Coloured stove sightglass with colour-neutral transmission characteristics

Abstract

A sightglass for a stove is provided that has a substrate made of transparent coloured lithium aluminium silicate glass ceramic. The sightglass has a light transmittance of 0.1% to 50%. Standard illuminant D65 light, after passing through the glass ceramic, at a thickness of 4 mm, has a colour locus in the white region W1 determined by the following coordinates in the chromaticity diagram CIExyY-2: TABLE-US-00001 White region W1 x y 0.27 0.21 0.22 0.25 0.32 0.37 0.45 0.45 0.47 0.34 0.36 0.29.

Claims

1. A sightglass for a stove, the sightglass comprising: a substrate made of transparent colored lithium aluminum silicate glass ceramic, wherein, in the wavelength range of 380 nm to 780 nm, the glass ceramic has a light transmittance of 0.1% to 50% when illuminated with a D65 standard illuminant light according to the DIN EN 410 (2011) standard, and has, when illuminated with the D65 standard illuminant light, after passing through the glass ceramic, at a thickness of 4 mm, a color locus in a white region W1 determined by coordinates in a chromaticity diagram CIExyY-2: TABLE-US-00014 White region W1 X y 0.27 0.21 0.22 0.25 0.32 0.37 0.45 0.45 0.47 0.34 0.36 0.29, wherein the substrate comprises 0.003-0.5% by weight of MoO.sub.3 as a coloring component.

2. The sightglass of claim 1, wherein the substrate comprises, as the coloring component, less than 0.2% by weight of Nd.sub.2O.sub.3.

3. A sightglass for a stove, the sightglass comprising: a substrate made of transparent coloring lithium aluminum silicate glass ceramic, wherein, in the wavelength range of 380 nm to 780 nm, the glass ceramic has a light transmittance of 0.1% to 50% when illuminated with a D65 standard illuminant light according to the DIN EN 410 (2011) standard, and has, when illuminated with the standard illuminant D65 light, after passing through the glass ceramic, at a thickness of 4 mm, a color locus in a white region W1 determined by coordinates in a chromaticity diagram CIExyY-2: TABLE-US-00015 White region W1 X y 0.27 0.21 0.22 0.25 0.32 0.37 0.45 0.45 0.47 0.34 0.36 0.29, wherein the substrate comprises from 1 ppm to less than 0.015% by weight of V.sub.2O.sub.5 as a coloring component.

4. The sightglass of claim 1, wherein the substrate has an SnO.sub.2 content of 0.05-0.8% by weight.

5. The sightglass of claim 1, wherein the substrate has an infrared transmission of 45-85% at a wavelength of 1600 nm.

6. The sightglass of claim 1, wherein the sightglass comprises in % by weight based on oxide: Li.sub.2O 2-5.5; Al.sub.2O.sub.3 16-26; SiO.sub.2 58-72; and MoO.sub.3 0.003-0.5.

7. The sightglass of claim 1, further comprising high quartz mixed crystals as a main crystal phase.

8. The sightglass of claim 1, wherein the substrate is configured as a stove sightglass and has a thickness of 2 to 8 mm.

9. The sightglass of claim 1, wherein the substrate is configured as a baking oven sightglass and has a thickness of 2 to 8 mm.

10. The sightglass of claim 1, wherein the substrate is configured as a barbecue sightglass and has a thickness of 2 to 8 mm.

11. The sightglass of claim 1, wherein the substrate comprises less than 0.01% by weight of V.sub.2O.sub.5.

12. The sightglass of claim 1, wherein the light transmittance of the glass ceramic is 0.1% to 10%.

13. The sightglass of claim 1, wherein the light transmittance of the glass ceramic is 2% to 6%.

14. The sightglass of claim 1, wherein the substrate comprises MoO.sub.3 and V.sub.2O.sub.5 as coloring components in a relationship (in % by weight) of MoO.sub.3/V.sub.2O.sub.5 that is greater than 1.

15. The sightglass of claim 14, wherein the relationship of MoO.sub.3/V.sub.2O.sub.5 is greater than 3.

16. The sightglass of claim 14, wherein the relationship of MoO.sub.3/V.sub.2O.sub.5 is greater than 5.

17. The sightglass of claim 14, wherein the relationship of MoO.sub.3/V.sub.2O.sub.5 is greater than 10.

18. A sightglass for a stove, the sightglass comprising: a substrate made of transparent coloring lithium aluminum silicate glass ceramic, wherein, in the wavelength range of 380 nm to 780 nm, the glass ceramic has a light transmittance of 0.1% to 50% when illuminated with a D65 standard illuminant light according to the DIN EN 410 (2011) standard, and that prevents viewing into the stove when the stove is not in operation and has, when illuminated with the standard illuminant D65 light, after passing through the glass ceramic, at a thickness of 4 mm, a color locus in a white region W1 determined by coordinates in a chromaticity diagram CIExyY-2: TABLE-US-00016 White region W1 X Y 0.27 0.21 0.22 0.25 0.32 0.37 0.45 0.45 0.47 0.34 0.36 0.29, and wherein the glass ceramic comprises in % by weight based on oxide: Li.sub.2O 2-5.5; Al.sub.2O.sub.3 16-26; SiO.sub.2 58-72.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIGS. 1a and b show chromaticity diagrams of the CIExyY colour space with 2 standard observer (CIExyY-2).

