JP2009061769A - Optical sheet for surface light source and its manufacturing process - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a process of efficiently manufacturing an optical sheet for a surface light source which is preferably used for a display apparatus of a large area and which has neither camber nor flexure and further has no winding peculiarity (curling). <P>SOLUTION: The manufacturing process of the optical sheet for the surface light source includes a supplying process of winding out a base material film 13 of a roll wound shape out of a roll and supplying it to a drum having a shaping mold of a prism part 16 on its surface, a hardening process of press-sticking the base material film to the shaping mold charged with a resin for forming the prism part and then hardening the resin for forming the prism part, a transfer process of transferring the hardened prism part to the base material film by exfoliating the base material film from the drum, a winding up process of roll-winding a prism part forming sheet where the prism part is formed, a sticking process of sticking a base material film side of the prism part forming sheet onto a base material sheet by simultaneously supplying the prism part forming sheet 20 of a roll-winding shape and the base material sheet 12 of a leaf shape or the roll-winding shape, and a cutting process of cutting the stuck sheet to a predetermined shape. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing an optical sheet for a surface light source, and an optical sheet for a surface light source obtained by the method, and more specifically, a method for producing an optical sheet for a surface light source and a surface preferably used for a large-area display device The present invention relates to a light source optical sheet.

  In recent years, display devices such as liquid crystal televisions and electric type advertising panels have a tendency to increase in area. Such a display device includes a surface light source device that emits light from the back surface, and the surface light source device includes an optical sheet for a surface light source that refracts and transmits light from the light source toward the display panel. The surface light source optical sheet has a prism portion formed by arranging a plurality of unit prisms, and is disposed on the light output surface on the display panel side in both the edge light type surface light source device and the direct type surface light source device. ing. Note that an edge light type surface light source device usually receives light from one end surface of a plate-shaped light guide such as a transparent acrylic resin, and a liquid crystal panel or the like from a light exit surface as one surface of the light guide. The direct-type surface light source device is a device in which a liquid crystal panel and a reflecting plate are arranged in a manner that sandwiches the light source, and is usually from a light source. It is an apparatus configured to reflect light to the back surface of a liquid crystal panel or the like by a reflecting plate.

An optical sheet for a surface light source used in a large area display device is supplied by unwinding and supplying a roll-wrapped base film from the roll according to the flow of increasing the area, forming a unit prism on the base film, It is manufactured by a method in which the obtained long optical sheet for a surface light source is wound in a rolled state (see, for example, Patent Document 1).
JP-A-6-324205 (Example 1, FIG. 19)

  Due to the recent increase in the area of display devices, the surface light source optical sheet used in the surface light source device is also required to have a larger area. However, the conventional surface light source optical sheet has a thin base film as a whole. The prism portion, which is generally made of a cross-linkable curable resin, shrinks when cured, and the thermal expansion coefficient and hygroscopic expansion coefficient after curing are generally different from those of the base film. Causes warping or deflection. In general, warpage or deflection is not necessarily uniform over the entire surface but may have a distribution, resulting in non-uniform distortion. As a result, there is a problem that the optical sheet is deformed from a flat surface, remains warped and bent after being mounted on the surface light source device, and further causes uneven brightness of the surface light source device.

  In order to efficiently manufacture an optical sheet for a surface light source using a roll-to-roll described in Patent Document 1 using a thick base sheet, a warp or a deflection caused by a thin film is used. Although the deformation is eliminated, this time, by increasing the thickness of the base sheet, the flexibility of the obtained optical sheet for surface light source is lowered, and therefore, it is difficult to form a prism portion that requires flexibility. . Furthermore, there is a problem that curling occurs when the roll is wound, which eventually causes deformation from another kind of flat surface. In addition to this, as a result of trial and error, it has been found that a thickness of 250 μm or more is required in order to prevent the warpage and deflection due to the increase in the thickness of the substrate. However, on the other hand, although the cause of the polyester resin base material used exclusively as the base material of such an optical sheet is unknown, the hue increases yellow when the thickness exceeds 250 μm. For this reason, it has been impossible to simply improve the warpage and deflection by increasing the thickness of the base material.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to efficiently provide an optical sheet for a surface light source that is preferably used in a display device having a large area and has no warping, bending, or curling. It is to provide a method of manufacturing. Another object of the present invention is to provide an optical sheet for a surface light source obtained by the method for producing an optical sheet for a surface light source.

  An optical sheet for a surface light source according to the first aspect of the present invention for solving the above-described problem includes a translucent substrate having a substrate sheet and a substrate film having a thickness smaller than that of the substrate sheet, A method of manufacturing an optical sheet for a surface light source, comprising: a prism portion formed by arranging a large number of unit prisms on a surface of a translucent substrate on the substrate film side, the roll-wrapped substrate film Unwinding from the roll, supplying the prism part shaping mold to the drum having the surface, and pressing the base film on the shaping mold filled with the prism part forming resin, Curing process for curing the resin for forming the prism part, a transferring process for peeling the base film from the drum and transferring the cured prism part to the base film, and forming the prism part with the prism part formed Low sheet Winding step to wind, roll-shaped prism part forming sheet and sheet-fed, roll-wound or continuous extruded base sheet are simultaneously supplied, and the prism part forming sheet is provided on the base sheet The base material film side is bonded, and the sheet after the bonding is cut into a predetermined shape.

  According to this invention, a prism portion is formed on a thin base film by roll-to-roll, and then the base film and a thick base sheet are bonded together, and then cut without being wound up. Manufacturing optical sheets. As a result, the prism part can be efficiently formed by roll-to-roll in order to perform the prism part forming process that requires flexibility for a thin film and highly flexible substrate. it can. In addition, the thick base sheet bonded after the completion of the processing that requires flexibility can solve the deformation from the flat surface of the optical sheet due to warping, bending, curling, etc. Since it cuts, the optical sheet for surface light sources which does not produce curl can be manufactured. The surface light source optical sheet thus obtained can be preferably applied to a surface light source device for a large-area display device.

  The preferable aspect of the manufacturing method of the optical sheet for surface light sources which concerns on the 1st aspect of this invention is comprised so that the said bonding process may have a correction means which corrects the curl of the said base material sheet supplied by roll winding. To do.

  According to this invention, since the correction | amendment means which corrects a curl is provided in a bonding process, for example, when a base material sheet is supplied by roll winding, the curl of the base material sheet can be eliminated.

  An optical sheet for a surface light source according to the second aspect of the present invention for solving the above-described problem is a translucent substrate having a substrate sheet and a substrate film having a thickness smaller than that of the substrate sheet, A method of manufacturing an optical sheet for a surface light source, comprising: a prism portion formed by arranging a large number of unit prisms on a surface of a translucent substrate on the substrate film side, the roll-wrapped substrate film Unwinding from the roll, supplying the prism part shaping mold to the drum having the surface, and pressing the base film on the shaping mold filled with the prism part forming resin, Curing process for curing the resin for forming the prism part, a transferring process for peeling the base film from the drum and transferring the cured prism part to the base film, and forming the prism part with the prism part formed Low sheet The winding step of winding, the roll-shaped prism part forming sheet is unwound from the roll, and the melted resin melt-extruded is laminated on the surface of the prism part forming sheet that has been unwound, and the molten resin is laminated. By cooling and solidifying the resin to form the base sheet, a bonding step of bonding the base sheet to the base film side of the prism portion forming sheet, and cutting the sheet after bonding into a predetermined shape And a cutting step.

