JP2010026222A - Base sheet for optical sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a base sheet for optical sheet which is superior in anti-sticking property, includes high total light transmittance, can effectively suppress interference phenomenon and luminance irregularity and includes high economical efficiency and thin film characteristic. <P>SOLUTION: The base sheet for optical sheet includes a transparent base film and an anti-sticking layer laminated on one side surface of the base film, wherein the anti-sticking layer includes fillers and a resin binder, an average thickness of a flat part of the anti-sticking layer is 50 nm to 150 nm and an average particle size of the fillers is 70 nm to 200 nm. Preferably, the average particle diameter of the fillers is set to be larger than the average thickness of the flat part of the anti-sticking layer. Preferably, a content of the fillers in the anti-sticking layer is set to be 20 mass% to 50 mass%. The binder polymer includes preferably a three-dimensional crosslinking structure. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a substrate sheet for an optical sheet, and in particular, has optical functions such as diffusion to transmitted light, refraction in the normal direction side, and condensing, and is particularly suitable for a liquid crystal display device. The present invention relates to a base sheet for an optical sheet.

  In the liquid crystal display device, a backlight method in which a liquid crystal layer is illuminated from the back surface is widely used, and a backlight unit such as an edge light type or a direct type is provided on the lower surface side of the liquid crystal layer. As shown in FIG. 4A, the edge light type backlight unit 50 basically includes a linear lamp 51 as a light source, and a rectangular plate arranged so that an end thereof is along the lamp 51. A light guide plate 52 and a plurality of optical sheets stacked on the light guide plate 52. The optical sheet has predetermined optical functions such as a function of refracting the peak direction of light rays to the normal direction side and a function of diffusing the luminance distribution. Specifically, the optical sheet is provided on the surface side of the light guide plate 52. There are a light diffusion sheet 53, a prism sheet 54, and the like. Although not shown, as the optical sheet, in addition to the light diffusion sheet 53 and the prism sheet 54, a reflection sheet disposed on the back side of the light guide plate 52, a microlens sheet having a microlens array on the surface, and the like. There is.

  The function of the backlight unit 50 will be described. First, light rays incident on the light guide plate 52 from the lamp 51 are reflected dots on the back surface of the light guide plate 52 and a reflection sheet (not shown) disposed on the back surface side of the light guide plate 52. And the light is reflected from each side surface of the light guide plate 52 and emitted from the surface of the light guide plate 52. The light beam emitted from the light guide plate 52 enters the light diffusion sheet 53, and has a predetermined optical action such as diffusion and refraction in the normal direction, and is emitted from the surface of the light diffusion sheet 53. Thereafter, the light beam emitted from the light diffusion sheet 53 is incident on the prism sheet 54 and is emitted as a light beam having a distribution having a peak in a substantially upward direction by the prism portion 54a formed on the surface.

  In this manner, the light beam emitted from the lamp 51 is refracted to the surface side by the light guide plate 52, diffused by the light diffusion sheet 53, and further refracted by the prism sheet 54 so as to have a peak in a substantially upward direction. The upper surface of the liquid crystal layer (not shown) is illuminated. Although not shown, there is also a backlight unit in which another prism sheet or a light diffusion sheet is disposed on the surface side of the prism sheet 54.

  As a conventional light diffusion sheet 53, generally as shown in FIG. 4B, a base film 55, a light diffusion layer 56 formed on the surface of the base film 55, and a base film 55 And an anti-sticking layer 57 laminated on the back surface (see, for example, JP 2000-89007 A). The light diffusion layer 56 is configured to exhibit a light diffusion function with respect to transmitted light, and has a light diffusion agent 59 in a binder 58.

  In the conventional light diffusion sheet 53, the anti-sticking layer 57 is formed by applying a resin composition containing a polymer constituting the binder, resin beads 61, a solvent, and the like to the back surface of the base film 55. The resin beads 61 are dispersed in the binder 60, and the resin beads 61 have a convex portion on the back surface. The convex portion formed on the back surface of the sticking prevention layer 57 prevents the inconvenience that the back surface of the light diffusing sheet 53 is brought into close contact with the light guide plate 52 and the like to generate interference fringes.

  As the resin beads 61 of the anti-sticking layer 57, acrylic beads having an average particle diameter of 10 μm to 20 μm are used from the viewpoint of preventing sticking. For this reason, the anti-sticking layer 57 has a disadvantage that light rays incident from the back surface are scattered to some extent by reflection and refraction at the interface of the resin beads 61. Accordingly, the conventional light diffusion sheet 53 may cause a decrease in optical functions such as light transmittance due to the anti-sticking layer 57.

  The average thickness of the anti-sticking layer 57 is set to 5 μm or more and 15 μm or less in order to fix the resin beads 61 having the above average particle diameter. Therefore, the conventional light diffusing sheet 53 is contrary to the current demand for thinning of the liquid crystal display device, and the refraction at both interfaces of the anti-sticking layer 57 causes an interference phenomenon in the transmitted light, leading to moire and the like. There is a risk.

  Further, since the anti-sticking layer 57 contains the resin beads 61, the convex portions on the back surface are relatively soft, and scratches are generated during the assembly of the liquid crystal display device or during storage and transportation. There is a fear. Due to the scratch on the back surface of the anti-sticking layer 57, there is a possibility that inconveniences such as a decrease in luminance of the screen of the liquid crystal display device and uneven luminance due to light scattering may occur.

Since the anti-sticking layer 57 is formed by coating or the like as described above, the light diffusing sheet 53 is manufactured by forming a base film 55 and applying light to the surface of the base film 55. In order to reduce the manufacturing cost, which is a current requirement, requires at least three steps: a step of forming the diffusion layer 56 and a step of laminating the anti-sticking layer 57 on the back surface of the base film 55. Therefore, there is a demand for simplification of the manufacturing process.
JP 2000-89007 A

  The present invention has been made in view of these inconveniences, has excellent anti-sticking properties, has a high total light transmittance, can effectively suppress interference phenomenon and luminance unevenness, and has further improved economic efficiency and thin film properties. An object of the present invention is to provide a base sheet for an optical sheet.

The invention made to solve the above problems is
A substrate sheet for an optical sheet comprising a transparent substrate film and an anti-sticking layer laminated on one surface of the substrate film,
This anti-sticking layer contains a filler and its resin binder,
The average thickness of the flat portion of the anti-sticking layer is 50 nm or more and 150 nm or less,
An average particle size of the filler is 70 nm or more and 200 nm or less.

