JP2010023343A - Base sheet for optical sheet and manufacturing process of optical sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing process of base sheets for optical sheets which can suppress manufacturing costs and keep productivity and operational efficiency improved and a manufacturing process of optical sheets which not only solves these issues and but also enables the development of excellent optical functions. <P>SOLUTION: The invention relates to a manufacturing process of optical sheets composed of transparent base films and sticking-preventive layers laminated on one side of the base films. The manufacturing process comprises a base film formation step to form an extruded body of the base film consisting of a thermoplastic resin by extrusion molding using a T dye, a lamination step to laminate a sticking-preventive layer on one side of the extruded body of the base film, and a stretch step to stretch the laminate of the extruded body of the base film and the sticking-preventive layer. The manufacturing process of optical sheets is characterized in that the lamination step is conducted prior to the stretch process. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing a base sheet for an optical sheet used for a liquid crystal display device and the like, and a method for producing an optical sheet comprising the 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. 8A, the edge light type backlight unit 50 basically includes a linear lamp 51 as a light source, and a rectangular plate shape disposed so that the end of the lamp 51 is along the end. The light guide plate 52 and various optical sheets disposed on the surface side of the light guide plate 52 are provided. Examples of such an optical sheet include a light diffusion sheet 53 disposed on the surface side of the light guide plate 52 and a prism sheet 54 disposed on the surface side of the light diffusion sheet 53.

  The function of the backlight unit 50 will be described. First, a light beam incident on the light guide plate 52 from the lamp 51 is reflected by a reflective dot or a reflection sheet (not shown) on the back surface of the light guide plate 52, and is reflected from the surface of the light guide plate 52. Emitted. Light rays emitted from the light guide plate 52 enter the light diffusion sheet 53, are diffused by the light diffusion sheet 53, and are emitted from the surface of the light diffusion sheet 53. Thereafter, the light beam emitted from the light diffusion sheet 53 enters the prism sheet 54 and is emitted as a light beam having a distribution having a peak in a substantially normal direction by the prism portion 54 a formed on the surface of the prism sheet 54.

  In this way, the light beam emitted from the lamp 51 is diffused by the light diffusion sheet 53 and refracted by the prism sheet 54 so as to show a peak in a substantially normal direction, and further a liquid crystal layer (not shown) on the surface side. ) Illuminates the entire surface. Although not shown, the surface of the prism sheet 54 is used for the purpose of relaxing the light condensing characteristics of the prism sheet 54, protecting the prism portion 54a, or preventing sticking between the prism sheet 54 and a liquid crystal panel such as a polarizing plate. An optical sheet is further arranged on the side.

  As the light diffusion sheet 53 provided in the backlight unit 50, generally, as shown in FIG. 8B, light in which a light diffusing agent 59 is dispersed in a transparent base material layer 55 and a binder 58. A bead-coated type light diffusion sheet having a diffusion layer 56 and an anti-sticking layer 57 in which beads 61 are dispersed in a binder 60 (see, for example, JP-A-7-5305 and JP-A-2000-89007) is used. Has been. Further, instead of coating beads, an embossed type light diffusion sheet (for example, Japanese Patent Application Laid-Open No. 2006-47608, which is disclosed in Japanese Patent Application Laid-Open No. 2006-47608, in which the uneven shape is transferred to the surface of a transparent base layer using a mold having an uneven shape. No. 2006-335028) is also used. These types of light diffusing sheets exhibit a light diffusing function due to the fine uneven shape on the surface.

Such a light diffusion sheet 53 is generally formed by extruding a molten thermoplastic resin from a T-die, and subsequently stretching the extruded body in the film longitudinal direction and the film width direction to form a base film. A step of laminating a composition for anti-sticking layer in which beads are dispersed in a binder on the back surface of the base film, and a composition for light diffusion layer in which a light diffusing agent is dispersed in the binder It is manufactured by performing the process of laminating | stacking on the surface of a base film. In this method, a composition for anti-sticking layer and a composition for light diffusion layer are prepared in advance, and these compositions are sequentially laminated on the base film in a production line different from the production line for base film formation. (Referred to as an off-line laminating method because the production line for forming the base film including the stretching step and the production line for laminating are separate). However, the manufacturing method of the light diffusing sheet that requires such a plurality of production lines increases the manufacturing cost and makes the manufacturing process complicated, resulting in inconveniences in terms of productivity and work efficiency.
Japanese Patent Laid-Open No. 7-5305 JP 2000-89007 A JP 2006-47608 A JP 2006-335028 A

  The present invention has been made in view of these inconveniences, and can solve the manufacturing method of the base sheet for an optical sheet, which can suppress the manufacturing cost, the productivity and the working efficiency are improved, and the problems. An object of the present invention is to provide a method for producing an optical sheet that can exhibit an excellent optical function at the same time.

The invention made to solve the above problems is
A method for producing a base sheet for an optical sheet comprising a transparent base film and an anti-sticking layer laminated on one surface of the base film,
A base film forming step of forming a base film extrudate made of a thermoplastic resin by an extrusion method using a T-die,
A laminating step of laminating the anti-sticking layer composition on one surface of the base film extrudate;
A stretching step of stretching the laminate of the base film extrudate and the composition layer for the anti-sticking layer,
It is a manufacturing method of the base sheet for optical sheets characterized by performing the said lamination process before the said extending process.

  According to the base sheet manufacturing method for an optical sheet, sticking prevention is performed on one surface of the base film extrudate before the stretching step of stretching the laminate of the base film extrudate and the anti-sticking layer composition layer. In order to perform the lamination process which laminates | stacks the composition for layers, a lamination process can be implemented in the same production line as a base film formation process and a extending process (namely, as an inline lamination process). Therefore, according to the method, it becomes possible to manufacture the base sheet for optical sheets in a form in which the manufacturing cost is suppressed and the productivity and work efficiency are improved.

  Between the said base film formation process and the said lamination | stacking process, you may have the preliminary extending process which pre-extends a base film extrudate. Even in the case of having the preliminary stretching step as described above, the lamination step of laminating the composition for the anti-sticking layer on one side of the preliminary stretched base film extrudate is performed as the base film forming step. Since it can be carried out on the same production line as the preliminary stretching step and the stretching step, the manufacturing cost can be further suppressed, and the productivity and work efficiency can be improved.

