WO2006112093A1 - Planar lighting apparatus - Google Patents

Abstract

A beam (LR3) emitted backward from side planes (24b, 24c) of a LED (24) is reflected forward by a front inclined plane of a fine prism (40) of a reflecting plate (38) and is permitted to enter a light guide plate (12). A light incoming angle to the light guide plate (12) is modified and a rate of light reaching a leading end section of the light guide plate (12) is increased by permitting beams (LF4, LF5) emitted forward from the side planes (24b, 24c) of the LED (24) to be reflected by the front inclined plane of the fine prism (40). In the fine prism (40) of the reflecting plate (38), the front inclined plane is relatively gently inclined and the rear inclined plane is relatively steeply inclined.

Description

 Specification

 Surface lighting device

 Technical field

 TECHNICAL FIELD [0001] The present invention relates to a sidelight type planar illumination device, and more particularly to a planar illumination device that is used as an illumination means for a liquid crystal display device.

 Background art

 [0002] Liquid crystal display devices are widely used as display means of today's electronic devices, but since this liquid crystal display device is not self-luminous, it is necessary to ensure visibility at night or in dark places. The lighting means is necessary. Conventionally, planar illumination devices have been used as such illumination means.

 Further, as one form of the planar lighting device, a sidelight type planar lighting device is widely used. A sidelight type planar illumination device is composed of a light guide plate having translucency and a bar light source or one or more point light sources arranged on the side end face of the light guide plate. In recent years, surface illumination devices in the form of a point light source capable of simplifying the drive circuit have been used due to an increase in applications to small electronic devices such as portable information terminals. Yes. FIG. 15 schematically shows the light guide plate 12 and a plurality of point light sources (LEDs) 14 arranged on the side end surfaces of the side light type planar illumination device 10.

By the way, the planar illumination device 10 using the LED 14 shown in FIG. 15 has a light guide plate 12 illuminated by the LED 14 because the light emitted from the LED 14 to the light guide plate 12 has a certain directivity. The vicinity of the LED 14 is clearly divided into bright part A and buttocks B. As a measure to eliminate the difference between the bright part and the bright part and to obtain an average brightness, as shown in FIG. 16, on the surface 12a of the light guide plate 12 facing the LED 14, there is a fine prism row or the like. An optical diffuse reflection pattern 12b is provided, or as shown in FIG. 17, the LED 16 in which a part of the exterior member is a semi-cylindrical protruding portion 16a is used, and the light guide plate 12 includes the protruding portion 16a. A semi-cylindrical recess 12c to be fitted is provided, and light from the LED chip 17 is emitted radially from a slit formed in the protrusion 16a (see, for example, Patent Document 1). LED18 like LED18 A lamp house 20 that covers the lamp 19 and controls the directivity of light by changing the height of the lamp house 20 and the inclination angle of the inclined surface 20a (for example, Patent Document 2). reference.). In FIG. 18, reference numeral 22 denotes a translucent resin for sealing the LED chip 19 in the lamp house 20.

[0004] Patent Document 1: JP-A-10-199316 ([0023], [0026] to [0028])

 Patent Document 2: Japanese Patent Application Laid-Open No. 2002-217459 ([Claim 1], FIG. 8)

 Disclosure of the invention

 Problems to be solved by the invention

 [0005] The present inventor further studied a measure for obtaining an average brightness by eliminating the difference between the bright part and the dark part as described above in the planar lighting device, and from the upper and lower surfaces of the LED 14. The inventors have invented a method for allowing the LED 14 force and other light beams to enter the light guide plate 12 without leaving the reflectors by reflecting the leaking light on at least one of the upper and lower surfaces of the LED. In the course of its development, the challenges of using reflectors became clear. FIGS. 19 (a) and 19 (b) show the locus of light rays emitted from the LED 14 when the reflectors 36 are provided on the upper and lower surfaces of the LED 14 in the planar illumination device 10 shown in FIG. . FIG. 19A shows the light guide plate 12 from the side surface 14b other than the surface 14a facing the light guide plate 12 of the LED 14 (hereinafter also referred to as “side surface in a direction parallel to the light guide plate” or simply “side surface”). The trajectory of the light beam emitted in the direction (hereinafter also referred to as “forward”) is schematically shown using the symbols LF1, LF2, and LF3. Each of these trajectories is a force with different emission angles from the side surface 14b of the LED. Light rays LF1 and LF2, whose emission angles are relatively gentle, are totally reflected by the surface of the light guide plate 12 and travel inside the light guide plate 12. The light beam LF3 having a relatively steep emission angle is reflected by the reflecting plate 36 and enters the light guide plate 12.

