JP2010146987A - Lens for illumination, light-emitting device, plane light source, and liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lens for illumination capable of further widening directionality of a light source. <P>SOLUTION: The lens for illumination 1 includes an incident surface 11 and an emission surface 12. The emission surface 12 includes a first emission surface 121 being convex toward a tip of a light axis A, and a second emission surface 122 enlarging from a peripheral edge part of the first emission surface 121 toward outside. The first emission surface 121 takes on a shape, in which an emission light with an angle from the light axis A to be a predetermined angle or more among emission lights reaching the first emission surface 121 emitted from an origin P which is to be a light source position on the light axis A is made to reach an illuminated surface 3 by being refracted at a second-time reaching point after total reflection at a first-time reaching point. The second emission surface 122 takes on a shape, which makes the emission light reach the second emission surface 122 emitted from the origin P to be refracted at its reaching point and reach the illuminated surface 3. On the emission surface 12, a reflection layer 15 reflecting light is formed at a boundary part with the first emission surface 121 and the second emission surface 122. <P>COPYRIGHT: (C)2010,JPO&INPIT

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 lights. 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. By using a large number of light emitting diodes, uniform brightness can be obtained on the surface of the backlight. 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.
Japanese Patent No. 3875247

  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 the light emitting diode, the 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, as shown in FIG. The light which goes to the front direction is diverged by refraction. Thereby, as shown in FIG.15 (b), the illumination intensity vicinity of the optical axis in an irradiated surface can be suppressed, and it can be set as a wide illumination intensity distribution.

  By the way, the light emission of the light emitting diode is not a point but has a certain light emission region. The light emitted from the periphery of the light emitting region takes a different path from the light emitted from the central portion of the light emitting region. In FIG. 15A, the path of light emitted from the central portion of the light emitting region is indicated by a solid line, and the path of light emitted from the peripheral portion of the light emitting region is indicated by a wavy line.

  In order to make the illuminance distribution wider, it is conceivable to reduce the radius of curvature of the concave surface near the optical axis. In this way, the incident angle of the light from the central portion of the light emitting region to the concave surface is increased, and this light can be refracted largely to the surroundings as shown by the solid line in FIG. However, the light from the periphery of the light emitting region causes total reflection because the incident angle to the concave surface is locally increased as shown by the wavy line in FIG. For this reason, as shown in FIG.16 (b), the illumination intensity on a to-be-irradiated surface falls locally, and a dark place is formed in a ring shape. As a result, luminance unevenness occurs when the surface light source is used. As described above, the lens disclosed in Patent Document 1 has a limit in widening the directivity of the light source due to the influence of total reflection of light around the light emitting region.

  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 object, the inventor of the present invention considers that how to distribute strong light around the light emitting diode chip in the front direction is important for widening the directivity. I intentionally came up with the idea of using total internal reflection to distribute the light going to the front of the LED chip to the surroundings. 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 output surface that is axisymmetric, and the output surface is convex toward the apex on the optical axis, and forms a convex surface while spreading outward from the peripheral edge of the first output surface. A second emission surface, and the first emission surface emits radiation from the base point and reaches the first emission surface when the position of the light source on the optical axis is a base point. Of these, the second arrival point at which the total reflected radiation reaches after the total reflection of the emitted light whose angle from the optical axis is a predetermined angle or more at the first arrival point at which the emitted light first arrives. And has a shape that is refracted by and reaches the irradiated surface, and the second exit surface is the base point Radiated from the radiated light reaching the second exit surface and refracting at the arrival point to reach the irradiated surface, and on the exit surface, the first exit surface and the Provided is an illumination lens in which a reflection layer for reflecting light is formed at a boundary portion of a second emission surface.

  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 said structure, the 1st output surface is a convex surface which makes it light-emitted, after once totally reflecting the light from the light emission area center part of a light source. For this reason, the light from the periphery of the light emitting region of the light source also reaches the irradiated surface after being totally reflected by the first emission surface. That is, according to the first emission surface, it is possible to irradiate a wider area centering on the optical axis of the lens on the irradiated surface with substantially the entire amount of light reaching the first emission surface. On the other hand, according to the 2nd output surface which forms a convex surface, the light which reaches the 2nd output surface can be irradiated to the field far from the optical axis of the lens in an irradiated surface. Therefore, according to the present invention, the directivity of the light source can be broadened by effectively distributing strong light traveling from the light source in the front direction without any conventional restrictions.

