JP2006188018A - Multilayer extrusion molding apparatus, multilayer film manufacturing method, and multilayer stretched film manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multilayer film extrusion molding apparatus capable of suppressing thickness unevenness of an inner layer portion of at least three multilayer films without increasing the size of the apparatus.
In the multilayer extrusion molding apparatus 20 of the present invention, electric heaters 54 and 56 for adjusting the temperature of the molten resin in the manifold 28 capable of forming the inner layer 3 of the multilayer film 2 are arranged closer to the manifold 28 side. It is. The electric heaters 54 and 56 are provided with heat insulating materials 60 and 62 in contact with the opposite side (manifold 26 and 30 side) of the manifold 28 to be heated. In the control device 80, the voltage amount of the electric heaters 54 and 56 is appropriately controlled based on the thickness data sent from the thickness detection device 70, and the temperature of the molten resin in the manifold 28 is controlled at a 0.1 ° C. level. Such a voltage adjustment signal is sent to the electric heaters 54 and 56. The thickness of the inner layer 3 of the multilayer film 2 is adjusted by changing the temperature of the molten resin in the manifold 28 and changing the flow rate of the molten resin flowing through the flow path 36.
[Selection] Figure 2

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). Although unstretched film) can be stretched without breaking, thickness unevenness may occur in the stretched film. As described above, the technique for suppressing the thickness unevenness of the inner layer portion of the multilayer film of at least three layers is desired not only for optical applications such as the above-mentioned retardation film but also in the fields of packaging films and protective films.

  Incidentally, Patent Document 2 discloses a multilayer extrusion molding apparatus. In this apparatus, an outermost layer manifold, an inner layer manifold, and an outermost layer manifold to which a plurality of molten resins having different properties extruded from a plurality of extruders are supplied are formed in this order. 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 the two outermost layer flow paths, a choke bar for adjusting the flow path gap and a plurality of choke bar adjusting bolts that can push and pull the choke bar from the opposite side of the flow path are arranged. The inner layer channel also includes a choke bar that adjusts the gap between the channel and a plurality of choke bar adjustment bolts that can push and pull the choke bar from the opposite side of the channel so that the inner layer channel is sandwiched therebetween. Located on the side.

  In the apparatus of Patent Document 2, since the choke bar and the choke bar adjusting bolt for adjusting the gap between the inner layer flow paths are provided for the inner layer flow path, the thickness of the molten resin flowing in the inner layer flow path is individually set. Although it is possible to adjust, there is a drawback that the apparatus becomes too large.

  In Patent Document 3, a 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. On both sides of the flow path, a pair of heaters are disposed at predetermined intervals across the flow path, and a plurality of heaters are intermittently disposed at predetermined intervals along the width direction of the flow path.

In the device of Patent Document 3, the resin discharged from the lip portion is heated and the temperature of the molten resin flowing in the flow path is adjusted by appropriately operating a pair of heaters arranged across the flow path. It is possible to reduce the thickness unevenness of the film.
JP-A-2-256603 JP-A-10-217310 JP-A-5-138718

  SUMMARY OF THE INVENTION An object of the present invention is to provide a multilayer film multilayer extrusion apparatus capable of suppressing thickness unevenness of an inner layer portion of at least three multilayer films without increasing the size of the apparatus, and a multilayer film manufacturing method using the apparatus. And the manufacturing method of the multilayer stretched film using the multilayer film manufactured by this method is provided.

  When the technique of Patent Document 3 is applied to multilayer extrusion molding as it is, one electric heater formed between a pair of flow paths not only adjusts the molten resin temperature in one target manifold, The present inventor has conceived that the molten resin temperature in other manifolds may be changed, and as a result, the thickness unevenness of the inner layer portion cannot be suppressed and a multilayer film cannot be obtained with a high yield.

