JP2011014831A - Light emitting device, surface light source, and liquid crystal display device - Google Patents

Abstract

Provided is a light emitting device capable of realizing a large light emitting region of a light emitting diode.
A light emitting device includes a light emitting diode that extends in a direction orthogonal to the optical axis direction, and a lens that covers the light emitting diode. The lens 4 has a shape extending along the light emitting diode 3, and spreads light emitted from the light emitting diode 3 in the width direction of the light emitting diode 3. According to the light emitting device 1A, the light emitting region of the light emitting diode 3 can be increased in size and light distribution.
[Selection] Figure 1

Description

  The present invention relates to a light emitting device that expands the light distribution characteristics of a light emitting diode with a lens. Furthermore, the present invention relates to a surface light source including a plurality of light emitting 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.

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 increase the illumination area illuminated by one light emitting diode. In other words, it is necessary to expand the light distribution characteristics of the light emitting diode by expanding the light from the light emitting diode. For this reason, in Patent Document 1, a circular lens is arranged on the light emitting diode in a plan view for controlling the light distribution characteristics 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.

  The light emitting diode emits the most light in the front direction (optical axis direction) of the chip. In the lens disclosed in Patent Document 1, the light directed from the chip toward the front direction is refracted by the concave surface near the optical axis by refraction. To diverge. 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.

  In order to further increase the illumination area illuminated by one light emitting diode and reduce the number of light emitting diodes, it is necessary to increase the luminous flux emitted by each light emitting diode. In order to realize this, it is necessary to increase the area of the light emitting region of the light emitting diode.

  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. For this reason, when the area of the light emitting region is increased as described above, the incident angle at which the light from the periphery of the light emitting region is incident on the concave surface near the optical axis becomes too large and the light causes total reflection. Become. That is, in the light emitting device using the lens disclosed in Patent Document 1, there is a limit to increasing the size of the light emitting region of the light emitting diode due to the influence of total reflection of light around the light emitting region.

  In view of such circumstances, an object of the present invention is to provide a light emitting device capable of realizing a large light emitting region of a light emitting diode, and to provide a surface light source and a liquid crystal display device using the light emitting device. .

  In order to solve the above problems, the present invention provides a light emitting diode extending in a direction orthogonal to an optical axis direction, and a lens covering the light emitting diode, the shape extending along the light emitting diode, and the light emitting diode. And a lens that spreads light emitted from the light emitting diode in the width direction of the light emitting diode.

  Also, a plurality of light emitting devices arranged in a plane and a diffusion that is arranged so as to cover the plurality of light emitting devices and radiates light irradiated on one surface from the plurality of light emitting devices while being diffused from the other surface Each of the plurality of light emitting devices is the above light emitting device, and the plurality of light emitting devices are arranged in a longitudinal direction and a width direction of the light emitting diode. Provide a light source.

  Furthermore, 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 is provided.

  According to the light emitting device of the present invention, since the light emitting diode and the lens extend in the same direction, the light emitting area of the light emitting diode in that direction can be enlarged. Thereby, the light beam which a light emitting diode emits can be increased. In addition, since the light from the light emitting diode is spread in the width direction perpendicular to the longitudinal direction of the light emitting diode by the lens, wide light distribution can also be realized.

  Further, according to the surface light source of the present invention, a uniform surface light source can be obtained with a small number of light emitting diodes by using the light emitting device. Moreover, it can be set as a surface light source with little brightness nonuniformity by a diffuser plate.

  Furthermore, according to the liquid crystal display device of the present invention, the manufacturing cost can be reduced by using the surface light source.

1 is a perspective view of a light emitting device according to Embodiment 1 of the present invention. Optical path diagram of light emitted from light emitting device according to embodiment 1 of the present invention Explanatory drawing of (theta) i which shows the curvature C of the micro area of an output surface, and the position of the micro area (A) And (b) is a derivation method explanatory drawing of curvature C of a minute section Parameter explanatory diagram of equation (4) Illuminance distribution of a light emitting device using the lens of Example 1 Illuminance distribution of only the light emitting diode for confirming the effect of the lens of Example 1 The graph which shows the relationship between (theta) i of the lens of Example 1, and the curvature C of a micro area. The graph which shows the relationship between (theta) i of the lens of Example 1, and Cx (n-1) / di. The graph which shows the relationship between (theta) i of Example 1 and the curvature C and sag amount of a micro area. Luminous intensity distribution of light emitted from the exit surface of the lens of Example 1 Illuminance distribution of a light emitting device using the lens of Example 2 Illuminance distribution of only the light emitting diode for confirming the effect of the lens of Example 2 The graph which shows the relationship between (theta) i of the lens of Example 2, and the curvature C of a micro area. The graph which shows the relationship between (theta) i of the lens of Example 2, and Cx (n-1) / di. The graph which shows the relationship between (theta) i of the lens of Example 2, the curvature C of a micro area, and the amount of sag. Luminous intensity distribution of light emitted from the exit surface of the lens of Example 2 The perspective view of the light-emitting device concerning Embodiment 2 of this invention. The perspective view of the light-emitting device concerning Embodiment 3 of this invention. (A) Y direction sectional drawing of the light-emitting device which concerns on Embodiment 3 of this invention, (b) is Y direction sectional drawing of the light-emitting device of a modification. X direction sectional view of the lens of the modified example The perspective view of the surface light source using the light-emitting device which concerns on Embodiment 3 of this invention. The perspective view of the liquid crystal display device using the surface light source shown in FIG.