  Here, at the boundary portion between the first emission surface and the second emission surface, a manufacturing error is likely to occur, and there is a possibility that the designed shape may not be realized. In such a case, the light emitted from the boundary portion may reach an unexpected position on the irradiated surface, resulting in uneven illuminance. On the other hand, in the present invention, since the reflection layer that reflects light is formed at the boundary between the first emission surface and the second emission surface, unevenness in illuminance on the irradiated surface can be reduced.

(Embodiment 1)
The illumination lens according to Embodiment 1 of the present invention will be described with reference to the drawings. 1A is a configuration diagram of the illumination lens 1 of Example 1 according to Embodiment 1, and FIG. 1B is a configuration diagram of the illumination lens 1 of Example 2 according to Embodiment 1. FIG. The difference between the illuminating lens 1 of Example 1 and the illuminating lens 2 of Example 2 is only the presence or absence of a second reflective film 16 described later, and both will be described together below.

  The illumination lens 1 is arranged between a directional light source (not shown in FIGS. 1A and 1B) 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. 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. 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. However, since the illumination lens 1 plays the role of a sealing resin, it is not necessary to separately arrange the sealing resin. 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 convex toward the apex 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 P is defined, and the radiation emitted from the base point P is considered. Here, the base point P is the position of the light source on the optical axis A. 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 P 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 P 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 P, and the optical axis A makes | forms. And the second exit surface 122.

  The first emission surface 121 emits radiated light whose angle from the optical axis A is equal to or larger than a predetermined angle θf (see FIGS. 5A and 5B) among the radiated light radiated from the base point P and reaches the first emission surface 121. After total reflection at the first arrival point 131 (see FIGS. 3A and 3B) where light first arrives, the second arrival point 132 (see FIGS. 3A and 3B) where the totally reflected radiation reaches. ) And refracted to reach the irradiated surface 3. Thus, the radiated light from the base point P, which has reached the first emission surface 121 and has an angle from the optical axis A of the predetermined angle θf or more, is subjected to one total reflection and one refraction action, and has a great course. Then, the irradiated surface 3 is irradiated with the change. Here, the first arrival point 131 and the second arrival point 132 are preferably located on opposite sides of the optical axis A. That is, it is preferable that the light beam from the first arrival point 131 to the second arrival point 132 intersects the optical axis.

  The predetermined angle θf, which is the starting angle at which the first emission surface 121 totally reflects the radiation light from the base point P, is such that most of the radiation light from the base point P reaching the first emission surface 121 is totally reflected once. It may be substantially 0 degrees. Here, “substantially 0 degree” means an angle of less than 1 degree. In order to realize this, the apex of the first emission surface 121 may be sharpened. In this way, the amount of light reaching the portion near the optical axis A on the irradiated surface 3 can be suppressed, and the light from the light source can be distributed more to the surroundings.

  However, when the surface light source is configured by using a plurality of light emitting diodes, the predetermined angle θf is preferably set to 3 to 7 degrees. If θf is less than 3 degrees, the portion near the optical axis A on the irradiated surface 3 becomes too dark, and if θf exceeds 7 degrees, the portion near the optical axis A on the irradiated surface 3 becomes too bright. This is because it is difficult to achieve a uniform illuminance distribution when a surface light source is used.

  Further, when the predetermined angle θf is 3 to 7 degrees, the angle from the optical axis A among the radiated light radiated from the base point P and reaching the first output surface 121 is less than the predetermined angle θf. It is preferable that the radiated light is refracted at the arrival point 133 (see FIG. 5A) to reach the irradiated surface 3. In order to realize this, the radius of curvature of the vicinity of the apex of the first emission surface 121 may be increased. In this way, it is possible to illuminate the vicinity of the optical axis A on the irradiated surface 3, and to reduce uneven brightness in the surface when a surface light source is used. However, in Example 2, the second reflective film 16 described later intentionally prevents light from being emitted from the vicinity of the apex of the first emission surface 121 as shown in FIG. 5B. In this way, the light reflected by the second reflecting film 16 is reflected by, for example, a reflecting plate disposed on the incident surface 11 side of the illumination lens 1 and finally reaches the irradiated surface 3. Thus, the light in the vicinity of the strongest optical axis can be distributed to the surroundings.

