EP2575124A2 - Display device, electric device and display method - Google Patents

Abstract

The device (14) has a first LED e.g. surface mount-LED, with defined output spectrum for illuminating a reddish-brown glass ceramic cook field plate (12) of an electrical hob (11). A second LED (17b') emits white light in color coordinates. A third LED (17b'') is provided in spatial proximity to color and/or color coordinates such that a seven segment display is viewed as a white light display when illuminating the cook field plate of the hob with the LEDs. One of the color coordinates of the third LED lies at left of one of the color coordinates of the second LED. The LED comprises semiconductor crystal doped with phosphorus. An independent claim is also included for a method for controlling a display device.

Description

The invention relates to a display device for an electrical appliance with a cover, wherein the cover is colored or colored and has an inhomogeneous transmission profile for light. Furthermore, the invention relates to an electrical appliance with such a display device and a method for controlling such a display device.

In electrical appliances with a cover over a display device, for example, with light sources such as LED, the color of a visual display also depends significantly on the color or the transmission of the cover. As a result, the color of a display can be colored or a desired color can be achieved only to a limited extent, depending on the transmission profile of the cover and the color of the light source.

For example, in cooktops as an electrical appliance with cooktop plate of glass ceramic as a cover, there is a transmission profile for light that is inhomogeneous and has a high transmission in the range of wavelengths greater than 700 nm. The transmission in the range of wavelengths smaller than 700 nm is very low and is sometimes less than 1% or even 0%. The reason for this lies in the material properties of glass-ceramic, which are optimized for suitable use in electric cooktops with requirements for stability on the one hand and the highest possible transmission in the wavelength range of radiant heaters on the other hand, and just give the initially mentioned low transmission at low wavelengths. Thus, with a display device of conventional design in a described Cover colors with low wavelength, so in the yellow, green and blue range, not or only barely displayed.

From the WO 2012/076412 A1 is a display device is known in which with three LED primary color lights by appropriate mixing a larger color bandwidth can be created for a display, especially for a white display. On the one hand, however, this is considered to be relatively expensive. On the other hand, a combination of three cooperating LEDs can not be provided for each practically usable display. For example, in so-called seven-segment displays with a height of usually less than 2 cm, this is not practical.

Task and solution

The invention is based on the object to provide an aforementioned display device, an electrical device provided therewith and a method for operating such a display device, with which problems of the prior art can be avoided and in particular with differently translucent covers, preferably with reddish-brown Coloring, a white appearing display can be achieved.

This object is achieved by a display device having the features of claims 1 or 4, by an electrical appliance with such a display device having the features of claim 13 and by a method for controlling such a display device having the features of claim 15. Advantageous and preferred embodiments of The invention are specified in the further claims and are explained in more detail below. Some of the features mentioned below are described only for the display device, the electrical device or the method. However, they should regardless of both the display device, the electrical appliance and the Procedure may apply. The wording of the claims is incorporated herein by express reference. Furthermore, the text of the priority application DE 102011114741.5 of September 28, 2011 by the same Applicant by expressly referring to the content of the present specification.

It is envisaged that the cover has an inhomogeneous transmission profile for light with high transmission in the range of wavelengths greater than 700 nm. In the range of wavelengths less than 700 nm, the transmission is lower and can decrease to a maximum of a few percent at significantly less than 700 nm For a single display, that is to say for a single display location or a luminous spot or a luminous symbol, which is usually also represented by a single light source, the display device has at least one light source with a defined output spectrum for transmission through the cover of the electrical appliance. In the case of an electrical appliance in the form of a said electric cooktop panel with cooktop panel, the display device or the light source just radiates through this cooktop panel as a cover.

In a first basic embodiment of the invention, the one light source emits white. In this case, it can have the coordinates (x; y) of (0.3, 0.3) as the CIE color locus, or a similar color location, for example also (x; y) = (0.33, 0.33). In addition, or in close proximity thereto, in particular as close as possible as it is structurally possible, a further light source is provided. This second light source has such a color or such a chromaticity that when passing through the cover of the electrical device with two light sources together with a coordinated intensity, a white light display is visible as a display or is perceived by a viewer for the sensation of the human eye. The color location of this second light source is to the left of the color location of the first white light source, that is, has a lower value for (x). So can with something increased effort in the form of the second light source, a light in the display device are generated, which looks white after passing through the cover with the aforementioned transmission profile or perceived as white.

