JP6105398B2 - Light guide plate and instrument - Google Patents

Description

  The present invention relates to a light guide plate disposed behind a dial plate of an automobile instrument or the like, and an instrument provided with the light guide plate.

  As this type of light guide plate, there is known a light guide plate having a circular arc shape in front view that guides light from a light source incident from an end face in the circumferential direction so that the dial is illuminated from the back. Patent Document 1 describes a light guide plate in which radial grooves are formed on the back surface of a light guide plate having an arc shape when viewed from the front, and arc-shaped grooves are formed on the back surface or the front surface.

  The action of the radial grooves formed on the back surface of the conventional light guide plate described in Patent Document 1 will be described with reference to FIGS. 14 (a) and 14 (b).

  As shown in FIG. 14A, of the light L201 and L202 that travel while reflecting inside the light guide plate 210 by the front surface 210A and the back surface 210B of the light guide plate 210, the incident angle relative to the wall 212a of the radial groove 212. A part of the light L201 is transmitted through the wall 212a of the radial groove 212 by decreasing the incident angle, and the other part of the light L202 is transmitted by the wall 212a of the radial groove 212 by increasing the incident angle. Reflected.

  As shown in FIG. 14B, the light L201 transmitted through the wall 212a of the radial groove 212 is diffused and reflected by the diffuse reflector 6 disposed behind the light guide plate 210, and is again transmitted through the light guide plate 210. Proceed toward the dial 2. On the other hand, the light L202 reflected by the wall 212a of the radial groove 212 proceeds toward the dial plate 2 with strong light.

  At this time, the light L201 transmitted through the wall 212a of the radial groove 212 is diffusely reflected by the diffuse reflection plate 6 and uniformly illuminates the dial 2 over a wide range, so that it is directly reflected by the wall 212a of the radial groove 212. Weaker than the emitted light L202. For this reason, luminance spots due to the radial grooves 212 are generated.

JP 2011-40367 A

  As described above, when the radial groove 212 is formed on the back surface of the light guide plate 210, light directly reflected by the wall 212a of the radial groove 212 is likely to be generated, and thus a luminance spot due to the radial groove 212 may occur. it was high.

  The present invention has been made in view of the above-described circumstances, and an object thereof is to provide a light guide plate capable of eliminating luminance unevenness as much as possible and illuminating the dial from behind with uniform light, and the light guide plate. Is to provide an instrument.

The above object of the present invention can be achieved by the following constitution.
(1) Between the dial on the front and the diffuse reflector disposed on the back of the dial, the dial and the diffuse reflector are respectively disposed via an air layer, and are arranged in the circumferential direction. A light-transmitting light guide plate having a circular arc shape in front view that guides light from a light source incident from an end surface so as to illuminate the dial from the back;
The front surface facing the dial has a plurality of arc-shaped grooves extending in the circumferential direction of the arc shape and spaced apart in the radial direction of the arc shape, and the diffuse reflector has A light guide plate having a large number of radial ridges extending radially along the radial direction of the arc shape and spaced apart in the circumferential direction of the arc shape on the back surface facing each other.

  (2) The light guide plate according to (1), wherein the interval between the radial ridges is set so as to gradually decrease as the distance from the end face on which light from the light source is incident. .

(3) The light guide plate according to (1) or (2) is disposed between the dial plate and the diffuse reflector, with an air layer interposed between the dial plate and the diffuse reflector, respectively. Instrument,
A measuring instrument, wherein a recess for securing the air layer on the back surface of the light guide plate is provided on at least one of the back surface of the light guide plate and the front surface of the diffuse reflection plate facing each other.

(4) The light guide plate according to the above (1) or (2) is disposed between the dial plate and the diffuse reflector, with an air layer interposed between the dial plate and the diffuse reflector, respectively. Instrument,
An instrument, wherein a spacer for securing the air layer on the back surface of the light guide plate is sandwiched between the back surface of the light guide plate and the front surface of the diffuse reflection plate facing each other.

  According to the light guide plate having the configuration (1), the arc-shaped groove is formed on the surface, and the radial ridges are formed on the back surface instead of the radial grooves, so that a lot of light can be guided along the arc shape. The incident angle of a large amount of light incident on the radial ridge wall can be reduced, and as much light as possible can be transmitted through the radial ridge wall and directed toward the diffuse reflector. That is, it is possible to reduce the light directly reflected by the walls of the radial ridges, to eliminate luminance spots as much as possible, and to illuminate the dial from behind with uniform light.

