Display assembly comprising a glass-ceramic plate

Abstract

Display assembly 1 comprising, on the one hand, a glass-ceramic plate 2 of the lithium aluminosilicate type, the optical transmission of which for a thickness of 4 mm is between 0.2% and 4% for at least one wavelength between 400 and 500 nm and, on the other hand, a luminous device 4, characterized in that the luminous device 4 comprises at least one polychromatic light source 5 having at least a first emission of nonzero intensity at said wavelength between 400 and 500 nm and at least a second emission of more than 500 nm, and such that the positioning of said source 5 is designed to allow display through said glass-ceramic plate 2.

Claims

1. A display assembly, comprising a glass-ceramic plate comprising a lithium aluminosilicate and a luminous device comprising a polychromatic light source, wherein: the glass-ceramic plate comprises, in percentages by weight: TABLE-US-00005 SiO.sub.2 64-70% Al.sub.2O.sub.3 18-25% Li.sub.2O 2.5-3.8% K.sub.2O 0-<1.0 Na.sub.2O 0-<1.0% ZnO 1.2-2.8% MgO 0.30-1.5% CaO 0.2-2.5% BaO 0-3% SrO 0-1.4% TiO.sub.2 1.8-3.2% ZrO.sub.2 1.0-2.5%; an optical transmission of the glass-ceramic plate for a thickness of 4 mm is between 0.2% and 4% for at least one wavelength between 400 and 500 nm; the polychromatic light source has at least one first emission of nonzero intensity at said wavelength between 400 and 500 nm and at least one second emission at a wavelength of more than 500 nm; the polychromatic light source is positioned to allow display through said glass-ceramic plate, the glass-ceramic plate further comprises tin oxide in an amount by weight of between 0.2% and 0.35%, the glass-ceramic plate further comprises vanadium oxide in a weight content of between 0.01% and 0.03%, the glass-ceramic plate further comprises As.sub.2O.sub.3 in a weight content of from 0% to 0.01%, the glass-ceramic plate further comprises at least one reducing agent, the glass-ceramic plate further comprises less than or equal to 0.01% by weight of chromium oxide, the glass-ceramic plate further comprises cobalt oxide in an amount by weight of 0.12% or less, the glass-ceramic plate comprises no nickel oxide, and the at least one first emission and the at least one second emission through the glass-ceramic plate allow for display of different colors.

2. The display assembly of claim 1, wherein an optical transmission of the glass-ceramic plate, for a thickness of 4 mm, is between 0.4% and 1.5% for at least one wavelength between 400 and 500 nm.

3. The display assembly of claim 1, wherein the glass-ceramic plate comprises antimony oxide and arsenic oxide in amounts not exceeding 0.01% by weight.

4. The display assembly of claim 1, wherein the glass-ceramic plate comprises less than or equal to 0.1% by weight of manganese oxide.

5. The display assembly of claim 1, wherein the polychromatic light source is a polychromatic LED.

6. The display assembly of claim 1, wherein the polychromatic light source is a polychromatic LED which emits with a first emission peak between 430 and 470 nm and a second peak between 540 and 560 nm.

7. The display assembly of claim 6, wherein the second peak is of lower intensity than the first peak.

8. The display assembly of claim 1, wherein the polychromatic light source is a polychromatic LED comprising three monochromatic sources, the intensities of which are regulated independently.

9. A hob, comprising the display assembly of claim 1 and a heating element.

10. The display assembly of claim 1, wherein the glass-ceramic plate comprises antimony oxide and arsenic oxide in amounts not exceeding 0.001% by weight.

11. The display assembly of claim 1, wherein the glass-ceramic plate contains no antimony oxide and no arsenic oxide.

12. The display assembly of claim 1, wherein the reducing agent comprises at least one metal sulfide.

13. The display assembly of claim 1, wherein the reducing agent comprises tin oxide and at least one metal sulfide.

Description

(1) The invention will be better understood in the light of the examples, together with the appended drawings and graphs, given solely by way of illustration, which must in no way be interpreted as being limiting, in which:

(2) FIG. 1 shows, seen side-on and in cross section, one embodiment of a display assembly according to the present invention;

(3) FIGS. 2 and 3 represent the optical transmission spectrum of various glass-ceramic plates used in a display assembly according to the present invention (FIG. 3 is an enlargement of the spectrum shown in FIG. 2). In the graph, the percentage amount of light transmitted by the plate is plotted on the y-axis as a function of the wavelength, in nanometers, of the transmitted beam, given on the x-axis;

(4) FIGS. 4, 6, 8, 10 and 12 represent the emission spectrum of an example of polychromatic LEDs of a display assembly according to the invention. In these figures, relative emitted light intensity with respect to the maximum, taken as equal to 1, is plotted on the y-axis as a function of the wavelength, in nanometers, of the incident beam, given on the x-axis;

(5) FIGS. 5, 7, 9, 11 and 13 represent the spectrum of the radiation transmitted by the polychromatic LEDs, the emission spectra of which are illustrated in FIGS. 4, 6, 8, 10 and 12 respectively, through the glass-ceramic plates having the transmission spectra shown in FIGS. 2 and 3. In these FIGS. 5, 7, 9, 11 and 13, the relative transmitted light intensity with respect to the maximum, taken as equal to 1, is plotted on the y-axis as a function of the wavelength, in nanometers, of the transmitted beam, given on the x-axis; and

(6) FIG. 14 shows the spectrum of the radiation emitted by a polychromatic LED obtained through two glass-ceramic plates of different composition. The dotted curve corresponds to the emission of the LED selected at the start in order to carry out the calculations. An identical display through two plates is obtained with the spectrum corresponding to the solid curve.

