EP1948727B1 - Device for illuminating using blue, green, yellow, or red light emitting diodes - Google Patents

Abstract

The invention relates to an apparatus for illumination with blue, green, yellow or red light-emitting diodes (LEDS), comprising one or more coloured LEDs and a light-scattering cover associated with the LED colour and composed of coloured plastic and having a base colour derived from one or more non-fluorescent dyes, characterized in that the light-scattering cover comprises, in addition to the base colour, at least one fluorescent dye associated in terms of colour with the base colour, where the dye mixture has been adjusted in such a way that the reflectance of the light-scattering cover is at least 28% at the wavelength of the energy maximum of the LED(S) used, where, based on the standard chromaticity diagram and on the colour loci of the reflected light from the light-scattering cover and on the colour locus of the LED(s) used, the following alternative relationship applies to the absolute value of the difference between the x value of the light-scattering cover and the x value of the LED and the absolute value of the difference between the y value of the light-scattering cover and the y value of the LED: a) for blue LED illumination: absolute value for x smaller than 0.03/absolute value for y smaller than 0.05 b) for green LED illumination: absolute value for x smaller than 0.05/absolute value for y smaller than 0.08 c) for yellow LED illumination: absolute value for x smaller than 0.0025/absolute value for y smaller than 0.02 d) for red LED illumination: absolute value for x smaller than 0.03/absolute value for y smaller than 0.003.

Description

The invention relates to a device for lighting with blue, green, yellow or red light emitting diodes (LEDs), consisting essentially of an LED light source and a light scattering cover of colored plastic associated with the light source.

State of the art

Illuminable devices, eg. B. for billboards, consisting essentially of a light source and the light source associated light-diffusing cover of colored plastic are known in principle (sz B. JP 61159440 ). In general, incandescent or fluorescent tubes are used as light sources, which have a good luminosity and emit a wide spectrum of light. Due to the wide spectrum of light corresponding colored plastic covers appear in unlit condition, ie z. B. in daylight, in the same color impression, which can be perceived even with backlighting by means of said light sources.

Light-emitting diodes are of significantly lower luminance compared to light sources such as incandescent lamps or fluorescent tubes. However, colored light-emitting diodes are nevertheless very noticeable in the dark, since they radiate a substantially or almost monochromatic light, which in turn is relatively intense in the respective wavelength range. Corresponding colored LEDs are available from several manufacturers z. B. in the colors red, green, blue and yellow available.

Dyeing and Dyeing process for plastics such. B. polymethyl methacrylate are well known z. B. off EP-A 130 576 ,

WO 03/052315 describes an illuminable device consisting essentially of a light source and a light-diffusing cover made of colored plastic associated with the light source, characterized in that the light source consists of one or more light-emitting diodes (LEDs) emitting a colored substantially monochromatic light and the associated light-scattering Cover at the wavelength of the relative energy maximum of the LED has a transmission (DIN 5036) of at least 35% and a reflection (DIN 5036) of at least 15%. According to the WO 03/052315 The object is achieved to provide an alternative to the known illuminable devices in which colored plastic covers are illuminated by means of incandescent or fluorescent tubes. The coloring of the light-scattering cover takes place by means of non-fluorescent dyes or colorants. In particular, the device allows optically in about the same color impression in incident light, so z. B. in daylight, as well as fluoroscopy. The device also allows devices with a smaller overall depth and lower power consumption compared to conventionally illuminated devices due to the use of LEDs.

Task and solution

Illuminable devices according to the WO 03/052315 allow optically in about the same color impression in reflected light, so z. B. in daylight, as well as fluoroscopy. It has been seen as an object the devices according to the WO 03/052315 develop so that the color impression appears even more brilliant in daylight, as well as in fluoroscopy, without there being noticeable deviations of the two color impressions. The task is solved by a

1. a) für blaue LED-Beleuchtung: Betrag x kleiner 0,03 / Betrag y kleiner 0,05
2. b) für grüne LED-Beleuchtung: Betrag x kleiner 0,05 / Betrag y kleiner 0,08
3. c) für gelbe LED-Beleuchtung: Betrag x kleiner 0,0025 / Betrag y kleiner 0,02
4. d) für rote LED-Beleuchtung: Betrag x kleiner 0,03 / Betrag y kleiner 0,003

Device for illuminating with blue, green, yellow or red light-emitting diodes (LEDs), containing one or more colored LEDs and a light-diffusing cover of colored plastic assigned to the LED color, which has a base coloring by means of one or more non-fluorescent dyes, characterized in that the light-scattering cover contains at least one of the basic coloring color-associated fluorescent dye in addition to the basic coloring, the dye mixture being adjusted such that the light-scattering cover has a reflection of at least 28% at the wavelength of the maximum energy of the LED or LEDs used,
wherein, based on the standard color chart and the color loci of the reflection of the light-diffusing cover and the color location of the LEDs or LEDs used, the amount of the difference of the x value of the light-diffusing cover with the x value of the LED and the amount of the difference of the y Value of the light-diffusing cover with the y-value of the LED behaves alternatively as follows:

1. a) for blue LED illumination: amount x less than 0.03 / amount y less than 0.05
2. b) for green LED illumination: amount x less than 0.05 / amount y less than 0.08
3. c) for yellow LED illumination: amount x less 0.0025 / amount y less 0.02
4. d) for red LED lighting: amount x less than 0.03 / amount y less 0.003

The invention is based on the transmission and the reflection of the light-diffusing plastic cover similar to that in the WO 03/052315 described, so adapt to the monochromatic light of the LED used that almost the same color impression can be obtained in reflected light and in transmitted light. The color location of the transmission of the light-scattering cover will simplify with the color location of the LED (x _LED / y _LED ) equated, since the light of the LED is monochromatic and is virtually unchanged by the light-scattering cover. The invention achieves, by the addition of the fluorescent dye with simultaneous adjustment of Basiseinfärbung, one on the WO 03/052315 In addition, approximation of the color locus of the reflection of the light-scattering cover ((x _reflection / y _reflection ) in incident light) and the color locus of the LED ((x _LED / y _LED ) in the illuminated state). With knowledge of the present invention, a person skilled in the art can make the appropriate adjustments to the coloring. Corresponding advertising or information boards appear optically approximately the same both during the day and in the backlit state. Opposite the WO 03/052315 In this case, the reflection values are generally significantly increased and always closer to the corresponding color location of the LED, while the values for the transmission and its color location are not or only slightly changed. The visually perceived appearance is noticeably brighter, more brilliant, and therefore more attractive to the user, both during the day and at night.

