JP2011034770A - Light emitting device and display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light emitting device in which unevenness of luminance of light emitted from a light emitting element is suppressed to a minimum. <P>SOLUTION: The light emitting device includes a light emitting diode 330 which is arranged on a plane and emits light in a normal direction of the plane, and a circular lens 340 which is arranged on the light emitting diode 330 and of which the center of circle is arranged so as to coincide with the optical axis L of the light emitted from the light emitting diode 330, and which has a first region which is provided on the emitting surface 341 of the light of the lens 340 and in which an annular transmission refraction surface and an annular reflection surface are alternately arranged centering on the optical axis L and which refracts and emits the light emitted from the light emitting diode 330 and reflects inward by the reflection surface, and a second region which is provided on the emitting surface 341 of the light, is formed on the outside than the first region to the optical axis L, and refracts and emits the light emitted from the light emitting diode 330, and reflects the light reflected inward by the reflection surface of the first region and emits toward the plane side on which the light emitting diode 330 is arranged. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a light emitting device and a display device.

  2. Description of the Related Art In recent years, in an image display device such as a television receiver, a backlight type light emitting device in which a plurality of light emitting diodes (LEDs) are arranged immediately below the display panel is used with an increase in the size of the display panel. Often done. Due to the directivity of the LED, the LED shines brighter near the center of the LED. For this reason, it is required that light is sufficiently diffused before the display panel is illuminated to reduce luminance unevenness in the display panel.

  As a method for preventing the occurrence of luminance unevenness, for example, there are techniques described in Patent Documents 1 and 2 below. Patent Document 1 describes a technique for improving diffusibility by forming a lens shape that reduces internal reflection. Japanese Patent Application Laid-Open No. H10-228561 describes a technique of alternately arranging light reflecting surfaces and light emitting surfaces to suppress the amount of light emitted from directly above the LED.

JP 2009-44016 A JP 2005-259909 A

  However, in the technique described in Patent Document 1, it is necessary to form the lens concave surface on the LED side deeply and steeply in order to reduce internal reflection, resulting in a problem that the thickness of the lens increases. Even if the light beam is directed in a direction away from immediately above the LED by refraction at the lens surface, there is a limit to the angle, and even if the internal reflection is reduced, the light beam that has been interface-reflected on the output surface is the surface on the light emitting element side. Therefore, it is difficult to improve the luminance unevenness.

  Moreover, the technique described in Patent Document 2 is intended to collimate light rays and does not diffuse light, and thus cannot be directly applied to a display panel such as a television receiver. Further, since the light reflected by the step-like reflecting surface is further reflected and emitted in an undesired direction, it is difficult to suppress the occurrence of uneven brightness and unevenness in brightness.

  Therefore, the present invention has been made in view of the above problems, and an object of the present invention is a novel and capable of minimizing the occurrence of luminance unevenness due to light emitted from the light emitting element. An object of the present invention is to provide an improved light emitting device and display device.

  In order to solve the above-described problems, according to one aspect of the present invention, a light emitting element disposed on a plane and having a light emitting direction directed in a normal direction of the plane, and a circular lens disposed on the light emitting element The circular center is arranged so as to coincide with the optical axis of the light emitted from the light emitting element, and the light emitted from the light emitting element is refracted and emitted and emitted from the light emitting element. A lens in which a part of the light is internally reflected; an annular transmission / refractive surface centered on the optical axis; and an annular reflective surface centered on the optical axis. Alternately arranged, refracting and emitting light emitted from the light emitting element by the transmission refracting surface, and internally reflecting the light emitted from the light emitting element by the reflecting surface; and Provided on the light exit surface, And formed outside the first region, refracts and emits the light emitted from the light emitting element, and reflects the light internally reflected by the reflecting surface of the first region to reflect the light. There is provided a light emitting device comprising: a second region directed toward a plane side on which the light emitting element is disposed.

  Moreover, the irregular reflection member of the shape which does not coat | cover the said light emitting element may be arrange | positioned on the said plane where the said light emitting element is arrange | positioned.

  Moreover, the irregular reflection surface which consists of fine uneven | corrugated shape may be provided in the surface of the plane side where the said light emitting element is arrange | positioned among the surfaces which comprise the said lens.

  In addition, an annular protrusion shape centering on the optical axis may be provided on a surface on the flat surface side where the light emitting element is arranged among the surfaces constituting the lens.

  In the first region, the transmission refracting surface and the reflecting surface may be provided stepwise.

  In the second region, the light exit surface of the lens may be a continuous curved surface.

Further, the relationship between the inclination angle θa of the transmission refracting surface and the inclination angle θb of the reflection surface adjacent to the transmission refracting surface a on the optical axis side may satisfy the following (Equation 1).
(Formula 1) θa ≧ −π / 2 + 2 + θb + θ1

Where θa: angle formed by the normal of the optical axis and the transmission refractive surface (tilt angle of the transmission refractive surface)
θb: angle formed by the normal of the optical axis and the reflecting surface (inclination angle of the reflecting surface)
θ ₁ is an angle formed by the optical axis when a light beam emitted from the center of the light emitting element enters the reflecting surface.

Further, the relationship between the inclination angle θb of the reflection surface and the inclination angle θa of the transmission refracting surface adjacent to the reflection surface on the optical axis side may satisfy the following (Equation 2).
(Formula 2) θb ≦ π / 2 + θa−sin ⁻¹ {n · sin (θ1 + θa)}
Where θa: angle formed by the normal of the optical axis and the transmission refractive surface (tilt angle of the transmission refractive surface)
θb: angle formed by the normal of the optical axis and the reflecting surface (inclination angle of the reflecting surface)
θ ₁ : Angle formed by the optical axis when light emitted from the center of the light-emitting element enters the refracting refractive surface n: Refractive index of the lens.

