JP2007329114A - Light guide plate, and planar light emitting device equipped with it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light guide plate for uniformly guiding light by effectively confine light emitted from a solid light emitting element in it, and a planar light emitting device equipped with it. <P>SOLUTION: The solid light emitting element 2 is disposed at a prescribed position on the first face 6 side of a light guide plate body 3a, and a recessed part 4 is formed in the prescribed region of a second face 5. The recessed part 4 is formed so as to remove a region in which the optical path of the component of light emitted to the outside of the light guide plate body 3a through the second face 5, out of light advancing toward the second face 5 side in the inside of the light guide plate body 3a by being emitted from the solid light emitting element 2, is positioned. The side wall face 4a exposed on the side wall of the recessed part 4 is used as a face for totally reflecting light emitted from the solid light emitting element 2 so as not to make it emit to the outside of the light guide plate body 3a. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a light guide plate and a planar light emitting device including the same, and more particularly to a light guide plate used as a backlight of a liquid crystal display device and a planar light emitting device including such a light guide plate.

  In recent years, thin and lightweight liquid crystal displays have become widespread as displays mounted on portable electronic devices such as televisions and personal computers. As shown in FIG. 38, the liquid crystal display 200 includes a liquid crystal display panel 151 for displaying an image and a backlight device 110. The backlight device 110 has a function of clearly displaying an image displayed on the liquid crystal display panel 151 by irradiating light from the back surface of the liquid crystal display panel 151.

The backlight device 110 includes a light source, a circuit for driving the light source, and various optical films. In general, a cold cathode fluorescent lamp 152 is used as a light source of the backlight device 110. However, since mercury (Hg) is used for the cold cathode fluorescent lamp 152, for example, when the backlight device 110 is damaged, the mercury may flow out, which may adversely affect the environment. There is.

  Therefore, a solid light emitting element (LED: Light Emitting Diode) typified by a light emitting diode has been proposed as a light source to replace the cold cathode fluorescent lamp. As the solid light emitting element, a solid light emitting element that emits red (R), green (G), and blue (B) light and a solid light emitting element that emits white light have been developed.

  In the backlight device, it is desirable to irradiate the liquid crystal display panel with white light. Therefore, as an aspect of use of the solid light emitting element, there is an aspect in which a solid light emitting element that emits white light is used alone or three solid light emitting elements that emit red, green, and blue light are used. . When three solid light emitting elements are used, white light is formed by mixing three lights emitted from the respective solid light emitting elements, and the white light is irradiated onto the liquid crystal panel.

  By the way, the solid-state light emitting device is smaller in size than the cold cathode fluorescent lamp, and the range (region) irradiated by the emitted light is narrow. Therefore, when a solid light emitting element is used as a light source of a backlight device of a large liquid crystal display panel used for, for example, a television, a plurality of solid light emitting elements are arranged in a line or a plane directly under the liquid crystal display panel. Will be. Such a backlight device of a liquid crystal display device is referred to as a direct type LED backlight.

  However, as a light emission characteristic of light emitted from a general solid light emitting element, the intensity of the light where the solid light emitting element is located is the strongest, and the intensity decreases as the distance from the solid light emitting element increases. Therefore, when the solid light emitting element is used as the light source of the direct type LED backlight, the luminance becomes non-uniform in the plane of the liquid crystal display panel in relation to the position of the solid light emitting element. In other words, the portion of the liquid crystal display panel directly above where the solid light emitting element is disposed has the highest luminance, and the liquid crystal display panel is located immediately above the region between one solid light emitting element and the adjacent solid light emitting element. In this part, the luminance is low.

  In addition, when three solid-state light emitting elements that emit red, green, and blue light are used as the light source, the luminance is non-uniform for each color within the surface of the liquid crystal display panel, so that sufficient color mixing is possible. This is not done, and color irregularities of red, green and blue may occur in the liquid crystal display panel.

  In order to solve such a problem, a sufficient length of light path is ensured from the time when the solid light emitting element is emitted until it reaches the liquid crystal display panel, and the light emitted from each solid light emitting element in the middle of the optical path. There has been proposed a method of sufficiently mixing the colors and irradiating the liquid crystal display panel.

  For example, Patent Document 1 proposes a backlight device in which a solid light-emitting element disposed on a substrate is covered with a resin having an upper surface formed of a part of a side surface of a cylinder or a part of a spherical surface. In this backlight device, first, the light emitted from the solid light emitting element is totally reflected on the curved surface and guided in the resin. The light guided through the resin is scattered by the light diffusion portion provided on the upper surface of the substrate and is emitted as light having a uniform intensity.

Further, Patent Document 2 proposes a backlight device having a mode for guiding light emitted from a side emitter type solid-state light emitting element to a light guide plate. Further, Patent Document 3 proposes a light emitting device in which a recess is formed in a light guide plate. In this light guide plate, an LED is disposed on the lower surface side of the light guide plate, and a depression is formed on the upper surface side of the light guide plate facing the LED. This recess is formed so as to gradually expand as it approaches the upper surface.
JP 2005-340750 A Japanese Patent Laying-Open No. 2005-310611 JP 2002-298629 A

  However, the conventional backlight device has the following problems. First, in the backlight device disclosed in Patent Document 1, the surface shape of the resin covering the solid-state light emitting element is a part of the side surface of the cylinder or a part of the spherical surface as described above. Here, as shown in FIG. 39, this curved surface (side surface of the cylinder) is divided into two curved surfaces P and Q with the solid-state light emitting element 102 as the center. In order to confine all the light incident on the curved surface P among the light emitted from the solid state light emitting element 102 in the resin 103, when the refractive index of the resin 103 is 1.5 and the radius of the sphere is 2 mm, The distance D between the center C and the substrate 101 must be set to about 0.24 mm or less. On the other hand, considering that the height H of the solid light emitting element 102 is 0.1 mm or more, the gap between the solid light emitting element 102 disposed on the substrate 101 and the end face of the resin 103 is almost eliminated at this distance. As a result, there is a problem that the area where light can be guided through the resin 103 is reduced and the color mixing effect is deteriorated.

  Of the light emitted from the solid state light emitting element 102, the light incident on the curved surface Q does not satisfy the total reflection condition. Therefore, the light incident on the curved surface Q is emitted outside the resin 103, and the coupling efficiency into the resin 103 is deteriorated.

  Further, Patent Document 1 proposes a resin having an upper surface composed of four curved surfaces (corresponding to the curved surface P) as a resin for the backlight device. In this backlight device, four curved surfaces each forming a part of a spherical surface meet at one intersection, and a solid state light emitting element is disposed immediately below the intersection. However, in the case of this backlight device, there are three curved surfaces (corresponding to the curved surface Q) extending from the curved surface that form part of the spherical surface. Accordingly, for the four curved surfaces (curved surface P), there are twelve curved surfaces (curved surface Q) connected to the respective curved surfaces.

For this reason, of the light emitted from the solid state light emitting element located immediately below the intersection of the four curved surfaces (curved surface P), the light that has reached these 12 surfaces (curved surface Q) is emitted out of the resin without being totally reflected. Resulting in. Therefore, most of the light emitted from the solid state light emitting element is emitted outside the resin without being confined in the resin, and there is a problem that uniform luminance cannot be obtained.

  In the backlight device disclosed in Patent Document 2, an air layer exists between the solid light emitting element (LED) package and the light guide plate. Therefore, the difference in refractive index due to the presence of air at the interface between the LED package and the light guide plate causes total reflection of light emitted from the solid light emitting element, and light cannot be emitted from the solid light emitting element package. There has been a problem that the amount of light that can be used as the light source of the backlight device is reduced.

  Furthermore, in the light emitting device disclosed in Patent Document 3, a conical shape is preferable as the shape of the depression if the light is spread in all directions, and a triangular pyramid shape is preferable for spreading the light in a specific direction. . In any concavity such as a conical shape, acute corners tend to cause linear luminance unevenness, and chamfering is preferable to eliminate this. However, since the light source disposed immediately below the depression has a size, a part of the light emitted from the light source from a specific position in the light source does not undergo total reflection in the depression. In some cases, the light is emitted outside the light guide plate.

