JP6347760B2 - Shape imparting roller and film manufacturing method - Google Patents

Description

The present invention relates to a shape imparting roller and a film manufacturing method .

  In recent years, liquid crystal display devices (LCD) have become widespread. This liquid crystal display device has features such as low power consumption and thinness, and various devices ranging from large devices such as home televisions to small devices such as notebook computer monitors, digital cameras, and mobile phones. Has been used. As such a liquid crystal display device, a backlight type that illuminates a liquid crystal panel with a backlight is widely used.

  A general configuration of a backlight type liquid crystal display device includes a liquid crystal panel that changes light transmittance in accordance with an electrical signal, and a light source unit (backlight) that emits light from behind. The liquid crystal panel includes a pair of polarizing plates arranged in crossed Nicols and a liquid crystal cell that changes the polarization state of light that is sandwiched and transmitted between them. The light source unit includes a light source such as a fluorescent tube and an LED, and a diffusion sheet that scatters and diffuses light from the light source in order to uniformly illuminate the entire surface of the liquid crystal panel and a so-called BEF (brightness enhancement film) that improves front luminance. ) Is called a brightness enhancement sheet.

  A prism sheet is often used as the brightness enhancement sheet. This prism sheet deflects light emitted from the light source in an oblique direction in the normal direction of the liquid crystal panel. For a prism sheet in which a large number of prisms having a triangular cross section are formed on one surface at a constant pitch, the direction of the surface on which the prism is formed (hereinafter referred to as the prism surface) faces the liquid crystal panel (opposite to the light source) Refracting prism sheet (so-called upward prism sheet) and total reflection prism sheet (so-called downward prism sheet) with the prism surface facing the light source. The upward prism sheet refracts a light beam incident from a surface opposite to the prism surface toward the normal direction of the liquid crystal panel when the light beam is emitted from the slope of the prism. One downward prism sheet emits a light beam from a light source that has entered from one slope of the prism and traveled through the prism, totally reflected toward the normal direction of the liquid crystal panel on the other slope.

  As a method for manufacturing a prism sheet, one described in Patent Document 1 is known. In this manufacturing method, a prism sheet composed of a prism layer and a support is manufactured by laminating a layer to be a prism layer on a film as a support and transferring the shape of the prism to this layer. Moreover, what was described in patent document 2 is known as a method of manufacturing a prism sheet from a cellulose triacetate (henceforth TAC). In this manufacturing method, a dope in which TAC is dissolved in a solvent is cast on a support to form a cast film, the cast film is dried to 15 to 40% by weight of TAC, and a prism is formed. Process. Then, in the step of forming the prism, a plurality of prisms are formed by pressing an embossing roller having irregularities according to the shape of the prism to be formed against the casting film dried to 15 to 40% by weight of TAC. ing.

JP 2014-178689 A Special table 2009-501360

  However, in the manufacturing method of Patent Document 1, the number of steps is large, such as the step of laminating on a support and the step of transferring the shape of the prism, and the manufacturing efficiency is poor. In addition, the manufacturing method of Patent Document 2 has a problem that the shape of the prism is difficult to attach. If the shape of the prism is difficult to be applied, it is necessary to increase the pressing force of the embossing roller against the casting film or to increase the pressing time. Increasing the pressing force causes a crack or the like in the film, and increasing the pressing time causes a bad effect such as improvement in manufacturing efficiency. Furthermore, in the prism sheet, a target light collecting function or the like cannot be obtained unless the prism is formed in a target shape.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a solution casting method in which a desired prism shape is formed and an optical film is easily and efficiently manufactured.

In order to solve the above problems, the shape-imparting roller of the present invention has a plurality of concave portions and convex portions formed on the peripheral surface, and presses a web being conveyed containing a polymer and a solvent from one surface side, A plurality of concavities and convexities that refract incident light and collect or diffuse them are continuously formed on the one surface, and the height of the convex portion is HR μm, and the top of the concavity and convexity formed on one surface is formed. When the height is HW μm and the solvent content in the web is CS%, 0.9 × HW × {(CS / 100) +1} ≦ HR ≦ 1.1 × HW × {(CS / 100) +1} HR / PR is not less than 0.3 and not more than 2.0 when the pitch between adjacent protrusions and protrusions is PR μm, and includes a pressure regulator that adjusts the pressing force against the web. Web with a pressing force in the range of 5 MPa to 15 MPa Pressed, solvent content is configured as characterized by pressing the web within the scope of the following 350% 50% or more.

  The plurality of concave portions and convex portions are alternately formed along the circumferential direction and have a triangular cross section extending in the web width direction, and the web irregularities are preferably prisms.

  It is preferable that a first temperature controller for adjusting the temperature of the peripheral surface is provided, and the temperature of the peripheral surface is set within a range of 5 ° C. or more and 35 ° C. or less by the first temperature controller.

The film manufacturing method of the present invention includes a casting step, a peeling step, a shape imparting step, and a drying step, and an optical device that has a plurality of concavities and convexities that refract incident light and collect or diffuse the incident light on one film surface. A film is manufactured. In the casting step, a casting film is formed by continuously casting a dope in which a polymer is dissolved in a solvent on a running casting support. In the peeling step, the wet film is formed by peeling the cast film from the cast support while the solvent remains. In the shape imparting step, a shape imparting roller in which a plurality of concave portions and convex portions are formed on a peripheral surface of a cast film or a wet film being transported in a state where the solvent content is in a range of 50% to 350%. By pressing from one surface side, a plurality of irregularities are continuously formed on one surface of the cast film or wet film. A drying process dries the cast film or wet film which passed through the shape provision process. The height of the convex portion of the shape imparting roller is HR μm, the height of the top of the unevenness on one film surface is HW μm, and the solvent content when pressed by the shape imparting roller of the cast film or wet film is CS% Then, the shape imparting roller satisfies 0.9 × HW × {(CS / 100) +1} ≦ HR ≦ 1.1 × HW × {(CS / 100) +1}. In the shape imparting step, the cast film or the wet film is pressed with a pressing force in the range of 1.5 MPa to 15 MPa.

In the shape imparting step, it is preferable to press a shape imparting roller having a peripheral surface temperature in the range of 5 ° C. or higher and 35 ° C. or lower against the cast film or wet film.

  In the shape imparting step, it is preferable that the cast film or the wet film is sandwiched and pressed between the shape imparting roller and the rotation roller provided rotatably with the rotation axes parallel to each other, and the shape imparting roller. The temperature of the peripheral surface of the rotating roller is preferably in the range of −25 ° C. or more and 10 ° C. or less.

  ADVANTAGE OF THE INVENTION According to this invention, the optical film in which the shape of the target prism was formed can be manufactured easily and efficiently.

It is explanatory drawing which shows an example of a structure of the liquid crystal display device using the prism sheet manufactured by the solution casting method of this invention. It is a perspective view which shows the external appearance of a prism sheet. It is sectional drawing of a prism sheet. It is explanatory drawing which shows the outline of the solution casting apparatus which implemented this invention. It is explanatory drawing which shows the structure of a shape provision apparatus. It is sectional drawing which shows the recessed part and convex part of a shape provision roller.