  In the base sheet for optical sheets, the anti-sticking layer contains a filler and a resin binder, the average thickness of the flat portion of the anti-sticking layer is 50 nm or more and 150 nm or less, and the average particle diameter of the filler is 70 nm or more and 200 nm. Because of the following, the nano-sized filler has a relatively large and uniform number of fine protrusions on the outer surface of the anti-sticking layer. As a result, the light guide plate, prism sheet, etc. The fine protrusions make contact in a scattered manner, have high anti-sticking properties, and can prevent the occurrence of interference fringes due to sticking.

  Moreover, since the average particle size of the filler that exhibits anti-sticking property is 70 nm or more and 200 nm or less, the average particle size of the filler is smaller than the wavelength of visible light, Even if it mix | blends, inhibiting light transmittance is reduced dramatically and it has a high total light transmittance.

  Furthermore, since the average thickness of the flat part of the anti-sticking layer is 50 nm or more and 150 nm or less, the average thickness of the flat part of the anti-sticking layer is larger than the wavelength of visible light. The interference phenomenon of transmitted light due to refraction at both interfaces of the anti-sticking layer is reduced, and generation of moire or the like can be effectively suppressed.

  Further, the base sheet for optical sheets has an average thickness of the flat portion of the anti-sticking layer that is much smaller than that of the conventional one, and can promote thinning of the liquid crystal display device that is demanded today. Furthermore, the base sheet for optical sheet contains a filler in the anti-sticking layer to form fine convex portions on the outer surface, and does not contain resin beads like conventional optical sheets. An anti-sticking layer can be laminated in-line in the molding process of the base film, and as a result, it is possible to omit other processes such as coating after creating a base film like a conventional optical sheet, and manufacturing workability In addition, reduction of manufacturing cost is greatly promoted.

  The average particle diameter of the filler is preferably larger than the average thickness of the flat portion of the anti-sticking layer. Thus, by making the average particle diameter of the filler larger than the average thickness of the flat portion of the anti-sticking layer, fine protrusions are remarkably formed on the outer surface of the anti-sticking layer, and the anti-sticking property can be further improved. .

  As the filler, it is preferable to contain a small-diameter filler as a main component and a large-diameter filler as an accessory component having an average particle diameter larger than that of the small-diameter filler, and the average particle diameter of the small-diameter filler is from 50 nm to 150 nm. In this way, by including the main component small-diameter filler and the subcomponent large-diameter filler as the filler, a fine convex portion is formed on the outer surface of the anti-sticking layer by the main component small-diameter filler almost on one side, and the subcomponent As a result of relatively large convex portions being formed in a scattered manner by the large-diameter filler, the anti-sticking property is remarkably improved.

  The filler content in the anti-sticking layer is preferably 20% by mass or more and 50% by mass or less. Thus, by making the filler content of the anti-sticking layer in the above range, the uniformity and density of fine protrusions formed on the outer surface of the anti-sticking layer are suitable for anti-sticking, and the anti-sticking property is further improved. improves.

  The polymer constituting the binder preferably has a three-dimensional crosslinked structure. As described above, the binder polymer having a three-dimensional cross-linking structure improves the fixing property and protective property of the filler in the anti-sticking layer, and contributes to the uniform dispersibility of the filler and thus the anti-sticking property. Further, since the binder polymer has a three-dimensional cross-linked structure, the slipping property and the scratch resistance of the anti-sticking layer are improved.

  The binder may be formed from a polymer composition containing an acrylic polyol and a curing agent. Thus, by using a polymer composition containing an acrylic polyol and a curing agent as a binder forming material, the stacking operation of the anti-sticking layer on the base film is easy and reliable, and the binder has high transparency, Furthermore, the three-dimensional crosslinked structure can be easily formed by selecting a curing agent.

  Colloidal silica is preferable as the filler. Such colloidal silica is excellent in light transmittance in the anti-sticking layer, has good dispersibility in the binder polymer, and thus contributes to improvement in heat resistance, rigidity and the like of the anti-sticking layer.

  The variation coefficient of the particle size distribution of the small filler is preferably 20% or less. Thus, by setting the coefficient of variation of the small-diameter filler to 20% or less, the uniformity and protrusion height of the fine protrusions formed on the outer surface of the anti-sticking layer are suitable for anti-sticking, and the anti-sticking property is further improved. improves.

  An antistatic agent may be dispersed and contained in the anti-sticking layer. As described above, the antistatic agent is dispersed and contained in the anti-sticking layer, so that the base sheet for the optical sheet is provided with antistatic properties, and the light guide plate is superimposed on the base sheet for the optical sheet and the back side thereof. Further, the sticking prevention property for the prism sheet and the like is further improved.

  The base sheet for an optical sheet is suitably used for a backlight unit of a liquid crystal display device, and contributes to high brightness, uniform brightness, ease of assembly work, low cost, thinning, etc. of the liquid crystal display device. .

  Here, the “flat portion of the anti-sticking layer” means a region of the anti-sticking layer where no filler is present. “Average particle size” and “coefficient of variation of particle size distribution” are numerical values based on volume.

  As described above, the base sheet for optical sheets of the present invention is excellent in anti-sticking property, has a high total light transmittance, can effectively suppress interference phenomenon and luminance unevenness, and is further economical and thin. As a result, it is possible to promote high brightness, uniform brightness, low cost and thinning of the liquid crystal display device used.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as appropriate. 1 is a schematic cross-sectional view showing a base sheet for an optical sheet according to an embodiment of the present invention, FIG. 2 is a schematic bottom view of the base sheet for an optical sheet in FIG. 1, and FIG. 3 is an optical sheet in FIG. It is typical sectional drawing which shows the base material sheet for optical sheets which concerns on the form different from the base material sheet for images.

  The optical sheet substrate sheet 1 of FIG. 1 includes a substrate film 2 and an anti-sticking layer 3 laminated on the back surface of the substrate film 2.

  Since the base film 2 needs to transmit light, it is made of a synthetic resin that is transparent, particularly colorless and transparent. The synthetic resin used for the base film 2 is not particularly limited, and examples thereof include polyester polymers such as polyethylene terephthalate and polyethylene naphthalate, cellulose polymers such as diacetyl cellulose and triacetyl cellulose, polycarbonate polymers, Acrylic polymers such as polymethyl methacrylate, styrene polymers such as polystyrene and acrylonitrile / styrene copolymers, polyethylene, polypropylene, polyolefins having a cyclic or norbornene structure, olefin polymers such as ethylene / propylene copolymers, vinyl chloride Polymers, amide polymers such as nylon and aromatic polyamide, imide polymers, sulfone polymers, polyethersulfone polymers, polyethers Teruketon based polymers, polyphenylene sulfide polymers, vinyl alcohol polymers, vinylidene chloride polymers, vinyl butyral polymers, arylate polymers, polyoxymethylene-based polymers, epoxy-based polymers, 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.

