Decorative film

Abstract

To provide a decorative film that improves a problem of a conventional technology, exhibits a metallic tone over a wide viewing angle without using metal, and suppresses a change in a color tone when viewed from various viewing angles.SOLUTION: There is provided a decorative film that has a structure with a total of 51 or more layers in which a layer (A layer) made of a thermoplastic resin A as a main component and a layer (B layer) made of a thermoplastic resin B different from the thermoplastic resin A as a main component are alternately laminated in a thickness direction, and that satisfies the following conditions 1 and 2. Condition 1: a surface roughness Rzjis of at least one surface is 5 μm to 100 μm. Condition 2: when setting an incident angle to 45° and an acceptance angle to 5° increments between -70° and 70°, a range of acceptance angles over which an average spectral reflectance coefficient is 1 or more in a wavelength range of 400 nm to 700 nm is 20° or more.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a decorative film having excellent designability and a molded article using the same. [Background technology]

[0002] In recent years, growing environmental awareness has led to increased demand for solvent-free coatings and decorative methods that replace plating in fields such as building materials, automotive parts, mobile phones, and electrical products, and the introduction of decorative methods using films is progressing. There is also a high demand for metallic and high-gloss finishes, which can create a high level of design. In addition, as infrared sensors are increasingly being installed in various electronic devices, there is also a need for decorations that ensure infrared transparency while concealing the sensors from the outside.

[0003] Known methods for applying metallic decoration using film include forming a design layer mainly composed of aluminum, indium, chromium, etc. on the film using methods such as vacuum deposition, sputtering, or ion plating, and then transferring this to the target component. Another known method is to realize a metallic appearance by forming an optical interference multilayer film on the target component that highly reflects visible light and highly transmits near-infrared light, utilizing the optical interference phenomenon that occurs when two or more materials with different refractive indices are alternately laminated in layers with thicknesses at the wavelength of light (Patent Document 1).

[0004] Furthermore, as a method for improving the design of the above-mentioned metallic film, a film has been proposed in which a hard coat layer is applied to the surface of the metallic film, and the hard coat layer is scratched and extruded to impart a metallic design (Patent Document 2). Furthermore, a method has also been proposed in which the texture applied to the mold is transferred to the surface of the metallic film during injection molding of a decorated molded product using the metallic film, thereby obtaining a molded product with improved design (Patent Document 3). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-210142 [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-290360 [Patent Document 3] International Publication No. 2010 / 053142 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the metallic film of Patent Document 1 has the problem that, while it reflects a large amount of light in the direction of specular reflection, the amount of reflected light drops sharply when it deviates from the direction of specular reflection, making it appear dark. The film of Patent Document 2 has the problem that the surface gloss decreases when scratched and the color tone changes depending on the viewing direction. Furthermore, the texture transfer method of Patent Document 3 is performed using the heat and pressure of the injected resin flowing inside the cavity, making it difficult to transfer the texture uniformly, resulting in problems such as changes in the metallic tone due to uneven transfer. The objective of the present invention is to improve these problems of the prior art and provide a decorative film that expresses a metallic tone over a wide viewing angle without using metal and suppresses changes in color tone when viewed from various viewing angles. [Means for solving the problem]

[0007] In order to solve the above problems, the decorative film of the present invention has the following configuration: a total of 51 or more layers (A layers) each having a thermoplastic resin A as a main component and a layer (B layers) each having a thermoplastic resin B as a main component different from the thermoplastic resin A are alternately laminated in the thickness direction, and the decorative film satisfies the following conditions 1 and 2. Condition 1: The surface roughness Rzjis of at least one surface is 5 μm to 100 μm. Condition 2: When the incident angle is 45° and the receiving angle is set in 5° increments within the range of -70° to 70°, the range of receiving angles over which the average value of the spectral reflectance coefficient in the wavelength range of 400 nm to 700 nm is 1 or greater is 20° or greater. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a decorative film that exhibits a metallic tone over a wide viewing angle without using metal and that suppresses changes in color tone when viewed from various viewing angles. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram showing an example of a process for forming projections and recesses using a press (embossed plate) to obtain the decorative film of the present invention. [Figure 2] FIG. 1 is a schematic diagram showing an example of a process for forming projections and recesses using an embossing roll to obtain the decorative film of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] The decorative film of the present invention has a structure in which a total of 51 or more layers (A layers) whose main component is thermoplastic resin A and a layer (B layers) whose main component is thermoplastic resin B different from thermoplastic resin A are alternately laminated in the thickness direction, and satisfies the following conditions 1 and 2. Condition 1: The surface roughness Rzjis of at least one surface is 5 μm to 100 μm. Condition 2: When the incident angle is 45° and the receiving angle is set in 5° increments within the range of -70° to 70°, the range of receiving angles over which the average value of the spectral reflectance coefficient in the wavelength range of 400 nm to 700 nm is 1 or greater is 20° or greater.

[0011] Detailed aspects of the present invention will be described below.

[0012] The decorative film of the present invention has a structure in which a total of 51 or more layers (A layers) whose main component is thermoplastic resin A and a layer (B layers) whose main component is thermoplastic resin B different from the thermoplastic resin A are alternately laminated in the thickness direction. More preferably, a total of 251 or more layers of A layers and B layers are alternately laminated in the thickness direction, even more preferably, a structure in which 401 or more layers are laminated, and particularly preferably, a structure in which 801 or more layers are laminated. There is no particular upper limit on the number of layers, but from the viewpoints of productivity and cost, 2001 layers is preferable. If the number of laminated layers is less than 51, visible light cannot be reflected uniformly, and the film may have high saturation.

