JP2006231763A - Multilayer extrusion molding apparatus, method for manufacturing multilayer film and multilayer stretched film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multilayer extrusion molding apparatus of a multilayer film which can eliminate thickness unevenness of an outermost layer member and an inner layer member of a multilayer film of at least three layers by performing fine temperature control of a melting resin. <P>SOLUTION: The thickness of the outermost layer of a multilayer film 2 is roughly adjusted by the moving of choke bars 44 and 46 by the advancing and retreating of choke bar adjusting bolts 48 and 50. The choke bars 44 and 46 are heated and the resin temperature of a melting resin which flows in passages 34 and 38 is changed by controlling the quantity of heat of rod-shaped electric heaters embedded in each of bolts 48 and 50. Thereby, the minute thickness adjustment is performed. A controller 80 controls the voltage of the rod-shaped electric heaters appropriately based on the thickness data sent out from a thickness detection device 70, and sends out a voltage adjustment signal which controls the resin temperature of the melting resin to the rod-shaped electric heaters. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a multilayer extrusion molding apparatus suitable for manufacturing a multilayer film used in an optical apparatus such as a flat panel display, a multilayer film manufacturing method using the apparatus, and a multilayer film manufactured by the method. It is related with the manufacturing method of the used multilayer stretched film.

  Various optical films are used for a liquid crystal display as an example of a flat panel display. An example of the optical film is a retardation film. As such a retardation film, it is known that a uniaxial or biaxially stretched film made of a resin having a negative intrinsic birefringence value (for example, a vinyl aromatic polymer) is useful (see Patent Document 1). . However, an unstretched film made of a resin having a negative intrinsic birefringence value has a drawback that when it is stretched alone, it is easily broken because of its insufficient strength.

  Therefore, the present applicant forms another unstretched laminate (multilayer film) by laminating another resin layer (outermost layer) on both sides of an unstretched film made of a resin having a negative intrinsic birefringence value. The technique which described that it extends was proposed previously (Japanese Patent Application No. 2004-84969). An unstretched laminate including an unstretched film made of a resin having a negative intrinsic birefringence value between a pair of outermost layers is prepared and stretched to form an inner layer portion (made of a resin having a negative intrinsic birefringence value). The unstretched film) can be stretched without breaking, but thickness unevenness may occur in the inner layer portion of the stretched film. The thickness unevenness of the inner layer portion may be caused by the thickness unevenness of each outermost layer portion.

  As described above, the technique for suppressing the thickness unevenness of the inner layer portion of at least the three-layered multilayer film is not limited to optical applications such as the above-described retardation film, but is also desired in the fields of packaging films and protective films. .

  The unstretched laminate (multilayer film) described above is manufactured by multilayer extrusion, and several proposals have been made as an apparatus for this purpose.

  For example, Patent Document 2 discloses a multilayer extrusion molding apparatus. In this apparatus, a plurality of manifolds are formed to which a plurality of molten resins having different properties extruded from a plurality of extruders are supplied. On the downstream side of each manifold, there are formed a merging portion where a plurality of molten resins flowing out from each manifold are stacked in multiple layers, and a plurality of flow paths connecting the respective manifolds and the merging portion. A lip portion is formed on the downstream side of the merging portion to discharge the multilayer film superimposed at the merging portion to the outside. In any one of the plurality of flow paths, at least one wall surface of the flow path is provided on the downstream side of the first thin-walled portion and the first thin-walled portion that becomes the center of rotation when the wall surface is deformed. In addition, a second thin-walled portion connected to the channel gap adjusting means for setting the deformation amount of the wall surface, and a third thin-walled thickness for setting the thickness of the layer to be formed provided on the downstream side of the second thin-walled portion. And a flow path gap adjusting means is disposed in a space provided between the wall surface of the flow path and the flow path adjacent thereto. In the apparatus of Patent Document 2, since any one of the plurality of flow paths is provided with a mechanism for physically adjusting the flow gap, the thickness of the molten resin flowing in the flow paths is individually adjusted. It is possible.

  In the apparatus of Patent Document 2, since the flow path gap is adjusted by physically moving the specific flexible structure, the thickness of the molten resin can be roughly adjusted, but cannot be finely adjusted. For this reason, uneven thickness may occur.

  In addition, although it is not a multilayer extrusion molding apparatus, in patent document 3, the single layer extrusion molding apparatus is disclosed. In this apparatus, a manifold is formed to which molten resin extruded from a single extruder is supplied. A flow path is connected to the downstream side of the manifold, and a lip portion that discharges outside while adjusting the thickness of the molten resin is formed on the downstream side of the flow path. A plurality of vertical slits that do not reach the lip surface are formed on the back of the lip, the back is divided into a plurality of elements in the width direction, and a planar heater is attached to the back of each element. With the surface heater, the lip surface corresponding to each element can be heated and controlled independently and at a substantially uniform temperature. In the apparatus of Patent Document 3, since the molten resin flowing in the flow path is heated and the temperature is adjusted by appropriately operating the planar heater, the thickness unevenness of the resin film discharged from the lip portion is reduced. Can do.

