MXPA97007082A - Luminous source of line that includes a colorantefluoresce - Google Patents

Abstract

A line light source (10) includes a point light source (16) and a light distribution assembly (11) for transporting the light from the point source (16). A fluorescent dye is included in the light distribution assembly (1

Description

LUMINOUS SOURCE OF LINE THAT INCLUDES A FLUORESCENT COLORING FIELD OF THE INVENTION The present invention relates to light sources that employ light conduits that operate on the principle of total internal reflection. In particular, the present invention relates to a line light source that includes a fluorescent dye.

BACKGROUND The light sources used in traffic control and navigation are generally point sources or almost point sources. Common examples include traffic lights and hazard lights commonly placed around road construction areas. The most recent line light sources have been introduced in traffic control and hazard warning applications. A line light source, exemplary, described in U.S. Patent No. 5,043,850 (Dreyer, Jr.), employs a light conduit of the type described in U.S. Patent No. 4,805,984 (Cobb, REP: 25612 Jr.). Two light sources that differ in at least one optical property are optically coupled to the opposite ends of the light conduit. If the optical property that differs is color, the light pipe will look like a first color when viewed from one direction and a second color when viewed from the opposite direction. An additional line light source is described in U.S. Patent No. 5,258,896 (Dreyer, Jr.). Line light sources provide excellent warning improvement in low ambient light environments such as, for example, at night or in a dense, cloud cover. It has been determined that light sources that have a power level or base power as small as 20 watts may be sufficient to illuminate line light sources in low ambient light environments. However, environments of relatively high ambient light levels such as, for example, daytime conditions present particular warning problems. Because sunlight is essentially white light, a line light source that emits white light is less perceptible in sunlight than at night. One method to increase the daytime perceptibility of a line light source that emits white light is to increase its brightness when using higher wattage light sources. This requires energy inputs into the system above the base power level required to provide sufficient luminance for viewing conditions at night time. This additional energy is essentially consumed when the line light source is used in low ambient light environments. A second method for increasing the daytime perceptibility of a line light source is to place color light filters adjacent to the light sources to produce colored or colored light, as described in U.S. Patent No. 5,043,850. Due to the contrasts of color light with white ambient light, a colored, colored line light source is more noticeable than a line light source, not colored. However, because the color filters absorb a portion of the white light emitted by the light source, this method also requires additional energy to produce a desired luminance.

Accordingly, there is a need in the art for a line light source that is highly noticeable in an environment of high ambient brightness such as, for example, daytime conditions. There is also a need in the art for a line power source of sufficient power that does not require substantial increases in energy input above a base level required to provide perceptibility at night to produce high perceptibility under high ambient light conditions.

BRIEF DESCRIPTION OF THE INVENTION The present invention provides a line light source that exhibits improved perceptibility in environments of high ambient light conditions. According to one embodiment of the present invention, a line light source includes a light conduit comprising a thin film of an internal and fully reflective material, a light source optically coupled to the light conduit for introducing the light at a first end of the light conduit, and a colorant fluorescent in the film that directs the light. In another embodiment, of the present invention, the light conduit is substantially substantially disposed completely within a tubular housing. In this embodiment, either the thin film or the housing may include a fluorescent dye. In an alternative embodiment of the present invention, a separate thin film comprising a fluorescent dye may be employed. Advantageously, fluorescent dyes increase the perceptibility of the line light source in high ambient light environments without substantially reducing the light output of the tubes in low ambient light environments. Yet another embodiment of the present invention at least one of the tubular housing or the light conduit comprises a polymeric matrix, a dye, and an hindered amine light stabilizer, wherein the dye contains at least one of the dyes selected from the group of thioxanthone, perylene amide and thioindigoid compounds and the polymer matrix comprises polycarbonate.

BRIEF DESCION OF THE DRAWINGS Figure 1 is a cross-sectional view of a portion of a mode of a line light source according to the principles of the present invention along its main axis; Figure 2 is a cross-sectional view of the line light source shown in Figure 1 perpendicular to its main axis; Figure 3 is a graph showing the experimental data comparing the optical performance of a fluorescent line light source according to the present invention with non-fluorescent line light sources.