  In FIG. 1, the liquid crystal display device 10 includes a liquid crystal panel 11 and a light source unit 12. The liquid crystal panel 11 includes a liquid crystal cell 13 and two polarizing plates 14 and 15. The liquid crystal cell 13 has liquid crystal sealed between transparent glass substrates, and changes the polarization state of transmitted light by applying a voltage between transparent electrodes formed on the inner surface of each glass substrate. The polarizing plates 14 and 15 are arranged in a crossed Nicols state, and the liquid crystal cell 13 is disposed between them. Thereby, the polarization state of the linearly polarized illumination light transmitted through the polarizing plate 15 is changed by the liquid crystal cell 13 for each pixel, and the amount of light transmitted through the polarizing plate 14 is adjusted to display an image.

  The polarizing plate 14 includes a polarizing film 14a and a pair of protective films 14b and 14c attached to both surfaces thereof. The polarizing plate 15 includes a polarizing film 15a, a protective film 15b, and a prism sheet 16. The protective film 15b is attached to the surface of the polarizing film 15a on the liquid crystal cell 13 side. The prism sheet 16 is cut out into a sheet form from an optical film 32 (see FIG. 4) manufactured using a solution casting method described later. The prism sheet 16 is attached to the surface of the polarizing film 15a on the light source unit 12 side, and functions as a protective film for the polarizing film 15a and a total reflection prism sheet (downward prism sheet) for improving luminance.

  The light source unit 12 illuminates the liquid crystal panel 11 from behind, and is of an edge light type comprising a light source lamp 17, a light guide plate 18, and a reflective film 19. The light source lamp 17 uses, for example, a rod-like fluorescent tube or a number of LEDs (light emitting diodes) arranged in a line, and is arranged along the end (edge) of the wedge-shaped light guide plate 18. The illumination light emitted from the light source lamp 17 is reflected directly or by the reflector 17 a and enters the inside from the end of the light guide plate 18. The light guide plate 18 emits the incident illumination light in an oblique direction with an inclination with respect to the normal line of the liquid crystal panel 11 from the exit surface 18a having the same size as the liquid crystal panel 11 by reflecting the illumination light inside. The reflection film 19 reflects the illumination light emitted from the surface of the light guide plate 18 opposite to the liquid crystal panel 11 and returns it to the light guide plate 18.

  As shown in FIG. 2, the prism sheet 16 has a plurality of prisms 16a each having a triangular cross section on one surface. The plurality of prisms 16a are formed side by side in a direction orthogonal to the extending direction of each prism 16a. The surface of the prism sheet 16 opposite to the surface on which the prism 16a is formed (hereinafter referred to as the prism surface) is a flat surface. The prism sheet 16 is attached with the flat surface in close contact with the polarizing film 15a with the prism surface facing the light source unit 12 side. In FIG. 2, the prism surface is drawn upward.

  The prism sheet 16 deflects the illumination light emitted from the light guide plate 18 in an oblique direction so as to be in the normal direction of the liquid crystal panel 11, thereby increasing the amount of illumination light emitted in the normal direction of the liquid crystal panel 11. Control the distribution of illumination light. Specifically, the illumination light emitted in the oblique direction from the light guide plate 18 is incident on one inclined surface of the prism 16a, travels through the prism 16a, and is totally reflected by the other inclined surface. To be biased. The prism sheet 16 is approximately the same size as the back surface of the liquid crystal panel 11.

  In FIG. 3, the thickness T16 of the prism sheet 16 is in the range of 75 μm to 200 μm. The apex angle (hereinafter referred to as prism apex angle) θ1 of the prism 16a is in the range of 80 ° to 120 °, and the opening angle θ2 of the bottom is in the range of 80 ° to 120 °. The height of the top of the prism 16a, that is, the height from the bottom to the top of the prism 16a (hereinafter referred to as prism height) HW (unit: μm) is in the range of 1 μm to 100 μm, and in this embodiment is 25 μm. Yes. A pitch (hereinafter referred to as a prism pitch) P16a, which is a distance between the bottom of the prism 16a, is in the range of 10 μm to 100 μm, and is 50 μm in this embodiment.

The solution casting apparatus 30 shown in FIG. 4 manufactures the optical film 32 described above from the dope 31. The dope 31 is obtained by dissolving a polymer in a solvent. In this embodiment, the dope 31 is obtained by dissolving cellulose triacetate (hereinafter referred to as TAC) as a transparent thermoplastic polymer in a solvent. However, instead of TAC, other cellulose acylates may be used. That is, instead of the acetyl group, another acyl group may be used. Among cellulose acylates, the present invention is particularly effective when the substitution degree of the acyl group to the hydroxyl group (hydroxy group) of cellulose satisfies the following formulas (I) to (III). In the formulas (I) to (III), A and B represent the substitution degree of the acyl group to the hydrogen atom in the hydroxyl group of cellulose, A is the substitution degree of the acetyl group, and B is the acyl having 3 to 22 carbon atoms. The degree of substitution of the group. The total acyl group substitution degree Z of cellulose acylate is a value determined by A + B.
(I) 2.7 ≦ A + B ≦ 3.0
(II) 0 ≦ A ≦ 3.0
(III) 0 ≦ B ≦ 2.9

The present invention is also particularly effective when using DAC (cellulose diacetate) in which the substitution degree of the acyl group to the hydroxyl group of cellulose satisfies the following formula (IV) instead of or in addition to TAC. .
(IV) 2.0 ≦ A + B <2.7

From the viewpoint of retardation wavelength dispersion, while satisfying the formula (IV), the substitution degree A of the acetyl group of DAC and the total substitution degree B of the acyl group having 3 to 22 carbon atoms are represented by the following formula (V). And (VI) are preferred.
(V) 1.0 <A <2.7
(VI) 0 ≦ B <1.5

  The glucose unit having β-1,4 bonds constituting cellulose has free hydroxyl groups (hydroxyl groups) at the 2nd, 3rd and 6th positions. Cellulose acylate is a polymer obtained by esterifying some or all of these hydroxyl groups with an acyl group having 2 or more carbon atoms. The degree of acyl substitution means the ratio at which the hydroxyl group of cellulose is esterified at each of the 2-position, 3-position and 6-position (the substitution degree is 1 in the case of 100% esterification).

  Details of cellulose acylate are described in paragraphs [0140] to [0195] of JP-A-2005-104148, and these descriptions can also be applied to the present invention. The same applies to additives such as solvents and plasticizers, deterioration inhibitors, UV absorbers (UV agents), optical anisotropy control agents, retardation control agents, dyes, matting agents, release agents, and release accelerators. It is described in detail in paragraphs [0196] to [0516] of JP-A-2005-104148, and these descriptions can also be applied to the present invention.

  The polymer used for the dope 31 is not limited to cellulose acylate, and may be any transparent thermoplastic polymer that can be used in the solution casting method. For example, PMMA (polymethyl methacrylate), PC (polycarbonate), or the like may be used.

