Laminate film and glass laminate for display protection

Abstract

To provide a laminate film which is less colored by uniformly reflecting visible light, is excellent in heat shielding property and can reduce optical characteristic change by heat.SOLUTION: A laminate film satisfies all of the following (1) to (3). (1) Two hundred and one or more layers of layers (A layers) containing a thermoplastic resin A as a main component and layers (B layers) containing a thermoplastic resin B as a main component are alternately laminated, and a ratio (thickness of A layer / thickness of B layer) of the A layer to the B layer adjacent to each other is 1.5 or more and 4.0 or less. (2) Average reflectance in the wavelength band of 400 to 700 nm is 25% or more and 50% or less. (3) Average reflectance in each section partitioned at intervals of 50 nm from 400 nm in the wavelength band of 400 to 1,150 nm is within the range of ±20% of the average reflectance in the wavelength band of 400 to 700 nm.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a laminate film and a glass laminate for protecting a display. [Background technology]

[0002] In recent years, the market for outdoor use of various display devices, including digital signage, an advertising medium that uses digital technology for display and communication, has been expanding. When used outdoors, display devices can be damaged by the heat of sunlight, especially in the summer, so the use of heat-shielding films that can block the inflow of heat from sunlight has been attracting attention.

[0003] Examples of laminated films with heat-shielding properties include laminated films in which several hundred resin layers with different refractive indexes are laminated in a regular arrangement, and light is reflected by interference reflection. Some of these laminated films have heat-shielding properties, but since the laminated films themselves are exposed to heat, laminated films with less performance change due to heat are required. In addition, if the visible light band, in which the thermal energy of sunlight is high, is uniformly reflected, high design properties such as metallic luster can be achieved, so it is preferable to reflect both visible light and near-infrared light bands.

[0004] Methods for suppressing changes in the performance of heat-shielding films due to heat include a method in which amorphous polyester is used to maintain the reflectance after heating in post-processing (Patent Document 1), and a method in which a polymer that suppresses oriented crystallization is used to suppress changes in optical properties due to heat while reflecting visible light to near-infrared light (Patent Document 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2014-228837 A [Patent Document 2] International Publication No. 2015 / 095097 [Patent Document 3] JP 2016-066063 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the method described in Patent Document 1, the biaxially oriented polyester film has a low visible light reflectance, and the suppression of the reflection performance when heated is not sufficient. In the method described in Patent Document 2, high designability cannot be achieved, and it is difficult to provide a laminated film that suppresses color change even after heating. Therefore, the object of the present invention is to provide a laminated film that uniformly reflects visible light, has little coloring, has excellent heat shielding properties, and can reduce changes in optical properties due to heat. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention employs the following means.

[0008] [1] A laminated film that satisfies all of the following (1) to (3). (1) The laminate is composed of 201 or more layers (A layers) whose main component is thermoplastic resin A and 201 or more layers (B layers) whose main component is thermoplastic resin B, and the thickness ratio between adjacent A layers and B layers (thickness of A layers / thickness of B layers) is 1.5 or more and 4.0 or less. (2) The average reflectance in the wavelength band of 400 to 700 nm is 25% or more and 50% or less. (3) In the wavelength band of 400 to 1150 nm, the average reflectance of each section divided into 50 nm intervals starting from 400 nm is within ±20% of the average reflectance in the wavelength band of 400 to 700 nm. [2] The laminate film according to [1], in which the change in average reflectance in the wavelength range of 400 to 700 nm after heating at 150° C. for 2 hours is 5% or less compared to the average reflectance in the wavelength range of 400 to 700 nm before heating. [3] The laminated film according to [1] or [2], in which the absolute values ​​of the a* and b* values ​​of reflected light measured by the method described in JIS Z8722 (2019) are both 10 or less, and the change Δa* in a* and the change Δb* in b* when heated at 150°C for 2 hours are both 3 or less. [4] The laminate film according to any one of [1] to [3], wherein the haze change Δhaze when heated at 150° C. for 2 hours is 2.5% pt or less. [5] The laminate film according to any one of [1] to [4], which has a heat shrinkage rate in the main orientation direction after heat treatment at 150° C. for 30 minutes of 1.4% or less. [6] A glass laminate for protecting a display, comprising the laminate film according to any one of [1] to [5]. Effect of the Invention

[0009] According to the present invention, it is possible to provide a laminate film that uniformly reflects visible light, thereby causing little coloring, has excellent heat-shielding properties, and is capable of reducing changes in optical properties due to heat. [Brief description of the drawings]

[0010] [Figure 1] FIG. 2 is a diagram in which the thickness of layer A and the thickness of layer B are plotted against the layer number in one embodiment of the laminate film of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The laminated film of the present invention is formed by alternately laminating 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 thermoplastic resin A. Here, the main component refers to a component that is contained in an amount of more than 50 mass% and not more than 100 mass% when all components constituting the layer are taken as 100 mass%, and can be interpreted similarly hereinafter.

[0012] As a combination of thermoplastic resin A and thermoplastic resin B, a combination of resins with different crystallinity is preferable, since it is easier to control the refractive index difference between the layer made of thermoplastic resin A (layer A) and the layer made of thermoplastic resin B (layer B).

[0013] Thermoplastic resin A and thermoplastic resin B may be homopolymers or copolymers. Furthermore, each of thermoplastic resin A and thermoplastic resin B may be composed of only a single resin or may be a mixture of two or more types of resins. Among them, thermoplastic resins A and B are preferably polyester resins from the viewpoints of strength, heat resistance, transparency, and versatility.

[0014] The polyester resin is preferably a polyester obtained by polymerization of a monomer mainly composed of an aromatic dicarboxylic acid or an aliphatic dicarboxylic acid and a diol. Examples of the aromatic dicarboxylic acid 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 the aliphatic dicarboxylic acid include adipic acid, suberic acid, sebacic acid, dimer acid, dodecanedioic acid, cyclohexanedicarboxylic acid, and ester derivatives thereof. Among them, terephthalic acid and 2,6-naphthalenedicarboxylic acid, which have a high refractive index, are preferred. These acid components may be used alone or in combination of two or more, and may be partially copolymerized with oxyacids such as hydroxybenzoic acid.

[0015] Examples of the diol 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 preferably used. The diol may be used alone or in combination of two or more.

[0016] As the thermoplastic resins A and B, from the viewpoints of strength and versatility, it is preferable to use, among the above-mentioned polyesters, polyethylene terephthalate and its copolymers, polyethylene naphthalate and its copolymers, polybutylene terephthalate and its copolymers, polybutylene naphthalate and its copolymers, polyhexamethylene terephthalate and its copolymers, polyhexamethylene naphthalate and its copolymers, etc.

[0017] A preferred combination of thermoplastic resins A and B is one in which both thermoplastic resins have the same basic skeleton. Here, the basic skeleton refers to the structural unit that is most abundant in all structural units constituting the thermoplastic resin. For example, if the thermoplastic resin is polyethylene terephthalate, the basic skeleton is an ethylene terephthalate skeleton. As such a combination of thermoplastic resins A and B, for example, one thermoplastic resin is polyethylene terephthalate, and the other thermoplastic resin is a polymer (copolymer) consisting of ethylene terephthalate units and cyclohexane 1,4-dimethylene terephthalate units, with a relatively large amount of ethylene terephthalate units. When thermoplastic resins with the same basic skeleton are used, problems such as lamination defects such as flow marks and peeling between layers are less likely to occur during film formation.

