JPS6064302A - Optical retroreflector - Google Patents

Abstract

PURPOSE:To improve resilience and visibility including colors in the nighttime by using small glass balls having >=1.9 refractive index and coating concentrical semispherical shell-like transparent resin film having 0.01-5mu thickness on the front exposed surface of the small glass balls of a reflector. CONSTITUTION:Small high index glass balls 3 having 80mu diameter and 2.25 refractive index are tentatively embedded at 50% rate of embedment by 3min of heating in a 20mu thick PE film 2 laminated on a polyester film 1. Aluminum having about 800Angstrom thickness is deposited by metal evaporation on the exposed surface of the small glass balls 3 to form a reflecting layer 4 and a stucking binder layer 5 is coated thereon to 30mu thickness and thereafter said layer is laminated to the film 5 by heating for 3min at 100 deg.C, by which the layer is fixed. The laminates 1, 2 embedded tentatively with the small glass balls are stripped to expose the half parts of the small glass balls into air. The semi-processed good of the optical retroreflector is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a previously discovered and unused optical retroreflector ρ structure. In detail, * refers to the high refractive index glass sphere used and the colorless or transparent thin resin film (hereinafter referred to as 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. The present invention also relates to a high-intensity optical retroreflector obtained by directly providing a reflective layer (for example, a metal vapor-deposited film) on the rear exposed surface of the 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 and closed types of conventional optical retroreflectors and compensates for the shortcomings of each. It has a structure that fully demonstrates its performance.

As shown in Fig. 1, the conventional open type optical retroreflector uses a glass sphere (3) with a medium refractive index and low refractive index of 1.9 or less, and the front part of the sphere is After exposing the rear hemisphere to the air, a reflective layer (4) was directly applied, followed by a binder (15), and then a support (6) was applied.
It had four structures. This product has a high reflective purple color, excellent single reflection angle characteristics, and a simple structure.

Since it has a small basis weight and is thin, it has the characteristics that it can be used as a light retroreflector 2 for clothing with excellent sewability.

However, on the other hand, it also has one serious drawback.

That is, 1. For example, if the hemispherical part of the front part of the glass sphere that appears on the surface KM 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 retroreflector, it is important to
As shown in the figure, a method is used in which the binder portion (5) connecting the glass spheres (3) and glass spheres (3)' is colored to form a colored layer to impart a necessary external color.

However, with this coloring method, even if the colors are clear under scattered light during the day, when viewed under three-ray illumination light (convergent light) at night, the light rays are reflected by the light retroreflector. When the coloring layer 9 is not present in the incident and return path of the light, no color is recognized at all. 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, water will penetrate into the rear hemisphere of the glass bulb, degrading the bonding agent, causing the glass bulb to fall off, and reducing brightness due to deterioration of the reflective layer. 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 drawbacks, the front exposed surface of the glass bulb of the open type light retroreflector is placed on the exposed surface side.

A method has been adopted in which a transparent thin plate (12) is attached via an air layer (+4) as shown in FIG. 2r to protect the glass ball lens. The surface of this transparent thin plate is colored or printed and used as an all-weather, high-brightness 4-degree retroreflector.

However, since the air space 04) is a necessary condition for such a device, the bonding area (13) between the glass small sphere surface and the transparent thin plate 02) must be made as small as possible. However, it is extremely difficult to balance the reflectivity with the surface area, which is also adhesive strength.

As a result, the adhesive often peels off during outdoor use, causing cracks in the transparent thin plate, as well as moisture and rainwater.

Accidents have occurred in which the optical retroreflector loses its performance due to penetration of dew, etc. In addition, since the structure is complex, it is necessary to take sufficient care in handling the transparent thin plate (121) so as not to damage it when used as a traffic sign or for clothing.

On the other hand, in a closed type optical retroreflector,
A high refractive glass sphere with a refractive index of 2.0 or more is used, and as shown in Fig. 3, a smooth transparent resin surface layer (151) is formed on the front hemisphere of the glass sphere, and a glass sphere is also formed on the rear hemisphere. One layer of transparent resin binder in the shape of a hemispherical shell concentric to the center of the sphere (16)
Furthermore, a reflective layer (4) made of metal vapor deposition is provided behind the binder layer.

5- Optical retroreflection function is now available.

In this way, the front hemisphere and the rear hemisphere of the glass sphere have a layer of surface resin 05) and a layer of binder resin ([6), respectively, so the transmission loss of light is extremely large, making it difficult to use a closed type optical retroreflector. The brightness value is only about 1/4 to 115 of that of the open type optical retroreflector described above. and,
Reflectors for clothing can be obtained by using the above-mentioned laminated resin that surrounds the glass globules with high flexibility, but closed type retroreflectors for clothing constructed in this way are difficult to sew.

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.

