EP1618415B1 - Household appliance provided with a symbol display - Google Patents

Abstract

Existing household appliances comprising a symbol display are provided with a light source (25) for illuminating a displayed symbol (7) and an optical filter (10, 27) for reducing the perusal of said displayed symbol when the light source (25) is switched off. The aim of said invention is to optically represent the displayed symbol (7). For this purpose, the optical filter (10, 27) is embodied in such a way that it is transparent for a predefined light colour and opaque to another light colour.

Description

The invention relates to a household appliance with a symbol display, which has a light source for illuminating a display symbol and an optical filter, with the light source is turned off, a view of the display symbol is reduced.

From DE 7 538 571 U generic household appliance with a translucent front panel with printed symbols, name or the like and with a lighting is known. Facing the light source, a white coating is provided on the front panel, which causes a diffuse passage of light. Furthermore, the front panel is formed with a thin, largely translucent dark intermediate coating. Due to the dark intermediate coating, a reflection of external light is largely prevented when the lighting of the household appliance is switched off, as a result of which the symbols optically fade into the background.

The object of the present invention is to provide a household appliance with a symbol display, which is presented in a visually appealing manner.

The object of the present invention is achieved by a household appliance with the features of claim 1. The optical filter is substantially transparent to light of a predetermined color and is substantially opaque to light of other colors. By an appropriate choice of the optical filter, therefore, the color can be adjusted, in which the display symbol is perceived by a viewer.

The optical filter has a transmittance that is different depending on the wavelength of the light so as to be substantially transparent to light of a predetermined color and substantially impermeable to light of other colors. According to the invention can therefore be adjusted depending on the spectral curve of the transmittance of the optical filter, the color in which the display symbol is to be perceived by the viewer. Such filters may be color filters that are transparent to light of its own color and opaque to light of other colors.

1. 1) Bei ausgeschalteter Lichtquelle tritt nur das wenig strahlungsintensive Tageslicht oder Raumlicht durch den optischen Filter. Dieses wird an der Lichtquelle entgegen seiner Einfallsrichtung reflektiert und tritt durch den optischen Filter wieder nach außen. Der optische Filter reduziert den Anteil des Raunilichts im kurz -und/oder langwelligen Spektralbereich nur geringfügig. Aufgrund der geringen Strahlungsintensität des Raumlichts reicht diese geringfügige Reduzierung jedoch bereits aus, damit es vom Auge nicht mehr wahrnehmbar sind. Somit verhindert der Filter bei ausgeschalteter Lichtquelle eine Durchsicht durch den optischen Filter nahezu vollständig.
2. 2) Bei eingeschalteter Lichtquelle tritt das wesentlich strahlungsintensivere, von der Lichtquelle erzeugte Lichtstrahlen durch den optischen Filter nach außen. Der durchgelassene Anteil an kurz- und/oder langwelligem Licht ist in diesem Fall wesentlich größer als bei Raumlicht. Trotz der Strahlungsreduzierung des optischen Filters ist daher der durchgelassene Anteil an kurz- und/oder langwelligem Licht ausreichend groß, um eine gute Wahrnehmung des Anzeigesymbols zu gewährleisten.

According to an advantageous embodiment, the light transmitted by the optical filter of the predetermined color lies in the short-wave and / or long-wave range of the light spectrum. To understand this embodiment, it is important that the photosensitivity of the human eye changes depending on the wavelength. Thus, the eye is the most sensitive to light in the medium spectral range. In the short or long-wave spectral range, however, the sensitivity of the eye is lower. That is, with the same radiation intensity, yellow-green light (wavelength at approx. 550 nm) appears much brighter to the eye than long-wave red light (wavelength at approx. 650 nm) or entertaining blue light (wavelength at approx. 470 nm). Accordingly, the optical filter according to the invention achieves the following effects even at a low radiation reduction (ie at a high transmittance) in the short-wave and / or long-wave spectral range:

1. 1) When the light source is switched off, only the low-intensity daylight or room light passes through the optical filter. This is reflected at the light source counter to its direction of incidence and passes through the optical filter back to the outside. The optical filter reduces the proportion of Raunilichts only slightly in the short and / or long-wave spectral range. Due to the low radiation intensity of the room light, however, this slight reduction is already sufficient so that it is no longer perceptible by the eye. Thus, with the light source turned off, the filter almost completely prevents viewing through the optical filter.
2. 2) When the light source is switched on, the light rays that are considerably more radiation-intensive and produced by the light source pass through the optical filter to the outside. The transmitted content of short and / or long-wave light is much larger in this case than in room light. Despite the radiation reduction of the optical filter, therefore, the transmitted portion of short and / or long-wave light is sufficiently large to ensure a good perception of the display symbol.

