JP5457360B2 - Optical sheet manufacturing method, optical sheet, light source unit including the optical sheet, and display device - Google Patents

Description

  The present invention relates to a method for producing an optical sheet having a precise surface shape for exhibiting functionality. Further, the present invention relates to an optical sheet in which a precise surface shape manufactured by the manufacturing method significantly affects the performance, a light source unit including the optical sheet, and a display device.

  Thermoplastic resins are widely used as materials such as wood, metal, and glass from the viewpoints of heat resistance, impact resistance, weight, ease of processing, and the like. In particular, sheet materials are widely used as materials for exterior materials such as roofing materials, outer wall materials, etc., wood materials, metals, etc., interior materials such as top plates and inner wall materials, and outdoor signboards. Among these, the transparent thermoplastic resin is excellent in heat resistance, impact resistance, and transparency, so the sheet material is used as an optical material instead of glass for building materials such as window materials, for impact resistant transparent materials for automobile windows, Widely used in pressure-resistant transparent materials for large aquarium tanks.

  The surface shape of such a thermoplastic resin sheet is not only glossy and smooth, but also has an embossed tone with a fine concavo-convex pattern or a two-dimensional or three-dimensional regular concavo-convex pattern. In general, it is common to form continuously using a transfer roll during extrusion molding.

  These surface shapes lead to a thermoplastic embossed roll that is melted and softened on a metal embossing roll formed in a shape that reverses the pattern and unevenness to fully exhibit the original design performance on the outer peripheral surface. The shape of the roll is formed by transferring it onto a sheet. Specific examples of the disclosure include the following patent documents.

  Patent Document 1 discloses a method for producing an optical sheet that is free from appearance defects such as waving, uneven thickness, and wrinkles as a whole by adjusting the temperature of the extruded thermoplastic resin.

  In Patent Document 2, in a method for producing a surface-molded resin sheet in which at least one surface is surface-molded by extrusion molding, precise irregularities are molded by adjusting the temperature of the die or the resin temperature immediately before the surface molding. It is disclosed that things are possible.

  Patent Document 3 discloses that in a method for producing a polycarbonate resin sheet in which at least both surfaces are surface-molded by extrusion molding, the surface molding can be efficiently transferred to both surfaces by adjusting the temperature of the die and the temperature of each cooling roll. Is disclosed.

  Further, in Patent Document 4, in the method for producing a thermoplastic resin sheet that is not subjected to surface shaping using a plurality of rolls, there is variation in thickness unevenness and retardation by adjusting the peripheral speed of the second roll and the third roll. It is disclosed that an optically suitable sheet can be obtained with less.

  In Patent Document 5, the thermoplastic resin discharged from the die is disposed downstream of the peripheral speed of the second roll (mold roll) adjacent to the first roll (nip roll) and the third roll (peeling roll) that subsequently contacts. It is disclosed that by adjusting the peripheral speed of the provided take-up roll (draw roll), surface shaping can be efficiently performed, the warpage of the entire sheet is eliminated, and an optically suitable sheet is obtained. .

  Patent Document 6 discloses that the thermoplastic resin discharged from the die adjusts the peripheral speed of the first roll (mirror roll) and the peripheral speed of the second roll (molding roll) that comes into contact with the thermoplastic resin. It is disclosed that fine surface molding can be efficiently performed rather than setting a mirror surface roll to 3 rolls.

JP 2003-245966 A JP-A-10-180846 Japanese Patent Laid-Open No. 6-190917 JP 2003-236914 A JP 2007-216481 A JP 2006-130901 A

  However, an optical sheet having a surface molding (for example, an optical element having a high molding rate and a thickness accuracy of 200 μm or less) that achieves high optical performance, which is used for a member of a flat panel display such as a liquid crystal type in recent years. The continuous production by the extruder is the solution means for adjusting the resin temperature of the thermoplastic resin during the extrusion described in Patent Documents 1 to 3, and the extrusion molding with the contents described in Patent Documents 4 to 5 The method of adjusting the peripheral speed of the roll at the time cannot be achieved. Moreover, even if these disclosures are simply combined and implemented, it is impossible to stably obtain a resin sheet with a high moldability and high thickness accuracy in the process, and an optical sheet using the same, and It was impossible to develop a direct light source unit and display device using the optical sheet.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a method of manufacturing an optical sheet with a surface shape that solves the above-described problems of the prior art and sufficiently exhibits the original design performance. It is another object of the present invention to provide an optical sheet produced by such a manufacturing method, a light source unit using the optical sheet, and a display device.

  As a first embodiment for achieving the above object, the present invention provides a method for producing an optical sheet that is surface-molded using a molding roll that has been surface-treated so that the optical element is molded into the sheet. An optical sheet manufacturing method characterized in that when the peripheral speed of the shaping roll is Va and the peripheral speed of the take-up roll (draw roll) is Vb, the peripheral speed Vb is 103 to 130% of the peripheral speed Va. provide.

  As a second embodiment, in the first embodiment, the optical element is shaped substantially parallel to the take-off direction, and the top of the convex or arc-shaped cross section is concave or the cross section is concave. Provided is a method for producing an optical sheet, which is a substantially bowl-shaped optical element in which a large number of concave arc-shaped valleys are alternately arranged in parallel.

  Furthermore, as a third embodiment, in the first and second embodiments, the distance between the top and the top of the substantially bowl-shaped optical element or the distance between the valley and the valley is 200 μm or less. A method for producing an optical sheet is provided.

  The optical sheet manufactured in this way exhibits excellent performance as an optical sheet, in particular, because the surface molding is transferred with a reproducible shape in accordance with the optical design. In addition, a light source unit and a display device using the optical sheet also exhibit excellent performance.

  The take-up direction is the sheet traveling direction, that is, the sheet longitudinal direction.

  As described above, according to the present invention, an optical sheet that sufficiently exhibits the original design performance can be efficiently manufactured. Further, the optical sheet of the present invention produced in this way exhibits excellent performance as an optical sheet, since the surface molding is transferred in accordance with the optical design. In addition, a light source unit and a display device using the optical sheet also exhibit excellent performance.

It is explanatory drawing of an example of the manufacturing process of the resin sheet by the extrusion molding of this invention. It is explanatory drawing of an example of the shaping roll by which the surface process was carried out so that a substantially bowl-shaped optical element was shape | molded substantially parallel to the take-up direction of a sheet | seat. It is explanatory drawing of an example of a shaping roll. It is explanatory drawing of an example of the manufacturing process of the resin sheet by the extrusion molding of this invention. It is explanatory drawing which shows the arrangement | positioning form which the roll group of FIG. 1, FIG. 4 can take. It is explanatory drawing which shows an example of the form of the substantially bowl-shaped lens of this invention. It is explanatory drawing which shows an example of the form of the substantially bowl-shaped lens of this invention.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings, but the present invention is not limited thereto.

  The present invention relates to a method for producing an optical sheet having a precise optical element (pitch of 200 μm or less) for exhibiting functionality on at least one side.

  The optical sheet of the present invention (in the present invention, “sheet” and “film” are used synonymously and both refer to a resin molded body having a thickness of 0.05 to 5 mm. Hereinafter, they are collectively referred to as “sheet”). The manufacturing method can be applied to any thermoplastic resin conventionally used for manufacturing a sheet. Specific examples include polyethylene, polypropylene, ethylene-propylene copolymer, polystyrene, polyacrylonitrile, acrylonitrile-styrene copolymer, polyvinyl chloride, polymethyl methacrylate, polyethylene terephthalate, polybutylene terephthalate, polycarbonate, and alicyclic structure. Polymer resin etc. are mentioned. Details will be described later.

