JP2024001426A - laminated polyester film roll - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminated polyester film roll that is excellent in metallic luster tone and suppresses color irregularity.

SOLUTION: A laminated polyester film roll has a laminated polyester film wound around a core, the laminated polyester film having all of the following features 1 to 5. Feature 1: Average reflectance in the wavelength band of 400 to 800 nm is 60% or more and 100% or less. Feature 2: Average reflectance in the wavelength band of 1000 to 2000 nm is 1% or more and 15% or less. Feature 3: It has a laminated structure in which a total of 99 or more layers with different refractive indexes are alternately laminated. Feature 4: The difference between the maximum and minimum values of the average reflectance in the wavelength band of 600 to 1000 nm at each point dividing a straight line parallel to the width direction into 11 equal parts is 1% or more and 10% or less. Feature 5: ΔE at each point dividing a straight line parallel to the width direction into 11 equal parts is smaller than 5.

SELECTED DRAWING: None

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to a laminated polyester film roll that suppresses color unevenness.

In recent years, as environmental awareness has increased, there has been an increasing demand for solvent-free painting and plating alternatives for decorating molded parts for building materials, automobile parts, mobile phones, home appliances, computers, etc., and the introduction of decorative methods using films has increased. It's progressing. As for decorative designs, wood grain, cloth grain, and metal-like designs are used to enhance the design. Among them, there is a high need for metallic designs because they bring out a sense of luxury, but since molding from metal increases the weight, it is often decorated with metallic luster using resin base materials such as decorative films. There is.

As for the properties required for decorative films, moldability that can follow the shape of molded parts is important, but for example, when used to decorate large area molded parts such as large home appliances such as refrigerators and automobile parts, Color stability is also required because uneven color tone impairs the appearance quality.

Under such circumstances, Patent Document 1 has an excellent design with a metallic luster tone, color stability that shows no color difference even over a large area, and resistance to imprinting, and also suppresses appearance defects called flow marks. A decorative metallic luster film is disclosed. Further, Patent Document 2 proposes a laminated film with small chroma and a small change in chroma during molding, and few defects in appearance due to viscosity characteristics and a thick layer in the laminated portion, and a decorated molded article using the same. There is.

Japanese Patent Application Publication No. 2015-164798 Japanese Patent Application Publication No. 2016-16883

However, although the techniques disclosed in Patent Documents 1 and 2 can reduce appearance defects, they are not sufficiently effective in improving color unevenness due to thickness unevenness. Therefore, an object of the present invention is to provide a laminated polyester film roll that has excellent metallic luster and suppresses color unevenness.

The present invention consists of the following configuration in order to solve the above problems. That is, it is a laminated polyester film roll in which a laminated polyester film is wound around a core, and the laminated polyester film roll is characterized in that the laminated polyester film has all of the following features 1 to 5.
Feature 1: Average reflectance in the wavelength band of 400 to 800 nm is 60% or more and 100% or less.
Feature 2: Average reflectance in the wavelength band of 1000 to 2000 nm is 1% or more and 15% or less.
Feature 3: It has a laminated structure in which a total of 99 or more layers with different refractive indexes are alternately laminated.
Feature 4: The difference between the maximum and minimum values of the average reflectance in the wavelength band of 600 to 1000 nm at each point dividing a straight line parallel to the width direction into 11 equal parts is 1% or more and 10% or less.
Feature 5: ΔE at each point dividing a straight line parallel to the width direction into 11 equal parts is smaller than 5.

Moreover, the laminated polyester film roll of the present invention can also be made into the following aspects, and it can also be made into the following molded decorative body using this.
(1) A laminated polyester film roll in which a laminated polyester film is wound around a core, the laminated polyester film roll having all of the following features 1 to 5.
Feature 1: Average reflectance in the wavelength band of 400 to 800 nm is 60% or more and 100% or less.
Feature 2: Average reflectance in the wavelength band of 1000 to 2000 nm is 1% or more and 15% or less.
Feature 3: It has a laminated structure in which a total of 99 or more layers with different refractive indexes are alternately laminated.
Feature 4: The difference between the maximum and minimum values of the average reflectance in the wavelength band of 600 to 1000 nm at each point dividing a straight line parallel to the width direction into 11 equal parts is 1% or more and 10% or less.
Feature 5: ΔE at each point dividing a straight line parallel to the width direction into 11 equal parts is smaller than 5.
(2) When the layer with a low refractive index in the laminated structure is the A layer and the layer with a high refractive index is the B layer, the difference between the in-plane average refractive index of the A layer and the in-plane average refractive index of the B layer. The laminated polyester film roll according to (1), wherein is 0.040 or more and 0.120 or less.
(3) The main component of the A layer is polyethylene terephthalate or polyethylene naphthalate, and the B layer contains a copolymerized polyester resin whose main constituent units are spiroglycol and cyclohexanedicarboxylic acid units (1) or (2). ) The laminated polyester film roll described in ).
(4) A decorated molded article using the laminated polyester film constituting the laminated polyester film roll according to any one of (1) to (3).