It is advantageous if the light source only emits light of a predetermined color. As a result, the existing radiation power of the light source is concentrated to only the predetermined color. The light source is thus energy efficient and cost interpretable. The optical filter and the light source can be even more easily matched to each other when the light source emits monochromatic light. In this case, the wavelengths of the light source beams are within a narrow spectral width. It is cost effective if the light source is designed as an LED.

The radiation intensity of the light source in the direction of the display symbol can be considerably increased without much energy expenditure if the light source is assigned a reflector which aligns the light source beams with the display symbol.

In order to achieve an even distribution of the light over the display symbol, the light generated by the light source can be passed via a light guide to the display symbol. The light guide produces a diffused light that illuminates the display symbol evenly.

In order to achieve a specific spectral transmission profile of the optical filter, the optical filter is combined from at least a first filter and a second filter, which are arranged one behind the other. In this case, each of the filters specializes in a special optical filtering effect. The transmittance of the filter combination results from the product of the transmittances of the individual filters. Such a filter combination generates an additional degree of freedom for varying the transmission profile.

In the filter combination, the first filter may be designed as a color filter that transmits only light of a particular color and is substantially impermeable to light of other colors. The second filter can be designed as a so-called gray filter, which reduces the proportion of the light transmitted by the first filter.

It is optically particularly advantageous if, with the light source switched off, the color of the optical filter essentially corresponds to a color of an opaque environment of the display symbol. The optical filter therefore occurs completely in the background with the light source switched off for the viewer.

Manufacturing technology in a particularly simple manner, the display symbol can be realized by a combination of a translucent area with an opaque area. For the formation of the optical filter, at least the light-permeable region can be adapted accordingly. The translucent area therefore at least partially performs the function of the optical filter at the same time. In terms of component reduction can thus be dispensed with the known from the prior art additional light filter intermediate layers. Such intermediate layers are susceptible to dirt or fingerprints.

A particularly space-saving design of the display symbol is made possible if its translucent and opaque areas on a translucent base material, e.g. a thin film or on a film composite consisting of several films are applied.

In the production of the symbol display, it is advantageous if the film is held to the light source, for example, is glued to it by means of an adhesive layer. In this case, the film together with the light source forms an easily manageable component unit. In such a component unit, the display symbol is particularly easy to align with the light source. Thus, a uniform illumination of the display symbol is guaranteed.

In order to avoid optically disadvantageous refraction of light between the display symbol and a front glass pane of the symbol display, the display symbol and the front glass pane can lie flush against each other over a large area or be arranged at a distance from one another. From a manufacturing point of view, it is advantageous if the display symbol and the front glass pane are spaced apart from one another, ie arranged without contact. In this case, can be dispensed with a difficult to produce flush and large-scale system between the display symbol and the front glass. The distance between the display symbol and the front glass pane can be up to 5 mm, preferably up to 1 mm. A larger distance may, at an unfavorable angle, at least partially obscure or distort the observer display symbol located behind the front glass pane.

For optical reasons, it is particularly advantageous if the printing or the coating on the light-transmitting base material is formed on the side facing away from the viewer. The reflection of external room light at the printing therefore takes place on the side facing away from the viewer. Thus, the perceived by the viewer contrast difference between the translucent and opaque areas is reduced.

It is optically particularly appealing when the opaque region of the translucent base material is dark, preferably dull black. In this case, the translucent area of the translucent base material is also the same color as the base material, namely brown or gray.

Figur 1

in einer Vorderansicht einen Ausschnitt aus einem Backofen bei eingeschalteter Lichtquelle gemäß dem ersten Ausführungsbeispiel;

Figur 2

den Backofen in einer Seitenschnittansicht entlang der Linie A-A aus der Figur 1;

Figur 3

in einer Ansicht entsprechend der Figur 2 den Backofen gemäß dem zweiten Ausführungsbeispiel; und

Figuren 4 bis 7

Diagramme, die in Abhängigkeit von einer Lichtwellenlänge die Lichtempfindlichkeit des Auges, die Strahlungsintensitätskurven einer LED und beispielhaft einer üblichen Tageslichtstrahlung, sowie die Lichtdurchlässigkeit eines ersten und eines zweiten optischen Filters zeigen.

