JP2004311250A - Optical unit and backlight unit using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical unit having remarkably high optical functions such as condensing, refraction toward the direction of a normal line or the like, whereby the optical functions are easily and surely controlled, and damaging an optical sheet is suppressed, and to provide a backlight unit of which the quality enhancement such as making luminance in the front high, uniforming luminance or the like is expedited. <P>SOLUTION: This optical unit is provided with a plurality of optical sheets to be superimposed, and a micro lens sheet 2 and a light diffusing sheet 3 are used as these optical sheets. This micro lens sheet 2 is provided with a micro lens array 5 composed of a plurality of micro lens 6 on its surface. This light diffusing sheet 3 is provided with a substrate layer 7 and a light diffusing layer 8 containing a light diffusing agent 10 in a binder 9. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００８２】
間隔比（Ｓ／Ｄ）と正面輝度相対値との関係を下記表２及び図６のグラフに示す。この表２及び図６のグラフは、間隔比（Ｓ／Ｄ）が１／２以下で正面輝度相対値が高くなり、間隔比（Ｓ／Ｄ）が１／５以下で特に高くなることを示している。
【００８３】
【表２】

【００８４】
レンズ充填率と正面輝度相対値との関係を下記表３及び図７のグラフに示す。この表３及び図７のグラフは、レンズ充填率が４０％以上で正面輝度相対値が正面輝度相対値が高くなり、レンズ充填率が６０％以上でより高くなり、レンズ充填率が７５％以上で特に高くなることを示している。
【００８５】
【表３】

【００８６】
最後に、エッジライト型バックライトユニットにおいて、ランプ及び導光板の条件を固定し、光学ユニットの構成が（ａ）１枚の光拡散シートを備える場合、（ｂ）２枚の前記光拡散シートを重畳する場合、（ｃ）３枚の前記光拡散シートを重畳する場合、及び（ｄ）前記光拡散シートとマイクロレンズシートとを重畳する場合（本件発明の構成）のそれぞれの正面輝度を実測した。その結果を下記表４に示す。
【００８７】
【表４】

【００８８】
上記表４に示すように、本件発明の上記（ｄ）の構成の光学ユニットが、３枚の光拡散シートを重畳する上記（ｃ）の構成の光学ユニットよりも正面輝度が格段に向上している。従って、本件発明の光学ユニットによれば、高い正面輝度が得られ、光学シートの装備枚数の低減化が促進されることが解る。
【００８９】
なお、本発明の光学ユニット及びバックライトユニットは、上記実施形態に限定されるものではなく、例えば光拡散シートの表面側にマイクロレンズシートを重畳する光学ユニットも可能である。この光学ユニットは、表面側のマイクロレンズシートによって高い法線方向側への屈折機能を有している。この光学ユニットの場合、光拡散シートの基材層裏面に上記スティッキング防止層１６を積層するとよい。このスティッキング防止層１６によって光拡散シートと導光板とのスティッキングが防止される。
【００９０】
また、本発明の光学ユニットは、光拡散シート及びマイクロレンズシートを２枚以上備えることや、他の光学シートを備えることも可能である。
【００９１】
【発明の効果】
以上説明したように、本発明の光学ユニットによれば、集光、法線方向側への屈折、拡散等の光学的機能が格段に高く、その光学的機能の制御が容易かつ確実であり、光学シートの傷付きや他部材への傷付けが抑制される。また、当該光学ユニットを用いたバックライトユニットによれば、正面方向の高輝度化、輝度の均一化等の品質の向上が促進される。
【図面の簡単な説明】
【図１】図１は、本発明の一実施形態に係る光学ユニットを示す模式的断面図である。
【図２】図２（ａ）及び（ｂ）は、図１の光学ユニットに備えられる光学シートを示す部分平面図及び部分断面図である。
【図３】図３は、図１の光学ユニットを備えるバックライトユニットを示す模式的断面図である。
【図４】図４は、図２の光学シートとは異なる形態に係る光学シートを示す部分断面図である。
【図５】図５は、高さ比と正面輝度相対値との関係を示すグラフである。
【図６】図６は、間隔比と正面輝度相対値との関係を示すグラフである。
【図７】図７は、レンズ充填率と正面輝度相対値との関係を示すグラフである。
【図８】図８（ａ）は、従来の一般的なエッジライト型バックライトユニットを示す模式的斜視図である。図８（ｂ）は、従来のビーズ塗工シートを示す模式的断面図である。
【符号の説明】
１ 光学ユニット
２ マイクロレンズシート
３ 光拡散シート
４ 基材層
５ マイクロレンズアレイ
６ マイクロレンズ
７ 基材層
８ 光拡散層
９ バインダー
１０ 光拡散剤
１１ 導光板
１２ ランプ
１５ マイクロレンズシート
１６ スティッキング防止層
１７ バインダー
１８ ビーズ[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical unit having various functions such as light collection, diffusion, and refraction to a normal direction side, and particularly suitable for a backlight unit of a liquid crystal display device, and a backlight unit using the same. .
[0002]
[Prior art]
2. Description of the Related Art As a liquid crystal display device, a backlight system in which a liquid crystal layer is illuminated from the back has become widespread, and a backlight unit such as an edge light type (side light type) or a direct type is provided on the lower surface side of the liquid crystal layer. As shown in FIG. 8A, the edge light type backlight unit 20 generally has a rod-shaped lamp 21 as a light source, and a rectangular plate-shaped lamp 21 arranged so that an end thereof is along the lamp 21. And an optical unit 23 laminated on the surface side of the light guide plate 22. The optical unit 23 includes a plurality of optical sheets superimposed on each other, and has optical functions such as focusing, diffusing, and refracting transmitted light. The optical sheets provided in the optical unit 23 include (1) a light diffusion sheet 24 which is provided on the surface side of the light guide plate 22 and mainly has a light diffusion function, and (2) is provided on the surface side of the light diffusion sheet 24. For example, a prism sheet 25 having a function of refracting toward the normal direction is used.
[0003]
The function of the backlight unit 20 will be described. First, a light ray incident on the light guide plate 22 from the lamp 21 is reflected by a reflection dot or a reflection sheet (not shown) on the back surface of the light guide plate 22 and on each side surface. Emitted from the surface. Light emitted from the light guide plate 22 enters the light diffusion sheet 24, is diffused, and is emitted from the surface. Thereafter, the light beam emitted from the surface of the light diffusion sheet 24 enters the prism sheet 25, and is emitted by the prism portion 25a formed on the surface as a light beam having a distribution having a peak almost directly above. In this manner, the light beam emitted from the lamp 21 is diffused by the optical unit 23, refracted so as to show a peak almost directly above, and further illuminates the entire liquid crystal layer (not shown) above.
