JP5919017B2 - Light guiding unit - Google Patents

Description

  The present invention relates to a light guide unit that uses a light guide plate and is capable of surface light emission on an exit surface of the light guide plate.

  In a backlight using a light emitting diode (LED), the LED is arranged in a simple manner because the directivity of the LED is high, so that the LED can be seen through in a dotted manner, and uneven brightness tends to occur. It was necessary to increase the distance. There are also products in which a light guide unit for diffusion is arranged between the LED and the face plate to disperse the light emitted from the LED's point light emission, but even in that case, a certain distance between the LED and the face plate is required. I was trying.

The structure in which the light incident part from the LED is arranged at the center bottom part of the light guide plate and the funnel-shaped depression is provided on the center upper surface of the light guide plate is a low loss radially toward the LED light entering the light guide plate. It is generally used as a method of propagation in In order to emit surface light, it is necessary to emit light propagating radially inside the light guide plate to the output surface on the front side. Usually, white printing is applied to the bottom surface, or uneven shapes are provided and reflected at that portion. The light is scattered and emitted to the emission surface side.
By changing the concentration distribution of light diffusion inside the light guide plate according to the distance from the light source, etc., or changing the depth, shape, density, etc. of the uneven part that scatters light toward the exit surface, A more uniform luminance distribution can be obtained (see, for example, Patent Document 1).

JP 2007-109554 A

  However, in white printing, loss due to absorption on the printing surface occurs, and in the method of providing an uneven shape, reflected and scattered light is emitted not only from the exit surface side but also from the bottom surface side, so the efficiency of utilization of light incident on the light guide plate (Rate emitted from the emission surface) decreases. For light emitted from the bottom surface side, a reflector or the like may be installed on the bottom surface side, but the cost increases.

  This invention is made | formed in view of the said situation, and makes it a subject to provide the light guide unit which can be surface-emitted in the output surface of a light guide plate using a light guide plate.

To solve the above problems, the present invention includes a light incident portion for arranging the light source, an exit surface for emitting light, a first reflection for reflecting the light incident from the light incident portion to the emission surface A light guide plate, and the light incident portion is provided on a bottom surface portion of the light guide plate on a side opposite to the emission surface, and the light guide plate is formed on the light incident portion of the bottom surface portion. The first reflective portion is provided around the first reflective portion, and the distance between the first reflective portion and the surface including the incident surface increases as the distance from the light source increases along a direction parallel to the incident surface of the light incident portion. A plurality of first reflecting surfaces provided stepwise at predetermined intervals, and each of the plurality of first reflecting surfaces is separated from the light source along a direction parallel to the incident surface. The plurality of first reflecting surfaces have a shape of a slope that increases a distance from a surface including an incident surface, and the plurality of first reflecting surfaces are external air. Has become the interface, the light guide plate, at least both sides of the plane between the plurality of first reflecting surface and the plurality of first reflecting surface, V-shaped cross section of the first reflecting part a plurality of reflective grooves surface is a reflective surface, wherein the emitting surface along the bottom surface portion is opposite, have a light incident portion radially centered, the light incident portion, the light source A conical depression is formed in the opposite central part, and there are a plurality of reflection grooves that are reflecting surfaces on both sides of the V-shaped cross section radially around the conical depression. The funnel-like shape in which the distance between the exit surface and the surface including the entrance surface increases continuously with distance from the light source along a direction parallel to the entrance surface with the position facing the light incident portion as a center. A second reflection surface having a shape of the second reflection surface, the second reflection surface reflecting the light incident from the light incident portion The exit surface has a funnel-shaped depression at the center facing the light source, and the second reflecting surface in the second reflecting portion is located at the second position from the position facing the light source. The second reflecting surface is an interface between the light guide plate and the outside air. A light guide unit is provided.

Wherein for a plurality of first reflecting surface, said plurality of reflective grooves opening angle of both side surfaces of the V-shaped cross section around the groove bottom is in the range of 80 to 100 ° of the front Symbol bottom portion It can also be set as the structure which formed.
A configuration in which the plurality of reflection grooves having an opening angle of 90 ° on both side surfaces of a V-shaped cross-section with the groove bottom as the center are formed with respect to the plurality of first reflection surfaces in the bottom surface portion. It can also be.

The plurality of opening angles of both side surfaces of a V-shaped cross section centered on the groove bottom with respect to a surface between the plurality of first reflecting surfaces of the bottom surface portion is in a range of 60 to 90 °. It is also possible to adopt a configuration in which a reflection groove is formed .
The plurality of reflection grooves formed around the conical depression in the light incident part have a configuration in which an opening angle of both side surfaces of a V-shaped cross section centering on the groove bottom is in a range of 60 to 90 °. It can also be.

  According to the present invention, in at least a part of the first reflection part that reflects light toward the emission surface, the plurality of reflection grooves whose both side surfaces of the V-shaped cross section are reflection surfaces are opposite to the emission surface. By arranging them radially along the bottom surface, which is the side, the incident angle with respect to the reflecting surface of the light propagated inside the light guide plate is increased, and the incident angle is greater than the critical angle. Since the ratio satisfying the reflection condition increases, the utilization efficiency of light incident on the light guide plate (the ratio of light emitted from the light exit surface) can be improved.

