Laminated polyester film

Abstract

To provide a laminated polyester film that allows control of fine irregularities on the film surface, exhibits high smoothness, and ensures good adhesion to a release layer.SOLUTION: A laminated polyester film comprises a polyester film with one surface (A) comprising a crystal nucleating agent. The surface (A) is covered with a resin layer composed of a resin composition comprising (a) a binder resin and (b) a crosslinker. The resin layer surface satisfies the following (1) and (2): (1) an average surface roughness (Sa) of 1-10 nm and (2) a maximum peak height (Sp) of 150 nm or less.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] In recent years, with the increasing electrification of automobiles and the sophistication of smartphones, multi-layered ceramic capacitors (MLCCs) have become smaller and more powerful. Multilayer ceramic capacitors are manufactured as follows: First, a ceramic slurry containing ceramic components and binder resin is applied to a release film and dried to create a ceramic green sheet (dielectric sheet). Electrodes are then printed onto this sheet using screen printing or similar methods to form internal electrodes. After drying, the printed ceramic green sheet is peeled off the release film, and multiple such green sheets are stacked. The stacked green sheets are then pressed together to form a single unit, and finally cut into individual chips. Subsequently, the internal electrodes and dielectric layers are sintered in a firing furnace to manufacture a multilayer ceramic capacitor.

[0003] As MLCCs become smaller and their capacity increases, the ceramic green sheet is being made thinner. When the ceramic green sheet is made even thinner, to 0.5 μm (thickness after drying) or less, if there are minute protrusions on the surface of the release film used as the carrier film, these will cause pinholes and other defects in the ceramic green sheet. 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 manufacturing ceramic green sheets, comprising 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 side of the smoothing layer opposite to the substrate, wherein the smoothing layer is formed by heating and curing a smoothing layer forming composition containing a thermosetting compound with a weight-average molecular weight of 950 or less, 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] Furthermore, Patent Document 2 describes a release polyester film with excellent surface smoothness, particularly with few fine defects on the film surface, and with a number of depression defects of 0.5 μm or more in depth of 5 per square meter. 2 The following is disclosed: a release polyester film having a centerline average roughness SRa of at least one surface of 15 to 35 nm and a ten-point average roughness SRz of 1000 nm or less.

[0006] Furthermore, Patent Document 3 describes a polyester film roll made by winding up a polyester film, wherein the slack defect present in the polyester film is eliminated by 100m 2 A polyester film is disclosed that has fewer than 5 particles per unit area. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2014-177093 [Patent Document 2] Japanese Patent Publication No. 2013-7054 [Patent Document 3] Japanese Patent Publication No. 2018-90803 [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] Traditionally, the surface condition of a film was controlled by adjusting the type of particles used, their average particle size, and the amount added to create fine irregularities. However, with the increasing thinning of ceramic green sheets, more precise control of surface irregularities is now required, and conventional particle-based methods for controlling the film surface have reached their limits. Therefore, there is a need for a film that allows for precise design of surface irregularities.

[0009] Furthermore, the film used as a support for the release film is required to have no effect on the release layer provided on the film (e.g., inhibit curing) and to have good adhesion to the release layer.

[0010] Therefore, the object of the present invention is to provide a laminated polyester film in which the fine irregularities on the film surface are controlled, resulting in high smoothness and good adhesion to the release layer. [Means for solving the problem]

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

[14] .

[0012] [1] A laminated polyester film comprising a resin layer formed on one surface (A) of a polyester film containing a crystal nucleating agent, and the resin layer formed on the surface (A) of a resin composition containing (a) a binder resin and (b) a crosslinking agent, wherein the surface of the resin layer satisfies the following (1) and (2). (1) The average surface roughness (Sa) is 1 to 10 nm. (2) The maximum peak height (Sp) must be 150 nm or less. [2] The laminated polyester film according to [1], wherein the crystal nucleating agent is a fatty acid metal salt represented by the following general formula (X). (CH3(CH2) n COO)m M ···(X) (In the above formula, n is an integer of 4 or more, M is Na, Ca or Li. Also, m is 1 when M is Na or Li, and 2 when M is Ca.) [3] The ratio (Sp / Sa) of the maximum peak height (Sp) to the average surface roughness (Sa) of the resin layer surface is 50 or less, the laminated polyester film according to [1] or [2]. [4] The (a) binder resin contains a polyester resin or a polyvinyl alcohol-based resin, the laminated polyester film according to any one of [1] to [3]. [5] The (b) crosslinking agent contains a melamine compound, the laminated polyester film according to any one of [1] to [4]. [6] The (b) crosslinking agent contains two or more kinds of compounds, the laminated polyester film according to any one of [1] to [5]. [7] The polyester film has a three-layer structure, the laminated polyester film according to any one of [1] to [6]. [8] The polyester film has a surface layer C on the surface opposite to the one surface (A), the laminated polyester film according to [7]. [9] The average surface roughness (Sa) of the surface layer C is 3 nm or more and 20 nm or less, the laminated polyester film according to [8].

[10] The maximum peak height (Sp) of the surface layer C is 10 nm or more and 220 nm or less, the laminated polyester film according to [8] or [9].

[11] The resin layer has a release layer, the laminated polyester film according to any one of [1] to

[10] .

[12] The release layer contains a curable silicone resin, the laminated polyester film according to

[11] .

[13] In the manufacturing process of a laminated ceramic capacitor, used as a support for a ceramic green sheet, the laminated polyester film according to any one of [1] to

[12] .

[14] In the manufacturing process of an automotive ceramic capacitor, the laminated polyester film according to any one of [1] to

[12] , which is used as a support for a ceramic green sheet.

Effect of the Invention

[0013] According to the present invention, it is possible to provide a laminated polyester film in which fine irregularities on the film surface are controlled, having high smoothness and good adhesion to a release layer. Further, since the laminated polyester film of the present invention has extremely excellent surface smoothness, for example, in the manufacturing process of a laminated ceramic capacitor, by using it as a support for a ceramic green sheet, there is an advantage that there is little possibility of defects occurring in the ceramic green sheet due to the fine irregularities on the surface of the laminated polyester film of the present invention.

Brief Description of the Drawings

[0014] [Figure 1] It shows the (presumed) crystallization mechanism of polyester thermodynamically by using a crystal nucleating agent in a polyester resin. [Figure 2] It shows the (presumed) formation mechanism of surface irregularities by using a crystal nucleating agent during the production of a polyester film.

Mode for Carrying Out the Invention

[0015] 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). Further, in the present invention, a combination of preferred embodiments is a more preferred embodiment. Also, in the present invention, when referring to a "film", it includes a "sheet", and when referring to a "sheet", it includes a "film".

[0016] [Laminated Polyester Film] The laminated polyester film of the present invention (hereinafter also referred to as "this laminated film") is a laminated polyester film in which one surface (A) of the polyester film contains a crystal nucleating agent, and a resin layer formed on the surface (A) of a resin composition containing (a) a binder resin and (b) a crosslinking agent, wherein the surface of the resin layer is a film that satisfies all of the following (1) and (2). (1) The average surface roughness (Sa) is 1 to 10 nm. (2) The maximum peak height (Sp) must be 150 nm or less.

[0017] In the present invention, the resin layer surface formed on one surface (A) of the polyester film refers, for example, to the surface on which the ceramic green sheet is laminated when used as a support for the ceramic green sheet in the manufacturing process of a multilayer ceramic capacitor. By satisfying the above conditions (1) and (2), the resin layer surface can accommodate thinning of the ceramic green sheet, and a multilayer ceramic capacitor can be manufactured in a suitable condition. Furthermore, from the viewpoint of using it as a support for the ceramic green sheet, the resin layer surface is suitable as the surface on which the release layer described later is provided.

[0018] Due to the above-described structure, this laminated film has controlled fine irregularities on its surface, resulting in high smoothness. Therefore, it can be used to create thin films of ceramic green sheets during manufacturing. The reason why this laminated film achieves the aforementioned effect can be presumed to be as follows. According to the present invention, by including a crystal nucleating agent on one surface (A) of the polyester film, the rate of polyester crystallization in the polyester film can be increased, as shown in Figure 1, and the size of the formed crystals can be reduced. Therefore, since the fine irregularities on the surface of the polyester film can be controlled, the fine irregularities on the surface of the resin layer formed on one surface (A) of the polyester film can also be controlled. As a result, the surface of the resin layer can satisfy the above conditions (1) and (2), and a laminated polyester film with high smoothness can be obtained. Furthermore, by having the above-described structure, this laminated film can suppress the occurrence of wrinkles and pinholes during film manufacturing. Furthermore, because the resin layer surface of this laminated film has the above-described structure, the occurrence of pinholes due to surface irregularities can be suppressed, thus enabling the thinning of ceramic green sheets and allowing for the manufacture of multilayer ceramic capacitors in a suitable condition.

[0019] As described above, this laminated film, with the above configuration, enables even more precise control of the uneven shape of the film surface, making it suitable for use in the manufacture of multilayer ceramic capacitors. In particular, it can be suitably used in situations where thin ceramic green sheets with a thickness (after drying) of 0.5 μm or less are required.

[0020] The thickness of this laminated film is preferably 19 μm to 38 μm, and more preferably 25 μm to 32 μm. Furthermore, the film roll obtained by winding the laminated film is a film roll wound around a core such as a paper tube, metal tube, or plastic tube, and is preferably 0.2 m or more in width, more preferably 0.3 m or more, even more preferably 1.0 m or more, and even more preferably 1.5 m or more. The upper limit of the film width is not particularly limited, but from the viewpoint of handling, it is preferably 2.3 m or less, and more preferably 2.0 m or less. Furthermore, the length of the laminated film wound onto the film roll is not particularly limited, but is preferably 1000m or more, more preferably 6000m or more, and even more preferably 12000m or more.