The inventive equipment, it is possible to make the device appear much brighter and more brilliant with the same power consumption or reduced power consumption at least an equivalent effect as that of WO 03/052315 to achieve. The inventively illuminable devices require smaller depths, as LEDs are smaller than corresponding incandescent or fluorescent tubes. Opposite the WHERE 03/052315 It is possible to reduce the number of LEDs included, making complex shapes even easier to realize. The power consumption is lower, with almost the same visibility in the backlit state. Since LEDs can be operated with low voltages, the electrical safety of the devices according to the invention is considered to be higher or easier to ensure. The maintenance is also lower, since LEDs usually have to be replaced less often than other bulbs, such. B. fluorescent tubes.

characters

The invention is illustrated by the following figures, but without being limited to the illustrated embodiments.

Fig. 1/2:

• 3 = Grün 3: Nur Basiseinfärbung (Stand der Technik, gemäß WO 03/052315 )
• 1 = Grün 1: Basiseinfärbung + Fluoreszenzfarbstoff (erfindungsgemäß)
• 2 = Grün 2: Basiseinfärbung + Fluoreszenzfarbstoff + TiO₂-Zusatz
  (erfindungsgemäß)

Reflectance spectrum of three colored, light-scattering plastic discs when illuminated with a green LED with a relative maximum energy at about 520 nm. (Compositions: see Examples 1 - 3, Green 1 -3)

• 3 = green 3: only basic coloring (prior art, according to WO 03/052315 )
• 1 = green 1: basic coloring + fluorescent dye (according to the invention)
• 2 = green 2: base stain + fluorescent stain + TiO _{2 added}
  (Invention)

Fig. 2/2:

• U = Unbuntpunkt (x/y = 0,33/0,33)
• LED = Farbort einer grünen LED (x_LED/y_LED)
• R = Farbort der Reflexion einer lichtstreuenden Abdeckung (x_Reflexion/y_Reflexion)

Schematic representation of the standard color chart.

• U = achromatic point (x / y = 0.33 / 0.33)
• LED = color location of a green LED (x _LED / y _LED )
• R = color location of the reflection of a light-scattering cover (x _reflection / y _reflection )

Embodiment of the invention contraption

1. a) für blaue LED-Beleuchtung: Betrag x_Diff kleiner 0,03 / Betrag y_Diff kleiner 0,05
2. b) für grüne LED-Beleuchtung: Betrag x_Diffkleiner 0,05 / Betrag y_Diff kleiner 0,08
3. c) für gelbe LED-Beleuchtung: Betrag x_Diff kleiner 0,0025/ Betrag y_Diff kleiner 0,02
4. d) für rote LED-Beleuchtung: Betrag x_Diff kleiner 0,03 / Betrag y_Diff kleiner 0,003 '

The invention relates to a
Device for lighting with blue, green, yellow or red light-emitting diodes (LEDs), containing one or more colored LEDs and one of the LED color or the color of the LED in the luminous state associated, light-diffusing cover made of colored plastic, a base coloring by means of a or more non-fluorescent dyes, characterized in that
the light-scattering cover contains, in addition to the base coloration, at least one colorant associated with the base coloration, wherein the colorant coverage has a reflectance of at least 28% at the energy maximum wavelength of the LED or LEDs used , relative to the standard color chart (DIN 5033) and the color locus of the reflection of the light diffusing cover ((x _reflection / y _reflection ) in incident light) and the color locus of the LED ((x _LED / y _LED ) in the illuminated state), the amount of the difference (Amount x _diff ) of the x value of the light scattering cover (x _reflection ) with the x value of the LED (x _LED ) and the amount of difference (amount y _diff ) of the y value of the light scattering cover (y _reflection ) with the y value of the LED (y _LED ) alternatively behaves as follows:

1. a) for blue LED illumination: amount x _diff less than 0.03 / amount y _diff less than 0.05
2. b) for green LED illumination: amount x _diff less than 0.05 / amount y _diff less than 0.08
3. c) for yellow LED illumination: Amount x _Diff less 0.0025 / Amount y _Diff less 0.02
4. d) for red LED illumination: amount x _diff less 0.03 / amount y _diff less 0.003 '

It comes only to the absolute difference or the distance of the x or. y values to each other, not their relative position on the standard color chart. This difference or distance should be as small as possible, ideally close to or equal to zero. However, it should at least not exceed the upper limits specified above. It is also irrelevant whether the formation of the difference of the corresponding x or y values leads mathematically to a positive or to a negative value. For this reason, the invention is based on the amount of the difference of the x-value of the light-diffusing cover with the x-value of the LED and the amount of the difference of the y-value of the light-diffusing cover with the y-value of the LED. Using the present invention, it advantageously becomes possible to make a very close adaptation of the color locus of the reflection of the light-diffusing cover to the color locus of the LEDs used in the luminous state. In this way, illuminable devices are provided, which convey a largely coincident and at the same time very brilliant color impression in the unlit and in the illuminated state.

The invention relates to an illuminable device comprising a light source in the form of one or more colored light-emitting diodes (LEDs) and a light-scattering cover of colored plastic associated with the light source. The device thus consists essentially of the components indispensable for the function, namely the light source and the light-scattering cover of colored plastic associated with the light source. In addition, further, for the functionality of the invention, however, uncritical elements, such as a frame, housing or fasteners, etc. may be present.

The device may be designed such that the LEDs and the light-diffusing cover are associated with each other at a distance of 3 to 12, preferably 4 to 10 cm. At this distance a good illumination is achieved. If the distance is too short, the position of the LED will be visible as a bright spot. If the distance is too great, the brightness decreases too much.

The LEDs can z. B. in a box or frame, of the light-diffusing cover, z. B. in plate form, is covered. The cover may be provided with an information-bearing layer, e.g. As a film provided or even already have the form of information, for. B. in letter or number form.

General example

The following general example illustrates a device according to the invention for yellow LED lighting and is mutatis mutandis applicable to blue, green or red LED lighting.

• Betrag x_Diff = x_Reflexion minus x_LED = 0,498 - 0,5 = 0,002. Der Wert ist kleiner als 0,0025 und liegt damit im erfindungsgemäß geforderten Bereich.
• Betrag y_Diff = Y_Reflexion minus y_LED = 0,485 - 0,5 = 0,015. Der Wert ist kleiner als 0,02 und liegt damit ebenfalls im erfindungsgemäß geforderten Bereich. Die entsprechende Vorrichtung ist demnach erfindungsgemäß.

