Backlight device and liquid crystal display device

Abstract

To provide a backlight device capable of suppressing the display quality degradation of a liquid crystal display unit, and the liquid crystal display unit including the backlight device.SOLUTION: A backlight device includes an LED substrate on the main face of which a plurality of light-emitting device are arranged for emitting exciting light, a fluorescent material layer including fluorescent material for receiving the exciting light to issue fluorescent light, a wavelength selective reflection layer arranged between the fluorescent material layer and the LED substrate, and a louver film arranged between the wavelength selective reflection layer and the LED substrate and having a plurality of louvers, the wavelength selective reflection layer having transmission factors different according to the wavelengths and / or incident angles of incident light, the louver film serving for shading fluorescent light and the exciting light entering at an angle which is a first angle or larger and smaller than 90° to the normal direction of the film surface of the louver film.SELECTED DRAWING: Figure 1A

Description

[Technical Field]

[0001] The present invention relates to a backlight device and a liquid crystal display device. [Background technology]

[0002] Many LCD devices are equipped with a backlight device equipped with multiple LEDs. The multiple LEDs are divided into multiple regions, and only the LEDs in the regions requiring illumination are turned on, or the brightness of each region is adjusted to the required level. This type of backlight driving method is called segmented driving, partial driving, area driving, or local dimming. The segmented driving method can improve the contrast ratio between the brightness of bright and dark areas of an LCD device.

[0003] BACKGROUND ART In recent years, in order to improve the display quality of display devices, liquid crystal display devices that support high dynamic range (hereinafter referred to as "HDR") have become commercially available.

[0004] Furthermore, as a liquid crystal display device compatible with the UHD Premium standard (color reproducibility of 90% or more of the BT2020 standard, HDR10 standard), a liquid crystal display device that employs a remote phosphor system and is equipped with a backlight device that can suppress color unevenness using a dichroic filter, as described in Patent Document 1, for example, is being considered. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2019 / 244351 Summary of the Invention [Problem to be solved by the invention]

[0006] According to the study by the present inventors, the liquid crystal display device of Patent Document 1 may have a problem in that it is not possible to sufficiently prevent deterioration in display quality due to the occurrence of color unevenness, as will be described in detail later.

[0007] The present invention has been made to solve the above problems, and aims to provide a backlight device that can suppress deterioration in the display quality of a liquid crystal display device, and a liquid crystal display device equipped with such a backlight device. [Means for solving the problem]

[0008] According to an embodiment of the present invention, the following solutions are provided:

[0009] [Item 1] an LED substrate having a main surface and a plurality of light-emitting elements that emit excitation light arranged on the main surface; a phosphor layer containing a phosphor that emits fluorescence upon receiving the excitation light; a wavelength-selective reflective layer disposed between the phosphor layer and the LED substrate, the wavelength-selective reflective layer having a transmittance that varies depending on the wavelength and / or incident angle of incident light; a louver film disposed between the wavelength selective reflection layer and the LED substrate, the louver film having a plurality of louvers, which blocks the fluorescence and the excitation light incident at an angle of at least a first angle and less than 90° with respect to a normal direction of a film surface of the louver film; A backlight device comprising: [Item 2] Item 2. The backlight device according to item 1, wherein the louver film is supported by the LED substrate. [Item 3] 3. The backlight device according to item 2, wherein the louver film is provided on the main surface of the LED substrate. [Item 4] 4. The backlight device according to item 2 or 3, wherein the louver film has a plurality of openings that overlap with the plurality of light-emitting elements when viewed from the normal direction of the main surface of the LED substrate. [Item 5] 5. The backlight device according to any one of items 2 to 4, wherein, when viewed from the normal direction of the main surface of the LED substrate, each of the plurality of louvers is arranged in a position that does not overlap each of the plurality of light-emitting elements. [Item 6] 6. The backlight device according to any one of items 2 to 5, further comprising a diffusion plate disposed between the louver film and the wavelength-selective reflection layer. [Item 7] Item 2. The backlight device according to item 1, wherein the louver film is provided on a main surface of the wavelength selective reflection layer facing the LED substrate. [Item 8] 8. The backlight device according to item 7, further comprising a diffusion plate disposed between the louver film and the LED substrate. [Item 9] The wavelength selective reflective layer is a transmittance for the excitation light incident at an incident angle of a second angle is higher than a transmittance for the fluorescence incident at the incident angle of the second angle; Item 9. The backlight device according to any one of items 1 to 8, wherein the transmittance for the excitation light incident at a third angle greater than the second angle is lower than the transmittance for the fluorescent light incident at the third angle. [Item 10] the second angle is greater than or equal to 0° and less than 40°; Item 10. The backlight device according to item 9, wherein the third angle includes an angle equal to or greater than 70° and less than 90°. [Item 11] 11. The backlight device according to any one of items 1 to 10, wherein the first angle is 15° or more. [Item 12] Item 12. The backlight device of any one of items 1 to 11, further comprising an optical layer stack disposed on the phosphor layer opposite the wavelength-selective reflecting layer. [Item 13] Item 13. The backlight device according to item 12, wherein the optical layer laminate has two prism sheets arranged so that the ridge lines of the prisms are approximately perpendicular to each other, and a polarized light selective reflection layer arranged on the two prism sheets. [Item 14] Item 14. The backlight device of any one of items 1 to 13, wherein the phosphor includes a quantum dot phosphor. [Item 15] A liquid crystal display panel; the backlight device according to any one of items 1 to 14, which emits light toward the rear surface of the liquid crystal display panel; A liquid crystal display device comprising: [Effects of the Invention]

