Illumination device

Abstract

To provide a lighting device which can be reduced in size.SOLUTION: A lighting device of the present embodiment comprises: a light guide plate having an upper face, a lower face, and an incident face; a first light emission part for radiating light in a first wavelength range; a second light emission part for radiating light in a second wavelength range; and a third light emission part for radiating light in a third wavelength range. The upper face includes a first face connected to the incident face, a second face located between the first face and the lower face in a thickness direction, and parallel with the first face, a third face located between the second face and the lower face in the thickness direction, and parallel with the second face, and a fourth face. The first face, the second face, the third face, and the fourth face are aligned in a first direction in this order, a width of the first face is narrower than a width of the second face, a width of the second face is narrower than a width of the third face, an angle formed of the incident face and the first face is an acute angle, and the first light emission part, the second light emission part and the third light emission part oppose the incident face, and are aligned in the first direction in this order.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] Embodiments of the present invention relate to a lighting device.

Background Art

[0002] For example, a light-emitting device in which a first semiconductor laser element that emits red light, a second semiconductor laser element that emits green light, and a third semiconductor laser element that emits blue light are packaged together has been proposed. Such a light-emitting device can be applied to, for example, a lighting device (backlight device) that illuminates a liquid crystal panel. In recent years, the demand for thinning of liquid crystal display devices has been further increasing, and thinning of lighting devices has been demanded.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object of the present invention is to provide a lighting device that can be miniaturized.

Means for Solving the Problems

[0005] The lighting device according to this embodiment is A light guide plate having an upper surface, a lower surface facing the upper surface, and a light incident surface connecting the upper surface and the lower surface; a first light emitting unit configured to emit light in a first wavelength range; a second light emitting unit configured to emit light in a second wavelength range different from the first wavelength range; and a third light emitting unit configured to emit light in a third wavelength range different from the first wavelength range and the second wavelength range. The upper surface includes a first surface connected to the light incident surface, a second surface spaced from the first surface and located between the first surface and the lower surface in the thickness direction of the light guide plate and parallel to the first surface, a third surface spaced from the second surface and located between the second surface and the lower surface in the thickness direction and parallel to the second surface, and a fourth surface. The first surface, the second surface, the third surface, and the fourth surface are arranged in a first direction in this order. Regarding the width along the first direction, the width of the first surface is smaller than the width of the second surface, the width of the second surface is smaller than the width of the third surface. The lower surface includes a fifth surface facing and parallel to the fourth surface. The angle formed by the light incident surface and the first surface is an acute angle. The first light emitting unit, the second light emitting unit, and the third light emitting unit face the light incident surface and are arranged in the first direction in this order.

Brief Description of the Drawings

[0006]

Figure 1

Figure 2

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Figure 10

[0007] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the disclosure is merely an example, and for those that can be easily conceived by those skilled in the art with appropriate modifications while maintaining the gist of the invention, they are naturally included in the scope of the present invention. In addition, the drawings may be schematically represented in terms of the width, thickness, shape, etc. of each part compared to the actual aspect for clearer explanation, but this is merely an example and does not limit the interpretation of the present invention. Also, in this specification and each drawing, components that exhibit the same or similar functions as those described above with respect to the already shown drawings may be given the same reference numerals, and detailed descriptions of duplicates may be omitted as appropriate.

[0008] Note that in the drawings, for easy understanding as necessary, an X-axis, a Y-axis, and a Z-axis orthogonal to each other are described. The direction along the X-axis is referred to as the X direction or the first direction, the direction along the Y-axis is referred to as the Y direction or the second direction, and the direction along the Z-axis is referred to as the Z direction or the third direction. The plane defined by the X-axis and the Y-axis is referred to as the X-Y plane, and the plane defined by the X-axis and the Z-axis is referred to as the X-Z plane. Looking at the X-Y plane is referred to as a plan view. The first direction X and the second direction Y correspond to directions parallel to the main surface of the light guide plate included in the lighting device, and the third direction Z corresponds to the thickness direction of the light guide plate.

[0009] FIG. 1 is a diagram for explaining a lighting device IL according to the present embodiment. The lighting device IL includes a light guide plate 1 and a light emitting device 2. Note that the light guide plate 1 and the light emitting device 2 shown in FIG. 1 do not accurately reflect their shapes.