  Note that an angle θb formed by a line connecting the boundary between the first emission surface 121 and the second emission surface 122 and the base point P and the optical axis A (this is also the final angle of the first emission surface 121 and is the second emission surface 122. Is also in the range of 15 to 25 degrees. When θb degree is less than 15 degrees, the effect of the first emission surface 121 becomes small, and a large diffusion effect cannot be obtained. When θb exceeds 25 degrees, the vicinity of the optical axis A on the irradiated surface 3 becomes too bright.

  On the other hand, the second emission surface 122 has a shape in which the radiated light radiated from the base point P and reaches the second emission surface 122 is refracted at the arrival point 14 (see FIGS. 4A and 4B) to reach the irradiated surface 3. have. The angle between the emitted light from the base point P and the optical axis A increases toward the outside of the second exit surface 122, but the ray of radiation with respect to the normal at the arrival point 14 where the emitted light has reached 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 with the normal optical axis A increases as the distance from the optical axis A increases. Become convex.

  Furthermore, in the first embodiment, the reflection film 15 that reflects light is formed on the emission surface 12 at the boundary between the first emission surface 121 and the second emission surface 122. The reflection film 15 has a ring shape along the boundary line between the first emission surface 121 and the second emission surface 122. Here, the boundary portion means a range of θb ± 10 degrees. In particular, it is preferable that the reflective film 15 is formed in a region of 5 degrees on the optical axis A side from θb and 8 degrees on the opposite side from the boundary portion.

  The reflective film 15 is an example of a reflective layer, and can be formed by applying and curing a reflective material. The reflectance of the reflective film 15 is preferably 80% or more. As another example of the reflective layer, the reflective layer can be formed by attaching a reflective sheet.

  Furthermore, in Example 2, the radiated light having an angle from the optical axis A of the radiated light radiated from the base point P and reaching the first output surface 121 reaches the first output surface 121 less than the predetermined angle θf. A second reflective film 16 that reflects light is formed in the region. The second reflective film 16 is an example of a second reflective layer, and can be formed by applying and curing a reflective material, like the reflective film 15. Moreover, you may form a 2nd reflective layer by sticking a reflective sheet. The reflectance of the second reflective film 16 is also preferably 80% or more.

  As described above, the first emission surface 121 is a convex surface that emits light after being totally reflected once from the light emitting region central portion of the light source, as indicated by a solid line in FIGS. 3A and 3B. For this reason, as indicated by the wavy line in FIGS. 3A and 3B, the light from the periphery of the light emitting region of the light source also reaches the irradiated surface 3 after being totally reflected by the first emission surface 121. In other words, according to the first emission surface 121, substantially the entire amount of light reaching the first emission surface 121 can be applied to a wider area centered on the optical axis A of the lens on the irradiated surface 3. On the other hand, according to the 2nd output surface 122 which forms a convex surface, the light which arrives at the 2nd output surface 122 can be irradiated to the area | region away from the optical axis of the lens in the to-be-irradiated surface 3. FIG. Therefore, according to the illumination lens 1 of the first embodiment, the directivity of the light source can be effectively distributed by effectively distributing strong light traveling in the front direction from the light source without any conventional restrictions. Can be wider.

  Further, in the first embodiment, since the reflection film 15 that reflects light is formed at the boundary portion between the first emission surface 121 and the second emission surface 122, the light emitted from the boundary portion is irradiated surface 3. Irradiance unevenness on the irradiated surface 3 can be reduced without reaching the above unexpected position.

  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)
2A is a configuration diagram of the light-emitting device 7 according to Embodiment 2 of the present invention using the illumination lens 1 of Example 1, and FIG. 2B is a diagram using the illumination lens 1 of Example 2. It is a block diagram of the light-emitting device 7 which concerns on Embodiment 2 of this 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.

  3A and 3B are optical path diagrams of the light emitting device 7. 3A and 3B, an optical path of a light beam that is emitted from a light source at a small angle and reaches the first emission surface 121 will be described. The light emitted from the light emitting diode 2 passes through the incident surface 11 and reaches the first emitting surface 121. The position where the light reaches on the first emission surface 121 is defined as a first arrival point 131. At the first arrival point 131, the light from the light emitting diode 2 is incident on the first emission surface 121 at a large incident angle, and thus cannot be transmitted through the first emission surface 121, and is reflected entirely. The reflected light intersects the optical axis and reaches the first exit surface 121 again. The position where the light reaches again on the first emission surface 121 is defined as a second arrival point 132. At the second arrival point 132, the light reflected by the first arrival point 131 is incident on the first emission surface 121 at a small incident angle, and thus passes through the first emission surface 121 while being refracted. The transmitted light reaches the irradiated surface 3.

