JP2012242508A - Retroreflective member, retroreflective building material and construction method of building - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem with a conventional retroreflective sheet which is structured to reflect incident light from a specific direction straight back therein as much as possible and thereby sometimes reflecting the incident light, which varies season by season and hour by hour such as sunlight from outer space, even in an unintended direction such as the direction toward the ground.SOLUTION: A retroreflective member has concave sections which respectively have a shape of an inclined triangular pyramid where: three side faces collectively forming an apex with an opening in a shape of a triangle as a bottom face; and a projection point of the apex on the bottom face is deviated from a barycentric position of the bottom face to a reference side of the triangle. In each concave section, a reflection surface is formed on at least one of the three side faces.

Description

  The present invention relates to a retroreflective member, a retroreflective building material, and a building construction method.

Conventionally, a retroreflective sheet is known in which corner cubes, beads, and the like are arranged in a plane to reflect incident light rays in the incident direction. The retroreflective sheet is used for security products such as road signs. On the other hand, a proposal has been made to prevent global warming by using a retroreflective member for a wall of a building and reflecting sunlight in the incident direction without reflecting the sunlight in the ground direction (for example, Patent Document 1).
[Prior art documents]
[Patent Literature]
[Patent Document 1] Japanese Patent Application Laid-Open No. 2006-317648

  However, the conventional retroreflective sheet is structured so as to reflect the incident light incident from a specific direction as much as possible. Therefore, depending on the season and time, such as sunlight coming from outer space. There is a problem that the incident light that changes may be reflected in an unplanned direction such as the ground direction.

  In order to solve the above-mentioned problem, the retroreflective member according to the first aspect of the present invention has three side surfaces that form a vertex with a triangular opening as a bottom surface, and the projected position from the vertex to the bottom surface is the position of the center of gravity of the bottom surface. And a concave portion having a triangular pyramid shape displaced from the reference side of the triangle, and at least one of the three side surfaces is formed on the reflecting surface.

  In order to solve the above-mentioned subject, the retroreflective building material in the 2nd mode of the present invention contains the above-mentioned retroreflective member.

  In order to solve the above-mentioned problem, the building construction method according to the third aspect of the present invention has three side surfaces forming a vertex with a triangular opening as a bottom surface, and the projection position from the vertex to the bottom surface is the bottom surface. A retroreflective member having a triangular oblique pyramid-shaped concave portion displaced from the center of gravity to the reference side of the triangle and having a reference surface including the reference side among at least three of the side surfaces is formed on the reflection surface. It includes an installation stage in which the reference plane is installed so as to be orthogonal to the mid-time solar rays.

  In order to solve the above-mentioned problem, the retroreflective member according to the fourth aspect of the present invention has n side surfaces forming apexes with an n-gonal (n is a natural number of 3 or more) opening as a bottom surface. The projection position on the bottom surface is provided with an n-angle oblique pyramid-shaped concave portion whose position is shifted from the gravity center position of the bottom surface to the n-side reference side, and at least one of the n side surfaces is formed on the reflection surface.

  It should be noted that the above summary of the invention does not enumerate all the necessary features of the present invention. In addition, a sub-combination of these feature groups can also be an invention.

