Display device

Abstract

The purpose of the present invention is to reduce yellow shift around blue LEDs in a backlight using blue LEDs and a color conversion sheet. In order to achieve the purpose, the present invention assumes a configuration such as the following. A display device having a display panel and a backlight is characterized in that: the backlight has a plurality of LEDs 31 disposed on a substrate 33, and a color conversion sheet 40 disposed between the plurality of LEDs 31 and the display panel; the color conversion sheet 40 is formed by a color conversion material 41 and a binder 42; and the color conversion sheet 40 has a ring-shaped region in which the color conversion material is not present, so as to surround the respective LEDs 31 in a plan view.

Description

[Technical Field]

[0001] The present invention relates to a display device having a direct backlight in which a large number of LEDs are arranged on a plane. [Background technology]

[0002] A liquid crystal display device has a TFT substrate on which pixel electrodes and thin film transistors (TFTs) are formed in a matrix, an opposing substrate facing the TFT substrate, and 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.

[0003] Since LCD panels themselves do not emit light, they require a backlight. Direct-type LEDs, which are LEDs (light-emitting diodes) 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 for achieving this: one is to mix the light emitted from three colored LEDs to obtain white light, and the other is to convert the light from a single colored LED into white using an optical conversion sheet. With either method, there is the challenge of completely mixing the light to obtain white light.

[0004] Patent Document 1 describes a configuration in which a large number of monochromatic LEDs are arranged on a plane, and for each LED, a QD box is arranged with a QD sheet on the inner wall and an opening through which light is emitted upward. In the configuration of Patent Document 1, the light from the LEDs is converted by the QD sheet, and the light from the LEDs and the converted light are sufficiently mixed inside the QD box, and white light is emitted from the opening. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2018-198187 Summary of the Invention [Problem to be solved by the invention]

[0006] A commonly used method for obtaining white light in a backlight is to use a single-color LED and a color conversion sheet, as this method has a relatively simple structure. For example, mixing blue and yellow can produce a pseudo-white color. Therefore, 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 mixture of blue and yellow will be emitted from the color conversion sheet.

[0007] The problem with this method is that the ratio of blue and yellow may vary from place to place, which can lead to uneven color even when white is desired. Patent Document 1 locates a QD box for each LED, and emits white light that is a sufficient mix of light of multiple wavelengths from the opening of the QD box, but this method has a relatively complicated structure.

[0008] An object of the present invention is to obtain a white backlight that is relatively simple in configuration and that is less prone to color unevenness by using a single-color LED and a color conversion sheet. [Means for solving the problem]

[0009] The present invention is intended to solve the above problems, and the main specific means are as follows.

[0010] (1) A display device having a display panel and a backlight, the backlight includes a plurality of LEDs arranged on a substrate, and a color conversion sheet arranged between the plurality of LEDs and the display panel; the color conversion sheet is formed from a color conversion material and a binder, The display device is characterized in that the color conversion sheet has, in a plan view, ring-shaped regions in which the color conversion material is not present, surrounding each of the plurality of LEDs.

[0011] (2) A display device having a display panel and a backlight, wherein the backlight is configured with a plurality of LEDs arranged on a substrate, and a color conversion sheet arranged between the plurality of LEDs and the display panel, the color conversion sheet being formed from a color conversion material and a binder, and the color conversion sheet having ring-shaped areas in which the color conversion material is less than other areas, surrounding each of the plurality of LEDs when viewed in a plane.