The first light source and the second light source should just as advantageously be arranged as close to each other as possible, for example, as close as possible their housing, which can be advantageously carried out in SMD technology, as well as their electrical wiring.

In a further embodiment of the invention, the color location of the second light source may advantageously have a similar y-coordinate as the color locus of the white first light source. The second light source may have a slightly lower y-coordinate. Advantageously, the x-coordinate of the color locus of the second light source is between 0.0 and 0.13. It can be, for example, about 0.05.

In an exemplary development of the invention, the second light source is designed so that it emits spectrally pure or radiates very narrow band. It can advantageously have a wavelength of about 470 to 510 nm, particularly advantageously about 490 nm, that is to say approximately turquoise to the human eye. The combination of the light of this second light source, for example in turquoise, with the white light of the first light source causes a substantially turn turquoise to bluish light. After passing through a said reddish-brown cover, in particular a conventional hob plate of glass ceramic with reddish-brown color, the human eye perceives a white glowing display.

In a second basic embodiment of the invention according to the preamble of claim 1, only the single light source per display is used, so there is no second light source provided directly next to it, whose light is mixed with the first light source becomes. The color location of this single light source is shifted from white to the left or the x-coordinate of the CIE color locus is smaller. This second light source can thus advantageously have a blue cast or turquoise sting. The light of this single light source appears through an aforementioned cover, especially from reddish-brown glass ceramic, white again to the human eye.

In an advantageous embodiment of the invention, the color location of this aforementioned single light source with respect to the y-coordinate is almost the same as that of white light, that is between 0.20 and 0.28, for example, slightly above 0.24. The x-coordinate of its color locus is much further left than for white light, advantageously between 0.1 and 0.2, more preferably about 0.18. The light appears bluish to the human eye. The said single light source can be designed to have a broadband beam, in particular it radiates in the green and blue regions with appreciable intensity.

In an advantageous development of the invention, said single light source can have a light spectrum normalized to 1, which has a maximum normalized intensity of 1.0 at a wavelength of 450 nm to 470 nm. In particular, this maximum is about 460 nm. Before the maximum, there may be a steep rise from 0, for example from about 420 nm. Similarly, after the maximum, there may be a steep fall to a relative intermediate low whose normalized intensity is between 0.3 and 0 , 4 lies. It may be at a wavelength between 480 nm and 500 nm, for example at about 490 nm. After the relative intermediate depth, there is a relative intermediate high with a normalized intensity between 0.35 and 0.45, that at a wavelength between 500 nm and 520 nm may be present, in particular at about 510 nm.

After the relative intermediate high, the normalized intensity drops again, first steep and then flat again. In this At a wavelength of about 570 nm, the normalized intensity can be less than 0.1, and at less than 0.01 at a wavelength above 700 nm. This means that this light source has a strong share in the blue area and an intermediate high in the green or turquoise-green area. Red light is barely present in the spectrum.

Advantageously, LEDs are generally used as light sources with a semiconductor crystal for the invention. Usually, the semiconductor crystals are treated with phosphorus or doped to affect the color. Thus, the light sources mentioned for the two basic embodiments of the invention may be formed. The semiconductor crystals can thus be doped with phosphorus as well as treated or doped with other materials in order to produce the desired colors or color spectra.

In a display device according to the invention, a plurality of displays can be provided. For above-described individual displays as a symbol or light point, only a single color-corrected white light source can be provided in each case, as defined in one of claims 4 to 9. Thus, such individual ads can be realized with the least possible effort. For a so-called seven segment display, either the same color corrected white light sources may be used, one single per luminous segment. Then, the entire display device only one type of light sources or louder identical light sources, so that there are no color differences due to design variations or aging or the like. can give. Alternatively, for example due to design or cost reasons, be provided purely white light sources, which are moved with a second light source to a color location according to claim 5 out. This second type can be used for seven-segment displays or, advantageously, for individual displays.

In a further embodiment of the invention, it is possible that in the provision of multiple light sources for a single display, the intensities of narrow-band and broadband light sources are adjustable. Thus, even more colors can be displayed except a white display, which significantly increases the versatility and usability.