  As a forming material of this base film 2, the said polymer can be used 1 type or in mixture of 2 or more types. Moreover, various additives etc. can be mixed with the forming material of the base film 2 in order to improve and modify workability, heat resistance, weather resistance, mechanical properties, dimensional stability, and the like. Examples of the additive include a lubricant, a crosslinking agent, an antioxidant, an ultraviolet absorber, a light stabilizer, a filler, a reinforcing fiber, a reinforcing agent, an antistatic agent, a flame retardant, a flame retardant, a foaming agent, and an antifungal agent. , Fillers, pigments, plasticizers, deterioration inhibitors, dispersants and the like.

  The thickness (average thickness) of the base film 2 is not particularly limited, but is preferably 10 μm or more and 250 μm or less, and particularly preferably 20 μm or more and 188 μm or less. When the thickness of the base film 2 is less than the above range, curling occurs when a polymer composition for forming an optical layer (a layer for functioning as an optical sheet) is laminated on the surface of the base film 2. Inconveniences such as easy handling and difficult handling occur. On the contrary, if the thickness of the base film 2 exceeds the above range, the brightness of the liquid crystal display device equipped with the base sheet for optical sheet 1 may be lowered, and the thickness of the backlight unit is large. Thus, it is contrary to the demand for thinning the liquid crystal display device.

  The anti-sticking layer 3 has a plurality of fillers 4 arranged in layers and spaced apart from each other, and a binder 5 that fixes the fillers 4 to the back side of the base film 2. In the anti-sticking layer 3, a plurality of convex portions 6 are relatively densely and uniformly formed on the back surface by the filler 4 protruding from the back surface (outer surface) of the binder 5. Therefore, when the optical sheet base sheet 1 is laminated with a light guide plate or the like, the convex portions 6 formed relatively densely and uniformly contact the surface of the light guide plate or the like, and the optical sheet base sheet 1 The entire back surface does not come into contact with the light guide plate or the like. This effectively prevents sticking between the optical sheet base sheet 1 and the light guide plate, and suppresses uneven brightness on the screen of the liquid crystal display device.

  Specific materials of the filler 4 are roughly classified into inorganic fillers and organic fillers. Examples of the inorganic filler include oxides of elements selected from Groups 2 to 6 of the Periodic Table of Elements (for example, silicon, aluminum, zinc, titanium, zirconium, etc.), aluminum hydroxide, barium sulfide, magnesium silicate, or the like. Can be used. Of these, colloidal silica is preferred because it is easy to obtain a nano-level particle size and has a small light shielding property. As the organic filler, for example, acrylic resin, acrylonitrile resin, polyurethane, polyvinyl chloride, polystyrene, polyacrylonitrile, polyamide and the like can be used. Among them, an acrylic resin having high transparency when cured is preferable, and polymethyl methacrylate (PMMA) is particularly preferable.

  The shape of the filler 4 is not particularly limited, and examples thereof include a spherical shape, a spindle shape, a needle shape, a rod shape, a cubic shape, a plate shape, a scale shape, and a fiber shape. A spherical shape that is excellent in the formability of the convex portion 6 and that exhibits good anti-sticking properties is preferable.

  The lower limit of the average particle diameter of the filler 4 is 70 nm, and 100 nm is particularly preferable. On the other hand, the upper limit of the average particle diameter of the filler 4 is 200 nm, and 150 nm is particularly preferable. When the average particle size of the filler 4 is less than the above lower limit, the surface energy becomes high, so that it is difficult to disperse the binder 4 in the binder 5, and the convex portion 6 formed on the back surface of the sticking prevention layer 3 by the filler 4 is small. Therefore, there is a possibility that the anti-sticking function cannot be performed. On the contrary, when the average particle diameter of the filler 4 exceeds the above upper limit, the effect of shielding light transmission due to the influence of a short wavelength is increased, leading to a decrease in the total light transmittance of the base sheet 1 for optical sheets. There is a fear. Further, the anti-sticking layer 3 containing the filler 4 having the average particle diameter range can be easily laminated without directly forming the easy-adhesion layer on the back surface of the base film 2, Cost reduction, weight reduction and thinning are possible. Further, the anti-sticking layer 3 containing such nano-sized fillers 4 has good antistatic effect and anti-scratch effect in addition to the light transmittance and anti-sticking property.

  As a minimum of content of filler 4 in sticking prevention layer 3 (content of solid content conversion in a composition for sticking prevention layers), 20 mass% is preferred and 30 mass% is especially preferred. On the other hand, as an upper limit of content of the filler 4, 50 mass% is preferable and 40 mass% is especially preferable. If the content of the filler 4 is less than the above lower limit, the uniform dispersibility and density of the protrusions 6 formed on the back surface of the anti-sticking layer 3 may be reduced, and the anti-sticking effect may not be sufficiently obtained. On the other hand, if the content of the filler 4 exceeds the above upper limit, further improvement of the sticking prevention effect cannot be obtained, and the light transmittance may be lowered.

  The variation coefficient of the particle size distribution of the filler 4 is preferably 20% or less, particularly preferably 10% or less. By setting the variation coefficient of the filler 4 within the above range, the uniformity of the protrusion height of the fine protrusions 6 formed on the back surface of the anti-sticking layer 3 is improved, and the anti-sticking property is further improved. Further, by setting the coefficient of variation of the filler 4 within the above range, the reduction of the small-diameter filler 4 that does not contribute to the prevention of sticking and the reduction of the filler 4 per unit area are promoted. The effect of preventing deterioration of the optical function due to scattering or the like can be promoted.

  The binder 5 is formed by curing a polymer composition containing a base polymer. By this binder 5, the filler 4 is arranged and fixed on the back surface of the base film 2 at substantially equal density.

  The base polymer itself used for the binder 5 is preferably transparent from the viewpoint of increasing light transmittance, and particularly preferably colorless and transparent. The base polymer is not particularly limited, and is, for example, a polymethacrylic acid resin such as polymethacrylic acid or polycarboxyphenylmethacrylamide, or a polyolefin resin represented by a polystyrene resin such as poly (biphenyl) styrene. Resin, polyether resin typified by poly (2,6-dimethyl-1,4-phenylene oxide), typified by poly (oxycarbonyloxy-1,4-phenyleneisopropylidene-1,4-phenylene) Polycarbonate resin, polyester resin represented by poly (oxy-2,2,4,4-tetramethyl-1,3-cyclobutyleneoxyterephthaloyl), poly (oxy-1,4-phenylenesulfonyl-1) , 4-phenylene), poly (oxy-1,4-phenylene isopropylide) Polysulfone resin represented by -1,4-phenyleneoxy-1,4-phenylenesulfonyl-1,4-phenylene) and polyamide represented by poly (iminoisophthaloirimino-4,4′-biphenylene) Resin, polysulfide resin represented by poly (thio-1,4-phenylenesulfonyl-1,4-phenylene), unsaturated polyester resin, epoxy resin, melamine resin, diallyl phthalate resin, phenol resin , Polyimide resins, polyphosphazene resins, siloxane resins composed of organoalkoxysilane compounds, and the like. These polymers can be used alone or in combination.