  According to this invention, as in the first aspect, after the prism portion is formed on a thin base film by roll-to-roll, the base film and a thick base sheet formed by melt extrusion are bonded together. Then, the sheet is cut without being wound up to produce an optical sheet for a surface light source. As a result, the prism part can be efficiently formed by roll-to-roll in order to perform the prism part forming process that requires flexibility for a thin film and highly flexible substrate. it can. In addition, the thick base sheet bonded after the completion of the processing that requires flexibility can solve the deformation from the flat surface of the optical sheet due to warping, bending, curling, etc. Since it cuts, the optical sheet for surface light sources which does not produce curl can be manufactured. The surface light source optical sheet thus obtained can be preferably applied to a surface light source device for a large-area display device. In particular, in the present invention, as a thick base sheet, a melt-extruded molten resin is laminated in a molten state on the surface of the prism portion forming sheet on the base film side, and then the molten resin is cooled and solidified. There is no curl like a base sheet supplied by roll winding, and efficient continuous production becomes possible.

  The preferable aspect of the manufacturing method of the optical sheet for surface light sources which concerns on the 1st, 2nd aspect of this invention is the said bonding process WHEREIN: The said base material sheet and the said prism part formation sheet are passed through an adhesive agent or an adhesive. Configure to stick together.

  In this invention, when the base sheet after cooling and solidifying the melt-extruded molten resin is used as the base sheet formed by melt extrusion (first aspect), the base sheet and the prism portion forming sheet are It is preferable to configure it so that it is bonded via an adhesive or pressure-sensitive adhesive, but after the molten extruded molten resin is laminated on the surface of the prism part forming sheet on the base film side, the molten resin is cooled and solidified. In the case of forming a base sheet (second embodiment), such an adhesive or pressure-sensitive adhesive may or may not be present.

  The surface light source optical sheet of the present invention is manufactured by the method for manufacturing a surface light source optical sheet according to the first and second aspects of the present invention.

  According to this invention, since the optical sheet for surface light sources is manufactured by the above-described method, the optical sheet for surface light sources without curling and having a waist can be obtained at low cost and with high quality.

  According to the method for producing an optical sheet for a surface light source of the present invention, a prism portion is rolled to perform a prism portion forming process that requires flexibility on a thin film and highly flexible film-shaped substrate. -It can be formed efficiently with tow rolls. And the deformation | transformation from the flat surface by the curvature of an optical sheet, bending, a curl, etc. can be solved with the thick base material sheet bonded after the process which requires flexibility was completed. Furthermore, since it cuts into a predetermined shape after bonding, the optical sheet for surface light sources that does not cause warping or bending due to curling can be manufactured at low cost and with high quality.

  According to the optical sheet for surface light source of the present invention, since it is manufactured by the above-described method, the optical sheet for surface light source with no curl and low waist can be obtained at low cost and high quality, and a large area display can be obtained. The present invention can be preferably applied to a surface light source device for a device.

  Hereinafter, the manufacturing method of the optical sheet for surface light sources of this invention and the optical sheet for surface light sources obtained by the method are demonstrated in detail with reference to drawings. In addition, this invention is not limited to the following embodiment.

[Optical sheet for surface light source]
FIG. 1 is a schematic perspective view showing an example of an optical sheet for a surface light source according to the present invention. The surface light source optical sheet 10 of the present invention (hereinafter also simply referred to as “optical sheet”) is manufactured by the method for manufacturing the surface light source optical sheet of the present invention (the manufacturing method according to the first and second embodiments) described later. The light-transmitting substrate 11 and the prism portion 16 formed by arranging a large number of unit prisms 14 on the light-transmitting substrate 11 are provided. In particular, the optical sheet 10 of the present invention is configured such that the translucent substrate 11 has a relatively thick substrate sheet 12 and a relatively thin substrate film 13. The prism portion 16 is formed on the base film surface S3 having a small thickness of the translucent base 11. Each structure of this optical sheet 10 is demonstrated in the column of the manufacturing method of the optical sheet for surface light sources below.

[Method for Manufacturing Optical Sheet for Surface Light Source (First Aspect)]
2 and 3 are schematic views for explaining a method of manufacturing an optical sheet according to the first aspect of the present invention. Specifically, FIG. 2 is a process diagram for winding up the prism portion forming sheet 20 which is an intermediate sheet in which the prism portion 16 is formed on the base film 13 having a relatively small thickness, and FIG. FIG. 3 is a process diagram from the pasting of the part forming sheet 20 and the base sheet 12 to the production of the optical sheet 10 by cutting.

  The optical sheet manufacturing method according to the first aspect of the present invention is a method according to the first aspect for manufacturing the optical sheet 10 according to the present invention shown in FIG. 1 as shown in FIGS. A supply step of unwinding the wound base film 13 and supplying the shaping mold 42 of the prism portion 16 to the drum 41 on the surface, and the shaping mold 42 filled with the prism portion forming resin 43 on the substrate After the film 13 is pressure-bonded, a curing step for curing the prism portion forming resin 43, a transfer step for peeling the base film 13 from the drum 41 and transferring the cured prism portion 16 onto the base film 13, A winding step of rolling the prism portion forming sheet 20 having the prism portion 16 formed on the base film 13, and a roll-shaped prism portion forming sheet 20 and a single wafer, a roll, or a continuous shape The material sheet 12 is supplied at the same time, and the bonding step of bonding the base film side of the prism portion forming sheet 20 onto the base material sheet 12 and the cutting step of cutting the sheet 10 ′ after bonding into a predetermined shape And. Hereinafter, it demonstrates in order of each process.

(Supply process)
As shown in FIG. 2, in the supplying step, the belt-like base film 13 wound up in the state of the roll winding 31 is unwound from the roll winding 31, and this is applied to the shaping mold 42 of the prism portion 16 on the surface. This is a step of supplying the drum 41 having the same. The base film 13 is wound into a roll shape as represented by reference numeral 31, and the base film 13 drawn out from the roll winding 31 passes through the guide roller 26 and the transport rollers 25, 25 to the drum 41. Supplied.

  The supplied base film 13 constitutes a translucent base material 11 together with a base material sheet 12 to be described later, and acts as a base material for the prism portion 16 and transmits most of the light from the light source to the prism portion 16 side. Acts like The base film 13 may be any light-transmitting base material, and in particular, a base film having a transmittance of 85% or more is preferably used. In addition, the transmittance here is a value measured by a light transmittance meter (model: HM-150) manufactured by Murakami Color Research Laboratory Co., Ltd.

