JP7219965B2 - Manufacturing method of retroreflective material - Google Patents

Description

The present invention relates to a retroreflecting material manufacturing method and a retroreflecting material.

In recent years, as typified by liquid lenses, new optical device forming techniques using liquids have attracted attention (see Non-Patent Documents 1 to 3 below). Many liquids are transparent to visible light, and their interfaces are smooth with angstrom precision (Non-Patent Document 4 below). Therefore, it has been found to be an excellent material for the realization of optical devices, as it is possible to realize high-precision refracting surfaces when properly formed.

By the way, many food materials are liquid. Considering jelly as a typical example, this is obtained by dissolving high molecular weight agar, polysaccharide thickener, or gelatin consisting of protein in hot water, and then gelling by lowering the temperature. The main component of jelly is water, which has high transparency to visible light. In addition, since it can be formed in a mold, it is theoretically easy to control its surface shape. All of these properties are required for forming optical devices, and it can be said that they are suitable as materials for optical devices.

In this way, certain types of food have excellent properties as materials for optical devices, and so far there have been reports, such as papers proposing the application of lenses made of candy to optical education (see below). Non-Patent Document 5).

Therefore, the present inventors have focused on optical markers using food, particularly retroreflecting materials, and various edible retroreflecting materials (this may be referred to as "edible" in this specification). I tested it and examined it.

There are two main advantages of edible retroreflectors.

The first is that the retroreflective material can be placed directly on food that people eat. For example, if retroreflective material can be placed on top of food, it will be easier to obtain food location information from camera images, making it possible to create new effects such as projection mapping on a wedding cake brought to a wedding ceremony. It is considered to be. However, many conventional optical devices are made of inedible materials such as glass and plastic. Therefore, if it is put on food, it must be removed before eating, and there is a risk that the material is toxic or that it is accidentally ingested or ingested. An optical device made of food does not have these problems, and can be placed on top of food with confidence and safety.

The second point is that edible retroreflecting materials are suitable for installation in the mouth of a person or on the surface of the digestive tract. If a retroreflector can be placed above the gastrointestinal tract, it will function as a reference point for surgical navigation. In addition, it can be applied to optical measurement, so it can be expected to contribute to the improvement of measurement accuracy. If the optical device is made of food, it is thought that there is almost no toxicity or effect on the human body. is assumed.

The inventors of the present invention conducted various experiments to realize a retroreflecting material using familiar foodstuffs, especially assuming the first application to cooking. As a result, it was found that the retroreflective performance is particularly high when agar is used (Patent Document 1 below).

International Publication 2018/154916

Berge, B. and Peseux, J. Variable focal lens controlled by an external voltage: An application of electrowetting. The European Physical Journal E, 2000, vol.3, p.159-163. Kuiper, S. and Hendriks, B. H. W. Variable-focus liquid lens for miniature cameras. Applied Physics Letters, 2004, vol.85, no.7, p.1128-1130. Oku, H. and Ishikawa, M. High-speed liquid lens with 2 msresponse and 80.3 nm root-mean-square wavefront error. Applied Physics Letters, 2009, vol.94, p.221108. Gennes, P.-G. de, Wyart, F. B.- and D. Quere. Physics of Surface Tension: The World of Drops, Bubbles, Water Drops and Ripples. Yoshioka Shoten, 2004. Bunton, P. Edible optics: Using gelatin to demonstrate properties of light, Phys. Teach, 1997, vol.35, p.421.

Retroreflective materials using agar lose their optical function due to deformation due to drying and precipitation of sugar. Therefore, when left outside, there is a limit to how long it can be used continuously. It is conceivable to prevent the agar from drying out by covering the surroundings, but the package needs to be devised. In addition, since agar is gel-like, it has low shape retention, and there is also the problem that it is difficult to apply it to applications in which a plurality of retroreflecting materials are combined to form a three-dimensional shape.

An object of the present invention is to provide a technique capable of solving such problems.

Means for solving the above problems can be described as the following items.

(Item 1)
A step of placing powdery reduced isomaltulose on a base material surface having the shape of a retroreflective surface;
contacting water with the reduced isomaltulose on the surface of the base material;
a step in which the reduced isomaltulose changes into a paste by absorbing the water, and the shape of the surface of the base material is transferred to the reduced isomaltulose;
Heating the base material and the paste-like reduced isomaltulose to evaporate at least part of the water; and solidifying the reduced isomaltulose in contact with the base material surface, A method for manufacturing a retroreflecting material, comprising the step of forming a light-transmissive retroreflecting material having a retroreflective surface.

