Light-emitting diode and backlight device

Abstract

The present technology relates to a light-emitting diode and a backlight device that make it possible to improve wide light distribution characteristics. A light-emitting diode according to the present invention comprises: a first transparent substrate; a light-emitting layer that is disposed on one surface side of the first transparent substrate; a second transparent substrate that is disposed on the other surface side of the first transparent substrate; a wavelength conversion layer that is disposed between the first transparent substrate and the second transparent substrate; and a light-reflecting layer that is formed on a surface of the second transparent substrate on the opposite side from the wavelength conversion layer. The present technology is applicable to a backlight device.

Description

Light Emitting Diode and Backlight Device

[0001] The present technology relates to a light emitting diode and a backlight device, and particularly to a light emitting diode and a backlight device capable of improving the wide light distribution characteristics.

[0002] Conventionally, a liquid crystal display using a light emitting diode called a mini LED (Light Emitting Diode) as a light source of a backlight device is known.

[0003] For such a liquid crystal display, cost reduction is required. As one method of cost reduction, instead of providing a wavelength conversion sheet for white light emission, a method of providing a phosphor on each light emitting diode has been proposed (see, for example, Patent Document 1). For example, in Patent Document 1, it is disclosed that by covering a light emitting element with two wavelength conversion members (phosphors) and providing a light transmissive member between these wavelength conversion members, the light extraction efficiency can be improved.

[0004] Japanese Patent Application Laid-Open No. 2022-101066

[0005] By the way, for cost reduction of a liquid crystal display, widening the light distribution of a light emitting diode is also required. This is because by improving the wide light distribution characteristics of the light emitting diode, the number of light emitting diodes used in the liquid crystal display can be reduced.

[0006] However, it has been difficult to obtain good wide light distribution characteristics with the above-described technology.

[0007] For example, in the technology described in Patent Document 1, the light emitting surface of the light emitting diode is formed by a wavelength conversion member (phosphor), and isotropic scattering occurs on the emitting surface, so widening the light distribution could not be achieved.

[0008] The present technology has been made in view of such a situation, and is intended to improve the wide light distribution characteristics.

[0009] The first aspect of this technology is a light-emitting diode comprising a first transparent substrate, a light-emitting layer disposed on one side of the first transparent substrate, a second transparent substrate disposed on the other side of the first transparent substrate, a wavelength conversion layer disposed between the first transparent substrate and the second transparent substrate, and a light-reflecting layer formed on the side of the second transparent substrate opposite to the wavelength conversion layer.

[0010] The light-emitting diode of the second aspect of this technology comprises a transparent substrate, a light-emitting layer disposed on one side of the transparent substrate, a wavelength conversion layer disposed on the other side of the transparent substrate, and a light-reflecting layer formed on the side of the wavelength conversion layer opposite to the transparent substrate.

[0011] A third aspect of this technology, the backlight device comprises a light-emitting diode and a light guide layer disposed around the light-emitting diode, wherein the light-emitting diode comprises a first transparent substrate, a light-emitting layer disposed on one side of the first transparent substrate, a second transparent substrate disposed on the other side of the first transparent substrate, a wavelength conversion layer disposed between the first transparent substrate and the second transparent substrate, and a light-reflecting layer formed on the side of the second transparent substrate opposite to the wavelength conversion layer.

[0012] A fourth aspect of this technology, the backlight device comprises a light-emitting diode and a light guide layer disposed around the light-emitting diode, wherein the light-emitting diode comprises a transparent substrate, a light-emitting layer disposed on one side of the transparent substrate, a wavelength conversion layer disposed on the other side of the transparent substrate, and a light-reflecting layer formed on the side of the wavelength conversion layer opposite to the transparent substrate.

[0013] This is a diagram showing an example of the configuration of a display device. This is a diagram showing a cross-section of a display device. This is a diagram showing an example of the configuration of a light-emitting diode. This is a diagram explaining wide light distribution. This is a diagram showing the intensity within the medium. This is a diagram showing the transmittance. This is a diagram explaining the characteristics of the output light emitted from the output surface. This is a diagram explaining the characteristics of the output light emitted from the output surface. This is a diagram showing an example of the configuration of a light-emitting diode. This is a diagram showing an example of the configuration of a display device. This is a diagram showing a cross-section of a display device. This is a diagram explaining the light scattering region. This is a diagram showing a cross-section of a display device.

[0014] The following describes embodiments to which this technology is applied, with reference to the drawings.

[0015] <First Embodiment> <Example of Display Device Configuration> Figure 1 shows an example of the configuration of one embodiment of a display device to which this technology is applied.

