Backlight and display apparatus

Abstract

To reduce a yellow shift around blue LEDs in a backlight including the blue LEDs and a color conversion sheet.SOLUTION: Provided is a backlight including a light source including blue LEDs 31 arranged in a matrix, on a plane, at first intervals, and a color conversion sheet 40 arranged to cover the light source, where red quantum dots 411 that emit red light in response to blue light and green quantum dots 412 that emit green light in response to blue light are dispersed in the color conversion sheet 40, short-wavelength LEDs 311 that emit light of a shorter wavelength than that of blue light are arranged near the blue LEDs 31, and blue quantum dots 413 that emit blue light in response to the short-wavelength light are arranged in the color conversion sheet 40, at positions overlapping the short-wavelength LEDs 311 in plan view.SELECTED DRAWING: Figure 10

Description

[Technical field]

[0001] The present invention relates to a direct-type backlight in which a large number of LEDs are arranged on a plane, and to a display device using the same. [Background technology]

[0002] As a backlight for the display area of ​​a liquid crystal display device or the like, a configuration in which many single-color LEDs are arranged on a flat surface and a color conversion sheet is placed over them to obtain white light is often used. An example of a liquid crystal display device is shown below.

[0003] In a liquid crystal display device, a TFT substrate on which pixel electrodes and thin film transistors (TFTs) are formed in a matrix and an opposing substrate are disposed opposite the TFT substrate, with a liquid crystal layer sandwiched between the TFT substrate and the opposing substrate. Images are formed by controlling the light transmittance of the liquid crystal molecules for each pixel.

[0004] LCD panels themselves do not emit light, so a backlight is required. Direct-light type LEDs, which are light-emitting diodes (LEDs) arranged on a flat surface, can achieve high brightness. LEDs emit light of a specific wavelength. On the other hand, white light is required for backlighting. There are two methods available: one that mixes light emitted from three color LEDs to obtain white light, and one that converts light from a single color LED to white using a light conversion sheet. Either method faces the challenge of completely mixing the light to obtain white light.

[0005] Patent Document 1 describes a configuration in which a large number of monochromatic LEDs are arranged on a plane, and a QD box having a QD sheet on the inner wall and an opening for emitting light upward is arranged for each LED. In the configuration of Patent Document 1, the light from the LED is converted by the QD sheet, and the light from the LED and the converted light are sufficiently mixed inside the QD box to emit white light from the opening. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent Publication 2018-198187 Summary of the Invention [Problem to be solved by the invention]

[0007] A commonly used method for obtaining white light in a backlight is to use a single-color LED and a color conversion sheet to obtain white light, as this method has a relatively simple structure. For example, a pseudo-white color can be obtained by mixing blue and yellow. If a color conversion sheet that converts blue to yellow is placed in the direction of the blue LED's light output, a white light that is a mix of blue and yellow will be emitted from the color conversion sheet.

[0008] The problem with this method is that the ratio of blue and yellow may vary from place to place, and color unevenness is likely to occur even when white is to be displayed. Patent Document 1 radiates white light, which is a sufficient mix of multiple wavelengths of light, from the opening of the QD box by placing a QD box for each LED, but this method has a relatively complicated structure.

[0009] An object of the present invention is to obtain a white backlight that is relatively simple in configuration and is less prone to color unevenness by using a single-color LED and a color conversion sheet. [Means for solving the problem]

[0010] The present invention is intended to solve the above problems, and the main specific means are as follows.

[0011] (1) A backlight comprising a light source in which blue LEDs are arranged in a matrix with a first interval between them in a planar manner, and a color conversion sheet arranged to cover the light source, wherein red quantum dots that emit red light in response to blue light and green quantum dots that emit green light in response to blue light are dispersed in the color conversion sheet, a short-wavelength LED that emits light with a wavelength smaller than that of blue is arranged near the blue LED, and blue quantum dots that emit blue light in response to the short-wavelength light are arranged in a position overlapping with the short-wavelength LED in a planar view on the color conversion sheet.

