Polyester film roll

Abstract

To provide a polyester film roll which has high smoothness, has good scratch prevention property and can cope with a long size.SOLUTION: A polyester film roll is formed by winding a film having a cured resin layer and a polyester film in this order, wherein the cured resin layer is a cured product of a cured resin composition containing (A) a crosslinking agent and (B) a binder resin, and simultaneously satisfies the following (1) to (3). (1) An average surface roughness (Sa) of the surface of the curable resin layer of 1-5 nm. (2) A maximum peak height (Sp) of the surface of the cured resin layer of 43 nm or less. (3) The relation between surface hardness X (MPa) of a surface on a side contacting the cured resin layer of the polyester film and surface harness Y (MPa) of the cured resin layer by nanoindenter measurement satisfying X-130≤Y≤X+50.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a polyester film roll suitable as a support for a process release film used in the manufacturing process of a multilayer ceramic capacitor. [Background technology]

[0002] In recent years, with the increasing use of electronics in automobiles and the increasing functionality of smartphones, multi-layered ceramic capacitors (MLCCs) have become increasingly smaller and have higher capacitance. The multilayer ceramic capacitor is manufactured as follows. First, a ceramic slurry containing ceramic components and a binder resin is applied to a release film and dried to produce a ceramic green sheet (dielectric sheet), which is then printed with electrodes by screen printing or other methods to form internal electrodes. After drying, the printed ceramic green sheet is peeled off from the release film and multiple such green sheets are stacked. The stacked green sheets are pressed together and then cut into individual chips. Thereafter, the internal electrodes and dielectric layers are sintered in a firing furnace to produce a multilayer ceramic capacitor.

[0003] As MLCCs become smaller and have higher capacities, ceramic green sheets are becoming thinner. When ceramic green sheets are further thinned to 0.5 μm (thickness after drying) or less, any minute protrusions on the surface of the release film used as a carrier film can cause pinholes or other defects in the ceramic green sheets. For this reason, the release film is required to have an even higher level of surface smoothness.

[0004] Conventionally, as a support for this type of release film, Patent Document 1 discloses a release film for producing a green sheet, which comprises a substrate having a first surface and a second surface, a smoothing layer provided on the first surface side of the substrate, and a release agent layer provided on the surface of the smoothing layer opposite the substrate, wherein the smoothing layer is formed by heating and curing a composition for forming a smoothing layer that contains a thermosetting compound having a mass average molecular weight of 950 or less, and wherein the arithmetic mean roughness Ra1 of the outer surface of the release agent layer is 8 nm or less and the maximum peak height Rp1 of the outer surface of the release agent layer is 50 nm or less.

[0005] Patent Document 2 also describes a polyester film for release that has excellent surface smoothness and particularly few fine defects on the film surface, with the number of depression defects of 0.5 μm or more in depth being 5 / m 2 and a release polyester film having a center line average roughness SRa of 15 to 35 nm and a ten-point average roughness SRz of 1000 nm or less on at least one surface thereof.

[0006] As green sheets become thinner, higher lamination accuracy is required when laminating thin green sheets into multiple layers. As a result, the flatness of release films is becoming increasingly important, and efforts are being made to control heat wrinkles, etc.

[0007] As an example of this type of film, Patent Document 3 describes a polyester film roll obtained by winding a polyester film, in which slack defects present in the polyester film are removed within 100 m. 2 No. 5,000,000 per roll of polyester film is disclosed. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-177093 [Patent Document 2] Japanese Patent Application Laid-Open No. 2013-7054 [Patent Document 3] Japanese Patent Application Laid-Open No. 2002-273719 Summary of the Invention [Problem to be solved by the invention]

[0009] As ceramic green sheets become thinner (for example, sheet thickness (after drying) is about 0.5 μm to 1.5 μm), the dielectric layer is required to have higher smoothness. Furthermore, as polyester films become more smooth, the frequency of scratches on the film surface tends to increase during the manufacturing process as the production speed is increased or the film winding length is lengthened to improve productivity.

[0010] Therefore, an object of the present invention is to provide a polyester film roll that has high smoothness, good scratch resistance, and can be made into a long length. [Means for solving the problem]

[0011] In view of the above circumstances, the present inventors have conducted extensive research and found that the above problems can be easily solved by using a polyester film roll having a specific configuration, and have thus completed the present invention. That is, the present invention provides the following items [1] to

[14] . [1] A polyester film roll obtained by winding up a film having a cured resin layer and a polyester film in this order, wherein the cured resin layer is a cured product of a cured resin layer composition containing (A) a crosslinking agent and (B) a binder resin, and the polyester film roll simultaneously satisfies the following (1) to (3): (1) The average surface roughness (Sa) of the cured resin layer surface is 1 to 5 nm. (2) The maximum peak height (Sp) of the surface of the cured resin layer is 43 nm or less. (3) The relationship between the surface hardness X (MPa) of the polyester film surface in contact with the cured resin layer and the surface hardness Y (MPa) of the cured resin layer, as measured with a nanoindenter, satisfies X-130≦Y≦X+50. [2] The polyester film roll according to [1], wherein the thickness of the cured resin layer is 150 to 350 nm. [3] The polyester film roll according to [1] or [2], wherein the content of the crosslinking agent in the cured resin layer composition is 20 to 80 mass % based on the total non-volatile components in the cured resin layer composition. [4] The polyester film roll according to any one of [1] to [3], wherein the polyester film is a polyester film having at least three layers, and the cured resin layer is in contact with the surface layer A of the polyester film. [5] The polyester film roll according to any one of [1] to [4], wherein the polyester film is a three-layer polyester film, and the cured resin layer is in contact with the surface layer A of the polyester film. [6] The polyester film roll according to [5], wherein the intermediate layer B of the polyester film contains particles. [7] The polyester film roll according to [6], wherein the particle content of the intermediate layer B is 0.5% by mass or less. [8] The polyester film roll according to any one of [4] to [7], wherein the polyester constituting the surface layer A has an intrinsic viscosity (IV) of 0.50 dL / g or more. [9] The polyester film roll according to any one of [4] to [8], wherein the surface layer A contains a titanium compound.

[10] The polyester film roll according to any one of [4] to [9], wherein the surface layer A contains an antimony compound and / or a titanium compound, and the content of the antimony compound is 100 ppm or less.

[11] The polyester film roll according to any one of [3] to

[10] , wherein the surface layer A is substantially free of particles.

[12] The polyester film roll according to any one of [1] to

[11] , which has a release layer on the cured resin layer.

[13] The polyester film roll according to any one of [1] to

[12] , which is used as a support for a ceramic green sheet in a process for producing a multilayer ceramic capacitor.

[14] The polyester film roll according to any one of [1] to

[13] , which is used as a support for a ceramic green sheet in a process for producing a multilayer ceramic capacitor for an automobile. [Effects of the Invention]

[0012] The polyester film roll of the present invention has extremely excellent surface smoothness, and therefore has the advantage that when the film is used as a support for a ceramic green sheet in, for example, a production process for a multilayer ceramic capacitor, there is little risk of defects in the ceramic green sheet due to fine irregularities on the film surface.

[0013] Furthermore, the polyester film roll of the present invention has excellent surface smoothness and excellent scratch resistance. Therefore, when used as a support for a ceramic green sheet in the manufacturing process of a multilayer ceramic capacitor, for example, the ceramic slurry can be uniformly applied, resulting in the formation of a uniform dielectric layer. Furthermore, as the polyester film roll lengthens, the frequency of film roll replacement decreases, contributing to improved productivity. Furthermore, when the polyester film roll of the present invention has a release layer, the cured resin layer exhibits excellent adhesion to the release layer, making it suitable for situations where durability of the release layer is required (e.g., repeated use of a release film). In particular, the polyester film roll is suitable as a support for a ceramic green sheet used in an automotive multilayer ceramic capacitor. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, the present invention will be described in detail. In this specification, the term "A to B" regarding the description of numerical values means "A or more and B or less" (when A < B) or "A or less and B or more" (when A > B). Also, in the present invention, a combination of preferred embodiments is a more preferred embodiment.