  The thickness of the base film 13 is in the range of 20 to 150 μm, preferably 50 to 75 μm. The base film 13 having a thickness within this range can be rolled, and can be supplied to the drum 41 in a state in which no curl is left during the roll winding. If the thickness is less than 20 μm, the cost of the base film 13 is increased, and if the thickness exceeds 150 μm, the flexibility is lowered and it is difficult to make the base film 13 adhere along the surface of the drum 41. Therefore, it becomes difficult to form the prism portion 16 with the apparatus as shown in FIG. In addition, although the width | variety of the base film 13 is not specifically limited, From recent enlargement and taking a plurality in the width direction etc., it can select arbitrarily from the wide range of 500-1800 mm, for example.

  Examples of the constituent material of the base film 13 include polyester resins such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, and acrylics such as polymethyl (meth) acrylate and methyl (meth) acrylate-butyl (meth) acrylate copolymer. Examples thereof include thermoplastic resins such as resin, polycarbonate resin, polystyrene resin, and polymethylpentene resin. Here, “(meth) acrylate” means acrylate or methacrylate.

  It is preferable that the base film 13 is produced by single layer extrusion. In addition, the base film 13 may be produced by other methods. The base film 13 produced by extrusion or the base film 13 produced by other methods is usually stretched. This stretching process may be a biaxial stretching process or a uniaxial stretching process, but usually a biaxial stretching process is preferably applied.

(Curing process)
As shown in FIG. 2, the curing step is a step of curing the prism portion forming resin 43 after the base film 13 is pressure-bonded to the shaping mold 42 filled with the prism portion forming resin 43. The pressing roll 21 shown in FIG. 2 presses the supplied band-shaped base film 13 against the forming surface of the shaping mold 42 of the drum 41. The drum 41 is usually made of a metal cylinder, and the surface thereof has a shaping die 42 having a shape in which unit prisms having a substantially triangular prism shape are arranged in parallel in a direction perpendicular to the ridgeline. Although not shown, the drum 41 rotates around the central axis. Further, the direction of the peripheral speed of the drum 41 is matched with the traveling direction of the supplied base film 13. The shaping die 42 of the drum 41 is supplied with and filled with prism portion forming resin 43 from a T-die nozzle 45 (see the cross section in FIG. 2).

  The pressing roll 21 presses the base film 13 onto the drum 41 at the same speed as the rotation speed of the drum 41, but the shaping mold 42 on the surface of the drum 41 is filled with a resin 43 for forming a prism portion. Therefore, the pressed base film 13 is in close contact with the shaping mold 42 with the prism portion forming resin 43 interposed therebetween. After that, as shown in FIG. 2, when an ionizing radiation curable resin is used as the prism portion forming resin 43 in a state where the base film 13 is pressure-bonded on the shaping mold 42, the ionizing radiation source 22, The ionizing radiation (for example, ultraviolet rays, electron beam, etc.) from 22 is irradiated from the base film 13 side. By such irradiation, the prism portion forming resin 43 between the base film 13 and the shaping mold 42 can be cross-linked and cured and simultaneously bonded to the base film 13, and at the same time, the prism portion forming resin is cross-linked and hardened. 43 is shaped into the shape of the shaping mold 42.

  In addition, although the ionizing radiation to irradiate is typically ultraviolet rays or electron beams, electromagnetic waves such as visible rays, X-rays and γ rays, or charged particle beams such as α rays can also be used. Such ionizing radiation, irradiation intensity thereof, and the like are arbitrarily selected depending on the type of the prism portion forming resin 44.

  As the prism portion forming resin 43, for example, a resin composition for an optical sheet similar to the conventional one can be applied. For example, homopolymers of (meth) acrylic acid esters such as poly (meth) methyl acrylate and poly (meth) butyl butyl, or (meth) methyl acrylate- (meth) butyl acrylate copolymers Copolymer of (meth) acrylic acid ester (herein, “(meth) acrylic acid” means acrylic acid or methacrylic acid), polyester such as polyethylene terephthalate and polybutylene terephthalate, polycarbonate, polystyrene A transparent resin such as a thermoplastic resin such as polymethylpentene, or an ionizing radiation curable resin cross-linked with an ionizing radiation such as an ultraviolet ray or an electron beam is used. Examples of the ionizing radiation curable resin include polyfunctional urethane (meth) acrylate, (meth) acrylate such as polyester (meth) acrylate, (meth) acrylate oligomer such as unsaturated polyester, methyl (meth) acrylate, ethyl (meth) 1 type selected from monofunctional monomers such as acrylate), (meth) acrylate polyfunctional monomers such as hexanediol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, etc. Alternatively, two or more kinds of compounds are used. When using ultraviolet rays or visible rays as ionizing radiation, a photoinitiator is added. As the photoinitiator, known photoinitiators such as benzophenone series, benzoin series, and thioxanthone series are used.

  Among these, an ionizing radiation curable resin composition composed of epoxy (meth) acrylate, urethane (meth) acrylate, monofunctional monomer, polyfunctional monomer, photoinitiator and the like is preferably used. The blending ratio of the constituent materials of the ionizing radiation curable resin composition is not particularly limited, but preferably, polyfunctional epoxy (meth) acrylate oligomer: 5 to 50 parts by weight, polyfunctional urethane (meth) acrylate oligomer: 5 to 50 Parts by weight, monofunctional monomer: 1-60 parts by weight, polyfunctional monomer: 5-30 parts by weight, photoinitiator: 0.01-10 parts by weight. The number of functional groups per molecule of the polyfunctional monomer or polyfunctional oligomer is about 2 to 8.

  In addition, as a resin composition, the compound (monomer component) containing (meth) acryloyl group and vinyl group other than the said monofunctional monomer and polyfunctional monomer as an arbitrary component can also be used. Moreover, what is generally used as an initiator for optical sheets can also be used as a photoinitiator (photopolymerization initiator). In addition to the above components, the resin composition may contain silicone, antioxidant, polymerization inhibitor, mold release agent, antistatic agent, ultraviolet absorber, light stabilizer, antifoaming agent, solvent, as necessary. Non-reactive acrylic resins, non-reactive urethane resins, non-reactive polyester resins, pigments, dyes, light diffusing agents, and the like can be used in combination.

  In addition, it is preferable that the refractive index of the prism part 16 is 1.555 or more, and the said resin composition is adjusted so that it may become such a refractive index. The upper limit of the refractive index of the prism portion 16 is not particularly limited, but is preferably 1.600 or less from the viewpoint of cost.

  As shown in FIG. 1, the representative shape of the formed prism portion 16 is such that the main cutting surface (cross section orthogonal to the ridge line) has a substantially triangular cross section, and the unit prism 14 having the ridge line at the apex is replaced by the ridge line. Are arranged in parallel in a direction orthogonal to the direction. When this prism portion 16 is used in the mode shown in FIG. 4 described later (a mode in which the top portion does not face the light guide 82), the angle of the top portion of the unit prism 14 is 80 ° to 110 °, preferably 90 ° or substantially. 90 ° is preferable, and in this case, the base angle represented by the slope extending from the valley between the unit prisms and the imaginary line parallel to the base film surface S3 is 45 ° or approximately 45 °. It is preferable that Therefore, the unit prism 14 in this case is usually in a cross-sectional shape composed of an isosceles triangle having a top portion of 90 ° or approximately 90 °.