[0006] On the other hand, FIG. 19 (b) shows the trajectory of light emitted from the side surface 14b of the LED in the direction opposite to the direction of the light guide plate 12 (hereinafter also referred to as “rear”). This is shown schematically using LR2. These loci LR1 and LR2 both reflect repeatedly between the reflector 36 and the side surfaces 14b and 14c of the LED, leak out to the rear of the LED 14, and do not enter the light guide plate 12. . Therefore, unless such leakage light is used effectively, it will be difficult to further increase the brightness and make the brightness uniform of the planar illumination device using LEDs. As for the light emitted forward as shown in FIG. 19 (a), the light beams LF2 and LF3 having a relatively steep emission angle have a relatively steep incident angle to the light guide plate 12. The percentage of light reaching the tip of the light guide plate 12 is low. It has been found that the planar lighting device using LEDs does not contribute sufficiently to further increasing the brightness and making the brightness uniform. .

[0007] The present invention has been made in view of the above problems, and an object of the present invention is to further increase the luminance and make the luminance uniform in a planar lighting device in which a light guide plate is combined with an LED. There is.

 Means for solving the problem

 [0008] In order to solve the above problems, a planar illumination device according to the present invention is a planar illumination device including a plate-shaped light guide plate and an LED disposed on a side end surface of the light guide plate. A reflecting plate is disposed along a side surface in a direction parallel to the light guide plate, and a plurality of fine prisms having a triangular cross section with different inclination angles of the front and rear inclined surfaces are arranged on the surface of the reflecting plate facing the LED. It is characterized by being.

 According to the present invention, a light beam emitted backward from the side surface of the LED can be reflected forward by the front inclined surface of the fine prism of the reflection plate and can enter the light guide plate. In addition, by reflecting the light emitted from the side of the LED forward to the front inclined surface, the incident angle to the light guide plate is relaxed and the percentage of light reaching the tip of the light guide plate is increased. be able to.

 [0009] In the present invention, it is desirable that the fine prism of the reflecting plate has a front inclined surface formed with a relatively gentle slope and a rear inclined surface formed with a relatively steep slope.

 According to this configuration, the light beam emitted backward from the side surface of the LED is reflected forward by the relatively gently inclined front inclined surface, thereby reducing the incident angle to the light guide plate, and The ratio of light reaching the tip can be increased. In addition, for the light emitted forward from the side of the LED, it is a force S to increase the relaxation effect of the incident angle to the light guide plate.

[0010] In addition, an angle formed between the front inclined surface and a plane facing the surface on which the fine prisms of the reflector plate are formed is 20 ° or more and 50 ° or less, and the rear inclined surface and the opposite surface are formed. The angle formed with the plane of the shot plate is 70 ° or more and is not parallel to the front inclined surface. It is desirable that the angle is in the range.

 With this configuration, it is possible to exhibit the angle conversion action of the light beam necessary for the reflecting plate while considering the productivity of the reflecting plate.

 [0011] In addition, when each ridgeline of the fine prism is formed in parallel and linear

The productivity of the reflector is the highest. In addition, when the ridge lines of the fine prism are formed concentrically, it is possible to cause the reflector to exhibit an optimum light beam angle conversion function over a wide angle in front of the LED. Furthermore, even if each ridgeline of the fine prism is formed in a concentric polygonal shape, it is possible to exert an effective angle conversion function of light rays on the reflector over a wide angle in front of the LED.

[0012] In the present invention, the LED does not have a lamp house and the translucent resin that seals the LED chip is exposed, and the outer shape of the translucent resin is forward in the light emitting direction of the LED. And a value obtained by dividing the protrusion height by the radius of the continuous curved surface is preferably in the range of 0.3 or more and 0.6 or less.

