JP2021190417A - Planar light source, and liquid crystal display device - Google Patents

Abstract

To suppress luminance uniformity which occurs at a peripheral edge, in a planar light source whose planar shape is an irregular shape.SOLUTION: A planar light source comprises: a mounting board in an irregular shape; a plurality of light sources arrayed in a two-dimensional manner in a first direction and a second direction vertical to the first direction on the mounting board in a planar view; and a light diffusion plate provided above the plurality of light sources. The light diffusion plate includes a thick plate part and a thin plate part which is thinner than the thick plate part. The thin plate part is provided in at least a part of the light diffusion plate positioned outside of each of the light sources disposed in an outermost periphery in a planar view. In one light source and the other light source positioned in an end in the first direction among the plurality of light sources, a distance from an optical axis of the one light source to an outer edge of the light diffusion plate in the first direction is longer than a distance from an optical axis of the other light source to the outer edge of the optical diffusion plate in the first direction. Regarding a width of the thin plate part in the first direction in a planar view, the width in the first direction from the optical axis of the one light source to the outer edge of the light diffusion plate is larger than the width in the first direction from the optical axis of the other light source to the outer edge of the light diffusion plate.SELECTED DRAWING: Figure 5

Description

The present disclosure relates to a planar light source and a liquid crystal display device.

A planar light source using a light emitting element such as a light emitting diode is widely used as various light sources such as a backlight of a liquid crystal display device and a display.

As an example of such a planar light source, there is a configuration including a light emitting element arranged two-dimensionally and a light diffusing plate arranged above each light emitting element. In this planar light source, the light diffusing plate contains diffused particles for diffusing light from the light emitting portion of the light emitting element, and is a light emitting element in at least a region corresponding to the light emitting portion of the light emitting element on the surface of the light emitting element side. A convex portion that protrudes in a gentle curved shape on the side is integrally formed.

Japanese Unexamined Patent Publication No. 2012-221779

The present disclosure aims at suppressing the luminance unevenness generated in the peripheral edge of a planar light source having an irregular planar shape.

The planar light sources according to the embodiment of the present disclosure are two-dimensionally arranged with an irregularly shaped mounting substrate in a first direction on the mounting substrate and a second direction perpendicular to the first direction in a plan view. It has a plurality of light sources and a light diffusing plate provided above the plurality of light sources, and the light diffusing plate has a thick plate portion and a thin plate portion having a thickness thinner than the thick plate portion. The thin plate portion is provided on at least a part of the light diffusing plate located outside each of the light sources arranged on the outermost periphery in a plan view, and is provided in the first direction among the plurality of light sources. In one light source and another light source located at the end, the distance from the optical axis of the one light source to the outer edge of the light diffuser in the first direction is the distance from the optical axis of the other light source in the first direction. Longer than the distance to the outer edge of the light diffusing plate, the width of the thin plate portion in the first direction is the width of the thin plate portion in the first direction from the optical axis of the one light source toward the outer edge of the light diffusing plate. The width is wider than the width in the first direction from the optical axis of the other light source toward the outer edge of the light diffusing plate.

According to one embodiment of the present disclosure, it is possible to suppress the luminance unevenness generated on the peripheral edge of a planar light source having an irregular planar shape.

It is a schematic plan view which illustrates the planar light source which concerns on 1st Embodiment. It is a schematic partial enlarged plan view of the E part of FIG. It is sectional drawing which follows the AA line of FIG. It is a plane schematic diagram which illustrates the arrangement of each light source in the planar light source which concerns on 1st Embodiment. It is a plane schematic diagram which illustrates the light diffusing plate in the planar light source which concerns on 1st Embodiment. It is a partially enlarged sectional view in the vicinity of a light source of FIG. It is a schematic plan view (the 1) explaining the width of a thin plate part. It is a schematic plan view (the 2) explaining the width of a thin plate part. It is a figure (the 1) which shows the result of the simulation about a light diffusing plate. It is a figure (the 2) which shows the result of the simulation about a light diffusing plate. It is a schematic cross-sectional view explaining the arrangement of an optical member. FIG. 1 is a schematic partially enlarged cross-sectional view (No. 1) illustrating a light diffusing plate in a planar light source according to a modification 1 of the first embodiment. FIG. 2 is a schematic partially enlarged cross-sectional view (No. 2) illustrating a light diffusing plate in a planar light source according to a modification 1 of the first embodiment. FIG. 3 is a schematic partially enlarged cross-sectional view (No. 3) illustrating a light diffusing plate in a planar light source according to a modification 1 of the first embodiment. FIG. 3 is a schematic plan view illustrating the light diffusing plate of FIG. It is a schematic partial enlarged plan view of the partition member which concerns on the modification 2 of 1st Embodiment. 16 is a cross-sectional view taken along the line BB of FIG. It is a schematic partial enlarged cross-sectional view (No. 1) near the outer edge of a planar light source. FIG. 2 is a schematic partially enlarged cross-sectional view (No. 2) near the outer edge of the planar light source. It is a plane schematic diagram explaining the outer shape of the substrate in the planar light source which concerns on the modification 3 of 1st Embodiment. It is a block diagram which illustrates the liquid crystal display device which concerns on 2nd Embodiment.

Hereinafter, embodiments for carrying out the invention will be described with reference to the drawings. In the following description, terms indicating a specific direction or position (for example, "upper", "lower", and other terms including those terms) are used as necessary. However, the use of these terms is to facilitate understanding of the invention with reference to the drawings, and the meaning of these terms does not limit the technical scope of the invention. Further, the parts having the same reference numerals appearing in a plurality of drawings indicate the same or equivalent parts or members.

Further, the embodiments shown below exemplify a planar light source for embodying the technical idea of the present invention, and do not limit the present invention to the following. Further, the dimensions, materials, shapes, relative arrangements, etc. of the components described below are not intended to limit the scope of the present invention to the specific description, but are exemplified. It was intended. Further, the contents described in one embodiment can be applied to other embodiments and modifications. In addition, the size and positional relationship of the members shown in the drawings may be exaggerated in order to clarify the explanation.

<First Embodiment>
(Surface light source 10)
FIG. 1 is a schematic plan view illustrating a planar light source according to the first embodiment. FIG. 2 is a schematic partially enlarged plan view of the E portion of FIG. FIG. 3 is a cross-sectional view taken along the line AA of FIG. FIG. 4 is a schematic plan view illustrating the arrangement of each light source in the planar light source according to the first embodiment, and is a diagram in which the partition member and the light diffusing plate are removed from FIG. FIG. 5 is a schematic plan view illustrating the light diffusing plate in the planar light source according to the first embodiment. FIG. 6 is a partially enlarged cross-sectional view in the vicinity of the light source of FIG.

As shown in FIGS. 1 to 6, the planar light source 10 is a surface light emitting device having a substrate 11, a light source 12, a partition member 13, and a light diffusing plate 14. However, the partition member 13 is not an essential constituent requirement of the planar light source 10, but is provided as needed. When the partition member 13 is not provided, for example, a support for supporting the light diffusing plate 14 may be provided.

In the following description, the planar view means that the object is viewed from the normal direction of the upper surface 11 m of the substrate 11, and the planar shape is the shape of the object viewed from the normal direction of the upper surface 11 m of the substrate 11. Shall point to.

A plurality of light sources 12 including a light emitting diode are arranged on the substrate 11 which is a mounting substrate. The number of light sources 12 arranged on the substrate 11 is not limited, and any number of light sources 12 may be arranged on the substrate 11.

The partition member 13 is arranged on the same side as the light source 12 of the substrate 11. The partition member 13 includes a top portion 13a arranged in a grid pattern in a plan view and a wall portion 13b surrounding each of the light source 12 in a plan view, and has a plurality of regions surrounding the light source 12. For example, the wall portion 13b of the partition member 13 extends from the top portion 13a toward the substrate 11, and in cross-sectional view, the width of the region surrounded by the facing wall portions 13b becomes narrower toward the substrate 11.

