JP2005288784A - Laminated film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the lowering of color purity or discoloring by higher order reflection, degradation by ultraviolet ray scattering, etc., while performance as a filter or a reflection member is kept. <P>SOLUTION: In a laminated film. at least five layers (layers A) of a thermoplastic resin A and at least five layers (layers B) of a thermoplastic resin B are laminated alternately. The film has at least one reflection peak of at least 30% reflectance and at least one higher order reflection zone (which is) 30% or below in reflectance. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a laminated film in which at least two types of layers made of a thermoplastic resin are laminated.

  Various films have been proposed in which a thermoplastic resin is laminated in multiple layers. For example, by sticking a film laminated in a multilayer with excellent tear resistance on the glass surface, breakage and scattering of the glass can be largely prevented. (See, for example, Patent Documents 1 to 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.

However, in the conventional technique, since a plurality of reflection peaks are observed in addition to the desired reflection peak, for example, when trying to design a colorless film that reflects near infrared rays, it is actually due to higher-order reflection. When it is used as a filter or the like because the color purity of the reflective film decreases or UV rays are reflected as a higher-order reflection in the case of a film that reflects visible light, or in the case of a film that reflects visible light There was a problem of promoting deterioration of peripheral members.
Japanese Patent Laid-Open No. 6-190995 (page 2) Japanese Patent Laid-Open No. 6-190997 (page 2) JP 10-76620 A (2nd page) Japanese Patent Laid-Open No. 3-41401 (2nd page) JP 4-295804 A (page 2) Japanese National Publication No. 9-506837 (2nd page)

  In view of the above-described problems of the prior art, the object of the present invention is to suppress deterioration in color purity due to higher-order reflection, coloring, deterioration due to ultraviolet scattering, etc. while maintaining the performance as a filter or a reflecting member. Let it be an issue.

  In order to solve the above problems, the laminated film of the present invention includes a structure in which five or more layers each composed of a thermoplastic resin A (A layer) and a thermoplastic resin B (B layer) are alternately laminated. Thus, it has at least one reflection peak having a reflectance of 30% or more and at least one higher-order reflection band having a reflectance of 30% or less.

  The laminated film of the present invention comprises a structure in which 5 layers or more of layers made of thermoplastic resin A (A layer) and layers of thermoplastic resin B (B layer) are alternately laminated, and the reflectance is 30%. Since there is at least one higher-order reflection band having at least one reflection peak as described above and a reflectance of 30% or less, a laminated film in which the reflectance of any higher-order wavelength is controlled is provided. did it.

  In addition, by using a laminated film in which the thickness of the laminated film is periodically changed in the longitudinal direction or the width direction of the film, there is no influence on the color due to higher-order reflection wavelengths, and the color has changed periodically in the past. It was possible to give a design property that was not.

  The reflection peak referred to in the present invention refers to a band having a reflectance of 30% or more when the reflectance is measured with respect to the wavelength of light. Unless otherwise specified, the reflectance measured with an integrating sphere with a spectrophotometer for light incident on the film surface with a difference angle of 10 ° from the vertical axis. Say. Here, the reflectance of the reflection peak is preferably 60% or more, and more preferably 80% or more. A reflectance of 80% or more is preferable because an extremely high filter function and reflection performance can be obtained. The incident angle referred to here is the difference angle between the direction perpendicular to the film surface and the direction in which light enters. Further, the higher-order reflection band refers to the observed reflection peak on the highest wavelength side as the primary reflection peak, and the wavelength band X of the primary reflection peak is the order N (N is an integer of 2 or more). Each wavelength band X / N ± 25 nm obtained by dividing by. In addition, this ± 25 nm takes into consideration a measurement error and a peak reading error.

  In the present invention, at least one of the higher-order reflection bands must have a reflectance of 30% or less. Here, when at least one of the higher-order reflection bands has a reflectance of 30% or less, when the wavelength band X of the first-order reflection peak is composed of, for example, certain wavelength regions X1 to X2, the interval of X1 / N to X2 / N It has having at least one area | region where a reflectance is 30% or less. More preferably, at least one of the higher-order reflection bands has a reflectance of 20% or less, and more preferably has a reflectance of 15% or less. By having at least one higher-order reflection band having a reflectance of 30% or less in this way, coloring due to the higher-order reflection band, a decrease in color purity, deterioration due to ultraviolet rays, and the like are less likely to occur. Further, if the reflectance is 15% or less, it is almost the same level as the surface reflection of the laminated film, so that it is optimal with almost no effect as coloration, reduction in color purity, and promotion of deterioration by ultraviolet rays.

  Further, it is more preferable that the order of the higher-order reflection band of the present invention is 2nd order or more and 4th order or less. More preferably, it is 2 or more and 3 or less. Wavelength region that causes particularly significant problems such as coloring due to higher-order reflection, color purity degradation, and deterioration due to ultraviolet rays when there is at least one reflection band of 2nd order to 4th order with a reflectance of 30% or less This means that strong reflection does not occur.

