TW202307532A - Optical sheet laminate, backlight unit, liquid crystal display device, and information apparatus - Google Patents

Abstract

An optical sheet laminate 100 that is to be interposed between a light source 42 and a prism sheet 44 of a backlight unit 40. The optical sheet laminate 100 comprises a plurality of light diffusion sheets 43 that have a plurality of substantially inverted-rectangular-pyramid-shaped recesses 22 at one surface. The recesses 22 of a first light diffusion sheet 43A that is closest to the prism sheet 44 are at a light emission surface 21a. The recesses 22 of at least one second light diffusion sheet 43B of the light diffusion sheets 43 that are not the first light diffusion sheet 43A are at a light incidence surface 21b. The first light diffusion sheet 43A contains 0-2 mass% of a diffusion agent.

Description

Optical sheet laminate, backlight unit, liquid crystal display device, and information equipment

The invention relates to an optical sheet laminate, a backlight unit, a liquid crystal display device, and information equipment.

In recent years, liquid crystal display devices (hereinafter, sometimes also referred to as liquid crystal displays) have been widely used as display devices of various information devices such as smartphones and tablet terminals. As a backlight of a liquid crystal display, a direct-type type in which a light source is arranged on the back of a liquid crystal panel, or an edge-light type in which a light source is arranged near a side surface of a liquid crystal panel has become mainstream.

In the case of using a direct-type backlight, in order to diffuse light from light sources such as LEDs (Light Emitting Diodes; Light Emitting Diodes) and improve the uniformity of brightness and chromaticity throughout the entire screen, a light diffusion sheet or a light diffusion sheet is used. and other optical sheets (for example, refer to Patent Document 1).

In the direct-lit backlight unit of thin displays such as notebook computers or flat panels, the uniformity of brightness can be improved by overlapping multiple light-diffusing sheets. [Prior Art Literature] [Patent Document] [Patent Document 1] Japanese Patent Laid-Open No. 2011-129277.

[Problem to be Solved by the Invention]

For portable information terminals such as notebook computers or tablets, further low power consumption is required. Accordingly, for the optical sheet assembled into the backlight unit, it is also required to be able to realize a high-brightness picture with low power consumption.

However, in general, the brightness uniformity tends to decrease in the configuration of a backlight with increased brightness. In other words, there is a trade-off relationship between brightness and brightness uniformity.

The object of the present invention is to maintain brightness uniformity in a backlight unit and realize a high-brightness screen even with low power. [Means to solve the problem]

In order to achieve the above-mentioned purpose, the optical sheet lamination system of the present invention is assembled between the aforementioned multiple light sources and the optical sheet in a liquid crystal display device in which multiple light sources are dispersedly arranged on the back side of the display screen. The optical sheet laminate of the present invention includes a plurality of light-diffusing sheets provided with a plurality of recesses in the shape of a substantially inverted quadrangular pyramid on one surface. In the first light-diffusing sheet that is closest to the above-mentioned light-diffusing sheet among the aforementioned plurality of light-diffusing sheets, the aforementioned plurality of recesses are arranged on the light-emitting surface. In at least one 2nd light-diffusion sheet among the said several light-diffusion sheets other than the said 1st light-diffusion sheet, the said some recessed part is arrange|positioned in a light incident surface. The content rate of the diffusing agent in the said 1st light-diffusion sheet is 0 mass % or more and 2 mass % or less.

According to the optical sheet laminate of the present invention, the uniformity of luminance can be improved by stacking a plurality of light-diffusing sheets (hereinafter, sometimes also referred to as pyramid sheets) provided with a plurality of recesses approximately in the shape of an inverted quadrangular pyramid on one side. . In addition, in the first light-diffusing sheet that is closest to the sheet, the substantially inverted quadrangular pyramid-shaped concave portion is arranged on the light-emitting surface, so it is easier to direct the emitted light to the edge compared with the case where the concave portion is arranged on the light-incident surface. The lenses converge. Furthermore, by suppressing the content rate of the diffusing agent in a 1st light-diffusion sheet to 2 mass % or less, the convergence property of the emitted light of a 1st light-diffusion sheet improves, Therefore Even with low electric power, luminance can be increased.

Therefore, by using the optical sheet laminate of the present invention for a backlight unit, uniformity of brightness can be maintained and a high-brightness screen can be realized even with low power.

In the optical sheet laminate of the present invention, when the second light-diffusing sheet is thicker than the first light-diffusing sheet, the following effects can be obtained. That is, if the thickness of the second light-diffusing sheet in which the substantially inverted quadrangular pyramid-shaped recesses are arranged on the light-incident surface becomes thicker, the light diffused in the recesses on the light-incident surface and advances obliquely in the second light-diffusing sheet The optical path of light becomes longer. Therefore, the diffusion distance of light in the direction parallel to the light incident surface becomes longer, so that the light diffusibility increases, and the brightness uniformity is further improved. Moreover, by making a 1st light-diffusion sheet thinner than a 2nd light-diffusion sheet, the thickness as an optical sheet laminated body as a whole can also be suppressed, and thickness reduction of a backlight unit, ie, a liquid crystal display device can be aimed at.

The backlight unit of the present invention is assembled into the aforementioned liquid crystal display device, and the light emitted from the aforementioned plurality of light sources is introduced into the aforementioned backlight unit on the side of the display screen, and the aforementioned inventive method is provided between the aforementioned plurality of light sources and the aforementioned wafer. Optical sheet laminates.

