JP2011003459A - Illumination lens, light emitting device, surface light source, and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an illumination lens capable of further widening directivity of a light source.SOLUTION: An outgoing face 12 of an illumination lens 1 has a first outgoing face 121 which is depressed toward a point on an optical axis A and a second outgoing face 122 which widens to the outside from a periphery part of the first outgoing face 121. The first outgoing face 121 includes a transmission region which transmits emission light of which angle from the optical axis A is less than a prescribed angle out of the emission light emitted from a base point Q being the position of the light source on the optical axis, and a total reflection region which totally reflects the emission light of which angle from the optical axis A is the prescribed angle or more out of the emission light emitted from the base point Q. A reflecting layer 10 which reflects the light reaching a bottom face 13 out of the light from the light source by repeating total reflection at the outgoing face 12 is formed on the bottom face 13 facing the opposite side to the outgoing face 12 at the surrounding of the incident face 11.

Description

  The present invention relates to an illumination lens that widens the directivity of a light source such as a light emitting diode, and an illumination device using the illumination lens. Furthermore, the present invention relates to a surface light source including a plurality of illumination devices, and a liquid crystal display device in which the surface light source is disposed behind a liquid crystal panel as a backlight.

  In the backlight of a conventional large-sized liquid crystal display device, a large number of cold cathode tubes are arranged directly under the liquid crystal panel, and these cold cathode tubes are used together with members such as a diffusion plate and a reflecting plate. In recent years, a light emitting diode has been used as a light source of a backlight. Light-emitting diodes have been improved in efficiency in recent years, and are expected as light sources with low power consumption instead of fluorescent lamps. As a light source for the liquid crystal display device, the power consumption of the liquid crystal display device can be reduced by controlling the brightness of the light emitting diodes according to the image.

  In a backlight using light emitting diodes of a liquid crystal display device as a light source, a large number of light emitting diodes are arranged instead of cold cathode tubes. Although a uniform brightness can be obtained on the surface of the backlight by using a large number of light emitting diodes, there is a problem that a large number of light emitting diodes are necessary and cannot be made inexpensive. Efforts have been made to increase the output of one light emitting diode and reduce the number of light emitting diodes used. For example, Patent Document 1 proposes a lens that can obtain a uniform surface light source even with a small number of light emitting diodes. Has been.

  In order to obtain a uniform surface light source with a small number of light emitting diodes, it is necessary to enlarge the illuminated area illuminated by one light emitting diode. That is, it is necessary to expand the light from the light emitting diode to widen the directivity. Therefore, in Patent Document 1, a circular lens is arranged on the light emitting diode in a plan view for controlling the directivity of the chip light emitting diode. The lens has a concave surface in the vicinity of the optical axis on the light exit surface that emits light, and a convex surface that is continuous with the concave surface on the outer side.

  In Patent Document 2, as a lens for obtaining a more uniform surface light source, reflected light returning to the incident surface side after Fresnel reflection on the exit surface of the lens is reflected again by total reflection and directed toward the irradiated surface. A lens has been proposed.

Japanese Patent No. 3875247 JP 2008-305923 A

  In the light emitting diode, most light is emitted in the front direction of the chip of the light emitting diode, and in the lens disclosed in Patent Document 1, light directed in the front direction from the chip is diverged by refraction by a concave surface near the optical axis. I am letting. Thereby, it is possible to suppress the illuminance in the vicinity of the optical axis on the surface to be irradiated and to form a broad illuminance distribution.

  However, in the lens of Patent Document 1, it is necessary to suppress the height difference between the concave surface and the convex surface to some extent from the necessity of refracting light from the light source, and there is a limit to widen the directivity of the light source. This is the same in the lens of Patent Document 2 because the light from the chip is distributed by refraction.

  It is an object of the present invention to provide an illumination lens capable of further widening the directivity of a light source, and to provide a light emitting device, a surface light source, and a liquid crystal display device including the illumination lens.

  In order to achieve the above-mentioned object, the inventors of the present invention believe that how to distribute strong light around the light-emitting diode chip in the front direction is important for widening the directivity. The idea came up with the intentional distribution of light going in front of the LED chip using total internal reflection. Therefore, the inventors of the present invention have devised the following illumination lens.

  The illumination lens is an illumination lens that expands light from a light source and irradiates a surface to be irradiated. An illumination surface on which light from the light source enters and an axis with respect to an optical axis that emits the incident light. A symmetric emission surface. The exit surface includes a first exit surface that is recessed toward a point on the optical axis, and a second exit surface that forms a convex surface while spreading outward from the peripheral edge of the first exit surface. . The first emission surface has a predetermined angle from the optical axis among the radiated light radiated from the base point and reaching the first emission surface when the position of the light source on the optical axis is a base point. A transmissive region that transmits less radiated light, and a total reflection region that totally reflects radiated light that is emitted from the base point and reaches the first exit surface with an angle from the optical axis equal to or greater than the predetermined angle. And. The second emission surface has a shape that transmits substantially the entire amount of radiation emitted from the base point and reaching the second emission surface.

