JP2019204734A - Light guide plate for illumination and lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an illuminating light guide plate capable of suppressing the occurrence of a boundary based on the difference in brightness and darkness when utilizing leaked light and suppressing the spread of light traveling to the side opposite to the leaked light. A light guide plate (12) includes an incident surface (13) on which light is incident and a first prism group (20) having a plurality of first prisms (22), which is a surface that is substantially perpendicular to the incident surface (13), and leaks light. And a second surface 15 that is a surface that is substantially perpendicular to the incident surface 13 and that faces the first surface 14 and that includes a second prism group 30 that has a plurality of second prisms 32. .. The area ratio of the second prism group 30 to the second surface 15 is smaller than the area ratio of the first prism group 20 to the first surface 14. The bottom angle of each of the plurality of second prisms 32 forming the second prism group 30 is 35 ° or less. [Selection diagram] Figure 2

Description

  The present disclosure relates to an illumination light guide plate and an illumination device.

  Patent Document 1 describes a light guide plate used for a backlight for a liquid crystal display device. The light from the light source is incident on the incident surface of the light guide plate and is emitted from the emission surface (upper surface) having a different orientation with respect to the incident surface. In FIGS. 4 and 5 of Patent Document 1, it is described that prisms are formed on the exit surface and the surface (lower surface) opposite to the exit surface, respectively.

JP 2007-134344 A

  By the way, in the illuminating light guide plate that is erected, light is incident on the inside from the bottom surface (incident surface), and the prism structure is formed on the prism forming surface (first surface) substantially perpendicular to the bottom surface. It is conceivable to irradiate the wall with leakage light by refracting and transmitting it or reflecting it with its prism structure. In this configuration, the area above the predetermined height of the wall surface to which the leakage light is irradiated can be brightly illuminated, but the area below the predetermined height may be less irradiated with the leakage light. In this case, a light / dark boundary may be noticeable due to a clear difference between light and dark near a predetermined height position on the wall surface.

  On the other hand, by making the entire surface of the prism structure a diffusion surface on which light is diffused, it is conceivable to reduce the above difference in brightness by the light emitted while being diffused by the diffusion surface. Since the light (control light) going to the opposite side spreads, it becomes difficult to control the light distribution. In the above description, the case where the wall surface is irradiated with the illuminating light guide plate is described. However, when the ceiling surface is irradiated with the leakage light with the light guide plate for illumination, the light source plate is based on the difference in brightness at a predetermined position on the ceiling surface. The boundary may be noticeable.

  An object of the present disclosure is to provide an illumination light guide plate and an illumination device that can suppress the occurrence of a boundary based on a difference in brightness when using leaked light, and can suppress the spread of light toward the side opposite to the leaked light. It is.

  The light guide plate for illumination according to the present disclosure includes an incident surface on which light is incident and a surface that is substantially perpendicular to the incident surface, includes a first prism group having a plurality of first prisms, and emits leaked light. And a second surface including a second prism group having a plurality of second prisms, the second prism being substantially perpendicular to the incident surface and facing the first surface. The coverage, which is the area ratio of the group, is smaller than the coverage, which is the area ratio of the first prism group with respect to the first surface, and the base angle of each of the plurality of second prisms constituting the second prism group is 35 ° or less. It is a light guide plate for illumination.

  Moreover, the illuminating device which concerns on this indication is an illuminating device provided with the light guide plate for illumination which concerns on this indication, and the light source which irradiates light into the inside of the light guide plate for illumination from the entrance plane of the light guide plate for illumination.

  According to the illumination light guide plate and the illumination device according to the present disclosure, it is possible to suppress the occurrence of a boundary based on the difference in brightness due to the leaked light when the leaked light is used. Further, in order to suppress the occurrence of this boundary, the entire surface of the first prism disposed on the first surface from which the leaked light is emitted does not have to be a diffusion surface for diffusing light, and the first surface is flat. The light reflected by the portion can be efficiently emitted from the second surface. Thereby, the spread of the light toward the opposite side to the leaked light can be suppressed.