The color of a yellow glowing LED can z. B. at x _LED = 0.5 / y _LED = 0.5 are. The color locus of the reflection of a yellow-colored, light-scattering cover (eg Yellow 1 with a reflectance value of 40%, see in particular Example 1 and Tables 4 and 6) which has been adapted in accordance with the invention in the Farbbort, can be obtained, for example. For example, x _reflection = 0.498 / y _reflection = 0.485. The amount of the difference, amount x _diff , of the x value of the light-diffusing cover (x _reflection ) with the x-value of the LED (x _LED ) and the amount of the difference, amount y _diff , the y value of the light-diffusing cover (y _Reflection ) with the y-value of the LED (y _LED ) behaves as follows:

• Amount x _Diff = x _Reflection minus x _LED = 0.498 - 0.5 = 0.002. The value is less than 0.0025 and is therefore within the range required by the invention.
• Amount y _Diff = Y _Reflection minus y _LED = 0.485 - 0.5 = 0.015. The value is less than 0.02 and is thus also in the invention required range. The corresponding device is accordingly according to the invention.

In an analogous manner, the amounts x _diff and y _diff can be calculated for other colors.

light source

The light source consists of one or more or a plurality of colored light-emitting diodes (LEDs). Optionally, LEDs of different colors can be used simultaneously.

Colored LEDs are of significantly lower luminance compared to light sources such as incandescent or fluorescent tubes. However, colored LEDs are still very noticeable in the dark, as they radiate a substantially or almost monochromatic light, which in the respective. Wavelength range is again relatively intense. Corresponding colored LEDs are available from several manufacturers z. B. in the colors red, green, blue and yellow available. Unsuitable for the purposes of the invention are white LEDs, since they do not produce a nearly monochromatic but a broad spectrum of light, similar to a conventional light bulb.

Colored LEDs emit almost or substantially monochromatic light. The term "almost or substantially" monochromatic light is meant to express that the light of commercially available colored LEDs is simplified and often referred to as monochromatic in comparison to other normal light sources, but strictly speaking it is not. In practice, the wavelength spectrum of a colored LED has a narrow, peak-like distribution. In addition to the wavelength of the relative energy maximum (peak maximum) characteristic of the respective LED, adjacent wavelengths with lower intensity are always found. One skilled in the art would therefore call the light of colored LEDs almost or substantially monochromatic.

The color of the LED depends on the wavelength of its relative energy maximum. This relative energy maximum can z. B. be determined spectrophotometrically and drawn in a wavelength spectrum. You can see the light source z. B. in a Ulbricht'sche ball (see DIN 5036) bring and measure the exiting light. The highest point (peak) of the curve indicates the wavelength of the relative energy maximum.

The number of LEDs depends on the size of the device, the luminosity of the LEDs used and the overall desired brightness of the device in the transilluminated state. LEDs are z. B as modules of 4 LEDs in each a holder available, from which optionally a variety can be installed in the device.

Light emitting diodes (LEDs),

Suitable LEDs are z. For example, commercially available red, blue, yellow or green LEDs.

A red LED has a relative energy maximum in the range of about 610 to 640 nm. The color locus of a red-emitting LED in the luminous state can, for. B. at about x = 0.67 and y = 0.33.
The red LED (Osram LM03-BA) has z. B. a relative energy maximum at about 620 nm.

A blue LED has a relative energy maximum in the range of about 440 to 500 nm. The color locus of a blue-emitting LED in the illuminated state can, for. B. at about x = 0.14 and y = 0.06.
The blue LED (Osram LM03-BB) has z. B is an energy maximum at about 460 nm.
The blue LED (ESS Blue) has z. B is an energy maximum at about 475 nm.

A yellow LED has a relative energy maximum in the range of about 570 to 610 nm. The color locus of a yellow glowing LED in the illuminated state can, for. B. at about x = 0.5 and y = 0.5.

The yellow LED (Osram LM03-BY) has z. B is an energy maximum at about 590 nm.

A green LED has a relative energy maximum in the range of approximately 500 to 540 nm. The color locus of a green-emitting LED in the luminous state can, for. B. at about x = 0.16 and y = 0.73.
The green LED (Osram LM03-BT) has z. B is an energy maximum at about 520 nm.

Light-diffusing plastic cover plastics

• Polymethylmethacrylat-Kunststoff (gegossen oder extrudiert), schlagzäh modifiziertes Polymethylmethacrylat, Polycarbonat-Kunststoff, Polystyrol-Kunststoff, Styrol-Acryl-Nitril-Kunststoff, Polyethylentherephthalat-Kunststoff, glykolmodifizierter Polyethylentherephthalat-Kunststoff, Polyvinylchlorid-Kunststoff, transparenter Polyolefin-Kunststoff, Acrylnitril-Butadien-Stryrol (ABS)-Kunststoff oder Mischungen (Blends) verschiedener thermoplastischer Kunststoffe.

The light-diffusing cover is made of plastic, preferably a thermoplastic or a thermo-elastic plastic. Preferably, the plastic used should be transparent or translucent in the non-colored state. Suitable plastics can z. For example:

• Polymethyl methacrylate plastic (cast or extruded), impact modified polymethyl methacrylate, polycarbonate plastic, polystyrene plastic, styrene-acrylonitrile plastic, polyethylene terephthalate plastic, glycol-modified polyethylene terephthalate plastic, polyvinyl chloride plastic, transparent polyolefin plastic, acrylonitrile butadiene -Stryrol (ABS) plastic or mixtures (blends) of various thermoplastics.

based coloring

The light-diffusing plastic cover has a base coloring, ie a coloring by means of one or more non-fluorescent dyes. This type of coloring is known in principle WO 03/052315 , Not however, in the inventive adaptation described herein in connection with a fluorescent dye or fluorescent dyes.

According to the WO 03/052315 has a light-scattering cover, which is provided with a base coloring by means of one or more non-fluorescent dyes, at the wavelength of the relative energy maximum of the LED used a transmission (DIN 5036) of at least 35% and a reflection (DIN 5036) of at least 15% ,

When adding one or more fluorescent dyes according to the invention, it is preferable to use base staining with respect to WO 03/052315 adapt. The adjustment is usually necessary to avoid too large right angle deviations of the original color locus from the straight line passing through the achromatic point (x / y = 0.33 / 0.33) and the color locus of the LED and associated color shifts counteract.

A person skilled in the art can make such an adjustment easily by adapting the concentration of the non-fluorescent dyes accordingly, as a rule, slightly decreasing them in total or z. B. instead of two non-fluorescent dyes only one used and the concentration of the remaining changes accordingly. Suitable adaptations are also apparent from the comparison of the inventive examples disclosed herein with those of the inventive examples.

Fluorescent dye

The plastic light-diffusing cover contains a base stain, which is preferably adapted due to the presence of the fluorescent dye over a base stain of the prior art.