  In particular, the base polymer is preferably a polyol because it has high processability and can easily form the anti-sticking layer 3 by means such as coating. The base polymer is preferably a polyolefin copolymer from the viewpoint of the formability of a three-dimensional crosslinked structure described later.

  The polymer 7 constituting the binder 5 preferably has a three-dimensional crosslinked structure as shown in FIG. As described above, the polymer 7 constituting the binder 5 has a three-dimensional cross-linked structure, so that the fixing and protecting properties of the filler 4 in the anti-sticking layer 3 are improved, and the uniform dispersibility of the filler 4 and thus the anti-sticking property. Contributes to improvement. In addition, since the polymer 7 constituting the binder 5 has a three-dimensional crosslinked structure, the hardness, slipperiness, scratch resistance, and the like of the antisticking layer 3 are improved.

  The means for constructing this three-dimensional crosslinked structure is not particularly limited, and a known means is adopted, but in general, the polyfunctional simple monomer having two or more unsaturated groups in the polymer composition of the base polymer is used. It is formed by containing a monomer. The polyfunctional monomer having two or more unsaturated groups is a monomer having two or more unsaturated functional groups copolymerizable with the monomer or prepolymer, and the copolymerizable functional group is a vinyl group. , Methyl vinyl group, acrylic group, methacryl group and the like. In addition, a monomer containing two or more different copolymerizable functional groups in one molecule is also included in the polyfunctional monomer referred to in the present invention.

  Examples of the polyfunctional monomer having two or more unsaturated groups include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, glycerol (di / tri) (meta ), Polymethyl alcohol di-, tri-, tetra- (meth) acrylates such as acrylate, trimethylolpropane (di / tri) (meth) acrylate, pentaerythritol (di / tri / tetra) (meth) acrylate, p -Raw materials are aromatic polyfunctional monomers such as divinylbenzene and o-divinylbenzene, esters such as (meth) acrylic acid vinyl ester and (meth) acrylic acid allyl ester, dienes such as butadiene, hexadiene and pentadiene, and dichlorophosphazene As polymerization officer Monomers having a phosphazene skeleton introduced with groups, such as a polyfunctional monomer having a heteroatom ring skeleton such triallyl di isocyanurate.

  The blending amount of the polyfunctional monomer having two or more unsaturated groups is preferably 2% by mass or more and 80% by mass or less in the three-dimensional crosslinked polymer. When the amount is less than the above range, the three-dimensional crosslinking does not proceed sufficiently, and a decrease in heat resistance, solvent resistance and the like tends to be observed. On the other hand, when the above range is exceeded, impact resistance and the like are lowered, and the characteristics as a plastic may be lowered.

  Examples of the polyol include a polyol obtained by polymerizing a monomer component containing a hydroxyl group-containing unsaturated monomer, a polyester polyol obtained under the condition of excess hydroxyl group, and the like alone or in combination of two or more. Can be used as a mixture.

  Examples of the hydroxyl group-containing unsaturated monomer include (a) 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, allyl alcohol, homoallyl alcohol, Keihi Hydroxyl group-containing unsaturated monomers such as alcohol and crotonyl alcohol, (b) for example ethylene glycol, ethylene oxide, propylene glycol, propylene oxide, butylene glycol, butylene oxide, 1,4-bis (hydroxymethyl) cyclohexane, phenylglycidyl Dihydric alcohols or epoxy compounds such as ether, glycidyl decanoate, Plaxel FM-1 (manufactured by Daicel Chemical Industries, Ltd.) and, for example, acrylic acid, methacrylic acid, maleic acid, fumaric acid, Tonsan, and the like hydroxyl group-containing unsaturated monomers obtained by reaction of an unsaturated carboxylic acid such as itaconic acid. One or more selected from these hydroxyl group-containing unsaturated monomers can be polymerized to produce a polyol.

  In addition, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, tert-butyl acrylate, ethyl hexyl acrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-methacrylic acid n- Butyl, tert-butyl methacrylate, ethyl hexyl methacrylate, glycidyl methacrylate, cyclohexyl methacrylate, styrene, vinyl toluene, 1-methylstyrene, acrylic acid, methacrylic acid, acrylonitrile, vinyl acetate, vinyl propionate, vinyl stearate, acetic acid Allyl, diallyl adipate, diallyl itaconate, diethyl maleate, vinyl chloride, vinylidene chloride, acrylamide, N-methylol acrylamide, N-butoxymethyl acrylate One or more ethylenically unsaturated monomers selected from amide, diacetone acrylamide, ethylene, propylene, isoprene and the like, and a hydroxyl group-containing unsaturated monomer selected from the above (a) and (b) A polyol can also be produced by polymerizing the product.

  The number average molecular weight of a polyol obtained by polymerizing a monomer component containing a hydroxyl group-containing unsaturated monomer is from 1,000 to 500,000, preferably from 5,000 to 100,000. The hydroxyl value is 5 or more and 300 or less, preferably 10 or more and 200 or less, more preferably 20 or more and 150 or less.

  The polyester polyol obtained under the condition of excess hydroxyl group is (c), for example, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, neopentyl. Glycol, hexamethylene glycol, decamethylene glycol, 2,2,4-trimethyl-1,3-pentanediol, trimethylolpropane, hexanetriol, glycerin, pentaerythritol, cyclohexanediol, hydrogenated bisphenol A, bis (hydroxymethyl) Polyhydric alcohols such as cyclohexane, hydroquinone bis (hydroxyethyl ether), tris (hydroxyethyl) isosinurate, xylylene glycol, and (d) for example malee , Fumaric acid, succinic acid, adipic acid, sebacic acid, azelaic acid, trimetic acid, terephthalic acid, phthalic acid, isophthalic acid and other polybasic acids, and propanediol, hexanediol, polyethylene glycol, trimethylolpropane, etc. It can be produced by reacting under the condition that the number of hydroxyl groups in the monohydric alcohol is larger than the number of carboxyl groups of the polybasic acid.