[0010] According to the embodiments of the present invention, a backlight device and a liquid crystal display device are provided that can suppress a decrease in the display quality of the liquid crystal display device. [Brief explanation of the drawings]

[0011] [Figure 1A] FIG. 1 is a cross-sectional view schematically showing a backlight device 50A according to a first embodiment of the present invention. [Figure 1B] FIG. 1 is a cross-sectional view that schematically shows a liquid crystal display device 100A that includes a backlight device 50A. [Figure 1C] FIG. 10 is a schematic cross-sectional view when partial driving is performed using a backlight device 50A. [Figure 1D] 1 is a plan view of a backlight device 50A, and is a diagram schematically showing an example of the positional relationship between a louver 42l and a light emitting element 22. FIG. [Figure 1E] 10 is another example of a schematic plan view of a louver film 43 included in another backlight device of Embodiment 1. FIG. [Figure 1F] 10 is a schematic plan view of another louver film 44 that is further included in another backlight device of Embodiment 1. FIG. [Figure 1G] 1 is a schematic cross-sectional view of an example of an optical layer stack 30 included in a backlight device 50A. [Figure 1H] 10 is a cross-sectional view schematically showing a backlight device 50A1 according to a modified example of the first embodiment. FIG. [Figure 2A] FIG. 10 is a cross-sectional view schematically showing a backlight device 50B according to a second embodiment. [Figure 2B] FIG. 10 is a schematic cross-sectional view when partial driving is performed using a backlight device 50B. [Figure 2C] 10 is a plan view of a backlight device 50B, and is a diagram schematically illustrating an example of the positional relationship between a louver 45l and a light emitting element 22. FIG. [Figure 3A] 1 is a cross-sectional view that schematically shows a backlight device 950 of Comparative Example 1. FIG. [Figure 3B] 10 is a schematic cross-sectional view when partial driving is performed using a backlight device 950 of Comparative Example 1. FIG. [Figure 4A] 10 is a schematic cross-sectional view when partial driving is performed using a backlight device 950R of Comparative Example 2. FIG. [Figure 4B] 10 is a diagram schematically showing an image pattern displayed on a liquid crystal display device 900R having a backlight device 950R of Comparative Example 2. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. However, the present invention is not limited to the following embodiment. In the following drawings, components having substantially the same functions are designated by common reference numerals, and their description may be omitted.

[0013] (Embodiment 1) A backlight device 50A according to the present embodiment and a liquid crystal display device 100A including the backlight device 50A will be described with reference to Figures 1A, 1B, 1C, and 1D. Figure 1A is a cross-sectional view schematically showing the backlight device 50A according to Embodiment 1, and Figure 1B is a cross-sectional view schematically showing the liquid crystal display device 100A including the backlight device 50A. Figure 1C is a cross-sectional view schematically showing partial driving using the backlight device 50A. Figure 1D is a schematic plan view of the backlight device 50A, and is a diagram schematically showing an example of the arrangement relationship between multiple louvers 42l and light-emitting elements 22.