[0018] As the thermoplastic resin A, it is preferable to use polyethylene terephthalate or polyethylene naphthalate from the viewpoints of resistance to pressure marks (dent resistance) and stiffness of the film itself.

[0019] From the viewpoint of suppressing an increase in the refractive index, it is preferable to use, as the thermoplastic resin B, a copolymer having the same basic skeleton as the thermoplastic resin A, which contains, as a constituent unit, isophthalic acid, naphthalenedicarboxylic acid, diphenyl acid, or cyclohexanedicarboxylic acid, or which contains spiroglycol, cyclohexanedimethanol, bisphenoxyethanolfluorene, or bisphenol A component, either mixed with the thermoplastic resin A or alone.

[0020] In the laminated film of the present invention, the thickness ratio between adjacent A layer and B layer (A layer thickness / B layer thickness) must be 1.5 or more and 4.0 or less, and is preferably 1.7 or more and 3.5 or less. If the thickness ratio between adjacent A layer and B layer exceeds 4.0, the secondary reflection described below occurs strongly only in a part of the visible light band, and the visible light band cannot be reflected uniformly. If the thickness ratio between adjacent A layer and B layer is less than 1.5, the reflection of the primary reflection becomes strong, causing the reflection of the visible light band to become non-uniform, and the secondary reflection in the visible light band becomes weak, making it impossible to reduce the change in color tone and reflectance before and after heating.

[0021] From the viewpoint of uniformly reflecting visible light, it is important that the total number of A layers and B layers is 201 or more in the laminated film of the present invention. By having the total number of A layers and B layers be 201 or more, preferably 401 or more, more preferably 601 or more, and even more preferably 801 or more, the film can reflect visible light more uniformly and can reflect a long wavelength band of 400 to 1150 nm, thereby achieving both high designability and heat shielding properties. From the viewpoint of uniformly reflecting visible light, the more layers the better, but increasing the number of layers leads to an increase in the size of the device and deterioration of handling, so the upper limit of the total number of A layers and B layers is preferably 2001 layers.

[0022] From the viewpoint of appearance and handling, the laminated film of the present invention preferably has three or more thick film layers having a thickness of 1 μm or more and 20 μm or less, and two of them are the outermost layers on both sides of the laminated film. Since the thick film layer is a layer having a larger thickness than the other layers constituting the film, the thickness of the layers other than the thick film layer constituting the film is at the nm level. From the above viewpoint, the thickness of the thick film layer is more preferably. By having a thickness of 1 μm or more, preferably 5 μm or more, it is possible to suppress the occurrence of flow marks due to lamination defects and to suppress appearance defects due to streaks caused by surface unevenness. In addition, since the lamination accuracy is improved, the variation in the reflection spectrum due to lamination defects is also reduced, and a laminated film with little coloring can be obtained. On the other hand, by having a thickness of the thick film layer of 20 μm or less, preferably 10 μm or less, it is possible to suppress the overall thickness of the laminated film and prevent it from becoming too stiff for display use and becoming difficult to handle.

[0023] When the layer having a relatively high crystallinity is Layer A, it is preferred that the thick layer of the laminated film is formed from Layer A in terms of improving impression resistance.

[0024] Examples of methods for forming such a thick film layer include a method for adjusting the layer structure of the feed block used for lamination and the slit thickness. The thickness of the thick film layer can be measured by observing a cross section in the thickness direction (a cross section parallel to the thickness direction, in other words, a cross section perpendicular to the film surface) using a transmission electron microscope, and the details of the measurement method will be described later.

[0025] In the laminated film of the present invention, from the viewpoint of suppressing the variation of the reflection spectrum, it is preferable that the number of layer pairs having a layer pair thickness of 10 nm or more and less than 220 nm is greater than the number of layer pairs having a layer pair thickness of 220 nm or more and 350 nm or less. Here, "layer pair" refers to a combination of adjacent individual A layers and B layers, and "layer pair thickness" refers to the thickness of each layer pair. In addition, the layer pair thickness must be the sum of the layer thickness of the mth A layer counted from one film surface for only the A layer and the layer thickness of the mth B layer counted from the same surface for only the adjacent B layer. Here, m represents an integer. For example, when the layers are arranged in the order of A1 layer / B1 layer / A2 layer / B2 layer / A3 layer / B3 layer... from one film surface to the opposite surface, the A1 layer and the B1 layer are the first layer pair, the A2 layer and the B2 layer are the second layer pair, and the A3 layer and the B3 layer are the third layer pair.

[0026] When the number of layer pairs having a layer pair thickness of 10 nm or more and less than 220 nm is greater than the number of layer pairs having a layer pair thickness of 220 nm or more and less than 350 nm, the decrease in reflectance on the low wavelength side in the reflection band of the wavelength band 400 nm to 1150 nm is suppressed, so that the redness of the film can be reduced. This is because the density of the layer pairs that cause reflection on the low wavelength side is maintained. Therefore, it is preferable that the layer pair thickness sequence of the layers constituting the film does not increase or decrease monotonically in an arithmetic progression, but increases or decreases in a geometric progression while satisfying the above conditions. More preferably, the number of layer pairs having a layer pair thickness of 120 nm or more and less than 220 nm is 1.05 times or more and 2.50 times or less than the number of layer pairs having a layer pair thickness of 220 nm or more and less than 350 nm. In addition, when the film contains a thick film layer described later, the layer pair is counted including the thick film layer. However, since the layer pair including the thick film layer has a thickness exceeding 350 nm, it does not fall into either the layer pair with a layer-pair thickness of 10 nm or more and less than 220 nm, or the layer pair with a layer-pair thickness of 220 nm or more and 350 nm or less.

[0027] An example of a preferred layer structure of the laminated film of the present invention will be described with reference to the drawings. FIG. 1 is a diagram in which the thicknesses of layers A and B are plotted against layer numbers in a laminated film in which layers A and B are alternately laminated in the thickness direction. Layer thicknesses correspond only to integer layer numbers in FIG. 1, with layers A corresponding to odd numbers and layers B corresponding to even numbers. Also, the reference numbers 1 to 5 in FIG. 1 respectively mean layer number, layer thickness, thickness of thick film layer, thickness of layer A, and thickness of layer B. The layer numbers can be assigned in order starting from any surface.

[0028] In the case of a layer structure in which the layer thickness increases and then decreases from one surface to the opposite surface, as in the layer structure shown in Figure 1, even if lamination defects occur in a very small part and deviate from the design value, there are layer pairs of layer thicknesses of approximately the same thickness in other parts, so the variation in the reflection spectrum is suppressed. In addition, lamination defects are likely to occur at the point where the layer structure changes from decrease to increase or from increase to decrease, which causes variation in the reflection spectrum, so it is preferable to provide a thick film layer with a thickness of 1 μm or more and 20 μm or less at the point indicated by reference number 3. When a thick film layer is provided, lamination defects are reduced, making it difficult for the reflection of light to shift from the design value, and the variation in the reflection spectrum of the film is suppressed.

[0029] For the sake of convenience, in the present invention, the layer thickness configuration as shown in Fig. 1 is referred to as a four-step gradient structure. Here, the "four-step gradient structure" refers to a structure in which the layer thickness can be approximated by four monotonically increasing and / or decreasing curves.

