Backlight device and liquid crystal display device

Abstract

A backlight device is characterized by comprising: an LED substrate in which a plurality of light-emitting elements for emitting excitation light are arranged on a main surface; a phosphor layer containing a phosphor that emits fluorescence by receiving the excitation light; a wavelength selective reflection layer disposed between the phosphor layer and the LED substrate; and a shutter film disposed between the wavelength selective reflection layer and the LED substrate and having a plurality of shutter blades. The wavelength selective reflection layer has different transmittances according to the wavelength and / or angle of incidence of the incident light. The shutter film shields the fluorescent light and the excitation light that are incident at a first angle or more and less than 90 DEG with respect to the normal direction of the film surface of the shutter film.

Description

Technical Field

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

[0002] Most liquid crystal display devices have a backlight device, which has a plurality of LEDs. For example, the plurality of LEDs are divided into a plurality of regions, and only the LEDs in the region that requires illumination light are lit, or the brightness required for each region is adjusted. Such a driving method of the backlight source is called split drive, partial drive, regional drive or local dimming. If the split drive method is adopted, the contrast of the brightness of the bright and dark parts of the liquid crystal display device can be improved.

[0003] In recent years, in order to improve the display quality of display devices, liquid crystal display devices corresponding to high dynamic range (High Dynamic Range, hereinafter referred to as "HDR") have been commercially available.

[0004] In addition, as a liquid crystal display device that can correspond to the UHD Premium specification (color reproduction of BT2020 standard 90% or more, HDR10 specification), for example, as described in Patent Document 1, a liquid crystal display device is being studied that has a backlight device that adopts a remote phosphor method and can suppress color unevenness using a dichroic filter. Prior art literature Patent Literature

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

[0006] According to the research conducted by the present inventors, the liquid crystal display device of Patent Document 1 has a problem that a decrease in display quality due to color unevenness cannot be sufficiently suppressed. Details will be described later.

[0007] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a backlight device capable of suppressing a decrease in the display quality of a liquid crystal display device, and a liquid crystal display device including such a backlight device. Solutions to Solve Problems

[0008] According to an embodiment of the present invention, a solution described in the following items is provided.

[0009] [Project 1] A backlight device, characterized by comprising: An LED substrate having a main surface on which a plurality of light-emitting elements emitting excitation light are arranged; a phosphor layer comprising a phosphor that receives the excitation light and emits fluorescence; a wavelength selective reflection layer, which is disposed between the phosphor layer and the LED substrate and has different transmittances according to the wavelength and / or incident angle of incident light; and A louver film is arranged between the wavelength selective reflection layer and the LED substrate, has a plurality of louvers, and shields the fluorescence and the excitation light incident at an angle greater than a first angle and less than 90° relative to the normal direction of the film surface of the louver film. [Item 2] In the backlight device described in Item 1, the louver film is supported on the LED substrate. [Item 3] In the backlight device according to Item 2, the louver film is provided on the main surface of the LED substrate. [Item 4] In the backlight device according to Item 2 or 3, the louver film has a plurality of openings that overlap with the plurality of light-emitting elements when viewed in a normal direction to the main surface of the LED substrate. [Item 5] In the backlight device according to any one of Items 2 to 4, the plurality of louvers are respectively arranged at positions that do not overlap with any of the plurality of light emitting elements when viewed in the normal direction of the main surface of the LED substrate. [Item 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] In the backlight device according to Item 1, the louver film is provided on the main surface of the wavelength selective reflection layer on the LED substrate side. [Item 8] The backlight device according to Item 7 further includes a diffusion plate arranged between the louver film and the LED substrate. [Item 9] The backlight device according to any one of Items 1 to 8, wherein the wavelength selective reflection layer has a higher transmittance to the excitation light incident at a second angle than to the fluorescence incident at the second angle. The wavelength selective reflection layer has a lower transmittance for the excitation light incident at a third angle greater than the second angle than a transmittance for the fluorescence incident at the third angle. [Item 10] In the backlight device described in Item 9, the second angle includes an angle greater than 0° and less than 40°, and the third angle includes an angle greater than 70° and less than 90°. [Item 11] In the backlight device according to any one of Items 1 to 10, the first angle is greater than or equal to 15°. [Item 12] The backlight device according to any one of Items 1 to 11, further comprising an optical laminated body arranged on the side of the phosphor layer opposite to the wavelength selective reflection layer. [Item 13] In the backlight device described in Item 12, the optical laminate has two prism sheets and a polarization selective reflection layer, the two prism sheets are arranged so that the ridges of the prisms are substantially orthogonal to each other, and the polarization selective reflection layer is arranged on the two prism sheets. [Item 14] In the backlight device according to any one of Items 1 to 13, the phosphor includes a quantum dot phosphor. [Item 15] A liquid crystal display device comprising: a liquid crystal display panel; and A backlight device according to any one of items 1 to 14, which emits light toward the back side of the liquid crystal display panel. Effects of the Invention