It is a figure which shows the installation state of the illuminating device containing the light guide plate for illumination of embodiment. It is the A section enlarged view of FIG. FIG. 3 is a diagram showing leakage light emitted from the first surface and light reflected by the first surface in the B part enlarged view of FIG. 2. In the C section enlarged view of FIG. 2, it is a figure which shows the light reflected by the 2nd surface. It is a figure which shows the wall surface irradiated with the leak light of the illuminating device of embodiment. It is a figure which shows the illuminating device containing the light guide plate for illumination of a comparative example. It is a figure which shows the wall surface irradiated with the leak light of the illuminating device of a comparative example. It is a figure which shows the light distribution curve of the illuminating device containing the light guide plate for illumination of a comparative example. In the illuminating device containing the illumination light-guide plate of a comparative example, it is a figure which shows the luminous intensity characteristic of the range of 135 degrees-180 degrees among the light distribution curves of the leakage light of FIG. In a comparative example, it is an image figure which shows the relationship between the brightness | luminance in a wall surface by leak light, and a height position. In a comparative example, it is an image figure which shows the relationship between the brightness | luminance in a wall surface, and a height position by the leakage light of the lower side reflected on the surface of the prism after refracting | transmitting with the prism of the 1st surface among leaked light. It is a figure which shows the illuminating device used for the calculation for the effect confirmation of embodiment. It is a figure which shows the calculation result for the effect confirmation of embodiment, Comprising: It is a figure which shows the relationship between the change of the base angle of the prism in a 2nd surface, and the brightness | luminance and height position in a wall surface. FIG. 5 is a view corresponding to FIG. 4 in an illumination light guide plate according to another example of the embodiment. In FIG. 14, it is a figure which shows the light reflected by the 2nd surface. It is a figure which shows the illuminating device containing the light-guide plate for illumination of another example of embodiment. It is a figure which shows the illuminating device containing the light guide plate for illumination of a reference example. (A) is the E section enlarged view of FIG. 17, (b) is the F section enlarged view of (a). FIG. 19 is a view corresponding to FIG. 18B in an illumination light guide plate of another example of the reference example. FIG. 19 is a view corresponding to FIG. 18B in an illumination light guide plate of another example of the reference example.

  Hereinafter, an example of an embodiment of an illumination light guide plate and an illumination device according to the present disclosure will be described in detail with reference to the drawings. Since the drawings referred to in the description of the embodiments are schematically described, the dimensional ratio of each component should be determined in consideration of the following description. In the following description, specific shapes, materials, quantities, and the like are examples for facilitating understanding of the present disclosure, and can be appropriately changed according to the specifications of the lighting device. Moreover, it is assumed from the beginning that the constituent elements of the plurality of embodiments described below are selectively combined. Below, the same code | symbol is attached | subjected and demonstrated to the same element in all the drawings.

(Structure of lighting device)
FIG. 1 is a diagram illustrating an installation state of an illumination device 10 including an illumination light guide plate 12 according to an embodiment. FIG. 2 is an enlarged view of part A in FIG. FIG. 3 is a diagram illustrating leakage light emitted from the first surface 14 and light reflected by the first surface 14 in the enlarged view of the B part in FIG. 2. FIG. 4 is a diagram showing light reflected by the second surface 15 in the enlarged view of the portion C of FIG.

  As shown in FIG. 1, the lighting device 10 is used by being arranged near a wall surface 92 along a vertical direction on a floor surface 90. As shown in FIG. 2, the illumination device 10 includes an illumination light guide plate 12, an instrument main body 50, and a light source 60. The illumination light guide plate 12 is a rectangular thin plate member having six surfaces and a predetermined thickness. Hereinafter, the light guide plate 12 for illumination is referred to as a light guide plate 12. The light guide plate 12 guides and emits light incident on the light guide plate 12. The light guide plate 12 is formed of a translucent resin material such as polycarbonate or acrylic. The six surfaces of the light guide plate 12 are an incident surface 13 that is a bottom surface and two surfaces that are substantially perpendicular to the incident surface 13, and the first surface 14 and the first surface 14 on both sides in the thickness direction (left-right direction in FIG. 2). It has two surfaces 15 and an emission end surface 16 that is an upper surface.

  The incident surface 13 is a substantially horizontal plane on which light from a light source 60 described later enters. The first surface 14 is a surface on the wall surface 92 side among both side surfaces in the thickness direction. The first surface 14 includes a first prism group 20 having a plurality of first prisms 22 and leaks light. The second surface 15 is a surface on the opposite side to the wall surface 92 out of both side surfaces in the thickness direction, and faces the first surface 14. The second surface 15 includes a second prism group 30 having a plurality of second prisms 32. The emission end face 16 is a plane inclined upward toward the upper end of the first face.