[0030] In the laminated film of the present invention, the thick film layer formed by the A layer is preferably located at the outermost layer on both sides of the film and at the change point of the monotonically increasing curve and / or monotonically decreasing curve, i.e., the intermediate layer. In addition, if the thick film layer has a gradient of two or more steps including three or more layers, even if a lamination defect occurs in a very small part and the designed layer thickness is deviated from, layers of the same thickness exist in other parts, so that the variation in the reflection spectrum of the film can be suppressed.

[0031] The laminated film of the present invention preferably has an easy-adhesion layer on at least one surface. The easy-adhesion layer refers to a layer for enhancing adhesion to other films and other members. The method for forming the easy-adhesion layer is not particularly limited, but a coating method is preferred in that a thin film layer can be formed uniformly. The coating method may be a so-called offline coating method in which a coated film is obtained by unwinding a film, coating and drying the film in a separate process from the film production process, or a so-called in-line coating method in which a thermoplastic resin is extruded by an extruder, the thermoplastic resin is formed into a sheet-like film, and coating is performed during the film production process to obtain a coated film in one go.

[0032] The adhesive layer may contain known polyester, acrylic, urethane, epoxy, and other resins, either alone or in combination, to provide various functions such as holding lubricant particles and sealing oligomers precipitated from the film. It may also contain a melamine, oxazoline, or carbodiimide crosslinking agent.

[0033] Furthermore, it is preferable that the component of the easy-adhesion layer contains a conductive polymer from the viewpoint of preventing static electricity. By doing so, it is possible to prevent foreign matter from being mixed into the adhesive layer described later due to static electricity, and to prevent defects in appearance. Examples of conductive polymers include polypyrrole, polyaniline, polyacetylene, polythiophene vinylene, polyphenylene sulfide, poly-p-phenylene, polyheterocycle vinylene, etc., and (3,4-ethylenedioxythiophene) (PEDOT) is particularly preferable. These components may be used alone or in combination.

[0034] The average reflectance of the laminated film of the present invention in the wavelength band of 400 to 700 nm must be 25% or more and 50% or less. Hereinafter, the average reflectance in the wavelength band of 400 to 700 nm is also referred to as the "visible light reflectance". If the visible light reflectance is less than 25%, metallic luster or high gloss cannot be achieved, and a laminated film with high designability cannot be obtained. If the average reflectance in the band exceeds 50%, the film is highly reflective when used outdoors, and when an image is displayed on a display from the back, sufficient light does not transmit, making the image unrecognizable, and the film is not suitable for applications requiring light transmission.

[0035] In order to make the image clearly visible when viewed from the rear, the average transmittance of the laminated film of the present invention in the wavelength range of 400 to 700 nm is preferably 25% or more, more preferably 40% or more. Hereinafter, the average transmittance in the wavelength range of 400 to 700 nm is also referred to as "visible light transmittance".

[0036] In the wavelength band of 400 to 1150 nm, the laminated film of the present invention must have an average reflectance in each section divided into 50 nm intervals from 400 nm (hereinafter also referred to as "section reflectance") within a range of ±20% of the visible light reflectance. Hereinafter, the average reflectance in each section divided into 50 nm intervals is also referred to as "section reflectance".

[0037] In the wavelength band of 400 to 700 nm, the interval reflectances are all within the range of ±20% of the visible light reflectance, preferably within the range of ±15%, so that coloring of the laminated film due to non-uniform reflection can be suppressed, and the color of the image can be prevented from changing when the image is displayed on the display from the back. In addition, in the wavelength band of 700 to 1150 nm, the interval reflectances are all -20% or more of the visible light reflectance, preferably -15% or more, so that the light in the band where the thermal energy of sunlight is highly distributed can be reflected, and the solar heat reflectance described later can be achieved. On the other hand, in the wavelength band of 700 to 1150 nm, the interval reflectances are all +20% or less of the visible light reflectance, preferably +15% or less, so that the secondary reflected light described later can be made uniform in the wavelength band of 400 to 700 nm, and coloring can be suppressed to make the film suitable for light transmission applications.

[0038] The laminated film of the present invention preferably has a solar reflectance of 20% or more. The solar reflectance here is defined by ISO 9050. By having a solar heat reflectance of 20% or more, more preferably 25% or more, the film reflects the thermal energy of sunlight and exhibits excellent heat shielding properties.

[0039] The reflectance and color of the laminated film of the present invention can be controlled by the difference in refractive index between the layer made of thermoplastic resin A (layer A) and the layer made of thermoplastic resin B (layer B) and the number of layers. The reflection of the wavelength obtained by the following formula (i) is called the first reflection. Based on this, higher order reflections such as second order, third order, and fourth order also appear, and the wavelength of the higher order wavelength is calculated by λ / N (N: order, an integer of 2 or more). Formula (i): 2 × (na·da + nb·db) = λ na: Average in-plane refractive index of A layer nb: Average in-plane refractive index of B layer da: A layer thickness (nm) db: Layer thickness of B layer (nm) λ: Main reflection wavelength (first reflection wavelength).

[0040] Higher-order reflections become stronger as the ratio of adjacent A layers to B layers moves away from 1.0. In a film that reflects the 400-1150 nm wavelength band, if the ratio of A layers to B layers is increased, secondary reflections will occur at 200-575 nm, and most of the visible light band of 400-700 nm can be reflected by primary and secondary reflections, resulting in stable color tone. If the reflective wavelength band is expanded to the long wavelength side of 1150 nm or more, tertiary reflections will appear around the 400 nm wavelength in the 400-700 nm visible light band, and the reflection of the visible light band will become uneven, making it impossible to reduce the color tone.

[0041] When heated at 150°C for 2 hours, the orientation state of the less crystalline B layer changes, causing changes in reflectivity and color. However, by reflecting most of the visible light band of 400 to 700 nm in combination with primary and secondary reflection, the changes in reflectivity and color can be suppressed.

[0042] As for the characteristics before and after heating, the laminate film of the present invention preferably has a change in average reflectance in the wavelength band of 400 to 700 nm before heating and in the average reflectance in the wavelength band of 400 to 700 nm after heating at 150°C for 2 hours of 5%pt or less, more preferably 3%pt or less.

[0043] From a similar viewpoint, it is preferable that the absolute values ​​of the a* and b* values ​​of reflected light measured by the measurement method described in JIS Z8722 (2019) are both 10 or less, and that the change Δa* in a* and the change Δb* in b* when heated at 150°C for 2 hours are both 3 or less, and more preferably 2 or less.

[0044] Furthermore, the laminated film of the present invention preferably has a Δhaze of 2.5%pt or less, which is the change in haze when heated for 2 hours at 150° C. By having a Δhaze of 2.5%pt or less, more preferably 2.0%pt or less, and even more preferably 1.5%pt or less when heated for 2 hours at 150° C., the film can maintain a clear display even in a high-temperature outdoor environment when used for a mirror display intended for outdoor use.

[0045] Generally, when a laminated film is heated at 150°C for 2 hours, the layer of the resin with low crystallinity crystallizes, and the haze increases. However, for example, in the heat treatment in a tenter in the laminated film manufacturing method described later, the film can be heat-treated at 220°C or higher, more preferably 230°C or higher, to break down the crystal structure of layer B, and the crystallization of layer B during heating can be suppressed. The haze can be measured according to JIS K 7136 (2000), and the details of the measurement method will be described later.