  The light emitted from the light emitting element has a maximum intensity in the direction of the optical axis, and the first light is incident on a region where light within an angle range of 45 ° with respect to the optical axis is incident on the emission surface. These areas may be included.

  In order to solve the above problems, according to another aspect of the present invention, a display panel for displaying an image, and a plurality of light emitting elements arranged on a plane and having a light emitting direction directed in a normal direction of the plane And a circular lens disposed on each light emitting element, the circular center being arranged so as to coincide with the optical axis of the light emitted from the light emitting element, and refracting the light emitted from the light emitting element And a lens in which a part of the light emitted from the light emitting element is internally reflected, an annular transmission refracting surface centered on the optical axis, provided on the light emission surface of the lens, Lights emitted from the light emitting element by the reflecting surface are arranged alternately with annular reflecting surfaces centered on the optical axis, refracted and emitted from the light emitting element by the transmission refracting surface. A first region for reflecting the inner surface; The light is emitted from the light emitting element, is formed outside the first region with respect to the optical axis, refracts the light emitted from the light emitting element, and emits the light from the first region. A second region that reflects the light internally reflected by the reflecting surface and directs the light toward a flat surface on which the light emitting element is disposed, and a surface light source that irradiates the display panel from the back. A display device is provided.

  Moreover, the irregular reflection member of the shape which does not coat | cover the said light emitting element may be arrange | positioned on the said plane where the said light emitting element is arrange | positioned.

  Moreover, the irregular reflection surface which consists of fine uneven | corrugated shape may be provided in the surface of the plane side where the said light emitting element is arrange | positioned among the surfaces which comprise the said lens.

  In addition, an annular protrusion shape centering on the optical axis may be provided on a surface on the flat surface side where the light emitting element is arranged among the surfaces constituting the lens.

  In the first region, the transmission refracting surface and the reflecting surface may be provided stepwise.

  In the second region, the light exit surface of the lens may be a continuous curved surface.

Further, the relationship between the inclination angle θa of the transmission refracting surface and the inclination angle θb of the reflection surface adjacent to the transmission refracting surface a on the optical axis side may satisfy the following (Equation 1).
(Formula 1) θa ≧ −π / 2 + 2 + θb + θ1

Where θa: angle formed by the normal of the optical axis and the transmission refractive surface (tilt angle of the transmission refractive surface)
θb: angle formed by the normal of the optical axis and the reflecting surface (inclination angle of the reflecting surface)
θ ₁ is an angle formed by the optical axis when a light beam emitted from the center of the light emitting element enters the reflecting surface.

Further, the relationship between the inclination angle θb of the reflection surface and the inclination angle θa of the transmission refracting surface adjacent to the reflection surface on the optical axis side may satisfy the following (Equation 2).
(Formula 2) θb ≦ π / 2 + θa−sin ⁻¹ {n · sin (θ1 + θa)}
Where θa: angle formed by the normal of the optical axis and the transmission refractive surface (tilt angle of the transmission refractive surface)
θb: angle formed by the normal of the optical axis and the reflecting surface (inclination angle of the reflecting surface)
θ ₁ : Angle formed by the optical axis when light emitted from the center of the light-emitting element enters the refracting refractive surface n: Refractive index of the lens.

  The light emitted from the light emitting element has a maximum intensity in the direction of the optical axis, and the first light is incident on a region where light within an angle range of 45 ° with respect to the optical axis is incident on the emission surface. These areas may be included.

  According to the present invention, it is possible to minimize the occurrence of luminance unevenness due to the light emitted from the light emitting element.

It is a perspective view which shows the structure of the image display apparatus concerning each embodiment of this invention. It is sectional drawing which shows the structure of an image display apparatus. It is a functional block diagram which shows the structure of a display apparatus. FIG. 3 is an enlarged cross-sectional view showing a periphery of a light emitting diode in a region A1 in FIG. It is a schematic diagram which shows the shape of the light emission surface in a 1st area | region. It is a schematic diagram which expands and shows the output surface of a 1st area | region. It is a schematic diagram which expands and shows the output surface of a 1st area | region. It is a schematic diagram which shows a mode that the light ray reflected by the reflective surface is reflected by the adjacent refracting surface, and goes to the surface direction. It is a schematic diagram which shows a mode that reflected light returns to an output surface again and is output from an output surface. It is a schematic diagram which shows the structure of the lens which concerns on 2nd Embodiment. In 1st and 2nd embodiment, it is a schematic diagram for demonstrating the method of setting the boundary of a 1st area | region and a 2nd area | region. It is a schematic diagram which shows the intensity | strength of light. It is a schematic diagram which shows the relationship between the distance from the optical axis L of a light emitting diode, and a brightness | luminance. It is a schematic diagram which shows the lens of a comparative example. It is a characteristic view which shows distribution of a brightness | luminance about four light emitting diodes arrange | positioned adjacently. It is a top view which shows the state which looked at the lens from the display panel side. It is a characteristic view which shows the luminance distribution by six light emitting diodes along the dashed-dotted line I-I 'in FIG.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

The description will be made in the following order.
1. 1. First embodiment (1) Overall configuration of display device according to each embodiment of the present invention (2) Lens configuration according to the first embodiment Second Embodiment (1) Configuration of Lens According to Second Embodiment 3. 3. Method for setting the size of the first region Results of luminance distribution simulation

1. First Embodiment [(1) Overall Configuration of Display Device According to Each Embodiment of Present Invention]
FIG. 1 is a perspective view showing a configuration of an image display device 100 according to each embodiment of the present invention. 2 is a cross-sectional view showing the configuration of the image display apparatus 100, and shows a cross section taken along the alternate long and short dash line II ′ in FIG. The image display apparatus 100 is configured such that required parts are arranged inside a housing 102. The housing 102 includes a front panel 104 and a rear panel 106. The front panel 104 and the rear panel 106 are joined at the front and rear.