  The instrument body 50 is a case-like member in which the light guide plate 12 is fixed with the lower end portion of the light guide plate 12 inserted inward, and a light source 60 and a power supply circuit (not shown) are attached inside.

  The light source 60 is fixed to the instrument body 50 so as to face the vicinity of the incident surface 13 of the light guide plate 12. The light source 60 includes, for example, a substrate and a plurality of LED elements that are light sources attached to a plurality of positions in the longitudinal direction (front and back direction of the paper surface of FIG. 1) of the surface of the substrate that faces the incident surface 13.

  The plurality of LED elements irradiate light from the incident surface 13 into the light guide plate 12. Part of the light incident on the inside of the light guide plate 12 is emitted from the second surface 15 as control light. Part of the light incident on the inside of the light guide plate 12 is emitted from the first surface 14 as leakage light. The leak light irradiates the wall surface 92. Thereby, since it is possible to illuminate a region that is difficult to illuminate with a normal appliance, it is possible to illuminate many of the rooms in which the illumination device 10 is arranged.

  The LED element is, for example, an SMD (Surface Mount Device) type. The SMD type LED element is a package type LED element in which an LED chip (light emitting element) is mounted in a resin-molded cavity, and a phosphor-containing resin is sealed in the cavity. The LED element is connected to a power supply unit via a switch unit (not shown) such as a semiconductor switch, and the on / off state of the switch unit is controlled by a control unit (not shown). Thereby, the LED element is switched between lighting and extinguishing. The LED element may be controlled by the control unit to perform light adjustment and toning.

  The light source 60 is not limited to such a configuration, and a COB (Chip On Board) type light emitting module in which an LED chip is directly mounted on a substrate may be used. The light source is not limited to the LED element, and may be a semiconductor light emitting element such as a semiconductor laser, or an EL element such as an organic EL (Electro Luminescence) or an inorganic EL.

(Prism configuration)
The plurality of first prisms 22 are arranged in a distributed manner in the height direction and the horizontal direction of the first surface 14 (the front and back direction of the paper surface of FIG. 2). The plurality of first prisms 22 emit light emitted from the first surface 14 to a relatively wide range in the height direction. As shown in FIG. 3, the first prism 22 is a conical recess having a circular cross section formed so as to be recessed in the light guide plate 12, for example. The plurality of first prisms 22 have substantially the same shape and size. The entire surface of the first prism 22 is a mirror surface (smooth surface without unevenness). For example, the surface roughness (for example, the maximum height Rz) of the surface of the first prism 22 is substantially the same as the surface roughness of the flat portion 14 a other than the first prism 22 on the first surface 14. The first prism 22 may be a concave portion having an elliptical conical surface having an elliptical cross section, a concave portion having a quadrangular pyramid shape, or the like. In the configuration of this example, the area ratio of the first prism group 20 to the first surface 14 is substantially the same on the incident surface 13 side (lower side in FIG. 2) and the emission end surface 16 side (upper side in FIG. 2). At this time, the area of the first prism group 20 is the sum of the opening areas of the plurality of first prisms 22.

  The light emitted from the inside of the light guide plate 12 without being reflected by the first prism 22 while being refracted by the surface on the incident surface 13 side of the first prism 22 as indicated by the solid line arrow in FIG. As shown in FIG. The light transmitted from the inside of the light guide plate 12 while being refracted on the surface on the incident surface 13 side (the upper side in FIG. 3) of the first prism 22 as indicated by the one-dot chain line arrow in FIG. Reflected by the surface on the 16th side (the lower side in FIG. 3), the lower side is irradiated as the lower leakage light.

  On the other hand, the light (control light) totally reflected by the first prism 22 after being reflected from the inside of the light guide plate 12 by the flat portion 14a of the first surface 14 as indicated by the broken line arrow in FIG. Figure 2) Head to the side. Although not shown, there is also light that irradiates the outside from the inside of the light guide plate 12 through the flat portion 14 a of the first surface 14.

  Returning to FIG. 2, the plurality of second prisms 32 are arranged in a distributed manner in the height direction and the lateral direction of the second surface 15 (front and back direction of the paper surface of FIG. 2). Similar to the first prism 22, the light emitted from the second surface 15 is also irradiated to a relatively wide range by the plurality of second prisms 32. As shown in FIG. 4, the second prism 32 is a conical recess having a circular cross section formed so as to be recessed in the light guide plate 12, for example. The plurality of second prisms 32 have substantially the same shape and size. The entire surface of the second prism 32 is a mirror surface. For example, the surface roughness (for example, the maximum height Rz) of the surface of the second prism 32 is substantially the same as the surface roughness of the flat surface 15 a other than the second prism 32 on the second surface 15.

