JP2003112355A - Method and apparatus for manufacturing multilayer film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and an apparatus for manufacturing a multilayer laminated film in which a light having an arbitrary wavelength band is selectively reflected or transmitted by alternatively laminating many layers each having a high refractive index and many layers each having a low refractive index and controlling the ratio of the maximum value to the minimum value of the thicknesses of the respective layers. SOLUTION: The method for manufacturing the multilayer laminated film comprises the steps of individually melting a resin A and a resin B by an extruder, branching the molten resins to multiple layers via pores in a multilayer feeding block, then guiding the branched resin A and resin B to a flat channel partitioned by a parallel plate so as to alternatively inflow the resins A and B in 11 layers or more further introducing the resins to a combining unit 12 in the block, then extruding the resins A and B in a sheet-like state in a direction to become the multilayers in the thickness direction from a die 13 continued to the unit 12, cooling to solidify the resin at a casting drum 15, and at least unidirectionally stretching the unstretched film 16 in longitudinal and lateral directions. The method further comprises the steps of controlling the temperature distribution of the block, and thereby regulating the thicknesses of the layers A and B of the multilayer film in the range of 0.01 to 0.5 μm.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method and an apparatus for producing a multilayer film. More specifically, the present invention relates to a method and an apparatus for producing a multi-layer film capable of efficiently controlling the thickness distribution of a multi-layer film laminated with 11 or more layers, and particularly to a multi-layer film in which a high refractive index layer and a low refractive index layer are alternately laminated. The present invention relates to a method and an apparatus for producing a multilayer film capable of controlling the thickness and efficiently producing a multilayer film capable of selectively reflecting or transmitting light in an arbitrary wavelength band.

[0002]

2. Description of the Related Art A multi-layer film is an optical interference film that selectively reflects or transmits light of a specific wavelength due to structural optical interference between layers having a high refractive index and a low refractive index, for example. Become. By making the wavelength region of light that is selectively reflected or transmitted in the visible light region, such laminated films are increasingly used as reflective polarizing plates, color-developing films, metallic luster films, and reflection mirror films. In addition, in the near-infrared reflective film that can be used for the image display panel surface of plasma display etc.,
In order to prevent malfunction of peripheral devices, it is necessary to absorb near infrared rays in a wavelength range having a certain width (820 to 980 nm). In addition, a window film for cutting solar radiation or the like can also reduce solar radiation by cutting the near infrared region.

For such a laminated film, a film in which the thickness of each layer is changed is disclosed in JP-A-2000-329.
It is proposed in Japanese Patent No. 935, etc. However, in the case of producing a laminated film in which each layer has a thickness change, in a feed block of a type in which a resin is branched into multiple layers with pores,
There is a problem because a dedicated feed block having a complicated structure in which the width of the pores gradually changes according to the amount of change in thickness must be used, and its production involves technical difficulties and great cost.

Further, when it is desired to change the amount of change in the thickness of each layer or to make the thickness of each layer uniform, it is necessary to newly create a dedicated feed block for each layer, which causes a problem of enormous cost. . In addition, it is necessary to replace the feed block according to the type of the multilayer film on the film formation, which causes problems such as time-consuming work and poor film formation efficiency.

[0005]

The object of the present invention is to solve the above-mentioned problems and to control the thickness distribution of a multilayer film efficiently, and in particular, a multilayer in which a large number of layers having a high refractive index and a plurality of layers having a low refractive index are alternately laminated. It is an object of the present invention to provide a method and an apparatus for producing a multilayer film, which can efficiently produce the film.

[0006]

The object of the present invention is, according to the present invention, to provide a multilayer film in which (1) an A layer made of a resin A and a B layer made of a resin B are alternately laminated in 11 or more layers. In the manufacturing method, the resin A and the resin B are separately melted by an extruder, and each molten resin is branched into multiple layers by the pores in the multilayer feed block, and then the branched resin A and the resin B are alternately laminated in 11 layers or more. After being led to a flat flow path partitioned by parallel plates so as to flow in, and further led to the confluence in the multi-layer feed block, a sheet-like shape in which resin A and resin B are multilayered in the thickness direction from the die that follows To a non-stretched film by cooling and solidifying with a casting drum, and stretching the unstretched film in at least one of the machine direction and the transverse direction. It can be achieved by the method for producing a multilayer film characterized by adjusting the thickness of the A layer and B layer of the multilayer film in the range of 0.01~0.5μm by controlling.