[0013] The decorative film of the present invention may be provided with another layer other than Layer A and Layer B, as long as the effects of the present invention are not impaired. Specific examples include a method in which another resin layer is co-extruded when Layer A and Layer B are laminated by the method described below, or a method in which another sheet is laminated by a known method after obtaining an alternating laminate of Layers A and B. The resin used in this layer is not particularly limited, but is preferably a thermoplastic resin when transferring the unevenness of a textured plate or embossing roll described below.

[0014] Furthermore, the main component of the thermoplastic resin constituting Layer A (thermoplastic resin A) and the main component of the thermoplastic resin constituting Layer B (thermoplastic resin B) are not particularly limited as long as they are different resins. Here, the main component refers to the resin that accounts for the largest mass % when all components constituting each layer (e.g., Layer A) are taken as 100 mass %. Furthermore, "different" thermoplastic resins refer to cases where the basic skeletons are different, or cases where the basic skeletons are the same but 30 mol % or more of the total structural units differ.

[0015] The decorative film of the present invention has a surface roughness Rzjis of 5 μm to 100 μm on at least one side. By providing such a surface roughness on at least one side, it is possible to provide high brightness even in an angular region away from the specular reflection direction and reduce color tone change over a wide viewing angle. From the above viewpoints, the surface roughness Rzjis is more preferably in the range of 10 μm to 70 μm, even more preferably 20 μm to 50 μm, and particularly preferably 22 μm to 50 μm. From the above viewpoints, it is sufficient for the surface roughness Rzjis to be 5 μm to 100 μm on at least one side, but since the surface to which the desired unevenness is imparted during decoration usually becomes the front surface, it is preferable that the surface with the larger Rzjis be 5 μm to 100 μm, and more preferably that the surface roughness Rzjis be 5 μm to 100 μm on both sides (the same applies to the above preferred ranges). The surface roughness Rzjis can be measured by a known surface roughness meter, and the measuring device may be, for example, "SURFTEST" (registered trademark) SV-2100M4 manufactured by Mitutoyo Corporation. The details of the measuring method when using this device will be described later.

[0016] If the surface roughness Rzjis is less than 5 μm, the brightness of the surface will decrease in an angle range away from the specular reflection direction, and the color tone will change significantly depending on the viewing angle. On the other hand, if the surface roughness Rzjis of both surfaces exceeds 100 μm, the decorative film may be torn due to distortion during the textured processing. Methods for making the surface roughness Rzjis of at least one surface of the decorative film of the present invention 5 μm to 100 μm include, but are not limited to, methods of applying textured processing using press molding, vacuum molding, embossing rolls, etc. at an appropriate temperature. Detailed processing methods and conditions will be described later.

[0017] The decorative film of the present invention has a range of light-receiving angles of 20° or more over which the average spectral reflectance coefficient in the wavelength range of 400 nm to 700 nm is 1 or greater when the incident angle is 45° and the receiving angle is set at 5° intervals within the range of -70° to 70° (hereinafter, the "spectral reflectance coefficient in the wavelength range of 400 nm to 700 nm" may be simply referred to as the "spectral reflectance coefficient"). While this requirement is generally satisfied on at least one side, since the surface that is typically the surface for decoration is the surface to which the desired texture is applied, it is preferable that the requirement be satisfied on the side with a large Rzjis (the same applies to the preferred ranges described below). The spectral reflectance coefficient can be measured using a known measuring device, such as the goniospectrophotometer GCMS-3B manufactured by Murakami Color Research Laboratory Co., Ltd., and a detailed measurement method using this device will be described below.

[0018] The range of light-receiving angles over which the average value of the spectral reflectance coefficient is 1 or greater is an index of the width of the viewing angle at which the metallic tone can be visually recognized; the wider this range, the wider the viewing angle at which the metallic tone can be recognized. From this perspective, the range of light-receiving angles over which the average value of the spectral reflectance coefficient is 1 or greater is more preferably 30° or greater, and even more preferably 40° or greater. From this perspective, there is no particular upper limit to the range of light-receiving angles, but from the perspective of maintaining the metallic luster tone, it is preferably 90° or less.

[0019] One method for making the range of light-receiving angles where the average value of the spectral reflectance coefficient is 1 or more 20° or more or within the above-mentioned preferred range is to provide a decorative film having an alternating layer structure of A layer / B layer with an uneven surface, thereby changing the shape of the alternating layer structure of A layer / B layer in the thickness direction. The detailed processing method and conditions will be described later.

[0020] The thickness of the decorative film of the present invention is preferably 30 μm or more in order to impart a metallic tone to the decorative film and to prevent film tearing during texture processing. From the above viewpoints, it is preferably 60 μm or more, and more preferably 80 μm or more. On the other hand, from the viewpoints of film formability and moldability, the thickness of the decorative film of the present invention is preferably 500 μm or less. From the above viewpoints, it is preferably 300 μm or less, and more preferably 150 μm or less. The thickness of the decorative film can be adjusted by appropriately combining adjustment of the cast take-up speed during film formation and adjustment of the amount of molten resin extruded from the die per unit time.

[0021] From the viewpoint of producing a metallic tone, the decorative film of the present invention preferably has an average transmittance of 60% or less, more preferably 40% or less, in the wavelength range of 400 nm to 800 nm. Here, the average transmittance in the wavelength range of 400 nm to 800 nm means the average transmittance in the wavelength range of 400 nm to 800 nm when measured at an incident angle of 0° (meaning perpendicular to the film surface). The average transmittance can be measured using a known spectrophotometer, the details of which will be described later.

