Polyester Film Roll

Abstract

To provide a polyester film roll which has high smoothness, prevents generation of wrinkles, has good winding property of the film roll, and can cope with a longer life.SOLUTION: A polyester film roll is obtained by winding a film having a polyester film and a curable resin layer in this order, wherein the curable resin layer is a cured product of a curable resin composition containing (A) a crosslinking agent, (B) a binder resin and (C1) particles, an average particle diameter of (C1) the particles is three times or less of that of the curable resin layer, and the film simultaneously satisfies the following (1) to (3). (1) Average surface roughness (Sa) on the surface of the curable resin layer of 1-10 nm, (2) surface height distribution peak (Sku) on the surface of the curable resin layer of 50 or more, and (3) average surface roughness (Sa) on a surface opposite to a surface in contact with the curable resin layer of the polyester film of 1-10 nm.SELECTED DRAWING: None

Description

[Technical field]

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

[0002] In recent years, with the increasing use of electrification in automobiles and the increasing sophistication 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 onto a release film and dried to produce a ceramic green sheet (dielectric sheet), on which electrodes are printed by screen printing or the like to form internal electrodes, and 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 the dielectric layers are sintered in a firing furnace to produce a multilayer ceramic capacitor.

[0003] Ceramic green sheets are becoming thinner as MLCCs become smaller and higher capacity. When ceramic green sheets are further thinned to 0.5 μm (thickness after drying) or less, if there are minute protrusions on the surface of the release film used as a carrier film, these will cause pinholes and the like to form in the ceramic green sheets. For this reason, the release film is required to have a higher degree 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 side 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 protrusion height Rp1 of the outer surface of the release agent layer is 50 nm or less.

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

[0006] As green sheets become thinner, there is a demand for higher lamination accuracy when laminating thin green sheets in multiple layers. For this reason, the flatness of release films is becoming more important, and efforts are being made to control heat wrinkles, etc.

[0007] As an example of this type of film, Patent Document 3 discloses a polyester film roll obtained by winding up a polyester film, in which slack defects present in the polyester film are reduced within 100 m. 2 No. 5,513,233 is disclosed. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2014-177093 A [Patent Document 2] JP 2013-7054 A [Patent Document 3] JP 2002-273719 A Summary of the Invention [Problem to be solved by the invention]

[0009] As ceramic green sheets become thinner, the dielectric layers are required to have higher smoothness. Furthermore, as polyester films become more smooth, there are issues with increasing the production speed or lengthening the film roll during the manufacturing process to improve productivity, making it difficult to achieve good winding properties for the film roll and making the film prone to wrinkling.

[0010] Therefore, an object of the present invention is to provide a polyester film roll that has high smoothness, is less prone to wrinkles, has good winding properties, and can be made long. [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 structure, and have completed the present invention. That is, the present invention provides the following items [1] to

[10] .

[0012] [1] A polyester film roll obtained by winding up a film having a polyester film and a cured resin layer in this order, wherein the cured resin layer is a cured product of a cured resin layer composition containing a (A) crosslinking agent, a (B) binder resin, and (C1) particles, the (C1) particles have an average particle size of 100 nm or more, and the average particle size of the (C1) particles is three times or less than the thickness of the cured resin layer, and the film simultaneously satisfies the following (1) to (3): (1) The average surface roughness (Sa) of the cured resin layer is 1 nm to 10 nm. (2) The surface height distribution kurtosis (Sku) of the surface of the cured resin layer is 50 or more. (3) The average surface roughness (Sa) of the surface of the polyester film opposite to the surface in contact with the cured resin layer is 1 nm to 10 nm. [2] The polyester film roll according to [1], wherein the binder resin (B) is a polyester resin. [3] The polyester film roll according to [1] or [2], wherein the cured resin layer has a thickness of 50 nm or more and 500 nm or less. [4] The polyester film roll according to any one of [1] to [3], wherein the cured resin layer further contains microparticles (C2) having an average particle size of less than 100 nm. [5] The polyester film roll according to any one of [1] to [4], wherein the polyester constituting the polyester film has an intrinsic viscosity (IV) of 0.50 dL / g or more. [6] The polyester film roll according to any one of [1] to [5], wherein the polyester film contains a titanium compound. [7] The polyester film roll according to any one of [1] to [6], wherein the surface of the polyester film opposite to the surface in contact with the cured resin layer is substantially free of particles. [8] The polyester film roll according to any one of [1] to [7], further comprising a release layer on a surface of the polyester film opposite to a surface in contact with the cured resin layer. [9] The polyester film roll according to any one of [1] to [8], which is used as a support for a ceramic green sheet in a production process of a multilayer ceramic capacitor.

[10] The polyester film roll according to any one of [1] to [9], which is used as a support for a ceramic green sheet in a production process of an automotive ceramic capacitor. Effect of the Invention

[0013] According to the present invention, it is possible to provide a polyester film roll that has high smoothness, is less prone to wrinkles, has good winding properties, and can be made long.

[0014] In addition, since the polyester film roll of the present invention has extremely excellent surface smoothness, if the film is used as a support for a ceramic green sheet in, for example, the manufacturing process of a multilayer ceramic capacitor, there is an advantage that defects are less likely to occur in the ceramic green sheet due to fine irregularities on the film surface.

[0015] Moreover, the polyester film roll of the present invention has extremely excellent surface smoothness, and the surface of the cured resin layer has a characteristic uneven shape, so it has good wrinkle prevention properties. If the film is used as a support for a ceramic green sheet in, for example, the manufacturing process of a multilayer ceramic capacitor, a uniform dielectric layer can be formed by uniformly applying a ceramic slurry, and since the winding property of the film roll is good, wrinkles are less likely to occur, which can contribute to productivity improvement due to a reduction in switching frequency as the length of the polyester film roll increases. In particular, it can be preferably used as a support for a ceramic green sheet used in a multilayer ceramic capacitor for automobiles.

Mode for Carrying Out the Invention

[0016] 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.

