Light diffusion sheet, backlight unit, liquid crystal display device, information device, and stacked light diffusion sheet

Abstract

A light diffusion sheet 43B has a plurality of inverted substantially polygonal pyramid-shaped recesses 105 on a first surface 102a that acts as a light emission surface or a light incidence surface. A second surface 101a on the opposite side to the first surface 102a is a matt surface, and a flattened layer (e.g., a flattened printed layer 103) composed of a light-transmitting resin (e.g., a light-transmitting ink 106) is provided to cover unevenness on the matt surface.

Description

Technical Field

[0001] The present disclosure relates to a light diffuser, a backlight unit, a liquid crystal display device, an information device, and stacked light diffusers. Background Art

[0002] Liquid crystal display devices (hereinafter referred to as LCDs) are widely used as display devices in various information devices such as smartphones and tablet terminals. As the backlight device of an LCD, a direct-type system is mainly used, in which the light source is arranged on the rear surface of the liquid crystal panel.

[0003] In direct-lit backlights, a light diffuser is used to diffuse light from a light source, such as an LED (light-emitting diode), to improve the uniformity of brightness and color across the entire screen. PTL 1 discloses a light diffuser (hereinafter also referred to as a pyramid sheet) having a plurality of inverted pyramid-shaped recesses.

[0004] Reference List

[0005] Patent Literature

[0006] PTL 1: Japanese Patent Application Publication No. 2011-129277 Summary of the Invention

[0007] Technical issues

[0008] However, in a conventional pyramid sheet, particularly a thin pyramid sheet having a thickness of about 120 μm or less, there arises a problem in that defects on the recess forming surface are easily visible on a display screen.

[0009] An object of the present disclosure is to make it possible to suppress visibility of defects on a recess-forming surface in a light diffusion sheet provided with a plurality of inverted substantially polygonal pyramid recesses.

[0010] Solution to the problem

[0011] To achieve the above objectives, the inventors of the present application conducted various studies on the visibility of defects on the concave-forming surface of a pyramid sheet and discovered that when the surface opposite the concave-forming surface is matte, the visibility of defects on the concave-forming surface is reduced compared to when the opposite surface is flat. This is presumably due to the influence of light scattering on the matte surface. Furthermore, after examining the brightness and brightness uniformity of the pyramid sheet, the inventors discovered that when the surface opposite the concave-forming surface is matte, the brightness and brightness uniformity on the display screen are lower than when the opposite surface is flat.

[0012] Furthermore, as a result of further examination, the inventors of the present application discovered that by forming the surface opposite to the concave portion forming surface of the pyramid sheet into a matte surface and covering the matte surface with light-transmitting ink to flatten the matte surface, the brightness and brightness uniformity were improved compared to the pyramid sheet on which the matte surface was exposed.

[0013] The light diffuser according to the present disclosure is based on the above-mentioned findings, and more specifically is a light diffuser having a plurality of inverted, substantially polygonal pyramidal recesses arranged on a first surface, the first surface serving as a light emitting surface or a light incident surface, wherein a second surface on the side opposite to the first surface is a matte surface, and a flattened printed layer composed of light-transmitting ink is arranged to cover the unevenness on the matte surface.

[0014] The light diffuser sheet according to the present disclosure can suppress the visibility of defects on the concave portion-forming surface provided with inverted, substantially polygonal pyramidal concave portions due to its matte surface. Furthermore, since the flattened printed layer is provided to cover the matte surface, brightness and brightness uniformity can be improved compared to a case where the matte surface is exposed.

[0015] Note that, in the present disclosure, a "light diffuser sheet" is considered to include a "light diffuser plate" in the form of a plate and a "light diffuser film" in the form of a film.

[0016] In the light diffuser sheet according to the present disclosure, the thickness of the flattened printed layer may be 5 μm or greater. Therefore, even a matte surface with relatively large surface roughness can be flattened by the flattened printed layer.

[0017] In the light diffuser sheet disclosed herein, multiple particles can be added to the flattened printed layer. Consequently, scratches and sticking are less likely to occur during the manufacture of the light diffuser sheet. For example, when multiple sheets are wound around a roller, the sheets have a large contact area with each other, which can prevent problems such as interference patterns and pressure-bonded marks on the sheet surfaces, or scratches caused by adhesion between the recessed surface and the printed surface when the sheets are peeled. Consequently, large-scale production efficiency can be improved.

[0018] In the light diffuser sheet according to the present disclosure, the average particle size of the plurality of particles can be greater than the thickness of the flattened printed layer. Therefore, scratches, sticking, etc. are less likely to occur during the manufacture of the light diffuser sheet.

[0019] In the light diffuser sheet according to the present disclosure, the mass ratio of the plurality of particles to the light-transmitting ink in the flattened printed layer can be 1% or more and 10% or less. Therefore, the occurrence of scratches and sticking during the manufacture of the light diffuser sheet can be suppressed, while also suppressing a decrease in brightness and brightness uniformity.

[0020] In the light diffuser according to the present disclosure, the plurality of concave portions may be formed in an inverted substantially quadrangular pyramid shape and arranged in a two-dimensional matrix pattern. Therefore, the light diffuser may be manufactured with high accuracy to exhibit excellent luminance uniformity.

[0021] In the light diffusion sheet according to the present disclosure, as long as the ten-point average roughness Rz (based on JIS B 0601-1994) of the unevenness on the matte surface is about 50 μm or less, the unevenness on the matte surface can be covered and flattened by printing light-transmitting ink.

[0022] The backlight unit according to the present disclosure is incorporated into a liquid crystal display device to guide light emitted from a plurality of light sources to a display screen. The backlight unit includes the light diffuser according to the present disclosure, which is disposed between the display screen and the plurality of light sources.

[0023] Since the backlight unit according to the present disclosure includes the light diffusion sheet according to the present disclosure, visibility of defects on the concave portion forming surface of the light diffusion sheet can be suppressed while improving brightness and brightness uniformity.

[0024] The liquid crystal display device according to the present disclosure includes a liquid crystal display panel and the backlight unit according to the present disclosure.

[0025] Since the liquid crystal display device according to the present disclosure includes the backlight unit according to the present disclosure, the visibility of defects on the concave portion forming surface of the light diffusion sheet can be suppressed while improving the brightness and brightness uniformity.

[0026] The information device according to the present disclosure includes the aforementioned liquid crystal display device according to the present disclosure.

[0027] Since the information device according to the present disclosure includes the liquid crystal display device according to the present disclosure, the visibility of defects on the recessed portion forming surface of the light diffusion sheet can be suppressed while improving the brightness and brightness uniformity.