[0004]
Although not shown, in consideration of the light guide characteristics of the light guide plate 22 and the optical function of the optical sheet provided in the optical unit 23, more optical sheets such as a light diffusion sheet and a prism sheet are provided. There is also an optical unit 23.
[0005]
As shown in FIG. 8B, the conventional light diffusion sheet 24 generally includes a base layer 26 made of a transparent synthetic resin and a light diffusion layer 27 laminated on the surface of the base layer 26. (For example, refer to JP-A-2000-89007). This light diffusion layer 27 generally contains resin beads 29 in a binder 28. Due to the presence of the resin beads 29, lens-shaped fine irregularities are formed on the surface of the light diffusion sheet 24. Optical functions such as diffusion and condensing of the light diffusion sheet 24 are exhibited by the lens-shaped fine irregularities and refraction and reflection at the interface of the resin beads 29.
[0006]
[Patent Document 1]
JP 2000-89007 A
[0007]
[Problems to be solved by the invention]
In the light diffusion sheet 24 provided in the above-mentioned conventional optical unit 23, since the surface of the resin beads 29 is covered with the binder 28, the resin beads 29 are unlikely to protrude sufficiently, and it is difficult to form the intended lens-like fine irregularities. There are certain limitations in improving optical functions such as diffusion and the like. Therefore, in the conventional optical unit 23, a relatively large number of optical sheets are provided, and it is difficult to improve the front luminance of the backlight unit 20.
[0008]
The light diffusion sheet 24 can control the optical functions such as light condensing by changing the particle diameter, compounding amount, and coating amount of the resin beads 29. However, the uniform dispersion of the resin beads 29 and the uniform coating can be achieved. Since the processing is difficult due to aggregation or the like, accurate control of the optical function is impossible.
[0009]
The present invention has been made in view of these inconveniences, and the optical functions such as light collection, refraction to the normal direction, and diffusion are remarkably high, and the optical functions can be easily and reliably controlled. It is an object of the present invention to provide an optical unit and a backlight unit which uses the same to promote quality improvement such as higher brightness in the front direction and uniform brightness.
[0010]
[Means for Solving the Problems]
The invention made to solve the above problem includes a plurality of optical sheets to be superimposed, a microlens sheet and a light diffusion sheet are used as the optical sheets, and the microlens sheet includes a plurality of microlenses. The optical unit is provided with a micro lens array to be provided on the surface, and the light diffusion sheet includes a base layer and a light diffusion layer containing a light diffusion agent in a binder.
[0011]
Since the optical unit includes the microlens sheet having an excellent optical function, optical functions such as light collection, refraction toward the normal direction, and diffusion are remarkably improved. In addition, since the optical unit includes the light diffusion sheet in addition to the microlens sheet, the light diffusion function is significantly improved, and moire, glare, luminance unevenness, and the like caused by overlapping geometric shapes are reduced. Occurrence is reduced and quality is improved. Further, the optical unit adjusts the diameter (D), the height ratio (H / R), the spacing ratio (S / D), the filling ratio, the arrangement pattern, and the like of the microlenses of the microlens sheet. Optical functions are easily and reliably controlled.
[0012]
The diameter (D) of the microlens in the microlens sheet is 10 μm or more and 1000 μm or less, and the height ratio (H / R) of the height (H) of the microlens to the radius of curvature (R) is 5/8 or more and 1 or less. The distance ratio (S / D) of the distance (S) between the lenses of the microlenses to the diameter (D) is 以下 or less, the filling rate of the microlenses is 40% or more, and the refraction of the material constituting the microlens array. The ratio is preferably 1.3 or more and 1.8 or less. By setting the height ratio (H / R), the interval ratio (S / D), the filling rate, and the refractive index of the material within the above ranges, the optical functions such as light condensing are further enhanced.
[0013]
An equilateral triangular lattice pattern is preferable as the arrangement pattern of the microlenses in the surface shape of the microlens sheet. In this equilateral triangular lattice pattern, hemispherical microlenses can be densely arranged. Therefore, according to the equilateral triangular lattice pattern, the filling rate of the microlenses in the microlens sheet is easily increased, and optical functions such as light collection, refraction toward the normal direction, and diffusion are remarkably improved.
[0014]
In addition, a random pattern is also preferable as the arrangement pattern of the microlenses in the surface shape of the microlens sheet. Thus, according to the random pattern, the occurrence of moire when the microlens sheet is overlapped with another optical member is further reduced.
[0015]
It is preferable to provide a sticking prevention layer in which beads are dispersed in a binder on the back surface of the optical sheet. By providing the anti-sticking layer on the back surface, sticking between the optical sheet and a light guide plate, another optical sheet, or the like disposed on the back surface side is prevented.
[0016]
Therefore, in a backlight unit for a liquid crystal display device that disperses light rays emitted from a lamp and guides the light rays to the surface side, if the optical unit having high optical functions such as light collection, refraction to the normal direction, and diffusion is provided. In addition, quality such as high luminance in the front direction and uniform luminance can be improved, and furthermore, the number of optical sheets can be reduced to promote thinning.
[0017]
Here, the “microlens” means a microlens whose interface is partially spherical, and corresponds to, for example, a hemispherical convex lens or a hemispherical concave lens. "Diameter (D)" means the diameter of the base or aperture of the microlens. The “height (H)” is a vertical distance from the base surface of the micro lens to the top when the micro lens is a convex lens, and a vertical distance from the opening surface of the micro lens to the bottom when the micro lens is a concave lens. Means distance. “Distance between lenses” means the shortest distance between a pair of adjacent microlenses. “Filling rate” means the area ratio of the microlens per unit area in the surface projection shape. The “regular triangular lattice pattern” refers to a pattern in which the surface is divided into equilateral triangles having the same shape, and a microlens is provided at each vertex of the equilateral triangle.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as appropriate. FIG. 1 is a schematic cross-sectional view illustrating an optical unit according to an embodiment of the present invention, and FIGS. 2A and 2B are schematic partial plan views and schematic views illustrating a microlens sheet provided in the optical unit in FIG. FIG. 3 is a schematic cross-sectional view showing a backlight unit including the optical unit shown in FIG. 1, and FIG. 4 is a schematic partial cross-sectional view showing a microlens sheet having a different form from the microlens sheet shown in FIG. 5 is a graph showing a relationship between the height ratio and the front luminance relative value, FIG. 6 is a graph showing a relationship between the interval ratio and the front luminance relative value, and FIG. 7 is a graph showing a relationship between the lens filling factor and the front luminance relative value. It is a graph.
