JP4967486B2 - Stretched film and its molded product - Google Patents

Description

  The present invention relates to a stretched film in which layers composed of at least two types of thermoplastic resins are laminated, and a molded product thereof.

  Products having the property of transmitting or reflecting only light of a specific wavelength are used in various applications. For example, those that reflect light in the visible region at a high rate are used as cold mirrors, those that reflect only a specific narrow band of light are widely used as dichroic mirrors, and those that reflect light in the infrared region are widely used as heat ray cut filters. Has been.

  In addition, those molded products are also used in various fields, for example, molded products that reflect light in the visible region have the same overview as metal, so various home appliances including automobile-related decorative parts, Used in products (parts) such as building materials.

  The most commonly used technique for imparting the characteristic of transmitting or reflecting a specific wavelength to various molded parts is painting. Although painting can be easily adjusted in appearance, it often uses various chemicals and has a great impact on the environment. In addition, recycling may not be easy due to the influence of the coating film, and the existence of a coating process is regarded as a problem in the recent increase in environmental problems.

  Another method includes metal plating and vapor deposition. In the case of plating or vapor deposition, there is a problem that recycling is difficult due to the metal layer. However, in the case of plating in particular, since the influence of heavy metals on the environment is great, an alternative is strongly demanded. Furthermore, in the case of plating or vapor deposition, because of its electromagnetic shielding properties due to its metal layer, it is becoming a problem when used as a decorative material for automobiles and mobile phones, which may cause radio interference. .

  On the other hand, various films have been proposed in which a thermoplastic resin is laminated in multiple layers. For example, by attaching a film laminated in a multilayer with excellent tear resistance to the glass surface, breakage and scattering of the glass are greatly prevented. It is utilized as what can be done (for example, refer patent documents 1-3).

    In addition, there are films (for example, see Patent Documents 4 to 6) that selectively reflect a specific wavelength by alternately laminating resin layers having different refractive indexes. Among these, a film that selectively reflects a specific wavelength acts as a filter that transmits or reflects specific light, and is used as a film for a backlight such as a liquid crystal display. These films can be recycled and can reduce environmental burdens such as not using heavy metals.

However, the multilayer laminated film produced by such a method can be re-stretched in a high-temperature atmosphere in the molding process, but the film's optical properties change and the desired performance can be obtained. There is a problem of not.
Japanese Patent Laid-Open No. 6-190995 (page 2) Japanese Patent Laid-Open No. 6-190997 (page 2) JP 10-76620 A (2nd page) JP 2005-352237 A (2nd page) JP 2005-313586 A (2nd page) JP 2005-288784 A (2nd page)

An object of this invention is to provide the stretched film which an optical characteristic does not change when a film is redrawn in a high temperature atmosphere in view of the problem of an above-described prior art.

In order to solve the above problems, a stretched film in which 50 layers or more of layers made of thermoplastic resin A (layer A) and layers of thermoplastic resin B (layer B) are alternately laminated, and the thermoplastic resin a is a polyethylene terephthalate, a thermoplastic resin B is isophthalic acid, cyclohexane dimethanol, cyclo hexane Dziga carboxylic acid, at least one or more polyesters comprising spiro glycol structural unit selected from adipic acid, And it is a stretched film characterized in that the amount of change in density when it is re-stretched 1.4 times at the same time in the longitudinal and lateral directions at a stretching speed of 230 ° C. and 10% / Sec is 0.4% or less. .

  The present invention is a stretched film in which 50 layers or more of layers made of thermoplastic resin A (A layer) and layers of thermoplastic resin B (B layer) are alternately laminated, and 230 ° C., 10% / Sec. In the stretching process under a high-temperature atmosphere, the amount of change in density when the film is re-stretched 1.4 times at the same time in the longitudinal and lateral directions at a stretching speed of 0.4% or less. This makes it possible to provide a stretched film whose optical properties do not change when re-stretched.

  Moreover, since it is a stretched film whose maximum reflectance in 250 nm-2600 nm is 60% or more, sufficient performance as a reflective filter can be provided now.

In order to solve the above-mentioned object, a stretched film in which 50 layers or more of layers made of thermoplastic resin A (A layer) and layers of thermoplastic resin B (B layer) are alternately laminated, and 230 ° C., 10 The stretched film is characterized in that the amount of change in density when the film is re-stretched by 1.4 times in the longitudinal and lateral directions at a stretching speed of% / Sec is 0.4% or less.

  The stretched film of the present invention needs to have a density change of 0.4% or less when restretched at a stretch rate of 230 ° C. and 10% / Sec simultaneously by 1.4 times in the longitudinal and lateral directions. The density is related to the degree of orientation crystallization in the stretching process, and a low amount of change in density means that the degree of orientation crystallization in the stretching process is small. A general resin increases its refractive index by orientation crystallization, but the laminated film of the present invention has a characteristic that its reflection characteristics change in response to a change in refractive index. As a result, the reflection characteristics change. In various forming processes such as vacuum forming, vacuum pressure forming, plug-assisted vacuum forming, in-mold forming, insert forming, cold forming and press forming, partial film stretching occurs in a high-temperature atmosphere. As a result, partial reflection characteristics change. Therefore, by providing a stretched film that hardly changes in density, it is possible to provide a laminated film in which the color and reflection characteristics hardly change in various molding processes. More preferably, the amount of change in density is 0.2% or less, and in this case, it is possible to provide a stretched film suitable for molding processing without any change in reflection characteristics in various molding processing.

