Procedure for reproduction of a photographic picture in an article of glass

SWEDEN (12) PATENT (13) C2 di) 526 280 (19) SE (51)

International class ⁷

C03C 17/00, B44C 1/00

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PATENT AND REGISTRATION (45) (41) (22) (24) (62) (86) (86) (83)

Patent issued 2005-08-16

Application generally available 2005-08-16 The patent application was filed on 22 March 2004

Running day 2004-03-22

Tribal application number

International filing day

Filing date for European patent application

Deposit of microorganism (21) Patent Application Number 0400721 ​​7

Application received as:

Swedish patent application completed international patent application with number □ converted European patent application with number (30) Priority information (72) INVENTOR (74) EMPLOYEE (54) TITLE (73) PATENT LAW Nadja Ekman, Katarina Bangata 17 116 39 Stockholm SE

Ewa Stackelberg, Regeringsgatan 70 A 111 39 Stockholm SE Nadja Ekman, Stockholm SE Ewa Stackelberg, Stockholm SE Bo Erixon

PROCEDURE FOR REPRODUCING A PHOTOGRAPHIC IMAGE IN A GLASS ARTICLE (56) QUOTE PUBLICATIONS:

JP Al 4 285 039 (57) SUMMARY. The invention relates to a method for applying images, preferably color images, to the surface of a glass article. The images are separated into different templates for their colors, for example silkscreen printing, or for another method of applying the colors to the glass.

The colors are burned according to a sequence diagram into the surface of a glass article to level with it.

The numbers in parentheses indicate the INID code.

526 280

Summary

The invention relates to a method for applying images, preferably color images, to the surface of a glass article. The images are separated into different templates for their colors, for example silkscreen printing, or for another method of applying the colors to the glass.

The colors are burned according to a sequence diagram into the surface of a glass article to level with it.

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The present invention relates to a method for reproducing an image in a glass article. More specifically, the invention relates to a method for reproducing color images, especially photographs, in a glass article.

It is known to provide glass surfaces with different types of decoration or images, for example by printing or painting images directly on the glass in a mechanized or manual manner. However, such application methods have the disadvantage that the images have low resistance. Furthermore, through such simple application method limited expression possibilities are obtained, and a lasting high-quality appearance cannot be achieved.

US-A-5,269,826 discloses a process for producing decorated glass ceramic articles. This procedure appears to be primarily intended for ceramic hobs, where wear is evident. It is therefore desirable to be able to apply a relatively thick color layer to the glass surface. This known process comprises a preliminary process step, which means that the surface of the glass article is heat treated with a succinic acid at a temperature between 50 and 800 ° C. Subsequently, the glass is decorated with a ceramic color, for example a commercially available suspension of a powder with oxides, and with lead borate as the binder. After the pattern is applied, the article is burned in the oven. According to the patent, treating with Brönsted acid causes the ceramic color to sink into the glass during the subsequent firing, and slowly crystallizes, whereby the glass surface after the burn, despite a thick color layer, seems relatively smooth.

EP-A1 0778 154 discloses a process for multicolor printing on glass or other transparent materials, the printed image being light transmissible. Printing is done by silk screen method and inks, of which four colors are used. The colors must dry through various physical reactions, referred to as drying for a period of up to 10 seconds by visible light. No smearing of the paint in the glass surface occurs.

A further method of multi-color printing on a glass surface is known, where the different colors have substantially equal melting temperatures which are in a temperature range uncritical to the glass. Subsequent firing takes place for a short time of only 2 to 6 minutes and at a temperature not exceeding 660 ° C. Thus, only the printed colors are melted, while the glass remains virtually unaffected. The advantage of this known method is that it is fast and suitable

526 280 for industrial production.

One problem with the burning of ceramic colors on flat standard glass, a so-called float glass, is that the surface of the glass becomes cloudy and thus less transparent than before the burning. The phenomenon is called seizure. This is due to the fact that float glass has, above all, the side thereof, which during the manufacture lay against the tin bath, doped with tin ions. Such have an affinity for siliceous materials such as glass, and form the fitting.

Summary of the Invention

The object of the present invention is to provide a method for reproducing color images in glass, especially photographs with a high degree of detail.

A further object is to provide a method for reproducing color images in glass in such a way that the imaged glass is color resistant and has a high brightness.

This object is achieved by the method set out at the outset which comprises the steps of:

• providing an image containing one or more colors; • transferring the image to a surface of the glass article by applying said color or colors to the surface; and • burning the colored article for a specified time at a suitable temperature, whereby a portion of at this time a maximum temperature is reached at which said colors melt into the glass.

