JP2011039292A - Optical sheet, and die for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical sheet capable of improving defect shieldability without lowering display brightness, and to provide a die used for manufacturing the optical sheet, and a method for manufacturing the optical sheet that uses the die, concerning the optical sheet used for a backlight, or the like, in a liquid crystal device. <P>SOLUTION: The optical sheet is for making a light entering the incident surface inside propagate, and emit the light from an emission surface includes: a prism pattern including a plurality of prism rows formed on the incident surface; and a plurality of projections which are nano-order projections, provided over the whole surface or a part of a surface forming the prism pattern. Although the light entering the optical sheet is scattered by the fine nano-order projections, accompanying luminance is hardly lowered and shieldability is improved, because the size of the projections is of very fine nano-order. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an optical sheet that can be used for optical equipment and information equipment, a mold for manufacturing the optical sheet, and a method for manufacturing the mold for manufacturing the optical sheet.

  In a liquid crystal display device, as a typical illumination method for displaying an image, there are a display device of a rear light source type, an edge light type surface light source that performs image display using a light source arranged behind a liquid crystal panel, and the like. can give.

  In such a display device, increasing the display luminance is particularly important in increasing the commercial value of the display device. Therefore, it is disclosed in Japanese Patent Publication No. 7-27136 (Patent Document 1) and Japanese Patent Publication No. 7-27137 (Patent Document 2) that are not a refractive index type that can use light of a light source with high efficiency. A downward prism sheet was devised. However, the total reflection type prism sheet has a problem of low defect concealment and low yield in manufacturing.

  In general, in a back light source type display device, a diffusion sheet having a high defect concealment property is provided between an optical sheet and a liquid crystal panel, or on the back surface or the inside where the prism pattern of the optical sheet is not provided. A function having an effect of concealing defects, such as an uneven shape, is provided. However, there is a problem that the cost and thickness of the display device increase.

  In order to solve such a problem, an optical sheet having a concavo-convex shape on a prism pattern as shown in Japanese Patent Application Laid-Open No. 2007-304564 (Patent Document 3) has been proposed. However, since the size of the concavo-convex shape is large, there is a problem that the concavo-convex itself is easily visually recognized as a defect. In addition, International Publication No. 2007-046337 (Patent Document 4) proposes a technique in which fine concavo-convex portions are provided only on the convex portions of the prism pattern of the mold by deforming the mold by blasting. Yes. However, the top of the convex part of the prism pattern is deformed by blasting, so that the releasability is remarkably deteriorated and the yield is lowered. Furthermore, in prism sheets used for mobile devices, the pitch of prisms is generally small, but in a small prism array with a fine pitch, large irregularities tend to be visually recognized as defects. However, conventionally, it has been difficult to form even smaller irregularities on a fine pitch prism array with a fine pitch.

Japanese Patent Publication No. 7-27136 Japanese Patent Publication No. 7-27137 (Patent Document 2) JP 2007-304564 A International Publication No. 2007-046337

  As described above, in any of the above methods, there is a problem that an attempt to improve the concealing property causes an undesirable increase in thickness and cost, and a significant decrease in productivity and luminance. Therefore, in the present invention, an optical sheet that solves the above-described problems and suppresses a decrease in display luminance and has improved defect concealment, a mold used for manufacturing the optical sheet, and a method for manufacturing the mold It is an issue to provide.

  The optical sheet according to the present invention has a plurality of prism rows arranged on at least one surface of a sheet-like substrate, and a plurality of prisms having a height of 20 nm to 400 nm are formed on at least a part of the surface of the prism rows. The convex part is formed.

  According to the present invention configured as described above, since the size of the convex portion is as very small as nano-order, it is possible to conceal defects generated in the optical sheet while suppressing a decrease in luminance.

  The mold for manufacturing an optical sheet according to the present invention is a mold for manufacturing an optical sheet, the prism pattern formed on the surface of the mold, and provided in at least a part of the prism pattern, the depth Has a plurality of recesses of 20 nm to 400 nm.

  According to the present invention configured as described above, since the size of the convex portion is as very small as nano order, the optical sheet can be easily released.

  In the method for producing a mold for producing an optical sheet according to the present invention, a step of forming a prism pattern in which prisms having a substantially triangular prism section are arranged in parallel on the surface of a mold base, Using a plating solution containing 1 to 35% by volume of fine particles of 02 to 0.1 μm, a step of performing plating containing the fine particles on the surface of the mold base, and the mold base subjected to the plating And a step of removing at least a part of the fine particles from the material.