[0015] <Polyester film roll> The polyester film roll of the present invention is a polyester film roll formed by winding a film having a cured resin layer and a polyester film in this order, wherein the cured resin layer is a cured product of a cured resin layer composition containing (A) a crosslinking agent and (B) a binder resin, and is characterized by simultaneously satisfying the following (1) to (3). (1) The average surface roughness (Sa) of the surface of the cured resin layer is 1 to 5 nm. (2) The maximum peak height (Sp) of the surface of the cured resin layer is 43 nm or less. (3) The relationship between the surface hardness X (MPa) of the surface of the polyester film on the side in contact with the cured resin layer and the surface hardness Y (MPa) of the cured resin layer measured by nanoindentation satisfies X - 130 ≤ Y ≤ X + 50.

[0016] The polyester film roll of the present invention (hereinafter also referred to as "this roll") is a polyester film roll formed by winding a film (hereinafter also referred to as "this film") having a cured resin layer and a polyester film in this order. This roll is a polyester film roll wound around a core such as a paper tube, a metal tube, or a plastic tube, and preferably has a width of 0.2 m or more, more preferably 0.3 m or more, particularly preferably 1.0 m or more, and most preferably 1.5 m or more. The upper limit of the width of the polyester film roll is not particularly limited, but is preferably 2.3 m or less, and more preferably 2.0 m or less. Also, the length of this film wound around this roll is not particularly limited, but is preferably 1000 m or more, more preferably 6000 m or more, and still more preferably 12000 m or more.

[0017] The thickness of the present film is preferably 19 μm or more and 38 μm or less, more preferably 25 μm or more and 32 μm or less. A thickness of 38 μm or less allows for further film lengthening within a certain range of roll outer diameter, contributing to improved continuous productivity by reducing switching losses. Furthermore, a thickness of 19 μm or more makes it easier to keep the tensile strength and elongation of the present film within appropriate ranges, ensuring good film running stability during ceramic green sheet processing.

[0018] [Surface properties] (1) Average surface roughness (Sa) of the cured resin layer The average surface roughness (Sa) of the cured resin layer surface of this film must be 1 to 5 nm. If the average surface roughness (Sa) of the cured resin layer surface is greater than 5 nm, the smoothness of the polyester film roll will be insufficient, and defects such as pinholes will be more likely to occur due to fine irregularities. On the other hand, if the average surface roughness (Sa) is less than 1 nm, the film surface will be too flat, resulting in insufficient scratch resistance and making the surface of the polyester film roll and the surface of the ceramic green sheet more susceptible to scratches. The average surface roughness (Sa) of the cured resin layer surface of the present film is preferably 1.5 to 4.5 nm, more preferably 2.0 to 4.0 nm, from the viewpoints of improving smoothness, suppressing pinholes, and improving scratch resistance. In the present invention, the average surface roughness (Sa) of the cured resin layer surface can be adjusted, for example, by adjusting the blending ratio of (A) the crosslinking agent and (B) the binder resin, which will be described later.

[0019] In this specification, the average surface roughness (Sa) is one of the surface roughness parameters (ISO 25178), which is a three-dimensional extension of the two-dimensional Ra, and is calculated by dividing the volume enclosed by the surface profile curve and the average surface by the measured area, and is calculated using the following formula (1): When the surface is the XY plane and the height direction is the Z axis, A is the defined area (the entire image), and Z(x,y) is the height of the image point (x,y) from the plane with height 0, it can be expressed as follows.

[0020]

number

[0021] (2) Maximum peak height of the cured resin layer surface (Sp) The maximum peak height (Sp) of the cured resin layer surface of this film must be 43 nm or less. If the maximum peak height (Sp) of the cured resin layer surface exceeds 43 nm, the smoothness of the surface of the polyester film roll will be insufficient, and defects such as pinholes will be more likely to occur due to minute irregularities. The maximum peak height (Sp) of the cured resin layer surface of the present film is preferably 40 nm or less from the viewpoint of improving smoothness and suppressing pinholes. Although there is no particular lower limit for the maximum peak height (Sp) of the cured resin layer surface, from the viewpoint of improving the handleability and scratch resistance of the present film, it is preferably 10 nm or more, more preferably 15 nm or more, and even more preferably 20 nm or more. In the present invention, the maximum peak height (Sp) of the surface of the cured resin layer can be adjusted, for example, by adjusting the blending ratio of (A) the crosslinking agent and (B) the binder resin, which will be described later.

[0022] In this specification, the maximum peak height (Sp) is one of the surface roughness parameters (ISO 25178), and represents the maximum value of the height from the mean plane of the surface, and is expressed by the following formula (2).

[0023]

number

[0024] (3) Relationship between the surface hardness X (MPa) of the polyester layer in contact with the cured resin layer and the surface hardness Y (MPa) of the cured resin layer, measured with a nanoindenter The relationship between the surface hardness X (MPa) of the polyester film surface in contact with the cured resin layer and the surface hardness Y (MPa) of the cured resin layer, as measured with a nanoindenter, must satisfy the following relationship: X-130≦Y≦X+50. If the surface hardness Y (MPa) of the cured resin layer is greater than X+50, the hardness of the cured resin layer is too great, so the uneven structure of the polyester film surface is reflected on the surface of the cured resin layer, making it difficult to smooth the surface of the polyester film roll and making defects such as pinholes more likely to occur due to the fine unevenness. Furthermore, if the surface hardness Y (MPa) of the cured resin layer is less than X-130, the effect of mitigating the impact of particles contained in the polyester film is insufficient, making it difficult to achieve the desired surface roughness. On the other hand, in the present invention, when the film satisfies the relationship X-130≦Y≦X+50, the smoothness of the cured resin layer surface is improved, and it is possible to reduce both the average surface roughness (Sa) and the maximum protrusion roughness (Sp) of the cured resin layer surface. In the present invention, the relationship between the surface hardness X (MPa) and Y (MPa) is preferably X-130≦Y≦X+30, more preferably X-120≦Y≦X+20, and even more preferably X-100≦Y≦X+10. In the present invention, the surface hardness Y (MPa) of the cured resin layer can be adjusted, for example, by adjusting the contents of the (A) crosslinking agent and (B) binder resin, which will be described later.

[0025] [Polyester film] (polyester) The polyester in the polyester film roll of the present invention refers to a polyester that is a raw material for polyester films, etc., and refers to a polymer compound having continuous ester bonds in the main chain. In the present invention, the polyester may be a homopolyester or a copolymer polyester, and specific examples include polyesters obtained by polycondensation reaction of a dicarboxylic acid component and a diol component.

[0026] In the present invention, it is preferable to use a polyester containing more than 50% of an aromatic dicarboxylic acid or an aliphatic dicarboxylic acid when the dicarboxylic acid component is taken as 100 mol %.

[0027] Examples of the dicarboxylic acid component include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, 4,4'-diphenyletherdicarboxylic acid, and 4,4'-diphenylsulfonedicarboxylic acid, and aliphatic dicarboxylic acids such as adipic acid, suberic acid, sebacic acid, dimer acid, dodecanedioic acid, cyclohexanedicarboxylic acid, and ester derivatives thereof.

[0028] Examples of the diol component include ethylene glycol, 1,2-propanediol, 1,3-propanediol, neopentyl glycol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-hexanedimethanol, diethylene glycol, triethylene glycol, polyalkylene glycol, 2,2-bis(4-hydroxyethoxyphenyl)propane, isosorbate, and spiroglycol.

[0029] When the polyester is a homopolyester, it is preferably one obtained by polycondensing an aromatic dicarboxylic acid with an aliphatic glycol. Examples of the aromatic dicarboxylic acid include terephthalic acid and 2,6-naphthalenedicarboxylic acid, and examples of the aliphatic glycol include ethylene glycol, diethylene glycol, and 1,4-cyclohexanedimethanol. Typical examples of polyester include polyethylene terephthalate (PET) and polyethylene-2,6-naphthalenedicarboxylate (PEN).

[0030] On the other hand, when the polyester is a copolymer polyester, it is preferably a copolymer containing 30 mol % or less of a third component. The third component is a component other than the compound that is the main component of the dicarboxylic acid component constituting the polyester and the compound that is the main component of the diol component, and in the case of polyethylene terephthalate, it is a component other than terephthalic acid and ethylene glycol. Examples of the dicarboxylic acid component of the copolymer polyester include one or more of isophthalic acid, terephthalic acid phthalate, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, and oxycarboxylic acid. Examples of the glycol component of the copolymer polyester include one or more of ethylene glycol, diethylene glycol, propylene glycol, butanediol, 1,4-cyclohexanedimethanol, neopentyl glycol, and the like.