  On the other hand, when the prism portion 16 is used in the mode shown in FIG. 5 described later (a mode in which the top portion faces the light guide 82), the angle of the top portion of the unit prism 14 is in the range of 40 ° to 70 °. Further, the same base angle as described above is preferably in the range of 70 ° to 55 °. Therefore, the unit prism 14 in this case is usually in a cross-sectional shape composed of isosceles triangles in the range of 40 ° to 70 ° at the apex.

  The unit prisms 14 that are arranged are arranged in parallel in a direction orthogonal to the ridgeline, and the pitch is usually formed, for example, about 10 to 300 μm, but the value is not particularly limited.

  Further, as the shape of the prism portion 16, other than the above can be applied. The term “prism” used in the present specification includes so-called lenses (Fresnel lens, lenticular lens, etc.) in addition to so-called various prisms in a narrow sense. For example, as a cross-sectional shape, in addition to a triangle, a polygon such as a quadrangle, a pentagon, a hexagon, an octagon, a curve such as a circle, an ellipse, and a sine curve, or a sector, a shape provided with a curvature near the vertex of the triangle, etc. A combination shape of a straight line and a curved line can be appropriately used according to desired optical characteristics. In addition, the unit prisms in the plane are arranged in a one-dimensional direction (linear array) in which columnar bodies as shown in FIG. 1 are arranged in a one-dimensional direction (perpendicular to the ridge line in FIG. 1). It is also possible to use a two-dimensional array (a typical example is a moth-eye lens) formed by arraying in a two-dimensional direction (vertical and horizontal directions).

(Transfer process)
As shown in FIG. 2, the transfer process is a process of peeling the base film 13 from the drum 41 and transferring the cured prism portion 16 to the base film 13. The peeling roll 23 shown in FIG. 2 is provided so as to be in contact with the base film 13 that is in close contact with the drum 41, and is bonded to the cured prism portion forming resin 43 in the shaping mold 42. 13 is peeled off together with the cured resin 43. Thus, the prism portion 16 in which a plurality of unit prisms 14 are arranged is transferred onto the base film 13. The intermediate sheet thus obtained is called a prism part forming sheet 20.

(Winding process)
As shown in FIG. 2, the winding step is a step of rolling the prism portion forming sheet 20 on which the prism portion 16 is formed. The intermediate sheet roll 32 after being rolled is wound around the prism portion 16 as the center side, but may be wound around the prism portion 16 outside. The roll winding can be performed by rotating the central axis of the intermediate sheet roll 32 with a predetermined torque.

(Bonding process)
As shown in FIG. 3, the bonding step includes the prism part forming sheet 20 fed from the intermediate sheet roll 32 of the prism part forming sheet 20 and the base sheet 12 fed from the winding roll 71 of the base sheet 12. It is a process of supplying the substrate film 12 at the same time and bonding the substrate film side of the prism portion forming sheet 20 onto the substrate sheet 12. In the example shown in FIG. 3, the base sheet 12 is rolled. However, the base sheet 12 is not necessarily supplied by roll winding, and the single-wafer base sheet 12 cut into a predetermined size is supplied. It is also possible to supply a continuously extruded base sheet obtained by cooling and solidifying a melt-extruded molten resin.

  The bonding is usually performed by applying an adhesive or a pressure-sensitive adhesive to either the prism portion forming sheet 20 or the base sheet 12. In the example of FIG. 3, the adhesive layer 18 is formed on the surface of the prism portion forming sheet 20 on the base film 13 side by the roll coater 51 to form the adhesive layer 18, for example, opposite to the traveling direction of the base film 13. The coating amount is defined by the rotating metering roll 54, and the base sheet 12 is bonded and integrated on the adhesive layer forming surface. The type of adhesive or pressure-sensitive adhesive is not particularly limited. For example, examples of the material of the adhesive include ionizing radiation curable resins and two-component curable urethane resins similar to those exemplified as the prism portion forming resin. Examples of the material for the pressure-sensitive adhesive include acrylic resin and rubber. In addition, when ionizing radiation curable resin is used as an adhesive, after the prism part forming sheet 20 and the base material sheet 12 are bonded together, a curing process by ionizing radiation irradiation is performed. When a thermosetting resin is used as the adhesive, the prism portion forming sheet 20 and the base sheet 12 are bonded together, and then a curing process is performed by heating.

  The method of applying the adhesive or the pressure-sensitive adhesive is not particularly limited, and various methods such as a comma coater and a bar coater can be adopted without being limited to the roll coater of the aspect shown in FIG. The thicknesses of the adhesive layer 18 and the pressure-sensitive adhesive layer applied in this way are not particularly limited, but may be any thickness within a range of 5 to 30 μm, for example.

  You may give other functions, such as light diffusibility, to an adhesive bond layer or an adhesive layer. For example, when providing light diffusibility, for example, light diffusing fine particles can be contained in the adhesive layer or the pressure-sensitive adhesive layer. As the light diffusing fine particles, light diffusing fine particles generally used for optical sheets are used. For example, poly (meth) methyl acrylate (acrylic) beads, poly (meth) butyl butyl beads, polycarbonate System beads, polyurethane beads, calcium carbonate beads, silica beads and the like are used. Further, an antistatic agent, an ultraviolet absorber, or the like can be added to provide an antistatic function or an ultraviolet absorbing function.

  As shown in FIG. 3, the bonding is performed by putting the drawn prism portion forming sheet 20 and the base sheet 12 drawn by the opposed conveying rollers 63 and 64 between two opposed rollers 61 and 62. It can be carried out by feeding it and then subjecting it to a curing treatment as required. The urging force of the rollers 61 and 62 facing each other is such that the adhesive layer 18 or the adhesive layer interposed between the prism portion forming sheet 20 and the base sheet transport roller 12 can sufficiently adhere and adhere both. It is preferable that the force is such that the unit prism 14 is not deformed.

  The base material sheet 12 supplied in this step constitutes the translucent base material 11 together with the base material film 13 described above, and acts as a base material for the prism portion 16, and much of the light from the light source is supplied to the prism portion 16. Acts to penetrate to the side. The base material sheet 12 may be a light-transmitting base material like the base material film 13, and a base material having a transmittance of 85% or more as a single base material is preferably used. In addition, the transmittance here is a value measured by a light transmittance meter (model: HM-150) manufactured by Murakami Color Research Laboratory Co., Ltd.

  The constituent material of the base sheet 12 is also the same as the base film 13 described above, for example, a polyester resin such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, an acrylic resin such as polymethyl methacrylate, a polycarbonate resin, a polystyrene resin, Preferred examples include thermoplastic resins such as polymethylpentene resin.