[0021] (Surface properties) In the present invention, the surface of the resin layer is characterized by satisfying the following (1) and (2). (1) The average surface roughness (Sa) is 1 to 10 nm. (2) The maximum peak height (Sp) must be 150 nm or less.

[0022] (1) Average surface roughness (Sa) In this invention, the average surface roughness (Sa) of the resin layer surface must be 1 to 10 nm. If the average surface roughness (Sa) of the resin layer surface exceeds 10 nm, defects such as pinholes are more likely to occur due to fine irregularities on the film surface, making it impossible to thin the ceramic green sheet. On the other hand, if the average surface roughness (Sa) is less than 1 nm, the film surface becomes too flat, reducing the film's slipperiness and impairing its processability. In the present invention, the average surface roughness (Sa) of the resin layer surface is preferably 1 to 8 nm, more preferably 1.5 to 5 nm, and even more preferably 2 to 4 nm, from the viewpoint of controlling fine irregularities on the surface of the laminated film and having high smoothness, from the viewpoint of improving processability and accommodating thinning of the ceramic green sheet.

[0023] Average surface roughness (Sa) is one of the surface roughness parameters (ISO 25178), and is an extension of the two-dimensional Ra to three dimensions. It is calculated by dividing the volume of the area enclosed by the surface shape curve and the average surface by the measured area, and can be obtained from the following equation (1). When the surface is the XY plane and the height direction is the Z axis, if A is the defined region (the entire image) and Z(x,y) is the height of the image point (x,y) from the plane with height 0, then it can be expressed as shown in equation (1) below.

[0024]

number

[0025] (2) Maximum mountain height (Sp) In this invention, the maximum peak height (Sp) on the surface of the resin layer must be 150 nm or less. When the maximum peak height (Sp) on the resin layer surface exceeds 150 nm, defects such as pinholes are more likely to occur due to fine irregularities on the film surface, making it impossible to thin the ceramic green sheet. In the present invention, the maximum peak height (Sp) of the resin layer surface is preferably 140 nm or less, more preferably 100 nm or less, and even more preferably 50 nm or less, from the viewpoint of thinning the ceramic green sheet. Furthermore, there is no particular limit to the lower limit of the maximum peak height (Sp), but from the viewpoint of improving the winding properties of the film, it is preferably 5 nm or more, more preferably 10 nm or more, and even more preferably 15 nm or more.

[0026] Maximum peak height (Sp) is one of the surface roughness parameters (ISO 25178), representing the maximum height from the mean surface, and is expressed by the following equation (2).

[0027]

number

[0028] Furthermore, in the present invention, the relationship between the average surface roughness (Sa) and the maximum peak height (Sp) of the resin layer surface, more specifically the ratio of the maximum peak height (Sp) to the average surface roughness (Sa) (Sp / Sa), is preferably 50 or less, more preferably 45 or less, and even more preferably 40 or less. The relationship between average surface roughness (Sa) and maximum peak height (Sp), Sp / Sa, is 50 or less. By maintaining the average surface roughness (Sa) while controlling the maximum peak height (Sp), the laminated film can have fine surface irregularities controlled, ensuring processability while maintaining high smoothness. As a result, this laminated film makes it easier to form thin ceramic green sheets, thus enabling the thinning of ceramic green sheets. Furthermore, while there are no particular limitations on the lower limit of the relationship between average surface roughness (Sa) and maximum peak height (Sp), a value of 5 or higher is preferred, 10 or higher is more preferred, and 15 or higher is even more preferred, from the viewpoint of controlling the fine irregularities on the surface of the laminated film, ensuring processability, and achieving high smoothness.

[0029] In the present invention, the surface properties of the resin layer surface can be adjusted, for example, by adjusting the type and content of the nucleating agent contained in one surface (A) of the polyester film, or by controlling the conditions of the cooling roll during film manufacturing. Furthermore, the properties can also be adjusted by controlling the type and content of compounds contained in the resin layer formed on one surface (A) of the polyester film, or by controlling the thickness of the resin layer.

[0030] <Polyester film> This laminated film is characterized in that one surface (A) of the polyester film (hereinafter also referred to as "this film") contains a crystal nucleating agent.

[0031] (Crystallizing agent) The nucleating agent used in the present invention is preferably a fatty acid metal salt represented by the following general formula (X). (CH3(CH2) n COO) m M ···(X) (In the above formula, n is an integer greater than or equal to 4, and M is Na, Ca, or Li. Also, m is 1 if M is Na or Li, and 2 if M is Ca.)

[0032] The crystal nucleating agent is a fatty acid metal salt represented by the above general formula (X), which promotes the crystallization of the polyester resin and makes it easier to suppress the aggregation of the crystal nucleating agent in the molten polyester raw material during the manufacture of the polyester film. As a result, the crystal nucleating agent can be uniformly distributed in the polyester raw material, which controls the fine irregularities on one surface (A) of the polyester film, and the resin layer surface formed on one surface (A) of the polyester film can satisfy the above conditions (1) and (2).

[0033] In the above general formula (X), M represents a metal ion in the fatty acid metal salt, and is one of Na, Ca, or Li, with Na being preferred. By having one of Na, Ca, or Li as the metal ion, it is possible to suppress the decrease in molecular weight of the polyester resin due to heat retention during polyester film manufacturing.

[0034] Furthermore, in the above general formula (X), n is an integer of 4 or more, preferably between 6 and 35, more preferably between 8 and 33, even more preferably between 10 and 30, and even more preferably between 15 and 28. In the general formula (X), having n within the above range improves the compatibility between the crystal nucleating agent and the polyester resin, enabling the thinning of ceramic green sheets. In the fatty acid metal salt represented by the above general formula (X), specific examples of fatty acids include caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, undecanoic acid, lauric acid, tridecanoic acid, myristic acid, pentadecanoic acid, palmitic acid, margaric acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, and montanic acid, among which montanic acid is preferred.

[0035] In the present invention, the melting point of the fatty acid metal salt used as a crystal nucleating agent is preferably 140°C to 220°C, more preferably 150°C to 210°C, and even more preferably 160°C to 200°C. By having a melting point of 220°C or lower, it is possible to suppress the maximum peak height (Sp) on the polyester film surface from becoming too large, and by having a melting point of 140°C or higher, it is possible to form fine irregularities on one surface (A) of the polyester film. Therefore, the resin layer surface formed on one surface (A) of the polyester film can be more easily satisfied with (1) and (2) above, so that the fine irregularities on the surface of the laminated film can be controlled and it can have high smoothness. As a result, it is possible to easily handle the thinning of the ceramic green sheet. In the present invention, the melting point of the fatty acid metal salt can be measured by simultaneous thermogravimetric and differential thermal analysis (TG-DTA), specifically by the method described in the examples.

[0036] From the viewpoint of controlling the fine irregularities on the surface of the laminated film, achieving high smoothness, and improving handling, the amount of nucleating agent added is preferably 2000 ppm or more by mass relative to the film, more preferably 4000 ppm to 25000 ppm, even more preferably 6000 ppm to 20000 ppm, and among these, particularly preferably 8000 ppm to 15000 ppm.

[0037] The above-mentioned nucleating agents may be used alone or in combination of two or more types.

[0038] (polyester) In the present invention, polyester refers to polyester used as a raw material for polyester film, and is a polymer compound having ester bonds continuously in its main chain. In the present invention, polyester may be homopolyester or copolymer polyester, and specifically, polyester obtained by polycondensation reaction of a dicarboxylic acid component and a diol component can be mentioned.

[0039] In this invention, it is preferable to use a polyester that contains more than 50 mol% of aromatic dicarboxylic acid or aliphatic dicarboxylic acid when the dicarboxylic acid component is 100 mol%.

[0040] 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'-diphenylsulfondicarboxylic acid, as well as aliphatic dicarboxylic acids such as adipic acid, suberic acid, sebacic acid, dimer acid, dodecanedionic acid, cyclohexanedicarboxylic acid, and their ester derivatives.

[0041] 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.

[0042] When the above polyester consists of a homopolyester, it is preferable to obtain one obtained by polycondensation of an aromatic dicarboxylic acid and an aliphatic glycol. Examples of the aforementioned aromatic dicarboxylic acids include terephthalic acid and 2,6-naphthalenedicarboxylic acid, and examples of aliphatic glycols include ethylene glycol, diethylene glycol, and 1,4-cyclohexanedimethanol. Typical examples of polyesters include polyethylene terephthalate (PET) and polyethylene-2,6-naphthalenedicarboxylate (PEN).

[0043] On the other hand, if the polyester is a copolymerized polyester, it is preferable that it 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 that constitutes 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 dicarboxylic acid components in copolymerized polyesters include one or more types of isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, and oxycarboxylic acid. Examples of glycol components in copolymerized polyesters include one or more of ethylene glycol, diethylene glycol, propylene glycol, butanediol, 1,4-cyclohexanedimethanol, and neopentyl glycol.

[0044] Furthermore, the polyester is preferably composed of 80 mol% or more, preferably 90 mol% or more, of polyethylene terephthalate units, such as polyethylene terephthalate, or polyethylene-2,6-naphthalate units, such as polyethylene-2,6-naphthalate.

[0045] Normally, when polyester is produced (polycondensed) using ethylene glycol as one of the raw materials, diethylene glycol is produced as a by-product from ethylene glycol. In this specification, this diethylene glycol is referred to as by-product diethylene glycol. The amount of diethylene glycol produced as a by-product from ethylene glycol varies depending on the type of polycondensation, but it is approximately 5 mol% or less of the ethylene glycol. In the present invention, 5 mol% or less of diethylene glycol is considered as by-product diethylene glycol, and this by-product diethylene glycol is also included in ethylene glycol and distinguished from copolymer components. On the other hand, depending on the diethylene glycol content, more specifically if diethylene glycol is present in amounts exceeding 5 mol%, the diethylene glycol is treated as a copolymer component rather than as a by-product diethylene glycol.