(7) The display assembly 1 shown in FIG. 1 comprises a glass-ceramic plate 2 of chemical composition 3a, 3b, 3c or 3d, and a luminous device 4 comprising a polychromatic source 5 (consisting of an LED 6a, 6b, 6c, 6d or 6e) and a control means 7. In operation, the polychromatic source 5 emits a light beam that passes through the plate 2 in the display zone 8. The distance between the source 5 and the plate 2 is less than or equal to 5 mm, and may especially be less than 2 mm or even 1 mm.

(8) The beam emitted by the source 5 has a width of between 0 and 5 mm. In the present case, the width of the beam is greater than 0.5 mm.

(9) Table 1 gives the chemical compositions C1, 3a, 3b, 3c and 3d of various glass-ceramic plates 2, indicating the percentage contents by weight of the oxides.

(10) Composition C1 (comparative example) is the chemical composition of a glass-ceramic plate having very low transmissions between 400 and 500 nm, resulting in practically zero visibility of the LEDs that emit only within this range of the spectrum (blues to green . . . ).

(11) Compositions 3a to 3d are examples of the chemical composition of the glass-ceramic plate 2 of the display assembly 1 according to the invention.

(12) TABLE-US-00004 TABLE 1 C1 3a 3b 3c 3d SiO.sub.2 68.7 65.5 65.5 65.5 64.7 Al.sub.2O.sub.3 18.9 20.3 20.3 20.3 20.45 Li.sub.2O 3.5 3.8 3.8 3.8 3.75 TiO.sub.2 2.6 2.9 2.9 2.9 3.02 ZrO.sub.2 1.7 1.3 1.3 1.3 1.35 ZnO 1.6 1.5 1.5 1.5 1.52 MgO 1.3 0.4 0.4 0.4 0.36 CaO 0.5 0.4 0.4 0.44 BaO 0.8 2.6 2.6 2.6 2.5 Na.sub.2O 0.1 0.6 0.6 0.6 0.62 K.sub.2O 0.1 0.2 0.2 0.2 0.25 MnO 0.02 0.02 0.02 SnO.sub.2 0.3 0.3 0.3 0.25 V.sub.2O.sub.5 0.2 0.028 0.028 0.028 0.025 Fe.sub.2O.sub.3 0.1 0.1 0.1 0.1 0.087 As.sub.2O.sub.3 0.4 <0.01 Sb.sub.2O.sub.3 <0.01 Cr.sub.2O.sub.3 0.0054 0.0017 0.0012 CoO 0.0147 P.sub.2O.sub.5 0.07 Rb.sub.2O 0.09 B.sub.2O.sub.3 and/or F <0.01 White LED Zero Good Good Good Good visibility

(13) Table 1 gives compositions of glass-ceramic plate specimens 3a, 3b, 3c and 3d, of the display assembly 1 for which white displays are obtained. The transmission spectra given in FIGS. 5, 7, 9, 11 and 13 show that a white display is obtained by using the appropriate LEDs (LEDs 6a to 6e), the spectral emission characteristics of which are given in FIGS. 4, 6, 8, 10 and 12.

Emission of the Transmission Spectra Measurement Protocol

(14) The various glass-ceramic plates are measured on specimens measuring 50 mm50 mm, the textured (pimpled) face of which was removed by thinning/polishing the specimen. The measurement is carried out by means of a spectrophotometer, for example a Perkin Elmer Lambda950 spectrophotometer.
The emission of the transmission spectra are measured using an integrating sphere (for example a SphereOptics SPH-12-X integrating sphere) coupled to a spectrophotometer (for example an Instrument Systems CAS140 spectrophotometer).

(15) FIGS. 2 and 3 show the transmission spectra of the plates having the compositions C1, 3a, 3b, 3c and 3d given in Table 1. The specimens of plates 2 of compositions 3a to 3d all have a relatively high optical transmission between 400 and 500 nm, compared with the specimen of plate 2 of composition C1. This is because composition C1 is typically that of plates normally used in cooking ranges that transmit well only for wavelengths in the red.

(16) FIGS. 4, 6, 8, 10 and 12 show the emission spectrum of an example of polychromatic LEDs 6a to 6e of the luminous device 4 of the display assembly 1. These LEDs were selected so as to obtain a white color rendition of the display through the glass-ceramic plate 2. These LEDs 6a to 6e all have in particular a first emission peak with a maximum between 400 and 500 nm and a second emission peak with a maximum between 500 and 650 nm.