Below, two embodiments of the invention are illustrated with reference to the accompanying figures. Show it:

FIG. 1

in a front view of a section of an oven with the light source according to the first embodiment;

FIG. 2

the oven in a side sectional view along the line AA of Figure 1;

FIG. 3

in a view corresponding to Figure 2 the oven according to the second embodiment; and

FIGS. 4 to 7

Diagrams which show the photosensitivity of the eye as a function of a light wavelength, the radiation intensity curves of an LED and, for example, a typical daylight radiation, as well as the light transmission of a first and a second optical filter.

1 shows a detail of an oven according to the first embodiment is shown in front view. Shown is a oven door 1 with a translucent front glass 2 arranged above it. Behind the windscreen 2, a symbol display with a display symbol 7 is arranged. The display symbol 7 is shown as a clock. In the figure 1, the oven is shown in an on state, in which the display icon 7 is visually well perceived. As will be described later, when the oven is off, visual presentation of the display icon 7 in the windshield 2 is substantially avoided.

According to FIG. 2, the glass front pane 2 has a large-area, opaque aperture 8. In the opaque aperture 8, a translucent cutout 9 is recessed. At a distance a of about 1 to 2 mm behind the windscreen 2, a dark colored film 10 is arranged. On the, the windshield 2 side facing the film 10 is coated with an opaque printing 13. The opaque printing 13 can be seen by a viewer through the windshield 2 through as a dull-black surface, which is indicated in the figure 1 by a hatching. In order to form the display symbol "clock" 7 shown in FIG. 1, an annular first surface region 14 is arranged in the opaque printing 13 of the film 10 and an angular second surface region 15 is arranged therein, both of which are translucent. The colored film 10 is bonded to a lighting component 17 by means of an adhesive layer 16. The adhesive layer 16 extends only in the region of the opaque printing 13. On the other hand, in the light-permeable surface regions 14, 15 the adhesive layer 16 is dispensed with in order to ensure trouble-free passage of light through the surface regions 14, 15.

According to FIG. 2, the lighting component 17 consists of an opaque plastic injection-molded part 21. In the plastic injection-molded part 21, a cavity 23 is formed. This extends through the plastic injection-molded part 21 and widens conically in the direction of the dark-colored film 11. On the inner wall of the cavity 23, a reflector 24 is provided, which aligns incident light in the direction of the film 10. At the end remote from the film 11 of the cavity 23, an LED 25 is arranged, which emits monochromatic light in red color in the present case. In the cavity 23 serving as a light guide, translucent potting compound 27 is poured. This fixes the LED 25 in the plastic injection-molded part 21 and forwards their light to the display symbol 7. In the present case, the translucent potting compound 27 is colored red in the plastic injection-molded part 21.

The effect of the invention will be described below with reference to the diagrams of FIGS. 3 to 6:

In the diagram of Figure 4, the radiation intensity of the LED 25 is shown. The LED 25 emits light of high intensity in a wavelength interval between about 600 nm and 700 nm. This light appears to the viewer in red. In addition to the radiation intensity curve of the LED 25, FIG. 4 shows a radiation intensity curve 28 which represents the radiation intensity of a conventional type of daylight. The curve 28 runs in the range of an average radiation intensity, which is significantly below the maximum value of the radiation intensity curve of the LED 25.

The high radiation intensity of the LED 25 in the region of the long-wave light is necessary because the human eye is comparatively insensitive to long-wave light of red color, as can be seen from the diagram of FIG. Accordingly, a viewer with the same radiation intensity yellow-green light (wavelength λ at about 550 nm) appears much brighter than long-wavelength red light (wavelength λ at about 650 nm) or short-wave blue light (wavelength λ at about 470 nm).

When the LED 25 is turned on, light is initially generated in accordance with the diagram from FIG. These are passed over the red-colored light guide 27 to the dark colored film 10. On the one hand, the light guide 27 produces a uniform diffuse light distribution over the two light-permeable surface regions 14, 15 of the film 10. On the other hand, the light guide 27 acts as a first optical filter due to its red coloration. The wavelength-dependent course of the transmittance τ ₁ of the light guide 27 is shown in FIG. 5 Accordingly, the light guide 27 is formed as a color filter, the light of a wavelength λ from about 630 nm passes almost unhindered. For light up to about 630 nm, the light guide 27, however, is substantially impermeable. The spectral width of the light emitted by the LED 25 light is therefore reduced, resulting in a more advantageous color perception of the display symbol 7 for the viewer.

