film laminate

Abstract

To provide a film laminate which has excellent low dielectric characteristics and transparency, and is suitable for outdoor use.SOLUTION: A film laminate includes a polyester layer (X) and a resin layer (Y), and has light transmittance at a wavelength of 380 nm of 25% or less, wherein the polyester layer (X) contains polybutylene naphthalate, and has a dielectric loss tangent at 28 GHz of less than 0.0050.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to a film laminate. [Background technology]

[0002] In recent years, with the increasing performance and functionality of electrical and electronic devices, there has been a growing need for high-speed information communication. For example, with the launch of 5G (fifth-generation mobile communication system) high-speed communication services for smartphones, these services are becoming widespread not only in the consumer sector but also in the industrial sector (factories, automobiles, etc.). 5G's high-speed, high-capacity data communication utilizes radio waves in the "millimeter wave" band (wavelength 1-10 mm, frequency 30-300 GHz). Advantages of millimeter waves include the ability to transmit large amounts of data at once and the potential for high-resolution images.

[0003] On the other hand, when a high-frequency digital signal such as millimeter waves is passed through a circuit board, dielectric loss occurs where a portion of the transmitted digital signal is consumed as heat on the wiring of the circuit board, resulting in a so-called "transmission loss" where the digital signal reaches the receiving side attenuated. Therefore, measures to reduce transmission loss are required in the materials used. The aforementioned transmission loss is the sum of dielectric loss and conductor loss, and the dielectric loss α d It is calculated from the following formula (1).

[0004]

number

[0005] Note that f is frequency, c is the speed of light, and ε r is the relative permittivity, and tanδ is the dielectric loss tangent.

[0006] For example, in FPCs (Flexible Printed Circuits), which are flexible circuit boards formed from resin film and copper foil, the resin film has dielectric loss α to reduce transmission loss. d A reduction in ε is required. More specifically,r Attempts have been made to lower tanδ, particularly to reduce tanδ. Specifically, examples of fluororesins used as materials for FPCs include liquid crystal polymers (LCP), which have a dielectric loss of approximately 1 / 10th that of polyimide (PI); cycloolefin polymers (COP), which have a dielectric loss of approximately 1 / 50th; and polytetrafluoroethylene (PTFE), which has a dielectric loss of approximately 1 / 100th (Non-Patent Literature 1).

[0007] However, LCP and COP have the problem of low heat resistance, fluororesins have poor adhesion strength to other materials such as copper foil, and are difficult to drill with UV lasers due to their UV absorber properties. Furthermore, fluororesins are expensive. Therefore, there is a demand for a resin film that has low dielectric loss and is versatile.

[0008] Polyester film is a highly versatile resin film. Polyester film excels in heat resistance, weather resistance, mechanical strength, and transparency, and is also readily available at a reasonable price. Therefore, it is used in various applications such as packaging materials and optical applications, but its low dielectric properties have not been given much consideration.

[0009] For example, Patent Document 1 discloses a laminated biaxially oriented polyester film containing 5 to 45 volume percent of voids inside, as a polyester film having excellent low dielectric properties. By containing voids, air gaps can be dispersed, achieving a low dielectric constant and low dielectric loss tangent.

[0010] Incidentally, a "transparent antenna film" (hereinafter also referred to as "transparent antenna"), which has an invisible, ultra-fine metal mesh wiring formed on a transparent film, is currently being considered, and there is a need to reduce the dielectric loss of the film, or more specifically, to lower the dielectric constant and dielectric loss tangent of the film. The aforementioned millimeter waves are more susceptible to interference from nearby products than conventional microwaves, which presents challenges such as limited flexibility in antenna placement, and the need to increase the number of antennas to ensure a better communication environment than before due to the strong directivity of radio waves. The transparent antenna film being considered to address these challenges does not impair the aesthetics of the device, and therefore can be applied not only to mobile devices but also to windows and other glass surfaces of buildings and vehicles to receive 5G radio waves. [Prior art documents] [Patent Documents]

[0011] [Patent Document 1] Japanese Patent Publication No. 2006-352470 [Non-patent literature]

[0012] [Non-Patent Document 1] "Development Trends of High-Frequency Compatible Materials and Their Applications to 5G and Millimeter-Wave Radar," Technical Information Association, Chapter 3, Section 2, pp. 77-84, "Development Trends of High-Speed, High-Frequency Compatible FPCs and Reduction of Transmission Loss" [Overview of the project] [Problems that the invention aims to solve]

[0013] The cavity-containing laminated biaxially oriented polyester film described in Patent Document 1 above is formed by mixing different materials to create cavities. However, in such cases, it is difficult to control the size of the cavities or the dispersion state of the different materials. For example, if the dispersion state of the different materials is insufficient, the desired low dielectric properties may not be obtained. Furthermore, depending on the different materials used, the inherent transparency of the polyester film may not be achieved. In addition, light refraction at the cavity interfaces could reduce transparency.

[0014] In addition, as described above, since the transparent antenna film is attached to buildings such as window glass and glass of vehicle bodies, etc., it is desirable that it can be suitably used outdoors.

[0015] The problem to be solved by the present invention is to solve the above problems, provide a film laminate having excellent low dielectric characteristics and transparency, and being suitable for outdoor use.

Means for Solving the Problems

[0016] As a result of intensive studies to achieve the above problems, the present inventor has completed the present invention. One aspect of the present invention has the following gist in [1] to

[25] . [1] A film laminate comprising a polyester layer (X) and a resin layer (Y), having a light transmittance at a wavelength of 380 nm of 25% or less, wherein the polyester layer (X) contains polybutylene naphthalate and has a dielectric tangent at 28 GHz of less than 0.0050. [2] The film laminate according to [1] above, wherein the polyester layer (X) contains 5 to 70% by mass of the polybutylene naphthalate. [3] The film laminate according to [1] or [2] above, wherein the relative dielectric constant of the polyester layer (X) at 28 GHz is 3.5 or less. [4] The film laminate according to any one of [1] to [3] above, wherein the polyester layer (X) further contains a crystalline polyester. [5] The film laminate according to [4] above, wherein the crystalline polyester is polyethylene naphthalate. [6] The film laminate according to [5] above, wherein the polyethylene naphthalate has an acid component having a benzene skeleton as another copolymerization component other than 2,6-naphthalenedicarboxylic acid of 5 mol% or less in all dicarboxylic acid components. [7] The film laminate according to any one of [1] to [6] above, wherein the thickness of the polyester layer (X) is 9 to 300 μm. [8] A film laminate according to any one of [1] to [7] above, having an adhesive layer between the polyester layer (X) and the resin layer (Y). [9] The film laminate according to [8] above, wherein the dielectric constant of the adhesive layer is 3.9 or less.

[10] The film laminate according to [8] or [9] above, wherein the thickness of the adhesive layer is 1 to 200 μm.

[11] The film laminate according to any one of [1] to

[10] above, wherein a cured resin layer (CFB) is provided on at least one side of the polyester layer (X).

[12] The film laminate according to

[11] , comprising a metal layer on the cured resin layer (CFB).

[13] The film laminate according to

[12] above, wherein the metal layer is patterned.

[14] The film laminate according to

[12] or

[13] above, wherein the metal layer is made of copper or silver.

[15] A film laminate according to any one of

[11] to

[14] , wherein the polyester layer (X) has a cured resin layer (CFA) on the side opposite to the side on which the cured resin layer (CFB) is laminated.

[16] The film laminate according to

[15] , wherein at least one of the cured resin layer (CFA) and the cured resin layer (CFB) is formed from a resin composition containing a crosslinking agent in an amount of 70% by mass or more relative to the nonvolatile components.

[17] The film laminate according to any one of [1] to

[16] above, wherein the resin layer (Y) is a polyester layer.

[18] The film laminate according to any one of [1] to

[17] above, wherein the resin layer (Y) contains an ultraviolet absorber.

[19] A film laminate according to any of [1] to

[18] above, wherein the thickness of the resin layer (Y) is 9 to 300 μm.

[20] A film laminate according to any of [1] to

[19] above, wherein the hysteresis loss rate when a tensile cycle test is performed up to 5% tensile strain in both the longitudinal direction (MD) and the width direction (TD) is 55% or less in both directions.

[21] A film laminate according to any of [1] to

[20] above, wherein the haze is 4.0% or less.

[22] A film laminate according to any of [1] to

[21] above, having a total thickness of 19 to 800 μm.

[23] A film laminate according to any of the above [1] to

[22] , for use in high-speed communication circuits.

[24] A film laminate according to any of the above [1] to

[23] , for use as a transparent antenna.

[25] A film laminate according to any of the above [1] to

[24] , for use as an outdoor transparent antenna. [Effects of the Invention]

[0017] The film laminate of the present invention has excellent low dielectric properties and can therefore be suitably used for high-speed communication circuits. Furthermore, the film laminate of the present invention has excellent transparency, making it particularly suitable as a component for transparent antennas. Furthermore, the film laminate of the present invention also possesses excellent ultraviolet absorption performance, making it suitable for outdoor use. [Brief explanation of the drawing]

[0018] [Figure 1] This is a stress-strain curve profile. [Modes for carrying out the invention]

[0019] The present invention will be described in detail below. However, the present invention is not limited to the embodiments described below.

[0020] <<<Film Laminate>>> The film laminate of the present invention (hereinafter also referred to as "this film laminate") comprises a polyester layer (X) and a resin layer (Y). Furthermore, this film laminate has a light transmittance of 25% or less at a wavelength of 380 nm.

[0021] <<Polyester layer (X)>> This film laminate has a polyester layer (X) (hereinafter also referred to as "this polyester layer (X)"), which contains polybutylene naphthalate (hereinafter also referred to as "PBN") and has a dielectric loss tangent of less than 0.0050 at 28 GHz. In this invention, we believe that by making the polyester layer (X) constituting the film laminate low dielectric properties and efficiently reducing transmission loss, it is possible to provide a film laminate equipped with a highly versatile polyester layer (X) without impairing the excellent heat resistance, weather resistance, mechanical strength, and cost performance of the polyester film.

[0022] As described above, this polyester layer (X) contains PBN. The mechanism by which this polyester layer (X) possesses excellent low dielectric properties due to the inclusion of PBN is not entirely clear, but it is presumed that the stacking of aromatic rings suppresses the motion of dipoles. Generally, when a dielectric material is placed in an electric field, its dipoles orient themselves. Then, the dipoles rotate and reverse direction in accordance with the phase of the alternating electric field. This rotational and reversal motion of the dipoles generates friction, resulting in dielectric loss. Therefore, it is hypothesized that suppressing the motion of the dipole leads to excellent low dielectric properties.

[0023] More specifically, from the perspective of suppressing dipole motion through aromatic ring stacking, it is thought that stronger stacking leads to a greater suppression effect, and that having a naphthalene skeleton rather than a benzene skeleton allows for better low dielectric properties. Therefore, from the viewpoint of low dielectric properties, it is preferable for the aromatic ring to have a naphthalene skeleton rather than a benzene skeleton.

[0024] <Polybutylene naphthalate> The PBN constituting this polyester layer (X) is a polyester containing 2,6-naphthalenedicarboxylic acid as the dicarboxylic acid component (a-1) and 1,4-butanediol as the diol component (a-2), preferably mainly composed of 2,6-naphthalenedicarboxylic acid and 1,4-butanediol. Specifically, it is preferable that the dicarboxylic acid component (a-1) contains 50 mol% or more of 2,6-naphthalenedicarboxylic acid and the diol component (a-2) contains 50 mol% or more of 1,4-butanediol. In particular, the PBN used in the present invention more preferably contains 90 mol% or more of 2,6-naphthalenedicarboxylic acid as the dicarboxylic acid component (a-1) and 90 mol% or more of 1,4-butanediol as the diol component (a-2).

[0025] The dicarboxylic acid component (a-1) constituting the PBN includes 2,6-naphthalenedicarboxylic acid, and of the dicarboxylic acid component (a-1), it is more preferable that 2,6-naphthalenedicarboxylic acid is 92 mol% or more, even more preferable that it is 94 mol% or more, particularly preferable that it is 96 mol% or more, especially preferable that it is 98 mol% or more, and most preferably that all (100 mol%) of the dicarboxylic acid component (a-1) is 2,6-naphthalenedicarboxylic acid. By using 2,6-naphthalenedicarboxylic acid as the dicarboxylic acid component (a-1) at a concentration of 90 mol% or more, the glass transition temperature and crystallinity of PBN are improved, and consequently, the heat resistance and mechanical properties of the polyester layer (X) are enhanced. Furthermore, by using 2,6-naphthalenedicarboxylic acid as the dicarboxylic acid component (a-1) at a concentration of 90 mol% or more, the naphthalene skeleton content increases, thereby enhancing the effect of suppressing dipole motion through stacking. As a result, the low dielectric properties are improved.

[0026] The aforementioned PBN may be copolymerized with acid components other than 2,6-naphthalenedicarboxylic acid for the purpose of improving moldability and heat resistance. Specifically, examples include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,5-frandicarboxylic acid, 2,4-frandicarboxylic acid, 3,4-frandicarboxylic acid, benzophenone dicarboxylic acid, 4,4'-diphenyldicarboxylic acid, 3,3'-diphenyldicarboxylic acid, and 4,4'-diphenyl ether dicarboxylic acid; and aliphatic dicarboxylic acids such as cyclohexanedicarboxylic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid. These acid components can be used individually or in combination of two or more. Among these, isophthalic acid, 2,5-franglicarboxylic acid, 2,4-franglicarboxylic acid, and 3,4-franglicarboxylic acid are preferred from the viewpoint of moldability. Furthermore, from the viewpoint of low dielectric properties, acid components having a naphthalene skeleton with strong stacking properties are preferred among these, for example, acid components having a benzene skeleton such as terephthalic acid or isophthalic acid are preferably 5 mol% or less, more preferably 3 mol% or less, and even more preferably 1 mol% or less. Furthermore, it is preferable that the content of acid components other than 2,6-naphthalenedicarboxylic acid be 10 mol% or less of the total acid components including 2,6-naphthalenedicarboxylic acid.

[0027] The diol component (a-2) constituting the PBN contains 1,4-butanediol, and of the diol component (a-2), it is more preferable that 1,4-butanediol accounts for 92 mol% or more, even more preferably 94 mol% or more, particularly preferably 96 mol% or more, and especially preferably 98 mol% or more, with the most preferable being that all (100 mol%) of the diol component (a-2) is 1,4-butanediol. By setting the diol component (a-2) to 90 mol% or more of 1,4-butanediol, the compatibility with the mixed polyester is improved, further improving the glass transition temperature and crystallinity of the PBN, and consequently improving the heat resistance and mechanical properties of the polyester layer (X).