<Basic configuration of process and equipment>
In the method for producing an optical sheet of the present invention, a sheet-like molten thermoplastic resin extruded from an extruder is passed through a gap between two rolls of a first roll and a second roll, and rolled into a sheet-like melt thermoplastic. A step of obtaining a resin, a step of transporting the rolled sheet-like molten thermoplastic resin as it is to the second roll and then the third third roll in order, and then transferring the sheet-like molten thermoplastic resin. A production method having a step of taking up by a take-up roll can be preferably employed.

  As the extruder used in the present invention, any of a single-shaft type, a biaxial type, and a multi-axial type having two or more axes may be used. It is preferable to provide a vent in order to remove oligomers during polymerization, low molecular compounds generated during molding, and oxygen and moisture dissolved in the extruder. The vacuum degree of the vent is preferably 500 hectopascals or less, more preferably 200 hectopascals or less. From the viewpoint of thickness accuracy and shaping of the substantially bowl-shaped lens, it is preferable to use a gear pump in order to quantitatively discharge the melt-kneaded material. In the case of multilayering for the purpose of providing a functional layer having ultraviolet absorbing ability or antistatic ability on the surface, a multilayer extrusion apparatus can be used. Any of a feed block method and a multi-manifold method may be used for multilayering. In addition, the above-mentioned thing can be used suitably for the extruder used for a multilayer. As the T-die, it is essential to use a choke bar system in order to ensure stability during continuous production. From the viewpoint of thickness accuracy, it is preferable to use a screw type bending lip or a heat bolt type bending lip. It is also possible to use an automatic T die with a heat bolt type bending lip fed back from an on-line thickness measuring machine, a bank monitor or the like.

<Roll arrangement>
With reference to FIG. 1 of the present invention as an example, the arrangement of the roll of the present invention for carrying out the embodiment will be described. FIG. 1 shows that a sheet-like molten thermoplastic resin extruded from a die (1) of an extruder is passed through a gap between two rolls of a first roll (2) and a second roll (3) and rolled. A step of obtaining a sheet-like molten thermoplastic resin, and a step of transferring the rolled sheet-like molten thermoplastic resin as it is to the second roll (3) and then to the third third roll (4) in that order. And the manufacturing method which has a pair of take-off roll (5a, 5b) for peeling and transferring the sheet-shaped molten thermoplastic resin surface-molded from the 3rd roll (4) is shown.

  Since the first roll (2) is an important roll for determining the thickness of the sheet, a mirror-finished roll is preferably used instead of a surface-processed roll. Further, when the thickness accuracy is insufficient due to the influence of the linear pressure, a drum-shaped crowning roll can be used. The second roll (3) is any one of a mirror surface roll for producing a smooth surface, an embossing roll for transferring a mat, embossing, and the like, and a roll for shaping an optical element as necessary. Is selected. These may be used appropriately according to the purpose, but especially for the purpose of preventing damage to the sheet and more efficient light diffusion of the backlight light, the arithmetic average roughness Ra is about 0.1 to 5 μm. It is preferable to use a roll having a mat and an embossed pattern, and an embossing roll produced by a bead blasting method can be preferably used.

  The third roll (4) is a shaping roll (see FIGS. 2 and 3) whose surface is processed so that the optical element is shaped on the sheet. Since the object of the present invention is to obtain an optical sheet having precise optical shaping on at least one side, the second roll (3) and the third roll (4) are each constituted only by a mirror roll and an emboss roll. No combination is selected. 2 and 3 show a forming roll that can form a substantially elliptical bowl-shaped optical element on a sheet.

  The setting position of the take-up roll may be set anywhere as long as the take-up roll is sufficiently cooled to such an extent that the thermoplastic resin sheet is not deformed when the take-up roll contacts. What is necessary is just to set to the position where the shaping | molding of the surface of a sheet | seat deform | transforms with the pressure between two take-up rolls, or the deformation | transformation of appearance defects, such as curvature and a wave, does not occur in the whole sheet | seat. In the present invention, the take-up roll may be made of any material as long as it does not impair the uneven shape of the resin material and does not easily cause roll slip. For example, a material whose surface has a rubber hardness specified by JIS K6301 of 60 to 90 degrees can be used. If a take-up roll having such a rubber hardness on the roll surface is used, the uneven shape of the resin material is not impaired, and slippage of the roll hardly occurs and a sheet can be produced efficiently. The surface shape of the take-up roll may be any shape as long as the take-up roll can be taken out without any obstacles such as slip without deforming the surface shape formed by the first, second and third rolls.

  Separation of the third roll (4) between the third roll (4) and the take-up rolls (5a, 5b) in order to more smoothly separate the optical sheet on which the optical element is shaped from the third roll (4). More preferably, a take-off roll (6) is installed in the vicinity of the line (see FIG. 4).

  The take-off roll may or may not be able to adjust the peripheral speed. Preferably, the one that can adjust the peripheral speed independently of the first roll, the second roll, and the third roll is selected. The peripheral speed of the take-off roll is usually 0.3 m / min to 30 m / min, and the most preferable range is 0.5 m / min to 20 m / min. When the take-off roll cannot adjust the peripheral speed, or when the peripheral speed is not adjusted, the peripheral speed is usually set from the viewpoint of sheet productivity. If the peripheral speed can be adjusted, the peripheral speed ratio with the take-up roll is preferably 98-125%, more preferably 100-115%, in order to improve moldability. It is preferable. If the peripheral speed ratio is smaller than this range, the take-off property from the third roll is deteriorated, and the molded product is likely to be swelled, and the original purpose is lost. A flow mark may occur), which is not preferable.

  The take-off roll is preferably selected to be capable of adjusting the temperature independently of the first roll, the second roll, and the third roll. The preferable range of the temperature of the take-off roll is Tg-50 ° C to Tg + 30 ° C, more preferably Tg-30 ° C to Tg + 10 ° C. If the temperature is lower than this range, there is a concern that slip marks may occur between the take-off roll and the optical sheet and warping and wrinkling of the molded product may occur, and if the temperature is higher, the peelability of the sheet from the third roll is not preferable. It may decrease, or undulation may occur in the molded product. Further, the sheet sticks to the take-off roll, and the plate thickness and surface accuracy may decrease, which is not preferable.

  The take-off roll arrangement position and conditions (pressing, spacing, etc.) may be set so that the sheet is peeled off from the third roll and the sheet is smoothly moved to the take-up roll, and adjusted by a known method. I can do it.

  The form of arrangement of the first to third rolls is not limited to the form shown in FIG. 1, and for example, forms such as (a) to (c) in FIG.

  Further, as the spatial arrangement of the forming rolls (first to third rolls), any of vertical arrangement, horizontal arrangement, oblique arrangement, and polygon arrangement may be used. In the case of the vertical arrangement, the molding may be performed from either the upper middle roll gap or the lower middle roll gap.

<Roll peripheral speed>
First, the peripheral speed of the first roll is determined from the viewpoint of the discharge amount of the thermoplastic resin from the die, the stable sheet running through the entire process, and the productivity. The preferable range of the peripheral speed of the first roll is 0.3 m / min to 30 m / min, and the most preferable range is 0.5 m / min to 20 m / min.

