JP2018151501A - Light retroreflective sheet - Google Patents

Abstract

A light retroreflective sheet capable of improving the degree of freedom of design is provided. A first layer 11 on which a first design is drawn by translucent ink is in contact with the first layer 11 and when light enters from the first layer 11 side, the light recurs to the light incident side. The retroreflective layer 12 having the concavo-convex portion 12A to be reflected, and the ink contacting the part of the concavo-convex portion 12A on the surface opposite to the surface where the retroreflective layer 12 and the first layer 11 are in contact with each other. And the second layer 13 on which the design of 2 is drawn, and when the first layer 11 side is irradiated with light having higher directivity than the surrounding ambient light, the light transmitted through the first layer 11 Part of the light reaches the retroreflective layer 12 and the second printed layer 13, and a part of the light reaching the retroreflective layer 12 is retroreflected, so that the first design cannot be visually recognized and the second It was set as the optical retroreflection sheet 1 which can visually recognize a design. [Selection] Figure 1

Description

  The present invention relates to a light retroreflective sheet.

  Despite the incorporation of characters, etc., these characters cannot be seen under normal diffuse light conditions, but they can be recognized only under light retroreflection conditions. A reflection sheet is known (see, for example, Patent Document 1).

  The light retroreflective sheet shown in Patent Document 1 has a first colored layer and a second colored layer, and the second colored layer on which characters and the like are expressed is partially below the first colored layer. It is given to. The second colored layer is configured such that the hue, brightness, and saturation of the color of the second colored layer are the same as or substantially the same as the color of the first colored layer. Although characters and the like expressed in the layer cannot be visually recognized, these characters and the like can be visually recognized only under the light retroreflective observation condition.

JP 2000-32414 A (FIG. 2, paragraph 0009, etc.)

  According to the light retroreflective sheet disclosed in Patent Document 1, in order to camouflage characters and the like expressed in the second colored layer, the hue, brightness, and saturation of the colors of the first colored layer and the second colored layer are It is essential that they be the same or substantially the same (see paragraph 0019 of Patent Document 1). Therefore, a plurality of designs having completely different hues, lightnesses, and saturations of colors of the first colored layer and the second colored layer, for example, a person and a landscape are printed and superimposed on the first colored layer and the second colored layer, respectively. Only one of these different designs cannot be seen under normal diffuse light conditions and optical retroreflection observation conditions. That is, in the conventional light retroreflective sheet, since it is difficult to express using a plurality of designs having completely different hues, lightnesses, and saturations, the degree of freedom in design is limited.

  An object of this invention is to provide the optical retroreflection sheet which can improve the freedom degree of design in view of the subject mentioned above.

  The light retroreflective sheet according to the present invention is in contact with the first layer on which the first design is drawn by translucent ink and the first layer, and when light enters from the first layer side, The retroreflective layer having a concavo-convex portion to be retroreflected on the incident side, and the second ink by the ink in contact with a part of the concavo-convex portion on the surface opposite to the surface where the retroreflective layer and the first layer are in contact. A second layer on which the design is drawn, and when light having a higher directivity than the surrounding ambient light is irradiated from the first layer side, part of the light transmitted through the first layer is It reaches the retroreflective layer and the second printed layer, and a part of the light reaching the retroreflective layer is retroreflected, whereby the first design becomes invisible and the second design can be visually recognized. .

  The light retroreflective sheet according to the present invention is provided on the opposite side of the first layer composed of a light-transmitting ink and the contact surface with the first layer, which is in contact with the first layer. A retroreflective layer having a concavo-convex portion, and a second layer in contact with a light-transmitting ink layer in a part of the concavo-convex portion of the retroreflective layer, and the optical retroreflective sheet On the other hand, when light having a higher directivity than the surrounding ambient light is irradiated from the first layer side, the light is retroreflected to the first layer side at a portion where the retroreflective layer and the ink layer are not in contact with each other. The portion where the reflective layer and the ink layer are in contact with each other is characterized in that the degree of retroreflection is weaker than the portion where the retroreflective layer and the ink layer are not in contact with each other.