  In the preliminary stretching step, the base film extrudate is preferably stretched in the film longitudinal direction, and in the stretching step, the laminate of the base film extrudate and the anti-sticking layer composition layer is preferably stretched in the film width direction. According to such a stretching method, it is possible to obtain a base sheet for an optical sheet having a desired thickness with good flatness and dimensional stability and with little thickness unevenness. In addition, by combining the preliminary stretching step and the stretching step with the base film forming step and the laminating step in a predetermined order, the manufacturing cost is maintained while maintaining the flatness, dimensional stability, and thickness unevenness at a good level. Can be suppressed, and productivity and work efficiency can be improved.

  Moreover, in the said base material sheet manufacturing method for optical sheets, you may perform the said base film formation process and the said lamination | stacking process simultaneously by the coextrusion molding method using T-die. In this case, the melt of each of the thermoplastic resin and the anti-sticking layer composition constituting the substrate film extrudate is supplied to a multilayered T-die and coextruded to form a base in one step. A laminate of the material film extrudate and the anti-sticking layer composition layer can be obtained. Furthermore, since a lamination process involving coextrusion molding is performed before the stretching process of stretching the laminate of the base film extrudate and the anti-sticking layer composition layer, the manufacturing cost is further reduced, and the productivity and work efficiency are reduced. It becomes possible to improve.

  The step of stretching the laminate of the base film extrudate and the anti-sticking layer composition layer obtained by the co-extrusion method using a T die may be performed by sequential biaxial stretching or simultaneous biaxial stretching. According to the sequential biaxial stretching, it is possible to obtain a base sheet for an optical sheet having good flatness and dimensional stability and little thickness unevenness. On the other hand, according to simultaneous biaxial stretching, it is possible to obtain a base sheet for an optical sheet having a good in-plane balance. In addition, by combining the stretching process by any of these methods with the above-mentioned coextrusion molding, the manufacturing cost is suppressed and the productivity and work efficiency are improved while maintaining the flatness or the like or the in-plane balance at a good level. be able to.

  In the base sheet manufacturing method for an optical sheet, the anti-sticking layer composition may contain an inorganic filler and a synthetic resin binder (the inorganic filler has an average particle diameter of, for example, 50 nm or more and 150 nm or less). By using such an anti-sticking layer composition, it is not necessary to lay an easy-adhesion layer on the back surface of the base film, which has been conventionally performed as a pretreatment for laminating the anti-sticking layer composition. Reduction, thinning and weight reduction are possible. Moreover, the optical sheet having such an anti-sticking layer has excellent light transmittance, and the anti-sticking effect (adhesion prevention effect), the anti-static effect and the scratch prevention effect are equal to or higher than those of conventional optical sheets.

  An optical layer forming step of producing a base sheet for an optical sheet by performing a base film forming step, a laminating step, and a stretching step as described above, and then forming an optical layer on the other surface of the optical sheet base sheet An optical sheet can be manufactured by performing the above. According to such a method for producing an optical sheet, when producing a base sheet for an optical sheet, the laminating step can be carried out on the same production line as the base film forming step and the stretching step, thereby reducing the production cost. It becomes possible to manufacture an optical sheet with improved productivity and work efficiency.

  The optical layer may contain a light diffusing agent and its binder. According to an optical sheet provided with an optical layer containing such a light diffusing agent and its binder, optical functions such as condensing, refraction in the normal direction, and diffusion can be improved.

  The optical layer may have a fine concavo-convex shape having refractive properties. According to the optical sheet provided with the optical layer having such a fine concavo-convex shape, it is possible to improve the light diffusibility, facilitate the control, and reduce the thickness of the optical sheet.

  In the present invention, the “base film extrudate” means a film-like formed body made of a thermoplastic resin formed by extrusion using a T die in the base film forming step. Such a base film extrudate finally constitutes the base film of the base sheet for optical sheets produced by the method of the present invention. In the present invention, the “anti-sticking layer composition” means a composition used as a material for the anti-sticking layer used in the laminating step. Such a composition for anti-sticking layer finally constitutes the anti-sticking layer of the base sheet for optical sheets produced by the method of the present invention.

  As explained above, since the manufacturing method of the base sheet for optical sheets of the present invention can carry out the laminating step on the same production line as the base film forming step and the stretching step, the manufacturing cost is suppressed, It becomes possible to manufacture a base sheet for an optical sheet with improved productivity and work efficiency. Moreover, since the manufacturing method of the optical sheet of this invention can implement a lamination process on the same production line as a base film formation process and an extending process when manufacturing the base sheet for optical sheets, manufacturing cost is reduced. It becomes possible to manufacture an optical sheet in a form that suppresses and improves productivity and work efficiency.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as appropriate. FIG. 1 is a flowchart showing a method for producing a base sheet for optical sheets according to an embodiment of the present invention, FIG. 2 is a schematic diagram showing an apparatus for carrying out the method for producing a base sheet for optical sheets in FIG. 3 is a schematic cross-sectional view showing a product of each step of the method for manufacturing the base sheet for optical sheets in FIG. 1, and FIG. 4 is a flow showing the method for manufacturing the base sheet for optical sheets according to a form different from FIG. FIG. 5 is a schematic view showing an apparatus for carrying out the method for producing the base sheet for optical sheets in FIG. 4, and FIG. 6 is a schematic view showing products in each step of the method for producing the base sheet for optical sheets in FIG. 7A is a schematic sectional view showing an optical sheet manufactured by the method for manufacturing an optical sheet according to an embodiment of the present invention, and FIG. 7B is different from FIG. 7A. The optical sheet manufactured by the manufacturing method of the optical sheet concerning a form is shown. It is a schematic cross-sectional view.

  The manufacturing method of the base sheet for optical sheets of FIG. 1 has a base film formation process (STP1), a preliminary extending process (STP2), a lamination process (STP3), and an extending process (STP4).