(Embodiment 1)
A light-emitting device according to Embodiment 1 of the present invention will be described with reference to the drawings. 1 is a perspective view of a light emitting device 1A according to Embodiment 1. FIG.

  The light emitting device 1A of the present embodiment includes a light emitting diode (LED) 3 extending in a direction orthogonal to the optical axis direction, a substrate 2 on which the light emitting diode 3 is mounted, and a lens that is bonded to the substrate 2 and covers the light emitting diode 3 4 is provided.

  In this specification, for convenience of explanation, as shown in FIG. 1, the longitudinal direction of the light emitting diode 3 is perpendicular to the Y direction, and the width direction of the light emitting diode 3 (the longitudinal direction of the light emitting diode 3 and the optical axis direction). Direction) is called the X direction.

  The light emitting device 1A has a light distribution characteristic of the light emitting diode 3 by disposing a lens 4 having refractive power in the X direction between the long light emitting diode 3 and the irradiated surface 5 (see FIG. 2). Enlarging in the X direction is realized.

  The light emitting diode 3 has a long light emitting area that is enlarged in one direction in order to increase the output, and has a rectangular light emitting surface 3a extending in the Y direction perpendicular to the optical axis direction. By using the light emitting diode 3 that is long in one direction, it is possible to increase the area of the light emitting region and secure the necessary light flux.

  The lens 4 is an anisotropic refractive power lens that spreads light emitted from the light emitting diode 3 in the X direction, and has a shape extending along the light emitting diode 3. Specifically, as shown in FIG. 2, the lens 4 has an incident surface 41 on which light from the light emitting diode 3 is incident, and an output surface 42 that emits incident light. The light emitted from the light emitting diode 3 enters the lens 4 from the incident surface 41, is then emitted from the emission surface 42, and reaches the irradiated surface 5. The light from the light emitting diode 3 is spread in the X direction by the action of the emission surface 42 and reaches a wide range of the irradiated surface 5.

  The light emitting diode is usually covered with a sealing resin so as not to be exposed to air. However, since the lens 4 serves as 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 lens 4 is made of a transparent material having a predetermined refractive index. The refractive index of the transparent material is, for example, about 1.40 to 1.53. 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.

  It is preferable that the incident surface 41 has a shape that matches the shape of the light emitting diode 3 so that it can be in close contact with the light emitting diode 3. The incident surface 41 is optically bonded to the light emitting surface 3a of the light emitting diode 3 by a bonding material.

  On the other hand, the emission surface 42 is an anamorphic surface having a strong refractive power in the X direction. In the present embodiment, the emission surface 42 is an aspheric cylindrical surface that is plane-symmetric with respect to the optical axis surface S that passes through the center of the light emitting diode 3 and is perpendicular to the X direction.

  More specifically, the emission surface 42 includes a concave surface portion 42a that intersects the optical axis surface S, and convex surface portions 42b that are located on both sides of the concave surface portion 42a in the X direction. The convex surface portion 42b and the concave surface portion 42a therebetween are continuous.

  In the light emitting device 1A described above, since the light emitting diode 3 and the lens 4 both extend in the Y direction, it is possible to increase the size of the light emitting region of the light emitting diode 3 in the Y direction. Thereby, the light beam emitted from the light emitting diode 3 can be increased. In addition, since the light from the light emitting diode 3 is spread in the X direction by the lens 4, wide light distribution can be realized.

  The basic aspect of the light emitting device 1A of the present embodiment has been described above, but a preferable aspect of the light emitting device 1A will be described below.

The light emitting device 1A preferably satisfies the following formula (1).
Sw / Lw <0.15 (1)
(More preferably, Sw / Lw <0.13 (1) ′)
However,
Sw: the width of the light emitting diode 3 Lw: the width of the lens 4 in the X direction (see FIG. 2).