[0010] According to the embodiment of the present invention, a backlight device and a liquid crystal display device capable of suppressing a decrease in the display quality of the liquid crystal display device are provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1A 1 is a cross-sectional view schematically showing a backlight device 50 according to Embodiment 1 of the present invention. Figure 1B 1 is a cross-sectional view schematically showing a liquid crystal display device 100A including a backlight device 50A. Figure 1C 2 is a schematic cross-sectional view of a case where a backlight device 50A is used for partial driving. Figure 1D 2 is a plan view of the backlight device 50 , and schematically shows an example of the arrangement relationship between the louvers 421 and the light emitting elements 22 . Figure 1E This is another example of a schematic plan view of the louver film 43 included in the other backlight device according to the first embodiment. Figure 1F This is an example of a schematic plan view of another louver film 44 that another backlight device according to Embodiment 1 further includes. Figure 1G 1 is an example of a schematic cross-sectional view of the optical layered body 30 included in the backlight device 50A. Figure 1H This is a cross-sectional view schematically showing a backlight device 50A1 according to a modified example of the first embodiment. Figure 2A 1 is a cross-sectional view schematically showing a backlight device 50B according to the second embodiment. Figure 2B 2 is a schematic cross-sectional view of a case where a partial driving is performed using the backlight device 50B. Figure 2C 2 is a plan view of the backlight device 50B, and is a diagram schematically showing an example of the arrangement relationship between the louvers 451 and the light emitting elements 22 . Figure 3A is a cross-sectional view schematically showing a backlight device 950 according to Comparative Example 1. Figure 3B 1 is a schematic cross-sectional view of a backlight device 950 according to Comparative Example 1 when partially driven. Figure 4A 1 is a schematic cross-sectional view of a backlight device 950R according to Comparative Example 2 when partially driven. Figure 4B 2 is a diagram schematically showing an image pattern displayed on a liquid crystal display device 900R having a backlight device 950R according to Comparative Example 2. DETAILED DESCRIPTION

[0012] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In addition, the present invention is not limited to the following embodiments. In the following drawings, components having substantially the same functions are denoted by common reference numerals, and their descriptions are sometimes omitted.

[0013] (Implementation Method 1) One side reference Figure 1A , Figure 1B , Figure 1C as well as Figure 1D , while describing a backlight device 50A according to the present embodiment and a liquid crystal display device 100A including the backlight device 50A. Figure 1A is a cross-sectional view schematically showing a backlight device 50A according to Embodiment 1, Figure 1B 1 is a cross-sectional view schematically showing a liquid crystal display device 100A including a backlight device 50A. Figure 1C 2 is a schematic cross-sectional view of a case where a backlight device 50A is used for partial driving. Figure 1D 4 is a schematic plan view of the backlight device 50A, and is a diagram schematically showing an example of the arrangement relationship between the plurality of louvers 421 and the light emitting elements 22 .