  According to the light guide plate having the configuration (2), the distance of light transmission decreases as the distance from the light source increases, but the density of the radial ridges increases as the distance from the light source increases, so that the arc-shaped light guide The distribution of the illumination light quantity in the circumferential direction can be made uniform.

  According to the instrument having the configuration of (3), the air layer having a constant interval is secured between the light guide plate and the diffuse reflector by the concave portion provided on at least one of the opposing surfaces of the light guide plate and the diffuse reflector. And the presence of the air layer can widen the diffuse reflection range of light on the diffuse reflector. Therefore, the illumination range for the dial plate by the light transmitted through the light guide plate can be expanded, which can contribute to the improvement of luminance spots.

  According to the instrument configured as described in (4) above, a spacer is sandwiched between the light guide plate and the diffuse reflector, so that an air layer of a constant interval can be secured between the light guide plate and the diffuse reflector, Due to the presence of the air layer, the diffuse reflection range of light on the diffuse reflector can be expanded. Therefore, the illumination range for the dial plate by the light transmitted through the light guide plate can be expanded, which can contribute to the improvement of luminance spots.

  According to the present invention, the luminance unevenness can be eliminated as much as possible, and the dial can be illuminated from behind with uniform light.

  The present invention has been briefly described above. Further, the details of the present invention will be further clarified by reading through a mode for carrying out the invention described below (hereinafter referred to as “embodiment”) with reference to the accompanying drawings. .

FIG. 1 is a front view of an instrument incorporating a light guide plate according to an embodiment of the present invention. FIG. 2 is a cross-sectional view taken along the line II-II in FIG. 3A and 3B are a front view and a rear view of the light guide plate shown in FIG. 4 is a perspective view schematically showing an enlarged part of the light guide plate shown in FIG. FIG. 5 is an operation explanatory view of the arc-shaped groove on the front surface of the light guide plate shown in FIG. 3, and FIG. 5 (a) is an explanatory view showing how light traveling inside the light guide plate travels along the arc-shaped groove. 5 (b) is an explanatory view of an incident angle when the light of FIG. 5 (a) is incident on the radial ridge on the back surface of the light guide plate, and FIG. 5 (c) is a diagram of the light of FIG. It is explanatory drawing which shows a mode that it permeate | transmits a wall. FIG. 6 is an operation explanatory view in the case of the comparative example without the arc-shaped groove on the front surface of the light guide plate shown in FIG. 3, and FIG. 6 (a) is an explanatory view showing the path of light traveling inside the light guide plate. 6B is an explanatory view of an incident angle when the light of FIG. 6A is incident on the radial protrusion on the back surface of the light guide plate, and FIG. 6C is a part of the light of FIG. It is explanatory drawing which shows a mode that it reflects by the wall of a stripe | line. FIG. 7 is a diagram showing a simulation result for demonstrating the light path of FIG. FIG. 8 is an operation explanatory view of the radial ridges on the back surface of the light guide plate shown in FIG. 3, and FIG. 8 (a) is a diagram showing a state in which the light traveling inside the light guide plate is transmitted through the walls of the radial ridges; FIG. 8B is a diagram showing a state in which the light of FIG. 8A is diffusely reflected by the diffuse reflector, passes through the light guide plate again, and proceeds toward the dial. FIG. 9A is a schematic explanatory view showing the diffusion of light when an air layer is secured on the back surface of the light guide plate, and FIG. 9B is the light when no air layer is secured on the back surface of the light guide plate. It is a schematic explanatory drawing which shows spreading | diffusion. FIG. 10A to FIG. 10C are schematic cross-sectional views respectively showing configuration examples for securing an air layer on the back surface of the light guide plate. FIG. 11A to FIG. 11C are diagrams showing variations in the cross-sectional shape of the arc-shaped groove. 12 (a) to 12 (c) are diagrams showing variations in the cross-sectional shape of the radial ridges. 13A and 13B are configuration diagrams of a light guide plate according to another embodiment of the present invention. FIG. 13A is a perspective view seen from the front side, and FIG. 13B is a perspective view seen from the back side. FIG. 14 is a diagram for explaining the operation of the radial grooves formed on the back surface of the conventional light guide plate. FIG. 14A shows a part of the light traveling through the light guide plate through the walls of the radial ridges. The figure which shows a mode that a part of other light is reflected by the wall of a radial convex strip, FIG.14 (b) is a figure which shows a mode that the transmitted light and reflected light of Fig.14 (a) advance toward a dial plate. It is.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1 is a front view of a meter incorporating the light guide plate of the embodiment, FIG. 2 is a sectional view taken along the line II-II in FIG. 1, and FIGS. 3A and 3B are a front view and a rear view of the light guide plate. FIG. 4 is a perspective view schematically showing an enlarged part of the light guide plate.