(Item 2)
The method for manufacturing a retroreflective material according to Item 1, wherein the base material is made of silicone.

(Item 3)
After heating the reduced isomaltulose and before solidifying the reduced isomaltulose, a degassing step of removing or moving air bubbles existing between the reduced isomaltulose and the surface of the base material 3. The manufacturing method according to item 1 or 2, further comprising:

(Item 4)
4. The manufacturing method according to any one of items 1 to 3, wherein the retroreflective surface is a corner cube type retroreflective surface.

(Item 5)
Equipped with a reflective body with light transparency,
The reflective material body is a solid candy-like substance containing reduced isomaltulose as a main component,
one surface side of the reflector main body serves as an incident surface for allowing incident light to enter the interior of the reflector main body,
The retroreflection material, wherein the other surface side of the reflector main body is formed as a retroreflection surface that reflects the incident light that has entered the interior of the reflector main body in a direction substantially parallel to the incident direction.

(Item 6)
6. The retroreflector according to item 5, wherein the retroreflection surface is a corner cube-shaped retroreflection surface.

(Item 7)
An edible retroreflector configured by combining a plurality of retroreflectors according to item 5 or 6,
The incident surfaces of the plurality of retroreflectors are formed in a substantially smooth planar or curved surface,
A retroreflector, wherein the plurality of retroreflectors are arranged so as to form a three-dimensional shape as a whole, with the incident surface facing outward and the retroreflective surface facing inward.

(Item 8)
An edible retroreflector configured by combining at least two retroreflectors according to item 5 or 6,
the incident surfaces of the two retroreflectors are formed in a substantially smooth planar or curved surface,
and the two retroreflective materials are brought close to each other with their retroreflective surfaces facing each other,
The retroreflective surface of at least one of the retroreflective materials is formed with a protruding portion that protrudes outward,
The projecting portion is brought into contact with the retroreflective surface of the other retroreflective material, thereby separating the retroreflective surfaces of the two retroreflective materials,
The retroreflector, wherein the incident surface of the retroreflector is positioned outside the retroreflector.

ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the retroreflective material which has high retroreflection performance, although it is edible and solid. Moreover, it is possible to provide a manufacturing method suitable for manufacturing such a retroreflective material.

1 is a cross-sectional view of a main part of a retroreflective material according to one embodiment of the present invention; FIG. FIG. 2 is an explanatory diagram for explaining an example of a method for manufacturing the retroreflective material of FIG. 1; BRIEF DESCRIPTION OF THE DRAWINGS It is explanatory drawing for demonstrating the outline of the experimental apparatus used for the experimental example. 10 is a graph showing the results of Experimental Example 2, in which the horizontal axis is the observation angle (degrees) and the vertical axis is the illuminance (lux). It is a graph showing the results of Experimental Example 3, in which the horizontal axis is the incident angle (degrees) and the vertical axis is the illuminance (lux). 4 is a graph showing the results of Experimental Example 4, in which the horizontal axis is the incident angle (degrees) and the vertical axis is the illuminance (lux). FIG. 10 is a cross-sectional view of a main part of an edible retroreflector according to Modification 1;

A retroreflective material according to an embodiment of the present invention will be described below with reference to FIG.

(retroreflector)
This retroreflector has a reflector main body 10 having optical transparency. The reflector main body 10 is a solid candy-like substance containing reduced isomaltulose as a main component. As a result, the reflector body 10 has a refractive index greater than 1, preferably greater than 1.3. A method for manufacturing such a reflector main body 10 will be described later.

One surface side (upper surface in FIG. 1) of the reflector main body 10 is an incident surface 20 for allowing incident light to enter the reflector main body 10 . Although the entrance surface 20 is flat in this embodiment, it can have various shapes depending on the application.

The other surface side (lower surface in FIG. 1) of the reflector main body 10 is formed as a retroreflecting surface 30 that reflects incident light entering the reflector main body 10 in a direction substantially parallel to the incident direction. The directions of incident light and reflected light in the retroreflective material of this example are exemplarily shown by dashed-dotted lines in FIG.

