JP4496066B2 - Multilayer sheet manufacturing method, multilayer film manufacturing method, and multilayer sheet manufacturing apparatus - Google Patents

Description

  The present invention relates to a method and apparatus for producing a multilayer film. More specifically, the production of a multilayer film in which each layer thickness distribution of a multilayer film laminated with five or more layers can be made uniform in the width direction, or the thickness distribution of each layer can be actively controlled in both the thickness direction and the width direction. It relates to a method and an apparatus.

  For example, when a plurality of layers having a high refractive index and a plurality of low layers are alternately laminated, the multilayer film becomes an optical interference film that selectively reflects or transmits light of a specific wavelength by structural optical interference between these layers. Such a laminated film has a wide range of uses for a reflective polarizing plate, a coloring film, a metallic gloss film, and a reflective mirror film by making the wavelength region of light selectively reflected or transmitted into the visible light region. For example, in the case of a red colored film, the thickness of each layer may be adjusted so that the wavelength is selectively reflected in the vicinity of 650 nm. In addition, a near-infrared reflective film that can be used on the surface of an image display panel such as a plasma display needs to reflect near-infrared light in a wavelength region (820 to 980 nm) having a certain width in order to prevent malfunction of peripheral devices. . Also, solar radiation can be reduced by cutting the near-infrared region even with a solar-cut window covering film or the like.

  In producing a multilayer film using a coextrusion feed block, for example, a production method is disclosed in US Pat. No. 3,557,265 and US Pat. No. 4,627,138, and a production apparatus is disclosed in US Pat. No. 3,884,606. However, even if these apparatuses and methods are used, the thickness distribution of each layer cannot be uniformly extruded across the width direction of the film. This is thought to be due to a change in the layer thickness distribution at each point in the film width direction because a change occurs in the lamination state of each layer in the die.

  Also, US Pat. No. 5,389,324 discloses a method and apparatus for distributing the thickness of each layer. In this method, the thickness distribution of each layer can be arbitrarily adjusted. However, when there is an unintended change in the thickness of each layer in the width direction of the film in the die, there is a problem that this change cannot be adjusted.

U.S. Pat. No. 3,557,265 U.S. Pat. No. 4,627,138 U.S. Pat. No. 3,884,606 US Pat. No. 5,389,324

  An object of the present invention is to solve the above-described problems, to control the thickness distribution of the multilayer film in the width direction of the film, and to produce a multilayer film having a uniform thickness distribution of each layer in the width direction of the film. And providing an apparatus.

According to the present invention, according to the present invention, the resin A and the resin B are separately melted by an extruder, and the resin A and the resin B are led from different directions to the merging block in the multilayer feed block, Five or more layers of the resin A and the resin B are alternately flowed into each flat flow path formed by being partitioned by a partition provided in the merge block, and when the merge block is exited, the resin A and the resin B Resin B is merged to form a resin flow in which the resin A and the resin B are alternately laminated, and the merged resin is supplied to the die following the multilayer feed block and extruded from the die into a sheet shape. In the method for producing a multilayer sheet, a multilayer sheet in which the resin A and the resin B are alternately laminated in the thickness direction in the direction of the multilayer,
Regarding the thickness in the width direction of each layer of the multilayer sheet formed by the flow of resin flowing from the flat flow path to the introduction side (FE point side) and the development side (BE point side) into the die, the thickness is The flow rate of the resin flowing toward the FE point side or the BE point side on one side which becomes smaller is larger than the flow rate of the resin flowing on the BE point side or the FE point side where the thickness is increased. The length of the flow path through which the resin flows on the one side of the FE point side or the BE point side is compared with the length of the flow path through which the resin flows on the other side of the BE point side or the FE point side. By setting it to be shorter, the thickness of each layer of the multilayer sheet can be made uniform in the width direction .

In the present invention, in order to more uniform the thickness distribution of each layer, it is not preferable that the length of the flow path is linearly changed to set linearly from the FE point side to the BE point side .

