Light guide body, and light emitting device

Abstract

To provide a light guide body and light emitting device that can change ease-of-view of display object more greatly according to an observation position relative to the light guide body.SOLUTION: In a light guide body 1, upon viewing from a direction orthogonal to a light guide direction D1 of light and a normal line direction of a reflection surface 12, a cross section of a first prism 21 has a first hypotenuse 211 and a second hypotenuse 212 that extend from the reflection surface 12. Respective cross sections of a plurality of second prisms 22 have a third hypotenuse 221 and a fourth hypotenuse 222 that extend from the reflection surface 12. A first angle θ1 of the first hypotenuse 211 and a second angle θ2 of the second hypotenuse 212 both with respective to the reflection surface 12 are different from each other. One of a third angle θ3 of the third hypotenuse 221 and a fourth angle θ4 of the fourth hypotenuse 222 both with respect to the reflection surface 12 is equal to either of the first angle θ1 and the second angle θ2, and the other of the third angle θ3 and the fourth angle θ4 is different from the first angle θ1 and the second angle θ2.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to a light guide and a light emitting device. [Background technology]

[0002] The display device of Patent Document 1 includes a light guide plate and a light source.

[0003] The light guide plate is formed of a transparent member, has an incident surface, and is capable of displaying a plurality of patterns, each of which is visible from a different direction. The light source is disposed to face the incident surface. The light guide plate has a plurality of prisms. The plurality of prisms are arranged on one surface of the light guide plate along each of the plurality of patterns, and have a reflective surface that reflects light emitted from at least one light source and incident on the light guide plate from the incident surface toward a direction in which the pattern is visible. The light guide plate can switch between the visible patterns depending on the direction from which the visible pattern is viewed, by making the visible directions of the plurality of patterns different from one another. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2019-86653 A Summary of the Invention [Problem to be solved by the invention]

[0005] There is a demand for a light guide that can more significantly change the visibility of a displayed object depending on the viewing position relative to the light guide.

[0006] An object of the present disclosure is to provide a light guide and a light emitting device that can more significantly change the visibility of a displayed object depending on the observation position relative to the light guide. [Means for solving the problem]

[0007] A light guide according to an embodiment of the present disclosure has an exit surface, guides incident light, and emits it from the exit surface. The light guide has a reflecting surface facing the exit surface. The reflecting surface is formed with a first prism group having at least one first prism formed with a cone-shaped recess, and a second prism group having a plurality of second prisms formed with cone-shaped recesses surrounding the first prism group. When viewed from a direction perpendicular to the light guide direction and the normal direction of the reflecting surface, a cross section of the at least one first prism has a first hypotenuse and a second hypotenuse extending from the reflecting surface, and a cross section of each of the plurality of second prisms has a third hypotenuse and a fourth hypotenuse extending from the reflecting surface. A first angle, which is an angle of the first hypotenuse with respect to the reflecting surface, and a second angle, which is an angle of the second hypotenuse with respect to the reflecting surface, are different from each other. One of a third angle, which is the angle of the third hypotenuse relative to the reflecting surface, and a fourth angle, which is the angle of the fourth hypotenuse relative to the reflecting surface, is equal to either the first angle or the second angle, and the other of the third angle and the fourth angle is different from the first angle and the second angle.

[0008] A light emitting device according to one aspect of the present disclosure includes the above-described light guide and a light source unit that causes the light to be incident on the light guide. Effect of the Invention

[0009] The present disclosure has an advantage in that the visibility of a displayed object can be changed more significantly depending on the observation position relative to a light guide. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a perspective view showing a light emitting device including a light guide according to an embodiment. [Diagram 2] FIG. 2 is a plan view showing the rear surface of the light guide body. [Diagram 3] FIG. 3 is a cross-sectional view of a portion of the light guide as viewed from above. [Figure 4] FIG. 4 is a top view of the light guide and an observation position. [Diagram 5]FIG. 5 is a diagram showing a display form of the exit surface of the light guide body of the above embodiment. [Figure 6] FIG. 6 is a diagram showing a display form of the exit surface of the light guide body of the above embodiment. [Figure 7] FIG. 7 is a diagram showing a display form of the exit surface of the light guide body of the above embodiment. [Figure 8] FIG. 8 is a cross-sectional view of a portion of the light guide as viewed from above. [Figure 9] FIG. 9 is a view of the light guide and the observation position of the same as above. [Figure 10] FIG. 10 is a plan view showing the rear surface of the light guide of the first modified example. [Figure 11] FIG. 11 is a cross-sectional view of a portion of the light guide as viewed from above. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The present disclosure relates generally to light guides and light emitting devices. More particularly, the present disclosure relates to light guides and light emitting devices comprising prisms.

[0012] Hereinafter, the light guide and the light emitting device according to the embodiment will be described with reference to the drawings. However, the following embodiment is merely one of various embodiments of the present disclosure. The following embodiment can be modified in various ways according to the design, etc., as long as it can achieve the object of the present disclosure and does not deviate from the technical idea of ​​the present disclosure. In addition, each figure described in the following embodiment is a schematic diagram, and the ratio of the size and thickness of each component in the figure does not necessarily reflect the actual dimensional ratio.

[0013] (Embodiment) (1) Overview 1 and 2 show a light emitting device 100 including a light guide 1 of this embodiment. FIG. 3 shows cross sections of a first prism 21 and a second prism 22 of the light guide 1.