Since only a relatively thick product can be obtained, the so-called sewability is poor, the texture is very poor, and the manufacturing cost is high due to the large amount 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 object of the optical retroreflector of the present invention is to obtain a high-luminance product that is highly flexible and has excellent visibility including two colors at night. Use a high refractive index glass sphere with a refractive index of 1.9 or higher and a good index of 20 or higher. High brightness can be achieved by coating a transparent resin layer in the form of a concentric hemispherical shell, or by printing a circular colored transparent I resin layer.

It is characterized by being flexible and able to be colored arbitrarily.

In this case, by using a resin with high flexibility as the transparent resin, the resin layer is extremely flexible and has excellent sewability, combined with the thinness of the resin layer, and can be used for high-brightness clothing that can obtain any reflective color regardless of day or night. It becomes possible to manufacture optical retroreflectors.

Since no glass spheres are exposed on the surface of the reflector of the present invention, it has excellent stain resistance, and even if dirt or soot adheres to it, it can be easily wiped clean with a rag or the like. In addition, drop-off of the glass spheres can be completely prevented and water will not enter the interior of the reflector, thereby eliminating performance deterioration and extending the service life.

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 all cases due to technical constraints in manufacturing the reflector, so the refractive index Glass beads with a refractive index of about 1.9 have been used for open types, and glass beads with a refractive index of about 20 have been used for closed types.

In the optical 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 despite the large refractive index of the glass sphere (approximately 2.0), that is, the open type. This is a novel invention that uses a reflection mechanism. More specifically, conventionally, when using high refractive index glass beads having a refractive index of 20 or more, it is common to have a so-called closed type structure (see FIG. 3). However, the structure of the optical retroreflector of the present invention uses a high refractive index glass sphere and directly deposits metal on its rear hemisphere.

Alternatively, after providing a reflective layer made of a resin layer mixed with a light-reflective substance such as aluminum powder, a thickness of 0.5 mm is provided on the front hemispherical surface of the glass sphere. A retroreflective function is imparted by closely covering a concave lens with a 4 to 5 micron transparent film, and this is achieved by simply using conventionally used high refractive index glass spheres with a refractive index of 2.0 or more. The method is completely different. 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. Furthermore, even if a high refractive index glass sphere with a refractive index of 20 or more is used, if the transparent coating covering the front hemispherical surface of the glass sphere is as thick as about 10μ and the surface in contact with air is almost flat, cannot obtain sufficient reflective performance. Furthermore, in the case where a layer of binder and a reflective layer are provided at the rear of the glass bulb, no retroreflection function is achieved even if the transparent coating covering the front hemispherical surface of the glass bulb has the film shape of the present invention. is not obtained.

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 using an electron microscope, it is found that it covers the glass sphere in the form of a concentric elliptical hemispherical shell, and its thickness is 0 when the diameter of the glass sphere is 500 μm or less. It was in the 10- range of .01 to 5μ. Moreover, the thickness of the coating increases as the diameter of the glass sphere increases.

In this way, the optical retroreflector of the present invention has a refractive index of 1
．． A glass ball with a high refractive index of 9 or more is used, and a concentric elliptical hemispherical shell-shaped coating is provided on the front surface of the glass sphere, and a reflective layer is closely attached to the rear surface.This can be done by combining conventionally known means. be able to.

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 a semi-finished product (7) (hereinafter referred to as semi-finished product) of a light retroreflector made of the polyester-polyethylene laminate (Ij, (2+) shown in Figure 4, which is peeled off to expose the glass sphere (3) in the air. Fig. 6 is a cross-sectional view of a glass sphere (3) in which a transparent or colored transparent resin coating (8) in the form of a concentric elliptical hemispherical shell is closely adhered to the front hemispherical surface of the glass sphere (3). A concentric elliptical hemispherical shell-shaped resin coating (8) is placed on the front of the glass sphere (3) of the reflector.

This is an estimation of the path and reflection mechanism of light from the outside when a reflective film (4) is provided at the rear. Namely.

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 the second refraction, the air and transparent resin are separated. Due to the appropriate combination of the refractive index and thickness of resin and glass, the focal point of the lens of the glass sphere is located at point (10) VC on its rear hemisphere. 10), the incident light ray (9) is reflected, and the reflected light ray (11) passes through the transparent resin from the glass sphere again.
, and reflection of light occurs in a direction parallel to and opposite to the incident ray (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, a polyester film (1) and a 20μ thick polyethylene film (2) laminated thereon are coated with high refractive index glass having a diameter of 80μ and a refractive index of 2.25. The small sphere (3) is temporarily buried by heating at 110° C. for 3 minutes at a burial rate of 50 cm. Next, on the exposed surface of the glass sphere (3), aluminum with a thickness of about 800 angstroms is metal-deposited to form a reflective layer (4), and a layer of adhesive binder (5) is applied on top of this to a thickness of 30 μm. After that, the support film (6) and 100c were fixed by heat lamination for 3 minutes, and then the glass spheres were temporarily immersed in a polyester-polyethylene laminate (11, (21) was peeled off to form the embedded glass spheres. A semi-finished product of a retroreflector was obtained by exposing half of the product to the air.