[0014] The backlight device 50A includes: an LED substrate 21, on which a plurality of light-emitting elements 22 emitting excitation light are arranged on a main surface 21s; a phosphor layer 24 including a phosphor that receives excitation light and emits fluorescence; a wavelength selection reflection layer 28 disposed between the phosphor layer 24 and the LED substrate 21; and a louver film 42 disposed between the wavelength selection reflection layer 28 and the LED substrate 21 and having a plurality of louvers 421. The wavelength selection reflection layer 28 has different transmittances depending on the wavelength and / or incident angle of light incident on the wavelength selection reflection layer 28. The louver film 42 shields the fluorescence and the excitation light incident at an angle greater than or equal to a first angle and less than 90° relative to the normal direction of the film surface of the louver film 42. In the illustrated example, the louver film 42 has: two opposing base films 42b1 and 42b2; and a plurality of louver blades 421, which are arranged between the two base films 42b1 and 42b2, and each has a main surface intersecting with the main surface of the base film 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. 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 in the illustrated example, and the normal direction of the film surface of the louver film 42 is a direction parallel to the z direction in the illustrated example. In the illustrated example, the plurality of louver blades 421 are plate-shaped with a main surface parallel to the yz plane, and are arranged to be substantially parallel to each other. "The louver film 42 blocks the fluorescence and excitation light that are incident at an angle greater than a first angle and less than 90° relative to the normal direction of the film surface of the louver film 42" includes: the transmittance of the louver film 42 relative to the fluorescence and excitation light incident on the louver film 42 is less than 50%, and the angle of the fluorescence and excitation light relative to the normal direction of the film surface of the louver film 42 is greater than a first angle and less than 90°. The first angle is, for example, greater than 30°, and may also be greater than 15°. For example, the plurality of louvers 421 of the louver film 42 have the function of shielding 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 on the LED substrate 21. That is, the louver film 42 is fixed to the LED substrate 21. The louver film 42 is arranged on the main surface 21s of the LED substrate 21. The louver film 42 may also 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 by means of an adhesive layer. In the illustrated example, the louver film 42 has a plurality of openings 42h. In this example, each opening 42h has an opening 42h1 arranged on the base film 42b1 and an opening 42h2 arranged on the base film 42b2. Each of the plurality of openings 42h overlaps with any one of the plurality of light-emitting elements 22 when viewed from the normal direction of the main surface 21s of the LED substrate 21. The plurality of light-emitting elements 22 are exposed in the plurality of openings 42h.

[0016] like Figure 1A as well as Figure 1D As shown, when viewed from the normal direction of the main surface 21s of the LED substrate 21, the plurality of louvers 421 are respectively arranged between adjacent light-emitting elements 22 among the plurality of light-emitting elements 22. When viewed from the normal direction of the main surface 21s of the LED substrate 21, the plurality of louvers 421 are respectively arranged at positions that do not overlap with the plurality of light-emitting elements 22. The plurality of louvers 421 may include: louvers 421 that are divided into a plurality of parts in the y direction so as not to overlap with the light-emitting elements 22 when viewed from the normal direction of the main surface 21s of the LED substrate 21; and louvers 421 whose length in the y direction is substantially equal to the length L2 of the LED substrate 21 in the y direction. The distance between adjacent louvers 421 may not be fixed. In the backlight device 50A, two or more louvers 421 are arranged between adjacent light-emitting elements 22 among the plurality of light-emitting elements 22. As the louver film of the backlight device of this embodiment, for example, a security / privacy filter (product name: PF430W9B) manufactured by 3M Company can be used. By providing a plurality of openings in such a filter, the louver film 42 shown in the figure can also be obtained.

[0017] The backlight device 50A further includes a diffusion plate 48 disposed between the louver film 42 and the wavelength selective reflection layer 28. Figure 1C In the figure, for simplicity, the diffuser plate 48 is omitted. The wavelength selective reflection layer 28 and the phosphor layer 24 may also be supported by the diffuser plate 48. For example, the wavelength selective reflection layer 28 and the phosphor layer 24 may be sequentially stacked on the diffuser plate 48, or these layers may be fixed to the diffuser plate 48 in a state where they are bonded to each other via an adhesive layer. It should be noted that the diffuser plate 48 may be omitted.

[0018] like Figure 1BAs shown, 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 the rear surface 10 r of the liquid crystal display panel 10 .