[0028] The stacked light diffuser sheets according to the present disclosure include the light diffuser sheet according to the present disclosure and another light diffuser sheet adhered to the light diffuser sheet, with the flattened printed layer between the two.

[0029] The stacked light diffuser sheets according to the present disclosure can achieve similar effects to those of the light diffuser sheets described above, and can also achieve the following effects. Specifically, by adhering the light diffusers together, the risk of damage to the light diffusers can be reduced, thereby improving productivity, compared to the case of handling the plurality of light diffusers individually. Furthermore, the time required to assemble a liquid crystal display device can be reduced, thereby improving production yield.

[0030] It should be noted that in the above-mentioned light diffuser according to the present disclosure, the flattening printed layer is formed by printing a light-transmitting ink on the second surface, but alternatively, a flattening layer composed of a light-transmitting resin can be formed by a method other than printing so as to cover the second surface or in other words, cover the unevenness on the matte surface.

[0031] Advantageous Effects of the Invention

[0032] According to the present disclosure, a light diffuser capable of suppressing the visibility of defects on a recessed portion forming surface having a plurality of inverted substantially polygonal pyramidal recesses can be provided; as well as a backlight unit, a liquid crystal display device, an information device, and stacked light diffusers using the light diffuser. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] [ Figure 1 ] Figure 1 is a cross-sectional view of a liquid crystal display device according to an embodiment.

[0034] [ Figure 2 ] Figure 2 is a cross-sectional view of a backlight unit according to an embodiment.

[0035] [ Figure 3 ] Figure 3 is a view showing a first example of a cross-sectional configuration of a light diffusion sheet used in a backlight unit according to an embodiment.

[0036] [ Figure 4 ] Figure 4 is a view showing a second example of the cross-sectional configuration of the light diffusion sheet used in the backlight unit according to the embodiment.

[0037] [ Figure 5 ] Figure 5 is a view showing a third example of the cross-sectional configuration of the light diffusion sheet used in the backlight unit according to the embodiment.

[0038] [ Figure 6 ] Figure 6 1 is a perspective view showing a light diffusion sheet according to an embodiment viewed from a surface on which inverted pyramid-shaped recesses are provided.

[0039] [ Figure 7 ] Figure 7 are views illustrating a planar configuration and a cross-sectional configuration of an inverted pyramid-shaped recess provided in a light diffusion sheet according to an embodiment.

[0040] [ Figure 8 ] Figure 8are views showing the relationship between the arrangement direction of light sources and the arrangement direction of inverted pyramid-shaped recesses on a light diffusion sheet in a backlight unit according to an embodiment, wherein (a) shows the arrangement of the light sources and (b) shows the arrangement of the inverted pyramid-shaped recesses.

[0041] [ Figure 9 ] Figure 9 is a cross-sectional view of a backlight unit according to an example.

[0042] [ Figure 10 ] Figure 10 is a view illustrating an exemplary cross-sectional configuration of stacked light diffusion sheets according to another embodiment. DETAILED DESCRIPTION

[0043] (Example)

[0044] The following will describe a light diffuser, a backlight unit, a liquid crystal display device, an information device, and a stacked light diffuser according to an embodiment with reference to the accompanying drawings. It should be noted that the scope of the present disclosure is not limited to the embodiments described below, and any modifications may be made without departing from the scope of the technical concept of the present disclosure.

[0045] <Liquid Crystal Display Device>

[0046] Figure 1 An example of a cross-sectional configuration of the liquid crystal display device according to this embodiment is shown.

[0047] like Figure 1 As shown, the liquid crystal display device 50 includes a liquid crystal display panel 5, a first polarizing plate 6 adhered to the bottom surface of the liquid crystal display panel 5, a second polarizing plate 7 adhered to the top surface of the liquid crystal display panel 5, and a backlight unit 40 provided on the rear surface side of the liquid crystal display panel 5 via the first polarizing plate 6. The liquid crystal display panel 5 includes a TFT substrate 1 and a CF substrate 2 provided facing each other, and a liquid crystal layer 3 provided between the TFT substrate 1 and the CF substrate 2.

[0048] From the front ( Figure 1 The shape of the display screen 50a of the liquid crystal display device 50 as seen above in the figure is typically rectangular or square, but is not limited thereto, and may be any desired shape, such as a rectangular shape with rounded corners, an elliptical shape, a circular or trapezoidal shape, or the shape of a dashboard of a car.

[0049] In the liquid crystal display device 50, a voltage of a predetermined magnitude is applied to the liquid crystal layer 3 in each sub-pixel corresponding to each pixel electrode to change the alignment state of the liquid crystal layer 3. As a result, the transmittance of light entering from the backlight unit 40 through the first polarizing plate 6 is adjusted. The light with the adjusted transmittance is emitted through the second polarizing plate 7, thereby displaying an image.

[0050] The liquid crystal display device 50 according to this embodiment is used as a display device incorporated into any of different information devices (for example, a vehicle-mounted device for car navigation, etc., a personal computer, a mobile phone, a portable information terminal, a portable game console, a copier, a ticket vending machine, or an ATM).

[0051] For example, the TFT substrate 1 includes: a plurality of TFTs arranged in a matrix pattern on a glass substrate; an interlayer insulating film arranged to cover the TFTs; a plurality of pixel electrodes arranged in a matrix pattern on the interlayer insulating film and respectively connected to the plurality of TFTs; and an alignment film arranged to cover the pixel electrodes. For example, the CF substrate 2 includes: a black matrix arranged in a grid pattern on a glass substrate; a color filter including a red layer, a green layer, and a blue layer respectively arranged between the grids of the black matrix; a common electrode arranged to cover the black matrix and the color filter; and an alignment film arranged to cover the common electrode. The liquid crystal layer 3 is composed of a nematic liquid crystal material containing liquid crystal molecules having electro-optical properties, etc. For example, the first polarizing plate 6 and the second polarizing plate 7 include a polarizer layer with a polarization axis in one direction and a pair of protective layers arranged to sandwich the polarizer layer.

[0052] <Backlight Unit>

[0053] Figure 2 An example of a cross-sectional configuration of the backlight unit according to this embodiment is shown.