  The light retroreflective sheet of the present invention can improve the degree of design freedom.

FIG. 1 is a cross-sectional view of a light retroreflective sheet according to an embodiment of the present invention, (A) is a diagram for explaining a cross-sectional structure, and (B) is a diagram for explaining the principle of retroreflection. It is a figure for doing. FIG. 2 is a view showing a design that is a light retroreflective sheet according to an embodiment of the present invention and can be visually recognized under normal diffused light conditions. FIG. 3 is a view showing a design that is a light retroreflective sheet according to an embodiment of the present invention and that can be visually recognized under light retroreflective conditions. FIG. 4 is a light retroreflective sheet according to another embodiment of the present invention, and shows a state under normal diffused light conditions. FIG. 5 is a diagram showing a design that is the light retroreflective sheeting shown in FIG. FIG. 6 is a diagram for explaining sensory evaluation of the retroreflective sheet on which the design shown in FIGS. 2 and 3 is drawn. FIG. 7 is a diagram for explaining sensory evaluation of the retroreflective sheet on which the design shown in FIGS. 4 and 5 is drawn.

  The optical retroreflection sheet according to the present invention will be described with reference to examples. However, the present invention is not limited to the embodiments described below. Note that “optical retroreflection” in the following description refers to reflection in which reflected light selectively returns in a direction substantially along the optical path of the incident angle over a wide irradiation angle. In addition, “under normal diffused light conditions” in the following description refers to visibility of an object in an environment where the surroundings are relatively bright, for example, in the daytime outdoors or indoors. In addition, in the following description, “light retroreflective conditions” means, for example, that a reflected object is viewed from the direction of the light source in a relatively dark environment, such as a situation where there is no illumination outdoors or indoors at night. Say sex. In general, diffuse reflection diffuses light energy in all directions, so that the reflection efficiency in the direction of the light source is deteriorated. For example, the visibility of the reflector from the light source direction is deteriorated at night. On the other hand, in retroreflection, since incident light returns in the direction of the light source, the visibility of the reflecting object from the direction of the light source is improved at night.

  FIG. 1 is a cross-sectional view of a light retroreflective sheet 1 according to an embodiment of the present invention, (A) is a diagram for explaining a cross-sectional structure, and (B) is a diagram illustrating the principle of retroreflection. It is a figure for demonstrating. As illustrated in FIG. 1, the light retroreflective sheet 1 includes a first layer 11, a retroreflective layer 12, and a second layer 13.

  The first layer 11 is a layer in which a first design is drawn with a light-transmitting ink. In addition, although illustration of the 1st design in the 1st layer 11 is abbreviate | omitted in FIG. 1, with a 1st design, the character, pattern, figure drawn on the surface or the inside of the 1st layer 11, for example , Colors, landscapes, buildings, people or combinations thereof. It is preferable that the first design is printed on the first layer 11 using a light-transmitting ink by a common printing method such as a screen printing method or a gravure printing method. It may be formed by a known method. The film thickness of the first layer 11 can be widely changed depending on the desired effect and its formation method, but it is usually preferable to be in the range of about 2 to 20 μm. However, the film thickness of the first layer 11 may be outside the range of about 2 to 20 μm. Further, the first layer 11 does not necessarily need to be composed of only a light-transmitting ink.

  The retroreflective layer 12 is a layer in contact with the first layer 11 and having a concavo-convex portion 12 </ b> A that retroreflects on the light incident side when light is incident from the first layer 11 side. The uneven portion 12A forms a cube corner type retroreflective structure. The cube-corner type retroreflective structure is composed of a plurality of cube-corner type triangular pyramids arranged in close packing with a common bottom surface (a flat surface in contact with the first layer 11 in FIG. 1). The cube-corner type triangular pyramid has a concave-convex relationship with respect to the bottom surface.