[0028] The aforementioned PBN may be copolymerized with diol components other than 1,4-butanediol for the purpose of improving moldability and heat resistance. Specifically, examples include 1,2-propanediol, 1,3-propanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, ethylene glycol, diethylene glycol, triethylene glycol, polyalkylene glycol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, hydroquinone, bisphenol, spiroglycol, 2,2,4,4-tetramethylcyclobutane-1,3-diol, isosorbide, and the like. These diol components can be used individually or in combination of two or more. Among these, ethylene glycol, diethylene glycol, 1,3-propanediol, 1,3-cyclohexanedimethanol, and 1,4-cyclohexanedimethanol are preferred from the viewpoint of moldability. Furthermore, it is preferable that the content of diol components other than 1,4-butanediol is 10 mol% or less of the total diol components including 1,4-butanediol.

[0029] The PBN content is preferably 5 to 70% by mass when the polyester layer (X) is considered to be 100% by mass. If the content is 5% by mass or more, the low dielectric properties of PBN are exhibited. If the content is 70% by mass or less, an appropriate amount of at least one polyester, as described later, can be secured, thereby improving the extrusion and stretchability during film formation while achieving a good balance of low dielectric properties, mechanical properties, and weather resistance.

[0030] In particular, from the viewpoint of achieving even better low dielectric properties, the PBN content is preferably 35 to 70% by mass, more preferably 40 to 65% by mass, even more preferably 45 to 62% by mass, and especially preferably 50 to 60% by mass.

[0031] <At least one type of polyester> The polyester layer (X) preferably contains two or more types of polyester, at least one of which is PBN. By including at least one type of polyester in addition to PBN in this polyester layer (X), the crystallization rate can be controlled, resulting in superior performance in extrusion molding and stretching processes, which are difficult with PBN alone.

[0032] The aforementioned at least one polyester is not particularly limited, and examples include those consisting of a dicarboxylic acid component and a diol component as described below. Examples of dicarboxylic acid components include terephthalic acid, isophthalic acid, orthophthalic acid, phthalic acid, 4,4'-diphenyldicarboxylic acid, 2,5-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 2-potassium sulfoterephthalic acid, 5-sodium sulfisoisophthalic acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, glutaric acid, succinic acid, trimellitic acid, trimesic acid, pyromellitic acid, trimellitic anhydride, phthalic anhydride, p-hydroxybenzoic acid, monopotassium salt of trimellitic acid, and their ester-forming derivatives.

[0033] Examples of diol components include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,6-hexanediol, 2-methyl-1,5-pentanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, p-xylylene glycol, bisphenol A-ethylene glycol adduct, diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polytetramethylene oxide glycol, dimethylolpropionic acid, glycerin, trimethylolpropane, sodium dimethylolethylsulfonate, potassium dimethylolpropionate, and the like. From the above compounds, one or more can be appropriately selected, and polyesters can be synthesized by conventional polycondensation reactions. The above-mentioned at least one polyester includes a polyester equivalent to the above-mentioned PBN, but in the present invention, the above-mentioned at least one polyester is different from the above-mentioned PBN.

[0034] The at least one polyester is preferably a crystalline polyester, and more preferably the crystalline polyester has a higher glass transition temperature than the PBN. By mixing the crystalline polyester with PBN, the crystallization rate of PBN can be controlled, thereby improving its extrusion and stretchability. Furthermore, because the crystalline polyester has a higher glass transition temperature than PBN, a resin composition with a higher glass transition temperature than PBN alone can be obtained, resulting in good heat resistance. Furthermore, by mixing in the aforementioned crystalline polyester, high crystallinity can be maintained, resulting in an excellent balance of low dielectric properties, mechanical properties, and weather resistance.

[0035] The crystalline polyester can preferably be polyethylene naphthalate or polycyclohexylene dimethylene terephthalate, and it is more preferable to include polyethylene naphthalate (hereinafter also referred to as "PEN") from the viewpoint of improving the balance between low dielectric properties, mechanical properties, and weather resistance. Furthermore, since PEN has a naphthalene skeleton in its structure, it has a significant effect of suppressing dipole movement due to the stacking of aromatic rings, which can further improve the low dielectric properties of the polyester layer (X).

[0036] (Polyethylene naphthalate) The PEN may be a homopolyester or a copolymerized polyester, but it is preferable that the acid component having a benzene skeleton as a copolymer component other than 2,6-naphthalenedicarboxylic acid is 5 mol% or less of the total dicarboxylic acid component. Alternatively, it may not contain any other copolymer components, and all of the dicarboxylic acid component (100 mol%) may be 2,6-naphthalenedicarboxylic acid. Among these, homopolyester is preferred from the viewpoint of maintaining high crystallinity. Furthermore, homopolyester is preferred from the viewpoint of increasing the naphthalene skeleton content to enhance the effect of suppressing dipole motion through stacking, thereby making it easier to improve low dielectric properties. Furthermore, homopolyester and copolymerized polyester may be blended, but if homopolyester and one type of copolymerized polyester are blended, it shall be considered as if two types of crystalline polyester were used.

[0037] When PEN consists of a homopolyester, it is obtained by polycondensation of 2,6-naphthalenedicarboxylic acid as the dicarboxylic acid component (b-1) and ethylene glycol as the diol component (b-2). Normally, when polyester is produced (polycondensed) using ethylene glycol as one of the raw materials, diethylene glycol is produced as a by-product from ethylene glycol. In this specification, this diethylene glycol is referred to as by-product diethylene glycol. The amount of diethylene glycol produced as a by-product from ethylene glycol varies depending on the type of polycondensation, but it is approximately 5 mol% or less of the ethylene glycol. In the present invention, the by-product diethylene glycol of 5 mol% or less is also included in ethylene glycol. On the other hand, depending on the content of diethylene glycol, more specifically, if the content of diethylene glycol exceeds 5 mol%, then the diethylene glycol is distinguished from ethylene glycol.

[0038] On the other hand, when PEN consists of copolymerized polyester, 2,6-naphthalenedicarboxylic acid is an essential component as the dicarboxylic acid component (b-1), and other copolymerization components may be added as needed. Other copolymer components include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,5-frandicarboxylic acid, 2,4-frandicarboxylic acid, 3,4-frandicarboxylic acid, benzophenone dicarboxylic acid, 4,4'-diphenyldicarboxylic acid, 3,3'-diphenyldicarboxylic acid, and 4,4'-diphenyletherdicarboxylic acid; aliphatic dicarboxylic acids such as cyclohexanedicarboxylic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, and dimer acid; and oxycarboxylic acids such as p-oxybenzoic acid. Among these, isophthalic acid, 2,5-frandicarboxylic acid, 2,4-frandicarboxylic acid, and 3,4-frandicarboxylic acid are preferred from the viewpoint of moldability. Furthermore, from the viewpoint of low dielectric properties, copolymer components having a naphthalene skeleton with strong stacking properties are preferred. These copolymer components can be used individually or in combination of two or more.

[0039] Ethylene glycol is an essential component of the diol component (b-2), and other copolymer components may be used as needed, including 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, diethylene glycol, triethylene glycol, propylene glycol, polyalkylene glycol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, hydroquinone, spiroglycol, 2,2,4,4-tetramethylcyclobutane-1,3-diol, isosorbide, 1,4-cyclohexanedimethanol, polytetramethylene ether glycol, dimer diol, and bisphenols (bisphenol compounds such as bisphenol A, bisphenol F, or bisphenol S, or their derivatives, or their ethylene oxide adducts). Of these, 1,4-cyclohexanedimethanol, polytetramethylene ether glycol, dimer diol, and bisphenols are preferred. In particular, bisphenols are preferred from the viewpoint of maintaining strength. Furthermore, it is preferable to use bisphenol A-ethylene oxide adducts as the bisphenol compounds. These copolymer components can be used individually or in combination of two or more.

[0040] The copolymer polyester constituting PEN preferably contains 2,6-naphthalenedicarboxylic acid as the dicarboxylic acid component (b-1), and ethylene glycol and a bisphenol A-ethylene oxide adduct as the diol component (b-2).

[0041] The copolymerized polyester contains, preferably, 0 mol% to 10 mol%, more preferably 0 mol% to 8 mol%, even more preferably 0 mol% to 6 mol%, particularly preferably 0 mol% to 4 mol%, and especially preferably 0 mol% to 2 mol% of other copolymerized components in the dicarboxylic acid component. By keeping the content of other copolymer components in the dicarboxylic acid component within the above numerical range, the glass transition temperature and crystallinity of the copolymerized polyester are improved, and consequently, the heat resistance and mechanical properties of the polyester layer (X) are improved. A particularly preferred configuration is, as described above, the use of a copolymer component having a naphthalene skeleton with strong stacking properties as another copolymer component. For example, the acid component having a benzene skeleton, such as terephthalic acid or isophthalic acid, is preferably 5 mol% or less, more preferably 3 mol% or less, and even more preferably 1 mol% or less.

[0042] The copolymerized polyester preferably contains 90 mol% or more, more preferably 92 mol% or more, even more preferably 94 mol% or more, particularly preferably 96 mol% or more, and especially preferably 98 mol% or more of 2,6-naphthalenedicarboxylic acid in the dicarboxylic acid component, and all (100 mol%) of the dicarboxylic acid component may be 2,6-naphthalenedicarboxylic acid. By keeping the content of 2,6-naphthalenedicarboxylic acid in the dicarboxylic acid component within the above numerical range, the glass transition temperature and crystallinity of the copolymerized polyester are improved, and consequently, the heat resistance and mechanical properties of the polyester layer (X) are improved. Furthermore, by keeping the content of 2,6-naphthalenedicarboxylic acid in the dicarboxylic acid component within the above numerical range, the naphthalene skeleton content increases, enhancing the effect of suppressing dipole motion due to stacking. As a result, the low dielectric properties are improved.

[0043] The copolymerized polyester contains, preferably, 4 mol% to 70 mol%, more preferably 4.2 mol% to 60 mol%, even more preferably 4.4 mol% to 50 mol%, particularly preferably 4.6 mol% to 40 mol%, and especially preferably 4.8 mol% to 30 mol% of other copolymerized components in the diol component. By keeping the content of other copolymer components in the diol component within the above numerical range, the glass transition temperature of the copolymerized polyester is improved, and consequently, the heat resistance of the polyester layer (X) is enhanced. Furthermore, because the crystallinity can be controlled, the crystallization rate can be slowed, improving the extrusion and stretchability of the film. In addition, if the content is 70 mol% or less, the melting point will not become too high. Therefore, there is no need to set a high molding temperature, and there is no concern about thermal decomposition.

[0044] The copolymerized polyester contains ethylene glycol in the diol component, preferably 30 mol% to 96 mol%, more preferably 40 mol% to 95.8 mol%, even more preferably 50 mol% to 95.6 mol%, particularly preferably 60 mol% to 95.4 mol%, and especially preferably 70 mol% to 95.2 mol%. By keeping the ethylene glycol content in the diol component within the above numerical range, the crystallinity of the copolymerized polyester is maintained, and consequently, the heat resistance of the polyester layer (X) is improved.

[0045] The content of the crystalline polyester such as PEN is preferably 50 parts by mass or more and 1000 parts by mass or less per 100 parts by mass of PBN, more preferably 55 parts by mass or more and 980 parts by mass or less, even more preferably 60 parts by mass or more and 950 parts by mass or less, and particularly preferably 65 parts by mass or more and 900 parts by mass or less, from the viewpoint of balancing low dielectric properties, mechanical properties, weather resistance and moldability. If the content of the crystalline polyester in the polyester layer (X) is 50 parts by mass or more, the crystallization rate can be slowed down, thereby improving the extrusion moldability and stretchability during film formation. Furthermore, if the content is 50 parts by mass or more, the glass transition temperature can be improved, thereby improving the heat resistance of the polyester layer (X). On the other hand, if the content of the crystalline polyester is 1,000 parts by mass or less, the balance of the low dielectric properties, mechanical properties, and weather resistance of PBN is not significantly impaired, and the resulting polyester layer (X) has a good balance of dielectric properties, mechanical properties, and weather resistance.

[0046] In particular, from the viewpoint of achieving even better low dielectric properties, the content of the crystalline polyester such as PEN is preferably 50 parts by mass or more and 185 parts by mass or less per 100 parts by mass of PBN, more preferably 55 parts by mass or more and 150 parts by mass or less, even more preferably 60 parts by mass or more and 125 parts by mass or less, and especially preferably 65 parts by mass or more and 110 parts by mass or less.

[0047] For example, when PEN is used as the crystalline polyester, both PBN and PEN are polyesters having a naphthalene skeleton. However, as the amount of PBN increases, the dielectric loss tangent decreases, and transmission loss can be efficiently reduced, resulting in superior low dielectric properties. This is thought to be related to density. The dielectric constant is a parameter that indicates the degree of polarization. As the number of molecules per unit volume increases, the sum of dipoles increases, so it is thought that the dielectric constant increases with higher density. On the other hand, the dielectric loss tangent is a parameter that indicates the degree of energy loss caused by the vibration of dipoles when an AC voltage is applied. From this, it can be inferred that when the density is high, the vibrations of the dipoles cancel each other out, resulting in a smaller energy loss, i.e., a smaller dielectric loss tangent. In other words, when the polyester layer (X) contains the aforementioned PBN and PEN, the density increases as the PBN content increases, so it is thought that the dielectric loss tangent is effectively reduced.

[0048] <Other resins> The polyester layer (X) may contain other resins other than the PBN and at least one polyester, as long as it does not impair the effects of the present invention. Other resins include polystyrene resins, polyvinyl chloride resins, polyvinylidene chloride resins, chlorinated polyethylene resins, polycarbonate resins, polyamide resins, polyacetal resins, acrylic resins, ethylene vinyl acetate copolymers, polymethylpentene resins, polyvinyl alcohol resins, cyclic olefin resins, polylactic acid resins, polybutylene succinate resins, polyacrylonitrile resins, polyethylene oxide resins, cellulose resins, polyimide resins, polyurethane resins, polyphenylene sulfide resins, polyphenylene ether resins, polyvinyl acetal resins, polybutadiene resins, polybutene resins, polyamide-imide resins, polyamide-bismaleimide resins, polyetherimide resins, polyetherether ketone resins, polyethersulfone resins, polyketone resins, polysulfone resins, aramid resins, and fluorine resins.

[0049] <Other> There are no particular restrictions on the polymerization catalyst for polyester, and conventionally known compounds can be used, such as titanium compounds, germanium compounds, antimony compounds, manganese compounds, aluminum compounds, magnesium compounds, and calcium compounds.