 According to the present invention, the LED does not have a lamp house and the translucent resin that seals the LED chip is exposed, so that the thickness of the lamp house does not increase, and the surface illumination device can be made thinner. Will be promoted. In addition, since the outer shape of the translucent resin has the above-mentioned predetermined shape, it contributes to the uniformity of the luminance of the front illumination device and the luminance of the planar illumination device, which contributes to higher brightness of the planar illumination device. It is possible to balance the angle of the emitted light of the LED at a high level.

 [0013] In the present invention, the radius of the projecting portion constituted by the continuous curved surface is not less than a value obtained by multiplying the length when the LED chip is projected in a direction orthogonal to the light guide plate by 1.5. It is hoped that it will be formed to become.

 According to the present invention, the LED chip is completely sealed in the translucent resin while the outer shape of the translucent resin has the predetermined shape.

[0014] Furthermore, if a notch portion is formed on the side end surface of the light guide plate facing the LED, the cutout portion following the outer shape of the projecting portion, the LED having the predetermined outer shape is formed. The translucent resin and the light guide plate are in close contact with each other, making it possible to make the light emission distribution of light entering the light guide plate from the LED equal to the light emission distribution of the LED alone. Uniform Will contribute.

 The invention's effect

 [0015] Since the present invention is configured as described above, it is possible to further increase the luminance and make the luminance uniform in the planar lighting device in which the light guide plate is combined with the LED.

 Brief Description of Drawings

 FIG. 1 is a perspective view showing an example in which a reflecting plate is arranged along a side surface in a direction parallel to an LED light guide plate in a planar lighting device according to an embodiment of the present invention; ) Is an exploded view, and (b) is a partially enlarged view of the reflector.

 FIG. 2 is a view A in FIG. 1 (b).

 FIG. 3 is a partially enlarged view of the reflector shown in FIGS. 1 and 2. FIG. 3 (a) shows a case where the angle formed between the rear inclined surface of the fine prism of the reflector and the plane of the reflector is a right angle. (B) shows the case where the angle is an obtuse angle.

 FIG. 4 is a diagram showing the trajectory of light emitted from the side surface of the LED in the planar illumination device of FIG. 1 and FIG. 2, (a) shows the trajectory of outgoing light, and (b) Indicates the trajectory of the outgoing light beam to the rear.

 FIG. 5 is a perspective view showing a state in which a reflector according to an application example is arranged along a side surface in a direction parallel to the LED light guide plate of the planar illumination device according to the embodiment of the present invention; a) is an exploded view, and (b) is a partially enlarged view of the reflector.

 FIG. 6 is an arrow C view of FIG. 5 (b).

 FIG. 7 shows a reflector according to still another example of the planar lighting device according to the embodiment of the present invention, together with a manufacturing procedure, (a) showing an initial step and (b) showing an intermediate step. , (C) shows the completed state.

 FIG. 8 is a schematic diagram showing an outer shape of a translucent resin for sealing an LED chip of an LED in the planar lighting device according to the embodiment of the present invention.

 FIG. 9 is an external perspective view showing a specific structural example of the LED shown in FIG.

 10 is a cross-sectional view showing a specific structure example of the LED shown in FIG.

FIG. 11 shows an LED chip sealed inside the LED shown in FIG. 8, where (a) is a plan view and (b) is a side view. [FIG. 12] A table summarizing the half-value width Θ indicating the angle of emitted light and the forward emitted light quantity ratio ξ. [FIG. 13] A graph based on the straight line in FIG.

 FIG. 14 is an explanatory diagram for explaining the full width at half maximum of FIGS. 12 and 13.

 FIG. 15 is a plan view showing a basic configuration of a planar illumination device using a conventional LED.

 FIG. 16 is a plan view showing a conventional planar lighting device in which measures are taken to obtain average brightness.

 FIG. 17 is a plan view showing a conventional planar lighting device in which measures are taken to obtain average brightness.

 [FIG. 18] A plan view showing a conventional LED in which measures are taken to obtain an average brightness.

 FIG. 19 is a diagram showing a locus of light rays emitted from the side surface of the LED in the surface illumination device in the process of developing the surface illumination device according to the present invention. FIG. The trajectory is shown, and (b) shows the trajectory of the outgoing light beam backward.

