JP4693500B2 - Method for producing multilayer film - Google Patents

Description

  The present invention relates to a method for producing a multilayer film in which thermoplastic polymer polymers (hereinafter referred to as “polymers”) are laminated in multiple layers.

  For example, when a plurality of thin film layers having a high refractive index and a plurality of thin film layers having a high refractive index are alternately laminated, the multilayer film becomes an optical interference film that selectively reflects or transmits light having a specific wavelength by optical interference between these layers. Such a laminated film can be used for, for example, a reflective polarizing plate, a coloring film, a film having a metallic luster, or a reflective mirror film by setting the wavelength region of light that is selectively reflected or transmitted to the visible light region. Is spreading. Moreover, it can be used as a film that selectively cuts ultraviolet rays by adjusting the number of layers and the interlayer thickness, and can also be used as an agricultural film for insect repellent. Furthermore, if the near infrared is selectively cut, it is useful as a film for window covering for solar radiation or a film for a video display panel such as a plasma display. It can be used as a film for preventing. Further, in order to project an image on a show window, it is also promising as a hologram film using a film in which a multilayer film that selectively transmits each hue of RGB (red, green, blue) appropriately and appropriately is bonded.

  In view of this, various methods and apparatuses for manufacturing a multi-layered film that can be used for various applications have been proposed. For example, in Japanese Patent Application Laid-Open No. 4-278324 or Japanese Patent Application Laid-Open No. 2004-34299, two types of molten thermoplastic polymer polymers (hereinafter referred to as “polymers”) are formed into a predetermined number of layers using a multilayer feed block. A multilayer film manufacturing method and an apparatus therefor have been proposed, in which alternately stacked layered flows are formed, the layered flows are divided and then re-laminated to increase the number of layers.

  However, in such a conventional technique, for example, as shown in FIG. 3A, when a poorly laminated portion is generated at the end portion 22 of the laminated flow having a rectangular cross section formed in the multilayer feed block, this is illustrated. As shown in FIG. 3 (a), when the layer is divided on the F-plane and re-stacked as shown in FIG. 3 (b), the portion 22 having a poor thickness distribution (the layer thickness is uneven) Appears in the center of the film.

The reason why the layer flow is nonuniform in the multi-layer feed block having a rectangular channel cross section is that there is a stagnation part where the flow velocity becomes slow in the vicinity of the four corners of the cross section. This is probably because the thickness changes. In particular, in the vicinity of the outer layer portion and in the vicinity of both ends in the film width direction, since the polymer in a melt flow state passes through the tube wall portion, the flow rate becomes slow, and an unintended distribution is attached to each layer thickness. This is considered to be a cause of distortion and non-uniform distribution of layer thickness.
In this way, increasing the number of layers and increasing the proportion of defective layers included in the finally obtained multilayer film will cause each layer to be distorted or the layer thickness to be unevenly distributed. As a result, the optical properties of the multilayer film vary.

JP 04-278324 A JP 2004-34299 A

  An object of the present invention is to solve the above-mentioned problems of the prior art and provide a method for producing a multilayer film having a uniform thickness and having little variation in optical characteristics and the like.

Here, the above-mentioned problems are related to the present invention. (1) In a multilayer feed block, a laminated flow having a rectangular cross section in which at least two types of molten polymer are alternately laminated in three or more layers is formed. Are divided by a cross section perpendicular to the laminated surface to form independent branched flows, and the branched flows are rearranged so that the laminated surfaces are parallel to and in contact with each other so as to increase the number of laminated layers, and recombined. When manufacturing a multilayer film by increasing the number, the ratio (w / t) of the outer layer portion thickness (w) to the inner layer portion thickness (t) of the laminated flow formed by the multilayer feed block is 5 to 200. This can be achieved by a method for producing a multilayer film.
As a more preferred embodiment, (2) the number of layers of the multilayer film is 11 or more, the method for producing a multilayer film according to (1), and (3) a product obtained by longitudinally uniaxially stretching the multilayer film This can be solved by the method for producing a multilayer film according to any one of (1) to (2) .

  According to the present invention described above, the outer layer portion causing the layer distortion and the non-uniform distribution of the layer thickness is increased, and conversely, the thickness of the inner layer portion having the small layer distortion and the non-uniform distribution of the layer thickness is reduced. It is small. Therefore, each layer constituting the inner layer portion that bears the optical characteristics can be laminated with a uniform thickness, thereby producing a very remarkable effect that a multilayer film with uniform optical characteristics in the width direction can be produced.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram illustrating one embodiment of the present invention, and shows how a flow laminated in multiple layers in a molten state is divided, arranged, and re-laminated. FIG. 2 shows the state of the layer distribution of split relamination in a cross section of a conventional multilayer film without a special outermost layer.

