JP5541895B2 - Casting method, casting apparatus, solution casting method and solution casting equipment - Google Patents

Description

  The present invention relates to a casting method, a casting apparatus, a solution casting method, and a solution casting equipment.

  The liquid crystal display device includes a liquid crystal display panel and a backlight unit that emits light to the liquid crystal display panel, and uses the light from the backlight unit to display a desired image on the liquid crystal display panel. The liquid crystal display panel includes a liquid crystal cell and a pair of polarizing plates provided on both sides of the liquid crystal cell, and the backlight unit includes a light source for applying light to the liquid crystal display panel, a liquid crystal display panel, and a light source. It has a diffusion film and a brightness enhancement film provided between them.

  The diffusion film is overlapped with the brightness enhancement film, and is disposed closer to the light source side or the viewing side than the brightness enhancement film, so that the light from the light source is irradiated to the entire liquid crystal display panel through the brightness enhancement film. To suppress the occurrence of uneven brightness. As a structure of the diffusion film, for example, a diffusion film formed on a support member and a light diffusion layer formed on the support member and made of a highly translucent polymer (see, for example, Patent Documents 1 and 2). Etc. have been proposed. This light diffusion layer contains fine particles having high translucency. On the other hand, an electroconductive film is comprised from the support body and this electroconductive layer provided on this support body, and is used for the antistatic film, the surface film for touch panels, etc. These laminated films such as a diffusion film and a conductive film can be obtained by applying a predetermined coating solution to a separately manufactured support member and forming a diffusion layer or a conductive layer on the support member.

The support member can be produced by either a solution casting method or a melt casting method. However, when the laminated film is used as an optical component, the support member is melted in order to meet demands such as optical isotropy. Production by solution casting is preferable to film production. The solution casting method has an advantage that not only a single layer structure but also a film having a plurality of layers (hereinafter referred to as a laminated film) can be produced. Therefore, according to solution casting, a laminated film for optical use can be produced without a post-process such as coating.
JP 2003-149413 A JP 2003-195015 A

  By the way, it is not preferable that the diffusibility of the diffusion film and the brightness enhancement film is low because scratches are generated due to rubbing between the films and the front brightness cannot be improved efficiently. Therefore, it can be said that the diffusion film is one of the important factors in the overlay property with the brightness enhancement film. However, in the diffusion films described in Patent Documents 1 and 2, the surface of the light diffusion layer is formed to be uneven, and the overlayability with the brightness enhancement film is not high. Further, in Patent Documents 1 and 2, since the coating liquid for forming the light diffusion layer is applied on the support, both the support member manufacturing process and the application process are required. Also in the case of a conductive film, it is the same as a diffusion film, and when the surface of the conductive layer is formed to be uneven, it is not possible to ensure a certain overlay property with other members provided overlapping the conductive film. In addition, both the support member manufacturing process and the coating process are required.

  Accordingly, the present invention provides a solution casting method capable of efficiently producing a laminated film having a support member and a high-functional layer such as a light diffusion layer and a conductive layer provided on the support member and having a smooth surface, and Provided are a solution casting apparatus, a casting method and a casting apparatus used in the solution casting method and the solution casting apparatus.

Casting method of the present invention, joins the main dope of _M polymer and viscosity and a solvent mu, the first sub-dope viscosity is less mu _M, at an acute angle θ1 with respect to the direction of flow of the main dope by a first merging step of making a first multilayer dope comprising a first sub-layer the main dope consisting main layer and the thickness than the main layer is made of thin the first sub dope viscosity following mu _M The second sub-dope is joined to the first multi-layer dope from the first sub-layer side at an angle θ2 equal to or less than the angle θ1 with respect to the flow direction of the first multi-layer dope, and the main layer, the first sub-dope A second merging step of forming a second laminated dope comprising a layer and a second sub-layer having a thickness smaller than that of the main layer and comprising the second sub-dope, and discharging the second laminated dope to a support, The main layer, the first sub layer, and the second sub layer that are sequentially provided from the support side Possess a film forming step of forming a multilayer cast film comprising, angle θ1 is 45 ° to 70 ° or less, the angle θ2 is equal to or is less than 45 ° 25 ° or more.

The third sub-dope viscosity is less mu _M, at an acute angle θ3 with respect to the direction of flow of the main dope, from the opposite direction as the first sub-dope are joined, by merging into the main dope, a third merging step of making a third multilayer dope comprising a third sub-layer consisting of the main layer and the third sub-doping, the following fourth sub dope viscosity mu _M, against the direction of flow of the main dope A fourth sub-layer comprising the main layer, the third sub-dope, and the fourth sub-dope joined to the third stacked dope from the third sub-layer side at an angle θ4 equal to or smaller than the angle θ3. A fourth merging step of forming a laminated dope, wherein the angle θ3 is not less than 55 ° and not more than 70 °, the angle θ4 is not less than 35 ° and not more than 45 °, and in the film forming step, the main layer is disposed on the support side. the third sublayer provided et al is, the fourth sub to the support side of the third sub-layer It is preferable to form the laminated casting film is provided.

Wherein the first sub-doping, particles having a light-transmitting property, has a refractive index different from that of the particles, the binder to become a binder polymer of the particles, and it is not preferable to contain a solvent of the binder polymer. It is preferred to pre-Symbol polymer or the binder polymer comprises cellulose acylate.

  The solution casting method of the present invention includes the casting method described above, a stripping step of stripping the laminated casting membrane from the support as a wet film, and a drying step of drying the wet film. And

Casting apparatus of the present invention, a support for travel, the polymer solvent and provided the main channel through which main dope viscosity mu _M includes a first substream flows first sub dope viscosity is less mu _M A road is connected to the main flow path at an acute angle θ1 from the downstream side in the running direction of the support, and a main layer made of the main dope and the first sub dope are joined by the merge of the main dope and the first sub dope a first merging unit will make a first multilayer dope comprising a first sub-layer is thinner thickness than the main layer from the than the first converging portion provided in the main passage on the downstream side, viscosity mu _M or less A second sub-channel through which the second sub-dope flows is connected to the main channel at an angle θ2 equal to or smaller than the angle θ1 from the downstream side in the running direction of the support, and the first stacked dope and the second sub-dope The main layer, the first sub-layer, and the second sub-dope A second merging portion for forming a second laminated dope including a second sublayer having a thickness smaller than that of the main layer; and communicating with the main flow channel; discharging the second laminated dope; and sequentially providing from the support side And a discharge port for forming a laminated casting film including the main layer, the first sublayer, and the second sublayer on the support , the angle θ1 being 45 ° or more and 70 ° or less, and the angle θ2 being characterized in der Rukoto 25 ° to 45 °.

The third sub-passage flow viscosity is mu _M or less of the third sub-dope, from the running direction downstream side of said support and connected to the main channel at an acute angle .theta.3, of the main dope and the third sub-doped by merging, the main layer and the third third confluence unit thickness than the main layer consists of sub-doped make third multilayer dope comprising a thin third sublayer provided Rutotomoni, viscosity mu _M following A fourth sub-flow channel through which the fourth sub-dope flows is connected to the main flow channel at an angle θ4 equal to or smaller than the angle θ3 from the downstream side in the running direction of the support, and the third laminated dope and the third sub-dope merge The fourth merge part that forms the fourth laminated dope including the fourth sub layer comprising the main layer, the third sub layer, and the fourth sub dope and having a thickness smaller than that of the main layer is the third merge part. The angle θ3 is 55 ° or more and 7 0 ° or less, the angle θ4 is 45 ° or less 35 ° or more, the laminated casting film is to have a third sub-layer on the support side of the main layer, the support side of the third sub-layer it is preferable to have a fourth sublayer.