However, if the technique of Patent Document 3 is applied to multilayer extrusion as it is, the total thickness can be adjusted, but each layer cannot be adjusted individually, and as a result, the thickness unevenness of the outermost layer portion is suppressed. I could not.
JP-A-2-256603 JP 2000-25092 A JP-A-6-87148

  An object of the present invention is to control the thickness unevenness of the outermost layer portion of the multilayer film of at least three layers by adjusting the temperature of the molten resin more finely, and thereby eliminate the thickness unevenness of the inner layer portion. A multilayer extrusion molding apparatus, a method for producing a multilayer film using the apparatus, and a method for producing a multilayer stretched film using the multilayer film produced by the method.

In order to achieve the above object, according to the present invention,
A multilayer having (1) a die, (2) thickness detection means, and (3) control means, which is used to form a multilayer film of three or more layers having one or more inner layers between two outermost layers. In extrusion equipment,
(1) The dice includes two outermost layer manifolds supplied with molten resin, and one or more inner layer manifolds provided at a predetermined interval between the two outermost layer manifolds,
Two outermost flow paths and one or more inner flow paths that extend downstream from the manifold and eventually merge into one;
Two choke bars that are provided continuously along the width direction of each outermost layer flow path and adjust the gap between the flow paths;
Along the longitudinal direction of the choke bar corresponding to the width direction of each outermost layer flow path, the choke bars are arranged at a predetermined interval on the opposite side of the choke bar flow path, and the tip portion is in the axial direction with respect to the choke bar. A plurality of choke bar adjustment bolts supported so as to freely advance and retreat;
A resin temperature micro-adjustment means for finely adjusting the temperature of the molten resin flowing in each of the outermost layer flow paths;
A lip portion disposed on the downstream side of the merging portion of each of the outermost channel and the inner layer channel;
Each molten resin flowing out from each manifold through each flow path is joined at the joining portion to be multilayered, and can be continuously extruded as a multilayer film from the lip portion,
(2) The thickness detection means is capable of detecting the thickness of each outermost layer of the multilayer film extruded from the die,
(3) The control means adjusts the temperature of the outermost layer resin temperature so as to change the temperature of the molten resin flowing in each outermost layer flow path according to the detected thickness of each outermost layer of the multilayer film. There is provided a multilayer extrusion molding apparatus capable of controlling the above.

  Preferably, as the resin temperature fine adjustment means for the outermost layer, an extremely fine bar heater embedded in each choke bar adjustment bolt is used. Alternatively, a heat transfer (radiation) heat device using oil circulation embedded in a choke bar may be used.

  According to this invention, the manufacturing method of a multilayer film including the process of extruding three or more layers of multilayer films using the said multilayer extrusion molding apparatus is provided.

  According to this invention, the manufacturing method of a multilayer stretched film including the process of extending | stretching the multilayer film extruded by the said method is provided.

  The multilayer extrusion molding apparatus of the present invention can suppress unevenness in the thickness of the outermost layer portion of the multilayer film of at least three layers by adjusting the temperature of the molten resin more finely, and thus eliminate unevenness in the thickness of the inner layer portion. it can. When a multilayer film is produced using the apparatus, the thickness unevenness of each outermost layer portion is reduced, and even when the obtained film is stretched, the thickness unevenness remains small, and the retardation unevenness does not appear in the inner layer portion.

  The multilayer film produced using the multilayer extrusion molding apparatus of the present invention is useful as a raw material film for various optical films such as a retardation film, a polarizing plate protective film, a viewing angle compensation film, a brightness enhancement film, and a plastic cell. .

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a sectional view showing an example of a multilayer film that can be formed by the apparatus or method of the present invention. FIG. 2 is a side sectional view showing an example of a multilayer extrusion molding apparatus of the present invention suitable for producing the multilayer film of FIG. 3 is a front view of FIG. 2 (however, it is smaller than FIG. 2), FIG. 4 is a schematic view showing the main part in the vicinity of the choke bar and the choke bar adjusting bolt, and FIG. 5 is a cross section of the choke bar adjusting bolt. Figure.

  In this embodiment, first, the multilayer film 2 shown in FIG. 1 is illustrated, and then an apparatus 20 and a method for manufacturing the multilayer film 2 will be described.

As shown in FIG. 1, a multilayer film 2 according to this embodiment is manufactured by a method using an apparatus described later, and an inner layer 3 is formed between a pair of outermost layers 4 and 5. It is an unstretched laminate.

  The inner layer 3 and the outermost layers 4 and 5 can be made of a material having a positive intrinsic birefringence value or a material having a negative intrinsic birefringence value.