  This will be described. As shown in FIG. 40, the light emitted from the center (origin O) of the solid light emitting element 102 with respect to the depression 104 formed immediately above the solid light emitting element 102, as indicated by optical paths 164 and 165, Thus, the light is totally reflected and proceeds in the light guide plate main body 103a along the direction in which the light guide plate main body 103a extends. On the other hand, of the light emitted from the end (point P1) of the solid state light emitting element 102, the light traveling toward the center of the depression 104 does not undergo total reflection in the depression 104, as indicated by the optical path 166, and the light guide plate body 103a. It will be emitted outside. As described above, in the recess 104 of the light guide plate 103 of the light emitting device disclosed in Patent Document 3, since the size of the light source (solid light emitting element 102) is not considered, a sufficient amount of light is secured as the backlight device. There was a problem that could not be done.

  The present invention has been made to solve the above-described problems, and one object is to provide a light guide plate that effectively confines light emitted from a solid-state light emitting element and guides the light uniformly. An object of the present invention is to provide a planar light emitting device that includes such a light guide plate and emits light uniformly in a plane.

  The light guide plate according to the present invention is a light guide plate used for a backlight of a liquid crystal display device, and includes a plate-like light guide plate main body and a recess. The plate-shaped light guide plate body has a first surface on which light emitted from a predetermined light emitting element is incident and a second surface opposite to the first surface. The recess is formed on the second surface of the light guide plate body and has a predetermined side wall surface. The concave portion is a guide in which an optical path of a component of light that travels through the second surface to the outside of the light guide plate body out of the light emitted from the light emitting element and traveling toward the second surface side. It is formed in the region of the optical plate body. The side wall surface of the recess includes a surface that totally reflects the light component so that the light component is not emitted outside the light guide plate body.

  According to this configuration, the light guide plate main body passes through the second surface out of the light emitted from the light emitting element and traveling inside the light guide plate main body toward the second surface on the second surface portion of the light guide plate main body. A recess is formed so as to remove the region where the optical path of the component of the light emitted to the outside is located, and the light emitted from the light emitting element is exposed to the outside of the light guide plate body on the side wall surface exposed to the side wall of the recess. It is totally reflected so as not to be emitted. As a result, most of the light emitted from the light emitting element toward the second surface is totally reflected, and the loss of light from the second surface is greatly reduced, and the light emitted from the light emitting element is efficiently and evenly distributed. To the inside of the light guide plate body.

  More specifically, as such a recess, the side wall surface is preferably a conical side surface or a part of a paraboloid of revolution. The light emitting element is more preferably arranged at a predetermined position in relation to the focal point of the paraboloid of revolution.

  The sidewall surface of the recess is preferably a part of a curved surface formed by rotating a curve expressed as an exponential function around a predetermined axis, and the curve expressed as such an exponential function is , Α is a total reflection angle of −90 degrees, and C is a constant, r and θ obtained by the equation r = exp (θ / tan α + C) using the curvature coordinates (r, θ) are expressed by the equation X = r · cos θ and Y More preferably, it is a curve converted into rectangular coordinates (X, Y) by r · sin θ.

  Furthermore, the side wall surface of the recess has a plurality of cones having different apex angles so as to follow a curved surface obtained by rotating a predetermined curve satisfying the total reflection condition around a predetermined axis in relation to the position of the light emitting element. It is preferable that the surface is formed by connecting a part of each of the side surfaces.

  Furthermore, the side wall surface of the recess is preferably a surface that totally reflects light emitted from any part of the light emitting element.

  Thereby, the light emitted from the light emitting element can be confined, and the confined light can be guided along the direction in which the light guide plate body extends. It should be noted that a curved surface based on a cone, a rotating paraboloid, or an exponential function is not intended to be a mathematically exact shape but naturally includes manufacturing errors.

  The planar light emitting device according to the present invention includes a substrate having a main surface, a light emitting element, and a light guide plate. The light emitting element is disposed on the main surface of the substrate. The light guide plate is disposed on the main surface of the substrate so as to cover the light emitting element. The light guide plate includes a plate-like light guide plate main body, a concave portion, and an optical path changing portion. The plate-shaped light guide plate main body has a first surface and a second surface facing each other. The concave portion is a portion of the second surface of the light guide plate main body that emits light from the light emitting element and travels inside the light guide plate main body toward the second surface. A side wall surface including a predetermined surface that is formed in a portion of the region of the light guide plate main body where the optical path of the component is located and totally reflects the light component so as not to emit the light component out of the light guide plate main body. . The optical path conversion unit converts the optical path so that the light traveling inside the light guide plate main body including the light component totally reflected on the side wall surface of the concave portion is emitted outward from the second surface.

  According to this configuration, the light totally reflected on the side wall surface of the concave portion proceeds inside along the extending direction of the light guide plate main body without being emitted outside the light guide plate main body. The light traveling in the light guide plate main body is emitted from the second surface of the light guide plate main body by breaking the total reflection condition by changing the optical path by the optical path conversion unit. Thereby, light can be uniformly emitted from the second surface of the light guide plate main body together with the light that travels in the light guide plate main body without being reflected by the side wall surface of the concave portion and whose optical path is changed by the optical path changing portion.

  More specifically, such an optical path conversion unit includes an opening that exposes a predetermined surface that emits light that travels through diffusion particles and the light guide plate body to the outside of the light guide plate body. In the case of diffusing particles, light will be reflected at the surface of the diffusing particles. In the case of the opening, light is reflected on the side wall surface of the opening. In order to emit light uniformly, in the case of diffusing particles, for example, it is preferably disposed uniformly in the light guide plate body. In the case of openings, it is preferable that a plurality of openings be concentrically arranged with the light emitting element as the center. In this case, it is more preferable that a plurality of openings are arranged so that the size increases as the distance from the light emitting element increases.

  Moreover, it is preferable that the substrate, the light emitting element, and the light guide plate are one light emitting module having a predetermined size, and it is more preferable that a plurality of light emitting elements are arranged in a row in the light emitting module.

  In this case, compared with the case where the light emitting elements are two-dimensionally arranged, the region where the light emitting elements are arranged can be narrowed, and the cost can be reduced. In addition, light can be guided over a relatively long distance in the light guide plate, and the color mixing property can be enhanced as a backlight device.

  Moreover, it is preferable that a plurality of such light emitting modules are arranged in a planar shape. In this case, it is possible to easily cope with a liquid crystal display panel having a larger size as a liquid crystal display device, and even when some of the light emitting elements stop emitting light, Can be prevented.

  Further, a package part disposed on the main surface of the substrate and on which the light emitting element is placed, and a reflection surface formed on the package part for reflecting light emitted from the light emitting element toward the light guide plate, A resin filled between the light guide plate and the package may be provided so as to seal the light emitting element.

  In this case, the light emitting element can be replaced when the light emitting element is defective, as compared with the case where the light emitting element is directly attached to the substrate by arranging the light emitting element in the package part. Can be performed more easily.

  In order to reduce light loss and guide light from the light emitting element to the light guide plate, the light guide plate is preferably disposed on the substrate without an air layer interposed between the light emitting element and the light guide plate.

Embodiment 1
The 1st example of the light-guide plate used for the planar light-emitting device based on Embodiment 1 of this invention is demonstrated. As shown in FIGS. 1 and 2, the light guide plate body 3 a that substantially constitutes the light guide plate 3 includes a front surface (second surface) 5 and a back surface (first surface) 6 that are made of resin and face each other. It has a plate-like shape. The solid light emitting element 2 is disposed at a predetermined position on the back surface 6 side of the light guide plate body 3a. The solid state light emitting device 2 is mounted on the surface of the substrate 1 with a reflective sheet 30 interposed.