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

[0020] The phosphor layer 24 includes a phosphor that emits fluorescence when excited by the excitation light emitted from the light-emitting element 22. For example, when 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 perspective of obtaining 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, for example, include 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-value width of the peak wavelength of the emission spectrum and high color purity. Therefore, for example, it is expected to meet the UHD Premium standard (color reproducibility BT2020 standard 90% or more, HDR10 standard). Alternatively, well-known phosphors such as red sulfide phosphors (e.g., calcium sulfide phosphors) and green sulfide phosphors (e.g., thiogallate phosphors) may also be used. A protective layer may be provided on both sides or on any one side of the phosphor layer 24 .

[0021] When the incident angle of light incident on the wavelength selective reflection layer 28 (for example, a dichroic filter) (the angle of the wavelength selective reflection layer 28 with respect to the normal direction of the film surface) is smaller than a predetermined angle (for example, smaller than 40°), the transmittance of the wavelength selective reflection layer 28 with respect to the excitation light emitted from the plurality of light emitting elements 22 is higher than the transmittance of the wavelength selective reflection layer 28 with respect to the fluorescence emitted from the phosphor layer 24. That is, the transmittance of the wavelength selective reflection layer 28 with respect to the excitation light incident on the wavelength selective reflection layer 28 at the second angle of incidence of 0° or more and less than 40° is higher than the transmittance of the wavelength selective reflection layer 28 with respect to the fluorescence incident on the wavelength selective reflection layer 28 at the second angle of incidence. On the other hand, the transmittance of the wavelength selective reflection layer 28 with respect to the excitation light incident on the wavelength selective reflection layer 28 at a third angle of incidence greater than the second angle is lower than the transmittance of the fluorescence incident on the wavelength selective reflection layer 28 at the third angle of incidence. The third angle is, for example, an angle of 70° or more and less than 90°. For light incident on the wavelength selective reflection layer 28 at the second angle of incidence, at least a portion of the wavelength region of the excitation light emitted from the plurality of light emitting elements 22 is transmitted, and at least a portion of the fluorescence emitted from the phosphor layer 24 is reflected. It is preferred that for light incident on the wavelength selective reflection layer 28 at the second angle of incidence, all of the excitation light emitted from the plurality of light emitting elements 22 is transmitted, and all of the light emitted from the phosphor layer 24 is reflected. For example, in the case where the light emitting element 22 is a blue LED, for light incident on the wavelength selective reflection layer 28 at the second angle of incidence, the wavelength selective reflection layer 28 transmits light in the emission wavelength region of the blue LED (i.e., blue light), and reflects light in the wavelength region from green to red. For light incident on the wavelength selective reflection layer 28 at the third angle of incidence, at least a portion of the fluorescence emitted from the phosphor layer 24 is transmitted, and at least a portion of the wavelength region of the excitation light emitted from the plurality of light emitting elements 22 is reflected. For example, the wavelength selective reflection layer 28 reflects blue light and transmits red light for light incident on the wavelength selective reflection layer 28 at the incident angle of the third angle. In addition, in this specification, light emitted by a phosphor is sometimes referred to as "fluorescence". Unless otherwise specified, "fluorescence" includes fluorescence in a narrow sense and phosphorescence. The wavelength selective reflection layer 28 is, for example, an optical multilayer film having a laminated structure in which films with different refractive indices are laminated.

[0022] As described below, the backlight device 50A includes the wavelength selective reflection layer 28 , and thus can suppress color unevenness during partial driving.

[0023] The effects of the backlight device 50 of the present embodiment will be described while being compared with the backlight device of the comparative example. Figure 3A 1 is a cross-sectional view schematically showing a liquid crystal display device 900 including a backlight device 950 according to Comparative Example 1. Figure 3B 1 is a schematic cross-sectional view of a backlight device 950 according to Comparative Example 1 when partially driven. Figure 4A 1 is a schematic cross-sectional view of a backlight device 950R according to Comparative Example 2 when partially driven. Figure 4B Schematic diagram when viewed from the normal direction of the liquid crystal display panel of the liquid crystal display device 900R having the backlight device 950R of Comparative Example 2. The backlight device 950 of Comparative Example 1 is different from the backlight device 50A involved in the embodiment of the present invention in that it does not have a louver film. The backlight device 950 and the liquid crystal display device 900 of Comparative Example 1 are equivalent to the backlight device described in Patent Document 1 and the liquid crystal display device having the backlight device. The backlight device 950R of Comparative Example 2 is different from the backlight device 950 of Comparative Example 1 in that it does not have a wavelength selective reflection layer 28.