[0017] <Polyester Film Roll> The polyester film roll of the present invention is a polyester film roll obtained by winding up a film having a polyester film and a cured resin layer in this order, wherein the cured resin layer is a cured product of a cured resin layer composition containing (A) a crosslinking agent, (B) a binder resin, and (C1) particles, the (C1) particles have an average particle size three times or less of the cured resin layer, and the film simultaneously satisfies the following (1) to (3): (1) The average surface roughness (Sa) of the cured resin layer surface is 1 nm to 10 nm. (2) The surface height distribution kurtosis (Sku) of the cured resin layer surface is 50 or more. (3) The average surface roughness (Sa) of the surface of the polyester film opposite to the surface in contact with the cured resin layer is 1 nm to 10 nm.

[0018] The polyester film roll of the present invention (hereinafter also referred to as "the present roll") is a polyester film roll obtained by winding up a film having a cured resin layer and a polyester film in this order (hereinafter also referred to as "the present film"). The roll is a polyester film roll wound around a core such as a paper tube, a metal tube, a plastic tube, etc., and has a width of preferably 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, more preferably 2.0 m or less. The length of the present film wound onto the present roll is not particularly limited, but is preferably 1000 m or more, more preferably 6000 m or more, and even more preferably 12000 m or more. Furthermore, the thickness of the present film is preferably 19 μm or more and 38 μm or less, and more preferably 25 μm or more and 32 μm or less.

[0019] [Surface characteristics] (1) Average surface roughness (Sa) of the cured resin layer In this film, the average surface roughness (Sa) of the cured resin layer surface is 1 to 10 nm. If the average surface roughness (Sa) of the cured resin layer of this film is greater than 10 nm, when the film is rolled with a ceramic green sheet on it, the fine irregularities on the surface of the cured resin layer will be transferred, leading to a decrease in the quality of the ceramic green sheet. Also, if the average surface roughness (Sa) of the cured resin layer surface is 1 nm or less, the film surface will be too flat, the film's slipperiness will decrease, and it will be easily scratched. The average surface roughness (Sa) of the cured resin layer surface is preferably 1 to 8 nm, more preferably 1 to 6 nm, and even more preferably 1 to 3 nm, from the viewpoint of accommodating thinner ceramic green sheets.

[0020] In addition, from the viewpoint of suppressing the transfer of fine irregularities on the surface of the cured resin layer to other surfaces, the maximum peak height (Sp) of the present film is preferably 300 nm or less, more preferably 280 nm or less, even more preferably 200 nm or less, and even more preferably 150 nm or less. There is no particular restriction on the lower limit of the maximum peak height (Sp), but from the viewpoint of film winding properties, it is preferably 50 nm or more, more preferably 70 nm or more, and even more preferably 90 nm or more.

[0021] Average surface roughness (Sa) is one of the surface roughness parameters (ISO 25178), and is a three-dimensional extension of the two-dimensional Ra. It is calculated by dividing the volume enclosed by the surface profile and the average surface by the measured area, and is given by the following formula (1). If 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.

[0022]

number

[0023] In addition, the maximum peak height (Sp) is one of the surface roughness parameters (ISO 25178), and represents the maximum value of the height from the average plane of the surface, and is expressed by the following formula (2).

[0024]

number

[0025] (2) Surface height distribution peaks (Sku) of the cured resin layer surface The surface height distribution kurtosis (Sku) of the cured resin layer surface must be 50 or more. By having the surface height distribution kurtosis (Sku) of the cured resin layer surface be 50 or more, when the film is wound into a film roll, even if the film surface opposite the side having the cured resin layer is very smooth, the air between the film layers can easily escape, the occurrence of wrinkles in the film can be suppressed, and the film can be easily wound into a roll. From the viewpoint of facilitating the escape of air between the films and suppressing wrinkles in the film, the surface height distribution kurtosis (Sku) of the cured resin layer surface is preferably at least 100, more preferably at least 105, and even more preferably at least 110, and is preferably at most 250, more preferably at most 230, and even more preferably at most 200.

[0026] The surface height distribution kurtosis (Sku) is a measure of the sharpness of the surface profile curve and characterizes the spread of the surface height distribution. It is defined by the following equation (3):

[0027]

number

[0028] In the above formula, Sq is a three-dimensional extension of the two-dimensional Rq (RMS), which represents the standard deviation σ in statistics. It is the root-mean-square deviation obtained by dividing the volume of the area between the curved surface obtained by squaring the distance between the surface shape curved surface and the average surface and the average surface by the measured area, and then calculating the square root, and can be calculated from the following formula (4).

[0029]

number

[0030] It should be noted that an Sku of 3 indicates a normal distribution, and as this value decreases, the surface height distribution has a gentler shape, while as the value increases, the protrusions become sharper.

[0031] (3) Average surface roughness (Sa) of the surface of the polyester film that comes into contact with the cured resin layer and the opposite surface The average surface roughness (Sa) of the polyester film on the surface opposite to the surface in contact with the cured resin layer must be 1 to 10 nm, preferably 1 to 10 nm, more preferably 1 to 5 nm, and further preferably 1 to 3 nm. By having the average surface roughness (Sa) of the polyester layer surface on the opposite side to the surface in contact with the cured resin layer of the polyester film within the above range, when a ceramic slurry is applied using the highly smooth surface, the application properties are good and no pinholes are generated, making it possible to form a uniform ceramic green sheet.

[0032] [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 an ester bond continuous in the main chain. It may be a homopolyester or a copolymer polyester, and specifically, it may be a polyester obtained by polycondensation reaction of a dicarboxylic acid component and a diol component.

[0033] 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 %.

[0034] 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.

[0035] 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.

[0036] When the polyester is a homopolyester, it is preferably one obtained by polycondensation of an aromatic dicarboxylic acid and 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. Representative examples of polyester include polyethylene terephthalate (PET) and polyethylene-2,6-naphthalenedicarboxylate (PEN).

[0037] On the other hand, when the polyester is a copolymer polyester, it is preferable that the polyester is 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 isophthalic acid, terephthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, and oxycarboxylic acid, and the like, either alone or in combination. Examples of the glycol component of the copolymer polyester include one or more of ethylene glycol, diethylene glycol, propylene glycol, butanediol, 1,4-cyclohexanedimethanol, and neopentyl glycol.

[0038] As the polyester, preferred are polyethylene terephthalate in which 80 mol % or more, preferably 90 mol % or more, is an ethylene terephthalate unit, and polyethylene-2,6-naphthalate in which ethylene-2,6-naphthalate unit is, and the like.

