TWI848128B - Light emitting module - Google Patents

Abstract

A light emitting module comprising a light guide plate and a light source. The light guide plate has a polygonal shape with a plurality of corners in a plan view. The light guide plate has a first primary face which serves as an emission face, a second primary face opposing the first primary face, and a recessed portion in the second primary face. The light source is disposed in the recessed portion. The recessed portion has an opening on the second primary face, and a bottom face having a polygonal shape in a plan view. The light source has lateral faces along sides of the bottom face of the recessed portion. In a plan view, diagonal lines connecting opposing corners of the first primary face intersect with the sides of the bottom face of the recessed portion.

Description

Light emitting module

The present invention relates to a light emitting module.

Light-emitting modules using light-emitting elements such as light-emitting diodes are widely used in surface light sources such as backlight sources of liquid crystal displays. For example, in direct-type liquid crystal displays that configure a surface light source on the back of a liquid crystal panel, there is a high demand for thinning of the surface light source. If the distance between the light source and the light-emitting surface of the light guide plate becomes shorter as the surface light source becomes thinner, the light will not be fully scattered, and uneven brightness or color will easily occur on the light-emitting surface. [Prior art literature] [Patent literature]

[Patent Document 1] Japanese Patent Application Publication No. 2018-133304

[The problem the invention is trying to solve]

The present invention provides a light-emitting module capable of reducing uneven brightness or color within the light-emitting surface of a light guide plate. [Technical means for solving the problem]

According to one aspect of the present invention, the light-emitting module has a light guide plate and a light source. The light guide plate is angular with a plurality of corners when viewed from above, and has: a first main surface that becomes a light-emitting surface, a second main surface on the opposite side of the first main surface, and a recessed portion provided on the second main surface. The light source is provided in the recessed portion. The recessed portion has: an opening on the side of the second main surface, and a bottom surface that is angular when viewed from above. The light source has a side surface along the edge of the bottom surface of the recessed portion. When viewed from above, the diagonal line connecting the plurality of corners of the first main surface intersects with the edge of the bottom surface of the recessed portion. [Effect of the invention]

According to the present invention, a light-emitting module is provided which can reduce uneven brightness or color within the light-emitting surface of a light guide plate.

Hereinafter, the embodiments will be described with reference to the drawings. In addition, the same symbols are given to the same elements in each drawing.

FIG1 is a schematic top view of the light-emitting module 1 in an implementation form. FIG2 is an A-A cross-sectional view of FIG1 .

The light emitting module 1 includes a light guide plate 10 and a light source 20 . The light source 20 includes a light emitting element 21 , a fluorescent layer 22 , and a covering member 23 .

The light guide plate 10 has a transmittance to the light emitted by the light source 20. The material of the light guide plate 10 may be a thermoplastic resin such as acrylic, polycarbonate, cyclic polyolefin, polyethylene terephthalate, polyester, a thermosetting resin such as epoxy, silicone, glass, etc. Among them, polycarbonate is preferred because of its high transparency and low cost.

The light guide plate 10 has a first main surface 11 serving as a light emitting surface, a second main surface 12 opposite to the first main surface 11, and a recess 15 provided on the second main surface 12. Furthermore, the light guide plate 10 has a side surface 13 connected to the first main surface 11, and an inclined surface 14 provided between the side surface 13 and the second main surface 12.

At least the fluorescent layer 22 of the light source 20 is disposed in the recess 15 of the light guide plate 10. The light emitting element 21 is disposed on the surface of the fluorescent layer 22 opposite to the first main surface 11 of the light guide plate 10. The recess 15 can function as a positioning portion for the light source 20 to the light guide plate 10.

The light emitting element 21 has a main light emitting surface 21b and a pair of positive and negative electrodes 21a disposed on the opposite sides of the main light emitting surface 21b. The light emitting element 21 has a semiconductor multilayer structure. The semiconductor multilayer structure may include, for example, _{InxAlyGa1 -xyN (} 0≦x, 0≦y, x+y≦1) and emits blue light.

