JP2018194566A - Diffusion lens and light emitting device - Google Patents

Abstract

To provide a diffusion lens having high degree of freedom in designing of surface shape, which is easily designed and formed and capable of suppressing brightness unevenness.SOLUTION: Disclosed lens 4 has a circular shape in plan view, and each of a surface 6 and a rear face 8 is formed generally symmetrically with respect to the central axis X passing through the center of the circular shape. In a central area of the rear face 8, a concave incident part 9 is formed so that light from an LED 2, which is disposed so that the central axis X coincides with the optical axis, enters. The rear face 8 is formed in a taper which is inclined upward at a predetermined angle when viewed from the incident part 9 side.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a diffusing lens for diffusing light such as a light emitting diode (LED) used for a backlight of an image display device, and a light emitting device including the diffusing lens.

  A light emitting element such as an LED has a characteristic that the amount of light is concentrated in the vicinity of the optical axis. For example, an LED used for a backlight of an image display device such as a liquid crystal television diffuses light emission in order to suppress luminance unevenness. A diffusing lens is used.

  As such a diffusing lens, a lens of a light emitting device described in Patent Document 1 is conventionally known. The lens described in this document diffuses the light emission of the LED arranged on the back side, and is transmitted at a slant with respect to a plane whose normal is the optical axis at the center of the front surface (outgoing surface). A first region in which a refracting surface and a steep reflecting surface are alternately formed in a staircase shape is provided, and a second region formed by a continuous curved surface is provided on the outer periphery of the first region. Yes. Then, in the first region, a part of the light beam is reflected by the reflecting surface, thereby suppressing the occurrence of luminance unevenness due to the concentrated emitted light having a high intensity near the optical axis.

JP 2011-34770 A

  However, in the diffusing lens described in Patent Document 1, since the shape of the first region is particularly complicated, the design and molding thereof is not easy and the manufacturing cost is high, and the molding of the first region is also difficult. Along with this, there is a problem in that the degree of freedom in designing the surface shape of the lens is lost because a dent is formed on the surface side of the lens.

  The present invention has been made in view of the above circumstances, and includes a diffusing lens that has a high degree of freedom in designing a surface shape, can be easily designed and molded, and can suppress luminance unevenness, and such a diffusing lens. An object is to provide a light-emitting device.

  In order to solve the above problems, a diffusing lens according to the present invention has a circular shape in plan view, and each of a front surface and a back surface is formed substantially symmetrically with respect to a central axis passing through the center of the circle, and the center of the back surface The portion is provided with a concave incident portion on which light from a light source arranged so that the central axis and the optical axis coincide with each other, and the back surface is upward at a predetermined angle when viewed from the incident portion side. It is characterized by being formed in a tapered shape.

  The light-emitting device according to the present invention includes a light source and a diffusion lens that diffuses light emitted from the light source, and the diffusion lens has a circular shape in plan view and has a surface with respect to a central axis passing through the center of the circle. Each of the back surface and the back surface is formed substantially symmetrically, and a concave incident portion on which light from the light source is disposed so that the central axis and the optical axis coincide with each other is provided at a center portion of the back surface, The back surface is formed in a tapered shape inclined upward at a predetermined angle when viewed from the incident portion side.

  In the diffusing lens and the light emitting device according to the present invention, the back surface of the diffusing lens is formed in a tapered shape inclined upward at a predetermined angle when viewed from the incident portion side, so that the light source has a light amount near the optical axis. Even in the case of a concentration characteristic, the peak light quantity near the optical axis is reduced, and the light quantity away from the optical axis is increased correspondingly to suppress luminance unevenness. In other words, this effect can be obtained simply by forming the back surface into a tapered shape at a predetermined angle without processing the surface of the diffusion lens into a complicated shape. The degree of freedom is high, design and molding are easy, and luminance unevenness can be suppressed.

  Further, since the back surface is formed in a tapered shape, the heat of the light source which tends to be scattered near the incident portion is easily dissipated from the lower space on the back surface, and the heat dissipation effect can be improved.

  The predetermined angle is preferably 2.5 degrees or more and 6 degrees or less with respect to a plane having the central axis as a normal line, and thereby, the peak light amount is greatly reduced and luminance unevenness is effectively suppressed. can do.

  According to the present invention, the diffusing lens can have a high degree of freedom in designing the surface shape, can be easily designed and molded, and can suppress uneven brightness.