[0054] like Figure 2 As shown, the backlight unit 40 mainly includes a plurality of light sources 42 and a light diffuser 43 arranged on the upper side of the plurality of light sources 42. The plurality of light sources 42 can be arranged two-dimensionally on the reflective sheet 41. The plurality of light sources 42 can be, for example, white light sources or blue light sources. A plurality of light diffusers 43 can be arranged. In this example, the light diffuser 43 includes two first light diffusers 43A arranged on the upper side of the plurality of light sources 42 and a second light diffuser 43B arranged on the upper side of the first light diffuser 43A. The first light diffuser 43A and the second light diffuser 43B each include a substrate layer 101 and a light diffuser 102 arranged on the substrate layer 101. In this example, the light diffuser 102 is arranged to face the direction of the light source 42 (in other words, on the light incident surface), and a plurality of recesses 105 are provided on the light diffuser 102, the plurality of recesses having an inverted substantially polygonal pyramid shape, or more specifically an inverted substantially quadrangular pyramid shape (hereinafter also referred to as an inverted pyramid shape). Meanwhile, the surface of the base material layer 101 serving as the light emitting surface is a matte surface, and the matte surface is exposed on each first light diffusion sheet 43A, while the flattened printed layer 103 is provided to cover the matte surface on the second light diffusion sheet 43B.

[0055] A wavelength selective sheet 44A and a color conversion sheet 44B may be disposed above the second light diffuser 43B. The wavelength selective sheet 44A is disposed below the color conversion sheet 44B. The wavelength selective sheet 44A selectively transmits light having the wavelength emitted by the light source 42 and reflects light having other wavelengths. The color conversion sheet 44B converts the color of the light emitted by the light source 42.

[0056] First prism sheet 45 and second prism sheet 46 may be sequentially disposed on the upper side of color conversion sheet 44B to enhance brightness. For example, brightness enhancement sheet 47 (such as a one-way reflective polarizing film) may be additionally disposed on the upper side of second prism sheet 46 to further enhance brightness.

[0057] [Reflective sheet]

[0058] The reflection sheet 41 is made of, for example, a white polyethylene terephthalate resin film, a silver vapor deposition film, or the like.

[0059] [light source]

[0060] There is no particular limitation on the type of light source 42, and the light source 42 may be, for example, an LED element, a laser element, or the like. From the perspective of cost, productivity, etc., an LED element may be used. When viewed in a plan view, the light source 42 may have a rectangular shape, and in this case, the length of one side may be 10 μm or greater (preferably, 50 μm or greater) and 20 mm or less (preferably, 10 mm or less, and more preferably, 5 mm or less). When an LED is used as the light source 42, a plurality of LED chips may be deployed on the reflective sheet 41 at fixed intervals. A lens may be mounted on the LED acting as the light source 42 in order to adjust the emission angle characteristics of the LED. Although there is no particular limitation on the number of light sources 42 deployed, when the plurality of light sources 42 are deployed in a distributed manner, the light sources 42 are preferably regularly deployed on the reflective sheet 41. Regularly deployed means deployed with fixed regularity, and corresponds to, for example, a case where the light sources 42 are deployed at equal intervals. When the light sources 42 are arranged at equal intervals, the center-to-center distance between two adjacent light sources 42 may be 0.5 mm or more (preferably, 2 mm or more) and 20 mm or less.

[0061] [Light Diffuser]

[0062] The light diffusion sheet 43 diffuses light entering from the light source 42 and collects the light on the normal direction side (in other words, collects and diffuses light). Figure 2An example of a case where two first light diffusers 43A and one second light diffuser 43B are provided as the light diffuser 43 in the backlight unit 40 is shown, but the light diffuser 43 may be composed of one second light diffuser 43B alone, or composed of two, four or more sheets including at least one second light diffuser 43B. There is no particular limitation on the matrix resin constituting the light diffuser 43, as long as the matrix resin is composed of a material that transmits light, and for example, the matrix resin may be polycarbonate, acrylic, polystyrene, MS (methyl methacrylate-styrene copolymer) resin, polyethylene terephthalate, polyethylene naphthalate, cellulose acetate, polyimide, or the like. There is no particular limitation on the thickness of the light diffuser 43, but for example, it may be greater than or equal to 50 μm and less than or equal to 3 mm. When the thickness of the light diffuser 43 exceeds 3 mm, it becomes more difficult to achieve a reduction in the thickness of the liquid crystal display, and when the thickness of the light diffuser 43 drops below 50 μm, it becomes difficult to obtain a sufficient light diffusion effect. When a plurality of light diffusers 43 are used, such as Figure 2 As shown, the total thickness may be about several hundred μm to several mm. The light diffusion sheet 43 may also be in the form of a film or a plate. The configuration of the light diffusion sheet 43 and its manufacturing method will be described in detail later.

[0063] [Wavelength Selective Sheet and Color Converter Sheet]

[0064] The wavelength-selective sheet 44A selectively transmits light having the emission wavelength of the light source 42 (e.g., blue light) and reflects light of other wavelengths. The color conversion sheet 44B converts the light from the light source 42 (e.g., blue light) into light having a peak wavelength of a desired color (e.g., green or red). For example, the color conversion sheet 44B converts blue light having a wavelength of 450 nm into green light having a wavelength of 540 nm and red light having a wavelength of 650 nm. In this case, when a light source 42 emitting blue light having a wavelength of 450 nm is used, the blue light is partially converted into green light and red light by the color conversion sheet 44B, thereby converting the light transmitted through the color conversion sheet 44B into white light. For example, a QD (quantum dot) sheet, a fluorescent sheet, or the like can be used as the color conversion sheet 44B. Since the wavelength-selective sheet 44A is disposed below the color conversion sheet 44B, light whose wavelength has been changed by the color conversion sheet 44B can only pass upward from the color conversion sheet 44B.

[0065] The wavelength selection sheet 44A and the color conversion sheet 44B can be disposed at any position between the light source 42 and the first prism sheet 45. For example, the wavelength selection sheet 44A and the color conversion sheet 44B can be disposed between the light source 42 and the first light diffuser 43A, or between the first light diffuser 43A and the second light diffuser 43B. When a white light source is used as the light source 42, the wavelength selection sheet 44A and the color conversion sheet 44B can be omitted.