  The base film forming step (STP1) in the manufacturing method of the base sheet for optical sheets in FIG. 1 is a long strip formed of the thermoplastic resin 1 as shown in FIG. 3 by a known extrusion method using a T die. This is a step of forming the base film extrudate 2 as a body. As a known extrusion molding method using a T-die, for example, a polishing roll method and a chill roll method can be cited.

  As the thermoplastic resin 1, a synthetic resin having light transmittance when cured can be used. The thermoplastic resin 1 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, and polymethyl methacrylate. Acrylic polymer, polystyrene, styrene polymer such as acrylonitrile / styrene copolymer, polyethylene, polypropylene, polyolefin having cyclic or norbornene structure, olefin polymer such as ethylene / propylene copolymer, vinyl chloride polymer, nylon or aromatic Amide polymers such as aromatic polyamides, imide polymers, sulfone polymers, polyether sulfone polymers, polyether ether ketone polymers Chromatography, polyphenylene sulfide polymers, vinyl alcohol polymers, vinylidene chloride polymers, vinyl butyral polymers, arylate polymers, polyoxymethylene-based polymers, epoxy-based polymers, and the like. These thermoplastic resins can be used alone or in combination.

  The thickness of the extruded base film extrudate 2 is not particularly limited, but is appropriately set depending on the structure of the T-die used and the ratio of stretching performed later, and can be about 40 μm or more and 2000 μm or less.

  The base film forming step (STP1) is performed by an extrusion molding apparatus that occupies a part of the schematic diagram shown in FIG. This extrusion molding apparatus mainly includes an extruder and a T-die 30, a pair of pressing rolls 31, a winder, and the like. As the extruder, a single screw extruder or a twin screw extruder can be used. As the T die 30, for example, a well-known one such as a fish tail die, a manifold die, a coat hanger die, or the like can be used. The pair of pressing rolls 31 are arranged adjacently and in parallel, and the extruder and the T die 30 are configured to be able to extrude the molten thermoplastic resin 1 into a nip between the pair of pressing rolls 31. The pair of pressing rolls 31 is provided with a temperature control means, and is configured to be able to control the surface temperature to a temperature optimum for extrusion molding. As the pressing roll 31, it is preferable to use a metal elastic roll comprising a metal roll and a flexible roll whose surface is covered with an elastic body. By using the extrusion molding apparatus having such a structure, first, the molten thermoplastic resin 1 is supplied to the T die 30, the thermoplastic resin is extruded by the extruder and the T die 30, and pressed by a pair of pressing rolls 31. The material film extrudate 2 is formed. The melting temperature of the thermoplastic resin 1 extruded from the T die 30 is appropriately selected in consideration of the melting point of the thermoplastic resin used.

  In the preliminary stretching step (STP2) in the method for producing the base sheet for optical sheets in FIG. 1, the base film extrudate 2 is preliminarily stretched prior to the lamination of the anti-sticking layer composition, as shown in FIG. This is a step of forming the substrate film extrudate 3 that has been preliminarily stretched.

  In order to form the preliminarily stretched base film extrudate 3 from the base film extrudate 2, the base film extrudate 2 may be stretched in the film longitudinal direction or stretched in the film width direction. May be. In accordance with the well-known sequential biaxial stretching order, the base film extrudate 2 is stretched in the longitudinal direction of the film in the preliminary stretching step, and the base film extrudate and the anti-sticking layer composition layer in the stretching step described later. It is preferable to stretch the laminate in the film width direction.

  This preliminary stretching can be performed at an appropriate temperature between the softening temperature and the melting temperature of the thermoplastic resin 1 constituting the base film extrudate 2. The stretching ratio of the preliminary stretching can be adjusted depending on the desired thickness of the substrate sheet for optical sheets, but is generally 2 to 5 times. The thickness of the preliminarily stretched base film extrudate 3 is thinner than the thickness of the base film extrudate 2 by the reciprocal of this stretch ratio.

  The preliminary stretching step (STP2) is performed by a stretching apparatus 32 having a well-known structure that occupies a part of the schematic diagram shown in FIG. The stretching device 32 mainly includes a heat stretching unit, a heat treatment unit, and the like. In this preliminary stretching step, the base film extrudate 2 is first introduced into the heat stretching section and stretched at an appropriate ratio in the film longitudinal direction or the film width direction, and then plane stability and dimensional stability are imparted. The preliminarily stretched base film extrudate 3 is formed by heat treatment.

  As shown in FIG. 3, the lamination step (STP3) in the method for producing the base sheet for an optical sheet in FIG. 1 has a binder composition 5 and a pre-stretched base film extrudate 3 on one surface. By laminating the anti-sticking layer composition 7 containing the filler 6 using a known roll coating technique, a laminated body 8 of the anti-sticking layer composition layer 4 and the substrate film extrudate 3 that has been preliminarily stretched. Is a step of forming.

  Although not shown, in order to facilitate the adhesion between the base film extrudate and the anti-sticking layer composition layer prior to this lamination step, it was formed by blending an antistatic agent, an inorganic filler, etc. in the binder. You may perform the process of providing the layer (easy-adhesion layer) of a composition.

  The binder composition 5 contained in the anti-sticking layer composition 7 contains a base polymer. When the binder composition 5 is cured, the fillers 6 are arranged and fixed at substantially equal density in the binder. In addition to the base polymer, the binder composition 5 includes, for example, a curing agent, an antistatic agent, a plasticizer, a dispersant, various leveling agents, an ultraviolet absorber, an antioxidant, a viscosity modifier, a lubricant, a light A stabilizer and the like may be appropriately blended.

  The base polymer is not particularly limited, and includes, for example, an acrylic resin, polyurethane, polyester, fluorine resin, silicone resin, polyamideimide, epoxy resin, ultraviolet curable resin, or organoalkoxysilane compound. A siloxane resin etc. are mentioned, These polymers can be used 1 type or in mixture of 2 or more types. In particular, the base polymer is preferably a polyol with high processability. The base polymer is preferably transparent when cured from the viewpoint of increasing light transmittance.

  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.