The adapted basic coloring with the associated fluorescent dye causes as a dye mixture that the light-scattering cover at the wavelength of the energy maximum of the LED used has a reflection (DIN 5036), which is at least 28, preferably at least 30, more preferably at least 35% and at least at least 50% above the value that would be achieved with a (non-matched) base stain without a fluorescent dye. As a result, the color appears much more brilliant than with a coloring according to the WO 03/052315 is reachable. In particular, in a light-scattering cover according to the invention, the color location of the reflection is closer to the color locus of the LED than to a corresponding cover of the prior art.

Suitable fluorescent dyes are in particular those fluorescent dyes which emit fluorescent light in the range of the wavelength of the energy maximum of the colored LEDs used. The effect according to the invention can be achieved with surprisingly small amounts, for. B. with 0.001 to 0.01 wt .-%, based on the plastic of the light-scattering covers,

Suitable fluorescent dyes are, for. B. perylene-based or Perylenderivate, for example, under the trade name Lumogen® BASF available fluorescent dyes.

For light-scattering coverings dyed yellow in the base coloration, the addition of a yellow-fluorescent dye, preferably a yellow-fluorescent perylene dye, in particular the fluorescent dye Lumogen® F Yellow 170, is suitable.

For light-scattering coverings colored red in the base coloring, the addition of a red-fluorescent dye, preferably a red-fluorescent perylene dye, in particular the fluorescent dye Lumogen® F Red 305 or Lumogen® F Rosa 285 is suitable.

For light-diffusing covers dyed green in the base coloring, the addition of a green fluorescent dye, preferably a green fluorescent perylene dye, in particular the fluorescent dyes Lumogen® F Yellow 083 or Lumogen® F Yellow 170, is suitable.

For light-scattering covers dyed blue in the base coloring, the addition of a blue-fluorescent dye, preferably a blue-fluorescent perylene dye, in particular the fluorescent dyes Lumogen® F Violet 570 or Lumogen® F Blue 650 is suitable.

Opposite the WO 03/052315 The main difference is that the reflection at the wavelength of the maximum energy of the LED used, due to the color mixture of base coloring and at least one, the base coloring associated fluorescent dye is significantly increased. It is surprising that this succeeds without or with only a slight change in the values for the transmission or the color locus. Viewed visually, the light-diffusing cover used according to the invention appears opposite to one according to FIG WO 03/052315 once again much more brilliant. The color as such appears virtually unchanged when viewed with the naked eye.
The plastic light-scattering cover thus assigned according to the invention preferably has a transmission (DIN 5036, see parts 1 and 3) of at least 20%, preferably at least 35%, preferably at least 38%, particularly preferably at least 41, at the wavelength of the relative energy maximum of the light-emitting diode % and a reflection (DIN 5036, parts 1 and 3, reflection or remission) of at least 28%, preferably at least 40%, particularly preferably at least 50%. The reflection is advantageously at least 50%, preferably at least 75%, more preferably at least 100% above the value that would be achieved with a corresponding base coloring of the prior art without fluorescent dye.

Advantageously, the transmission of a light-diffusing cover according to the invention is higher than that of a corresponding light-diffusing cover of the prior art (see Tables 4 and 5).
In a yellow-colored light-diffusing cover according to the invention, the transmission increases by approximately 1 to 2% in comparison.
In a red-colored light-scattering cover according to the invention, the transmission increases by about 30 to 35% in comparison.
In a green-colored light-scattering cover according to the invention, the transmission increases by about 15 to 25% in comparison.
In a light-scattering cover dyed blue according to the invention, the transmission increases by about 7 to 15% in comparison.

In particular, the transmission of a light-diffusing cover associated with a yellow LED can be at least 50%, preferably at least 60%. be. The corresponding reflection can be at least 28%, preferably at least 30%, in particular at least 40%.

In particular, the transmission of a light-scattering cover assigned to a red LED can amount to at least 40%, preferably at least 45%. The corresponding reflection can be at least 28%, preferably at least 45%.

In particular, the transmission of a light-diffusing cover associated with a green LED can amount to at least 40%, preferably at least 42%. The corresponding reflection can be at least 28%, preferably at least 30%, in particular at least 40%.

In particular, the transmission of a light-diffusing cover assigned to a blue LED can amount to at least 40%, preferably at least 42%. The corresponding reflection can be at least 25%, preferably at least 30%.

In the event that LEDs of different colors are used simultaneously to achieve mixed colors, eg. B. yellow and green LEDs give a yellow-green color impression, should the associated light-diffusing plastic cover at least at the wavelength of the relative energy maximum of one of the LEDs used, ie, for. As the yellow or green LED, the above-required reflection values and preferably also have the above-mentioned transmission values.

The associated light-diffusing cover consists of a plastic which is a plastic which is transparent in the non-colored state and without scattering agent, or preferably a transmittance (DIN 5036, s. Parts 1 and 3 / D65) of at least 50%, preferably at least 70, particularly preferably from 75 to 92%. With scattering agent but without colorant, the transmittance may favorably be at least 40%, more preferably at least 50%.

Suitable plastics are z. Polymethyl methacrylate plastic, impact modified polymethyl methacrylate, polycarbonate plastic, polystyrene plastic, styrene-acrylonitrile plastic, polyethylene terephthalate plastic, glycol-modified polyethylene terephthalate plastic, polyvinyl chloride plastic, transparent polyolefin plastic, acrylonitrile-butadiene-styrene ( ABS) plastic or blends of various thermoplastics.

Because of their high weather resistance, in particular for outdoor applications polymethyl methacrylate plastics from cast or extruded polymethylmethacrylate, z. B. with a methyl methacrylate content of 85 to 100 wt .-%, preferably. Optionally, up to 15 wt .-% of suitable comonomers such as. Esters of methacrylic acid (eg, ethyl methacrylate, butyl methacrylate, hexyl methacrylate, cyclohexyl methacrylate), esters of acrylic acid (eg, methyl acrylate, ethyl acrylate, butyl acrylate, hexyl acrylate, cyclohexyl acrylate), or styrene and styrene derivatives such as α-methylstyrene or p-butyl methacrylate. Methylstyrene be polymerized or contained in the polymer.

The light scattering capacity of the cover can, measured according to DIN 5036, preferably have a value of at least 0.5, more preferably of at least 0.6, in particular at least 0.7. The better the light scattering capability, the smaller the spacing of the LEDs from the cover and the associated depths of the device can be realized.

Light-scattering agent

As a light scattering agent z. As BaSO ₄ , polystyrene or Lichtstreuperlen be used from a crosslinked plastic.

BaSO ₄ or polystyrene are preferred and are preferably introduced in an amount of 1.5 to 2.5 wt .-% in the plastic.