[0046] In addition, the laminated film of the present invention preferably has a heat shrinkage rate of 1.4% or less in the main orientation direction after heat treatment at 150°C for 30 minutes. By making the heat shrinkage rate of 1.4% or less in the main orientation direction after heat treatment at 150°C for 30 minutes, when used in mirror display applications where flat glass is often used, it is possible to achieve a display display with little shrinkage even when heated during glass lamination, and with little appearance defects due to wrinkles, etc. The main orientation direction referred to here is the direction of the orientation angle measured at an incident angle of 0° using a retardation measuring device (for example, KOBRA-21ADH manufactured by Oji Scientific Instruments Co., Ltd.). The method for identifying the main orientation direction will be described in detail later.

[0047] Generally, when a laminate film is heated at 150°C for 30 minutes, the laminate film undergoes thermal shrinkage. However, for example, in the heat treatment in a tenter in the laminate film manufacturing method described below, the film is heat-treated at about 240°C to enhance the crystallization of the highly crystalline A layer and suppress thermal shrinkage during heating.

[0048] In order for the laminated film of the present invention to have the optical properties as described above, it is preferable that, for example, the total number of A layers and B layers of the film described below is 201 or more, and that the basic skeleton of the thermoplastic resin that is the main component of both layers is the same. Here, the basic skeleton of the thermoplastic resin refers to the structural unit that is most abundant in the molecular chain of the thermoplastic resin, and for example, if the thermoplastic resin is polyethylene terephthalate, the ethylene terephthalate unit corresponds to the basic skeleton.

[0049] The laminated film of the present invention is preferably a film having a large area and more uniform optical properties so that it can be used in large displays. A method for obtaining such a film includes, but is not limited to, the method described in Patent Document 3.

[0050] Next, an example of a preferred method for producing the laminated film of the present invention will be described below, although the laminated film of the present invention is not limited to the following example.

[0051] Thermoplastic resin A and thermoplastic resin B are prepared in the form of pellets. The pellets are dried in hot air or under vacuum as necessary, and then fed to two extruders, respectively. In each extruder, each thermoplastic resin is heated and melted at a temperature equal to or higher than its melting point, and the extrusion amount is uniformized and extruded using a gear pump or the like. After that, foreign matter and denatured resins are removed from each extruded thermoplastic resin through a filter or the like.

[0052] Next, the thermoplastic resin A and the thermoplastic resin B sent out from different flow paths using two extruders are sent to a multi-layer lamination device. As the multi-layer lamination device, a multi-manifold die, a feed block, a static mixer, etc. can be used, but in particular, in order to efficiently obtain the film constituting the sheet of the present invention, it is desirable to use a feed block containing at least two or more separate members having a large number of fine slits. When such a feed block is used, the device does not become extremely large, so that there is little foreign matter due to thermal deterioration, and even if the number of layers is extremely large, lamination can be performed with high precision. In addition, the lamination precision in the width direction is significantly improved compared to the conventional technology, and it is also easy to form an arbitrary layer thickness configuration. In this device, the thickness of each layer can be adjusted by the slit shape (length, width, gap), so that an arbitrary layer thickness can be achieved, and the layer configuration required for the laminated film of the present invention can be easily achieved.

[0053] When the layer thickness distribution has a gradient structure of two or more steps, the change in layer thickness from a thin layer to a thick layer or from a thick layer to a thin layer becomes very steep. As described above, a feed block containing at least two or more separate members having a large number of fine slits is preferably used to manufacture the film constituting the sheet of the present invention. However, at the point where the thermoplastic resins fed from the separate feed blocks join, the layer thickness distribution changes immediately after joining, which is a major factor in causing color variation in the width direction. Furthermore, the resin speed near the pipe is reduced due to the influence of the wall surface of the pipe on the path from the feed block to the die, and the color uniformity in the width direction of the film is further deteriorated due to the difference in flow speed between the wall surface of the pipe and the center of the pipe.

[0054] Therefore, by replacing a certain distance of the resin joining part of the film's outermost layer and the separate feed block with the same polymer to provide a thick film layer, a film that expresses a uniform color tone in the width direction can be obtained without destroying the lamination ratio. In this case, if the outermost layers on both sides of the film are made of thermoplastic resin A, the layer (A layer) made of thermoplastic resin A becomes the thick film layer. In addition, the resin for the middle thick film layer is preferably a thermoplastic resin with relatively high crystallinity to improve the resistance to pressure marks, and is usually the same layer as the outermost layer. The thickness of the thick film layer is preferably adjusted by adjusting each flow rate corresponding to the thickness of the corresponding layer with the gap of the slit, and in this case, the gap accuracy of each slit gap is preferably ±10 μm or less. By using such a special feed block, a film with high accuracy and a gradient structure of two or more stages can be obtained.

[0055] The molten laminate thus formed into the desired layer structure is then molded into a desired shape by a die and discharged. The multi-layer laminated sheet discharged from the die is then extruded onto a rotating cooling body such as a casting drum, and cooled and solidified to obtain a cast film (unstretched film). In this case, it is preferable to use a wire-shaped, tape-shaped, wire-shaped, or knife-shaped electrode to adhere to a rotating cooling body such as a casting drum by electrostatic force and rapidly solidify. In addition, a method of rapidly solidifying by blowing air from a slit-shaped, spot-shaped, or planar device to adhere to a rotating cooling body such as a casting drum or by adhering to a rotating cooling body with a nip roll is also preferable.

[0056] The thus obtained casting film (unstretched film) is preferably biaxially stretched as necessary. Biaxial stretching refers to stretching in the longitudinal direction and the width direction. Stretching may be performed in two axial directions sequentially, or in two directions simultaneously. Furthermore, the film may be re-stretched in the longitudinal direction and / or the width direction. The longitudinal direction refers to the running direction of the film (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 film plane.

[0057] First, the case of sequential biaxial stretching will be described. In the case of sequential biaxial stretching, first, longitudinal stretching is performed to obtain a uniaxially stretched film. The longitudinal stretching here refers to stretching for giving molecular orientation to the film in the longitudinal direction, and is usually performed by the difference in peripheral speed of the rolls. This stretching may be performed in one stage or in multiple stages using a plurality of pairs of rolls. The stretching ratio varies depending on the type of thermoplastic resin, but is usually preferably 2 to 15 times, and when polyethylene terephthalate is used as either thermoplastic resin A or B, 2 to 7 times is particularly preferably used. In addition, the stretching temperature is preferably the glass transition temperature of the higher of the thermoplastic resins A and B that constitute the film to the glass transition temperature + 100°C, and when polyethylene terephthalate is used as either thermoplastic resin A or B, 75°C to 175°C is preferable.

[0058] When providing an easy-adhesion layer on a laminated film, a method of coating and laminating with a coating agent containing the above-mentioned components is preferred. Methods of coating with a coating agent include a method of coating in a separate process from the film manufacturing process, that is, a so-called offline coating method, and a so-called in-line coating method, that coats the easy-adhesion layer at once by coating during the film manufacturing process. It is preferable to adopt the in-line coating method from the viewpoint of cost and uniformity of the coating thickness, and the solvent of the coating liquid used in this case is preferably aqueous from the viewpoint of environmental pollution and explosion resistance, and the most preferred embodiment is to use water.