According to the backlight unit of the present invention, which includes the above-mentioned optical sheet laminate of the present invention, uniformity of brightness can be maintained and a high-brightness screen can be realized even with low power.

In the backlight unit of the present invention, the plurality of light sources may be disposed on a reflective sheet that is disposed on the opposite side of the aforementioned optical sheet laminate as viewed from the aforementioned optical sheet laminate. In this way, light is further diffused due to multiple reflections between the light diffusion sheet and the reflection sheet constituting the optical sheet laminate, so that the brightness uniformity is further improved.

In the backlight unit of the present invention, the distance between the plurality of light sources and the optical sheet laminate may be 2 mm or less. In this way, the thickness of the backlight unit can be reduced.

A liquid crystal display device of the present invention includes the aforementioned backlight unit and a liquid crystal display panel of the present invention.

According to the liquid crystal display device of the present invention, since the above-mentioned backlight unit of the present invention is provided, uniformity of brightness can be maintained and a high-brightness screen can be realized even with low power.

The information equipment of the present invention includes the aforementioned liquid crystal display device of the present invention.

According to the information equipment of the present invention, which includes the above-mentioned liquid crystal display device of the present invention, uniformity of brightness can be maintained and a high-brightness screen can be realized even with low power. [Efficacy of the invention]

According to the present invention, uniformity of brightness can be maintained in the backlight unit, and a high-brightness screen can be realized even with low power.

[implementation form]

Hereinafter, an optical sheet laminate, a backlight unit, a liquid crystal display device, and information equipment according to embodiments will be described with reference to the drawings. In addition, the scope of the present invention is not limited to the following embodiments, and can be changed arbitrarily within the scope of the technical idea of the present invention. [Configuration of liquid crystal display device]

As shown in Figure 1, the liquid crystal display device 50 has: a liquid crystal display panel 5; a first polarizer 6 attached to the lower surface of the liquid crystal display panel 5; a second polarizer 7 attached to the upper surface of the liquid crystal display panel 5 ; and the backlight unit 40 is provided on the back side of the liquid crystal display panel 5 via the first polarizing plate 6 .

The liquid crystal display panel 5 has: a TFT (Thin Film Transistor; Thin Film Transistor) substrate 1 and a CF (Color Filter; color filter) substrate 2, arranged in a manner facing each other; a liquid crystal layer 3, arranged on the TFT substrate 1 and between the CF substrates 2 ; and a sealing material (not shown in the figure), which is arranged in a frame shape to seal the liquid crystal layer 3 between the TFT substrate 1 and the CF substrate 2 .

The shape of the display screen 50a of the liquid crystal display device 50 observed from the front (top of FIG. 1 ) is in principle a rectangle or a square, but it is not limited thereto. , trapezoid, or any shape such as the instrument panel (instrument panel) of a car.

In the liquid crystal display device 50 , in each sub-pixel corresponding to each pixel electrode, a voltage of a predetermined magnitude is applied to the liquid crystal layer 3 to change the alignment state of the liquid crystal layer 3 . Thereby, the transmittance of the incident light from the backlight unit 40 through the first polarizer 6 is adjusted. The light with the adjusted transmittance is emitted through the second polarizer 7 to display an image.

The liquid crystal display device 50 of this embodiment can be used to be assembled into various information equipment (for example, vehicle-mounted devices such as car navigation, portable information terminals such as personal computers, mobile phones, notebook computers or tablets, portable game machines, photocopiers, Display devices in ticket vending machines, automatic teller machines, etc.).

The TFT substrate 1 includes, for example: a plurality of TFTs arranged in a matrix on a glass substrate; an interlayer insulating film arranged to cover each TFT; a plurality of pixel electrodes arranged in a matrix on the interlayer insulating film and connected to the plurality of TFTs. connected respectively; and an alignment film is provided to cover each pixel electrode. The CF substrate 2 includes, for example: a black matrix arranged on a glass substrate in a lattice shape; a color filter including a red layer, a green layer and a blue layer respectively arranged between each lattice of the black matrix; It is arranged to cover the black matrix and color filters; and the alignment film is arranged to cover the common electrode. The liquid crystal layer 3 is composed of a nematic liquid crystal material including liquid crystal molecules having photoelectric properties. The first polarizer 6 and the second polarizer 7 include, for example, a polarizer layer having a unidirectional polarization axis, and a pair of protective layers provided to sandwich the polarizer layer. [Constitution of backlight unit and optical sheet laminate]

As shown in Figure 2, the backlight unit 40 has: a reflection sheet 41; a plurality of light sources 42 are two-dimensionally arranged on the reflection sheet 41; an optical sheet laminate 100 is arranged on the upper side of the plurality of light sources 42; and a pair of ribs The lens 44 and the glass sheet 45 are provided on the upper side of the optical sheet laminate 100 .