[0046] Polyester polycondensation catalyst Examples of polycondensation catalysts used when polycondensing the above-mentioned polyester include antimony compounds, germanium compounds, aluminum compounds, and titanium compounds. Among these, at least one of antimony compounds and titanium compounds is preferred. Therefore, it is preferable that the polyester film contains at least one of an antimony compound and a titanium compound.

[0047] It is preferable that the polyester constituting the outermost layer of this film (also called the "surface layer," for example, one surface (A) of a polyester film, or the surface layer on which the resin layer is laminated) uses a titanium compound as its polycondensation catalyst. By using a titanium compound, the number of metal-containing aggregates derived from the titanium compound, so-called coarse foreign matter, in the film can be reduced, thereby reducing the maximum peak height (Sp) of the laminated film and enabling it to have high smoothness. Preferably, the titanium element content in the outermost layer derived from the titanium compound is 1 ppm to 40 ppm, more preferably 2 ppm to 20 ppm, and even more preferably 3 ppm to 10 ppm. Within the above range, catalyst-induced foreign matter can be reduced without decreasing the manufacturing efficiency of polyester. Furthermore, when the polyester film has a laminated structure, from the viewpoint of productivity, it is preferable not to use a titanium compound as the polycondensation catalyst for the polyester constituting the intermediate layer described later. Furthermore, from a similar viewpoint, it is preferable that the antimony compound content in the outermost layer of this film be 100 ppm or less. For example, the surface layer A described later contains at least one of an antimony compound and a titanium compound, and it is preferable that the antimony compound content in surface layer A is 100 ppm or less. In this case, surface layer A does not have to contain an antimony compound.

[0048] ≪Intrinsic Viscosity of Polyester (IV)≫ The intrinsic viscosity (IV) of the polyester constituting this film is preferably 0.50 dL / g or higher, more preferably 0.55 dL / g or higher, and even more preferably 0.60 dL / g or higher. In the present invention, by using a polyester with an intrinsic viscosity (IV) of 0.40 dL / g or higher as the polyester constituting the polyester film, the shear stress during kneading of the polyester increases, the nucleating agent in the polyester resin is easily dispersed, the fine irregularities on one surface (A) of the polyester film are controlled, and the surface characteristics of the resin layer formed on one surface (A) of the polyester film can be easily brought within the above range. Furthermore, from the viewpoint of the fluidity of the nucleating agent, the upper limit of the intrinsic viscosity (IV) of the polyester is preferably 1.00 dL / g or less, more preferably 0.85 dL / g or less, and even more preferably 0.75 dL / g or less.

[0049] Furthermore, from the same viewpoint as above, if the film has a laminated structure, the intrinsic viscosity (IV) of the polyester constituting the surface layer, specifically the outermost layer of the film (for example, one surface (A) of the polyester film, or the surface layer on which the 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. Also, from the viewpoint of the fluidity of the crystal nucleating agent, the upper limit of the intrinsic viscosity (IV) of the polyester constituting the surface layer is preferably 1.00 dL / g or less, more preferably 0.85 dL / g or less, and even more preferably 0.75 dL / g or less.

[0050] Furthermore, "the intrinsic viscosity (IV) of the polyester constituting this film" refers to the intrinsic viscosity (IV) of the mixed resin when two or more polyesters with different intrinsic viscosities (IV) are used.

[0051] (Composition of polyester film) In the present invention, the polyester film may be a single-layer polyester film or a laminated polyester film having two or more layers. In the present invention, the polyester film is preferably a laminated polyester film having two or more layers, and more preferably a polyester film with a three-layer structure, from the viewpoint of easily controlling the surface properties of the resin layer formed on one surface (A) within the above range. Furthermore, in the present invention, if the polyester film is a laminated polyester having two or more layers, a three-layer configuration of A / B / C consisting of a surface layer A, an intermediate layer B, and a surface layer C is preferred.

[0052] In the present invention, when the polyester film is a laminated polyester film having two or more layers, it is preferable that the surface layer A contains the above-mentioned nucleating agent. Here, the surface layer A is the surface layer that forms one surface (A) of the polyester film in the present invention, and in a laminated polyester film, by containing the above-mentioned nucleating agent in the surface layer A, it is easier to control the surface properties of the resin layer formed on one surface (A) of the polyester film within the above range, and it is easier to accommodate thinning of the ceramic green sheet.

[0053] The content of the crystal nucleating agent in surface layer A is preferably 2000 ppm or more by mass, more preferably 4000 ppm to 25000 ppm, even more preferably 6000 ppm to 20000 ppm, and even more preferably 8000 ppm to 15000 ppm, from the viewpoint of controlling the fine irregularities on the surface of the laminated film, achieving high smoothness, and improving handling.

[0054] Surface layer C is a surface layer formed on the side opposite to surface layer A. In other words, it is preferable that this film has surface layer C on the side opposite to surface layer A, that is, one surface (A) of the polyester film. It is preferable that surface layer A has an average surface roughness (Sa) and a maximum peak height (Sp) that is equal to or less than that of surface layer C. The average surface roughness (Sa) of surface layer C is preferably 3 nm to 20 nm, more preferably 4 nm to 18 nm, and even more preferably 5 nm to 15 nm. The maximum peak height (Sp) of surface layer C is preferably 10 nm to 220 nm, more preferably 30 nm to 200 nm, and even more preferably 50 nm to 180 nm. By having the average surface roughness (Sa) or maximum peak height (Sp) of the surface layer C within the above range, the surface layer C can be provided with the necessary roughness to improve handling, making it easier to improve the handling properties of this laminated film.

[0055] From the viewpoint of improving the handling of the film, the surface layer C preferably contains particles. Examples of the aforementioned 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; 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 resins. Among these, crosslinking molecules, silica, calcium carbonate, and aluminum oxide are preferred, and silica is more preferred. Furthermore, examples of crosslinked polymer particles for organic particles include divinylbenzene polymer, ethyl vinylbenzene-divinylbenzene copolymer, styrene-divinylbenzene copolymer, styrene-ethyl vinylbenzene-divinylbenzene copolymer, ethylene glycol dimethacrylate polymer, styrene-ethylene glycol dimethacrylate copolymer, and methyl methacrylate-divinylbenzene copolymer. In addition, crosslinked polymer particles composed of three or more components may be used, and a copolymer of divinylbenzene, methylstyrene, methacrylic acid, and styrene is preferred. In the surface layer C, the above particles may be used individually or in combination of two or more types.

[0056] From the viewpoint of improving the handling of this film, the average particle size is preferably 0.1 to 1.5 μm, more preferably 0.1 to 1.2 μm, and even more preferably 0.2 to 1.0 μm.

[0057] Furthermore, it is particularly preferable that the particles have a narrow particle size distribution and a nearly uniform average particle size (i.e., possess so-called monodisperse properties). As particles having a narrow particle size distribution and a nearly uniform average particle size, when the particle size distribution of the particles is defined as follows, if the particle size at which the cumulative number of particles is 10% is D10, the particle size at which the cumulative number of particles is 50% is D50, and the particle size at which the cumulative number of particles is 90% is D90, then particles in which (D90-D10) / D50 is 0.4 or less are preferred, and particles in which it is 0.3 or less are particularly preferred. The related relationship (D90-D10) / D50 indicates the variation in particle size relative to D50. Particles with (D90-D10) / D50 of 0.4 or less have a sharp particle size distribution with a small difference between D90 and D10, and can be given extremely high smoothness to this film while maintaining excellent handling properties. The particle size distribution of the aforementioned particles is measured using a laser diffraction measuring device.

[0058] The surface layer C may contain two or more types of particles with different average particle sizes, from the viewpoint of improving the handling of the film. In such cases, the maximum difference in average particle size between two or more particles with different average particle sizes is preferably 0.1 μm or more, more preferably 0.2 μm or more, and even more preferably 0.3 μm or more. A difference in average particle size of 0.1 μm or more makes it easier to improve the slipperiness of the polyester film surface and thus improve the handling of the film. Furthermore, from the viewpoint of suppressing the occurrence of pinholes due to unevenness, the upper limit of the maximum difference in average particle size is preferably 1.5 μm or less, preferably 1.2 μm or less, and more preferably 1.0 μm or less.

[0059] Intermediate layer B is preferably configured to function as the thickest main layer, and in order to reduce costs, it is preferable that it is substantially free of particles or contains particles at a lower concentration than surface layer C. The particles used in intermediate layer B are the same as those used in intermediate layer C described above, and the preferred range is also the same. Furthermore, "substantially absent" means intentionally absent, and specifically refers to a particle content (particle concentration) of 200 ppm or less, more preferably 150 ppm or less.

[0060] In the present invention, the intermediate layer B of the polyester film may contain recycled polyester raw material, and in such cases, it is preferable that it contains 50% by mass or more, preferably 70% by mass or more, more preferably 90% by mass or more, and even more preferably 100% by mass. By containing recycled polyester raw material in the intermediate layer B within the above range, for example, CO2 emissions can be reduced, and the burden on the environment can be reduced.

[0061] Furthermore, the film is particularly preferably configured to include surface layer A and / or surface layer C as shown in (W) below. By adopting this configuration, the laminated film can be endowed with excellent handling properties and surface smoothness.

[0062] (W) Particularly preferred embodiment (1) In the configuration of A / B / C described above, the surface layer A is a form that includes a titanium compound and a fatty acid metal salt as a crystal nucleating agent. (2) In the above (1), the surface layer C is a form that contains particles. (3) In either (1) or (2) above, the surface layer C contains an antimony compound and / or a titanium compound, wherein the content of the antimony compound is 100 ppm or less. (4) In any of (1) to (3) above, the particles of the surface layer C are such that when D10 is the particle diameter at which the cumulative number of particles reaches 10%, D50 is the particle diameter at which the cumulative number of particles reaches 50%, and D90 is the particle diameter at which the cumulative number of particles reaches 90%, (D90-D10) / D50 is 0.4 or less. (5) In (4) above, the crystal nucleating agent is in the form of a sodium fatty acid salt.