It is a figure which shows the case where the retroreflection member which concerns on this embodiment is applied to the wall surface of a building. It is explanatory drawing which shows the direction in which the retroreflection member which concerns on this embodiment retroreflects an incident light ray. It is an external appearance perspective view which shows the retroreflection member which concerns on this embodiment. It is a definition figure regarding calculation of retroreflection efficiency. It is a figure which shows each cross section and coordinate value when a recessed part is a straight weight shape. It is a figure which shows the time change of the reflective efficiency in each season with respect to a straight weight shape. It is a figure which shows a mode that a recessed part is receiving sunlight at the time of south and middle. It is a figure which shows each cross section and coordinate value of a 1st oblique pyramid shape. It is a figure which shows the time change of the reflective efficiency in each season with respect to a 1st cone shape. It is a figure which shows each cross section and coordinate value of a 2nd oblique pyramid shape. It is a figure which shows the time change of the reflective efficiency in each season with respect to a 2nd cone shape. It is a figure which shows each cross section and coordinate value of a 3rd cone weight shape. It is a figure which shows the time change of the reflective efficiency in each season with respect to a 3rd cone weight shape. It is a figure which shows each cross section and coordinate value of a 4th oblique pyramid shape. It is a figure which shows the time change of the reflective efficiency in each season with respect to a 4th cone shape. It is an external view which shows the other retroreflection member which concerns on this embodiment. It is an external view which shows the other retroreflection member which concerns on this embodiment. It is a figure explaining the other retroreflection member which concerns on this embodiment. It is a figure explaining the process of installing the retroreflection member which concerns on this embodiment on the wall surface of a building as a building material.

  Hereinafter, the present invention will be described through embodiments of the invention, but the following embodiments do not limit the invention according to the claims. In addition, not all the combinations of features described in the embodiments are essential for the solving means of the invention.

  FIG. 1 is a diagram illustrating a case where the retroreflective member 10 according to the present embodiment is applied to a wall surface of a building 20. The retroreflective member 10 is used as a part of the outer wall material of the building 20.

  The retroreflective member 10 according to the present embodiment reflects sunlight in which the incident angle changes depending on the season and time, for example, in the direction of outer space when the total reflection amount throughout the year is evaluated. It has the property of releasing energy. In other words, it has a property of reducing reflection in an undesired direction such as the direction of the ground surface in summer.

  Recently, the outer walls of buildings are often covered with reflective members such as glass, and sunlight is regularly reflected by the reflective members, so that intense summer light and heat are irradiated toward the ground. Has become a social problem. In particular, it is a well-known fact that the heat energy accumulated on the ground causes the heat island phenomenon and is one of the causes of global warming. Therefore, with the retroreflective member 10 according to the present embodiment, the sunlight irradiated to the building is not reflected as much as possible toward the ground, and in the summer, the solar energy is retroreflected to release solar energy to outer space.

  Specifically, when the incident light 101 that is sunlight enters the retroreflective member 10 spread on the wall surface of the building 20, most of the reflected light 102 is reflected toward the sun almost along the incident direction. . The energy of the reflected reflected light 102 is eventually released into outer space while being partially absorbed by the atmosphere.

  On the other hand, the reflection of sunlight by the ground in summer is one of the causes of the heat island phenomenon. Therefore, when the retroreflective member reflects incident light in the incident direction regardless of the incident direction, reflection from the ground is reflected again toward the ground, resulting in a further acceleration of heat storage by the ground.

  Therefore, the retroreflective member 10 according to the present embodiment diffuses by diffusely reflecting on the surface thereof when the reflected light 104 of the incident light 103 applied to the ground is incident. That is, the retroreflective member 10 has retroreflectivity for incident light from the direction in which sunlight directly enters, and diffuses without retroreflecting incident light incident from other directions.

  FIG. 2 is an explanatory diagram showing a direction in which the retroreflective member 10 according to the present embodiment retroreflects incident light rays. The retroreflective member 10 is spread on the south side wall surface of the building 20. Specifically, as will be described later, it is preferable that the specific direction for retroreflecting most efficiently is the south-mid altitude of the summer solstice. In this case, the direction of the sun from which a predetermined retroreflectance can be obtained is an effective direction 110 included in a certain south direction sandwiched between the solar path 111 of the summer solstice and the solar path 112 of the winter solstice.

  Next, the structure of the retroreflective member 10 will be described. FIG. 3 is an external perspective view showing the retroreflective member 10 according to the present embodiment. The retroreflective member 10 is unitized with a fixed size, and when it is spread on the wall surface of the building 20 as described above, a plurality of units are mounted side by side.