  When the base sheet 12 is supplied as a roll-shaped base sheet, the thickness of the base sheet 12 is in the range of 100 to 250 μm, preferably in the range of 120 to 200 μm. Since the base material sheet 12 having a thickness within this range can be rolled, it is convenient in production. By making the thickness of the base material sheet 12 within this range, it is possible to prevent warping and deflection from occurring in the translucent base material 11 obtained by being bonded to the base material film 13, and to some degree of rigidity. Therefore, it is possible to ensure the independence when mounted on a large screen surface light source device, and to suppress warping. When the thickness of the substrate sheet 12 is less than 100 μm, the translucent substrate 11 combined with the substrate film 13 is thin, so that the overall stiffness is weak, and the substrate sheet 12 is attached to a large area surface light source device. Later warping and deflection may remain. On the other hand, if the thickness of the substrate sheet 12 exceeds 250 μm, roll winding may not be possible, and even if roll winding is possible, it may be difficult to remove the curl, so manufacturing is somewhat problematic. As a result, the optical sheet 10 finally obtained becomes heavier and the cost is increased. Furthermore, particularly in the case of polyethylene terephthalate, if the sheet thickness exceeds 250 μm, the hue becomes yellowish, which is not preferable. Although the width of the base sheet 12 is not particularly limited, it is preferable to make it the same level as the base film 13 described above. In addition, when a curl, warp, etc. remain in the roll-shaped base material sheet 12, a curl, warp, etc. can be eliminated by the correction means mentioned later.

  Moreover, when supplying the base material sheet 12 as a sheet-like base material sheet (not shown), the thickness of the base material sheet is in the range of 100 to 1000 μm, preferably in the range of 120 to 250 μm. The sheet-like base material sheet can be manufactured by various methods, for example, the base material sheet 12 fed out from the winding roll 71 as shown in FIG. Alternatively, it may be produced by cutting a continuous base sheet obtained by melt extrusion into a predetermined size. Therefore, even if the base sheet before cutting has curling wrinkles or warpage, if the correction means can be added before cutting to eliminate curling wrinkles or warpage, the above-described roll-wrapped base sheet A base sheet having a thickness in the range of 100 to 2000 μm produced by the above-described method can be used. The reason for the lower limit value and the upper limit value of the thickness is the same as that of the roll-wrapped base sheet described above except for the reason such as curl.

  Further, as in the case of the base film 13, the base sheet 12 may be a continuous extruded base sheet made by single layer extrusion. The continuously extruded base sheet can be produced by continuously solidifying the melt-extruded molten resin by cooling and solidifying it in air or in a refrigerant. In the case of supplying such a continuously extruded base sheet (not shown), the thickness of the base sheet is in the range of 100 to 2000 μm, preferably in the range of 120 to 500 μm. The continuous extruded base sheet does not have, for example, a curl or the like like a base sheet supplied by roll winding, and enables efficient continuous production. Therefore, the continuous extruded base sheet is continuous with the prism portion forming sheet 20 as it is. Alternatively, they may be bonded together, or may be bonded after being cut to a predetermined size. Such a base sheet can be preferably used because it is unlikely to warp, but even if the base sheet has warp or the like, it can be eliminated by adding a correction means, as described above. It is also possible to use a substrate sheet having a thickness of 100 to 5000 μm, which is produced by the above-described method, which is thicker than a roll-shaped substrate sheet. The reason for the lower limit value and the upper limit value of the thickness is the same as that of the roll-wrapped base sheet described above except for the reason of warpage.

  In addition, the base material sheet 12 may be produced by a method other than the above. The continuously extruded substrate sheet 12 produced by extrusion or the substrate sheet 12 produced by other methods is usually subjected to stretching treatment such as biaxial stretching treatment or uniaxial stretching treatment, but usually biaxial stretching. Treatment is preferably applied.

(Cutting process)
As shown in FIG. 3, the cutting step is a step of cutting the bonded sheet 10 ′ obtained in the bonding step into a predetermined shape. The cutting means is not particularly limited, and may be cut by a cutter 73 as shown. The cutting position can be performed by controlling the feed amounts of the rollers 61 and 62 and the operation timing of the cutter 73. The optical sheet 10 obtained by cutting is then transported by transport rollers 65 and 66 to another process or the like.

(Correction means)
In this invention, it is preferable to comprise so that the said bonding process may have the correction means 72 which corrects the curl etc. of the base material sheet 12 supplied by roll winding. Various methods can be used as the correcting means 72. For example, the speed of the transport rollers 65 and 66 is made slower than the speed of the rollers 61 and 62, and a back tension is applied to the base sheet 12 to form the base sheet. A method of eliminating twelve curling flaws can be mentioned. Further, when a base sheet manufactured by melt extrusion or other methods is used, even when the base sheet has a warp or the like, the same correction means can be added to eliminate the warp or the like.

  The flatness of the base sheet 12 thus corrected is prepared by preparing a test piece obtained by cutting out the base sheet 12 into a square having a size of 200 mm × 200 mm, and first, on one surface of the test piece on a horizontal and flat glass plate. Are placed facing each other, and the distance from the glass plate surface at the four corners of the test piece is measured to a unit of 0.5 mm. Subsequently, the front and back of the test piece are reversed and placed on the glass plate with the other surface facing the glass plate, and the distance from the glass plate surface at the four corners is measured in the same manner. If the maximum value of the eight measured values is expressed as a result of measurement by an evaluation method (similar to evaluation of deformation from the flat surface of the optical sheet described later) as the value of “flatness” of the base sheet, 5 mm It is preferable to be within the following range.

  As described above, according to the method of manufacturing the surface light source optical sheet according to the first aspect of the present invention, the prism portion 16 is formed on the thin base film 13 by roll-to-roll, and then the base material is formed. Since the optical sheet 10 for surface light sources is manufactured by laminating the film 13 and the thick base sheet 12 and then cutting without winding, the prism portion 16 can be efficiently formed by roll-to-roll. In addition, the warped and bent can be solved by the thick base sheet 12 bonded. Furthermore, since it cuts into a predetermined shape after bonding, the optical sheet 10 for surface light sources which does not produce curl etc. can be manufactured. The surface light source optical sheet 10 thus obtained can be preferably applied to a surface light source device for a display device having a large area.

[Method for Manufacturing Optical Sheet for Surface Light Source (Second Aspect)]
The optical sheet manufacturing method (not shown) according to the second aspect of the present invention is a method according to the second aspect of manufacturing the optical sheet 10 according to the present invention shown in FIG. 1, and the manufacturing according to the first aspect described above. Although the supply mode of the base material sheet 12 shown in FIG. 3 is different from the method, the other manufacturing methods are the same. That is, the manufacturing method of this aspect passes through the same supplying process, curing process, transfer process, and winding process as in the first aspect, and then passes through the following bonding process that is different from the first aspect, and then again in the above process. The same cutting process as the 1st mode is provided. Hereinafter, only the bonding process peculiar to the second aspect will be described, and the other processes are the same as those of the first aspect, and the description thereof will be omitted.