In this embodiment, as the light source 42, for example, a blue light source can be used. In this case, as shown in FIG. 2 , a color conversion sheet 46 may be provided between the optical sheet laminate 100 and the sapphire sheet 44 and the smear sheet 45 . Alternatively, as the light source 42, for example, a white light source can be used. In this case, the color conversion sheet 46 may not be provided. The optical sheet laminate 100 can also be formed by laminating, for example, three light-diffusing sheets 43 provided with a plurality of recesses 22 in the shape of an approximately inverted quadrangular pyramid on one side. Alternatively, the optical sheet laminate 100 may be formed by laminating two or more light diffusion sheets 43 . The pair of slats 44 and 45 may be the lower slat 44 and the upper slat 45 in a direction in which the slant extends (the direction in which the ridgeline extends) to be orthogonal to each other. Each light-diffusing sheet 43 , and the light-diffusing sheet 44 and the light-emitting sheet 45 constituting the optical sheet laminate 100 may be in the form of a film, or may be in the form of a flat plate (plate). These optical sheets can also be laminated in the frame (not shown) of the backlight unit 40 by their own weight without using an adhesive.

The reflective sheet 41 is formed of, for example, a white polyethylene terephthalate resin film, a silver vapor-deposited film, or the like.

The type of the light source 42 is not particularly limited, and may be, for example, an LED element or a laser element, and an LED element may also be used from the viewpoints of cost and productivity. The light source 42 may have a rectangular shape when viewed from above. In this case, the length of one side may be 10 μm or more (preferably 50 μm or more) and 20 mm or less (preferably 10 mm or less, more preferably 5 mm or less). In the case of using an LED element as the light source 42, a plurality of LED chips of several mm square may be arranged on the reflection sheet 41 at regular intervals. In order to adjust the light emission angle characteristics of the LED element used as the light source 42, a lens may also be installed on the LED element. The number of light sources 42 to be arranged is not particularly limited, and when a plurality of light sources 42 are dispersedly arranged, they are preferably arranged regularly on the reflection sheet 41 . Regularly arranged means arranged with a certain regularity, for example, corresponding to the situation where light sources 42 are arranged at equal intervals. When the light sources 42 are arranged at equal intervals, the distance between the centers of two adjacent light sources 42 may be 0.5 mm or more (preferably 2 mm or more) and 20 mm or less. When a blue light source is used as the light source 42 , the blue light source can emit, for example, light of x<0.24 and y<0.18 in the chromaticity coordinates of CIE (International Commission on illumination; International Commission on Illumination) 1931. In the case of using a white light source as the light source 42, the white light source is composed of LED elements whose peak wavelength is in the blue region, LED elements whose peak wavelength is in the green region, and LED elements whose peak wavelength is in the red region. In the chromaticity coordinates of CIE1931, it is the light of 0.24<x<0.42, 0.18<y<0.48.

Among the plurality of light diffusion sheets 43 constituting the optical sheet laminate 100 , in the first light diffusion sheet 43A that is closest to the lower surface sheet 44 , the plurality of recesses 22 are arranged on the light exit surface 21 a. In at least one 2nd light-diffusion sheet 43B among the several light-diffusion sheets 43 other than the 1st light-diffusion sheet 43A, some recessed part 22 is arrange|positioned in the light incident surface 21b. In this embodiment, all the two light-diffusion sheets 43 other than the 1st light-diffusion sheet 43A are set as the 2nd light-diffusion sheet 43B in which the recessed part 22 was arrange|positioned in the light incident surface 21b. However, it is also possible to replace only one of the light-diffusing sheets 43 of the first layer or the second layer from the light source 42 side as the second light-diffusing sheet 43B, and the other may be provided with The 1st light-diffusion sheet 43A of the recessed part 22.

As shown in (a) and (b) of FIG. 3 , each of the light-diffusing sheet 43A and the light-diffusing sheet 43B has the base material layer 21 . The light-diffusing sheet 43A and the light-diffusing sheet 43B have the light-emitting surface 21 a and the light-incident surface 21 b. That is, the light-diffusion sheet 43A and the light-diffusion sheet 43B are arrange|positioned so that the light incident surface 21b may face the light source 42. As shown in FIG. The substrate layer 21 is not particularly limited as long as it is made of a resin material that allows light to pass through, for example, it can be acrylic, polystyrene, polycarbonate, MS (methyl methacrylate-styrene copolymer) resin, polyparaffin, etc. Ethylene phthalate, polyethylene naphthalate, cellulose acetate, polyimide, etc. The base material layer 21 may contain other additives of the diffusing agent, or may not contain the additives substantially. When adding a diffusing agent to the base material layer 21 of 43 A of 1st light-diffusion sheets, the content rate of a diffusing agent may be 0 mass % or more and 2 mass % or less. The additives that can be contained in the substrate layer 21 are not particularly limited, for example, they can be inorganic particles such as silicon dioxide, titanium oxide, aluminum hydroxide, barium sulfate, for example, they can also be acrylic acid, acrylonitrile, polysiloxane, polystyrene , polyamide and other organic particles.

The thickness of the light-diffusing sheet 43A and the light-diffusing sheet 43B is not particularly limited, and may be, for example, 3 mm or less (preferably 2 mm or less, more preferably 1.5 mm or less, further preferably 1 mm or less) to 0.1 mm or more. If the thickness of the light-diffusion sheet 43A and the light-diffusion sheet 43B is 3 mm or less, a liquid crystal display can be thinned. When the thickness of the light-diffusion sheet 43A and the light-diffusion sheet 43B is 0.1 mm or more, brightness uniformity improves.