[0019]
The optical unit 1 of FIG. 1 includes a microlens sheet 2 and a light diffusion sheet 3 as optical sheets, and the light diffusion sheet 3 is superimposed on the front side of the microlens sheet 2.
[0020]
As shown in FIGS. 2A and 2B, the microlens sheet 2 includes a sheet-shaped base layer 4 and a microlens array 5 provided on the surface of the base layer 4. The microlens sheet 2 has excellent optical functions such as light condensing, refraction to the normal direction side, and diffusion by the microlens array 5 on the surface.
[0021]
The base material layer 4 is formed of a transparent, particularly colorless and transparent synthetic resin because it is necessary to transmit light. The synthetic resin used for the base layer 4 is not particularly limited, and may be, for example, polyethylene terephthalate, polyethylene naphthalate, acrylic resin, polycarbonate, polystyrene, polyolefin, cellulose acetate, weatherable vinyl chloride, active energy ray curing. Mold resin and the like. Among these, an active energy ray-curable resin such as an ultraviolet ray-curable resin or an electron beam-curable resin, which is excellent in moldability of the microlens array 5, and polyethylene terephthalate, which is excellent in transparency and strength, are particularly preferable. It is also preferable to use a polyethylene terephthalate film, a polyethylene naphthalate film or a polycarbonate film as the base material layer 4, and form the microlenses 6 thereon with an ultraviolet curable resin or the like.
[0022]
The thickness (average thickness) of the base layer 4 is not particularly limited, but is, for example, 10 μm or more and 500 μm or less, preferably 35 μm or more and 250 μm or less, and particularly preferably 50 μm or more and 188 μm or less. When the thickness of the base material layer 4 is less than the above range, inconveniences such as curling easily occurring when exposed to heat in a backlight unit and the like and difficulty in handling occur. Conversely, if the thickness of the base material layer 4 exceeds the above range, the brightness of the liquid crystal display device may decrease, and the thickness of the backlight unit increases, which is contrary to the demand for thinning the liquid crystal display device. It will be.
[0023]
The micro lens array 5 is composed of a number of micro lenses 6. The microlens 6 has a hemispherical shape (including a shape similar to a hemispherical shape), and protrudes from the surface of the base material layer 4. The microlens 6 is formed of a transparent, particularly colorless and transparent synthetic resin because it is necessary to transmit light rays. Specifically, the same synthetic resin as that of the base layer 4 is used. The microlens 6 is not limited to the hemispherical convex lens, but may be a hemispherical concave lens. Such a hemispherical concave lens microlens also has excellent optical functions like the microlens 6 described above.
[0024]
The base layer 4 and the microlens 6 may contain, for example, a filler, a plasticizer, a stabilizer, a deterioration inhibitor, a dispersant, and the like, in addition to the synthetic resin described above.
[0025]
The microlenses 6 are disposed relatively densely and geometrically on the surface of the base material layer 4. Specifically, the microlenses 6 are arranged in a regular triangular lattice pattern on the surface of the base material layer 4. Therefore, the pitch (P) and the distance (S) between the lenses of the microlenses 6 are all constant. With this arrangement pattern, the microlenses 6 can be arranged most densely. In addition, the arrangement pattern of the microlenses 6 is not limited to the above-described equilateral triangular lattice pattern that can be densely filled, and may be, for example, a square lattice pattern or a random pattern. According to this random pattern, the occurrence of moire when the microlens sheet 2 is overlapped with another optical member is reduced.
[0026]
The lower limit of the diameter (D) of the microlens 6 is preferably 10 μm, particularly 100 μm, and more preferably 200 μm. On the other hand, the upper limit of the diameter (D) of the microlens 6 is preferably 1000 μm, particularly preferably 700 μm. If the diameter (D) of the microlens 6 is smaller than 10 μm, the influence of diffraction becomes large, and the optical performance and color separation are liable to occur, resulting in quality deterioration. On the other hand, when the diameter (D) of the microlens 6 exceeds 1000 μm, the thickness and the luminance unevenness are apt to occur, and the quality is lowered. Further, by setting the diameter (D) of the microlenses 6 to 100 μm or more, the number of the microlenses 6 per unit area is reduced, so that the microlens sheet 2 can easily have a large area. Cost burden is reduced.
[0027]
The lower limit of the surface roughness (Ra) of the microlens 6 is preferably 0.01 μm, particularly preferably 0.03 μm. On the other hand, the upper limit of the surface roughness (Ra) of the microlens 6 is preferably 0.1 μm, particularly preferably 0.07 μm. By setting the surface roughness (Ra) of the microlens 6 to be equal to or more than the above lower limit, the moldability of the microlens array 5 of the microlens sheet 2 becomes relatively easy, and the technical and cost in terms of manufacturing are increased. The burden on the target is reduced. On the other hand, by setting the surface roughness (Ra) of the microlens 6 to be less than the upper limit, light scattering on the surface of the microlens 6 is reduced. The refraction function is enhanced, and high brightness in the front direction can be achieved due to the favorable optical function.
[0028]
The lower limit of the height ratio (H / R) of the height (H) of the microlens 6 to the radius of curvature (R) is preferably 5/8, and particularly preferably 3/4. On the other hand, the upper limit of the height ratio (H / R) is preferably 1. By setting the height ratio (H / R) of the microlenses 6 in the above range, the lens-like refraction effect of the microlenses 6 is effectively exerted, and the microlens sheet 2 is used for optical condensing and the like. Function is remarkably improved.
[0029]
The upper limit of the distance ratio (S / D) of the distance (S; PD) between the lenses of the microlens 6 to the diameter (D) is preferably 1/2, and particularly preferably 1/5. By setting the inter-lens distance (S) of the microlens 6 to be equal to or less than the upper limit, the flat portion that does not contribute to the optical function is reduced, and the optical function of the microlens sheet 2 such as condensing is markedly improved. Be improved.
[0030]
The lower limit of the filling rate of the microlenses 6 is preferably 40%, particularly preferably 60%. By setting the filling rate of the microlenses 6 to be equal to or more than the lower limit, the occupation area of the microlenses 6 is increased, and the optical function of the microlens sheet 2 such as condensing light is remarkably improved.
[0031]
The lower limit of the refractive index of the material constituting the microlens array 5 is preferably 1.3, and particularly preferably 1.45. On the other hand, the upper limit of the refractive index of this material is preferably 1.8, and particularly preferably 1.6. Within this range, the refractive index of the material constituting the microlens array 5 is most preferably 1.5. By setting the refractive index of the material constituting the microlens array 5 to the above-described range, the lens-like refraction of the microlens 6 is effectively performed, and the optical function of the microlens sheet 2 such as light condensing is performed. Is further enhanced.