[0059] When laminating the easy-adhesion layer by in-line coating, the coating agent constituting the easy-adhesion layer is continuously applied to the uniaxially stretched film. For example, the coating agent (water-based coating agent) using water as a solvent can be applied by reverse coating, spray coating, bar coating, gravure coating, rod coating, and die coating. The easy-adhesion layer may contain a crosslinking agent, an antioxidant, a heat stabilizer, a weather stabilizer, an ultraviolet absorber, an organic slippery material, a pigment, a dye, organic or inorganic particles, a filler, a surfactant, etc., as long as the effect of the invention is not impaired.

[0060] The subsequent stretching in the width direction refers to stretching to give molecular orientation in the width direction of the film, and is usually performed by using a tenter to convey the uniaxially stretched film while holding both ends in the width direction with clips, preheating the film by applying heat, and then stretching it in the width direction. The water-based coating agent applied just before the tenter is dried during this preheating. The stretching ratio varies depending on the type of thermoplastic resin, but is usually preferably 2 to 15 times, and when polyethylene terephthalate is used as either thermoplastic resin A or B, it is particularly preferably 2 to 7 times. In addition, the stretching temperature is preferably the glass transition temperature of the higher of the thermoplastic resins A and B that constitute the film to the glass transition temperature + 120°C, and when polyethylene terephthalate is used as either thermoplastic resin A or B, it is preferably 75°C to 195°C.

[0061] The biaxially stretched film is preferably heat-treated in a tenter at a temperature equal to or higher than the stretching temperature and equal to or lower than the melting point in order to impart flatness and dimensional stability. After the biaxially stretched film is heat-treated, it is uniformly cooled slowly to room temperature and wound up by a winder. If necessary, a relaxation treatment or the like may be performed in combination during the heat treatment and the slow cooling.

[0062] Next, the case of simultaneous biaxial stretching will be described. In the case of simultaneous biaxial stretching, the coating agent that forms the easy-adhesion layer is continuously applied to the obtained cast film. As the coating method of the coating agent (water-based coating agent) that uses water as a solvent, for example, reverse coating method, spray coating method, bar coating method, gravure coating method, rod coating method and die coating method can be used.

[0063] Next, the cast film (unstretched film) coated with the coating agent is introduced into a simultaneous biaxial tenter, and the film is conveyed while both ends are held by clips, and stretched simultaneously and / or stepwise in the longitudinal and transverse directions. The simultaneous biaxial stretching machine may be of the pantograph type, screw type, drive motor type, or linear motor type, but the drive motor type or linear motor type is preferred, since it can change the stretching ratio at any desired position and can perform relaxation treatment at any desired location. The stretching ratio varies depending on the type of thermoplastic resin, but usually, an area ratio of 6 to 50 times is preferred, and an area ratio of 8 to 30 times is particularly preferred. In particular, in the case of simultaneous biaxial stretching, in order to suppress the in-plane orientation difference, it is preferred that the stretching ratios in the longitudinal and transverse directions are the same and that the stretching speeds are approximately the same. In addition, the stretching temperature is preferably the glass transition temperature of the higher of the thermoplastic resins A and B constituting the film to the glass transition temperature + 120°C, and when polyethylene terephthalate is used as either the thermoplastic resin A or B, it is preferably 75°C to 195°C.

[0064] The biaxially stretched film is preferably subsequently subjected to heat treatment in a tenter at a temperature equal to or higher than the stretching temperature and equal to or lower than the melting point in order to impart flatness and dimensional stability. During this heat treatment, it is also preferable to instantly perform a relaxation treatment in the longitudinal direction immediately before and / or immediately after entering the heat treatment zone in order to suppress the distribution of the main orientation axis in the width direction. After the heat treatment is performed on the biaxially stretched film in this way, it is uniformly cooled slowly to room temperature and wound up by a winder. If necessary, a relaxation treatment may be performed in the longitudinal direction and / or width direction during the heat treatment and slow cooling, and it is also preferable to instantly perform a relaxation treatment in the longitudinal direction immediately before and / or immediately after entering the heat treatment zone.

[0065] The glass laminate for protecting a display of the present invention is formed using the laminate film of the present invention, and is preferably formed by laminating glass, a pressure-sensitive adhesive, and a laminate film in this order.

[0066] The glass laminate for protecting a display of the present invention preferably has a hard coat layer on one surface thereof. The hard coat layer can prevent the laminate film from being scratched and improve the handling properties during processing. However, for applications that do not require a hard coat layer from the viewpoint of cost, the hard coat layer does not necessarily have to be provided.

[0067] The hard coat layer may be made of, for example, an acrylic resin, a urethane resin, a melamine resin, an organic silicate resin, a silicone resin, etc. Among these, from the viewpoints of hardness, durability, and productivity, silicone resins and acrylic resins are preferred, acrylic resins are more preferred, and actinic radiation curable acrylic resins are particularly preferred.

[0068] The composition of the hard coat layer may contain various additives as necessary within the range that does not impair the effects of the present invention. For example, an antioxidant, a light stabilizer, a stabilizer such as an ultraviolet absorber, a surfactant, a leveling agent, an antistatic agent, etc. may be used.

[0069] The thickness of the hard coat layer is determined according to the application, but is usually preferably 0.1 μm or more and 30 μm or less. By making the thickness of the hard coat layer 0.1 μm or more, more preferably 1 μm or more, the effect of preventing scratches by the cured hard coat layer can be effectively obtained. By making the thickness of the hard coat layer 30 μm or less, more preferably 15 μm or less, it is possible to prevent cracks from occurring in the cured film due to stress such as bending.

[0070] When the hard coat layer is provided, the glass laminate for protecting a display of the present invention is preferably formed by laminating the glass, the adhesive, the laminate film, and the hard coat layer in this order. When the glass laminate is attached to a display, the hard coat layer is applied to the outermost layer, which can prevent scratches during attachment processing and suppress a decrease in yield.

[0071] As the adhesive in the present invention, since high transparency is required from the viewpoints of high visibility, aesthetics and appearance required for display applications, it is preferable to use an optically clear adhesive (OCA). The optically clear adhesive here refers to a double-sided adhesive that does not have a supporting substrate such as a film or sheet. In particular, in the present invention, it is preferable to use an acrylic adhesive containing an acrylic resin in view of adhesion to the laminated film of the half mirror material and followability during stretching and molding.