[0012] (2) A backlight comprising a light source in which blue LEDs are arranged in a planar matrix with a first interval between them, and a color conversion sheet arranged to cover the light source, wherein red quantum dots that emit red light when exposed to blue light and green quantum dots that emit green light when exposed to blue light are dispersed in the color conversion sheet, and wherein, when viewed in a planar manner, the color conversion sheet has a ring-shaped region around the blue LED where the proportion of green quantum dots is higher than in other regions. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a plan view of a liquid crystal display device. [Diagram 2] FIG. 1 is a cross-sectional view of a liquid crystal display device. [Diagram 3] FIG. 2 is a plan view showing an example of a segment in a liquid crystal display device. [Figure 4] FIG. 2 is a plan view showing four segments in a backlight. [Diagram 5] 5 is a cross-sectional view taken along line AA in FIG. 4. [Figure 6] This is an example of a quantum dot. [Figure 7] FIG. 13 is a plan view illustrating the yellow shift. [Figure 8] FIG. 13 is a cross-sectional view illustrating a yellow shift. [Figure 9] FIG. 1 is a plan view of the first embodiment. [Figure 10] FIG. 2 is a cross-sectional view of the first embodiment. [Figure 11] FIG. 4 is a cross-sectional view of another embodiment of the first embodiment. [Figure 12] FIG. 11 is a plan view of the second embodiment. [Figure 13] FIG. 11 is a cross-sectional view of the second embodiment. [Figure 14] FIG. 13 is a cross-sectional view of another example of the backlight. [Figure 15] FIG. 11 is a cross-sectional view of yet another example of a backlight. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The backlight according to the present invention can be used in various display devices. Among display devices using a backlight, a liquid crystal display device is a representative one, and therefore the present invention will be described below with reference to a liquid crystal display device.

[0015] Fig. 1 is a plan view showing an example of a liquid crystal display device. In Fig. 1, a TFT substrate 100 and a counter substrate 200 are bonded with a sealant 16, and liquid crystal is sandwiched between them. A display area 14 is formed in an area where the TFT substrate 100 and the counter substrate 200 overlap. In the display area 14, scanning lines 11 extend in the horizontal direction (x direction) and are arranged in the vertical direction (y direction). Video signal lines 12 extend in the vertical direction and are arranged in the horizontal direction. Pixels 13 are formed in an area surrounded by the scanning lines 11 and the video signal lines 12.

[0016] 1, the portion where the TFT substrate 100 does not overlap with the counter substrate 200 is a terminal region 15. A flexible wiring board 17 is connected to the terminal region 15 in order to supply power and signals to the liquid crystal display panel. A driver IC that drives the liquid crystal display panel is mounted on the flexible wiring board 17. A backlight is disposed on the rear side of the TFT as shown in FIG.

[0017] Fig. 2 is a cross-sectional view of a liquid crystal display device. In Fig. 2, a backlight 20 is disposed on the back surface of a liquid crystal display panel 10. The liquid crystal display panel 10 has the following configuration. That is, a counter substrate 200 on which a black matrix and a color filter are formed is disposed opposite a TFT substrate 100 on which pixel electrodes, common electrodes, TFTs, scanning lines, video signal lines, etc. are formed. The TFT substrate 100 and the counter substrate 200 are bonded to each other at their peripheries by a sealant 16, and liquid crystal 300 is enclosed inside.

[0018] The liquid crystal molecules are initially aligned by alignment films formed on the TFT substrate 100 and the counter substrate 200. When a voltage is applied between the pixel electrode and the common electrode, the liquid crystal molecules rotate, and an image is formed by controlling the light from the backlight 20 for each pixel. Since the liquid crystal 300 can only control polarized light, a lower polarizer 101 is disposed below the TFT substrate 100, and only the polarized light is incident on the liquid crystal 300. The light modulated by the liquid crystal 300 is analyzed by the upper polarizer 201, and the image is visually recognized.