Lichtstreuperlen of a crosslinked plastic are preferably introduced in an amount of 0.1 to 10 wt .-% in the plastic.

The requirement for high transmission with high light scattering is a difficult requirement. High scattering power is achieved by titanium dioxide. Since this colorant but reflects a large part of the light, only low light transmittances are possible. More favorable are colorless scattering pigments which deviate in refractive index to about 0.2 from the refractive index of the acrylic glass. For example, calcium carbonate, magnesium carbonate, aluminum trihydroxide, magnesium hydroxide, barium sulfate, etc. are suitable.
Likewise, polymers which lie in the suitable refractive index range can be used. For example, in the monomer methyl methacrylate, polystyrene can be dissolved which then precipitates during polymerization and results in a material with good light scattering. However, it is also possible to add crosslinked polymer particles, for example polymer beads of crosslinked polystyrene or crosslinked copolymers of methyl methacrylate with phenyl (meth) acrylate or benzyl (meth) acrylate.

Production of colored light-scattering plastic cover

Dispersants and colorants can the plastic in the production by polymerization in the polymerizable mixture (casting) or during thermoplastic processing of the polymer in the melt state, for. B. by extrusion or injection, in a conventional manner added or incorporated. In addition to the plate shape, any profiles, such as pipes, rods, etc. can be manufactured.

In this way, for. B. plastic plates, z. B. with a thickness of z. B. 0.5 to 10, preferably 1 to 5 mm are obtained, which can be used as covers for illuminable devices according to the invention with rectangular boxes, frame or bracket. Corresponding pieces can be converted and adapted as required by cutting, milling, sawing or other processing in virtually any shape and adapted.

Colorants for basic coloring

Non-fluorescent colorants for base coloration are preferably non-fluorescent organic colorants for the purposes of the invention, since they have high brilliance and luminosity both in reflected light and in transmitted light. To protect the acrylic against the effects of light and weather, light stabilizers, UV absorbers, antioxidants, etc. can be added.

• Für gelbe Einfärbungen: Pyrazolon-Gelb oder Perinon Orange bzw. Mischungen daraus.
• Für rote Einfärbungen: Mischungen aus Pyrazolon-Gelb oder Antrachinonrot oder Naphtol AS oder DPP-Rot bzw. Mischungen daraus.
• Für grüne Einfärbungen: Cu-Phtalocyanin-Grün oder Pyrazolon-Gelb bzw. Mischungen daraus.
• Für blaue Einfärbungen: Anthrachinon-Blau oder Ultramarin-Blau bzw. Mischungen daraus.

Suitable colorants in plastic are in particular non-fluorescent soluble dyes or non-fluorescent organic pigments but also less preferably insoluble inorganic color pigments. To name a few are exemplary:

• For yellow colorations: pyrazolone yellow or perinone orange or mixtures thereof.
• For red colorations: mixtures of pyrazolone yellow or anthraquinone red or naphtol AS or DPP red or mixtures thereof.
• For green colorations: Cu-phthalocyanine green or pyrazolone yellow or mixtures thereof.
• For blue colorations: anthraquinone blue or ultramarine blue or mixtures thereof.

Chromaticity diagram

The standard color chart according to DIN 5033 is well known to the person skilled in the art. The standard color chart according to DIN 5033 makes it possible to clearly classify the colors of light sources and body colors (eg for spreads, light filters, etc.) according to their color.

The classification presupposes a measurement of the standard color value components x, y; The coordinates thus uniquely determine the color location of a color type (eg red, green, yellow or blue or color mixtures). Corresponding color measurements can be carried out with commercially available colorimeters. Such colorimeters usually allow a non-contact measurement of light sources and object colors. Suitable is z. For example, the colorimeter Chroma-Meter® CS-1 00 from Minolta or similar equipment from other manufacturers.

The standard color chart represents a shoe sole-like area in an x, y coordinate system. Each point on this shoe sole-like area of the color chart clearly represents a color type. Colors of the same color type have the same color location with identical x and y coordinates and can only differ in their brightness.

In the middle area of the standard color chart, the so-called achromatic point lies at the coordinates x = 0.33 and y = 0.33. The achromatic point represents white, gray to black depending on the brightness. Between the achromatic point and the edge curve of the shoe sole-like surface of the standard color chart are all other (colorful) color grades. The rays emanating from the uncoloured point each contain the same hue colors in increasing saturation or increasing brilliance, ie from pale to saturated or brilliant. The standard color chart is based on this rule.

The boundary curve of the shoe sole-like surface of the standard color chart is composed of the spectral color train and the so-called purple line. The farther a chromaticity, defined by its x, y coordinates, is at the edge of the shoe sole-like surface of the standard color chart, the more brilliant it appears. For example, the coordinates x = 0.02, y = 0.7 represent a brilliant green; the coordinates x = 0.7, y = 0.26 stand for a brilliant red; the coordinates x = 0.18, y = 0.02 stand for a brilliant blue.

chromaticity

The invention is based on the consideration that the closer the color point of the reflection of the colored cover at the color location of the LED, the match of the color impression in reflected light and fluoroscopy should be even better. However, it has been shown that a match of a coloring with a given LED color point practically only is approximately feasible. In general, deviations that lie on or near the straight line that passes through the achromatic point (x / y = 0.33 / 0.33) and the color locus of the LED, can be tolerated rather than deviations that are equal, but further away from the described straights lie.

It is desirable that the color locations are located as far as possible at the edge of the color standard table (see, for example, DIN 5033 or corresponding standard literature), since the color brilliance here is the maximum. This is also due to the fact that the color locations of the LEDs are also due to the monochromatic light at the edge or near the edge of the standard color chart.

In many cases, corresponding colorations can not be achieved with a colorant alone. When mixing, make sure that the individual components are not too far away from each other on the color standard board, as the mixed color may then have too low a brilliance.