[0014] The light guide 1 has an exit surface 11 and guides incident light to emit it from the exit surface 11. The light guide 1 has a reflecting surface 12 facing the exit surface 11. The reflecting surface 12 is formed with a first prism group 2a having at least one first prism 21 formed with a cone-shaped recess, and a second prism group 2b having a plurality of second prisms 22 formed with cone-shaped recesses surrounding the first prism group 2a.

[0015] When viewed from a direction perpendicular to the light guide direction D1 and the normal direction of the reflecting surface 12, the cross section of the first prism 21 has a first hypotenuse 211 and a second hypotenuse 212 extending from the reflecting surface 12, and the cross section of the second prism 22 has a third hypotenuse 221 and a fourth hypotenuse 222 extending from the reflecting surface 12. A first angle θ1 which is the angle of the first hypotenuse 211 with respect to the reflecting surface 12 and a second angle θ2 which is the angle of the second hypotenuse 212 are different from each other. One of a third angle θ3 which is the angle of the third hypotenuse 221 with respect to the reflecting surface 12 and a fourth angle θ4 which is the angle of the fourth hypotenuse 222 is equal to either the first angle θ1 or the second angle θ2, and the other of the third angle θ3 and the fourth angle θ4 is different from the first angle θ1 and the second angle θ2.

[0016] When an observer views the exit surface 11 of the light guide 1 having the above-mentioned configuration from a certain observation position, both the light from the first prism group 2a and the light from the second prism group 2b are visible, and when the observer views the exit surface 11 from another observation position, only the light from the first prism group 2a is visible among the first prism group 2a and the second prism group 2b. When both the light from the first prism group 2a and the light from the second prism group 2b are visible, the observer cannot distinguish between the light from the first prism group 2a and the light from the second prism group 2b, and it becomes difficult to see the light from the first prism group 2a as a display object. When only the light from the first prism group 2a is visible among the first prism group 2a and the second prism group 2b, it becomes easy for the observer to see the light from the first prism group 2a as a display object.

[0017] In this way, the light guide 1 can change the visibility of a displayed object to a greater extent depending on the observation position relative to the light guide 1.

[0018] Note that "the two angles are equal" is not limited to a case where the two angles are completely the same, but also includes a case where the two angles are slightly misaligned to an extent that includes an error.

[0019] (2)Details 1 includes a light guide 1 and a light source unit 9. The light emitting device 100 is incorporated into a signage system, an electric device, a sign device, and the like, and displays a display object such as a character, a sign, or a symbol to a person.

[0020] The light emitting device 100 uses a so-called edge light method for emitting light. In Fig. 1, a light source unit 9 is attached to an end of a light guide 1, and the light source unit 9 causes light to enter the inside of the light guide 1 from the end of the light guide 1. The light emitting device 100 causes the light that has entered the light guide 1 from the end of the light guide 1 to be emitted from the light guide 1.

[0021] In the following description, the X-axis direction, which is the arrangement direction of the light guide 1 and the light source units 9 in Fig. 1, is defined as the left-right direction, the Y-axis direction, which is the thickness direction of the light guide 1, is defined as the front-rear direction, and the direction perpendicular to the X-axis direction and the Y-axis direction is defined as the up-down direction. Furthermore, the positive direction in the X-axis direction is defined as the right side, the positive direction in the Y-axis direction is defined as the front side, and the positive direction in the Z-axis direction is defined as the top side. Note that these directions are merely examples and are not intended to limit the directions in which the light emitting device 100 and the light guide 1 are used. Also, the arrows indicating the various directions in the drawings are merely shown for the purpose of explanation and do not have any substance.

[0022] (2.1) Light source unit The light source unit 9 has an LED module 91 in which LEDs (Light Emitting Diodes) serving as light sources are mounted on a substrate, and a housing 92 that houses the LED module 91. The housing 92 is formed in a long box shape with an open right side. The LEDs of the LED module 91 are arranged to emit light toward the right side of the housing 92.

[0023] The light source unit 9 is attached to the light guide 1 so that the right surface of the light source unit 9 faces the incident surface 13 of the light guide 1 .

[0024] The light source unit 9 may have other solid-state light-emitting elements, such as organic electroluminescence (OEL) elements or semiconductor laser diodes (LD), instead of LEDs.

[0025] (2.2) Light guide The light guide 1 is formed in the shape of a rectangular parallelepiped flat plate from a material that is translucent (light-transmitting) at least to visible light. The translucent material is, for example, a synthetic resin material or a glass material. The resin material is, for example, an acrylic resin or a polycarbonate. The thickness (dimension in the front-rear direction) of the light guide 1 is preferably, for example, about several mm to several cm. The material of the light guide 1 is not limited to a specific material and may be other than the above.

[0026] Specifically, the light guide 1 has a rectangular front surface as an exit surface 11, and a rectangular rear surface as a reflecting surface 12. Furthermore, the light guide 1 has a rectangular left end surface as an entrance surface 13. A light source unit 9 is attached to the entrance surface 13. Light emitted from the light source unit 9 is incident on the entrance surface 13. The light that enters the light guide 1 from the entrance surface 13 is guided from left to right inside the light guide 1, and after the traveling direction of the light is optically controlled (light distribution control) by the reflecting surface 12, it is emitted from the exit surface 11. An observer in front of the exit surface 11 can see the light emitted from the exit surface 11.