  In the stretched film of the present invention, the difference between the reflectance of the film before stretching and the reflectance after re-stretching 1.4 times at the same time in the longitudinal and lateral directions at a stretching speed of 230 ° C. and 10% / Sec is 25% or less. Is desirable. If the difference in refractive index after re-stretching is 20% or less, stretched film in various forming processes such as vacuum forming, vacuum pressure forming, plug assist vacuum pressure forming, in-mold forming, insert forming, cold forming, press forming When the film is partially re-stretched, the refractive index of the layer changes corresponding to the stretch ratio, and as a result, it is possible to suppress the shift of the reflection band and the change of the reflectivity. It becomes possible to provide a laminated film in which color and reflection characteristics hardly change. The difference in reflectance is preferably 15% or less, more preferably 5% or less. When the difference in refractive index after re-stretching is 5% or less, it becomes possible to provide a stretched film suitable for a molding process in which the reflection characteristics do not change in various molding processes.

The stretched film of the present invention must include a layer made of a thermoplastic resin having a photoelastic coefficient of 100 × 10 ⁻¹² Pa ⁻¹ or less in the A layer or the B layer. When the photoelastic coefficient is 100 × 10 ⁻¹² Pa ⁻¹ or more, it can be used in a high temperature atmosphere such as vacuum forming, vacuum pressure forming, plug assist vacuum pressure forming, in-mold forming, insert forming, cold forming, press forming, etc. This is because the refractive index changes due to the stress applied when the stretched film is re-stretched in various molding processes, and as a result, a partial shift of the reflection band on the stretched film and a change in the reflectance occur. Preferably, the A layer or the B layer contains a thermoplastic resin having a photoelastic coefficient of 50 × 10 ⁻¹² Pa ⁻¹ or less. As the photoelastic coefficient becomes smaller, it becomes possible to provide a stretched film suitable for a molding process in which the reflection characteristics do not change in various molding processes.

  As for the stretched film of this invention, it is desirable that the maximum reflectance in 250-2600 nm is 60% or more. When the maximum reflectance is 60% or more, sufficient performance as a filter or mirror can be exhibited in a specific band. The maximum reflectance is preferably 70% or more, more preferably 80% or more. When the maximum reflectance is 80% or more, the light in the design band can be substantially reflected, and the performance as a high-quality filter or mirror is exhibited.

  Including the structure in which the layers made of the resin A (A layer) and the layers made of the resin B (B layer) are alternately laminated includes the structure in which the A layers and the B layers are alternately laminated in the thickness direction. Is defined to exist. That is, it is preferable that the order of arrangement in the thickness direction of the A layer and the B layer in the film of the present invention is not in a random state, and the order of arrangement of the third layer or more other than the A layer and the B layer is as follows. It is not particularly limited. Moreover, when it has a C layer which consists of A layer, B layer, and resin C, it is more preferable to laminate | stack by regular permutation, such as A (BCA) n, A (BCBA) n, A (BABCBA) n. . Here, n is the number of repeating units. For example, in the case of A (BCA) n where n = 3, this indicates that the layers are stacked in a permutation of ABCABCABCA in the thickness direction.

  Further, in the present invention, 50 layers or more of the layers made of the resin A (A layer) and the layers made of the resin B (B layer) must be included alternately. If the structure in which 50 layers or more of the A layer and the B layer are laminated is not included, sufficient reflectance cannot be obtained, and sufficient performance as a reflection filter cannot be imparted. More preferably, it is 200 layers or more, More preferably, the total number of layers of A layer and B layer is 600 layers or more. As the number of layers in which the A layer and the B layer are stacked increases, the reflectance can be increased and the reflection band can be widened. When the total number of stacked layers of the A layer and the B layer is 600 or more, the wavelength band is 400 nm. It becomes easy to set the reflectance of ˜1000 nm to 60% or more. Further, the upper limit value of the number of layers is not particularly limited, but it is 1500 layers or less in consideration of a decrease in wavelength selectivity accompanying a decrease in stacking accuracy due to an increase in the size of the device or an increase in the number of layers. It is preferable.

  The resin in the present invention may be either a thermoplastic resin or a thermosetting resin, a homo resin, a copolymer or a blend of two or more. More preferably, it is a thermoplastic resin because of good moldability. In each resin, various additives such as antioxidants, antistatic agents, crystal nucleating agents, inorganic particles, organic particles, viscosity reducers, thermal stabilizers, lubricants, infrared absorbers, ultraviolet absorbers, A dopant for adjusting the refractive index may be added.

  Examples of thermoplastic resins include polyolefin resins such as polyethylene, polypropylene, polystyrene, and polymethylpentene, alicyclic polyolefin resins, polyamide resins such as nylon 6 and nylon 66, aramid resins, polyethylene terephthalate, polybutylene terephthalate, and polypropylene terephthalate.・ Polybutyl succinate ・ Polyester resin such as polyethylene-2,6-naphthalate, polycarbonate resin, polyarylate resin, polyacetal resin, polyphenylene sulfide resin, tetrafluoroethylene resin, trifluoroethylene resin, trifluorochloroethylene resin・ Fluorine resin such as ethylene tetrafluoride-6-propylene copolymer / vinylidene fluoride resin, acrylic resin, methacrylic resin, polyacetal resin, It can be used polyglycolic acid resin, polylactic acid resin, and the like. Among these, polyester is particularly preferable from the viewpoint of strength, heat resistance, and transparency.

  The polyester referred to in the present invention refers to a homopolyester or a copolyester that is a polycondensate of a dicarboxylic acid component skeleton and a diol component skeleton. Here, typical examples of the homopolyester include polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polyethylene-2,6-naphthalate, poly-1,4-cyclohexanedimethylene terephthalate, and polyethylene diphenylate. In particular, polyethylene terephthalate is preferable because it is inexpensive and can be used in a wide variety of applications.