1. a) für blaue LED-Beleuchtung: x kleiner 0,03 / y kleiner 0,05
2. b) für grüne LED-Beleuchtung: x kleiner 0,05 / y kleiner 0,08
3. c) für gelbe LED-Beleuchtung: x kleiner 0,0025/ y kleiner 0,02
4. d) für rote LED-Beleuchtung: x kleiner 0,03 / y kleiner 0,003

Based on the standard color chart (see, for example, DIN 5033 or corresponding standard literature) and the color loci of the reflection of the light-scattering cover and the color locus of the LEDs or LEDs used, the amounts of the difference between the x value of the light-scattering cover and the x behave Value of the LED and the amount of the difference of the y-value of the light-diffusing cover with the y-value of the LED alternatively as follows (see example 6):

1. a) for blue LED illumination: x less than 0.03 / y less 0.05
2. b) for green LED illumination: x less than 0.05 / y smaller than 0.08
3. c) for yellow LED illumination: x less than 0.0025 / y less than 0.02
4. d) for red LED illumination: x less than 0.03 / y less 0.003

The color locus of the reflection of the light-scattering cover is measured by placing the light-scattering cover against a white background (eg a box painted white, see the examples) with a 150 W daylight lamp (D65 according to DIN 6173, quality class 1, eg Siemens) is illuminated from above at a distance of 60 cm and the color measurement is also performed from above at a distance of 100 cm. For measuring color grades, commercially available measuring instruments are available to the person skilled in the art. The color measurement can z. B. be carried out with the colorimeter Chroma Meter CS-100 Minolta. The color location of the LED can z. B. are calculated from their emission spectrum or is known from the manufacturer.

Device for yellow (or yellow-green) illumination

The LEDs used can, for. B. radiate a yellow (or yellow-green) light and have a color location in the range of coordinates x / y = (0.5 / 0.5) +/- 0.02.

The plastic of the cover in this case may be a base color of a mixture of 0.075 to 0.09, preferably 0.081 to 0.084 wt .-% pyrazolone yellow and 0.002 to 0.004, preferably 0.0028 to 0.0032 wt .-% perinone orange exhibit. In addition, a fluorescent dye, preferably a perylene-based fluorescent dye, more preferably the fluorescent dye Lumogen® F Yellow 170 (BASF), preferably in a concentration of 0.005 to 0.015 wt .-%, be contained.

It is convenient to combine this coloring with BaSO ₄ as a spreading agent in an amount of 1.5 to 2.5 wt .-%.

Device for red lighting

The LEDs used can, for. B. radiate red light and have a color location in the range of coordinates x / y = (0.67 / 0.33) +/- 0.02.

The plastic of the cover in this case may have a base coloring of 0.2 to 0.3, preferably 0.22 to 0.28 wt .-% pyrazolone yellow. In addition, a fluorescent dye, preferably a perylene-based fluorescent dye, more preferably the fluorescent dye Lumogen® F Red 305 (BASF), preferably in a concentration of 0.0025 to 0.0075 wt .-%, be included.

It is convenient to combine this coloring with polystyrene as a spreading agent in an amount of 1.5 to 2.5 wt .-%.

Device for green lighting

The LEDs used can, for. B. radiate a green light and have a color location in the range of coordinates x / y = (0.16 / 0.73) +/- 0.02.

The plastic of the cover in this case may have a base color of 0.03 to 0.05, preferably 0.035 to 0.045 wt .-% Cu-phthalocyanine green. In addition, a fluorescent dye, preferably a perylene-based fluorescent dye, more preferably the fluorescent dye fluorescent dye Lumogen® F Yellow 083 (BASF), preferably in a concentration of 0.01 to 0.03 wt .-%, may be included.

It is convenient to combine this coloring with BaSO ₄ or polystyrene as a spreading agent in an amount of 1.5 to 2.5 wt .-%.

Device for blue lighting

The LEDs used can, for. B. radiate a blue light and have a color location in the range of coordinates x / y = (0.14 / 0.06) +/- 0.02.

The plastic of the cover may also be colored with 0.005 to 0.015, preferably 0.007 to 0.012 wt .-% anthraquinone blue. In addition, a fluorescent dye, preferably a perylene-based fluorescent dye, more preferably the fluorescent dye fluorescent dye Lumogen® F Violet 570 (BASF), preferably in a concentration of 0.05 to 0.15 wt .-%, be contained.

It is convenient to combine this coloring with polystyrene as a spreading agent in an amount of 1.5 to 2.5 wt .-%.

Addition of TiO ₂

In a preferred embodiment, the plastic of the cover additionally contains TiO ₂ in a concentration of 0.001 to 0.05 wt .-%. As a result, an increase of the reflection value by about 2 to 10% can be achieved again. When viewed visually with the naked eye, the brilliance of the coloring appears to be markedly increased again.

uses

In the apparatus according to the invention, the described streumittelhaltigen, colored plastic elements are used as a cover and colored LEDs as a light source.

luminance

• Bei Abdeckungen für blaue LED-Beleuchtung größer/gleich 12,5 Cd/m²,
• bei Abdeckungen für grüne LED-Beleuchtung größer/gleich 30, bevorzugt größer/gleich 40 besonders bevorzugt größer/gleich 50 Cd/m²,
• bei Abdeckungen für gelbe LED-Beleuchtung größer/gleich 100, bevorzugt größer/gleich 110 besonders bevorzugt größer/gleich 120 Cd/m²,
• bei Abdeckungen für rote LED-Beleuchtung größer/gleich 25, bevorzugt größer/gleich 30 besonders bevorzugt größer/gleich 40 Cd/m².

The luminances Y in Cd / m ² measured in incident light (see Example 6) are in accordance with the invention color-adjusted light-scattering covers:

• For blue LED lighting covers greater than or equal to 12.5 cd / m ² ,
• for covers for green LED illumination greater than or equal to 30, preferably greater than / equal to 40, particularly preferably greater than or equal to 50 Cd / m ² ,
• in the case of covers for yellow LED lighting greater than or equal to 100, preferably greater than / equal to 110, particularly preferably greater than or equal to 120 Cd / m ² ,
• for covers for red LED lighting greater than or equal to 25, preferably greater than / equal to 30, particularly preferably greater than / equal to 40 Cd / m ² .

The luminance Y is measured in Cd / m ^{2 of} the light-scattering cover by placing the light-scattering cover against a white background (eg a box painted white, see the examples) with a 150 W daylight lamp (D65 according to DIN 6173, quality class 1, eg from Siemens) is illuminated from above at a distance of 60 cm and the luminance measurement is also carried out from above at a distance of 100 cm. For the measurement of luminance, commercially available measuring devices are available to the person skilled in the art. The luminance measurement can be z. For example, use the Chroma Meter CS-100 colorimeter from Minolta, which measures color locations and luminance.

Reflectance measurement / transmission measurement

The remission measurement can z. B. under determination of the mixed reflection, ie, the proportions of the directed reflection and the scattered reflection are detected (DIN 5036, Part 1 point 6).
The transmission measurement z. B. can be done by determining the mixed transmission, ie, the proportions of the directional transmission and the scattered transmission are recorded (DIN 5036, Part 1 point 7).
The chosen arrangement of the measuring geometry is preferably directional / semi-spatial (DIN 5036, Part 3, Item 2 or 3 and Tab.1)
The construction of the measuring arrangement (two-beam measuring instrument with integrating sphere) is preferably carried out according to DIN EN ISO 13468-2 and DIN 5036, Part 3, Item. 4)

hash

The measurement of the scattering value is preferably carried out by determining the luminance at different angles (DIN 5036, Part 1, Point 5.1)
The measurement setup can z. B. according to ASTM E 2387-05.

