Light-emitting diode with moulded bi-directional optics

FIELD: physics, optics.

SUBSTANCE: invention can be used for light applications other than backlights, where the vertical beam pattern (collimation pattern) and the side-light emission pattern can be substantially independently specified. A double-moulded lens for a LED includes an outer lens moulded around the periphery of a LED chip and a collimating inner lens moulded over the top surface of the LED chip and partially defined by a central opening in the outer lens. The outer lens is formed using silicone having a relatively low refraction index such as n=1.33-1.47, and the inner lens is formed from silicon with a higher refraction index, such as n=1.54-1.76, to cause total internal reflection within the inner lens.

EFFECT: shorter mixing region, thinner LED without loss of efficiency.

15 cl, 15 dwg

The technical field to which the invention relates

The present invention relates to lenses for light-emitting diodes (LED) (LED) and, in particular, to a double extruded lenses using two materials having different refractive indices to form a light emitting forward and sideways.

The level of technology

Backlight for liquid crystal displays (LCD) are sometimes formed using a rectangular plastic optical fiber (or waveguide) with one or more LEDs, optically connected to the edge of the light guide. The LEDs may include a coating of phosphor to create white light.

Figure 1 presents a top view of the section of the optical fiber 10 to illuminate three identical LEDs 12, optically connected to the edge of the light guide 10. Each led can contain a blue emitting led crystal 14 (for example, the led on the gallium nitride, GaN), mounted on the substrate 16, the phosphor layer of the phosphor (not shown) above the crystal to enter the components of the red light and green light to produce white light, and dome-shaped lens 18. The lens 18 is generally hemispherical, so that the emission light was diffuse. The lens is formed of plastic or silicone with a high refractive index (n), to increase the light emission of the led crystal 14, increasing Cree is practical angle on the border with crystal. Therefore, when using such lenses 18 total internal reflection (TIR) inside the crystal 14 is reduced compared with when the led crystal 14 has no lens and has a boundary transition crystal/air.

In the light guide for illumination, illuminated by numerous LEDs along its edges, the light of the led will be combined and mixed within the light guide to be generally homogeneous. This mixing occurs naturally as the light from each led is diffused inside the light guide and combined. However, the light around the edges of the light guide 10, in the region of 20 mixing, heterogeneous, so the area of the light pipe 10 near the LEDs 12 is not used to illuminate the liquid crystal display 24 (figure 2). The light rays (shown as lines with arrows) are refracted in the direction normal as light passes from a medium with low n in the environment with higher n, as, for example, air gaps, as shown in figure 1, in a plastic (for example, polymethylmethacrylate, PMMA) optical fiber 10. This refraction increases the depth of field of 20 mixing near the edge. This area mixing adds to the illumination width, which is undesirable. One solution for reducing the area of mixing is to reduce the step LEDs, but this increases the cost.

Figure 2 presents a side view of podsi the key, shown in figure 1, where it is visible, as the light beam 25 from the led 12 is directed onto the upper surface of the light guide 10 at an angle greater than the critical, totally internally reflected (TIR) from the smooth upper surface of the light guide 10. This total internal reflection is important in order to prevent the uneven passage of light through the top surface. The light guide 10 generally has a prism 22 or has the surface roughness of the bottom surface to reflect the light up to evenly pass through the upper surface for lighting the liquid crystal display 24.

The light guide 10 must be thick enough to take a high percentage of the light emitted by the led connected to its edge. The reflector around the led may be used for the lateral direction of the light from the led to the edge of the light guide, but such reflector increases in volume and value.

For LEDs, the required optics, which optically connects the led crystal with backlight so that the area of the mixing was shorter and so that the fiber could be made thinner without losing efficiency.

The invention

Describes dual molded lens for led. External lens first, then pressed around the periphery of the led chip, and the outer lens is formed using si the icons with a relatively low refractive index, such as n=of 1.33 to 1.47. The shape of the outer lens determines mainly the radiation pattern side emitting led. The inner lens is then pressed inside the Central hole of the outer lens to be positioned directly above the upper surface of the led chip, and the inner lens is made of silicone with a higher refractive index, such as n=1,54-1,76. Light emitted from the top surface of the led chip, collyriums inner lens, as inside the interior of the lens there is total internal reflection due to its refractive index higher than the refractive index of the outer lens. The inner lens may have a cylinder shape, a parabolic shape or a different shape, which colliery, essentially, most of the light entering into the internal lens. For example, collimated light entering into the light guide, may be at an angle in the range 28° from normal. The light from the led chip, aimed at the side wall of the inner lens at an angle smaller than a critical angle to provide total internal reflection, is applied to the external lens. The shape of the outer lens determines the pattern of lateral light emission (for example, the peak intensity at an angle of 45° relative to the normal).