  The peripheral speeds of the second roll and the third roll are preferably 102 to 104% and 100 to 110%, respectively, with respect to the peripheral speed of the first roll. Moreover, regarding the gap (t1) between the first roll and the second roll and the gap (t2) between the second roll and the third roll, it is preferable that t1: t2 = 100: 60 to 100, and further, 100: 70. More preferably, it is set to -95. By selecting such a setting, it is possible to improve the shaping stability. If the relationship between t1 and t2 is made smaller than this range, the second bank is likely to occur between the second roll and the third roll, and a streak-like defect or wrinkle occurs in the molded product. The balance between the plate thickness accuracy and the transferability may be difficult to achieve, which is not preferable. If it is increased, the pressing force by the third roll is insufficient, and there is a possibility that transfer may be insufficient.

  As with the first roll, the peripheral speed Va of the third roll (4) is determined from the viewpoint of the discharge amount of the thermoplastic resin from the die, the stable sheet running through the whole process, and the productivity. The peripheral speed Vb of 5a, 5b) is determined from the viewpoint of stable surface shaping. Regarding the setting of the peripheral speed Va and the peripheral speed Vb, the peripheral speed Vb is preferably set to 103 to 130% of the peripheral speed Va, more preferably 104 to 125%, and still more preferably 105 to 120%. If the setting of the peripheral speeds Va and Vb is outside this range, for example, if it is less than 103%, the sheet will sag, or peeling from the third roll will become difficult and the sheet will wrap around the roll. Sexual problems occur. Further, the optical element type transfer formed on the roll surface is incomplete, and an optical sheet having optical characteristics as designed cannot be obtained. On the other hand, if it is larger than 130%, the tension between the third roll and the take-up roll is increased, so that excessive peeling occurs, and the resin roll adheres to the third roll, and the sheet tears from that point, which is not preferable. Further, the optical element type shape formed on the roll surface is displaced in the width direction, and the optical performance of the completed sheet is not as designed, which is not preferable.

<Roll temperature>
When the embodiment of FIG. 1 is selected, the temperatures of the first to third rolls can be adjusted, and these temperatures are selected according to the thermoplastic resin used in the present invention. In general, the first to third rolls are intended to cool the thermoplastic resin at the same time as the sheet is molded. Therefore, the temperature of each roll is set lower than the discharge temperature of the thermoplastic resin from the die.

  The discharge temperature is adjusted by the die temperature. In the case of the present invention, the temperature setting (Td) of the die is preferably Tg + 100 ° C. to Tg + 150 ° C., more preferably Tg + 110 ° C., where Tg (° C.) is the glass transition temperature of the thermoplastic resin that is the main component in molding. ~ Tg + 130 ° C.

  The temperature T1 of the first roll is Tg-50 ° C to Tg + 20 ° C, more preferably Tg-30 ° C to Tg + 10 ° C. If the temperature of the first roll is lower than this range, the shape of the lens shape in the third roll is deteriorated, which is not preferable. In addition, it is not preferable because there is an increased risk of operation failure due to the sheet being wound around the first roll, and appearance failure such as distortion of the surface wave. On the other hand, if it is higher than this range, there is a possibility that flow marks may be generated or the molded sheet may be wound around the first roll. Further, among the waves of the completed sheet, there is an increased possibility that optical performance defects due to appearance failures such as distortion and thickness are not constant, and running failure of the sheet due to poor circumscribing to the second roll, etc. are undesirable.

  The set temperature T2 of the second roll is Tg + 20 ° C. to Tg + 60 ° C., more preferably Tg + 30 ° C. to Tg + 50 ° C., and further preferably Tg + 40 ° C. to Tg + 50 ° C. Moreover, set temperature T3 of the 3rd roll used as a shaping roll is Tg + 20 degreeC-Tg + 60 degreeC, More preferably, it is Tg + 30 degreeC-Tg + 50 degreeC, More preferably, it is Tg + 40 degreeC-Tg + 50 degreeC. Moreover, when installing the take-off roll mentioned above as a 4th roll, it is preferable that the setting temperature T4 of a 4th roll shall be Tg-50 degreeC-Tg + 30 degreeC. If the temperature setting is out of these ranges, the operation failure due to the sheet being wound around the roll, incomplete transfer of the optical elements, and the appearance of the surface of the finished sheet, such as distortion, etc. The possibility of occurrence of optical performance defects due to obstacles is undesirably increased.

  In order to adjust the temperature of the roll, it is preferable to use a heat transfer oil when molding at 100 ° C. or higher. In addition, the roll temperature in this invention means the temperature of the roll which can be measured. The measurable temperature includes the surface temperature of the roll or the temperature of the heat medium used for adjusting the temperature of the roll. From the viewpoint of operation, the temperature of the heat medium used for adjusting the temperature of the roll is preferably used.

  Although there is no restriction | limiting in particular in the thickness of a sheet | seat, From the point used as an optical sheet, it is preferable to set it as 5 mm or less, More preferably, it is 3 mm or less, More preferably, it is 2 mm or less.

<Roll shape and material>
In the present invention, the first roll, the second roll, and the third roll may be any material that does not cause deformation or the like even if heated and cooled until the thermoplastic resin forming the sheet can be adjusted to a moldable temperature. Usually, metal is often used. Each of these rolls can be adjusted to an arbitrary temperature independently with a heating medium, a heater, or the like, and the number of rotations of the rolls needs to be independently adjustable.

  The take-up roll may be made of any material as long as it does not impair the uneven shape of the resin material and does not easily cause roll slip. For example, a material whose surface has a rubber hardness specified by JIS K6301 of 60 to 90 degrees can be used. If a take-up roll having such a rubber hardness on the roll surface is used, the uneven shape of the resin material is not impaired, and slippage of the roll hardly occurs and a sheet can be produced efficiently. The surface shape of the take-up roll may be any shape as long as the take-up roll can be taken out without any obstacles such as slip without deforming the surface shape formed by the first, second and third rolls. The number of rotations of the roll can be adjusted independently of each take-up roll and the first to third rolls. The temperature of the take-up roll may be adjustable. The take-up roll is preferably set so that the sheet surface temperature is Tg or less, preferably Tg-30 ° C. or less, but temperature adjustment is not necessary. A roll for adjusting the travel of the sheet may be appropriately provided between the third roll and the take-up roll.

  Then, the optical sheet manufactured by this invention is demonstrated.

<Thermoplastic resin of optical sheet>
The thermoplastic resin constituting the optical sheet according to the present invention is not particularly limited as long as it is transparent and has an appropriate strength as a main component of the optical sheet. For example, polycarbonate resin; acrylic resin such as polymethyl methacrylate; styrene resin such as polystyrene, polyvinyl toluene, and poly (p-methylstyrene); MS resin (copolymer of methyl methacrylate and styrene); norbornene resin; poly An arylate resin; a polyethersulfone resin; a ring structure-containing polymer resin; a mixed resin of two or more of these can be used. A polycarbonate resin, a styrene resin, a norbornene resin, or a ring structure-containing polymer resin is preferably used. Among these, polycarbonate resin is particularly preferable as a resin for an optical sheet because it is excellent in transparency, heat resistance, and workability and has a good balance. Moreover, since the ring structure-containing polymer resin is excellent in optical performance, it is also particularly preferable as a resin for an optical sheet.