By such a method, it is possible to produce glass products with complicated image motifs, whereby the images are completely blended into the glass, thus forming an integral part of the glass. In this way, opaque, transparent and semi-transparent colors can be used. Because the colors blend into the glass, the product is very resistant to abrasion, ie the images have the same high surface resistance as the glass.

According to a development of the method, the colors of the image during the burn are completely blended into the surface of the glass. This ensures that all the paint after the burn forms an integral part of the glass. After burning, the surface will not show any elevations caused by the colors, but these have completely flatly joined the glass. However, the glass with a suitable shaped support can be phased to soften during firing, highlighting the image in raised or lowered relief.

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According to a further development of the method according to the invention, the burning takes place according to a scheme which comprises a plurality of successive burning sequences, each of which occurs at its temperature. The burning sequences may be an initial, relatively long sequence up to a first temperature, a relatively short main sequence at a second temperature higher than the first temperature, and a terminating relatively long sequence at a third temperature lower than the second. temperature. Advantageously, said second temperature is at least 700 ° C, preferably 790 ° C, and in some cases up to 810 ° C, and under certain conditions even above.

According to a further development of the method, said color or colors comprise a ceramic color, so-called porcelain color, which can withstand the highest temperature. The colors can be opaque, transparent or a mixture of opaque and transparent colors.

According to a further development of the procedure, the surface of the substrate must be clean in importance, especially free of tenions. Thus, the glass may not be shaped on a tin bath. (Pilkington method.) Nor is there any coating, of any other material. In this way it is possible to achieve a clear glass product with a good transparency. For example, said substrate for the image may be a glass made according to the Pittsburg process, that is, roll drawn glass.

According to a further development of the method, the article is placed during the firing on a mold having a forming surface, the article being placed on the forming surface with the colored surface facing upwards from the forming surface. The forming surface may be planar or non-planar. In this way, glass articles with many different outer shapes can be manufactured according to the invention.

According to a development of the method, said color application is made by printing on the surface in one or more steps, with a color in each of the printing steps. Furthermore, preferably the surface of the substrate prior to printing is preferably flat. Advantageously, said printing of the image can be done by means of a silk screen printing method. Silk screen printing allows printing on a variety of substrates such as paper, glass, enamel and concrete. The method allows printing with opaque colors, transparent colors and colors that are semi-opaque or colloidal.

According to a further development of the method, said transfer comprises the steps of:

• separating the image into four separate images on each film, each of the images

526 280 refers to one color, and • making a print template for each of the colors, using the respective image.

Each of the films can advantageously be screened, for example by means of a so-called stochastic screen, which is adapted in coarse size and character with respect to the nature of the paint, especially viscosity and degree of dispersion.

According to a further development of the method, said separation comprises the steps of:

• preparation of a black and white negative film for each of the colors, and • exposure and magnification of each negative to a positive one with a size corresponding to the respective print template. Such are prepared for silk screen printing by means of a lattice or lamella or stomping method.

According to a further development of the method, the paint application is carried out by spraying one or more colors on the surface of the article by means of at least one nozzle. Such a color application can be done in a simple and fast way by means of a spray device of, for example, the type of inkjet printer. In this way, image processing is first done in a manner known per se by means of a scanner and a computer with an image processing program.

Description of preferred embodiments of the invention

The invention is described below with respect to preferred embodiments of the method of reproducing a color image, or color graphic, in an article of glass.

The process is based on an image, which may be a black-and-white or color photograph, a drawing, a painting or the like to be reproduced in the glass. The image can have a great deal of detail. Here is described a first embodiment of the method of reproducing a photograph by printing an image on glass with subsequent firing to a final product. According to a second embodiment of the method, the image can be spray-painted on the glass with subsequent firing to a final product.

In a first step, a separated image is produced for each color. Four different colors are used, namely the basic colors yellow, red (magenta), blue (cyan) and black. The actual separation is done digitally in a computer by means of an appropriate image processing program, whereby a black-and-white print is produced for each of the four colors.

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With traditional photo technique and using a repro camera, an original film is produced for each color in the desired format for the intended image, for example 60x80 cm. The films are then rasterized and, if necessary, the raster is placed at a selected angle relative to one of its edges, to avoid disturbing pattern formation (moiré effect). The grid may conveniently be stochastic, providing a high-quality image sharpness. The films can also be produced digitally.

The printing templates are produced by prior art, wherein the mesh size of the silk screen is selected based on the properties of the colors used.

