Patent Application
20060040575
The present invention is generally related to retroreflective garments and, more particularly, is related to garments that are constructed of retroreflective fabrics.
Retroreflectivity is a characteristic in which obliquely incident light is reflected in the same direction to the incident direction such that an observer at or near the light source receives the reflected light. This unique characteristic has led to the wide-spread use of retroreflective materials on various substrates because substrates coated with retroreflective materials are more easily identified during nighttime conditions. For example, retroreflective articles can be used on flat inflexible substrates, such as road signs and barricades; on irregular surfaces, such as corrugated metal truck trailers, license plates, and traffic barriers; and on flexible substrates, such as road construction personnel safety vests, running shoes, roll-up signs, and canvas-sided trucks.
There are two major types of retroreflective materials: beaded materials and cube-corner materials. Beaded materials commonly use a multitude of glass or ceramic microspheres partially coated with a specular reflective coating to retroreflect incident light. Typically, the microspheres are partially embedded in a support film, where the specular reflective coating is adjacent the support film. The reflective coating can be a metal coating such as, for example, an aluminum coating, or an inorganic dielectric mirror made up of multiple layers of inorganic materials that have different refractive indices.
In lieu of microspheres, cube-corner articles typically employ a multitude of cube-corner elements to retroreflect incident light. The cube-corner elements project from the back surface of a body layer. In this configuration, incident light enters the sheet at a front surface, passes through the body layer to be internally reflected by the faces of the cube-corner elements, and subsequently exits the front surface to be returned towards the light source. Reflection at the cube-corner faces can occur by total internal reflection when the cube-corner elements are encased in a lower refractive index media (e.g. air) or by reflection off a specular reflective coating such as a vapor deposited aluminum film.
Retroreflective articles typically include a layer of retroreflective optical elements, microspheres, and/or cube-cornered elements, coated with a specular reflective coating. Generally, the retroreflective elements are embedded in a binder layer attached to the article. Typically, the optical elements are transparent microspheres that are partially embedded in the binder layer such that a substantial portion of each microsphere protrudes from the binder layer. The specular reflective coating is disposed on the portion of the transparent microsphere, which is embedded in the binder layer. Light striking the front surface of the retroreflective articles passes through the transparent microspheres, is reflected by the specular reflective coating, and is collimated by the transparent microspheres to travel back in a direction parallel to the incident light.
As discussed above, the use of retroreflective articles is widespread. For example, road construction personnel, utility personnel, and firefighter personnel often wear retroreflective clothing to make the wearer conspicuously visible at nighttime. The retroreflective articles displayed on this clothing typically comprises retroreflective stripes. Unfortunately, retroreflective stripes can have several significant drawbacks. For example, clothing provided with retroreflective stripes only reflects light from the stripe. Consequently, the person observing the reflected light may not be able to differentiate the reflecting stripes as representing a person, sign, or other obstacle. Further, if the person wearing the reflective stripe is positioned such that the stripe is blocked from the light, then the reflective stripe is ineffective. An additional disadvantage is that excessive layers of retroreflective material can make the garments heavier, less flexible, and can increase product cost.
Thus, a heretofore unaddressed need exists in the industry to provide garments that address the aforementioned deficiencies and inadequacies.
Embodiments of the present invention provide for a retroreflective garment constructed of flame resistant fabric. The garment is light-weight and single or double layered. Garments that can be constructed of flame resistant fabric with a plurality of retroreflective elements directly applied thereon include garments such as, for example, shirts, pants, coveralls, jumpsuits, jackets, gloves, hats, etc. The flame resistant fabric has a coefficient of retroreflection of about 10 to about 500 candelas per lux per square meter. In addition, the plurality of retroreflective elements covers at least about 5 percent of the outer surface of the flame resistant fabric. The flame resistant fabric is composed of flame resistant fibers such as, for example, aramid fibers, polybenzimidazole fibers, polybenzoxazole fibers, melamine fibers, modacrylic fibers, flame resistant rayon, flame resistant cotton, or blends thereof.
Another embodiment provides for a method of constructing a retroreflective garment that is light-weight and is either single or double layered. The method includes applying the outer surface of the flame resistant fabric with a plurality of retroreflective elements and constructing a light-weight, retroreflective garment from the flame resistant fabric so that the outer surface that has the plurality of retroreflective elements applied thereon faces away from the body of the wearer. The plurality of retroreflective elements can be applied to the flame resistant fabric by process techniques such as, for example, flat screen printing techniques, rotary screen printing techniques, and retroreflective transfer film techniques.