It is sectional drawing which shows an example of the light guide unit of this invention. It is a perspective view which shows the bottom face part side of the light guide unit shown in FIG. It is a perspective view which shows the output surface side of the light guide unit shown in FIG. (A) is a perspective view schematically showing a state of reflection in a plurality of reflection grooves, (b) is a projection view of (a) along the longitudinal direction of the plurality of reflection grooves, and (c) is θv. It is sectional drawing explaining the reflection direction when = 90 degree. (A) is explanatory drawing of the incident angle with respect to the reflective surface in a reflective groove, (b) is a projection figure of (a) along the longitudinal direction of a reflective groove, (c) is perpendicular | vertical to virtual plane P '. It is a projection figure of (a) from a direction. It is sectional drawing which shows the mode of the main reflection and output in the inside of the light guide unit shown in FIG. It is sectional drawing which expands and shows the conical hollow of a light-incidence part. It is a top view which shows the example of the other shape of a light guide unit. It is a top view which shows the example of the other shape of a light guide unit. (A) And (b) is sectional drawing explaining the reflective direction when (theta) v <90 degrees.

The present invention will be described below based on preferred embodiments with reference to the drawings.
1 to 3 show a light guide unit of the present invention. The light guide unit 10 includes a light incident portion 13 in which the light source 12 is disposed, an emission surface 14 that emits light, and a first reflection portion that reflects light incident from the light incident portion 13 toward the emission surface 14. 16 is provided.
In the case of the illustrated example, the first reflecting portion 16 is provided on the bottom surface portion 15 on the opposite side of the light guide plate 11 from the emission surface 14. The light incident part 13 is provided at the center of the bottom surface part 15 of the light guide plate 11, and the first reflecting part 16 is provided around the light incident part 13.

  As shown in FIGS. 1 and 2, the light guide plate 11 has a plurality of reflection grooves G in which both side surfaces P of the V-shaped cross section are reflection surfaces. These reflection grooves G are formed radially along the bottom surface portion 15 with the light incident portion 13 as the center. The light guide plate 11 is made of a material transparent to the light of the light source 12, and the reflection groove G is in contact with outside air (air) on the reflection surface P. The reflection surface P of the reflection groove G has a property of reflecting the light L due to a refractive index difference (refractive index ratio) when the light L is about to enter the surrounding air from the light guide plate 11.

As shown in FIG. 6, the light L propagating through the light guide plate 11 is emitted from the emission surface 14 by reflection at the reflection surfaces 17 a to 17 e of the first reflection unit 16. At this time, when the incident angle with respect to the reflecting surfaces 17a to 17e satisfies the total reflection condition (the incident angle is equal to or larger than the critical angle), the ratio of the amount of light to be reflected is preferably increased. If the total reflection condition is not satisfied because the incident angle is less than the critical angle, the amount of light transmitted through the bottom surface portion 15 without being reflected increases. For this reason, it is desirable for the incident angle with respect to the reflective surfaces 17a-17e to be as large as possible.
Here, the incident angle is an angle with respect to the normal line of the interface, and the critical angle is an incident angle when the refraction angle with respect to the normal line of the interface is 90 °.

  In the case of the light guide unit 10 of this embodiment, a plurality of reflection grooves G formed radially with the light incident portion 13 as the center are formed close to each other as shown in FIG. The light L incident on the reflection surface P on the inclined surface of the reflection groove G is reflected twice between the adjacent reflection grooves G as shown in FIG. 4 and reflected to the emission surface 14 side (upper side in FIG. 4). . The direction in which the reflected light propagates is the same angle and direction as when reflected by the bottom surface portion 15 without the reflection groove G, but the reflection surface of the light L that has propagated through the light guide plate 11 (V-groove-like shape). The incident angle with respect to the side surface P) of the reflection groove G becomes larger, and the ratio of satisfying the total reflection condition that the incident angle is equal to or larger than the critical angle increases. Thereby, the utilization efficiency of light incident on the light guide plate (rate emitted from the emission surface) can be improved. In this specification, “radial” may be radial when the light guide plate 11 is viewed in a plane perpendicular to the incident surface 13a.

The length of the reflection groove G is such that the reflection groove G is less likely to be interrupted between the point reflected by the point R ₁ on the reflection surface P and the point reflected by the point R ₂ on the adjacent reflection surface P. It is preferable to secure a certain length or more in the radial direction centering on 13. In order to increase the probability of reflection twice by two adjacent reflecting surfaces P, it is preferable that a plurality of reflecting grooves G are formed without gaps as shown in FIG. The width W and depth D of the reflection groove G can be appropriately designed between the dimension of the light guide plate 11 and the wavelength of the light L, and can be selected from about 1 μm to about 10 mm, for example.

  Here, when the reflection groove G is provided as compared with the case where the reflection groove G is not provided on the bottom surface portion 15, the incident angle θ when the light L is reflected by the side surface P of the V-shaped reflection groove G is as follows. The increase will be described with reference to FIG. In FIG. 5, when the light guide plate 11 is viewed in plan (see FIG. 5C), the direction in which the light L propagates (direction indicated by AOB) matches the longitudinal direction of the reflection groove G. Indicates the case.