  Expression (1) (or Expression (1) ′) normalizes the width of the light emitting diode 3 by the width of the lens 4. When Sw / Lw is 0.15 or more, effective wide light distribution becomes difficult due to the influence of total reflection of light around the light emitting region of the light emitting diode 3.

  Moreover, it is preferable that the curvature C of the minute section on the emission surface 42 is maximized in the region of the convex surface portion 42b in the X-direction cross section when the lens 4 is cut perpendicularly to the Y direction.

  Here, the curvature C of the minute section will be described with reference to FIG. 3 and FIGS. 4 (a) and 4 (b). FIG. 3 shows the curvature C of the minute section of the emission surface 42 and θi indicating the position of the minute section. With reference to the light source position P on the optical axis plane S, the curvature C of the minute section is defined as follows. The “light source position P on the optical axis surface S” is a position where the optical axis surface S intersects the light emitting surface 3 a of the light emitting diode 3. That is, the light source position P is separated from the incident surface 41 on the optical axis plane S by the thickness of the bonding material described above.

  As shown in FIGS. 4A and 4B, an nth minute section from the optical axis plane S between the points A and B on the emission surface 42 is considered, and the point A and the light source position P are connected. The angle between the ellipse and the optical axis plane S is θi (n), and the angle between the line connecting the point B and the light source position P and the optical axis is θi (n + 1). However, θi (n + 1) −θi (n) is about 0.5 °. The angle between the tangent line of the exit surface 42 at the point A and the plane perpendicular to the optical axis plane S is θs (n), and the angle between the tangent line of the exit surface 42 at the point B and the plane perpendicular to the optical axis plane S is defined. Let θs (n + 1). Let Δd (n) be the length of the exit surface 42 between point A and point B. If the exit surface 42 between the points A and B is configured with a single radius of curvature R assuming that the distance between the points A and B is sufficiently small, the center O of R is the exit surface at the point A. The normal line 42 and the normal line of the emission surface 42 at point B intersect, and the angle ∠AOB formed by the two normal lines can be expressed by θs (n + 1) −θs (n). The radius R of the arc between point A and point B with O as the center can be expressed as Δd (n) / (θs (n + 1) −θs (n)). The curvature C is 1 / R. Therefore, the curvature C of the nth minute section is (θs (n + 1) −θs (n)) / Δd (n). However, θs (n) and θs (n + 1) are calculated in radians. In the above definition, the sign of the curvature C is positive when the curvature center O is closer to the light emitting diode 3 than the emission surface 42 and negative when it is on the opposite side.

Furthermore, it is preferable that the curvature C of the minute section in the X-direction cross section of the emission surface 42 is maximized within a range defined by the following expression (2).
60 ° <θi <80 ° (2)
However,
θi: angle formed by the line Li connecting the center of the minute section and the light source position P on the optical axis plane S and the optical axis plane S, that is, θi≈ (θi (n + 1) + θi (n)) / 2
(See FIG. 3).

  Expression (2) defines the shape of the emission surface 42 when the light beam emitted from the light emitting diode 3 is incident on the radiation angle θi from the light source position P. When the curvature C is maximized in the range of θi of 80 ° or more, the tolerance for ensuring the light distribution characteristic becomes severe, and the luminance unevenness in the surface becomes large when the surface light source is used. When the curvature C is maximized in the range of θi of 60 ° or less, the light distribution characteristic becomes narrow, and the luminance unevenness in the surface becomes large when the surface light source is used.

Or it is preferable that the curvature C of the micro area in the X direction cross section of the output surface 42 becomes the maximum within the range prescribed | regulated by the following formula | equation (3).
0.88 <Yr <0.98 (3)
However,
Yr: Ratio of the distance Di from the optical axis plane S to the center of the minute section with respect to half of the effective width Le of the lens 4, that is, Di / 0.5Le
(See FIG. 3). The “effective width Le of the lens 4” refers to the width of a region on the surface of the lens 4 where light emitted from the light emitting diode 3 is incident.

  Expression (3) defines the shape of the emission surface 42 when the light beam emitted from the light emitting diode 3 enters the position of Yr. When the curvature C is maximized when Yr is in the range of 0.98 or more, the tolerance for securing the light distribution characteristics becomes severe, and the luminance unevenness in the surface becomes large when the surface light source is used. When the curvature C is maximized in a range where Yr is 0.88 or less, the light distribution characteristic is narrowed, and the luminance unevenness in the surface becomes large when the surface light source is used.