  In one aspect of the method for producing a mold according to the present invention, the fine particles are fine particles made of a resin, and in the step of removing the fine particles, the mold base subjected to the plating is fired, At least a part of the fine particles are burned off from the plating.

  According to such a mold manufacturing method, a minute recess is formed because it is not necessary to perform mechanical processing on the mold in order to form a minute recess by burning fine particles from plating. The mold can be easily manufactured. Furthermore, the occurrence of defects in the optical sheet due to burrs and streaks that occur in the mold due to machining or the like is suppressed, and the release of the optical sheet can be facilitated by making the minute recesses into nano-order recesses. it can.

  According to the present invention, mold release is easy and yield can be improved while maintaining defect concealment. Furthermore, the optical sheet having a very small pitch of the plurality of convex portions used for mobile use and the like exhibits a great effect. In the present invention, highly difficult processing with a prism pitch of about 10 μm or less is possible.

It is a perspective view which shows the optical sheet which concerns on this invention. It is a side view of the manufacturing apparatus of the optical sheet which concerns on this invention. It is sectional drawing which shows the outer peripheral surface vicinity of the roll metal mold | die which concerns on this invention. It is sectional drawing which shows the optical sheet formed using the roll metal mold | die which concerns on this invention. It is a block diagram which shows the plating processing apparatus for performing a plating process to a roll metal mold | die. It is sectional drawing of the plating processing tank with which the plating processing apparatus was equipped. It is sectional drawing which looked at this plating processing apparatus from the side.

  Hereinafter, an optical sheet according to an embodiment of the present invention will be described with reference to the drawings with reference to a prism sheet using a backlight of a liquid crystal display device or the like. FIG. 1 is a perspective view showing an optical sheet (prism sheet).

  First, as shown in FIG. 1, the prism sheet 1 has a sheet incident surface 3 on which light emitted from an external light source is incident, and emits light that enters the sheet incident surface 3 and enters the prism sheet 1. The sheet emission surface 5 is provided. On the sheet incident surface 3 of the prism sheet 1, a plurality of triangular prism-shaped prism rows 7 formed by curing an activated energy ray-curable resin are arranged in parallel. The pitch between the prism rows 7 is 10 to 500 μm.

  Such a prism sheet 1 is formed by arranging the prism row 7 on one surface of a sheet base material 9 having translucency. Further, a diffusion layer 11 may be provided on the other surface of the sheet base material 9, and the light in the sheet base material 9 may be diffused and emitted.

  The prism row 7 provided on one surface of the sheet substrate 9 has a plurality of minute convex portions formed on the surface thereof. The height of the minute protrusion is preferably 20 nm to 400 nm, and more preferably 30 nm to 300 nm. When the height of the convex part exceeds 400 nm, the decrease in luminance tends to be noticeable, and when it is 20 nm or less, there is a tendency that almost no improvement in concealment is observed.

  The prism row 7 is formed so that its refractive index is 1.52 or more, preferably 1.55 or more, and more preferably 1.6 or more. The activation energy ray-curable resin forming the prism array 7 may be any resin that can be cured by an activation energy ray such as an ultraviolet ray or an electron beam. From the viewpoint, it is preferable to use an acrylate resin such as polyester, epoxy resin, polyester acrylate, epoxy acrylate, or urethane acrylate. The activated energy ray curable composition used for such a curable resin includes a polyfunctional acrylate and / or a polynosyl methacrylate, a monoacrylate and / or a monomethacrylate, in terms of handleability and curability, and the like. It is preferable to use a photopolymerization initiator by an activation energy ray as a main component. Typical polyfunctional acrylates and / or polyfunctional methacrylates include polyol poly (meth) acrylate, polyester poly (meth) acrylate, epoxy poly (meth) acrylate, urethane poly (meth) acrylate, and the like. These are used alone or as a mixture of two or more. Examples of monoacrylate and / or monomethacrylate include monoalcohol mono (meth) acrylate ester, polyol mono (meth) acrylate ester, and the like.

  The sheet substrate 9 is a glass plate having a thickness of 10 to 500 μm, preferably 30 to 300 μm, a polyester resin such as polyethylene terephthalate or polyethylene naphthalate, an acrylic resin such as polymethyl methacrylate, diacetyl cellulose or triacetyl cellulose. Cellulose meter resins such as polyethylene, polypropylene, polyolefins having cyclic or norbornene structures and olefin resins such as ethylene / propylene copolymers, nylon and aromatic polyamide polyamide resins, polycarbonate resins, vinyl chloride resins, Or it forms with transparent resin sheets, such as a polymethacrylimide type resin, or a film. And in order to improve the adhesiveness of activation energy ray hardening-type resin, the anchor coat process may be given to the surface of the sheet | seat base material 9. FIG.