  As shown in FIGS. 1 and 2, the instrument 1 is an instrument (also referred to as a display device) provided on an instrument panel of an automobile, and includes a dial 2 provided with a design such as a warning and a scale, and a dial 2, a pointer 3 provided to rotate in front of the circuit board 2, a casing 4, a circuit board 5 provided behind the dial 2, and a guide provided behind the dial 2 and in front of the circuit board 5. Light plate 10, diffuse reflector 6 provided behind circuit board 5 behind light guide plate 10, light guide plate light source 8 such as LED and warning light source 9 mounted on circuit board 5, dial plate 2 and a front glass 7 covering the front face of 2.

  The light guide plate 10 is provided between the dial plate 2 and the diffuse reflection plate 6 provided behind the dial plate 2, and the front surface (surface) 10 </ b> A of the light guide plate 10 is connected to the dial plate via the air layer K. The back surface (back surface) 10B of the light guide plate 10 faces the front surface of the diffuse reflector 6 via the air layer K. The front surface of the diffuse reflector 6 is formed, for example, as a white smooth surface so that light can be diffusely reflected forward. For example, a part of the wall surface formed integrally with the casing 4 is used for the diffuse reflector 6.

  The light guide plate 10 is made of a light transmissive material such as an acrylic resin, and is formed as a smooth plane in which the front surface 10A and the back surface 10B are parallel to each other. Further, as shown in FIG. 3, the light guide plate 10 is formed in an arc shape when viewed from the front along the scale provided on the dial 2, and the outer peripheral surface 14 and the inner peripheral surface 15 are smooth arc surfaces. It is configured.

  Further, both ends in the circumferential direction of the light guide plate 10 are bent toward the circuit board 5, and end surfaces of the bent portions are light incident ends 18 into which light from the light source 8 for the light guide plate is incident. The light guide plate 10 has a function of guiding the light from the light source 8 incident on the light incident end 18 to illuminate the scale provided on the dial 2 from behind.

  As shown in FIGS. 3A and 4, the front surface 10A of the light guide plate 10 facing the dial 2 (see FIG. 2) extends along the circumferential direction of the arc shape of the light guide plate 10 and is guided. A large number of arc-shaped grooves 11 are formed at regular intervals in the radial direction of the arc shape of the optical plate 10. As shown in FIGS. 3B and 4, the back surface 10 </ b> B facing the diffuse reflector 6 (see FIG. 2) extends radially along the radial direction of the arc shape of the light guide plate 10. A large number of radial ridges 12 are formed at intervals in the circumferential direction of the arc shape of the light guide plate 10. As shown in FIG. 4, the arc-shaped grooves 11 and the radial ridges 12 have a relationship of intersecting substantially vertically with a distance therebetween.

  As shown in FIG. 4, the arc-shaped groove 11 on the front surface 10 </ b> A of the light guide plate 10 has a cross section having both side walls 11 a perpendicular to the front surface 10 </ b> A of the light guide plate 10 and bottom walls 11 b parallel to the front surface 10 </ b> A of the light guide plate 10. It is formed in a square shape. Further, as shown in FIG. 4, the radial ridges 12 on the back surface 10 </ b> B of the light guide plate 10 are formed in a triangular cross section having two inclined side walls 12 a that obliquely intersect the back surface 10 </ b> B of the light guide plate 10. Further, as shown in FIG. 3 (b), the interval at which the radial ridges 12 are arranged is set so as to gradually decrease as the distance from the light incident end 18 (in the direction indicated by the arrow X), Accordingly, the radial ridges 12 are formed with higher density as the distance from the light incident end 18 increases (the closer to the center in the circumferential direction).