  The above polyols are ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, tert-butyl acrylate, ethyl hexyl acrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, methacrylic acid. N-butyl acid, tert-butyl methacrylate, ethyl hexyl methacrylate, glycidyl methacrylate, cyclohexyl methacrylate, styrene, vinyl toluene, 1-methylstyrene, acrylic acid, methacrylic acid, acrylonitrile, vinyl acetate, vinyl propionate, stearic acid Vinyl, allyl acetate, diallyl adipate, diallyl itaconate, diethyl maleate, vinyl chloride, vinylidene chloride, acrylamide, N-methylolacrylamide, N-but One or more ethylenically unsaturated monomers selected from dimethyl acrylamide, diacetone acrylamide, ethylene, propylene, isoprene and the like, and hydroxyl group-containing unsaturated selected from the above (a) and (b) It can also be produced by polymerizing a monomer.

  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 binder composition 5 is obtained by polymerizing the above polyester polyol and the monomer component containing the hydroxyl group-containing unsaturated monomer, and is a (meth) acryl unit. Etc. are preferred. By using a binder composition having such a polyester polyol or acrylic polyol as a base polymer, the weather resistance of the binder formed by curing the composition is improved. 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 in the curing reaction decreases. Coating physical properties such as solvent resistance, water resistance, heat resistance and surface hardness tend to decrease.

  The binder composition 5 may contain isocyanate as a curing agent. Thus, when an isocyanate hardening | curing agent is contained in a binder composition, when the composition hardens | cures, it can be set as a still stronger crosslinked structure. As this isocyanate, an aliphatic isocyanate is preferable.

  In particular, when a polyol is used as the base polymer, one or more of hexamethylene diisocyanate, isofurone diisocyanate and xylene diisocyanate may be mixed and used as a curing agent to be blended in the binder composition. When these curing agents are used, the curing reaction rate of the binder composition increases.

  The filler 6 contained in the anti-sticking layer composition 7 is roughly classified into an inorganic filler and an organic filler.

  The inorganic filler contained in the anti-sticking layer composition 7 is, for example, aluminum hydroxide, oxidation of an element selected from Groups 2 to 6 of the periodic table (for example, silicon, aluminum, zinc, titanium, zirconium, etc.) Products, barium sulfide, magnesium silicate, or a mixture thereof. As the inorganic filler, it is particularly preferable to use colloidal silica at a nano level (average particle diameter is about 10 nm or more and 150 nm or less).

  Examples of the organic filler contained in the anti-sticking layer composition 7 include acrylic resin, acrylonitrile resin, polyurethane, polyvinyl chloride, polystyrene, polyacrylonitrile, polyamide, and the like. Among them, an acrylic resin having high transparency when cured is preferable, and polymethyl methacrylate (PMMA) is particularly preferable.

  The shape of the filler 6 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. Among these, a spherical filler is preferable.

  The lower limit of the average particle diameter of the filler 6 is preferably 10 nm, particularly 50 nm, and more preferably 100 nm. On the other hand, the upper limit of the average particle diameter of the filler 6 is preferably 10 μm, particularly 5 μm, and more preferably 1 μm. An optical sheet provided with an anti-sticking layer containing a filler having an average particle diameter in such a range has excellent light transmittance. Moreover, when the composition for anti-sticking layers containing colloidal silica having an average particle diameter of about 10 nm to 150 nm is used, the anti-sticking layer can be formed without forming an easy adhesion layer on the back surface of the base film. The composition can be easily laminated, and the manufacturing cost can be reduced, the weight can be reduced, and the thickness can be reduced (the thickness of the anti-sticking layer is about 50 nm to 150 nm). Furthermore, the optical sheet having such an anti-sticking layer containing nano-sized colloidal silica has excellent light transmittance, and the anti-sticking effect, the antistatic effect, and the scratch prevention effect are also good.

  The blending amount of the filler 6 (the blending amount in terms of solid content in the anti-sticking layer composition 7) is preferably 1% by mass or more and 80% by mass or less, and more preferably 20% by mass or more and 50% by mass or less. If the amount of filler is less than this range, the effect of preventing sticking cannot be obtained sufficiently. On the other hand, if the filler content exceeds this range, the sticking prevention effect cannot be further improved, and the light transmittance decreases.

  In the lamination step (STP3), the thickness of the laminated anti-sticking layer composition layer 4 is not particularly limited, but is appropriately set depending on the structure of the lamination T-die used and the ratio of stretching performed later, and is 2 μm or more and 50 μm. The following can be set.

  The roll coating in the lamination step (STP3) is performed by a roll coater having a known structure that occupies a part of the schematic diagram shown in FIG. The roll coater mainly includes a coater pan 33, a pickup roll 34a, an adjustment roll 34b, a coating roll 34c, and a backup roll 34d. A direct roll coater in which the rotation direction of the coating roll and the traveling direction of the coating object are the same or a reverse roll coater in which the rotation direction of the coating roll and the traveling direction of the coating object are reversed can be used. The coater pan 33 is filled with the anti-sticking layer composition 7 containing the binder composition 5 and the filler 6, and the anti-sticking layer composition 7 is pumped from the coater pan 33 by the rotation of the pickup roll 34a. Thus, the anti-sticking layer composition 7 adheres to the outer peripheral surface of the pickup roll 34a and is delivered to the coating roll 34c. Meanwhile, the adjustment roll 34b adjusts the amount of the anti-sticking layer composition 7 attached to the outer peripheral surface of the pickup roll 34a. The application roll 34c with the anti-sticking layer composition 7 is rotated in the same direction as or in the opposite direction to the delivery direction of the preliminarily stretched base film 3, so that the application roll 34c and the backup roll 34d are rotated. An anti-sticking layer composition 7 is laminated on a supported pre-stretched base film 3, and a laminate of the anti-sticking layer composition 4 and a pre-stretched base film extrudate 3 8 is formed.

  As shown in FIG. 3, the stretching step (STP4) in the method for producing the base sheet for optical sheets in FIG. 1 includes the anti-sticking layer composition layer 4 formed in the laminating step and a prestretched substrate. The process of forming the base sheet 9 for optical sheets (it has the base film 10 and the sticking prevention layer 11) by extending | stretching the laminated body 8 of the film extrusion body 3 in a different direction from a preliminary extending process (STP2). It is.

