JP2023106164A - Illuminating device - Google Patents

Abstract

To provide an illuminating device having high luminance.SOLUTION: An illuminating device comprises a plurality of first light emitting elements arranged in a matrix state, a light guide plate, and a plurality of second light emitting elements provided on at least a first side surface out of side surfaces of the light guide plate. Each of the plurality of first light emitting elements and each of the plurality of second light emitting elements emit blue light with an emission peak wavelength of 500 nm or less. A color conversion sheet absorbs the blue light, and emits light with a wavelength of 500 nm or more.SELECTED DRAWING: Figure 2A

Description

Embodiments of the present invention relate to lighting devices.

Illumination devices using monochromatic light have been developed as backlights for illuminating display panels.

Japanese Patent Application Laid-Open No. 2002-100229 JP-A-06-018882

This embodiment provides a lighting device with high brightness.

A lighting device according to one embodiment includes:
a wiring board;
a plurality of first light emitting elements provided on the wiring substrate and arranged in a matrix;
a transparent resin layer covering the first light emitting element;
a color conversion sheet provided on the transparent resin layer;
a dichroic sheet provided between the transparent resin layer and the color conversion sheet;
a light guide plate provided between the transparent resin layer and the color conversion sheet;
a plurality of second light emitting elements provided on at least a first side surface of the light guide plate;
a prism sheet provided on the color conversion sheet;
with
each of the plurality of first light emitting elements and each of the plurality of second light emitting elements emit blue light having an emission peak wavelength of 500 nm or less;
The color conversion sheet absorbs the blue light and emits light with a wavelength of 500 nm or longer.

Further, the lighting device according to one embodiment includes:
a wiring board;
a plurality of first light emitting elements provided on the wiring substrate and arranged in a matrix;
a transparent resin layer covering the first light emitting element;
a light guide plate provided on the transparent resin layer;
a plurality of second light emitting elements provided on at least a first side surface of the light guide plate;
a diffusion sheet provided on the light guide plate;
a prism sheet provided on the diffusion sheet;
with
Each of the plurality of first light emitting elements and each of the plurality of second light emitting elements emits white light in a wavelength range of 360 nm to 830 nm.

FIG. 1 is an exploded perspective view showing an example of a schematic configuration of a display device according to this embodiment. FIG. 2A is a cross-sectional view showing an example of a schematic configuration of the lighting device of this embodiment. FIG. 2B is a plan view showing an example of a schematic configuration of the lighting device of this embodiment. FIG. 3A is a cross-sectional view showing another configuration example of the lighting device according to the embodiment. FIG. 3B is a plan view showing another configuration example of the lighting device according to the embodiment; FIG. 4 is a cross-sectional view showing another configuration example of the lighting device according to the embodiment. FIG. 5 is a cross-sectional view showing another configuration example of the lighting device according to the embodiment.

Each embodiment of the present invention will be described below with reference to the drawings. It should be noted that the disclosure is merely an example, and those skilled in the art can easily conceive appropriate modifications while keeping the gist of the invention are, of course, included in the scope of the present invention. In addition, in order to make the description clearer, the drawings may schematically show the width, thickness, shape, etc. of each part compared to the actual embodiment, but this is only an example, and the interpretation of the present invention is not intended. It is not limited. In addition, in this specification and each figure, the same reference numerals may be given to the same elements as those described above with respect to the existing figures, and detailed description thereof may be omitted as appropriate.
Hereinafter, a lighting device according to an embodiment will be described in detail with reference to the drawings.

In this embodiment, the first direction X, the second direction Y, and the third direction Z are orthogonal to each other, but they may intersect at an angle other than 90 degrees. The direction toward the tip of the arrow in the third direction Z is defined as upward or upward, and the direction opposite to the direction toward the tip of the arrow in the third direction Z is defined as downward.

In addition, when "the second member above the first member" and "the second member below the first member" are used, the second member may be in contact with the first member or separated from the first member. may be located In the latter case, a third member may be interposed between the first member and the second member. On the other hand, when "the second member above the first member" and "the second member below the first member" are used, the second member is in contact with the first member.

In addition, it is assumed that there is an observation position for observing the lighting device on the tip side of the arrow in the third direction Z, and from this observation position the XY plane defined by the first direction X and the second direction Y is viewed. This is called planar view. Viewing a cross section of the lighting device on the XZ plane defined by the first direction X and the third direction Z or the YZ plane defined by the second direction Y and the third direction Z is referred to as a cross-sectional view.