  The front panel 104 of the housing 102 has an opening penetrating in the front-rear direction, and a display panel 200 that displays an image is disposed at a position where the opening is closed from the inside. The display panel 200 is configured, for example, by sandwiching a transmissive color liquid crystal panel between two polarizing plates from the front and the rear, and displays a full color image by being driven by an active matrix method. The display panel 200 is not limited to a liquid crystal panel, and the present embodiment can be applied to all display panels 200 that are irradiated from the back surface by a surface-emitting light source. In the following description, a liquid crystal panel is used as the display panel 200. Is illustrated.

  As shown in FIG. 2, a surface light source device (backlight, light emitting device) 300 is arranged inside the housing 102. The surface light source device 300 is configured by arranging necessary parts in a housing 302. The housing 302 is formed in a box shape that is flat in the front-rear direction of the display device 100 and opened forward, using a metal material having high thermal conductivity. An optical sheet 308 and a diffusion plate 320 are attached to the front end of the housing 302.

  The optical sheet 308 is formed by laminating various sheets having a predetermined optical function, such as a prism sheet that refracts light emitted from the light emitting diode 330 described later and guides the light in a predetermined direction, and a polarization direction conversion sheet that converts a polarization direction. Arranged and configured.

  The optical sheet 308 is attached to the front surface of the diffusion plate 320, and the diffusion plate 320 is disposed to face the light emitting diode 330. The diffusion plate 320 has a function of diffusing the light emitted from the light emitting diode 330 inside the housing 302 and irradiating the display panel 200 from the back surface to reduce luminance variation in the display panel 200.

  A circuit board 310 is disposed on the bottom surface of the housing 302. A plurality of light emitting diodes 330 are arranged in a matrix on the circuit board 310.

  The light emitting diode 330 emits white light, for example, but is not limited to emitting white light, and may emit red, blue, and green light. For example, a plurality of light emitting diodes 330 that emit red light, light emitting diodes 330 that emit blue light, and two light emitting diodes 330 that emit two green lights, which are configured as a set of light emitting units, are arranged in a matrix. May be. Thus, the number of light emitting diodes 330 and the color of the emitted light are arbitrary.

  Lenses 340 are attached to the individual light emitting diodes 330 closer to the display panel 200 than the light emitting diodes 330. The lens 340 is made of a transparent resin material such as acrylic.

  When the light from the light emitting diode 330 is directly applied to the diffuser plate 320, the point light source region of the light emitting diode 330 appears on the display screen, and the brightness within the surface of the display panel 200 varies. However, by irradiating the diffusing plate 320 via the lens 340, it is possible to reliably prevent the point light source region from appearing on the display screen. Further, by irradiating the diffuser plate 320 with the light of the light emitting diode 330 via the lens 340, it is possible to suppress the generation of a point light source region on the display screen, so that the light emitting diode 330 and the diffuser plate 320 are brought close to each other. Thus, the display device 100 can be thinned.

  FIG. 3 is a functional block diagram illustrating the configuration of the display device 100. The display device 100 includes a display panel 200 having a color filter substrate, a liquid crystal layer, and the like, a surface light source device 300 disposed on the back side of the display panel 200, a control unit 400 that controls the display panel 200 and the surface light source device 300, and The power supply unit 410 is configured. Note that the control unit 400 and the power supply unit 410 may be configured integrally with the display device 100 or may be configured separately from the display device 100.

  The display device 100 displays an original image corresponding to the image signal in a predetermined display area (an area corresponding to the display unit 202 of the display panel 200). The input image signal input to the display device 100 corresponds to, for example, an image (frame image) with a frame rate of 60 Hz.

  The display panel 200 includes a display unit 202 in which a plurality of openings that transmit white light from the surface light source device 300 are arranged. The display panel 200 also includes a source driver 204 and a gate driver 206 that send drive signals to transistors (TFTs: Thin Film Transistors (not shown)) provided in the respective openings of the display unit 202.

  White light that has passed through the opening of the display unit 202 is converted into red, green, or blue light by a color filter formed on a color filter substrate (not shown). A set of three openings that emit red, green, and blue light corresponds to one pixel of the display unit 202.

  The surface light source device 300 emits white light in a light emitting area corresponding to the display unit 202. The light emitting area of the surface light source device 300 may be divided into a plurality of blocks (areas), and light emission may be individually controlled for each of the divided blocks (divided light emission driving).

  The control unit 400 includes a display luminance calculation unit 402, a light source control unit 404, and a display panel control unit 406. The display luminance calculation unit 402 is supplied with an image signal corresponding to each frame image. The display luminance calculation unit 402 calculates the luminance distribution of the frame image from the supplied image signal, and further calculates the necessary display luminance for each block from the luminance distribution of the frame image. The calculated display luminance is supplied to the light source control unit 404 and the display panel control unit 406.