[0063] In the above (W), by using polyester polycondensed with a titanium compound as a catalyst in surface layer A and surface layer C, catalyst-induced foreign matter can be reduced, and high surface smoothness can be achieved.

[0064] (Method of manufacturing polyester film) The following is an example of a method for manufacturing this film. First, raw materials, such as polyester chips, are supplied to an extruder by known methods, heated to a temperature above the melting point of each polymer, the molten polymer is extruded from the die, and cooled and solidified on a rotating cooling drum to a temperature below the glass transition point of the polymer, thereby obtaining a substantially amorphous, unoriented sheet.

[0065] Next, the unoriented sheet is stretched in one direction using a roll or tenter type stretcher. At this time, the stretching temperature is usually 25 to 120°C, preferably 35 to 100°C, and the stretching ratio is usually 2.5 to 7 times, preferably 2.8 to 6 times.

[0066] Next, the material is stretched in a direction perpendicular to the stretching direction of the first stage. At this time, the stretching temperature is usually 50 to 140°C, and the stretching ratio is usually 3.0 to 7 times, preferably 4.0 times or more, and more preferably 4.5 to 5.0 times.

[0067] Then, the film can be heat-fixed at a temperature of 180-220°C under tension or under relaxation of 30% or less to obtain the film as a biaxially oriented film. This heat-fixing process may be carried out in two or more steps at different temperatures. Furthermore, cooling may be performed in a cooling zone after the heat-setting treatment. The cooling temperature is preferably higher than the glass transition temperature (Tg) of the polyester resin constituting the polyester film, and more specifically, it is preferably in the range of 100 to 160°C. This cooling may be carried out in two or more stages at different temperatures. Furthermore, in the aforementioned extension, a method can be adopted in which the extension is carried out in two or more stages in one direction. By combining this with the above stretching conditions, the uneven shape can be adjusted by further promoting crystallization by increasing the thickness of surface layer A. Furthermore, by increasing the stretching ratio while increasing the thickness of surface layer A, it is possible to make it easier to form protrusions. For example, if the thickness of this film is between 19 μm and 38 μm and it consists of three layers, the desired uneven shape can be achieved by adjusting the thickness of surface layer A within the range of 0.5 μm to 5 μm, and the surface properties of the resin layer formed on the surface (A) can also be easily adjusted to the desired uneven shape.

[0068] In the manufacturing method of this film, the thermodynamic crystallization mechanism of polyester and the mechanism of surface formation during the melt extrusion process of the polyester raw material are presumed to be as follows. The thermodynamic crystallization mechanism of polyester can be considered as follows, based on the following equation (Y). ΔG = -NΔg + Aσ ···(Y) In equation (Y) above, ΔG represents the crystal nucleation free energy, N is the volume of the crystal nucleus, Δg is the melting free energy, A is the number of repeating units in the crystal, and σ is the free energy. When a nucleating agent is incorporated into polyester, as shown in Figure 1, the energy barrier required for the formation of primary crystal nuclei is lowered, resulting in a higher crystallization rate. Therefore, it is presumed that a large number of primary crystal nuclei can be formed within the polyester film, and consequently, the crystal size becomes smaller. Furthermore, the mechanism for the formation of these irregularities is considered as follows. We focused on the fact that when a polyester raw material containing a crystal nucleating agent is melt-extruded and comes into contact with the casting drum from the die, the surface condition of the film differs between the side facing the atmosphere and the side in contact with the casting drum. As shown in Figure 2, the polyester film surface on the side in contact with the casting drum is rapidly cooled, which suppresses crystal growth and reduces the size of the crystals formed. Therefore, it is presumed that irregularities are less likely to form even after longitudinal and transverse stretching. On the other hand, the film surface on the atmospheric side that is not in close contact with the casting drum is cooled slowly, which promotes crystal growth and increases the size of the crystals formed. Therefore, it is presumed that after longitudinal stretching and transverse stretching, minute irregularities will be formed.

[0069] <Resin layer> The laminated film is characterized by comprising a resin layer (hereinafter also referred to as "the resin layer") formed on one surface (A) of a polyester film using a resin composition (hereinafter also referred to as "the composition") that includes (a) a binder resin and (b) a crosslinking agent. By containing compounds (a) and (b) above, this composition can not only suppress the effect on the release layer provided on the resin layer (e.g., inhibition of curing), but also improve adhesion to the release layer.

[0070] (Binder resin) There are no particular restrictions on the binder resin (a) of the compound, and conventionally known binder resins can be used. Examples of binder resins (a) include polyester resins, (meth)acrylic resins, polyurethane resins, polyvinyl resins (polyvinyl alcohol-based resins, vinyl chloride vinyl acetate copolymers, etc.), polyalkylene glycols, polyalkyleneimines, methylcellulose, hydroxycellulose, starches, etc. Among these, it is preferable to use at least one of polyester resins, (meth)acrylic resins, polyurethane resins, and polyvinyl alcohol-based resins from the viewpoint of film-forming properties and adhesion to polyester films, and it is more preferable to include polyester resins or polyvinyl alcohol-based resins from the viewpoint of suppressing the effect on the release layer provided on the resin layer (e.g., curing inhibition). In this composition, the binder resin (a) may be used alone or two or more may be used in combination.

[0071] Polyester resin Examples of polyester resins include those whose main components consist of polycarboxylic acids and polyhydroxy compounds, as listed below. In other words, as polycarboxylic acids, terephthalic acid, isophthalic acid, orthophthalic acid, phthalic acid, 4,4'-diphenyldicarboxylic acid, 2,5-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 2-potassium sulfoterephthalic acid, 5-sodium sulfisoisophthalic acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, glutaric acid, succinic acid, trimellitic acid, trimesic acid, pyromellitic acid, trimellitic anhydride, phthalic anhydride, p-hydroxybenzoic acid, monopotassium salt of trimellitic acid, and their ester-forming derivatives can be used. Examples of polyvalent hydroxy compounds that can be used include ethylene glycol, 1,2-propanediol, 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, dimethylolpropionic acid, glycerin, trimethylolpropane, sodium dimethylolethylsulfonate, and potassium dimethylolpropionate. From these compounds, one or more can be appropriately selected, and a polyester resin can be synthesized by a conventional polycondensation reaction.

[0072] Furthermore, as part of the above-mentioned polycarboxylic acid, sulfoisophthalic acids such as 5-sodium sulfoisophthalic acid are copolymerized to introduce sulfonic acid groups into the polyester skeleton, which are then neutralized and hydrophilized, and these are preferably used. The amount copolymerized is usually 1 to 13 mol%, preferably 3 to 10 mol%, and more preferably 5 to 9 mol%, relative to the total polycarboxylic acid. By introducing an appropriate amount of sulfonic acid groups, the water dispersion stability can be further improved.

[0073] (Meth)acrylic resin (Meth)acrylic resin is a polymer composed of polymerizable monomers, including acrylic and methacrylic monomers. These may be homopolymers, copolymers, or copolymers with polymerizable monomers other than acrylic and methacrylic monomers. (Meth)acrylic polymers are polymers having structural units derived from (meth)acrylic acid or alkyl (meth)acrylate esters. A (meth)acrylic polymer may be at least one polymer selected from (meth)acrylic acid and alkyl (meth)acrylate esters, or it may be a copolymer of at least one selected from these and at least one selected from other monomers, such as styrene or styrene derivatives, monomers containing hydroxyl groups, etc. Furthermore, copolymers of these polymers with other polymers (e.g., polyester, polyurethane, etc.) are also included. Examples include block copolymers and graft copolymers. In other words, the (meth)acrylic resin may be a (meth)acrylic-modified polyester resin or a (meth)acrylic-modified polyurethane resin. Alternatively, polymers (or mixtures of polymers, in some cases) obtained by polymerizing polymerizable monomers in a polyester solution or polyester dispersion are also included. Similarly, polymers (or mixtures of polymers, in some cases) obtained by polymerizing polymerizable monomers in a polyurethane solution or polyurethane dispersion are also included. In the same manner, polymers (or mixtures of polymers, in some cases) obtained by polymerizing polymerizable monomers in other polymer solutions or dispersions are also included, and these are also referred to herein as (meth)acrylic modified polyester resins or (meth)acrylic modified polyurethane resins. The polyesters and polyurethanes used in (meth)acrylic resins described above can be appropriately selected from those exemplified as polyesters and polyurethanes used in (a) binder resins. Furthermore, (meth)acrylic resin may contain hydroxyl groups and amino groups to further improve adhesion with polyester film.

[0074] The polymerizable monomers mentioned above are not particularly limited, but some representative compounds include, for example, various carboxyl group-containing monomers such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, fumaric acid, maleic acid, and citraconic acid, and their salts; various hydroxyl group-containing monomers such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, monobutyl hydroxyfumarate, and monobutyl hydroxyitaconate; and methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, and lauryl (meth)acrylate. Examples include various alkyl(meth)acrylic acid esters; various nitrogen-containing monomers such as (meth)acrylamide, diacetone acrylamide, or (meth)acrylonitrile; hydroxyl-containing nitrogen-containing monomers such as N-methylol(meth)acrylamide; various styrene derivatives such as styrene, α-methylstyrene, divinylbenzene, and 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.