FIG. 1 is an exploded perspective view showing an example of a schematic configuration of a display device according to this embodiment. The display device DSP includes an illumination device ILD and a display panel PNL. In this embodiment, the display panel PNL is a generally known transmissive or transflective liquid crystal display panel.

The illumination device ILD includes a wiring board CBS, a plurality of light emitting elements LEM, a drive unit DVM, a protective layer OC, a light guide plate LG, a dichroic sheet DCS, a color conversion sheet CVS, and a prism sheet PSM. ing. The wiring board CBS, the light emitting elements LEM, the protective layer OC, the light guide plate LG, the dichroic sheet DCS, the color conversion sheet CVS, and the prism sheet PSM are laminated in the third direction Z in this order.

In other words, the dichroic sheet DCS is provided between the protective layer OC and the color conversion sheet CVS. The light guide plate LG is provided between the protective layer OC and the color conversion sheet CVS. The light guide plate LG is provided between the protective layer OC and the dichroic sheet DCS.

In this embodiment, the wiring board CBS is composed of a printed circuit board (PCB). However, the wiring board CBS is not limited to the printed circuit board, and may be configured by a flexible printed circuit (FPC). The wiring board CBS has a main surface MSF. A light emitting area LA is provided on the main surface MSF.

A plurality of light emitting elements LEM are provided in the light emitting area LA. The plurality of light emitting elements LEM are arranged in a matrix along the first direction X and the second direction Y. As shown in FIG. In this embodiment, the light emitting element LEM is a mini LED (mini light emitting diode). On the main surface MSF, outside the light emitting area LA, a driving unit DVM for driving the plurality of light emitting elements LEM is mounted. The light emitting element LEM emits light in a specific wavelength range. For example, the light emitting element LEM emits blue light with an emission peak wavelength of 500 nm or less.

In plan view, the light emitting element LEM has a square shape. However, the shape of the light emitting element LEM may have a shape other than square, such as a rectangle. In plan view, the length of one side of the light emitting element LEM, which is a mini LED, is, for example, more than 100 μm and less than 300 μm. The length of one side of the light emitting element LEM which is a mini LED may be more than 100 μm and 200 μm or less.

The light-emitting element LEM may be a micro-LED having a longest side length of 100 μm or less, which is smaller than the mini-LED. Alternatively, the light emitting element LEM may be an LED whose longest side is 1 mm or less. Alternatively, the light-emitting element LEM may be an LED having a longest side length of 1000 μm or more, which is a general LED that is larger than the mini-LED. The length of one side of the light-emitting element LEM, which is the general LED, is, for example, 300 μm or more and 350 μm or less.

The light emitting elements LEM are simultaneously or separately driven on and off by the driver DVM. For example, the driving unit DVM can be driven by a technique called local dimming. In the local dimming drive, the plurality of light emitting elements LEM are independently driven and controlled for each divided area. Only the area of the image that needs to be illuminated is illuminated by the light emitting element LEM, and the area of the image that does not need to be illuminated is not illuminated by the illumination light from the light emitting element LEM. That is, the plurality of light emitting elements LEM are turned on only in areas of the image that need to be illuminated, and the light emitting elements LEM are turned off in areas that do not need to be illuminated. This makes it possible to further increase the contrast ratio of the image displayed on the display panel PNL.

The protective layer OC is configured as a light transmission layer that transmits the wavelength of light emitted by the light emitting element LEM. The protective layer OC is made of transparent resin, more specifically silicone resin, for example. The protective layer OC may be provided so as to cover the light emitting element LEM.

The light guide plate LG has side surfaces S1 and S2 facing each other and located on opposite sides. A plurality of light emitting elements LS are provided on the side surface S1. In FIG. 1, the plurality of light emitting elements LS are arranged side by side along a direction parallel to the second direction Y. In FIG. Although not shown, the light guide plate LG is provided with, for example, triangular prism-shaped or dot-shaped projections or grooves on the main surface parallel to the XY plane.
The light guide plate LG has a predetermined thickness and also has the function of diffusing the light emitted from the light emitting element LEM.

The light emitting element LS emits light in a specific wavelength range, like the light emitting element LEM. For example, the light emitting element LS emits blue light with an emission peak wavelength of 500 nm or less. The light emitting elements LS and LEM may emit light in the same range of wavelength regions. The light emitting element LS may be a light emitting diode (LED), but may be a mini LED or a micro LED.

Note that when there is no local dimming drive, for example, when the display panel PNL displays a still image, only the light emitting element LS may be lit without lighting the light emitting element LEM. Thereby, it is possible to reduce the power consumption of the illumination device ILD.