In FIG. 5, the incident angle θ with respect to the reflecting surface P in the reflecting groove G is defined as an angle formed by the direction in which the light L propagates with the normal line N of the reflecting surface P. Here, the traveling direction of the light L may have a certain extent, but here, a typical direction is indicated by a white arrow.
When the light L travels radially around the light incident portion 13, as described above, the reflection groove G is formed radially along the bottom surface portion 15 around the light incident portion 13. The longitudinal direction of the reflection groove G is a direction along the direction in which the light L propagates. FIG. 5A shows a situation where the light L attempts to be reflected at an arbitrary point O on the reflecting surface P. A line AB in FIG. 5A indicates a straight line that is parallel to the longitudinal direction of the reflection groove G and includes the point O. Point A indicates the side closer to the light incident part 13, and point B indicates the side farther from the light incident part 13.

The incident angle θ ′ with respect to the reflecting surface P ′ when the reflecting groove G is not provided on the bottom surface portion 15 is defined as an angle formed by the direction in which the light L propagates with the normal line N ′ of the reflecting surface P ′. Here, the reflection surface P ′ indicates a virtual surface that is parallel to the bottom surface portion 15 when the reflection groove G is not provided and includes the point O.
When the light L travels radially around the light incident portion 13, there is a probability that the direction in which the light L propagates is included in a plane perpendicular to the reflective surface P ′ when the reflective groove G is not provided. highest.

  Thus, when the propagation direction of the light L is included in a plane perpendicular to the reflecting surface P ′ (see FIGS. 5B and 5C), the incident angle θ ′ with respect to the reflecting surface P ′ is minimum. become. On the other hand, when the reflection surface P in the reflection groove G is inclined at the inclination angle α with respect to the reflection surface P ′, the incident angle θ with respect to the reflection surface P becomes larger than the incident angle θ ′. Specifically, the relationship between the incident angle θ and the incident angle θ ′ is expressed by the following formula (1).

cos θ = cos α · cos θ ′ (1)

  The inclination angle α can be defined as an angle formed by the surface P and the surface P ′ or an angle formed by the normal line N and the normal line N ′, and an equal angle is given by any definition. Therefore, if α is not 0 °, 0 ≦ cos α <1, so the relationship expressed by the following mathematical formula (2) is established.

0 ≦ cos θ <cos θ ′ ≦ 1 ⇒ 0 ° ≦ θ ′ <θ ≦ 90 ° (2)

  That is, if the incident angle is defined within the range of 0 to 90 °, θ ′ <θ, and the incident angle θ with respect to the reflecting surface P of the reflecting groove G is equal to the incident angle θ with respect to the reflecting surface P ′ when the reflecting groove G is not provided. It is shown to be greater than '.

  The effect of providing the radial reflection grooves G on the bottom surface portion 15, particularly the reflection surface, is significant when the direction in which the light L propagates in the plan view matches the longitudinal direction of the reflection grooves G. In this case, the incident angle can be increased in the same manner not only when the light L is incident on the left reflecting surface P in FIG. 5B but also when the light L is incident on the right reflecting surface P. If the deviation between the propagation direction of the light L and the longitudinal direction of the reflection groove G is large, the effect is reduced. If the deviation is too large, the incident angle may not necessarily be increased.

  The reflection groove G is a surface in which the direction of propagation of the light L inside the light guide plate 11 is a relatively shallow angle with respect to the surface (a surface having a relatively large incident angle defined as an angle with respect to the normal direction of the surface). Therefore, it is preferably provided on the surface on which the reflection of the light L is intended. The reflection groove G is preferably formed at least on the reflection surfaces 17a to 17e. 1 and 2, the reference numeral 17g is given to the reflection groove G formed in the reflection surfaces 17a to 17e. Further, the reflection groove G may be formed on the surfaces (propagation surfaces) 18a to 18d between the first reflection surfaces and the incident surface 13a. Reference numeral 18g is given to the reflection groove G formed on the propagation surfaces 18a to 18d. Further, reference numeral 13g is given to the reflection groove G formed on the incident surface 13a. In the illustrated example, the reflection groove G is not formed on the cylindrical surface 20 around the light incident portion 13. In addition, in the bottom face part 15, as for the 1st reflective surfaces 17a-17e, the inclination angle with respect to the incident surface 13a is suitable for the reflection to the output surface 14 (it is although it does not specifically limit, for example, 30-60 degrees). The propagation surfaces 18a to 18d have an angle suitable for propagating from the light incident part 13 to the outer peripheral side with an inclination angle with respect to the incident surface 13a (not particularly limited, for example, 0 to 20 °). Have.