(2) FIG. 2 shows the transmission curves for the glass of Examples 5, 6, and 7.

(3) FIGS. 3a and 3b show the transmission curves for the glass of Examples 1, 4, 5, and 6 at different wavelengths.

(4) FIG. 4 shows the transmission curves for the glass of Examples 1, 4, and 5.

(5) FIGS. 5a and 5b show the transmission curves for the glass of Examples 6, 7, 8, and 9 at different wavelengths.

DETAILED DESCRIPTION

(6) FIGS. 1a and b show chromaticity diagrams of the CIExyY colour space with 2 standard observer (CIExyY-2). FIG. 1a depicts the black-body curve as a dotted line, the two white regions W1 and W2 as a dashed line, the colour coordinates of the inventive examples as black squares, and examples from the prior art as black crosses. The examples shown from the prior art correspond to the glass ceramic types known from WO 2012076414 A1 and commercially available glass ceramics from SCHOTT AG and Eurokera. The examples from the prior art are all outside the white region W1. All the colour loci shown relate to a material thickness of 4 mm. FIG. 1b shows an enlarged detail of FIG. 1a.

(7) FIGS. 2, 3a, 3b, 4, 5a, and 5b show the transmission curves for some crystallizable glasses detailed and the glass ceramic examples with thickness 4 mm in various wavelength ranges.

(8) The crystallizable glasses 1 to 35 were melted from technical batch raw materials that are customary in the glass industry at temperatures of 1620 C. for 4 hours. With this choice, the demands for economically viable raw materials and a low impurity content of unwanted impurities can be reconciled. After the melting of the batch in crucibles made of sintered silica glass, the melts were poured into Pt/Rh crucibles with an inner silica glass crucible and homogenized by stirring at temperatures of 1600 C. for 60 minutes. After this homogenization, the glasses were refined at 1640 C. for 2 hours. Subsequently, pieces of size about 12014030 mm.sup.3 were cast and cooled down to room temperature in a cooling oven beginning from 640 C. in order to dissipate stresses. The castings were divided into the sizes required for the studies and for the ceramization.

(9) The impurities through typical trace elements in the technical raw materials used are 200 ppm B.sub.2O.sub.3, 30 ppm Cl, 1 ppm CoO, 3 ppm Cr.sub.2O.sub.3, 200 ppm Cs.sub.2O, 3 ppm CuO, 200 ppm F, 400 ppm HfO.sub.2, 3 ppm NiO, 500 ppm Rb.sub.2O, 5 ppm V.sub.2O.sub.5.

(10) Table 1 shows a base composition for crystallizable glasses and the properties thereof. The base composition base glass 1 corresponds to the comparative glass 1 according to the prior art, which cannot be used to produce sightglasses of the disclosure. Table 1 also lists the following properties in the vitreous state: transformation temperature Tg [ C.], working temperature VA [ C.], 10.sup.2 temperature [ C.] and upper devitrification limit UDL [ C.]. For measurement of the UDL, the glasses were fused in Pt/Rh10 crucibles. Subsequently, the crucibles were kept at different temperatures in the region of the working temperature for 5 hours. The uppermost temperature at which the first crystals occur at the contact surface of the glass melt with the crucible wall determines the UDL. The glass properties of the base glass are altered to a minor degree by doping with small amounts of colouring compounds.

(11) Different contents of colouring compounds are added to the batch raw materials of this base composition, and new glasses are fused. By addition of the MoO.sub.3 component, compositions of the disclosure are obtained. The glasses thus obtained in Table 2 have the base composition of glass 1 and differ merely in the colouring compounds specified and optionally reducing additives. They are crystallized by the ceramization programs listed in Table 2. The transmission properties and scatter of the glass ceramics obtained are listed. The main crystal phase measured by x-ray diffraction is also listed. For some examples, thermal expansion between 20 C. and 300 or 700 C. was also measured.

(12) Examples 1 and 2 are comparative examples from the prior art (WO 2010102859 A1), with a V.sub.2O.sub.5 content of 0.023% by weight, which were ceramized from comparative glass 1 with different programs. Inventive examples 3 and 4 contain less than 0.015% by weight of V.sub.2O.sub.5. By comparison with V.sub.2O.sub.5-free examples, these shift light of the standard illuminant D65 more strongly in the red direction, namely to x coordinates >0.4. By contrast with Comparative Examples 1 and 2, however, the value is still in the region of x<0.5. Light transmitted through the glass ceramics of Examples 3 and 4 at a thickness of 4 mm is within the white region W1, but is not within the white region W2 owing to the V.sub.2O.sub.5 content. Examples 3 and 4 are the only inventive examples that are not also within the particularly preferred white region W2.

(13) The further Comparative Examples 16 and 26 contain more than 0.01% by weight of Cr.sub.2O.sub.3. Light of the standard illuminant D65 transmitted through such glass ceramics is no longer within the white region W1.