  It is also possible to form the monomer forming the prism row 7 and the sheet base material 9 from the same material. In this case, as the sheet substrate 9, a synthetic resin having a high light transmittance such as an acrylic resin, a polycarbonate resin, a polyester resin, or a vinyl chloride resin can be used. Among these resins, acrylic resins can be used from the viewpoints of high light transmittance, heat resistance, mechanical properties, moldability, and the like. In this case, a resin mainly composed of methyl methacrylate is used as the acrylic resin, and the content thereof is preferably 80% by weight or more.

  The diffusion layer 11 may be formed by dispersing a light diffusing agent in a translucent resin. In this case, the light diffusing agent protrudes from the surface of the translucent resin disposed on the sheet substrate 9, and the surface of the translucent resin is formed to be uneven. Moreover, you may use methods, such as providing an unevenness | corrugation directly in the other surface of the sheet | seat base material 9. FIG.

(Optical sheet manufacturing method)
FIG. 2 is a side view showing such a prism sheet manufacturing apparatus. The prism sheet manufacturing apparatus includes a roll die 21, a nip roll 23 disposed in the vicinity of the roll die 21, and a peeling roller (not shown). In addition, the prism sheet manufacturing apparatus includes a tank 27 for storing an activated energy ray-curable composition disposed on the sheet substrate 9 conveyed by the roll mold 21, the nip roll 23, and the peeling roller, and the tank 27. The coating apparatus 29 which apply | coats the activation energy ray hardening-type composition of the inside on the sheet | seat base material 9, and the UV lamp 31 which radiate | emits the ultraviolet-ray as an activation energy ray are provided. The prism sheet manufacturing apparatus is configured such that the sheet base material 9 is conveyed in the arrow B direction while being wound around the outer peripheral surface of a cylindrical column-shaped roll mold 21 that is rotationally driven in the arrow A direction.

  The activated energy ray-curable composition stored in the tank 27 is preferably maintained at a predetermined viscosity in order to make the thickness of each prism row 7 constant. The viscosity range is preferably 20 to 3000 mPa · S, and more preferably 100 to 1000 mPa · S. By setting the viscosity of the activated energy ray-curable composition to 20 mPa · S or more, the nip pressure is set relatively low in order to make the thickness of the formed prism row 7 constant, or the roll mold 21 There is no need to make the rotation speed extremely fast. Further, when the nip pressure is relatively low, the operation of the nip roll 23 is not stable, so that the thickness of the prism row 7 becomes non-uniform. Moreover, when the rotational speed of the roll mold 21 is extremely increased, the irradiation amount of the activation energy ray is insufficient, and the activation energy ray curable composition tends to be insufficiently cured. In addition, by setting the viscosity of the activated energy beam curable composition to 3000 mPa · S or less, the activated energy beam curable composition can be sufficiently distributed to the details of the shape transfer surface structure of the roll mold 21. Thus, accurate transfer of the prism row 7 and minute irregularities described later is not difficult, defects due to mixing of bubbles are not likely to occur, and productivity is not deteriorated due to an extremely low molding speed. For this reason, in order to keep the viscosity of the activated energy ray-curable composition constant, a sheathed heater is provided outside or inside the tank 27 so that the temperature of the activated energy ray-curable composition can be sufficiently controlled. It is preferable to install a heat source facility such as a hot water jacket.

(Mold manufacturing method)
FIG. 3 is a cross-sectional view showing the vicinity of the outer peripheral surface of the roll mold. As shown in FIG. 3, a prism pattern including a plurality of processing convex portions 41 is formed on the outer peripheral surface of the roll mold 21. The processing convex portion 41 is formed of a triangular prism-like body that extends in the circumferential direction of the roll mold 21. A plurality of triangular prisms are arranged in parallel on the outer periphery of the roll mold 21 to form a prism pattern. Each processing convex portion 41 is provided with a plating layer 45 containing a nano-order concave portion 43. Then, on the entire surface or a part of each processing convex portion 41, a minute processing pattern 47 is formed by the concave portion 43. Such a convex portion 41 for processing is a columnar body having a triangular cross section with a height of 5 to 500 μm, and the arrangement pitch in the axial direction of the roll mold 21 is set to 5 to 500 μm.