  4A and 4B are optical path diagrams of the light emitting device 7. 4A and 4B, 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. On the second emission surface 122, the light beam is refracted and transmitted, and reaches the irradiated surface 3.

  5A and 5B are optical path diagrams of the light emitting device 7. 5A and 5B, an optical path of a light beam emitted from a light source at a small angle near the optical axis and reaching the first emission surface 121 will be described. In the light emitting device 7 of FIG. 5A using the illumination lens of Example 1, the light emitted from the light emitting diode 2 passes through the incident surface 11 and reaches the first emitting surface 121. On the first exit surface 121, the light beam is refracted and transmitted and reaches the irradiated surface 3. In this way, the light incident in the vicinity of the optical axis of the first emission surface 121 is not totally reflected, is transmitted through the refracting action, and reaches the irradiated surface 3, thereby the vicinity of the optical axis in the irradiated surface 3. It is possible to prevent the illuminance of the portion from becoming darker than necessary. On the other hand, in the light-emitting device 7 of FIG. 5B using the illumination lens of Example 2, the light emitted from the light-emitting diode 2 passes through the incident surface 11 and reaches the first emission surface 121. On the first exit surface 121, the light beam is reflected by the second reflecting film 16 covering the top portion of the first exit surface 121, and then passes through the other part of the first exit surface 121 or the second exit surface 122 to be covered. Or reach the irradiation surface 3.

  Specific examples 1 and 2 are shown below as specific numerical examples of the present invention.

<Specific example 1>
6A is a configuration diagram of Example 1 of the light-emitting device using the illumination lens of Example 1. FIG. The present specific example 1 is a design example aiming at widening directivity by using a light emitting diode of 0.5 mm square as a light source. In FIG. 6A, θ ₁ is an angle between the optical axis A and a straight line connecting a light source position (base point P) on the optical axis A and an arbitrary position on the emission surface 12. Further, θ _{3 in} FIG. 6A is emitted in the angle direction of θ ₁ from the normal line of the emission surface 12 at an arbitrary position on the emission surface 12, in other words, from the light source position (base point P) on the optical axis A. The normal line of the emission surface 12 at the position where the emitted light reaches the emission surface 12 is an angle formed with the optical axis A. Further, sagY in FIG. 6A is a distance measured in the optical axis direction from a light source position (base point P) on the optical axis A to an arbitrary position on the emission surface 12.

  Next, specific numerical values are shown in Table 1.

FIG. 7A is a graph of θ ₁ and sagY in Table 1. FIG. 8A is a graph showing the relationship between r / R and θ ₁ −θ ₃ . 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 emission surface 12 with the lens outermost radius (r: from the optical axis). Distance in a direction parallel to the incident surface to an arbitrary position on the exit surface, R: lens outermost radius).

θ ₁ −θ ₃ represents the incident angle of the light emitted in the angle direction θ ₁ from the light source position (base point P) on the optical axis A at an arbitrary position on the emission surface 12 with respect to the emission surface 12. Yes. In this specific example 1, the lens is made of a material having a refractive index of 1.41, and the emission surface 12 faces air (n = 1). For this reason, the condition of total reflection at the first arrival point 131 on the first emission surface 121 is θ ₁ −θ ₃ of 45.172 degrees or more. FIG. 8A shows that the first emission surface 121 has a shape that totally reflects the light emitted from the light source position (base point P) on the optical axis A except in the vicinity of the optical axis A, and the second emission surface 122 It shows a shape that refracts light emitted from the light source position (base point P) on the optical axis A.

  FIG. 9A shows an irradiated surface obtained by calculation when the light emitting device of Example 1 (illumination lens and light emitting diode of Example 1) is disposed and the irradiated surface is disposed at a position 8 mm away from the light emitting diode. Represents the illuminance distribution. FIG. 10 shows the illuminance distribution on the irradiated surface obtained by calculation when only the same light emitting diode as in FIG. 9A is disposed and the irradiated surface is disposed at a position 8 mm away from the light emitting diode. Comparing FIG. 9A and FIG. 10, it can be seen that the illuminated surface can be widely illuminated by the effect of the illumination lens.

<Specific example 2>
6B is a configuration diagram of a specific example 2 of the light-emitting device using the illumination lens of Example 2. FIG. The present specific example 2 is a design example for the purpose of expanding directivity by using a 0.5 mm square light-emitting diode as a light source. Θ ₁ , θ ₃ and sagY in FIG. 6B are the same as those in FIG. 6A.