  When the reflection grooves G (17g and 18g) are formed in the reflection surfaces 17a, 17b, 17c, 17d, and 17e and the propagation surfaces 18a, 18b, 18c, and 18d, the reflection grooves 17g on the reflection surface and the reflection grooves on the propagation surface. 18g may be connected and the reflective groove may be divided for every surface. The number of the reflection grooves, the groove width, the groove depth, the interval between the grooves, and the like may be different between the inner peripheral side and the outer peripheral side. For example, the number of reflection grooves on the inner peripheral side (number per central angle centered on the light incident portion 13) is decreased to increase the number on the outer peripheral side, or the width and depth of the reflection grooves on the inner peripheral side are decreased. Thus, it can be made larger on the outer peripheral side. The parameters relating to these grooves can be changed at a location where the orientation of the surface of the bottom surface portion 15 changes (for example, the boundary between the reflecting surfaces 17a to 17e and the propagation surfaces 18a to 18d), and can be changed within the same surface. You can also.

  The opening angle θv (see FIG. 4) of both side surfaces P of the V-shaped cross section centered on the groove bottom V of the plurality of reflection grooves G is not limited to about 90 °, and can be set as appropriate. The inclination angle α shown in FIG. 5 has a relationship of θv = 180 ° −2α with respect to the opening angle θv. Therefore, if 0 <θv <180 ° and 0 <α <90 °, the incident angle θ when the reflective groove G is provided is made larger than the incident angle θ ′ when the reflective groove G is not provided. Has an effect. As θv is closer to 0 ° (α is closer to 90 °), the effect of increasing the incident angle θ becomes more prominent, but on the other hand, the groove width of the reflection groove G is narrower and the reflection groove G is formed without a gap. The number required for this is increased. For this reason, considering the improvement of the light utilization efficiency and the workability of the reflection groove, the preferable range of the opening angle θv can be exemplified by a range of 60 to 120 ° or 80 to 100 °, for example.

Of the bottom surface portion 15, the reflection groove 17g formed in the first reflection surfaces 17a, 17b, 17c, 17d, and 17e preferably has an opening angle θv in the range of 80 to 100 °. In particular, when the opening angle θv of the reflection groove 17g provided on the first reflection surface is 90 °, two cross-sectional views perpendicular to the longitudinal direction of the reflection groove G shown in FIGS. When reflected twice by the reflecting surface P, it is reflected at the same angle as the incident direction (parallel and opposite direction), which is preferable. For example, as shown in FIG. 10B, the angle formed by the incident direction L ₀ and the normal line N ₁ of the reflection surface P ₁ on the cross section (cross section perpendicular to the longitudinal direction of the reflection groove G) is φ. Then, the angle z formed by L ₀ and L _{2 on} the cross section is equal to z = 180 ° −2θv, and if θv = 90 °, z = 0 °.
Note that z = 180 ° −2θv. In FIG. 10B, the sum of the inner angles of the triangle formed by the center of the angle z and the points R ₁ and R ₂ is 180 °, and the size of the inner angle with the point R ₁ as the vertex is 2φ, the size of the interior angles whose vertices R ₂ is 180 ° -2x. As described later, since x = 90 ° + φ−θv, z = 180 ° −2φ− (180 ° −2x) = 2x−2φ = 180 ° −2θv.

The reflection groove 18g formed in the surfaces (propagation surfaces) 18a, 18b, 18c, and 18d between the first reflection surfaces in the bottom surface portion 15 preferably has an opening angle θv in the range of 60 to 90 °.
When a plurality of reflection grooves 13g are formed around the conical depression 13b in the light incident portion 13, the opening angle θv of both side surfaces P of the V-shaped cross section around the groove bottom V is 60 to 90 °. A range is preferable.

The reflective groove G (13 g, 17 g, 18 g) when the opening angle θv of less than 90 °, even considering the specular reflection only (scattering is not considered), as shown in FIG. 10, the reflecting surface _{P 1} Reflected at the point R ₁ , reflected at the point R ₂ of the adjacent reflecting surface P ₂ , and further reflected on the reflecting surface P ₁ , etc., and reflected by the one reflecting groove G three times, and further four times or more. It is possible to do. In FIG. 10, the two reflecting surfaces are distinguished from P ₁ and P ₂ .
For example, when the angle formed between the incident direction L ₀ and the normal line N ₁ of the reflection surface P _{1 on} the cross section in a cross-sectional view perpendicular to the longitudinal direction of the reflection groove G shown in FIG. The magnitude is less than 90 ° by its definition. In the figure, the incident direction is L ₀ , the first reflection position is R ₁ , the first reflection direction is L ₁ , the second reflection position is R ₂ , the second reflection direction is L ₂ , and the third reflection position. Is R ₃ , and the third reflection direction is L ₃ .
In the discussion based on FIG. 10, in regular reflection, the direction of reflected light is within a plane (incident surface) including the direction of incident light and the normal of the reflecting surface, and the incident angle and the reflecting angle are equal. Is used. The cross section perpendicular to the longitudinal direction of the reflection groove G does not necessarily coincide with the incident surface, but is perpendicular to the two reflection surfaces of the reflection groove G. Each reflecting surface is projected in a straight line in a sectional view, and the normal line of the reflecting surface is perpendicular to the line in the sectional view of the reflecting surface. Therefore, in such a cross-sectional view, the angle formed by the incident direction and the normal of the reflecting surface (not necessarily coincident with the incident angle) is the angle formed by the reflecting direction and the normal of the reflecting surface (not necessarily coincident with the reflecting angle). equal.