(17) FIG. 4 shows the normalized emission spectrum of the LED 6a, the characteristics of which are the following:

(18) Blue peak: Intensity=1.0 (unitless) Position=450 nm Width=20 nm

(19) Yellow peak: Intensity=0.22 (unitless) Position=540 nm Width=93 nm.

(20) This spectrum has the CIE 1931 color coordinates x.sub.s=0.211; y.sub.s=0.219.

(21) The normalized spectrum transmitted from the LED 6a through the glass-ceramic plate specimen of composition 3b is plotted in FIG. 5. This spectrum has the color coordinates x.sub.t=0.335 and y.sub.t=0.339, giving a white color rendition of the LED display through the glass-ceramic plate in question.

(22) FIG. 6 shows a normalized emission spectrum of the OSRAM LED with the reference LUW-G5AP Ultra-White (LED 6b). This spectrum has the following characteristics:

(23) Blue peak: Intensity=1.0 (unitless) Position=432 nm Width=20 nm

(24) Yellow peak: Intensity=0.13 (unitless) Position=555 nm Width=105 nm.

(25) This spectrum has the CIE 1931 color coordinates x.sub.s=0.230; y.sub.s=0.180.

(26) The normalized spectrum transmitted from the LED 4b through the glass-ceramic plate specimen of composition 3c is plotted in FIG. 7. The transmitted spectrum has the color coordinates x.sub.t=0.356 and y.sub.t=0.263, giving a pinky white color rendition of the LED through the glass-ceramic plate in question.

(27) FIG. 8 shows the normalized emission spectrum of an RGB LED 6c, the characteristics of which are the following:

(28) Blue peak: Intensity=1.0 (unitless) Position=460 nm Width=20 nm

(29) Green peak: Intensity=0.47 (unitless) Position=525 nm Width=35 nm.

(30) Red peak: Intensity=0.11 (unitless) Position=630 nm Width=15 nm.
This spectrum has the CIE 1931 color coordinates x.sub.s=0.184; y.sub.s=0.250.

(31) The normalized spectrum transmitted from the LED 6c through the glass-ceramic plate specimen of composition 3b is plotted in FIG. 9. The transmitted spectrum has the color coordinates x.sub.t=0.335 and y.sub.t=0.338, giving a white color rendition of the LED through the glass-ceramic plate in question.

(32) FIG. 10 shows a normalized emission spectrum of the OSRAM RGB LED with the reference LRTD-C9TP (LED 6d). This spectrum has the following characteristics:

(33) Blue peak: Intensity=1.0 (unitless) Position=453 nm Width=25 nm

(34) Green peak: Intensity=0.38 (unitless) Position=520 nm Width=33 nm

(35) Red peak: Intensity=0.07 (unitless) Position=632 nm Width=18 nm.

(36) This spectrum may be obtained with said LED by independently controlling the current with which each of the chips (R, G, or B) is supplied. By so doing, the spectrum of the LED has the CIE 1931 color coordinates x.sub.s=0.173; y.sub.s=0.185.

(37) The normalized spectrum transmitted from the LED 6d through the glass-ceramic plate specimen of composition 3a is plotted in FIG. 11. The transmitted spectrum has the color coordinates x.sub.t=0.337 and y.sub.t=0.332, giving a white color rendition of the LED through the glass-ceramic plate in question.

(38) FIG. 12 shows a normalized emission spectrum of the 7-segment LED display from Avago Technologies (reference HDSM-431W) (LEDs 6e). This spectrum has the following characteristics:

(39) Blue peak: Intensity=1.0 (unitless) Position=455 nm Width=20 nm

(40) Yellow peak: Intensity=0.3 (unitless) Position=551 nm Width=108 nm.
This spectrum has the CIE 1931 color coordinates x.sub.s=0.250; y.sub.s=0.270.
The normalized spectrum transmitted from the LED system 6e through the glass-ceramic plate specimen of composition 3d is plotted in FIG. 13. The transmitted spectrum has color coordinates x.sub.t=0.401 and y.sub.t=0.353, giving an orangey-white color rendition of the LEDs through the glass-ceramic plate in question.

(41) FIG. 14 shows a result obtained by applying the method of adjusting and/or selecting a light source. The plate specimens from which the calculations were made are the two glass-ceramic plates of composition 3b and 3d. The dotted curve represents the initial normalized emission spectrum of the LED used at the start of the method of selecting a light source. The solid curve represents the normalized final emission spectrum of the LED obtained at the end of the method. The acceptable limit value, as defined in step 3 of the method, is taken as 0.01.

(42) The characteristics of these spectra are the following:

Initial Spectrum

(43) Blue peak: Intensity=1.0 (unitless) Position=450 nm Width=20 nm

(44) Yellow peak: Intensity=0.50 (unitless) Position=555 nm Width=100 nm

Final Spectrum

(45) Blue peak: Intensity=1.0 (unitless) Position=4660 nm Width=10 nm

(46) Yellow peak: Intensity=0.25 (unitless) Position=542.9 nm Width=98.5 nm.

(47) The predictions made beforehand by the calculations, in accordance with the method of selecting the light source of the polychromatic luminous device of the display assembly according to the invention are therefore confirmed.