(14) In the case of crystallizable starting glasses of the same oxide composition, the effect of different ceramizations and the addition of reducing compounds and of shards to the batch on transmission should be noted. In the case of addition of sugar, this is oxidized without measurable residues, but affects the redox state of the glass. In the case of glass 29, 0.07% by weight of S is added to the batch as ZnS. In the glass, the analysed concentration of S is <10 ppm below the detection limit. The addition both of sugar and of S leads to a significant enhancement of colouring by Mo.

(15) FIGS. 5a and 5b show how different transmission spectra are obtained from the crystallizable glass 6 by different ceramizations. It can also be inferred from FIGS. 5a-5b and FIG. 2 that colouring with Mo sets in only with the ceramization.

(16) In the case of the glass ceramics of Table 2 with high quartz mixed crystals as main crystal phase, thermal expansion is altered to a minor degree by the doping with colouring compounds. For selected examples, thermal expansion was measured between 20 and 300 C. and between 20 and 700 C., and in each case is within a range of less than =0.07.Math.10.sup.6/K around the averages 0.27 and 0.13.Math.10.sup.6/K. The values for the non-measured examples are also assumed to be within this region.

(17) Table 3 shows the compositions of further crystallizable glasses and selected properties. Comparative glass 22, in terms of its composition, corresponds to the KeraVision glass ceramic from EuroKera. The glass doped with Fe, V, Mn and Co, after transformation to the comparative glass ceramic 29 (Table 4), does not attain the low colour of the disclosure; more particularly, light transmitted through such a glass ceramic is no longer within the white region W1. Examples 30 and 38 have a higher TiO.sub.2 content and show an enhancement of colouring with molybdenum oxide. Examples 31 and 32 produced from the crystallizable glasses 23 and 24 have been refined not with SnO.sub.2 but with As.sub.2O.sub.3. The described disadvantages of the weaker redox partner As are manifested. Compared to Sn, colouring with MoO.sub.3 is much lower, and even the addition of reducing compounds cannot significantly reduce the brightness, unlike in the case of SnO.sub.2-refined glass ceramics.

(18) The ceramization program 1 involves heating up to a temperature of 600 C. in the ceramization oven within 20 min. The oven is heated up further. The total time from room temperature to 680 C. is 23 min. The temperature range from 680 C. to 800 C. is important for nucleation. Therefore, the oven is heated up further. The total time between 680 C. and 800 C. is 19 min. Above about 800 C., the desired high quartz mixed crystal phase crystallizes. The total time from 800 C. until attainment of the maximum temperature of 918 C. is 24 min (heating rate 5 C./minute). At the maximum temperature of 918 C., hold time 10 min, the composition of crystals and residual glass is established and the microstructure is homogenized. This establishes the chemical and physical properties of the glass ceramic. Cooling is effected in a controlled manner to 800 C. (cooling rate 6 C./min), then the sample is quenched to room temperature by opening the oven door; in other words, in summary:

(19) Ceramization program 1 (ceramization time 96 min): heating within 23 minutes from room temperature to 680 C.; temperature increase from 680 to 800 C. within 19 min, involving heating at 10 C./min to 730 C., further heating at 5 C./min to 800 C.; temperature increase from 800 C. to 918 C. within 24 min and hold time of 10 min at maximum temperature; cooling down to 800 C. within 20 minutes, then rapid cooling to room temperature.

(20) In ceramization program 2, the ceramization time has been shortened. Ceramization program 2 (ceramization time 68 min): rapid heating from room temperature to 740 C. within 26 min, b) temperature increase from 740 to 825 C. within 18 min (heating rate 4.7 C./min), temperature increase from 825 C. to 930 C. within 4 min (heating rate 26 C./min), hold time of 4 min at maximum temperature, cooling down to 800 C. within 16 minutes, then rapid cooling to room temperature.

(21) An additional ceramization program 3 effected transformation to glass ceramics with keatite mixed crystals as main crystal phase. In this program, the procedure of program 1 was followed up to 800 C. Then, in a departure from program 1, heating was effected at a heating rate of 5 C./min to a maximum temperature of 960 C. with hold time 10 min. Cooling was effected from the maximum temperature at 6 C./min to 800 C., and then cooling was effected rapidly to room temperature.

(22) The glass ceramics of Examples 9 and 11 that were produced by the ceramization program 3 contain, measured by x-ray diffraction, 79% keatite mixed crystals as main crystal phase. At the same time, crystallite sizes are enlarged at about 120 nm, and so disruptive scatter occurs when display elements are used below the glass ceramic. The other glass ceramics produced with the ceramization programs 1 and 2 contain high quartz mixed crystals at generally more than 90% of the total crystal phase content. Further crystal phases are the nucleator phases ZrTiO.sub.4. At the same time, crystallite sizes are so small at less than 70 nm that no disruptive scatter occurs when display elements are used below the glass ceramic.

(23) The thermal expansion of the glass ceramics with high quartz mixed crystal as main crystal phase is 00.5.Math.10.sup.6/K in the range of 20-700 C., i.e. meets the demands for thermally stable glass ceramics. For example, thermal expansion for the base composition of example 1 is 0.13.Math.10.sup.6/K, and for Example 36 is 0.34.Math.10.sup.6/K, in the range of 20-700 C. For Example 11, the CTE is 0.710.sup.6/K in the range of 20-700 C.