  The multilayer sheet obtained by the production method of the present invention can be cooled and solidified with a casting drum to form an unstretched film, and the unstretched film can be stretched in at least one direction of the machine direction and the transverse direction to form a multilayer film. In this multilayer film, the thickness of the A layer and the thickness of the B layer are substantially uniform in the film width direction, and the thickness of each layer of the multilayer film is preferably 0.01 to 0.5 μm.

Next, as a multi-layer sheet manufacturing apparatus according to the present invention for solving the above-described problems, resin A and resin B provided in a multi-layer feed block and separately melted by an extruder are alternately provided in five or more layers. The flow path into which the flow path is divided is formed by a partition wall, and the resin A and the resin B are merged when exiting the merge block and extruded into a sheet shape so that the resin A and the resin B are in the thickness direction. In a multilayer sheet manufacturing apparatus comprising at least a die that is a multilayer sheet in which five or more layers are alternately laminated in a direction to be multilayered,
Regarding the thickness in the width direction of each layer of the multilayer sheet formed by the flow of resin flowing from the flat flow path to the die introduction side (FE point side) and the development side (BE point side),
The flow rate of the resin flowing to the FE point side or the BE point side on the one side where the thickness is reduced is larger than the flow rate of the resin flowing on the BE point side or the FE point side on the other side where the thickness is increased. Compare the length of the flow path through which the resin flows on the one side of the FE point side or the BE point side with the length of the flow path on the other side of the BE point side or the FE point side so as to increase. Thus, a multilayer sheet manufacturing apparatus that is set shorter is provided.
At this time, in order to more uniform the thickness distribution of each layer, the manufacturing apparatus of the present invention, that the length of the channel is changing linearly linearly from the FE point side to the BE point side preferable.

  According to the present invention, the thickness of each layer can be made uniform in the width direction by adjusting the channel length among the individual channels of the merge block.

Hereinafter, the present invention will be described in detail. For convenience of explanation, the drawings are cited.
FIG. 1 is a perspective view of a confluence block of a multilayer feed block illustrating one embodiment of the present invention. 2 illustrates the flat flow path of FIG. 1, FIG. 2 (a) shows the flow path of resin A, and FIG. 2 (b) shows the flow path of resin B. 3, 4 (a), and 4 (b) are explanatory diagrams of a conventional multilayer feed block. FIG. 5 is a front view illustrating one embodiment of the present invention, and shows an extruder to a casting drum in a multilayer film extrusion apparatus.

  The multilayer film extrusion apparatus includes an extruder 1, a gear pump 2, a filter 3, a polymer pipe 4a in order from the upstream side in the flow direction of the resin B. Similarly, an extruder 5, a gear pump 6 in order from the upstream side in the flow direction of the resin A, The filter 7 and the polymer pipe 4b are configured such that two molten resins are merged inside the multilayer feed block 9 and the molten resin 11 is extruded as a multilayer sheet from the single-layer die 10 as a multilayer sheet and cooled by the casting drum 8. It has become.

  In the present invention, a multilayer film in which A layers and B layers are alternately stacked can be laminated as follows. That is, the molten resin A for the A layer guided to the feed block 9 by the polymer pipe 4b as shown in FIG. 5 is once spread in the width direction in the manifold not shown in the figure, and is a flat flow arranged in a line as shown in FIG. It flows in from the direction 22 to the path 27 and is extruded in the direction 23. On the other hand, the molten resin B for the B layer is guided to the feed block 9 by the polymer pipe 4a as shown in FIG. 5 and once spread in the width direction in the manifold (not shown), and flat and 90 aligned in a row as shown in FIG. With respect to the flow path 25 that is turned every time, it flows in from the direction 21 and is pushed out in the direction 23. Inside the merge block 20, the resin A and the resin B are already alternately arranged via the partition walls, and the molten resins are contacted in a fluid state at the exit of the merge block and are alternately stacked and led to the die 10.