Top poverhnost.delo molded lens may be flat, so that it can directly rests against the edge of the plastic optical fiber. So there is no air gap (n=1), which could cause much light refracted towards the normal when entering the light guide. Therefore, the mixing region within the optical fiber becomes shorter, allowing you to use the fiber optic cable smaller. Additionally, the pattern of lateral radiation that is emitted external lens can be adjusted for a particular application of the fiber (for example, step LEDs)to ensure good mixing with the light from adjacent LEDs on the edge or near the edge of the light guide, thereby further reducing the area of mixing. The inner collimation lens creates a more narrow beam (compared with a domed lens), which, in fact, mixed with other collimated beams more deeply inside the fiber, but the light closer to the edge already is homogeneous due to the mixing side of the world.

In another embodiment, the material of the outer lens forms a layer directly on the upper surface of the crystal, and the material of the inner lens is pressed over this layer. The layer may have optical characteristics, such as concave or dispersion. Disclosed various other designs of the lenses.

The invention may also be used in order to find for applications related to lighting, non-lighting, where the vertical radiation pattern of the light (chart callmerobbie) and the pattern of lateral light emission can be determined essentially independently.

Brief description of drawings

Figure 1 is a top view in cross section of the led of the prior art, optically associated with the area of the light guide to illuminate the LCD display.

Figure 2 is a side view in cross section of a light guide for illumination, shown in figure 1.

Figure 3 is a side view in cross section of a double molded lens over the led chip in accordance with one embodiment of the invention.

4 is a top view in cross-section area of the light guide for illumination, optically connected with the led, shown in figure 3.

5 is a top view in cross-section area of the light guide for illumination, shown in figure 4.

6 is a side view in cross section of a double injection molded lenses other forms of generating a beam of collimated beam and beam side light radiation.

Fig.7 is an enlarged image of a portion of the upper surface of the led chip, shown in Fig.6, and the radiation pattern of the lens molded over the surface Crist is the lia for light scattering, for beam forming lateral light emission.

Fig - magnified image of the cross section of the upper surface of the inner lens is presented in figure 3, or 6, indicating that the top surface may have an optical beam formed for light scattering.

Fig.9 is a view in cross section of the led shown in Fig.6, optically connected to the section of the light guide to illuminate the LCD display.

Figure 10 is a side view in cross section of a double injection molded lenses other form.

11 is a side view in cross section of a double injection molded lenses other form.

Fig is an example of the directivity diagram of the radiation of the led, using double pressed the lens, where the pattern of the front light radiation and the radiation pattern of lateral light emission can be formed individually for a specific application.

Fig - the first stage of compression for molding the outer lens.

Fig the second stage of compression for molding the inner lens, which is at least partially determined by the shape of the inner surface of the outer lens where the refractive index of the material used for molding the inner lens is higher than the refractive index of the material, ispolzuemogo for molding the outer lens, in order to achieve total internal reflection.

Fig is a block diagram of a sequence of operations that identifies the different steps used for forming double molded led lens in accordance with one embodiments of the invention.

The same elements or equivalents are indicated by the same reference position.

Detailed description

The present invention can use a standard led crystal white light, such as AlInGaN blue LEDs with a phosphor layer manufactured by the present assignee. In the examples for simplicity, use crossover led crystal. Examples of molding LEDs are described in U.S. patent No. 6649440 and 6274399, both assigned Philips Lumileds Lighting and incorporated here by reference. A layer of phosphor on a blue led chip that emits components of red and green makes blue led to emit white light. Forming a ceramic phosphor plates is described in patent publication U.S. 20050269582, entitled Luminescent Ceramic for a Light Emitting Diode, the author Gerd Muller and others, included here by reference. The term "led crystal"as used here, contains either uncoated crystal, or crystal, with the freight phosphor or phosphor plate.

