JPH0411002B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a structure of an optical retroreflector that has not been previously discovered and used. Specifically, the high refractive index glass sphere used, a colorless or transparent thin resin film (hereinafter referred to as a coating) in the shape of a concentric elliptical hemispherical shell formed on the front exposed surface side of the glass sphere so as to cover the exposed surface; Furthermore, the present invention relates to a high-intensity optical retroreflector obtained by directly providing a reflective layer (for example, a metal vapor-deposited film or the like) on the rear exposed surface of a glass bulb. The performance of the product of the present invention is based on an innovative optical retroreflector that takes advantage of the characteristics of both open type and closed type conventional optical retroreflectors and compensates for the shortcomings of each type. It has a structure that fully demonstrates its performance. The conventional open type optical retroreflector is
As shown in the figure, a glass sphere 3 with a medium or low refractive index of 1.9 or less is used, the front part of the sphere is exposed to the air, and the rear hemispherical part is directly covered with a reflective layer 4.
It had a structure in which a binder 5 was then applied, and a support 6 was attached. This material has high reflective brightness, excellent reflection angle characteristics, and has a simple structure, and has a small basis weight and is thin, so it can be used as a light retroreflector for clothing with excellent sewability. However, on the other hand, it has serious drawbacks. That is, for example, if the hemispherical part of the front part of the glass sphere exposed on the surface of this open type light retroreflector is coated with a substance having an optical refractive index such as transparent resin or water, the lens action of the glass sphere will be affected. As a result, the retroreflection function of the light retroreflector decreases, causing a significant decrease in brightness.
In addition, when coloring an open type light retroreflector, the binder portion 5 that connects the glass spheres 3 and 3' is colored as shown in Figure 1 so as not to interfere with the lens action of the glass spheres. A method is used in which a colored layer is created by adding the required external color. However, with this coloring method, even if the colors are clear under scattered light during the day, when viewed under illumination light (almost convergent light) at night, when the light is reflected by the light retroreflector, the color will change. Since the layer is not present in the light input and return path, no color is discernible. Further, as described above, if the exposed hemispherical portion of the front portion of the glass bulb is coated with transparent resin, the lens action changes, so printing or the like cannot be applied to the surface of the open type light retroreflector at all. In addition, if the bonding agent part of the glass bulb is not made water resistant, moisture will penetrate into the rear hemisphere of the glass bulb, degrading the bonding agent and causing problems such as dropping of the glass bulb and reduction in brightness due to deterioration of the reflective layer. An inconvenience will occur. Furthermore, when used outdoors, if dust, dirt, soot, etc. adhere to the exposed surface of the glass bulb on the surface of the light retroreflector, it is difficult to remove and tends to cause a decrease in brightness and poor appearance. In order to compensate for the above-mentioned drawbacks, on the front exposed surface side of the glass bulb of the open type light retroreflector,
A method has been adopted in which a transparent thin plate 12 is attached via an air layer 14 as shown in FIG. 2 to protect the small glass lens. The surface of this transparent thin plate 12 is colored or printed and used as an all-weather high-intensity light retroreflector. However, since the air space 14 is a necessary condition for such a device, the bonding area 13 between the glass spherical surface and the transparent thin plate 12 must be made as small as possible. However, it is extremely difficult to strike a balance between the reflective ability and the surface area, which is also adhesive strength, and as a result, the adhesive part often peels off during outdoor use, causing cracks in the transparent thin plate, and rainwater, dew, etc. Accidents have occurred in which the optical retroreflector loses its performance due to penetration. In addition, since the structure is complicated, the transparent thin plate 12 is not suitable for use as a traffic sign or for clothing.