If the opening angle θv is less than 90 °, the angle φ can be larger than the opening angle θv as shown in FIG. 10A, and in this case, the angle formed by L ₁ and P ₂ on the cross section. Since x exceeds 90 °, after reflection at the point R ₂ on the reflection surface P ₂ , the third reflection can occur at the point R ₃ on the reflection surface P ₁ . In this case, the point R ₃ is located farther from the groove bottom V than the point R ₁ . From the geometrical consideration, in FIG. 10A, the angle y formed by L ₀ and P ₁ on the cross section is equal to 90 ° −φ, and x + y + θv is equal to 180 °, which is the sum of the inner angles of the triangle. The angle x is equal to 90 ° + φ−θv. Therefore, if φ> θv, x> 90 °.
If the opening angle θv is less than 90 °, even if the angle φ is smaller than the opening angle θv, as shown in FIG. 10B, if x is larger than θv, L ₂ is the reflecting surface P _1. Is reflected at the point R ₂ on the reflecting surface P ₂ , and then the third reflection can be caused at the point R ₃ on the reflecting surface P ₁ . Point R ₃ is located closer to the groove bottom V of the point R _1, Depending on the relationship of the depth of the position and the groove of the point R _1, may not cause reflections third. From the geometrical consideration, also in FIG. 10B, the angle y formed on the cross section by L ₀ and P ₁ is equal to 90 ° −φ, and x + y + θv is equal to 180 °, which is the sum of the inner angles of the triangle. Therefore, the angle x is equal to 90 ° + φ−θv. Therefore, if φ <θv, x <90 °. Since the reflection from L ₁ to L ₂ is a specular reflection at point R ₂ , the angle formed by L ₂ and P ₂ on the cross section is equal to the angle x formed by L ₁ and P ₂ on the cross section. . Therefore, considering the condition that x> θv when x = 90 ° + φ−θv, x> θv is satisfied when φ> 2θv−90 °.
Although not shown in particular, when φ = θv, x = 90 °. That is, since L ₁ is incident perpendicularly to the reflecting surface P ₂ , if it is further regularly reflected at the point R ₂ , it returns to the point R ₁ again, and the third reflection can be caused on the reflecting surface P ₁ .

As shown in FIG. 6, the emission surface 14 preferably has a funnel-shaped depression 14 b in the central portion facing the light source 12. The light incident on the light guide plate 11 from the light source 12 is reflected by the refractive index difference between the light guide plate 11 and the external air in the recess 14b. The opening angle θ ₄ of the tip of the funnel-shaped recess 14b is such that the light L reflected by the reflection surface 19a formed on the inner surface of the recess 14b is as large as possible in the first reflecting surfaces 17a, 17b, 17c, It is preferable to set so as to propagate toward 17d and 17e.

The light incident part 13 preferably has a conical depression 13 b in the central part facing the light source 12. Accordingly, as shown in FIG. 7, when the light L is incident on the light guide plate 11 from the outside on the side surface of the depression 13 b, the refraction angle θ ₁ becomes larger than the incident angle θ ₂ due to the refraction of the light. The angular distribution of light incident on the light guide plate 11 is widened, the proportion of light propagating relatively perpendicular to the incident surface 13a is relatively small, and the proportion of components having a small angle with respect to the incident surface 13a is increased. Around the conical depression 13b in the light incident portion 13, a plurality of reflecting grooves 13g having reflecting surfaces on both side surfaces P of the V-shaped cross section are formed in a conical shape, similar to the above-described radial reflecting groove G. It can also be provided radially with the recess 13b as the center.

With respect to the incident surface of the light incident portion from the LED, there is a decrease in light incident efficiency due to Fresnel reflection on a simple flat surface. In addition, in the configuration in which the funnel-shaped depression is provided on the center upper surface of the light guide plate, when the inclination angle of the depression is insufficient, the incident angle with respect to the funnel surface becomes smaller than the critical angle out of the light hitting the funnel surface incident from the light source The part increases. Since the total reflection condition (incident angle is not less than the critical angle) is not satisfied, the amount of light that is transmitted without being reflected by the funnel surface increases. By combining the conical depression 13b with the funnel-shaped depression 14b, the light refracted by the conical depression 13b has little light hitting the vicinity of the apex of the funnel-like depression 14b, and more light hitting the skirt portion. Unintentional leakage light from the vicinity of the apex of the depression 14b can be reduced.
The opening angle θ ₃ at the tip of the conical recess 13 b is set so that light that hits the inner surface of the recess 13 b from the light source 12 is dispersed and propagated toward the funnel-shaped recess 14 b or the first reflecting portion 16. It is preferable to set.

  The material constituting the light guide plate 11 is not particularly limited as long as the light from the light source 12 can be sufficiently transmitted. For example, an organic material such as acrylic resin or polycarbonate resin, multi-component glass, quartz glass, or the like is used. A material transparent to the light of the light source 12 such as an inorganic material is suitable. The color of the light guide plate may be colorless and transparent, or may have a predetermined color.

