Light diffusing sheet, backlight unit, liquid crystal display device, and information device

Abstract

A light diffuser sheet is provided that is easier and more stable to manufacture with the desired precision, suppresses moiré fringes, and has better brightness uniformity. The light diffuser sheet (44) disclosed herein is a light diffuser sheet for a backlight unit, having a first surface (62a) as a light emitting surface and a second surface (63a) as a light incident surface. On the first surface (62a), a first parallel prism microstructure (65) composed of a plurality of first prisms (65a) extending along a first direction (d11) is provided. On the second surface (63a), a second parallel prism microstructure (64) composed of a plurality of second prisms (64a) extending along a second direction (d12) is provided. The angle θ0 between the first direction (d11) and the second direction (d12) is 10° or more and 80° or less when viewed from above.

Description

Technical Field

[0001] This invention relates to a light diffuser, a backlight unit, a liquid crystal display device, and an information device. Background Technology

[0002] Liquid crystal displays (LCDs) are widely used in various information devices such as car navigation systems, personal computers, monitors, mobile phones, smartphones, laptops, tablets, portable game consoles, photocopiers, ticket vending machines, automatic cash deposit machines, and virtual reality (VR) goggles. For the backlight of LCDs, two methods are used: direct-lit backlighting with the light source positioned on the back of the LCD panel and backlighting with a light guide plate. In recent years, there has been a strong push to reduce the thickness of LCDs, and several devices using the light guide plate method have been proposed as suitable for thinner designs.

[0003] In addition, in order to reduce the residual image of the light guides arranged on the light guide surface due to the moiré fringe (interference fringe) phenomenon, various light diffusers have been used from the viewpoint of improving the uniformity of in-plane brightness (for example, Patent Document 1 and Patent Document 2).

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: U.S. Patent Application Publication No. 2020 / 0379159

[0007] Patent Document 2: U.S. Patent Application Publication No. 2022 / 0197086 Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] However, in the light diffuser sheet with a beaded coating disclosed in Patent Document 1, it is difficult to uniformly arrange the coated microbeads within the surface. On the other hand, in the light diffuser sheet with an inverted polygonal vertices disclosed in Patent Document 2, due to the complexity of the shape, it is difficult to ensure processing accuracy and uniformly control each inverted polygonal vertices. Therefore, the reduced brightness uniformity caused by the inhomogeneity of these in-plane shapes becomes a problem. This problem is arguably even more important in advancing the thinning process.

[0010] Therefore, the purpose of this disclosure is to provide a light diffuser that is easy and more stable to manufacture with the desired precision and has better brightness uniformity by suppressing moiré fringes.

[0011] Technical means to solve the problem

[0012] To achieve the aforementioned objective, one aspect of this disclosure involves a light diffuser sheet for a backlight unit, which has a first surface as a light emitting surface and a second surface as a light incident surface. On the first surface, a first parallel prism microstructure composed of a plurality of first prisms extending along a first direction is provided, and on the second surface, a second parallel prism microstructure composed of a plurality of second prisms extending along a second direction is provided. The angle between the first direction and the second direction is more than 10° and less than 80° when viewed from above.

[0013] One aspect of this disclosure is a backlight unit, which includes a light source in the form of a light guide plate, a light guide plate, a light diffuser sheet as described in one aspect of this disclosure, a first prism sheet arranged on the light emitting side of the light diffuser sheet, and a second prism sheet arranged on the light emitting side of the first prism sheet, wherein the light diffuser sheet, the first prism sheet, and the second prism sheet are arranged sequentially on the light guide plate.

[0014] One aspect of this disclosure is a liquid crystal display device, which includes a backlight unit and a liquid crystal display screen as described in one aspect of this disclosure.

[0015] One aspect of this disclosure is an information device, which includes the liquid crystal display device involved in one aspect of this disclosure.

[0016] The effects of the invention

[0017] According to one aspect of this disclosure, a light diffuser sheet, a backlight unit, and a liquid crystal display device with superior brightness uniformity and easier and more stable manufacturing to the desired precision can be provided. Attached Figure Description

[0018] [ Figure 1 ] Figure 1 This is a schematic cross-sectional view illustrating an embodiment of a liquid crystal display device.

[0019] [ Figure 2 ] Figure 2 These are schematic cross-sectional and top views illustrating the structure of the backlight unit in the embodiment.

[0020] [ Figure 3 ] Figure 3 This is a schematic cross-sectional view of the light diffuser sheet in the embodiment.

[0021] [ Figure 4 ] Figure 4 This is a perspective view of the first prism, which constitutes the first parallel prism microstructure of the embodiment.

[0022] [ Figure 5 ] Figure 5 This diagram schematically illustrates the overlapping arrangement of the layers of the backlight unit in an embodiment.

[0023] [ Figure 6 ] Figure 6 This diagram schematically illustrates the overlapping arrangement of the layers of the backlight unit in an embodiment.

[0024] [ Figure 7 ] Figure 7 This diagram schematically illustrates the overlapping arrangement of the layers of the backlight unit in an embodiment.

[0025] [ Figure 8 ] Figure 8 This is a diagram illustrating another example of the prism shape of the first prism constituting the first parallel prism microstructure of the embodiment.

[0026] [ Figure 9 ] Figure 9 This is a diagram illustrating another example of the prism shape of the first prism constituting the first parallel prism microstructure of the embodiment.

[0027] [ Figure 10 ] Figure 10 This is a schematic cross-sectional view illustrating the structure of the backlight unit in the embodiment.

[0028] [ Figure 11 ] Figure 11 This is a graph showing the evaluation results of the moiré fringes of the backlight unit in the embodiment. Detailed Implementation

[0029] (Implementation Method 1)

[0030] The embodiments of this disclosure will now be described with reference to the accompanying drawings. Furthermore, the scope of this disclosure is not limited to the following embodiments, and modifications can be made freely within the scope of the technical concept of this disclosure.

[0031] <Liquid Crystal Display Device>

[0032] like Figure 1 As shown, the liquid crystal display device 50 of this embodiment includes: a liquid crystal display screen 5, a first polarizing plate 6 attached to the lower surface of the liquid crystal display screen 5, a second polarizing plate 7 attached to the upper surface of the liquid crystal display screen 5, and a backlight unit 40 disposed on the back side of the liquid crystal display screen 5 via the first polarizing plate 6.

[0033] The liquid crystal display screen 5 includes a thin film transistor (TFT) substrate 1 and a color filter (CF) substrate 2 arranged opposite to each other, a liquid crystal layer 3 disposed between the TFT substrate 1 and the CF substrate 2, and a frame-shaped sealing material (not shown) for sealing the liquid crystal layer 3 between the TFT substrate 1 and the CF substrate 2.

[0034] The backlight unit 40 is a side-mounted backlight unit that guides light 48 emitted by the light source 41 located at the end, which is approximately parallel to the liquid crystal display screen 5, to the side of the liquid crystal display screen 5.