  The solution casting apparatus 30 includes a casting device 34, a shape imparting device 35, a drying device 36, a first cutting device 37, a drying chamber 40, a second cutting device 41, and a winding device 42.

  The casting apparatus 34 forms a wet film 43 as a web containing a solvent from the dope 31. The casting apparatus 34 includes a belt 46, a pair of backup rollers 47, a casting die 48, and the like. The belt 46 is an endless casting support body that is formed into an annular shape. The belt 46 is stretched over a pair of backup rollers 47 so that the space between the backup rollers 47 is horizontal. A drive unit (not shown) is connected to one drive shaft 47a of the pair of backup rollers 47, and the drive unit rotates in the circumferential direction indicated by an arrow A1. The rotation of the backup roller 47 causes the belt 46 to circulate.

  The casting die 48 continuously discharges the dope 31 onto the surface of the running belt 46. As a result, the casting film 50 is continuously formed on the surface of the belt 46. Since the casting film 50 is also formed continuously in this way, it is a long object, that is, a web. The decompression chamber 49 decompresses the back side (upstream side in the running direction of the belt 46) of the portion of the dope 31 from the discharge port of the casting die 48 until it reaches the surface of the belt 46, and vibrates the portion. Prevent breakage.

  The temperature controller 51 supplies the temperature-adjusted heat transfer medium into each backup roller 47. Thereby, the temperature of the casting film 50 is controlled via each backup roller 47 and belt 46. In this embodiment, the dry casting, that is, the casting membrane is gelled only by drying, and the temperature controller 51 controls the temperature so as to promote the evaporation of the solvent of the casting membrane 50. Drying proceeds only by blowing, but heating may be performed in addition to blowing. By heating, gelation proceeds more quickly.

  Instead of dry casting, so-called cooling casting in which the casting film 50 is gelled by drying and cooling may be used. In this case, the temperature controller 51 supplies the cooled heat transfer medium to the backup roller 47, thereby cooling the belt 46 so that the fluidity of the casting film 50 is lower than in the case of only drying. To do. Further, the casting support is not limited to the belt 46. For example, instead of the belt 46, a drum may be used, and the dope 31 may be discharged and cast onto the peripheral surface of the rotating drum. In the case of so-called dry casting in which the cast film is dried and solidified, the belt 46 is often used, and in the case of cooling casting, a drum is often used. A belt may be used for casting. When the temperature of the casting film is controlled by using the drum as a casting support in cooling casting, the temperature of the peripheral surface of the drum may be lowered by flowing a cooled heat transfer medium through the drum.

  A blower 52 and a back surface heater 53 are arranged along the conveyance path of the casting film 50 by the belt 46, and these adjust the drying speed of the casting film 50. The casting apparatus 34 includes both the blower 52 and the back surface heater 53, but may be provided with either one. The blower 52 is disposed facing the casting surface 46a (see FIG. 5) of the belt 46 on which the dope 31 is cast to form the casting film 50, and is dried at a predetermined temperature from each nozzle 52a. A gas (for example, dry air) flows out in the vicinity of the casting film 50. In the present embodiment, two blowers 52 are provided along the traveling direction of the belt 46, but the number of blowers 52 is not particularly limited, and may be one or three or more. The back surface heater 53 is disposed opposite to the surface of the belt 46 opposite to the casting surface 46 a and heats the casting film 50 via the belt 46. In the present embodiment, one back surface heater 53 is provided, but the number of back surface heaters 53 is not particularly limited, and may be 1 or 3 or more.

  The casting apparatus 34 further includes a peeling roller 56 (see FIG. 5) and a chamber 57. The belt 46, the casting die 48, the decompression chamber 49, etc. are accommodated in the chamber 57. In the chamber 57, a condenser (condenser) that condenses the solvent evaporated from each of the dope 31, the casting film 50, and the wet film 43 is provided. The solvent liquefied by this condenser is sent to a recovery device and recovered. In addition, illustration of a condenser and a collection | recovery apparatus is abbreviate | omitted.

  The casting film 50 is dried during conveyance by the belt 46, and is peeled off from the belt 46 in a gel state that contains a solvent but loses fluidity, and is conveyed downstream. A shape imparting device 35 is disposed in the vicinity of the peeling position PP (see FIG. 5) where the casting film 50 is peeled off from the belt 46. Further, a blower 58 is disposed between the shape imparting device 35 and the backup roller 47.

  The shape imparting device 35 of the present embodiment has a function of peeling the casting film 50 from the belt 46, and the prism 16a is applied to the casting film 50 peeled off in a state containing a solvent by this function, that is, the wet film 43. Has the function of forming. In this embodiment, the shape imparting device 35 includes a belt 46, a casting die 48. Although provided inside the chamber 57 surrounding the decompression chamber 49 and the like, it may be provided outside the chamber 57, that is, between the casting device 34 and the drying device 36. Details of the shape imparting device 35 and the blower 58 will be described later.

  The wet film 43 from the shape imparting device 35 is sent to the drying device 36. The drying device 36 proceeds to dry the wet film 43 while conveying the wet film 43 in a state where the width is regulated. The drying device 36 includes a plurality of clips 60, an air supply unit 61, and an air outflow unit 62. Each clip 60 grips the side portion of the wet film 43. The plurality of clips 60 are attached to an annular chain (not shown) at predetermined intervals, and the chains are provided so as to be movable along rails arranged on both sides of the transport path of the wet film 43. The moving direction is defined by the rail. As a result, each clip 60 moves along the rail. In this example, one rail and the other rail are arranged in a straight line, and the distance between them is constant, but the present invention is not limited to this. For example, the wet film 43 can be stretched in a direction perpendicular to the conveyance path by increasing the distance between the one rail and the other rail toward the downstream of the conveyance path. The air supply unit 61 supplies the dry gas adjusted to various temperatures to the air outflow unit 62, and sprays the dry gas from the air outflow unit 62 onto the wet film 43 in the drying device 36. By this drying device 36, the wet film 43 is further dried while the width is kept constant. In the drying device 36, it is preferable that the wet film 43 has a temperature of both the peeling surface 43a and the anti-peeling surface 43b of (boiling point of solvent + 50 ° C.) or less.

  In this example, the clip 60 is a holding member that holds the wet film 43. However, the holding member is not limited to the clip 60, and may be, for example, a pin plate that penetrates and holds a plurality of pins on the side of the wet film 43. If the wet film 43 has a very high solvent content, and the wet film 43 is torn by being held by the clip 60, a pin plate may be used.

  The first excision device 37 is for excising the side end where the clip 60 is gripped from the wet film 43. The first cutting device 37 includes an upper blade and a lower blade as cutting blades, and these cutting blades are arranged at the passing positions of the respective side portions of the wet film 43.

  In the drying chamber 40, a plurality of rollers 63 are arranged inside, and heated dry gas is supplied. The wet film 43 is further dried while passing through the drying chamber 40 to form the optical film 32. In the drying chamber 40, the wet film 43 preferably has a temperature on both sides of the peeling surface 43a and the anti-peeling surface 43b (the boiling point of the solvent + 50 ° C.) or less. The second excision device 41 is for continuously cutting both side portions of the optical film 32 to have a predetermined width. The second excision device has the same configuration as the first excision device 37. The winding device 42 is for winding the optical film 32 having a predetermined width in a roll shape, and a core 64 around which the optical film 32 is wound is set.

