JP2004094051A - Optical sheet and back light unit using the sheet - Google Patents

Optical sheet and back light unit using the sheet Download PDF

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Publication number
JP2004094051A
JP2004094051A JP2002257030A JP2002257030A JP2004094051A JP 2004094051 A JP2004094051 A JP 2004094051A JP 2002257030 A JP2002257030 A JP 2002257030A JP 2002257030 A JP2002257030 A JP 2002257030A JP 2004094051 A JP2004094051 A JP 2004094051A
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JP
Japan
Prior art keywords
optical sheet
layer
prism
sheet according
light
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
JP2002257030A
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Japanese (ja)
Inventor
Motohiko Okabe
岡部 元彦
Original Assignee
Keiwa Inc
恵和株式会社
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Priority to JP2002257030A priority Critical patent/JP2004094051A/en
Publication of JP2004094051A publication Critical patent/JP2004094051A/en
Application status is Pending legal-status Critical

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Abstract

An object of the present invention is to provide an optical sheet having a high optical function such as a deflection function and a backlight unit having a good front luminance and a good viewing angle.
An optical sheet (1) for directing a transmitted light beam incident from a back surface to a normal direction side, comprising a plurality of resin layers (base layer (2), prism layer (3) and intermediate embedding layer (4)). A plurality of convex ridges 5 are formed in a stripe shape on the back surface of the resin layer (prism layer 3) constituting the interface, and the cross-sectional shape of the convex ridges 5 is a mountain-like polygon (equilateral trapezoid). It is characterized by the following. The mountain-shaped polygon is preferably bilaterally symmetric, and particularly preferably a mountain-shaped trapezoid or a mountain-shaped pentagon. Preferably, the plurality of convex prism portions 5 are juxtaposed at predetermined intervals.
[Selection diagram] Fig. 1

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical sheet having various functions such as refraction, diffusion, light collection, and reflection, 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 to emit light has become widespread, and a backlight unit of an edge light type, a direct type or the like is provided on a lower surface side of the liquid crystal layer. As shown in FIG. 11, such an edge light type backlight unit 90 generally includes a rod-shaped lamp 91 as a light source, and a rectangular plate-shaped light guide plate arranged so that an end thereof is along the lamp 91. The light guide plate 92 is provided with a plurality of optical sheets 93 stacked on the front surface side of the light guide plate 92. The optical sheet 93 has a specific optical function such as refraction and diffusion. Specifically, (1) a diffusive optical element mainly disposed on the surface of the light guide plate 92 and mainly having a light diffusion function. A sheet (a so-called light diffusion sheet) 94 and (2) a refraction optical sheet (a so-called prism sheet) 95 disposed on the surface side of the diffusion optical sheet 94 and having a refraction function in a normal direction side correspond to the sheet.
[0003]
The function of the backlight unit 90 will be described. First, a light beam incident on the light guide plate 92 from the lamp 91 is reflected by a reflection dot or a reflection sheet (not shown) on the back surface of the light guide plate 92 and each side surface. Emitted from the surface. Light emitted from the light guide plate 92 enters the diffusive optical sheet 94, is diffused, and is emitted from the surface. Thereafter, the light beam emitted from the diffusing optical sheet 94 enters the refracting optical sheet 95, and is emitted by the prism portion 95a formed on the surface thereof as a light beam having a distribution showing a peak almost directly above. In this manner, the light beam emitted from the lamp 91 is diffused by the optical sheet 93, refracted so as to show a peak almost directly above, and illuminates the entire liquid crystal layer (not shown) further above.
[0004]
[Problems to be solved by the invention]
In the above-described conventional backlight unit 90, the light beam emitted from the surface of the light guide plate 92 has a relatively sharp peak that is inclined. On the other hand, the diffusing optical sheet 94 or the refracting optical sheet 95 alone does not have a very large light diffusing property or a refracting property (gonotropism) toward the normal direction. Therefore, the above-mentioned conventional backlight unit 90 needs to be provided with a plurality of optical sheets 93 in order to refract outgoing light rays toward the normal direction side, correct the viewing angle, and the like. Therefore, in the above-mentioned conventional backlight unit 90, the thickness, cost, light loss, and the like are increased due to the plurality of optical sheets 93 provided.
[0005]
The present invention has been made in view of these inconveniences, and has as its object to provide an optical sheet having a high optical function such as a bending function and a backlight unit having good front luminance and a good viewing angle.
[0006]
[Means for Solving the Problems]
The invention made in order to solve the above-mentioned problem is an optical sheet for directing a transmitted light beam incident from the back surface to a normal direction side, and includes a plurality of resin layers, and a plurality of resin layers on the back surface of the resin layer constituting the interlayer interface. Is formed in a stripe shape, and the cross-sectional shape of the convex prism portion is a mountain-shaped polygon.
[0007]
In the optical sheet, a plurality of convex stripe prism portions are formed in a stripe shape on the back surface of at least one resin layer, and the convex prism portions constitute an interlayer interface. Since the cross-sectional shape of the ridge prism portion is a mountain-shaped polygon, the optical sheet has a stripe-like interlayer interface inclined by a predetermined angle with respect to the sheet surface by the side surface of the ridge prism portion. . Therefore, the optical sheet can effectively direct the transmitted light beam incident from the back surface to the normal direction side by the action of refraction, reflection, and the like at the inclined striped interlayer interface. In other words, the optical sheet has a high deflection function. In addition, since the convex prism portion on the back surface of the resin layer having the deflection function constitutes an interlayer interface and is embedded in the sheet, the interface shape is maintained over time, and the deterioration of the deflection function is prevented. .
[0008]
The mountain-like polygon is preferably symmetrical in the left-right direction. By making the cross-sectional shape of the ridge prism portion symmetrical in this manner, the formation of the resin layer having the ridge prism portion is facilitated, and the angle is changed even if rotated 180 ° with respect to the direction of the ridge prism portion. The functions are the same. Therefore, for example, in assembling into an edge light type backlight unit, only the direction of the convex prism portion of the optical sheet needs to be considered, and workability is improved.
[0009]
The mountain-shaped polygon is preferably a mountain-shaped trapezoid or a mountain-shaped pentagon. By making the cross-sectional shape of the convex prism portion a mountain-like trapezoid or a mountain-like pentagon in this manner, the interlayer interface inclined at a predetermined angle is formed relatively large, and the bending function is improved. In particular, in the case of the mountain-shaped pentagon, in addition to the side surface of the protruding ridge prism portion, the tip portion also has an inclined surface, so that the number of interlayer interfaces contributing to the refraction of transmitted light increases, so that the bending function is further enhanced. .