Furthermore, it is preferable that the emission surface 42 satisfies the following expression (4).
0.90 <θmp / θmc <1.05 (4)
However,
θmc: angle formed by the line L connecting the center of the minute section where the curvature C is the maximum in the minute section and the light source position P on the optical axis plane S and the optical axis plane S θmp: emitted from the emission plane 42 This is the emission angle that becomes the maximum luminous intensity when the light is viewed for each emission angle that is an angle with respect to the optical axis plane S (see FIG. 5).

  Equation (4) defines the ratio between θmp and θmc. If the upper limit of the equation is exceeded, θmp with respect to θmc becomes too large, the radiation intensity decreases, and the light distribution characteristic becomes narrow. If the lower limit of the equation is exceeded, an inflection point that swells the light distribution characteristics occurs, which causes uneven brightness.

Furthermore, it is preferable that the emission surface 42 satisfies the following expression (5).
0.9 <Cm × (n−1) / d <1.5 (5)
However,
Cm: Maximum value of the curvature C n: Refractive index of the lens 4 d: Distance from the light source position P on the optical axis plane S to the center of the minute section where the curvature C is the largest among the minute sections, that is, the length of the line L (See FIG. 5).

  Expression (5) normalizes the maximum value of the curvature of the shape of the emission surface 42 by the distance from the light source position P to the emission surface 42. If the upper limit of the equation is exceeded, the radiation intensity at the angle at which the radiation intensity is maximum decreases. If the lower limit of the equation is exceeded, the radiation intensity at the angle at which the radiation intensity is maximum decreases.

Furthermore, when the sag amount of the exit surface 42 is normalized at a position where the exit surface 42 intersects the optical axis surface S, the exit surface 42 satisfies the following expressions (6) and (7). preferable.
5 ° <θo <20 ° (6)
25 ° <θs <45 ° (7)
However,
θo: angle formed by the line connecting the position where the curvature C on the exit surface 42 changes from negative to positive and the light source position P on the optical axis plane S and the optical axis plane S θs: sag amount on the exit plane 42 Is the angle formed between the optical axis plane S and the line connecting the position where the maximum is and the light source position P on the optical axis plane S.

  Expressions (6) and (7) define the shape of the emission surface 42. If the upper limit of Expression (6) is exceeded, the incident angle of the light beam toward the exit surface 42 becomes large, total reflection occurs, and a desired brightness distribution cannot be obtained. growing. When the lower limit of Expression (6) is exceeded, the light beam toward the center of the surface to be irradiated 5 becomes large, and when the surface light source is used, uneven brightness in the surface becomes large. Moreover, when the upper limit of Formula (7) is exceeded, the tolerance for ensuring light distribution characteristics becomes severe. When the lower limit of Expression (7) is exceeded, the light distribution characteristic becomes narrow, and the luminance unevenness in the surface becomes large when the surface light source is used.

  Furthermore, the emission surface 42 is recessed in an V shape (that is, at an angle) on the optical axis surface S. In other words, the concave surface portion 42a forms a groove having a ridge line on the optical axis surface S. It is preferable. With this configuration, when the surface light source is used, a smooth luminance distribution can be obtained, and luminance unevenness can be reduced.

Furthermore, it is preferable that 1 A of light-emitting devices satisfy the following formula | equation (8).
1.40 <n <1.52 (8)

  Expression (8) defines the refractive index of the lens 4. When n is 1.52 or more, the refracting action at the exit surface 42 becomes strong, and the light distribution characteristics are not sufficient. When n is 1.40 or less, the refracting action on the exit surface 42 is weakened, and if the shape of the exit surface 42 is changed to strengthen the refracting action, the tolerance becomes severe.

Furthermore, it is preferable that 1 A of light-emitting devices satisfy the following formula | equation (9).
Sw / t <0.6 (9)
However,
t: the thickness of the lens 4 on the optical axis plane S (see FIG. 3).

  Equation (9) defines the width of the light emitting diode 3 with respect to the center thickness of the lens 4. When Sw / t is 0.6 or more, the size of the light emitting diode 3 with respect to the size of the lens 4 becomes too large, and the incident angle of the light beam toward the exit surface 42 becomes large, so that total reflection occurs and a desired luminance distribution is obtained. Is not obtained, and the luminance unevenness in the surface becomes large when the surface light source is used.

<Example>
Examples 1 and 2 are shown below as specific numerical examples of the lens 4 used in the light emitting device 1A. In each example, the unit of length in the table to be described later is “mm”, and the unit of angle is “°”. In the surface data of each example, r is a radius of curvature, d is a surface interval or thickness, and n is a refractive index with respect to the d line. In each embodiment, the exit surface is an aspherical cylindrical surface, and the cross-sectional shape in the X direction is defined by the following formula.