  A cutting device (not shown) having the same configuration as the first cutting device 37 may be disposed between the casting device 34 and the drying device 36. This excision device is for excising the deformed both sides from the wet film 43, and this excision makes the holding of the drying device 36 by the clip 60 more reliable.

  As shown in FIG. 5, the shape imparting device 35 includes the above-described peeling roller 56 and a shape imparting roller 68. The stripping roller 56 has a rotation shaft arranged in parallel with the rotation shaft of the backup roller 47. The peeling roller 56 is disposed on the opposite side of the belt 46 with respect to the conveyance path of the wet film 43, and the wet film 43 is wound around the peripheral surface. The peeling roller 56 is driven to rotate as the wet film 43 is conveyed. With the wet film 43 wound around the peeling roller 56, the casting film 50 is pulled from the belt 46 at a predetermined peeling position PP by being pulled toward the downstream side of the solution casting equipment 30. . Note that the peeling roller 56 may be rotated by a motor in synchronization with the conveyance of the wet film. In this way, the stripping roller 56 may be a rotating roller that is rotatably provided.

  The shape imparting roller 68 is rotatably provided facing the stripping roller 56 so that the stripping roller 56 and the rotation axis are parallel to each other, and in cooperation with the stripping roller 56, the prism 16a is provided. Form. That is, the stripping roller 56 functions as a stripping unit for stripping the casting film 50 to form the wet film 43, and also as a shape applying unit for forming the prism 16 a on the wet film 43. Function.

  In order to form the prism 16 a on the wet film 43, a plurality of concave portions 68 a and convex portions 68 b each having a triangular cross section are formed on the peripheral surface of the shape imparting roller 68. The concave portions 68 a and the convex portions 68 b extend in the rotation axis direction of the shape imparting roller 68, that is, in the width direction of the wet film 43, and are alternately formed along the circumferential direction of the shape imparting roller 68. The shape imparting roller 68 is rotated by a motor 69 while the wet film 43 is held between the shape imparting roller 68 and the peeling roller 56. The rotation direction of the shape imparting roller 68 is a direction in which the wet film 43 is conveyed (counterclockwise in the figure). The shape imparting roller 68 presses the wet film 43 being conveyed from the side of the peeling surface 43a peeled off from the belt 46 on the peeling roller 56, and a concave portion 68a and a convex portion 68b are formed on the peeling surface 43a. The plurality of prisms 16a are continuously formed by transferring the shape.

  In the shape imparting roller 68 of this example, the recesses 68a and the projecting portions 68b extend in the width direction of the wet film 43, and are alternately formed along the circumferential direction of the shape imparting roller 68. Not limited. For example, a concave portion and a convex portion having a triangular cross section extend in the circumferential direction of the shape imparting roller, and the shape imparting roller in which these are alternately formed along the width direction of the wet film 43 may be used.

  When the peripheral speed of the shape imparting roller 68 is V (unit; m / second) and the conveyance speed of the wet film 43 toward the shape imparting roller 68 is W (unit; m / second), 0.9 W ≦ V It is preferable to satisfy ≦ 1.1W. By satisfying 0.9W ≦ V ≦ 1.1W, a plurality of prisms 16a having a uniform shape and size can be more reliably formed. The peripheral speed V is the deepest position (bottom) of the recess 68a of the shape imparting roller 68.

  The shape imparting roller 68 is pressed against the wet film 43 whose solvent content is in the range of 50% or more and 350% or less with respect to the solid component containing cellulose triacetate as a polymer, and the concave portion 68a and the convex portion 68b. The shape is transferred to form a plurality of prisms 16a. That is, the temperature of the backup roller 47, the temperature and the wind speed of the drying gas from the blowers 52 and 58, and the temperature of the back surface heater 53 are gelled so that the casting film 50 can be peeled off from the belt 46, and The solvent content of the wet film 43 while being in contact with the shape imparting roller 68 is controlled so as to be in the range of 50% to 350%. In this control, the transport speed and transport length of the casting film 50 are taken into consideration.

In the present specification, the solvent content CS is defined as T1 (unit: μm) of the wet film 43 or the casting film 50 to be measured, and the wet film 43 or the casting film 50 is determined. When the thickness after complete drying is T2 (unit: μm), this is a so-called dry amount reference value (unit:%) obtained by the equation (1). “Completely dry” does not require that the residual amount of solvent be strictly “0”. In this embodiment, the mass after performing the drying process for 3 hours or more with respect to the wet film 43 of a measuring object in a thermostat with 120 degreeC or more and relative humidity 10% or less is set to T2. Examples of the solid component include, but are not limited to, a matting agent, an optical control agent, and a plasticizer in addition to the polymer component (cellulose triacetate).
CS = {(T1-T2) / T2} × 100 (1)

  As described above, by controlling the solvent content of the wet film 43 while being in contact with the shape-imparting roller 68, the wet film as a whole is made soft so that the shape of the concave portions 68a and the convex portions 68b can be easily and The prism 16a is formed by reliably transferring. From the viewpoint of reliably forming a plurality of prisms 16a having a uniform shape and size, the solvent content of the wet film 43 while in contact with the shape imparting roller 68 is in the range of 100% to 300%. More preferably, it is more preferably in the range of 150% to 250%.

  When the solvent content of the wet film 43 is high as described above and the prism 16a is formed in a soft state as a whole film, the wet film 43 after the shape imparting shrinks in the thickness direction as it is dried. Therefore, the shapes of the concave portions 68a and the convex portions 68b of the shape imparting roller 68 will be described in detail later with reference to another drawing. However, the prism content to be formed and the solvent content of the wet film 43 while in contact with the shape imparting roller. It is decided accordingly. By using the shape imparting roller 68 in which the shapes of the concave portions 68a and the convex portions 68b are determined in this way, a plurality of prisms that are uniform in the desired shape and size in consideration of shrinkage due to drying after the shape provision. 16a is reliably formed.

  Further, the shape imparting roller 68 is preferably provided with a pressure regulator 70 as in the present embodiment. The pressure adjuster 70 adjusts the pressing force of the shape-imparting roller 68 against the wet film 43 when transferring the shapes of the concave portions 68a and the convex portions 68b. The pressure adjuster 70 adjusts the pressing force to form the prism 16 a more reliably on the wet film 43.