  Although it does not specifically limit as the light source 12, LED (light emitting diode), a light bulb, various lamps, etc. are mentioned. Moreover, it is also possible to use LED of variable colors such as RGB (Red-Green-Blue). In this case, the luminescent color changes with time, and it becomes possible to obtain a dynamic expression with an arbitrary color, which is preferable because the variety of expression is increased.

The difference in refractive index between the material constituting the light guide plate 11 and the outside air is a total reflection condition expressed by sin θ _c = n ₂ / n ₁ (where θ _c is a critical angle, and n ₁ is the light guide plate 11). In consideration of the refractive index of the material to be used, n ₂ is the refractive index of air (approximately 1), and n ₁ > n ₂ ), the reflective surface formed at the interface should be set to obtain a suitable reflectance. Is preferred. The outer surface of the light guide plate 11 may be exposed to the outside air, or a cover may be provided so that the air is enclosed in a cavity or the like inside the light guide unit. Further, a gap or the like communicating with the outside air can be provided in the cover or the like.

  The light guide plate 11 of the present embodiment has a first reflecting portion 16 around the light incident portion 13 in the bottom surface portion 15. As shown in FIGS. 1 and 6, the distance between the first reflecting portion 16 and the surface including the incident surface 13 a increases as the distance from the light source 12 increases in the direction parallel to the incident surface 13 a of the light incident portion 13. As described above, a plurality of first reflecting surfaces 17a, 17b, 17c, 17d, and 17e provided in a staircase pattern at a predetermined interval are provided. Each of the plurality of first reflecting surfaces 17a, 17b, 17c, 17d, and 17e has a slope shape in which the distance from the surface including the incident surface 13a increases as the distance from the light source 12 increases in the direction parallel to the incident surface 13a. have.

The number of the plurality of first reflecting surfaces in the first reflecting portion 16 is five concentrically in the example shown in FIGS. 1 to 3, but is not particularly limited. If the number of light sources 12 is two or more, the number of first reflection surfaces can be set to a desired number.
The “distance from the surface including the incident surface” means the distance from the surface including the incident surface 13a to the reflecting portion (if the incident surface 13a is a sufficiently wide plane, the distance from the incident surface 13a to the reflecting portion). Is equal to the distance) in the direction perpendicular to the incident surface 13a. When the incident surface 13a is a curved surface, a plane in contact with the vicinity of the incident surface 13a facing the light source 12 can be used as a reference.

These first reflecting surfaces 17a, 17b, 17c, 17d, and 17e are arranged at intervals from each other along a direction parallel to the incident surface 13a. In a plan view perpendicular to the incident surface, the first reflecting surfaces 17a, 17b, 17c, 17d, and 17e are formed concentrically around the installation position of the light source 12 (see FIG. 2). In addition, the space | interval of several 1st reflective surfaces in a 1st reflection part can be set suitably, and does not need to be equal intervals.
In the case of this embodiment, the plurality of first reflecting surfaces 17a, 17b, 17c, 17d, and 17e in the first reflecting portion 16 are interfaces with external air, and no special reflecting film is particularly provided. However, a desired reflectance can be obtained.

In the case of the first reflecting portion 16 shown in FIG. 2, a plurality of first reflecting surfaces 17a, 17b, 17c, 17d, and 17e and the surfaces 18a, 18b, 18c, and 18d therebetween are connected to each other to form a stepped cross section. Have It is sufficient that at least the first reflecting surfaces 17a, 17b, 17c, 17d, and 17e of the first reflecting portion 16 can reflect light.
The surfaces 18a, 18b, 18c, and 18d between the first reflecting surfaces are parallel to the incident surface 13a in the example shown in FIG. 1, but are inclined, curved, or bent with respect to the surface parallel to the incident surface 13a. And so on. From the viewpoint of suppressing the thickness of the light guide plate 11, it is preferable that the surfaces 18a, 18b, 18c, and 18d between the first reflecting surfaces are parallel to the incident surface 13a as shown in FIG.

  The exit surface 14 has a funnel-like shape in which the distance from the surface including the incident surface 13a increases continuously as the distance from the light source 12 increases along the direction parallel to the incident surface 13a with the position facing the light incident portion 13 as the center. By having the depression 14b, the second reflection part 19 that reflects the light incident from the light incident part 13 is provided.

  The second reflecting portion 19 includes a second reflecting surface 19a having a shape in which the distance from the surface including the incident surface 13a continuously increases as the distance from the light source 12 increases in the direction parallel to the incident surface 13a. In the case of this embodiment, the second reflecting surface 19a of the second reflecting portion 19 is continuous with a cross-section bent or curved from the position facing the light source 12 to the outer peripheral edge of the second reflecting portion 19. , One reflective surface.