  The retroreflective member 10 mainly includes a base member 31, a plurality of concave portions 32 provided in the base member 31, and a connection portion 33 for connecting the base members 31 to each other. The base member 31 is a highly rigid base material made of, for example, ceramics or plastic. The recess 32 has a truncated pyramid shape with a triangular opening with respect to the base member 31 as a bottom surface. That is, the concave portion 32 has a conical shape in which a perpendicular (projection position) that vertically drops from the deepest vertex to the bottom surface that is the opening does not pass through the center of gravity of the triangle on the bottom surface. And at least one part of the surface is formed with the reflecting material. The reflective material may be a reflective material adhered, vapor-deposited or applied to the recess 32, or the base member 31 itself formed of a reflective material. For example, alumina, titania, zirconia, aluminum or the like is used as the reflective material. The connection part 33 is a bolt through hole, for example, provided on the peripheral part of the retroreflective member 10 and fixed to the wall part while being connected to the other retroreflective member 10.

  Next, a specific weight shape of the recess 32 will be sequentially described. FIG. 4 is a definition diagram relating to the calculation of retroreflective efficiency. The recess 32 is triangular on the yz plane with respect to the x axis extending north and south with the south direction as the positive direction, the y axis extending to the top and bottom with the zenith direction as the positive direction, and the z axis extending east and west with the east direction as the positive direction. The bottom opening is provided and defined. That is, it is assumed that the retroreflective member 10 is installed on a vertical wall surface facing south.

  A triangle serving as a bottom opening is defined by vertices P10, P11, and P12 as shown. Then, P00, which is the apex of the weight shape, formed as an intersection of the three side surfaces (inner surfaces) exists in the negative region of the x axis. Of the three weight-shaped inner surfaces, the surface surrounded by P00, P10, and P11 is S0, the surface surrounded by P00, P11, and P12 is S1 (reference surface), and the surface is surrounded by P00, P12, and P10. Is S2.

  From the sun altitude and azimuth angle at each time point, the N incident lights 120 are made incident on the bottom opening to calculate the direction of the reflected light. At this time, the reflectance of each surface of S0 to S2 is R, and the energy of one light beam is 1. At this time, the total energy of the incident light 120 is N.

The retroreflected light 121 in the present embodiment is defined as light that travels straight inside the cone 130 that is formed with an allowable angle θ with respect to a light ray that is opposite to the incident light 120 after reflection. The light reflected toward the outside of the cone 130 is defined as non-retroreflective light 122. If the number of retroreflected light 121 included in the cone 130 among the light rays reflected by the concave portion 32 is M (0 ≦ M ≦ N), the number of reflections of each retroreflected light 121 is i (0 ≦ i). ≦ N) and can be expressed as r (i). At this time, the total energy E of the retroreflected light 121 is expressed as follows.

Then, by dividing the total energy E of the retroreflected light 121 by the total energy of the incident light 120, the retroreflective efficiency ε is defined as follows. That is, the retroreflective efficiency ε is the ratio of the energy of reflected light reflected in the cone having the allowable angle θ to the energy of sunlight incident on the recess 32 of the retroreflective member 10 installed on the wall surface.

  The weight shape of the recess 32 will be described using the above definition. In the present embodiment, a series of calculations is performed by applying N = 100, R = 0.9, and θ = 30 ° as specific numerical values.

  FIG. 5 is a diagram showing cross sections and coordinate values when the concave portion 32 has a straight weight shape. The straight weight shape is a shape in which a centroid (projection position) vertically dropped from the apex toward the bottom surface that is an opening overlaps the center of gravity of the triangle on the bottom surface. In the straight weight of FIG. 5, the surfaces S0 to S1 are orthogonal to each other. In the example shown in the figure, an opening of an equilateral triangle having one side of 25.98 mm, and P00 is defined at a position where the depth of the recess is 10.66 mm.

  With respect to such a recess 32, the reflection efficiency was calculated every 6 hours from 16:00 to 18:00 on the summer solstice, spring equinox / autumn and winter solstice in Tokyo (34.7 ° north latitude, 135.5 ° east longitude). The result is shown in FIG. In particular, FIG. 6A shows the temporal change in retroreflective efficiency in each season, and FIG. 6B shows the non-retroreflective light 122 in each season of light rays reflected below the z plane, which is the horizontal plane. The time change of reflection efficiency is shown.