  In the bonding step in the manufacturing method of the second aspect, the roll-shaped prism portion forming sheet 20 is unwound from the roll (intermediate sheet roll 32), and the surface on the base film 13 side of the unrolled prism portion forming sheet 20 is provided. The molten resin that has been melt-extruded is laminated, and the molten resin is cooled and solidified to form the substrate sheet 12, whereby the substrate sheet 12 is bonded to the substrate film 13 side of the prism portion forming sheet 20.

  At this time, lamination of the molten resin on the surface of the prism portion forming sheet 20 on the base film 13 side is performed by extruding the molten resin melted by heating from a predetermined shape extrusion die that can be extruded into a sheet shape, and the prism is left in a molten state It is performed so as to be bonded to the surface of the part forming sheet 20 on the base film 13 side. Examples of the resin used include polyester resins such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, acrylic resins such as polymethyl (meth) acrylate, methyl (meth) acrylate-butyl (meth) acrylate copolymer, polycarbonate resins, Examples thereof include thermoplastic resins such as polystyrene resin and polymethylpentene resin. Here, “(meth) acrylate” means acrylate or methacrylate.

  Cooling and solidification of the molten resin after lamination is performed by bringing it into contact with air or a refrigerant, or by bringing it into contact with a cooling roll. Examples of the cooling performed in contact with air or a refrigerant include a method of performing forced air blowing on the molten resin after laminating cold air subjected to heat exchange. In addition, as the cooling performed by contacting the cooling roll, for example, a laminated sheet that is still in a high temperature state including residual heat is wound around a part of the surface of the cooling roll, and the residual heat is applied to the cooling roll. And a method of cooling the laminated sheet by conducting the process. A typical example of such a cooling roll has a configuration in which a coolant such as water or chlorofluorocarbon is circulated in a hollow portion of a hollow metal roll. In addition, a method of supplying a refrigerant such as water or chlorofluorocarbon to the molten resin after lamination and bringing it into contact with each other, or putting the molten resin and the prism portion forming sheet 20 after lamination into the refrigerant at the same time can be mentioned. .

  The base sheet 12 obtained in this way does not have a curl like a base sheet supplied by, for example, roll winding, and enables efficient continuous production.

  In this second aspect, since the molten resin is laminated on the prism part forming sheet 20, the bonding of the base sheet 12 and the prism part forming sheet 20 is not changed depending on the materials of the base sheet 12 and the prism part forming sheet 20. In some cases, good adhesion may be exhibited. In that case, an adhesive or a pressure-sensitive adhesive may not be interposed. For example, when the base material sheet 12 and the prism part forming sheet 20 are the same kind of thermoplastic resins, or when the base material sheet 12 and the prism part forming sheet 20 are a combination of a polypropylene resin and a polyethylene resin, it is easy to exhibit good adhesion. On the other hand, depending on the material of the base material sheet 12 and the prism portion forming sheet 20, such adhesion may not be exhibited, and in that case, as in the case of the first aspect, it is preferable to bond them together using an adhesive or an adhesive. Configure.

  As described above, according to the method for manufacturing a surface light source optical sheet according to the second aspect of the present invention, the prism portion 16 is placed on the thin base film 13 in the roll-toe-like manner as in the case of the first aspect. After forming with a roll, the base film 13 and the thick base sheet 12 formed by melt extrusion are bonded together, and then cut without being wound up to produce the optical sheet 10 for surface light source. As a result, the prism portion 16 is efficiently formed by roll-to-roll in order to perform a prism portion forming process requiring flexibility on a thin film and highly flexible film-shaped substrate. Can do. In addition, the thick base sheet 12 bonded after the completion of the processing requiring flexibility can solve the deformation from the flat surface of the optical sheet 10 due to warpage, bending, curl, etc. Since it cuts into a shape, the optical sheet 10 for surface light sources which does not produce curl can be manufactured. The surface light source optical sheet 10 thus obtained can be preferably applied to a surface light source device for a display device having a large area. In particular, in the present invention, as a thick base sheet, a melt-extruded molten resin is laminated in a molten state on the surface of the prism portion forming sheet on the base film side, and then the molten resin is cooled and solidified. There is no curl like a base sheet supplied by roll winding, and efficient continuous production becomes possible.

  The optical sheet 10 manufactured by the manufacturing method according to the first and second aspects is provided with a light diffusion layer (not shown) on the flat surface on the side where the prism portion 16 is not formed, or a so-called mat treatment is performed. Can go. There have been many proposals for providing such a light diffusing function, and will not be described in detail here. However, for example, the mat processing is performed by giving a flat surface a predetermined surface roughness to provide a light diffusing function. Examples of the means include a method of mechanically roughening the surface, and forming an uneven layer containing particles.

  Further, the obtained optical sheet 10 can be mounted on the surface light source device in a single sheet configuration, but has a prism portion 16 in order to control the light diffusion angle in two directions (vertical direction and horizontal direction). Two optical sheets 10 may be laminated so that their ridges cross each other and attached to the surface light source device. The crossing angle at this time is usually about 15 ° to 90 ° (orthogonal). In this case, it is most preferable that the prism surfaces are oriented in the same direction, so that the light transmittance is the highest, but the prism portion 16 side faces each other, or the prism portion side 16 faces back to back. You may comprise.

[Surface light source device]
FIG. 4 is a perspective sectional view showing a typical example of a surface light source device mounted with the optical sheet 10 of the present invention, (A) shows an example of an edge light type surface light source device, and (B) is a direct type. An example of a surface light source device is shown. Of course, the surface light source device to which the optical sheet of the present invention can be applied is not limited to these two forms, but may be other forms such as an EL (electroluminescence). A surface light source device 80 shown in FIG. 4A is a so-called edge light type surface light source device, and light introduced from at least one (two in the illustrated example) end face 82A is light on one surface. A light guide 82 that emits light from the emission surface 82B and a light source 84 that allows light to enter the inside from an end surface 82A of the light guide 82 are provided. The optical sheet 10 is disposed so that the flat surface side of the translucent substrate 11 faces the light emission surface 82B side of the surface light source device 80. The optical sheet 10 may be disposed as it is as illustrated, or may be provided via a light diffusion film. In FIG. 4A, the light source 84 is a two-sided surface light source device, but the light source 84 is a single-sided surface light source device (not shown) having only one end surface. Also good.

  A surface light source device 90 shown in FIG. 4B is a so-called direct-type surface light source device, and irradiates light from the opposite surface of the optical sheet 10 according to the present invention and the prism portion 16 side of the optical sheet 10. 84 and a concave reflector 94 that is disposed on the opposite side of the optical sheet 10 as viewed from the light source 84 and reflects light from the light source 84 in the direction of the optical sheet 10.