[0016] The display device 11 shown in Figure 1 is, for example, a display device such as a liquid crystal display or a liquid crystal television. More specifically, Figure 1 shows only a part of the configuration of the display device 11, particularly the configuration around the backlight portion.

[0017] The display device 11 includes a liquid crystal cell 21, an optical sheet 22, a diffuser plate 23, and a printed circuit board 24. In particular, in this example, the portion from the optical sheet 22 to the printed circuit board 24 functions as a backlight device 31 that outputs light to serve as a backlight.

[0018] In the display device 11, multiple light-emitting diodes to which this technology is applied are arranged in a row on the upper surface (upper surface in the figure) of the printed circuit board 24. In particular, when the upper surface of the printed circuit board 24 is viewed from a direction perpendicular to its upper surface, multiple light-emitting diodes are arranged in a row in the vertical and horizontal directions.

[0019] A diffuser plate 23 is positioned on the upper surface of the printed circuit board 24 at a predetermined distance from the upper surface. An optical sheet 22 is positioned adjacent to the side of the diffuser plate 23 opposite to the printed circuit board 24. Furthermore, a liquid crystal cell 21 is positioned adjacent to the side of the optical sheet 22 opposite to the diffuser plate 23.

[0020] Figure 2 shows a cross-sectional view of the display device 11.

[0021] As described above, multiple light-emitting diodes 61 are arranged in a row on the upper surface of the printed circuit board 24, and these light-emitting diodes 61 are covered with a transparent potting resin 62 made of silicon or the like. In Figure 2, for the sake of clarity, only some of the multiple light-emitting diodes 61 and potting resin 62 are labeled with reference numerals.

[0022] In Figure 2, the lower part shows a magnified view of the area surrounding one light-emitting diode 61. In this example, the potting resin 62 covering the light-emitting diode 61 is hemispherical in shape, with the light-emitting diode 61 positioned at the center of the hemisphere.

[0023] The light-emitting diode 61 consists of an LED chip and functions as an LED light source. That is, the light-emitting diode 61 outputs light that serves as a backlight. For example, the light-emitting diode 61 outputs white light.

[0024] The light-emitting diode 61 emits light that spreads laterally in the figure and is directed toward the diffuser plate 23. The light emitted by the light-emitting diode 61 (hereinafter also referred to as output light) passes through the potting resin 62 and enters the diffuser plate 23, where it is diffused to a uniform distribution before entering the optical sheet 22.

[0025] The optical sheet 22 controls the viewing angle, enhances brightness through a light-gathering effect, and controls the polarization direction (polarization state) of the output light incident from the diffuser plate 23. The output light emitted from the optical sheet 22 passes through the liquid crystal cell 21 and is output to the outside of the display device 11. The liquid crystal cell 21 adjusts the light intensity of the output light incident from the optical sheet 22 and outputs the adjusted light intensity to display a predetermined image. The liquid crystal cell 21 may also be provided with a color filter.

[0026] <Example of Light-Emitting Diode Configuration> Figure 3 shows a more detailed example of the configuration of the light-emitting diode 61.

[0027] In the example shown in Figure 3, the light-emitting diode 61 has a light-reflecting layer 81, a transparent substrate 82, a wavelength conversion layer 83, a sapphire substrate 84, a light-emitting layer 85, and an electrode layer 86.

[0028] In the light-emitting diode 61, the electrode layer 86 to the light-reflecting layer 81 are arranged in order from the printed circuit board 24 side, that is, from the bottom in the diagram.

[0029] The light-emitting layer 85 is an epitaxial layer made of semiconductor material, and its lower surface in the diagram is connected to the printed circuit board 24 via an electrode layer 86. When a predetermined voltage is applied to the light-emitting layer 85 via the electrode layer 86, the light-emitting layer 85 emits light. That is, the light-emitting layer 85 emits light (output light) of a predetermined color. For example, the output light emitted by the light-emitting layer 85 may be blue light.

[0030] The sapphire substrate 84 is a transparent substrate and is provided between the light-emitting layer 85 and the wavelength conversion layer 83. Specifically, the light-emitting layer 85 is provided adjacent to one side of the sapphire substrate 84 (the lower side in the figure), and the wavelength conversion layer 83 is provided adjacent to the other side of the sapphire substrate 84 (the upper side in the figure). The sapphire substrate 84 guides the output light incident from the light-emitting layer 85 to the wavelength conversion layer 83.

[0031] The wavelength conversion layer 83 is made of phosphor and is placed between the sapphire substrate 84 and the transparent substrate 82. The wavelength conversion layer 83 converts the wavelength of the output light incident from the sapphire substrate 84 and directs it onto the transparent substrate 82. For example, in the wavelength conversion layer 83, blue output light is converted into white output light.