  (A) As shown in the figure, when the recess 32 has a straight weight shape, the retroreflective efficiency is 0 in the summer solstice where the highest retroreflective efficiency is required, and it exceeds 60% in the morning and afternoon in the winter solstice. As a result, the retroreflective efficiency is obtained. Further, as shown in FIG. 5B, a large amount of non-retroreflective light 122 that is reflected in the morning and evening directions below the horizontal level is generated. The non-retroreflected light 122 that reflects in the direction below the horizontal is unfavorable reflected light because it has many harmful effects such as a pedestrian feeling uncomfortable. Therefore, the concave portion 32 having a straight weight shape is not preferable from the viewpoint of the retroreflective efficiency and from the viewpoint of the reflection direction of the non-retroreflective light 122.

  Therefore, the optimum shape of the recess 32 will be described below from these viewpoints. FIG. 7 is a diagram illustrating a state in which the concave portion 32 receives sunlight during the south-central time in Tokyo in the summer solstice. In particular, FIG. 7A shows a perspective view, and FIG. 7B shows an xy sectional view.

  First, for the purpose of energy saving and environmental measures, it is desirable to retroreflect sunlight most effectively after summer noon in summer. The sun's south-middle altitude at the summer solstice is represented by 90 °-(latitude-23.5 °). Applying the latitude of Tokyo as 35 °, the south-central altitude at Tokyo in the summer solstice is 78.5 °.

  In order to reflect sunlight in the south and central times in the same direction with a single reflection, the S1 surface should be orthogonal to the light rays from this angle, and the S0 and S2 surfaces should not shield incident light and reflected light. Is a condition. That is, with respect to the shape of the xy section of the recess 32, “the angle formed by the x-axis and the S1 plane is equal to the complementary angle of the south-south altitude of the sun at the summer solstice = latitude −23.5 °” and “the S1 plane and the ridgeline P00 The two conditions “the angle formed by −P10 is 90 ° or less” must be satisfied.

  The former condition is a condition in which the S1 surface is orthogonal to the sun rays in the middle of the south, and the latter condition is a condition in which the surfaces S0 and S2 do not shield incident light and reflected light. Note that the angle between the x-axis and the S1 plane is about 11.5 ° at a latitude of about 35 ° in Tokyo.

  The straight line P00-P10 is preferably included in the xy plane, but even if it is not in this position, it hardly affects the retroreflective efficiency at the time of the summer solstice. However, it affects the reflection characteristics of spring and autumn morning and evening. In the above conditions, optimization is performed so that the maximum retroreflective efficiency is exhibited during the south-south sun of the summer solstice. For example, when optimizing the south-south altitude of the sun at an appropriate time in July and August, for example. May be used instead of the solar mid-sea altitude at the summer solstice. In practice, it may be established within a range of about ± 3 °. In particular, if the reflection direction is simply determined instead of strict optimization, the former condition is that the projection position from the vertex P00 to the aperture triangle P10-P11-P12 is the reference edge from the center of gravity of the aperture triangle. What is necessary is just to determine a triangular-pyramid shape so that it may become a position displaced to a certain P11-P12 side.

  Below, a preferable example is demonstrated in order about the shape of the recessed part 32. FIG. FIG. 8 is a diagram showing each cross section and coordinate values of the first inclined pyramid shape. The concave portion 32 in the first oblique pyramid shape has an equilateral triangular opening with a side of 25.98 mm, and the depth from the opening to P00 is 4.4 mm. Moreover, P10 of the triangle of opening is a shape which faces a zenith, and P00 has shifted 6.6 mm below from the center of the equilateral triangle. Note that the first oblique pyramid shape satisfies the above-mentioned condition because the angle formed by the x-axis and the S1 surface is 11.56 ° and the angle formed by the S1 surface and the ridgelines P00 to P10 is 90 °. .