  From the viewpoint of uniformly applying the pressing force to the wet film 43, the pressing force of the shape imparting roller 68 by the pressure adjuster 70 is preferably in the range of 1.5 MPa to 15 MPa. Here, the wet film 43 while in contact with the shape imparting roller 68 contains a large amount of solvent as described above, and the entire wet film is soft. Join locally in the direction. For this reason, when the pressing force is excessively high with respect to the hardness of the wet film 43, the polymer containing the solvent swelled on the upstream side of the portion where the shape imparting roller 68 starts to contact the wet film 43. So-called resin accumulation may occur. When the resin pool is generated, the shape transferred to the wet film 43 is disturbed when the press of the shape imparting roller 68 is released, and the accuracy of the shape of the prism sheet 16 may be deteriorated. Generation | occurrence | production of such a resin pool can be reliably suppressed compared with the case where it exceeds 15 MPa by making pressing force into 15 MPa or less. Further, if the pressing force is excessively low with respect to the hardness of the wet film 43, the target shape may not be transferred. Such a shortage of transfer can be surely avoided by setting the pressing force to 1.5 MPa or more as compared with the case of less than 1.5 MPa. The pressing force of the shape imparting roller 68 is more preferably in the range of 2.0 MPa to 10 MPa, and further preferably in the range of 2.5 MPa to 5.0 MPa.

  The shape imparting roller 68 is preferably provided with a first temperature controller 73 that adjusts the temperature of the peripheral surface as in this embodiment. In the first temperature controller 73, the peeling surface 43a side of the gelled wet film 43 has a sufficient fluidity to give the shapes of the concave portions 68a and the convex portions 68b of the shape imparting roller 68. As described above, the temperature of the peripheral surface of the shape imparting roller 68 is adjusted. As described above, the wet film 43 is in contact with the shape imparting roller 68 by adjusting the temperature of the peripheral surface of the shape imparting roller 68 so that the peeling surface 43a side of the wet film 43 is in a fluid state. The side 43 of the peeling surface 43a enters the bottom of the concave portion 68a of the shape imparting roller 68, and the shapes of the concave portion 68a and the convex portion 68b are more reliably transferred.

  Thus, from the viewpoint of more surely entering the peeling surface 43a side of the wet film 43 to the bottom of the recess 68a of the shape imparting roller 68, the temperature of the peripheral surface of the shape imparting roller 68 is preferably 5 ° C. or higher. Further, from the viewpoint of more reliably preventing foaming of the wet film 43 due to rapid evaporation of the solvent component contained in the wet film 43, it is preferable that the temperature of the peripheral surface of the shape imparting roller 68 is lower than the boiling point of the solvent. When the solvent is a mixture composed of a plurality of components, the boiling point of the mixture may be regarded as the boiling point of the solvent. From the viewpoint of suppressing such foaming, the temperature of the peripheral surface of the shape imparting roller 68 is more preferably 35 ° C. or lower. When dichloromethane is contained in the solvent component, the effect of preventing foaming is particularly remarkable when the temperature of the peripheral surface of the shape imparting roller 68 is 35 ° C. or less. Thus, the temperature of the peripheral surface of the shape imparting roller 68 is preferably in the range of 5 ° C. or more and less than the boiling point of the solvent, more preferably in the range of 5 ° C. or more and 35 ° C. or less, and 7.5 More preferably, the temperature is in the range of not lower than 30 ° C. and not higher than 30 ° C., and particularly preferably in the range of not lower than 10 ° C. and lower than 25 ° C.

  In this example, the wet film 43 is not wound around the shape imparting roller 68, and the shape imparting roller 68 and the wet film 43 are generally in line contact. However, the present invention is not limited to this, and the wet film 43 is wound around the shape-imparting roller 68 from the viewpoint that the peeling surface 43a side of the wet film 43 further enters the bottom of the recess 68a of the shape-imparting roller 68 as described above. It is preferable to make the contact time with the shape imparting roller 68 longer. The effect is higher as the production speed is increased. That is, as the manufacturing speed is increased, the winding angle of the wet film 43 with respect to the shape imparting roller 68 is preferably increased.

  The stripping roller 56 is also preferably provided with a second temperature controller 74 that adjusts the temperature of the peripheral surface as in this embodiment. The second temperature controller 74 adjusts the temperature of the peripheral surface of the peeling roller 56 so that the anti-peeling surface 43b side opposite to the peeling surface 43a of the wet film 43 is maintained in a gel state. Thereby, the anti-peeling surface 43b side of the wet film 43 while being pressed by the shape imparting roller 68 is harder than the peel surface 43a, and the convex portions 68b of the shape imparting roller 68 are more uniform from the peel surface 43a side. The depth penetrates into the wet film 43, and the concave portions 68a and the convex portions 68b are transferred with higher accuracy. Thus, from the viewpoint of accurate transfer, the temperature of the peripheral surface of the peeling roller 56 is preferably 10 ° C. or less. Further, from the viewpoint of not excessively reducing the temperature of the peripheral surfaces of the shape imparting rollers 68 whose peripheral surfaces face each other via the wet film 43, the temperature of the peripheral surface of the peeling roller 56 is −25 ° C. or higher. Is preferred. Thus, the temperature of the peripheral surface of the peeling roller 56 is preferably in the range of −25 ° C. or more and 10 ° C. or less, and is set to −20 ° C. in this embodiment. The temperature of the peripheral surface of the peeling roller 56 is more preferably in the range of −20 ° C. or more and 5 ° C. or less, and further preferably in the range of −15 ° C. or more and 0 ° C. or less.

  Further, from the viewpoint of accurate transfer as described above, it is preferable to increase the wrapping angle of the wet film 43 with respect to the peeling roller 56 and to increase the contact time between the wet film 43 and the peeling roller 56. . The effect is higher as the production speed is increased. That is, as the manufacturing speed is increased, the winding angle of the wet film 43 with respect to the peeling roller 56 is preferably increased.

  As described above, by adjusting the respective peripheral surface temperatures of the shape-imparting roller 68 and the peeling roller 56, the shape of the concave portion 68a and the convex portion 68b of the shape-imparting roller 68 becomes the peeling surface of the wet film 43. Transfer to the 43a side more easily and reliably.

As described above, the shape imparting roller 68 is determined according to the shape of the concave portion 68a and the convex portion 68b of the shape imparting roller 68 according to the prism to be formed and the solvent content of the wet film 43 while in contact with the shape imparting roller. ing. Here, the height of the convex portion 68b (hereinafter referred to as the convex portion height) is HR (unit: μm). As shown in FIG. 6, the convex portion height HR is determined from the apex of the convex portion 68 b with respect to a circle CR passing through the deepest position (bottom) of the concave portion 68 a when the shape imparting roller 68 is viewed from the circular end surface side. This is the length of the lowered vertical line PL. In addition, the two-point difference line which attached | subjected the code | symbol CL in FIG. 6 is a tangent of the circle CR in the leg | foot of this perpendicular line PL. The shape imparting roller 68 is formed to satisfy the formula (2). That is, the convex portion height HR is in the range of 0.9 × HW × {(CS / 100) +1} to 1.1 × HW × {(CS / 100) +1}.
0.9 × HW × {(CS / 100) +1} ≦ HR ≦ 1.1 × HW × {(CS / 100) +1} (2)