 Explanation of symbols

 [0017] 10: planar illumination device, 12: light guide plate, 24: LED, 24b, 24c: side surface parallel to the light guide plate, 38, 42, 46: reflector, 38a: facing surface of LED, 38b : Plane facing the surface on which the fine prism is formed, 40, 44: fine prism, 40a: front inclined surface, 40b: rear inclined surface BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Here, parts that are the same as or equivalent to those of the prior art are denoted by the same reference numerals, and detailed description thereof is omitted.

Similar to the conventional planar illumination device shown in FIG. 15, the planar illumination device according to the embodiment of the present invention includes a plate-shaped light guide plate 12 and LEDs 24 arranged on the side end surfaces of the light guide plate 12. It is. As shown in FIGS. 1 to 3, a reflector 38 is disposed along a side surface of the LED 24 in a direction parallel to the light guide plate 12. A plurality of fine prisms 40 having a triangular cross section with different inclination angles of the front and rear inclined surfaces are arranged on the surface 38a of the reflecting plate 38 facing the LED 24. The pitch of the fine prism 40 is within the range where there is no adverse effect due to light diffraction. Set as appropriate. In the example shown in FIGS. 1 and 2, each ridgeline of the fine prism 40 of the reflecting plate 38 is formed in parallel and linear.

 Further, the LED 24 used here does not have a lamp house as shown in FIGS. 8 to 10 and has a structure exposed as a translucent resin force protrusion 26 that seals the LED chip 25. (Note that LED24 will be explained later.) Further, a notch portion 12d that follows the outer shape of the protruding portion 26 is formed on the side end surface 12a of the light guide plate 12 facing the LED 24.

 [0020] As shown in FIGS. 3 (a) and 3 (b), the fine prism 40 of the reflector 38 is formed such that the front inclined surface 40a has a relatively gentle inclination and the rear inclined surface 40b has a relatively steep inclination. Has been. The angle θ 1 formed between the front inclined surface 40a and the plane 38b facing the surface 38a on which the fine prism 40 of the reflecting plate 38 is formed is preferably 20 ° or more and 50 ° or less. Further, the angle Θ2 formed by the rear inclined surface 40b and the flat surface 38b of the reflecting plate 38 is preferably 70 ° or more, and is formed in an angle that is not parallel to the front inclined surface 40a.

 The example of FIG. 3A shows a case where Θ2 is a right angle, and it becomes easy to form the fine prism 40 on the reflecting plate 38 using a mold. On the other hand, the example in Fig. 3 (b) shows the case where Θ2 is an obtuse angle. When the prism shape of Fig. 3 (b) is molded with a mold, the slide insert slides in the direction of arrow B, i.e., the direction in which the negatively inclined rear inclined surface 40b can be removed. It is possible to perform molding by using a mold with a metal plate or by using an elastically deformable material such as rubber as the material of the reflector 38 and by performing die cutting of the reflector 38 by so-called `` reasoning '' It becomes.

 Here, exemplarily shown in FIG. 3 (a), a specific column of the reflector 38 in which the inclination angle of the rear inclined surface is in the range of 70 ° ≤ Θ 2 ≤ 90 ° is given as Θ 1 = 30. , Θ 2 = 80 °, and the arrangement pitch of the fine yarn field prism 40 is 0.1 mm. The base of the reflector 38 is made of PET (Polyethylene Terepht halate) and has a thickness of 0.05 mm. The fine prism 40 is a so-called 2p method (injecting a transparent liquid resin that can be controlled arbitrarily at room temperature, such as a UV curable resin, into a prism molding die and curing it integrally with the substrate. It can be formed by the manufacturing method. It is also possible to directly transfer the shape of the fine prism 40 to the thermoplastic resin film by a hot press mold in which the prism shape is formed.