The range surrounded by the wall portion 13b (that is, the area and the space) is defined as one section C, and the section member 13 includes a plurality of sections C. In the present embodiment, one light source 12 is arranged in one section C. However, two or more light sources 12 may be arranged in one section C. In this case, for example, three light sources 12 of red, green, and blue may be arranged in one section C. Alternatively, two light sources 12 having a daylight color and a light bulb color may be arranged in one section C.

The light diffusing plate 14 is an optical member placed on the top portion 13a of the partition member 13 and arranged above the light source 12. By having the light diffusing plate 14, the planar light source 10 can improve the uniformity of light. The light diffusing plate 14 according to the present embodiment is provided with a portion having a thin plate thickness on the peripheral edge in order to suppress the luminance unevenness generated on the peripheral edge of the planar light source 10.

In a plan view, the outermost contour portion of each member is referred to as an outer edge, and a region having a width including the outer edge is referred to as a peripheral edge. In particular, the peripheral edge of the light diffusing plate 14 is a region of the light diffusing plate 14 located outside each of the light sources 12 arranged on the outermost periphery in a plan view. The perimeter does not necessarily indicate an annular region.

Hereinafter, each element constituting the planar light source 10 will be described in detail.

(Board 11)
The substrate 11 is a member for mounting a plurality of light sources 12, and has an irregular shape. Here, the irregular shape refers to a shape other than the rectangular shape, and is, for example, a shape obtained by adding a partial deformation or a total deformation to a perfect rectangular shape in order to match a specific product shape.

As shown in FIG. 6, conductor wirings 18A and 18B for supplying electric power to the light source 12 such as the light emitting element 12a are formed on the upper surface 11m of the substrate 11. Of the conductor wirings 18A and 18B, the regions that are not electrically connected are preferably covered with the covering member 15.

The material of the substrate 11 may be any material as long as it can insulate and separate at least a pair of conductor wirings 18A and 18B, and examples thereof include ceramics, resin, and composite materials. Examples of the ceramics include alumina, mullite, forsterite, glass ceramics, nitride-based (for example, AlN), carbide-based (for example, SiC), and LTCC. Examples of the resin include phenol resin, epoxy resin, polyimide resin, BT resin, polyphthalamide (PPA), polyethylene terephthalate (PET) and the like. As the composite material, a mixture of the above-mentioned resin and _{an inorganic filler such as glass fiber, SiO 2} , TiO ₂ , Al ₂ O ₃ , a glass fiber reinforced resin (glass epoxy resin), and an insulating layer formed on a metal member. Examples include metal substrates.

The thickness of the substrate 11 can be appropriately selected. The substrate 11 may be either a flexible substrate or a rigid substrate that can be manufactured by a roll-to-roll method. The rigid substrate may be a bendable thin rigid substrate. The materials of the conductor wirings 18A and 18B are not particularly limited as long as they are conductive members, and materials normally used as a wiring layer such as a circuit board can be used. A plating film, a light reflection film, or the like may be formed on the surfaces of the conductor wirings 18A and 18B.

The covering member 15 is preferably made of an insulating material. Examples of the material of the covering member 15 include the same materials as those exemplified as the material of the substrate 11. By using the above-mentioned resin containing a white filler or the like as the covering member 15, the light emitted from the light source 12 is reflected, and the light extraction efficiency of the planar light source 10 can be improved. ..

(Light source 12)
The plurality of light sources 12 are arranged two-dimensionally in a first direction on the substrate 11 and in a second direction perpendicular to the first direction in a plan view. The first direction and the second direction are, for example, the X direction and the Y direction as shown in FIG.

The light source 12 is a member that emits light, for example, a light emitting element itself that emits light by itself, a light emitting element sealed with a translucent resin or the like, or a surface-mounted light emitting device (LED) in which the light emitting element is packaged. Also called) etc. For example, as the light source 12, as shown in FIG. 6, a light emitting element 12a coated with a sealing member 12b can be mentioned. The light source 12 may be one using one light emitting element 12a, but may be one light source 12 by using a plurality of light emitting elements. Further, the light source 12 may include a resin including a light-reflecting material that surrounds the side surface of the light-emitting element, and a translucent member that covers the upper surface of the light-emitting element and the upper surface of the resin containing the light-reflecting material. The configuration may include a translucent member that covers the upper surface of the light emitting element, and a resin containing a light reflecting material that surrounds the side surface of the light emitting element and the side surface of the translucent member. The translucent member here may include a fluorescent substance. A translucent joining member for adhering the light emitting element and the translucent member may be provided between the light emitting element and the translucent member.

The light source 12 may have any light distribution characteristics, but it may have a wide light distribution in order to illuminate each section C surrounded by the wall portion 13b of the section member 13 with less luminance unevenness. preferable. In particular, it is preferable that each of the light sources 12 has a butt wing light distribution characteristic. As a result, the amount of light emitted in the direction directly above the light source 12 is suppressed, the light distribution of each light source 12 is expanded, and the expanded light is applied to the wall portion 13b and the bottom portion 13c, thereby being surrounded by the wall portion 13b. It is possible to suppress uneven brightness in each section C.

Here, the bat wing light distribution characteristic is defined as having a light emission intensity distribution in which the light emission intensity is stronger than 0 ° at an angle where the absolute value of the light distribution angle is larger than 0 °, where the optical axis OA is 0 °. .. As shown in FIG. 6, the optical axis OA is defined by a line that passes through the center of the light source 12 and intersects the upper surface 11 m of the substrate 11 perpendicularly.

In particular, examples of the light source 12 having the butt wing light distribution characteristic include those using a light emitting element 12a having a light reflecting film 12c on the upper surface as shown in FIG. By providing the light reflecting film 12c on the upper surface of the light emitting element 12a, most of the upward light of the light emitting element 12a is reflected by the light reflecting film 12c, the amount of light directly above the light emitting element 12a is suppressed, and the bat wing light distribution is performed. You can get the characteristics. Since the light reflecting film 12c can be formed directly on the light emitting element 12a, it is not necessary to separately combine a special lens for bat wing light distribution, and the thickness of the light source 12 can be reduced.

The light reflecting film 12c may be a metal film such as silver or copper, a resin containing a white filler or the like, or a combination thereof. Further, the light reflecting film 12c may be a dielectric multilayer film (DBR film) and may have a reflectance angle dependence on the incident angle with respect to the emission wavelength of the light emitting element 12a. Specifically, it is preferable to set the reflectance of the light reflecting film 12c so that the oblique incident is lower than the vertical incident. As a result, the change in brightness directly above the light emitting element 12a becomes gradual, and it is possible to suppress extremely darkening such that the area directly above the light emitting element 12a becomes a dark spot.

Examples of the light source 12 include those having a height of the light emitting element 12a directly mounted on the substrate 11 of 100 μm to 500 μm. The thickness of the light reflecting film 12c may be 0.1 μm to 3.0 μm. Even if the sealing member 12b is included, the thickness of the light source 12 can be about 0.5 mm to 2.0 mm.

It is preferable that the plurality of light sources 12 can be driven independently of each other and are wired on the substrate 11 so that dimming control (for example, local dimming or high dynamic range) for each light source 12 is possible. ..

(Light emitting element 12a)
As the light emitting element 12a, a known one can be used. For example, it is preferable to use a light emitting diode as the light emitting element 12a. As the light emitting element 12a, one having an arbitrary wavelength can be selected. For example, as the blue and green light emitting devices, those using a nitride semiconductor such as GaN, InGaN, AlGaN, and AlInGaN can be used. Further, as the red light emitting element, GaAlAs, AlInGaP and the like can be used. Further, a semiconductor light emitting device made of a material other than this may be used. The composition, emission color, size, number, etc. of the light emitting element to be used can be appropriately selected according to the purpose.

As shown in FIG. 6, the light emitting element 12a may be flip-chip mounted via a joining member 19 so as to straddle a pair of positive and negative conductor wirings 18A and 18B provided on the upper surface 11m of the substrate 11. However, the light emitting element 12a may be face-up mounted as well as flip chip mounted.