  The plurality of nano-order concave portions 43 are provided on the entire surface or a part of the processing convex portion 41. The position can be freely selected by processing. The height of the nano-order concave portion 43 is preferably 30 nm to 300 nm, and more preferably 50 nm to 200 nm. Increasing the number of nano-order convex portions 43 that form the micro-processed pattern 47 improves the concealment of defects generated in the prism row 7 formed by the processing convex portions 41. The nano-order concave portions 43 constituting the microfabricated pattern 47 are preferably present non-uniformly. Although details will be described later, the plating layer 45 is obtained by immersing and baking the base material of the roll mold 21 on which the processing convex portions 41 are formed in a plating solution in which fine particles of Teflon (registered trademark) are mixed. Formed with.

  FIG. 4 is a cross-sectional view showing a prism formed using such a roll mold. As shown in FIG. 4, the prism row 7 includes a prism 51 having a shape and size complementary to the processing convex portion 41 of the roll mold 21 and a nano-order convex portion 53. The prism 51 has a substantially triangular cross section that is complementary to the processing convex portion 41. The angle of the apex of the prism 51 having a triangular cross section forming the prism row 7 is set as a range of 40 to 150 °. The angle of the top of the prism 51 can be changed according to the use of the optical sheet 1. When the optical sheet is used as a prism sheet for a backlight of a liquid crystal device, the angle of the top is 45 to 70. It is good to be considered as °. When the optical sheet is used in combination with the light guide plate of the liquid crystal device, the angle of the top of the prism 51 is preferably in the range of 80 to 100 °, and more preferably in the range of 85 to 95 °. The pitch between the prism rows 7 is complementary to the pitch of the valleys of the processing convex portion 41, and is 10 to 500 μm. As indicated by an arrow C, light incident on the surface of the prism 51 at an angle smaller than the critical angle of the prism 51 is guided into the prism sheet 1.

  The nano-order convex portion 53 has a shape and size complementary to the nano-order minute concave portion 43 provided on the outer periphery of the roll mold 21. The plurality of nano-order convex portions 53 are formed by the micro-processed pattern 47 so as to be recessed from the surface of the processing convex portion 41. As shown by the arrow D, the convex portion 53 scatters the incident light and guides it into the prism sheet 1. And the height of the convex part 53 is preferably 20 nm to 400 nm, more preferably 30 nm to 300 nm, and still more preferably 50 to 200 nm. When the height exceeds 400 nm, a decrease in luminance starts to be noticeable, and when it is 20 nm or less, the improvement in concealment is hardly observed.

  FIG. 5 is a block diagram showing a plating apparatus for plating a roll mold, and FIG. 6 is a cross-sectional view of the plating tank provided in the plating apparatus as seen from the front. 7 is a cross-sectional view of the plating apparatus as viewed from the side.

  As shown in FIG. 5, the plating apparatus 61 includes a plating tank 65 for immersing the roll mold base 63, and a water washing process and a degreasing process provided on the upstream side of the processing line from the plating tank 65. A pretreatment tank 67 for performing treatment, acid activation treatment, and the like, and a posttreatment tank 69 for performing water washing treatment, drying treatment, and the like provided on the downstream side of the processing line from the plating treatment tank 65 are provided. These processing tanks 65, 67, and 69 are arranged in parallel, and the roll mold base 63 is conveyed from the upstream side to the downstream side of the processing line by the arm 71 provided on the top of each processing layer. Is done. Then, the roll mold base 63 is introduced into the processing tanks 65, 67, 69 or taken out from the processing tanks 65, 67, 69 by moving the roll mold base 63 up and down by the arm 71. It is supposed to be.

  As shown in FIGS. 6 and 7, the plating tank 65 includes an inner tank 81 that stores a nickel plating solution containing fine particles such as Teflon (registered trademark), and an outer portion that receives the nickel plating solution overflowing from the inner tank 81. A tank 83 and an inlet 85 for allowing the plating solution to flow into the inner tank 81 are provided.

  The inner tank 81 is formed in a rectangular box shape having a long side longer than the length of the roll mold base 63 in the longitudinal direction. Further, when the roll mold base 63 supported by the arm 71 comes down, the shaft 89 of the roll mold base 63 fits into the wall 87 at the end in the longitudinal direction of the inner tank 81. It has a notch (not shown). The roll mold base 63 supported by the arm 71 and immersed in the inner tank 81 is rotated around the shaft 89 in the direction of arrow E by the arm 71 when the plating process is performed. Yes. Teflon (registered trademark) having a particle size of 0.02 to 0.1 μm is used, and the concentration of fine particles in the plating solution is preferably 1 to 35% by volume.