It is necessary to take sufficient care in handling to avoid damage. On the other hand, in a closed type light retroreflector, a high refractive glass sphere with a refractive index of 2.0 or more is used, and a smooth transparent resin surface layer 15 is provided on the front hemispherical surface of the glass sphere as shown in FIG. However, on the rear hemispherical surface, there is a transparent resin binder layer 16 in the shape of a hemispherical shell concentrically with respect to the center of the glass sphere, and furthermore, a reflective layer 4 made of metal vapor deposition is provided at the rear of the binder layer to provide light reflection. Reflective functions are now available. Since the front hemisphere and the rear hemisphere of the glass sphere have the surface resin layer 15 and the binder resin layer 16, respectively, the transmission loss of light is very large, and the brightness value of the closed type light retroreflector is 1/4~ of the aforementioned open type optical retroreflector
It's only about 1/5. Reflectors for clothing can be obtained by using a highly flexible laminated resin surrounding the glass globules, but closed-type retroreflectors for clothing constructed in this way are difficult to use during sewing. The resin on the surface is flexible, which prevents the sewing machine's presser foot from slipping, and the large number of layers increases the fabric weight, resulting in relatively thick products, resulting in poor sewability and a very poor texture. ,
The drawback was that manufacturing costs were high because of the large number of constituent materials. The optical retroreflector of the present invention takes advantage of the advantages of both types of optical retroreflectors and compensates for their deficiencies. That is, the purpose of the optical retroreflector of the present invention is to obtain a high-luminance product that is highly flexible and has excellent visibility including color at night. Preferably, a high refractive index glass sphere of 2.0 or more is used, and the front exposed surface of the glass sphere of the reflector is provided with an extremely thin concentric elliptical hemispherical shell with a thickness of about 0.01μ to 5μ that covers the exposed surface. By applying a shaped transparent resin layer or by printing a colored transparent resin layer of the same shape, it is characterized by high brightness, flexibility, and the ability to be colored arbitrarily. In this case, by using a resin with high flexibility as the transparent resin, the resin layer is thin, and together with it, it is extremely flexible and has excellent sewability, and high brightness clothing that can obtain any reflective color regardless of day or night. It becomes possible to manufacture optical retroreflectors for use. Further, since the glass beads are not exposed on the surface of the reflector of the present invention, it has excellent stain resistance, and even if dirt or soot adheres to the surface, it can be easily wiped clean with a rag or the like. In addition, drop-off of the glass beads can be completely prevented, and water will not enter the interior of the reflector, so there will be no deterioration in performance and the service life will be extended. Furthermore, the deterioration in performance due to water wetting that occurs in conventional open type optical retroreflectors can be completely prevented. The optical retroreflector of the present invention, which has such excellent performance, is equipped with a surprising and mysterious reflection mechanism as described below. In other words, conventionally, the focal length of a retroreflector is determined by the refractive index and diameter of the glass sphere, but the diameter is limited to approximately the same degree in each case due to technical constraints in manufacturing the reflector. Therefore, glass beads with a refractive index of approximately 1.9 have been used for open types, and those with a refractive index of approximately 2.0 have been used for closed types. In the light retroreflector of the present invention, the position of the reflective film (i.e., the focal position of the lens) is on the surface of the glass sphere even though the glass sphere has a large refractive index (approximately 2.0), that is, it has an open type reflection mechanism. This is a new invention that takes To explain in more detail, conventionally, when using high refractive index glass spheres with a refractive index of 2.0 or more, a so-called closed type structure (third type) was used.
(see figure). However, the structure of the optical retroreflector of the present invention uses a high refractive index glass sphere and uses metal vapor deposition directly on the rear hemispherical surface, or a reflective layer made of a resin layer mixed with a light reflective substance such as aluminum powder. After installation, a transparent coating with a thickness of 0.01 to 5 μm is tightly coated on the front hemispherical surface of the glass bulb in the shape of a concave lens, thereby imparting a reflexive function. This is completely different from the method of using high refractive index glass spheres with a refractive index of 2.0 or higher. On the other hand, even if a reflector with the same structure as the product of the present invention is manufactured using glass beads with a low or medium refractive index used in an open type optical retroreflector, the retroreflection performance is extremely low. I can't get it. or,
Even if a high refractive index glass sphere with a refractive index of 2.0 or more is used, the transparent coating covering the front hemispherical surface of the glass sphere is only 10 μm.
If the surface is relatively thick and the surface in contact with air is almost flat, sufficient reflective performance cannot be obtained. Furthermore, if a binder layer and then a reflective layer are provided at the rear of the glass bulb, no retroreflective function can be obtained even if the transparent coating covering the front hemispherical surface of the glass bulb has the film shape of the present invention. It cannot be done. As described above, the thickness and shape of the transparent coating coated on the front part of the high refractive index glass sphere, and the closeness of the reflective layer to the rear part of the glass sphere are important points for deriving the retroreflection function of the present invention. It turns out that there is something. Although the detailed retroreflection function is unknown, it is presumed that it is due to a change in the lens action of the glass sphere due to the concave lens effect of the transparent coating. Although the cause is currently unknown, it can be said that this is a completely surprising phenomenon that no one could have ever predicted. To explain this in more detail, the thickness of the coating tightly adhered to the front hemispherical surface of the glass sphere is controlled by the diameter of the glass sphere, and if the diameter is constant, the reflection will change depending on the increase or decrease in the thickness of the coating. Performance changes. Therefore, it was found that there is a most suitable thickness for the coating. When this suitable coating is observed with an electron microscope, it has a concentric elliptical hemispherical shell shape covering the glass sphere, and its thickness is 0.01 mm when the diameter of the glass sphere is 500μ or less. It was in the range of ~5μ. Moreover, the thickness of the coating increases as the diameter of the glass sphere increases. In this way, the optical re-reflection of the present invention uses existing high refractive index glass spheres with a refractive index of 1.9 or more,
The same concentric elliptical hemispherical shell-shaped coating may be provided on the front surface, and a reflective layer may be provided in close contact with the rear surface, and these can be produced by combining conventionally known means. Next, the effects of the present invention will be explained in more detail using Examples and drawings, but the present invention is not limited thereto. FIG. 4 shows a cross-sectional view of a semi-finished product of the optical retroreflector of the present invention, the detailed description of which will be given in the embodiment of the semi-finished product manufacturing method. Figure 5 shows the polyester shown in Figure 4.