Furthermore, it is possible that an aforementioned light source, which appears white after irradiating the cover, is combined with further light sources. Preferably, these are light sources that radiate spectrally pure or narrow band, in particular green with a wavelength between 540 nm and 550 nm and red with a wavelength between 600 nm and 610 nm. With the white radiating light source and one green and one red, so a total of three Light sources, so a display device or display with the colors white, green, yellow and red and mixed colors thereof can be created. For a narrow-band light spectrum, the bandwidth of these light sources should not be greater than 20 nm, if possible even less than 10 nm. Thus, in the resulting RGW color space also different mixed colors can be achieved. This will be explained in more detail below with reference to the corresponding figure.

In a method for controlling a display device mentioned, the light sources can be controlled with a conventional control for a display, in particular with a hob control. The control only has to be adjusted in its wiring to the changed flux voltage of the light sources.

Above all, the exact wavelengths or spectra of the wavelength distribution of a single light source or two light sources must be adapted to a cover used. However, by relatively simple experimentation or calculation, these wavelengths can be accurately determined.

These and other features will become apparent from the claims but also from the description and drawings, wherein the individual features each alone or more in the form of sub-combination in one embodiment of the invention and in other areas be realized and advantageous and protectable Represent embodiments for which protection is claimed here. The subdivision of the application into individual sections as well as intermediate headings does not restrict the general validity of the statements made thereunder.

Short name of the drawings

Fig. 1

eine Draufsicht auf ein Elektrokochfeld als Elektrogerät mit Abdeckung und vier Anzeigen darunter, die die Abdeckung durchleuchten,

Fig. 2

eine Schnittdarstellung durch ein Elektrokochfeld entsprechend Fig. 1,

Fig. 3

der Verlauf der Transmission über der Wellenlänge für verschiedene Glaskeramiken als Abdeckungen entsprechend der Fig. 1 und 2,

Fig.4

das Spektrum einer erfindungsgemäßen Lichtquelle, das Transmissionsspektrum der Glaskeramik und das normierte Spektrum des durch die Glaskeramik hindurch zu sehenden Lichts,

Fig. 5

eine Darstellung der CIE-Normfarbtafel mit eingezeichneten Verläufen sowie den eingezeichneten Farborten für verschiedene Lichtquellen bzw. Filter und

Fig. 6

die drei Tristimulus-Kurven der menschlichen Wahrnehmung für die drei Grundfarben.

Embodiments of the invention are shown schematically in the drawings and are explained in more detail below. In the drawings show:

Fig. 1

a top view of an electric hob as an electrical appliance with cover and four displays below, which illuminate the cover,

Fig. 2

a sectional view through an electric hob accordingly Fig. 1 .

Fig. 3

the course of transmission over the wavelength for various glass ceramics as covers according to the Fig. 1 and 2 .

Figure 4

the spectrum of a light source according to the invention, the transmission spectrum of the glass ceramic and the normalized spectrum of the light to be seen through the glass ceramic,

Fig. 5

a representation of the CIE standard color chart with drawn gradients and the marked color locations for different light sources or filters and

Fig. 6

the three tristimulus curves of human perception for the three primary colors.

Detailed description of the embodiments

In Fig. 1 is shown in plan view an electric hob 11 as an inventive electrical appliance, which has a cooktop plate 12 made of glass ceramic. Under the hob plate 12 known heaters are provided, for example, radiation heaters, induction heaters or Kontaktheizeinrichtungen. These are known to the skilled person and therefore neither in the Fig. 1 still in the Fig. 2 shown. The Fig. 1 shows a display area 14 of the hob, which is located for example in a front portion of the hob plate 12 near to a front edge of the electric cooktop 11 down, so to an operator. The display area 14 has four displays 15a to 15d, which differ and will be explained in more detail below. Their light sources are advantageously LED and / or applied as SMD components on a printed circuit board 13 as a carrier.

In Fig. 2 an indicator 15b is off Fig. 1 shown in section. It has an LED 17b 'on the left of the printed circuit board 13 and an LED 17b "on the right next to it, which are arranged close to each other, and may also be designed as SMD components and be provided as close together as possible with respect to mounting and mounting The LED 17b 'and 17b "are arranged together within a shield 19b or in a chamber formed thereof. Alternatively or in addition to the shield 19b could be provided on the underside of the hob plate 12 is still a mask with a corresponding cutout, which also provides for a clearly defined and clearly visible light phenomenon.