[0039] (Polyester polycondensation catalyst) Examples of the polycondensation catalyst 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 by 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, originating from the titanium compound in the film can be reduced, and a film having high surface smoothness, in particular a small maximum peak height (Sp) on at least one side, can be obtained.

[0040] It is preferable that the polyester constituting the outermost layer (also called the "surface layer") of the polyester film uses a titanium compound as a 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 foreign matter caused by the catalyst can be reduced without decreasing the production efficiency of the polyester. From the viewpoint of productivity, it is preferable that the polyester constituting the intermediate layer (base layer B described later) 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 polyester film is preferably 100 ppm or less. For example, the surface layer A (the layer on the opposite side of the polyester film in contact with the cured resin layer) described later 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 need to contain an antimony compound.

[0041] (Intrinsic viscosity of polyester (IV)) 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.

[0042] 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 resin.

[0043] From the above viewpoint, particularly when the polyester film has a laminated structure, the intrinsic viscosity (IV) of the polyester constituting the surface layer, specifically the outermost layer of the polyester film (for example, the surface layer 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 upper limit of the intrinsic viscosity (IV) of the polyester is preferably 1.00 dL / g or less.

[0044] (Structure of polyester film) The polyester film may be either a single layer or a laminated film having two or more layers.

[0045] (Polyester film particles) The polyester film may contain particles in the surface layer in order to improve the handling of the film. In addition, it is preferable that the surface of the polyester film opposite to the surface in contact with the cured resin layer of the polyester film does not substantially contain particles. Since the surface of the polyester film opposite to the surface in contact with the cured resin layer does not substantially contain particles, it is preferable that pinholes and the like are unlikely to occur when a green sheet is formed by laminating an ultra-thin ceramic layer on the release layer formed on the surface layer side.

[0046] Preferred examples of the particles include the particles in the cured resin layer described below.

[0047] (Laminated structure of polyester film) When the polyester film has a laminated structure having two or more layers, a three-layer structure such as A / B / C consisting of a base layer B and a surface layer A and a surface layer C, or A / B / A consisting of a base layer B and a surface layer A is preferred, and a three-layer structure such as A / B / C is particularly preferred.

[0048] It is preferable that the layer (surface layer A) on the side of the polyester film opposite to the surface in contact with the cured resin layer contains substantially no particles, from the viewpoints of making the ceramic layer thinner and preventing pinholes. "Substantially not contained" means not intentionally contained, and specifically means that the particle content (particle concentration) is 200 ppm or less, more preferably 150 ppm or less, and particularly 100 ppm or less.

[0049] Moreover, it is preferable that the surface layer A has both an average surface roughness (Sa) and a maximum peak height (Sp) smaller than those of the layer (surface layer C) on the side of the polyester film that is in contact with the cured resin layer.

[0050] 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. The upper limit of the average surface roughness (Sa) of the surface layer C is preferably 20 nm or less. By adopting such a laminated structure, the surface layer C can be provided with a rough surface required for improving handling, and the surface layer A can be provided with the smoothness required for providing a thin ceramic layer. From the above viewpoints, the average surface roughness (Sa) of the surface layer A is preferably 15 nm or less, and the maximum peak height (Sp) is preferably 200 nm or less.

[0051] In the three-layer structure of A / B / C and A / B / A, the surface layer C may contain particles to ensure ease of handling.

[0052] In the above-mentioned A / B / C and A / B / A three-layer structures, the surface layer C preferably contains particles having a narrow particle size distribution and a substantially uniform average particle size (so-called monodispersity).

[0053] As the above-mentioned 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 the particle size at which the cumulative number is 10% is D10, the particle size at which the cumulative number is 50%, and the particle size at which the cumulative number is 90% is D50, and the particle size at which the cumulative number is 90%, respectively, 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.

[0054] The average particle size of the particles is, for example, 0.05 to 0.8 μm, preferably 0.1 to 0.5 μm, and more preferably 0.1 to 0.3 μm, from the viewpoint of suppressing an increase in average surface roughness (Sa) and a maximum peak height (Sp), i.e., improving handleability and suppressing pinholes.

[0055] Moreover, the surface layer C preferably contains particles having an average particle size of 0.1 to 0.5 μm.

[0056] 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, in the case of non-spherical particles, the average value of the longest and shortest diameters can be measured as the diameter of each particle.

[0057] The polyester film contains the particles in a mass ratio of, for example, 900 ppm or more, preferably 2000 to 10000 ppm, more preferably 2500 ppm to 9500 ppm, and even more preferably 3000 ppm to 9000 ppm. The mass ratio here refers to the ratio of the particles in each surface layer.

[0058] Moreover, it is particularly preferable that the surface layer C contains the particles in a mass ratio of less than 5000 ppm, and it is most preferable that the surface layer C contains the particles in a mass ratio of 2000 ppm or more and 4000 ppm or less.

[0059] The base layer B preferably functions as the thickest main layer, and in order to reduce costs, it preferably does not substantially contain particles or contains particles at a lower concentration than the surface layer C.

[0060] The term "substantially not contained" means that it is not intentionally contained, and specifically means that the particle content (particle concentration) is 200 ppm or less, more preferably 150 ppm or less.

[0061] As described above, the surface layer A is a layer different from the surface layer C. Specifically, examples of the surface layer A include a layer having different particle types, average particle sizes, and blending amounts, as well as a layer thickness.

[0062] Moreover, the configurations including the surface layer A and / or the surface layer C shown in the following (X) and (Y) are particularly preferable. By adopting such a configuration, the present film can have excellent handling properties and surface smoothness.

[0063] (Production method of polyester film) An example of a method for producing a polyester film 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.

[0064] Next, the unoriented sheet is stretched in one direction by a roll or tenter type stretching machine, at a stretching temperature of usually 25 to 120° C., preferably 35 to 100° C., and a stretching ratio of usually 2.5 to 7 times, preferably 2.8 to 6 times.

[0065] Then, the film is stretched in a direction perpendicular to the first-stage stretching direction. At this time, the stretching temperature is usually 50 to 140° C., and the stretching ratio is usually 3.0 to 7 times, preferably 4.5 times or more, and more preferably 4.5 to 5.0 times.