  The second layer 13 is a layer that is partially in contact with the surface (back surface) opposite to the surface with which the first layer 11 and the retroreflective layer 12 are in contact. The second layer 13 is composed of an air layer 13A and an ink layer 13B, and is a layer in which a second design different from the first design is drawn by a combination of these layers. . Here, the second design includes, for example, a character, a pattern, a figure, a color, a landscape, a building, a person, or a combination thereof. In the second layer 13, as in the first layer 11, the second design is drawn using a light-transmitting ink by a common printing method such as a screen printing method or a gravure printing method. Is preferred. The film thickness of the second layer 13 can be widely changed depending on the desired effect and the formation method thereof, but it is usually preferably in the range of about 2 to 20 μm. However, the film thickness of the second layer 13 may be outside the range of about 2 to 20 μm.

  Note that the second design differs from the first design in hue, brightness, and saturation. When the color difference ΔE between the first design and the second design is comprehensively expressed in consideration of lightness, hue, and saturation (for example, when expressed by the CIE color difference method according to the standard of Japanese Industrial Standard JIS Z8730) The color difference ΔE is assumed to have a relationship exceeding 3.0. However, when the color difference ΔE is 3.0 or less and further the color difference ΔE is 0, that is, the first design and the second design are the same color, the present invention can be applied. Note that the first design and the second design described above are different from each other even when the hue, brightness, and saturation are the same or substantially the same, when viewed from the first layer 11 side. In addition, the position, size, and range (ratio) occupied in the first layer 11 are different.

(About the principle)
Hereinafter, the principle by which the designs drawn on the first layer 11 and the second layer 13 can be visually recognized under normal diffused light conditions and light retroreflective conditions will be described. Under normal diffused light conditions, the first design can be visually recognized because the first layer 11 reflects. In addition, although the ink used for the first layer 11 has translucency, the second design drawn on the second layer 13 cannot be seen from the first layer 11 side at all. Is very difficult.

  On the other hand, under the light retroreflection condition, the light from the light source direction can reach the internal retroreflective layer 12 and the second layer 13. This is because the first layer 11 does not have a retroreflective structure only with this layer and is drawn with a light-transmitting ink. That is, the diffused light under the light retroreflection condition diffuses the light energy in all directions and the reflection efficiency in the direction of the light source is deteriorated. Therefore, the first design even from the first layer 11 side. Cannot be seen at all, or it becomes very difficult to see. Furthermore, since the incident light is returned to the light source direction by the retroreflective layer 12, the visibility of the reflected object from the light source direction is improved, and thereby the second design is visually recognized from the first layer 11 side. Will be able to.

  More specifically, the light that has passed through the first layer 11 is optically recurred by the cube-corner retroreflective structure of the retroreflective layer 12 where the retroreflective layer 12 and the air layer 13A overlap. Reflective reflection occurs and finally retroreflects toward the light source. On the other hand, when the retroreflective layer 12 and the ink layer 13B overlap with each other, the cube corner type retroreflective structure does not function well as compared with the portion overlapped with the air layer 13A, and some light is absorbed or refracted. As a result, the reflection efficiency is lowered in the direction of the light source, and retroreflection is not performed. That is, in the second layer 13, a portion that reflects light retroreflects and a portion that does not reflect light retroreflectively occur, and the combination of these makes it possible to visually recognize the second design from the light source direction. ing. Hereinafter, an embodiment of a light retroreflective sheet using such a principle will be described with reference to FIGS.

  FIG. 2 is a diagram showing a design that is a light retroreflective sheet 10 according to an embodiment of the present invention and that can be visually recognized under normal diffused light conditions. FIG. 3 is a diagram showing a design that is the light retroreflective sheet 10 shown in FIG. 2 and that can be visually recognized under the light retroreflective conditions. A first design 21 is printed on the first layer 11 of the light retroreflective sheet 10, and a second design 22 is printed on the second layer 13.