As a further preferred embodiment of the present invention,
(2) By adjusting the temperature distribution in the multilayer feed block, the thickness of the thickest layer of layers A and B of the multilayer film divided by the thickness of the thinnest layer is adjusted to be 1.2 or more (1 ) The method for producing a multilayer film according to
(3) Temperature difference of the multi-layer feed block is 10 to 100 ° C
The method for producing a multilayer film according to (2), which is in the range of
(4) By controlling the temperature difference of the multilayer feed block to be less than 10 ° C., the value obtained by dividing the thickness of the thickest layer of layers A and B of the multilayer film by the thickness of the thinnest layer is less than 1.2. In the method for producing a multilayer film according to (1) to be adjusted, (5) in the unstretched film, the difference between the in-plane direction refractive index of the resin A and the in-plane direction refractive index of the resin B is 0.005 or more (1 ) The method for producing a multilayer film according to
(6) In the film stretched in at least one direction, the difference between the in-plane refractive index of the resin A and the in-plane refractive index of the resin B is 0.005 or more, and the method for producing a multilayer film according to (1). , (7) Resin A is polyethylene-2,6-
The method for producing a multilayer film according to (1) containing naphthalate as a main component, (8) the resin B is polyethylene-2,6-
The method for producing a multilayer film according to (7), which contains a mixture of naphthalate and polyethylene terephthalate as a main component,
(9) The method for producing a multilayer film according to (7), wherein the resin B has a polyethylene terephthalate copolymer having a melting point of 210 to 245 ° C as a main component, and (10) the copolymerization component of the polyethylene terephthalate copolymer is ethylene isophthalate. The method for producing a multilayer film according to (9) can be mentioned.

Another object of the present invention is to provide (11) a method for producing a multi-layer film in which 11 or more layers of resin A and B of resin B are alternately laminated. Separately melted by an extruder, branched each molten resin into multiple layers by the pores in the multi-layer feed block, and then flattened with parallel plates so that branched resin A and resin B alternately flow into 11 or more layers. To a confluent part in the multi-layer feed block and then extruded into a sheet form from the die following that in which the resin A and the resin B are multi-layered in the thickness direction, and cooled and solidified by a casting drum. An unstretched film, which is a method for producing a multilayer film in which the unstretched film is stretched in at least one of the longitudinal direction and the transverse direction. Using the thickness of the A layer and B layer of the film production method of the multilayer film and adjusting the range of 0.01 to 0.5 [mu] m, it can be achieved by a multilayer feed block having a control means of the temperature distribution.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below with reference to the drawings. FIG. 1 is a plan view of a multi-layer feed block illustrating one embodiment of the present invention. FIG. 2 is a sectional side view showing a flow passage cross section in the multilayer feed block of the molten resin A for A layer, and FIG. 3 is a sectional side view showing a flow passage cross section in the multilayer feed block of molten resin A for B layer. is there. Figure 4 shows the molten resin in a multi-layer feed block extruded from a die
It is a schematic diagram showing arrangement of each device at the time of cooling with a casting drum and making it an unstretched film.

In FIGS. 1 to 3, 1 and 1a are upper and lower restraining blocks, 2 and 2a are upper and lower branch blocks, 3 is a merging block, 4a to 4d are upper heaters, and 5a to 5d are lower. Side heaters, 6 and 6a are on the upper side, lower manifolds, 7 and 7a are on the upper side,
Lower side pores, 8 is a flat flow path partitioned by parallel plates, 9 is a parallel plate, a is the flow direction of the molten resin A forming the A layer, and b is the flow direction of molten resin B forming the B layer. Is.

In FIG. 4, 10 is a conduit for molten resin B to the multilayer feed block, 11 is a conduit for molten resin A to the multilayer feed block, 12 is a multilayer feed block, 13 is an extrusion die, and 14 is a die. An extruded sheet, 15 is a casting drum, and 16 is an unstretched film.

Each of the feed block diagrams of FIGS. 1 to 3 illustrates one embodiment, and the pores 7 and the parallel plates 9 and the pores 7a and the parallel plates 9 are joined vertically. However, in order to average the residence time due to the path difference of the resin, they may be joined at an angle at an angle, and either the flow direction a of the resin A or the flow direction b of the resin B may be straightened. It is also possible to use a flow path.

The molten resin B for layer B introduced into the feed block is once spread in the width direction in the manifold 6,
Through the pores 7 arranged in a line, the flat channels 8 partitioned by the parallel plates 9 are reached. On the other hand, the molten resin A for the layer A similarly reaches the flat flow path 8 partitioned by the parallel plate 9 through the manifold 6a and the pores 7a. In the flat flow path 8 (gap between each member of the parallel plate 9) partitioned by the parallel plate 9, the resin A has already been used.
And the resin B are alternately arranged, and thereafter, the molten resins of the layer A and the layer B are alternately laminated in a fluid state by merging in the void portion of the merging block 3 at the exit of the flat flow path 8 partitioned by the parallel plate. It

If the widths of the pores 7 and 7a are too narrow, the flow rate of each layer is sensitive to the width dimension, so that highly precise processing is required. Since the flow rate tends to vary, 0.2-2 mm is preferable,
0.5-1 mm is more preferable. If the pores are made to have substantially the same size, for example, if the temperature is controlled so that the temperature difference in the width direction of the feed block is less than 10 ° C. (isothermal state), the multilayer lamination in which the thickness of each layer is uniform is achieved. A film can be formed, or when the thickness of each layer is changed, it can be dealt with by the temperature control described later. The length of the pores is preferably 5 to 20 mm, more preferably 7 to 12 mm, because it cannot be processed if it is too long in view of electric discharge machining with a wire.