DETAILED DESCION OF THE INVENTION Structure of the Linea Light Source Figures 1 and 2 are cross-sectional views of one embodiment of the invention, designated as a line light source 10. The embodiment as shown comprises a light source 16 and a light distribution assembly 11 comprising two hollow members, in general cylindrical that have a common long axis, that is, one inside the other. The outer member is a strong, optically transparent, strong protective cover 12, and while preferred, this is not required. The inner member is a thin, fully reflective, internally substantially substantial and optically transparent light conduit 14. As used herein, the term "optically transparent" is widely used to describe materials that transmit light without diffusion or significant distortion. Specifically, as used herein, the term "optically transparent" should not exclude materials that transmit specific wavelengths of light, and thereby appear colored or colored for an observer's eye. The diameter of the cover 12 may be large enough to create an air space 13 between the cover 12 and the light conduit 14, but this is also not required. In one embodiment of the present invention, the cover 12 is a substantially optically transparent, substantially cylindrical tube formed of a dielectric acrylic or polymeric material such as polypropylenes, polyurethanes, polystyrenes and polyvinyl chlorides. In a preferred embodiment, the tube comprises a polycarbonate matrix. However, it will be appreciated that the cover 12 could be in a different form or a different material to accommodate different applications. For example, in certain signaling applications, it may be desirable for only a portion of the cover 12 to comprise a substantial and optically transparent polymeric material. The light conduit 14 comprises a hollow, longitudinal structure in a preferential manner made of a substantial and optically transparent dielectric material, as taught in U.S. Patent No. 4,805,984 (Cobb, Jr.,). The hollow structure is formed of a flexible, thin polymeric film having a smooth surface (the inner side as shown in Figure 2) and a structured outer surface. One suitable film for light conduit 14 is the 3M Optical Lighting Film ™ commercially available from the Minnesota Mining and Manufacturing Company of St. Paul, Minnesota. A preferred structured surface includes a linear array of substantially straight angled isosceles prisms, arranged side by side. The perpendicular sides of each prism make an angle of approximately 45 ° with the tangent to the adjacent smooth surface opposite the structured surface. In one construction, the prisms extend longitudinally along the length of the outer surface of the light conduit 14. However, it will be appreciated that the prisms may extend along the longitudinal axis of the light conduit 14 in a form Helic, as described in commonly assigned U.S. Patent No. 5,363,470, the disclosure of which is incorporated herein by reference. The preferred light conduit 14 is made of a material that must be substantially and optically transparent, and preferably it is flexible, homogeneous and isotropic. Suitable materials include commercially available acrylics and polycarbonates having nominal refractive indexes of 1.49 and 1.58, respectively. Other possible materials, selected to provide the required functionality, include polypropylenes, polyurethanes, polystyrenes and polyvinyl chlorides. In general, polycarbonates are preferred because of their relatively high refractive indexes and physical properties. A suitable thickness of the film used for the light conduit 14 is approximately 0.38 millimeters, measured from the smooth inner surface to the lowest point of the grooves. For such a film, approximately 27 peaks per centimeter of perimeter are preferred. This film can be bent into a cylinder as small as approximately 7.6 centimeters in diameter without substantially affecting the optical properties of the film. The light conduit 14 can be a single section or multiple sections joined together, as required by the particular application. In one embodiment of the invention, an assembly of the light injector 16 is positioned adjacent to at least one end of the light conduit 14 and the cover 12 to direct the light in the light conduit 14. The assembly of the light injector 16 includes a box or cover 18, which can be made of any material that can be exposed to the environment, suitably rigid, but is preferably a metal, such as aluminum. Within the box or cover 18 is a luminous source partially aligned. As shown in Figure 1, the light source includes a lamp 20 and a parabolic reflector 22. However, it will be appreciated that other aligned light sources can be used. The line light source 10 may optionally include an absorber 24 for absorbing highly non-aligned light, as described in U.S. Patent No. 5,258,896, which is incorporated herein by reference. The absorber 24 can be of any material and color that will absorb the light emitted by the lamp 20. If, as is often the case, the lamp 20 emits white light, the absorber 24 is preferably black opaque. The metallic absorbers painted in opaque black can be used. However, if the lamp 20 emits color light, the absorber 24 can be any color that will absorb the light of the color emitted by the lamp 20. The combination of the shape of the structured surface, and the optical properties of the selected material, they produce a total internal reflection of light, if the light is properly directed inside the light conduit 14.