  On the other hand, the recessed part 4 is formed in the predetermined area | region of the surface 5 of the light-guide plate main body 3a. As shown in FIG. 2 and FIG. 3, the recess 4 is formed on the light guide plate body 3 a through the surface 5 out of the light emitted from the solid light emitting element 2 and traveling toward the surface 5 toward the surface 5. It is formed so as to remove the region where the optical path of the component of the light emitted to the outside is located. The side wall surface 4a exposed at the side wall of the recess 4 is a surface that totally reflects the light emitted from the solid light emitting element 2 so as not to be emitted outside the light guide plate body 3a. In this light guide plate 3, the recess 4 is formed in a substantially conical shape, and the exposed side wall surface 4a forms the side surface of the cone.

  The structure of the recess 4 will be described in more detail. The surface 5 and the side wall surface 4a of the recess 4 formed on the surface 5 serve as an interface in contact with air. The light incident on the interface from the inside of the light guide plate main body 3a is a component of light emitted from the interface to the outside of the light guide plate main body 3a at the incident angle θ (hereinafter referred to as “component A”), and the interface. , And a light component (hereinafter referred to as “component B”) that travels through the light guide plate main body 3a after being totally reflected.

  If the refractive index of the resin constituting the light guide plate body 3a is 1.5, for example, light incident at an angle of about 42 degrees or more is totally reflected at the interface. On the other hand, light incident at an angle of 0 degrees to about 42 degrees is emitted from the inside of the light guide plate body 3a to the outside. Total reflection refers to a phenomenon in which when light enters a medium having a high refractive index into a medium having a low refractive index, the incident light is reflected without being refracted at an incident angle greater than a specific angle. Further, the incident angle θ is defined as an angle formed between the normal line of the incident surface and the optical path of incident light.

  On the other hand, light is generally emitted from the solid state light emitting device 2 at all emission angles. As shown in FIG. 3, for example, as shown in FIG. 3, assuming a light guide plate body 3a having a back surface 6 and a surface 5 on which no recess is formed, light that does not undergo total reflection at the interface between the light guide plate body 3a and air. Ingredients are present. That is, assuming that the normal direction of the surface 5 passing through the solid-state light emitting element 2 is an incident angle of 0 degrees, light having an incident angle in the range of 0 degrees to about 42 degrees (see light components 61 to 63) is not totally reflected. The light is emitted outside the light guide plate body 3a.

  In order to totally reflect the light component to be emitted out of the light guide plate main body 3a and confine it in the light guide plate main body 3a, the light guide plate main body 3a located immediately above the solid light emitting element 2 serves as an interface. A side wall surface 4a of the recess 4 that satisfies the total reflection condition is formed. In the light guide plate main body 3a, the recess 4 is formed as a substantially conical depression, and the side wall surface (interface) 4a corresponds to the substantially conical side surface. The substantially conical shape is a concept including a shape obtained by combining a plurality of conical shapes having different apex angles, as will be described later.

  In the light guide plate 3 configured as described above, among the components of the light emitted from the solid state light emitting element 2, the component A is totally reflected on the side wall surface 4a of the recess 4, and the light guide plate main body 3a to the light guide plate main body 3a. The light guide plate main body 3a is advanced without being emitted to the outside. The component B is totally reflected on the surface 5 and proceeds inside the light guide plate body 3a. The light totally reflected in this way is reflected on the back surface 6 and then travels through the inside of the light guide plate body 3a while being totally reflected on the front surface 5 until the condition for total reflection is not satisfied.

  Here, the shape of the recess that does not allow the light emitted from any part of the solid-state light emitting element to be emitted outside the light guide plate will be examined. First, as shown in FIG. 4, it is assumed that the center of the solid state light emitting device 2 is the origin O and light is emitted only from the origin O. That is, a point light source is assumed. In this case, in the recess 4, the light component 71 emitted from the origin O and incident on the bottom portion (point C) of the recess 4 is totally reflected (condition A), and the recess 4 and the light guide plate body It is required that the light component 72 incident on the boundary portion (point D) with the upper surface 5 of 3a is totally reflected (condition B).

  As described above, when the refractive index of the resin constituting the light guide plate body 3a is 1.5, light incident at an angle of about 42 degrees or more is totally reflected at the interface. Then, as an example of the shape of the conical recess 4 that satisfies the conditions A and B, for example, the thickness (L2) of the light guide plate body 3a is 7.93 mm, and the distance (L3) between the origin O and the point C is 1. 0.5 mm, and the cone bottom diameter (L1) is 14.28 mm (radius 7.14 mm).

  Next, as shown in FIG. 5, a light source having a predetermined size is assumed as the solid state light emitting device 2. In this case, assuming that the position of one end of the solid state light emitting device 2 is a point P1, the light component 71 emitted from the point P1 and incident on the bottom portion (point C) of the recess 4 is totally reflected in the recess 4. (Condition A), and the component 72 of the light emitted from the point P1 and incident on the boundary portion (point D) between the recess 4 and the upper surface 5 of the light guide plate body 3a is totally reflected (Condition B). Is required. In order to satisfy both conditions A and B, the recess 4 has a shape in which at least two cones are combined.

  In this case, the following shape is mentioned as an example of the shape of the recessed part 4 which satisfy | fills the conditions A and B. First, the distance (L4) between the origin O and the point C is 1.5 mm, the distance (L7) between the origin O and the point E is 5.0 mm, and the distance (L5) between the origin O and the point P1 is 0. Assuming 3 mm, the cone satisfying the condition A has a bottom surface diameter (L2) of 10 mm (radius 5 mm) with the point C as an apex, and a distance (L6) from the solid light emitting element 2 to the portion corresponding to the bottom surface is 8.16 mm. It becomes this cone (side wall surface 4d). Further, the distance (L3) between the origin O and the point D is 11.2 mm.

  Then, the cone satisfying the condition B is a cone (side wall surface 4e) having a diameter (L1) of the bottom surface with the point E as an apex and having a diameter of 20.0 mm (radius 10.0 mm). The concave portion 4 is formed by combining a part of the two conical side wall surfaces 4d and 4e so that light emitted from every part of the solid state light emitting element 2 is totally reflected on the side wall surfaces 4d and 4e. it can.

  According to the light guide plate 3 composed of the plate-shaped light guide plate main body 3 described above, the light guide plate main body 3a is emitted from the solid light emitting element 2 toward the surface 5 of the light guide plate main body 3a toward the surface 5 side. The recess 4 is formed so as to remove the region where the optical path of the component of the light emitted to the outside of the light guide plate body 3a through the surface 5 from the light traveling through the interior of the light is further exposed to the side wall of the recess 4 On the side wall surfaces 4a, 4d, and 4e, the light emitted from the solid light emitting element 2 is totally reflected so as not to be emitted outside the light guide plate body 3a.

  As a result, most of the light emitted from the solid-state light emitting element 2 toward the surface 5 is totally reflected by the concave portion 4 and is uniformly guided into the light guide plate body 3a, and the loss of light by the surface 5 is greatly reduced. The light emitted from the solid state light emitting device 2 can be efficiently guided to the inside of the light guide plate body 3a. As a result, the amount of light emitted from the solid state light emitting element 2 and guided to the light guide plate 3 is increased, and a sufficient amount of light as a light source of the backlight device can be secured.

Embodiment 2
The 2nd example of the light-guide plate used for the planar light source device based on Embodiment 2 of this invention is demonstrated. As shown in FIG. 6 and FIG. 7, a recess 4 is formed in a predetermined region of the surface 5 of the light guide plate body 3 a constituting the light guide plate 3 to expose the side wall surface 4 b that forms a part of the paraboloid of revolution. Yes. In addition, since it is the same as that of the light-guide plate 3 mentioned above about another structure, the same code | symbol is attached | subjected to the same member and the description is abbreviate | omitted.

  The structure of the recess 4 will be described in more detail. First, as shown in FIG. 8, a two-dimensional parabola 20 with the X axis as an axis is considered. The solid light-emitting element 2 (see FIG. 7) having a size is disposed so that one end thereof is positioned at the focal point 21 of the parabola. The light emitted from the solid state light emitting element 2 is reflected by the parabola 20 and travels parallel to the X axis. As shown in FIG. 9, the side wall surface 4b of the recess 4 of the light guide plate main body 3a according to the present embodiment is a rotational paraboloid obtained by rotating the parabola 20 around the Y axis (arrow 30). Consists of a part. Therefore, the solid light emitting element 2 having a size is positioned at the focal point of a parabola having one end P1 extending in the positive direction of the X axis and the parabola having the other end P2 extending in the negative direction of the X axis. Will be located at the focal point.