[0024] First, refer to Figure 4A and Figure 4B , explaining the function and effect of the wavelength selective reflection layer 28.

[0025] like Figure 4A and Figure 4B As shown, the backlight device 950R of Comparative Example 2 has a lighting region Ron where the light emitting element 22 is lit and an off region Roff where the light emitting element 22 is not lit when the partial driving is performed. Figure 4B Schematically shows an image pattern displayed by a liquid crystal display device 900R having a backlight device 950R of Comparative Example 2. The region at the end of the lit region Ron (in other words, the region in the lit region Ron close to the boundary with the extinguished region Roff) is shown as region R1, and the region in the extinguished region Roff surrounding the lit region Ron is shown as region R2. Figure 4A , together with a schematic cross-sectional view of a backlight device 950R of Comparative Example 2 (lower section), schematically shows the colors displayed in each region (upper section) and the blue light L in each region. B , Green light L G And red light L R Brightness (middle section). Figure 4A The upper part of schematically shows the degree of blue or yellow coloring with respect to the colors displayed in each region, taking the region (region R0) other than region R1 of the lit region Ron as a reference. Figure 4A The middle section of the blue light L in area R0 B The brightness of the blue light L in each area is schematically shown by the size of the arrow. B , Green light L G And red light L R Later, in Figure 4AThe same figure (schematic cross-sectional view when partially driven) is represented in the same manner.

[0026] When the backlight device 950R of Comparative Example 2 is partially driven, color unevenness (sometimes referred to as color halo) may occur. Figure 4B As shown, in the extinguished area Roff which should be a dark part, the yellow sense is sometimes enhanced in the area R2 around the lit area Ron. Furthermore, in the area R1 at the end of the lit area Ron, it sometimes looks blue and dark. As one of the causes of the former phenomenon, it is considered that the light L2 emitted from the phosphor layer 24 of the lit area Ron to the rear (LED substrate 21 side) is reflected by the main surface 21s of the LED substrate 21 and enters the extinguished area Roff. The light L2 contains more light in the wavelength range from red to green than blue light. Therefore, the area R2 looks yellower than the area R0 outside the area R1 of the lit area Ron. The latter color unevenness is caused by the following reasons. Since the area R1 is adjacent to the extinguished area Roff, the excitation light L1 (here is blue light) incident on the phosphor layer 24 at an angle inclined from the normal direction of the main surface of the phosphor layer 24 (from the inclined direction) is less than the area R0 outside the area R1 of the lit area Ron. Therefore, since region R1 receives blue light and the brightness of green light emitted by the green phosphor and red light emitted by the red phosphor is lower than that of region R0, color unevenness occurs that appears bluer and darker than region R0.

[0027] In contrast, Figure 3A The backlight device 950 of the comparative example 1 shown has a wavelength selective reflection layer 28 between the phosphor layer 24 and the LED substrate 21. Since the transmittance of the wavelength selective reflection layer 28 for the fluorescence emitted from the phosphor layer 24 and incident on the wavelength selective reflection layer 28 at the second angle of incidence is lower than the transmittance of the wavelength selective reflection layer 28 for the excitation light emitted from the plurality of light emitting elements 22 and incident on the wavelength selective reflection layer 28 at the second angle of incidence, the wavelength selective reflection layer 28 can suppress the fluorescence emitted from the phosphor layer 24 to the rear (LED substrate 21 side) from reaching the main surface 21s of the LED substrate 21. Therefore, it is possible to suppress the fluorescence emitted from the phosphor layer 24 to the rear (LED substrate 21 side) and reflected on the main surface 21s of the LED substrate 21 from entering the phosphor layer 24 in the extinguishing area Roff. The backlight device 950 of the comparative example 1 has the wavelength selective reflection layer 28, and can suppress color unevenness (especially color unevenness that appears yellowish in the area R2) when partial driving is performed.