Note that it is not an essential matter of the present invention that the entire second reflecting portion 19 is the second reflecting surface 19a, and (i) a portion that is not a reflecting surface, or (ii) a light reflecting surface 12 that is not a reflecting surface. Since a portion having a shape in which the distance from the surface including the incident surface 13a does not increase (constant or decreases) in a direction away from the second reflecting portion 19 is locally present within the range of the second reflecting portion 19, the second reflecting portion There may be a plurality of second reflecting surfaces 19.
In the case of this embodiment, the second reflecting surface 19a of the second reflecting portion 19 is an interface with the external air, and a desired reflectance can be obtained without providing a separate reflecting film. it can.

  In the light guide unit 10 of this embodiment, the first reflecting portion 16 located on the incident surface 13a side and the second reflecting portion 19 located on the emitting surface 14 side have the above-described shape, so that the light guide plate 11, the light is reflected and scattered mainly as shown in FIG.

  Usually, the incident light L incident on the light guide plate 11 from the light source 12 is a beam having a predetermined range of divergence angles and optical power distribution. Of the second reflecting surface 19a of the second reflecting portion 19, the vicinity of the light source 12 is conical (conical in this embodiment), and most of the light L is reflected (preferably totally reflected). Then, the light is reflected in the direction away from the light source 12 along the incident surface 13a. The tip of the second reflecting portion 19 facing the light source 12 may be a flat surface parallel to the incident surface 13a or a rounded curved surface such as a spherical surface.

  As shown in FIG. 6, the light L incident on the light guide plate 11 from the light source 12 through the incident surface 13 a is mainly emitted along the incident surface 13 a by the second reflecting surface 19 a in the second reflecting portion 19. Reflect in the direction away from. The shape of the second reflecting surface 19a in the second reflecting portion 19 is preferably designed so that light is substantially totally reflected according to the position and angle of incidence from the light source 12 to the second reflecting portion 19. Further, near the center of the light guide plate 11, there is also light L <b> 0 emitted from the vicinity of the center of the emission surface 14 without being reflected.

  When the light reflected by the second reflecting surface 19a in the second reflecting portion 19 further enters the plurality of first reflecting surfaces 17a, 17b, 17c, 17d, and 17e in the first reflecting portion 16, mainly, Reflected toward the exit surface 14. Thereby, the light L1, L2, L3, L4, and L5 reflected by the first reflecting surfaces 17a, 17b, 17c, 17d, and 17e are emitted from different positions inside and outside in the radial direction. Although only one side is illustrated in FIG. 2 for symmetry, the outgoing lights L1, L2, L3, L4, and L5 obtained by reflection on the first reflecting surfaces 17a, 17b, 17c, 17d, and 17e are on the left side of FIG. Also occurs. Further, there may be light that is repeatedly reflected between the first reflecting portion 16 and the second reflecting portion 19.

  As a result, the incident light L from the light source 12 can be branched into a plurality of outgoing lights L0, L1, L2, L3, L4, and L5 and emitted from a wide range of the outgoing surface 14 of the light guide plate 11, with uniformity. High planar light emission is possible. Furthermore, although not shown in FIG. 6, light that is scattered or refracted without being regularly reflected by the first reflecting portion 16 or the second reflecting portion 19, light that is reflected at the external interface of the light guide plate 11, or the like. Therefore, the position and direction in which light exits from the exit surface 14 varies.

The outgoing lights L0, L1, L2, L3, L4, and L5 may be refracted when passing through the second reflecting portion 19, that is, when passing through the outgoing face. Therefore, it is preferable to design the cross-sectional shape of the exit surface 14 in consideration of the refraction angle at the exit surface 14.
In the present embodiment, the center of the exit surface 14 is a funnel-shaped depression 14b, but this is a flat surface, a convex surface, a concave surface, etc., and the intensity when the emitted light L0 at the center passes through the exit surface 14 The distribution can be further adjusted.

  The number, position, area, inclination angle, etc. of the plurality of reflecting surfaces can be arbitrarily controlled according to the desired intensity distribution in the plane of the exit surface. Since the exit surface is located opposite to the entrance surface, not only the light reflected by the reflection surface but also the light transmitted without reflection is emitted from the exit surface, and the amount of light exiting from the entrance surface or side surface is extremely reduced. Therefore, the light from the light source 12 can be used efficiently.

  As mentioned above, although this invention has been demonstrated based on suitable embodiment, this invention is not limited to the above-mentioned example, Various modifications are possible in the range which does not deviate from the summary of this invention.

At least one of the plurality of first reflecting surfaces in the first reflecting portion is a convex surface (a shape protruding from the outside of the light guide plate to the inside) or a concave surface (a shape recessed from the inside of the light guide plate to the outside). If there is, there is an effect as a lens, and the emitted light can be diverged or converged. In addition, when at least one of the plurality of first reflecting surfaces in the first reflecting portion has a textured shape (a rough surface such as a satin-like shape or a sand-like shape) made of fine irregularities, the light incident on the reflecting surface is Can be diffused. Therefore, the intensity distribution of the emitted light can be controlled as desired by arbitrarily combining these surface shapes.
The roughening treatment for forming the embossed shape can be carried out by locally applying an embossing process such as sandblasting, etching, or transfer from a mold.