The main light-emitting surface 21b of the light-emitting element 21 is bonded to the phosphor layer 22 by, for example, a light-transmitting adhesive. In the examples shown in FIGS. 2 and 3 , the side surface of the light-emitting element 21 and the electrode 21a are located outside the recess 15. Alternatively, the light-emitting element 21 may be disposed in the recess 15. A covering member 23 is provided on the side surface of the light-emitting element 21. The covering member 23 is also provided between the electrodes 21a on the lower surface of the light-emitting element 21. The covering member 23 has reflectivity for light emitted by the light-emitting element 21 and the phosphor in the phosphor layer 22, and is, for example, a resin containing a white dye or the like. In particular, the covering member 23 is preferably a silicone resin containing titanium oxide.

The fluorescent layer 22 has a base material and a fluorescent body dispersed in the base material. The base material of the fluorescent layer 22 may be made of, for example, epoxy resin, silicone resin, glass, etc. From the viewpoint of light resistance and easy formability, silicone resin is preferably used as the base material.

The phosphor is excited by the light emitted by the light emitting element 21 and emits light of a wavelength different from the wavelength of the light emitted by the light emitting element 21. For example, as the phosphor, YAG phosphor, LAG phosphor, β-sialon (β-SiAlON) phosphor, CASN phosphor, KSF series phosphor, quantum dot phosphor, etc. can be used. The phosphor layer 22 can include a plurality of phosphors.

An optical function portion 32 is provided on the first main surface 11 side of the light guide plate 10. The optical function portion 32 is provided at a position opposite to the recess 15 formed on the second main surface 12. It is preferred that the optical axis of the light emitting element 21 is substantially consistent with the optical axis of the optical function portion 32. The shape of the optical function portion 32 is, for example, an inverted cone, an inverted quadrangular pyramid, an inverted hexagonal pyramid, an inverted pyramid, or an inverted pyramid or an inverted polygonal pyramid.

The optical function part 32 is a light-transmitting resin, glass or air layer having a refractive index lower than that of the light guide plate 10, and can function as a lens that refracts light at the interface between the light guide plate 10 and the optical function part 32 and diffuses light in the surface direction of the light guide plate 10. Alternatively, for example, a light-reflective material (such as a reflective film of metal or white resin) may be provided in a recess having an inclined surface.

The recess 15 opens from the second main surface 12 side and has a bottom surface 17 on the side closer to the first main surface 11 than the second main surface 12. A light scattering layer 31 containing a light scattering agent is provided on the bottom surface 17 of the recess 15. The light scattering layer 31 is provided between the bottom surface 17 of the recess 15 and the fluorescent layer 22. The light scattering layer 31 scatters part of the light emitted in the direction directly above the light-emitting element 21 and returns it downward. Thereby, it is possible to prevent the area directly above the light source 20 in the light-emitting surface of the light-emitting module 1, that is, the first main surface 11 of the light guide plate 10, from becoming too bright compared to other areas. The light scattering layer 31 can also be omitted, and the fluorescent layer 22 can be directly provided on the bottom surface 17 of the recess 15.

A light-transmitting portion 60 is provided around the light source in the recess 15 (around the fluorescent layer 22 and around the light scattering layer 31). The light-transmitting portion 60 is a light-transmitting resin portion that is transparent to the light emitted by the light source 20. The refractive index of the light-transmitting resin portion is lower than the refractive index of the light guide plate 10. Alternatively, the light-transmitting portion 60 may also be a gap (air layer).

The light guide plate 10 has an inclined surface 14 which forms a blunt angle with the second main surface 12 and is continuous with the second main surface 12. The inclined surface 14 and the second main surface 12 are covered with a light reflective resin portion 40.