  In the light retroreflective sheet 10 shown in FIG. 2 and FIG. 3, the first layer 21 is diffusely reflected under normal diffused light conditions, so that the first design 21 as shown in FIG. 2 is visually recognized. Can do. On the other hand, as shown in FIG. 3, under the light retroreflective condition, light is reflected by the light retroreflection in the second layer 13 where the retroreflective layer 12 and the air layer 13A overlap, At the place where the retroreflective layer 12 and the ink layer 13B overlap, the function of light retroreflection is weakened, and the second design 22 can be viewed from the direction of the light source by the combination of the part that does not reflect and the part that does not reflect. . By using such a light retroreflective sheet 10 as a poster, for example, the first design 21 shows a design in which a person is drawn in the daytime. However, at night, light such as a spotlight or a flashlight is used. Is applied, it becomes a poster in which the second design 22 in which only a tree is drawn in the middle appears, and it becomes possible to express a completely different design day and night.

  As described above, the light retroreflective sheets 1 and 10 are in contact with the first layer 11 in which the first design 21 is drawn by the light-transmitting ink, the first layer 11, and the first layer 11. When the light is incident from the layer 11 side, the retroreflective layer 12 composed of the concavo-convex portion 12A that is retroreflected to the light incident side, and the surface where the retroreflective layer 12 and the first layer 11 are in contact with each other A second layer 13 that is partly in contact with the back surface on the opposite side and on which a second design 22 different from the first design is drawn, and the surrounding environment from the first layer 11 side When light having a higher directivity than light is irradiated, part of the light transmitted through the first layer 11 reaches the retroreflective layer 12 and the second printed layer 13, and the light that has reached the retroreflective layer 12 A part of the retroreflected light makes the first design 21 invisible and the second design 22 visible. Thereby, in order to camouflage characters and the like expressed in the second colored layer as in the light retroreflective sheet disclosed in Patent Document 1, the hue and brightness of the colors of the first colored layer and the second colored layer And the restriction that the saturation must be the same or nearly the same. Therefore, in an article using the light retroreflective sheets 1 and 10, a plurality of designs can be expressed, and the degree of design freedom can be further improved.

(Modification)
The light retroreflective sheets 1 and 10 according to the embodiments of the present invention have been described above, but the present invention can be variously modified. For example, in order to protect the first layer 11, it is possible to provide a protective layer above the first layer 11. Further, for example, a protective layer can be provided below the second layer 13 in order to protect the second layer 13.

  In addition, the first design 21 and the second design 22 of the light retroreflective sheet 10 described with reference to FIGS. 2 and 3 are completely different design combinations, but similar designs are combined. Also good. For example, a human face is printed as a first design, and a human face drawn on the first design is changed as a second design (smile, crying face, angry face, sad Face) may be drawn. By using such a light retroreflective sheet, it is possible to express a person's face with different expressions day and night. In the case of a light retroreflective sheeting, it is not limited to day and night, and a change in facial expression of a person can be visually recognized by directly illuminating a light source such as a light provided in a smartphone under normal diffused light conditions. It is also possible.

  Further, for example, the design can be expressed only by the second layer 13 without expressing the design by the first layer 11. FIG. 4 is a light retroreflective sheet 40 according to another embodiment of the present invention, in which (A) is a front view showing a state under normal diffused light conditions, and (B) is (A). It is a rear view shown from the opposite side of the light retroreflection sheet 40 shown in FIG. FIG. 5 is the light retroreflective sheet 40 shown in FIG. 4A, where FIG. 5A is a front view showing a state under retroreflective conditions, and FIG. 5B is a light retroreflective sheet. FIG. 4 is a diagram illustrating an example of a cross section of a sheet 40. Note that the ratio and positional relationship between the air layer 43A and the ink layer 43B in the cross-sectional view shown in FIG. 5B are merely examples, and the front side of the light retroreflective sheet 40 shown in FIGS. It does not show a specific cross section of the figure and the rear view.