[0031] The polyester is preferably polyethylene terephthalate, in which 80 mol % or more, preferably 90 mol % or more, is an ethylene terephthalate unit, or polyethylene-2,6-naphthalate, in which 80 mol % or more, preferably 90 mol % or more, is an ethylene-2,6-naphthalate unit.

[0032] (Polyester polycondensation catalyst) Examples of polycondensation catalysts used in polycondensing the polyester include antimony compounds, germanium compounds, aluminum compounds, titanium compounds, etc. Among these, at least one of antimony compounds and titanium compounds is preferred, and it is particularly preferred to use a polyester obtained using a titanium compound. Therefore, the polyester film preferably contains at least one of an antimony compound and a titanium compound, and more preferably contains a titanium compound. By using the titanium compound, the number of metal-containing aggregates, so-called coarse foreign matter, derived from the titanium compound in the film can be reduced, and a film with high surface smoothness, particularly a small maximum peak height (Sp) on at least one side, can be obtained.

[0033] The polyester constituting the outermost layer of the polyester film (also called the "surface layer", for example, surface layer A on which a cured resin layer is laminated) preferably uses a titanium compound as its polycondensation catalyst. The content of titanium element derived from the titanium compound in the outermost layer is preferably 3 ppm or more and 40 ppm or less, and more preferably 4 ppm or more and 35 ppm or less. Within the above range, the amount of catalyst-induced foreign matter can be reduced without reducing the production efficiency of polyester. From the viewpoint of productivity, it is preferable that the polyester constituting the intermediate layer (intermediate layer B described below) does not use a titanium compound as a polycondensation catalyst. From the same viewpoint, the content of antimony compounds in the outermost layer of the present film is preferably 100 ppm or less. For example, the surface layer A described below contains at least one of an antimony compound and a titanium compound, and the content of the antimony compound in the surface layer A is preferably 100 ppm or less. In this case, the surface layer A does not necessarily contain the antimony compound.

[0034] (Intrinsic viscosity (IV) of polyester) The intrinsic viscosity (IV) of the polyester constituting the polyester film is preferably 0.50 dL / g or more, more preferably 0.55 dL / g or more, and even more preferably 0.60 dL / g or more. When a polyester having an intrinsic viscosity (IV) of 0.50 dL / g or more is used as the resin constituting the polyester film, there are advantages such as high particle dispersion due to increased shear stress during kneading.

[0035] In addition, when two or more polyesters having different intrinsic viscosities (IV) are used, the "intrinsic viscosity (IV) of the polyester constituting the polyester film" means the intrinsic viscosity (IV) of the mixed resins.

[0036] From the above viewpoint, particularly when the polyester film has a laminate structure, the intrinsic viscosity (IV) of the polyester constituting the surface layer, specifically the outermost layer of the present film (for example, surface layer A on which the cured resin layer is laminated) is preferably 0.50 dL / g or more, more preferably 0.55 dL / g or more, and even more preferably 0.60 dL / g or more. The intrinsic viscosity (IV) of the polyester is, for example, 1.00 dL / g or less.

[0037] (Polyester film composition) The polyester film in the polyester roll of the present invention may have either a single layer or a laminate structure having two or more layers (laminated film), but preferably has a laminate structure having three or more layers.

[0038] (particle) The polyester film preferably has a surface layer C containing particles on at least one surface. By adopting such a configuration, the handleability of the film can be improved. Alternatively, the film may have a surface layer A on one surface and a surface layer C (described later) on the other surface. The surface layer A may contain particles or may be substantially free of particles, but from the viewpoints of making the ceramic layer thinner and suppressing pinholes, it is preferable that the surface layer A be substantially free of particles. Furthermore, the intermediate layer of the polyester film (for example, intermediate layer B described below) may contain particles or may be substantially free of particles, but it is preferable that it contains particles from the viewpoint of improving the mechanical properties of the polyester film, such as tensile strength and elongation.

[0039] Examples of the particles include inorganic particles such as silica, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, calcium phosphate, magnesium phosphate, kaolin, aluminum oxide, and titanium oxide, as well as organic particles such as crosslinked polymers such as crosslinked silicone resin particles, crosslinked acrylic resin particles, crosslinked styrene-acrylic resin particles, and crosslinked polyester particles, calcium oxalate, and ion exchange resins. Of these, organic particles, silica, aluminum oxide, and the like are preferred. In addition, from the viewpoint of improving recyclability, the particles are more preferably particles derived from recycled polyester raw materials.

[0040] (Polyester film laminate structure) When the polyester film has a laminated structure having two or more layers, a three-layer structure such as A / B / C consisting of an intermediate layer B and a surface layer A and a surface layer C, or A / B / A consisting of an intermediate layer B and a surface layer A, is preferred, but a three-layer structure such as A / B / C may also be used. In the polyester roll of the present invention, the polyester film is preferably a polyester film having at least three layers, more preferably a polyester film having a three-layer structure. In the polyester roll of the present invention, the cured resin layer is preferably in contact with the surface layer A of the polyester film.

[0041] The surface of the polyester film that comes into contact with the cured resin layer (surface layer A) may contain particles or may be substantially free of particles, but from the viewpoint of making the ceramic layer thinner and suppressing pinholes, it is preferable that it be substantially free of particles. "Substantially not contained" means not intentionally contained, and specifically means that the particle content (particle concentration) is preferably 0.02% by mass or less, more preferably 0.015% by mass or less, and even more preferably 0.01% by mass or less.

[0042] Furthermore, it is preferable that the surface layer A is equal to or smaller than the surface layer C in both average surface roughness (Sa) and maximum peak height (Sp).

[0043] In the above-mentioned A / B / C laminated structure, the surface layer C preferably has an average surface roughness (Sa) of 5 nm or more or a maximum peak height (Sp) of 220 nm or less. In this case, the average surface roughness (Sa) may be approximately 20 nm or less. By adopting such a laminated structure, the surface layer C can be provided with the rough surface necessary for improving handling, and the surface layer A can be provided with the smoothness necessary for providing a thin ceramic layer. From the above viewpoints, the average surface roughness (Sa) of the surface layer A must be 1 nm or more and 5 nm or less, more preferably 1 nm or more and 4 nm or less, and the maximum peak height (Sp) must be 43 nm or less, preferably 40 nm or less.

[0044] In the above three-layer structure of A / B / C, the surface layer C preferably contains particles to ensure ease of handling.

[0045] In the above-mentioned three-layer structure of A / B / C, it is particularly preferable that the surface layer C contains particles having a narrow particle size distribution and a substantially uniform average particle size (so-called monodispersity).

[0046] As the particles having a narrow particle size distribution and a substantially uniform average particle size, when the particle size distribution of the particles is such that D10 is the particle size at which the cumulative number is 10%, D50 is the particle size at which the cumulative number is 50%, and D90 is the particle size at which the cumulative number is 90%, the ratio (D90-D10) / D50 is preferably 0.4 or less, and particularly preferably 0.2 or less. The relationship (D90-D10) / D50 indicates the variation in particle size based on D50, and particles with a (D90-D10) / D50 of 0.4 or less have a sharp particle size distribution with a small difference between D90 and D10, and can impart extremely high smoothness to the present film while maintaining excellent handleability. The particle size distribution of the particles is measured by a laser diffraction measuring device.

[0047] The average particle size of the particles is preferably 0.05 to 0.8 μm, more preferably 0.1 to 0.6 μm, and even more preferably 0.1 to 0.5 μm, from the viewpoint of improving handleability and suppressing pinholes, while keeping the average surface roughness (Sa) and maximum peak height (Sp) within desired ranges. The average particle size of the particles contained in the surface layer C is preferably 0.05 to 0.8 μm, more preferably 0.1 to 0.6 μm, and even more preferably 0.1 to 0.5 μm, from the viewpoint of improving handleability and suppressing pinholes, while keeping the average surface roughness (Sa) and maximum peak height (Sp) within the desired ranges.

[0048] The average particle size of particles can be determined by measuring the diameters of 10 or more particles using a scanning electron microscope (SEM) and taking the average value. In this case, for non-spherical particles, the average value of the longest and shortest diameters can be measured as the diameter of each particle.

[0049] The content of the particles in the surface layer C is preferably 0.5% by mass or less, more preferably 0.2% by mass or more and 0.4% by mass or less, in terms of mass percentage. When the content of the particles in the surface layer C is within the above range, the surface layer C can be provided with a rough surface necessary for improving handleability.