  The parabola will be described in more detail. When the X coordinate of the point P is p and the slope at X = 0 is a, the parabola is expressed by the following equation.

Y = a × p ^0.5 × ((X + p) ^0.5 )
First, as shown in FIG. 10, when one end P <b> 1 of the solid light emitting element 2 is positioned at the focal point 21, the light component 64 emitted from the one end P <b> 1 of the solid light emitting element 2 is parabolic (parabolic surface) 20. Then, the light is totally reflected and proceeds inside the light guide plate body 3a. Further, the light component 65 emitted from the portion located inside the one end P1 is incident on the parabola (parabolic surface) 20 at an angle shallower than the incident angle of the light component 64, thereby forming a parabola (parabolic surface). ) Perform total reflection at 20.

  On the other hand, as shown in FIG. 11, for example, when the center O of the solid state light emitting device 2 is arranged at the focal point 21, the light component 66 emitted from the end P <b> 1 of the solid state light emitting device 2 is a parabola (parabolic). The object surface 20 is emitted outside the light guide plate body 3a because the total reflection condition is not satisfied. Therefore, it is desirable to dispose the solid light emitting element 2 so that the one end P1 coincides with the position of the focal point 21.

  In the light guide plate 3 configured as described above, among the components of the light emitted from the solid light emitting element 2, the component A is totally reflected on the side wall surface 4b of the recess 4, and the light guide plate main body 3a to the light guide plate main body 3a. The light guide plate main body 3a travels along the direction in which the light guide plate main body 3a extends without being emitted to the outside. The component B is totally reflected on the surface 5 and proceeds inside the light guide plate body 3a. For example, if the thickness L2 of the light guide plate body 3a is 4 mm, the maximum diameter L1 of the recess 4 is 8 mm (radius 4 mm), and the depth L3 of the recess 4 is 2.6 mm, the light emitted from the solid light emitting element 2 All can be guided to the light guide plate body 3a.

  According to the light guide plate 3 described above, the following effects can be obtained in addition to the effects of the light guide plate 3 described above. That is, in the light guide plate 3 described above, in particular, the light totally reflected by the side wall surface 4b formed of a part of the paraboloid of revolution is substantially parallel to the back surface 6 (or the front surface 5) of the light guide plate body 3a. By being guided into the light guide plate 3a, the light guide plate main body 3a travels within the shortest distance, and light loss due to absorption of light by the resin constituting the light guide plate main body 3a can be reduced.

Modification In the light guide plate 3 described above, depending on the combination of the size of the solid light emitting element 2 and the depth L3 of the recess 4, the light emitted directly above the light emitted from the solid light emitting element 2 is outside the light guide plate main body 3a. The case where it radiates to is considered. Therefore, as a modified example, the concave portion 4 of the light guide plate 3 based on a parabola that does not allow light emitted from any part of the solid light emitting element 2 having a predetermined size to be emitted outside the light guide plate body 3a will be described.

  In this case, as shown in FIG. 12, assuming that the position of one end of the solid state light emitting device 2 is a point P1, the light emitted from the point P1 and incident on the bottom portion (point C) of the concave portion 4 enters the concave portion 4. And the component 72 of the light incident from the point P1 and entering the boundary portion (point D) between the concave portion 4 and the upper surface 5 of the light guide plate body 3a is totally reflected. Reflection (condition B) is required.

When the refractive index of the resin constituting the light guide plate body 3a is 1.5, light incident at an angle of about 42 degrees or more is totally reflected at the interface. Then, as an example of the shape of the recess 4 that satisfies the condition A and the condition B, the parabolic equation constituting the rotating paraboloid is expressed by Y ² = 2 × h × a × (in the XY plane (see FIG. 8). X + (h / 2 × a)). Here, h represents the distance between the solid state light emitting device 2 and the bottom of the recess 4 (point C), and a represents the inclination of the parabola at X = 0.

  Based on this paraboloid, assuming that the diameter L1 of the upper surface 5 of the light guide plate body 3a of the recess 4 is 8 mm (radius 4 mm), the thickness L2 of the light guide plate body 3a is 4.55 mm. At this time, even if the length of the solid light emitting element 2 from the origin O to the end point P1 is 0.3 mm, the light emitted from every part of the solid light emitting element 2 Total reflection can be achieved at 4b.

  Thus, the light totally reflected on the side wall surface 4b of the recess 4 based on the parabola is guided into the light guide plate main body 3a substantially parallel to the back surface 6 (or the front surface 5) of the light guide plate main body 3a, whereby the light guide plate main body 3a. It will travel in the shortest distance. As a result, light loss due to light being absorbed by the resin constituting the light guide plate main body 3a can be reduced.

Embodiment 3
As a third example of the light guide plate used in the planar light source device according to the third embodiment of the present invention, here, a recess 4 based on a curved surface different from the paraboloid of revolution shown in FIG. 13 is formed. The light guide plate 3 will be described.

First, the curved surface forming the recess 4 is expressed by the following polar coordinate (r, θ) formula:
r = exp (θ / tan α + C)
For each point represented by
X = r · cos θ
Y = r · sinθ
Based on the curve connecting the points (X, Y) transformed by. FIG. 14 shows this curve 25. In the equation of the coordinate system, α is an angle obtained by subtracting 90 degrees from the total reflection angle (total reflection angle −90 degrees), and C is a constant determined by the thickness of the light guide plate body 3a and the like. The curve 25 based on the above equation shows that when a point light source is arranged at the origin O (see FIG. 14), when light emitted from the light source with various emission angles enters the curve, all the light has the same total reflection angle. It is a curved line with total reflection.

  For example, if the refractive index of the resin constituting the light guide plate body 3a is 1.4, the total reflection angle is about 45.6 degrees. When a point light source is disposed at the origin O and the length from the point light source to the upper surface 5 of the light guide plate body 3a (see FIG. 13) is 3.5 mm, α = −44.4 degrees, C = 2. .4. On the curved surface obtained by rotating the curved line 25 around the Y axis as the curved surface constituting the concave portion, all the light emitted from the origin is totally reflected.

  Next, the case of a solid light emitting element having a predetermined size as a light source will be considered. As shown in FIG. 13, when the length from the center O of the solid light emitting element 2 to the one end P1 is 0.3 mm, light emitted from every point of the solid light emitting element 2 is totally reflected in the concave portion 4. In this case, since the light emitted from the one end P1 needs to be totally reflected on the curved line (curved surface), a curved line 26 obtained by moving the original curved line 25 by 0.3 in the X-axis direction as shown in FIG. Think. A curved surface (side wall surface 4f) constituting the concave portion 4 of the light guide plate body 3a shown in FIG. 13 is a curved surface obtained by rotating the curved line 26 around the Y axis.

  A light component 71 emitted from the point P1 and incident on the bottom portion (point C) of the concave portion 4 and a boundary portion (point D) between the concave portion 4 and the upper surface 5 of the light guide plate body 3a emitted from the point P1. The incident light component 72 undergoes total reflection on this curved surface (side wall surface 4f). Furthermore, the light emitted from the portion between the origin O and the one end P1 can also be totally reflected at the recess 4. As a result, the light emitted from every part of the solid state light emitting device 2 can be totally reflected.

  As an example of the shape of such a recess 4, the diameter L1 of the recess 4 is 5.08 mm (radius 2.54 mm), and the depth L3 of the recess 4 is 1 mm. And thickness L2 of the light-guide plate main body 3a shall be 2.5 mm. Thereby, in the light guide plate main body 3a (see FIG. 12) in which the concave portion 4 based on the parabola is formed, the light guide plate main body 3a described above is compared with the thickness L2 of the light guide plate main body 3a being 4.55 mm. Then, the thickness L2 can be reduced by about 2 mm.