[0027] The direction in which light incident on the incident surface 13 enters the light guide 1 and propagates inside the light guide 1 is sometimes referred to as the light guide direction D1 (see FIG. 1). The propagation direction is the direction in which the light incident on the incident surface 13 propagates inside the light guide 1 before being reflected and refracted by a first prism 21 and a second prism 22, which will be described later. In this embodiment, the light guide direction D1 is the direction from left to right along the X-axis.

[0028] Reflective surface 12 is formed with a prism having a cone-shaped recess, and the prism optically controls the traveling direction of light propagating inside light guide 1 (light distribution control). Reflective surface 12 will be described in detail below. In the following description, the observation position refers to the position of an observer present in front of exit surface 11.

[0029] (2.3) Reflective surface 2 shows a plan view of the reflecting surface 12. The reflecting surface 12 is formed with a plurality of first prisms 21 and a plurality of second prisms 22 as a plurality of prisms each having a cone-shaped recess. The prisms (the first prism 21 and the second prism 22) are formed on the reflecting surface 12 by performing, for example, thermal processing such as laser processing, or mechanical processing, and the prisms become cone-shaped recesses formed on the reflecting surface 12. Note that the "cone-shaped" in this disclosure includes not only a shape in which the apex of the cone coincides with the center of the circular base of the cone, but also an approximately cone-shaped shape in which the apex of the cone is offset from the center of the circular base of the cone.

[0030] 2, a first prism group 2a consisting of a plurality of first prisms 21 is surrounded by a second prism group 2b consisting of a plurality of second prisms 22. In Fig. 2, the plurality of first prisms 21 and the plurality of second prisms 22 are mixed and arranged in a staggered pattern on the reflecting surface 12. However, the plurality of first prisms 21 and the plurality of second prisms 22 are not limited to being arranged in a staggered pattern, and may be arranged randomly or in a lattice pattern.

[0031] In Fig. 2, the first prism group 2a is formed by arranging a plurality of first prisms 21 in the shape of the letter "P," and corresponds to the letter "P" that is to be displayed. Note that Fig. 2 is a plan view of the reflecting surface 12 as seen from behind, so the left and right of the letter "P" are inverted. As the first prism group 2a has a plurality of first prisms 21, the first prism group 2a can accommodate various display objects such as letters, signs, and symbols.

[0032] The second prism group 2b is formed by arranging a plurality of second prisms 22 around the first prism group 2a. In the second prism group 2b, the plurality of second prisms 22 are positioned on the outside and inside of the letter "P," surrounding the first prism group 2a, and corresponding to the background of the letter "P" to be displayed.

[0033] The light that enters the light guide 1 from the incident surface 13 propagates from left to right inside the light guide 1 and is reflected and refracted by the first prism group 2a (plurality of first prisms 21) and the second prism group 2b (plurality of second prisms 22) to be emitted forward from the exit surface 11. At this time, of the light that is incident on the incident surface 13, the light that heads toward the exit surface 11 via the first prism group 2a forms the letter "P" to be displayed on the exit surface 11. Of the light that is incident on the incident surface 13, the light that heads toward the exit surface 11 via the second prism group 2b brightens the background of the letter "P" to be displayed.

[0034] The traveling direction of light emitted from the exit surface 11 via the first prism 21 is determined by the shape of the first prism 21. In other words, the observation position in front of the light guide 1 where the bright (brightly shining) letter "P" can be seen as a display object is determined by the shape of the first prism 21.

[0035] The traveling direction of light emitted from exit surface 11 via second prism 22 is determined by the shape of second prism 22. In other words, the observation position in front of light guide 1 from which a bright (brightly shining) background can be seen is determined by the shape of second prism 22.

[0036] In this embodiment, by adjusting the shapes of the first prism 21 and the second prism 22, an observation position where both the letter "P" and the background appear bright is created in front of the light guide 1. Also, by adjusting the shapes of the first prism 21 and the second prism 22, an observation position where the letter "P" appears bright and the background appears dark is created. Also, by adjusting the shapes of the first prism 21 and the second prism 22, it is also possible to create an observation position where the letter "P" appears dark and the background appears bright. Also, by adjusting the shapes of the first prism 21 and the second prism 22, it is also possible to create an observation position where both the letter "P" and the background appear dark in front of the light guide 1.

[0037] (2.3.1) First example of a prism Fig. 3 is a cross-sectional view of the light guide 1 including the first prism 21 and the second prism 22 in the first example, viewed from above. That is, Fig. 3 shows the cross sections of the first prism 21 and the second prism 22 viewed from a direction (up-down direction along the Z axis) perpendicular to the light guide direction D1 and the normal direction of the reflecting surface 12 (front-back direction along the Y axis). The cross section of the first prism 21 is a cross section passing through the apex of the cone-shaped first prism 21, and is triangular. The cross section of the second prism 22 is a cross section passing through the apex of the cone-shaped second prism 22, and is triangular.

[0038] The first prism 21 is a cone-shaped recess formed on the reflecting surface 12. Therefore, when viewed from a direction (up-down direction) perpendicular to the light guide direction D1 and the normal direction of the reflecting surface 12, the cross section of the first prism 21 has a first hypotenuse 211 and a second hypotenuse 212 extending from the reflecting surface 12. The first hypotenuse 211 is located on the left side of the second hypotenuse 212. That is, in the light guide direction D1, the first hypotenuse 211 and the second hypotenuse 212 are located in this order. The angle of the first hypotenuse 211 with respect to the reflecting surface 12 is defined as a first angle θ1. The angle of the second hypotenuse 212 with respect to the reflecting surface 12 is defined as a second angle θ2. The first angle θ1 and the second angle θ2 are different (θ1 ≠ θ2). In FIG. 3, the first angle θ1 is greater than the second angle θ2 (θ1>θ2). The first angle θ1 and the second angle θ2 are interior angles of a triangle having the first hypotenuse 211 and the second hypotenuse 212.