[0010]
Preferably, the plurality of convex prism portions are juxtaposed at predetermined intervals. By arranging a plurality of convex ridge prisms in parallel at intervals as described above, relatively perpendicular incident light is transmitted as it is in the space between the convex ridge prisms, and relatively inclined incident light is transmitted to the convex prism. The light can be refracted toward the normal direction and transmitted through the inclined interface formed by the portion, and as a result, the emitted light beam on the normal direction can be increased.
[0011]
It is preferable that the predetermined interval is smaller than the width of the ridge prism portion (base portion width). In this way, by reducing the interval between the convex prism portions than the width of the convex prism portions, it is possible to reduce the occurrence of stray light due to the incidence of oblique rays on the interval between the convex prism portions, and to reduce the occurrence of stray light on the normal direction side. The emitted light can be increased.
[0012]
It is preferable that a concave portion having a V-shaped cross section is provided at a space between the plurality of convex prism portions. As described above, the V-shaped concave ridges provided in the space between the convex prisms allow relatively perpendicular incident light among the light entering the space between the convex prisms to pass through as it is, The inclined incident light beam can be reflected and reused, and as a result, the outgoing light beam in the normal direction can be increased.
[0013]
It is preferable that the resin layer having the convex prism portion and the resin layer laminated on the back surface of the resin layer have different refractive indexes. By making the refractive indexes of the pair of resin layers constituting the interlayer interface contributing to refraction in the normal direction side different as described above, the angle-varying function is enhanced, and the outgoing light rays in the normal direction side can be increased. it can.
[0014]
It is preferable that the refractive index of the resin layer laminated on the back surface of the resin layer be larger than the refractive index of the resin layer having the convex prism portion. By making the refractive index of the resin layer on the incident side constituting the interlayer interface larger than the refractive index of the resin layer on the emitting side, refraction in the normal direction becomes possible, and emission in the normal direction becomes possible. Light rays can be increased.
[0015]
The outermost surface of the optical sheet may be a substantially smooth surface. By smoothing the outermost surface in this way, local stress is reduced to act on the optical sheet, and temporal deformation, wear, etc. of the shape of the interface between the layers contributing to the bending function are prevented. In addition, the deterioration of the deflection function is prevented.
[0016]
The optical sheet preferably has a plurality of spherical lens portions on the outermost surface. As described above, since the plurality of spherical lens portions provided on the outermost surface have a lens-like refraction function, the optical sheet can have a light diffusing function and a light condensing function in addition to the angle-changing function. Therefore, the number of optical sheets required for the backlight unit can be reduced, and the viewing angle, quality, front luminance, and the like can be increased.
[0017]
Also, a plurality of spindle-shaped lens portions may be provided on the outermost surface with their central axes aligned in substantially the same direction. By having a plurality of spindle-shaped lens portions on the outermost surface as described above, the optical sheet has a large diffusion action in the direction perpendicular to the central axis of the spindle-shaped lens portion, and the diffusion in the direction parallel to the central axis of the spindle-shaped lens portion. An anisotropic diffusion function with a small effect can be achieved. Therefore, the left, right, up, and down viewing angles of the backlight unit can be individually controlled.
[0018]
The resin layer preferably contains a light diffusing agent. As described above, the light diffusing agent contained in the resin layer allows the optical sheet to exhibit a good light diffusing function and a light condensing function, thereby reducing the number of optical sheets required for the backlight unit, and improving the quality and frontal luminance. Etc. can be improved.
[0019]
Further, it is preferable that a light diffusing layer is provided on the outermost surface, and the light diffusing layer contains a light diffusing agent in a binder. As described above, the light diffusing agent contained in the light diffusing layer can provide a good light diffusing function and a good light condensing function. In addition, by including the light diffusing agent in the light diffusing layer laminated on the outermost surface, scattering inside the resin layer is prevented, and obstruction of the bending function by a plurality of resin layers is prevented. As a result, according to the optical sheet, both the deflection function and the light diffusion function can be enhanced, and these functions can be individually controlled. Further, fine lens-like irregularities are formed almost uniformly on the surface of the light diffusing layer, which is the outermost surface, by a light diffusing agent. Light function is remarkably improved.
[0020]
Further, it is preferable that the anti-sticking layer is provided on the rearmost surface, and the anti-sticking layer contains beads dispersed in a binder. By providing the sticking prevention layer in which beads are dispersed and contained in the binder as described above, sticking (optical adhesion) with a light guide plate or a prism sheet disposed so as to overlap with the optical sheet is prevented, and a screen of a liquid crystal display device is provided. Luminance unevenness is suppressed.
[0021]
Therefore, in a backlight unit for a liquid crystal display device that guides the light emitted from the lamp to the surface side by dispersing, the variable angle function is high, and the optical sheet having the optical function such as the light diffusion function is provided. The number of optical sheets provided is reduced, and the backlight unit is made thinner, the brightness is improved, and the cost is reduced.
[0022]
Here, the “mountain-shaped polygon” means a polygon whose width decreases in the direction toward the tip end, specifically, a triangle, a mountain-shaped trapezoid (a trapezoid whose base apexes are acute), a mountain A pentagonal pentagon (a pentagon in which a triangle is continuous from the top of a mountain trapezoid), a hexagonal hill (a hexagon in which a mountain-shaped trapezoid continues from the top of a mountain trapezoid), and the like. The “spherical lens part” means a convex part or a concave part having a partial sectional shape of a sphere. The “spindle shape” means a shape in which both ends of a cylinder whose axial length is larger than its diameter are progressively thinner, and does not have a cylindrical portion (a linear portion in the circumferential axis direction) at an intermediate portion. The concept includes a case, for example, and includes a spheroid rotating around a long axis, a rotator rotating an arc around its chord, and the like. The “spindle-shaped lens portion” means a convex portion or a concave portion having a spindle-shaped partial cross-sectional shape.
[0023]
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 sectional view showing an optical sheet according to an embodiment of the present invention, FIG. 2 is a schematic sectional view showing an edge light type backlight unit including the optical sheet of FIG. 1, and FIGS. FIG. 2 is a schematic cross-sectional view illustrating an optical sheet according to a mode different from the optical sheet of FIG. 1.