In FIG. 1, P ₀ is a laminated polymer flow (hereinafter simply referred to as “laminated flow”) having a rectangular cross section laminated in advance in multiple layers, 1 is an outer layer portion disposed at both ends, and 2 is sandwiched between the outer layer portions 1 The inner layer portions P ₁ and P ₂ are branched polymer flows (hereinafter simply referred to as “branch flows”) that are divided and branched from the laminated flow P ₀ having a rectangular cross section, 6 is a multi-layered distortion portion, and S 1 Is a split branch operation for splitting and splitting the laminated flow P ₀ having a rectangular cross section, S2 is a rearrangement operation for rearranging the position of the split split flow P _{0 to} the stack position, and S3 for each branch. laminating operation flow P ₁ and P ₂ is and Somen becomes parallel layer surface is laminated in contact with each other, F is the cross section perpendicular to the layer surface of the laminated flow P ₀ having a rectangular cross section (cutting plane), C _1, C _{2, C 3} and _{C 4} is the fourth laminated stream having a rectangular cross-section Corners of, and, w and t is the outer layer and inner layer portions of the thickness (see FIG. 2), respectively.

In the multilayer film manufacturing method performed as illustrated in FIG. 1, the laminated flow P ₀ having a rectangular cross section is described in, for example, Japanese Patent Application Laid-Open No. 2003-251675 or Japanese Patent Application Laid-Open No. 2003-112355. By using a multilayer feed block, it can be formed according to a conventional method. Therefore, the detailed description is abbreviate | omitted here.

First, in the present invention, a laminated flow P ₀ having a rectangular cross section formed by a multilayer feed block is divided by a cutting plane F in a division branch operation S1, and then branched into a branch flow P ₁ and a branch flow P ₂ , respectively. It is done. Then, the rearrangement operation S2, the branch flow P ₁ and the branch flow P ₂ that is allowed to branch, respectively, as the number of layers increases, the layer surfaces of the respective branched flow P ₁ and P ₂ are parallel to each other and that The layer surfaces are rearranged so that they are in contact with each other.

The relocation operation S2 branch flow P ₁ and P ₂ which are rearranged by is re stacked are attached to each other together in the direction increasing number of layers by lamination operation S3. If the thickness (w) of the outer layer portion 1 is not made thicker than the thickness (t) of the inner layer portion 2 in this lamination operation S3, there arises a problem that the optical properties of the obtained multilayer film vary in the width direction. This point will be described below with reference to FIG.

As illustrated in FIG. 2, when the multilayer flow P ₀ formed by the multilayer feed block is sequentially subjected to the split branch operation S 1, the rearrangement operation S 2, and the lamination operation S 3 to form a multilayer film, _The portions corresponding to the _four corners C ₁ , C ₂ , C _3, and C ₄ of 0 are relatively thick, and the outer layer portion 1 has a non-uniform layer thickness. The reason for this is considered to be a stagnation point at which the flow rate of the polymer flow becomes slow at the corners C ₁ , C ₂ , C ₃ and C ₄ , and this is considered to cause a layer change.

  On the other hand, in the inner layer part 2, as shown in the figure, there is a laminated part having a uniform layer thickness as it goes to the center part. Therefore, if the optical properties of the multilayer film are imparted to the inner layer portion 2 in which the layers are not distorted and the layer thickness is uniform, each layer constituting the inner layer portion 2 that bears the optical properties is uniform. It can be laminated to a thickness, whereby a multilayer film with uniform optical properties in the width direction can be produced. In FIG. 2, for convenience of explanation, the outer layer portion 1 is also described as having a multilayer structure, but this portion may be a single layer.

At that time, as illustrated in FIGS. 1 and 2, it is important that the thickness (w) of the outer layer portion 1 is made larger than the thickness (t) of the inner layer portion 2 for the reason described above. . At this time, the ratio (w / t) needs to be 5 to 200 because the number of layers can be increased by laminating the layers constituting the multilayer film in a uniform thickness. In addition, when (w / t) is larger than 200, the total thickness of the multilayer film becomes large, and its application may be limited. On the other hand, when (w / t) is smaller than 5, the thickness of the layer becomes relatively thick at the portions corresponding to the corner portions C ₁ , C ₂ , C ₃ and C ₄ of the outer layer portion 1, Since the non-uniform portion is generated, there arises a problem that the optical characteristics vary in the width direction.