[0075] Among the (meth)acrylic resins mentioned above, polymers obtained by polymerizing polymerizable monomers containing acrylic and methacrylic monomers are preferred, and polymers containing alkyl (meth)acrylic acid esters are more preferred. Furthermore, it is preferable to dilute this composition containing (meth)acrylic resin with a solvent to prepare a coating solution, as described later, and it is preferable that the solvent is primarily water (50% by mass or more). In other words, from the viewpoint of facilitating dissolution or dispersion when the coating solution is aqueous, it is preferable that the polymerizable monomer has hydrophilic groups such as hydroxyl groups or carboxyl groups. Therefore, polymers obtained by polymerizing alkyl (meth)acrylic acid esters with polymerizable monomers containing hydrophilic group monomers such as monomers containing hydroxyl groups and monomers containing carboxyl groups are also preferred as acrylic resins. Furthermore, the acrylic resin may also be an emulsion polymer obtained by polymerizing polymerizable monomers in the presence of a surfactant, for example.

[0076] Polyurethane resin Polyurethane resin is a polymer compound having urethane bonds within its molecule, and is preferably water-dispersible or water-soluble. In this invention, it may be used alone or in combination of two or more types.

[0077] To impart water dispersibility or water solubility, it is common and preferable to introduce hydrophilic groups such as hydroxyl groups, carboxyl groups, sulfonic acid groups, sulfonyl groups, phosphate groups, and ether groups into the polyurethane resin. Among these hydrophilic groups, carboxyl groups or sulfonic acid groups are particularly preferred from the viewpoint of adhesion between the resin layer and the polyester film.

[0078] One method for producing polyurethane resin involves the reaction of a hydroxyl group-containing compound with an isocyanate. Polyols are preferably used as the hydroxyl group-containing compound, such as polyether polyols, polyester polyols, polycarbonate polyols, polyolefin polyols, and acrylic polyols. These compounds may be used individually or in combination.

[0079] Examples of polyether polyols include polyethylene glycol, polypropylene glycol, polyethylene propylene glycol, polytetramethylene ether glycol, and polyhexamethylene ether glycol.

[0080] Polyester polyols include those obtained from the reaction of polycarboxylic acids or their acid anhydrides with polyhydric alcohols. Examples of polycarboxylic acids include malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, sebacic acid, fumaric acid, maleic acid, terephthalic acid, isophthalic acid, etc. Examples of polyhydric alcohols include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 2-methyl-1,3-propanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 2-methyl-2,4-pentanediol, 2-methyl-2-propyl-1,3-propanediol, 1 Examples include ,8-octanediol, 2,2,4-trimethyl-1,3-pentanediol, 2-ethyl-1,3-hexanediol, 2,5-dimethyl-2,5-hexanediol, 1,9-nonanediol, 2-methyl-1,8-octanediol, 2-butyl-2-ethyl-1,3-propanediol, 2-butyl-2-hexyl-1,3-propanediol, cyclohexanediol, bishydroxymethylcyclohexane, dimethanolbenzene, bishydroxyethoxybenzene, alkyldialkanolamines, lactonediols, etc.

[0081] Examples of polycarbonate-based polyols include polycarbonate diols obtained by de-alcoholization reactions of polyhydric alcohols with dimethyl carbonate, diethyl carbonate, diphenyl carbonate, ethylene carbonate, etc., such as poly(1,6-hexylene) carbonate and poly(3-methyl-1,5-pentylene) carbonate.

[0082] Among the above, polyester polyols are preferred.

[0083] Examples of polyisocyanate compounds used to obtain polyurethane resins include aromatic diisocyanates such as tolylene diisocyanate, xylylene diisocyanate, methylenediphenyl diisocyanate, phenylene diisocyanate, naphthalene diisocyanate, and tolidine diisocyanate; aliphatic diisocyanates having aromatic rings such as α,α,α',α'-tetramethylxylylene diisocyanate; aliphatic diisocyanates such as methylene diisocyanate, propylene diisocyanate, lysine diisocyanate, trimethylhexamethylene diisocyanate, and hexamethylene diisocyanate; and alicyclic diisocyanates such as cyclohexane diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, and isopropylidene dicyclohexyl diisocyanate. These may be used individually or in combination of multiple types.

[0084] A chain extender may be used when synthesizing polyurethane resin. The chain extender is not particularly limited as long as it has two or more active groups that react with isocyanate groups. Generally, chain extenders having two hydroxyl groups or amino groups can be used.

[0085] Examples of chain extenders having two hydroxyl groups include aliphatic glycols such as ethylene glycol, propylene glycol, and butanediol; aromatic glycols such as xylylene glycol and bishydroxyethoxybenzene; and ester glycols such as neopentyl glycol hydroxypivalate.

[0086] Examples of chain extenders having two amino groups include aromatic diamines such as tolylenediamine, xylylenediamine, and diphenylmethanediamine; aliphatic diamines such as ethylenediamine, propanediamine, hexanediamine, 2,2-dimethyl-1,3-propanediamine, 2-methyl-1,5-pentanediamine, trimethylhexanediamine, 2-butyl-2-ethyl-1,5-pentanediamine, 1,8-octanediamine, 1,9-nonanediamine, and 1,10-decanediamine; and alicyclic diamines such as 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane, dicyclohexylmethanediamine, 1,4-diaminocyclohexane, and 1,3-bisaminomethylcyclohexane.

[0087] ≪Polyvinyl alcohol-based resin≫ A polyvinyl alcohol-based resin is a compound having a polyvinyl alcohol moiety. Conventional known polyvinyl alcohol-based resins can be used, including modified compounds that have been partially acetalized or butyralized. The degree of polymerization of the polyvinyl alcohol-based resin is not particularly limited, but is usually 100 or higher, preferably in the range of 300 to 40000. A degree of polymerization of 100 or higher makes it easier to improve the water resistance of the resin layer. Furthermore, the degree of saponification of the polyvinyl alcohol-based resin is not particularly limited, but polyvinyl acetate saponified with a degree of saponification of 70 mol% or higher, preferably in the range of 70 to 99.9 mol%, more preferably 80 to 97 mol%, and even more preferably 86 to 95 mol%, is commonly used in practice.

[0088] The content of compound (a) in this composition is preferably in the range of 10 to 80% by mass, more preferably 15 to 70% by mass, as a percentage of the total nonvolatile components in this composition. A content of 10% by mass or more is preferable from the viewpoint of film-forming properties and adhesion to polyester films. If the content exceeds 80% by mass, the coating strength may not be sufficient.

[0089] (Crosslinking agent) The crosslinking agent (b) is not particularly limited, and conventionally known crosslinking agents can be used. Examples include melamine compounds, epoxy compounds, oxazoline compounds, carbodiimide compounds, isocyanate compounds, silane coupling compounds, etc. Among these, from the viewpoint of increasing the strength of the resin layer and improving adhesion with the polyester film, it is preferable to include at least one selected from epoxy compounds and melamine compounds, and more preferably to include a melamine compound. Furthermore, from a similar viewpoint, it is also preferable to include two or more compounds as crosslinking agents. When two or more compounds are included as crosslinking agents, it is preferable to include at least an epoxy compound and a melamine compound.

[0090] Melamine compounds Melamine compounds are compounds that have a melamine skeleton in their composition. Examples include alkylolated melamine derivatives, compounds obtained by reacting alkylolated melamine derivatives with alcohol to partially or completely etherify them, and mixtures thereof. Examples of alkylolation include methylolation, ethylolation, isopropylroleation, n-butylolation, and isobutylolation. Among these, methylolation is preferred from the viewpoint of reactivity. Suitable alcohols for etherification include methanol, ethanol, isopropanol, n-butanol, and isobutanol, with methanol being the most preferred among these. Furthermore, the melamine compound may be a monomer, a polymer of two or more commensals, or a mixture thereof. In addition, a compound in which urea or the like is co-condensed with a portion of the melamine can be used, and a catalyst may also be used in this composition to increase the reactivity of the melamine compound.

[0091] Epoxy compounds Epoxy compounds are compounds that have an epoxy group in their molecule. Examples include condensates of hydroxyl or amino groups such as epichlorohydrin, ethylene glycol, polyethylene glycol, glycerin, polyglycerin, and bisphenol A, as well as polyepoxy compounds, diepoxy compounds, monoepoxy compounds, and glycidylamine compounds. Examples of polyepoxy compounds include sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, diglycerol polyglycidyl ether, triglycidyl tris(2-hydroxyethyl) isocyanate, glycerol polyglycidyl ether, and trimethylolpropane polyglycidyl ether. Examples of diepoxy compounds include neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, resorcinol diglycidyl ether, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, and polytetramethylene glycol diglycidyl ether. Examples of monoepoxy compounds include allyl glycidyl ether, 2-ethylhexyl glycidyl ether, and phenyl glycidyl ether, while examples of glycidylamine compounds include N,N,N',N'-tetraglycidyl-m-xylylenediamine and 1,3-bis(N,N-diglycidylamino)cyclohexane. From the viewpoint of improving the adhesion of the resin layer to the polyester film, polyether-based epoxy compounds are preferred. Furthermore, regarding the amount of epoxy groups, polyfunctional polyepoxy compounds with three or more functions are preferred over those with two functions.

[0092] ≪Oxazoline compounds≫ Oxazoline compounds are compounds having an oxazoline group in their molecule, and polymers containing an oxazoline group are particularly preferred. These can be produced by polymerization of an addition-polymerizable oxazoline group-containing monomer alone or with other monomers. Examples of addition-polymerizable oxazoline group-containing monomers include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, and 2-isopropenyl-5-ethyl-2-oxazoline. One or more of these can be used. Among these, 2-isopropenyl-2-oxazoline is preferred because it is readily available industrially. Other monomers are not limited as long as they are copolymerizable with addition-polymerizable oxazoline group-containing monomers, for example (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 their salts (sodium salt, potassium salt, ammonium salt, tertiary amine salt, etc.); unsaturated nitriles such as acrylonitrile and methacrylonitrile; (meth)acrylamide, N-alkyl(meth) Examples of unsaturated amides such as acrylamide and N,N-dialkyl(meth)acrylamide (alkyl groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, 2-ethylhexyl, and cyclohexyl groups); 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. Furthermore, the oxazoline compound may have a polyalkylene oxide chain, such as a polyethylene oxide chain, and other monomers such as (meth)acrylates having a polyalkylene oxide chain may also be used.