[0050] The intermediate layer B preferably functions as the thickest main layer. The intermediate layer B preferably contains the particles, which can improve the mechanical properties of the polyester film, such as tensile strength and elongation. The particle content of the intermediate layer B is preferably 0.5% by mass or less, more preferably 0.1% by mass or less, and even more preferably 0.05% by mass or less. By having the particle content of the intermediate layer B be 0.5% by mass or less, the surface roughness of the polyester film surface is prevented from increasing, and the average surface roughness (Sa) of the cured resin layer surface can be easily adjusted to a desired range. Furthermore, the lower limit of the particle content of the intermediate layer B is preferably 0.01% by mass or more, from the viewpoint of improving mechanical properties such as tensile strength and elongation. The average particle size of the particles contained in the intermediate layer B is preferably 0.05 to 1.2 μm, more preferably 0.1 to 1.0 μm, and even more preferably 0.15 to 0.8 μm, from the viewpoint of improving the dispersibility of the particles in the intermediate layer B.

[0051] As described above, surface layer A is a layer different from surface layer C. Specifically, examples include a form in which the type of particles, average particle size, and blending amount are different, as well as a form in which the layer thickness is different.

[0052] Furthermore, a configuration including the surface layer A and / or the surface layer C shown in the following (X) and (Y) is particularly preferred. By adopting such a configuration, the present film can have excellent handling properties and surface smoothness.

[0053] (X) Particularly preferred embodiment 1 (1) In the A / B / C structure, the surface layer C contains particles and a titanium compound, and the surface layer A does not substantially contain particles. (2) In the above (1), the surface layer C contains inorganic particles having an average particle size of at least 0.1 to 0.8 μm. (3) In any one of (1) to (2), the surface layer C contains an antimony compound and / or a titanium compound, and the content of the antimony compound is 100 ppm or less. (4) In any one of (1) to (3), the particle diameter at which the cumulative number of particles reaches 10% is D10, the particle diameter at which the cumulative number reaches 50% is D50, and the particle diameter at which the cumulative number reaches 90% is D90, where D90 is the particle diameter at which the cumulative number reaches 90%. The particle diameter (D90-D10) / D50 is 0.4 or less. (5) In the above (4), the particles are silica particles.

[0054] In the above (X), by using polyester polycondensed using a titanium compound as a catalyst in each of the surface layer A and the surface layer C, it is possible to reduce catalyst-induced foreign matter and provide high surface smoothness.

[0055] (Y) Particularly preferred embodiment 2 (1) In the A / B / A structure, the surface layer A does not substantially contain particles. (2) In the above (1), the surface layer A contains an antimony compound and / or a titanium compound, and the content of the antimony compound is 100 ppm or less. (3) In the above (1) or (2), the intrinsic viscosity (IV) of the polyester constituting the surface layer A is 0.50 dL / g or more, preferably 0.55 dL / g or more, more preferably 0.60 or more.

[0056] In the above (Y), the surface layer A is substantially free of particles, and a polyester film having high surface smoothness, particularly a small maximum peak height (Sp) on at least one surface, can be obtained.

[0057] (Production method of polyester film) An example of a method for producing a polyester film in the polyester roll of the present invention will be described below. First, using a known method, raw materials, such as polyester chips, are fed into a melt extrusion device, heated above the melting point of each polymer, the molten polymer is extruded through a die, and cooled and solidified on a rotating cooling drum to a temperature below the glass transition point of the polymer, thereby obtaining an unoriented sheet in a substantially amorphous state.

[0058] Next, the unoriented sheet is stretched in one direction using a roll or tenter type stretching machine, at a stretching temperature of usually 25 to 120°C, preferably 35 to 100°C, and at a stretching ratio of usually 2.5 to 7 times, preferably 2.8 to 6 times.

[0059] Next, the film is stretched in a direction perpendicular to the first-stage stretching direction, at a stretching temperature of usually 50 to 140° C. and a stretching ratio of usually 3.0 to 7 times, preferably 4.5 times or more, and more preferably 4.5 to 5.0 times.

[0060] Subsequently, the polyester film is heat-set at a temperature of 180 to 220°C under tension or relaxation of 30% or less to obtain the present copolymerized polyester film as a biaxially oriented film. This heat-set may be performed in two or more steps at different temperatures. After the heat setting treatment, the film may be cooled in a cooling zone. The cooling temperature is preferably higher than the glass transition temperature (Tg) of the polyester resin constituting the film, and more specifically, preferably in the range of 100 to 160° C. This cooling may be performed in two or more steps at different temperatures. In the above-mentioned stretching, a method of performing unidirectional stretching in two or more stages can also be employed.

[0061] [Cured resin layer] <Cured resin layer composition> The present film is provided with a cured resin layer on at least one surface of a polyester film, and the cured resin layer must be a cured product of a cured resin layer composition containing (A) a crosslinking agent and (B) a binder resin, as described below. The present film has a cured resin layer as described above, which allows the cured resin layer to have a highly smooth surface. Furthermore, when the present film has a release layer as described below, the present film can have a highly smooth release layer surface.

[0062] ((A): Crosslinking agent) The cured resin layer composition in the polyester film roll of the present invention contains at least one crosslinking agent to provide surface smoothness (low Sa, low Sp) of the cured resin layer.

[0063] (epoxy compounds) Epoxy compounds are compounds having an epoxy group in the molecule, and examples thereof include condensation products of epichlorohydrin, ethylene glycol, polyethylene glycol, glycerin, polyglycerin, bisphenol A, etc. with a hydroxyl group or an amino group, 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, and examples of glycidylamine compounds include N,N,N',N'-tetraglycidyl-m-xylylenediamine and 1,3-bis(N,N-diglycidylamino)cyclohexane. From the viewpoint of improving adhesion, polyether-based epoxy compounds are preferred. Furthermore, in terms of the number of epoxy groups, polyepoxy compounds with trifunctional or higher functionality are preferred over bifunctional ones.

[0064] (Carbodiimide compounds) A carbodiimide compound is a compound having a carbodiimide structure, and is a compound having one or more carbodiimide structures in the molecule. However, in order to achieve surface smoothness (low Sa, low Sp) and better adhesion of the cured resin layer, a polycarbodiimide compound having two or more carbodiimide structures in the molecule is more preferred.

[0065] Carbodiimide compounds can be synthesized by conventionally known techniques, and generally involve the condensation reaction of a diisocyanate compound. The diisocyanate compound is not particularly limited, and either an aromatic or aliphatic diisocyanate can be used. Specific examples include tolylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, phenylene diisocyanate, naphthalene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, cyclohexane diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, dicyclohexyl diisocyanate, and dicyclohexylmethane 4,4'-diisocyanate.

[0066] The content of carbodiimide groups contained in the carbodiimide compound, in terms of carbodiimide equivalent (weight [g] of the carbodiimide compound required to provide 1 mol of carbodiimide groups), is usually in the range of 100 to 1,000, preferably 250 to 800, and more preferably 300 to 700. Use within the above range can facilitate improvement in the durability of the cured resin layer.

[0067] Furthermore, within the scope of the present invention, in order to improve the water solubility or water dispersibility of the polycarbodiimide compound, a surfactant may be added, or a hydrophilic monomer such as a polyalkylene oxide, a quaternary ammonium salt of a dialkylamino alcohol, or a hydroxyalkyl sulfonate may be added.

[0068] (Oxazoline compounds) An oxazoline compound is a compound having an oxazoline group in the molecule. A polymer containing an oxazoline group is particularly preferred. The compound can be prepared by polymerizing an addition-polymerizable oxazoline group-containing monomer alone or with other monomers. Examples of the addition-polymerizable oxazoline group-containing monomer 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. These monomers can be used alone or in combination. Among these, 2-isopropenyl-2-oxazoline is preferred because it is readily available industrially. The other monomer is not limited as long as it is copolymerizable with the addition-polymerizable oxazoline group-containing monomer, and examples thereof include (meth)acrylic acid esters such as alkyl(meth)acrylate (the alkyl group can be methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, 2-ethylhexyl, and cyclohexyl); unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, styrenesulfonic acid, and salts thereof (sodium salt, potassium salt, ammonium salt, tertiary amine salt, etc.); unsaturated nitriles such as acrylonitrile and methacrylonitrile; (meth)acrylamide, N-alkyl(meth)acrylate, N-methyl-N ... Examples of suitable monomers include unsaturated amides such as t)acrylamide and N,N-dialkyl(meth)acrylamide (the alkyl group can be a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a t-butyl group, a 2-ethylhexyl group, a cyclohexyl group, and the like); 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, and one or more of these monomers can be used.From the viewpoint of improving the surface smoothness (low Sa, low Sp) and adhesion 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 1 to 9 mmol / g, even more preferably 3 to 8 mmol / g, and particularly preferably 4 to 6 mmol / g.

