Light field modulation layer, backlight structure and display device

[0065] The embodiments of the application provide a light field modulation layer, a backlight structure, and a display device, which are used to uniformly distribute the energy and direction of light emitted from the light field modulation layer, reduce the thickness of the backlight structure, and reduce the use of LEDs in the backlight structure Number, reduce costs.

[0066] An optical field modulation layer provided by an embodiment of the application, and an optical field modulation layer provided by an embodiment of the application, includes a waveguide layer and a grating structure. The waveguide layer has a first surface and a second surface opposite to each other. The grating structure is arranged on the first surface or the second surface of the waveguide layer, and the grating structure is used for guiding the light incident on the grating structure into the waveguide layer and totally reflecting and propagating in the waveguide layer. Such as figure 2 As shown, the optical field modulation layer 2 includes a waveguide layer 4 and a grating structure 3. The waveguide layer 4 has a first surface 24 and a second surface 25 opposite to each other. The grating structure is provided on the first surface 24 of the waveguide layer. Of course, the grating structure 3 can also be arranged on the second surface 25 of the waveguide layer.

[0067] The light field modulation layer provided by the embodiments of the present application includes a waveguide layer and a grating structure, so that the energy and direction of the light emitted from the light field modulation layer are evenly distributed, and because the light is totally reflected and transmitted in the waveguide layer, when the backlight structure includes the present application In the light field modulation layer provided by the embodiment, the backlight structure does not have a light mixing distance, and there is no problem that the uniformity of the point light source of the backlight structure is difficult to control, and there is no need to increase the longitudinal light mixing distance of the light source to achieve uniform light output, thereby reducing the backlight structure The overall thickness reduces production costs.

[0068] Optionally, the light field modulation layer provided by the embodiment of the present application further includes: a light extraction layer, the light extraction layer is disposed on the first surface or the second surface of the waveguide layer, and the light extraction layer is used to: The light that is totally reflected and propagated in the waveguide layer is uniformly emitted. Such as image 3 In the light field modulation layer 2 shown, the grating structure 3 is provided on the first surface 24 of the waveguide layer 4, and the light extraction layer 5 is provided on the second surface 25 of the waveguide layer 4. Of course, the grating structure and the light-trapping layer can be provided on the second surface of the waveguide layer at the same time. When the grating structure and the light-trapping layer are provided on the second surface of the waveguide layer at the same time, the position where the grating structure is provided may not be provided with the light-trapping layer.

[0069] Preferably, in the light field modulation layer provided by the embodiment of the present application, both the grating structure and the waveguide layer are made of transparent materials. For example, the material of the grating structure can be silicon nitride (Si 3 N 4 ), the material of the waveguide layer can be indium tin oxide (ITO) or Si 3 N 4.

[0070] It should be noted that in the light field modulation layer provided by the embodiments of the present application, the refractive index of the waveguide layer is greater than the refractive index of the medium in contact with the light field modulation layer, so that the light modulated by the grating structure is in the waveguide layer. Total reflection transmission, such as image 3 In the light field modulation layer shown, the medium in contact with the light field modulation layer 2 is air or a base substrate, that is, the refractive index of the waveguide layer needs to be greater than that of air or the base substrate.

[0071] For the light field modulation layer provided by the embodiment of the application, when the backlight structure includes the light field modulation layer provided by the embodiment of the application, the backlight structure does not have a light mixing distance, and the uniformity of the light emitted through the light field modulation layer is determined by the light extraction Layer control, in this way, a single light source can provide a single area of ​​the overall backlight, which can greatly reduce the number of light sources in the backlight structure, thereby reducing costs.

[0072] Optionally, the light extraction layer includes one or a combination of the following: multiple dot structures and multiple grating structures.

[0073] It should be noted that the distance between the light source and the light extraction layer is different, and the light intensity of the light reaching the light extraction layer is also different. It is necessary to design the size and density of the dot structure according to the light intensity reaching the light extraction layer, or according to The light intensity reaching the light extraction layer is designed for the period, duty cycle and groove depth of the grating structure. Optionally, the typical size of the dot structure (length or width of the dot structure) is in the range of 0.1 to 1 mm. Optionally, when the grating structure is a diffraction grating, grating structures with different diffraction efficiencies are arranged at different positions on the surface of the waveguide layer. Preferably, the diffraction efficiency of the grating structure near the light source is smaller than the diffraction efficiency of the grating far away from the light source , So that the energy of the light emitted from the light extraction layer is evenly distributed.