[0022] Further, the anti-inclined surface of the reflecting plate 38 has a high anti-inclined surface such as aluminum or silver on the prism forming surface. It may also be configured by applying a white or milky white paint that may be formed by forming a metal thin film having a high emissivity. Furthermore, it is also possible to combine the above-described structures, in which the anti-inclined surface of the reflecting plate 38 may be formed by an increased reflection film formed by laminating a dielectric coating film. In any case, since the ridge lines of the fine prisms 40 of the reflector 38 are formed in parallel and straight lines (see FIG. 1 (b)), a reflector having a large area is formed in the manufacturing process. The reflector 38 can be mass-produced by cutting it out to a required size.

 [0023] In addition, one example of the light guide plate 12 is specifically shown. The light guide plate 12 is made of polycarbonate, has a width of 30 mm, a length of 40 mm, and a thickness of 0.6 mm. (Scattering pattern) is formed. Further, the entire lower surface of the light guide plate 12 (the surface from which light is not emitted) is provided with a reflector made of a reflective material such as white resin or silver plating. Furthermore, the light diffusion plate and two brightness enhancement films with the prism directions orthogonal to each other are overlaid on the upper surface of the light guide plate 12 (the surface from which light is emitted), so that the backlight is Composed.

 Note that the reflector 38 only needs to have at least an area that covers the side surfaces 24b and 24c of the LED 24, but may be formed into a simple rectangle as illustrated in consideration of productivity and the like. . In addition, the reflector, diffuser, and brightness enhancement film stacked on the light guide plate 12 as described above may be installed on the reflector 38 if there is a demand to reduce the thickness of the entire planar lighting device 10. If the demand for power is eased, the notch is not formed in the installation part of the reflector 38, but it is installed on the reflector 38.

FIG. 4 shows the locus of light rays emitted from the LED 24 in the planar illumination device 10 in which the reflectors 38 are provided on the upper and lower surfaces of the LED 24 according to the embodiment of the present invention. FIG. 19 corresponds to FIG. 19 showing a light reflection locus of the planar illumination device in the process of developing the planar illumination device according to the invention.

In the planar lighting device 10 according to the embodiment of the present invention, as shown in FIGS. 4 (a) and 4 (b), the surface provided with the fine prism 40 is opposed to each of the side surfaces 24b and 24c of the LED 24. The reflection plate 38 is arranged so as to. As shown in FIG. 4 (a), the outgoing light beams LF4 and LF5 emitted from the side surface 24b of the LED 24 have a relatively steep angle. The angle of light incident on the light guide plate 12 becomes relatively gradual because the angle of the light beam is reflected by the inclined surface 40a (see FIG. 3) and converted. Although not shown in the drawing, the forward angle light emitted from the side surface 24c of the LED 24 is also subjected to the same angle conversion action. It will also be understood that light rays emitted in a direction perpendicular to the side surfaces 24b and 24c of the LED 24 are subjected to the same angle conversion action.

 [0025] As shown in Fig. 4 (b), the light beam LR3 emitted backward from the side surface 24b of the LED 24 is also reflected by the front inclined surface 40a (see Fig. 3) of the fine prism 40, and The light is incident on the light guide plate 12 by changing the angle. Although illustration is omitted, it will be apparent that the backward angle rays emitted from the side surface 24c of the LED 24 are also subjected to the same angle conversion action.

 FIG. 5 and FIG. 6 show application examples of the reflector 38. In this example, the ridge line forces of the fine prisms 44 of the reflector 42 are formed concentrically. The relationship between the slanted front and back slopes of the fine prism 44 and the flat surface 42b of the reflector 42 is the same as that of the reflector 38 shown in FIGS. It is desirable that the center of the concentric circle of the fine prism 44 coincides with the LED chip 25 of the LED 24.

 [0027] FIG. 7 shows another application example of the reflector. The reflector 46 shown in FIG. 7 (c) is obtained by cutting out a plurality of triangular pieces 48 from the reflector 38 shown in FIG. 7 (a) as shown in FIG. 7 (b), as shown in FIG. 7 (c). In this manner, each triangular piece 48 is fixed in a fan shape, and each ridgeline of the fine prism 40 is formed in a concentric polygonal shape. Further, the reflector 46 in FIG. 7 (c) may be further cut into a rectangle if necessary.