[0012] (3) A display device having a display panel and a backlight, wherein the backlight is configured with a plurality of LEDs arranged on a substrate and a color conversion sheet arranged between the plurality of LEDs and the display panel, the color conversion sheet being formed of a color conversion material and a binder, the color conversion sheet having, in a planar view, a first circle around each of the plurality of LEDs in which the color conversion material is present, and an area outside the first circle in which the color conversion material is not present, and the amount of the color conversion material at the center of the first circle is greater than that around the periphery of the first circle in a planar view. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a plan view of a liquid crystal display device. [Figure 2] FIG. 1 is a cross-sectional view of a liquid crystal display device. [Figure 3] FIG. 1 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. [Figure 5] 5 is a cross-sectional view taken along the line AA in FIG. 4. [Figure 6] This is an example of quantum dots. [Figure 7] FIG. 10 is a plan view illustrating a yellow shift. [Figure 8] FIG. 10 is a cross-sectional view illustrating a yellow shift. [Figure 9] FIG. 1 is a plan view of a first embodiment. [Figure 10] FIG. 1 is a cross-sectional view of Example 1. [Figure 11]FIG. 10 is a plan view of the second embodiment. [Figure 12] FIG. 10 is a cross-sectional view of Example 2. [Figure 13] FIG. 10 is a plan view of the third embodiment. [Figure 14] FIG. 10 is a cross-sectional view of Example 3. [Figure 15] FIG. 10 is a plan view of the fourth embodiment. [Figure 16] FIG. 10 is another plan view of the fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0014] 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, with liquid crystal sandwiched between them. A display area 14 is formed in the 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 the area surrounded by the scanning lines 11 and the video signal lines 12.

[0015] In Fig. 1, the portion where the TFT substrate 100 does not overlap with the counter substrate 200 is a terminal region 15. A flexible wiring substrate 17 is connected to the terminal region 15 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 substrate 17. A backlight is arranged on the back of the TFT as shown in Fig. 2.

[0016] 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: a counter substrate 200, on which a black matrix and color filters 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 together at their peripheries with a sealant 16, and liquid crystal 300 is sealed inside.

[0017] 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 placed below the TFT substrate 100, and only 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 an image is visible.

[0018] 2, a backlight 20 is disposed on the back of the liquid crystal display panel. The backlight 20 has a configuration in which a color conversion sheet 40 is disposed on a light source unit 30, and an optical sheet group 50 is disposed on top of that. There are two types of backlights 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.

[0019] 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. The group of optical sheets 50 may include a prism sheet, a diffusion sheet, etc. A polarized reflection sheet may also be used to improve the efficiency of use of 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.

[0020] 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, about 2 mm. The dotted lines indicating the segments in FIG. 3 are imaginary lines, and do not actually exist in the display area.

[0021] In Figure 3, the LEDs, which are the light sources, are placed at the center of each segment. In other words, when viewed from above, 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.

[0022] FIG. 4 is a plan view illustrating four segments 141 shown in FIG. 3. In FIG. 4, an LED 31 is placed in the center of the segment 141. As shown in FIG. 4, the LEDs 31 can be said to be placed at the vertices of a square. A color conversion sheet 40 is placed to cover the LEDs 31. One sheet is used as the color conversion sheet 40 for the entire display area. The dotted lines in FIG. 4 are imaginary lines that indicate the boundaries of the segments 141.

[0023] Fig. 5 is a cross-sectional view showing the configuration of a backlight, and corresponds to the AA cross-section of Fig. 4. In Fig. 5, LEDs 31 are mounted on a backlight circuit board 33. A blue light-emitting diode (hereinafter also referred to as a blue LED) is used as the LEDs 31. The LEDs 31 are covered with a transparent resin 32. The transparent resin 32 may be, for example, an acrylic resin or a silicone resin.

[0024] 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 color conversion material 41, or a QD sheet (hereinafter also referred to as a quantum dot sheet) in which QDs (quantum dots) are dispersed as color conversion material 41. In Fig. 5, a QD sheet is used.

[0025] As shown in Figure 5, the color conversion sheet (QD sheet) 40 is made by sandwiching quantum dots 41 dispersed in a transparent binder 42 between thin transparent resin films 43 that also serve as a barrier layer. The thin transparent resin film 43 used 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.

[0026] FIG. 6 is a schematic diagram of the quantum dot 41 used in FIG. 5. The quantum dot 41 is a semiconductor particle, and the wavelength of the converted light emitted varies depending on the particle diameter. The diameter dd of the quantum dot is generally 20 nm or less. In FIG. 6, P1 and P2 are semiconductors. P1 is, for example, a spherical CdSe, and P2 is surrounded by P1, which is ZnS.