[0024]
The optical sheet 1 of FIG. 1 includes a base layer 2, a prism layer 3 disposed on the surface side of the base layer 2, and an intermediate embedding filled between the base layer 2 and the prism layer 3. And a layer 4. The base layer 2, the prism layer 3, and the intermediate burying layer 4 correspond to the resin layer.
[0025]
The base material layer 2 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 2 is not particularly limited, and includes, for example, polyethylene terephthalate, polyethylene naphthalate, acrylic resin, polycarbonate, polystyrene, polyolefin, cellulose acetate, weather resistant vinyl chloride, and the like. . Among them, polyethylene terephthalate having excellent transparency and high strength is preferable, and polyethylene terephthalate having improved bending performance is particularly preferable.
[0026]
The thickness (average thickness) of the base layer 2 is not particularly limited, but is, for example, 10 μm to 500 μm, preferably 35 μm to 250 μm, and particularly preferably 50 μm to 188 μm. When the thickness of the base material layer 2 is less than the above range, inconveniences such as curling easily occurring when the resin composition for forming the intermediate embedding layer 4 is applied and difficulty in handling are caused. Occurs. Conversely, if the thickness of the base material layer 2 exceeds the above range, the brightness of the liquid crystal display device may be reduced, and the thickness of the backlight unit may be increased, contradicting the demand for thinner liquid crystal display devices. It will be.
[0027]
The prism layer 3 is formed of a transparent, especially colorless and transparent synthetic resin because it is necessary to transmit light rays, similarly to the base layer 2. The synthetic resin used for the prism layer 3 is not particularly limited. 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 them, an active energy ray-curable resin, such as an ultraviolet ray-curable resin or an electron beam-curable resin, which is excellent in the moldability of the ridge prism portion 5 is particularly preferable.
[0028]
On the rear surface of the prism layer 3, a plurality of convex prism portions 5 are formed in a stripe shape. The cross-sectional shape of the convex stripe prism portion 5 is a bilaterally symmetric mountain-like trapezoidal shape (equilateral trapezoidal shape having a shorter bottom than the base). Therefore, the convex prism portion 5 has a pair of inclined surfaces 6 inclined at a predetermined angle with respect to the sheet surface. The plurality of convex stripe prism portions 5 are arranged side by side at a predetermined pitch A, and are arranged side by side at a predetermined interval B. The predetermined interval B is set to be larger than the width (base width) C of the ridge prism portion 5.
[0029]
The inclination angle α of the inclined surface 6 with respect to the sheet surface is not particularly limited, and the outgoing light beam is directed in the normal direction in consideration of the refractive index difference between the prism layer 3 and the intermediate embedding layer 4 and the incident angle of the incident light beam. It may be designed appropriately to bend to the side. In the case of a general edge light type backlight unit, the lower limit of the inclination angle α of the inclined surface 6 with respect to the sheet surface is preferably 70 °, and particularly preferably 75 °. On the other hand, the upper limit of the inclination angle α is preferably 90 °, particularly preferably 85 °. Among them, the inclination angle α of about 80 ° is most preferable.
[0030]
The intermediate embedding layer 4 is densely filled between the front surface of the base material layer 2 and the back surface of the prism layer 3. Specifically, the intermediate buried layer 4 may be filled in a layer shape between the base material layer 2 and the prism layer 3, and the concave ridge formed between the convex prism portions 5 on the back surface of the prism layer 3. Only the part may be filled. That is, the base layer 2 and the prism layer 3 may be separated from each other by the intermediate embedding layer 4, and the protruding ridge portion 5 of the prism layer 3 may be in contact with the base layer 2. The intermediate embedding layer 4 is formed of a transparent, particularly colorless and transparent synthetic resin because it is necessary to transmit light rays, similarly to the base layer 2. The synthetic resin used for the intermediate embedding layer 4 is not particularly limited, and examples thereof include an acrylic resin, a polyurethane, a polyester, a fluororesin, a silicone resin, a polyamideimide, an epoxy resin, and an active energy ray-curable resin. No.
[0031]
The base layer 2, the prism layer 3 and the intermediate burying layer 4 may contain, for example, a filler, a plasticizer, a stabilizer, a deterioration inhibitor, a dispersant, and the like, in addition to the synthetic resin. .
[0032]
The optical sheet 1 has an interlayer interface (an interlayer interface between the prism layer 3 and the intermediate burying layer 4) inclined at a predetermined angle with respect to the sheet surface by the inclined surface 6 of the convex prism portion 5 in a stripe shape. . For this reason, the optical sheet 1 has a high angle-changing function of effectively directing the transmitted light beam incident from the back surface to the normal direction side by the action of refraction, reflection, and the like at the inclined striped interlayer interface. Further, since the convex stripe portion 5 having the function of changing the angle forms an interlayer interface and is embedded in the sheet, the shape of the interface is maintained over time, and the deterioration of the function of changing the angle is prevented. Furthermore, since the optical sheet 1 has the predetermined interval B between the convex prism portions 5, the relatively perpendicular incident light beam is transmitted as it is at the interval portion, and the relatively inclined incident light beam is inclined by the convex prism portion 5. The light can be refracted and reflected toward the normal direction side at the interface and transmitted, and as a result, the emitted light beam on the normal direction side can be increased. Further, since the predetermined interval B is made smaller than the width C of the convex prism portion 5, the generation of stray light which does not exit to the front surface side can be reduced, and the exit light beam in the normal direction can be increased.
[0033]
It is preferable to make the refractive index of the prism layer 3 different from that of the intermediate burying layer 4. As described above, by making the refractive indices of the two layers 3 and 4 constituting the interlayer interface contributing to the angle-changing function different, the angle-changing function can be enhanced and the number of rays emitted in the normal direction can be increased. Preferably, the refractive index of the intermediate burying layer 4 on the rear surface side is larger than the refractive index of the prism layer 3 on the front surface side. By making the refractive index of the intermediate buried layer 4 on the incident side constituting the interlayer interface larger than the refractive index of the prism layer 3 on the exit side in this manner, the inclined surface 6 of the convex stripe prism portion 5 that is incident on the incident light beam is formed. The refraction function is mainly exerted, and the bending function is further enhanced.