  According to this illumination lens, the directivity of the light source can be made wider by positively utilizing total reflection. By the way, in this illumination lens, as shown in FIG. 17, the light totally reflected in the total reflection region of the first emission surface on the emission surface 112 is totally reflected also on the second emission surface outside the first emission surface. Some of them repeatedly reach the bottom surface 113 facing the exit surface 112 around the entrance surface 111. Thus, the light that reaches the bottom surface 113 is transmitted through the bottom surface 113, reflected by a member 130 (for example, a substrate) facing the bottom surface 113, and directed toward the irradiated surface. In this case, the position where the light reflected by the member 130 reaches the surface to be irradiated is determined by the clearance between the bottom surface 113 and the member 130. However, it is expensive to maintain the clearance with high accuracy. Therefore, it is desired to stabilize the illuminance on the irradiated surface with a cheaper configuration. The present invention has been made from such a viewpoint.

  That is, the present invention is an illumination lens for extending light from a light source to irradiate a surface to be irradiated, the incident surface on which light from the light source is incident, and an optical axis for emitting the incident light. An exit surface that is axially symmetric, and a bottom surface facing the opposite side of the exit surface around the entrance surface, the exit surface including a first exit surface that is recessed toward a point on the optical axis; and A second emission surface that forms a convex surface while spreading outward from the peripheral edge of the first emission surface, and the first emission surface is based on the position of the light source on the optical axis, Of the radiated light radiated from the base point and arriving at the first emission surface, a transmission region that transmits radiated light whose angle from the optical axis is less than a predetermined angle, and radiated from the base point and reached the first emission surface Of the radiated light that totally reflects the radiated light whose angle from the optical axis is equal to or greater than the predetermined angle. And the second emission surface transmits substantially the entire amount of radiated light radiated from the base point and reaches the second emission surface, and is totally reflected by the total reflection region. It has a shape that totally reflects almost the entire amount of radiated light that reaches the surface, and on the bottom surface, the light that reaches the bottom surface is reflected by repeating total reflection on the exit surface of the light from the light source. Provided is an illumination lens having a reflective layer formed thereon.

  Here, “substantially total amount” means 90% or more of the total amount, and may be the total amount or a slightly smaller amount than the total amount.

  Further, the present invention is a light emitting device comprising: a light emitting diode that emits light; and an illumination lens that expands light from the light emitting diode and irradiates a surface to be irradiated. Provided is a light-emitting device that is an illumination lens.

  Further, the present invention provides a plurality of light emitting devices arranged in a plane and a state in which light emitted from one surface of the plurality of light emitting devices is diffused from the other surface. A surface light source comprising: a diffuser plate that radiates at a plurality of light emitting devices, wherein each of the plurality of light emitting devices provides the surface light source.

  Moreover, this invention provides a liquid crystal display device provided with a liquid crystal panel and said surface light source arrange | positioned at the back side of the said liquid crystal panel.

  According to the present invention, not only can the directivity of the light source be made wider, but also the illuminance on the irradiated surface can be stabilized with an inexpensive configuration in which a reflective layer is formed on the bottom surface.