[0010] Although the details of the light guide plate 1 will be described later, the light guide plate 1 has an upper surface 11 facing the illumination object 3 in the third direction Z, a lower surface 12 facing the upper surface 11, and a light incident surface 13 connecting the upper surface 11 and the lower surface 12.

[0011] The upper surface 11 has a main surface (a fourth surface to be described later) which is a flat surface extending in the first direction X. The lower surface 12 has a main surface (a fifth surface to be described later) which is a flat surface extending in the first direction X. The region where these pair of main surfaces face each other corresponds to the effective region AA of the light guide plate 1. The effective region AA is a region where the light propagated inside the light guide plate 1 is emitted. The region outside the effective region AA including the light incident surface 13 corresponds to the peripheral region PA of the light guide plate 1.

[0012] The light emitting device 2 is located on one end side of the light guide plate 1 along the first direction X and faces the light incident surface 13. Although the details of the light emitting device 2 will be described later, the light emitting device 2 includes a light emitting portion configured to emit light in a predetermined wavelength range.

[0013] The illumination object 3 is, for example, a display panel. The display panel is, for example, a display panel (liquid crystal panel) provided with a liquid crystal layer, a display panel provided with an electrophoretic element, a display panel applying MEMS (micro electro mechanical systems), and the like. Such a display panel has a display region DA for displaying an image and a non-display region ND outside the display region DA. The display region DA faces the effective region AA in the third direction Z. Also, the non-display region ND faces the peripheral region PA.

[0014] When the display panel is a transmissive panel that displays an image by selectively transmitting illumination light, the illumination device IL functions as a backlight device. Also, when the display panel is a reflective panel that displays an image by selectively reflecting illumination light, the illumination device IL functions as a frontlight device. By combining the illumination device IL according to the present embodiment and the display panel which is the illumination object 3, a display device can be configured.

[0015] FIG. 2 is a cross-sectional view showing an example of the lighting device IL shown in FIG. 1. In FIG. 2, the peripheral region PA of the light guide plate 1 is shown enlarged.

[0016] First, the light guide plate 1 will be described. The light guide plate 1 is made of resin such as polycarbonate or acrylic, for example, but may be made of glass.

[0017] The upper surface 11 of the light guide plate 1 has a first surface 111, a second surface 112 spaced apart from the first surface 111, a third surface 113 spaced apart from the second surface 112, a fourth surface 114 adjacent to the third surface 113, a first connection surface 115 connecting the first surface 111 and the second surface 112, and a second connection surface 116 connecting the second surface 112 and the third surface 113. Each of these surfaces 111 to 116 is a flat surface.

[0018] The first surface 111, the first connection surface 115, the second surface 112, the second connection surface 116, the third surface 113, and the fourth surface 114 are arranged in the first direction in this order. In the example shown in FIG. 2, the third surface 113 and the fourth surface 114 are directly connected, but another connection surface may be interposed between the third surface 113 and the fourth surface 114. The first surface 111, the first connection surface 115, the second surface 112, the second connection surface 116, and the third surface 113 are located in the peripheral region PA. The fourth surface 114 is located in the effective region AA.

[0019] The first surface 111 is the uppermost in the third direction (the thickness direction Z of the light guide plate 1) among the surfaces constituting the upper surface 11 and is the farthest from the lower surface 12. The first surface 111 is the farthest from the effective region AA in the first direction X among the surfaces constituting the upper surface 11. Alternatively, the first surface 111 is located on one end side of the peripheral region PA in the first direction X. The first surface 111 has a width W1 along the first direction X.

[0020] The second surface 112 is located between the first surface 111 and the lower surface 12 in the third direction Z. The second surface 112 has a width W2 along the first direction X. The width W2 is larger than the width W1 (W2>W1).

[0021] The third surface 113 is located between the second surface 112 and the lower surface 12 in the third direction Z. The third surface 113 is located on the other end side of the peripheral region PA in the first direction X. The third surface 113 has a width W3 along the first direction X. The width W3 is larger than the width W2 (W3 > W2).

