Method For Manufacturing A Multi-Color Dental Restoration

Abstract

A process for the preparation of multi-coloured dental restorations is described, in which glasses and glass ceramics with various compositions are given the shapes of dental restorations and colour changes are effected in the glasses and glass ceramics by irradiating them with artificial electromagnetic radiation and subjecting them to a heat treatment.

Claims

1. A process for the preparation of a multi-coloured dental restoration, in which a) a glass or a glass ceramic is given the shape of a dental restoration, and b) in at least one part of the glass or the glass ceramic a colour change is effected by irradiating the at least one part with artificial electromagnetic radiation and subjecting this irradiated part to a heat treatment.

2. The process according to claim 1, in which the irradiating and the heat treatment in step b) is performed in one step.

3. The process according to claim 1, in which the glass and the glass ceramic comprise at least one oxidizable component and at least one reducible colouring component.

4. The process according to claim 1, in which the glass and the glass ceramic comprise Ce, calculated as CeO.sub.2, in an amount of 0.01 to 1.5 wt.-%.

5. The process according to claim 1, in which the glass and the glass ceramic comprise Ag, calculated as Ag.sub.2O, in an amount of 0.0005 to 1.3 wt.-%.

6. The process according to claim 1, in which the glass and the glass ceramic comprise Au, calculated as Au.sub.2O, in an amount of 0.0001 to 0.65 wt.-%.

7. The process according to claim 1, in which the glass and the glass ceramic comprise Ce as well as Ag and/or Au.

8. The process according to claim 1, in which the glass and the glass ceramic comprise CI, Br and/or I in an amount of 0.0001 to 0.9 wt.-%.

9. The process according to claim 1, in which the glass and the glass ceramic comprise P.sub.2O.sub.5 in an amount of 0.5 to 11.0 wt. %.

10. The process according to claim 1, in which the glass and the glass ceramic comprise 1.0 to 12.0 wt.-% K.sub.2O.

11. The process according to claim 1, in which the glass and the glass ceramic comprise 0 to 14.0 wt.-% Al.sub.2O.sub.3.

12. The process according to claim 1, in which the glass and the glass ceramic comprise at least one of the following components in the amounts given: TABLE-US-00022 Component wt.-% SiO.sub.2 61.0-88.0  Li.sub.2O 5.0-24.0 Al.sub.2O.sub.3 .sup. 0-14.0 P.sub.2O.sub.5 0.5-11.0 Ce, calculated as CeO.sub.2 0.01-1.5  Ag, calculated as Ag.sub.2O 0.0005-1.3   Au, calculated as Au.sub.2O 0.0001-0.65  

13. The process according to claim 1, in which the radiation has a wavelength of not more than 380 nm.

14. The process according to claim 1, in which the heat treatment is effected at a temperature in the range of 300 to 1000° C.

15. The process according to claim 1, in which the heat treatment is effected for a duration of up to 120 min.

16. The process according to claim 1, in which in the at least one part of the glass ceramic the colour change is effected by heating the at least one part to at least 150° C. and irradiating it at this temperature.

17. The process according to claim 1, in which in the at least one part of the glass ceramic the colour change is effected by first subjecting at a temperature T.sub.1 to a first irradiating and then subjecting the at least one part at a temperature T.sub.2 to a first heat treatment, and then subjecting the at least one part or another part of the glass ceramic at a temperature T.sub.3 fora second irradiating and simultaneously a second heat treatment, wherein T1<T.sub.2 and T.sub.3<T.sub.2.

18. The process according to claim 1, in which in the at least one part of the glass or the glass ceramic a yellow colouring is effected and in another part of the glass or the glass ceramic a red colouring is effected.

19. The process according to claim 1 in which the glass and the glass ceramic are selected from the group consisting of lithium silicate glass, lithium aluminosilicate glass, lithium silicate glass ceramic, lithium aluminosilicate glass ceramic and quartz glass ceramic.

20. The process according to claim 19, in which the glass ceramic comprises lithium metasilicate, lithium disilicate, low quartz or lithium aluminosilicate as main crystal phase.

21. The process according to claim 1 in which the glass and the glass ceramic in which the colour change is effected, consist of only one glass and glass ceramic, respectively.

22. The process according to claim 1, in which the glass and the glass ceramic are given the shape of the dental restoration by pressing or machining.

23. The process according to claim 22, in which the machining is effected in a CAD/CAM process.

24. The process according to claim 1, in which the dental restoration is a bridge, an inlay, an onlay, a veneer, an abutment, a partial crown, a crown or a facet.

25. A multi-coloured dental restoration which is obtainable by the process according to claim 1.

26. (canceled)

27. (canceled)

Description

EXAMPLES

[0130] Glasses with the chemical compositions specified in Tables 1 to 5A were prepared. For this, a corresponding batch of raw materials, such as oxides, carbonates, phosphates and halides, was melted at a melting temperature (T.sub.s) of from 1000 to 1650° C. for a melting duration (t.sub.s) of from 60 to 300 min. Optionally, the preparation of the glass melt was effected in a two-step process with two melting temperatures (T.sub.s1, T.sub.s2) and two melting durations (t.sub.s1, t.sub.s2).

[0131] The components of the glasses and glass ceramics, unless otherwise indicated, are calculated as oxides, as is usual with glasses and glass ceramics.

[0132] Multi-coloured dental restorations were prepared from the glasses by means of the process according to the invention, wherein the conditions specified in Tables 6 to 16 were used for the irradiation and heat treatment. In Tables 6 to 16 the following meanings apply [0133] T.sub.g glass transition temperature, [0134] T.sub.s melting temperature, [0135] t.sub.s melting duration, [0136] T.sub.N nucleation temperature, [0137] t.sub.N nucleation duration, [0138] QT mercury vapour lamp, type TQ 150 high-pressure Hg lamp from Heraeus, Hanau, Germany, [0139] LED LED light source, type LCS-0310-03-23 from Mightex Systems, Ontario, Canada, or type M300L4 from ThorLabs Inc., NJ, USA, [0140] σ.sub.B biaxial strength, determined according to ISO 6872 (2008).

[0141] The process steps given in Tables 6 to 16 are listed according to their temporal sequence, wherein process steps listed at the top in the respective table are effected earlier than process steps listed further down.