[0014] The backlight device 50A includes an LED substrate 21 having a plurality of light-emitting elements 22 that emit excitation light arranged on a main surface 21s, a phosphor layer 24 containing a phosphor that emits fluorescence upon receiving the excitation light, a wavelength-selective reflecting layer 28 that is disposed between the phosphor layer 24 and the LED substrate 21, and a louver film 42 that has a plurality of louvers 42l and is disposed between the wavelength-selective reflecting layer 28 and the LED substrate 21. The wavelength-selective reflecting layer 28 has a transmittance that varies depending on the wavelength and / or incident angle of light that is incident on the wavelength-selective reflecting layer 28. The louver film 42 blocks the fluorescence and excitation light that are incident at an angle that is equal to or greater than a first angle and less than 90° with respect to the normal direction of the film surface of the louver film 42. In the illustrated example, the louver film 42 includes two opposing base films 42b1 and 42b2 and a plurality of louvers 42l disposed between the two base films 42b1 and 42b2, each having a main surface intersecting the main surfaces of the base films 42b1 and 42b2. The film surface of the louver film 42 is a plane parallel to the main surface of the base film 42b1 or 42b2. In the illustrated example, the film surface of the louver film 42 (i.e., the plane parallel to the main surface of the base film 42b1 or 42b2) is a plane parallel to the xy plane, and the normal direction to the film surface of the louver film 42 is a direction parallel to the z direction. In the illustrated example, each of the plurality of louvers 42l is plate-shaped and has a main surface parallel to the yz plane, and is disposed approximately parallel to one another. The phrase "the louver film 42 blocks the fluorescence and excitation light incident at an angle greater than or equal to a first angle and less than 90° relative to the normal to the film surface of the louver film 42" includes the louver film 42 having a transmittance of 50% or less for the fluorescence and excitation light incident on the louver film 42 at an angle greater than or equal to a first angle and less than 90° relative to the normal to the film surface of the louver film 42. The first angle is, for example, 30° or greater, and may be 15° or greater. For example, the multiple louvers 42l of the louver film 42 have the function of blocking at least a portion of the fluorescence emitted from the phosphor layer 24 and the excitation light emitted from the light-emitting element 22.

[0015] In the backlight device 50A, the louver film 42 is supported by the LED substrate 21. That is, the louver film 42 is fixed to the LED substrate 21. The louver film 42 is provided on the main surface 21s of the LED substrate 21. The louver film 42 may be in contact with the main surface 21s of the LED substrate 21. The louver film 42 may be placed on the main surface 21s of the LED substrate 21, or may be attached to the main surface 21s of the LED substrate 21 via an adhesive layer. In the illustrated example, the louver film 42 has multiple openings 42h. In this example, each opening 42h has an opening 42h1 provided in the base film 42b1 and an opening 42h2 provided in the base film 42b2. When viewed from the normal direction of the main surface 21s of the LED substrate 21, each of the multiple openings 42h overlaps one of the multiple light-emitting elements 22. The multiple light-emitting elements 22 are exposed at the multiple openings 42h.

[0016] As shown in FIGS. 1A and 1D , when viewed from the normal direction of the main surface 21s of the LED substrate 21, each of the multiple louvers 42l is disposed between adjacent light-emitting elements 22 among the multiple light-emitting elements 22. When viewed from the normal direction of the main surface 21s of the LED substrate 21, each of the multiple louvers 42l is disposed at a position that does not overlap with each of the multiple light-emitting elements 22. When viewed from the normal direction of the main surface 21s of the LED substrate 21, the multiple louvers 42l may include a louver 42l divided into multiple sections in the y direction so as not to overlap with the light-emitting elements 22, and a louver 42l whose length in the y direction is approximately equal to the length L2 of the LED substrate 21 in the y direction. The distance between adjacent louvers 42l does not have to be constant. In the backlight device 50A, two or more louvers 42l are disposed between adjacent light-emitting elements 22 among the multiple light-emitting elements 22. The louver film of the backlight device of this embodiment may be, for example, a security / privacy filter (product name: PF430W9B) manufactured by 3M Co. The louver film 42 shown in the figure may be obtained by providing a plurality of openings in such a filter.

[0017] The backlight device 50A further includes a diffuser plate 48 disposed between the louver film 42 and the wavelength-selective reflecting layer 28. Note that the diffuser plate 48 is omitted from FIG. 1C for simplicity. The wavelength-selective reflecting layer 28 and the phosphor layer 24 may be supported by the diffuser plate 48. For example, the wavelength-selective reflecting layer 28 and the phosphor layer 24 may be stacked in this order on the diffuser plate 48, or these layers may be fixed to the diffuser plate 48 in a state where they are adhered to each other via an adhesive layer. Note that the diffuser plate 48 may be omitted.

[0018] 1B, the liquid crystal display device 100A includes a liquid crystal display panel 10 and a backlight device 50A. In the liquid crystal display device 100A, the backlight device 50A emits light toward a rear surface 10r of the liquid crystal display panel 10.

[0019] The backlight device 50A is a direct backlight of the remote phosphor type. In the remote phosphor type, the phosphor layer 24 is disposed away from the light emitting elements 22, so that deterioration of the phosphor due to heat generated by the light emitting elements 22 can be suppressed.

[0020] The phosphor layer 24 includes a phosphor that is excited by excitation light emitted from the light-emitting element 22 and emits fluorescence. For example, if the light-emitting element 22 is a blue LED that emits blue light, the phosphor layer 24 may include a green phosphor that emits green fluorescence and / or a red phosphor that emits red fluorescence, or may include a yellow phosphor that emits yellow fluorescence. From the viewpoint of achieving high color rendering, the phosphor layer 24 preferably includes a green phosphor that emits green fluorescence and a red phosphor that emits red fluorescence. The phosphor layer 24 may include, for example, a quantum dot green phosphor that emits green fluorescence and / or a quantum dot red phosphor that emits red fluorescence. Quantum dot phosphors generally have the advantages of a narrow half-width at the peak wavelength of their emission spectrum and high color purity, and are therefore considered promising for meeting, for example, the UHD Premium standard (color reproducibility BT2020 standard 90% or more, HDR10 standard). Alternatively, known phosphors such as red sulfide phosphors (e.g., calcium sulfide phosphors) and green sulfide phosphors (e.g., thiogallate phosphors) may be used. A protective layer may be provided on either or both sides of the phosphor layer 24.