Fluorescent Dyes According to the present invention, the light distribution assembly of the line light source 10 is provided with a fluorescent dye to increase its daytime perceptibility. As used herein, the term "colorant" should mean any pigment or dye or other substance or combination of substances used to impart or impart nuance or brightness or value to an article. In one embodiment of the present invention, the cover 12 is provided with a fluorescent dye, while in another embodiment the light conduit 14 is provided with a fluorescent dye. In yet another embodiment of the present invention, a separate thin film having a fluorescent dye may be included with the line light source 10. It will be appreciated that the present invention also anticipates combinations of one or more of these elements. In a preferred embodiment, the fluorescent dyes of the invention are dyes selected from the classes of thioxanthone, perylene imide and thioindigoids of the compounds, as described in commonly assigned US Patent Application Serial No. 08 / 345,608, the description of which is incorporated herein by reference. The invention anticipates that a single fluorescent dye or dye may be used to color an article of the invention or that a combination of one or more fluorescent dyes and one or more conventional dyes may be used. Typically, between about 0.01 and about 2.00 percent by weight, and preferably between about 0.05 and about 0.70 percent by weight and more preferably between about 0.1 and about 0.5 percent by weight of a fluorescent dye is contained in the article of the present invention. It will be understood that articles with dye charges outside this range may be used in accordance with the invention. Although the dye load may vary depending on the final application, these charges are typical for a film of approximately 0.075 to 0.25 mm in thickness. However, if the dye is added to a thicker film, the lower dye charges can give the same visual effect. As known to those skilled in the art, articles having heavier dye charges will exhibit brighter fluorescence color and / or deeper color than will articles with lighter dye charges of the same dye. However, articles that have very high fluorescent dye charges may exhibit a self-extinguishing phenomenon that occurs when the fluorescent dye molecules absorb the energy emitted by adjacent fluorescent dye molecules. This self-extinction causes an undesirable decrease in fluorescent brightness. In some embodiments, the colorants in the articles of the present invention will consist essentially of one or more dyes selected from the perylene imide, thioindigoid, and thioxanthone classes of the compounds. In other examples, the article may also contain other coloring agents such as pigments or other dyes in addition to those described to adjust the color and appearance of the article. For example, polycarbonate typically has a yellow tone. Minor amounts, for example, about 0.01 weight percent or less, of pigments sometimes referred to as "building agents" may be incorporated to neutralize the yellow appearance. Other non-fluorescent or conventional dyes or pigments can also be added to the present invention. However, care must be taken in the selection of such dyes and filler dye loads that the dyes do not significantly interfere with the performance of the fluorescent dyes. The dyes or pigments should not undesirably deteriorate the transparency of the article as they would deteriorate the retroreflective properties of the article.