[0142] A Programat-type furnace from Ivoclar Vivadent AG was used for all heat treatments indicated in the examples.

[0143] Crystal phases of glass ceramics were determined by means of X-ray diffraction analyses.

[0144] The colour values (L*a*b) of glass ceramics produced were determined in the measurement range of 400-700 nm by means of a CM-3700d spectrophotometer (Konica-Minolta). The CR value (translucency) was determined according to British Standard BS 5612.

TABLE-US-00003 TABLE 1 Example 1-5 6-8 9 10 11 12-13 14-16 17 18 19 20 21 Composition wt.-% wt.-% wt.-% wt.-% wt.-% wt.-% wt.-% wt.-% wt.-% wt.-% wt.-% wt.-% SiO.sub.2 70.21 70.11 73.91 71.48 72.44 73.70 73.73 70.62 70.6 70.51 71.44 68.11 Li.sub.2O 10.97 10.96 12.68 14.22 14.41 15.29 15.31 11.04 11.04 11.02 11.17 19.92 Na.sub.2O 2.58 2.58 2.25 2.25 2.00 2.60 2.60 2.59 2.63 K.sub.2O 3.93 3.92 3.42 3.42 3.42 3.99 3.99 3.94 3.94 3.94 4.00 4.13 Al.sub.2O.sub.3 6.80 6.79 3.70 4.60 3.70 3.51 3.51 6.83 6.83 6.82 6.92 3.64 SnO* 0.07 0.07 0.07 0.07 0.07 0.07 0.08 CeO.sub.2 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.09 0.03 0.03 Sb.sub.2O.sub.3 0.40 0.40 0.40 0.40 0.40 0.41 0.44 Ag.sub.2O 0.12 0.25 0.12 0.12 0.12 0.12 0.12 0.13 AgCl* 0.09 0.03 0.03 0.05 P.sub.2O.sub.5 4.89 4.89 3.42 3.42 3.42 3.39 3.40 4.91 4.91 4.91 3.21 3.52 *used as raw material

TABLE-US-00004 TABLE 2 Example 22 23-25 26 27 28 29 30 31 32 33 34-38 39 40-53 Composition wt.- % wt.-% wt.-% wt.-% wt.-% wt.-% wt.-% wt.-% wt.-% wt.-% wt.-% wt.-% wt.-% SiO.sub.2 73.67 75.17 72.78 74.55 73.11 72.89 72.89 73.68 73.71 73.716 73.713 72.771 73.527 Li.sub.2O 13.09 13.35 13.92 12.36 14.54 14.50 14.50 15.30 15.31 15.31 15.31 15.11 15.27 Na.sub.2O 2.23 2.25 2.24 2.21 1.75 2.00 2.00 3.99 3.99 3.99 3.99 3.94 3.98 K.sub.2O 3.42 3.42 3.42 Al.sub.2O.sub.3 7.33 5.55 7.38 7.28 3.70 3.70 3.70 3.51 3.51 3.51 3.51 3.46 3.50 SnO* 0.07 0.07 0.07 0.07 0.03 0.025 0.025 0.025 0.025 CeO.sub.2 0.03 0.03 0.03 0.03 0.031 0.031 0.031 0.06 0.03 0.032 0.032 0.031 0.032 Sb.sub.2O.sub.3 0.40 0.40 0.40 0.40 Au.sub.2O 0.07 0.02 0.004 0.007 0.0004 0.006 Ag.sub.2O 0.12 0.12 0.10 0.06 AgCl* 0.026 0.013 0.013 0.003 0.0105 AgBr* 0.034 AgI* 0.043 P.sub.2O.sub.5 3.06 3.06 3.08 3.04 3.42 3.42 3.42 3.39 3.40 3.40 3.40 4.66 3.65 *used as raw material

TABLE-US-00005 TABLE 3 Example 54 55 56 57 58 59 60 61 62 63 64 65 66 67 Composition wt.-% wt.-% wt.-% wt.-% wt.-% wt.-% wt.-% wt.-% wt.-% wt.-% wt.-% wt.-% wt.-% wt.-% SiO.sub.2 75.59 70.24 69.23 72.68 71.79 73.13 73.37 72.90 70.08 70.04 70.03 70.06 73.65 73.49 Li.sub.2O 15.69 14.58 14.38 15.09 14.91 15.19 15.23 15.14 14.55 14.54 14.54 14.55 15.30 15.25 K.sub.2O 4.08 3.80 3.75 3.93 3.89 3.96 3.97 3.95 3.79 3.79 3.78 3.79 3.99 3.98 MgO 4.98 CaO 4.95 SrO 5.03 ZnO 5.01 Al.sub.2O.sub.3 3.60 3.33 3.29 3.46 3.42 3.37 3.50 3.47 3.34 3.33 3.34 3.34 3.51 3.50 ZrO.sub.2 1.13 SnO* 0.03 CeO.sub.2 0.03 0.03 0.03 1.00 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.06 CeF.sub.3 0.36 AgCl* 0.03 0.03 0.03 0.50 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.03 CuCl* 0.04 Ta.sub.2O.sub.5 0.81 Nb.sub.2O.sub.5 0.49 MoO.sub.3 2.61 WO.sub.3 6.10 P.sub.2O.sub.5 0.98 7.99 3.19 3.34 3.32 3.48 3.38 3.35 3.23 3.21 3.24 3.22 3.39 3.39 *used as raw material

TABLE-US-00006 TABLE 4 Example 68 69 70 71 72 73 74-75 76 77 78-79 Composition wt.-% wt.-% wt.-% wt.-% wt.-% wt.-% wt.-% wt.-% wt.-% wt.-% SiO.sub.2 70.79 76.72 68.86 73.39 68.63 79.96 71.29 73.03 72.79 72.10 Li.sub.2O 7.63 8.27 14.39 15.18 15.71 15.29 12.40 10.38 10.34 15.02 Na.sub.2O 0.94 K.sub.2O 9.57 3.61 9.99 3.96 3.93 1.07 3.40 3.64 3.63 3.95 MgO 1.71 1.85 1.60 1.86 1.85 CaO 3.10 3.36 2.32 3.38 3.37 Al.sub.2O.sub.3 3.57 3.86 3.40 3.35 3.33 4.02 3.89 3.87 3.34 Er.sub.2O.sub.3 0.70 0.34 SnO.sub.2 0.03 0.03 0.07 0.03 0.03 GeO.sub.2 4.74 1.91 CeO.sub.2 0.23 0.24 0.03 0.03 0.03 0.03 0.03 0.12 0.12 0.03 Sb.sub.2O.sub.3 0.42 Ag.sub.2O 0.12 AgCl* 0.05 0.05 0.03 0.03 0.03 0.03 0.05 0.05 0.03 P.sub.2O.sub.5 3.32 2.01 3.30 3.36 3.60 2.68 4.33 3.62 3.61 3.62 *used as raw material