  A solution casting apparatus of the present invention comprises the above casting apparatus, a stripping apparatus for stripping the laminated casting film from the support as a wet film, and a drying apparatus for drying the wet film. And

According to the present invention, the main dope viscosity mu _M, viscosity by merging at an angle θ1 of the first sub-doped follows mu _M, making the first multilayer dope, the following second sub-doped viscosity mu _M Are joined to the first laminated dope from the first sub-dope side at the angle θ2 of the angle θ1 or less to form the second laminated dope, so that a laminated film having a smooth surface can be efficiently produced. . Therefore, according to the present invention, a laminated film having a smooth surface can be efficiently produced.

(Solution casting method)
As shown in FIG. 1, the solution casting apparatus 10 includes a casting chamber 12, a pin tenter 13, a clip tenter 14, a drying chamber 15, a cooling chamber 16, and a winding chamber 17.

  The casting chamber 12 includes three types of dopes including a polymer and a solvent, that is, a feed block 27 for forming a laminated dope described later from a main dope 21, a first subdope 22 and a second subdope 23, and a laminated dope. A casting die 28 that flows out, a casting drum 30 that is a support and forms a laminated casting film 29 from a laminated dope, a peeling roller 33 that peels the laminated casting film 29 from the casting drum 30, and a temperature Preparation devices 34 and 35, a condenser (condenser) 36, and a recovery device 37 are provided.

  The condenser 36 condenses the solvent contained in the atmosphere in the casting chamber 12. Under the control of a control unit (not shown), the recovery device 37 recovers the solvent liquefied by the condenser 36 and keeps the gas dew point TR of the atmosphere in the casting chamber 12 within a predetermined range. The gas dew point is a temperature at which the solvent contained in the atmosphere in the casting chamber 12 is condensed. The recovered solvent is regenerated by a regenerator and then reused as a dope preparation solvent. Under the control of the control unit, the temperature adjustment device 35 maintains the temperature of the atmosphere in the casting chamber 12 within a predetermined range.

  The casting drum 30 is rotated around the shaft 30a by a driving device (not shown) under the control of the control unit. Due to the rotation of the casting drum 30, the peripheral surface 30b travels at a predetermined speed. The temperature control device 34 circulates the heat transfer medium adjusted to a desired temperature under the control of the control unit in the flow path provided in the casting drum 30. Due to the circulation of the heat transfer medium, the temperature of the peripheral surface 30b of the casting drum 30 can be maintained at a desired temperature.

  The casting drum 30 is preferably made of stainless steel, and more preferably made of SUS316 so as to have sufficient corrosion resistance and strength. The chromium plating treatment applied to the peripheral surface 30b of the casting drum 30 is preferably so-called hard chromium plating with a Vickers hardness of Hv 700 or more and a film thickness of 2 μm or more.

  As shown in FIGS. 2 and 3, the feed block 27 joins the dopes 21 to 23 sent from the flow paths 41 to 43 to form a laminated dope 45, and the laminated dope 45 having a predetermined flow rate is cast into the casting die. Send to 28. The casting die 28 discharges the laminated dope 45 from the discharge port 28a toward the peripheral surface 30b of the rotating casting drum 30. The discharged laminated dope 45 forms a laminated casting film 29 on the peripheral surface 30 b of the casting drum 30. Then, the casting drum 30 is cooled while rotating about 3/4, and the laminated casting film 29 has self-supporting property due to gelation. Thus, the laminated casting film 29 is peeled off from the casting drum 30 by the peeling roller 33.

  As shown in FIG. 1, the decompression chamber 47 may be disposed upstream of the casting die 28 in the traveling direction of the peripheral surface 30b. The decompression chamber 47 decompresses the upstream side in the traveling direction of the casting bead to a desired pressure. Under the control of a control unit (not shown), the decompression chamber 47 can decompress the upstream side in the running direction of the casting bead so that the pressure on the upstream side of the casting bead is lower than the pressure on the downstream side. The pressure difference between the upstream side and the downstream side of the casting bead is preferably 10 Pa or more and 2000 Pa or less.

  On the downstream side of the casting chamber 12, a crossover 50, a pin tenter 13, a clip tenter 14, a drying chamber 15, a cooling chamber 16, and a winding chamber 17 are sequentially installed. The transfer section 50 introduces the wet film 52 peeled off by the peeling roller 33 into the pin tenter 13 by the roller 53.

  The pin tenter 13 has a large number of pin plates that pass through and hold both side edges of the wet film 52, and the pin plates travel on a track. Dry air is sent to the wet film 52 traveling by the pin plate, and the wet film 52 is dried to form a laminated film 55. The pin tenter 13 may be omitted.

  The clip tenter 14 has a number of clips that grip both side edges of the laminated film 55 in the width direction, and these clips travel on the stretching track. Dry air is sent to the laminated film 55 traveling by the clip, and the laminated film 55 is subjected to a drying process along with a stretching process in the width direction. The clip tenter 14 may be omitted.

  Ear openers 57a and 57b are provided downstream of the pin tenter 13 and the clip tenter 14, respectively. The edge-cutting devices 57a and 57b cut both side edges in the width direction of the laminated film 55. The cut side edges are sent to the crushers 58a and 58b by air blowing, pulverized, and reused as a raw material such as a dope.

  A large number of rollers 59 are provided in the drying chamber 15, and a laminated film 55 is wound around these rollers and conveyed. The temperature and humidity of the atmosphere in the drying chamber 15 are adjusted by an air conditioner (not shown), and the laminated film 55 is dried by passing through the drying chamber 15. An adsorption recovery device 60 is connected to the drying chamber 15, and the solvent evaporated from the laminated film 55 is absorbed and recovered.

  A cooling chamber 16 is provided on the outlet side of the drying chamber 15, and the laminated film 55 is cooled in this cooling chamber 16 until it reaches room temperature. A forced charge removal device (charge removal bar) 61 is provided downstream of the cooling chamber 16, and the laminated film 55 is discharged. Further, a knurling application roller 62 is provided on the downstream side of the forced static elimination device 61, and knurling is applied to both side edges of the laminated film 55. In the winding chamber 17, a winding machine 64 having a press roller 63 is installed, and the laminated film 55 is wound around the winding core 65 in a roll shape.

  Next, details of the feed block 27 and the casting die 28 will be described. As shown in FIG. 2, in the following description, the width direction of the feed block 27 is the X direction, the height direction of the feed block 27 is the Z direction, and the X direction and the direction orthogonal to the Z direction are the Y direction.

(Feed block)
As shown in FIGS. 2 and 3, a main channel 71, a first sub-channel 72, and a second sub-channel 73 are provided in the feed block 27. The main flow path 71 is formed at a substantially central portion of the feed block 27 so as to penetrate in the Z direction, and an inlet 75 is opened on the upper surface of the feed block 27 and an outlet 76 is opened on the lower surface. In the main channel 71, a first junction 71a and a second junction 71b are sequentially provided from the inlet 75 toward the outlet 76.

  The first sub-channel 72 and the second sub-channel 73 are provided on the downstream side in the traveling direction of the peripheral surface 30b in the vicinity of the discharge port 28a with respect to the main channel 71. The first sub-channel 72 extends from the downstream side in the traveling direction of the peripheral surface 30b in the vicinity of the discharge port 28a toward the upstream side, and is connected to the main channel 71 at the first merging portion 71a. Similarly, the second sub-channel 73 extends from the downstream side in the traveling direction of the peripheral surface 30b in the vicinity of the discharge port 28a toward the upstream side, and is connected to the main channel 71 at the second junction 71b. The angle θ1 formed by the first sub-channel 72 and the main channel 71 is an acute angle, and the angle θ2 formed by the second sub-channel 73 and the main channel 71 is equal to or less than the angle θ1.

  In the first junction portion 71a, a vane 78a as a partition member is swingably attached between the main channel 71 and the first sub-channel 72 via an attachment shaft 79a. In the 1st junction part 71a, the column-shaped distribution pin 80a is arrange | positioned in the X direction at the exit of the 1st subchannel 72, and it can rotate centering on an axis | shaft. Similarly, a vane 78b is swingably attached via a mounting shaft 79b between the main flow path 71 and the second sub flow path 73 in the second junction 71b. In the second junction 71b, a cylindrical distribution pin 80b is disposed in the X direction at the outlet of the second sub-flow path 73, and is rotatable about an axis. The vanes 78a and 78b may be omitted.