  A rectifying plate 91 is provided at the bottom of the inner tank 81 so as to cover an inlet 85 for allowing the plating solution to flow into the inner tank 81. Further, a shielding plate 93 is provided between the roll mold base 63 and the current plate 91 when the roll mold base 63 is immersed. Furthermore, the inner tank 81 is provided with heating means (not shown) such as an electric heater so that the temperature of the plating solution can be adjusted. In addition, an electrode (not shown) is provided in the inner tank 81, and the surface of the roll mold base 63 is plated using this electrode. Further, a shower (not shown) is provided on the upper part of the inner tank 81, and the plating solution adhering to the surface of the roll mold base 63 pulled up from the inner tank 81 by the arm 71 is washed. ing.

  The outer tub 83 is a box-shaped tub formed to be slightly larger than the inner tub 81, and is disposed so as to surround the inner tub 81. A gap is provided between each wall of the outer tank 83 and the inner tank 81, and the plating solution overflowing from the inner tank 81 is received by the outer tank 83 by this gap. Further, the arm 71 can be lowered to a predetermined position. A reflux port 95 for refluxing the plating solution to the inner tank 81 is provided at the bottom of the outer tank 83, and a pipe 97 extending from the reflux port 95 allows the plating solution to flow into the inner tank 81. The tube 99 is joined. Then, the plating solution refluxed from the reflux port 95 is supplied to the inflow port 85. Further, a pump 101 is connected to a pipe 97 extending from the reflux port 95 so that the plating solution that has entered the reflux port 95 is pumped to the inflow port 85. Similarly to the inner tank 81, the outer tank 83 is provided with heating means (not shown) that can adjust the temperature of the plating solution. The pipes 97 and 99 extending from the inner tank 81 and the outer tank 83 branch between the inner tank 81 and the outer tank 83, and drain the plating solution in the inner tank 81 and the outer tank 83 as necessary. It can be done.

  The inflow port 85 is provided at the center of the bottom of the inner tank 81. And the baffle plate 91 which covers the inflow port 85 opens on the downstream side in the rotation direction when the roll mold base 63 is immersed in the inner tank 81 and is rotated, and covers the inflow port 85 so as to close the upstream side. It is like that. As a result, the plating solution introduced into the inner tank 81 from the inlet 85 hits the current plate 91 and flows toward the downstream side of the roll mold base 63 in the rotational direction, that is, in the direction of arrow F. The shielding plate 93 is a plate-like member having a substantially V-shaped cross section that extends along the longitudinal direction of the inner tank 81, and plating that flows toward the downstream side in the rotational direction of the roll mold base 63 by the rectifying plate 91. The liquid is prevented from directly hitting the roll mold base 63. Further, by making the shielding plate 93 substantially V-shaped, it is possible to prevent the shielding plate 93 from obstructing the flow of the plating solution in the inner tank 81.

  Next, the manufacturing method of the roll metal mold | die 21 is explained in full detail.

  First, a roll mold base 63 is prepared. As the roll mold base 63, a cylindrical steel roll is used, and a copper plating layer by hard copper plating having a thickness of 100 to 1000 μm and a Vickers hardness of 180 to 250 Hv is formed on the outer peripheral surface thereof. Then, the copper plating layer is cut using a lathe to which a cutting tool such as a cemented carbide tool, a CBN tool, or a diamond tool is attached to form a prism pattern including a plurality of processing convex portions 41.

  Then, such a roll mold base 63 is attached to the arm 71 of the plating apparatus 61. Next, the roll 71 is moved toward the downstream side of the processing line while the arm 71 is moved and sequentially conveyed to the pretreatment tank 67 of the roll mold 63. Next, the roll mold base 63 is immersed in the plating solution in the inner tank 81 of the plating treatment tank 65.