  The polycarbonate resin is obtained by reacting a dihydric phenol and a carbonate precursor by an interfacial polycondensation method or a melting method. Representative examples of the dihydric phenol include 2,2-bis (4-hydroxyphenyl) propane [commonly known as bisphenol A], 1,1-bis (4-hydroxyphenyl) ethane, and 1,1-bis (4-hydroxy). Phenyl) cyclohexane, 2,2-bis (3-methyl-4-hydroxyphenyl) propane, 2,2-bis (3,5-dimethyl-4-hydroxyphenyl) propane, bis (4-hydroxyphenyl) sulfide, bis (4-hydroxyphenyl) sulfone and the like can be mentioned, and among them, bisphenol A is preferable. These dihydric phenols can be used alone or in admixture of two or more.

  As the carbonate precursor, carbonyl halide, carbonate ester, haloformate or the like is used, and specific examples include phosgene, diphenyl carbonate, dihaloformate of dihydric phenol, and the like.

  In producing polycarbonate resin by reacting the above dihydric phenol and carbonate precursor by interfacial polycondensation method or melting method, it is necessary to prevent oxidation of catalyst, terminal terminator and dihydric phenol as necessary. An antioxidant or the like may be used. The polycarbonate resin may be a branched polycarbonate resin copolymerized with a trifunctional or higher polyfunctional aromatic compound, or may be a polyester carbonate resin copolymerized with an aromatic or aliphatic difunctional carboxylic acid, Moreover, the mixture which mixed 2 or more types of the obtained polycarbonate resin may be sufficient. As the polycarbonate resin used in the present invention, a polycarbonate resin obtained by an interfacial polycondensation method (generic name: phosgene method) is preferably used. In addition, it is more preferable to directly extrude a polycarbonate resin that does not melt the resin such as an extruder or a kneader because discoloration due to a thermal history can be prevented.

The molecular weight of the polycarbonate resin is usually 15,000 to 40,000, preferably 18,000 to 35,000, expressed as a viscosity average molecular weight. The viscosity average molecular weight referred to in the present invention is obtained by inserting the specific viscosity (ηsp) obtained from a solution of 0.7 g of polycarbonate resin in 100 ml of methylene chloride at 20 ° C. into the following equation.
ηsp / c = [η] + 0.45 × [η] ² c
[Η] = 1.23 × 10 ⁻⁴ M ^0.83
(Where c = 0.7, [η] is the intrinsic viscosity)

  In addition to the above components, the polycarbonate resin has other components as long as the purpose and effect are not impaired, for example, phosphorous acid, phosphoric acid, phosphorous acid ester, phosphoric acid ester, phosphonic acid ester and other thermal stabilizers, triazole series UV absorbers such as acetophenone and salicylic acid esters, bluing agents, low molecular weight polycarbonates of tetrabromobisphenol A, tetrabromobisphenol A, flame retardants such as decabromodiphenylene ether, and flame retardant aids such as antimony trioxide You may mix | blend the quantity which the effect expresses, such as additives, as needed.

  The phosphorus-containing heat stabilizer can prevent a decrease in molecular weight and a deterioration in hue during molding. Specific examples of the phosphorus-containing heat stabilizer include phosphite compounds such as triphenyl phosphite, phosphate compounds such as tributyl phosphate, bis (2,4-di-tert-butylphenyl) -biphenylphosphonite. And phosphonic acid ester compounds such as benzene phosphonic acid dimethyl. Among them, tris (2,4-di-tert-butylphenyl) phosphite, tetrakis (2,4-di-tert- Butylphenyl) -4,4′-biphenylene diphosphonite and bis (2,4-di-tert-butylphenyl) -biphenylphosphonite are preferred.

  These heat stabilizers may be used alone or in combination of two or more. The amount of the heat stabilizer used is preferably 0.001 to 0.15 parts by mass with respect to 100 parts by mass of the polycarbonate resin.

  Furthermore, a fatty acid ester compound can be blended with the polycarbonate resin for the purpose of improving releasability from the mold during molding. Such a fatty acid ester is preferably a partial ester or a total ester of a monovalent or polyhydric alcohol having 1 to 20 carbon atoms and a saturated fatty acid having 10 to 30 carbon atoms. Such partial esters or total esters of monohydric or polyhydric alcohols and saturated fatty acids include stearic acid monoglyceride, stearic acid diglyceride, stearic acid triglyceride, stearic acid monosorbite, behenic acid monoglyceride, pentaerythritol monostearate, pentaerythritol. Tetrastearate, pentaerythritol tetrapelargonate, propylene glycol monostearate, stearyl stearate, palmityl palmitate, butyl stearate, methyl laurate, isopropyl palmitate, biphenyl biphenate, sorbitan monostearate, 2-ethylhexyl stearate Rate, etc. Among them, stearic acid monoglyceride, stearic acid triglyceride, pentaerythris Tall tetrastearate are preferably used. The amount of the fatty acid ester used is preferably 0.001 to 0.5 parts by mass with respect to 100 parts by mass of the polycarbonate resin.

  Moreover, a ring structure containing polymer resin can also be used suitably as a thermoplastic resin which comprises the optical sheet of this invention. As the ring structure-containing polymer resin, a thermoplastic acrylic copolymer having a ring structure in the main chain is preferable. The main chain contains a ring structure and a structure derived from a (meth) acrylate monomer. The total content of the structural units derived from the (meth) acrylate monomer and the content of the ring structure is preferably 50% by mass or more, more preferably 70% by mass or more, and still more preferably 90% by mass in the copolymer. Preferably it is 95 mass% or more, Most preferably, it contains 99 mass% or more.

  The ring structure of the main chain usually has a positive birefringence, and the structure derived from the (meth) acrylate monomer has a weak negative birefringence. ) The negative birefringence due to the structure derived from the acrylate monomer cancels each other, and a film having low birefringence can be obtained even after stretching. Here, positive birefringence means refractive index anisotropy that increases the refractive index in the same direction when the polymer molecular chain, which is a component of the film, is oriented by stretching. Is expressed. On the other hand, negative birefringence means that when a polymer molecular chain, which is a component constituting a film, is molecularly oriented by being stretched, the refractive index in the same direction is reduced, and at the same time, the refraction in the orthogonal direction is reduced. It means expressing the refractive index anisotropy that increases the rate.

  Specific examples of the (meth) acrylate monomer constituting the ring structure-containing polymer resin include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, t -(Meth) acrylic acid alkyl esters such as butyl (meth) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate and cyclohexyl (meth) acrylate; benzyl (meth) acrylate; chloromethyl (meth) acrylate 2-cyclomethyl (meth) acrylate; dicyclopentanyloxyethyl (meth) acrylate; dicyclopentanyl (meth) acrylate; 2-hydroxyethyl (meth) acrylate; 3-hydroxypropyl (meth) acrylate; , 4,5-penta hydroxyhexyl (meth) acrylate; 2,3,4,5-hydroxyhexyl (meth) acrylate and the like, may be used alone or two or more of them. Among them, (meth) acrylic acid alkyl ester is preferable and methyl methacrylate is particularly preferable in terms of excellent thermal stability and optical characteristics.