[0019] 2, a backlight 20 is disposed on the back of a liquid crystal display panel 10. The backlight 20 has a configuration in which a color conversion sheet 40 is disposed on a light source section 30, and an optical sheet group 50 is disposed on top of that. There are two types of backlight 20 for display devices: a side light type in which light sources such as LEDs are disposed on the side of a light guide plate, and a direct type in which light sources such as LEDs are disposed on the underside of a light guide plate; in the present invention, a direct type backlight is used.

[0020] In FIG. 2, a color conversion sheet 40 is disposed on the light source unit 30. The configuration of the color conversion sheet will be explained later. A group of optical sheets 50 is disposed on the color conversion sheet 40. A prism sheet, a diffusion sheet, etc. are used for the group of optical sheets 50. A polarizing reflection sheet may also be used to improve the efficiency of using light from the backlight 20. The type of optical sheet to be used, or the number of optical sheets to be used, is determined by the display device.

[0021] Fig. 3 is a plan view of a liquid crystal display panel in which the display area is divided into segments 141. An LED is arranged in the backlight for each segment 141. Fig. 3 is a schematic diagram, and in reality, the display is divided into more segments than shown in Fig. 3. The size of each segment is 4 mm or less, and in most cases is about 2 mm. The dotted lines indicating the segments in Fig. 3 are imaginary lines, and no such lines actually exist in the display area.

[0022] In Fig. 3, the LEDs, which are the light sources, are placed at the center of each segment. In other words, when viewed in a plan view, the LEDs are arranged in a matrix on the circuit board at equal intervals in the x and y directions. In other words, they are arranged at the vertices of a square.

[0023] FIG. 4 is a plan view of four segments 141 shown in FIG. 3. In FIG. 4, an LED 31 is arranged in the center of the segment 141. As shown in FIG. 4, the LEDs 31 can be said to be arranged at the vertices of a square. When a mini LED is used, the LED 31 has a size of about 100 μm to 300 μm. In FIG. 4, the LED 31 is square, but it may also be rectangular. The spacing between the LEDs 31 is 2 mm, the same size as the segments.

[0024] A color conversion sheet 40 is disposed covering the LEDs 31. A single sheet is used as the color conversion sheet 40 for the entire display area. The dotted lines in Fig. 4 are imaginary lines indicating the boundaries of the segments 141. QDs 41, which are a mixture of red QDs 411 and green QDs 412, are dispersed within the color conversion sheet, as will be described in Fig. 5.

[0025] Fig. 5 is a cross-sectional view showing the configuration of the backlight, and corresponds to the cross-sectional view taken along line AA in Fig. 4. In Fig. 5, LED 31 is mounted on backlight circuit board 33. A blue light-emitting diode (hereinafter also referred to as a blue LED) is used as LED 31. LED 31 is covered with transparent resin 32. For example, acrylic resin or silicone resin is used as transparent resin 32.

[0026] In Fig. 5, a color conversion sheet 40 is placed on a transparent resin 32 that covers an LED 31. The color conversion sheet 40 may use a phosphor sheet in which phosphor particles are dispersed as a color conversion material 41, or a QD sheet (hereinafter also referred to as a quantum dot sheet) in which QDs (Quantum Dots, hereinafter also referred to as quantum dots) are dispersed. In Fig. 5, a QD sheet is used.

[0027] As shown in Fig. 5, the color conversion sheet (QD sheet) 40 is a transparent binder 42 in which quantum dots 41 are dispersed, sandwiched between a thin transparent resin film 43 that also serves as a barrier layer. The thin transparent resin film 43 as a barrier layer is made of acrylic, polycarbonate, PET (polyethylene terephthalate), or the like. The overall thickness of the color conversion sheet 40 is 80 to 300 microns.