Next, the operation of the light guide plate 10 having the above configuration will be described.
FIG. 5 is an operation explanatory diagram of the arc-shaped groove on the front surface of the light guide plate, and FIG. 6 is an operation explanatory diagram in the case of the comparative example having no arc-shaped groove on the front surface of the light guide plate. In these FIGS. 5 and 6, only one arcuate groove 11 and radial ridge 12 are shown as representatives.

  First, the path of light when there is no arc-shaped groove 11 [see FIG. 5A] on the front surface 10A of the light guide plate 10 will be described with reference to FIG. 6A is an explanatory diagram showing paths of the lights L11, L12, and L13 traveling inside the light guide plate 10, and FIG. 6B is a back view of the light guide plate 10 where the lights L11, L12, and L13 of FIG. FIG. 6C is an explanatory view showing a state in which a part of the light in FIG. 6B is reflected by the side wall 12 a of the radial ridge 12. is there.

  As shown in FIG. 6A, the light L11 that travels near the outer peripheral surface 14 among the light L11, L12, and L13 incident from the light source 8 into the light guide plate 10 is an outer peripheral surface that is curved in an arc shape. 14 is incident and reflected at an incident angle θ1 at a position close to the front side of the light traveling direction (lower side in FIG. 6A). The light L12 traveling through the intermediate position between the outer peripheral surface 14 and the inner peripheral surface 15 is incident on the outer peripheral surface 14 curved in an arc shape at a position farther than the light L11 and is reflected. Further, the light L13 traveling near the inner peripheral surface 15 is incident on the outer peripheral surface 14 curved in an arc shape at an incident angle θ1 at a position farther than the lights L11 and L12 and is reflected.

  Therefore, the incident angles with respect to the outer peripheral surface 14 become smaller as the light beams L12 and L13 travel closer to the inner peripheral surface 15 (θ1> θ2> θ3). As a result, the light L11 traveling near the outer peripheral surface 14 is reflected by the outer peripheral surface 14 and travels in the light guide plate 10 substantially along the arc shape. However, the light L12 and L13 traveling on the inner peripheral side are guided. The light is reflected from the outer peripheral surface 14 of the optical plate 10 toward the inner peripheral side of the light guide plate 10 with a small reflection angle, and is difficult to travel along the arc shape of the light guide plate 10.

  Therefore, as shown in FIG. 6B, the light L11 is incident at an angle α1 (corresponding to a small incident angle) substantially perpendicular to the radial ridges 12, but the lights L12 and L13 are radially convex. It does not enter at an angle close to perpendicular to the strip 12 (that is, α2 and α3 are greatly deviated from 90 °, and the incident angle with respect to the radial convex strip 12 is increased). Therefore, although the light that is perpendicularly incident on the radial ridge 12 is transmitted through the side wall 12a of the radial ridge 12, as shown in FIG. 6C, the light L12 and L13 that are incident at an angle (incident angle). Large light) is reflected inside the light guide plate 10 by the side wall 12a of the radial ridge 12. In this way, when the light L12 and L13 directly reflected by the wall 12a of the radial ridge 12 without being transmitted toward the diffusive reflecting plate 6 travels toward the dial 2, it leads to generation of luminance spots. When it does not advance toward the dial 2, it becomes easy to lead to a decrease in illumination efficiency, and there is a need for improvement.

  Next, the light path when the arc-shaped groove 11 is provided on the front surface 10A of the light guide plate 10 will be described with reference to FIG. 5A is an explanatory diagram showing paths of the light L11, L12, and L13 traveling inside the light guide plate 10, and FIG. 5B is a back view of the light guide plate 10 where the lights L11, L12, and L13 of FIG. FIG. 5C is an explanatory view showing a state in which a part of the light in FIG. 5B is transmitted through the wall 12a of the radial ridge 12. .