  Next, specific numerical values are shown in Table 2.

FIG. 7B is a graph of θ ₁ and sagY in Table 1. FIG. 8B is a graph showing the relationship between r / R and θ ₁ −θ ₃ . The r / R and θ ₁ −θ _{3 in} FIG. 8B are the same as those in FIG. 8A.

In the second specific example, as in the first specific example described above, the lens is made of a material having a refractive index of 1.41, and the emission surface 12 faces the air (n = 1). For this reason, the condition of total reflection at the first arrival point 131 on the first emission surface 121 is θ ₁ −θ ₃ of 45.172 degrees or more. FIG. 8B shows that the first emission surface 121 has a shape that totally reflects the light emitted from the light source position (base point P) on the optical axis A except in the vicinity of the optical axis A, and the second emission surface 122 It shows a shape that refracts light emitted from the light source position (base point P) on the optical axis A.

  FIG. 9B is a calculation when the light emitting device of Example 2 (the illumination lens of Example 2 and the same light emitting diode as in FIG. 9A) is arranged, and the irradiated surface is arranged at a position 8 mm away from the light emitting diode. The obtained illuminance distribution on the irradiated surface is represented. Comparing FIG. 9B and FIG. 10, it can be seen that the illuminated surface can be widely illuminated by the effect of the illumination lens.

(Embodiment 3)
FIG. 11A is a configuration diagram of the surface light source 8 according to Embodiment 3 of the present invention using the illumination lens of Example 1, and FIG. 11B illustrates the present invention using the illumination lens of Example 2. It is a block diagram of the surface light source 8 which concerns on this Embodiment 3. FIG. The surface light source 8 includes a plurality of light emitting devices 7 described in the second embodiment, which are arranged in a plane, and a diffuser plate 4 arranged so as to cover these light emitting devices 7. Note that the light emitting devices 7 may be arranged in a matrix or zigzag.

  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.

  FIG. 12A is a calculation when four light emitting devices of Example 1 including the illumination lens and the light emitting diode of Example 1 are arranged on a straight line at a pitch of 20 mm, and a diffusion plate is arranged at a position 8 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. FIG. 12B is a calculation when four light emitting devices of Example 2 including the illumination lens and the light emitting diode of Example 2 are arranged on a straight line at a pitch of 20 mm, and a diffusion plate is arranged at a position 8 mm away from the light emitting diode. It represents the illuminance distribution on the entrance surface of the diffuser obtained in step (1). FIG. 13 shows the illuminance distribution on the entrance surface of the diffuser obtained by calculation when only four light emitting diodes are arranged in a straight line at a pitch of 20 mm and the diffuser is placed at a position 8 mm away from the light emitting diode. Comparing FIG. 12A and FIG. 12B with FIG. 13, it can be seen that the diffusion plate incident surface can be illuminated uniformly by the effect of the illumination lens.

(Embodiment 4)
14A is a configuration diagram of the liquid crystal display device according to Embodiment 4 of the present invention using the illumination lens of Example 1, and FIG. 14B is the present invention using the illumination lens of Example 2. It is a block diagram of the liquid crystal display device which concerns on Embodiment 4. FIG. This liquid crystal display device includes a liquid crystal panel 5 and the surface light source 8 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 diffuser 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.

  As shown in FIGS. 14A and 14B, a sheet 41 such as a diffusion sheet or a prism sheet is disposed between the liquid crystal panel 5 and the surface light source 8 and diffuses in a portion where the light emitting device 7 does not exist. It is preferable that the reflector 6 is disposed. 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 diffuse reflector 6 is reflected by the diffuse reflector 6 and enters the diffuser plate 4 again. The light transmitted through the diffusion plate 4 is further diffused by the sheet 41 and illuminates the liquid crystal panel 5.