[0034]
Refractive index n of intermediate buried layer 4 on the back side 1 And the refractive index n of the prism layer 3 on the front side 2 Difference (n 1 -N 2 The lower limit of ()) is preferably 0.05, particularly 0.08, and more preferably 0.10. On the other hand, the upper limit of the refractive index difference is preferably 0.35, particularly 0.30, and more preferably 0.20. Since the optical sheet 1 has the function of changing the angle due to the inclined interlayer interface as described above, a sufficient function of changing the angle is exhibited even with such a relatively small refractive index difference. Therefore, a general synthetic resin is used as a material for forming the prism layer 3 and the intermediate burying layer 4, and reduction in manufacturing cost is promoted.
[0035]
The method for producing the optical sheet 1 is not particularly limited as long as a laminate having the above structure can be formed, and various methods are employed. In particular, (1) the base layer 2 and the prism layer 3 are formed beforehand, and the respective layers are laminated by extruding the resin composition constituting the intermediate embedding layer 4 between the two layers 2 and 3 by a T-die method or the like. And (2) forming the intermediate embedding layer 4 on the surface of the base material layer 2 with an ultraviolet curable resin or the like, and coating the prism layer 3 on the surface of the intermediate embedding layer 4 by coating with an ultraviolet curable resin or the like. The method of laminating is suitable.
[0036]
The method for forming the base material layer 2 is not particularly limited, and a known method suitable for the above-mentioned forming material is employed. Generally, (a) extrusion molding such as a T-die method or inflation method for extruding a molten synthetic resin into a film, or (b) extruding a molten synthetic resin into a film from a T-die, and then stretching in two orthogonal directions. And (c) casting a synthetic resin dissolved in a solvent through a plate-shaped mold such as a stainless steel belt and drying the solvent.
[0037]
The method for forming the prism layer 3 in the manufacturing method (1) and the intermediate burying layer 4 in the manufacturing method (2) is not particularly limited as long as a structure having stripe-shaped ridges can be formed. In general,
(A) A synthetic resin is laminated on a sheet type having a shape in which the back surface shape of the prism layer 3 (or the surface shape of the intermediate embedding layer 4) is inverted, and the sheet type is peeled off. A method of forming layer 4),
(B) an injection molding method of injecting a molten resin into a mold having an inverted shape of the back surface of the prism layer 3 (or the front surface of the intermediate embedding layer 4);
(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) A molten sheet-like resin is passed through a nip between a roll having an inverted shape of the back surface of the prism layer 3 (or the front surface of the intermediate embedding layer 4) and another roll to transfer the shape. Extruded sheet molding method,
(E) An ultraviolet-curable resin is applied to the substrate film, pressed onto a roll having the same inverted shape as above, and the shape is transferred to an uncured ultraviolet-curable resin. How to cure,
(F) Method of using electron beam-curable resin instead of ultraviolet-curable resin
and so on.
[0038]
As a method for forming the prism layer 3 in the manufacturing method of the above (2), for example, (a) an ultraviolet curable resin is applied to the surface of the intermediate embedding layer 4 and pressed with a smooth roll and then irradiated with ultraviolet light. A method of curing and a method of (b) applying a thermosetting resin on the surface of the intermediate embedding layer 4 and thermosetting are preferably used.
[0039]
The edge light type backlight unit shown in FIG. 2 includes a light guide plate 7 and a pair of linear lamps 8 disposed on the opposite sides of the light guide plate 7. The optical sheets 1 are arranged in an overlapping manner. The light emitted from the lamp 8 and emitted from the surface of the light guide plate 7 has a relatively strong peak inclined at a predetermined angle with respect to the normal direction. With the single optical sheet 1 provided, the optical sheet 1 can be directed more toward the normal direction. Therefore, according to the backlight unit, it is possible to reduce the number of optical sheets (prism sheets and the like) required in the related art, and to promote the reduction in thickness, improvement in brightness, and reduction in cost of the backlight unit. Further, since the edge light type backlight unit includes a pair of lamps 8 on the opposite sides of the light guide plate 7, the light emitted from the surface of the light guide plate 7 is inclined symmetrically with respect to the lamp 8 in the vertical direction. However, as described above, since the cross-sectional shape of the ridge prism portion 5 of the optical sheet 1 is left-right symmetric as described above, and the optical sheet 1 has alternately symmetrically inclined stripe-like interlayer interfaces, a pair of mating pairs is formed. Both light beams emitted from the lamp 8 and symmetrically inclined can be similarly directed to the normal direction side.
[0040]
The optical sheet 11 shown in FIG. 3 includes a base layer 2, a prism layer 12 disposed on the surface side of the base layer 2, and an intermediate embedding filled between the base layer 2 and the prism layer 12. And a layer 4. Since the base material layer 2 and the intermediate burying layer 4 are the same as those of the optical sheet 1, the same numbers are given and the description is omitted. The material and manufacturing method of the prism layer 12 are the same as those of the optical sheet 1, but the cross-sectional shape of the convex prism portion 13 formed in a stripe on the back surface is different from that of the optical sheet 1.
[0041]
The cross-sectional shape of the ridge prism portion 13 is a bilaterally symmetric mountain-shaped pentagon. Accordingly, the protruding ridge prism portion 13 has a first inclined surface 14 on the base portion side and a second inclined surface 15 on the distal end portion side. The inclination angle α of the first inclined surface 14 with respect to the sheet surface is the same as that of the inclined surface 6 of the optical sheet 1. On the other hand, the lower limit of the inclination angle β of the second inclined surface 15 is preferably 35 °, particularly 40 °, and the upper limit of the inclination angle β is preferably 55 °, particularly 50 °. Among them, the inclination angle β of about 45 ° is most preferable.
[0042]
According to the optical sheet 11, the second inclined surface 15 having a V-shaped cross section is also provided on the tip end side of the convex stripe prism portion 13, and the interlayer inclined at a predetermined angle with respect to the sheet surface by the second inclined surface 15. Since the interface has a stripe shape, the inclined incident light beam is effectively transmitted to the normal direction side, and the angle-changing function is further enhanced.
[0043]
The optical sheet 21 shown in FIG. 4 includes a base layer 2, a prism layer 22 disposed on the surface side of the base layer 2, and an intermediate embedding filled between the base layer 2 and the prism layer 22. And a layer 4. The base layer 2, the intermediate burying layer 4, and the protruding prism portions 5 on the back surface of the prism layer 22 are the same as those of the optical sheet 1, and thus are denoted by the same reference numerals and description thereof is omitted. The constituent material and manufacturing method of the prism layer 22 are the same as those of the optical sheet 1.