[0072] Examples of monomer components constituting the acrylic resin include alkyl acrylates, alkyl methacrylates (alkyl groups and methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, 2-ethylhexyl, lauryl, stearyl, cyclohexyl, phenyl, benzyl, phenylethyl, etc.), hydroxyl group-containing monomers such as 2-hydroxyacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, and 2-hydroxypropyl methacrylate, acrylamide, methacrylamide, N-methylacrylamide, N-methylmethacrylamide, N-methylol acrylate, and the like. Amino group-containing monomers such as N-methylol methacrylamide, N,N-dimethylolacrylamide, N-methoxymethylacrylamide, N-methoxymethyl methacrylamide, and N-phenylacrylamide, amino group-containing monomers such as N,N-diethylaminoethyl acrylate and N,N-diethylaminoethyl methacrylate, amino group-containing monomers such as glycidyl acrylate and glycidyl methacrylate, and monomers containing a carboxyl group or a salt thereof such as acrylic acid, methacrylic acid, and salts thereof (lithium salt, sodium salt, potassium salt, etc.), can be used, and these monomers can be copolymerized using one or more of these monomers. Furthermore, these can be copolymerized with various types of monomers.Examples of the various monomers that can be used include epoxy group-containing monomers such as acrylic glycidyl ether, monomers containing sulfonic acid groups or salts thereof such as styrene sulfonic acid, vinyl sulfonic acid, and salts thereof (lithium salt, sodium salt, potassium salt, ammonium salt, etc.), monomers containing carboxyl groups or salts thereof such as crotonic acid, itaconic acid, maleic acid, fumaric acid, and salts thereof (lithium salt, sodium salt, potassium salt, ammonium salt, etc.), monomers containing acid anhydrides such as maleic anhydride and itaconic anhydride, vinyl isocyanate, allyl isocyanate, styrene, vinyl methyl ether, vinyl tris alkoxysilane, alkyl maleic acid monoester, alkyl fumaric acid monoester, acrylonitrile, methacrylonitrile, alkyl itaconic acid monoester, vinylidene chloride, vinyl acetate, vinyl chloride, etc. Modified acrylic copolymers, such as block copolymers and graft copolymers modified with polyester, urethane, and epoxy, can also be used.

[0073] Further, examples of commercially available acrylic adhesives include OCA, 8146, 8171, 8172, 8173D, 8180, 8182, 8185, 8187, 8188, 8189, 8191, 8192, 8095, 9483, 8146, CEF08A04, 05, 06, and 07 series manufactured by 3M USA or Sumitomo 3M, and MO-3005C / G manufactured by Lintec Corporation. , MO-3006C / G, MO-2105G / I, MO-2106G / I, CR9707, CS9621T, CS9622T, CS3623, CS9663L, CS9662L manufactured by Nitto Denko Corporation, TD06A, TI14A, MA54A manufactured by Tomoegawa Paper Co., Ltd., SANCUARY (registered trademark) OP, DH, DK types manufactured by San-A Chemical Co., Ltd., 5400 series 5402, 5405 manufactured by Sekisui Chemical Co., Ltd., Daitac (registered trademark) 8080, 8080NR, 0835N, LT6003W, Z87011W, Z87012W manufactured by DIC Corporation, FS601 manufactured by Toyo Ink Co., Ltd., Fineset TE-250S121 manufactured by Hitachi Chemical Co., Ltd., and PDS1 manufactured by PANAC Corporation.

[0074] The thickness of the adhesive in the present invention is preferably 25 μm to 400 μm, more preferably 50 μm to 200 μm. If it is less than 25 μm, the unevenness of the defect brightness distribution may become large. If it exceeds 400 μm, defects such as burrs may occur after lamination.

[0075] The adhesive of the present invention may contain various additives, such as viscosity modifiers, plasticizers, leveling agents, antigelling agents, antioxidants, heat stabilizers, light stabilizers, ultraviolet absorbers, lubricants, pigments, dyes, organic or inorganic fine particles, fillers, antistatic agents, nucleating agents, curing agents, etc. EXAMPLES

[0076] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. Various properties were measured by the following methods, and the raw materials used in the production of the laminated sheet were as follows.

[0077] [Evaluation method of various characteristics] (1) Film layer structure, layer thickness, and total thickness A film sample was obtained by cutting out a cross section perpendicular to the film surface using a microtome. Next, a transmission electron microscope (TEM) (Hitachi, Ltd., H-7100FA type) was used to observe the cross section of the film at 40,000 times magnification at an acceleration voltage of 75 kV, and the cross section was photographed to confirm the layer structure, and the layer thickness was measured using the length measurement function of the transmission electron microscope. The total thickness of each layer was taken as the total film thickness. In addition, the sample was stained using RuO4 to obtain high contrast during observation.

[0078] The cross-sectional image obtained in the TEM observation was converted into a compressed image file (JPEG format), and position-brightness data was obtained by line profile along the thickness direction of the film using ImagePro (registered trademark)-10 (sold by Hakuto Co., Ltd.). Then, a five-point moving average process was performed on the profile obtained by plotting the relationship between position and brightness using a spreadsheet software (Microsoft Corporation "Excel" (registered trademark) 2016). The process was performed by averaging brightness for five consecutive measurement positions, and the same calculation was performed by changing the position one point at a time and continuously processing, and an averaged position-brightness profile was obtained. In the obtained averaged position-brightness profile, the position surrounded by the inflection points where the slope changes from positive to negative or negative to positive was determined to be one layer. For each layer obtained by this method, position-brightness data was then obtained in the planar direction of the film (direction perpendicular to the thickness direction). After calculating the average value and standard deviation of the brightness obtained for each layer, if the difference between the average brightness of the two adjacent layers was greater than any of the standard deviations of the brightness of the adjacent thermoplastic resin layers, these two adjacent layers were determined to be different. The difference (distance) between the positions of the inflection points was calculated as the layer thickness of each layer. The average value of the sum of the layer thicknesses of adjacent A and B layers from one film surface to the opposite surface was calculated for all pairs in sequence. A group in which the difference between the average layer thickness of a pair of adjacent A and B layers and the average layer thickness of an adjacent pair is continuously and monotonically increasing or decreasing within a range of 50 nm or less was defined as a gradient structure. A gradient structure is one that has a positive or negative gradient such that the square of R is 0.5 or more when the relationship between the pair number and the average layer thickness is approximated by least squares. For example, the configuration in Figure 1 is called a four-step gradient structure. However, the average thickness of the pair including the thick layer was excluded from the least squares approximation.

[0079] (2)Visible light reflectance A 10 cm x 10 cm sample was cut out from the center of a laminated film measuring 50 cm square. Next, the relative reflectance of each sample at an incident angle of 10° was measured using a spectrophotometer (U-4100 Spectrophotometer, Hitachi, Ltd.). The inner wall of the integrating sphere attached to the spectrophotometer used was made of barium sulfate, and the standard plate was made of aluminum oxide. The measurement conditions were a wavelength band of 300 nm to 2500 nm, a slit of 2 nm (visible) / automatic control (infrared), a gain of 2, and a scanning speed of 600 nm / min. The sample was placed on a holder behind the integrating sphere. Under the above conditions, the reflection spectrum of each sample was obtained from 400 nm to 700 nm. The average reflectance was calculated by calculating the area surrounded by the reflection curve and the wavelength band based on the Simpson method formula using the data on the absolute reflectance at every 1 nm wavelength, and dividing it by 300 nm, which is the width of the wavelength band, to calculate the visible light reflectance. The spectrophotometer measurements were performed at the center of the sample.

[0080] (3) Maximum and minimum values ​​of section reflectance A 10cm x 10cm sample was cut from the center of a 50cm x 50cm laminated film, and the reflection spectrum was measured in the wavelength range of 400 to 1150nm using the same method as in (2). The range was divided into 50nm intervals from 400nm (400-450nm, 450-500nm, ... 1000-1150nm), and the average reflectance (interval reflectance) was calculated for each interval. The maximum and minimum values ​​of the interval reflectance were then determined.