Light emitted from the light emitting element LS enters the light guide plate LG from the side surface S1 and propagates through the inside of the light guide plate LG while being totally reflected. The reflection angle of the light is changed by the projections or grooves, and the light is emitted upward.

A dichroic sheet DCS is an optical sheet that reflects light in a specific wavelength range and transmits light in other wavelength ranges. Of the light emitted from the light guide plate LG, the dichroic sheet DCS transmits only blue light and reflects light in other wavelength regions. By reflecting the light in the other wavelength range, it is possible to suppress the light in the unnecessary wavelength range from entering the color conversion sheet CVS.

The color conversion sheet CVS is a wavelength conversion element that absorbs light emitted from the light emitting element LEM and emits light with a wavelength of 500 nm or more. For example, the color conversion sheet CVS may be a phosphor, absorbs blue light, and emits white light.

The prism sheet PSM is composed of two orthogonally arranged refractive prism sheets PSM1 and PSM2. However, the prism sheet PSM may be composed of a total reflection prism sheet instead of the refractive prism sheet PSM1. The total reflection type prism sheet has a simple structure and is excellent in light utilization efficiency and vertical light convergence.

Here, consider a lighting device in which the light emitting element LS is not provided.
A backlight for illuminating the display panel needs to have high luminance when the size of the display area of the display panel (the size on the XY plane) is small and the definition is high. In particular, in a lighting device (backlight) using mini-LEDs, increasing the current flowing through the mini-LEDs or increasing the number of mini-LEDs is conceivable in order to achieve higher brightness.

However, increasing the current flowing through the mini-LEDs may increase the power consumption of the lighting device and the temperature of the lighting device. Increasing the number of mini-LEDs may increase the manufacturing cost of the lighting device. Moreover, the fact that the size of the display area of the display panel is small means that the size of the illumination device must also be small. This limits the number of mini-LEDs that can be mounted.

The illumination device ILD of the present embodiment is provided with a light emitting element LS in addition to the light emitting element LEM. As a result, it is possible to increase the brightness without changing the size of the illumination device ILD.

FIG. 2A is a cross-sectional view showing an example of a schematic configuration of the lighting device of this embodiment. FIG. 2B is a plan view showing an example of a schematic configuration of the lighting device of this embodiment. Some of the components shown in FIG. 1 have been omitted from FIGS. 2A and 2B for clarity of illustration.
A flexible wiring board FC is connected to the plurality of light emitting elements LS. A drive signal from the outside is input to the light emitting element LS via the flexible wiring board FC. Lighting and extinguishing of the light emitting element LS are controlled based on the drive signal.

Let WX and WY be the lengths of one light emitting element LEM in the first direction X and the second direction Y, respectively. In the present embodiment, the lengths WX and WY are each, for example, 0.1 mm or more and 0.5 mm or less (100 μm or more and 500 μm or less).
Let PX and PY be the pitches of adjacent light emitting elements LEM in the first direction X and the second direction Y, respectively. In the present embodiment, the pitches PX and PY are, for example, 0.3 mm or more and 0.7 mm or less, and more preferably 0.3 mm or more and 0.4 mm or less.

The illumination device ILD of this embodiment includes a light emitting element LEM arranged directly below the display panel PNL and a light emitting element LS provided on the side surface of the light guide plate LG. As a result, even if the size of the illumination device ILD is small, it is possible to emit illumination light with high brightness.

<Configuration example 1>
FIG. 3A is a cross-sectional view showing another configuration example of the lighting device according to the embodiment. FIG. 3B is a plan view showing another configuration example of the lighting device according to the embodiment; The configuration example shown in FIGS. 3A and 3B is different from the configuration example shown in FIGS. 2A and 2B in that light emitting elements are provided on both side surfaces of the light guide plate.

In the lighting device ILD shown in FIGS. 3A and 3B, a plurality of light emitting elements LS are provided not only on the side surface S1 of the light guide plate LG but also on the side surface S2. These light emitting elements LS are provided with a flexible wiring board FC like the light emitting elements LS provided on the side surface S1.
This configuration example also has the same effect as the embodiment.

<Configuration example 2>
FIG. 4 is a cross-sectional view showing another configuration example of the lighting device according to the embodiment. The configuration example shown in FIG. 4 differs from the configuration example shown in FIG. 2A in that the dichroic sheet DCS is positioned between the protective layer OC and the light guide plate LG.
In the illumination device ILD shown in FIG. 2A, the light guide plate LG is provided between the protective layer OC and the dichroic sheet DCS. On the other hand, in the illumination device ILD shown in FIG. 4, the dichroic sheet DCS is provided between the protective layer OC and the light guide plate LG.