  FIG. 9 is a diagram showing the temporal change in the reflection efficiency in each season with respect to the first inclined pyramid shape. The preconditions for the calculation are the same as the conditions that led to the results of FIG. As can be seen from the figure, the retroreflective efficiency after noon in the summer solstice is 80% or more, a maximum of 60% in the spring and autumn minutes, and a maximum of 30% in the winter solstice.

  FIG. 10 is a diagram illustrating each cross section and coordinate values of the second oblique pyramid shape. The concave portion 32 in the second oblique pyramid shape has an equilateral triangular opening with a side of 25.98 mm, and the depth from the opening to P00 is 15 mm. Further, the triangular shape P10 of the opening has a shape facing the zenith, and P00 is shifted 4 mm downward from the center of the regular triangle. In addition, since the angle formed between the x-axis and the S1 surface is 11.56 ° and the angle formed between the S1 surface and the ridgelines P00 to P10 is 64.84 °, the second inclined pyramid shape satisfies the above condition. ing.

  FIG. 11 is a diagram showing the temporal change in reflection efficiency in each season with respect to the second inclined pyramid shape. The preconditions for the calculation are the same as the conditions that led to the results of FIG. As can be seen from the figure, the retroreflective efficiency after noon in the summer solstice is 80% or more, and the maximum is 20% or less in the spring equinox, autumn equinox, and winter solstice, showing that the retroreflective efficiency is high mainly in the summer.

  FIG. 12 is a diagram showing the cross-sections and coordinate values of the third oblique pyramid shape. The recess 32 in the third oblique pyramid shape has an opening of a right isosceles triangle having a long side of 30 mm and a height of 15 mm, and the depth from the opening to P00 is 3 mm. Moreover, P10 of the triangle of opening is a shape which faces a top | zenith, and P00 has shifted 4 mm upwards from the base. In addition, since the angle formed between the x-axis and the S1 surface is 11.30 ° and the angle formed between the S1 surface and the ridgelines P00 to P10 is 90 °, the third inclined pyramid shape satisfies the above-described condition. .

  FIG. 13 is a diagram showing the temporal change in the reflection efficiency in each season with respect to the third inclined pyramid shape. The preconditions for the calculation are the same as the conditions that led to the results of FIG. As can be seen, the retroreflective efficiency after noon in the summer solstice is about 70%, with a maximum of 40% in the spring and autumn minutes and a maximum of 20% or less in the winter solstice, showing a high retroreflective efficiency in the summer.

  FIG. 14 is a diagram showing each cross section and coordinate values of the fourth oblique pyramid shape. The concave portion 32 in the fourth oblique pyramid shape has an opening of a right isosceles triangle having a long side of 30 mm and a height of 15 mm, and the depth from the opening to P00 is 3 mm. Further, the triangular P10 of the opening is shaped to face the ground, and P00 is shifted from the bottom by 0.6 mm upward. In addition, since the angle formed between the x-axis and the S1 surface is 11.30 ° and the angle formed between the S1 surface and the ridgelines P00 to P10 is 90 °, the fourth inclined pyramid shape satisfies the above-described condition. .

  FIG. 15 is a diagram showing a temporal change in the reflection efficiency in each season with respect to the fourth inclined pyramid shape. The preconditions for the calculation are the same as the conditions that led to the results of FIG. As can be seen, the retroreflective efficiency after noon in the summer solstice is about 70%, with a maximum of 40% in the spring and autumn minutes and a maximum of 20% or less in the winter solstice, showing a high retroreflective efficiency in the summer.