[0039] The second prism 22 is a cone-shaped recess formed on the reflecting surface 12. Therefore, when viewed from a direction (up-down direction) perpendicular to the light guide direction D1 and the normal direction of the reflecting surface 12, the cross section of the second prism 22 has a third hypotenuse 221 and a fourth hypotenuse 222 extending from the reflecting surface 12. The third hypotenuse 221 is located on the left side of the fourth hypotenuse 222. That is, in the light guide direction D1, the third hypotenuse 221 and the fourth hypotenuse 222 are located in this order. The angle of the third hypotenuse 221 with respect to the reflecting surface 12 is defined as a third angle θ3. The angle of the fourth hypotenuse 222 with respect to the reflecting surface 12 is defined as a fourth angle θ4. The third angle θ3 is different from the fourth angle θ4 (θ3≠θ4). In FIG. 3, the third angle θ3 is greater than the fourth angle θ4 (θ3>θ4). The third angle θ3 and the fourth angle θ4 are interior angles of a triangle having the third hypotenuse 221 and the fourth hypotenuse 222.

[0040] 3, the first angle θ1 of the first prism 21 and the third angle θ3 of the second prism 22 are equal (θ1=θ3), and the second angle θ2 of the first prism 21 and the fourth angle θ4 of the second prism 22 are different (θ2≠θ4). The second angle θ2 is greater than the fourth angle θ4 (θ2>θ4).

[0041] In this case, a portion of the light L1 traveling in the light guide direction D1 within the light guide 1 is reflected by the first hypotenuse 211 of the first prism 21, and then becomes light L11 traveling diagonally forward to the left, and the light L11 is emitted from the exit surface 11. A portion of the light L1 traveling in the light guide direction D1 within the light guide 1 is refracted by the first hypotenuse 211 of the first prism 21, and then refracted by the second hypotenuse 212 of the first prism 21, and then becomes light L12 traveling diagonally forward to the right, and the light L12 is emitted from the exit surface 11.

[0042] Moreover, the light L2 traveling in the light guide direction D1 within the light guide 1 is reflected by the third oblique side 221 of the second prism 22, and then becomes light L21 traveling diagonally forward and left, and the light L21 is emitted from the exit surface 11. Moreover, a part of the light L2 traveling in the light guide direction D1 within the light guide 1 is refracted by the third oblique side 221 of the second prism 22, and then refracted by the fourth oblique side 222 of the second prism 22, and then becomes light L22 traveling substantially forward (slightly diagonally forward and right), and the light L22 is emitted from the exit surface 11.

[0043] 3, since the first angle θ1 and the third angle θ3 are equal, both light L11 and light L21 travel diagonally forward to the left, and the traveling direction of light L11 and the traveling direction of light L21 are the same. The traveling direction of light L22 is almost forward (slightly diagonally forward to the right), and the traveling direction of light L12 is diagonally forward to the right. In other words, the traveling direction of light L12 is inclined more to the right from the normal direction to the emission surface 11 than the traveling direction of light L22.

[0044] 4, the observer at observation position Q1 diagonally in front of the right of the light guide 1 can easily see the light L12 out of the light L11 and L12 from the first prism 21, but has difficulty seeing the light L21 and L22 from the second prism 22. As a result, the observer at observation position Q1 can see the letter "P", which is a display object that is brighter than the background, and the dark background surrounding the letter "P" on the exit surface 11, as shown in FIG.

[0045] 4, an observer at observation position Q2 substantially in front of the light guide 1 can easily see the light L22 out of the light L21 and L22 from the second prism 22, but has difficulty seeing the light L11 and L12 from the first prism 21. As a result, an observer at observation position Q2 can see the letter "P", which is darker than the background, and the light background surrounding the letter "P", at the exit surface 11, as shown in FIG.

[0046] 4, the observer at observation position Q3 diagonally in front and to the left of the light guide 1 can easily see the light L11 of the light L11 and L12 from the first prism 21, and can also easily see the light L21 of the light L21 and L22 from the second prism 22. As a result, on the exit surface 11 seen by the observer at observation position Q3, as shown in Fig. 7, a bright letter "P" and a bright background surrounding the letter "P" are formed, so that almost the entire exit surface 11 becomes bright, making it difficult for the observer to see the letter "P" that is the display target.

[0047] As described above, the light emitting device 100 and the light guide 1 can change the visibility of the displayed object (the bright letter "P") to a greater extent depending on the observation position relative to the light guide 1.

[0048] Furthermore, when the observation position moves between observation positions Q1, Q2, and Q3, the brightness of the letter "P" and the background surrounding the letter "P" changes continuously.

[0049] (2.3.2) Second example of a prism Fig. 8 is a cross-sectional view of the light guide 1 including the first prism 21 and the second prism 22 in the second example, viewed from above. That is, Fig. 8 shows the cross sections of the first prism 21 and the second prism 22 viewed from a direction (up-down direction along the Z axis) perpendicular to the light guide direction D1 and the normal direction of the reflecting surface 12 (front-back direction along the Y axis). The cross section of the first prism 21 is a cross section passing through the apex of the cone-shaped first prism 21, and is triangular. The cross section of the second prism 22 is a cross section passing through the apex of the cone-shaped second prism 22, and is triangular.