  The light retroreflective sheet 40 shown in FIGS. 4 and 5 includes a surface layer 41, a retroreflective layer 42, and a print layer 43. The print layer 43 is made of a transparent ink and has a back air layer 43A. The combination with the ink layer 43B is configured so that the logo 50 is visible only under retroreflective conditions. Specifically, since the design is not expressed on the surface layer 41 under normal diffused light conditions, the logo 50 drawn with a dotted line near the center is visually recognized as shown in FIG. I can't do it. On the other hand, as shown in FIG. 5A, the retroreflective layer 42 and the air layer 43 </ b> A overlap with each other by the combination of the air layer 43 </ b> A and the ink layer 43 </ b> B of the print layer 43 under the light retroreflective condition. Although light retroreflection occurs in the places, retroreflection does not occur in other places, so that the logo 50 can be clearly recognized.

  In other words, the first layer 41 made of translucent ink and the recursion having the concavo-convex portion 42A that is in contact with the first layer 41 and is provided on the opposite side of the contact surface with the first layer 41. A reflective layer 42 and a second layer 43 in contact with the light-transmitting ink layer in a part of the concavo-convex portion 42A of the retroreflective layer 42, with respect to the light retroreflective sheet 40. When the light having higher directivity than the surrounding ambient light is irradiated from the first layer 41 side, the light is retroreflected to the first layer 41 side in the part where the retroreflective layer 42 and the ink layer 43 do not contact, The portion where the retroreflective layer 42 and the ink layer 43 are in contact has a weaker degree of retroreflection compared to the portion where the retroreflective layer 42 and the ink layer 43 are not in contact with each other. Invisible or almost invisible design) It can be generated. Moreover, since the design is not expressed on the surface of the printing layer 41, it is excellent in abrasion resistance compared with the light retroreflective sheet which expresses the design on the surface. Further, in the conventional light retroreflective sheet, it is general that the light is reflected on all surfaces. However, the ink layer 43B having translucency such as a transparent ink is formed on the retroreflective layer 42. By partially forming below, a portion that is not retroreflected can be newly formed in the light retroreflective sheet 40. In other words, the design can be freely expressed by a combination of a portion to be reflected and a portion not to be reflected in the light retroreflective sheet 40, so that the degree of freedom in design can be improved.

  Further, the retroreflective layers 12 and 42 described in the above embodiment are not limited to the cube corner type, and a reflective structure of an encapsulated lens type sheet or a capsule lens type sheet may be adopted. For example, in the case of an encapsulated lens type sheet, the retroreflective layers 12 and 42 can be formed by providing a reflective layer at a predetermined site and applying a focus resin layer encapsulating a plurality of glass beads thereon. it can.

  The present invention can be applied to small items such as signs for road signs, construction signs, etc., visual tapes for automobiles, motorcycles, etc., safety materials such as clothes, life preservers, signs for signs, posters used in the dark, accessories, etc. Can also be applied.

(About sensory evaluation of each embodiment)
FIG. 6 is a view for explaining sensory evaluation of the retroreflective sheet 10 on which the design shown in FIGS. 2 and 3 is drawn. The retroreflective sheet 10 shown in FIG. 6 is a view seen from the first layer 11 side. FIG. 6A shows a state in which the first design 21 can be clearly seen under normal diffused light conditions, but the second design 22 cannot be seen at all. FIG. 6B shows the retroreflective sheet 10 under normal diffused light conditions, but the first design 21 is all visible, but in the partial region of the first design 21, This shows a state where a part of the design 22 can be visually recognized. FIG. 6C shows the retroreflective sheet 10 under a light retroreflective condition. The second design 22 can be visually recognized in the center portion, and the first design 21 is the background of the second design 22. A state where a part of the part is visible is shown. FIG. 6D shows the retroreflective sheet 10 under a light retroreflective condition, in which the first design 21 is not visible and only the second design 22 is visible.