  The copolyester in the present invention is defined as a polycondensate comprising at least three or more components selected from the following components having a dicarboxylic acid skeleton and components having a diol skeleton. Components having a dicarboxylic acid skeleton include terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, and 4,4′-diphenyldicarboxylic acid. 4,4′-diphenylsulfone dicarboxylic acid, adipic acid, sebacic acid, dimer acid, cyclohexanedicarboxylic acid and ester derivatives thereof. Examples of the component having a glycol skeleton include ethylene glycol, 1,2-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentadiol, diethylene glycol, polyalkylene glycol, and 2,2-bis. (4′-β-hydroxyethoxyphenyl) propane, isosorbate, 1,4-cyclohexanedimethanol, spiroglycol and the like can be mentioned.

  In the stretched film of the present invention, it is desirable that the thermoplastic resin A is made of polyethylene terephthalate and the thermoplastic resin B is a polyester containing spiroglycol. The polyester comprising spiroglycol refers to a copolyester copolymerized with spiroglycol as a diol skeleton, or a homopolyester, or a polyester blended with them. Polyester comprising spiroglycol is less susceptible to orientational crystallization in the stretching process compared to polyethylene terephthalate, and as a result, the amount of change in density at the time of re-stretching in a photoelastic coefficient and high temperature atmosphere is reduced. It is possible to provide a stretched film suitable for a molding process in which there is no change in reflection characteristics in the molding process. Further, compared to polyesters containing other aliphatic diols, the glass transition point is close to that of polyethylene terephthalate, so that it is difficult to be over-stretched at the time of molding and is also difficult to delaminate.

  In the stretched film of the present invention, it is desirable that the thermoplastic resin A is made of polyethylene terephthalate, and the thermoplastic resin B is a polyester containing isophthalic acid, cyclohexanedimethanol, spiroglycol, cyclohexanedigalbonic acid, and adipic acid. The polyester comprising isophthalic acid, cyclohexanedimethanol, spiroglycol, cyclohexanedigalbonic acid and adipic acid refers to a copolyester obtained by copolymerizing these as monomers, a homopolyester, or a polyester obtained by blending them. Polyesters containing these monomers are less susceptible to orientational crystallization during the stretching process than polyethylene terephthalate, resulting in a smaller amount of change in photoelastic coefficient and density during re-stretching in a high-temperature atmosphere. It becomes possible to provide a stretched film suitable for molding without change in reflection characteristics during processing. More preferably, it contains two or more of these monomers. By including two or more kinds of these monomers, the effect is more remarkably exhibited, and the glass transition point and the refractive index can be easily adjusted. Adjusting the glass transition point is preferable because it is difficult to be overstretched at the time of molding and is also difficult to delaminate, and by adjusting the refractive index, it is possible to express desired reflection characteristics.

  The stretched film of the present invention comprises a thermoplastic resin A having a melting point Tm of 2 ° C. or higher when re-stretched at a stretch rate of at least 230 ° C. and 10% / Sec at the same time by 1.4 times in the longitudinal and lateral directions. It is desirable to include. An increase in the melting point indicates that the crystallinity of the resin is increasing, and as a result, the refractive index of the resin is increased. When the increase in the refractive index of the layer made of the resin A is larger than the increase in the refractive index of the layer made of the resin B, the difference in the in-plane refractive index of each layer becomes large. It is possible to prevent the reflectance from being lowered during various moldings such as plug-assist vacuum / pneumatic molding, in-mold molding, insert molding, cold molding, and press molding.

  Regarding the A layer and B layer referred to in the present invention, the in-plane average refractive index of the A layer is relatively higher than the in-plane average refractive index of the B layer. The difference between the in-plane average refractive index of the A layer and the in-plane average refractive index of the B layer is preferably 0.03 or more. More preferably, it is 0.05 or more, More preferably, it is 0.1 or more. When the refractive index difference is smaller than 0.03, a sufficient reflectance cannot be obtained, which is not preferable. Further, when the difference between the in-plane average refractive index and the thickness direction refractive index of the A layer is 0.03 or more, and the difference between the in-plane average refractive index and the thickness direction refractive index of the B layer is 0.03 or less, the incident angle Even if becomes larger, the reflectance of the reflection peak does not decrease, which is more preferable.

  As a preferable combination of the resin A and the resin B in the present invention, it is first preferable that the absolute value of the difference in SP value between the resin A and the resin B is 1.0 or less. When the absolute value of the difference in SP value is 1.0 or less, delamination hardly occurs. More preferably, it has a layer made of the resin A and a layer made of the resin B containing the same basic skeleton as the resin A. Here, the basic skeleton is a repeating unit constituting the resin. For example, when one resin is polyethylene terephthalate, ethylene terephthalate is the basic skeleton. As another example, when one resin is polyethylene, ethylene is a basic skeleton. When the resin A and the resin B are resins containing the same basic skeleton, peeling between layers is less likely to occur.

  As a preferred combination of the resin A and the resin B, secondly, the glass transition temperature difference between the resin A and the resin B is preferably 20 ° C. or less. When the glass transition temperature difference is larger than 20 ° C., the thickness uniformity when the laminated film is formed becomes poor, and desired optical characteristics cannot be obtained. Also, when a laminated film is formed, problems such as overstretching tend to occur.