[0032]
The method for manufacturing the microlens sheet 2 is not particularly limited as long as the above structure can be formed, and various methods are adopted. As a method of manufacturing the microlens sheet 2, a method of separately forming the microlens array 5 after forming the base layer 4 and a method of integrally forming the base layer 4 and the microlens array 5 are possible. ,In particular,
(A) a method of forming the microlens sheet 2 by laminating a synthetic resin on a sheet mold having an inverted shape of the surface of the microlens array 5 and peeling off the sheet mold;
(B) an injection molding method of injecting a molten resin into a mold having an inverted shape on the surface of the microlens array 5;
(C) a method of transferring the shape by reheating the sheeted resin, pressing between a mold and a metal plate as described above, and pressing the same;
(D) an extruded sheet molding method in which a molten resin is passed through a nip between a roll mold having a reverse shape of the surface of the microlens array 5 on the peripheral surface and another roll, and the shape is transferred.
(E) A UV curable resin is applied to the base material layer, pressed onto a sheet mold, a mold or a roll mold having the same inverted shape as above to transfer the shape to the uncured UV curable resin, Method to cure the ultraviolet curing resin
(F) A mold or roll mold having the same inverted shape as described above is filled and coated with an uncured UV-curable resin, pressed and leveled by a base material layer, and irradiated with UV rays to cure the UV-curable resin. Method,
(G) Method of using electron beam-curable resin instead of ultraviolet-curable resin
and so on.
[0033]
As a method of manufacturing a mold having a reverse shape of the microlens array 5, for example, a spot-shaped three-dimensional pattern is formed on a base material using a photoresist material, and the three-dimensional pattern is curved by heating and fluidizing. Then, a microlens array model is produced, a metal layer is laminated on the surface of the microlens array model by an electroforming method, and the metal layer is peeled off.
[0034]
According to the above manufacturing method, the microlens array 5 having an arbitrary shape is easily and reliably formed. Therefore, the diameter (D), the height ratio (H / R), the interval ratio (S / D), the filling rate, and the like of the microlenses 6 constituting the microlens array 5 are easily and surely adjusted, and as a result, the microlens 6 can be adjusted. The optical function of the lens sheet 2 is easily and reliably controlled.
[0035]
The microlens sheet 2 is provided with a microlens array 5 on the surface, which significantly improves the optical functions such as condensing, refraction toward the normal direction, and diffusion, and makes the optical functions easy and reliable. Controlled. In addition, by adjusting the height of the microlens 6 to be constant, stress concentration is suppressed in the microlens sheet 2 and damage to another member (such as the light diffusion sheet 3) to be superimposed is prevented.
[0036]
The light diffusion sheet 3 includes a base layer 7 and a light diffusion layer 8 laminated on the surface of the base layer 7. The material, thickness, and the like of the base layer 7 are the same as those of the base layer 4 of the microlens sheet 2.
[0037]
The light diffusing layer 8 includes a binder 9 and a light diffusing agent 10 contained in the binder 9. The light diffusing agent 10 contained in the light diffusing layer 8 can uniformly diffuse the light passing through the light diffusing layer 8 from the back side to the front side. Further, fine irregularities are formed substantially uniformly on the surface of the light diffusing layer 8 by the light diffusing agent 10. The fine irregularities formed on the surface of the light diffusion sheet 3 can diffuse the light rays better. The thickness of the light diffusion layer 8 (meaning the thickness of the binder 9 excluding the light diffusion agent 10) is not particularly limited, but is, for example, about 1 μm or more and 30 μm or less. Further, since the binder 9 needs to transmit light, it is transparent, and particularly preferably colorless and transparent.
[0038]
The light diffusing agent 10 is a particle having a property of diffusing light rays, and is roughly classified into an inorganic filler and an organic filler. Specifically, silica, aluminum hydroxide, aluminum oxide, zinc oxide, barium sulfide, magnesium silicate, or a mixture thereof can be used as the inorganic filler. Specific examples of the material of the organic filler include acrylic resin, acrylonitrile resin, polyurethane, polyvinyl chloride, polystyrene, polyacrylonitrile, and polyamide. Among them, acrylic resins having high transparency are preferable, and polymethyl methacrylate (PMMA) is particularly preferable.
[0039]
The shape of the light diffusing agent 10 is not particularly limited, and examples thereof include a spherical shape, a cubic shape, a needle shape, a rod shape, a spindle shape, a plate shape, a scale shape, and a fibrous shape. Are preferred.
[0040]
The lower limit of the average particle diameter of the light diffusing agent 10 is preferably 1 μm, particularly 2 μm, more preferably 5 μm, and the upper limit of the average particle diameter of the light diffusing agent 10 is preferably 50 μm, particularly 20 μm, and more preferably 15 μm. If the average particle diameter of the light diffusing agent 10 is less than the above range, the unevenness of the surface of the light diffusing layer 8 formed by the light diffusing agent 10 becomes small, and the light diffusing property required for the light diffusing sheet is not satisfied. Conversely, if the average particle diameter of the light diffusing agent 10 exceeds the above range, the thickness of the light diffusing sheet 3 increases, and uniform diffusion becomes difficult.
[0041]
The lower limit of the blending amount of the light diffusing agent 10 (the blending amount in terms of solid content with respect to 100 parts of the base polymer in the polymer composition as the material for forming the binder 9) is preferably 10 parts, particularly 20 parts, and more preferably 50 parts. . On the other hand, the upper limit of the amount is preferably 500 parts, particularly 300 parts, and more preferably 200 parts. This is because if the amount of the light diffusing agent 10 is less than the above range, the light diffusing property becomes insufficient, while if the amount of the light diffusing agent 10 exceeds the above range, the light diffusing agent 10 is fixed. This is because the effect of doing so is reduced.
[0042]
The binder 9 is formed by crosslinking and curing a polymer composition containing a base polymer. The light diffusing agent 10 is arranged and fixed at substantially the same density over the entire surface of the base material layer 7 by the binder 9. The polymer composition for forming the binder 9 may further include, for example, a fine inorganic filler, a curing agent, a plasticizer, a dispersant, various leveling agents, an ultraviolet absorber, an antioxidant, a viscosity modifier, A lubricant, a light stabilizer and the like may be appropriately compounded.
[0043]
The base polymer is not particularly limited, and examples thereof include acrylic resins, polyurethanes, polyesters, fluorine resins, silicone resins, polyamide imides, epoxy resins, and ultraviolet curable resins. Can be used alone or in combination of two or more. In particular, as the base polymer, a polyol having high processability and capable of easily forming the light diffusion layer 8 by means such as coating is preferable. The base polymer used for the binder 9 is transparent because it is necessary to transmit light, and is preferably colorless and transparent.