TABLE-US-00007 TABLE 5 Example 80 81 82 83 84 85 86 87 88 89 90 Composition wt.-% wt.-% wt.-% wt.-% wt.-% wt.-% wt.-% wt.-% wt.-% wt.-% wt.-% SiO.sub.2 73.85 75.59 75.50 76.33 77.47 76.89 73.08 78.50 69.11 78.08 74.65 Li.sub.2O 7.96 8.15 8.14 8.23 6.42 8.29 7.88 8.46 7.45 8.42 8.05 K.sub.2O 5.67 3.57 3.56 3.60 3.51 3.63 3.45 3.71 3.26 3.69 3.53 MgO 1.78 1.82 1.82 1.84 1.79 4.96 1.90 1.66 1.88 1.80 CaO 3.23 3.31 3.31 3.35 3.26 3.37 3.21 3.43 3.03 4.38 Al.sub.2O.sub.3 3.72 3.81 3.80 3.85 3.74 3.88 3.68 11.93 3.94 3.77 SnO.sub.2 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.03 CeO.sub.2 0.24 0.12 0.24 0.24 0.24 0.24 0.24 0.24 0.23 0.24 0.24 AgCl* 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 P.sub.2O.sub.5 3.47 3.55 3.55 2.48 3.49 3.62 3.42 3.68 3.25 3.67 3.50 *used as raw material

TABLE-US-00008 TABLE 5A Example 92 93 94 95 96 97 98 99 100 101 Composition as Exp. 23 as Exp. 28 as Exp. 29 as Exp. 30 Wt.-% as Exp. 27 as Exp. 40 Wt.-% Wt.-% Wt.-% SiO.sub.2 71.76 73.84 72.93 72.00 Li.sub.2O 14.87 14.69 10.36 7.76 Na.sub.2O 2.26 2.00 K.sub.2O 2.00 3.64 8.02 MgO 1.86 1.73 CaO 3.38 3.15 Al.sub.2O.sub.3 7.45 4.00 3.89 3.63 SnO.sub.2 0.03 0.03 SnO 0.07 CeO.sub.2 0.03 0.08 0.24 0.24 Sb.sub.2O.sub.3 0.40 Au.sub.2O AgCl* 0.02 0.05 0.05 AgBr* 0.03 AgI* 0.04 Ag.sub.2O 0.08 P.sub.2O.sub.5 3.08 3.30 3.62 3.39 Example 102 103 104 105 106 107 108 109 110 Composition as Exp. 80 Wt.-% Wt.-% Wt.-% as Exp. 31 as Exp. 32 Wt.-% as Exp. 34 Wt.-% SiO.sub.2 75.50 74.36 76.15 73.70 68.54 Li.sub.2O 8.14 8.01 7.58 15.31 20.05 Na.sub.2O K.sub.2O 3.56 3.51 3.54 3.99 4.15 MgO 1.82 1.79 1.81 CaO 3.31 3.26 3.29 Al.sub.2O.sub.3 3.80 3.75 3.78 3.51 3.65 SnO.sub.2 0.03 0.03 0.03 SnO 0.03 CeO.sub.2 0.24 0.24 0.24 0.03 0.03 Sb.sub.2O.sub.3 Au.sub.2O 0.02 0.04 AgCl* 0.05 0.05 0.05 0.01 AgBr* AgI* Ag.sub.2O P.sub.2O.sub.5 3.55 5.00 3.53 3.40 3.54 *used as raw material

Examples 1 to 8: Colour Change by Irradiation of a Glass with a Mercury Vapour Lamp and Heat Treatment

[0145] A heat treatment for the formation of crystal nuclei was first carried out on the lithium silicate glasses of Examples 1 to 5. Then, the nuclei-containing glasses were subjected to an irradiation with a mercury vapour lamp (type TQ 150 high-pressure Hg lamp, Heraeus, Hanau, Germany) for 15 to 60 min and to a heat treatment at 470 to 610° C. for 15 to 60 min. The conditions used in each case, the colours effected by the irradiation and heat treatment and the determined crystal phases of the glass ceramic produced are specified in Table 6. A nucleation duration of 0 min means that the glasses were transferred into a furnace set to the nucleation temperature after pouring, and cooled there without holding time.

[0146] After irradiation of the nuclei-containing glasses and subsequent heat treatment, yellow and red colourings were found in the glass ceramics. It was furthermore observed, e.g. in the glass ceramics of Examples 1 and 2, that a longer irradiation effected a more intense and darker colouring.

[0147] It can also be recognized from the comparison of Examples 3 to 5 that the colour effected by the colour change was dependent on the temperature of the heat treatment. The heat treatment of Example 4, which was effected at a high temperature compared with Examples 3 and 5, resulted in a more intense and darker colouring of the glass ceramic than in the glass ceramics of Examples 3 and 5.

[0148] A reduced translucency was observed in the glass ceramic of Example 4 after irradiation and heat treatment.

[0149] It is apparent from the comparison of the colour of the irradiated and heat-treated regions of the glass ceramics of Examples 6 and 8 that a more intense and darker colour could be effected by a longer irradiation.

[0150] The glass ceramics prepared in Examples 1 to 5 included 0.12 wt.-% Ag.sub.2O, whereas there was 0.25 wt.-% Ag.sub.2O present in the glass ceramics of Examples 6 to 8. From the colours which were produced in the glass ceramics of Examples 2 and 6, it becomes clear that a more intense colour can be effected if the glass or the glass ceramic contains a larger amount of Ag.