  A monomer other than the (meth) acrylate monomer may be used to constitute the ring structure-containing polymer resin. For example, styrene monomers such as styrene and α-hydroxyethylstyrene; acrylonitrile; methyl vinyl ketone, ethylene, Olefins such as propylene and 4-methyl-1-pentene; vinyl acetate; allylic alcohols such as methallyl alcohol, allyl alcohol and 2-hydroxymethyl-1-butene; unsaturated such as acrylic acid, methacrylic acid and crotonic acid Carboxylic acids; 2- (hydroxyalkyl) acrylic acid esters such as methyl 2- (hydroxymethyl) acrylate and ethyl 2- (hydroxymethyl) acrylate; N-vinylpyrrolidone; N-vinylcarbazole and the like. These monomers may be used alone or in combination of two or more.

  As the ring structure of the main chain, N-substituted maleimide such as phenylmaleimide, benzylmaleimide, cyclohexylmaleimide, and methylmaleimide or maleic anhydride is copolymerized to obtain a ring structure derived from N-substituted maleimide or a ring derived from maleic anhydride. A structure may be introduced, or a lactone ring structure, a glutaric anhydride structure, a glutarimide structure, a ring structure derived from N-substituted maleimide, etc. may be introduced into the main chain by a cyclization reaction after polymerization. . From the viewpoint of heat resistance, those having a ring structure derived from N-substituted maleimide, a lactone ring structure, or a glutarimide structure are preferred. Among them, the main chain has a lactone ring structure because it is low in color and has excellent optical properties. Those are particularly preferred.

  As a method for producing a thermoplastic acrylic copolymer having a ring structure in the main chain, a known production method can be applied. For example, a method for producing an acrylic resin containing a lactone ring structure is described in JP-A-2006-96960, JP-A-2006-171464, and JP-A-2007-63541. Regarding a thermoplastic acrylic copolymer copolymerized with N-substituted maleimide and a thermoplastic acrylic copolymer containing a glutaric anhydride structure or a glutarimide structure, JP2007-31537A, WO2007 / A manufacturing method described in Japanese Patent No. 26659 or WO 2005/108438 may be used.

  The lactone ring structure of the main chain may be a 4- to 8-membered ring, but a 5- to 6-membered ring is more preferable, and a 6-membered ring is still more preferable in terms of structural stability. Further, when the main chain lactone ring structure is a 6-membered ring, examples include the structure represented by the general formula (1) and Japanese Patent Application Laid-Open No. 2004-168882, but before introducing the lactone ring structure into the main chain. In terms of synthesizing the polymer, it is easy to obtain a polymer having a high polymerization yield, a high content ratio of the lactone ring structure, and a good copolymerizability with (meth) acrylate such as methyl methacrylate. A structure represented by the following general formula (1) is preferable.

(In the formula, R ¹ , R ² and R ³ each independently represent a hydrogen atom or an organic residue having 1 to 20 carbon atoms. The organic residue may contain an oxygen atom.)

  The content of the ring structure is preferably 15% by mass or less in the copolymer, more preferably 1 to 15% by mass, still more preferably 3 to 15% by mass, particularly preferably 5 to 12% by mass, and most preferably. Is 5-10 mass%. When the content of the ring structure is more than 15% by mass, the positive birefringence is increased, which is not preferable. By having the ring structure, heat resistance, solvent resistance, and surface hardness are improved.

  The thermoplastic acrylic copolymer preferably has a Tg of 110 ° C. or higher. More preferably, it is 115 degreeC or more, More preferably, it is 120 degreeC or more. Although the upper limit of Tg is not specifically limited, 200 degreeC or less is preferable from a moldability. The weight average molecular weight of the thermoplastic acrylic copolymer is preferably 10,000 to 300,000, more preferably 50,000 to 300,000, still more preferably 100,000 to 250,000, particularly preferably. 120,000 to 200,000.

<Performance adjustment of optical sheet>
Although there is no restriction | limiting in particular in the thickness of the optical sheet of this invention, It is preferable to set it as 5 mm or less from the point used as an optical sheet, More preferably, it is 3 mm or less, More preferably, it is 2 mm or less. Moreover, although it may be comprised only with transparent resin, in order to adjust light diffusibility, you may provide a light-diffusion layer. The light diffusing layer may be uniformly or randomly dispersed in the entire optical sheet, only the lens portion, the entire portion other than the lens portion, only the light exit surface layer, only the light entrance surface layer, or the intermediate layer. The light diffusion layer is one in which light diffusing particles are dispersed in a thermoplastic resin, and diffuses light in a predetermined direction.

  The thickness of the light diffusion layer can be appropriately adjusted according to the thickness of the optical sheet and is not particularly limited, but can usually be about 0.005 mm or more and 5 mm or less. This is because if it is less than 0.005 mm, the light diffusing action cannot be sufficiently exhibited, and if it exceeds 5 mm, the upper limit of the thickness of the optical sheet of the present invention is exceeded, and the entire apparatus may not be made compact.

<Light diffusing particles>
The optical sheet of the present invention may have light diffusing particles. Examples of the material for the light diffusing particles include (meth) acrylic resins, styrene resins, polyurethane resins, polyester resins, silicone resins, fluorine resins, and synthetic resins such as copolymers thereof; glass; And clay compounds such as smectite and kaolinite; inorganic oxides such as silica and alumina; and the like. Of these materials, (meth) acrylic resins, silicone resins, and silica are particularly suitable.

  The amount of the light diffusing particles used is preferably 0.005 parts by mass or more and 20 parts by mass or less, more preferably 0.01 parts by mass or more and 10 parts by mass with respect to 100 parts by mass of the thermoplastic resin constituting the optical sheet. Or less. If the amount used is less than 0.005 parts by mass, the light incident on the optical sheet may not be sufficiently diffused to exhibit the expected effect of containing fine particles. On the other hand, when the amount used exceeds 20 parts by mass, it may be difficult to extrude the optical sheet, or the amount of transmitted light may be reduced, resulting in a decrease in luminance. In addition, it is good also as a laminated structure which uses the light-diffusion layer which has light diffusable particle | grains as a part of optical sheet of this invention. At this time, the preferable usage amount is a preferable usage amount in the light diffusion layer. The thermoplastic resin of the light diffusion layer may be the same as or different from the thermoplastic resin constituting the optical sheet other than the light diffusion layer.

  When using organic fine particles obtained by radical polymerization as light diffusing particles, as raw material monomers for fine particles, (meth) acrylic acid, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, iso-propyl (meth) acrylate, n-butyl (meth) acrylate, iso-butyl (meth) acrylate, t-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate, benzyl (meth) (Meth) acrylates such as acrylate, hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate; styrenes such as styrene, p-methylstyrene, vinyltoluene, pt-butylstyrene; N-phenylmaleimi , N-cyclohexylmaleimide, N-benzylmaleimide and other maleimides; (meth) acrylamide, N-methylol (meth) acrylamide and other (meth) acrylamides; (meth) acrylonitrile and other acrylonitriles; N-vinylpyrrolidone; One or a mixture of two or more of these can be used.

  In addition, in the case of using crosslinked organic fine particles obtained by radical polymerization as light diffusing particles, in addition to the above monomers, as raw material monomers for crosslinking, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, propylene Polyfunctional (meth) acrylates such as glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, bishydroxyethylbisphenol A di (meth) acrylate; divinyloxyethoxy (meth) ) Radical polymerizable crosslinking agents such as acrylate, diallyl phthalate, allyl (meth) acrylate, divinylbenzene; bisphenol A diglycidyl ether, diethylene glycol diglycidyl ether, ne One kind of polyfunctional epoxy compounds such as pentyl glycol diglycidyl ether; polyfunctional isocyanate compounds such as tolylene diisocyanate, xylylene diisocyanate and isophorone diisocyanate; polyfunctional methylol compounds such as N-methylol melamine and N-methylol benzoguanamine; Two or more of these can be mixed and used.