According to the present invention, it is possible to provide a laminated polyester film roll that has excellent metallic luster and suppresses color unevenness.

FIG. 2 is a schematic view of the multilayer merging device used in Examples, with no partition walls inserted, as viewed from the longitudinal direction. FIG. 3 is a schematic view of a state in which a partition wall portion is inserted into the multilayer merging device used in Examples, as viewed from the thickness direction. FIG. 2 is a schematic diagram showing a state in which the partition wall of the multilayer merging device used in the example is inserted, observed from the longitudinal direction, and an enlarged view of the groove portion.

Hereinafter, the laminated polyester film roll of the present invention will be explained. The laminated polyester film roll of the present invention is a laminated polyester film roll in which a laminated polyester film is wound around a core, and is characterized in that the laminated polyester film has all of the following features 1 to 5.
Feature 1: Average reflectance in the wavelength band of 400 to 800 nm is 60% or more and 100% or less.
Feature 2: Average reflectance in the wavelength band of 1000 to 2000 nm is 1% or more and 15% or less.
Feature 3: It has a laminated structure in which a total of 99 or more layers with different refractive indexes are alternately laminated.
Feature 4: The difference between the maximum and minimum values of the average reflectance in the wavelength band of 600 to 1000 nm at each point dividing a straight line parallel to the width direction into 11 equal parts is 1% or more and 10% or less.
Feature 5: ΔE at each point dividing a straight line parallel to the width direction into 11 equal parts is smaller than 5.

Note that a laminated polyester film refers to a sheet-like product that contains more than 50% by mass and 100% by mass or less of polyester resin, and has two or more layers, when all components constituting the film are 100% by mass. . Moreover, polyester resin refers to a resin having a structure in which dicarboxylic acid units and diol units are alternately repeated via ester bonds.

The laminated polyester film constituting the laminated polyester film roll of the present invention needs to have an average reflectance of 60% or more and 100% or less in the wavelength band of 400 to 800 nm from the viewpoint of realizing a metallic design. If the average reflectance is less than 60%, the reflectance in the visible light region will be insufficient, resulting in insufficient gloss and poor metallic design. From the above viewpoint, the average reflectance is more preferably greater than 70% and less than or equal to 100%.

The average reflectance and the average reflectance in another band described later can be measured as the relative reflectance at the incident angle Φ = 10 degrees using a known spectrophotometer under the following conditions, and the detailed procedure and conditions are as follows. is shown in Examples. Note that the spectrophotometer is not particularly limited as long as it is capable of measurement, and for example, U-4100 Spectrophotometer (manufactured by Hitachi, Ltd.) can be used.

As a method for making the average reflectance of a laminated polyester film within the above range, for example, a laminated structure in which a total of 99 or more layers with different refractive indexes are laminated alternately, and further from one side to the opposite side is used. On the other hand, there is a method of gradually increasing or decreasing the layer thickness in the range of 20 nm or more and 500 nm or less to bring the reflective band closer to a desired value.

The laminated polyester film constituting the laminated polyester film roll of the present invention needs to have an average reflectance of 1% to 15% in the wavelength band of 1000 to 2000 nm from the viewpoint of use in applications requiring infrared transmission. . If the average reflectance is 15% or more, infrared rays will be reflected, resulting in insufficient infrared transmittance, and as a result, the operation of devices using infrared sensors may be hindered. From the above viewpoint, the average reflectance in the wavelength band of 1000 to 2000 nm is more preferably 1% or more and 13% or less. In order to make the average reflectance in the wavelength band of 1000 to 2000 nm within the above range, a method similar to the method for setting the average reflectance in the wavelength band of 400 to 800 nm to 60% or more can be used.

The laminated polyester film constituting the laminated polyester film roll of the present invention has a laminated structure in which a total of 99 or more layers with different refractive indexes are alternately laminated from the viewpoint of adjusting the reflectance in each wavelength band to a suitable range by interference reflection. has. Here, "the refractive indexes differ" means that the in-plane average refractive indexes differ by 0.040 or more. From the above viewpoint, the total number of layers is more preferably 399 or more layers, and even more preferably 749 or more layers. Note that the reflectance increases in proportion to the number of layers, so it is not particularly limited, but the number is set to 999 layers in consideration of an increase in the size of the device.

In addition, from the viewpoint of achieving high reflectance, the laminated polyester film constituting the laminated polyester film roll of the present invention has a laminated structure in which the layer with a low refractive index is layer A, and the layer with a high refractive index is layer B. It is preferable that 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 0.040 or more and 0.120 or less. Generally, the larger the difference between the in-plane average refractive index of the A layer and the in-plane average refractive index of the B layer, the greater the interference reflection. Therefore, from the viewpoint of increasing the reflectance, the refractive index difference is preferably 0.05 or more. and more preferably 0.100 or more. Furthermore, in order to increase the reflectance by increasing the difference between the in-plane average refractive index of the A layer and the in-plane average refractive index of the B layer, it is necessary to configure the A layer and the B layer with resins with significantly different chemical structures. As a result, interlayer adhesion deteriorates. Considering the above points, the upper limit of the refractive index difference is 0.120. Note that it is more preferable that the difference between the in-plane average refractive index and the refractive index in the thickness direction of the A layer is 0.120 or less because the reflectance does not decrease even if the incident angle becomes large.