[0035] From the front ( Figure 1 The shape of the display screen 50a of the liquid crystal display device 50 observed from above is, in principle, rectangular or square, but not limited to these. It can also be any shape such as a rectangle with rounded corners, ellipse, circle, trapezoid, or car dashboard.

[0036] In the liquid crystal display device 50, a predetermined voltage is applied to the liquid crystal layer 3 in each sub-pixel corresponding to each pixel electrode, thereby changing the orientation state of the liquid crystal layer 3. This adjusts the transmittance of light incident from the backlight unit 40 via the first polarizing plate 6. The light with adjusted transmittance is then emitted via the second polarizing plate 7 to display an image.

[0037] The liquid crystal display device 50 of this embodiment is used as a display device assembled in various information devices (such as in-vehicle devices such as car navigation systems, personal computers, monitors, mobile phones, smartphones, portable information terminals such as laptop computers or tablet computers, portable game consoles, photocopiers, ticket vending machines, automatic cash deposit and withdrawal machines, VR goggles, etc.).

[0038] The TFT substrate 1 includes, for example, a plurality of TFTs arranged in a matrix on a glass substrate, an interlayer insulating film disposed covering each TFT, a plurality of pixel electrodes arranged in a matrix on the interlayer insulating film and respectively connected to the plurality of TFTs, and an alignment film disposed covering each pixel electrode. The CF substrate 2 includes, for example, a black matrix arranged in a lattice on a glass substrate, color filters comprising red, green, and blue layers disposed between each grid of the black matrix, a common electrode disposed covering the black matrix and the color filters, and an alignment film disposed covering the common electrode. The liquid crystal layer 3 is composed of a nematic liquid crystal material containing liquid crystal molecules with electro-optic properties. The first polarizing plate 6 and the second polarizing plate 7 include, for example, a polarizing element layer having a unidirectional polarization axis and a pair of protective layers disposed to hold the polarizing element layer.

[0039] <Backlight Unit>

[0040] Figure 2 An example of the structure of the backlight unit 40 according to this embodiment is shown. Figure 3 This is a schematic cross-sectional view of the light diffuser 44 in the embodiment. Figure 4 This is a three-dimensional view of the first prism 65a, which constitutes the first parallel prism microstructure 65.

[0041] Figure 2The backlight unit 40 is shown on the left side. The backlight unit 40 includes a side-mounted light source layer 47, a light diffuser 44, a first prism sheet 45 disposed on the light-emitting side of the light diffuser 44, and a second prism sheet 46 disposed on the light-emitting side of the first prism sheet. The light source layer 47 includes a side-mounted light source 41, a reflector 42, and a light guide plate 43. The light diffuser 44, the first prism sheet 45, and the second prism sheet 46 are sequentially arranged on the light guide plate 43. However, for ease of viewing, the layers are shown with a large gap between them. That is, in the backlight unit 40, the layers are actually substantially connected. Furthermore, cross-sections are schematically shown for each layer, and for the layers including prisms, cross-sections cut perpendicular to the extending direction of the prisms constituting each layer are shown.

[0042] The light from the light source layer 47 is diffused by the first prism sheet 45 and the second prism sheet 46, which helps to emit light with high brightness and uniformity across the entire surface of the liquid crystal display 5. However, for these prism sheets to function, it is desirable for the light to be incident at an angle within a predetermined range.

[0043] In contrast, since the light source layer 47 is a side-lit light source layer containing the light source 41 at its end, the light emitted from the light source layer 47 is at an angle nearly parallel to the light source layer 47. Therefore, if the first prism sheet 45 and the second prism sheet 46 are directly disposed on the light source layer 47, the angle at which light is incident on these prism sheets is not necessarily desired. As a result, the light is difficult to diffuse properly, leading to reduced uniformity and brightness.

[0044] Therefore, the backlight unit 40 includes a light diffuser 44 between the light source layer 47 and the first prism sheet 45. The light diffuser 44 refracts the light emitted from the light source layer 47 to the side of the first prism sheet 45, so that the light is incident on the first prism sheet 45 and the second prism sheet 46 at the desired angle. As a result, the backlight unit 40 achieves uniform and high-brightness light emission.

[0045] Figure 2 The right side schematically shows the direction from the vertical direction ( Figure 2 The views are taken from above (i.e., from above) of the stacked layers. These views are shown in the actual stacking direction within the backlight unit 40. The individual elements will be described in detail below.

[0046] <Light Source Layer>

[0047] The light source layer 47 includes a light source 41, a reflective sheet 42, and a light guide plate 43. The light guide plate 43 is stacked on the reflective sheet 42. The light source 41 directs light 48 from the end of the light guide plate 43 in a manner substantially parallel to the light guide plate 43. The light guide plate 43 guides the light 48 toward the side opposite to the light source 41 and emits the light 48 at a small angle relative to the surface of the light guide plate 43 toward the liquid crystal display screen 5. The reflective sheet 42 reflects the light that is to be emitted toward the opposite side of the liquid crystal display screen 5, directing it toward the liquid crystal display screen 5.

[0048] The reflector 42 is made of, for example, a film made of white polyethylene terephthalate resin, a silver vapor-deposited film, etc. The light guide plate 43 can be, for example, a cylindrical lens sheet made of polycarbonate, polyethylene terephthalate, acrylic resin, etc. In this case, each cylindrical lens 43a (refer to...) Figure 2 (The cross-sectional view) extends along the incident direction of light 48. Furthermore, when the light guide plate 43 (and even the display screen 50a) is rectangular, the incident direction of light 48 is usually perpendicular to the side where the light source layer 47 is located.

[0049] Although the direction in which light 48 is incident on the light guide plate 43 is emitted from the light source 41 with a certain degree of diffusion, it can be considered as the direction in which its center faces. Furthermore, in this embodiment, the light guiding direction d1 in the light guide plate 43 is the direction in which the center faces, and it is also the extension direction of the cylindrical lens 43a. In addition, the term "plate" in relation to light diffusers, etc., refers to all shapes that are relatively thin and flat, including plate-like and film-like shapes.

[0050] There is no particular limitation on the type of light source 41. For example, it can be a light-emitting diode (LED) element or a laser element. From the point of view of cost and productivity, an LED element can be used. When using an LED element, multiple LED chips can be included.

[0051] Furthermore, this embodiment describes a side-mounted light source, but the backlight unit of this disclosure is not limited to this method; any light source that is a light guide plate type light source is acceptable.

[0052] <Light Diffuser>

[0053] exist Figure 2 In the diagram, the light-emitting surface of the light diffuser 44 is shown as the first surface 62a. Figure 2 Above), the light incident surface is shown as the second surface 63a ( Figure 2Below. A first parallel prism microstructure 65, consisting of a plurality of first prisms 65a extending along a first direction d11, is provided on the first surface 62a. A second parallel prism microstructure 64, consisting of a plurality of second prisms 64a extending along a second direction d12, is provided on the second surface 63a. The first parallel prism microstructure 65 and the second parallel prism microstructure 64 together include prisms formed adjacent to each other and having a cross-section of an isosceles triangle.