In addition, glass globules with different refractive index, i.e. 1
．． ．． 5], 1.92, and 2.1, three semi-finished products were created in the same manner.

Examples 1 to 4 A transparent resin having the following composition was applied to the exposed surface of the glass sphere of the semi-finished product (7) as shown in FIG. A sample having the resin coating (8) shown in FIG. 5 was prepared by performing a hot air drying process for 3 minutes.

Composition Methacrylic acid alkyl ester polymerized resin 10
0 parts Melamine curing agent 5 parts Total 135 parts The relationship between the light retroreflection performance (brightness value) of each sample and the refractive index of the glass spheres is clarified in Example Nos. 1 to 4 in Table 1 below.

The brightness values in Table 1 indicate the amount of reflected light for a constant amount of incident light.
The larger the value, the better the reflector performance. 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 When a high refractive index glass sphere is used as in the results obtained in Examples 1 to 4, the transparent 14-coat coated on the front part of the glass sphere and the lactic effect of the glass sphere match, resulting in high brightness. It turns out that the value can be obtained. Furthermore, the relationship between the thickness of the coating coated on the glass sphere and the diameter of the glass sphere was as follows. That is, in the aforementioned semi-finished product using glass spheres with a refractive index of 225° and a diameter of 80μ, the following colored transparent resins were applied in varying amounts on the exposed surface of the glass spheres to form resin coatings of two different thicknesses. (8) was formed and the brightness value was measured.

Composition Melamine formalin polymer resin 100 parts total 1
Part 15 As a result, there is a certain relationship between the thickness of the coating and the brightness value as shown in Figure 7, and in order to obtain high brightness reflection performance, an appropriate value must be set for the diameter of the glass sphere. It was found that a range of thicknesses exists.

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. As shown, the exposed surface of the glass sphere had a diameter of about 01μ near the top, and 5μ at the base, with an average diameter of about 2.5μ.

As mentioned above, the reflective performance of a 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, the diameter of the glass globules is essentially arbitrary.

Due to technical constraints in forming the film into a concentric elliptical shell shape, a thickness of 500 μm or less is appropriate.

Examples 6-9. Comparative examples 1 to 4 When making a semi-finished product of the optical retroreflector of the present invention.

When the support is made of nylon knitted tricot, semi-finished clothing products can be produced. Then, by applying the following printing ink to the exposed surface of the glass globules of the semi-finished product to form a concentric elliptical hemispherical shell-like coating, high-brightness clothing with a good color match and whose reflected color does not change day or night can be created. 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, a benzidine-based yellow pigment, a perylene-based red pigment, a cyanine-based blue pigment, and a cyanine-based green pigment were used to create yellow pigments. , after preparing red, blue and green printing inks and then screen printing with a 220 mesh polyester A411 screen.

After drying with hot air at 120°C for 5 minutes, a film with a thickness of about 3μ was formed with a refractive index of 2.25. It was formed on the exposed surface of a glass sphere having an average diameter of 80 μm, and the reflection performance, ie, the brightness value, as shown in Table 2 was obtained. For comparison, Japanese Industrial Standard JIS-Z-9117
The brightness values of the reflective material stipulated in 17-2 are also listed, and it is clear that each color has significantly superior reflectivity. , and had good sewability.

[Brief explanation of the drawing]

An example of the structure of the optical retroreflector of the present invention is schematically shown in 18-. 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. Observation conditions are observation angle of front brightness value 02°, incident angle -4
°. In the figure, (1) is a polyester film, (2) is a polyethylene layer, (3) is a glass sphere, (4) is a reflective layer, and (5) is a polyester film.
) is a single layer of fixed binder, (6) is a support, (7) is +3
1. (4), (51, (6) are collectively referred to as semi-finished products of optical retroreflectors, r8) is a concentric elliptical hemispherical shell-shaped coating, (9
) is the incident ray, +10) is the focal point, (II) is the reflected light a, O2) is the transparent thin plate, (13) is the adhesive part, (1(
b) indicates an air layer. Patent applicant Unitika Sparklight Co., Ltd. Agent
Yuzo Kodama

Claims (3)

[Claims] (1) 4 in the fixed binder resin layer held on the support
Burial rate of 0 to 80, diameter 500μ or less, refractive index 1.9
As described above, a glass ball with a high refractive index, preferably 2.0 or more, is buried, and a direct reflection layer such as a metal vapor-deposited film is provided at the rear part of the buried part of the glass ball. A coating of a colorless or colored transparent resin having a thickness of 0.01 to 5 μm in the shape of a concentric elliptical hemispherical shell is placed on the front exposed surface side to cover the exposed surface. An optical retroreflector characterized in that it is formed to maintain an optical relationship. (2) The light retroreflector according to claim 1, wherein the transparent resin film is a film of synthetic polymer resin or printing ink, and is printed with an arbitrary colored pattern. (3) The light retroreflector according to claim 1, wherein the support is a synthetic resin film, a woven fabric, or a nonwoven fabric.