[0027] The quantum dots 41 trap 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 this embodiment, 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.

[0028] Figures 7 and 8 are diagrams illustrating problems with the backlights 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 top of the LEDs 31. The LEDs 31 emit blue light, some of which is converted to yellow light by the quantum dots 41, and the rest remains blue and is emitted as is, so the design is such that white light is emitted overall.

[0029] However, in reality, as shown in FIG. 7, a yellowish region Y appears around the LED 31 in a plan view. Hereinafter, this region will also be referred to as the yellow-shifted region. This region is, for example, the hatched ring shape in FIG. 7. FIG. 7 is a schematic diagram, and the yellow-shifted region does not have a clear boundary. The dotted circle in FIG. 7 indicates the approximate region where the yellow shift occurs.

[0030] Figure 8 is a cross-sectional view of one segment of the backlight. The optical sheets are omitted from Figure 8. In Figure 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 quantum dots 41 dispersed in a binder 42, which is sandwiched between transparent barrier layers 43.

[0031] 8, light traveling from the LED 31 in the normal direction to 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 within the color conversion sheet 40 by light traveling in the normal direction is d1, and the distance traveled within the color conversion sheet 40 by light traveling at an angle θ with respect to the normal direction is d2, where d2>d1.

[0032] In other words, 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 a higher probability of blue light being converted to yellow light. This phenomenon varies depending on the magnitude of the angle θ, but becomes noticeable to the human eye when the angle θ exceeds a certain value. On the other hand, since the yellow shift is caused by the ratio of blue light to yellow light, if the angle θ becomes even larger, the blue light itself also becomes more scattered, and the amount of blue light converted to yellow light again becomes balanced, resulting in the emitted light returning 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, light having an angle θ within a certain range will be yellowish.

[0033] 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. [Example]

[0034] FIG. 9 is a plan view showing the features of Example 1. FIG. 9 is a plan view of four segments corresponding to FIG. 7. FIG. 9 shows a state in which the LED 31 is not yet lit. In FIG. 9, as in FIG. 7, the LED 31 is located at the center of the segment, and the color conversion sheet 40 is arranged to cover the LED 31. FIG. 9 differs from FIG. 7 in that the quantum dots 41 on the color conversion sheet 40 are not present in the ring-shaped region corresponding to the yellow-shifted region in FIG. 7.

[0035] In other words, only the binder 42 made of a transparent resin is present in this ring-shaped region. In this ring-shaped region of the color conversion sheet 40, blue light is not color converted by the quantum dots 41, so blue light becomes dominant over yellow light, and the yellow shift is reduced. In Figure 9, the region of the color conversion sheet 40 where quantum dots 41 do not exist is a ring-shaped region with a width w1 between the center of the segment and the radius r1 to r2.

[0036] 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. The configuration in Fig. 10 is the same as Fig. 8 except for the color conversion sheet 40. In Fig. 10, as in Fig. 8, 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 is d2, where d2 > d1.

[0037] 10 differs from FIG. 8 in that the color conversion sheet 40 has a region of width w1 between radii r1 and r2 where quantum dots 41 are not present. Therefore, light traveling at an angle θ with respect to the normal direction travels a distance d1 through the region in the color conversion sheet 40 where quantum dots 41 are present, and then travels through the region where quantum dots 41 are not present.

[0038] Therefore, the range over which light traveling at an angle θ to the normal direction of the color conversion sheet 40 is affected by the quantum dots 41 is the same distance d1 as that of light traveling in the normal direction. In other words, if the color conversion sheet of Figure 10 is used, no yellow shift will occur.

[0039] 9 and 10, quantum dots 41 are present outside the radius r2. If this were not the case, light traveling at a large angle θ with respect to the normal direction of the color conversion sheet 40 would not be affected by the quantum dots 41 in the color conversion sheet, and only blue light would be emitted, causing a blue shift in this range.