Equation (2) is derived as follows. Since the thickness of the wet film 43 gradually decreases due to drying after the release of pressing, the height of the prism 16a formed by pressing is also considered to decrease at the same rate of change as the thickness of the entire film. The reference value HR (S) is expressed by equation (3). The convex portion height HR need not be a single value, and if it is within a certain range, the target prism 16a can be formed, and the reference value HR (for obtaining the above certain range) ( S) is provided. Here, the thickness of the wet film 43 during pressing, that is, during contact with the shape-imparting roller 68 is defined as T1 in the formula (3). In this embodiment, since the wet film 43 is not wound around the shape imparting roller 68, the shape imparting roller 68 and the wet film 43 are in line contact (see FIG. 5). And “at the end of contact” can be regarded as coincident, and “in contact” in the case of obtaining T1 in Expression (3) may be at the time of contact. When the wet film 43 is wound around the shape imparting roller 68, the contact starts at the upstream end of the winding region wound around the shape imparting roller 68, and the contact ends at the downstream end. In this case, the time when the contact with the shape imparting roller 68 ends is the time when the contact is ended when the T1 in the equation (3) is calculated. Further, T1 and T2 in the formula (3) are not the thickness of the wet film 43 with the prism 16a applied, but when the prism 16a is not applied, that is, when both film surfaces are in a so-called flat film state. The thickness of the film.
HR (S) = HW × (T1 / T2) (3)

Further, when the formula (1) is modified, the following formula (1a) is obtained. T1 in this equation is also the thickness of the wet film 43 in contact with the shape imparting roller 68, similarly to T1 in equation (3).
T1 = {(CS / 100) × T2} + T2 (1a)

Substituting equation (3) into equation (1a) yields equation (4).
HR (S) = HW × [{(CS / 100) × T2} + T2] / T2
= HW × {(CS / 100) +1} (4)

If the value obtained by subtracting 10% of HR (S) from HR (S) is within a range obtained by adding 10% of HR (S) to HR (S), the prism 16a is the target prism. It was found to be formed at a height HW. That is, the protrusion height HR may be in the range of {HR (S) × 0.9} or more and {HR (S) × 1.1} or less, which is expressed by the following formula (5). The Equation (2) is obtained by substituting Equation (4) into Equation (5). Thus, the convex part height HR is calculated | required based on the change of the thickness by the drying after contact cancellation.
0.9 × HR (S) ≦ HR ≦ 1.1 × HR (S) (5)

  When the convex portion height HR is less than 0.9 × HW × {(CS / 100) +1} and larger than 1.1 × HW × {(CS / 100) +1}, the target prism height It is difficult to accurately express the height HW. The shape imparting roller 68 preferably has a convex portion height HR satisfying 0.95 × HW × {(CS / 100) +1} ≦ HR ≦ 1.05 × HW × {(CS / 100) +1}, It is more preferable that 0.98 × HW × {(CS / 100) +1} ≦ HR ≦ 1.02 × HW × {(CS / 100) +1}, and the convex portion height HR is HW × {(CS / The closer to 100) +1}, the more reliable the effect of forming the prism 16a in the target shape.

  When the pitch between the convex portions 68b adjacent to each other in the circumferential direction (hereinafter, convex portion pitch) is PR (unit: μm), the aspect ratio obtained by HR / PR is 0.3 or more and 2.0 or less. Is preferably within the range of 0.4 or more and 1.75 or less, and more preferably within the range of 0.5 or more and 1.5 or less. The convex pitch PR is the distance between the apexes of the convex portions 68b, and is, for example, the same as the prism pitch P16a, and is 100 μm or less. The apex angle of the convex portion 68b (hereinafter referred to as the roller apex angle) may be in the range of 20 ° or more and 100 ° or less in consideration of shrinkage due to drying after the pressing by the shape imparting roller 68 is released. preferable. The opening angle of the recess 68a is preferably in the range of 20 ° or more and 100 ° or less in consideration of shrinkage due to drying after the pressing by the shape imparting roller 68 is released.

  In addition, although the recessed part 68a and the convex part 68b are formed in the whole surrounding surface, the shape provision roller 68 of this example is not restricted to this. For example, when the prism 16a is not formed on both sides in the width direction of the casting film 50 or the wet film 43 and the prism 16a is formed only at the center between both sides, The concave portion 68a and the convex portion 68b may be formed only in the central portion in the axial direction. In this case, the region where the concave portion 68a and the convex portion 68b are formed so that the outer side than the region where the concave portion 68a and the convex portion 68b are formed is not in contact with the casting film 50 or the wet film 43. More preferably, it is a small diameter region having a smaller diameter. By providing such a small-diameter region and forming a non-contact portion that does not come into contact with the casting film 50 or the wet film 43, the concave portion 68a and the convex portion 68b can be reliably formed while suppressing the pressing force. . Since the mechanical load is reduced by suppressing the pressing force, the optical film 32 can be manufactured at a higher manufacturing speed, so that the manufacturing efficiency is further improved. Moreover, by suppressing the pressing force, the wear of the concave portion 68a and the convex portion 68b of the shape imparting roller is further suppressed, and the durability of the shape imparting roller is improved.

  The operation of the above configuration will be described. The dope 31 is supplied to the casting die 48 and discharged toward the traveling belt 46. As a result, the casting film 50 is formed on the belt 46 whose temperature is controlled by the backup roller 47. Since the dope 31 is continuously discharged from the casting die 48 and the belt 46 continues to run, the casting film 50 is continuously formed.

  The formed cast film 50 is conveyed as the belt 46 travels. During the conveyance, the solvent in the casting film 50 evaporates due to the heating by the backup roller 47, the supply of the dry gas by the blower 52, and the heating by the back surface heater 53, and the casting film 50 is dried, and gelation occurs. To do. In the case of cooling casting, during this conveyance, the casting film 50 is dried by evaporation of the solvent by cooling by the backup roller 47, supply of dry gas by the blower 52, and cooling by the back surface heater 53. As it goes on, it cools and gels.

  The cast film 50 which has been dried and gelled is peeled off from the belt 46 by the peeling roller 56 at the peeling position PP while remaining in a gel state. The cast film 50 that has been peeled off, that is, the wet film 43 is conveyed toward the shape imparting device 35. By controlling the peripheral surface temperature of the peeling roller 56, the gel state is maintained even when the anti-peeling surface 43 b side of the wet film 43 contacts the peeling roller 56.

  When the wet film 43 is conveyed to the position of the shape imparting roller 68, the wet film 43 is sandwiched between the rotating shape imparting roller 68 and the peeling roller 56 and pressed by the shape imparting roller 68 from the peeling surface 43a side. . Thereby, the shape of the recessed part 68a or the convex part 68b is transcribe | transferred to the peeling surface 43a in the part of the wet film 43 pinched. Since the shape imparting roller 68 rotates as the wet film 43 is conveyed, the plurality of prisms 16 a are sequentially formed on the peeling surface 43 a of the wet film 43.