[0066] [Prism]

[0067] The first prism sheet 45 and the second prism sheet 46 refract light entering from the light diffuser 43 in a normal direction. For example, a plurality of groove lines having isosceles triangular cross-sections are arranged adjacent to each other on the respective light-emitting surfaces of the prism sheets 45 and 46, and the prisms are formed by triangular prism sections sandwiched between adjacent pairs of groove lines. For example, the vertex angle of the prisms is approximately 90°. The groove lines formed in the first prism sheet 45 and the groove lines formed in the second prism sheet 46 can be arranged to be orthogonal to each other. Therefore, light entering from the light diffuser 43 can be refracted in a normal direction by the first prism sheet 45, and light emitted from the first prism sheet 45 can be refracted by the second prism sheet 45 so as to travel substantially perpendicular to the light incident surface of the brightness enhancement sheet 47. The prism sheets 45 and 46 can be stacked as separate bodies, or they can be formed integrally. For example, the total thickness of the prism sheets 45 and 46 can be approximately 100μm to 400μm. As the prism sheets 45 and 46 , for example, PET (polyethylene terephthalate) films in which a prism shape is formed using a UV-curable acrylic resin can be used.

[0068] [Brightness Enhancement Film]

[0069] Brightness enhancement sheet 47 can improve brightness by utilizing double reflection and integrating light with the refractive index when light passes through the sheet. Alternatively, brightness enhancement sheet 47 can increase brightness by recycling S waves that have not passed through first polarizing plate 6 of liquid crystal display device 50 and converting the recycled S waves into P waves that pass through first polarizing plate 6. When prism sheets 45 and 46 provide a sufficient brightness enhancement effect, brightness enhancement sheet 47 can be omitted.

[0070] <Configuration of Light Diffuser>

[0071] like Figure 3 and Figure 4As shown, each of the first light diffuser 43A and the second light diffuser 43B mainly includes a substrate layer 101 and a light diffuser 102 provided on the substrate layer 101. Each of the light diffusers 43A and 43B has a first surface (the front surface of the light diffuser 102) 102a serving as a light incident surface and a second surface (the front surface of the substrate layer 101) 101a serving as a light emitting surface. The plurality of recesses 105 are provided on the light diffuser 102 to diffuse light, and the plurality of recesses have an inverted roughly polygonal pyramid shape, or more specifically, an inverted roughly quadrangular pyramid shape (inverted pyramid shape). The second surface 101a of each of the light diffusers 43A and 43B is a matte surface. The matte surface is a finely roughened surface having a surface roughness of approximately 1 μm to 10 μm. The unevenness on the matte surface can be randomly arranged. Note that, in this disclosure, surface roughness refers to the arithmetic mean roughness Ra according to JIS B 0601-1994.

[0072] Note that in this example, the first surface 102a of each of the light diffusion sheets 43A and 43B serves as a light incident surface, and the second surface 101a serves as a light emission surface. However, alternatively, the first surface 102a may be a light emission surface, and the second surface 101a may be a light incident surface. Alternatively, the plurality of light diffusion sheets 43 may include a sheet on which the first surface 102a is a light incident surface and the second surface 101a is a light emission surface, and a sheet on which the first surface 102a is a light emission surface and the second surface 101a is a light incident surface.

[0073] On the first light diffuser 43A, as shown in FIG. Figure 3 As shown, the second surface 101a (ie, the matte surface) is exposed. Figure 4 As shown, the second light diffuser 43B is provided with a flattening print layer 103, which is composed of, for example, an acrylic urethane-based light-transmitting ink 106, so as to cover the unevenness on the second surface 101a (i.e., the matte surface). It is to be noted that the surface roughness of the second surface (matte surface) 101a of the second light diffuser 43B provided with the flattening print layer 103 is preferably 1 μm or more and 6 μm or less, more preferably 2 μm or more and 5 μm or less, and even more preferably 2.8 μm or more and 4 μm or less. In addition, as long as the second surface (matte surface) 101a has a ten-point average roughness Rz of approximately 50 μm or less (according to JIS B 0601-1994), the unevenness on the second surface 101a can be covered and flattened by printing with the light-transmitting ink 106. In addition, as Figure 5 As shown, for example, a plurality of acrylic particles (hereinafter also referred to as beads) 107 may be added to the flattened printed layer 103 .

[0074] [Base material layer]

[0075] The substrate layer 101 of each of the light diffusers 43A and 43B needs to transmit light and is therefore formed using a transparent (e.g., colorless and transparent) synthetic resin as a main component. The main component of the substrate layer 101 is not particularly limited, and 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 the term "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 101 may contain a diffusing agent or other additives, or may be substantially free of additives. The additives that may be included are not particularly limited, but may be inorganic particles such as silica, titanium oxide, aluminum hydroxide, barium sulfate, etc., or organic particles such as acrylic acid, acrylonitrile, silicone, polystyrene, polyamide, etc.

[0076] The lower limit of the average thickness of the substrate layer 101 is preferably about 10 μm, more preferably about 35 μm, and even more preferably about 50 μm. Due to the risk of curling, the upper limit of the average thickness of the substrate layer 101 is preferably about 500 μm, more preferably about 250 μm, and even more preferably about 180 μm. Conversely, when the average thickness of the substrate layer 101 exceeds the upper limit, the brightness of the liquid crystal display device 50 may decrease, and it may be difficult to respond to the demand for making the liquid crystal display device 50 thinner. Note that in this disclosure, the term "average thickness" refers to the average value of the thickness at any ten points.

[0077] [Light diffusion layer]

[0078] The light diffusion layer 102 of each of the light diffusion sheets 43A and 43B needs to transmit light and is therefore formed using a transparent (e.g., colorless and transparent) synthetic resin as a main component. The light diffusion layer 102 may be integrally molded with the base material layer 101 during extrusion molding of the base material resin forming the base material layer 101, or may be separately molded using a UV curable resin after molding the base material layer 101.

[0079] like Figure 6As shown, for example, the multiple inverted, roughly quadrangular pyramid-shaped (inverted pyramid-shaped) recesses 105 provided on the light diffusion layer 102 can be arranged in a two-dimensional matrix pattern. In other words, the multiple recesses 105 can be arranged along two mutually orthogonal directions. Adjacent recesses 105 are separated by a ridge line 111. The ridge line 111 extends along the two directions in which the recesses 105 are arranged. The arrangement spacing of the recesses 105 can be, for example, about 50 μm or more and about 500 μm or less. The center (vertex of the inverted pyramid) 112 of the recess 105 is the deepest part of the recess 105. The center (deepest part) 112 of the recess 105 can reach the front surface (light emitting surface) of the substrate layer 101. In other words, the depth of the recess 105 can be set to be equal to the thickness of the light diffusion layer 102. It should be noted that, although for the sake of simplicity, Figure 6 A state in which the recesses 105 are arranged in a 5×5 matrix pattern is shown, but the actual number of arranged recesses 105 is much larger.