[0074] Optionally, the refractive index of the grating structure is greater than the refractive index of the waveguide layer. In this way, it can be ensured that the light passing through the light field modulation layer provided by the embodiments of the present application has a high light coupling efficiency, so that when the backlight structure includes the light field modulation layer provided by the embodiments of the present application, the utilization rate of the light source can be improved and energy can be saved. .

[0075] Optionally, the grating structure includes a plurality of two-dimensional gratings.

[0076] The two-dimensional grating can be for example Figure 4 In the structure shown, the two-dimensional grating includes a plurality of cubic structures 22, and the two-dimensional grating has periodicity along the X and Y directions of the rectangular coordinate plane in which it is located, that is, the cubic structures 22 are periodically arranged along the X and Y directions. cloth. Figure 4 The lengths of a and e correspond to the line width of the two-dimensional grating in the X direction and Y direction, the length of c corresponds to the groove depth of the two-dimensional grating, and the lengths of b and d correspond to the two-dimensional grating in the X direction and Y respectively. The period of the direction. The lengths of a and e can be equal or unequal, and the lengths of b and d can be equal or unequal, that is, the line width and period of the two-dimensional grating along the X direction and the Y direction are equal. Figure 4 There is a gap between two adjacent cubic structures 22. Of course, the two-dimensional grating can also be set to a structure without gaps between the two adjacent cubic structures 22, that is, the two-dimensional grating in the X and Y directions The line width is equal to the period of the two-dimensional grating in the X and Y directions. It should be noted that such as Figure 4 In the two-dimensional grating shown, the cubic structures 22 are periodically arranged along the X direction and the Y direction, that is, a cubic structure 22 corresponds to one period of the two-dimensional grating. Of course, in the two-dimensional grating, it corresponds to a period of the two-dimensional grating. Correspondingly, it can also be a structure of other shapes.

[0077] Optionally, in the light field modulation layer provided by the embodiment of the present application, the two-dimensional grating includes a first sub-grating and a plurality of second sub-gratings surrounding the first sub-grating, and the first sub-grating is in the waveguide The orthographic projection on the layer is a circle, and the orthographic projection of the plurality of second sub-gratings on the waveguide layer is a ring concentric with the circle and a different radius. Take a two-dimensional grating including three sub-gratings as an example for illustration, such as Figure 5 As shown, the orthographic projection of the first sub-grating 8 on the waveguide layer is a circle, and the orthographic projections of the remaining two second sub-gratings 9'and 9" on the waveguide layer are rings that are concentric with the circle and have different radii. Of course, the two-dimensional grating in the light field modulation layer provided by the embodiment of the present application may also have other shapes, and the first sub-grating and the second sub-grating may also have other shapes.

[0078] It should be noted that the structure of the two-dimensional grating in the light field modulation layer provided by the embodiment of the present application can be optimized through rigorous coupled wave theory and related algorithms (for example, simulated annealing algorithm). Such as Image 6 As shown, when the light-emitting source is an LED light source, the optimization of the two-dimensional grating that efficiently couples the light beam with the divergence angle of the LED from -60° to 60° into the waveguide layer for total reflection transmission includes the following steps:

[0079] S101: Determine the light field size of the light source on the lower surface of the waveguide layer;

[0080] Starting from the optical field angle (the effective light output range of the light source), quantify the light angle range of the LED at a specific position of the waveguide layer, such as Figure 7 As shown, the LED6 is arranged below the waveguide layer 4. Since the light emitted by the LED is distributed symmetrically, Figure 7 It is a schematic diagram of the light field of the right half of the LED. For a light source with a distance d from the waveguide layer, since its main energy is concentrated in the range of 0°-60°, the light field size L of the light source on the lower surface of the waveguide layer can be determined : L=d/tan(30°);

[0081] S102. Divide the sample of the lower surface L of the waveguide layer into several equally spaced small areas P, so that the light coupling efficiency of the light of the LED passing through each small area P meets a preset condition;