[0050] To suppress the precipitation of oligomer components, the film may be manufactured using polyester with a low oligomer content as the raw material. Various known methods can be used to manufacture polyester with a low oligomer content, such as a method of solid-phase polymerization after polyester production. Alternatively, polyester may be obtained by esterification or transesterification, followed by further increasing the reaction temperature and melt polycondensation under reduced pressure.

[0051] The polyester layer (X) may be an unstretched film (sheet) or a stretched film. In particular, it is preferably a film that is stretched in at least one direction, specifically a uniaxial or biaxially oriented film, and more preferably a biaxially oriented film from the viewpoint of balance of mechanical properties, flatness, and thinness.

[0052] The intrinsic viscosity of the polyester is not particularly limited, but from the viewpoint of film-forming properties and productivity, it is preferably 0.45 to 1.0 dL / g, and more preferably 0.5 to 0.9 dL / g.

[0053] The polyester layer (X) may also contain particles, primarily for the purpose of providing slipperiness and preventing damage during each process. The types of particles mentioned above are not particularly limited as long as they can impart slipperiness. Examples include inorganic particles such as silica, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, calcium phosphate, magnesium phosphate, kaolin, aluminum oxide, and titanium oxide; and organic particles such as acrylic resin, styrene resin, urea resin, phenolic resin, epoxy resin, and benzoguanamine resin. Furthermore, during the polyester manufacturing process, precipitated particles obtained by precipitating and finely dispersing a portion of metal compounds such as catalysts can also be used.

[0054] There are no particular restrictions on the shape of the particles used; spherical, lumpy, rod-shaped, flattened, etc., may be used. Furthermore, there are no particular restrictions on their hardness, specific gravity, color, etc. These particles may be used individually or in combination of two or more types as needed.

[0055] The average particle size of the particles used is not particularly limited, but is usually 5 μm or less, preferably in the range of 0.01 to 3 μm. An average particle size of 5 μm or less is preferable because it ensures the transparency of the film and prevents the surface roughness of the film from becoming too rough. If the average particle size is 0.01 μm or more, effects such as providing slipperiness and preventing scratch formation can be ensured. The average particle size can be determined by measuring the diameters of 10 or more particles using a scanning electron microscope (SEM) and taking the average value. In the case of non-spherical particles, the average of the longest and shortest diameters can be used as the diameter of each individual particle.

[0056] The particle content in the layer containing the above-mentioned particles is not particularly limited, but is usually less than 5% by mass, preferably in the range of 0.0003 to 3% by mass. If no particles are present, or if the particle content is low, a film with excellent transparency is obtained. On the other hand, if particles are included within the above range, a film with sufficient slipperiness is obtained. Even if particles are present, sufficient transparency of the film can be ensured if the particle content is less than 5% by mass. When incorporating particles into the polyester layer (X), it is preferable to provide, for example, a surface layer and an intermediate layer, and to incorporate particles into at least one of the surface layers. Furthermore, if the polyester layer (X) is a single layer, the layer containing particles is the entire polyester layer (X).

[0057] The method for adding particles to the polyester layer (X) is not particularly limited, and conventionally known methods can be employed. For example, the particles can be added at any stage in the production of the polyester raw material, but it is preferable to add them after the esterification or transesterification reaction is completed.

[0058] In addition to the particles mentioned above, conventionally known antioxidants, ultraviolet absorbers, antistatic agents, heat stabilizers, lubricants, dyes, pigments, etc., may be added to the polyester layer (X) as needed.

[0059] The thickness of the polyester layer (X) is preferably 9 to 300 μm, more preferably 30 to 250 μm, and even more preferably 50 to 200 μm. If the total thickness of the polyester layer (X) is 9 μm or more, the film strength is maintained within a practical range. On the other hand, if the total thickness is 300 μm or less, it can be easily incorporated into mobile devices and is suitable for use in high-speed communication circuits. In particular, when used for transparent antennas, the thickness of the polyester layer (X) is preferably 40 to 150 μm. The lower limit of this thickness is more preferably 50 μm, even more preferably 75 μm, and particularly preferably 100 μm. The upper limit of this thickness is preferably 140 μm, and even more preferably 130 μm. The total thickness of the polyester layer (X) was determined by cutting a roughly square sample piece with sides of 40 mm from the polyester layer (X), measuring the thickness at five arbitrary points on the film surface using a dial gauge with a scale of 1 / 1000 mm, and calculating the average value.

[0060] <Method for manufacturing the polyester layer (X)> The method for manufacturing the polyester layer (X) will be described below. However, the following description is just one example of a method for manufacturing the polyester layer (X) and is not limited to that method.

[0061] For example, when manufacturing a biaxially oriented film as a polyester layer (X), the method described above, in which the polyester raw material is extruded from a die as a molten sheet using an extruder and cooled and solidified in a rotating cooling drum (casting drum) to obtain an unstretched sheet, is preferred. In this case, in order to improve the flatness of the sheet, it is preferable to increase the adhesion between the sheet and the rotating cooling drum, and electrostatic application adhesion and / or liquid coating adhesion methods are preferably employed. An unstretched sheet is obtained in this way. The polyester raw material should be supplied to the extruder after being appropriately dried, such as in the form of pellets. Particles, UV absorbers, and other additives may also be blended into the pellets as appropriate.

[0062] Next, the obtained unstretched sheet is stretched in two axial directions. First, the unstretched sheet is stretched in one direction using a roll or tenter type stretcher. The stretching temperature is usually 70 to 120°C, preferably 80 to 110°C, and the stretching ratio is usually 2.5 to 7 times, preferably 3.0 to 6 times. Next, the material is stretched in a direction perpendicular to the first stretching direction. In this case, the stretching temperature is usually 70 to 170°C, and the stretching ratio is usually 3.0 to 7 times, preferably 3.5 to 6 times.

[0063] Then, the film is heat-treated at a temperature of 180-270°C under tension or under relaxation of 30% or less to obtain a biaxially oriented film. In the above stretching, a method of performing unidirectional stretching in two or more stages can also be employed. In that case, it is preferable to perform the stretching so that the final stretching ratios in both directions are within the above ranges.

[0064] Furthermore, a simultaneous biaxial stretching method can also be used to manufacture the polyester layer (X). The simultaneous biaxial stretching method is a method of simultaneously stretching and oriented the aforementioned unstretched sheet in the longitudinal and width directions under temperature control, usually at 70 to 120°C, preferably 80 to 110°C, with a stretching ratio of 4 to 50 times, preferably 7 to 35 times, and more preferably 10 to 25 times in terms of area. Then, heat treatment is carried out at a temperature of 170-250°C under tension or under relaxation of 30% or less to obtain a stretched and oriented film. For the simultaneous biaxial stretching apparatus employing the above stretching method, conventional known stretching methods such as screw type, pantograph type, and linear drive type can be used.

[0065] The longitudinal direction (MD) of the film refers to the direction in which the film progresses during the film manufacturing process, i.e., the winding direction of the film roll. The width direction (TD) refers to the direction parallel to the film surface and perpendicular to the longitudinal direction, that is, the direction parallel to the central axis of the roll when the film is in a roll form.

[0066] <Physical properties of the polyester layer (X)> The dielectric loss tangent of this polyester layer (X) at 28 GHz is less than 0.0050. If the dielectric loss tangent is 0.0050 or higher, a good reduction in transmission loss cannot be obtained. From this viewpoint, the dielectric loss tangent of this polyester layer (X) is preferably 0.0045 or less, more preferably 0.0040 or less, even more preferably 0.0035 or less, and particularly preferably 0.0030 or less. The lower limit is not particularly limited, but is 0.0010 or higher. If the dielectric loss tangent of the polyester layer (X) is within this range, the low dielectric properties of the polyester layer (X) will be good, and it can be suitably used for high-speed communication circuits. Furthermore, the dielectric loss tangent can be adjusted by the type and content of polyester in the polyester layer (X), as well as the film formation and stretching conditions of the polyester layer (X).

[0067] The relative permittivity of the polyester layer (X) at 28 GHz is preferably 3.5 or less, more preferably 3.4 or less, even more preferably 3.3 or less, and particularly preferably 3.2 or less. The lower limit is not particularly limited, but is 2.0 or more. If the dielectric constant of the polyester layer (X) is within this range, the low dielectric properties of the polyester layer (X) will be good, and it can be suitably used for high-speed communication circuits. The dielectric constant can be adjusted by the type and content of polyester in the polyester layer (X), as well as the film formation and stretching conditions of the polyester layer (X).

[0068] The dielectric loss tangent and relative permittivity of the polyester layer (X) are values ​​measured by the method described in the examples.

[0069] When the polyester layer (X) is subjected to tensile cycle testing up to 5% tensile strain in both the longitudinal direction (MD) and the width direction (TD), the hysteresis loss rate is preferably 60% or less in both directions. The lower limit is not particularly restricted, but is 0.1% or more. The smaller the hysteresis loss rate, the greater the film's resilience and the easier it is to return to its original state, meaning it has excellent flexural resistance. If the hysteresis loss rate of this polyester layer (X) is 60% or less, the film's resilience increases, resulting in good flexural resistance. When this polyester layer (X) also possesses excellent flexural resistance, it can be suitably used for flexible displays equipped with high-speed communication circuits, and the like. From this viewpoint, the hysteresis loss rate of the polyester layer (X) is more preferably 58% or less, even more preferably 56% or less, and particularly preferably 54% or less, in both the longitudinal direction (MD) and the width direction (TD). The hysteresis loss rate can be adjusted by the type and content of polyester in the polyester layer (X), as well as the film formation and stretching conditions of the polyester layer (X).

[0070] The haze content of the polyester layer (X) is preferably 4.0% or less, more preferably 3.0% or less, even more preferably 2.5% or less, particularly preferably 2.0% or less, especially preferably 1.5% or less, and most preferably 1.0% or less. The lower limit is not particularly limited, but is 0.1% or more. If the haze is present within the range, the polyester layer (X) can be said to have good transparency, and the film laminate having the polyester layer (X) can be suitably used as a component for transparent antennas. The haze value was measured using the method described in the examples.

[0071] The heat shrinkage rate of the polyester layer (X) after heat treatment at 150°C for 30 minutes is preferably -5 to 5% in both the longitudinal direction (MD) and the width direction (TD), more preferably -3 to 3%, and even more preferably -2 to 2%. Within the range of thermal shrinkage, the film possesses sufficient flatness and heat resistance. The thermal shrinkage rate was measured by the method described in the examples, where a positive value represents the shrinkage rate and a negative value represents the expansion rate.

[0072] <<Resin layer (Y)>> This film laminate has a resin layer (Y). The resin layer (Y) (hereinafter also referred to as "this resin layer (Y)") can be a resin film formed by creating a film of polymers such as polyethylene, polypropylene, cycloolefin polymer (COP), polyester, polystyrene, acrylic resin, polycarbonate, polyurethane, triacetylcellulose (TAC), polyvinyl chloride, polyethersulfone, polyamide, polyimide, or polyamideimide. Alternatively, if it is possible to form a film, it may be a mixture of these materials (polymer blend) or a composite of constituent units (polymer).

[0073] Among the films exemplified above, polyester film is particularly preferred because it has excellent physical properties such as heat resistance, flatness, optical properties, and strength. The polyester film described above may be a single layer or a multilayer film (i.e., a laminated film) having two or more layers with different properties. The polyester film is a film whose main component resin is polyester. Furthermore, the polyester film may be an unoriented film (sheet) or an oriented film. In particular, an oriented film stretched in either a uniaxial or biaxial direction is preferred. Among these, a biaxially oriented film is more preferred from the viewpoint of balance of mechanical properties and planarness. Therefore, a biaxially oriented polyester film is even more preferred as the resin layer (Y).

[0074] <UV absorber> The resin layer (Y) preferably contains an ultraviolet absorber. The inclusion of an ultraviolet absorber results in a film laminate with excellent ultraviolet absorption performance, making it suitable for outdoor use. Furthermore, if the film is made of a multilayer polyester film, it is preferable that at least one polyester layer contains an ultraviolet absorber. From the viewpoint of preventing the ultraviolet absorber from bleeding out, it is even more preferable that the ultraviolet absorber be contained in the intermediate layer (the YB layer in the case of a YA / YB / YC configuration, or the YA layer in the case of a YB / YA / YB configuration). UV absorbers include organic and inorganic UV absorbers, but organic UV absorbers are preferred from the viewpoint of transparency. Organic UV absorbers are not particularly limited, but examples include benzophenone-based UV absorbers, benzotriazole-based UV absorbers, triazine-based UV absorbers, benzoxazine-based UV absorbers, salicylic acid-based UV absorbers, and cyanoacrylate-based UV absorbers. These UV absorbers can be used individually or in combination of two or more.

[0075] Examples of benzophenone-based UV absorbers include 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2-hydroxy-4-bendyloxybenzophenone, 2-hydroxy-4-methoxy-5-sulfoxybenzophenone, 2-hydroxy-4-methoxy-5-sulfoxytrihydridebenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2,2',4,4'-tetrahydroxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxy-5-sodium sulfoxybenzophenone, bis(5-benzoyl-4-hydroxy-2-methoxyphenyl)methane, 2-hydroxy-4-n-dodecyloxybenzophenone, and 2-hydroxy-4-methoxy-2'-carboxybenzophenone.

[0076] Examples of benzotriazole-based UV absorbers include 2-(2-hydroxy-5-methylphenyl)benzotriazole, 2-(2-hydroxy-5-tert-octylphenyl)benzotriazole, 2-(2-hydroxy-3,5-dicumylphenyl)phenylbenzotriazole, 2-(2-hydroxy-3-tert-butyl-5-methylphenyl)-5-chlorobenzotriazole, 2,2'-methylenebis[4-(1,1,3,3-tetramethylbutyl)-6-(2H-benzotriazole-2-yl)phenol], 2-(2-hydroxy-3,5-di-tert-butylphenyl)benzotriazole, and 2-(2-H Examples include droxy-3,5-di-tert-butylphenyl)-5-chlorobenzotriazole, 2-(2-hydroxy-3,5-di-tert-amylphenyl)benzotriazole, 2-(2-hydroxy-5-tert-octylphenyl)benzotriazole, 2-(2-hydroxy-5-tert-butylphenyl)benzotriazole, 2-(2-hydroxy-4-octoxyphenyl)benzotriazole, 2,2'-methylenebis(4-cumyl-6-benzotriazolephenyl), and 2-[2-hydroxy-3-(3,4,5,6-tetrahydrophthalimidomethyl)-5-methylphenyl]benzotriazole.