[0044]
The prism layer 22 of the optical sheet 21 has a concave stripe portion 23 having a V-shaped cross section at an interval between the convex stripe prism portions 5. Therefore, in the optical sheet 21, the interlayer interface inclined by the concave ridges 23 is also formed between the convex ridges 5, and the function of changing the angle is further improved.
[0045]
The optical sheet 31 shown in FIG. 5 includes a base layer 32 and a prism layer 3 laminated on the front side of the base layer 32. Since the prism layer 3 is the same as the optical sheet 1, the same reference numerals are given and the description is omitted. The base layer 32 has a shape in which the base layer 2 of the optical sheet 1 and the intermediate embedding layer 4 are integrated. Therefore, similarly to the optical sheet 1, the optical sheet 31 also has an interlayer interface inclined by a predetermined angle by the convex stripe prism portion 5 in a stripe shape, and has a good angle-changing function by refraction and reflection at the interlayer interface. Have.
[0046]
The method for manufacturing the optical sheet 31 is not particularly limited as long as a laminate having the above structure is formed. For example, any one of the base layer 32 and the prism layer 3 may be formed by using the above (1) of the optical sheet 1. The method of forming the other layer by the same method as the prism layer 3 in the method (2) of manufacturing the optical sheet 1 is preferably used.
[0047]
The optical sheet 41 shown in FIG. 6 includes a base layer 2, a prism layer 42 disposed on the surface side of the base layer 2, and an intermediate embedding filled between the base layer 2 and the prism layer 42. And a layer 4. The base layer 2, the intermediate embedding layer 4, and the protruding prism portions 5 on the back surface of the prism layer 42 are the same as those of the optical sheet 1, and thus are denoted by the same reference numerals and description thereof is omitted. Therefore, similarly to the optical sheet 1, the optical sheet 41 has an interlayer interface inclined at a predetermined angle by the convex stripe prism portion 5 in a stripe shape, and a good angle-changing function by refraction and reflection at the interlayer interface. have.
[0048]
The prism layer 42 has a plurality of hemispherical convex lens portions 43 on the surface. The hemispherical convex lens portion 43 is disposed on the surface of the prism layer 42 in a densely packed structure. In the optical sheet 41, since the hemispherical convex lens portion 43 has a lens-like refraction effect on the transmitted light, the optical sheet 41 can have a light diffusing function and a light condensing function in addition to the above-described variable angle function. Further, the optical sheet 41 has a light diffusion function due to the hemispherical convex lens portion 43 on the outermost surface. As a result, the optical sheet 41 can enhance both the variable angle function and the light diffusion function, and can individually control each of these functions. Note that the hemispherical convex lens portion 43 may be formed integrally with the prism layer 42 or may be added thereto.
[0049]
The method for manufacturing the optical sheet 41 is not particularly limited as long as the laminate having the above structure is formed. For example, the method (2) for manufacturing the optical sheet 1 is preferably used, and the surface of the prism layer 42 is used. It is preferable to apply ultraviolet curing or thermosetting after pressing the coated surface of the ultraviolet curable resin or thermosetting resin with a roll having an inverted shape on the surface.
[0050]
The optical sheet 51 shown in FIG. 7 includes a base layer 2, a prism layer 52 disposed on the surface side of the base layer 2, and an intermediate embedding filled between the base layer 2 and the prism layer 52. And a layer 4. The base layer 2, the intermediate burying layer 4, and the protruding ridge prism portion 5 on the back surface of the prism layer 52 are the same as those of the optical sheet 1, and thus are denoted by the same reference numerals and description thereof is omitted. Therefore, similarly to the optical sheet 1, the optical sheet 51 also has an interlayer interface inclined at a predetermined angle by the ridge prism portion 5 in a stripe shape, and a good angle changing function by refraction and reflection at the interlayer interface. have.
[0051]
The prism layer 52 has a plurality of half spindle-shaped convex lens portions 53 on the surface, and the center axes of these half spindle-shaped convex lens portions 53 are aligned in substantially the same direction. In the optical sheet 51, since the half-spun spindle-shaped convex lens portion 53 has a lens-like refraction effect on a transmitted light beam, the optical sheet 51 can have a light diffusing function in addition to the variable angle function. The light diffusion function of the optical sheet 51 is such that the diffusion action in the direction perpendicular to the central axis of the half spindle-shaped convex lens part 53 is large, and the diffusion action in the direction parallel to the central axis of the half spindle-shaped convex lens part 53 is small. have. Therefore, the left, right, up, and down viewing angles of the backlight unit can be individually controlled.
[0052]
The optical sheet 61 shown in FIG. 8 includes a base layer 2, a prism layer 3 disposed on the surface of the base layer 2, and an intermediate embedded layer filled between the base layer 2 and the prism layer 3. 4 and a light diffusion layer 62 laminated on the surface of the prism layer 3. Since the base layer 2, the prism layer 3, and the intermediate burying layer 4 are the same as those of the optical sheet 1, the same reference numerals are given and the description is omitted. Therefore, similarly to the optical sheet 1, the optical sheet 61 has an interlayer interface inclined at a predetermined angle by the convex stripe prism portion 5 in a stripe shape, and a good angle-changing function due to refraction and reflection at the interlayer interface. have.
[0053]
The light diffusion layer 62 has a binder 63 and a light diffusion agent 64 dispersed in the binder 63. By dispersing the light diffusing agent 64 in the light diffusing layer 62 in this manner, the light transmitted through the light diffusing layer 62 from the back side to the front side can be diffused uniformly. Further, fine irregularities are formed substantially uniformly on the surface of the light diffusing layer 62 by the light diffusing agent 64, and each concave portion and convex portion of the fine irregularities are formed in a lens shape. The optical sheet 61 exhibits an excellent light diffusion function due to the lens-like refraction effect of the fine unevenness, and the refraction function of refracting the transmitted light beam toward the normal direction due to the light diffusion function and the method of controlling the transmitted light beam. It also has a light condensing function that condenses light macroscopically in the linear direction. The thickness of the light diffusion layer 62 (meaning the thickness of the binder 63 excluding the light diffusion agent 64) is not particularly limited, but is, for example, about 10 μm or more and 30 μm or less. Further, the binder 63 is transparent because it is necessary to transmit light, and is preferably colorless and transparent.
