JPH06273608A - Reversing reflector - Google Patents

Abstract

PURPOSE:To provide the reversing reflector having a high reflection efficiency by constituting it of plural kinds of cube corner patterns which are arranged in the mixed state on the reflecting surface and are different by sizes. CONSTITUTION:A cube corner 1 is a regular triangle, and its center point 2 is lowest, and three faces having the same shape and dimensions are obliquely raised from the center point 2 at the same angle to form reflecting faces 3 to 5, and first patterns 6 having hexagonal planes and second patterns 7 having regularly triangular planes are combined. These cube corners are regularly arranged on a base material to obtain the reversing reflector. When light is made incident on a non-hatched part, it exits in the direction opposite to the direction of incidence after being certainly reflected three times; but when light is made incident on a hatched part, it does not exit in the direction opposite to the direction of incidence after being certainly reflected twice. That is, the direction of incident light is reversed in areas S1 and S2, and the numerical aperture is 0.889, and this reversing reflector has a high reflection factor.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to retrograde reflectors used to retroreflect incident light rays.

[0002]

2. Description of the Related Art As a retrograde reflector, a prism system utilizing a cube corner and a glass bead system utilizing a spherical surface are known. Since the prism type has higher reflection efficiency than the glass bead type, it is used in various applications requiring high reflection efficiency. As a conventional retrograde reflector using such a prism system, JP-A-1-231 is known.
Japanese Patent Publication No. 004 is disclosed.

FIG. 11 is a plan view of a retroreflective sheet showing a lattice state in this prior art, FIG. 12 is a plan view of a micro prism retroreflective molded article, and FIG. 13 is an optical path after incidence through a front surface. FIG. 3 is a cross-sectional view of a reflective sheet showing FIG. In these figures, 30 is a main body portion, 32 is a micro prism, 34 is a metal coating, 36 is a second coating material, 38
Is a backing material, and 50 is a coating material portion.

In this retrograde reflector, the light rays incident on the coating material portion 50 are reflected by the metal coating 34 with the conventional efficiency, but the light rays incident on the main body portion 30 are the minute prisms 32 and the backing material 38. Since the space is air, it is reflected by the micro prism 32 with high efficiency.

[0005]

However, even if the space between the minute prism 32 and the backing material 38 is completely filled with air, the reflectance at the time of total reflection = 1 is the limit, and the reflection efficiency (hereinafter, It is smaller than 1 when the numerical aperture) is calculated as the retroreflection range / incident range.

Next, the specific aperture ratio of the above-mentioned prior art will be determined. FIG. 14 shows a micro prism retroreflective molded article as in FIG. 12, and FIG. 15 is a sectional view taken along line CC in FIG. Indicates. When a light ray is incident on the unhatched portion of the one cube corner 40 shown by the thick line in FIG. 14, it always reflects three times and then exits in the direction opposite to the incident light ray, but the cube corner 40 is hatched. When a ray of light is incident on a part, it is always reflected and emitted twice, so that it is not emitted in the opposite direction of the incident ray. Figure 1
6 illustrates this graphically, and the cube corner 40
Has a shape in which the center point 41 is the lowest. When light rays 42 and 43 are obliquely incident on the cube corner 40, the light ray 42 incident on the unhatched portion is reflected by the three surfaces of the first surface 46, the second surface 47 and the third surface 48, As a result, it is emitted in the direction opposite to and parallel to the incident light ray 42. On the other hand, the light ray 43 incident on the hatched portion is reflected at the relatively shallow position of the cube corner 40, and therefore is reflected by the first surface 46 and the second surface 47, but is reflected by the third surface 48. Without doing
It emits as it is. As a result, there is no emission in the direction opposite to the incident light ray 43.

FIG. 17 shows a cube corner 40 which is a constituent unit of the retroreflector. When the length of one side of an equilateral triangle is 3a, the pitch P for each cube corner 40 shown in FIG. 16 is P = 3a. Further, at this time, the depth d ₀ to the corner is given by the _equation 1. The region that can be emitted in the direction opposite to the incident light beam is a regular hexagonal region that is not hatched. Therefore, the aperture ratio was 2 / 3≈0.667 regardless of a, and the reflection efficiency could not be increased any further.