(24) The transmission measurements were conducted on polished plates with the Perkin-Elmer Lambda 900 instrument. Transmission was determined on samples having a thickness of 3.5 to 4.1 mm and converted to a thickness of 4 mm. Spectral transmittances are reported for selected wavelengths. The measured spectral values in the range between 380 nm and 780 nm, which represents visible light, are used to calculate the brightness L* and the colour coordinates a*, b* in the CIELAB colour system, and the brightness Y and colour coordinates x, y to DIN 5033 in the CIE colour system for the chosen standard illuminant and observer angle 2. Chromaticity c* and the colour separation d from the colour coordinates of light of the standard illuminant D65, x=0.3127 and y=0.3290, are reported. This was calculated as follows:
d={square root over ((x0.3127).sup.2+(y0.3290).sup.2)}.

(25) For some samples, the colour coordinates in the CIELAB colour system were measured in reflectance. For this purpose, the Konica Minolta CM-700d spectrophotometer, using D65 standard illuminant, a 10 standard observer, was used to measure the colour locus in reflectance. The black trap used was the CM-A511 black glass tile from Konica Minolta. In this context, the expression measurement against a black trap means that the sample to be measured is disposed between the measuring instrument and a black trap. The values are reported for 4 mm-thick polished samples. The colour coordinates of the samples correspond to a colour-neutral black hue.

(26) The profile of the transmission curve in the range from 470 to 630 nm was used to calculate the flatness of the curve (quotient of highest to lowest transmission in this range). The wavelengths for the maximum and minimum transmission are likewise reported. The values are reported for 4 mm-thick polished samples.

(27) The scatter of the glass ceramics is determined by measuring haze. This involves measuring samples of thickness 3.5-4.1 mm that have been polished on both sides with a commercial Haze-gard plus measuring instrument from BYK Gardner (standard ASTM D1003-13) with standard light C. Scatter is characterized by the haze value in the tables.

(28) In addition, a visual assessment is conducted on the samples with a commercial white LED of the 7-segment display type (manufacturer: opto devices, model: OS39D3BWWA). The polished glass ceramic samples were placed onto the white LED at a distance of 1 mm and viewed from above at a distance of 31 cm over the entire angle range, i.e. perpendicularly to obliquely to the glass ceramic surface. Depending on the brightness of the glass ceramic sample, the luminance of the white LED at this distance at right angles to the glass ceramic plate was regulated to 60 cd/m.sup.2, or, in the case of very dark glass ceramic samples Y<0.5%, operated at maximum power. In order to rule out the influence of outside light, the assessment is undertaken in a dark chamber with low ambient lighting of about 4 lux.

(29) The visual assessments in the tables mean: 1=no scatter perceptible, 2=low but tolerable scatter, 3=visible scatter, requires additional work for the configuration of the cooktop, 4=distinctly visible scatter, intolerable. Ratings over and above stage 4 are impermissible, and those over and above stage 3 should preferably be avoided. Apart from the Examples 9 and 11 with keatite mixed crystal (KMC) as main crystal phase, the examples have no visible scatter.

(30) Apart from those cited as comparative examples, all the glass ceramics adduced by way of example are suitable for use in the sightglasses of the disclosure. They especially fulfil all the demands for use in stoves, baking ovens and barbecues.

(31) TABLE-US-00010 TABLE 1 COMPOSITION AND PROPERTIES OF THE CRYSTALLIZABLE BASE GLASS 1 WITH BASE COMPOSITION. Glass No. % by wt. 1 Composition Li.sub.2O 3.80 Na.sub.2O 0.60 K.sub.2O 0.25 MgO 0.29 CaO 0.40 SrO 0.02 BaO 2.23 ZnO 1.53 Al.sub.2O.sub.3 20.9 SiO.sub.2 65.0 TiO.sub.2 3.10 ZrO.sub.2 1.38 P.sub.2O.sub.5 0.09 SnO.sub.2 0.25 As.sub.2O.sub.3 Fe.sub.2O.sub.3 0.090 V.sub.2O.sub.5 0.023 MoO.sub.3 MnO.sub.2 0.025 Cr.sub.2O.sub.3 CeO.sub.2 WO.sub.3 H.sub.2O content (-OH) mm.sup.1 0.39 Properties in glass form Transformation temperature Tg C. 662 10.sup.2 temperature C. 1742 Working temperature V.sub.A C. 1306 UDL temperature C. 1260