[0028] However, according to the research of the present inventors, in the backlight device 950 of Comparative Example 1, the color unevenness is sometimes not sufficiently suppressed during partial driving. The transmittance of the wavelength selective reflection layer 28 for the excitation light incident on the wavelength selective reflection layer 28 at the incident angle of the third angle is lower than the transmittance of the fluorescence incident on the wavelength selective reflection layer 28 at the incident angle of the third angle. For example, if the incident angle incident on the wavelength selective reflection layer 28 becomes larger, the transmittance of the light in the red wavelength region sometimes increases. Therefore, among the fluorescence emitted from the phosphor layer 24 in the lighting area Ron, the light L3 emitted to the rear (LED substrate 21 side) and incident on the wavelength selective reflection layer 28 at an incident angle greater than a specified angle passes through the wavelength selective reflection layer 28, is reflected by the main surface 21s of the LED substrate 21, and is incident on the extinguishing area Roff. The light L3 contains a large amount of light in the red wavelength region. Therefore, as shown in reference Figure 4B As described above, it is not possible to sufficiently suppress the yellowish color unevenness of the region R2 around the lighting region Ron in the extinguished region Roff.

[0029] In contrast, the backlight device 50A of the present embodiment has the louver film 42, and can suppress the color unevenness (especially the color unevenness that the region R2 looks yellow) generated when performing partial driving in the backlight device 950 of the comparative example 1. In the backlight device 50A, the fluorescence emitted from the phosphor layer 24 in the lighting region Ron is incident on the wavelength selection reflection layer 28 at an incident angle greater than a predetermined angle, and the light L3 reflected by the main surface 21s of the LED substrate 21 through the wavelength selection reflection layer 28 is shielded by the plurality of louvers 421, thereby suppressing the light from entering the extinguishing region Roff. The backlight device 50A can suppress the reduction in the display quality of the liquid crystal display device.

[0030] Other examples of the louver film that the backlight device of this embodiment can have are described below. Figure 1E Like the louver film 43 shown in FIG. 1 , for example, when viewed from the normal direction of the main surface 21s of the LED substrate 21, the louvers 431 extending in the first direction (y direction in the figure) can also be arranged in parallel with each other. That is, when viewed from the normal direction of the main surface 21s of the LED substrate 21, the plurality of louvers 431 are formed in a stripe shape. Figure 1E In the example shown, the plurality of louvers 431 are regularly arranged (the pitch between adjacent louvers 431 is P2). The louver film 43, like the above-mentioned louver film 42, shields 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 also has two opposing base films, and the plurality of louvers 431 are arranged between the two base films.

[0031] The backlight device of this embodiment has Figure 1EIn addition to the louver film 43 shown, other louver films 44 ( Figure 1F ), the other louver film 44 has a plurality of louvers 441 extending in a second direction different from the first direction (for example, the x direction in the figure). The louver film 44, like the louver film 43, also shields the fluorescence emitted from the phosphor layer 24 and at least a portion of the excitation light emitted from the light-emitting element 22. The louver film 44 also has two opposing base films, and the plurality of louvers 441 are arranged between the two base films. The louver film 44 can be configured so that, for example, when observed from the normal direction of the main surface 21s of the LED substrate 21, the plurality of louvers 431 of the louver film 43 and the plurality of louvers 441 of the louver film 44 are approximately orthogonal. For example, the spacing P2 between adjacent louvers 431 and the spacing P3 between adjacent louvers 441 may also be equal. Alternatively, instead of using the louver film 43 and the louver film 44, a louver film having a plurality of louvers formed in a lattice shape in a mutually orthogonal manner may be used. However, in the backlight device of the present embodiment, it is preferable that the plurality of louvers are arranged so as not to overlap with each of the plurality of light emitting elements 22 when viewed in the normal direction of the principal surface 21 s of the LED substrate 21 .