In the present invention, the thickness of each layer can be controlled in the film width direction as follows. FIG. 9 shows the thickness distribution of each layer of the film cross section when the conventional feed block (FIG. 3) is used, and exemplifies the case where the surface layer is thin on the FE point side and the layer thickness is relatively uniform on the BE point side. ing. This is presumably because the resin flow path is different between the FE point side and the BE point side of the die as shown in the die 10 of FIG. In the case of FIG. 9, since the optical characteristics of the film change in the film width direction, the thickness distribution of each layer is preferably uniform in the width direction as shown in FIGS. 8 and 10, as shown in FIG. Can be solved with a simple confluence block. That, FE point as the flow rate of the FE point is greater than the flow rate of the BE point as the flow path 26 falls surface side of the flow path of the resin of the A layer side in the combination block 20 of FIG. 1 FIGS. 2 (a) Shorten the channel on the side ( LMIN ). Similarly, the flow path 24 corresponding to the surface layer among the flow paths of the resin on the B layer side shortens the flow path on the FE point side so that the flow rate at the FE point is larger than the flow rate at the BE point as shown in FIG. ( LMIN ). Thereby, each layer thickness can be made uniform in the width direction.

In the present invention, if the width W is too narrow among the cross-sectional shapes of the flat flow paths 24, 25, 26, and 27 to be processed into the merge block 20, each layer flow rate reacts sensitively to the width dimension, so that high-precision processing is performed. On the contrary, if the pressure is too wide, the pressure in the flow path does not rise, and the flow rate of each layer tends to vary with a slight disturbance, so 0.2 to 3 mm is preferable, and 0.5 to 1.5 mm is more preferable. The lengths L, LMIN, and LMAX of the flow paths 26 and 27 on the A layer side are preferably 10 to 120 mm, and more preferably 30 to 90 mm, because the length L, LMIN, and LMAX are difficult to process if they are too long due to the relationship of electric discharge machining with wires. The lengths L, LMIN, and LMAX of the flow paths 24 and 25 on the B layer side are preferably 5 to 100 mm, and more preferably 10 to 60 mm, because the discharge electrode is stamped and dug, and if this is too deep, it is difficult to process. In order to control the thickness of each layer in the film width direction, the method of adjusting the lengths of LMIN and MAX can be exemplified by a method of adjusting the length by digging into a pyramid shape like the digging portion 28 in FIG. 2 (a) and 2 (b) exemplify the case where the length of the flow path from LMIN to LMAX changes linearly and linearly, other than this, linear combinations, curves and step shapes, The length may be changed by a combination of a curve and a linear shape. Further, like the digging portion 36 in FIG. 6, the width of each layer is obtained by digging so that the digging depth changes in the width direction of the block, and gradually changing the volume of the respective flat flow paths. The thickness distribution in the direction can be corrected independently and precisely, and the films shown in FIGS. 8 and 10 can be manufactured. Further, as a method for controlling the thickness of each layer in the film width direction, for example, in FIG. 2A, processing takes time, but the flow path width W can be gradually changed in the direction of height H. You may combine with the method of changing length.

  As can be seen from the above, the merging blocks 20 and 31 constituting the feed block 9 need to be processed with high precision and complexity, and a hard material such as SUS630 or SUS420 (J2) is preferable.

The layered state of the A layer and the B layer in the present invention is such that the A layer and the B layer are alternately stacked in a total number of 5 layers or more, preferably 31 layers or more. If the number of stacked layers is less than 5, the selective reflection due to multiple interference is small and a sufficient reflectance cannot be obtained. The upper limit of the number of stacked layers is preferably 301 layers from the viewpoint of manufacturing the feed block. Depending on the number of layers of the multilayer film, you may prepare a dedicated feed block, but it is better to control the number of layers by inserting an inner deckle that closes the resin inlet of the flat flow path according to the required number of layers. It is advantageous in terms of cost.
In addition, each of the A layer and the B layer has a thickness of 0.01 to 0.5 μm, which is necessary for selectively reflecting light by optical interference between layers.