[0077] Examples of triazine-based UV absorbers include 2-(2-hydroxy-4-methoxyphenyl)-4,6-diphenyl-1,3,5-triazine, 2-(2-hydroxy-4-ethoxyphenyl)-4,6-diphenyl-1,3,5-triazine, 2-(2-hydroxy-4-propoxyphenyl)-4,6-diphenyl-1,3,5-triazine, 2-(2-hydroxy-4-butoxyphenyl)-4,6-diphenyl-1,3,5-triazine, and 2-(2-hydroxy-4-hexyloxyphenyl)-4,6-diphenyl-1,3,5-triazine. Azine, 2-(2-hydroxy-4-octyloxyphenyl)-4,6-diphenyl-1,3,5-triazine, 2-(2-hydroxy-4-dodecyloxyphenyl)-4,6-diphenyl-1,3,5-triazine, 2-(2-hydroxy-4-benzyloxyphenyl)-4,6-diphenyl-1,3,5-triazine, 2,4-bis(2-hydroxy-4-butoxyphenyl)-6-(2,4-dibutoxyphenyl)-1,3-5-triazine, 2,4,6-tris(2-hydroxy-4-hexyloxy-3-methylphenyl)-1, 3,5-triazine, 2-(2-hydroxy-4-[1-octyloxycarbonylethoxy]phenyl)-4,6-bis(4-phenylphenyl)-1,3,5-triazine, 2-[4-[(2-hydroxy-3-dodecyloxypropyl)oxy]-2-hydroxyphenyl]-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine, 2-[4-[(2-hydroxy-3-tridecyloxypropyl)oxy]-2-hydroxyphenyl]-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine, 2-[4- [(2-hydroxy-3-(2'-ethyl)hexyl)oxy]-2-hydroxyphenyl]-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine, 2,4-bis(2,4-dimethylphenyl)-6-[2-hydroxy-4-(3-octyloxy-2-hydroxypropyloxy)-5-α-cumylphenyl]-s-triazine, 2,4-bis(2,4-dimethylphenyl)-6-[2-hydroxy-4-(3-nonyloxy-2-hydroxypropyloxy)-5-α-cumylphenyl]-s-triazine 2,4-bis(2,Examples include 4-dimethylphenyl)-6-[2-hydroxy-4-(3-decyloxy-2-hydroxypropyloxy)-5-α-cumylphenyl]-s-triazine and 2-(2-hydroxy-4-acryloyloxyethoxyphenyl)-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine.

[0078] Examples of benzoxazine-based UV absorbers include 2,2'-(p-phenylene)di-3,1-benzoxazin-4-one, 2,2'-(1,4-phenylene)bis(4H-3,1-benzoxazinon-4-one), 2-methyl-3,1-benzoxazin-4-one, 2-butyl-3,1-benzoxazin-4-one, and 2-phenyl-3,1-benzoxazin-4-one. Examples of salicylic acid-based UV absorbers include phenyl salicylate, p-tert-butylphenyl salicylate, and p-octylphenyl salicylate. Examples of cyanoacrylate-based ultraviolet absorbers include 2-ethylhexyl-2-cyano-3,3'-diphenyl acrylate and ethyl-2-cyano-3,3'-diphenyl acrylate.

[0079] Among these, benzophenone-based UV absorbers, benzotriazole-based UV absorbers, triazine-based UV absorbers, and benzoxazine-based UV absorbers are preferred from the viewpoint of efficiently exhibiting excellent UV absorption performance. Of these, benzoxazine-based UV absorbers are more preferred from the viewpoint of covering a wide UV absorption range and producing less coloration.

[0080] From the viewpoint of improving light resistance reliability, the lower limit of the UV absorber content is preferably 0.1 parts by mass or more, and more preferably 0.5 parts by mass or more, per 100 parts by mass of the resin layer (Y) containing the UV absorber. On the other hand, the upper limit of the UV absorber content is preferably 15 parts by mass or less, more preferably 12 parts by mass or less, even more preferably 10 parts by mass or less, particularly preferably 8 parts by mass or less, and most preferably 7 parts by mass or less, per 100 parts by mass of the resin layer (Y) containing the UV absorber.

[0081] <Other> The thickness of the resin layer (Y) is preferably 9 to 300 μm, more preferably 12 to 250 μm, and even more preferably 25 to 125 μm. If the thickness of the resin layer (Y) is greater than or equal to the lower limit mentioned above, it can exhibit excellent ultraviolet absorption performance when an ultraviolet absorber is included. On the other hand, if the thickness of the resin layer (Y) is less than or equal to the upper limit mentioned above, it can be suitably used for high-speed communication circuits, especially for transparent antennas.

[0082] <<Adhesive layer>> The film laminate preferably has an adhesive layer between the polyester layer (X) and the resin layer (Y). The adhesive composition constituting the adhesive layer (hereinafter also referred to as "the adhesive composition") preferably contains a (meth)acrylic polymer (A), a polyfunctional (meth)acrylate (B), and a radical polymerization initiator (C).

[0083] <(meth)acrylic polymer (A)> Examples of the above-mentioned (meth)acrylic polymers include alkyl (meth)acrylate homopolymers as well as copolymers obtained by polymerizing alkyl (meth)acrylate with monomer components copolymerizable with alkyl (meth)acrylate. Examples of copolymers include those obtained by copolymerizing alkyl (meth)acrylate (a1), which has 4 to 18 carbon atoms in its side chain, as the main component, with monomer components copolymerizable with alkyl (meth)acrylate. The above-mentioned main components refer to components that have a significant influence on the properties of the (meth)acrylic polymer (A), and the content of these components is usually 30% by mass or more, preferably 35% by mass or more, of the total (meth)acrylic polymer (A). Furthermore, the above-mentioned (meth)acrylic polymer (A) may contain two or more (meth)acrylic polymers with different glass transition temperatures, from the viewpoint of ensuring processability, adhesiveness, stress relaxation properties, heat resistance reliability, and moisture heat haze resistance.

[0084] Examples of the above side chain alkyl(meth)acrylates (a1) with 4 to 18 carbon atoms include linear alkyl(meth)acrylates such as n-butyl(meth)acrylate, pentyl(meth)acrylate, hexyl(meth)acrylate, heptyl(meth)acrylate, n-octyl(meth)acrylate, nonyl(meth)acrylate, decyl(meth)acrylate, undecyl(meth)acrylate, lauryl(meth)acrylate, tridecyl(meth)acrylate, tetradecyl(meth)acrylate, cetyl(meth)acrylate, stearyl(meth)acrylate, isobutyl(meth)acrylate, sec-butyl(meth)acrylate, t-butyl(meth)acrylate, isope Examples include branched alkyl (meth)acrylates such as phthal(meth)acrylate, neopentyl(meth)acrylate, 2-ethylhexyl(meth)acrylate, isooctyl(meth)acrylate, isononyl(meth)acrylate, isodecyl(meth)acrylate, and isostearyl(meth)acrylate; alicyclic (meth)acrylates such as cyclohexyl(meth)acrylate, t-butylcyclohexyl(meth)acrylate, 3,5,5-trimethylcyclohexane(meth)acrylate, dicyclopentanyl(meth)acrylate, dicyclopentenyl(meth)acrylate, dicyclopentenyloxyethyl(meth)acrylate, and isobornyl(meth)acrylate. These may be used individually or in combination of two or more.

[0085] The content of the alkyl (meth)acrylate (a1) is preferably 3% by mass or more, more preferably 5% by mass or more, even more preferably 8% by mass or more, particularly preferably 10% by mass or more, and most preferably 12% by mass or more, relative to the total components of the (meth)acrylic polymer (A), from the viewpoint of improving stress relaxation and heat resistance reliability when used as an adhesive sheet or adhesive layer. Furthermore, from the viewpoint of suppressing a decrease in adhesive strength, the content of the alkyl (meth)acrylate (a1) is preferably 80% by mass or less, more preferably 75% by mass or less, even more preferably 70% by mass or less, and particularly preferably 65% ​​by mass or less, relative to the total components of the (meth)acrylic polymer (A).

[0086] Examples of monomer components copolymerizable with the alkyl (meth)acrylate (a1) having 4 to 18 carbon atoms in its side chain include hydroxyl group-containing (meth)acrylate monomers (a2), (meth)acrylate monomers or vinyl ester monomers having 1 to 3 carbon atoms in their side chain (a3), functional group-containing ethylenically unsaturated monomers (a4), and other copolymerizable monomers (a5).

[0087] Examples of the hydroxyl group-containing monomers (a2) mentioned above include hydroxy(meth)acrylates such as 2-hydroxyethyl(meth)acrylate, 4-hydroxybutyl(meth)acrylate, 5-hydroxypentyl(meth)acrylate, 6-hydroxyhexyl(meth)acrylate, and 8-hydroxyoctyl(meth)acrylate; caprolactone-modified monomers such as caprolactone-modified 2-hydroxyethyl(meth)acrylate; oxyalkylene-modified monomers such as diethylene glycol(meth)acrylate and polyethylene glycol(meth)acrylate; primary hydroxyl group-containing monomers such as 2-acryloyloxyethyl-2-hydroxyethylphthalic acid; secondary hydroxyl group-containing monomers such as 2-hydroxypropyl(meth)acrylate, 2-hydroxybutyl(meth)acrylate, and 3-chloro2-hydroxypropyl(meth)acrylate; and tertiary hydroxyl group-containing monomers such as 2,2-dimethyl2-hydroxyethyl(meth)acrylate. These can be used individually or in combination of two or more.

[0088] Among the above hydroxyl group-containing monomers (a2), primary hydroxyl group-containing monomers are preferred, particularly 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and especially 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate, due to their excellent balance of moisture resistance and heat resistance.

[0089] From the viewpoint of improving moisture and heat resistance, the lower limit of the content of the above-mentioned hydroxyl group-containing monomer (a2) is usually 3% by mass or more, preferably 5% by mass or more, more preferably 8% by mass or more, even more preferably 10% by mass or more, and particularly preferably 12% by mass or more, relative to the total components of the (meth)acrylic polymer (A). On the other hand, the upper limit of the content of the hydroxyl group-containing monomer (a2) is usually 60% by mass or less, preferably 45% by mass or less, more preferably 35% by mass or less, even more preferably 30% by mass or less, and particularly preferably 25% by mass or less, from the viewpoint of suppressing the self-crosslinking reaction of the adhesive composition and improving processability and heat resistance reliability.

[0090] Examples of (meth)acrylate monomers or vinyl ester monomers (a3) ​​having 1 to 3 carbon atoms in the side chain include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, vinyl propionate, vinyl acetate, etc. These monomers (a3) ​​may be used individually or in combination of two or more. Among the components of (a3) ​​above, it is preferable to use methyl (meth)acrylate or ethyl (meth)acrylate from the viewpoint of improving cohesive force when used as an adhesive.

[0091] When the above-mentioned component (a3) ​​is included, the lower limit of its content is preferably 5% by mass or more, more preferably 7% by mass or more, and even more preferably 10% by mass or more, relative to the total components of the (meth)acrylic polymer (A), from the viewpoint of improving cohesive strength when used as an adhesive. Furthermore, when the above-mentioned component (a3) ​​is included, the upper limit of its content is preferably 40% by mass or less, more preferably 30% by mass or less, and even more preferably 20% by mass or less, relative to the total components of the (meth)acrylic polymer (A), from the viewpoint of improving processability.

[0092] Examples of functional group-containing ethylenically unsaturated monomers (a4) include carboxyl group-containing monomers, monomers containing a nitrogen atom-containing functional group, acetoacetyl group-containing monomers, isocyanate group-containing monomers, and glycidyl group-containing monomers. Among these, monomers containing a functional group having a nitrogen atom are preferred in terms of imparting cohesive force and crosslinking-promoting effect, monomers containing an amino group or an amide group are more preferred, and monomers containing an amino group are even more preferred. Examples of monomers containing a carboxyl group include (meth)acrylic acid, carboxyethyl (meth)acrylate, 2-(meth)acryloyloxyethyl hexahydrophthalic acid, 2-(meth)acryloyloxypropyl hexahydrophthalic acid, 2-(meth)acryloyloxyethyl phthalic acid, 2-(meth)acryloyloxypropyl phthalic acid, 2-(meth)acryloyloxyethyl maleic acid, 2-(meth)acryloyloxypropyl maleic acid, 2-(meth)acryloyloxyethyl succinic acid, 2-(meth)acryloyloxypropyl succinic acid, crotonic acid, fumaric acid, maleic acid, itaconic acid, monomethyl maleic acid, monomethyl itaconic acid, and the like.

[0093] Examples of the above-mentioned amino group-containing monomers include primary amino group-containing (meth)acrylates such as aminomethyl (meth)acrylate and aminoethyl (meth)acrylate; secondary amino group-containing (meth)acrylates such as t-butylaminoethyl (meth)acrylate and t-butylaminopropyl (meth)acrylate; and tertiary amino group-containing (meth)acrylates such as ethylaminoethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, dimethylaminopropyl (meth)acrylate, diethylaminopropyl (meth)acrylate, and dimethylaminopropylacrylamide.

[0094] Examples of the above-mentioned amide group-containing monomers include (meth)acrylamides; N-alkyl(meth)acrylamides such as N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, N-propyl(meth)acrylamide, Nn-butyl(meth)acrylamide, diacetone(meth)acrylamide, and N,N'-methylenebis(meth)acrylamide; N,N-dialkyl(meth)acrylamides such as N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N,N-dipropyl(meth)acrylamide, N,N-ethylmethyl(meth)acrylamide, and N,N-diallyl(meth)acrylamide; hydroxyalkyl(meth)acrylamides such as N-hydroxymethyl(meth)acrylamide and N-hydroxyethyl(meth)acrylamide; and alkoxyalkyl(meth)acrylamides such as N-methoxymethyl(meth)acrylamide and N-(n-butoxymethyl)(meth)acrylamide.

[0095] Examples of the above-mentioned acetoacetyl group-containing monomers include 2-(acetoacetoxy)ethyl (meth)acrylate and allyl acetoacetate.

[0096] Examples of the above-mentioned isocyanate group-containing monomers include 2-acryloyloxyethyl isocyanate, 2-methacryloyloxyethyl isocyanate, and their alkylene oxide adducts. The isocyanate group may be protected with a blocking agent such as methyl ethyl ketone oxime, 3,5-dimethylpyrazole, 1,2,4-triazole, or diethyl malonate.

[0097] Examples of the above-mentioned glycidyl group-containing monomers include glycidyl (meth)acrylate and allyl glycidyl (meth)acrylate.

[0098] These functional group-containing ethylenically unsaturated monomers (a4) may be used individually or in combination of two or more.

[0099] From the viewpoint of improving the heat resistance and light resistance of the adhesive composition, the upper limit of the content of the above-mentioned functional group-containing ethylenically unsaturated monomer (a4) is preferably 30% by mass or less, more preferably 20% by mass or less, even more preferably 10% by mass or less, and particularly preferably 5% by mass or less, relative to the total components of the (meth)acrylic polymer (A).