[0080] For example, the vertex angle θ of the concave portion 105 is set to about 90°. Figure 7 As shown, the vertex angle θ of the concave portion 105 is a plane (vertical cross section) perpendicular to the placement surface (horizontal plane) of the light diffusion sheet 43, formed by the inclined surfaces of the concave portion 105 that pass through the vertex 112 of the inverted pyramid and face each other with the vertex 112 as the center, and the concave portion 105 is cut perpendicular to the pair of ridge lines 111 on the cross section ( Figure 7 Note that Figure 7 The upper figure shows the planar configuration of the recess 105. Figure 7 , "H" represents the depth of the recess 105 (the height of the pyramid shape), and "P" represents the horizontal width of the recess 105 (in other words, the arrangement pitch of the recess 105). The depth H of the recess 105 is determined by the arrangement pitch P of the recess 105 and the vertex angle θ of the recess 105.

[0081] When the plurality of light sources 42 are arranged in a square shape, as shown in FIG. Figure 8 As shown in (a), relative to the arrangement direction of the light source 42, the arrangement direction of the recess 105 can be inclined, for example, by about 45°. Figure 8 When the recess 105 is formed in an inverted pyramid shape, by setting the arrangement direction of the light sources 42 and the arrangement direction of the recess 105 to intersect, the brightness uniformity can be improved more than when the two arrangement directions are aligned.

[0082] Although in this embodiment, the inverted pyramid-shaped (inverted roughly quadrangular pyramid-shaped) recesses 105 are arranged in a two-dimensional matrix pattern to form an uneven shape, the recesses 105 can be randomly arranged as long as the function and effect of the present invention are not lost. When the recesses 105 are regularly arranged in a two-dimensional arrangement, gaps can be set between the recesses 105, but gaps are not necessarily set. The recesses 105 can have an inverted roughly polygonal pyramid shape other than the inverted roughly quadrangular pyramid shape. For example, the "inverted polygonal pyramid" shape of the recess 105 can be an inverted triangular pyramid or an inverted hexagonal pyramid, which can be deployed two-dimensionally without gaps, similar to an inverted quadrangular pyramid. When the "inverted polygonal pyramid" shape of the recess 105 is an inverted quadrangular pyramid, it is easy to improve the accuracy of the surface cutting operation of the metal mold (metal roller) used in the manufacturing process (such as extrusion molding or injection molding) performed when providing the recess 105.

[0083] Although the term "inverted substantially polygonal pyramid" is used in this disclosure in consideration of the fact that it is difficult to form a geometrically strict inverted polygonal pyramid-shaped recess using ordinary shape transfer technology, the term "inverted substantially polygonal pyramid" is considered to include shapes that can be regarded as inverted true or substantially polygonal pyramids. In addition, the term "substantially" means "can be approximated," so that, for example, an "inverted substantially quadrangular pyramid" refers to a shape that can be approximated as an inverted quadrangular pyramid. For example, similarly with respect to an "inverted truncated polygonal pyramid" having a flat top, shapes with a small top area are also considered to be included in the "inverted substantially polygonal pyramid" as long as the effects and effects of the present invention are not lost. In addition, shapes that are deformed from an "inverted polygonal pyramid" within the inevitable range of shape variability caused by machining accuracy in industrial production are also considered to be included in the "inverted substantially polygonal pyramid."

[0084] [Flatten the printed layer]

[0085] In this embodiment, the flattening printed layer 103 is composed of light-transmitting ink 106 and is provided to cover the second surface 101a of the second light diffuser 43B, or in other words, to cover the unevenness of the matte surface. The flattening printed layer 103 is formed, for example, by solid-state printing of the light-transmitting ink 106 onto the second surface 101a. The provision of the flattening printed layer 103 improves brightness and brightness uniformity compared to a case where the second surface 101a (i.e., the matte surface) of the second light diffuser 43B is exposed.

[0086] Note that the surface roughness of the flattened printed layer 103 is not particularly limited as long as it is less than the surface roughness of the second surface 101a (i.e., matte surface) of the second light diffuser 43B. However, the surface roughness of the flattened printed layer 103 is preferably less than 1 μm, more preferably 0.1 μm or less, and even more preferably 0.01 μm or less.

[0087] Furthermore, the thickness of the flattened printed layer 103 is not particularly limited, as long as the unevenness on the second surface 101a (i.e., the matte surface) of the second light diffuser 43B can be covered by it. However, the thickness of the flattened printed layer 103 is preferably 5 μm or greater, and more preferably 8 μm or greater. On the other hand, in order to suppress the increase in the thickness of the second light diffuser 43B, the thickness of the flattened printed layer 103 is preferably not more than 20 μm, and more preferably not more than 15 μm. It should be noted that in this disclosure, the thickness of the flattened printed layer 103 refers to the "average thickness" and is substantially equal to the thickness of the light-transmitting ink 106 constituting the flattened printed layer 103 when solid-state printed on a flat surface.

[0088] The material of the light-transmitting ink 106 constituting the flattened print layer 103 is not particularly limited as long as it can transmit light, and for example, acrylic, polyester, vinyl, urethane acrylate, silicone, cellulose, epoxy resin, phenol, etc. can be used. The light-transmitting ink 106 is not a liquid ink but a solid ink formed from a material such as a thermosetting resin or a thermoplastic resin and having light-transmitting properties.

[0089] Regarding the addition of particles 107 to the flattened print layer 103 (see Figure 5 ), and their material, shape, and size are not particularly limited, as long as particles 107 can diffuse or reflect light. Particles 107 can be made of, for example, acrylic, styrene, titanium, silica, nylon, urethane, etc. Particles 107 can be monodisperse or polydisperse. Particles 107 can have a hollow structure. In this case, particles 107 can be single-hollow or multi-hollow particles.

[0090] The particles 107 can be in the form of beads, such as acrylic beads, or fibers, such as cellulose nanofibers. To prevent problems that arise when the second light diffuser 43B is wound onto a roll, such as interference patterns, tacking marks, and the like remaining on the flattened printed layer 103, or the surface where the recesses 105 are formed (first surface 102a) adhering to the surface of the flattened printed layer 103 and causing scratches when these surfaces are peeled off, the average particle size of the particles 107 can be set to be larger than the average thickness of the flattened printed layer 103. As a result, the particles 107 are more likely to be exposed from the surface of the flattened printed layer 103, and thus, the aforementioned problems are less likely to occur. However, it should be noted that to prevent the particles 107 from falling off the flattened printed layer 103, the average particle size of the particles 107 is preferably approximately several μm (approximately 1 μm to 5 μm) larger than the average thickness of the flattened printed layer 103. In this disclosure, the average particle size of the particles 107 refers to the average diameter of the particles 107 when they are beads and the average length of the particles 107 when they are fibers.