(32) TABLE-US-00011 TABLE 2 DOPANTS AND PROPERTIES OF THE GLASS CERAMICS SUITABLE FOR SIGHTGLASSES OF THE DISCLOSURE AND COMPARATIVE GLASS CERAMICS 1 AND 2 Example No. 1 2 3 4 5 6 Glass No. 1 1 2 3 4 5 Base glass 1 1 1 1 1 1 Dopants (% by wt.) Fe.sub.2O.sub.3 0.090 0.090 0.120 0.088 0.088 0.088 V.sub.2O.sub.5 0.023 0.023 0.010 0.013 MoO.sub.3 0.057 0.046 0.078 0.170 MnO.sub.2 0.025 0.025 0.025 0.025 0.025 0.025 Cr.sub.2O.sub.3 CeO.sub.2 WO.sub.3 Addition to batch Ceramization # 1 2 1 1 1 1 program Properties in ceramized form Transmission, thickness 4 mm 470 nm % 1.2 0.7 2.9 2.4 13.3 2.7 630 nm % 9.9 6.6 12.6 9.5 17.2 3.9 950 nm % 73.0 71.9 66.5 67.7 60.8 45.0 1600 nm % 76.4 76.3 70.9 75.7 74.8 70.3 3700 nm % 52.0 51.1 50.0 53.2 52.2 50.4 Colour coordinates (CIE) in transmission, thickness 4 mm, D65 x 0.502 0.517 0.447 0.436 0.337 0.348 y 0.367 0.358 0.365 0.351 0.334 0.327 Brightness Y % 3.6 2.2 5.8 4.4 13.6 2.6 Colour distance d 0.193 0.207 0.139 0.125 0.025 0.035 Colour coordinates (CIELAB) in reflectance L* 25.19 24.99 25.74 26.52 a* 0.28 0.04 0.39 0.16 b* 0.66 0.78 0.80 0.80 c* 0.72 0.78 0.89 0.82 Flatness of nm 8.4 10.0 4.4 4.0 1.4 1.7 transmission 630/ 630/ 630/ 630/ 630/ 630/ (wavelength at 470 470 470 470 529 538 max./min.) Visual assessment 1 1 1 1 1 1 Haze % 0.8 0.5 1.5 1.5 1.5 1.1 Thermal expansion (10.sup.6/K) .sub.20/300 0.26 0.29 .sub.20/700 0.13 0.17 X-ray diffraction Main crystal phase HQMC HQMC HQMC HQMC HQMC HQMC DOPANTS AND PROPERTIES OF THE GLASS CERAMICS Example No. 7 8 Glass No. 6 6 Base glass 1 1 Dopants (% by wt.) Fe.sub.2O.sub.3 0.088 0.088 V.sub.2O.sub.5 MoO.sub.3 0.170 0.170 MnO.sub.2 0.025 0.025 Cr.sub.2O.sub.3 CeO.sub.2 WO.sub.3 Addition to batch 50% shards 50% shards Ceramization program 1 2 Properties in ceramized form Transmission, thickness 4 mm 470 nm 2.3 2.0 630 nm 3.9 2.3 950 nm 41.5 35.3 1600 nm 69.8 68.5 3700 nm 51.8 52.0 Colour coordinates (CIE) in transmission, thickness 4 mm, D65 x 0.338 0.329 y 0.318 0.311 Brightness Y 2.0 1.6 Colour distance d 0.028 0.024 Colour coordinates (CIELAB) in transmission L* 15.7 13.4 a* 5.2 4.5 b* 0.1 1.1 c* 5.2 4.7 Flatness of transmission 2.2 1.6 (wavelength at 630/545 630/552 max./min.) Scatter at thickness 4 mm Visual assessment 1 1 Haze 0.4 2.3 Thermal expansion .sub.20/300 .sub.20/700 X-ray diffraction Main crystal phase HQMC HQMC Example No. 9 10 11 12 13 14 Glass No. 6 7 8 9 10 11 Base glass 1 1 1 1 1 1 Dopants (% by wt.) Fe.sub.2O.sub.3 0.088 0.017 0.086 0.090 0.084 0.062 V.sub.2O.sub.5 MoO.sub.3 0.170 0.170 0.013 0.057 0.150 0.150 MnO.sub.2 0.025 0.025 0.025 0.025 0.025 Cr.sub.2O.sub.3 CeO.sub.2 WO.sub.3 Addition to batch 50% shards 0.1% sugar without nitrate Ceramization # 3 1 3 1 1 1 program Properties in ceramized form Transmission, thickness 4 mm 470 nm % 0.4 0.8 33.5 16.7 0.12 1.2 630 nm % 0.5 0.6 43.7 21.7 0.07 1.9 950 nm % 27.0 28.9 73.0 62.1 11.2 36.7 1600 nm % 60.1 75.3 76.3 75.1 56.9 71.5 3700 nm % 56.2 48.5 56.1 51.0 48.7 52.4 Colour coordinates (CIE) in transmission, thickness 4 mm, D65 x 0.341 0.290 0.3401 0.337 0.271 0.323 y 0.322 0.275 0.3553 0.339 0.264 0.305 Brightness Y % 0.3 0.5 38.2 17.6 0.1 1.4 Colour distance d 0.029 0.059 0.038 0.026 0.077 0.026 Colour coordinates (CIELAB) in reflectance L* 25.66 a* 0.15 b* 0.9 c* 0.91 Flatness of nm 1.8 1.9 1.3 1.3 2.4 1.6 transmission 630/ 630/ 630/ 630/ 470/ 630/ (wavelength at 552 567 470 524 580 553 max./min.) Scatter at thickness 4 mm Visual assessment 