  Furthermore, in the present invention, it is preferable to have at least one higher-order reflection band having a reflectance of 15% or less at an incident angle of 45 °. Conventionally, as the incident angle increases, the reflectance of the higher-order reflection band shifts to the problematic wavelength band, causing problems such as coloring due to the higher-order reflection band, lowering of color purity, and deterioration due to ultraviolet rays. It was.

  Examples of the thermoplastic resin in the present invention 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, poly Polyethylene resins such as butylene terephthalate, polypropylene terephthalate, polybutyl succinate, polyethylene-2,6-naphthalate, polycarbonate resin, polyarylate resin, polyacetal resin, polyphenylene sulfide resin, tetrafluoroethylene resin, trifluoroethylene resin, 3 Fluorinated resins such as fluorinated ethylene resin, ethylene tetrafluoride-6-propylene copolymer, vinylidene fluoride resin, acrylic resin, methacryl Fat, can be used polyacetal resins, polyglycolic acid resins, polylactic acid resins, and the like. Among these, polyester is particularly preferable from the viewpoint of strength, heat resistance, and transparency. Further, these thermoplastic resins may be homo resins, copolymerized or blends of two or more. Also, in each thermoplastic resin, various additives such as antioxidants, antistatic agents, crystal nucleating agents, inorganic particles, organic particles, thickeners, thermal stabilizers, lubricants, infrared absorbers, ultraviolet absorbers. An agent, a dopant for adjusting the refractive index, and the like may be added.

  The thermoplastic resin of the present invention is more preferably polyester. The polyester 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 dicarboxylic acid component skeleton and diol component skeleton. Examples of the dicarboxylic acid skeleton component include terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 4,4′-diphenyldicarboxylic acid, 4 4,4'-diphenylsulfone dicarboxylic acid, adipic acid, sebacic acid, dimer acid, cyclohexanedicarboxylic acid and ester derivatives thereof. Examples of the glycol skeleton component 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 and the like.

  Particularly in the present invention, it is preferable that the thermoplastic resin A is polyethylene terephthalate and the thermoplastic resin B is a polyester copolymerized with cyclohexanedimethanol. More preferred is an ethylene terephthalate polycondensate having a copolymerization amount of cyclohexanedimethanol of 15 mol% or more and 60 mol% or less. By doing so, the change in the optical characteristics after heating is reduced while having high reflection performance.

  In the present invention, the thermoplastic resin A is preferably polyethylene terephthalate, and the thermoplastic resin B is preferably a polyester obtained by copolymerizing an aliphatic dicarboxylic acid such as adipic acid or sebacic acid or an ester derivative thereof. More preferably, the thermoplastic resin B is an ethylene terephthalate polycondensate obtained by copolymerizing adipic acid. More preferably, it is an ethylene terephthalate polycondensate obtained by copolymerization of 15 to 35 mol% of adipic acid. Such a configuration is preferable because higher reflection performance can be obtained than before.

  In the laminated film of the present invention, 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. Moreover, it is more preferable that the difference between the in-plane average refractive index of the A layer and the refractive index in the thickness direction is 0.03 or less because the angle dependency of the reflection band is reduced.

  Including the structure in which the layers (A layer) made of the thermoplastic resin A and the layers (B layer) made of the thermoplastic resin B of the present invention are alternately laminated, the A layer and the B layer are regularly laminated in the thickness direction. It is defined that there is a part having the above structure. 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. In addition, in the case of having a C layer composed of an A layer, a B layer, and a thermoplastic resin C, they are laminated in a regular permutation such as A (BCA) n, A (BCBA) n, A (BABCBA) n. Is more preferable. 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, it is necessary to alternately include 5 layers or more of layers composed of the thermoplastic resin A (A layer) and layers composed of the thermoplastic resin B (B layer). More preferably, it is 25 layers or more, and more preferably 50 layers or more. If a structure in which five or more A layers and B layers are laminated is not included, sufficient reflectance cannot be obtained. Further, the upper limit is not particularly limited, but it is preferably 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 and an increase in the number of layers. .

  In the laminated film of the present invention, it is more preferable that the thickness periodically changes in the longitudinal direction or the width direction of the film. When the film thickness periodically changes in the longitudinal direction or the width direction in this way, the wavelength of the reflected wavelength peak corresponds to the thickness fluctuation. For example, when the film has a reflected peak in the visible wide range, the color is periodically changed in the film. It is possible to impart design properties that have not changed in the past. For this reason, it becomes suitable with a designable film or a film for preventing forgery.

  A preferable range of the periodic thickness change rate R (R = maximum thickness / minimum thickness × 100 (%)) is 5 to 500%. If the rate of change in thickness is 5% or more, the change in reflection interference color becomes large, so that the design is excellent, and if it is 500% or less, it is preferable from the viewpoint of productivity. Moreover, as a more preferable range of thickness change rate, 7 to 300%, and a more preferable range is 10 to 200%.

  In the method of periodically changing the film thickness, (1) the discharge amount is periodically changed in the film extrusion step. (2) Periodically changing the casting speed in the film casting process. (3) A voltage or current is periodically changed by an electrostatic application device in a film casting process. (4) In the longitudinal stretching step, stretching is performed at a high temperature at which the stretching tension does not rise. (5) The die die bolt is mechanically and thermally operated to change the die lip interval. However, the method for producing the film of the present invention is of course not limited thereto.