The light-reflective resin portion 40 has reflectivity for the light emitted from the light source 20 and is, for example, a resin containing a white dye, etc. In particular, the light-reflective resin portion 40 is preferably a silicone resin containing titanium oxide.

The electrode 21a of the light emitting element 21 is bonded to the wiring 52. The light reflecting resin portion 40 has insulating properties and covers the side surface of the electrode 21a of the light emitting element 21.

The light-reflective resin portion 40 is bonded to the wiring substrate 50. The wiring substrate 50 has an insulating base 51, wiring 54 provided on the back of the base 51, and a via hole 53 penetrating the base 51. The via hole 53 connects the wiring 52 and the wiring 54, and the electrode 21a of the light-emitting element 21 is electrically connected to the wiring 54 via the wiring 52 and the via hole 53.

As the base material 51 of the wiring board 50, for example, resin or ceramic can be used, and as the wirings 52 and 54 and the via hole 53, for example, copper can be used.

In this specification, the plan view refers to a plan view of the first main surface 11 of the light guide plate 10 as shown in Fig. 1. In this plan view, the first main surface 11 is an angular shape having a plurality of corners 11a, for example, a quadrangular shape having four corners 11a.

In a plan view, the bottom surface 17 of the recess 15 is also angular. For example, the bottom surface 17 of the recess 15 has four long sides 17a and four short sides 17b that are shorter than the long sides 17a. Furthermore, the bottom surface 17 has a corner between the long sides 17a and the short sides 17b.

The fluorescent layer 22 is rectangular in a plan view. The fluorescent layer 22 is, for example, quadrangular in a plan view and has four side surfaces 22a. The four side surfaces 22a are along the long sides 17a of the bottom surface 17 of the recess 15. The corners of the fluorescent layer 22 are located opposite to the short sides 17b of the bottom surface 17 of the recess 15 in a plan view.

In a plan view, a diagonal line connecting the corners 11a of the first main surface 11 at diagonal positions intersects with the long side 17a of the bottom surface 17 of the recess 15. The fluorescent layer 22 is positioned on the bottom surface 17 of the recess 15 in such a manner that the side surface 22a of the fluorescent layer 22 is along the long side 17a of the bottom surface 17 of the recess 15.

The light source 20, which is a quadrangle in a plan view, is arranged to be rotated, for example, 45 degrees relative to the quadrangle of the first main surface 11 of the light guide plate 10. In a plan view, the diagonal connecting the corners 11a of the first main surface 11 intersects with the side surface of the light source 20, i.e., the side surface 22a of the fluorescent layer 22 (the edge of the quadrangle fluorescent layer 22). In a plan view, the corner of the light source 20 (the corner of the fluorescent layer 22) is not located on the diagonal connecting the corners 11a of the first main surface 11, and is not located opposite to the corner 11a. In a plan view, the corner of the light source 20 (the corner of the fluorescent layer 22) is located in the area demarcated by the diagonal connecting the corners 11a of the first main surface 11.

In the fluorescent layer 22 , the side surface 22 a has a wider area than the corner portion, and there is a tendency that the brightness of light emitted from the side surface 22 a of the fluorescent layer 22 becomes higher than the brightness of light emitted in a diagonal direction of the fluorescent layer 22 .

In addition, in the quadrangular first main surface 11 of the light guide plate 10, the distance between the center and the corner 11a of the fluorescent layer 22 is longer than the distance between the center and the side, so that light tends not to diffuse toward the four corners of the first main surface 11.

According to the present embodiment, the fluorescent layer 22 is arranged relative to the light guide plate 10 in such a manner that the diagonal line connecting the corners 11a of the first main surface 11 intersects with the side surface 22a of the fluorescent layer 22, and is positioned in such a manner that the side surface 22a of the fluorescent layer 22 faces the corners 11a of the first main surface 11, so that the light emitted from the fluorescent layer 22 can be easily diffused toward the four corners of the first main surface 11 of the light guide plate 10. This reduces the uneven brightness or color in the light emitting surface of the light emitting module 1, that is, the first main surface 11.