[0151] The colour changes were effected on the glass and the glass ceramic of Example 7 in two steps, which comprised in each case one irradiation and one heat treatment. The first colour change comprised an irradiation of nuclei-containing glass with a mercury vapour lamp and a heat treatment. The heat treatment of the first colour change also brought about a crystallization of the nuclei-containing glass. The glass ceramic formed in the process was irradiated again with an LED light source (LCS-0310-03-23 from Mightex Systems, ON, Canada) and subjected to a further heat treatment for the colour change and further crystallization.

TABLE-US-00009 TABLE 6 Example 1 2 3 4 5 6 7 8 Tg/° C. T.sub.S/° C. 1500 1500 1500 1500 1500 1500 1500 1500 t.sub.S/min 120 120 120 120 120 120 120 120 T.sub.N/° C. 530 530 530 530 530 530 530 530 t.sub.N/min 0 0 0 0 0 0 0 0 Irradiation of glass Radiation source Wavelength/ QT QT QT QT QT QT QT QT nm Duration/min Intensity (%) 15 60 15 15 15 60 15 45 1.sup.st heat treatment Temperature/° C. 550 550 550 610 470 550 550 550 Duration/min 60 60 15 15 15 60 15 60 Irradiation of glass ceramic Radiation source LED Wavelength (nm) 310 Duration (min) 15 Intensity (%) 100 2.sup.nd heat treatment Temperature (° C.) 600 Duration (min) 10 Crystal phases Li.sub.2SiO.sub.3 Li.sub.2SiO.sub.3 Li.sub.2SiO.sub.3 Li.sub.2SiO.sub.3 Li.sub.2SiO.sub.3 Li.sub.2SiO.sub.3 Li.sub.2SiO.sub.3 Li.sub.2SiO.sub.3 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 Colour impression of the yellow- orange- yellow orange green- red- orange- dark glass ceramic red red grey black pink red- brown

Examples 9 to 12: Colour Change by Irradiation of a Glass with an LED with a Wavelength of 300 nm and Heat Treatment

[0152] The lithium silicate glasses of Examples 9 to 12 were irradiated with radiation having a wavelength of 300 nm for 15 minutes by means of an LED (M300L4 from ThorLabs Inc., NJ, USA).

[0153] The irradiated glasses were subjected to the heat treatments specified in Table 7. The colours brought about by the colour change in the glass ceramic produced are likewise specified in Table 7. Different colourings were found in Examples 9 to 11 in glass ceramics with CeO.sub.2, Ag, Sb.sub.2O.sub.3 and SnO. A brown-yellow colouring was observed in Example 12, in which the irradiated glass included Ce, Ag and Cl.

Examples 13 to 18: Colour Change in a Ce-, Ag- and Cl-Containing Glass Ceramic by Irradiation with an LED and Heat Treatment

[0154] The lithium silicate glasses of Examples 13 to 18 were first subjected to a heat treatment for nucleation and a heat treatment for crystallization. The glass ceramics were irradiated with an LED (LCS-0310-03-23 from Mightex Systems, ON, Canada) for 15 min, wherein the radiation contained a portion with a wavelength of 310 nm. Then, the irradiated glass ceramics were subjected to a further heat treatment. The colours effected by the colour change are likewise specified in Table 7.

[0155] A very high biaxial strength advantageous for the use as dental material of 604±104 MPa was determined for the glass ceramic produced in Example 16.

Examples 19 to 21: Colour Change in a Glass Ceramic by Irradiation with an LED or Mercury Vapour Lamp and Heat Treatment

[0156] The lithium silicate glasses of Examples 19 to 21 were first subjected to a heat treatment for nucleation and a heat treatment for crystallization. The glass ceramics were irradiated with an LED (LCS-0310-03-23 from Mightex Systems, ON, Canada) or mercury vapour lamp for 15 min and subjected to a further heat treatment. The colours effected by the colour change are specified in Table 8.

Examples 22 to 27: Colour Change in a Glass Ceramic which was Crystallized by Means of Two Heat Treatments by Irradiation with an LED and Heat Treatment

[0157] The lithium silicate glasses of Examples 22 to 27 were first subjected to one heat treatment for nucleation and two heat treatments for crystallization. The glass ceramics were irradiated with an LED (LCS-0310-03-23 from Mightex Systems, ON, Canada) for 15 min and subjected to a further heat treatment.

[0158] In the glass ceramics of Examples 23 and 24 a darker colour could be effected by a longer duration of the heat treatment after the irradiation.

[0159] In the glass ceramics of Examples 23 and 25 a darker and more intense colour could be effected by a higher temperature of the heat treatment after the irradiation.

TABLE-US-00010 TABLE 7 Example 9 10 11 12 13 14 15 16 17 18 T.sub.g/° C. 458.2 451.7 449.9 453.6 453.6 453.6 453.6 T.sub.S/° C. 1400 1400 1400 1400 1400 1400 1400 t.sub.S/min 60 60 60 60 60 60 60 T.sub.N/° C. 490 490 490 490 490 530 530 t.sub.N/min 0 0 10 10 10 0 0 Irradiation of glass Radiation source LED LED LED LED Wavelength/nm 300 300 300 300 Duration/min 15 15 15 15 Intensity/% 100 100 100 100 1.sup.st heat treatment Temperature/° C. 550 550 550 550 850 850 850 900 800 600 Duration/min 15 15 15 15 15 15 15 60 10 10 Irradiation of glass ceramic Radiation source LED LED LED LED LED LED Wavelength/nm 310 310 310 310 310 310 Duration/min 15 15 15 15 15 15 Intensity/mA 400 400 400 400 400 400 2.sup.nd heat treatment Temperature/° C. 650 650 650 550 550 650 550 550 550 Duration/min 20 20 20 30 30 30 15 30 30 3.sup.rd heat treatment Temperature/° C. 800 Duration/min 10 Crystal phases Li.sub.2SiO.sub.3 Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.2SiO.sub.3 Li.sub.3PO.sub.4 Li.sub.2SiO.sub.3 Li.sub.2SiO.sub.3 Li.sub.2SiO.sub.3 Li.sub.2SiO.sub.3 Li.sub.3PO.sub.4 Li.sub.2SiO.sub.3 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 σ.sub.B (MPa) 604 ± 104 CR (translucency) 88.3 Colour impression of the light intense yellow brown- yellow yellow yellow- yellow- yellow, yellow, glass ceramic yellow yellow yellow brown light light light brown brown brown