[0082] Figure 7 Each small area P in the two-dimensional grating corresponds to each sub-grating of the two-dimensional grating. Since the size of the LED is determined, the angle range of the small area P sampled by the light beam emitted by the LED is determined, that is, the LED passes through each The field angle of the small area P is determined. In the light field modulation layer provided in the embodiment of the present application, in order to achieve high coupling efficiency, the angle distribution range of the light passing through each small area P may be limited to within 5°, for example. It should be noted that the angular distribution range of the light passing through each small area P can be determined according to the size of the LED and the distance between the LED and the waveguide layer. The structure of each sub-grating is optimized, so that the light emitted by the light source that reaches the two-dimensional grating again is transmitted by total reflection in the waveguide layer, and the coupling efficiency of the chief ray in each small sampling area is the highest. Ensure that the coupling efficiency of the edge rays of each sampling area is as high as possible. In this way, by quantifying the light angle range of the LED from the field of view, the structure of each sub-grating in the two-dimensional grating structure can be optimized. The preset condition that the optical coupling efficiency meets can be set according to actual needs. The preset condition of the optical coupling efficiency selected in the embodiment of the present application is: the light emitted by the light source that reaches the two-dimensional grating is optically coupled. The efficiency is greater than 60%.

[0083] According to the above-mentioned optimization ideas for the two-dimensional grating, the size of the two-dimensional grating on the surface of the waveguide layer corresponds to the entire light field of the LED. Optionally, the two-dimensional grating meets the following conditions:

[0084]

[0085] Wherein, D is the diameter of the two-dimensional grating, and d is the distance between the light source and the surface of the waveguide layer close to the two-dimensional grating.

[0086] Optionally, in the light field modulation layer provided by the embodiment of the present application, the period, line width, and groove depth of the first sub-grating and the second sub-grating are not completely the same, and the period, line width, and groove depth of the second sub-grating are different. Not exactly the same.

[0087] Since the grating is relatively sensitive to the angle of incident light, the light field modulation layer provided in the embodiment of the present application is provided with multiple sub-gratings, and different sub-gratings have different periods, line widths and groove depths, so that a two-dimensional grating pair can be realized. The coupling efficiency of incident light from multiple angles is high, which further improves the utilization rate of the light source.

[0088] Optionally, in the light field modulation layer provided by the embodiment of the present application, in any period of the first sub-grating, the first sub-grating includes a plurality of sub-structures with unequal line widths and unequal heights. In any period of each second sub-grating, each second sub-grating includes a plurality of sub-structures with unequal line widths and different heights; or, in any period of the first sub-grating , The first sub-grating includes a plurality of sub-structures with equal line widths and unequal heights. In any period of each second sub-grating, each second sub-grating includes a plurality of line widths with equal line widths and unequal heights. Or, in any period of the first sub-grating, the first sub-grating includes a plurality of sub-structures with unequal line widths and equal heights, and in any period of each second sub-grating Inside, each second sub-grating includes a plurality of sub-structures with unequal line widths and equal heights.

[0089] The examples of this application provide Figure 5 The two-dimensional grating shown includes a first sub-grating 8 and a plurality of second sub-gratings 9'and 9" surrounding the first sub-grating. The orthographic projection of the first sub-grating 8 on the waveguide layer is a circle The orthographic projection of the plurality of second sub-gratings 9'and 9" on the waveguide layer is a ring that is concentric with the circle and has a different radius. Such as Figure 5 As shown in the two-dimensional grating, the cross-sectional view of the first sub-grating 8 along the direction parallel to the waveguide layer is as Figure 8 As shown, the first sub-grating 8 along Figure 8 The cross-sectional view of AA’ is as Picture 9 As shown, each period 26 of the first sub-grating 8 includes three ring-shaped sub-structures 23 (the sub-structure corresponding to the center of the first sub-grating can be regarded as a ring with an inner ring radius of 0). Figure 8 , 9 The line width and height of the three substructures 23 in any period of the first two-dimensional sub-grating shown are not equal. Of course, the cross-sectional view of the first two-dimensional sub-grating along its diameter can also be as Picture 10 As shown, the line widths of the three substructures 23 in any period are equal, but the heights are not equal; or the cross-sectional view of the first two-dimensional sub-grating along its diameter is as Picture 11 As shown, the line width and height of the ring-shaped substructure 23 in each period 26 are the same. It can be understood that when the line width and height of the substructure are the same, there are gaps between adjacent substructures.