The joining member 19 is a member for fixing the light emitting element 12a to the substrate or the conductor wiring, and examples thereof include an insulating resin or a conductive member. In the case of flip-chip mounting as shown in FIG. 6, a conductive member is used. Specifically, Au-containing alloys, Ag-containing alloys, Pd-containing alloys, In-containing alloys, Pb-Pd-containing alloys, Au-Ga-containing alloys, Au-Sn-containing alloys, Sn-containing alloys, Sn-Cu-containing alloys, Sn- Examples thereof include Cu-Ag-containing alloys, Au-Ge-containing alloys, Au-Si-containing alloys, Al-containing alloys, Cu-In-containing alloys, and mixtures of metals and fluxes.

(Sealing member 12b)
The sealing member 12b protects the light emitting element 12a from the external environment and optically controls the light output from the light emitting element 12a (for example, obtains bad wing light distribution characteristics), and the like, the light emitting element 12a To cover. The sealing member 12b is made of a translucent material. As the material of the sealing member 12b, a translucent resin such as an epoxy resin, a silicone resin, or a resin mixed thereof, glass, or the like can be used. Of these, it is preferable to use a silicone resin in consideration of light resistance and ease of molding. The sealing member 12b may contain a diffusing agent for diffusing the light from the light emitting element 12a, a coloring agent corresponding to the light emitting color of the light emitting element 12a, and the like. As the diffusing agent, the coloring agent and the like, those known in the art can be used.

The sealing member 12b may be in direct contact with the substrate 11. The sealing member 12b is adjusted to a viscosity capable of printing, applying a dispenser, and the like, and can be cured by heat treatment and light irradiation. Examples of the shape of the sealing member 12b include, but are not limited to, a substantially hemispherical shape, a vertically long convex shape in a cross-sectional view, a flat convex shape in a cross-sectional view, a circular shape or an elliptical shape in a plan view, and the like. Here, the vertically long convex shape is a shape in which the maximum length in the direction perpendicular to the upper surface 11m of the substrate 11 is longer than the maximum length in the direction parallel to the upper surface 11m of the substrate 11 in a cross-sectional view. Further, the flat convex shape is a shape in which the maximum length in the direction parallel to the upper surface 11m of the substrate 11 is longer than the maximum length in the direction perpendicular to the upper surface 11m of the substrate 11 in a cross-sectional view. The sealing member 12b may be arranged as an underfill 12d between the lower surface of the light emitting element 12a and the upper surface 11m of the substrate 11.

(Division member 13)
The wall portions 13b of the partition member 13 can be arranged in a grid pattern in a plan view. In plan view, the boundary of adjacent compartments C can be regarded as the top 13a. The partition member 13 preferably has a bottom portion 13c connected to the lower end of the wall portion 13b in the compartment C. In other words, it is preferable that the partition member 13 constitutes the section C by the bottom portion 13c and the wall portion 13b. The bottom portion 13c may extend to the peripheral edge of the substrate 11 in a plan view. In this case, the bottom portion 13c may be located on the outer edge side of the substrate 11 with respect to the outermost peripheral wall portion 13b. The peripheral edge of the partition member 13 may have a portion that overlaps with the peripheral edge of the substrate 11. The partition member 13 is preferably a member having reflexivity.

The partition member 13 has, for example, a through hole 13d in which the light source 12 is arranged in the substantially center of the bottom portion 13c in the partition C. As shown in FIG. 6, it is preferable that the light source 12 is arranged in the through hole 13d. The shape and size of the through hole 13d may be any shape and size as long as the entire light source 12 is exposed, and it is preferable to set the outer edge of the through hole 13d so as to be located only in the vicinity of the light source 12. As a result, when the partition member 13 has reflectivity, the light from the light source 12 can be reflected even at the bottom portion 13c, and the light extraction efficiency can be improved.

The top 13a is the highest part of the wall 13b. The top portion 13a may be a flat surface, but it is preferable that the vicinity of the top portion 13a has a ridge shape. That is, it is preferable that the vertical cross section of the wall portion 13b constituting the top portion 13a constitutes an acute-angled triangle, and more preferably an acute-angled isosceles triangle.

The acute angle of the acute triangle or the acute isosceles triangle, that is, the angle of the wall portion 13b on the top 13a side (α in FIG. 6) is preferably 60 ° to 90 °, for example. By setting such a range, the space and area occupied by the partition member 13 can be reduced, the height of the partition member 13 can be reduced, and the planar light source 10 can be made smaller and thinner.

The pitch P between the top portions 13a of the partition member 13 can be appropriately adjusted depending on the size of the light source used, the size and performance of the intended planar light source, and the like. Examples of the pitch P include 1 mm to 50 mm, preferably 5 mm to 20 mm, and more preferably 6 mm to 15 mm. The wall portion 13b surrounding the light source 12 is preferably composed of a surface inclined so as to spread from the vicinity of the bottom portion 13c and the upper surface 11m of the substrate 11 toward the upper portion on the partition C side.

Further, the height of the partition member 13 itself, that is, the length from the lower surface of the bottom portion 13c of the partition member 13 to the top portion 13a is preferably 8 mm or less, and is about 1 mm to 4 mm in the case of a thinner planar light source. Is preferable. The distance from the lower surface of the bottom portion 13c of the partition member 13 to the light diffusing plate 14 is preferably about 8 mm or less, and when a thinner planar light source is used, it is preferably about 2 mm to 4 mm. As a result, the backlight unit including the optical member such as the light diffusing plate 14 can be made extremely thin. Examples of the thickness of the partition member 13 include 100 μm to 300 μm.

The shape of the compartment C formed by the compartment member 13 surrounding the light source 12, that is, the shape of the region divided by the wall portion 13b is a quadrangle in a plan view, but is not limited thereto. For example, it may be circular, oval, or the like. However, in order to efficiently arrange the plurality of light sources 12, polygons such as triangles, quadrangles, and hexagons are preferable. As a result, it becomes easy to divide the light emitting region into an arbitrary number by the wall portion 13b according to the area of the light emitting surface of the planar light source 10, and the light emitting region can be arranged at a high density.

The number of compartments C divided by the wall 13b can be arbitrarily set, and the shape and arrangement of the wall 13b, the number of compartments C, and the like can be changed according to the desired size of the planar light source. The partition member 13 is shown in FIG. 2 in a plan view, for example, in which three compartments C are adjacent to each other and the ends of the three tops are concentrated at one point, depending on the number and position of the light sources 12 arranged on the substrate 11. As described above, various shapes can be obtained, such as those in which the four compartments C are adjacent to each other and the four tops are concentrated, and those in which the six compartments C are adjacent to each other and the six tops are concentrated at one point. When the four compartments C are adjacent to each other and the four tops are concentrated, the shape of the compartment C in a plan view is quadrangular.

The partition member 13 is preferably arranged on the substrate 11, and preferably one in which the lower surface of the bottom portion 13c of the partition member 13 and the upper surface 11m of the substrate 11 are fixed. In particular, it is preferable to fix the periphery of the through hole 13d with a light-reflecting adhesive member so that the light emitted from the light source 12 does not enter between the substrate 11 and the partition member 13. For example, it is more preferable to arrange the light-reflecting adhesive member in a ring shape along the outer edge of the through hole 13d. The adhesive member may be a double-sided tape, a hot-melt type adhesive sheet, or a resin-based adhesive such as a thermosetting resin or a thermoplastic resin. These adhesive members preferably have high flame retardancy. However, the partition member 13 may be fixed on the substrate 11 by screwing or the like.

As described above, the partition member 13 preferably has light reflectivity. As a result, the light emitted from the light source 12 can be efficiently reflected by the wall portion 13b and the bottom portion 13c. In particular, when the wall portion 13b has an inclination as described above, the light emitted from the light source 12 is applied to the wall portion 13b, and the light can be reflected upward. Therefore, even when the adjacent compartment C is not lit, the contrast ratio can be further improved. Moreover, the light can be reflected upward more efficiently.

