etching solutions is used. Abrasive methods are also common, for example grinding or sanding.

To allow the possibility of thermal after-treatment, paints resistant to temperatures above 600 ⁰ C (glass and ceramics

paints, etc.) are used. In other cases organic or inorganic paints are used.

On the decorated side, the plate is chemically or abrasively resistant to damage during passage at temperatures necessary for further thermal treatment - thermal curing, hardening and bending .