[0100] In the present invention, other copolymerizable monomers (a5) can be used as copolymerization components of the acrylic resin as needed.

[0101] Other copolymerizable monomers (a5) include, for example, aromatic (meth)acrylic acid ester monomers such as phenyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenyldiethylene glycol (meth)acrylate, phenoxypolyethylene glycol (meth)acrylate, phenoxypolyethylene glycol-polypropylene glycol (meth)acrylate, and nonylphenol ethylene oxide adduct (meth)acrylate, as well as 4-acryloyloxybenzophenone, 4-acryloyloxyethoxybenzophenone, 4-acryloyloxy-4'-methoxybenzophenone, 4-acryloyloxyethoxy-4'-methoxybenzophenone, 4-acryloyloxy-4'-bromobenzophenone, 4-acryloyloxyethoxy-4'-bromobenzophenone, 4-methacryloyloxybenzophenone, and 4-methacryloyl Examples include (meth)acrylic acid ester monomers having a benzophenone structure, such as oxyethoxybenzophenone, 4-methacryloyloxy-4'-methoxybenzophenone, 4-methacryloyloxyethoxy-4'-methoxybenzophenone, 4-methacryloyloxy-4'-bromobenzophenone, 4-methacryloyloxyethoxy-4'-bromobenzophenone and mixtures thereof; vinyl monomers such as acrylonitrile, methacrylonitrile, styrene, α-methylstyrene, vinyl stearate, vinyl chloride, vinylidene chloride, alkyl vinyl ether, vinyltoluene, vinylpyridine, vinylpyrrolidone, dialkyl itaconate, dialkyl fumarate, allyl alcohol, acrylic chloride, methyl vinyl ketone, N-acrylamidomethyltrimethylammonium chloride, allyltrimethylammonium chloride, and dimethylallyl vinyl ketone. These can be used individually or in combination of two or more.

[0102] The (meth)acrylic polymer (A) of the present invention may have polymerizable carbon double bond groups introduced into its side chains. This can increase the crosslinking sensitivity of the adhesive composition, allowing it to be crosslinked by irradiation with lower energy active ray irradiation, thereby imparting cohesive strength and heat resistance.

[0103] One method for introducing polymerizable carbon double bond groups into the side chains of a (meth)acrylic polymer (A) is to prepare a copolymer containing the hydroxyl group-containing monomer (a2) or the functional group-containing ethylenically unsaturated monomer (a4) mentioned above, and then to carry out a condensation or addition reaction with a compound (a6) having a functional group that can react with these functional groups and a polymerizable carbon double bond group, while maintaining the activity of the polymerizable carbon double bond group. Examples of these functional group combinations include epoxy group (glycidyl group) and carboxyl group, amino group and carboxyl group, amino group and isocyanate group, epoxy group (glycidyl group) and amino group, hydroxyl group and epoxy group, and hydroxyl group and isocyanate group. Among these functional group combinations, the combination of hydroxyl group and isocyanate group is preferred due to the ease of reaction control. In particular, the combination in which the copolymer has a hydroxyl group and the compound has an isocyanate group is preferred. Examples of isocyanate compounds having polymerizable carbon double bond groups include the aforementioned 2-acryloyloxyethyl isocyanate, 2-methacryloyloxyethyl isocyanate, and their alkylene oxide adducts.

[0104] From the viewpoint of improving tackiness and stress relaxation, the amount of compound (a6) added is preferably 10 parts by mass or less, more preferably 8 parts by mass or less, even more preferably 5 parts by mass or less, and particularly preferably 3 parts by mass or less, per 100 parts by mass of (meth)acrylic polymer (A). The mass-average molecular weight of the (meth)acrylic polymer (A) is preferably 100,000 or more, more preferably 300,000 or more, and even more preferably 500,000 or more, from the viewpoint of obtaining an adhesive composition with high cohesive strength. Furthermore, the upper limit of the mass-average molecular weight of the (meth)acrylic polymer (A) is preferably 2 million or less, more preferably 1.5 million or less, and even more preferably 1 million or less, from the viewpoint of obtaining an adhesive composition with high fluidity and stress relaxation.

[0105] <Polyfunctional (meth)acrylate (B)> The polyfunctional (meth)acrylate (B) is a compound or composition that forms a crosslinked structure in the adhesive composition, and examples include (meth)acrylic monomers and (meth)acrylic oligomers having two or more functional groups. By containing a polyfunctional (meth)acrylate (B), this adhesive composition forms a cross-linked structure, thereby imparting cohesive force and durability to the adhesive sheet.

[0106] Examples of (meth)acrylic monomers include 1,4-butanediol di(meth)acrylate, glycerin di(meth)acrylate, neopentyl glycol di(meth)acrylate, glycerin glycidyl ether di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, tricyclodecane di(meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, bisphenol A polyethoxy di(meth)acrylate, and bisphenol A polyacrylate. Lopoxydi(meth)acrylate, bisphenol F polyethoxydi(meth)acrylate, ethylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, trimethylolpropane trioxyethyl(meth)acrylate, ε-caprolactone modified tris(2-hydroxyethyl) isocyanurate tri(meth)acrylate, pentaerythritol tri(meth)acrylate, propoxylated pentaerythritol tri(meth)acrylate, ethoxylated pentaerythritol tri(meth)acrylate Pentaerythritol tetra(meth)acrylate, propoxylated pentaerythritol tetra(meth)acrylate, ethoxylated pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, polytetramethylene glycol di(meth)acrylate, tris(acryloxyethyl) isocyanurate, dipentaerythritol hexa(meth)acrylate, dipentaerythritol Examples include thritol penta(meth)acrylate, tripentaerythritol hexa(meth)acrylate, tripentaerythritol penta(meth)acrylate, neopentyl glycol hydroxyvivariate di(meth)acrylate, di(meth)acrylate of the ε-caprolactone adduct of neopentyl glycol hydroxyvivariate, trimethylolpropane tri(meth)acrylate, trimethylolpropane triethoxytri(meth)acrylate, and ditrimethylolpropane tetra(meth)acrylate. In particular, (meth)acrylic monomers are preferred from the viewpoint of imparting appropriate toughness to the cured product, and among them, polyfunctional (meth)acrylic monomers having an alkylene glycol skeleton, such as polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, and polytetramethylene glycol di(meth)acrylate, are more preferred. The molecular weight of the (meth)acrylic monomer is preferably 200 or more, more preferably 300 or more, even more preferably 400 or more, and particularly preferably 500 or more, from the viewpoint of imparting appropriate flexibility to the cured product.

[0107] Examples of (meth)acrylic oligomers include polyfunctional (meth)acrylic oligomers such as polyester (meth)acrylate, epoxy (meth)acrylate, urethane (meth)acrylate, and polyether (meth)acrylate. In particular, urethane (meth)acrylate oligomers are preferred from the viewpoint of imparting appropriate toughness to the cured product. The molecular weight of the (meth)acrylic oligomer is preferably 3000 or more, more preferably 5000 or more, even more preferably 8000 or more, and particularly preferably 10000 or more, from the viewpoint of imparting appropriate flexibility to the cured product.

[0108] The amount of polyfunctional (meth)acrylate (B) is preferably 1 part by mass or more, more preferably 2 parts by mass or more, even more preferably 4 parts by mass or more, and particularly preferably 10 parts by mass or more, per 100 parts by mass of (meth)acrylic polymer (A), from the viewpoint of providing shape stability of the adhesive sheet and durability when formed into a laminate. Regarding the upper limit of the content mass of the polyfunctional (meth)acrylate (B), from the viewpoint of ensuring adhesiveness, it is preferable that it be 100 parts by mass or less, more preferably 60 parts by mass or less, even more preferably 40 parts by mass or less, and particularly preferably 30 parts by mass or less, per 100 parts by mass of (meth)acrylic polymer (A).

[0109] <Radical polymerization initiator (C)> A radical polymerization initiator can be any substance capable of initiating radical polymerization by irradiation with active energy rays such as light and heating. For example, examples of thermal radical polymerization initiators include hydrogen peroxide, organic peroxides such as perbenzoic acid, and azo compounds such as azobisbutyronitrile.

[0110] Photoradical polymerization initiators can be broadly classified into two types based on their radical generation mechanism: cleavage-type photoradical polymerization initiators, which can generate radicals by cleaving and decomposing the single bonds of the photoradical polymerization initiator itself; and hydrogen abstraction-type photoradical polymerization initiators, which form an excited complex with a hydrogen donor in the system after being photoexcited, and can transfer hydrogen from the hydrogen donor.

[0111] Among these, the cleavage-type photoradical polymerization initiator decomposes into a different compound when radicals are generated by light irradiation, and once excited, it loses its function as a reaction initiator. Therefore, it is preferable because it does not remain as an active species in the adhesive after the crosslinking reaction is complete, and does not cause unexpected photodegradation of the adhesive. On the other hand, hydrogen abstraction type photoradical polymerization initiators are useful because they can maintain their function as reaction initiators even after multiple photoirradiations, and they do not produce decomposition products like cleavage type photoradical polymerization initiators during radical generation reactions caused by irradiation with active energy rays such as ultraviolet light. Therefore, they are less likely to become volatile components after the reaction is complete, thus reducing damage to the substrate.

[0112] When using a photoradical polymerization initiator, it is preferable that the initiator generates radicals by irradiation with light in the wavelength range of 380 nm to 700 nm, for example, and serves as the starting point for the crosslinking reaction of the adhesive composition.

[0113] Examples of the cleavage-type photoradical polymerization initiators include 2,2-dimethoxy-1,2-diphenylethane-1-one, 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-(4-(2-hydroxyethoxy)phenyl)-2-hydroxy-2-methyl-1-propan-1-one, 2-hydroxy-1-[4-{4-(2-hydroxy-2-methylpropionyl)benzyl}phenyl]-2-methylpropan-1-one, oligo(2-hydroxy-2-methyl-1-(4-(1-methylvinyl)phenyl)propanone), methyl phenylglyoxyate, and 2-benzyl-2-dimethylamino-1- Examples include (4-morpholinophenyl)butan-1-one, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, 2-(dimethylamino)-2-[(4-methylphenyl)methyl)-1-[4-(4-morpholinyl)phenyl]-1-butanone, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, (2,4,6-trimethylbenzoyl)ethoxyphenylphosphine oxide, bis(2,6-dimethoxybenzoyl)2,4,4-trimethylpentylphosphine oxide, and their derivatives. Among these, acylphosphine oxide-based photoinitiators such as bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, (2,4,6-trimethylbenzoyl)ethoxyphenylphosphine oxide, and bis(2,6-dimethoxybenzoyl)2,4,4-trimethylpentylphosphine oxide are preferred from the viewpoint of becoming decomposition products and decolorizing after the reaction.

[0114] Examples of the hydrogen abstraction type photoradical polymerization initiators include bis(2-phenyl-2-oxoacetic acid)oxybisethylene, phenylglyoxylic acid methyl ester, a mixture of oxy-phenyl-acetylic acid 2-[2-oxo-2-phenylacetoxy-ethoxy]ethyl ester and oxy-phenyl-acetylic acid 2-[2-hydroxy-ethoxy]ethyl ester, thioxanthone, 2-chlorothioxanthone, 3-methylthioxanthone, 2,4-dimethylthioxanthone, anthraquinone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-tert-butylanthraquinone, 2-aminoanthraquinone, camphorquinone, and their derivatives. Among these, it is preferable that it be one or more selected from the group consisting of phenylglyoxylic acid methyl ester, oxy-phenyl-acetyl acid 2-[2-oxo-2-phenylacetoxy-ethoxy]ethyl ester, and oxy-phenyl-acetyl acid 2-[2-hydroxy-ethoxy]ethyl ester.

[0115] Note that the photoradical polymerization initiator is not limited to the substances listed above. Any one of the photoradical polymerization initiators listed above or a derivative thereof may be used, or two or more may be used in combination. A thermal radical polymerization initiator and a photoradical polymerization initiator may also be used in combination.

[0116] The content of the radical polymerization initiator (C) is not particularly limited, but from the viewpoint of allowing the polymerization reaction to proceed sufficiently and improving the shape stability of the adhesive sheet, it is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, even more preferably 1 part by mass or more, and particularly preferably 1.5 parts by mass or more, per 100 parts by mass of the (meth)acrylic polymer (A). Furthermore, from the viewpoint of ensuring tackiness, the upper limit of the radical polymerization initiator (C) content is preferably 15 parts by mass or less, more preferably 10 parts by mass or less, even more preferably 6 parts by mass or less, and particularly preferably 4 parts by mass or less, per 100 parts by mass of (meth)acrylic polymer (A).

[0117] <Thickness of the adhesive layer> The thickness of the adhesive layer is preferably 1 μm or more, more preferably 5 μm or more, even more preferably 10 μm or more, and particularly preferably 20 μm or more, from the viewpoint of protecting the polyester layer (X). On the other hand, the upper limit of the thickness is preferably 200 μm or less, more preferably 175 μm or less, and even more preferably 150 μm or less, from the viewpoint of contributing to the thinning of the film laminate.

[0118] <Method for forming an adhesive layer> This adhesive composition can be diluted, for example, with an organic solvent, applied to a release film, and dried to form an adhesive sheet. If the film laminate has a cured resin layer (CFA) between the polyester layer (X) and the resin layer (Y), the adhesive sheet can be laminated on the cured resin layer (CFA) and then exposed to light before use. When this adhesive composition is curable by active energy rays, curing the adhesive composition by irradiating it with light after laminating an adhesive sheet onto a cured resin layer (CFA) or after laminating a resin layer (Y) onto this adhesive sheet results in stronger adhesion between the cured resin layer (CFA) and the resin layer (Y), thereby improving the reliability of the laminate. From the viewpoint of suppressing damage to the film and controlling the reaction, ultraviolet and visible light are preferred as light sources. While there are no particular limitations regarding irradiation time or irradiation method, it is preferable to irradiate the polyester layer (X) from the side opposite to the cured resin layer (CFA) side (the cured resin layer (CFB) side, which will be described later).

[0119] Furthermore, there are no particular limitations regarding the irradiation energy of the active energy rays, irradiation time, or irradiation method; the only requirement is that the initiator is activated and the (meth)acrylate component is polymerized.

[0120] <Physical properties of the adhesive layer> The relative permittivity of the adhesive layer is preferably 3.9 or less. This is preferable because it does not impair the excellent low dielectric properties of the polyester layer (X) of the film laminate. The relative permittivity of the adhesive layer is preferably 3.8 or less. The dielectric constant of the adhesive layer is the value measured by the method described in the examples.