[0054]
The light diffusing agent 64 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.
[0055]
The shape of the light diffusing agent 64 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.
[0056]
The lower limit of the average particle diameter of the light diffusing agent 64 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 64 is preferably 50 μm, particularly 20 μm, and more preferably 15 μm. If the average particle diameter of the light diffusing agent 64 is less than the above range, the unevenness of the surface of the light diffusing layer 62 formed by the light diffusing agent 64 becomes small, and the light diffusing property required as an optical sheet may not be satisfied. Conversely, if the average particle diameter of the light diffusing agent 64 exceeds the above range, the thickness of the optical sheet 61 increases, and uniform diffusion becomes difficult.
[0057]
The lower limit of the blending amount of the light diffusing agent 64 (the blending amount in terms of solid content with respect to 100 parts of the polymer component in the polymer composition as the material for forming the binder 63) is preferably 10 parts, particularly 20 parts, and more preferably 50 parts. 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 64 is less than the above range, the light diffusing property becomes insufficient, while if the amount of the light diffusing agent 64 exceeds the above range, the light diffusing agent 64 is fixed. This is because the effect of doing so is reduced.
[0058]
The binder 63 is formed by curing (crosslinking or the like) a polymer composition containing a base polymer. With this binder 63, the light diffusing agent 64 is arranged and fixed at substantially equal density over the entire surface of the prism layer 3. The polymer composition for forming the binder 63 is, for example, a fine inorganic filler, a curing agent, a plasticizer, a dispersant, various leveling agents, an antistatic agent, an ultraviolet absorber, an antioxidant, in addition to the base polymer. , A viscosity modifier, a lubricant, a light stabilizer and the like may be appropriately compounded.
[0059]
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 which has high workability and can easily form the light diffusion layer 62 by means such as coating is preferable. In addition, the base polymer used for the binder 63 is transparent because it is necessary to transmit light, and is preferably colorless and transparent.
[0060]
As the polyol, for example, (a) a polyester polyol obtained under the condition of excess hydroxyl group and (b) a monomer component containing a hydroxyl group-containing unsaturated monomer are obtained by polymerization, and (meth) acrylic unit And the like. The binder 63 using such a polyester polyol or an acrylic polyol as a base polymer has high weather resistance and can suppress yellowing and the like of the light diffusion layer 62. Note that either one of the polyester polyol and the acrylic polyol may be used, or both may be used.
[0061]
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.
[0062]
As the base polymer, a polyol having a cycloalkyl group is preferable. As described above, by introducing a cycloalkyl group into the base polymer (polyol) constituting the binder 63, hydrophobicity such as water repellency and water resistance of the binder 63 is increased, and the binder 63 is subjected to a high temperature and high humidity condition. The bending resistance, dimensional stability and the like of the optical sheet 61 are improved. In addition, the basic properties of the coating film such as the hardness, weather resistance, texture, and solvent resistance of the light diffusion layer 62 are improved. Further, the affinity with the fine inorganic filler having the organic polymer fixed on the surface described later and the uniform dispersibility of the fine inorganic filler are further improved.
[0063]
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.
[0064]
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.
[0065]
When a polyol is used as the base polymer as described above, the polymer composition may contain a polyisocyanate compound as a curing agent. The polyisocyanate compound is a derivative such as a dimer, trimer, or tetramer obtained by polymerizing diisocyanate. The curing reaction rate of the polymer composition is increased by the incorporation of the polyisocyanate compound. Therefore, even if a cationic antistatic agent contributing to the dispersion stability of the fine inorganic filler is contained in the polymer composition, the cationic antistatic agent can be used. This can sufficiently compensate for the decrease in the curing reaction rate due to the agent, and can further enhance the productivity.
[0066]
The polyisocyanate compound is preferably a xylene diisocyanate derivative or a mixture of the xylene diisocyanate derivative and an aliphatic diisocyanate derivative. Since the xylene diisocyanate derivative has a large effect of improving the reaction rate of the polymer composition, and among the aromatic diisocyanate derivatives, yellowing and deterioration due to heat or ultraviolet rays are relatively small, the light transmittance of the optical sheet 61 with time is reduced. Reduction can be reduced. On the other hand, the aliphatic diisocyanate derivative has a small effect on improving the reaction rate as compared with the aromatic diisocyanate derivative, but the yellowing and deterioration due to ultraviolet rays and the like are remarkably small. And the effect of preventing yellowing and the like can be achieved in a well-balanced manner.
[0067]
As the aliphatic diisocyanate derivative, an isophorone diisocyanate derivative and a hexamethylene diisocyanate derivative are preferable. Among the aliphatic diisocyanate derivatives, the isophorone diisocyanate derivative and the hexamethylene diisocyanate derivative have a relatively large effect of improving the curing reaction rate, and can promote the above-described productivity and heat resistance.
[0068]
The type of the derivative of the diisocyanate is preferably a TMP adduct type, an isocyanurate type, or a burette type. According to these types of derivatives, the above-mentioned curing reaction rate can be effectively increased.
[0069]
The lower limit of the blending amount of the polyisocyanate compound (the blending amount in terms of solid content with respect to 100 parts of the polymer component in the polymer composition) is preferably 2 parts, and particularly preferably 5 parts. On the other hand, the upper limit of the amount of the curing agent is preferably 20 parts, and particularly preferably 15 parts. By setting the amount of the polyisocyanate compound in the above range, the effect of improving the curing reaction rate of the polymer composition can be effectively exerted.
[0070]
Further, the polymer composition may contain a fine inorganic filler. By dispersing and containing the fine inorganic filler in the binder 63, the heat resistance of the light diffusion layer 62 and thus the entire optical sheet 61 can be increased, and as a result, the backlight unit is exposed to the heat of the lamp or moisture in the air. Even so, the deformation of the optical sheet 61 can be remarkably suppressed.
[0071]
The inorganic substance constituting the fine inorganic filler is not particularly limited, but an inorganic oxide is particularly 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. 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.
[0072]
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 optical sheet 61 may become cloudy under the influence of the short wavelength and the transparency of the optical sheet 61 may be reduced.