  As shown in FIG. 5A, the light L11 that travels near the outer peripheral surface 14 among the light L11, L12, and L13 incident from the light source 8 into the light guide plate 10 is an outer peripheral surface curved in an arc shape. 14 is incident and reflected at an incident angle θ1 at a position close to the front side of the light traveling direction (lower side in FIG. 5A). Further, the light L12 traveling through the intermediate position between the outer peripheral surface 14 and the inner peripheral surface 15 is incident on the side wall 11a of the arc-shaped groove 11 provided on the front surface 10A of the light guide plate 10 at an incident angle θ2, and is reflected. Further, the light L13 traveling near the inner peripheral surface 15 is incident on the side wall 11a of the arc-shaped groove 11 provided on the front surface 10A of the light guide plate 10 at an incident angle θ3 and is reflected.

  As described above, the lights L12 and L13 are reflected by the arc-shaped groove 11 instead of the outer peripheral surface 14 of the light guide plate 10 as in the comparative example of FIG. θ1, the incident angle θ2 of the light L12 with respect to the arc-shaped groove 11 and the incident angle θ3 of the light L13 with respect to the arc-shaped groove 11 can be made substantially equal (θ1≈θ2≈θ3). Therefore, the lights L11, L12, and L13 reflected by the outer peripheral surface 14 and the arc-shaped groove 11 can be made substantially parallel, and any of the lights L11, L12, and L13 can be guided substantially along the arc shape. It becomes like this.

  It can be confirmed from the simulation result shown in FIG. 7 that the light incident from the light incident end 18 can be guided substantially along the arc shape by providing the arc-shaped groove 11 as described above.

  Therefore, as shown in FIG. 5B, any of the lights L11, L12, and L13 can be incident substantially perpendicularly to the radial ridges 12 (α1≈α2≈α3≈90 °), and FIG. As shown to c), many light L11, L12, L13 can permeate | transmit the side wall 12a of the radial protruding item | line 12, and can inject into the diffuse reflection board 6. FIG.

  FIG. 8 is an operation explanatory view of the radial ridges 12 on the back surface 10 </ b> B of the light guide plate 10, and FIG. 8A shows how the light L <b> 1 traveling inside the light guide plate 10 passes through the side walls 12 a of the radial ridges 12. FIG. 8B is a diagram illustrating a state in which the light L <b> 1 in FIG. 8A is diffusely reflected by the diffusive reflecting plate 6, passes through the light guide plate 10 again, and proceeds toward the dial 2.

  In this light guide plate 10, the radial ridges 12 are formed on the back surface 10 </ b> B of the light guide plate 10 instead of the radial grooves as in the prior art. Therefore, as shown in FIG. 8A, the side walls of the radial ridges 12 are formed. The incident angle of a lot of light L1 incident on 12a can be reduced (can be made incident at an angle close to vertical), and as much light as possible is transmitted through the side wall 12a of the radial ridge 12, It can be directed to the diffuse reflector 6. That is, since the light directly reflected by the side wall 12a of the radial ridge 12 can be reduced and the light diffusely reflected by the diffuse reflector 6 can be increased as shown in FIG. As much as possible, the dial 2 can be illuminated from behind with uniform light L1.

  Further, in this light guide plate 10, the amount of light transmission decreases as the distance from the light source 8 decreases. However, as the distance from the light source 8 increases so as to compensate for this, the density of the radial ridges 12 increases. The distribution of the illumination light quantity in the circumferential direction of the optical plate 10 can be made uniform.

  Further, in the meter 1 using the light guide plate 10, an air layer K is secured between the light guide plate 10 and the diffuse reflector 6 because the radial ridges 12 are provided on the back surface 10 </ b> B of the light guide plate 10. Therefore, the diffuse reflection range of light at the diffuse reflector 6 can be expanded. This point will be described with reference to FIG. FIG. 9A is a schematic explanatory view showing the diffusion of light when an air layer is secured on the back surface of the light guide plate, and FIG. 9B is the light when no air layer is secured on the back surface of the light guide plate. It is a schematic explanatory drawing which shows spreading | diffusion.

  As shown in FIG. 9B, when an air layer is not secured between the light guide plate 10 and the diffuse reflector 6, the diffuse reflection range of light on the diffuse reflector 6 becomes narrow. Therefore, there is a tendency that the illumination range H <b> 2 for the dial plate by the light transmitted through the light guide plate 10 is narrowed. On the other hand, as shown in FIG. 9A, when the air layer K is secured between the light guide plate 10 and the diffuse reflector 6, the diffuse reflection range of light on the diffuse reflector 6 is widened. be able to. Therefore, the illumination range H1 with respect to the dial plate by the light transmitted through the light guide plate 10 can be widened, which can contribute to the improvement of luminance spots.