Figure 3 presents the traditional inverted led crystal 30, mounted on a standard substrate 32. The substrate 32 may be a ceramic, silicon, or may be made of a different material. The substrate 32 includes upper pads for direct connections to the anode and cathode metal contacts on the bottom surface of the led crystal 30. Contact pads on the substrate 32 are connected by walkways or bridges with other sites, which are connected with the lead frame housing or printed circuit Board. Mount led crystal to the substrate is described in U.S. patent No. 7344902, author Gregory basin, entitled Overmolded Lens Over the LED Die, assigned to the present assignee and is incorporated here by reference.

Around the periphery of the led crystal 30 is pressed outer lens 34, formed of silicone having a relatively low refractive index (n) of about 1.33. Can use other values of n, such as approximately to 1.47. Such material is commercially available. The process of pressing leaves in the outer lens 34 of the Central hole. The inner lens 36 is then pressed within the outer lens 34, and the inner lens 36 is molded from silicone with a higher value of refractive index n=1,54-1,76. Such material is commercially on stupen. Since the shape of the inner lens 36 is partially defined by the Central hole of the outer lens 34, the requirement for admission during pressing is reduced. In the example shown in figure 3, the inner lens 36, in essence, is formed in a parabolic shape. As led crystal 30 is not a point source, not all the field of led crystal are in the focus of a parabolic shape, so that light emitted from the inner lens 36, is not fully collimated. As n inner lens 36 is higher than n the outer lens 34 will be total internal reflection of light incident at an angle greater than the critical determined by law Snell. The shape of the inner lens 36 and the relative values of n of lens materials determine the directivity of light emitted from the inner lens 36. Figure 3 shows one light beam 37.

The outer lens 34 may be in the form suitable to create any beam of light that passes through the sides of the inner lens 36.

Lens height 34/36 can be up to 6 mm for led crystal with an area of 1 mm². The width of the entire lens 34/36 depends on the desired pattern of radiation. The inner lens 36 may have an output diameter corresponding to three times the width of the led chip. Lens 34/36 can be with Metrica Central axis (to have a circular shape), when viewed from the top, or the lens 34/36 may have a rectangular shape, or other asymmetric shape for better mixing of light within the light guide.

Figure 4 presents a flat upper surface of the lens 34/36, shown in figure 3, is optically connected to the edge of the plastic (e.g., PMMA) fiber 40 without air gap between them. A thin layer of silicone with a high refractive index can attach the lens to the optical fiber 40 or inclined edge may cause the lens to snuggle up to the edge of the light guide 40. Since there is no air interface no (n=l), at the entrance to the fiber (n is approximately equal to 1.5) there is a small light refraction in the direction of the normals, so the area 42 of the mixing shorter than region 20 mixing, shown in figure 1. Also the shape of the inner lens 36 can be designed to provide radiation in the optical fiber 40 in wide angle or narrow angle to achieve the desired mixing of the light. In one embodiment, the angle of radiation at the level of half intensity from the inner lens 36 in the optical fiber 40 is approximately 28° from normal, but the angle may be more or less depending on the optimum angle for mixing. Side light from the outer lens 36 adjacent LEDs coming into the light guide 40, will be mixed in front of the edge or near the edge, when the odya in the short region 42 of the mixing.

Figure 5 presents a side view of a light guide 40 figure 4, showing how light rays incident at an angle greater than the critical, totally reflected from the upper surface of the light guide 40. Prism 44 or other light-diffusing characteristics on the lower surface of the light guide 40 to reflect light upwards, so that it is uniformly passed through the upper surface for lighting the liquid crystal display 46. Since the area 42 of the mixing is short, the edge of the liquid crystal display 46 may be located closer to the edge of the light guide 40, allowing the use of the light conductor 40 of a smaller size.

Figure 6 presents a view in cross section of another design of the lens, where the silicone inner lens 50 is essentially cylindrical, and the silicone outer lens 52 has a generally hemispherical shape to obtain a relatively wide beam of radiation. Internal lens 50 has a value of n greater than the value of n for the outer lens 52 to cause total internal reflection.

During the pressing process, it is difficult to prevent the formation of a layer of material of the outer lens on the upper surface of the led chip, so as fragile led crystal should not touch the mold. Figure 7 shows a close-up of the plot led crystal 30, showing how it is the cue layer of material of the outer lens over the led chip can contain extruded light-diffusing form 56, to increase the amount of light emerging from the inner lens 50 in the outer lens 52, causing more light to fall at an angle less than the critical to pass through the side wall of the inner lens 50.