  The refractive index of the light diffusing particles is different from the refractive index of the thermoplastic resin constituting the optical sheet or the light diffusing layer. If organic fine particles having the same refractive index are used, light is not refracted, and the brightness uniformity cannot be sufficiently increased. However, on the other hand, since the refractive index of the resin differs depending on the type, the types of the resin constituting the light diffusing particles and the thermoplastic resin may be different. In addition, as the selection of particles, it is possible to use a mixture of crosslinkable particles and other particles.

  You may mix | blend antioxidant further with the thermoplastic resin which comprises the light diffusable particle | grains or optical sheet of this invention. Since the antioxidant can suppress coloring of the optical sheet and light diffusing particles due to oxidation and deterioration during thermoforming, the luminance of the light source unit to which the optical sheet of the present invention is applied can be more reliably exhibited. .

  A conventionally well-known thing can be used as antioxidant. For example, pentaerythritol tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] or octadecyl-3- (3,5-di-t-butyl-1-hydroxyphenyl) propionate Hindered phenolic antioxidants; tris (2,4-di-t-butylphenyl) phosphite and tris [2-[[2,4,8,10-tetra-t-butyldibenzo [d, f] [ Phosphorous antioxidants such as 1,3,2] dioxaphosphin-6-yl] oxy] ethyl] amine; thiodiethylenebis [3- (3,5-di-t -Butyl-4-hydroxyphenyl) propionate] and the like having no aromatic ring, such as pentaerythrityltetrakis (3-laurylthiopropionate). Sulfur-based antioxidants; lactone-based antioxidants such as 3-hydroxy-5,7-di-t-butyl-furan-2-one and o-xylene reaction products; alkyls based on reduced beef tallow Hydroxylamine antioxidants such as oxidation products of amines; 3,4-dihydro-2,5,7,8-tetramethyl-2- (4,8,12-trimethyltridecyl) -2H-benzopyran-6 -Vitamin E-based antioxidants such as oals can be used.

  Although the usage-amount of antioxidant may be adjusted suitably, normally, what is necessary is just to add about 0.05 mass part or more and 0.3 mass part or less with respect to 100 mass parts of thermoplastic resins or light diffusable particle | grains.

<Optical element of optical sheet>
A lens group is formed as an optical element on at least one surface of the optical sheet of the present invention. The lens in the present invention is a lens such as a prism that is independent of each other, a certain length, an isosceles triangle, an inequilateral triangle, a part of an ellipse, a part of a circle, and a parabola. A substantially bowl-shaped lens having a cross-sectional shape such as a part or a combination of these shapes can be cited, and refers to a lens that can diffuse or condense incident light within each fixed visual field. The substantially bowl-shaped lens is a lens in which the cross-sectional shape continuously extends in the sheet longitudinal direction (take-off direction).

  When each lens is an independent lens, the shape of each lens is not particularly limited as long as it can diffuse light in the sheet width direction (direction orthogonal to the sheet longitudinal direction), but a prism (quadrangular pyramid: pyramid). ), But long pyramids, hemispheres, rugby balls such as triangular pyramids, pentagonal pyramids, hexagonal pyramids, cones, etc. For example, a semi-flat bulb or the like cut along an axis. When each lens is an independent lens, it is preferable to perform the surface treatment of the shaping roll so that each lens is disposed substantially parallel to the longitudinal direction of the optical sheet.

  Further, the cross-sectional shape of the substantially bowl-shaped lens is not particularly limited as long as it can diffuse light in the sheet width direction (direction perpendicular to the sheet longitudinal direction). For example, an isosceles triangle, an unequal triangle, a part of a circle, Examples include a part of an ellipse, a parabolic shape, a rectangular shape at the bottom, and a semicircle at the top (see FIG. 6). The apex angle of the isosceles triangle can be 60 ° or more and 120 ° or less. Further, the central angle of a part of the circle is not limited to 180 °, and may be adjusted so that light can be diffused in a certain direction.

  Each lens does not necessarily have the same shape. As shown in FIG. 7, the height of the top and / or the depth of the valley may be different, and the difference between them may be periodic at a certain interval. It doesn't matter. Based on the respective optical designs, the optical elements need only be surface-molded accurately.

  As described above, depending on the designed optical performance, the top and valley of the optical element may not have a certain height and depth, but the optical element has a certain fine shape accurately transferred to the sheet. If the surface is not molded, high optical performance is not exhibited. The surface shape in which the accurate transfer effect of the present invention appears is that the average gap between the top and the top or the average gap between the valley and the valley (so-called lens pitch) is preferably in the range of 10 to 200 μm in the shape and arrangement of the lenses. More preferably, the thickness is in the range of 30 to 160 μm, and the uniformity of the optical performance can be improved by accurately transferring this setting to the sheet. In addition, the average value of the length of the perpendicular line (so-called lens height) dropped from the top to the straight line connecting the adjacent valleys is the average gap between the top and the top or the average gap between the valley and the valley. The range of 0.2: 1.0 to 0.8: 1.0 is preferable, and the range of 0.3: 1.0 to 0.7: 1.0 is more preferable for improving the optical characteristics.

  A plurality of lenses are formed on at least one surface of the optical sheet of the present invention. Adjacent lenses may be spaced from each other, but are preferably adjacent to each other without a spacing in order to increase light diffusion efficiency. Moreover, although a lens may be formed in the full length of an optical sheet, in order to fix with another member, you may leave an edge part flat.

  As the resin constituting the lens, the same resin as that constituting the optical sheet can be used, and the resin other than the lens portion and the lens portion may be different, but usually the same resin. In the thermoplastic resin constituting the lens, the same light diffusing particles (such as crosslinked organic fine particles) that are dispersed in the light diffusing layer may be dispersed. The major axis direction of the light diffusing particles (crosslinked organic fine particles, etc.) is preferably substantially the same as the longitudinal direction of the optical sheet. Shall.

<Addition of functions other than optical elements of optical sheet>
In the optical sheet of the present invention, an ultraviolet absorber, an antistatic agent, a lubricant, and a near infrared absorber can be used within a range that does not impair the gist of the present invention. In particular, on the surface set on the light source side, a layer containing an ultraviolet absorber, a layer containing an antistatic agent, or both an ultraviolet absorber-containing layer and an antistatic agent-containing layer are preferably formed. That is, a layer having an action other than the light dispersion action may be formed on at least one side of the optical sheet (light diffusion layer). The ultraviolet absorber-containing layer is preferably provided at least on the light source facing surface side of the first optical sheet, but from the viewpoint of maintaining functions in various light source device installation environments and member storage environments, and extending life. It may be provided on the surface. Similarly, the antistatic agent-containing layer may be provided only on one side of the first optical sheet or on both sides. The entire first optical sheet may be an antistatic agent-containing layer or an ultraviolet absorber-containing layer. The layer having a function different from the light diffusion function reduces the ultraviolet ray emitted from the light emitter to suppress the coloring of the optical sheet, or suppresses the charging to suppress the luminance decrease due to the adhesion of dust. The function of extending the life of the electronic device is imparted to the optical sheet of the present invention.