[0073]
The lower limit of the blending amount of the fine inorganic filler (only the inorganic component) (the blending amount in terms of solid content with respect to 100 parts of the polymer in the polymer composition) is preferably 10 parts, and particularly preferably 50 parts. On the other hand, the upper limit of the amount of the fine inorganic filler is preferably 500 parts, and particularly preferably 200 parts. This is because if the blending amount of the fine inorganic filler is less than the above range, the heat resistance of the optical sheet 61 may not be able to be sufficiently exhibited, and conversely, if the blending amount exceeds the above range. This is because blending into the polymer composition becomes difficult, and the light transmittance of the light diffusion layer 62 may be reduced.
[0074]
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 63 and the affinity with the binder 63 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.
[0075]
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 compatible 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.
[0076]
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.
[0077]
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. With such an alkoxy group, affinity with a matrix resin constituting the binder 63 and dispersibility in the binder 63 can be improved.
[0078]
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.
[0079]
The content of the organic polymer in the organic polymer-fixed fine inorganic filler 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.
[0080]
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 63; 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 63 are bonded in a crosslinked structure, and the storage stability, stain resistance, flexibility, weather resistance, storage stability, and the like are improved. It becomes glossy.
[0081]
Further, an antistatic agent may be contained in the polymer composition. 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 that has a relatively large antistatic effect and does not impair the stability of the dispersed state of the fine inorganic filler is preferable. Further, among the cationic antistatic agents, ammonium salts and betaines which can further promote the antistatic property for the above-mentioned highly hydrophobic binder 63 are particularly preferable.
[0082]
The lower limit of the blending amount of the antistatic agent (the blending amount in terms of solid content with respect to 100 parts of the polymer component in the polymer composition) is preferably 0.1 part, and particularly preferably 0.5 part. On the other hand, the upper limit of the amount of the antistatic agent is preferably 10 parts, more preferably 5 parts. If the amount of the antistatic agent is smaller than the lower limit, the above-described antistatic effect may not be sufficiently exerted. Conversely, if the amount of the antistatic agent exceeds the upper limit, the charge may be reduced. This is because the incorporation of the inhibitor may cause inconveniences such as a decrease in total light transmittance and a decrease in strength.
[0083]
The method for forming the light diffusion layer 62 includes, for example, (a) a step of producing a light diffusion layer coating liquid by mixing a light diffusion agent 64 with a polymer composition constituting the binder 63; A step of applying the coating liquid to the surface of the prism layer 3 to laminate the light diffusion layer 62.
[0084]
The optical sheet 61 can exhibit a good light diffusing function and a good light condensing function by the light diffusing agent 64 contained in the light diffusing layer 62. Further, since the optical sheet 61 has a light diffusion function by the light diffusion layer 62 on the outermost surface, it is possible to prevent the above-mentioned angle changing function from being hindered and to control each of these functions individually.
[0085]
The optical sheet 71 shown in FIG. 9 includes a base layer 2, a prism layer 3 disposed on the surface of the base layer 2, and an intermediate embedded layer filled between the base layer 2 and the prism layer 3. 4, a light diffusion layer 62 laminated on the front surface of the prism layer 3, and a sticking prevention layer 72 laminated on the back surface of the base material layer 2. The base layer 2, the prism layer 3, and the intermediate burying layer 4 are the same as those of the optical sheet 1, and the light diffusion layer 62 is the same as the optical sheet 61. . Therefore, like the optical sheet 1, the optical sheet 71 has an interlayer interface inclined by a predetermined angle by the convex prism portion 5 in a stripe shape, and has a good angle-changing function by refraction and reflection at the interlayer interface. have. In addition, the optical sheet 71 has a high light diffusion function and the like by the light diffusion layer 62, similarly to the optical sheet 61.
[0086]
The sticking prevention layer 72 includes a binder 73 and beads 74 dispersed in the binder 73. The binder 73 is also formed by curing (crosslinking and curing) the same polymer composition as the binder 63 of the light diffusion layer 62. The same material as the light diffusing agent 64 of the light diffusing layer 62 is used as the material of the beads 74. The thickness of the anti-sticking layer 72 (the thickness of the portion of the binder 73 excluding the beads 74) is not particularly limited, but is, for example, about 1 μm or more and 10 μm or less.
[0087]
The compounding amount of the beads 74 is relatively small, and the beads 74 are separated from each other and dispersed in the binder 73, and most of the beads 74 have their lower ends projecting a very small amount from the binder 73. Therefore, when the optical sheet 71 is laminated on the light guide plate, the lower end of the projected bead 74 comes into contact with the surface of the light guide plate or the like, and the entire back surface of the optical sheet 71 does not come into contact with the light guide plate or the like. Thereby, sticking between the optical sheet 71 and the light guide plate or the like is prevented, and uneven brightness on the screen of the liquid crystal display device is suppressed.
[0088]
The method for forming the anti-sticking layer 72 includes, for example, (a) a step of producing a coating solution for the anti-sticking layer by mixing beads 74 with a polymer composition constituting the binder 73; Applying a layer coating solution to the back surface of the base material layer 2 to laminate the anti-sticking layer 72.
[0089]
The optical sheet 81 shown in FIG. 10 includes a base layer 2, a prism layer 82 disposed on the surface side of the base layer 2, and an intermediate embedding filled between the base layer 2 and the prism layer 82. And a layer 4. The base material layer 2 and the intermediate embedding layer 4 are the same as the optical sheet 1 described above, and the shape of the convex prism portion 13 on the back surface of the prism layer 82 is the same as that of the optical sheet 11. Since the concave ridges 23 provided between them are the same as those of the optical sheet 21, the same numbers are given and the description is omitted. Accordingly, the optical sheet 81 has a plurality of interlayer interfaces that are inclined at a predetermined angle by the first inclined surface 14, the second inclined surface 15, and the V-shaped inclined surface of the concave ridge portion 23 of the convex stripe prism portion 13 in a stripe shape. And has a good bending function due to the refraction and reflection at the interlayer interface.