On Fig presents an enlarged cross-section of the upper surface of the inner lens 3 or 6, showing that the upper surface can be extruded so as to have a chart 59 orientation suitable for dispersion or redirect light. The surface can be teksturirovanie different ways to dissipate or redirect light, such as the use of prisms, potholes, depressions, truncated pyramids, random roughness or surface relief hologram. The surface roughness may also be given by shot peening. Optical film coating can also be used to redirect light.

Figure 9 presents the led 58, shown in Fig.6, optically coupled to the edge of the light guide 60 for illumination. Internal lens 50, the outer lens 52, the step of LEDs 58 and other factors can be selected so that the area of the mixing inside the light guide 60 to create a uniform light was short.

Figure 10 presents the internal lens 64 having a convex upper surface for more control on the front is the d-rays. Material 65 external lenses also pressed to be molded over the top surface of the led crystal thick region, affecting the pattern of radiation in the forward and lateral directions. Material 65 external lenses, lying above led crystal 30 has a concave shape in order to reduce total internal reflection of light rays, usually upward. Several of the light rays 66 is shown to demonstrate the different effects created by the forms of lenses. Giving the lenses a certain form can be done to improve the uniformity of light in the light guide for illumination and/or shortening the field mixing of light in the light guide for illumination. Alternative, giving a certain form can be done to achieve any beam of light for use, non-illuminated, such as the use in the automotive industry.

Figure 11 shows a thicker layer of material 52 of the outer lens on the upper surface of the led chip and to increase the lateral radiation. Internal lens 67 is similar to that shown in figure 10.

On Fig presents balanced level of half intensity pattern 70 radiation led with double molded lens, showing a chart 72 directional frontal irradiation is Oia, defined by an inner lens, and a chart 74 of the lateral direction of the radiation determined by the external lens. The form of diagrams of front and side radiation can be regulated, essentially, independently, by changing the shape of the inner and outer lenses. In one embodiment, the peak intensity of the lateral petals radiation falls on the 45°-65° from normal, and collimated frontal radiation has a scattering angle of 10°-35° relative to the normal to the light guide, when there is a connection directly with the fiber without the air gap.

On Fig and 14 presents the process of double pressing with a solid substrate. Led crystal 30 are mounted on the substrate 32, containing possibly hundreds of identical led crystal 30.

Mold 80 has a notch 81 corresponding to the desired shape of the outer lens located over each led crystal 30. Mold 80 is preferably made of metal with non-stick surface or separation layer.

The notches 81 of the mold are filled with a liquid or softened targetfilename silicone 84 having a refractive index, such as 1,33.

The substrate 32 and mold 80 are connected, and between the periphery of the substrate 32 and the mold 80 creates a vacuum seal. Therefore, each led Halloween gift is hydrated crystal 30 is inserted into the silicone 84, and silicone 84 is under pressure.

Mold 80 is then heated to approximately 150 degrees Celsius (or to another appropriate temperature) and held for some time that the silicone 84 hardened.

Then, the substrate 32 is separated from the mold 80. Silicone 84 may then be further cured with heat or ultraviolet light. On Fig shows the resulting external lens 85 with a thin layer over the top surface of the led crystal 30 formed by the gap between the upper surface of the crystal and solid the mold 80. In the thin layer can be formed of light-scattering elements (shown in Fig.7).

On Fig second mold 86 has a recess 88, which in combination with the inner surface of the outer lens 85 are used for molding the inner lens. The notches 88 in the mold are filled with a liquid or softened teplopoteryami silicone 90 having a high refractive index, such as 1,54-1,76. The substrate 32 and mold 86 are connected to each other, as described earlier. Silicone 90 then cured, and the substrate 32 and mold 86 are separated to receive the LEDs shown in figure 3. All the LEDs on the substrate 32 are processed simultaneously.

The substrate 32 is then cut to separate the LEDs. Mean the key with LEDs can then be mounted on the strip circuit Board together with other substrates led to use for illumination.

On Fig presents a flowchart of the sequence of operations used for molding lenses in accordance with one embodiment of the invention.

At step 92, the optimum pattern for collimation and beam pattern for lateral radiation is defined for each led for a particular application, such as a private use for illumination, and for step LEDs.

At step 93, the shape of the inner lens and the shape of the outer lens for a specific value of n silicone, used for lenses, are selected to achieve the desired directional diagrams for collimation and a side radiation.

At step 94 external lenses simultaneously pressed on the periphery of all of led crystals mounted on the substrate, using the first mold containing the first silicone with high n. The material of the outer lens may also be sealed each led chip, providing a layer over the top surface of the led chip.