An elliptical hemisphere concentric with the front hemisphere of the glass sphere 3 of a semi-finished product 7 of a light retroreflector (hereinafter referred to as a semi-finished product) in which the polyethylene laminates 1 and 2 are peeled off to expose the glass sphere 3 in the air. It is a cross-sectional view of a shell-like transparent or colored transparent resin film 8 coated closely. FIG. 6 shows a concentric elliptical hemispherical shell-shaped resin coating 8 on the front part of the glass sphere 3 of the light retroreflector of the present invention.
is an estimation of the path and reflection mechanism of light from the outside when a reflective film 4 is provided at the rear of the same. That is, the incident light ray 9 is first refracted toward the center of the glass sphere at the surface of the coating 8 and enters the glass sphere, but is refracted again at the surface of the glass sphere, and in this double refraction, air and transparent resin, transparent resin and glass When the focal point of the lens of the glass sphere is located at a point 10 on its rear hemisphere by a suitable combination of the refractive index and thickness of each of , the reflected light beam 11 passes through the transparent resin from the glass sphere again, and the light is reflected in a direction parallel to and opposite to the incident light beam 9 (respectively indicated by the direction of the arrow). The respective functions and effects will be explained in further detail in Examples. Example of semi-finished product manufacturing method As shown in Figure 4, polyester film 1
A high refractive index glass sphere 3 having a diameter of 80 μm and a refractive index of 2.25 is temporarily buried in a polyethylene film 2 having a thickness of 20 μm laminated thereon by heating at 110° C. for 3 minutes with a burial rate of 50%. Next, aluminum with a thickness of about 800 angstroms is metal-deposited on the exposed surface of the glass sphere 3 to form a reflective layer 4, and then a fixed binder layer 5 is applied to a thickness of 30 μm on top of this. A certain film 6 was fixed by heat lamination at 100°C for 3 minutes, and then the polyester-polyethylene laminates 1 and 2 in which the glass spheres were temporarily embedded were peeled off to expose half of the buried glass spheres to the air. A semi-finished product of a light retroreflector was obtained. In addition, glass globules with different refractive indexes,
That is, three semi-finished products were created using the same method using three types: 1.51, 1.92, and 2.1. Examples 1 to 4 A transparent resin having the following composition was coated on the exposed surface of the glass sphere of the semi-finished product 7 described above as shown in FIG.
After coating to a thickness of 2μ, a hot air drying treatment was performed at 130° C. for 3 minutes to prepare a sample having the resin coating 8 shown in FIG. Composition: Methacrylic acid alkyl ester polymer resin
100 parts Melamine curing agent 5 parts Toluene 30 parts Total 135 parts The relationship between the light retroreflection performance (brightness value) of each sample and the refractive index of the glass spheres was clarified with Example Nos. 1 to 4 in Table 1 below. do.