[0091] The mass ratio of the particles 107 to the light-transmitting ink 106 in the flattened printed layer 103 is not particularly limited, as long as the occurrence of the above-mentioned problems, that is, the occurrence of scratches and blocking during the production of the second light diffuser 43B, can be suppressed. However, it should be noted that in order to suppress the occurrence of scratches and blocking while suppressing the reduction in brightness and brightness uniformity, the mass ratio of the particles 107 is preferably 1% or more and 10% or less, more preferably 2% or more and 8% or less, and even more preferably 4% or more and 6% or less.

[0092] When the particles 107 are added to the light-transmitting ink 106, for example, the light-transmitting ink 106 (which is a thermosetting resin, UV-curable resin, etc.) can be printed after the particles 107 are dispersed through the light-transmitting ink 106, after which the light-transmitting ink 106 can be cured by ultraviolet rays or hot air. The method for printing the light-transmitting ink 106 is not particularly limited, and may be, for example, screen printing, gravure printing, etc., and may be included in the categories of analog printing, inkjet printing, laser printing, etc., and may be included in the categories of digital printing, hybrid printing combining both analog printing and digital printing methods, etc.

[0093] <Method for Manufacturing Light Diffusing Sheet>

[0094] The method for manufacturing the light diffusion sheet 43 including the second light diffusion sheet 43B is not particularly limited, and for example, the light diffusion sheet 43 can be manufactured using any one of the following manufacturing methods.

[0095] In the first manufacturing method, a pelletized base resin (plastic resin) is first formed into a resin film using an extruder. Next, a roller with a convex pyramidal shape on its surface is used as one of two metal rollers, and a roller with an inverted shape having a matte surface is used as the other. These two rollers are pressed against the resin film to produce a light diffuser 43 having an inverted pyramidal shape (concave portions 105) on one surface and a matte surface on the other. In this manufacturing method, the base layer 101 and the light diffuser layer 102 are integrally formed. The flattened printed layer 103 is then formed on the matte surface of the second light diffuser 43B.

[0096] In the second manufacturing method, a substrate layer 101 having, for example, polyethylene terephthalate as its main component is first prepared. While the substrate layer 101 is being fed between a pair of pressing rollers, a UV-curable resin (a resin composition for forming projections) is supplied to one surface of the substrate layer 101 immediately before it enters the pair of pressing rollers. A pressing roller having a plurality of substantially quadrangular pyramidal projections on its outer circumferential surface is used as the pressing roller on the side that comes into contact with the UV-curable resin, and a roller having an inverted shape with a matte surface on its surface is used as the other roller. After the pair of pressing rollers is pressed against the substrate layer 101 to which the UV-curable resin has been supplied, the UV-curable resin is cured by UV irradiation, thereby transferring a plurality of inverted pyramidal shapes (recesses 105) that are inverted shapes of the plurality of substantially quadrangular pyramidal projections. This results in the manufacture of a light-diffusing sheet 43 having the light-diffusing layer 102 provided on one surface of the substrate layer 101 and a matte surface provided on the other surface. In this manufacturing method, the base material layer 101 and the light diffusion layer 102 are formed separately. Then, the flattened printed layer 103 is formed on the matte surface of the second light diffusion sheet 43B.

[0097] <Features of the embodiment>

[0098] The second light diffuser 43B of this embodiment is a light diffuser 43 having a plurality of inverted, substantially polygonal pyramidal recesses 105 provided on a first surface 102a, which serves as a light emitting surface or a light incident surface. A second surface 101a on the opposite side of the first surface 102a is a matte surface, and a flattened printed layer 103 composed of light-transmitting ink 106 is provided to cover the unevenness on the matte surface.

[0099] According to the second light diffuser 43B of this embodiment, the visibility of defects on the first surface 102a (the recessed portion forming surface) provided with the inverted substantially polygonal pyramidal recessed portions 105 can be suppressed by the matte surface shape of the second surface 101a. In addition, since the flattened printed layer 103 is provided to cover the second surface 101a (i.e., the matte surface), the brightness and brightness uniformity can be improved compared to the case where the second surface 101a (i.e., the matte surface) is exposed.

[0100] In the second light diffusion sheet 43B of this embodiment, the thickness of the flattening printed layer 103 may be 5 μm or more. Therefore, even a matte surface (second surface 101 a ) having relatively large surface roughness can be flattened by the flattening printed layer 103 .

[0101] In the second light diffuser 43B of this embodiment, the plurality of particles 107 can be added to the flattened printed layer 103. Therefore, scratches and sticking are less likely to occur during the manufacture of the second light diffuser 43B. For example, when the second light diffuser 43B is wound onto a roll, problems such as interference patterns and pressure-bonding marks remaining on the surface (printing surface) of the flattened printed layer 103, or the surface where the recesses 105 are formed (the first surface 102a) and the printing surface sticking together, which could cause scratches when these surfaces are peeled off, can be suppressed. Consequently, large-scale production efficiency can be improved.

[0102] In the second light diffuser 43B of this embodiment, the average particle size of the plurality of particles 107 may be larger than the thickness (average thickness) of the flattened printed layer 103. Therefore, scratches, blocking, etc. are less likely to occur during the manufacture of the second light diffuser 43B.

[0103] In the second light diffuser 43B of this embodiment, the mass ratio of the particles 107 in the flattened printed layer 103 to the light-transmitting ink 106 can be 1% or more and 10% or less. Therefore, the occurrence of scratches and blocking during the manufacture of the second light diffuser 43B can be suppressed, while also suppressing a decrease in brightness and brightness uniformity.

[0104] In the second light diffuser 43B of this embodiment, the plurality of recesses 105 may be formed in an inverted substantially quadrangular pyramid shape and arranged in a two-dimensional matrix pattern. Therefore, the second light diffuser 43B may be manufactured with high accuracy to exhibit excellent luminance uniformity.

[0105] In the second light diffusion sheet 43B of this embodiment, as long as the matte surface (second surface 101a) has a ten-point average roughness Rz of about 50 μm or less (based on JIS B 0601-1994), unevenness on the second surface 101a can be covered and flattened by printing the light-transmitting ink 106.