  Further, the base angle θ of each of the plurality of second prisms 32 is 35 ° or less, preferably 30 ° or less. Thereby, as described later, when the leaked light emitted from the first surface 14 (FIGS. 2 and 3) is used, it is possible to suppress the occurrence of a boundary based on the difference in brightness due to the leaked light. The second prism 32 may be a concave portion having an elliptical conical surface having an elliptical cross section, a concave portion having a quadrangular pyramid shape, or the like. In the configuration of this example, the area ratio of the second prism group 30 to the second surface 15 is substantially the same on the incident surface 13 side and the emission end surface 16 side. At this time, the area of the second prism group 30 is the sum of the opening areas of the plurality of second prisms 32.

  The light (control light) totally reflected by the second prism 32 after being reflected from the inside of the light guide plate 12 by the flat portion 15a of the second surface 15 as indicated by the broken line arrow in FIG. 4 is the first surface 14 (FIG. 2). , FIG. 3) head. Although not shown, there is also light that irradiates the outside from the inside of the light guide plate 12 through the flat portion of the second surface 15. Similarly to the case of FIG. 3, the second prism 32 is refracted on the incident surface 13 side (the lower side in FIG. 4) while being refracted and emitted without being reflected by the second prism 32. There is also light that irradiates the upper side of the second prism 32 after being refracted and transmitted through the surface on the incident surface 13 side of the second prism 32 and then reflected by the surface on the outgoing end surface side of the second prism 32.

  Further, as shown in FIG. 2, the coverage that is the area ratio of the second prism group 30 to the second surface 15 is smaller than the coverage that is the area ratio of the first prism group 20 to the first surface 14.

(Effects of light guide plate and lighting device)
According to the light guide plate 12 and the illumination device 10 described above, when the leaked light emitted from the first surface 14 is used, it is possible to suppress the occurrence of a boundary based on the difference in brightness due to the leaked light. Further, in order to suppress the occurrence of this boundary, the entire surface of the first prism 22 disposed on the first surface 14 does not need to be a diffusion surface having unevenness for diffusing light. The coverage that is the area ratio of the second prism group 30 to the second surface 15 is smaller than the coverage that is the area ratio of the first prism group 20 to the first surface 14. For this reason, since the light reflected by the flat part 14a of the 1st surface 14 can be radiate | emitted from the 2nd surface 15 efficiently, the breadth of the light which goes to the opposite side to leak light can be suppressed.

  FIG. 5 is a diagram illustrating the wall surface 92 irradiated with the leakage light of the illumination device 10 of the embodiment. The portions other than the black background at both ends in the left-right direction in FIG. In FIG. 5, the brightest part is shown by the plain part, and the slightly dark part is shown by the sand part. Further, in FIG. 5, it is shown that the boundary between light and dark is not clear by the one-dot chain line. As shown in FIG. 5, according to the embodiment, it is possible to suppress the occurrence of a boundary based on the difference in brightness on the wall surface 92.

  FIG. 6 is a diagram illustrating an illumination device 10a including a light guide plate 12a of a comparative example. The first surface 14 on the wall surface side of the light guide plate 12a includes a first prism group 20 having a plurality of first prisms 22 as in the embodiment. On the other hand, the entire surface of the second surface 15 opposite to the wall surface of the light guide plate 12 is a flat portion where the second prism is not formed. In the comparative example, other configurations are the same as those of the embodiment of FIGS.

  FIG. 7 is a diagram illustrating the wall surface 92 irradiated with the leakage light of the illumination device 10a of the comparative example. A portion other than the black background at both ends in the left-right direction in FIG. In FIG. 7, the brightest part is shown by the plain part, the dark part is shown by the rough (low density) sand part, and the considerably dark part is shown by the fine (high density) sand part. In FIG. 7, the illuminance of the wall surface 92 is shown on the left side. As shown in FIG. 7, according to the comparative example, the boundary based on the difference in brightness on the wall surface 92 is conspicuous. In particular, the difference in brightness between the bright part and the considerably darker part on the lower side clearly appears at a predetermined height position H that is the boundary between the lower region α and the upper region β. Next, the reason will be described.