[0044]
Examples of the polyol include a polyol obtained by polymerizing a monomer component containing a hydroxyl group-containing unsaturated monomer, and a polyester polyol obtained under the condition of an excess of hydroxyl groups. These may be used alone or in combination of two or more. Can be used.
[0045]
Examples of the hydroxyl group-containing unsaturated monomer include (a) 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, allyl alcohol, homoallyl alcohol, Hydroxyl group-containing unsaturated monomers such as cinnamon alcohol and crotonyl alcohol; (b) for example, ethylene glycol, ethylene oxide, propylene glycol, propylene oxide, butylene glycol, butylene oxide, 1,4-bis (hydroxymethyl) cyclohexane, phenyl A dihydric alcohol or an epoxy compound such as glycidyl ether, glycidyl decanoate, or Praxel FM-1 (manufactured by Daicel Chemical Industries, Ltd.), for example, acrylic acid, methacrylic acid, maleic acid, or fumaric acid Crotonic acid, and the like react with the resulting hydroxyl group-containing unsaturated monomer with an unsaturated carboxylic acid such as itaconic acid. One or more selected from these hydroxyl-containing unsaturated monomers can be polymerized to produce a polyol.
[0046]
Also, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, tert-butyl acrylate, ethylhexyl acrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-methacrylate Butyl, tert-butyl methacrylate, ethylhexyl methacrylate, glycidyl methacrylate, cyclohexyl methacrylate, styrene, vinyl toluene, 1-methylstyrene, acrylic acid, methacrylic acid, acrylonitrile, vinyl acetate, vinyl propionate, vinyl stearate, acetic acid Allyl, diallyl adipate, diallyl itaconate, diethyl maleate, vinyl chloride, vinylidene chloride, acrylamide, N-methylolacrylamide, N-butoxymethylacryl One or more ethylenically unsaturated monomers selected from amide, diacetone acrylamide, ethylene, propylene, isoprene and the like, and a hydroxyl-containing unsaturated monomer selected from the above (a) and (b) A polyol can also be produced by polymerizing the polymer.
[0047]
The number average molecular weight of a polyol obtained by polymerizing a monomer component containing such a hydroxyl group-containing unsaturated monomer is from 1,000 to 500,000, preferably from 5,000 to 100,000. The hydroxyl value is 5 or more and 300 or less, preferably 10 or more and 200 or less, and more preferably 20 or more and 150 or less.
[0048]
Polyester polyols obtained under the condition of excess hydroxyl groups include (c), for example, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, neopentyl Glycol, hexamethylene glycol, decamethylene glycol, 2,2,4-trimethyl-1,3-pentanediol, trimethylolpropane, hexanetriol, glycerin, pentaerythritol, cyclohexanediol, hydrogenated bisphenol A, bis (hydroxymethyl) Polyhydric alcohols such as cyclohexane, hydroquinone bis (hydroxyethyl ether), tris (hydroxyethyl) isocinurate and xylylene glycol; and (d) maleic And polybasic acids such as fumaric acid, succinic acid, adipic acid, sebacic acid, azelaic acid, trimetic acid, terephthalic acid, phthalic acid, and isophthalic acid; and propanediol, hexanediol, polyethylene glycol, and trimethylolpropane. It can be produced by reacting under conditions where the number of hydroxyl groups in the polyhydric alcohol is larger than the number of carboxyl groups of the polybasic acid.
[0049]
The number average molecular weight of the polyester polyol obtained under such hydroxyl group excess conditions is from 500 to 300,000, preferably from 2,000 to 100,000. The hydroxyl value is 5 or more and 300 or less, preferably 10 or more and 200 or less, and more preferably 20 or more and 150 or less.
[0050]
The polyol used as the base polymer of the polymer composition is obtained by polymerizing the above-mentioned polyester polyol and a monomer component containing the above-mentioned hydroxyl group-containing unsaturated monomer, and (meth) acrylic unit. Is preferred. The binder 9 using such a polyester polyol or an acrylic polyol as a base polymer has high weather resistance and can suppress yellowing of the light diffusion layer 8 and the like. Note that either one of the polyester polyol and the acrylic polyol may be used, or both may be used.
[0051]
The number of hydroxyl groups in the polyester polyol and acrylic polyol is not particularly limited as long as it is 2 or more per molecule, but when the hydroxyl value in the solid content is 10 or less, the number of crosslinking points decreases, and the solvent resistance is reduced. In addition, the coating properties such as water resistance, heat resistance, and surface hardness tend to decrease.
[0052]
The polymer composition may contain a fine inorganic filler. By containing the fine inorganic filler in the binder 9, the heat resistance of the light diffusion layer 8 and thus the light diffusion sheet 3 is improved. The inorganic substance constituting the fine inorganic filler is not particularly limited, and an inorganic oxide is preferable. This inorganic oxide is defined as various oxygen-containing metal compounds in which a metal element mainly forms a three-dimensional network through a bond with an oxygen atom. Further, as the metal element constituting the inorganic oxide, for example, an element selected from Groups II to VI of the Periodic Table of the Elements is preferable, and an element selected from Groups III to V of the Periodic Table of the Elements is more preferable. Among them, an element selected from Si, Al, Ti and Zr is particularly preferable, and colloidal silica in which the metal element is Si is most preferable as the fine inorganic filler in view of the heat resistance improving effect and the uniform dispersibility. The shape of the fine inorganic filler may be any particle shape such as a sphere, a needle, a plate, a scale, and a crushed shape, and is not particularly limited.
[0053]
The lower limit of the average particle size of the fine inorganic filler is preferably 5 nm, particularly preferably 10 nm. On the other hand, the upper limit of the average particle diameter of the fine inorganic filler is preferably 50 nm, particularly preferably 25 nm. This is because when the average particle diameter of the fine inorganic filler is less than the above range, the surface energy of the fine inorganic filler is increased, and aggregation or the like is likely to occur.Conversely, when the average particle diameter exceeds the above range, This is because the light diffusion sheet 3 becomes cloudy due to the influence of the short wavelength, and the transparency of the light diffusion sheet 3 cannot be completely maintained.