On the light-emitting surface 21a of the first light-diffusing sheet 43A and the light-incident surface 21b of the second light-diffusing sheet 43B, as shown in FIG. dimension matrix. In other words, the plurality of recesses 22 are arranged along two directions perpendicular to each other. Adjacent recesses 22 are divided by ridges 111 . The ridgeline 111 extends along the two directions in which the recesses 22 are arranged. The center (apex of the inverted pyramid) 112 of the concave portion 22 is the deepest portion of the concave portion 22 . In FIG. 4 , the case where the recesses 22 are arranged in a matrix of 5×5 is illustrated for convenience of description, but the actual number of arrangements of the recesses 22 is very large. In the two-dimensional array of the plurality of recesses 22, the recesses 22 may be provided without gaps, or may be provided at predetermined intervals. In addition, to the extent that the light diffusion effect is not impaired, some recesses 22 may be randomly arranged.

The apex angle θ of the recesses 22 is, for example, 90°, the arrangement pitch p of the recesses 22 is, for example, 100 μm, and the depth of the recesses 22 may be, for example, 50 μm. The apex angle θ of the so-called concave portion 22 refers to a plane (longitudinal section) perpendicular to the disposition surface of the light diffusion sheet 43, passing through the center of the concave portion 22 (the apex 112 of the inverted pyramid) vertically and sandwiching the The angle formed by the section lines of the inclined planes in the cross-section that appears when a pair of inclined planes facing each other are cut. In addition, the arrangement pitch p of the recesses 22 refers to the distance between the centers (apexes 112 of the inverted pyramids) of adjacent recesses 22 (the distance along the direction parallel to the arrangement surface of the light diffusion sheet 43 ).

The light incident surface 21b of the first light-diffusing sheet 43A and the light-emitting surface 21a of the second light-diffusing sheet 43B may be, for example, a matte surface, a flat surface (mirror surface), or an embossed surface. Moreover, you may provide the several recessed parts, such as a substantially inverted quadrangular pyramid shape (inverted pyramid shape), for example, in the light-emitting surface 21a of the 2nd light-diffusion sheet 43B. The light-diffusing sheet 43A and the light-diffusing sheet 43B can be constituted by a one-layer structure of the substrate layer 21 having a concavo-convex shape (recess 22 ) on one surface. The light-diffusing sheet 43A and the light-diffusing sheet 43B may also be constituted by a two-layer structure of a substrate layer having flat surfaces on both sides and a layer having a concavo-convex shape on one side. The light-diffusing sheet 43A and the light-diffusing sheet 43B may have a structure of three or more layers including a layer having a concavo-convex shape on one side. The manufacturing method of the light-diffusion sheet 43A and the light-diffusion sheet 43B is not specifically limited, For example, an extrusion molding method, an injection molding method, etc. can also be used.

The procedure for producing a single-layer light-diffusing sheet having a concavo-convex shape on the surface by extrusion molding is as follows. First, granular plastic particles with a diffusing agent added (at the same time, granular plastic particles without a diffusing agent can also be mixed) are fed into a single-screw extruder, and melted and kneaded while heating. Then, the molten resin extruded through the T-die is sandwiched between two metal rollers, cooled, conveyed using guide rollers, and sliced into flat sheets with a slicer to produce a light-diffusing sheet. Here, the molten resin is sandwiched between metal rollers with the reversed shape of the desired concave-convex shape on the surface, and the reverse shape of the roller surface is transferred to the resin, so that the desired concave-convex shape can be given Shaped to the surface of the light diffusion sheet. In addition, the shape transferred to the resin does not necessarily transfer 100% of the shape of the roller surface, so the shape of the roller surface can also be designed by inverse calculation based on the degree of transfer.

When using the extrusion molding method to manufacture a light diffusion sheet with a two-layer structure with concave-convex shapes on the surface, for example, after feeding the granular plastic particles required to form each layer into two single-screw extruders, each layer Carry out the same procedure as above, and laminate the produced sheets.

Or, the light-diffusion sheet of the 2-layer structure which has a concavo-convex shape on the surface can also be produced as follows. First, the granular plastic particles required to form each layer are fed into two single-screw extruders, and melted and kneaded while heating. Then, the molten resin to be each layer is poured into one T-die, laminated in the T-die, and the laminated molten resin extruded through the T-die is clamped by two metal rollers and cooled. Then, the laminated molten resin is conveyed with a guide roller, and cut into a sheet-like plate by a slicer, so that a light-diffusing sheet with a two-layer structure having a concave-convex shape on the surface can also be produced.

In addition, a light-diffusing sheet can also be produced by formative transfer using UV (ultraviolet rays) as follows. First, uncured ultraviolet curable resin is filled into a roll having a reverse shape of the concave-convex shape to be transferred, and the substrate is pressed against the resin. Next, in a state in which the roller filled with the ultraviolet curable resin is integrated with the substrate, ultraviolet rays are irradiated to harden the resin. Next, the sheet on which the concave-convex shape was transfer-printed by resin shaping was peeled off from the roll. Finally, the sheet was again irradiated with ultraviolet rays to completely harden the resin, thereby producing a light diffusion sheet having unevenness on the surface.