  Conventionally known UV absorbers and antistatic agents can be used. For example, as a UV absorber, a salicylic acid phenyl ester UV absorber; a benzophenone UV absorber; a triazine UV absorber; a benzotriazole UV absorber; a cyclic imino ester UV absorber; and a hindered phenol structure in the molecule Low molecular ultraviolet absorbers such as hybrid ultraviolet absorbers having a hindered amine structure; triphenylcyanoacrylate ultraviolet absorbers; oxalic anilide ultraviolet absorbers; malonic ester ultraviolet absorbers; and these low molecular ultraviolet absorbers Can be used, such as a polymer ultraviolet absorber (eg, Halus Hybrid (registered trademark) manufactured by Nippon Shokubai Co., Ltd.). Of these, triphenylcyanoacrylate ultraviolet absorbers; oxalic anilide ultraviolet absorbers; malonic ester ultraviolet absorbers are preferred because they absorb less light in the visible light region. When used for polycarbonate resin, oxalic acid anilide ultraviolet absorbers and malonic ester ultraviolet absorbers are more preferred.

  Antistatic agents include alkyl sulfonic acids, alkyl benzene sulfonic acids, olefinic sulfates such as Li, Na, Ca, Mg, and Zn salts thereof or metal salts thereof; anionic surface activity such as phosphate esters of higher alcohols. Agents; Cationic surfactants such as tertiary amines, quaternary ammonium salts, cationic acrylic ester derivatives, cationic vinyl ether derivatives; amphoteric salts of alkylamine betaines, amphoteric salts of alanine carboxylates or sulfonates, Amphoteric surfactants such as amphoteric salts of alkyl imidazolines; Nonionic surfactants such as fatty acid polyhydric alcohol esters, polyoxyethylene adducts of alkyl (amines); Polyamide elastomers such as polyether ester amides and polyester amides This Can. In addition, conductive resins such as polyvinyl benzyl type cationic resins and polyacrylic acid type cationic resins can also be used as an antistatic agent.

  Although the usage-amount of a ultraviolet absorber and an antistatic agent can be suitably adjusted according to each function, Usually, it is about 1-50 mass parts with respect to 100 mass parts of resin which comprises each layer. The layer having a function different from the light diffusion function is obtained by applying a sheet in which an ultraviolet absorber or an antistatic agent is uniformly dispersed in a thermoplastic resin similar to the light diffusion layer on the optical sheet by thermocompression bonding or an adhesive. What is necessary is just to adhere. Or you may dry or cool, after apply | coating the paste containing an ultraviolet absorber etc. on an optical sheet. Alternatively, a thermoplastic resin blended with a light diffusing agent and a thermoplastic resin blended with an ultraviolet absorber or an antistatic agent may be coextruded. The thicknesses of these layers may be appropriately adjusted according to each function and the like, but can usually be about 1 to 50 μm.

  The size and shape of the optical sheet of the present invention are not particularly limited, and may be adjusted to the size and shape of the liquid crystal display device, for example. By doing so, a light source unit having excellent optical characteristics can be configured. Further, by combining the light source unit of the present invention with a liquid crystal panel by a normal method, a liquid crystal display device having excellent optical performance can be configured.

<About Examples>
<Production Example 1>
100 parts of polycarbonate resin (“Iupilon (registered trademark) E2000FN”: manufactured by Mitsubishi Engineering Plastics, glass transition point (Tg) = 150 ° C.), phosphorus-based heat stabilizer (“Irgaphos (registered trademark) 168”): Ciba (Japan)) 0.1 part, Oxazole fluorescent whitening agent ("Ubitex (registered trademark) OB": Ciba Japan Co., Ltd.) 0.003 part, with vent and gear pump, 3 rolls 1 is supplied to the sheet extruder having the configuration shown in FIG. 1, the extruder outlet temperature is 265 ° C., the first roll temperature is 140 ° C., the second roll temperature is 188 ° C., the third roll temperature is 193 ° C., the die width is 1150 mm, and the thickness is 1. A 2 mm optical sheet was extruded. The first and second rolls are mirror surface flat rolls, and the third roll is a sculptured roll (lens ridgeline) so that an approximately elliptical rod-shaped lens having a lens pitch of 100 microns and a lens height of 50 microns can be formed. The sculpture was used so that the direction of was parallel to the rotation direction of the roll. The peripheral speed of the third roll was 2.0 m / min, and the peripheral speed of the take-up roll was 2.06 m / min.

<Production Example 2>
Except that the peripheral speed of the take-up roll was 2.6 m / min, the operation for producing the optical sheet was performed under the same conditions as in Production Example 1.

<Production Example 3>
The operation for producing the optical sheet was performed under the same conditions as in Production Example 1 except that the peripheral speed of the take-up roll was 2.3 m / min.

<Production Example 4>
The operation for producing the optical sheet was performed under the same conditions as in Production Example 1 except that the first roll temperature was 125 ° C, the second roll temperature was 197 ° C, and the third roll temperature was 193 ° C.

<Production Example 5>
An operation for producing an optical sheet was performed under the same conditions as in Production Example 1 except that the first roll temperature was 135 ° C, the second roll temperature was 191 ° C, and the third roll temperature was 191 ° C.

<Production Example 6>
The peripheral speed of the take-up roll is 2.3 m / min, the first roll temperature is 135 ° C., the second roll temperature is 191 ° C., the third roll temperature is 191 ° C., and the temperature is not adjusted between the third roll and the take-up roll, The operation for producing the optical sheet was performed under the same conditions as in Production Example 3 except that a take-off roll that did not adjust the peripheral speed was installed.

<Production Example 7>
An operation for producing an optical sheet was performed under the same conditions as in Production Example 6 except that the temperature of the take-off roll was 130 ° C.

<Production Example 8>
Except that the peripheral speed of the take-off roll was 2.3 m / min, an operation for producing an optical sheet was performed under the same conditions as in Production Example 7.

<Production Example 9>
An operation for producing an optical sheet was performed under the same conditions as in Production Example 4 except that a mat roll (arithmetic surface roughness Ra = 4.0 μm) was used as the second roll.

<Production Example 10>
Except that an embossing roll (arithmetic surface roughness Ra = 0.25 μm) was used as the second roll, an operation for producing an optical sheet was performed under the same conditions as in Production Example 4.

<Comparative Production Example 1>
The operation for producing the optical sheet was performed under the same conditions as in Production Example 1 except that the peripheral speed of the take-up roll was 2.0 m / min.

<Comparative Production Example 2>
Except that the peripheral speed of the take-up roll was 2.8 m / min, the operation for producing the optical sheet was performed under the same conditions as in Production Example 1.

<Comparative Production Example 3>
Except that the peripheral speed of the take-up roll was set to 3.0 m / min, the operation for producing the optical sheet was performed under the same conditions as in Production Example 1.

<Reference Production Example 1>
The first and third rolls use mirror rolls, and the second roll is a sculptured roll (in the direction of the lens ridgeline) so that an approximately elliptical rod-shaped lens having a lens pitch of 100 microns and a lens height of 60 microns can be formed. The operation for producing the optical sheet was carried out under the same conditions as in Production Example 1 except that engraving was used so that was parallel to the rotation direction of the roll.

<Reference Production Example 2>
Except for setting the first roll temperature to 155 ° C, the second roll temperature to 210 ° C, and the third roll temperature to 210 ° C, the operation for producing the optical sheet was performed under the same conditions as in Production Example 1.