The retroreflective surface 30 of the present embodiment is a corner cube type retroreflective surface. However, in FIG. 1, the two-dimensional shape of the retroreflective surface is shown in order to avoid complication. The actual retroreflective surface 30 has a shape in which three precise planes are combined at right angles to form vertices, and total reflection is performed on each surface to reflect light in the direction of the light source. It's becoming

(Method for producing retroreflective material of the present embodiment)
Next, a specific example of the procedure for producing the retroreflective material in this embodiment will be described with further reference to FIG.

(Fig. 2(a))
First, the clay 61 is arranged on the bottom surface of the container 60 and the prototype 70 is placed on the clay 61 . The upper surface of the master 70 is a retroreflective surface having the same shape as the retroreflective surface 30 of the reflector main body 10 .

(Fig. 2(b))
Next, fluid silicone 80 is poured into the container 60 . Thereby, the shape of the retroreflective surface of the master 70 can be transferred to the bottom surface of the silicone 80 . Allow some time for the silicone 80 to harden.

(Fig. 2(c))
After the silicone 80 has cured, the cured silicone 80 is removed. This cured silicone corresponds to the base material 40 . That is, according to the above-described procedure, the base material 40 made of silicone can be produced in this embodiment. This base material 40 has a surface 41 having the shape of a retroreflective surface.

(Fig. 2(d))
Next, powdery reduced isomaltulose (trade name: Palatinit) 50 is placed on the base material surface 41 having the shape of a retroreflective surface. Furthermore, water is dripped onto the reduced isomaltulose on the base material surface 41 to bring it into contact with the reduced isomaltulose. The amount of water can be, for example, 1.5 g per 5 g of reduced isomaltulose, but is not limited to this.

When the reduced isomaltulose 50 absorbs water, it changes into a paste, and the shape of the base material surface 41 is transferred to the lower surface of the reduced isomaltulose 50 .

(Fig. 2(e))
Then, the base material 40 and the paste-like reduced isomaltulose 50 are heated together. This allows at least part of the water to evaporate. Moreover, since the reduced isomaltulose 50 in a molten state at a high temperature touches the base material surface 41 , the shape of the base material surface 41 can be accurately transferred to the reduced isomaltulose 50 . As a heating means, for example, there is a method of heating the base material 40 and the reduced isomaltulose 50 together in a microwave oven. When a microwave oven is used, it can be heated for a short period of time, so it is possible to suppress the generation of bubbles due to excessive heating and caramelization of reduced isomaltulose (discoloration to brown or yellow). Further, by heating the base material 40 and the reduced isomaltulose 50 together, the temperature of the base material surface 41 also rises, so high transfer accuracy can be obtained.

After heating the reduced isomaltulose 50 and before the reduced isomaltulose 50 solidifies, a degassing step is performed to remove or move air bubbles existing between the reduced isomaltulose 50 and the base material surface 41. It can be carried out. This operation can be performed, for example, by scraping out air bubbles in the reduced isomaltulose 50 using a thin rod.

(Fig. 2(f))
Next, the reduced isomaltulose 50 in contact with the base material surface 41 is solidified. The solidified reduced isomaltulose 50 becomes a solid candy. As a result, a light-transmissive reflector main body (retroreflector) 10 having a retroreflective surface can be manufactured. Then, the resulting reflector main body 10 is taken out from the base material 40 . Here, since the base material 40 is made of elastic silicone, the removal work can be easily performed. In addition, by forming the base material 40 using food grade silicone, the hygienic condition of the reflector main body 10 can be improved.

(Experimental example 1)
Experiments were conducted on the basic characteristics of retroreflective materials using reduced isomaltulose. The results are shown below.

Three types of sugar, namely, granulated sugar, refined sugar, and reduced isomaltulose (trade name: Palatinit), were investigated on the degree of caramelization and crystallization when retroreflective materials were produced. The method of manufacturing the retroreflecting material was the same as the method described in the above embodiment. However, the materials used were changed according to the type of each sugar.

Specifically, each sugar was produced five times, the degree of retroreflection and chroma of the produced product were calculated, and the average was evaluated. For any sugar, 5 g of sugar and 1.6 g of water are placed on a silicone mold (corresponding to the base material 40 of the present embodiment described above), heated for 100 to 120 seconds until air bubbles settle, and a corner cube is formed. A method was used in which the air bubbles accumulated in the inside were removed with a toothpick, and then cooled to room temperature to harden. The same silicone mold was used for all.