The partition member 13 may be molded using a resin containing a reflective material composed of metal oxide particles such as titanium oxide, aluminum oxide, and silicon oxide, or after molding using a resin not containing a reflective material. , A reflective material may be provided on the surface. Alternatively, a resin containing a plurality of fine bubbles may be used. In this case, light is reflected at the interface of the bubbles. Examples of the resin used for the partition member 13 include acrylic resin, polycarbonate resin, cyclic polyolefin resin, thermoplastic resin such as polyethylene terephthalate (PET) or polyester, and thermosetting resin such as epoxy or silicone. The partition member 13 is preferably set so that the reflectance with respect to the light emitted from the light source 12 is 70% or more.

The partition member 13 can be formed by a molding method using a mold, a molding method by stereolithography, or the like. As a molding method using a mold, molding methods such as injection molding, extrusion molding, compression molding, vacuum molding, pressure molding, and press molding can be applied. For example, by vacuum forming using a reflective sheet formed of PET or the like, a partition member 13 in which the bottom portion 13c and the wall portion 13b are integrally formed can be formed.

(Light diffuser plate 14)
The light diffusing plate 14 is a member having an irregular shape that diffuses and transmits incident light, and one can be arranged above a plurality of light sources 12. The light diffusion plate 14 is preferably a flat plate-shaped member, but irregularities may be arranged on the surface thereof. It is preferable that the light diffusing plate 14 is arranged substantially parallel to the substrate 11.

When the pitch between the top portions 13a of the partition member 13 is P [mm], the light diffusing plate 14 has the light diffusing plate 14 so that the distance OD between the light diffusing plate 14 and the light source 12 is, for example, 0.3 P [mm] or less. It is preferably arranged, and more preferably it is arranged so as to be 0.25 P [mm] or less. Here, as shown in FIG. 6, the distance OD is the outermost surface of the substrate 11, that is, the lower surface of the light diffusing plate 14 from the outermost surface when the substrate 11 has a coating layer, a wiring layer, or the like on the surface thereof. Means the distance to. From another viewpoint, the light diffusing plate 14 preferably has, for example, a distance H from the upper surface of the bottom portion 13c of the partition member 13 shown in FIG. 6 of 1.5 mm to 5 mm, more preferably 2 mm to 3 mm. ..

The light diffusing plate 14 can be made of a material having little light absorption with respect to visible light, such as a polycarbonate resin, a polystyrene resin, an acrylic resin, and a polyethylene resin. In order to diffuse the incident light, the light diffusing plate 14 may have irregularities on its surface, or materials having different refractive indexes may be dispersed in the light diffusing plate 14. The unevenness can be made, for example, in a size of 0.01 mm to 0.1 mm. As the material having a different refractive index, for example, a polycarbonate resin, an acrylic resin, or the like can be selected and used.

The thickness of the light diffusing plate 14 and the degree of light diffusing can be appropriately set, and commercially available members such as a light diffusing sheet and a diffuser film can be used. For example, the thickness of the light diffusing plate 14 can be 1 mm to 2 mm at the thickest portion.

In the planar light source 10, since the substrate 11 has an irregular shape, when as many light sources 12 as possible are spread on the substrate 11 while maintaining the matrix arrangement in the first direction and the second direction, the outer edge side of the substrate 11 is used. There is an area where the light source 12 is not arranged. If no measures are taken, the peripheral edge of the planar light source 10 (for example, the region between the outermost periphery of the partition member 13 and the outer edge of the light diffusing plate 14) becomes a dark portion, and the peripheral edge of the planar light source becomes bright. Unevenness may occur. In FIG. 1, for example, a dark portion is conspicuous in the region surrounded by the alternate long and short dash line F. That is, if no measures are taken, uneven brightness will occur in a part of the peripheral edge of the planar light source 10. Therefore, in the planar light source 10, the occurrence of luminance unevenness is suppressed by making a part of the peripheral edge of the light diffusing plate 14 thinner than the central side. If necessary, the entire peripheral edge of the light diffusing plate 14 may be thinner than the central side. Hereinafter, the shape of the light diffusing plate 14 will be described in detail.

The light diffusion plate 14 includes a thick plate portion 14a and a thin plate portion 14b whose plate thickness is thinner than that of the thick plate portion 14a, and the thick plate portion 14a and the thin plate portion 14b are arranged adjacent to each other and integrally formed. ing. In FIG. 5, for convenience, the thick plate portion 14a is shown in white and the thin plate portion 14b is shown in a dot pattern. The light diffusion plate 14 may be composed of one sheet, or may be composed of two or more layers. When the light diffusion plate 14 is composed of two layers, for example, a second layer having a width narrower than that of the first layer may be provided on the first layer on the substrate side. At this time, the region where the second layer is arranged on the first layer can be the thick plate portion 14a, and the region where the second layer is not arranged on the first layer can be the thin plate portion 14b.

The boundary 14c between the thick plate portion 14a and the thin plate portion 14b is located, for example, at a position facing the outermost peripheral wall portion 13b of the partition member 13. As a result, the frequency of light diffusion can be reduced and the amount of light transmitted through the thin plate portion 14b can be increased on the outer edge side of the outermost peripheral wall portion 13b of the partition member 13. As a result, it is possible to suppress the occurrence of luminance unevenness at the periphery of the planar light source 10. The boundary 14c may be located at a position facing the top portion 13a of the outermost periphery of the partition member 13.

When there is a wall portion 13b directly below (FIG. 3) or near the boundary between the thick plate portion 14a and the thin plate portion 14b of the light diffusing plate 14, the light incident on the thin plate portion 14b of the light diffusing plate 14 from the light source 12 is light. A part of the light diffused by the thick plate portion 14a of the diffuser plate 14 is incident on the thin plate portion 14b. Since the film thickness of the thin plate portion 14b is thin, the light incident on the thin plate portion 14b is diffused less frequently. This improves the light extraction in the thin plate portion 14b.

The thickness of the thin plate portion 14b is preferably 0.5 times or less the thickness of the thick plate portion 14a. As a result, the amount of light extracted from the region of the thin plate portion 14b increases, and the occurrence of luminance unevenness on the peripheral edge of the planar light source 10 can be suppressed.

The lower surface 14n of the thick plate portion 14a (the surface on the light source 12 side) and the lower surface 14t of the thin plate portion 14b (the surface on the light source 12 side) are on the same plane, and the upper surface 14m of the thick plate portion 14a (on the opposite side of the light source 12). The position in the height direction is different between the surface) and the upper surface 14s (the surface opposite to the light source 12) of the thin plate portion 14b.

That is, the height from the upper surface 11m of the substrate 11 to the lower surface 14t of the thin plate portion 14b is the same as the height from the upper surface 11m of the substrate 11 to the lower surface 14n of the thick plate portion 14a. On the other hand, the height from the upper surface 11m of the substrate 11 to the upper surface 14s of the thin plate portion 14b is lower than the height from the upper surface 11m of the substrate 11 to the upper surface 14m of the thick plate portion 14a.

The thin plate portion 14b is provided on at least a part of the peripheral edge of the light diffusing plate 14 in a plan view. As shown in FIG. 5, in the present embodiment, as an example, the thin plate portion 14b is provided over the entire peripheral edge of the light diffusing plate 14 (the portion indicated by the dot pattern). By providing the thin plate portion 14b over the entire peripheral edge of the light diffusing plate 14, the brightness of the entire peripheral edge of the thin plate portion 14b can be increased and the brightness unevenness can be reduced. However, the present invention is not limited to this, and the thin plate portion 14b may be provided only in a part of the peripheral region of the light diffusing plate 14.