Other systems, methods, features, and advantages of the present invention will be or become apparent to one with skill in the art upon examination of the following drawings and detailed description. It is intended that all such additional systems, methods, features, and advantages be included within this description, be within the scope of the present invention, and be protected by the accompanying claims.
The invention can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the present invention. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.
Embodiments of the present invention include garments constructed of flame resistant fabrics that have had a plurality of retroreflective elements applied thereon, and therefore, have retroreflective characteristics. To overcome at least some of the deficiencies discussed above, a sufficient quantity of retroreflective elements are applied to the flame resistant fabric such that the entire garment, or at least a substantial portion thereof, is capable of retroreflecting incident light. Therefore, an observer near the incident light source will see an illuminated silhouette of a person wearing the garment, thereby enabling a driver of a vehicle to easily identify the silhouette as a person, rather than as an object. In contrast, if the wearer was wearing garments outfitted only with retroreflective stripes, then the driver may not identify the illuminated stripe as a person and drive with less care than if they saw an illuminated human silhouette. Thus, garments made with flame resistant fabric with a plurality of retroreflective elements applied thereon are advantageous in that they enable a person to be identified upon illumination with incident light, while also providing fire protection.
Garments that can be constructed of flame resistant fabric with retroreflective elements applied to the fabric include garments such as, for example, shirts, pants, coveralls, jumpsuits, jackets, gloves, hats, etc. Such retroreflective garments can be used by personnel, such as road construction personnel, EMS personnel, police personnel, military personnel, utility personnel, chemical plant personnel, and other personnel needing flame resistant garments that are retroreflective.
One way in which to measure the intensity of retroreflection of a garment 10 is to determine the coefficient of retroreflection of fabric of the garment 10. The coefficient of retroreflection is the ratio of the coefficient of luminous intensity of a plane retroreflecting surface to its area, as expressed in candelas per lux per square meter. Garments 10 of the present invention include flame resistant fabric characterized by a coefficient of retroreflection that is in the range of about 10 to about 500 candelas per lux per square meter. More particularly, the coefficient of retroreflection range is about 100 to about 300 candelas per lux per square meter, with about 150 to about 250 candelas per lux per square meter being preferred.
The microspheres 18 are substantially spherical in shape to provide uniform and efficient retroreflection. Generally, the microspheres 18 are highly transparent to minimize light absorption so that a large percentage of incident light is retroreflected. The microspheres 18 often are substantially colorless but may be tinted or colored in some other fashion. The microspheres 18 may be made from glass, a non-vitreous ceramic composition, or a synthetic resin. In general, glass and ceramic microspheres 18 are preferred because they tend to be harder and more durable than microspheres 18 made from synthetic resins. Examples of microspheres 18 that may be used are disclosed in the following U.S. Pat. Nos. 1,175,224; 2,461,011; 2,726,161; 2,842,446; 2,853,393; 2,870,030; 2,939,797; 2,965,921; 2,992,122; 3,468,681; 3,946,130; 4,192,576; 4,367,919; 4,564,556; 4,758,469; 4,772,511; and 4,931,414. The disclosures of these patents are incorporated herein by reference. By way of example, the microspheres 18 have an average diameter of about 10 to 500 micrometers and have a refractive index of about 1.2 to 3.0.
The reflective specular coating 19 typically comprises a hemispheric metal or inorganic dielectric mirror reflective coating that is applied to the microspheres 18. The specular reflective coating 19 gives the microsphere 18 the characteristic of being able to collimate light so that incident light is returned in an opposite direction substantially along the same path along which the incident light originated. Generally, the hemispherical reflective coating 12 covers approximately one half of the surface area of the microsphere 18.
A variety of metals may be used to provide a specular reflective coating 19. These include elemental forms of aluminum, silver, chromium, nickel, magnesium, gold, and alloys thereof. Aluminum and silver are the preferred metals for use in the specular reflective coating 19 because they tend to provide the highest retroreflective brightness. The metal may be a continuous coating such as is produced by vacuum-deposition, vapor coating, chemical-deposition, or electroless plating. In this form, the specular reflective coating 19 normally comprises pure metal. It is to be understood that in some cases, such as for aluminum, some of the metal may be in the form of the metal oxide and/or hydroxide. The metal coating should be thick enough to reflect incoming light. Typically, the specular reflective coating 19 is about 50 to 150 nanometers thick.