3 1 3 1 1 1 Haze % 9.2 0.8 10.7 1.3 2.6 0.5 Thermal expansion .sub.20/300 10.sup.6/K 0.56 0.24 .sub.20/700 10.sup.6/K 0.70 0.16 X-ray diffraction Main crystal phase KMC HQMC KMC HQMC HQMC HQMC DOPANTS AND PROPERTIES OF THE GLASS CERAMICS AND COMPARATIVE GLASS CERAMIC 16. Example No. 15 16 17 18 19 20 21 Glass No. 11 12 13 13 14 15 15 Base glass 1 1 1 1 1 1 1 Dopants (% by wt.) Fe.sub.2O.sub.3 0.062 0.080 0.062 0.062 0.061 0.062 0.062 V.sub.2O.sub.5 0.010 MoO.sub.3 0.150 0.150 0.150 0.150 0.150 0.040 0.040 MnO.sub.2 0.025 0.025 0.023 0.023 0.023 0.025 0.025 Cr.sub.2O.sub.3 0.0036 CeO.sub.2 0.060 0.060 WO.sub.3 0.050 Addition to 0.2% 0.2% batch sugar sugar without without nitrate nitrate Ceramization # 2 1 1 2 1 1 2 program Properties in ceramized form Transmission, thickness 4 mm 470 nm % 1.5 0.3 2.6 2.3 2.4 4.8 4.2 630 nm % 1.6 1.5 3.4 2.8 2.9 2.8 2.2 950 nm % 34.2 49.3 44.5 41.8 41.6 32.1 28.9 1600 nm % 70.9 70.9 73.7 73.1 73.3 75.7 74.7 3700 nm % 52.4 50.5 52.0 51.8 51.9 50.6 50.5 Colour coordinates (CIE) in transmission, thickness 4 mm, D65 x 0.315 0.490 0.341 0.331 0.329 0.268 0.260 y 0.299 0.367 0.324 0.316 0.311 0.276 0.266 Brightness Y % 1.2 0.6 2.4 2.0 2.1 3.0 2.5 Colour 0.030 0.181 0.028 0.023 0.024 0.069 0.082 distance d Colour coordinates (CIELAB) in transmission L* 10.3 5.4 17.4 15.3 15.9 20.2 18.1 a* 3.9 9.3 5.0 4.5 4.9 1.2 1.2 b* 2.6 5.9 0.9 0.5 1.1 9.3 10.4 c* 4.7 11.0 5.1 4.5 5.1 9.4 10.5 Flatness of nm 1.5 5.7 1.6 1.6 1.6 1.8 2.0 transmission 630/ 630/ 630/ 630/ 630/ 470/ 470/ (wavelength 558 470 542 549 545 594 601 at max./min.) Scatter at thickness 4 mm Visual 1 1 1 1 1 1 1 assessment Haze % 3.1 0.8 0.5 1.0 1.0 0.8 2.1 Thermal expansion (10.sup.6/K) .sub.20/300 0.23 0.21 0.27 0.25 0.27 0.32 .sub.20/700 0.17 0.17 0.11 0.15 0.14 0.09 X-ray diffraction Main crystal HQMC HQMC HQMC HQMC HQMC HQMC HQMC phase DOPANTS AND PROPERTIES OF INVENTIVE GLASS CERAMICS AND COMPARATIVE GLASS CERAMIC 26. Example No. 22 23 24 25 26 27 28 Glass No. 16 16 17 18 19 20 21 Base glass 1 1 1 1 1 1 1 Dopants (% by wt.) Fe.sub.2O.sub.3 0.062 0.062 0.061 0.062 0.062 0.062 0.061 V.sub.2O.sub.5 MoO.sub.3 0.015 0.015 0.019 0.014 0.150 0.150 0.150 MnO.sub.2 0.025 0.025 0.025 0.025 0.025 0.025 0.025 CoO 0.020 Cr.sub.2O.sub.3 0.020 Nd.sub.2O.sub.3 0.042 NiO 0.027 Addition to batch 0.1% sugar without nitrate Ceramization # 1 2 1 1 1 1 1 program Properties in ceramized form Transmission, thickness 4 mm 470 nm % 42.6 43.4 22.2 42.8 0.3 1.6 2.0 630 nm % 53.4 52.7 21.2 54.2 2.6 2.1 2.0 950 nm % 76.4 75.9 57.4 76.5 43.5 36.6 39.7 1600 nm % 80.8 80.4 78.1 80.8 73.1 63.8 66.7 3700 nm % 53.6 53.4 50.5 53.2 51.9 50.8 50.4 Colour coordinates (CIE) in transmission, thickness 4 mm, D65 x 0.335 0.332 0.311 0.334 0.475 0.341 0.315 y 0.348 0.345 0.326 0.348 0.452 0.309 0.257 Brightness Y % 47.6 47.4 20.4 47.8 1.5 1.3 1.2 Colour distance d 0.029 0.025 0.003 0.029 0.204 0.035 0.072 Colour coordinates (CIELAB) in reflectance L* 28.13 28.42 25.84 a* 0.32 0.30 0.05 b* 0.15 0.31 1.27 c* 0.35 0.43 1.27 Flatness of nm 1.3 1.2 1.1 1.3 7.8 2.0 2.4 transmission 630/ 630/ 470/ 630/ 630/ 630/ 630/ (wavelength at 470 470 572 470 470 538 546 max./min.) Scatter at thickness 4 mm Visual assessment 1 1 1 1 1 1 1 Haze % 1.9 1.6 2.7 0.6 0.6 0.7 Thermal expansion .sub.20/300 10.sup.6/K 0.24 0.28 0.24 0.21 0.23 0.23 .sub.20/700 10.sup.6/K 0.16 0.09 0.14 0.16 0.17 0.15 X-ray diffraction Main crystal phase HQMC HQMC HQMC HQMC HQMC HQMC HQMC