[0054] Figure 3 This is a diagram showing the light diffuser 44 of this embodiment. The light diffuser 44 includes a substrate layer 61, a first parallel prism microstructure 65, and a second parallel prism microstructure 64.

[0055] The overall thickness of the light diffuser 44 is more than 50 μm and less than 300 μm.

[0056] [Substrate Layer]

[0057] Because light needs to pass through, the substrate layer 61 is formed primarily of a transparent (e.g., colorless and transparent) synthetic resin. The main component of the substrate layer 61 is not particularly limited; for example, polycarbonate, polyethylene terephthalate, polyethylene naphthalate, acrylic resin, polystyrene, polyolefin, cellulose acetate, weather-resistant vinyl chloride, etc., can be used. It should be noted that "main component" refers to the component with the highest content, for example, a component with a content of 50% or more by mass. The substrate layer 61 may contain dispersants or other additives, or it may contain virtually no additives. The additives that can be contained are not particularly limited; for example, they can be inorganic particles such as silica, titanium dioxide, aluminum hydroxide, and barium sulfate, or organic particles such as acrylic acid, acrylonitrile, silicone, polystyrene, and polyamide.

[0058] From the viewpoint of suppressing curling, the lower limit of the average thickness of the substrate layer 61 is preferably about 10 μm, more preferably about 35 μm, and even more preferably about 50 μm. From the viewpoint of further improving brightness and achieving a thinner film, the upper limit of the average thickness of the substrate layer 61 is preferably about 500 μm, more preferably about 250 μm, and even more preferably about 180 μm. It should be noted that "average thickness" refers to the average thickness at any 10 points.

[0059] [Prism layer]

[0060] Prism layer 62 has a first parallel prism microstructure 65. The first parallel prism microstructure 65 is composed of a plurality of first prisms 65a extending along a first direction d11. Prism layer 63 has a second parallel prism microstructure 64. The second parallel prism microstructure 64 is composed of a plurality of second prisms 64a extending along a second direction d12.

[0061] The first parallel prism microstructure 65 and the second parallel prism microstructure 64 are constructed by multiple triangular prism portions with isosceles triangular cross sections. The first parallel prism microstructure 65 and the second parallel prism microstructure 64 can be formed, for example, using an ultraviolet (UV) curable acrylic resin.

[0062] In the first parallel prism microstructure 65 and the second parallel prism microstructure 64, the cross-section of each prism perpendicular to the length direction is an isosceles triangle, and the side of the substrate layer 61 is the base.

[0063] The shape of the cross-section perpendicular to the length direction of the first prism 65a is shown by its height h1 and apex angle θ1. Similarly, the shape of the cross-section perpendicular to the length direction of the second prism 64a is shown by its height h2 and apex angle θ2. Furthermore, the structures of the first parallel prism microstructure 65 and the second parallel prism microstructure 64 are shown by the spacing p1 of the first prism 65a and the spacing p2 of the second prism 64a, respectively. The spacing refers to the distance between the vertices corresponding to the apex angles of the triangles in the cross-section perpendicular to the length direction of each prism. Hereinafter, the shapes of the cross-sections perpendicular to the length direction of the first prism 65a and the second prism 64a will be simply referred to as "the apex angle of the first prism 65a" and "the height of the second prism 64a," etc. Additionally, the extension direction of the first prism 65a is the same as the first direction d11, and the extension direction of the second prism 64a is the same as the second direction d12. Furthermore, the apex angle θ1 of the first prism 65a and the apex angle θ2 of the second prism 64a are not limited to angles as in this embodiment, but can also be rounded.

[0064] In this embodiment, the arrangement of adjacent prisms without gaps between them is described; therefore, the spacing between each prism can also be described as the length of the base of each parallel prism microstructure. In another embodiment, the prisms can also be arranged with gaps between them. In this case, the length of the base of the triangle is not the same as the spacing.

[0065] More preferably, the length of the spacing p1 of the first prism 65a is greater than the length of the spacing p2 of the second prism 64a. This further improves brightness uniformity and reduces moiré fringes. Furthermore, from the viewpoint of suppressing moiré fringes and ensuring good brightness, the spacing p1 of the first prism 65a is preferably 5 μm or more, more preferably 10 μm or more, and from the viewpoint of suppressing moiré fringes and ensuring good brightness, it is preferably 50 μm or less, more preferably 40 μm or less. Similarly, from the viewpoint of suppressing moiré fringes and ensuring good brightness, the length of the spacing p2 of the second prism 64a is preferably 5 μm or more, more preferably 10 μm or more, and from the viewpoint of suppressing moiré fringes and ensuring good brightness, it is preferably 50 μm or less, more preferably 40 μm or less.

[0066] From the viewpoint of suppressing moiré fringes and ensuring good brightness, the apex angle θ1 of the first prism 65a is preferably 70° or more, more preferably 80° or more, and preferably 110° or less, more preferably 100° or less. Similarly, from the viewpoint of suppressing moiré fringes and ensuring good brightness, the apex angle θ2 of the second prism 64a is preferably 70° or more, more preferably 80° or more, and preferably 110° or less, more preferably 100° or less. Furthermore, more preferably, the apex angle θ1 of the first prism 65a is greater than or equal to the apex angle θ2 of the second prism 64a. With this structure, brightness uniformity can be further improved, and moiré fringes can be reduced.

[0067] From the viewpoint of suppressing moiré fringes and ensuring good brightness, the height h1 of the first prism 65a is preferably 5 μm or more, more preferably 6 μm or more, and preferably 30 μm or less, more preferably 20 μm or less. Similarly, from the viewpoint of suppressing moiré fringes and ensuring good brightness, the height h2 of the second prism is preferably 5 μm or more, more preferably 6 μm or more, and preferably 30 μm or less, more preferably 20 μm or less. Furthermore, it is more preferable that the height h1 of the first prism is higher than the height h2 of the second prism. With the above structure, brightness uniformity can be further improved, and moiré fringes can be suppressed.

[0068] Furthermore, the full width at half maximum (FWHM) of the first prism 65a for linearly transmitted light is preferably 1° or more and 40° or less. Additionally, the full WHM of the light diffuser 44 for linearly transmitted light is preferably 2° or more and 30° or less. Here, full WHM refers to the full width at half maximum (FWHM) of the diffused light. This structure further suppresses moiré fringes and ensures sufficient brightness.

[0069] Thus, the light diffuser 44 of this disclosure can improve brightness uniformity by appropriately employing preferred values ​​for the spacing, apex angle, height of the prisms, the first prism 65a, and the full width at half maximum (FWHM) of the light diffuser itself. A pressing issue in backlight units for liquid crystal display devices is improving brightness uniformity while maintaining a thin profile; however, this issue can be resolved by using the light diffuser of this disclosure.

[0070] In addition, Figure 3 In the diagram, the prisms are shown as geometrically strict isosceles triangles, with adjacent prisms connected to each other. However, this can be done without sacrificing the effectiveness of the present disclosure, or as long as it is within the range of unavoidable shape deviations caused by the precision of industrial manufacturing. Figure 3 The examples used may vary. For instance, the vertex portion can be circular or a flat trapezoid. In this case, the apex angle of the section perpendicular to the length of the prism is the angle when the section is imagined as a triangle and the sides are extended.