  The multilayer laminated film in the present invention is composed of, for example, a feed block illustrated in the figure with a resin block forming A layer mainly composed of polyethylene terephthalate and a polyethylene terephthalate copolymerized with isophthalic acid forming B layer. The layers are alternately stacked and developed on subsequent dies while maintaining the stacked state. The sheet extruded from the die is cooled and solidified by a casting drum to form an unstretched film. The unstretched film is stretched longitudinally and / or laterally at a predetermined temperature, heat-treated at the predetermined temperature, heat-relaxed if necessary, and wound.

By the way, the multilayer laminated film of the present invention is stretched in at least one direction, preferably biaxially stretched. However, when a polymer having a high refractive index is selected on the A layer side as illustrated, the stretching temperature is the A layer. It is preferable to carry out in the range of the glass transition point (Tg) of the resin of (Tg + 50) degreeC. In the case of uniaxial stretching, the stretching ratio may be 2 to 10 times, and the stretching direction may be vertical or horizontal. In the case of biaxial stretching, the area magnification is 5 to 25 times. The larger the draw ratio, the better the variation in the plane direction in the individual layers of the A layer and the B layer because the film thickness is reduced by stretching and the optical interference of the multilayer laminated film becomes uniform in the plane direction. As the stretching method, known stretching methods such as sequential biaxial stretching, simultaneous biaxial stretching, tubular stretching, and inflation stretching are possible, but sequential biaxial stretching is preferable in terms of productivity and quality. . In addition, the stretched film is preferably stabilized by heat treatment for thermal stabilization.
Moreover, you may provide the process of apply | coating a coating liquid and drying for the objective of giving the surface of a film the manufacturing process of the multilayer laminated film of this invention, or after manufacture.

  In the present invention, the resin constituting the A layer or the B layer can be further exemplified as follows. A thermoplastic resin mainly composed of a stretchable polymer, for example, an aromatic polyester such as polyethylene terephthalate, polyethylene-2,6-naphthalate and polybutylene terephthalate, a polyolefin such as polyethylene and polypropylene, and a polyvinyl such as polystyrene. , Polyamides such as nylon 6 (polycaprolactam) and nylon 66 (poly (hexamethylenediamine-co-adipic acid)), aromatic polycarbonates such as bisphenol A polycarbonate, homopolymers such as polysulfone, A resin mainly composed of coalescence can be mentioned. Moreover, the mixture of resin illustrated may be sufficient. When a copolymer is used, the copolymer component may be a dicarboxylic acid component or a glycol component. Examples of the dicarboxylic acid component include aromatic dicarbomonic acids such as isophthalic acid, phthalic acid, and naphthalenedicarboxylic acid. An aliphatic dicarboxylic acid such as adipic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, and the like; an alicyclic dicarboxylic acid such as cyclohexanedicarboxylic acid, and the like. Examples of the glycol component include butanediol and hexanediol. Examples thereof include aliphatic diols such as cycloaliphatic diols such as cyclohexanedimethanol.

  In the present invention, at least one of the resins constituting the A layer or the B layer preferably has an average particle diameter of 0.01 to 2 μm, more preferably 0.05 to 1 μm, in order to improve the winding property of the film. Preferably, the inert particles in the range of 0.1 to 0.3 μm are contained in a proportion of preferably 0.001 to 0.5% by weight, more preferably 0.005 to 0.2% by weight. If the average particle size of the inert particles is less than 0.01 μm or the content is less than 0.001% by weight, the improvement in the winding property of the film tends to be insufficient, while the average particle size of the inert particles exceeds 2 μm or When the content exceeds 0.5% by weight, the optical properties are easily deteriorated by the particles, and the light transmittance of the entire film may be reduced. Examples of such inert particles include inorganic inert particles such as silica, alumina, calcium carbonate, calcium phosphate, kaolin, and talc, and organic inert particles such as silicone, crosslinked polystyrene, and styrene-divinylbenzene copolymer. I can give you.