[0066] Then, the polyester film is heat-set under tension or relaxation of 30% or less at a temperature of 180 to 220° C. 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, is preferably in the range of 100 to 160° C. This cooling may be performed in two or more steps with different temperatures. In the above-mentioned stretching, a method in which the stretching in one direction is carried out in two or more stages can also be adopted.

[0067] [Cured resin layer] <Cured resin layer composition> The present film has a cured resin layer on at least one surface of a polyester film, and the cured resin layer is formed from a cured resin layer composition containing (A) a crosslinking agent, (B) a binder resin, and (C) particles, which will be described later. By having the cured resin layer, the present film is less likely to develop wrinkles when wound into a roll, and can be made long.

[0068] ((A): Crosslinking agent) The cured resin layer composition in the polyester film roll of the present invention preferably contains at least one crosslinking agent selected from the group consisting of epoxy compounds and carbodiimide compounds for the purpose of improving the durability of the cured resin layer.

[0069] (Epoxy compounds) The epoxy compound is a compound having an epoxy group in the molecule, and examples thereof include condensations 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, trimethylolpropane polyglycidyl ether, etc. 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, polytetramethylene glycol diglycidyl ether, etc. Examples of the monoepoxy compound include allyl glycidyl ether, 2-ethylhexyl glycidyl ether, and phenyl glycidyl ether, and examples of the glycidylamine compound 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. In terms of the amount of epoxy groups, polyepoxy compounds having three or more functional groups are preferred over those having two functional groups.

[0070] (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. For better adhesion, etc., a polycarbodiimide compound having two or more carbodiimide structures in the molecule is more preferred.

[0071] Carbodiimide compounds can be synthesized by conventionally known techniques, and generally, condensation reaction of diisocyanate compounds is used. The diisocyanate compounds are not particularly limited, and both aromatic and aliphatic compounds can be used, and 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.

[0072] 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 1000, preferably 250 to 800, and more preferably 300 to 700. By using within the above range, the durability of the coating film is improved.

[0073] 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 hydroxyalkylsulfonate may be added.

[0074] (Other crosslinking agents) Within the scope of the present invention, other crosslinking agents may be used in combination, for example, in an amount of 5% by mass or less, preferably 3% by mass or less, based on the non-volatile components in the cured resin layer.

[0075] (Oxazoline compounds) The oxazoline compound is a compound having an oxazoline group in the molecule, and in particular, a polymer containing an oxazoline group is preferred, and can be prepared by polymerization of 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, and one or a mixture of two or more of these can be used. Among these, 2-isopropenyl-2-oxazoline is suitable because it is easily available industrially. The other monomer is not limited as long as it is a monomer that can be copolymerized with the addition-polymerizable oxazoline group-containing monomer, and examples thereof include (meth)acrylic acid esters such as alkyl (meth)acrylates (alkyl groups include 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 salts thereof (sodium salts, potassium salts, ammonium salts, tertiary amine salts, etc.); unsaturated nitriles such as acrylonitrile and methacrylonitrile; (meth)acrylamide, N-alkyl (meth)acrylate, etc. Examples of the monomer 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. One or more of these monomers can be used.From the viewpoint of improving adhesion, 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, further preferably 3 to 8 mmol / g, and particularly preferably 4 to 6 mmol / g.

[0076] (Melamine compounds) The melamine compound is a compound having a melamine skeleton in the compound, and for example, an alkylolated melamine derivative, a compound partially or completely etherified by reacting an alcohol with an alkylolated melamine derivative, and a mixture thereof can be used. As the alcohol used for etherification, methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butanol, isobutanol, etc. are preferably used. In addition, the melamine compound may be either a monomer or a dimer or higher polymer, or a mixture thereof may be used. Furthermore, a product obtained by co-condensing a part of melamine with urea or the like can also be used, and a catalyst can also be used to increase the reactivity of the melamine compound.

[0077] (Isocyanate compounds) The isocyanate compound is 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'-tetramethyl xylylene 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, methylene bis(4-cyclohexyl isocyanate), and isopropylidenedicyclohexyl diisocyanate. In addition, polymers and derivatives such as biuretized products, isocyanurate products, uretdione products, and carbodiimide modified products of these isocyanates are also included. These may be used alone or in combination. Among the above isocyanates, aliphatic isocyanates or alicyclic isocyanates are more preferable than aromatic isocyanates in order to prevent yellowing due to ultraviolet rays.

[0078] 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, which may be used alone or in combination of two or more.

[0079] The isocyanate compound may be used alone or as a mixture or bond with various polymers. In terms of improving the dispersibility and crosslinking property of the isocyanate compound, it is preferable to use a mixture or bond with a polyester resin or a urethane resin.

[0080] ((B): Binder resin) (polyester resin) The cured resin layer composition in the polyester film roll of the present invention needs to contain a binder resin for the purpose of improving the durability of the cured resin layer. As the binder resin, a polyester resin is preferred from the viewpoint of improving the durability of the cured resin layer. 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 polyvalent carboxylic acids. Dicarboxylic acids such as 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; tricarboxylic 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; and monopotassium trimellitic acid salt; and ester-forming derivatives thereof can be used. Examples of the diol component include the following polyhydric hydroxy compounds, and examples of the compounds that can be used include 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, polytetramethylene oxide glycol, etc. 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 may be appropriately introduced into the polyester resin.

[0081] In the present invention, the glass transition temperature (Tg) of the polyester resin in the binder resin (B) is preferably 0° C. or higher, more preferably 40° C. or higher, and particularly preferably 80° C. or higher. When the Tg of the polyester resin in the binder resin (B) is in the above range, the cured resin layer has excellent solvent resistance even when exposed to a solvent atmosphere when a release layer is provided on the opposite side, and also has the advantage that the cured resin layer is less likely to fall off from the polyester film when used at room temperature.

[0082] In the present invention, from the viewpoint of improving adhesion, the polyester resin of the binder resin (B) 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. The dicarboxylic acid component having 10 or less carbon atoms may be used alone or in combination of two or more kinds. As the dicarboxylic acid component, the above-listed carboxylic acids can be suitably used, and it is more preferable to use terephthalic acid, isophthalic acid, or 5-sodium sulfoisophthalic acid.

[0083] Furthermore, in the present invention, the polyester resin of the binder resin (B) 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, from the viewpoint of improving adhesion. 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 ([content of ethylene glycol] / [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.