[0071] Additionally, using Figure 4 Describe the shape of the prism's edges. For example... Figure 4 As shown, the height h1 of the edge line of the first prism 65a is constant (i.e., the edge line is a straight line parallel to the substrate layer 61). The same applies to the second prism 64a.

[0072] <Prism Sheet>

[0073] A first prism sheet 45 and a second prism sheet 46 are provided on the light diffuser sheet 44. Both are arranged in a manner with multiple grooves having an isosceles triangular cross-section adjacent to each other, and both have a structure in which a triangular prism portion is formed by being held between adjacent pairs of grooves. For example, the first prism sheet 45 and the second prism sheet 46 can also be made of materials that are formed into prism shapes by using a UV-curable acrylic resin on a polyethylene terephthalate (PET) film.

[0074] like Figure 2As shown in the cross-sectional view, the first prism sheet 45 and the second prism sheet 46 are arranged such that each prism 45a faces the side opposite to the light source layer 47.

[0075] Furthermore, while using two prism sheets as in this embodiment on the light diffuser 44 is a preferred structure, it is not mandatory. Only one prism sheet can be used, or three or more prism sheets can be used, and a light diffuser sheet with a different structure than the one including the prisms can also be used.

[0076] Additionally, a protrusion 46b can be provided on the back side of the second prism sheet 46 (on the side of the light source layer 47). The protrusion 46b can be, for example, the shape of part of a sphere. With this configuration, it is possible to prevent the prism sheet from adhering to other sheets.

[0077] <Color Conversion Piece>

[0078] Although not illustrated, the light diffuser of this disclosure may include a color conversion sheet. A color conversion sheet is a wavelength conversion sheet that converts light (e.g., blue light) from a light source 41 into light with a peak wavelength of any color (e.g., green or red). For example, a color conversion sheet converts blue light with a wavelength of 450 nm into green light with a wavelength of 540 nm and red light with a wavelength of 650 nm. In this case, if a light source 41 emitting blue light with a wavelength of 450 nm is used, the light passing through the color conversion sheet becomes white light because the blue light is partially converted into green and red light by the color conversion sheet. Quantum dot (QD) sheets or fluorescent sheets may also be used as color conversion sheets, for example.

[0079] The placement of the color conversion sheet is not particularly limited. For example, in this embodiment, it can be placed between the light guide plate 43 and the light diffuser 44, between the light diffuser 44 and the first prism sheet 45, or on top of the second prism sheet 46 (on the side opposite to the first prism sheet 45). It can be placed in one or more of these locations. In addition, this embodiment describes the case where there is only one light diffuser 44, but as described below, multiple light diffusers 44 can be provided. In this case, the color conversion sheet can be placed between the light diffusers 44.

[0080] [Orientation of each floor]

[0081] Next, use Figure 5 The overlapping method of each layer of the backlight unit 40 is explained. Figure 5 This diagram schematically illustrates the overlapping arrangement of the layers and shows the orientation of each layer when viewed from above. For example... Figure 5 As shown, the layers of the backlight unit 40 are preferably overlapped in the following ways with the following angles.

[0082] From the viewpoint of suppressing moiré fringes while ensuring sufficient brightness, the angle θ0 between the first direction d11 and the second direction d12 of the first parallel prism microstructure 65 and the second parallel prism microstructure 64 (e.g.) Figure 5 As shown, the difference between the angle between the Y-axis and the first direction d11 and the angle between the Y-axis and the second direction d12 is 10° or more, preferably 20° or more, and more preferably 30° or more when viewed from above. Furthermore, from the viewpoint of suppressing moiré fringes and ensuring sufficient brightness, it is 80° or less, preferably 70° or less, and more preferably 60° or less. θ0 can be the angle of the second direction d12 viewed clockwise from the first direction d11, or the angle of the second direction d12 viewed counterclockwise from the first direction d11. In other words, θ0 can be 100° or more and 170° or less, preferably 110° or more and 170° or less. This is because if θ0 when viewing the second direction clockwise from the first direction d11 is 10° or more, 80° or less, and preferably 70° or less, then θ0 when viewing the second direction d12 counterclockwise from the first direction d11 is 100° or more and 170° or less. The first direction d11 refers to the extension direction of the edge line 44a of the first parallel prism microstructure 65 included in the light diffuser 44, and the second direction d12 refers to the extension direction of the edge line 44b of the second parallel prism microstructure 64.

[0083] More preferably, the light guiding direction d1, the first direction d11, the second direction d12 of the light guide plate 43, and the extension direction d13 of the prism of the first prism sheet 45 and the extension direction d14 of the prism of the second prism sheet 46 are all different. With this configuration, a backlight unit that further suppresses moiré fringes is formed.

[0084] In this specification, the first direction d11 and the second direction d12 in the light diffuser 44, and the extension direction d13 of the prism of the first prism sheet 45 and the extension direction d14 of the prism of the second prism sheet 46 are each set with the same reference direction as the light guiding direction d1. If we take... Figure 5 When designing the first direction d11 and the second direction d12 in the light diffuser 44, and the extension direction d13 of the prism of the first prism sheet 45 and the extension direction d14 of the prism of the second prism sheet 46, based on the X direction shown (i.e., the arrangement direction of the LEDs), the value based on the light guiding direction d1 described in this specification can be increased by 90° clockwise.

[0085] In the backlight unit 40, with the light guiding direction d1 as a reference, a first direction d11 extending from the edge line 44a of the first parallel prism microstructure 65 in the light diffuser 44 and a second direction d12 extending from the edge line 44b of the second parallel prism microstructure 64 are designed. The reference direction of the light diffuser 44 can be predetermined so that it is the same as the light guiding direction d1 in the backlight unit 40.

[0086] When viewed from above, the angle θ12 of the second direction d12 relative to the light guiding direction d1 of the light guide plate 43 is more preferably less than 40° counterclockwise and less than 10° clockwise.

[0087] When viewed from above, the angle θ12 of the second direction d12 relative to the light guiding direction d1 of the light guide plate 43 is more preferably 10° to 40° counterclockwise. This results in better brightness and suppression of moiré fringes.

[0088] Furthermore, when viewed from above, the angle θ12 of the second direction d12 relative to the light guiding direction d1 of the light guide plate 43 is more preferably 10° or more counterclockwise and less than 10° clockwise. This structure also improves brightness and suppresses moiré fringes.

[0089] Furthermore, as a point of view, the angle θ0 between the first direction and the second direction is more preferably the angle d12 clockwise from the first direction d11, satisfying the condition shown in the following formula. Therefore, the brightness in the backlight unit 40, including the light diffuser 44, will be better, and moiré fringes can be suppressed.

[0090] (Formula) {40 + |x|} ≤ θ0 ≤ {70 + |x|}

[0091] Where -10°≤x≤10°.

[0092] Here, x is the angle θ12 of the second direction relative to the reference direction, and the light guiding direction d1 is the same as the reference direction.