[0021] When the angle of incidence of light incident on the wavelength-selective reflecting layer 28 (e.g., a dichroic filter) (the angle relative to the normal to the film surface of the wavelength-selective reflecting layer 28) is smaller than a predetermined angle (e.g., less than 40°), the transmittance of the wavelength-selective reflecting layer 28 for excitation light emitted from the plurality of light-emitting elements 22 is higher than the transmittance of the wavelength-selective reflecting layer 28 for fluorescence emitted from the phosphor layer 24. That is, the transmittance of the wavelength-selective reflecting layer 28 for excitation light incident on the wavelength-selective reflecting layer 28 at a second angle of incidence that is equal to or greater than 0° and less than 40° is higher than the transmittance of the wavelength-selective reflecting layer 28 for fluorescence incident on the wavelength-selective reflecting layer 28 at the second angle of incidence. On the other hand, the transmittance of the wavelength-selective reflecting layer 28 for excitation light incident on the wavelength-selective reflecting layer 28 at a third angle of incidence that is greater than the second angle is lower than the transmittance of the wavelength-selective reflecting layer 28 for fluorescence incident on the wavelength-selective reflecting layer 28 at the third angle of incidence. The third angle is, for example, an angle that is equal to or greater than 70° and less than 90°. For light incident on the wavelength-selective reflecting layer 28 at the second incident angle, the wavelength-selective reflecting layer 28 transmits at least a portion of the wavelength range of the excitation light emitted from the plurality of light-emitting elements 22 and reflects at least a portion of the fluorescence emitted from the phosphor layer 24. For light incident on the wavelength-selective reflecting layer 28 at the second incident angle, it is preferable to transmit all of the excitation light emitted from the plurality of light-emitting elements 22 and reflect all of the light emitted from the phosphor layer 24. For example, if the light-emitting elements 22 are blue LEDs, the wavelength-selective reflecting layer 28 transmits light in the emission wavelength range of the blue LED (i.e., blue light) and reflects light in the wavelength range from green to red for light incident on the wavelength-selective reflecting layer 28 at the second incident angle. For light incident on the wavelength-selective reflecting layer 28 at a third incident angle, the wavelength-selective reflecting layer 28 transmits at least a portion of the fluorescence emitted from the phosphor layer 24 and reflects at least a portion of the wavelength range of the excitation light emitted from the plurality of light-emitting elements 22. For example, for light incident on the wavelength-selective reflecting layer 28 at a third incident angle, the wavelength-selective reflecting layer 28 reflects blue light and transmits red light. In this specification, light emitted by a phosphor may be referred to as "fluorescence." Unless otherwise specified, "fluorescence" includes both fluorescence in the narrow sense and phosphorescence. The wavelength-selective reflecting layer 28 is, for example, an optical multilayer film having a layered structure in which films with different refractive indices are stacked.

[0022] As will be described below, the backlight device 50A has the wavelength-selective reflective layer 28, which makes it possible to suppress color unevenness when performing partial driving.

[0023] The effects of the backlight device 50A according to this embodiment will be described in comparison with those of comparative examples. FIG. 3A is a cross-sectional view schematically illustrating a liquid crystal display device 900 including a backlight device 950 according to comparative example 1. FIG. 3B is a cross-sectional view schematically illustrating partial driving using the backlight device 950 according to comparative example 1. FIG. 4A is a cross-sectional view schematically illustrating partial driving using the backlight device 950R according to comparative example 2. FIG. 4B is a schematic view of a liquid crystal display device 900R including the backlight device 950R according to comparative example 2, viewed from the normal direction of the liquid crystal display panel. The backlight device 950 according to comparative example 1 differs from the backlight device 50A according to the embodiment of the present invention in that it does not include a louver film. The backlight device 950 and the liquid crystal display device 900 according to comparative example 1 correspond to the backlight device and the liquid crystal display device including the same described in Patent Document 1. The backlight device 950R according to comparative example 2 differs from the backlight device 950 according to comparative example 1 in that it does not include a wavelength-selective reflective layer 28.

[0024] First, the function and effect of the wavelength-selective reflecting layer 28 will be described with reference to FIGS. 4A and 4B.