  That is, the stretching direction in the stretching process is stretched in the film width direction when stretched in the film longitudinal direction in the preliminary stretching process, and stretched in the film longitudinal direction when stretched in the film width direction in the preliminary stretching process. Can do. In the preliminary stretching step, the base film extrudate 2 is stretched in the film longitudinal direction, and the laminate 8 of the anti-sticking layer composition layer 4 and the preliminarily stretched base film extrudate 3 in the stretching step. Can be stretched in the film width direction. According to such a stretching method, it is possible to obtain a base sheet for an optical sheet having a desired thickness with good flatness and dimensional stability and with little thickness unevenness.

  This stretching step is performed at an appropriate temperature between the softening temperature and melting temperature of the components constituting the laminate 8 of the composition layer 4 for anti-sticking layer and the preliminarily stretched substrate film extrudate 3. Can do. The stretching ratio in the stretching step can be adjusted depending on the desired thickness of the substrate sheet for optical sheets, but is generally 2 to 5 times.

  Although the thickness of the manufactured base sheet 9 for optical sheets is not specifically limited, Preferably it is 10 micrometers or more and 250 micrometers or less, Most preferably, they can be 20 micrometers or more and 200 micrometers or less. When the thickness of the base sheet for optical sheet 9 is less than the above range, curling tends to occur when a polymer composition for forming an optical layer or the like is applied, and handling becomes difficult. Inconvenience occurs. On the contrary, if the thickness of the base sheet 9 for the optical sheet exceeds the above range, the brightness of the liquid crystal display device may be lowered, and the thickness of the backlight unit is increased to make the liquid crystal display device thinner. It would be against the demands of

  The stretching step (STP4) is performed by a stretching apparatus 35 having a known structure that occupies a part of the schematic diagram shown in FIG. The stretching apparatus 35 mainly includes a heating stretching section, a heat treatment section, and the like. In this stretching step, the laminate 8 of the anti-sticking layer composition layer 4 and the preliminarily stretched base film extrudate 3 is first introduced into the heating stretch section and stretched in an appropriate ratio in a predetermined direction. Then, the base sheet 9 for optical sheets is formed by heat treatment for imparting planar stability and dimensional stability.

  The manufacturing method of the base sheet for optical sheets may include a cutting step of cutting the obtained base sheet 9 for optical sheets into a predetermined size after the stretching step (STP4). The cutting method of the optical sheet base sheet 9 in this cutting step is not particularly limited as long as it can be cut into a predetermined shape, and usually a punching press or the like is employed. By having a cutting step after the stretching step (STP4), it is possible to efficiently produce a desired base sheet for an optical sheet, curling due to winding of the base sheet for an optical sheet, peeling of the base film, etc. Can be suppressed.

  As described above, in the method for producing a base sheet for an optical sheet according to the present embodiment, the stretching step of stretching the laminate 8 of the anti-sticking layer composition layer 4 and the preliminarily stretched base film extrudate 3. Prior to (STEP 4), a laminating step (STP 3) for laminating the composition 7 for sticking prevention layer on one surface of the preliminarily stretched base film extrudate 3 is performed. Therefore, the laminating step (STP3) can be performed on the same production line as the base film forming step (STP1), the preliminary stretching step (STP2), and the stretching step (STEP4) (that is, as an inline laminating step). Therefore, according to the said method, the base sheet for optical sheets can be manufactured in the form which suppressed manufacturing cost and improved productivity and working efficiency.

  In the lamination step (STP3) of this embodiment, an air knife may be used to adjust the lamination thickness of the composition for anti-sticking layer. Further, instead of the roll coating method as described above, for example, a well-known coating method using a bar coater, a blade coater, a spin coater, a gravure coater, a flow coater, spraying, screen printing or the like may be used. The lamination process by such a coating method can be carried out on the same production line as the base film forming process (STP1), the preliminary stretching process (STP2), and the stretching process (STEP4).

  The manufacturing method of the base sheet for optical sheets of FIG. 4 has the base film formation process by the co-extrusion method using T-die, the simultaneous implementation process (STP1) of a lamination process, and an extending process (STP2). .

  The simultaneous execution step (STP1) of the base film forming step and the laminating step by the co-extrusion molding method is performed by a well-known co-extrusion molding method, as shown in FIG. This is a step of forming a coextruded molded body 18 which is a long strip formed of a layer 14 of the anti-sticking layer composition 17 containing a binder composition 15 and a filler 16. As a well-known co-extrusion molding method, for example, a feed block method using a multilayered T-die or a multilayer manifold method can be cited.

  As the thermoplastic resin 12, the same thing as said thermoplastic resin 1 can be used. Moreover, as the composition 17 for anti-sticking layer here, the thing similar to the said composition 7 for anti-sticking layer can be used. However, in order to perform coextrusion from the multilayer T-die, it is necessary to use a material essentially consisting of a thermoplastic resin as the base polymer of the binder composition 15.

  The thicknesses of the base film extrudate 13 and the anti-sticking layer composition layer 14 constituting the coextruded product 18 are not particularly limited, but depend on the structure of the multilayered T-die used and the ratio of stretching performed later. It is set appropriately and can be about 40 μm to 2000 μm and about 4 μm to 100 μm.