[0022] There are no particular limitations on the method for achieving the average transmittance in the wavelength range of 400 nm to 700 nm within the above range, but examples include a method in which the decorative film has the aforementioned laminated structure and the layer thicknesses of the A layer and the B layer or the in-plane average refractive index of the A layer and the B layer are controlled. More specifically, examples include a method in which the in-plane average refractive index of the A layer is different from the in-plane average refractive index of the B layer (preferably a method in which 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 0.005 or more and 0.200 or less), or a method in which the number of layers with a layer-to-layer thickness of 100 nm or more and less than 250 nm is 51 or more. These methods are described in detail below.

[0023] The decorative film of the present invention can easily achieve a metallic luster appearance by making the difference in the in-plane average refractive index between the two layers 0.005 or more. The difference in the in-plane average refractive index between the two layers is more preferably 0.020 or more, and when it is desired to particularly increase the brightness of the metallic luster, the difference in the in-plane refractive index is even more preferably 0.040 or more. On the other hand, by making the difference in the in-plane average refractive index between the two layers 0.200 or less, the occurrence of delamination between the layers during molding processing can be reduced.

[0024] In the decorative film of the present invention, the number of layers having a layer-to-layer thickness of 100 nm or more but less than 250 nm is preferably 51 or more. By making the number of layers having a layer-to-layer thickness of 100 nm or more but less than 250 nm 51 or more, a metallic tone is easily expressed. From the same viewpoint, the number of layers is preferably 150 or more, and more preferably 350 or more. When it is desired to particularly increase the brightness of the metallic luster tone, it is more preferable to make the number of layers having a layer-to-layer thickness of 100 nm or more but less than 250 nm 600 or more. There is no particular upper limit, but from the viewpoint of productivity and cost, it is 2000 layers.

[0025] In order to achieve a more uniform reflectance in the 400-800 nm wavelength range and suppress color tone changes, the decorative film of the present invention preferably has a greater number of layers with a layer-to-layer thickness of 100 nm or more but less than 200 nm than the number of layers with a layer-to-layer thickness of 200 nm or more but less than 250 nm. Here, "layer-to-layer thickness" refers to the sum of the thicknesses of adjacent A and B layers. Furthermore, the layer-to-layer thickness must be the sum of the thickness of the mth A layer counted from one film surface for the A layer alone and the mth B layer counted from the same film surface for the adjacent B layer alone. Here, m represents an integer. For example, if layers A1 / B1 / A2 / B2 / A3 / B3 are arranged in the order A1 / B1 / A2 / B2 / A3 / B3... from one film surface to the opposite surface, layers A1 and B1 are the first layer pair, layers A2 and B2 are the second layer pair, and layers A3 and B3 are the third layer pair.

[0026] When the number of layers with a layer-to-layer thickness of 100 nm or more but less than 200 nm is greater than the number of layers with a layer-to-layer thickness of 200 nm or more but less than 250 nm, the phenomenon of reflectivity decreasing toward lower wavelengths in the reflection band of 400 nm to 800 nm is suppressed, resulting in a less reddish appearance. This occurs because the density of layer pairs that cause reflection in the lower wavelength range is ensured. Therefore, the layer-to-layer thickness sequence of the layers constituting the decorative film preferably does not increase or decrease monotonically in an arithmetic progression, but rather increases or decreases in a geometric progression while satisfying the above conditions. From this perspective, it is preferable that the number of layers with a layer-to-layer thickness of 100 nm or more but less than 200 nm be 1.05 to 2.50 times the number of layers with a layer-to-layer thickness of 200 nm or more but less than 250 nm.

[0027] In the decorative film of the present invention, it is preferable that the thermoplastic resin A and the thermoplastic resin B are polyester resins. The polyester resin is a resin having a molecular structure in which dicarboxylic acid units and diol units are linked by ester bonds.

[0028] If the types of thermoplastic resin A and thermoplastic resin B are unknown, FT-IR, pyrolysis GC-MS, 1 H-NMR, 13 The type of resin can be identified by combining known methods such as C-NMR. If Layer A or Layer B is a mixture of multiple resins and the main resin component is unknown, the main component can be determined by separating the components using known methods such as solvent extraction or various types of chromatography and determining their content (mass%).

[0029] When the thermoplastic resin A and the thermoplastic resin B are polyester resins, polyesters obtained by polymerization of a monomer mainly composed of an aromatic dicarboxylic acid or an aliphatic dicarboxylic acid and a diol are preferred.

[0030] Examples of aromatic dicarboxylic acids 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'-diphenyletherdicarboxylic acid, and 4,4'-diphenylsulfonedicarboxylic acid. Examples of aliphatic dicarboxylic acids include adipic acid, suberic acid, sebacic acid, dimer acid, dodecanedioic acid, cyclohexanedicarboxylic acid, and their ester derivatives. Among these, terephthalic acid and 2,6-naphthalenedicarboxylic acid, which have high refractive indices, are preferred. These acid components may be used alone or in combination, or may be partially copolymerized with hydroxy acids such as hydroxybenzoic acid.

[0031] Examples of diol components include ethylene glycol, 1,2-propanediol, 1,3-propanediol, neopentyl glycol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-hexanedimethanol, diethylene glycol, triethylene glycol, polyalkylene glycol, 2,2-bis(4-hydroxyethoxyphenyl)propane, isosorbate, and spiroglycol. Among these, ethylene glycol is preferred. These diol components may be used alone or in combination.