  The number average molecular weight of the polyester polyol obtained under such an excessive hydroxyl group condition is 500 or more and 300,000 or less, and preferably 2000 or more and 100,000 or less. The hydroxyl value is 5 or more and 300 or less, preferably 10 or more and 200 or less, more preferably 20 or more and 150 or less.

  The polyol used as the base polymer of the polymer composition is obtained by polymerizing a monomer component containing the polyester polyol and the hydroxyl group-containing unsaturated monomer, and is a (meth) acryl unit or the like. An acrylic polyol having The binder 5 having such a polyester polyol or acrylic polyol as a base polymer has high weather resistance and can suppress yellowing of the anti-sticking layer 3. In addition, any one of this polyester polyol and acrylic polyol may be used, and both may be used.

  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 if the hydroxyl value in the solid content is 10 or less, the number of crosslinking points decreases, and the solvent resistance , Film properties such as water resistance, heat resistance and surface hardness tend to decrease.

  The base polymer is preferably a polyol having a cycloalkyl group. Thus, by introducing a cycloalkyl group into the polyol as the base polymer constituting the binder 5, the hydrophobicity such as water repellency and water resistance of the binder 5 is increased, and the said polymer under high temperature and high humidity conditions. The bending resistance, dimensional stability, etc. of the base sheet 1 for optical sheets are improved. Further, the basic properties of the coating film such as weather resistance, hardness, feeling of holding, and solvent resistance of the anti-sticking layer 3 are improved. Furthermore, the affinity with the filler 4 having an organic polymer fixed on the surface and the uniform dispersibility of the filler 4 are further improved.

  The cycloalkyl group is not particularly limited, and examples thereof include a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclononyl group, a cyclodecyl group, a cycloundecyl group, a cyclododecyl group, a cyclotridecyl group, Examples thereof include a cyclotetradecyl group, a cyclopentadecyl group, a cyclohexadecyl group, a cycloheptadecyl group, and a cyclooctadecyl group.

  The polyol having a cycloalkyl group can be 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 the molecule. The polymerizable unsaturated monomer is not particularly limited, and examples thereof include cyclohexyl (meth) acrylate, methylcyclohexyl (meth) acrylate, tert-butylcyclohexyl (meth) acrylate, and cyclododecyl (meth) acrylate.

  As described above, when a polyol is used as the base polymer, a polyisocyanate compound may be contained as a curing agent in the polymer composition. This polyisocyanate compound is a derivative of dimer, trimer, tetramer or the like obtained by polymerizing diisocyanate. By containing a polyisocyanate curing agent in the polymer composition, a three-dimensional crosslinked structure described later is easily and reliably formed, and the film physical properties of the anti-sticking layer 3 are further improved. In addition, since the curing reaction rate of the polymer composition is increased by blending the polyisocyanate compound, even if a cationic antistatic agent that contributes to the dispersion stability of the fine inorganic filler is contained in the polymer composition, the cationic charging is performed. The decrease in the curing reaction rate due to the inhibitor can be sufficiently compensated, and the productivity can be further increased.

  The polyisocyanate compound is preferably a xylene diisocyanate derivative or a mixture of this xylene diisocyanate derivative and an aliphatic diisocyanate derivative. This xylene diisocyanate derivative has a large effect of improving the reaction rate of the polymer composition, and among aromatic diisocyanate derivatives, yellowing and deterioration due to heat and ultraviolet rays are relatively small. A decrease in rate over time can be reduced. On the other hand, aliphatic diisocyanate derivatives have a smaller reaction rate improvement effect than aromatic diisocyanate derivatives, but yellowing, deterioration, etc. due to ultraviolet rays etc. are much smaller, so mixing with xylene diisocyanate derivatives can improve reaction rate. And the effect of preventing yellowing and the like can be achieved in a balanced manner.

  As a minimum of the compounding quantity of the said polyisocyanate compound (the compounding quantity of solid content conversion with respect to 100 parts of polymers in a polymer composition), 2 parts are preferable and 5 parts is especially preferable. On the other hand, the upper limit of the amount of the curing agent is preferably 20 parts, and particularly preferably 15 parts. Thus, by making the compounding quantity of a polyisocyanate compound into the said range, the above-mentioned hardening reaction rate improvement effect | action of a polymer composition can be show | played effectively.

  As the inorganic filler 4, it is preferable to use a material having an organic polymer fixed on the surface thereof. Thus, by using the inorganic filler 4 to which the organic polymer is fixed, the dispersibility in the binder 5 and the affinity with the binder 5 can be improved. The organic polymer to be fixed is not particularly limited with respect to its molecular weight, shape, composition, presence or absence of a functional group, and any organic polymer can be used. Moreover, about the shape of an organic polymer, the thing of arbitrary shapes, such as a linear form, a branched form, and a crosslinked structure, can be used.

  Specific resins constituting the organic polymer include, for example, (meth) acrylic resins, polystyrene, polyvinyl acetate, polyolefins such as polyethylene and polypropylene, polyesters such as polyvinyl chloride, polyvinylidene chloride, polyethylene terephthalate, and the like. Examples thereof include a resin partially modified with a functional group such as a copolymer, an amino group, an epoxy group, a hydroxyl group, or a carboxyl group. Among them, those having an organic polymer containing a (meth) acryl unit such as a (meth) acrylic resin, a (meth) acrylic-styrene resin, and a (meth) acrylic-polyester resin have a film forming ability. Is preferred. On the other hand, a resin having compatibility with the base polymer of the polymer composition is preferred, and therefore, the resin having the same composition as the base polymer contained in the polymer composition is most preferred.

  The inorganic filler 4 may contain an organic polymer in the fine particles. Thus, moderate softness and toughness can be imparted to the inorganic material that is the core of the filler 4.

  As the organic polymer, one containing an alkoxy group may be used, and the content is preferably 0.01 mmol or more and 50 mmol or less per 1 g of the filler 4 to which the organic polymer is fixed. Such an alkoxy group can improve the affinity with the matrix resin constituting the binder 5 and the dispersibility in the binder 5.

  The alkoxy group represents an RO group bonded to a metal element that forms a fine particle skeleton. 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. The same metal alkoxy group as the metal constituting the filler 4 is preferably used. When the filler 4 is colloidal silica, an alkoxy group having silicon as a metal is preferably used.

  The content of the organic polymer in the inorganic filler 4 to which the organic polymer is fixed is not particularly limited, but is preferably 0.5% by mass or more and 50% by mass or less based on the filler 4.