  In the manufacturing method of the base sheet for optical sheets in FIG. 4, the simultaneous execution step (STP1) of the base film forming step and the laminating step by the co-extrusion method is a part of the schematic diagram shown in FIG. It is carried out by an extrusion molding apparatus. This coextrusion molding apparatus mainly includes an extruder, a multilayered T-die 36, a pair of pressing rolls 37, a winder, and the like. As the extruder, a single screw extruder or a twin screw extruder can be used. As the multi-layered T die 36, for example, a known one such as a feed block type multi-layer T die or a manifold type multi-layer T die can be used. A pair of pressing rolls 37 are disposed adjacent to each other in parallel, and the extruder and the multilayered T-die 36 are laminated with the molten thermoplastic resin 12 and the anti-sticking layer composition 17 at the nip of the pair of pressing rolls 37. It is configured so that it can be extruded into a sheet shape. The pair of pressing rolls 37 is provided with a temperature control means, and is configured to be able to control the surface temperature to a temperature optimum for extrusion molding. It is preferable to use a metal elastic roll as the pressing roll 37. Using the coextrusion molding apparatus having such a structure, first, each of the molten thermoplastic resin 12 and the anti-sticking layer composition 17 is supplied to the multilayered T die 36, and these are fed by the extruder and the multilayered T die 36. The components are extruded together and pressed by a pair of pressing rolls 37 to form the coextruded product 18. The melting temperature of the thermoplastic resin 12 extruded from the multilayered T-die 36 and the anti-sticking layer composition 17 is the melting point of the thermoplastic resin and the binder composition (included in the anti-sticking layer composition) used, respectively. Is selected as appropriate.

  As shown in FIG. 6, the stretching step (STP2) in the method for producing the base sheet for optical sheets in FIG. 4 was formed in the simultaneous execution step of the base film forming step and the laminating step by the coextrusion molding method. In this process, the coextruded molded body 18 is stretched in the film longitudinal direction and the film width direction to form the optical sheet base sheet 19 (having the base film 20 and the sticking prevention layer 21).

  This stretching step (STP2) is performed at an appropriate temperature between the softening temperature and the melting temperature of the components constituting the coextruded molded body 18 composed of the base film extruded body 13 and the composition layer 14 for anti-sticking layer. Can do. The stretching ratio in the stretching step can be adjusted depending on the desired thickness of the base sheet 19 for optical sheets, but is generally 2 to 5 times each in the film longitudinal direction and the film width direction. The thickness of the stretched base sheet 19 for optical sheets is thinner than the thickness of the coextruded product 18 by the reciprocal of this stretch ratio (product). The thickness of the base sheet 19 for optical sheets can be made the same as the thickness of the base sheet 9 for optical sheets.

  The stretching step (STP2) is performed by a biaxial stretching apparatus 38 having a well-known structure that occupies a part of the schematic diagram shown in FIG. This biaxial stretching apparatus 38 mainly includes a heating stretching section, a heat treatment section, and the like. As the biaxial stretching method, a known method such as a tubular film biaxial stretching method or a flat film biaxial stretching method can be employed. Further, the biaxial stretching method may be a sequential biaxial stretching method in which stretching in the film longitudinal direction and stretching in the film width direction are separately performed, or simultaneously performing stretching in the film longitudinal direction and stretching in the film width direction simultaneously. A biaxial stretching method may be used. According to the sequential biaxial stretching, it is possible to obtain a base sheet for an optical sheet having good flatness and dimensional stability and little thickness unevenness. On the other hand, according to simultaneous biaxial stretching, it is possible to obtain a base sheet for an optical sheet having a good in-plane balance.

  As a method of sequential biaxial stretching, for example, the coextruded product 18 is guided to a heated roll group, stretched in the longitudinal direction of the film, and then guided to a heated tenter while holding both ends of the film with clips. It can be stretched in the width direction. As a method of simultaneous biaxial stretching, for example, the both ends of the co-extruded molded body 18 are guided to a heated tenter while being gripped by clips and stretched in the film width direction, and at the same time, the clip traveling speed is accelerated. The film can be stretched in the longitudinal direction. In general, heat treatment is performed to further impart planar stability and dimensional stability to these stretched products.

  The manufacturing method of the base sheet for optical sheets is a cutting step of cutting the obtained base sheet 19 for optical sheets into a predetermined size after the stretching step (STP2), as in the case of the embodiment described above. It is good to have. By having a cutting step after the stretching step (STP2), it is possible to efficiently produce a desired base sheet for an optical sheet, curling due to winding of the base sheet for an optical sheet, peeling of the base film, etc. Can be suppressed.

  As described above, in the method for producing a base sheet for an optical sheet according to the present embodiment, the respective melts of the thermoplastic resin 12 and the anti-sticking layer composition 17 are coextruded from a multilayered T die. The laminated body (coextrusion molding 18) of the base film extrudate 13 and the anti-sticking layer composition layer 14 can be obtained in a single step. Since the lamination process (coiling process in the same production line) accompanied by coextrusion molding is performed before the stretching process, it is possible to suppress manufacturing costs and improve productivity and work efficiency.

  In this embodiment, in order to facilitate adhesion between the base film extrudate 13 and the anti-sticking layer composition layer 14, an antistatic agent, an inorganic filler, etc. are blended in the binder between these layers. You may provide the layer (easy-adhesion layer) of the prepared composition. In this case, the melt of the composition constituting such an easy-adhesion layer is supplied to the multilayered T-die, and the three layers are formed by coextrusion molding together with the thermoplastic resin and the anti-sticking layer composition. Co-extruded bodies can be formed.

  Moreover, in the manufacturing method of the base sheet for optical sheets in the above-mentioned two embodiments, both stretching in the film longitudinal direction and stretching in the film width direction are performed, but only by stretching in any one of them. Can also produce a desired substrate sheet for an optical sheet.

  By performing the above-mentioned base film forming step, preliminary stretching step, laminating step and stretching step, or simultaneous execution step and stretching step of the base film forming step and the laminating step by coextrusion molding method, the base material for optical sheet An optical sheet can be manufactured by manufacturing a sheet and then performing a step of forming an optical layer on the other surface of the base sheet for optical sheet. That is, as shown in the optical sheet 40 of FIG. 7A, the composition for the optical layer 45 containing the light diffusing agent 47 and the binder 46 is used as the base sheet for the optical sheet (sticking containing the binder 43 and the filler 44). The optical layer 45 can be formed by laminating on the surface of the prevention layer 42 and the base film 41.

  As the composition of the light diffusing agent 47 and the binder 46 constituting the optical layer 45, the same composition as the above-described beads 6 and the binder composition 5 can be used. However, the lower limit of the average particle diameter of the light diffusing agent 47 is preferably 1 μm, particularly 2 μm, and further 5 μm, while the upper limit of the average particle diameter of the light diffusing agent 47 is preferably 50 μm, particularly 20 μm, and further 15 μm.