  As shown in FIG. 4, a cutout groove 81 formed to extend in the circumferential direction is provided on the peripheral surface of the distribution pin 80a. The notch groove 81 communicates the first sub-channel 72 and the main channel 71. The distribution pin 80b (see FIG. 3) is also provided in the same shape as the distribution pin 80a, and a notch groove provided in the peripheral surface communicates the second sub flow path 73 and the main flow path 71. It is preferable that the depth of the notch groove provided in each distribution pin and the width in the X direction are gradually increased or gradually decreased in the circumferential direction. By rotating the distribution pin around the axis, it is possible to adjust the flow rate of the dopes 22 and 23 flowing in the joining portions 71a and 71b and the flow width in the X direction.

(Casting die)
As shown in FIG. 5, the casting die 28 includes lip plates 86 and 87 and side plates (not shown). The lip plates 86 and 87 provided in the X direction are arranged in the Y direction so as to be separated from each other. The side plate is provided in the Y direction so as to close the gap between the lip plates 86 and 87. A portion surrounded by the lip plates 86 and 87 and the side plate is formed as a slot 88 on the casting die 28. The slot 88 communicates with an inlet 89 that communicates with the outlet 76 of the feed block 27 and an outlet 28 a that discharges the laminated dope 45. The discharge port 28a has a rectangular shape and is formed to extend in the X direction.

The slot 88 is preferably provided with a first slot 88s, a second slot 88t, and a first slot 88u sequentially from the upstream side to the downstream side in the direction in which the laminated dope flows.
The width Wuy of the third slot 88u in the Y direction is narrower than the width Wsy of the first slot 88s in the Y direction, and the width Wux of the third slot 88u in the X direction is smaller than the width Wsx of the first slot 88s in the X direction. wide. In addition, the width Wty of the second slot 88t in the Y direction gradually decreases from the width Wsy to the width Wuy from the upstream side to the downstream side in the direction in which the stacked dope flows, and the width Wtx of the second slot 88t in the X direction. Increases gradually from the width Wsx to the width Wux as it goes from the upstream side to the downstream side in the direction in which the laminated dope flows.

  Next, the operation of the present invention will be described. As shown in FIGS. 1 and 3, the main dope 21 is sent to the feed block 27 via the flow path 41 and flows through the main flow path 71. The first sub-dope 22 is sent to the feed block 27 via the flow path 42 and flows through the first sub-flow path 72. The second sub dope 23 is sent to the feed block 27 via the flow path 43 and flows through the second sub flow path 73.

  In the first merge portion 71a, the first sub-dope 22 merges with the main dope 21 at an acute angle θ1 with respect to the flowing direction of the main dope 21. In this way, in the 1st junction part 71a, the lamination | stacking dope 95 comprised from the main layer which consists of the main dope 21, and the 1st sublayer which consists of the 1st subdope 22 and is thinner than the main layer is produced. The laminated dope 95 flows through the main channel 71 toward the second junction 71b.

  In the second merge portion 71 b, the second sub-dope 23 merges with the multilayer dope 95 at an angle θ2 with respect to the direction in which the multilayer dope 95 flows. In the second merging portion 71b, a laminated dope 45 composed of the main layer, the first sublayer, and the second subdope 23, which is composed of a second sublayer that is thinner than the main layer, is formed. The laminated dope 45 flows through the main channel 71 and is sent to the casting die 28 via the outlet 76. The laminated dope 45 sent to the casting die 28 passes through the slot 88. The laminated dope 45 passing through the second slot 88t expands in the X direction while being compressed in the Y direction while maintaining the layer structure. In addition, the temperature of each dope 21-23, 45, and 95 is adjusted substantially constant in the range of 30 degreeC or more and 35 degrees C or less by the temperature controller provided in the feed block 27 or the casting die 28. FIG.

  As shown in FIG. 1, the temperature adjustment device 34 adjusts the temperature of the peripheral surface 30 b of the casting drum 30 to be substantially constant in the range of −20 ° C. to 0 ° C. The casting drum 30 rotates around the shaft 30a, and the peripheral surface 30b travels. The traveling speed of the peripheral surface 30b is preferably 35 m / min or more and 200 m / min or less, and more preferably 70 m / min or more and 150 m / min or less.

  The casting die 28 discharges the laminated dope 45 toward the peripheral surface 30 b of the casting drum 30. The laminated casting film 29 is formed on the peripheral surface 30b by the discharged laminated dope 45. Details of the laminated cast film 29 will be described later. The laminated cast film 29 is cooled on the peripheral surface 30b, becomes a gel, and exhibits self-supporting properties. Thereafter, the peeling roller 33 peels off the laminated casting film 29 exhibiting self-supporting properties as a wet film 52 from the casting drum 30 and guides it to the pin tenter 13 through the crossing portion 50.

  Here, the gel state includes a state in which the fluidity of the dope is lost in addition to a state in which the colloidal solution is solidified in a jelly shape. Note that “the fluidity of the dope has been lost” means that when the solute is a polymer, the fluidity is lost while the solvent is retained in the molecular chain of the solute, and as a result, the fluidity of the solution is reduced. In the meantime, it means a lost state. On the other hand, when the solute is a low molecule, it includes a state where the fluidity of the solution is lost due to the interaction between the solvent molecule and the solute molecule.

  The residual solvent amount of the laminated cast film 29 at the time of peeling is preferably 250% by weight or more and 300% by weight or less. In the present invention, the amount of solvent remaining in the film is shown on the basis of dry weight as the residual solvent amount. Moreover, the measurement method takes a sample from the target film, and when the weight of this sample is x and the weight after drying the sample is y, it is calculated as {(xy) / y} × 100. .

  In the pin tenter 13, a large number of pins are inserted and fixed to both end portions of the wet film 52, and then drying is promoted while the wet film 52 is conveyed to form a laminated film 55. Then, the laminated film 55 still containing the solvent is fed into the clip tenter 14. The laminated film 55 coming out of the pin tenter 13 and the clip tenter 14 is cut at both end portions by the edge-cutting devices 57a and 57b. The laminated film 55 whose both end portions are cut is wound up by the winder 64 in the winding chamber 17 via the drying chamber 15 and the cooling chamber 16.

  The laminated film 55 wound by the winder 64 is preferably at least 100 m in the longitudinal direction (casting direction). Moreover, it is preferable that the width | variety of the laminated | multilayer film 55 is 600 mm or more, and it is more preferable that they are 1400 mm or more and 2500 mm or less. The present invention is also effective when the width is greater than 2500 mm. Furthermore, the present invention is also applied when a thin film having a thickness of the laminated film 55 of 20 μm or more or 80 μm or less is manufactured.

  Next, details of the laminated cast film 29 will be described. As shown in FIG. 6, the laminated casting film 29 is formed on the peripheral surface 30 b of the casting drum 30 by the laminated dope 45 discharged from the casting die 28 (see FIG. 1). The laminated casting film 29 has a structure in which the main layer 101, the first sublayer 102, and the second sublayer 103 form layers in order from the peripheral surface 30 b side of the casting drum 30. The main layer 101 is made of the main dope 21 (see FIG. 3), the first sub layer 102 is made of the first sub dope 22 (see FIG. 3), and the second sub layer 103 is made of the second sub dope 23 (see FIG. 3). Consists of.

  Thickness unevenness is likely to occur in the laminated cast film 29, particularly the laminated cast film 29 immediately after the formation, and the occurrence of this thickness unevenness is significant in the second sublayer 103 located in the outermost layer of the laminated cast film 29. Become. As shown in FIG. 3, the uneven thickness is caused by stress generated in each dope in each merging portion 71 a and 71 b. It is preferable that the angles θ1 and θ2 at the merging portions 71a and 71b are as small as possible from the viewpoint of suppressing the generation of the stress as much as possible, but the length of the feed block 27 in the Z direction becomes longer as the angles θ1 and θ2 are decreased. Therefore, it is not preferable. When the length of the feed block 27 in the Z direction increases, the pressure of each of the dopes 21 to 23 for feeding to the feed block 27 increases. As a result, the casting die 28 is required to have a strength enough to withstand the dope pressure. As a result, the casting die becomes longer.