At the top of the shield 19b there is a diffuser 22b, for example in the form of a plate, which can be fixed to the shield 19b or glued or cast on. The two LEDs 17b 'and 17b "are according to the first basic embodiment of the invention trained as described above. This means, for example, that the LED 17b 'shines white with a color point for white. The other LED 17b "has a color locus to the left of it and is embodied, for example, as a purely turquoise-emitting light source with a wavelength of approximately 490 nm, so that the LED 17b 'emits white broadband while the LED 17b" radiates narrow-band turquoise. Their light intensities are matched by design and control that just after the radiant reddish-brown cooktop panel 12 made of glass ceramic, the display 15b appears in white light.

The diffuser 22b arranged above the LED 17b 'and 17b "does not shift the spectrum or colorize the emitted light, but rather evenens the light phenomenon, as well as achieving a better mixing of the light from the two light sources then through the cooktop plate 12 through glass ceramic light, which is visible above it as a pure white display 15b, for example in the symbol form as a plus sign.The two light sources in the form of the LED 17b 'and 17b "so especially with displays relatively large area compared to the size of an LED or a SMD LED or two of them are used, since the minimum space required of course depends on this added size.

Right in Fig. 2 is shown as yet another embodiment, a display 15c, which is a so-called seven-segment display, as the Fig. 1 makes it clear. On average, the Fig. 2 only one part is shown, for example, one of the three in Fig. 1 can generate or represent horizontally extending beams.

For the display 15c, a light source 17c is provided, which in turn is arranged in a shield 19c, which may be the housing of the seven-segment display. Such seven-segment displays are for example from the DE 20314391 U or the DE 102009024642 A known, to which expressly referred.

In a space within the shield 19c, therefore, the LED 17c is arranged and radiates upward through a diffuser 22c, also provided here, which in turn functions as described above.

The LED 17c is here designed so that it has a color point according to the aforementioned fundamental second embodiment of the invention, which is shifted from pure white starting something to the left, where it may have a blue cast or turquoise stich, as described above and in Below will be explained in more detail. This single LED 17c thus radiates with its light through the cooktop plate 12 made of glass ceramic, so that above it as a display 15c a pure white display is visible, especially as a pure white seven-segment display. By providing a single LED or light source according to the aforementioned prior art, a seven-segment display with a single housing can be created, which allows a pure white display in a reddish-brown glass ceramic.

In Fig. 3 the transmission spectrum of a hitherto known glass ceramic is shown in dashed lines. Here it can be seen that for wavelengths greater than 700 nm, the transmission T increases sharply or is large. This is particularly advantageous for the use of heating devices in the form of radiant heaters, as has been explained in the introduction. In the case of such known glass-ceramics, there is no transmission in the range of wavelengths significantly less than 700 nm, so this light is thus swallowed.

However, it is also possible to produce glass-ceramics which, in accordance with the course shown in solid lines, have a small but still present transmittance in the range well below 700 nm. Also, a transmission of a few% or about 1% or even a little less, for example, 0.5%, is sufficient to realize a luminous display through the glass ceramic with appropriate luminosity of the light sources. Such a glass ceramic is in the WO 2012/076412 A1 and available from Schott AG under the brand name CERAN HIGHTRANS eco.

In Fig. 4 the course of different spectra is shown. Dash-dotted is the transmission spectrum of an aforementioned glass ceramic from Schott AG. Although the transmission is low in the range of wavelengths less than 700 nm or very low below 550 nm. But it is still there after all, compare Fig. 3 ,

Shown dashed is a normalized to 1 spectrum of the light source according to the invention according to the second basic embodiment of the invention. The course shows a strong increase from about 420 nm on with the steepest area around 450 nm and a maximum at 460 nm. Then there is a similar drop to an intensity of about 0.35 at about 490 nm. From there, the intensity increases again slightly to a value of 0.4, and then again drop sharply to a value of about 0.1 at a wavelength of 570 nm. From then on, the curve asymptotically drops rapidly toward zero towards the region of longer wavelengths. Such a normalized spectrum of the light source is given in the case of an aforementioned light source after passage through the glass ceramic, ie with a color locus of approximately (x, y) = (0.32, 0.32) or (0.33, 0.33 ), which the human eye then sees as white. For glass ceramics with a different transmission spectrum, in particular with even more transmission, the spectrum can again look a little different. Furthermore, the color location can be elsewhere, which is based on Fig. 5 will be explained in more detail, for example, at about (x; y) = (0.25, 0.25).