[0032] The transparent substrate 82 is a transparent substrate, such as a sapphire substrate, and is positioned on the side opposite to the light-emitting layer 85 when viewed from the sapphire substrate 84. A wavelength conversion layer 83 is positioned adjacent to one side of the transparent substrate 82, that is, the side facing the sapphire substrate 84, and a light-reflecting layer 81 is formed (positioned) on the other side of the transparent substrate 82, that is, the side opposite to the sapphire substrate 84. The transparent substrate 82 and the sapphire substrate 84 may be formed from the same material such as sapphire, or they may be formed from different materials.

[0033] The light-reflecting layer 81 is a DBR (Distributed Bragg Reflector) layer consisting of a reflective film formed on the upper surface of the transparent substrate 82, that is, on the side opposite to the wavelength conversion layer 83, and reflects the output light incident from the transparent substrate 82.

[0034] In the transparent substrate 82, the surface adjacent to the wavelength conversion layer 83 is the incident surface 91 for the output light, and the output light emitted from the wavelength conversion layer 83 enters the transparent substrate 82 from the incident surface 91.

[0035] Furthermore, in the transparent substrate 82, the side surface of the transparent substrate 82 serves as the output light emission surface 92. The output light emitted from the wavelength conversion layer 83 enters the transparent substrate 82 from the incident surface 91, then exits from the emission surface 92, and enters the diffuser plate 23 via the potting resin 62.

[0036] In particular, in the example shown in Figure 3, the incident surface 91 and the exit surface 92 are formed such that the exit surface 92 is perpendicular or approximately perpendicular to the incident surface 91, in order to obtain good radiation angle characteristics in the light-emitting diode 61, or in other words, to obtain good wide-angle light distribution characteristics. That is, the angle between the incident surface 91 and the exit surface 92 of the output light on the transparent substrate 82 is 90 degrees or approximately 90 degrees. Here, approximately 90 degrees refers to an angle within a range of approximately ±10 degrees from 90 degrees. Therefore, 90 degrees or approximately 90 degrees refers to an angle within a range of approximately 80 to 100 degrees. In the following, when we refer to 90 degrees or approximately 90 degrees, we mean an angle within a range of approximately 80 to 100 degrees.

[0037] In the light-emitting diode 61, the output light generated by the light-emitting layer 85 is incident on the wavelength conversion layer 83 via the sapphire substrate 84. In the wavelength conversion layer 83, wavelength conversion is performed on the output light incident from the light-emitting layer 85 via the sapphire substrate 84, and the wavelength-converted output light is incident on the transparent substrate 82 from the wavelength conversion layer 83. That is, the output light emitted from the wavelength conversion layer 83 is incident on the interior of the transparent substrate 82 from the incident surface 91.

[0038] The output light that enters the interior of the transparent substrate 82 either travels through the transparent substrate 82 and is emitted to the outside from the emission surface 92, or, after traveling through the transparent substrate 82, is reflected once or multiple times by the light reflection layer 81, etc., and is emitted to the outside from the emission surface 92.

[0039] More specifically, a part of the output light output from the light emitting layer 85 exits from the side surface of the sapphire substrate 84 without entering the wavelength conversion layer 83. Therefore, in the light emitting diode 61, the concentration of the phosphor in the wavelength conversion layer 83 is adjusted so that the output light emitted from the transparent substrate 82 to the outside and the output light emitted from the side surface of the sapphire substrate 84 to the outside are combined and the white output light as a whole enters the diffusion plate 23.

[0040] Further, in the light emitting diode 61, the portion composed of the sapphire substrate 84, the light emitting layer 85, and the electrode layer 86 forms an LED chip, and the wavelength conversion layer 83 is formed on the upper surface of the LED chip.

[0041] Since the incident surface 91 of the transparent substrate 82 is flat, the portion composed of the portion from the sapphire substrate 84 to the electrode layer 86 (LED chip) and the wavelength conversion layer 83 in the light emitting diode 61, that is, the portion surrounded by the dotted line frame W11 can be regarded as a surface light source. Therefore, it can also be said that the configuration of the light emitting diode 61 is a configuration in which the transparent substrate 82 is disposed on the surface light source and the light reflecting layer 81 is formed on the upper surface of the transparent substrate 82.

[0042] The light emitting diode 61 is characterized in that the angle formed by the incident surface 91 and the exit surface 92 of the output light in the transparent substrate 82 is 90 degrees or approximately 90 degrees, no phosphor or the like is formed on the exit surface 92, and the light beam angle of the output light exit portion is maintained.

[0043] By having such characteristics, the light emitting diode 61 can achieve wide distribution of the output light, and as a result, the cost of the display device 11 can be reduced.

[0044] Hereinafter, referring to FIG. 4, the wide distribution of the output light will be described.