[0025] As shown in FIGS. 4A and 4B, the backlight device 950R of Comparative Example 2 has a lit region Ron where the light-emitting elements 22 are lit and an unlit region Roff where the light-emitting elements 22 are not lit when performing partial driving. FIG. 4B schematically shows an image pattern displayed on a liquid crystal display device 900R having the backlight device 950R of Comparative Example 2. The edge region of the lit region Ron (in other words, the region of the lit region Ron that is close to the boundary with the unlit region Roff) is shown as region R1, and the region of the unlit region Roff surrounding the lit region Ron is shown as region R2. FIG. 4A shows a schematic cross-sectional view (bottom) of the backlight device 950R of Comparative Example 2, as well as the colors displayed in each region (top) and the blue light L in each region. B , green light L G and red light L R The upper part of FIG. 4A shows the degree to which the color displayed in each area is blue or yellow, based on the area other than the area R1 (area R0) of the lighting area Ron. The middle part of FIG. 4A shows the brightness of the blue light L in each area. B , green light L G and red light L R The brightness of the blue light L in the region R0 B The brightness is shown as a reference (100%) and is indicated by the size of the arrow. Hereinafter, the same will be shown in the same manner in drawings similar to FIG. 4A (schematic cross-sectional views when partial driving is performed).

[0026] When partial driving is performed using the backlight device 950R of Comparative Example 2, color unevenness (sometimes called color halo) may occur. Specifically, as shown in FIG. 4B , in the unlit region Roff, which should be a dark area, the region R2 surrounding the lit region Ron may become yellowish. Furthermore, the region R1 at the edge of the lit region Ron may appear bluish. One possible cause of the former phenomenon is that light L2 emitted from the phosphor layer 24 in the lit region Ron toward the rear (toward the LED substrate 21) is reflected by the main surface 21s of the LED substrate 21 and enters the unlit region Roff. The light L2 contains more light in the red to green wavelength range than blue light. Therefore, the region R2 appears yellowish compared to the region R0 other than the region R1 of the lit region Ron. The latter color unevenness occurs due to the following reasons. Because region R1 is adjacent to the unlit region Roff, the excitation light L1 (here, blue light) incident on the phosphor layer 24 at an angle (oblique direction) from the normal direction of the main surface of the phosphor layer 24 is less than in region R0 other than region R1 in the lit region Ron. Therefore, in region R1, the luminance of the green light emitted by the green phosphor and the red light emitted by the red phosphor in response to the blue light is lower than in region R0, resulting in a color unevenness in which region R1 appears bluer and darker than region R0.

[0027] In contrast, the backlight device 950 of Comparative Example 1 shown in FIG. 3A has a wavelength-selective reflecting layer 28 between the phosphor layer 24 and the LED substrate 21. The transmittance of the wavelength-selective reflecting layer 28 for fluorescence emitted from the phosphor layer 24 and incident on the wavelength-selective reflecting layer 28 at the second incident angle is lower than the transmittance of the wavelength-selective reflecting layer 28 for excitation light emitted from the plurality of light-emitting elements 22 and incident on the wavelength-selective reflecting layer 28 at the second incident angle. This prevents the fluorescence emitted backward (toward the LED substrate 21) from the phosphor layer 24 from reaching the main surface 21s of the LED substrate 21. Therefore, it is possible to prevent the fluorescence emitted backward (toward the LED substrate 21) from the phosphor layer 24 and reflected by the main surface 21s of the LED substrate 21 from entering the phosphor layer 24 in the extinguished region Roff. The backlight device 950 of Comparative Example 1 has the wavelength-selective reflection layer 28, which reduces color unevenness (particularly color unevenness in which the region R2 appears yellowish) when partial driving is performed.

[0028] However, according to the inventor's investigations, even in the backlight device 950 of Comparative Example 1, color unevenness may not be sufficiently suppressed during partial driving. The wavelength-selective reflecting layer 28 has a lower transmittance for excitation light incident on the wavelength-selective reflecting layer 28 at a third incident angle than for fluorescent light incident on the wavelength-selective reflecting layer 28 at the third incident angle. For example, the transmittance of light in the red wavelength region may increase as the incident angle on the wavelength-selective reflecting layer 28 increases. Therefore, light L3 emitted from the phosphor layer 24 in the lit region Ron is emitted backward (toward the LED substrate 21) and incident on the wavelength-selective reflecting layer 28 at an incident angle equal to or greater than a predetermined angle. The light L3 is transmitted through the wavelength-selective reflecting layer 28 and reflected by the main surface 21s of the LED substrate 21, thereby entering the unlit region Roff. The light L3 contains a large amount of light in the red wavelength region. Therefore, as described with reference to FIG. 4B, the color unevenness in which the region R2 surrounding the lit region Ron in the unlit region Roff appears yellowish is not sufficiently suppressed.