  In the present invention, two types of combinations of the resin A and the resin B are illustrated, but from the viewpoint of controlling the distribution of the thickness of each layer in the film width direction, the resin C and the resin D can be further applied without any problem.

Hereinafter, the present invention will be further described by way of examples. The performance in the examples was measured by the following method.
(1) Thickness of each layer A multilayer film sample is cut into a triangle, fixed to an embedding capsule, and then embedded with an epoxy resin. Then, the embedded sample was made into a thin film slice having a thickness of 50 nm in a longitudinal direction with a microtome (ULTRACUT-S), and then observed and projected at 100 kv using a transmission electron microscope. The thickness of each layer was measured from the photograph.
(2) Evaluation of thickness distribution in the width direction The measurement points were FE and BE, respectively, at positions of about 50 mm from both edges of the biaxially stretched film. In the thickness direction, the fifth layer from the outermost layer was the surface layer and the center was the core layer, and the difference in thickness between FE and BE was evaluated.
○: The absolute value of the difference in thickness (FE-BE) is 10 nm or less. X: The absolute value of the difference in thickness (FE-BE) exceeds 10 nm.

[Example 1]
First, using the apparatus shown in FIG. 1, FIG. 2 (a), FIG. 2 (b), and FIG. 5, in the confluence block 20, there are 101 layer A channels and 100 layer B channels, and 201 layers. A multilayer film was formed. The number of the A-layer channels 26 is 15 in total, and the width W = 2 mm, the length LMIN = 55 mm, the length LMAX = 63 mm, the number of the A-layer channels 27 is 71, the width W = 2 mm, and the length The length L was 65 mm. The number of the B-layer channels 24 is 15 in total, and the width W = 1.5 mm, the length LMIN = 18 mm, the length LMAX = 28 mm, the number of the B-layer channels 25 is 70, and the width W = The length L was 1.5 mm and the length L was 30 mm.

  The resin is composed of polyethylene-2,6-naphthalate (PEN) having an intrinsic viscosity (orthochlorophenol, 35 ° C.) of 0.62 dl / g and polyethylene terephthalate having an intrinsic viscosity (orthochlorophenol, 35 ° C.) of 0.63 dl / g ( PET) was prepared. And for the A layer, 0.15 wt% of spherical silica particles (average particle size: 0.12 μm, ratio of major axis to minor axis: 1.02, average deviation of particle size: 0.1) added to PEN A mixture of PEN and PET containing no inert particles at a weight ratio of 30:70 was prepared as a resin for the B layer.

  The resin for the A layer was dried at 170 ° C. for 3 hours, and the mixed resin for the B layer was dried at 160 ° C. for 3 hours, and then supplied to the A layer extruder 5 and the B layer extruder 1 to melt. The resin A and the resin B are guided into the multilayer feed block 9, and after the branching block 20 in the multilayer feed block branches the A layer resin into 101 layers and the B layer resin into 100 layers, at the exit of the junction block A 201 layer laminated unstretched film in which the A layer and the B layer are alternately laminated, led to the die 10 while maintaining the laminated state, cast on a casting drum, and the A layer and the B layer are alternately laminated. Created.

  This unstretched laminated sheet was stretched 3.5 times in the longitudinal direction and then 4.0 times in the transverse direction, and after further heat setting, both edges of the film were trimmed, the width was about 1000 mm, and the thickness was about 18 μm. A biaxially stretched film was prepared. Table 1 shows the thickness of each layer of the obtained multilayer film. In addition, the obtained film was able to selectively reflect a wavelength of 620 nm and looked red visually.