[0045] As described above, the portion composed of the LED chip and the wavelength conversion layer 83 in the light emitting diode 61 can be regarded as a surface light source. Therefore, the configuration of the light emitting diode 61 is equivalent to a configuration in which the transparent substrate 82 is provided on the upper surface of the surface light source 111 and the light reflecting layer 81 is formed on the upper surface of the transparent substrate 82 as shown by the arrow Q11 in FIG. 4.

[0046] When the surface light source 111 emits light, the output light from the surface light source 111 is incident on the transparent substrate 82 from the incident surface 91. At this time, on the incident surface 91, the output light spreads isotropically and enters the transparent substrate 82. In FIG. 4, each arrow drawn in the transparent substrate 82 represents the output light. In particular, the direction of the arrow indicates the propagation direction of the output light.

[0047] Among the output light incident on the inside of the transparent substrate 82, those with a small angle with the incident surface 91 or those incident on the transparent substrate 82 at a position close to the exit surface 92 are directly emitted from the exit surface 92 without being reflected by the light reflection layer 81. The output light thus emitted from the exit surface 92 is emitted obliquely upward in the figure.

[0048] On the other hand, those of the output light with a large angle with the incident surface 91 are reflected by the light reflection layer 81. For example, a part of the output light reflected by the light reflection layer 81 travels obliquely downward in the figure and is emitted from the exit surface 92.

[0049] Therefore, the light distribution characteristics of the output light emitted from the exit surface 92, that is, the radiation angle characteristics, are as shown by the arrow Q12. More specifically, in the part indicated by the arrow Q12, the distribution of the light quantity of the output light emitted from each direction from the position (point) on the exit surface 92 is shown.

[0050] To explain the structure of the light-emitting diode 61 and the principle of the light distribution in more detail, since the radiation characteristics in the transparent substrate 82 are isotropic radiation from the surface light source 111 on the lower side in FIG. 4, it shows Lambertian characteristics as shown in FIG. 5. In FIG. 5, the horizontal axis represents the angle, and the vertical axis represents the in-medium intensity ratio. The angle here is the angle when looking at the cross-section of the transparent substrate 82, with the vertical direction in FIG. 4, that is, the direction perpendicular to the surface of the surface light source 111, being 0 degrees, and the horizontal direction in FIG. 4, that is, the direction parallel to the surface of the surface light source 111, being 90 degrees.

[0051] In addition, the transmission characteristics of the output light emitted from inside the transparent substrate 82 through the emission surface 92 are similar to those in Figure 5, but due to the difference in refractive index between the medium, i.e., the transparent substrate 82 and the resin (potting resin 62), they exhibit the characteristics shown in Figure 6. In Figure 6, the horizontal axis represents the same angle as in Figure 5, and the vertical axis represents the transmittance of the output light.

[0052] From these observations, the output light emitted from the emission surface 92 is the product of the radiation characteristics and transmission characteristics described above, resulting in the characteristics shown in Figure 7. In Figure 7, the horizontal axis represents the same angle as in Figure 5, and the vertical axis represents the intensity of the output light (emission light intensity).

[0053] Furthermore, when the characteristics in Figure 7 are illustrated in conjunction with the cross-sectional view of the light-emitting diode 61, the image becomes as shown on the right side of Figure 8, demonstrating that the characteristics achieve wide-angle illumination while suppressing light emission toward the front.

[0054] Returning to the explanation of Figure 4, in the section indicated by arrow B11, the direction and size (length) of the arrow originating from the emission surface 92 represent the direction of emission of the output light and the amount of output light emitted in that direction. Therefore, the dotted curves passing through the endpoints of each arrow show the distribution of the amount of output light emitted from the emission surface 92. Note that in the section indicated by arrow Q12, the distribution of output light is only shown for the emission surface 92 on the right side of the figure, but the distribution of light intensity for the emission surface 92 on the left side is similar (a symmetrical distribution).

[0055] In this example, since the surface light source 111 is located on the lower side of the transparent substrate 82 having an emission surface 92, the amount of output light emitted diagonally upward in the figure is greater than the amount of output light emitted diagonally downward in the figure.

[0056] Based on the above, the radiation angle characteristics of the light-emitting diode 61 as a whole, in other words, the light distribution characteristics, are as shown by arrow Q13.

[0057] In this example, the starting point of each arrow is the position of the light-emitting diode 61, and it can be seen that the output light spreads laterally from the light-emitting diode 61 and then travels upward in the diagram, that is, towards the diffuser plate 23. In other words, it can be seen that wide-angle light distribution of the output light has been achieved.