[0022] These first surface 111, second surface 112, and third surface 113 are parallel to each other. The fourth surface 114 is a plane parallel to the X-Y plane. When the fourth surface 114 is used as a reference plane, the first surface 111, second surface 112, and third surface 113 have the same inclination γ. In one example, the inclination γ is 0° or more and 15° or less. When the inclination γ is 0°, the third surface 113 and the fourth surface 114 form a continuous same plane. Also, when the inclination γ is 0°, the angle θ1 formed between the third surface 113 and the fourth surface 114 is 180°. The formed angle θ1 becomes smaller as the inclination γ increases. In one example, the formed angle θ1 is 165° or more and 180° or less.

[0023] The first connecting surface 115 and the second connecting surface 116 are inclined surfaces inclined with respect to the fourth surface 114 when the fourth surface 114 is used as a reference plane. The first connecting surface 115 and the second connecting surface 116 are parallel to each other. Note that the first connecting surface 115 and the second connecting surface 116 may not be parallel to each other.

[0024] The lower surface 12 of the light guide plate 1 has a fifth surface 125 and a connecting surface 126 that connects the fifth surface 125 and the light incident surface 13. Each of these surfaces 125 to 126 is a flat surface.

[0025] The fifth surface 125 faces the fourth surface 114 in the third direction Z. The fifth surface 125 is a plane parallel to the X-Y plane and parallel to the fourth surface 114. The fifth surface 125 extends across the effective region AA and the peripheral region PA. The light guide plate 1 has a thickness T1 along the third direction Z between the fourth surface 114 and the fifth surface 125 in the effective region AA.

[0026] In the peripheral region PA, the fifth surface 125 faces the third surface 113 and the second connection surface 116 in the third direction Z. The end portion 125E of the fifth surface 125, or the boundary between the fifth surface 125 and the connection surface 126, is located between the second surface 112 and the third surface 113 in the first direction X. Further, the end portion 125E faces the second connection surface 116 in the third direction Z.

[0027] The light incident surface 13 of the light guide plate 1 is a flat surface or an inclined surface inclined with respect to the fourth surface 114, the fifth surface 125, or the X - Y plane. The light incident surface 13 is connected to the first surface 111 and the connection surface 126. The connection position between the light incident surface 13 and the first surface 111 is located on one end side of the peripheral region PA in the first direction X. The angle θ2 formed between the light incident surface 13 and the first surface 111 is an acute angle (less than 90°). The light incident surface 13 faces the first surface 111, the first connection surface 115, and the second surface 112 in the third direction Z.

[0028] The light incident surface 13 has a width W13 along the first direction X. The width W13 is larger than the thickness T1 (W13 > T1). The thickness T1 is 1.5 mm or less, and in one example, it is 1.0 mm.

[0029] Next, the light emitting device 2 will be described. The light emitting device 2 includes a first light emitting portion 21, a second light emitting portion 22, and a third light emitting portion 23. The first light emitting portion 21, the second light emitting portion 22, and the third light emitting portion 23 are mounted on a circuit board 20 indicated by a dotted line. The first light emitting portion 21, the second light emitting portion 22, and the third light emitting portion 23 face the light incident surface 13 and are arranged in the first direction X in this order. Further, each of the first light emitting portion 21, the second light emitting portion 22, and the third light emitting portion 23 is configured to emit light toward the light incident surface 13. Specifically, it is as follows.

[0030] The first light emitting portion 21 is configured to emit light (first emitted light) in the first wavelength range. In one example, the first wavelength range is the wavelength range of red, and the first light emitting portion 21 includes a first semiconductor laser element that emits red light. The second light emitting unit 22 is configured to emit light (second emitted light) in a second wavelength range. The second wavelength range is different from the first wavelength range. In one example, the second wavelength range is a green wavelength range, and the second light emitting unit 22 includes a second semiconductor laser element that emits green light. The third light emitting unit 23 is configured to emit light (third emitted light) in a third wavelength range. The third wavelength range is different from the first wavelength range and the second wavelength range. In one example, the third wavelength range is a blue wavelength range, and the third light emitting unit 23 includes a third semiconductor laser element that emits blue light. The distance D along the light incident surface 13 from the first light emitting unit 21 to the third light emitting unit 23 is greater than the thickness T of the light guide plate 1 (D>T).

[0031] Next, the first surface 111, the second surface 112, and the third surface 113 will be described in more detail.