In a spectral measurement, the measurement result is practically independent of the choice of the light source. However, this should be such that in the desired wavelength range (usually in the entire visible range between 380nm and 780nm) light is emitted.

Measurements by the skilled person

A person skilled in the art will be familiar with the measured variables, measuring methods and relevant standards mentioned in the invention. He can select suitable conditions and arrangements for all necessary measurements due to his expertise. In some cases, the person skilled in the art may make adjustments to the requirements of the samples to be measured or usefully modify given measurement conditions. In principle, it is also possible that in individual cases several measuring methods or modifications of measuring methods for determining the measured variables mentioned in the context of the invention are equally suitable. On the basis of his specialist knowledge and based on the information and instructions disclosed here, the person skilled in the art independently obtains reliable and reproducible measurement results in the sense of the present invention.

EXAMPLES example 1 Light-diffusing cover with the colorings according to the invention red 1, Yellow 1, Blue 1 and Green 1

In 1000 parts prepolymer Metylmethacrylat syrup (viscosity about 1000 cP) are
1 part of 2,2'-azobis- (2,4-dimethylvaleronitrile) dissolved.
In this approach, one gives a color paste consisting of
3 parts of a soluble polymethylmethacrylate resin,
20 parts of barium sulfate and the colorants according to Table 1 , which in
30 parts of methyl methacrylate with a high-speed dispersant
(Rotor / stator principle) is dispersed, added.
The mixture is stirred vigorously, filled into a silicate glass chamber which is distanced with 3 mm thick cord and polymerized in a water bath at 45 ° C. for about 16 hours. The final polymerization is carried out in a tempering at 115 ° C for about 4 hours.

Colorants see Table 1 Example 2 Light-diffusing cover with the colorings according to the invention red 2, Yellow 2, Blue 2 and Green 2

Preparation as in Example 1, but with the colorants according to Table 2

Comparative Examples Light-diffusing cover with the non-inventive colorings red 3, yellow 3, blue 3 and green. 3

Preparation as in Example 1, but with the colorants according to Table 3 <u> Table 1 </ u> colour Cu phthalo cyanine green Pyrazolone yellow Anthraquinone blue Orange perinon -Lumogen Red 1 ---- 0.25 ---- ---- 0.005 F Red 305 Green 1 0.04 ---- ---- ---- 0.020 F yellow 083 Blue 1 ---- ---- 0.01 ---- 0.100 F Violet 570 Yellow 1 ---- 0.0825 ---- 0,003 0.010 F yellow 170 Data in% by weight colour Cu phthalo cyanine green Pyrazolone yellow Anthraquinone blue Orange perinon Titanium dioxide -Lumogen Red 2 ---- 0.25 ---- ---- 0.0075 0.005 F Red 305 Green 2 0.04 ---- ---- ---- 0.0075 0.020 F yellow 083 Blue 2 ---- ---- 0.01 ---- 0.0075 0.100 F Violet 570 Yellow 2 ---- 0.0825 ---- 0,003 0.0075 0.010 F yellow 170 Data in% by weight colour Cu phthalo cyanine green Pyrazolone yellow Anthraquinone blue Orange perinon Anthraquinone purple Anthraquinone red Red 3 ---- 0.1500 ---- ---- ---- 0.0200 Yellow 3 ---- 0.0825 ---- 0,003 ---- ---- Green 3 0.0200 0.0400 ---- --- ---- ---- Blue 3 ---- ---- 0.0100 ---- ---- ---- Data: in% by weight

Examples 4 (according to the invention) and 5 (comparative example) Color measurements and luminance

In a white-lacquered, open-topped metal box measuring 90 x 470 mm and 100mm in height, 32 light-emitting diodes, eg from OSRAM (8 modules a'4 LEDs), are mounted on the bottom. (There are standard LEDs from many manufacturers which have a comparable color to each other to have). With a power supply, the permissible operating current of between 320 and 400mA is set at an operating voltage of 10V, depending on the type.
The patterns described above are placed on this box and assessed by color. The incident light test (daytime effect) is performed by illumination with a daylight lamp with 150 W (D65 according to DIN 6173, quality class 1, eg from Siemens) at a distance of approx. 60cm from above. The LEDs are switched off. The transmitted light test is carried out in a darkened room with activated LEDs according to the above operating information. Color measurements are taken using the Chroma-Meter CS-100 colorimeter from Minolta. This device allows non-contact measurements of light sources and object colors. The distance sample / device is 1 m. The luminance Y in Cd / m ² is also measured with this device.

The results of color measurements and luminances in LED backlighting (color loci of transmission) of the light-diffusing covers according to Examples 1 and 2 are shown in Table 4 . Table 5 shows for comparison corresponding color measurements and luminances of the comparative experiments of Example 3.

Example 4

Table 4 (inventive colorings of Examples 1 and 2) colour LED λmax in nm Transmission at LED λmax Reflection at LED λmax Y in Cd / m ² x y Yellow 1 590 64% 40% 130 0,550 0.449 Yellow 2 590 63% 46% 133 0,550 0,448 Red 1 620 80% 56% 165 0.687 0.312 Red 2 620 79% 63% 162 0.687 0.312 Green 1 520 66% 46% 38.8 0.143 0,780 Green 2 520 61% 52% 36.1 0.143 0.782 Blue 1 440 56% 36% 6.32 0.138 0.046 Blue 2 440 52% 41% 6.34 0.138 0,045

Example 5

Table 5 (colorings not according to the invention, see Example 3) colour LED λmax in nm Transmission at LED λmax Reflection at LED λmax Y in Cd / m ² x y Yellow 3 590 62% 26% 127 0.545 0.453 Red 3 620 48% 23% 165 0.684 0.315 Green 3 520 43% 19% 36.3 0.143 0.782 Blue 3 440 43% 21% 6.34 0.138 0,045

The results (Table 4) show that with the colored acrylic glasses produced according to the above procedure, the colorings corresponding to the prior art (Table 5) differ only insignificantly with LED backlighting (night effect) in the color locus of the transmission , The light diffusion is so good that with a distance of only 40mm to the LED, a uniform illumination is achieved.

If the color coordinates according to Tab. 4 are entered in the standard color chart (see, for example, DIN 5033 or corresponding standard literature), it can be seen that the values (and therefore the color tones) in the limits required by the invention are close to the line of the color-tone-like wavelength ( Line between achromatic point and color location of the respective LED color) are. In the visual examination, the good match of the color tone in incident and transmitted light can be seen.