[0058] Regarding the light distribution characteristics of the light-emitting diode 61, the emission surface 92, which is the side wall of the transparent substrate 82 made of a sapphire substrate or the like, exhibits a wide-angle characteristic, while the upper surface of the transparent substrate 82 (the upper surface in Figure 4) has a Lambertian characteristic. Therefore, by providing a light-reflecting layer 81 on the upper surface of the transparent substrate 82 to suppress the emission of output light from the upper surface, and emitting output light from the emission surface 92 which is perpendicular or approximately perpendicular to the incident surface 91, light focusing can be obtained. In other words, good wide-angle light distribution characteristics can be obtained as shown by arrow Q13.

[0059] Furthermore, in the transparent substrate 82, the emission surface 92 is not in contact with a substance that diffuses (scatters) the output light, such as a phosphor, so the light-emitting diode 61 can be given a desired emission angle characteristic. In the light-emitting diode 61, a wavelength conversion layer 83 is provided to emit output light of a desired color, such as white light, but the light is scattered in the wavelength conversion layer 83. Therefore, in the light-emitting diode 61, by laminating a transparent substrate 82 with a light-reflecting layer 81 formed on its upper surface with respect to the wavelength conversion layer 83, it is not necessary to place a phosphor adjacent to the emission surface 92, and the emission characteristics of the wavelength conversion layer 83 can be controlled, making it possible to obtain a desired emission angle characteristic.

[0060] From the above, it is possible to improve the wide-angle light distribution characteristics of the output light even when the input of output light to the transparent substrate 82 is a point source exhibiting isotropic scattering.

[0061] In typical display devices, a wavelength conversion sheet the same size as the display screen is sometimes placed between the diffuser plate 23 and the optical sheet 22 to input white light to the liquid crystal cell 21. However, placing such a wavelength conversion sheet increases costs. Furthermore, in order to reduce the cost of display devices, there is a demand to reduce the number of light-emitting diodes (LEDs) that serve as the backlight source.

[0062] In a display device 11 to which this technology is applied, a wavelength conversion layer 83 made of phosphor is provided on each light-emitting diode 61, which makes it possible to reduce costs compared to providing a wavelength conversion sheet the same size as the display screen. Furthermore, as described above, this technology enables wide light distribution of the light-emitting diodes 61, making it possible to reduce the number of light-emitting diodes 61 provided in the display device 11. For these reasons, the display device 11 can be made more cost-effective compared to a general display device. Moreover, this technology does not require any special parts, and the light-emitting diodes 61 do not become larger, so a thin and low-cost display device 11 can be obtained.

[0063] Furthermore, by optimizing various conditions such as the size of the LED chip, the thickness of each layer, and the concentration and composition of the phosphor, it is possible to achieve the desired characteristics for the total emitted light color, luminous efficiency, and radiation angle characteristics.

[0064] <Second Embodiment> <Example of Light-Emitting Diode Configuration> The light-emitting diode provided in the display device 11 is not limited to the configuration shown in Figure 3, but may also be configured as shown in Figure 9. That is, in the display device 11, the light-emitting diode 141 shown in Figure 9 may be provided instead of the light-emitting diode 61 shown in Figure 3. Note that in Figure 9, the same reference numerals are used for parts corresponding to those in Figure 3, and their explanations are omitted as appropriate.

[0065] The light-emitting diode 141 shown in Figure 9 has a light-reflecting layer 81, a wavelength conversion layer 83, a sapphire substrate 84, a light-emitting layer 85, and an electrode layer 86. In other words, the configuration of the light-emitting diode 141 is the same as that of the light-emitting diode 61 but without the transparent substrate 82.

[0066] In the light-emitting diode 141, the electrode layer 86, light-emitting layer 85, sapphire substrate 84, wavelength conversion layer 83, and light-reflecting layer 81 are arranged in order from the printed circuit board 24 side, that is, from the bottom in the figure.

[0067] Therefore, in this example, an emissive layer 85 is arranged (formed) adjacent to one side of the transparent sapphire substrate 84, i.e., the lower side in the figure, and a wavelength conversion layer 83 is arranged (formed) adjacent to the other side of the sapphire substrate 84, i.e., the upper side in the figure. In addition, a light reflective layer 81 is formed adjacent to the side of the wavelength conversion layer 83 opposite to the sapphire substrate 84.

[0068] In the sapphire substrate 84, the surface adjacent to the light-emitting layer 85 is the incident surface 151 for the output light, and the output light emitted from the light-emitting layer 85 enters the sapphire substrate 84 from the incident surface 151.