Configuration diagram of illumination lens according to Embodiment 1 of the present invention 1 is an enlarged view of the main part of FIG. Configuration diagram of light-emitting device according to Embodiment 2 of the present invention Optical path diagram of light rays reaching the transmission region of the first emission surface of the light emitting device according to Embodiment 2 of the present invention Optical path diagram of light rays reaching the total reflection region of the first emission surface of the light emitting device according to Embodiment 2 of the present invention Optical path diagram of light emitted from the second emission surface of the light emitting device according to Embodiment 2 of the present invention The block diagram explaining Examples 1-3 of the light-emitting device based on Embodiment 2 of this invention The graph which shows the output surface shape of Example 1 of the light-emitting device based on Embodiment 2 of this invention, and shows the relationship between (theta) i and sagY (graphing Table 1). The graph which shows the output surface shape of Example 2 of the light-emitting device which concerns on Embodiment 2 of this invention, and shows the relationship between (theta) i and sagY (Table 2 is graphed). The graph which shows the output surface shape of Example 3 of the light-emitting device concerning Embodiment 2 of this invention, and shows the relationship between (theta) i and sagY (Table 3 is graphed). The graph which shows the relationship between r / R and (theta) i- (theta) n of Example 1 of the light-emitting device based on Embodiment 2 of this invention. The graph which shows the relationship between r / R and (theta) i- (theta) n of Example 2 of the light-emitting device concerning Embodiment 2 of this invention. The graph which shows the relationship between r / R and (theta) i- (theta) n of Example 3 of the light-emitting device based on Embodiment 2 of this invention. Illuminance distribution of Example 1 of light-emitting device according to Embodiment 2 of the present invention Illuminance distribution of Example 2 of light-emitting device according to Embodiment 2 of the present invention Illuminance distribution of Example 3 of light-emitting device according to Embodiment 2 of the present invention Illuminance distribution of only light-emitting diodes for confirming the effects of Examples 1 to 3 Configuration diagram of a surface light source according to Embodiment 3 of the present invention Partial sectional view of a surface light source according to Embodiment 3 of the present invention Illuminance distribution when the light emitting device of Example 1 is used with the surface light source according to Embodiment 3 of the present invention. Illuminance distribution when the light emitting device of Example 2 is used with the surface light source according to Embodiment 3 of the present invention. Illuminance distribution when the surface light source according to Embodiment 3 of the present invention uses the light-emitting device of Example 3 Illuminance distribution with a surface light source when a light-emitting device is configured only with light-emitting diodes for confirming the effects of Examples 1 to 3. Configuration diagram of a liquid crystal display according to Embodiment 4 of the present invention Illustrated diagram of the illumination lens previously conceived

(Embodiment 1)
The illumination lens according to Embodiment 1 of the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram of an illumination lens 1 according to the first embodiment. The illumination lens 1 is disposed between a directional light source (not shown in FIG. 1) and the irradiated surface 3, and extends the light from the light source to irradiate the irradiated surface 3. That is, the directivity of the light source is widened by the illumination lens 1. The illuminance distribution on the irradiated surface 3 decreases substantially monotonically as the distance on the optical axis A, which is the design center line of the illumination lens 1, reaches the maximum. The light source and the illumination lens 1 are arranged so that their optical axes coincide with each other.

  Specifically, the illumination lens 1 has an incident surface 11 on which light from a light source is incident and an output surface 12 that emits incident light. Further, the illumination lens 1 has a bottom surface 13 that faces the exit surface 12 around the entrance surface 11. Further, in the present embodiment, a ring portion 15 that projects radially outward is provided between the emission surface 12 and the bottom surface 13, and the outer periphery of the emission surface 12 is an outer surface having a substantially U-shaped cross section. And the outer peripheral edge of the bottom surface 13 are connected. However, the ring portion 15 can be omitted, and the peripheral edge of the emission surface 12 and the outer peripheral edge of the bottom surface 13 may be connected by an end surface having a linear cross section or an arc shape.

  The exit surface 12 is axisymmetric with respect to the optical axis A. The outline of the illumination lens 1 in plan view need not be axially symmetric with respect to the optical axis A. The incident surface 11 does not need to be axially symmetric with respect to the optical axis A. In the present embodiment, the area optically joined to the light source is the incident surface 11. The annular bottom surface 13 surrounding the incident surface 11 is preferably flat. In the illustrated example, the incident surface 11 and the bottom surface 13 are located on the same plane, but there may be a step between the incident surface 11 and the bottom surface 13. For example, the incident surface 11 may be closer to the exit surface 12 than the bottom surface 13, and the light source may be fitted into a recess formed by the steps. The incident surface 11 does not necessarily have to be directly joined to the light source, and may be recessed in a hemispherical shape so as to form an air layer between the light source and the light source, for example.

  The light from the light source is incident on the illumination lens 1 from the incident surface 11, is then emitted from the exit surface 12, and reaches the illuminated surface 3. The light emitted from the light source is expanded by the action of the emission surface 12 and reaches a wide range of the irradiated surface 3.

  As the light source, for example, a light emitting diode can be employed. The light-emitting diode is often a rectangular plate-shaped chip, and it is preferable that the incident surface 11 of the illumination lens 1 has a shape that matches the shape of the light-emitting diode so as to be in close contact with the light-emitting diode. The light emitting diode is in contact with the incident surface 11 of the illumination lens 1 via a bonding agent, and is optically bonded to the incident surface 11. The light emitting diode is usually covered with a sealing resin so as not to come into contact with air. As a sealing resin for a conventional light emitting diode, epoxy resin, silicon rubber, or the like is used.

  The illumination lens 1 is made of a transparent material having a predetermined refractive index. The refractive index of the transparent material is, for example, about 1.4 to 1.5. As such a transparent material, an epoxy resin, a silicon resin, an acrylic resin, a resin such as polycarbonate, or a rubber such as silicon rubber can be used. Among them, it is preferable to use an epoxy resin or silicon rubber used as a sealing resin for the light emitting diode.