[0050] In the first prism 21, the first angle θ1 and the second angle θ2 are different (θ1≠θ2). In Fig. 8, the first angle θ1 is smaller than the second angle θ2 (θ1<θ2).

[0051] In the second prism 22, the third angle θ3 is different from the fourth angle θ4 (θ3≠θ4). In Fig. 8, the third angle θ3 is greater than the fourth angle θ4 (θ3>θ4).

[0052] 8, the second angle θ2 of the first prism 21 and the fourth angle θ4 of the second prism 22 are equal (θ2=θ4), and the first angle θ1 of the first prism 21 and the third angle θ3 of the second prism 22 are different (θ1≠θ3). The first angle θ1 is smaller than the third angle θ3 (θ1<θ3).

[0053] In this case, a portion of the light L3 traveling in the light guide direction D1 within the light guide 1 becomes light L31 traveling forward after being reflected by the first hypotenuse 211 of the first prism 21, and the light L31 is emitted from the exit surface 11. A portion of the light L3 traveling in the light guide direction D1 within the light guide 1 is refracted by the first hypotenuse 211 of the first prism 21, and is further refracted by the second hypotenuse 212 of the first prism 21, and becomes light L32 traveling diagonally forward to the right, and the light L32 is emitted from the exit surface 11.

[0054] Furthermore, light L4 traveling in light guide direction D1 within light guide body 1 is reflected by third oblique side 221 of second prism 22, and then becomes light L41 traveling diagonally forward and left, and light L41 is emitted from exit surface 11. Furthermore, a portion of light L2 traveling in light guide direction D1 within light guide body 1 is refracted by third oblique side 221 of second prism 22, and then refracted by fourth oblique side 222 of second prism 22, and then becomes light L42 traveling diagonally forward and right, and light L42 is emitted from exit surface 11.

[0055] 8, both light L32 and light L42 travel diagonally forward to the right, and the traveling direction of light L32 is approximately the same as the traveling direction of light L42. The traveling direction of light L31 is forward, and the traveling direction of light L41 is diagonally forward to the left. In other words, the traveling direction of light L41 is inclined more to the left from the normal direction of the emission surface 11 than the traveling direction of light L31.

[0056] 9, a viewer at observation position Q11 on the front side (in front of) the light guide 1 can easily see the light L31 out of the light L31 and L32 from the first prism 21, but cannot easily see the light L41 and L42 from the second prism 22. As a result, a viewer at observation position Q11 can see the letter "P", which is a display object that is brighter than the background, and the dark background surrounding the letter "P", on the exit surface 11, as shown in FIG.

[0057] 9, an observer positioned at observation position Q12 diagonally to the front and left of the light guide 1 can easily see the light L41 out of the light L41 and L42 from the second prism 22, but has difficulty seeing the light L31 and L32 from the first prism 21. As a result, an observer positioned at observation position Q12 can see, at the exit surface 11, the letter "P" which is darker than the background, and the light background surrounding the letter "P," as shown in FIG.

[0058] 9, a viewer at observation position Q31 diagonally in front of the right of light guide 1 can easily see light L32 out of light L31, L32 from first prism 21, and can also easily see light L42 out of light L41, L42 from second prism 22. As a result, on exit surface 11 seen by an observer at observation position Q13, as shown in Fig. 7, a bright letter "P" and a bright background surrounding the letter "P" are formed, so that almost the entire exit surface 11 becomes bright, making it difficult for the observer to see the letter "P."

[0059] As described above, the light emitting device 100 and the light guide 1 can change the visibility of the displayed object (the bright letter "P") to a greater extent depending on the observation position relative to the light guide 1.

[0060] Furthermore, when the observation position moves between each of the observation positions Q11, Q12, and Q13, the brightness of the character "P" to be displayed and the background surrounding the character "P" changes continuously.

[0061] (2.3.3) Summary The above-mentioned first angle θ1, second angle θ2, third angle θ3, and fourth angle θ4 satisfy the following conditions. The first angle θ1 and the second angle θ2 are different from each other.

[0062] One of the third angle θ3 and the fourth angle θ4 is equal to either the first angle θ1 or the second angle θ2, and the other of the third angle θ3 and the fourth angle θ4 is different from the first angle θ1 and the second angle θ2.

[0063] Furthermore, it is preferable that the first angle θ1, the second angle θ2, the third angle θ3, and the fourth angle θ4 satisfy the following condition. The third angle θ3 is equal to the first angle θ1 and the fourth angle θ4 is different from the second angle θ2, or the third angle θ3 is different from the first angle θ1 and the fourth angle θ4 is equal to the second angle θ2.

[0064] The first angle θ1, the second angle θ2, the third angle θ3, and the fourth angle θ4 are appropriately set according to the light distribution control to be achieved while satisfying the above conditions.

[0065] (3) First Modification A light emitting device 100 of this modification includes a light guide 1A shown in Fig. 10, instead of the above-described light guide 1. Fig. 10 shows a plan view of a reflecting surface 12 of the light guide 1A.

[0066] The light guide 1A includes two first prism groups 2a, namely, first prism groups 2a(1) and 2a(2).