If the wall thickness of the parallel plate 9 is too thin, it will be easily damaged by maintenance, and it will bend due to the internal pressure of the resin during operation. If it is too thick, the width of the feed block will become wider and the size will increase if the number of layers is increased. 0.3 to 4 mm
Is preferable, and 0.5-2 mm is more preferable. Parallel plate 9
Also, the length of 5 is hard to break, and from the viewpoint of earning an appropriate pressure loss,
40 mm is preferable and 10-20 mm is more preferable.
The arrangement pitch of the parallel plates 9 is preferably matched with the width dimension of the pores 7 and 7a. By incorporating the parallel plates 9 without steps, it is possible to form a good film without resin retention deterioration.

As can be seen from the above, the feed blocks 1, 1a (upper and lower restraining blocks), 2, 2a
(Upper and lower branch blocks), 3 (merging block), 9
Each block of (parallel plate) requires high-precision processing, but has a weak strength structure, and a suitable material is hard SUS630 or SUS420 (J2). If the resin flow surface of each block is finished to 0.6 S or more, a multilayer laminated film having no line defects can be formed.

In the present invention, in order to change the thickness of each layer,
The temperature of the heaters 4a to 4d is controlled independently to give a temperature difference in the width direction of the feed block. This results in pores 7,
7a and the parallel plate 9 also individually have a temperature distribution in the width direction, and the molten resin of each of the layers A and B flowing in contact with them has a melt viscosity that changes mainly at the contact surface with the metal, resulting in pressure loss. Changes, and as a result, the flow rate changes, and the thickness of each layer can be controlled. Heaters 5a-5d are replaced by heaters 4a-4d
When the temperature control is performed in correspondence with the above, the thickness of each of the A layer and the B layer can be changed at substantially the same ratio.
For example, when it is desired to make the thickness change on the A layer side extremely or to make it uniform, the heaters 5a to 5d may be controlled independently of the heaters 4a to 4d.

In the method for producing a multilayer film of the present invention, by controlling the temperature distribution in the multilayer feed block,
The value obtained by dividing the thickness of the thickest layer of the A layer and the B layer in the multilayer film by the thickness of the thinnest layer (hereinafter sometimes referred to as "thickness ratio") can be adjusted to 1.2 or more, Further, the thickness ratio can be adjusted to be less than 1.2. The thickness ratio of the multilayer film can be selected according to the purpose of use for which the multilayer film is used.

When a multi-layer film having a thickness ratio of 1.2 or more is obtained, the temperature control range of the heater is kept at the upper limit.
The temperature difference between the temperature of the block and the lower holding block 1a is 10 to 100.
It is preferable to control the temperature to ° C. The upper limit of this temperature difference is 10
If it exceeds 0 ° C, the feed block may be thermally deformed. Therefore, the upper limit of the temperature difference is more preferably 60 ° C. In addition, although the case where the number of heaters is four on one side is illustrated in FIG. 1, it is possible to finely control the thickness of each layer by arranging more heaters than this in view of the characteristics of the present invention.
The purpose can be achieved if there are more than one piece. As a heating method,
A conventionally known and used method can be used, and a contact type heater such as an aluminum casting heater or a band heater, a non-contact type heater such as an IR infrared heater, or a heating method using a vapor heating medium can be exemplified. Further, cooling may be used in combination with these heating methods, or the temperature may be controlled by locally cooling with a fan or hot water.

In the present invention, when the multilayer film is used as a near-infrared cut film for solar radiation cutting, a reflection type polarizing plate or a coloring film, a metallic luster film, a reflection mirror film, etc., the thickness ratio is 1.2 or more. It is preferable that the multilayer feed block has a temperature distribution so that This thickness ratio is preferably 1.5 or more in order to achieve the purpose of selectively reflecting light in a wider wavelength band, which was not possible with the conventional laminated film, and is preferably 1.5 or more.
It is more preferable to set it as above.

Either the thickness of the A layer or the B layer is continuously changed by the temperature control described above, or slit processing or a heat insulating material is inserted into the feed block to increase the independence of the temperature control. Therefore, the thickness of each layer may be changed stepwise in several steps. In this case, there is an advantage that mutual interference of heat is reduced and temperature control is easily stabilized.