  A polyfunctional isocyanate compound, a melamine compound and an aminoplast resin having a hydroxyl group as the organic polymer fixed to the filler 4 and having two or more functional groups capable of reacting with a hydroxyl group in the polymer composition constituting the binder 5 It is good to contain at least 1 sort (s) chosen from. As a result, the filler 4 and the matrix resin of the binder 5 are bonded in a cross-linked structure, the storage stability, stain resistance, flexibility, weather resistance, storage stability, etc. are improved, and the resulting coating has a glossy appearance. It will have.

  Further, an antistatic agent may be mixed in the polymer composition in a finely dispersed state. By forming the binder 5 from the polymer composition in which such an antistatic agent is mixed, an antistatic effect is exerted on the base sheet 1 for the optical sheet, and it is difficult to suck dust or to overlap with a prism sheet or the like. It is possible to prevent inconveniences caused by electrostatic charging such as. Further, when the surface is coated with an antistatic agent, the surface becomes sticky or contaminated, but such an adverse effect is reduced by kneading into the polymer composition. The antistatic agent is not particularly limited. For example, anionic antistatic agents such as alkyl sulfates and alkyl phosphates, cationic antistatic agents such as quaternary ammonium salts and imidazoline compounds, polyethylene glycol type Nonionic antistatic agents such as polyoxyethylene sorbitan monostearate and ethanolamides, polymer antistatic agents such as polyacrylic acid, conductive metal powders, metal oxide powders, carbon nanotubes, etc. Used. Among these, a cationic antistatic agent having a relatively large antistatic effect is preferable, and an antistatic effect is exhibited by addition of a small amount.

  The polymer composition for forming the binder 5 includes, for example, a plasticizer, a dispersant, various leveling agents, an ultraviolet absorber, and an antioxidant in addition to the base polymer, filler 4, curing agent, and antistatic agent. , Viscosity modifiers, lubricants, light stabilizers and the like may be appropriately blended.

  The lower limit of the average thickness T (average thickness in the region where no filler 4 is present) of the flat portion of the anti-sticking layer 3 is 50 nm, and 70 nm is particularly preferable. On the other hand, the upper limit of the average thickness T of the flat portion of the sticking prevention layer 3 is 150 nm, and 120 nm is particularly preferable. If the average thickness T of the sticking prevention layer 3 is smaller than the lower limit, it may be difficult to fix the filler 4 to the back surface of the base film 2. On the other hand, when the average thickness T of the anti-sticking layer 3 exceeds the above upper limit, the convex portion 6 formed on the back surface of the anti-sticking layer 3 by the filler 4 becomes small, and as a result, the sticking prevention of the optical sheet base sheet 1 is achieved. Functions may be reduced. Further, if the average thickness T of the anti-sticking layer 3 exceeds the upper limit, a phenomenon of interference of transmitted light due to refraction at both interfaces of the anti-sticking layer 3 may occur, and moire may occur.

  The arithmetic average roughness (Ra) of the back surface of the anti-sticking layer 3 is preferably 0.05 μm or more and 0.15 μm or less, particularly preferably 0.08 μm or more and 0.12 μm or less. The maximum height (Ry) of the back surface of the anti-sticking layer 3 is preferably 0.4 μm or more and 0.9 μm or less, and particularly preferably 0.6 μm or more and 0.7 μm or less. The ten-point average roughness (Rz) of the back surface of the sticking prevention layer 3 is preferably 0.3 μm or more and 0.8 μm or less, and particularly preferably 0.5 μm or more and 0.6 μm or less. When the arithmetic average roughness (Ra), maximum height (Ry), and ten-point average roughness (Rz) of the back surface of the anti-sticking layer 3 are smaller than the above ranges, the fine convex portions on the back surface of the anti-sticking layer 3 become small. There is a risk that the anti-sticking property is lowered. On the other hand, if the arithmetic average roughness (Ra) of the back surface of the sticking prevention layer 3 exceeds the above range, glare of the screen of the liquid crystal display device may occur and the quality may be lowered.

  The method for producing the base sheet 1 for optical sheets is not particularly limited as long as the above-described structure can be produced. (A) A base film extrudate made of a thermoplastic resin is formed by an extrusion method using a T die. A base film forming step, (b) a laminating step of laminating the anti-sticking layer composition on one surface of the base film extrudate, and (c) a base film extrudate and an anti-sticking layer composition. A production method having a stretching step of stretching the layered product is suitably used. Moreover, it is also possible to perform the said base film formation process and the said lamination | stacking process simultaneously by the coextrusion molding method using T-die. According to the manufacturing method using such an extrusion molding method, before the stretching step of stretching the laminate of the base film extrudate and the anti-sticking layer composition layer, on one surface of the base film extrudate. Since the lamination process of laminating the composition for the anti-sticking layer can be performed, the lamination process can be performed on the same production line as the base film forming process and the stretching process (that is, as an inline lamination process), resulting in a manufacturing cost. It is possible to manufacture a base sheet for an optical sheet in a form in which productivity and work efficiency are improved.

  In the optical sheet base sheet 1, the anti-sticking layer 3 includes a filler 4 and a resin binder 5, and the average thickness of the flat portion of the anti-sticking layer 3 is 50 nm or more and 150 nm or less. Since the particle diameter is 70 nm or more and 200 nm or less, the nano-sized filler 4 forms a relatively large and uniform fine convex portion 6 on the outer surface of the anti-sticking layer 3, and as a result, is superimposed on the back surface side. The fine convex portions 6 abut on the light guide plate, the prism sheet and the like in a scattered manner, have high anti-sticking properties, and can prevent the occurrence of interference fringes due to sticking.

  Moreover, since the average particle diameter of the filler 4 that exhibits the anti-sticking property is 70 nm or more and 200 nm or less, the average particle diameter of the filler 4 is smaller than the wavelength of visible light. Even if the filler 4 is blended, inhibiting the light transmittance is drastically reduced and has a high total light transmittance.

  Furthermore, since the optical sheet base sheet 1 has an average thickness of the flat portion of the anti-sticking layer 3 of 50 nm or more and 150 nm or less, the average thickness of the flat portion of the anti-sticking layer 3 is visible light. The interference phenomenon of transmitted light due to refraction at both interfaces of the anti-sticking layer 3 is smaller than the wavelength, and the occurrence of moire or the like can be effectively suppressed.

  Further, the optical sheet base sheet 1 has an average thickness of the flat portion of the anti-sticking layer 3 that is much smaller than that of the conventional one, and can promote the thinning of the liquid crystal display device that is required today. Furthermore, the base sheet 1 for optical sheets contains the filler 4 in the anti-sticking layer 3 in order to form the fine protrusions 6 on the outer surface, and does not contain resin beads like the conventional optical sheet, The sticking prevention layer 3 can be laminated in-line in the molding process of the base film 2 by the extrusion molding method. As a result, it is possible to omit other processes such as coating after the base film creation like a conventional optical sheet. Therefore, the reduction of manufacturing workability and manufacturing cost is greatly promoted.