[0093] For example, when angle θ12 is 0°, angle θ0 is preferably 10° to 80°, more preferably 20° to 70°, and even more preferably 40° to 70°. Furthermore, when angle θ12 is 10°, angle θ0 is preferably 10° to 80°, more preferably 20° to 80°, and even more preferably 50° to 80°. That is, since the backlight unit 40 of this disclosure has good brightness, θ0 is preferably 20° or more, and θ0 is more preferably 50° or more. This results in better brightness and suppression of moiré patterns.

[0094] In addition, such as Figure 5As shown, more preferably, when viewed clockwise, the first direction d11, the light guiding direction d1 of the light guide plate 43, and the second direction d12 exist sequentially. Furthermore, this relationship is also satisfied when viewed counterclockwise. Therefore, the brightness is better and moiré fringes are suppressed.

[0095] Furthermore, the extension direction d13 of the first prism sheet or the extension direction d14 of the second prism sheet is more preferably 10° or more and 30° or less relative to the light guiding direction d1 of the light guide plate 43, and the extension direction d14 of the second prism sheet is even more preferably 10° or more and 30° or less relative to the light guiding direction d1 of the light guide plate 43. This results in better brightness and suppression of moiré fringes.

[0096] [Another example of how different floors face]

[0097] Next, use Figure 6 and Figure 7 Here is another example illustrating the overlapping method of the layers of the backlight unit 40. Figure 6 and Figure 7 This diagram illustrates another example of how the layers overlap, showing the orientation of each layer when viewed from above. Components that have the same function as those described in the examples are labeled with the same symbols and will not be described again.

[0098] like Figure 6 and Figure 7 As shown, the layers of the backlight unit 40 can be overlapped in the following way: when viewed clockwise, the light guiding direction d1, the second direction d12, and the first direction d11 of the light guide plate 43 exist in sequence.

[0099] (Another example of the shape of the edges of a prism)

[0100] In this embodiment, such as Figure 4 As shown, the heights (h1, h2) of the first prism 65a and the second prism 64a are fixed (i.e., the prism lines are straight lines parallel to the surface direction of the substrate layer 61), but the light diffuser sheet of this disclosure is not limited to this method. For example, the heights may not be fixed, and the prism lines may be straight, stepped, non-straight, wavy, or curved. If these shapes are used, the moiré fringes can be further improved.

[0101] Linear changes refer to increases or decreases along a single straight line; stepped changes refer to increases or decreases along two or more straight lines; non-linear changes refer to increases or decreases along a combination of straight lines and curves; and curved changes refer to increases or decreases along one or more curves. These ridgeline shapes can be a single shape or a combination of two or more ridgeline shapes. When the ridgeline is a wavy curve, it can be a wave with a regular wavelength and width, or it can be a random wave.

[0102] Figure 8 and Figure 9 This is another diagram illustrating the shape of an edge. (See diagram below.) Figure 8 As shown, prism layer 62 may have a first prism 65b with wavy edges. The prisms constituting prism layer 62 may each have a wavy shape with the same shape, for example, as shown in the diagram. Figure 8 As shown, it can be constructed by arranging multiple first prisms 65b of the same shape. Alternatively, it can be constructed as follows: Figure 9 As shown in the first prism 65b and first prism 65c, the shape of the prism lines is a randomly different wave shape for each prism. If these shapes are used, the moiré fringes can be further improved.

[0103] (Implementation Method 2)

[0104] use Figure 10 The backlight unit 140 of this embodiment will be described. Furthermore, for ease of explanation, components that have the same function as those described in the previous embodiment will be labeled with the same symbols and will not be described again.

[0105] like Figure 10 As shown, the backlight unit 140 includes two light diffusers 44. Thus, the backlight unit of this disclosure may include two diffusers. Alternatively, although not shown, it may include three or more. Thus, since the backlight unit including multiple diffusers also uses diffusers that are easy to shape the surface to the desired precision more stably, it is easy to manufacture a backlight with stable quality that suppresses moiré patterns and has excellent brightness uniformity.

[0106] Multiple light diffuser sheets 44 can be bonded together. There is no particular limitation on the bonding method. For example, a method can be given by placing an adhesive layer using a known adhesive sheet or the like between the light diffuser sheets 44 and bonding the light diffuser sheets 44 together.

[0107] <Summary>

[0108] As described above, the light diffuser sheet involved in Scheme 1 of this disclosure is a light diffuser sheet for a backlight unit, having a first surface as a light emitting surface and a second surface as a light incident surface. On the first surface, a first parallel prism microstructure composed of a plurality of first prisms extending along a first direction is provided, and on the second surface, a second parallel prism microstructure composed of a plurality of second prisms extending along a second direction is provided. The angle between the first direction and the second direction is more than 10° and less than 80° when viewed from above.

[0109] According to this solution, since both the light emitting surface and the light incident surface are parallel prism microstructures composed of multiple prisms, the shape is simple and can be manufactured by simple methods such as extrusion molding. For example, by extrusion molding, it is not necessary to process the surface as in Patent Documents 1 and 2, and it is easier to uniformly arrange them in the surface. Therefore, it is easy to stably manufacture the desired surface accuracy. In addition, by setting the angle between the first direction and the second direction as described above, moiré fringes can be further suppressed. Therefore, it is possible to provide a light diffuser sheet that is easy to manufacture with the desired accuracy more stably and has better brightness uniformity by suppressing moiré fringes.

[0110] In addition, in this disclosure, "light diffusion sheet" includes a plate-shaped "light diffusion plate" or a film-shaped "light diffusion film".

[0111] Solution 2 of this disclosure is based on the light diffuser of Solution 1, and has a reference direction that serves as a reference for both the first and second directions. The angle of the second direction relative to the reference direction is preferably less than 10° clockwise and less than 40° counterclockwise when viewed from above. According to this solution, moiré fringes can be further suppressed, and brightness uniformity can be further improved.

[0112] Solution 3 of this disclosure is based on the light diffuser of Solution 2, wherein the angle of the second direction relative to the reference direction can be more than 10° and less than 40° counterclockwise when viewed from above. According to this solution, moiré fringes can be further suppressed, and brightness uniformity can be further improved.

[0113] Furthermore, in Scheme 4 of this disclosure, based on the light diffuser of Scheme 2, the angle of the second direction relative to the reference direction can be less than 10° clockwise and less than 10° counterclockwise when viewed from above. According to this scheme, moiré fringes can be further suppressed, and brightness uniformity can be further improved.

[0114] Furthermore, in Scheme 5 of this disclosure, based on the light diffuser of Scheme 4, the angle θ0 between the first direction and the second direction satisfies the condition shown in the following formula:

[0115] (Formula) {40 + |x|} ≤ θ0 ≤ {70 + |x|}:

[0116] Here, more preferably, x is the angle θ12 of the second direction relative to the reference direction. According to this scheme, moiré fringes can be further suppressed, and brightness uniformity can be further improved.