In the laminated polyester film constituting the laminated polyester film roll of the present invention, the main component of the A layer is polyethylene terephthalate or polyethylene naphthalate, and the B layer is spiroglycol, from the viewpoints of strength, heat resistance, versatility, and reflectivity. It is preferable to include a copolymerized polyester resin having cyclohexanedicarboxylic acid units as a main structural unit. Here, the main component refers to a component that is contained in an amount exceeding 50% by mass and not more than 100% by mass when all components constituting the layer are 100% by mass.

The A layer may contain resins other than polyethylene terephthalate and polyethylene naphthalate within a range that does not impede the object of the present invention. Examples of such resins include polyolefin resins, polystyrene resins, polyacrylic resins, polycarbonate resins, polysulfone resins, and cellulose resins. Further, particles of colloidal silica, titanium oxide, crosslinked polystyrene, etc. may be included in order to impart functions such as winding properties, rigidity, and optical properties. The amount of these resins and particles added is not limited as long as it does not impede the effects of the present invention, but the preferred range is less than 5% by mass in the layer.

The B layer preferably contains a polyester obtained by copolymerizing spiroglycol and cyclohexanedicarboxylic acid from the viewpoint of reducing interlayer peeling and optical performance. In this case, it is particularly preferable that the copolymerized amount of spiroglycol and cyclohexanedicarboxylic acid is 5 to 30 mol%, respectively, of an ethylene terephthalate polycondensate, and the B layer is an alloy of polyethylene terephthalate and the copolymerized polyester. I don't mind.

In the laminated polyester film roll of the present invention, the difference between the maximum value and the minimum value of the average reflectance in the wavelength band of 600 to 1000 nm at each point dividing a straight line parallel to the width direction into 11 equal parts is 1% or more and 10% or less. This is very important. Such an embodiment means that color unevenness is suppressed to a low level over a wide range, and a laminated polyester film roll that satisfies the requirements can be suitably used for decorating various devices, etc. described below. From the above viewpoint, the difference between the maximum value and the minimum value of the average reflectance in the wavelength band of 600 to 1000 nm at each point dividing a straight line parallel to the width direction into 11 equal parts is preferably 1% or more and 6% or less. Note that the reflectance in the wavelength band of 600 to 1000 nm can be measured using a known spectrophotometer, and the details will be described later.

Further, in the laminated polyester film roll of the present invention, it is important that ΔE at each point dividing a straight line parallel to the width direction into 11 equal parts is smaller than 5. ΔE at each point dividing a straight line parallel to the width direction into 11 equal parts can be measured by the following procedure. First, on a laminated polyester film roll, determine each point that divides the roll into 11 equal parts on a straight line parallel to the width direction, and cut out 10 rectangular samples of 110 mm (longitudinal direction) x 30 mm so that each point is the center. . For each sample obtained, the lightness L* and chromaticity (a ^* , b ^* ) were measured using a spectrophotometer, and the average value of each measurement value was calculated as the lightness L* and chromaticity (a ^* , b ^* ), respectively. shall be the standard value. Further, regarding lightness L* and chromaticity (a ^* , b ^* ), the difference (ΔL ^* , Δa ^* , and Δb ^* ) between the measured value of each sample and the reference value is determined, and ΔE is calculated from the following formula.
ΔE=((ΔL ^* ) ² +(Δa ^* ) ²⁺ (Δb ^* ) ² ) ^1/2 .

A ΔE of less than 5 means that the color unevenness of the laminated polyester film is suppressed over a wide range, and the closer the ΔE is to 0, the less change in color tone, and the closer the ΔE is to 2, the less the visual appearance. By observing, you will notice a change in color. By suppressing ΔE to a range smaller than 5, a laminated polyester film that satisfies the requirements can be suitably used for decorating various devices and the like, which will be described later. From the above viewpoint, ΔE is preferably 3 or less.

To reduce the difference between the maximum and minimum values of average reflectance in the wavelength band of 600 to 1000 nm at each point that divides a straight line parallel to the width direction into 11 equal parts, or to reduce ΔE, for example, a partition wall is installed on the inner surface of the outer wall. A groove for inserting the plate and a recess for the convex part of the partition plate are provided, and by using a multilayer lamination merging device that allows the partition plate to be attached and detached, it is possible to prevent stacking disorder of each layer in the direction parallel to the width direction. One method is to suppress uneven thickness. At this time, in order to prevent the partition plate from deforming even if it expands due to heat, it is preferable to provide a gap between the partition plate and the groove assuming the expansion of the partition plate.