  FIG. 5 is a perspective sectional view showing another example of the surface light source device to which the optical sheet of the present invention is mounted. FIG. 5A shows another example of the edge light type surface light source device, and FIG. The other example of the type | mold surface light source device is shown. The surface light source device 80 ′ shown in FIG. 5A is different from the surface light source device 80 in FIG. 4A described above in the direction of the prism portion 16 constituting the optical sheet 10, and the prism portion 16 is the same. In this embodiment, light is emitted from the light source 84 toward the optical sheet 10, that is, on the light emission surface 82 B side of the light guide 82. Further, the surface light source device 90 ′ shown in FIG. 5B is different from the surface light source device 90 shown in FIG. 4B in the direction of the prism portion 16 constituting the optical sheet 10, and the optical sheet 10 Is formed on the side from which light is emitted from the light source 84 toward the optical sheet 10, that is, on the light source 94 side.

  The light guide 82 is a plate-like body made of a translucent material, and emits light introduced from the end faces 82A on both sides in FIGS. 4A and 5A from the light emission surface 82B. It is configured. The light guide 82 is made of a light-transmitting material similar to the material of the optical sheet 10, but is usually made of acrylic or polycarbonate resin. The thickness of the light guide 82 is usually about 1 to 10 mm, and the thickness may be constant over the entire range. In the case of a single box type (not shown), the thickness of the end face 82A on which the light source 84 is disposed. It may be a wedge (taper) shape that is thickest at the position and gradually thins on the other side where there is no light source. In order to emit light from a wide surface (light emission surface 82B), it is preferable that the light guide 82 has a light scattering function added to the inside or the surface thereof.

  The light source 84 causes light to enter the inside from at least one end face 82 </ b> A of the light guide 82, and is disposed along the end face 82 </ b> A of the light guide 82. The light source 84 is not limited to a linear light source such as a fluorescent lamp, and a point light source such as an incandescent light bulb or an LED (light emitting diode) may be arranged in a line along the end surface 82A. A plurality of small flat fluorescent lamps may be arranged along the end face 82A.

  The optical sheet 10 described above is provided on the light emission surface 82B of the light guide 82 via a light diffusion film as necessary. As shown in FIG. 4, the optical sheet 10 may be provided so that the opposite surface of the prism portion 16 becomes the light emission surface 82B of the light guide 82, or the prism side is guided as shown in FIG. The light emitting surface 82B of the light body 82 may be provided.

  The reflectors 86 and 94 are provided on the surface opposite to the light emitting surface 82B of the light guide 82, and are for reflecting light emitted from this surface back into the light guide 82. As the reflector 86 shown in FIGS. 4A and 5A, a thin metal plate deposited with aluminum or the like, white foamed PET (polyethylene terephthalate), or the like is used. On the other hand, the reflector 94 shown in FIGS. 4 (B) and 5 (B) is also made of a thin metal plate deposited with aluminum or the like, similar to the above, but the shape thereof is the light from the light source 84. Any shape can be used as long as it can be uniformly reflected as parallel rays, and a shape such as a concave arc shape, a parabolic column shape, a hyperbolic column shape, or an elliptical column shape is selected.

  In the surface light source devices 90 ′ and 90 shown in FIGS. 4B and 5B, light from the light source 84 passes through the optical sheet 10 toward the light emission surface 92 on the optical sheet 10 side, There is one that passes through the optical sheet 10 toward the light emission surface 92 after being reflected by the reflector 94.

  As described above, since the surface light source device shown in FIGS. 4 and 5 employs the optical sheet 10 described above, when the optical sheet 10 is disposed on the front surface of the surface light source device, curling is caused. Since neither light modulation nor unevenness occurs, it can be preferably applied as a surface light source device for a display device with a large display area and a good display area.

  Next, the present invention will be described in more detail with reference to examples and comparative examples.

(Example 1)
As the base film 13, a roll 31 of a biaxially stretched polyethylene terephthalate (hereinafter referred to as “PET”) long film having a width of 900 mm, a thickness of 125 μm, and a refractive index of 1.56 is prepared. It was set in the feeder section of the manufacturing apparatus shown in FIG. On the other hand, a drum 41 having a prism-shaped shaping die 42 formed by arranging triangular prism-shaped unit prisms in parallel in the ridge direction on a metal cylinder surface is prepared, and while rotating this around the central axis, A prism portion forming resin 43 composed of an ultraviolet curable acrylate oligomer and an acrylate monomer was supplied from the T-die nozzle 45 to the surface of the drum 41 and filled into the shaping die 42 of the unit prism. Next, the base film 13 is unwound from the roll winding 31 at a speed synchronized with the rotational peripheral speed of the drum 41, and the base film 13 is pressure-bonded to the surface of the drum 41 by the pressing roll 21, so that the prism portion forming resin 43 is obtained. At the same time, the ultraviolet rays from the ultraviolet irradiation devices 22 and 22 are irradiated from the base film 13 side as it is, and the prism portion forming resin 43 is crosslinked and cured in the shaping mold 42 at the same time. The substrate film 13 was adhered. Next, the base film 13 traveling using the peeling roll 23 was peeled off together with the prism portion 16 adhered thereto, thereby obtaining the optical sheet 10 having the form shown in FIG. 1 in which a plurality of unit prisms composed of triangular prisms were arranged. Thereafter, the long optical sheet 10 was wound up as the prism portion forming sheet 20 with the prism portion 16 as the inner peripheral side.

  Next, the intermediate sheet roll 32 of the prism portion forming sheet 20 is set in the supply portion of the apparatus shown in FIG. 3, and the prism portion forming sheet 20 is fed out from the intermediate sheet roll 32 so that the prism portion 16 is not formed. An adhesive layer 18 was formed on the side surface. This adhesive layer 18 was formed by applying an acrylic resin-based pressure-sensitive adhesive so as to have a thickness of 5 μm with a roll coater. On the other hand, a roll 71 of biaxially stretched polyethylene terephthalate (hereinafter referred to as “PET”) long sheet having a width of 900 mm, a thickness of 250 μm, and a refractive index of 1.56 is prepared as the base sheet 12. Was set in another supply section of the manufacturing apparatus shown in FIG. This base material sheet 12 was unwound from the roll 71 and bonded to the surface of the prism part forming sheet 20 on the adhesive layer 18 side. The bonding was performed by applying a predetermined urging pressure between the rollers 61 and 62 facing each other. After both were pressure-bonded and bonded together, the substrate sheet 12 and the substrate film 14 were bonded together with good adhesion. After that, the optical sheet 10 according to Example 1 was manufactured by cutting into a size corresponding to a 15-inch display having a length of 240 mm × width of 320 mm by the cutter 73.

  The base sheet 12 was corrected on the front side of the rollers 61 and 62. The substrate sheet 12 was corrected by applying a back tension between the rollers 61 and 62 and the rollers 65 and 66 provided on the supply line side. The back tension was performed by applying torque to the rollers 65 and 66 with respect to the rotation of the rollers 61 and 62.