[0028] FIG. 6 is a schematic diagram of the quantum dot 41 used in FIG. 5. The quantum dot 41 is a semiconductor microparticle, and the wavelength of the converted and emitted light varies depending on the particle diameter. The diameter dd of the quantum dot 41 is generally 20 nm or less. In FIG. 6, P1 and P2 are semiconductors. P1 is, for example, a spherical CdSe, and P2, which is ZnS, covers P1.

[0029] The quantum dots 41 confine the incident light and emit light with a longer wavelength than the incident light. The incident light is light from the LED 31, and may be blue light or ultraviolet light. In FIG. 5, the light from the LED 31 is blue light. L in the quantum dots 41 in FIG. 6 is called a ligand, and makes it easier for the quantum dots 41 to be dispersed in the resin. The quantum dots 41 shown in FIG. 6 are dispersed in a transparent resin 42 called a binder. Examples of the resin used as the binder 42 include silicone resin and epoxy resin.

[0030] Figures 7 and 8 are diagrams showing problems with the backlight shown in Figures 4 and 5. Figure 7 shows the light emission pattern from the color conversion sheet 40 when the LEDs 31 are turned on in the same four segments as in Figure 4. The configuration in Figure 7 is the same as in Figure 4, with the color conversion sheet 40 placed on the LEDs 31. The LEDs 31 emit blue light, some of which is converted into yellow light by the quantum dots 41, and the rest remains blue and is emitted as such, so that the LEDs are designed to emit white light overall.

[0031] However, in reality, as shown in FIG. 7, a yellowish area Y appears around the LED 31 in plan view. Hereinafter, this area will also be referred to as the yellow-shifted area. This area is, for example, a hatched circle in FIG. 7. FIG. 7 is a schematic diagram, and the yellow-shifted area does not have a clear boundary. The dotted circle in FIG. 7 shows the approximate area where the yellow shift occurs. That is, in FIG. 7, the part corresponding to the LED 31 is white, the hatched area has undergone a yellow shift, and the area outside the hatching is white again.

[0032] Fig. 8 is a cross-sectional view of one segment of the backlight. The optical sheets are omitted in Fig. 8. In Fig. 8, a blue LED 31 is disposed on a circuit board 33, and the blue LED 31 is covered with a transparent resin 32. A color conversion sheet 40 is disposed on the transparent resin 32. The color conversion sheet 40 has a configuration in which quantum dots 41 are dispersed in a binder 42, which is sandwiched between transparent barrier layers 43.

[0033] 8, light traveling from the LED 31 in the normal direction of the color conversion sheet 40 and light traveling at an angle θ with respect to the normal direction travel different distances within the color conversion sheet 40. The distance traveled by light traveling in the normal direction within the color conversion sheet 40 is d1, and the distance traveled by light traveling at an angle θ with respect to the normal direction within the color conversion sheet 40 is d2, where d2>d1.

[0034] That is, the light traveling at an angle θ with respect to the normal direction has a higher probability of being captured by the quantum dots 41, and therefore the probability of blue light being converted to yellow light is higher. This phenomenon differs depending on the size of the angle θ, but becomes noticeable to the human eye when the angle θ is larger than a certain value. On the other hand, since the cause of the yellow shift is the ratio of blue light to yellow light, when the angle θ becomes even larger, the amount of blue light converted to yellow light again becomes competitive, and the emitted light returns to white. In other words, of the light from the LED 31 traveling at an angle θ with respect to the normal direction of the color conversion sheet 40, the light having an angle θ within a certain range becomes yellowish.

[0035] The present invention is intended to solve the above problems, and the present invention will be described in detail with reference to the following examples. EXAMPLES

[0036] FIG. 9 is a plan view showing the characteristics of the first embodiment. FIG. 9 is a plan view of four segments corresponding to FIG. 7. In FIG. 9, as in FIG. 7, the blue LED 31 is located at the center of the segment, and the color conversion sheet 40 is arranged to cover the blue LED 31. Red and green quantum dots 41 (411, 412) are dispersed in the color conversion sheet 40. FIG. 9 differs from FIG. 4 or FIG. 7 in that in the region where the yellow shift occurs in FIG. 7, blue quantum dots 413 are dispersed in addition to the red quantum dots 411 and green quantum dots 412. In FIG. 9, this portion is designated as 41 (411, 412, 413) to be distinguished from the other portions 41 (411, 412). The hatched region 41 (411, 412, 413) in FIG. 9 is formed in a ring shape surrounding the light source 31.