For the above purpose, the thickness ratio of the multilayer film is preferably 1.2 or more, but the thickness of the thickest layer of A layer in the multilayer film is divided by the thickness of the thinnest layer of A layer. It is more preferable that the value (hereinafter sometimes referred to as "thickness ratio of A layer") is 1.2 or more, and the thickness of the thickest layer of the B layer in the multilayer film is the thickness of the thinnest layer of the B layer. It is more preferable that the divided value (hereinafter, also referred to as “B layer thickness ratio”) be 1.2 or more at the same time.

The laminated state of the A layer and the B layer in the present invention is as follows.
Alternating layers A and B alternately for a total of 11 layers or more, preferably 31 layers
It is a laminate of more than one layer. If the number of layers is less than 11, the selective reflection due to multiple interference is small and a sufficient reflectance cannot be obtained. The upper limit of the number of layers is preferably 301 from the viewpoint of productivity. Dedicated feed blocks may be prepared individually according to the number of layers of the multilayer laminated film, but in the case of the device of the present invention and a device for branching into multiple layers by the pores, the resin inlet of the pores may be selected according to the required number of layers. It is more advantageous in terms of cost to insert an inner deckle to block the number of layers to control the number of layers.

Further, each of the A layer and the B layer must have a thickness of 0.01 to 0.5 μm in order to selectively reflect light by optical interference between the layers.

When a multilayer film having a thickness ratio of less than 1.2 is obtained, that is, when a multilayer film in which the thickness of each layer is uniform, heaters 4a to 4d and heaters 5a to 5d are used.
Control the temperature difference in the width direction of the feed block by 10 ° C.
Be less than. As a result, the temperature becomes uniform in the width direction of the pores 7 and 7a and the parallel plate 9, and the molten resin of each of the layers A and B flowing in contact with them has a uniform melt viscosity, so that the thickness of each layer is uniform. It is possible to obtain various multilayer films.

The multilayer laminated film in the present invention is, for example, A containing polyethylene-2,6-naphthalate as a main component.
The layer-forming polymer and the layer-B forming polymer are alternately laminated in two layers by the feed block illustrated in the figure, and are spread on the die that follows while maintaining the laminated state. The sheet extruded from the die is cooled and solidified by a casting drum to be an unstretched film. The unstretched film is stretched in a longitudinal and / or transverse direction at a predetermined temperature, heat-treated at a predetermined temperature, optionally heat-relaxed, and wound.

By the way, the multilayer laminated film of the present invention is stretched in at least one direction, preferably biaxially stretched. However, in the present invention, a polymer having a high refractive index is selected for the A layer side, and therefore the stretching temperature is Is preferably carried out within the range of (Tg + 50) ° C. from the glass transition point (Tg) of the resin of layer A. In the case of uniaxial stretching, the stretching ratio is 2 to 10 times, and the stretching direction may be vertical or horizontal. In the case of biaxial stretching, the area magnification is 5 to 25 times. The larger the draw ratio, the more preferable that the variation in the surface direction of each of the A layer and the B layer becomes absolutely small due to the thinning due to the drawing, and the optical interference of the multilayer laminated film becomes uniform in the surface direction. As the stretching method, sequential biaxial stretching and simultaneous 2
Known stretching methods such as axial stretching, tubular stretching and inflation stretching are possible, but sequential biaxial stretching is preferable in terms of productivity and quality.

Further, the stretched film is preferably stabilized by heat treatment for thermal stabilization. The heat treatment temperature is preferably higher than (melting point of layer B −30) ° C. and lower than (melting point of layer A −30) ° C.

Furthermore, in the multilayer laminated polyester film of the present invention, the glass transition point of the polymer forming the A layer is usually higher than that of the polymer forming the B layer when the B layer is present on either one of the both end layers. When heating with a roll or the like for stretching, the temperature cannot be raised to the stretching temperature necessary for stretching the layer A, or the temperature cannot be raised to prevent the surface layer B from melting during heat setting. Problems such as insufficient thermal stability may occur. On the other hand, when the A layer is in both end layers, the thermally unstable B layer is located in the inner layer, so that it can be produced at a sufficient stretching temperature or heat setting temperature. Those located in both end layers are preferable. The both end layers referred to in the present invention are the outermost layers in the direction perpendicular to the surface direction of the multilayer laminated film.

In addition, a step of applying a coating liquid and drying may be provided for the purpose of, for example, the step of producing the multilayer laminated film of the present invention, or the purpose of imparting functionality to the surface of the film after the production.