TABLE-US-00011 TABLE 8 Example 19 20 21 22 23 24 25 26 27 T.sub.g/° C 441.8 T.sub.S/° C. 1400 1500 1400 t.sub.S/min 60 120 60 T.sub.N/° C. 530 530 460 480 480 480 480 470 510 t.sub.N/min 0 0 10 10 10 10 10 10 10 1.sup.st heat treatment Temperature/° C. 600 750 600 600 590 590 590 600 600 Duration/min 10 10 10 20 40 40 40 20 20 Irradiation of glass ceramic Radiation source LED QT LED Wavelength/nm 310 310 Duration/min 15 60 15 Intensity/mA 400 400 2.sup.nd heat treatment Temperature/° C. 550 550 550 800 780 780 780 800 800 Duration/min 60 30 30 10 15 15 15 10 10 Irradiation of glass ceramic Radiation source LED LED LED LED LED LED Wavelength/nm 310 310 310 310 310 310 Duration/min 15 15 15 15 15 15 Intensity/mA 400 400 400 400 400 400 3.sup.rd heat treatment Temperature/° C. 650 700 700 580 650 Duration/min 5 15 30 15 15 Crystal phases Li.sub.2SiO.sub.3 Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.3PO.sub.4 Li.sub.0.155Al.sub.0.155— cristo- cristo- cristo- Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 Si.sub.0.845O.sub.2 balite balite balite Li.sub.xAl.sub.xSi.sub.3−xO.sub.6 β-quartz Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 (virgilite) cristo- LiAlSi.sub.2O.sub.6 LiAlSi.sub.2O.sub.6 LiAlSi.sub.2O.sub.6 LiAlSi.sub.2O.sub.6 Li.sub.0.4Al.sub.0.4— balite Si.sub.0.6O.sub.2 Colour impression of the yellow- orange- yellow- yellow intense orange- light yellow yellow glass ceramic light brown light yellow brown yellow brown brown

Examples 28 to 30: Colour Change in a Glass Ceramic which Comprises Ag as Well as Cl or Br or I by Irradiation with an LED and Heat Treatment

[0160] Glasses were produced using AgCl, AgBr or AgI as raw material and subjected to one heat treatment for nucleation and two heat treatments for crystallization. The glass ceramics were irradiated and subjected to another heat treatment.

TABLE-US-00012 TABLE 9 Example 28 29 30 T.sub.N/° C. 470 460 460 t.sub.N/min 10 30 30 1.sup.st heat treatment Temperature/° C. 630 600 700 Duration/min 15 30 10 2.sup.nd heat treatment Temperature/° C. 880 830 870 Duration/min 1 5 2 Irradiation of glass ceramic Radiation source LED LED LED Wavelength/nm 310 310 310 Duration/min 15 15 15 Intensity/mA 400 400 400 3.sup.rd heat treatment Temperature/° C. 650 650 550 Duration/min 15 15 60 Crystal phases Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 Li.sub.2SiO.sub.3 Li.sub.3PO.sub.4 σ.sub.B/MPa 554 510 Colour impression of yellow yellow yellow the glass ceramic

[0161] A yellow colouring was observed in glass ceramics of Examples 28 to 30 after irradiation and heat treatment.

Examples 31 to 53: Colour Change in a Glass Ceramic which Comprises Ce as Well as Au and Optionally Ag

[0162] The compositions of Examples 31 and 32 included Ce and Au. In those of Examples 33 to 53, Ag was also included in addition to Ce and Au.

[0163] Lithium silicate glasses were prepared in a two-step melting process, wherein the first step was effected for 30 min at 1000° C. and the second step was effected for 60 min at 1450° C. The lithium silicate glasses were then subjected to a heat treatment for nucleation for 10 min at 480° C.

[0164] After a first heat treatment for crystallization, Examples 31 to 39 were subjected to an irradiation with an LED light source (LCS-0310-03-23 from Mightex Systems, ON, Canada) at 310 nm, 400 mA. The irradiated glass ceramics were subjected to a further heat treatment and the colour impression was determined.

Examples 31 and 32

[0165] These examples illustrate that a reddish colouring can be achieved by irradiation and heat treatment of a glass ceramic which comprises Ce and Au. A more intense red colouring could be achieved by a higher Au content.

Examples 33 to 35

[0166] These examples illustrate that a more intense colouring can be achieved by a longer heat treatment after the irradiation of a glass ceramic comprising Ce, Au and Ag. It could be observed in particular that a longer heat treatment brings about a stronger red colouring.

Examples 36 to 38

[0167] In these examples it was found that a higher temperature of the heat treatment following the irradiation effects a more intense colouring. In particular, a stronger red colouring was found at a higher temperature.

[0168] Examples 40 to 53 were first subjected to two heat treatments for crystallization and then irradiated with an LED light source (LCS-0310-03-23 from Mightex Systems, ON, Canada) at 310 nm, 400 mA. The irradiated glass ceramics were subjected to a further heat treatment and the colour impression was determined.

Examples 40 to 42

[0169] These examples illustrate that a more intense colouring, in particular a stronger red colouring, can be achieved by a longer heat treatment after the irradiation of a glass ceramic comprising Ce, Au and Ag.

Examples 42 to 44

[0170] In these examples it was found that a higher temperature of the heat treatment following the irradiation effects a more intense colouring in glass ceramics comprising Ce, Au and Ag. In particular, a stronger red colouring was found at a higher temperature.

Examples 45 to 47

[0171] The comparison of these examples with Examples 42 to 44 shows that a desired colour effect can be achieved if the heat treatment of the irradiated glass ceramic is effected for a shorter duration but at an increased temperature. A more intense colouring, in particular a stronger red colouring, could again be effected by a higher temperature.

Examples 48 to 50 and Examples 51 to 53

[0172] These examples illustrate that a more intense colouring can be effected by a longer irradiation duration. In particular, a stronger red colouring was observed in the case of a longer irradiation duration.