Regarding the degree of retroreflection, the light source, camera, and lens are optically coaxially installed via a half mirror, and the image of each retroreflecting material is captured in the area of the entire retroreflecting material. It was obtained by calculating the average of the pixel values. Saturation was obtained by converting the color space of images shot under the same lighting conditions into HSV and calculating the average of the saturation values (values of S) in the entire area of the retroreflecting material.

The degree of retroreflection and the mean and variance of chroma for each sugar were as follows.

The following can be said from these results. When reduced isomaltulose (trade name: Palatinit) is used, higher retroreflective performance can be obtained than when other sugars are used. Moreover, since the saturation is low, it can be seen that the degree of caramelization is low.

(Experimental example 2)
At what angle and how much light is reflected by the retroreflective material of this embodiment, the intensity is measured using an illuminance meter 91 (AS ONE LM-331), a light source 92 (HOYA-SCHOTT MEGALIGHT100), and a desktop darkroom (Fig. (not shown... AS ONE ADR-D1) was used for measurement (see Fig. 3). In the experimental method, the angle formed by the straight line connecting the light source 92 and the reflector main body 10 and the normal to the reflector main body 10 is defined as the incident angle α, and the "straight line connecting the light source 92 and the reflector main body 10" and the line connecting the illuminance meter 91 is defined as an observation angle β, and the illuminance at each angle is measured by changing these parameters. As measurement conditions, the illuminance of the light source 92 at the position to be measured was 411 lux, and the distance _L1 from the light source 92 to the reflector body 10 was 660 mm.

First, the incident angle α was fixed at 0 degree, and the illuminance was measured when the observation angle β was changed to ±(60, 40, 20, 10, 5, 4 degrees). For comparison, measurements were also performed when the reflector main body 10 was not arranged. The results are shown graphically in FIG. In FIG. 4, the solid line indicates the results of this example, and the dashed line indicates the results of the comparative example. From this result, it can be seen that when the observation angle is 4 degrees, the maximum value is 27 lux, and about 7% of the light source is reflected. In addition, the illuminance decreases as the observation angle increases, and no reflection is seen in the entire range of 10 degrees or more on both positive and negative sides. From these results, it can be seen that the reflector main body 10 made of candy performs retroreflection.

(Experimental example 3)
Next, the observation angle β was fixed at 4 degrees, and the illuminance was measured when the incident angle α was changed to 0, 5, 10, 15, 20, 25, 30, 35, 40, and 45 degrees. The results are shown in FIG. For reference, an illuminance of 8 lux at an observation angle of 4 degrees with no candy retroreflective material is indicated by a dashed line (straight line). From this result, it can be seen that the maximum value is 27 lux when the incident angle is 0 degree. In addition, it can be seen that the illuminance decreases as the incident angle increases, and at an incident angle of 45 degrees, the illuminance is almost the same as when the reflector body is not arranged.

(Experimental example 4)
The produced reflector body 10 was photographed using a system in which a light source, a camera, and a lens were optically coaxially installed via a half mirror. Then, an experiment was conducted to determine how much the intensity of light reflected by the entire reflector changes when the incident angle with respect to the reflector main body 10 is changed.

The results are shown graphically in FIG. The horizontal axis is the angle with respect to the optical axis, and the vertical axis is the average of pixel values (pixel values in the camera image) in the entire reflector body 10 . The result shows that the maximum value is 139.766 when the incident angle is 0 degree. Although the average pixel value decreases as the incident angle increases, this point can be improved by adjusting the refractive index of the material.

(Modification 1)
Next, an edible retroreflector constructed by combining two reflector main bodies (retroreflector) 10 according to the present invention will be described as Modified Example 1 with reference to FIG. In the description of Modification 1, the same reference numerals are used for the configurations that are basically the same as those of the retroreflection material of the above-described embodiment, thereby avoiding duplication of description.

In Modification 1, the retroreflective surface 30 of one of the reflector bodies 10 is formed with a protruding portion 31 that protrudes outward. Then, the two reflector main bodies 10 are combined with their respective retroreflective surfaces 30 facing each other. The projecting portion 31 is brought into contact with the retroreflective surface 30 of the other reflector main body 10, thereby separating the opposing retroreflective surfaces 30 from each other. The protrusion 31 of this example is provided at a position near the end of the retroreflective surface 30 (see FIG. 7). Although only one protrusion 31 is shown in FIG. 7, it is preferable to provide a plurality of protrusions 31 along the peripheral edge of the retroreflective surface 30 .