[0093] Carbodiimide compounds A carbodiimide compound is a compound having a carbodiimide structure, specifically a compound having one or more carbodiimide structures in its molecule. However, polycarbodiimide compounds having two or more carbodiimide structures in their molecule are more preferable for better adhesion between the resin layer and the polyester film.

[0094] Carbodiimide compounds can be synthesized using conventionally known techniques, and generally involve the condensation reaction of diisocyanate compounds. The diisocyanate compounds are not particularly limited and can be either aromatic or aliphatic. Specifically, 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. Furthermore, to the extent that it does not impair the spirit of the present invention, surfactants may be added, or hydrophilic monomers such as polyalkylene oxides, quaternary ammonium salts of dialkylamino alcohols, and hydroxyalkyl sulfonates may be added to improve the water solubility and water dispersibility of the polycarbodiimide compound.

[0095] <Isocyanate compounds> Isocyanate compounds are compounds having an isocyanate derivative structure, such as isocyanates or blocked isocyanates. Examples of isocyanates include aromatic isocyanates such as tolylene diisocyanate, xylylene diisocyanate, methylenediphenyl diisocyanate, phenylene diisocyanate, and naphthalene diisocyanate; aliphatic isocyanates having an aromatic ring such as α,α,α',α'-tetramethylxylylene diisocyanate; aliphatic isocyanates such as methylene diisocyanate, propylene diisocyanate, lysine diisocyanate, trimethylhexamethylene diisocyanate, and hexamethylene diisocyanate; and alicyclic isocyanates such as cyclohexane diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, methylenebis(4-cyclohexyl isocyanate), and isopropylidene dicyclohexyl diisocyanate. Furthermore, polymers and derivatives of these isocyanates, such as biuretized, isocyanurateized, uretdioneized, and carbodiimide-modified products, are also mentioned. These may be used individually or in combination. Among the above isocyanates, aliphatic isocyanates or alicyclic isocyanates are more preferred than aromatic isocyanates in order to avoid yellowing due to ultraviolet light.

[0096] When used in the form of blocked isocyanates, examples of blocking agents include bisulfites; phenolic compounds such as phenol, cresol, and ethylphenol; alcoholic compounds such as propylene glycol monomethyl ether, ethylene glycol, benzyl alcohol, methanol, and ethanol; active methylene compounds such as methyl isobutanoylacetate, dimethyl malonate, diethyl malonate, methyl acetoacetate, ethyl acetoacetate, and acetylacetone; mercaptan compounds such as butyl mercaptan and dodecyl mercaptan; lactam compounds such as ε-caprolactam and δ-valerolactam; amine compounds such as diphenylaniline, aniline, and ethyleneimine; acid amide compounds such as acetanilide and acetic acid amide; and oxime compounds such as formaldehyde oxime, acetaldehyde oxime, acetone oxime, methyl ethyl ketone oxime, and cyclohexanone oxime. These may be used individually or in combination of two or more.

[0097] Silane coupling compounds Silane coupling compounds are organosilicon compounds that contain both an organic functional group and a hydrolysis group such as an alkoxy group within a single molecule. For example, epoxy group-containing compounds such as 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; vinyl group-containing compounds such as vinyltrimethoxysilane and vinyltriethoxysilane; styryl group-containing compounds such as p-styryltrimethoxysilane and p-styryltriethoxysilane; (meth)acrylic group-containing compounds such as 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, and 3-(meth)acryloxypropylmethyldiethoxysilane; 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, and N-2-(aminoethyl)-3 Examples include amino group-containing compounds such as -aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldiethoxysilane, 3-triethoxysilyl-N-(1,3-dimethylbutylidene)propylamine, N-phenyl-3-aminopropyltrimethoxysilane, and N-phenyl-3-aminopropyltriethoxysilane; isocyanurate group-containing compounds such as tris(trimethoxysilylpropyl)isocyanurate and tris(triethoxysilylpropyl)isocyanurate; and mercapto group-containing compounds such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropylmethyldimethoxysilane, and 3-mercaptopropylmethyldiethoxysilane.

[0098] The content of compound (b) in this composition is preferably in the range of 10 to 60% by mass, more preferably 20 to 50% by mass, as a percentage of the total nonvolatile components in this composition. A content of 10% by mass or more improves the strength of the coating film. Furthermore, a content of 60% by mass or less suppresses the influence on the release layer provided on the resin layer (e.g., curing inhibition).

[0099] (Antistatic agent) An antistatic agent can be used in this resin layer. By using an antistatic agent, it is possible to suppress the adhesion of foreign matter to the film surface due to static electricity during the manufacturing and processing processes.

[0100] The antistatic agent used in this resin layer is preferably an ionically conductive antistatic agent, and among these, a compound containing a quaternary ammonium group is more preferred. A compound containing a quaternary ammonium group refers to a compound having a quaternized ammonium group in its molecule, and is particularly preferably a polymer compound, and also preferably a water-soluble compound. In the present invention, for example, a polymer containing a monomer having a quaternary ammonium group as a component can be used.

[0101] Specific examples of such polymers include polymers having the constituent elements shown in Formula 1 or Formula 2 below as repeating units. These may be homopolymers, copolymers, or copolymers of multiple other components.

[0102] [ka]

[0103] In the above equation (1), R 1 , R 2is independently a hydrogen atom, an alkyl group, a phenyl group, etc., and these alkyl groups and phenyl groups may be substituted with the groups shown below. Substitutable groups include, for example, a hydroxy group, an amide group, an ester group, an alkoxy group, a phenoxy group, a naphthoxy group, a thioalkoxy, a thiophenoxy group, a cycloalkyl group, a trialkylammonium alkyl group, a cyano group, and a halogen. Also, R 1 and R 2 may be chemically bonded, for example, -(CH2) m -(where m is an integer from 2 to 5), -CH(CH3)CH(CH3)-, -CH=CH-CH=CH-, -CH=CH-CH=N-, -CH=CH-N=C-, -CH2OCH2-, -(CH2)2O(CH2)2-, etc. can be mentioned.

[0104]

Chemical formula

[0105] In the above formula (2), R 2 is -O- or -NH-, R 3 is an alkylene group or another structure capable of forming the structure of formula 2, R 1 , R 4 , R 5 , R 6 are each a hydrogen atom, an alkyl group, a phenyl group, etc., and these alkyl groups and phenyl groups may be substituted with the groups shown below. Substitutable groups include, for example, a hydroxy group, an amide group, an ester group, an alkoxy group, a phenoxy group, a naphthoxy group, a thioalkoxy, a thiophenoxy group, a cycloalkyl group, a trialkylammonium alkyl group, a cyano group, and a halogen.

[0106] In the above formulas (1) and (2), X - can be appropriately selected within a range that does not impair the gist of the present invention. For example, halogen ions, sulfonates, phosphates, nitrates, alkyl sulfonates, carboxylates, etc. can be mentioned.

[0107] If the resin layer contains an antistatic agent, the amount of the antistatic agent in the composition is preferably 20 to 60% by mass, more preferably 30 to 50% by mass, as a percentage of the total nonvolatile components in the composition. By setting the content to 20% by mass or more, antistatic properties are obtained to suppress the adhesion of foreign matter to the film surface due to static electricity during manufacturing and processing. Furthermore, by setting the content to 60% by mass or less, it is possible to suppress the effect on the release layer provided on the resin layer (e.g., curing inhibition).

[0108] (Other ingredients) Within the limits of not impairing the spirit of the present invention, other additives such as crosslinking catalysts, defoaming agents, coating properties improvers, surfactants, thickeners, organic lubricants, ultraviolet absorbers, antioxidants, foaming agents, dyes, and pigments may be further added as appropriate, in addition to the above-mentioned components.

[0109] (solvent) This composition may be diluted with a solvent to form a coating solution. That is, this composition may be applied as a liquid coating solution to, for example, this film, and then dried and cured as necessary to form a resin layer. The components constituting this composition (compounds (a) and (b), the antistatic agent, and other components, etc.) may be dissolved in the solvent or dispersed in the solvent. When used as a coating solution, the concentration of the total non-volatile components of this composition in the coating solution is preferably 0.1 to 50% by mass. If it is 0.1% by mass or more, a resin layer of the desired thickness can be efficiently formed. On the other hand, if it is 50% by mass or less, the viscosity during coating can be suppressed, thereby improving the appearance of the resin layer and increasing the stability in the coating solution.

[0110] There are no particular restrictions on the solvent, and either water or an organic solvent can be used. From the viewpoint of environmental protection, it is preferable to use an aqueous coating solution with water as the main solvent (50% by mass or more of the total solvent). The water content is preferably 60% by mass or more, more preferably 70% by mass or more. The aqueous coating solution may contain a small amount of organic solvent. The specific amount of organic solvent should be less than or equal to the amount of water by mass, for example, 50% by mass or less, preferably 40% by mass or less, and more preferably 30% by mass or less of the solvent. Examples of organic solvents used in combination with water include alcohols such as ethanol, isopropanol, ethylene glycol, and glycerin; ethers such as ethyl cellosolve, t-butyl cellosolve, propylene glycol monomethyl ether, and tetrahydrofuran; ketones such as acetone and methyl ethyl ketone; esters such as ethyl acetate; and amines such as dimethylethanolamine. These can be used individually or in combination. By appropriately selecting and including these organic solvents in the aqueous coating solution as needed, the stability and coating properties of the coating solution can be improved.