  FIG. 8 is a diagram illustrating a light distribution curve of the illumination device 10a including the light guide plate 12a of the comparative example. In FIG. 8, the left side is the first surface 14 side on the wall surface side where leaked light is emitted, the right side is the second surface 15 side opposite to the wall surface, and the lower side is the floor surface side. The right side of FIG. 8 shows the control light emitted from the second surface 15. As shown in FIG. 8, when the horizontal direction is 180 ° and the vertical upper direction is 90 °, the leaked light is irradiated to a relatively wide range in the height direction by the first prism 22. In FIG. 8, the angle range α1 on the lower side and the angle range β1 on the higher side are divided between 135 ° and 180 °. The angle ranges α1 and β1 correspond to the lower region α and the upper region β in FIG.

  FIG. 9 is a diagram illustrating luminous intensity characteristics in the range of 135 ° to 180 ° in the light distribution curve of the leaked light in FIG. 8 in the illumination device 10a including the light guide plate 12a of the comparative example. As shown in FIG. 9, the luminous intensity of the leaked light changes rapidly at the boundary between the angle range α1 and the angle range β1, which is a predetermined angle between 135 ° and 180 °, that is, the side where the angle becomes lower, that is, the upper side. As it goes to, the brightness increases rapidly. Thereby, as shown in FIG. 7, it is considered that the difference in brightness on the wall surface 92 appears clearly. The reason for this is further analyzed.

  FIG. 10 is an image diagram illustrating the relationship between the luminance and the height position on the wall surface 92 due to leaked light in the comparative example. FIG. 11 shows the luminance at the wall surface 92 due to the lower leakage light reflected from the surface of the first prism 22 after being refracted and transmitted by the first prism 22 of the first surface 14 in the comparative example. It is an image figure which shows the relationship with a height position.

  As shown in FIG. 10, in the lower region α of the wall surface 92, the luminance hardly changes regardless of the height. On the other hand, the higher the upper region β of the wall surface 92, the higher the luminance, and the luminance changes rapidly at the boundary between the lower region α and the upper region β. This first reason is that, in the comparative example, the relatively upper space on the first surface 14 side is on the incident surface 13 side of the first prism 22 as in the light indicated by the solid line arrow in the embodiment shown in FIG. The light is irradiated by the upper leakage light that is transmitted without being reflected by the first prism 22 while being refracted on the surface. The upper leakage light irradiates the upper region β of the wall surface 92, and the higher the luminance, the higher the luminance. Further, the second reason is that the relatively lower space on the first surface 14 side is on the incident surface 13 side of the first prism 22 as in the light indicated by the one-dot chain arrow in the embodiment shown in FIG. After being refracted by the surface, the light is irradiated by the lower leakage light reflected by the surface of the first prism 22 on the output end face 16 side. This lower leakage light irradiates the lower region α of the wall surface 92. As shown in FIG. 11, it is known that the luminance of the lower leakage light rapidly decreases near the boundary between the lower region α and the upper region β. Thereby, in the comparative example, the brightness changes sharply at the predetermined height position as shown in FIG. 10, so that a difference in brightness appears clearly at the predetermined height position H of the wall surface 92 as shown in FIG. it is conceivable that.

  According to the embodiment of FIGS. 1 to 4, the plurality of second prisms 32 are arranged on the second surface 15 of the light guide plate 12, and the base angle of each second prism 32 is 35 ° or less. As a result, as shown in FIG. 4, the light reflected by the second prism 32 is emitted from the first surface 14, and a large amount of light is irradiated near the predetermined height position corresponding to the boundary where the difference in brightness is large in the comparative example. It becomes easy to be done. For this reason, generation | occurrence | production of the boundary based on the difference of the brightness by the leaked light can be suppressed.

  The results of calculations performed to confirm the effect of restricting the skirt angle θ of the second prism 32 in the embodiment will be described with reference to FIGS. 12 and 13. FIG. 12 is a diagram illustrating the lighting device 10 used for calculation for effect confirmation of the embodiment. In this calculation, the first to fifth light guide plates, which are five types of light guide plates, were used. Hereinafter, the first to fourth light guide plates are referred to as first to fourth light guide plates 12. Among the five types of light guide plates, in the first to fourth light guide plates 12, the first surface 14 and the second surface 15 are respectively in the first prism group 20 as in the embodiment shown in FIGS. And the second prism group 30. Further, the first prism 22 constituting the first prism group 20 was formed as a conical recess having an opening end with a diameter of 250 μm. In the first to fourth light guide plates 12, the base angle of the first prism 22 is fixed at 50 °.