[0032] The first surface 111 is located on the first optical path PT1 of the principal ray among the first emitted light emitted from the first light emitting unit 21. Also, the first optical path PT1 is orthogonal to the light incident surface 13. The first emitted light includes diffused light that diffuses at a diffusion angle δ with respect to the principal ray in addition to the principal ray. The first surface 111 is a total reflection surface configured to totally reflect the first emitted light. That is, the first surface 111 has an inclination γ set so as to totally reflect substantially all of the first emitted light including the principal ray and the diffused light.

[0033] The second surface 112 is located on the second optical path PT2 of the principal ray among the second emitted light emitted from the second light emitting unit 22. The second optical path PT2 is orthogonal to the light incident surface 13 and parallel to the first optical path PT1. The second emitted light includes diffused light that diffuses at a diffusion angle δ with respect to the principal ray in addition to the principal ray. The length of the second optical path PT2 from the second light emitting unit 22 to the second surface 112 is longer than the length of the first optical path PT1 from the first light emitting unit 21 to the first surface 111. The second surface 112 is a total reflection surface configured to totally reflect the second emitted light. That is, the second surface 112 has an inclination γ set so as to totally reflect almost all of the second emitted light including the principal ray and the diffused light. As described above, the second surface 112 is parallel to the first surface 111 and has the same inclination γ as the first surface 111.

[0034] The third surface 113 is located on the third optical path PT3 of the principal ray among the third emitted light emitted from the third light emitting portion 23. The third optical path PT3 is orthogonal to the incident surface 13 and parallel to the second optical path PT2. The third emitted light includes diffused light that diffuses at a diffusion angle δ with respect to the principal ray in addition to the principal ray. The length of the third optical path PT3 from the third light emitting portion 23 to the third surface 113 is longer than the length of the second optical path PT2 from the second light emitting portion 22 to the second surface 112. The third surface 113 is a total reflection surface configured to totally reflect the third emitted light. That is, the third surface 113 has an inclination γ set so as to totally reflect almost all of the third emitted light including the principal ray and the diffused light. As described above, the third surface 113 is parallel to the first surface 111 and has the same inclination γ as the first surface 111.

[0035] FIG. 3 is a plan view of the light guide plate 1 shown in FIG. 2. On the upper surface 11, the first surface 111, the second surface 112, the third surface 113, the first connection surface 115, and the second connection surface 116 are each formed in a rectangular shape extending in the second direction Y in plan view. The fourth surface 114 has the largest area on the upper surface 11. Also, the connection surface 126 of the lower surface 12 and the incident surface 13 are each formed in a rectangular shape extending in the second direction Y in plan view. The fifth surface 125 has the largest area on the lower surface 12.

[0036] FIG. 4 is a diagram for explaining the total reflection surface. Here, the inclination γ will be described by taking the third surface 113 of the total reflection surface as an example. The angles of the optical paths described below are shown as the angles formed by the fourth surface 114 and the optical paths.

[0037] As described above, the third emitted light that enters from the light incident surface 13 includes the principal ray B0, and diffused lights B1 and B2 that are diffused at the diffusion angle δ. Let the angle of the optical path of the principal ray B0 from the light incident surface 13 to the third surface 113 be α0, the angle of the optical path of the diffused light B1 be α0 + δ, and the angle of the optical path of the diffused light B2 be α0 - δ. Let the angle of the optical path of the principal ray B0 reflected by the third surface 113 be α, the angle of the optical path of the diffused light B1 be α + δ, and the angle of the optical path of the diffused light B2 be α - δ.

[0038] For the third emitted light to be totally reflected by the third surface 113, the angle β formed by the optical path of the diffused light B1 and the third surface 113 needs to satisfy the total reflection condition shown below. β < 90° - θc …(1) Here, θc is the critical angle. When the refractive index of air is 1 and the refractive index of the light guide plate 1 is 1.5, the critical angle θc is 41.8°. β is equal to (α + δ + γ). As an example, when α is 26.5° and δ is 6.5°, the range of the inclination γ is as follows. γ < 15.2° That is, it is desirable that the inclination γ be 15° or less. At this time, α + δ is 33° and α - δ is 20°.

[0039] The relationship between α0 and α is as follows. α0 = α + 2γ When γ is 9°, α0 is 44.5°, α0 + δ is 51°, α0 - δ is 38°, and β is 42°.