[0084] In the present invention, the binder resin (B) is preferably a polyester resin containing a polycyclic compound as an acid component. By having the polyester resin of the binder resin (B) 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 within the above-mentioned glass transition temperature range, so that the physical properties of the cured resin layer can be made suitable. 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. As the polycyclic aromatic compound, the carboxylic acids listed above can be suitably used, and it is preferred to use 2,5-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid and 2,7-naphthalenedicarboxylic acid, and it is more preferred to use 2,6-naphthalenedicarboxylic acid. The polycyclic compound may be used alone or in combination of two or more. In addition, the above-mentioned dicarboxylic acid component having 10 or less carbon atoms may be used in combination with the polycyclic compound.

[0085] ((Meth)acrylic resin) The (meth)acrylic resin is a polymer 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. The (meth)acrylic polymer is a polymer having (meth)acrylic acid or a (meth)acrylic acid alkyl ester as a constituent unit, and may be a copolymer of styrene or a styrene derivative and (meth)acrylic acid or a (meth)acrylic acid alkyl ester. Also included are copolymers of these polymers with other polymers (e.g., polyester, polyurethane, etc.), such as 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, it also includes a polymer (sometimes a mixture of polymers) obtained by polymerizing a polymerizable monomer in a polyester solution or polyester dispersion. Similarly, it also includes a polymer (sometimes a mixture of polymers) obtained by polymerizing a polymerizable monomer in a polyurethane solution or polyurethane dispersion. Similarly, it also includes a polymer (sometimes a mixture of polymers) obtained by polymerizing a polymerizable monomer in another polymer solution or dispersion, 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 those exemplified as polyesters and polyurethanes used in the binder resins described later. The (meth)acrylic resin may contain a hydroxy group or an amino group in order to further improve the adhesion to the base film.

[0086] 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, vinyltrimethoxysilane, or the like; phosphorus-containing vinyl monomers; various vinyl halides such as vinyl chloride and vinylidene chloride; and various conjugated dienes such as butadiene.

[0087] (Other binder resins) Within the scope of the present invention, other binder resins may be used in combination, for example, in an amount of 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.

[0088] ((C1):particle) The cured resin layer composition in the polyester film roll of the present invention must contain particles (C1) having an average particle size of 100 nm or more. By including particles having an average particle size of 100 nm or more in the cured resin composition, the average surface roughness (Sa) and surface height distribution kurtosis (Sku) of the cured resin layer can be set within the above-mentioned ranges, the winding properties of the polyester film roll can be improved, and when ceramic green sheets or the like are manufactured using this film, deterioration in the quality of the ceramic green sheets can be suppressed. The average particle size of the (C1) particles is preferably 150 nm or more, more preferably 200 nm or more, from the viewpoint of improving the winding property of the polyester film, while the upper limit is preferably 800 nm or less, more preferably 600 nm or less, and even more preferably 500 nm or less, from the viewpoint of preventing the particles from falling off from the cured resin layer.

[0089] In addition, the average particle size of the particles must be three times or less the thickness of the cured resin layer. By making the average particle size of the particles three times or less the thickness of the cured resin layer, the average surface roughness (Sa) and surface height distribution kurtosis (Sku) of the cured resin layer can be set within the above-mentioned ranges, and the winding properties of the polyester film roll can be improved. Furthermore, it is possible to prevent particles from falling off the cured resin layer. As a result, when a ceramic green sheet or the like is manufactured using this film, deterioration in the quality of the ceramic green sheet can be suppressed. From the above viewpoint, the average particle size of the particles is preferably 2.8 times or less, more preferably 2.5 times or less, even more preferably 2.3 times or less, and most preferably 2 times or less, the thickness of the cured resin layer.

[0090] 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 crosslinked polymers such as crosslinked silicone resin particles, crosslinked acrylic resin particles, crosslinked styrene-acrylic resin particles, and crosslinked polyester particles, and organic particles such as calcium oxalate and ion exchange resin. Among these, silica is preferred. Furthermore, the particles may be used alone or in combination of two or more kinds. Furthermore, when two or more kinds are used in combination, they may be two or more kinds with different average particle diameters.

[0091] ((C2): Microparticles) The cured resin layer composition in the polyester film roll of the present invention preferably contains (C2) fine particles having an average particle size of less than 100 nm in addition to the above-mentioned (C1) particles. By including in the cured resin layer composition the fine particles (C2) having an average particle size of less than 100 nm, the flat edge of the film can be made finely uneven, thereby providing scratch protection. As the (C2) fine particles, the inorganic particles and organic particles exemplified for the (C1) particles can be suitably used, and among these, it is preferable to use silica. The average particle size of the (C2) microparticles is preferably 80 nm or less, more preferably 70 nm or less, and even more preferably 60 nm or less. The lower limit of the average particle size of the (C2) microparticles is preferably 15 nm or more, more preferably 20 nm or more, even more preferably 25 nm or more, and even more preferably 30 nm or more.

[0092] (Other ingredients) In forming the cured resin layer, particles can be used in combination for the purpose of improving anti-blocking properties, slip properties, etc., within the scope of the present invention.

[0093] The proportion of the (A) crosslinking agent in the total non-volatile components in the cured resin layer composition is preferably 5 to 70 mass %, more preferably 15 to 60 mass %. When the proportion of the (A) crosslinking agent 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 proportion of the (A) crosslinking agent is equal to or more than the lower limit, the durability of the coating film can be good.

[0094] The proportion of the (B) binder resin in the total non-volatile components in the cured resin layer composition is preferably 30 to 95 mass%, more preferably 40 to 90 mass%. If the proportion of the (B) binder resin is below the upper limit, the proportions of other components are high, so sufficient adhesion is obtained and the coating appearance is not insufficient. On the other hand, if the proportion of the (B) binder resin is above the lower limit, adhesion is good and sufficient film-forming properties are ensured, resulting in a uniform coating film.