  Among these methods, an electrostatic application device in the film casting process that can be adjusted arbitrarily and efficiently with various thickness cycle changes such as various sine waves, triangular waves, rectangular waves, sawtooth waves, impulse waves, etc. A method of periodically changing is more preferable because it can be adjusted to a change rate of an arbitrary thickness.

  Further, as a method for analyzing the fluctuation cycle of the film thickness, a method in which the film thickness is continuously measured and subjected to Fourier transform (hereinafter referred to as “FFT treatment”) of the obtained data is preferably used. It is done. As for FFT processing, for example, “Mathematics of Engineer 1” first edition (Kyoritsu Publishing Co., Ltd. Kyoritsu Zensho 516) etc. about the theory of Fourier transform, “Optical Engineering” first edition (Kyoritsu Publishing Co., Ltd.) etc. about FFT processing techniques As described. In the laminated film of the present invention, it is preferable that one or more spectral peaks having a Pw value of 0.04 to 25 at a wave number of 0.5 to 100,000 (1 / m) are observed when Fourier transform analysis is performed. . A more preferable range of the wave number band in which this peak is observed is 1 to 10000 (1 / m), and more preferably 10 to 1000 (1 / m). Moreover, the more preferable range of observed Pw value is 0.1-20, More preferably, it is 0.2-10, Most preferably, it is 0.3-5. If the wave number band is within the above range, it can be preferably used when the film of the present invention is used for anti-counterfeiting purposes, and if the Pw value is within the above range, periodicity can be easily observed. Is preferred.

Here, Pw is obtained by converting the thickness change data into an absolute value of the thickness, and using the data obtained by converting the average value so as to be the center value of the thickness change, by FFT processing. It is the spectral intensity Pwn at a certain wave number, which is determined by the following equation when the real part is an and the imaginary part is bn.
Pwn = 2 (an ² + bn ² ) 1/2 / N
n: Wave number (m-1)
N: Number of measurements When the half width of this peak is kw and the peak wave number is kt, the preferable range of kw / kt is 0.001 to 0.5, more preferably 0.01 to 0.2, and most preferably. Is 0.1 to 0.2. When kw / kt is within the above range, the obtained film is very excellent in design, and when used as a forgery-preventing film, the encryption function and authenticity are added to the laminated film itself at the same time as the hologram layer. Since the determination function is provided, it has a double security effect, which is preferable.

  In the laminated film of the present invention, it is preferable to have a layer mainly composed of polyethylene terephthalate of 3 μm or more on at least one side of the laminated film. 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. If there is no layer made of polyethylene terephthalate having a thickness of 3 μm or more, the reflectance distribution becomes abnormal when the surface is scratched or the like, which is not preferable.

  In the laminated film of the present invention, it is preferable that layers other than the outermost layer contain substantially no particles having an average particle diameter of 20 nm or more and 20 μm or less. When particles having an average particle diameter of 20 nm or more and 20 μm or less are contained in the laminated film, it is not preferable because transparency is deteriorated or diffuse reflection occurs. Moreover, it is not preferable because only the stacking accuracy causes a sagging and there is a possibility that the reflection performance is lowered.

  In the laminated 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 anti-reflection layer, a color correction layer, an electromagnetic wave shielding layer, an ultraviolet absorption layer, printing Functional layers such as a layer, a metal layer, a transparent conductive layer, a gas barrier layer, a hologram layer, a release layer, an adhesive layer, and an adhesive layer may be formed.

  In particular, when the laminated film of the present invention is used for a design film, a color absorbing layer that absorbs black or a color complementary to a reflection peak, a metal layer such as aluminum, silver, gold, or indium, a printed layer, or an adhesive layer It is preferable to form on the film surface.

In addition, when used for an anti-counterfeit film, a hologram layer, a printing layer, an adhesive layer, a metal layer such as aluminum, silver, gold, or indium, Al ₂ O ₃ , Sb ₂ O ₃ , Sb ₂ S ₃ , As ₂ S ₃ , BeO, Bi ₂ O ₃ , CdO, CdSe, CdS, CdTe, Ce ₂ O ₃ , Cr ₂ O ₃ , SiO, AgCl, Na ₃ AlF ₆ , SnO ₂ , TiO ₂ , TiO, WO ₂ , ZnSe, It is desirable to form a transparent metal compound layer such as ZnS or ZnO ₂ on the film surface. A film in which such a layer is formed on the surface of the laminated film is particularly suitable as a material for an embossed hologram.

  When used as an optical filter, a slippery / adhesive layer, a hard coat layer, an antistatic layer, an antireflection layer, a color correction layer, an electromagnetic wave shielding layer, an ultraviolet absorbing layer, and an infrared absorbing layer are formed on the film surface. It is desirable. The laminated film of the present invention having such a functional layer is also suitable as an optical filter. Optical filters include near-infrared cut filters in plasma displays, reflectors that efficiently reflect the three primary colors of backlights in liquid crystal displays, and selective transmission / reflection of the three primary colors in various displays and CCD cameras. Examples include a color adjustment filter to be enhanced, a heat ray blocking film for cutting near infrared rays / infrared rays used for building materials and window glass for vehicles.