Stabilized Amine Light Stabilizers The hindered amine light stabilizers (HALS) are included in one embodiment of the present invention. This is a somewhat surprising combination because, as one skilled in the art will recognize, it is not recommended to combine amines with polycarbonate. It has been traditionally known that amines attacked the carbonyl group of the polycarbonate, thereby degrading the polycarbonate (for example see Schenell, Chemistry and Physics of Polycarbonates, page 183, 1964). Without proposing to be bound by the theory, it is believed that the combination of a spatially hindered amine, a polycarbonate matrix and a dye according to the present invention prevents an undefined degradation and / or reaction between the dye and the polycarbonate which could otherwise it will happen. As to how they are currently known, the advantages of this embodiment of the present invention are achieved through the combination of the dye, the polymer matrix material, and the hindered amine light stabilizer described herein. The dyes according to the present invention are thought to act as singlet oxygen sensitizers. The energy transfer, which in general occurs from the triplet state of the dye, is extinguished by the molecular oxygen in the ground state to produce the active singlet oxygen. The singlet oxygen is then released to react with the dye, causing the degradation of the dye. Alternatively, singlet oxygen may react with the polymer, leading to degradation of the polycarbonate. However, a representative hindered amine light stabilizer present in the invention is capable of directly extinguishing the singlet oxygen formed, preventing the initiation of degradation reactions. The hindered amine light stabilizers can also prevent secondary reactions initiated by the polymer oxidation of the process. These reactions include a number of chain reactions based on peroxide or radicals that are believed to occur in the photo-oxidation of the polycarbonate which can result in degradation of the polymer and the dye. Preventing these reactions increases the durability of the polycarbonate and the dye in the dye system. Any hindered amine light stabilizer is suitable for the present invention such as 2,2,6,6-tetraalkyl piperidine compounds, but preferably 2,2,6,6-tetramethyl piperidine compounds are used as light stabilizers. amine hindered due to the easy availability of the compounds. Amine-hindered light stabilizers are included in articles of the present invention from about 0.05 to about 1.00 percent by weight and preferably from about 0.10 to about 0.75 percent by weight and more preferably from about 0.1 to about 0.5 Procent in weight. Use and Operation In operation, the light originating from the lamp 20 either enters directly into the light conduit 14, or is reflected within it by the reflector 22. If the line light source 10 includes an absorber 24, as discussed above, the highly unaligned light will be absorbed by the absorber 24. The remaining light of the light injector assembly 16 is directed into the light conduit 14. Because the light conduit 14 operates at the beginning of the Total internal reflection, most of the light entering the light conduit 14 propagates down the length of the light conduit 14 without being absorbed or otherwise extinguished. Because the light conduit 14 is closed at each end, the only way light in the light conduit can escape is through a leak. The light leakage from the light conduit 14 occurs due to imperfections in the light conduit 14 such as anisotropy in materials, or construction errors. The light that emerges from a light conduit by a leak leaves the conduit substantially at the same angle of incidence as that in which it strikes the conduit. This is in contrast to the light extraction of the light conduits taught in the prior art, which depends on the diffusers or extractors to significantly change the direction of the light rays within the light conduit by means of scattering, so that the rays hit the inner surface of the light conduit at the angles of incidence that approach the normal. Such techniques produce relatively small intensities when viewed at angles close to the axis of the light conduit, the opposite of the effect produced by the present invention. Advantageously, when a line light source 10 according to the present invention is placed in an environment of high ambient light, the fluorescent dyes in line light source 10 are excited by ambient light and fluorescence. Fluorescent light increases the perceptibility of the line light source in a high ambient light environment. In contrast, in an environment of low ambient light conditions such as, for example, brightness at night, the line light source 10 is illuminated by the light source 16. The use of fluorescent dyes provide two advantages in low ambient environments. environmental luminosity. First, it has been determined that including fluorescent dyes within the concentration described above in the assembly of the light distribution does not significantly reduce the optical performance of the line light source 10 in ambient light environments. More specifically, the inclusion of lime-green fluorescent dyes does not reduce the illuminance of the line light source 10 when the light source 16 is the illumination source, and may increase the illuminance of the line light source 10. This is discussed further in Example 2, below. A second advantage associated with the use of a lime-green fluorescent dye is that the inclusion of the fluorescent dye does not alter the color of the line light source at night. Without wishing to be bound by theory, Applicants believe that the line light source 10 does not appear fluorescent lime-green at night because the amount of fluorescent light emitted from the light distribution assembly 11 is relatively small in relation to the light source. to the total amount of light transmitted through the light distribution assembly 11. Therefore, the fluorescent light is essentially fading and is not particularly visible to the naked eye for the human eye under normal viewing conditions. This is an important feature of the present invention because the traffic regulations in the Manual for Uniform Traffic Control Devices require that the line light sources used to differentiate the traffic hazards look yellow when used on the left side of a road appear yellow and white when used on the right side of a road. A line light source with a fluorescent dye exhibits increased daytime perceptibility and remains in accordance with the regulations governing nighttime brightness.

Example 1 A line light source according to the principles of the present invention was constructed using a fluorescent film and an optically clear housing and a light conduit. Alternating sections of a line light source were covered with two distinctly colored fluorescent films: a fluorescent yellow-green film and an orange fluorescent film. Fluorescent films were attached to the outer surface of the optically clear housing and the line light source was placed in a test site at the 3M Transportation Safety Center in Cottage Grove, Minnesota, USA. The line light source was observed from various angles under various daylight conditions. The fluorescent sections of the line light source exhibited significantly superior perceptibility under the daylight conditions when compared to the optically clear sections of the line light source.