In Fig. 5 In turn, the so-called CIE standard color chart is now displayed with x-coordinates and y-coordinates. In the triangular area between 0 and 1.0 for each of the two coordinates is the range of theoretical colors. The SFL line is the spectral color line along which the wavelengths of the pure narrowband colors are recorded. The starting point at 330 nm and the end point at 790 nm right are connected by the so-called purple line PL. Furthermore, the BBL line is drawn as a black-body curve indicating the color temperatures for different normalized radiators, which starts at the rightmost of the spectral color line SFL at 1000 K and over a value of, for example, 7500 K to a point of infinitely high temperature, where it ends so left. All the dots on this BBL line appear white to the human eye, so in general, the light from the light source should be on or near this BBL line after passing through the cover or glass-ceramic. Furthermore, the triangular form shows the RGB color space as a large triangle and the aforementioned RGW color space as the upper smaller triangle.

One out Fig. 2 apparent pure white light source has a color location as shown as 17b '. This color locus is approximately (x; y) = (0.3, 0.3) on the BBL line. At the color location with approximately the position (x; y) = (0.13, 0.31), the LED 17c is correspondingly located Fig. 2 , Whose light with this wavelength or with this spectrum or color location per se, although bright turquoise blue green for the human eye. After irradiating the reddish-brown glass ceramic with the transmission spectrum accordingly Fig. 4 however, a user sees white light corresponding to the color location 17b '.

The light source 17b 'off Fig. 2 is formed as a pure white light source with the color locus 17b '. The second light source 17b "is located at a color location 17b" on the spectral color line SFL at a wavelength of about 490 nm and is also shown. As previously described is, it is a very narrow-band luminous light source or just radiates spectral clean with the wavelength of about 490 nm and almost no radiation above or below.

Furthermore, it is still shown with the color locus 18 which light phenomenon the human eye perceives when only a pure white light source corresponding to the color locus 17b 'radiates through a reddish-brown glass ceramic. The resulting hue is light red or pink.

Depending on the transmission behavior of the glass ceramic, of course, other colors or color locations of a display to be seen by the human eye can be achieved in accordance with the considerations presented here. Furthermore, the invention can of course also be used in other electrical appliances except electric hobs with hobs made of glass ceramic. There are also other electrical appliances, their covers, under which a light display is arranged, the light display is to be visible above the cover, are prepared according to the invention or are constructed. In addition to ovens or other cooking appliances as kitchen appliances are devices from the entertainment electronics or even, due to the stable mechanical properties of glass ceramic covers, electrical appliances in the public area such as ticket machines odgl ..

A calculation of the color location for the searched single light source can be done as follows: It must be considered that the sensitivities of the eye are different for the colors and the RGB colors. These are determined empirically and in the diagram in Fig. 5 shown. There is the so-called CIE standard observer. From the solid normalized spectrum of the intensity acc. Fig. 4 For example, you can record the intensity for each wavelength λ and the intensity of each of the individual RGB spectra. as it perceives the human eye accordingly Fig. 6 , multiply λ at exactly this wavelength. The three tristimulus curves in Fig. 6 show the human perception for BLUE, dot the perception for GREEN and dash the perception for RED.

These values of the multiplication are then summed up for all wavelengths λ, and this then gives the values for the three individual colors of the RGB spectrum. If one proceeds in a simplified way, that this is done for every 1 nm steps, a summation is obtained. Theoretically, it is an integration of the three colors over all wavelengths, which, however, is hardly feasible mathematically.

With the result of the summation in turn can determine the required color in the known three-dimensional RGB color space, which must have the light source or LED, after passing through the glass ceramic for the human eye with the sensitivities Fig. 6 white appears.