Moreover, it is preferable that the thickness of the outermost layer of the laminated polyester film constituting the laminated polyester film roll of the present invention is 0.05 μm or more and less than 5 μm. If the outermost layer is 5 μm or more, minute patterns or color changes that occur near the interface of the multilayer may become difficult to visually recognize from the surface. From the above viewpoint, the thickness of the outermost layer is more preferably 0.06 μm or more and 3 μm or less, and even more preferably 0.06 μm or more and 1 μm or less.

A preferred embodiment is also a laminated sheet in which a printed layer is further provided on at least one surface of the laminated polyester film constituting the laminated polyester film roll of the present invention. It is preferable that the printed layer partially colors the surface of the laminated film, since the gloss of the laminated film can be directly seen from the uncolored part, and a design with a mother-of-pearl appearance can be provided. The printing layer is for expressing colored surfaces and patterns, and includes a group of pigment ink layers consisting of pigments and resin binders, glitter pigment layers consisting of pearl pigments and resin binders, and dye ink layers consisting of dyes and resin binders. It can be composed of at least one layer selected from the following. The printing layer may be formed by a normal printing method such as an offset printing method, a gravure printing method, or a screen printing method, or a coating method such as a roll coating method or a spray coating method. The appearance of the printed layer is preferably a deep black like lacquer, blackish purple, crimson, vermilion, amber brown, etc., as this emphasizes the contrast with the gloss of the laminated film. A preferred embodiment is to add a pattern such as wood grain to these colors.

Hereinafter, the decorated molded article of the present invention will be explained. The decorated molded article of the present invention is made using a laminated polyester film that constitutes the laminated polyester film roll of the present invention. The laminated film of the present invention can be applied to various molding methods such as vacuum forming, vacuum-pressure forming, plug-assisted vacuum-pressure forming, in-mold forming, insert molding, cold forming, press forming, and drawing forming, so it can be formed into a molded product at low cost. It is possible to obtain Such molded bodies can be preferably used for mobile phones, telephones, personal computers, audio equipment, home appliances, wireless communication equipment, in-vehicle parts, building materials, game machines, amusement equipment, packaging containers, and the like.

In particular, the molded article of the present invention can be used in devices having the function of wirelessly communicating information (wireless information communication devices) such as mobile phones, telephones, personal computers, audio equipment, home appliances, wireless communication devices, in-vehicle parts, and game consoles. Preferably, it is used as a decorative component. The molded article of the present invention has both a metallic appearance and electromagnetic wave permeability, and can reduce electromagnetic interference while maintaining the design of conventional metallic decorative materials. In addition, the molded product of the present invention can be made into a thin film more easily than metal, and is also superior in weight, so if it is used to decorate the above-mentioned wireless information communication equipment, it is possible to make the equipment smaller and thinner. This increases the degree of freedom in circuit design inside information communication equipment.

As a specific example of a preferred method for manufacturing the laminated polyester film roll of the present invention, a method for manufacturing the laminated polyester film roll by a multilayer lamination extrusion method will be described below. However, the method for manufacturing the laminated polyester film roll of the present invention is not limited to the following.

First, two types of polyester resins (polyester resin A and polyester resin B) having different refractive indexes are prepared in the form of pellets or the like. After the pellets are dried in hot air or under vacuum as necessary, they are supplied to a separate extruder, and the resin supplied to the extruder is heated and melted within the extruder at a temperature above its melting point. The resin heated above the melting point in each extruder is extruded using a gear pump or the like to equalize the amount of extrusion, and then the molten resin is filtered to remove foreign matter and resin knits. Thereafter, polyester resin A and polyester resin B are laminated through a laminating device such as a multi-manifold die, feed block, square mixer, static mixer, or the like. Thereafter, the obtained molten laminate is melt-extruded into a sheet using a T-shaped die or the like, and the sheet is cooled and solidified on a casting drum to obtain an unstretched film.

The polyester film constituting the laminated polyester film roll of the present invention can be suitably obtained by using a feed block, and the structure of the feed block includes at least two or more separate members having a large number of fine slits. It is preferable to use feed blocks, more preferably three or more. By using such a feed block, the equipment does not become extremely large, so it is possible to reduce the amount of foreign matter caused by thermal deterioration, and even when the number of laminated layers is extremely large, it is possible to improve the lamination accuracy in the width direction and achieve high performance. It becomes possible to stack layers with precision. In addition, by using such a feed block, the thickness of each layer can be adjusted by the slit shape (length, width, gap), making it easy to form an arbitrary layer thickness configuration. Therefore, the layered structure characteristic of laminated polyester films can be easily achieved.

When the laminated polyester film has a gradient structure of two or more stages, the change in layer thickness from a thin layer to a thick layer or from a thick layer to a thin layer becomes very abrupt. In the present invention, it is preferable to use a feed block that includes at least three or more separate members having a large number of fine slits. However, at the point where the resins fed from these separate feedblocks join together, the layer thickness distribution changes immediately after the joining, which is a major cause of variation in color tone in the width direction. Furthermore, since the resin velocity near the pipe decreases due to the effect of the pipe wall on the path from the feed block to the mouthpiece, the color tone uniformity in the width direction deteriorates due to the difference in flow velocity between the pipe wall and the center of the pipe. Therefore, it is possible to obtain a laminated film that exhibits a uniform color tone in the width direction without changing the lamination ratio by replacing a certain distance between the outermost layer of the film and the resin confluence of separate feed blocks with the same polymer. can.