[0040] When the light incident surface 13 is orthogonal to the optical path of the principal ray B0, the inclination φ of the light incident surface 13 is 45.5°. Also, the angle θ2 formed by the first surface 111 and the light incident surface 13 is 54.5°.

[0041] FIG. 5 is a cross-sectional view showing an example of the lighting device IL. In the example shown in FIG. 5, the inclinations γ of the first surface 111, the second surface 112, and the third surface 113 are all 9°.

[0042] The radiation light (R) emitted from the first light-emitting unit 21, the radiation light (G) emitted from the second light-emitting unit 22, and the radiation light (B) emitted from the third light-emitting unit 23 are incident on the light guide plate 1 through the incident surface 13, respectively. The radiation light including the principal ray R0 and the diffused lights R1 and R2 is reflected by the first surface 111. The radiation light including the principal ray G0 and the diffused lights G1 and G2 is reflected by the second surface 112. The radiation light including the principal ray B0 and the diffused lights B1 and B2 is reflected by the third surface 113. The reflected light of each color propagates inside the light guide plate 1 while being reflected by the fifth surface 125 and the fourth surface 114. Among the light propagating inside the light guide plate 1, the light that deviates from the total reflection condition is emitted from the fourth surface 114 in the effective region AA.

[0043] FIG. 6 is a plan view showing an example of the lighting device IL. In a plan view, in the peripheral region PA of the light guide plate 1, the radiation light R emitted from the first light-emitting unit 21, the radiation light G emitted from the second light-emitting unit 22, and the radiation light B emitted from the third light-emitting unit 23 propagate along the first direction X while mixing with each other to form illumination light. Also, in the effective region AA, the illumination light emitted from the light-emitting devices 2 adjacent to each other in the second direction Y spreads in the second direction Y while propagating along the first direction X and mixes with each other.

[0044] In FIG. 6, although the states in which the radiation lights R, G, and B spread are schematically shown, the spreading conditions or directivities of the radiation lights R, G, and B in the X-Y plane are not necessarily the same. When the directivities of the radiation lights R, G, and B are different from each other, the light-emitting unit that emits light with a high directivity (difficult to spread) is preferably arranged at a position far from the effective region AA, and the light-emitting unit that emits light with a low directivity (easy to spread) is preferably arranged at a position close to the effective region AA. That is, in the example shown in FIG. 6, a combination such that the light emitted from the first light-emitting unit 21 has a high directivity and the light emitted from the third light-emitting unit 23 has a low directivity can be applied.

[0045] According to such a lighting device IL, compared with an edge lighting method in which the first light emitting part 21, the second light emitting part 22, and the third light emitting part 23 arranged in the second direction Y face the side surface of the light guide plate 1, the distance along the first direction X required for lights of different wavelengths to mix with each other can be shortened. That is, the length of the peripheral region PA along the first direction X can be shortened. Further, according to the above lighting device IL, compared with another edge lighting method in which the first light emitting part 21, the second light emitting part 22, and the third light emitting part 23 arranged in the third direction Z face the side surface of the light guide plate 1, the thickness of the light guide plate 1 can be reduced. Thereby, miniaturization of the lighting device IL can be realized.

[0046] In addition, the first surface 111, the second surface 112, and the third surface 113 are total reflection surfaces. For this reason, at the first surface 111, the second surface 112, and the third surface 113, a reflection layer for reflecting the emitted light of each color is unnecessary. For this reason, the cost of the lighting device IL can be reduced.

[0047] FIG. 7 is a view showing another example of the light guide plate 1 shown in FIG. 1. The light guide plate 1 in the example shown in FIG. 7 is different from the light guide plate 1 shown in FIG. 5 in that the inclination γ is 0°. That is, the first surface 111, the second surface 112, and the third surface 113 are parallel to the fourth surface 114 which is a reference surface. Further, the third surface 113 and the fourth surface 114 form a continuous same plane. The angle θ1 formed by the third surface 113 and the fourth surface 114 is 180°.