  The light source control unit 404 calculates the backlight luminance of the surface light source device 300 based on the display luminance supplied from the display luminance calculation unit 402. When performing the divided light emission drive, the light source control unit 404 calculates the backlight luminance in each block of the surface light source device 300 based on the display luminance of each block supplied from the display luminance calculation unit 402. Then, the light source control unit 404 controls the light emission amount of the light emitting diodes 330 of each block so as to obtain the calculated backlight luminance by PWM (Pulse Width Modulation) control. Thus, by controlling the light emission luminance of the surface light source device 300 for each block according to the input image signal, optimal light emission according to the image displayed on the display panel 200 is possible.

  The light source control unit 404 also performs light emission control for correcting light emission luminance or chromaticity based on the light emission luminance or chromaticity of each block detected by a sensor arranged in the backlight 300. Here, the sensor is an illuminance sensor or a color sensor.

  The backlight luminance of each block of the surface light source device 300 calculated by the light source control unit 404 is supplied to the display panel control unit 406. The display panel control unit 406 displays the liquid crystal aperture of each pixel of the display unit 202 based on the display luminance for each block supplied from the display luminance calculation unit 402 and the backlight luminance for each block supplied from the light source control unit 404. Calculate the rate. Then, the display panel control unit 406 supplies drive signals to the source driver 204 and the gate driver 206 of the display panel 200 so as to achieve the calculated liquid crystal aperture ratio, and drives and controls the TFTs of each pixel of the display unit 202. . The power supply unit 410 supplies predetermined power to each unit of the display device 100.

[(2) Configuration of Lens According to First Embodiment]
FIG. 4 is an enlarged cross-sectional view showing the periphery of the light emitting diode 330 in the region A1 in FIG. The light emitting diode 330 is mounted on the circuit board 310, and its planar shape is, for example, a square. The light emitting diode 330 is provided with a light emitting portion 330a. As shown in FIG. 4, a straight line that passes through the light emitting unit 330 a and is perpendicular to the surface of the circuit board 310 is an optical axis L of the light emitting diode 330.

  A lens 340 is disposed on the light emitting diode 330. One lens 340 is provided for each light emitting diode 330. The lens 340 has a circular outer shape when viewed from the display panel 200 side, and the center of the circular outer shape coincides with the position of the optical axis L.

  A surface 341 of the lens 340 on the display panel 200 side is an emission surface that emits light from the light emitting diode 330. On the surface 341, a recess 342 that is recessed toward the light emitting diode 330 is provided in the vicinity of the optical axis L. The concave portion 342 is formed of a curved surface that is rotationally symmetric about the optical axis L. Further, on the light emitting diode 330 side of the lens 340, a refracting surface 344 composed of a curved surface that is rotationally symmetric about the optical axis L is provided. The surface 345 of the lens 340 on the light emitting diode 330 side is a flat surface, and the refracting surface 344 is concave with respect to the surface 345.

  FIG. 4 shows a state where light emitted from the light emitting diode 330 is refracted by the lens 340 and travels toward the display panel 200 side. As shown in FIG. 4, the light emitted from the light emitting unit 330 a of the light emitting diode 330 proceeds radially, and first, on the refracting surface 344, the direction in which the angle with the optical axis L becomes wider, that is, the light traveling direction is The light is refracted in a direction closer to the surface direction of the circuit board 310. The light refracted by the refractive surface 344 travels through the lens 340 and is emitted from the surface 341.

  As shown in FIG. 4, a first region and a second region are defined on the surface 341 of the lens 340 with the optical axis L as the center. The first region is a region defined by a circle with a predetermined radius centered on the optical axis L. The second area is an area outside the first area.

  In the present embodiment, the surface shape of the surface 341 is defined so that when the light incident on the lens 340 is emitted from the surface 341, the first region and the second region behave differently. FIG. 5 is a schematic diagram showing the shape of the surface 341 in the first region. As shown in FIG. 5, in the first region, the surface 341 is stepped, and the transmission refracting surface 346 having a gentle inclination with respect to the surface direction of the circuit board 310 (direction orthogonal to the optical axis L) and the steep inclination are obtained. Reflective surfaces 348 are alternately provided in a staircase pattern. The transmission refracting surface 346 and the reflecting surface 348 are provided in an annular shape with the optical axis L as the center when viewed from the display panel 200 side.

  6 and 7 are schematic views showing an enlarged surface 341 of the first region. As shown in FIG. 6, the transmission refracting surface 346 has a relatively small angle θa with respect to the optical axis L, and has a gentle inclination with respect to the direction orthogonal to the optical axis L. Is refracted by the transmission refracting surface 346 and emitted to the display panel 200 side. A very small part of the light incident on the transmissive refracting surface 346 is reflected by the transmissive refracting surface 346 as interface reflected light, but most of the light rays are emitted to the display panel 200 side.

  On the other hand, as shown in FIG. 7, the reflection surface 348 has a relatively large angle θa with the normal axis to the optical axis L, and has a steep inclination with respect to the direction orthogonal to the optical axis L. The reflected light is totally reflected by the reflecting surface 348. Then, as shown in FIG. 7, the light reflected by the reflecting surface 348 travels in the direction of the outer shape of the lens 340 (direction orthogonal to the optical axis).

  As a result, a part of the light beam emitted from the light emitting unit 330a of the light emitting diode 330 and incident on the surface 341 of the first region is reflected by the reflecting surface 348 and is emitted from the surface 341 to the display panel 200 side. It will be in a state that is not. Therefore, it is possible to reduce the light emitted from the surface 341 in the first region, and it is possible to reliably suppress luminance unevenness due to the intensity of the light emitted from the first region being increased.