  The stretched film of the present invention preferably has a tensile stress of 3 MPa or more and 90 MPa or less at 100% elongation in the film longitudinal direction and width direction in a tensile test at 150 ° C. In such a case, the moldability is excellent, and in any shape such as vacuum forming, vacuum pressure forming, plug assist vacuum pressure forming, in-mold forming, insert forming, cold forming, press forming, etc., it is formed into an arbitrary shape. Easy to do. More preferably, in a tensile test at 150 ° C., the tensile stress at 100% elongation in the film longitudinal direction and the width direction is 3 MPa or more and 50 MPa or less. In such a case, molding can be performed even with a higher drawing ratio. In the tensile test at 150 ° C., in order for the tensile stress at 100% elongation in the film longitudinal direction and the width direction to be 3 MPa or more and 90 MPa or less, the resin A is a crystalline resin and the resin B is cyclohexanedimethanol, spiro. It is preferably an amorphous resin having a bulky group such as glycol or neopentyl glycol. In such a case, since the resin B is hardly oriented and crystallized even after biaxial stretching, the tensile stress is low.

  The stretched film of the present invention preferably has a layer mainly composed of 3 μm or more of polyethylene terephthalate on at least one side. More preferably, it has a layer mainly composed of polyethylene terephthalate of 5 μm or more. Further, it is more preferable to have a layer mainly composed of polyethylene terephthalate of 3 μm or more on both sides. When there is no layer made of polyethylene terephthalate having a thickness of 3 μm or more, it is not preferable because the scratches are very visible when the surface is scratched.

  In the stretched film of the present invention, an easy-adhesion layer, an easy-slip layer, a hard coat layer, an antistatic layer, an anti-abrasion layer, an antireflection layer, a color correction layer, an ultraviolet absorption layer, a printing layer, a metal layer, a transparent surface Functional layers such as a conductive layer, a gas barrier layer, a hologram layer, a release layer, an adhesive layer, an emboss layer, and an adhesive layer may be formed.

  The molded body of the present invention must contain the stretched film. In addition to the stretched film of the present invention, it is also preferable to include any of a hard coat layer, an embossed layer, a weather resistant layer (UV cut layer), a colored layer, an adhesive layer, a base resin layer, and the like. Such a molded body can be composed only of a polymer and does not contain metal or heavy metal, and therefore has a low environmental load, is excellent in recyclability, and does not cause electromagnetic interference. In addition, since various molding methods such as vacuum molding, vacuum pressure molding, plug assist vacuum pressure molding, in-mold molding, insert molding, cold molding, and press molding can be applied, it is possible to obtain a molded body at low cost. . The molded body of the present invention is suitable as a metallic decorative material for automobile interiors and exteriors, mobile phones, various home appliances, building material parts and the like.

  Next, the preferable manufacturing method of the stretched film of this invention is demonstrated below.

  Two types of resins A and B are prepared in the form of pellets. The pellets are dried in hot air or under vacuum as necessary, and then supplied to a separate extruder. In the extruder, the resin melted by heating to a temperature equal to or higher than the melting point is made uniform in the amount of resin extruded by a gear pump or the like, and foreign matter or denatured resin is removed through a filter or the like.

Resins A and B sent out from different flow paths using these two or more extruders are then fed into the multilayer laminating apparatus. As the multi-layer laminating apparatus, a multi-manifold die, a field block, a static mixer, or the like can be used. Moreover, you may combine these arbitrarily. In order to achieve a structure in which 50 layers or more of layers made of resin A (layer A) and resin B (layer B), which are features of the present invention, are alternately laminated, It is preferable to use a feed block that has at least one member having the above. Furthermore, in order to efficiently obtain the effects of the present invention, it is preferable to use a feed block (FIGS. 1 to 4) including at least two members having a large number of fine slits separately. When such a feed block is used, since the apparatus does not become extremely large, there is little foreign matter due to thermal degradation, and high-precision lamination is possible even when the number of laminations is extremely large. Also, the stacking accuracy in the width direction is significantly improved as compared with the prior art. It is also possible to form an arbitrary layer thickness configuration. For this reason, it becomes easy to achieve the following structure which is a preferable aspect of this invention.
a) The total number of layers of the layer made of resin A (A layer) and the layer made of resin B (B layer) is 600 layers or more.
b) The maximum reflectance in the wavelength band of 250 nm to 2600 nm is 60% or more. c) It has a layer mainly composed of polyethylene terephthalate of 3 μm or more on at least one side.

  Here, the feed block including at least two members having a large number of fine slits will be described in detail below. FIG. 1 shows a portion (referred to as “lamination device”) for forming a laminate from resins A and B supplied separately in the feed block. In FIG. 1, members 1 to 9 are stacked in this order to form a stacking apparatus 10.

  The laminating apparatus 10 shown in FIG. 1 has four resin inlets derived from the resin introduction members 2, 4, 6, and 8. For example, the resin A is supplied from the introduction ports 11 of the resin introduction members 2 and 6, and the resin B is supplied from the introduction port 11 of the resin introduction members 4 and 8.

  Then, the slit member 3 receives supply of resin A from the resin introduction member 2 and resin B from the resin introduction member 4, and the slit member 5 receives supply of resin A from the resin introduction member 6 and resin B from the resin introduction member 4. The receiving and slit member 7 receives supply of the resin A from the resin introducing member 6 and the resin B from the resin introducing member 8.