 Also in this example, the relationship between the front and rear inclined surfaces of the fine prism 40 and the plane of the reflecting plate 46 is the same as that of the reflecting plate 38 shown in FIGS. 1 to 4, and detailed description thereof is omitted. Also in this example, it is desirable that the center of the concentric polygon of the fine prism 40 is coincident with the LED chip 25 of the LED 24.

 [0028] Next, the LED 24 that is optimal for the embodiment of the present invention will be described. LED24 figure

As shown in FIG. 8 to FIG. 10, it does not have a lamp house and has a structure in which a translucent resin 26 for sealing the LED chip 25 is exposed. In addition, the outer shape of the translucent resin 26 has a protruding portion 28 formed of a continuous curved surface protruding forward in the light emitting direction of the LED 24. Also illustrated In this example, the protrusion 28 is perpendicular to the light guide plate in the direction parallel to the light guide plate (the direction parallel to the paper surface of the light guide plate 12 shown in FIG. 15) (the paper surface of the light guide plate 12 shown in FIG. 15). And a base 29 made of a rectangular parallelepiped translucent resin. Further, the continuous curved surface constituting the protruding portion 28 has a constant radius R in the illustrated example. When the protrusion height of the protrusion 28 (protrusion height from the base 29) is H, the range is 0.3≤H /R≤0.6, more preferably 0.4≤H / R≤0 It is formed to be in the range of 5. Further, the radius of the protrusion 28 is the length when the LED chip 25 is projected in a direction perpendicular to the light guide plate (the length in the direction parallel to the longitudinal direction of the LED 24. It is formed so that it is equal to or greater than 1.5 multiplied by 1.5 (1.5X≤R).

 [0029] As a more detailed structure of the LED 24, the translucent resin 26 has a peripheral force around the LED chip 25.

 9.As shown in Fig. 10, it is sealed with a layer 30 mixed with yttrium-aluminum-garnet (YAG) fine particles activated by cerium, which is a phosphor emitting yellow light, in a hard silicone resin, and its surroundings. It has a structure in which a transparent hard silicone resin layer 32 is added to the (upper layer). Therefore, in the illustrated example, the protruding portion 28 is formed in the transparent hard silicone resin layer 32. The LED chip 25 has a light emitting layer 25b made of a nitride compound semiconductor such as GaN or GaAIN formed on a sapphire substrate 25a as shown in FIG. 11 (blue light emitting element). Is used. Then, as shown in FIG. 10, the LED chip 25 is bonded onto a substrate (PCB) 34 having an electrode portion, and an anode, a force sword electrode formed on the LED chip 25 and a wiring pattern on the substrate 34 are connected. , It has a structure connected with gold wire of φ 20 / im. 9 to 11 show examples of specific dimensions of the LED 24 and the LED chip 25 (unit: mm).

[0030] In the LED 24 having the above structure, part of the blue light emission of the LED chip 25 is absorbed by the YAG fine particles (phosphor) of the YAG fine particle mixed layer 30 and converted to a longer wavelength than the light emission of the LED chip 25. The LED chip 25 emits a pseudo white light by causing a color mixture with the blue light emission. Note that the YAG fine particle mixed layer 30 of the translucent resin 26 is not limited to the structure in which the transparent layer 32 is completely separated into two layers as shown in FIGS. 9 and 10, but at least around the blue light emitting LED chip 25. It is also possible to adopt a structure in which only the YAG fine particle mixed layer 30 is formed and the entire periphery is covered with the transparent layer 32. Further, the translucent resin 26 may be a thermosetting transparent resin, such as a transparent epoxy resin, in addition to the hard silicone resin, as long as it is a transparent resin having heat resistance. . In addition, highly heat-resistant thermoplastic resins and inorganic materials such as glass can be applied as necessary.

 FIG. 12 shows a half-value width indicating the angle of the emitted light of the LED 24 by variously changing the H / R value of the LED 24 used in the planar lighting device according to the embodiment of the present invention. The changes in Θ and the forward emission light quantity ratio ξ are summarized in a chart. FIG. 13 is a graph based on the values in FIG. As shown in FIG. 14, the “half-value width Θ” is half the peak value の of the emitted light intensity (usually, it appears in the vicinity of Θ = 0, which is the front direction of the LED 24). The angle of the emitted light when the emission intensity 1 / 2P is obtained is called the “half-value width” and is a value generally used as an index of the emitted light distribution. FIG. 14 exemplifies the half-value width Θ of an LED with R = 0.9 mm, H = 0.4 mm, and H / R = 0.44.