[0069] (melamine compounds) The melamine compound refers to a compound having a melamine skeleton within the compound. Examples of such compounds include alkylolated melamine derivatives, compounds obtained by reacting alkylolated melamine derivatives with alcohols to partially or completely etherify them, and mixtures thereof. Suitable alcohols for etherification include methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butanol, and isobutanol. The melamine compound may be a monomer or a dimer or higher polymer, or a mixture thereof. Furthermore, melamine may be partially co-condensed with urea or the like, and a catalyst may be used to increase the reactivity of the melamine compound.

[0070] (Isocyanate compounds) The isocyanate compound refers to a compound having an isocyanate or an isocyanate derivative structure, such as a blocked isocyanate. Examples of the isocyanate include aromatic isocyanates such as tolylene diisocyanate, xylylene diisocyanate, methylene diphenyl 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 isopropylidenedicyclohexyl diisocyanate. Further examples include polymers and derivatives of these isocyanates, such as biuretized products, isocyanurated products, urethodionated products, and carbodiimide-modified products. These may be used alone or in combination. Among the above isocyanates, aliphatic isocyanates or alicyclic isocyanates are more preferred than aromatic isocyanates in order to prevent yellowing due to ultraviolet rays.

[0071] When used in the form of a blocked isocyanate, examples of the blocking agent include bisulfites; phenolic compounds such as phenol, cresol, and ethylphenol; alcohol 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 oxime, acetaldoxime, acetone oxime, methyl ethyl ketone oxime, and cyclohexanone oxime, and these may be used alone or in combination of two or more.

[0072] The isocyanate compound may be used alone or as a mixture or bond with various polymers. In order to improve the dispersibility and crosslinkability of the isocyanate compound, it is preferable to use a mixture or bond with a polyester resin or a urethane resin.

[0073] ((B): Binder resin) The cured resin layer composition in the polyester film roll of the present invention contains a binder resin for the purpose of improving the surface smoothness (low Sa, low Sp) and durability of the cured resin layer. In addition, when the present film has a release layer described below, the cured resin layer composition contains a binder resin, which can improve the adhesion between the cured resin layer and the release layer. As the binder resin, polyester resin is preferred from the viewpoint of improving the adhesion between the cured resin layer and the release layer described below, and improving the surface smoothness (low Sa, low Sp) and durability of the cured resin layer.

[0074] The polyester resin in the binder resin may be composed of, for example, the following acid component and diol component as main constituent components. Examples of the acid component include the following polycarboxylic acids. Examples of the acid component that can be used 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 sulfoisophthalic acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, glutaric acid, and succinic acid; dicarboxylic acids such as trimellitic acid and trimesic acid; tetracarboxylic acids such as pyromellitic acid; acid anhydrides such as trimellitic anhydride and phthalic anhydride; p-hydroxybenzoic acid; monopotassium trimellitic acid; and ester-forming derivatives thereof. Examples of the diol component include the following polyhydric hydroxy compounds, such as ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,3-propanediol, 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, and polytetramethylene oxide glycol. One or more of these compounds may be appropriately selected, and a polyester resin may be synthesized by a conventional polycondensation reaction. The polyester resin may be prepared as a water dispersion, and in this case, a hydrophilic functional group or the like may be appropriately introduced into the polyester resin.

[0075] In the present invention, the glass transition temperature (Tg) of the polyester resin in the binder resin is preferably 0° C. or higher, more preferably 30° C. or higher, and particularly preferably 50° C. or higher. When the Tg of the polyester resin in the binder resin is within the above range, the cured resin layer has excellent solvent resistance when processing the silicone adhesive layer, and also has the advantage that the cured resin layer is less likely to fall off the polyester film when used at room temperature.

[0076] In the present invention, the polyester resin of the binder resin preferably contains, as an acid component, a dicarboxylic acid component having 10 or less carbon atoms, and more preferably a dicarboxylic acid component having 8 or less carbon atoms, from the viewpoint of improving the surface smoothness (low Sa, low Sp) and durability of the cured resin layer, as well as improving adhesion. The dicarboxylic acid component having 10 or less carbon atoms may be used alone, or two or more types may be used in combination. As the dicarboxylic acid component, the carboxylic acids listed above can be suitably used, and it is more preferable to use terephthalic acid, isophthalic acid, or 5-sodium sulfoisophthalic acid.

[0077] From the viewpoint of improving the surface smoothness (low Sa, low Sp) and durability of the cured resin layer, as well as improving adhesion, the polyester resin of the binder resin is preferably a polyester resin containing, as a diol component, ethylene glycol and at least one selected from 1,4-butanediol, diethylene glycol, and triethylene glycol. When the polyester resin contains the above diol component, the mass ratio of the content of ethylene glycol to the content of diol components other than ethylene glycol ([ethylene glycol content] / [content of diol components other than ethylene glycol]) is preferably 40 / 60 to 90 / 10, more preferably 40 / 60 to 80 / 20, and even more preferably 45 / 55 to 75 / 25.

[0078] In the present invention, the binder resin is preferably a polyester resin containing a polycyclic compound as an acid component. By having the polyester resin of the binder resin contain a polycyclic compound as an acid component, the glass transition temperature of the polyester resin can be easily increased and can be adjusted to fall within the above-mentioned glass transition temperature range, thereby making the physical properties of the cured resin layer favorable. As the polycyclic compound, a polycyclic aromatic compound is preferred, a polycyclic aromatic compound having 12 or more carbon atoms is more preferred, and a polycyclic aromatic compound having a naphthalene ring is even more preferred. Furthermore, as the polycyclic aromatic compound, the carboxylic acids listed above can be suitably used, and 2,5-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, and 2,7-naphthalenedicarboxylic acid are preferred, and 2,6-naphthalenedicarboxylic acid is more preferred. The polycyclic compound may be used alone or in combination of two or more. Furthermore, the above-mentioned dicarboxylic acid component having 10 or less carbon atoms may be used in combination with the polycyclic compound.

[0079] ((Meth)acrylic resin) (Meth)acrylic resins are polymers made of polymerizable monomers including acrylic and methacrylic monomers. These may be homopolymers or copolymers, or may be copolymers with polymerizable monomers other than acrylic and methacrylic monomers. (Meth)acrylic polymers are polymers whose constituent units are (meth)acrylic acid or (meth)acrylic acid alkyl esters, and may be copolymers of styrene or a styrene derivative with (meth)acrylic acid or (meth)acrylic acid alkyl esters. Also included are copolymers of these polymers with other polymers (such as polyesters and polyurethanes). For example, these include block copolymers and graft copolymers. That is, the (meth)acrylic resin may be a (meth)acrylic-modified polyester resin or a (meth)acrylic-modified polyurethane resin. Further included are polymers (and in some cases, polymer mixtures) obtained by polymerizing polymerizable monomers in a polyester solution or polyester dispersion. Similarly, included are polymers (and in some cases, polymer mixtures) obtained by polymerizing polymerizable monomers in a polyurethane solution or polyurethane dispersion. Similarly, included are polymers (and in some cases, polymer mixtures) obtained by polymerizing polymerizable monomers in other polymer solutions or dispersions, and these are also referred to as (meth)acrylic-modified polyester resins and (meth)acrylic-modified polyurethane resins in this specification. The above-mentioned polyesters and polyurethanes used in the (meth)acrylic resins can be appropriately selected from the polyesters and polyurethanes exemplified for use in the binder resins described below. The (meth)acrylic resin may contain a hydroxy group or an amino group in order to further improve adhesion to the substrate film.

[0080] The polymerizable monomer is not particularly limited, but particularly representative compounds include various carboxyl group-containing monomers such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, fumaric acid, maleic acid, and citraconic acid, and salts thereof; various hydroxyl group-containing monomers such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, monobutylhydroxyfumarate, and monobutylhydroxyitaconate; methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, lauryl (meth)acrylate, and the like. various nitrogen-containing compounds such as (meth)acrylamide, diacetone acrylamide, N-methylolacrylamide, or (meth)acrylonitrile; various styrene derivatives such as styrene, α-methylstyrene, divinylbenzene, or vinyltoluene; various vinyl esters such as vinyl propionate; various silicon-containing polymerizable monomers such as γ-methacryloxypropyltrimethoxysilane and vinyltrimethoxysilane; phosphorus-containing vinyl monomers; various vinyl halides such as vinyl chloride and vinylidene chloride; and various conjugated dienes such as butadiene.