[0037] Meanwhile, in the light source section, a short-wavelength LED 311 that emits light with a shorter wavelength than the blue LED 31 is disposed in correspondence with the region in which the blue quantum dots 413 are dispersed. The blue light is enhanced by the blue quantum dots 413 due to the light from the short-wavelength LED 311, and the yellow shift can be offset.

[0038] There are no particular limitations on the short-wavelength LED 311 as long as it has the ability to excite the blue quantum dots 413. For example, it may be a purple LED or a purple-emitting LED. In addition, since the short-wavelength LED 311 is intended only to eliminate the yellow shift, the light quantity may be smaller than that of the blue LED 31, which is the main light source.

[0039] The position of the short-wavelength LED 311 may be anywhere within the range overlapping with the quantum dots 41 (411, 412, 413) in Fig. 9, but is preferably near the center in the width direction of the area including the quantum dots 41 (411, 412, 413) as shown in Fig. 9. In other words, when the interval between the blue LEDs 31 is d, it is desirable that the position of the short-wavelength LED 311 be within a range of d / 4 from the blue LED.

[0040] Fig. 10 is a cross-sectional view of one segment of the backlight corresponding to Fig. 9. The optical sheets are omitted in Fig. 10. In Fig. 10, quantum dots 41 (411, 412, 413) including blue quantum dot 413 are dispersed in the hatched area, and quantum dots 41 (411, 412) are dispersed in the other parts.

[0041] The upper part of FIG. 10 shows an example of the distribution of blue quantum dots 413. This distribution resembles a normal distribution with the peak shifted outward. However, this is merely an example, and other distributions can also achieve the purpose. That is, the blue quantum dots 413 only need to make the yellow shift less noticeable, so there is no need to precisely control the distribution. Note that FIG. 10 does not specify the distribution of the blue quantum dots 413 in the thickness direction (z direction) of the color conversion sheet 40. The distribution of the blue quantum dots 413 in the z direction may be uniform or may have a distribution.

[0042] In Fig. 10, short-wavelength LEDs 311 that emit light with a shorter wavelength than the blue LED 31 are arranged on both sides of the blue LED 31, which is the main light source. The short-wavelength LEDs 311 may be any LED as long as they have the ability to excite the blue quantum dots 413 and emit blue light. Since the size of the mini LED is about 100 to 300 μm, it is possible to arrange the short-wavelength LEDs 311 as shown in Fig. 10.

[0043] In Fig. 9, four short wavelength LEDs 311 are used around the blue LED 31. Fig. 9 is an example, and the number of short wavelength LEDs 311 may be reduced taking into consideration costs and effectiveness. For example, two short wavelength LEDs 311 may be arranged to sandwich the blue LED 31. Furthermore, the effect can be achieved with just one short wavelength LED 311. In these cases, it is effective to disperse many blue quantum dots 413 in the area corresponding to the short wavelength LEDs 311.

[0044] Fig. 11 is a cross-sectional view showing an example of the distribution of blue quantum dots 413 in the thickness direction (z direction) of the color conversion sheet 40. In Fig. 11, the blue quantum dots 413 are distributed within a thickness d3 near the upper surface of the color conversion sheet 40. This can be rephrased as saying that, for example, when the thickness of the color conversion sheet 40 at which the quantum dots 41 exist is d1, the blue quantum dots 413 exist within d1 / 2 from the upper surface.