  For laminating the optical layer 45 on the base sheet for optical sheets, for example, a known coating method using the above roll coater, bar coater, blade coater, spin coater, gravure coater, flow coater, spray, screen printing, etc. Can be adopted. The average thickness of the optical layer 45 is not particularly limited, but can be, for example, about 1 μm or more and 30 μm or less.

  Moreover, as shown in the optical sheet 48 of FIG.7 (b), the fine uneven | corrugated shape 49 which has refractive property may be formed in the other surface of the base material sheet for optical sheets, and you may function as an optical layer. Alternatively, an optical layer having a fine uneven shape may be separately formed on the other surface of the base sheet for optical sheets. As the material for the optical layer when separately formed in this manner, the same material as that for the base film can be used.

  The method for producing an optical sheet of the type that forms a fine concavo-convex shape 49 having refractive properties on the other surface of the base sheet for an optical sheet and functions as an optical layer is not particularly limited. The method can be adopted.

  That is, (a) a method of forming an optical sheet by laminating a synthetic resin on a sheet mold having an inverted shape of the surface of the optical sheet and peeling the sheet mold, (b) a gold having an inverted shape of the surface of the optical sheet An injection molding method in which a molten resin is injected into a mold, (c) a method in which a sheet-shaped resin is reheated and pressed between a mold and a metal plate, and the shape is transferred ( d) An extruded sheet molding method in which a molten resin is passed through a nip between a roll mold having an inverted shape of the surface of the optical sheet on the peripheral surface and another roll, and the above shape is transferred.

  In addition, the method for producing an optical sheet of a type in which an optical layer having a fine uneven shape is separately formed on the other surface of the base sheet for optical sheets is not particularly limited, but the following method is adopted, for example. can do.

  That is, (d) the molten resin and the base sheet are passed through the nip between the roll mold having the reverse shape of the surface of the optical sheet on the peripheral surface and another roll, and the above shape is applied to the molten resin on the surface side of the base sheet (E) A radiation curable resin is applied to the surface of the substrate sheet, and pressed against a sheet mold, mold or roll mold having the same reverse shape as above, and uncured radiation curing. A method of transferring the shape to a mold resin and applying radiation such as ultraviolet rays to cure the radiation curable resin, (f) filling an uncured radiation curable resin into a mold or roll mold having the same inverted shape as above The method of apply | coating, pressing down with a base material sheet, leveling, and applying radiations, such as an ultraviolet-ray, and hardening a radiation curable resin is mentioned.

  Also in these optical sheet manufacturing methods, as described above, since the lamination process can be performed on the same production line as the base film forming process and the stretching process when manufacturing the base sheet for optical sheets, the manufacturing cost This makes it possible to manufacture an optical sheet with improved productivity and work efficiency. Furthermore, according to the optical sheet 40 provided with the optical layer 45 containing the light diffusing agent 47 and the binder 46, optical functions such as condensing, refraction in the normal direction side, and diffusion can be improved. . Moreover, according to the optical sheet 48 provided with the optical layer having the above-described fine uneven shape, it is possible to improve the optical function such as light diffusibility and reduce the thickness of the optical sheet.

  As the optical layer laminated on the other surface of the base sheet for optical sheets, in addition to the above, for example, (i) a microlens sheet having a microlens array composed of a plurality of hemispherical microlenses on the surface, (Ii) a prism sheet having a plurality of triangular prisms on the surface in a stripe shape, (iii) a lenticular lens sheet having a plurality of semi-cylindrical cylindrical lenses on the surface, and (iv) a lens on the surface. It is also possible to use a Fresnel lens sheet or the like in which only the curvature is arranged. These optical layers can also be laminated on the base sheet for optical sheets according to a known coating method.

  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 A composition for anti-sticking layer containing 50 parts of colloidal silica was prepared, and a laminate of the anti-sticking layer composition and the PET film extrudate was formed by a roll coating method. 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. According to JIS-K7105, when the total light transmittance of the base sheet for optical sheets was measured with a haze meter manufactured by Suga Test Instruments Co., Ltd., it was as good as 93.1%. According to JIS B0601-1994, with a cutoff λc of 2.5 mm and an evaluation length of 12.5 mm, using a stylus type surface roughness measuring machine “Surfcom 470A” manufactured by Tokyo Seimitsu Co., Ltd., the base sheet for optical sheet When the arithmetic average roughness (Ra), maximum height (Ry), and ten-point average roughness (Rz) of the anti-sticking layer surface were measured, they were 0.09 μm, 0.63 μm, and 0.52 μm, respectively. Moreover, the pencil hardness of the sticking prevention layer of the base sheet for optical sheets was H to 2H.

Next, 100 parts of a binder resin compound (Toyobo Co., Ltd. “Byron 200”) having polyester polyol as a base polymer, 50 parts of colloidal silica having an average particle diameter of 20 nm, a curing agent (Nippon Polyurethane Co., Ltd.) In a polymer composition containing 5 parts of “Coronate HX” and 5 parts of a light stabilizer (“PUVA-1033” from Otsuka Chemical Co., Ltd.), acrylic resin beads (Sekisui Plastics Industries ( Co., Ltd. “MBX-15”) 50 parts were mixed to prepare a coating solution. This coating liquid was applied to the surface of the base sheet for optical sheets by a roll coating method at 15 g / m ² (in terms of solid content) and cured to form an optical layer, whereby an optical sheet was obtained.

  Even when this optical sheet 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. Further, the optical sheet cut as described above was superposed on an acrylic plate with water interposed, and left for 24 hours under environmental test conditions (70 ° C. × RH 95%). After leaving, the optical sheet and the acrylic plate were peeled easily when peeled. Further, when the total light transmittance of the optical sheet was measured with a haze meter manufactured by Suga Test Instruments Co., Ltd. according to JIS-K7105, it was as good as 69.5%.