[0054]
The lower limit of the amount of the fine inorganic filler relative to 100 parts of the base polymer (the amount of the inorganic component alone) is preferably 5 parts in terms of solids, and particularly preferably 50 parts. On the other hand, the upper limit of the amount of the fine inorganic filler is preferably 500 parts, more preferably 200 parts, and particularly preferably 100 parts. If the amount of the fine inorganic filler is less than the above range, the heat resistance of the light diffusion sheet 3 may not be sufficiently exhibited, and conversely, the amount exceeds the above range. This is because compounding into the polymer composition becomes difficult, and the light transmittance of the light diffusion layer 8 may decrease.
[0055]
As the fine inorganic filler, a material having an organic polymer fixed on its surface is preferably used. By using the organic polymer-fixed fine inorganic filler as described above, the dispersibility in the binder 9 and the affinity with the binder 9 are improved. This organic polymer is not particularly limited with respect to its molecular weight, shape, composition, presence or absence of a functional group and the like, and any organic polymer can be used. Regarding the shape of the organic polymer, any shape such as a linear, branched, or crosslinked structure can be used.
[0056]
Specific resins constituting such an organic polymer include, for example, (meth) acrylic resin, polystyrene, polyvinyl acetate, polyolefins such as polyethylene and polypropylene, polyvinyl chloride, polyvinylidene chloride, polyesters such as polyethylene terephthalate and the like. Examples include copolymers and resins partially modified with functional groups such as amino groups, epoxy groups, hydroxyl groups, and carboxyl groups. Among them, those having an organic polymer containing a (meth) acrylic unit as an essential component such as a (meth) acrylic resin, a (meth) acryl-styrene resin, and a (meth) acryl-polyester resin have a film forming ability. It is suitable. On the other hand, a resin having compatibility with the base polymer of the polymer composition is preferable, and therefore, a resin having the same composition as the base polymer contained in the polymer composition is most preferable.
[0057]
In addition, the fine inorganic filler may include an organic polymer in the fine particles. This makes it possible to impart appropriate softness and toughness to the inorganic substance as the core of the fine inorganic filler.
[0058]
The organic polymer preferably contains an alkoxy group, and the content thereof is preferably 0.01 mmol or more and 50 mmol or less per 1 g of the fine inorganic filler to which the organic polymer is fixed. By such an alkoxy group, affinity with a matrix resin constituting the binder 9 and dispersibility in the binder 9 can be improved.
[0059]
Here, the alkoxy group refers to an RO group bonded to a metal element forming the skeleton of the fine particles. R is an alkyl group which may be substituted, and the RO groups in the fine particles may be the same or different. Specific examples of R include methyl, ethyl, n-propyl, isopropyl, n-butyl and the like. It is preferable to use the same metal alkoxy group as the metal constituting the fine inorganic filler. When the fine inorganic filler is colloidal silica, it is preferable to use an alkoxy group containing silicon as a metal.
[0060]
The content of the organic polymer in the fine inorganic filler to which the organic polymer is fixed is not particularly limited, but is preferably 0.5% by mass or more and 50% by mass or less based on the fine inorganic filler.
[0061]
As described above, a polymer having a hydroxyl group is used as the organic polymer fixed to the fine inorganic filler, and a polyfunctional isocyanate compound having two or more functional groups that react with the hydroxyl group in the polymer composition constituting the binder 9, melamine It is preferable to contain at least one selected from a compound and an aminoplast resin. Thereby, the fine inorganic filler and the matrix resin of the binder 9 are bonded in a cross-linked structure, and the storage stability, stain resistance, flexibility, weather resistance, storage stability, and the like are improved, and the obtained coating film is further improved. It becomes glossy.
[0062]
Examples of the polyfunctional isocyanate compound include aliphatic, alicyclic, aromatic and other polyfunctional isocyanate compounds and modified compounds thereof. Specific examples of the polyfunctional isocyanate compound include, for example, tolylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, lysine diisocyanate, 2,2,4-trimethylhexylmethane diisocyanate, methylcyclohexane diisocyanate, 1,6 A trimer such as a biuret or isocyanurate of hexamethylene diisocyanate; and 2 formed by the reaction of these polyfunctional isocyanates with polyhydric alcohols such as propanediol, hexanediol, polyethylene glycol and trimethylolpropane. Compounds in which at least two isocyanate groups remain; these polyfunctional isocyanate compounds are Choles, compounds having a phenolic hydroxyl group such as phenol and cresol, acetoximes, oximes such as methyl ethyl ketoxime, ε-caprolactam, blocked polyfunctional isocyanate compounds blocked with a lactam such as γ-caprolactam and the like. Can be mentioned. In addition, the said polyfunctional isocyanate compound can be used individually by 1 type or in mixture of 2 or more types. Among them, a non-yellowing polyfunctional isocyanate compound having no isocyanate group directly bonded to an aromatic ring is preferable in order to prevent yellowing of the coating.
[0063]
Examples of the melamine compound include dimethylol melamine, trimethylol melamine, tetramethylol melamine, pentamethylol melamine, hexamethylol melamine, isobutyl ether melamine, n-butyl ether melamine, and butylated benzoguanamine.
[0064]
Examples of the aminoplast resin include an alkyl etherified melamine resin, a urea resin, a benzoguanamine resin, and the like. These aminoplast resins can be used alone or as a mixture or cocondensate of two or more. The alkyl etherified melamine resin is obtained by methylolating an aminotriazine and alkyl etherifying it with cyclohexanol or an alkanol having 1 to 6 carbon atoms. Resin is a typical one. Further, a sulfonic acid-based catalyst for accelerating curing, for example, paratoluenesulfonic acid and its amine salt can be used.
[0065]
As the base polymer, a polyol having a cycloalkyl group is preferable. As described above, by introducing the cycloalkyl group into the base polymer (polyol) constituting the binder 9, the hydrophobicity such as the water repellency and the water resistance of the binder 9 is increased, and the hydrophobicity of the binder 9 under high temperature and high humidity conditions is increased. The deflection resistance, dimensional stability, and the like of the light diffusion sheet 3 are improved. In addition, the basic properties of the light diffusion layer 8 such as hardness, weather resistance, texture, and solvent resistance are improved. Further, the affinity with the fine inorganic filler having the organic polymer fixed on the surface and the uniform dispersibility of the fine inorganic filler are further improved.
[0066]
The cycloalkyl group is not particularly limited, for example, cyclobutyl group, cyclopentyl group, cyclohexyl group, cycloheptyl group, cyclooctyl group, cyclononyl group, cyclodecyl group, cycloundecyl group, cyclododecyl group, cyclotridecyl group, Examples include a cyclotetradecyl group, a cyclopentadecyl group, a cyclohexadecyl group, a cycloheptadecyl group, and a cyclooctadecyl group.