[0032] Among the polyester resins, from the viewpoint of increasing the in-plane average refractive index of layer A and making it easier to make the difference between the in-plane average refractive index of layer A and layer B 0.005 or more, preferably 0.040 or more, it is preferable to use polyethylene terephthalate and copolymers thereof, polyethylene naphthalate and copolymers thereof, polybutylene terephthalate and copolymers thereof, polybutylene naphthalate and copolymers thereof, and further polyhexamethylene terephthalate and copolymers thereof, polyhexamethylene naphthalate and copolymers thereof, etc.

[0033] The combination of thermoplastic resin A and thermoplastic resin B is preferably one in which both thermoplastic resins share a common basic skeleton. Here, the term "basic skeleton" as used herein refers to the smallest repeating unit constituting the resin and the one that is most abundant. For example, in the case of polyethylene terephthalate, the basic skeleton is ethylene terephthalate. An example of such a combination is one in which one thermoplastic resin is polyethylene terephthalate and the other thermoplastic resin is a polymer (copolymer) composed of ethylene terephthalate units and cyclohexane 1,4-dimethylene terephthalate units, with ethylene terephthalate units being the most abundant. Using resins with the same basic skeleton for thermoplastic resin A and thermoplastic resin B reduces the likelihood of problems such as flow marks and other lamination defects and interlayer peeling during the production of a decorative film.

[0034] A crystalline resin is preferably used as the thermoplastic resin A to improve the resistance to pressure marks (dents) and to increase the stiffness of the decorative film itself. Polyethylene terephthalate or polyethylene naphthalate is preferably used as the thermoplastic resin A. On the other hand, an amorphous resin is preferably used as the thermoplastic resin B to suppress an increase in refractive index and form an amorphous film. A polyethylene terephthalate or polyethylene naphthalate copolymer containing isophthalic acid, naphthalenedicarboxylic acid, diphenyl acid, or cyclohexanedicarboxylic acid, or containing spiroglycol, cyclohexanedimethanol, bisphenoxyethanolfluorene, or bisphenol A as structural units, is preferably used as the thermoplastic resin B. When the endothermic heat absorption during heating of a resin is measured using a differential scanning calorimeter (DSC) at a heating rate of 10°C / min in accordance with JIS K7121:2012, a resin that exhibits an endothermic peak is considered crystalline, while a resin that does not exhibit an endothermic peak is considered amorphous.

[0035] Furthermore, when the thermoplastic resin A and thermoplastic resin B constituting the decorative film of the present invention are polyesters, a biaxially oriented film is preferred from the viewpoints of film strength, heat resistance, and versatility. A biaxially oriented film is a film having molecular orientation in two perpendicular directions, and is typically obtained by stretching an unstretched sheet in two perpendicular directions (usually the longitudinal direction and the width direction). An example of a preferred production method is described below, but the film production method is not limited to this. The longitudinal direction refers to the direction in which the film runs during the production process (the winding direction in the case of a film roll), and the width direction refers to the direction perpendicular to the longitudinal direction within the plane of the film.

[0036] The method for producing a film before texture processing according to the present invention will be described below with examples, but is not limited to the following examples.

[0037] First, thermoplastic resin A and thermoplastic resin B are prepared in pellet form. The pellets are dried in hot air or vacuum, as needed, and then fed into two extruders. The thermoplastic resins are heated to above their melting points in each extruder, and the extrusion rate is uniformed using a gear pump or similar device. Further, foreign matter and denatured resins are removed through a filter or similar device. Thermoplastic resin A and thermoplastic resin B are delivered from separate flow paths using the two extruders, and then fed into a multi-layer lamination device. While multi-manifold dies, feed blocks, static mixers, and other devices can be used as multi-layer lamination devices, it is particularly desirable to use a feed block containing at least two or more separate members with numerous fine slits to efficiently achieve the laminate structure of the decorative film of the present invention. Using such a feed block prevents the device from becoming excessively large, reduces foreign matter due to thermal degradation, and enables high-precision lamination even when the number of layers is extremely large. Furthermore, the lamination accuracy in the width direction is significantly improved compared to conventional technology, and it is also easy to form arbitrary layer thickness configurations. With this device, the thickness of each layer can be adjusted by changing the slit shape (length, width, gap), making it possible to easily achieve any desired layer thickness.

[0038] In this case, in order to achieve "an average transmittance of 60% or less in the wavelength band of 400 nm to 700 nm," which is a preferred embodiment of the decorative film of the present invention, it is preferable to design the layer thickness of each layer of the decorative film based on the following formula 1. The decorative film is capable of reflecting / transmitting light, and its reflectance can be controlled by the difference in refractive index between the layer made of thermoplastic resin A and the layer made of thermoplastic resin B and the number of layers. Equation 1: 2×(na·da+nb·db)=λ na: In-plane average refractive index of the layer made of resin A nb: In-plane average refractive index of the layer made of resin B da: Layer thickness (nm) of the layer made of resin A db: Layer thickness of the layer made of resin B (nm). λ: Main reflection wavelength (first reflection wavelength) The molten laminate with the desired layer structure is extruded into a sheet from a die slit, and the sheet is extruded onto a cooling roller such as a casting drum and cooled to solidify, yielding a cast film (unstretched film). In this case, it is preferable to use a wire-, tape-, wire-, or knife-shaped electrode to electrostatically contact the sheet with the cooling roller such as a casting drum to rapidly solidify it. It is also preferable to blow air from a slit-, spot-, or planar-shaped device to rapidly solidify the sheet, or to contact the cooling roller with a nip roll to rapidly solidify it. The temperature of the cooling roller is preferably 0°C to 50°C.