[0095] From the viewpoint of imparting handleability, the content of the (C1) particles, as a proportion of all non-volatile components in the cured resin layer composition, is preferably 900 ppm or more by mass, more preferably from 2000 ppm to 10000 ppm, even more preferably from 2500 ppm to 9500 ppm, and still more preferably from 3000 ppm to 9000 ppm. Furthermore, when the cured resin layer contains (C2) microparticles, the content of the (C2) microparticles as a proportion of all non-volatile components in the cured resin layer composition is, from the viewpoint of preventing scratches on the film surface, preferably from 25,000 ppm to 40,000 ppm by mass, more preferably from 28,000 ppm to 38,000 ppm, and even more preferably from 30,000 ppm to 36,000 ppm.

[0096] The total content of the (A) crosslinking agent and the (B) binder resin in the cured resin layer composition is, relative to 100% by mass of the cured resin layer composition, preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more, and is less than 100% by mass. The blending ratio (A) / (B) (mass ratio) of the crosslinking agent (A) and the binder resin (B) in the cured resin layer is preferably 5 / 95 to 50 / 50, more preferably 10 / 90 to 30 / 70. When the blending ratio (A) / (B) is within the above range, a cured resin layer having good strength and transparency can be obtained.

[0097] <Cured resin layer> The cured resin layer according to the present invention is a cured product of the cured resin composition formed from the above-mentioned cured resin layer composition. The thickness of the cured resin layer is preferably 50 nm to 500 nm, more preferably 100 nm to 400 nm, and even more preferably 150 nm to 300 nm. If the thickness of the cured resin layer is within the above range, the durability of the cured resin layer itself can be improved. 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, based on 100% by mass of the cured resin layer. It can be assumed that unreacted compounds, reacted compounds, or mixtures thereof of various compounds of the cured resin layer composition are present in the cured resin layer.

[0098] <Method for producing polyester film roll (method for forming 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 such as reverse gravure coating, direct gravure coating, roll coating, die coating, bar coating, curtain coating, etc. can be used. 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 performed 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 preferable to carry out heat treatment at 70 to 280° C. for 3 to 200 seconds as a guideline.

[0099] 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. In-line coating is a method of coating within the polyester film manufacturing process, specifically, a method of coating at any stage from melt extrusion of polyester to stretching, heat setting and winding up. Usually, 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, and a film after heat setting and before winding up. Although not limited to the following, for example, in sequential biaxial stretching, a method of coating a uniaxially stretched film stretched in the longitudinal direction (longitudinal direction) and then stretching in the transverse direction is particularly excellent. According to this method, film formation and cured resin layer formation can be performed simultaneously, which is advantageous in terms of production costs, and also. Since stretching is performed after coating, the thickness of the cured resin layer can be changed by the stretching ratio, and thin film coating can be performed more easily than with offline coating films. In addition, by providing a cured resin layer on the film before stretching, the cured resin layer can be stretched together with the polyester film, and the cured resin layer can be firmly attached to the polyester film. Furthermore, in the production of biaxially stretched polyester films, by stretching the film while holding the film ends with clips or the like, the film can be restrained in the longitudinal and lateral 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 the cured resin layer and the polyester film to adhere more firmly to each other.

[0100] When the cured resin layer is provided 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.

[0101] 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 of the present invention may be previously subjected to a surface treatment such as a corona treatment or a plasma treatment.

[0102] [Release layer] The polyester film roll of the present invention can be used in a form having a release layer on the surface (surface layer A) opposite to the cured resin layer of the present film. The release layer is preferably laminated on the surface of the present film opposite to the surface in contact with the cured resin layer (the surface layer A side of the polyester film) having an average surface roughness (Sa) of 1 nm or more and 10 nm or less. Therefore, for example, in the case of an A / B / C structure, a release layer is laminated on the surface side of layer A, resulting in a structure of release layer / A / B / C / cured resin layer. By laminating a release layer on the highly 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.

[0103] 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 preferable that the release agent composition contains a silicone resin. Specifically, it is preferable that the release agent composition contains a type mainly composed of a curable silicone resin, 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.

[0104] 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. In addition, multiple types of curable silicone resins may be used in combination. Furthermore, there is no particular limitation on the form in which the curable silicone resin is applied when forming the release layer, and it may be in any form, such as a solution in an organic solvent, a water-based emulsion, or a solventless form.

[0105] The release agent composition forming the release layer may further contain, as necessary, a binder, an antifoaming agent, a coatability improving agent, 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.

[0106] The release layer is formed by coating the film with a release agent composition. Either in-line coating, which is performed during the film production process, or so-called off-line coating, in which the release layer is applied outside the system onto a film that has already been produced, may be used.

[0107] The method for providing a release layer on the present film includes conventionally known coating methods such as reverse gravure coating, direct gravure coating, roll coating, die coating, bar coating, and curtain coating.

[0108] 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 performed 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.

[0109] 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.

[0110] The coating amount of the release layer (after drying) is usually 0.005 to 5 g / m2 from the viewpoint of coatability. 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 it is less than this, the coating property will lack stability, and it may be difficult to obtain a uniform coating film.

[0111] On the other hand, 5g / m 2 If the coating thickness exceeds this value, the coating adhesion and curing properties of the release layer itself may decrease.

[0112] The coating amount is calculated from the liquid mass per coating time (before drying), the non-volatile content of the coating liquid, the coating width, the stretching ratio, the line speed, and the like.

[0113] (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), for multilayer circuit boards, and for manufacturing ceramic green sheets for multilayer ceramic capacitors. In release and process applications, the film is used, for example, as a support, and various materials, such as ceramic slurries, may be applied or laminated on the support.

[0114] In particular, as described above, the present film has excellent smoothness while also having good film roll winding properties, and therefore can be suitably used as a support for ceramic green sheets in the production process of multilayer ceramic capacitors.

[0115] In the future, as the use of electrical equipment in automobiles progresses, the ceramic green sheets used will become thinner as the capacitors become smaller and have higher capacity, and from the perspective of further improving productivity, the polyester film roll will become longer, and the film roll will have good winding properties, which will contribute to improving productivity by reducing the frequency of changeover. In particular, this film can be suitably used as a support for ceramic green sheets used in automobiles. EXAMPLES

[0116] 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.

[0117] <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.

[0118] 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 over 3 hours under normal pressure, and then held at 225°C for 1 hour and 15 minutes with stirring while distilling off methanol to carry out an ester exchange reaction. The ester exchange reaction was essentially completed, yielding a polyester oligomer.