Following the light guide 27, the light passes through the two translucent surface regions 14 and 15 of the dark-colored film 10. The dark-colored film 10 acts like a second optical filter, which is designed here as a so-called gray filter is. That is, the dark-colored film 10 has, according to the diagram of FIG. 6, a transmittance τ ₂ which, independently of the wavelength λ, is approximately constant at approximately 70%. The dark-colored film 10 therefore passes about 70% of the radiation-intensive LED light in the wavelength interval between about 630 nm and about 700 nm. However, the transmitted content of 70% of the radiation-intensive LED light is sufficiently large to ensure a pleasant lighting effect of the display symbol 7.

When the LED 25 is turned off, only external room light passes through the transparent areas 14, 15 of the film 10. The outer room light is reflected at the light guide 27 against its direction of incidence. Furthermore, the external room light has a comparatively low radiation intensity, as shown in the diagram of FIG.

Since the light guide 27 is colored red, it essentially only reflects long-wave red light, which can only be perceived reducedly by the human eye, as shown in the diagram of FIG. The light reflected by the light guide 27 red light is reduced when passing through the transparent areas 14, 15 of the film to about 70%. However, this reduction is already sufficient so that the emerging long-wave light is no longer perceptible by the human eye.

The interaction between the red-colored light guide 27 and the dark foil 10 ensures that when the LED 25 is switched off, a view of the light guide 27 and the LED 25 is prevented. The viewer sees the translucent areas 14, 15 in the color matt black. That the translucent areas 14, 15 are color matched when the LED 25 is turned off the matte-black opaque coating 13 held. It has proven particularly advantageous if the dark-colored film 10 is tinted brown or gray. By means of such a hue, the contrast between the opaque and translucent regions 13, 14, 15 has almost disappeared.

The arrangement of the second embodiment of Figure 7 corresponds in construction and operation substantially the arrangement described in Figures 1 to 6. In contrast to the first embodiment, however, the opaque Printed on the 13 facing away from the front glass pane 9 side of the colored film 11 applied. Room light beams are therefore reflected on the side facing away from the viewer side of the film 11. Perceptible to the viewer differences in gloss level between the black print 13 and the light-transmitting area 15 are thus almost completely eliminated.

Claims (13)

1. Domestic appliance with a symbol display comprising a display symbol carrier (10) of a light-permeable base material, which is formed with at least one light-permeable region (14, 15) and at least one light-impermeable region (13), and a light source (25) for illuminating the display symbol carrier (10) as well as an optical filter (10, 27), characterised in that the optical filter (10, 27) comprises as at least one first filter (27) a colour filter, which is substantially permeable to light of a predetermined colour and substantially impermeable to light of other colours, and as a second filter (10), which is arranged in series, a filter of dark colour by which inspection of the display symbol (7) is reduced when the light source (25) is switched off.
2. Domestic appliance according to one of the preceding claims, characterised in that the light of the predetermined colour transmitted by the optical filter (10, 27) lies substantially in the short-wave and/or long-wave range of the light spectrum.
3. Domestic appliance according to one of the preceding claims, characterised in that the light source (25) emits only light of a predetermined colour.
4. Domestic appliance according to one of the preceding claims, characterised in that the light source (25) is constructed as an LED.
5. Domestic appliance according to one of the preceding claims, characterised in that a reflector (24) for increasing a radiation intensity in direction towards the display symbol (7) is associated with the light source (25).
6. Domestic appliance according to one of the preceding claims, characterised in that an optical waveguide (27) which distributes the light produced by the light source uniformly over the display symbol (7) is arranged between the light source (25) and the display symbol (7).
7. Domestic appliance according to one of the preceding claims, characterised in that the optical filter (10, 27) comprises at least one first filter (27) and at least one second filter (10), which are arranged in series.
8. Domestic appliance according to one of the preceding claims, characterised in that when the light source (25) is switched off the colour of the optical filter (10, 27) substantially corresponds with a colour of a light-impermeable surrounding (13) of the display symbol (7).
9. Domestic appliance according to one of the preceding claims, characterised in that the symbol display comprises a display symbol carrier (10) of a light-permeable base material constructed with at least one light-permeable region (14, 15) and at least one light-impermeable region (13).
10. Domestic appliance according to claim 9, characterised in that for construction of the optical filter (10, 27) the light-permeable base material of the display symbol carrier (10) is correspondingly adapted at least in the light-permeable region (14, 15).
11. Domestic appliance according to one of claims 9 and 11, characterised in that the display symbol carrier (10) is formed by at least one foil.
12. Domestic appliance according to one of claims 9 to 11, characterised in that the light-impermeable region (13) of the display symbol carrier (10) is formed by a light-impermeable coating or printing on the display symbol carrier (10).
13. Domestic appliance according claim 12, characterised in that the light-permeable coating (13) is formed on a side of the display symbol carrier (10) remote from an observer.

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