[0117] Furthermore, in Scheme 6 of this disclosure, based on any one of the light diffusers in Schemes 1 to 4, the angle between the first direction and the second direction is more preferably 10° or more and 70° or less when viewed from above. According to this scheme, moiré fringes can be further suppressed, and brightness uniformity can be further improved.

[0118] Furthermore, Scheme 7 of this disclosure is based on any one of the light diffusers in Schemes 1 to 6, wherein the spacing of the first prism is greater than or equal to the spacing of the second prism. According to this scheme, moiré fringes can be further suppressed, and brightness uniformity can be further improved.

[0119] Furthermore, in Scheme 8 of this disclosure, based on any one of the light diffusers in Schemes 1 to 7, the full width at half maximum (FWHM) of the first prism for linearly transmitted light is greater than 1° and less than 40°. According to this scheme, moiré fringes can be further suppressed, and brightness uniformity can be further improved.

[0120] Furthermore, Scheme 9 of this disclosure is based on any one of the light diffusers in Schemes 1 to 8, wherein the full width at half maximum (FWHM) of the light diffuser for linearly transmitted light is greater than 2° and less than 30°. According to this scheme, moiré fringes can be further suppressed, and brightness uniformity can be further improved.

[0121] Solution 10 of this disclosure is a backlight unit, comprising: a light source in the form of a light guide plate, a light guide plate, any one of the light diffusers from solutions 1 to 9, a first prism sheet disposed on the light-emitting side of the light diffuser sheet, and a second prism sheet disposed on the light-emitting side of the first prism sheet, wherein the light diffuser sheet, the first prism sheet, and the second prism sheet are sequentially disposed on the light guide plate. According to the backlight unit of this disclosure, due to the inclusion of the light diffuser sheet, the brightness uniformity is superior, and it is easier and more stable to manufacture to the desired precision.

[0122] Solution 11 of this disclosure is based on the backlight unit of Solution 10, wherein the light guiding direction of the light guide plate, the first direction, the second direction, the extension direction of the prism of the first prism sheet, and the extension direction of the prism of the second prism sheet are all different. According to this solution, moiré fringes can be further suppressed, and brightness uniformity can be further improved.

[0123] Solution 12 of this disclosure is a backlight unit, comprising: a light source in the form of a light guide plate, a light guide plate, a light diffuser sheet as described in any one of claims 2 to 5, a first prism sheet disposed on the light emitting side of the light diffuser sheet, and a second prism sheet disposed on the light emitting side of the first prism sheet, wherein the light diffuser sheet, the first prism sheet, and the second prism sheet are sequentially disposed on the light guide plate, and the reference direction is the same as the light guiding direction of the light guide plate. According to the backlight unit of this disclosure, due to the inclusion of the light diffuser sheet, the brightness uniformity is superior, and it is easier and more stable to manufacture to the desired precision.

[0124] Solution 13 of this disclosure is based on the backlight unit of Solution 12, wherein the light guiding direction of the light guide plate, the first direction, the second direction, the extension direction of the prism of the first prism sheet, and the extension direction of the prism of the second prism sheet are all different. According to this solution, moiré fringes can be further suppressed, and brightness uniformity can be further improved.

[0125] Solution 14 of this disclosure is based on the backlight unit of Solution 10 or 11, wherein the angle of the second direction relative to the light guiding direction of the light guide plate is more than 10° and less than 40° counterclockwise when viewed from above. According to this solution, moiré fringes can be further suppressed and brightness uniformity can be further improved.

[0126] Scheme 15 of this disclosure is based on any one of the backlight units in schemes 10 to 14, wherein when viewed clockwise or counterclockwise, the first direction, the light guiding direction of the light guide plate, and the second direction exist sequentially. According to this scheme, moiré fringes can be further suppressed, and brightness uniformity can be further improved.

[0127] Solution 16 of this disclosure is based on any one of the backlight units in solutions 10 to 15, wherein the extension direction of the prism of the first prism sheet or the extension direction of the prism of the second prism sheet is 10° or more and 30° or less relative to the light guiding direction of the light guide plate. According to this solution, moiré fringes can be further suppressed and brightness uniformity can be further improved.

[0128] Solution 17 of this disclosure is based on any one of the backlight units in solutions 10 to 15, wherein the extension direction of the prism of the second prism sheet is 10° or more and 30° or less relative to the light guiding direction of the light guide plate. According to this solution, moiré fringes can be further suppressed and brightness uniformity can be further improved.

[0129] Solution 18 of this disclosure is a liquid crystal display device, which includes any one of the backlight units of solutions 10 to 15 and a liquid crystal display screen. According to the liquid crystal display device of this disclosure, since it includes the backlight unit, the brightness uniformity is better and it is easier to manufacture to the desired accuracy more stably.

[0130] Solution 19 of this disclosure is an information device that includes the liquid crystal display device of solution 18. According to the information device of this disclosure, due to the inclusion of the liquid crystal display device, the brightness uniformity is superior, and it is easier and more stable to manufacture to the desired accuracy.

[0131] This invention is not limited to the embodiments described herein, and various modifications can be made within the scope of the claims. Embodiments obtained by appropriately combining the disclosed technical means into different embodiments are also included within the technical scope of this invention.

[0132] Example

[0133] The following describes an embodiment of the present invention. The brightness in each example is as follows: Figure 2 In the state of the backlight unit 40 with the structure shown, the color luminance was measured using a BM-7AC color luminance meter (Topcon Technohouse Inc.), and the relative values ​​are shown with Comparative Example 101 as the reference (100%) (in Table 3, the example of Comparative Example 301 with θ13=65° and θ14=-25° is used as the reference).

[0134] (Evaluation of brightness and moiré fringes 1)

[0135] The shapes of the light diffusers for each embodiment and comparative example are shown in the tables. In Tables 1 and 2, when "prism (H)" is mentioned, the shapes are used for each embodiment and comparative example. / P / θ °)( When H is a numerical value, it indicates that a prism (a first parallel prism microstructure or a second parallel prism microstructure) is provided on the surface (first surface or second surface) of the light diffuser. The height h1 or h2 of the prism is... μm, P This indicates that the prism spacing p1 or p2 is... μm, θ ° represents the apex angle θ1 or apex angle θ2 of the prism. °. In addition, in each embodiment and comparative example, a first parallel prism microstructure, a second parallel prism microstructure, or a chamfered pyramid structure made of UV-curable acrylic resin is formed on both sides of a PET sheet (50 μm thick).

[0136] Additionally, in each table, θ11 is the angle of the first direction d11 relative to the light guiding direction d1.

[0137] θ0 is the angle between the first direction d11 and the second direction d12. An angle that is clockwise from the first direction d11 to the second direction d12 is marked as positive, and an angle that is counterclockwise is marked as "-".

[0138] θ11 is the angle between the light guiding direction d1 and the first direction d11. The clockwise angle from the light guiding direction d1 is recorded as positive, and the counterclockwise angle is marked as "-".

[0139] θ12 is the angle between the light guiding direction d1 and the second direction d12. The clockwise angle from the light guiding direction d1 is recorded as positive, and the counterclockwise angle is marked as "-".