[0090]
The prism layer 82 contains the light diffusing agent 64 in the binder 63. Since the binder 63 and the light diffusing agent 64 are the same as those of the optical sheet 61, the same reference numerals are given and the description is omitted. The optical sheet 81 can uniformly diffuse a light beam transmitted from the back side to the front side by the light diffusing agent 64 included in the prism layer 82. Further, fine irregularities are formed substantially uniformly on the surface of the prism layer 82 by the light diffusing agent 64, and each concave portion and convex portion of the fine irregularities are formed in a lens shape. The optical sheet 81 exhibits an excellent light diffusing function by the lens-like refraction of the fine unevenness, and the refraction function of refracting the transmitted light beam in the normal direction due to the light diffusion function and the method of controlling the transmitted light beam. It also has a light condensing function for macroscopically condensing light in the linear direction. Further, in the optical sheet 81, the portion having the light diffusion function and the like exists on the surface side of the interlayer interface (interlayer interface between the prism layer 82 and the intermediate embedding layer 4) having the angle-changing function. Is prevented.
[0091]
The method for manufacturing the optical sheet 81 is not particularly limited as long as the laminate having the above structure is formed. For example, the intermediate burying layer 4 is formed on the surface of the base material layer 2 with an ultraviolet curable resin or the like. Then, it is preferable to manufacture by applying the same resin composition as the material for forming the light diffusion layer 62 on the surface of the intermediate embedding layer 4.
[0092]
Note that the optical sheet of the present invention is not limited to the above-described embodiment. For example, the convex prism portions can be arranged side by side without leaving an interval, and the convex prism portion is wider than the convex prism portion width. It is also possible to increase the spacing between them. Further, a light diffusing agent can be contained in the base material layer or the intermediate embedding layer, and the light diffusing function can be exhibited by the light diffusing agent contained in the resin layer.
[0093]
【The invention's effect】
As described above, according to the optical sheet of the present invention, optical functions such as a variable angle function are remarkably improved. Therefore, according to the backlight unit including the optical sheet, the front luminance and the viewing angle can be increased.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view showing an optical sheet according to an embodiment of the present invention.
FIG. 2 is a schematic cross-sectional view showing an edge light type backlight unit including the optical sheet of FIG.
FIG. 3 is a schematic cross-sectional view showing an optical sheet having a different form from the optical sheet of FIG.
FIG. 4 is a schematic cross-sectional view showing an optical sheet in a form different from the optical sheets of FIGS. 1 and 3.
FIG. 5 is a schematic cross-sectional view showing an optical sheet having a form different from the optical sheets of FIGS. 1, 3 and 4;
FIG. 6 is a schematic cross-sectional view showing an optical sheet in a form different from the optical sheets of FIGS. 1 and 3 to 5;
FIG. 7 is a schematic cross-sectional view showing an optical sheet in a form different from the optical sheets of FIGS. 1, 3 to 6;
FIG. 8 is a schematic cross-sectional view showing an optical sheet having a form different from the optical sheets shown in FIGS. 1 and 3 to 7;
FIG. 9 is a schematic cross-sectional view showing an optical sheet having a form different from the optical sheets of FIGS. 1, 3 to 8;
FIG. 10 is a schematic cross-sectional view showing an optical sheet having a different form from the optical sheets shown in FIGS. 1 and 3 to 9;
FIG. 11 is a schematic perspective view showing a general edge light type backlight unit.
[Explanation of symbols]
1 Optical sheet
2 Base material layer
3 Prism layer
4 Intermediate embedded layer
5 Prism section
6 slope
7 Light guide plate
8 lamps
11 Optical sheet
12 Prism layer
13 convex prism
14 1st slope
15 2nd slope
21 Optical sheet
22 Prism layer
23 Concave strip
31 Optical sheet
32 Base material layer
41 Optical sheet
42 Prism layer
43 Hemispheric convex lens part
51 Optical sheet
52 prism layer
53 Half Spindle Shape Convex Lens
61 Optical sheet
62 Light diffusion layer
63 binder
64 light diffusing agent
71 Optical sheet
72 Sticking prevention layer
73 binder
74 beads
81 Optical Sheet
82 prism layer

Claims (16)

  1. An optical sheet for directing a transmitted light beam incident from the back side to the normal direction side,
    It has multiple resin layers,
    A plurality of convex stripe prism portions are formed in a stripe shape on the back surface of the resin layer constituting the interlayer interface,
    An optical sheet characterized in that the cross-sectional shape of the convex prism portion is a mountain-shaped polygon.
  2. The optical sheet according to claim 1, wherein the mountain-shaped polygon is bilaterally symmetric.
  3. The optical sheet according to claim 1, wherein the mountain-shaped polygon is a mountain-shaped trapezoid.
  4. The optical sheet according to claim 1, wherein the mountain-shaped polygon is a mountain-shaped pentagon.
  5. The optical sheet according to any one of claims 1 to 4, wherein the plurality of convex stripes are arranged side by side at predetermined intervals.
  6. The optical sheet according to claim 5, wherein the predetermined interval is smaller than a width of the ridge prism portion.
  7. The optical sheet according to claim 5, further comprising a concave portion having a V-shaped cross section at an interval between the plurality of convex prism portions.
  8. The optical sheet according to any one of claims 1 to 7, wherein a refractive index of the resin layer having the convex prism portion is different from a refractive index of a resin layer laminated on the back surface of the resin layer.
  9. The optical sheet according to claim 8, wherein the refractive index of the resin layer laminated on the back surface of the resin layer is larger than the refractive index of the resin layer having the convex stripe prism portion.
  10. The optical sheet according to any one of claims 1 to 9, wherein an outermost surface is a substantially smooth surface.
  11. The optical sheet according to any one of claims 1 to 9, having a plurality of spherical lens portions on the outermost surface.
  12. The optical sheet according to any one of claims 1 to 9, further comprising a plurality of spindle-shaped lens units on the outermost surface, wherein the center axes of these spindle-shaped lens units are aligned in substantially the same direction.
  13. The optical sheet according to any one of claims 1 to 12, wherein the resin layer contains a light diffusing agent.
  14. The optical sheet according to any one of claims 1 to 13, further comprising a light diffusing layer laminated on the outermost surface, wherein the light diffusing layer contains a light diffusing agent in a binder.
  15. The optical sheet according to any one of claims 1 to 14, further comprising a sticking prevention layer laminated on the rearmost surface, wherein the sticking prevention layer contains beads dispersedly in a binder.
  16. 16. A backlight unit for a liquid crystal display device for dispersing a light beam emitted from a lamp and guiding the light beam to a front surface side, comprising: the optical sheet according to any one of claims 1 to 15. Backlight unit for display device.
JP2002257030A 2002-09-02 2002-09-02 Optical sheet and back light unit using the sheet Pending JP2004094051A (en)

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