[0048] The first surface 111 is a total reflection surface that reflects the emitted light including the principal ray R0 and the diffused rays R1 and R2, the second surface 112 is a total reflection surface that reflects the emitted light including the principal ray G0 and the diffused rays G1 and G2, and the third surface 113 is a total reflection surface that reflects the emitted light including the principal ray B0 and the diffused rays B1 and B2. The optical paths of the principal rays R0, G0, and B0 are parallel to each other.

[0049] The light incident surface 13 is inclined so as to be orthogonal to the optical paths of the principal rays R0, G0, and B0. When the angle α of the optical path of the totally reflected principal ray is 26.5°, the angle α0 of the optical path of the principal ray from the incident surface 13 to the total reflection surface is 26.5°, and the inclination φ of the incident surface 13 is 63.5°. Also, the angle θ2 formed between the first surface 111 and the incident surface 13 is 63.5°.

[0050] Comparing the light guide plate 1 in the example shown in FIG. 5 with the light guide plate 1 in the example shown in FIG. 7, it can be seen that as the inclination γ becomes smaller, the width W1 of the first surface 111, the width W2 of the second surface 112, and the width W3 of the third surface 113 increase, and the formed angle θ2 also increases.

[0051] FIG. 8 is a diagram showing another example of the light guide plate 1 shown in FIG. 1. FIG. 8 shows cross-sections of several light guide plates 1 with different inclinations γ, but the illustration of the first surface is omitted. Here, the light guide plate 1 with an inclination γ of 15°, the light guide plate 1 with an inclination γ of 9°, the light guide plate 1 with an inclination γ of 5°, the light guide plate 1 with an inclination γ of 0°, and the light guide plate 1 with an inclination γ of -5° are respectively illustrated.

[0052] The shape of each illustrated light guide plate 1 is optimized to satisfy the following conditions. That is, the emitted light R reflected by the first reflection surface reaches the fifth surface 125, the emitted light G is reflected by the second surface 112 and its reflected light reaches the fifth surface 125, and the emitted light B is reflected by the third surface 113 and its reflected light reaches the fifth surface 125.

[0053] When comparing the light guide plates 1 with the shapes optimized under the above conditions, it can be seen that the larger the inclination γ, the smaller the peripheral region PA can be made. Also, it can be seen that the smaller the inclination γ, the greater the thickness T2 of the peripheral region PA. From these viewpoints, it is desirable that the inclination γ is 0° or more.

[0054] FIG. 9 is a diagram showing another example of the light guide plate 1 shown in FIG. 1. FIG. 9 shows cross-sections of several light guide plates 1, but the illustration of the first surface is omitted.

[0055] In the example shown in FIG. 9, the diffusion angles δ of the emitted light radiated from the first light emitting unit 21, the second light emitting unit 22, and the third light emitting unit 23 are different from each other. In this case, the inclination γ of the first surface 111, the second surface 112, and the third surface 113 is determined based on the largest diffusion angle δ.

[0056] Here, a case where the diffusion angle δ of the emitted light R is the largest and the diffusion angle δ of the emitted light G is the smallest will be described. In this case, the inclination γ is determined based on the diffusion angle δ of the emitted light R. In one example, the diffusion angle δ of the emitted light G is 6.5°, the diffusion angle δ of the emitted light B is 6.7°, and the diffusion angle δ of the emitted light R is 8.8°.

[0057] Assuming that the refractive index of air is 1, the refractive index of the light guide plate 1 is 1.5, the critical angle θc is 41.8°, α is 26.5°, and δ is 8.8°, the range of the inclination γ based on the relational expression (1) described with reference to FIG. 4 is as follows. γ < 12.9°

[0058] The shape of each light guide plate 1 shown in FIG. 9 is optimized to satisfy the following conditions. That is, the condition that the inclination γ is less than 12.9° is satisfied, the emitted light R reflected by the first reflection surface reaches the fifth surface 125, the emitted light G is reflected by the second surface 112 and its reflected light reaches the fifth surface 125, and the emitted light B is reflected by the third surface 113 and its reflected light reaches the fifth surface 125.

[0059] In the example shown in the upper part of FIG. 9, the first light emitting unit 21 is configured to emit the emitted light R in the first wavelength range which is the red wavelength range, the second light emitting unit 22 is configured to emit the emitted light B in the second wavelength range which is the blue wavelength range, and the third light emitting unit 23 is configured to emit the emitted light G in the third wavelength range which is the green wavelength range.