FIG3 is a cross-sectional view taken along line B-B of FIG1. FIG4 is a three-dimensional view of the elements (light scattering layer 31, fluorescent layer 22, and light-transmitting portion 60) in the recess 15 of the light guide plate 10 of the light-emitting module 1 in the embodiment.

The shape of the opening 16 of the recess 15 is, for example, a quadrangle, and the shape of the opening 16 of the recess 15 is different from the shape of the bottom surface 17 of the recess 15 .

The recess 15 has an inclined surface 18 that is inclined to form a blunt angle with respect to the bottom surface 17 of the recess 15. The light-transmitting portion 60 is connected to the inclined surface 18 of the recess 15 and has an inclined surface 61 that is opposite to the inclined surface 18 of the recess 15.

2 and 4 , the light-transmitting portion 60 has an upper surface 63 in contact with the bottom surface 17 of the recess 15 , and a vertical surface 62 perpendicular to the bottom surface 17 of the recess 15 . The vertical surface 62 is also in contact with the light guide plate 10 .

In the transparent portion 60, the contact area with the light guide plate 10 can be enlarged by forming the inclined surface 61, compared with the case where the surfaces in contact with the light guide plate 10 are only the upper surface 63 and the vertical surface 62. That is, the interface between different materials can be enlarged, and the light emitted from the fluorescent layer 22 can be easily captured by the light guide plate 10 from the transparent portion 60.

1, the inclined surface 61 is located between the corner 11a of the first main surface 11 and the side surface 22a of the fluorescent layer 22, and is located at a position opposite to the corner 11a of the first main surface 11. Therefore, it is easy to diffuse the light emitted from the fluorescent layer 22 toward the four corners of the first main surface 11 of the light guide plate 10 through the inclined surface 61 of the light-transmitting portion 60, and the brightness unevenness or color unevenness in the first main surface 11 can be reduced.

FIG. 5 is a schematic diagram of the interface between the light guide plate 10 and the light-transmitting portion 60 .

By providing the inclined surface 61 on the light-transmitting portion 60, the difference in refractive index between the light-transmitting portion 60 and the light guide plate 10 is utilized, so that the light emitted from the light source 20 is easily directed in the diffusion direction. In this way, it is possible to prevent the area immediately above the light source 20 in the first main surface 11 of the light guide plate 10 from becoming too bright compared to other areas, and to reduce uneven brightness or color. Similarly, when the light-transmitting portion 60 is a gap (air layer), the difference in refractive index with the light guide plate 10 is utilized, so that the light emitted from the light source 20 is directed in the diffusion direction.

6A to 6C are schematic cross-sectional views showing a method for manufacturing the light emitting module 1 according to an embodiment.

First, as shown in FIG. 6A , a light guide plate 10 is prepared. The light guide plate 10 can be formed by, for example, injection molding, transfer molding, thermal transfer, etc. By forming the recess 19 for setting the optical function part 32 and the recess 15 for setting the fluorescent layer 22 together with a mold, the positioning accuracy of the optical function part 32 and the light emitting element 21 can be improved.

6B, for example, a light-transmitting resin is supplied to the concave portion 15 to form the light-transmitting portion 60. The light-transmitting resin is supplied to the concave portion 15 in a liquid or fluid state by a method such as pouring, printing, or spraying.

After the light-transmitting portion 60 is supplied to the concave portion 15, as shown in FIG6C, the light source 20 is disposed in the concave portion 15 together with the light-scattering layer 31. The light-scattering layer 31 is in contact with the bottom surface 17 of the concave portion 15.