  A material having a positive intrinsic birefringence value (hereinafter may be simply referred to as “positive material”) is a material having optically uniaxial characteristics when molecules are oriented in a uniaxial order. Specifically, when light is incident on a layer formed with molecules having a uniaxial orientation, the refractive index of light in the orientation direction is larger than the refractive index of light in a direction perpendicular to the orientation direction. Say material. Examples of the positive material include various materials such as a resin, a rod-like liquid crystal, and a rod-like liquid crystal polymer. These may be used individually by 1 type and may use 2 or more types together. In these, resin is preferable among these in this invention.

  Resins as positive materials include olefins (eg, ethylene, propylene, norbornene, cycloolefin, etc.), esters (eg, ethylene terephthalate, butylene terephthalate, etc.), arylene sulfide (eg, phenylene sulfide, etc.), vinyl alcohol, carbonate , Arylates, cellulose esters (some of which have a negative intrinsic birefringence value), a single polymer of monomers such as ether sulfone, sulfone, allyl sulfone, vinyl chloride, etc. Original, ternary, etc.) copolymers. In the present invention, among these, a polymer of an olefin monomer is preferable, and among the polymers of an olefin monomer, from the viewpoints of light transmittance characteristics, heat resistance, dimensional stability, photoelastic characteristics, etc. A polymer of norbornene monomer is particularly preferred.

  The polymer of norbornene monomer has a repeating unit derived from a norbornene skeleton. Specific examples thereof include JP-A-62-252406, JP-A-62-2252407, and JP-A-2- No. 133413, JP-A-63-145324, JP-A-63-264626, JP-A-1-240517, JP-B-57-8815, JP-A-5-39403, JP-A-5-1993 No. 43663, JP-A-5-43834, JP-A-5-70655, JP-A-5-279554, JP-A-6-206985, JP-A-7-62028, JP-A-8-176411 Although what was described in gazette, Unexamined-Japanese-Patent No. 9-241484, etc. can be utilized suitably, it is not limited to these. Moreover, these may be used individually by 1 type and may use 2 or more types together.

  A material having a negative intrinsic birefringence value (hereinafter sometimes simply referred to as “negative material”) has a characteristic of exhibiting optically negative uniaxiality when molecules are oriented in a uniaxial order. When light enters a material, specifically, a layer in which molecules have a uniaxial orientation, the refractive index of light in the orientation direction is smaller than the refractive index of light in the direction perpendicular to the orientation direction. The material which becomes. Examples of the negative material include various materials such as resin, discotic liquid crystal, and discotic liquid crystal polymer. These may be used individually by 1 type and may use 2 or more types together. In these, resin is preferable among these in this invention.

  The resin as the negative material includes a single monomer such as styrene, a styrene derivative, acrylonitrile, methyl methacrylate, maleic anhydride, butadiene, or cellulose ester (some have a positive intrinsic birefringence value). Examples thereof include a polymer, and a multi-component (binary, ternary, etc.) copolymer of the monomers. In the present invention, among these, a polymer of a styrene monomer; at least one selected from styrene and / or a styrene derivative, acrylonitrile, maleic anhydride, methyl methacrylate, and butadiene, from the viewpoint of high birefringence. Multi-component (binary, ternary, etc.) copolymers with seeds are more preferred, and multi-component (binary, ternary, etc.) co-polymerization of styrene and / or styrene derivatives with maleic anhydride in terms of high heat resistance Coalescence is particularly preferred.

  The inner layer 3 and the outermost layers 4 and 5 may be made of three different materials, or the outermost layers 4 and 5 may be made of the same material and only the inner layer 3 may be made of different materials. In the present embodiment, when the inner layer 3 is made of a material having a positive intrinsic birefringence value, the outermost layers 4 and 5 are preferably made of a material having a negative intrinsic birefringence value. On the other hand, when the inner layer 3 is made of a material having a negative intrinsic birefringence value, the outermost layers 4 and 5 are preferably made of a material having a positive intrinsic birefringence value.

  The inner layer 3 and the outermost layers 4 and 5 may be substantially non-oriented or may be oriented. Note that “substantially non-oriented” means that the difference between the refractive indexes nBx and nBy in the x and y directions orthogonal in the outermost layers 4 and 5 is small, and the refraction in the x and y directions orthogonal in the inner layer 3 When the ratio is nAx, nAy, the thickness of the inner layer 3 is dA, and the thickness of the outermost layers 4 and 5 is dB, the value of | (nAx−nAy) dA | + | (nBx−nBy) dB | It is 1.1 or less of the value of | (nAx−nAy) dA |.

  Various additives (for example, an antioxidant, a heat stabilizer, a light stabilizer, an ultraviolet absorber, etc.) may be added to the inner layer 3 and the outermost layers 4 and 5 as necessary.

  The average thickness of the inner layer 3 is about 10 to 200 μm. The thickness unevenness of the entire inner layer 3 is preferably controlled within ± 3%, more preferably within ± 1% with respect to the average thickness. “Thickness unevenness” is a value obtained by dividing the difference between the maximum value and the minimum value of the thickness of the inner layer 3 by the average thickness.

  The thickness of the outermost layers 4 and 5 is about 10 to 200 μm.