[0060] In the example shown in the middle part of FIG. 9, the first light emitting unit 21 is configured to emit the emitted light B in the first wavelength range which is the blue wavelength range, the second light emitting unit 22 is configured to emit the emitted light G in the second wavelength range which is the green wavelength range, and the third light emitting unit 23 is configured to emit the emitted light R in the third wavelength range which is the red wavelength range.

[0061] In the example shown in the lower part of FIG. 9, the first light emitting unit 21 emits the emitted light B in the first wavelength range which is the blue wavelength range, the second light emitting unit 22 emits the emitted light R in the second wavelength range which is the red wavelength range, and the third light emitting unit 23 emits the emitted light G in the third wavelength range which is the green wavelength range.

[0062] When comparing the light guide plate 1 with the shape optimized under the above conditions, when the diffusion angle of the emitted light emitted from the second light emitting unit 22 is larger than the diffusion angle of the light emitted from the first light emitting unit 21 and the diffusion angle of the light emitted from the third light emitting unit 23 (the example shown in the lower part of FIG. 9), the peripheral region PA can be made smaller, and furthermore, the thickness T1 in the effective region AA can be made thinner.

[0063] FIG. 10 is a view showing another example of the light guide plate 1 shown in FIG. 1. FIG. 10 shows cross-sections of several light guide plates 1, but the illustration of the first surface is omitted.

[0064] In the example shown in FIG. 10, the case where the diffusion angle δ of the emitted light R is the largest and the diffusion angle δ of the emitted light B is the smallest will be described. In this case, the inclination γ is determined based on the diffusion angle δ of the emitted light R. In one example, the diffusion angle δ of the emitted light G is 7.5°, the diffusion angle δ of the emitted light B is 5°, and the diffusion angle δ of the emitted light R is 10°.

[0065] Assuming the refractive index of air is 1, the refractive index of the light guide plate 1 is 1.5, the critical angle θc is 41.8°, α is 26.5°, and δ is 10°, the range of the inclination γ based on the relational expression (1) described with reference to FIG. 4 is as follows. γ < 11.7°

[0066] The shape of each light guide plate 1 shown in FIG. 10 is optimized to satisfy the following conditions. That is, the inclination γ is 11°, the emitted light R reflected by the first reflection surface reaches the fifth surface 125, the emitted light G is reflected by the second surface 112 and its reflected light reaches the fifth surface 125, and the emitted light B is reflected by the third surface 113 and its reflected light reaches the fifth surface 125.

[0067] In the example shown in the upper part of FIG. 10, the first light emitting unit 21 emits the radiation light R in the first wavelength range which is the red wavelength range, the second light emitting unit 22 emits the radiation light G in the second wavelength range which is the green wavelength range, and the third light emitting unit 23 is configured to emit the radiation light B in the third wavelength range which is the blue wavelength range.

[0068] In the example shown in the middle part of FIG. 10, the first light emitting unit 21 emits the radiation light B in the first wavelength range which is the blue wavelength range, the second light emitting unit 22 emits the radiation light G in the second wavelength range which is the green wavelength range, and the third light emitting unit 23 is configured to emit the radiation light R in the third wavelength range which is the red wavelength range.

[0069] In the example shown in the lower part of FIG. 10, the first light emitting unit 21 emits the radiation light B in the first wavelength range which is the blue wavelength range, the second light emitting unit 22 emits the radiation light R in the second wavelength range which is the red wavelength range, and the third light emitting unit 23 is configured to emit the radiation light G in the third wavelength range which is the green wavelength range.

[0070] When comparing the light guide plate 1 with the optimized shape under the above conditions, when the diffusion angle of the radiation light emitted from the second light emitting unit 22 is larger than the diffusion angle of the light emitted from the first light emitting unit 21 and the diffusion angle of the light emitted from the third light emitting unit 23 (the example shown in the lower part of FIG. 10), the peripheral area PA can be reduced, and further, the thickness T1 in the effective area AA can be made thinner.

[0071] According to the above-described embodiment of the present invention, an illumination device capable of miniaturization can be provided.

[0072] As described above, based on the illumination device described as an embodiment of the present invention, all illumination devices that can be appropriately designed and modified by those skilled in the art and implemented also belong to the scope of the present invention as long as they include the gist of the present invention.