  Here, the type of resin introduced into each slit is determined by the positional relationship between the bottom surface of the liquid reservoir 12 in the resin introduction members 2, 4, 6 and 8 and the end of each slit in the slit member. That is, as shown in FIG. 3, the ridge line 13 at the top of each slit in the slit member has an inclination with respect to the thickness direction of the slit member (FIGS. 2B and 2C). The height of the bottom surface of the liquid reservoir 12 in the resin introduction members 2, 4, 6, and 8 is located between the upper end portion 14 and the lower end portion 15 of the ridge line 13. As a result, resin is introduced from the liquid reservoir 12 of the resin introduction members 2, 4, 6 and 8 from the side where the ridgeline 13 is raised (16 in FIG. 3), but from the side where the ridgeline 13 is lowered. Is in a state where the slit is sealed and no resin is introduced. Thus, since the resin A or B is selectively introduced for each slit, a flow of resin having a laminated structure is formed in the slit members 3, 5, 7, and the outlets below the members 3, 5, 7 are formed. It flows out from 17.

  As the shape of the slit, it is preferable that the slit area on the side where the resin is introduced is not the same as the slit area on the side where the resin is not introduced. With such a structure, the flow rate distribution on the side where the resin is introduced and the side where the resin is not introduced can be reduced, so that the laminating accuracy in the width direction is improved. Further, (slit area on the side where no resin is introduced) / (slit area on the side where the resin is introduced) is preferably 0.2 or more and 0.9 or less. More preferably, it is 0.5 or less. Moreover, it is preferable that the pressure loss in a feed block will be 1 Mpa or more. Moreover, it is preferable that the slit length (the longer one of the Z-direction slit lengths in FIG. 1) is 20 mm or more. On the other hand, the thickness of each layer can be controlled by adjusting the gap and length of the slit.

  It is also preferable to have a manifold corresponding to each slit. Because the manifold makes the flow velocity distribution in the width direction (Y direction in FIG. 1) uniform inside the slit, the lamination ratio in the width direction of the laminated films can be made uniform, and even a large area film can be accurately obtained. Stacking is possible, and the reflectance of the reflection peak can be controlled with high accuracy.

  More preferably, the resin is supplied from one liquid reservoir to two or more slit members. In this way, even if there is a slight flow distribution in the width direction inside the slit, it is further laminated by the confluence apparatus described below, so the total lamination ratio is uniform, It becomes possible to reduce unevenness of the next reflection band.

  As shown in FIG. 1, the outlets 17 below the slit members 3, 5, and 7 are arranged in a positional relationship in which three resin flow laminated structures are arranged in parallel, and are separated from each other by the resin introduction members 4 and 6. (19L, 20L, 21L in FIG. 4). Therefore, the merging device 18 as shown in FIG. 4 changes the arrangement by restricting the flow path, such as from the middle LL ′ to MM ′ (19M, 20M, and 21M in FIG. 4). The laminated structure of the three resin flows is also in series. The resin flow is widened from M-M ′ to N-N ′ in FIG. 4 and merges downstream from N-N ′ in FIG. 4.

  Thus, arbitrary and highly accurate lamination of an extremely thin resin layer is possible. In this apparatus, since the thickness of each layer can be adjusted by the shape (length, width) of the slit, any layer thickness can be achieved. On the other hand, in the conventional apparatus, in order to achieve lamination of 300 layers or more, it is common to use a square mixer together. However, in such a method, the lamination flow is deformed and laminated in a similar shape. In addition, it has been difficult to achieve an arbitrary layer thickness.

Next, in order to set the maximum reflectance in the wavelength band 250 nm to 2600 nm, which is a feature of the present invention, to 60% or more, the layer thickness of each layer is set to at least a part of the wavelength band 250 nm to 2600 nm based on the following formula 1. It is necessary to design so that reflection occurs. The reflectance is controlled by the difference in refractive index between the A layer and the B layer and the number of layers of the A layer and the B layer.
2 × (na · da + nb · db) = λ Equation 1
na: In-plane average refractive index of the A layer nb: In-plane average refractive index of the B layer da: Layer thickness (nm) of the A layer
db: Layer thickness of layer B (nm)
λ: main reflection wavelength (primary reflection wavelength)
It is preferable to design a layer structure in which the thickness gradually decreases from the maximum layer pair thickness to the minimum layer pair thickness. At this time, slight stacking unevenness is allowed.

  The molten laminate formed in the desired layer configuration in this way is then formed into a desired shape by a die and then discharged. And the sheet | seat laminated | stacked in the multilayer discharged | emitted from die | dye is extruded on cooling bodies, such as a casting drum, and is cooled and solidified, and a casting film is obtained. At this time, it is preferable to use a wire-like, tape-like, needle-like, or knife-like electrode to be brought into close contact with a cooling body such as a casting drum by an electrostatic force and rapidly solidify. Also preferred is a method in which air is blown out from a slit-like, spot-like, or planar device to be brought into close contact with a cooling body such as a casting drum and rapidly cooled and solidified, or brought into close contact with a cooling body with a nip roll and rapidly solidified.

  The casting film thus obtained is preferably biaxially stretched as necessary. Biaxial stretching refers to stretching in the longitudinal direction and the width direction. Stretching may be performed sequentially in two directions or simultaneously in two directions. Further, re-stretching may be performed in the longitudinal direction and / or the width direction. In particular, in the present invention, it is preferable to use simultaneous biaxial stretching from the viewpoint of suppressing in-plane orientation difference and suppressing surface scratches.

  First, the case of sequential biaxial stretching will be described. Here, stretching in the longitudinal direction refers to stretching for imparting molecular orientation in the longitudinal direction to the film, and is usually performed by a difference in peripheral speed of the roll, and this stretching may be performed in one step. Alternatively, a plurality of roll pairs may be used in multiple stages. Although it changes with kinds of resin as a magnification of extending | stretching, 2 to 15 times is preferable normally, and when polyethylene terephthalate is used for either of the resin which comprises a laminated | multilayer film, 2 to 7 times are used especially preferably. Moreover, as extending | stretching temperature, the glass transition temperature-glass transition temperature +100 degreeC of resin which comprises a laminated | multilayer film are preferable.