Therefore, the inventors have
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 die 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;
Each of the outermost layer manifolds is provided between at least one outermost layer manifold that extends downstream from the outermost layer manifold and the inner layer channel, and the temperature of the molten resin in the inner layer manifold is adjusted. An inner layer resin temperature adjusting means to adjust;
A heat insulating material provided between the inner layer resin temperature adjusting means and the outermost layer flow path adjacent to the inner layer resin temperature adjusting means, and suppressing an influence on the temperature of the molten resin in the outermost layer manifold; ,
A lip portion disposed on the downstream side of the merging portion of the outermost layer flow path and the inner layer flow path,
Each molten resin that flows 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 can detect the thickness of the multilayer film extruded from the die, and
(3) The control means has a multilayer extrusion molding apparatus that can control the inner layer resin temperature adjusting means to change the resin temperature in the inner layer manifold according to the detected thickness of the multilayer film. It was.

  The multilayer extrusion molding apparatus of the present invention can suppress uneven thickness of the inner layer portion of at least three layers of multilayer film without increasing the size of the apparatus. When a multilayer film is produced using the apparatus, the thickness unevenness of the inner layer portion is reduced, and even when the obtained film is stretched, the thickness unevenness remains small and no retardation unevenness is produced.

  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 (which is smaller than FIG. 2), and FIGS. 4A and 4B are cross-sectional views taken along line IV-IV of FIG. 2 (however, FIG. 2). Is smaller than the above).

  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.

Multilayer Extrusion Apparatus An example of the multilayer extrusion apparatus of the present invention is shown in FIGS. As shown in FIGS. 2 and 3, the multilayer extrusion molding apparatus 20 of the present embodiment includes a molding die 22 that continuously extrudes the multilayer film 2 shown in FIG. 1, a thickness detection apparatus 70, and a control apparatus 80. And have.

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 commonly 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 vertical trapezoidal cross sections for adjusting the flow gap are arranged in the flow paths 34 and 38 except the flow path 36. The choke bars 44 and 46 are continuously extended from one end (one die width end) to the other end (the other die width end) in the width direction (paper surface direction in FIG. 2) of the flow paths 34 and 38. It extends. 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. 2) on the opposite side of the choke bars 44 and 46. 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. Then, by moving the bolts 48 and 50 back and forth (pushing and pulling) in the axial direction, the choke bars 44 and 46 move, the gap between the flow paths 34 and 38 is adjusted, and the molten resin flowing through the flow paths 34 and 38 The thickness distribution in the width direction (paper surface direction in FIG. 2) 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 distribute the gap amount between the flow paths 34 and 38 immediately before the merging portion 32. As a result, the thickness of each layer is determined in the width direction of the flow path, that is, the multilayer film. 2 in the width direction.

  In the vicinity of the lip portion 40, a plurality of lip adjustment bolts 42 that adjust the gap between the lip portions 40 are provided at predetermined intervals along the width direction of the lip portion 40 (the paper surface direction in FIG. 2).

  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.

  Inside the die body 24, electric heaters 52, 54, 56, 58 as resin temperature adjusting means are arranged so as to extend along the manifold 28 (inner layer manifold) and the flow path 36, respectively. The temperature of the molten resin in the manifolds 26, 28, and 30 (and thus the resin viscosity) can be controlled. Among them, the electric heaters 54 and 56 (both examples of inner layer resin temperature adjusting means) are provided close to both sides of the manifold 28 so as to sandwich the manifold 28.

  In the present embodiment, the electric heaters 54 and 56 can change the temperature of the molten resin in the manifold 28 based on a signal sent from the control device 80. When the temperature of the molten resin in the manifold 28 changes, the resin viscosity changes, and the flow rate of the molten resin flowing through the flow path 36 changes. As a result, the thickness can be controlled. Therefore, it is not necessary to provide many inner layer choke bars as in the prior art, and the apparatus can be miniaturized.

  Although not shown in the present embodiment, in addition to the electric heaters 52, 54, 56, 58, an electric heater for keeping the die body warm for heating the entire die body 24, for example, the electric heaters 52, 58, is used. You may provide in the outer side.