[0121] <Method for applying the adhesive layer> The adhesive layer preferably has the ability to absorb steps. In this film laminate, when the adhesive layer is bonded to a surface on which antenna wiring is provided on a cured resin layer (CFA), for example, it is preferable to pre-cur it by heat treatment or the like. By pre-curing the adhesive layer, the adhesive layer can be made to follow the steps of the antenna wiring sufficiently. Furthermore, by crosslinking the adhesive layer through pre-curing to a degree that is not too flexible, the adhesive layer can follow the steps without generating air bubbles, ensuring that it reaches every corner of the antenna wiring and easing the stress caused by the steps. Moreover, even if the part in contact with the steps is exposed to a high temperature and high humidity environment or to rapid temperature changes, foaming and peeling at the bonding interface can be prevented. After bonding, the desired adhesive strength can be achieved by further secondary curing. As mentioned above, by employing a two-stage curing method, the adhesive layer itself can be given the ability to absorb unevenness.

[0122] <<Cured resin layer>> The film laminate preferably has a cured resin layer (CFB) on at least one side of the polyester layer (X), and preferably has the resin layer (Y), the polyester layer (X), and the cured resin layer (CFB) in that order. Furthermore, it is preferable that the film laminate has a cured resin layer (CFA) on the side of the polyester layer (X) opposite to the side on which the cured resin layer (CFB) is laminated, and it is more preferable that it has the resin layer (Y), optionally the adhesive layer, the cured resin layer (CFA), and the polyester layer (X) in that order.

[0123] This film laminate, by having a hardened resin layer (CFB), can improve adhesion to the metal layer (an optional layer, described later). Preferably, at least one of the cured resin layer (CFA) and the cured resin layer (CFB) is formed from a resin composition containing a crosslinking agent at a concentration of 70% by mass or more relative to the non-volatile components, and more preferably, both the cured resin layer (CFA) and the cured resin layer (CFB) are formed from a resin composition containing a crosslinking agent at a concentration of 70% by mass or more relative to the non-volatile components. Furthermore, other layers may be present between the cured resin layer (CFB) and the polyester layer (X), between the polyester layer (X) and the cured resin layer (CFA), between the cured resin layer (CFA) and the adhesive layer, or between the adhesive layer and the resin layer (Y).

[0124] <Crosslinking agent> Various known crosslinking agents can be used as the aforementioned crosslinking agent, including, for example, oxazoline compounds, melamine compounds, epoxy compounds, isocyanate compounds, carbodiimide compounds, silane coupling compounds, and the like. Among these, for example, when a metal layer is provided on a cured resin layer, oxazoline compounds are preferably used from the viewpoint of improving durability and adhesion. Furthermore, melamine compounds are preferably used from the viewpoint of preventing oligomer precipitation on the film surface due to heating and improving the durability of the cured resin layer.

[0125] (Oxazoline compounds) Oxazoline compounds are compounds having an oxazoline group in their molecule, and polymers containing an oxazoline group are particularly preferred. These can be produced by polymerization of an addition-polymerizable oxazoline group-containing monomer alone or with other monomers. Examples of addition-polymerizable oxazoline group-containing monomers include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, and 2-isopropenyl-5-ethyl-2-oxazoline. One or more of these can be used. Among these, 2-isopropenyl-2-oxazoline is preferred because it is readily available industrially. Other monomers are not limited as long as they are copolymerizable with addition-polymerizable oxazoline group-containing monomers. Examples include alkyl (meth)acrylates, with alkyl groups including methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, 2-ethylhexyl, and cyclohexyl groups. Unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, styrenesulfonic acid, and their salts are also included, with examples of salts including sodium salts, potassium salts, ammonium salts, and tertiary amine salts. Furthermore, examples include unsaturated nitriles such as acrylonitrile and methacrylonitrile; unsaturated amides such as (meth)acrylamide, N-alkyl(meth)acrylamide, and N,N-dialkyl(meth)acrylamide, with alkyl groups including methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, 2-ethylhexyl, and cyclohexyl groups. Other examples include vinyl esters such as vinyl acetate and vinyl propionate; vinyl ethers such as methyl vinyl ether and ethyl vinyl ether; α-olefins such as ethylene and propylene; halogen-containing α,β-unsaturated monomers such as vinyl chloride and vinylidene chloride; and α,β-unsaturated aromatic monomers such as styrene and α-methylstyrene. One or more of these monomers can be used. From the viewpoint of improving the durability of the cured resin layer, the amount of oxazoline groups in the oxazoline compound is preferably in the range of 0.5 to 10 mmol / g, more preferably 3 to 9 mmol / g, and even more preferably 5 to 8 mmol / g.

[0126] (Melamine compound) Melamine compounds are compounds that have a melamine skeleton in the compound. For example, alkylolated melamine derivatives, compounds that have been partially or completely etherified by reacting alkylolated melamine derivatives with alcohol, and mixtures thereof can be used. Suitable alcohols for etherification include methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butanol, and isobutanol. Furthermore, the melamine compound may be a monomer, a polymer of two or more units, or a mixture thereof. In addition, a compound in which urea or the like is co-condensed with a portion of the melamine can be used, and a catalyst can be used to increase the reactivity of the melamine compound.

[0127] (Epoxy compound) Epoxy compounds are compounds that have an epoxy group in their molecule. Examples include condensates of epichlorohydrin, ethylene glycol, polyethylene glycol, glycerin, polyglycerin, and bisphenol A with hydroxyl or amino groups, as well as polyepoxy compounds, diepoxy compounds, monoepoxy compounds, and glycidylamine compounds. Examples of polyepoxy compounds include sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, diglycerol polyglycidyl ether, triglycidyl tris(2-hydroxyethyl) isocyanate, glycerol polyglycidyl ether, and trimethylolpropane polyglycidyl ether. Examples of diepoxy compounds include neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, resorcinol diglycidyl ether, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, and polytetramethylene glycol diglycidyl ether. Examples of monoepoxy compounds include allyl glycidyl ether, 2-ethylhexyl glycidyl ether, and phenyl glycidyl ether, while examples of glycidylamine compounds include N,N,N',N'-tetraglycidyl-m-xylylenediamine and 1,3-bis(N,N-diglycidylamino)cyclohexane.

[0128] (Isocyanate compounds) Isocyanate compounds are compounds having an isocyanate derivative structure, such as isocyanates or blocked isocyanates. Examples of isocyanates include aromatic isocyanates such as tolylene diisocyanate, xylylene diisocyanate, methylenediphenyl diisocyanate, phenylene diisocyanate, and naphthalene diisocyanate; aliphatic isocyanates having an aromatic ring such as α,α,α',α'-tetramethylxylylene diisocyanate; aliphatic isocyanates such as methylene diisocyanate, propylene diisocyanate, lysine diisocyanate, trimethylhexamethylene diisocyanate, and hexamethylene diisocyanate; and alicyclic isocyanates such as cyclohexane diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, methylenebis(4-cyclohexyl isocyanate), and isopropylidene dicyclohexyl diisocyanate. Furthermore, polymers and derivatives of these isocyanates, such as biuretized, isocyanurateized, uretdioneized, and carbodiimide-modified compounds, can also be mentioned. These may be used individually or in combination. Among the above isocyanates, aliphatic isocyanates or alicyclic isocyanates are more preferred than aromatic isocyanates in order to avoid yellowing due to ultraviolet light.

[0129] When used in the form of blocked isocyanates, examples of blocking agents include phenolic compounds such as bisulfites, phenol, cresol, and ethylphenol; alcoholic compounds such as propylene glycol monomethyl ether, ethylene glycol, benzyl alcohol, methanol, and ethanol; active methylene compounds such as methyl isobutanoylacetate, dimethyl malonate, diethyl malonate, methyl acetoacetate, ethyl acetoacetate, and acetylacetone; mercaptan compounds such as butyl mercaptan and dodecyl mercaptan; lactam compounds such as ε-caprolactam and δ-valerolactam; amine compounds such as diphenylaniline, aniline, and ethyleneimine; acid amide compounds such as acetanilide and acetic acid amide; and oxime compounds such as formaldehyde, acetaldehyde oxime, acetone oxime, methyl ethyl ketone oxime, and cyclohexanone oxime. These may be used individually or in combination of two or more.

[0130] Furthermore, isocyanate compounds may be used alone or as mixtures or binders with various polymers. It is preferable to use mixtures or binders with polyester resins or urethane resins to improve the dispersibility and crosslinking properties of the isocyanate compounds.

[0131] (Carbodiimide compounds) A carbodiimide compound is a compound having a carbodiimide structure, specifically a compound having one or more carbodiimide structures within its molecule. However, polycarbodiimide compounds having two or more carbodiimide structures within their molecule are more preferable for better adhesion and other properties.

[0132] Carbodiimide compounds can be synthesized using conventionally known techniques, and generally, condensation reactions of diisocyanate compounds are employed. The diisocyanate compounds are not particularly limited and can be either aromatic or aliphatic. Specifically, examples include tolylene diisocyanate, xylene diisocyanate, diphenylmethane diisocyanate, phenylene diisocyanate, naphthalene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, cyclohexane diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, dicyclohexyl diisocyanate, and dicyclohexylmethane diisocyanate.

[0133] The amount of carbodiimide groups contained in a carbodiimide compound is typically in the range of 100 to 1000, preferably 250 to 700, and more preferably 300 to 500, in terms of carbodiimide equivalents (weight [g] of the carbodiimide compound required to give 1 mol of carbodiimide groups). Using a compound within this range improves the durability of the cured resin layer.

[0134] Furthermore, to the extent that it does not impair the spirit of the present invention, surfactants may be added, or hydrophilic monomers such as polyalkylene oxides, quaternary ammonium salts of dialkylamino alcohols, and hydroxyalkyl sulfonates may be added to improve the water solubility and water dispersibility of the polycarbodiimide compound.

[0135] (Silane coupling compounds) Silane coupling compounds are organosilicon compounds that contain both an organic functional group and a hydrolysis group such as an alkoxy group within a single molecule. For example, epoxy group-containing compounds such as 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; vinyl group-containing compounds such as vinyltrimethoxysilane and vinyltriethoxysilane; styryl group-containing compounds such as p-styryltrimethoxysilane and p-styryltriethoxysilane; (meth)acrylic group-containing compounds such as 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, and 3-(meth)acryloxypropylmethyldiethoxysilane; 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)- Examples include amino group-containing compounds such as 3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldiethoxysilane, 3-triethoxysilyl-N-(1,3-dimethylbutylidene)propylamine, N-phenyl-3-aminopropyltrimethoxysilane, and N-phenyl-3-aminopropyltriethoxysilane; isocyanurate group-containing compounds such as tris(trimethoxysilylpropyl)isocyanurate and tris(triethoxysilylpropyl)isocyanurate; and mercapto group-containing compounds such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropylmethyldimethoxysilane, and 3-mercaptopropylmethyldiethoxysilane.

[0136] These crosslinking agents may be used individually or in combination of two or more, but using two or more in combination can improve the ability to prevent oligomer precipitation after heating. Furthermore, using two or more crosslinking agents in combination can improve the adhesion between the cured resin layer and the metal layer, for example, when the film laminate has a metal layer on top of the cured resin layer. Among these, a combination of an oxazoline compound, which can particularly improve adhesion to the metal layer on the cured resin layer, and a melamine compound, which has good ability to prevent oligomer precipitation after heating, is preferred.

[0137] Furthermore, when the film laminate has a metal layer on top of the cured resin layer, it is more preferable to combine three or more crosslinking agents to further improve the adhesion between the cured resin layer and the metal layer. As for the combination of three or more crosslinking agents, it is preferable to select a melamine compound as one of the crosslinking agents, and more preferably, an oxazoline compound and an epoxy compound, or a carbodiimide compound and an epoxy compound are used as crosslinking agents to be combined with the melamine compound.

[0138] When such a crosslinking agent is included, components that promote crosslinking, such as a crosslinking catalyst, can be used in combination.

[0139] The proportion of the crosslinking agent to the total nonvolatile components in the resin composition forming at least one of the cured resin layers is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more. A proportion of 70% by mass or more of the crosslinking agent to the total nonvolatile components in the resin composition forming the cured resin layer is preferable because it provides good oligomer precipitation prevention after heating, and is also preferable if the film laminate further has a metal layer on the cured resin layer because it provides good adhesion between the cured resin layer and the metal layer. For both the cured resin layer (CFA) and the cured resin layer (CFB), it is preferable that the ratio of the crosslinking agent to the non-volatile component in the resin composition forming the cured resin layer is within the above range.

[0140] <Binder resin> The resin composition may also contain a binder resin, to the extent that it does not impair the spirit of the present invention, for purposes such as improving the appearance of the cured resin layer or improving adhesion with a metal layer that may be provided on the cured resin layer. While conventionally known binder resins can be used, it is preferable to use polyester resin, acrylic resin, or urethane resin from the viewpoint of improving adhesion with the layer provided on the cured resin layer.

[0141] <Particle> Furthermore, the resin composition may also contain particles for the purpose of blocking and improving slipperiness. From the viewpoint of film transparency, the average particle size is preferably 1.0 μm or less, more preferably 0.5 μm or less, and even more preferably 0.2 μm or less. On the other hand, in order to more effectively improve slipperiness, it is preferably 0.01 μm or more, more preferably 0.03 μm or more, and particularly preferably in a range greater than the film thickness of the cured resin layer. Specific examples of particles include silica, alumina, kaolin, calcium carbonate, and organic particles.

[0142] <Other> Furthermore, to the extent that the spirit of the present invention is not impaired, the resin composition may optionally contain crosslinking catalysts, defoaming agents, coating properties improvers, thickeners, organic lubricants, antistatic agents, ultraviolet absorbers, antioxidants, foaming agents, dyes, pigments, and the like.

[0143] Furthermore, the analysis of various compounds (components) in the cured resin layer can be performed, for example, by TOF-SIMS, ESCA, or X-ray fluorescence.

[0144] The film thickness of the cured resin layer (after drying) is preferably 0.003 to 1.0 μm, more preferably 0.005 to 0.5 μm, and even more preferably 0.01 to 0.2 μm. If the film thickness is 1.0 μm or less, the appearance and blocking resistance of the cured resin layer are sufficient. On the other hand, if the film thickness is 0.003 μm or more, the amount of oligomer precipitated from the film is reduced, which is preferable.

[0145] <Method for forming cured resin layer (CFA) and cured resin layer (CFB)> The following description will explain a method for forming a cured resin layer. However, this description is merely one example of a method for forming a cured resin layer and is not limited to this method.