 In addition, the “front emission light quantity ratio” contributes to higher brightness of the planar lighting device that is emitted in front of the LED (including the upper and lower spaces) out of the omnidirectional light emitted from the LED. This is a value that represents the ratio of the former when classified into light and light that is emitted behind (including the space above and below) the LED and does not contribute to the high brightness of the planar lighting device.

 [0032] As is clear from these specific numerical examples, in the range of 0.3 ≤ H / R ≤ 0.6, sufficiently good values are obtained for both the full width at half maximum Θ and the forward emission light quantity ratio ξ. . In addition, in order to achieve higher brightness and uniform brightness of the planar lighting device, in order to balance the full width at half maximum Θ and the forward light intensity ratio ξ at a higher level, 0.4 ≤ H A range of /R≤0.5 is desirable. Note that in the case of H / R = 0 (the LED 14 with a flat front light emitting surface as shown in FIG. 16), the value of the front emission light quantity ratio ξ has decreased to the lowest level, and the surface illumination device It is understood that it is difficult to increase the brightness. In addition, in H / R = l (LED16 that emits light from a semi-cylindrical protrusion 16a as shown in Fig. 17), the brightness of the planar lighting device is markedly reduced by the half-value width Θ. It is understood that it is difficult to equalize.

[0033] It should be noted that the LED used in the planar illumination device according to the embodiment of the present invention is not limited to the LED 24 shown in FIG. 8 and FIG. It will be clear that the type of LED is also applicable. In addition, with light guide plate 12 LED24 Needless to say, by providing a light incident prism (optical diffuse reflection pattern) on the opposite surface, the light emission distribution of light incident from the LED to the light guide plate can be controlled more precisely. That is.

 [0034] According to the embodiment of the present invention configured as described above, the following operational effects can be obtained. First, as illustrated in FIG. 4 (b), the light beam (LR3) emitted backward from the side surfaces 24b and 24c of the LED 24 is reflected by the front inclined surface 40a (FIG. 3) of the fine prism 40 of the reflector 38. It is possible to reflect the light forward and enter the light guide plate 12. In addition, as illustrated in FIG. 4 (a), the light beams (LF4, LF5) emitted forward from the side surfaces 24b, 24c of the LED 24 are also reflected to the front inclined surface 40a to the light guide plate 12. The light incident angle of the light guide plate 12 can be relaxed, and the proportion of light reaching the tip of the light guide plate 12 can be increased.

 [0035] Further, in the fine prism 40 of the reflector 38, the front inclined surface 40a has a relatively gentle inclination, and the rear inclined surface 40b has a relatively steep inclination, so that the side surfaces 24b, 24c of the LED 24 are formed. Force The light beam (LR3) emitted backward is reflected forward by the relatively gently inclined front inclined surface 40a, so that the light incident angle to the light guide plate 12 is relaxed, and the tip of the light guide plate 12 is The rate of light reaching up to can be increased. In addition, the light S emitted from the side surfaces 24b and 24c of the LED 24 forward is also a force S to increase the effect of relaxing the incident angle on the light guide plate 12.

 Specifically, it is formed at an angular force of 20 ° or more and 50 ° or less between the front inclined surface 40a and the plane 38b facing the surface on which the fine prism 40 of the reflector 38 is formed, and the rear inclined surface 40b. Reflecting while considering the productivity of the reflecting plate, which is desired to be formed at an angle of 70 ° or more with respect to the flat surface 38b of the reflecting plate 38 and not parallel to the front inclined surface 40a. It becomes possible to exhibit the light beam angle conversion action required for the plate.

In addition, as shown in FIGS. 1 and 2, when the ridge lines of the fine prisms 40 of the reflector 38 are formed in parallel and straight lines, the reflector 38 with the highest productivity is obtained. It becomes. In addition, as shown in FIGS. 5 and 6, when the ridges of the fine prisms 44 of the reflector 42 are formed concentrically, the optimal light beam for the reflector 42 is spread over a wide angle in front of the LED 24. An angle conversion action can be exhibited. Furthermore, as shown in FIG. 7 (c), each ridgeline of the fine prism 40 of the reflector 46 is formed in a concentric polygonal shape. It is possible to cause the reflecting plate 46 to exhibit an effective angle conversion effect of light over a wide angle in front.