  In general, the intensity of light emitted from the light emitting diode 330 increases as the light beam is near the optical axis L. In the present embodiment, in the first region where the light intensity is high, a part of the light beam is reflected by the reflecting surface 348 so as not to be emitted to the display panel 200 side. Therefore, it is possible to reliably suppress the occurrence of luminance unevenness due to the concentrated outgoing light having high light intensity in the vicinity of the optical axis L.

  As shown in FIG. 4, the light beam reflected by the reflecting surface 348 provided in the first region proceeds in the direction of the outer shape of the lens 340 (direction orthogonal to the optical axis), and the surface 341 of the second region. Is incident on. The light beam reflected by the reflecting surface 348 is further reflected by the surface 341 of the second region and travels toward the surface 345 on the circuit board 310 side. Further, the interface reflected light reflected by the transmission refracting surface 346 also travels toward the surface 345 on the circuit board 310 side. Then, the total reflection light from the reflection surface 348 and the interface reflection light of the transmission refracting surface 346 enter the surface 345 in the vicinity of the outer edge of the lens 330.

  An irregular reflection surface is formed on the surface 345. The irregular reflection surface is formed, for example, by forming a fine uneven surface on the surface 345. In the case where the lens 340 is molded from a resin molded product, the surface 345 can be provided with an irregular reflection surface (pear surface) by subjecting the mold to sand blasting. Thereby, the total reflection light from the reflection surface 348 and the interface reflection light from the transmission refracting surface 346 are diffusely reflected by the irregular reflection surface and diffused in the lens 340. Therefore, the strong light in the vicinity of the optical axis L can be reflected by the reflecting surface 348 and further diffused in the lens 340. Therefore, when the lens 340 is viewed from the display panel 200 side, in a specific region. It is possible to suppress the occurrence of a peak in luminance.

  In addition, an irregular reflection member 352 having a shape that does not cover the light emitting diode 330 is disposed on the circuit board 310. The irregular reflection member 352 irregularly reflects the light beam incident from the lens 340 in the same manner as the irregular reflection surface of the surface 345. Therefore, the light beam transmitted from the inside of the lens 340 through the surface 345 is diffusely reflected by the irregular reflection member 352, whereby the light beam can be prevented from being emitted again from the surface 341, and a luminance peak is generated. You can avoid.

  On the other hand, in the second region, the surface 341 is formed by a continuous curved surface as shown in FIG. A light beam having a larger angle with the optical axis L is incident on the surface 341 of the second region. For this reason, in the second region, light is incident at a shallow angle with respect to the surface 341. Therefore, the light incident on the surface 341 is refracted by the surface 341 and emitted to the display panel 200 side. A light beam incident on the surface 341 in the second region has a light intensity lower than a light beam incident on the surface 341 in the first region. For this reason, even if all the light rays are emitted from the surface 341 toward the display panel 200, the luminance in the second region does not become excessively high, and does not cause luminance variation. Therefore, in the first region, a part of the light beam incident on the surface 341 is reflected by the reflecting surface 348, and in the second region, the light beam incident on the surface 341 is emitted to the display panel 200 side, so that the lens 340 It is possible to reliably suppress the occurrence of uneven brightness in the light emitted to the display panel.

In FIG. 7, the relationship between the inclination angle θa of the transmission refracting surface 346 provided annularly with respect to the optical axis L and the inclination angle θb of the annular reflection surface 348 adjacent to the transmission refractive surface 346 on the optical axis side is as follows. It is assumed that the following formula (1) is satisfied.
θa ≧ −π / 2 + 2 + θb + θ1
In formula (1),
θa: an angle formed by the normal line of the optical axis L and the annular transmission refracting surface 346 (inclination angle of the transmission refracting surface 346)
θb: angle formed by the normal of the optical axis L and the annular reflecting surface 348 (inclination angle of the reflecting surface 348)
θ1: An angle formed by the optical axis when a light beam emitted from the center of the light emitting portion 330a of the light emitting diode 330 enters the annular reflecting surface 348.

  By satisfying the expression (1), the light beam reflected by the reflecting surface 348 does not enter the transmissive refracting surface 346 adjacent to the outside, and the light reflected by the reflecting surface 348 is surely reflected in the outer shape of the lens 340. It can be directed in the direction. Here, when the light beam reflected by the reflecting surface 348 enters the transmissive refracting surface 346 adjacent to the outside, the light beam is further reflected by the transmissive refracting surface 346 and proceeds toward the surface 345. In this case, the light beam is reflected by the surface 345, returns to the first region again, and is emitted to the display panel 200 side, which causes generation of luminance unevenness in the vicinity of the optical axis L. Therefore, by satisfying the expression (1), it is possible to reliably avoid that the light beam reflected by the reflecting surface 348 is reflected in the lens 340 and returns to the first region.

In addition, in FIG. 6, the relationship between the inclination angle θb of the reflection surface 348 provided in an annular shape with respect to the optical axis L and the inclination angle θa of the transmission refractive surface 346 adjacent to the reflection surface 348 on the optical axis L side Suppose that the following formula (2) is satisfied. In equation (2), n is the refractive index of the lens. Θ1 is an angle formed between the direction of light incident on the transmission refracting surface 346 and the optical axis L.
θb ≦ π / 2 + θa−sin ⁻¹ {n · sin (θ1 + θa)} (2)

  By satisfying the expression (2), it is possible to reliably prevent the light emitted from the transmission refracting surface 346 toward the display panel 200 from entering the reflecting surface 348 and entering the lens 340. Therefore, in the first region, the light emitted from the transmissive refracting surface 346 can surely reach the display panel 200, and the light beam emitted from the transmissive refracting surface 346 returns to the lens 340. A decrease in luminance in the vicinity can be suppressed.