[0090] When the period, line width, and groove depth of different sub-gratings are different, the orthographic projection on the waveguide layer is as Figure 5 The cross-sectional view of the two-dimensional grating shown along its diameter is as Picture 12 As shown, the two-dimensional grating includes a first sub-grating 8, two second sub-gratings 9'and 9", the first sub-grating 8 and the two second sub-gratings 9'and 9" each include at least two periods, The first sub-grating 8 and the second sub-gratings 9'and 9" include three sub-structures 23 with unequal line widths and heights within a period 26.

[0091] According to the above design method, the coupled wave algorithm based on the simulated annealing algorithm is selected to optimize the two-dimensional grating in a global manner. The specific parameters are as follows: LED size is 0.2mm, d=2mm, the refractive index of the waveguide layer is 1.5, and the two-dimensional grating The refractive index is 2, quantized L at equal intervals (L=3.5mm) and the number of small-spaced regions is 19, and the chief ray angle through each sub-grating is optimized (that is, the incident angle of the chief ray incident on each small area P ) The corresponding optical coupling efficiency diagram is as follows Figure 13 Shown. From Figure 13 It can be seen that for each sub-grating, the optical coupling efficiency of the chief ray is greater than 60%. The structural parameters of the corresponding sub-grating are shown in Table 1. The optimized result is within one period of any sub-grating, along the two-dimensional grating The cross-sectional view in the diameter direction is as Figure 14 As shown, it includes four substructures 23 that have different line widths and different heights. Correspondingly, the partial optimization results of the optical coupling efficiency of each sub-grating of the two-dimensional grating are as follows Figure 15 As shown, Figure 15 The angle I in represents the incident angle of the light incident on the grating, T represents the transmission efficiency of the grating, R represents the reflection efficiency of the grating, and the numbers after T and R represent the diffraction order. Figure 15 The part enclosed by the thick medium and black line represents the diffraction angle whose angle satisfies the total reflection condition. From the efficiency column, it can be seen that the optimized two-dimensional grating can deflect most of the light diffraction at the total reflection angle, achieving Coupling in the waveguide layer, that is, total reflection transmission occurs.

[0092] It should be noted that in the process of optimizing the two-dimensional grating, when the light field size L is divided into a number of small areas P, the size of each small area P may also be unequal, so that any corresponding sub-grating is along two The width in the radial direction of the dimensional grating is also not equal. The optimized two-dimensional grating structure, as long as the light entering the waveguide layer through the two-dimensional grating is totally reflected and transmitted in the waveguide layer and has a higher coupling efficiency. Each sub-grating period can also include equal line widths. Substructures with unequal heights, or substructures with equal heights but unequal line widths.

[0093] Table 1

[0094] Small area P serial number

[0095] In order to ensure that the light emitted from the LED is coupled through the two-dimensional grating into the waveguide layer for total reflection transmission, the light is not damaged by the two-dimensional grating layer, optionally, in the light field modulation layer provided in the embodiment of the present application, the waveguide layer meets the following conditions : Wherein, h is the thickness of the waveguide layer, and θ is the incident angle of light emitted by the light source and incident on the waveguide layer after reaching the two-dimensional grating. It should be noted that the diffraction of light entering the waveguide layer at the interface between the waveguide layer and the two-dimensional grating layer will destroy the total reflection process of the light. Therefore, the thickness of the waveguide layer meets the above conditions and diffracts from the center of the two-dimensional grating into the waveguide. During the total reflection transmission process, the light in the layer will not be modulated by the diffraction of the two-dimensional grating layer to destroy the total reflection transmission condition.

[0096] Optionally, in the light field modulation layer provided by the embodiment of the present application, the thickness of the waveguide layer may be, for example, 2 microns, and of course, the thickness of the waveguide layer may also be increased to several tens of microns.

[0097] Optionally, the two-dimensional grating in the light field modulation layer provided in the embodiment of the present application is a two-dimensional nano-holographic grating.

[0098] A backlight structure provided by an embodiment of the present application includes the light field modulation layer provided by the embodiment of the present application, and a light source disposed opposite to the first surface or the second surface of the waveguide layer. Such as Figure 16 As shown, an embodiment of the present application provides a backlight structure. The embodiment of the present application provides that each light source 1 faces the light field modulation layer 2. The light field modulation layer 2 includes a grating structure 3, a waveguide layer 4, and a light extraction layer 5.