[0029] In contrast, the backlight device 50A according to the present embodiment, by including the louver film 42, can suppress the color unevenness (particularly the color unevenness in which the region R2 appears yellowish) that occurs when partial driving is performed in the backlight device 950 of Comparative Example 1. In the backlight device 50A, of the fluorescence emitted from the phosphor layer 24 in the lit region Ron, light L3 that is incident on the wavelength-selective reflecting layer 28 at an incident angle equal to or greater than a predetermined angle, passes through the wavelength-selective reflecting layer 28, and is reflected by the main surface 21s of the LED substrate 21 is blocked by the multiple louvers 42l, and is therefore prevented from entering the unlit region Roff. The backlight device 50A can suppress a deterioration in the display quality of a liquid crystal display device.

[0030] Another example of a louver film that may be included in the backlight device according to this embodiment will be described. As in the louver film 43 shown in FIG. 1E, when viewed from the normal direction of the main surface 21s of the LED substrate 21, louvers 43l extending in a first direction (the y direction in the figure) may be arranged parallel to one another. That is, when viewed from the normal direction of the main surface 21s of the LED substrate 21, multiple louvers 43l are formed in a striped pattern. In the example shown in FIG. 1E, the multiple louvers 43l are regularly arranged (the pitch between adjacent louvers 43l is P2). Like the louver film 42 described above, the louver film 43 blocks at least a portion of the fluorescence emitted from the phosphor layer 24 and the excitation light emitted from the light-emitting element 22. The louver film 43 further includes two opposing base films, and the multiple louvers 43l are arranged between the two base films.

[0031] In addition to the louver film 43 shown in FIG. 1E, the backlight device according to this embodiment may further include another louver film 44 (FIG. 1F) having multiple louvers 44l extending in a second direction (e.g., the x direction in the figure) different from the first direction. Like the louver film 43, the louver film 44 also blocks at least a portion of the fluorescence emitted from the phosphor layer 24 and the excitation light emitted from the light-emitting element 22. The louver film 44 further includes two opposing base films, and the multiple louvers 44l are disposed between the two base films. The louver film 44 may be disposed such that the multiple louvers 43l of the louver film 43 and the multiple louvers 44l of the louver film 44 are substantially perpendicular to each other when viewed, for example, from the normal direction of the main surface 21s of the LED substrate 21. For example, the pitch P2 between adjacent louvers 43l and the pitch P3 between adjacent louvers 44l may be equal. Alternatively, instead of using louver films 43 and 44, a single louver film having a plurality of louvers formed in a lattice pattern so as to intersect at right angles with one another may be used. However, in the backlight device according to this embodiment, it is preferable that the plurality of louvers are arranged so as not to overlap with the plurality of light-emitting elements 22 when viewed from the normal direction of main surface 21s of LED substrate 21.

[0032] The backlight device 50A may further include an optical layer stack 30 disposed on the opposite side of the phosphor layer 24 from the wavelength-selective reflection layer 28. For example, as shown in FIG. 1G, the optical layer stack 30 includes two prism sheets 34a and 34b arranged so that the ridges of the prisms intersect substantially perpendicularly with each other, and a polarized-light selective reflection layer 32 disposed on the two prism sheets 34a and 34b. The prism sheet 34a includes, for example, a base film 34ba and a prism layer 34pa formed on the base film 34ba. The prism sheet 34b includes, for example, a base film 34bb and a prism layer 34pb formed on the base film 34bb. The prism sheets 34a and 34b may be, for example, BEF manufactured by 3M. The polarized-light selective reflection layer 32 is, for example, an optical multilayer film having a layered structure in which films with different refractive indices are stacked. The polarized-light selective reflection layer 32 may be, for example, DBEF (registered trademark) manufactured by 3M. The layer structure of the optical layer stack 30 is not limited to the example shown in the drawings, and can be modified as appropriate.

[0033] Fig. 1H shows a backlight device according to a modified example of the present embodiment. Backlight device 50A1 shown in Fig. 1H differs from backlight device 50A in that it does not have diffusion plate 48. Like backlight device 50A, backlight device 50A1 can also suppress degradation in the display quality of a liquid crystal display device.

[0034] (Embodiment 2) The backlight device according to this embodiment will be described with reference to Figures 2A, 2B, and 2C. Figure 2A is a cross-sectional view schematically showing a backlight device 50B according to embodiment 2, and Figure 2B is a cross-sectional view schematically showing a partial drive mode using the backlight device 50B. Figure 2C is a plan view schematically showing an example of the positional relationship between a plurality of louvers 45l and light-emitting elements 22.