  The film of the present invention is suitably used as a design film. The film for design is a film for imparting a color or a specific color pattern, for example, a decorative film for a design used for automobile interior or exterior, a decorative film for a design used for various packaging, Examples include anti-counterfeit films intended for authenticity determination used for banknotes, cash vouchers, gift certificates, securities, and the like, films for hologram substrates, and films for reflectors.

Next, the preferable manufacturing method of the laminated | multilayer film of this invention is demonstrated below.
Two types of thermoplastic resins A and B are prepared in the form of pellets. If necessary, the pellets are pre-dried in hot air or under vacuum and supplied to an extruder. In the extruder, the resin heated and melted to a temperature equal to or higher than the melting point is homogenized by a gear pump or the like, and foreign matter or denatured resin is removed through a filter or the like.

  The thermoplastic resin sent out from different flow paths using these two or more extruders is then fed into the laminating apparatus. As a laminating apparatus, a method of laminating in multiple layers using a multi-manifold die, a field block, a static mixer, or the like can be used. Moreover, you may combine these arbitrarily. Here, in order to efficiently obtain the effects of the present invention, a multi-manifold die or a feed block capable of individually controlling the layer thickness for each layer is preferable. Furthermore, in order to control the thickness of each layer with high accuracy, a feed block provided with fine slits for adjusting the flow rate of each layer by electric discharge machining or wire electric discharge machining with a machining accuracy of 0.1 mm or less is preferable. At this time, in order to reduce nonuniformity of the resin temperature, heating by a heat medium circulation method is preferable. Moreover, in order to suppress the wall resistance in the feed block, the roughness of the wall surface is preferably 0.4 S or less, or the contact angle with water at room temperature is 30 ° or more.

Here, in order to have at least one reflection peak at which the reflectance is 30% or more, which is the first feature of the present invention, it is important to laminate five layers of A layers and B layers alternately. It is. Further, the layer thickness of each layer needs to be designed so as to obtain a desired reflection peak based on the following formula 1, and the in-plane average refractive index and the layer thickness are distributed within a range of 40% or less. Even if this occurs, it is acceptable. Moreover, in order that the reflectance of the reflection peak which is a preferable embodiment of the present invention is 60% or more, the number of stacked layers is preferably 50 or more. Moreover, in order that the reflectance of the reflection peak which is a more preferable aspect of the present invention is 80% or more, the number of laminated layers is preferably 100 or more.
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)
In addition, in order to have at least one higher-order reflection band having a reflectance of 30% or less, which is the second feature of the present invention, most of the adjacent A layer and B layer satisfy the following formula 2. It is important to have a configuration. In order to efficiently obtain the effect of the present invention, it is preferable that the following formula 2 is satisfied, but the in-plane average refractive index and the layer thickness are acceptable even if a deviation of 10% or less occurs. In order to have at least one higher-order reflection band having a reflectance of 15% or less, which is a preferred embodiment of the present invention, the layer thickness deviation is 5% or less, and the layer thickness deviation is adjacent. Rather than being regular between layers, it is preferable to be random. The reflectivity of the reflection peak is 80% or more, and very high stacking accuracy is required to satisfy Equation 2, but such stacking accuracy cannot be easily and stably achieved by conventional methods. In order to achieve such a high lamination accuracy, 100 or more having a surface roughness of 0.1 S or more and 0.6 S or less, particularly in discharge wire processing with a processing accuracy of 0.01 mm or less. It is particularly preferable that the layers are laminated with a feed block having 300 or less fine slits, and then are not widened in the thickness direction in the flow path from the die to the discharge portion.
na · da = nb · db × (N−1) Equation 2
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)
N: degree (integer of 2 or more)
In the present invention, it is preferable to adjust the thickness of each layer in the laminating apparatus so that the distribution range of the thickness ratio of the adjacent A layer and B layer in a certain cross section is 5% or more and 40% or less. More preferably, it is 5% or more and 10% or less. If the thickness ratio distribution is smaller than 5%, the repetition periodicity of the layer is too high, and high-order reflection is very likely to occur. On the other hand, if it exceeds 40%, the lamination accuracy is too low, so that the reflectance of the desired reflection peak is lowered, and a reflection peak appears in an unexpected wavelength band, which is not preferable.

  In order to achieve the order of the higher-order reflection band having a reflectance of 30% or less, which is a preferred embodiment of the present invention, from 2nd to 4th, N in Formula 2 is 2 or more and 4 or less. Is preferred.

  In order to have at least one higher-order wavelength band having a reflectance of 20% or less at an incident angle of 45 °, which is a preferred embodiment of the present invention, the in-plane average refractive index and thickness of the thermoplastic resin A layer The difference in refractive index in the direction is 0.05 or more, the difference between the average refractive index in the plane of the thermoplastic resin B layer and the refractive index in the thickness direction is 0.03 or less, and the surface of the thermoplastic resin A layer It is preferable that the difference between the average refractive index inside and the average refractive index within the plane of the thermoplastic resin B layer is 0.06 or more. By doing so, the reflectance of extraordinary light can be reduced, and it becomes easy to make the reflectance at an incident angle of 45 ° 20% or less.