TABLE-US-00013 TABLE 10 Example 31 32 33 34 35 36 37 38 39 1.sup.st heat treatment Temperature/° C. 900 900 900 900 900 900 900 900 820 Duration/min 60 60 60 60 60 60 60 60 10 Irradiation of glass ceramic Radiation source LED LED LED LED LED LED LED LED LED Wavelength/nm 310 310 310 310 310 310 310 310 310 Duration/min 15 15 15 60 15 15 15 15 15 2.sup.nd heat treatment Temperature/° C. 600 600 600 600 600 650 600 550 600 Duration/min 15 15 15 20 30 10 10 10 10 Crystal phases Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 Colour impression of the red- pink yellow- yellow- yellow- red yellow- yellow light glass ceramic purple light light red red yellow orange red

TABLE-US-00014 TABLE 11 Example 40 41 42 43 44 45 46 47 48 Irradiation of glass ceramic Radiation source LED LED LED LED LED LED LED LED LED Wavelength/nm 310 310 310 310 310 310 310 310 310 Duration/min 15 15 15 15 15 15 15 15 15 3.sup.rd heat treatment Temperature/° C. 650 650 650 700 600 850 800 750 800 Duration /min 45 30 15 15 15 1 1 1 1 Crystal phases Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 Colour impression of the red- yellow- yellow- red- light pink orange- yellow orange- glass ceramic yellow light very yellow yellow pink pink red light red

TABLE-US-00015 TABLE 12 Example 49 50 51 52 53 Irradiation of glass ceramic Radiation source LED LED LED LED LED Wavelength/nm 310 310 310 310 310 Duration/min 10 5 15 10 5 3.sup.rd heat treatment Temperature/° C. 800 800 770 770 770 Duration/min 1 1 1 1 1 Crystal phases Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 Colour impression of light very light light yellow- yellow- the glass ceramic orange- orange- orange orange light pink pink orange

Examples 54 to 74 and 76 to 78: Colour Change in a Glass Ceramic by Irradiation with an LED and Heat Treatment

[0173] The glasses of these examples were first subjected to a heat treatment for nucleation and a heat treatment for crystallization. The glass ceramics were irradiated with an LED light source (LCS-0310-03-23 from Mightex Systems, ON, Canada) and subjected to a further heat treatment.

[0174] These examples illustrate that a colour change can be effected by means of irradiation and heat treatment in glass ceramics with clearly different compositions, e.g. with low (Example 54) or high (Example 55) P.sub.2O.sub.5 content, high Ce and Ag content (Example 57) or with ZrO.sub.2 content (Example 61).

Examples 71 and 77

[0175] These examples illustrate that the colour change effected by irradiation and heat treatment can be combined with other colouring processes. The Er.sub.2O.sub.3 present in the compositions of Examples 71 and 77 led in the glass ceramic produced to a slight red colouring, although the overall impression of the glass ceramic irradiated and heat-treated according to the invention was yellow. The red colouring of the glass ceramics of Examples 71 and 77 was quantified by a determination of the a* values. The a* values were increased compared with glass ceramics which included no red colouring component, such as Example 70.

Example 78

[0176] The examination of the chemical resistance according to ISO 6872 (2008) of the glass ceramic according to Example 78 resulted in an acid solubility of 18 μg/cm.sup.2.

Examples 80 to 90: Colour Change in Low Quartz and Lithium Aluminosilicate Glass Ceramics

[0177] The glasses were produced in a two-step melting process and subjected to a heat treatment for nucleation. After a heat treatment for crystallization, a colour change was carried out by irradiation and heat treatment and the obtained crystal phases were determined.

[0178] The examples illustrate that a colour change can also be effected by irradiation and heat treatment in glass ceramics which have low quartz or lithium aluminosilicate as main crystal phase.

TABLE-US-00016 TABLE 13 Example 54 55 56 57 58 59 T.sub.g/° C. 455.5 474.7 461.9 T.sub.S1/° C. 1400 1400 1400 1450 1400 1400 t.sub.S1/min 60 60 60 30 60 60 T.sub.S2/° C. 1650 t.sub.S2/min 30 T.sub.N/° C. 490 490 540 480 480 490 t.sub.N/min 10 10 10 10 10 10 1.sup.st heat treatment Temperature/° C. 840 820 820 900 810 850 Duration/min 15 15 30 60 10 10 Irradiation of glass ceramic Radiation source LED LED LED LED LED LED Wavelength/nm 310 310 310 310 310 310 Duration/min 15 15 15 15 15 15 Intensity/mA 400 400 400 400 400 400 2.sup.nd heat treatment Temperature/° C. 550 550 550 550 550 550 Duration/min 15 15 15 15 15 60 3.sup.rd heat treatment Temperature/° C. 550 Duration/min 45 Crystal phases Li.sub.2SiO.sub.3 Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 cristo- Li.sub.2SiO.sub.3 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 balite Li.sub.3PO.sub.4 WP.sub.2O.sub.7 Li.sub.2SiO.sub.3 Li.sub.2SiO.sub.3 cristo- Li.sub.2WO.sub.4 cristo- cristo- balite balite balite Colour impression of the yellow yellow orange- yellow yellow- yellow glass ceramic brown brown Example 60 61 62 63 64 65 T.sub.g/° C. 453.3 451.7 450.4 452.2 T.sub.S1/° C. 1400 1400 1400 1400 1400 1400 t.sub.S1/min 60 60 60 60 60 60 T.sub.S2/° C. t.sub.S2/min T.sub.N/° C. 500 500 480 470 470 470 t.sub.N/min 10 10 10 10 10 10 1.sup.st heat treatment Temperature/° C. 800 840 700 830 810 780 Duration/min 10 10 30 30 30 30 Irradiation of glass ceramic Radiation source LED LED LED LED LED LED Wavelength/nm 310 310 310 310 310 310 Duration/min 15 15 15 15 15 15 Intensity/mA 400 400 400 400 400 400 2.sup.nd heat treatment Temperature/° C. 550 550 550 550 550 600 Duration/min 60 15 60 60 60 60 3.sup.rd heat treatment Temperature/° C. Duration/min Crystal phases Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 Li.sub.2SiO.sub.3 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 Li.sub.2SiO.sub.3 Li.sub.2SiO.sub.3 Li.sub.2SiO.sub.3 cristo- LiSr (PO.sub.4) balite Colour impression of the yellow yellow yellow yellow yellow yellow glass ceramic