[0008]

[Equation 1]

The present invention has been made in consideration of the above circumstances, and an object thereof is to provide a retrograde reflector having a high reflection efficiency by increasing the aperture ratio from the cube corner of-.

[0010]

The retroreflector of the present invention increases reflection efficiency by being composed of a plurality of cube corner patterns of different sizes arranged in a mixed state on the reflecting surface. It is a thing.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a plan view of the first embodiment of the present invention, and FIG. 2 is a sectional view taken along the line AA of FIG. 1, in which a large number of cube corner patterns are formed. In FIG. 1, 1 indicated by a thick line
Is a unit of cube corner. The cube corner 1 is an equilateral triangle, and the center point 2 is the lowest, and three surfaces having the same shape and the same size rise from the center point 2 in an oblique direction at the same angle to form reflecting surfaces 3, 4, and 5. is doing.

3 and 4 show this cube corner 1
The pattern which comprises is shown. Cube corner 1 is shown in Figure 3
4 is formed by a combination of a first pattern 6 having a hexagonal plane and a second pattern 7 having a regular triangle shown in FIG.

The center point 2 of the first pattern 6 has the lowest depth d _1, and the depths of the ridges of the reflecting surfaces 3 and 5 are d ₂ (d ₂ <d ₁ ). . The center point 8 of the second pattern 7 whose plane is an equilateral triangle has the lowest depth d _3, and from this center point 8 the three reflecting surfaces 9,
10, 11 are provided in an inclined shape.

The second pattern 7 is formed so as to be in contact with every other three sides 12, 13, and 14 with respect to the first pattern, whereby one unit of cube corner 1 is formed. Therefore, the length of one side of the second pattern 7
The length of one side of the first pattern 6 is set to have the same dimension a. Here, the depth d ₁ of the center point of the first pattern 6 is given by Equation 2, and the depth d ₂ is given by Equation 3. Also,
The depth d ₃ of the center point 8 of the second pattern 7 is given by Equation 4.

[0015]

[Equation 2]

[0016]

[Equation 3]

[0017]

[Equation 4]

FIG. 5 shows one unit of a cube corner 1 formed by combining the first pattern 6 and the second pattern 7, and the cube corner 1 has a pitch P = 3a (see FIG. 2). Therefore, by arranging regularly on the base material, the retroreflector shown in FIG. 1 can be obtained. In FIG. 5 and FIG. 1, when a light ray is incident on a non-hatched portion, it is always reflected three times as described above, and then emitted in the opposite direction to the incident light ray, but the light ray is applied to the hatched portion. When incident,
Since it is always reflected twice, it is never emitted in the direction opposite to the incident light beam. For this reason, the regions where the incident light rays can be emitted in the opposite directions are the unhatched regions S ₁ and S ₂ in FIG. Therefore, the aperture ratio is a
8 / 9≈0.889 regardless of the value of, and a retrograde reflector having high reflection efficiency can be obtained. In particular, in this embodiment, all the ridge lines can be shortened, and the amount of diffused reflected light due to the ridge lines can be reduced, so that there is an advantage that the reflection efficiency can be increased.

6 and 7 are a plan view and a sectional view taken along line BB of the second embodiment of the present invention. In FIG. 6, the thick line 20 is one unit of the cube corner. FIG. 8 shows this one unit of cube corner 20,
The first pattern 6 whose plane shown in FIG. 3 is a regular hexagon, and FIG.
The plane whose one side has the dimension a is a third equilateral triangle
The pattern 21 of FIG. That is, it is configured by arranging three third patterns 21 at 120 ° intervals with the first pattern 6 as the center. And, P = this cube corner 20
By arranging regularly at a pitch of 3a, the retrograde reflector shown in FIG. 6 is formed. Here, the dimensions d ₁ and d ₂ of the first pattern 6 have the same values as in FIG. 3, but the dimensions d ₄ and d ₅ (see FIG. 9) in the third pattern 20 are expressed by
It becomes the number 6.