[0035] The backlight device 50B differs from the backlight device 50A in that the louver film 45 is disposed closer to the wavelength-selective reflecting layer 28 than to the LED substrate 21 (if a diffuser 48 is provided, the louver film 45 is disposed between the wavelength-selective reflecting layer 28 and the diffuser 48). The louver film 45 is supported by, for example, the diffuser 48. The louver film 45 is disposed on, for example, the main surface of the wavelength-selective reflecting layer 28 facing the LED substrate 21. The louver film 45 includes two opposing base films 45b1 and 45b2 and a plurality of louvers 45l disposed between the two base films 45b1 and 45b2. The base film 45b2 closer to the wavelength-selective reflecting layer 28 may be bonded to the main surface of the wavelength-selective reflecting layer 28 facing the LED substrate 21 via, for example, an adhesive layer. The backlight device 50B further includes a diffuser 48 disposed between the LED substrate 21 and the louver film 45. The diffuser 48 may be omitted. In FIG. 2B, the diffuser plate 48 is omitted for simplicity.

[0036] The use of the backlight device 50B, like the backlight device 50A, can also suppress degradation in the display quality of the liquid crystal display device. The use of the backlight device 50B, like the backlight device 50A, can also suppress color unevenness, such as the yellowish appearance of the region R2 surrounding the lit region Ron during partial driving. In the backlight device 50B, of the fluorescence emitted from the phosphor layer 24 in the lit region Ron, light L3 that is incident on the wavelength-selective reflecting layer 28 at an incident angle equal to or greater than a predetermined angle and that is transmitted through the wavelength-selective reflecting layer 28 is blocked by the multiple louvers 45l, and is therefore prevented from entering the unlit region Roff.

[0037] Furthermore, the backlight device 50B can more effectively suppress color unevenness during partial driving than the backlight device 50A. The backlight device 50B can also suppress the bluish-dark color unevenness in the region R1 at the edge of the lighting region Ron, as described with reference to FIGS. 4A and 4B. In the backlight device 50B, the louver film 45 is disposed closer to the wavelength-selective reflecting layer 28 than the LED substrate 21 (for example, the louver film 45 is provided on the principal surface of the wavelength-selective reflecting layer 28 facing the LED substrate 21). This allows the louver film 45 to block excitation light L1 that would otherwise be incident on the phosphor layer 24 at an angle inclined from the normal to the principal surface of the phosphor layer 24 (obliquely). Therefore, the difference in the amount of excitation light incident on the phosphor layer 24 between the region R1 and the region R0 outside the region R1 of the lighting region Ron is small. This can also suppress the bluish-dark color unevenness in the region R1.

[0038] 2C , when viewed from the normal direction of the main surface 21s of the LED substrate 21, the louver film 45 has louvers 45l extending in the y direction in the figure arranged parallel to one another. That is, when viewed from the normal direction of the main surface 21s of the LED substrate 21, the multiple louvers 45l are formed in a striped pattern. The multiple louvers 45l are regularly arranged, and the pitch of the multiple louvers 45l is smaller than the pitch P1 of the multiple light-emitting elements 22. When viewed from the normal direction of the main surface 21s of the LED substrate 21, the multiple louvers 45l include louvers 45l arranged to overlap any of the multiple light-emitting elements 22. [Industrial Applicability]

[0039] By using the backlight device according to the embodiment of the present invention, it is possible to suppress a decrease in the display quality of a liquid crystal display device. [Explanation of symbols]

[0040] 10: liquid crystal display panel, 21: LED substrate, 21s: main surface, 22: light emitting element, 24: phosphor layer, 28: wavelength selective reflection layer, 30: optical layer laminate, 32: polarized selective reflection layer, 34a, 34b: prism sheet, 34ba, 34bb: base film, 34pa, 34pb: prism layer, 42, 43, 44, 45: louver film, 42b1, 42b2, 45b1, 45b2: base film, 42h, 42h1, 42h2: opening, 42l, 43l, 44l, 45l: louver, 48: diffusion plate, 50A, 50A1, 50B: backlight device, 100A: liquid crystal display device

Claims

1. an LED substrate having a main surface on which a plurality of light-emitting elements that emit excitation light are arranged; a phosphor layer containing a phosphor that emits fluorescence upon receiving the excitation light; a wavelength-selective reflective layer disposed between the phosphor layer and the LED substrate, the wavelength-selective reflective layer having a transmittance that varies depending on the wavelength and / or the angle of incidence of incident light; a louver film disposed between the wavelength selective reflection layer and the LED substrate, the louver film having a plurality of louvers, which blocks the fluorescence and the excitation light incident at an angle of equal to or greater than a first angle and less than 90° with respect to a normal direction of a film surface of the louver film; and The wavelength selective reflective layer is a transmittance for the excitation light incident at a second incident angle is higher than a transmittance for the fluorescence incident at the second incident angle; a backlight device in which the transmittance for the excitation light incident at a third angle greater than the second angle is lower than the transmittance for the fluorescent light incident at the third angle;

2. The backlight device according to claim 1 , wherein the louver film is supported by the LED substrate.

3. An LED substrate having a main surface and a plurality of light-emitting elements that emit excitation light arranged on the main surface; a phosphor layer containing a phosphor that emits fluorescence upon receiving the excitation light; a wavelength-selective reflective layer disposed between the phosphor layer and the LED substrate, the wavelength-selective reflective layer having a transmittance that varies depending on the wavelength and / or the angle of incidence of incident light; a louver film disposed between the wavelength selective reflection layer and the LED substrate, the louver film having a plurality of louvers, which blocks the fluorescence and the excitation light incident at an angle of equal to or greater than a first angle and less than 90° with respect to a normal direction of a film surface of the louver film; and the louver film is supported by the LED substrate; The louver film is provided on the main surface of the LED substrate so as to be in contact with the main surface.