TABLE-US-00017 TABLE 14 Example 66 67 68 69 70 71 72 T.sub.g/° C. 464.4 475 474.6 463 459 T.sub.S1/° C. 1400 1400 1500 1500 1450 1450 1450 t.sub.S1/min 60 60 30 30 120 120 120 T.sub.S2/° C. 1650 1650 t.sub.S2/min 30 30 T.sub.N/° C. 490 490 490 490 470 480 480 t.sub.N/min 10 10 10 10 10 10 10 1.sup.st heat treatment Temperature/° C. 900 900 800 800 640 840 840 Duration/min 60 60 30 30 30 15 30 Irradiation of glass ceramic Radiation source LED LED LED LED LED LED LED Wavelength/nm 310 310 310 310 310 310 310 Duration/min 15 15 15 15 15 20 60 Intensity/mA 400 400 400 400 400 400 400 2.sup.nd heat treatment Temperature/° C. 550 550 550 550 640 650 650 Duration/min 15 15 60 15 5 30 15 Crystal phases Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.2SiO.sub.3 Li.sub.2Si.sub.2O.sub.5 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 α-quartz Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 cristo- balite σ.sub.B/MPa 314 327 CR (translucency) 75.59 84.61 L* 91.8 86.43 a* −2.8 2.6 b* 20.65 25.06 Colour impression of the brown brown yellow- light yellow yellow yellow glass ceramic light yellow brown Example 73 74 76 77 78 T.sub.g/° C. 456 465 471.2 462.7 T.sub.S1/° C. 1550 1500 1450 1450 1450 t.sub.S1/min 120 120 300 120 120 T.sub.S2/° C. t.sub.S2/min T.sub.N/° C. 470 480 490 490 490 t.sub.N/min 10 0 60 60 10 1.sup.st heat treatment Temperature/° C. 710 750 750 750 850 Duration/min 30 60 30 30 30 Irradiation of glass ceramic Radiation source LED LED LED LED LED Wavelength/nm 310 310 310 310 310 Duration/min 5 30 30 30 15 Intensity/mA 400 400 400 400 400 2.sup.nd heat treatment Temperature/° C. 710 750 600 550 850 Duration/min 30 5 15 60 60 Crystal phases Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 cristo- α-quartz α-quartz α-quartz Li.sub.2SiO.sub.3 balite σ.sub.B/MPa 207 CR (translucency) 66.09 64.24 64.5 L* 91.52 90.89 86.71 a* 0.89 −2.09 1.44 b* 17.03 12.76 16.92 Colour impression of the yellow- yellow yellow yellow yellow glass ceramic grey

TABLE-US-00018 TABLE 15 Example 80 81 82 83 84 85 T.sub.g/° C. 476.7 471.2 476.6 469 T.sub.S1/° C. 1500 1500 1500 1500 1500 1500 t.sub.S1/min 30 30 15 30 30 30 T.sub.S2/° C. 1650 1650 1650 1650 1650 1650 t.sub.S2/min 30 30 45 30 30 30 T.sub.N/° C. 500 490 490 500 520 490 t.sub.N/min 10 0 0 10 10 10 1.sup.st heat treatment Temperature/° C. 830 750 750 800 780 730 Duration/min 60 30 30 60 60 60 Irradiation of glass ceramic Radiation LED LED LED LED LED LED source Wavelength/nm 310 310 310 310 310 310 Duration/min 15 15 15 15 15 15 Intensity/mA 400 400 400 400 400 400 2.sup.nd heat treatment Temperature/° C. 550 550 550 550 550 550 Duration/min 10 15 15 15 10 15 Crystal phases α-quartz α-quartz α-quartz α-quartz α-quartz α-quartz Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 Ca.sub.2Al.sub.2SiO.sub.7 Colour impression of the yellow yellow yellow yellow yellow yellow glass ceramic Example 86 87 88 89 90 T.sub.g/° C. 467.9 467.3 475.6 486.8 480.6 T.sub.S1/° C. 1500 1500 1500 1500 1500 t.sub.S1/min 30 30 30 30 30 T.sub.S2/° C. 1650 1650 1650 1650 1650 t.sub.S2/min 30 30 30 30 30 T.sub.N/° C. 490 490 500 490 500 t.sub.N/min 10 10 10 10 10 1.sup.st heat treatment Temperature/° C. 800 750 800 830 800 Duration/min 60 10 60 60 60 Irradiation of glass ceramic Radiation source LED LED LED LED LED Wavelength/nm 310 310 310 310 310 Duration/min 15 15 15 15 15 Intensity/mA 400 400 400 400 400 2.sup.nd heat treatment Temperature/° C. 550 550 550 550 550 Duration/min 15 + 45 10 10 15 15 Crystal phases α-quartz α-quartz Li.sub.0.155— α-quartz α-quartz Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Al.sub.0.155— Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 Si.sub.0.845O.sub.2 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 cristo- Li.sub.2Si.sub.2O.sub.5 cristo- balite Li.sub.3PO.sub.4 balite Colour impression of the yellow light yellow yellow light glass ceramic yellow yellow

Example 91: Colour Change by Irradiation with X-Radiation and Heat Treatment

[0179] A glass ceramic was prepared according to Example 74, with the difference that the nucleation duration t.sub.N was 10 min. After the heat treatment for crystallization, Li.sub.2Si.sub.2O.sub.5 was determined as main crystal phase, and Li.sub.3PO.sub.4 and low quartz were determined as secondary crystal phases. The glass ceramic was irradiated for 2 hours with Cu—K.sub.α radiation using an X-ray diffractometer (D8 Advance, Bruker, Karlsruhe, Germany) with an operating voltage of 40 kV. After the irradiation with the high-energy radiation, which is already accompanied by a heat effect, a slight yellow colouring of the glass ceramic was already observed. The yellow colouring was intensified by the subsequent heat treatment (750° C., 10 min).

Examples 92 to 110: Colour Change by a One-Step Colouring Process

[0180] The glasses were prepared in a two-step melting process and subjected to a heat treatment for nucelation. The glasses of the examples 92 to 99 were subjected to two heat treatments and the glasses of the examples 100 to 110 were subjected to one heat treatment for crystallisation to prepare glass ceramics.

[0181] In the glass ceramics a colour change was effected in a one-step process by heating the glass ceramics to a temperature in the range of 200 to 800° C. and irradiating them in the heated state. The parameters of the heat treatments and of the colour changing process as well as the resulting colours and the crystal phases determined in the coloured glass ceramics are given in tables 15 A and 15 B.