[0039] The cast film (unstretched film) thus obtained is preferably biaxially stretched as needed. Biaxial stretching refers to stretching in the longitudinal direction and the width direction. The stretching may be performed in two axial directions sequentially or simultaneously in two directions. Furthermore, the film may be further re-stretched in the longitudinal direction and / or the width direction.

[0040] First, we will explain the case of sequential biaxial stretching. Here, longitudinal stretching refers to stretching to impart molecular orientation to the film in the longitudinal direction, and is usually performed by varying the peripheral speed of the rolls. This stretching can be performed in a single stage using a pair of stretching rolls, or in multiple stages using multiple pairs of stretching rolls. The stretching ratio varies depending on the type of resin, but is usually preferably 2.0 to 15 times. When polyethylene terephthalate is used as one of the thermoplastic resins constituting the decorative film, a ratio of 2.0 to 7.0 times is particularly preferred. Furthermore, the preheating temperature and stretching temperature, depending on the composition of the thermoplastic resins A and B constituting the decorative film, are preferably 50°C to 200°C. During stretching, the cast film may be rapidly heated using a radiation heater to improve stretchability.

[0041] The subsequent widthwise stretching refers to stretching to impart molecular orientation to the film in the width direction. Typically, a tenter is used to convey the film while holding both ends with clips. The film is heated and preheated to 50°C to 200°C, and then stretched in the width direction. The aqueous coating applied just before the tenter is dried during this preheating. The stretching ratio varies depending on the type of resin, but is typically preferably 2.0 to 15 times. When polyethylene terephthalate is used as either thermoplastic resin A or thermoplastic resin B, a ratio of 2.0 to 7.0 times is particularly preferred. The biaxially stretched film is preferably heat-treated in the tenter at a temperature above the stretching temperature and below 300°C to impart flatness and dimensional stability. After heat treatment, the film is uniformly and slowly cooled to room temperature and wound on a winder. If necessary, a relaxation treatment or the like may be performed during the heat treatment and slowly cooling process.

[0042] During this heat treatment, in order to suppress the distribution of the main orientation axis in the width direction, it is preferable to instantaneously perform a relaxation treatment in the longitudinal direction immediately before and / or immediately after entering the heat treatment zone. After heat treatment in this manner, the film is uniformly and slowly cooled, then cooled to room temperature, and wound up on a winder. If necessary, relaxation treatment may also be performed in the longitudinal direction and / or width direction during the slow cooling period after heat treatment. It is preferable to instantaneously perform a relaxation treatment in the longitudinal direction immediately before and / or immediately after entering the heat treatment zone. The relaxation rate in this case is preferably 0.5% to 15%. After heat treatment in this manner, the film is uniformly and slowly cooled, then cooled to room temperature, and wound up on a winder.

[0043] Thereafter, the biaxially stretched film thus obtained is provided with irregularities by the method described below so that the surface roughness Rzjis is 5 μm to 100 μm.

[0044] The method for producing a decorative film of the present invention is characterized in that a film having a structure in which a total of 51 or more layers (A layers) mainly composed of thermoplastic resin A and a layer (B layers) mainly composed of a thermoplastic resin B different from the thermoplastic resin A are alternately laminated in the thickness direction is subjected to transfer of the unevenness of a textured plate or the shape of an embossing roll, thereby adjusting the surface roughness Rzjis to 5 μm to 100 μm. As the "film having a structure in which a total of 51 or more layers (A layers) mainly composed of thermoplastic resin A and a layer (B layers) mainly composed of a thermoplastic resin B different from the thermoplastic resin A are alternately laminated in the thickness direction," for example, a film having a structure in which 51 or more A layers and B layers are alternately laminated, obtained by the method described above, can be used.

[0045] In the method for producing the decorative film of the present invention, it is important to adjust the surface roughness Rzjis to 5 μm to 100 μm by transferring the unevenness of a textured plate or the shape of an embossing roll to the film. Specific methods for this will be described below with reference to the drawings.

[0046] FIG. 1 shows an example of a textured processing process using a press (embossed plate). In the embodiment shown in FIG. 1, a film (101) unwound from a winding roll (100) is sandwiched between a pair of guide rolls (102). After a certain amount of unwound film is unwound, the film is sandwiched between a press (202) equipped with upper and lower press dies (200, 201) to transfer the textured pattern. After the press dies are opened, the next amount of film is unwound and similarly processed intermittently. The textured film (106) is wound up on a take-up roll (107). Alternatively, punching can be performed simultaneously with textured processing. The temperature of the upper and lower dies used in this processing depends on the material of the film to be processed, but is preferably set to 100°C to 220°C, more preferably 120°C to 200°C, and even more preferably 150°C to 180°C.

[0047] Next, an example of an uneven processing process using an embossing roll is shown in Figure 2. Since uneven processing using an embossing roll allows for continuous processing, it is generally possible to process at higher speeds than processing using the press machine mentioned above.

[0048] The film (101) unwound from the unwinding roll (100) is sandwiched between a pair of guide rolls (102) and then preheated in a preheating furnace (103). The film is then pressed with an embossing roll (104) and a support roll (105) to transfer the textured pattern to the film, after which the textured film (106) is taken up by a take-up roll (107). This processing method allows continuous unwinding from the roll without stopping, making it suitable for high-speed textured processing with the same pattern across the entire length of the film. Alternatively, the support roll (105) may also be shaped to impart textured patterns to both sides of the film.