[0069] Furthermore, the side surface of the sapphire substrate 84 serves as the output light emission surface 152. The output light emitted from the light-emitting layer 85 enters the sapphire substrate 84 from the incident surface 151, then proceeds through the sapphire substrate 84 and is emitted to the outside from the emission surface 152, or it proceeds from the sapphire substrate 84 to the wavelength conversion layer 83, and is reflected by the light reflection layer 81, etc., one or more times before being emitted to the outside from the emission surface 152.

[0070] In the example shown in Figure 9, similar to the example in Figure 3, the incident surface 151 and the exit surface 152 are formed such that the exit surface 152 is perpendicular or approximately perpendicular to the incident surface 151 in order to obtain good wide-angle light distribution characteristics. That is, the angle between the incident surface 151 and the exit surface 152 of the output light on the sapphire substrate 84 is 90 degrees or approximately 90 degrees.

[0071] Furthermore, in the light-emitting diode 141, the phosphor concentration in the wavelength conversion layer 83 is adjusted so that the output light emitted from the output surface 152 without passing through the wavelength conversion layer 83 from the sapphire substrate 84 and the output light emitted from the output surface 152 after passing through the wavelength conversion layer 83 are combined to produce white output light incident on the diffuser plate 23.

[0072] Even with the light-emitting diode 141 configured as described above, the wide light distribution characteristics can be improved by the same principle as explained with reference to Figure 4.

[0073] <Third Embodiment> <Example of Display Device Configuration> In the display device, instead of the light-emitting diode 61 shown in Figure 3 being covered by potting resin 62, the light-emitting diode 61 may be covered by a light guide layer.

[0074] In such cases, the display device is configured as shown in Figure 10, for example. Note that in Figure 10, the same reference numerals are used for parts corresponding to those in Figure 1, and their explanations are omitted as appropriate.

[0075] The display device 181 shown in Figure 10 includes a liquid crystal cell 21, an optical sheet 22, a diffuser plate 23, a light guide layer 191, and a printed circuit board 24. In particular, in this example, the portion from the optical sheet 22 to the printed circuit board 24 functions as a backlight device 201.

[0076] In the display device 181, multiple light-emitting diodes 61, configured as shown in Figure 3, are arranged in a row on the upper surface (upper surface in the figure) of the printed circuit board 24. However, in the example of Figure 10, unlike in Figure 1, the light-emitting diodes 61 are not covered with potting resin 62.

[0077] On the upper surface of the printed circuit board 24, a light guide layer 191 is arranged to surround each of the multiple light-emitting diodes 61, and a diffuser plate 23 is positioned at a predetermined distance from the light guide layer 191. The light guide layer 191 is made of a transparent resin such as silicone resin or acrylic resin (PMMA (Polymethyl methacrylate)).

[0078] Figure 11 shows a cross-sectional view of the display device 181.

[0079] As described above, multiple light-emitting diodes 61 are arranged in a row on the upper surface of the printed circuit board 24, and a light guide layer 191 is placed around these light-emitting diodes 61. In particular, each light-emitting diode 61 is covered by the light guide layer 191. Note that in Figure 11, for the sake of clarity, only some of the multiple light-emitting diodes 61 are labeled with reference numerals.

[0080] In Figure 11, the lower part shows a magnified view of the area surrounding one light-emitting diode 61. In this example, the area around the light-emitting diode 61 is covered by a light guide layer 191.

[0081] When the light-emitting diode 61 emits output light, that output light enters the light guide layer 191 and is guided to the diffuser plate 23 by the light guide layer 191. In other words, the light guide layer 191 directs the output light incident from each light-emitting diode 61 to the diffuser plate 23.

[0082] The output light that enters the diffuser plate 23 is output to the outside of the display device 181 through the optical sheet 22 and the liquid crystal cell 21, just as in the display device 11.

[0083] In the display device 181, by providing a light guide layer 191 between the light-emitting diode 61 and the diffuser plate 23, the output light can be incident on the diffuser plate 23 more efficiently and uniformly.

[0084] By adopting the above configuration, a thin and low-cost display device 181 can be obtained, similar to the case of the display device 11.

[0085] Furthermore, a predetermined scattering pattern may be formed on at least one surface of the light guide layer 191. That is, a light scattering region having a predetermined scattering pattern may be formed on at least one surface of the light guide layer 191.

[0086] In such cases, for example, as shown in Figure 12, it is conceivable to form a light scattering region 231 on the surface of the light guide layer 191 that faces the printed circuit board 24, that is, on the surface where the light-emitting diode 61 is located. In this example, the output light emitted from the light-emitting diode 61 diagonally downward in the figure is scattered by the light scattering region 231 and guided to the diffuser plate 23.