  The exit surface 12 includes a first exit surface 121 that is recessed toward a point on the optical axis A, and a second exit surface 122 that forms a convex surface while spreading outward from the peripheral edge of the first exit surface 121. The light that enters the illumination lens 1 from the incident surface 11 has a large angular range. Light having a small angle from the optical axis A reaches the first emission surface 121, and light having a large angle from the optical axis A reaches the second emission surface 122.

  Next, the shapes of the first emission surface 121 and the second emission surface 122 will be described. For this purpose, first, the base point Q is defined, and the radiation emitted from the base point Q is considered. Here, the base point Q is the position of the light source on the optical axis A, and when a light emitting diode is adopted as the light source, it is the intersection of the optical axis A and the emission surface that is the front of the light emitting diode. That is, the base point Q is separated from the incident surface 11 by the thickness of the bonding agent described above. And the radiated light radiated | emitted from the base point Q is the 1st output surface 121 bordering on angle (theta) b which the line which connected the boundary of the 1st output surface 121 and the 2nd output surface 122, and the base point Q, and the optical axis A makes | forms. And the second exit surface 122.

  As shown in FIG. 2, the first emission surface 121 radiates from the transmission point 123 that transmits the radiated light having an angle from the optical axis A less than the predetermined angle θp among the radiated light radiated from the base point Q, and the base point Q. The total reflection region 124 totally reflects the radiated light whose angle from the optical axis A is equal to or greater than a predetermined angle θp. That is, θp is an angle formed by a line connecting the point P and the base point Q and the optical axis A when a point on the boundary between the transmission region 123 and the total reflection region 124 is a point P.

  On the other hand, the 2nd output surface 122 has the shape which permeate | transmits the radiated light radiated | emitted from the base point Q over the whole surface. The angle between the radiated light from the base point Q and the optical axis A increases toward the outside of the second exit surface 122, but the angle of the ray of the radiation with respect to the normal at the point where the radiated light reaches the second exit surface 122 Is an incident angle with respect to the second exit surface 122, and if the incident angle becomes too large, total reflection occurs. In order to prevent total reflection, it is necessary not to increase the incident angle, and the shape of the second exit surface 122 is such that the angle between the normal and the optical axis A increases as the distance from the optical axis A increases. Become convex.

  The second emission surface 122 is not necessarily required to transmit the radiated light emitted from the base point Q over the entire surface, and has a shape that totally reflects part of the radiated light emitted from the base point Q and transmits the rest. You may have.

  Furthermore, in the present embodiment, as shown in FIG. 1, an annular reflective layer 10 is formed on the bottom surface 13. The reflective layer 10 preferably has a ring shape with the optical axis A as the center. The light from the light source reaches the second emission surface 122 after being totally reflected by the total reflection region 124 of the first emission surface 121 (see FIG. 5). A part of the light reaching the second emission surface 122 is transmitted through the second emission surface 122, but most of the remaining light is totally reflected again once or a plurality of times by the second emission surface 122. The light that has been totally reflected again once or a plurality of times on the second emission surface 122 reaches the bottom surface 13 along the second emission surface 122. The reflection layer 10 reflects the light that has reached the bottom surface 13 in this way. That is, the reflective layer 10 reflects light that reaches the bottom surface 13 by repeating total reflection at the emission surface 12 (total reflection region 124 and second emission surface 122 of the first emission surface 121).

  The reflective layer 10 may be composed of a reflective film obtained by applying a reflective material to the bottom surface 13 and cured, or may be composed of a reflective sheet adhered to the bottom surface 13. Note that the reflectance of the reflective layer 10 is preferably 65% or more. This is because if the reflectance is less than 65%, the loss of light by the reflective layer 10 increases, which causes a decrease in irradiation efficiency and illuminance unevenness.

  In the case of the illumination lens 1 as described above, most of the light emitted from the light source and reaching the transmission region 123 located on the center side of the first emission surface 121 is refracted in the transmission region 123 and irradiated surface 3. Is irradiated to an area centered on the optical axis A of the lens. On the other hand, most of the light emitted from the light source and reaching the total reflection region 124 located on the outer peripheral side of the first emission surface 121 is totally reflected by the total reflection region 124, and most of the light reaches the bottom surface 13 and reaches the reflection layer. 10 is reflected and irradiated to the irradiated surface 3. Further, most of the light emitted from the light source and reaching the second emission surface 122 is refracted by the second emission surface 122 and irradiated to an area away from the optical axis A of the lens on the irradiated surface 3. Therefore, according to the illumination lens 1 of the present embodiment, the directivity of the light source can be made wider. For this reason, it is possible to make the outer diameter of the lens smaller than that of a conventional lens that is only refracted on the concave surface.