[0040] 10, the region of the color conversion sheet 40 where no quantum dots 41 exist, i.e., the optimal region of width w1 between radii r1 and r2, varies depending on the angle θ with respect to the normal direction of the color conversion sheet. Furthermore, light does not actually travel in a straight line within the color conversion sheet, but rather travels while being scattered.

[0041] 10 shows the basic concept for preventing the yellow shift. In the color conversion sheet 40, the region without the actual ring-shaped quantum dots 41, i.e., the region with width w1 between radii r1 and r2, is designed so that the yellow shift Y shown in FIG. 7 is least noticeable, taking into account various angles θ.

[0042] The advantage of Example 1 is that the yellow shift can be addressed by changing the dimensions of the region where the quantum dots 41 are present, rather than by changing the density of the quantum dots 41 in the color conversion sheet 40. This configuration is easier to manufacture than when the density of the quantum dots 41 is changed in the color conversion sheet 40. For example, a color conversion sheet 40 containing quantum dots 41 and having many ring-shaped holes formed therein can be manufactured, and then the ring-shaped holes can be filled with the binder 42.

[0043] 7, the yellow-shifted region is a circular ring, but it may be elliptical or rectangular with rounded corners, depending on the distribution of light from the light source LED 31. In such cases, the region of the color conversion sheet 40 without quantum dots 41 will also be elliptical or rectangular with rounded corners. [Example]

[0044] FIG. 11 is a plan view illustrating the characteristics of Example 2. FIG. 11 is a plan view of four segments corresponding to FIG. 7. FIG. 11 shows a state in which the LED 31 is not yet lit. In FIG. 11, as in FIG. 7, the LED 31 is located at the center of the segment, and the color conversion sheet 40 is arranged to cover the LED 31. FIG. 11 differs from FIG. 7 in that the amount of quantum dots 41 in the color conversion sheet 40 is small in the ring-shaped region corresponding to the yellow-shifted region in FIG. 7. The small amount of quantum dots 41 does not refer to the density of the quantum dots 41, but rather to the fact that there is a range in the thickness direction of the color conversion sheet 40 where quantum dots 41 are not present, as shown in FIG. 12.

[0045] Figure 12 is a cross-sectional view of one segment of the backlight, corresponding to Figure 11. The only difference between Figure 12 and Figure 10 of Example 1 is the color conversion sheet 40. In the color conversion sheet 40 of Figure 12, unlike Figure 10, in the region of width w2 between radius r1 and radius r2, quantum dots 41 are present from the lower surface of the color conversion sheet 40 to height h1, just like in other regions, but no quantum dots 41 are present on the upper surface side beyond h1.

[0046] As shown in Fig. 12, the same effect as in Fig. 10 is obtained for light incident at an angle θ with respect to the normal direction of the color conversion sheet 40. That is, yellow shift is suppressed. On the other hand, for light incident at an angle greater than the angle θ with respect to the normal direction of the color conversion sheet 40, Example 2 shown in Fig. 12 and Example 1 shown in Fig. 10 have different effects. That is, for light incident at an angle greater than the angle θ with respect to the normal direction of the color conversion sheet 40, the quantum dots 41 affect the light over a longer distance in Fig. 12 than in Fig. 10.

[0047] This is because the quantum dots 41 are present from the bottom to a height of h1 in the region of width w1 in the color conversion sheet 40 in Figure 12. The presence of the quantum dots 41 from the bottom to a height of h1 makes it possible to change the width or position of the ring for reducing the yellow shift in Figure 7. In other words, in Example 2, the degree of freedom in design for reducing the yellow shift in Figure 7 can be increased. [Example]

[0048] FIG. 13 is a plan view of Example 3, and FIG. 14 is a cross-sectional view of Example 3. FIG. 13 is a plan view of four segments corresponding to FIG. 7. FIG. 13 shows a state in which the LED 31 is not yet lit. In FIG. 13, as in FIG. 7, the LED 31 is located at the center of the segment, and a color conversion sheet 40 is arranged to cover the LED 31. FIG. 13 differs from FIG. 7 in that the region in which the quantum dots 41 exist is within a radius r3 from the center of the segment, and the amount of quantum dots 41 gradually decreases within this region from the center to the radius r3.