  On the other hand, in the first to fourth light guide plates 12, the second prism 32 constituting the second prism group 30 is also a conical concave portion having an opening end diameter of 250 μm, like the first prism 22. The base angle of the second prism 32 was changed at 50 °, 40 °, 30 °, and 25 °. In the case of the first prism group 20, the coverage that is the area ratio of the first prism group 20 to the first surface 14 is 40%, and the coverage that is the area ratio of the second prism group 30 to the second surface 15 is the first prism group 20. Smaller than 10%.

  Among the five types of light guide plates, in the fifth light guide plate, the first surface 14 includes the first prism group 20 as in the light guide plate 12a of the comparative example shown in FIG. The configuration does not include the second prism group. Further, the first prism 22 constituting the first prism group 20 was formed as a conical recess having an opening end with a diameter of 250 μm. In the fifth light guide plate, the base angle of the first prism 22 is set to 50 °.

  Then, in each of the five types of lighting devices 10 each incorporating the five types of light guide plates, leakage emitted from the first surface 14 with the first surface 14 facing the wall surface 92 as shown in FIG. The wall surface 92 was irradiated with light, and the relationship between the brightness and the height position was obtained. At this time, the distance d (FIG. 1) from the light guide plate 12 to the wall surface 92 was 600 mm.

  FIG. 13 is a diagram showing the result of the above calculation, and is a diagram showing the relationship between the change in the skirt angle of the second prism 32 on the second surface 15 and the luminance and height position on the wall surface 92. In FIG. 13, the curves shown as 25 °, 30 °, 40 °, and 50 ° indicate the base angle θ of the second prism 32 in the illumination device 10 using each of the first to fourth light guide plates 12. ing. In addition, the curve indicated as “no prism” indicates an illumination device using the fifth light guide plate.

  From the calculation result of FIG. 13, when the second surface 15 is the fifth light guide plate not including the second prism group, the luminance of the wall surface 92 changes abruptly at the position indicated by P in FIG. You can see clearly. On the other hand, in the case where the second surface 15 is the first to fourth light guide plates 12 including the second prism group 30, the brightness of the wall surface 92 is generally higher than when the fifth light guide plate is used. . At this time, in the first and second light guide plates 12 in which the base angle θ of the second prism 32 was 25 ° and 30 °, there was no position where the luminance changed rapidly. On the other hand, in the third and fourth light guide plates 12 in which the skirt angle θ of the second prism 32 is 40 ° and 50 °, it can be seen that a valley of luminance occurs at the positions indicated by Q1 and Q2 in FIG. It was. Thereby, in this embodiment, when the base angle θ of the second prism 32 is set to 30 ° or less, it has been confirmed that the generation of the boundary based on the difference in brightness due to the leaked light can be suppressed.

[Another example of the embodiment]
FIG. 14 is a view corresponding to FIG. 4 in a light guide plate 12b according to another example of the embodiment. FIG. 15 is a diagram showing light reflected by the second surface 15 in FIG. In the light guide plate 12 of the present example, in each of the plurality of second prisms 32a constituting the second prism group 30a on the second surface 15, the incident surface 13 (see FIG. 2) side (the lower side in FIGS. 14 and 15). This surface is a diffusion surface 34 that diffuses light. The diffusion surface 34 is a surface including a plurality of irregularities. For example, a plurality of recesses may be formed in the form of dots on the diffusion surface 34, or a plurality of recesses may be formed side by side so that the cross-section is corrugated. For example, the surface roughness (for example, the maximum height Rz) of the diffusing surface 34 may be larger than the surface roughness of the flat portion 15 a of the second surface 15. On the other hand, in each of the second prisms 32a, the surface on the emission end face 16 (see FIG. 2) side (the upper side in FIGS. 14 and 15) is a smooth mirror surface 36 with no irregularities.

  According to the configuration of this example, the light reflected from the flat portion 15a of the second surface 15 and then totally reflected by the second prism 32a from the inside of the light guide plate 12b as shown by the broken arrow in FIG. The flat surface 15a of the two surfaces 15 is directed toward the first surface 14 (FIGS. 2 and 3) (left side in FIG. 15) at many different inclination angles. Thereby, according to this example, as can be seen from a comparison between FIG. 15 and FIG. 4, a large amount of reflected light on the second surface 15 can be scattered. For this reason, generation | occurrence | production of the boundary based on the light and dark by the leakage light radiate | emitted from the 1st surface 14 can be suppressed more. In this example, the other configurations and operations are the same as those in FIGS.