  In the present invention, since the angle θ2 when the second sub-dope 23 merges with the laminated dope 95 is equal to or smaller than the angle θ1 in the second merge portion 71b, the length of the feed block 27 is prevented from being increased, The stress acting on each dope can be reduced. Therefore, according to the present invention, the thickness unevenness generated in the laminated cast film 29 due to the stress at the time of merging is suppressed, the surface is smooth, and the laminated film 55 (which has the same layer structure as the laminated cast film 29) 1) can be manufactured.

Further, since the viscosity μ _S2 of the second sub-dope 23 is equal to or lower than the viscosity μ _M of the main dope 21, it has a certain fluidity. For this reason, even when the thickness non-uniformity occurs in the laminated cast film 29, the thickness non-uniformity is eliminated or alleviated before the laminated cast film 29 is peeled off by the flow of the second sub-dope 23 in the laminated cast film 29. be able to.

  As shown in FIG. 6, the thickness unevenness generated in the laminated cast film 29 is not limited to the thickness unevenness of the second sublayer 103, but is caused by the thickness unevenness of the first sublayer 102 or the main layer 101. In addition, the layers 101 to 103 include those resulting from uneven thickness of a plurality of layers. According to the present invention, it is possible to eliminate or alleviate the thickness unevenness regardless of the thickness unevenness generated in the laminated cast film 29.

  As shown in FIG. 3, the angle θ1 is preferably not less than 45 ° and not more than 70 °. The angle θ2 is preferably greater than 0 ° and 45 ° or less.

  The flow path width of the main flow path 71 in the Y direction may be constant from the inflow port 75 to the outflow port 76, or a portion of the main flow path 71 upstream from the first merge portion 71 a, the first merge portion 71 a and the second flow path. You may make it wide as it becomes a part between the junction parts 71b, and a downstream part from the 2nd junction part 71b.

  As shown in FIG. 6, the thickness of the main layer 101 can be adjusted by the channel width in the Y direction of the main channel 71, particularly the main channel 71 on the upstream side of the first junction. Further, the thickness of the first sublayer 102 can be adjusted by the depth of the notch groove 81 provided in the distribution pin 80a, and the thickness of the second sublayer 103 is set in the notch groove provided in the distribution pin 80b. It is adjustable by the depth.

  In the above embodiment, the laminated dope 45 is discharged toward the support using the casting apparatus including the feed block 27 and the casting die 28. Instead of this casting apparatus, the multi-manifold type shown in FIG. A casting die 128 may be used. The casting die 128 has manifolds 131 to 133, a main flow path 136, and first to second sub flow paths 137 to 138. The main channel 136 communicates with the channel 41 (see FIG. 1), the first sub channel 137 has a channel 42 (see FIG. 1), and the second sub channel 138 has a channel 43 (see FIG. 1). , Communicate with each other. The main flow path 136 is provided so as to penetrate the casting die 128 in the Z direction. An inlet (not shown) is formed on the upper surface of the casting die 128, and a discharge port is formed on the lower surface of the casting die 128. 128a is formed. In the main flow path 136, a manifold 131, a first merging portion 136a, and a second merging portion 136b are sequentially provided from the inflow port toward the discharge port 128a. The first to second sub-channels 137 to 138 are provided on the downstream side in the traveling direction of the support in the vicinity of the discharge port 128a of the main channel. The first sub flow path 137 is provided with a manifold 132, and the second sub flow path 138 is provided with a manifold 133. In the first junction 136a, the first sub-flow path 137 is connected to the main flow path 136 at an angle θ1. In the second junction 136b, the second sub-flow path 138 is connected to the main flow path 136 at an angle θ2.

  When the main dope 21 is supplied to the casting die 128 to the manifold 131 and the first sub dope 22 and the second sub dope 23 are respectively supplied to the manifolds 132 to 133 via a pipe (not shown), the first junction 136a The main dope 21 and the first sub-dope 22 merge to form a laminated dope in which each of the dopes 21 to 22 forms a layer. Then, in the 2nd junction part 136b, lamination | stacking dope and the 2nd sub dope 23 merge, and each dope 21-23 becomes the lamination | stacking dope 45 which comprises a layer. In this way, it is possible to discharge the laminated dope 45 from the discharge port 128a toward the support using the casting die 128.

  In the above embodiment, the self-supporting property is expressed in the laminated casting film 29 by cooling. However, the present invention is not limited to this, and the self-supporting in the laminated casting film 29 is caused by evaporation of the solvent contained in the laminated casting film 29. Sex may be expressed.

  In the above embodiment, the casting drum 30 is used as the support, but the present invention is not limited to this, and an endless band 140 as shown in FIG. 8 may be used instead of the casting drum 30. Next, the solution casting apparatus 141 having the endless band 140 will be described. In the casting chamber 12, a rotating roller 142 is provided so as to be rotatable about an axis. The endless band 140 is stretched around the rotating roller 142. When the rotation roller 142 is rotated by a control unit (not shown), the endless band 140 travels on a travel path provided in the casting chamber 12. The material and surface treatment of the endless band 140 are preferably the same as those of the casting drum 30 (see FIG. 1). In the casting chamber 12, ducts 144 a to 144 c that apply dry air to the laminated casting film 29 formed on the endless band 140 may be appropriately provided. The solvent can be evaporated from the laminated cast film 29 by contact with the drying air. The laminated casting film 29 having self-supporting properties is peeled off from the endless band 140, becomes a laminated film 55, and is sent to the clip tenter 14 or the drying chamber 15.

  In the above embodiment, the laminated dope 45 is cast on a traveling support, but the present invention is not limited to this, and the laminated dope 45 may be cast on a stationary support.

(Dope)
Each dope 21 to 23 includes a polymer and a solvent. Viscosity mu _M of main dope 21 is preferably at the first viscosity _{mu S2} more viscosity _{mu S1} and the second sub-doping 23 of the sub-dope. Further, the viscosity μ _S1 of the first sub dope 22 is not particularly limited, but is preferably _{equal to} or higher than the viscosity μ _S2 of the second sub dope 23. The viscosities of the dopes 21 to 23 can be determined based on JIS K 7117.

  Therefore, the polymer concentration of the main dope 21 is preferably higher than that of the first sub-dope 22 and the second sub-dope 23. The polymer concentration of the first sub-dope 22 is not particularly limited, but is preferably higher than that of the second sub-dope 23. The polymer concentration of the main dope 21 is preferably 15% by mass or more and 30% by mass or less. The polymer concentration of the first sub-dope 22 is preferably 15% by mass or more and 25% by mass or less. The polymer concentration of the second sub-dope 23 is preferably 10% by mass or more and 25% by mass or less.

(polymer)
Hereinafter, the polymer used when preparing each dope 21-23 in this invention is demonstrated.

In the present embodiment, cellulose acylate is used as the polymer, and cellulose triacetate (TAC) is particularly preferable as the cellulose acylate. Among cellulose acylates, those in which the substitution degree of the acyl group to the hydroxyl group of cellulose satisfies all of the following formulas (I) to (III) are more preferable. In the following formulas (I) to (III), A and B represent the substitution degree of the acyl group with respect to the hydrogen atom in the hydroxyl group of cellulose, A is the substitution degree of the acetyl group, and B is 3 carbon atoms. The substitution degree of the acyl group of ˜22. In addition, it is preferable that 90 weight% or more of TAC is a particle | grain of 0.1-4 mm. However, the polymer that can be used in the present invention is not limited to cellulose acylate.
(I) 2.5 ≦ A + B ≦ 3.0
(II) 0 ≦ A ≦ 3.0
(III) 0 ≦ B ≦ 2.9

  Glucose units having β-1,4 bonds constituting cellulose have free 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 groups of cellulose are esterified at each of the 2-position, 3-position and 6-position (the substitution degree is 1 in the case of 100% esterification).