[0099] The backlight structure provided by the embodiments of the present application includes the light field modulation layer, and the energy and direction of the light emitted from the light field modulation layer are evenly distributed, and because the light is totally reflected and transmitted in the waveguide layer, the backlight structure does not have a light mixing distance. There is a problem that the uniformity of the point light source of the backlight structure is difficult to control, and there is no need to increase the longitudinal light mixing distance of the light source to achieve uniform light output, thereby reducing the overall thickness of the backlight structure and reducing production costs.

[0100] The light source in the direct-lit backlight structure provided by the embodiments of the present application may be an LED, and the LED chip may be, for example, an inorganic semiconductor material or an organic light-emitting material.

[0101] Optionally, the light source in the backlight structure provided in the embodiment of the present application is a monochromatic light source. For example, you can choose an LED whose light color is blue, or you can choose an LED whose light waveband is in the ultraviolet range, of course, you can also choose a monochromatic light source whose light color is other colors.

[0102] Optionally, the backlight structure provided by the embodiment of the present application further includes: a monochromatic light conversion layer located above the light field modulation layer, and a reflective layer located below the light field modulation layer, the monochromatic light conversion layer Used to convert the light emitted by the light source into white light; the light source is arranged on the reflective layer and located between the reflective layer and the light modulation layer, or the light source is arranged on the monochromatic light On the conversion layer and between the light modulation layer and the monochromatic light conversion layer.

[0103] The backlight structure provided by the embodiment of the application will inevitably have reflection diffraction loss due to the utilization of the two-dimensional grating coupling the light emitted by the LED. In the backlight structure provided by the embodiment of the application, a reflective layer is provided, thereby causing the reflection diffraction loss The light is reused. Optionally, the reflective layer can be a metal film layer, and the metal material can be aluminum or silver, for example, and the reflective layer can also be a multilayer dielectric film or other materials that reflect light.

[0104] Optionally, in the backlight structure provided by the embodiment of the present application, the monochromatic light conversion layer includes one or a combination of the following: a fluorescent film layer and a quantum dot film layer. For example, the fluorescent film layer can be cerium doped yttrium aluminum garnet 3 Al 5 O 12 :Ce^3+); The quantum dot film layer includes quantum dot material. The quantum dot is composed of a finite number of atoms, and its three dimensions are on the order of nanometers. Quantum dots are generally spherical or quasi-spherical. They are usually made of semiconductor materials composed of elements from IIB to VIA or IIIA to VA in the periodic table. They can also be composed of two or more semiconductor materials, such as elements from IIB to VIA. The composition of the semiconductor material can be, for example, cadmium sulfide (CdS), cadmium selenide (CdSe), cadmium telluride (CdTe), zinc selenide (ZnSe), etc., and the semiconductor material composed of elements of IIIA to VA can be, for example, indium phosphide. (InP), indium arsenide (InAs), etc., quantum dots are nanoparticles with a stable diameter of 2-20nm.

[0105] In some possible implementation manners, the backlight structure provided by the embodiments of the present application includes: an LED, a light field modulation layer, a reflective layer, and a fluorescent film layer, where the light field modulation layer includes a nano-holographic grating, a waveguide layer, and multiple dot structures , LED and nano holographic grating correspond one to one. The backlight structure provided by the embodiment of the application is as Figure 17 As shown, the LED6 is arranged on the reflective layer 10 and located between the light field modulation layer 2 and the reflective layer 10. The nano-holographic grating 11 is arranged on the surface of the waveguide layer 4 close to the LED6, and the dot structure 12 is arranged on the waveguide layer 4 away from the LED6. On the surface, the fluorescent film layer 13 is located on the dot structure 12, and the nano-holographic grating 11 is a diffraction grating.

[0106] Such as Figure 18 As shown, in the backlight structure provided by the embodiment of the application, the nano-holographic grating 11 and the dot structure 12 can also be arranged on the surface of the waveguide layer 4 away from the LED 6. At this time, the distance between the LED 6 and the waveguide layer 4 is approximately zero. The position where the layer 4 is provided with the nano-holographic grating 11 is not provided with the dot structure 12, and the nano-holographic grating 11 is a reflective grating. In such Figure 18 Based on the backlight structure shown, it is also possible to make the LED6 directly contact the first surface of the waveguide layer 4 close to the LED6, such as Figure 19 As shown, the distance between the LED6 and the waveguide layer 4 is zero, compared to Figure 18 The backlight structure shown in the embodiment of the application is as Figure 19 The backlight structure shown can further reduce the thickness of the backlight structure.