[Example 2]
First, using the apparatus shown in FIG. 6 and FIGS. 7 (a) to 7 (d) and FIG. 5, in the merging block 31, there are 101 layer A channels and 100 layer B channels and 201 layers. A multilayer film was formed. As for the flow path of the A layer, two of the flow paths 34 at both ends have a width W = 2 mm, a length LMIN = 56 mm, a length LMAX = 60 mm, and one of the central flow paths 35 has a width W = 2 mm and a length. LMIN = 60 mm, length LMAX = 64 mm, and B layer has two channels 32 at both ends, width W = 1.5 mm, length LMIN = 24 mm, length LMAX = 28 mm, center channel 33 The width W = 1.5mm, the length LMIN = 26mm, the length LMAX = 28mm, and the flow path of the A layer and the B layer is dug so that the length gradually changes from both ends to the center. I dug 36.

  A multilayer film as in Example 1 except that PET added with true spherical silica particles was used for the A layer, and a PET copolymer obtained by copolymerizing 12 mol% of isophthalic acid not containing inert particles was used as the B layer resin. Got. Table 1 shows the thickness of each layer of the obtained multilayer film.

[Example 3]
In the feed block used in Example 2, two of the flow paths 34 at both ends are the width W = 2 mm, the length LMIN = 46 mm, the length LMAX = 50 mm, and one of the central flow paths 35. However, the width W = 2 mm, the length LMIN = 60 mm, the length LMAX = 64 mm, and the B layer has two channels 32 at both ends, the width W = 1.5 mm, the length LMIN = 14 mm, and the length. LMAX = 18 mm, two of the central flow path 33 are width W = 1.5 mm, length LMIN = 26 mm, length LMAX = 28 mm, and gradually from both ends of the flow paths of the A layer and the B layer to the center. The dug 36 was dug so that the length would change. A multilayer film was obtained in the same manner as Example 2 except for these. Table 1 shows the thickness of each layer of the obtained multilayer film.

[Comparative Examples 1 and 2]
In the apparatus shown in FIG. 3, FIG. 4 (a), FIG. 4 (b) and FIG. 5, the number of the A-layer flow paths 27 is 101, the width W is 2 mm, the length L is 60 mm, The number of channels 25 is 100, the width W is 1.5 mm, and the length L is 30 mm. A multilayer film was obtained in the same manner as in Examples 1 and 2 except for these. Table 1 shows the thickness of each layer of the obtained multilayer film.

  The present invention can be suitably used for producing a multilayer film in which a large number of layers are laminated, particularly a super multilayer film.

It is a perspective view of the confluence | merging block of the multilayer feed block which shows one embodiment of this invention. (A) is a perspective view of the flat flow path which A layer resin of the confluence | merging block 20 which shows one embodiment of this invention passes, (b) is B of the confluence | merging block 20 which shows one embodiment of this invention. It is a perspective view of the flat flow path through which layer resin passes. It is a perspective view of the confluence | merging block of the conventional feed block. (A) is a perspective view of the flat flow path through which A layer resin of the conventional confluence block 30 passes. (B) is a perspective view of the flat flow path through which B layer resin of the conventional confluence block 30 passes. In one embodiment of the present invention, it is a front view showing the arrangement of an extruder, a multilayer feed block, a die, a cooling drum and the like. It is a perspective view of the confluence | merging block of the multilayer feed block which shows one embodiment of this invention. (A) is a perspective view of the flat flow path through which A layer resin corresponding to the surface layer of the confluence | merging block 31 which shows one Embodiment of this invention passes. (B) is a perspective view of the flat flow path through which A layer resin corresponding to the core layer of the confluence | merging block 31 which shows one Embodiment of this invention passes. (C) is a perspective view of the flat flow path through which B layer resin corresponding to the surface layer of the confluence | merging block 31 which shows one Embodiment of this invention passes. (D) is a perspective view of the flat flow path through which B layer resin corresponding to the core layer of the confluence | merging block 31 which shows one Embodiment of this invention passes. It is a figure in case the distribution of each layer thickness of a multilayer film cross section is uniform in the width direction. It is a figure in case the distribution of each layer thickness of a multilayer film cross section is non-uniform | heterogenous in the width direction. It is a figure in case the distribution of each layer thickness of a multilayer film cross section is distributed in the thickness direction, but is uniform in the width direction. It is a figure in case the distribution of each layer thickness of a multilayer film cross section is non-uniform | heterogenous in the width direction. It is a figure of the arrow C of FIG. 3, and is a figure of the exit of a merge block.