At this time, when the outermost thick film layers on both sides of the laminated film are made of polyester resin A, the layer made of polyester resin A corresponds to the surface thick film layer (the outermost layer on both sides). The resin forming the surface thick film layer is preferably a highly crystalline resin in order to alleviate shearing during injection molding. Furthermore, the resin used as the intermediate thick film layer is preferably a highly crystalline resin in order to alleviate shearing during injection molding. The thickness of the thick film layer is preferably adjusted by adjusting each flow rate corresponding to the thickness of the layer using the gap between the slits, and in this case, the gap accuracy of each slit gap is preferably ±10 μm or less. By using such a special feed block, it is possible to obtain a laminated film with high precision and forming a sloped structure of two or more stages.

Next, in order to satisfy one of the characteristics of the laminated polyester film constituting the laminated polyester film roll of the present invention, "average reflectance in the wavelength band of 400 to 800 nm is 60% or more and 100% or less". , it is necessary to design the layer thickness of each layer based on the following formula A. Such a design makes it possible to control the reflection characteristics of the laminated film, and the reflectance can be controlled by the refractive index difference between the layer made of polyester resin A and the layer made of polyester resin B and the number of layers.
Formula A: 2×(na・da+nb・db)=λ
na: average in-plane refractive index of the layer made of resin A nb: average in-plane refractive index of the layer made of resin B da: layer thickness (nm) of the layer made of resin A
db: Layer thickness (nm) of the layer made of resin B
λ: Main reflection wavelength (primary reflection wavelength)
Before reaching the die, the molten resin laminate obtained by the feed block passes through a multilayer merging device where the partition walls forming the flow paths disappear and the flow paths merge into one. The molten resin laminate that has passed through the multilayer laminate merging device is then formed into a thinner sheet using a die and discharged to a cast drum, where it is cooled and solidified to become an unstretched sheet. Therefore, "before reaching the cap" here means upstream from the exit of the multilayer laminating device. By merging the flow paths into one before reaching the cap, it is possible to merge into one molten resin laminate, which has been improved in lamination accuracy by dividing the flow into multiple flow paths and adjusting the flow. As a result, the number of laminated molten resin laminates can be increased without reducing the lamination accuracy.

The multi-layered molten material is discharged in the form of a sheet onto a cooling drum from a T-die. At that time, for example, a method of applying electrostatic charge using a wire-like electrode or a tape-like electrode, a casting method in which a water film is created between the casting drum and the extruded polymer sheet, and a method of setting the temperature of the casting drum to the glass transition point of the polyester resin ( A sheet-like polymer is brought into close contact with a casting drum by a method of making the extruded polymer stick to a glass transition temperature of -20° C.) or by a method of combining two or more of these methods, and is cooled and solidified to obtain an unstretched film. Among these casting methods, when polyester is used, a method of applying electrostatic charge is preferably used from the viewpoint of productivity and flatness.

Next, the unstretched film is stretched in the longitudinal direction and then in the width direction, or by a sequential biaxial stretching method in which the unstretched film is stretched in the width direction and then stretched in the longitudinal direction, or the film is stretched in the longitudinal direction and the width direction. Stretching is carried out by a simultaneous biaxial stretching method in which both are stretched almost simultaneously.

The stretching ratio in each direction is preferably 2.5 to 3.5 times, more preferably 2.8 to 3.5 times, particularly preferably 3 to 3.4 times. Ru. Further, the stretching speed is preferably 1,000 to 200,000%/min. Further, the stretching temperature is from the glass transition point to (glass transition point + 50°C), more preferably from 90 to 130°C, particularly preferably from 100 to 120°C for longitudinal stretching, and for widthwise stretching. The temperature is preferably 90 to 110°C. Further, stretching may be performed multiple times in each direction.

Furthermore, the film is heat treated after biaxial stretching. The heat treatment can be performed by any conventionally known method such as in an oven or on a heated roll. This heat treatment is carried out at a temperature of 120°C or higher and lower than the melting point of the polyester, preferably at a heat treatment temperature of 200 to 240°C. From the viewpoint of film transparency and dimensional stability, the temperature is more preferably 210 to 235°C. Further, the heat treatment time can be set arbitrarily as long as the properties are not deteriorated, and the heat treatment time is preferably 1 to 60 seconds, more preferably 1 to 30 seconds. Furthermore, the heat treatment may be performed by relaxing the film in the longitudinal direction and/or width direction. Furthermore, before the lateral stretching step, at least one side may be subjected to corona treatment or a coating layer may be provided in order to improve the adhesive strength with the ink printing layer, adhesive, or vapor deposited layer. The coating solution at this time is applied to the transparent substrate using a known coating means such as a roll coater, gravure coater, microgravure coater, bar coater, die coater, dip coater, or the like.