<Reference Production Example 3>
The operation for producing the optical sheet was performed under the same conditions as in Production Example 1 except that the first roll temperature was 125 ° C, the second roll temperature was 145 ° C, and the third roll temperature was 165 ° C.

<About driving>
For continuous operation for 6 hours, ○ indicates that stable operation was possible without adding fine adjustment from the first setting condition, Δ indicates that stable operation was possible by adding fine adjustment, and operation was performed without adding fine adjustment. Those that stopped due to obstacles were evaluated as x. The results are summarized in Table 1.

<About the molding rate>
The molding rate is measured by measuring the lens pitch and lens height by SEM photographing at the center of the obtained optical sheet in the width direction, calculating the lens height / lens pitch of the optical sheet, and calculating the value as a mold. (Engraving) It was performed by dividing by roll lens height / lens pitch. For example, the lens pitch of the optical sheet obtained in Example 1 is 98.5 microns, the lens height is 48.3 microns, the lens pitch of the mold (engraving) roll is 100 microns, and the lens height is 50 microns. Therefore, (molding rate) = (48.3 / 98.5) × 100 / (50/100) = 98 (%). The closer this value is to 100, the better the moldability. The results are summarized in Table 1.

<About uniformity>
The uniformity was measured by taking a sample of 9 points in the width direction of the obtained optical sheet, measuring each lens pitch by SEM imaging, and measuring the minimum / maximum value ratio. For example, since the minimum lens pitch of the optical sheet obtained in Example 1 is 98.0 microns and the maximum lens pitch is 99.2 microns, (uniformity) = (98.0 / 99.2) × 100 = 99 (%). The closer this value is to 100, the better the moldability. The results are summarized in Table 1.

<About thickness accuracy>
The thickness is measured using a micrometer for the thickness of the center, the center left and right 25 cm, and the center left and right 50 cm in the TD (Transverse Direction: width direction) direction of the obtained optical sheet original plate. Measurement was carried out by calculating the difference between the maximum thickness and the minimum thickness and dividing it by the average value of the thicknesses at five locations. For example, since the difference between the maximum thickness and the minimum thickness of the optical sheet obtained in Example 1 is 0.03 mm, and the average value of the thicknesses at five locations is 1.19 mm, (thickness accuracy) = (0.03 / 1 .19) × 100 = 2.5 (%). It is determined that the smaller the value, the better the thickness accuracy. The results are summarized in Table 1.

<About warping>
The 1000 mm × 1000 mm sheet cut out from the obtained optical sheet original plate was left on a surface plate installed in a room with an air temperature of 23 ° C. and a humidity of 60% for 1 h, and then placed horizontally. The gap (warpage) was measured with a gauge. When the warpage is less than 2 mm, it is evaluated as ◯, when the warpage is less than 3 mm and less than 3 mm, and Δ when it is 3 mm or more.

<Optical performance>
The optical performance was measured by the following method. A backlight portion mounted on a thin liquid crystal television (WOOO UT-32-HV700) manufactured by Hitachi, Ltd. was taken out and used as a light source for luminance measurement. Each optical sheet obtained by the manufacturing example and the comparative manufacturing example is cut to a size that can be incorporated into the light source (* the direction of the ridgeline of the approximately elliptical saddle-shaped lens is parallel to the long side direction of the sheet; that is, the backlight The cold cathode fluorescent lamp and the ridge line of the substantially elliptical lens are parallel to each other), and the lens surface is opposite to the light source. On top of that, one 32 inch size prism sheet (UTE-30; manufactured by MN Tech) and one microlens sheet (UTE-21; manufactured by MN Tech) have a lens surface facing away from the light source. It was arrange | positioned on the diffusion plate so that it might become.

Next, the cold cathode tube was turned on, and A: the luminance directly above the cold cathode tube and B: the luminance between the cold cathode tube and the cold cathode tube were measured using a Topcon color luminance meter (BM-7). . The temperature of the atmosphere was 25 ° C., the humidity was 60% RH, the measurement distance was 50 cm from the cold cathode tube (distance in the normal direction with respect to the backlight surface), and the viewing angle was 0.2 °. The luminance and luminance unevenness were calculated by the following formula. The results are summarized in Table 1.
Luminance = (A + B) / 2
Luminance unevenness (%) = | Kou-B | * 100 / Luminance

  According to the present invention, an optical sheet with a surface shape that sufficiently exhibits the original design performance can be efficiently produced. In addition, the optical sheet of the present invention produced in this way exhibits excellent performance as an optical sheet, in particular, because the shape of the roll surface is transferred according to the optical design. In addition, a light source unit and a display device using the optical sheet also exhibit excellent performance.

1: Die 2: First roll 3: Second roll 4: Third roll (surface shaping roll)
5a: Take-up roll a
5b: Take-up roll b
6: Take-off roll

Claims (9)

A method for producing an optical sheet that is surface-molded using a shaping roll that has been surface-treated so that a substantially bowl-shaped optical element is molded substantially parallel to the sheet take-up direction,
The average distance between the tops of the substantially bowl-shaped optical elements or the average distance between the valleys and the valleys is 10 to 200 μm,
Passing the sheet-like molten thermoplastic resin extruded from the die of the extruder through the gap between the two rolls of the first roll and the second roll to obtain a rolled sheet-like molten thermoplastic resin, and the rolling The step of transporting the sheet-like molten thermoplastic resin as it is to the second roll and then the third third roll in that order, and then peeling the sheet-like molten thermoplastic resin from the third roll; Having a step of taking up by a pair of take-up rolls for transporting,
The first roll is a mirror roll, the second roll is a mirror roll, mat roll or emboss roll, the shaping roll is installed on the third roll, the circumferential speed of the shaping roll is Va, and the take-up roll (draw roll) ), The peripheral speed Vb is set to 103 to 130% of the peripheral speed Va.   The optical element is shaped substantially parallel to the take-off direction, and a plurality of ridges having a convex or convex arc cross section and a plurality of concave or concave arc troughs arranged alternately in parallel. The method for producing an optical sheet according to claim 1, wherein the optical sheet is an optical element.   The average value of the lengths of the perpendiculars extending from the top of the substantially bowl-shaped optical element to the straight line connecting the adjacent valleys is 0 with respect to the average interval between the peaks and the peaks or the average interval between the valleys and the valleys. The method for producing an optical sheet according to claim 1 or 2, wherein the ratio is from 2: 1.0 to 0.8: 1.0. When the glass transition temperature (° C) of the thermoplastic resin to be used is expressed as Tg, the set temperature of the extruder die is Tg + 100 ° C to Tg + 150 ° C, the set temperature of the first roll is Tg-50 ° C to Tg + 20 ° C, The manufacturing method of the optical sheet as described in any one of Claims 1-3 which sets the preset temperature of 2 rolls to Tg + 20 degreeC-Tg + 60 degreeC. The manufacturing method of the optical sheet as described in any one of Claims 1-4 which installs a take-off roll between a shaping roll (3rd roll) and a take-up roll. When the glass transition temperature (degreeC) of the thermoplastic resin to be used is represented by Tg, the temperature of the shaping roll (third roll) is set to Tg + 20 ° C to Tg + 60 ° C. Manufacturing method of optical sheet. An optical sheet produced by the production method according to any one of claims 1 to 6 . A light source unit comprising the optical sheet according to claim 7 . A display device using the light source unit according to claim 8 .