  Further, in the present embodiment, the light reaching the bottom surface 13 can be decisively directed toward the irradiated surface 3 with an inexpensive configuration in which the reflective layer 10 is formed on the bottom surface 13. Illuminance can be stabilized.

  Although the basic aspect of the illumination lens 1 of the present embodiment has been described above, a preferable aspect of the illumination lens 1 of the present embodiment will be described below.

The reflective layer 10 has a circular ring shape, and preferably satisfies the following expressions (1) and (2).
R _LS / R <R _in /R<0.78 (1)
0.75 <R _out / R (2)
However,
R _in : inner radius of the reflective layer R _out : outer radius of the reflective layer R _LS : radius of the smallest circle circumscribing the light source R: outermost radius of the illumination lens.

Expressions (1) and (2) are expressions defining the ratio of the reflecting layer 10 to the bottom surface 13 and give a range in which the light irradiated on the irradiated surface 3 can be adjusted to an appropriate amount. With respect to the formula (1), when R _in / R is equal to or less than R _LS / R, a reflective layer is interposed between the lens and the light source, and the amount of light emitted from the light source is reduced. In addition, when the reflective layer is a reflective sheet, if the hole diameter of the sheet is small when the reflective sheet is adhered to the bottom surface of the lens, the reflective sheet cannot be neatly adhered to the lens. Or the like, it becomes impossible to obtain an optically close structure, or the lens is decentered at the time of adhesion, which causes uneven illuminance. Further, when R _in / R is 0.78 or more, the influence of the reflective layer on the light becomes small, and it becomes impossible to adjust the irradiation efficiency and uneven illuminance. With respect to the expression (2), when R _out / R is 0.75 or less, the influence of the reflective layer on the light becomes small, and it becomes impossible to adjust the irradiation efficiency and uneven illuminance.

  The reflective layer 10 may be a material that regularly reflects light reaching the bottom surface 13, but is preferably a material that irregularly reflects light reaching the bottom surface 13. If it becomes like this, illumination intensity can be easily adjusted with the reflective characteristic of the reflective layer 10. FIG.

  The illumination lens of the present invention can also be applied to a light source other than a light emitting diode (for example, a laser or an organic EL).

(Embodiment 2)
FIG. 3 is a configuration diagram of the light-emitting device 7 according to Embodiment 2 of the present invention. The light-emitting device 7 includes a light-emitting diode 2 that emits light, and the illumination lens 1 described in the first embodiment that expands light from the light-emitting diode 2 and irradiates the irradiated surface 3.

  The light emitting diode 2 is disposed in close contact with the incident surface 11 of the illumination lens 1 with a bonding agent and optically bonded. The light emitted from the emission surface 12 of the illumination lens 1 reaches the illuminated surface 3 and illuminates the illuminated surface 3.

  The light emission in the light emitting diode 2 is light having no directivity, but the refractive index of the light emitting region is 2.0 or more, and when light enters a region where the refractive index is low, the interface refraction influences the interface. The maximum intensity is in the normal direction, and the greater the angle from the normal direction, the lower the light intensity. Thus, the light emitting diode 2 has directivity, and in order to illuminate a wide range, it is necessary to widen the directivity with the illumination lens 1.

  FIG. 4 is an optical path diagram of the light emitting device 7. FIG. 4 illustrates an optical path of a light beam that is emitted from a light source at a small angle and reaches the transmission region 123 (see FIG. 2) of the first emission surface 121. The light emitted from the light emitting diode 2 passes through the incident surface 11 and reaches the transmission region 123 of the first emission surface 121. The reached light passes through the transmission region 123 of the first emission surface 121 while being refracted, and then reaches the irradiated surface 3.

  FIG. 5 is an optical path diagram of the light emitting device 7. FIG. 5 illustrates an optical path of a light beam that is emitted from a light source at a small angle and reaches the total reflection region 124 (see FIG. 2) of the first emission surface 121. The light emitted from the light emitting diode 2 passes through the incident surface 11 and reaches the total reflection region 124 of the first emission surface 121. The reached light is totally reflected in the total reflection region 124 of the first emission surface 121. The light close to the optical axis A reaches the second exit surface 122 by total reflection, and then passes through the second exit surface 122 while being refracted. When a reflecting plate is disposed on the incident surface 11 side of the illumination lens 1, almost all of the light transmitted through the second exit surface 122 reaches the irradiated surface 3. On the other hand, the light away from the optical axis A reaches the second emission surface 122 by total reflection, and then reaches the bottom surface 13 by repeating total reflection one or more times at the second emission surface 122 and is reflected by the reflection layer 10. By doing so, the irradiated surface 3 is finally irradiated.