[0073] Within the scope of the idea of the present invention, those skilled in the art can conceive of various modifications, and those modifications are also understood to fall within the scope of the present invention. For example, for the above-described embodiments, those in which those skilled in the art appropriately add, delete, or change the design of components, or add, omit, or change conditions of processes, are also included in the scope of the present invention as long as they have the gist of the present invention.

[0074] In addition, regarding other operational effects brought about by the aspects described in the above-described embodiments, those that are obvious from the description of this specification or that can be appropriately conceived by those skilled in the art are naturally understood to be brought about by the present invention.

Explanation of Reference Numerals

[0075] IL… Lighting device 1… Light guide plate 11… Upper surface 111… First surface 112… Second surface 113… Third surface 114… Fourth surface 115… First connection surface 116… Second connection surface 12… Lower surface 125… Fifth surface 126… Connection surface 13… Light incident surface AA… Effective area PA… Peripheral area 2… Light emitting device 21… First light emitting part 22… Second light emitting part 23… Third light emitting part

Claims

1. A light guide plate having an upper surface, a lower surface facing the upper surface, and a light incident surface connecting the upper surface and the lower surface; A first light emitting portion configured to emit light in a first wavelength range; A second light emitting portion configured to emit light in a second wavelength range different from the first wavelength range; A third light emitting portion configured to emit light in a third wavelength range different from the first wavelength range and the second wavelength range, comprising: The upper surface includes a first surface connected to the light incident surface, a second surface spaced from the first surface and located between the first surface and the lower surface in the thickness direction of the light guide plate and parallel to the first surface, a third surface spaced from the second surface and located between the second surface and the lower surface in the thickness direction and parallel to the second surface, and a fourth surface; The first surface, the second surface, the third surface, and the fourth surface are arranged in a first direction in this order; Regarding the width along the first direction, the width of the first surface is smaller than the width of the second surface, and the width of the second surface is smaller than the width of the third surface; The lower surface includes a fifth surface facing the fourth surface and parallel to the fourth surface; The angle formed by the light incident surface and the first surface is an acute angle; The first light emitting portion, the second light emitting portion, and the third light emitting portion face the light incident surface and are arranged in the first direction in this order, a lighting device.

2. The inclination of each of the first surface, the second surface, and the third surface with respect to the fourth surface as a reference surface is 15° or less, the lighting device according to Claim 1.

3. The inclination is 0° or more, the lighting device according to Claim 2.

4. The upper surface further includes a first connection surface connecting the first surface and the second surface, and a second connection surface connecting the second surface and the third surface and parallel to the first connection surface, the lighting device according to Claim 1.

5. The end portion of the fifth surface is located between the second surface and the third surface in the first direction, the lighting device according to Claim 1.

6. The light incident surface faces the first surface and the second surface in the thickness direction; The fifth surface faces the third surface in the thickness direction, the lighting device according to Claim 5.

7. The first surface is located on a first optical path of the principal ray of the light emitted from the first light emitting portion; The second surface is located on a second optical path of the principal ray of the light emitted from the second light emitting portion; The lighting device according to claim 1, wherein the third surface is located on a third optical path of a principal ray of light emitted from the third light-emitting portion.

8. The lighting device according to claim 7, wherein the first optical path, the second optical path, and the third optical path are parallel to each other.

9. The first surface is a total reflection surface configured to totally reflect light emitted from the first light-emitting portion. The second surface is a total reflection surface configured to totally reflect light emitted from the second light-emitting portion. The lighting device according to claim 1, wherein the third surface is a total reflection surface configured to totally reflect light emitted from the third light-emitting portion.

10. The lighting device according to claim 1, wherein a width along the light incident surface from the first light-emitting portion to the third light-emitting portion is larger than a thickness between the fourth surface and the fifth surface.

11. The lighting device according to claim 10, wherein the thickness is 1.5 mm or less.

12. The lighting device according to claim 1, wherein a diffusion angle of light emitted from the second light-emitting portion is larger than a diffusion angle of light emitted from the first light-emitting portion and a diffusion angle of light emitted from the third light-emitting portion.

13. The lighting device according to claim 12, wherein the second wavelength range is a red wavelength range.

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