In addition, the incident surfaces 20 of these reflector main bodies 10 are arranged outside the retroreflector. The incident surface 20 is substantially smooth and planar. However, it may have a substantially smooth curved surface. Here, "substantially smooth" means that when the user eats the retroreflector, it is smooth enough that the user does not feel any discomfort or danger in the mouth. can decide.

According to Modification 1, since the opposing retroreflective surfaces 30 are separated from each other by the protruding portion 31, an air layer can be interposed between the opposing retroreflective surfaces. Retroreflection by the reflective surface 30 can be performed. Moreover, since the incident surface 20 having a substantially smooth shape is arranged on the outside, there is an advantage that the retroreflector can be eaten safely.

Furthermore, in this example, since the projecting portion 31 is provided near the end of the retroreflective surface 30, the effect of the projecting portion 31 on the retroreflective performance can be suppressed. Further, if a plurality of protrusions 31 are provided along the periphery of the retroreflecting surface 30, there is an advantage that the gap between the facing retroreflecting surfaces 30 can be stably maintained.

A configuration is also possible in which a projecting portion is provided on each of the facing retroreflective surfaces 30 .

(Modification 2)
Next, an edible retroreflector configured by combining a plurality of reflector main bodies (retroreflectors) 10 according to the present invention will be described as Modified Example 2. FIG. In the description of Modified Example 2, the same reference numerals are used for the configurations that are basically the same as those of the retroreflective material of the above-described embodiment to avoid duplication of description.

In Modified Example 2, a plurality of reflector main bodies 10 are arranged so as to form a three-dimensional shape as a whole, with the incident surface 20 facing outward and the retroreflective surface 30 facing inward. Here, the three-dimensional shape is, for example, a spherical shape or a polyhedral shape.

Also, the incident surfaces 20 of the plurality of reflector main bodies 10 are formed in a substantially smooth planar or curved surface. Here, the meaning of "substantially smooth" is the same as in Modification 1 described above.

According to the retroreflector of Modification 2, the outer surface of the three-dimensional shape can be made smooth, so there is an advantage of safety. Further, by configuring the retroreflector in a spherical or polyhedral shape, it is possible to retroreflect light from various directions.

Then, for example, when performing motion capture of an animal, by attaching this retroreflector to the animal's body, the position and orientation of each part of the animal can be obtained from the camera image. Moreover, since the retroreflector of this example is edible, it is safe even if an animal eats the retroreflector. Furthermore, since the retroreflector has a smooth outer surface, there is no risk of injury.

Also, for example, by attaching this retroreflector to the body of a pet such as a dog and taking it for a walk, there is an advantage that the safety of the pet can be improved even at night. Also in this case, since the retroreflector of this example is edible, there is an advantage that it is safe even if the pet eats the retroreflector. Also, for the same reason as above, there is no fear of injury.

In addition, the contents of the present invention are not limited to the above embodiments. The present invention allows various changes to be made to the specific configuration within the scope of the claims.

For example, it is possible to add a modifier for adjusting the refractive index and other additives to the reduced isomaltulose.

10 reflector body (retroreflector)
20 incident surface 30 retroreflective surface 31 protrusion 40 base material 41 surface of base material 50 reduced isomaltulose 60 container 61 clay 70 prototype 80 silicone 91 illuminometer 92 light source

Claims (4)

A step of placing powdery reduced isomaltulose on a base material surface having the shape of a retroreflective surface;
contacting water with the reduced isomaltulose on the surface of the base material;
a step in which the reduced isomaltulose changes into a paste by absorbing the water, and the shape of the surface of the base material is transferred to the reduced isomaltulose;
Heating the base material and the paste-like reduced isomaltulose to evaporate at least part of the water; and solidifying the reduced isomaltulose in contact with the base material surface, A method for manufacturing a retroreflecting material, comprising the step of forming a light-transmissive retroreflecting material having a retroreflective surface. The method of manufacturing a retroreflective material according to claim 1, wherein the base material is made of silicone. After heating the reduced isomaltulose and before solidifying the reduced isomaltulose, a degassing step of removing or moving air bubbles existing between the reduced isomaltulose and the surface of the base material 3. The manufacturing method according to claim 1 or 2, further comprising: The manufacturing method according to any one of claims 1 to 3, wherein the retroreflective surface is a corner cube type retroreflective surface.

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