  Next, a configuration example for securing the air layer K on the back surface 10B side of the light guide plate 10 will be described with reference to FIGS. 10 (a) to 10 (c).

  In the example of FIG. 10A, a recess 25 is formed on the back surface 10B of the light guide plate 10, and the air layer K is secured between the back surface 10B of the light guide plate 10 and the front surface of the diffuse reflector 6 by the recess 25. ing. In this case, the radial ridges 12 (see FIG. 8) on the back surface 10 </ b> B of the light guide plate 10 are formed on the inner bottom surface of the recess 25.

  In the example of FIG. 10B, a concave portion 25 is formed on the front surface of the diffuse reflector 6 constituted by a part of the wall of the casing 4, and the concave portion 25 forms the back surface 10 </ b> B of the light guide plate 10 and the diffuse reflector 6. An air layer K is secured between the front surface. In this case, the radial ridges 12 (see FIG. 8) on the back surface 10B of the light guide plate 10 are formed in a range where at least the recesses 25 are formed.

  In the example of FIGS. 10A and 10B, the concave portion 25 is formed on one of the back surface 10 </ b> B of the light guide plate 10 and the front surface of the diffuse reflector 6 facing each other. The air layer K may be secured by forming recesses on both the back surface 10B of the light source and the front surface of the diffuse reflector 6.

  Further, in the example of FIG. 10C, the spacer 26 is sandwiched between the back surface 10 </ b> B of the light guide plate 10 and the front surface of the diffuse reflector 6, so that the back surface 10 </ b> B of the light guide plate 10 and the front surface of the diffuse reflector 6 are An air layer K is secured between them.

  As in the configuration examples shown in FIGS. 10A to 10C, the light guide plate 10 and the diffuse reflection plate 6 are provided with a recess 25, or the spacer 26 is sandwiched between the light guide plate 10 and the diffuse reflection plate 6. As a result, it is possible to secure an air layer K having a constant interval between the light guide plate 10 and the diffuse reflector 6. Then, the presence of the air layer K can widen the diffuse reflection range of the light at the diffuse reflection plate 6, thereby widening the illumination range for the dial 2 by the light transmitted through the light guide plate 10. Thus, it becomes possible to contribute to the improvement of luminance spots.

  In addition, this invention is not limited to embodiment mentioned above, A deformation | transformation, improvement, etc. are possible suitably. In addition, the material, shape, dimensions, number, arrangement location, and the like of each component in the above-described embodiment are arbitrary and are not limited as long as the present invention can be achieved.

  FIG. 11A to FIG. 11C are diagrams showing variations in the cross-sectional shape of the arc-shaped groove.

  In the light guide plate 10 of the above embodiment, as shown in FIG. 11A, the case where the arc-shaped groove 11 having a square cross section is formed on the front surface 10A of the light guide plate 10 is shown, but as shown in FIG. In this way, the arc-shaped groove 11B having a triangular cross section may be formed, or as shown in FIG. 11C, the arc-shaped groove 11C having a semicircular cross section or a semielliptical cross section may be formed.

  12 (a) to 12 (c) are diagrams showing variations in the cross-sectional shape of the radial ridges.

  In the light guide plate 10 of the above embodiment, as shown in FIG. 12A, the case where the radial protrusions 12 having a triangular cross section are formed on the back surface 10B of the light guide plate 10 is shown. Thus, the radial ridge 12B having a trapezoidal cross section may be formed, or the radial ridge 12C having a semicircular cross section or a semielliptical cross section may be formed as shown in FIG.

  In the above embodiment, the light guide plate 10 having the light incident ends 18 at both ends in the circumferential direction is shown. However, the present invention can also be applied to a light guide plate having a light incident end at only one end in the circumferential direction. . FIGS. 13A and 13B are configuration diagrams of a light guide plate of another embodiment having a light incident end only at one end, FIG. 13A is a perspective view seen from the front side, and FIG. 13B is a perspective view seen from the rear side. FIG.