[Example 2]
The same anti-sticking layer composition and PET as used in Example 1 were respectively supplied to a multilayer die and co-extruded to form a sticking prevention layer composition layer and a PET film extrudate layer. A coextruded body was formed. 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. According to JIS-K7105, when the total light transmittance of the base sheet for optical sheets was measured with a haze meter manufactured by Suga Test Instruments Co., Ltd., it was as good as 91%. According to JIS B0601-1994, with a cutoff λc of 2.5 mm and an evaluation length of 12.5 mm, using a stylus type surface roughness measuring machine “Surfcom 470A” manufactured by Tokyo Seimitsu Co., Ltd., the base sheet for optical sheet When the arithmetic average roughness (Ra) of the anti-sticking layer surface was measured, it was 26.5 nm.

Next, the same coating solution as that used in Example 1 was prepared. This coating liquid was applied to the surface of the base sheet for optical sheets by a roll coating method at 15 g / m ² (in terms of solid content) and cured to form an optical layer, whereby an optical sheet was obtained.

  Even when this optical sheet 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. Further, the optical sheet cut as described above was superposed on an acrylic plate with water interposed, and left for 24 hours under environmental test conditions (70 ° C. × RH 95%). After leaving, the optical sheet and the acrylic plate were peeled easily when peeled. Further, when the total light transmittance of the optical sheet was measured with a haze meter manufactured by Suga Test Instruments Co., Ltd. according to JIS-K7105, it was as good as 69.5% as in Example 1.

  Thus, according to the base sheet manufacturing method and the optical sheet manufacturing method of the present invention, the stacking step of stacking the anti-sticking layer composition on one surface of the base film extrudate is performed as a base film. Since it is carried out in the same production line as the forming step and the stretching step, the production efficiency of the optical sheet base sheet and the optical sheet can be remarkably improved, and the optical sheet produced by the present invention has excellent adhesion. It was found to have a preventive effect and optical function.

  The base sheet for an optical sheet and the optical sheet obtained by the production method of the present invention are useful as components of a liquid crystal display device, and are particularly suitable for use in a transmissive liquid crystal display device.

It is a flowchart which shows the manufacturing method of the base sheet for optical sheets which concerns on one Embodiment of this invention. It is a schematic diagram which shows the apparatus which enforces the manufacturing method of the base material sheet for optical sheets of FIG. It is typical sectional drawing which shows the product of each step of the manufacturing method of the base material sheet for optical sheets of FIG. It is a flowchart which shows the manufacturing method of the base sheet for optical sheets which concerns on the form different from FIG. It is a schematic diagram which shows the apparatus which enforces the manufacturing method of the base material sheet for optical sheets of FIG. It is typical sectional drawing which shows the product of each step of the manufacturing method of the base material sheet for optical sheets of FIG. (A) is typical sectional drawing which shows the optical sheet manufactured by the manufacturing method of the optical sheet which concerns on one Embodiment of this invention, (b) is by the manufacturing method of the optical sheet which concerns on a different form from (a). It is typical sectional drawing which shows the manufactured optical sheet. (A) is a typical perspective view which shows a general edge light type backlight unit, (b) is a typical sectional view which shows the conventional general light-diffusion sheet.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Thermoplastic resin 2 Base film extrudate 3 Preliminarily stretched base film extrudate 4 Composition layer 5 for anti-sticking layer Binder composition 6 Filler 7 Composition for anti-sticking layer 8 Base film extrudate and Laminate 9 of composition layer for anti-sticking layer Substrate sheet for optical sheet 10 Substrate film 11 Anti-sticking layer 12 Thermoplastic resin 13 Extruded substrate film 14 Composition layer for anti-sticking layer 15 Binder composition 16 Filler 17 Anti-Sticking Layer Composition 18 Coextrusion Molded Body (Laminate of Extruded Base Film and Composition Layer for Anti-Sticking Layer)
DESCRIPTION OF SYMBOLS 19 Base sheet 20 for optical sheets Base film 21 Sticking prevention layer 30 T die 31 A pair of press roll 32 A drawing apparatus 33 Coater pan 34a Pickup roll 34b Adjustment roll 34c Coating roll 34d Backup roll 35 Stretching apparatus 36 Multilayer T die 37 A pair Pressure roll 38 stretching device 40 optical sheet 41 substrate film 42 anti-sticking layer 43 binder 44 filler 45 optical layer 46 binder 47 light diffusing agent 48 optical sheet 49 fine uneven shape

Claims (9)

A method for producing a base sheet for an optical sheet comprising a transparent base film and an anti-sticking layer laminated on one surface of the base film,
A base film forming step of forming a base film extrudate made of a thermoplastic resin by an extrusion method using a T-die,
A laminating step of laminating the anti-sticking layer composition on one surface of the base film extrudate;
A stretching step of stretching the laminate of the base film extrudate and the composition layer for the anti-sticking layer,
The manufacturing method of the base sheet for optical sheets characterized by performing the said lamination process before the said extending process.   The manufacturing method of the base sheet for optical sheets of Claim 1 which has the preliminary | backup extending process of extending | stretching a base film extrudate preliminarily between the said base film formation process and the said lamination | stacking process.   The base film extrudate is stretched in the film longitudinal direction in the preliminary stretching step, and the laminate of the base film extrudate and the anti-sticking layer composition layer is stretched in the film width direction in the stretching step. The manufacturing method of the base material sheet for optical sheets of description.   The manufacturing method of the base sheet for optical sheets of Claim 1 which performs the said base film formation process and the said lamination | stacking process simultaneously by the co-extrusion molding method using T-die.   The manufacturing method of the base sheet for optical sheets of Claim 4 which performs the said extending process by sequential biaxial stretching or simultaneous biaxial stretching.   The method for producing a base sheet for an optical sheet according to any one of claims 1 to 5, wherein the composition for an anti-sticking layer contains an inorganic filler and a synthetic resin binder. A base film forming step, a laminating step and a stretching step in the method for producing a base sheet for an optical sheet according to any one of claims 1 to 6,
An optical layer forming step of forming an optical layer on the other surface of the base sheet for an optical sheet manufactured by this manufacturing method.   The method for producing an optical sheet according to claim 7, wherein the optical layer contains a light diffusing agent and a binder thereof.   The method for producing an optical sheet according to claim 7, wherein the optical layer has a fine uneven shape having refractive properties.

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