Glass ceramic as a cooktop for induction heating having improved colored display capability and heat shielding, method for producing such a cooktop, and use of such a cooktop
A glass ceramic as cooktop for induction heating having improved colored display capability and heat shielding is provided. The cooktop includes a transparent, dyed glass ceramic plate having high-quartz mixed crystals as a predominant crystal phase. The glass ceramic contains none of the chemical refining agents arsenic oxide and/or antimony oxide and has a transmittance values greater than 0.4% at at least one wavelength in the blue spectrum between 380 and 500 nm, a transmittance >2% at 630 nm, a transmittance of less than 45% at 1600 nm, and a light transmittance of less than 2.5% in the visible spectrum.
1. A glass ceramic suitable for use as a cooktop for induction heating having improved colored display capability and heat shielding, comprising:
a transparent, dyed glass ceramic plate having high-quartz mixed crystals as a predominant crystal phase, wherein the glass ceramic plate contains none of the chemical refining agents arsenic oxide or antimony oxide, apart from inevitable traces;
transmittance values of the glass ceramic plate of:
>0.4% at at least one wavelength in a blue spectrum between 380 and 500 nm,
>2% at 630 nm,
<45% at 1600 nm; and
a light transmittance in a visible spectrum of less than 2.5%.
2. The glass ceramic according to claim 1 , wherein the transmittance values of the glass ceramic plate comprises <40% at 1600 nm.
3. The glass ceramic according to claim 1 , wherein the transmittance values of the glass ceramic plate of greater than 0.1% in the range of visible light in the entire wavelength range of the visible range greater than 500 nm, a transmittance of <12% at 630 nm, a transmittance of greater than 30% in the near infrared at 950 nm, and a transmittance of 0.5-2% in the visible spectrum.
4. The glass ceramic according to claim 1 , further comprising a composition in wt % on an oxide basis comprising:
Li 2 O
1.5-4.2;
Σ Na 2 O + K 2 O
0.2-1.5;
MgO
0-3;
Σ CaO + SrO + BaO
0-4;
ZnO
0-3;
B 2 O 3
0-2;
Al 2 O 3
19-23;
SiO 2
60-69;
TiO 2
1.5-6;
ZrO 2
0.5-2;
P 2 O 5
0-3;
SnO 2
0.1-<0.6;
and
ΣTiO 2 +ZrO 2 +SnO 2 3.8-6, and a combination of at least two coloring oxides selected from the group consisting of with total contents of up to 1 wt %:
V 2 O 5
≧0-0.06;
Fe 2 O 3
0.03-0.3;
CoO
≧0-0.3;
Cr 2 O 3
≧0-0.3; and
NiO
≧0-0.3.
5. The glass ceramic according to claim 1 , further comprising good fusibility and fast ceramization ability of a starting glass and a composition comprising in wt % on an oxide basis:
Li 2 O
2-4.2;
Na 2 O
0.1-1;
K 2 O
0.1-1;
Σ Na 2 O + K 2 O
0.3-1.3;
MgO
0-2.6;
Σ CaO + SrO + BaO
0.1-4;
ZnO
0-2.5;
B 2 O 3
0-1;
Al 2 O 3
19-22.5;
SiO 2
60-68;
TiO 2
2.0-6;
ZrO 2
0.8-1.8;
P 2 O 5
0-1.5;
SnO 2
0.1-0.5;
and
ΣTiO 2 +ZrO 2 +SnO 2 4-6, and a combination of at least two coloring oxides selected from the group consisting of with total contents of 0.1 to 1 wt %:
V 2 O 5
≧0-0.05;
Fe 2 O 3
≧0.03-0.3;
CoO
≧0-0.3;
Cr 2 O 3
≧0-0.3; and
NiO
≧0-0.3.
6. The glass ceramic according to claim 1 , further comprising a glass melt temperature of greater than 1700° C. and a bubble number of less than 3 bubbles/kg.
7. The glass ceramic according to claim 6 , wherein the glass melt temperature is greater than 1750° C.
8. The glass ceramic according to claim 1 , further comprising one or more colored displays having a color selected from the group consisting of blue, green, yellow, orange, and white.
9. The glass ceramic according to claim 1 , further comprising Fe 2 O 3 of 0.03 to 0.3 wt % combined with NiO and/or CoO in minimum contents of 0.05 wt % in order to adjust the infrared transmittance at 1600 nm to less than 45%.