Next, the case of simultaneous biaxial stretching will be explained. In the case of simultaneous biaxial stretching, the resulting cast film is subjected to surface treatments such as corona treatment, flame treatment, and plasma treatment as necessary, and then subjected to surface treatments such as smoothness, easy adhesion, and antistatic properties. Functions may also be imparted by in-line coating.

Thereafter, the cast film is introduced into a simultaneous biaxial tenter, and conveyed while holding both ends of the film with clips, and is stretched simultaneously and/or in stages in the longitudinal direction and the width direction. There are three types of simultaneous biaxial stretching machines: pantograph type, screw type, drive motor type, and linear motor type. A linear motor system is preferred. The stretching magnification varies depending on the type of resin, but is usually preferably an area magnification of 6 to 50 times, and when polyethylene terephthalate is used as one of the resins constituting the laminated film, an area magnification of 8 to 30 times. is particularly preferably used. Particularly in the case of simultaneous biaxial stretching, in order to suppress in-plane orientation differences, it is preferable that the stretching ratios in the longitudinal direction and the width direction are the same, and the stretching speeds are also approximately the same. Further, the stretching temperature is preferably from the glass transition temperature of the resin constituting the laminated film to the glass transition temperature +120°C.

In order to impart flatness and dimensional stability to the biaxially stretched film, it is preferable that the film be subsequently subjected to heat treatment in a tenter at a temperature above the stretching temperature and below the melting point. 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 being heat-treated in this way, it is uniformly slowly cooled, cooled to room temperature, and then wound up with a winder. Further, if necessary, relaxation treatment may be performed in the longitudinal direction and/or width direction during slow cooling after heat treatment. In this case, the relaxation treatment in the longitudinal direction is instantaneously performed immediately before and/or immediately after entering the heat treatment zone.

Furthermore, the laminated polyester film of the present invention is unwound, the laminated polyester film of the present invention is unwound, both ends in the width direction are slit parallel to the longitudinal direction, the portions gripped by the clips of the tenter are removed, and the laminated polyester film of the present invention is rolled up again. Obtainable.

The present invention will be described below with reference to Examples, but the present invention is not limited to these Examples. In addition, various characteristics were measured by the following methods.

(1) Layer structure and layer thickness of the film Samples approximately 1 cm square were cut out from the laminated polyester film roll, centering on each point that divided a straight line parallel to the width direction into 11 equal parts. Furthermore, a cross section of each sample in the thickness direction (direction perpendicular to the film surface) was cut using a microtome. Thereafter, each cross section was observed and photographed using a transmission electron microscope (TEM H-7100FA model, manufactured by Hitachi, Ltd.) at an acceleration voltage of 75 kV at a magnification of 40,000 times. The layer structure was identified from the obtained image and the layer thickness was measured using the method described below. Moreover, the total thickness of each layer was defined as the overall thickness of the laminated film. Note that during observation, the sample was stained with RuO ₄ in order to obtain a high contrast between layers.

Hereinafter, the method for specifying and calculating the layer structure and layer thickness will be specifically explained. A 40,000x TEM photograph was taken at an image size of 729 dpi using "CanoScan" (registered trademark) D1230U (manufactured by Canon Inc.). The image was saved in JPEG format, and then the JPEG file was opened using image processing software (Imagc-Pro Plus ver. 4, sold by Planetron Co., Ltd.) and image analysis was performed. The image analysis process was performed in vertical thick profile mode, and the relationship between the average brightness in the area sandwiched between the two lines in the thickness direction and width direction was read as numerical data. Using spreadsheet software (“Excel” (registered trademark) 2000 Microsoft Corporation), after collecting data in sampling step 6 (thinning 6) for position (nm) and brightness data, numerical processing of 3-point moving average was performed. was applied. Furthermore, the obtained data whose brightness changes periodically is differentiated, the maximum and minimum values of the differential curve are read using a VBA (Visual Basics for Applications) program, and the intervals between these adjacent ones are calculated in one layer. Calculated as layer thickness. This operation was performed for each photograph to calculate the layer thickness of all layers and also confirm the layer structure.

(2) Average reflectance A 5 cm square film sample was cut out from a laminated polyester film roll centered on each point that divided a straight line parallel to the width direction into 11 equal parts. Next, the relative reflectance at an incident angle Φ=10 degrees was measured using a spectrophotometer (U-4100 Spectrophotometer, manufactured by Hitachi, Ltd.). The inner wall of the included integrating sphere is barium sulfate, and the standard plate is aluminum oxide that is included with this measuring device. The measurement wavelength was 250 nm to 1200 nm, the slit was 2 nm (visible)/automatically controlled (infrared), the gain was set to 2, and the measurement was performed at a scanning speed of 600 nm/min at 1 nm intervals. At this time, a black vinyl tape (No. 21 manufactured by Nitto Denko Corporation) was pasted on the back side of the sample to prevent interference due to reflection from the back side. Reflectance was measured. The average value of the relative reflectance of the measured wavelength bands was taken as the average reflectance in each wavelength band.