  An adhesive layer may be formed between the inner layer 3 and the outermost layers 4 and 5. That is, the multilayer film 2 may have a three-kind five-layer structure of outermost layer 4 -adhesive layer-inner layer 3 -adhesive layer-outermost layer 5.

  The adhesive layer is composed of a material having affinity for both the inner layer 3 and the outermost layers 4 and 5. For example, a polymer of norbornene monomer is used as a resin having a positive intrinsic birefringence value that constitutes one of the inner layer 3 and the outermost layers 4 and 5, and the other of the inner layer 3 and the outermost layers 4 and 5 is used as the other. As the resin having a negative intrinsic birefringence value, a polymer of a styrene monomer (or a multi-component (binary, ternary, etc.) copolymer of styrene and / or a styrene derivative and maleic anhydride) was used. In this case, the adhesive layer includes a polymer of an olefin monomer and a polymer of a styrene monomer (or multiple (binary, ternary, etc.) co-polymerization of styrene and / or a styrene derivative and maleic anhydride. The one containing any component of (combined) is used. As such a thing, an ethylene- (meth) acrylic acid ester copolymer, an ethylene-type copolymer, etc. are mentioned, for example.

  The thickness of the adhesive layer is about 1 to 50 μm.

  Since the multilayer film 2 of the present embodiment having the above-described configuration is an unstretched laminate, it can be formed into a stretched multilayer film suitable for a retardation film or the like by stretching it as described later. is there.

  The multilayer film 2 is later stretched to obtain an optical film (stretched multilayer film) such as a retardation film. Here, when the glass transition temperatures of the resin (A) of the inner layer 3 and the resin (B) of the outermost layers 4 and 5 are Tg (A) ° C. and Tg (B) ° C., respectively, when the multilayer film 2 is co-stretched When the temperature is stretched in the vicinity of Tg (A) ° C., the birefringence characteristics of the inner layer 3 can be expressed sufficiently and uniformly.

When the multilayer film 2 is co-stretched around Tg (A) ° C., the outermost layers 4 and 5 are hardly oriented when each resin is selected so as to satisfy the relationship of Tg (A)> Tg (B) + 20 ° C. Thus, the film can be stretched stably while being in a substantially non-oriented state and preventing the inner layer 3 from being broken.

  When the multilayer film 2 is co-stretched around Tg (A) ° C., if each resin is selected so that the difference between Tg (A) and Tg (B) is within ± 20 ° C., the outermost layer 4 and 5 are also oriented and can be stably stretched while preventing the inner layer 3 from being broken.

As shown in multilayer extrusion molding apparatus Figure 2 and Figure 3, multilayer extrusion molding apparatus 20 according to an embodiment of the present invention, the molding die 22 of the method of extruding a multi-layer film 2 shown in FIG. 1 continuously, thickness It has a detection device 70 and a control device 80.

The molding die 22 has a die body 24. Although the constituent material of the die body 24 is not particularly limited in the present invention, it can be made of generally used die steel, stainless steel (SUS), or the like. As the die steel, SKD hot die steel (thermal conductivity: about 30 W / m ° C.) or the like can be used. As the stainless steel, SUS420J2 (thermal conductivity: about 25 W / m ° C.) or the like can be used. Inside the die body 24, manifolds 26, 28, and 30 are formed to which a plurality of molten resins A, B, and C having different properties such as viscosity that are extruded from a plurality of extruders (not shown) are supplied. Yes. In the present embodiment, the manifolds 26 and 30 correspond to the outermost layer manifold, and the manifold 28 corresponds to the inner layer manifold.
In this embodiment, the molten resins A and C correspond to resins having a positive intrinsic birefringence value that can form the outermost layers 4 and 5 of the multilayer film 2 shown in FIG. 1, and the molten resin B is shown in FIG. The case where the resin with a negative intrinsic birefringence value which can comprise the inner layer 3 of the multilayer film 2 corresponds is illustrated.

  On the downstream side of the manifolds 26, 28, 30, a joining portion 32 that superimposes a plurality of molten resins flowing out from the manifolds 26, 28, 30 in multiple layers, and the manifolds 26, 28, 30 and the joining portion 32 are connected. A plurality of flow paths 34, 36, and 38 are formed. In the present embodiment, the channels 34 and 38 correspond to the outermost layer channel, and the channel 36 corresponds to the inner layer channel.

  On the downstream side of the merging portion 32, a lip portion 40 that discharges the laminated body (which will later become the multilayer film 2) overlapped at the merging portion 32, and a merging channel 41 that connects the merging portion 32 and the lip portion 40 are formed. Has been.

  In the present embodiment, the lip portion 40 is ceramic coated. By applying ceramic coating, it is possible to reduce adhesion of resin and the like, and reduction of die line and thickness unevenness can be expected. In the present embodiment, the inner surfaces of the flow paths 34, 36, and 38 and the combined flow path 41 are H-Cr plated. By polishing the lip portion 40 to prevent die line by H-Cr plating, it is possible to accurately produce R (smooth the lip portion 40) and reduce resin adhesion and the like. As a result, a reduction in die line and thickness unevenness can be expected.