  Further, in the curve 26 described above, since the inclination becomes 0 at a predetermined value of X, the point where the inclination becomes 0 is defined as a connection portion between the side wall surface 4f of the recess 4 and the upper surface 5 of the light guide plate body 3a. Thus, the side wall surface 4f and the upper surface 5 can be smoothly connected. When the thickness L2 of the light guide plate body 3a is 2.5 mm, the light is emitted from the solid light emitting element 2 having a length from the center O to one end P1 of 0.6 mm as the solid light emitting element 2. Light can be totally reflected.

Embodiment 4
The 4th example of the light-guide plate used for the planar light source device based on Embodiment 4 of this invention is demonstrated. As shown in FIGS. 15 and 16, the aforementioned paraboloidal side wall surface 4 b and a plurality of conical side surfaces are sequentially formed in a predetermined region of the surface 5 of the light guide plate body 3 a constituting the light guide plate 3. A concave portion 4 is formed to expose the approximate side wall surface 4c by joining together. In addition, since it is the same as that of the light-guide plate 3 mentioned above about another structure, the same code | symbol is attached | subjected to the same member and the description is abbreviate | omitted.

  The structure of the recess 4 will be described in more detail. As shown in FIG. 17, the side wall surface 4c is configured by a plurality of ring-shaped curved surfaces 44a to 44f. Each of the curved surfaces 44a to 44f is composed of a part of side surfaces of a plurality of cones having different apex angles. For example, the curved surface 44 a is a part of the side surface of the cone 41, and the curved surface 44 c is a part of the side surface of the cone 42. The curved surface 44e is a part of the side surface of the cone 43. These curved surfaces 44a to 44f are connected to each other so as to approximate a paraboloid of revolution and constitute a side wall surface 4c.

  In the light guide plate 3 configured as described above, among the components of the light emitted from the solid state light emitting device 2, the curved surface 44 a to 44 f that forms the side wall surface 4 c of the recess 4 and approximates the paraboloid for component A. In any of the cases, the light is totally reflected and proceeds inside the light guide plate main body 3a substantially along the extending direction without exiting from the light guide plate main body 3a to the outside of the light guide plate main body 3a. The component B is totally reflected on the surface 5 and proceeds inside the light guide plate body 3a.

According to the light guide plate 3 described above, the following effects can be obtained in addition to the effects of the light guide plate 3 described above. That is, in the light guide plate 3 described above, a part of the side surfaces of the plurality of cones (curved surfaces 44a to 44f) having different apex angles are connected to each other as the side wall surface 4c so as to approximate the paraboloid of revolution. Thereby, when forming the light-guide plate main body 3a, compared with the case where a rotation paraboloid is formed, it becomes unnecessary to form a smooth curved surface, and the light-guide plate main body 3a can be produced cheaply.

  In the light guide plate 3 described above, the side surfaces 4c are described as examples of the curved surface constituting the concave portion 4 connected to each other so as to approximate the rotary paraboloid. It is good also as a side wall surface mutually connected so that the curved surface (side wall surface 4f) based on the polar coordinate shown by FIG. 13 may be approximated.

Embodiment 5
Next, a planar light emitting device to which the light guide plate described above as the fifth embodiment is applied will be described. First, the light inside the light guide plate body continues to travel inside the light guide plate body as long as the condition of total reflection is satisfied on the surface of the light guide plate body (interface between the light guide plate body and air). When the light guide plate is applied to a planar light emitting device, it is necessary to emit light traveling inside the light guide plate body to the outside in the middle of the optical path. For this purpose, the light guide plate body is provided with an optical path conversion unit for converting the optical path.

  As shown in FIG. 18, in the planar light emitting device 10 according to the present embodiment, as an example of such an optical path conversion unit 7, diffusion particles 7 a that diffuse light in the light guide plate body 3 a are arranged approximately uniformly. Has been. Further, on the surface 5 of the light guide plate main body 3a, for example, a side wall surface 4b forming a part of a paraboloid or a side wall surface 4f forming a part of a curved surface obtained by rotating a curve based on polar coordinates is exposed. A concave portion 4 is formed. In addition, since it is the same as that of the light-guide plate mentioned above about another structure, the same code | symbol is attached | subjected to the same member and the description is abbreviate | omitted.

  In the planar light emitting device 10, among the components of the light emitted from the solid light emitting element 2, the component A is totally reflected on the side wall surface 4 b of the recess 4 and emitted from the light guide plate body 3 a to the outside of the light guide plate body 3 a. Without going through, the inside of the light guide plate main body 3a proceeds substantially along the extending direction. The component B is totally reflected on the surface 5 and proceeds inside the light guide plate body 3a.

  Next, the light path of the light traveling inside the light guide plate main body 3a is changed on the surface of the diffusion particles 7a disposed in the resin constituting the light guide plate main body 3a. Of the light whose optical path has been changed, the light traveling toward the surface 5 includes a component that does not satisfy the total reflection condition. Such light that does not satisfy the total reflection condition is emitted from the surface 5 to the outside of the light guide plate body 3a, and irradiates a liquid crystal display panel (not shown) from the rear. Thus, the light traveling inside the light guide plate main body 3a is changed in its optical path on the surface of the diffusing particles 7a disposed in the light guide plate main body 3a, so that the light is made uniform from the surface 5 of the light guide plate main body 3a as a backlight. It will be emitted.

  Although the diffusion particle 7a has been described as an example of the optical path conversion unit 7 provided in the light guide plate body 3a in the planar light emitting device 10 described above, for example, as shown in FIG. An opening 7b that is recessed toward the back surface 6 may be formed on the front surface 5. Light that does not satisfy the total reflection condition with respect to the side wall surface of the opening 7b is emitted from the side wall surface to the outside of the light guide plate body 3a.

  Further, instead of providing the opening 7b on the front surface 5 of the light guide plate body 3a, for example, as shown in FIG. 20, an opening 7b recessed toward the front surface 5 may be formed on the back surface 6. In this case, as shown in FIG. 21, if there is no opening 7b, the opening for the light whose light path reflected by the back surface 6 of the light guide plate body 3a satisfies the total reflection condition with respect to the surface. By providing the portion 7b, such light is refracted on the side wall surface (interface between the light guide plate main body and air) of the opening 7b, and from the surface to the outside of the light guide plate main body 3a at an angle that does not satisfy the total reflection condition. Can be emitted.

Embodiment 6
As a planar light emitting device according to the sixth embodiment, a structure for making the intensity of light emitted through the optical path changing unit constant will be described. As shown in FIG. 22, the opening 7 b as the optical path changing unit 7 formed on the surface 5 of the light guide plate body 3 a of the planar light emitting device 10 is a concentric circle centering on the position where the solid light emitting element 2 is disposed. A plurality are formed along each circumference. The opening 7b
The shape is schematically represented by a square, but it may be circular or polygonal.

  The intensity of the light emitted from the solid light emitting element 2 is absorbed and attenuated by the resin constituting the light guide plate body 3a as the light travels through the light guide plate body 3a. Therefore, the intensity of the light emitted from the solid light emitting element 2 is the strongest in the vicinity of the solid light emitting element 2 and becomes weaker as the distance from the solid light emitting element 2 increases. Light is emitted from the solid light emitting element 2 in all directions, so that the same intensity is obtained at the same distance from the solid light emitting element 2. For this reason, the intensity of light in the light guide plate body 3a has a concentric intensity distribution centering on the position where the solid light emitting element 2 is disposed.

  In the light guide plate main body 3a described above, the opening 7b as the optical path conversion unit 7 is formed along the circumference of the concentric circle, and the shape of the opening formed on one circumference is the same shape. The As a result, the amount of light whose optical path is converted in the opening can be made constant, and the intensity of light emitted from the opening 7b formed along the circumference of the one concentric circle can be made constant. can do.

Embodiment 7
As a planar light emitting device according to Embodiment 7, a structure for making the intensity of light emitted through the optical path changing unit constant regardless of the distance from the solid light emitting element will be described.