[0106] The backlight unit 40 according to this embodiment is incorporated into a liquid crystal display device 50 so as to guide the light emitted from the plurality of light sources 42 toward the display screen 50a. The backlight unit 40 includes a second light diffuser 43B of this embodiment, which is disposed between the display screen 50a and the light sources 42. Therefore, the visibility of defects on the surface (first surface 102a) where the recesses 105 of the second light diffuser 43B are formed can be suppressed, while improving brightness and brightness uniformity. It should be noted that in the backlight unit 40, the effect of suppressing the visibility of defects is greater when the second light diffuser 43B is disposed so that the first surface 102a serves as the light incident surface.

[0107] In the backlight unit 40 of this embodiment, the plurality of light sources 42 may be disposed on a reflective sheet 41, which is disposed on the side opposite to the display screen 50a when viewed from the light diffuser 43. Therefore, light is further diffused by multiple reflections between the light diffuser 43 and the reflective sheet 41, thereby further improving brightness uniformity.

[0108] In the backlight unit 40 according to this embodiment, a plurality of light diffusers 43, including a second light diffuser 43B, can be disposed between the display screen 50a and the plurality of light sources 42. Therefore, the plurality of light diffusers 43 can be used to further improve brightness uniformity. In this case, when the second light diffuser 43B is disposed at the top, the effect of suppressing the visibility of defects is greater.

[0109] The liquid crystal display device 50 according to this embodiment includes the liquid crystal display panel 5 and the backlight unit 40 of this embodiment. Therefore, it is possible to suppress the visibility of defects on the surface (first surface 102a) where the recessed portion 105 of the second light diffusion sheet 43B is formed, while improving brightness and brightness uniformity. Similar effects can be achieved in information devices (personal computers, mobile phones, etc.) incorporating the liquid crystal display device 50 of this embodiment.

[0110] It should be noted that in this embodiment, a direct-type backlight unit in which a plurality of light sources 42 are disposed in a distributed manner on the rear surface side of the display screen 50a of the liquid crystal display device 50 is used as the backlight unit 40. Therefore, in order to reduce the size of the liquid crystal display device 50, it is necessary to reduce the distance between the light source 42 and the light diffusion sheet 43 (in the embodiment of FIG. Figure 2 In the example shown, the distance between the first light diffuser 43A closest to the light source 42 is 10 mm. However, when this distance is reduced, a phenomenon (brightness unevenness) is more likely to occur in which the brightness of the portion of the display screen 50a located in the area between the distributed light sources 42 decreases compared to the other portions. However, the use of the second light diffuser 43B of this embodiment can be used to suppress brightness unevenness. More specifically, in the case where the thickness of small and medium-sized liquid crystal displays is expected to be reduced in the future, it is considered that the usefulness of the second light diffuser 43B of this embodiment will become even more apparent when the distance between the light source 42 and the light diffuser 43 (in the case of using multiple light diffusers 43, the light diffuser 43 closest to the light source 42) is set to 10 mm or less, preferably 5 mm or less, more preferably 2 mm or less, even more preferably 1 mm or less, and finally 0 mm. For example, even if a sufficient distance between the light source and the sheet cannot be ensured in order to achieve thickness reduction, such as when the distance between the light source 42 and the light diffuser sheet 43 is 0 mm or greater and 1 mm or less, the deterioration of the in-plane brightness uniformity can be suppressed by the light diffusion performance of the second light diffuser sheet 43B of this embodiment.

[0111] <Example>

[0112] Examples and comparative examples will be described below.

[0113] As Example 1, a Figure 4 The second light diffuser 43B is arranged as shown in FIG. Figure 9 Components in the backlight unit 40 of the configuration shown. More specifically, Figure 9 The backlight configuration shown is achieved by: Figure 2 In the illustrated backlight configuration, a glass plate 48 is placed on the color conversion sheet 44B without providing the prism sheets 45 and 46 and the brightness enhancement sheet 47. Furthermore, a flattened printed layer 103 having an average thickness of 10 μm is provided by solid-state printing of an acrylic urethane-based light-transmitting ink 106 so as to cover the unevenness on the matte surface of the second surface 101 a forming the second light diffusion sheet 43B.

[0114] As Example 2, a Figure 5 The second light diffuser 43B is arranged as shown in FIG. Figure 9 Components of the backlight unit 40 in the illustrated configuration. More specifically, a flattened printed layer 103 having an average thickness of 10 μm is provided by solid-state printing of an acrylic urethane-based light-transmitting ink 106, to which a plurality of particles 107 are added to cover unevenness on the matte surface of the second surface 101a forming the second light diffuser 43B. Acrylic beads having an average particle size of 12 μm are used as particles 107, and are added at a ratio of 5 parts by mass to 100 parts by mass of light-transmitting ink 106.

[0115] As a comparative example, Figure 9 In the backlight unit 40 of the illustrated configuration, no component for flattening the printed layer 103 is provided on the second light diffusion sheet 43B.

[0116] In all of Examples 1 and 2, as well as the comparative examples, a sheet obtained by providing a light diffusion layer 102 on a polycarbonate substrate layer 101 having a thickness of 110 μm using an acrylate-based UV-curable resin was used as the light diffusion sheet 43, including a second light diffusion sheet 43B. In this light diffusion layer, a plurality of inverted pyramid-shaped recesses 105 were arranged in a two-dimensional matrix pattern. The vertex angle and arrangement pitch of the recesses 105 were 90° and 100 μm, respectively. All light diffusion sheets 43 were arranged so that the arrangement direction of the recesses 105 intersected the arrangement direction of the light sources 42 at a 45-degree angle. An array of blue LEDs arranged in a square shape with a pitch of 3.5 mm x 4.5 mm was used as the multiple light sources 42. The thickness of the wavelength selective sheet 44A was set to 50 μm, and the thickness of the color conversion sheet 44B was set to 60 μm.

[0117] In the backlight unit configurations of Examples 1 and 2 and the comparative example described above, the luminance and luminance uniformity were evaluated in the following manner in a state where the transparent glass plate 48 was placed on the color conversion sheet 44B to prevent the sheet from rising. First, the luminance (cd / m²) in the vertically upward direction (the direction from the LED array toward the glass plate) was measured using a two-dimensional colorimeter SR-5000 manufactured by Topcon Technohaus Co., Ltd. 2 ). Next, the obtained two-dimensional brightness distribution image is corrected for variations in the emission intensity of each LED, filtering processing is performed to suppress bright and dark spot noise caused by foreign matter, etc., the average value and standard deviation of the brightness of all pixels are calculated, and the brightness and brightness uniformity are determined using "brightness" defined as "brightness average" and "brightness uniformity" defined as "brightness average / brightness standard deviation".