  The uniaxially stretched film thus obtained is subjected to surface treatment such as corona treatment, flame treatment, and plasma treatment as necessary, and then functions such as slipperiness, easy adhesion, and antistatic properties are provided. It may be applied by in-line coating.

  The stretching in the width direction refers to stretching for giving the film an orientation in the width direction. Usually, the tenter is used to convey the film while holding both ends of the film with clips, and the film is stretched in the width direction. Although it changes with kinds of resin as a magnification of extending | stretching, 2 to 15 times is preferable normally, and when polyethylene terephthalate is used for either of the resin which comprises a laminated | multilayer film, 2 to 7 times are used especially preferably. Moreover, as extending | stretching temperature, the glass transition temperature-glass transition temperature +120 degreeC of resin which comprises a laminated | multilayer film are preferable.

  The biaxially stretched film is preferably subjected to a heat treatment at a temperature not lower than the stretching temperature and not higher than the melting point in the tenter in order to impart flatness and dimensional stability. After being heat-treated in this way, it is gradually cooled down uniformly, then cooled to room temperature and wound up. Moreover, you may use a relaxation process etc. together in the case of annealing from heat processing as needed.

  Next, the case of simultaneous biaxial stretching will be described. In the case of simultaneous biaxial stretching, the resulting cast film is subjected to surface treatment such as corona treatment, flame treatment, and plasma treatment as necessary, and then, such as slipperiness, easy adhesion, antistatic properties, etc. The function may be imparted by in-line coating.

  Next, the cast film is guided to a simultaneous biaxial tenter, and conveyed while holding both ends of the film with clips, and stretched in the longitudinal direction and the width direction simultaneously and / or stepwise. As simultaneous biaxial stretching machines, there are pantograph method, screw method, drive motor method, linear motor method, but it is possible to change the stretching ratio arbitrarily and drive motor method that can perform relaxation treatment at any place or A linear motor system is preferred. Although the stretching magnification varies depending on the type of resin, it is usually preferably 6 to 50 times as the area magnification. When polyethylene terephthalate is used as one of the resins constituting the laminated film, the area magnification is 8 to 30 times. Is particularly preferably used. In particular, in the case of simultaneous biaxial stretching, it is preferable to make the stretching ratios in the longitudinal direction and the width direction the same and to make the stretching speeds substantially equal in order to suppress the in-plane orientation difference. Moreover, as extending | stretching temperature, the glass transition temperature-glass transition temperature +120 degreeC of resin which comprises a laminated | multilayer film are preferable.

  The film thus biaxially stretched is preferably subsequently subjected to a heat treatment not less than the stretching temperature and not more than the melting point in the tenter in order to impart flatness and dimensional stability. In order to suppress the distribution of the main alignment axis in the width direction during this heat treatment, it is preferable to perform a relaxation treatment in the longitudinal direction immediately before and / or immediately after entering the heat treatment zone. After being heat-treated in this way, it is gradually cooled down uniformly, then cooled to room temperature and wound up. Moreover, you may perform a relaxation | loosening process in a longitudinal direction and / or the width direction at the time of annealing from heat processing as needed. Immediately before and / or immediately after entering the heat treatment zone, a relaxation treatment is performed in the longitudinal direction.

An evaluation method of physical property values used in the present invention will be described.
(Method for evaluating physical properties)
(1) Lamination thickness, the number of laminations, and lamination structure The layer structure of the film was obtained by observing an electron microscope with respect to a sample obtained by cutting a cross section using a microtome. That is, using a transmission electron microscope H-7100FA type (manufactured by Hitachi, Ltd.), the cross section of the film was magnified 40000 times at an acceleration voltage of 75 kV, a cross-sectional photograph was taken, and the layer configuration and each layer thickness were measured. In some cases, in order to obtain high contrast, a staining technique using a known RuO ₄ or OsO ₄ may be used.