  As shown in FIGS. 23 and 24, the opening 7b as the optical path changing unit 7 formed on the surface 5 of the light guide plate body 3a of the planar light emitting device 10 is away from the position where the solid light emitting element 2 is disposed. The depth is formed so as to increase. In addition, since it is the same as that of the planar light-emitting device mentioned above about another structure, the same code | symbol is attached | subjected to the same member and the description is abbreviate | omitted.

  In the planar light emitting device 10, when the depth of the opening 7 b as the optical path conversion unit 7 becomes deep, the amount of light incident on the optical path conversion unit 7 increases. On the other hand, the intensity of the light emitted from the solid light emitting element 2 becomes weaker as the distance from the solid light emitting element 2 increases. As a result, more weak light is incident on the optical path conversion unit 7 located further away from the solid light emitting element 2, thereby reducing the intensity of the light emitted from the optical path conversion unit 7. The intensity of light incident on the optical path conversion unit 7 located nearby and emitted from the optical path conversion unit 7 can be made substantially the same. As a result, the light guide plate 3 can emit light having a substantially constant intensity to the outside of the light guide plate 3 regardless of the distance from the solid light emitting element 2.

  In the planar light emitting device 10 described above, the opening 7b having a deeper depth has been described as an example of the optical path conversion unit 7 that makes more weak light incident at a location farther from the solid state light emitting element 2. In addition to this, for example, as shown in FIGS. 25 and 26, as the optical path conversion unit 7 moves away from the solid state light emitting device 2, more diffusing particles 7 a may be disposed. The optical path changing unit 7 is formed by applying a resin having a refractive index substantially the same as that of the light guide plate body 3a and containing the diffusing particles 7a.

  In this way, as more diffusing particles 7a are disposed away from the solid state light emitting device 2, the intensity of the light emitted from the optical path conversion unit 7 is made to be an optical path located relatively close to the solid state light emitting device 2. The intensity of the light incident on the conversion unit 7 and emitted from the optical path conversion unit 7 can be made substantially the same. As a result, the light guide plate 3 can emit light having a substantially constant intensity to the outside of the light guide plate 3 regardless of the distance from the solid light emitting element 2.

Embodiment 8
As a planar light emitting device according to the eighth embodiment, an example of a planar light emitting device to which a light guide plate including a plurality of light guide plate bodies is applied will be described. As shown in FIG. 27, in the planar light emitting device 10, a light guide plate 3 in which a plurality of light guide plate bodies 3a shown in FIG. 1 or FIG. . One light guide plate body 3a and another light guide plate body 3a adjacent to each other are connected without interposing an air layer therebetween. Each light guide plate main body 3a is not particularly shown with an optical path conversion unit for simplification of the drawing, but an optical path conversion unit as shown in FIGS. 18 to 20 is formed. In addition, since it is the same as that of the planar light-emitting device mentioned above about another structure, the same code | symbol is attached | subjected to the same member and the description is abbreviate | omitted.

  According to the planar light emitting device 10 described above, the following effects can be obtained in addition to the effects of the light guide plate 3. That is, in this planar light emitting device 10, the size of the planar light emitting device 10 can be freely changed by periodically arranging rectangular light guide plate bodies 3a having the same dimensions. Thereby, as compared with the case where a light guide plate corresponding to the size is applied for each size of the liquid crystal display panel as the planar light emitting device 10, liquid crystal of various sizes can be obtained only by combining the light guide plate main bodies having the basic minimum size. The display panel can be used, and the manufacturing cost can be greatly reduced.

  In the planar light emitting device 10 described above, the light guide plate 3 in which a plurality of light guide plate bodies 3a each having a rectangular planar shape is described as an example. In addition to this, for example, as shown in FIG. A light guide plate 3 in which a plurality of hexagonal light guide plate main bodies 3a are arranged may be applied. In such a light guide plate 3 in which a plurality of light guide plate bodies 3a having a hexagonal shape are arranged, the distance between one solid light emitting element 2 and another solid light emitting element 2 adjacent to each other is the same. Become a distance. Thereby, the in-plane uniformity of the light guide plate 3 with the intensity of light emitted from the light guide plate 3 can be further improved.

Embodiment 9
Another example of the planar light source device to which the light guide plate body is applied will be described as the planar light emitting device according to the ninth embodiment. As shown in FIG. 29, in the planar light emitting device 10, the solid state light emitting device 2 is mounted on a predetermined package 8, and the package 8 is mounted on the surface of the substrate 1 with solder. The package 8 has a recess formed in a portion where the solid light emitting element 2 is mounted, and a predetermined resin 9 is filled in the recess so as to seal the solid light emitting element 2. A light guide plate 3 composed of a light guide plate main body 3 a is attached on the solid light emitting element 2 sealed with the resin 9.

  As shown in FIG. 30, the package 8 is provided with an inclined surface 8a that constitutes a recess. The inclination angle θ of the inclined surface 8a is emitted from the solid state light emitting element 2 with an emission angle of 0 degree and reflected on the inclined surface 8a of the package 8, and the incident angle of light incident on the surface 5 of the light guide plate 3 satisfies the total reflection condition. Is set as follows. For example, the angle θ is preferably set to about 24.5 degrees or less when the distance L from the solid light emitting element 2 to the upper surface of the light guide plate 3 is 4 mm and the refractive index of the resin 9 is about 1.5. .

  In the planar light emitting device 10, the light incident on the side wall surface 4 b exposed from the concave portion 4 out of the light emitted from the solid light emitting element 2 is totally reflected on the side wall surface 4 b and travels inside the light guide plate body 3 a. The light traveling through the light guide plate body 3a remains confined in the light guide plate body 3a unless the optical path is converted by the optical path conversion unit.

In the case of the side wall surface 4b formed of a part of the paraboloid as the side wall surface of the recess 4, the light totally reflected on the side wall surface 4b does not enter the recess of the package 8 and is incident on the light guide plate body 3a. It will be guided along the extending direction. If the light totally reflected on the side wall surface 4b enters the concave portion of the package 8, the light does not satisfy the total reflection condition in the light guide plate main body 3a, and the light guide plate main body 3a from the portion other than the optical path changing portion (not shown). The light is emitted to the outside, and uniform light emission in the planar light emitting device is hindered.

  Of the light emitted from the solid state light emitting device 2, the light incident on the inclined surface 8a of the package 8 is reflected on the inclined surface 8a and totally reflected on the surface 5 of the light guide plate main body 3a and travels inside the light guide plate main body 3a. The light traveling inside the light guide plate body 3a remains confined in the light guide plate body 3a unless the optical path is converted by the optical path conversion unit. Thus, when the light emitted from the solid light emitting element 2 and traveling through the light guide plate main body 3a is incident on the optical path changing unit (not shown), the total reflection condition is broken and emitted to the outside of the light guide plate main body 3a. Become.

  In the planar light emitting device 10 described above, the following effects are obtained in addition to the effects of the light guide plate 3. That is, in the planar light emitting device 10, the solid light emitting element 2 is not directly attached to the substrate 1 with silver paste and sealed with resin, but is mounted on a predetermined package 8, and the solid light emitting element 2 is mounted. The mounted package 8 is mounted on the substrate 1 with solder. Thereby, for example, when a defect occurs in the solid state light emitting device 9, the entire package 8 may be replaced, and maintenance work can be easily performed. In addition, the value of the refractive index of the resin 9 in the planar light emitting device 10 described above is an example, and a resin having another refractive index may be used. The angle of the inclined surface 8a of the package 8 depends on the refractive index. Will be set.

Embodiment 10
As a planar light emitting device according to the tenth embodiment, an example of a planar light emitting device including a light guide plate main body and an optical path changing unit will be described. As shown in FIG. 31, the package 8 is mounted on the surface of the substrate 1, and the solid light emitting element 2 is mounted on the package 8. A light guide plate body 3 a constituting the light guide plate 3 is disposed above the solid light emitting element 2. A resin 9 is filled between the light guide plate body 3 a and the package 8 so as to seal the solid light emitting element 2. The light guide plate body 3a and the resin 9 are bonded to each other with a predetermined adhesive (not shown) without interposing an air layer. The materials of the light guide plate body 3a, the adhesive, and the resin 9 are selected so that the refractive index values match.