  FIG. 8 is a schematic diagram showing a state in which the light beam reflected by the reflecting surface 348 is reflected by the adjacent transmission refracting surface 346 toward the surface 345. As shown in FIG. 8, when the light beam reflected by the reflecting surface 348 is reflected by the transmission refracting surface 346, the light beam is directed toward the surface 345 and reflected by the surface 345. In this case, the light reflected by the surface 345 may return to the surface 341 again and be emitted from the surface 341 as shown in FIG. In the present embodiment, by satisfying Expression (2), it is possible to reliably suppress the occurrence of the state shown in FIGS. Further, since the irregular reflection surface is provided on the surface 345, even if the light beam reflected by the reflection surface 348 is reflected by the adjacent transmission refracting surface 346 and directed toward the surface 345, it is diffused by the irregular reflection surface. The occurrence of uneven brightness can be suppressed.

  As described above, according to the first embodiment, the exit surface 341 of the lens 340 that emits the light of the light emitting diode 330 is divided into two regions, and in the first region close to the optical axis L, the transmission refracting surface 346 and Two of the reflective surfaces 348 were alternately provided. Thereby, in the vicinity of the optical axis L where the light intensity is strong, the luminance can be lowered by reflecting the light by the reflecting surface 348. Thereby, it can suppress that a brightness | luminance becomes high near the optical axis L, and can suppress that a peak arises in a brightness | luminance. In addition, since the light incident on the second region has a relatively low intensity, the decrease in luminance can be suppressed in the peripheral region of the lens 340 by emitting the light incident on the surface 341 to the display panel 200 side. The occurrence of uneven brightness can be reliably suppressed.

2. Second Embodiment [(1) Configuration of Lens According to Second Embodiment]
Next, a second embodiment of the present invention will be described. FIG. 10 is a schematic diagram illustrating a configuration of a lens 340 according to the second embodiment. The shape of the surface 341 of the lens 340 according to the second embodiment is the same as that of the first embodiment. That is, also in the lens 340 according to the second embodiment, the reflective surface 348 and the transmission refracting surface 346 are alternately provided on the surface 341 in the first region. In the second region, the surface 341 is a continuous curved surface.

  As shown in FIG. 10, the lens 340 according to the second embodiment is provided with a protrusion 350 on a surface 345. The protrusion shape 350 is provided in an annular shape with respect to the optical axis L, and has a function of refracting the light beam reflected by the reflection surface 348 in the outer peripheral direction of the side surface of the lens 340.

  Similar to the first embodiment, the light beam reflected by the reflecting surface 348 provided in the first region proceeds in the direction of the outer periphery of the lens 340 and is reflected by the surface 341 of the second region. The light enters the surface 345 at a position inside the outer shape. The protrusion shape 350 is provided in the vicinity of a region where the light beam reflected by the reflecting surface 348 enters the surface 345. As described in the first embodiment, the interface reflected light from the transmission refracting surface 346 is incident on the surface 345 at the same position as the total reflected light from the reflecting surface 348, so that the interface reflected light also has a projection shape 350. Incident.

  The light beam incident on the protrusion shape 350 is emitted to the outside of the lens 340 as shown in FIG. As shown in FIG. 10, the protrusion shape 350 is provided so that both the total reflection light from the reflection surface 348 and the interface reflection light from the transmission refracting surface 346 are transmitted without being reflected by the protrusion shape 350. ing. Therefore, by providing the projection shape 350 on the surface 345, it is possible to reliably avoid the light reflected by the reflecting surface 348 from being further reflected by the surface 345 and returning to the surface 341. Thereby, when the lens 340 side is viewed from the display panel 200 side, it is possible to reliably suppress the occurrence of luminance unevenness due to the total reflected light of the reflection surface 348 returning to the display panel 200 side.

  As described above, according to the second embodiment, by providing the projection shape 350 on the surface 345 of the lens 340, the light reflected by the reflecting surface 348 is emitted from the side surface or the back surface of the lens 340 and is discharged. Can do. Therefore, since the light that causes luminance unevenness can be discharged out of the lens 340, it is possible to reliably suppress the occurrence of luminance unevenness.

3. FIG. 11 is a schematic diagram for explaining a method for setting the boundary between the first region and the second region in the first and second embodiments. . As shown in FIG. 11, of the light emitted from the light emitting diode 330, a region where a light beam having an angle with respect to the optical axis L is θc or less is emitted from the surface 341, and the outside is a second region. And Here, θc is an angle range close to the optical axis corresponding to a half of the total reflected light on the irregular reflection surface 345. When the light reflected from the irregular reflection surface is completely diffused, θc = 45 °.

  In the first and second embodiments, the light of the light emitting diode 330 is totally reflected by the reflection surface 348 and converted into diffused light by the lower surface 345 in the first region. This is because if the component inclined to the plane 345 side than the average angle component is converted, the opposite effect is obtained.

  FIG. 12 is a schematic diagram showing the intensity of light. When the luminous intensity of the reflected light is I (θ), the total luminous flux F can be expressed by the following formula (3).

  When the reflected light is completely diffused, I (θ) = cos θ, and the total luminous flux F can be expressed by the following equation (4).