[0067]
The polyol having a cycloalkyl group is obtained by copolymerizing a polymerizable unsaturated monomer having a cycloalkyl group. The polymerizable unsaturated monomer having a cycloalkyl group is a polymerizable unsaturated monomer having at least one cycloalkyl group in a molecule. The polymerizable unsaturated monomer is not particularly limited, and includes, for example, cyclohexyl (meth) acrylate, methylcyclohexyl (meth) acrylate, tert-butylcyclohexyl (meth) acrylate, cyclododecyl (meth) acrylate, and the like.
[0068]
Further, the polymer composition preferably contains an isocyanate as a curing agent. By including the isocyanate curing agent in the polymer composition in this manner, a stronger crosslinked structure is obtained, and the physical properties of the light diffusion layer 8 are further improved. As this isocyanate, the same substance as the above-mentioned polyfunctional isocyanate compound is used. Among them, aliphatic isocyanates that prevent yellowing of the coating film are preferred.
[0069]
In particular, when a polyol is used as the base polymer, one or more of hexamethylene diisocyanate, isofuron diisocyanate, and xylene diisocyanate may be used as a curing agent to be mixed into the polymer composition. When these curing agents are used, the curing reaction speed of the polymer composition increases, so that even if a cationic one that contributes to the dispersion stability of the fine inorganic filler is used as the antistatic agent, the cationic antistatic agent can be used. Can sufficiently compensate for the decrease in the curing reaction rate. Further, the improvement in the curing reaction rate of the polymer composition contributes to the uniform dispersibility of the fine inorganic filler in the binder. As a result, the light diffusion sheet can remarkably suppress bending and yellowing due to heat, ultraviolet light, and the like.
[0070]
Further, an antistatic agent may be kneaded in the polymer composition. By forming the binder 9 from the polymer composition in which the antistatic agent is kneaded in this manner, an antistatic effect is exerted on the light diffusion sheet 3, and it becomes difficult to attract dust or overlap with a prism sheet or the like. It is possible to prevent inconveniences caused by static electricity such as becoming. In addition, when the surface is coated with an antistatic agent, stickiness and turbidity of the surface are caused, but such adverse effects are reduced by kneading the polymer composition in such a manner. The antistatic agent is not particularly limited. For example, anionic antistatic agents such as alkyl sulfates and alkyl phosphates, quaternary ammonium salts, cationic antistatic agents such as imidazoline compounds, polyethylene glycol-based Nonionic antistatic agents such as polyoxyethylene sorbitan monostearate and ethanolamide, and high molecular antistatic agents such as polyacrylic acid are used. Among them, a cationic antistatic agent having a relatively large antistatic effect is preferable, and an antistatic effect can be obtained by adding a small amount.
[0071]
Next, a method for manufacturing the light diffusion sheet 3 will be described. The method for manufacturing the light diffusion sheet 3 includes: (a) a step of manufacturing a coating liquid for a light diffusion layer by mixing a light diffusion agent 10 with a polymer composition constituting a binder 9; Applying the layer coating liquid to the surface of the base material layer 7 to laminate the light diffusion layer 8.
[0072]
The light diffusion sheet 3 has a high light diffusion function due to reflection and refraction at the interface of the light diffusion agent 10 contained in the light diffusion layer 8 and refraction at fine irregularities formed on the surface of the light diffusion layer 8. Due to this light diffusion function, it has a refraction function toward the normal direction.
[0073]
In the optical unit 1, optical functions such as condensing, refraction toward the normal direction, and diffusion are significantly improved by the microlens sheet 2, and the light diffusion sheet 3 provided on the surface side of the microlens sheet 2 is improved. Due to the excellent light diffusion function, the occurrence of moire, glare, luminance unevenness, etc. is reduced, and the quality is improved. In addition, the optical unit 1 adjusts the diameter (D), the height ratio (H / R), the interval ratio (S / D), the filling rate, and the like of the microlenses 6 of the microlens sheet 2 to provide an optical device. Functions are easily and reliably controlled. Further, in the optical unit 1, by adjusting the height (D) of the microlenses 6 of the microlens sheet 2 to be constant, stress concentration is suppressed, and the light diffusion sheet 3 to be superimposed is damaged or overlapped. Damage to the member is prevented.
[0074]
The edge light type backlight unit shown in FIG. 3 includes a light guide plate 11 and a pair of linear lamps 12 arranged on the opposite sides of the light guide plate 11. The optical units 1 are arranged in an overlapping manner. The light emitted from the lamp 12 and emitted from the surface of the light guide plate 11 has a relatively strong peak inclined at a predetermined angle with respect to the normal direction. The front luminance is remarkably increased by the optical unit 1 having a function, a function of changing the angle in the normal direction, and the like. Further, in the backlight unit, the emitted light is more uniformly diffused by the light diffusing sheet superimposed on the front surface side of the microlens sheet 2, thereby preventing luminance unevenness and glare. Therefore, according to the backlight unit, the number of optical sheets conventionally required can be reduced, and the backlight unit can be made thinner, the brightness can be improved, and the cost can be reduced. The edge light type backlight unit may be equipped with four or six lamps 12.
[0075]
The microlens sheet 15 in FIG. 4 includes the base layer 4, the microlens array 5 provided on the surface of the base layer 4, and the anti-sticking layer 16 laminated on the back surface of the base layer 4. Since the substrate layer 4 and the microlens array 5 are the same as the microlens sheet 2, the same numbers are given and the description is omitted. Therefore, the microlens sheet 15 also has excellent optical functions such as light condensing, refraction toward the normal direction side, and diffusion similarly to the microlens sheet 2.
[0076]
The anti-sticking layer 16 includes a binder 17 and beads 18 dispersed in the binder 17. The binder 17 is formed by crosslinking and curing the same polymer composition as the binder 9 of the light diffusion layer 8. The same beads 18 as the light diffusing agent 10 of the light diffusing layer 8 are used. The thickness of the anti-sticking layer 16 (the thickness of the portion of the binder 17 excluding the beads 18) is not particularly limited, but is, for example, about 1 μm or more and 10 μm or less.
[0077]
The blending amount of the beads 18 is relatively small, and the beads 18 are separated from each other and dispersed in the binder 17. Many of the beads 18 have a lower end projecting from the binder 17 by a very small amount. Therefore, when the microlens sheet 15 is laminated on the light guide plate, the lower ends of the protruding beads 18 contact the surface of the light guide plate or the like, and the entire back surface of the micro lens sheet 15 does not contact the light guide plate or the like. Thereby, sticking between the microlens sheet 15 and the light guide plate or the like is prevented, and uneven brightness on the screen of the liquid crystal display device is suppressed.