In the present invention, the resin A constituting the layer A is a thermoplastic resin containing a stretchable polymer as a main component, for example, a fragrance such as polyethylene terephthalate, polyethylene-2,6-naphthalate or polybutylene terephthalate. Group polyesters, polyolefins such as polyethylene, polypropylene, polyvinyls such as polystyrene, polyamides such as nylon 6 (polycaprolactam), nylon 66 (poly (hexamethylenediamine-co-adipic acid)), such as bisphenol A polycarbonate A homopolymer such as aromatic polycarbonate or polysulfone or a resin containing a copolymer thereof as a main component can be used.

Among the above-mentioned thermoplastic resins, aromatic polyesters, polyolefins, which are capable of molecular orientation by stretching,
Polyamide is preferable, and polyethylene-2,6-naphthalate, which has excellent optical, mechanical and thermal properties when the molecules are biaxially oriented, is particularly preferable.

In the present invention, when a resin mainly composed of polyethylene-2,6-naphthalate is used as the resin A constituting the layer A, copolymerized polyethylene-2,6-containing ethylene-2,6-naphthalate units as main constituents. A composition mainly containing naphthalate or polyethylene-2,6-naphthalate can be used. The term "mainly" means that the proportion of ethylene-2,6-naphthalate units in the copolymer or composition accounts for 85 mol% or more based on all components. When a copolymer is used, its copolymerization component is preferably 15 mol% or less, more preferably 2 mol% or less. The copolymerization component may be a dicarboxylic acid component or a glycol component, and examples of the dicarboxylic acid component include aromatic dicarumbonic acid such as isophthalic acid, phthalic acid and naphthalenedicarboxylic acid; adipic acid, azelaic acid and sebacine. Acids, aliphatic dicarboxylic acids such as decanedicarboxylic acid, alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid, and the like. Examples of glycol components include aliphatic diols such as butanediol and hexanediol; cyclohexanedimethanol Examples thereof include alicyclic diols and the like.

The resin B in the present invention is a thermoplastic resin having a refractive index different from that of the thermoplastic resin constituting the layer A, and has a refractive index lower than that of the resin A by 0.005 or more, more preferably 0.02 or more. Low thermoplastic resins Low resins can be mentioned. The term "refractive index" as used herein refers to the in-plane refractive index of a sheet-shaped or film-shaped resin.

In the present invention, when polyethylene-2,6-naphthalate is used as the resin A constituting the layer A, the resin B is preferably a resin having a lower refractive index than that of polyethylene-2,6-naphthalate. It is preferable that the resin has a refractive index lower than that of polyethylene-2,6-naphthalate by 0.005 or more, and particularly a refractive index of 0.02.
It is preferable that the resin is low. As such a thermoplastic resin, the following three types (1) to (3) can be preferably mentioned.

(1) A mixture of polyethylene-2,6-naphthalate and polyethylene terephthalate (2) Syndiotactic polystyrene (3) A polyethylene terephthalate copolymer having a melting point of 210 ° C to 245 ° C.

Among these, the B layer is polyethylene-
A mixture of 2,6-naphthalate and polyethylene terephthalate or a mixture of syndiotactic polystyrene is preferable, and in particular, the mixture of the B layer is preferable because the refractive index of the B layer can be easily changed. The polymer constituting the B layer in
(1) The case of a mixture of polyethylene-2,6-naphthalate and polyethylene terephthalate will be described in detail.

When the polymer constituting the layer B in the present invention is a mixture of polyethylene-2,6-naphthalate and polyethylene terephthalate, the mixing ratio of both is 5:95 to 95: 5 by weight, particularly 20: 80 ~
It is preferably in the range of 80:20. In the mixing ratio, the ratio of polyethylene terephthalate is 5% by weight.
When the proportion of polyethylene-2,6-naphthalate exceeds 95% by weight, the difference in refractive index from the layer A tends to be insufficient, while when the proportion of polyethylene terephthalate exceeds 95% by weight or polyethylene-2. When the proportion of 6-naphthalate is less than 5% by weight, the difference in melt viscosity between the layer A and the layer A becomes excessively large, and it becomes extremely difficult to maintain the multilayered state.

By the way, since the refractive index of the B layer can be adjusted by changing the mixing ratio of polyethylene terephthalate and polyethylene-2,6-naphthalate, it is necessary to prepare various polymers for adjusting the reflectance. There is no. In other words, there is an advantage that a multilayer laminated stretched film having various reflectances can be easily obtained only by adjusting the mixing ratio in the mixture. In addition, when the polymer of the layer B is copolymerized, it becomes low in crystallinity, and therefore a special extruder or dryer may be required for extruding the molten polymer. However, in the present invention, since it is a mixture, there is an advantage that the decrease in crystallinity is small and the above-mentioned special equipment is not required.

The polyethylene terephthalate and polyethylene-2,6-naphthalate in the mixture forming the layer B will be described in more detail.