  Before the roll mold base 63 is immersed, the inner bath 81 is supplied with a plating solution containing Teflon (registered trademark) from the inlet 85. At the same time, the plating solution is heated by the heating means. At this time, the inner tank 81 is supplied with an amount of plating solution that overflows from the inner tank 81, and the overflowed plating solution is received by the outer tank 83 and returned from the outer tank 83 to the inner tank 81. Then, the plating solution refluxed from the outer tub 83 flows in a fixed direction by the rectifying plate 91, and in the inner tub 81, in the same direction as the direction of rotation when the roll mold base 63 is immersed. A flow of plating solution is produced. At this time, a part of the plating solution overflows into the outer tub 83 and returns to the inner tub 81 again. By recirculating the plating solution in this way, the plating solution in the inner tub 81 is returned. Thus, the plating layer 45 having a constant film thickness can be formed. At this time, the reflux amount of the plating solution or the amount of the plating solution overflowing from the inner tank is about 80 to 110 liters / minute with respect to the inner tank 81 having a volume of about 250 liters. Moreover, the temperature of the plating solution in the inner tank 81 is kept at 80 to 95 ° C, preferably 84 to 90 ° C. Further, by providing the shielding plate 93 between the rectifying plate 91 and the roll mold base 63, only the plating solution flowing in the rotation direction of the roll mold base 63 is applied to the roll mold base 63. Become.

  Next, the roll mold base 63 is immersed in the inner tank 81, and a voltage is applied to the electrodes while rotating around the shaft 89, causing a current to flow in the inner tank 81. Electrolytic plating is performed.

  Here, when the roll mold base 63 is rotated, it is preferably rotated at a speed of 7.5 to 25 times per minute with respect to the outer periphery of the roll mold. That is, the rotation speed is preferably 1.5 to 5 m / min, more preferably 1.7 to 5 m / min, and more preferably 1.8 to 5 m / min. When the peripheral speed is less than 7.5 times (that is, less than 1.5 m / min in the case of a die having an outer periphery of 200 mm), hydrogen gas generated on the outer periphery of the roll mold base 63 is released from the outer periphery. It becomes difficult to detach, and defects due to the flow of hydrogen gas easily occur on the outer peripheral surface. On the other hand, when the peripheral speed of the roll mold base 63 exceeds 25 times (that is, 5 m / min in the case of a mold having an outer circumference of 200 mm), the thickness of the plating layer 45 becomes non-uniform and plating spots are generated. It becomes easy to do. Note that the peripheral speed of the roll mold base 63 can be adjusted according to the outer diameter thereof.

  Then, the roll mold base 63 is rotated in the plating solution, and the current is stopped after a predetermined time. The nickel plating layer 45 is formed on the outer peripheral surface of the roll mold base 63 by such electrolytic plating. Then, after the current is stopped, the electroless plating process is performed while rotating the roll mold base 63 for a predetermined time. Thereby, a nickel plating layer containing Teflon (registered trademark) is formed. Thereafter, the roll mold 21 is conveyed toward the downstream side of the processing line by the arm 71 in the post-treatment tank 69 while undergoing post-treatment such as water washing, hot water washing, and drying.

  Here, in a state where the roll mold base 63 is immersed in the plating solution, the time for applying the voltage to the electrode is 10 to 60 seconds, more preferably 15 to 40 seconds. Then, after the elapse of this time, the energization to the electrode is stopped, and thereafter, the plating process is performed with an autocatalyst, whereby a very thin plating layer can be formed.

  Furthermore, when the roll mold base 63 is heat-treated at 450 ° C. to 650 ° C. for 1 hour or more in a clean oven or the like, the Teflon (registered trademark) contained in the nickel layer can be burned out. The part where the registered trademark) is burned out becomes a minute recess, and a nano-order minute recess shape can be obtained.

  Further, as the roll mold base 63, a cylindrical steel roll is used, and nickel plating containing 50 to 600 μm thick Teflon (registered trademark) powder is applied to the outer peripheral surface thereof, and then the nickel plating layer. May be cut using a lathe to which a cutting tool such as a cemented carbide tool, a CBN tool, or a diamond tool is attached to form a prism pattern including a plurality of convex portions 41 for processing.

  Furthermore, when the roll mold base 63 is heat-treated at 450 ° C. to 650 ° C. for 1 hour or more in a clean oven or the like, the Teflon (registered trademark) contained in the nickel layer can be burned out. The part where the registered trademark) is burned out becomes a minute recess, and a nano-order minute recess shape can be obtained.

  As described above, according to the embodiment of the present invention, an optical sheet that improves the defect concealing property without reducing the display luminance is provided by the roll mold including the prism pattern and the micro-fabricated pattern 47 formed thereon. can do.

  In the above-described embodiment, when the roll mold is manufactured, the axis of the roll mold is held in the horizontal direction, and the roll mold is immersed in the plating solution while rotating. These axes may be immersed vertically in the plating solution.