[0146] The resin composition is generally preferably diluted with water, an organic solvent, or a mixture thereof. The cured resin layer is formed by coating the surface of the polyester layer (X) with the diluted resin composition as a coating solution and drying it. Conventional coating methods can be used to apply the coating solution to the film, such as air doctor coating, blade coating, rod coating, bar coating, knife coating, squeeze coating, impregnation coating, reverse roll coating, transfer roll coating, gravure coating, kiss roll coating, cast coating, spray coating, curtain coating, calender coating, and extrusion coating. Furthermore, in order to improve the applicability and adhesion of the coating agent (coating liquid) to the film, the film may be subjected to chemical treatment, corona discharge treatment, plasma treatment, etc., before coating.

[0147] In this film laminate, the cured resin layer (CFB) is preferably formed in the order of resin layer (Y), polyester layer (X), and cured resin layer (CFB) by coating at least one side of the polyester layer (X) with the above resin composition. Alternatively, the cured resin layer (CFA) and cured resin layer (CFB) can be formed on both surfaces of the polyester layer (X) by coating both surfaces of the polyester layer (X) with the resin composition. Coating methods include in-line coating and offline coating, but in-line coating is preferred. In-line coating is a method of coating within the manufacturing process of the polyester layer (X), and specifically, it is a method of coating at any stage from melting and extruding the raw material polyester to stretching, heat fixing, and winding. Usually, the coating is applied to an unstretched sheet obtained by melting and rapidly cooling, a stretched uniaxially oriented film, a biaxially oriented film before heat fixing, or a polyester layer (X) after heat fixing and before winding, but a method of coating a uniaxially oriented film stretched in the longitudinal direction (vertical direction) and then stretching it in the width direction (lateral direction) is particularly preferred. Furthermore, when a cured resin layer is provided by in-line coating, it is preferable to use a coating solution prepared by adjusting the solid content concentration to approximately 0.1 to 50% by mass using the above-mentioned series of compounds as an aqueous solution or aqueous dispersion. In addition, within the limits that do not impair the spirit of the present invention, the coating solution may contain a small amount of one or more organic solvents for the purpose of improving dispersibility in water, improving film-forming properties, etc.

[0148] The drying and curing conditions when forming a cured resin layer on a film are not particularly limited. For example, when providing a cured resin layer by offline coating, it is preferable to perform heat treatment at 80-200°C for 3-40 seconds, and more preferably at 100-180°C for 3-40 seconds. On the other hand, when a cured resin layer is provided by in-line coating, it is preferable to perform heat treatment at 70 to 280°C for approximately 3 to 200 seconds.

[0149] Furthermore, regardless of whether it is offline coating or in-line coating, heat treatment and active energy ray irradiation such as ultraviolet irradiation may be used in combination as needed.

[0150] <Physical properties of cured resin layer (CFA) and cured resin layer (CFB)> When this film laminate has a cured resin layer, it is effective in preventing the deposition of oligomers on the film surface by heating. By reducing the deposition of oligomers, it is possible to suppress the decrease in visibility due to the whitening of the film appearance caused by the deposition and whitening of the oligomers. The deposition amount of oligomers (ester cyclic trimer) on the surface of at least one cured resin layer in this film laminate is 0.40 mg / m 2 It is preferably below, and more preferably 0.35 mg / m 2 It is even more preferably below, and still more preferably 0.30 mg / m 2 It is even more preferably below, and particularly preferably 0.25 mg / m 2 It is particularly preferably below, and especially preferably 0.20 mg / m 2 It is especially preferably below. If the oligomer deposition amount is 0.40 mg / m 2 or less, it is preferable because there is no decrease in visibility due to the whitening of the film appearance caused by the deposition and crystallization of oligomers on the surface, no occurrence of defects in post-processing, and no contamination in the process or of components. The lower limit is not particularly limited, but it is 0.01 mg / m 2 or more. Note that the oligomer deposition amount is a value obtained by the method described in the examples.

[0151] <<Particularly preferred form>> As described above, this film laminate includes a polyester layer (X) and a resin layer (Y). Among them, this film laminate preferably further includes a cured resin layer (CFB), a cured resin layer (CFA), and / or an adhesive layer in addition to the above polyester layer (X) and resin layer (Y), and more preferably has a structure in which the cured resin layer (CFB), the polyester layer (X), the cured resin layer (CFA), the adhesive layer, and the resin layer (Y) are sequentially laminated.

[0152] <<Metal layer>> This film laminate may have a metal layer on the cured resin layer (CFB). For example, it may further have, in order, a resin layer (Y), a polyester layer (X), a cured resin layer (CFB), and a metal layer. Furthermore, other layers may be present between the cured resin layer (CFB) and the metal layer.

[0153] The metal layer is a layer that contains metal as its main component. Here, "main component" means that metal accounts for 50% or more by mass, more preferably 70% or more by mass, even more preferably 80% or more by mass, and particularly preferably 90% or more by mass of the metal layer. Regarding the metals to be used, examples include copper, copper alloys, silver, stainless steel, nickel, nickel alloys, aluminum, aluminum alloys, titanium, and titanium alloys. However, from the viewpoint of electromagnetic wave shielding properties, copper or silver is preferred, and from the viewpoint of flexibility, copper is more preferred.

[0154] From the viewpoint of maintaining the transparency of the film laminate, the metal layer is preferably patterned, for example, in the form of a mesh or wire.

[0155] The thickness of the metal layer is preferably 0.001 to 30 μm, more preferably 0.01 to 20 μm, particularly 0.01 to 15 μm, and even more preferably 0.01 to 10 μm. A thickness of the metal layer above the lower limit ensures sufficient conductivity, while a thickness below the upper limit reduces visibility when the metal layer is provided, which is preferable. The thickness of the metal layer can be measured by observing the sample cross-section with an electron microscope.

[0156] <<<Physical properties of film laminates>>> This film laminate has a light transmittance of 25% or less at 380nm. If the light transmittance of the film laminate at 380nm exceeds 25%, it may not be suitable for outdoor use. From this viewpoint, the light transmittance of the film laminate at 380 nm is preferably 20% or less, more preferably 15% or less, and even more preferably 10% or less. The lower limit of this light transmittance is not particularly limited, but is 0.1% or more. Methods for achieving a light transmittance of 25% or less in this film laminate include incorporating an ultraviolet absorber into at least one of the polyester layer (X), adhesive layer, and resin layer (Y). In particular, considering applications such as window glass in buildings or vehicle glass, it is preferable to incorporate the ultraviolet absorber into the resin layer (Y), which is most exposed to ultraviolet light when applied. The method for incorporating the ultraviolet absorber into the resin layer (Y) is as described above.

[0157] When a tensile cycle test is performed on the longitudinal (MD) and widthwise (TD) directions of this film laminate up to a 5% tensile strain, the hysteresis loss rate is preferably 55% or less, more preferably 50% or less, and even more preferably 48% or less. The smaller the hysteresis loss rate, the greater the restorative force of the film, making it easier to return to its original state, meaning it has excellent bending resistance. If the hysteresis loss rate of this film laminate is 55% or less, the restorative force is greater and bending resistance is good. When this film laminate also has excellent bending resistance, it can be suitably used for flexible displays equipped with high-speed communication circuits, etc.

[0158] The film laminate preferably has a film haze value of 4.0% or less. If the haze of the film laminate is 4.0% or less, it can be said to have excellent transparency and is particularly suitable for use as a component for transparent antennas. From this viewpoint, the film haze value is more preferably 3.0% or less, even more preferably 2.5% or less, and particularly preferably 2.0% or less. There is no specific lower limit, but it should be 0.1% or higher.

[0159] As described above, the film laminate comprising a polyester layer (X) and a resin layer (Y), and optionally further comprising a cured resin layer (CFB), a cured resin layer (CFA), and / or an adhesive layer, preferably has a total thickness of 19 to 800 μm. A total thickness of 19 μm or more is preferable because it maintains strength within a practical range. If the total thickness of the film laminate is 800 μm or less, it becomes easy to incorporate into mobile devices and can be suitably used for high-speed communication circuits. From this viewpoint, the total thickness of the film laminate is more preferably 30 to 750 μm, even more preferably 50 to 700 μm, particularly preferably 100 to 500 μm, and especially preferably 200 to 400 μm.

[0160] <<<Usage>>> This film laminate maintains transparency and possesses excellent low dielectric properties. Therefore, it can be suitably used for high-speed communication circuits. Examples of high-speed communication circuit applications include FPCs (Flexible Printed Circuits), which are flexible circuit boards formed from resin film and copper foil, and transparent antennas, which have invisible, ultra-fine metal mesh wiring formed on a transparent film. In particular, it can be suitably used as a component for transparent antennas where high transparency is required. Furthermore, because this film laminate has low light transmittance at 380 nm and good ultraviolet absorption performance, it can be suitably used for outdoor use in transparent antennas, i.e., as a component for outdoor transparent antennas.

[0161] Furthermore, because this polyester layer (X) has excellent bending resistance, if the entire film laminate also has excellent bending resistance, it can be suitably used for flexible displays equipped with high-speed communication circuits. The flexible display is a general term for displays that have excellent resilience and resistance to repeated bending, and examples include bendable, rollable, stretchable, and foldable displays. Examples of displays include mobile phones, smartphones, digital cameras, and personal computers, and there are no particular limitations on the type of display, such as liquid crystal displays, plasma displays, and organic EL displays.

[0162] <<<Explanation of terms and phrases>>> In this invention, the term "film" includes "sheets," and the term "sheet" includes "film." In this invention, when "X~Y" (where X and Y are any numbers) is written, unless otherwise specified, it means "X or greater and Y or less," and also includes the meaning of "preferably greater than X" or "preferably less than Y." Furthermore, when "X or greater" (where X is any number) is written, unless otherwise specified, it includes the meaning of "preferably greater than X," and when "Y or less" (where Y is any number) is written, unless otherwise specified, it also includes the meaning of "preferably less than Y." [Examples]

[0163] Next, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the examples described below.

[0164] <Evaluation Method> (1) Intrinsic viscosity of polyester 1 g of polyester was accurately weighed, dissolved in 100 ml of a phenol / tetrachloroethane mixed solvent (50 / 50 by mass ratio), and measured at 30°C.

[0165] (2) Dielectric loss tangent and relative permittivity of a laminate (hereinafter also referred to as "polyester film with cured resin layer") in which a cured resin layer (CFA), a polyester layer (X), and a cured resin layer (CFB) are laminated in that order, and relative permittivity of the adhesive layer. For the polyester films with cured resin layers used in the examples, comparative examples, and reference examples, the dielectric loss tangent and relative permittivity at a frequency of 28 GHz were measured in accordance with JIS R1641 using a dielectric constant measurement system (cavity resonator (TE mode), control software, and vector network analyzer MS46122B (manufactured by Anritsu Corporation)) manufactured by AET Co., Ltd., and the relative permittivity for the adhesive layer was measured.

[0166] (3) Hysteresis loss rate of the polyester layer (X) and the film laminate In accordance with JIS K 7312:1996, the hysteresis loss rate at 23°C was determined by the following method. The measuring device used was a tensile testing machine (Autograph AG-I, manufactured by Shimadzu Corporation). The test specimens were cut from any location on the polyester layer (X) or film laminate to be measured, forming rectangles with a length of 100 mm and a width of 10 mm in the measurement direction. The specimens were chucked at both ends in the longitudinal direction with a chuck distance of 50 mm, and the specimens were raised to a strain of 5% at a crosshead speed of 0.5 mm / min. A stress-strain curve was obtained from one cycle of tensile cycling testing, in which the specimens were lowered to the initial position at the same speed. The stress-strain curves took the profile shown in Figure 1, and the hysteresis loss rate was calculated from the obtained stress-strain curves using the area A1 (abcda) of the curve obtained during the upward movement and the area A2 (abcef), which is the difference between area A1 and the area of ​​the curve obtained during the downward movement, using the following formula (2). The test was performed three times, and the average value was calculated. The above tensile cycling test was performed in both the longitudinal direction (MD) and the axial direction (TD) of the film. Hysteresis loss rate = A2 / A1 × 100 ... Equation (2)

[0167] (4) Haze of the polyester layer (X) and film laminate Measurements were taken in accordance with JIS K 7136:2000, using a haze meter DH-2000 manufactured by Nippon Denshoku Industries Co., Ltd.

[0168] (5) Heat shrinkage rate of the polyester layer (X) A 1.5 cm x 15 cm sample film was heat-treated for 30 minutes in a hot-air oven maintained at a predetermined temperature (150°C) in a tension-free state. The length of the sample film was measured before and after the treatment, and the length was calculated using the following formula. Measurements were taken in both the longitudinal direction (MD) and the width direction (TD) of the film. Thermal shrinkage rate (%) = {(Sample length before heat treatment) - (Sample length after heat treatment)} ÷ (Sample length before heat treatment) × 100

[0169] (6) Amount of oligomer (ester cyclic trimer) precipitated on the surface of the cured resin layer due to heating For the polyester films with cured resin layers that constitute the film laminates of the examples and comparative examples, both cured resin layers (cured resin layer (CFA) and cured resin layer (CFB)) were heat-treated for 120 minutes in a hot air oven maintained at a predetermined temperature (180°C) as sample specimens measuring 300 mm in length and 225 mm in width. After heat treatment, a box-shaped specimen measuring 200 mm in length and 125 mm in width with an open top was prepared with the measurement surface as the inner surface. Next, 10 mL of DMF (dimethylformamide) was placed in the box-shaped container described above and left for 3 minutes. After the DMF was recovered, it was supplied to a liquid chromatograph (Shimadzu Corporation: LC-7A, mobile phase A: acetonitrile, mobile phase B: 2% aqueous acetic acid solution, column: Mitsubishi Chemical Corporation "MCI GEL ODS 1HU", column temperature: 40°C, flow rate: 1 mL / min, detection wavelength: 254 nm) to determine the amount of ester cyclic trimers in the DMF. This value was then divided by the film area in contact with the DMF to determine the amount of oligomers (ester cyclic trimers) on the surface of the cured resin layer (mg / m²). 2 The ester cyclic trimers in DMF were determined from the peak area ratio of the standard sample peak area to the measured sample peak area (absolute calibration curve method). The standard sample was prepared by accurately weighing a pre-parate ester cyclic trimer and dissolving it in accurately weighed DMF.

[0170] (7) Light transmittance of the film laminate at 380 nm The light transmittance of the film laminates of the examples and comparative examples in the wavelength range of 380 nm was measured using a spectrophotometer (Shimadzu Corporation; instrument name "UV2450").

[0171] (8) Thickness of the polyester layer (X), adhesive layer, and resin layer (Y) Using a 1 / 1000 mm dial gauge, measurements were taken at five unspecified points within the surface, and the average of these measurements was taken as the thickness.