In the planar light source 10, the farther the distance from the optical axis of the light source 12 located at the end in the X direction to the outer edge of the light diffusing plate 14 in the X direction is, the wider the width of the thin plate portion 14b in the X direction is. wide. _{For example, as shown in FIG. 7, in one light source 12 1} and the other light source 12 ₂ located at the end in the X direction among the plurality of light sources 12, the optical axis OA ₁ of the one light source 12 _{1 is in} the X direction. distance _{L 1} to the outer edge of the light diffusion plate 14 is longer than the distance _{L 2} from the optical axis OA ₂ of the other light source 12 ₂ to the outer edge of the X direction of the light diffusing plate 14. In this case, as shown in FIG. 8, in a plan view, the width of the thin plate portion 14b in the X direction is _{the width W 1 in the} X direction from the optical axis OA _{1 of one} light source 12 1 toward the outer edge of the light diffusion plate 14. It is wider than the X direction width _{W 2} toward the optical axis OA ₂ of the other light sources 12 ₂ to the outer edge of the light diffusion plate 14.

Further, in a plan view, the farther the distance from the optical axis of the light source 12 located at the end in the Y direction to the outer edge of the light diffusing plate in the Y direction, the wider the width of the thin plate portion 14b in the Y direction. For example, as shown in FIG. 7, in the light source 12 ₃ and the other light sources 12 ₄ one located at the end of the Y-direction among the plurality of light sources 12, one of the light source 12 ₃ from the optical axis OA ₃ in the Y-direction distance _{L 3} to the outer edge of the light diffusion plate 14 is longer than the distance _{L 4} from the optical axis OA ₄ of the other light sources 12 ₄ to the outer edge of the Y direction of the light diffusing plate 14. In this case, as shown in FIG. 8, in a plan view, Y-direction width of the thin plate section 14b, the Y-direction width W ₃ toward the optical axis OA ₃ of one light source 12 ₃ at the outer edge of the light diffusion plate 14 It is wider than the Y-direction width _{W 4} of the heading from the optical axis OA ₄ of the other light sources 12 ₄ to the outer edge of the light diffusion plate 14.

9 and 10 are diagrams showing the results of a simulation relating to the light diffusing plate. FIG. 9 shows the simulation result of the planar light source 10, and FIG. 10 shows the simulation result of the planar light source 10X equipped with the light diffusing plate 14X having a constant plate thickness instead of the light diffusing plate 14 of the planar light source 10. Example). In FIGS. 9 and 10, a large number of thin lines indicate light rays.

Comparing the portions surrounded by the broken lines in FIGS. 9 and 10, the planar light source 10 provided with the thin plate portion 14b has more portions with higher light beam densities than the planar light source 10X without the thin plate portion. It can be confirmed that the light extraction at the peripheral edge of the light diffusing plate 14 is good. That is, it can be confirmed that the uneven brightness of the light emitting surface on the peripheral edge of the light diffusing plate 14 can be suppressed. This is because by providing the thin plate portion 14b on the light diffusion plate 14, the frequency of light diffusion in the thin plate portion 14b is reduced, and the light transmitted through the thin plate portion 14b is increased. Further, the light emitted from the side surface of the thick plate portion 14a exposed to the thin plate portion 14b and the light reflected on the side surface of the thick plate portion 14a through the thin plate portion 14b are directed toward the upper surface side of the light diffusing plate. This is because the density of light on the upper surface side of the diffuser plate becomes high.

For the light diffusing plate 14, a simulation was performed when the thickness of the thick plate portion 14a was 1.2 mm and the thickness of the thin plate portion 14b was changed to 0.4 mm, 0.2 mm, and 0.1 mm, respectively, and the thin plate portion 14b was thinned. The brightness of the light transmitted through the thin plate portion 14b in the region of the portion 14b was calculated. As shown in Table 1, when the thin plate portion 14b is 0.4 mm, the thin plate portion 14b is 1.2 mm (that is, the thin plate portion 14b has the same thickness as the thick plate portion 14a). The result was a one-fold increase. Similarly, when the thin plate portion 14b is 0.2 mm, a result of 1.12 times increase is obtained. Further, when the thin plate portion 14b was 0.1 mm, a result of 1.17 times increase was obtained.

Further, when comparing the light leaking to the outside from the side surface of the light diffusing plate, it can be confirmed that the planar light source 10 provided with the thin plate portion 14b has less leakage than the planar light source 10X not provided with the thin plate portion. That is, in the planar light source 10, the light that has conventionally leaked to the side can be directed to the upper surface side of the light diffusing plate 14, and the frequency of light diffusing in the thin plate portion 14b is reduced, so that the thin plate can be directed. The density of light rays on the upper surface side of the portion 14b can be increased.

Further, in the planar light source 10, by providing the thin plate portion 14b on the light diffusing plate 14, the amount of light leaking to the outside from the side surface of the light diffusing plate 14 can be reduced.

In the planar light source 10, a wavelength conversion sheet that converts light from the light source 12 into light having a different wavelength may be arranged above the light diffusing plate 14. When the wavelength conversion sheet is arranged above the light diffusing plate 14, if light leaks from the side surface of the light diffusing plate, the end portion of the planar light source looks like the emission color (for example, blue) of the light emitting element 12a. .. However, in the planar light source 10, by providing the thin plate portion 14b on the light diffusing plate 14, the amount of light leaking to the outside from the side surface of the light diffusing plate 14 can be reduced, so that the end portion of the planar light source 10 is the light emitting element 12a. It is possible to suppress the phenomenon of appearing as a luminescent color. That is, when the wavelength conversion sheet is arranged above the light diffusion plate 14, it is possible to suppress the phenomenon that light having a wavelength different from the wavelength converted by the wavelength conversion sheet leaks to the outside from the side surface of the light diffusion plate 14.

As described above, in the planar light source 10, since the substrate 11 has an irregular shape, when as many light sources 12 as possible are spread on the substrate 11 while maintaining the matrix arrangement in the first direction and the second direction, the substrate 11 is used. There is an area on the outer edge side of the light source 12 where the light source 12 is not arranged. If no measures are taken, for example, the region between the outermost circumference of the partition member 13 and the outer edge of the light diffusing plate 14 becomes a dark portion. That is, if no measures are taken, uneven brightness will occur in a part of the peripheral edge of the planar light source 10. However, by providing the thin plate portion 14b on the peripheral edge of the light diffusion plate 14, the thin plate portion 14b can prioritize light extraction over light diffusion, reduce the frequency of light diffusion, and increase the light transmitted through the thin plate portion 14b. .. As a result, it is possible to suppress the occurrence of luminance unevenness at the periphery of the planar light source 10.

However, since the thin plate portion 14b may be provided in a portion where uneven brightness may occur, it is not always necessary to provide the thin plate portion 14b over the entire peripheral edge of the light diffusing plate 14, and the thin plate portion 14b may be provided on the peripheral edge of the light diffusing plate 14. The thin plate portion 14b may be provided only in a part of the region.

Further, for the same reason, the width of the thin plate portion 14b becomes wider as the distance from the optical axis of the light source 12 located at the end to the outer edge of the light diffusion plate 14 is longer in both the X direction and the Y direction. No need. That is, in at least one of the X direction and the Y direction, the width of the thin plate portion 14b may be wider as the distance from the optical axis of the light source 12 located at the end to the outer edge of the light diffusion plate 14 is longer.

The planar light source 10 includes at least one selected from a group consisting of a wavelength conversion sheet, a prism sheet, and a polarizing sheet that convert light from the light source 12 into light having a different wavelength above the light diffusing plate 14. You may. Specifically, as shown in FIG. 11, the wavelength conversion sheet 72 and the prism sheet (first prism) are directly or indirectly above the light diffusing plate 14 at a predetermined distance or on the upper surface of the light diffusing plate 14. An optical member such as a sheet 73 and a second prism sheet 74) and a polarizing sheet 75 can be arranged, and a liquid crystal panel can be arranged on the optical member to form a surface emitting light emitting device used as a light source for a direct backlight. .. The stacking order of these optical members can be set arbitrarily.