The polyethylene-2,6-naphthalate in the mixture is polyethylene-2,6-naphthalate homopolymer, or at least 80 mol%, preferably 90 mol% or more of all repeating units are ethylene-2,6-. It is a copolymer occupied by naphthalate. Among these, the above homopolymers are preferable. Examples of the copolymerization component that constitutes the above copolymer include other aromatic carboxylic acids such as terephthalic acid, isophthalic acid, and 2,7-naphthalenedicarboxylic acid; adipic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, and the like. Such as aliphatic dicarboxylic acids; acid components such as alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid; fatty acid diols such as butanediol and hexanediol; glycol components such as alicyclic diols such as cyclohexanedimethanol. it can.

The polyethylene terephthalate in the mixture is a polyethylene terephthalate homopolymer or a copolymer in which at least 80 mol%, preferably 90 mol% or more of all repeating units are occupied by ethylene terephthalate. Among these, the above homopolymers are preferable. Examples of the copolymerization component constituting the above-mentioned copolymer include other aromatic carboxylic acids such as isophthalic acid and 2,7-naphthalenedicarboxylic acid; aliphatic compounds such as adipic acid, azelaic acid, sebacic acid and decanedicarboxylic acid. Dicarboxylic acids; aliphatic diols such as cyclohexanedicarboxylic acid; glycol components such as alicyclic diols such as cyclohexanedimethanol. Among these copolymers, the copolymer of isophthalic acid is preferred.

By the way, the melting point of the mixture forming the B layer is lower than the melting point of the original polymer, but two peaks derived from each polymer are formed. Among the melting point peaks of the mixture forming these B layers, the higher peak temperature is 220 ° C to 265 ° C, and further 240 to 26 ° C.
Those in the range of 0 ° C. are preferable. Further, the temperature difference between the melting point of the polymer forming the A layer and the higher melting point peak of the mixture forming the B layer is preferably at least 10 ° C. and more preferably at least 20 ° C. If this difference in melting point is at least 10 ° C., the difference in orientation due to heat treatment tends to increase,
Easy to make a difference in refractive index.

In the present invention, the stretched film is
For thermal stabilization, it is preferable to perform a heat treatment (heat setting treatment), and when a mixture of polyethylene-2,6-naphthalate and polyethylene terephthalate is used as the polymer constituting the layer B, the layer A is used. Based on the melting point (TmA) of the polymer of (TmA-60) ° C ~
It is preferable to perform heat treatment at a temperature in the range of (TmA-10) ° C.

In the present invention, at least one of the polymers constituting the layer A or the layer B has an average particle size of preferably 0.01 to 2 in order to improve the film winding property.
μm, more preferably 0.05 to 1 μm, most preferably 0.1 to 0.3 μm, preferably 0.001 to 0.5% by weight, more preferably 0.0 to 0.5% by weight of the inert particles.
It is contained at a rate of 05 to 0.2% by weight. If the average particle size of the inert particles is less than 0.01 μm or the content thereof is less than 0.001% by weight, the improvement of the film winding property tends to be insufficient, while the average particle size of the inert particles exceeds 2 μm, or If the content exceeds 0.5% by weight, the deterioration of the optical characteristics due to the particles is likely to be remarkable, and the light transmittance of the entire film may decrease. The light transmittance is preferably 70% or more, and if it is lower than this, the performance is insufficient for optical applications.

Examples of such inert particles include inorganic inert particles such as silica, alumina, calcium carbonate, calcium phosphate, kaolin and talc, organic inert materials such as silicone, crosslinked polystyrene and styrene-divinylbenzene copolymer. Active particles can be mentioned.

[0047]

EXAMPLES The present invention will be further described below with reference to examples. The physical properties in the examples were measured by the following methods.

(1) Thickness of Each Layer (Maximum Thickness and Minimum Thickness) A sample was cut into a triangle and fixed in an embedding capsule.
Embed with epoxy resin. Then, after embedding the sample into a thin film section with a thickness of 50 nm in a cross section parallel to the longitudinal direction with a microtome (ULTRACUT-S), it was observed with a transmission electron microscope at 100 kv of accelerated electrons.
The thickness of each layer was measured from the projected image and photographed. Regarding the layers A and B, the thickest layer of each layer was the maximum thickness, and the thinnest layer was the minimum thickness.

(2) Reflectance Using a spectrophotometer MPC-3100 manufactured by Shimadzu Corporation, the relative specular reflectance with respect to the aluminum-deposited mirror at each wavelength is measured in the wavelength range of 350 to 2100 nm. The maximum reflectance among the measured reflectance is the maximum reflectance.

(3) Peak inverse value width The same measurement as the wavelength maximum reflectance is carried out, and the values on the short wavelength side and the long wavelength side of the wavelength which is the half-value width of the maximum reflectance are respectively defined on the short wavelength side and the long wavelength side. The wavelength range was used.