 [0037] Further, the LED 24 does not have a lamp house, and since the translucent resin 26 that seals the LED chip 25 is exposed, the thickness of the lamp house does not increase. Thinning of the equipment will be promoted. However, since the outer shape of the translucent resin has a shape that satisfies 0.3 ≤ H / R ≤ 0.6, the ratio of the amount of light emitted from the front of the LED that contributes to higher brightness of the planar lighting device and Therefore, it is possible to balance the half-value width Θ of the LED, which contributes to uniform brightness of the planar lighting device, at a high level.

 [0038] Further, the radius R force of the protruding portion 28 of the LED 24 is formed to satisfy 1.5X≤R, so that the LED chip 25 is not exposed from the translucent resin 26. It is completely sealed. Therefore, it is possible to reliably increase the yield of LED24 and reduce the cost of the planar lighting device.

 Further, if a notch 12d is formed on the side end surface 12a of the light guide plate 12 facing the LED 24 so as to follow the outer shape of the projecting portion 28, the translucent resin 26 of the LED 24 and the light guide plate 12 The light emission distribution of the light entering the light guide plate from the LED 24 can be made equal to the light emission distribution of the LED alone, contributing to the uniform brightness of the planar lighting device. That power S is said.

 [0039] In addition, it is preferable from the viewpoint of productivity that the continuous curved surface constituting the protruding portion 28 of the LED 24 has a constant radius R as shown in the figure. For example, the protruding portion 28 has a constant radius. Even if it is configured by a spherical surface or the radius R is gradually changed from the top part of the projecting part 28 toward the base part 29, the above-described effects can be obtained.

 The planar illumination device according to the embodiment of the present invention can be applied to so-called backlights and front lights.

Claims

The scope of the claims  [1] In a planar lighting device including a plate-shaped light guide plate and an LED disposed on a side end surface of the light guide plate, a reflector is disposed along a side surface of the LED in a direction parallel to the light guide plate. A planar illuminating device, wherein a plurality of microscopic prisms having a triangular cross-section with different inclination angles of front and rear inclined surfaces are arranged on a surface of the reflecting plate facing the LED.  [2] The planar illumination device according to [1], wherein the fine prism of the reflecting plate has a relatively slanted front inclined surface and a relatively steep rear inclined surface. .  [3] An angle formed between the front inclined surface and a plane facing the surface on which the fine prisms of the reflecting plate are arranged is formed to be 20 ° or more and 50 ° or less, and the rear inclined surface and the reflecting plate 3. The planar lighting device according to claim 2, wherein an angle formed with a flat surface is 70 ° or more and is in a range not parallel to the front inclined surface.  [4] The planar illumination device according to any one of claims 1 to 3, wherein each of the ridge lines of the fine prism is formed in a parallel and linear shape.  5. The planar illumination device according to any one of claims 1 to 3, wherein each ridge line of the fine prism is formed in a concentric circle shape.  [6] The planar illumination device according to any one of claims 1 to 3, wherein each ridgeline of the fine prism is formed in a concentric polygonal shape.  [7] The LED does not have a lamp house and the translucent resin that seals the LED chip is exposed, and the outer shape of the translucent resin is a continuous curved surface that protrudes forward in the light emission direction of the LED. 7. The method according to any one of claims 1 to 6, characterized by being configured and having a value force in a range of 0.3 or more and 0.6 or less obtained by dividing the protruding height by the radius of the continuous curved surface. The area lighting device according to item 4.  [8] The radius of the projecting portion constituted by the continuous curved surface is formed to be not less than a value obtained by multiplying the length when the LED chip is projected in a direction orthogonal to the light guide plate by 1.5. 8. The planar lighting device according to claim 7, wherein:  9. The planar illumination device according to claim 7 or 8, wherein a cutout portion that follows the outer shape of the protruding portion is formed on a side end surface of the light guide plate facing the LED.