[0119] The oligomer was then transferred to a polycondensation reactor equipped with a stirrer and a distillation tube. An ethylene glycol solution of magnesium acetate tetrahydrate was added to the transferred oligomer so that the amount of magnesium acetate added was 0.09% by mass relative to the resulting polyester resin content. 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.

[0120] 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 raised 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.

[0121] (2) Manufacture 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 1.7 mass % of silica particles having an average primary particle size of 0.3 μm was added.

[0122] (3) Production of Polyester C Polyester C having an intrinsic viscosity (IV) of 0.63 dL / g was obtained in the same manner as Polyester A, except that 0.75 mass % of alumina particles having an average primary particle size of 0.05 μm was added.

[0123] [Example 1] Polyester A was used as the raw material. It was fed into a vented extruder and melt-extruded at 280°C. It was then cooled and solidified on a cooling roll with a surface temperature set at 15°C using an electrostatic adhesion method to obtain a single-layer unstretched film.

[0124] Next, the unstretched film was stretched 3.5 times in the machine direction (MD direction) at a temperature of 86°C using the difference in roll peripheral speed, and then this machine-stretched film was introduced into a tenter, and the following cured resin composition was applied so that the thickness after stretching and drying would be 180 nm, and then the film was stretched 4.5 times in the transverse direction (TD direction) at 105°C. Heat treatment was performed at 170°C, 240°C, 240°C, and 140°C in heat treatment (fixing) zones 1, 2, and 3 and cooling zone 4 in the tenter, respectively, and the film was wound up into a roll on a 3-inch plastic core to obtain a polyester film roll of Example 1 with a thickness of 31 μm.

[0125] (Cured resin layer composition 1) The following (A), (B), (C1), and (C2) were mixed in a mass ratio of (A) / (B) / (C1) / (C2)=10.0 / 85.6 / 0.9 / 3.5 to obtain a cured resin layer composition 1. (A) Crosslinker: Hexamethoxymethylolmelamine (B) Binder resin: Water dispersion of polyester resin copolymerized with the following composition Monomer composition: (acid component) terephthalic acid / isophthalic acid / 5-sodium sulfoisophthalic acid / / (diol component) ethylene glycol / 1,4-butanediol / diethylene glycol = 56 / 40 / 4 / / 70 / 20 / 10 (molar ratio) (C1) Particle 1: Silica particles with an average particle size of 300 nm (C2) Particle 2 (microparticle): Silica particles with an average particle size of 45 nm

[0126] [Example 2] A polyester film roll of Example 2 having a thickness of 31 μm was obtained in the same manner as in Example 1, except that the following cured resin layer composition 2 was used to form a cured resin layer having a thickness of 225 nm.

[0127] (Cured resin layer composition 2) The following (A), (B), (C1), and (C2) were mixed in a mass ratio of (A) / (B) / (C1) / (C2)=10.0 / 86.4 / 0.7 / 2.9 to obtain a cured resin layer composition 2. (A) Crosslinker: Hexamethoxymethylolmelamine (B) Binder resin: Water dispersion of polyester resin copolymerized with the following composition Monomer composition: (acid component) terephthalic acid / isophthalic acid / 5-sodium sulfoisophthalic acid / / (diol component) ethylene glycol / 1,4-butanediol / diethylene glycol = 56 / 40 / 4 / / 70 / 20 / 10 (molar ratio) (C1) Particle 1: Silica particles with an average particle size of 450 nm (C2) Particle 2 (microparticle): Silica particles with an average particle size of 45 nm

[0128] [Comparative Example 1] A polyester film roll of Comparative Example 1 having a thickness of 31 μm was obtained in the same manner as in Example 1, except that a cured resin layer having a thickness of 110 nm was formed using the following cured resin layer composition 3. (Cured resin layer composition 3) The following (A), (B), (C1), and (C2) were mixed in a mass ratio of (A) / (B) / (C1) / (C2)=10.0 / 82.5 / 1.5 / 6.0 to obtain a cured resin layer composition 3. (A) Crosslinker: Hexamethoxymethylolmelamine (B) Binder resin: Water dispersion of polyester resin copolymerized with the following composition Monomer composition: (acid component) terephthalic acid / isophthalic acid / 5-sodium sulfoisophthalic acid / / (diol component) ethylene glycol / 1,4-butanediol / diethylene glycol = 56 / 40 / 4 / / 70 / 20 / 10 (molar ratio) (C1) Particle 1: Silica particles with an average particle size of 450 nm (C2) Particle 2 (microparticle): Silica particles with an average particle size of 45 nm

[0129] [Comparative Example 2] The raw material for surface layer A was a blend of 87% polyester A and 13% polyester C by mass, the raw material for intermediate layer (base layer B) was 100% polyester A, and the raw material for surface layer C was a blend of 80% polyester A and 20% polyester B by mass. These were fed into a vented extruder and melt-extruded at 280°C. After that, the layers A and C were the outermost layers (surface layers) and the layer B was the intermediate layer, resulting in a three-type three-layer (A / B / C) layer structure. The extrusion conditions were co-extruded with an electrostatic application adhesion method, and the layer structure was cooled and solidified on a cooling roll with a surface temperature set at 15°C, so that the thickness composition ratio under the extrusion conditions was A / B / C = 2 / 27 / 2.

[0130] Next, the film was stretched 3.5 times in the longitudinal direction (MD direction) at a film temperature of 86°C using the difference in roll peripheral speed, and then this longitudinally stretched film was introduced into a tenter and stretched 4.5 times in the transverse direction (TD direction) at 105°C. Heat treatment was performed at 170°C, 240°C, 240°C, and 140°C in heat treatment (fixing) zones 1, 2, and 3 and cooling zone 4 within the tenter, respectively. After that, the film was wound up into a roll on a 3-inch plastic core to obtain a polyester film roll of Comparative Example 2 having a thickness of 31 μm. The properties of each of the obtained film rolls are shown in Table 1 below.

[0131] <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.

[0132] (1) Intrinsic viscosity (IV) 1 g of polyester was precisely weighed, dissolved in 100 mL of a mixed solvent of phenol / tetrachloroethane = 50 / 50 (mass ratio), and the viscosity was measured at 30 °C using a viscosity (IV) measuring device (Rigo Co., Ltd. "VMS-022UPC·F10").