[0049] The heating temperature of the film in the preheating furnace depends on the material of the film before processing, but is preferably in the range of 100°C to 220°C from the viewpoints of the transferability of the embossing roll and the prevention of thermal degradation and delamination of the film, with 150°C to 200°C being more preferable from the above viewpoints. The temperature of the embossing roll may be controlled or not, but temperature control is desirable for the transferability of the textured patterns. The temperature of the roll is preferably controlled to 50°C or higher but less than 100°C, as this can be achieved with a general temperature controller. However, if the transfer of textured patterns is desired, it is also possible to heat the roll to 100°C or higher using a pressurized water temperature controller, oil temperature controller, electromagnetic heating roll, or the like. However, if the roll temperature is too high, the film's releasability from the roll may be impaired, potentially resulting in delamination, so a temperature of 200°C or lower is preferable. Furthermore, when the embossing roll temperature is 150°C or higher, textured processing may be performed without a preheating furnace, depending on the film thickness, processing speed, and the height of the textured patterns to be transferred.

[0050] The texturing of the plate and the embossing of the embossing roll can be carried out by known techniques such as etching, laser processing, and machining. Examples of the texturing or embossing pattern include matte finish, leather grain, and geometric patterns, and can be appropriately selected from those that can adjust the surface roughness Rzjis of the decorative film to 5 to 100 μm. Furthermore, since the textured film processing using a press or embossing produces fine textured patterns without melting the film, it is preferable that the height and depth of the textured plate or embossing roll be 1.0 to 1.5 times the desired textured film.

[0051] The decorative film of the present invention exhibits a metallic tone over a wide viewing angle, suppresses color tone changes when viewed from various viewing angles, and has excellent formability, making it suitable for use as a molded body. The molded body of the present invention is formed using the decorative film of the present invention. The method for forming the molded body is not particularly limited as long as it does not impair the effects of the present invention, and molding methods such as insert molding and vacuum / pressure molding can be used. Furthermore, in order to improve adhesion between the decorative film of the present invention and a resin part, it is also possible to provide an adhesive layer on the film surface or to laminate another thermoplastic resin film to the film via an adhesive layer.

[0052] The resin used in insert molding is not particularly limited as long as it does not impair the effects of the present invention, and examples thereof include polybutadiene resins, polystyrene resins, polypropylene resins, acrylic resins, polyacrylonitrile-styrene copolymer resins, polyacrylonitrile-butadiene-styrene copolymer resins, polycarbonate resins, and polyacrylonitrile-ethylene propylene-styrene copolymer resins. Furthermore, various additives may be added as long as they do not impair the effects of the present invention. Preferred additives include ultraviolet absorbers and pigments for coloring purposes.

[0053] Furthermore, the molding substrate used in vacuum and compressed air molding is not particularly limited as long as it does not impair the effects of the present invention, and examples thereof include resins such as polybutadiene resins, polystyrene resins, polypropylene resins, acrylic resins, polyacrylonitrile-styrene copolymer resins, polyacrylonitrile-butadiene-styrene copolymer resins, polycarbonate resins, and polyacrylonitrile-ethylene propylene-styrene copolymer resins; metals such as aluminum and magnesium; glass; and carbon fiber moldings.

[0054] Furthermore, in order to enhance the design of the molded body, a partial print layer may be provided on the decorative film by a known method before insert molding or vacuum / compressed air molding. [Example]

[0055] The present invention will be explained in more detail below by showing examples, but the present invention is not limited to these examples.

[0056] [Measurement and evaluation methods] The measurements and evaluations shown in the examples were carried out under the following conditions.

[0057] (1) Layer structure of decorative film, layer thickness, number of layers with a layer-to-layer thickness of 250 nm or more and less than 300 nm, and number of layers with a layer-to-layer thickness of 100 nm or more and less than 250 nm A cross section parallel to the thickness direction was cut from a decorative film sample using a microtome. Next, the cross section of the decorative film was observed and photographed at 40,000x magnification using a Hitachi H-7100FA transmission electron microscope (TEM) at an accelerating voltage of 75 kV. The layer structure and layer thickness were measured using the obtained images, as described below. To achieve high contrast, the sample was stained using RuO4.

[0058] Next, a specific method for determining the layer structure and layer thickness of the decorative film will be described. A cross-sectional photograph taken with a TEM at approximately 40,000x magnification was captured at an image size of 729 dpi using a "CanonScan" (registered trademark) D123U (Canon Inc.). The image was saved in JPEG format, and then the JPEG file was opened and analyzed using image processing software Imagc-Pro Plus ver. 4 (sold by Planetron Co., Ltd.). Image analysis was performed in vertical thick profile mode, and the relationship between the average brightness in the region sandwiched between two lines in the thickness and width directions was read as numerical data. Using spreadsheet software ("Excel" (registered trademark) 2000, Microsoft Corporation), data was collected for position (nm) and brightness data at a sampling step of 6 (thinning 6), and then numerical processing was performed using a three-point moving average. Furthermore, the obtained data showing periodic changes in brightness were differentiated, and the maximum and minimum values ​​of the differential curve were read using a VBA (Visual Basic for Applications) program. The distance between adjacent values ​​was calculated as the layer thickness of one layer. This procedure was performed for each photograph, and the layer thickness was calculated for all layers. Of the layer thicknesses obtained, thin layers were defined as layers with a thickness of less than 1 μm. For thin layers, the average sum of the layer thicknesses of adjacent A and B layers was calculated sequentially for all pairs, and the number of layers with a layer-to-layer thickness of 250 nm or more but less than 300 nm and the number of layers with a layer-to-layer thickness of 100 nm or more but less than 250 nm were counted.