  In the recess 4 of the light guide plate body 3a, for example, a side wall surface 4b made of a part of a paraboloid of rotation is exposed. In addition, an opening 7b that forms the optical path conversion unit 7 is formed at a predetermined position on the surface 5 of the light guide plate body 3a. The thickness L2 of the light guide plate body 3a is 3 mm, the maximum diameter L1 of the recess 4 is 8 mm, and the depth L4 of the recess 4 is 2.6 mm. The solid light-emitting element 2 has a planar shape of a square having a side of 0.3 mm and a height of 0.1 mm.

  A substantially conical opening 7 b is formed as an opening 7 b of the optical path conversion unit 7 along a concentric circle centering on the center of the recess 4. Of the opening 7b, the substantially conical opening 7b located closest to the solid state light emitting device 2 has an opening diameter of about 1 mm (opening radius 0.5 mm) and a depth D1 of about 0.5 mm. Is done. On the other hand, in the substantially conical opening 7b located farthest from the solid light emitting element 2, the opening diameter is about 3 mm (opening radius 1.5 mm), and the depth D2 is about 1.5 mm.

  Fifteen openings 7b are formed with an interval of 2 mm between the opening 7b located closest to the solid state light emitting element 2 and the opening 7b located farthest. The light guide plate body 3a has a substantially square shape (60 mm × 60 mm) with a planar shape of 60 mm on a side, and has a length of 30 mm from the solid light emitting element 2 to one end and the other end of the light guide plate body 3a. The opening 7b described above is formed.

Next, the light intensity distribution of the planar light emitting device 10 described above will be described. FIG. 32 is a graph (graph A) showing the evaluation result of the light intensity by simulation together with the comparative example (graph B).
It is. The vertical axis represents the relative intensity of light, and the horizontal axis represents the distance (unit: mm) from the solid state light emitting device. In the planar light emitting device according to the comparative example, as shown in the graph B, the light intensity is about 1/10 of the light intensity at the position where the solid light emitting element is located (origin) at a distance of 30 mm from the solid light emitting element. It turns out that it has fallen to the extent.

  On the other hand, in the planar light emitting device 10, as shown in the graph A, the light intensity at a distance of 30 mm from the solid light emitting element is approximately the same as the light intensity at the position where the solid light emitting element is located (origin). It was found that the light intensity was. As a result, the planar light emitting device 10 includes the light guide plate main body 3a including the concave portion 4 exposing the side wall surface 4b for total reflection and the optical path changing unit 7 for emitting the light totally reflected by the concave portion 4. Thus, it was proved that the light emitted from one solid state light emitting device 2 can be emitted more uniformly in the plane.

  Each planar light emitting device 10 described above is used as a backlight device of a liquid crystal display device. Here, a mode in which the planar light emitting device 10 is used as a backlight device of a liquid crystal display device will be briefly described. As an example thereof, as shown in FIG. 33, in the liquid crystal display device 50, a diffusion plate 53 is mounted on the back surface of the liquid crystal display panel 51 with an optical sheet 52 interposed. The planar light emitting device 10 is disposed behind the diffusion plate 53 with a predetermined spacer (not shown) interposed therebetween. As another example, as shown in FIG. 34, the planar light source device 10 may be directly disposed on the back surface of the liquid crystal display panel 51 with an optical sheet 52 interposed, without a spacer.

Embodiment 11
Here, another example of the planar light emitting device will be described. As shown in FIG. 35, in the planar light emitting device, the recess 4 is formed to extend linearly. The cross-sectional shape of the concave portion 4 in the direction orthogonal to the linearly extending direction is the same shape as the cross-sectional shape of any of the concave portions 4 provided in the light guide plate body 3a described in the above-described embodiments. The

  The solid light emitting element 2 is disposed along the recess 4 at a predetermined position where light emitted from the solid light emitting element 2 is totally reflected at a linear interval. In addition, an optical path changing portion (not shown) for emitting light to the outside of the light guide plate body 3a is formed around the recess 4.

  In the planar light emitting device described above, the solid light emitting elements 2 are arranged in a straight line, so that, for example, as shown in FIG. 27, compared to the planar light emitting device in which the solid light emitting elements 2 are arranged in a matrix. Thus, the region of the substrate (mounting substrate) on which the solid-state light emitting element 2 is disposed is limited to the region 14 located immediately below the concave portion 4 extending linearly. Thereby, the area | region of the mounting board | substrate which arrange | positions the solid light emitting element 2 can be reduced, and cost reduction can be aimed at.

  In particular, the cross-sectional shape of the recess 4 is the same as the cross-sectional shape of the recess 4 based on the polar coordinates described in the third embodiment, so that the side wall surface 4f of the recess 4 and the upper surface 5 of the light guide plate main body 3a. Can be smoothly connected to each other, and luminance unevenness and color unevenness of the planar light emitting device can be reduced. Furthermore, a plurality of planar light emitting devices shown in FIG. 35 may be prepared, and as shown in FIG. 36, these may be arranged in a direction orthogonal to the direction in which the concave portion 4 extends linearly. In the case of this planar light emitting device, as shown in FIG. 37, it can be applied as a backlight device 10 of a large liquid crystal panel 51 in a liquid crystal display device 50.

  In each of the above-described embodiments, the concave portion that exposes the side wall surface that satisfies the total reflection condition is described as an example of the concave portion formed on the surface 5 of the light guide plate body constituting the light guide plate. The wall surface does not need to be composed of a surface that satisfies the total reflection condition in order to emit more uniform light. If a surface that satisfies the total reflection condition is provided, the total reflection condition is not satisfied. You may have the surface which emits the light of a part.

  Further, in each of the above-described embodiments, as the concave portion, the side wall surface is a conical side surface, a part of a paraboloid of revolution, or a part of a curved surface obtained by rotating a curve based on polar coordinates. Although described as an example, the recess is not limited to having such a side wall surface, and has a side surface such as a quadrangular pyramid or a polygonal pyramid as long as it has a surface that satisfies the total reflection condition. Also good.

  Further, as the optical path conversion unit 7 for emitting the light traveling inside the light guide plate main body 3a to the outside of the light guide plate main body 3a, the diffusion particles 7a arranged uniformly on the light guide plate main body 3a have been described as an example. The region in which the particles 7a are disposed is not limited to this, and may be disposed in a specific region in order to emit more uniform light, for example, a region having a predetermined depth from the surface 5 of the light guide plate body 3a. Alternatively, the diffusing particles may be disposed in the region, or the diffusing particles may be disposed in a region other than the region immediately below the recess 4. Moreover, you may change according to the area | region which arrange | positions the magnitude | size and density of the diffusion particle 7a. Furthermore, although the substantially conical opening 7b has been described as an example of the optical path conversion unit 7, the opening 7b includes a surface that emits light outside the light guide plate body 3a without satisfying the total reflection condition. If it is, it is not restricted to a substantially conical shape.