[0045] However, it may be difficult to distribute the blue quantum dots 413 uniformly in the thickness direction of the color conversion sheet 40 in terms of the process. On the other hand, since the role of the blue quantum dots 413 is to suppress the yellow shift, it is not necessary to make the emission of blue light by the blue quantum dots 413 very large. Therefore, the thickness d3 of the blue quantum dots 413 in the z direction can be made smaller than the thickness of the quantum dot 41 (411, 412) layer. In other words, in FIG. 11, the amount of blue light can also be changed by the thickness d3 of the blue quantum dots 413.

[0046] The distribution diagram shown at the top of Fig. 11 shows the density distribution of blue quantum dots 413 in the planar direction (x direction). The density distribution in Fig. 11 is the same as the density distribution in Fig. 10. However, the density distribution in this case is also an example, and other distributions may be used. For example, in Fig. 11, the thickness d3 of blue quantum dots 413 is small, so the distribution in the planar direction (x direction) may be flat.

[0047] In any case, the distribution of the blue quantum dots 413 in Fig. 11 is an example, and the range of the blue quantum dots 413 may be changed to be easier to control than that shown in Fig. 11. The other configurations in Fig. 11 are the same as those in Fig. 10. EXAMPLES

[0048] FIG. 12 is a plan view of the color conversion sheet 40 and the light source unit 30 of the second embodiment. In FIG. 12, the blue LED 31 as the light source and its arrangement are the same as those in FIG. 7. However, the configuration of the color conversion sheet 40 is different from that in FIG. 7. In the color conversion sheet 40 in FIG. 12, the quantum dots 41 are also configured such that red quantum dots 411 and green quantum dots 412 are dispersed. The feature of FIG. 12 is that 45 (411, 412) are used as quantum dots in the portion where the yellow shift occurs as shown in FIG. 7. Both the quantum dots 41 and 45 use the red quantum dots 411 and the green quantum dots 412, but the proportion of the green quantum dots 412 is greater in the quantum dots 45 than in the quantum dots 41.

[0049] If the ratio of green quantum dots 412 is high, the emitted light will shift from yellow to the short wavelength side. In other words, it will shift to the blue wavelength side. As a result, the yellow shift in FIG. 7 will be reduced. Unlike the first embodiment, this method does not require an auxiliary light source.

[0050] Fig. 13 is a cross-sectional view showing Example 2. In the color conversion sheet in Fig. 13, the quantum dots 45 (411, 412) in the hatched portion are regions where the proportion of green quantum dots 412 is higher than the quantum dots 41 (411, 412) in other portions. In the hatched region in Fig. 13, the extent to which the emitted light is shifted from yellow to the short wavelength side can be controlled by the proportion of the green quantum dots 412 and the red quantum dots 411.

[0051] The hatched area in FIG. 13 can be a mixed area of ​​quantum dots 41 (411, 412) and quantum dots 45 (411, 412). The mixing ratio may be a constant ratio, but may also have a distribution. The distribution diagram at the top of FIG. 13 is a graph showing an example of the increase ratio of green quantum dots 412 in the hatched area. By varying the increase ratio of green quantum dots 412, the yellow shift can be corrected more accurately.

[0052] 13 is merely an example, and various other distributions are possible. Note that the range in which the proportion of green quantum dots 412 is greater than the other parts has a radius of d / 4 or less, where d is the distance between the blue LEDs 31.

[0053] As described above, the countermeasures against the yellow shift in Example 2 can be controlled by the ratio of the green quantum dots 412 and the red quantum dots 411 in the quantum dots 45 (411, 412) within the hatched area in Figure 13, and can also be controlled by the ratio or distribution of the quantum dots 41 and the quantum dots 45.