[0078]
The method for forming the anti-sticking layer 16 includes, for example, (a) a step of producing a coating liquid for the anti-sticking layer by mixing beads 18 with a polymer composition constituting the binder 17; Coating the anti-sticking layer 16 by applying a layer coating liquid to the back surface of the base material layer 4.
[0079]
Next, a simulation shows how the front luminance changes when the height ratio (H / R), the interval ratio (S / D), and the filling rate are changed in the optical sheet. The analysis of the luminance in this simulation is performed by non-sequential ray tracing using the Monte Carlo method. The obtained front luminance relative value indicates the relative front luminance when each parameter is changed.
[0080]
The relationship between the height ratio (H / R) and the front luminance relative value is shown in Table 1 below and the graph of FIG. The graphs in Table 1 and FIG. 5 show that the front luminance relative value is increased when the height ratio (H / R) is 5/8 or more, and is particularly increased when the height ratio (H / R) is 3/4 or more. Is shown. Further, as the height ratio (H / R) approaches 1, the increase amount of the front luminance relative value decreases.
[0081]
[Table 1]

[0082]
The relationship between the interval ratio (S / D) and the front luminance relative value is shown in Table 2 below and the graph of FIG. The graphs in Table 2 and FIG. 6 show that when the interval ratio (S / D) is １ ／ or less, the front luminance relative value increases, and that the interval ratio (S / D) particularly increases when the interval ratio (S / D) is １ ／ or less. ing.
[0083]
[Table 2]

[0084]
The relationship between the lens filling factor and the front luminance relative value is shown in Table 3 below and the graph of FIG. The graphs in Table 3 and FIG. 7 show that when the lens filling rate is 40% or more, the front luminance relative value becomes higher, the lens filling rate becomes higher when the lens filling rate is 60% or more, and the lens filling rate becomes 75% or more. Indicates that it is particularly high.
[0085]
[Table 3]

[0086]
Finally, in the edge light type backlight unit, the conditions of the lamp and the light guide plate are fixed, and when the configuration of the optical unit includes (a) one light diffusion sheet, (b) two light diffusion sheets are used. The front luminance was actually measured in the case of superimposing, (c) in the case of superimposing the three light diffusion sheets, and (d) in the case of superimposing the light diffusion sheet and the microlens sheet (the configuration of the present invention). . The results are shown in Table 4 below.
[0087]
[Table 4]

[0088]
As shown in Table 4 above, the front luminance of the optical unit having the configuration (d) according to the present invention is remarkably improved as compared with the optical unit having the configuration (c) in which three light diffusion sheets are superimposed. I have. Therefore, according to the optical unit of the present invention, it is understood that a high front luminance can be obtained, and reduction in the number of optical sheets provided can be promoted.
[0089]
Note that the optical unit and the backlight unit of the present invention are not limited to the above embodiment, and for example, an optical unit in which a microlens sheet is superimposed on the front surface side of a light diffusion sheet is also possible. This optical unit has a high refraction function in the normal direction due to the microlens sheet on the front side. In the case of this optical unit, the anti-sticking layer 16 may be laminated on the back surface of the base layer of the light diffusion sheet. The sticking prevention layer 16 prevents sticking between the light diffusion sheet and the light guide plate.
[0090]
Further, the optical unit of the present invention may include two or more light diffusion sheets and microlens sheets, or may include another optical sheet.
[0091]
【The invention's effect】
As described above, according to the optical unit of the present invention, light collection, refraction to the normal direction side, optical functions such as diffusion are extremely high, the control of the optical functions is easy and reliable, Damage to the optical sheet and damage to other members are suppressed. Further, according to the backlight unit using the optical unit, quality improvement such as higher luminance in the front direction and uniform luminance is promoted.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view showing an optical unit according to an embodiment of the present invention.
FIGS. 2A and 2B are a partial plan view and a partial cross-sectional view illustrating an optical sheet provided in the optical unit of FIG. 1;
FIG. 3 is a schematic sectional view showing a backlight unit including the optical unit of FIG. 1;
FIG. 4 is a partial cross-sectional view showing an optical sheet according to a form different from the optical sheet of FIG. 2;
FIG. 5 is a graph showing a relationship between a height ratio and a front luminance relative value.
FIG. 6 is a graph showing a relationship between an interval ratio and a front luminance relative value.
FIG. 7 is a graph showing a relationship between a lens filling factor and a front luminance relative value.
FIG. 8A is a schematic perspective view showing a conventional general edge light type backlight unit. FIG. 8B is a schematic sectional view showing a conventional bead-coated sheet.
[Explanation of symbols]
1 Optical unit
2 Micro lens sheet
3 Light diffusion sheet
4 Base material layer
5 Micro lens array
6 micro lens
7 Base material layer
8 Light diffusion layer
9 binder
10 Light diffuser
11 Light guide plate
12 lamps
15 Micro lens sheet
16 Anti-sticking layer
17 Binder
18 beads

Claims (10)

With a plurality of optical sheets to be superimposed, a micro lens sheet and a light diffusion sheet are used as the optical sheets,
This microlens sheet has a microlens array composed of a plurality of microlenses on its surface,
An optical unit in which a light diffusion sheet includes a base layer and a light diffusion layer containing a light diffusion agent in a binder. The optical unit according to claim 1, wherein a diameter (D) of the microlens in the microlens sheet is 10 µm or more and 1000 µm or less. The optical unit according to claim 1, wherein a height ratio (H / R) of a height (H) of the microlenses to a radius of curvature (R) of the microlens sheet is 5/8 or more and 1 or less. 4. The optical unit according to claim 1, wherein an interval ratio (S / D) of a distance (S) between lenses of the microlens to a diameter (D) of the microlens sheet is 以下 or less. 5. . The optical unit according to any one of claims 1 to 4, wherein a filling rate of the microlenses in the microlens sheet is 40% or more. The optical unit according to any one of claims 1 to 5, wherein a refractive index of a material constituting the microlens array in the microlens sheet is 1.3 or more and 1.8 or less. The optical unit according to any one of claims 1 to 6, wherein the arrangement pattern of the microlenses in the surface shape of the microlens sheet is a regular triangular lattice pattern. The optical unit according to any one of claims 1 to 6, wherein the arrangement pattern of the microlenses in the surface shape of the microlens sheet is a random pattern. The optical unit according to any one of claims 1 to 8, further comprising a sticking prevention layer in which beads are dispersed in a binder, on a back surface of the optical sheet. In a backlight unit for a liquid crystal display device, which disperses a light beam emitted from a lamp and guides the light to a surface side,
A backlight unit for a liquid crystal display device, comprising the optical unit according to any one of claims 1 to 9.

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