The light scattering layer 31, the fluorescent layer 22, and the light emitting element 21 are integrated in a mutually bonded state and supplied to the recess 15. At this time, the fluorescent layer 22, which is a quadrangular shape in a plan view, is self-aligned and positioned in a manner such that its side surface 22a is along the long side 17a of the bottom surface 17 of the recess 15. Therefore, the light emitting element 21 is also self-aligned and positioned with respect to the light guide plate 10. In addition, since the area of the opening 16 of the recess 15 is larger than the area of the bottom surface 17, it is easy to supply the light scattering layer 31 and the fluorescent layer 22 into the recess 15.

2 is provided in the concave portion 19 on the first main surface 11 side of the light guide plate 10, and further, a light reflective resin portion 40 is provided to cover the inclined surface 14 and the second main surface 12 of the light guide plate 10. A wiring substrate 50 is attached below the light reflective resin portion 40.

In the light-emitting module 1 of the implementation form, since the light-emitting element 21 is mounted on the light guide plate 10 instead of the wiring substrate 50, the distance between the light guide plate 10 and the light-emitting element 21 can be shortened, and the light-emitting module 1 can be made thinner. Such a light-emitting module 1 can be used, for example, as a backlight source of a liquid crystal display. For example, in a direct-type liquid crystal display in which the backlight source is arranged on the back of the liquid crystal panel, since the distance between the liquid crystal panel and the light-emitting module 1 is relatively close, the unevenness of the brightness or color of the light-emitting module 1 is likely to affect the unevenness of the brightness or color of the liquid crystal display. By using the light-emitting module 1 with less unevenness of brightness or color as in the implementation form as the backlight source of the direct-type liquid crystal display, the unevenness of the brightness or color of the liquid crystal display can be reduced.

FIG. 7 is a schematic top view of a light emitting module 100 according to another embodiment.

The light emitting module 100 includes a light guide plate 10 and a plurality of cells 2 periodically arranged on the light guide plate 10. One cell 2 has the same structure as the aforementioned light emitting module 1.

That is, a plurality of optical function parts 32 are provided on the first main surface 11 side of one light guide plate 10, and a plurality of recesses 15 are formed on the second main surface 12. In the recesses 15, the light scattering layer 31, the light source 20, and the light transmitting part 60 are arranged.

FIG. 7 is a plan view of the first main surface 11 of the light guide plate 10. In this plan view, one unit 2 is formed into, for example, a quadrangular shape having four corners 2a. Each unit 2 is arranged in such a manner that its edge is along the edge of the quadrangular first main surface 11 of the light guide plate 10. Moreover, in this plan view, the long side 17a of the bottom surface 17 of the recess 15 of each unit 2 and the side surface of the light source (the side surface 22a of the fluorescent layer 22) face the corner 2a of each unit 2. The diagonal line connecting the corners 2a of one unit 2 intersects with the long side 17a of the bottom surface 17 of the recess 15 of the unit 2. The diagonal line connecting the corners 2a of one unit 2 intersects with the side surface 22a of the fluorescent layer 22 of the unit 2.

Therefore, the light emitted from the fluorescent layer 22 in each cell 2 is easily diffused toward the four corners of the cell 2. In the entire light-emitting surface of the light-emitting module 100, i.e., the first main surface 11, the brightness concentration in the center of each cell 2 is suppressed, and the brightness unevenness or color unevenness in the light-emitting surface of the light-emitting module 100 can be easily reduced.

The above description is made with reference to specific examples while focusing on the implementation forms of the present invention. However, the present invention is not limited to the specific examples. Based on the above implementation forms of the present invention, all forms of implementation that can be appropriately designed and modified by a person familiar with the technology are also within the scope of the present invention as long as they include the gist of the present invention. In addition, within the scope of the idea of the present invention, as long as a person familiar with the technology can think of various variations and modifications, it should be understood that such variations and modifications are also within the scope of the present invention.