[0081] (Other binder resins) Within the scope of the present invention, other binder resins may be used in combination in an amount of, for example, 5% by mass or less, preferably 3% by mass or less, based on the non-volatile components in the cured resin layer. Examples of other binder resins include urethane resins.

[0082] (Other ingredients) In forming the cured resin layer, particles may be used in combination for the purpose of improving anti-blocking properties and slip properties, within the scope of the present invention.

[0083] The content of the crosslinking agent in the cured resin layer composition is preferably 20 to 80 mass %, more preferably 25 to 75 mass %, and even more preferably 30 to 70 mass %, based on the total non-volatile components in the cured resin layer composition. When the crosslinking agent content is equal to or less than the upper limit, the strength and transparency of the cured resin layer are good. On the other hand, when the crosslinking agent content is equal to or more than the lower limit, the durability of the coating film is good and the desired adhesion can be obtained.

[0084] The content of the binder resin in the cured resin layer composition is preferably 20 to 80% by mass, more preferably 25 to 75% by mass, and even more preferably 30 to 70% by mass, as a proportion of all non-volatile components in the cured resin layer composition. When the proportion of the binder resin is below the upper limit, the proportions of other components become high, resulting in sufficient adhesion and preventing insufficient coating appearance. On the other hand, when the proportion of the binder resin is above the lower limit, good adhesion is achieved, sufficient film-forming properties can be ensured, and a uniform coating film can be obtained.

[0085] The total content of the crosslinking agent and binder resin in the cured resin layer composition is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and even more preferably 97% by mass or more, and is 100% by mass or less. The blending ratio of the crosslinking agent to the binder resin in the cured resin layer composition, [crosslinking agent] / [binder resin] (mass ratio), is preferably 20 / 80 to 80 / 20, more preferably 30 / 70 to 70 / 30. When the blending ratio [crosslinking agent] / [binder resin] is within the above range, a cured resin layer having good strength and transparency can be obtained, and desired adhesion can also be obtained.

[0086] <Cured resin layer> The cured resin layer according to the present invention is a cured product of the above-mentioned cured resin layer composition. The thickness of the cured resin layer is preferably 150 nm to 500 nm. It is preferably 200 nm to 400 nm, more preferably 250 nm to 400 nm. If the thickness of the cured resin layer is within the above range, the cured resin layer has an appropriate surface elastic modulus, as described above, which can mitigate the influence of the unevenness from the underlying polyester surface layer A. As a result, the smoothness of the cured resin layer surface is improved, and both the average surface roughness (Sa) and the maximum peak height (Sp) can be reduced. In particular, when a polyester film having a cured resin layer has an A / B / C structure, in which the surface layer A in contact with the cured resin layer is substantially particle-free and the intermediate layer B contains particles, the influence of the fine unevenness on the surface of the underlying surface layer A on the formation of unevenness on the cured resin layer surface (for example, the impact from the surface layer A) can be more effectively mitigated.

[0087] The content of the cured resin layer composition in the cured resin layer is preferably 90% by mass or more, more preferably 95% by mass or more, and even more preferably 98% by mass or more, and 100% by mass or less, relative to 100% by mass of the cured resin layer. It can be assumed that unreacted compounds of the various compounds in the cured resin layer composition, reacted compounds, or a mixture thereof are present in the cured resin layer.

[0088] (Method for manufacturing a polyester film roll (method for forming a cured resin layer)) Next, a method for forming the cured resin layer constituting the polyester film roll will be described. The method for forming the cured resin layer is not particularly limited, and any conventionally known coating method can be used, such as reverse gravure coating, direct gravure coating, roll coating, die coating, bar coating, curtain coating, etc. The cured resin layer can be formed by in-line coating or off-line coating. The drying and curing conditions are not particularly limited, and when the cured resin layer is formed by off-line coating, the heat treatment is usually carried out at 80 to 200°C for 3 to 40 seconds, preferably at 100 to 180°C for 3 to 40 seconds. On the other hand, when the cured resin layer is provided by in-line coating, it is usually recommended to carry out heat treatment at 70 to 280° C. for 3 to 200 seconds.

[0089] In the present invention, it is preferable to form the protective layer by in-line coating, which is a method of treating the surface of a polyester film during the film-forming process. Inline coating is a method of coating within the polyester film production process. Specifically, it is a method of coating at any stage between melt extrusion of polyester, stretching, heat setting, and winding up. Typically, coating is performed on any of the following: an unstretched sheet obtained by melting and quenching, a stretched uniaxially stretched film, a biaxially stretched film before heat setting, or a film after heat setting and before winding up. While not limited to the following, for example, in sequential biaxial stretching, a method in which coating is performed on a uniaxially stretched film stretched in the longitudinal direction (machine direction) and then stretched in the transverse direction is particularly advantageous. This method offers advantages in terms of production cost, as film formation and cured resin layer formation can be performed simultaneously. Since stretching is performed after coating, the thickness of the cured resin layer can be changed by adjusting the stretch ratio, making thin-film coating easier than with offline coating. Furthermore, by providing a cured resin layer on the film before stretching, the cured resin layer can be stretched together with the polyester film, thereby firmly adhering the cured resin layer to the polyester film. Furthermore, in the production of a biaxially stretched polyester film, by stretching the film while holding its edges with clips or the like, the film can be restrained in both the longitudinal and transverse directions, and in the heat setting step, high temperatures can be applied while maintaining flatness and without wrinkles, etc. Therefore, the heat treatment performed after coating can be performed at a high temperature that cannot be achieved by other methods, improving the film-forming properties of the cured resin layer and enabling stronger adhesion between the cured resin layer and the polyester film, and further enabling a stronger cured resin layer to be formed, thereby improving the performance of various functional layers that can be formed on the cured resin layer, such as adhesion to a release layer and moist heat resistance.

[0090] When a cured resin layer is formed by in-line coating, it is preferable to produce a laminated polyester film by coating a cured resin layer composition, which is prepared by preparing an aqueous solution or aqueous dispersion of the above-mentioned series of compounds so that the solid content (total non-volatile components) is adjusted to approximately 0.1 to 50 mass %, onto a polyester film.

[0091] Regardless of whether off-line coating or in-line coating is used, heat treatment and irradiation with active energy rays such as ultraviolet rays may be used in combination, if necessary. The polyester film constituting the laminated polyester film of the present invention may be previously subjected to a surface treatment such as a corona treatment or a plasma treatment.

[0092] [Release layer] The polyester film roll of the present invention preferably further has a release layer on the cured resin layer. The release layer is preferably laminated on the surface of the present film having an average surface roughness (Sa) of 1 to 5 nm or less. Therefore, for example, if the polyester film has an A / B / C structure, a release layer is laminated on the surface side of layer A via a cured resin layer, resulting in a structure of release layer / cured resin layer / A / B / C. By laminating a release layer on the smooth surface of the present film, pinholes and the like are less likely to occur when an ultrathin ceramic layer is laminated on the release layer to form a green sheet, which is preferable.

[0093] The release layer is laminated on the present film via a cured resin layer. As described above, the cured resin layer preferably contains (A) a crosslinking agent and (B) a binder resin in order to improve the surface smoothness.

[0094] The release layer is formed from a release agent composition containing a release agent, and from the viewpoint of obtaining good release performance, it is particularly preferred that the release agent composition contains a silicone resin. Specifically, it is preferred that the release agent composition contains a type containing a curable silicone resin as the main component, a modified silicone type obtained by graft polymerization with an organic resin such as a urethane resin, an epoxy resin, or an alkyd resin, or a fluorosilicone resin.

[0095] As the curable silicone resin, any of the existing curing reaction types can be used, such as heat-curable types such as addition types and condensation types, and electron beam-curable types such as ultraviolet-curable types, and multiple types of curable silicone resins can be used in combination. Furthermore, there are no particular limitations on the form in which the curable silicone resin is applied when forming the release layer, and it may be in the form of a solution in an organic solvent, in the form of a water-based emulsion, or in a solventless form.