  Choke bars 44 and 46 having a substantially trapezoidal longitudinal section for adjusting the gap between the channels are disposed in a part of the channels 34 and 38 except the channel 36. The choke bars 44 and 46 extend from one end (one die width end) to the other end (the other die width end) in the width direction of the flow paths 34 and 38 (the direction of the paper in FIG. It extends continuously.

  A plurality of choke bar adjusting bolts 48 and 50 are arranged at predetermined intervals along the longitudinal direction of the choke bars 44 and 46 (the paper surface direction in FIG. ing. The front ends of the bolts 48 and 50 are supported so as to be movable forward and backward with respect to the choke bars 44 and 46. By moving the bolts 48 and 50 back and forth in the axial direction (pushing and pulling), the choke bars 44 and 46 are moved, the gap between the flow paths 34 and 38 is adjusted, and the molten resin flowing roughly through the flow paths 34 and 38. The thickness distribution in the width direction (the paper surface direction in FIG. 2; the same applies hereinafter) is adjusted. When it is desired to partially reduce the thickness in the width direction of the molten resin flowing through each flow path 34, 38, the choke bars 44, 46 are pushed by adjusting the bolts 48, 50 corresponding to the portions, What is necessary is just to make small the amount of gaps of the part. On the other hand, when it is desired to partially increase the thickness, the choke bars 44 and 46 may be pulled by adjusting the bolts 48 and 50 corresponding to the portions to increase the gap amount of the portions. By performing this operation for each of the bolts 48 and 50, it is possible to give a rough distribution to the gaps between the flow paths 34 and 38 immediately before the merging portion 32. As a result, the thickness of the outermost layers 4 and 5 is set to the flow path. It can be made uniform in the width direction, that is, in the width direction of the multilayer film 2.

  The number of the choke bar adjusting bolts 48 and 50 is not particularly limited, and the larger the number, the more the choke bars 44 and 46 can be partially moved. As a result, the gap between the flow paths 34 and 38 can be finely adjusted. This is preferable. However, if the number of bolts 48 and 50 is excessively increased, the number of bolt holes formed in the choke bars 44 and 46 increases, resulting in insufficient strength of the dies themselves. Therefore, in the present embodiment, it is desirable that the adjacent bolts 48 and 50 are arranged in a number of bolts with a spacing W of 40 to 50 mm (see FIG. 4).

  As shown in FIG. 5, the outer diameter D1 of each bolt 48, 50 is preferably large from the viewpoint of maintaining the bolt strength, but the strength of the choke bars 44, 46 to which the bolts 48, 50 are screwed is reduced. From the viewpoint of preventing this, it is desirable that it is small. In the present embodiment, the outer diameter D1 of each bolt 48, 50 is preferably 10 to 30 mm, more preferably from the viewpoint of maintaining the strength of each bolt 48, 50 without suppressing the strength reduction of the choke bars 44, 46. Is 14 to 24 mm.

  In the present embodiment, the choke bar adjustment bolts 48 and 50 are provided with ultrathin rod-shaped electric heaters 482 as an example of the outermost layer resin temperature fine adjustment means for finely adjusting the temperature of the molten resin flowing in the flow paths 34 and 38. , 502 are embedded. In this embodiment, one end of the rod-shaped electric heater penetrates from the bolts 48 and 50.

  The thickness distribution in the width direction of the molten resin flowing in the flow paths 34 and 38 can be adjusted by adjusting the gaps between the flow paths 34 and 38 by moving the choke bars 44 and 46 back and forth. Can't do it. In the present invention, rod-shaped electric heaters 482 and 502 are embedded in the respective bolts 48 and 50, and the choke bars 44 and 46 are heated by energizing or interrupting the rod-shaped heaters 482 and 502 to control the amount of heat generated. It is possible to give a temperature distribution in the longitudinal direction of 44 and 46 and to finely adjust the resin temperature of the molten resin flowing through the flow paths 34 and 38, and as a result, thickness unevenness can be suppressed.

  The outer diameter D2 of the rod-shaped electric heaters 482 and 502 is preferably 75% or less, more preferably 30 to 50% with respect to the outer diameter D1 of the bolts 48 and 50. While it is technically problematic to make D2 too small with respect to D1, if D2 is too large with respect to D1, the strength of each bolt 48, 50 is lowered.

  In the present embodiment, the rod-shaped electric heaters 482 and 502 can have a temperature distribution in the longitudinal direction of the choke bars 44 and 46 based on a signal sent from the control device 80. When the temperature of a portion in the longitudinal direction of the choke bars 44 and 46 changes, the resin temperature of the molten resin flowing through the flow paths 34 and 38 changes slightly to change the resin viscosity, and the molten resin flowing through the flow paths 34 and 38 changes. The flow rate changes. As a result, the thickness can be controlled.