  Assuming that the angle range near the optical axis corresponding to F / 2 (half the light amount of the total luminous flux F) is θc, F / 2 can be expressed by the following equation (5). As a result, θc = π / 4 = 45 °.

4). Next, the luminance distribution by the lens 340 of the first and second embodiments described above will be described. FIG. 13 is a schematic diagram showing a simulation result of the relationship between the distance from the optical axis L of the light emitting diode 330 and the luminance. Here, the luminance on the vertical axis is a schematic diagram showing the luminance distribution when the light emitting diode 330 is viewed from the direction of the optical axis L (from the display panel 200 side). In FIG. 13, 0 indicates the position of the optical axis L. As shown in the characteristics of FIG. 13, the luminance decreases as the distance from the optical axis L increases.

  In FIG. 13, the luminance distribution by the lens 340 of the first embodiment (indicated by ◯ in FIG. 13), the luminance distribution by the lens 340 of the second embodiment (indicated by Δ in FIG. 13), and the lens of the comparative example The luminance distribution (shown by x in FIG. 13) is shown. Here, the comparative example has shown the simulation result of the luminance distribution in the lens of the shape shown in FIG. The lens shown in FIG. 14 corresponds to the lens described in Patent Document 1 described above, and the surface 341 is formed by a continuous curved surface.

  As shown in FIG. 13, when the lens 340 of the first and second embodiments is used, the light beam is reflected by the reflecting surface 348 of the first region, so that the luminance near the optical axis L is lowered. be able to. Therefore, it is possible to suppress the occurrence of a luminance peak around the optical axis L, and it is possible to minimize the occurrence of luminance unevenness and luminance variation in the surface direction of the display panel 200.

  On the other hand, in the lens 340 of the comparative example, the light in the vicinity of the optical axis L is basically not totally reflected by the surface 341, so that the light emitted from the light emitting diode 330 is refracted by the surface 341 and then the display panel 200. Emitted to the side. As described above, since the light intensity (luminance) is high in the vicinity of the optical axis L, the light beam in the vicinity of the optical axis L is emitted to the display panel 200 side in the lens 340 of the comparative example. As a result, the brightness in the vicinity of the screen becomes high, and the brightness becomes uneven.

  FIG. 15 is a characteristic diagram showing the luminance distribution of four light emitting diodes 330 arranged adjacent to each other, and the vertical axis shows the luminance. FIG. 16 is a plan view showing a state in which the circuit board 310 and the lens 340 are viewed from the display panel 200 side. As shown in FIG. 16, the lenses 340 are arranged in a matrix corresponding to the positions of the light emitting diodes 330. FIG. 15 shows the luminance distribution by the four light emitting diodes 330 and the lens 340 in the region B shown in FIG. Here, FIG. 15A shows the luminance distribution by the lens of the comparative example shown in FIG. FIG. 15B shows the luminance distribution by the lens 340 of the first embodiment, and FIG. 15C shows the luminance distribution by the lens 340 of the second embodiment. Thus, according to the result of FIG. 15, when the lens 340 of the first embodiment is used, the luminance peak due to the four light emitting diodes 340 can be reduced as compared with the comparative example. In addition, when the lens 340 of the second embodiment is used, the luminance peak can be further reduced.

  FIG. 17 is a characteristic diagram showing the luminance distribution of the six light emitting diodes 330 located in the center among the light emitting diodes 330 along the alternate long and short dash line I-I ′ in FIG. 16. As in FIG. 13, in FIG. 17, the luminance distribution by the lens 340 of the first embodiment (indicated by a circle in FIG. 17) and the luminance distribution by the lens 340 of the second embodiment (indicated by a triangle in FIG. 17). ) And the luminance distribution (indicated by x in FIG. 17) by the lens of the comparative example of FIG.

  Also in the characteristics shown in FIG. 17, when the lens 340 of the first embodiment is used as compared with the comparative example, the luminance peak due to the six light emitting diodes 340 can be reduced. Further, when the lens 340 of the second embodiment is used, it is possible to further reduce the luminance peak. In general, the luminance decreases toward the periphery as compared with the center of the circuit board 310. Therefore, in the characteristic of FIG. 17, the luminance of the light emitting diode 340 located at the end gradually decreases from the center. .

  The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 100 Image display apparatus 200 Display panel 300 Surface light source device (backlight)
330 Light Emitting Diode 340 Lens 341 Emission Surface 346 Transmission Refraction Surface 348 Reflection Surface

Claims (18)