  In the configurations of FIGS. 14 and 15, the entire second prism 32 a including the surface on the emission end face 16 (FIG. 2) side (upper side of FIGS. 14 and 15) may be a diffusing surface. In the configurations of FIGS. 14 and 15, at least a part of the second prisms 32a constituting the second prism group 30a may have at least the surface on the incident surface 13 side as the diffusion surface 34.

  FIG. 16 is a diagram illustrating an illumination device 10b including a light guide plate 12c according to another example of the embodiment. In the light guide plate 12c of this example, the area ratio of the first prism group 20 to the first surface 14 is closer to the incident surface 13 than the emission end surface 16 side (upper side in FIG. 16), which is the side away from the incident surface 13. (Lower side in FIG. 16). In the light guide plate 12, the amount of light is larger on the incident surface 13 side (lower side in FIG. 16) than on the emission end surface 16 side (upper side in FIG. 16), but the light from the first prism 22 on the first surface 14 is reflected. More reflective parts can be provided on the exit end face 16 side than on the entrance face 13 side. Thereby, since the luminance distribution of the first surface 14 when viewed from the first surface 14 side can be made closer to the uniform, the appearance of the light guide plate 12 can be improved.

  Further, in this example, the area ratio of the second prism group 30 to the second surface 15 is larger on the side closer to the incident surface 13 than on the emission end surface 16 side. As a result, when the area ratio of the first prism group 20 on the first surface 14 is smaller on the incident surface 13 side than on the emission end surface 16 side, the light reflected on the incident surface 13 side of the second surface 15 is reduced. Most of the light can be emitted from the first surface 14 through the flat portion 14 a other than the first prism 22 of the first surface 14. For this reason, as shown in the comparative example shown in FIG. Irradiation can be performed. Therefore, the occurrence of the above-described light / dark boundary can be more efficiently suppressed. In this example, other configurations and operations are the same as those in FIGS.

  In the configuration of this example, each second prism 32 can also be configured as shown in FIGS. Further, in the configuration of this example, the area ratio of the second prism group 30 to the second surface 15 may be substantially the same on the incident surface 13 side and the emission end surface 16 side, as in the configurations of FIGS. Good. In the case of this configuration as well, the luminance distribution of the first surface 14 when viewed from the first surface 14 side can be made closer to the uniform as in the configuration of FIG.

[Reference example]
FIG. 17 is a diagram illustrating an illumination device 10c including a light guide plate 12c of a reference example. 18A is an enlarged view of a portion E in FIG. 17, and FIG. 18B is an enlarged view of a portion F in FIG. 18A. In the light guide plate 12c of this example, unlike the configuration of FIGS. 1 to 4, the second surface 15 does not include the second prism group and is a flat surface as a whole. On the other hand, as shown in FIG. 18, in each of the plurality of first prisms 22a constituting the first prism group 20 on the first surface 14, the surface far from the incident surface 13 (the upper side in FIG. 18A) is The diffusion surface 24 has a plurality of irregularities and diffuses light. On the other hand, in each first prism 22a, the surface closer to the incident surface 13 (the lower side in FIG. 18A) is a smooth mirror surface 26 with no irregularities. For example, a plurality of concave portions may be formed on the diffusing surface 24 in the form of dots, or a plurality of concave portions may be formed side by side so that the cross section has a waveform. For example, the surface roughness (for example, the maximum height Rz) of the diffusion surface 24 may be larger than the surface roughness of the flat portion 14a of the first surface 14.

  According to the configuration of this example, the light that has passed through the mirror surface 26 on the incident surface 13 side of the first prism 22 from the inside of the light guide plate 12d as indicated by the one-dot chain line arrow in FIG. The light is reflected while diffusing in many different directions on the diffusing surface 24 on the emission end face 16 side. Thereby, it is possible to suppress the occurrence of a light / dark boundary of leaked light generated in a configuration in which the second prism 15 is not provided on the second surface 15 as in the comparative example illustrated in FIG. 6. In the comparative example, as described above, a light / dark boundary of leaked light is likely to occur based on the light that is transmitted through the incident surface side of the first prism and then reflected on the output end surface side of the first prism. In this example, this boundary can be made clear.