Furthermore, in the present invention, considering that it is difficult to form a geometrically strict inverted quadrangular pyramid recess by the usual shape transfer technology, the expression "approximately inverted quadrangular pyramid" is used, but "approximately inverted quadrangular pyramid" includes A true inverted quadrangular pyramid or a substantially inverted quadrangular pyramid shape. In addition, the so-called "approximately" means that it can be approximated, and the so-called "approximately inverted quadrangular pyramid" refers to a shape that can be approximated to an inverted quadrangular pyramid. For example, even with regard to the "inverted quadrangular pyramid trapezoid" with a flat top, a shape whose top area is small enough not to lose the effect of the present invention is included in the "approximately inverted quadrangular pyramid". In addition, a shape deformed from an "inverted square pyramid" within the range of unavoidable shape deviations caused by processing precision in industrial production is also included in the "substantially inverted square pyramid".

Since it is necessary for light to pass through, the plywood sheet 44 and the plywood sheet 45 are formed mainly of a transparent (for example, colorless and transparent) synthetic resin. The 稜鏡 sheet 44 and the 稜鏡 sheet 45 can also be integrally formed. The lower fringe sheet 44 has a base material layer 44a, and a protrusion row composed of a plurality of protruding fringe portions 44b laminated on the surface of the base material layer 44a. Similarly, the upper side fringe sheet 45 has a base material layer 45a, and a projection row composed of a plurality of protruding fringe portions 45b laminated on the surface of the base material layer 45a. The protruding ribs 44b and the protruding ribs 45b are laminated in stripes on the surfaces of the base material layer 44a and the base material layer 45a, respectively. The protrusions 44b and the protrusions 45b are triangular columns whose inner surfaces are in contact with the surfaces of the base material layer 44a and the base material layer 45a, respectively. The extending direction of the protruding rib portion 44b and the extending direction of the protruding rib portion 45b are perpendicular to each other. Thereby, the light incident from the first light diffusing sheet 43A is refracted toward the normal direction side by the lower side sheet 44 , and the light emitted from the lower side sheet 44 is refracted relative to the display screen by the upper side sheet 45 . 50a refracts in a substantially vertically advancing manner.

The lower limit of the thickness (the height from the inner surfaces of the base material layer 44a and the base material layer 45a to the apexes of the protruding rib part 44b and the protruding rib part 45b) of the corrugated sheet 44 and the corrugated sheet 45 may be about 50 μm, for example, More preferably, it is about 100 μm. The upper limit of the thickness of the flake sheet 44 and the flake sheet 45 may be about 200 μm, more preferably about 180 μm. The lower limit of the distance between the protruding ribs 44 b and the protruding ribs 45 b in the ribs 44 and 45 may be, for example, about 20 μm, more preferably about 25 μm. The upper limit of the distance between the protruding ribs 44 b and the protruding ribs 45 b in the ribs 44 and 45 is, for example, about 100 μm, more preferably about 60 μm. The apex angles of the protrusions 44 b and the protrusions 45 b may be, for example, not less than 85° and not more than 95°. The lower limit of the refractive index of the protrusion 44b and the protrusion 45b may be, for example, 1.5, more preferably 1.55. The upper limit of the refractive index of the protruding rib portion 44b and the protruding rib portion 45b may be, for example, 1.7.

The sheet 44 and the sheet 45 can be, for example, formed with UV-curable acrylic resin on the substrate layer 44a and substrate layer 45a made of PET (polyethylene terephthalate; polyethylene terephthalate) film. The ribbed part 44b and the ribbed part 45b formed by transfer printing may also be the ribbed part 44b and the ribbed part 45b integrated with the base material layer 44a and the base material layer 45a Formed 稜鏡 pieces.

The color conversion sheet 46 is, for example, a wavelength conversion sheet that converts light from the light source 42 that is a blue light source into light having a wavelength of an arbitrary color (eg, green or red) as a peak wavelength. The color conversion sheet 46 converts, for example, 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 the light source 42 emitting blue light with a wavelength of 450nm is used, the blue light is partially converted into green light and red light by the color conversion sheet 46, so the light passing through the color conversion sheet 46 becomes white light. As the color conversion sheet 46 , for example, a QD (Quantum Dot; quantum dot) sheet or a fluorescent sheet may be used.

Although illustration is omitted, a light diffusion sheet for upper side may be further provided on the upper side (the side of the display screen 50 a ) of the front sheet 44 and the front sheet 45 . The light diffusing sheet above diffuses the light incident from the side of the upper side 45 to a certain degree, and suppresses brightness fluctuations caused by the shape of the ridge 44b and the shape of the ridge 45b of the rim 44 and 45. all. The light-diffusing sheet for the top can also be directly laminated on the surface of the upper side sheet 45 . The thickness of the upper light diffusion sheet is not particularly limited, and may be, for example, not less than 50 μm and not more than 3 mm. If the thickness of the upper light-diffusing sheet exceeds 3 mm, it will be difficult to achieve thinning of the liquid crystal display. On the other hand, if the thickness of the upper light-diffusing sheet is less than 50 μm, it will be difficult to obtain a sufficient light-diffusing effect. The upper light diffusion sheet can be in the form of a film, or in the form of a flat plate (plate). As the upper light-diffusing sheet, for example, a light-diffusing sheet in which a UV-curable acrylic resin is used on at least one surface of a PET film and provided with a concavo-convex shape can be used.