  The optical sheet substrate sheet 11 in FIG. 3 includes a substrate film 2 and a sticking prevention layer 12 laminated on the back surface of the substrate film 2. The anti-sticking layer 12 has a plurality of fillers 4 arranged in layers and spaced apart from each other, and a binder 5 that fixes the fillers 4 to the back side of the base film 2.

  Since the type, content, and shape of the base film 2 and the filler 4, the binder 5 and the manufacturing method are the same as those of the optical sheet base sheet 1 in FIG. Omitted.

  The optical sheet substrate sheet 11 includes, as the filler 4, the main component small-diameter filler 4a and the subcomponent large-diameter filler 4b having an average particle diameter larger than that of the small-diameter filler 4a.

  The optical sheet substrate sheet 11 contains the main component small-diameter filler 4a and the subcomponent large-diameter filler 4b as the filler 4, so that the main component small-diameter filler 4a is formed on the back surface (outer surface) of the sticking prevention layer 12. As a result, fine convex portions 6a are formed on almost one surface, and relatively large convex portions 6b are formed in a scattered manner by the large-diameter filler 4b as a subcomponent. As a result, the sticking prevention property is remarkably improved.

  As a minimum of the average particle diameter of small diameter filler 4a, 50 nm is preferred and 80 nm is especially preferred. On the other hand, the upper limit of the average particle size of the small-diameter filler 4a is preferably 150 nm, and particularly preferably 120 nm. When the average particle size of the small-diameter filler 4a is less than the above lower limit, the surface energy becomes high, so that it is difficult to disperse the binder 5 in the binder 5, and the convex portion 6a formed on the back surface of the sticking prevention layer 3 by the small-diameter filler 4a. There is a possibility that the anti-sticking function cannot be achieved. On the other hand, when the average particle diameter of the small-diameter filler 4a exceeds the above upper limit, the effect of shielding light transmission due to the influence of a short wavelength is increased, leading to a decrease in the total light transmittance of the base sheet 11 for optical sheets. There is a risk.

  As a minimum of the average particle diameter of large diameter filler 4b, 200 nm is preferred and 300 nm is particularly preferred. On the other hand, the upper limit of the average particle size of the large-diameter filler 4b is preferably 1.2 μm and particularly preferably 1 μm. If the average particle diameter of the large-diameter filler 4b is smaller than the above lower limit, the convex portions 6b formed in a scattered manner on the back surface of the anti-sticking layer 12 become small, and the effect of improving the anti-sticking property cannot be expected. On the other hand, when the average particle diameter of the large-diameter filler 4b exceeds the above upper limit, the fixability of the large-diameter filler 4b in the anti-sticking layer 12 is deteriorated, which is contrary to the demand for thinning the anti-sticking layer 12.

  As a compounding ratio of the large-diameter filler 4b with respect to all the fillers 4, 5 mass% or more and 30 mass% or less are preferable, and 10 mass% or more and 20 mass% or less are especially preferable. When the blending ratio of the large-diameter filler 4b is smaller than the above range, the density of the relatively large convex portions 6b formed in a scattered manner on the back surface of the anti-sticking layer 12 as described above is lowered, and the above anti-sticking property is obtained. The improvement effect cannot be expected. On the other hand, if the blending ratio of the large-diameter filler 4b exceeds the above range, the effect of improving the anti-sticking property cannot be expected, and conversely, the light transmittance of the base sheet 11 for optical sheets is reduced by blending the large-diameter filler 4b. There is a risk.

  In addition, the base material sheet for optical sheets of this invention is not limited to the said embodiment. For example, the polymer composition can contain an ultraviolet absorber. By forming the binder 5 from the polymer composition containing the ultraviolet absorber in this way, the base sheet for the optical sheet is given an ultraviolet cut function, and a small amount of ultraviolet rays emitted from the lamp of the backlight unit are cut. The liquid crystal layer can be prevented from being broken by ultraviolet rays.

  The ultraviolet absorber is not particularly limited as long as it is a compound that absorbs ultraviolet rays and can be efficiently converted into thermal energy, and is stable to light, and a known one can be used. . Among them, salicylic acid-based UV absorbers, benzophenone-based UV absorbers, benzotriazole-based UV absorbers, and cyano have a high UV-absorbing function, good compatibility with the above-mentioned base polymer, and exist stably in the base polymer. An acrylate ultraviolet absorber is preferable, and one or more selected from these groups may be used. Further, as the ultraviolet absorber, a polymer having an ultraviolet absorbing group in a molecular chain (for example, “Udable UV” series of Nippon Shokubai Co., Ltd.) is also preferably used. By using a polymer having an ultraviolet absorbing group in such a molecular chain, the binder 5 is highly compatible with the main polymer, and deterioration of the ultraviolet absorbing function due to bleeding out of the ultraviolet absorbent can be prevented. A polymer having an ultraviolet absorbing group in the molecular chain can be used as the base polymer of the binder 5. Further, it is possible to use the polymer to which the ultraviolet absorbing group is bonded as the base polymer of the binder 5 and further to contain an ultraviolet absorbent in the base polymer, and the ultraviolet absorbing function can be further improved.

  The lower limit of the content of the ultraviolet absorber relative to the base polymer of the binder 5 is preferably 0.1% by mass, particularly 1% by mass, and more preferably 3% by mass, and the upper limit of the content of the ultraviolet absorber is 10% by mass. In particular, 8% by mass, and further 5% by mass are preferable. This is because, if the mass ratio of the ultraviolet absorber to the base polymer is smaller than the lower limit, the ultraviolet absorbing function of the base sheet for optical sheets cannot be effectively achieved. If the mass ratio exceeds the above upper limit, the base polymer is adversely affected, and the strength, durability and the like of the binder 5 are reduced.

  It is also possible to use an ultraviolet stabilizer (including a base polymer in which an ultraviolet stabilizing group is bonded to a molecular chain) instead of the ultraviolet absorbent or together with the ultraviolet absorbent. By this ultraviolet stabilizer, radicals generated by ultraviolet rays, active oxygen and the like are inactivated, and ultraviolet stability, weather resistance and the like can be improved. As this ultraviolet stabilizer, a hindered amine ultraviolet stabilizer having high stability against ultraviolet rays is preferably used. In addition, the combined use of an ultraviolet absorber and an ultraviolet stabilizer significantly improves deterioration prevention and weather resistance due to ultraviolet rays.