[0059] (2) Surface roughness Rzjis A 10 cm square sample was cut out from the center of the decorative film. Next, one side of the cut-out sample was measured using a "SURFTEST" (registered trademark) SV-2100M4 model manufactured by Mitutoyo Corporation under the conditions of λc = 8 mm, λs = 8 μm, section 2, and measurement length L = 16 mm, and the 10-point average roughness was calculated from the obtained cross-sectional curve. Measurements were taken three times at different positions within the 10 cm square sample, and the average value of the 10-point average roughness obtained was taken as Rzjis. Similar measurements were taken three times on the other side, and Rzjis was calculated.

[0060] (3) The range of acceptance angles in which the average value of the spectral reflectance coefficient in the wavelength range of 400 nm to 700 nm is 1 or more when the incident angle is 45° and the acceptance angle is set in 5° intervals in the range of -70° to 70°. A 10cm square sample was cut from the center of the decorative film. Next, a goniospectrophotometer GCMS-3B manufactured by Murakami Color Research Laboratory Co., Ltd. was used to measure at 5-degree intervals, with an incident angle of 45° and acceptance angles of -75° to 75°. The measurement wavelength was set to 390nm to 730nm (measurement interval: 10nm). The average value of the light intensity data for the wavelength range of 400nm to 700nm obtained for each acceptance angle was calculated, and the range of acceptance angles within the acceptance angle range of -70° to 70° where the average light intensity value was 1 or greater was determined.

[0061] For example, if the average light intensity is less than 1 in the light-receiving angle ranges of -70° to 30° and 55° to 70°, and the average light intensity is 1 or greater at light-receiving angles of 35°, 40°, 45°, and 50°, the width of the light-receiving angle range (35° to 50°) where the average light intensity value is 1 or greater is 15°.

[0062] (4) Average transmittance in the wavelength range of 400 to 800 nm A 5cm square sample was cut from the decorative film. The transmittance was measured at an incident angle Φ = 0° using a Hitachi U-4100 spectrophotometer. The inner wall of the attached integrating sphere was made of barium sulfate. The measurement wavelength was 250nm to 1200nm, the slit was 2nm (visible) / automatic control (infrared), the gain was set to 2, and the scan speed was 600nm / min. The average transmittance was then calculated over a wavelength range of 400nm to 800nm. The average reflectance was calculated based on the Simpson method using absolute reflectance data at wavelength intervals of 1nm. The area enclosed by the reflectance curve and the wavelength band was calculated and divided by 400nm, the width of the wavelength band, to obtain the average transmittance. A detailed explanation of the Simpson method is provided in "Numerical Calculation Methods for Electronic Computers I" by Jiro Yamauchi et al. (Baifukan Publishing, 1965).

[0063] (5) In-plane refractive index of layer A or B The resin used for Layer A was melted at 290°C in a vented twin-screw extruder, passed through a gear pump and filter, and then introduced into a T-die to form a sheet. The sheet was then pressed against a casting drum maintained at a surface temperature of 25°C by electrostatic application, resulting in a 100 μm-thick cast film. A sample was taken from the center of the width direction of the resulting film, and the refractive indices in the machine and width directions of the film were measured using an Abbe refractometer NAR 4T (manufactured by Atago Co., Ltd.) with a sodium D line as a light source. The average of these values ​​was taken as the in-plane refractive index. A cast film was also prepared for Layer B using the resin used for Layer B, and the in-plane refractive index was determined.

[0064] (6) Lightness L*, chromaticity a*, b* at an incident angle of 5° or 45° A 5cm square sample was cut out from the decorative film. Using a BYK-Chemie colorimeter BYK-mac i, the incident angle and receiving angle were both set to 5°, and the reflected lightness L*, and reflected chromaticity a* and b* were measured. Similarly, the incident angle and receiving angle were both set to 45°, and the reflected lightness L*, and reflected chromaticity a* and b* were measured.

[0065] [Thermoplastic resins, etc. used in the manufacture of decorative films] The following thermoplastic resins were used to obtain films for decorative films. Among the following thermoplastic resins, A-1 is crystalline, and B-1 and B-2 are amorphous.

[0066] (Thermoplastic resin A-1) To a mixture of 100 parts by mass of dimethyl terephthalate and 60 parts by mass of ethylene glycol, 0.09 parts by mass of magnesium acetate and 0.03 parts by mass of antimony trioxide were added relative to the amount of dimethyl terephthalate, and the mixture was heated to a temperature by a conventional method to carry out an ester exchange reaction. Next, 0.020 parts by mass of an 85% aqueous solution of phosphoric acid relative to the amount of dimethyl terephthalate was added to the ester exchange reaction product, and the mixture was then transferred to a polycondensation reaction tank. The reaction system was gradually reduced in pressure while being heated, and a polycondensation reaction was carried out at 290°C under a reduced pressure of 1 mmHg by a conventional method, yielding polyethylene terephthalate (hereinafter sometimes referred to as PET) with an intrinsic viscosity (IV) of 0.63. This was designated thermoplastic resin A-1.

[0067] (Thermoplastic resin B-1) A copolymer polyester resin having an intrinsic viscosity (IV) of 0.55, obtained by copolymerizing 21 mol % of spiroglycol (SPG) and 24 mol % of cyclohexanedicarboxylic acid (CHDC), was designated as thermoplastic resin B-1.

[0068] (Thermoplastic resin B-2) A copolymer polyester resin copolymerized with 30 mol % of cyclohexanedimethanol (CHDM) and having an intrinsic viscosity (IV) of 0.72 was designated as thermoplastic resin B-2.

[0069] (Thermoplastic resin B-3) A copolymer polyester resin mixture obtained by mixing thermoplastic resin A-1 and thermoplastic resin B-2 at a mass ratio of 45:55 was used as thermoplastic resin B-3.