  When the roll mold was subjected to heat treatment temperatures of 400 ° C., 500 ° C., 600 ° C., and 700 ° C. in a clean oven and the respective surfaces were observed with an SEM, no micro concave shape could be confirmed at 400 ° C. At 500 ° C., minute concave shapes of 30 nm to 100 nm were confirmed. At 600 ° C., a fine concave shape of 80 nm to 300 nm was confirmed. When the temperature reached 700 ° C., the minute concave shape could not be confirmed again. Moreover, when it heat-processed at 650 degreeC, the 100-500-nm minute concave shape was able to be confirmed.

  Teflon (registered trademark) has been described as an example of the fine particles used so far, but the fine particles are not limited to Teflon (registered trademark) as long as they can be dispersed in the plating solution and can be burned off. Further, depending on the fine particles to be used, the firing temperature may be changed, or the fine particles may be extracted by a method other than the firing. For example, the fine particles may be extracted using an acid or the like. Similarly, the plating solution has been described by taking nickel as an example, but is not limited to nickel such as chromium, copper, and tin.

  Examples of the present invention will be described in detail below.

Example 1
First, a steel roll having an outer diameter of 200 mm and an image length of 150 mm was prepared as a roll mold base. And after grind | polishing the outer peripheral surface of a roll metal mold | die base material, copper plating was given to the outer peripheral surface, and the hard copper plating layer of thickness 500 micrometers and Vickers hardness 230Hv was provided. Next, the copper plating layer was turned using a diamond tool to form a prism pattern with a pitch of 30 μm. Then, an arm of a plating apparatus is attached to the central shaft of the roll mold base, and the roll mold base is rotated at a peripheral speed of 6.5 m / min while washing, degreasing, and acid in a pretreatment tank. Active treatment was performed.

  Next, the roll mold base material that has been pretreated is moved onto a plating treatment tank composed of an inner tank and an outer tank, and the peripheral speed of the roll mold base material is changed to 1.9 m / min. After that, the roll mold base was lowered into the inner tank by the arm while keeping the roll mold base substantially parallel. The roll mold base was immersed in a plating solution containing 25% by volume of Teflon (registered trademark) having a particle size of 0.03 μm and heated to 85 ° C. with a nickel concentration of 5 g / liter. And the voltage of 5V was applied to the electrode in an inner tank, and the electric current of 100 A was sent for 30 second, with the roll mold base material immersed in the inner tank. And even after stopping the power supply to the electrode, the roll mold base was kept immersed in the plating solution at 85 ° C. while rotating at a peripheral speed of 1.9 m / min. During the electroless nickel plating process, a nickel plating solution is introduced into the inner tank at a flow rate of 105 liters / minute from the inlet of the inner tank, and the plating solution overflowing from the inner tank is transferred from the outer tank to the inner tank. Refluxed to bath. This created a flow of plating solution in the same direction as the rotational direction of the roll mold base.

  Then, the pump was stopped 230 seconds after the start of immersion, and after 235 seconds from the start of immersion, water (room temperature) was ejected from the shower provided on the plating tank at 30 liters / minute, while the nickel plating solution in the inner tank Started to discharge. Further, immediately after the start of discharging the nickel plating solution, the arm was raised and the roll mold was pulled up. And from the shower, water (room temperature) was spouted from the diagonally upward toward the lower part of the roll mold at 30 liters / minute, and the roll mold was washed with water for 120 seconds.

  Thereafter, the roll mold was moved to a post-treatment tank, subjected to water washing treatment and drying treatment, and the roll mold was removed from the arm.

  The removed mold was heat-treated in a clean oven at 500 ° C. for 3 hours to eliminate the contained Teflon (registered trademark).

  Next, an optical sheet was manufactured using the roll mold and an acrylic ultraviolet curable composition (manufactured by Mitsubishi Rayon Co., Ltd., RP4000S) using an optical sheet manufacturing apparatus. Between a roll mold and a nipple roll, a polyethylene terephthalate (PET) film (Toyobo Co., Ltd., A4100, thickness: 188 μm, width: 470 mm) with an adhesion improving treatment on one side is used as a sheet base material. It was introduced into the manufacturing apparatus so as to wrap around the outer peripheral surface of the mold.