  In the present invention, in order to broaden the wavelength band of the reflection peak, the thickness of the A layer or / and the thickness of the B layer include a portion that gradually increases from the film surface side to the opposite surface side. More preferably, the thickness of the A layer and / or the thickness of the B layer gradually increases from the film surface side to the opposite surface side over substantially the entire film cross section.

  On the other hand, it is also preferable that the thickness of the A layer or / and the thickness of the B layer change from the film surface side toward the opposite surface side, and the convex shape is such that the layer thickness becomes substantially thick at the center of the film cross section. In such a case, the high wavelength end in the reflection wavelength band becomes very sharp, which is optimal for an edge filter that is required to have high wavelength resolution on the high wavelength side.

  It is also preferable that the thickness of the A layer and / or the thickness of the B layer change from the film surface side to the opposite surface side, and is a concave type in which the layer thickness is substantially reduced at the center of the film cross section. In such a case, the low wavelength end in the reflection wavelength band becomes very sharp, which is optimal for an edge filter that is required to have high wavelength resolution on the low wavelength side.

  Depending on the characteristics of the reflective film designed as described above, it is important to have an optimum laminated structure, but in the present invention, these adjustments can be made with a feed block having a fine slit corresponding to each layer. Particularly preferred.

  The molten laminate thus obtained is then formed into a desired shape with a die and then discharged. Here, as the die to be molded into a sheet shape, it is preferable that the widening ratio of the laminated body in the die is 1 to 100 times. More preferably, it is 1 to 50 times. When the width-expansion ratio of the laminated body in the die is larger than 100 times, the disturbance of the laminated thickness of the surface layer of the laminated body increases, which is not preferable. When the width-expansion rate of the laminated body in the die is 1 to 100 times, it becomes easy to make the difference in reflectance in the width direction of the laminated film within ± 10%.

  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, using a wire-like, tape-like, needle-like or knife-like electrode, it is brought into close contact with a cooling body such as a casting drum by electrostatic force and rapidly cooled and solidified, or from a slit-like, spot-like, or planar device. A method in which air is blown out and brought into close contact with a cooling body such as a casting drum and rapidly cooled and solidified, and a method in which the nip roll is brought into close contact with the cooling body and rapidly solidified is preferable.

  Here, as a method of periodically changing the film thickness which is one of the preferred embodiments of the film of the present invention, (1) the discharge amount is periodically changed in the film extrusion step. (2) Periodically changing the casting speed in the film casting process. (3) A voltage or current is periodically changed by an electrostatic application device in a film casting process. (4) In the longitudinal stretching step, stretching is performed at a high temperature at which the stretching tension does not rise. (5) The die die bolt is mechanically and thermally operated to change the die lip interval. However, the method for producing the film of the present invention is of course not limited thereto.

  Among these methods, an electrostatic application device in the film casting process that can be adjusted arbitrarily and efficiently with various thickness cycle changes such as various sine waves, triangular waves, rectangular waves, sawtooth waves, impulse waves, etc. A method of periodically changing is more preferable.

  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 biaxially or simultaneously in two directions. Further, the film may be redrawn in the longitudinal and / or 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 biaxially stretched film is preferably subsequently 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. In order to suppress the distribution of the main orientation axis in the width direction during the 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. A relaxation treatment in the longitudinal direction immediately before and / or immediately after entering the heat treatment zone is preferable because the difference in reflectance in the film width direction can be made ± 10% or less.

An evaluation method of physical property values used in the present invention will be described.
(Method for evaluating physical properties)
(1) Lamination Thickness, Number of Laminations The layer configuration of the film was determined by observation with an electron microscope for a sample cut out of a cross section using a microtome. That is, using a transmission electron microscope HU-12 (manufactured by Hitachi, Ltd.), the cross section of the film was magnified 40000 times, a cross-sectional photograph was taken, and the layer structure and each layer thickness were measured. The embodiment of the present invention was not carried out because a sufficient contrast was obtained, but the contrast may be increased by using a dyeing technique using RuO ₄ or OsO ₄ depending on the combination of thermoplastic resins used.

(2) Reflectance 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 band parameter was set to 2 / servo, the gain was set to 3, and the range from 187 nm to 2600 nm was set to 120 nm / min. Measured at a detection speed of. In order to standardize the reflectance, an attached Al ₂ O ₃ plate was used as a standard reflecting plate. In addition, the wavelength of the reflection peak was set to the peak top wavelength. In addition, when the wavelength band having a reflectance of 30% or more has a range of 50 nm or more, the wavelength of the reflection peak is represented by a region where the reflectance is 30% or more, and the reflectance averages the reflectance in the band. I asked for it.

  Further, when measuring the reflectance at an incident angle of 45 °, the reflectance was measured by attaching a self-made inclined spacer.

(3) Intrinsic viscosity Calculated from the solution viscosity measured at 25 ° C in orthochlorophenol. The solution viscosity was measured using an Ostwald viscometer. The unit is [dl / g]. The n number was 3, and the average value was adopted.