  In addition to the base film and the anti-sticking layer, the optical sheet base sheet may be laminated with other layers such as an ultraviolet absorber layer, an antistatic agent layer, a top coat layer, and an easy adhesion layer. .

  EXAMPLES Hereinafter, although this invention is explained in full detail based on an Example, this invention is not interpreted limitedly based on description of this Example.

[Example 1]
Polyethylene terephthalate (hereinafter referred to as “PET”) was supplied to a T-die and extruded to form a PET film extrudate, and the PET film extrudate was stretched three times in the film longitudinal direction. Next, 100 parts of polyester polyol (“Vylonal MD1250” manufactured by Toyobo Co., Ltd.), 120 parts of blocked isocyanate (“Elastoron H-3” manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) and an average particle size of 100 nm in terms of solid content An anti-sticking layer composition containing 50 parts of silica was prepared, and this anti-sticking layer composition was coated on a PET film extrudate by a roll coating method. The anti-sticking layer composition and the PET film extrudate A laminate was formed. Next, this laminate was stretched 3 times in the film width direction to obtain an optical sheet base sheet (an average thickness of the anti-sticking layer of 100 nm) having an average thickness of 188 μm. All of these steps were performed continuously on the same production line.

  Even if this base sheet for optical sheets was cut into 20 cm square and the anti-sticking layer was overlapped with the acrylic plate, no interference pattern was generated and the anti-sticking effect was good. Also, the base sheet for optical sheet cut as described above is superposed on an acrylic plate in the presence of water and allowed to stand for 24 hours under environmental test conditions (70 ° C. × RH 95%). Attempts were made to peel off the base sheet and the acrylic plate, and they were easily peeled off. When the total light transmittance of the base sheet for optical sheets was measured, it was as good as 93.1%. Further, the arithmetic average roughness (Ra), maximum height (Ry) and ten-point average roughness (Rz) of the back surface of the sticking-preventing layer of the base sheet for optical sheets were measured. 63 μm and 0.52 μm. The pencil hardness of the anti-sticking layer of the base sheet for optical sheets was H to 2H.

[Example 2]
The same anti-sticking layer composition and PET as used in Example 1 were respectively fed to a multilayer die and co-extruded to form a co-extrusion molding comprising an anti-sticking layer composition layer and a PET film extrudate. Formed body. Subsequently, this co-extruded product was simultaneously biaxially stretched at a stretch ratio of 3 times in the film longitudinal direction and 3 times in the film width direction to thereby form an optical sheet base sheet (average thickness of the anti-sticking layer of 100 nm) of 188 μm. ) All of these steps were performed continuously on the same production line.

  Even if this base sheet for optical sheets was cut into 20 cm square and the anti-sticking layer was overlapped with the acrylic plate, no interference pattern was generated and the anti-sticking effect was good. Also, the base sheet for optical sheet cut as described above is superposed on an acrylic plate in the presence of water and allowed to stand for 24 hours under environmental test conditions (70 ° C. × RH 95%). Attempts were made to peel off the base sheet and the acrylic plate, and they were easily peeled off. Moreover, when the total light transmittance of the said optical sheet was measured, it was as favorable as 91%. Moreover, it was 26.5 nm when the arithmetic mean roughness (Ra) of the sticking prevention layer back surface of the said base material sheet for optical sheets was measured.

  Thus, it turned out that the base material sheet for optical sheets of this invention has the optical functions, such as the outstanding adhesion prevention effect and a total light transmittance. The total light transmittance was measured with a haze meter manufactured by Suga Test Instruments Co., Ltd. according to JIS-K7105. In addition, the arithmetic average roughness (Ra), maximum height (Ry) and ten-point average roughness (Rz) of the surface properties are set to a cutoff λc of 2.5 mm and an evaluation length of 12.5 mm in accordance with JIS B0601-1994. Measured using a stylus type surface roughness measuring machine “Surfcom 470A” manufactured by Tokyo Seimitsu Co., Ltd.

  As described above, the base sheet for an optical sheet of the present invention is useful as a constituent element of a backlight unit of a liquid crystal display device, and is particularly suitable for use in a transmissive liquid crystal display device.

It is a typical sectional view showing the substrate sheet for optical sheets concerning one embodiment of the present invention. It is a typical bottom view of the base sheet for optical sheets of FIG. It is typical sectional drawing which shows the base material sheet for optical sheets which concerns on the form different from the base material sheet for optical sheets of FIG. (A) is a typical perspective view which shows a general edge light type backlight unit, (b) is a typical sectional view which shows a general optical sheet.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Base sheet for optical sheets 2 Base film 3 Sticking prevention layer 4 Filler 4a Small diameter filler 4b Large diameter filler 5 Binder 6 Convex part 6a Convex part 6b Convex part 11 Base sheet for optical sheet 12 Sticking prevention layer

Claims (10)

A substrate sheet for an optical sheet comprising a transparent substrate film and an anti-sticking layer laminated on one surface of the substrate film,
This anti-sticking layer contains a filler and its resin binder,
The average thickness of the flat portion of the anti-sticking layer is 50 nm or more and 150 nm or less,
The base sheet for optical sheets, wherein the filler has an average particle size of 70 nm or more and 200 nm or less.   The base sheet for an optical sheet according to claim 1, wherein the average particle diameter of the filler is larger than the average thickness of the flat portion of the sticking prevention layer. As the filler, contains a small-diameter filler of the main component, and a large-diameter filler of a subsidiary component having a larger average particle size than this small-diameter filler,
The base sheet for an optical sheet according to claim 1 or 2, wherein an average particle diameter of the small-diameter filler is 50 nm or more and 150 nm or less.   4. The base sheet for an optical sheet according to claim 1, wherein the content of the filler in the anti-sticking layer is 20% by mass or more and 50% by mass or less.   The base sheet for an optical sheet according to any one of claims 1 to 4, wherein the polymer constituting the binder has a three-dimensional crosslinked structure.   The base sheet for an optical sheet according to claim 5, wherein the binder is formed from a polymer composition containing an acrylic polyol and a curing agent.   The base sheet for optical sheets according to any one of claims 1 to 6, wherein colloidal silica is used as the filler.   The base sheet for an optical sheet according to any one of claims 3 to 7, wherein a coefficient of variation in particle size distribution of the small-diameter filler is 20% or less.   The base sheet for an optical sheet according to any one of claims 1 to 8, wherein an antistatic agent is dispersed and contained in the anti-sticking layer.   The base sheet for an optical sheet according to any one of claims 1 to 9, which is used in a backlight unit of a liquid crystal display device.

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