  The obtained optical sheet has a unit prism shape of a triangular prism, and more specifically, isosceles with a pitch of 50 μm, an apex angle of the unit prism at the main cutting plane of 90 °, and a base angle of 45 °. The triangles were formed so as to be adjacent to each other so that the ridgelines were parallel to each other.

(Comparative Example 1)
Comparative Example 1 was performed in the same manner as in Example 1 except that the thickness of the base film 13 shown in Table 1 was changed to 250 μm, which was the same as that of the base sheet 12 (base sheet thickness = base film thickness). An optical sheet was manufactured.

(Comparative Example 2)
Except for changing the thickness of the base film 13 shown in Table 1 to 250 μm and the thickness of the base sheet 12 to 196 μm (base sheet thickness <base film thickness), the same as in Example 1 The optical sheet of Comparative Example 2 was manufactured.

(Evaluation)
About each optical sheet of Example 1 and Comparative Examples 1 and 2, it mounted | worn with the edge-light type surface light source device (refer FIG. 5 (A)) corresponding to a 15-inch diagonal length display. As shown in FIG. 5 (A), the surface light source device 80 'is set up, the optical sheet obtained is placed on the front surface thereof, the light source is turned on, and the optical sheet 10 is warped, deformed, bent or curled. The unevenness of the light generated from the surface was observed visually. The visual judgment criteria were evaluated as “◯” when the luminance unevenness was visually identifiable, and “X” when the luminance unevenness was visually unidentifiable. The results are shown in Table 1.

  In addition, the deformation (flatness) from the flat surface due to warpage, bending, curling, etc. of the optical sheet was measured and evaluated by the following method. In addition, since the deformation from the flat surface tends to increase with time and tends to be accelerated by heating and humidification, the deformation from the flat surface of the optical sheet was measured after the heating and humidification acceleration test.

  A test piece is prepared by cutting each base sheet into a square having a size of 200 mm × 200 mm. The test piece is left for 24 hours in an atmosphere having an air temperature of 45 ° C. and a relative humidity of 95%. First, on a horizontal and flat 10 mm thick glass plate (installed on a desk), one surface of each test piece is placed facing each other, and the distance from the glass plate surface at the four corners of the test piece is determined. Measure to a unit of 0.5 mm. Subsequently, the front and back of the test piece are reversed, and the other surface of the test piece is placed on the glass plate so as to face the glass plate side, and the distances from the glass plate surfaces at the four corners are similarly measured. The maximum value of the eight measured values is taken as the value of “deformation from flat surface” of the base sheet. At this time, “deformation from a flat surface” was set to “◯” when 5 mm or less, and “x” when exceeding 5 mm.

  From the results in Table 1, a good result is obtained when the base film 13 having a thickness of 125 μm and the base sheet 12 having a thickness of 250 μm are combined (base film thickness <base sheet thickness). It was.

It is a typical perspective view which shows an example of the optical sheet for surface light sources of this invention. It is a schematic diagram for demonstrating the manufacturing method of the optical sheet of this invention. It is a schematic diagram for demonstrating the manufacturing method of the optical sheet of this invention. It is a perspective sectional view showing an example of a surface light source device equipped with an optical sheet of the present invention, (A) shows an example of an edge light type surface light source device, and (B) shows an example of a direct type surface light source device. Show. FIG. 6 is a perspective sectional view showing another example of the surface light source device mounted with the optical sheet of the present invention, (A) shows another example of the edge light type surface light source device, and (B) is a direct type surface light source. 3 shows another example of the device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Optical sheet 10 '... Sheet | seat after bonding 11 ... Translucent base material 12 ... Base material sheet 12' ... Base material sheet 13 after correction | amendment 13 ... Base film 14 ... Unit prism 16 ... Prism part 18 ... Adhesion Agent layer 20 ... Prism part forming sheet 21 ... Pressing roll 22 ... Ionizing radiation source 23 ... Peeling roll 25 ... Conveying roller 26 ... Guide roller 31 ... Roll winding 32 ... Intermediate sheet roll 41 ... Drum 42 ... Shaping type 43 ... Prism part Forming resin 45 ... T-die nozzle 61, 62 ... Roller 63, 64, 65, 66 ... Conveying roller 71 ... Winding roll 72 ... Correction means 73 ... Cutter 80, 80 ', 90, 90' ... Surface light source device 82 ... Light guide 82A ... End face 82B, 92 ... Light emission surface 84 ... Light source 86, 94 ... Reflector S1 ... Surface of substrate film on substrate sheet side S2 ... Of substrate sheet Surface of base film side S3 ... Base film surface of translucent base material

Claims (5)

A translucent base material having a base material sheet and a base material film that is thinner than the base material sheet, and a plurality of unit prisms arranged on the base film side surface of the translucent base material A method of manufacturing a surface light source optical sheet comprising a prism portion,
A supply step of unwinding the roll-shaped base film from a roll and supplying the roll to a drum having a shaping mold of the prism portion on the surface;
A curing step of curing the prism portion forming resin after the base film is pressure-bonded to the shaping mold filled with the prism portion forming resin;
A transfer step of peeling the base film from the drum and transferring the cured prism portion to the base film;
A winding step of rolling the prism portion forming sheet on which the prism portion is formed;
Simultaneously supplying the roll-shaped prism portion forming sheet and the single-wafer, roll-rolled or continuous extruded base sheet, and bonding the base film side of the prism portion forming sheet onto the base sheet A pasting process to be combined,
A cutting step of cutting the sheet after pasting into a predetermined shape;
A method for producing an optical sheet for a surface light source, comprising:   The manufacturing method of the optical sheet for surface light sources of Claim 1 with which the said bonding process has a correction means which corrects the curl of the said base material sheet supplied by roll winding. A translucent base material having a base material sheet and a base material film that is thinner than the base material sheet, and a plurality of unit prisms arranged on the base film side surface of the translucent base material A method of manufacturing a surface light source optical sheet comprising a prism portion,
A supply step of unwinding the roll-shaped base film from a roll and supplying the roll to a drum having a shaping mold of the prism portion on the surface;
A curing step of curing the prism portion forming resin after the base film is pressure-bonded to the shaping mold filled with the prism portion forming resin;
A transfer step of peeling the base film from the drum and transferring the cured prism portion to the base film;
A winding step of rolling the prism portion forming sheet on which the prism portion is formed;
The roll-shaped prism part forming sheet is unwound from a roll, and the molten resin extruded on the surface of the prism part forming sheet on the base film side is laminated, and the molten resin is cooled and solidified. By becoming a base sheet, a bonding step of bonding the base sheet to the base film side of the prism portion forming sheet,
A cutting step of cutting the sheet after pasting into a predetermined shape;
A method for producing an optical sheet for a surface light source, comprising:   The manufacturing of the optical sheet for a surface light source according to any one of claims 1 to 3, wherein in the bonding step, the base sheet and the prism part forming sheet are bonded together via an adhesive or a pressure-sensitive adhesive. Method.   An optical sheet for a surface light source, which is manufactured by the method for manufacturing an optical sheet for a surface light source according to any one of claims 1 to 4.

Images