4. An LED substrate having a main surface and a plurality of light-emitting elements that emit excitation light arranged on the main surface; a phosphor layer containing a phosphor that emits fluorescence upon receiving the excitation light; a wavelength-selective reflective layer disposed between the phosphor layer and the LED substrate, the wavelength-selective reflective layer having a transmittance that varies depending on the wavelength and / or the angle of incidence of incident light; a louver film disposed between the wavelength selective reflection layer and the LED substrate, the louver film having a plurality of louvers, which blocks the fluorescence and the excitation light incident at an angle of equal to or greater than a first angle and less than 90° with respect to a normal direction of a film surface of the louver film; and the louver film is supported by the LED substrate; The louver film has a plurality of openings that overlap with the plurality of light-emitting elements when viewed from a normal direction of the main surface of the LED substrate.

5. An LED substrate having a main surface and a plurality of light-emitting elements that emit excitation light arranged on the main surface; a phosphor layer containing a phosphor that emits fluorescence upon receiving the excitation light; a wavelength-selective reflective layer disposed between the phosphor layer and the LED substrate, the wavelength-selective reflective layer having a transmittance that varies depending on the wavelength and / or the angle of incidence of incident light; a louver film disposed between the wavelength selective reflection layer and the LED substrate, the louver film having a plurality of louvers, which blocks the fluorescence and the excitation light incident at an angle of equal to or greater than a first angle and less than 90° with respect to a normal direction of a film surface of the louver film; and the louver film is supported by the LED substrate; When viewed from the normal direction of the main surface of the LED substrate, each of the plurality of louvers is disposed at a position where it does not overlap each of the plurality of light-emitting elements.

6. An LED substrate having a main surface and a plurality of light-emitting elements that emit excitation light arranged on the main surface; a phosphor layer containing a phosphor that emits fluorescence upon receiving the excitation light; a wavelength-selective reflective layer disposed between the phosphor layer and the LED substrate, the wavelength-selective reflective layer having a transmittance that varies depending on the wavelength and / or the angle of incidence of incident light; a louver film disposed between the wavelength selective reflection layer and the LED substrate, the louver film having a plurality of louvers, which blocks the fluorescence and the excitation light incident at an angle of equal to or greater than a first angle and less than 90° with respect to a normal direction of a film surface of the louver film; and the louver film is supported by the LED substrate; The backlight device further comprises a diffusion plate disposed between the louver film and the wavelength-selective reflection layer.

7. The backlight device according to claim 1 , wherein the louver film is provided on a main surface of the wavelength selective reflection layer facing the LED substrate.

8. The backlight device according to claim 7 , further comprising a diffusion plate disposed between the louver film and the LED substrate.

9. the second angle is greater than or equal to 0° and less than 40°; The backlight device according to claim 1 , wherein the third angle includes an angle equal to or greater than 70° and less than 90°.

10. The backlight device according to claim 1 , wherein the first angle is equal to or greater than 15°.

11. The backlight device according to claim 1 , further comprising an optical layer stack disposed on the phosphor layer opposite to the wavelength-selective reflecting layer.

12. An LED substrate having a main surface and a plurality of light-emitting elements that emit excitation light arranged on the main surface; a phosphor layer containing a phosphor that emits fluorescence upon receiving the excitation light; a wavelength-selective reflective layer disposed between the phosphor layer and the LED substrate, the wavelength-selective reflective layer having a transmittance that varies depending on the wavelength and / or the angle of incidence of incident light; a louver film disposed between the wavelength selective reflection layer and the LED substrate, the louver film having a plurality of louvers, which blocks the fluorescence and the excitation light incident at an angle of equal to or greater than a first angle and less than 90° with respect to a normal direction of a film surface of the louver film; and an optical layer stack disposed on the opposite side of the phosphor layer from the wavelength-selective reflecting layer; The backlight device includes two prism sheets arranged so that the ridge lines of the prisms are substantially perpendicular to each other, and a polarized light selective reflection layer arranged on the two prism sheets.

13. The backlight device of claim 1 , wherein the phosphor includes a quantum dot phosphor.

14. A liquid crystal display panel; The backlight device according to any one of claims 1 to 9 and 12, which emits light toward a rear surface of the liquid crystal display panel; A liquid crystal display device comprising:

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