[0172] (9) Thickness of the cured resin layer The surface of the cured resin layer was stained with RuO4 and embedded in epoxy resin. Subsequently, sections prepared by the ultrathin sectioning method were stained with RuO4, and the cross-section of the cured resin layer was measured using a transmission electron microscope (TEM) (Hitachi High-Technologies Corporation, H-7650, accelerating voltage 100kV).

[0173] <Materials used> [Polyester raw material] Raw material A: Homopolybutylene naphthalate (intrinsic viscosity = 1.13 dL / g) Raw material B: Homopolyethylene naphthalate Raw material C: Homopolyethylene terephthalate (intrinsic viscosity = 0.640 dL / g) Raw material D: Homopolyethylene terephthalate (intrinsic viscosity = 0.585 dL / g) Raw material E: A masterbatch containing 0.7% by mass of silica particles with an average particle size of 3 μm, made from homopolyethylene terephthalate (intrinsic viscosity = 0.590 dL / g). Raw material F: A masterbatch (intrinsic viscosity = 0.610 dL / g) containing 10% by mass of a UV absorber (Siasorb UV-3638F, manufactured by Sun Chemical Co., Ltd.) in homopolyethylene terephthalate.

[0174] [Cured resin layer] The following resin composition was used to form the cured resin layer. (A1): Hexamethoxymethylolmelamine (A2): Epocross (manufactured by Nippon Shokubai Co., Ltd.), an oxazoline compound; oxazoline group content 7.7 mmol / g (A3): Polyglycerol polyglycidyl ether (B1): Silica particles with an average particle size of 0.07 μm

[0175] The compositions of the coating solutions used in the examples and comparative examples are shown in Table 1. More specifically, the resin compositions obtained by stirring and mixing the compositions shown in Table 1 below were diluted with water to prepare the coating solutions.

[0176] [Table 1]

[0177] [Adhesive layer] ((meth)acrylic polymer (A)) The copolymer was obtained by copolymerizing 2-ethylhexyl acrylate (a1): 65% by mass, methyl acrylate (a3): 6% by mass, ethyl acrylate (a3): 11% by mass, 2-hydroxyethyl acrylate (a2): 13% by mass, and 4-hydroxybutyl acrylate (a2): 5% by mass. The mass-average molecular weight (Mw) of the acrylic acid ester copolymer polymer, as measured by GPC, was 900,000.

[0178] (Polyfunctional (meth)acrylate (B)) Polypropylene glycol #700 diacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., APG-700)

[0179] (Radical polymerization initiator (C)) 2,4,6-Trimethylbenzoyldiphenylphosphine oxide (Omnirad TPO₄H, manufactured by IGM Resins)

[0180] (others) Solvent: Ethyl acetate Silane coupling agent: 3-Glycidoxypropyltrimethoxysilane (Shin-Etsu Silicone Co., Ltd., KBM-403) Rust inhibitor: 1,2,3-triazole

[0181] In the examples and comparative examples, adhesive sheets were prepared by the following method. A tack resin composition was prepared by uniformly mixing 200 parts by mass of the above (meth)acrylic polymer (A) solution (dilution solvent: ethyl acetate, solid content concentration: 50% by mass), 25 parts by mass of the above polyfunctional (meth)acrylate (B), 3 parts by mass of the above radical polymerization initiator (C), 0.3 parts by mass of 3-glycidoxypropyltrimethoxysilane (manufactured by Shin-Etsu Silicone Co., Ltd., KBM-403), which is a silane coupling agent, 0.3 parts by mass of 1,2,3-triazole, which is a rust inhibitor, and 101 parts by mass of ethyl acetate. A sheet of adhesive composition was applied to a 100 μm thick release film (Mitsubishi Chemical's Diafoil MRV (V04)) that had been treated with silicone release agent, so that the thickness of the adhesive composition after solvent drying was 150 μm.

[0182] Next, the sheet-like adhesive composition, along with the release film, was placed in a dryer heated to 95°C and held for 10 minutes to allow the solvent contained in the adhesive composition to evaporate. Furthermore, a 75 μm thick release film (Diafoil MRQ, manufactured by Mitsubishi Chemical Corporation), which has been treated with a silicone release agent, is laminated onto the sheet-like adhesive composition from which the solvent has been evaporated to form a laminate. Using a high-pressure mercury lamp, the adhesive composition is irradiated through the release film with an integrated dose of 1000 mJ / cm² at a wavelength of 365 nm. 2 The cumulative irradiation dose at a wavelength of 405 nm was 1400 mJ / cm². 2 Light irradiation was performed to obtain a release film-coated adhesive sheet (adhesive sheet thickness: 150 μm) with release films laminated on both the front and back sides.

[0183] [Resin layer (Y)] (Biaxially oriented polyester film (Y1) (containing UV absorber)) Raw materials C and E were mixed in a mass ratio of 92:8 as the raw material for the surface layer, and raw materials C, D, and F were mixed in a mass ratio of 25:69:6 as the raw material for the intermediate layer. The mixed raw materials for the surface layer and the intermediate layer were each fed into separate twin-screw extruders, co-extruded at 280°C, and then cooled and solidified on cooling rolls set to 25°C to obtain two types of three-layer (surface layer / intermediate layer / surface layer) unstretched laminated sheets. Next, the obtained unstretched laminated sheet was stretched 3.3 times in the longitudinal direction (MD) at 85°C using a roll stretcher. Furthermore, after preheating in a tenter at 80°C, it was stretched 3.6 times in the width direction (TD) at 110°C. Finally, it was heat-treated at 200°C to obtain a biaxially oriented polyester film (Y1) with a thickness of 50 μm (each surface layer: 2.5 μm, intermediate layer: 45 μm).

[0184] (Biaxially oriented polyester film (Y2) (without UV absorber)) Raw materials C and E were mixed in a mass ratio of 91:9 as the raw material for the surface layer, and raw materials C and D were mixed in a mass ratio of 61:39 as the raw material for the intermediate layer. The mixed raw materials for the surface layer and the intermediate layer were each fed into separate twin-screw extruders, co-extruded at 280°C, and then cooled and solidified on cooling rolls set to 25°C to obtain two types of three-layer (surface layer / intermediate layer / surface layer) unstretched laminated sheets. Next, the obtained unstretched laminated sheet was stretched 3.5 times in the longitudinal direction (MD) at 85°C using a roll stretcher. Furthermore, after preheating in a tenter at 80°C, it was stretched 4.6 times in the width direction (TD) at 124°C. Finally, it was heat-treated at 237°C to obtain a biaxially oriented polyester film (Y2) with a thickness of 50 μm (each surface layer: 2.5 μm, intermediate layer: 45 μm).

[0185] [Polyester layer (X)] Raw materials A and B were mixed in a mass ratio of 60:40, fed into a twin-screw extruder, extruded at 280°C, and then cooled and solidified on a cooling roll set to 50°C to obtain an unstretched sheet. Next, the obtained unstretched sheet was stretched 3.0 times in the longitudinal direction (MD) at 100°C using a roll stretcher. Furthermore, after preheating in a tenter at 100°C, it was stretched 4.5 times in the width direction (TD) at 110°C. Finally, it was heat-treated at 200°C to obtain a biaxially oriented polyester film (polyester layer (X)) with a thickness of 125 μm. The properties of the obtained polyester layer (X) were evaluated using the method described above. The evaluation results are shown in Table 2.

[0186] In the production of the polyester layer (X) described above, after stretching in the longitudinal direction (MD) and before stretching in the width direction (TD), a coating solution of the resin composition that forms the cured resin layer described above was applied to both sides of the uniaxially oriented polyester film so that the film thickness (after drying) was 0.04 μm. Then, by performing stretching and heat treatment in the width direction under the conditions described above, a polyester film with a cured resin layer was obtained, in which a cured resin layer (CFA) with a film thickness (after drying) of 0.04 μm, the polyester layer (X), and a cured resin layer (CFB) with a film thickness (after drying) of 0.04 μm were laminated in that order. The properties of the resulting polyester film with a cured resin layer were evaluated using the method described above. The evaluation results are shown in Table 3.

[0187] (Example 1) The 75 μm thick release film (MRQ75) was peeled off from the prepared adhesive sheet with release film, and the cured resin layer (CFA) side of the polyester film with cured resin layer, prepared as described above, was bonded to the adhesive sheet.

[0188] Furthermore, after peeling off a 100 μm thick release film (MRV100(V04)) from the adhesive sheet laminated on the polyester layer (X), the biaxially oriented polyester film (Y1) described above was laminated to the exposed adhesive layer surface to obtain a film laminate. The properties of the obtained film laminate were evaluated using the method described above. The evaluation results are shown in Table 3.

[0189] (Comparative Example 1) A film laminate was obtained by manufacturing in the same manner as in Example 1, except that the biaxially oriented polyester film (Y1) used in Example 1 was replaced with a biaxially oriented polyester film (Y2). The properties of the obtained film laminate were evaluated using the method described above. The evaluation results are shown in Table 3 below.

[0190] [Table 2]

[0191] The manufacturing methods for the reference examples in Table 2 are shown below. First, raw material C was fed into a twin-screw extruder, extruded at 280°C, and then cooled and solidified on a cooling roll set to 20°C to obtain an unstretched sheet. Next, the obtained unstretched sheet was stretched 3.2 times in the longitudinal direction (MD) at 85°C using a roll stretcher. Furthermore, after preheating in a tenter at 110°C, it was stretched 4.3 times in the width direction (TD) at 140°C. Finally, it was heat-treated at 240°C to obtain a biaxially oriented polyester film with a thickness of 125 μm.

[0192] [Table 3]

[0193] Note that the 0.17 / 0.17 in Table 3 refers to the amount of oligomer precipitated on one side (cured resin layer (CFA) surface) being 0.17 mg / m². 2 The amount of oligomer precipitated on the other side (the surface of the hardened resin layer (CFB)) was 0.17 mg / m². 2 It means that.

[0194] The results from Example 1 and Comparative Example 1 show that the film laminate of the present invention has good ultraviolet absorption performance due to its low light transmittance at 380 nm, and also has a low haze value and high transparency. Furthermore, since the hysteresis loss rate of the film laminate of the present invention is 55% or less in both the longitudinal direction (MD) and the width direction (TD), it can be seen that the film has great resilience and excellent bending resistance. Furthermore, the polyester layer (X) used as a constituent member of the film laminate of the present invention is a polyester film with high versatility, and since low dielectric properties, particularly low dielectric tangent properties, have been achieved, the film laminate of the present invention can be expected to have the potential as a low dielectric property film. Also, in the laminate (polyester film with a cured resin layer) laminated in the order of the cured resin layer (CFA), the polyester layer (X), and the cured resin layer (CFB), the amount of oligomer (mainly the cyclic trimer derived from the polyester layer (X)) deposited from the surface of the cured resin layer is low. Therefore, the film laminate of the present invention can prevent the deterioration of visibility associated with the deposition of the oligomer.

[0195] As described above, the film laminate of the present invention has excellent low dielectric properties and transparency, has a low risk of foreign matter adhesion due to oligomer deposition or the like, has good visibility, and can be used outdoors. Therefore, it is suitable as a member for a transparent antenna.

Industrial Applicability

[0196] The film laminate of the present invention has excellent low dielectric properties and transparency, and also has excellent ultraviolet absorption performance. Therefore, it is very useful as a member for a transparent antenna among high-speed communication circuit applications.

Claims

1. It comprises a polyester layer (X) and a polyester layer (Y) containing a UV absorber, The light transmittance at a wavelength of 380 nm is 25% or less. The polyester layer (X) contains polybutylene naphthalate and polyethylene naphthalate, and the dielectric loss tangent at 28 GHz is less than 0.0050, in a film laminate for high-speed communication circuits.

2. The film laminate for high-speed communication circuits according to claim 1, wherein the polyester layer (X) contains 5 to 70% by mass of the polybutylene naphthalate.

3. The film laminate for high-speed communication circuits according to claim 1 or 2, wherein the relative permittivity of the polyester layer (X) at 28 GHz is 3.5 or less.

4. The film laminate for high-speed communication circuits according to claim 1 or 2, wherein the polyester layer (X) further comprises a crystalline polyester.

5. The polyethylene naphthalate is such that, of the total dicarboxylic acid components, the acid component having a benzene skeleton as a copolymer component other than 2,6-naphthalenedicarboxylic acid is 5 mol% or less, as described in claim 1 or 2, for the film laminate for high-speed communication circuits.

6. The film laminate for high-speed communication circuits according to claim 1 or 2, wherein the thickness of the polyester layer (X) is 9 to 300 μm.

7. The film laminate for high-speed communication circuits according to claim 1 or 2, further comprising an adhesive layer between the polyester layer (X) and the polyester layer (Y) containing the ultraviolet absorber.

8. The film laminate for high-speed communication circuits according to claim 7, wherein the relative dielectric constant of the adhesive layer is 3.9 or less.

9. The film laminate for high-speed communication circuits according to claim 7, wherein the thickness of the adhesive layer is 1 to 200 μm.

10. The film laminate for high-speed communication circuits according to claim 1 or 2, wherein the polyester layer (X) has a cured resin layer (CFB) on at least one side.

11. The film laminate for high-speed communication circuits according to claim 10, further comprising a metal layer on the cured resin layer (CFB).

12. The film laminate for high-speed communication circuits according to claim 11, wherein the metal layer is patterned.

13. The film laminate for high-speed communication circuits according to claim 11, wherein the metal layer is made of copper or silver.

14. The film laminate for high-speed communication circuits according to claim 10, wherein the polyester layer (X) has a cured resin layer (CFA) on the side opposite to the side on which the cured resin layer (CFB) is laminated.

15. The film laminate for high-speed communication circuits according to claim 14, wherein at least one of the cured resin layer (CFA) and the cured resin layer (CFB) is formed from a resin composition containing a crosslinking agent in an amount of 70% by mass or more relative to the nonvolatile components.

16. The film laminate for high-speed communication circuits according to claim 1 or 2, wherein the thickness of the polyester layer (Y) containing the ultraviolet absorber is 9 to 300 μm.

17. The high-speed communication circuit film laminate according to claim 1 or 2, wherein the hysteresis loss rate when subjected to a tensile cycle test up to 5% tensile strain in both the longitudinal direction (MD) and the width direction (TD) is 55% or less.

18. A film laminate for a high-speed communication circuit according to claim 1 or 2, wherein the haze is 4.0% or less.

19. A film laminate for high-speed communication circuits according to claim 1 or 2, wherein the total thickness is 19 to 800 μm.

20. A film laminate for a high-speed communication circuit according to claim 1 or 2, which is for use as a transparent antenna.

21. A film laminate for a high-speed communication circuit according to claim 20, which is for use as an outdoor transparent antenna.

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