The polymer used in the present invention comprises at least two kinds. For example, when two types of polymers are used as the minimum configuration, two types of polymers are alternately laminated in the inner layer portion 2 to form a multilayer, and either one of the polymers used in the multilayer portion (inner layer portion 2) is formed in the outer layer portion 1. Can be used. Moreover, when using 3 types of polymers, the outer layer part 1 can use another polymer with the inner layer part 2 which comprises an alternating laminated body, for example, the multilayer film manufactured by the method of this invention was remelted. but it may also be used, such as playback polymer in the outer layer portion 1.

Next, the preferred number of layers of the film produced in the present invention is 11 to 4800 layers, and at least two kinds of polymers are alternately laminated, and the incident light to the film is selected using the difference in refractive index of each polymer. In particular, it is preferably used for the purpose of transmission, reflection and refraction, or the purpose of increasing the strength of the film by increasing the number of layers. On the other hand, the number of layers of laminated flow P ₀ having a rectangular cross-section to form a multilayer feed block is preferably 3-301 layers.

  The multi-layer film of the present invention described above is formed by extruding a polymer stream laminated in multiple layers in the molten state by the above-described laminating operation S3 from a die to form an unstretched multi-layer sheet. The multilayer sheet is stretched in the machine direction and / or transverse direction at a predetermined temperature, heat-treated at a predetermined temperature, heat-relaxed if necessary, and re-longitudinal and / or re-laterally stretched and wound as necessary. It can be a film. In addition, you may provide the process of apply | coating a coating liquid to a film and drying during the manufacturing process of a multilayer film in that case, or in that case.

  Since the multilayer film of the present invention thus produced has no distortion in each layer and the layer thickness distribution is uniform, the optical properties required from the center to the vicinity of the end of the film are sufficient. Satisfied. Therefore, for example, in a deflection film application in which an unstretched film is longitudinally uniaxially stretched and subjected to a treatment such as heat setting as necessary, it has a feature that the width of a good product portion can be widened. That is, in the case of the present invention, a wide product can be efficiently collected even with longitudinal uniaxial stretching. On the other hand, when the non-stretched film has a small number of non-defective parts in the longitudinal-transversely stretched film of the conventional method, it is possible to extend the non-defective part in the width direction to extend the product width to suit the application. Required.

  Here, as the polymer constituting the multilayer film in the present invention, a thermoplastic polymer mainly composed of a stretchable polymer can be used, such as polyethylene terephthalate, polyethylene-2,6-naphthalate, and polybutylene terephthalate. Aromatic polyester, Polyolefin such as polyethylene and polypropylene, Polyvinyl such as polystyrene, Polyamide such as nylon 6 (polycaprolactam), nylon 66 (poly (hexamethylenediamine-co-adipic acid)), and bisphenol A polycarbonate Examples thereof include homopolymers such as aromatic polycarbonate and polysulfone, and polymers mainly composed of these copolymers. Examples of the copolymer component include isophthalic acid copolymerized polyethylene terephthalate and 2,6-naphthalenedicarboxylic acid copolymerized polyethylene terephthalate. Among the above thermoplastic polymers, aromatic polyesters, polyolefins, and polyamides capable of molecular orientation by stretching are preferred, and polyethylene that exhibits excellent optical, mechanical, and thermal properties when the molecules are biaxially oriented. 2,6-naphthalate is also preferred. These polymers may be blended with additives such as weathering agents, lubricants, antistatic agents, and pigments as necessary.

Hereinafter, the present invention will be further described by way of examples. The physical properties in the examples were measured by the following methods.
(1) Color A sample film was cut out and the intensity of the color was visually observed under a fluorescent lamp.
(2) Deflection Uniaxially stretched film samples were visually observed for the presence or absence of deflection with deflection glasses.
(3) Maximum reflectance Using a spectrophotometer MPC-3100 manufactured by Shimadzu Corporation, the relative specular reflectance with an aluminum-deposited mirror at each wavelength is measured in the wavelength range of 350 to 2100 nm. The largest of the measured reflectances is the maximum reflectance. The measurement positions were 5 points (equal intervals) including both edges in the film width direction.
(4) Thickness of outer layer portion and inner layer portion A sample is cut into a triangle, fixed to an embedding capsule, and then embedded with an epoxy resin. Then, the embedded sample was made into a thin film slice having a thickness of 50 nm in a longitudinal direction with a microtome (ULTRACUT-S), and then observed and projected at 100 kv using a transmission electron microscope. The thickness of each layer was measured from the photographs to obtain the thickness of the outer layer portion and the inner layer portion. However, when the measured thickness has variation in the width direction, the average value of the minimum value and the maximum value is defined as the thickness of the layer.