  FIG. 6 is an optical path diagram of the light emitting device 7. In FIG. 6, an optical path of a light beam that is emitted from a light source at a large angle and reaches the second emission surface 122 will be described. The light emitted from the light emitting diode 2 passes through the incident surface 11 and reaches the second emission surface 122. When the second light exit surface 122 does not have a shape that totally reflects a part of the light, the light that has arrived passes through the second light exit surface 122 while being refracted, and then reaches the irradiated surface 3. .

  Examples 1 to 3 are shown below as specific numerical examples of the present invention.

  FIG. 7 is a configuration diagram of light emitting devices according to Examples 1 to 3 of Embodiment 2 of the present invention. The first embodiment is a design example for the purpose of widening directivity by using a light emitting diode of 0.8 mm square as a light source. In FIG. 7, θi is an angle between the optical axis A and a straight line connecting a light source position (base point Q) on the optical axis A and an arbitrary position on the emission surface 12. Further, θn in FIG. 7 is emitted in the angle direction of θi from the normal line of the emission surface 12 at an arbitrary position on the emission surface 12, in other words, the light source position (base point Q) on the optical axis A. The normal line of the emission surface 12 at the position where the light reaches the emission surface 12 is an angle formed with the optical axis A. Further, sagY in FIG. 7 is a distance measured in the optical axis direction from a light source position (base point Q) on the optical axis A to an arbitrary position on the emission surface 12.

Example 1
Next, specific numerical values of Example 1 are shown in Table 1.

  FIG. 8A is a graph of θi and sagY in Table 1. FIG. 9A shows a graph of the relationship between r / R and θi−θn. Here, r / R is a value obtained by normalizing the distance in the direction parallel to the incident surface 11 from the optical axis A to an arbitrary position on the exit surface 12 with the lens outermost radius (r: from the optical axis). Distance in a direction parallel to the incident surface up to an arbitrary position on the exit surface, R: lens outermost radius (see FIG. 7)).

  θi−θn is the angle of the ray of the radiation with respect to the normal at the point where the radiated light radiated at the angle θi reaches the exit surface 12, and represents the angle of incidence on the exit surface 12. The condition of the total reflection region 124 of the first exit surface 121 is that θi−θn is 42.1 deg or more because the refractive index of the transparent material constituting the lens of the first embodiment is 1.492. Therefore, FIG. 9A shows that a narrow range near the optical axis on the first emission surface 121 is the transmission region 123 and a wide range away from the optical axis is the total reflection region 124 in the first embodiment. Show. FIG. 9A also shows that in the first embodiment, the second emission surface 122 totally reflects the radiated light emitted from the base point Q over the entire surface.

In the first embodiment, R _in shown _in FIG. 7 is 4.5, R _out is 5.5, R _LS is 1.41, and R is 6.95. Accordingly, R _in /R=0.65 and R _out /R=0.79, which satisfy the expressions (1) and (2). Further, in Example 1, the reflectance of the reflective layer 10 is 67.7%.

  FIG. 10A shows an irradiated surface obtained by calculation when the light emitting device of Example 1 (illuminating lens and light emitting diode of FIG. 8A) is arranged and the irradiated surface is arranged at a position 16.4 mm away from the light emitting diode. Represents the illuminance distribution. FIG. 11 shows the illuminance distribution on the irradiated surface obtained by calculation when only the same light emitting diode as in FIG. 10A is disposed and the irradiated surface is disposed at a position 16.4 mm away from the light emitting diode. 10A and 11 show illuminance distribution curves on the irradiated surface when the optical axis center illuminance is normalized as 1. FIG. Comparing FIG. 10A and FIG. 11, it can be seen that the irradiated surface can be widely illuminated by the effect of the illumination lens.

(Example 2)
Next, specific numerical values of Example 2 are shown in Table 2.

  FIG. 8B is a graph of θi and sagY in Table 2. FIG. 9B shows a graph of the relationship between r / R and θi−θn. The r / R and θi−θn in FIG. 9B are the same as those in FIG. 9A.

  In Example 2, as in Example 1 described above, the lens is made of a material having a refractive index of 1.492. Therefore, the condition of the total reflection region 124 of the first emission surface 121 is θi−θn of 42.1 deg or more as in the first embodiment. Therefore, FIG. 9B shows that in the second embodiment, a range similar to that of the first embodiment is the transmission region 123 and a narrower range than the first embodiment is the total reflection region 124. FIG. 9B also shows that in the second embodiment, the second emission surface 122 totally reflects part of the radiated light emitted from the base point Q and transmits the rest.

In the second embodiment, R _in shown _in FIG. 7 is 2.50, R _out is 5.90, R _LS is 1.41, and R is 6.00. Therefore, R _in /R=0.42 and R _out /R=0.98, which satisfy the above expressions (1) and (2). Furthermore, in Example 2, the reflectance of the reflective layer 10 is 97.7%.