Explanation of symbols

1: B layer extruder 2: B layer gear pump 3: B layer filter 4a, 4b: Polymer pipe 5: A layer extruder 6: A layer gear pump 7: A layer filter 8: Casting drum 9: Multilayer feed block 10: Die 11: Unstretched film 20: Merge block 21: Flow direction of B layer resin 22: Flow direction of A layer resin 23: Flow direction of resin after merge 24: B layer Flat flow path (length change) through which resin passes
25: Flat flow path (constant length) through which B layer resin passes
26: Flat flow path (length change) through which the A layer resin passes
27: Flat flow path (constant length) through which the A layer resin passes
28: digging portion 31: confluence block 32: flat flow path 33 through which B layer resin corresponding to the outermost layer passes: flat flow path 34 through which B layer resin corresponding to the core layer passes: A layer corresponding to the outermost layer Flat flow path 35 through which resin passes: Flat flow path through which A layer resin corresponding to the core layer passes

Claims (5)

Resin A and resin B are melted separately by an extruder, and the resin A and the resin B are guided from different directions to the merge block in the multilayer feed block, and are separated by partition walls provided in the merge block. Five or more layers of the resin A and the resin B are alternately flowed into each formed flat flow path, and the resin A and the resin B are merged at the exit of the merge block. Form a resin flow in which the resin B is alternately laminated, extrude into a sheet form from the die following the multilayer feed block, and laminate five or more layers alternately in the direction in which the resin A and the resin B are multilayered in the thickness direction In the method for producing a multilayer sheet as a multilayer sheet,
Regarding the thickness in the width direction of each layer of the multilayer sheet formed by the flow of resin flowing from the flat flow path to the introduction side (FE point side) and the development side (BE point side) into the die, the thickness is The flow rate of the resin flowing toward the FE point side or the BE point side on one side which becomes smaller is larger than the flow rate of the resin flowing on the BE point side or the FE point side where the thickness is increased. The length of the flow path through which the resin flows on the one side of the FE point side or the BE point side is compared with the length of the flow path through which the resin flows on the other side of the BE point side or the FE point side. A method for producing a multilayer sheet, characterized in that the thickness of each layer of the multilayer sheet is made uniform in the width direction by setting it short . The method for producing a multilayer sheet according to claim 1, wherein the length of the flow path is set to linearly and linearly change from the FE point side to the BE point side .   A method for producing a multilayer film, wherein the multilayer sheet obtained in claim 1 is cooled and solidified with a casting drum to form an unstretched film, and the unstretched film is stretched in at least one direction of the longitudinal direction and the transverse direction to form a multilayer film. A merge block formed in a multi-layer feed block and formed by dividing a flow path into which five or more layers of resin A and resin B, which are separately melted by an extruder, alternately flow, are divided by partition walls; Upon exiting, the resin A and the resin B are merged and extruded into a sheet shape, and the die is formed into a multilayer sheet in which the resin A and the resin B are alternately laminated in a thickness direction in a multilayer direction. In the multilayer sheet manufacturing apparatus provided at least,
Regarding the thickness in the width direction of each layer of the multilayer sheet formed by the flow of resin flowing from the flat flow path to the die introduction side (FE point side) and the development side (BE point side),
The flow rate of the resin flowing to the FE point side or the BE point side on the one side where the thickness is reduced is larger than the flow rate of the resin flowing on the BE point side or the FE point side on the other side where the thickness is increased. The length of the flow path through which the resin flows on the one side of the FE point side or the BE point side is compared with the length of the flow path on the other side of the BE point side or the FE point side so as to increase. An apparatus for producing a multilayer sheet, characterized by being set shorter . The multilayer sheet manufacturing apparatus according to claim 4 , wherein the length of the flow path linearly and linearly changes from the FE point side to the BE point side .

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