[Table] The brightness value indicates the amount of reflected light for a constant incident quantity, and the larger the value, the better the performance of the reflector. From the results in Table 1, it was confirmed that the higher the refractive index of the glass sphere, the higher the brightness value obtained. Example 5 As shown in the results obtained in Examples 1 to 4, when a high refractive index glass sphere is used, the transparent coating covering the front part of the glass sphere matches the lens action of the glass sphere, resulting in a high brightness value. It turned out that it was possible. Furthermore, the relationship between the thickness of the coating applied to the glass sphere and the diameter of the glass sphere was as follows. That is, the refractive index is 2.25,
In the aforementioned semi-finished product using glass globules with a diameter of 80μ, the following colored transparent resins were applied to the exposed surface of the glass globules in varying amounts to form resin coatings 8 of various thicknesses, and the brightness values were determined. was measured. Composition: Melamine-formalin polymer resin 100 parts Benzidine-based yellow pigment 15 parts Total 115 parts As a result, there is a certain relationship between the thickness of the film and the brightness value as shown in Figure 7, and high brightness reflection performance is achieved. It has been found that there is an appropriate thickness range for the diameter of the glass globules. When the sample showing the highest brightness value among the samples prepared in this example was observed using an electron microscope, the shape of the coating was a concentric elliptical hemispherical shell 8 with respect to the glass sphere, and the coating thickness was as shown in Figure 7. The exposed surface of the glass sphere had a thickness of about 0.1μ near the top, and 5μ at the base, with an average thickness of about 2.5μ. As mentioned above, the reflective performance of the reflector, that is, the brightness, is better as the refractive index of the glass sphere used is higher, but the thickness of the coating is not directly related to the refractive index, but rather the thickness of the glass sphere. A relationship is recognized that takes the optimum value for the size, that is, the diameter.
Therefore, although the diameter of the glass globules is essentially arbitrary, it is appropriate to have a diameter of 500 μm or less due to the technical constraints of forming the coating into a concentric elliptical shell shape. Examples 6 to 9, Comparative Examples 1 to 4 When making semi-finished products of the optical retroreflector of the present invention,
A semi-finished product for clothing can be produced by using a nylon knitted tricot as the support. When the exposed surface of the glass globules of the semi-finished product is coated with the following printing ink to form a concentric elliptical hemispherical shell-like coating, it is possible to create high-brightness clothing that has a good color and the reflected color does not change day or night. A light retroreflector for use was obtained. Ink Composition One-part urethane screen ink Transparent liquid 100 parts Pigment 30 parts Methyl ethyl ketone 10 parts Total 140 parts In addition to the above pigments, benzidine yellow pigment, perylene red pigment, cyanine blue pigment, and cyanine green pigment were used. After making yellow, red, blue and green printing inks and then screen printing with a 220 mesh polyester fiber screen,
By drying with hot air at 120℃ for 5 minutes, a film with a thickness of approximately 3μ was formed on the exposed surface of a glass sphere with a refractive index of 2.25 and an average diameter of 80μ, and the reflection performance, that is, the brightness value, as shown in Table 2 was obtained. Ta. For comparison, Japanese Industrial Standard JIS-
The luminance values of the reflective material specified in Z-9117 are also listed, and it is clear that each color has extremely excellent reflective performance.

[Table] The obtained reflector for clothing had a very elegant color, was soft to the touch, had flexibility, and had good sewability.

[Brief explanation of drawings]

1 schematically shows an example of the structure of the optical retroreflector of the present invention. Figure 1 is a cross-sectional view of a conventional open type optical retroreflector, Figure 2 is a cross-sectional view of an improved open type reflector with an air layer, and Figure 3 is a cross-sectional view of a conventional closed type optical retroreflector. It is a diagram. FIG. 4 is a sectional view of a semi-finished product of the light retroreflector of the present invention, and FIG. 5 is a light retroreflector of the present invention in which a transparent or colored transparent resin coating in the form of a concentric elliptical hemispherical shell is coated and adhered to the front part of a glass sphere. FIG. 2 is a cross-sectional view of a sexual reflector. Figure 6 is a cross-sectional view estimating the incident and reflection paths of light from the outside for a glass sphere coated with a concentric hemispherical shell, and Figure 7 shows the relationship between the average thickness of the coating and the brightness value. It is an experimental diagram,
The observation conditions are an observation angle of 0.2° for the front brightness value and an incident angle of -4°. In the figure, 1 is a polyester film, 2 is a polyethylene layer, 3 is a glass ball, 4 is a reflective layer, 5 is a fixed binder layer, 6 is a support, 7 is 3, 4, 5,
6 is a semi-finished product of a light retroreflector, 8 is a concentric elliptical hemispherical shell-like coating, 9 is an incident light beam, 10 is a focal point, 11 is a reflected light beam, 12 is a transparent thin plate, 13 is an adhesive part, and 14 is air. Show layers.

Claims (1)

[Claims] 1. Diameter 500 μ or less, refractive index 1.9 with 40 to 80% immersion rate in the fixed binder resin layer held on the support.
The above-mentioned high refractive index glass sphere is buried, and a reflective layer is provided directly on the buried rear part of the glass sphere, and a reflective layer is provided on the front exposed surface side of the glass sphere so as to cover the exposed surface. An optical retroreflector characterized by having a concentric elliptical hemispherical shell-like coating of a colorless or colored transparent resin having a thickness of 0.01 to 5 μm formed in the shape of a concave lens.