[0032] The backlight device 50A may further include an optical laminate 30 disposed on the opposite side of the wavelength selective reflection layer 28 of the phosphor layer 24. Figure 1G As shown, the optical stack 30 has two prism sheets 34a and 34b arranged in a manner that the ridges of their respective prisms are approximately orthogonal to each other, and a polarization selective reflection layer 32 arranged on the two prism sheets 34a and 34b. The prism sheet 34a, for example, has a base film 34ba and a prism layer 34pa formed on the base film 34ba, and the prism sheet 34b, for example, has a base film 34bb and a prism layer 34pb formed on the base film 34bb. As the prism sheets 34a and 34b, for example, BEF manufactured by 3M can be used. The polarization selective reflection layer 32 is, for example, an optical multilayer film having a stacked structure in which films with different refractive indices are stacked. As the polarization selective reflection layer 32, for example, DBEF (registered trademark) manufactured by 3M can be used. The stacked structure of the optical stack 30 is not limited to the example shown in the figure and can be appropriately changed.

[0033] Figure 1H A backlight device according to a modified example of the present embodiment is shown. Figure 1H The backlight device 50A1 shown is different from the backlight device 50A in that it does not include the diffusion plate 48. In the backlight device 50A1, similarly to the backlight device 50A, it is possible to suppress a decrease in the display quality of the liquid crystal display device.

[0034] (Implementation Method 2) One side reference Figure 2A, Figure 2B as well as Figure 2C , while explaining the backlight device of this embodiment. Figure 2A is a cross-sectional view schematically showing a backlight device 50B according to Embodiment 2. Figure 2B 2 is a schematic cross-sectional view of a case where a partial driving is performed using the backlight device 50B. Figure 2C 4 is a schematic plan view of the backlight device 50B, and is a diagram schematically showing an example of the arrangement relationship between the plurality of louvers 451 and the light emitting elements 22 .

[0035] In the backlight device 50B, the louver film 45 is arranged at a position closer to the wavelength selective reflection layer 28 than the LED substrate 21 (when a diffuser plate 48 is provided, it is arranged between the wavelength selective reflection layer 28 and the diffuser plate 48), which is different from the backlight device 50A. The louver film 45 is supported by the diffuser plate 48, for example. The louver film 45 is provided on the main surface of the wavelength selective reflection layer 28 on the LED substrate 21 side, for example. The louver film 45 has two opposing base films 45b1 and 45b2, and a plurality of louvers 451 arranged between the two base films 45b1 and 45b2. The base film 45b2 close to the wavelength selective reflection layer 28 may also be bonded to the main surface of the wavelength selective reflection layer 28 on the LED substrate 21 side via, for example, an adhesive layer. The backlight device 50B also has a diffuser plate 48 arranged between the LED substrate 21 and the louver film 45. In addition, the diffuser plate 48 can be omitted. In Figure 2B In the figure, the diffuser plate 48 is omitted for simplicity.

[0036] By using the backlight device 50B, it is possible to suppress the reduction in the display quality of the liquid crystal display device, similarly to the backlight device 50A. By using the backlight device 50B, it is possible to suppress the yellowing of the area R2 around the lighting area Ron when partial driving is performed, similarly to the backlight device 50A. In the backlight device 50B, the fluorescence emitted from the phosphor layer 24 of the lighting area Ron is incident on the wavelength selective reflection layer 28 at an incident angle greater than a predetermined angle, and the light L3 that has passed through the wavelength selective reflection layer 28 is shielded by the plurality of louvers 451, thereby suppressing the incident light on the extinguishing area Roff.

[0037] In addition, the backlight device 50B can more effectively suppress the occurrence of color unevenness when partial driving is performed than the backlight device 50A. The backlight device 50B can also suppress the occurrence of color unevenness when partial driving is performed. Figure 4A and Figure 4BThe color unevenness that looks bluish in the region R1 at the end of the lighting region Ron described above. In the backlight device 50B, since the louver film 45 is arranged at a position closer to the wavelength selective reflection layer 28 than the LED substrate 21 (for example, the louver film 45 is provided on the main surface of the wavelength selective reflection layer 28 on the LED substrate 21 side), the excitation light L1 that is incident on the phosphor layer 24 at an angle inclined from the normal direction of the main surface of the phosphor layer 24 (from the inclined direction) is shielded by the louver film 45. Therefore, the difference in the excitation light incident on the phosphor layer 24 is small between the region R1 and the region R0 other than the region R1 of the lighting region Ron. Therefore, the color unevenness that looks bluish can also be suppressed in the region R1.