  The total degree of acylation substitution, that is, the value of DS2 + DS3 + DS6 is preferably 2.00 to 3.00, more preferably 2.22 to 2.90, and particularly preferably 2.40 to 2.88. Further, the value of DS6 / (DS2 + DS3 + DS6) is preferably 0.28 or more, more preferably 0.30 or more, and particularly preferably 0.31 to 0.34. Here, DS2 is the ratio of the hydrogen of the hydroxyl group at the 2-position in the glucose unit (hereinafter referred to as the acyl substitution degree at the 2-position), and DS3 is the hydroxyl group at the 3-position in the glucose unit. This is the rate at which hydrogen is substituted by an acyl group (hereinafter referred to as the 3-position acyl substitution degree), and DS6 is the rate at which the hydrogen at the 6-position hydroxyl group is substituted by an acyl group in a glucose unit (hereinafter, (Referred to as the degree of acyl substitution at the 6-position).

  Only one type of acyl group may be used in the cellulose acylate of the present invention, or two or more types of acyl groups may be used. When two or more kinds of acyl groups are used, it is preferable that one of them is an acetyl group. The sum of the degree of substitution of the hydroxyl groups at the 2nd, 3rd and 6th positions by acetyl groups is DSA, and the sum of the degree of substitution of the hydroxyl groups at the 2nd, 3rd and 6th positions by acyl groups other than acetyl groups When DSB is DSB, the value of DSA + DSB is preferably 2.22 to 2.90, and particularly preferably 2.40 to 2.88.

  The DSB is preferably 0.30 or more, particularly preferably 0.7 or more. Further, 20% or more of DSB is preferably a substituent at the 6-position hydroxyl group, more preferably 25% or more, further preferably 30% or more, and particularly preferably 33% or more. Further, the value of DSA + DSB at the 6-position of cellulose acylate is 0.75 or more, more preferably 0.80 or more, and particularly preferably cellulose acylate of 0.85 or more. These cellulose acylates By using, a solution (dope) having better solubility can be produced. In particular, when a non-chlorine organic solvent is used, a dope having excellent solubility, low viscosity and excellent filterability can be produced.

  Cellulose, which is a raw material for cellulose acylate, may be obtained from either linter or pulp.

  The acyl group having 2 or more carbon atoms of the cellulose acylate in the present invention may be an aliphatic group or an aryl group, and is not particularly limited. For example, cellulose alkylcarbonyl ester, alkenylcarbonyl ester, aromatic carbonyl ester, aromatic alkylcarbonyl ester and the like may be mentioned, and each may further have a substituted group. Preferred examples of these include propionyl group, butanoyl group, pentanoyl group, hexanoyl group, octanoyl group, decanoyl group, dodecanoyl group, tridecanoyl group, tetradecanoyl group, hexadecanoyl group, octadecanoyl group, iso-butanoyl group , T-butanoyl group, cyclohexanecarbonyl group, oleoyl group, benzoyl group, naphthylcarbonyl group, cinnamoyl group and the like. Among these, a propionyl group, a butanoyl group, a dodecanoyl group, an octadecanoyl group, a t-butanoyl group, an oleoyl group, a benzoyl group, a naphthylcarbonyl group, a cinnamoyl group and the like are more preferable, and a propionyl group and a butanoyl group are particularly preferable. It is.

(solvent)
Solvents for preparing the dope include aromatic hydrocarbons (eg, benzene, toluene, etc.), halogenated hydrocarbons (eg, dichloromethane, chlorobenzene, etc.), alcohols (eg, methanol, ethanol, n-propanol, n-butanol, Diethylene glycol, etc.), ketones (eg, acetone, methyl ethyl ketone, etc.), esters (eg, methyl acetate, ethyl acetate, propyl acetate, etc.) and ethers (eg, tetrahydrofuran, methyl cellosolve, etc.). In the present invention, the dope means a polymer solution or dispersion obtained by dissolving or dispersing a polymer in a solvent.

  Among the above halogenated hydrocarbons, halogenated hydrocarbons having 1 to 7 carbon atoms are preferably used, and dichloromethane is most preferably used. From the viewpoint of physical properties such as solubility of TAC, peelability of cast film from the support, mechanical strength and optical properties of the film, one or several kinds of alcohols having 1 to 5 carbon atoms are mixed in addition to dichloromethane. It is preferable to do. The content of alcohol is preferably 2 to 25% by weight, more preferably 5 to 20% by weight, based on the entire solvent. Examples of the alcohol include methanol, ethanol, n-propanol, isopropanol, n-butanol, etc., but methanol, ethanol, n-butanol, or a mixture thereof is preferably used.

  Recently, a solvent composition not using dichloromethane has been studied for the purpose of minimizing the influence on the environment. In this case, an ether having 4 to 12 carbon atoms, a ketone having 3 to 12 carbon atoms, an ester having 3 to 12 carbon atoms, and an alcohol having 1 to 12 carbon atoms are preferable. Sometimes used. For example, a mixed solvent of methyl acetate, acetone, ethanol, and n-butanol can be mentioned. These ethers, ketones, esters and alcohols may have a cyclic structure. A compound having two or more functional groups of ether, ketone, ester and alcohol (that is, —O—, —CO—, —COO— and —OH) can also be used as the solvent.

(Additive)
Each dope 21 to 23 may contain an additive. The first sub-dope 22 may contain additives such as an ultraviolet absorber, a retardation control agent, and a plasticizer. Further, the main dope 21 and the second sub-dope 23 have a peeling accelerator (for example, citrate ester, etc.) that facilitates peeling from the casting band as a support, and when the film is wound into a roll. Additives such as a matting agent (for example, silicon dioxide), a deterioration preventing agent, a plasticizer, an ultraviolet absorber, and a retardation control agent that suppress adhesion between films may be contained. Alternatively, a highly light-transmitting particle may be added to the dope, and the dope may be used as a particle binder. Details of the dope and particles when the dope is a particle binder will be described later.

  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. JP-A-2005-104148 describes in detail in paragraphs [0196] to [0516], and these descriptions can also be applied to the present invention.

(Use)
The diffusion film 155 shown in FIGS. 9 and 10 can be manufactured by adding particles having translucency to the first sub-dope 22. The diffusion film 155 is provided on the support layer 161 having translucency, the support layer 161, scatters incident light inside, and emits the scattered light to the outside, and on the light diffusion layer 162. A smooth layer 163 that is provided and exposed on the first surface 155a of the diffusion film 155 has a smooth layer. When the thickness of the support layer 161 is TH1, the thickness of the light diffusion layer 162 is TH2, and the thickness of the smooth layer 163 is TH3, TH1> TH2 is preferable, and TH1> TH3 is preferable. Further, TH2 and TH3 may be equal, or one of them may be larger than the other.

  The light diffusion layer 162 includes a plurality of particles 171 and a binder 172 that connects the particles 171. The binder 172 is made of a transparent polymer, and the particles 171 and the binder 172 have different refractive indexes. It is more preferable that any of the particles 171 is arranged so as not to protrude from the light diffusion layer 162, but the particle 171 may protrude from the light diffusion layer 162 to the smooth layer 163 so as to partially enter the smooth layer 163. The particles 171 are preferably dispersed inside the light diffusion layer 162 so as not to overlap in the thickness direction of the diffusion film 155.

  In the diffusion film 155 having such a configuration, when light is incident from the second surface 155 b where the support layer 161 is exposed, the incident light is transmitted through the support layer 161 and reflected at the interface between the binder 172 and the particles 171. As described above, the light incident from the second surface 155 b is scattered inside the diffusion film 155 and then emitted from the first surface 155 a to the outside via the smoothing layer 163. Such a diffusion film 155 has a function of scattering and diffusing light, and also has a higher front luminance enhancement function than a conventional diffusion film. Furthermore, since the first surface 155a is smooth, the diffusion film 155 has good adhesion to the brightness enhancement film and can prevent light leakage in the direction along the film surface.