[0087] Furthermore, as shown by arrow Q51, the degree of scattering at each position in the light scattering region 231 may be made to change according to the distance from the light-emitting diode 61. That is, a scattering pattern may be formed such that the degree of scattering at each position in the light scattering region 231 increases or decreases as the distance from the light-emitting diode 61 increases. In this way, more uniform output light can be incident on the diffuser plate 23. Note that in Figure 12, an air layer (gap) is provided between the light-emitting diode 61 and the light guide layer 191, but this is not the only option, and various conditions can be optimally designed even in a configuration without an air layer.

[0088] <Fourth Embodiment> <Example of Display Device Configuration> The light-emitting diodes provided in the display device 181 are not limited to the configuration shown in Figure 3, but may also be configured as shown in Figure 9. That is, in the display device 181, the light-emitting diode 141 shown in Figure 9 may be provided instead of the light-emitting diode 61 shown in Figure 3.

[0089] In such cases, the display device 181 is configured as shown in Figure 13, for example. In particular, Figure 13 shows a cross-section of the display device 181, similar to the case in Figure 11. Note that parts in Figure 13 that correspond to those in Figure 11 or Figure 12 are given the same reference numerals, and their explanations are omitted as appropriate.

[0090] The display device 181 shown in Figure 13 includes a liquid crystal cell 21, an optical sheet 22, a diffuser plate 23, a light guide layer 191, and a printed circuit board 24, with the portion from the optical sheet 22 to the printed circuit board 24 functioning as a backlight device 201.

[0091] Multiple light-emitting diodes 141 are arranged in a row on the upper surface of the printed circuit board 24, and a light guide layer 191 is placed around these light-emitting diodes 141. In particular, each light-emitting diode 141 is covered by the light guide layer 191. Note that in Figure 13, for the sake of clarity, only some of the multiple light-emitting diodes 141 are labeled with reference numerals.

[0092] In Figure 13, the lower part shows a magnified view of the area surrounding one light-emitting diode 141. In this example, the area around the light-emitting diode 141 is covered by a light guide layer 191. A light scattering region 231 is formed on the printed circuit board 24 side of the light guide layer 191. Similar to the example in Figure 12, the degree of scattering in this light scattering region 231 changes depending on the distance from the light-emitting diode 141. That is, the light scattering region 231 has a scattering pattern in which the degree of scattering at each position in the light scattering region 231 increases or decreases as the distance from the light-emitting diode 141 increases.

[0093] In the display device 181 shown in Figure 13, when the light-emitting diode 141 emits output light, the output light enters the light guide layer 191 and is guided by the light guide layer 191 to the diffuser plate 23. The output light that enters the diffuser plate 23 is then diffused and output to the outside of the display device 181 through the optical sheet 22 and the liquid crystal cell 21.

[0094] By adopting the above configuration, a thin and low-cost display device 181 can be obtained, similar to the case in Figure 10. In Figure 13, an air layer (gap) is provided between the light-emitting diode 141 and the light guide layer 191, but this is not the only option, and various conditions can be optimally designed even in a configuration without an air layer.

[0095] Furthermore, the embodiments of this technology are not limited to those described above, and various modifications are possible without departing from the spirit of this technology.

[0096] Furthermore, this technology can also be configured as follows:

[0097] (1) A light-emitting diode comprising: a first transparent substrate; an emitting layer disposed on one side of the first transparent substrate; a second transparent substrate disposed on the other side of the first transparent substrate; a wavelength conversion layer disposed between the first transparent substrate and the second transparent substrate; and a light-reflecting layer formed on the side of the second transparent substrate opposite to the side of the wavelength conversion layer. (2) The light-emitting diode according to (1), wherein the angle between the incident surface of light from the emitting layer and the exit surface of light on the second transparent substrate is 90 degrees or approximately 90 degrees. (3) A light-emitting diode comprising: a transparent substrate; an emitting layer disposed on one side of the transparent substrate; a wavelength conversion layer disposed on the other side of the transparent substrate; and a light-reflecting layer formed on the side of the wavelength conversion layer opposite to the side of the transparent substrate. (4) The light-emitting diode according to (3), wherein the angle between the incident surface of light from the emitting layer and the exit surface of light on the transparent substrate is 90 degrees or approximately 90 degrees. (5) A backlight device comprising a light-emitting diode and a light guide layer disposed around the light-emitting diode, wherein the light-emitting diode comprises a first transparent substrate, a light-emitting layer disposed on one side of the first transparent substrate, a second transparent substrate disposed on the other side of the first transparent substrate, a wavelength conversion layer disposed between the first transparent substrate and the second transparent substrate, and a light-reflecting layer formed on the side of the second transparent substrate opposite to the wavelength conversion layer. (6) The backlight device according to (5), wherein the light guide layer is disposed to cover the periphery of the light-emitting diode. (7) The backlight device according to (5) or (6), wherein a light-scattering region is formed on at least one surface of the light guide layer. (8) The backlight device according to (7), wherein the degree of scattering at each position of the light-scattering region changes according to the distance from the light-emitting diode. (9) The backlight device according to any one of (5) to (8), wherein the angle between the light incident surface from the light-emitting layer and the light emission surface of the second transparent substrate is 90 degrees or approximately 90 degrees.(10) A backlight device comprising a light-emitting diode and a light guide layer disposed around the light-emitting diode, wherein the light-emitting diode comprises a transparent substrate, a light-emitting layer disposed on one side of the transparent substrate, a wavelength conversion layer disposed on the other side of the transparent substrate, and a light-reflecting layer formed on the side of the wavelength conversion layer opposite to the transparent substrate. (11) The backlight device according to (10), wherein the light guide layer is disposed to cover the periphery of the light-emitting diode. (12) The backlight device according to (10) or (11), wherein a light-scattering region is formed on at least one surface of the light guide layer. (13) The backlight device according to (12), wherein the degree of scattering at each position of the light-scattering region changes according to the distance from the light-emitting diode. (14) The backlight device according to any one of (10) to (13), wherein the angle between the incident surface of light from the light-emitting layer and the outgoing surface of light on the transparent substrate is 90 degrees or approximately 90 degrees.