[0118] As a result, the brightness of the comparative example is 6085cd / m 2 , while the brightness of Sample 1 and Sample 2 are 6173cd / m 2 and 6178cd / m 2 Furthermore, the brightness uniformity of the comparative example is 21.29, while the brightness uniformities of Example 1 and Example 2 are 21.41 and 21.86, respectively.

[0119] As described above, in all examples, the configuration that can suppress the visibility of defects on the recessed portion forming surface can improve brightness and brightness uniformity and improve quality productivity (only Example 2 is used to improve quality productivity). In other words, the effectiveness of providing the flattened printed layer 103 on the second light diffuser 43B was confirmed.

[0120] (Other embodiments)

[0121] Although the above describes embodiments of the present disclosure (including examples: the same applies below), the present disclosure is not limited to the above embodiments, and various modifications can be made within the scope of the present disclosure. In other words, the foregoing description of the embodiments is illustrative in nature and is not intended to limit the present disclosure, its application, or its uses.

[0122] More specifically, in the above Figure 2 or Figure 9 In the backlight unit 40 of the illustrated embodiment, a stacked light diffuser sheet 100 in which two second light diffusers 43B are adhered to each other may be used instead of the upper first light diffuser sheet 43A and the second light diffuser sheet 43B. Figure 10As shown. In the stacked light diffuser sheet 100, two second light diffusers 43B are adhered to each other, and the flattened printed layer 103 of the lower second light diffuser sheet 43B is located between the two. For example, the stacked light diffuser sheet 100 can be formed by printing a light-transmitting ink 106 containing a UV-curable resin on the second surface 101a of each second light diffuser sheet 43B, and then curing the light-transmitting ink 106 by ultraviolet rays in a state where the first surface 102a of the upper second light diffuser sheet 43A is pressed against the second surface 101a of the lower second light diffuser sheet 43B. It should be noted that in the stacked light diffuser sheet 100, a first light diffuser sheet 43A without a flattened printed layer 103 or another light diffuser sheet can be provided instead of the upper light diffuser sheet 43B. Further, in Figure 10 In the illustrated stacked light diffuser sheet 100, the second surfaces 101a of the respective light diffuser sheets 43B are adhered to each other to form a light-emitting surface. However, alternatively, the second surfaces 101a of the respective light diffuser sheets 43B may be adhered to each other to form a light-incident surface. In this case, a first light diffuser sheet 43A or another light diffuser sheet without the flattened printed layer 103 may be provided in place of the lower light diffuser sheet 43B. As described above, by adhering the light diffusers to each other, the risk of damage to the light diffusers can be reduced compared to handling the plurality of light diffusers individually, thereby improving productivity. Furthermore, the time required to assemble the liquid crystal display device can be reduced, thereby improving production output.

[0123] Furthermore, in the second light diffuser 43B of the above embodiment, the flattening printed layer 103 is formed by printing the light-transmitting ink 106 on the second surface 101a. However, alternatively, a flattening layer composed of a light-transmitting resin may be formed by a method other than printing to cover the unevenness on the second surface 101a, or in other words, the matte surface. For example, the flattening layer composed of a light-transmitting resin may be provided by applying a liquid light-transmitting UV-curable resin using a roller coater to cover the unevenness on the matte surface of the second surface 101a serving as the second light diffuser 43B, and then irradiating the resin with ultraviolet rays.

[0124] List of Reference Numerals

[0125] 1 TFT substrate

[0126] 2 CF substrate

[0127] 3 Liquid crystal layer

[0128] 5 LCD panel

[0129] 6. First polarizing plate

[0130] 7 Second polarizing plate

[0131] 40 Backlight unit

[0132] 41 reflective sheet

[0133] 42 Light Source

[0134] 43 Light Diffuser

[0135] 43A First light diffuser

[0136] 43B Second light diffuser

[0137] 44A Wavelength Selective Plate

[0138] 44B color conversion film

[0139] 45 First Prism

[0140] 46 Second prism

[0141] 47 Brightness Enhancement Film

[0142] 48 Glass Plate

[0143] 50 Liquid crystal display device

[0144] 50a display

[0145] 100 stacked light diffusers

[0146] 101 base material layer

[0147] 101a Second surface

[0148] 102 light diffusion layer

[0149] 102a first surface

[0150] 103 Flattening the Printing Layer

[0151] 105 recess

[0152] 106 Translucent Ink

[0153] 107 particles

[0154] 111 Ridge of concave part

[0155] 112 Center of recess

Claims

1. A light diffuser having a plurality of inverted substantially polygonal pyramidal recesses provided on a first surface, the first surface serving as a light emitting surface or a light incident surface, wherein: The second surface on the side opposite to the first surface is a matte surface, and A flattened print layer composed of light-transmitting ink is provided to cover the irregularities on the matte surface.

2. The light diffuser according to claim 1, wherein: The flattened printed layer has a thickness of 5 μm or greater.

3. The light diffuser according to claim 1, wherein: A plurality of particles is added to the flattened print layer.

4. The light diffuser according to claim 3, wherein: The average particle size of the plurality of particles is greater than the thickness of the flattened print layer.

5. The light diffuser according to claim 3, wherein: A mass ratio of the plurality of particles to the light-transmitting ink in the flattened printing layer is 1% or more and 10% or less. The light diffuser according to claim 1 , wherein: The plurality of recesses are formed in an inverted substantially quadrangular pyramid shape and are arranged in a two-dimensional matrix pattern.

7. The light diffuser according to claim 1, wherein: The ten-point average roughness Rz (according to JIS B 0601-1994) of unevenness on the matte surface is 50 μm or less.

8. A backlight unit incorporated into a liquid crystal display device so as to guide light emitted from a plurality of light sources to a display screen, the backlight unit comprising The light diffuser according to any one of claims 1 to 7, wherein the light diffuser is disposed between the display screen and the plurality of light sources.

9. A liquid crystal display device, comprising: The backlight unit according to claim 8; as well as Liquid crystal display panel. 10 . An information device comprising the liquid crystal display device according to claim 9 .

11. A stacked light diffuser, comprising: The light diffuser according to any one of claims 1 to 7; as well as Another light diffuser sheet is adhered to the light diffuser sheet with the flattened printed layer therebetween.

12. A light diffusion sheet, wherein a plurality of inverted substantially polygonal pyramid-shaped recesses are provided on a first surface, the first surface serving as a light emitting surface or a light incident surface, wherein The second surface on the side opposite to the first surface is a matte surface, and A flattening layer composed of a light-transmitting resin is provided to cover the unevenness on the matte surface.

Images