  In FIG. 6, the average outgoing directions of the outgoing lights L0, L1, L2, L3, L4, and L5 are all substantially perpendicular to the incident surface 13a. However, the present invention is particularly limited to this. Is not to be done. The plurality of first reflection surfaces 17a and 17b are arranged such that the average emission direction of the emitted light L0, L1, L2, L3, L4, and L5 is inclined toward the outer circumferential direction as the distance from the light source 12 in the direction along the incident surface 13a is increased. , 17c, 17d, and 17e can be adjusted. In this case, the light emission area can be further increased. On the other hand, the inclination angle of the first reflecting surface can be adjusted so that the average emission direction of the light reflected by the plurality of first reflecting surfaces is inclined toward the center of the light guide plate. It is. Moreover, it is also possible to configure so that the average emission direction of the light reflected by the plurality of first reflecting surfaces is mixed with those inclined toward the outer periphery of the light guide plate and those inclined toward the center. is there.

As the outer shape of the side surface of the light guide plate, various shapes such as a polygon such as a rectangle (square, rectangle) shown in FIG. 8, an ellipse, a semicircle, and a fan shape can be adopted.
The installation position of the light source is not limited to the center of the light guide plate, and the light source can be installed at a position offset from the center. Moreover, as shown in FIG. 9, the light source 12 can also be provided on the side surface (side surface including the diameter) of the semicircular light guide plate 11B.

  A plurality of light sources may be used for one light guide plate. In this case, a radial reflection groove according to the present invention, a first reflection portion having a plurality of first reflection surfaces, a second reflection portion having a second reflection surface, and the like may be provided for each light source.

G ... reflection groove, L ... light, N ... normal, P ... side face, V ... groove bottom, 10 ... light guide unit, 11, 11A, 11B ... light guide plate, 12 ... light source, 13 ... light incident part, 13a ... Incident surface, 13b: conical depression, 13g: reflecting groove on incident surface, 14 ... emitting surface, 14b ... funnel-shaped depression, 15 ... bottom surface portion, 16 ... first reflecting portion, 17a, 17b, 17c, 17d , 17e: first reflection surface, 17g: reflection groove on the reflection surface, 18a, 18b, 18c, 18d ... propagation surface (surface between the reflection surfaces), 18g: reflection groove on the propagation surface, 19 ... second reflection Part, 19a ... 2nd reflective surface.

Claims (5)

Includes a light incident portion for arranging the light source, an exit surface for emitting light, a light guide plate having a first reflecting portion for reflecting the light incident from the light incident portion to the emission surface,
The light incident portion is provided on the bottom surface portion of the light guide plate on the side opposite to the emission surface,
The light guide plate has the first reflecting portion around the light incident portion of the bottom surface portion,
The first reflecting portion is provided in a stepped manner at a predetermined interval so that the distance from the surface including the incident surface increases as the distance from the light source increases in a direction parallel to the incident surface of the light incident portion. Each of the plurality of first reflecting surfaces includes a plurality of first reflecting surfaces, and each of the plurality of first reflecting surfaces has a slope whose distance from the surface including the incident surface increases as the distance from the light source increases along a direction parallel to the incident surface. The plurality of first reflection surfaces are interfaces with external air,
The light guide plate includes a plurality of V-shaped cross-sections that are reflective surfaces on at least a surface between the plurality of first reflective surfaces and the plurality of first reflective surfaces of the first reflective portion. the reflective groove of said the output surface along the bottom surface portion is opposite, have a light incident portion radially centered,
The light incident portion has a conical depression at a central portion facing the light source, and a plurality of reflection grooves having both sides of a V-shaped cross section as reflection surfaces are formed around the conical depression. Have a radial center around the dent,
The exit surface has a funnel-like shape in which the distance from the surface including the incident surface increases continuously as the distance from the light source is increased in a direction parallel to the incident surface with a position facing the light incident portion as a center. A second reflecting surface having a shape, and a second reflecting portion that reflects light incident from the light incident portion,
The exit surface has a funnel-shaped depression at a central portion facing the light source, and the second reflective surface of the second reflective portion is located at a position of the second reflective portion from a position facing the light source. To the outer peripheral edge is a single reflecting surface whose cross section is bent or curved, and the second reflecting surface is an interface between the light guide plate and external air.
Light guiding unit. The plurality of reflection grooves in which an opening angle of both side surfaces of a V-shaped cross section centered on the groove bottom is in a range of 80 to 100 ° with respect to the plurality of first reflection surfaces in the bottom surface portion. Formed,
The light guide unit according to claim 1 . The plurality of reflection grooves having an opening angle of 90 ° on both side surfaces of a V-shaped cross section centered on the groove bottom is formed with respect to the plurality of first reflection surfaces of the bottom surface portion.
The light guide unit according to claim 1 . The plurality of opening angles of both side surfaces of a V-shaped cross section centered on the groove bottom with respect to a surface between the plurality of first reflecting surfaces of the bottom surface portion is in a range of 60 to 90 °. Formed a reflection groove,
The light guide unit according to any one of claims 1 to 3 . The plurality of reflection grooves formed around the conical depression in the light incident part have a range of 60 to 90 ° on both sides of a V-shaped cross section centered on the groove bottom.
Light unit according to any one of claims 1 to 4.

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