(particle)
In view of further enhancing the light diffusion effect, it is preferable to use particles 171 having a higher refractive index than that of the binder 172. The particles 171 may be solid or liquid. When the binder 172 is cellulose triacetate (TAC, refractive index = 1.48), solids having a higher refractive index than this are polystyrene (PS, refractive index = 1.6), polyethylene (PE, refractive index = 1). .53), glass beads (refractive index = 1.5), silica (refractive index = 1.54), mica (refractive index = 1.58), etc., the liquid is silicone oil (refractive index = 1.50), Benzene (refractive index = 1.50). Further, it is preferable that the difference dN1 obtained by subtracting the refractive index NB of the binder 172 from the refractive index NP of the particle 171 is at least 0.02, in order to improve the scattering effect inside the particle 171 more reliably.

  When the volume of the binder 172 is VB and the volume of the particles 171 is VP, the light diffusion layer 162 has a volume ratio calculated by VP / VB so as not to be less than 0.15, that is, larger than 0.15. Has been. Thereby, the function of light diffusion can be reliably expressed. The volume ratio VP / VB is more preferably in the range of more than 0.15 and not more than 2.0, more preferably in the range of not less than 0.2 and not more than 1.5, and not less than 0.6 and not more than 1.0. It is especially more preferable that it is the range of these.

(Particle shape)
The particle 171 is most preferably a sphere whose shape is a perfect circle in a cross section in any direction, but the shape of the particle 171 is not limited thereto.

(Particle size)
When the particle 171 is a sphere having a perfectly circular cross section, the particle size of the particle 171 is preferably in the range of 2 μm to 15 μm. When forming a film by solution casting, particles such as so-called matting agents that have been included in the film to improve the slip of the film have a particle size that is too small to achieve both light diffusion and brightness enhancement effects. Difficult to get. On the other hand, when the particle size of the particle 171 is larger than 15 μm, the effect of light diffusion may not be obtained. In the case where the particle 171 is a sphere having a perfectly circular cross section, the more preferable particle diameter is in the range of 3 μm to 10 μm. Furthermore, it is preferable that all the particle sizes are substantially the same.

(Particle distribution)
The particles 171 are randomly distributed in the light diffusion layer 162. Thereby, the moire by the particle | grains 171 in the light source and the light-diffusion layer 162 can be eliminated. It is preferable that the particle 171 and the particle 171 are arranged at intervals in the direction parallel to the film surface, that is, arranged separately.

  The particles 171 are most preferably distributed so as not to overlap in the thickness direction. Thereby, in addition to the light diffusion effect, an increase in haze due to particle overlap can be suppressed.

(Binder)
The binder 172 is made of TAC. However, as described above, the binder 172 is made of a known polymer compound (polymer) that is transparent, that is, has a high light transmittance and can be formed into a thin film like a sheet. it can. Further, the polymer is more preferably one having no optical anisotropy, that is, one having optical isotropy. A preferred polymer that satisfies these conditions is cellulose acylate.

  In the said embodiment, although demonstrated using the diffusion film 155 comprised by the light-diffusion layer 162, the support layer 161, and the smooth layer 163, this invention is not limited to this. For example, a conductive substance such as conductive particles or a conductive filler is used instead of the particles 171, and the conductive layer formed of such a conductive substance and the binder 172 is replaced with the light diffusion layer 162, and one of the conductive layers The present invention can also be applied to the case where a conductive film having a multilayer structure in which the support layer 161 is overlapped on the surface and the smooth layer 163 is overlapped on the other surface is manufactured. Furthermore, the present invention can also be applied to a laminated film in the case of using a cured resin for the smooth layer 163 to form a high hardness smooth layer.

  In the above embodiment, after discharging the laminated dope having a three-layer structure toward the traveling support and forming the laminated casting film having the three-layer structure, the laminated casting film peeled off from the support is dried, Although a laminated film having a three-layer structure is manufactured, the present invention is not limited to this, and a laminated film having a structure of four or more layers may be manufactured by discharging a laminated dope having a structure of four or more layers.

  Next, a casting apparatus for producing a laminated dope having a structure of four or more layers will be described.

  As shown in FIG. 11, the feed block 180 is provided with sub-channels 181 and 182 in addition to the main channel 71 and the sub-channels 72 and 73. The sub channel 181 communicates with the channel 185 that supplies the third sub dope 184, and the sub channel 182 communicates with the channel 187 that supplies the fourth sub dope 186.

  The sub flow paths 181 and 182 are provided to face the sub flow paths 72 and 73 with the main flow path 71 interposed therebetween. In the main channel 71, a third junction 71c and a fourth junction 71d are sequentially provided in the direction in which the main dope 21 flows. In the feed block 180, the 3rd junction part 71c is provided between the 1st junction part 71a and the 2nd junction part 71b, and the 4th junction part 71d is provided in the downstream of the 2nd junction part 71b. In addition, you may provide the 4th junction part 71d between the 1st junction part 71a and the 2nd junction part 71b.

  In the third merging portion 71c, the sub-channel 181 is connected to the main channel 71 at an acute angle θ3, and in the fourth merging portion 71d, the sub-channel 182 is connected to the main channel 71 at an angle θ4 that is equal to or smaller than the angle θ3. The angle θ3 is preferably 45 ° or greater and 70 ° or less. The angle θ4 is preferably greater than 0 ° and not greater than 45 °.

  In the third junction 71c, a distribution pin may be provided at the outlet of the sub-channel 181 and a vane may be provided between the main channel 71 and the sub-channel 181. In the fourth junction 71d, A distribution pin may be provided at the outlet of the path 182 and a vane may be provided between the main flow path 71 and the sub flow path 182.

  When the dopes 21 to 23, 184 and 186 are supplied to the feed block 180 through the flow paths 41 to 43, 185 and 187, each of the dopes 21 to 23, 184 and 186 is layered. 188 is formed. When the feed block 180 supplies the laminated dope 188 to the casting die 28, the casting die 28 discharges the laminated dope 188, and a laminated casting film having a five-layer structure can be formed on the support.

  In the said embodiment, although the 3rd junction part 71c was provided between the 1st junction part 71a and the 2nd junction part 71b, this invention is not limited to this. For example, the installation position of the third merging portion 71c is the same position as the upstream position of the first merging portion 71a, the downstream position of the second merging portion 71b, or the first merging portion 71a or the second merging portion 71b. Also good. Moreover, if the installation position of the 4th junction part 71d is the downstream of the 3rd junction part 71c, the position of the upstream of the 1st junction part 71a, the position between the 1st junction part 71a and the 2nd junction part 71b. And the downstream position of the second merging portion 71b or the same position as the first merging portion 71a and the second merging portion 71b.

  As shown in FIG. 12, the casting die 190 is provided with the sub-channels 191 and 192 in addition to the main channel 136 and the sub-channels 137 and 138. The sub flow paths 191 and 192 are provided so as to face the sub flow paths 137 and 138 through the main flow path 136. The sub flow channel 191 communicates with the flow channel for supplying the third sub dope, and the sub flow channel 192 communicates with the flow channel for supplying the fourth sub dope. Further, the sub-channel 191 is provided with a manifold 195, and the sub-channel 192 is provided with a manifold 196.

  In the main flow path 136, a third merging portion 136c and a fourth merging portion 136d are sequentially provided in the direction in which the main dope flows. In the casting die 190, the third joining portion 136c is provided between the first joining portion 136a and the second joining portion 136b, and the fourth joining portion 136d is provided on the downstream side of the second joining portion 136b. In addition, you may provide the 4th junction part 136d between the 1st junction part 136a and the 2nd junction part 136b.

  In the third merge portion 136c, the sub flow channel 191 is connected to the main flow channel 136 at an angle θ3, and in the fourth merge portion 71d, the sub flow channel 192 is connected to the main flow channel 136 at an angle θ4 that is equal to or smaller than the angle θ3.