  FIG. 16 is an external view showing another retroreflective member 11 according to this embodiment. The recess 32 described so far exhibits each retroreflective efficiency without depending on its size. Therefore, when many concave portions 32 are to be provided in the base member 31, the efficiency of the retroreflective member as a whole increases as long as the concave portions 32 having different sizes are spread. That is, as shown in the drawing, a small recess 322 may be provided in the gap between the large recesses 321. When laying down recesses of different sizes, it is more effective to lay down a plurality of types of recesses to form, for example, a fractal, without being limited to two types of recesses. Of course, from the viewpoint of design, not only regular arrangement but also random arrangement may be adopted. Further, the retroreflective member 11 may be formed with only one concave portion 321, 322 having a different size. In this case, the retroreflective members 11 of various sizes can be combined and spread.

  FIG. 17 is an external view showing another retroreflective member 12 according to this embodiment. Retroreflective efficiency can be increased in addition to laying out recesses of different sizes as described with reference to FIG. Specifically, the above-described third and fourth oblique pyramid shapes have the same relationship in shape of the bottom openings, and when they are combined, a dense arrangement can be realized in the base member 31. . What is arranged in this way is the retroreflective member 12 shown in FIG. 17, in which the concave portion 323 having the third oblique pyramid shape and the concave portion 324 having the fourth oblique pyramid shape are arranged densely adjacent to each other. The retroreflective member 12 as a whole has the retroreflective efficiency shown in FIG. 13 exhibited by the third oblique pyramid shape and the retroreflective efficiency shown in FIG. 15 exhibited by the fourth oblique pyramid shape, Adds retroreflective efficiency.

  FIG. 18 is a diagram illustrating another retroreflective member 13 according to this embodiment. In the above-mentioned retroreflective member, the recessed part 32 was arrange | positioned in the aspect which the triangle as a bottom face opening is visually recognized. However, in order to arrange the concave portions 32 more densely, a structure in which triangles as bottom openings are virtually overlapped and arranged may be used. This will be specifically described below.

  FIG. 18A is a diagram illustrating a case where the bottom openings, which are equilateral triangles, are virtually overlapped so that the bases share half of each other. That is, the left regular triangles P10, P11, and P12 and the right regular triangles P10 ′, P11 ′, and P12 ′ share a base between P11 and P12 ′ as shown in the figure. At this time, the vertices of the respective oblique pyramid shapes are P00 and P00 ′. In this way, the three-dimensional shape formed by overlapping the bottom openings is actually a shape in which a part of two adjacent triangular pyramid shapes are cut off and the ridge line is shared as shown by the solid line in the figure. In this case, the opening is hexagonal in appearance. However, the hexagon of the opening has a three-dimensional structure in which each side does not exist on the same plane, and three non-adjacent vertices and the other three vertices exist on different planes. As described above, when the recesses are developed two-dimensionally by overlapping the bottom openings in the vertical direction, the retroreflective member 13 shown in FIG. In addition, FIG. (C) is AA sectional drawing in FIG. (B). Since the retroreflective member 13 that employs a three-dimensional structure arranged densely in this manner does not have a parallel surface with respect to the base member 31, it achieves a high retroreflective efficiency as a whole.

  In the present embodiment described above, Tokyo has been described as the installation location. When other installation locations are assumed, the shape of the recess may be changed as appropriate in accordance with the above conditional expression. Further, the bottom opening is not limited to a triangle but may be a polygon. That is, if the shape of the concave portion is an n-angled pyramid shape whose bottom opening is an n-gon (n is a natural number of 3 or more), an effect similar to the above-described shape is exhibited.

  FIG. 19 is a diagram illustrating a process of installing the retroreflective member 10 according to the present embodiment on the wall surface of the building 20 as a retroreflective building material. When the retroreflective member 10 is combined and installed on the wall surface as described above, as shown in FIG. 19A, the reference plane S1 is orthogonal to the sun rays of the sun 90 at the time of the south and middle at the summer solstice. It is as described above that it is important to install in this way.

  When the retroreflective member 10 is installed on the wall surface of the building 20, an installation process such as fixing each with a bolt 40 is performed as shown in FIG. At this time, the retroreflective member 10 having the concave portion 32 that satisfies the above conditions can be selected and employed by calculating the south-middle altitude at the summer solstice from the latitude at which the building 20 is located. Alternatively, the angle can be adjusted by fastening the bolt 40 so that the recess 32 of the retroreflective member 10 to be installed satisfies the above conditions. Even in the case of using an adhesive or the like without using the bolt 40, the angle can be adjusted similarly.