[0098] 11 Display device, 21 Liquid crystal cell, 22 Optical sheet, 23 Diffuser plate, 24 Printed circuit board, 31 Backlight device, 61 Light-emitting diode, 81 Light-reflecting layer, 82 Transparent substrate, 83 Wavelength conversion layer, 84 Sapphire substrate, 85 Light-emitting layer, 86 Electrode layer, 91 Incident surface, 92 Outlet surface, 141 Light-emitting diode, 151 Incident surface, 152 Outlet surface, 181 Display device, 191 Light guide layer, 201 Backlight device, 231 Light scattering region

Claims

A first transparent substrate and A light-emitting layer disposed on one side of the first transparent substrate, A second transparent substrate is disposed on the other side of the first transparent substrate, A wavelength conversion layer disposed between the first transparent substrate and the second transparent substrate, A light-reflecting layer formed on the side of the second transparent substrate opposite to the wavelength conversion layer side, and A light-emitting diode (LED). 　 In the second transparent substrate, the angle between the light incident surface from the light-emitting layer and the light exit surface is 90 degrees or approximately 90 degrees. The light-emitting diode according to claim 1. 　 Transparent substrate and A light-emitting layer disposed on one side of the transparent substrate, A wavelength conversion layer disposed on the other side of the transparent substrate, A light-reflecting layer formed on the side of the wavelength conversion layer opposite to the transparent substrate side, A light-emitting diode (LED). 　 In the transparent substrate, the angle between the light incident surface from the light-emitting layer and the light exit surface is 90 degrees or approximately 90 degrees. The light-emitting diode according to claim 3. 　 Light-emitting diodes and A light guide layer arranged around the light-emitting diode and It has, The light-emitting diode is A first transparent substrate and A light-emitting layer disposed on one side of the first transparent substrate, A second transparent substrate is disposed on the other side of the first transparent substrate, A wavelength conversion layer disposed between the first transparent substrate and the second transparent substrate, A light-reflecting layer formed on the side of the second transparent substrate opposite to the wavelength conversion layer side, and has Backlight device. 　 The light guide layer is arranged to surround the light-emitting diode. The backlight device according to claim 5. 　 A light scattering region is formed on at least one surface of the light guide layer. The backlight device according to claim 5. 　 The degree of scattering at each position in the light scattering region changes depending on the distance from the light-emitting diode. The backlight device according to claim 7. 　 In the second transparent substrate, the angle between the light incident surface from the light-emitting layer and the light exit surface is 90 degrees or approximately 90 degrees. The backlight device according to claim 5. 　 Light-emitting diodes and A light guide layer arranged around the light-emitting diode and It has, The light-emitting diode is Transparent substrate and A light-emitting layer disposed on one side of the transparent substrate, A wavelength conversion layer disposed on the other side of the transparent substrate, A light-reflecting layer formed on the side of the wavelength conversion layer opposite to the transparent substrate side, has Backlight device. 　 The light guide layer is arranged to surround the light-emitting diode. The backlight device according to claim 10. 　 A light scattering region is formed on at least one surface of the light guide layer. The backlight device according to claim 10. 　 The degree of scattering at each position in the light scattering region changes depending on the distance from the light-emitting diode. The backlight device according to claim 12. 　 In the transparent substrate, the angle between the light incident surface from the light-emitting layer and the light exit surface is 90 degrees or approximately 90 degrees. The backlight device according to claim 10.

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