Flat screen printing, rotary screen printing, and transfer film techniques are used to apply the retroreflective elements 16 to flame resistant fabrics 12, although it will be understood that any technique that can apply the retroreflective material 19 to flame resistant fabrics 12 can be used. Typically, flat screen printing techniques involve placing a screen on top of the flame resistant fabric 12. A printing medium is poured upon the screen and a squeegee is moved back and forth within the confines of the screen. The squeegee forces the printing medium through the interstices of the screen and into contact with the flame resistant fabric 12. The screen is then lifted, the flame resistant fabric 12 is shifted relative to the frame so as to locate an untreated portion at the printing station, and the cycle is repeated. The printing medium may be a composition such as an ink or paste that includes microspheres 18. Alternatively, the microspheres 18 can be applied onto the printing medium after the printing medium has been applied to the flame resistant fabric 12.
Rotary screen printing refers to a printing process in which a perforated cylindrical screen is used to apply the printing medium onto a flame resistant fabric 12. The printing medium is pumped into the inner portion of the screen and forced out onto the flame resistant fabric 12 through the screen perforations. As the cylindrical screen rotates, the flame resistant fabric 12 moves and the printing medium is forced onto the flame resistant fabric 12. Numerous variables exist in rotary screen printing that may be altered to obtain the desired deposition of the printing medium. These variables include, for example, the speed at which the fabric is printed, the pressures used to force the printing medium through the screen, the screen type and mesh size, the viscosity of the printing medium, the percent of non-volatile substances within the printing medium, the drying temperature, and the length and type of dryer. As with flat screen printing, the printing medium may include the microspheres 18 or the microspheres can be applied onto the printing medium after the printing medium has been applied to the flame resistant fabric 12.
Retroreflective transfer film techniques include cascading a monolayer of microspheres 18 onto a carrier sheet. The microspheres 18 are releasably secured to the surface of the carrier sheet by applying heat and/or pressure. Next, a specularly reflective coating 19 is applied to the exposed surfaces of microspheres 18. The deposition on the exposed surface portion of the microspheres 18 to be covered with the specularly reflective coating 19 may be controlled in part by controlling the depth to which the microspheres 18 are embedded in the carrier sheet prior to application of the specular reflective coating 19. After the specular reflective coating 19 is applied to the microspheres 18, a binding material, such as, for example, an ink, polymer, or thermoplastic layer, is applied onto the mircrospheres 18 and carrier layer. Upon cooling, the binding material retains the microspheres 18 in the desired arrangement. Subsequently, the carrier sheet is heat-laminated to the flame resistant fabric 12. Applying heat and/or pressure to the carrier layer and flame resistant fabric 12 causes the microspheres 18 to adhere to the flame resistant fabric 12. The heat-lamination can be conducted so that a substantial portion the microspheres 18 are partially embedded into the flame resistant fabric 12. Thereafter, the carrier layer is striped away, such that a substantial majority, preferably substantially all, of the microspheres 18 are retained on the flame resistant fabric 12. In addition to the method described above, the binding material can be applied onto the flame resistant fabric 12 via the rotary screen technique. The heat and/or pressure can be used to transfer the microspheres 18 from the film to the surface of the flame resistant fabric 12 as opposed to applying the binding material onto the film.
For a further discussion of processes for applying microspheres 12 to fabrics, see U.S. Pat. Nos. 4,763,985; 5,128,804; and 5,200,262, the disclosures of which are incorporated herein by reference.
The garment 10 can be constructed once the retroreflective elements 16 have been applied to the flame resistant fabric 12. As discussed above, the garment 10 is constructed of flame resistant fabric 12, where the outer surface of the flame resistant fabric 12 has the retroreflective elements 16 applied thereon. The garment 10 is light-weight and can be single or double layered. The single layered garment is constructed of the flame resistant fabric 12. The double layered garment has an inner layer and an outer layer, where the outer layer is constructed of the flame resistant fabric 12. The inner layer can be constructed of any material known in the art and is typically disposed on the inside portion of the garment 10 in-between the body of the wearer and the outer layer. The inner layer and the outer layer can be attached in any manner known in the art. The weight of the flame resistant fabric 12 of the single or double layered garment 10 is less than about 10 ounces per square yard. Preferably, the weight of the flame resistant fabric 12 is less than about 7 ounces per square yard. More particularly, the weight of the flame resistant fabric 12 is less than about 5 ounces per square yard. The retroreflective elements 16 can be, for instance, purchased from Reflective Technology Industries, Ltd. (Cheshire, United Kingdom) or 3M Innovative Properties Company (St. Paul, Minn.).
Many variations and modifications may be made to the above-described embodiments of the invention without departing substantially from the spirit and principles of the invention. All such modifications and variations are intended to be included herein within the scope of this disclosure and the present invention and protected by the following claims.