[0070] Example 1 (Manufacturing of film (before texture processing)) Thermoplastic resins A-1 and B-3 were melted at 290°C in separate vented twin-screw extruders, then passed through a gear pump and filter to a 901-layer feedblock with four separate 225-slit members. The outermost layers on both sides, forming thick layers, were thermoplastic resin A, with thermoplastic resin A and thermoplastic resin B alternately laminated, and the thicknesses of adjacent layers of thermoplastic resin A and thermoplastic resin B were approximately the same. The resulting mixture was then introduced into a T-die and molded into a sheet. It was then rapidly solidified by contact with a casting drum maintained at a surface temperature of 25°C by electrostatic application, yielding a cast film. The resulting cast film was then heated using a group of rolls set at 75°C and stretched 3.3 times in the machine direction (longitudinal direction) within a 100mm stretching section while rapidly heating both sides of the film using a radiation heater. It was then cooled once to obtain a uniaxially stretched film. The obtained uniaxially stretched film was introduced into a tenter, preheated with hot air at 100° C., and then stretched 3.5 times in the transverse direction at a temperature of 110 to 150° C. The biaxially stretched film was then heat-treated with hot air at 240° C. in the tenter, and then subjected to a 7% relaxation treatment in the transverse direction at the same temperature, after which it was cooled to room temperature and taken up on a winder.

[0071] (Film texture processing) In a vacuum press machine VH1.5-2194 manufactured by Kitagawa Seiki Co., Ltd., the following were stacked in this order from bottom to top: (1) a mold having a matte pattern (TH117) on the surface of a 5 mm thick, 100 mm square carbon steel (50C) plate, (2) the film described above before the texture processing, (3) Kinyo Board (registered trademark) F-200 manufactured by Kinyosha Co., Ltd., and (4) an unprocessed carbon steel (50C) plate. The temperatures of the upper and lower molds were set to 180°C, and the molds were pressed at a pressure of 4 MPa for 5 minutes to obtain a decorative film.

[0072] Examples 2 to 9 A decorative film was obtained in the same manner as in Example 1, except that the type of thermoplastic resin B and the pattern of the mold used for processing the film into recesses and protrusions were as shown in Table 1.

[0073] (Comparative Example 1) A decorative film was obtained in the same manner as in Example 1, except that a single film (before forming the irregularities) was produced using only the thermoplastic resin A-1. The evaluation results are shown in Table 1.

[0074] (Comparative Example 2) The film obtained in Example 3 (before forming the irregularities) was used as it was without being subjected to irregularity processing. The evaluation results are shown in Table 1.

[0075] (Comparative Example 3) A decorative film was obtained in the same manner as in Example 3, except that the temperatures of the upper and lower molds during the uneven processing were set to 80° C. The evaluation results are shown in Table 1.

[0076] Comparative Example 4 A decorative film was obtained in the same manner as in Example 3, except that the unevenness was formed by scratching instead of by die pressing. The evaluation results are shown in Table 1.

[0077] (Comparative Example 5) A decorative film was obtained in the same manner as in Example 3, except that the pattern of the mold used for the uneven processing was as shown in Table 1. The evaluation results are shown in Table 1.

[0078] [Table 1]

[0079] The films of each of the Examples and Comparative Examples 2 to 5 all contain three or more thick layers with a thickness of 1 μm or more and 20 μm or less, and the number of layers with a thickness of 100 nm or more and 200 nm or less is greater than the number of layers with a thickness of 200 nm or more and 250 nm or less. This layer structure was achieved by adjusting the structure of the feed block using the method described in JP 2007-176154 A. [Industrial Applicability]

[0080] The present invention provides a decorative film that exhibits a metallic tone over a wide viewing angle without using metal and suppresses changes in color tone when viewed from various viewing angles. Because the molding film of the present invention has the above-mentioned excellent properties, it can be suitably used for decorating molded components such as building materials, automobile parts, mobile phones, electrical products, housing equipment, and gaming machine parts. [Explanation of symbols]

[0081] 100: Film roll for unwinding 101: Film before texture processing 102: Guide roll 103: Film heating preheating furnace 104: Embossing roll 105: Support roll 106: Textured film 107: Roll of textured film 200: Upper die for press 201: Press lower die 202: Press machine

Claims

1. A decorative film having a structure in which a total of 51 or more layers (A layers) whose main component is thermoplastic resin A and a layer (B layers) whose main component is thermoplastic resin B different from the thermoplastic resin A are alternately laminated in the thickness direction, and the film satisfies the following conditions 1 and 2. Condition 1: The surface roughness Rzjis of at least one surface is 5 μm to 100 μm. Condition 2: When the incident angle is 45° and the receiving angle is set in 5° increments within the range of -70° to 70°, the range of receiving angles over which the average value of the spectral reflectance coefficient in the wavelength range of 400 nm to 700 nm is 1 or greater is 20° or greater.

2. 2. The decorative film according to claim 1, wherein the average transmittance in the wavelength range of 400 nm to 800 nm is 60% or less.

3. The decorative film according to claim 1 or 2, wherein the thermoplastic resin A and the thermoplastic resin B are polyester resins.

4. A method for manufacturing a decorative film, comprising: a film having a structure in which a layer (A layer) whose main component is thermoplastic resin A and a layer (B layer) whose main component is thermoplastic resin B different from the thermoplastic resin A are alternately laminated in the thickness direction, for a total of 51 layers or more; and a method for adjusting the surface roughness Rzjis to 5 μm to 100 μm by transferring the irregularities of a textured plate or embossing roll to the film.

5. A molded article obtained by using the decorative film according to claim 1 or 2.

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