[0049] FIG. 14 is a cross-sectional view of a backlight corresponding to one segment of FIG. 13 . However, in the color conversion sheet 40, a portion of the area where quantum dots 41 corresponding to an adjacent segment are present is also shown. In the color conversion sheet 40 in FIG. 14 , the quantum dots 41 are formed across the entire thickness of the color conversion sheet 40 directly above the LED 31. The area where the quantum dots 41 are present in the thickness direction of the color conversion sheet 40 decreases with increasing distance from the center, reaching zero at a radius r3 from the center. That is, outside the radius r3 from the center, there are no quantum dots 41, and only the transparent binder 42 is present. However, as shown in FIG. 14 , just outside r3, there is an area where quantum dots 41 corresponding to an adjacent segment are formed, so the area where only the transparent binder 42 is present is not very large.

[0050] 14, the distance over which light traveling from the LED 31 in the normal direction to the color conversion sheet 40 is scattered by the quantum dots 41 is d1. The distance over which blue light traveling from the LED 31 in a direction forming an angle θ with the normal direction to the color conversion sheet 40 is scattered by the quantum dots 41 is also d1. Therefore, the amount of scattering by the quantum dots 41 is the same for both blue light beams, and in principle, no color shift occurs.

[0051] 14, the region where the quantum dots 41 exist is set so that the distance over which the blue light is scattered by the quantum dots 41 is approximately the same as d1 even when the angle θ that the blue light from the LED 31 makes with the normal direction of the color conversion sheet 40 changes. Conversely, in Fig. 14, the curve cv that defines the formation range of the quantum dots 41 is set so that the distance over which the blue light is scattered by the quantum dots 41 is approximately the same as d1 for various angles θ.

[0052] 14, if the angle θ that the blue light from the LED 31 makes with the normal direction of the color conversion sheet 40 becomes very large, it may be difficult to ensure the distance d1 at which the blue light is scattered by the quantum dots 41. However, the LED 31, which is the light source, also has directionality in the emission angle, and the amount of light emitted when the angle θ is extremely large is extremely limited. Therefore, the effect of such light is minor, and it is possible to prevent color shifts.

[0053] 13, in Example 3, the amount of quantum dots 41 is gradually reduced from the center of the segment toward the periphery, but this is achieved by defining the area in which the quantum dots 41 are formed, rather than by changing the density of the quantum dots 41. Therefore, compared to when the density of the quantum dots 41 is changed, manufacturing is easier and the characteristics can be stabilized. [Example]

[0054] In Examples 1 to 3, the shape of the segments is quadrangular. On the other hand, as shown in FIG. 7, the range of yellow shift is circular ring-shaped. Therefore, the yellow shift countermeasures described in Examples 1 to 3 are effective in different directions, depending on whether the segments are diagonal or axial. The yellow shift countermeasures described in Examples 1 to 3 are most effective when the segments are circular. However, circular segments cannot be closest packed. A method to achieve closest packing, closer to a circle, is to make the segments hexagonal, i.e., honeycomb structure.

[0055] Incidentally, the dotted lines indicating the boundaries of the segments in Figure 3 are imaginary lines, so changing the shape of the segments does not affect the configuration of the display panel. When viewed from a plan view, the LED 31 at the center of the segment can be positioned to match the honeycomb structure. In other words, if the LED 31 is positioned at the vertex of a regular triangle, the corresponding segment will have a honeycomb structure. The range where quantum dots 41 are present or absent, as explained in Examples 1 to 3, can be set based on the LED 31 at the center of the segment.