(Wavelength conversion sheet 72)
The wavelength conversion sheet 72 may be arranged on either the upper surface or the lower surface of the light diffusing plate 14, but it is preferably arranged on the upper surface of the light diffusing plate 14 as shown in FIG. The wavelength conversion sheet 72 absorbs a part of the light emitted from the light source 12, and emits light having a wavelength different from the wavelength of the light emitted from the light source 12. For example, the wavelength conversion sheet 72 can realize a planar light source 10 that absorbs a part of blue light from the light source 12 to emit yellow light, green light and / or red light, and emits white light. Since the wavelength conversion sheet 72 is separated from the light emitting element 12a of the light source 12, it is possible to use a phosphor or the like having inferior heat or light intensity resistance, which is difficult to use in the vicinity of the light emitting element 12a. Thereby, the performance of the planar light source 10 as a backlight can be improved. The wavelength conversion sheet 72 has a sheet shape or a layer shape, and includes the above-mentioned phosphor and the like. The wavelength conversion sheet may be referred to as a wavelength conversion layer.

(1st prism sheet 73 and 2nd prism sheet 74)
The first prism sheet 73 and the second prism sheet 74 have a shape in which a plurality of prisms extending in a predetermined direction are arranged on the surface thereof. For example, the first prism sheet 73 has a plurality of prisms extending in the Y direction when the plane of the sheet is viewed two-dimensionally in the X direction and the Y direction perpendicular to the X direction, and the second prism sheet 74 has X. It can have a plurality of prisms extending in a direction. The first prism sheet 73 and the second prism sheet 74 can refract light incident from various directions toward the display panel facing the planar light source 10. As a result, the light emitted from the light emitting surface of the planar light source 10 can be emitted mainly in the direction perpendicular to the upper surface, and the brightness when the planar light source 10 is viewed from the front can be increased.

(Polarizing sheet 75)
The polarizing sheet 75 selectively transmits light in a polarization direction that matches the polarization direction of a polarizing plate arranged on the backlight side of a display panel such as a liquid crystal display panel, and polarizes in a direction perpendicular to the polarization direction. Can be reflected toward the first prism sheet 73 and the second prism sheet 74. A part of the polarized light returned from the polarizing sheet 75 is reflected again by the first prism sheet 73, the second prism sheet 74, the wavelength conversion sheet 72, and the light diffusing plate 14. At this time, the polarization direction changes, and for example, it is converted into polarized light having the polarization direction of the polarizing plate of the liquid crystal display panel, is incident on the polarizing sheet 75 again, and is emitted to the display panel. As a result, the polarization directions of the light emitted from the planar light source 10 can be aligned, and the light in the polarization direction effective for improving the brightness of the display panel can be emitted with high efficiency. As the polarizing sheet 75, the first prism sheet 73, the second prism sheet 74, and the like, commercially available optical members for the backlight can be used.

In the planar light source 10, instead of providing the wavelength conversion sheet 72, a phosphor or the like that absorbs the light from the light emitting element 12a into the sealing member 12b and emits light having a wavelength different from the output light from the light emitting element 12a. May contain the wavelength conversion material of. Thereby, for example, a planar light source 10 can be realized in which a part of blue light from the light source 12 is absorbed by the sealing member 12b to emit yellow light, green light and / or red light, and white light is emitted.

In addition to the wavelength conversion material, the sealing member 12b may contain a diffusing agent for diffusing the light from the light emitting element 12a, a coloring agent corresponding to the light emitting color of the light emitting element 12a, and the like. As the diffusing agent, the coloring agent and the like, those known in the art can be used. Further, the sealing member 12b does not contain a wavelength conversion material such as a phosphor, and for example, the light emitting element 12a in which the nitride semiconductor is covered with the wavelength conversion material such as a phosphor, that is, the light emitting element 12a itself emits white light. It is also possible to use the one that emits light.

<Modification 1 of the first embodiment>
Modification 1 of the first embodiment shows an example in which the cross-sectional shape of the thin plate portion of the light diffusing plate is different from that of the first embodiment. In the first modification of the first embodiment, the description of the same component as that of the above-described embodiment may be omitted.

12 to 14 are schematic partially enlarged cross-sectional views illustrating a light diffusing plate in a planar light source according to a modification 1 of the first embodiment. FIG. 15 is a schematic plan view illustrating the light diffusing plate of FIG.

In the light diffusing plate 24 shown in FIG. 12, the height from the upper surface 11m of the substrate 11 to the lower surface 24t of the thin plate portion 24b is the same as the height from the upper surface 11m of the substrate 11 to the lower surface 24n of the thick plate portion 24a. The thickness of the thin plate portion 24b gradually decreases as it approaches the outer edge of the light diffusing plate 24 from the boundary 24c with the thick plate portion 24a.

As described above, the boundary between the thick plate portion and the thin plate portion does not have to be stepped as shown in FIG. 3, and may have a shape in which the thickness changes smoothly as shown in FIG. In this case as well, the thin plate portion 24b can prioritize light extraction over light diffusion, reduce the frequency of light diffusion, and increase the amount of light transmitted through the thin plate portion 24b. As a result, it is possible to suppress the occurrence of luminance unevenness at the periphery of the planar light source.

Further, unlike the light diffusing plate 24 shown in FIG. 12, the thin plate portion 24b does not have a shape in which the entire thin plate portion 24b gradually becomes thinner, but the thickness gradually increases as the thin plate portion approaches the outer edge of the light diffusing plate from the boundary with the thick plate portion. It may have a shape having a thinned portion. For example, as in the light diffusing plate 34 shown in FIG. 13, the thin plate portion 34b has a plate thickness gradually decreasing portion 34b1 whose thickness gradually decreases as it approaches the outer edge of the light diffusing plate 34 from the boundary 34c with the thick plate portion 34a. Further, the plate thickness constant portion 34b2 may be provided on the outer edge side of the light diffusing plate 34 with respect to the plate thickness gradually decreasing portion 34b1. The plate thickness of the plate thickness constant portion 34b2 is, for example, the same plate thickness as the thinnest portion of the plate thickness gradually decreasing portion 34b1.

Further, as in the light diffusing plate 44 shown in FIGS. 14 and 15, the thin plate portion 44b is located on the outer edge side of the light diffusing plate 44 with respect to the first thin plate portion 44b1 on the thick plate portion 44a side and the first thin plate portion 44b1. It may include a second thin plate portion 44b2 which is located and has a thinner plate thickness than the first thin plate portion 44b1. In this way, by changing the plate thickness of the thin plate portion 44b in two steps, the brightness of the end portion of the planar light source can be increased. That is, since the dark portion becomes more conspicuous as the distance from the light source 12 increases, the thickness of the light diffusing plate 14 can be reduced as the distance from the light source 12 increases to suppress the occurrence of luminance unevenness on the periphery of the planar light source. The change in the plate thickness of the thin plate portion 44b may be made in two or more steps. Further, the cross-sectional shape of the thin plate portion 44b may be a shape in which the shapes shown in FIGS. 12 to 14 are appropriately combined.

The second thin plate portion 44b2 is arranged, for example, in a plan view on the outer edge side of the light diffusion plate 44 with respect to the region where the through hole 13d of the partition member 13 is arranged. The second thin plate portion 44b2 may be arranged in the section C in which the light source 12 is not arranged. The boundary 44c between the first thin plate portion 44b1 and the second thin plate portion 44b2 may be located at a position overlapping the top portion 13a of the partition member 13 in a plan view.

It is not always necessary to provide the first thin plate portion 44b1 and the second thin plate portion 44b2 over the entire peripheral edge of the light diffusion plate 44, and only the first thin plate portion 44b1 may be arranged in a region where uneven brightness is unlikely to occur. For example, in the region R in which the light source 12 is arranged linearly in FIG. 15, uneven brightness is unlikely to occur, so that only the first thin plate portion 44b1 may be arranged. Alternatively, when the luminance unevenness hardly occurs in the region R in which the light source 12 is linearly arranged in FIG. 15, the thin plate portion 44b may not be provided in the region R.

<Modification 2 of the first embodiment>
In the second modification of the first embodiment, an example is shown in which the partition member has a partition having a different size on the peripheral edge. In the second modification of the first embodiment, the description of the same component as that of the above-described embodiment may be omitted.