  As shown in FIG. 13 (a), the light guide plate 110 has a circular arc shape when viewed from the front, and is provided with an arc-shaped groove 11 on the front surface 10A, and on the back surface 10B as shown in FIG. 13 (b). Radial ridges 12 are provided. In this case, since the light incident end 18 is provided only at one end in the circumferential direction, the distance between the radial ridges 12 becomes farther from the light incident end 18 (goes in the direction indicated by the arrow X). The radial ridges 12 are formed with a higher density as the distance from the light incident end 18 increases (the closer to the end farther from the light incident end 18).

  Here, the features of the embodiments of the light guide plate and the meter according to the present invention described above are briefly summarized and listed in the following [1] to [4], respectively.

[1] Between the front dial (2) and the diffuse reflector (6) disposed on the back of the dial (2), the dial (2) and the diffuse reflector (6), respectively. Between the light source (8) and the light source (8) incident from the end face (18) in the circumferential direction guides the dial (2) from the back so as to illuminate the dial (2) from the back. An arc-shaped light-transmitting light guide plate (10, 110),
A number of arc-shaped grooves (11) extending along the circumferential direction of the arc shape and spaced in the radial direction of the arc shape on the front surface (10A) facing the dial (2) And a large number of the back surface (10B) facing the diffuse reflector (6) extending radially along the radial direction of the arc shape and spaced apart in the circumferential direction of the arc shape A light guide plate (10, 110) having a radial ridge (12).

  [2] The distance between the radial ridges (12) formed is set so as to gradually decrease as the distance from the end face (18) on which light from the light source (8) is incident is increased. The light guide plate (10, 110) according to claim 1.

[3] The light guide plate (10, 110) according to the above [1] or [2] is provided between the dial plate (2) and the diffuse reflector (6). A meter (1) disposed between the diffuse reflector (6) via an air layer (K),
The air layer on the back surface (10B) of the light guide plate (10, 110) on at least one of the back surface (10B) of the light guide plate (10, 110) and the front surface of the diffuse reflector (6) facing each other. A meter (1) characterized in that a recess (25) for securing (K) is provided.

[4] The light guide plate (10, 110) according to the above [1] or [2] is provided between the dial plate (2) and the diffuse reflector (6). A meter (1) disposed between the diffuse reflector (6) via an air layer (K),
The air layer (K) on the back surface (10B) of the light guide plate (10, 110) between the back surface (10B) of the light guide plate (10, 110) facing each other and the front surface of the diffuse reflector (6). ) (1), wherein a spacer (26) is secured.

2 Dial 6 Diffuse reflector 8 LED (light source)
DESCRIPTION OF SYMBOLS 10 Light guide plate 10A Front surface 10B Rear surface 11 Arc-shaped groove 12 Radial convex strip 18 Light incident end (end surface in the circumferential direction where light is incident)
25 concave portion 26 spacer 110 light guide plate K air layer

Claims (4)

Between the front dial and the diffuse reflector arranged on the back of the dial, the dial and the diffuse reflector are respectively arranged via an air layer and incident from the end face in the circumferential direction. A light-transmitting light guide plate having a circular arc shape in front view that guides the light from the light source so as to illuminate the dial from the back,
The front surface facing the dial has a plurality of arc-shaped grooves extending in the circumferential direction of the arc shape and spaced apart in the radial direction of the arc shape, and the diffuse reflector has A light guide plate having a large number of radial ridges extending radially along the radial direction of the arc shape and spaced apart in the circumferential direction of the arc shape on the back surface facing each other.   2. The light guide plate according to claim 1, wherein an interval at which the radial ridges are formed is set so as to gradually decrease as the distance from an end face on which light from the light source is incident. The light guide plate according to claim 1 or 2, wherein the light guide plate is an instrument that is disposed between the dial plate and the diffuse reflector, with an air layer interposed between the dial plate and the diffuse reflector. ,
A measuring instrument, wherein a recess for securing the air layer on the back surface of the light guide plate is provided on at least one of the back surface of the light guide plate and the front surface of the diffuse reflection plate facing each other. The light guide plate according to claim 1 or 2, wherein the light guide plate is an instrument that is disposed between the dial plate and the diffuse reflector, with an air layer interposed between the dial plate and the diffuse reflector. ,
An instrument, wherein a spacer for securing the air layer on the back surface of the light guide plate is sandwiched between the back surface of the light guide plate and the front surface of the diffuse reflection plate facing each other.

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