  FIG. 10B shows an irradiated surface obtained by calculation when the light emitting device of Example 2 (illuminating lens and light emitting diode of FIG. 8B) is arranged and the irradiated surface is arranged at a position 16.4 mm away from the light emitting diode. Represents the illuminance distribution. 10B shows an illuminance distribution curve on the irradiated surface when the optical axis central illuminance is normalized as 1, as in FIG. 10A. Comparing FIG. 10B and FIG. 11, it can be seen that the illuminated surface can be widely illuminated by the effect of the illumination lens.

(Example 3)
Next, specific numerical values of Example 3 are shown in Table 3.

  FIG. 8C is a graph of θi and sagY in Table 3. FIG. 9C shows a graph of the relationship between r / R and θi−θn. The r / R and θi−θn in FIG. 9C are the same as those in FIG. 9A.

  Also in the third embodiment, as in the first embodiment, the lens is made of a material having a refractive index of 1.492. Therefore, the condition of the total reflection region 124 of the first emission surface 121 is θi−θn of 42.1 deg or more as in the first embodiment. Therefore, FIG. 9C shows that in this third embodiment, a range similar to that of the first embodiment is the transmission region 123 and a range similar to that of the first embodiment is the total reflection region 124. . FIG. 9C also shows that in the third embodiment, the second emission surface 122 totally reflects the radiated light emitted from the base point Q over the entire surface.

In the third embodiment, R _in shown _in FIG. 7 is 1.60, R _out is 6.25, R _LS is 1.41, and R is 6.25. Therefore, R _in /R=0.26 and R _out /R=1.00, which satisfy the above formulas (1) and (2). Further, in Example 3, the reflectance of the reflective layer 10 shown in FIG. 7 is 98.7%.

  FIG. 10C shows an irradiated surface obtained by calculation when the light emitting device of Example 3 (illuminating lens and light emitting diode of FIG. 8C) is arranged and the irradiated surface is arranged at a position 16.4 mm away from the light emitting diode. Represents the illuminance distribution. 10C shows an illuminance distribution curve on the irradiated surface when the optical axis center illuminance is normalized as 1, similarly to FIG. 10A. Comparing FIG. 10C and FIG. 11, it can be seen that the illuminated surface can be widely illuminated by the effect of the illumination lens.

(Embodiment 3)
FIG. 12 is a configuration diagram of the surface light source 9 according to Embodiment 3 of the present invention. The surface light source 9 includes a plurality of light emitting devices 7 described in the second embodiment, which are arranged in a plane, and a diffusion plate 4 which is arranged so as to cover these light emitting devices 7. The light emitting devices 7 may be arranged in a matrix as shown in FIG. 12, or may be arranged in a staggered manner.

  The surface light source 9 includes a substrate 8 that faces the diffusion plate 4 with the light emitting device 7 interposed therebetween. As shown in FIG. 13, the light emitting diode 2 of each light emitting device 7 is mounted on the substrate 8. In the present embodiment, the reflector 6 is disposed on the substrate 8 so as to cover the substrate 2 while avoiding the light emitting diode 2.

  The light emitting device 7 irradiates the one surface 4 a of the diffusion plate 4 with light. That is, one surface 4a of the diffusion plate 4 is the irradiated surface 3 described in the first and second embodiments. The diffusing plate 4 radiates light irradiated on the one surface 4a in a state of being diffused from the other surface 4b. Each light emitting device 7 irradiates light having a uniform illuminance over a wide range on one surface 4a of the diffusion plate 4, and this light is diffused by the diffusion plate 4 so that there is little luminance unevenness in the surface. A surface light source is created.

  The light from the light emitting device 7 is scattered by the diffusion plate 4 and returns to the light emitting device side or passes through the diffusion plate 4. The light that returns to the light emitting device side and enters the reflection plate 6 is reflected by the reflection plate 6 and then enters the diffusion plate 4 again.

  FIG. 14A is a calculation when five light emitting devices of Example 1 including the illumination lens and the light emitting diode of FIG. 8A are arranged on a straight line at a pitch of 60 mm, and a diffusion plate is arranged at a position 16.4 mm away from the light emitting diode. The illuminance distribution on the diffusion plate incident surface (one surface on the light emitting device side) obtained in (5) is expressed. This is because fine waves are seen in the illuminance distribution, but the number of light rays to be evaluated is insufficient in executing the illuminance calculation. The illuminance distribution obtained using the light emitting device of Example 2 and the illuminance distribution obtained using the light emitting device of Example 3 obtained in the same manner are shown in FIGS. 14B and 14C, respectively.

  FIG. 15 shows the illuminance distribution on the entrance surface of the diffuser obtained by calculation when only five light emitting diodes are arranged on a straight line at a pitch of 60 mm and the diffuser is placed at a position 16.4 mm away from the light emitting diode.