(4) Film thickness variation Using a film thickness tester “KG601A” and an electronic micrometer “K306C” manufactured by Anritsu Corporation, the thickness of a film sampled 30 mm wide and 10 m long in the longitudinal direction of the film was continuously measured. The change rate of the film thickness was a value (%) obtained by dividing the difference between the maximum thickness and the minimum thickness within 1 m of the film length by the average thickness and multiplying by 100. In addition, about the change rate of this film thickness, it measured by n number 5 times.

(5) Fourier Analysis of Film Thickness Variation At the time of measuring the thickness variation in the longitudinal direction described above, the output from the electronic micrometer was digitized using KEYENCE “NR-1000” and captured in a computer. Data acquisition was performed by sampling 1024 points at intervals of 0.1 seconds during measurement of thickness variation of about 1 m in length (conveyance measurement was performed at 0.6 m / min (using a low-speed winding motor)). (2 × 1024 × 0.6 m / min ÷ 60 sec / min, about 1 m thickness fluctuation data is taken in). The numerical data taken in this way was converted into a quantitative thickness using Microsoft Excel 2000), and a Fourier transform (FFT) process was performed on the thickness variation. At this time, the thickness change data was converted into an absolute value of the thickness, and the average value was converted to the center value of the thickness change and used for analysis. At this time, if the length (m) of the film is taken as a variable in the flow direction, an intensity distribution with respect to the wave number (1 / m) can be obtained by FFT processing. Here, the obtained real part a _n, when the imaginary part and b _n, spectral intensity Pw ⁿ can be expressed as the following equation.
^{_{Pw n = 2 (a n 2}} + b n 2) 1/2 / N
n: Wave number (m ^-1 )
N: 1024 (number of measurements).

(Example 1)
A thermoplastic resin A and a thermoplastic resin B were prepared as two types of thermoplastic resins. As the thermoplastic resin A, polyethylene terephthalate (PET) [Toray F20S] having an intrinsic viscosity of 0.65 was used. Further, as the thermoplastic resin B, polyethylene terephthalate (CHDM copolymerized PET) obtained by copolymerizing 30 mol% of cyclohexanedimethanol with respect to ethylene glycol [PETG6763 manufactured by Eastman] was used. These thermoplastic resins A and B were each dried and then supplied to an extruder.
The thermoplastic resins A and B were each melted at 280 ° C. with an extruder, passed through a gear pump and a filter, and then merged in a 201-layer feed block. The joined thermoplastic resins A and B are formed so that the thickness of each layer is almost constant from the surface side to the opposite surface side in the feed block, the thermoplastic resin A is 101 layers, and the thermoplastic resin B is 100 layers. It was set as the structure laminated | stacked alternately in the thickness direction. The thickness of each layer was adjusted by the shape of fine slits (formed with a processing accuracy of 0.01 mm) provided in the flow path of each layer in the feed block. In addition, both surface layer parts were made to become the thermoplastic resin A. Here, the shape of the feed block and the discharge amount were adjusted so that the thickness ratio of the adjacent A layer and B layer (A layer thickness / B layer thickness) was 0.95. A casting drum in which a total of 201 layers thus obtained was supplied to a fishtail die, formed into a sheet shape, and then maintained at a surface temperature of 25 ° C. by electrostatic application (DC voltage 8 kV). It was rapidly cooled and solidified above.
The obtained cast film was subjected to corona discharge treatment in air on both sides, the base film had a wet tension of 55 mN / m, and the treated surface (polyester resin having a glass transition temperature of 18 ° C.) / (Glass transition temperature). Is a 82 ° C. polyester resin) / laminate-forming film coating liquid composed of silica particles having an average particle diameter of 100 nm to form a transparent, easy-sliding and easy-adhesive layer.
This cast film was led to a linear motor type simultaneous biaxial stretching machine, preheated with hot air at 95 ° C., and then stretched 3.5 times in the longitudinal and transverse directions. The stretched film is directly heat-treated in a tenter with hot air at 230 ° C., and at the same time it is subjected to 5% relaxation treatment in the longitudinal direction, followed by 5% relaxation treatment in the transverse direction, and then slowly cooled to room temperature. Wound up. The thickness of the obtained film was 21.1 μm. The obtained results are shown in Table 1. Since the obtained film had almost no secondary reflection peak, unnecessary reflection in the ultraviolet region was hardly recognized.

(Example 2)
The conditions were the same as in Example 1, except that the casting drum speed was adjusted in Example 1 to set the film thickness to 16.6 μm. The obtained results are shown in Table 1. Since the obtained film had almost no secondary reflection peak, unnecessary reflection in the ultraviolet region was hardly recognized.

(Example 3)
The conditions were the same as in Example 1 except that the casting drum speed was adjusted to 14.5 μm in Example 1. The obtained results are shown in Table 1. Since the obtained film had almost no secondary reflection peak, unnecessary reflection in the ultraviolet region was hardly recognized.

Example 4
In Example 1, the thickness ratio of the adjacent A layer and B layer (A layer thickness / B layer thickness) was 1.89, and the casting drum speed was adjusted to set the film thickness to 47.2 μm. 1 was used. The obtained results are shown in Table 1. Since the obtained film had almost no third-order reflection peak, an unnecessary reflection peak was hardly observed in the visible light region, and a colorless near-infrared reflection film was obtained.