The dichroic sheet DCS transmits blue light in a direction parallel to the third direction Z. However, light incident obliquely with respect to the third direction Z can be reflected. For example, part of the light emitted from the light emitting element LS passes through the light guide plate LG and is emitted below the light guide plate LG. The part of the light is emitted obliquely with respect to the third direction Z. As shown in FIG. The dichroic sheet DCS reflects such light. Some of the reflected light passes through the dichroic sheet DCS again and is emitted upward. This makes it possible to obtain illumination light with high brightness.

A plurality of light emitting elements LS are provided on the side surface S1 of the light guide plate LG. As in FIG. 3A, a plurality of light emitting elements LS may also be provided on the side surface S2.
This configuration example also has the same effect as the embodiment.

<Configuration example 3>
FIG. 5 is a cross-sectional view showing another configuration example of the lighting device according to the embodiment. The configuration example shown in FIG. 5 is different from the configuration example shown in FIG. 2A in that the light emitting element emits white light.
The lighting device ILD shown in FIG. 5 includes a wiring board CBS, a light emitting element LEM, a protective layer OC, a light guide plate LG, a diffusion sheet DFS, and a prism sheet PSM, which are laminated in this order along the third direction Z. there is

A plurality of light emitting elements LS are provided on the side surface S1 of the light guide plate LG. As in FIG. 3A, a plurality of light emitting elements LS may also be provided on the side surface S2.

The light-emitting elements LEM and LS are, for example, light-emitting elements that emit white light in a wavelength range of 360 nm or more and 830 nm or less.
The illumination device ILD shown in FIG. 5 does not have a dichroic sheet and a color conversion sheet. A diffusion sheet DFS is provided between the light guide plate LG and the prism sheet PSM. The diffusion sheet DFS diffuses incident light to uniform the brightness of the light.
This configuration example also has the same effect as the embodiment.

In this disclosure, the light emitting elements LEM and LS are referred to as the first light emitting element and the second light emitting element, respectively.
Sides S1 and S2 of the light guide plate LG are also referred to as a first side and a second side, respectively.

While several embodiments of the invention have been described, these embodiments have been presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and modifications can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the scope of the invention described in the claims and equivalents thereof.

CBS... wiring board, CVS... color conversion sheet, DCS... dichroic sheet, DSP... display device, DVM... drive unit, ILD... illumination device, LEM... light emitting element, LG... light guide plate, LS... light emitting element, S1... side surface, S2... side.

Claims (7)

a wiring board;
a plurality of first light emitting elements provided on the wiring substrate and arranged in a matrix;
a transparent resin layer covering the first light emitting element;
a color conversion sheet provided on the transparent resin layer;
a dichroic sheet provided between the transparent resin layer and the color conversion sheet;
a light guide plate provided between the transparent resin layer and the color conversion sheet;
a plurality of second light emitting elements provided on at least a first side surface of the light guide plate;
a prism sheet provided on the color conversion sheet;
with
each of the plurality of first light emitting elements and each of the plurality of second light emitting elements emit blue light having an emission peak wavelength of 500 nm or less;
The lighting device, wherein the color conversion sheet absorbs the blue light and emits light having a wavelength of 500 nm or more. The lighting device according to claim 1, wherein the color conversion sheet emits white light. The lighting device according to claim 1, wherein the light guide plate is provided between the transparent resin layer and the dichroic sheet. The lighting device according to claim 1, wherein the dichroic sheet is provided between the transparent resin layer and the light guide plate. the plurality of second light emitting elements provided on a second side surface opposite to the first side surface;
2. The lighting device of claim 1, further comprising: a wiring board;
a plurality of first light emitting elements provided on the wiring substrate and arranged in a matrix;
a transparent resin layer covering the first light emitting element;
a light guide plate provided on the transparent resin layer;
a plurality of second light emitting elements provided on at least a first side surface of the light guide plate;
a diffusion sheet provided on the light guide plate;
a prism sheet provided on the diffusion sheet;
with
The illumination device, wherein each of the plurality of first light emitting elements and each of the plurality of second light emitting elements emits white light in a wavelength range of 360 nm or more and 830 nm or less. the plurality of second light emitting elements provided on a second side surface opposite to the first side surface;
7. The lighting device of claim 6, further comprising:

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