  In this embodiment, when the shortest distance between the electric heater 54 and the manifold 28 is D1, and the shortest distance between the electric heater 54 and the manifold 26 is D2, D1 <D2 (preferably D2−D1 ≧ 0.2 cm). The electric heater 54 is disposed so as to satisfy the above relationship. That is, the electric heater 54 is arranged closer to the manifold 28 side. In this way, when the electric heater 54 is operated, the amount of heat given to the molten resin in the manifold 26 can be reduced.

  When the shortest distance between the electric heater 56 and the manifold 28 is D3 and the shortest distance between the electric heater 56 and the manifold 30 is D4, the relationship of D3 <D4 (preferably D4-D3 ≧ 0.2 cm) is established. An electric heater 56 is arranged for satisfaction. That is, the electric heater 56 is arranged closer to the manifold 28 side. In this way, when the electric heater 56 is operated, the amount of heat given to the molten resin in the manifold 30 can be reduced.

  The electric heaters 52 and 58 are also preferably arranged from the outside of the manifolds 26 and 30 to be heated.

  The electric heaters 52, 54, 56, and 58 are preferably provided separately in the width direction (the paper surface direction in FIG. 2). As for the number of arrangement | sequences, 5 or more series are preferable, for example, it is preferable to install at intervals of about 65-75 mm (preferably about 70 mm). If the installation interval is too wide, the thickness cannot be controlled in the width direction, and if it is too narrow, the thickness cannot be controlled due to the interference of the electric heater. With reference to FIG. 4 (A) and FIG. 4 (B), the example of an arrangement | sequence of the electric heaters 52, 54, 56, and 58 is demonstrated. In the present embodiment, the electric heaters may be arranged in a staggered manner as shown in FIG. 4 (A) or in parallel as shown in FIG. 4 (B). preferable. The staggered arrangement has the advantage that the temperature adjustment section in the width direction can be reduced without increasing the number of electric heaters.

  There is no limitation in particular in the shape of each electric heater 52,54,56,58, For example, plate shape, a column shape, etc. are mentioned.

  When a cylindrical electric heater is used, if the diameter of the heater is reduced, the installation interval can be reduced and the number of installations can be increased accordingly. However, if the installation number is too large, the output of the electric heater tends to be insufficient. On the other hand, when the diameter of the heater is increased, interference is likely to occur. In these respects, 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, the electric heaters 54 and 56 are respectively provided with heat insulating materials 60 and 62 in contact with the opposite side (manifold 26 and 30 side) of the manifold 28 to be heated. Thereby, only the temperature of the molten resin in the target manifold can be controlled, and the molten resin that does not require heating is not heated excessively. The heat insulating materials 60 and 62 are not limited to be placed in contact with the electric heaters 54 and 56, but are brought into contact with the electric heater 54 between the electric heater 54 and the manifold 26 and the flow path 34. You may install without. The same applies to the electric heater 56. In addition, the heat insulating material should just be comprised with the material whose heat conductivity is lower than the constituent material of the die main body 24 mentioned above, The constituent material is not specifically limited.

  In the present embodiment, temperature sensors 64, 66, and 68 capable of measuring the temperature of the molten resin in the manifolds 28, 30, and 32 are arranged. As the temperature sensors 64, 66, and 68, for example, a thermocouple, a platinum resistance sensor, or the like can be used.

  In the present embodiment, when the shortest distance between the temperature measuring portion (tip portion) of the temperature sensor 66 and the manifold 28 is D5, the shortest distance D1 between the manifold 28 and the electric heater 54 is D5 ≦ (D1) / 2. It is preferable that the temperature sensor 66 is disposed at such a position.

  In the present embodiment, the temperature data of the molten resin in the manifold 30 measured by the temperature sensor 66 is sent to the control device 80 as a predetermined command signal. Similarly, the temperature data of the molten resin in the manifolds 28 and 32 measured by the other temperature sensors 64 and 68 may be sent to the control device 80 as a predetermined command signal. It is not always necessary in the invention.