[0038] like Figure 2C As shown, when viewed from the normal direction of the main surface 21s of the LED substrate 21, the louver film 45 is configured so that the louvers 451 extending in the y direction in the figure are parallel to each other. That is, when viewed from the normal direction of the main surface 21s of the LED substrate 21, the plurality of louvers 451 are formed in a stripe shape. The plurality of louvers 451 are regularly arranged, and the pitch between the plurality of louvers 451 is smaller than the pitch P1 of the plurality of light-emitting elements 22. When viewed from the normal direction of the main surface 21s of the LED substrate 21, the plurality of louvers 451 include louvers 451 configured in a manner overlapping with any one of the plurality of light-emitting elements 22.

[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 the liquid crystal display device.

Claims

1. A backlight device, characterized in that: have: An LED substrate having a main surface on which a plurality of light-emitting elements emitting excitation light are arranged; a phosphor layer comprising a phosphor that receives the excitation light and emits fluorescence; a wavelength selective reflection layer, which is disposed between the phosphor layer and the LED substrate and has different transmittances according to the wavelength and / or incident angle of the incident light; as well as A louver film is arranged between the wavelength selective reflection layer and the LED substrate, has a plurality of louvers, and shields the fluorescence and the excitation light incident at an angle greater than a first angle and less than 90° relative to the normal direction of the film surface of the louver film.

2. The backlight device according to claim 1, characterized in that: The shutter film is supported by the LED substrate.

3. The backlight device according to claim 2, characterized in that: The louver film is disposed on the main surface of the LED substrate.

4. The backlight device according to claim 2, characterized in that: The louver film has a plurality of openings, and when viewed in a normal direction of the main surface of the LED substrate, the plurality of openings overlap with the plurality of light emitting elements.

5. The backlight device according to any one of claims 2 to 4, characterized in that: When viewed in the normal direction of the main surface of the LED substrate, each of the plurality of louvers is arranged at a position not overlapping with each of the plurality of light emitting elements.

6. The backlight device according to any one of claims 2 to 4, characterized in that: A diffusion plate is further provided, and the diffusion plate is arranged between the louver film and the wavelength selective reflection layer.

7. The backlight device according to claim 1, characterized in that: The louver film is provided on the main surface of the wavelength selective reflection layer on the LED substrate side.

8. The backlight device according to claim 7, characterized in that: A diffusion plate is also provided, and the diffusion plate is arranged between the louver film and the LED substrate.

9. The backlight device according to any one of claims 1 to 4, 7 and 8, characterized in that: The wavelength selective reflection layer has a transmittance of the excitation light incident at a second angle of incidence higher than a transmittance of the fluorescence incident at the second angle of incidence, The wavelength selective reflection layer has a lower transmittance to the excitation light incident at a third angle greater than the second angle than a transmittance to the fluorescent light incident at the third angle.

10. The backlight device according to claim 9, characterized in that: The second angle includes an angle greater than 0° and less than 40°, and the third angle includes an angle greater than 70° and less than 90°.

11. The backlight device according to any one of claims 1 to 4, 7, 8 and 10, characterized in that: The first angle is greater than 15°.

12. The backlight device according to any one of claims 1 to 4, 7, 8 and 10, characterized in that: The invention further includes an optical stacked body disposed on the side of the phosphor layer opposite to the wavelength selective reflection layer.

13. The backlight device according to claim 12, characterized in that: The optical laminate has two prism sheets and a polarization selective reflection layer. The two prism sheets are arranged so that the ridge lines of the prisms are orthogonal to each other, and the polarization selective reflection layer is arranged on the two prism sheets.

14. The backlight device according to any one of claims 1 to 4, 7, 8, 10 and 13, characterized in that: The phosphor comprises a quantum dot phosphor.

15. A liquid crystal display device, characterized in that: have: a liquid crystal display panel; and The backlight device according to any one of claims 1 to 14, which emits light toward the back surface of the liquid crystal display panel.

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