However, the meaning of each code | symbol in numerical formula is as follows.
S: Distance from a point on the aspherical surface at a height h from the central axis to the tangent plane of the aspherical vertex h: Height from the central axis C: Curvature of the aspherical vertex (C = 1 / R)
K: Conic constant A _n : nth-order aspheric coefficient

Example 1
The lens of Example 1 has a cross-sectional shape corresponding to FIG. The present embodiment is a design example in which a light emitting diode having an X direction width Sx of 0.5 mm and a Y direction width Sy of 5.0 mm is used as a light source, and the light distribution characteristic of the light emitting diode is expanded in the X direction. is there. The X-direction width Lw of the lens of Example 1 is 4.0 mm. Table 1 shows surface data of the lens of Example 1, and Table 2 shows aspherical data.

[Table 1] Surface data surface r dn
Incident surface ∞ 0.964 1.41
Outgoing surface 8.373E-13 7.036
Irradiated surface ∞

[Table 2] Aspheric data K = -1.0268E + 01, A ₃ = 1.9628E + 00, A ₄ = -8.3686E + 00, A ₅ = 1.9670E + 01
A ₆ = -3.6276E + 01, A ₇ = 4.6681E + 01, A ₈ = -3.0918E + 01, A ₉ = -1.0909E-01
A ₁₀ = 1.0608E + 01, A ₁₁ = -7.0489E-03, A ₁₂ = -4.5201E + 00, A ₁₃ = 1.2256E-02
A ₁₄ = 1.4688E + 00, A ₁₅ = 3.4825E-04, A ₁₆ = -3.1939E-01, A ₁₇ = -7.9209E-04
A ₁₈ = 4.0742E-02, A ₁₉ = 3.5721E-05, A ₂₀ = -2.2613E-03

  FIG. 6 shows the illuminance distribution in the X direction on the irradiated surface obtained by calculation when the lens and the light emitting diode of Example 1 are arranged and the irradiated surface is arranged at a position 8 mm from the light emitting surface of the light emitting diode. To express. FIG. 7 shows the illuminance distribution in the X direction on the irradiated surface obtained by calculation when only the same light emitting diode is disposed and the irradiated surface is disposed at a position 8 mm from the light emitting surface of the light emitting diode.

  Comparing FIG. 6 and FIG. 7, it can be seen that the illuminated surface can be widely illuminated by the effect of the lens of Example 1.

  FIG. 8 shows the curvature C of a minute section in the lens of Example 1. The horizontal axis is an angle θi formed by the line Li connecting the center of the minute section and the light source position P on the optical axis plane S and the optical axis plane S (see FIG. 3). The sign of the curvature C is inverted when θi = 13.77 ° and becomes maximum when θi = 69.8 °.

  FIG. 9 shows C × (n−1) / di related to Expression (5) in the lens of Example 1. In addition, di is the distance from the light source position P on the optical axis surface S to the center of the minute section, that is, the length of the line Li in FIG. C × (n−1) / di becomes maximum at θi = 69.8 °, and its value is 1.33.

  FIG. 10 shows the curvature C and the sag amount of a minute section in the lens of Example 1. In FIG. 10, θo = 13.77 °, θs = 37.06 °, and θmc = 69.8 °.

  FIG. 11 shows the luminous intensity in terms of relative luminous intensity when the light emitted from the exit surface of the lens of Example 1 is viewed at each emission angle. In FIG. 11, θmp = 67.7 °. Therefore, θmp / θmc = 0.97.

Example 2
The lens of Example 2 has a cross-sectional shape corresponding to FIG. This embodiment is a design example for the purpose of expanding the light distribution characteristic of the light emitting diode in the X direction using a light emitting diode having an X direction width Sx of 0.65 mm and a Y direction width Sy of 5.0 mm. is there. The X direction width Lw of the force lens of Example 2 is 4.5 mm. Table 3 shows surface data of the lens of Example 2, and Table 4 shows aspherical data.

[Table 3] Surface data surface r dn
Entrance plane ∞ 1.2 1.41
Outgoing surface 1.088E-12 6.8
Irradiated surface ∞

[Table 4] Aspheric data K = -1.0268E + 01, A ₃ = 1.5843E + 00, A ₄ = -5.9328E + 00, A ₅ = 1.0800E + 01
A ₆ = -1.3014E + 01, A ₇ = 1.0470E + 01, A ₈ = -4.6299E + 00, A ₉ = -2.1226E-02
A ₁₀ = 9.6894E-01, A ₁₁ = -7.9260E-02, A ₁₂ = -2.3661E-01, A ₁₃ = -1.8210E-03
A ₁₄ = 6.44025E-02, A ₁₅ = 1.2197E-03, A ₁₆ = -1.0393E-02, A ₁₇ = -1.3892E-04
A ₁₈ = 8.1619E-05, A ₁₉ = 6.2396E-04, A ₂₀ = -1.5184E-04

  FIG. 12 shows the illuminance distribution in the X direction on the irradiated surface obtained by calculation when the lens and the light emitting diode of Example 2 are disposed and the irradiated surface is disposed at a position 8 mm from the light emitting surface of the light emitting diode. To express. FIG. 13 shows the illuminance distribution in the X direction on the irradiated surface obtained by calculation when only the same light emitting diode is disposed and the irradiated surface is disposed at a position 8 mm from the light emitting surface of the light emitting diode.