1,100: Light-emitting module 2: Unit 2a: Corner of unit 10: Light guide plate 11: First main surface 11a: Corner of first main surface 12: Second main surface 13: Side surface 14: Inclined surface 15: Recessed part 16: Opening of recessed part 17: Bottom of recessed part 17a: Long side 17b: Short side 18: Inclined surface 19: Recessed part 20: Light source 21: Light Optical element 21a: Electrode 21b: Main light-emitting surface 22: Fluorescent layer 22a: Side surface of fluorescent layer 23: Coating member 31: Light scattering layer 32: Optical functional part 40: Light reflective resin part 50: Wiring board 51: Base material 52,54: Wiring 53: Through hole 60: Translucent part 61: Inclined surface of translucent part 62: Vertical surface 63: Top surface

FIG. 1 is a schematic top view of a light-emitting module of an implementation form. FIG. 2 is an A-A cross-sectional view of FIG. 1. FIG. 3 is a B-B cross-sectional view of FIG. 1. FIG. 4 is a three-dimensional view of an element in a concave portion of a light-emitting module of an implementation form. FIG. 5 is a schematic view of an edge interface between a light-emitting plate and a light-transmitting portion of a light-emitting module of an implementation form. FIG. 6A is a schematic cross-sectional view showing a method for manufacturing a light-emitting module of an implementation form. FIG. 6B is a schematic cross-sectional view showing a method for manufacturing a light-emitting module of an implementation form. FIG. 6C is a schematic cross-sectional view showing a method for manufacturing a light-emitting module of an implementation form. FIG. 7 is a schematic top view of a light-emitting module of another implementation form.

1: Light-emitting module

10: Light guide plate

11: 1st main surface

11a: Corner of the first main surface

15: Concave part

16: Opening of the concave part

17: Bottom of the concave part

17a: Long side

17b: Short side

22: Fluorescent layer

22a: Lateral surface of the fluorescent layer

32: Optical function department

61: Inclined surface of the light-transmitting part

Claims (8)

A light-emitting module comprises: a light-guiding plate, which is angular with a plurality of corners in a plan view, and has: a first main surface serving as a light-emitting surface, a second main surface on the opposite side of the first main surface, and a concave portion provided on the second main surface; and a light source provided in the concave portion; the concave portion has an opening on the side of the second main surface, and a bottom surface in a plan view that is angular; the light source has a side surface along the edge of the bottom surface of the concave portion; in a plan view, a diagonal line connecting the plurality of corners of the first main surface intersects with the edge of the bottom surface of the concave portion; the concave portion has an inclined surface that is inclined to form a blunt angle with the bottom surface; the light-emitting module further comprises a light-transmitting portion provided in the concave portion around the light source, and the light-transmitting portion is in contact with the inclined surface. As in claim 1, the light-emitting module, wherein in a top view, the diagonal line connecting the aforementioned multiple corners of the aforementioned first main surface intersects with the aforementioned side surface of the aforementioned light source. As in claim 1, a plurality of units each comprising the aforementioned concave portion and the aforementioned light source and having a quadrangular shape in a plan view are periodically arranged on one aforementioned light guide plate; and in a plan view, the aforementioned bottom surface, the aforementioned edge of the aforementioned concave portion of each aforementioned unit and the aforementioned side surface of the aforementioned light source are oriented toward the corner of each aforementioned unit. As in the light-emitting module of claim 1, the aforementioned light-transmitting portion is a light-transmitting resin portion. As in claim 4, the light-emitting module, wherein the refractive index of the aforementioned light-transmitting resin portion is lower than the refractive index of the aforementioned light guide plate. As in claim 1, the light-emitting module, wherein the area of the opening before the aforementioned recess is larger than the area of the bottom surface before the aforementioned recess. The light-emitting module of claim 1 is further provided with an optical functional portion, which is disposed on the aforementioned first main surface of the aforementioned light guide plate at a position opposite to the aforementioned recessed portion and has a refractive index lower than that of the aforementioned light guide plate. As in claim 1, the light-emitting module, wherein the light source comprises a light-emitting element and a fluorescent layer bonded to the main light-emitting surface of the light-emitting element.