Configuration diagram of the illumination lens of Example 1 according to Embodiment 1 of the present invention Configuration diagram of the illumination lens of Example 2 according to Embodiment 1 of the present invention Configuration diagram of a light-emitting device according to Embodiment 2 of the present invention using the illumination lens of Example 1 Configuration diagram of a light-emitting device according to Embodiment 2 of the present invention using the illumination lens of Example 2 2A is an optical path diagram of light rays emitted from the first emission surface of the light emitting device of FIG. 2A. 2B is an optical path diagram of light rays emitted from the first emission surface of the light emitting device of FIG. 2B. FIG. 2A is an optical path diagram of light rays emitted from the second emission surface of the light emitting device. 2B is an optical path diagram of light rays emitted from the second emission surface of the light emitting device of FIG. 2B. 2A is an optical path diagram of light rays emitted from the first emission surface in the vicinity of the optical axis of the light emitting device of FIG. 2A. 2B is an optical path diagram of light rays emitted from the first emission surface in the vicinity of the optical axis of the light emitting device of FIG. 2B. 1 is a configuration diagram illustrating a specific example 1 of a light-emitting device using the illumination lens of Example 1. FIG. FIG. 6 is a configuration diagram illustrating a specific example 2 of a light-emitting device using the illumination lens of the second example. The graph which shows the output surface shape of the specific example 1 of the light-emitting device which concerns on Embodiment 2 of this invention, and shows the relationship between (theta) ₁ and sagY (Table 1 is graphed). The graph which shows the output surface shape of the specific example 2 of the light-emitting device which concerns on Embodiment 2 of this invention, and shows the relationship between (theta) ₁ and sagY (Table 2 is graphed). The graph which shows the relationship between r / R and (theta) _{1- (} theta) ₃ of the specific example 1 of the light-emitting device concerning Embodiment 2 of this invention. The graph which shows the relationship between r / R and (theta) _{1- (} theta) ₃ of the specific example 2 of the light-emitting device concerning Embodiment 2 of this invention. Illuminance distribution of specific example 1 of the light-emitting device according to Embodiment 2 of the present invention Illuminance distribution of specific example 2 of the light-emitting device according to Embodiment 2 of the present invention Illuminance distribution of only light-emitting diodes for confirming the effects of specific example 1 and specific example 2 Configuration diagram of a surface light source according to Embodiment 3 of the present invention using the illumination lens of Example 1 Configuration diagram of a surface light source according to Embodiment 3 of the present invention using the illumination lens of Example 2 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 in a surface light source when a light emitting device is configured only by light emitting diodes for confirming the effects of specific example 1 and specific example 2 The block diagram of the liquid crystal display which uses the lens for illumination of Example 1 and which concerns on Embodiment 4 of this invention. Configuration diagram of a liquid crystal display according to Embodiment 4 of the present invention using the illumination lens of Example 2 (A) is an optical path diagram of a conventional illumination lens, (b) is an illuminance distribution when a conventional illumination lens is used. (A) And (b) is explanatory drawing explaining the limit of the lens for conventional illuminations

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Illumination lens 11 Incident surface 12 Output surface 121 1st output surface 122 2nd output surface 131 1st time arrival point 132 2nd time arrival point 133 Arrival point 14 Arrival point 15 Reflective film (reflection layer)
16 Second reflective film (second reflective layer)
2 Light emitting diode (light source)
DESCRIPTION OF SYMBOLS 3 Surface to be irradiated 4 Diffusion plate 41 Diffusion sheet or prism sheet 5 Liquid crystal panel 6 Diffuse reflection plate 7 Light emitting device 8 Surface light source A Optical axis P Base

Claims (6)

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, and an emission surface that is axially symmetric with respect to the optical axis and emits the incident light,
The exit surface has a first exit surface that is convex toward the apex 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. The above radiated light is totally reflected at the first arrival point where the radiated light first arrives, and then refracted at the second arrival point where the totally reflected radiated light arrives to reach the irradiated surface. Have a shape,
The second exit surface has a shape that refracts radiated light that reaches the second exit surface by being radiated from the base point and reaches the irradiated surface by refracting at the arrival point.
On the exit surface, a reflective layer that reflects light is formed at a boundary portion between the first exit surface and the second exit surface.
Lens for lighting. The predetermined angle is 3 to 7 degrees,
The first exit surface refracts the radiated light whose angle from the optical axis is less than the predetermined angle out of the radiated light radiated from the base point and reaches the first exit surface. The illumination lens according to claim 1, having a shape that reaches the surface.   On the first emission surface, light is reflected from the radiated light radiated from the base point and reaching the first emission surface to a region where the radiated light whose angle from the optical axis is less than the predetermined angle reaches. The illumination lens according to claim 2, wherein a second reflective layer is formed. 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, wherein the illumination lens is the illumination lens according to any one of claims 1 to 3. 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 4.   A liquid crystal display device comprising: a liquid crystal panel; and a surface light source according to claim 5 disposed on a back side of the liquid crystal panel.

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