  When the wet film 43 having a solvent content of less than 50% is pressed by the shape imparting roller 68, it is difficult for the wet film 43 to enter the deepest portion of the concave portion 68a, and the shapes of the concave portion 68a and the convex portion 68b are different. It is difficult to be transferred. In addition, when the wet film 43 having a solvent content of more than 350% is pressed by the shape-imparting roller 68, the amount of shrinkage due to drying after releasing the press is too large, and the target prism height HW is expressed. Is difficult. Therefore, as described above, the wet film 43 is soft and small because the solvent content of the wet film 43 when the shape imparting roller 68 presses the wet film 43 is in the range of 50% to 350%. The wet film 43 can be easily deformed by the pressing force in accordance with the shapes of the concave portions 68a and the convex portions 68b.

  The shape imparting roller 68 has a convex portion height HR satisfying the formula (2), and is formed with a concave portion 68a and a convex portion 68b in consideration of shrinkage in the thickness direction due to drying after the pressure is released. On the wet film 43 immediately after that, the prism 16 a higher than the target prism height HW, that is, the prism height HW in the optical film 32 is formed. Thereby, the optical film 32 obtained by reducing the thickness by drying after releasing the pressure is formed by the prism 16a having a desired shape.

  As described above, the aspect ratio determined by HR / PR is in the range of 0.3 to 2.0, so that the convex portion 68b of the shape imparting roller 68 has a more uniform depth from the peeling surface 43a side. The wet film 43 enters the wet film 43 and the wet film 43 more reliably enters the deepest position of the concave portion 68a, so that the concave portion 68a and the convex portion 68b are transferred with higher accuracy.

  While the prism 16a is formed as described above, the temperature of the peripheral surface of the shape imparting roller 68 is in the range of 5 ° C. or more and 35 ° C. or less. It becomes a state with fluidity. Therefore, the wet film 43 enters the deepest portion of the recess 68a, and the shapes of the recess 68a and the protrusion 68b are transferred more reliably and easily.

  As described above, the temperature of the peripheral surface of the peeling roller 56 is in the range of −25 ° C. or more and 10 ° C. or less, so that the convex portion 68b of the shape imparting roller 68 from the peeling surface 43a side has a more uniform depth. Now, it enters the wet film 43, and the concave portions 68a and the convex portions 68b are transferred with higher accuracy.

  As described above, the pressing force of the shape-imparting roller 68 against the wet film 43 is in the range of 1.5 MPa or more and 15 MPa or less. Is prevented.

  The wet film 43 is sent from the shape imparting device 35 to the drying device 36 in a state where the prism 16a is formed higher than the target prism height HW by the shape imparting roller 68 as described above. When the wet film 43 is guided to the drying device 36, both sides thereof are gripped by the clips 60, and the wet film 43 is conveyed in a state where the width is kept constant by the movement of the clips 60. During the conveyance, the drying of the wet film 43 is further promoted while the width of the wet film 43 is kept constant by blowing the dry gas from the air outflow portion 62, and the thickness of the prism 16 a is reduced as the thickness decreases. Will decrease.

  The wet film 43 dried by the drying device 36 is cut off on both sides by the first cutting device 37 and guided to the drying chamber 40. The wet film 43 is further dried while passing through the drying chamber 40, whereby the optical film 32 having a target prism height HW is obtained. The optical film 32 is wound into a roll by the winding device 42. The optical film 32 wound in a roll shape is cut into a predetermined size in a subsequent process and used as the prism sheet 16.

  In the above-described embodiment, the shape of the prism 16a is imparted to the wet film 43 on the peeling roller 56 by the shape imparting roller 68. The position where the shape is imparted is determined by the solvent content of the wet film 43. Other positions may be used as long as they are within the range of 50% to 350%. For example, a shape imparting roller 68 and a nip roller (not shown) may be disposed on the conveyance path between the peeling roller 56 and the drying device 36 to impart a shape to the wet film 43. Further, the shape imparting roller 68 may be pressed against the casting film 50 on the casting support such as the belt 46 or the drum to impart the shape.

  In the above embodiment, an example in which the manufactured optical film is used as a total reflection type prism sheet has been described. However, the optical film can also be used as a refraction type prism sheet.

  In the above example, the optical film 32 to be the prism sheet 16 is manufactured, but the optical film to be manufactured is not limited to this, and a plurality of irregularities are provided on one surface, thereby refracting incident light. Any optical film that collects or diffuses light may be used. Examples of such an optical film include a brightness enhancement film, a diffusion film, and an antireflection film. These optical films may not have irregularities regularly arranged like the optical film 32 described above, and may have irregularities irregularly formed. Further, the shape of the unevenness may be a pyramid shape, a conical shape, or an indefinite shape. Further, the size of the irregularities of these shapes may be non-uniform. In such a case, a shape-imparting roller in which a concave portion and a convex portion corresponding to the target irregular shape are formed on the peripheral surface is used in place of the shape-giving roller 68.

  Even in the case of manufacturing an optical film with irregularities irregularly formed, the pressing by the shape imparting roller is applied to the wet film 43 or the casting film 50 having a solvent content in the range of 50% to 350%. Do it against. Further, it is assumed that the concave portion and the convex portion of the shape imparting roller are formed so as to satisfy Expression (2). The height of the unevenness of the optical film to be formed, that is, the highest unevenness when the distance from the deepest position of the concave portion to the highest position of the convex portion forming the concave portion is not uniform in the thickness direction of the film. The height HR of the shape imparting roller is obtained by the expression (2) with the height of HW as HW. Further, the convex pitch PR when calculating the aspect ratio is obtained by calculating the distance between the vertices of the two convex portions closest to each other on the peripheral surface and the convex portions. The part pitch PR.

  In addition, a moth-eye film is mentioned as an example of an antireflection film. In the moth-eye film, convex portions or concave portions are formed on one film surface at a pitch of visible light wavelength (about 380 nm) or less. The arrangement of the irregularities on the film surface of the moth-eye film may be regular or irregular.

[Example 1] to [Example 8]
The optical film 32 was each manufactured on each condition shown in Table 1 with the solution casting apparatus 30, and it was set as Examples 1-5. The target prism height HW of the optical film 32 was 25 μm, and the prism pitch P16a was 50 μm.

The dope 31 was prepared by adding a solid component having the following composition to a solvent and dissolving it with stirring so that the concentration of TAC was approximately 19% by mass.
[Solid component]
Cellulose triacetate (substitution degree 2.8) 89.3% by mass
Plasticizer A (triphenyl phosphate) 7.1% by mass
Plasticizer B (biphenyldiphenyl phosphate) 3.6% by mass

As the solvent, a mixed solution having the following composition was used.
[solvent]
Dichloromethane 80% by mass
Methanol 13.5% by mass
n-butanol 6.5% by mass

  The dope 31 is filtered through a filter paper (Toyo Filter Paper Co., Ltd., # 63LB), filtered through a sintered metal filter (Nihon Seisen Co., Ltd. 06N, nominal pore size 10 μm), and further filtered through a mesh filter. Once stored in the stock tank. At the time of casting, the dope 31 was supplied to the casting die 48 from the stock tank.