For printing, ceramic paints, called porcelain paints, are used, which contain one or more ceramic pigments and a printing oil. The ceramic paints used, which can be of the lead-containing type, can withstand a high temperature without losing their color shade. Prior to printing, the pigments are prepared by mortar, or ball milling. The pigments are mixed with an appropriate amount of pressure oil (Heraeus Siebdruck - medium no. 218). Advantageously, a type of pigment intended for porcelain painting can be used, for example, Cebex H64 four-color series, manufacturers

Heraeus. In the described embodiment, as mentioned above, four colors are used, namely yellow, red (magenta), blue (cyan) and black. It should be noted that the black color to create a more nuanced image can be changed to dark brown (H64 228) or grain blue (Heraeus H64 196).

In accordance with the invention, the paint should be printed on a surface of the glass article. The glass is preferably a so-called culture glass made according to, for example, the Pittsburg process.

The glass is a flat glass of suitable thickness, or has at least one flat surface on which the printing is to take place. The surface of the glass should be clean from primarily tinions, but need not be dusty. The first print template, that is, the one exposed to the separated image for yellow, is attached to a frame holder, after which the silk screen cloth is moistened and color is poured over it. With the aid of a suitable tool, for example, razors, the color is spread over the cloth during printing, and the four colors are printed in turn through the four different printing templates. The colors are superimposed on the same glass surface with a fixed drying time between each printing. The colors are printed in the following order: yellow, red, blue and black (alternatively brown or dark blue). In this work, it is very important to have as accurate a match as possible, in order for the four colors to match, and the end result to be image-wise.

526 280 is perceived as a photograph.

When the inks have dried, the glass should be burnt. It is then placed on a mold having a molding surface, the printed glass surface facing away from the molding surface. This may be arbitrary, that is, substantially planar or have a desired curvature, possibly be double-curved convex or concave. A flat forming surface can be realized by means of, for example, a silimanite plate or a ceramic mold plate. The mold can also be cast, for example in plaster, to provide a desired molding surface. Such an arbitrary molding surface may also be provided by means of a powder containing powdered silicates, which are brushed or sprinkled on said plate, and built up to the desired shape, for example, to give any part of the image relief. For example, the glass placed on the mold or plate is inserted into a heat treating furnace, preferably of the so-called fusing type with heat-releasing means only in the oven roof. The mold or plate can be placed on spacer blocks located on the bottom of the oven. Thereafter, the glass is burned according to a predetermined firing schedule which comprises a number of successive burning sequences as follows. Such a scheme can be for 3 mm thick carrier glass according to the following example.

The firing is started at room temperature, and the temperature is increased to the order of 3 70 ° C, in order to keep it stable for a few minutes, before the temperature rise goes beyond 500 ° C. This process step takes place for 135 to 400 minutes, depending on the properties of the supporting glass and the colors.

In a second process step, the temperature is raised as quickly as possible, to at least 700 ° C, at certain glass types to above 820 ° C. The high temperature is maintained for one to fifteen minutes. Then, in a third step, the energy supply is stopped, and the oven temperature quickly drops to the order of 540 ° C. This temperature reduction can occur during forced ventilation of the oven. For example, the temperature of 540 ° C is maintained for 200 minutes.

The learned step means that the temperature decrease continues as the furnace gives off heat, possibly with energy additions at 420 ° C. However, heat should be added to keep the temperature in the 370 degree range for an arbitrary amount of time, for example 300 minutes.

In the final step, some cooling may be required for the oven to be ready for a new firing within 24 hours of the start of the previous one.

It should be noted that the times and temperatures indicated vary depending on the glassware

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Ί size. Steps 2 and 4 should be short, and are intended only to raise and lower the temperature of the stove, respectively. The firing thus comprises at least one initial, relatively long sequence 1, a relatively short main sequence 2, and a terminating, relatively long sequence 4 with the temperature decrease slowed down between 390 ° C and 350 ° C. The main sequence 2 occurs for a relatively short time of over 1 minute and the temperature should be at least 700 ° C.

After the burn, the pigment has flatly joined with the glass and the reproduced image in the glass is thus light and color stable.

Printing can be done in a number of steps other than four. For example, printing can be done in two, three or more steps with the corresponding number of colors.

It should also be noted that the paint application may be made by other means than the printing method described above, for example by other printing methods, or by spraying said paint or colors on the surface by at least one nozzle. Such a color application can be carried out by means of a syringe device, for example of the type of inkjet printer. The image to be reproduced on the glass can then be scanned and processed in a computer with an image processing program. According to this color application method, colors suitable for the process are to be used. The subsequent burning of the glass article takes place in the same manner as stated above.

The process can also be used to produce other glass products with reproduced images. For example, a glass slab can be placed on top of the printed surface before so-called "fusing", or after firing. This sheet of glass can then be phased in to blend with the underlying glass and the colors. Furthermore, the different colors can be printed on each glass sheet, which are then burned together in a package with the different glass sheets lying one on the other. These will then merge.

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