In addition, although illustration is omitted, a polarizer may be provided on the upper side (the side of the display screen 50 a ) of the polarized sheet 44 and the polarized sheet 45 . The polarizer prevents the light emitted from the backlight unit 40 from being absorbed by the first polarizer 6 of the liquid crystal display device 50, so as to increase the brightness of the display screen 50a. [features of the embodiment]

The optical sheet laminate 100 of this embodiment is assembled between the light sources 42 and the light sources 44 and 45 in the backlight unit 40 of the liquid crystal display device 50 in which a plurality of light sources 42 are distributed on the back side of the display screen 50a. The optical sheet laminate 100 of this embodiment is equipped with the several light-diffusion sheet 43 in which the several recessed part 22 of substantially inverted quadrangular pyramid shape was provided in one surface. In the 1st light-diffusion sheet 43A which is the closest to the corrugated sheet 44 and the corrugated sheet 45 among the several light-diffusion sheets 43, the some recessed part 22 is arrange|positioned in the light output surface 21a. In the 2nd light-diffusion sheet 43B of at least one of the several light-diffusion sheets 43 other than the 1st light-diffusion sheet 43A, the several recessed part 22 is arrange|positioned in the light incident surface 21b. The content rate of the diffusing agent in 43 A of 1st light-diffusion sheets is 0 mass % or more and 2 mass % or less.

According to the optical sheet laminate 100 of this embodiment, by stacking a plurality of light-diffusing sheets (hereinafter, also referred to as pyramid sheets) 43 having a plurality of recesses 22 in the shape of substantially inverted quadrangular pyramids on one side, it can be used. Improve brightness uniformity. In addition, in the first light-diffusing sheet 43A that is closest to the scalloped sheet 44 and the slatted sheet 45, the substantially inverted quadrangular pyramid-shaped concave portion 22 is arranged on the light-emitting surface 21a, so it is the same as the case where the concave portion 22 is arranged on the light-incident surface 21b. In contrast, it is easy to converge the emitted light toward the ray sheet 44 and the ray sheet 45 . Furthermore, by suppressing the content of the diffusing agent in the first light-diffusing sheet 43A to 2% by mass or less, the converging properties of the emitted light from the first light-diffusing sheet 43A are improved, so that brightness can be increased even with low power. big.

Therefore, by using the optical sheet laminate 100 of this embodiment for the backlight unit 40, it is possible to maintain uniformity of luminance and realize a high-luminance screen even with low power.

In the optical sheet laminate 100 of the present embodiment, if the second light-diffusing sheet 43B is thicker than the first light-diffusing sheet 43A, the following effects can be obtained. That is, if the thickness of the second light-diffusing sheet 43B in which the substantially inverted quadrangular pyramid-shaped recesses 22 are disposed on the light-incident surface 21b is thickened, the recesses 22 on the light-incident surface 21b diffuse and spread over the second light-diffusing sheet 43B. The optical path of light traveling in an oblique direction becomes longer. Therefore, the diffusion distance of light in the direction parallel to the light incident surface 21b becomes longer, so that the light diffusivity increases, and the brightness uniformity is further improved. Also, by making the first light-diffusing sheet 43A thinner than the second light-diffusing sheet 43B, the thickness of the optical sheet laminate 100 as a whole can be suppressed, and the backlight unit 40 , that is, the liquid crystal display device 50 can be thinned.

The backlight unit 40 of this embodiment is incorporated into the liquid crystal display device 50, and guides the light emitted from the light source 42 to the side of the display screen 50a. The backlight unit 40 of the present embodiment is provided with the optical sheet laminate 100 of the present embodiment between the light source 42 and the laminated sheet 44 and the laminated sheet 45 .

According to the backlight unit 40 of this embodiment, since it is equipped with the optical sheet laminated body 100 of this embodiment, it can maintain brightness|luminance uniformity, and can realize a high-luminance screen even with low electric power.

In the backlight unit 40 of the present embodiment, the light source 42 may also be arranged on the reflective sheet 41 that is disposed on the opposite side of the glazing sheet 44 and the glazing sheet 45 as viewed from the optical sheet laminate 100 . In this way, light is further diffused due to multiple reflections between the light diffusion sheet 43 and the reflective sheet 41 constituting the optical sheet laminate 100, so that the brightness uniformity is improved.

In the backlight unit 40 of this embodiment, if the distance between the light source 42 and the optical sheet laminate 100 is 2 mm or less, the backlight unit 40 can be miniaturized. In addition, in view of the thinning of small and medium-sized liquid crystal displays in the future, the distance between the light source 42 and the optical sheet laminate 100 may be set to 1 mm or less, and ultimately to 0 mm.

The liquid crystal display device 50 of the present embodiment includes the backlight unit 40 and the liquid crystal display panel 5 of the present embodiment. Therefore, according to the backlight unit 40 of the present embodiment, it is possible to maintain brightness uniformity and realize a high-brightness screen even with low power. Information equipment (such as portable information terminals such as notebook computers or tablets) assembled with the liquid crystal display device 50 can also obtain the same effect. [Example]

Hereinafter, examples will be described.