(33) TABLE-US-00012 TABLE 3 COMPOSITIONS AND PROPERTIES OF CRYSTALLIZABLE GLASSES AND COMPARATIVE GLASS NO. 22 Glass No. % by wt. 22 23 24 25 26 Composition Li.sub.2O 3.83 3.82 3.83 3.79 3.71 Na.sub.2O 0.57 0.60 0.61 0.60 0.46 K.sub.2O 0.21 0.27 0.27 0.26 0.14 MgO 0.19 0.30 0.30 0.29 0.98 CaO 0.36 0.43 0.43 0.43 SrO 0.02 0.02 0.02 BaO 2.41 2.22 2.21 2.23 ZnO 1.41 1.52 1.49 1.47 1.58 Al.sub.2O.sub.3 20.2 20.9 20.9 21.0 20.9 SiO.sub.2 65.8 64.8 64.8 65.0 67.5 TiO.sub.2 3.02 4.10 3.14 3.05 2.47 ZrO.sub.2 1.39 0.43 1.40 1.40 1.69 P.sub.2O.sub.5 0.11 0.10 0.10 0.10 0.09 SnO.sub.2 0.30 0.25 0.23 As.sub.2O.sub.3 0.28 0.15 Fe.sub.2O.sub.3 0.090 0.061 0.062 0.061 0.0600 V.sub.2O.sub.5 0.016 MoO.sub.3 0.150 0.150 0.150 0.1500 MnO.sub.2 0.021 0.024 0.025 0.025 0.024 CoO 0.027 Addition to batch (% by 0.2% wt.) sugar without nitrate Properties in glass form Transformation temperature C. 667 671 672 674 Tg 10.sup.2 temperature C. 1729 Working temperature V.sub.A C. 1313 1294 1297 1301 1310 UDL temperature C. 1280 COMPOSITIONS AND PROPERTIES OF CRYSTALLIZABLE GLASSES Glass No. % by wt. 27 28 29 30 Composition Li.sub.2O 4.03 3.82 3.31 3.30 Na.sub.2O 0.42 0.60 0.37 0.36 K.sub.2O 0.40 0.26 0.36 0.36 MgO 0.77 0.30 0.56 0.56 CaO 0.43 0.58 0.58 SrO 0.02 0.01 BaO 0.39 2.23 1.62 1.63 ZnO 0.56 1.48 1.92 1.90 Al.sub.2O.sub.3 20.1 21 21.4 21.4 SiO.sub.2 68.0 64.5 64.8 64.7 TiO.sub.2 4.69 3.08 3.20 4.02 ZrO.sub.2 1.40 1.35 0.68 P.sub.2O.sub.5 0.11 0.56 0.04 0.03 SnO.sub.2 0.24 0.23 0.24 0.22 As.sub.2O.sub.3 Fe.sub.2O.sub.3 0.062 0.062 0.099 0.100 V.sub.2O.sub.5 MoO.sub.3 0.140 0.040 0.160 0.149 MnO.sub.2 0.025 Nd.sub.2O.sub.3 Addition to batch (% by 0.07% S wt.) Properties in glass form Transformation temperature C. 670 668 675 670 Tg 10.sup.2 temperature C. 1733 Working temperature V.sub.A C. 1319 1299 1300 1295 UDL temperature C. 1275 Glass No. % by wt. 31 32 33 34 35 Composition Li.sub.2O 2.67 4.13 3.22 3.67 3.73 Na.sub.2O 0.54 0.64 0.78 0.77 0.78 K.sub.2O 0.24 0.29 0.20 0.21 0.58 MgO 1.73 0.24 0.81 0.77 0.20 CaO 0.69 0.52 0.21 0.21 0.21 SrO 0.02 BaO 1.97 2.05 2.42 0.68 2.41 ZnO 1.65 1.16 0.90 0.93 Al.sub.2O.sub.3 20.0 21.7 19.8 22.2 20.0 SiO.sub.2 64.9 65.8 66.9 65.4 66.4 TiO.sub.2 5.04 3.58 2.68 4.26 2.83 ZrO.sub.2 0.64 1.44 0.54 1.40 P.sub.2O.sub.5 0.07 0.03 SnO.sub.2 0.24 0.25 0.20 0.19 0.39 As.sub.2O.sub.3 Fe.sub.2O.sub.3 0.091 0.065 0.110 0.085 0.033 V.sub.2O.sub.5 MoO.sub.3 0.099 0.026 0.043 0.079 0.045 MnO.sub.2 0.018 Addition to batch (% by 0.1% 0.2% wt.) sugar sugar without without nitrate nitrate Properties in glass form Transformation C. 671 685 680 675 674 temperature Tg 10.sup.2 temperature C. 1774 1770 1693 1770 Working temperature V.sub.A C. 1296 1327 1331 1294 1331 UDL temperature C. 1265 1255 1260