(Example 5)
In Example 1, the thickness ratio of the adjacent A layer and B layer (A layer thickness / B layer thickness) was 2.85, and the casting drum speed was adjusted to set the film thickness to 47.0 μm. 1 was used. The obtained results are shown in Table 2. Since the obtained film had almost no fourth-order reflection peak, an unnecessary reflection peak was hardly recognized in the ultraviolet region.

(Example 6)
A thermoplastic resin A and a thermoplastic resin B were prepared as two types of thermoplastic resins. As the thermoplastic resin A, polyethylene terephthalate [Toray F20S] having an intrinsic viscosity of 0.65 was used. Further, as the thermoplastic resin B, polyethylene terephthalate [PETG6763 manufactured by Eastman] obtained by copolymerizing 30 mol% of cyclohexanedimethanol with respect to ethylene glycol was used. These thermoplastic resins A and B were each dried and then supplied to an extruder.
The thermoplastic resins A and B were each melted at 280 ° C. with an extruder, passed through a gear pump and a filter, and then merged in a 801-layer feed block. The merged thermoplastic resins A and B are changed so that the thickness of each layer gradually increases from the surface side to the opposite surface side in the feed block. The thermoplastic resin A is 401 layers, and the thermoplastic resin B is It was set as the structure laminated | stacked alternately in the thickness direction which consists of 400 layers. The thickness of each layer was adjusted by the shape of fine slits (formed with a processing accuracy of 0.01 mm) provided in the flow path of each layer in the feed block. In addition, both surface layer parts were made to become the thermoplastic resin A. Here, the shape of the feed block and the discharge amount were adjusted so that the thickness ratio of the adjacent A layer and B layer was 0.95. After the laminated body composed of the total of 801 layers thus obtained is supplied to the multi-manifold die, and further, a layer made of the thermoplastic resin A supplied from another extruder is formed on the surface layer, and then formed into a sheet shape Then, it was rapidly cooled and solidified on a casting drum maintained at a surface temperature of 25 ° C. by electrostatic application.
The obtained cast film was subjected to corona discharge treatment in the air on both sides, the wetting tension of the base film was 55 mN / m, and the treated surface (polyester resin having a glass transition temperature of 18 ° C.) / (Glass transition temperature). Is a 82 ° C. polyester resin) / laminate-forming film coating liquid composed of silica particles having an average particle diameter of 100 nm to form a transparent, easy-sliding and easy-adhesive layer.
This cast film was led to a linear motor type simultaneous biaxial stretching machine, preheated with hot air at 95 ° C., and then stretched 3.5 times in the longitudinal and transverse directions. The stretched film is directly heat-treated in a tenter with hot air at 230 ° C., and at the same time it is subjected to 5% relaxation treatment in the longitudinal direction, followed by 5% relaxation treatment in the transverse direction, and then slowly cooled to room temperature. Wound up. The thickness of the obtained film was 130 μm. The obtained results are shown in Table 2. In this example, while reflecting the broadband near-infrared rays efficiently, almost no high-order reflection was observed in the visible light region, so that a colorless and transparent near-infrared filter was obtained.

(Example 7)
In Example 6, the gap between the slits corresponding to each layer of the feed block is adjusted, and the thickness of each layer is increased from the surface side to the vicinity of the center portion, and is decreased from the vicinity of the center portion to the opposite surface side. The conditions were the same as in Example 6 except that. The thickness of the obtained film was 138 μm. The obtained results are shown in Table 2. In this example, while reflecting near infrared rays efficiently, almost no high-order reflection was observed in the visible light region, and the high wavelength side end in the reflection band became very sharp.

(Example 8)
In Example 6, the gap between the slits corresponding to each layer of the feed block is adjusted, and the thickness of each layer is reduced from the surface side to the vicinity of the center portion, and the concave laminated structure is increased from the vicinity of the center portion to the opposite surface side. The conditions were the same as in Example 6 except that. The thickness of the obtained film was 138 μm. The obtained results are shown in Table 2. In this example, while reflecting near-infrared rays efficiently, almost no high-order reflection is observed in the visible light region, and the low-wavelength side end in the reflection band becomes very sharp, making it ideal for near-infrared filters such as PDPs. Edge filter.

Example 9
In Example 1, the same as Example 1 except that a copolymer polyester having an intrinsic viscosity of 0.95 obtained by copolymerizing 20 mol% of adipic acid and 10 mol% of isophthalic acid with respect to terephthalic acid was used as the thermoplastic resin B. Conditions. The thickness of the obtained film was 21.0 μm. The obtained results are shown in Table 3. In this example, visible light corresponding to red was reflected very efficiently, but there was almost no secondary reflection in the ultraviolet region.

(Comparative Example 1)
In Example 4, the thickness ratio of the adjacent A layer and B layer (A layer thickness / B layer thickness) was 3.2, and the casting drum speed was adjusted to set the film thickness to 47.0 μm. The same conditions as in No. 5 were used. The obtained results are shown in Table 3. Since many high-order reflections were observed, the obtained film became a near-infrared reflective / ultraviolet reflective film colored green.