The optical sheet laminate 100 of the embodiment is formed by stacking three light-diffusing sheets (pyramid sheets) 43 provided with a plurality of recesses 22 in the shape of substantially inverted quadrangular pyramids on one side. Specifically, as shown in Table 1 below, a first light-diffusing sheet having a thickness of 160 μm and a surface (pyramid surface) on which the concave portion 22 is provided is the light-emitting surface 21 a on the upper layer (the layer closest to the lower side slat sheet 44 ). 43A, two second light-diffusing sheets 43B with a pyramidal surface and a thickness of 220 μm on the light-incident surface 21b are arranged in the lower layer and the middle layer to form the optical sheet laminate 100 of the embodiment. The arrangement pitch and apex angle of the recesses (inverted pyramids) 22 in the first light-diffusing sheet 43A were set to 100 μm and 90°, respectively, and the arrangement pitch and apex angle of the recesses (inverted pyramids) 22 in the second light-diffusing sheet 43B were 100 μm and 90° respectively. They were set to 180 μm and 80°, respectively. In addition, as the optical sheet laminate 100 of the example, the content rate of the diffusing agent in the first light-diffusing sheet 43A was changed stepwise from 0 mass % to 8 mass % (specifically, set to 0 mass %). , 0.2 mass%, 0.4 mass%, 0.8 mass%, 2 mass%, 4 mass%, 8 mass%) of various samples. Here, the content rate of a diffusing agent means the ratio of the weight of a diffusing agent with respect to the whole weight of 43 A of 1st light-diffusion sheets. In addition, no diffusing agent was added to the 2nd light-diffusion sheet 43B of 2 sheets. [Table 1] Composition of 3 Pyramid Sheets Comparative example 1 Comparative example 2 Example Down middle superior Down middle superior Down middle superior Diffusion agent concentration (wt%) 0 0 0.8 0 0 0~8 0 0 0~8 Thickness (μm) 190 190 220 210 210 160 210 210 160 The orientation of the pyramid face incident side incident side incident side incident side incident side incident side incident side incident side light side

In the embodiment, the light-diffusing sheet 43A and the light-diffusing sheet 43B are respectively processed by extruding polycarbonate that will become the base material layer 21, and are formed in a single-layer structure with two-dimensionally arranged concave portions 22 in the shape of inverted pyramids. form. Moreover, the light incident surface 21b of 43 A of 1st light-diffusion sheets, and the light-emitting surface 21a of the 2nd light-diffusion sheet 43B are each processed into a matte surface. In addition, as a diffusing agent added to the first light diffusing sheet 43A, silicone beads having an average particle diameter of 2 μm were used.

The optical sheet laminate 100 of the embodiment described above was incorporated into the backlight unit 40 shown in FIG. 2 , and the luminance was measured using a 2D spectroradiometer SR-5000HS of TOPCON TECHNOHOUSE. As the plurality of light sources 42, a light source in which blue LEDs are arranged in an array at a pitch of 2.8 mm is used. In the luminance measurement, use the luminance unevenness measuring device to obtain the two-dimensional luminance distribution in the range of 40mm square, carry out the correction of the overall luminance balance, and then calculate the average value and standard deviation of the luminance, defined as "brightness = average value", " Brightness uniformity = average value/standard deviation", calculate brightness and brightness uniformity.

In addition, the optical sheet laminates 100 of Comparative Example 1 and Comparative Example 2 shown in Table 1 were incorporated into the backlight unit 40 shown in FIG. 5 and FIG. 6 , respectively, and the same luminance measurement as in the examples was performed. Specifically, a third light-diffusing sheet 43C with a pyramidal surface of 220 μm in thickness on the light incident surface 21 b is arranged on the upper layer, and two second light-diffusing sheets with a pyramidal surface of 190 μm in thickness on the light incident surface 21 b are arranged on the lower and middle layers. 43B, constitutes the optical sheet laminate 100 of Comparative Example 1. In addition, a fourth light-diffusing sheet 43D with a pyramidal surface of 160 μm in thickness on the light-incident surface 21b is arranged on the upper layer, and two second light-diffusing sheets 43B with a pyramidal surface of 210 μm in thickness on the light-incident surface 21b are arranged in the lower and middle layers. The optical sheet laminate 100 of Comparative Example 2 was constituted.

In addition, the arrangement pitch and apex angle of the recesses (inverted pyramids) 22 in each of the third light-diffusing sheet 43C (comparative example 1) and the fourth light-diffusing sheet 43D (comparative example 2) were set to 100 μm and 90 μm, respectively. °. In addition, regarding Comparative Example 1, the content rate of the diffusing agent in the third light-diffusing sheet 43C was set to 0.8% by mass. The content rate was changed stepwise from 0% by mass to 8% by mass (specifically, set to 0% by mass, 0.2% by mass, 0.4% by mass, 0.8% by mass, 2% by mass, 4% by mass, and 8% by mass). Various samples.

In addition, in Comparative Example 1 and Comparative Example 2, the third light-diffusing sheet 43C and the fourth light-diffusing sheet 43D are respectively processed by extrusion molding polycarbonate that will become the base material layer 21, and are arranged two-dimensionally. The single-layer structure of the concave portion 22 in the shape of an inverted pyramid is formed. Moreover, the light incident surface 21b of each of 43 C of 3rd light-diffusion sheets and 43D of 4th light-diffusion sheets is processed into a matte surface. In addition, as the diffusing agent added to the third light-diffusing sheet 43C and the fourth light-diffusing sheet 43D, silicone beads with an average particle diameter of 2 μm were used.

FIG. 7 is a graph showing the results of investigation of the relationship between brightness and brightness uniformity in the optical sheet laminate 100 of the above-described Examples, Comparative Examples 1 and 2. FIG. In addition, the numerical value shown in a figure shows the content rate of the diffusing agent in the said sheet|seat when the weight of the light-diffusion sheet of an upper layer was made into 1. In addition, brightness|luminance is represented by the relative brightness|luminance when the brightness|luminance of the comparative example 1 was set to 1.