[0081] (4) Maximum difference between visible light reflectance and interval reflectance The greater of the difference between the maximum value of the interval reflectance calculated in (3) and the visible light reflectance calculated in (2) and the difference between the visible light reflectance calculated in (2) and the minimum value of the interval reflectance calculated in (3) was determined as the maximum difference between the visible light reflectance and the interval reflectance.

[0082] (5) Reflected light |a before heating * |value, |b * |Value A 10cm x 10cm sample was cut out from the center of a 50cm x 50cm laminated film, and the a * , b * The a of the reflected light before heating was measured and the average value of n=5 was used. * , b * The obtained a * , b * The absolute value of the reflected light |a * |value, |b * | value. Mode: Reflection, SCI / SCE simultaneous calibration Measuring diameter: 8mm Sample: Black tape attached to the non-measurement side Light source: D65.

[0083] (6) Δ|a of reflected light after heating * |value, Δ|b * |Value (5) |a * |value, |b * The sample used for measuring the |a value was placed in a hot air oven maintained at 150°C, and the film was left for 2 hours without any load, and then taken out to room temperature. * |value, |b * While keeping the measurement position of |a value the same, measure |a value after heating by the method of (5). * |value, |b * The value of |a before heating was measured. * value from the heating value of |a * The absolute value obtained by subtracting the | value is the Δ|a value of the reflected light after heating. * |value, |b before heating * value from the heating value of |b * The absolute value obtained by subtracting the | value is the Δ|b * | value.

[0084] (7) Change in visible light reflectance after heating (%pt) The sample used for measuring the visible light reflectance by the method described in (2) was placed in a hot air oven maintained in an atmosphere of 150°C, and the film was left for 2 hours without load, and then removed to room temperature. The visible light reflectance (%) of this sample after heating was measured by the method described in (2) while keeping the measurement position of the average reflectance the same. The value obtained by subtracting the visible light reflectance (%) after heating from the visible light reflectance (%) before heating was defined as the change in visible light reflectance after heating (%pt).

[0085] (8) Haze before heating (%) A 10 cm x 10 cm sample was cut out from the center of a 50 cm square laminated film. Haze was measured using a turbidity meter (NDH-5000, manufactured by Nippon Denshoku Industries Co., Ltd.) according to JIS K 7136 (2000), and the average value of 5 values ​​was used to determine the haze (%) before heating.

[0086] (9) Haze after heating (%) The sample used for measuring the haze before heating by the method described in (8) was placed in a hot air oven maintained at an atmosphere of 150°C, and the film was left for 2 hours without load, and then taken out to room temperature. The haze of this sample was measured by the method described in (8) while keeping the measurement position the same as that before heating, and this was recorded as the haze after heating (%).

[0087] (10) Haze change upon heating ΔHaze (%pt) (9) The haze (%) after heating was subtracted from the haze (%) before heating (8) to determine the haze change upon heating, Δ haze (%pt).

[0088] (11) Heat shrinkage rate in the main orientation direction (%) The retardation measuring device used was KOBRA-WR manufactured by Oji Scientific Instruments Co., Ltd. The sample was cut out from the center of the laminated film to a size of 10 cm x 10 cm, and the film's fast axis was set at an angle of 0° defined by this measuring device, and the orientation angle at an incident angle of 0° was measured to determine the main orientation direction. Next, the sample was cut out from the center of the laminated film to a size of 300 mm in the main orientation direction and 300 mm in the direction perpendicular to the main orientation in the film plane. Next, a pair of marks was made in the main orientation direction of the sample so that the original length (L0) was 200 mm apart. The sample was placed in a hot air oven kept at an atmosphere of 150°C, left unloaded for 30 minutes, and then taken out at room temperature. The distance between the pair of marks on the taken-out sample was measured and used as the length after treatment (L1). The thermal shrinkage was calculated according to the following formula, and the average of n number 5 was used as the thermal shrinkage in the main orientation direction (%). Thermal shrinkage rate (%) = 100 × (L0-L1) / L0 ... (formula).

[0089] (12) Visible light transmittance, solar reflectance A 10cm x 10cm sample was cut out from the center of a 50cm x 50cm laminated film, and the sample was placed on a holder in front of an integrating sphere. The transmission spectrum was measured in the wavelength range of 300 to 2500nm in the same manner as in (2). The visible light transmittance and solar reflectance as specified in ISO9050 were calculated by combining the data with the reflectance data obtained in (2).

[0090] [Raw materials] (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 per 100 parts by mass of dimethyl terephthalate, and the mixture was heated and heated in a conventional manner to carry out an ester exchange reaction. Next, 0.020 parts by mass of an 85% aqueous solution of phosphoric acid was added per 100 parts by mass of dimethyl terephthalate to the ester exchange reaction product, and the mixture was transferred to a polycondensation reaction tank. Further, the reaction system was gradually depressurized while heating and heating, and a polycondensation reaction was carried out at 290°C under a reduced pressure of 1 mmHg in a conventional manner to obtain polyethylene terephthalate (hereinafter sometimes referred to as PET) having an intrinsic viscosity (IV) of 0.61, which was a crystalline resin, and named Resin A-1.

[0091] (Resin A-2) Except for using dimethyl 2,6-naphthalenedicarboxylate instead of dimethyl terephthalate, the ester exchange reaction and polycondensation reaction were carried out in the same manner as for Resin A-1, to obtain a crystalline resin, polyethylene naphthalate (hereinafter sometimes referred to as PEN), with an intrinsic viscosity (IV) of 0.67, which was named Resin A-2.

[0092] (Resin B-1) A copolymerized polyethylene terephthalate mixture obtained by mixing polyethylene terephthalate copolymerized with 30 mol % of cyclohexanedimethanol (CHDM) having an intrinsic viscosity (IV) of 0.75, which is an amorphous resin, and Resin A-1 in a ratio of 82:18 was used as Resin B-1.

[0093] (Resin B-2) A copolymerized polyethylene terephthalate mixture obtained by mixing polyethylene terephthalate copolymerized with 30 mol % of cyclohexanedimethanol (CHDM) having an intrinsic viscosity (IV) of 0.75, which is an amorphous resin, and Resin A-1 in a ratio of 65:35 was used as Resin B-2.

[0094] (Resin B-3) A copolymerized polyethylene terephthalate mixture obtained by mixing polyethylene terephthalate copolymerized with 30 mol % of cyclohexanedimethanol (CHDM) having an intrinsic viscosity (IV) of 0.75, which is an amorphous resin, and Resin A-1 in a ratio of 55:45 was used as Resin B-3.

[0095] (Resin B-4) Resin B-4 was prepared by mixing polyethylene terephthalate copolymerized with 21 mol% of spiroglycol (SPG) and 24 mol% of cyclohexanedicarboxylic acid (CHDC), an amorphous resin with an intrinsic viscosity (IV) of 0.60, in a 50:50 ratio with Resin A-1.

[0096] (Resin B-5) A copolymerized polyethylene terephthalate mixture obtained by mixing polyethylene terephthalate copolymerized with 30 mol % of cyclohexanedimethanol (CHDM) having an intrinsic viscosity (IV) of 0.75, which is an amorphous resin, and Resin A-1 in a ratio of 50:50 was named Resin B-5.