  When the main dope and the first to fourth sub dopes are supplied to the casting die 190, a laminated dope 188 having a five-layer structure in which each dope forms a layer is formed. Then, when the casting die 190 discharges the laminated dope 188, a laminated casting film having a five-layer structure can be formed on the support.

  As shown in FIG. 13, the casting apparatus 200 includes a feed block 27 and a casting die 201. The casting die 201 is provided with a third sub-channel 191 and a fourth sub-channel 192 in addition to the slot 88 supplied with the laminated dope produced by the feed block 27. The sub flow channel 191 communicates with the flow channel for supplying the third sub dope, and the sub flow channel 192 communicates with the flow channel for supplying the fourth sub dope. Further, the sub-channel 191 is provided with a manifold 195, and the sub-channel 192 is provided with a manifold 196.

  The slot 88 is provided with a third joining portion 88c and a fourth joining portion 88d sequentially in the direction in which the laminated dope flows. In the third junction 88c, the sub-channel 191 is connected to the slot 88 at an angle θ3, and in the fourth junction 88d, the sub-channel 192 is connected to the slot 88 at an angle θ4 that is equal to or smaller than the angle θ3.

  In the said embodiment, although the 1st junction part and the 2nd junction part were provided in the feed block, this invention is not restricted to this, A 1st junction part is provided in a feed block and a 2nd junction part is provided in a casting die. Alternatively, the first joining portion and the second joining portion may be provided on the casting die. Moreover, in the said embodiment, although the 3rd merge part and the 4th merge part were provided in the casting die, this invention is not restricted to this, A 3rd merge part is provided in a feed block, and a 4th merge part is cast. You may provide in a die | dye and you may provide a 1st junction part and a 2nd junction part in a feed block.

The viscosity [mu] _S3 of the third sub-dope and the viscosity [mu] _S4 of the fourth sub-dope are preferably less than or equal to the viscosity [mu] _M of the main dope 21. Further, the viscosity μ _S3 of the third sub dope is not particularly limited, but is preferably _{equal to} or higher than the viscosity μ _S4 of the fourth sub dope.

  Therefore, the polymer concentration of the main dope is preferably higher than that of the third subdope 22 or the fourth subdope. The polymer concentration of the third sub-dope is not particularly limited, but is preferably higher than that of the fourth sub-dope. The polymer concentration of the third sub-dope is preferably 15% by mass or more and 25% by mass or less. The polymer concentration of the fourth sub-dope is preferably 10% by mass or more and 25% by mass or less.

  A predetermined compound may be added to the third sub-dope 22 or the fourth sub-dope. Examples of these compounds include the same particles and conductive materials as those of the first sub-dope and the second sub-dope.

  The laminated film 210 shown in FIG. 14 is obtained by using each casting apparatus provided with a 1st junction part-a 4th junction part. The laminated film 210 includes a third layer 213 and a fourth layer 214 in addition to the support layer 161, the light diffusion layer 162, and the smooth layer 163. The third layer 213 is provided so as to face the light diffusion layer 162 with the support layer 161 interposed therebetween. The fourth layer 214 is provided so as to face the support layer 161 with the third layer 213 interposed therebetween. When the thickness of the third layer 213 is TH4 and the thickness of the fourth layer 214 is TH5, TH1> TH4 is preferable, and TH1> TH5 is preferable. Further, TH4 and TH5 may be equal, or one of them may be larger than the other.

  Whether the second surface 155b is formed by the third layer 213 or the second surface 155b is formed by the fourth layer 214 or the like, the third layer 213 is formed as the second layer of the laminated film 210. The smoothness of the second surface 155b of the laminated film 210 is improved if the back surface smoothing layer has the characteristic of increasing the smoothness of the front surface 155b. The laminated film 210 having such a back surface smooth layer is excellent in overlayability also on the second surface 155b.

  The fourth layer 214 may be a scratch resistance imparting layer. The scratch resistance imparting layer has a characteristic that the surface hardness of the layer is high. A laminated film having such a scratch resistance imparting layer has high resistance to scratches between films.

  In the above embodiment, the laminated casting film 29 (see FIG. 6), the diffusion film 155 (see FIG. 9), and the laminated film 210 (see FIG. 14) are shown with boundaries between the respective layers for convenience of explanation. If the polymers of the layers are the same, there is no layer boundary. Therefore, the laminated cast film 29 (see FIG. 6), the diffusion film 155 (see FIG. 9), and the laminated film 210 (see FIG. 14) without the boundary of each layer are also obtained by the present invention. include.

  In the said embodiment, although the laminated film 210 of the 5 layer structure was manufactured, this invention is not restricted to this, The film of a 4 layer structure and the laminated film of 6 layers or more can also be manufactured. In the case of manufacturing a film having a four-layer structure, for example, the feed block 180 (see FIG. 11) in which the fourth merging portion 71d and the auxiliary flow path 182 are omitted, the fourth merging portion 136d, the auxiliary flow path 192, and the manifold 196, for example. Alternatively, a casting die 190 (see FIG. 12) in which the “.” Is omitted, or a casting apparatus 200 (see FIG. 13) in which the fourth joining portion 88d, the auxiliary flow path 192, and the manifold 196 are omitted may be used.

  Next, in order to confirm the presence or absence of the effect of the present invention, Experiments 1 to 17 were performed. Details will be described in Experiment 1. For Experiments 2 to 17, description of the same conditions as in Experiment 1 is omitted, and only different parts will be described.

(Experiment 1)
A laminated film 55 was manufactured using the solution casting apparatus 10 shown in FIG. In order to adjust the temperature of the laminated dope 45 to be substantially constant at about 34 ° C., a jacket (not shown) was provided on the casting die 28 and the temperature of the heat transfer medium supplied into the jacket was adjusted. By driving the shaft 30a, the speed in the traveling direction of the peripheral surface 30b was set to about 35 m / min. The temperature control device 34 adjusted the temperature of the peripheral surface 30b of the casting drum 30 to be substantially constant at −10 ° C.

  A pump (not shown) sent the dopes 21 to 23 to the feed block 27. The feed block 27 made a laminated dope 45 from each of the dopes 21 to 23 and sent the laminated dope 45 to the casting die 28. In the casting die 28, the laminated dope 45 was discharged onto the peripheral surface 30b so that the thickness of the laminated film 55 was 100 μm, and the laminated cast film 29 was formed on the peripheral surface 30b. The angle θ1 at the first junction 71a of the feed block 27 was 45 °, and the angle θ2 at the second junction 71b was 25 °. The film thickness of the main layer 101 in the laminated cast film 29 immediately after the formation was 80 μm, the film thickness of the first sublayer 102 was 15 μm, and the film thickness of the second sublayer 103 was 5 μm.

  After the laminated cast film 29 became self-supporting by cooling, the laminated cast film 29 was peeled off as the wet film 52 from the casting drum 30 using the peeling roller 33. The wet film 52 thus peeled off was dried in each part, and a laminated film 55 was obtained. Finally, the laminated film 55 was wound up by the winder 64.

(Evaluation)
The following evaluation was performed on the manufactured laminated film 55 and the like.

1. Thickness unevenness evaluation The laminated film 55 was measured for thickness unevenness. The procedure for measuring the thickness unevenness is as follows. First, a sample film approximately 6 cm square was cut out from the laminated film 55. Second, the refractive index difference of the sample film was measured using an apparatus that can convert the refractive index difference of the sample film into a thickness difference. As this device, FX-03 FRINGEANALYZER (manufactured by FUJINON Co., Ltd.) was used. Third, this refractive index difference was measured over the entire area of the sample film, and this average value was taken as the thickness unevenness of the laminated film. The thickness unevenness thus obtained was evaluated according to the following criteria. In addition, the thickness of a laminated film is an average value of the thickness of six places of the sample film measured with the micrometer.
A: The thickness unevenness was less than 1.5% with respect to the thickness of the film.
○: The thickness unevenness was 1.5% or more and less than 1.8% with respect to the thickness of the film.
Δ: The thickness unevenness was 1.8% or more and less than 2.2% with respect to the thickness of the film.
X: The thickness unevenness was 2.2% or more with respect to the thickness of the film.