FIG. 16 is a schematic partially enlarged plan view of the partition member according to the second modification of the first embodiment. FIG. 17 is a cross-sectional view taken along the line BB of FIG. In the partition member 23 shown in FIGS. 16 and 17, the top portion 23a and the wall portion 23b constituting the outermost section C are arranged in the vicinity of the outer edge of the substrate 11. That is, in at least a part of the outermost section C, the area of the region surrounded by the wall portion 23b is larger than that of the inner peripheral section C in a plan view. In the examples of FIGS. 16 and 17, the area of the area surrounded by the wall portion 23b of the outermost section C is expanded in the X direction, but it may be expanded in the Y direction. Alternatively, a portion in which the area of the area surrounded by the wall portion 23b of the outermost section C is expanded in the X direction and a portion in which the area is expanded in the Y direction may coexist.

Thus, in the examples of FIGS. 2 and 3, in plan view, the area of the bottom portion 23c exposed in the compartment C was equal in all compartments C, but is not limited to this. As in the examples of FIGS. 16 and 17, in a plan view, at least one of the areas surrounded by the wall portion 23b located on the outermost circumference of the partition member 23 is the wall portion 23b located on the inner peripheral side of the outermost circumference. The area may be larger than the area surrounded by.

In the structure of the partition member 23 shown in FIGS. 16 and 17, the wall portion 23b constituting the outermost partition C is located near the outer edge of the substrate 11, so that light extraction to the exit surface side is improved. That is, in the structure of the partition member 23 shown in FIGS. 16 and 17, since the wall portion 23b is also located on the peripheral edge of the substrate 11, more light can be sent to the thin plate portion 14b of the light diffusion plate 14. As a result, it is possible to further suppress the occurrence of luminance unevenness at the periphery of the planar light source 10. However, the wall portion 23b may not be provided on at least a part of the outermost circumference of the partition member 23. In addition, in FIGS. 16 and 17, the wall portion 23b of the partition member is not arranged at the position of the boundary between the thick plate portion 14a and the thin plate portion 14b of the light diffusion plate 14, but the wall portion 23b may be provided at this position. ..

<Modification 3 of the first embodiment>
Modification 3 of the first embodiment shows a modification of a member other than the light diffusing plate and the partition member. In the third modification of the first embodiment, the description of the same component as that of the above-described embodiment may be omitted.

FIG. 18A is a schematic partial enlarged cross-sectional view near the outer edge of the planar light source. As shown in FIG. 18A, the planar light source may have a frame body 26 that surrounds the substrate 11 and the light diffusing plate 14. The frame body 26 has a deformed shape, for example, has a shape similar to that of the substrate 11, and has a bottom portion 26a that is one size larger than the substrate 11 in a plan view.

The peripheral edge of the bottom portion 26a is annularly exposed to the outside of the substrate 11, and a side wall 26b is provided in the exposed portion so as to surround the substrate 11. A lid 27 surrounding the outer edges of the substrate 11 and the light diffusing plate 14 may be provided on the side opposite to the bottom portion 26a of the side wall 26b. The lid 27 is arranged at a position that does not interfere with the light emitted from each light source 12. The frame body 26 and the lid body 27 are formed of various materials such as a resin including a reflective material, a metal, and ceramics.

As shown in FIG. 18B, the wavelength conversion member 28 containing the phosphor can be arranged in the region between the substrate 11 and the light diffusing plate 14 on the inner side surface of the side wall 26b. As a result, a part of the light from the light source 12 is wavelength-converted by the wavelength conversion member 28 arranged on the inner side surface of the side wall 26b, and the wavelength-converted light is taken out. Therefore, the end portion of the planar light source 10 is a light emitting element. It is possible to suppress the phenomenon of appearing as the emission color of. When the wavelength conversion member 28 is arranged on the inner side surface of the side wall 26b, the wall portion 13b of the partition member 13 may or may not be arranged between the light source 12 and the side wall 26b in the cross-sectional view of the planar light source. You may. The wavelength conversion member 28 may be arranged on the entire inner side surface of the side wall 26b, or may be arranged on the inner side surface of the side wall 26b in a region below the lower surface of the light diffusing plate 14. When the wavelength conversion member 28 is arranged in a region below the lower surface of the light diffusing plate 14, the thin plate portion 14b of the light diffusing plate 14 may or may not cover the upper part of the wavelength conversion member 28. As the wavelength conversion member 28, a material that emits yellow light (for example, YAG) can be used. The wavelength conversion member 28 arranged on the inner surface of the side wall 26b may be singular or plural.

By providing the frame body 26 and the lid body 27 in the planar light source in this way, the substrate 11 and the light diffusing plate 14 can be protected from external impacts and the like. The light diffusing plate 14, the substrate 11, and the frame body 26 may have similar deformed shapes.

FIG. 19 is a schematic plan view illustrating the outer shape of the substrate in the planar light source according to the first embodiment, and shows only the substrate, the light source, and the partition member. The shape of the light diffusing plate may be, for example, the same as in FIG. The substrate 21 of the planar light source 20 shown in FIG. 19 has an irregular shape, and has a shape in which a region where the light source 12 is not arranged is cut off as compared with the substrate 11 shown in FIG. That is, the outermost shape of the substrate 21 has a shape corresponding to the outermost shape of the partition member 13. In the example of FIG. 19, the substrate 21 is located at a position (lower side of the partition member 13) overlapping with the partition member 13 in a plan view.

As described above, the substrate 21 used for the planar light source may have a shape in which the region where the light source 12 is not arranged is cut off. Also in this case, by using the light diffusing plate 14 having the same shape as that of FIG. 5, the frequency of light diffusion at the peripheral edge of the light diffusing plate 14 can be reduced and the light transmitted through the light diffusing plate 14 can be increased. As a result, it is possible to suppress the occurrence of luminance unevenness at the periphery of the planar light source.

The cross-sectional shape of the planar light source 10 may be a linear shape parallel to the XY plane as shown in FIG. 11 or the like, or may be a curved shape with respect to the XY plane. For example, it may have a curved shape such that the exit surface side is recessed in the X direction.

<Second Embodiment>
The second embodiment shows an example of a liquid crystal display device using the planar light source according to the first embodiment as a backlight light source. In the second embodiment, the description of the same component as that of the above-described embodiment may be omitted.

FIG. 20 is a configuration diagram illustrating the liquid crystal display device according to the second embodiment. As shown in FIG. 20, the liquid crystal display device 1000 includes a liquid crystal panel 120, an optical sheet 110, and a planar light source 10 according to the first embodiment in this order from the upper side. In the planar light source 10, reference numeral 70 indicates an optical member such as a light diffusing plate or a wavelength conversion sheet. Here, the optical sheet 110 can be provided with a DBEF (reflection type polarizing sheet), a BEF (luminance increasing sheet), a color filter, or the like by adding or partially changing the optical member.

The liquid crystal display device 1000 is a so-called direct type liquid crystal display device in which a planar light source 10 is laminated below the liquid crystal panel 120. The liquid crystal display device 1000 irradiates the liquid crystal panel 120 with the light emitted from the planar light source 10. In addition to the above-mentioned constituent members, a member such as a color filter may be further provided.

Generally, in a direct-type liquid crystal display device, the distance between the liquid crystal panel and the planar light source is short, so that the color unevenness and the luminance unevenness of the planar light source may affect the color unevenness and the luminance unevenness of the liquid crystal display device. be. Therefore, as a planar light source for a direct-type liquid crystal display device, a planar light source with less color unevenness and luminance unevenness is desired. By using the planar light source 10 for the liquid crystal display device 1000, the thickness of the planar light source 10 can be reduced to 5 mm or less, 3 mm or less, 1 mm or less, etc., while suppressing the brightness unevenness generated on the peripheral edge and increasing the overall brightness unevenness. Color unevenness can be reduced.

The case where one planar light source 10 is used as a backlight of one liquid crystal display device 1000 is not limited, and a plurality of planar light sources 10 are arranged side by side and used as a backlight of one liquid crystal display device 1000. You may. For example, by manufacturing a plurality of small planar light sources 10 and inspecting each of them, the yield can be improved as compared with the case of manufacturing one large planar light source 10 having a large number of mounted light sources 12. can.