[0067] The first prism group 2a(1) is formed into a quadrangle by a plurality of first prisms 21(1), and the display target by the first prism group 2a(1) is a quadrangle. Of the light incident on the entrance surface 13, the light traveling toward the exit surface 11 via the first prism group 2a(1) forms the figure to be displayed, a quadrangle, on the exit surface 11.

[0068] The first prism group 2a(2) is formed into a triangular shape by a plurality of first prisms 21(2), and the display target by the first prism group 2a(2) is a triangular figure. Of the light incident on the entrance surface 13, the light traveling toward the exit surface 11 via the first prism group 2a(2) forms the figure "triangle" that is the display target on the exit surface 11.

[0069] A first prism group 2a(1) consisting of a plurality of first prisms 21(1), and a first prism group 2a(2) consisting of a plurality of first prisms 21(2) are surrounded by a second prism group 2b consisting of a plurality of second prisms 22. The second prism group 2b corresponds to the background of the figures "rectangle" and "triangle" to be displayed.

[0070] Then, the light that enters the inside of light guide 1A from incident surface 13 propagates inside light guide 1A in light guide direction D1 and is reflected and refracted by first prism group 2a(1) (plurality of first prisms 21(1)), first prism group 2a(2) (plurality of first prisms 21(2)), and second prism group 2b (plurality of second prisms 22), and is emitted forward from exit surface 11.

[0071] In this modified example, by adjusting the shapes of the first prisms 21(1), 21(2) and the second prism 22, it is possible to change the appearance of the figures “square”, “triangle”, and the background on the exit surface 11 for each observation position.

[0072] FIG. 11 is a cross-sectional view of the light guide 1A including the first prisms 21(1), 21(2), and the second prism 22, seen from above. That is, FIG. 11 shows the cross sections of the first prisms 21(1), 21(2), and the second prism 22, seen from a direction (up-down direction along the Z axis) perpendicular to the light guide direction D1 and the normal direction of the reflecting surface 12 (front-back direction along the Y axis). The cross section of the first prism 21(1) is a cross section passing through the apex of the cone-shaped first prism 21(1). The cross section of the first prism 21(2) is a cross section passing through the apex of the cone-shaped first prism 21(2). The cross section of the second prism 22 is a cross section passing through the apex of the cone-shaped second prism 22.

[0073] The first prism 21(1) is a cone-shaped recess formed on the reflecting surface 12. Therefore, when viewed from a direction (up-down direction) perpendicular to the light guide direction D1 and the normal direction of the reflecting surface 12, the cross section of the first prism 21(1) has a first hypotenuse 211(1) and a second hypotenuse 212(1) extending from the reflecting surface 12. The first hypotenuse 211(1) is located on the left side of the second hypotenuse 212(1). That is, in the light guide direction D1, the first hypotenuse 211(1) and the second hypotenuse 212(1) are located in this order. The angle of the first hypotenuse 211(1) with respect to the reflecting surface 12 is defined as a first angle θ1(1). The angle of the second hypotenuse 212(1) with respect to the reflecting surface 12 is defined as a second angle θ2(1). The first angle θ1(1) and the second angle θ2(1) are different (θ1(1) ≠ θ2(1)). In FIG. 11, the first angle θ1(1) is greater than the second angle θ2(1) (θ1(1) > θ2(1)). Note that the first angle θ1(1) and the second angle θ2(1) are interior angles of a triangle having first hypotenuse 211(1) and second hypotenuse 212(1).

[0074] The first prism 21(2) is a cone-shaped recess formed on the reflecting surface 12. Therefore, when viewed from a direction (up-down direction) perpendicular to the light guide direction D1 and the normal direction of the reflecting surface 12, the cross section of the first prism 21(2) has a first hypotenuse 211(2) and a second hypotenuse 212(2) extending from the reflecting surface 12. The first hypotenuse 211(2) is located on the left side of the second hypotenuse 212(2). That is, in the light guide direction D1, the first hypotenuse 211(2) and the second hypotenuse 212(2) are located in this order. The angle of the first hypotenuse 211(2) with respect to the reflecting surface 12 is defined as a first angle θ1(2). The angle of the second hypotenuse 212(2) with respect to the reflecting surface 12 is defined as a second angle θ2(2). The first angle θ1(2) and the second angle θ2(2) are interior angles of a triangle having the first hypotenuse 211(2) and the second hypotenuse 212(2).

[0075] The second prism 22 is a cone-shaped recess formed on the reflecting surface 12. Therefore, when viewed from a direction (up-down direction) perpendicular to the light guide direction D1 and the normal direction of the reflecting surface 12, the cross section of the second prism 22 has a third hypotenuse 221 and a fourth hypotenuse 222 extending from the reflecting surface 12. The third hypotenuse 221 is located on the left side of the fourth hypotenuse 222. That is, in the light guide direction D1, the third hypotenuse 221 and the fourth hypotenuse 222 are located in this order. The angle of the third hypotenuse 221 with respect to the reflecting surface 12 is defined as a third angle θ3. The angle of the fourth hypotenuse 222 with respect to the reflecting surface 12 is defined as a fourth angle θ4. The third angle θ3 and the fourth angle θ4 are interior angles of a triangle having the third hypotenuse 221 and the fourth hypotenuse 222.