  14A to 14C and FIG. 15, it can be seen that the diffusion plate incident surface can be uniformly illuminated by the effect of the illumination lens.

(Embodiment 4)
FIG. 16 is a configuration diagram of a liquid crystal display device according to Embodiment 4 of the present invention. This liquid crystal display device includes a liquid crystal panel 5 and the surface light source 9 described in the third embodiment, which is disposed on the back side of the liquid crystal panel 5.

  A plurality of light emitting devices 7 composed of the light emitting diodes 2 and the illumination lens 1 are arranged in a plane, and the light diffusing plate 4 is illuminated by these light emitting devices 7. The back surface (one surface) of the diffusion plate 4 is irradiated with light with uniform illuminance, and this light is diffused by the diffusion plate 4 to illuminate the liquid crystal panel 5.

  An optical sheet such as a diffusion sheet or a prism sheet is preferably disposed between the liquid crystal panel 5 and the surface light source 9. In this case, the light transmitted through the diffusion plate 4 is further diffused by the optical sheet to illuminate the liquid crystal panel 5.

DESCRIPTION OF SYMBOLS 1 Illumination lens 10 Reflective layer 11 Incident surface 12 Outgoing surface 121 First outgoing surface 122 Second outgoing surface 123 Transmission region 124 Total reflection region 13 Bottom surface 2 Light emitting diode (light source)
3 Surface to be irradiated 4 Diffusion plate 5 Liquid crystal panel 6 Reflector 7 Light emitting device 8 Substrate 9 Surface light source A Optical axis Q Base point

Claims (10)

An illumination lens that expands light from a light source and irradiates an irradiated surface,
An incident surface on which light from the light source is incident; an emission surface that is axially symmetric with respect to an optical axis that emits the incident light; and a bottom surface that faces the opposite side of the emission surface around the incident surface;
The exit surface includes a first exit surface that is recessed toward a point on the optical axis, and a second exit surface that forms a convex surface while spreading outward from the peripheral edge of the first exit surface,
The first emission surface has a predetermined angle from the optical axis among the radiated light radiated from the base point and reaching the first emission surface when the position of the light source on the optical axis is a base point. A transmissive region that transmits less radiated light, and a total reflection region that totally reflects radiated light that is emitted from the base point and reaches the first exit surface with an angle from the optical axis equal to or greater than the predetermined angle. And including
The second emission surface transmits substantially the entire amount of radiated light radiated from the base point and reaches the second emission surface, and radiated light that is totally reflected by the total reflection region and reaches the second emission surface. It has a shape that totally reflects almost the entire amount of
On the bottom surface, a reflection layer is formed that reflects the light reaching the bottom surface by repeating total reflection on the emission surface of the light from the light source.
Lens for lighting. The bottom surface is flat;
The illumination lens according to claim 1, wherein the reflective layer has a ring shape centered on the optical axis and satisfies the following expression.
R _LS / R <R _in /R<0.78
0.75 <R _out / R
However,
R _in : inner radius of the reflective layer R _out : outer radius of the reflective layer R _LS : radius of the smallest circle circumscribing the light source R: outermost radius of the illumination lens.   The illumination lens according to claim 1, wherein a reflectance of the reflective layer is 65% or more.   The illumination lens according to claim 1, wherein the reflection layer diffusely reflects light reaching the bottom surface.   The illumination lens according to any one of claims 1 to 4, wherein the second emission surface transmits the radiated light emitted from the base point over the entire surface.   The illumination lens according to any one of claims 1 to 4, wherein the second emission surface totally reflects a part of the radiated light emitted from the base point and transmits the remaining part. A light emitting device comprising: a light emitting diode that emits light; and an illumination lens that expands the light from the light emitting diode to irradiate the irradiated surface,
The light emitting device according to claim 1, wherein the illumination lens is the illumination lens according to claim 1. A plurality of light emitting devices arranged in a plane, and a diffusion plate arranged so as to cover the plurality of light emitting devices and radiating light irradiated on one surface from the plurality of light emitting devices in a state of diffusing from the other surface; A surface light source comprising:
Each of these light-emitting devices is a surface light source which is the light-emitting device of Claim 7.   A substrate opposed to the diffusion plate with the plurality of light emitting devices interposed therebetween, the substrate on which the light emitting diodes of each of the plurality of light emitting devices are mounted, and the substrate so as to cover the substrate while avoiding the light emitting diodes The surface light source according to claim 8, further comprising a reflector disposed on the surface.   A liquid crystal display apparatus provided with a liquid crystal panel and the surface light source of Claim 8 or 9 arrange | positioned at the back side of the said liquid crystal panel.

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