[0054] In the first and second embodiments, the configuration of the backlight 20 shown in FIG. 2 has been described. However, the present invention can be applied to various backlights other than the backlight shown in FIG. 2. The backlight in FIG. 14 is an example in which, in addition to the configuration of the backlight in FIG. 2, a dichroic sheet 60 is disposed between the light source 30 and the color conversion sheet 40. The backlight in FIG. 15 is an example in which, in addition to the configuration of FIG. 14, a polycarbonate plate 70 is disposed between the light source 30 and the dichroic sheet 60. The polycarbonate plate 70 has a very high transmittance, and can be used instead of disposing a space between the light source and the dichroic sheet or another sheet.

[0055] In the above description, the color conversion sheet 40 uses the quantum dots 41, but the color conversion sheet 40 may use a phosphor. [Explanation of symbols]

[0056] 10...display panel, 11...scanning line, 12...video signal line, 13...pixel, 14...display area, 15...terminal area, 16...sealing material, 17...flexible wiring board, 20...backlight, 30...light source section, 31...blue LED, 32...transparent resin, 33...circuit board, 40...color conversion sheet, QD sheet, 41...quantum dot, 42...binder, 43...barrier layer, transparent resin film 50...optical sheet group, 60...dichroic sheet, 70...polycarbonate plate, 100...TFT substrate, 101...lower polarizing plate, 141...segment, 200...opposite substrate, 201...upper polarizing plate, 300...liquid crystal layer, 311...short wavelength LED, 411...red quantum dot, 412...green quantum dot, 413...blue quantum dot, P1: Semiconductor, P2: Semiconductor, L: Ligand

Claims

1. A backlight having a light source in which blue LEDs are arranged in a matrix in a planar manner with a first interval, and a color conversion sheet disposed to cover the light source, wherein in the color conversion sheet, red quantum dots that emit red light upon receiving blue light and green quantum dots that emit green light upon receiving blue light are dispersed, a short-wavelength LED that emits light having a wavelength shorter than that of blue is disposed in the vicinity of the blue LED, when viewed in a plane, the color conversion sheet is characterized in that blue quantum dots that emit blue light upon receiving the light of the short-wavelength LED are disposed at positions overlapping the short-wavelength LED.

2. The backlight according to claim 1, wherein the blue quantum dots are dispersed together with the red quantum dots and the green quantum dots.

3. The backlight according to claim 1, wherein the blue quantum dots are arranged in a ring shape centered on the blue LED when viewed in a plane and do not overlap with the blue LED.

4. The backlight according to claim 3, wherein the blue quantum dots have a distribution in the planar direction of the color conversion sheet, and the peak of the distribution exists outside the center of the width of the ring-shaped region.

5. The backlight according to claim 1, wherein the blue quantum dots have a distribution in the cross-sectional direction of the color conversion sheet, and the color conversion sheet has a higher density on the side farther from the light source than the center in the cross-sectional direction of the color conversion sheet.

6. The backlight according to claim 1, wherein the interval between the short-wavelength LED and the blue LED is 1 / 4 or less of the first interval.

7. The backlight according to claim 1, wherein four short-wavelength LEDs are arranged so as to sandwich the blue LED when viewed in a plane.

8. The backlight according to claim 1, wherein two short-wavelength LEDs are arranged so as to sandwich the blue LED when viewed in a plane.

9. A liquid crystal display device having a backlight on the back surface of a liquid crystal display panel, wherein the backlight is the backlight according to claim 1.

10. A backlight having a light source in which blue LEDs are arranged in a matrix in a planar manner with a first interval, and a color conversion sheet disposed to cover the light source, wherein In the color conversion sheet, red quantum dots that emit red light when receiving blue light and green quantum dots that emit green light when receiving blue light are dispersed. When viewed in a plane, the backlight is characterized in that in the color conversion sheet, there is a region where the ratio of the green quantum dots is higher in a ring shape around the blue LED than in other regions.

11. The backlight according to claim 10, wherein the width of the region where the ratio of the green quantum dots is higher than that in other regions is ¼ or less of the first interval.

12. A liquid crystal display device having a backlight on the back surface of a liquid crystal display panel, wherein the backlight is the backlight according to claim 10.

Images