[0076] The above-mentioned first angles θ1(1), θ1(2), second angles θ2(1), θ2(2), third angle θ3, and fourth angle θ4 satisfy the following conditions. The first angle θ1(1) and the second angle θ2(1) are different from each other. The first angle θ1(2) and the second angle θ2(2) are different from each other. One of the first angle θ1(1) and the second angle θ2(1) is equal to either the first angle θ1(2) or the second angle θ2(2), and the other of the first angle θ1(1) and the second angle θ2(1) is different from the first angle θ1(2) and the second angle θ2(2). Also, one of the first angle θ1(2) and the second angle θ2(2) is equal to either the first angle θ1(1) or the second angle θ2(1), and the other of the first angle θ1(2) and the second angle θ2(2) is different from the first angle θ1(1) and the second angle θ2(1). That is, one of the first angle θ1 and one of the second angle θ2 of the first prisms 21 belonging to each of the multiple first prism groups 2a are equal to each other.

[0077] One of the third angle θ3 and the fourth angle θ4 is equal to either the first angle θ1(1) or the second angle θ2(1), and the other of the third angle θ3 and the fourth angle θ4 is different from the first angle θ1(1) and the second angle θ2(1).

[0078] The other of the third angle θ3 and the fourth angle θ4 is equal to either the first angle θ1(2) or the second angle θ2(2), and one of the third angle θ3 and the fourth angle θ4 is different from the first angle θ1(2) and the second angle θ2(2).

[0079] The first angles θ1(1), θ1(2), the second angles θ2(1), θ2(2), the third angle θ3, and the fourth angle θ4 are set appropriately according to the light distribution control to be achieved while satisfying the above conditions.

[0080] In this modified example, by adjusting the shapes of the first prisms 21(1), 21(2) and the second prism 22 (first angles θ1(1), θ1(2), second angles θ2(1), θ2(2), third angle θ3, and fourth angle θ4), it is possible to create an observation position where the figure "rectangle" appears bright and the figure "triangle" and the background appear dark. In this case, to the observer, the figure "rectangle" appears bright, and the figure "triangle" and the background appear dark.

[0081] In addition, by adjusting the shapes of the first prisms 21(1), 21(2) and the second prism 22, it is possible to create an observation position where the figure "triangle" appears bright and the figure "square" and the background appear dark. In this case, the observer sees the figure "triangle" as bright and the figure "square" and the background as dark.

[0082] In addition, by adjusting the shapes of the first prisms 21(1), 21(2) and the second prism 22, it is possible to create an observation position where the figures "triangle" and "rectangle" appear bright and the background appears dark. In this case, the observer sees the figures "triangle" and "rectangle" as bright and the background as dark.

[0083] In addition, by adjusting the shapes of the first prisms 21(1), 21(2) and the second prism 22, it is possible to create an observation position where the figures "square" and "triangle" and the background all appear bright. In this case, almost the entire exit surface 11 becomes bright, making it difficult for the observer to visually recognize the figures "square" and "triangle".

[0084] In addition, by adjusting the shapes of the first prisms 21(1), 21(2) and the second prism 22, it is possible to create an observation position where the figures "square" and "triangle" and the background all appear dark. In this case, almost the entire exit surface 11 becomes dark, making it difficult for the observer to visually recognize the figures "square" and "triangle".

[0085] As described above, in this modification, the visibility of the multiple display objects (bright squares, triangles) can be changed more significantly depending on the observation position relative to the light guide 1A. Also, the visibility of the multiple display objects (bright squares, triangles) can be changed individually.

[0086] (4) Second Modification The shape of each of the first prism 21 and the second prism 22 is not limited to a cone shape, but may be a pyramid shape.

[0087] The number of first prisms 21 constituting the first prism group 2a is not limited to a plurality, and may be 1. That is, one first prism 21 can constitute the first prism group 2a.

[0088] The reflecting surface 12 may include three or more first prism groups 2a.

[0089] The light from the first prism group 2a (first prism 21) may form a display object including at least one of characters, signs, and symbols.

[0090] (5) Summary The light guide (1, 1A) of the first aspect of the embodiment has an exit surface (11) and guides incident light to emit it from the exit surface (11). The light guide (1, 1A) has a reflecting surface (12) facing the exit surface (11). The reflecting surface (12) is formed with a first prism group (2a) having at least one first prism (21) formed of a pyramidal recess, and a second prism group (2b) having a plurality of second prisms (22) formed of pyramidal recesses surrounding the first prism group (2a). When viewed from a direction perpendicular to the light guide direction (D1) and the normal direction of the reflecting surface (12), the cross section of at least one first prism (21) has a first hypotenuse (211) and a second hypotenuse (212) extending from the reflecting surface (12). A cross section of each of the multiple second prisms (22) has a third hypotenuse (221) and a fourth hypotenuse (222) extending from the reflecting surface (12). A first angle (θ1) which is the angle of the first hypotenuse (211) with respect to the reflecting surface (12) and a second angle (θ2) which is the angle of the second hypotenuse (212) are different from each other. One of a third angle (θ3) which is the angle of the third hypotenuse (221) with respect to the reflecting surface (12) and a fourth angle (θ4) which is the angle of the fourth hypotenuse (222) is equal to either the first angle (θ1) or the second angle (θ2), and the other of the third angle (θ3) and the fourth angle (θ4) is different from the first angle (θ1) and the second angle (θ2).

[0091] The above-described light guide (1, 1A) can greatly change the visibility of a displayed object depending on the observation position relative to the light guide (1, 1A).