As shown in FIG. 7 , in the optical sheet laminate 100 of the embodiment, the content rate of the diffusing agent in the first light-diffusing sheet 43A arranged on the upper layer with the light-emitting surface 21a as a pyramidal surface is 0% by mass (0) In the range from above to 2% by mass (0.02) below, compared with Comparative Example 1, the brightness uniformity can be maintained at the same level, and the brightness can be increased by 3% or more.

On the other hand, in the optical sheet laminate 100 of Comparative Example 2, the content of the diffusing agent in the fourth light-diffusing sheet 43D arranged on the upper layer with the light incident surface 21b as a pyramidal surface is 0% by mass (0) In the range from above to 2% by mass (0.02) below, the luminance uniformity can be maintained at the same level as that of Comparative Example 1, but on the other hand, the increase in luminance does not reach 3%. [Other Embodiments]

In the aforementioned embodiments (including Examples, the same below), the shape of the recess 22 provided on one side of the light-diffusing sheet 43A and the light-diffusing sheet 43B included in the optical sheet laminate 100 is set as an inverted quadrangular pyramid. Instead, other inverted polygonal pyramid shapes that can be arranged two-dimensionally, such as inverted triangular pyramids or inverted hexagonal pyramids, may be used. In addition, instead of the recessed part 22 which can be arrange|positioned two-dimensionally, you may provide protrusion rows, such as a protrusion part.

As mentioned above, although embodiment of this invention was described, this invention is not limited only to the said embodiment, Various changes are possible within the range of invention. That is, the description of the above-mentioned embodiment is merely an illustration in nature, and is not intended to limit the present invention, the application target of the present invention, or the use of the present invention.

1: TFT substrate 2: CF substrate 3: Liquid crystal layer 5: LCD display panel 6: The first polarizer 7: The second polarizer 21: Substrate layer 21a: Light-emitting surface 21b: light incident surface 22: Concave 40:Backlight unit 41: reflector 42: light source 43 (43A, 43B, 43C, 43D): light diffuser 44: lower side scallop 44a: substrate layer 44b: protruding part 45: Upper side scallops 45a: substrate layer 45b: protruding part 46:Color conversion film 50: Liquid crystal display device 50a: display screen 100: Optical sheet laminate 111: Ridge 112: The center of the concave part (vertex of the inverted pyramid) θ: Vertex angle p: Arrangement pitch

[ Fig. 1 ] is a cross-sectional view of a liquid crystal display device including a backlight unit according to an embodiment. [ Fig. 2 ] is a cross-sectional view of a backlight unit incorporating an optical sheet laminate according to an embodiment. [ Fig. 3 ] is a cross-sectional view of a light-diffusing sheet included in an optical sheet laminate according to an embodiment. [FIG. 4] It is a perspective view of the light-diffusion sheet contained in the optical sheet laminate of embodiment. [ Fig. 5 ] is a cross-sectional view of a backlight unit incorporating the optical sheet laminate of Comparative Example 1. [ Fig. 6] Fig. 6 is a cross-sectional view of a backlight unit incorporating an optical sheet laminate of Comparative Example 2. [ Fig. 7 ] is a graph showing the results of investigation of the relationship between brightness and brightness uniformity in the optical sheet laminates of Examples and Comparative Examples.

21: Substrate layer

21a: Light-emitting surface

21b: light incident surface

22: Concave

40:Backlight unit

41: reflector

42: light source

43A, 43B: light diffuser

44: lower side scallop

44a: substrate layer

44b: protruding part

45: Upper side scallops

45a: substrate layer

45b: protruding part

46:Color conversion film

100: Optical sheet laminate

Claims (7)

An optical sheet laminate, which is assembled between the aforementioned plurality of light sources and the optical sheet in a liquid crystal display device in which a plurality of light sources are dispersedly arranged on the back side of a display screen; It has a plurality of light diffusion sheets provided with a plurality of recesses in the shape of approximately inverted quadrangular pyramids on one side; In the first light-diffusing sheet that is closest to the above-mentioned light-diffusing sheet among the aforementioned plurality of light-diffusing sheets, the aforementioned plurality of recesses are arranged on the light-emitting surface; In the second light-diffusing sheet of at least one of the plurality of light-diffusing sheets other than the first light-diffusing sheet, the plurality of recesses are arranged on the light incident surface; The content rate of the diffusing agent in the said 1st light-diffusion sheet is 0 mass % or more and 2 mass % or less. The optical sheet laminate according to claim 1, wherein the second light-diffusing sheet is thicker than the first light-diffusing sheet. A backlight unit, which is assembled into the aforementioned liquid crystal display device, and guides the light emitted from the aforementioned plurality of light sources to the aforementioned display screen side; An optical sheet laminate as described in Claim 1 or 2 is provided between the aforementioned plurality of light sources and the aforementioned sapphire sheet. The backlight unit as described in claim 3, wherein the plurality of light sources are arranged on a reflective sheet that is arranged on the opposite side of the aforementioned glazing sheet when viewed from the aforementioned optical sheet laminate. The backlight unit according to claim 3, wherein the distance between the plurality of light sources and the optical sheet laminate is 2 mm or less. A liquid crystal display device comprising: The backlight unit described in any one of claims 3 to 5; and LCD panel. An information device is equipped with a liquid crystal display device as described in Claim 6.

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