(34) TABLE-US-00013 TABLE 4 PROPERTIES FOR THE SIGHTGLASSES OF SUITABLE GLASS CERAMICS AND COMPARATIVE GLASS CERAMIC OF EXAMPLE 29 Example No. 29 30 31 32 33 34 Glass No. 22 23 24 25 26 27 Cera- 2 1 1 1 2 1 mization program Properties in ceramized form Transmission, thickness 4 mm 470 nm % 1.9 0.9 43.4 39.4 2.5 0.8 630 nm % 10.8 0.6 57.1 52.3 7.8 1.7 950 nm % 72.0 25.6 82.2 83.1 55.4 37.6 1600 nm % 67.5 73.5 82.9 82.8 70.8 73.5 3700 nm % 49.4 51.5 53.6 52.0 49.9 52.4 Colour coordinates (CIE) in transmission, thickness 4 mm, D65 x 0.476 0.276 0.342 0.342 0.414 0.393 y 0.322 0.265 0.355 0.351 0.359 0.350 Brightness % 3.5 0.5 48.7 43.7 4.2 1.0 Y Colour 0.163 0.089 0.024 0.037 0.106 0.083 distance d Colour coordinates (CIELAB) in reflectance L* 29.38 a* 0.46 b* 0.78 c* 0.91 Flatness of nm 8.0 2.1 1.3 1.3 3.1 2.3 trans- 630/ 470/ 630/ 630/ 630/ 630/ mission 504 571 470 470 470 509 (wave- length at max./ min.) Scatter at thickness 4 mm Visual 1 1 1 1 1 1 assess- ment Haze % 0.2 3.3 2.0 1.4 0.8 0.1 Thermal expansion (10.sup.6/K) .sub.20/300 0.40 0.13 0.24 0.27 0.45 0.14 .sub.20/700 0.03 0.23 0.16 0.12 0.15 0.14 X-ray diffraction Main HQMC HQMC HQMC HQMC HQMC HQMC crystal phase PROPERTIES OF THE GLASS CERAMICS Example No. 35 36 37 38 Glass No. 28 29 29 30 Ceramization program 1 1 2 1 Properties in ceramized form Transmission, thickness 4 mm 470 nm % 1.8 5.8 5.2 0.6 630 nm % 0.6 8.3 7.0 1.0 950 nm % 18.6 53.4 50.9 28.2 1600 nm % 73.2 69.1 68.1 66.1 3700 nm % 49.2 46.3 46.4 47.8 Colour coordinates (CIE) in transmission thickness 4 mm, D65 x 0.234 0.344 0.338 0.357 y 0.238 0.325 0.320 0.331 Brightness Y % 0.9 5.9 5.0 0.6 Colour distance d 0.120 0.032 0.027 0.044 Colour coordinates (CIELAB) in transmission L* 7.9 29.1 26.8 5.6 a* 1.2 7.1 6.5 3.2 b* 11.0 1.7 0.4 1.3 c* 11.1 7.3 6.5 3.5 Flatness of transmission nm 2.9 1.6 1.6 1.8 (wavelength at 470/ 630/ 630/536 630/533 max./min.) 609 527 Scatter at thickness 4 mm Visual assessment 1 1 1 1 Haze % 0.2 0.6 3.4 0.3 Thermal expansion (10.sup.6/K) .sub.20/300 0.28 0.05 0.00 0.30 .sub.20/700 0.12 0.34 0.27 0.55 X-ray diffraction Main crystal phase HQMC HQMC HQMC HQMC Example No. 39 40 41 42 43 Glass No. 31 32 33 34 35 Cerami- 2 1 2 2 2 zation program Properties in ceramized form Transmission, thickness 4 mm 470 nm % 0.7 12.1 33.2 1.9 12.5 630 nm % 1.4 27.4 46.1 2.8 10.8 950 nm % 34.6 54.0 71.6 33.1 51.8 1600 nm % 71.3 72.1 72.3 69.9 82.7 3700 nm % 44.3 49.9 46.1 47.7 47.0 Colour coordinates (CIE) in transmission thickness 4 mm, D65 x 0.389 0.389 0.342 0.350 0.302 y 0.366 0.385 0.348 0.347 0.313 Brightness Y % 0.9 19.6 38.5 2.1 10.3 Colour distance d 0.085 0.095 0.035 0.041 0.019 Colour coordinates (CIELAB) in transmission L* 8.1 51.4 68.4 16.0 38.4 a* 4.0 5.9 4.3 2.8 1.3 b* 5.3 21.7 9.4 3.9 3.9 c* 6.7 22.5 10.3 4.8 4.1 Flatness of nm 2.1 2.3 1.4 1.5 1.3 transmission 630/ 630/ 630/470 630/470 470/575 (wavelength at 470 470 max./min.) Scatter at thickness 4 mm Visual assessment 1 2 1 1 1 Haze % 2.5 1.1 2.9 1.1 Thermal expansion (10.sup.6/K) .sub.20/300 1.23 0.37 0.32 0.23 0.14 .sub.20/700 1.49 0.01 0.59 0.51 0.26 X-ray diffraction Main crystal phase HQMC HQMC HQMC HQMC HQMC