  The embodiment disclosed this time is an example, and the present invention is not limited to this. The present invention is defined by the terms of the claims, rather than the scope described above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a perspective view which shows the light-guide plate which concerns on Embodiment 1 of this invention. FIG. 2 is a cross-sectional view taken along a cross-sectional line II-II shown in FIG. 1 in the same embodiment. In the same embodiment, it is sectional drawing for demonstrating the area | region where a recessed part is formed. In the same embodiment, it is the 1st sectional view for explaining the relation between the shape of a crevice and a solid light emitting element. In the same embodiment, it is the 2nd sectional view for explaining the relation between the shape of a crevice and a solid light emitting element. It is a perspective view which shows the light-guide plate which concerns on Embodiment 2 of this invention. FIG. 7 is a cross-sectional view taken along a cross-sectional line VII-VII shown in FIG. 6 in the same embodiment. In the same embodiment, it is a figure which shows the parabola for demonstrating the shape of a recessed part. In the same embodiment, it is sectional drawing which shows the rotation paraboloid for demonstrating the shape of a recessed part. In the same embodiment, it is the 1st sectional view showing the positional relationship of a solid light emitting element and a paraboloid of revolution. In the same embodiment, it is the 2nd sectional view showing the positional relationship of a solid light emitting element and a paraboloid of revolution. In the same embodiment, it is sectional drawing for demonstrating the optical path of the light radiate | emitted from the solid light emitting element. It is sectional drawing of the light-guide plate which concerns on Embodiment 3 of this invention. In the same embodiment, it is a figure which shows the curve for demonstrating the shape of a recessed part. It is a perspective view which shows the light-guide plate which concerns on Embodiment 4 of this invention. FIG. 16 is a cross-sectional view taken along a cross-sectional line XVI-XVI shown in FIG. 15 in the same embodiment. In the embodiment, it is a partial expanded sectional view for demonstrating the shape of a recessed part. It is sectional drawing which shows the planar light-emitting device concerning Embodiment 5 of this invention. In the embodiment, it is sectional drawing which shows the planar light-emitting device which concerns on a modification. In the same embodiment, it is sectional drawing which shows the planar light-emitting device which concerns on another modification. FIG. 21 is a partial enlarged cross-sectional view showing how light travels in the planar light emitting device shown in FIG. 20 in the same embodiment. It is a top view which shows the planar light-emitting device concerning Embodiment 6 of this invention. It is sectional drawing which shows the planar light-emitting device concerning Embodiment 7 of this invention. FIG. 24 is a partially enlarged cross-sectional view showing how light travels in the planar light emitting device shown in FIG. 23 in the same embodiment. In the embodiment, it is sectional drawing which shows the planar light-emitting device which concerns on a modification. FIG. 26 is a partial enlarged cross-sectional view of the planar light emitting device shown in FIG. 25 in the same embodiment. It is a perspective view which shows the planar light-emitting device concerning Embodiment 8 of this invention. In the same embodiment, it is a fragmentary top view which shows the planar light-emitting device which concerns on a modification. It is sectional drawing which shows the planar light-emitting device concerning Embodiment 9 of this invention. FIG. 30 is a partial enlarged cross-sectional view of the planar light emitting device shown in FIG. 29 in the same embodiment. It is sectional drawing which shows the planar light-emitting device concerning Embodiment 10 of this invention. FIG. 32 is a graph showing light intensity distribution by the planar light emitting device shown in FIG. 31 in the same embodiment. FIG. It is a fragmentary sectional view which shows an example of a structure in the case where the planar light-emitting device concerning each embodiment is applied to a liquid crystal display device as a backlight apparatus. It is a fragmentary sectional view which shows the other example of a structure in the case where the planar light-emitting device which concerns on each embodiment is applied to a liquid crystal display device as a backlight apparatus. It is a perspective view which shows the planar light-emitting device based on Embodiment 11 of this invention. FIG. 36 is a perspective view showing a planar light emitting device in which a plurality of planar light emitting devices shown in FIG. 35 are arranged in the embodiment. FIG. 37 is a perspective view showing a configuration when the planar light emitting device shown in FIG. 36 is applied to a liquid crystal display device as a backlight device in the embodiment. It is a disassembled perspective view which shows the conventional liquid crystal display. It is a partial expanded sectional view for demonstrating the problem of the conventional backlight apparatus. It is a partial expanded sectional view for demonstrating the problem of the other conventional backlight apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Board | substrate, 2 Solid light emitting element, 3 Light guide plate, 3a Light guide plate main body, 4 Concave part, 4a-4f
Side wall surface, 5 surface, 6 back surface, 7 optical path changing part, 7a diffusing particle, 7b opening, 8 package, 9 resin, 10 planar light emitting device, 30 reflecting sheet, 50 liquid crystal display device, 51 liquid crystal display panel, 52 optical Sheet, 53 Diffuser.

Claims (19)

A light guide plate used in a backlight of a liquid crystal display device,
A plate-shaped light guide plate main body having a first surface on which light emitted from a predetermined light emitting element is incident and a second surface facing the first surface;
A concave portion having a predetermined side wall surface formed on the second surface of the light guide plate body,
Of the light emitted from the light emitting element and traveling inside the light guide plate main body toward the second surface, the concave portion is a component of light traveling outside the light guide plate main body through the second surface. Formed in the portion of the region of the light guide plate body where the optical path is located,
The light guide plate, wherein the side wall surface of the recess includes a surface that totally reflects the light component so that the light component is not emitted outside the light guide plate body.   The light guide plate according to claim 1, wherein the side wall surface of the recess is a conical side surface.   The light guide plate according to claim 1, wherein the side wall surface of the recess is a part of a paraboloid of revolution.   The light guide plate according to claim 3, wherein the light emitting element is disposed at a predetermined position in relation to a focal point of the paraboloid of revolution.   The light guide plate according to claim 1, wherein the side wall surface of the concave portion is a part of a curved surface formed by rotating a curve expressed as an exponential function around a predetermined axis. The curve expressed as the exponential function is
If α is a total reflection angle of −90 degrees, and C is a constant, the following equation using the curved coordinates (r, θ):
r = exp (θ / tan α + C)
R and θ obtained by the following equation:
X = r · cos θ
Y = r · sinθ
The light guide plate according to claim 5, wherein the light guide plate is a curved line converted into a rectangular coordinate (X, Y).   The sidewall surface of the recess has a plurality of apex angles different from each other so as to follow a curved surface obtained by rotating a predetermined curve satisfying the total reflection condition around a predetermined axis in relation to the position of the light emitting element. The light guide plate according to claim 1, wherein the light guide plate is a surface formed by connecting a part of a side surface of a cone.   The light guide plate according to any one of claims 1 to 7, wherein the side wall surface of the concave portion is a surface that totally reflects light emitted from every portion of the light emitting element. A substrate having a main surface;
A light emitting device disposed on a main surface of the substrate;
A light guide plate disposed on the main surface of the substrate so as to cover the light emitting element,
The light guide plate is
A plate-shaped light guide plate body having a first surface and a second surface facing each other;
Out of the light on the second surface of the light guide plate body, out of the light guide plate body through the second surface of the light emitted from the light emitting element and traveling inside the light guide plate body toward the second surface. A predetermined surface that is formed in a portion of the region of the light guide plate body where the optical path of the light component traveling to is located and totally reflects the light component so as not to emit the light component out of the light guide plate body A recess having a side wall surface including:
An optical path conversion unit that converts an optical path so that light traveling inside the light guide plate main body including the light component totally reflected on the side wall surface of the recess is emitted from the second surface to the outside. , Planar light emitting device.   The planar light-emitting device according to claim 9, wherein the optical path changing unit includes diffusing particles.   The planar light-emitting device according to claim 10, wherein the diffusion particles are uniformly disposed in the light guide plate body.   The planar light-emitting device according to claim 9, wherein the optical path conversion unit includes an opening that exposes a predetermined surface that emits light traveling through the light guide plate body to the outside of the light guide plate body.   The planar light-emitting device according to claim 12, wherein a plurality of the openings are concentrically arranged around the light-emitting element.   The planar light-emitting device according to claim 13, wherein a plurality of the openings are disposed so as to increase in size as the distance from the light-emitting element increases.   The planar light emitting device according to any one of claims 9 to 14, wherein the substrate, the light emitting element, and the light guide plate are formed as one light emitting module having a predetermined size.   The planar light-emitting device according to claim 15, wherein a plurality of the light-emitting elements are arranged in a row in the light-emitting module.   The planar light-emitting device according to claim 15 or 16, wherein a plurality of the light-emitting modules are arranged in a planar shape. A package part disposed on the main surface of the substrate and on which the light emitting element is placed;
A reflective surface for reflecting light emitted from the light emitting element toward the light guide plate, formed on the package unit;
The planar light-emitting device according to any one of claims 9 to 17, comprising a resin filled between the light guide plate and the package so as to seal the light-emitting element.   The planar light-emitting device according to claim 18, wherein the light guide plate is disposed on the substrate without interposing an air layer between the light emitting element and the light guide plate.

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