[0096] The release agent composition for forming the release layer may further contain, as necessary, a binder, an antifoaming agent, a coatability improver, a thickener, inorganic or organic particles, an organic lubricant, an antistatic agent, a conductive agent, an ultraviolet absorber, an antioxidant, a foaming agent, a dye, a pigment, and the like.

[0097] The release layer is formed by coating the film with a release agent composition. Either in-line coating, which is carried out during the film production process, or so-called off-line coating, in which the release agent composition is applied outside the system onto a film that has already been produced, may be employed.

[0098] The release layer can be provided on the film by any of the conventional coating methods such as reverse gravure coating, direct gravure coating, roll coating, die coating, bar coating, and curtain coating.

[0099] The curing conditions for forming the release layer are not particularly limited. When forming the release layer by offline coating, the heat treatment is usually carried out at 80°C or higher for 10 seconds or more, preferably at 100 to 200°C for 3 to 40 seconds, and more preferably at 120 to 180°C for 3 to 40 seconds.

[0100] If necessary, the heat treatment may be combined with irradiation with active energy rays such as ultraviolet rays. As the energy source for curing by irradiation with active energy rays, known devices and energy sources can be used.

[0101] The coating amount of the release layer (after drying) is usually 0.005 to 5 g / m from the viewpoint of coating properties. 2 , preferably 0.005 to 1 g / m 2 , and more preferably 0.005 to 0.1 g / m 2 The coating amount (after drying) is in the range of 0.005 g / m 2 If the thickness is less than this, the coating will lack stability, making it difficult to obtain a uniform coating film. On the other hand, 5g / m 2 If the coating thickness exceeds this, the coating adhesion and curing properties of the release layer itself may be reduced.

[0102] The coating amount is calculated from the liquid mass (before drying) per coating time, the non-volatile content concentration of the coating liquid, the coating width, the stretching ratio, the line speed, and the like.

[0103] (Application) The present film can be suitably used for various release applications. For example, it can be used for various release and process applications, such as dry film resist (DFR), multilayer circuit boards, and the production of ceramic green sheets for multilayer ceramic capacitors. In release and process applications, the film is used, for example, as a support, onto which various materials such as ceramic slurries can be applied or laminated.

[0104] In particular, as described above, this film has extremely excellent surface smoothness and good scratch resistance. When this film is used as a support for a ceramic green sheet, for example, in the manufacturing process of a multilayer ceramic capacitor, the ceramic slurry can be uniformly applied, forming a uniform dielectric layer. Furthermore, as the polyester film roll lengthens, the frequency of film roll replacement decreases, contributing to improved productivity. Furthermore, the cured resin layer of the present invention itself has good adhesion to the release layer, making it suitable for situations where durability of the release layer is required (e.g., repeated use of a release film). In particular, this film is suitable for use as a support for a ceramic green sheet in the manufacturing process of an automotive multilayer ceramic capacitor. [Example]

[0105] EXAMPLES The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0106] <Production of polyester> (1) Production of Polyester A 100 parts by mass of dimethyl terephthalate and 65 parts by mass of ethylene glycol were charged into an ester exchange reaction vessel equipped with a stirrer, a temperature raising device, and a distillate separation column, and heated to 150° C. to melt the dimethyl terephthalate.

[0107] Next, an ethylene glycol solution of magnesium acetate tetrahydrate was added so that the amount of magnesium acetate added was 0.09% by mass based on the obtained polyester. The mixture was then heated to 225°C under normal pressure over 3 hours, and then stirred and maintained at 225°C for 1 hour and 15 minutes while distilling off methanol to carry out an ester exchange reaction. The ester exchange reaction was essentially completed, yielding a polyester oligomer.

[0108] The oligomer was then transferred to a polycondensation reactor equipped with a distillation tube and a stirrer. An ethylene glycol solution of magnesium acetate tetrahydrate was added to the transferred oligomer so that the amount of magnesium acetate added would be 0.09% by mass relative to the polyester resin content obtained. Thereafter, an ethylene glycol solution of phosphoric acid was added as a heat stabilizer so that the amount of phosphoric acid added to the resulting polyester was 0.017% by mass.

[0109] Next, an ethylene glycol solution of tetrabutyl titanate was added as a polycondensation catalyst to the oligomer so that the titanium atom content was 4.5 ppm by mass relative to the resulting polyester. The pressure was then reduced from 101.3 kPa to 0.4 kPa over 85 minutes and maintained at 0.4 kPa, while the temperature was increased from 225°C to 280°C over 2 hours and maintained at 280°C for 1.5 hours to carry out a melt polycondensation reaction, yielding polyester A with an intrinsic viscosity (IV) of 0.63 dL / g.

[0110] (2) Production of Polyester B Polyester B having an intrinsic viscosity (IV) of 0.63 dL / g was obtained in the same manner as Polyester A, except that instead of adding tetrabutyl titanate in Polyester A, antimony trioxide was added as a polycondensation catalyst so that the antimony atom content was 300 ppm by mass relative to the polyester resin content obtained.

[0111] (3) Production of Polyester C 1.0% by mass of spherical silica particles having an average primary particle size of 0.5 μm were added to the polyester B, and the mixture was kneaded using a vented twin-screw kneader to obtain polyester C having an intrinsic viscosity (IV) of 0.63 dL / g.

[0112] (4) Production of Polyester D 2.0% by mass of calcium carbonate particles having an average primary particle size of 0.7 μm were added to the polyester B and kneaded using a vented twin-screw kneader to obtain polyester D having an intrinsic viscosity (IV) of 0.63 dL / g.

[0113] [Example 1] The raw material for Layer A was 100% by mass of polyester A, the raw material for Layer B was a blend of 97.5% by mass of polyester A and 2.5% by mass of polyester D, and the raw material for Layer C was a blend of 70% by mass of polyester A and 30% by mass of polyester C. These were fed into a vented extruder and melt-extruded at 280°C. After that, the layers were co-extruded using an electrostatically applied adhesion method to form a three-type, three-layer (A / B / C) structure with layers A and C as the outermost layers (surface layers) and layer B as the middle layer, with a thickness composition ratio of A / B / C = 4 / 25 / 2. The film was then cooled and solidified on a cooling roll with a surface temperature set at 25°C to obtain an unstretched film.

[0114] Next, the unstretched film was stretched 3.5 times in the machine direction (MD direction) at a temperature of 85°C using the difference in roll peripheral speed, and then this machine-stretched film was introduced into a tenter, and the cured resin layer composition described below was applied to the surface on the Layer A side so that the thickness after stretching and drying would be 305 nm. Then, the film was stretched 4.5 times in the transverse direction (TD direction) at 105°C to obtain a polyester film roll with a thickness of 31 μm.

[0115] (Cured resin layer composition) The following (A) and (B) were mixed at a mass ratio of (A) / (B)=30 / 70 to obtain a cured resin layer composition. (A) Crosslinking agent: partially etherified melamine having a methylol group, a methoxy group, and an imino group. (B) Binder resin: Aqueous dispersion of polyester resin copolymerized with (acid components) terephthalic acid / isophthalic acid / 5-sodium sulfoisophthalic acid / / (diol components) ethylene glycol / 1,4-butanediol / diethylene glycol = 56 / 40 / 4 / / 70 / 20 / 10 (mol %).

[0116] [Example 2] A polyester film roll was obtained in the same manner as in Example 1, except that the thickness of the cured resin layer and the blending ratio of the cured resin layer composition were changed as shown in Table 1.

[0117] [Comparative Example 1] to [Comparative Example 2] A polyester film roll was obtained in the same manner as in Example 1, except that the thickness of the cured resin layer and the blending ratio of the cured resin layer composition were changed as shown in Table 1.

[0118] Comparative Example 3 A polyester film roll was obtained in the same manner as in Example 1, except that the cured resin layer was not provided. The properties of each film roll obtained are shown in Table 1 below.

[0119] <Measurement and evaluation methods> The measurement and evaluation methods used in the examples and comparative examples are as follows. The measurement and evaluation results are summarized in Table 1.

[0120] (1) Intrinsic viscosity (IV) 1 g of polyester was precisely weighed and dissolved in 100 mL of a 50 / 50 (mass ratio) phenol / tetrachloroethane mixed solvent, and the viscosity (IV) was measured at 30°C using a viscosity (IV) measuring device (Rigo Co., Ltd., VMS-022UPC·F10).