Example 2 The optical performance of five line light sources was compared under night-light conditions to determine the effect of including fluorescent dyes in the light distribution assembly. The results, illustrated in Figure 3, demonstrate that the inclusion of a lime-green fluorescent dye in a line light source does not substantially reduce, and may increase the light output of the line light source in low light conditions environmental. Four line light sources, colored with an optically clear line light source, were compared. Each colored light source comprised a substantially transparent and optically transparent light conduit and a colored housing. The four colors tested were: fluorescent green lime, amber, fluorescent amber and fluorescent red. Each line light source measured approximately 6.1 meters (20 feet) in length and 15.25 centimeters (6.0 inches) in diameter. Each line light source was connected to a 12-volt Osram ARlll light source at one end and the luminance readings were taken at 30.5 centimeters (one foot) intervals from the light source using a luminance meter. The results are presented in Figure 3, which records the measured light output of the line light source as a function of the distance from the light source. The light output of the optically clear line light sources is represented by the solid line 1. The light output of the line light source, fluorescent lime-green color is represented by the dotted line 2. The light output of the amber line light source is represented by dotted line 3. The light output of the fluorescent amber line light source is represented by dotted line 4. The light output of the light source of line, fluorescent red is represented by dotted line 5. Figure 3 shows that the light output of the fluorescent lime-green line light source was greater than the light output of a substantial line light source and optically clear on much of the length of the light source. Therefore, the use of lime-green fluorescent dyes can also increase the nocturnal perceptibility of a line light source.

It is noted that in relation to this date, the best method known by the applicant to carry out the aforementioned invention, is the conventional one for the manufacture of the objects to which it relates.

Having described the invention as above, property is claimed as contained in the following:

Claims (8)

1. A line light source, characterized in that it comprises: a light source; a light distribution assembly optically coupled to the light source and including: (a) a hollow tubular housing having a first end and a second end and having a length extending along a major axis of the housing , at least a portion of the housing comprising a substantial and optically transparent material; and (b) a light conduit substantially and completely enclosed within and extending along at least a portion of the length of the housing, the light conduit consisting essentially of a thin film of an internal reflection material and completely , wherein at least one of the tubular housing and the light conduit comprises a polymeric matrix, and a fluorescent dye, and wherein the fluorescent dye contains a dye selected from the group of dyes consisting of thioxanthone, perylene imide and thioindigoid compounds.

2. A line light source, characterized in that it comprises: a light source; a light distribution assembly optically coupled to the light source and including: (a) a hollow tubular housing having a first end and a second end and having a length extending along a major axis of the housing , at least a portion of the housing comprising a substantial and optically transparent material; (b) a light duct substantially and completely enclosed within and extending along at least a portion of the length of the housing, the light duct consisting essentially of a thin film of an internal reflection material and completely; wherein at least one of the tubular housing or the light conduit comprises a polymer matrix, and a dye, and an hindered amine light stabilizer, and wherein the colorant contains at least one of the dyes selected from the group of compounds of thioxanthone, perylene imide and thioindigoid and the polymer matrix comprises polycarbonate.

3. A line light source according to claim 1 or 2, characterized in that: at least one of the tubular housing or the light conduit comprises a fluorescent dye in a concentration of between 0.01 weight percent and 2.00 weight percent.

4. A line light source, according to claim 1 or 2, characterized in that: at least one of the tubular housing or the light conduit comprises a fluorescent dye in a concentration of between O * 1 percent by weight and 0.5 percent by weight weight.

5. A line light source according to claim 2, characterized in that: at least one of the tubular housing or the light conduit comprises an amine light stabilizer hindered in a concentration of between 0.05 to 1.00 weight percent.

6. A line light source according to claim 2, characterized in that: at least one of the tubular housing or the light conduit comprises an amine light stabilizer hindered in a concentration of between 0.10 to 0.75 weight percent.

7. A line light source according to claim 2, characterized in that: at least one of the tubular housing or the light conduit comprises an amine light stabilizer hindered in a concentration of between 0.1 to 0.5 weight percent.

8. A line light source according to claim 2, characterized in that: the hindered amine light stabilizer comprises 2,2,6,6-tetraalkyl piperidine compounds.