[0092] In the first aspect of the light guide (1, 1A) according to the second aspect of the embodiment, the first angle (θ1) and the second angle (θ2) are positioned in the order of the first angle (θ1) and the second angle (θ2) in the light guide direction (D1). The third angle (θ3) and the fourth angle (θ4) are positioned in the order of the third angle (θ3) and the fourth angle (θ4) in the light guide direction (D1). It is preferable that the third angle (θ3) is equal to the first angle (θ1) and the fourth angle (θ4) is different from the second angle (θ2), or that the third angle (θ3) is different from the first angle (θ1) and the fourth angle (θ4) is equal to the second angle (θ2).

[0093] The above-described light guide (1, 1A) can greatly change the visibility of a displayed object depending on the observation position relative to the light guide (1, 1A).

[0094] In the light guide (1A) of the third aspect according to the embodiment, in the first or second aspect, it is preferable that there are a plurality of first prism groups (2a). The second prism groups (2b) surround each of the plurality of first prism groups (2a).

[0095] The light guide (1A) described above can greatly change the visibility of a plurality of display objects depending on the observation position relative to the light guide (1A).

[0096] In the fourth aspect of the light guide (1A) according to the embodiment, in the third aspect, it is preferable that one of the first angle (θ1) and the second angle (θ2) of at least one first prism (21) belonging to each of the multiple first prism groups (2a) is equal to each other.

[0097] The above-mentioned light guide (1A) can individually change the visibility of a plurality of display objects.

[0098] In the light guide (1, 1A) of the fifth aspect according to the embodiment, in any one of the first to fourth aspects, it is preferable that the first prism group (2a) has a plurality of first prisms (21).

[0099] The above-mentioned light guide (1, 1A) can be adapted to various display objects.

[0100] In the sixth aspect of the light guide (1, 1A) of the embodiment, in any one of the first to fifth aspects, it is preferable that the incident light traveling toward the exit surface (11) via the first prism group (2a) forms a display object including at least one of letters, signs, and symbols.

[0101] The above-described light guide (1, 1A) can change the visibility of at least one of characters, signs, and symbols to a greater extent depending on the observation position relative to the light guide (1, 1A).

[0102] In the seventh aspect of the light guide (1, 1A) according to the embodiment, in any one of the first to sixth aspects, it is preferable that at least one first prism (21) is formed as a cone-shaped recess, and the multiple second prisms (22) are formed as cone-shaped recesses.

[0103] In the above-described light guide (1, 1A), the first prism (21) and the second prism (22) can be easily formed by using a laser or the like.

[0104] A light emitting device (100) according to an eighth aspect of the present embodiment includes a light guide (1, 1A) according to any one of the first to seventh aspects, and a light source unit (9) that introduces light into the light guide (1, 1A).

[0105] The above-described light emitting device (100) can greatly change the visibility of a displayed object depending on the observation position relative to the light guide (1, 1A). [Explanation of symbols]

[0106] 100 Light emitting device 1, 1A light guide 11. Exit surface 12 Reflective surface 2a First prism group 2b Second prism group 21 First Prism 22 Second Prism 211 First hypotenuse 212 Second hypotenuse 221 Third hypotenuse 222 4th hypotenuse D1 Light guiding direction θ1 1st angle θ2 2nd angle θ3 3rd angle θ4 4th angle

Claims

1. A light guide having an exit surface and guiding incident light to emit it from the exit surface, A reflecting surface facing the light exit surface is provided, The reflective surface is a first prism group including at least one first prism having a cone-shaped concave portion; a second prism group having a plurality of second prisms each having a cone-shaped recess surrounding the first prism group; When viewed from a direction perpendicular to the light guide direction and the normal direction of the reflecting surface, a cross section of the at least one first prism having a first hypotenuse and a second hypotenuse extending from the reflective surface; a cross section of each of the second prisms has a third hypotenuse and a fourth hypotenuse extending from the reflecting surface; a first angle, which is an angle of the first hypotenuse with respect to the reflecting surface, and a second angle, which is an angle of the second hypotenuse with respect to the reflecting surface, are different from each other; One of a third angle, which is an angle of the third hypotenuse with respect to the reflecting surface, and a fourth angle, which is an angle of the fourth hypotenuse with respect to the reflecting surface, is equal to either the first angle or the second angle, and the other of the third angle and the fourth angle is different from the first angle and the second angle. Light guide.

2. the first angle and the second angle are positioned in the light guiding direction in this order: the first angle, the second angle; the third angle and the fourth angle are positioned in the light guiding direction in this order: the third angle, the fourth angle; the third angle being equal to the first angle and the fourth angle being different from the second angle; Or, The third angle is different from the first angle, and the fourth angle is equal to the second angle. The light guide of claim 1.

3. the first prism group is a plurality of prisms, The second prism group surrounds each of the first prism groups. The light guide of claim 1.

4. One of the first angle and the second angle of the at least one first prism belonging to each of the plurality of first prism groups is equal to each other. The light guide of claim 3.

5. The first prism group includes a plurality of the first prisms. The light guide of claim 1.

6. The light that is incident on the light source and travels through the first prism group toward the exit surface forms a display object including at least one of a character, a sign, and a symbol. The light guide of claim 1.

7. the at least one first prism comprises a cone-shaped recess; The second prisms are formed of cone-shaped recesses. The light guide of claim 1.

8. A light guide according to any one of claims 1 to 7; a light source unit that causes the light to enter the light guide body; Light emitting device.

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