  Comparing FIG. 12 and FIG. 13, it can be seen that the illuminated surface can be widely illuminated by the effect of the lens of Example 2.

  FIG. 14 shows the curvature C of a minute section in the lens of Example 2. The horizontal axis is an angle θi formed by a line Li connecting the center of the minute section and the light source position P on the optical axis plane S and the optical axis (see FIG. 3). The sign of the curvature C is inverted when θi = 12.5 ° and becomes maximum when θi = 67.2 °.

  FIG. 15 shows C × (n−1) / di related to Expression (4) in the lens of Example 2. In addition, di is the distance from the light source position P on the optical axis surface S to the center of the minute section, that is, the length of the line Li in FIG. C × (n−1) / di is maximum at θi = 67.2 °, and its value is 0.995.

  FIG. 16 shows the curvature C and the sag amount in a minute section in the lens of Example 2. In FIG. 16, θo = 12.5 °, θs = 35.38 °, and θmc = 67.2 °.

  FIG. 17 shows the relative luminous intensity when the light emitted from the exit surface of the lens of Example 2 is viewed at each emission angle. In FIG. 17, θmp = 62.5 °. Therefore, θmp / θmc = 0.93.

  Corresponding values for the conditions of the expressions (1) to (9) in the lenses of the respective examples are as shown in Table 5 below.

(Embodiment 2)
FIG. 18 is a perspective view of a light emitting device 1B according to Embodiment 2 of the present invention. In the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted. This is the same in the third embodiment described later.

  In the light emitting device 1B of the present embodiment, a plurality of light emitting diodes 3 (three in the illustrated example) are provided, and these light emitting diodes 3 are mounted on the substrate 2 in a state of being arranged in the Y direction. The light emitting diodes 3 may all be the same size (for example, the width is 0.5 mm and the length is 5.0 mm).

  The lens 4 has a shape extending along all the light emitting diodes 3 and covers all the light emitting diodes 3.

  The light emitting device 1B of the present embodiment illuminates the irradiated surface in the same manner as in the first embodiment except that a plurality of light emitting diodes 3 are used. In the light emitting device 1B, by using the plurality of light emitting diodes 3, the illumination area can be widened in the Y direction, and the irradiated surface can be illuminated with a larger amount of light flux.

  In the light emitting device 1B of the present embodiment, it is preferable that the preferred mode described in the first embodiment is adopted (for example, the conditions of formulas (1) to (9) are satisfied). This is the same in the third embodiment described later.

(Embodiment 3)
FIG. 19 is a perspective view of a light emitting device 1C according to Embodiment 3 of the present invention. The light emitting device 1C of the present embodiment has the same configuration as that of the light emitting device 1B of the second embodiment, but reflects light diffused by reflecting light emitted from the light emitting diodes 3 between the light emitting diodes 3. The difference is that a diffusion unit 25 is provided.

  Specifically, the reflection diffusion portion 25 is formed on the substrate 2. Each reflection diffusion portion 25 of the present embodiment has a quadrangular pyramid shape crushed in the X direction. The size of each light emitting diode 3 is, for example, a width of 0.5 mm and a length of 3.0 mm. As for the size of the bottom surface of each reflection diffusion part 25, for example, the short side in the X direction is 0.5 mm and the long side in the Y direction is 2.0 mm. In order to form the reflection diffusion portion 25 on the substrate 2, a resin molded product previously molded into a desired shape may be bonded to the substrate 2. The reflection diffusion unit 25 forms a pseudo light source by reflecting and diffusing the light from the light emitting diode 3.

  In the light emitting device 1 </ b> C, the length of the light emitting diode 3 can be shortened by providing the reflection diffusion portion 25 between the plurality of light emitting diodes 3, so that the effect of Embodiment 2 can be obtained at a lower cost.

(Modification)
In each of the embodiments described above, the exit surface 42 is plane-symmetric with respect to the optical axis plane S. However, the exit surface 42 is asymmetric with respect to the optical axis plane S as shown in FIG. It may be.