[0140] Furthermore, for ease of reading the table, the same angle can be recorded as either a positive or negative value. For example, when θ0 is recorded as -42° or 138°, these are considered the same value.

[0141] Furthermore, in each embodiment and comparative example, a side-mounted backlight unit with LEDs arranged on one side (hereinafter referred to as "LED-A", also shown as "A" in the "Backlight" row of the table) or a side-mounted backlight unit with LEDs arranged on both sides (hereinafter referred to as "LED-B", also shown as "B" in the "Backlight" row of the table) was used as the backlight unit. LED-B was used in all the embodiments and comparative examples shown in Table 1.

[0142] Furthermore, in embodiments using prism sheets corresponding to the first and second prism sheets, the first and second prism sheets are sequentially stacked on top of each light diffuser sheet. In the embodiments and comparative examples in Table 1, both the first and second prism sheets were used. The embodiments and comparative examples in Table 2 are as shown in the table. Additionally, the first and second prism sheets are made of PET and UV-curable acrylic resin, respectively. The prisms of the first and second prism sheets each have a height of 10 μm, a spacing of 24 μm, and a apex angle of 90° (all measured values), forming a seamless arrangement of prisms.

[0143] Additionally, the device includes a first prism sheet and a second prism sheet, wherein the angle θ13 of the extension direction d13 of the first prism sheet relative to the light guiding direction d1 is 65° clockwise from the light guiding direction d1, and the angle θ14 of the extension direction d14 of the second prism sheet relative to the light guiding direction d1 is 25° counterclockwise from the light guiding direction d1.

[0144] Additionally, in Comparative Example 101, "pyramid" indicates a "beveled pyramid" structure with the shape described in the table. Similar to the shape of the prism, H represents the height (depth) of the beveled pyramid, P represents the spacing between the beveled pyramids, and θ represents the apex angle of the beveled pyramid. Furthermore, except for θ0, θ11, and θ12 as shown in each table, Comparative Examples 201 to 204 are the same as Example 201. Comparative Example 301 in Table 3 is the same as Example 101, except that the first prism sheet and the second prism sheet are sequentially stacked on the light diffuser so that Comparative Example 101 is in the orientation shown in Table 3.

[0145] In the embodiments and comparative examples shown in Table 2, moiré fringes were evaluated. The evaluation of moiré fringes was performed visually; if no moiré fringes were found, it was marked as ○; if moiré fringes were found but few, it was marked as △; and if moiré fringes were found, it was marked as ×.

[0146] In all embodiments and comparative examples, the substrate layer is made of polyethylene terephthalate (PET) with a thickness of 75 μm. Furthermore, in all embodiments and comparative examples, the first prism and the second prism are arranged without gaps on the light diffuser. That is, the spacing is consistent with the length of the base of the triangle in the cross-section perpendicular to the length direction of the prism.

[0147] The results are shown in the tables above.

[0148]

[0149]

[0150]

[0151] As shown in Tables 1 and 2, the backlight unit of this disclosure has the same or better brightness as Comparative Example 101.

[0152] As shown in Table 1, Examples 101, 102, 111 to 114, 115 and 116 show that the length of the spacing p1 of the first prism 65a is greater than the length of the spacing p2 of the second prism 64a.

[0153] As shown in Table 2, good brightness can be obtained and moiré fringes can be suppressed by setting θ0 to above 10° and below 70°.

[0154] As shown in Table 3, it is demonstrated that by making the light guiding direction d1, the first direction d11, the second direction d12 of the light guide plate, the extension direction d13 of the first prism sheet, and the extension direction d14 of the second prism sheet all different, brightness equal to or better than that of Comparative Example 301 can be obtained. Furthermore, as... Figure 3 As shown, in the examples of θ14 = -25°, -22°, and -8°, the brightness is good. Good brightness can be obtained when the angle θ14 between the extension direction d14 of the second prism sheet and the light guiding direction d1 of the light guide plate is greater than 10° and less than 30°.

[0155] (Evaluation of moiré stripes 2)

[0156] For Example 107 and Comparative Example 101, the moiré fringes were evaluated simultaneously with the brightness measurement (using the first and second prisms). The evaluation was performed visually; if no moiré fringes were observed, it was marked as ○, and if moiré fringes were observed, it was marked as ×.

[0157] The results are as follows Figure 11 As shown. Figure 11 As shown, the backlight unit according to this disclosure can suppress moiré patterns.

[0158] (Evaluation of half-peak full width)

[0159] For each embodiment of the first prism 65a shown in Table 4, and for each embodiment of the light diffuser including the first prism 65a and the second prism 64a shown in Table 5, their full width at half maximum (FWHM) for linearly transmitted light was evaluated. Furthermore, in embodiments 401 to 404, the second surface of the light diffuser is a flat structure. Additionally, the angular distribution of the scattered intensity for linearly transmitted light was measured using a goniometer. The rotation direction of the receiver of the goniometer is as described in the table. Based on the angular distribution of light intensity, the FWHM of the light intensity peak at the angle closest to 0° was calculated by rounding the angle to one decimal place. The results are shown in Tables 4 and 5. Furthermore, the linearly transmitted light from below is essentially divided at 0° for the upward-convex prism, but since the two divided beams with light intensity peaks at the angle closest to 0° overlap, there is sometimes light intensity at 0° as well. Therefore, for example, there are the following cases: overlapping with a light intensity peak at 0°, overlapping with a light intensity peak at the angle closest to 0°, and overlapping with a light intensity peak but not overlapping at the angle closest to 0°. In this evaluation, the case of overlapping with a light intensity peak at 0° is to calculate the full width at half maximum (FWHM) of the overlapping light as a single light, while the other two cases are to calculate the FWHM of the individual light.

[0160]

[0161] As shown in Tables 4 and 5, in the light diffuser of this disclosure, which achieves good brightness and suppresses moiré fringes as described above, the first prism 65a has a full width at half maximum (FWHM) of 1° or more and 40° or less for linearly transmitted light, and the light diffuser has a full WHM of 2° or more and 30° or less for linearly transmitted light.

[0162] (Evaluation of brightness and moiré fringes 2)

[0163] Similar to the evaluation of brightness and moiré fringes, in such... Figure 2 With the backlight unit 40 of the structure shown, a colorimeter BM-7AC (Topcon Technohouse Inc.) was used to evaluate the brightness of Examples 601 to 611, Comparative Examples 601 to 604, and to evaluate the moiré fringes visually. The brightness in the evaluation 2 of brightness and moiré fringes is shown as a relative value with Comparative Example 601 as the reference (100%).

[0164] In each of Examples 601 to 611 and Comparative Examples 601 to 604, the following sheet was prepared: a first parallel prism microstructure, a second parallel prism microstructure, or a chamfered pyramid structure made of UV-curable acrylic resin was formed on both sides of a sheet made of PET (thickness of 50 μm).