[0111] Furthermore, when using only organic solvents as the solvent, examples of such organic solvents include aromatic hydrocarbons such as toluene; aliphatic hydrocarbons such as hexane, heptane, and isooctane; esters such as ethyl acetate and butyl acetate; ketones such as ethyl methyl ketone and isobutyl methyl ketone; alcohols such as ethanol and 2-propanol; and ethers such as diisopropyl ether and dibutyl ether. These may be used individually or in combination, taking into consideration their solubility, coating properties, boiling point, etc.

[0112] It can be inferred that the resin layer contains unreacted compounds, reacted compounds, or mixtures thereof of each component constituting this composition (compounds (a) and (b), antistatic agent, and other components). Furthermore, the individual components in the resin layer can be analyzed using methods such as TOF-SIMS, ESCA, and X-ray fluorescence.

[0113] (Method for forming a resin layer) Next, the method for forming the resin layer that constitutes this laminated film will be described. This resin layer may be formed by applying this composition to a polyester film and, if necessary, performing treatments such as drying, curing, and heat treatment on the applied composition. The method of applying the resin composition is not particularly limited, and conventionally known coating methods such as reverse gravure coating, direct gravure coating, roll coating, die coating, bar coating, and curtain coating can be used.

[0114] Furthermore, methods for forming the resin layer include in-line coating and off-line coating. The method for heat-treating the applied resin composition is not particularly limited. For example, when providing a resin layer by off-line coating, it is generally recommended to heat-treat at 80-200°C for 3-40 seconds, preferably at 100-180°C for 3-40 seconds. On the other hand, when providing a resin layer by in-line coating, it is generally recommended to heat-treat at 70-280°C for 3-200 seconds. Furthermore, the heat treatment may be carried out in two or more stages with different temperatures within the above temperature range. At least a portion of the heat treatment may be carried out by heating during stretching. Drying and curing may also be carried out in conjunction with the heating during the heat treatment described above.

[0115] In the present invention, the resin layer is preferably formed by in-line coating, which treats the film surface during the polyester film manufacturing process. In-line coating is a method of coating within the polyester film manufacturing process. Specifically, it involves coating at any stage from melt extrusion of polyester to stretching, heat fixing, and winding. Typically, the coating is applied to an unstretched sheet obtained by melting and rapid cooling, a stretched uniaxially oriented film, a biaxially oriented film before heat fixing, or a film after heat fixing but before winding.

[0116] While not limited to the following, for example, in sequential biaxial stretching, a method in which a uniaxially stretched film stretched in the longitudinal direction (vertical direction) is coated and then stretched in the transverse direction is particularly advantageous. With this method, film formation and resin layer formation can be performed simultaneously, which has advantages in terms of manufacturing costs. Furthermore, because stretching is performed after coating, the thickness of the resin layer can be changed according to the stretching ratio, making thin-film coating easier compared to offline coated films.

[0117] Furthermore, by providing a resin layer on the film before stretching, the resin layer can be stretched together with the polyester film, thereby allowing the resin layer to adhere firmly to the polyester film.

[0118] Furthermore, in the manufacturing of biaxially oriented polyester film, the film can be restrained in both the longitudinal and transverse directions by gripping the film edges with clips or the like while stretching it. This allows for high temperatures to be applied during subsequent heat treatment (heat setting process) without wrinkles or other defects, while maintaining flatness. Therefore, because the heat treatment applied after coating can reach temperatures that cannot be achieved by other methods, the film-forming properties of the resin layer are improved, and the resin layer and polyester film can be bonded more firmly. Furthermore, a strong resin layer can be formed, improving properties such as resistance to migration and resistance to humid heat to various functional layers that may be formed on the resin layer.

[0119] Furthermore, regardless of whether it is offline coating or in-line coating, heat treatment and active energy ray irradiation such as ultraviolet irradiation may be used in combination as needed. The polyester film constituting this laminated polyester film may be subjected to surface treatment such as corona treatment or plasma treatment in advance.

[0120] The thickness of this resin layer is preferably 0.005 to 1 μm, more preferably 0.01 to 0.5 μm, and even more preferably 0.01 to 0.1 μm. Within this thickness range, it is possible to suppress the influence on the release layer provided on the resin layer (e.g., curing inhibition), and to achieve good adhesion with the release layer.

[0121] <Release layer> This laminated film can be used in a form that has a release layer on at least one side. The release layer is preferably laminated on the resin layer. In other words, the laminated polyester film of the present invention preferably has a release layer on the resin layer. In other words, in this laminated film, it is preferable that the polyester film has a resin layer and a release layer in this order on one surface (A). Therefore, if this film has, for example, an A / B / C configuration, and surface (A) corresponds to surface layer A, then the resin layer and release layer are laminated in that order on the surface layer A side, resulting in a release layer / resin layer / A / B / C configuration. By laminating a release layer on the resin layer side formed on one surface (A) of the polyester film, it is preferable that pinholes and other defects are less likely to occur when forming a ceramic green sheet by laminating an ultra-thin ceramic layer on the release layer.

[0122] As described above, the release layer is laminated onto the polyester film via a resin layer.

[0123] The release layer is formed from a release agent composition containing a release agent, but from the viewpoint of obtaining good release performance, it is particularly preferable that the release agent composition contains a silicone resin. Specifically, it is preferable to contain a type mainly composed of a curable silicone resin, a modified silicone type produced by graft polymerization with organic resins such as urethane resin, epoxy resin, or alkyd resin, or a fluorosilicone resin. Among these, it is more preferable that the release layer contains a curable silicone resin.

[0124] As the curable silicone resin, any existing curing reaction type can be used, such as addition-type, condensation-type, or other thermosetting types, or electron beam-curing types such as ultraviolet-curing types. Multiple types of curable silicone resins may also be used in combination. Furthermore, there are no particular restrictions on the coating form of the curable silicone resin used to form the release layer; it may be in the form of a solution in an organic solvent, an aqueous emulsion, or a solvent-free form.

[0125] The mold release agent composition that forms the mold release layer may also contain, as needed, a binder, an antifoaming agent, a coating property 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, and a pigment.

[0126] The release layer is formed by coating the laminated film with a release agent composition, and either in-line coating performed within the film manufacturing process or so-called off-line coating applied outside the system to a film that has already been manufactured may be employed.

[0127] Methods for providing a release layer on the laminated film include conventionally known coating methods such as reverse gravure coating, direct gravure coating, roll coating, die coating, bar coating, and curtain coating.

[0128] The curing conditions for forming the release layer are not particularly limited. When providing a release layer by offline coating, it is generally preferable to perform heat treatment at 80°C or higher for 10 seconds or more, preferably at 100-200°C for 3-40 seconds, and more preferably at 120-180°C for 3-40 seconds.

[0129] Furthermore, if necessary, heat treatment may be used in combination with irradiation using active energy rays such as ultraviolet irradiation. Furthermore, known devices and energy sources can be used as the energy source for curing by activated energy ray irradiation.

[0130] The amount of release layer applied (after drying) is typically 0.005 to 5 g / m², considering the coating properties. 2 Preferably 0.005 to 1 g / m 2 , more preferably 0.005~0.1 g / m 2 It is within this range. The coating amount (after drying) is 0.005 g / m². 2 If the amount is less than 5 g / m², the coating may lack stability in terms of applicability, making it difficult to obtain a uniform coating film. 2 When applying a thicker coat than the recommended thickness, the adhesion and curing properties of the release layer itself may decrease. The coating amount is calculated based on the liquid mass per unit of time applied (before drying), the non-volatile content concentration of the coating liquid, the application width, the stretching ratio, the line speed, etc.

[0131] <Application> This laminated 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 manufacture of ceramic green sheets for multilayer ceramic capacitors. In release and process applications, this laminated film can be used, for example, as a support, and various materials such as ceramic slurry can be applied or laminated onto the support.

[0132] In particular, as mentioned above, this laminated film has excellent smoothness and can be used to thin ceramic green sheets, making it suitable for use as a support for ceramic green sheets in the manufacturing process of multilayer ceramic capacitors.

[0133] Furthermore, in the future, as multilayer ceramic capacitors for automobiles become increasingly electrified, it is predicted that the thinning of the ceramic green sheet used will progress, particularly as the capacitors become smaller and their capacitance increases. Therefore, in particular, this laminated film can be suitably used as a support for ceramic green sheets used in multilayer ceramic capacitors for automobiles. [Examples]

[0134] 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.

[0135] <Polyester raw materials> Table 1 shows the polyester raw materials used in the examples and comparative examples. Polyester raw materials A to D listed in Table 1 are all homopolyethylene terephthalate (homopolyester). Furthermore, when manufacturing polyester C, a fatty acid metal salt crystal nucleating agent (Licomont NaV101(CH3(CH2) manufactured by Clariant) is used. 26 COONa (melting point 171°C) was added at a concentration of 10% by mass relative to the polyester. In addition, during the production of polyester D, monodisperse spherical silica with an average primary particle size of 0.5 μm ((D90-D10) / D50=0.27) was added at a concentration of 1.0% by mass relative to the polyester.

[0136] [Table 1]

[0137] [Example 1] A raw material blend of polyester A at 90% mass and polyester C at 10% mass was used for surface layer A, a raw material of polyester B at 100% mass was used for intermediate layer B, and a raw material blend of polyester A at 70% mass and polyester D at 30% mass was used for surface layer C. These materials were supplied to a vented extruder and melt-extruded at 290°C. A three-layer structure (A / B / C) was then obtained, with surface layer A and C as the outermost layer (surface layer) and intermediate layer B as the intermediate layer. The material was co-extruded under extrusion conditions such that the thickness composition ratio A / B / C = 3 / 27 / 1, and the material was cooled and solidified on a cooling roll with a surface temperature set to 40°C using an electrostatic application adhesion method to obtain an amorphous film. In this case, surface layer C is the side that contacts the cooling roll.