[0121] (2) Average particle size and particle size distribution The powder was observed from the layer A side of the polyester film of the polyester film rolls of the Examples and Comparative Examples using a scanning electron microscope (manufactured by HITACHI, "S3400N"). The size of each particle was measured from the obtained image data, and the average value of 10 points was taken as the average primary particle size. Furthermore, a dispersion liquid with a solid content of 0.03 g / mL was prepared by adding a mixed solvent of phenol / tetrachloroethane = 2 / 3 to the particles, and for this dispersion liquid, the particle diameter D10 at which the cumulative number reached 10%, the particle diameter D50 at which the cumulative number reached 50%, and the particle diameter D90 at which the cumulative number reached 90% were measured by a laser diffraction scattering method using an "MT3300EXII" manufactured by Microtrackbell, and (D90-D10) / D50 was calculated.

[0122] (3) Average surface roughness (Sa) and maximum peak height (Sp) The surface of the polyester film on the Layer A side of the polyester film rolls of the Examples and Comparative Examples was measured using a surface roughness measuring device (Ametec Co., Ltd., "NewView" (registered trademark)), and the average surface roughness Sa value and the maximum peak height Sp value were calculated from the obtained surface profile curves.

[0123] (4) Surface hardness of polyester film and cured resin layer The surface hardness of the polyester film and the cured resin layer was measured using a nanoindenter (TI-980, manufactured by Bruker) as follows. Indentation tests were performed using a diamond Berkovich-type (triangular pyramidal) probe to obtain displacement-load hysteresis curves. The indentation tests were performed in load-controlled mode with a maximum load of 6–20 μN, a loading time of 5 s, a holding time of 2 s, and an unloading time of 5 s. The maximum load was adjusted for each sample so that the Berkovich-type probe indentation depth was 20–30 nm. Numerical processing was performed using the instrument's accompanying software (triboscan) for the load range of 20–95% to calculate the indentation hardness, which was used as the surface hardness of the polyester film and cured resin layer. The Area Function (a calibration curve for the relationship between the probe indentation depth and the contact cross-sectional area) used to correct the Berkovich probe shape was obtained from an indentation test of quartz glass using a Berkovich probe under the same conditions as above.

[0124] (5) Scratch resistance Regarding scratches and defects on the film surface, the polyester film rolls of the examples and comparative examples were 2 The sample film was checked for visual recognition of scratches (fine scratches, scratch-like defects, grain-like patterns, etc.) using "transmitted light indoors under a three-wavelength fluorescent lamp" and "reflected light from a halogen lamp in a dark room." If scratches were confirmed, the number of scratches was counted and judged according to the following evaluation criteria. <Evaluation criteria> A: 0 to 4 scratches with a depth of 0.3 μm or more that can be seen both in transmitted light under indoor three-wavelength fluorescent lighting and reflected light under a halogen lamp. B: Five or more scratches with a depth of 0.3 μm or more that can be seen in both transmitted light under indoor three-wavelength fluorescent lighting and reflected light under a halogen lamp.

[0125] (6) Smoothness The polyester film rolls of the Examples and Comparative Examples were evaluated for smoothness according to the following evaluation criteria. <Evaluation criteria> A: The maximum peak height (Sp) of the cured resin layer surface is 43 nm or less, and the surface hardness is also moderately flexible. (As the ceramic green sheet becomes thinner, there is a low risk of pinholes occurring when applying ceramic slurry.) B: The maximum peak height (Sp) of the cured resin layer surface exceeds 43 nm, and the surface hardness is high. (As the ceramic green sheet becomes thinner, there is a high risk of pinholes occurring when the ceramic slurry is applied.)

[0126] [Table 1]

[0127] The polyester film rolls of Examples 1 and 2 had an average surface roughness (Sa) of 1 nm to 5 nm on the cured resin layer surface, as measured with a nanoindenter, and a maximum peak height (Sp) of 43 nm or less on the cured resin layer surface. The relationship between the surface hardness X (MPa) of the polyester film surface in contact with the cured resin layer and the surface hardness Y (MPa) of the cured resin layer satisfied X-130≦Y≦X+50, and therefore had high smoothness and good scratch resistance. The results of Examples 1 and 2 show that in order for the surface shape of the cured resin layer to have both low Sa and low Sp, it is necessary to apply the cured resin layer with an appropriate thickness. However, it was also found from Comparative Example 1 that simply applying a thick cured resin layer has little effect in reducing Sp. Furthermore, it was found that, in terms of the relationship between the surface hardness X (MPa) of the polyester layer in contact with the cured resin layer and the surface hardness Y (MPa) of the cured resin layer, it is more preferable to satisfy the above-mentioned relationship by, for example, adjusting the contents of the (A) crosslinking agent and the (B) binder resin, in order to achieve both low Sa and low Sp on the surface of the cured resin layer. In Comparative Example 2, the thickness of the cured resin layer was small, so it was not effective in mitigating the influence of the fine unevenness of Layer A (surface layer) of the polyester film, and in particular, it was not effective in reducing the maximum peak height (Sp). Comparative Example 3 showed poor scratch resistance, possibly due to the absence of a cured resin layer. [Industrial Applicability]

[0128] The polyester film roll of the present invention has high smoothness and improved scratch resistance, allowing for further lengthening of the film as productivity of the polyester film roll improves. For example, when used as a support for ceramic green sheets in the manufacturing process of multilayer ceramic capacitors, it is possible to form a uniform thin dielectric layer and contribute to improving productivity by reducing the frequency of switching polyester film rolls. Furthermore, because the cured resin layer of the present invention itself has an appropriate surface hardness, it is less affected by the fine irregularities on the surface of the polyester layer of the base layer, and can maintain a high level of smoothness (low Sa and low Sp). In particular, it can be suitably used as a support for ceramic green sheets used in multilayer ceramic capacitors for automobiles.

Claims

1. A polyester film roll obtained by winding up a film having a cured resin layer and a polyester film in this order, the film having a release layer on the cured resin layer, the cured resin layer is a cured product of a cured resin layer composition containing (A) a crosslinking agent and (B) a binder resin, the (A) crosslinking agent is a melamine resin, and the (B) binder resin is a polyester resin; A polyester film roll that simultaneously satisfies the following (1) to (3): (1) The average surface roughness (Sa) of the cured resin layer surface is 1 to 5 nm. (2) The maximum peak height (Sp) of the surface of the cured resin layer is 43 nm or less. (3) The relationship between the surface hardness X (MPa) of the polyester film surface in contact with the cured resin layer and the surface hardness Y (MPa) of the cured resin layer, as measured with a nanoindenter, satisfies X-130≦Y≦X+50.

2. 2. The polyester film roll according to claim 1, wherein the cured resin layer has a thickness of 150 to 350 nm.

3. 3. The polyester film roll according to claim 1, wherein the content of the crosslinking agent in the cured resin layer composition is 20 to 80% by mass, in terms of a ratio of the crosslinking agent to the total non-volatile components in the cured resin layer composition.

4. 4. The polyester film roll according to claim 1, wherein the polyester film has at least three layers, and the cured resin layer is in contact with a surface layer A of the polyester film.

5. 5. The polyester film roll according to claim 1, wherein the polyester film is a three-layer polyester film, and the cured resin layer is in contact with a surface layer A of the polyester film.

6. The polyester film roll according to claim 5 , wherein the intermediate layer B of the polyester film contains particles.

7. The polyester film roll according to claim 6 , wherein the intermediate layer B has a particle content of 0.5% by mass or less.

8. The polyester film roll according to any one of claims 4 to 7, wherein the polyester constituting the surface layer A has an intrinsic viscosity (IV) of 0.50 dL / g or more.

9. The polyester film roll according to any one of claims 4 to 8, wherein the surface layer A contains a titanium compound.

10. 10. The polyester film roll according to claim 4, wherein the surface layer A contains an antimony compound and / or a titanium compound, and the content of the antimony compound is 100 ppm or less.

11. The polyester film roll according to any one of claims 4 to 10, wherein the surface layer A is substantially free of particles.

12. 12. The polyester film roll according to claim 1, wherein a blending ratio of the crosslinking agent to the binder resin in the cured resin layer composition, [crosslinking agent] / [binder resin] (mass ratio), is 20 / 80 to 80 / 20.

13. The polyester film roll according to any one of claims 1 to 12, which is used as a support for a ceramic green sheet in a process for producing a multilayer ceramic capacitor.

14. The polyester film roll according to any one of claims 1 to 13, which is used as a support for a ceramic green sheet in a process for producing a multilayer ceramic capacitor for an automobile.

Images