(4) Temperature difference of heaters In FIG. 2, each heater (4a-4d, 5a-5d)
Thermocouples were inserted (not shown) into the upper and lower restraining blocks corresponding to, and the difference between the maximum value and the minimum value among the temperatures at each measurement point was taken as the temperature difference.

(5) Sample with a refractive index of sodium D line (589 nm) as a light source, methylene iodide as a mount solution, and an Abbe refractometer equipped with a polarizing plate at 25 ° C. and 65% RH. The refractive index (nMD) in the longitudinal direction and the refractive index (nTD) in the width direction of the sample were measured, and the average value of nMD and nTD was defined as the in-plane refractive index (nAve). However, in the stretched film of the present invention, two lines corresponding to resin A and resin B are visible, so the high refractive index side is the A resin and the low refractive side is the B resin. The sample was prepared as follows.

(Refractive Index of Unstretched Film of Resin A) The resin A was supplied to both the A layer extruder and the B layer extruder used in each example and melted, and the molten resin A was used in each example. Introduced into the multi-layer feed block used in, the polymer is branched into multi-layers in the multi-layer feed block, and then layers A are alternately laminated at the confluence of the multi-layer feed block, and then guided to a die and cast on a casting drum. Then, an unstretched film in which layers A were laminated was prepared. The in-plane refractive index of this sheet was measured and used as the refractive index of the unstretched film of resin A.

(Refractive Index of Unstretched Film of Resin B) Same as the above measurement of the refractive index of Resin A, except that the resin B was supplied to both the extruder for layer A and the extruder for layer B used in each example. Then, the refractive index of the unstretched film of the resin B was measured.

(Refractive Index of Stretched Film) The in-plane refractive index of the stretched film obtained in each Example was measured.

Example 1 First, in the apparatus shown in FIGS.
The number of pores 7a in the A layer is 151, and the width is 0.5.
SUS6 having a size of 5 mm, a depth of 7 mm, the number of pores 7a of the B layer is 150, the width is 0.55 mm, and the depth is 7 mm.
Multi-layer feed block made of 30 and manifolds 6, 6a
Inner deckles made of aluminum for closing the pores were inserted at both ends of the layer to form 31 layers of A layer and 30 layers of B layer.

Further, the resin A has an intrinsic viscosity (orthochlorophenol, 35 ° C.) of 0.62 dl / g polyethylene-2,6-naphthalate (PEN), and the resin b has an intrinsic viscosity (orthochlorophenol, 35 ° C.). 0.63dl /
g polyethylene terephthalate (PET) was prepared. Then, the spherical silica particles (average particle size:
0.12 μm, ratio of major axis to minor axis: 1.02, average deviation of particle diameter: 0.1) 0.11 wt% was added as resin for layer A, and PEN and PET containing no inactive particles 5
The mixture for the weight ratio of 0:50 was prepared as the resin for layer B.

The resin for layer A was dried at 160 ° C. for 3 hours, and the mixed resin for layer B was dried at 160 ° C. for 3 hours, and then fed to the extruder for layer A and the extruder for layer B to melt and melt. The resulting resin A and resin B are introduced into the multi-layer feed block, the layer A polymer is branched into 31 layers and the layer B polymer is branched into 30 layers in the multi-layer feed block. And B layers are alternately laminated, and while maintaining the laminated state, they are guided to a die head and cast on a casting drum to gradually change the thickness of each layer, so that the A layer and the B layer are alternately laminated. A laminated unstretched film was prepared.

At this time, the heaters 4a to 4d are provided on one side of the heater 4a-4d.
a is 285 ° C., 4d is 315 ° C. and the temperature difference is 30 ° C., the heaters 5a to 5d are adjusted in the same manner, and the extrusion amount of the A layer and the B layer is 1: 0.8. Was adjusted. This unstretched laminated sheet was stretched 3.5 times in the longitudinal direction at a temperature of 150 ° C., further stretched 5.5 times in the transverse direction at a stretching temperature of 155 ° C., and heat set at 230 ° C. for 3 seconds. went. Table 1 shows the physical properties of the obtained multilayer film. Incidentally, the refractive index of the resin A, which was separately measured, was 1.647 for the unstretched film and 1.717 for the stretched film, and the refractive index of the resin B (resin H) was 1.612 for the unstretched film, and the stretched film. Was 1.651.

[Examples 2 to 6] Multilayer films were obtained in the same manner as in Examples except that the combination of the heater temperature, the number of layers and the resin was changed as shown in Table 1. Table 1 shows the results of measuring the physical properties of the obtained film.

[0061]

[Table 1]

The resins for layer B shown in Table 1 are as follows. Resin H: PEN and PET containing no inert particles 50:
Mixed in a weight ratio of 50.