  In addition, the emission surface 42 does not necessarily have a depressed central portion, and may be, for example, a cylindrical surface with a semispherical cross section. However, if the emission surface 42 includes the concave surface portion 42a and the convex surface portion 42b, the illuminance in the vicinity of the optical axis on the irradiated surface 5 can be suppressed to obtain a wide illuminance distribution.

  Furthermore, in the light emitting device 1C according to Embodiment 3, the lens 4 having a constant cross-sectional shape and extending in the Y direction is used as shown in FIG. 20A. The lens 4 is shown in FIG. Like the light emitting device 1C ′ of the modification, the light from the light emitting diode 3 and the reflection diffusion unit 25 may be refracted in the Y direction immediately above the reflection diffusion unit 25. Similarly, the lens 4 used in Embodiments 1 and 2 may be shaped to refract light from the light emitting diode 3 in the Y direction at a position where the light emitting diode 3 does not exist.

<Surface light source>
FIG. 22 is a perspective view of the surface light source 6 using the light emitting device 1C according to Embodiment 3 of the present invention. The surface light source 6 includes a plurality of light emitting devices 1C arranged in a plane and a diffusion plate 63 arranged to cover these light emitting devices 1C.

  The light emitting device 1 </ b> C is arranged in a matrix on the diffuse reflection plate 61. The light emitting device 1C is arranged in the X direction and the Y direction. The diffuse reflector 61 is supported by a support plate 62.

  The light emitting device 1C irradiates one surface (incident surface) of the diffusion plate 63 with light. That is, one surface of the diffusion plate 63 is the irradiated surface 5 shown in FIG. The diffusing plate 63 radiates light irradiated on one surface in a state of being diffused from the other surface (outgoing surface). Further, the light reflected by the diffusion plate 63 is reflected by the diffusion reflection plate 61 and is irradiated again to the diffusion plate 63.

The surface light source 6 preferably satisfies the following formula (10).
0.2 <h / p <0.6 (10)
However,
h: distance from the light emitting surface 3a of the light emitting diode 3 in the light emitting device 1C to the incident surface of the diffusion plate 63 p: the arrangement pitch of the light emitting device 1C in the X direction.

  Expression (10) defines the distance between the light emitting surface 3a of the light emitting diode 3 and the diffusion plate 63 with respect to the arrangement pitch of the light emitting devices 1C in the X direction. When h / p is 0.6 or more, the diffusion plate 63 is too far from the light emitting device 1C with respect to the arrangement pitch of the light emitting devices 1C, and the surface light source 6 is increased in size. When h / p is 0.2 or less, it becomes difficult to ensure the uniformity of the luminance distribution on the diffusing plate 63, and the luminance unevenness in the plane increases.

  In the surface light source 6 described above, the luminous flux from the light emitting device 1C is widely distributed in the X direction, so that the distance h between the light emitting surface 3a of the light emitting diode 3 and the incident surface of the diffusion plate 63 is as thin as 8 mm. The arrangement pitch p of the light emitting devices 1C in the X direction can be realized with, for example, 30 mm. For example, if 16 rows of light emitting devices 1C are arranged in the X direction, 37 inches (wide 16: 9) can be realized. At this time, h / p in the formula (10) is 0.267.

  Further, by using the light emitting device 1C, the illuminance is made uniform on the incident surface of the diffusion plate 63, so that the surface light source 6 with low cost, thinness, high luminance, and high image quality (uniform luminance distribution) can be realized. This effect can be similarly obtained even when the light emitting devices 1A and 1B of the first and second embodiments are used instead of the light emitting device 1C of the third embodiment.

<Liquid crystal display device>
FIG. 23 is a perspective view of a liquid crystal display device 7 using the surface light source 6 shown in FIG. The liquid crystal display device 7 includes a liquid crystal panel 71 and a surface light source 6 disposed on the back side of the liquid crystal panel 71.

  By using the surface light source 6, it is possible to uniformly illuminate the liquid crystal panel 71, and it is possible to realize a liquid crystal display device 7 of low cost, thinness, high luminance, and high image quality (uniform luminance distribution). This effect can be similarly obtained even when the surface light source 6 uses the light emitting devices 1A and 1B of the first and second embodiments instead of the light emitting device 1C of the third embodiment.