  In the above embodiment, the retroreflective building material in which the retroreflective member 10 is formed at least as a part of the reflective outer wall material has been described as an example. However, the retroreflective member 10 is not limited to the reflective outer wall material, and may be various. Can take form. Even retroreflective building materials in the form of reflective outer wall tiles, reflective flooring materials, reflective tiles, etc. are sufficiently practical. For example, in the case of a reflective flooring, the installation direction is a direction orthogonal to the walling material, so that the concave portion 32 suitable for the floor surface that satisfies the above-described conditions may be formed.

  As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be added to the above-described embodiment. It is apparent from the scope of the claims that the embodiments added with such changes or improvements can be included in the technical scope of the present invention.

10, 11, 12 Retroreflective member, 20 Building, 31 Base member, 32 Recessed part, 33 Connection part, 40 Volts, 90 Sun, 101 Incident light, 102 Reflected light, 103 Incident light, 104 Reflected light, 110 Effective direction, 111 Sun Solst Path, 112 Winter Solstice Path, 120 Incident Light, 121 Retroreflective Light, 122 Non-Retroreflective Light, 130 Cone, 321, 322, 323, 324 Recess

Claims (14)

A triangular pyramid-shaped concave portion having three side surfaces forming a vertex with a triangular opening as a bottom surface, and a projection position from the vertex to the bottom surface being deviated from the center of gravity position of the bottom surface toward the reference side of the triangle With
A retroreflective member in which at least one of the three side surfaces is formed as a reflective surface. Any of the three side surfaces is the reflecting surface,
The retroreflective member according to claim 1, wherein the light incident on the bottom surface is reflected by a reference surface including the reference side among the reflective surfaces, and then reflected by another reflective surface and retroreflected.   The retroreflective member according to claim 2, wherein an angle formed by the reference surface and a ridge line of the other reflection surface is 90 degrees or less.   The retroreflection member according to any one of claims 1 to 3, comprising a plurality of the recesses.   The retroreflective member according to claim 4, wherein the plurality of concave portions include similar shapes having different sizes, and are arranged so that the reference sides are parallel to each other.   The retroreflective member according to claim 4, wherein the plurality of concave portions are arranged densely by sharing the ridge line with the adjacent concave portions by overlapping the triangles as the bottom surfaces.   A retroreflective building material comprising the retroreflective member according to claim 1.   The retroreflective building material according to claim 7, wherein the reference surface including the reference side is provided so as to be orthogonal to a direction in which the retroreflectance is maximized.   The retroreflective building material of Claim 7 or 8 formed as a part of at least reflective outer wall tile.   The retroreflective building material of Claim 7 or 8 formed as a part of at least reflective outer wall material.   The retroreflective building material according to claim 7 or 8, which is formed as at least a part of a reflective flooring.   The retroreflective building material of Claim 7 or 8 formed as a part of at least reflective tile.   A triangular pyramid-shaped concave portion having three side surfaces forming a vertex with a triangular opening as a bottom surface, and a projection position from the vertex to the bottom surface being deviated from the center of gravity position of the bottom surface toward the reference side of the triangle A retroreflective member in which a reference surface including the reference side among the three side surfaces is formed on at least a reflection surface so that the reference surface is orthogonal to the sun rays at the time of south and middle in the summer solstice A construction method of a building including a retroreflective member installation stage. An n-side (n is a natural number of 3 or more) opening has n side surfaces forming a vertex with a bottom surface, and a projected position from the vertex to the bottom surface is a position of the reference side of the n-side from the center of gravity of the bottom surface. It is provided with a concave portion of an n-angle oblique pyramid shape displaced to the side,
A retroreflective member in which at least one of the n side surfaces is formed as a reflective surface.

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