For the CIE color chart according to Fig. 5 For example, normalization may take place by obtaining the values for the x-coordinate and the y-coordinate by adding up the values for the three colors according to the previous calculation, and for the x-coordinate, that is, the color red, the reciprocal of When added to the value for RED, and for the y-coordinate, ie the color green, the reciprocal of the addition is multiplied by the value for GREEN. The value for the color blue is then obtained by subtracting the values for the color red and for the color green from 1.

Claims (15)

A display device for an electrical appliance with a cover, wherein the cover is colored, in particular reddish-brown, and has an inhomogeneous transmission path for light with high transmission in the range of wavelengths greater than 700 nm and with low transmission in the range of wavelengths smaller than 700 nm, wherein the display device for a display comprises at least one light source with a defined output spectrum for transmission through the cover of the electrical appliance, characterized in that the one light source radiates white, in particular with a color location (x; y) of (0.3; 0.3) , And in addition, in particular in spatial proximity thereto, a further light source is provided with such a color or such a color point, that when viewing the cover of the electrical appliance with both light sources, the display is visible as a white glowing display, wherein the color location of the second light source to the left of the color place of he white light source. Display device according to claim 1, characterized in that the color location of the second light source has almost the same y-coordinate as that of the first white light source, wherein preferably the x-coordinate of the color locus of the second light source is between 0.0 and 0.1, in particular approximately 0.05. Display device according to claim 1 or 2, characterized in that the second light source is designed so that it spectrally radiates very narrow band or radiates pure, preferably with a wavelength of 470 nm to 510 nm, in particular about 490 nm. Display device according to the preamble of claim 1, characterized in that only a single light source per display is used without a second light source directly next to it, wherein the color locus is shifted from white to the left and preferably the light source has a bluish cast, so that by a reddish Through the brown cover, the display will be visible as a substantially white illuminated display. Display device according to claim 4, characterized in that the color location of the single light source has almost the same y-coordinate as white light of about 0.3, in particular between 0.28 and 0.35, wherein the x-coordinate of the color locus is between 0, 1 and 0.2, in particular about 0.18. Display device according to claim 4 or 5, characterized in that the one light source is formed broadband or broadband radiates. Display device according to one of claims 4 to 6, characterized in that the single light source has a normalized to 1 spectrum with a maximum normalized intensity of 1.0 at a wavelength of 450 nm to 470 nm, in particular at about 460 nm, with a steep Rise before it starts at zero and a steep drop thereafter to a relative intermediate depth with a normalized intensity between 0.3 and 0.4 at a wavelength between 480 nm and 500 nm. Display device according to claim 7, characterized in that thereafter a relative intermediate high follows with a normalized intensity between 0.35 and 0.45 at a wavelength between 500 nm and 520 nm, in particular from there the normalized intensity drops again to below 0 , 1 from one wavelength of about 570 nm, preferably with asymptotic approximation to zero. Display device according to one of claims 4 to 8, characterized in that the single light source has a doped with phosphorus semiconductor crystal such that the desired color is achieved. Display device according to one of the preceding claims, characterized in that a plurality of advertisements are provided in the display device, for displaying a symbol, light spot, or the segments of a seven segment display as a display in each case a single, color coordinates corrected white light source is provided in accordance with one of claims 4 to 9. Display device according to one of the preceding claims, characterized in that light sources are provided with a color locus of the RGW color space, wherein the intensities of these light sources between a minimum value and a maximum value are adjustable to display other colors. Display device according to claim 11, characterized in that a light source according to one of claims 4 to 11, which appears white after irradiating the cover, is combined with further light sources, preferably with light sources which radiate spectrally pure or narrow band, in particular green with a wavelength between 540 nm and 550 nm and red with a wavelength between 600 nm and 610 nm, for a display with the colors white, green, yellow and red and mixed colors thereof. Electric appliance with a display device according to one of the preceding claims, characterized in that a cover of the electrical appliance has a reddish-brown color and is translucent, wherein preferably the electric appliance is an electric hob and the cover is a hob plate, in particular of glass ceramic. Electrical device according to claim 13, characterized in that the transmission of the cover in the range of wavelengths smaller than 700 nm is less than 5%, and preferably about 2% or less. Method for driving a display device according to claim 1 or 4, characterized in that broadband light sources with white light, which has a strong blue cast, is radiated through a cover of the electrical appliance, wherein an adjustment of the forward voltage of commonly used light sources to the white light sources done with strong blue cast.

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