(Comparative Example 2)
In Example 6, the thickness ratio of the adjacent A layer and B layer (A layer thickness / B layer thickness) was set to 1.5, and the casting drum speed was adjusted to set the film thickness to 114 μm. The same conditions were used. The obtained results are shown in Table 3. Since many high-order reflections were observed, the obtained film became a near-infrared reflective / ultraviolet reflective film colored blue-violet.

(Example 10)
In Example 2, the electrostatic application for tightly contacting the casting drum is a condition that a sine wave having a center voltage of 8 kV and a voltage amplitude of 4 kV (peak-peak) is periodically applied, and the casting drum speed is adjusted, The conditions were the same as in Example 2 except that the average film thickness was 15.5 μm. The obtained results are shown in Table 3. In the obtained film, green and blue were periodically present in the horizontal direction at a pitch of about 50 mm in the film surface, but high-order reflection was not observed in the film surface expressing each color. It had a bright color.

(Example 11)
In Example 1, the conditions were the same as in Example 1 except that the film forming speed was adjusted to set the film thickness to 31.1 μm. Table 4 shows the obtained results. In this example, since the near-infrared light was reflected very efficiently, there was almost no secondary reflection appearing in the visible light region, so that a transparent and colorless near-infrared cut film was obtained.

(Comparative Example 3)
In Example 11, a copolymerized polyester having an intrinsic viscosity of 0.67 obtained by copolymerizing 25 mol% of isophthalic acid with respect to terephthalic acid was used as the thermoplastic resin B, and the discharge amounts of the thermoplastic resin A and the thermoplastic resin B were set to be as follows. The conditions were the same as in Example 11 except that the thickness ratio of the adjacent A layer and B layer was adjusted to 2. The thickness of the obtained film was 31.0 μm. Table 4 shows the obtained results. In this example, while reflecting near-infrared rays very efficiently, there was strong secondary reflection in the visible light region, so a blue-green film was formed, resulting in a colored near-infrared cut film.

(Example 12)
In Example 11, the conditions were the same as in Example 11 except that the discharge amounts of the thermoplastic resin A and the thermoplastic resin B were adjusted so that the thicknesses of the adjacent A layer and B layer were 1.02. The thickness of the obtained film was 31.0 μm. Table 4 shows the obtained results. In this example, since the secondary reflection in the visible light region could be substantially suppressed while efficiently reflecting the near infrared rays, the near infrared cut film colored slightly blue-green was obtained.

(Example 13)
In Example 11, the conditions were the same as in Example 11 except that the discharge amounts of the thermoplastic resin A and the thermoplastic resin B were adjusted so that the thicknesses of the adjacent A layer and B layer were 1.0. The thickness of the obtained film was 31.0 μm. Table 4 shows the obtained results. In this example, the secondary reflection in the visible light region was almost suppressed while efficiently reflecting near infrared rays, so that a colorless infrared cut film was obtained. However, when it was exposed to light in a dark room or when viewed at an angle, it could appear slightly colored.

  The present invention relates to design materials used for building materials, packaging, automobile interior and exterior, anti-counterfeiting materials such as holograms, various displays such as liquid crystal displays, plasma displays, field emission displays, organic electronics displays, and optical printing. It is suitably used as a reflective film or optical filter for various optical devices such as devices and cameras, as a heat ray blocking window film for in-vehicle use and building materials.

Claims (12)

  It includes a structure in which five layers or more of layers made of thermoplastic resin A (layer A) and layers of thermoplastic resin B (layer B) are alternately laminated, and has a reflection peak with a reflectance of 30% or more. A laminated film having one and at least one higher-order reflection band having a reflectance of 30% or less.   2. The laminated film according to claim 1, wherein the order of a high-order reflection band having a reflectance of 30% or less is 2nd to 4th.   The laminated film according to claim 1 or 2, wherein the laminated film has at least one high-order reflection band having a reflectance of 15% or less.   The laminated film according to any one of claims 1 to 3, which has at least one high-order reflection band having a reflectance of 20% or less at an incident angle of 45 °.   The laminated film according to any one of claims 1 to 4, wherein the thermoplastic resin A is made of polyethylene terephthalate, and the thermoplastic resin B is made of polyester obtained by copolymerizing at least cyclohexanedimethanol.   The laminated film according to any one of claims 1 to 4, wherein the thermoplastic resin A is made of polyethylene terephthalate, and the thermoplastic resin B is made of polyester obtained by copolymerizing at least adipic acid.   The laminated film according to any one of claims 1 to 6, wherein the thickness of the laminated film is periodically changed in the longitudinal direction or the width direction of the film.   8. One or more spectral peaks having an intensity of 0.04 to 25 at a wave number of 0.5 to 100,000 (1 / m) are observed when Fourier fluctuations of film thickness variation are analyzed. The laminated film according to any one of the above.   The designable film using the laminated | multilayer film in any one of Claims 1-8.   The film for forgery prevention using the laminated | multilayer film in any one of Claims 1-8.   The optical filter using the laminated | multilayer film in any one of Claims 1-8.   A hologram using the laminated film according to claim 1.