Next, the roll mold was rotated at a peripheral speed of 7 m / min while supplying the acrylic ultraviolet curable composition at 40 ° C. supplied from the resin tank between the sheet base material and the roll mold. In a state where the supplied acrylic ultraviolet curable composition is held between the sheet base material and the roll mold, the irradiation amount (irradiation energy) is from a 9.6 kW (120 W / cm) radiation irradiation device. Ultraviolet rays were irradiated so as to be 200 mJ / cm ² , the acrylic ultraviolet curable composition was cured and molded, and then the sheet substrate was peeled from the roll mold to obtain an optical sheet.

  When the cross section and surface of the obtained optical sheet were observed with an SEM, it was confirmed that innumerable non-uniform nano-order convex portions were formed on the entire surface of the optical sheet.

Then, the obtained optical sheet was cut into a 14.1 (wide) size, and this was placed on the light exit surface of a 14.1 W (wide) size acrylic resin light guide with a cold cathode tube arranged on the side. . At this time, the optical sheet was arranged so that the surface on which the prism was formed faced downward, that is, so as to face the exit surface of the light guide plate. Note that a light guide plate having a predetermined number of defects such as scratches formed in advance is used. And the side surface in which the cold cathode tube is not arrange | positioned in a light-guide plate, and the surface on the opposite side to an output surface were covered with the reflective sheet, and the surface light source device was formed. In this surface light source device, the cold cathode tube was turned on, and the normal luminance and the half-value width were measured using a luminance meter (trade name BM-7, manufactured by Topcon Corporation). As a result, the normal luminance was 1995 Cd / m ² . In addition, among the scratches formed on the surface of the light guide plate, the number of scratches confirmed even when the prism sheet was arranged was counted.

(Example 2)
In Example 2, when the roll mold substrate was immersed in the plating solution, the roll mold substrate was immersed in the vertical direction. At this time, the roll mold was stopped during the plating process without rotating. Then, when the same processing as in Example 1 was performed, an optical sheet similar to that in Example 1 could be obtained.
(Comparative Example 1)
The concealability, brightness, and half-value width of the optical sheet manufactured in Example 1 were compared with those of the optical sheet manufactured by the method described in Japanese Patent Application Laid-Open No. 2007-70658, which is a conventional technique. As a result, it was 1998 Cd / m ² for the optical sheet of Example 1. The conventional product is 2004 Cd / m ² , and in the optical sheet of Example 1, almost no reduction in luminance was observed. In addition, the concealability of defects formed between the prisms increased by 75%. In addition, evaluation of concealment was calculated based on the number of invisible when the defect confirmed in the optical sheet manufactured by the prior art was changed to the optical sheet manufactured in Example 1. Table 1 shows the brightness and concealment of the examples and comparative examples. The relative luminance in the table is a relative value when the luminance of the comparative example is 100.

Prism sheet 1
Sheet entrance surface 3
Sheet exit surface 5
Prism array 7
Sheet base material 9
Diffusion layer 11
Roll mold 21
Nip roll 23
Tank 27
Coating device 29
Convex part 41 for processing
Recess 43
Plating layer 45
Microfabrication pattern 47
Prism 51
Convex part 53
Plating equipment 61
Roll mold base 63
Plating tank 65
Pretreatment tank 67
Post-treatment tank 69
Arm 71
Inner tank 81
Outer tank 83
Inlet 85
Wall 87
Shaft 89
Current plate 91
Shielding plate 93
Reflux port 95
Tube 97, 99
Pump 101

Claims (5)

  It has a plurality of prism rows arranged on at least one surface of a sheet-like substrate, and a plurality of convex portions having a height of 20 nm to 400 nm are formed on at least a part of the surface of the prism rows. An optical sheet characterized by that.   A mold for manufacturing an optical sheet, which has a prism pattern formed on the surface of the mold and a plurality of concave portions having a depth of 20 nm to 400 nm provided on at least a part of the surface of the prism pattern. Mold characterized by. A method of manufacturing a mold for manufacturing an optical sheet,
Forming a prism pattern in which prisms having a substantially triangular prism section are arranged in parallel on the surface of the mold base;
Using a plating solution containing 1 to 35% by volume of fine particles having a particle size of 0.02 to 0.1 μm, and performing plating containing the fine particles on the surface of the mold base;
And a step of removing at least a part of the fine particles from the mold base on which the plating has been performed.   The fine particles are fine particles made of a resin, and in the step of removing the fine particles, the mold base on which the plating is performed is baked, and at least a part of the fine particles is burned off from the plating. The manufacturing method of the metal mold | die of Claim 3.   The manufacturing method of the optical sheet which manufactures an optical sheet using the said metal mold | die obtained by the method of Claim 3 thru | or 4.