  2 and 3, in the vicinity of the lip portion 40, a plurality of lip adjustment bolts 42 for adjusting the gap of the lip portion 40 are provided in the width direction of the lip portion 40 (the same as the paper direction in FIG. 2). Are provided at predetermined intervals.

  By adjusting the gap of the lip portion 40 by moving the lip adjusting bolt 42 in the axial direction, the flow resistance of the laminated body overlapped at the merging portion 32 is partially changed. As a result, the flow rate of the laminated body is partially increased. The thickness of the entire multilayer film 2 discharged from the lip 40 is adjusted. By performing this operation for each bolt 42, a distribution is given to the gap amount immediately before the lip portion 40. Note that an electric heater is attached to the lip adjustment bolt 42. By energizing or interrupting the electric heater, the lip adjustment bolt 42 is expanded and contracted, and as a result, the gap of the lip portion 40 is changed. It is good also as a structure.

  In the present embodiment, electric heaters 52, 54, 56, 58 as resin temperature adjusting means are arranged inside the die body 24 so as to extend along the manifold 28 (inner layer manifold) and the flow path 36. May be. The electric heaters 52, 54, 56, and 58 are for controlling the temperature (and consequently the resin viscosity) of the molten resin in each of the manifolds 26, 28, and 30, respectively. The shape of each electric heater 52,54,56,58 is not specifically limited, For example, plate shape, a column shape, etc. are mentioned. When a cylindrical electric heater is used, the diameter of the heater is usually about 15 to 25 mm (preferably about 20 mm). When using a plate-shaped electric heater, the thickness of the heater is usually about 15 to 25 mm.

  In the present embodiment, in addition to the electric heaters 52, 54, 56, and 58, an electric heater for keeping the die main body for heating the entire die main body 24 may be provided outside the electric heaters 52 and 58, for example. .

  A thickness detecting device 70 capable of detecting the thickness of at least the outermost layers 4 and 5 of the extruded multilayer film 2 is provided outside the lip portion 40 of the die body 24. The structure of the thickness detection apparatus 70 is not specifically limited, For example, the commercially available thickness gauge apparatus for multilayers, such as an infrared thickness meter and an X-ray thickness meter, can be used.

  The thickness data of the outermost layers 4 and 5 of the multilayer film 2 detected by the thickness detection device 70 is sent to the control device 80 as a predetermined command signal.

  In the control device 80, the means for holding the received thickness data of the outermost layers 4 and 5, the means for comparing the desired value and the measured value of the outermost layer thickness, and proportional to the obtained difference, The electric power of the electric heater is controlled in proportion to the integral value of the difference or in proportion to the temporal change of the difference. When the thickness data of the outermost layers 4 and 5 from the thickness detection device 70 are input to the control device 80, the data are compared with the data α and data β, and the outermost layers 4 and 5 of the multilayer film 2 are compared. In order to bring the thickness closer to a desired value, the choke bars 44 and 46 are heated to have a temperature distribution in the longitudinal direction of the choke bars 44 and 46 (the paper surface direction in FIG. 2), and consequently the molten resin flowing through the flow paths 34 and 38. A voltage adjustment signal for finely adjusting the resin temperature, for example, at a level of 0.1 ° C., is sent to the rod-shaped electric heaters 482 and 502 embedded in the respective bolts 48 and 50.

  When the voltage applied to the electric heater is increased, the temperature of the electric heater rises. As a result, the choke bars 44 and 46 are heated, a temperature distribution is generated in the longitudinal direction of the choke bars 44 and 46, and the molten resin flowing through the flow paths 34 and 38. The resin temperature increases. When the resin temperature of the molten resin flowing through the flow paths 34 and 38 increases, the resin viscosity decreases and the resin easily flows, and as a result, the resin thickness increases. Conversely, when the voltage applied to the electric heater is lowered, the electric heater temperature is lowered, and finally the resin temperature of the molten resin flowing through the flow paths 34 and 38 is lowered. When the resin temperature of the molten resin flowing through the flow paths 34 and 38 becomes low, the resin viscosity becomes high and the resin hardly flows, and as a result, the resin thickness becomes thin.

Using the multilayer extrusion molding apparatus 20 having the above configuration, the multilayer film 2 shown in FIG. 1 is manufactured as follows.

  First, molten resins extruded from three melt extruders (not shown) are supplied to the manifolds 26, 28, and 30.

  Next, the molten resin supplied to the manifolds 26, 28, and 30 is merged at the merging portion 32 through the respective flow paths 34, 36, and 38, and the molten resins are stacked in multiple layers at the merging portion 32. Then, it is pushed out from the lip portion 40 through the joint channel 41. In this molding, the flow is expanded in the width direction (paper surface direction in FIG. 2) of the flow paths 34, 36, 38 by the manifolds 26, 28, 30 to form a sheet-like flow.