[0107] As provided in the examples of this application Figure 17 , 18 In the backlight structure shown in 19, the medium in contact with the light field modulation layer is the fluorescent film layer and air respectively, so the refractive index of the waveguide layer is greater than the refractive index of the fluorescent film layer and air, so light can be totally reflected in the waveguide layer 4. transmission.

[0108] Such as Picture 20 As shown, in the backlight structure provided by the embodiment of the present application, the LED 6 is arranged on the fluorescent film layer 13, and is located between the waveguide layer 4 and the fluorescent film layer 13 and emits light toward the waveguide layer 4. The nano holographic grating 11 and the dot structure 12 are both arranged on The waveguide layer 4 is away from the surface of the LED 6. At this time, the distance between the LED 6 and the waveguide layer 4 is approximately zero, and the dot structure 12 is not provided at the position where the nano holographic grating 11 is provided on the waveguide layer 4, and the nano holographic grating 11 is a reflective grating. In such Picture 20 Based on the backlight structure shown, it is also possible to make the LED6 directly contact the surface of the waveguide layer 4 close to the LED6, such as Figure 21 As shown, the distance between the LED6 and the waveguide layer 4 is zero, compared to Picture 20 The backlight structure shown in the embodiment of the application is as Figure 21 The backlight structure shown can further reduce the thickness of the backlight structure. Such as Picture 20 , 21 In the backlight structure shown, the media in contact with the light field modulation layer are air and the reflective layer respectively. Therefore, the refractive index of the waveguide layer is greater than that of the air and the reflective layer, so that light can be totally reflected and transmitted in the waveguide layer.

[0109] It should be noted that in the backlight structure provided by the embodiments of the present application, the distance between the light source and the waveguide layer has no effect on the light output uniformity of the backlight structure, and the distance between the light source and the waveguide layer only affects the light coupling efficiency of the backlight structure. In principle, The greater the distance between the light source and the waveguide layer, the higher the light coupling efficiency of the backlight structure. When designing the backlight structure, it is necessary to combine the thickness of the backlight structure and the light coupling efficiency required by the backlight structure to determine the relationship between the light source and the waveguide layer the distance. Optionally, in the backlight structure provided by the embodiment of the present application, the distance between the light source and the waveguide layer is greater than or equal to zero.

[0110] A display device provided by an embodiment of the present application includes the backlight structure provided by the embodiment of the present application.

[0111] For example, the display device provided in the embodiment of the present application may be a liquid crystal display device.

[0112] Such as Figure 22 As shown, the display device provided by the embodiment of the present application includes a backlight structure 15, a lower polarizer layer 16 on the backlight structure 15, a display panel 17 on the lower polarizer layer 16, and a display panel 17 on the In the upper polarizer layer 18, the backlight structure 15 can be any backlight structure provided in the embodiments of the present application.

[0113] It should be noted that when the examples provided in this application are used Image 6 In the process of optimizing the two-dimensional grating in the method shown, it can only be optimized for one polarization direction of the light, that is, the light with only one polarization direction is modulated by the two-dimensional grating and has a higher optical coupling efficiency. Optionally, in the backlight structure provided by the embodiment of the present application, the two-dimensional grating makes the light coupling efficiency of light in any polarization direction emitted by the light source meet a preset condition. The preset condition satisfied by the optical coupling efficiency may be, for example, that the optical coupling efficiency is greater than 60%. For example, the first two-dimensional grating structure is obtained by optimizing the first polarization direction of the light, and then the second polarization direction of the light is optimized. The first polarization direction of the light is different from the second polarization direction of the light, and the second Two-dimensional grating structure, and then optimize the first two-dimensional grating structure and the second two-dimensional grating structure obtained by optimization again (for example, adjust the groove depth and line width of different positions in the two-dimensional direction of the grating), and superimpose to form a two-dimensional grating, The two-dimensional grating makes the light coupling efficiency of the light in the first polarization direction and the second polarization direction both greater than 60%, that is, the two-dimensional grating makes the light in the two polarization directions emitted by the light source have high light coupling efficiency, Further improve the utilization rate of the light source in the backlight structure.