Resin I: PET copolymer obtained by copolymerizing 12 mol% of isophthalic acid containing no inert particles. The refractive index of this resin was 1.590 for the unstretched film and 1.630 for the stretched film.

[0064]

According to the present invention, by controlling the temperature of the multi-layer feed block, the thickness of each layer of the multi-layer laminated stretched film can be easily varied, and the multi-layer laminated stretched film selectively reflects light over a wide wavelength range. Can provide film.

[Brief description of drawings]

FIG. 1 is a plan view of a multi-layer feed block showing one embodiment of the present invention.

FIG. 2 is a sectional side view showing a channel cross section of an A layer, showing one embodiment of the present invention.

FIG. 3 is a sectional side view showing a channel cross section of a B layer, showing one embodiment of the present invention.

FIG. 4 is a perspective view showing an arrangement of a multi-layer feed block, an extrusion die, a cooling drum, etc. in one embodiment of the present invention.

[Explanation of symbols]

1, 1a: Upper and lower restraining blocks 2, 2a: upper and lower branch blocks 3: Confluence block 4a-4d: Upper heater- 5a-5d: Lower heater 6, 6a: upper and lower manifolds 7, 7a: upper and lower pores 8: Flat flow path partitioned by parallel plates 9: Parallel plate 10: Conduit of molten resin B to multi-layer feed block 11: Conduit of molten resin A to multi-layer feed block 12: Multi-layer feed block 13: Extrusion die 14: Sheet extruded from die 15: Casting drum 16: Unstretched film a: Flow direction of the molten resin A forming the A layer b: Flow direction of the molten resin B forming the B layer

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) // B29K 67:00 B29K 67:00 B29L 7:00 B29L 7:00 9:00 9:00 11:00 11:00 F-term (reference) 4F100 AK41A AK41B AK42B AL05B BA02 BA03 BA04 BA05 BA06 GB90 JA04B JN06 JN08 JN18 4F207 AA26 AG01 AG03 AR06 AR12 KA01 KA17 KB26 KL65 KL84 KW41 4J002 CF05X CF08W

Claims (11)

[Claims] 1. A layer made of resin A and B made of resin B
In a method for producing a multilayer film in which 11 or more layers are alternately laminated, resin A and resin B are separately melted by an extruder, and each molten resin is branched into multiple layers by pores in a multilayer feed block. , The branched resin A and the resin B are introduced into a flat flow path partitioned by parallel plates so that 11 or more layers of the resin flow alternately, and further to a confluent portion in the multi-layer feed block. And a resin B are extruded in a sheet form in a multilayered direction in the thickness direction, cooled and solidified by a casting drum to give an unstretched film, and the unstretched film is stretched in at least one of the longitudinal direction and the transverse direction. A method for controlling the temperature distribution of the multilayer feed block to adjust the thicknesses of the A layer and the B layer of the multilayer film in the range of 0.01 to 0.5 μm. Method of manufacturing a multilayer film to be. 2. A multilayer feed block is provided with a temperature distribution so that a value obtained by dividing the thickness of the thickest layer of layers A and B of the multilayer film by the thickness of the thinnest layer is 1.2 or more. The method for producing a multilayer film according to claim 1. 3. A multi-layer feed block having a temperature difference of 10 to 10.
The method for producing a multilayer film according to claim 2, wherein the temperature is in the range of 100 ° C. 4. The temperature difference of the multi-layer feed block is 10 ° C.
The production of the multilayer film according to claim 1, wherein the value obtained by dividing the thickness of the thickest layer of the A layer and the B layer of the multilayer film by the thickness of the thinnest layer is less than 1.2 by controlling the thickness to be less than 1.2. Method. 5. In an unstretched film, the difference between the in-plane refractive index of resin A and the in-plane refractive index of resin B is 0.005.
The method for producing a multilayer film according to claim 1, which is the above. 6. The multilayer film according to claim 1, wherein in the film stretched in at least one direction, the difference between the in-plane direction refractive index of the resin A and the in-plane direction refractive index of the resin B is 0.005 or more. Production method. 7. The method for producing a multilayer film according to claim 1, wherein the resin A contains polyethylene-2,6-naphthalate as a main component. 8. The method for producing a multilayer film according to claim 7, wherein the resin B contains a mixture of polyethylene-2,6-naphthalate and polyethylene terephthalate as a main component. 9. The resin B is mainly composed of a polyethylene terephthalate copolymer having a melting point of 210 to 245 ° C.
The method for producing a multilayer film according to. 10. The copolymerization component of the polyethylene terephthalate copolymer is ethylene isophthalate.
The method for producing a multilayer film according to. 11. A multi-layer feed block provided with a temperature distribution control means used in the method for producing a multi-layer film according to claim 1.