[0182] The examples illustrate that a colour change can be effected in glass ceramics by irradiating and heat treatment also in a one step process, in which the heated glass ceramics are irradiated.

[0183] Moreover, the examples show that by means of one-step colouring processes yellow colouring or the red or pink colouring can be effected in glass ceramics. For achieving the yellow colouring typically lower temperatures are sufficient than for achieving the red colouring. The intensity of the colouring can be controlled for example by means of the amount of Ag, Au and/or Ce as well as the temperature during irradiating.

TABLE-US-00019 TABLE 15A Example 92 93 94 95 96 97 98 99 100 101 T.sub.g/C 473.5 T.sub.S1/° C. 1500 1500 1500 1500 1500 1500 1000 1500 1500 1500 t.sub.S1/min 60 60 60 60 60 60 30 60 15 30 T.sub.S2/° C. 1500 1500 1500 1500 1500 1500 1450 1500 1650 1650 t.sub.S2/min 60 60 60 60 60 60 60 60 45 30 T.sub.N/° C. 480 470 460 460 490 510 480 460 490 490 t.sub.N/min 10 10 30 30 10 10 10 30 0 10 1. Heat treatment Temperature/° C. 590 630 600 700 600 600 550 630 750 810 Duration/min 40 15 30 10 20 20 60 35 30 30 2. Heat treatment Temperature/° C. 780 880 830 870 780 800 850 810 Duration/min 15 1 5 2 10 10 7 7 Irradiation of Glass ceramic Radiation source LED LED LED LED LED LED LED LED LED LED Wavelength/nm 310 310 310 310 310 310 310 310 310 310 Intensity/mA 400 400 400 400 400 400 400 400 400 400 Duration/min 10 10 10 10 10 10 10 10 10 10 Temperature/° C. 600 500 400 500 800 600 500 400 300 400 Crystal phases Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Cristo- Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 Li.sub.2SiO.sub.3 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 balite Li.sub.3PO.sub.4 Li.sub.XAl.sub.XSi.sub.3−xO.sub.6 β-Quartz α-Quartz Li.sub.3PO.sub.4 (Virgilit) Cristo- LiAlSi.sub.2O.sub.6 Li.sub.2SiO.sub.3 balite Colour impression of yellow yellow yellow intense yellow yellow yellow yellow dark yellow Glass ceramic yellow yellow

TABLE-US-00020 TABLE 15B Example 102 103 104 105 106 107 108 109 110 T.sub.g/C 476.7 466.3 471.1 T.sub.S1/° C. 1500 1500 1500 1500 1000 1000 1000 1000 1000 t.sub.S1/min 30 15 30 15 30 30 30 30 30 T.sub.S2/° C. 1650 1650 1650 1650 1450 1450 1450 1450 1450 t.sub.S2/min 30 45 30 45 60 60 60 60 60 T.sub.N/° C. 500 490 490 480 480 480 480 480 480 t.sub.N/min 10 0 10 0 10 10 10 10 10 1. Heat treatment Temperature/° C. 830 750 730 780 900 900 900 900 700 Duration/min 60 30 30 30 60 60 60 60 10 Irradiation of Glass ceramic Radiation source LED LED LED LED LED LED LED LED LED Wavelength/nm 310 310 310 310 310 310 310 310 310 Intensity/mA 400 400 400 400 400 400 400 400 400 Duration/min 10 10 10 10 15 15 15 15 15 Temperature/° C. 300 400 200 200 700 700 700 600 700 Crystal phases α-Quartz α-Quartz α-Quartz α-Quartz Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.2SiO.sub.3 Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 Colour impression of yellow dark light light pink light intense yellow pink Glass ceramic yellow yellow yellow pink yellow

Example 111: Preparation of a Multi-Coloured Glass Ceramic in a Three-Step Colouring Process

[0184] A glass was prepared according to example 40, heated for 10 min at 480° C. for nucleation and then subjected to two heat treatments for crystallisation. The first heat treatment was performed for 60 min at 550° C. and the second heat treatment for 7 min at 850° C.

[0185] The glass ceramic was then subjected to a three-step colouring process. First of all, a red colouring was effected by irradiating (310 nm LED, 400 mA) the glass ceramic in a first step for 15 minutes at 100° C. and subsequently in a second step subjecting it to a heat treatment. The heat treatment was conducted for 10 min at 850° C. and the heating rate and the cooling rate were each 60 K min.sup.−1. In a third step a yellow colouring was additionally achieved in the red coloured glass ceramic. For this purpose, the glass ceramic was in a similar way as in examples 91 to 109 irradiated (310 nm LED, 400 mA) for 10 min at 500° C. Different areas of the glass ceramic were at least in part subjected to the first and the second irradiation.

[0186] The resulting glass ceramic showed after the third step a red colouring as well as a yellow colouring, wherein the differently irradiated parts of the glass ceramic showed different colors. In the multi-coloured glass ceramic the crystal phases lithium disilicate (Li.sub.2Si.sub.2O.sub.5) and lithium phosphate (Li.sub.3PO.sub.4) were determined.

Comparison Examples 75 and 79: No Irradiation of the Glass or the Glass Ceramic

[0187] The lithium silicate glasses of Comparison Examples 75 and 79 were subjected to a heat treatment for nucleation and a heat treatment for crystallization. Unlike the glasses and glass ceramics which were additionally exposed to an irradiation and heat treatment, e.g. the glass ceramic produced in Comparison Example 75 was uncoloured.

TABLE-US-00021 TABLE 16 Example 75 79 T.sub.g/° C. 465 462.7 T.sub.S1/° C. 1500 1450 t.sub.S1/min 120 120 T.sub.N/° C. 480 490 t.sub.N/min 10 10 1.sup.st heat treatment Temperature/° C. 750 840 Duration/min 30 30 Crystal phases Li.sub.2Si.sub.2O.sub.5 Li.sub.2Si.sub.2O.sub.5 Li.sub.3PO.sub.4 Li.sub.3PO.sub.4 α-quartz Li.sub.2SiO.sub.3 σ.sub.B/MPa 331 Colour impression of uncoloured uncoloured the glass ceramic

[0188] The glass ceramic according to Comparison Example 79, precisely like the glass ceramic according to Example 74, had a fracture toughness of 2.46 MPa m.sup.0.5 (determined as K.sub.IC value according to the SEVNB method, described in ISO 6872 from 2008).