  The retroreflective sheet 10 according to the embodiment of the present invention has an ideal relationship between the ambient light, the illuminance of the light to be irradiated, and the intensity of directivity, as shown in FIG. The state shown in FIG. However, the retroreflective sheet 10 is in the state of FIG. 6A and FIG. 6C depending on the relationship between the brightness of the surrounding environmental light and the illuminance and directivity intensity of the light emitted from the light source. Although there may be a state of (B) and (D), it does not have a big influence on the appearance of each other's design. However, when two designs having a color difference Δ of 3.0 or more are stacked on the same layer by the method described in the conventional patent document 1, for example, the relationship shown in FIGS. 6B and 6C. Thus, the appearance of each other's design is considerably affected regardless of whether it is under ordinary diffused light conditions or light retroreflective conditions. That is, in the retroreflective sheet 10 in the present embodiment, designs with different designs can be clearly visually recognized under normal diffused light conditions and optical retroreflective conditions.

  FIG. 7 is a diagram for explaining sensory evaluation of the retroreflective sheet 40 on which the design shown in FIGS. 4 and 5 is drawn. The retroreflective sheet 40 shown in FIG. 7 is a view seen from the first layer 41 side. FIG. 7A shows a state in which the logo 50 is not visible at all under normal diffused light conditions. FIG. 7B shows the retroreflective sheet 40 under normal diffused light conditions, but shows a state where a part of the logo 50 can be visually recognized. (C) of FIG. 7 is the retroreflection sheet 40 under normal diffused light conditions, and shows a state where the logo 50 can be visually recognized in the central portion. (D) of FIG. 7 is the retroreflection sheet 40 under light retroreflection conditions, and is the state which the logo 50 can be visually recognized by retroreflection. The retroreflective sheet 40 according to the embodiment of the present invention has an ideal relationship between the ambient light and the illuminance and directivity intensity of the irradiated light. The state shown in FIG. However, in the retroreflective sheet 40, depending on the relationship between the ambient ambient light, the illuminance of the irradiating light, and the intensity of directivity, the states shown in FIGS. However, when the design is shown by the method described in the conventional patent document 1, for example, the relationship shown in (C) and (D) of FIG. The only difference is whether it looks. That is, in the retroreflective sheet 40 according to the present embodiment, the different appearances (the design is visible, the design is completely invisible, or the design is almost invisible) under the normal diffused light condition and the light retroreflective condition. ) Can be changed.

DESCRIPTION OF SYMBOLS 1,10,40: Light retroreflective sheet | seat, 11: 1st layer, 12: Retroreflective layer, 12A: Uneven part, 13: 2nd layer, 13A: Air layer, 13B: Ink layer, 21: 1st 1 design, 22 2nd design

Claims (2)

A first layer on which a first design is drawn with translucent ink;
A retroreflective layer in contact with the first layer and having a concavo-convex portion for retroreflecting the light incident side when light is incident from the first layer side;
A second layer in which a second design is drawn by ink in contact with a part of the concavo-convex portion on a surface opposite to a surface in contact with the retroreflective layer and the first layer; Have
When irradiating light having higher directivity than ambient light from the first layer side, a part of the light transmitted through the first layer reaches the retroreflective layer and the second printed layer. The light retroreflective sheeting is characterized in that a part of the light reaching the retroreflective layer is retroreflected, whereby the first design cannot be visually recognized and the second design can be visually recognized.
A first layer composed of translucent ink;
A retroreflective layer in contact with the first layer and having a concavo-convex portion provided on the opposite side of the contact surface with the first layer;
A part of the concavo-convex portion of the retroreflective layer, a second layer in contact with the light-transmitting ink layer,
When the light retroreflective sheet is irradiated with light having higher directivity than ambient light from the first layer side, the light is reflected at a portion where the retroreflective layer and the ink layer are not in contact with each other. Retroreflected toward the first layer, and the portion where the retroreflective layer and the ink layer are in contact with each other is less retroreflective than the portion where the retroreflective layer and the ink layer are not in contact with each other. Light retroreflective sheet.