A specific method for obtaining the laminated structure will be described. About 40,000 times as many TEM photographic images were captured with CanonScan D123U at an image size of 720 dpi. The image is saved in the JPEG format, and then image processing software Image-Pro Plus ver. 4 (sales company Planetron Co., Ltd.) was used to open this JPG file and perform image analysis. In the image analysis process, the relationship between the thickness in the thickness direction and the average brightness of the area sandwiched between the two lines in the width direction was read as numerical data in the vertical thick profile mode. Using the spreadsheet software (Excel2000), the position (nm) and brightness data were subjected to numerical processing of sampling step 6 (decimation 6) and 3-point moving average. Furthermore, the data obtained by periodically changing the brightness is differentiated, and the maximum value and the minimum value of the differential curve are read by the VBA program. Calculated. This operation was performed for each photograph, and the layer thicknesses of all layers were calculated.
(2) Maximum reflectance before heating A φ60 integrating sphere 130-0632 (Hitachi Ltd.) and a 10 ° inclined spacer were attached to a spectrophotometer (U-3410 Spectrophotometer) manufactured by Hitachi, Ltd., and the reflectance was measured. The bandpass is set to 2 nm / servo, the gain is set to 3, and the range from 250 nm to 2600 nm is set to 120 nm / min. The scanning speed was measured. In order to standardize the reflectance, an aluminum oxide plate attached to the apparatus was used as a standard reflecting plate, and at the time of sample measurement, black paint was applied with magic ink to eliminate interference caused by reflection from the back surface. The maximum value of the reflectance is the maximum value of the spectral reflectance at a wavelength of 250 to 2600 nm, and the wavelength is taken as the reflection wavelength.
(3) Glass transition temperature / melting point It measured and calculated according to JIS-K-7122 (1987) using differential calorimetry (DSC). First, at 1st Run, 20 ° C./min. From 25 ° C. to 290 ° C. The temperature was raised at 290 ° C., held at 290 ° C. for 5 minutes, and then rapidly cooled to 25 ° C. In the 2nd Run that follows, 20 ° C./min. From 25 ° C. to 290 ° C. The temperature was raised. The glass transition temperature and melting point of the resin were values at 2nd Run.
Equipment: “Robot DSC-RDC220” manufactured by Seiko Electronics Industry Co., Ltd.
Data analysis "Disc Session SSC / 5200"
Sample mass: 5 mg.
(4) Photoelastic coefficient A sample having a short side of 1 cm and a long side of 7 cm was cut out. The thickness of this sample is d (μm). Using this sample, TRANSDUCER U3C1-5K manufactured by Shimadzu Corporation, the checker was placed 1 cm above and below, and a tension (F) of 1 kg / mm ² (9.81 × 10 ⁶ Pa) was applied in the long side direction. . In this state, the phase difference R (nm) was measured using a polarizing microscope 5892 manufactured by Nikon Corporation. Sodium D line (589 nm) was used as a light source. These numerical values were applied to photoelastic coefficient = R / (d × F) to calculate the photoelastic coefficient.
(5) Density The density of the film was measured using an aqueous sodium bromide solution by the density gradient tube method of JIS-K-7112 (revised in 1980).
(6) Amount of change in maximum reflectivity after heating test A sample whose reflectivity was measured by the method described in (2) was preheated at 230 ° C for 20 minutes, and 230 ° C, 10% / The film was redrawn 1.4 times in the longitudinal and lateral directions at a rate of min. With respect to this sample, the reflectance was measured by the method described in (2) while maintaining the same reflectance measurement position. The maximum reflectance after heating is the maximum value of the spectral reflectance at a wavelength of 250 to 2600 nm, and the maximum reflectance after heating (R2) / the maximum reflectance before heating (R1) is defined as the amount of change in the maximum reflectance. did.
(7) Change in melting point after heating test For a sample similar to the sample whose melting point was measured by the method described in (3), preheat at 230 ° C for 20 minutes, and use a stretcher at 230 ° C and 10%. The film was re-stretched 1.4 times in the longitudinal and lateral directions at a rate of / min. About this sample, melting | fusing point was measured by the method as described in (3). The melting point after heating (Tm2) −the melting point before heating (Tm1) was defined as the amount of change in melting point.
(8) Density change after heating test The sample whose density was measured by the method described in (5) was preheated at 230 ° C for 20 minutes, and a rate of 230 ° C and 10% / min using a stretcher. The film was re-stretched 1.4 times at the same time vertically and horizontally. About this sample, the density was measured by the method as described in (5). Note that {density after heating (D2) −density before heating (D1)} / D2 was defined as the amount of change in density.
Example 1
A thermoplastic resin A and a thermoplastic resin B were prepared as two types of thermoplastic resins. In Example 1, as the resin A, polyethylene terephthalate (PET) [Toray F20S] containing 0.04 wt% of aggregated silica particles having an average particle diameter of 1 μm was used. Further, as the resin B, polyethylene terephthalate (PE / SPG / CHDC) obtained by copolymerizing 29 mol% of cyclohexanedicarboxylic acid with respect to terephthalic acid and 21 mol% of spiro glycol with respect to ethylene glycol was used. These resins A and B were each dried and then fed to separate extruders.

  Resins A and B were each melted at 280 ° C. by an extruder, passed through a gear pump and a filter, and then joined by a 801-layer feed block. As the 801-layer feed block, an apparatus as shown in FIGS. 1 and 4 was used. The feed block was composed of three slit members having 267 slits. In the feed block, the merged resins A and B are changed so that the thickness of each layer gradually increases from the surface side toward the opposite surface side, and the thickness direction in which the resin A is 401 layers and the resin B is 400 layers. It was set as the structure laminated | stacked alternately. Here, the thickness of each layer pair was targeted at the line A in FIG. 5, the flow rate of each slit was calculated from this, and the shape of the fine slit provided in the flow path of each layer in the feed block was adjusted. Moreover, the slit shape was designed so that both surface layer parts might be resin A, and the layer thickness of the adjacent A layer and B layer might become substantially the same. In this design, a reflection band exists between 400 nm and 1200 nm. The thus obtained laminate comprising 801 layers is supplied to a multi-manifold die, and further, a layer made of resin A supplied from another extruder is formed on the surface layer, and after forming into a sheet shape, Rapid solidification was effected on a casting drum maintained at a surface temperature of 25 ° C. by application of electricity. The flow path shape and the total discharge amount were set so that the time from when the resin A and the resin B merged to when rapidly solidified on the casting drum was about 8 minutes.

  The obtained cast film was heated with a roll group set at 75 ° C., and then stretched 3.0 times in the longitudinal direction while rapidly heating from both sides of the film with a radiation heater between 100 mm in the stretch section length. Cooled down. Subsequently, both sides of this uniaxially stretched film were subjected to corona discharge treatment in air, the wetting tension of the base film was set to 55 mN / m, and the treated surface (polyester resin having a glass transition temperature of 18 ° C.) / (Glass transition) Polyester resin having a temperature of 82 ° C.) / Laminate-forming film coating liquid composed of silica particles having an average particle diameter of 100 nm was applied to form a transparent, easy-sliding, and easy-adhesion layer.