[0138] Next, using the difference in roll peripheral speed, the film was stretched 3.5 times in the longitudinal direction (MD direction) at a film temperature of 85°C. Then, a coating solution having the following composition was applied to one side of this longitudinally stretched film to a thickness (after drying) of 0.02 μm. The film was then guided into a tenter and stretched 4.5 times in the transverse direction (TD direction) at 105°C. Heat treatment was then performed in heat treatment (fixing) zones 1, 2, and 3 and cooling zone 4 within the tenter at 170°C, 230°C, 230°C, and 140°C, respectively, to obtain a laminated polyester film having a resin layer R1 on the surface layer A of a 31 μm thick polyester film.

[0139] The coating solution in Example 1 was prepared by diluting a resin composition obtained by stirring and mixing the following composition with water. (Compound (a) Binder resin) Polyvinyl alcohol-based resin: 20% by mass of polyvinyl alcohol with a degree of saponification of 88 mol% and a degree of polymerization of 500. (Compound (b) Crosslinking agent) Melamine compound: Hexamethoxymethylolmelamine 40% by mass (Antistatic agent) Poly(trimethylammonium ethyl methacrylate methanesulfonate) 40% by mass The above-mentioned compound content percentages represent the proportion of each compound in the total non-volatile components of this composition.

[0140] [Example 2] In Example 1, the coating solution was changed as follows, but otherwise the same procedure was followed to obtain a laminated polyester film having a resin layer R2 on a surface layer A of a 31 μm thick polyester film.

[0141] The coating solution in Example 2 was prepared by diluting a resin composition obtained by stirring and mixing the following composition with water. (Compound (a) Binder resin) Polyester resin: 60% by mass of an aqueous dispersion of polyester resin copolymerized with the following composition. Monomer composition: (Acid component) 2,6-Naphthalenedicarboxylic acid / 5-Sodium sulfisoisophthalic acid / / (Diol component) Ethylene glycol / Diethylene glycol = 92 / 8 / / 80 / 20 (mol%) (Compound (b) Crosslinking agent) Melamine compound: Hexamethoxymethylolmelamine 10% by mass Epoxy compound: Polyglycerol polyglycidyl ether 30% by mass The above-mentioned compound content percentages represent the proportion of each compound in the total non-volatile components of this composition.

[0142] [Comparative Example 1] In Example 1, the coating solution was changed as follows, but otherwise the same procedure was followed to obtain a laminated polyester film having a resin layer R3 on a surface layer A of a 31 μm thick polyester film.

[0143] The coating solution in Comparative Example 1 was prepared by diluting a resin composition obtained by stirring and mixing the following composition with water. (Compound (b) Crosslinking agent) Melamine compound: Hexamethoxymethylolmelamine 60% by mass Oxazoline compound: Epocross (manufactured by Nippon Shokubai Co., Ltd.) Oxazoline group content 7.7 mmol / g 40% by mass The above-mentioned compound content percentages represent the proportion of each compound in the total non-volatile components of this composition.

[0144] [Comparative Example 2] In Example 1, the same procedure was followed except that a resin layer was not provided, to obtain a polyester film with a thickness of 31 μm.

[0145] [Comparative Example 3] In Example 1, the raw material blending ratio of surface layer A was changed as shown in Table 1, and a resin layer was omitted. Otherwise, the same procedure as in Example 1 was followed to obtain a polyester film with a thickness of 31 μm.

[0146] <Measurement and Evaluation Methods> The measurement and evaluation methods used in the examples and comparative examples are as follows:

[0147] (1) Intrinsic viscosity (IV) 1 g of polyester was accurately weighed, dissolved in 100 mL of a phenol / tetrachloroethane mixed solvent (50 / 50 mass ratio), and measured at 30°C using a viscosity (IV) measuring device (VMS-022UPC·F10, manufactured by Rigosha).

[0148] (2) Average particle size and particle size distribution Using a scanning electron microscope (HITACHI, "S3400N"), the powder was observed on the surface of the films in the examples and comparative examples. The size of a single particle was measured from the obtained image data, and the average of 10 points was defined as the average primary particle size. Furthermore, a dispersion with a solid content of 0.03 g / mL was prepared by adding a mixed solvent of phenol / tetrachloroethane = 2 / 3 to the particles. Using a Microtrac-Bel "MT3300EXII" laser diffraction scattering method, the particle sizes D10 (where the cumulative number of particles reaches 10%), D50 (where the cumulative number of particles reaches 50%), and D90 (where the cumulative number of particles reaches 90%) were measured for this dispersion, and (D90-D10) / D50 was calculated.

[0149] (3) Average surface roughness (Sa), maximum peak height (Sp) Using a surface roughness measuring instrument (AMETEK Co., Ltd., "NewView" registered trademark), the surface of the resin layer (or surface layer A if there is no resin layer) and the surface of surface layer C of the films in the examples and comparative examples were measured, and the average surface roughness (Sa) and maximum peak height (Sp) were determined from the obtained surface profile curves.

[0150] (4) Adhesion of the release layer to the coating The following release layer composition is applied to the resin layer (or surface layer A if there is no resin layer) of the film in the examples and comparative examples at a coating rate (after drying) of 0.1 g / m². 2 The film was coated in such a manner, and after heat treatment at 150°C for 30 seconds, a film with a release layer (release film) was obtained. The release layer surface of the obtained release film was rubbed five times with a hand, and the presence or absence of detachment of the release layer was determined according to the following criteria. Furthermore, the sample films were stored at 23°C and 50±3%RH for the period indicated in Table 2, and the change in the adhesion of the release layer (whether or not the release layer peeled off) over time was confirmed using the same method. (Release layer composition) Curing-type silicone resin (Shin-Etsu Chemical Co., Ltd.: KS-847H) 99% by mass Hardening agent (Shin-Etsu Chemical: PL-50T) 1% by mass The above release agent was adjusted to 2% by mass using a toluene / MEK mixed solvent (mixing ratio 1:1). "Judgment criteria" ○: No paint film peeling is observed, or the paint film turns white but does not peel off (practical level) ×: Paint film peeling was observed (to a level that makes it unusable).

[0151] [Table 2]

[0152] As shown in Table 2, the films of Examples 1 and 2 have high smoothness with an average surface roughness (Sa) of 1 to 10 nm, and the maximum peak height (Sp) can be controlled while maintaining the average surface roughness (Sa) by using a crystal nucleating agent. Furthermore, the films of Examples 1 and 2, having a specific resin layer, did not inhibit curing of the release layer and exhibited good adhesion to the release layer.

[0153] On the other hand, the film of Comparative Example 3 is an example in which the surface layer A does not contain a crystal nucleating agent and does not have a resin layer, but it is too smooth, which may reduce its slipperiness and impair its processability. In addition, the maximum peak height (Sp) has not been reduced relative to the average surface roughness (Sa), making it difficult to achieve both smoothness and processability. Furthermore, it can be seen that the adhesion of the release layer to the coating deteriorates over time. Furthermore, in cases where a release layer is directly applied to surface layer A containing a crystal nucleating agent, as in the film of Comparative Example 2, or where a release layer is applied to a resin layer that does not contain a binder resin, as in the film of Comparative Example 1, the adhesion was poor immediately after the release layer was applied, indicating that curing inhibition of the release layer occurred due to the crystal nucleating agent component. [Industrial applicability]

[0154] The laminated polyester film of the present invention has the advantage of having high smoothness and good adhesion to the release layer. Furthermore, when used as a support for a ceramic green sheet in the manufacturing process of a multilayer ceramic capacitor, a uniform thin dielectric layer can be formed. In particular, it can be suitably used as a support for a ceramic green sheet used in multilayer ceramic capacitors for automobiles.

Claims

1. A laminated polyester film having one surface (A) of the polyester film containing a crystal nucleating agent, a resin layer formed on the surface (A) of a resin composition containing (a) a binder resin and (b) a crosslinking agent, and a surface layer C containing particles on the surface opposite to the one surface (A), A laminated polyester film in which the surface of the resin layer satisfies the following (1) and (2). (1) The average surface roughness (Sa) is 1 to 10 nm. (2) The maximum peak height (Sp) is 150 nm or less.

2. The laminated polyester film according to claim 1, wherein the nucleating agent is a fatty acid metal salt represented by the following general formula (X). (CH ３ (CH ２ ) ｎ COO) ｍ M ・・・(X) (In the above formula, n is an integer greater than or equal to 4, and M is Na, Ca, or Li. Also, m is 1 if M is Na or Li, and 2 if M is Ca.)

3. The laminated polyester film according to claim 1, wherein the ratio (Sp / Sa) of the maximum peak height (Sp) of the resin layer surface to the average surface roughness (Sa) is 50 or less.

4. The laminated polyester film according to claim 1, wherein the binder resin (a) comprises a polyester resin or a polyvinyl alcohol-based resin.

5. The laminated polyester film according to claim 1, wherein the crosslinking agent (b) comprises a melamine compound.

6. The laminated polyester film according to claim 1, wherein the crosslinking agent (b) comprises two or more compounds.

7. The laminated polyester film according to claim 1, wherein the polyester film has a three-layer structure.

8. The laminated polyester film according to claim 1, wherein the average surface roughness (Sa) of the surface layer C is 3 nm or more and 20 nm or less.

9. The laminated polyester film according to claim 1, wherein the maximum peak height (Sp) of the surface layer C is 10 nm or more and 220 nm or less.

10. The laminated polyester film according to claim 1, having a release layer on the resin layer.

11. The laminated polyester film according to claim 10, wherein the release layer contains a curable silicone resin.

12. A laminated polyester film according to any one of claims 1 to 11, used as a support for a ceramic green sheet in the manufacturing process of a multilayer ceramic capacitor.

13. A laminated polyester film according to any one of claims 1 to 11, used as a support for a ceramic green sheet in the manufacturing process of an automotive ceramic capacitor.

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