  Further, according to the configuration of the present example, the incident surface 13 side of the first prism 22a is the mirror surface 26, so that the light is accurately reflected from the inside of the light guide plate 12 by the mirror surface 26 as indicated by the broken arrow in FIG. Can be made. As a result, the direction of the light emitted from the second surface 15 can be changed more accurately by changing the base angle on the incident surface 13 side of the first prism 22a.

  Further, in order to suppress the occurrence of the above-described boundary, it is not necessary to make the entire surface of the first prism 22a disposed on the first surface 14 a diffusion surface for diffusing light, and the flat portion 14a of the first surface 14 is used. Can be efficiently emitted from the second surface 15. Thereby, the spread of the light toward the opposite side to the leaked light can be suppressed. In this example, the other configurations and operations are the same as those in FIGS.

  17 and 18, only a part of the first prisms 22a constituting the first prism group 20 has a surface far from the incident surface 13 as a diffusion surface 24 as shown in FIG. A surface closer to the surface 13 may be a mirror surface 26.

  FIG. 19 is a view corresponding to FIG. 18B in a light guide plate 12e of another example of the reference example. In the light guide plate 12e of this example, the first prism 22b constituting the first prism group 20 on the first surface 14 has a polygonal cross section on the diffusion surface 24a far from the incident surface 13 (FIG. 17). A plurality of recesses are formed side by side. Further, the plurality of concave portions of the diffusion surface 24a have a shape without undercut. Specifically, when the diffusion surface 24a of the first prism 22b is viewed from a direction parallel to the direction orthogonal to the flat portion 14a (FIG. 17) of the first surface 14, the concave portion of the diffusion surface 24a is As shown by the arrows in FIG. 19, the inner surface is not hidden when viewed from any direction. Other configurations and operations in this example are the same as those in FIGS. 17 and 18.

  FIG. 20 is a diagram corresponding to FIG. 18B in a light guide plate 12f of another example of the reference example. In the light guide plate 12f of this example, in the first prism 22c constituting the first prism group 20 on the first surface 14, the cross section has a curved waveform on the diffusion surface 24b far from the incident surface 13 (FIG. 17). A plurality of recesses are formed side by side. Further, the plurality of concave portions of the diffusion surface 24b have a shape without undercut. Other configurations and operations in this example are the same as the configurations in FIGS. 17 and 18 or 19.

  In the above description, the lighting device that irradiates the wall surface with the light guide plate standing upright has been described. However, each of the above embodiments is applied to the lighting device that is configured using the light guide plate arranged in a substantially horizontal direction and is mounted near the ceiling. Any of the form and the light guide plate of each reference example may be used. In this case, when the ceiling surface is irradiated with leakage light by the lighting device, it is possible to suppress the occurrence of a boundary based on the difference in brightness on the ceiling surface.

  10, 10a, 10b Illumination device, 12, 12a-12f Illumination light guide plate (light guide plate), 13 entrance surface, 14 first surface, 14a flat portion, 15 second surface, 15a flat portion, 16 exit end surface, 20th 1 prism group, 22, 22a to 22c first prism, 24, 24a, 24b diffusing surface, 26 mirror surface, 30 second prism group, 32, 32a second prism, 34 diffusing surface, 36 mirror surface, 50 instrument body 60 light source, 90 floors, 92 walls.

Claims (5)

An incident surface on which light is incident;
A first surface that is substantially perpendicular to the incident surface, includes a first prism group having a plurality of first prisms, and from which leakage light is emitted;
A second surface including a second prism group which is a surface substantially perpendicular to the incident surface and faces the first surface and includes a plurality of second prisms,
The coverage that is the area ratio of the second prism group to the second surface is smaller than the coverage that is the area ratio of the first prism group to the first surface,
The illuminating light guide plate, wherein the base angle of each of the plurality of second prisms constituting the second prism group is 35 ° or less. The light guide plate for illumination according to claim 1,
In at least some of the plurality of second prisms constituting the second prism group, at least a surface on the incident surface side is a diffusion surface for diffusing light. In the light guide plate for illumination according to claim 1 or 2,
The light guide plate for illumination, wherein the area ratio of the first prism group to the first surface is smaller on the side closer to the incident surface than on the side away from the incident surface. The light guide plate for illumination according to claim 3,
The light guide plate for illumination, wherein the area ratio of the second prism group to the second surface is larger on the side closer to the incident surface than on the side away from the incident surface. The light guide plate for illumination according to any one of claims 1 to 4,
A light source for irradiating light from the incident surface of the illumination light guide plate into the illumination light guide plate;
Lighting device.

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