It is sectional drawing of the light-emitting device which concerns on the form for inventing. It is a perspective view which shows the surface side of the lens of the light-emitting device of FIG. It is a perspective view which shows the back surface side of the lens of the light-emitting device of FIG. FIG. 2 is an explanatory diagram illustrating a path of emitted light from an LED in the light emitting device of FIG. 1. In the light-emitting device of FIG. 1, it is explanatory drawing which shows the change of the peak light quantity when changing the inclination-angle of the back surface of a lens. 1A is an explanatory diagram showing the illuminance distribution on the irradiated surface when the tilt angle of the back surface of the lens is 0 degree, and FIG. 1B is a diagram when the tilt angle of the back surface of the lens is 4.5 degrees. It is explanatory drawing which shows the illumination intensity distribution in the irradiation surface. FIG. 2 is an explanatory diagram showing the light distribution on the irradiated surface when the inclination angle of the back surface of the lens is 0 degree and 3 degrees for the light emitting device of FIG. 1. It is explanatory drawing which illustrates the path | route of the emitted light of LED in the other light-emitting device which concerns on the form for inventing. FIG. 9 is an explanatory diagram showing a light distribution on the irradiated surface when the inclination angle of the back surface of the lens is 0 degree and 3 degrees for the light emitting device of FIG. 8. It is explanatory drawing which illustrates the path | route of the emitted light of LED in the further another light-emitting device based on the form for inventing. FIG. 11 is an explanatory diagram showing a light distribution on the irradiated surface when the inclination angle of the rear surface of the lens is 0 degree and 3 degrees for the light emitting device of FIG. 10.

  Embodiments for carrying out the present invention will be described with reference to the drawings.

  FIG. 1 shows a light emitting device including a diffusing lens according to this embodiment. The light emitting device 1 can be used as a backlight of an image display device such as a liquid crystal television, and includes an LED 2, a substrate 3, and a lens 4.

  The LED 2 is driven by a power supply (not shown) and emits white light.

  The substrate 3 has a rectangular shape in plan view, and the upper surface 5 is provided with a reflective coating, and a plurality of LEDs 2 are provided along the longitudinal direction. The LED 2 is fixed to the substrate 3 so that its optical axis is parallel to the normal line of the substrate 3, and emits light upward (toward the side opposite to the substrate 3).

  Here, the lens 4 is integrally formed of PMMA resin having a transmittance of 95% or more and a refractive index of about 1.5, and has a circular shape in plan view as shown in FIG. The lens 4 is provided above the LED 2 so that the central axis X passing through the center of the circle coincides with the optical axis of the LED 2.

  The surface 6 of the lens 4 has a dome shape with a convex portion 7 formed on the top, and the shape of the surface 6 in any cross section including the central axis X is substantially symmetric with respect to the central axis X.

  A concave incident portion 9 into which light from the LED 2 is incident is provided at the center of the back surface 8 of the lens, and the shape of the incident portion 9 in an arbitrary cross section including the central axis X is substantially symmetric with respect to the central axis X. It is.

  Further, the back surface 8 is formed in a tapered shape inclined upward at a predetermined angle θ (see FIG. 1) when viewed from the incident portion 9 side, and the shape of the back surface 8 in an arbitrary cross section including the central axis X is also the center. It is substantially symmetric with respect to the axis X.

  As shown in FIG. 3, on the outer side of the incident portion 9, three leg portions 10 having a circular shape in a bottom view are formed so as to be located at an equal distance from the central axis X and to be separated from each other at an equal distance, The lens 4 is fixed on the substrate 3 by the legs 10.

  In this light emitting device 1, as shown in FIG. 4, the light from the LED 2 enters and refracts the incident part 9 of the lens 4, a part of which is reflected by the surface 6, and the remaining part is transmitted through the surface 6 and emitted. To do. A part of the light reflected by the front surface 6 is transmitted through the back surface 8 and the remaining part is reflected by the back surface 8, and the light transmitted through the back surface 8 is reflected by the top surface 5 of the substrate 3 and passes from the back surface 8 to the lens 4. Incident again. The light reflected by the back surface 8 and the light reflected by the upper surface 5 are finally transmitted through the front surface 6 and emitted for illumination.

  At this time, the back surface 8 is formed in a taper shape that is inclined upward at a predetermined angle when viewed from the incident portion 9 side, so that the peak light amount in the vicinity of the optical axis of the LED 2 (near the central axis X of the lens 4) is increased. The amount of light decreases and the amount of light away from the optical axis increases accordingly. As shown in FIG. 5, when the inclination angle between the tapered surface (rear surface 8) and the plane having the central axis X as a normal line is changed by 0.5 degrees, the peak light amount becomes the minimum value near 4.5 degrees. In particular, when the tilt angle is 2.5 degrees or more and 6 degrees or less, the peak light amount is cut by 5% or more as compared with the case where the back surface is not tapered, and as shown in FIG. A point (a central white point in FIG. 6A) is not observed.