[0165] In Comparative Example 601, the first surface of the light diffuser is a pyramid (with a chamfered pyramid shape; spacing 30 μm, height 15 μm, and a 90° apex angle), and the second surface is a prism (with a 13 μm spacing, height 6.5 μm, and a 90° apex angle). In Examples 601-611 and Comparative Examples 602-604, the first surface is a prism (with a prism shape; spacing 13 μm, height 6.5 μm, and a 90° apex angle), and the second surface is also a prism (with a prism shape; spacing 13 μm, height 6.5 μm, and a 90° apex angle).

[0166] In addition, in Examples 601 to 611 and Comparative Examples 601 to 604, a first prism sheet and a second prism sheet are included. The angle θ13 of the extension direction d13 of the first prism sheet relative to the light guiding direction d1 is 0° clockwise from the light guiding direction d1, and the angle θ14 of the extension direction d14 of the second prism sheet relative to the light guiding direction d1 is 90° clockwise from the light guiding direction d1.

[0167] Furthermore, in the evaluation of brightness and moiré fringes of Examples 601 to 611 and Comparative Examples 601 to 604, a backlight unit with LEDs arranged on one side, namely LED-A, was used.

[0168] [Table 6]

[0169]

[0170] As shown in Table 6, good brightness and suppression of moiré fringes can be obtained by setting θ0 to 10° or higher and 80° or lower. The backlight unit of this disclosure has the same or better brightness as Comparative Example 601. When the angle θ12 is 0°, the backlight unit of this disclosure has the same or higher brightness as Comparative Example 601 when the angle θ0 is 10° to 80°, high brightness when the angle θ0 is 20° to 70°, and even higher brightness when the angle θ0 is 40° to 70°. Furthermore, when the angle θ12 is 10°, the backlight unit of this disclosure has the same or higher brightness as Comparative Example 601 when the angle θ0 is 10° to 80°, high brightness when the angle θ0 is 20° to 80°, and even higher brightness when the angle θ0 is 50° to 80°. As described above, the backlight unit of this disclosure tends to have high brightness when θ0 is 20° or higher, and even higher brightness when θ0 is 50° or higher.

[0171] Explanation of icon numbers

[0172] 1: TFT substrate

[0173] 2: CF substrate

[0174] 3: Liquid crystal layer

[0175] 5: LCD screen

[0176] 6: First polarizing plate

[0177] 7: Second polarizing plate

[0178] 40, 140: Backlight unit

[0179] 41: Light source

[0180] 42: Reflector

[0181] 43: Light guide plate

[0182] 43a: Cylindrical lens

[0183] 44: Light diffusion sheet

[0184] 45: First Prism Slide

[0185] 45a: Prism

[0186] 46: Second Prism Slide

[0187] 46a: Prism

[0188] 47: Light Source Layer

[0189] 50: Liquid crystal display device

[0190] 50a: Display screen

[0191] 61: Substrate layer

[0192] 62, 63: Prism layer

[0193] 62a: First page

[0194] 63a: Second page

[0195] 64: Second parallel prism microstructure

[0196] 64a: Second prism

[0197] 65: First parallel prism microstructure

[0198] 65a, 65b, 65c: First prism

[0199] d1: Light guiding direction

[0200] d11: First direction

[0201] d12: Second direction

[0202] d13, d14: Direction of extension

Claims

1. A light diffuser sheet for a backlight unit, It has a first surface that serves as the light exit surface and a second surface that serves as the light incident surface. On the first surface, a first parallel prism microstructure composed of a plurality of first prisms extending along a first direction is provided. On the second surface, a second parallel prism microstructure composed of a plurality of second prisms extending along the second direction is provided. The angle between the first direction and the second direction is greater than 10° and less than 80° when viewed from above.

2. The light diffuser according to claim 1, having a reference direction that serves as a reference for the first direction and the second direction, wherein the angle of the second direction relative to the reference direction is less than 10° clockwise and less than 40° counterclockwise when viewed from above.

3. The light diffuser sheet according to claim 2, wherein, The angle of the second direction relative to the reference direction is more than 10° and less than 40° counterclockwise when viewed from above.

4. The light diffuser sheet according to claim 2, wherein, The angle of the second direction relative to the reference direction is less than 10° clockwise and less than 10° counterclockwise when viewed from above.

5. The light diffuser sheet according to claim 4, wherein, The angle θ0 between the first direction and the second direction satisfies the condition shown in the following equation: (Formula) {40 + |x|} ≤ θ0 ≤ {70 + |x|} Here, x is the angle θ12 of the second direction relative to the reference direction.

6. The light diffuser sheet according to claim 1, wherein, The angle between the first direction and the second direction is greater than 10° and less than 70° when viewed from above.

7. The light diffuser sheet according to claim 1, wherein, The spacing between the first prisms is greater than or equal to the spacing between the second prisms.

8. The light diffuser sheet according to claim 1, wherein, The full width at half maximum (FWHM) of the first prism for linear transmitted light is greater than 1° and less than 40°.

9. The light diffuser sheet according to claim 1, wherein, The light diffuser has a full width at half maximum (FWHM) of 2° or more and 30° or less for linearly transmitted light.

10. A backlight unit comprising a light source in the form of a light guide plate, a light guide plate, a light diffuser sheet as described in any one of claims 1 to 9, a first prism sheet disposed on the light emitting side of the light diffuser sheet, and a second prism sheet disposed on the light emitting side of the first prism sheet, wherein the light diffuser sheet, the first prism sheet, and the second prism sheet are sequentially disposed on the light guide plate.

11. The backlight unit according to claim 10, wherein, The light guiding direction of the light guide plate, the first direction, the second direction, the extension direction of the prism of the first prism sheet, and the extension direction of the prism of the second prism sheet are all different.

12. A backlight unit, comprising a light source in the form of a light guide plate, a light guide plate, a light diffuser sheet as described in any one of claims 2 to 5, a first prism sheet disposed on the light emitting side of the light diffuser sheet, and a second prism sheet disposed on the light emitting side of the first prism sheet, wherein the light diffuser sheet, the first prism sheet, and the second prism sheet are sequentially disposed on the light guide plate. The reference direction is the same as the light guiding direction of the light guide plate.

13. The backlight unit according to claim 12, wherein, The light guiding direction of the light guide plate, the first direction, the second direction, the extension direction of the prism of the first prism sheet, and the extension direction of the prism of the second prism sheet are all different.

14. The backlight unit according to claim 5, wherein, The angle between the second direction and the light guiding direction of the light guide plate is more than 10° and less than 40° counterclockwise when viewed from above.

15. The backlight unit according to claim 5, wherein, When viewed clockwise or counterclockwise, the first direction, the light guiding direction of the light guide plate, and the second direction exist sequentially.

16. The backlight unit according to claim 5, wherein, The extension direction of the prism of the first prism sheet or the extension direction of the prism of the second prism sheet is 10° or more and 30° or less relative to the light guiding direction of the light guide plate.

17. The backlight unit according to claim 5, wherein, The extension direction of the prism of the second prism sheet is more than 10° and less than 30° relative to the light guiding direction of the light guide plate.

18. A liquid crystal display device, include: The backlight unit as described in claim 5 or 11; as well as LCD screen.

19. An information device, comprising the liquid crystal display device as described in claim 18.

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