  A thickness detecting device 70 capable of detecting the thickness of at least the inner layer 3 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 inner layer 3 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, a means for holding the received thickness data of the inner layer 3, a means for comparing the desired value and the measured value of the inner layer thickness to obtain a difference, and an integral value of the difference in proportion to the obtained difference. The electric power of the electric heater is controlled in proportion to the time difference or in proportion to the time change of the difference. When the temperature data from the temperature sensors 54 and 56 and the thickness data of the inner layer 3 from the thickness detector 70 are input to the control device 80, the data are compared with the data α and the data β, and the multilayer film 2 In order to bring the thickness of the inner layer 3 close to a desired value, a voltage adjustment signal for controlling the temperature of the molten resin in the manifold 28 at a level of, for example, 0.1 ° C. is sent to the electric heaters 54 and 56. It has become.

  When the voltage applied to the electric heater is increased, the electric heater temperature rises, and as a result, the temperature of the molten resin in the manifold 28 also rises. When the temperature of the molten resin in the manifold 28 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 as a result, the temperature of the molten resin in the manifold 28 is also lowered. When the temperature of the molten resin in the manifold 28 decreases, the resin viscosity increases and the resin does not flow easily. As a result, the resin thickness decreases.

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.

  At this time, the temperature of the molten resin in the manifold 28 is measured by the temperature sensor 66, and the temperature data measured here is sent to the control device 80 as a predetermined command signal.

  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 pushed out from the lip portion 40 passes through the thickness detector 70, and the thickness of the inner layer 3 of the multilayer film 2 is detected. The detected thickness data is controlled as a predetermined command signal. Sent to the device 80.

  In the control device 80, the relationship between the molten resin temperature in the manifold 28 -the voltage applied to the electric heaters 54, 56 and the relationship between the thickness of the inner layer 3 of the extruded multilayer film 2 -the voltage applied to the electric heaters 54, 56 is provided. Since the data β is input in advance, the temperature data sent from the temperature sensors 54 and 56 and the thickness data sent from the thickness detector 70 are compared with the data α and the data β, and the inner layer of the multilayer film 2 is compared. A voltage adjustment signal for controlling the temperature of the molten resin in the manifold 28 at, for example, a level of 0.1 ° C. is sent to the electric heaters 54 and 56 so that the thickness of 3 approaches a desired value.

  Specifically, when it is determined that the sent temperature data and thickness data are higher than the desired thickness of the multilayer film 2, the control device 80 decreases the amount of voltage applied to the electric heaters 54 and 56. A command signal like this is sent out. When the voltage applied to the electric heaters 54 and 56 decreases, the resin temperature in the manifold 28 decreases, the resin viscosity increases, and the resin does not flow easily. As a result, the resin thickness tends to decrease.

  Conversely, when it is determined that the sent temperature data and thickness data are lower than the desired thickness of the multilayer film 2, the control device 80 increases the amount of voltage applied to the electric heaters 54 and 56. Send command signal. When the voltage applied to the electric heaters 54 and 56 increases, the resin temperature in the manifold 28 increases, the resin viscosity decreases and the resin flows easily, and as a result, the resin thickness tends to increase.

  In the present embodiment, feedback control is performed as described above so that the thickness of the inner layer 3 of the multilayer film 2 passing through the thickness detection device 70 is kept at a desired value.

  In the present embodiment, the electric heaters 54 and 56 for adjusting the temperature of the molten resin in the manifold 28 that can form the inner layer 3 of the multilayer film 2 are arranged closer to the manifold 28 side. The amount of heat applied to the molten resin in the manifolds 26 and 30 that can form the outermost layers 4 and 5 can be reduced, interference between the electric heaters can be reduced, and independent control can be performed.