  Even if the light ray distribution on the irradiation surface when the inclination angle is 0 degree and 3 degrees is seen, as shown in FIG. 7, the irradiation range (distribution range) L1 at 3 degrees is 7 degrees. It can be seen that the light quantity is wider than the range L2.

  In short, in this embodiment, the back surface 8 of the lens 4 is formed in a tapered shape that is inclined upward at a predetermined angle (inclination angle) when viewed from the incident portion 9 side, so that the peak light amount near the optical axis of the LED 2 is obtained. Decreases, and accordingly, the amount of light away from the optical axis increases to suppress uneven brightness. This effect can be obtained simply by forming the back surface 8 into a tapered shape at a predetermined angle without processing the surface of the lens 4 into a complicated shape. According to this embodiment, the lens 4 is designed to have a surface shape design. The degree of freedom is high, design and molding are easy, and luminance unevenness can be suppressed.

  Further, since the back surface 8 is formed in a taper shape, the heat of the LED 2 that tends to be scattered near the incident portion 9 is easily dissipated from the lower space of the back surface 8 (the space between the back surface 8 and the upper surface 5 of the substrate 3). Thus, the heat dissipation effect can be improved.

  The predetermined angle is desirably 2.5 degrees or more and 6 degrees or less, and thereby, the peak light quantity can be significantly reduced and luminance unevenness can be effectively suppressed.

  FIG. 8 shows another example of a light emitting device including a diffusing lens according to the present invention. This light-emitting device 11 is the same as the light-emitting device 1 according to Example 1 except that the convex portion 7 is not formed on the top of the surface 6, and the light distribution corresponding to FIG. 7 is as shown in FIG. become.

  FIG. 10 shows still another example of the light emitting device including the diffusing lens according to the present invention. The light emitting device 12 is the same as the light emitting device 1 according to Example 1 except that the convex portion 7 is not formed at the top of the surface 6 but the concave portion 13 is formed, and the light distribution corresponding to FIG. Is as shown in FIG.

  As mentioned above, although the form for implementing this invention was illustrated, embodiment of this invention is not restricted to what was mentioned above, You may change suitably etc. in the range which does not deviate from the meaning of invention.

  For example, in the above embodiment, the LED 2 emits white light, but may emit light of red, green, blue, or the like.

  Further, the lens 4 may not be integrally formed of PMMA resin, and ABS (acrylonitrile / butadiene / styrene copolymer), PC (polycarbonate) or other transparent materials may be used.

  Further, the surface shape of the lens is not limited to those shown in the first to third embodiments, and it is also conceivable that the back surface is tapered with respect to a square or elliptical lens whose shape in plan view is not circular.

  The present invention can be suitably used when, for example, a backlight of a large screen image display apparatus is configured with a small number of light emitting elements.

1, 11, 12 Light-emitting device 2 LED (light source)
3 Substrate 4 Lens (Diffusion lens)
6 Front surface 8 Back surface 9 Incident part X Central axis

Claims (4)

It has a circular shape in plan view, and each of the front surface and the back surface is formed substantially symmetrically with respect to the central axis passing through the center of the circle.
A concave incident portion into which light from a light source arranged so that the central axis and the optical axis coincide with each other is provided at the center of the back surface,
The diffusing lens is characterized in that the back surface is formed in a tapered shape inclined upward at a predetermined angle when viewed from the incident portion side.   The diffusing lens according to claim 1, wherein the predetermined angle is 2.5 degrees or more and 6 degrees or less with respect to a plane having the central axis as a normal line. A light source, and a diffusion lens that diffuses the light emitted from the light source,
The diffuser lens has a circular shape in plan view, and each of the front and back surfaces is formed substantially symmetrically with respect to a central axis passing through the center of the circle.
A concave incident portion into which light from the light source is arranged so that the central axis and the optical axis coincide with each other is provided at the center of the back surface,
The light-emitting device, wherein the back surface is formed in a tapered shape inclined upward at a predetermined angle when viewed from the incident portion side.   The light emitting device according to claim 3, wherein the predetermined angle is 2.5 degrees or more and 6 degrees or less with respect to a plane having the central axis as a normal line.