  The cellulose triacetate used had a residual acetic acid content of 0.1% by mass or less, a Ca content of 58 ppm, a Mg content of 42 ppm, a Fe content of 0.5 ppm, free acetic acid 40 ppm, and sulfate ions. Was 15 ppm. The degree of substitution of the acetyl group with respect to the hydrogen at the 6-position hydroxyl group was 0.91. Further, 32.5% of all acetyl groups were acetyl groups in which the hydrogen of the hydroxyl group at the 6-position was substituted. Moreover, the acetone extraction part which extracted this TAC with acetone was 8 mass%, and the weight average molecular weight / number average molecular weight ratio of TAC was 2.5. The yellow index of this TAC was 1.7, the haze was 0.08, and the transparency was 93.5%. This TAC was synthesized using cellulose collected from cotton as a raw material.

[Shaping roller]
The shape imparting rollers 68 of Examples 1 to 8 have a roller diameter of 150 mm. The shape imparting roller of Example 6 has a roller diameter of 150 mm. Table 1 shows the roller apex angle, the convex portion height HR, the convex portion pitch PR, the aspect ratio HR / PR, and the peripheral surface temperature for each of the shape imparting rollers 68 of Examples 1 to 8. Each of the shape imparting rollers 68 of Examples 1 to 8 satisfies the formula (2).

  In Table 1, “solvent content”, “pressing force”, and “temperature of the peripheral surface of the peeling roller” are the solvent content of the wet film 43 being pressed by the shape imparting roller 68 of Examples 1 to 8, respectively. And the pressing force against the wet film 43 and the temperature of the peripheral surface of the peeling roller 56.

  About each optical film 32 obtained in the said Examples 1-8, the shape of the prism 16a was evaluated in the cross section in the thickness direction. In the evaluation, first, each cross section was observed with an optical microscope, and the prism height HW of the optical film 32 was obtained. The magnification with an optical microscope was 1500 times. For the optical film 32, arbitrarily select five prisms 16a in the observation image, measure the prism heights HW1 to HW5 for each of the selected ones, determine the average value thereof by the calculation formula of (HW1 + HW2 + HW3 + HW4 + HW5) / 5, The average value was defined as the prism height HW.

By evaluating the obtained prism height HW according to the following criteria, the shape of the prism 16a was evaluated. The target prism height HW (25 μm) is hereinafter referred to as “target height”, and the obtained prism height HW is hereinafter referred to as “calculated height”. A to C are acceptable and D is unacceptable.
A: Calculated height is (target height × 0.95) or more (target height × 1.05) B: Calculated height is (target height × 0.90) or more (target height × 0) .95) or less than (target height × 1.05) and not more than (target height × 1.10) C; calculated height is not less than (target height × 0.85) (target height) × 0.90) or less than (target height × 1.10) and less than (target height × 1.15) D; calculated height is less than (target height × 0.85) Or larger than (target height x 1.15)

[Comparative Example 1] to [Comparative Example 5]
An optical film was produced by the solution casting equipment 30 under the conditions shown in Table 1, and designated as Comparative Examples 1 and 2. Moreover, it replaced with the shape provision roller in which the convex part of the convex part height HR shown in Table 1 was formed in the shape forming roller 68 of the solution film-forming equipment 30, and it was set as Comparative Examples 3-5. Other conditions of these comparative examples are the same as those of the above-described examples.

  About the obtained optical film, the shape of the prism in the cross section in the thickness direction was evaluated by the same method and standard as in the examples. The evaluation results are shown in Table 1.

16 Prism sheet 16a Prism 30 Solution casting equipment 32 Optical film 35 Shape imparting device 43 Wet film 50 Casting film 56 Stripping roller 68 Shape imparting roller 68a Concavity 68b Convex

Claims (8)

A plurality of depressions and projections are formed on the peripheral surface, and the plurality of depressions and projections that refract incident light to collect or diffuse by pressing a web that is being transported containing a polymer and a solvent from one surface side. In the shape imparting roller that is continuously formed on one surface,
When the height of the protrusion is HR μm, the height of the top of the unevenness formed on the one surface is HW μm, and the solvent content in the web is CS%,
0.9 × HW × {(CS / 100) +1} ≦ HR ≦ 1.1 × HW × {(CS / 100) +1}
The filling,
HR / PR is 0.3 or more and 2.0 or less when the pitch between the adjacent protrusions and the protrusions is PR μm,
A pressure regulator for adjusting the pressing force against the web is provided, and the web is pressed with the pressing force within a range of 1.5 MPa or more and 15 MPa or less,
A shape-giving roller, wherein the web is pressed with the solvent content in a range of 50% to 350%. The plurality of concave portions and convex portions are alternately formed along the circumferential direction, and have a triangular cross section extending in the width direction of the web.
The shape imparting roller according to claim 1 , wherein the unevenness of the web is a prism. Comprising a first temperature controller for regulating the temperature of the circumferential surface, the shape according to claim 1 or 2 wherein the temperature of the peripheral surface is in the range of 5 ° C. or higher 35 ° C. or less by the first temperature controller Giving roller. In a film manufacturing method for manufacturing an optical film having a plurality of concavities and convexities that refract incident light and collect or diffuse the incident light on one film surface,
A casting process in which a dope in which a polymer is dissolved in a solvent is continuously cast on a running casting support to form a casting film;
A peeling step of forming a wet film by peeling the casting film from the casting support in a state where the solvent remains;
In a state where the solvent content is in a range of 50% or more and 350%, a shape imparting roller in which a plurality of concave portions and convex portions are formed on the peripheral surface of the cast film or the wet film being conveyed is provided on one surface. A shape imparting step of continuously forming the plurality of irregularities on the one surface of the cast film or the wet film by pressing from the side;
A drying step of drying the cast film or the wet film that has undergone a shape imparting step,
When the height of the convex portion of the shape imparting roller is HR μm and the height of the top of the unevenness on the one film surface is HW μm and is pressed by the shape imparting roller of the casting film or the wet film When the solvent content of CS is CS%, the shape imparting roller satisfies 0.9 × HW × {(CS / 100) +1} ≦ HR ≦ 1.1 × HW × {(CS / 100) +1}. It meets,
The shape imparting roller has an HR / PR of 0.3 or more and 2.0 or less when the pitch between the adjacent convex portions and the convex portions is PR μm,
The said shape provision process presses the said cast film or the said wet film with the pressing force in the range of 1.5 MPa or more and 15 MPa or less, The film manufacturing method characterized by the above-mentioned . The unevenness of the film is a prism,
The film manufacturing method according to claim 4 , wherein the plurality of concave portions and convex portions of the shape imparting roller are alternately formed along a circumferential direction and have a triangular cross section extending in the width direction of the film. 6. The film production according to claim 4 , wherein the shape imparting step presses the shape imparting roller having a temperature of the peripheral surface within a range of 5 ° C. or more and 35 ° C. or less against the cast film or the wet film. Method. The shape imparting step sandwiches and presses the casting film or the wet film between the shape imparting roller and a rotation roller that is rotatably provided with rotation axes parallel to each other, and the shape imparting roller. 4 to process the film production according to any one of 6. The film manufacturing method according to claim 7 , wherein the temperature of the peripheral surface of the rotating roller is in a range of −25 ° C. or more and 10 ° C. or less.

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