  The multilayer film 2 pushed out from the lip portion 40 is cooled, for example, on a rotating cooling drum 90, and then wound around a winder (not shown). In the present embodiment, as shown in FIG. 2, a thickness detection device 70 is disposed at a position after the cooling drum 90 (up to the winder). For this reason, the multilayer film 2 extruded from the lip portion 40 passes through the thickness detector 70, and the thicknesses of the outermost layers 4 and 5 of the multilayer film 2 are detected. The thickness data detected here is a predetermined command. The signal is sent to the control device 80 as a signal.

  The control device 80 includes the relationship data α of the resin temperature of the molten resin flowing through the flow paths 34 and 38 and the voltage applied to the rod-shaped electric heaters 482 and 502, the thickness of the outermost layers 4 and 5 of the extruded multilayer film 2, and the rod shape. Since the voltage relation data β applied to the electric heaters 482 and 502 is input in advance, the thickness data sent from the thickness detector 70 is compared with the data α and data β, and the outermost layer 4 of the multilayer film 2 is compared. , 5 is embedded in each of the bolts 48 and 50 so as to control the resin temperature of the molten resin flowing through the flow paths 34 and 38 at a level of, for example, 0.1 ° C. so that the thickness of the To the rod-shaped electric heaters 482, 502.

  Specifically, when it is determined that the sent thickness data is higher than the desired thickness of the multilayer film 2, the control device 80 reduces the amount of voltage applied to the rod-shaped electric heaters 482 and 502. Send command signal. When the voltage applied to the rod-shaped electric heaters 482 and 502 decreases, the resin temperature of the molten resin flowing through the flow paths 34 and 38 becomes lower, the resin viscosity becomes higher and the resin does not flow easily, and as a result, the resin thickness tends to be thinner. It is in.

  Conversely, when it is determined that the sent thickness data is lower than the desired thickness of the multilayer film 2, the control device 80 causes the command signal to increase the amount of voltage applied to the rod-shaped electric heaters 482 and 502. Is sent out. When the voltage applied to the rod-shaped electric heaters 482 and 502 increases, the resin temperature flowing through the flow paths 34 and 38 increases, the resin viscosity decreases and the resin easily flows, and as a result, the resin thickness tends to increase.

  In the present embodiment, as described above, feedback control is performed so that the thicknesses of the outermost layers 4 and 5 of the multilayer film 2 passing through the thickness detection device 70 are set to desired values.

  In the present embodiment, the thicknesses of the outermost layers 4 and 5 of the multilayer film 2 are roughly adjusted by changing the gap amounts of the flow paths 34 and 38 by a choke bar mechanism. By controlling the amount of heat generated by the rod-shaped electric heaters 482 and 502 embedded in the adjusting bolts 48 and 50, the choke bars 44 and 46 are heated, and finally the resin temperature of the molten resin flowing through the flow paths 34 and 38 is adjusted. As a result, a mechanism for adjusting the flow rate by changing the flow rate of the molten resin flowing through the flow paths 34 and 38 is adopted. The control device 80 appropriately controls the voltage amount of the rod-shaped electric heaters 482 and 502 based on the thickness data sent from the thickness detection device 70, and finally the resin temperature of the molten resin flowing through the flow paths 34 and 38. Is sent to the bar-shaped electric heaters 482 and 502 to control the voltage at a level of 0.1 ° C. For this reason, it becomes possible to suppress the thickness nonuniformity of the outermost layers 4 and 5 of the multilayer film 2 efficiently.

Optical film (multilayer stretched film) can be obtained by stretching the obtained multilayer film (unstretched laminate) 2. This optical film is useful as a retardation film.

  The retardation film is a film having a uniform retardation at a desired value over the entire film surface. Examples of the retardation film include retardation films such as λ / 2 and λ / 4 of the wavelength λ of light to be used.

  There is no particular limitation on the stretching method, and a conventionally known method can be applied. Specifically, a uniaxial stretching method such as a method of uniaxial stretching in the longitudinal direction using the difference in peripheral speed on the roll side, a method of uniaxial stretching in the transverse direction using a tenter; simultaneous biaxial stretching method, sequential biaxial Examples thereof include a biaxial stretching method such as a stretching method; a method of stretching obliquely using a specific tenter stretching machine; and the like. The stretching temperature is preferably Tg (A) -10 to Tg (A) + 20 ° C. when the glass transition temperature of the resin constituting the inner layer 3 is Tg (A) ° C. The draw ratio is usually 1.05 to 10 times, preferably 1.1 to 5 times in the length direction, and usually about 1.01 to 5 times in the width direction.

  Examples of the optical film other than the retardation film include a polarizing plate protective film, a viewing angle compensation film, a brightness enhancement film, and a plastic cell.

Other Embodiments Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and can be implemented in various modes without departing from the scope of the present invention. Of course.

  For example, in the above-described embodiment, the rod-shaped electric heaters 482 and 502 embedded in the respective choke bar adjustment bolts 48 and 50 are illustrated as the resin temperature fine adjustment means for the outermost layer. However, the present invention is not limited to this. Any means may be used as long as it can change the temperature of the molten resin flowing through the flow paths 34 and 38 based on a signal sent from the control device 80. As the outermost resin temperature fine adjustment means, for example, a heat transfer (release) heat device by oil circulation embedded in the choke bars 44 and 46 may be applied.