1A to 1C Light emitting device 3 Light emitting diode 3a Light emitting surface 4 Lens 42 Outgoing surface 42a Concave surface 42b Convex surface 5 Irradiated surface 6 Surface light source 63 Diffusion plate 7 Liquid crystal display device 71 Liquid crystal panel

Claims (18)

A light emitting diode extending in a direction perpendicular to the optical axis direction;
A lens that covers the light-emitting diode, has a shape extending along the light-emitting diode, and spreads light emitted from the light-emitting diode in a width direction of the light-emitting diode;
A light emitting device comprising:   The light emitting device according to claim 1, further comprising a substrate on which the light emitting diode is mounted, wherein the lens is bonded to the substrate.   The light emitting device according to claim 2, wherein a plurality of the light emitting diodes are arranged so as to be aligned in a longitudinal direction of the light emitting diodes, and the lens covers the plurality of light emitting diodes.   The light emitting device according to claim 3, wherein a reflection diffusion portion that reflects and diffuses light emitted from the light emitting diodes is formed between the light emitting diodes on the substrate. The light emitting device according to any one of claims 1 to 4, which satisfies the following formula (1).
Sw / Lw <0.15 (1)
However,
Sw: width of the light emitting diode Lw: width of the lens in the width direction of the light emitting diode. The light emitting device according to any one of claims 1 to 4, which satisfies the following formula (1) '.
Sw / Lw <0.13 (1) '
However,
Sw: width of the light emitting diode Lw: width of the lens in the width direction of the light emitting diode. The lens has an emission surface that is plane-symmetric with respect to an optical axis plane that passes through the center of the light emitting diode and is perpendicular to the width direction of the light emitting diode,
The emission surface includes a concave surface portion intersecting the optical axis surface, and convex surface portions located on both sides of the concave surface portion in the width direction of the light emitting diode,
The curvature C of a minute section on the emission surface is maximized in the region of the convex portion in a cross section in the width direction when the lens is cut perpendicularly to the longitudinal direction of the light emitting diode. The light-emitting device as described in any one. The light-emitting device according to claim 7, wherein the curvature C is maximized within a range defined by the following formula (2).
60 ° <θi <80 ° (2)
However,
θi: an angle formed by a line connecting the center of the minute section and the light source position on the optical axis plane and the optical axis plane. The light-emitting device according to claim 7, wherein the curvature C is maximized within a range defined by the following expression (3).
0.88 <Yr <0.98 (3)
However,
Yr: The ratio of the distance from the optical axis surface to the center of the minute section with respect to half of the effective width of the lens. The light emitting device according to any one of claims 7 to 9, wherein the emission surface satisfies the following expression (4).
0.90 <θmp / θmc <1.05 (4)
However,
θmc: an angle formed by a line connecting the center of the minute section having the maximum curvature C in the minute section and the light source position on the optical axis surface and the optical axis surface θmp: emitted from the emission surface The emission angle is the maximum luminous intensity when light is viewed at each emission angle that is an angle with respect to the optical axis plane. The light emitting device according to any one of claims 7 to 10, wherein the emission surface satisfies the following expression (5).
0.9 <Cm × (n−1) / d <1.5 (5)
However,
Cm: Maximum value of the curvature C n: Refractive index of the lens d: Distance from the light source position on the optical axis surface to the center of the minute section where the curvature C is maximum among the minute sections. The sign of the curvature C is positive when the center of curvature is closer to the light emitting diode than the exit surface, and negative when the center of curvature is on the opposite side, and the sag amount of the exit surface intersects the optical axis surface. When standardized at the position where
The light emitting device according to any one of claims 7 to 11, wherein the emission surface satisfies the following expressions (6) and (7).
5 ° <θo <20 ° (6)
25 ° <θs <45 ° (7)
However,
θo: an angle formed by a line connecting a position where the curvature C on the exit surface changes from negative to positive and a light source position on the optical axis surface and the optical axis surface θs: a sag amount on the output surface It is an angle formed by a line connecting the maximum position and the light source position on the optical axis plane and the optical axis plane.   The light emitting device according to any one of claims 7 to 12, wherein the concave surface portion is recessed in a V shape on the optical axis surface. The light-emitting device according to claim 1, wherein the light-emitting device satisfies the following formula (8).
1.40 <n <1.52 (8)
However,
n: Refractive index of the lens. The light-emitting device according to claim 1, wherein the light-emitting device satisfies the following formula (9).
Sw / t <0.6 (9)
However,
Sw: width of the light emitting diode t: thickness of the lens on the optical axis surface. 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 the plurality of light emitting devices is the light emitting device according to any one of claims 1 to 15, wherein the plurality of light emitting devices are arranged in a longitudinal direction and a width direction of the light emitting diode. light source. The surface light source of Claim 16 which satisfies the following formula | equation (10).
0.2 <h / p <0.6 (10)
However,
h: distance from the light emitting surface of the light emitting diode in the light emitting device to the one surface of the diffusion plate p: the arrangement pitch of the light emitting devices in the width direction of the light emitting diode.   A liquid crystal display device comprising: a liquid crystal panel; and the surface light source according to claim 16 or 17 disposed on a back side of the liquid crystal panel.

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