[0114] For such as Figure 22 In the display device shown, the two-dimensional grating in the backlight structure has a high coupling efficiency for light in two polarization directions. Figure 23 As shown, the two-dimensional grating 21 is formed by the optimized superposition of the first two-dimensional grating and the second two-dimensional grating obtained by optimization again. It should be noted that, Figure 23 The middle two-dimensional grating 21 is a schematic cross-sectional view along the plane parallel to the waveguide layer. The structure corresponding to the cross section 19 of the two-dimensional grating 21 along the Y direction and the structure corresponding to the cross section 20 of the two-dimensional grating 21 along the X direction respectively make two polarizations The optical coupling efficiency of the light in the direction meets the preset condition, the double-headed arrow represents the polarization direction of the light whose polarization direction is parallel to the paper surface, and the solid circle represents the polarization direction of the light whose polarization direction is perpendicular to the paper surface. The structure corresponding to the cross section 19 of the two-dimensional grating 21 along the Y direction has less reflection of light whose polarization direction is consistent with the direction corresponding to the solid circle dot and has high optical coupling efficiency, while for light whose polarization direction is consistent with the direction corresponding to the double-headed arrow The structure corresponding to the cross-section 20 of the two-dimensional grating 21 along the X direction has less reflection of light whose polarization direction is the same as the direction corresponding to the double-headed arrow and has a higher optical coupling efficiency, while the polarization direction corresponds to a solid circle. The light reflected in the same direction is more. The angles a and b in the figure are greater than the critical angle of total reflection when the waveguide layer satisfies the condition of total reflection. Therefore, the structure and two corresponding to the cross section 19 of the two-dimensional grating 21 along the Y direction The light in the polarization direction corresponding to the structure corresponding to the cross section 20 of the dimensional grating 21 in the X direction enters the waveguide layer for total reflection transmission.

[0115] It should be noted that the display device provided by the embodiment of the present application may adopt local backlight adjustment (Localdiming) technology to reduce power consumption, improve imaging contrast, increase the number of gray levels, and reduce residual images. Divide the backlight structure of the display device into multiple small areas (Block); when the display device is working, adjust the brightness of the backlight according to the grayscale of the corresponding display content in the corresponding small area; thereby achieving the purpose of saving energy and increasing image quality .

[0116] In summary, the light field modulation layer, backlight structure, and display device provided by the embodiments of the present application include the waveguide layer and the grating structure, so the energy and direction of the light emitted from the light field modulation layer are evenly distributed, and because the light is in the waveguide Layer total reflection transmission. When the backlight structure includes the light field modulation layer provided in the embodiments of the application, the backlight structure does not have a light mixing distance, and there is no problem that the uniformity of the point light source of the backlight structure is difficult to control, and there is no need to increase the longitudinal light mixing of the light source. Distance to achieve uniform light emission, thereby reducing the overall thickness of the backlight structure and reducing production costs. For the light field modulation layer provided by the embodiment of the application, when the backlight structure includes the light field modulation layer provided by the embodiment of the application, the backlight structure does not have a light mixing distance, and the uniformity of the light emitted through the light field modulation layer is determined by the light extraction Layer control, in this way, a single light source can provide a single area of ​​the overall backlight, which can greatly reduce the number of light sources in the backlight structure, thereby reducing costs. In the light field modulation layer provided by the embodiment of the application, the refractive index of the grating structure is greater than the refractive index of the waveguide layer, which can ensure that the light field modulation layer provided by the embodiment of the application has a higher light coupling efficiency, thereby improving the utilization of the light source Rate and save energy. In the light field modulation layer provided by the embodiment of the present application, the waveguide layer meets the following conditions: Wherein, h is the thickness of the waveguide layer, and θ is the incident angle of the light emitted by the light source and incident on the waveguide layer after reaching the two-dimensional grating, so that the light diffracted from the center of the two-dimensional grating into the waveguide layer During the total reflection transmission process, the light will not be modulated by the diffraction of the two-dimensional grating layer to destroy the total reflection transmission condition. In the light field modulation layer provided by the embodiment of the present application, the two-dimensional grating makes the light coupling efficiency of light in any polarization direction emitted by the light source meet a preset condition, so that the light in any polarization direction emitted by the light source can be Both have high light coupling efficiency, and further improve the utilization rate of the light source in the backlight structure.

[0117] Obviously, those skilled in the art can make various changes and modifications to the application without departing from the spirit and scope of the application. In this way, if these modifications and variations of this application fall within the scope of the claims of this application and their equivalent technologies, this application also intends to include these modifications and variations.