(3) Difference between the maximum and minimum average reflectance (2) Similarly to the reflectance, 10 film samples were obtained and the relative reflectance in the wavelength range of 600 to 1000 nm was measured. The difference between the minimum and maximum values obtained was defined as the "difference between the maximum and minimum average reflectance values."

(4) Saturation and color difference ΔE
Ten film samples measuring 110 mm (longitudinal direction) x 30 mm were cut out from the laminated polyester film roll, centering on each point that divided a straight line parallel to the width direction into 11 equal parts. Next, the lightness L ^* and chromaticity (a ^* , b ^* ) of each film sample were measured using a spectrophotometer CM-3600d manufactured by Konica Minolta Sensing Co., Ltd., and the respective values of L ^* , Δa ^* , Δb ^* were measured. The average value was calculated and used as the reference value. Thereafter, the differences (ΔL ^* , Δa ^* , and Δb ^* ) between each measured value and the reference value were determined, and ΔE was determined using the following formula.
ΔE = ((ΔL ^* ) ² + (Δa ^* ) ² + (Δb ^* ) ² ) ^1/2
In addition, the measurement was performed under the following conditions after performing zero configuration of the reflectance using the zero configuration box attached to the spectrophotometer, and then performing 100% calibration using the attached white calibration plate.
Mode: Reflection, SCI/SCE simultaneous measurement Measurement diameter: 8mm
Light source: D65
Viewing angle: 10 degrees Sample: Black vinyl tape was attached to the non-measurement side (Nitto Denko No. 21).

(5) Refractive index difference The laminated film and the raw materials used for layer B are melted at 280 degrees using an extruder and discharged onto a cast drum, and the cooled and solidified sheet-like film is collected. A test piece with a size of 20 mm was cut out. The in-plane refractive index of each test piece was measured at 23° C. and a wavelength of 589 nm using an Abbe refractometer (manufactured by Atago, DR-M 2), and the average value of n number 5 was calculated. The difference in in-plane refractive index of each film was defined as the refractive index difference.

(material)
(Resin A-1)
0.09 parts by mass of magnesium acetate and 0.03 parts by mass of antimony trioxide were added to a mixture of 100 parts by mass of dimethyl terephthalate and 60 parts by mass of ethylene glycol, and the mixture was heated and heated in a conventional manner. A transesterification reaction was carried out. Next, 0.020 parts by mass of an 85% (mass ratio) aqueous solution of phosphoric acid was added to the transesterification product based on the amount of dimethyl terephthalate, and then transferred to a polycondensation reaction tank. Furthermore, the pressure of the reaction system was gradually reduced while heating and temperature was increased, and a polycondensation reaction was carried out in a conventional manner at 290°C under a reduced pressure of 1 mmHg. ) was obtained. This PET was designated as resin A-1.
(Resin B-1)
Polyethylene terephthalate (intrinsic viscosity (IV) 0.55) copolymerized with 21 mol% of spiroglycol (SPG) and 24 mol% of cyclohexanedicarboxylic acid (CHDC).
(Resin B-2)
Polyethylene terephthalate (intrinsic viscosity (IV) 0.72) copolymerized with 30 mol% of cyclohexanedimethanol (CHDM).
(Resin B-3)
A mixture of resin A-1 and resin B-2 at a ratio of 1:3 (mass ratio).
(Resin B-4)
A mixture of resin A-1 and resin B-2 at a ratio of 1:1 (mass ratio).

(Configuration of multilayer laminated merging device)
The configuration of the multilayer merging device used in each example and each comparative example will be described below with reference to the drawings. FIG. 1 is a schematic view of the multilayer merging device used in the example, when the partition wall portion is not inserted, when observed from the longitudinal direction. FIG. 2 is a schematic view of the state in which the partition wall portion is inserted into the multilayer merging device used in the example, as viewed from the thickness direction. FIG. 3 is a schematic view of the state in which the partition wall of the multilayer merging device used in the example is inserted, observed from the longitudinal direction, and an enlarged view of the groove portion thereof. As shown in Fig. 1, in the multilayer merging device, a groove part 2 into which the partition plate is inserted is provided on the inner surface of the outer wall part 1, and a depression part 3 for the convex part of the partition plate is provided. The partition plate 4 is inserted into the groove part 2 of the part 1, and the outer wall part 1 and the partition plate 4 are fixed by the recessed part 3 and the convex part 5 of the partition plate. As shown in Fig. 3, a molten resin laminate in which polyester resin A and polyester resin B are alternately laminated flows through the two channels formed by the partition plate 4 and the outer wall 1, and the outlet where the partition plate disappears (not shown) All the molten resin laminates join together.

(Multi-layer laminated confluence device A)
The thickness 7 of the partition plate in which the partition plate is inserted into the inner surface of the outer wall part parallel to the width direction in FIG. 3 is 3 mm, the width length is 200 mm, the width 8 of the groove part of the outer wall part is 3.5 mm, and the end of the recessed part A multilayer merging device in which the distance 9 between the convex portion of the partition plate and the convex portion of the partition plate is 2.5 mm.