2. Evaluation of die lengthening The lengthening of the die was evaluated based on the following criteria using the pressure P of the dope fed to the feed block 27 as an index. The pressure P is a pressure value indicated by a pressure gauge (315-A341 manufactured by Asahi Keiki Kogyo Co., Ltd.) provided in the flow path 41 immediately before the entrance of the feed block 27.
A: The pressure P was 500 kPa or more and less than 1000 kPa.
○: The pressure P was 1000 kPa or more and less than 1200 kPa.
Δ: The pressure P was 1200 kPa or more and less than 1500 kPa.
X: The pressure P was 1500 kPa or more.

(Experiments 2-17)
A laminated film was produced in the same manner as in Experiment 1 except that the conditions were changed to the values shown in Table 1. In Experiments 6 to 9, instead of the feed block 27 and the casting die 28, the feed block 180 and the casting die 28 of FIG. 11 were used. In Experiments 10 to 13, instead of the feed block 27 and the casting die 28, the casting die 190 of FIG. 12 was used. In Experiments 14 to 17, the feed block 27 and the casting die 201 of FIG. 13 were used in place of the feed block 27 and the casting die 28.

  Table 1 shows the values of angles θ1 to θ4 and the evaluation results for each evaluation item in Experiments 1 to 17. The number of the evaluation result in Table 1 represents the number assigned to each evaluation item. In Experiments 1 to 5 using the feed block 27 and the casting die 28, θ3 and θ4 are represented as “−”.

  From Table 1, it was found that according to the present invention, it is possible to easily produce a laminated film having a smooth surface with reduced thickness unevenness. Furthermore, in the thickness unevenness suppressing effect, the casting apparatus of FIG. 12 is better than the casting apparatus of FIG. 11, and in particular, the casting apparatus of FIG. all right.

It is the schematic of a 1st solution casting apparatus. It is a perspective view about each apparatus distribute | arranged to the 1st feed block and 1st casting die which comprise a 1st casting apparatus, and these periphery. It is sectional drawing about the YZ surface of a 1st feed block. It is a perspective view of a distribution pin and a vane. It is sectional drawing about the YZ surface of the 1st casting die. It is sectional drawing of a laminated cast film. It is sectional drawing about the YZ surface which shows the outline | summary of the 2nd casting die of a multi-manifold type. It is the schematic of the 2nd solution casting apparatus. It is sectional drawing of a diffusion film. It is XX sectional drawing of a diffusion film. It is sectional drawing about the YZ surface of a 2nd feed block. It is sectional drawing about the YZ surface of the 3rd casting die. It is sectional drawing about the YZ surface of the casting apparatus comprised from a 3rd feed block and a 4th casting die. It is sectional drawing of a laminated film.

DESCRIPTION OF SYMBOLS 10 Solution film forming equipment 12 Casting chamber 13 Pin tenter 14 Clip tenter 15 Drying chamber 16 Cooling chamber 17 Winding chamber 21 Main dope 22 First sub dope 23 Second sub dope 27 Feed block 28 Casting die 29 Multilayer cast film 30 Casting drums 45 and 95 Laminated dope 47 Depressurization chamber 55 Laminated film 101 Main layer 102 First sublayer 103 Second sublayer

Claims (8)

The main dope of the polymer and viscosity and a solvent mu _M, the first sub-dope viscosity is less mu _M, and are merged at an acute angle θ1 with respect to the direction of flow of the main dope, comprising the main dope A first merging step of creating a first laminated dope comprising a main layer and a first sublayer having a thickness smaller than the main layer and comprising the first subdope;
The viscosity mu _M or less in the second sub-doping, said at an angle θ1 less angle θ2 from the first sub-layer side are merged in the first multilayer dope to the direction of flow of the first multilayer dope, the main A second merging step of creating a second laminated dope comprising a layer, the first sublayer, and a second sublayer that is thinner than the main layer and comprises the second subdope;
A film forming step of discharging the second laminated dope to a support and forming a laminated casting film including the main layer, the first sublayer, and the second sublayer sequentially provided from the support side; Yes, and
The casting method is characterized in that the angle θ1 is 45 ° to 70 ° and the angle θ2 is 25 ° to 45 ° . The third sub-dope viscosity is less mu _M, at an acute angle θ3 with respect to the direction of flow of the main dope, from the opposite direction as the first sub-dope are joined, by merging into the main dope, A third merging step for producing a third laminated dope including a third sublayer comprising the main layer and the third subdope ;
The viscosity fourth sub doped follows mu _M, the angle θ3 from the third sub-layer side under the following angles θ4 by merging the third multilayer dope to the direction of flow of the main dope, the main layer, wherein the third sub-doped, and has a degree fourth confluence Engineering making a fourth multilayer dope comprising a fourth sub-layer made of the fourth sub-doped,
The angle θ3 is 55 ° to 70 °, the angle θ4 is 35 ° to 45 °,
In the film forming step, the main layer and the support side the third sublayer provided et al is in the, form a pre-Symbol third said laminated casting film the fourth sublayer on the support side of the sub-layer is provided The casting method according to claim 1, wherein: The first sub-dope includes translucent particles, a binder polymer having a refractive index different from that of the particles and serving as a binder for the particles, and a solvent for the binder polymer. Item 3. The casting method according to Item 1 or 2 . The casting method according to claim 3, wherein the polymer or the binder polymer contains cellulose acylate. Forming the laminated cast film by the casting method according to any one of claims 1 to 4 ,
A stripping step of stripping the laminated cast film as a wet film from the support;
And a drying process for drying the wet film. A traveling support;
Provided the main channel the main dope flows viscosity mu _M comprises a polymer and a solvent, the first sub flow path through which the first sub-dope viscosity is less mu _M, acute angle from the running direction downstream side of the support A first sublayer connected to the main flow path at an angle θ1 and having a thickness smaller than the main layer, the main layer consisting of the main dope and the first subdope, by the merge of the main dope and the first subdope A first junction for producing a first laminated dope containing:
Than said first merging portion provided in the main passage on the downstream side, the second sub-flow path through which the second sub-dope viscosity is less mu _M, the running direction downstream side of the support wherein the angle θ1 following Connected to the main flow path at an angle θ2, and composed of the main layer, the first sublayer, and the second subdope by the merging of the first stacked dope and the second subdope, and having a thickness larger than that of the main layer. A second junction for creating a second laminated dope comprising a thin second sublayer;
A multilayer casting film including the main layer, the first sublayer, and the second sublayer, which is provided in order from the support side, is connected to the main flow path, discharges the second laminated dope, and the support body. A discharge port formed on the top ,
The angle θ1 is 45 ° to 70 °, and the angle θ2 is 25 ° to 45 ° . The third sub-passage flow viscosity is mu _M or less of the third sub-dope, from the running direction downstream side of said support and connected to the main channel at an acute angle .theta.3, of the main dope and the third sub-doped confluence, the third merging portion is provided to make the third multilayer dope thickness than the main layer consists of the main layer and the third sub-dope comprises a thin third sublayer Rutotomoni,
A fourth sub-passage flow viscosity is mu _M or less in the fourth sub-doped, connecting from the running direction downstream side of the support to the main channel at the angle θ3 following angles .theta.4, the third multilayer dope and the A fourth merge part for forming a fourth laminated dope including a fourth sub-layer comprising the main layer, the third sub-layer, and the fourth sub-dope and having a thickness smaller than the main layer by the merge of the third sub-dope , Provided in the main channel on the downstream side of the third merging portion,
The angle θ3 is 55 ° to 70 °, the angle θ4 is 35 ° to 45 °,
The laminated casting film is to have a third sub-layer on the support side of the main layer, according to claim 6, characterized in that it comprises a fourth sub-layer on the support side of the third sub-layer Casting equipment. A casting apparatus according to claim 6 or 7 ,
A stripping device for stripping the laminated cast film as a wet film from the support;
A solution casting apparatus comprising a drying device for drying the wet film.

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