[0056] FIG. 15 is a plan view of the color conversion sheet 40 in Example 4, in which the segments have a honeycomb structure. In plan view, an LED 31 is placed at the center of each hexagonal segment. The countermeasure against yellow shift using the color conversion sheet 40 in FIG. 15 is the same as that described in Example 1. That is, in FIG. 15, the ring-shaped region between the inner and outer circles is a region where quantum dots 41 are not formed. This makes it possible to reduce the yellow shift, as described in FIG. 10 of Example 1. A feature of FIG. 15 is that the shape of the segments is close to a circle, so that the countermeasure against yellow shift can be more uniformly implemented than in Example 1.

[0057] Like Example 1, Example 2 can also be applied to honeycomb structure segments. The principle of the countermeasures is also the same as that explained in Example 2. If the configuration explained in Example 2 is applied to honeycomb structure segments, a more uniform countermeasure against yellow shift can be implemented.

[0058] FIG. 16 is a plan view of a color conversion sheet 40 when the configuration of Example 3 is applied to a honeycomb structure. In plan view, an LED 31 is placed at the center of a hexagonal segment. The countermeasure against yellow shift using the color conversion sheet 40 in FIG. 16 is the same as that described in Example 3. That is, in plan view, the amount of quantum dots 41 decreases from the center to the periphery inside the circle in FIG. 16. The decrease in the amount of quantum dots 41 does not mean that the density of the quantum dots 41 is reduced, but rather that the range of the area where the quantum dots 41 are formed in the thickness direction of the color conversion sheet 40 is changed, as shown in FIG. 14 of Example 3.

[0059] The configuration in Fig. 16 can reduce the yellow shift, as explained in Fig. 14 of Example 3. The feature of Fig. 16 is that the shape of the segments is close to a circle, so that the yellow shift can be countered more uniformly than in Example 3.

[0060] In the embodiment described above, the color conversion sheet 40 is placed directly on the transparent resin 32 that covers the LED 31. However, the present invention is not limited to this, and can also be applied to a configuration in which a dichroic sheet or a polycarbonate sheet for controlling the optical density (OD value) is placed between the LED 31 and the color conversion sheet 40. The dichroic sheet sharpens the spectrum of the light from the LED, thereby enabling more accurate wavelength conversion by the color conversion sheet.

[0061] The above describes the case where a QD sheet (Quantum Dot Sheet) is used as the color conversion sheet 40. However, the present invention is not limited to a QD sheet and can also be applied to a color conversion sheet that uses phosphor dots. [Explanation of symbols]

[0062] 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...LED, 32...transparent resin, 33...circuit board, 40...color conversion sheet, QD sheet, 41...quantum dot, 42...binder, 43...barrier layer, transparent resin film, 40...color conversion sheet, 50...optical sheet group, P1...semiconductor, P2...semiconductor, L...ligand

Claims

1. A display device having a display panel and a backlight, the backlight includes a plurality of LEDs arranged on a substrate, and a color conversion sheet arranged between the plurality of LEDs and the display panel; the color conversion sheet is formed from a color conversion material and a binder, the color conversion sheet has, in a plan view, a region in which a color conversion material is present within a first circle centered around each of the plurality of LEDs, and a region outside the first circle in which no color conversion material is present; A display device characterized in that, in plan view, the amount of the color conversion material is greater at the center of the first circle than at the periphery of the first circle.

2. When viewed in cross section of the color conversion sheet, at the center of the first circle, the color conversion material is present throughout the color conversion sheet in the thickness direction, 2. The display device according to claim 1, wherein, in the periphery of the first circle, the color conversion material is present on the LED side of the color conversion sheet, but not on the display panel side.

3. 2. The display device according to claim 1, wherein the color conversion material is a quantum dot.

4. 2. The display device according to claim 1, wherein the plurality of LEDs are blue LEDs.

5. 5. The display device according to claim 1, wherein the plurality of LEDs are arranged at vertices of a square on the substrate.

6. 5. The display device according to claim 1, wherein the plurality of LEDs are arranged on the substrate at vertices of an equilateral triangle.

Images