[0133] (2) Average particle size and particle size distribution The powder in the polyester film rolls of the examples and comparative examples was observed 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. In addition, 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 is 10%, the particle diameter D50 at which the cumulative number is 50%, and the particle diameter D90 at which the cumulative number is 90% were measured by a laser diffraction scattering method using a Microtrackbell "MT3300EXII", and (D90-D10) / D50 was calculated.

[0134] (3) Average surface roughness (Sa), maximum peak height (Sp) and surface height distribution kurtosis (Sku) The surfaces of the polyester film rolls of the Examples and Comparative Examples were measured using a surface roughness measuring device (AMETEK Co., Ltd., "NewView" (registered trademark)), and the average surface roughness Sa value, maximum peak height Sp value, and surface height distribution kurtosis Sku value were determined from the obtained surface profile curves.

[0135] (4) Air leakage index Measurements were made using a DigiBec smoothness tester (manufactured by Toyo Seiki Co., Ltd., "DB-2") in accordance with JIS P8119, under an atmosphere of 23°C temperature and 50% RH. The pressure of the pressurizing device was 100 kPa, and the vacuum container had a volume of 38 ml. The time it took for 1 mL of air to flow, i.e., the time (seconds) for the pressure inside the container to change from 50.7 kPa to 48.0 kPa, was measured, and the air leakage index was calculated by multiplying the number of seconds obtained by the measurement. The sample size of the test film was 70 mm square, and 20 sheets of the test film were stacked so that the front and back of the test film overlapped to make a test laminate film. A 5mm hole was made in the center of the test laminate film, and the air leakage index was measured as described above. The higher the air leakage index value, the longer it takes for air to leak through the gaps between the films, indicating that the films are more closely attached to each other, and therefore the greater the risk of wrinkles occurring when the film is rolled up.

[0136] (5) Particle shedding test A BEMCOT ("M-3II" manufactured by Asahi Kasei Fibers Corporation) was attached to a rubbing tester (manufactured by Ohira Rika Kogyo Co., Ltd.) and rubbing was performed 5 times with an arm load of 680 g on the surface of the polyester film roll of each of the Examples and Comparative Examples (surface of the cured resin layer or layer A) to carry out a drop test. The amount of Si element was quantitatively evaluated by XRF on the polyester film roll surface before and after the drop test, and the amount of remaining particles (%) was calculated from the obtained amount of Si element using the following formula, and evaluated according to the following criteria. (Formula for calculating the remaining amount of particles) (Remaining amount of particles (%)) = {(Amount of silicon element before shedding test) - (Amount of silicon element after shedding test)} / (Amount of silicon element before shedding test) x 100 (Judgment criteria) A: The remaining amount of particles is 90% or more. B: Less than 90% of particles remain.

[0137] [Table 1]

[0138] It was found that the polyester film rolls of Examples 1 and 2 had high smoothness and a good air leakage index, and therefore had good film winding properties and were less susceptible to particle shedding.

[0139] Comparative Example 1 exhibits high smoothness and a good air leakage index, but it was confirmed that particles tend to fall off. In addition, the results of Example 1 revealed that the surface of the cured resin layer formed a characteristic uneven shape (low Sa and high Sku) that had not been seen before. On the other hand, Comparative Example 2 had a different uneven shape on the film surface and tended to have high Sa and low Sku. The air leakage index values ​​show that Comparative Example 2 took longer to leak, which suggests that it was difficult for the air to escape between the films, and that there was a high risk of wrinkles occurring when the film was rolled up. Furthermore, it was found that it is preferable that surface layer A contains an antimony compound and / or a titanium compound, that the content of the antimony compound is 100 ppm or less, and that the intrinsic viscosity (IV) of the polyester constituting surface layer A is 0.50 dL / g or more. [Industrial Applicability]

[0140] The polyester film roll of the present invention has high smoothness, a good air leakage index, minimal wrinkle generation, and improved roll winding properties, and therefore, as the productivity of the polyester film roll improves, the film can be made even longer. For example, in the manufacturing process of a multilayer ceramic capacitor, if the polyester film is used as a support for a ceramic green sheet, a uniform thin dielectric layer can be formed, and the frequency of changing the polyester film roll due to the lengthening can be reduced, which contributes to improving productivity. In particular, the polyester film can be suitably used as a support for a ceramic green sheet used in a multilayer ceramic capacitor for automobiles.

Claims

1. A polyester film roll obtained by winding up a film having a polyester film and a cured resin layer in this order, the cured resin layer is a cured product of a cured resin layer composition containing (A) a crosslinking agent, (B) a binder resin, (C1) silica particles, and (C2) silica microparticles, The (A) crosslinking agent is a melamine compound, The (B) binder resin is a polyester resin, The (C1) silica particles have an average particle size of 200 nm or more and 500 nm or less, the average particle size of the (C1) silica particles is 3 times or less the thickness of the cured resin layer, The (C2) silica microparticles are particles having an average particle size of 30 nm or more and 60 nm or less, The film satisfies the following (1) to (3) simultaneously, A polyester film roll, wherein the surface of the polyester film opposite to the surface in contact with the cured resin layer is substantially free of particles. (1) The average surface roughness (Sa) of the cured resin layer is 1 nm to 10 nm. (2) The surface height distribution kurtosis (Sku) of the surface of the cured resin layer is 50 or more. (3) The average surface roughness (Sa) of the surface of the polyester film opposite to the surface in contact with the cured resin layer is 1 nm to 10 nm.

2. 2. The polyester film roll according to claim 1, wherein the cured resin layer has a thickness of 50 nm to 500 nm.

3. 3. The polyester film roll according to claim 1, wherein the polyester constituting the polyester film has an intrinsic viscosity (IV) of 0.50 dL / g or more.

4. The polyester film roll according to any one of claims 1 to 3, wherein the polyester film contains a titanium compound.

5. The polyester film roll according to any one of claims 1 to 4, further comprising a release layer on a surface of the polyester film opposite to a surface in contact with the cured resin layer.

6. The polyester film roll according to any one of claims 1 to 5, which is used as a support for a ceramic green sheet in a production process of a multilayer ceramic capacitor.

7. The polyester film roll according to any one of claims 1 to 6, which is used as a support for a ceramic green sheet in a production process of an automotive ceramic capacitor.

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