  Moreover, since the heat insulating materials 60 and 62 are wound around the electric heaters 54 and 56 on the opposite side (manifold 26 and 30 side) to the manifold 28 side for heating, the outermost layers 4 and 5 of the multilayer film 2 are wound. It is possible to appropriately adjust the temperature of the molten resin in the manifold 28 that can form the inner layer 3 of the multilayer film 2 while reducing the adverse effect on the molten resin in the manifolds 26 and 30 that can form the film.

  In addition, the control device 80 appropriately controls the voltage amounts of the electric heaters 54 and 56 based on the thickness data sent from the thickness detection device 70, and the temperature of the molten resin in the manifold 28 is at a 0.1 ° C. level. Since the voltage adjustment signal to be controlled is sent to the electric heaters 54 and 56, the thickness unevenness of the inner layer 3 of the multilayer film 2 can be efficiently suppressed.

  Further, the thickness of the inner layer 3 of the multilayer film 2 is not adjusted by changing the gap amount of the flow path 36 by the choke bar mechanism, but the temperature of the molten resin in the manifold 28 is changed. Since a mechanism that adjusts by changing the flow rate of the molten resin flowing through 36 is adopted, it is possible to efficiently suppress uneven thickness of the inner layer 3 of the multilayer film 2 without increasing the size of the apparatus.

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 electric heaters 52, 54, 56, and 58 are exemplified as the resin temperature adjusting means. However, the present invention is not limited to this, and the signal sent from the control device 80 is not limited thereto. Any means capable of changing the temperature of the molten resin in the manifold 28 may be used. As the resin temperature adjusting means, for example, a heat transfer (release) heat device by oil circulation may be applied.

  In the above-described embodiment, the power applied to the electric heaters 54 and 56 may be controlled only by the detection result of the thickness detection device 70, and as a result, the temperature of the molten resin in the manifold 28 may be adjusted. After providing the sensors 64, 66, and 68, the temperature of the molten resin in the manifold may be adjusted by controlling the electric power of the electric heater in consideration of the temperature of the molten resin.

  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). 4A and 4B are cross-sectional views taken along line IV-IV in FIG. 2 (however, they are smaller than FIG. 2).

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 ... Flow path 40 ... Lip part 41 ... Merge Road 42 ... Lip adjustment bolts 44, 46 ... Choke bars 48, 50 ... Choke bar adjustment bolts 52, 54, 56, 58 ... Electric heaters 60, 62 ... Insulation materials 64, 66, 68 ... Temperature sensors 70 ... Thickness detector 80 … Control device

Claims (6)

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;
Each of the outermost layer manifolds is provided between at least one outermost layer manifold that extends downstream from the outermost layer manifold and the inner layer channel, and the temperature of the molten resin in the inner layer manifold is adjusted. An inner layer resin temperature adjusting means to adjust;
A heat insulating material provided between the inner layer resin temperature adjusting means and the outermost layer flow path adjacent to the inner layer resin temperature adjusting means;
A lip portion disposed on the downstream side of the merging portion of the outermost layer flow path and the inner layer flow path,
Each molten resin that flows 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 can detect the thickness of the multilayer film extruded from the die, and
(3) The multilayer extrusion molding apparatus, wherein the control means can control the inner layer resin temperature adjusting means to change the resin temperature in the inner layer manifold according to the detected thickness of the multilayer film. The inner layer resin temperature adjusting means is provided so as to extend closer to the inner layer manifold side and the inner layer manifold and the flow path than the one outermost layer manifold side. 2. The multilayer extrusion molding apparatus according to 1. The heat insulating material is placed in contact with the outermost layer flow path side of the inner layer resin temperature adjusting means, or without being in contact with the inner layer resin temperature adjusting means, the inner layer resin temperature adjusting means and the outermost layer The multilayer extrusion molding apparatus of Claim 1 or 2 installed between the flow paths. The multilayer extrusion molding apparatus according to any one of claims 1 to 3, wherein an electric heater is used as the resin temperature adjusting means for the inner layer. 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 in any one of Claims 1-4. The manufacturing method of a multilayer stretched film including the process of extending | stretching the multilayer film extruded by the method of Claim 5.

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