At step 95 of the inner collimation lens then simultaneously pressed over the upper surface of all the led crystals mounted on the substrate using the second mold containing a second silicone having a higher n than the first silicone, so that the inside of the inner lens has malopolske internal reflection. Wall of the Central hole in the outer lens define the side walls of the inner lens.

At step 96 LEDs with double pressed lenses optically connected directly to the edge of the light guide for illumination, where the shape of the lens and the refractive index of the silicone determine the mixing of the light within the fiber. The LEDs can also be used for applications in the automobile industry or for other uses.

To obtain the required beam radiation can be used any combination of the disclosed forms of the inner and outer lenses. All lenses can be symmetric about the Central axis, to achieve essentially symmetrical beam radiation, or may be asymmetric, in order to achieve the asymmetric pattern of radiation.

Although there have been shown and described specific embodiments of the present invention, for specialists in the art should be obvious that there may be changes and modifications, without departing from this invention in its broader aspects, and therefore, the appended claims should include within its scope all such changes and modifications that fall within the valid scope and essence of the present invention.

1. The way the fo is mounia lighting device, containing phases in which:
provide led crystal mounted on the substrate, and the led crystal has an upper surface;
pressed by the outer lens on the substrate having the led chip, so that the outer lens surrounds at least the periphery of the led chip, and forms a layer over the top surface of the led chip, using the first silicone having a first refractive index, and in the outer lens is formed the recess relative to the upper surface of the outer lens over the top surface of the led crystal; and
after pressing, the outer lens is pressed by the inner lens inside the grooves, using a second silicone having a second refractive index that is higher than the first refractive index,
the form of an internal lens act to colliergate light emitted from the upper surface through total internal reflection (TIR), and
the shape of the outer lens affects the pattern of lateral light emission without internal reflection at the inner lens.

2. The method according to claim 1, wherein the first refractive index is equal to, at least 1.3, and the second refractive index is at least equal, 1,6.

3. The method according to claim 1, in which the pressing of the outer lens includes pressing out who it lenses so to create a peak emission in the range of 45°-65° relative to the perpendicular to the upper surface.

4. The method according to claim 1, in which the pressing of the inner lens includes pressing the inner lens to create a scatter of light in the range of 10°-35° relative to the perpendicular to the upper surface.

5. The method according to claim 1, in which the pressing of the outer lens includes pressing an external lens with the outer surface of the side wall of the hemispherical form.

6. The method according to claim 1, in which the pressing of the inner lens includes pressing the inner lens so that the upper part of the inner lens was flat.

7. The method according to claim 1, in which the pressing of the inner lens includes pressing the inner lens so that the upper part of the inner lens had a light scattering element.

8. The method according to claim 1, in which the pressing of the inner lens and pressing the outer lens contain the pressing of the inner lens and the outer lens so that they are symmetrical with respect to the Central axis.

9. The method according to claim 1, in which the pressing of the inner lens includes pressing the inner lens so that it had a cylindrical shape.

10. The method according to claim 1, in which the pressing of the inner lens includes pressing the inner lens so that animela parabolic shape.

11. The method according to claim 1, wherein a layer over the top surface of the led crystal has a non-planar shape to obtain a desired pattern of radiation.

12. The method according to claim 11, in which the layer contains a light-diffusing elements.

13. Lighting device, comprising:
led crystal mounted on the substrate, and the led crystal has an upper surface;
the pressed outer lens, surrounding at least the periphery of the led chip, and covering the upper surface of the led chip, and the outer lens includes a first silicone having a first refractive index, and the outer lens has a recess relative to the upper surface of the outer lens over the top surface of the led crystal; and
the pressed inner lens inside the recess, and the inner lens includes a second silicone having a second refractive index that is higher than the first refractive index, and
the shape of the inner lens acting to colliergate light emitted from the upper surface through total internal reflection (TIR),
the shape of the outer lens, affecting the pattern of lateral light emission without internal reflection at the inner lens.

14. The device according to item 13, in which plural what about the LEDs, having an inner lens and an outer lens, optically connected to the edge of the light guide for illumination.

15. The device according to item 13, in which the outer lens creates a peak emission in the range of 45°-65° relative to the perpendicular to the top surface, and the inner lens creates a pattern of light scattering between 10°-35° relative to the perpendicular to the upper surface.