(Multi-layer laminated confluence device B)
The thickness 7 of the partition plate in which the partition plate is inserted into the inner surface of the outer wall part parallel to the width direction in FIG. 3 is 5 mm, the width length is 200 mm, the width of the groove part of the outer wall part is 3.8 mm, and the end of the recess A multilayer laminated merging device in which the distance 9 from the convex portion of the partition plate is 4 mm.

(Multilayer laminated confluence device C)
A multilayer laminated merging device in which the partition wall part and the outer wall are integrated, and the partition wall plate thickness is 5 mm and the width length is 200 mm.

(Multi-layer lamination merging device D)
A multi-layer laminated merging device 3 has a partition wall plate thickness of 20 mm and a width of 200 mm.

(Example 1)
Resin A-1 was used as polyester resin A, and resin B-1 was used as polyester resin B. These polyester resins were each fed into separate vented twin-screw extruders and brought to a molten state at 280° C. under temperature control. Thereafter, the two types of molten polyester resins are extruded, and through separate gear pumps and filters, a member having 401 slits and configured with polyester resin A as the outermost and thick layer is individually separated. The mixture was fed into a feed block having two molten laminates, to obtain two molten laminates in which polyester resins A and B were alternately laminated. The obtained molten resin laminate is transported toward the nozzle using a multilayer laminate merging device A, and the two molten resin laminates are merged just before reaching the nozzle, thereby producing a molten resin laminate with a total number of layers of 801 layers. I got it. Thereafter, the molten resin laminate discharged from the nozzle was rapidly cooled and solidified on a casting drum whose surface temperature was maintained at 25° C. by electrostatic application to obtain a cast film. The obtained cast film was heated with a group of rolls set at 75°C, and then stretched 3.3 times in the transport direction of the film, that is, in the longitudinal direction, while rapidly heating both sides of the film with a radiation heater during a stretching section of 100 mm. After that, the film was once cooled to obtain a uniaxially stretched film. Next, a laminate-forming film coating liquid consisting of (polyester resin with a glass transition temperature of 18°C)/(polyester resin with a glass transition temperature of 82°C)/silica particles with an average particle size of 100 nm is applied to both sides of the uniaxially stretched film to make it transparent. - Formed an easily slippery and easily adhesive layer. 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 width direction of the film perpendicular to the transport direction at a temperature of 110°C. The stretched film was directly heat-treated in a tenter with hot air at 240°C, then subjected to a 7% relaxation treatment in the width direction at the same temperature, slowly cooled to room temperature, and then wound up with a winder. Table 1 shows the evaluation results of the obtained laminated polyester film roll and the laminated polyester film constituting it.

(Examples 2-4, Comparative Examples 1-4)
A laminated polyester film roll was obtained in the same manner as in Example 1, except that the resin of each layer, the number of layers, and the multilayer lamination merging device were changed as shown in Table 1. Table 1 shows the evaluation results of the obtained laminated polyester film roll and the laminated polyester film constituting it.

According to the present invention, it is possible to provide a laminated polyester film roll that has excellent metallic luster and suppresses color unevenness. The laminated polyester film roll that constitutes this laminated polyester film roll has suppressed streak-like color unevenness over a wide area, so it can be used for decorative purposes such as home appliances, furniture, furniture, building materials, automobiles and train cars. It can be suitably used for the interior and exterior of etc.

1 Outer wall 2 Groove 3 Recess 4 Partition plate 5 Convex part 6 Enlarged view of the vicinity of groove 2 7 Thickness of partition plate 8 Width of groove 9 Distance between the end of the recess and the convex part of the partition plate

Claims (4)

A laminated polyester film roll having a laminated polyester film wound around a core, the laminated polyester film roll having all of the following features 1 to 5.
Feature 1: Average reflectance in the wavelength band of 400 to 800 nm is 60% or more and 100% or less.
Feature 2: Average reflectance in the wavelength band of 1000 to 2000 nm is 1% or more and 15% or less.
Feature 3: It has a laminated structure in which a total of 99 or more layers with different refractive indexes are alternately laminated.
Feature 4: The difference between the maximum and minimum values of the average reflectance in the wavelength band of 600 to 1000 nm at each point dividing a straight line parallel to the width direction into 11 equal parts is 1% or more and 10% or less.
Feature 5: ΔE at each point dividing a straight line parallel to the width direction into 11 equal parts is smaller than 5. When the layer with a low refractive index in the laminated structure is a layer A and the layer with a high refractive index is a layer B, 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. The laminated polyester film roll according to claim 1, which has a molecular weight of 0.040 or more and 0.120 or less. The laminate according to claim 1 or 2, wherein the main component of the A layer is polyethylene terephthalate or polyethylene naphthalate, and the B layer contains a copolymerized polyester resin whose main constituent units are spiroglycol and cyclohexanedicarboxylic acid units. Polyester film roll. A decorated molded article using the laminated polyester film constituting the laminated polyester film roll according to claim 1 or 2.

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