This uniaxially stretched film was guided to a tenter, preheated with hot air at 100 ° C., and stretched 3.3 times in the transverse direction at a temperature of 110 ° C. The stretched film was directly heat-treated in a tenter with hot air of 240 ° C., then subjected to a relaxation treatment of 8% in the width direction at the same temperature, and then gradually cooled to room temperature and wound up. The film thus obtained had a thickness of 100 μm. The obtained results are shown in Table 1.
(Example 2)
The same apparatus as Example 1 except that polyethylene terephthalate (PE / SPG / CHDC) obtained by copolymerizing 50 mol% of cyclohexanedicarboxylic acid with respect to terephthalic acid and 50 mol% of spiroglycol with respect to ethylene glycol was used as resin B.・ Film was formed under conditions. The obtained results are shown in Table 1.
(Example 3)
The same apparatus as in Example 1 except that polyethylene terephthalate (PE / SPG / A) obtained by copolymerizing 29 mol% of adipic acid with respect to terephthalic acid and 21 mol% of spiroglycol with respect to ethylene glycol was used as resin B. Film formation was performed under conditions. The obtained results are shown in Table 1.
Example 4
The same apparatus as in Example 1 except that polyethylene terephthalate (PE / SPG / I) obtained by copolymerizing 50 mol% of isophthalic acid with respect to terephthalic acid and 50 mol% of spiro glycol with respect to ethylene glycol was used as resin B. Film formation was performed under conditions. The obtained results are shown in Table 1.
( Reference Example 1 )
As resin B, 50% polyethylene terephthalate (PET / I) copolymerized with 50% by mole of isophthalic acid with respect to terephthalic acid, and 50% polyethylene terephthalate (CHDM copolymerized PET) with 50% by mole of cyclohexanediethanol copolymerized with ethylene glycol: A film was formed under the same apparatus and conditions as in Example 1 except that a resin kneaded and alloyed in a twin screw extruder was used at a weight ratio of 50. The obtained results are shown in Table 1.
( Reference Example 2 )
As resin B, 50% polyethylene terephthalate (PET / A) copolymerized with 25 mol% adipic acid with respect to terephthalic acid and 50 mol% cyclohexanediethanol with ethylene glycol (CHDM copolymerized PET) A film was formed under the same apparatus and conditions as in Example 1 except that a resin kneaded and alloyed in a twin screw extruder was used at a weight ratio of 50. The obtained results are shown in Table 1.
(Comparative Example 1)
As the resin B, polyethylene terephthalate (CHDM copolymerized PET) obtained by copolymerizing 30 mol% of cyclohexanedimethanol with ethylene glycol [PETG6763 manufactured by Eastman] and polyethylene terephthalate are kneaded in a twin screw extruder at a weight ratio of 85:15. A film was formed under the same apparatus and conditions as in Example 1 except that an alloyed resin was used. The obtained results are shown in Table 1.
(Comparative Example 2)
A film was formed under the same apparatus and conditions as in Example 1 except that polyethylene terephthalate (PET / A) in which 15 mol% of cyclohexanedicarboxylic acid was copolymerized with terephthalic acid was used as resin B. The obtained results are shown in Table 1.
(Comparative Example 3)
A film was formed under the same apparatus and conditions as in Example 1 except that 17.5 mol% (PET / I) of isophthalic acid was used as resin B with respect to terephthalic acid. The obtained results are shown in Table 1.
(Comparative Example 4)
A film was formed under the same apparatus and conditions as in Example 1 except that polybutylene terephthalate (PBT) was used as the resin B. The obtained results are shown in Table 1.

Laminating apparatus and its components Slit part Sectional view of the state where the slit part and the resin supply part are connected Junction device

Explanation of symbols

1: Side plate 2: Resin A supply part 3: Slit part 3a, 3b: Slit 4: Resin B supply part 5: Slit part 6: Resin A supply part 7: Slit part 8: Resin B supply part 9: Side plate 10: Lamination Device 11: Inlet 12: Liquid reservoir 18: Junction device

Claims (6)

It is a stretched film in which layers of thermoplastic resin A (A layer) and layers of thermoplastic resin B (B layer) are alternately laminated by 50 layers or more, and thermoplastic resin A is made of polyethylene terephthalate, thermoplastic resin B is isophthalic acid, cyclohexane dimethanol, a cyclo hexane Dziga carboxylic acid, at least one or more polyesters comprising a spiro glycol as a constituent unit selected from adipic acid, and 230 ° C., 10% / A stretched film having a density change amount of 0.4% or less when re-stretched by 1.4 times at the same time in the longitudinal and lateral directions at a Sec stretching speed. 2. The stretching according to claim 1, wherein the change in reflectance after re-stretching by 1.4 times in the longitudinal and lateral directions at the same time as the reflectance of the film before stretching and at 230.degree. the film. The stretched film according to claim 1, wherein the photoelastic coefficient of at least one of the A layer and the B layer is 100 × 10 ⁻¹² Pa ⁻¹ or less. The stretched film according to any one of claims 1 to 3, wherein the maximum reflectance at 250 nm to 2600 nm is 60% or more. The stretched film according to any one of claims 1 to 4, wherein the melting point Tm after re-stretching at a stretch rate of 230 ° C, 10% / Sec at the same time in the longitudinal and lateral directions 1.4 times increases by 2 ° C or more as compared to before stretching. . The molded article using the stretched film in any one of Claims 1-5 .

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