To Fig. 1 / 2 for green LEDs it can be seen that at 520 nm (energy maximum for green LEDs), the reflection of the coloration green 1 and green 2 are clearly above the value for the comparative experiment without fluorescent dye (green 3). The reflectance values in these areas are significantly higher than the required 28% and more than 50% above the value for the comparative experiment Green 3.

The results of the color measurements and luminances in reflected light (color loci of reflection) of the light-diffusing covers according to Examples 1 and 2 are shown in Table 6 . Table 7 shows for comparison corresponding color measurements and luminances of the comparative experiments of Example 3.

The results of the luminous densities Y in Cd / m ² (Table 6) show that with the colored acrylic glasses produced according to the above procedure, compared to the colorations which correspond to the prior art (Table 7), significantly higher brilliance in reflected light (day effect ) can be achieved.

Example 6

Table 6 (inventive colorings of Examples 1 and 2) colour Y in Cd / m ² x y Amount x LED x sample Amount y LED-y sample LED blue ---- 0.14 0.06 Blue 1 12.6 0.168 0,107 0.028 0.047 Blue 2 13.1 0.166 0.105 0.026 0,045 LED green --- 0.16 0.73 Green 1 59.3 0.194 0.661 0.034 0,069 Green 2 62.3 0.19 0.673 0,030 0.057 LED yellow --- 0.5 0.5 Yellow 1 123 0.498 0.485 0,002 0,015 Yellow 2 126 0.499 0.485 0.001 0,015 LED red --- 0.67 0.33 Red 1 41.8 0,655 0.328 0,015 0,002 Red 2 43.1 0.66 0,329 0,010 0.001

Example 7

Table 7 (colorings not according to the invention, see Example 3) colour Y in Cd / m ² x y Amount x LED x sample Amount y LED-y sample LED blue --- 0.14 0.06 Blue 3 12.1 0.176 0,128 0,036 0,068 LED green --- 0.16 0.73 Green 3 28 0.221 0.628 0,061 0,102 LED yellow --- 0.5 0.5 Yellow 3 97.5 0,497 0.485 0,003 0,015 LED red --- 0.67 0.33 Red 3 23.7 0.636 0.327 0.034 0,003

Claims (18)

1. Apparatus for illumination with blue, green, yellow or red light-emitting diodes (LEDs), comprising one or more coloured LEDs and a light-scattering cover associated with the LED colour and composed of coloured plastic and having a base colour derived from one or more non-fluorescent dyes, characterized in that
   the light-scattering cover comprises, in addition to the base colour, at least one fluorescent dye associated in terms of colour with the base colour, where the dye mixture has been adjusted in such a way that the reflectance of the light-scattering cover is at least 28% at the wavelength of the energy maximum of the LED(s) used, where, based on the standard chromaticity diagram and on the colour loci of the reflected light from the light-scattering cover and on the colour locus of the LED(s) used, the following alternative relationship applies to the absolute value of the difference between the x value of the light-scattering cover and the x value of the LED and the absolute value of the difference between the y value of the light-scattering cover and the y value of the LED:

   a) for blue LED illumination: absolute value for x smaller than 0.03/absolute value for y smaller than 0.05

   b) for green LED illumination: absolute value for x smaller than 0.05/absolute value for y smaller than 0.08

   c) for yellow LED illumination: absolute value for x smaller than 0.0025/absolute value for y smaller than 0.02

   d) for red LED illumination: absolute value for x smaller than 0.03/absolute value for y smaller than 0.003.
2. Apparatus according to Claim 1, characterized in that a fluorescent dye is present which emits light in the region of the wavelength of the energy maximum of the coloured LEDs used.
3. Apparatus according to Claim 1 or 2, characterized in that a fluorescent dye is present which is a perylene derivative.
4. Apparatus according to one or more of Claims 1 to 3, characterized in that the separation between the LEDs and the light-scattering cover is from 3 to 12 cm.
5. Apparatus according to one or more of Claims 1 to 4, characterized in that the light-scattering cover is composed of a cast or extruded polymethyl methacrylate plastic.
6. Apparatus according to one or more of Claims 1 to 5, characterized in that the light-scattering coefficient, measured to DIN 5036, of the plastic of the cover is at least 0.5.
7. Apparatus according to Claim 6, characterized in that the light-scattering agent present comprises BaSO₄, polystyrene or light-scattering beads composed of a crosslinked plastic.
8. Apparatus according to Claim 7, characterized in that the light-scattering agent used comprises an amount of from 1.5 to 2.5% by weight of BaSO₄ or polystyrene.
9. Apparatus according to one or more of Claims 1 to 8, characterized in that the location of the LEDs is in a box or frame which is covered by the light-scattering cover.
10. Apparatus according to one or more of Claims 1 to 9, characterized in that the colour loci of the transmitted and the reflected light from the coloured cover composed of plastic, based on the standard chromaticity diagram, are in a region whose distance, based on a straight line which runs through the achromatic point (x/y = 0.33/0.33) and through the colour locus of the LED, is not more than 0.2 x/y units from the colour locus of the LED in the direction of the straight line and not more than 0.05 x/y units in the directions perpendicular to the two sides of the straight line.
11. Apparatus according to one or more of Claims 1 to 10, characterized in that the LEDs emit yellow light and their colour locus is within the range of coordinates x/y = (0.5/0.5) +/- 0.02.
12. Apparatus according to one or more of Claims 1 to 10, characterized in that the LEDs emit red light and their colour locus is within the range of coordinates x/y = (0.67/0.33) +/- 0.02.
13. Apparatus according to one or more of Claims 1 to 10, characterized in that the LEDs emit green light and their colour locus is within the range of coordinates x/y = (0.16/0.73) +/- 0.02.
14. Apparatus according to one or more of Claims 1 to 10, characterized in that the LEDs emit blue light and their colour locus is within the range of coordinates x/y = (0.14/0.06) +/- 0.02.
15. Apparatus according to one or more of Claims 1 to 14, characterized in that the plastic of the cover also comprises TiO₂ at a concentration of from 0.001 to 0.05% by weight.
16. Apparatus according to one or more of Claims 1 to 15, characterized in that the transmittance of the light-scattering cover is at least 20%.
17. Use, as cover for an illuminable apparatus according to one or more of Claims 1 to 16, of a coloured plastics element comprising scattering agent.
18. Use, as light source in an illuminable apparatus according to one or more of Claims 1 to 16, of LEDs emitting coloured and, respectively, almost monochromatic light.

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