[Example 1]
With the apparatus shown in FIG. 1, a multilayer film having 402 layers and a total thickness of 42 μm was prepared.
First, two types of polymers are prepared, one of which is polyethylene-2,6-naphthalate (PEN) having an intrinsic viscosity (orthochlorophenol, 35 ° C.) of 0.62 dl / g, and spherical silica particles (average particle diameter: 0.11 μm, 0.12 μm, ratio of major axis to minor axis: 1.02, average deviation of particle diameter: 0.1) was added. The other is polyethylene terephthalate (PET) having an intrinsic viscosity (orthochlorophenol, 35 ° C.) of 0.63 dl / g and polyethylene-2,6-naphthalate (PEN) having an intrinsic viscosity (orthochlorophenol, 35 ° C.) of 0.62 dl / g. ) Was blended at a weight percentage of 50:50.

Each polymer pellet was dried at 160 ° C. for 5 hours, fed to a separate extruder, melted, filtered through a polymer filter while metering with a gear pump, and led to a known multilayer feedblock. Next, two polymers are alternately laminated in 201 layers in the inner layer part 2 in the multilayer feed block, and further, the outer layer part 1 is laminated so that (w / t) becomes 10, and the flow path has a rectangular cross section. In the apparatus shown in FIG. 1, after being guided, it is divided into two in the cross section F and branched into the branch flow P ₁ and the branch flow P ₂ , and after being arranged, they are laminated and bonded together. And cast on a casting drum to prepare a laminated unstretched sheet.

  This unstretched laminated sheet was stretched 3.2 times in the machine direction at a temperature of 150 ° C., further stretched 3.5 times in the transverse direction at a stretch temperature of 155 ° C., and heat-fixed at 230 ° C. for 3 seconds. After removing from the tenter, both edges were trimmed by about 200 mm to obtain a multilayer film having a width of 1200 mm. The obtained film was a film that reflects light having a wavelength of about 550 nm out of visible light, and was a film that looked red visually. The measured values are shown in Table 1.

[Example 2]
A 402-layer film was collected under the same conditions as in Example 1 except that w / t = 100 and that the total thickness was adjusted to 70 μm.

[Example 3]
In the first embodiment, the laminated flow P ₀ having a rectangular cross section is divided and divided so that there are three branch flows, and the flow ratio of each of the three branch flows is 1: 1.3: 1.8. The unstretched multilayer sheet thus obtained was stretched 6.5 times in the longitudinal direction to obtain a multilayer film. At this time, lateral stretching was omitted. Then, both edges of the obtained multilayer film were trimmed by about 70 mm to obtain a longitudinal uniaxial multilayer film having a width of 350 mm. The film was checked for deflection.

[Comparative example]
In Example 1, a 402-layer film was sampled under the same conditions as in Example 1 except that the outermost layer 2 was adjusted not to have a special outermost layer and the total thickness was adjusted to 38 μm. The film was a film in which red color development was weak at the edge portion, and color variation was found visually in the width direction. The thickness ratio (w / t) between the outer layer portion and the inner layer portion was 0.4.

  According to the manufacturing method of the present invention, the layers constituting the inner layer portion that bears the optical characteristics can be laminated with a uniform thickness, and a multilayer film with uniform optical characteristics in the width direction can be efficiently produced.

It is a conceptual diagram for demonstrating the method of this invention, and is the figure explaining the operation procedure until the division | segmentation branching, rearrangement, and lamination | stacking of the flow laminated | stacked in the multilayer in the molten state. It is a figure for demonstrating the defective part which arises in an outer layer part, and the uniform layer which arises in an inner layer part. It is a figure for demonstrating the defective location which arises in the conventional method.

Explanation of symbols

1: outer layer 2: inner layer portion S1: dividing Branch Operation S2: Relocation Operation S3: laminating operation F: cut surface _C 1 of the laminated flow _{P 0, C 2, C 3} , C 4: corners _{P 0:} rectangular section Laminar flow P ₁ , P _{2 having} : each branch flow t: inner layer thickness w: outer layer thickness

Claims (3)

In the multilayer feed block, a laminar flow having a rectangular cross section in which at least two types of molten polymer are alternately laminated in three or more layers is formed, and the laminar flow is divided by a cross section perpendicular to the laminating surface to be an independent branch flow When the multi-layer film is manufactured by increasing the number of layers, the multi-layer feed is re-arranged so that each of the branched flows is parallel and in contact with each other so that the number of layers increases. The manufacturing method of the multilayer film characterized by making ratio (w / t) of the thickness (w) of the outer-layer part of the laminated flow formed by a block, and the thickness (t) of an inner-layer part into 5-200 . The method for producing a multilayer film according to claim 1, wherein the number of layers of the multilayer film is 11 or more . The method for producing a multilayer film according to claim 1 or 2, wherein the multilayer film is longitudinally uniaxially stretched into a product .

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