As described above, since the planar light source 10 emits uniform light from the optical member 70, it is suitable to be used as a backlight of the liquid crystal display device 1000.

However, the present invention is not limited to this, and the planar light source 10 can be suitably used as a backlight for televisions, tablets, smartphones, smart watches, head-up displays, digital signage, bulletin boards, and the like. The planar light source 10 can also be used as a light source for lighting, and can also be used for emergency lights, line lighting, various illuminations, installation for automobiles, and the like. It should be noted that the planar light source 10 may be appropriately subjected to one or more modifications shown in Modifications 1 to 3 of the first embodiment.

Although the preferred embodiments and the like have been described in detail above, they are not limited to the above-described embodiments and the like, and various modifications and substitutions are made to the above-mentioned embodiments and the like without departing from the scope described in the claims. Can be added.

For example, in the above embodiment, the lower surface of the thick plate portion (the surface on the light source side) of the light diffusing plate and the lower surface of the thin plate portion (the surface on the light source side) are on the same plane. The upper surface of the thick plate portion (the surface opposite to the light source) and the upper surface of the thin plate portion (the surface opposite to the light source) may be on the same plane. That is, the lower surface side of the light diffusing plate may be thinned to provide a thin plate portion. For example, the light diffusing plate 14 shown in FIG. 6, the light diffusing plate 24 shown in FIG. 12, the light diffusing plate 34 shown in FIG. 13, and the light diffusing plate 44 shown in FIG. 14 may be inverted upside down. In these cases, it cannot be expected that the light from the side surface of the thick plate portion toward the upper surface side of the light diffusing plate will increase, but since the frequency of light diffusion in the thin plate portion decreases and the light transmitted through the thin plate portion increases, the light diffusing plate A certain effect of suppressing uneven brightness of the light emitting surface at the periphery of the light emitting surface can be obtained.

Further, the light diffusing plate may contain scattered particles such as titanium oxide particles and phosphor particles, and the concentration of the scattered particles contained in the thin plate portion may be lower than the concentration of the scattered particles contained in the thick plate portion. As a result, the frequency of light diffusion in the thin plate portion can be further reduced and the light transmitted through the thin plate portion can be further increased, so that the effect of suppressing the uneven brightness of the light emitting surface on the peripheral edge of the light diffusion plate can be improved. Alternatively, a scattered particle layer containing scattered particles is formed on the upper surface and / or the lower surface of the light diffusing plate, and the concentration of the scattered particles in the scattered particle layer formed in the thin plate portion is adjusted to the scattered particle layer formed in the thick plate portion. The same effect can be obtained even if the concentration is lower than the concentration of the scattered particles in.

10, 20 planar light source 11, 21 substrate 11m, 14m, 14s top surface 12 light source 12a light emitting element 12b sealing member 12c light reflecting film 12d underfill 13, 23 partition member 13a, 23a top 13b, 23b wall 13c, 23c, 26a Bottom 13d Through hole 14, 24, 34, 44 Light diffuser 14a, 24a, 34a, 44a Thick plate 14b, 24b, 34b, 44b Thin plate 14c, 24c, 34c, 44c Boundary 14n, 14t, 24n, 24t Bottom surface 15 Covering member 18A, 18B Conductor wiring 19 Joining member 26 Frame body 26b Side wall 27 Cover body 28 Wavelength conversion member 34b1 Plate thickness tapering part 34b2 Plate thickness constant part 44b1 First thin plate part 44b2 Second thin plate part 70 Optical member 72 Wavelength conversion sheet 73 1st prism sheet 74 2nd prism sheet 75 Polarizing sheet 110 Optical sheet 120 Liquid crystal panel 1000 Liquid crystal display device

Claims (18)

An irregularly shaped mounting board and
A plurality of light sources arranged two-dimensionally in a first direction on the mounting board and a second direction perpendicular to the first direction in a plan view.
It has a light diffusing plate provided above the plurality of light sources, and has.
The light diffusing plate includes a thick plate portion and a thin plate portion having a thinner plate thickness than the thick plate portion.
The thin plate portion is provided on at least a part of the light diffusing plate located outside each of the light sources arranged on the outermost periphery in a plan view.
In one light source and another light source located at the end of the first direction among the plurality of light sources, the distance from the optical axis of the one light source to the outer edge of the light diffuser in the first direction is the above. Longer than the distance from the optical axis of the other light source to the outer edge of the light diffuser in the first direction,
In a plan view, the width of the thin plate portion in the first direction is the width of the first direction from the optical axis of the one light source toward the outer edge of the light diffusing plate, and the width of the first direction is the light from the optical axis of the other light source. A planar light source wider than the width of the first direction toward the outer edge of the diffuser. In one light source and another light source located at the end of the second direction among the plurality of light sources, the distance from the optical axis of the one light source to the outer edge of the light diffuser in the second direction is the said. Longer than the distance from the optical axis of the other light source to the outer edge of the light diffuser in the second direction,
In a plan view, the width of the thin plate portion in the second direction is the width of the second direction from the optical axis of the one light source toward the outer edge of the light diffusing plate, and the width of the second direction is the light from the optical axis of the other light source. The planar light source according to claim 1, which is wider than the width in the second direction toward the outer edge of the diffuser plate. The height from the upper surface of the mounting board to the surface of the thin plate portion on the light source side is the same as the height from the upper surface of the mounting board to the surface of the thick plate portion on the light source side.
The height from the upper surface of the mounting board to the surface of the thin plate portion opposite to the light source is lower than the height from the upper surface of the mounting board to the surface of the thick plate portion opposite to the light source. The planar light source according to 1 or 2. The height from the upper surface of the mounting board to the surface of the thin plate portion on the light source side is the same as the height from the upper surface of the mounting board to the surface of the thick plate portion on the light source side.
The planar light source according to claim 1 or 2, wherein the thin plate portion has a portion whose thickness gradually decreases as it approaches the outer edge of the light diffusing plate from the boundary with the thick plate portion. The planar light source according to any one of claims 1 to 4, wherein the thin plate portion is provided over the entire peripheral edge of the light diffusing plate. The planar light source according to any one of claims 1 to 5, further comprising a partition member including a wall portion surrounding each of the light sources in a plan view and having a plurality of regions surrounded by the wall portions. The planar light source according to claim 6, wherein the boundary between the thin plate portion and the thick plate portion is located at a position facing the outermost peripheral wall portion of the partition member. The partition member has a bottom portion connected to the lower end of the wall portion.
The planar light source according to claim 6 or 7, wherein the bottom portion has a through hole in which the light source is arranged. The planar light source according to claim 8, wherein the bottom portion extends to the peripheral edge of the mounting substrate in a plan view. The thin plate portion is located on the first thin plate portion on the thick plate portion side and the outer edge side of the light diffusion plate with respect to the first thin plate portion, and the second thin plate portion having a thinner plate thickness than the first thin plate portion. The planar light source according to any one of claims 1 to 9, further comprising. The planar light source according to any one of claims 6 to 9, wherein the wall portion is not provided on at least a part of the outermost periphery of the partition member. The planar light source according to any one of claims 1 to 11, further comprising a frame body surrounding the mounting substrate and the light diffusing plate. The planar light source according to claim 12, wherein the frame has an irregular shape and a shape similar to that of the mounting substrate. The planar light source according to claim 12 or 13, wherein the light diffusing plate has a deformed shape. The planar light source according to any one of claims 12 to 14, wherein the light diffusing plate, the mounting substrate, and the frame have similar shapes. In any one of claims 6 to 9, at least one of the regions located on the outermost circumference of the partition member has a larger area than the region located on the inner peripheral side of the outermost circumference in a plan view. The planar light source described. The planar light source according to any one of claims 1 to 16, further comprising a wavelength conversion layer that converts light from the light source into light having a different wavelength above the light diffusing plate. A liquid crystal display device using the planar light source according to any one of claims 1 to 17 as a backlight light source.

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