  In the above-described embodiment, the electric power applied to the rod-shaped electric heaters 482 and 502 is controlled only by the detection result of the thickness detection device 70, and as a result, the temperature of the molten resin flowing through the flow paths 34 and 38 is adjusted. Although the temperature sensors (not shown) are provided in the flow paths 34 and 38, the electric power of the rod-shaped electric heaters 482 and 502 is controlled in consideration of the temperature of the molten resin, and the melting in the flow paths 34 and 38 is good. The temperature of the resin may be adjusted.

  In the above-described embodiment, the method of producing the multilayer film 2 of two types and three layers of the outermost layer 4 -the inner layer 3 -the outermost layer 5 has been exemplified, but the outermost layer 4 -adhesive layer-inner layer 3 -adhesive layer -You may apply when manufacturing the multilayer film of the 3 types 5 layers of the outermost layer 5, or more. For example, in the case of producing a multilayer film of 3 types and 5 layers, first, an adhesive layer is merged on both sides of the inner layer 3 to form a laminate of adhesive layer-inner layer 3-adhesive layer, and then each adhesive The outermost layer 4 may be joined to the surface of the layer to form a laminated structure of the outermost layer 4 -adhesive layer-inner layer 3 -adhesive layer-outermost layer 5.

  Alternatively, first, the outermost layer 4 and the adhesive layer are merged to form an outermost layer 4-adhesive layer laminate and an adhesive layer-outermost layer 4 laminate. It is good also as a laminated structure of the outermost layer 4-adhesive layer-inner layer 3-adhesive layer-outermost layer 5 by making the adhesive layer of a laminated body oppose and merge.

FIG. 1 is a cross-sectional view showing an example of a multilayer film that can be formed by the apparatus or method of the present invention. FIG. 2 is a side sectional view showing an example of the multilayer extrusion molding apparatus of the present invention suitable for manufacturing the multilayer film of FIG. 3 is a front view of FIG. 2 (however, it is smaller than FIG. 2). FIG. 4 is a schematic view showing a main part near the choke bar and the choke bar adjusting bolt. FIG. 5 is a sectional view of the choke bar adjusting bolt.

Explanation of symbols

2. Multi-layer film (unstretched laminate)
3 ... Inner layer 4, 5 ... Outermost layer 20 ... Multi-layer extrusion molding device 22 ... Molding die 24 ... Die body 26, 28, 30 ... Manifold 32 ... Merge part 34, 36, 38 ... Channel 40 ... Lip part 41 ... Merge Road 42 ... Lip adjustment bolts 44, 46 ... Choke bars 48, 50 ... Choke bar adjustment bolts 482, 502 ... Rod-shaped electric heaters 52, 54, 56, 58 ... Electric heater 70 ... Thickness detection device 80 ... Control device

Claims (4)

A multilayer having (1) a die, (2) thickness detection means, and (3) control means, which is used to form a multilayer film of three or more layers having one or more inner layers between two outermost layers. In extrusion equipment,
(1) The dice includes two outermost layer manifolds supplied with molten resin, and one or more inner layer manifolds provided at a predetermined interval between the two outermost layer manifolds,
Two outermost flow paths and one or more inner flow paths that extend downstream from the manifold and eventually merge into one;
Two choke bars that are provided continuously along the width direction of each outermost layer flow path and adjust the gap between the flow paths;
Along the longitudinal direction of the choke bar corresponding to the width direction of each outermost layer flow path, the choke bars are arranged at a predetermined interval on the opposite side of the choke bar flow path, and the tip portion is in the axial direction with respect to the choke bar. A plurality of choke bar adjustment bolts supported so as to freely advance and retreat;
A resin temperature micro-adjustment means for finely adjusting the temperature of the molten resin flowing in each of the outermost layer flow paths;
A lip portion disposed on the downstream side of the merging portion of each of the outermost channel and the inner layer channel;
Each molten resin flowing out from each manifold through each flow path is joined at the joining portion to be multilayered, and can be continuously extruded as a multilayer film from the lip portion,
(2) The thickness detection means is capable of detecting the thickness of each outermost layer of the multilayer film extruded from the die,
(3) The control means adjusts the temperature of the outermost layer resin temperature so as to change the temperature of the molten resin flowing in each outermost layer flow path according to the detected thickness of each outermost layer of the multilayer film. Multi-layer extrusion molding apparatus that can control. The multilayer extrusion molding apparatus according to claim 1, wherein the outermost resin temperature fine adjustment means is a very fine rod heater embedded in each choke bar adjustment bolt. The manufacturing method of a multilayer film including the process of extruding a multilayer film of three or more layers using the multilayer extrusion molding apparatus of Claim 1 or 2. The manufacturing method of a multilayer stretched film including the process of extending | stretching the multilayer film extruded by the method of Claim 3.

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