[0097] [Example 1] Resin A-1 was melted at 290°C as thermoplastic resin A in a single screw extruder, and resin B-1 was melted at 285°C as thermoplastic resin B in a vented twin screw extruder, and then the melted resins were merged in an 801-layer feed block having four separate members each having 201 slits through a gear pump and a filter. The outermost layers on both sides of the thick film layer were resin A-1, and resin A-1 and resin B-1 were alternately laminated, and the layer thickness of the adjacent layer made of resin A-1 and layer made of resin B-1 were made to be almost the same. Next, the melt laminate was introduced into a T-die to be molded into a sheet, and then it was brought into contact with a casting drum whose surface temperature was kept at 25°C by applying electrostatic force, and rapidly cooled and solidified to obtain a casting film.

[0098] The obtained casting film was heated with a group of rolls set at 75°C, and then stretched 3.3 times in the machine direction while rapidly heating from both sides with a radiation heater within a stretching section length of 100 mm, and then cooled once to obtain a uniaxially oriented film. Next, a coating liquid for forming an easy-adhesion layer containing (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) was applied to both sides of the uniaxially oriented film with a #4 metabar.

[0099] The uniaxially oriented film coated with the coating liquid 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 125°C. The stretched film was heat-treated with hot air at 240°C in the tenter as it was, and then subjected to a 1.5% relaxation treatment in the width direction at the same temperature. The film was then cooled to room temperature and wound up with a winder to obtain a laminated film. The total thickness of the obtained laminated film was 125 μm. The layer design of this film is as shown in Figure 1, and the layer thickness of each layer was controlled by adjusting the slit gap. The cross section of the film in the thickness direction was observed with a TEM, and the layer thickness distribution was obtained by image processing. The thickness ratio of adjacent layers A and B was 2.1. The evaluation results of the obtained laminated film are shown in Table 1.

[0100] [Examples 2 and 3] A laminated film was obtained in the same manner as in Example 1, except that the thermoplastic resin B was changed as shown in Table 1. The evaluation results of the laminated film are shown in Table 1.

[0101] [Example 4] A laminate film was obtained in the same manner as in Example 1, except that the thickness ratio between adjacent layers A and B was changed to 3.8, and the total thickness of the laminate film was adjusted to 140 μm in order to adjust the reflection band. The evaluation results of the laminate film are shown in Table 1.

[0102] [Example 5] A laminate film was obtained in the same manner as in Example 1, except that the thickness ratio between adjacent layers A and B was changed to 1.5, and the total thickness of the laminate film was adjusted to 120 μm in order to adjust the reflection band. The evaluation results of the laminate film are shown in Table 1.

[0103] [Example 6] Except for changing the thermoplastic resin B-1 to the thermoplastic resin B-4, a laminated film was obtained in the same manner as in Example 1. The evaluation results of the laminated film are shown in Table 1.

[0104] [Example 7] A laminate film was obtained in the same manner as in Example 1, except that the feed block was changed, the layer design of the laminate film was changed to a four-stage gradient of 201 layers, and the total thickness of the laminate film was adjusted to 49 μm in order to adjust the reflection band. The evaluation results of the laminate film are shown in Table 1.

[0105] [Example 8] A glass plate with dimensions of 130 cm x 100 cm x 3 mm thickness was prepared, and an acrylic adhesive (OCA) 8172 manufactured by 3M was prepared as the adhesive. The thickness of the adhesive layer was 50 μm. In a clean room, a sheet laminator was used to first bond the adhesive to the laminated film prepared in the procedure of Example 1, and then the laminated film with the adhesive attached was bonded to the glass plate to obtain a half mirror glass laminate. The results are shown in Table 2.

[0106] [Example 9] A laminated film was obtained in the same manner as in Example 1, except that the temperature of the hot air in the tenter, i.e., the heat treatment temperature, was changed to 225° C. The evaluation results of the laminated film are shown in Table 2.

[0107] [Comparative Example 1] A laminate film was obtained in the same manner as in Example 1, except that the thermoplastic resin B was changed as shown in Table 1 and the total thickness of the laminate film was adjusted to 115 μm in order to adjust the reflection band. The evaluation results of the laminate film are shown in Table 2.

[0108] [Comparative Example 2] A laminated film was obtained in the same manner as in Example 1, except that the thermoplastic resin B was changed as shown in Table 1. The evaluation results of the laminated film are shown in Table 2.

[0109] [Comparative Example 3] A laminate film was obtained in the same manner as in Example 1, except that the thickness ratio between adjacent layers A and B was changed to 4.5, and the total thickness of the laminate film was adjusted to 135 μm in order to adjust the reflection band. The evaluation results of the laminate film are shown in Table 2.

[0110] [Comparative Example 4] A laminated film was obtained in the same manner as in Example 1, except that the thickness ratio of adjacent layers A and B was changed to 1.1. The total thickness of the obtained laminated film was 110 μm. The evaluation results of the laminated film are shown in Table 2.

[0111] [Comparative Example 5] A laminate film was obtained in the same manner as in Example 1, except that the feed block was changed, the layer design of the laminate film was changed to 141 layers with a four-stage gradient, and the total thickness of the laminate film was adjusted to 43 μm in order to adjust the reflection band. The evaluation results of the laminate film are shown in Table 2.

[0112] [Table 1]

[0113] [Table 2] [Industrial Applicability]

[0114] The laminated film of the present invention has a good balance between visible light reflection and visible light reflection and transmission, has little coloring, and has excellent heat-shielding properties by blocking near-infrared rays. Changes in optical properties due to heat are also small, so that it can be suitably used, for example, in mirror displays that are also intended for outdoor use. [Explanation of symbols]

[0115] 1: Axis showing layer number 2: Axis showing layer thickness 3: Points indicating the location and thickness of the thick film layer 4: Line showing the change in thickness of layer A 5: Line showing thickness change of layer B

Claims

1. A laminated film that satisfies all of the following (1) to (3): (1) The laminate is composed of 201 or more layers (A layers) whose main component is thermoplastic resin A and 201 or more layers (B layers) whose main component is thermoplastic resin B, and the thickness ratio between adjacent A layers and B layers (thickness of A layer / thickness of B layer) is 1.5 or more and 4.0 or less. (2) The average reflectance in the wavelength band of 400 to 700 nm is 25% or more and 50% or less. (3) In the wavelength band of 400 to 1150 nm, the average reflectance of each section divided at intervals of 50 nm from 400 nm is within a range of ±20% of the average reflectance in the wavelength band of 400 to 700 nm.

2. 2. The laminate film according to claim 1, wherein the change in average reflectance in the wavelength range of 400 to 700 nm after heating at 150° C. for 2 hours is 5% or less compared to the average reflectance in the wavelength range of 400 to 700 nm before heating.

3. The absolute values ​​of the a* and b* values ​​of reflected light measured by the measurement method described in JIS Z8722 (2019) are both 10 or less, and the change Δa* in a* and the change Δb* in b* when heated at 150°C for 2 hours are both 3 or less. The laminate film according to claim 1 or 2.

4. 3. The laminated film according to claim 1, wherein the haze change Δhaze when heated at 150° C. for 2 hours is 2.5% pt or less.

5. 3. The laminated film according to claim 1, which has a heat shrinkage rate of 1.4% or less in the main orientation direction after heat treatment at 150° C. for 30 minutes.

6. A glass laminate for protecting a display, comprising the laminate film according to claim 1 or 2.

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