A light-emitting element disposed on a plane and directing the light emission direction in the normal direction of the plane;
A circular lens disposed on the light emitting element, the circular lens being disposed so that a center of the circle coincides with an optical axis of light emitted from the light emitting element, and refracting light emitted from the light emitting element. A lens that emits and part of the light emitted from the light emitting element is internally reflected;
An annular transmission / refractive surface centered on the optical axis and an annular reflection surface centered on the optical axis are alternately arranged on the light exit surface of the lens, and the light is emitted by the transmission / refractive surface. A first region that refracts and emits light emitted from the element, and internally reflects the light emitted from the light emitting element by the reflective surface;
Provided on the light exit surface of the lens, formed outside the first region with respect to the optical axis, and refracts and emits the light emitted from the light emitting element. A second region that reflects the light that is internally reflected by the reflecting surface of the light-emitting element toward the plane on which the light-emitting element is disposed;
A light emitting device comprising:   The light-emitting device according to claim 1, wherein an irregular reflection member having a shape that does not cover the light-emitting element is disposed on the plane on which the light-emitting element is disposed.   The light-emitting device according to claim 1, wherein an irregular reflection surface having a fine uneven shape is provided on a surface on a flat surface side where the light-emitting element is arranged among surfaces constituting the lens.   2. The light emitting device according to claim 1, wherein an annular protrusion shape centering on the optical axis is provided on a surface on a flat surface side on which the light emitting element is disposed among surfaces constituting the lens.   The light emitting device according to claim 1, wherein in the first region, the transmission refracting surface and the reflecting surface are provided in a stepped shape.   The light emitting device according to claim 1, wherein in the second region, the light emitting surface of the lens is configured by a continuous curved surface. 2. The light emitting device according to claim 1, wherein a relationship between an inclination angle θa of the transmission refracting surface and an inclination angle θb of the reflection surface adjacent to the transmission refracting surface a on the optical axis side satisfies the following (Equation 1).
(Formula 1) θa ≧ −π / 2 + 2 + θb + θ1

Where θa: angle formed by the normal of the optical axis and the transmission refractive surface (tilt angle of the transmission refractive surface)
θb: angle formed by the normal of the optical axis and the reflecting surface (inclination angle of the reflecting surface)
θ ₁ is an angle formed by the optical axis when a light beam emitted from the center of the light emitting element enters the reflecting surface. 2. The light emitting device according to claim 1, wherein a relationship between an inclination angle θb of the reflection surface and an inclination angle θa of the transmission refracting surface adjacent to the reflection surface on the optical axis side satisfies the following (Equation 2).
(Formula 2) θb ≦ π / 2 + θa−sin ⁻¹ {n · sin (θ1 + θa)}
Where θa: angle formed by the normal of the optical axis and the transmission refractive surface (tilt angle of the transmission refractive surface)
θb: angle formed by the normal of the optical axis and the reflecting surface (inclination angle of the reflecting surface)
θ ₁ : Angle formed by the optical axis when light emitted from the center of the light-emitting element enters the refracting refractive surface n: Refractive index of the lens.   The light emitted from the light emitting element has the maximum intensity in the direction of the optical axis, and the first region is in a region where light within an angle range of 45 ° with respect to the optical axis is incident on the emission surface. The light emitting device according to claim 1, wherein: A display panel for displaying images,
A plurality of light emitting elements arranged on a plane and having a light emitting direction directed to a normal direction of the plane, and a circular lens disposed on each light emitting element, wherein a circular center is emitted from the light emitting element A lens disposed so as to coincide with the optical axis of the light, refracting and emitting the light emitted from the light emitting element, and a part of the light emitted from the light emitting element being internally reflected; An annular refracting surface centered on the optical axis and an annular reflecting surface centered on the optical axis are alternately arranged on the light exit surface, and emitted from the light emitting element by the transmissive refracting surface. The light is refracted and emitted, and is provided on the light emission surface of the lens, the first region for reflecting the light emitted from the light emitting element by the reflection surface on the inner surface, and the light axis Formed outside the first region, A second region that refracts and emits light emitted from the element and reflects the light internally reflected by the reflecting surface of the first region toward a plane side on which the light emitting element is disposed; And a surface light source for irradiating the display panel from the back surface,
A display device comprising:   The display device according to claim 10, wherein an irregular reflection member having a shape that does not cover the light emitting element is disposed on the plane on which the light emitting element is disposed.   The display device according to claim 10, wherein an irregular reflection surface having a fine uneven shape is provided on a surface on a plane side on which the light emitting element is disposed among surfaces constituting the lens.   11. The display device according to claim 10, wherein an annular protrusion shape centering on the optical axis is provided on a surface on a plane side on which the light emitting element is disposed among surfaces constituting the lens.   The display device according to claim 10, wherein in the first region, the transmission refracting surface and the reflecting surface are provided stepwise.   The display device according to claim 10, wherein, in the second region, the light emission surface of the lens is a continuous curved surface. The display device according to claim 10, wherein a relationship between an inclination angle θa of the transmission refracting surface and an inclination angle θb of the reflection surface adjacent to the transmission refracting surface a on the optical axis side satisfies the following (Equation 1).
(Formula 1) θa ≧ −π / 2 + 2 + θb + θ1

Where θa: angle formed by the normal of the optical axis and the transmission refractive surface (tilt angle of the transmission refractive surface)
θb: angle formed by the normal of the optical axis and the reflecting surface (inclination angle of the reflecting surface)
θ ₁ is an angle formed by the optical axis when a light beam emitted from the center of the light emitting element enters the reflecting surface. The display device according to claim 10, wherein a relationship between an inclination angle θb of the reflection surface and an inclination angle θa of the transmission refractive surface adjacent to the reflection surface on the optical axis side satisfies the following (Equation 2).
(Formula 2) θb ≦ π / 2 + θa−sin ⁻¹ {n · sin (θ1 + θa)}
Where θa: angle formed by the normal of the optical axis and the transmission refractive surface (tilt angle of the transmission refractive surface)
θb: angle formed by the normal of the optical axis and the reflecting surface (inclination angle of the reflecting surface)
θ ₁ : Angle formed by the optical axis when light emitted from the center of the light-emitting element enters the refracting refractive surface n: Refractive index of the lens.   The light emitted from the light emitting element has the maximum intensity in the direction of the optical axis, and the first region is in a region where light within an angle range of 45 ° with respect to the optical axis is incident on the emission surface. The display device according to claim 10, comprising:

Images