[0020]

[Equation 5]

[0021]

[Equation 6]

In the second embodiment as well, when a light ray is incident on the unhatched portion, it is reflected three times and then emitted in the direction opposite to the incident light ray, but the light ray is applied to the unhatched portion. When incident, it is always reflected twice, so that it does not emerge in the direction opposite to the incident ray.
Therefore, the areas that can be emitted in the opposite directions are the hatched areas S ₁ and S in FIG.
₃ , the aperture ratio is 8 / 9≈0.889 regardless of a, and can be a large value. In Example 2 as described above, the difference in depth between the first pattern 6 and the third pattern 21 is smaller than that in Example 1, so that there is less loss during reflection of coherent light such as laser light. There is.

In the present invention, the above-described first and second embodiments
It is also possible to form another retrograde reflector by combining the three types of patterns 6, 7, and 21 shown in FIG. For example,
By embedding the pattern 21 shown in FIG. 9 in the hatched equilateral triangular region of the basic configuration shown in FIG. 5 with the same size, the two-thirds thereof can be made an effective reflection region. Further, by embedding the pattern 7 shown in FIG. 4 in the hatched equilateral triangular region of the basic configuration shown in FIG.
3 can be an effective reflection area. Further, by embedding patterns 7 and 21 having different sizes (see FIGS. 4 and 9) in the remaining 1/3 region, the aperture ratio can be made as close to 1 as possible.

When the number of different pattern types used here is n (even if the sizes are different, they are different types), the aperture ratio can be calculated from equation 7.

[0025]

[Equation 7]

In both the above-mentioned first and second embodiments, n = 2
Therefore, from Expression 7, 8 / 9≈0.889 as described above. Also, when n = 3 and n = 4, 26/27 respectively
≈0.963, 80 / 81≈0.988. Therefore, as n is increased in this way, the aperture ratio is increased and can be brought close to 1 infinitely.

Further, in order to increase the reflection efficiency, it is effective to deposit a high-reflectance substance on the pattern surface. Although the surface reflection by the pattern has been described above for the convenience of description, it is actually effective to fill the concave portion of the pattern with a transparent material to protect the surface. FIG. 10 shows this structure, and 61 is a transparent material having a flat surface 62 and the cube corner pattern 63 described above. For example, a single pattern mold machined by a well-known machining method is prepared for each kind of cube corner pattern. ,
It can be formed by a known forming method using a forming die for the cube corner pattern 63 and a forming die for the flat surface 62, which are obtained by sequentially aligning and processing by the electric discharge machining method. . Reference numeral 64 denotes a metal reflection film for the cube corner pattern 63 to obtain a high reflectance, which is deposited on the surface of the cube corner pattern 63. 6
Reference numeral 5 is a base material for protecting the cube corner pattern 63 and for obtaining the overall strength.
Is deposited on the surface of the cube corner pattern 63 of the transparent material 61, and then the surface of the metal reflection film 64 is closely filled.

In such a structure, the total thickness t
By setting the thickness to be thin, a sheet-shaped retroreflector having the cube corner pattern 63 inside can be formed.

[0029]

As described above, since the retroreflector of the present invention is a combination of a plurality of types of cube corner patterns, it can have high reflection efficiency.

[Brief description of drawings]

FIG. 1 is a plan view of a first embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a diagram showing a first pattern of cube corners.

FIG. 4 is a diagram showing a second pattern of cube corners.

FIG. 5 is a plan view showing one unit of a cube corner.

FIG. 6 is a plan view of the second embodiment.

7 is a sectional view taken along line BB of FIG.

FIG. 8 is a plan view of one unit of the cube corner of the second embodiment.

FIG. 9 is a diagram showing a third pattern of cube corners.

FIG. 10 is a cross-sectional view showing an example for increasing reflection efficiency.

FIG. 11 is a plan view of a conventional retrograde reflective sheet.

FIG. 12 is a plan view of a conventional retroreflective molding.

FIG. 13 is a sectional view showing reflection of incident light rays.

FIG. 14 is a plan view of a conventional retroreflective molding.

15 is a cross-sectional view taken along line CC of FIG.

FIG. 16 is a plan view illustrating reflection.

FIG. 17 is a diagram showing one unit of a conventional cube corner.

[Explanation of symbols]

 1 Cube Corner 3, 4, 5 Reflective Surface 6 First Pattern 7 Second Pattern

Claims (1)

[Claims] 1. A retrograde reflector comprising a plurality of types of cube corner patterns of different sizes arranged in a mixed state on a reflecting surface.